FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Bauschlicher, CW Ricca, A AF Bauschlicher, CW Ricca, A TI The heat of formation of C2F4 SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; ELECTRON CORRELATION; WAVE-FUNCTIONS; FORCE-FIELD; ATOMS; ENERGIES AB The CCSD(T) atomization energies are extrapolated to the complete basis set limit, and are corrected for zero-point energy, spin-orbit, core-valence, and scalar relativistic effects. Our best heats of formation at 298 K for CF4 and C2F4 are -223.1 +/- 1.1 and -160.5 +/- 1.5 kcal/mol, respectively. The CF, value is in excellent agreement with experiment (- 223.04 +/- 0.18 kcal/mol), while the C2F4 result suggests that the experimental value (- 157.6 +/- 0.6 kcal/mol) has a larger error than believed. Our value for C2F4 also shows that the G3 value has the expected error of +/-2 kcal/mol. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 30 TC 15 Z9 15 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD DEC 31 PY 1999 VL 315 IS 5-6 BP 449 EP 453 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 272KN UT WOS:000084649300022 ER PT J AU Nealson, KH Conrad, PG AF Nealson, KH Conrad, PG TI Life: past, present and future SO PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES LA English DT Article DE biosignature; metabolic evolution; extremophile; metabolic taxonomy; bioenergetics; life detection ID ATMOSPHERIC OXYGEN; FERROUS IRON; BACTERIA; EVOLUTION; SEDIMENT; MICROORGANISMS; PERSPECTIVE; OXIDATION; EARTH AB Molecular methods of taxonomy and phylogeny have changed the way in which life on earth is viewed; they have allowed us to transition from a eukaryote-centric (five-kingdoms) view of the planet to one that is peculiarly prokarote-centric, containing three kingdoms, two of which are prokaryotic unicells. These prokaryotes are distinguished from their eukaryotic counterparts by their toughness, tenacity and metabolic diversity Realization of these features has, in many ways, changed the way we feel about life on earth, about the nature of life past and about the possibility of finding life elsewhere. In essence, the limits of life on this planet have expanded to such a degree that our thoughts of both past and future life have been altered. The abilities of prokaryotes to withstand many extreme conditions has led to the term extremophiles, used to describe the organisms that thrive under conditions thought just a few years ago, to be inconsistent with life. Perhaps the most extensive adaptation to extreme conditions, however, is represented by the ability of many bacteria to survive nutrient conditions not compatible with eukaryotic life. Prokaryotes have evolved to use nearly every redox couple that is in abundance on earth, filling the metabolic niches left behind by the oxygen-using, carbon-eating eukaryotes. This metabolic plasticity leads to a common feature in physically stratified environments of layered microbial communities, chemical indicators of the metabolic diversity of the prokaryotes. Such 'metabolic extremophily' forms a backdrop by which we can view the energy flow of life on this planet, think about what the evolutionary past of the planet might have been, and plan ways to look for life elsewhere, using the knowledge of energy flow on earth. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 183-301,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM knealson@jpl.nasa.gov NR 35 TC 70 Z9 72 U1 4 U2 30 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 0962-8436 EI 1471-2970 J9 PHILOS T R SOC B JI Philos. Trans. R. Soc. B-Biol. Sci. PD DEC 29 PY 1999 VL 354 IS 1392 BP 1923 EP 1939 DI 10.1098/rstb.1999.0532 PG 17 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 273AF UT WOS:000084683100003 PM 10670014 ER PT J AU Hansen, J Ruedy, R Glascoe, J Sato, M AF Hansen, J Ruedy, R Glascoe, J Sato, M TI GISS analysis of surface temperature change SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AIR-TEMPERATURE; CLIMATE-CHANGE; TROPOSPHERIC TEMPERATURE; INTERDECADAL VARIATIONS; NORTHERN-HEMISPHERE; TIME-SERIES; EL-NINO; TRENDS; SEA; SATELLITE AB We describe the current GISS analysis of surface temperature change for the period 1880-1999 based primarily on meteorological station measurements. The global surface temperature in 1998 was the warmest in the period of instrumental data. The rate of temperature change was higher in the past 25 years than at any previous time in the period of instrumental data. The warmth of 1998 was too large and pervasive to be fully accounted for by the recent El Nine. Despite cooling in the first half of 1999, we suggest that the mean global temperature, averaged over 2-3 years, has moved to a higher level, analogous to the increase that occurred in the late 1970s. Warming in the United States over the past 50 years has been smaller than in most of the world, and over that period there was a slight cooling trend in the eastern United States and the neighboring Atlantic Ocean. The spatial and temporal patterns of the temperature change suggest that more than one mechanism was involved in this regional cooling. The cooling trend in the United States, which began after the 1930s and is associated with ocean temperature change patterns, began to reverse after 1979. We suggest that further warming in the United States to a level rivaling the 1930s is likely in the next decade, but reliable prediction requires better understanding of decadal oscillations of ocean temperature. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Hansen, J (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM jhansen@giss.nasa.gov NR 87 TC 445 Z9 490 U1 3 U2 33 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1999 VL 104 IS D24 BP 30997 EP 31022 DI 10.1029/1999JD900835 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 273DQ UT WOS:000084692900009 ER PT J AU Loeb, NG Hinton, PO Green, RN AF Loeb, NG Hinton, PO Green, RN TI Top-of-atmosphere albedo estimation from angular distribution models: a comparison between two approaches SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NIMBUS-7 ERB; EARTH; IDENTIFICATION AB Empirical angular distribution models (ADMs) are commonly used to convert satellite-measured radiances to top-of-atmosphere (TOA) radiative fluxes. This study compares two methods of developing ADMs: (I) the radiance pairs method (RPM), which composits ratios of near-simultaneous radiance measurements over the same scene to construct the ADMs; (2) the sorting-into-angular-bins (SAB) method, which estimates ADM anisotropic factors from the ratio of the mean radiance in each angular bin to the mean flux determined by direct integration of the mean radiances. Theoretical simulations and analyses of measurements from the CERES (Clouds and Earth's Radiant Energy System) satellite instrument show that the RPM method provides a better estimate of the true mean ADM for a population of scenes, while the SAB method is better suited for top-of-atmosphere flux estimation. The CERES results also show that a variable field of view size with viewing zenith angle can cause an approximate to 10% (relative) change in estimated all-sky mean albedo with viewing zenith angle. C1 Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. Sci Applicat Int Corp, Hampton, VA USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Loeb, NG (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23665 USA. EM n.g.loeb@larc.nasa.gov NR 14 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1999 VL 104 IS D24 BP 31255 EP 31260 DI 10.1029/1999JD900935 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 273DQ UT WOS:000084692900026 ER PT J AU Wen, GY Tsay, SC Cahalan, RF Oreopoulos, L AF Wen, GY Tsay, SC Cahalan, RF Oreopoulos, L TI Path radiance technique for retrieving aerosol optical thickness over land SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DISCRETE-ORDINATE-METHOD; SCALE AIR-POLLUTION; SATELLITE MEASUREMENTS; RADIATIVE-TRANSFER; ATMOSPHERIC CORRECTIONS; ALGORITHM; SCATTERING; IMAGERY; OCEANS; MASS AB The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a "path radiance" method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the "dark object" approach to extract the aerosol signal. This method uses the signature of the correlation of visible and middle-IR reflectance at the surface and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma southern Great Plains site of the Department of Energy Atmospheric Radiation Measurement (ARM) program on September 27, 1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 mu m) during the first Landsat Intensive Observation Period. The retrieved mean aerosol optical thickness for TM band 1 at 0.49 mu m and band 3 at 0.66 mu m agree very well with the ground-based Sun photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Catonsville, MD USA. RP Wen, GY (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Code 913, Greenbelt, MD 20771 USA. EM wen@climate.gsfc.nasa.gov RI Oreopoulos, Lazaros/E-5868-2012; Cahalan, Robert/E-3462-2012; Tsay, Si-Chee/J-1147-2014 OI Oreopoulos, Lazaros/0000-0001-6061-6905; Cahalan, Robert/0000-0001-9724-1270; NR 37 TC 30 Z9 33 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1999 VL 104 IS D24 BP 31321 EP 31332 DI 10.1029/1999JD900964 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 273DQ UT WOS:000084692900031 ER PT J AU Eck, TF Holben, BN Reid, JS Dubovik, O Smirnov, A O'Neill, NT Slutsker, I Kinne, S AF Eck, TF Holben, BN Reid, JS Dubovik, O Smirnov, A O'Neill, NT Slutsker, I Kinne, S TI Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SIZE DISTRIBUTION; VARIABILITY; VEGETATION; EXTINCTION; MODEL AB The Angstrom wavelength exponent alpha, which is the slope of the logarithm of aerosol optical depth (tau(a)) versus the logarithm of wavelength (lambda), is commonly used to characterize the wavelength dependence of tau(a) and to provide some basic information on the aerosol size distribution. This parameter is frequently computed from the spectral measurements of both ground-based sunphotometers and from satellite and aircraft remote sensing retrievals. However, spectral variation of alpha is typically not considered in the analysis and comparison of values from different techniques. We analyze the spectral measurements of tau(a) from 340 to 1020 nm obtained from ground-based Aerosol Robotic Network radiometers located in various locations where either biomass burning, urban, or desert dust aerosols are prevalent. Aerosol size distribution retrievals obtained from combined solar extinction and sky radiance measurements are also utilized in the analysis. These data show that there is significant curvature in the ln tau(a) versus ln lambda relationship for aerosol size distributions dominated by accumulation mode aerosols (biomass burning and urban). Mie theory calculations of alpha for biomass burning smoke (for a case of aged smoke at high optical depth) agree well with observations, confirming that large spectral variations in a are due to the dominance of accumulation mode aerosols, A second order polynomial fit to the ln tau(a) versus ln lambda data provides excellent agreement with differences in tau(a) of the order of the uncertainty in the measurements (similar to 0.01-0.02). The significant curvature in ln tau(a) versus ln lambda for high optical depth accumulation mode dominated aerosols results in alpha values differing by a factor of 3-5 from 340 to 870 nm. We characterize the curvature in ln tau(a) versus ln lambda by the second derivative alpha' and suggest that this parameter be utilized in conjunction with alpha to characterize the spectral dependence of tau(a). The second derivative of ln tau(a) versus ln lambda gives an indication of the relative influence of accumulation mode versus coarse mode particles on optical properties. C1 NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Univ Maryland, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space & Naval Warfare Syst Ctr, Tropospher Branch, San Diego, CA USA. Univ Sherbrooke, Ctr Applicat & Rech Teledetect, Sherbrooke, PQ J1K 2R1, Canada. RP Eck, TF (reprint author), NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Code 923, Greenbelt, MD 20771 USA. EM tom@spamer.gsfc.nasa.gov; brent@spamer.gsfc.nasa.gov; jreid@spawar.navy.mil; dubovik@spamer.gsfc.nasa.gov; asmirnov@spamer.gsfc.nasa.gov; norm@spamer.gsfc.nasa.gov; ilya@spamer.gsfc.nasa.gov; kinne@spamer.gsfc.nasa.gov RI Dubovik, Oleg/A-8235-2009; Smirnov, Alexander/C-2121-2009; ECK, THOMAS/D-7407-2012; Reid, Jeffrey/B-7633-2014 OI Dubovik, Oleg/0000-0003-3482-6460; Smirnov, Alexander/0000-0002-8208-1304; Reid, Jeffrey/0000-0002-5147-7955 NR 41 TC 904 Z9 931 U1 11 U2 80 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1999 VL 104 IS D24 BP 31333 EP 31349 DI 10.1029/1999JD900923 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 273DQ UT WOS:000084692900032 ER PT J AU Whiteman, DN Melfi, SH AF Whiteman, DN Melfi, SH TI Cloud liquid water, mean droplet radius, and number density measurements using a Raman lidar SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DETECTION LIMITS; SIZE DEPENDENCE; SCATTERING; AEROSOLS; SPECTROSCOPY; ATMOSPHERE; VAPOR; MICROPARTICLES; RESONANCES; RADIATION AB A new technique for measuring cloud liquid water, mean droplet radius, and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid microspheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested. C1 Univ Maryland, Dept Phys, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Laser Remote Sensing Branch, Greenbelt, MD 20771 USA. RP Whiteman, DN (reprint author), Univ Maryland, Dept Phys, Baltimore, MD 21250 USA. EM david.whiteman@gsfc.nasa.gov NR 32 TC 54 Z9 54 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1999 VL 104 IS D24 BP 31411 EP 31419 DI 10.1029/1999JD901004 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 273DQ UT WOS:000084692900038 ER PT J AU Anagnostou, EN Negri, AJ Adler, RF AF Anagnostou, EN Negri, AJ Adler, RF TI A satellite infrared technique for diurnal rainfall variability studies SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article; Proceedings Paper CT 6th International Conference of Precipitation on Predictability of Rainfall at the Various Scales CY JUN 29-JUL 01, 1998 CL MAUNA LANI BAY, HI SP Amer Geophys Union, Amer Meterol Soc, Mauna Lani Bay Hotel & Bungalows ID CONVECTIVE RAINFALL; STRATIFORM; PRECIPITATION; CLOUD AB The development of a satellite infrared technique for estimating convective and stratiform rainfall area and volume and its application in studying the diurnal variability of rainfall in Amazonia are presented. Cloud systems are defined in the technique by the 253 K infrared (IR) temperature isotherm. The convective and stratiform rain areas within these cloud systems are then related to morphologic characteristics of the IR temperature fields. Rainfall rates are assigned to the defined convective and stratiform areas using IR-microwave-derived rain rate probability matching relationships. The training data set consists of three months of collocated IR observations and microwave (MW) rain rate retrievals over a region in the Amazon Basin. Evaluation of instantaneous rain rate estimates over a second independent region in the Amazon showed 25% (-40%) systematic error and 55% (70%) residual random error standard deviation in morning (evening) MW overpasses. The method is used to derive the mean diurnal cycle of rainfall and investigate the relative contribution from its convective and stratiform components. Finally, the technique is applied to study the time evolution of rainfall and the transition from convective to stratiform over selected sites in the Amazon. C1 Univ Connecticut, Dept Civil & Environm Engn, Storrs, CT 06269 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Anagnostou, EN (reprint author), Univ Connecticut, Dept Civil & Environm Engn, U-37,261 Glenbrook Rd, Storrs, CT 06269 USA. EM manos@engr.uconn.edu NR 20 TC 32 Z9 33 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1999 VL 104 IS D24 BP 31477 EP 31488 DI 10.1029/1999JD900157 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 273DQ UT WOS:000084692900044 ER PT J AU Mishchenko, MI Travis, LD Hovenier, JW AF Mishchenko, MI Travis, LD Hovenier, JW TI Introduction to special section: Electromagnetic scattering by nonspherical particles SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Free Univ Amsterdam, Dept Phys & Astron, NL-1081 HV Amsterdam, Netherlands. Univ Amsterdam, Astron Inst Anton Pannekoek, NL1098 SJ Amsterdam, Netherlands. RP Mishchenko, MI (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM crmim@giss.nasa.gov RI Mishchenko, Michael/D-4426-2012 NR 10 TC 1 Z9 3 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1999 VL 104 IS D24 BP 31671 EP 31672 DI 10.1029/1999JD900491 PG 2 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 273DQ UT WOS:000084692900058 ER PT J AU Caines, H Albergo, S Bellwied, R Bennett, M Boemi, D Bonner, B Caccia, Z Christie, W Cina, G Costa, S Crawford, H Cronqvist, M Debbe, R Engelage, J Flores, I Greiner, L Hallman, T Hoffman, G Huang, H Humanic, TJ Igo, G Insolia, A Jensen, P Judd, E Kainz, K Kaplan, M Kelly, S Kotov, I Kunde, G Lindstrom, P Ljubicic, T Llope, W Lo Curto, G Longacre, R Lynn, D Madansky, L Mahzeh, N Milosevich, Z Mitchell, JT Mitchell, J Nehmeh, S Nociforo, C Paganis, S Pandey, SU Potenza, R Platner, E Riley, P Russ, D Saulys, A Schambach, J Sheen, J Stokley, C Sugarbaker, E Takahashi, J Tang, J Trentalange, S Tricomi, A Tull, C Tuve, C Whitfield, J Wilson, K AF Caines, H Albergo, S Bellwied, R Bennett, M Boemi, D Bonner, B Caccia, Z Christie, W Cina, G Costa, S Crawford, H Cronqvist, M Debbe, R Engelage, J Flores, I Greiner, L Hallman, T Hoffman, G Huang, H Humanic, TJ Igo, G Insolia, A Jensen, P Judd, E Kainz, K Kaplan, M Kelly, S Kotov, I Kunde, G Lindstrom, P Ljubicic, T Llope, W Lo Curto, G Longacre, R Lynn, D Madansky, L Mahzeh, N Milosevich, Z Mitchell, JT Mitchell, J Nehmeh, S Nociforo, C Paganis, S Pandey, SU Potenza, R Platner, E Riley, P Russ, D Saulys, A Schambach, J Sheen, J Stokley, C Sugarbaker, E Takahashi, J Tang, J Trentalange, S Tricomi, A Tull, C Tuve, C Whitfield, J Wilson, K TI First results from the H-0 di-baryon search and hyperon production measurements by the AGS Experiment 896. SO NUCLEAR PHYSICS A LA English DT Article; Proceedings Paper CT 14th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions CY MAY 10-15, 1999 CL TURIN, ITALY SP Ist Nazl Fica Nucleare, Univ Torino, Univ Piemonte Orientale, Regione Piemonte, Provincia Torino, Compagnia San Paolo, Cassa Risparmio Torino, Caen, Hamamatsu, Canberra, Tecnol Avanzate ID H-DIBARYON; COLLISIONS AB The AGS Experiment 896 was designed to study strangeness production in Au-Au collisions at 11.6A GeV/c, in particular the formation of a six-quark di-baryon the H-0. Heavy ion collisions provide favorable conditions for the H-0 formation either via coalescence of two Lambda particles (owing to the large Lambda production cross section) or direct production from the possible formation of a quark-gluon plasma. E896 also measured strange meson and baryon distributions from mid-rapidity. Preliminary results from this experiment are presented as well as details of the expected sensitivity for the H-0 search. C1 Ohio State Univ, Columbus, OH 43210 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. Univ Calif Los Angeles, Los Angeles, CA 90095 USA. Carnegie Mellon Univ, Pittsburgh, PA 15213 USA. Univ Catania, I-95129 Catania, Italy. Johns Hopkins Univ, Baltimore, MD 21218 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Rice Univ, Houston, TX 77251 USA. Univ Texas, Austin, TX 78712 USA. Wayne State Univ, Detroit, MI 48201 USA. Yale Univ, New Haven, CT 06520 USA. RP Caines, H (reprint author), Ohio State Univ, Columbus, OH 43210 USA. RI Takahashi, Jun/B-2946-2012; Insolia, Antonio/M-3447-2015; TUVE', Cristina/P-3933-2015 OI Takahashi, Jun/0000-0002-4091-1779; Insolia, Antonio/0000-0002-9040-1566; TUVE', Cristina/0000-0003-0739-3153 NR 11 TC 5 Z9 5 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9474 J9 NUCL PHYS A JI Nucl. Phys. A PD DEC 27 PY 1999 VL 661 BP 170C EP 176C DI 10.1016/S0375-9474(99)00451-0 PG 7 WC Physics, Nuclear SC Physics GA 277XJ UT WOS:000084958600018 ER PT J AU Lo Curto, G Albergo, S Bellwied, R Bennett, M Boemi, D Bonner, B Caccia, Z Caines, H Christie, W Cina, G Costa, S Crawford, H Cronqvist, M Debbe, R Engelage, J Flores, I Greiner, L Hallman, T Hoffman, G Huang, H Humanic, TJ Igo, G Insolia, A Jensen, P Judd, E Kainz, K Kaplan, M Kelly, S Kotov, I Kunde, G Lindstrom, P Ljubicic, T Llope, W Longacre, R Lynn, D Madansky, L Mahzeh, N Milosevich, Z Mitchell, JT Mitchell, J Nehmeh, S Nociforo, C Paganis, S Pandey, SU Potenza, R Platner, E Riley, P Russ, D Saulys, A Schambach, J Sheen, J Stokley, C Sugarbaker, E Takahashi, J Tang, J Trentalange, S Tricomi, A Tull, C Tuve, C Whitfield, J Wilson, K AF Lo Curto, G Albergo, S Bellwied, R Bennett, M Boemi, D Bonner, B Caccia, Z Caines, H Christie, W Cina, G Costa, S Crawford, H Cronqvist, M Debbe, R Engelage, J Flores, I Greiner, L Hallman, T Hoffman, G Huang, H Humanic, TJ Igo, G Insolia, A Jensen, P Judd, E Kainz, K Kaplan, M Kelly, S Kotov, I Kunde, G Lindstrom, P Ljubicic, T Llope, W Longacre, R Lynn, D Madansky, L Mahzeh, N Milosevich, Z Mitchell, JT Mitchell, J Nehmeh, S Nociforo, C Paganis, S Pandey, SU Potenza, R Platner, E Riley, P Russ, D Saulys, A Schambach, J Sheen, J Stokley, C Sugarbaker, E Takahashi, J Tang, J Trentalange, S Tricomi, A Tull, C Tuve, C Whitfield, J Wilson, K TI Strange and multi-strange baryon measurement in Au plus Au collisions at 11.6A(GeV/c) with the silicon drift detector array from the AGS experiment E896 SO NUCLEAR PHYSICS A LA English DT Article; Proceedings Paper CT 14th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions CY MAY 10-15, 1999 CL TURIN, ITALY SP Ist Nazl Fica Nucleare, Univ Torino, Univ Piemonte Orientale, Regione Piemonte, Provincia Torino, Compagnia San Paolo, Cassa Risparmio Torino, Caen, Hamamatsu, Canberra, Tecnol Avanzate AB The main purpose of experiment E896 is to study the production of strange hadrons, in particular the predicted six-quark di-baryon, the H-0. The placement of the silicon drift detector array (SDDA) close to the target in a 6.2T magnetic field is optimized for the reconstruction of a short lived H-0 as well as of strange baryons (Lambda, <(Lambda)over bar>, Xi(-)). Simulations show that with the present data sample a detailed study of the A and Xi(-) yields and distributions may be performed and a clear <(Lambda)over bar> signal might be detected. Simulations as well as a preliminary analysis of the SDDA data will be presented. C1 Ohio State Univ, Columbus, OH 43210 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. Univ Calif Los Angeles, Los Angeles, CA 90024 USA. Carnegie Mellon Univ, Pittsburgh, PA 15213 USA. Univ Catania, Catania, Italy. Johns Hopkins Univ, Baltimore, MD 21218 USA. Lawrence Berkeley Lab, Space Sci Lab, Berkeley, CA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Rice Univ, Houston, TX 77251 USA. Univ Texas, Austin, TX 78712 USA. Wayne State Univ, Detroit, MI 48202 USA. Yale Univ, New Haven, CT 06520 USA. RP Lo Curto, G (reprint author), Ohio State Univ, Columbus, OH 43210 USA. RI Takahashi, Jun/B-2946-2012; Insolia, Antonio/M-3447-2015; TUVE', Cristina/P-3933-2015 OI Takahashi, Jun/0000-0002-4091-1779; Insolia, Antonio/0000-0002-9040-1566; TUVE', Cristina/0000-0003-0739-3153 NR 10 TC 1 Z9 1 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9474 J9 NUCL PHYS A JI Nucl. Phys. A PD DEC 27 PY 1999 VL 661 BP 489C EP 492C DI 10.1016/S0375-9474(99)00504-7 PG 4 WC Physics, Nuclear SC Physics GA 277XJ UT WOS:000084958600071 ER PT J AU Anderson, FS Smrekar, SE AF Anderson, FS Smrekar, SE TI Tectonic effects of climate change on Venus SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MANTLE FLOW TECTONICS; WRINKLE RIDGES; FRACTURE PATTERNS; ISHTAR TERRA; LAVA FLOWS; EVOLUTION; LITHOSPHERE; MAGELLAN; PLAINS; ORIGIN AB Venusian plains regions are commonly crossed by small-strain deformation features such as wrinkle ridges, polygonal terrains, and gridded terrains. Of these, polygonal terrains are observed to have a relatively uniform spacing and are widely distributed on plains that formed during global resurfacing. Models of Venusian climate that assume resurfacing occurred through massive volcanic events suggest that surface temperatures could have dramatically changed over a billion years, propagating thermal stresses into the surface and potentially causing small-strain features. We investigate this hypothesis by approximating the temperatures predicted by climate models as a step function and employ a fixed plate and strength envelope model to predict the resulting depth of failure and amount of strain. Our calculations indicate that strains due to temperature changes of 50-100 K, which are favored for volcanic resurfacing events of 1-10 km thickness, are consistent with the observed spacing of polygonal and gridded terrains as well as some wrinkle ridges. The global nature of the climate change event is consistent with the global distribution and uniformity of such features and implies that such terrains may be a global stratigraphic marker. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Anderson, FS (reprint author), CALTECH, Jet Prop Lab, MS 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 63 TC 19 Z9 19 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD DEC 25 PY 1999 VL 104 IS E12 BP 30743 EP 30756 DI 10.1029/1999JE001082 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 272CV UT WOS:000084633700003 ER PT J AU Mills, FP AF Mills, FP TI A spectroscopic search for molecular oxygen in the Venus middle atmosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID NIGHTSIDE; AIRGLOW AB The results from a new attempt to detect ground state molecular oxygen in the Venus middle atmosphere are presented. The upper limit inferred from the January 1995 observations using the Ultra High Resolution Facility (UHRF) spectrometer at the Anglo-Australian Observatory (AAO) is equivalent to a uniform volume mixing ratio of 3 x 10(-6) at and above the 300 mbar level. This is comparable to the upper limit inferred from observations in the early 1970s and is a factor of 10 larger than the upper limit inferred fi-om observations in 1982. These observations indicate the observed secular decrease in the abundance of SO2 and SO from the early 1980s to 1995 did not result in an O-2 abundance that could be detected within the sensitivity of the present observations. Radiative transfer calculations show the sensitivity of observations to the vertical profile of O-2. These calculations show that all three spectroscopic observations (1973, 1982, and 1995) would have detected the presence of O-2 if its mixing ratio near 50 km altitude had been 10(-5) as was reported by in situ measurements in 1980. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mills, FP (reprint author), CALTECH, Jet Prop Lab, MC 183-601,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 30 TC 14 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD DEC 25 PY 1999 VL 104 IS E12 BP 30757 EP 30763 DI 10.1029/1999JE001085 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 272CV UT WOS:000084633700004 ER PT J AU Rubincam, DP AF Rubincam, DP TI Mars secular obliquity change due to water ice caps SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID CLIMATE FRICTION; OBLATENESS FEEDBACK; EARTHS OBLIQUITY; PRECESSION; GLACIATION; INSOLATION; REGOLITH; SYSTEM; TILT AB Mars may have substantially changed its average axial tilt over geologic time due to the waxing and waning of water ice caps through the phenomenon of climate friction (also called obliquity-oblateness feedback). Depending upon Mars' climate and internal structure, water caps of the order of 10(17) - 10(18) kg cycling with the obliquity oscillations could have either increased or decreased the average obliquity by possibly tens of degrees. This is in contrast to previous results, which indicated that 10(17) kg carbon dioxide caps only increased the axial tilt. Since the south polar cap appears to be mostly uncompensated, Mars may be largely rigid on the obliquity timescale. Further, Mars may be a water-rich planet so that there is a large phase angle between insolation forcing and the size of the obliquity-driven water caps. A stiff, water-rich planet indicates the obliquity may have decreased over the eons. Such a decrease might account for the apparent youthfulness of the polar layered terrain, the idea being that fewer volatiles were available to be cycled into and out of the terrain at high obliquity because of more even insolation between equator and pole, so that the movement of volatiles produced thin layers or perhaps no layers at all. As the obliquity decreased, the insolation contrast between high and low latitiudes increased, and more volatiles might have shuttled into and out of the polar regions, forming the observed thick layers. In another but perhaps less likely scenario, Mars' average obliquity may have either increased or decreased until it became "stuck" at its present value of similar to 24 degrees. In this case the idea is that Mars' climate dynamics altered as the average tilt changed. Once the rate of increase in tilt caused by the deformation of the solid planet equaled the rate of decrease caused by the caps, the obliquity evolution ceased, leaving Mars at its present tilt. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Geodynam Branch, Greenbelt, MD 20771 USA. RP Rubincam, DP (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. RI Rubincam, David/D-2918-2012 NR 33 TC 5 Z9 5 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD DEC 25 PY 1999 VL 104 IS E12 BP 30765 EP 30771 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 272CV UT WOS:000084633700005 ER PT J AU Bills, BG AF Bills, BG TI Obliquity-oblateness feedback on Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID CLIMATE FRICTION; EARTHS OBLIQUITY; SOLAR-SYSTEM; GROUND ICE; MOTION; OSCILLATIONS; PRECESSION; INSOLATION; BEHAVIOR; MODELS AB A simple model is presented for the coupled dynamics of the orbit-rotation-climate system of Mars. Changes in the orientation of the spin pole, relative to the orbit pole, influence the spatiotemporal pattern of incident radiation and thus drive climatic mass transport into and out of the polar regions on a variety of timescales. Changes in the mass distribution occur from direct climatic forcing and compensating viscous flow in the interior. The net change in mass distribution influences the rate of spin axis precession and thereby influences obliquity. The rate of secular obliquity drift depends on several poorly known parameters, including the magnitudes and response times of volatile inventories and viscosity structure within Mars. Even relatively modest secular obliquity drift can lead to trapping in nearby resonances. The dissipative nature of the coupled dynamical system makes reconstruction of past evolution much more difficult than for a purely inertial system. The long-term obliquity history of Mars is dominated by climate. C1 Univ Calif San Diego, Scripps Inst Oceanog, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP Bills, BG (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. RI Bills, Bruce/C-1156-2008 NR 77 TC 9 Z9 9 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD DEC 25 PY 1999 VL 104 IS E12 BP 30773 EP 30797 DI 10.1029/1999JE001057 PG 25 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 272CV UT WOS:000084633700006 ER PT J AU Dobrovolskis, AR Dacles-Mariani, JS Cuzzi, JN AF Dobrovolskis, AR Dacles-Mariani, JS Cuzzi, JN TI Production and damping of turbulence by particles in the solar nebula SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID PROTOPLANETARY NEBULA; PLANETESIMALS; DUST; ORIGIN; COMETS; MODEL AB We have developed a "one-equation" model for the turbulent boundary layer. surrounding the midplane of the solar nebula and compared it with the "zero-equation" (Prandtl) model used in our previous work. Unlike the Prandtl model, our current model includes local generation, transport, and dissipation of turbulence. In particular, our derivation of the equation governing the kinetic energy of turbulence explicitly includes the damping of turbulence by particle drag. We have also included the kinetic pressure of the particles in both models, analogous to the turbulent pressure of the gas phase, and refined certain dimensionless constants of the flow. We present numerical results for particles 60 cm in radius. Both the switch to the one-equation model and the inclusion of turbulence damping by particles tend to increase particle concentrations at the midplane of the nebula, but the particle pressure and the improved flow constants both decrease the particle concentration there. These effects nearly offset one another, supporting our previous conclusion that settling of particles to the midplane of the solar nebula is self-limiting, so that direct accretion of planetesimals by gravitational instability is inhibited. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Univ Calif Davis, Dept Aeronaut & Mech Engn, Davis, CA 95616 USA. RP Dobrovolskis, AR (reprint author), NASA, Ames Res Ctr, Mail Code 245-3, Moffett Field, CA 94035 USA. NR 31 TC 22 Z9 22 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD DEC 25 PY 1999 VL 104 IS E12 BP 30805 EP 30815 DI 10.1029/1999JE001053 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 272CV UT WOS:000084633700008 ER PT J AU Cui, YL Wu, J Kamanina, N Pasaje, A Leyderman, A Barrientos, A Vlasse, M Penn, BG AF Cui, YL Wu, J Kamanina, N Pasaje, A Leyderman, A Barrientos, A Vlasse, M Penn, BG TI Dielectric study of dynamics of organic glasses SO JOURNAL OF PHYSICS D-APPLIED PHYSICS LA English DT Article ID SUPERCOOLED-LIQUID-STATE; ALPHA-RELAXATION; 2ND-HARMONIC GENERATION; MOLECULAR-DYNAMICS; CRYSTAL; 2-CYCLOOCTYLAMINO-5-NITROPYRIDINE; CRYSTALLIZATION; SPECTROSCOPY; TRANSITIONS; PNP AB The dynamics of organic compounds 2-cyclo-octylamino-5-nitropyridine (COANP), (S)-2-N-alpha-(methylbenzylamino)-5-nitropyridine (MBANP), 2-(N-prolinol)-5-nitropyridine (PNP), and N-(4-nitrophenyl)-(L)-prolinol (NPP) were studied by dielectric relaxation spectroscopy in the frequency range of 10 Hz-2 MHz and differential scanning calorimetry (DSC). The dielectric and DSC studies showed that COANP, MBANP and PNP underwent glass transition. However, NPP crystallized so rapidly upon cooling that the glass state could not be observed. It was found that the crystalline process of COANP did not slow the structure relaxation of COANP glass. The relaxation times fitted well to the empirical Vogel-Fulcher equation tau = tau(infinity) exp[E-a/k(b)(T - T-VF)]. The activation energies E-a and the Vogel-Fulcher temperature T-VF were 54.5 meV and 239 K for COANP, 86.2 meV and 249 K for MBANP and 84.9 meV and 245 K for PNP, respectively. The crystalline temperatures of COANP and MBANP were given as 300 K and 330 K, respectively. An anomalous behaviour of the dielectric permittivity of PNP glass was observed. C1 UPR RUM, Dept Phys, Mayaguez, PR 00680 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Leyderman, A (reprint author), UPR RUM, Dept Phys, Mayaguez, PR 00680 USA. NR 21 TC 21 Z9 21 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0022-3727 J9 J PHYS D APPL PHYS JI J. Phys. D-Appl. Phys. PD DEC 21 PY 1999 VL 32 IS 24 BP 3215 EP 3221 DI 10.1088/0022-3727/32/24/318 PG 7 WC Physics, Applied SC Physics GA 272YC UT WOS:000084678200022 ER PT J AU Mishchenko, MI Geogdzhayev, IV Cairns, B Rossow, WB Lacis, AA AF Mishchenko, MI Geogdzhayev, IV Cairns, B Rossow, WB Lacis, AA TI Aerosol retrievals over the ocean by use of channels 1 and 2 AVHRR data: sensitivity analysis and preliminary results SO APPLIED OPTICS LA English DT Article ID REFLECTED SUNLIGHT; OPTICAL DEPTH; SATELLITE MEASUREMENTS; TROPOSPHERIC AEROSOLS; SPECTRAL REFLECTANCE; ISCCP; RADIANCES; ATMOSPHERES; SCATTERING; ABSORPTION AB We outline the methodology of interpreting channels 1 and 2 Advanced Very High Resolution Radiometer (AVHRR) radiance data over the oceans and describe a detailed analysis of the sensitivity of monthly averages of retrieved aerosol parameters to the assumptions made in different retrieval algorithms. The analysis is based on using real AVHRR data and exploiting accurate numerical techniques for computing single and multiple scattering and spectral absorption of light in the vertically inhomogeneous atmosphere-ocean system. We show that two-channel algorithms can be expected to provide significantly more accurate and less biased retrievals of the aerosol optical thickness than one-channel algorithms and that imperfect cloud screening and calibration uncertainties are by far the largest sources of errors in the retrieved aerosol parameters. Both underestimating and overestimating aerosol absorption as well as the potentially strong variability of the real part of the aerosol refractive index may lead to regional and/or seasonal biases in optical-thickness retrievals. The Angstrom exponent appears to be the aerosol size characteristic that is least sensitive to the choice of aerosol model and should be retrieved along with optical thickness as the second aerosol parameter. (C) 1999 Optical Society of America OCIS codes: 010.1100, 010.1110, 010.1310, 010.7030. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys & Appl Math, New York, NY 10025 USA. RP Mishchenko, MI (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM crmim@giss.nasa.gov RI Lacis, Andrew/D-4658-2012; Rossow, William/F-3138-2015; Mishchenko, Michael/D-4426-2012; OI Cairns, Brian/0000-0002-1980-1022 NR 59 TC 175 Z9 180 U1 1 U2 9 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD DEC 20 PY 1999 VL 38 IS 36 BP 7325 EP 7341 DI 10.1364/AO.38.007325 PG 17 WC Optics SC Optics GA 269NL UT WOS:000084484400003 PM 18324281 ER PT J AU Hoge, FE Wright, CW Lyon, PE Swift, RN Yungel, JK AF Hoge, FE Wright, CW Lyon, PE Swift, RN Yungel, JK TI Satellite retrieval of the absorption coefficient of phytoplankton phycoerythrin pigment: theory and feasibility status SO APPLIED OPTICS LA English DT Article ID MARINE UNICELLULAR CYANOBACTERIA; INHERENT OPTICAL-PROPERTIES; DISSOLVED ORGANIC-MATTER; OCEAN COLOR; FLUORESCENCE MEASUREMENTS; RADIANCE MODEL; SYNECHOCOCCUS; WATERS; SPECTRA; VARIABILITY AB Oceanic radiance model inversion methods are used to develop a comprehensive algorithm for retrieval of the absorption coefficients of phycourobilin (PUB) pigment, type I phycoerytkrobilin (PEB) pigment rich in PUB, and type II FEB deficient in PUB pigment (together with the usual 'big three" inherent optical properties: the total backscattering coefficient and the absorption coefficients of chromophoric dissolved organic matter (CDOM)- detritus and phytoplankton). This fully modeled inversion algorithm is then simplified to yield a hybrid modeled-unmodeled inversion algorithm in which the phycoerythrin (PE) absorption coefficient is retrieved as unmodeled 488-nm absorption (which exceeds the modeled phytoplankton and the CDOM-detritus absorption coefficients). Each algorithm was applied to water-leaving radiances, but only hybrid modeled-unmodeled inversions yielded viable retrievals of the PE absorption coefficient. Validation of the PE absorption coefficient retrieval was achieved by relative comparison with airborne laser-induced FEB fluorescence. The modeled-unmodeled retrieval of four inherent optical properties by direct matrix inversion is rapid and well conditioned, but the accuracy is strongly Limited by the accuracy of the three principal inherent optical property models across all four spectral bands. Several research areas are identified to enhance the radiance-model-based retrievals: (ai improved FEB and PUB absorption coefficient models, (b) PE spectral shifts induced by PUB chromophore substitution at chromophore binding sites, (c) specific absorption-sensitive phytoplankton absorption modeling, (d) total constituent backscattering modeling, (e) unmodeled carotinoid and phycocyanin absorption that are not now accounted for in the chlorophyll-dominated phytoplankton absorption coefficient model, and (f) iterative inversion techniques to solve for six constituents with only live radiances. Although considerable progress has been made toward the satellite recovery of PE absorption, the maturity of the retrieval is presently insufficient for routine global application. Instead it must currently be used on a regional basis where localized ship and aircraft, validation can be made available. The algorithm was developed for the MODIS (Moderate-Resolution Imaging Spectroradiometer) sensor but is applicable to any sensor having comparable band locations. OCIS codes: 010.4450, 280.0280, 300.6550, 030.5620. C1 NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA. EG&G Inc, Wallops Flight Facil, Wallops Isl, VA 23337 USA. RP Hoge, FE (reprint author), NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA. EM hoge@osb.wff.nasa.gov NR 36 TC 23 Z9 24 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD DEC 20 PY 1999 VL 38 IS 36 BP 7431 EP 7441 DI 10.1364/AO.38.007431 PG 11 WC Optics SC Optics GA 269NL UT WOS:000084484400019 PM 18324297 ER PT J AU Kawamura, J Chen, J Miller, D Kooi, J Zmuidzinas, J Bumble, B LeDuc, HG Stern, JA AF Kawamura, J Chen, J Miller, D Kooi, J Zmuidzinas, J Bumble, B LeDuc, HG Stern, JA TI Low-noise submillimeter-wave NbTiN superconducting tunnel junction mixers SO APPLIED PHYSICS LETTERS LA English DT Article ID SIS MIXERS; RADIO ASTRONOMY; TUNING CIRCUITS; 1 THZ; RECEIVERS AB We have developed a low-noise 850 GHz superconductor-insulator-superconductor quasiparticle mixer with NbTiN thin-film microstrip tuning circuits and hybrid Nb/AlN/NbTiN tunnel junctions. The mixer uses a quasioptical configuration with a planar twin-slot antenna feeding a two-junction tuning circuit. At 798 GHz, we measured an uncorrected double-sideband receiver noise temperature of T-RX=260 K at 4.2 K bath temperature. This mixer outperforms current Nb SIS mixers by a factor of nearly 2 near 800 GHz. The high-gap frequency and low loss at 800 GHz make NbTiN an attractive material with which to fabricate tuning circuits for SIS mixers. NbTiN mixers can potentially operate up to the gap frequency, 2 Delta/h similar to 1.2 THz. (C) 1999 American Institute of Physics. [S0003- 6951(99)02651-0]. C1 CALTECH, Pasadena, CA 91125 USA. Jet Prop Lab, Ctr Space Microelect Technol, San Marino, CA 91108 USA. RP Kawamura, J (reprint author), CALTECH, 320-47, Pasadena, CA 91125 USA. NR 23 TC 52 Z9 53 U1 3 U2 16 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD DEC 20 PY 1999 VL 75 IS 25 BP 4013 EP 4015 DI 10.1063/1.125522 PG 3 WC Physics, Applied SC Physics GA 265KG UT WOS:000084242700037 ER PT J AU Borne, KD Colina, L Bushouse, H Lucas, RA AF Borne, KD Colina, L Bushouse, H Lucas, RA TI Hubble Space Telescope observations of the serendipitous X-ray companion to Markarian 273: Cluster at z=0.46? SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : clusters : general; galaxies : individual (Markarian 273) galaxies : Seyfert; X-rays : galaxies ID TYPE-2 SEYFERT-GALAXIES; ACTIVE GALACTIC NUCLEI; FUNDAMENTAL PLANE; ASCA OBSERVATIONS; RADIO; IC-5063; EMISSION; QUASARS; SAMPLE; SOFT AB We have used Hubble Space Telescope (HST) I-band images to identify Mrk 273X, the very unusual high-redshift X-ray-luminous Seyfert 2 galaxy found by ROSAT in the same held of view as Mrk 273. We have measured the photometric properties of Mrk 273X and have also analyzed the luminosity distribution of the faint galaxy population seen in the HST image. The luminosity of the galaxy and the properties of the surrounding environment suggest that Mrk 273X is the brightest galaxy in a relatively poor cluster at z approximate to 0.46. Its off-center location in the cluster and the presence of other galaxy groupings in the HST image may indicate that this is a dynamically young cluster on the verge of merging with its neighboring clusters. We find that Mrk 273X is a bright, featureless elliptical galaxy, with no evidence for a disk. It follows the de Vaucouleurs (r(1/4)) surface brightness law very well over a range of 8 mag. Although the surface brightness profile does not appear to be dominated by the active galactic nucleus (AGN), the galaxy has very blue colors that do appear to be produced by the AGN. Mrk 273X is most similar to the IC 5063 class of active galaxies-a hybrid Seyfert 2/powerful radio galaxy. C1 NASA, Raytheon Informat Technol & Sci Serv, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Fac Ciencias, UC, CSIC, Inst Fis Cantabria, Santander 39005, Spain. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Borne, KD (reprint author), NASA, Raytheon Informat Technol & Sci Serv, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 39 TC 3 Z9 3 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1999 VL 527 IS 2 BP 554 EP 560 DI 10.1086/308132 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 270XD UT WOS:000084561700008 ER PT J AU Millard, J Branch, D Baron, E Hatano, K Fisher, A Filippenko, AV Kirshner, RP Challis, PM Fransson, C Panagia, N Phillips, MM Sonneborn, G Suntzeff, NB Wagoner, RV Wheeler, JC AF Millard, J Branch, D Baron, E Hatano, K Fisher, A Filippenko, AV Kirshner, RP Challis, PM Fransson, C Panagia, N Phillips, MM Sonneborn, G Suntzeff, NB Wagoner, RV Wheeler, JC TI Direct analysis of spectra of the Type Ic supernova SN1994I SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (M51); radiative transfer; supernovae : general; supernovae : individual (SN 1994I) ID GAMMA-RAY BURST; 25 APRIL 1998; OPTICAL-SPECTRA; HELIUM; M51; EVOLUTION; LINES; HE; IA AB Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to observed photospheric-phase spectra of the Type Ic supernova SN 1994I. The observed optical spectra can be well matched by synthetic spectra that are based on the assumption of spherical symmetry. We consider the identification of the infrared absorption feature observed near 10250 Angstrom which previously has been attributed to He I lambda 10830 and regarded as strong evidence that SN 1994I ejected some helium. We have difficulty accounting for the infrared absorption with He I alone. It could be a blend of He I and C I lines. Alternatively, we find that it can be fitted by Si I lines without compromising the fit in the optical region. In synthetic spectra that match the observed spectra, from 4 days before to 26 days after the time of maximum brightness, the adopted velocity at the photosphere decreases from 17,500 to 7000 km s(-1). Simple estimates of the kinetic energy carried by the ejected mass give values that are near the canonical supernova energy of 10(51) ergs. The velocities and kinetic energies that we find for SN 1994I in this way are much lower than those that we find elsewhere for the peculiar Type Ic SNe 1997ef and 1998bw, which therefore appear to have been hyperenergetic. C1 Univ Oklahoma, Dept Phys & Astron, Norman, OK 73019 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Stockholm Observ, S-13336 Saltsjobaden, Sweden. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Carnegie Inst Washington, Las Campanas Observ, La Serena, Chile. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Natl Opt Astron Observ, CTIO, La Serena, Chile. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. RP Millard, J (reprint author), Univ Oklahoma, Dept Phys & Astron, Norman, OK 73019 USA. RI Baron, Edward/A-9041-2009 OI Baron, Edward/0000-0001-5393-1608 NR 33 TC 61 Z9 61 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1999 VL 527 IS 2 BP 746 EP 756 DI 10.1086/308108 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 270XD UT WOS:000084561700024 ER PT J AU Kaufman, MJ Wolfire, MG Hollenbach, DJ Luhman, ML AF Kaufman, MJ Wolfire, MG Hollenbach, DJ Luhman, ML TI Far-infrared and submillimeter emission from Galactic and extragalactic photodissociation regions SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : ISM; infrared : ISM : lines and bands; infrared : ISM : continuum; ISM : atoms; ISM : molecules; submillimeter ID POLYCYCLIC AROMATIC-HYDROCARBONS; FINE-STRUCTURE TRANSITIONS; PHOTON-DOMINATED REGIONS; 1-0 LINE EMISSION; INTERSTELLAR-MEDIUM; MOLECULAR CLOUDS; STAR-FORMATION; MAGELLANIC CLOUDS; 158 MICRON; C-II AB Photodissociation region (PDR) models are computed over a wide range of physical conditions, from those appropriate to giant molecular clouds illuminated by the interstellar radiation field to the conditions experienced by circumstellar disks very close to hot massive stars. These models use the most up-to-date values of atomic and molecular data, the most current chemical rate coefficients, and the newest grain photoelectric heating rates, which include treatments of small grains and large molecules. In addition, we examine the effects of metallicity and cloud extinction on the predicted line intensities. Results are presented for PDR models with densities over the range n = 10(1)-10(7) cm(-3) and for incident far-ultraviolet radiation fields over the range G(0) = 10(-0.5)-10(6.5) (where G(0) is the far-ultravioliet [FUV] flux in units of the local interstellar value), for metallicities Z = 1 and 0.1 times the local Galactic value, and for a range of PDR cloud sizes. We present line strength and/or line ratio plots for a variety of useful PDR diagnostics: [C II] 158 mu m, [O I] 63 mu m and 145 mu m, [C I] 370 mu m and 609 mu m, CO J = 1-0, J = 2-1, J = 3-2, J = 6-5, and J = 15-14, as well as the strength of the far-infrared continuum. These plots will be useful for the interpretation of Galactic and extragalactic far-infrared and submillimeter spectra observable with the Infrared Space Observatory (ISO), the Stratospheric Observatory for Infrared Astronomy, the Submillimeter Wave Astronomy Satellite, the Far Infrared and Submillimeter Telescope, and other orbital and suborbital platforms. As examples, we apply our results to ISO and ground-based observations of M82, NGC 278, and the Large Magellanic Cloud. Our comparison of the conditions in M82 and NGC 278 show that both the gas density and FUV flux are enhanced in the starburst nucleus of M82 compared with those in the normal spiral NGC 278. We model the high [C II]/CO ratio observed in the 30 Doradus region of the LMC and find that it can be explained either by lowering the average extinction through molecular clouds or by enhancing the density contrast between the atomic layers of PDRs and the CO-emitting cloud cores. The ratio L[CO]/M[H-2] implied by the low extinction model gives cloud masses too high for gravitational stability. We therefore rule out low-extinction clouds as an explanation for the high [C II]/CO ratio and instead appeal to density contrast in A(V) = 10 clouds. C1 San Jose State Univ, Dept Phys, San Jose, CA 95192 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. RP Kaufman, MJ (reprint author), San Jose State Univ, Dept Phys, San Jose, CA 95192 USA. NR 78 TC 397 Z9 397 U1 1 U2 7 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1999 VL 527 IS 2 BP 795 EP 813 DI 10.1086/308102 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 270XD UT WOS:000084561700027 ER PT J AU Armstrong, JW Estabrook, FB Tinto, M AF Armstrong, JW Estabrook, FB Tinto, M TI Time-delay interferometry for space-based gravitational wave searches SO ASTROPHYSICAL JOURNAL LA English DT Article DE gravitation; instrumentation : interferometers; space vehicles; waves ID RADIATION; TRACKING; DETECTOR; PROJECT AB Ground-based, equal-arm-length laser interferometers are being built to measure high-frequency astrophysical gravitational waves. Because of the arm-length equality, laser light experiences the same delay in each arm and thus phase or frequency noise from the laser itself precisely cancels at the photodetector. This laser noise cancellation is crucial. Raw laser noise is orders of magnitude larger than other noises and the desired sensitivity to gravitational waves cannot be achieved without very precise cancellation. Laser interferometers in space, e.g., the proposed three-spacecraft LISA detector, will have much longer arm lengths and will be sensitive to much lower frequency gravitational radiation. In contrast with ground-based interferometers, it is impossible to maintain equal distances between spacecraft pairs; thus laser noise cannot be cancelled by direct differencing of the beams. We analyze here an unequal-arm three-spacecraft gravitational wave detector in which each spacecraft has one free-running laser used both as a transmitter (to send to the other two spacecraft) and as a local oscillator (to monitor the frequencies of beams received from the other two spacecraft). This produces six data streams, two received time series generated at each of the three spacecraft. We describe the apparatus in terms of Doppler transfer functions of signals and noises on these one-way transits between pairs of test masses. Accounting for time-delays of the laser light and gravitational waves propagating through the apparatus, we discuss several simple and potentially useful combinations of the six data streams, each of which exactly cancels the noise from all three lasers while retaining the gravitational wave signal. Three of these combinations are equivalent to unequal-arm interferometers, previously analyzed by Tinto & Armstrong. The other combinations are new and may provide design and operational advantages for space-based detectors. Since at most three laser-noise-free data streams can be independent, we provide equations relating the combinations reported here. We give the response functions of these laser-noise-canceling data combinations for both a gravity wave signal and for the remaining noncancelled noise sources. Finally, using spacecraft separations and noise spectra appropriate for the LISA mission, we calculate the expected gravitational wave sensitivities for each laser-noise-canceling data combination. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Armstrong, JW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 121 Z9 123 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1999 VL 527 IS 2 BP 814 EP 826 DI 10.1086/308110 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 270XD UT WOS:000084561700028 ER PT J AU Oluseyi, HM Walker, ABC Santiago, DI Hoover, RB Barbee, TW AF Oluseyi, HM Walker, ABC Santiago, DI Hoover, RB Barbee, TW TI Observation and modeling of the solar transition region. II. Identification of new classes of solutions of coronal loop models SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : chromosphere; Sun : corona; Sun : transition region ID RAY BRIGHT POINTS; ENERGY-BALANCE; DIAGNOSTIC SPECTROMETER; MAGNETIC-STRUCTURE; ACTIVE REGIONS; FAST DOWNFLOWS; SCALING LAW; NETWORK; SUN; CHROMOSPHERE AB In the present work we undertake a study of the quasi-static loop model and the observational consequences of the various solutions found. We obtain the most general solutions consistent with certain initial conditions. Great care is exercised in choosing these conditions to be physically plausible (motivated by observations). We show that the assumptions of previous quasi-static loop models, such as the models of Rosner, Tucker, & Vaiana (RTV) and Veseckey, Antiochos, & Underwood, (VAU) are not necessarily valid for small loops at transition region temperatures. We find three general classes of solutions for the quasi-static loop model, which we denote radiation-dominated loops, conduction-dominated loops, and classical loops. These solutions are then compared with observations. Departures from the classical scaling law of RTV are found for the solutions obtained. It is shown that loops of the type that we model here can make a significant contribution to lower transition regions emission via thermal conduction from the upper transition region. C1 Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Stanford Univ, Ctr Space Sci & Astrophys, Stanford, CA 94305 USA. Stanford Univ, Dept Phys & Appl Phys, Stanford, CA 94305 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Lawrence Livermore Natl Lab, Dept Chem & Mat Sci, Livermore, CA 94550 USA. RP Stanford Univ, Dept Phys, Stanford, CA 94305 USA. EM Hakeem@Banneker.Stanford.edu; Walker@Banneker.Stanford.edu; David@spacetime.stanford.edu; Ricard.Hoover@msfc.nasa.gov; barbee2@llnl.gov NR 69 TC 15 Z9 15 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1999 VL 527 IS 2 BP 992 EP 999 DI 10.1086/308113 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 270XD UT WOS:000084561700042 ER PT J AU Joubert, JM Latroche, M Cerny, R Bowman, RC Percheron-Guegan, A Yvon, K AF Joubert, JM Latroche, M Cerny, R Bowman, RC Percheron-Guegan, A Yvon, K TI Crystallographic study of LaNi5-xSnx (0.2 <= x <= 0.5) compounds and their hydrides SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article; Proceedings Paper CT International Symposium on Metal-Hydrogen Systems, Fundamentals and Applications CY OCT 04-09, 1998 CL ZHEJIANG, PEOPLES R CHINA SP Zhejiang Univ DE Sn; AB(5); hydrides; neutron diffraction; single crystal diffraction ID DIFFRACTION; NEUTRON; DEGRADATION; STABILITY; ISOTHERMS; PHASES; TIN AB The structural properties of tin substituted LaNi5 compounds and corresponding deuterides have been investigated by single crystal X-ray and neutron powder diffraction. Tin is found to substitute nickel exclusively on site 3g of space group P6/mmm. No other significant disorder occurs in the structure. At tin contents of x=0.4 and x=0.5, the crystal structures of the deuterides do not significantly deviate from those of other metal substituted LaNi5 deuterides. At a tin content of x=0.2, with higher deuterium content, however, a symmetry decrease to non-centrosymmetric space group P6mm is observed due to partial deuterium ordering. (C) 1999 Elsevier Science S.A. All rights reserved. C1 Lab Chim Met Terres Rares, F-94320 Thiais, France. Univ Geneva, Lab Cristallog, CH-1211 Geneva 4, Switzerland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Joubert, JM (reprint author), Lab Chim Met Terres Rares, 2-8 Rue Henri Dunant, F-94320 Thiais, France. RI Joubert, Jean-Marc/A-1259-2013; LATROCHE, MICHEL/L-6254-2014; OI LATROCHE, MICHEL/0000-0002-8677-8280; Bowman, Robert/0000-0002-2114-1713 NR 15 TC 55 Z9 55 U1 0 U2 4 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-8388 J9 J ALLOY COMPD JI J. Alloy. Compd. PD DEC 20 PY 1999 VL 293 BP 124 EP 129 DI 10.1016/S0925-8388(99)00311-4 PG 6 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 262KD UT WOS:000084065500023 ER PT J AU Cantrell, JS Bowman, RC AF Cantrell, JS Bowman, RC TI Phase composition and the effect of thermal cycling for VHx, V0.995C0.005Hx, and V0.975Zr0.020C0.005Hx SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article; Proceedings Paper CT International Symposium on Metal-Hydrogen Systems, Fundamentals and Applications CY OCT 04-09, 1998 CL ZHEJIANG, PEOPLES R CHINA SP Zhejiang Univ DE vanadium alloys; vanadium hydride; X-ray diffraction; pressure-composition-temperature isotherms; scanning electron microscopy ID HYDROGEN; VANADIUM; SYSTEM; CRYOCOOLERS; HYSTERESIS AB X-ray diffraction (XRD) studies were performed on hydride phases formed by vanadium and its carbon substituted alloys. It was previously found that thermal cycling of VHx across the beta-gamma mixed phase region changed the reversible hydrogen storage capacity and other properties. The present materials were compared where annealing was one prior treatment and the materials were cycled from 3 cycles to over 1000 cycles and one sample was cycled 6182 times. The effects on phase composition, c/a unit cell axial ratios, unit cell volume and crystallite particle size and BET surface area measurements were studied. Earlier studies placed the beta-gamma phase boundary at x = 0.82 for XRD studies. The phase boundaries of the substituted alloys are found to be virtually the same. Thermal cycling produced similar behavior for all the materials. (C) 1999 Elsevier Science S.A, All rights reserved. C1 Miami Univ, Dept Chem & Biochem, Oxford, OH 45056 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Cantrell, JS (reprint author), Miami Univ, Dept Chem & Biochem, Oxford, OH 45056 USA. NR 18 TC 5 Z9 5 U1 0 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-8388 J9 J ALLOY COMPD JI J. Alloy. Compd. PD DEC 20 PY 1999 VL 293 BP 156 EP 160 DI 10.1016/S0925-8388(99)00386-2 PG 5 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 262KD UT WOS:000084065500029 ER PT J AU Fishman, J Balok, AE AF Fishman, J Balok, AE TI Calculation of daily tropospheric ozone residuals using TOMS and empirically improved SBUV measurements: Application to an ozone pollution episode over the eastern United States SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TOMS/SBUV MEASUREMENTS; MAPPING SPECTROMETER; TRACE-A; PROFILES; ALGORITHM; AEROSOL; TRENDS AB A new technique for determining the integrated amount of ozone in the troposphere using concurrent observations from solar backscattered ultraviolet (SBUV) and Total Ozone Mapping Spectrometer (TOMS) data has been developed and is compared with various data sets. The technique makes use of the SBUV observations in the lowest three levels (1013-63 mbar) of archived SBUV data to construct a climatology that is consistent with ozonesonde measurements. In the lowest layer (1013-253 mbar), where ozone is almost always tropospheric, the SBUV measurements do not recreate the seasonality found in the ozonesonde data and consistently underestimate the amount of ozone at northern middle latitudes, the latitudes of interest for a later regional application. On the other hand, the key finding in this analysis shows that the integrated ozone amounts between 1013 and 63 mbar determined from SBUV are in good agreement with both the seasonality and the absolute ozone amount determined from the ozonesonde profiles. This result can then be used for determining a more accurate quantification of how much ozone is in both the troposphere and the stratosphere from any specific SEW measurement. When used in conjunction with concurrent total ozone measurements from TOMS, we obtain better information about the distribution of ozone in the troposphere using the tropospheric ozone residual (TOR) technique. The TOR are then computed for the eastern United States during 1988 and compared to the ozonesonde measurements from Wallops Island during that year. The resultant comparison between the TOR and the Wallops Island measurements is considerably better using this technique when compared to calculated TOR values when the SBUV data are not corrected. The methodology is then applied to determine the large-scale daily distribution of tropospheric ozone during times when surface concentrations of ozone were unusually high over vast regions on the eastern United States. These regional TOR patterns are analyzed in conjunction with various meteorological data sets and satellite imagery. Using such analyses, the relationship between the TOR distribution, meteorological processes in the lower troposphere, and the distribution of ozone at the surface during the 1988 episode is examined. This regional distribution of the TOR can be shown to be associated with the distribution of air masses that have evolved from the prevailing meteorological synoptic situation. The highest amounts of TOR are generally found off the coast of North Carolina and are consistent with the accumulation of ozone that had its origins over the northeastern United States and was subsequently advected southward off the North Carolina coast. The high TOR over the ocean is then caught in the persistent anticyclonic circulation where it becomes a source of ozone for the southeastern United States at a time when that region experiences numerous instances of surface ozone concentrations in violation of the Environmental Protection Agency hourly standards. When, over a period of several days, the dominating high-pressure system over the eastern United States breaks down, TOR values decline, consistent with the fact that cleaner air of tropical origin is transported into the region. C1 NASA, Langley Res Ctr, Atmospher Sci Res, Hampton, VA 23665 USA. RP Fishman, J (reprint author), NASA, Langley Res Ctr, Atmospher Sci Res, Hampton, VA 23665 USA. EM j.fishman@larc.nasa.gov NR 35 TC 39 Z9 42 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1999 VL 104 IS D23 BP 30319 EP 30340 DI 10.1029/1999JD900875 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 268DR UT WOS:000084399500016 ER PT J AU Strahan, SE AF Strahan, SE TI Climatologies of lower stratospheric NOy and O-3 and correlations with N2O based on in situ observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TOTAL REACTIVE NITROGEN; POLAR VORTEX; OZONE LOSS; AIRCRAFT MEASUREMENTS; AASE-II; WINTER; EXPEDITION; AEROSOL; DC-8; ER-2 AB This paper presents NOy and O-3 seasonal mean distributions as a function of equivalent latitude and height from more than 140 ER-2 flights. The observations span a, height range of 360-530 K (similar to 150-45 hPa) and have nearly pole-to-pole coverage in most seasons. These climatologies are intended to support efforts to evaluate the chemistry and dynamics of assessment models. Reasonable model representations of NOy, O-3, and their seasonal variations are necessary to assess the effects of aircraft exhaust on the stratosphere. ER-2 measurements of N2O are combined with the NOy data to examine their lower stratospheric relationship and to identify regions of denitrification. Measurements of these species above ER-2 altitudes in the Arctic vortex support the interpretation of some of the ER-2 NOy - N2O data, which suggest that transport rather than chemical denitrification causes deviations from the normally linear relationship. This places constraints on the use of a linear relationship to calculate denitrification. The observed relationship between N2O and O-3 is also presented. The spatial gradients in lower stratospheric O-3 photochemistry are used to explain observed variations in the N2O - O-3 relationship. The N2O - O-3 relationship above ER-2 altitudes in the Arctic vortex, much like the case of NOy - N2O, also differs in slope from lower altitudes. This points to the difficulties in using tracer correlations to infer O-3 values in the vortex prior. to polar stratospheric cloud processing. It is necessary to understand the photochemical and transport history of the air that descends into the lower stratospheric vortex in order to correctly quantify O-3 depletion. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. SAIC Gen Sci Corp, Beltsville, MD USA. RP Strahan, SE (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Code 910-3, Greenbelt, MD 20771 USA. EM strahan@prometheus.gsfc.nasa.gov RI Strahan, Susan/H-1965-2012 NR 45 TC 21 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1999 VL 104 IS D23 BP 30463 EP 30480 DI 10.1029/1999JD900775 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 268DR UT WOS:000084399500024 ER PT J AU Goldman, A Paton-Walsh, C Bell, W Toon, GC Blavier, JF Sen, B Coffey, MT Hannigan, JW Mankin, WG AF Goldman, A Paton-Walsh, C Bell, W Toon, GC Blavier, JF Sen, B Coffey, MT Hannigan, JW Mankin, WG TI Network for the detection of stratospheric change fourier transform infrared intercomparison at Table Mountain Facility, November 1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LINE-SHAPE DISTORTIONS; SPECTRA; INTERFEROMETERS; DATABASE AB An intercomparison of four Fourier transform infrared (FTIR) spectrometers, operated side by side by Jet Propulsion Laboratory (JPL), National Center for Atmospheric Research, and National Physical Laboratory groups, using two different spectral fitting algorithms, was conducted at JPL's Table Mountain Facility (TMF) during November 1996. A "blind" comparison of retrieved vertical column amounts, of preselected trace gases in preselected microwindows (mw), and subsequent reanalysis of the results are described. The species analyzed are N-2 (3 mw), HF (1 mw), HCl (1 mw), CH4 (1 mw), O-3 (2 mw), N2O (2 mw), HNO3 (2 mw), and CO2 (1 mw). The column agreements from the "blind" phase were within 0.5-2%, except that for HNO3, HF, and O-3 the disagreement of the results was up to 10%, 5%, and 4%, respectively. It was found that several systematic effects were neglected in the "blind" phase analysis. Taking these into account in the postanalysis reduced the disagreements to 0.5-1.0% for most cases, and to less than 4%, 3%, and 1% for HNO3, HF, and O-3 respectively. It was concluded that zero offsets caused by detector nonlinearity were the main cause of the large errors in HNO3 and other gases (i.e., CO2) retrieved from the HgCdTe spectra. At shorter wavelengths (i.e., HF) we conclude that incomplete modeling of the instrument line shapes (ILS) was the main cause of column differences larger than 1%. C1 Univ Denver, Dept Phys, Denver, CO 80208 USA. Natl Phys Lab, Teddington TW11 0LW, Middx, England. Natl Ctr Atmospher Res, Div Chem, Boulder, CO 80307 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Goldman, A (reprint author), Univ Denver, Dept Phys, Denver, CO 80208 USA. EM agoldman@du.edu; clare.paton-walsh@npl.co.uk; wb@newton.npl.co.uk; toon@mark4sun.jpl.nasa.gov; blavier@mark4sun.jpl.nasa.gov; sen@mark4sun.jpl.nasa.gov; coffey@ncar.ucar.edu; jamesw@ncar.ucar.edu; mankin@ncar.ucar.edu RI Paton-Walsh, Clare/B-2774-2009 OI Paton-Walsh, Clare/0000-0003-1156-4138 NR 25 TC 40 Z9 40 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1999 VL 104 IS D23 BP 30481 EP 30503 DI 10.1029/1999JD900879 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 268DR UT WOS:000084399500025 ER PT J AU McPeters, RD Hofmann, DJ Clark, M Flynn, L Froidevaux, L Gross, M Johnson, B Koenig, G Liu, X McDermid, S McGee, T Murcray, F Newchurch, MJ Oltmans, S Parrish, A Schnell, R Singh, U Tsou, JJ Walsh, T Zawodny, JM AF McPeters, RD Hofmann, DJ Clark, M Flynn, L Froidevaux, L Gross, M Johnson, B Koenig, G Liu, X McDermid, S McGee, T Murcray, F Newchurch, MJ Oltmans, S Parrish, A Schnell, R Singh, U Tsou, JJ Walsh, T Zawodny, JM TI Results from the 1995 Stratospheric Ozone Profile Intercomparison at Mauna Loa SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID INVERSION ALGORITHM; LIDAR; AEROSOL AB In August 1995, multiple instruments that measure the stratospheric ozone vertical distribution were intercompared at the Mauna Loa Observatory, Hawaii, under the auspices of the Network for the Detection of Stratospheric Change. The instruments included two UV lidar systems, one from the Jet Propulsion Laboratory and the other from Goddard Space Flight Center, electrochemical concentration cell balloon sondes, a ground-based microwave instrument, Dobson-based Umkehr measurements, and a new ground-based Fourier transform infrared instrument. The Microwave Limb Sounder instrument on the Upper Atmosphere Research Satellite provided correlative profiles of ozone, and there was one close overpass of the Stratospheric Aerosol and Gas Experiment II (SAGE II) instrument. The results show that much better consistency among instruments is being achieved than even a few years ago, usually to within the instrument uncertainties. The different measurement techniques in this comparison agree to within +/-10% at almost all altitudes, and in the 20-45 km region most agreed within +/-5%. The results show that the current generation of lidars is capable of accurate measurement of the ozone profile to a maximum altitude of 50 km. SAGE II agreed well with both lidar and balloon sonde down to at least 17 km. The ground-based microwave measurement agreed with other measurements from 22 km to above 50 km. One minor source of disagreement continues to be the pressure-altitude conversion needed to compare a measurement of ozone density versus altitude with a measurement of ozone mixing ratio versus pressure. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CIRES, Boulder, CO 80303 USA. NOAA, NESDIS, Camp Springs, MD 20746 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. Hughes STX Corp, Greenbelt, MD 20771 USA. NOAA, CMDL, Boulder, CO 80303 USA. Univ Denver, Dept Phys & Astron, Denver, CO 80208 USA. Univ Alabama, Dept Atmospher Sci, Huntsville, AL 35899 USA. Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. NOAA, Mauna Loa Observ 154, Hilo, HI 96720 USA. GATS Inc, Newport News, VA 23606 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP McPeters, RD (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. EM mcpeters@wrabbit.gsfc.nasa.gov; dhofmann@cmdl.noaa.gov; mark.clark@Colorado.edu; lflynn@orbit.nesdis.noaa.gov; lucien@mls.jpl.nasa.gov; bjohnson@cmdl.noaa.gov; koenig@cmdl1.cmdl.erl.gov; mcdermid@tmf.jpl.nasa.gov; mcgee@aeolus.gsfc.nasa.gov; murcray@ram.phys.du.edu; mike@vortex.atmos.uah.edu; soltmans@cmdl.noaa.gov; parrish@fcrao1.phast.umass.edu; rschnell@cmdl.noaa.gov; j.j.tsou@larc.nasa.gov; j.m.zawodny@larc.nasa.gov RI Flynn, Lawrence/B-6321-2009; McGee, Thomas/G-4951-2013; McPeters, Richard/G-4955-2013 OI Flynn, Lawrence/0000-0001-6856-2614; McPeters, Richard/0000-0002-8926-8462 NR 27 TC 26 Z9 26 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1999 VL 104 IS D23 BP 30505 EP 30514 DI 10.1029/1999JD900760 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 268DR UT WOS:000084399500026 ER PT J AU Steinbrecht, W Neuber, R von der Gathen, P Wahl, P McGee, TJ Gross, MR Klein, U Langer, J AF Steinbrecht, W Neuber, R von der Gathen, P Wahl, P McGee, TJ Gross, MR Klein, U Langer, J TI Results of the 1998 Ny-Alesund Ozone Monitoring Intercomparison SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PROFILER ASSESSMENT; LIDAR MEASUREMENTS; NETWORK; LAUDER; OPAL AB The Ny-Alesund Ozone Monitoring Intercomparison (NAOMI) took place at Ny-Alesund, Spitsbergen (78.92 degrees N, 11.95 degrees E), from January 20 to February 10, 1998, This paper focuses on comparing stratospheric ozone profiles measured by the Alfred Wegener Institute differential absorption lidar (AT;VI DIAL), in routine Network for Detection of Stratospheric Change (NDSC) operation at Ny-Alesund, the mobile Goddard Space Flight Center DIAL (GSFC DIAL), the University of Bremen microwave radiometer (mu Wave), and electrochemical concentration cell (ECC) ozonesondes, flown routinely by AWI, Below 30 km the two DIALs and the ECC sondes give virtually the same results, with instrumental precision (repeatability) better than +/-5% and no detectable bias. When their coarser altitude resolution is not accounted for, the mu Wave data show 15% low bias at 16 km and 15% high bias at 23 km, Considerably better agreement, better than +/-5% around 20 km and above 30 km, is found when the altitude resolution of the other data is degraded to match that of the mu Wave. During NAOMI the mu Wave data show high bias of up to 10% in a mixing ratio plateau around 25 km. Such bias has not been seen in routine intercomparisons between mu Wave and ECC sonde data at Ny-Alesund. It is likely caused by an a priori profile 40% higher than the true profile during NAOMI, Above 30 km the mu Wave data show the best precision (repeatability), about +/-3 to +/-5%. Precision of the GSFC DIAL data decreases from better than +/-5% at 30 km to about +/-10% at 40 km, and the precision for the AWI DIAL data decreases from better than +/-5% at 30 km to +/-30% at 40 km. From 34 to 38 km the AWI profile is 12% lower than the GSFC profile. AWI DIAL measurements that are low at 35 km often end below 40 km of show high values at 40 or 45 km, This behavior seems related to the way in which the AWI processing algorithm changes altitude resolution for data with poor signal-to-noise ratio. C1 Meteorol Observ Hohenpeissenberg, Deutsch Wetterdienst, D-82383 Hohenpeissenberg, Germany. Alfred Wegener Inst Polar & Marine Res, D-14401 Potsdam, Germany. NASA, Goddard Space Flight Ctr, Lab Atmospheres, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Earth Syst Technol, Baltimore, MD 21205 USA. Univ Bremen, Inst Umweltphys, D-28359 Bremen, Germany. RP Steinbrecht, W (reprint author), Meteorol Observ Hohenpeissenberg, Deutsch Wetterdienst, Albin Schwaiger Weg 10, D-82383 Hohenpeissenberg, Germany. EM wolfgang@mohp.dwd.d400.de; neuber@awi-potsdam.de; gathen@awi-potsdam.de; mcgee@aeolus.gsfc.nasa.gov; ulf@atm.physik.uni-bremen.de; langer@uni-bremen.de RI Steinbrecht, Wolfgang/G-6113-2010; von der Gathen, Peter/B-8515-2009; McGee, Thomas/G-4951-2013; Neuber, Roland/B-4923-2014 OI Steinbrecht, Wolfgang/0000-0003-0680-6729; von der Gathen, Peter/0000-0001-7409-1556; Neuber, Roland/0000-0001-7382-7832 NR 16 TC 12 Z9 12 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1999 VL 104 IS D23 BP 30515 EP 30523 DI 10.1029/1999JD900275 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 268DR UT WOS:000084399500027 ER PT J AU Dessler, AE Kim, H AF Dessler, AE Kim, H TI Determination of the amount of water vapor entering the stratosphere based on Halogen Occultation Experiment (HALOE) data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FOUNTAIN; BUDGET AB Using version 19 Halogen Occultation Experiment (HALOE) data, we estimate the abundance of water vapor entering the stratosphere [H2O](e) is 3.80+/-0.49 ppmv averaged over 1993-1997. The average of all of the recently published estimates of [H2O](e) is 3.85 ppmv, which we believe is the best estimate of [H2O](e). C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Dessler, AE (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM dessler@atmos.umd.edu RI Kim, Hyun/G-1315-2012; Dessler, Andrew/G-8852-2012 OI Kim, Hyun/0000-0003-3968-6145; Dessler, Andrew/0000-0003-3939-4820 NR 14 TC 24 Z9 26 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1999 VL 104 IS D23 BP 30605 EP 30607 DI 10.1029/1999JD900912 PG 3 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 268DR UT WOS:000084399500033 ER PT J AU Greenberg, JP Guenther, AB Madronich, S Baugh, W Ginoux, P Druilhet, A Delmas, R Delon, C AF Greenberg, JP Guenther, AB Madronich, S Baugh, W Ginoux, P Druilhet, A Delmas, R Delon, C TI Biogenic volatile organic compound emissions in central Africa during the Experiment for the Regional Sources and Sinks of Oxidants (EXPRESSO) biomass burning season SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NONMETHANE HYDROCARBONS; CHEMISTRY; FOREST; PHOTOCHEMISTRY; RADIATION; ISOPRENE; IMPACT AB The recent aircraft and ground-based Experiment for the Regional Sources and Sinks of Oxidants (EXPRESSO) campaign in central Africa studied atmospheric trace gases and aerosols during the biomass burning season. Isoprene, emitted from vegetation, was the most abundant nonmethane hydrocarbon observed over the forest and savanna, even though intense biomass burning activity was occurring several hundred kilometers to the north. The isoprene flux, measured directly from midmorning to noon by a relaxed eddy accumulation technique, was approximately 890 mu g isoprene m(-2) h(-1) from the tropical rain forest and semideciduous forest landscapes and 570 mu g isoprene m(-2) h(-1) from transitional and degraded woodland landscapes. Model estimates derived from satellite landscape characterization coupled with leaf enclosure emission measurements conducted during EXPRESSO compared well with these measured fluxes. Isoprene concentrations and fluxes were used to determine the oxidant balance over the forest and savanna. Radiative transfer calculations indicate that the observed strong vertical gradient of the NO2 photolysis rate coefficient could be explained by the presence of substantial amounts of absorbing aerosols, probably from biomass burning. Chemical (box) model simulations of the planetary boundary layer (PBL), constrained by measured isoprene emission fluxes and concentrations, show that this suppression of photolytic radiation lowers OH concentrations by about a factor of 2 relative to aerosol-free conditions. Consequently, the direct contribution of PBL photochemistry to ozone production, especially from biogenic isoprene, is small. C1 Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. Observ Midi Pyrenees, Lab Aerol, F-31400 Toulouse, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Greenberg, JP (reprint author), Natl Ctr Atmospher Res, Div Atmospher Chem, 1850 Table Mesa Dr, Boulder, CO 80307 USA. EM greenber@ucar.edu RI Ginoux, Paul/C-2326-2008; Madronich, Sasha/D-3284-2015; Guenther, Alex/B-1617-2008 OI Ginoux, Paul/0000-0003-3642-2988; Madronich, Sasha/0000-0003-0983-1313; Guenther, Alex/0000-0001-6283-8288 NR 30 TC 34 Z9 35 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1999 VL 104 IS D23 BP 30659 EP 30671 DI 10.1029/1999JD900475 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 268DR UT WOS:000084399500037 ER PT J AU Landgraf, M Augustsson, K Grun, E Gustafson, BAS AF Landgraf, M Augustsson, K Grun, E Gustafson, BAS TI Deflection of the local interstellar dust flow by solar radiation pressure SO SCIENCE LA English DT Article ID INTER-STELLAR GRAINS; ULYSSES; GALILEO; PARTICLES; FORCES; SYSTEM; CLOUD; GAS AB Interstellar dust grains intercepted by the dust detectors on the Ulysses and Galileo spacecrafts at heliocentric distances from 2 to 4 astronomical units show a deficit of grains with masses from 1 x 10(-17) to 3 x 10(-16) kilograms relative to grains intercepted outside 4 astronomical units. To divert grains out of the 2- to 4-astronomical unit region, the solar radiation pressure must be 1.4 to 1.8 times the force of solar gravity. These figures are consistent with the optical properties of spherical or elongated grains that consist of astronomical silicates or organic refractory material. Pure graphite grains with diameters of 0.2 to 0.4 micrometer experience a solar radiation pressure force as much as twice the force of solar gravity. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. ESA, European Space Operat Ctr, D-64293 Darmstadt, Germany. Royal Inst Technol, Dept Comp Sci & Syst, S-16440 Kista, Sweden. Stockholm Univ, S-16440 Kista, Sweden. Max Planck Inst Kernphys, D-69117 Heidelberg, Germany. Univ Florida, Dept Astron, Gainesville, FL 32661 USA. RP Landgraf, M (reprint author), NASA, Lyndon B Johnson Space Ctr, Mailcode SN2, Houston, TX 77058 USA. EM mlandgra@esoc.esa.de RI Gustafson, Bo/B-9526-2011 NR 36 TC 53 Z9 53 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD DEC 17 PY 1999 VL 286 IS 5448 BP 2319 EP 2322 DI 10.1126/science.286.5448.2319 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 266UK UT WOS:000084318500054 PM 10600737 ER PT J AU Ricca, A Bauschlicher, CW AF Ricca, A Bauschlicher, CW TI Heats of formation for GeHn (n=1-4) and Ge2Hn (n=1-6) SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID BOND-DISSOCIATION ENERGIES; GAUSSIAN-BASIS SETS; WAVE-FUNCTIONS; 3RD-ROW ATOMS; HARTREE-FOCK; PREDICTIONS; GEOMETRIES; MOLECULES; KINETICS; 1ST-ROW AB Heats of formation, accurate to 2 kcal/mol or better, have been computed for GeHn (n = 1-4) and Ge2Hn (n = 1-6). The effects of basis set saturation, Ge 3d correlation, spin-orbit, and scalar relativity have been accounted for. The results show that the experimental heats of formation of GeH4 and Ge2H6 are likely in error by up to 4 and 9 kcal/mol, respectively. However, for individual bond energies, the computed results agree with some experimental determinations. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ricca, A (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 36 TC 32 Z9 32 U1 0 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD DEC 16 PY 1999 VL 103 IS 50 BP 11121 EP 11125 DI 10.1021/jp992408s PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 268PP UT WOS:000084425000060 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI Heats of formation for POn and POnH (n=1-3) SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; GASEOUS DIPHOSPHORUS OXIDES; COUPLED-CLUSTER THEORY; WAVE-FUNCTIONS; SOLID ARGON; ABINITIO CHARACTERIZATION; ELECTRON CORRELATION; SPECTRA; PHOSPHORUS AB The geometries and frequencies are determined using density functional theory. The atomization energies are computed at the coupled cluster level of theory. The complete basis set limit is obtained by extrapolation. The scalar relativistic effect is computed using the Douglas-Kroll approach. Spin-orbit and core-valence effects are accounted for. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 38 TC 21 Z9 21 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD DEC 16 PY 1999 VL 103 IS 50 BP 11126 EP 11129 DI 10.1021/jp992409k PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 268PP UT WOS:000084425000061 ER PT J AU McCoy, TJ Lofgren, GE AF McCoy, TJ Lofgren, GE TI Crystallization of the Zagami shergottite: an experimental study SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE Zagami Meteorite; experimental studies; Mars; thermal history; crystallization; volcanism ID PARENT MAGMA; PETROGENESIS; METEORITES; INCLUSIONS; AMPHIBOLE; MANTLE; MELT AB The Zagami meteorite is a Martian basalt which exhibits multiple lithologies formed by fractional crystallization. While the rock has been widely studied petrologically, its genesis is poorly constrained from an experimental standpoint. Ongoing debates about the thermal history of this and other Martian meteorites affect our thinking about the environments in which they could have formed (e.g. lava flow vs. subsurface dike) and the types of rocks that surficial Mars exploration are likely to recover. We report on twelve equilibrium and nine dynamic crystallization experiments on a synthetic Zagami composition. Equilibrium experiments run at temperatures of 1260-1050 degrees C yield results similar to those of previous workers [E.H. Stolper, H.Y. McSween Jr., Geochim. Cosmochim. Acta 43 (1979) 1475-1498]. We observe crystallization of similar to 40 wt.% of magnesian pyroxenes comparable in composition to the most magnesian pyroxene in Zagami, even though petrologic studies suggest that this magnesian pyroxene comprises only similar to 20 wt.% of the meteorite. Experiments run at a range of f(O2) from IW to QFM + 3.9 log units suggest that crystallization of Zagami under conditions as reducing as QFM - 3 log units cannot explain this discrepancy. Resorption of pyroxenes may have been an important factor in explaining this discrepancy. The most likely explanation is that Zagami crystallized from a melt with a higher Fe/Mg ratio than used in this work. Dynamic crystallization experiments run at a range of cooling rates (0.5-10 degrees C/h) and nuclei densities (1-3 vol.%, produced by varying the peak temperature between 1230 degrees and 1250 degrees C) suggests that Zagami formed from a melt with a low nuclei density at a relatively slow cooling rate (<1 degrees C/h). Although these conditions produce a textural match for Zagami, important differences remain in the composition and chemical zoning of the experimental pyroxenes compared to Zagami. These differences might require either the use of a bulk composition with a higher Fe/Mg ratio or a slower (<0.1 degrees C/h) or multi-stage cooling rate. Published by Elsevier Science B.V. C1 Natl Museum Nat Hist, Dept Mineral Sci, Smithsonian Inst, Washington, DC 20560 USA. NASA, Lyndon B Johnson Space Ctr, Code SN4, Houston, TX 77058 USA. RP McCoy, TJ (reprint author), Natl Museum Nat Hist, Dept Mineral Sci, Smithsonian Inst, Washington, DC 20560 USA. NR 24 TC 32 Z9 32 U1 1 U2 10 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD DEC 15 PY 1999 VL 173 IS 4 BP 397 EP 411 DI 10.1016/S0012-821X(99)00241-1 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 267BY UT WOS:000084335700003 ER PT J AU Reames, DV Ng, CK Tylka, AJ AF Reames, DV Ng, CK Tylka, AJ TI Energy-dependent ionization states of shock-accelerated particles in the solar corona SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MEAN IONIC CHARGE; FAST HEAVY-IONS; PLASMA; NUCLEON AB We examine the range of possible energy dependence of the ionization states of ions that are shock-accelerated from the ambient plasma of the solar corona. If acceleration begins in a region of moderate density, sufficiently low in the corona, ions above similar to 0.1 MeV/amu approach an equilibrium charge state that depends primarily upon their speed and only weakly on the plasma temperature. We suggest that the large variations of the charge states with energy for ions such as Si and Fe observed in the 1997 November 6 event are consistent with stripping in moderately dense coronal plasma during shock acceleration. In the large solar-particle events studied previously, acceleration occurs sufficiently high in the corona that even Fe ions up to 600 MeV/amu are not stripped of electrons. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RP Reames, DV (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. RI Tylka, Allan/G-9592-2014 NR 30 TC 48 Z9 48 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1999 VL 26 IS 24 BP 3585 EP 3588 DI 10.1029/1999GL003656 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 271JQ UT WOS:000084590800002 ER PT J AU Barrington-Leigh, CP Inan, US Stanley, M Cummer, SA AF Barrington-Leigh, CP Inan, US Stanley, M Cummer, SA TI Sprites triggered by negative lightning discharges SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RED SPRITES; CURRENTS AB High altitude air breakdown, manifested as "red sprites," is reported in close associated with negative cloud-to-ground lightning (-CG) on at least two occasions above an unusual storm on August 29, 1998. Data from high speed photometry, low-light-level video, and receivers of lightning electromagnetic signatures in the frequency range 10 Hz to 20 kHz are used to establish the association and indicate that the causative -CG discharges effected unusually large vertical charge moment changes (Delta M-Qv) of up to 1550 C.km in 5 ms. The existence of sprites caused by -CG's, rather than the regularly associated +CG's, has immediate implications for sprite models and observations. C1 Stanford Univ, STAR Lab, Stanford, CA 94305 USA. New Mexico Inst Min & Technol, Dept Phys, Socorro, NM 87801 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Barrington-Leigh, CP (reprint author), Stanford Univ, STAR Lab, Stanford, CA 94305 USA. RI Cummer, Steven/A-6118-2008; OI Cummer, Steven/0000-0002-0002-0613; Barrington-Leigh, Christopher/0000-0002-3929-5390 NR 18 TC 71 Z9 73 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1999 VL 26 IS 24 BP 3605 EP 3608 DI 10.1029/1999GL010692 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 271JQ UT WOS:000084590800007 ER PT J AU Kimes, DS Nelson, RF Salas, WA Skole, DL AF Kimes, DS Nelson, RF Salas, WA Skole, DL TI Mapping secondary tropical forest and forest age from SPOT HRV data SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID ABANDONED PASTURES; EASTERN AMAZONIA; NEURAL NETWORKS; THEMATIC MAPPER; LAND-USE; DEFORESTATION; VEGETATION; ECOSYSTEMS; SUCCESSION; DYNAMICS AB Accurate mapping of secondary forest and the age of these forests is critical to assess the carbon budget in tropical regions accurately. Using SPOT HRV (High Resolution Visible) data, techniques were developed and tested to discriminate primary forest, secondary forest and deforested areas on a study site in Rondonia, Brazil. Six co-registered SPOT HRV images (1986, 1988, 1989, 1991, 1992 and 1994) were used to create a time series of classified images of land cover (primary forest, secondary forest and deforested). These trajectories were used to identify secondary forest age classes relative to the most recent (1994) image. The resultant 1994 map of primary forest, secondary forest age classes and deforested areas served as ground reference data to establish training and testing sites. Several band 2 and 3 texture measurements were calculated using a 3 x 3 window to quantify canopy homogeneity. Neural networks and linear analysis techniques were tested for discriminating between primary forest, secondary forest and deforested pixels. The techniques were also employed to extract secondary forest age. A neural network using band 3 and a texture measure of band 2 and 3 from a single image (1994) discriminated primary forest, secondary forest (1 to >9 years) and deforested pixel with an average accuracy of 95%. The use of texture information increased the secondary forest discrimination accuracy 6.4% (from 83.5 to 89.9%). Spectral and textural information were also used to predict secondary forest age as a continuous variable. The neural network with the highest accuracy produced a RMSE (predicted network age versus actual secondary forest age) of 2.0 years with a coefficient of determination (predicted versus true) of 0.38. These results were significantly improved by using multitemporal information. The spectral and textural information from two images (1994 and 1989) were used to extract secondary forest information. The neural network results showed that 95.5% of the secondary forest pixels were correctly classified as secondary forest pixels (as opposed to 89.9% of the pixels using only the 1994 image). The RMSE and R-2 accuracies in extracting secondary forest age as a continuous variable were 1.3 and 0.75, respectively. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Univ New Hampshire, Complex Syst Res Ctr, Durham, NH 03824 USA. Michigan State Univ, Dept Geog, E Lansing, MI 48824 USA. RP Kimes, DS (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. RI Nelson, Ross/H-8266-2014 NR 42 TC 44 Z9 45 U1 0 U2 9 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD DEC 15 PY 1999 VL 20 IS 18 BP 3625 EP 3640 DI 10.1080/014311699211246 PG 16 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 252BX UT WOS:000083481800014 ER PT J AU Cox, C Stepniewski, S Jorgensen, C Saeks, R Lewis, C AF Cox, C Stepniewski, S Jorgensen, C Saeks, R Lewis, C TI On the design of a neural network autolander SO INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL LA English DT Article DE adaptive critic; neural network; flight control AB A research program directed at the development of an autolander for NASA's X-33 prototype reusable launch vehicle is described. The autolander is based on a new linear quadratic adaptive critic algorithm. It is implemented by an array of Functional Link neural networks and is trained by a modified Levenberg-Marquardt method. A full stability theory is developed for the new adaptive critic algorithm. Simulation results are presented for the linear-quadratic case. (C) 1999 John Wiley & Sons, Ltd. C1 Accurate Automat Corp, Chattanooga, TN 37421 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Cox, C (reprint author), Accurate Automat Corp, 7001 Shallowford Rd, Chattanooga, TN 37421 USA. NR 20 TC 28 Z9 32 U1 1 U2 4 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1049-8923 J9 INT J ROBUST NONLIN JI Int. J. Robust Nonlinear Control PD DEC 15 PY 1999 VL 9 IS 14 BP 1071 EP 1096 DI 10.1002/(SICI)1099-1239(19991215)9:14<1071::AID-RNC453>3.0.CO;2-W PG 26 WC Automation & Control Systems; Engineering, Electrical & Electronic; Mathematics, Applied SC Automation & Control Systems; Engineering; Mathematics GA 266LZ UT WOS:000084302600006 ER PT J AU Greenblatt, BJ Zanni, MT Neumark, DM AF Greenblatt, BJ Zanni, MT Neumark, DM TI Femtosecond photoelectron spectroscopy of I-2(-)(Ar)(n) clusters (n=6,9,12,16,20) SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID NONADIABATIC MOLECULAR-DYNAMICS; GEMINATE RECOMBINATION DYNAMICS; VIBRATIONAL-RELAXATION; CHARGE FLOW; SOLVENT DYNAMICS; PHOTODISSOCIATION; IONS; I-2(-); ANION; I2 AB The photodissociation of I-2(-) embedded in mass-selected I-2(-)(Ar)(n) clusters (n = 6-20) was studied using femtosecond photoelectron spectroscopy. The (A) over tilde'<--(X) over tilde transition in the I-2(-) chromophore was excited using a femtosecond pump pulse, and the subsequent dynamics were followed by photodetachment with a femtosecond probe pulse and measurement of the resulting photoelectron spectrum. In all clusters, dissociation of the I-2(-) is complete by 300 fs. From 300 fs to 1 ps, the spectra yield the number of Ar atoms interacting with the I- fragment. At later times, recombination of I-2(-) occurs in I-2(-)(Ar)(n greater than or equal to 12) on both the (X) over tilde and (A) over tilde states. Analysis of the spectra yields the time scale for (X) over tilde state vibrational relaxation and solvent evaporation. In I-2(-)(Ar)(20), energy transfer from I-2(-) to Ar atoms through vibrational relaxation is slightly faster than energy loss from the cluster through Ar evaporation, indicating the temporary storage of energy within Ar cluster modes. (C) 1999 American Institute of Physics. [S0021-9606(99)01245-3]. C1 Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA. RP Greenblatt, BJ (reprint author), NASA, Ames Res Ctr, Atmospher Chem & Dynam Branch, Mail Stop 245-5, Moffett Field, CA 94035 USA. RI Zanni, Martin/K-2707-2013; Neumark, Daniel/B-9551-2009 OI Neumark, Daniel/0000-0002-3762-9473 NR 49 TC 37 Z9 37 U1 0 U2 5 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD DEC 15 PY 1999 VL 111 IS 23 BP 10566 EP 10577 DI 10.1063/1.480433 PG 12 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 260AY UT WOS:000083927200023 ER PT J AU Kerman, B Wadhams, P Davis, N Comiso, J AF Kerman, B Wadhams, P Davis, N Comiso, J TI Informational equivalence between synthetic aperture radar imagery and the thickness of Arctic pack ice SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-ICE; CLASSIFICATION; SUBMARINE; BASIN AB The negative exponential form of the conditional probability of both differences in synthetic aperture radar (SAR) intensity and differences in thickness between neighbors is used as the basis of a representation of structural information in terms of textural information for sea ice. The analysis is based on a unique data set involving airborne SAR flights over the track of a submarine that simultaneously profiled ice thickness by means of an upwardly directed sonar. It is shown that both sets of data, namely, imagery and thickness, possess an identical conditional probability relationship. This probability is composed of both a fractal property for spatial separations and a simple negative exponential distribution for intensity or thickness differences for fixed separations. These properties allow for the derivation of two forms of information: textural and structural. An intercomparison of the structural information in terms of the textural information is offered for the same ice field as imaged by a SAR and measured from a submarine for its thickness. It is shown that the information curves for both the imagery and thickness have a similar geometrical form. It is demonstrated that three subranges within the information curves correspond to three visibly identifiable ice types and three thickness ranges associated previously with these ice types. It is suggested that an understanding of the transformation between the two sets of information states might provide estimated statistics of Arctic ice thickness from SAR imagery. C1 Environm Canada, Canada Ctr Inland Waters, Atmospher Environm Serv, Burlington, ON L7R 4A6, Canada. Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England. NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RP Environm Canada, Canada Ctr Inland Waters, Atmospher Environm Serv, Burlington, ON L7R 4A6, Canada. EM bryan.kerman@cciw.ca; pw11@cam.ac.uk; nrd10@cam.ac.uk; comiso@joey.gsfc.nasa.gov NR 29 TC 4 Z9 4 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9275 EI 2169-9291 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD DEC 15 PY 1999 VL 104 IS C12 BP 29721 EP 29731 DI 10.1029/1999JC900187 PG 11 WC Oceanography SC Oceanography GA 268DT UT WOS:000084399600013 ER PT J AU Varnai, T Davies, R AF Varnai, T Davies, R TI Effects of cloud heterogeneities on shortwave radiation: Comparison of cloud-top variability and internal heterogeneity SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID INDEPENDENT PIXEL APPROXIMATION; ZENITH ANGLE DEPENDENCE; STRATOCUMULUS CLOUDS; MARINE STRATUS; ALBEDO; FIELDS; FLUXES; PARAMETERIZATION; REFLECTANCE; GEOMETRY AB This paper examines the processes through which cloud heterogeneities influence solar reflection. This question is important since present methods give numerical results only for the overall radiative effect of cloud heterogeneities but cannot determine the degree to which various mechanisms are responsible for it. This study establishes a theoretical framework that defines these mechanisms and also provides a procedure to calculate their magnitude. In deriving the framework, the authors introduce a one-dimensional radiative transfer approximation, called the tilted independent pixel approximation (TIPA). TIPA uses the horizontal distribution of slant optical thicknesses along the direct solar beam to describe the radiative influence of cloud heterogeneities when horizontal transport between neighbors is not considered. The effects for horizontal transport are then attributed to two basic mechanisms: trapping and escape of radiation, when it moves to thicker and thinner cloud elements, respectively. Using the proposed framework, the study examines the shortwave radiative effects of cloud-top height and cloud volume extinction coefficient variations. It is shown and explained that identical variations in cloud optical thickness can cause much stronger heterogeneity effects if they are due to variations in geometrical cloud thickness rather than in volume extinction coefficient. The differences in albedo can exceed 0.05, and the relative differences in reflectance toward the zenith can be greater than 25% for overhead sun and 50% for oblique sun. The paper also explains a previously observed phenomenon: it shows that the trapping of upwelling radiation causes the zenith reflectance of heterogeneous clouds to increase with decreasing solar elevation. C1 McGill Univ, Dept Atmospher & Ocean Sci, Montreal, PQ, Canada. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. RP NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Code 913, Greenbelt, MD 20771 USA. EM varnai@climate.gsfc.nasa.gov RI Davies, Roger/D-4296-2009 OI Davies, Roger/0000-0002-2991-0409 NR 45 TC 66 Z9 67 U1 0 U2 6 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 EI 1520-0469 J9 J ATMOS SCI JI J. Atmos. Sci. PD DEC 15 PY 1999 VL 56 IS 24 BP 4206 EP 4224 DI 10.1175/1520-0469(1999)056<4206:EOCHOS>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 267KX UT WOS:000084358100009 ER PT J AU Park, Y Liang, SD AF Park, Y Liang, SD TI Charge and spin dynamics of the Hubbard chains SO PHYSICA C LA English DT Article DE Hubbard chains; charge-spin separation; DMRG; recursion technique ID MATRIX RENORMALIZATION-GROUP; T-J MODEL; ZERO TEMPERATURE; DENSITY; SEPARATION; LADDER; SYSTEMS; STATES AB We calculate the local correlation functions of charge and spin for the one-chain and two-chain Hubbard model using the density matrix renormalization group method and the recursion technique. Keeping only finite number of states we get good accuracy for the low energy excitations. We study the charge and spin gaps, bandwidths and weights of the spectra for various values of the on-site Coulomb interaction U and the electron filling. In the low energy part, the local correlation functions are different for the charge and spin The bandwidths are proportional to t for the charge and I for the spin, respectively. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Acad Sinica, Inst Phys, Taipei 11529, Taiwan. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Park, Y (reprint author), Acad Sinica, Inst Phys, Taipei 11529, Taiwan. NR 35 TC 0 Z9 0 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-4534 J9 PHYSICA C JI Physica C PD DEC 15 PY 1999 VL 328 IS 3-4 BP 200 EP 206 DI 10.1016/S0921-4534(99)00522-5 PG 7 WC Physics, Applied SC Physics GA 267UL UT WOS:000084377600009 ER PT J AU Liao, XZ Zou, J Cockayne, DJH Qin, J Jiang, ZM Wang, X Leon, R AF Liao, XZ Zou, J Cockayne, DJH Qin, J Jiang, ZM Wang, X Leon, R TI Strain relaxation by alloying effects in Ge islands grown on Si(001) SO PHYSICAL REVIEW B LA English DT Article ID TRANSMISSION-ELECTRON-MICROSCOPY; MOLECULAR-BEAM EPITAXY; QUANTUM DOTS; HETEROEPITAXIAL GROWTH; SHAPE; EQUILIBRIUM; TRANSITIONS; NUCLEATION; PYRAMIDS; SI(100) AB Transmission electron microscopy is used to study the morphology and the composition profile of "pure'' Ge islands grown at high temperature on Si(001) by molecular beam epitaxy. An alloying process, involving mass transport from the substrate to the islands during the island growth, was identified. It was found that, as a result of Si mass transport to the Ge islands, the island/substrate interface moves towards the substrate, and trenches form on the substrate surface around the islands; Reduction of the misfit strain at the island/substrate interface is the driving force for this process. [S0163-1829(99)00738-1]. C1 Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. Fudan Univ, Surface Phys Lab, Shanghai 200433, Peoples R China. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liao, XZ (reprint author), Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. EM liao@emu.usyd.edu.au RI Liao, Xiaozhou/B-3168-2009; Zou, Jin/B-3183-2009 OI Liao, Xiaozhou/0000-0001-8565-1758; Zou, Jin/0000-0001-9435-8043 NR 36 TC 95 Z9 98 U1 1 U2 6 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD DEC 15 PY 1999 VL 60 IS 23 BP 15605 EP 15608 DI 10.1103/PhysRevB.60.15605 PG 4 WC Physics, Condensed Matter SC Physics GA 272BZ UT WOS:000084631800036 ER PT J AU Lobo, C Leon, R Marcinkevicius, S Yang, W Sercel, PC Liao, XZ Zou, J Cockayne, DJH AF Lobo, C Leon, R Marcinkevicius, S Yang, W Sercel, PC Liao, XZ Zou, J Cockayne, DJH TI Inhibited carrier transfer in ensembles of isolated quantum dots SO PHYSICAL REVIEW B LA English DT Article ID RADIATIVE RECOMBINATION; TEMPERATURE-DEPENDENCE; PHOTOLUMINESCENCE; LUMINESCENCE; INGAAS/GAAS; WIRES; WELL AB We report significant differences in the temperature-dependent and time-resolved photoluminescence (PL) from low and high surface density InxGa1-xAs/GaAs quantum dots (QDs). QD's in high densities are found to exhibit an Arrhenius dependence of the PL intensity, while low-density (isolated) QD's display more complex temperature-dependent behavior. The PL temperature dependence of high density QD samples is attributed to carrier thermal emission and recapture into neighboring QD's. Conversely, in low density QD samples, thermal transfer of carriers between neighboring QD's plays no significant role in the PL temperature dependence. The efficiency of carrier transfer into isolated dots is found to be limited by the rate of carrier transport in the InxGa1-xAs wetting layer. These interpretations are consistent with time-resolved PL measurements of carrier transfer times in low and high density QD's. [S0163-1829(99)04748-7]. C1 Australian Natl Univ, Res Sch Phys Sci & Engn, Dept Elect Mat Engn, Canberra, ACT 0200, Australia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Royal Inst Technol, Dept Phys Opt, S-10044 Stockholm, Sweden. Univ Oregon, Dept Phys, Eugene, OR 97403 USA. Univ Oregon, Inst Sci Mat, Eugene, OR 97403 USA. Univ Sydney, Australian Key Ctr Microscopy & Microanal, Electron Microscopy Unit, Sydney, NSW 2006, Australia. RP Lobo, C (reprint author), Australian Natl Univ, Res Sch Phys Sci & Engn, Dept Elect Mat Engn, Canberra, ACT 0200, Australia. RI Liao, Xiaozhou/B-3168-2009; Zou, Jin/B-3183-2009; Lobo, Charlene/G-5003-2011 OI Liao, Xiaozhou/0000-0001-8565-1758; Zou, Jin/0000-0001-9435-8043; Lobo, Charlene/0000-0002-2746-1363 NR 25 TC 113 Z9 113 U1 2 U2 10 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD DEC 15 PY 1999 VL 60 IS 24 BP 16647 EP 16651 DI 10.1103/PhysRevB.60.16647 PG 5 WC Physics, Condensed Matter SC Physics GA 274XX UT WOS:000084791300063 ER PT J AU Kaplinghat, M Lopez, RE Dodelson, S Scherrer, RJ AF Kaplinghat, M Lopez, RE Dodelson, S Scherrer, RJ TI Improved treatment of cosmic microwave background fluctuations induced by a late-decaying massive neutrino SO PHYSICAL REVIEW D LA English DT Article ID DEGREE ANGULAR SCALES; ANISOTROPY MEASUREMENT; RADIATION; CONSTRAINTS; MATTER AB A massive neutrino which decays after recombination ((t greater than or equal to 10(13) sec) into relativistic decay products produces an enhanced integrated Sachs-Wolfe effect, allowing constraints to be placed on such neutrinos from present cosmic microwave background anisotropy data. Previous treatments of this problem have approximated the decay products as an additional component of the neutrino background. This approach violates energy-momentum conservation, and we show that it leads to serious errors for some neutrino masses and lifetimes. We redo this calculation more accurately, by correctly incorporating the spatial distribution of the decay products. For low neutrino masses and long lifetimes, we obtain a much smaller distortion in the CMB. fluctuation spectrum than have previous treatments. We combine these new results with a recent set of CMB data to exclude the mass and lifetime range m(h) > 100 eV, tau > 10(12) sec. Masses as low as 30 eV are excluded for a narrower range in Lifetime. [S0556-2821(99)04824-9]. C1 Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. RP Kaplinghat, M (reprint author), Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. NR 65 TC 37 Z9 37 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD DEC 15 PY 1999 VL 60 IS 12 AR 123508 DI 10.1103/PhysRevD.60.123508 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 268PK UT WOS:000084424600013 ER PT J AU Hockensmith, CM Goldsby, JC Kacik, T AF Hockensmith, CM Goldsby, JC Kacik, T TI Thermal studies of new precursors to indium-tin oxides for use as sensor materials in the detection of NOx SO THERMOCHIMICA ACTA LA English DT Article DE sensors; NOx; indium-tin oxide; 2,3-dihydroxynaphthalene; Tiron(TM); caffeic acid ID THIN-FILMS; GAS SENSORS; SNO2 AB Control of combustion product emissions in both sub- and super-sonic jet engines can be facilitated by measurement of NOx levels with metal oxide sensors. In2O3, metal-doped SnO2, and SnO2 (as well as other materials) show resistivity changes in the presence of NOx but often their sensitivity, stability, and selectivity are low. This study was designed to develop new synthetic pathways to precursors that produce high purity, two phase In2O3-SnO2. The precursors were formed by complexation of tin(IV) with chelating aryloxide ligands to give the ammonium salt, (NH4)(2)[Sn(ligand)(3)]. xH(2)O or the neutral molecule, [Sn(ligand)(2)]. xH(2)O, followed by reaction with In(III) to form the monomolecular precursors. Thermal studies of these precursors were carried out by thermal gravimetry (TG) and differential scanning calorimetry (DSC). Further studies by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) were also conducted. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Austin Peay State Univ, Dept Chem, Clarksville, TN 37044 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hockensmith, CM (reprint author), Austin Peay State Univ, Dept Chem, Clarksville, TN 37044 USA. NR 9 TC 0 Z9 0 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0040-6031 J9 THERMOCHIM ACTA JI Thermochim. Acta PD DEC 14 PY 1999 VL 341 SI SI BP 315 EP 322 PG 8 WC Thermodynamics; Chemistry, Analytical; Chemistry, Physical SC Thermodynamics; Chemistry GA 265HK UT WOS:000084236400031 ER PT J AU Chernov, AA Rashkovich, LN Yaminski, IV Gvozdev, NV AF Chernov, AA Rashkovich, LN Yaminski, IV Gvozdev, NV TI Kink kinetics, exchange fluxes, 1D 'nucleation' and adsorption on the (010) face of orthorhombic lysozyme crystals SO JOURNAL OF PHYSICS-CONDENSED MATTER LA English DT Article; Proceedings Paper CT Workshop on Thin Films and Phase Transitions on Surfaces CY FEB 21-26, 1999 CL PAMPOROVO, BULGARIA ID ATOMIC-FORCE MICROSCOPY; GROWTH; PROTEIN; CANAVALIN; STEP AB Rare kinks (1.74 x 10(-3) kinks nm(-1)) on the otherwise molecularly straight (001) growth steps on the (010) face of orthorhombic lysozyme were studied. These straight steps are generated at the edge between the (010) and (110) faces. Each step is assumed to propagate by creation of one-dimensional (1D) 'nuclei'-the segments of a new molecular rows irreversibly attached to the straight step in the course of a trial and error process. Each 'nucleus' is built of two neighbouring unit cells and is thus limited by two kinks possessing opposite signs. The steps move along the face at a rate similar to 0.19 nm s(-1), at relative supersaturation about unity. Kink statistics and step rate measurements allowed us to evaluate the velocity of the kink along the step to be 19.3 nm s(-1), and corresponding average frequencies at which attachment to and detachment from a kink occur to be similar or equal to 50 and 25 molecules s(-1), respectively. The rate at which the ID 'nuclei' appear at a step was found experimentally to be J = 2.7 x 10(-5) nm(-1) s(-1). This rate was also calculated as a probability that a sole molecular species adsorbed at the otherwise straight step will stay there forever. The rate of an arbitrarily oriented step driven by the 1D nucleation was also theoretically found to have a non-singular minimum at the close-packed orientation. On this theoretical basis, the coverage of the (001) step by unit cells was extracted from experimental data to be 6.5 x 10(-6). Taking into account translational, rotational and vibrational partition functions Bat face coverage with adsorbed molecules was estimated. The calculated adsorption coverage fits with the experimental data if the molecular detachment energy from a kink is similar to 6.6 kcal mol(-1). The terrace adsorption coverage is similar to 10(-3). The same approach is used to outline simple equations for protein solubility. The predicted solubility either rises with rising temperature-at a higher ratio of intermolecular binding energy to kT-or diminishes as the temperature rises-in the opposite case. The latter retrograde solubility comes from a high entropy loss associated with crystallization. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35805 USA. Moscow MV Lomonosov State Univ, Dept Phys, Moscow 117234, Russia. RP Chernov, AA (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, 4950 Corporate Dr,Suite 100, Huntsville, AL 35805 USA. NR 36 TC 48 Z9 50 U1 0 U2 7 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0953-8984 J9 J PHYS-CONDENS MAT JI J. Phys.-Condes. Matter PD DEC 13 PY 1999 VL 11 IS 49 BP 9969 EP 9984 DI 10.1088/0953-8984/11/49/314 PG 16 WC Physics, Condensed Matter SC Physics GA 271LQ UT WOS:000084595800014 ER PT J AU Weichman, PB Glazman, RE AF Weichman, PB Glazman, RE TI Turbulent fluctuation and transport of passive scalars by random wave fields SO PHYSICAL REVIEW LETTERS LA English DT Article AB Turbulent transport of passive scalars by random wave fields is studied, with applications to statistics of chlorophyll concentration in the ocean. The existence of the small parameter mu(0)/c(0), where u(0) and co are the characteristic particle velocity and wave phase speed, respectively, allows essentially exact calculations, and as such provides a rich testing ground for quantitative comparisons between theory and observation. General expressions are derived for the diffusion constant and mean drift velocity. It is shown that the spectrum of passive scalar fluctuations displays at least two distinct inertial range power laws even when the wave velocity field has only one. C1 Blackhawk Geometr, Golden, CO 80121 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Weichman, PB (reprint author), Blackhawk Geometr, 301 Commercial Rd,Suite B, Golden, CO 80121 USA. NR 10 TC 9 Z9 9 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD DEC 13 PY 1999 VL 83 IS 24 BP 5011 EP 5014 DI 10.1103/PhysRevLett.83.5011 PG 4 WC Physics, Multidisciplinary SC Physics GA 263YC UT WOS:000084152000026 ER PT J AU Abrams, DS Lloyd, S AF Abrams, DS Lloyd, S TI Quantum algorithm providing exponential speed increase for finding eigenvalues and eigenvectors SO PHYSICAL REVIEW LETTERS LA English DT Article ID COMPUTER; SYSTEMS AB We describe a new polynomial time quantum algorithm that uses the quantum fast Fourier transform to find eigenvalues and eigenvectors of a local Hamiltonian, and that can be applied in cases (commonly found in ab initio physics and chemistry problems) for which all known classical algorithms require exponential time. Applications of the algorithm to specific problems are considered, and we find that classically intractable and interesting problems from atomic physics may be solved with between 50 and 100 quantum bits. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. MIT, Dept Mech Engn, dArbeloff Lab Informat Sci & Technol, Cambridge, MA 02139 USA. RP Abrams, DS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 147 Z9 149 U1 2 U2 5 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD DEC 13 PY 1999 VL 83 IS 24 BP 5162 EP 5165 DI 10.1103/PhysRevLett.83.5162 PG 4 WC Physics, Multidisciplinary SC Physics GA 263YC UT WOS:000084152000064 ER PT J AU Kastner, SO Bhatia, AK AF Kastner, SO Bhatia, AK TI A correction factor for Gaussian deconvolution of optically thick linewidths in homogeneous sources SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE line : profiles; radiative transfer; Sun : prominences ID OPACITY; LINES AB Profiles of optically thick, non-Gaussian emission lines convolved with Gaussian instrumental profiles are constructed, and are deconvolved on the usual Gaussian basis to examine the departure from accuracy thereby caused in 'measured' linewidths. It is found that 'measured' linewidths underestimate the true linewidths of optically thick lines, by a factor which depends on the resolution factor r equivalent to Doppler width/instrumental width and on the optical thickness tau(0). An approximate expression is obtained for this factor, applicable in the range of at least 0 less than or equal to tau(0)less than or equal to 10, which can provide estimates of the true linewidth and optical thickness. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Kastner, SO (reprint author), 1-A Ridge Rd, Greenbelt, MD 20770 USA. NR 9 TC 0 Z9 0 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD DEC 11 PY 1999 VL 310 IS 3 BP 693 EP 702 DI 10.1046/j.1365-8711.1999.02971.x PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 272QZ UT WOS:000084663600008 ER PT J AU Scoccimarro, R Zaldarriaga, M Hui, L AF Scoccimarro, R Zaldarriaga, M Hui, L TI Power spectrum correlations induced by nonlinear clustering SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : clusters : general; large-scale structure of universe; methods : numerical; methods : statistical ID LARGE-SCALE STRUCTURE; REDSHIFT SURVEYS; COSMOLOGICAL PERTURBATIONS; FLUCTUATIONS; EVOLUTION; STATISTICS; GALAXIES AB Gravitational clustering is an intrinsically nonlinear process that generates significant non-Gaussian signatures in the density field. We consider how these affect power spectrum determinations from galaxy and weak-lensing surveys. Non-Gaussian effects not only increase the individual error bars compared to the Gaussian case but, most importantly, lead to nontrivial cross-correlations between different band powers, correlating small-scale band powers both among themselves and with those at large scales. We calculate the power-spectrum covariance matrix in nonlinear perturbation theory (weakly nonlinear regime), in the hierarchical model (strongly nonlinear regime), and from numerical simulations in real and redshift space. In particular, we show that the hierarchical Ansatz cannot be strictly valid for the configurations of the trispectrum involved in the calculation of the power-spectrum covariance matrix. We discuss the impact of these results on parameter estimation from power-spectrum measurements and their dependence on the size of the survey and the choice of band powers. We show that the non-Gaussian terms in the covariance matrix become dominant for scales smaller than the nonlinear scale k(nl) similar to 0.2 h(-1) Mpc(-1), depending somewhat on power normalization. Furthermore, we find that crosscorrelations mostly deteriorate the determination of the amplitude of a rescaled power spectrum, whereas its shape is less affected. In weak lensing surveys the projection tends to reduce the importance of non-Gaussian effects. Even so, for background galaxies at redshift z similar to 1, the non-Gaussian contribution rises significantly around l similar to 1000 and could become comparable to the Gaussian terms depending upon the power spectrum normalization and cosmology. The projection has another interesting effect: the ratio between non-Gaussian and Gaussian contributions saturates and can even decrease at small enough angular scales if the power spectrum of the three-dimensional field falls faster than k(-2). C1 CITA, McLennan Phys Labs, Toronto, ON M5S 3H8, Canada. Inst Adv Study, Sch Nat Sci, Princeton, NJ 08540 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Scoccimarro, R (reprint author), CITA, McLennan Phys Labs, 60 St George St, Toronto, ON M5S 3H8, Canada. NR 34 TC 116 Z9 116 U1 1 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 1 EP 15 DI 10.1086/308059 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300001 ER PT J AU Mukherjee, R Bottcher, M Hartman, RC Sreekumar, P Thompson, DJ Mahoney, WA Pursimo, T Sillanpaa, A Takalo, LO AF Mukherjee, R Bottcher, M Hartman, RC Sreekumar, P Thompson, DJ Mahoney, WA Pursimo, T Sillanpaa, A Takalo, LO TI Broadband spectral analysis of PKS 0528+134: A report on six years of Egret observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (PKS 0528+134); gamma rays : observations; radiation mechanisms : nonthermal ID EXTRAGALACTIC RADIO-SOURCES; GAMMA-RAY EMISSION; SELF-COMPTON MODEL; BLAZAR 3C-279; PKS-0528+134; FLARE; JETS; CALIBRATION; VARIABILITY; MISSION AB The multiwavelength spectra of PKS 0528 + 134 during 6 yr of observations by EGRET have been analyzed using synchrotron self-Compton (SSC) and external radiation Compton (ERC) models. We find that a two-component model, in which the target photons are produced externally to the gamma-ray-emitting region, but also including an SSC component, is required to reproduce suitably the spectral energy distributions of the source. Our analysis indicates that there is a trend in the observed properties of PKS 0528 + 134, as the source goes from a gamma-ray low state to a flaring state. We observe that during the higher gamma-ray states, the bulk Lorentz factor of the jet increases and the ERC component dominates the high-energy emission. Our model calculations indicate the trend that the energies of the electrons giving rise to the synchrotron peak decrease, and the power-ratio of the gamma-ray and low-energy spectral components increases, as the source goes from a low to a high gamma-ray state. C1 Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA. Columbia Univ, New York, NY 10027 USA. Rice Univ, Houston, TX 77005 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Turku, Tuorla Observ, SF-21500 Piikkio, Finland. RP Mukherjee, R (reprint author), Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA. RI Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 54 TC 53 Z9 55 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 132 EP 142 DI 10.1086/308057 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300012 ER PT J AU Aikawa, Y Herbst, E Dzegilenko, FN AF Aikawa, Y Herbst, E Dzegilenko, FN TI Grain surface recombination of HCO+ SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM : molecules; molecular processes ID QUANTUM AB We investigate the recombination of the HCO+ ion on grain surfaces. This process is a key reaction in dense regions such as protoplanetary disks. The branching fraction among intact desorption, dissociation, and desorption with dissociation has been analyzed by a classical trajectory approach. It is found that dissociation (with or without desorption) dominates over intact desorption. C1 Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Aikawa, Y (reprint author), Ohio State Univ, Dept Phys, 174 W 18th Ave, Columbus, OH 43210 USA. NR 15 TC 9 Z9 9 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 262 EP 265 DI 10.1086/308079 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300024 ER PT J AU Smale, AP Wachter, S AF Smale, AP Wachter, S TI A cessation of X-ray dipping activity in X1254-690 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (X1254-690); stars : neutron; X-rays : stars ID STARS; GINGA AB We present results from a campaign of simultaneous X-ray and optical observations of X1254-690 conducted using the Rossi X-Ray Timing Explorer and the CTIO 1.5 m telescope. We find that the usually observed deep X-ray dipping is not seen during the times of our observations, with an upper limit of similar to 2% on any X-ray orbital variation, and that the mean optical variability has declined in amplitude from Delta V = 0.40 +/- 0.02 mag to 0.28 +/- 0.01 mag. These findings indicate that the vertical structure on the disk edge associated with the impact point of the accretion stream has decreased in angular size from 17 degrees-25 degrees to less than 10 degrees, and support the suggestions of previous modeling work that the bulge provides 35%-40% of the contribution to the overall optical modulation. The average optical and X-ray brightnesses are comparable to their values during dipping episodes, indicating that the mean hi and disk radius remain unchanged. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Cerro Tololo Interamer Observ, La Serena, Chile. Univ Space Res Assoc, Washington, DC USA. RP Smale, AP (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 14 TC 17 Z9 17 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 341 EP 344 DI 10.1086/308089 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300030 ER PT J AU Belloni, T Dieters, S van den Ancker, ME Fender, RP Fox, DW Harmon, BA van der Klis, M Kommers, JM Lewin, WHG van Paradijs, J AF Belloni, T Dieters, S van den Ancker, ME Fender, RP Fox, DW Harmon, BA van der Klis, M Kommers, JM Lewin, WHG van Paradijs, J TI On the nature of XTE J0421+560/CI Camelopardalis SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (XTE 50421+560 CI Camelopardalis); X-rays : stars ID RAY TIMING EXPLORER; X-RAY; TRANSIENT A0538-66; OUTBURST; ACCRETION AB We present the results of an analysis of RXTE, BATSE, and optical/infrared data of the 1998 outburst of the X-ray transient system XTE J0421+ 560 (CI Cam). The X-ray outburst shows a very fast decay (initial e-folding time similar to 0.5 days, slowing down to similar to 2.3 days). The X-ray spectrum in the 2-25 keV band is complex, softening considerably during decay and with strongly variable intrinsic absorption. A strong iron emission line is observed. No fast time variability is detected (<0.5% rms in the 1-4096 Hz band at the outburst peak). The analysis of the optical/IR data suggests that the secondary is a B[e] star surrounded by cool dust, and places the system at a distance of greater than or similar to 2 kpc. At this distance, the peak at 2-25 keV luminosity is similar to 4 x 10(37) ergs s(-1). We compare the properties of this peculiar system with those of the Be/NS LMC transient A 0538-66 and suggest that CI Cam is of similar nature. The presence of strong radio emission during outburst indicates that the compact object is likely to be a black hole or a weakly magnetized neutron star. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Ctr Space Plasma & Aeronom Res, Huntsville, AL 35899 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Belloni, T (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. NR 44 TC 33 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 345 EP 352 DI 10.1086/308055 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300031 ER PT J AU Boden, AF Lane, BF Creech-Eakman, MJ Colavita, MM Dumont, PJ Gubler, J Koresko, CD Kuchner, MJ Kulkarni, SR Mobley, DW Pan, XP Shao, M van Belle, GT Wallace, JK Oppenheimer, BR AF Boden, AF Lane, BF Creech-Eakman, MJ Colavita, MM Dumont, PJ Gubler, J Koresko, CD Kuchner, MJ Kulkarni, SR Mobley, DW Pan, XP Shao, M van Belle, GT Wallace, JK Oppenheimer, BR TI The visual orbit of 64 Piscium SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : visual; stars : individual (64 Piscium); techniques : interferometric ID SOLAR-TYPE STARS; OPTICAL INTERFEROMETRY; MASSES; GALAXY; MULTIPLICITY; LUMINOSITY; REDSHIFT; CATALOG AB We report on the determination of the visual orbit of the double-lined spectroscopic binary system 64 Piscium with data obtained by the Palomar Testbed Interferometer in 1997 and 1998. 64 Psc is a nearly equal-mass double-lined binary system whose spectroscopic orbit is well known. We have estimated the visual orbit of 64 Pse from our interferometric visibility data. Our 64 Psc orbit is in good agreement with the spectroscopic results, and the physical parameters implied by a combined fit to our interferometric visibility data and radial velocity data of Duquennoy & Mayor result in precise component masses that agree well with their spectral type identifications. In particular, the orbital parallax of the system is determined to be 43.29 +/- 0.46 mas, and masses of the two components are determined to be 1.223 +/- 0.021 M-. and 1.170 +/- 0.018 M-., respectively. Nadal et al. put forward arguments of temporal variability in some of the orbital elements of 64 Psc, presumably explained by an undetected component in the system. While our visibility data do not favor the Nadal temporal variability inference, neither is it definitive in excluding it. Consequently we have performed both high dynamic-range near-infrared imaging and spectroscopy of potential additional companions to the 64 Psc system. Our imaging and spectroscopic data do not support the conjecture of an additional component to 64 Psc, but we did identify a faint object with unusual red colors and spectra. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Calif San Diego, San Diego, CA 92103 USA. CALTECH, Palomar Observ, Pasadena, CA 91125 USA. RP Boden, AF (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RI Kuchner, Marc/E-2288-2012 NR 31 TC 31 Z9 31 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 360 EP 368 DI 10.1086/308067 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300033 ER PT J AU Rietmeijer, FJM Nuth, JA Karner, JM AF Rietmeijer, FJM Nuth, JA Karner, JM TI Metastable eutectic condensation in a Mg-Fe-SiO-H(2)-O(2) vapor: Analogs to circumstellar dust SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; dust, extinction; ISM : abundances; molecular processes; solar system : formation ID RICH AGB STARS; INTERPLANETARY DUST; PARTICLES; MINERALOGY; GRAINS; ENVELOPES; ELEMENTS; SPECTRA; DISKS AB Experimental studies of gas-to-solid condensation in a Fe-Mg-SiO-H(2)-O(2) vapor reveal that this process yields only solids with magnesiosilica (MgO.SiO(2)) and ferrosilica (Fe-oxide.SiO(2)) compositions that coincide with metastable eutectics in the MgO-SiO(2) and (FeO/Fe(2)O(3))-SiO(2) binary phase diagrams plus simple metal oxides (MgO, SiO(2), and FeO or Fe(2)O(3)). No solids form with mixed Mg-Fe-O compositions during condensation nor is there evidence for the formation of ferromagnesiosilica, MgO.Fe(y)O(x).SiO(2) solids. The experimental evidence demonstrates that condensation of multicomponent vapors yields only a limited number of metastable solids of well-defined composition. These results have interesting consequences for models of grain formation in circumstellar outflows, for predictions concerning the chemical and mineralogical composition of presolar silicates, and for the composition of condensates formed in protostellar systems. C1 Univ New Mexico, Inst Meteorit, Dept Earth & Planetary Sci, Albuquerque, NM 87131 USA. NASA, Goddard Space Flight Ctr, Astrochem Branch, Greenbelt, MD 20771 USA. RP Rietmeijer, FJM (reprint author), Univ New Mexico, Inst Meteorit, Dept Earth & Planetary Sci, Albuquerque, NM 87131 USA. EM fransjmr@unm.edu; uljan@lepvax.gsfc.nasa.gov RI Nuth, Joseph/E-7085-2012 NR 46 TC 110 Z9 110 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 395 EP 404 DI 10.1086/308080 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300035 ER PT J AU Bautista, MA AF Bautista, MA TI Continuum fluorescence excitation of [N I] and [O I] lines in gaseous nebulae SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic processes; HII regions; ISM : abundances; ISM : individual (Orion Nebula); ISM : structure ID LARGE MAGELLANIC CLOUD; ORION NEBULA; FE-II; PHYSICAL CONDITIONS; SUPERNOVA-REMNANTS; EMISSION-LINES; SPECTROPHOTOMETRY; OXYGEN; ABUNDANCE; SPECTRA AB We investigate the effects of photoexcitation of [N I] and [O I] lines by stellar continuum radiation under nebular conditions. It is found that the [N I] optical lines at 5198 and 5200 Angstrom are affected by fluorescence in many objects, including the Orion Nebula. [O I] lines are much less sensitive to fluorescence, except under conditions of low temperatures (less than or equal to 5000 K) and high-radiation fields. Furthermore, it is shown that recent diagnostics by Esteban et al, of the physical conditions of partially ionized zones in Orion using combinations of [N I] and [O I] are unreliable because the lines from these species are likely to come from different regions. The hypothesis about different conditions in [N I]- and [O I]/[Fe II]-emitting regions is supported by the lack of correlation between these lines in samples of planetary nebulae, supernova remnants, and Herbig-Haro objects. C1 NASA, Goddard Space Flight Ctr, High Energy Phys Lab, Greenbelt, MD 20771 USA. RP Bautista, MA (reprint author), NASA, Goddard Space Flight Ctr, High Energy Phys Lab, Greenbelt, MD 20771 USA. NR 37 TC 6 Z9 6 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP 474 EP 478 DI 10.1086/308086 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265EA UT WOS:000084227300043 ER PT J AU Colina, L Arribas, S Borne, KD AF Colina, L Arribas, S Borne, KD TI Integral field spectroscopy of Markarian 273: Mapping high-velocity gas flows and an off-nucleus Seyfert 2 nebula SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (Markarian 273); galaxies : interactions; galaxies : nuclei; galaxies : Seyfert; galaxies : starburst ID ULTRALUMINOUS INFRARED GALAXIES; IRAS GALAXIES; SUPERWINDS AB Integral field optical spectroscopy with the INTEGRAL fiber-based system is used to map the extended ionized regions and gas flows in Mrk 273, one of the closest ultraluminous infrared galaxies. The H beta and [O III] lambda 5007 maps show the presence of two distinct regions separated by 4" (3.1 kpc) along position angle (P.A.) 240 degrees. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [O In] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [O III] ionized gas shows (1) the presence of highly disturbed gas in the regions around the LINER nucleus, (2) a high-velocity gas flow with a peak-to-peak amplitude of 2.4 x 10(3) km s(-1), and (3) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst and that the quiescent gas is directly ionized by a nuclear source, similar to the ionization cones typically seen in Seyfert galaxies. C1 Fac Ciencias, UC, CSIC, Inst Fis Cantabria, Santander 39005, Spain. Inst Astrofis Canarias, Tenerife 38200, Spain. NASA, Goddard Space Flight Ctr, Raytheon Informat Technol & Sci Serv, Greenbelt, MD 20771 USA. RP Colina, L (reprint author), Fac Ciencias, UC, CSIC, Inst Fis Cantabria, Santander 39005, Spain. NR 20 TC 27 Z9 27 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP L13 EP L16 DI 10.1086/312389 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265GW UT WOS:000084235000004 ER PT J AU Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Hurley, K Gogus, E Preece, RD Giblin, TW Thompson, C Duncan, RC AF Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Hurley, K Gogus, E Preece, RD Giblin, TW Thompson, C Duncan, RC TI Hard burst emission from the soft gamma repeater SGR 1900+14 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : general; stars : individual (SGR 1900+14); X-rays : bursts ID MAGNETIZED NEUTRON-STARS; X-RAY PULSAR; BATSE OBSERVATIONS; SPECTRA AB We present evidence for burst emission from SGR 1900+14 with a power-law high-energy spectrum extending beyond 500 keV. Unlike previous detections of high-energy photons during bursts from soft gamma repeaters (SGRs), these emissions are not associated with extraordinarily bright flares. Not only is the emission hard, but the spectra are better fitted by D. Band's gamma-ray burst (GRB) function rather than by the traditional optically thin thermal bremsstrahlung model. We find that the spectral evolution within these hard events obeys a hardness/intensity anticorrelation. Temporally, these events are distinct from typical SGR burst emissions in that they are longer (similar to 1 s) and have relatively smooth profiles. Despite a difference in peak luminosity of greater than or similar to 10(11) between these bursts from SGR 1900+14 and cosmological GRBs, there are striking temporal and spectral similarities between the two kinds of bursts, aside from spectral evolution. We outline an interpretation of these events in the context of the magnetar model. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Washington, DC USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. RP Woods, PM (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 34 TC 21 Z9 21 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1999 VL 527 IS 1 BP L47 EP L50 DI 10.1086/312399 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 265GW UT WOS:000084235000012 ER PT J AU Kosovichev, AG Duvall, TL AF Kosovichev, AG Duvall, TL TI Solar tomography SO CURRENT SCIENCE LA English DT Article ID TIME-DISTANCE HELIOSEISMOLOGY; INSTRUMENT AB The solar tomography (or time-distance helioseismology) is a new promising method for probing 3-D structures and flows beneath the solar surface, which is potentially important for studying the birth of active regions in the Sun's interior and for understanding the relation between the internal dynamics of the active regions, and the chromospheric and coronal activity. In this method, the time for waves to travel along sub-surface ray paths is determined from the temporal cross correlation of signals at two separated surface points. By measuring the times for many pairs of points from Dopplergrams, covering the visible hemisphere, a tremendous quantity of information about the state of the solar interior is derived. As an example, we present the results on the internal structures of supergranulation, meridional circulation, active regions and sunspots. An active region which emerged on the solar disk in January 1998, was studied from SOHO/MDI for nine days, both before and after its emergence at the surface. The results show a complicated structure of the emerging region in the interior, and suggest that the emerging flux ropes travel very quickly through the depth range of our observations. C1 Stanford Univ, W W Hansen Expt Phys Lab, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Kosovichev, AG (reprint author), Stanford Univ, W W Hansen Expt Phys Lab, Stanford, CA 94305 USA. RI Duvall, Thomas/C-9998-2012 NR 15 TC 6 Z9 6 U1 0 U2 0 PU CURRENT SCIENCE ASSN PI BANGALORE PA C V RAMAN AVENUE, PO BOX 8005, BANGALORE 560 080, INDIA SN 0011-3891 J9 CURR SCI INDIA JI Curr. Sci. PD DEC 10 PY 1999 VL 77 IS 11 BP 1467 EP 1474 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 269FY UT WOS:000084467100027 ER PT J AU Lundgren, P Protti, M Donnellan, A Heflin, M Hernandez, E Jefferson, D AF Lundgren, P Protti, M Donnellan, A Heflin, M Hernandez, E Jefferson, D TI Seismic cycle and plate margin deformation in Costa Rica: GPS observations from 1994 to 1997 SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID GLOBAL POSITIONING SYSTEM; GEODETIC OBSERVATIONS; NICARAGUA EARTHQUAKE; STRAIN ACCUMULATION; RELATIVE MOTION; SUBDUCTION ZONE; LA-ESTRELLA; APRIL 22; AMERICA; TRENCH AB Global Positioning System (GPS) observations in Costa Pica from 1994 to 1997 reveal a complex pattern of motion consistent with the superposition of seismic cycle and secular plate margin deformation. In the south, velocity vectors are consistent with motion of the Panama Block plus postseismic deformation following the 1991 Limon earthquake and interseismic strain due to partial locking of the Middle America Trench (MAT) thrust. In the northwest, sites west of the volcanic are are moving to the NW as a forearc sliver. Superimposed on this sliver motion are vertical and horizontal interseismic deformations from the adjacent Nicoya segment of the MAT. We apply two different inverse methods to understand the source of the seismic strain in NW Costa Pica. We compare fault-locking models derived using a singular value decomposition inversion with that of a simulated annealing global optimization approach. Both methods yield similar models for partial locking of the thrust interface beneath the Nicoya Peninsula. Our results define an area of nearly fully locked fault beneath the outer coast of the southern portion of the peninsula, with somewhat lower coupling beneath the northern half and with low coupling elsewhere. These initial results show the promise for detailed imaging of the locked portion of a thrust interface responsible for future large subduction zone earthquakes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Nacl, Observ Vulcanol & Sismol Costa Rica, OVSICORI, Heredia, Costa Rica. RP Lundgren, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-233, Pasadena, CA 91109 USA. EM paul@dagobah.jpl.nasa.gov; jprotti@una.ac.cr; andrea@cobra.jpl.nasa.gov; mbh@cobra.jpl.nasa.gov; djeff@cobra.jpl.nasa.gov OI Protti, Marino/0000-0001-9818-0051 NR 39 TC 40 Z9 41 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD DEC 10 PY 1999 VL 104 IS B12 BP 28915 EP 28926 DI 10.1029/1999JB900283 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 268CE UT WOS:000084396100013 ER PT J AU Argus, DF Peltier, WR Watkins, MM AF Argus, DF Peltier, WR Watkins, MM TI Glacial isostatic adjustment observed using very long baseline interferometry and satellite laser ranging geodesy SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID CURRENT PLATE MOTIONS; MANTLE VISCOSITY; LINE INTERFEROMETRY; REFERENCE FRAME; GEOCENTER; VLBI; INVERSION; SCALE; MODEL AB In global space geodetic solutions, radial site motions are usually estimated relative to the geocenter (the center of figure of the solid Earth). Most geodesists estimate the motion of the geocenter assuming both that sites do not move radially and that sites move laterally as predicted by plate motion model NUVEL-1A [DeMets et at, 1990, 1994]. Here we estimate the motion of the geocenter assuming that the plate interiors deform radially and laterally as predicted by the postglacial rebound model of Peltier [1994] or that of Peltier [1996] without assuming a priori knowledge about relative plate motion. Radial site motions estimated relative to this rebound-adjusted geocenter are in the same reference frame as the rebound model predictions, whereas site motions estimated without adjusting for rebound are not. We further constrain the motion of the rebound-adjusted geocenter using satellite laser ranging's sensitivity to the center of mass (of the solid Earth, the oceans, and the atmosphere) by assuming that the mean velocity between the rebound-adjusted geocenter and the center of mass is negligible over the: time period of geodetic measurement. Twenty years of observation with satellite laser ranging and very long baseline interferometry record the isostatic response of the solid Earth to the unloading of the late Pleistocene ice sheets. The misfits of the postglacial rebound model of Peltier [1994] and that of Peltier [1996] are 34% and 16% less, respectively, than the misfit of the rigid plate model. Sites at Onsala (Sweden) and Algonquin Park (Ontario) are observed to be rising at 3 mm/yr and 2 mm/yr, respectively, reflecting unloading of the Fennoscandian and Laurentide ice sheets. Sites along the east coast of the United States are subsiding at < 2 mm/yr, indicating that the forebulge produced by the Laurentide ice sheet is currently collapsing very slowly. Sites beneath the margins of the ice sheets during the last glacial maximum are currently moving laterally away from the ice sheet centers at < 1.5 mm/yr, in disagreement with the moderately fast outward motion predicted by the model of Peltier [1996]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Toronto, Dept Phys, Toronto, ON M5S 1A7, Canada. RP Argus, DF (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 238-600, Pasadena, CA 91109 USA. EM Donald.F.Argus@jpl.nasa.gov; peltier@atmosp.physics.utoronto.ca; Michael.M.Watkins@jpl.nasa.gov RI Argus, Donald/F-7704-2011; Peltier, William/A-1102-2008 NR 35 TC 54 Z9 55 U1 4 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD DEC 10 PY 1999 VL 104 IS B12 BP 29077 EP 29093 DI 10.1029/1999JB000237 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 268CE UT WOS:000084396100020 ER PT J AU Chavez, FP Strutton, PG Friederich, CE Feely, RA Feldman, GC Foley, DC McPhaden, MJ AF Chavez, FP Strutton, PG Friederich, CE Feely, RA Feldman, GC Foley, DC McPhaden, MJ TI Biological and chemical response of the equatorial Pacific Ocean to the 1997-98 El Nino SO SCIENCE LA English DT Article ID SURFACE PARTIAL-PRESSURE; 40-50 DAY OSCILLATION; SOUTHERN OSCILLATION; WARM POOL; TROPICAL PACIFIC; CARBON-DIOXIDE; SEA; CO2; VARIABILITY; 150-DEGREES-W AB During the 1997-98 El Nino, the equatorial Pacific Ocean retained 0.7 x 10(15) grams of carbon that normally would have been Lost to the atmosphere as carbon dioxide. The surface ocean became impoverished in plant nutrients, and chlorophyll concentrations were the Lowest on record. A dramatic recovery occurred in mid-1998, the system became highly productive, analogous to coastal environments, and carbon dioxide flux out of the ocean was again high. The spatial extent of the phytoplankton bloom that followed recovery from El Nino was the Largest ever observed for the equatorial Pacific. These chemical and ecological perturbations were linked to changes in the upwelling of nutrient-enriched waters. The description and explanation of these dynamic changes would not have been possible without an observing system that combines biological, chemical, and physical sensors on moorings with remote sensing of chlorophyll. C1 Monterey Bay Aquarium Res Inst, Moss Landing, CA 95039 USA. NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Natl Marine Fisheries Serv, Honolulu Lab, Honolulu, HI 96822 USA. RP Chavez, FP (reprint author), Monterey Bay Aquarium Res Inst, 7700 Sandholdt Rd, Moss Landing, CA 95039 USA. EM chfr@mbari.org RI Strutton, Peter/C-4466-2011; McPhaden, Michael/D-9799-2016 OI Strutton, Peter/0000-0002-2395-9471; NR 50 TC 381 Z9 394 U1 6 U2 71 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD DEC 10 PY 1999 VL 286 IS 5447 BP 2126 EP 2131 DI 10.1126/science.286.5447.2126 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 264AK UT WOS:000084157300043 ER PT J AU Priscu, JC Adams, EE Lyons, WB Voytek, MA Mogk, DW Brown, RL McKay, CP Takacs, CD Welch, KA Wolf, CF Kirshtein, JD Avci, R AF Priscu, JC Adams, EE Lyons, WB Voytek, MA Mogk, DW Brown, RL McKay, CP Takacs, CD Welch, KA Wolf, CF Kirshtein, JD Avci, R TI Geomicrobiology of subglacial ice above Lake Vostok, Antarctica SO SCIENCE LA English DT Article ID PCR AB Data from ice 3590 meters below Vostok Station indicate that the ice was accreted from liquid water associated with Lake Vostok. Microbes were observed at concentrations ranging from 2.8 x 10(3) to 3.6 x 10(4) cells per milliliter; no biological incorporation of selected organic substrates or bicarbonate was detected. Bacterial 16S ribosomal DNA genes revealed Low diversity in the gene population. The phylotypes were closely related to extant members of the alpha- and beta-Proteobacteria and the Actinomycetes. Extrapolation of the data from accretion ice to Lake Vostok implies that Lake Vostok may support a microbial population, despite more than 10(6) years of isolation from the atmosphere. C1 Montana State Univ, Dept Biol Sci, Bozeman, MT 59717 USA. Montana State Univ, Dept Civil Engn, Bozeman, MT 59717 USA. Montana State Univ, Dept Earth Sci, Bozeman, MT 59717 USA. Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. Univ Alabama, Dept Geol, Tuscaloosa, AL 35487 USA. US Geol Survey, Reston, VA 20192 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Priscu, JC (reprint author), Montana State Univ, Dept Biol Sci, Bozeman, MT 59717 USA. NR 24 TC 233 Z9 258 U1 4 U2 65 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD DEC 10 PY 1999 VL 286 IS 5447 BP 2141 EP 2144 DI 10.1126/science.286.5447.2141 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 264AK UT WOS:000084157300047 PM 10591642 ER PT J AU Envia, E Nallasamy, M AF Envia, E Nallasamy, M TI Design selection and analysis of a swept and leaned stator concept SO JOURNAL OF SOUND AND VIBRATION LA English DT Article AB This paper describes a two-part analytical study of the benefits of stator sweep and lean for reducing rotor-stater interaction tone noise. The first part of the paper describes a design study aimed at selecting a sweep and lean configuration that maximizes noise reductions for a candidate low-noise stator. In the second part, the predicted noise reductions that can be achieved by such a stator are compared with its measured benefits. The results from the first part indicate that the kinematic relationship between the rotor wakes and stator vanes is the principal factor in determining the achievable noise reductions. It is shown that properly chosen sweep and lean enhance wake tilting as seen by the stator vanes. This, in turn, increases the number of wake intersections per vane leading to reduced noise levels. This argument suggests that to reduce noise, sweep and lean must be chosen in such a way that the number of wake intersections per vane is increased. Thus, a simple design rule is proposed for implementing sweep and lean. To achieve significant noise reductions, the rule calls for a sweep configuration for which vane tip is downstream of its root and vane lean that is in the direction of the rotor rotation. In the second part of the study, a detailed assessment of the acoustic performance of the swept and leaned stator is carried out by comparing its predicted and measured noise reductions. Overall, these comparisons show that the predicted benefits of the swept and leaned stator are in good agreement, qualitative as well as quantitative, with the measured reductions for the fan speeds that are relevant to the standard noise certification procedures. Furthermore, the results demonstrate the validity of the design criterion as well as the theoretical tools used in the design and analysis phases of this study. (C) 1999 Academic Press. C1 NASA, Glenn Res Ctr, Acoust Branch, Cleveland, OH 44135 USA. DYNACS Engn Co Inc, Dept Aeromech, Brook Pk, OH 44142 USA. RP Envia, E (reprint author), NASA, Glenn Res Ctr, Acoust Branch, Cleveland, OH 44135 USA. NR 26 TC 31 Z9 34 U1 0 U2 4 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD DEC 9 PY 1999 VL 228 IS 4 BP 793 EP 836 DI 10.1006/jsvi.1999.2441 PG 44 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 263WP UT WOS:000084148500005 ER PT J AU Gawronski, W AF Gawronski, W TI Simultaneous placement of actuators and sensors SO JOURNAL OF SOUND AND VIBRATION LA English DT Letter C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gawronski, W (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 2 TC 9 Z9 11 U1 1 U2 3 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD DEC 9 PY 1999 VL 228 IS 4 BP 915 EP 922 DI 10.1006/jsvi.1999.2466 PG 8 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 263WP UT WOS:000084148500011 ER PT J AU Dyall, KG Enevoldsen, T AF Dyall, KG Enevoldsen, T TI Interfacing relativistic and nonrelativistic methods. III. Atomic 4-spinor expansions and integral approximations SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; GENERAL CONTRACTION; NATURAL ORBITALS; DIRAC-EQUATION AB Two approximations to the normalized elimination of the small component are presented which enable the work of a relativistic calculation to be substantially reduced. The first involves fixing the ratio of the large and small components in atomic calculations, which corresponds to a basis set expansion in terms of positive energy atomic 4-spinors. The second involves the definition of a local, i.e., center-dependent, fine structure constant, which has the effect of making atoms with alpha=0 nonrelativistic. A series of test calculations on a variety of molecules and properties indicates that the errors incurred in the first approximation are negligible. In the second approximation, the errors are dependent on the property, the chemical environment and the atomic number. For the second period elements the errors in the approximation are for chemical purposes negligible. In the third period this is true for many properties, but for some, such as ligand-metal binding energies, there are discrepancies which may be a cause for concern in more accurate calculations. Beyond the third period it is usually necessary to treat atoms relativistically. (C) 1999 American Institute of Physics. [S0021-9606(99)30146-X]. C1 NASA, Thermosci Inst, Ames Res Ctr, Moffett Field, CA 94035 USA. Odense Univ, Dept Chem, DK-5230 Odense M, Denmark. RP Dyall, KG (reprint author), NASA, Thermosci Inst, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 14 TC 58 Z9 58 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD DEC 8 PY 1999 VL 111 IS 22 BP 10000 EP 10007 DI 10.1063/1.480353 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 258RK UT WOS:000083852700012 ER PT J AU Doke, T Hayashi, T Kikuchi, J Nagaoka, S Nakano, T Sakaguchi, T Terasawa, K Badhwar, GD AF Doke, T Hayashi, T Kikuchi, J Nagaoka, S Nakano, T Sakaguchi, T Terasawa, K Badhwar, GD TI Application of real-time radiation dosimetry using a new silicon LET sensor SO MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS LA English DT Article; Proceedings Paper CT International-Space-Lifesciences-Working-Group-on-Radiation-Biology Results of a Workshop CY NOV, 1997 CL BANFF, CANADA SP Int Space Lifesciences Working Grp Radiat Biology DE double-sided silicon detector; LET distribution; radiation dosimeter; real time; Space Shuttle; TLD ID SPACE AB A new type of real-time radiation monitoring device, RRMD-III, consisting of three double-sided silicon strip detectors (DSSDs), has been developed and tested on-board the Space Shuttle mission STS-84. The test succeeded in measuring the linear energy transfer (LET) distribution over the range of 0.2 keV/mu m to 600 keV/mu m for 178 h. The Shuttle cruised at an altitude of 300 to 400 km and an inclination angle of 51.6 degrees for 221.3 h, which is equivalent to the International Space Station orbit. The LET distribution obtained for particles was investigated by separating it into galactic cosmic ray (GCR) particles and trapped particles in the South Atlantic Anomaly (SAA) region. The result shows that the contribution in dose-equivalent due to GCR particles is almost equal to that from trapped particles. The total absorbed dose rate during the mission was 0.611 mGy/day; the effective quality factor, 1.64; and the dose equivalent rate, 0.998 mSv/day. The average absorbed dose rates are 0.158 mGy/min for GCR particles and 3.67 mGy/min for trapped particles. The effective quality factors are 2.48 for GCR particles and 1.19 for trapped particles. The absorbed doses obtained by the RRMD-III and a conventional method using TLD (Mg2SiO4), which was placed around the RRMD-III were compared. It was found that the TLDs showed a lower efficiency, just 58% of absorbed dose registered by the RRMD-III. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Waseda Univ, Adv Res Inst Sci & Engn, Shinjuku Ku, Tokyo 1698555, Japan. Natl Space Dev Agcy Japan, Tsukuba Space Ctr, Tsukuba, Ibaraki 3058505, Japan. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77508 USA. RP Doke, T (reprint author), Waseda Univ, Adv Res Inst Sci & Engn, Shinjuku Ku, Okubo 4-3-1, Tokyo 1698555, Japan. NR 10 TC 1 Z9 1 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0027-5107 J9 MUTAT RES-FUND MOL M JI Mutat. Res.-Fundam. Mol. Mech. Mutagen. PD DEC 6 PY 1999 VL 430 IS 2 BP 191 EP 202 DI 10.1016/S0027-5107(99)00130-X PG 12 WC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology SC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology GA 268BU UT WOS:000084395100005 PM 10631333 ER PT J AU Williams, JR Zhang, YG Zhou, HM Osman, M Cha, D Kavet, R Cuccinotta, F Dicello, JF Dillehay, LE AF Williams, JR Zhang, YG Zhou, HM Osman, M Cha, D Kavet, R Cuccinotta, F Dicello, JF Dillehay, LE TI Predicting cancer rates in astronauts from animal carcinogenesis studies and cellular markers SO MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS LA English DT Article; Proceedings Paper CT International-Space-Lifesciences-Working-Group-on-Radiation-Biology Results of a Workshop CY NOV, 1997 CL BANFF, CANADA SP Int Space Lifesciences Working Grp Radiat Biology DE cancer; radiation; cellular biomarkers; space; models ID ADAPTIVE RESPONSE; HUMAN-LYMPHOCYTES; MYELOID-LEUKEMIA; GAMMA-RAYS; RADIORESISTANCE; POPULATION; REPAIR; CELLS; MICE AB The radiation space environment includes particles such as protons and multiple species of heavy ions, with much of the exposure to these radiations occurring at extremely low average dose-rates. Limitations in databases needed to predict cancer hazards in human beings from such radiations are significant and currently do not provide confidence that such predictions are acceptably precise or accurate. In this article, we outline the need for animal carcinogenesis data based on a more sophisticated understanding of the dose-response relationship for induction of cancer and correlative cellular endpoints by representative space radiations. We stress the need for a model that can interrelate human and animal carcinogenesis data with cellular mechanisms. Using a broad model for dose-response patterns which we term the "subalpha-alpha-omega (SAO) model'', we explore examples in the literature for radiation-induced cancer and for radiation-induced cellular events to illustrate the need for data that define the dose-response patterns more precisely over specific dose ranges, with special attention to low dose, low dose-rate exposure. We present data for multiple endpoints in cells, which vary in their radiosensitivity, that also support the proposed model. We have measured induction of complex chromosome aberrations in multiple cell types by two space radiations, Fe-ions and protons, and compared these to photons delivered at high dose-rate or low dose-rate. Our data demonstrate that at least three factors modulate the relative efficacy of Fe-ions compared to photons: (i) intrinsic radiosensitivity of irradiated cells; (ii) dose-rate; and (iii) another unspecified effect perhaps related to reparability of DNA lesions. These factors can produce respectively up to at least 7-, 6- and 3-fold variability. These data demonstrate the need to understand better the role of intrinsic radiosensitivity and dose-rate effects in mammalian cell response to ionizing radiation. Such understanding is critical in extrapolating databases between cellular response, animal carcinogenesis and human carcinogenesis, and we suggest that the SAO model is a useful tool for such extrapolation. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Johns Hopkins Med Inst, Baltimore, MD 21287 USA. Elect Power Res Inst, Palo Alto, CA 94303 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Williams, JR (reprint author), Johns Hopkins Med Inst, 600 N Wolfe St, Baltimore, MD 21287 USA. FU NIEHS NIH HHS [R01 ES07076] NR 22 TC 16 Z9 18 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0027-5107 J9 MUTAT RES-FUND MOL M JI Mutat. Res.-Fundam. Mol. Mech. Mutagen. PD DEC 6 PY 1999 VL 430 IS 2 BP 255 EP 269 DI 10.1016/S0027-5107(99)00137-2 PG 15 WC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology SC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology GA 268BU UT WOS:000084395100012 PM 10631340 ER PT J AU Rothschild, LJ Cockell, CS AF Rothschild, LJ Cockell, CS TI Radiation: microbial evolution, ecology, and relevance to Mars missions SO MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS LA English DT Article; Proceedings Paper CT International-Space-Lifesciences-Working-Group-on-Radiation-Biology Results of a Workshop CY NOV, 1997 CL BANFF, CANADA SP Int Space Lifesciences Working Grp Radiat Biology DE Mars; ultraviolet radiation; DNA damage; DNA repair; photosynthesis; diurnal cycle; evolution ID TROPICAL SOLAR-RADIATION; ULTRAVIOLET-B RADIATION; OXYGENIC PHOTOSYNTHESIS; GLIDING CYANOBACTERIA; DIURNAL PATTERNS; CARBON FIXATION; DNA-REPAIR; UV-B; LIGHT; OZONE AB Ultraviolet (UV) radiation has been an important environmental parameter during the evolution of life on Earth, both in its role as a mutagen and as a selective agent. This was probably especially true during the time from 3.8 to 2.5 billion years ago, when atmospheric ozone levels were less than 1% of present levels. Early Mars may not have had an "ozone shield" either, and it never developed a significant one. Even though Mars is farther away from the Sun than the Earth, a substantial surficial UV flux is present on Mars today. But organisms respond to dose rate, and on Mars, like on Earth, organisms would be exposed to diurnal variations in UV flux. Here we present data on the effect of diurnal patterns of UV flux on microbial ecosystems in nature, with an emphasis on photosynthesis and DNA synthesis effects. These results indicate that diurnal patterns of metabolism occur in nature with a dip in photosynthesis and DNA synthesis in the afternoon, in part regulated by UV flux. Thus, diurnal patterns must be studied in order to understand the effect of UV radiation in nature. The results of this work are significant to the success of human missions to Mars for several reasons. For example, human missions must include photosynthetic organisms for food production and likely oxygen production. An evolutionary approach suggests which organisms might be best suited for high UV fluxes. The diurnal aspect of these studies is critical. Terraforming is a potential goal of Mars exploration, and it will require studies of the effect of Martian UV fluxes, including their diurnal changes, on terrestrial organisms. Such studies may suggest that diurnal changes in UV only require mitigation at some times of day or year. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Bay Area Environm Res Inst, Moffett Field, CA 94035 USA. RP Rothschild, LJ (reprint author), NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Mail Stop 239-20, Moffett Field, CA 94035 USA. NR 91 TC 16 Z9 16 U1 2 U2 24 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0027-5107 J9 MUTAT RES-FUND MOL M JI Mutat. Res.-Fundam. Mol. Mech. Mutagen. PD DEC 6 PY 1999 VL 430 IS 2 BP 281 EP 291 DI 10.1016/S0027-5107(99)00140-2 PG 11 WC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology SC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology GA 268BU UT WOS:000084395100015 PM 10631343 ER PT J AU Peterson, LE Cucinotta, FA AF Peterson, LE Cucinotta, FA TI Monte Carlo mixture model of lifetime cancer incidence risk from radiation exposure on shuttle and international space station SO MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS LA English DT Article; Proceedings Paper CT International-Space-Lifesciences-Working-Group-on-Radiation-Biology Results of a Workshop CY NOV, 1997 CL BANFF, CANADA SP Int Space Lifesciences Working Grp Radiat Biology DE Space Shuttle; International Space Station; space radiation; lifetime risk; malignant neoplasms; Monte Carlo uncertainty; analysis ID ATOMIC-BOMB SURVIVORS; MUTATION-INDUCTION; MAMMALIAN-CELLS; HEAVY-IONS; INACTIVATION; RAYS AB Estimating uncertainty in lifetime cancer risk for human exposure to space radiation is a unique challenge. Conventional risk assessment with low-linear-energy-transfer (LET)-based risk from Japanese atomic bomb survivor studies may be inappropriate for relativistic protons and nuclei in space due to track structure effects. This paper develops a Monte Carlo mixture model (MCMM) for transferring additive, National Institutes of Health multiplicative, and multiplicative excess cancer incidence risks based on Japanese atomic bomb survivor data to determine excess incidence risk for various US astronaut exposure profiles. The MCMM serves as an anchor point for future risk projection methods involving biophysical models of DNA damage from space radiation. Lifetime incidence risks of radiation-induced cancer for the MCMM based on low-LET Japanese data for nonleukemia (all cancers except leukemia) were 2.77% (90% confidence limit, 0.75-11.34) for males exposed to 1 Sv at age 45 and 2.20% (90% confidence limit, 0.59-10.12) for males exposed at age 55. For females, mixture model risks for nonleukemia exposed separately to I Sv at ages of 45 and 55 were 2.98% (90% confidence limit, 0.90-11.70) and 2.44% (90% confidence limit, 0.70-10.30), respectively. Risks for high-LET 200 MeV protons (LET = 0.45 keV/mu m), 1 MeV alpha-particles (LET = 100 keV/mu m), and 600 MeV iron particles (LET = 180 keV/mu m) were scored on a per particle basis by determining the particle fluence required for an average of one particle per cell nucleus of area 100 mu m(2) Lifetime risk per proton was 2.68 x 10(-2)% (90% confidence limit, 0.79 x 10-3%-0.514 x 10(-2) %). For a-particles, lifetime risk was 14.2% (90% confidence limit, 2.5%-31.2%). Conversely, lifetime risk per iron particle was 23.7% (90% confidence limit, 4.5%-53.0%). Uncertainty in the DDREF for high-LET particles may be less than that for low-LET radiation because typically there is very little dose-rate dependence. Probability density functions for high-LET radiation quality and dose-rate may be preferable to conventional risk assessment approaches. Nuclear reactions and track structure effects in tissue may not be properly estimated by existing data using in vitro models for estimating RBEs. The method used here is being extended to estimate uncertainty in spacecraft shielding effectiveness in various space radiation environments. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Baylor Coll Med, Dept Med, Chron Dis Prevent & Control Res Ctr, Houston, TX 77030 USA. NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Directorate, Houston, TX 77058 USA. RP Peterson, LE (reprint author), Baylor Coll Med, Dept Med, Chron Dis Prevent & Control Res Ctr, 1 Baylor Pl,ST-924, Houston, TX 77030 USA. OI Peterson, Leif/0000-0002-1187-0883 NR 22 TC 7 Z9 7 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0027-5107 J9 MUTAT RES-FUND MOL M JI Mutat. Res.-Fundam. Mol. Mech. Mutagen. PD DEC 6 PY 1999 VL 430 IS 2 BP 327 EP 335 DI 10.1016/S0027-5107(99)00145-1 PG 9 WC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology SC Biotechnology & Applied Microbiology; Genetics & Heredity; Toxicology GA 268BU UT WOS:000084395100020 PM 10631348 ER PT J AU Fu, JA Schamschula, MP Caulfield, HJ AF Fu, JA Schamschula, MP Caulfield, HJ TI Optical parallel database management system for page oriented holographic memories SO OPTICS EXPRESS LA English DT Article AB Current data recall rates from page oriented holographic memories far exceed the ability of electronics to even read or transmit the data. For database management, we must not only read those data but also query them-computationally, a far more complex task. That task is very severe for electronics. We show here the rudiments of an optical system that can do most of the query operations in parallel in optics, leaving the burden for electronics significantly less. Even here, electronics is the ultimate speed limiter. Nevertheless, we can query data far faster in our optical/ electronic system than any purely electronic system. (C) 1999 Optical Society of America. C1 Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. Fisk Univ, NASA, Ctr Photon Mat & Devices, Nashville, TN 37208 USA. RP Fu, JA (reprint author), Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1094-4087 J9 OPT EXPRESS JI Opt. Express PD DEC 6 PY 1999 VL 5 IS 12 BP 273 EP 285 PG 13 WC Optics SC Optics GA 265HY UT WOS:000084237700001 PM 19401732 ER PT J AU Fork, RL Cole, ST Gamble, LJ Diffey, WM Keys, AS AF Fork, RL Cole, ST Gamble, LJ Diffey, WM Keys, AS TI Optical amplifier for space applications SO OPTICS EXPRESS LA English DT Article ID LASERS AB We describe an optical amplifier designed to amplify a spatially sampled component of an optical wavefront to kilowatt average power. The goal is means for implementing a strategy of spatially segmenting a large aperture wavefront, amplifying the individual segments, maintaining the phase coherence of the segments by active means, and imaging the resultant amplified coherent field. Applications of interest are the transmission of space solar power over multi-megameter distances, as to distant spacecraft, or to remote sites with no preexisting power grid. (C) 1999 Optical Society of America. C1 Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Fork, RL (reprint author), Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. EM fork@ece.uah.edu NR 18 TC 7 Z9 7 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1094-4087 J9 OPT EXPRESS JI Opt. Express PD DEC 6 PY 1999 VL 5 IS 12 BP 292 EP 301 PG 10 WC Optics SC Optics GA 265HY UT WOS:000084237700003 PM 19401734 ER PT J AU Vinnikov, KY Robock, A Stouffer, RJ Walsh, JE Parkinson, CL Cavalieri, DJ Mitchell, JFB Garrett, D Zakharov, VF AF Vinnikov, KY Robock, A Stouffer, RJ Walsh, JE Parkinson, CL Cavalieri, DJ Mitchell, JFB Garrett, D Zakharov, VF TI Global warming and Northern Hemisphere sea ice extent SO SCIENCE LA English DT Article ID OCEAN ATMOSPHERE MODEL; NATURAL VARIABILITY; TRANSIENT RESPONSES; GRADUAL CHANGES; CLIMATE; CO2 AB Surface and satellite-based observations show a decrease in Northern Hemisphere sea ice extent during the past 45 years. A comparison of these trends to control and transient integrations (forced by observed greenhouse gases and tropospheric sulfate aerosols) from the Geophysical Fluid Dynamics Laboratory and Hadley Centre climate models reveals that the observed decrease in Northern Hemisphere sea ice extent agrees with the transient simulations, and both trends are much Larger than would be expected from natural climate variations. From Long-term control runs of climate models, it was found that the probability of the observed trends resulting from natural climate variability, assuming that the models' natural variability is similar to that found in nature, is Less than 2 percent for the 1978-98 sea ice trends and Less than 0.1 percent for the 1953-98 sea ice trends. Both models used here project continued decreases in sea ice thickness and extent throughout the next century. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Rutgers State Univ, Dept Environm Sci, New Brunswick, NJ 08901 USA. NOAA, Geophys Fluid Dynam Lab, Princeton, NJ 08542 USA. Univ Illinois, Dept Atmospher Sci, Urbana, IL 61801 USA. NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. Meteorol Off, Hadley Ctr Climate Predict & Res, Bracknell RG12 2SZ, Berks, England. NOAA, Climate Predict Ctr, Natl Weather Serv, Natl Ctr Environm Predict, Camp Springs, MD 20746 USA. Arctic & Antarctic Res Inst, St Petersburg 199397, Russia. RP Vinnikov, KY (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. RI Vinnikov, Konstantin/F-9348-2010; Parkinson, Claire/E-1747-2012; Robock, Alan/B-6385-2016 OI Parkinson, Claire/0000-0001-6730-4197; NR 24 TC 253 Z9 268 U1 6 U2 43 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD DEC 3 PY 1999 VL 286 IS 5446 BP 1934 EP 1937 DI 10.1126/science.286.5446.1934 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 261HH UT WOS:000084003400045 ER PT J AU Lissauer, JJ AF Lissauer, JJ TI How common are habitable planets? SO NATURE LA English DT Article ID IMPACTS; ASTEROIDS; SYSTEMS; COMETS; EARTH AB The Earth is teeming with life, which occupies a diverse array of environments; other bodies in our Solar System offer fewer, if any, niches that are habitable by life as we know it. Nonetheless, astronomical studies suggest that many habitable planets may be present within our Galaxy. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Lissauer, JJ (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. NR 12 TC 15 Z9 16 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD DEC 2 PY 1999 VL 402 IS 6761 SU S BP C11 EP C14 DI 10.1038/35011503 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 261MZ UT WOS:000084014100002 PM 10591221 ER PT J AU Labbe, SC Perez, LF Fitzgerald, S Longo, JMA Molina, R Rapuc, M AF Labbe, SC Perez, LF Fitzgerald, S Longo, JMA Molina, R Rapuc, M TI X-38 integrated aero- and aerothermodynamic activities SO AEROSPACE SCIENCE AND TECHNOLOGY LA English DT Article DE re-entry; lifting body; aerodynamics; aerothermodynamics; sub-, super- and hypersonic flows AB The characterisation of the aeroshape selected for the X-38 [Crew Return Vehicle (CRV) demonstrator] is presently being performed as a co-operative endeavour between NASA, DLR (through its TETRA Program), and the European Space Agency (ESA) with Dassault Aviation integrating the aerodynamic and aerothermodynamic activities. The: methodologies selected for characterizing the aerodynamic and aerothermodynamic environment of the X-38 are presented. (C) 1999 Editions scientifiques et medicales Elsevier SAS. C1 DLR, D-38108 Braunschweig, Germany. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Dassault Aviat, F-92552 St Cloud, France. RP Longo, JMA (reprint author), DLR, Lilienthalpl 7, D-38108 Braunschweig, Germany. NR 7 TC 12 Z9 12 U1 0 U2 2 PU GAUTHIER-VILLARS/EDITIONS ELSEVIER PI PARIS PA 23 RUE LINOIS, 75015 PARIS, FRANCE SN 0034-1223 J9 AEROSP SCI TECHNOL JI Aerosp. Sci. Technol. PD DEC PY 1999 VL 3 IS 8 BP 485 EP 493 DI 10.1016/S1270-9638(99)00109-1 PG 9 WC Engineering, Aerospace SC Engineering GA 277VB UT WOS:000084953300002 ER PT J AU Pauluhn, A Ruedi, I Solanki, SK Lang, J Pike, CD Schuhle, U Thompson, WT Hollandt, J Huber, MCE AF Pauluhn, A Ruedi, I Solanki, SK Lang, J Pike, CD Schuhle, U Thompson, WT Hollandt, J Huber, MCE TI Intercalibration of SUMER and CDS on SOHO. I. SUMER detector A and CDS NIS SO APPLIED OPTICS LA English DT Article ID ULTRAVIOLET SPECTROMETER SUMER; RADIOMETRIC CALIBRATION; SOLAR AB The results of an intercalibration between the extreme ultraviolet spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the Solar and Heliospheric Observatory (SOHO) are presented. During the joint observing program Intercal_01, CDS and SUMER were pointed at the same locations in quiet Sun areas and observed in the same wavelength bands located around the spectral lines He I 584 Angstrom, Mg x 609 Angstrom, and Mg x 624 Angstrom. The data sets analyzed here consist of raster images recorded by the CDS normal-incidence spectrometer and SUMER detector A and span the time from March 1996 to August 1996. Effects of the different spatial and spectral resolutions of both instruments have been investigated and taken into account in the analysis. We find that CDS measures generally a 30% higher intensity than SUMER in the He I 584-Angstrom line, while it measures 9% and 17% higher intensities in Mg x 609 A and Mg x 624 PI, respectively. Both instruments show very good temporal correlation and stability, indicating that solar variations dominate over changes in instrumental sensitivity. Our analysis also provides in-flight estimates of the CDS spatial point-spread functions. (C) 1999 Optical Society of America OCIS codes: 120.5630, 120.6200, 300.6540. C1 Eidgenoss Tech Hochshule Zentrum, Astron Inst, CH-8092 Zurich, Switzerland. INTEC Bern, Bern, Switzerland. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. NASA, Goddard Space Flight Ctr, SM&A Corp, Greenbelt, MD 20771 USA. Phys Tech Bundesanstalt, D-10587 Berlin, Germany. European Space Agcy, European Space Res & Technol Ctr, NL-2200 AG Noordwijk, Netherlands. RP Pauluhn, A (reprint author), Eidgenoss Tech Hochshule Zentrum, Astron Inst, CH-8092 Zurich, Switzerland. EM pauluhn@astro.phys.ethz.ch RI Thompson, William/D-7376-2012; Solanki, Sami/E-2487-2013; Hollandt, Jorg/A-2124-2014 OI Solanki, Sami/0000-0002-3418-8449; NR 18 TC 35 Z9 35 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD DEC 1 PY 1999 VL 38 IS 34 BP 7035 EP 7046 DI 10.1364/AO.38.007035 PG 12 WC Optics SC Optics GA 261RV UT WOS:000084023500008 PM 18324248 ER PT J AU Serabyn, E Wallace, JK Hardy, GJ Schmidtlin, EGH Nguyen, HT AF Serabyn, E Wallace, JK Hardy, GJ Schmidtlin, EGH Nguyen, HT TI Deep nulling of visible laser light SO APPLIED OPTICS LA English DT Article ID INTERFEROMETER AB Nulling interferometry, a proposed technique for dimming a star relative to its surroundings by destructively interfering the light collected by two individual telescopes [Bracewell, Nature 274, 780-781 (1978); Shao and Colavita, Arm. Rev. Astron. Astrophys. 30, 457-498 (1992)], has the potential to permit the direct detection of nearby extrasolar planets. However, because of the extremely high degree of symmetry required for useful levels of starlight nulling, the technique remains in its infancy. We present results of laboratory experiments with a rotational shearing interferometer that are aimed at demonstrating the feasibility of deep nulling at the levels needed for direct planet detection. Our first results include the successful nulling of red laser light to a part in 10(5) and the stabilization of the null leakage to a part in 10(4). (C) 1999 Optical Society of America. OCIS codes: 260.3160, 350.1260. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Serabyn, E (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 171-113, Pasadena, CA 91109 USA. EM gene.serabyn@jpl.nasa.gov NR 11 TC 51 Z9 51 U1 1 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD DEC 1 PY 1999 VL 38 IS 34 BP 7128 EP 7132 DI 10.1364/AO.38.007128 PG 5 WC Optics SC Optics GA 261RV UT WOS:000084023500019 PM 18324259 ER PT J AU LaRocco, MT Pierson, DL AF LaRocco, MT Pierson, DL TI Deep space exploration: Will we be ready? SO ASM NEWS LA English DT Article C1 St Lukes Episcopal Hosp, Houston, TX USA. Lyndon B Johnson Space Ctr, Houston, TX USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1325 MASSACHUSETTS AVENUE, NW, WASHINGTON, DC 20005-4171 USA SN 0044-7897 J9 ASM NEWS JI ASM News PD DEC PY 1999 VL 65 IS 12 BP 817 EP 821 PG 5 WC Microbiology SC Microbiology GA 265MH UT WOS:000084247600017 PM 11542641 ER PT J AU Schlegel, EM Ryder, S Staveley-Smith, L Petre, R Colbert, E Dopita, M Campbell-Wilson, D AF Schlegel, EM Ryder, S Staveley-Smith, L Petre, R Colbert, E Dopita, M Campbell-Wilson, D TI Physical properties of the X-ray-luminous SN1978K in NGC 1313 from multiwavelength observations SO ASTRONOMICAL JOURNAL LA English DT Article DE supernova : individual (SN 1978K) ID SPIRAL GALAXY NGC-1313; H-II REGION; SUPERNOVA-REMNANTS; CIRCUMSTELLAR INTERACTION; SN 1978K; EMISSION; RADIO; SN-1987A; SN-1978K; ROSAT AB We update the light curves from the X-ray, optical, and radio bandpasses which we have assembled over the past decade and present two observations in the ultraviolet using the Hubble Space Telescope Faint Object Spectrograph. The HRI X-ray light curve is constant within the errors over the entire observation period. This behavior is confirmed in the ASCA GIS data obtained in 1993 and 1995. In the ultraviolet, we detected Ly alpha, the [Ne IV] 2422/2424 Angstrom doublet, the Mg II. doublet at 2800 Angstrom, and a line at approximately 3190 Angstrom that we attribute to He I 3187. Only the Mg II and He I lines are detected at SN 1978K's position. The optical light curve is formally constant within the errors, although a slight upward trend may be present. The radio light curve continues its steep decline. The longer time span of our radio observations compared to previous studies shows that SN 1978K is in the same class of highly X-ray and radio-luminous supernovae as SN 1986J and SN 1988Z. The [Ne IV] emission is spatially distant from the location of SN 1978K and originates in the preshocked matter. The Mg II doublet flux ratio implies the quantity of line optical depth times density of approximately 10(14) cm(-3) for its emission region. The emission site must lie in the shocked gas. C1 Harvard Smithsonian Ctr Astrophys, Smithsonian Astrophys Observ, High Energy Astrophys Div, Cambridge, MA 02138 USA. Joint Astron Ctr, Hilo, HI 96720 USA. CSIRO, Australia Telescope Natl Facil, Epping, NSW 2121, Australia. NASA, Goddard Space Flight Ctr, Xray Astrophys Grp, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. Univ Sydney, Dept Astrophys, Sch Phys, Sydney, NSW 2006, Australia. RP Schlegel, EM (reprint author), Harvard Smithsonian Ctr Astrophys, Smithsonian Astrophys Observ, High Energy Astrophys Div, 60 Garden St, Cambridge, MA 02138 USA. RI Staveley-Smith, Lister/A-1683-2011; Dopita, Michael/P-5413-2014; OI Staveley-Smith, Lister/0000-0002-8057-0294; Dopita, Michael/0000-0003-0922-4986; Ryder, Stuart/0000-0003-4501-8100 NR 60 TC 26 Z9 26 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD DEC PY 1999 VL 118 IS 6 BP 2689 EP 2704 DI 10.1086/301145 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 274KY UT WOS:000084766100011 ER PT J AU Allamandola, LJ Hudgins, DM Bauschlicher, CW Langhoff, SR AF Allamandola, LJ Hudgins, DM Bauschlicher, CW Langhoff, SR TI Carbon chain abundance in the diffuse interstellar medium SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE molecular data; molecular processes; ISM : abundances; ISM : general; ISM : molecules; infrared : ISM : lines and bands ID ELECTRONIC ABSORPTION-SPECTRA; NEON MATRICES; INFRARED-ABSORPTION; CLUSTER ANIONS; C-2N+1 N=2-7; EMISSION; SPECTROSCOPY; BANDS; DUST AB Thanks to the mid-IR sensitivities of the ISO and IRTS orbiting spectrometers it is now possible to search the diffuse interstellar medium for heretofore inaccessible molecular emission. In view of the recent strong case for the presence of C-7(-) (Kirkwood et al. 1998, Tulej et al. 1998), and the fact that carbon chains possess prominent infrared active modes in a very clean portion of the interstellar spectrum, we have analyzed the IRTS spectrum of the diffuse interstellar medium for the infrared signatures of these species. Theoretical and experimental infrared band frequencies and absolute intensities of many different carbon chain species are presented. These include cyanopolyynes, neutral and anionic linear carbon molecules, and neutral and ionized, even-numbered, hydrogenated carbon chains. We show that - as a family - these species have abundances in the diffuse ISM on the order of 10(-10) with respect to hydrogen, values consistent with their abundances in dense molecular clouds. Assuming an average length of 10 C atoms per C-chain implies that roughly a millionth of the cosmically available carbon is in the form of carbon chains and that carbon chains can account for a few percent of the visible to near-IR diffuse interstellar band (DIB) total equivalent width (not DIB number). C1 NASA, Ames Res Ctr, Moffett Field, CA 94034 USA. RP Allamandola, LJ (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94034 USA. EM lallamandola@mail.arc.nasa.gov NR 32 TC 43 Z9 43 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1999 VL 352 IS 2 BP 659 EP 664 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 271ZF UT WOS:000084625000047 PM 11543325 ER PT J AU Doressoundiram, A Weissman, PR Fulchignoni, M Barucci, MA Le Bras, A Colas, F Lecacheux, J Birlan, M Lazzarin, M Fornasier, S Dotto, E Barbieri, C Sykes, MV Larson, S Hergenrother, C AF Doressoundiram, A Weissman, PR Fulchignoni, M Barucci, MA Le Bras, A Colas, F Lecacheux, J Birlan, M Lazzarin, M Fornasier, S Dotto, E Barbieri, C Sykes, MV Larson, S Hergenrother, C TI 4979 Otawara: flyby target of the Rosetta mission SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE minor planets, asteroids; planets and satellites : individual : 4979 Otawa ID ASTEROIDS; METEORITES; 253-MATHILDE; SEARCH; VESTA AB An international observing campaign was organized to determine the physical and chemical characteristics of asteroid 4979 Otawara, which is the first target of the Rosetta mission (flyby on July 10, 2006). Knowledge of the physical parameters of the flyby targets is required for both refinement of the design of the spacecraft and the instrument payload, and optimization of the mission trajectory and scenarios. We present the results of observations obtained from December, 1998 through March, 1999. The spectral classification of 4979 Otawara could be either a pyroxene and/or olivine-rich S-type asteroid or a V-type asteroid, a member of the Vesta dynamical family. Further observations are needed in order to discriminate between the two spectral types. The synodic rotation period of Otawara is P-syn = 2.107 +/- 0.005 hr. The lower limit for the axial ratio of the enveloping ellipsoid is a/b greater than or equal to 1.3. The circular effective radius is 2.0 or 1.3 km in the case of an S-type or a V-type asteroid, respectively. A lower limit on its density is obtained: rho(min) greater than or equal to 1.9 g cm(-3) if we assume that Otawara is an aggregate or rubble pile object. However, if Otawara is a single solid body, no constraint can be set on its density. 4979 Otawara is a small, fast rotating asteroid (FRA) and hence, will be a particularly interesting target to be studied from a spacecraft, since no fast rotator has been visited yet. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Observ Paris, DESPA, F-92190 Meudon, France. Univ Paris 07, Paris, France. IMCCE, F-75014 Paris, France. Osservatorio Astron Padova, I-35122 Padua, Italy. Univ Arizona, Steward Observ, Tucson, AZ 85719 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85719 USA. Osservatorio Astron Torino, I-10025 Pino Torinese, Italy. RP Doressoundiram, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM alain.doressoundiram@obspm.fr RI BIRLAN, Mirel/B-5283-2011; OI Dotto, Elisabetta/0000-0002-9335-1656 NR 26 TC 4 Z9 4 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1999 VL 352 IS 2 BP 697 EP 702 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 271ZF UT WOS:000084625000051 ER PT J AU Beuermann, K Hessman, FV Reinsch, K Nicklas, H Vreeswijk, PM Galama, TJ Rol, E van Paradijs, J Kouveliotou, C Frontera, F Masetti, N Palazzi, E Pian, E AF Beuermann, K Hessman, FV Reinsch, K Nicklas, H Vreeswijk, PM Galama, TJ Rol, E van Paradijs, J Kouveliotou, C Frontera, F Masetti, N Palazzi, E Pian, E TI VLT observations of GRB 990510 and its environment SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE galaxies : general; gamma rays : bursts; cosmology : miscellaneous ID GAMMA-RAY BURST; 25 APRIL 1998; SUPERNOVA AB We present BVRI photometry and spectrophotometry of GRB 990510 obtained with the ESO VLT/Antu telescope during the late decline phase. Between days 8 and 29 after the burst, the afterglow faded from R = 24.2 to similar to 26.4. The spectral flux distribution and the light curve support the interpretation of the afterglow as synchrotron emission from a jet. The light curve is consistent with the optical transient alone but an underlying SN with maximum brightness R > 27.4 or a galaxy with R > 27.6 (3-sigma upper limits) cannot be ruled out. To a 5-sigma detection threshold of R = 26.1, no galaxy is found within 6 " of the transient. A very blue V similar or equal to 24.5 extended object which may qualify as a starburst galaxy is located 12 " SE, but at unknown redshift. C1 Univ Sternwarte, D-37083 Gottingen, Germany. Univ Amsterdam, NL-1098 SJ Amsterdam, Netherlands. Astron Inst Anton Pannekoek, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Huntsville, AL 35812 USA. NASA, MSFC, Huntsville, AL 35812 USA. CNR, Ist Tecnol & Studi Radiaz Extraterrestri, I-40129 Bologna, Italy. Univ Ferrara, Dipartmento Fis, I-44100 Ferrara, Italy. RP Beuermann, K (reprint author), Univ Sternwarte, Geismarlandstr 11, D-37083 Gottingen, Germany. EM beuermann@uni-sw.gwdg.de RI Galama, Titus/D-1429-2014; Palazzi, Eliana/N-4746-2015 OI Galama, Titus/0000-0002-1036-396X; NR 20 TC 146 Z9 147 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1999 VL 352 IS 1 BP L26 EP L30 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266AX UT WOS:000084279400006 ER PT J AU Zinnecker, H Krabbe, A McCaughrean, MJ Stanke, T Stecklum, B Brandner, W Padgett, DL Stapelfeldt, KR Yorke, HW AF Zinnecker, H Krabbe, A McCaughrean, MJ Stanke, T Stecklum, B Brandner, W Padgett, DL Stapelfeldt, KR Yorke, HW TI A search for young solar system analogues with the VLT SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE telescopes; stars : formation; stars : pre-main sequence; ISM : jets and outflows ID HERBIG-HARO OBJECTS; CHAMELEON INFRARED NEBULA; GUM NEBULA; STAR FORMATION; LOW-MASS; OPTICAL POLARIZATION; COMETARY GLOBULES; RESOLUTION; EMISSION; JETS AB The VLT/UT1 telescope has been used with its facility near-IR camera ISAAC to obtain 1-2.5 mu m wavelength images at 0." 4 spatial resolution of six southern young low luminosity sources associated with extended reflection nebulosity. Two are in the Chamaeleon I dark cloud (Cha IR nebula, Cederblad 110IRS4), and the other four in the Gum Nebula (HH 46/47, CG 30, Re 4, Re 5). Complex structure is seen, including in most cases bipolar blue and red scattering lobes likely due to the illumination of outflow cavities by the central start(s), hidden by a flattened circumstellar disk or envelope. In one object (Re 4), a double jet appears to be emanating from the central source, suggestive of a binary system with nearly aligned disks. These images, when supplemented by polarimetry maps, will help determine the structure and geometry of the young stellar objects. and will also be compared to 3D radiative transfer models to match both the surface brightness distribution of the extended emission and the spectral energy distribution of the central source. Applied to a series of such objects, these analyses will lead to an improved evolutionary sequence for the formation of solar system analogues. C1 Astrophys Inst Potsdam, D-14482 Potsdam, Germany. German Aerosp Ctr, Inst Space Sensors & Planetary Res, D-12489 Berlin, Germany. Thuringer Landessternewarte, D-07778 Tautenburg, Germany. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. CALTECH, SIRTF, IPAC, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zinnecker, H (reprint author), Astrophys Inst Potsdam, Sternwarte 16, D-14482 Potsdam, Germany. EM hzinnecker@aip.de RI Stapelfeldt, Karl/D-2721-2012 NR 34 TC 23 Z9 23 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1999 VL 352 IS 1 BP L73 EP L78 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266AX UT WOS:000084279400015 ER PT J AU Smith, DA Levine, AM Bradt, HV Remillard, R Jernigan, JG Hurley, KC Wen, L Briggs, M Cline, T Mazets, E Golenetskii, S Frederics, D AF Smith, DA Levine, AM Bradt, HV Remillard, R Jernigan, JG Hurley, KC Wen, L Briggs, M Cline, T Mazets, E Golenetskii, S Frederics, D TI Localizations of 13 gamma-ray bursts by the All-Sky Monitor on the Rossi X-ray Timing Explorer SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; X-rays : bursts ID EMISSION; SEARCH AB The All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE) has been used to localize 13 confirmed X-ray counterparts to gamma-ray bursts (GRBs) detected over 3 yr of operation. We quantify the errors in ASM localizations of brief transient sources by using observations of persistent sources with well-known locations. We apply the results of this analysis to obtain accurate error boxes with reliable confidence levels for the 13 GRBs. In six of these 13 cases, multiple detections by the ASM allow the positions to be localized to a diamond of order similar to 15' x 3', In five further cases, the Interplanetary Network (IPN) constrains the usually similar to 3 degrees x 3' (full-width) ASM error box to an area of a few tens of square arcminutes. This work adds 11 burst localizations to the list of similar to 60 well-localized GRBs. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. MIT, Dept Phys, Cambridge, MA 02139 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. AF Ioffe Physicotech Inst, St Petersburg 194021, Russia. RP Smith, DA (reprint author), MIT, Ctr Space Res, Cambridge, MA 02139 USA. RI Golenetskii, Sergey/B-3818-2015 NR 46 TC 17 Z9 17 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1999 VL 526 IS 2 BP 683 EP 696 DI 10.1086/308029 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 263GF UT WOS:000084116500013 ER PT J AU Levenson, NA Graham, JR Snowden, SL AF Levenson, NA Graham, JR Snowden, SL TI The Cygnus Loop: A soft-shelled supernova remnant SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (Cygnus loop); supernova remnants; X-rays : ISM ID FAST SHOCK-WAVE; X-RAY; OPTICAL-EMISSION; EINSTEIN OBSERVATIONS; CLOUD; ROSAT; NOVA AB We present ROSAT Position Sensitive Proportional Counter (PSPC) pointed observations of the Cygnus Loop supernova remnant in two broad soft X-ray bands, characteristic of energies 0.25 and 1.25 keV. The spatial differences between the bands are obvious in an X-ray softness map, which is the ratio of the 0.25 and 1.25 keV emission. The most striking feature of the softness map is a spatially thin (< 5') shell that we detect around the entire rim of the supernova remnant. It is not an observational artifact, for the angular extent is greater than the instrumental resolution. Several known interactions with large interstellar clouds are prominent in the softest emission, and the brightest X-ray emission associated with these clouds appears to the interior of these soft features. We conclude that over most of the blast wave, genuinely lower temperatures behind slower shocks soften the X-ray spectrum, and this occurs where the cavity walls of the Cygnus Loop decelerate the blast wave. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Levenson, NA (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. RI Snowden, Steven/D-5292-2012 NR 27 TC 28 Z9 28 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1999 VL 526 IS 2 BP 874 EP 880 DI 10.1086/308018 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 263GF UT WOS:000084116500029 ER PT J AU Gogus, E Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Duncan, RC Thompson, C AF Gogus, E Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Duncan, RC Thompson, C TI Statistical properties of SGR 1900+14 bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; stars : individual (SCR 1900+14); X-rays : bursts ID MAGNETIZED NEUTRON-STARS; SELF-ORGANIZED CRITICALITY; SOFT GAMMA-REPEATERS; X-RAY; BEHAVIOR; PULSAR AB We study the statistics of soft gamma repeater (SGR) bursts using a database of 187 events detected with BATSE and 837 events detected with the Rossi X-Ray Timing Explorer Proportional Counter Array; all events are from SGR 1900+14 during its 1998-1999 active phase. We find that the fluence or energy distribution of bursts is consistent with a power law of index 1.66, over 4 orders of magnitude. This scale-free distribution resembles the Gutenberg-Richter law for earthquakes and gives evidence for self-organized criticality in SGRs. The distribution of time intervals between successive bursts from SGR 1900+14 is consistent with a lognormal distribution. There is no correlation between burst intensity and the waiting times till the next burst, but there is some evidence for a correlation between burst intensity and the time elapsed since the previous burst. We also find a correlation between the duration and the energy of the bursts, but with significant scatter. In all these statistical properties, SGR bursts resemble earthquakes and solar flares more closely than they resemble any known accretion-powered or nuclear-powered phenomena. Thus, our analysis lends support to the hypothesis that the energy source for SGR bursts is internal to the neutron star and plausibly magnetic. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Texas, Dept Astron, Austin, TX 78712 USA. Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. RP Gogus, E (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 32 TC 76 Z9 76 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1999 VL 526 IS 2 BP L93 EP L96 DI 10.1086/312380 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 263GG UT WOS:000084116600010 ER PT J AU Hunt, LK Malkan, MA Rush, B Bicay, MD Nelson, BO Stanga, RM Webb, W AF Hunt, LK Malkan, MA Rush, B Bicay, MD Nelson, BO Stanga, RM Webb, W TI Morphology of the 12 micron Seyfert galaxies. II. Optical and near-infrared image atlas SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE atlases; infrared : galaxies; galaxies : photometry; galaxies : Seyfert; galaxies : structure ID ACTIVE GALACTIC NUCLEI; PHOTOMETRIC STANDARD STARS; BAND SURFACE PHOTOMETRY; HOMOGENEOUS SAMPLE; STELLAR COMPONENTS; CELESTIAL EQUATOR; VARIABILITY; DECONVOLUTION; DECOMPOSITION; DISTRIBUTIONS AB We present 263 optical and near-infrared (NIR) images for 42 1s and 48 Seyfert 2s, selected from the Extended 12 mu m Galaxy Sample. Elliptically averaged profiles are derived from the images, and isophotal radii and magnitudes are calculated from these. We also report virtual aperture photometry that, judging from comparison with previous work, is accurate to roughly 0.05 mag in the optical, and 0.07 mag in the NIR. Our B-band isophotal magnitude and radii, obtained from ellipse fitting, are in good agreement with those of Third Reference Catalogue of Bright Galaxies. When compared with the B band, V, I, J, and K isophotal diameters show that the colors in the outer regions of Seyfert galaxies are consistent with the colors of normal spirals. Differences in the integrated isophotal colors and comparison with a simple model show that the active nucleus + bulge are stronger and redder in the NIR than in the optical. Finally, roughly estimated Seyfert disk surface brightnesses are significantly brighter in B and K than those in normal spirals of similar morphological type. C1 CNR, CAISMI, I-50125 Florence, Italy. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, SIRTF, Pasadena, CA 91109 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Florence, Ist Astron, I-50125 Florence, Italy. RP CNR, CAISMI, Largo E Farmi 5, I-50125 Florence, Italy. EM hunt@arcetri.astro.it; malkan@bonnie.astro.ucla.edu; rush@bonnie.astro.ucla.edu; michael.d.bicay@jpl.nasa.gov; nelson@ipac.caltech.edu; stanga@arcetri.astro.it; webb@bonnie.astro.ucla.edu OI Hunt, Leslie/0000-0001-9162-2371 NR 57 TC 24 Z9 24 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 EI 1538-4365 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD DEC PY 1999 VL 125 IS 2 BP 349 EP 362 DI 10.1086/313279 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277PA UT WOS:000084940900003 ER PT J AU Greenleaf, JE Chou, JL Stad, NJ Leftheriotis, GPN Arndt, NF Jackson, CGR Simonson, SR Barnes, PR AF Greenleaf, JE Chou, JL Stad, NJ Leftheriotis, GPN Arndt, NF Jackson, CGR Simonson, SR Barnes, PR TI Short-arm (1.9 m) +2.2 Gz acceleration: Isotonic exercise load-O-2 uptake relationship SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE maximal work capacity; centrifugation; exercise-acceleration; passive acceleration heart rate; pulmonary ventilation ID BED REST; MICROGRAVITY; SPACEFLIGHT AB Background: The deconditioning syndrome from prolonged bed rest (BR) or spaceflight includes decreases in maximal oxygen uptake ((V) over dot o(2)max), muscular strength and endurance, and orthostatic tolerance. In addition to exercise training as a countermeasure, +Gz (head-to-foot) acceleration training on 1.8-2.0 m centrifuges can ameliorate the orthostatic and acceleration intolerances induced by BR and immersion deconditioning. Purpose: Study A was designed to determine the magnitude and linearity of the heart rate (HR) response to human-powered centrifuge (HPC) acceleration with supine exercise vs. passive (no exercise) acceleration. Study B was designed to test the hypothesis that moderate +Gz acceleration during exercise will not affect the respective normal linear relationships between exercise load and (V) over dot o(2)max, HR, and pulmonary ventilation ((V) over dot EBTPS). Study C: TO determine if these physiological responses from the HPC runs (exercise + on-platform acceleration) will be similar to those from the exercise + off-platform acceleration responses. Methods: In Study A, four men and two women (31-62 yr) were tested supine during exercise + acceleration and only passive acceleration at 100% [maximal acceleration (rpm) = Amax] and at 25%, 50%, and 75% of Amax. In Studies B and C, seven men (33 +/- SD 7 yr) exercised supine on the HPC that has two opposing on-platform exercise stations. A (V) over dot o(2)max test and submaximal exercise runs occurred under three conditions: (EXA) exercise ton-platform cycle at 42%, 61%, 89% and 100% ((V) over dot o(2)max) with no acceleration; (HPC) exercise + acceleration via the chain drive at 25%,50%, and 100% Gzmax (35%, 72% and 100% (V) over dot o(2)max); and (EXA) exercise (on-platform cycle at 42%, 61%, 89%, and 100% (V) over dot o(2)max) with acceleration performed via the off-platform cycle operator at +2.2 +/- 0.2 Gz [50% of max (rpm) G]. Results: Study A: Mean (+/-SE) Amax was 43.7 +/- 1.3 rpm ((X) over bar = +3.9 +/- 0.2, range = 3.3 to 4.9 Gz). Amax run time for exercise + acceleration was 50-70 s,and 40-70 s for passive acceleration. Regression of (X) over bar HR on Gz levels indicated explained variances (r(2)) of 0.88 (exercise) and 0.96 (passive). The (X) over bar exercise HR of 107 +/- 4 (25%), to 189 +/- 13 (100%) bpm were 43-50 bpm higher (p < 0.05) than comparable passive HR of 64 +/- 2 to 142 +/- 22 bpm, respectively. Study B: There were no significant differences in (V) over dot o(2), HR or (V) over dot EBTPS at the submaximal or maximal levels between the EX and EXA runs. Mean (+/-SE) (V) over dot o(2)max for EX was 2.86 +/- 0.12 L . min(-1) (35 +/- 2 ml . min(-1) . kg(-1)) and for EXA was 3.09 +/- 0.14 L . min(-1) (37 +/- 2 ml . min(-1) . kg(-1)). Study C: There were no significant differences in the essentially linear relationships between the HPC and EXA data for (V) over dot o(2) (p = 0.45), HR (p < 0.08), (V) over dot EBTPS (p = 0.28), Or the RE (p = 0.15) when the exercise load was (V) over dot o(2)max. Conclusion: Addition of + 2.2 Gz acceleration does not significantly influence levels of oxygen uptake, heart rate, or pulmonary ventilation during submaximal or maximal cycle ergometer leg exercise on a short-arm centrifuge. C1 NASA, Gravitat Res Branch 221A2, Lab Human Environm Physiol, Ames Res Ctr, Moffett Field, CA 94035 USA. San Francisco State Univ, Dept Biol Sci, San Francisco, CA 94132 USA. Fac Med Angers, Physiol Lab, Angers, France. Calif State Univ Fresno, Dept Kinesiol, Fresno, CA 93740 USA. RP Greenleaf, JE (reprint author), NASA, Gravitat Res Branch 221A2, Lab Human Environm Physiol, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 22 TC 17 Z9 18 U1 0 U2 1 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD DEC PY 1999 VL 70 IS 12 BP 1173 EP 1182 PG 10 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 258VF UT WOS:000083859300005 PM 10596770 ER PT J AU Martin, DS D'Aunno, DS Wood, ML South, DA AF Martin, DS D'Aunno, DS Wood, ML South, DA TI Repetitive high G exposure is associated with increased occurrence of cardiac valvular regurgitation SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE pulmonic insufficiency; tricuspid regurgitation; echocardiography ID MULTIVALVULAR REGURGITATION; PREVALENCE AB Background: Exposure to repeated high +Gz loads and the methods to prevent loss of consciousness cause unique stresses on the cardiovascular system. The purpose of this study was to determine if the +Gz environment is associated with an increased occurrence of valvular regurgitation in pilots of high performance aircraft. Methods: There were 247 subjects who were divided into pilot (n = 46) and non-pilot (n = 201) groups. Pilots were defined as those individuals who had flown at least 1000 h in high performance aircraft. The echocardiographic data of these subjects were examined retrospectively. Results: We found a statistically significant association between pulmonic insufficiency and exposure to high +Gz stress in pilots vs. non-pilots (chi(2) = 13.09, p = 0.0002). In addition, there was a greater incidence of tricuspid regurgitation (chi(2) = 4.97, p = 0.025) and concurrent pulmonic insufficiency and tricuspid regurgitation (chi(2) = 14.1, p = 0.0002) in the pilot group. Conclusions There is a direct relationship between repetitive exposure to a +Gz environment and pulmonic insufficiency, tricuspid regurgitation, or concurrent pulmonic insufficiency and tricuspid regurgitation. This may be secondary to the transient increase in right ventricular pressure due to acceleration forces or straining maneuvers utilized to prevent or postpone +Gz induced loss of consciousness (G-LOC). C1 Wyle Labs, Houston, TX USA. Baylor Coll Med, Natl Space Biomed Res Inst, Houston, TX 77030 USA. RP D'Aunno, DS (reprint author), NASA, Lyndon B Johnson Space Ctr, SD361, Houston, TX 77058 USA. NR 14 TC 11 Z9 16 U1 0 U2 1 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD DEC PY 1999 VL 70 IS 12 BP 1197 EP 1200 PG 4 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 258VF UT WOS:000083859300009 PM 10596774 ER PT J AU Greenleaf, JE Shiraki, K Sagawa, S Miki, K Wada, F Nagaya, K Torii, R Keil, LC AF Greenleaf, JE Shiraki, K Sagawa, S Miki, K Wada, F Nagaya, K Torii, R Keil, LC TI Is the Gauer-Henry reflex important for immersion diuresis in men? SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE euhydration; diuresis; PVP threshold; urine to plasma osmotic ratio ID OUT WATER IMMERSION; ENDOCRINE RESPONSES; PLASMA VASOPRESSIN; DEHYDRATED HUMANS; NONHUMAN PRIMATE; URODILATIN; DRINKING; SUPPRESSION; EXCRETION; VOLUME AB Background: This study examines the relationship between the threshold for plasma vasopressin concentration [PVP] responses and diuresis (Cauer-Henry reflex), and tests the hypothesis that water intake would not influence diuresis. Methods: Eight men (19-25 yr) underwent four treatments: euhydration in air (Eu-air), euhydration in water immersion (Eu-H2O), and with prior 3.6% hypohydration in air (Hypo-air), and hypohydration in immersion (Hypo-H2O). Ad libitum drinking was allowed during the 3-h experimental and 1-h recovery periods. Results: Drinking was greatest during the first 10 min: 3.5 ml . kg(-1) with Hypo-air (450 ml . 3 h(-1)) and only 1.7 ml . kg(-1) (p < 0.05) with Hypo-H2O (235 ml . 3 h(-1)). At 1 h, concomitant [PVP] decreased from a control level of 6.6 +/- 1.5 to 4.0 +/- 1.0 pg . ml(-1) (Delta = 2.6 pg . ml(-1), p < 0.05) with Hypo-air, and from 5.9 +/- 0.6 to 2.3 +/- 0.2 pg . ml(-71) (A = 3.6 pg . ml(-1), p < 0.05) with Hypo-H2O. Urine flow was unchanged from control level (<1.0 ml . min(-1)) with Hypo-air, Hypo-H2O, and Eu-air, but increased to 4-5 ml . min(-1) with Eu-H2O. Neither water intake volume nor urine flow was related to the magnitude of [PVP] depression. Regression of Uosm/Posm ratio on [PVP] and urine flow indicated that [PVP] above 2 pg . ml(-1) did not affect urine flow. Thus, ad libitum water intake in previously hypohydrated subjects did not affect urine flow or the decrease in [PVP]. The threshold [PVP] to initiate significant diuresis was about 2 pg . ml(-1), and significant diuresis can occur with no change in [PVP] maintained at about 1 pg . ml(-1) during immersion in euhydrated subjects. Conclusions: Thus, it appears that the Cauer-Henry reflex is not the major mechanism for immersion-induced diuresis. Clearly, other diuretic factors are also involved. C1 NASA, Gravitat Res Branch 221A2, Lab Human Environm Physiol, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Occupat & Environm Hlth, Sch Med, Dept Physiol, Kitakyushu, Fukuoka 807, Japan. RP Greenleaf, JE (reprint author), NASA, Gravitat Res Branch 221A2, Lab Human Environm Physiol, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 27 TC 5 Z9 7 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD DEC PY 1999 VL 70 IS 12 BP 1201 EP 1205 PG 5 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 258VF UT WOS:000083859300010 PM 10596775 ER PT J AU Payne, DA Mehta, SK Tyring, SK Stowe, RP Pierson, DL AF Payne, DA Mehta, SK Tyring, SK Stowe, RP Pierson, DL TI Incidence of Epstein-Barr virus in astronaut saliva during spaceflight SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE herpesvirus 4; human stress spaceflight ID REPLICATION; LATENCY; STRESS; SPACE; CELLS; BLOOD AB Background: Astronauts experience psychological and physical stresses that may result in reactivation of latent viruses during spaceflight, potentially increasing the risk of disease among crewmembers. Hypothesis: The shedding of Epstein-Barr virus (EBV) in the saliva of astronauts will increase during spaceflight. Methods: A total of 534 saliva specimens were collected from 11 EBV-seropositive astronauts before, during, and after four space shuttle missions. The presence of EBV DNA in saliva, assessed by polymerase chain reaction (PCR), was used to determine shedding patterns before, during, and after spaceflight. Results: EBV DNA was detected more frequently before flight than during (p < 0.001) or after (p < 0.01) flight. No significant difference between the inflight and postflight periods was detected in the frequency of occurrence of EBV DNA. Conclusions: The increased frequency of shedding of EBV before flight suggests that stress levels may be greater before launch than during or after spaceflight. C1 NASA, Life Sci Res Labs, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Texas, Med Branch, Dept Pathol, Galveston, TX 77550 USA. Univ Texas, Med Branch, Dept Microbiol & Immunol, Galveston, TX 77550 USA. Univ Texas, Med Branch, Dept Dermatol, Galveston, TX 77550 USA. Enterprise Advisory Serv Inc, Houston, TX USA. Univ Space Res Assoc, Greenbelt, MD USA. RP Pierson, DL (reprint author), NASA, Life Sci Res Labs, Lyndon B Johnson Space Ctr, Mail Code SD3, Houston, TX 77058 USA. NR 23 TC 49 Z9 51 U1 0 U2 2 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD DEC PY 1999 VL 70 IS 12 BP 1211 EP 1213 PG 3 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 258VF UT WOS:000083859300012 PM 10596777 ER PT J AU Nayagam, V Balasubramaniam, R Ronney, PD AF Nayagam, V Balasubramaniam, R Ronney, PD TI Diffusion flame-holes SO COMBUSTION THEORY AND MODELLING LA English DT Article ID EDGE-FLAMES; TRIPLE-FLAME AB Recent models of straight diffusion flame edges are extended to consider the effect of a curved edge forming the perimeter of an axisymmetric 'hole', where a burning flame surrounds a quenched inner region. For 'free' flame-holes (without a heat sink near the axis), at small Damkohler number (Da), the holes grow if the initial radius is large but shrink if it is small. For large Da, the holes shrink for any initial radius. Thus, free flame-holes are not stable for any Da, which is consistent with experimental observations. When the flame-hole is 'anchored' by a heat sink near to the axis, stationary holes of finite radius can exist for sufficiently high Da, but the solutions revert to 'free' hole behaviour for radii sufficiently larger than the heat sink radius. Based on these results, it is suggested that quasi-stationary flame-holes are not likely to be a common feature of turbulent diffusion flames, except possibly when large lateral gradients of Da are present due to intense vortices passing through the flame front. C1 NASA, Glenn Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. RP Nayagam, V (reprint author), NASA, Glenn Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RI Ronney, Paul/B-4007-2009 OI Ronney, Paul/0000-0002-2779-6438 NR 16 TC 23 Z9 23 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 1364-7830 J9 COMBUST THEOR MODEL JI Combust. Theory Model. PD DEC PY 1999 VL 3 IS 4 BP 727 EP 742 DI 10.1088/1364-7830/3/4/307 PG 16 WC Thermodynamics; Energy & Fuels; Engineering, Chemical; Mathematics, Interdisciplinary Applications SC Thermodynamics; Energy & Fuels; Engineering; Mathematics GA 277JX UT WOS:000084931400007 ER PT J AU Boyle, R Banks, S Cleveland, P Turin, P AF Boyle, R Banks, S Cleveland, P Turin, P TI Design and performance of the HESSI cryostat SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1999 Space Cryogenics Workshop CY JUL 11-12, 1999 CL QUEBEC CITY, CANADA DE space cryogenics; stirling; cryostats; structural supports; adsorbents AB The High Energy Solar Spectroscopic Imager (HESSI) spacecraft, to be launched in July 2000, will be used to observe the Sun with the finest angular and energy resolutions ever achieved from a few keV to hundreds of keV. The spacecraft will use an array of nine germanium (Ge) detectors, each 7.1 cm in diameter and 8.5 cm long, operating at 75 K. The detectors are mounted in a cryostat on a common coldplate, and cooled by a small Stirling-cycle cryocooler. This paper describes the design of the cryostat, special accommodations for the Ge detectors, interfaces with the cryocooler, and thermal performance of the engineering test unit. (C) 2000 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Orbital Sci Corp, Greenbelt, MD 20770 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Boyle, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 3 TC 7 Z9 7 U1 1 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD DEC PY 1999 VL 39 IS 12 BP 969 EP 973 DI 10.1016/S0011-2275(99)00105-8 PG 5 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 291PV UT WOS:000085746000001 ER PT J AU Swift, WL Zagarola, MV Nellis, GF McCormick, JA Sixsmith, H Gibbon, JA AF Swift, WL Zagarola, MV Nellis, GF McCormick, JA Sixsmith, H Gibbon, JA TI Developments in Turbo Brayton technology for low temperature applications SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1999 Space Cryogenics Workshop CY JUL 11-12, 1999 CL QUEBEC CITY, CANADA DE Brayton cycle; space cryogenics; expanders AB A single stage reverse Brayton cryocooler using miniature high-speed turbomachines recently completed a successful space shuttle test flight demonstrating its capabilities for use in cooling the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST). The NICMIOS CryoCooler (NCC) is designed for a cooling load of about 8 W at 65 K, and comprises a closed loop cryocooler coupled to an independent cryogenic circulating loop. Future space applications involve instruments that will require 5-200 mW of cooling at temperatures between 4 and 10 K. This paper discusses the extension of Turbo Brayton technology to meet these requirements. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Creare Inc, Hanover, NH 03755 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Swift, WL (reprint author), Creare Inc, POB 71, Hanover, NH 03755 USA. NR 8 TC 10 Z9 13 U1 1 U2 7 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD DEC PY 1999 VL 39 IS 12 BP 989 EP 995 DI 10.1016/S0011-2275(99)00117-4 PG 7 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 291PV UT WOS:000085746000004 ER PT J AU Roach, PR Helvensteijn, BPM AF Roach, PR Helvensteijn, BPM TI Progress on a microgravity dilution refrigerator SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1999 Space Cryogenics Workshop CY JUL 11-12, 1999 CL QUEBEC CITY, CANADA DE dilution; He-3-He-4 mixtures; space cryogenics AB We have developed a shallow, single-cycle, helium dilution refrigerator that contains rather coarse metal sponge to study the ability to control the location of the liquid helium for microgravity applications. We have tested the refrigerator on the ground while tilting to put the mixing chamber either somewhat above or somewhat below the still. We calculated that the system could be tilted between 5 degrees and 10 degrees in either direction without interrupting the cooling. The initial test of this refrigerator gave cooling to below 0.060 K and operation for tilts of +/-16 degrees. The insights gained from this refrigerator allow the design of a continuously operating version. (C) 2000 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Atlas Sci, Sunnyvale, CA 94086 USA. RP Roach, PR (reprint author), NASA, Ames Res Ctr, MS 244-10, Moffett Field, CA 94035 USA. NR 4 TC 3 Z9 3 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD DEC PY 1999 VL 39 IS 12 BP 1015 EP 1019 DI 10.1016/S0011-2275(99)00116-2 PG 5 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 291PV UT WOS:000085746000008 ER PT J AU Nash, A Shields, P Abbott, R Craig, J Holmes, W AF Nash, A Shields, P Abbott, R Craig, J Holmes, W TI The fast alternative cryogenic experiment testbed SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1999 Space Cryogenics Workshop CY JUL 11-12, 1999 CL QUEBEC CITY, CANADA DE space cryogenics; cryostats; superfluid helium (He II); neon; instrumentation; temperature sensors AB Subsystems for a "proof of concept" cryogenic payload have been developed to demonstrate the ability to accommodate low temperature science investigations within the constraints of the Hitchhiker siderail (HH-S:) carrier on the Space Shuttle. These subsystems include: a hybrid solid neon - superfluid helium cryostat, a multi-channel Versa Modular European (VME) architecture Germanium Resistance Thermometer (GRT) readout and heater control servo system, and a multiple thermal isolation stage "probe" for thermal control of helium samples. The analysis and tests of these subsystems have proven the feasibility of a cryogenic HH-S carrier payload. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Janis Res Co, Wilmington, MA 01887 USA. Ball Aerosp & Technol Corp, Boulder, CO 80306 USA. Swales Aerosp, Pasadena, CA 91107 USA. RP Nash, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD DEC PY 1999 VL 39 IS 12 BP 1029 EP 1035 DI 10.1016/S0011-2275(99)00109-5 PG 7 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 291PV UT WOS:000085746000010 ER PT J AU Ivanov, PC Bunde, A Amaral, LAN Havlin, S Fritsch-Yelle, J Baevsky, RM Stanley, HE Goldberger, AL AF Ivanov, PC Bunde, A Amaral, LAN Havlin, S Fritsch-Yelle, J Baevsky, RM Stanley, HE Goldberger, AL TI Sleep-wake differences in scaling behavior of the human heartbeat: Analysis of terrestrial and long-term space flight data SO EUROPHYSICS LETTERS LA English DT Article ID RATE-VARIABILITY; CIRCADIAN PATTERN; TIME-SERIES; DYNAMICS; FLUCTUATION; COMPLEXITY; ARRHYTHMIA; FAILURE; DEATH; TRIAL AB We compare scaling properties of the cardiac dynamics during sleep and wake periods for healthy individuals, cosmonauts during orbital flight, and subjects with severe heart disease. For all three groups, we find a greater degree of anticorrelation in the heartbeat fluctuations during sleep compared to wake periods. The sleep-wake difference in the scaling exponents for the three groups is comparable to the difference between healthy and diseased individuals. The observed scaling differences are not accounted for simply by different levels of activity, but appear related to intrinsic changes in the neuroautonomic control of the heartbeat. C1 Boston Univ, Ctr Polymer Studies, Boston, MA 02215 USA. Boston Univ, Dept Phys, Boston, MA 02215 USA. Harvard Univ, Beth Israel Deaconess Med Ctr, Sch Med, Div Cardiovasc, Boston, MA 02215 USA. Univ Giessen, Inst Theoret Phys 3, Giessen, Germany. Bar Ilan Univ, Gonda Goldschmid Ctr, Ramat Gan, Israel. Bar Ilan Univ, Dept Phys, Ramat Gan, Israel. NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Minist Publ Hlth Russia, Inst Biomed Problems, Moscow, Russia. RP Ivanov, PC (reprint author), Boston Univ, Ctr Polymer Studies, Boston, MA 02215 USA. RI Amaral, Luis/A-4980-2008; Amaral, Luis N./C-5485-2009; Ivanov, Plamen /E-8004-2012 OI Amaral, Luis/0000-0002-3762-789X; FU NCRR NIH HHS [P41 RR13622] NR 34 TC 163 Z9 166 U1 0 U2 3 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0295-5075 J9 EUROPHYS LETT JI Europhys. Lett. PD DEC PY 1999 VL 48 IS 5 BP 594 EP 600 DI 10.1209/epl/i1999-00525-0 PG 7 WC Physics, Multidisciplinary SC Physics GA 260GA UT WOS:000083940100020 PM 11542917 ER PT J AU Brodeur, RD Mills, CE Overland, JE Walters, GE Schumacher, JD AF Brodeur, RD Mills, CE Overland, JE Walters, GE Schumacher, JD TI Evidence for a substantial increase in gelatinous zooplankton in the Bering Sea, with possible links to climate change SO FISHERIES OCEANOGRAPHY LA English DT Article DE Bering Sea; ecosystem change; physical-biological coupling; scyphomedusae ID SCYPHOMEDUSAN CHRYSAORA-QUINQUECIRRHA; PELAGIC CNIDARIANS; CHESAPEAKE BAY; ICE-EDGE; PREDATION; CTENOPHORES; POPULATIONS; ECOSYSTEMS; TEMPERATURE; PACIFIC AB We examined quantitative catches of large medusae from summer bottom trawl surveys that sampled virtually the same grid station on the eastern Bering Sea shelf using the same methodology every year from 1979 to 1997. This series shows a gradual increase in biomass of medusae from 1979 to 1989, followed by a dramatic increase in the 1990s. The median biomass increased tenfold between the 1982-1989 and 1990-1991 periods. Most of this biomass was found within the Middle Shelf Domain (50 < z < 100 m). The greatest rate of increase occurred in the north-west portion of this domain. Whether this dramatic increase in biomass of gelatinous zooplankton has resulted from some anthropogenic perturbation of the Bering Sea environment or is a manifestation of natural ecosystem variability is unclear. However, several large-scale winter/spring atmospheric and oceanographic variables in the Bering Sea exhibited concomitant changes beginning around 1990, indicating that a possible regime change occurred at this time. C1 Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Seattle, WA 98115 USA. Univ Washington, Friday Harbor Labs, Friday Harbor, WA 98250 USA. NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. Two Crow Environm Consultants, Silver City, NM 88062 USA. RP Brodeur, RD (reprint author), Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, 2030 Marine Sci Dr, Newport, OR 97365 USA. NR 68 TC 158 Z9 172 U1 3 U2 39 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 1054-6006 J9 FISH OCEANOGR JI Fish Oceanogr. PD DEC PY 1999 VL 8 IS 4 BP 296 EP 306 DI 10.1046/j.1365-2419.1999.00115.x PG 11 WC Fisheries; Oceanography SC Fisheries; Oceanography GA 273AW UT WOS:000084684500006 ER PT J AU Demirkol, MK Inan, US Bell, TF Kanekal, SG Wilkinson, DC AF Demirkol, MK Inan, US Bell, TF Kanekal, SG Wilkinson, DC TI Ionospheric effects of relativistic electron enhancement events SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID VLF SIGNALS; WAVE-GUIDE; PRECIPITATION; SOLAR AB The relativistic electron population as measured both at geosynchronous orbit and at low altitudes at subauroral latitudes exhibits pronounced fluctuations in association with magnetospheric substorm and solar activity. A ground-satellite correlative study based on amplitude and phase measurements of VLF signals propagating in the earth-ionosphere waveguide indicates that the relativistic electron enhancements are accompanied bq similar enhancements in nighttime ionospheric conductivity produced by associated enhanced precipitation. VLF signal amplitudes are found to exhibit >10 dB changes, showing the same 27 day cycle and 2-3 day rise and fall time pattern as relativistic electron enhancement events recorded by GOES 7 and SAMPEX, and indicating that the nighttime lower ionospheric electron density at subauroral latitudes is detectably affected by 27-day periodicity in solar rotation. C1 Stanford Univ, Space Telecommun & Radiosci Lab, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Geophys Data Ctr, Boulder, CO 80303 USA. RP Demirkol, MK (reprint author), Stanford Univ, Space Telecommun & Radiosci Lab, Stanford, CA 94305 USA. NR 15 TC 13 Z9 13 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 1 PY 1999 VL 26 IS 23 BP 3557 EP 3560 DI 10.1029/1999GL010686 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 261LN UT WOS:000084010800034 ER PT J AU Preston, CML Hill, DJT Pomery, PJ Whittaker, AK Jensen, BJ AF Preston, CML Hill, DJT Pomery, PJ Whittaker, AK Jensen, BJ TI Thermal and radiation curing of phenylethynyl terminated macromers SO HIGH PERFORMANCE POLYMERS LA English DT Article ID GLASS-TRANSITION; TEMPERATURE; CURE; POLYIMIDES AB The thermal and gamma-irradiation induced curing of two phenylethynyl terminated composite resin systems, DFB/BPF and PETI5A, was investigated. Thermal curing of these matrix resin samples was performed at a temperature of 360 degrees C, gamma irradiation of the samples was conducted at 300 degrees C at a dose rate of 2.2 kGy h(-1). The reaction and subsequent loss of ethynyl groups in the resins for both cure methods was demonstrated by observing the decrease of the 2215 cm(-1) peak in the Raman spectra of the resins. Fully cured resin samples were found to have glass transition temperatures of 244-246 degrees C and 278-280 degrees C for DFB/BPF and PETI5A respectively. Similar relationships between T-g and fractional conversion were observed in both resins. The apparent polymerization rate, R-p, for thermal cure at 360 degrees C, was found to be 4.79 x 10(-2)% s(-1) in PETI5A and 3.22 x 10(-2)% s(-1) in DFB/BPF. Catastrophic degradation under nitrogen was observed to commence near 450 degrees C and 530 degrees C, with 5% weight losses occurring at 455 degrees C and 540 degrees C for DFB/BPF and PETI5A respectively. Gamma radiation induced cure at 300 degrees C was shown to be feasible, with full cure being reached with doses of 40 kGy for DFB/BPF and 100 kGy for PETI5A. C1 Univ Queensland, Dept Chem, Polymer Mat & Radiat Grp, St Lucia, Qld 4067, Australia. Univ Queensland, Ctr magnet Resonance, St Lucia, Qld 4067, Australia. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Hill, DJT (reprint author), Univ Queensland, Dept Chem, Polymer Mat & Radiat Grp, St Lucia, Qld 4067, Australia. RI Preston, Christopher/H-5709-2013; Whittaker, Andrew/E-6172-2011 OI Whittaker, Andrew/0000-0002-1948-8355 NR 20 TC 7 Z9 7 U1 0 U2 4 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD DEC PY 1999 VL 11 IS 4 BP 453 EP 465 DI 10.1088/0954-0083/11/4/309 PG 13 WC Polymer Science SC Polymer Science GA 268LW UT WOS:000084418700009 ER PT J AU Little, B Anger, CD Ingersoll, AP Vasavada, AR Senske, DA Breneman, HH Borucki, WJ AF Little, B Anger, CD Ingersoll, AP Vasavada, AR Senske, DA Breneman, HH Borucki, WJ CA Galileo SSI Team TI Galileo images of lightning on Jupiter SO ICARUS LA English DT Article DE atmosphere dynamics; Jupiter atmosphere; meteorology ID WATER CLOUD; GENERATION; ATMOSPHERE; FLOW AB In October and November of 1997 the Galileo Solid State Imager (SSI) detected lightning from 26 storms on the night side of Jupiter, More than half the surface area of the planet was surveyed. The data include images of lightning against moonlit clouds (illuminated by light from Io) and images of the same storm on the day and night sides. The spatial resolution ranged from 23 to 134 km per pixel, while the storms ranged in size up to similar to 1500 km, Most storms were imaged more than once, and they typically exhibit many flashes per minute. The storms occur only in areas of cyclonic shear and near the centers of westward jets. Latitudes near 50 degrees in both hemispheres are particularly active, although the northern hemisphere has more lightning overall. The greatest optical energy observed in a single flash was 1.6 x 10(10) J, which is several times larger than terrestrial superbolts. The average optical power per unit area is 3 x 10(-7) W m(-2), which is close to the terrestrial value. The limited color information is consistent with line and continuum emission from atomic hydrogen and helium, The intensity profiles of resolved lightning strikes are bell-shaped, with the half-width at half-maximum ranging from similar to 45 to 80 km, We used these widths to infer the depth of the strikes, assuming that the appearance of each is the result of light scattering from a point source below the cloud-tops. We conclude that lightning must be occurring within or below the jovian water cloud. The occurrence of lightning in regions of cyclonic shear has important implications for the dynamics of Jupiter's atmosphere. (C) 1999 Academic Press. C1 ITRES Res, Calgary, AB T1Y 5Z6, Canada. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Little, B (reprint author), ITRES Res, Suite 155,E Atrium,2635 37th Ave NE, Calgary, AB T1Y 5Z6, Canada. EM blane@itres.com NR 34 TC 65 Z9 65 U1 1 U2 2 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 EI 1090-2643 J9 ICARUS JI Icarus PD DEC PY 1999 VL 142 IS 2 BP 306 EP 323 DI 10.1006/icar.1999.6195 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277TR UT WOS:000084950100001 ER PT J AU Edgington, SG Atreya, SK Trafton, LM Caldwell, JJ Beebe, RF Simon, AA West, RA AF Edgington, SG Atreya, SK Trafton, LM Caldwell, JJ Beebe, RF Simon, AA West, RA TI Ammonia and eddy mixing variations in the upper troposphere of Jupiter from HST Faint Object Spectrograph observations SO ICARUS LA English DT Article DE Jupiter, atmosphere; photochemistry; radiative transfer; spectroscopy; ultraviolet observations ID GREAT RED SPOT; UPPER-ATMOSPHERE; HIGH-RESOLUTION; PH3; STRATOSPHERE; ULTRAVIOLET; DYNAMICS; PLANETS; MODEL; NH3 AB Ultraviolet spectra of the northern and southern hemispheres of Jupiter taken with the Hubble Space Telescope Faint Object Spectrograph (FOS) in May 1992 and June 1993 have been used to derive the altitude profiles of NH3 in the vicinity of the tropopause. For a given pressure level, it is shown that the vertical profile of ammonia varies with latitude and the atmospheric feature being observed. The mixing ratio of ammonia present above the Great Red Spot (GRS) is 8 x 10(-8) at 250 mbar, whereas it is four times greater in the nearby South Equatorial Belt at the same pressure level. Our findings agree with those of C. A. Griffith, B. Bezard, T. Owen, and D. Gautier (1992, Icarus 98, 82-93), who find NH3 to be depleted over the GRS with respect to the South Tropical Zone at the time of the Voyager encounters. Variations of the ammonia mixing ratio in the northern and southern hemispheres are found to be nonnonotonic in latitude, indicating local dynamical effects. The observed latitudinal variation of the altitude profile of NH3 is likely to be caused by variations in the vertical eddy mixing (K), which competes with the photolysis and condensation losses of NH3. We also find this vertical mixing to be nonmonotonic with latitude. Instead, it shows high variability depending on the region and feature observed, consistent with the values of eddy mixing derived by L.-M. Lara, B. Bezard, C. A. Giffith, J. H. Lacy, and T. Owen (1998, Icarus 131, 317-333). Values at 13 degrees N, 18 degrees N, at the equator, and over the Great Red Spot region range between 3 and 10 x 10(3) cm(2) s(-1) at 250 mbar, while weaker mixing occurs at 20 degrees S, 33 degrees S, and 7 degrees N (<1 x 10(3) cm(2) s(-1) at 250 mbar). Typically, the eddy mixing profiles have a ledge-like vertical structure, where a large mixing coefficient is required below the photolysis region (p greater than or equal to 300 mbar), followed by a drop to a minimum as we proceed to lower pressures, and finally an increase again with decreasing pressure. In this paper, we also update our previous results on NH3 and K following the recalibration of the FOS data using the most recent recommendations of the Space Telescope Science Institute. (C) 1999 Academic Press. C1 Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Texas, McDonald Obser, Austin, TX 78712 USA. York Univ, Dept Phys & Astron, N York, ON M35 1P3, Canada. New Mexico State Univ, Dept Astron, Las Cruces, NM 88033 USA. RP Edgington, SG (reprint author), CALTECH, Jet Prop Lab, M-S 169-237,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Simon, Amy/C-8020-2012 OI Simon, Amy/0000-0003-4641-6186 NR 23 TC 18 Z9 18 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1999 VL 142 IS 2 BP 342 EP 356 DI 10.1006/icar.1999.6228 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277TR UT WOS:000084950100003 ER PT J AU Doute, S Schmitt, B Quirico, E Owen, TC Cruikshank, DP de Bergh, C Geballe, TR Roush, TL AF Doute, S Schmitt, B Quirico, E Owen, TC Cruikshank, DP de Bergh, C Geballe, TR Roush, TL TI Evidence for methane segregation at the surface of Pluto SO ICARUS LA English DT Article DE Pluto, surface; ices; spectrophotometry; Charon; radiative transfer ID THERMAL STRUCTURE; NITROGEN ICE; WATER FROST; ATMOSPHERE; CHARON; TRITON; N-2; SPECTROSCOPY; TEMPERATURE; CONSTRAINTS AB In May 1995, a set of spectrophotometric curves of the system Pluto-Charon were recorded with the UKIRT telescope equipped with the spectrometer CGS4, The spectra cover the near-infrared range between 1.4 and 2.55 mu m with a resolution of approximately 700, The existence of solid methane is confirmed by numerous absorption bands, and carbon monoxide and nitrogen ices are identified by their respective signatures at 2.35 and 2.15 mu m. We have modeled the spectrum of May 15 that corresponds to the maximum of Pluto's visible lightcurve using a radiative transfer algorithm dealing with compact and stratified media. A geographical mixture of three distinct units is required to explain all the significant structures of the analyzed spectrum. The first unit is a thin, fine-grained layer of pure CH4 covering a compact polycrystalline substratum of N-2-CH4-CO, which are in a molecular mixture (concentrations of CH4 and CO of the order of 0.5 and 0.1-0.2% respectively). It covers about 70% of the observed area and corresponds to volatile deposits that are sublimating under solar illumination. The second unit is either (a) a single thick layer of pure large-grained methane or (6) a unit with large-grained CH4 forming a substratum and the N-2-CH4-CO mixture a superficial layer of fine grains covering 20% of the surface. Finally, the third unit is bright and spectrally neutral and is first modeled as a layer of very fine grains of nearly pure N-2. Tholin, suggested to explain the red slope in the visible, is also found to be spectrally compatible with this unit. It covers the remainder of the surface (about 10-15%). All these results allow a better understanding of the processes of deposition, metamorphism, sublimation, and transport affecting the different ices detected on Pluto during its climatic cycles. (C) 1999 Academic Press. C1 Lab Glaciol & Geophys Environm, F-38402 St Martin Dheres, France. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Observ Paris, F-92195 Meudon, France. Joint Astron Ctr, Hilo, HI 96720 USA. San Francisco State Univ, Moffett Field, CA 94035 USA. RP Doute, S (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, 405 Hilgard,Box 951567, Los Angeles, CA 90095 USA. RI Schmitt, Bernard/A-1064-2009; quirico, eric/K-9650-2013 OI Schmitt, Bernard/0000-0002-1230-6627; quirico, eric/0000-0003-2768-0694 NR 45 TC 98 Z9 98 U1 0 U2 5 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1999 VL 142 IS 2 BP 421 EP 444 DI 10.1006/icar.1999.6226 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277TR UT WOS:000084950100008 ER PT J AU Lazzaro, D Mothe-Diniz, T Carvano, JM Angeli, CA Betzler, AS Florczak, M Cellino, A Di Martino, M Doressoundiram, A Barucci, MA Dotto, E Bendjoya, P AF Lazzaro, D Mothe-Diniz, T Carvano, JM Angeli, CA Betzler, AS Florczak, M Cellino, A Di Martino, M Doressoundiram, A Barucci, MA Dotto, E Bendjoya, P TI The Eunomia family: A visible spectroscopic survey SO ICARUS LA English DT Article DE asteroids; asteroids, composition; spectroscopy; surfaces, asteroids ID IMPROVED SEMIEMPIRICAL MODEL; ASTEROID FAMILIES; MAIN-BELT; LABORATORY EXPERIMENTS; COLLISIONAL EVOLUTION; PARENT BODY; NEAR-EARTH; RESONANCES; SPECTRA; IMPACT AB We observed 44 Eunomia family members at ESO (European Southern Observatory) and at CASLEO (Complejo Astronomico El Leoncito) in the wavelength range of 4900-9200 Angstrom. We found 41 objects with the same characteristics: a maximum around lambda = 7500 Angstrom, and a reflectivity gradient spanning a continuous but limited range. Only 3 objects display featureless spectra similar to C-type asteroids, and these should be considered as interlopers, The spectra of the 41 objects show a similarity which is consistent with the dynamical hypothesis of a common origin. On the other hand, the spread of distribution of surface composition also indicates that the Eunomia family was possibly formed from the fragmentation of a partially differentiated S-type parent body. (C) 1999 Academic Press. C1 Observ Nacl, Dept Astrofis, BR-20921 Rio De Janeiro, Brazil. CEFET PR, Dept Fis, BR-80000 Curitiba, Parana, Brazil. Osservatorio Astron Torino, I-10025 Pino Torinese, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Observ Paris, F-92195 Meudon, France. Univ Nice, F-06108 Nice 2, France. RP Lazzaro, D (reprint author), Observ Nacl, Dept Astrofis, BR-20921 Rio De Janeiro, Brazil. RI Mothe-Diniz, Thais/B-8987-2011; Lazzaro, Daniela/I-3509-2012; Cellino, Alberto/N-1570-2015; Ferreira Carvano, Jorge/I-4039-2016; OI Lazzaro, Daniela/0000-0002-4470-6043; Cellino, Alberto/0000-0002-6645-334X; Ferreira Carvano, Jorge/0000-0003-0670-639X; Dotto, Elisabetta/0000-0002-9335-1656 NR 53 TC 22 Z9 22 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1999 VL 142 IS 2 BP 445 EP 453 DI 10.1006/icar.1999.6213 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277TR UT WOS:000084950100009 ER PT J AU Weaver, HA Chin, G Bockelee-Morvan, D Crovisier, J Brooke, TY Cruikshank, DP Geballe, TR Kim, SJ Meier, R AF Weaver, HA Chin, G Bockelee-Morvan, D Crovisier, J Brooke, TY Cruikshank, DP Geballe, TR Kim, SJ Meier, R TI An infrared investigation of volatiles in Comet 21P/Giacobini-Zinner SO ICARUS LA English DT Article DE comets; composition ID NARROW-BAND PHOTOMETRY; HALE-BOPP C/1995-O1; GIACOBINI-ZINNER; MU-M; WATER; EMISSION; SPECTRUM; HYAKUTAKE; MOLECULES; P/HALLEY AB We obtained high resolution (lambda/delta lambda similar to 10,00-20,000) infrared (IR) spectra of Comet 21P/Giacobini-Zinner (GZ) at five different wavelengths between 1.9 and 5.0 mu m during 25-29 October 1998 using CSHELL at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. We also obtained a moderate resolution (lambda/delta lambda similar to 680) spectrum covering the wavelength range from 3.082 to 3.720 mu m on 29 October 1998 using CGS4 at the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea. Five rovibrational lines in three different vibrational bands of H(2)O were detected in the CSHELL spectra. Assuming that the rotational temperature was similar to 50 K, we derive a H(2)O production rate of similar to 2-3 x 10(28) molecules s(-1), which is similar to 2 times smaller than the value derived from nearly simultaneous radio observations of OH. After continuum subtraction, the CGS4 spectrum displays significant excess flux that we attribute mainly to CH(3)OH fluorescence, and we derive that the CH(3)OH production rate was similar to 2.7 x 10(26) molecules s(-1). The corresponding CH(2)OH/H(2)O relative abundance is similar to 0.9-1.4%, which falls within the range of values observed in other comets, albeit at the low end. The CGS4 spectrum also has significant excess flux near 3.43 mu m that is not explained by our CH(3)OH fluorescence model; a similar feature has been observed in several other comets, but its origin remains a mystery We did not detect any excess emission near 3.28 mu m, where some comets show a feature that may be associated with polycyclic aromatic hydrocarbons. We also searched for emissions from C(2)H(6), CO, HCN, C(2)H(2), and H(2)CO but did not detect any of these molecules. The 3 sigma upper limits for the abundances relative to H(2)O are 0.05-0.08% far C(2)H(6), 2-3% for CO, 0.2-0.3% for HCN, 0.3-0.4% for C(2)H(2), and 0.5-0.8% for H(2)CO, assuming that all species are parent molecules and that their rotational temperature in the coma is 50 K. C(2)H(6) is depleted by a factor of similar to 15 or more compared to its relative abundance in Comets Hale-Bopp (C/1995 O1) and Hyakutake (C/1996 B2); this depletion is similar to that observed for C(2) and C(3) from optical observations of GZ (A'Hearn et al. 1995) and suggests that the formation of volatile carbon-chain molecules was inhibited in GZ. We are unable to find any clear correlation between the C(2)H(6) and the C(2) and C(3) abundances in a sample of nine other comets, assuming that the residual emission near 3.35 mu m in moderate resolution spectra of seven of the comets provides an accurate indicator of the C(2)H(6) abundance. However, this latter assumption is questionable and highlights the need to obtain high spectral resolution data in order to make accurate abundance measurements of C(2)H(6). (C) 1999 Academic Press. C1 Johns Hopkins Univ, Dept Phys & Astron, Ctr Astrophys Sci, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Planetary Syst Branch, Greenbelt, MD 20771 USA. Observ Meudon Paris, F-92195 Meudon, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Gemini Observ, Hilo, HI 96720 USA. Kyung Hee Univ, Inst Nat Sci, Kyunggido 449701, South Korea. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. RP Weaver, HA (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Ctr Astrophys Sci, 3400 N Charles St, Baltimore, MD 21218 USA. EM weaver@pha.jhu.edu RI Chin, Gordon/E-1520-2012; Kim, Sang Joon/E-2383-2013; Weaver, Harold/D-9188-2016 NR 50 TC 38 Z9 38 U1 0 U2 3 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1999 VL 142 IS 2 BP 482 EP 497 DI 10.1006/icar.1999.6218 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277TR UT WOS:000084950100013 ER PT J AU Magee-Sauer, K Mumma, MJ DiSanti, MA Dello Russo, N Rettig, TW AF Magee-Sauer, K Mumma, MJ DiSanti, MA Dello Russo, N Rettig, TW TI Infrared spectroscopy of the nu(3) band of hydrogen cyanide in Comet C/1995 O1 Hale-Bopp SO ICARUS LA English DT Article DE comets, Hale-Bopp; composition; infrared observations; hydrogen cyanide ID GIOTTO SPACECRAFT ENCOUNTER; MONTE-CARLO SIMULATION; MILLIMETER WAVELENGTHS; PLANETARY-ATMOSPHERES; EXCITATION CONDITIONS; RADIO OBSERVATIONS; PARENT MOLECULES; EXTENDED SOURCE; B2 HYAKUTAKE; P-HALLEY AB Hydrogen cyanide (HCN) was detected in Comet Hale-Bopp at infrared wavelengths near 3.0 mu m on four dates between Feb 24.0 and May 1.0 1997 using high-resolution spectroscopy, The average rotational temperature retrieved far the (001) vibrational level on UT 1997 April 29.9 was (95 +/- 6) K near the nucleus, increasing to (122 +/- 8) K in the intermediate coma (4"-10" off the nucleus). The HCN production rate on April 29.9 was (3.09 +/- 0.13) x 10(28) molecules s(-1). When compared with the water production rate obtained from direct measurements of the H2O 100-010 band on common observation dates using the same instrument and data processing algorithms, the weighted average (for the four dates) of the relative abundance (HCN/H2O) was (0.40 +/- 0.05)%. The measured spatial distribution for HCN is consistent with its release at the nucleus--no significant contribution from a distributed source is required within 10,000 km of the nucleus, (C) 1999 Academic Press. C1 Rowan Coll, Dept Chem & Phys, Glassboro, NJ 08028 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Univ Notre Dame, Dept Phys & Astron, Notre Dame, IN 46556 USA. RP Magee-Sauer, K (reprint author), Rowan Coll, Dept Chem & Phys, Glassboro, NJ 08028 USA. RI mumma, michael/I-2764-2013; Magee-Sauer, Karen/K-6061-2015; Dello Russo, Neil/G-2727-2015 OI Magee-Sauer, Karen/0000-0002-4979-9875; Dello Russo, Neil/0000-0002-8379-7304 NR 76 TC 72 Z9 73 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1999 VL 142 IS 2 BP 498 EP 508 DI 10.1006/icar.1999.6215 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277TR UT WOS:000084950100014 ER PT J AU Dones, L Gladman, B Melosh, HJ Tonks, WB Levison, HF Duncan, M AF Dones, L Gladman, B Melosh, HJ Tonks, WB Levison, HF Duncan, M TI Dynamical lifetimes and final fates of small bodies: Orbit integrations vs Opik calculations SO ICARUS LA English DT Article DE asteroids; dynamics; celestial mechanics; comets, dynamics; meteoroids; orbits ID SHORT-PERIOD COMETS; EARTH-APPROACHING ASTEROIDS; SEMIMAJOR AXES SMALLER; TERRESTRIAL PLANET ACCUMULATION; MARTIAN METEORITE DELIVERY; LINEAR SECULAR RESONANCES; MAIN-BELT ASTEROIDS; OUTER SOLAR-SYSTEM; CLOSE ENCOUNTERS; IMPACT EJECTA AB The dynamical lifetimes of small bodies against ejection from the Solar System or collision with the Sun or a planet are often estimated by Monte Carlo codes based on the equations of Opik and using a method implemented by Arnold. Such algorithms assume that orbital changes are dominated by close encounters, and that successive encounters are uncorrelated, We have compared the results of an Opik code (H. J. Melosh and W. B, Tonks, Meteoritics 28, 398 (1993)) and a fast integrator (H, F. Levison and M, J, Duncan, Icarus 108, 18 (1994)) to investigate the regimes of validity of the Opik-Arnold approach, We investigate the transfer of ecliptic comets from Neptune-crossing orbits to observable Jupiter-family comets, the dynamics of Halley-type comets, and the transport of meteorites among the terrestrial planets, In all cases, the Opik code overestimates the median lifetime of the small bodies, although both codes show a rapid initial loss of objects followed by a slow decay, For martian impact ejecta, some of which find their way to Earth as the SNC meteorites, the Opik code substantially overestimates lifetimes because of its neglect of secular resonances, which rapidly pump eccentricities (B, J, Gladman ed at, Science 271, 1387 (1996)). (C) 1999 Academic Press. C1 San Jose State Univ Fdn, NASA, Moffett Field, CA 94035 USA. Observ Nice, Dept Cassini, F-06304 Nice 4, France. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Ricks Coll, Dept Phys, Rexburg, ID 83460 USA. SW Res Inst, Space Studies Dept, Boulder, CO 80302 USA. Queens Univ, Dept Phys, Kingston, ON K7L 3N6, Canada. RP Dones, L (reprint author), SW Res Inst, Space Studies Dept, 1050 Walnut St,Suite 426, Boulder, CO 80302 USA. RI Levison, Harold/C-6061-2013 OI Levison, Harold/0000-0001-5847-8099 NR 97 TC 40 Z9 40 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1999 VL 142 IS 2 BP 509 EP 524 DI 10.1006/icar.1999.6220 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 277TR UT WOS:000084950100015 ER PT J AU DiNardo, GT Wetherall, JA AF DiNardo, GT Wetherall, JA TI Accounting for uncertainty in the development of harvest strategies for the Northwestern Hawaiian Islands lobster trap fishery SO ICES JOURNAL OF MARINE SCIENCE LA English DT Article; Proceedings Paper CT ICES Symposium on Confronting Uncertainty in the Evaluation and Implementation of Fisheries-Management Systems CY NOV 16-19, 1998 CL UNIV CAPE TOWN, GRAD SCH BUSINESS, CAPE TOWN, SOUTH AFRICA SP Int Council Explorat Sea, European Comm, Fdn Res Dev SA, Irvin & Johnson Ltd SA, Int Ctr Living Aquat Resources, Int Fishmeal & Oil Manufactures Assoc, Marine & Coastal Management, S African Network Coastal & Ocean Res, Suidor Fishing Pty Ltd SA, UN Food & Agr Org, Univ Cape Town HO UNIV CAPE TOWN, GRAD SCH BUSINESS DE lobster trap fishery; risk-based harvest strategies; simulation model ID SPINY LOBSTER; RECRUITMENT AB The development of a new, risk-averse harvest policy for the Northwestern Hawaiian Islands lobster trap fishery, based on computer simulations, is described. The analysis results from a 1994 expert panel review recommendation to develop a new harvesting strategy that incorporated uncertainty in the stock assessment and variability in population processes, with the dual goals of achieving industry objectives (high average catch and catch stability) and low risk of recruitment overfishing. Monte Carlo projections of an age-based simulation model which allows for systematic, process, random and measurement error, as well as autocorrelation in recruitment innovations, were used to compare harvesting strategies and to assess their effects relative to the risk of overfishing over a range of discard mortality and retention scenarios. The expected effects of alternative strategies and consequences of uncertainty were presented to the Western Pacific Regional Fishery Management Council for evaluation, and a constant harvest rate strategy, subject to a 10% overfishing risk, was chosen. Because of the presumed high rate of discard mortality in the fishery, which has since been verified, the Council also chose a retain-all retention policy. The constant harvest rate associated with these objectives is 13%. (C) 1999 International Council for thr Exploration of the Sea. C1 Natl Marine Fisheries Serv, Honolulu Lab, SW Fisheries Sci Ctr, NOAA, Honolulu, HI 96822 USA. RP DiNardo, GT (reprint author), Natl Marine Fisheries Serv, Honolulu Lab, SW Fisheries Sci Ctr, NOAA, 2570 Dole St, Honolulu, HI 96822 USA. NR 10 TC 6 Z9 9 U1 0 U2 2 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1054-3139 J9 ICES J MAR SCI JI ICES J. Mar. Sci. PD DEC PY 1999 VL 56 IS 6 BP 943 EP 951 DI 10.1006/jmsc.1999.0543 PG 9 WC Fisheries; Marine & Freshwater Biology; Oceanography SC Fisheries; Marine & Freshwater Biology; Oceanography GA 285MH UT WOS:000085392500015 ER PT J AU Burke, KA AF Burke, KA TI High energy density regenerative fuel cell systems for terrestrial applications SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article AB Regenerative Fuel. Cell System (RFCS) technology for energy storage has been a NASA power system concept for many years. Compared to battery-based energy storage systems, RFCS has received relatively little attention or resources for development because the energy density and electrical efficiency were not sufficiently attractive relative to advanced battery systems. Even today, RFCS remains at a very low technology readiness level (TRL of about 2 indicating feasibility has been demonstrated). Commercial development of the Proton Exchange Membrane (PEM) fuel cells for automobiles and other terrestrial applications and improvements in lightweight pressure vessel design to reduce weight and improve performance make possible a high energy density RFCS energy storage system. The results from this study of a lightweight RFCS energy storage system for a remotely piloted, solar-powered, high altitude aircraft indicate an energy density up to 790 wh/kg with electrical efficiency of 53.4% is attainable. Such an energy storage system would allow a solar-powered aircraft to carry hundreds of kilograms of payload and remain in flight indefinitely for use in atmospheric research, Earth observation, resource mapping, and telecommunications. Future developments in the areas of hydrogen and oxygen storage, pressure vessel design, higher temperature and higher pressure fuel cell operation, unitized regenerative fuel cells, and commercial development of fuel cell technology will improve both the energy density and electrical efficiency of the RFCS. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Burke, KA (reprint author), NASA, Glenn Res Ctr, 21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 3 TC 5 Z9 6 U1 1 U2 10 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD DEC PY 1999 VL 14 IS 12 BP 23 EP 34 DI 10.1109/62.811091 PG 12 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA 265YZ UT WOS:000084275000006 ER PT J AU Gawronski, W Gudim, MA AF Gawronski, W Gudim, MA TI Design and performance of the monopulse control system SO IEEE ANTENNAS AND PROPAGATION MAGAZINE LA English DT Article DE servosystems; space vehicle tracking; monopulse radar; monopulse antenna AB Ka-band (32 GHz) monopulse tracking has been chosen for the upcoming NASA missions. This decision requires an increased pointing accuracy for the Deep Space Network antenna servo systems that can be maintained in a noisy environment. The noise sources include wind gusts, encoder imperfections, and receiver noise. This article describes the selection of the position and monopulse controllers for the improved tracking accuracy, and presents the results of linear and non-linear simulations to confirm that servo performance will meet the requirements. C1 CALTECH, Jet Prop Lab, Commun Ground Syst Sect, Pasadena, CA 91109 USA. RP Gawronski, W (reprint author), CALTECH, Jet Prop Lab, Commun Ground Syst Sect, 4800 Oak Grove Dr,M-S 238-528, Pasadena, CA 91109 USA. NR 7 TC 2 Z9 2 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1045-9243 J9 IEEE ANTENNAS PROPAG JI IEEE Antennas Propag. Mag. PD DEC PY 1999 VL 41 IS 6 BP 40 EP 50 DI 10.1109/74.815317 PG 11 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 272BL UT WOS:000084630600005 ER PT J AU Joshi, SS AF Joshi, SS TI The need for a systems perspective in control theory and practice SO IEEE CONTROL SYSTEMS MAGAZINE LA English DT Article ID FLEXIBLE SPACECRAFT; CONTROL DESIGN; OPTIMIZATION C1 CALTECH, Jet Prop Lab, Guidance & Control Anal Grp, Pasadena, CA 91109 USA. RP Joshi, SS (reprint author), CALTECH, Jet Prop Lab, Guidance & Control Anal Grp, 4800 Oak Grove Dr,MS 198-326, Pasadena, CA 91109 USA. NR 34 TC 3 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0272-1708 J9 IEEE CONTR SYST MAG JI IEEE Control Syst. Mag. PD DEC PY 1999 VL 19 IS 6 BP 56 EP 63 DI 10.1109/37.806917 PG 8 WC Automation & Control Systems SC Automation & Control Systems GA 258ZL UT WOS:000083869500007 ER PT J AU McInroy, JE Neat, GW O'Brien, JF AF McInroy, JE Neat, GW O'Brien, JF TI A robotic approach to fault-tolerant, precision pointing SO IEEE ROBOTICS & AUTOMATION MAGAZINE LA English DT Article DE pointing; fault tolerance; hexapod; Stewart platform; Gough platform; vibration isolation ID SYSTEM AB A novel strategy for meeting precision pointing requirements of applications such as deep-space laser communications and next-generation telescopes. C1 Univ Wyoming, Laramie, WY 82071 USA. Jet Propuls Lab, Interferometry Syst & Technol Sect, Pasadena, CA USA. RP McInroy, JE (reprint author), Univ Wyoming, Box 3295, Laramie, WY 82071 USA. NR 17 TC 8 Z9 9 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1070-9932 J9 IEEE ROBOT AUTOM MAG JI IEEE Robot. Autom. Mag. PD DEC PY 1999 VL 6 IS 4 BP 24 EP + DI 10.1109/100.813824 PG 9 WC Automation & Control Systems; Robotics SC Automation & Control Systems; Robotics GA 270RA UT WOS:000084548500004 ER PT J AU Gerke, RD Kromann, GB AF Gerke, RD Kromann, GB TI Solder joint reliability of high I/O ceramic-ball-grid arrays and ceramic quad-flat-packs in computer environments: The PowerPC 603 (TM) and PowerPC 604 (TM) microprocessors SO IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES LA English DT Article; Proceedings Paper CT 6th Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems CY MAY 27-30, 1998 CL SEATTLE, WASHINGTON SP Components, Packging & Mfg Technol Inst Elect & Electr Engn (CPMT/IEEE), Amer Soc Mech Engn (ASME), Heat Transfer Div, Heat Transfer Electron Equipment Comm (K-16), U S Natl Inst Stand & Technol (NIST), Int Microelectron & Packaging Soc (IMAPS) DE ceramic-ball-grid arrays; ceramic quad-flat-packs; failure mechanisms; held temperature measurements; microelectronics packaging accelerated thermal stress; package to board interconnection reliability; printed-circuit board temperature rise; solder joint failure; solder joint reliability AB Recent trends in wafer fabrication techniques have produced devices with smaller feature dimensions, increasing gate count and chip inputs/outputs (I/O's), This trend has placed increased emphasis on microelectronics packaging. Surface-mountable packages such as the ceramic quad-hat-pack (CQFP) have provided solutions for many high I/O package issues. As the I/O count gets higher, the pitch has been driven smaller to the point where other solutions also become attractive. Surface-mountabte ceramic-bah-grid array (CBGA) packages have proven to be good solutions in a variety of applications as designers seek to maximize electrical performance, reduce printed-circuit board red estate, and improve manufacturing process yields, In support of the PowerPC 603 and PowerPC 604 microprocessors, 21 mm CBGA (255 I/O's) and 32 mm (240 I/O's) and 40 mm (304 I/O's) CQFP's are being utilized. Both package types successfully meet computer environment applications. This paper describes test board assembly processes, accelerated thermal stress test setup, and solder joint failure criteria. Failure mechanisms for both packaging technologies will also be presented. The packages discussed in this paper were subjected to two accelerated thermal cycling conditions: 0 to 100 degrees Ce and -40 to 125 degrees C, The failure data are plotted using Weibull distributions. The accelerated failure distributions were used to predict failure distributions in application space for typical PowerPC 603 and PowerPC 604 microprocessors computer environments. To predict solder joint reliability of surface-mount technology, a key parameter is: the temperature rise above ambient at the solder joint, Delta T. In-situ held temperature measurements were taken for a range of computer platforms in an office environment, at the central-processing units. Printed-circuit boards (PCB) were not uniform, therefore only maximum temperature regions of the beard were measured. These maximum temperatures revealed the mean to be less than 20 degrees C above ambient (i.e., Delta T < 20 degrees C) regardless of the po,ver of the device. The largest Delta T measured in any system was less than 30 degrees C above ambient. These temperature measurements of actual computer systems are in dose agreement dth IPC-SM-785. By utilizing the measured PCB temperature rise, solder joint fatigue life was calculated for the 21 mm ceramic ball-grid-array (CBGA), the package for the PowerPC 603(TM) and PowerPC 604(TM) RISC microprocessors. The average on-off Delta T for most computer applications is approximately 20 CC. For an average on off Delta T of 30 degrees C, the 21 mm CBGA has an estimated fatigue life of over 25 years while the 32 nun and 10 mm CQFP's have an estimated fatigue life of over 50 years. C1 Motorola Inc, Networking & Computing Syst Grp, Austin, TX USA. RP Gerke, RD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 16 TC 7 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1521-3331 J9 IEEE T COMPON PACK T JI IEEE Trans. Compon. Packaging Technol. PD DEC PY 1999 VL 22 IS 4 BP 488 EP 496 DI 10.1109/6144.814963 PG 9 WC Engineering, Manufacturing; Engineering, Electrical & Electronic; Materials Science, Multidisciplinary SC Engineering; Materials Science GA 272BQ UT WOS:000084631000004 ER PT J AU Erickson, NR Grosslein, RM Erickson, RB Weinreb, S AF Erickson, NR Grosslein, RM Erickson, RB Weinreb, S TI A cryogenic focal plane array for 85-115 GHz using MMIC preamplifiers SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article; Proceedings Paper CT 1999 IEEE MTT-S International Microwave Symposium CY JUN 13-19, 1999 CL ANAHEIM, CALIFORNIA SP IEEE, Microwave Theory & Techniques Soc AB A new focal plane array for 85-115 GHz is described in this paper, This array has 16 pixels, and uses InP monolithic-microwave integrated-circuit preamplifiers with 40-dB gain, followed by a wide-band subharmonic mixer to convert to a 5-20-GHz intermediate-frequency band, A low-loss isolator is used to achieve an excellent input match, Square corrugated feed horns are used for efficient filling of the focal plane. Critical components are operated at a temperature of 20 K, Noise temperature varies from 50 to 130 K, including all pixels across the full band. C1 Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Erickson, NR (reprint author), Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. RI Weinreb, Steven/K-8747-2012 NR 7 TC 47 Z9 49 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD DEC PY 1999 VL 47 IS 12 BP 2212 EP 2219 DI 10.1109/22.808962 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 264VZ UT WOS:000084204800007 ER PT J AU Le Vine, DM AF Le Vine, DM TI Synthetic aperture radiometer systems SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article; Proceedings Paper CT 1999 IEEE MTT-S International Microwave Symposium CY JUN 13-19, 1999 CL ANAHEIM, CALIFORNIA SP IEEE, Microwave Theory & Techniques Soc DE interferometry; microwave radiometry; remote sensing; synthetic aperture radiometry ID REMOTE-SENSING APPLICATIONS; MICROWAVE RADIOMETER; EARTH AB Aperture synthesis Is; an emerging technology for passive microwave remote sensing from space, It is an interferometric technique similar to earth rotation synthesis employed in radio astronomy in which pail's of small antennas and signal processing are used to obtain the resolution of a single large antenna. The technique has the potential to overcome the barriers that antenna size has placed on passive microwave remote sensing From space, The technique has been demonstrated successfully for remote sensing at L-band with the aircraft prototype ESTAR. New aircraft instruments ape under development and propos- als have been submitted For instruments to demonstrate this technology in space. C1 Goddard Space Flight Ctr, Lab Hydrospher Processes, Microwave Sensors Branch, Greenbelt, MD 20771 USA. RP Le Vine, DM (reprint author), Goddard Space Flight Ctr, Lab Hydrospher Processes, Microwave Sensors Branch, Code 975, Greenbelt, MD 20771 USA. NR 20 TC 44 Z9 44 U1 2 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD DEC PY 1999 VL 47 IS 12 BP 2228 EP 2236 DI 10.1109/22.808964 PG 9 WC Engineering, Electrical & Electronic SC Engineering GA 264VZ UT WOS:000084204800009 ER PT J AU Johnston, AH Miyahira, T Swift, GM Guertin, SM Edmonds, LD AF Johnston, AH Miyahira, T Swift, GM Guertin, SM Edmonds, LD TI Angular and energy dependence of proton upset in optocouplers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID SILICON; DEPOSITION; CIRCUITS; ANALOG AB Transient upsets from protons in high-speed optocouplers were investigated over a range of incident angles and energies. At energies below 50 MeV, very large increases in cross section occurred at angles above 60 degrees, consistent with the increase in cross section that is expected when direct proton ionization begins to contribute to the cross section. The angular dependence of the cross section increases the number of transient upsets expected in orbit compared to upset rate calculations that do not take the angular dependence into account. Laboratory alpha particle measurements were used to measure critical charge in these devices. The critical charge and area of the photodiode provide a way to identify devices that are sensitive to direct ionization at large angles. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Johnston, AH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 17 Z9 17 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1335 EP 1341 DI 10.1109/23.819091 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500005 ER PT J AU Selva, LE Swift, GM Taylor, WA Edmonds, LD AF Selva, LE Swift, GM Taylor, WA Edmonds, LD TI On the role of energy deposition in triggering SEGR in power MOSFETs SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID EVENT GATE-RUPTURE; OXIDE THICKNESS; EXPRESSION; FAILURE AB Single event gate rupture (SEGR) was studied using three types of power MOSFET devices with ions having incident linear energy transfers (LETs) in silicon from 26 to 82 MeV.cm(2)/mg. Results are: 1) consistent with Wrobel's oxide breakdown for V-DS = 0 volts (for both normal incidence and angle); and 2) when V-GS = 0 volts, energy deposited near the Si/SiO2 interface is more important than the energy deposited deeper in the epi. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Calif State Univ Los Angeles, Dept Phys & Astron, Los Angeles, CA 90032 USA. RP Selva, LE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 14 Z9 15 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1403 EP 1409 DI 10.1109/23.819099 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500013 ER PT J AU Katz, R Wang, J McCollum, J Cronquist, B AF Katz, R Wang, J McCollum, J Cronquist, B TI The impact of software and CAE tools on SEU in field programmable gate arrays SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab AB Field programmable gate array (FPGA) devices, heavily used in spacecraft electronics, have grown substantially in size over the past few years, causing designers to work at a higher conceptual level, with computer aided engineering (CAE) tools synthesizing and optimizing the logic from a description. It is shown that the use of commercial-off-the-shelf (COTS) CAE tools can produce unreliable circuit designs when the device is used in a radiation environment and a flip-flop is upset. At a lower level, software can be used to improve the SEU performance of a flip-flop, exploiting the configurable nature of FPGA technology and on-chip delay, parasitic resistive, and capacitive circuit elements. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Actel Corp, Sunnyvale, CA 94086 USA. RP Katz, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 1 TC 1 Z9 1 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1461 EP 1468 DI 10.1109/23.819108 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500022 ER PT J AU Xapsos, MA Summers, GP Barth, JL Stassinopoulos, EG Burke, EA AF Xapsos, MA Summers, GP Barth, JL Stassinopoulos, EG Burke, EA TI Probability model for worst case solar proton event fluences SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab AB A predictive model of worst case solar proton event fluences is presented. It allows the expected worst case eve nt fluence to be calculated for a given confidence level and fbr periods of time corresponding to space missions. The proton energy range is from > 1 to > 300 MeV, so that the model is useful for a variety of radiation effects applications. For each proton energy threshold, the maximum entropy principle is used to select the initial distribution of solar proton event fluences. This turns out to be a truncated power law, i.e., a power law for smaller event fluences that smoothly approaches zero at a maximum fluence. The strong agreement of the distribution with satellite data for the last three solar cycles indicates this description captures the essential features of a solar proton event fluence distribution. Extreme value theory is then applied to the initial distribution of events to obtain the model of worst case fluences. C1 USN, Res Lab, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Xapsos, MA (reprint author), USN, Res Lab, Washington, DC 20375 USA. NR 18 TC 35 Z9 35 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1481 EP 1485 DI 10.1109/23.819111 PN 1 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500025 ER PT J AU Barak, J Reed, RA LaBel, KA AF Barak, J Reed, RA LaBel, KA TI On the figure of merit model for SEU rate calculations SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID ENERGY DEPOSITION; PROTON; UPSET AB Petersen has introduced a one parameter characterization of a device by the Figure Of Merit (FOM), It was claimed that this parameter was sufficient to estimate the SEU rate in almost all orbits. The present paper presents an analytic study of the FOM concept and compares the FOM model with other empirical models. It is found that indeed the FOM parameter gives, in most cases, a good agreement with the rates found using the full SEU cross section plots of the devices. The agreement is poorer in cases where a high portion of the proton flux comes from low energy protons and for very SEU-hard devices. This is demonstrated for certain devices (FPGAs) where the FOM predicted by proton may be smaller by an order of magnitude than the FOM from heavy ions. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Soreq NRC, IL-81800 Yvane, Israel. RP Barak, J (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 23 TC 20 Z9 24 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1504 EP 1510 DI 10.1109/23.819114 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500028 ER PT J AU Titus, JL Wheatley, CF Wheatley, TH Levinson, WA Burton, DI Barth, JL Reed, RA LaBel, KA Howard, JW VanTyne, KM AF Titus, JL Wheatley, CF Wheatley, TH Levinson, WA Burton, DI Barth, JL Reed, RA LaBel, KA Howard, JW VanTyne, KM TI Prediction of early lethal SEGR failures of VDMOSFETs for commercial space systems SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID EVENT-GATE-RUPTURE; VERTICAL POWER MOSFETS; CROSS-SECTION; EXPRESSION AB Quantitative risk assessments are presented for two radiation-hardened MOSFETs (Harris FSL11A0 and FRL11A0) using an extracted expression, integral flux curves representing different conditions, and experimentally-determined signature curves taken at different ion impact angles. The effectiveness of certain parameters including the selected orbit, spacecraft shielding thickness, drain and gate biases, device hardness, and time of exposure are discussed. Failures are studied using normalized Monte Carlo simulations validated by statistical methods. These validated Monte Carlo simulations are then used to extract and present an extracted expression. The concept of a lethal ion rate is discussed. Single event gate rupture (SEGR) failure thresholds at different ion impact angles are measured and reported on the Harris FSL11A0 and FRL11A0 (radiation-hardened vertical MOSFETs having similar layouts but with different SEGR sensitivities). Integral flux curves are presented for various orbits and conditions. Predictions of very early failures are performed using the extracted expression, the integral flux curves, and the new signature curves. Based upon these predictions, the influence of selected parameters are evaluated. C1 USN, Ctr Surface Warfare, Crane, IN 47522 USA. Harris Semicond Inc, Palm Bay, FL 32905 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA J&T, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Titus, JL (reprint author), USN, Ctr Surface Warfare, 300 Hwy 361, Crane, IN 47522 USA. NR 17 TC 14 Z9 14 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1640 EP 1651 DI 10.1109/23.819133 PN 1 PG 12 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500047 ER PT J AU Rax, BG Johnston, AH Miyahira, T AF Rax, BG Johnston, AH Miyahira, T TI Displacement damage in bipolar linear integrated circuits SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab AB The effects of proton and gamma radiation are compared for several types of integrated circuits with complex internal design and failure modes that are not as straightforward as the input bias current mechanism that is frequently used to study damage effects in linear devices. New circuit failure mechanisms were observed in voltage regulators that, cause them to fail at much lower levels when they are irradiated with protons compared to tests with gamma rays at equivalent total dose levels. Protons caused much larger changes in output voltage than tests with gamma rays,which limits the maximum radiation level of some types of voltage regulators in environments dominated by protons. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rax, BG (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 11 Z9 12 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1660 EP 1665 DI 10.1109/23.819135 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500049 ER PT J AU Islam, NE Schamiloglu, E Kirby, TH Shipley, B Kemp, WT Schoenberg, JSH Howard, JW AF Islam, NE Schamiloglu, E Kirby, TH Shipley, B Kemp, WT Schoenberg, JSH Howard, JW TI Electron irradiation effects on photoconductive semiconductor switches (PCSSs) used in sub-nanosecond transient generators SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID GALLIUM-ARSENIDE; GAAS-MESFETS; DELAY-TIME; TRANSPORT; DEVICES AB Radiation-induced damage occurs in GaAs photoconductive semiconductor switches used in sub-nanosecond transient generators when subjected to 600 keV and 6 MeV electron irradiation. These switches are made from semi-insulating (SI) compensated material through a EL2/carbon compensation mechanism, and the liquid encapsulated Czochralski process. New defect levels are formed as a result of the non-ionizing energy loss (NIEL) process. The formation of new defect levels in the device alters the compensating balance between the existing deep level EL2 trap/donors and carbon accepters, and changes the material properties. As a result; two important parameters of the device are adversely affected - the hold-off voltage of the switch at the pulse-charging (off) state, and the rise time during the conduction (on) state. The hold-off voltage shifts to a lower value since there are more trap-filled regions available that can fill up and alter the homogenous nature of the device material. Unstable filamentary conduction then occurs at a lower voltage and leads to premature breakdown. As with EL2 trap levels, new defect states induced by electron irradiation will further contribute to the delay in the rise time of the switch. The rise time determines the maximum energy transferred to the load. The electron damage mechanism and its effects on the switch characteristics depend on the material properties. Intrinsic material, or material made through compensation other than through the deep donor and shallow acceptor balancing process are not expected to behave similarly. Simulation results at higher bias show a marked degradation of material properties. The switch current-voltage (I-V) characteristic when the bias increases to the kilovolt range is similar to trap-dominated semiconductors. An initial sublinear current regime at low bias is followed by a super-linear regime of current now at higher bias, and is in agreement with earlier observations. C1 Univ New Mexico, Dept Elect & Comp Engn, Albuquerque, NM 87131 USA. Univ New Mexico, Hlth Sci Ctr, Albuquerque, NM 87131 USA. AFRL, Space Vehicle Directorate, Kirtland AFB, NM 87117 USA. AFRL, Directed Energy Directorate, Kirtland AFB, NM 87117 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Islam, NE (reprint author), Univ New Mexico, Dept Elect & Comp Engn, Albuquerque, NM 87131 USA. NR 17 TC 1 Z9 1 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1722 EP 1727 DI 10.1109/23.819145 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500059 ER PT J AU Wang, JJ Katz, RB Sun, JS Cronquist, BE McCollum, JL Speers, TM Plants, WC AF Wang, JJ Katz, RB Sun, JS Cronquist, BE McCollum, JL Speers, TM Plants, WC TI SRAM based re-programmable FPGA for space applications SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID LOGIC AB An SRAM (static random access memory)-based reprogrammable FPGA (field programmable gate array) is investigated for space applications. A new commercial prototype, named the RS family, was used as an example for the investigation. The device is fabricated in a 0.25 mu m CMOS technology. Its architecture is reviewed to provide a better understanding of the impact of single event upset (SEU) on the device during operation. The SEU effect of different memories available on the device is evaluated. Heavy ion test data and SPICE simulations are used integrally to extract the threshold LET (linear energy transfer). Together with the saturation cross-section measurement from the layout, a rate prediction is done on each memory type. The SEU in the configuration SRAM is identified as the dominant failure mode and is discussed in detail. The single event transient error in combinational logic is also investigated and simulated by SPICE. SEU mitigation by hardening the memories and employing EDAC (error detection and correction) at the device level are presented. For the configuration SRAM (CSRAM) cell, the trade-off between resistor de-coupling and redundancy hardening techniques are investigated with interesting results. Preliminary heavy ion test data show no sign of SEL (single event latch-up). With regard to ionizing radiation effects, the increase in static leakage current (static I-CC) measured indicates a device tolerance of approximately 50krad(Si). C1 Actel Corp, Sunnyvale, CA 94086 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wang, JJ (reprint author), Actel Corp, Sunnyvale, CA 94086 USA. NR 11 TC 41 Z9 46 U1 2 U2 12 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1728 EP 1735 DI 10.1109/23.819146 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500060 ER PT J AU Katz, R Wang, JJ Reed, R Kleyner, I D'Ordine, M McCollum, J Cronquist, B Howard, J AF Katz, R Wang, JJ Reed, R Kleyner, I D'Ordine, M McCollum, J Cronquist, B Howard, J TI The effects of architecture and process on the hardness of programmable technologies SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab AB Architecture and process, combined, significantly affect the hardness of programmable technologies. The effects of high energy ions, ferroelectric memory architectures, and shallow trench isolation are investigated. A detailed single event latchup (SEL) study has been performed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Actel Corp, Sunnyvale, CA 94086 USA. Orbital Sci Corp, Greenbelt, MD 20771 USA. Ball Aerosp & Technol Corp, Boulder, CO 80301 USA. Jackson & Tull Chartered Engineers, Seabrook, MD 20706 USA. RP Katz, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 7 TC 4 Z9 4 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1736 EP 1743 DI 10.1109/23.819147 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500061 ER PT J AU Nguyen, DN Guertin, SM Swift, GM Johnston, AH AF Nguyen, DN Guertin, SM Swift, GM Johnston, AH TI Radiation effects on advanced flash memories SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID SINGLE AB Radiation tests of advanced flash memories including, multi-level flash technology, are compared with results from previous generations. Total dose failure levels are comparable to or lower than those of older technologies, but are likely still caused by degradation of the internal charge pump. Small numbers of read errors were observed during single event tests of the multi-level devices that appear to be caused by shifts in the sense amplifier detection levels or cell threshold shifts and rather than loss of electrons off the floating gate. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Nguyen, DN (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 87 Z9 96 U1 0 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1744 EP 1750 DI 10.1109/23.819148 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500062 ER PT J AU Johnston, AH Rax, BG Selva, LE Barnes, CE AF Johnston, AH Rax, BG Selva, LE Barnes, CE TI Proton degradation of light-emitting diodes SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1999 IEEE Nuclear and Space Radiation Effects Conference (NSREC 99) CY JUL 12-16, 1999 CL NORFOLK, VIRGINIA SP IEEE Nuclear & Plasma Sci Soc, Raduat Effects Comm, Def Threat Redyct Agcy, Sandia Natl Lab, NASA Goddard Space Flight Ctr, Jet Propuls Lab, Air Force Res Lab ID DAMAGE AB Proton degradation is investigated for several types of light-emitting diodes with wavelengths in the near infrared region. Several basic light-emitting diode (LED) technologies are compared, including homojunction and double-heterojunction devices. Homojunction LEDs fabricated with amphoteric dopants are far more sensitive to displacement damage than double-heterojunction LEDs, and are strongly affected by injection-enhanced annealing. Unit-to-unit variability remains an important issue for all LED technologies. For some technologies, degradation of the forward voltage characteristics appears to be more significant than degradation of light output. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Johnston, AH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 15 TC 31 Z9 33 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1781 EP 1789 DI 10.1109/23.819154 PN 1 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RG UT WOS:000085058500068 ER PT J AU Kippen, RM Mallozzi, RS Rielage, K Pendleton, GN Christl, MJ Hink, PL Binns, WR Dowkontt, P Epstein, JW Fishman, GJ Parnell, TA Wilson, RB Richardson, GA Buckley, JH Israel, MH Koshut, TM AF Kippen, RM Mallozzi, RS Rielage, K Pendleton, GN Christl, MJ Hink, PL Binns, WR Dowkontt, P Epstein, JW Fishman, GJ Parnell, TA Wilson, RB Richardson, GA Buckley, JH Israel, MH Koshut, TM TI Results from the SIFTER (Scintillating Fiber Telescope for Energetic Radiation) beam test apparatus SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1998 Nuclear Science Symposium (NSS) CY NOV 08-14, 1998 CL TORONTO, CANADA SP IEEE AB The Scintillating Fiber Telescope for Energetic Radiation (SIFTER) is a large-area instrument concept for high-energy (E > 10 MeV) gamma-ray astronomy. It takes advantage of the technology of fine (similar to 1 mm(2)) plastic scintillating fibers in the context of a pair tracker/calorimeter telescope. In our on-going SIFTER research, we have developed a small test apparatus, consisting of 12 fiber planes, each with a potential active area of 10 cm x 10 cm covered with a thin tantalum foil converter. This apparatus was tested in July, 1998 with high-energy photons (similar to 0.5-1.6 GeV) at the Thomas Jefferson National Accelerator Laboratory Hall B tagged gamma-ray facility. We report on results of the beam test, concentrating on comparisons with detailed Monte Carlo simulations of the instrument performance, including track reconstruction, angular resolution and detection efficiency. C1 Univ Alabama, Huntsville, AL 35899 USA. Washington Univ, St Louis, MO 63130 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35805 USA. RP Kippen, RM (reprint author), Univ Alabama, Huntsville, AL 35899 USA. NR 6 TC 0 Z9 0 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1999 VL 46 IS 6 BP 1920 EP 1924 DI 10.1109/23.819254 PN 2 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 279RH UT WOS:000085058600014 ER PT J AU Chau, SN Alkalai, L Tai, AT Burt, JB AF Chau, SN Alkalai, L Tai, AT Burt, JB TI Design of a fault-tolerant COTS-based bus architecture SO IEEE TRANSACTIONS ON RELIABILITY LA English DT Article DE COTS; IEEE 1394 Bus; (IC)-C-2 bus; long-life deep space mission; bus network reliability; fault-tolerant bus architecture AB This paper describes our approach to using commercial-off-the-shelf (COTS) products in highly reliable systems. The methodology calls for multilevel fault-protection. The methodology realizes that COTS products are often not developed with high reliability in mind. Nevertheless, by using multi-level fault protection, the same level of reliability as the traditional full-custom fault tolerance approach can be achieved. This methodology allows more freedom for design trade-offs among the fault-protection levels, which can result in less complicated designs than the traditional strictly-enforced fault-containment policy. This paper covers our experiences & findings on the design of a fault-tolerant avionics bus architecture comprised of two COTS buses, the IEEE 1394, and the (IC)-C-2, for the avionics system of X2000 program at the Jet Propulsion Laboratory The X2000 design is judicious about ensuring the fault-tolerance provisions do not cause the bus design to deviate from commercial standard specifications, so that the economic attractiveness of using COTS is preserved. The hardware & software designs of the X2000 fault-tolerant bus are being implemented, and flight hardware will be delivered to the Europa Orbiter missions. This work provides an example of how to construct a highly reliable system with low-cost COTS interfaces. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Ctr Integrated Space Microsyst, Pasadena, CA 91109 USA. IA Tech, Los Angeles, CA 90024 USA. RP Chau, SN (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 16 TC 17 Z9 17 U1 2 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9529 J9 IEEE T RELIAB JI IEEE Trans. Reliab. PD DEC PY 1999 VL 48 IS 4 BP 351 EP 359 DI 10.1109/24.814517 PG 9 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 271UZ UT WOS:000084613200006 ER PT J AU Ploen, SR Park, FC AF Ploen, SR Park, FC TI Coordinate-invariant algorithms for robot dynamics SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article DE Lie algebra; Lie group; multibody dynamics; robot dynamics ID SPATIAL OPERATOR ALGEBRA AB In this article, we present, using methods from the theory of Lie groups and Lie algebras, a coordinate-invariant formulation of the dynamics of open kinematic chains. We first reformulate the recursive dynamics algorithm originally given in [8] for open chains in terms of standard Linear operators on the Lie algebra of the Special Euclidean group. Using straight forward algebraic manipulations, we then recast the resulting algorithm into a set of closed-form dynamic equations; this transformation allows one to move easily between O(n) recursive algorithms advantageous for computation, and closed-form equations advantageous for symbolic manipulation and analysis. The transformation also illuminates how the choice of link reference frames affects the computational structure. We then reformulate Featherstone's articulated body inertia algorithm [3] using this same geometric framework, and rederive Rodriguez et at's [11]-[13] square factorization of the mass matrix and its inverse. An efficient O(n) recursive algorithm for forward dynamics is also extracted from the inverse factorization. The resulting equations lead to a succinct high-level description of robot dynamics in both joint and operational space coordinates that minimizes symbolic complexity without sacrificing computational efficiency, and provides the basis for a dynamics formulation that does not require link reference frames in the description of the forward kinematics. C1 Seoul Natl Univ, Sch Mech & Aerosp Engn, Seoul, South Korea. RP CALTECH, Jet Prop Lab, Guidance & Control Anal Grp, 4800 Oak Grove Dr, Pasadena, CA 91009 USA. EM sploen@grover.jpl.nasa.gov; fcp@plaza.snu.ac.kr NR 14 TC 22 Z9 23 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD DEC PY 1999 VL 15 IS 6 BP 1130 EP 1135 DI 10.1109/70.817677 PG 6 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA 278XV UT WOS:000085015000015 ER PT J AU Featherstone, R Fijany, A AF Featherstone, R Fijany, A TI A technique for analyzing constrained rigid-body systems, and its application to the constraint force algorithm SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article DE constrained dynamics; dual vector space; robot dynamics algorithm ID HYBRID CONTROL; MANIPULATOR; DYNAMICS; ROBOT AB The constraint force algorithm, as originally described by Fijany et al., calculates the forward dynamics of a system comprising N rigid bodies connected together in an unbranched chain with joints from a restricted class of joint types. It was designed for parallel calculation of the dynamics, and achieves O(log N) time complexity on O(N) processors. This paper presents a new formulation of the Constraint Force Algorithm that corrects a major limitation in the original, and sheds new light on the relationship between it and other dynamics algorithms. The new version is applicable to systems with any type of joint, floating bases, and short branches off the main chain. It is obtained using a new technique for analysing constrained rigid-body systems by means: of a change of basis in a dual system of vector spaces. This new technique is also described. C1 Univ Oxford, Dept Engn Sci, Oxford, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Univ Wales, Dept Comp Sci, Aberystwyth SY23 3DB, Dyfed, Wales. NR 12 TC 18 Z9 19 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD DEC PY 1999 VL 15 IS 6 BP 1140 EP 1144 DI 10.1109/70.817679 PG 5 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA 278XV UT WOS:000085015000017 ER PT J AU Moller, KD Farmer, KR Ivanov, DVP Sternberg, O Stewart, KP Lalanne, P AF Moller, KD Farmer, KR Ivanov, DVP Sternberg, O Stewart, KP Lalanne, P TI Thin and thick cross shaped metal grids SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article DE metal grid; infrared; silicon substrate ID BANDPASS-FILTERS AB Thin cross shaped metal grids have been studied in the infrared for wavelengths smaller and larger than the periodicity constant. Resonance frequencies of thin grids, calculated using rigorous computational methods, agree well with experimental data and empirical formulas. Resonance wavelength and the Wood anomaly of metal meshes on silicon substrates show frequency shifts to longer wavelength, with shifts smaller than the refractive index for the resonance and equal to the refractive index for the Wood anomaly. An empirical formula for the wavelength of the "thickness" peak of free standing thick cross shaped grids is shown and agrees very well with experimental and computational results. (C) 1999 Elsevier Science B.V. All rights reserved. C1 New Jersey Inst Technol, Dept Phys, Newark, NJ 07102 USA. New Jersey Inst Technol, Microelect Res Ctr, Newark, NJ 07102 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CNRS, Lab Charles Fabry, Inst Opt Theor & Appl, F-91403 Orsay, France. RP Moller, KD (reprint author), 113 Seaview Ct, Neptune, NJ 07753 USA. NR 14 TC 22 Z9 22 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1350-4495 J9 INFRARED PHYS TECHN JI Infrared Phys. Technol. PD DEC PY 1999 VL 40 IS 6 BP 475 EP 485 DI 10.1016/S1350-4495(99)00031-6 PG 11 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 258ZB UT WOS:000083868600005 ER PT J AU Bar-Cohen, Y AF Bar-Cohen, Y TI Bookmarking the NDE capability and challenges near the dawn of the new millennium SO INSIGHT LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bar-Cohen, Y (reprint author), CALTECH, Jet Prop Lab, 82-105,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU BRITISH INST NON-DESTRUCTIVE TESTING PI NORTHAMPTON PA 1 SPENCER PARADE, NORTHAMPTON NN1 5AA, NORTHANTS, ENGLAND SN 1354-2575 J9 INSIGHT JI Insight PD DEC PY 1999 VL 41 IS 12 BP 801 EP 803 PG 3 WC Instruments & Instrumentation; Materials Science, Characterization & Testing SC Instruments & Instrumentation; Materials Science GA 264VB UT WOS:000084202600022 ER PT J AU Best, SR Rose, MF AF Best, SR Rose, MF TI A plasma drag hypervelocity particle accelerator (HYPER) SO INTERNATIONAL JOURNAL OF IMPACT ENGINEERING LA English DT Article; Proceedings Paper CT 6th Symposium on Hypervelocity Impact (HVIS 98) CY NOV 17-19, 1998 CL HUNTSVILLE, ALABAMA SP Army Res Lab, Army Res Off, Ernst Mach Inst, European Res Off, Lawrence Livermore Natl Lab, NASA Marshall Space Flight Ctr, Sandia Natl Lab, Univ Alabama, Huntsville, US Army Aviat & Missile Command AB Current debris models are able to predict the growth of the space debris problem and suggest that spacecraft must employ armor or bumper shields for some orbital altitudes now and that the problem will become worse as a function of time. The practical upper limit to the velocity distribution is on the order of 40 km/s and is associated with the natural environment. The velocity distribution of the man-made component peaks at 9-10 km/s with maximum velocity in the 14-16 km/s range. Experience in space has verified that the "high probability of impact" particles are in the microgram to milligram range. These particles can have very significant effects on coatings, insulators, and thin metallic layers. The surface of thick materials becomes pitted and the local debris component is enhanced by ejecta from the impact events. In this paper, the HYPER facility is described which produces a reasonable simulation of the man-made space debris spectrum in a controlled environment. The facility capability is discussed in terms of drive geometry, energetics, velocity distribution, diagnostics, and projectile/debris loading. The facility has been used to study impact phenomena on Space Station Freedom's solar array structure, the calibration of space debris collectors, other solar array materials, potential structural materials for use in the space, electrical breakdown in the space environment, and as a means of clarifying or duplicating the impact phenomena on surfaces which have been exposed in space. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Auburn Univ, Space Power Inst, Auburn, AL 36849 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Best, SR (reprint author), Auburn Univ, Space Power Inst, 231 Leach Sci Ctr, Auburn, AL 36849 USA. NR 5 TC 5 Z9 8 U1 1 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0734-743X J9 INT J IMPACT ENG JI Int. J. Impact Eng. PD DEC PY 1999 VL 23 IS 1 BP 67 EP 76 DI 10.1016/S0734-743X(99)00063-9 PN 1 PG 10 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 270EB UT WOS:000084521500010 ER PT J AU Christiansen, EL Cour-Palais, BG Friesen, LJ AF Christiansen, EL Cour-Palais, BG Friesen, LJ TI Extravehicular activity suit penetration resistance SO INTERNATIONAL JOURNAL OF IMPACT ENGINEERING LA English DT Article; Proceedings Paper CT 6th Symposium on Hypervelocity Impact (HVIS 98) CY NOV 17-19, 1998 CL HUNTSVILLE, ALABAMA SP Army Res Lab, Army Res Off, Ernst Mach Inst, European Res Off, Lawrence Livermore Natl Lab, NASA Marshall Space Flight Ctr, Sandia Natl Lab, Univ Alabama, Huntsville, US Army Aviat & Missile Command AB The penetration resistance to hypervelocity impact (HVI) has been determined based on test and analysis for the extravehicular mobility unit (EMU) space suit used by astronauts to perform extravehicular activities (EVA). The suit is broadly divided into two categories: soft goods and hard goods depending on their flexibility. In the soft good category, HVI tests were conducted on samples representative of the arms, legs, briefs, gloves, glove gauntlet, and overlap regions. Hard goods examined include the hard upper torso (HUT), portable life support system (PLSS), and helmet. Ballistic limit equations have been developed that define the particle size on the perforation threshold of the suit bladder as a function of impact conditions (velocity, angle, and density). Penetration equations have also been developed for predicting particle sizes causing uncontrollable leaks (i.e., with bladder hole sizes exceeding 4 mm diameter). These equations are necessary to perform orbital debris and meteoroid risk assessments for EVAs. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. SW Res Inst, San Antonio, TX 78228 USA. Lockheed Martin, Houston, TX 77058 USA. RP Christiansen, EL (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN3, Houston, TX 77058 USA. NR 7 TC 6 Z9 7 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0734-743X J9 INT J IMPACT ENG JI Int. J. Impact Eng. PD DEC PY 1999 VL 23 IS 1 BP 113 EP 124 DI 10.1016/S0734-743X(99)00067-6 PN 1 PG 12 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 270EB UT WOS:000084521500014 ER PT J AU Christiansen, EL Kerr, JH De la Fuente, HM Schneider, WC AF Christiansen, EL Kerr, JH De la Fuente, HM Schneider, WC TI Flexible and deployable meteoroid/debris shielding for spacecraft SO INTERNATIONAL JOURNAL OF IMPACT ENGINEERING LA English DT Article; Proceedings Paper CT 6th Symposium on Hypervelocity Impact (HVIS 98) CY NOV 17-19, 1998 CL HUNTSVILLE, ALABAMA SP Army Res Lab, Army Res Off, Ernst Mach Inst, European Res Off, Lawrence Livermore Natl Lab, NASA Marshall Space Flight Ctr, Sandia Natl Lab, Univ Alabama, Huntsville, US Army Aviat & Missile Command ID DEBRIS AB The penetration resistance of various flexible multi-layer shielding concepts has been assessed in hypervelocity impact (HVI) tests at NASA Johnson Space Center (JSC) and at Southwest Research Institute (SwRI). The shields tested consist of 3 to 4 spaced bumpers made of ceramic cloth (Nextel(TM)) and a rear wall composed of high-strength cloth (Kevlar(TM). Low-density polyurethane foam is used between bumper layers and rear wall to deploy the bumpers after the shield is delivered to orbit and maintain bumper standoff while on-orbit. Ballistic limit equations have been derived from the HVI test results. These equations are being used to size shielding for an inflatable module, which is planned for potential use on Space Station. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Christiansen, EL (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN, Houston, TX 77058 USA. NR 10 TC 23 Z9 29 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0734-743X J9 INT J IMPACT ENG JI Int. J. Impact Eng. PD DEC PY 1999 VL 23 IS 1 BP 125 EP 136 DI 10.1016/S0734-743X(99)00068-8 PN 1 PG 12 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 270EB UT WOS:000084521500015 ER PT J AU Robinson, JH AF Robinson, JH TI Orbital debris impact damage to reusable launch vehicles SO INTERNATIONAL JOURNAL OF IMPACT ENGINEERING LA English DT Article; Proceedings Paper CT 6th Symposium on Hypervelocity Impact (HVIS 98) CY NOV 17-19, 1998 CL HUNTSVILLE, ALABAMA SP Army Res Lab, Army Res Off, Ernst Mach Inst, European Res Off, Lawrence Livermore Natl Lab, NASA Marshall Space Flight Ctr, Sandia Natl Lab, Univ Alabama, Huntsville, US Army Aviat & Missile Command AB In an effort by the National Aeronautics and Space Administration (NASA), hypervelocity impact tests were performed on thermal protection systems (TPS) applied on the external surfaces of reusable launch vehicles (RLV) to determine the potential damage from orbital debris impacts. Three TPS types were tested, bonded to composite structures representing RLV fuel tank walls. The three heat shield materials tested were Alumina-Enhanced Thermal Barrier-12 (AETB-12), Flexible Reusable Surface Insulation (FRSI), and Advanced Flexible Reusable Surface Insulation (AFRSI). Using this test data, predictor equations were developed for the entry hole diameters in the three TPS materials, with correlation coefficients ranging from 0.69 to 0.86. Possible methods are proposed for approximating damage occurring at expected orbital impact velocities higher than tested, with references to other published work. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Robinson, JH (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 18 TC 3 Z9 3 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0734-743X J9 INT J IMPACT ENG JI Int. J. Impact Eng. PD DEC PY 1999 VL 23 IS 1 BP 783 EP 794 DI 10.1016/S0734-743X(99)00122-0 PN 2 PG 12 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 270ED UT WOS:000084521700025 ER PT J AU Noerdlinger, PD AF Noerdlinger, PD TI Atmospheric refraction effects in Earth remote sensing SO ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING LA English DT Article DE spaceborne imagery; atmospheric refraction; BRDF; satellite observations; Earth limb observations; terminator observations AB Just as refraction moves the apparent positions of stars from their true ones, it slightly distorts the view of Earth from space, as well as affecting the angle at which sunlight or moonlight illuminates its surface. The astronomer's problem is to correct the apparent position of a star for refraction, relating the position as observed from Earth to the true position. By contrast, the space observer's problem is to obtain the true (refracted) surface zenith angle z' of illumination or of viewing, when the zenith angle z(0) of the ray in space is known, and to correct for the apparent horizontal displacement of the surface point being viewed. This paper solves the problem of the refraction angle for a spherical atmosphere by a simple, analytic solution, depending only on the surface index of refraction mu(0) namely: sin(z(0))= mu(0) sin(z'). The problem of the apparent horizontal displacement of the point viewed is also solved analytically, but approximately, because the result depends weakly on an assumed vertical structure of the atmosphere. The results are useful primarily in cases where observation must be done at large zenith angle, or low Sun angle. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, SM&A, Greenbelt, MD 20771 USA. RP Noerdlinger, PD (reprint author), NASA, Goddard Space Flight Ctr, SM&A, Code 902,Bldg 32, Greenbelt, MD 20771 USA. NR 18 TC 15 Z9 16 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0924-2716 J9 ISPRS J PHOTOGRAMM JI ISPRS-J. Photogramm. Remote Sens. PD DEC PY 1999 VL 54 IS 5-6 BP 360 EP 373 DI 10.1016/S0924-2716(99)00030-1 PG 14 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 282ZX UT WOS:000085252600008 ER PT J AU Chen, ZX AF Chen, ZX TI Inter-element fractionation and correction in laser ablation inductively coupled plasma mass spectrometry SO JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY LA English DT Article ID LAM-ICP-MS; SAMPLE INTRODUCTION; MICROPROBE; GEOCHRONOLOGY; MINERALS; GLASS AB Inter-element fractionation in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis is one of the major challenges for using the technique for in situ trace element determination and isotopic ratio measurement of geological, environmental and biological solid samples. Attempts have been made to reduce inter-element fractionation in LA-ICP-MS analysis. However, this fractionation cannot be eliminated. The mechanism of the fractionation in LA-ICP-MS analysis is not very well understood. This study investigated the inter-element fractionation of seven elements (Ca, V, Zn, Ga, Sr, La and Nd) in three different sample matrices (NIST 613, BCR-2 and SY-4) using a UV 266 nm laser. The study showed that the inter-element fractionation depends on the sample matrices and varies with time. The inter-element fractionation behaviour of V, Zn and Ga in the synthetic silicate glass NIST 613 is different from that in the quenched glass of fused silicate rocks (BCR-2 and SY-4). Relative to Ca, V, Zn and Ga show less fractionation in NIST 613 but larger fractionation in BCR-2 and SY-4. The relative internal standard normalized element intensity (RISNEI) is not linear with time for a laser ablation period of 210 s. Therefore, data acquisition using prolonged laser ablation without a matrix match will not improve the precision and accuracy for elements whose fractionation behavior is different from that of the internal standard element. The RISNEI versus time relationship for the first 100 s laser ablation can be treated as linear to simplify the data calculation. In this paper, the internal standard normalized fractionation factor (ISNFF) is defined as the sum of the second half average RISNEI and the difference between the second and first half average RISNEI, divided by the second half RISNEI of data acquisition, for the analyte concentration calculation. The ISNFF was applied for the correction of the data reduction in LA-ICP-MS analysis. The data accuracy for these seven elements is generally improved, particularly for an element whose calibration standard normalized ISNFF is significantly greater or less than 1 (e.g., Zn and Ga in this study). Good accuracy can be obtained for elements without ISNFF correction and matrix matches only if the calibration standard normalized ISNFF of the elements is close to 1. C1 Univ Victoria, Sch Earth & Ocean Sci, Victoria, BC V8W 3P6, Canada. RP Chen, ZX (reprint author), Univ So Mississippi, Dept Marine Sci, Stennis Space Ctr, Stennis Space Ctr, MS 39529 USA. EM zhongxing.chen@usm.edu NR 19 TC 57 Z9 66 U1 0 U2 17 PU ROYAL SOC CHEMISTRY PI CAMBRIDGE PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND SN 0267-9477 J9 J ANAL ATOM SPECTROM JI J. Anal. At. Spectrom. PY 1999 VL 14 IS 12 BP 1823 EP 1828 DI 10.1039/a903272j PG 6 WC Chemistry, Analytical; Spectroscopy SC Chemistry; Spectroscopy GA 265MB UT WOS:000084247000003 ER PT J AU Smith, DD Yoon, Y Boyd, RW Campbell, JK Baker, LA Crooks, RM George, M AF Smith, DD Yoon, Y Boyd, RW Campbell, JK Baker, LA Crooks, RM George, M TI z-scan measurement of the nonlinear absorption of a thin gold film SO JOURNAL OF APPLIED PHYSICS LA English DT Article AB We have used the z-scan technique at a wavelength (532 nm) near the transmission window of bulk gold to measure the nonlinear absorption coefficient of continuous approximately 50-Angstrom-thick gold films, deposited onto surface-modified quartz substrates. For highly absorbing media such as metals, we demonstrate that determination of either the real or imaginary part of the third-order susceptibility requires a measurement of both nonlinear absorption and nonlinear refraction, i.e., both open- and closed-aperture z scans must be performed. Closed-aperture z scans did not yield a sufficient signal for the determination of the nonlinear refraction. However, open-aperture z scans yielded values ranging from beta = 1.9 x 10(-3) to 5.3 x 10(-3) cm/W in good agreement with predictions which ascribe the nonlinear response to a Fermi smearing mechanism. We note that the sign of the nonlinearity is reversed from that of gold nanoparticle composites, in accordance with the predictions of mean field theories. (C) 1999 American Institute of Physics. [S0021-8979(99)06523-8]. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Rochester, Inst Opt, Rochester, NY 14627 USA. Texas A&M Univ, Dept Chem, College Stn, TX 77842 USA. Univ Alabama, Dept Chem, Huntsville, AL 35899 USA. RP Smith, DD (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, SD48, Huntsville, AL 35812 USA. RI Baker, Lane/B-6452-2008 NR 17 TC 95 Z9 95 U1 0 U2 23 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD DEC 1 PY 1999 VL 86 IS 11 BP 6200 EP 6205 DI 10.1063/1.371675 PG 6 WC Physics, Applied SC Physics GA 256ML UT WOS:000083729000042 ER PT J AU Watcharapasorn, A DeMattei, RC Feigelson, RS Caillat, T Borshchevsky, A Snyder, GJ Fleurial, JP AF Watcharapasorn, A DeMattei, RC Feigelson, RS Caillat, T Borshchevsky, A Snyder, GJ Fleurial, JP TI Preparation and thermoelectric properties of some phosphide skutterudite compounds SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID TRANSPORT-PROPERTIES; ELECTRONIC-STRUCTURE; LAFE4P12 STRUCTURE; METAL PHOSPHIDES; RARE-EARTH; COSB3; CONDUCTIVITY; IRSB3 AB Thermoelectric properties of CoP3 and CeFe4P12 have been measured. These compounds were synthesized by a flux technique using Sn as the solvent. The samples were characterized by x-ray diffractometry and electron microprobe analyses. The Seebeck coefficient, the electrical resistivity, the Hall effect, and the thermal conductivity were measured over a wide range of temperatures. The results indicate that CoP3 and CeFe4P12 are semiconductors, in agreement with theoretical predictions. The thermal conductivity of CeFe4P12 is about 10 times larger than that for CeFe4Sb12 which is primarily due to both reduced motion of the Ce ions in smaller voids and lower hole-phonon scattering. The results are analyzed and discussed to provide guidelines for optimization of the thermoelectric properties of these materials. (C) 1999 American Institute of Physics. [S0021-8979(99)03923-7]. C1 Stanford Univ, Ctr Mat Res, Stanford, CA 94305 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Watcharapasorn, A (reprint author), Stanford Univ, Ctr Mat Res, McCullough Bldg Room 111, Stanford, CA 94305 USA. RI Snyder, G. Jeffrey/E-4453-2011; Snyder, G/I-2263-2015 OI Snyder, G. Jeffrey/0000-0003-1414-8682; NR 34 TC 30 Z9 30 U1 4 U2 27 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD DEC 1 PY 1999 VL 86 IS 11 BP 6213 EP 6217 DI 10.1063/1.371635 PG 5 WC Physics, Applied SC Physics GA 256ML UT WOS:000083729000044 ER PT J AU Stubenrauch, CJ Rossow, WB Scott, NA Chedin, A AF Stubenrauch, CJ Rossow, WB Scott, NA Chedin, A TI Clouds as seen by satellite sounders (3I) and imagers (ISCCP). Part III: Spatial heterogeneity and radiative effects SO JOURNAL OF CLIMATE LA English DT Article ID BUDGET EXPERIMENT; RESOLUTION; CLIMATE; SPACE AB Their relatively good spectral resolution makes infrared sounders very useful for the determination of cloud properties (day and night), and their coarse spatial resolution has less effect on clouds with large spatial extents like cirrus clouds. The Improved Initialization Inversion (31) algorithms convert TIROS-N Operational Vertical Sounder observations from the NOAA Polar Orbiting Environmental Satellites into atmospheric temperature and humidity profiles and into cloud and surface properties. On the other hand, the relatively high spatial resolution of the imagers from the geostationary and polar orbiting satellites used in the International Satellite Cloud Climatology Project (ISCCP) is important for the determination of properties of clouds with smaller spatial extents like boundary layer clouds. By combining these quire different datasets some insight into the behavior of retrieved cloud properties with spatial heterogeneity is gained. The effective cloud amount as determined by 31 and ISCCP agrees very well for homogeneous cloud types at all heights, but heterogeneous cloud scenes lead to a smaller 31 effective cloud amount than the one retrieved by ISCCP. In the case of chin cirrus overlying low clouds, 31 will determine the effective cloud amount of the cirrus, whereas ISCCP's information from the visible channel includes the lower cloud. The correlation between infrared cloud emissivity (31) and visible cloud optical thickness (ISCCP) agrees quite well for high clouds with the expected exponential behavior. Mesoscale heterogeneities in midlevel and low-level cloud fields, however, cause a flatter behavior between 31 retrieved cloud emissivity and ISCCP retrieved cloud optical thickness, which can be simulated in a GCM with a subgrid-scale cloud overlapping scheme. Cloud radiative effects are studied in combination with Earth Radiation Budget Experiment fluxes. The warming effect of clouds depends on cloud height and effective cloud amount, but also on atmospheric conditions like near-surface temperature and humidity. The variability ranges from nearly no effect for partially covered low clouds up to 150 W m(-2) for overcast high opaque clouds in the Tropics. The reprocessing of ISCCP produced a better distinction between the radiative effects of high opaque and cirrus clouds, in better agreement with the 31 results. Still, 31 high opaque clouds produce about 10 W m(-2) larger warming. The cooling effect of clouds during the daytime depends very much on solar inclination as well as cloud optical thickness and cover. C1 Ecole Polytech, Meteorol Dynam Lab, F-91128 Palaiseau, France. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Stubenrauch, CJ (reprint author), Ecole Polytech, Meteorol Dynam Lab, F-91128 Palaiseau, France. RI Rossow, William/F-3138-2015 NR 29 TC 39 Z9 39 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD DEC PY 1999 VL 12 IS 12 BP 3419 EP 3442 DI 10.1175/1520-0442(1999)012<3419:CASBSS>2.0.CO;2 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 264BX UT WOS:000084161100006 ER PT J AU Grasza, K Palosz, W Trivedi, SB AF Grasza, K Palosz, W Trivedi, SB TI Experimental study of low supersaturation nucleation in crystal growth by "contactless" physical vapor transport SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE theory and models of crystal growth; growth from the vapor ID TELLURIDE CRYSTALS; CADMIUM TELLURIDE; CDTE; PHASE; STABILITY AB The process of the development of the nuclei and of subsequent seeding in "contactless" physical vapor transport is investigated experimentally. Consecutive stages of low supersaturation nucleation in the "contactless" geometry for the growth of CdTe crystals from the vapor are shown. The effects of the temperature held, geometry of the system, and the experimental procedures on the process are presented and discussed. The experimental results are found to be consistent with our earlier numerical modeling results. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Polish Acad Sci, Inst Phys, PL-02668 Warsaw, Poland. NASA, George C Marshall Space Flight Ctr, USRA, Huntsville, AL 35812 USA. Brimrose Corp Amer, Baltimore, MD 21236 USA. RP Grasza, K (reprint author), Polish Acad Sci, Inst Phys, Al Lotnikow 32-46, PL-02668 Warsaw, Poland. NR 12 TC 6 Z9 6 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD DEC PY 1999 VL 207 IS 3 BP 179 EP 187 DI 10.1016/S0022-0248(99)00362-0 PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 258LZ UT WOS:000083841800003 ER PT J AU Yesilyurt, S Vujisic, L Motakef, S Szofran, FR Volz, MP AF Yesilyurt, S Vujisic, L Motakef, S Szofran, FR Volz, MP TI A numerical investigation of the effect of thermoelectromagnetic convection (TEMC) on the Bridgman growth of Ge1-xSix SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE thermoelectromagnetic convection; Bridgman growth; GeSi ID MAGNETIC-FIELDS; CRYSTAL-GROWTH; SEGREGATION; MELT AB Thermoelectric currents at the growth interface of GeSi during Bridgman growth are shown to promote convection when a low-intensity axial magnetic field is applied. TEMC, typically, is characterized by a meridional flow driven by the rotation of the fluid; meridional convection alters the composition of the melt. and shape of the growth interface substantially. TEMC effect is more important in micro-gravity environment than the terrestrial one, and can be used to control convection during directional solidification of GeSi. Tn this work, we report on the numerical simulation of the effect of TEMC on the growth of GeSi. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Cape Simulat Inc, Newton, MA 02458 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Yesilyurt, S (reprint author), Cape Simulat Inc, Suite 100,1 Bridge St, Newton, MA 02458 USA. RI Yesilyurt, Serhat/H-9546-2013 OI Yesilyurt, Serhat/0000-0001-5425-1532 NR 17 TC 34 Z9 35 U1 1 U2 10 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD DEC PY 1999 VL 207 IS 4 BP 278 EP 291 DI 10.1016/S0022-0248(99)00377-2 PG 14 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 267WG UT WOS:000084381800004 ER PT J AU Mulligan, T Russell, CT Anderson, BJ Lohr, DA Rust, D Toth, BA Zanetti, LJ Acuna, MH Lepping, RP Gosling, JT AF Mulligan, T Russell, CT Anderson, BJ Lohr, DA Rust, D Toth, BA Zanetti, LJ Acuna, MH Lepping, RP Gosling, JT TI Intercomparison of NEAR and Wind interplanetary coronal mass ejection observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC CLOUDS; MODELS; AU AB Nearly 4 months of continuous interplanetary magnetic field measurements September 1997 through December 1997 have allowed us to compare four interplanetary coronal mass ejection (ICME) events seen by the NEAR and Wind spacecraft. When the spacecraft are in close proximity (separated by 1 degrees in azimuth relative to the sun) the ICMEs seen by Wind and NEAR have similar signatures as expected for structures with dimensions along the solar wind flow of similar to 0.2 AU. When the NEAR spacecraft is separated by similar to 5.4 degrees in azimuth from the Earth the vector signature of ICMEs seen at NEAR begins to differ from those seen at Wind even though the magnitude of the field in the events and the background solar wind show similarities at the two spacecraft. When the spacecraft are separated by 11.3 degrees the magnetic signatures are quite different and sometimes ICMEs are seen only at one of the two locations. Nevertheless, in all cases the magnetic helicity of the cloud structures seen at NEAR is the same as at Wind. The radial speeds of the shock and ICME leading edge as they cross Wind and the time delays of those events, for which we have some assurance that they also arrived at NEAR, indicate that the ICMEs decelerate measurably as they travel near 1 AU. C1 Univ Calif Los Angeles, IGPP, Los Angeles, CA 90096 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90096 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Mulligan, T (reprint author), Univ Calif Los Angeles, IGPP, 405 Hilgard Ave, Los Angeles, CA 90096 USA. RI Anderson, Brian/I-8615-2012 NR 23 TC 27 Z9 27 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28217 EP 28223 DI 10.1029/1999JA900215 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800020 ER PT J AU Lu, JY Whang, YC Burlaga, LF AF Lu, JY Whang, YC Burlaga, LF TI Interaction of a strong interplanetary shock with the termination shock SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PRESSURE-BALANCED STRUCTURES; MERGED INTERACTION REGIONS; INTERSTELLAR PICKUP IONS; ANOMALOUS COSMIC-RAYS; SOLAR-WIND; VOYAGER-2 OBSERVATIONS; OUTER HELIOSPHERE; NEUTRAL HYDROGEN; MAGNETIC-FIELD; DISTANCE AB The 1991 global merged interaction region (GMIR) shock is a strong forward shock observed from Voyager 2 on day 146 of 1991 at 34.6 AU. As the GMIR shock propagated outward in the distant heliosphere, it eventually encounters the termination shock. We study the interaction of the GMIR shock with the termination shock taking into account the influence of interstellar pickup protons on the solar wind and the shocks. Because the location of the termination shock is an unknown parameter, it remains uncertain about when and where the GMIR shock penetrates through the termination shock. This paper carries out calculations for the interaction to take place over a wide range of possible locations between 70 and 110 AU. The interaction can significantly modify the conditions of both shocks. For the GMIR shock, the interaction can cause a decrease of the shock speed by similar to 120 km/s, a decrease of the shock Mach number from similar to 1.9 to similar to 1.4, and a decrease of the shock strength from similar to 2.2 to similar to 1.6. For the termination shock, the interaction can cause an increase of the shock speed by similar to 95 km/s, a decrease of the shock Mach number from similar to 3.6 to similar to 2.6, and a decrease of the shock strength from similar to 3.2 to similar to 2.8. C1 Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Lu, JY (reprint author), Chinese Acad Sci, Ctr Space & Appl Res, Beijing 100080, Peoples R China. NR 45 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28249 EP 28254 DI 10.1029/1999JA900421 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800023 ER PT J AU Whang, YC Lu, JY Burlaga, LF AF Whang, YC Lu, JY Burlaga, LF TI The termination shock: 1979-1995 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; OUTER HELIOSPHERE; INTERPLANETARY SHOCKS; PICKUP IONS; HELIOPAUSE; DISTANCE; HYDROGEN; MODEL; MOTION; GAS AB We study the varying location, jump condition, and shock speed of the termination shock in 1979-1995 taking into account the effects of pickup protons. Pickup protons and neutral hydrogen are calculated using a hot hydrogen model. Plasma and magnetic field data from Voyagers over a 17-year period from 1978 through 1994 are used as input. The steady state MHD equations are integrated to extrapolate input data from the Voyager trajectory to the upstream of the termination shock. This study continues to show that the location of the termination shock is anticorrelated with the sunspot number, moving inward or outward during the rising or declining phase of the solar cycle. We expect that this anticorrelation would repeat itself during the solar cycle 23 in an extension of this study beyond 1995, and the result can predict the Voyager crossing of the termination shock. If the average location of the termination shock is at 79 AU, the pickup proton effects reduce the average shock strength from 3.87 to 3.15 and reduce the average temperature ratio of the solar wind protons from 378 to 42.1. We use the empirical formula of Whang and Burlaga [1999] to calculate the postshock temperature of pickup protons, the average temperature ratio of pickup protons across the termination shock is similar to 4.5. C1 Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Whang, YC (reprint author), Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. EM whang@cua.edu; burlaga@lepvax.gsfc.nasa.gov NR 34 TC 15 Z9 15 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28255 EP 28262 DI 10.1029/1999JA900413 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800024 ER PT J AU Thejappa, G Goldstein, ML MacDowall, RJ Papadopoulos, K Stone, RG AF Thejappa, G Goldstein, ML MacDowall, RJ Papadopoulos, K Stone, RG TI Evidence for Langmuir envelope solitons in solar type III burst source regions SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ION-ACOUSTIC-WAVES; MAGNETIC-FIELD; RADIO-BURSTS; EMISSION MECHANISMS; PLASMA; TURBULENCE; COLLAPSE; STABILITY; WIND; INSTABILITY AB We present observational evidence for the generation of Langmuir envelope solitons in the source regions of solar type III radio bursts. The solitons appear to be formed by electron beams which excite either the modulational instability or oscillating two-stream instability (OTSI). Millisecond data from the Ulysses Unified Radio and Plasma Wave Experiment (URAP) show that Langmuir waves associated with type III bursts occur as broad intense peaks with timescales ranging from 15 to 90 ms (6 - 27 km). These broad field structures have the properties expected of Langmuir envelope solitons, namely, the normalized peak energy densities, W-L/n(e)T(e) similar to 10(-5), are well above the modulational instability threshold; the spatial scales L, which range from 1 to 5 Langmuir wavelengths, show a high degree of inverse correlation with (W-L/n(e)T(e))(1/2); and the observed widths of these broad peaks agree well with the predicted widths of envelope solitons. We show that the orientation of the Langmuir field structures is random with respect to the ambient magnetic field, indicating that they are probably isotropic structures that have evolved from initially pancake-like solitons. These observations suggest that strong turbulence processes, such as the modulational instability or the OTSI, stabilize the electron beams that produce type III bursts. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Thejappa, G (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI MacDowall, Robert/D-2773-2012; Goldstein, Melvyn/B-1724-2008 NR 45 TC 24 Z9 24 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28279 EP 28293 DI 10.1029/1999JA900363 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800026 ER PT J AU Pulkkinen, TI Baker, DN Cogger, LL Frank, LA Sigwarth, JB Kokubun, S Mukai, T Singer, HJ Slavin, JA Zelenyi, L AF Pulkkinen, TI Baker, DN Cogger, LL Frank, LA Sigwarth, JB Kokubun, S Mukai, T Singer, HJ Slavin, JA Zelenyi, L TI Spatial extent and dynamics of a thin current sheet during the substorm growth phase on December 10, 1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD MODEL; BURSTY BULK FLOWS; PLASMA SHEET; TAIL; MAGNETOSPHERE; MAGNETOTAIL; RECONNECTION; GEOTAIL AB Multispacecraft observations are analyzed to examine the dynamics of thin current sheet evolution during the early phases of a substorm during the period 0630-0800 UT on December 10, 1996, The ground signatures showed two activations, one latitudinally localized at 0731 UT and another, larger expansion around 0800 UT. A local model consisting of two current sheets (a thin current sheet and a thicker plasma sheet) was developed utilizing two-spacecraft magnetic field measurements within the magnetotail. Extension of the thin current sheet model to the inner magnetotail shows that during most of the growth phase, the thin current sheet intensified simultaneously and at the same fate in the mid- magnetotail (similar to 30 R-E) and near geosynchronous orbit. These results show that a thin current sheet extended from the near-geostationary region to the midtail, and that the entire current sheet responded to the driving in a coherent way. Furthermore, timings suggest that the onset-associated disturbances were observable in the midtail before the ground or geosynchronous signatures. C1 Univ Calgary, Dept Phys, Calgary, AB T2N 1N4, Canada. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Russian Acad Sci, Space Res Inst, Moscow 117810, Russia. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. RP Pulkkinen, TI (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80303 USA. RI Slavin, James/H-3170-2012; Pulkkinen, Tuija/D-8403-2012 OI Slavin, James/0000-0002-9206-724X; Pulkkinen, Tuija/0000-0002-6317-381X NR 24 TC 25 Z9 25 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28475 EP 28490 DI 10.1029/1999JA900240 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800040 ER PT J AU Lynch, KA Arnoldy, RL Kintner, PM Schuck, P Bonnell, JW Coffey, V AF Lynch, KA Arnoldy, RL Kintner, PM Schuck, P Bonnell, JW Coffey, V TI Auroral ion acceleration from lower hybrid solitary structures: A summary of sounding rocket observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WAVE COLLAPSE; ENERGIZATION MECHANISMS; SUPRAURORAL REGION; MAGNETIC-FIELD; IONOSPHERE; PLASMA; MAGNETOSPHERE; EIGENMODES; TURBULENCE; EVOLUTION AB In this paper we present a review of sounding rocket observations of the ion acceleration seen in nightside auroral zone lower hybrid solitary structures. Observations from Topaz3, Amicist, and Phaze2 are presented on various spatial scales, including the two-point measurements of the Amicist mission. From this collection of observations we will demonstrate the following characteristics of transverse acceleration of ions (TAI) in lower hybrid solitary structures (LHSS). The ion acceleration process is narrowly confined to 90 degrees pitch angle, in spatially confined regions of up to a few hundred meters across B, The acceleration process does not affect the thermal core of the ambient distribution and does not directly create a measurable effect on the ambient ion population outside the LHSS themselves. This precludes observation with these data of any nonlinear feedback between the ion acceleration and the existence or evolution of the density irregularities on which these LHSS events grow. Within the LHSS region the acceleration process creates a high-energy tail beginning at a few times the thermal ion speed. The ion acceleration events are closely associated with localized wave events. Accelerated ions bursts are also seen without a concurrent observation of a localized wave event, for two possible reasons. In some cases,the pitch angles of the accelerated tail ions are elevated above perpendicular; that is, the acceleration occurred below the observer and the mirror force has begun to act upon the distribution, moving it upward from the source. In other cases, the accelerated ion structure is spatially larger than the wave event structure, and the observation catches only the ion event. The occurrence rate of these ion acceleration events is related to the ambient environment in two ways: its altitude dependence can be modeled with the parameter B-2/n(e), and it is highest in regions of intense VLF activity. The cumulative ion outflow from these LHSS TAI is consistent with Freja statistics for VLF-type premidnight auroral upflow. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Space Plasma Phys Branch ES83, Huntsville, AL 35812 USA. Cornell Univ, Sch Elect Engn, Ithaca, NY 14853 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. RP Lynch, KA (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NR 39 TC 28 Z9 28 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28515 EP 28534 DI 10.1029/1999JA900289 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800043 ER PT J AU Collier, MR AF Collier, MR TI Evolution of kappa distributions under velocity space diffusion: A model for the observed relationship between their spectral parameters SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; DOUBLE-LAYERS; SOLITARY WAVES; FIELD LINES; HOT IONS; PLASMA; MAGNETOSPHERES; MAGNETODISC; GENERATION; PARTICLES AB Velocity space diffusion acting on superthermal ions whose distributions resemble kappa functions (Maxwellian core with a power law tail) will cause the distributions to evolve so that the high-energy spectral index kappa is linearly related to core temperature with a constant of proportionality that (1) scales inversely with the distribution's characteristic energy, (2) is independent of the diffusion coefficient, and (3) has a positive intercept. This type of behavior has been observed in five different studies covering the magnetospheres of Earth, Jupiter, and Saturn as well as the solar wind. These results indicate the following: (1) velocity space diffusion frequently plays the dominant role in shaping particle distribution functions in many diverse space plasma environments and (2) hotter distributions with steeper spectral indices are "older" distributions in that they have evolved considerably from the source distribution. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Collier, MR (reprint author), NASA, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. RI Collier, Michael/I-4864-2013 OI Collier, Michael/0000-0001-9658-6605 NR 37 TC 22 Z9 22 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28559 EP 28564 DI 10.1029/1999JA900355 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800046 ER PT J AU Ober, DM Thomsen, MF Gary, SP Gallagher, DL McComas, DJ AF Ober, DM Thomsen, MF Gary, SP Gallagher, DL McComas, DJ TI Survey of pancake-shaped warm ion distributions at geosynchronous orbit SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PITCH ANGLE DISTRIBUTIONS; EQUATORIAL MAGNETOSPHERE; CYCLOTRON INSTABILITY; PLASMA; PROTONS; WAVES; DAYSIDE; GEOS-2; MODEL; HE+ AB It has been proposed that the electromagnetic proton cyclotron instability is a strong source of heating for the anisotropic warm ions observed at geosynchronous orbit. We present here the results of a statistical study of pancake-shaped warm ion distributions using a 1-year interval of data observed with the Los Alamos magnetospheric plasma analyzer on the geosynchronous satellite 1994-084. Our results support previous findings that pancake-shaped warm ion distributions occur more frequently on the dayside of the magnetosphere and occur very close to the plasmapause. We also confirm that the electromagnetic proton cyclotron instability is operating and is constraining the hot proton temperature anisotropy. However, our results indicate that the pancake-shaped warm ion distributions observed at geosynchronous orbit are probably not generated by this instability but must be due to a different mechanism, possibly heating by lower hybrid waves. C1 Mission Res Corp, Nashua, NH 03062 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Ober, DM (reprint author), Mission Res Corp, 1 Tara Blvd,Suite 302, Nashua, NH 03062 USA. NR 28 TC 2 Z9 2 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1999 VL 104 IS A12 BP 28625 EP 28632 DI 10.1029/1999JA900150 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 266UN UT WOS:000084318800051 ER PT J AU Wolfenden, A Burris, CP Singh, M AF Wolfenden, A Burris, CP Singh, M TI Young's modulus and vibrational damping of sintered silicon carbide ceramics at high temperatures SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article ID ANELASTIC PROPERTIES C1 Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Wolfenden, A (reprint author), Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NR 9 TC 1 Z9 1 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0261-8028 J9 J MATER SCI LETT JI J. Mater. Sci. Lett. PD DEC PY 1999 VL 18 IS 24 BP 1995 EP 1997 DI 10.1023/A:1006685900597 PG 3 WC Materials Science, Multidisciplinary SC Materials Science GA 269BT UT WOS:000084456400007 ER PT J AU Handschuh, RF Bibel, GD AF Handschuh, RF Bibel, GD TI Experimental and analytical study of aerospace spiral bevel gear tooth fillet stresses SO JOURNAL OF MECHANICAL DESIGN LA English DT Article AB An aerospace-quality spiral bevel gearset was analytically and experimentally rolled through mesh to investigate tooth bending stress. A nonlinear finite element model utilized multiple teeth from the pinion and gear to simulate three-dimensional multitooth contact. The results were compared to those obtained experimentally with strain gages. A total of Jive strain gages, mounted in the root/fillet region of three teeth, were used. Effects of changing speed and load were measured. Tests were conducted from static (slow roll) to 14,400 rpm at power levels up to 537 kW (720 hp). C1 NASA, USA, Res Lab, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Handschuh, RF (reprint author), NASA, USA, Res Lab, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 25 TC 25 Z9 26 U1 2 U2 6 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 1050-0472 J9 J MECH DESIGN JI J. Mech. Des. PD DEC PY 1999 VL 121 IS 4 BP 565 EP 572 DI 10.1115/1.2829500 PG 8 WC Engineering, Mechanical SC Engineering GA 271KR UT WOS:000084593200016 ER PT J AU Wang, WF Sirota, JM Reuter, DC AF Wang, WF Sirota, JM Reuter, DC TI FTIR measurements of N-2-induced pressure broadening of allene (C3H4) in the nu(10) band SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID INFRARED-SPECTRUM; LINE-INTENSITIES; SYSTEM; ATMOSPHERE; NU(9) AB Nitrogen pressure-broadening coefficients have been measured in the 841 cm(-1) v(10) band of allene (H2C=C=CH2). The high-resolution absorption infrared spectra were recorded by a FTIR spectrometer at a temperature of 201 K The Voigt Line profile, convolved with a sine instrument function, was applied to the fit of the observed rovibrational Lines. No regular J or K dependence of the broadening coefficients was observed for this strong symmetric-top-molecule band. The power-exponential-gap (PEG) fitting law and the infinite-order-sudden (IOS) scaling law were modified for the fit of the N-2-broadening coefficients. The wavefunction mixing arising from the v(10)/v(9) Coriolis resonance was taken into account for the IOS law. A total of 180 broadening coefficients measured at 201 K were reproduced with an accuracy of 8.6 and 7.9% by the PEG and IOS laws, respectively. (C) 1999 Academic Press. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Planetary Syst Branch, Greenbelt, MD 20771 USA. RP Wang, WF (reprint author), Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, 1000 Hilltop Circle, Baltimore, MD 21250 USA. NR 32 TC 4 Z9 4 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD DEC PY 1999 VL 198 IS 2 BP 201 EP 208 DI 10.1006/jmsp.1999.7977 PG 8 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 259AP UT WOS:000083872100001 ER PT J AU Toth, RA AF Toth, RA TI Air- and N-2-broadening parameters of HDO and D2O, 709 to 1936 cm(-1) SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID LORENTZ-BROADENING COEFFICIENTS; LINE-SHIFT COEFFICIENTS; TRANSITION FREQUENCIES; STRENGTHS; NU(2)-BANDS; O-16 AB High-resolution measurements of air- and N-2-broadened widths and pressure-induced frequency shifts of HDO and D2O covering the spectral region between 700 and 2000 cm(-1) were obtained with absorption paths of 2.39, 25, 73, and 193 m. The majority of the measurements included the (010)-(000) bands of (HDO)-O-16 and D-2 O-16. Also measured were 17 lines of the pure rotational band of (HDO)-O-16 and several transitions of the (010)-(000) bands of (HDO)-O-18 and D-2 O-18 and a few transitions of the "hot", band, (020)-(010), for (HDO)-O-16 and D-2 O-16. The observed width coefficients ranged from 0.02 to 0.1 cm(-1)/atm and the pressure-induced shift coefficients fell between +0.012 and -0.012 cm(-1)/atm. Line mixing was observed for a few of the pairs of transitions of HDO but was of no consequence for D2O lines. However, the effects of line mixing were small and accurate results were obtained using the Voigt line profile. Collisional narrowing effects were not observed in the data (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 11 Z9 11 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD DEC PY 1999 VL 198 IS 2 BP 358 EP 370 DI 10.1006/jmsp.1999.7966 PG 13 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 259AP UT WOS:000083872100017 ER PT J AU Files, BS AF Files, Bradley S. TI NASA/JSC carbon nanotube project status SO JOURNAL OF NANOPARTICLE RESEARCH LA English DT Editorial Material C1 NASA, Mat & Proc Technol Branch EM2, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Files, BS (reprint author), NASA, Mat & Proc Technol Branch EM2, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. EM brad.files@jsc.nasa.gov NR 7 TC 4 Z9 4 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 1388-0764 J9 J NANOPART RES JI J. Nanopart. Res. PD DEC PY 1999 VL 1 IS 4 BP 507 EP 509 DI 10.1023/A:1010072116817 PG 3 WC Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary SC Chemistry; Science & Technology - Other Topics; Materials Science GA V19IV UT WOS:000208067000010 ER PT J AU Piorun, D Parusel, ABJ Rechthaler, K Rotkiewicz, K Kohler, G AF Piorun, D Parusel, ABJ Rechthaler, K Rotkiewicz, K Kohler, G TI Acid-base properties of bis-pyrazolopyridine derivatives in nonaqueous solutions SO JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY LA English DT Article DE acid-base equilibria; bis-pyrazolopyridines; hydrogen-bonding; charge transfer; fluorescence; semiempirical calculations ID CHARGE-TRANSFER; FLUORESCENCE; N,N-DIMETHYLANILINO-BIS-PYRAZOLOPYRIDINE; MODEL AB Acid-base properties of four 3,5-dimethyl-1,7-diphenlyl-bis-pyrazolo-[3,4-b; 4',3'-e]-pyridine derivatives with different substituents in position 4, i.e. N,N-dimethylaminophenyl, phenyl, nitrophenyl, and methoxyphenyl (DMA-DMPP, H-DMPP, NO(2)-DMPP, and CH(3)O-DMPP) were investigated in nonaqueous solutions. Absorption and stationary fluorescence as well as time-resolved spectroscopy were applied as methods. The acidity of the amino group in DMA-DMPP which is preferentially protonated in the ground state, does practically not change in the first excited state. The second protonation step of DMA-DMPP and the protonation of the other compounds occurs at the heterocyclic subunit, in the ground state most probably on the pyridine nitrogen. The basicity of this nitrogen atom increases remarkably in the first excited state. Experimental results were compared with those of semiempirical calculations. The amino group as the preferential site of protonation before the pyridine nitrogen in the ground state was confirmed. According to quantum mechanical computations, one pyrazolo nitrogen is preferentially protonated in the first excited state. The protonation is accompanied by a geometrical relaxation leading to a planarized conformer with a lower total energy. (C) 1999 Published by Elsevier Science S.A. All rights reserved. C1 Jan Kochanowski Univ Humanities & Sci, Inst Chem, PL-25020 Kielce, Poland. Univ Vienna, Inst Theoret Chem & Strahlenchem, A-1090 Vienna, Austria. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland. RP Piorun, D (reprint author), Jan Kochanowski Univ Humanities & Sci, Inst Chem, Checinska 5, PL-25020 Kielce, Poland. NR 12 TC 16 Z9 16 U1 0 U2 3 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 1010-6030 J9 J PHOTOCH PHOTOBIO A JI J. Photochem. Photobiol. A-Chem. PD DEC 1 PY 1999 VL 129 IS 1-2 BP 33 EP 41 DI 10.1016/S1010-6030(99)00182-3 PG 9 WC Chemistry, Physical SC Chemistry GA 257DX UT WOS:000083768100005 ER PT J AU Asakimori, K Burnett, TH Cherry, ML Chevli, K Christl, MJ Dake, S Derrickson, JH Fountain, WF Fuki, M Gregory, JC Hayashi, T Iwai, J Iyono, A Johnson, J Kobayashi, M Lord, JJ Miyamura, O Moon, KH Oda, H Ogata, T Olson, ED Parnell, TA Roberts, FE Shiina, T Strausz, SC Sugitate, T Takahashi, Y Tominaga, T Watts, JW Wefel, JP Wilczynska, B Wilczynski, H Wilkes, RJ Wolter, W Yokomi, H Zager, E AF Asakimori, K Burnett, TH Cherry, ML Chevli, K Christl, MJ Dake, S Derrickson, JH Fountain, WF Fuki, M Gregory, JC Hayashi, T Iwai, J Iyono, A Johnson, J Kobayashi, M Lord, JJ Miyamura, O Moon, KH Oda, H Ogata, T Olson, ED Parnell, TA Roberts, FE Shiina, T Strausz, SC Sugitate, T Takahashi, Y Tominaga, T Watts, JW Wefel, JP Wilczynska, B Wilczynski, H Wilkes, RJ Wolter, W Yokomi, H Zager, E CA JACEE Collaboration TI Interpreting anomalous electron pairs as new particle decays SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS LA English DT Letter ID HIGH-ENERGY COLLISIONS; SI-28 AB In heavy particle decays found in cosmic ray interactions recorded in the JACEE emulsion chambers, multiple electron pairs were previously reported. These pairs apparently originated from conversions of photons emitted in the decays. It is difficult to explain the overall properties of these decays in terms of known heavy particle decay modes. A recently published compilation of low-energy nuclear data suggests the presence of excess electron pairs with invariant mass of about 9 MeV/c(2), which may be explained by postulating the existence of a new neutral boson decaying into the electron pair. The feasibility of explaining the JACEE electron pairs with this hypothesis is presented. C1 Inst Nucl Phys, Krakow, Poland. Tezukayama Gakuin Univ, Nara, Japan. Hiroshima Int Univ, Hiroshima, Japan. Inst Cosm Ray Res, Tokyo, Japan. Hiroshima Univ, Hiroshima, Japan. KEK, Tsukuba, Ibaraki, Japan. Okayama Univ Sci, Okayama, Japan. Waseda Univ, Tokyo, Japan. Kochi Univ, Kochi 780, Japan. Kobe Univ, Kobe, Hyogo 657, Japan. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35899 USA. Louisiana State Univ, Baton Rouge, LA 70803 USA. Univ Washington, Seattle, WA 98195 USA. Kobe Womens Jr Coll, Kobe, Hyogo, Japan. RP Inst Nucl Phys, Krakow, Poland. EM Henryk.Wilczynski@ifj.edu.pl RI Wilkes, R.Jeffrey/E-6011-2013 NR 16 TC 4 Z9 4 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0954-3899 EI 1361-6471 J9 J PHYS G NUCL PARTIC JI J. Phys. G-Nucl. Part. Phys. PD DEC PY 1999 VL 25 IS 12 BP L133 EP L137 PG 5 WC Physics, Nuclear; Physics, Particles & Fields SC Physics GA 268NF UT WOS:000084421900001 ER PT J AU Cao, TT Zimmerman, DC AF Cao, TT Zimmerman, DC TI Procedure to extract Ritz vectors from dynamic testing data SO JOURNAL OF STRUCTURAL ENGINEERING-ASCE LA English DT Article ID EIGENSYSTEM REALIZATION-ALGORITHM AB Ritz vectors represent an alternative to mode shape vectors as suitable basis vectors for n-dimensional space. In numerical analysis, Ritz vectors have been shown to offer superior performance in model reduction and time-simulations. In this paper, we develop a methodology that is able to extract Ritz vectors from single and multiple shaker dynamic tests. It is shown that the identified "experimental'' Ritz vectors are identical to the analytically derived Ritz vectors when the dynamic test shaker locations and directions are used as the reference force locations in the analytical derivation. The sensitivity of the extraction algorithm to measurement noise is shown to be comparable to the sensitivity of modal parameters extracted from the same data set. Finally, to verify the feasibility and accuracy of the extraction algorithm, dynamic response data and static test results from the Space Shuttle vertical stabilizer assembly experimental database are utilized. Compared to static test data, accurate Ritz vectors were extracted using data from both accelerometer and laser-scanning vibrometer-based modal survey tests. C1 NASA, Lyndon B Johnson Space Ctr, Engn Struct & Dynam Branch, Houston, TX 77058 USA. Univ Houston, Dept Mech Engn, Houston, TX 77204 USA. RP Cao, TT (reprint author), NASA, Lyndon B Johnson Space Ctr, Engn Struct & Dynam Branch, Houston, TX 77058 USA. NR 9 TC 10 Z9 10 U1 0 U2 0 PU ASCE-AMER SOC CIVIL ENGINEERS PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2398 USA SN 0733-9445 J9 J STRUCT ENG-ASCE JI J. Struct. Eng.-ASCE PD DEC PY 1999 VL 125 IS 12 BP 1393 EP 1400 DI 10.1061/(ASCE)0733-9445(1999)125:12(1393) PG 8 WC Construction & Building Technology; Engineering, Civil SC Construction & Building Technology; Engineering GA 255PX UT WOS:000083679600005 ER PT J AU Zhao, H Sadhal, SS Trinh, EH AF Zhao, H Sadhal, SS Trinh, EH TI Internal circulation in a drop in an acoustic field SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID RADIATION FORCE; VISCOUS-FLUID; SPHERE; OSCILLATIONS; BUBBLE AB An: investigation of the internal flow field for a drop at the:antinode of a standing wave has been carried out. The main difference from the solid sphere case is-the inclusion of the shear stress and velocity continuity conditions at the liquid-gas interface. To the leading order of calculation, the internal flow field was found to be quite weak. Also, this order being fully time dependent has a zero mean flow. At the next higher order, steady internal flows are predicted and, as in the case of a solid sphere, there is a recirculating layer consisting of closed streamlines near the surface. In the case of a liquid drop, however, the behavior of this recirculating Stokes layer is quite interesting. It is predicted that the layer ceases to have recirculation when \M\>5/2 root 2[2+5(<(mu)over cap>/mu)], where <(mu)over cap> is the liquid viscosity, mu is the exterior gas-phase viscosity, and M is the dimensionless frequency parameter For the gas phase, defined by M=i omega a(2)rho/mu with a being the drop radius. Thorough experimental confirmation of this interesting new development needs to be conducted. Although it seems to agree with many experiments with levitated drops where no recirculating layer has been clearly observed, a new set of experiments for specifically testing this interesting development need to be carried out. (C) 1999 Acoustical Society of America. [S0001-4966(99)05511-3]. C1 Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. NASA Headquarters, Washington, DC 20546 USA. RP Zhao, H (reprint author), Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. NR 21 TC 25 Z9 26 U1 0 U2 8 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD DEC PY 1999 VL 106 IS 6 BP 3289 EP 3295 DI 10.1121/1.428182 PG 7 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 266YW UT WOS:000084328700027 PM 10615685 ER PT J AU Clark, RL Cox, DE AF Clark, RL Cox, DE TI Experimental demonstration of a band-limited actuator/sensor selection strategy for structural acoustic control SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID TURBULENT BOUNDARY-LAYER; ACTIVE CONTROL; SOUND RADIATION; PIEZOELECTRIC ACTUATORS; PLATE; SENSORS; TRANSMISSION; RESISTANCE; PLACEMENT AB A band-limited method of selecting actuators and sensors for structural acoustic control is reviewed, and experimental results are presented to demonstrate the approach. The selection methodology is based upon the decomposition of the Hankel singular values of a system model in terms of individual sensor and actuator configurations for lightly damped structures. The technique selects sensor and actuator combinations which couple well to structural modes that radiate efficiently. However, it rejects sensor and actuator combinations which couple well to modes that are inefficient acoustic radiators or are outside of the desired bandwidth of control. Selecting transducer combinations which filter modes outside of the desired bandwidth serves to minimize the potential for spillover and instability associated with unmodeled or poorly modeled dynamics. The approach is computationally efficient since it is based upon open-loop dynamics and does not require iterative nonlinear optimization. (C) 1999 Acoustical Society of Amer-ica. [S0001-4966(99)06812-5]. C1 Duke Univ, Dept Mech Engn & Mat Sci, Durham, NC 27708 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Duke Univ, Dept Mech Engn & Mat Sci, Durham, NC 27708 USA. NR 34 TC 6 Z9 7 U1 1 U2 1 PU ACOUSTICAL SOC AMER AMER INST PHYSICS PI MELVILLE PA STE 1 NO 1, 2 HUNTINGTON QUADRANGLE, MELVILLE, NY 11747-4502 USA SN 0001-4966 EI 1520-8524 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD DEC PY 1999 VL 106 IS 6 BP 3407 EP 3414 DI 10.1121/1.428194 PG 8 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 266YW UT WOS:000084328700040 ER PT J AU Cruise, JF Limaye, AS Al-Abed, N AF Cruise, JF Limaye, AS Al-Abed, N TI Assessment of impacts of climate change on water quality in the southeastern United States SO JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION LA English DT Article DE climate change; regional assessment; water quality; modeling ID MODEL; GIS AB An assessment of current and future water quality conditions in the southeastern United States has been conducted using the EPA BASINS GIS/database system. The analysis has been conducted for dissolved oxygen, total nitrate nitrogen and pH. Future streamflow conditions have been predicted for the region based on the United Kingdom Hadley Center climate model. Thus far, the analyses have been conducted at a fairly coarse spatial scale due to time and resource limitations. Two hydrologic modeling techniques have been employed in future streamflow prediction: a regional stochastic approach and the application of a physically based soil moisture model. The regional model has been applied to the entire area while the physically based model is being used at selected locations to enhance and support the stochastic model. The results of the study reveal that few basins in the southeast exhibit dissolved oxygen problems, but that several watersheds exhibit high nitrogen levels. These basins are located in regions of intense agricultural activity or in proximity to the gulf coast. In many of these areas, streamflow is projected to decline over the next 30-50 years,thus exacerbating these water quality problems. C1 Univ Alabama, Dept Civil & Environm Engn, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Jordan Univ Sci & Technol, Dept Agr Engn & Technol, Irbid 22110, Jordan. RP Cruise, JF (reprint author), Univ Alabama, Dept Civil & Environm Engn, Huntsville, AL 35899 USA. NR 10 TC 26 Z9 32 U1 6 U2 10 PU AMER WATER RESOURCES ASSOC PI HERNDON PA 950 HERNDON PARKWAY SUITE 300, HERNDON, VA 20170-5531 USA SN 1093-474X J9 J AM WATER RESOUR AS JI J. Am. Water Resour. Assoc. PD DEC PY 1999 VL 35 IS 6 BP 1539 EP 1550 DI 10.1111/j.1752-1688.1999.tb04236.x PG 12 WC Engineering, Environmental; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA 271ZB UT WOS:000084624600022 ER PT J AU Hatch, U Jagtap, S Jones, J Lamb, M AF Hatch, U Jagtap, S Jones, J Lamb, M TI Potential effects of climate change on agricultural, water use in the southeast US SO JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION LA English DT Article DE simulation modeling; crop response; agricultural economics and farm management; agricultural water use; irrigation; multidisciplinary AB Climate change has the potential to have dramatic effects on the agricultural sector nationally and internationally as documented in many research papers. This paper reports on research that was focused on a specific crop growing area to demonstrate how farm managers might respond to climate-induced yield changes and the implications of these responses for agricultural water use. The Hadley model was used to generate climate scenarios for important agricultural areas of Georgia in 2030 and 2090. Linked crop response models indicated generally positive yield changes, as increased temperatures were associated with increased precipitation and CO2. Using a farm management model, differences in climate-induced yield impacts among crops led to changes in crop mix and associated water use; non-irrigated cropland received greater benefit since irrigated land was already receiving adequate moisture. Model results suggest that farm managers will increase cropping intensity by decreasing fallowing and increasing double cropping; corn acreage decreased dramatically, peanuts decreased moderately and cotton and winter wheat increased. Water use on currently irrigated cropland fell. The potential for increased water use through conversion of agriculturally important. but currently non-irrigated, growing areas is substantial. C1 Auburn Univ, Dept Agr Econ & Rural Sociol, Auburn, AL 36849 USA. NASA, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Univ Florida, Dept Agr & Biol Engn, Gainesville, FL 32611 USA. USDA ARS, Natl Peanut Res Lab, Dawson, GA 31742 USA. RP Hatch, U (reprint author), Auburn Univ, Dept Agr Econ & Rural Sociol, Auburn, AL 36849 USA. NR 21 TC 15 Z9 15 U1 1 U2 3 PU AMER WATER RESOURCES ASSOC PI HERNDON PA 950 HERNDON PARKWAY SUITE 300, HERNDON, VA 20170-5531 USA SN 1093-474X J9 J AM WATER RESOUR AS JI J. Am. Water Resour. Assoc. PD DEC PY 1999 VL 35 IS 6 BP 1551 EP 1561 DI 10.1111/j.1752-1688.1999.tb04237.x PG 11 WC Engineering, Environmental; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA 271ZB UT WOS:000084624600023 ER PT J AU Strzepek, KM Major, DC Rosenzweig, C Iglesias, A Yates, DN Holt, A Hillel, D AF Strzepek, KM Major, DC Rosenzweig, C Iglesias, A Yates, DN Holt, A Hillel, D TI New methods of modeling water availability for agriculture under climate change: The US Cornbelt SO JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION LA English DT Article DE water demand; water supply; agriculture; irrigation; climate change; US Cornbelt ID OCEAN-ATMOSPHERE MODEL AB This paper reports on new methods of linking climate change scenarios with hydrologic, agricultural an water planning models to study future water availability for agriculture, an essential element of sustainability. The study is based on the integration of models of water supply and demand, and of crop growth and irrigation management. Consistent modeling assumptions, available databases, and scenario simulations are used to capture a range of possible future conditions. The linked models include WATBAL for water supply; CERES, SOYGRO, and CROPWAT for crop and irrigation modeling; and WEAP for water demand forecasting, planning and evaluation. These models are applied to the U.S. Cornbelt using forecasts of climate change, agricultural production, population and GDP growth. Results suggest that, at least in the near term, the relative abundance of water for agriculture can be maintained under climate change conditions. However, increased water demands from urban growth, increases in reservoir evaporation and increases in crop consumptive use must be accommodated by timely improvements in crop, irrigation and drainage technology, water management, and institutions. These improvements are likely to require substantial resources and expertise. In the highly irrigated basins of the region, irrigation demand greatly exceeds industrial and municipal demands. When improvements in irrigation efficiency are tested, these basins respond by reducing demand and lessening environmental stress with an improvement in system reliability, effects particularly evident under a high technology scenario. Rainfed lands in the Cornbelt are not forced to invest in irrigation, but there is some concern about increased water-logging during the spring and consequent required increased investment in agricultural drainage. One major water region in the Cornbelt also provides a useful caveat: change will not necessarily be continuous and monotonic. Under one GCM scenario for the 2010s, the region shows a significant decrease in system reliability, while the scenario for the 2020s shows an increase. C1 Univ Colorado, Boulder, CO 80309 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Stockholm Environm Inst, Boston, MA 02116 USA. RP Strzepek, KM (reprint author), Univ Colorado, Boulder, CO 80309 USA. NR 32 TC 13 Z9 13 U1 1 U2 18 PU AMER WATER RESOURCES ASSOC PI HERNDON PA 950 HERNDON PARKWAY SUITE 300, HERNDON, VA 20170-5531 USA SN 1093-474X J9 J AM WATER RESOUR AS JI J. Am. Water Resour. Assoc. PD DEC PY 1999 VL 35 IS 6 BP 1639 EP 1655 DI 10.1111/j.1752-1688.1999.tb04242.x PG 17 WC Engineering, Environmental; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA 271ZB UT WOS:000084624600028 ER PT J AU Barnes, NP Walsh, BM Hutcheson, RL Equall, RW AF Barnes, NP Walsh, BM Hutcheson, RL Equall, RW TI Pulsed F-4(3/2) to I-4(9/2) operation of Nd lasers SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID ROOM-TEMPERATURE; YAG LASER; 946 NM; DIODE-ARRAYS; GARNET AB Nd lasers operating on the F-4(3/2) to I-4(9/2) transition, usually at similar to 0.94 mu m, can provide a useful source for many applications when they operate efficiently. Both efficiency and energy output are substantially increased by two new approaches: improvement of the basic design and the use of new laser materials, specifically, Nd:GYAG. Laser performance and gain results for both Nd:YAG and Nd:GYAG lasers that operate on the F-4(3/2) to I-4(9/2) transition are reported as a function of temperature. For the sake of comparison, results for these lasers when they operate on the F-4(3/2) to I-4(11/2) transition at 1.064 mu m are reported as well. In addition, preliminary second-harmonic generation results for this 0.94-mu m laser are reported. (C) 1999 Optical Society of America [S0740-3224(99)00512-3]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Boston Coll, Chestnut Hill, MA 02167 USA. Sci Mat, Bozeman, MT 59715 USA. RP Barnes, NP (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 17 TC 29 Z9 34 U1 0 U2 5 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD DEC PY 1999 VL 16 IS 12 BP 2169 EP 2177 DI 10.1364/JOSAB.16.002169 PG 9 WC Optics SC Optics GA 262JT UT WOS:000084064300001 ER PT J AU Quattrochi, DA Luvall, JC AF Quattrochi, DA Luvall, JC TI Thermal infrared remote sensing for analysis of landscape ecological processes: methods and applications SO LANDSCAPE ECOLOGY LA English DT Review DE land-atmosphere energy exchanges; landscape thermal responses; thermal infrared remote sensing ID SURFACE-ENERGY BALANCE; SOIL-WATER CONTENT; NOAA-AVHRR DATA; LAND-SURFACE; DAILY EVAPOTRANSPIRATION; MULTISPECTRAL SCANNER; REGIONAL EVAPOTRANSPIRATION; TEMPERATURE MEASUREMENTS; SPATIAL-DISTRIBUTION; SATELLITE DATA AB Thermal infrared (TIR) remote sensing data can provide important measurements of surface energy fluxes and temperatures, which are integral to understanding landscape processes and responses. One example of this is the successful application of TIR remote sensing data to estimate evapotranspiration and soil moisture, where results from a number of studies suggest that satellite-based measurements from TIR remote sensing data can lead to more accurate regional-scale estimates of daily evapotranspiration. With further refinement in analytical techniques and models, the use of TIR data from airborne and satellite sensors could be very useful for parameterizing surface moisture conditions and developing better simulations of landscape energy exchange over a variety of conditions and space and time scales. Thus, TIR remote sensing data can significantly contribute to the observation, measurement, and analysis of energy balance characteristics (i.e., the fluxes and redistribution of thermal energy within and across the land surface) as an implicit and important aspect of landscape dynamics and landscape functioning. The application of TIR remote sensing data in landscape ecological studies has been limited, however, for several fundamental reasons that relate primarily to the perceived difficulty in use and availability of these data by the landscape ecology community, and from the fragmentation of references on TIR remote sensing throughout the scientific literature. It is our purpose here to provide evidence from work that has employed TIR remote sensing for analysis of landscape characteristics to illustrate how these data can provide important data for the improved measurement of landscape energy response and energy flux relationships. We examine the direct or indirect use of TIR remote sensing data to analyze landscape biophysical characteristics, thereby offering some insight on how these data can be used more robustly to further the understanding and modeling of landscape ecological processes. C1 NASA, Global Hydrol & Climate Ctr, George C Marshall Space Flight Ctr, Marshall Space Flight Ce, AL 35812 USA. RP Quattrochi, DA (reprint author), NASA, Global Hydrol & Climate Ctr, George C Marshall Space Flight Ctr, SD60, Marshall Space Flight Ce, AL 35812 USA. NR 112 TC 75 Z9 80 U1 3 U2 37 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0921-2973 J9 LANDSCAPE ECOL JI Landsc. Ecol. PD DEC PY 1999 VL 14 IS 6 BP 577 EP 598 DI 10.1023/A:1008168910634 PG 22 WC Ecology; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA 235VP UT WOS:000082563500006 ER PT J AU Herrero, F AF Herrero, F TI Instrument design benefits from computer assistance SO LASER FOCUS WORLD LA English DT Editorial Material C1 NASA, Explorer Technol Program, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Herrero, F (reprint author), NASA, Explorer Technol Program, Goddard Space Flight Ctr, Code 710-2, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PENNWELL PUBL CO PI NASHUA PA 98 SPIT BROOK RD, NASHUA, NH 03062-2801 USA SN 0740-2511 J9 LASER FOCUS WORLD JI Laser Focus World PD DEC PY 1999 VL 35 IS 12 BP 141 EP 142 PG 2 WC Optics SC Optics GA 268TL UT WOS:000084431600032 ER PT J AU Carsey, FD Chen, GS Cutts, J French, L Kern, R Lane, AL Stolorz, P Zimmerman, W Ballou, P AF Carsey, FD Chen, GS Cutts, J French, L Kern, R Lane, AL Stolorz, P Zimmerman, W Ballou, P TI Exploring Europa's ocean: A challenge for marine technology of this century SO MARINE TECHNOLOGY SOCIETY JOURNAL LA English DT Article ID SURFACE AB The Galileo spacecraft has sent back tantalizing image data hinting at a vast ocean beneath a thick ice crust on Europa, one of Jupiter's moons which is about the size of our moon. NASA plans to establish definitively whether this ocean exists with the Europa Orbiter mission to be launched in 2003. Should the Europa ocean be a reality, and this looks quite likely, it will mean that another planet besides Earth has an old, deep, salty ocean; the consequences of such an ocean are profound, and there are good reasons to be prepared to take the next step, an in-situ examination of this ocean. A deep subsurface in-situ study of another planetary body has never been attempted, and the challenges are considerable. In this paper we address the technology to be developed to be ready for this exciting mission, and we seek to initiate the exchanges needed between the marine technology and space exploration communities. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Deep Ocean Engn Inc, San Leandro, CA USA. RP Carsey, FD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 4 Z9 4 U1 0 U2 0 PU MARINE TECHNOLOGY SOC INC PI WASHINGTON PA C/O I CLAYION MATTHEWS, 1828 L ST, NW, 9TH FL, WASHINGTON, DC 20036 USA SN 0025-3324 J9 MAR TECHNOL SOC J JI Mar. Technol. Soc. J. PD WIN PY 1999 VL 33 IS 4 BP 5 EP 12 PG 8 WC Engineering, Ocean; Oceanography SC Engineering; Oceanography GA 290MU UT WOS:000085680700002 ER PT J AU Raffaelle, RP Potdevin, T Hepp, AF Bailey, SG AF Raffaelle, RP Potdevin, T Hepp, AF Bailey, SG TI Electrochemical synthesis of CuInSe2 for thin film devices SO MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING LA English DT Article ID CULNSE2; GROWTH AB We have been investigating the materials properties and electrical characteristics of Schottky barriers on electrochemically deposited thin film copper indium diselenide (CIS). Electrochemical deposition is a simple and inexpensive technique of producing thin-film CIS. Stoichiometric control of the as-deposited films is provided by the deposition potential. Native defects, arising from stoichiometric deviations, have allowed the production of both p- and n-type CIS thin films from a single aqueous solution. We have compared the crystallinity, composition and electrical characteristics of as-deposited films to similar films annealed in an Argon atmosphere. The crystallinity showed a significant improvement with annealing. Current versus voltage measurements were used to verify the rectifying behavior of the Schottky barriers and determine their barrier heights. A decrease in the barrier height with increasing carrier density was observed. The capacitance versus voltage dependence of Al Schottky contacts was used to determine the carrier densities in the films. Carrier densities were found to increase with deviation from stoichiometry and decrease with annealing temperature. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 Florida Inst Technol, Dept Phys & Space Sci, Melbourne, FL 32901 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Raffaelle, RP (reprint author), Florida Inst Technol, Dept Phys & Space Sci, 150 W Univ Blvd, Melbourne, FL 32901 USA. NR 18 TC 11 Z9 13 U1 0 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 1369-8001 J9 MAT SCI SEMICON PROC JI Mater. Sci. Semicond. Process PD DEC PY 1999 VL 2 IS 4 BP 289 EP 296 DI 10.1016/S1369-8001(99)00025-6 PG 8 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter SC Engineering; Materials Science; Physics GA 358EW UT WOS:000089545500001 ER PT J AU Lee, SMC Moore, AD Fritsch-Yelle, JM Greenisen, MC Schneider, SMF AF Lee, SMC Moore, AD Fritsch-Yelle, JM Greenisen, MC Schneider, SMF TI Inflight exercise affects stand test responses after space flight SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article DE microgravity; orthostasis; exercise countermeasures; aerobic exercise; heart rate; blood pressure ID NEGATIVE-PRESSURE EXERCISE; BED-REST; ORTHOSTATIC INTOLERANCE; ARTERIAL-PRESSURE; HEART-RATE; SPACEFLIGHT; HUMANS; ADAPTATION; TILT; GZ AB Purpose: The purpose of this study was to determine whether exercise performed by Space Shuttle crew members during short-duration space flights (9-16 d) affects the heart rate (HR) and blood pressure (BP) responses to standing within 2-4 h of landing, Methods: Thirty crew members performed self-selected inflight exercise and maintained exercise logs to monitor their exercise intensity and duration. Two subjects participated in this investigation during two different flights. A 10-min stand test, preceded by at least 6 min of quiet supine rest, was completed 10-15 d before launch (PRE) and within 4 h of landing (POST). Based upon their inflight exercise records, subjects were grouped as either high (HIex: greater than or equal to 3 times/week, HR greater than or equal to 70% HRmax greater than or equal to 20 min/session, N = 11), medium (MEDex: greater than or equal to 3 times/week, HR greater than or equal to 70% HRmax greater than or equal to 20 min/session, N = 10), or low (LOex: greater than or equal to 3 times/week, HR and duration variable, N = 11) exercisers. HR and BP responses to standing were compared between groups (ANOVA, P less than or equal to 0.05). Results: There were no PRE differences between the groups in supine or standing HR and BP. Although POST supine HR was similar to PRE, all groups had an increased standing HR compared with PRE. The increase in HR upon standing was significantly greater after flight in the LOex group (36 +/- 5 bpm) compared with HIex or MEDex groups (25 +/- 1 bpm; 22 +/- 2 bpm). Similarly, the decrease in pulse pressure (PP) from supine to standing was unchanged after space flight in the MEDex and HIex goups but was significantly greater in the LOex group (PRE: -9 +/- 3; POST: -19 +/- 4 mm Hg). Conclusions: Thus, moderate to high levels of inflight exercise attenuated HR and PP responses to standing after space flight. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Wyle Labs, Life Sci Syst & Serv Div, Houston, TX USA. RP Schneider, SMF (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SD3,2101 NASA Rd 1, Houston, TX 77058 USA. NR 34 TC 14 Z9 15 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD DEC PY 1999 VL 31 IS 12 BP 1755 EP 1762 DI 10.1097/00005768-199912000-00010 PG 8 WC Sport Sciences SC Sport Sciences GA 265MC UT WOS:000084247100010 PM 10613425 ER PT J AU Koss, MB LaCombe, JC Tennenhouse, LA Glicksman, ME Winsa, EA AF Koss, MB LaCombe, JC Tennenhouse, LA Glicksman, ME Winsa, EA TI Dendritic growth tip velocities and radii of curvature in microgravity SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID CRYSTAL-GROWTH; DENSITY CHANGE; SOLIDIFICATION; SUCCINONITRILE; CONVECTION; TERRESTRIAL; LIQUID; STATE AB Dendritic growth is the common mode of solidification encountered when metals and alloys freeze under low thermal gradients. The growth of dendrites in pure melts depends on the transport of latent heat from the moving crystal-melt interface and the influence of weaker effects like the interfacial energy, Experimental data for critical tests of dendritic growth theories remained limited because dendritic growth can be complicated by convection. The Isothermal Dendritic Growth Experiment (IDGE) was developed specifically to test dendritic growth theories by performing measurements with succinonitrile (SCN) in microgravity, thus eliminating buoyancy-induced convection. The first flight of the IDGE in 1994 operated for 9 days at a mean quasi-static acceleration of 0.7 x 10(-6) g(0). The velocity and radius data show that at supercoolings above approximately 0.4 K, dendritic growth in SCN under microgravity conditions is diffusion limited. By contrast, under terrestrial conditions, dendritic growth of SCN is dominated by convection for supercoolings below 1.7 K. The theoretical and experimental Peclet numbers exhibit modest disagreement, indicating that transport theories of dendritic solidification require some modification. Finally, the kinetic selection rule for dendritic growth, VR2 = constant, where V is the velocity of the tip and R is the radius of curvature at the tip, appears to be independent of the gravity environment, with a slight dependence on the supercooling. C1 Rensselaer Polytech Inst, Dept Mat Sci & Engn, Troy, NY 12180 USA. NASA, Glen Res Ctr, Fluids & Combust Facil, Micrograv Sci Div, Cleveland, OH 44135 USA. RP Koss, MB (reprint author), Rensselaer Polytech Inst, Dept Mat Sci & Engn, Troy, NY 12180 USA. OI Glicksman, Martin/0000-0002-2675-2759 NR 46 TC 57 Z9 58 U1 0 U2 17 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD DEC PY 1999 VL 30 IS 12 BP 3177 EP 3190 DI 10.1007/s11661-999-0228-0 PG 14 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 269DK UT WOS:000084460900015 ER PT J AU Kayali, S AF Kayali, S TI Reliability of compound semiconductor devices for space applications SO MICROELECTRONICS RELIABILITY LA English DT Review ID HYDROGEN; MESFETS AB Application of semiconductor devices in high reliability space systems requires a thorough understanding of the reliability and failure mechanisms associated with the selected devices. This paper provides a description of the reliability and qualification issues related to the application of compound semiconductor devices in critical space systems. A discussion of common failure mechanisms, radiation effects and other reliability concerns is provided along with a discussion of methods for technology qualification for high reliability space applications. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kayali, S (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 303-200, Pasadena, CA 91109 USA. NR 20 TC 4 Z9 4 U1 2 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0026-2714 J9 MICROELECTRON RELIAB JI Microelectron. Reliab. PD DEC PY 1999 VL 39 IS 12 BP 1723 EP 1736 DI 10.1016/S0026-2714(99)00180-8 PG 14 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA 266QH UT WOS:000084310300002 ER PT J AU Leech, KJ Volk, HJ Heinrichsen, I Hippelein, H Metcalfe, L Pierini, D Popescu, CC Tuffs, RJ Xu, C AF Leech, KJ Volk, HJ Heinrichsen, I Hippelein, H Metcalfe, L Pierini, D Popescu, CC Tuffs, RJ Xu, C TI [C II] 158-mu m observations of a sample of late-type galaxies from the Virgo cluster SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies : clusters : individual : Virgo; galaxies : general; galaxies : ISM; infrared : galaxies; infrared : ISM : lines and bands ID LONG-WAVELENGTH SPECTROMETER; SPIRAL GALAXIES; STAR-FORMATION; LINE; PERFORMANCE; AREA; MASS AB We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESA's Infrared Space Observatory (ISO) obtaining spectra around the [C II] 157.741-mu m fine-structure line. These 19 galaxies are quiescent in star-forming activity compared with previous studies from airborne observatories, sample RC3 types 0 to 5 and come from both the cluster core and the cluster periphery. The sample enables us to probe any difference in the [C II] emission between different RC3 types or between core and periphery galaxies. 14 of the 19 galaxies were detected in the [C II] line. Any influence of the Virgo cluster environment on the [C II] emission was found to be small compared with the strong dependence of the line emission on basic measurables such as morphology or bulk mass of the stellar component, as measured by the near-IR (K'-band) luminosity. While the range of the [C II]-to-far-IR ratio is less than in other surveys (reflecting the fact these galaxies are relatively quiescent), there is a good correlation between the strength of the [C II] line and the far-IR flux, as measured by IRAS (FIR). We find a trend of increasing [C II]-to-FIR flux ratio with increasing galaxy lateness. Moreover, the [C II]-to-K'-band flux ratio shows a two order of magnitude difference between RC3 type 0 and RC3 types later than 5. These two correlations express the relation between the mechanism of the [C II] emission and the massive star formation activity of the galaxy. C1 ESA, Div Astrophys, ISO Data Ctr, Villafranca, Spain. Max Planck Inst Kernphys, D-69117 Heidelberg, Germany. Max Planck Inst Astron, D-69117 Heidelberg, Germany. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Romanian Acad, Astron Inst, Bucharest 75212, Romania. RP Leech, KJ (reprint author), ESA, Div Astrophys, ISO Data Ctr, Villafranca, Spain. EM kleech@iso.vilspa.esa.es NR 23 TC 30 Z9 30 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PY 1999 VL 310 IS 2 BP 317 EP 323 DI 10.1046/j.1365-8711.1999.02924.x PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264PQ UT WOS:000084191000006 ER PT J AU Proga, D Stone, JM Drew, JE AF Proga, D Stone, JM Drew, JE TI Line-driven disc wind models with an improved line force SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; hydrodynamics; methods : numerical; stars : early-type; stars : mass-loss; galaxies : nuclei ID STELLAR WINDS; STARS AB We describe an efficient method of calculating the radiation pressure resulting from spectral lines, including all the terms in the velocity gradient tensor. We apply this method to calculate the two-dimensional, time-dependent structure of winds from luminous discs. Qualitative features of our new models are very similar to those we calculated including only the dominant terms in the tensor. In particular, we find that models which displayed unsteady behaviour in our earlier paper are also unsteady with the new method, and gross properties of the winds, such as mass-loss rate and characteristic velocity, are not changed by the more accurate approach. The largest change caused by the new method is in the disc-wind opening angle: winds driven only by the disc radiation are more polar with the new method, whilst winds driven by the disc and central object radiation are typically more equatorial. In the closing discussion, we provide further insight into the way the geometry of the radiation field and consequent flow determine the time properties of the flow. C1 Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Proga, D (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. EM proga@sobolev.gsfc.nasa.gov; jstone@astro.umd.edu; j.drew@ic.ac.uk OI Drew, Janet/0000-0003-1192-7082 NR 18 TC 52 Z9 52 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PY 1999 VL 310 IS 2 BP 476 EP 482 DI 10.1046/j.1365-8711.1999.02935.x PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264PQ UT WOS:000084191000020 ER PT J AU Heymsfield, GM Halverson, JB Caylor, IJ AF Heymsfield, GM Halverson, JB Caylor, IJ TI A wintertime gulf coast squall line observed by EDOP airborne Doppler radar SO MONTHLY WEATHER REVIEW LA English DT Article ID 10-11 JUNE 1985; MESOSCALE CONVECTIVE SYSTEMS; TOGA-COARE; PRECIPITATION STRUCTURE; NUMERICAL-SIMULATION; STRATIFORM RAIN; REAR-INFLOW; EVOLUTION; ORGANIZATION; OKLAHOMA AB An extensive wintertime squall line on 13 January 1995 occurring along the U.S. Gulf of Mexico coastline is examined using airborne radar observations combined with conventional data analysis. Flight tracks with the ER-2 Doppler radar (EDOP) mounted on the high-altitude (20 km) ER-2 aircraft provided a unique view of the vertical structure of this line. In this paper, the authors document the squall line structure, and compare and contrast this structure with Ether published cases. The squall line had several prominent features that differ from previous studies: 1) the stratiform region was wide in comparison to more typical systems that are 50-100 km wide; 2) the trailing stratiform region consisted of two to three separate embedded trailing bands rather than one continuous band; 3) vertical motions in the trailing stratiform region were nearly twice as strong as previously reported values, with mean values approaching 1 m s(-1) between 7- and 9-km altitude, and larger values (1.5 m s(-1)) in the embedded bands; 4) reflectivities were large with mean stratiform values of about 38 dBZ, and maximum convective values of about 55 dBZ; 5) the squall line rear inflow descended to the surface well behind the leading edge (similar to 200 km); 6) the convective and squall line inflow region exhibited unique microphysics with small graupel or hail falling out of the tilted squall line updraft, and a wavy, elevated melting region associated with the inflow; and 7) the squall-scale transverse circulation was directly coupled with a jet streak thermally direct circulation, and the ascending branch of this direct circulation may have enhanced production of widespread stratiform rainfall. A conceptual model is presented highlighting the features of this squall line and the coupling of the squall line to the larger-scale flow. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Earth Syst Technol, Baltimore, MD 21201 USA. RP Heymsfield, GM (reprint author), NASA, Goddard Space Flight Ctr, Code 912, Greenbelt, MD 20771 USA. NR 41 TC 12 Z9 12 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD DEC PY 1999 VL 127 IS 12 BP 2928 EP 2949 DI 10.1175/1520-0493(1999)127<2928:AWGCSL>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 263VJ UT WOS:000084145700012 ER PT J AU Rickenbach, TM AF Rickenbach, TM TI Cloud-top evolution of tropical oceanic squall lines from radar reflectivity and infrared satellite data SO MONTHLY WEATHER REVIEW LA English DT Article ID MESOSCALE CONVECTIVE SYSTEMS; PACIFIC WARM POOL; TOGA COARE; PASSIVE MICROWAVE; WESTERN PACIFIC; RAINFALL; STRATIFORM; SCALE; CLUSTERS; VARIABILITY AB Precipitation estimation over the tropical oceans is commonly performed using passive infrared (IR) measurements of cloud-top brightness temperature from geostationary satellites to infer the location of deep convection. It has been recognized in recent years that the majority of tropical precipitation is produced by mesoscale convective systems (MCSs). However, the relationship between the IR cloud-top patterns associated with MCSs and the underlying precipitation is not well understood. The assumption that the coldest cloud tops are associated with deep, active convection has been central to the characterization of cloud system motion and organization, and to many IR-based rainfall retrievals. Previous studies suggested that this View may be oversimplified when applied to propagating convective systems, such as squall lines. The goal of this study was to understand the evolution of the cold cloud associated with tropical oceanic squall line MCSs, and to discuss the implications for the retrieval of precipitation organization and rainfall rate from satellite IR data. Shipboard radar reflectivity and Geostationary Meteorological Satellite (Japan) brightness temperature data collected during the Tropical Oceans Global Atmospheres Coupled Ocean-Atmosphere Response Experiment have been used to study the evolution of two tropical oceanic squall line MCSs. Results suggested a complex, evolution-dependent relationship between the radar-derived precipitation pattern associated with mesoscale convective systems and the overlying cloud tops observed by the satellite. The coldest clouds formed in the wake of the leading edge of the propagating lines, following the intensification of deep convection on the leading edge. In an environment of deep tropospheric directional wind shear (e.g., during westerly wind bursts), the cold cloud shield became spatially decoupled from the source convection to form swaths of cold cloud. These cloud swaths were generally normal to the squall line orientation. As convection on the leading edge of the squall line weakened, the cord cloud shield expanded. As a result the coldest clouds were more closely associated with weaker surface precipitation. These results have implications for the interpretation of the location, shape, and motion of cold cloud features in the tropical western Pacific region. They may also help to explain the poor performance of IR rain retrieval algorithm when applied to instantaneous images. Results from this study may aid in the interpretation of twice-per-day "snapshots" of MCSs (from IR, microwave, and radar sensors) from the recently launched Tropical Rainfall Measuring Mission satellite. C1 NASA, Goddard Space Flight Ctr, TRMM Off, Greenbelt, MD 20771 USA. RP Rickenbach, TM (reprint author), NASA, Goddard Space Flight Ctr, TRMM Off, Code 910-1, Greenbelt, MD 20771 USA. NR 44 TC 25 Z9 25 U1 1 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD DEC PY 1999 VL 127 IS 12 BP 2951 EP 2976 DI 10.1175/1520-0493(1999)127<2951:CTEOTO>2.0.CO;2 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 263VJ UT WOS:000084145700013 ER PT J AU Sherwood, SC AF Sherwood, SC TI Convective precursors and predictability in the tropical western Pacific SO MONTHLY WEATHER REVIEW LA English DT Article ID SQUALL LINES; WATER-VAPOR; TOGA COARE; MESOSCALE; SYSTEMS; VARIABILITY; ATMOSPHERE; RAINFALL; MONSOON; MASS AB Conditions leading to convective outbreak in the Tropics are investigated by multivariate analysis of sounding and satellite data from the tropical western Pacific area. Circumstances that make the prediction problem difficult are discussed and addressed by applying linear "error-in-variables" and nonlinear statistical simulation techniques to a large dataset. Low- to midtropospheric moisture is identified as the dominant factor regulating convective outbreak in this region. Based on the results it is argued that such moisture is particularly important in regulating spontaneous convective outbreak, but instability and near-surface wind speed probably play some role in allowing previous shallow or midtopped cumulus activity to deepen. Mesoscale-mean convective available potential energy sufficient for convection is found to exist almost 90% of the time. Quantitative estimates of noise in the data are obtained and accounted for in reaching these conclusions. The results imply that large-scale mean fields alone may not contain enough information to determine the behavior of convection except probabilistically. Both types of statistical model predict that even under favorable mesoscale-mean conditions, convection is typically only 20%-30% likely to break out during a given 3-h period. C1 Victoria Univ Wellington, Sch Math & Comp Sci, Sch Earth Sci, Wellington, New Zealand. RP Sherwood, SC (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 916, Greenbelt, MD 20771 USA. RI Sherwood, Steven/B-5673-2008 OI Sherwood, Steven/0000-0001-7420-8216 NR 38 TC 100 Z9 100 U1 1 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD DEC PY 1999 VL 127 IS 12 BP 2977 EP 2991 DI 10.1175/1520-0493(1999)127<2977:CPAPIT>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 263VJ UT WOS:000084145700014 ER PT J AU Leys, D Tsapin, AS Nealson, KH Meyer, TE Cusanovich, MA Van Beeumen, JJ AF Leys, D Tsapin, AS Nealson, KH Meyer, TE Cusanovich, MA Van Beeumen, JJ TI Structure and mechanism of the flavocytochrome c fumarate reductase of Shewanella putrefaciens MR-1 SO NATURE STRUCTURAL BIOLOGY LA English DT Letter ID ANAEROBIC GROWTH; RESOLUTION; C(3); DEHYDROGENASE; RESPIRATION; REPLACEMENT; EXPRESSION; NCIMB400; PROGRAM; SITE AB Fumarate respiration is one of the most widespread types of anaerobic respiration. The soluble fumarate reductase of Shewanella putrefaciens MR-1 is a periplasmic tetraheme flavocytochrome c. The crystal structures of tbe enzyme were solved to 2.9 Angstrom for the uncomplexed form and to 2.8 Angstrom and 2.5 Angstrom for the fumarate and the succinate-bound protein, respectively. The structures reveal;a flexible capping domain linked to the FAD-binding domain. A catalytic mechanism for fumarate reduction based on the structure of the complexed protein is proposed. The mechanism for the reverse reaction is a model for the homologous succinate dehydrogenase (complex II) of the respiratory chain. In flavocytochrome c fumarate reductase, all redox centers are in van der Waals contact with one another, thus providing an efficient conduit of electrons from the hemes via the FAD to fumarate. C1 Dept Biochem Physiol & Microbiol, Lab Prot Biochem & Prot Engn, B-9000 Ghent, Belgium. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Arizona, Dept Biochem, Tucson, AZ 85721 USA. RP Van Beeumen, JJ (reprint author), Dept Biochem Physiol & Microbiol, Lab Prot Biochem & Prot Engn, KL Ledeganckstr 35, B-9000 Ghent, Belgium. NR 31 TC 103 Z9 107 U1 3 U2 19 PU NATURE AMERICA INC PI NEW YORK PA 345 PARK AVE SOUTH, NEW YORK, NY 10010-1707 USA SN 1072-8368 J9 NAT STRUCT BIOL JI Nat. Struct. Biol. PD DEC PY 1999 VL 6 IS 12 BP 1113 EP 1117 PG 5 WC Biochemistry & Molecular Biology; Biophysics; Cell Biology SC Biochemistry & Molecular Biology; Biophysics; Cell Biology GA 261RG UT WOS:000084022300012 PM 10581551 ER PT J AU Jacobson, NS Brady, MP Mehrotra, GM AF Jacobson, NS Brady, MP Mehrotra, GM TI Thermodynamics of selected Ti-Al and Ti-Al-Cr alloys SO OXIDATION OF METALS LA English DT Article DE Ti-Al; Ti-Al-Cr; thermodynamics; Knudsen-cell; mass spectrometry ID ALUMINA SCALE FORMATION; OXIDATION BEHAVIOR; MASS-SPECTROMETRY; SYSTEM; PHASE; STABILITY AB Two alloys in the Ti-Al system (Ti-45 a/o Al, Ti-62Al) and three alloys in the Ti-Al-Cr system (Ti-47Al-2Cr, Ti-47Al-13Cr, Ti-51Al-12Cr) were selected for a thermodynamic study because of interest in their high-temperature oxidation behavior. Activities of Al and Ti were measured using a twin Knudsen-cell assembly with one cell acting as an internal standard. For the Ti-45Al alloy. Al activity was also measured with an EMF technique. The Ti-Al-Cr data were consistent with the Al and Ti activities expected from the adjacent binary Ti-Al phase fields, Implications of this work on oxidation properties are discussed. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. Wright State Univ, Dayton, OH 45435 USA. RP NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RI Brady, Michael/A-8122-2008; Jacobson, Nathan/A-9411-2009 OI Brady, Michael/0000-0003-1338-4747; NR 47 TC 34 Z9 35 U1 6 U2 11 PU SPRINGER/PLENUM PUBLISHERS PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0030-770X EI 1573-4889 J9 OXID MET JI Oxid. Met. PD DEC PY 1999 VL 52 IS 5-6 BP 537 EP 556 DI 10.1023/A:1018820401533 PG 20 WC Metallurgy & Metallurgical Engineering SC Metallurgy & Metallurgical Engineering GA 227CH UT WOS:000082060400009 ER PT J AU Howard, A Padgett, C AF Howard, A Padgett, C TI A generalized approach to real-time pattern recognition in sensed data SO PATTERN RECOGNITION LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Howard, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 3 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0031-3203 J9 PATTERN RECOGN JI Pattern Recognit. PD DEC PY 1999 VL 32 IS 12 BP 2069 EP 2071 DI 10.1016/S0031-3203(99)00107-7 PG 3 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 230CH UT WOS:000082233900013 ER PT J AU Marcinkevicius, S Leon, R AF Marcinkevicius, S Leon, R TI Carrier dynamics in quantum dot structures with different interdot spacings SO PHYSICA B LA English DT Article; Proceedings Paper CT 11th International Conference on Nonequilibrium Carrier Dynamics in Semiconductors (HCIS 11) CY JUL 19-23, 1999 CL KYOTO, JAPAN SP Int Union Pure & Appl Phys, Phys Soc Japan, Japan Soc Appl Phys, IEEE, Electron Device Soc, Tokyo Chapter, Commemorat Assoc Japan World Exposit, Nagoya Univ Fdn, Inamori Fdn, Kajima Sci Fdn, Murata Sci Fdn, Res Fdn Electrotechnol Chubu, Support Ctr Adv Telecommun Technol Res, Telecommun Advancement Fdn, Denso Corp, Hitachi Europe, Matsushita Elect Ind Co Ltd, Mitsubishi Chem Corp, NTT, Basic Res Labs, Oki Elect Ind Co Ltd, Omron Corp, Sony Corp, Sumitomo Elect Ind Ltd, Toshiba Corp DE quantum dots; carrier dynamics; photoluminescence ID INGAAS/GAAS AB Photoexcited carrier dynamics have been examined by time-resolved photoluminescence in InGaAs/GaAs quantum dot structures with dot density ranging from 3.7 x 10(8) to 2.4 x 10(10) cm(-2). The time of carrier transfer into a dot decreases with increasing dot density as well as with photoexcited carrier density and temperature. It is suggested that potential barriers at the barrier, wetting layer and quantum dot interfaces hinder the carrier capture in low-density quantum dot structures. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Royal Inst Technol, Dept Phys Opt, S-10044 Stockholm, Sweden. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Marcinkevicius, S (reprint author), Royal Inst Technol, Dept Phys Opt, S-10044 Stockholm, Sweden. NR 7 TC 2 Z9 3 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-4526 J9 PHYSICA B JI Physica B PD DEC PY 1999 VL 272 IS 1-4 BP 36 EP 38 DI 10.1016/S0921-4526(99)00247-1 PG 3 WC Physics, Condensed Matter SC Physics GA 267TP UT WOS:000084375600012 ER PT J AU Fursa, DV Trajmar, S Bray, I Kanik, I Csanak, G Clark, REH Abdallah, J AF Fursa, DV Trajmar, S Bray, I Kanik, I Csanak, G Clark, REH Abdallah, J TI Integral cross sections for electron scattering by ground-state Ba atoms SO PHYSICAL REVIEW A LA English DT Article ID BARIUM VAPOR LASERS; ELASTIC-SCATTERING; PLASMA CLOUDS; IMPACT; EXCITATION; STRONTIUM; IONIZATION; CALCIUM AB We have used the convergent close-coupling method and a unitarized first-order many-body theory to calculate integral cross sections for elastic scattering and momentum transfer, for excitation of the 5d(21)S, 6s6p(1)P(1), 6s7p(1)P(1), 6s8p(1)P(1), 6s5d(1)D(2), 5d(21)D(2), 6S6d(1)D(2), 6p5d(1)F(3), 6s4f(1)F(3), 6p5d(1)D(2), 6s6p(3)P(0,1,2), 6s5d(3)D(1,2,3), and 6p5d(3)D(2) states, for ionization and for total scattering by electron impact on the ground state of barium at incident electron energies from 1 to 1000 eV. These results and all available experimental data have been combined to produce a recommended set of integral cross sections. [S1050-2947(99)02912-1]. C1 Flinders Univ S Australia, Adelaide, SA 5001, Australia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Fursa, DV (reprint author), Flinders Univ S Australia, GPO Box 2100, Adelaide, SA 5001, Australia. RI Fursa, Dmitry/C-2301-2009; Bray, Igor/B-8586-2009 OI Fursa, Dmitry/0000-0002-3951-9016; Bray, Igor/0000-0001-7554-8044 NR 38 TC 12 Z9 13 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD DEC PY 1999 VL 60 IS 6 BP 4590 EP 4599 DI 10.1103/PhysRevA.60.4590 PG 10 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 263WJ UT WOS:000084148000052 ER PT J AU Pinto, F AF Pinto, F TI Engine cycle of an optically controlled vacuum energy transducer SO PHYSICAL REVIEW B LA English DT Review ID KALUZA-KLEIN THEORIES; VANDERWAALS FORCES; CASIMIR ENERGY; DIELECTRIC FUNCTIONS; ANALYTIC REPRESENTATIONS; CARRIER RECOMBINATION; RADIATIVE CORRECTION; MACROSCOPIC BODIES; LIFSHITZ THEORY; DOPED SILICON AB An idealized system composed of two parallel, semiconducting boundaries separated by an empty gap of variable width is considered. A gedanken experiment is discussed to show that, in general, the total work done by the Casimir force along a closed path that includes appropriate transformations does not vanish. It is shown that, in the limit of an engine cycle bringing the two boundaries to a relatively small distance, positive net exchange of energy associated with the Casimir force field could quite possibly be achieved. Viable technological implementations of this idealized system are analyzed in some quantitative detail, in particular, in the case of doped and undoped c-Si boundaries. For the purpose of direct experimentation, measurements with both macroscopic and microelectromechanical de vices are suggested. A full theoretical and experimental study of systems of this kind on every scale will greatly contribute to a much deeper understanding of the nature of the Casimir force and associated concepts, including the possible manipulation of semiconducting nanostructures and the noninvasive optical characterization of semiconducting samples. In the event of no other alternative explanations, one should conclude that major technological advances in the area of endless, by-product free-energy production could be achieved. [S0163-1829(99)05345-X]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Pinto, F (reprint author), InterStellar Technol Corp, 639 W Foothill Blvd, Monrovia, CA 91016 USA. EM fpinto@brandx.net OI Pinto, Fabrizio/0000-0002-5883-8477 NR 151 TC 32 Z9 32 U1 0 U2 4 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD DEC 1 PY 1999 VL 60 IS 21 BP 14740 EP 14755 DI 10.1103/PhysRevB.60.14740 PG 16 WC Physics, Condensed Matter SC Physics GA 263TQ UT WOS:000084141700054 ER PT J AU Quijada, MA Tanner, DB Kelley, RJ Onellion, M Berger, H Margaritondo, G AF Quijada, MA Tanner, DB Kelley, RJ Onellion, M Berger, H Margaritondo, G TI Anisotropy in the ab-plane optical properties of Bi2Sr2CaCu2O8 single-domain crystals SO PHYSICAL REVIEW B LA English DT Article ID HIGH-TC SUPERCONDUCTORS; HIGH-TEMPERATURE SUPERCONDUCTORS; ELECTRON-PHONON INTERACTION; FERMI-LIQUID THEORY; PENETRATION DEPTH; CU-O; B-PLANE; INFRARED PROPERTIES; COHERENCE PEAK; NORMAL-STATE AB The ab-plane optical properties of the high-temperature superconductor Bi2Sr2CaCu2O8 are anisotropic in both the normal and the superconducting state. Consistent with the orthorhombic structure, the principal axes lie along the a and b crystallographic axes, nearly 45 degrees from the Cu-O bond direction. In the normal state, analysis of the temperature-dependent optical conductivity suggests a:scattering rate for the free carriers that shows ab anisotropy in both magnitude and temperature dependence. In;the superconducting state, the anisotropy in the oscillator strength of the superfluid response determined from the far-infrared frequency dependence of sigma(2)(omega) and from a sum-rule analysis leads to a penetration depth lambda(D) that is larger along the b axis than the a axis: (lambda(L)(b)>lambda(L)(a)). [S0163-1829(99)01845-7]. C1 Univ Florida, Dept Phys, Gainesville, FL 32611 USA. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. Ecole Polytech Fed Lausanne, Inst Phys Appl, CH-1015 Lausanne, Switzerland. RP Quijada, MA (reprint author), NASA, Goddard Space Flight Ctr, MS 551,Bldg 5,Rm C38, Greenbelt, MD 20771 USA. RI Margaritondo, Giorgio/B-1367-2008 NR 98 TC 72 Z9 72 U1 0 U2 3 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD DEC 1 PY 1999 VL 60 IS 21 BP 14917 EP 14934 DI 10.1103/PhysRevB.60.14917 PG 18 WC Physics, Condensed Matter SC Physics GA 263TQ UT WOS:000084141700078 ER PT J AU Panda, J Seasholtz, RG AF Panda, J Seasholtz, RG TI Measurement of shock structure and shock-vortex interaction in underexpanded jets using Rayleigh scattering SO PHYSICS OF FLUIDS LA English DT Article ID DENSITY-MEASUREMENTS; LIGHT-SCATTERING; SUPERSONIC JETS; FLOW; VELOCITY; PROFILES AB The density field of underexpanded supersonic free jets issuing from a choked circular nozzle was measured using a Rayleigh scattering-based technique. This reliable and nonintrusive technique is particularly suitable for high-speed flows and is fundamentally superior to the intrusive probes and particle-based techniques such as laser Doppler velocimetry. A continuous wave laser and photon counting electronics were employed for time and phase-averaged density measurements. The use of dust-free air for the entrained flow allowed measurements in the shear layer region. The free jets were produced in the plenum to ambient pressure ratio range of 1.88-5.75, which corresponded to a fully expanded Mach number range of 0.99 less than or equal to M(j)less than or equal to 1.8. A comparative study of schlieren photographs and time-averaged density data provided insight into the shock-cell structures. The radial profiles obtained at various axial stations covering a downstream distance of 10 jet diameters show the development of the jet shear layer and the decay of the shock-cells. The supersonic free jets produced screech sound. A phase-averaged photon counting technique, using the screech tone as the trigger source, was used to measure the unsteady density variation. The phase-averaged density data show the evolution of the large-scale turbulent vortices that are found to be modulated periodically along the flow direction. A comparison with previously obtained data showing near-field pressure fluctuation and convective speed of the organized vortices reveals many interesting dynamics. All quantities show regular spatial modulation. The locations of local maxima in density fluctuations are found to coincide with the high convective speed and the antinode points in the near-field pressure fluctuation. Interestingly, the periodicity of modulation is found to be somewhat different from the shock spacing. Instead it shows that the standing wave system, known to exist in the near-field pressure fluctuation, extends into the jet shear layer. The standing wave is formed between the downstream moving Kelvin-Helmholtz instability waves and the upstream propagating part of sound waves. A detailed field measurement of the unsteady density fluctuation was conducted for the M(j) = 1.19 and 1.42 jets for which the near-field pressure fluctuation data were obtained previously. The phase-matched, combined plots of the density fluctuation present inside the jet flow, and the pressure fluctuation present just outside the jet boundary provide a charming insight into the shock-vortex interaction leading to the sound wave generation. (C) 1999 American Institute of Physics. [S1070-6631(99)01712-2]. C1 Modern Technol Corp, Middleburg Hts, OH 44130 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Panda, J (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 41 TC 49 Z9 50 U1 0 U2 11 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD DEC PY 1999 VL 11 IS 12 BP 3761 EP 3777 DI 10.1063/1.870247 PG 17 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 252HK UT WOS:000083495900017 ER PT J AU Kuang, WJ AF Kuang, WJ TI Force balances and convective state in the earth's core SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Article DE magnetohydrodynamics; rotating fluid; convection; geodynamo ID INNER-CORE; GEODYNAMO; FIELD; DRIVEN; MODEL AB Kuang and Bloxham [Kuang, W., Bloxham, J., 1997a. An Earth-like numerical dynamo model. Nature 389, 371-374] found that numerical strong-field dynamo solutions in the earth's core depend strongly on viscous couplings introduced in simulation. In this paper, we discuss in detail how the force balances, the convective patterns and the magnetic field inside the core vary with the viscous couplings on the boundaries. We find that dynamo action region depends on the viscous couplings on the boundaries. When strong viscous couplings are retained in simulation, dynamo action is confined in the region near the inner core boundary (ICB) and within the tangent cylinder (the co-axial cylindrical surface across the core tangent to the inner core at the equator). Dynamo action occurs in the bulk of the fluid core when viscous couplings are neglected. The convective flow inside the tangent cylinder is very sensitive to the viscous couplings on the ICE, while the flow patterns outside the tangent cylinder do not vary qualitatively with the viscous couplings. We also find that when the viscous couplings are eliminated, the axial Lorentz torques acting on the co-axial cylindrical surfaces balance almost the fluid inertia, resulting in strong zonal flow (differential rotation) outside the tangent cylinder. However, they are strongly damped when the viscous couplings are retained. The thermal wind and the magnetic wind inside the tangent cylinder vary significantly with the viscous couplings on the ICE. With strong viscous couplings on the ICE, the magnetic wind is small compared with the thermal wind. Both winds are unidirectional, resulting in a zonal flow increasing with the depth and a super-rotating inner core. Without viscous coupling, both winds are comparable, Their directions vary with depth and with time, resulting in a zonal flow varying non-monotonically with the depth and an oscillating inner core. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. RP Kuang, WJ (reprint author), NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. RI Kuang, Weijia/K-5141-2012 OI Kuang, Weijia/0000-0001-7786-6425 NR 16 TC 25 Z9 29 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-9201 J9 PHYS EARTH PLANET IN JI Phys. Earth Planet. Inter. PD DEC PY 1999 VL 116 IS 1-4 BP 65 EP 79 DI 10.1016/S0031-9201(99)00116-8 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 262ND UT WOS:000084072600006 ER PT J AU Zhou, Y Girimaji, S AF Zhou, Y Girimaji, S TI Charles Gregory Speziale - Obituary SO PHYSICS TODAY LA English DT Biographical-Item C1 NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23665 USA. RP Zhou, Y (reprint author), NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23665 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD DEC PY 1999 VL 52 IS 12 BP 77 EP 77 DI 10.1063/1.882916 PG 1 WC Physics, Multidisciplinary SC Physics GA 263UA UT WOS:000084142600020 ER PT J AU Harmon, JK Campbell, DB Ostro, SJ Nolan, MC AF Harmon, JK Campbell, DB Ostro, SJ Nolan, MC TI Radar observations of comets SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT Western Pacific Geophysics Meeting on Terrestrial Planets and Early Solor System Evolution CY JUL, 1998 CL TAIPEI, TAIWAN ID ARAKI-ALCOCK 1983D; HYAKUTAKE C/1996 B2; CONTINUUM EMISSION; NUCLEUS; IMAGES; DUST; ASTEROIDS; HALLEY; ENCKE; GIOTTO AB Seven comets have been detected by Earth-based radars during the period 1980-1995. All but one of these gave a detectable echo fi om the nucleus, while three of the comets also showed a broad-band echo from large (similar to cm-size) grains in the inner coma. Although all observations have been of the CW (continuous-wave) type, which precludes direct size measurement, the radar cross sections are consistent with nucleus diameters averaging a few kilometers and varying over a range of ten. Comparisons with independent size estimates indicate relatively low radar albedos, implying nucleus surface densities of 0.5 to 1 g/cm(3), The surfaces of comet nuclei appear to be as rough as typical asteroid surfaces, but are considerably less dense. Analysis of coma echoes indicates that some comets emit large grains at rates (similar to ton/s) which are comparable with their gas and dust production rates, There is also some indirect evidence for grain evaporation or fragmentation within a few hundred to a few thousand kilometers of the nucleus. The highest priority of future radar observations will be to obtain delay-Doppler images of a nucleus, which would give direct size and shape estimates as well as a more reliable albedo. Delay-Doppler or interferometric imaging of the coma echo would also help to better characterize the grain halo. Ten short-period comets are potentially detectable during the next two decades, although the best radar opportunities may well come from comets yet to be discovered. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Arecibo Observ, Arecibo, PR 00612 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Harmon, JK (reprint author), Arecibo Observ, HC3 Box 53995, Arecibo, PR 00612 USA. RI Nolan, Michael/H-4980-2012 OI Nolan, Michael/0000-0001-8316-0680 NR 44 TC 27 Z9 27 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD DEC PY 1999 VL 47 IS 12 BP 1409 EP 1422 DI 10.1016/S0032-0633(99)00068-9 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 271AY UT WOS:000084570400002 ER PT J AU Potter, AE Killen, RM Morgan, TH AF Potter, AE Killen, RM Morgan, TH TI Rapid changes in the sodium exosphere of Mercury SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT Western Pacific Geophysics Meeting on Terrestrial Planets and Early Solor System Evolution CY JUL, 1998 CL TAIPEI, TAIWAN ID ATMOSPHERE; POTASSIUM AB We imaged Mercury in sodium D-1 and D-2 emission for 6 days during the period 13-20 November 1997 using a 10 x 10-arc a aperture image slicer coupled to a high-resolution spectrograph. We corrected the sodium images for smearing by the terrestrial atmosphere by computing the actual seeing function from surface reflection images, and used this function to correct the sodium images, During the period of observation, large daily changes took place in both the total amount of sodium and its distribution over the planet. Total sodium increased by a factor of about 3 during this period. The sodium emission was brightest at longitudes near the subsolar longitude in the range 130-150 degrees, with excess sodium at northern latitudes on some days, and excess sodium at southern latitudes on other days. There are no obviously outstanding geologic features at this longitude. The rapid changes observed Juring this period suggest a connection with solar activity, since the planet itself is apparently geologically inactive. The F10.7 cm solar Aux during this period varied only slightly, with an increase of about 15%, probably insufficient to account for the observed changes. However, there were a number of coronal mass ejection (CME) events, some of which were directed towards the general area of Mercury. We suggest that the changes in the visible neutral sodium atmosphere might be a result of the effect of CMEs on Mercury. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 Lunar & Planetary Inst, Houston, TX 77058 USA. SW Res Inst, San Antonio, TX USA. NASA Headquarters, Washington, DC 20546 USA. RP Potter, AE (reprint author), Lunar & Planetary Inst, 3600 Bay Area Blvd, Houston, TX 77058 USA. RI Morgan, Thomas/I-5943-2013 NR 15 TC 65 Z9 65 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD DEC PY 1999 VL 47 IS 12 BP 1441 EP 1448 DI 10.1016/S0032-0633(99)00070-7 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 271AY UT WOS:000084570400005 ER PT J AU Killen, RM Potter, A Fitzsimmons, A Morgan, TH AF Killen, RM Potter, A Fitzsimmons, A Morgan, TH TI Sodium D2 line profiles: clues to the temperature structure of Mercury's exosphere SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT Western Pacific Geophysics Meeting on Terrestrial Planets and Early Solor System Evolution CY JUL, 1998 CL TAIPEI, TAIWAN ID POTASSIUM ATMOSPHERES; SPATIAL-DISTRIBUTION; RADIATION PRESSURE; RELEVANCE; SURFACE; ATOMS AB The velocity distribution of atoms in an exosphere can be used to constrain source and loss processes. The velocity distribution itself can be constrained by observing the line profile of an atmospheric emission line, The only atomic species known to exist in the Hermean exosphere that has a strong enough resonance transition in the visible spectrum that its line profile can be observed from the ground with existing instruments is sodium. Line profiles of the sodium D2 emission (5889 A) were obtained at two facilities. On 29 and 30 May 1997, we obtained line profiles with the 107 inch telescope at The McDonald Observatory at coude focus. On 6 January 1998, we obtained line profiles at the Anglo-Australian telescope. The line profiles show that the sodium in Mercury's atmosphere is at least 700 It hotter than the surface temperature throughout the atmosphere. This implies that the interaction of the Na atoms with the surface is governed by energetic processes. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 SW Res Inst, San Antonio, TX 78284 USA. Lunar & Planetary Inst, Houston, TX 77058 USA. Queens Univ Belfast, Belfast BT7 1NN, Antrim, North Ireland. NASA Headquarters, Washington, DC 20546 USA. RP Killen, RM (reprint author), SW Res Inst, 6220 Culebra Rd,PODrawer 25810, San Antonio, TX 78284 USA. RI Morgan, Thomas/I-5943-2013 NR 25 TC 43 Z9 43 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD DEC PY 1999 VL 47 IS 12 BP 1449 EP 1458 DI 10.1016/S0032-0633(99)00071-9 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 271AY UT WOS:000084570400006 ER PT J AU Cockell, CS AF Cockell, CS TI Life on venus SO PLANETARY AND SPACE SCIENCE LA English DT Article ID DEEP-SEA; HYDROSTATIC-PRESSURE; AEROSOL-PARTICLES; PROTEIN STABILITY; GROWTH; TEMPERATURE; BACTERIUM; 250-DEGREES-C; ATMOSPHERE; SULFUR AB A fundamental question in exobiology remains the degree to which habitats on Venus, past and present, were, or are suitable for life. This has relevance for assessing the exobiological potential of extrasolar Venus-like greenhouse planets. In this paper the parameters of the Venusian surface and atmosphere are considered and the biochemical adaptations required to survive them are explored in the light of new information on microbial adaptations to extreme environments. Neither the pressure (9.5 MPa) nor the high carbon dioxide concentrations (97%) represent a critical constraint to the evolution of life on the surface or in the atmosphere. The most significant constraints to life on the surface are the lack of liquid water and the temperature (464 degrees C). In the lower and middle cloud layers of Venus, temperatures drop and water availability increases, generating a more biologically favorable environment. However, acidity and the problem of osmoregulation in hygroscopic sulfuric acid clouds become extreme and probably life-limiting If it is assumed that these constraints can be overcome, considerations on the survival of acidophilic sulfate-reducing chemoautotrophs suspended as aerosols in such an environment show that Venus does come close to possessing a habitable niche. Conditions on the surface and in the atmosphere may have been greatly ameliorated on early Venus and may also be ameliorated on extrasolar planets with early Venus-like characteristics where temperatures are less extreme and liquid water is available. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Cockell, CS (reprint author), NASA, Ames Res Ctr, MS 239-20, Moffett Field, CA 94035 USA. NR 79 TC 39 Z9 41 U1 2 U2 24 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD DEC PY 1999 VL 47 IS 12 BP 1487 EP 1501 DI 10.1016/S0032-0633(99)00036-7 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 271AY UT WOS:000084570400010 ER PT J AU Lorenz, RD McKay, CP Lunine, JI AF Lorenz, RD McKay, CP Lunine, JI TI Analytic investigation of climate stability on Titan: sensitivity to volatile inventory SO PLANETARY AND SPACE SCIENCE LA English DT Article ID VOYAGER-1 RADIO-OCCULTATION; HYPOTHESIZED OCEAN; EQUILIBRIUM-MODEL; ATMOSPHERE; SURFACE; EVOLUTION; METHANE; TEMPERATURE; TROPOSPHERE; REANALYSIS AB We develop a semiempirical grey radiative model to quantify Titan's surface temperature as a function of pressure and composition of a nitrogen-methane-hydrogen atmosphere, solar flux and atmospheric haze. We then use this model, together with non-ideal gas-liquid equilibrium theory to investigate the behavior of the coupled surface-atmosphere system on Titan. We find that a volatile-rich Titan is unstable with respect to a runaway greenhouse-small increases in solar luminosity from the present value can lead to massive increases in surface temperature. If methane has been photolyzed throughout Titan's history, then this runaway can only be avoided if the photolytic ethane is removed from the surface-atmosphere system. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. RP Lorenz, RD (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RI Lorenz, Ralph/B-8759-2016 OI Lorenz, Ralph/0000-0001-8528-4644 NR 42 TC 39 Z9 39 U1 2 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD DEC PY 1999 VL 47 IS 12 BP 1503 EP 1515 DI 10.1016/S0032-0633(99)00038-0 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 271AY UT WOS:000084570400011 PM 11543195 ER PT J AU van Belle, GT AF van Belle, GT TI Predicting stellar angular sizes SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID LUNAR OCCULTATION TECHNIQUE; LATE-TYPE STARS; VISUAL SURFACE BRIGHTNESS; HUBBLE-SPACE-TELESCOPE; EFFECTIVE TEMPERATURES; RESOLUTION MEASUREMENTS; DIAMETER MEASUREMENTS; SPECTRAL TYPES; CARBON STARS; GIANTS AB Reliable prediction of stellar diameters, particularly angular diameters, is a useful and necessary tool for the increasing number of milliarcsecond resolution studies being carried out in the astronomical community. A new and accurate technique of predicting angular sizes is presented for main-sequence stars, giant and supergiant stars, and more evolved sources such as carbon stars and Mira variables. This technique uses observed K and either V or B broadband photometry to predict V = 0 or B = 0 zero-magnitude angular sizes, which are then readily scaled to the apparent angular sizes with the V or B photometry. The spread in the relationship is 2.2% for main-sequence stars, 11%-12% for giant and supergiant stars, and 20%-26% for evolved sources. Compared to other simple predictions of angular size, such as linear radius-distance methods or blackbody estimates, zero-magnitude angular size predictions can provide apparent angular sizes with errors that are 2-5 times smaller. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP van Belle, GT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM gerard@huey.jpl.nasa.gov NR 56 TC 95 Z9 95 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD DEC PY 1999 VL 111 IS 766 BP 1515 EP 1523 DI 10.1086/316462 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 262XC UT WOS:000084092700004 ER PT J AU Lefsky, MA Cohen, WB Acker, SA Parker, GG Spies, TA Harding, D AF Lefsky, MA Cohen, WB Acker, SA Parker, GG Spies, TA Harding, D TI Lidar remote sensing of the canopy structure and biophysical properties of Douglas-fir western hemlock forests SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID LEAF-AREA INDEX; NORTHERN HARDWOOD FORESTS; PACIFIC-NORTHWEST; CONIFEROUS FORESTS; TROPICAL FORESTS; AIRBORNE LIDAR; LASER; BIOMASS; VOLUME; VEGETATION AB Scanning lidar remote sensing systems have recently become available for use in ecological applications. Unlike conventional microwave and optical sensors, lidar sensors directly measure the distribution of vegetation material along the vertical axis and can be used to provide three-dimensional, or volumetric, characterizations of vegetation structure. Ecological applications of scanning lidar have hitherto used one-dimensional indices to characterize canopy height. A novel three-dimensional analysis of lidar waveforms was developed to characterize the total volume and spatial organization of vegetation material and empty space within the forest canopy. These aspects of the physical structure of canopies have been infrequently measured, from either field or remote methods. We applied this analysis to 22 plots in Douglas-fir/western hemlock stands on the west slope of the Cascades Range in Oregon. Each plot had coincident lidar data and field measurements of stand structure. We compared results from the novel analysis to two earlier methods of canopy description. Using the indices of canopy structure from all three methods of description as independent variables in a stepwise multiple regression, we were able to make nonasymptotic predictions of biomass and leaf area index (LAI) over a wide range, up to 1200 Mg ha(-1) of biomass and art LAI of 12, with 90% and 75% of variance explained respectively. Furthermore, we were able to make accurate estimates of other stand structure attributes, including the mean and standard deviation of diameter at breast height, the number of steins greater than 100 cm in diameter and independent estimates of the basal area of Douglas-fir and western hemlock. These measurements can be directly related to indices of forest stand structural complexity, such as those developed for old-growth forest characterisation. Indices of canopy structure developed using the novel, three-dimensional analysis accounted for most of the variables used in predictive equations generated by the stepwise multiple regression. Published by Elsevier Science Inc. C1 US Forest Serv, USDA, Pacific NW Res Stn, Forestry Sci Lab, Corvallis, OR 97331 USA. Oregon State Univ, Dept Forest Sci, Forestry Sci Lab, Corvallis, OR 97331 USA. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. Smithsonian Environm Res Ctr, Edgewater, MD 21037 USA. RP Lefsky, MA (reprint author), US Forest Serv, USDA, Pacific NW Res Stn, Forestry Sci Lab, 3200 SW Jefferson Way, Corvallis, OR 97331 USA. RI Lefsky, Michael/A-7224-2009; Harding, David/F-5913-2012; OI Parker, Geoffrey/0000-0001-7055-6491 NR 76 TC 433 Z9 471 U1 22 U2 150 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD DEC PY 1999 VL 70 IS 3 BP 339 EP 361 DI 10.1016/S0034-4257(99)00052-8 PG 23 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 266JF UT WOS:000084296300009 ER PT J AU Schrage, DS Malarik, DC AF Schrage, DS Malarik, DC TI A novel quartz dendritic growth chamber for low temperature microgravity experimentation SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID CRYSTAL-GROWTH; SOLIDIFICATION AB The material science community has demonstrated keen interest in performing a range of thermodiffusional dendritic growth studies in microgravity. While each of these experiments differ in the thermal-physical properties of the test fluid, the initial dendrite seeding configuration, and the resultant dendrite morphology, they are similar as each must be conducted within a growth chamber. Clearly, the growth chamber is the single most crucial experimental component because the ambience delivered by the chamber intrinsically effects the resultant dendritic growth. A unique sample chamber, comprised nearly entirely of precision machined quartz components, was developed for use in the microgravity experiment Isothermal Dendritic Growth Experiment (IDGE), which was conducted in the cargo bay of the Space Shuttle Columbia, as part of the Fourth United States Microgravity Payload (USMP-4), in November 1997. The growth chamber discussed is conventional in the selection of the construction materials, but is unique and unconventional from the standpoint of the quartz fabrication and microgravity operation. First, the selection of a fused quartz material was design enabling because the test fluid, pivalic acid, an organic material which melts at 35.975 degrees C, could be maintained ultrapure over the three-year duration of the complete experiment (assembling, ground test, shuttle integration, flight). Second, the quartz chamber has demonstrated large-scale fabrication of complicated fused quartz pieces, into a final monolithic structure. Third, the quartz chamber was successfully interfaced with ancillary hardware and was not damaged or operationally compromised through ground testing, shuttle launch, microgravity experimentation and shuttle return. Fourth and finally, the chamber has demonstrated a novel means to control, in a microgravity environment, a vapor bubble, which was included in the chamber to provide a volume dedicated to the expansion of the sample fluid during heating. The bubble was controlled by applying a Couette flow device to generate a transient, controlled cavitation of the test fluid. Overall, the critical technologies derived in the present study should lend themselves directly to the development of future microgravity dendritic growth experiments, thereby minimizing program risk and cost. (C) 1999 American Institute of Physics. [S0034-6748(99)03312-2]. C1 Dynacs Engn Co Inc, Glenn Res Ctr Grp, Brook Pk, OH 44142 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Schrage, DS (reprint author), Dynacs Engn Co Inc, Glenn Res Ctr Grp, Brook Pk, OH 44142 USA. NR 13 TC 2 Z9 2 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD DEC PY 1999 VL 70 IS 12 BP 4624 EP 4633 DI 10.1063/1.1150124 PG 10 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 262EF UT WOS:000084052100029 ER PT J AU Rhim, WK Paradis, PF AF Rhim, WK Paradis, PF TI Laser-induced rotation of a levitated sample in vacuum SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID PARTICLES AB A method of systematically controlling the rotational state of a sample levitated in a high vacuum using the photon pressure is described. A zirconium sphere was levitated in the high-temperature electrostatic levitator and it was rotated by irradiating it with a narrow beam of a high-power laser on a spot off the center of mass. While the laser beam heated the sample, it also rotated the sample with a torque that was proportional both to the laser power and the length of the torque arm. A simple theoretical basis was given and its validity was demonstrated using a solid zirconium sphere at similar to 2000 K. This method will be useful to systematically control the rotational state of a levitated sample for the containerless materials processing at high temperature. (C) 1999 American Institute of Physics. [S0034-6748(99)04712-7]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rhim, WK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 34 Z9 34 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD DEC PY 1999 VL 70 IS 12 BP 4652 EP 4655 DI 10.1063/1.1150127 PG 4 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 262EF UT WOS:000084052100032 ER PT J AU Cobb, RG Sullivan, JM Das, A Davis, LP Hyde, TT Davis, T Rahman, ZH Spanos, JT AF Cobb, RG Sullivan, JM Das, A Davis, LP Hyde, TT Davis, T Rahman, ZH Spanos, JT TI Vibration isolation and suppression system for precision payloads in space SO SMART MATERIALS & STRUCTURES LA English DT Article AB This paper describes the design and performance testing of a vibration isolation and suppression system (VISS) which can be used to isolate a precision payload from spacecraft borne disturbances. VISS utilizes six hybrid isolation struts in a hexapod configuration. Central to the concept is a novel hybrid actuation concept which provides both passive isolation and active damping. The passive isolation is provided using a flight proven D-strut design. The passive design is supplemented by a voice-coil based active system. The active system is used to enhance the performance of the passive isolation system at lower frequencies, and provide the capability to steer the payload. C1 USAF, Res Lab, Kirtland AFB, NM 87117 USA. Honeywell Satellite Syst Operat, Glendale, AZ 85308 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 19 TC 70 Z9 83 U1 8 U2 26 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0964-1726 J9 SMART MATER STRUCT JI Smart Mater. Struct. PD DEC PY 1999 VL 8 IS 6 BP 798 EP 812 DI 10.1088/0964-1726/8/6/309 PG 15 WC Instruments & Instrumentation; Materials Science, Multidisciplinary SC Instruments & Instrumentation; Materials Science GA 270VM UT WOS:000084557900010 ER PT J AU Bronowicki, AJ Das, A Wada, BK AF Bronowicki, AJ Das, A Wada, BK TI Special issue on smart structures for space - Preface SO SMART MATERIALS & STRUCTURES LA English DT Editorial Material C1 USAF, Res Lab, Washington, DC USA. Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0964-1726 J9 SMART MATER STRUCT JI Smart Mater. Struct. PD DEC PY 1999 VL 8 IS 6 BP U3 EP U3 PG 1 WC Instruments & Instrumentation; Materials Science, Multidisciplinary SC Instruments & Instrumentation; Materials Science GA 270VM UT WOS:000084557900001 ER PT J AU Harvey, KL Jones, HP Schrijver, CJ Penn, MJ AF Harvey, KL Jones, HP Schrijver, CJ Penn, MJ TI Does magnetic flux submerge at flux cancelation sites? SO SOLAR PHYSICS LA English DT Article ID RAY BRIGHT POINTS; ACTIVE-REGION; SOLAR-ACTIVITY; QUIET SUN; CORONA; CANCELLATION; PHOTOSPHERE; FIELDS; MODEL AB Simultaneous measurements of the magnetic fields in the photosphere and chromosphere were used to investigate if magnetic flux is submerging at sites between adjacent opposite polarity magnetic network elements in which the flux is observed to decrease or 'cancel'. These data were compared with chromospheric and coronal intensity images to establish the timing of the emission structures associated with these magnetic structures as a function of height. We found that most of the cancelation sites show either that the bipole is observed longer in the photosphere than in the chromosphere and corona (44%) or that the timing difference of the disappearance of the bipole between these levels of the atmosphere is unresolved. The magnetic axis lengths of the structures associated with the cancelation sites are on average slightly smaller in the chromosphere than the photosphere. These observations suggest that magnetic flux is retracting below the surface for most, if not all, of the cancelation sites studied. C1 Solar Phys Res Corp, Tucson, AZ 85718 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, SW Solar Stn, Tucson, AZ 85718 USA. Lockheed Martin Solar Astrophys Lab, Palo Alto, CA 94304 USA. Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA. RP Harvey, KL (reprint author), Solar Phys Res Corp, 4720 Calle Desecada, Tucson, AZ 85718 USA. NR 33 TC 58 Z9 59 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD DEC PY 1999 VL 190 IS 1-2 BP 35 EP 44 DI 10.1023/A:1005237719407 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RP UT WOS:000087182100003 ER PT J AU Delannee, C Aulanier, G AF Delannee, C Aulanier, G TI Cme associated with transequatorial loops and a bald patch flare SO SOLAR PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; CURRENT-SHEET FORMATION; MAGNETIC-FIELD; SOLAR-FLARES; ACTIVE REGIONS; CONFIGURATIONS; ORIGIN; RECONNECTION; TOPOLOGY; COMPLEX AB We study a flare which occurred on 3 November 1997 at 10:31 UT in the vicinity of a parasitic polarity of AR 8100. Using SOHO/EIT 195 Angstrom observations, we identify the brightening of thin transequatorial loops connecting AR 8100 and AR 8102, and dimmings located between the two active regions. Difference images highlight the presence of a loop-like structure rooted near the flare location usually called an EIT wave. The coronal magnetic field derived from potential extrapolations from a SOHO/MDI magnetogram shows that the topology is complex near the parasitic polarity. There, a 'bald patch' (defined as the locations where the magnetic field is tangent to the photosphere) is present. We conclude that the flare was a 'bald patch flare'. Moreover, the extrapolation confirms that there is a large coronal volume filled with transequatorial field lines interconnecting AR 8100 and AR 8102, and overlaying the bald patch. We show that the dimmings are located at the footpoints of these large field lines, which can be also related to the thin bright loops observed during the flare. As this event was related to a coronal mass ejection (CME) observed by SOHO/LASCO, we propose that the observed dimmings are due to a decrease in plasma density during the opening of the transequatorial loops connecting both ARs. We propose a scenario where these large field lines are in fact pushed up by the opening of low-lying sheared field lines forming the bald patch. We finally discuss how the fast opening of these field lines can produce the brightening near the footpoints of the separatrix, observed as an 'EIT wave'. C1 NASA, Goddard Space Flight Ctr, SOHO EAF, Greenbelt, MD 20771 USA. Univ Paris 11, IAS, F-91405 Orsay, France. USN, Res Lab, Washington, DC 20375 USA. George Mason Univ, CSI, Fairfax, VA 22030 USA. RP NASA, Goddard Space Flight Ctr, SOHO EAF, Mail Code 6823,Bldg 26,Room G-1, Greenbelt, MD 20771 USA. NR 58 TC 177 Z9 180 U1 1 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD DEC PY 1999 VL 190 IS 1-2 BP 107 EP 129 DI 10.1023/A:1005249416605 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RP UT WOS:000087182100008 ER PT J AU Lites, BW Card, G Elmore, DF Holzer, T Lecinski, A Streander, KV Tomczyk, S Gurman, JB AF Lites, BW Card, G Elmore, DF Holzer, T Lecinski, A Streander, KV Tomczyk, S Gurman, JB TI Dynamics of polar plumes observed at the 1998 February 26 eclipse SO SOLAR PHYSICS LA English DT Article ID ULTRAVIOLET IMAGING TELESCOPE; EXPLOSIVE EVENTS; MAGNETIC RECONNECTION; NETWORK; EIT; CORONAGRAPH; HOLES; SUN AB This paper presents first observations of dynamics of the white-light solar corona detected during the few minutes of totality of a solar eclipse. Perturbations of a polar plume associated with an embedded `jet' structure observed simultaneously at 195 Angstrom with the EUV Imaging Telescope (EIT) aboard the SOHO spacecraft lead to estimates of the electron density fluctuations accompanying the jet: +/- 15%. The morphological behavior of the jet, its apparent upward propagation speed of approximate to 200 km s(-1), and the inferred density perturbations suggest that the jet is led by a weak, outward-propagating shock resulting from the injection of material at high velocity at the base of the corona. Smaller perturbations of the white-light corona are apparent at many other locations, sustaining hope that propagating Alfven waves may be measurable in the solar corona. Density perturbations associated with the jet follow from empirical electron density models of the polar inter-plume and plume regions, as derived from the ground-based eclipse measurements of coronal polarization brightness. These models indicate polar plume densities 4-6 times that of the interplume low corona. C1 Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lites, BW (reprint author), Natl Ctr Atmospher Res, High Altitude Observ, POB 3000, Boulder, CO 80307 USA. NR 33 TC 14 Z9 14 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD DEC PY 1999 VL 190 IS 1-2 BP 185 EP 206 DI 10.1023/A:1005209409104 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RP UT WOS:000087182100014 ER PT J AU Ireland, J Wills-Davey, M Walsh, RW AF Ireland, J Wills-Davey, M Walsh, RW TI Coronal heating events in high-cadence TRACE data SO SOLAR PHYSICS LA English DT Article ID RAY BRIGHT POINTS; TRANSITION REGION; WAVELET ANALYSIS; QUIET SUN; SOLAR; OSCILLATIONS; NETWORK; BALANCE; JETS AB On March 23rd 1999 a set of TRACE (Transition Region and Coronal Explorer) observations were taken in support of Solar and Heliospheric Observatory (SOHO)/TRACE Joint Observing Program 83. The program is designed to look for coronal heating mechanisms operating at high cadence and to observe their dynamical effects on coronal loop density, temperature and magnetic structure. We present here a study of 27 small, dynamic brightening events seen in this data. These events are seen in the quiet-Sun areas surrounding the active region. The data itself consists of 157 171 Angstrom 512x512 arc sec images at 1 arc sec resolution and 9 second cadence, a previously unavailable combination of cadence, resolution and image size. Three classes of events are introduced: complex, intermediate and simple. All three classes share the property of being dynamic on small time and length scales but differ in the complexity of their behavior. We find that the brightenings across all classes exhibit variations as part of a distribution of time scales (90-400 s) peaked around 228 s. The brightenings are no more than 5 arc sec in diameter. Motions between brightenings occur on time scales from 9 to 90 s and on length scales no greater than 10 arc sec. These motions have velocities estimated to be in the range 89-174 km s(-1). The position of these events in the spectrum of previously observed coronal heating events is discussed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. RP Ireland, J (reprint author), NASA, Goddard Space Flight Ctr, Bldg 26,Room G-1,Mail Code 6823, Greenbelt, MD 20771 USA. NR 27 TC 10 Z9 10 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD DEC PY 1999 VL 190 IS 1-2 BP 207 EP 232 DI 10.1023/A:1005204707463 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RP UT WOS:000087182100015 ER PT J AU Brekke, P AF Brekke, P TI Observations of transition region plasma SO SOLAR PHYSICS LA English DT Article ID CORONAL DIAGNOSTIC SPECTROMETER; LATE-TYPE STARS; SOLAR ATMOSPHERE; QUIET-SUN; EXPLOSIVE EVENTS; MAGNETIC RECONNECTION; SOHO/CDS OBSERVATIONS; SUMER INSTRUMENT; FAR-ULTRAVIOLET; DOPPLER SHIFTS AB Recent space missions have changed our view of the solar transition region. In particular the ESA/NASA Solar and Heliospheric Observatory (SOHO) and NASA's TRACE satellite have provided a unique opportunity to explore the solar atmosphere in detail. The combination of high spatial, spectral and temporal observations has made it possible to derive three dimensional images of the emission and velocity structures of solar features. Active region loop structures at transition region temperatures appear to be extremely time variable and dynamic, a result with profound implications for our understanding and modeling of the upper solar atmosphere. Large Dopplershifts have also been observed in these structures. A 3-minute transition region oscillation has been observed above sunspots suggesting upward-propagating acoustic waves. Clear evidence of velocity oscillations in the internetwork regions has also been observed in both the chromosphere and the transition region. The longstanding and puzzling problem of the apparent net red shift of emission lines from the transition region has been revisited. The extensive wavelength coverage of the SOHO spectrometers has made it possible to extend the measurements to much higher temperatures compared to previous instruments. The combination of magnetograms, EUV spectral imaging and the high resolution broad-band images from TRACE has also given us new insight concerning the structure of the transition region and its relation with the photospheric magnetic field. C1 NASA, Goddard Space Flight Ctr, ESA, Dept Space Sci, Greenbelt, MD 20771 USA. RP Brekke, P (reprint author), NASA, Goddard Space Flight Ctr, ESA, Dept Space Sci, Greenbelt, MD 20771 USA. NR 98 TC 23 Z9 23 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD DEC PY 1999 VL 190 IS 1-2 BP 379 EP 408 DI 10.1023/A:1005224709046 PG 30 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RP UT WOS:000087182100024 ER PT J AU Wills-Davey, MJ Thompson, BJ AF Wills-Davey, MJ Thompson, BJ TI Observations of a propagating disturbance in TRACE SO SOLAR PHYSICS LA English DT Article ID FLARE AB TRACE observations from 13 June 1998 in 171 and 195 Angstrom wavelengths show a propagating disturbance, initiated near the origin of a C-class flare. The wave moves through and disrupts diffuse, overarching coronal loops. Only these overlying structures are affected by the wave; lower-lying coronal structures are unperturbed. The front does not appear in contemporaneous Lyman-alpha observations. The disturbance creates two types of displacement: (1) that of the wave front itself, and (2) those of large anchored magnetic structures, which 'bob' due to the wave and show transverse velocities an order of magnitude smaller than those of the front. Comparisons between the 171 and 195 Angstrom data show that the front appears differently at different temperatures. Observations in 171 Angstrom (approx. 0.95 MK) show strong displacement of individual magnetic structures, while 195 Angstrom (approx. 1.4 MK) data reveals a strong wave front and associated dimming but resolve much less structural motion. There is also strong evidence of heating in the material engulfed by the wave front, and comparisons of the 171 and 195 Angstrom data allow us to constrain the temperature of the plasma through which the wave is propagating to 1-1.4 MK. Examination of the trajectories and velocities of points along the front suggests that the disturbance is Alfvenic in nature but contains a compressive component. This is best explained by a fast-mode magnetoacoustic wave. A comparison of the motion of anchored structures to that of the wave front gives a constraint on pulse width. Comparisons with contemporaneous SOHO-EIT full-disk 195 Angstrom data show evidence that the disturbance is contained within a set of transequatorial field lines, such that it propagates from a southern active region to a northern one with no extensive motion to the east or west. The associated transequatorial loops display residual motion for about a hour after they are initially disturbed. These results, coupled with the deflection of wave trajectories, lead us to speculate on field strength differences between the transequatorial loops and the region in the TRACE field of view. C1 Montana State Univ, Bozeman, MT 59715 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wills-Davey, MJ (reprint author), Montana State Univ, Bozeman, MT 59715 USA. RI Thompson, Barbara/C-9429-2012 NR 17 TC 132 Z9 134 U1 1 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD DEC PY 1999 VL 190 IS 1-2 BP 467 EP 483 DI 10.1023/A:1005201500675 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 316RP UT WOS:000087182100029 ER PT J AU Sobieszczanski-Sobieski, J Laba, K Kincaid, R AF Sobieszczanski-Sobieski, J Laba, K Kincaid, R TI Bell-curve based evolutionary optimization algorithm SO STRUCTURAL OPTIMIZATION LA English DT Article AB The paper presents an optimization algorithm that falls in the category of genetic, or evolutionary algorithms. While the bit exchange is the basis of most of the Genetic Algorithms (GA) in research and applications in America, some alternatives, also in the category of evolutionary algorithms, but using a direct, geometrical approach have gained popularity in Europe and Asia. The Bell-Curve Based Evolutionary Algorithm (BCB) is in this alternative category and is distinguished by the use of a combination of n-dimensional geometry and the normal distribution, the bell-curve, in the generation of the offspring. The tool for creating a child is a geometrical construct comprising a line connecting two parents and a weighted point on that line. The point that defines the child deviates from the weighted point in two directions: parallel and orthogonal to the connecting line, the deviation in each direction obeying a probabilistic distribution. Tests showed satisfactory performance of BCB. The principal advantage of BCB is its controllability via the normal distribution parameters and the geometrical construct variables. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Sobieszczanski-Sobieski, J (reprint author), NASA, Langley Res Ctr, MS 139, Hampton, VA 23681 USA. NR 8 TC 0 Z9 0 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0934-4373 J9 STRUCT OPTIMIZATION JI Struct. Optim. PD DEC PY 1999 VL 18 IS 4 BP 264 EP 275 PG 12 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary; Mechanics SC Computer Science; Engineering; Mechanics GA 273QB UT WOS:000084717400007 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI TiCl, TiH, and TiH+ bond energies: a test of a correlation-consistent Ti basis set SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Article DE basis set; bond energies; correlation-consistent; inner-shell correlation ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; MOLECULAR CALCULATIONS; ATOMIZATION ENERGIES; ELECTRON CORRELATION; WAVE-FUNCTIONS; HARTREE-FOCK; ROW ATOMS; 1ST-ROW AB Correlation-consistent basis sets are developed for the Ti atom. The polarization functions are optimized for the average of the F-3 and F-5 states. One series of correlation-consistent basis sets is for 3d and 4s correlation, while the second series includes 3s and 3p correlation as well as 3d and 4s correlation. These basis sets are tested using the Ti F-3-F-5 separation and the dissociation energies of TiCl X(4)Phi, TiH X(4)Phi, and TiH+ X(3)Phi. The CCSD(T) complete basis set limit values are determined by extrapolation. The Douglas-Kroll approach is used to compute the scalar relativistic effect. Spin-orbit effects are taken from experiment and/or are computed at the CASSCF level. The Ti F-3-F-5 separation is in excellent agreement with experiment, while the TiCl, TiH, and TiH+ bond energies are in good agreement with experiment. Extrapolation with the valence basis set is consistent with other atoms, while including 3s and 3p correlation appears to make extrapolation more difficult. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 27 TC 22 Z9 22 U1 0 U2 3 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD DEC PY 1999 VL 103 IS 2 BP 141 EP 145 DI 10.1007/s002140050524 PG 5 WC Chemistry, Physical SC Chemistry GA 266PJ UT WOS:000084308100006 ER PT J AU Bauschlicher, CW Hudgins, DM Allamandola, LJ AF Bauschlicher, CW Hudgins, DM Allamandola, LJ TI The infrared spectra of polycyclic aromatic hydrocarbons containing a five-membered ring: symmetry breaking and the B3LYP functional SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Article DE symmetry-breaking; density functional theory; vibrational frequencies ID EXCHANGE; ENERGY; APPROXIMATION; FREQUENCIES; STATES AB The infrared spectra of six molecules, each of which contains a five-membered ring, and their cations are determined using density functional theory; both the B3LYP and BP86 functionals are used. The computed results are compared with the experimental spectra. For the neutral molecules, both methods are in good agreement with experiment. Even the Hartree-Fock (HF) approach is qualitatively correct for the neutral species. For the cations, the HF approach fails, as found for other organic ring systems. The B3LYP and BP86 approaches are in good mutual agreement for five of the six cation spectra, and are in good agreement with experiment for four of the five cations where the experimental spectra are available. It is only for the fluoranthene cation where the BP86 and B3LYP functionals yield different results; the BP86 approach yields the expected C-2v symmetry, while the B3LYP approach breaks symmetry. The experimental spectra support the BP86 spectra over the B3LYP spectra, but the quality of the experimental spectra does not allow a critical evaluation of the accuracy of the BP86 approach for this difficult system. C1 NASA, Ames Res Ctr, Space Technol Div, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Astrophys Branch, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Space Technol Div, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 19 TC 35 Z9 35 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD DEC PY 1999 VL 103 IS 2 BP 154 EP 162 DI 10.1007/s002140050526 PG 9 WC Chemistry, Physical SC Chemistry GA 266PJ UT WOS:000084308100008 ER PT J AU Leon, R Lobo, C Liao, XZ Zou, J Cockayne, DJH Fafard, S AF Leon, R Lobo, C Liao, XZ Zou, J Cockayne, DJH Fafard, S TI Island shape instabilities and surfactant-like effects in the growth of InGaAs/GaAs quantum dots SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT Symposium on Growth Instabilities and Decomposit ion During Heteroepitaxy at the MRS Fall Meeting CY DEC, 1998 CL BOSTON, MASSACHUSETTS SP Mat Res Soc DE island shape instabilities; InGaAs/GaAs quantum dots; Stranski-Krastanow transformation ID SELF-ORGANIZED GROWTH; EPITAXIAL-GROWTH; GE; EVOLUTION; GAAS; TRANSFORMATION; SUPPRESSION; MORPHOLOGY; INXGA1-XAS; GAAS(100) AB InGaAs/GaAs island formation during vapor phase epitaxy showed diverging behaviors when varying group V partial pressures (PP). Differences include changes in critical thicknesses for the onset of the Stranski-Krastanow (S-K) transformation, surface coverages, ratios between coherent and incoherent islands, and dissimilar morphologies upon annealing. These results show that slightly different values for the 2D-3D transition can also be obtained in InGaAs/GaAs depending on AsH3 PP. Photoluminescence spectroscopy of capped islands showed that the wetting layer thickness does not change beyond the onset of the S-K transformation for conditions producing stable islands. Annealing experiments done at high AsH3 PP show Ostwald ripening, but we also observe that small, high density, lens-shaped islands are unaffected by prolonged annealing and do not ripen when an 'optimum' low AsH3 PP is used during the island growth and in-situ annealing. The later experiments show that small lens shaped islands can be found in equilibrium if InGaAs surface energies are minimized. These findings lead to the conclusion that AsH3 can raise surface energies acting as an impurity-free 'morphactant' in InGaAs growth. (C) Published by 1999 Elsevier Science S.A. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Australian Natl Univ, Res Sch Phys Sci, Canberra, ACT 0200, Australia. Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. Natl Res Council Canada, Inst Microstruct Sci, Ottawa, ON K1A 0R6, Canada. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Liao, Xiaozhou/B-3168-2009; Zou, Jin/B-3183-2009; Lobo, Charlene/B-3977-2013; Lobo, Charlene/G-5003-2011 OI Liao, Xiaozhou/0000-0001-8565-1758; Zou, Jin/0000-0001-9435-8043; Lobo, Charlene/0000-0002-2746-1363; Lobo, Charlene/0000-0002-2746-1363 NR 26 TC 10 Z9 10 U1 0 U2 3 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD DEC 1 PY 1999 VL 357 IS 1 BP 40 EP 45 DI 10.1016/S0040-6090(99)00472-1 PG 6 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 269QK UT WOS:000084488900010 ER PT J AU Krauzlis, RJ Stone, LS AF Krauzlis, RJ Stone, LS TI Tracking with the mind's eye SO TRENDS IN NEUROSCIENCES LA English DT Review ID CORTICAL AREAS MT; RETICULARIS TEGMENTI PONTIS; SACCADE TARGET SELECTION; PURKINJE-CELL ACTIVITY; TEMPORAL VISUAL AREA; SMOOTH-PURSUIT; PARIETAL CORTEX; ALERT MONKEY; VESTIBULAR NUCLEUS; MOTION PERCEPTION C1 Salk Inst Biol Studies, La Jolla, CA 92037 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Krauzlis, RJ (reprint author), Salk Inst Biol Studies, 10010 N Torrey Pines Rd, La Jolla, CA 92037 USA. FU NEI NIH HHS [EY12212-01] NR 91 TC 100 Z9 101 U1 2 U2 13 PU ELSEVIER SCIENCE LONDON PI LONDON PA 84 THEOBALDS RD, LONDON WC1X 8RR, ENGLAND SN 0166-2236 J9 TRENDS NEUROSCI JI Trends Neurosci. PD DEC PY 1999 VL 22 IS 12 BP 544 EP 550 DI 10.1016/S0166-2236(99)01464-2 PG 7 WC Neurosciences SC Neurosciences & Neurology GA 253EG UT WOS:000083543200008 PM 10542434 ER PT J AU Mikouchi, T Miyamoto, M McKay, GA AF Mikouchi, T Miyamoto, M McKay, GA TI The role of undercooling in producing igneous zoning trends in pyroxenes and maskelynites among basaltic Martian meteorites SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE crystallization; Martian meteorites; Mars; pyroxene group; maskelynite ID SHERGOTTITE METEORITES; PETROGENESIS; ALH84001; ZAGAMI; CRYSTALLIZATION; HISTORY; MAGMA; MARS AB Pyroxene and maskelynite are major minerals in basaltic Martian meteorites (Shergotty, Zagami, EETA79001, and QUE94201). They are chemically zoned in both major and minor elements, offering useful information on their crystallization history, Pigeonite and augite show two distinct textural occurrences of zoning patterns. In Shergotty and Zagami, pigeonite and augite are usually present as separate grains that are zoned from Mg-rich core to Fe-rich rim, respectively. Both pigeonite and augite usually have homogeneous cores, considered to be cumulus phases. Zagami pyroxenes are not zoned as extensively as those in Shergotty, but their mineralogy is quite similar. On the other hand, pigeonite and augite in EETA79001 and QUE94201 are both present in individual composite grains. These pyroxenes are complexly zoned, and typically the cores are Mg-rich pigeonites, mantled by Mg-rich augite, and the rims are Fe-rich pigeonite. Pyroxenes in lithology A of EETA79001 are small and show irregular zoning patterns, but most of them show similar zoning patterns to lithology B of EETA79001 and QUE94201. Maskelynite compositions also correspond to differences in pyroxene zoning. Maskelynites in Shergotty and Zagami are more alkali-rich than those in EETA79001 and QUE94201. Shergotty and Zagami maskelynites apparently nucleated on pyroxene crystals and grew outward (to lower An content) into interstitial melts, whereas EETA79001 and QUE94201 maskelynites have the most An-rich portions in the centers of grains, showing normal core-to-rim zoning. FeO in the maskelynite cores is different between Shergotty and Zagami (0.5-0.6 wt%) and EETA79001 and QUE94201 (0.3-0.4 wt%). The lower Fe content of EETA79001 and QUE94201 maskelynite cores reflects earlier crystallization of plagioclase. Al zoning in pyroxenes also marks the beginning of plagioclase crystallization. Decrease of the Al/Ti ratios observed in Al-Ti plots of pyroxenes further suggests plagioclase crystallization, and the Al-Ti distribution shows a clear difference between Shergotty and Zagami on one hand and EETA79001 and QUE94201 on the other Such mineralogical differences of EETA79001 and QUE94201 from Shergotty and Zagami can be understood by undercooling of the magmas from which they have crystallized. We believe that Shergotty and Zagami experienced only slight undercooling, resulting initially in cotectic growth of pigeonite and augite, later joined by plagioclase. On the other hand, EETA79001 and QUE94201 experienced significant undercooling of their melts, and their crystallization sequence was pigeonite, augite, plagioclase, and then Fe-rich pigeonite, with each phase crystallizing metastably alone, because the melt compositions did not follow the equilibrium phase boundaries. Lithology A of EETA79001 also experienced undercooling effects, but they are not so extensive as in lithology B, inasmuch as lithology A shows some features similar to Shergotty and Zagami. All of these inferences concerning supercooling are consistent with field emission gun scanning electron microscopy (FEG-SEM) observation of pyroxene microstructures if we consider that magmatic cooling rates are related to subsolidus cooling rates. That is, the pyroxene cores of Shergotty and Zagami have fine exsolution lamellae ja few tens to a few hundreds nm), whereas those of EETA79001 and QUE94201 do not contain such exsolution lamellae, indicating faster cooling rate even at subsolidus. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Tokyo, Grad Sch Sci, Inst Mineral, Bunkyo Ku, Tokyo 1130033, Japan. NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. RP Mikouchi, T (reprint author), Univ Tokyo, Grad Sch Sci, Inst Mineral, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1130033, Japan. NR 41 TC 22 Z9 22 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD NOV 30 PY 1999 VL 173 IS 3 BP 235 EP 256 DI 10.1016/S0012-821X(99)00188-0 PG 22 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 260GN UT WOS:000083941300008 ER PT J AU Waugh, DW Randel, WJ Pawson, S Newman, PA Nash, ER AF Waugh, DW Randel, WJ Pawson, S Newman, PA Nash, ER TI Persistence of the lower stratospheric polar vortices SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ANTARCTIC OZONE HOLE; INTERANNUAL VARIABILITY; GEOPOTENTIAL HEIGHT; VORTEX; REANALYSIS AB The persistence of the Arctic and Antarctic lower stratospheric vortices is examined over the period from 1958 to 1999. Three different vortex-following diagnostics (two using potential vorticity and one based solely on the zonal winds) are compared and are shown to give very similar results for the breakup date. The variability in the timing of the breakup of both vortices is qualitatively the same: There are large interannual variations together with smaller decadal-scale variations and there is a significant increase in the persistence since the mid-1980s (all variations are larger for the Arctic vortex). Also, in bath hemispheres, there is a high correlation between the persistence and the strength and coldness of the spring vortex, with all quantities having the same interannual and decadal variability. However, there is no such correlation between the persistence and the characteristics of the midwinter vortex. In the Northern Hemisphere, there is also a high correlation between the vortex persistence and the upper tropospheric/lower stratospheric eddy heat flux averaged over the 2 months prior to the breakup. This indicates that the variability in the wave activity entering the stratosphere over late winter to early spring plays a key role in the variability of the Arctic vortex persistence (and spring polar temperatures) on both interannual and decadal timescales. However, the extreme values of Arctic vortex coldness and persistence during the 1990's are not echoed as a similar extreme in the eddy heat flux. This suggests that the recent increase in vortex persistence is not solely due to changes in the wave activity entering the stratosphere. C1 Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Steven Myers & Associates Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Waugh, DW (reprint author), Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. EM waugh@jhu.edu; randel@ucar.edu; pawson@polska.gsfc.nasa.gov; newman@notus.gsfc.nasa.gov; nash@notus.gsfc.nasa.gov RI Newman, Paul/D-6208-2012; Pawson, Steven/I-1865-2014; Randel, William/K-3267-2016; Waugh, Darryn/K-3688-2016 OI Newman, Paul/0000-0003-1139-2508; Pawson, Steven/0000-0003-0200-717X; Randel, William/0000-0002-5999-7162; Waugh, Darryn/0000-0001-7692-2798 NR 18 TC 139 Z9 146 U1 0 U2 15 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27191 EP 27201 DI 10.1029/1999JD900795 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700002 ER PT J AU Agustsdottir, AM Barron, EJ Bice, KL Colarusso, LA Cookman, JL Cosgrove, BA De Lurio, JL Dutotn, JF Frakes, BJ Frakes, LA Moy, CJ Olszewski, TD Pancost, RD Poulsen, CJ Ruffner, CM Sheldon, DG White, TS AF Agustsdottir, AM Barron, EJ Bice, KL Colarusso, LA Cookman, JL Cosgrove, BA De Lurio, JL Dutotn, JF Frakes, BJ Frakes, LA Moy, CJ Olszewski, TD Pancost, RD Poulsen, CJ Ruffner, CM Sheldon, DG White, TS CA PSUCLIM TI Storm activity in ancient climates 1. Sensitivity of severe storms to climate forcing factors on geologic timescales SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PLANETARY-WAVES; SEA-ICE; MODEL; OCEAN; CIRCULATION; STRATIFICATION; PALEOGEOGRAPHY; VARIABILITY; SIMULATION; TRANSPORTS AB Severe storms are important agents of sediment transport, and they generate sedimentary structures and textures that can be identified in the geologic record. The genesis and the distribution of storms are associated with distinctive meteorological controls, which in many cases lend themselves to analysis using general circulation models of the atmosphere. The goal of this study is to predict the distribution of severe storms in Earth history and to evaluate the correspondence between climate model predictions and geologic observations for widely different past climate conditions. The first step toward achieving this goal is an assessment of the importance of different climatic forcing factors, including paleogeography, topography, solar luminosity, carbon dioxide concentrations, and ocean heat transport variations. This assessment is based on sensitivity experiments using the GENESIS general circulation model. Paleogeography plays the most important role in governing the distribution of winter storms and plays a major role in hurricane genesis and steering. In contrast, changes in carbon dioxide, ocean heat transport, and solar luminosity exhibit little influence on the distribution of winter storms or the steering of hurricanes. However, these factors influence the strength of winter storms and the area and frequency of hurricane generation. The relationships between climatic forcing factors and storm genesis and distribution provide considerable guidance in comparisons of model predictions with observations of severe storms in Earth history and for the interpretations of storm deposits. The comparison of model predictions to the geologic record is the subject PSUCLIM 2 [this issue]. C1 Penn State Univ, University Pk, PA 16802 USA. Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 USA. Goddard Space Flight Ctr, Greenbelt, MD 20906 USA. Netherlands Inst Ocean Sci, NL-1790 AB Den Burg, Netherlands. So Illinois Univ, Dept Geog, Carbondale, IL 62901 USA. Univ Massachusetts, Amherst, MA 01003 USA. Univ Iowa, Dept Geol, Iowa City, IA 52242 USA. RP Nordurbaer 2, IS-851 Hella, Iceland. RI Poulsen, Christopher/C-6213-2009 OI Poulsen, Christopher/0000-0001-5104-4271 NR 63 TC 6 Z9 6 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27277 EP 27293 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700007 ER PT J AU Agustsdottir, AM Barron, EJ Bice, KL Colarusso, LA Cookman, JL Cosgrove, BA De Lurio, JL Dutton, JF Frakes, BJ Frakes, LA Moy, CJ Olszewski, TD Pancost, RD Poulsen, CJ Ruffner, CM Sheldon, DG White, TS AF Agustsdottir, AM Barron, EJ Bice, KL Colarusso, LA Cookman, JL Cosgrove, BA De Lurio, JL Dutton, JF Frakes, BJ Frakes, LA Moy, CJ Olszewski, TD Pancost, RD Poulsen, CJ Ruffner, CM Sheldon, DG White, TS CA PSUCLIM TI Storm activity in ancient climates 2. An analysis using climate simulations and sedimentary structures SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID HUMMOCKY CROSS-STRATIFICATION; INTENSE WINTER STORMS; VARIABLE BEDDING SEQUENCES; TROPICAL HURRICANES; ATMOSPHERIC CO2; SHELF SEQUENCE; SOUTHWESTERN OREGON; SOIL CARBONATE; SOUTH-AFRICA; SEA-ICE AB Severe storms generate sedimentary structures and textures that can be identified in the geologic record. A companion paper [PSUCLIM, this issue] describes the genesis and distribution of both winter storms and hurricanes and their sensitivity to climatic and geographic variables. In this paper, a total of 90 storm deposits are compared to GENESIS climate simulations in order to examine storm activity from the Permian to the Cretaceous and to evaluate the ability of the model to predict storms in ancient environments. Approximately 70% of the observed deposits are predicted by the models. The majority of the missed deposits are associated with recognizable errors. If these specific sources of error are eliminated, the model predicts over 90% of observed deposits. This degree of accuracy allows the assignment of generative processes to individual deposits; however, causative differences between hummocky cross stratification and tempestite type deposits are not distinguishable. The distribution of severe storms through Earth history varies as a function of both continental geometry and climate. Elevated atmospheric CO2 appears to homogenize the latitudinal distribution of storm deposits by expanding the area of hurricane genesis. Geography exerted the dominant control on winter storm distribution and was responsible for a shift in the concentration of winter storm deposits from the Southern Hemisphere in the Early permian to the Northern Hemisphere in the mid-Cretaceous. C1 Penn State Univ, University Pk, PA 16802 USA. Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 USA. Goddard Space Flight Ctr, Greenbelt, MD 20906 USA. Netherlands Inst Ocean Sci, NL-1790 AB Den Burg, Netherlands. So Illinois Univ, Dept Geog, Carbondale, IL 62901 USA. Univ Adelaide, Dept Geol & Geophys, Adelaide, SA 5005, Australia. Univ Massachusetts, Amherst, MA 01003 USA. Univ Iowa, Dept Geol, Iowa City, IA 52242 USA. RP Nordurbaer 2, IS-851 Hella, Iceland. OI Poulsen, Chris/0000-0001-5104-4271 NR 140 TC 2 Z9 2 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27295 EP 27320 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700008 ER PT J AU Balachandran, NK Rind, D Lonergan, P Shindell, DT AF Balachandran, NK Rind, D Lonergan, P Shindell, DT TI Effects of solar cycle variability on the lower stratosphere anti the troposphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; MIDDLE ATMOSPHERE MODEL; INTERANNUAL VARIABILITY; DOWNWARD CONTROL; PLANETARY-WAVES; UV VARIABILITY; CIRCULATION; QBO; CLIMATE; ASSOCIATION AB The effects of solar irradiance variability on the lower stratosphere and the troposphere are investigated using observed and general circulation model (GCM)generated 30 and 100 mbar geopotential heights. The GCM includes changes in UV input (+ or -5% at wavelengths below 0.3 micron and no ozone photochemistry and transport) to roughly approximate the combined effects of UV and ozone changes associated with the solar variability. The annual and seasonal averages of the height differences between solar maximum and solar minimum conditions are evaluated. In the subtropics, observations indicate statistically highly significant increased geopotential heights during solar maximum, compared to solar minimum, in composite annual and seasonal averages. The model simulates this feature reasonably well, although the magnitude and statistical significance of the differences are often weaker than in observations, especially in summer. Both the observations and the model results show a strong dipole pattern of height differences when the data are partitioned according to the phase of the quasi-biennial oscillation (QBO), with the pattern reversing itself with the change in the phase of the QBO. The connection between solar variability and lower atmospheric charges are interpreted as follows: The solar changes directly affect the stratosphere by changing the vertical gradients of temperature and zonal wind. This leads to changes in propagation conditions for planetary waves resulting in changes of E-P flux divergence and then by the downward control principle, affecting the circulation in the lower stratosphere and the troposphere. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10027 USA. Sci Syst & Applicat, New York, NY USA. RP Balachandran, NK (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM cdnkb@giss.nasa.gov RI Shindell, Drew/D-4636-2012 NR 34 TC 62 Z9 62 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27321 EP 27339 DI 10.1029/1999JD900924 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700009 ER PT J AU Satheesh, SK Ramanathan, V Xu, LJ Lobert, JM Podgorny, IA Prospero, JM Holben, BN Loeb, NG AF Satheesh, SK Ramanathan, V Xu, LJ Lobert, JM Podgorny, IA Prospero, JM Holben, BN Loeb, NG TI A model for the natural and anthropogenic aerosols over the tropical Indian Ocean derived from Indian Ocean Experiment data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MARINE BOUNDARY-LAYER; SEA-SALT AEROSOL; CHARACTERIZATION EXPERIMENT ACE-1; SPECTRAL OPTICAL DEPTHS; SIZE DISTRIBUTIONS; LIGHT-SCATTERING; NORTHEAST ATLANTIC; RADIATION BUDGET; SULFATE AEROSOL; ARABIAN SEA AB The physical, chemical and radiative properties of aerosols are investigated over the tropical Indian Ocean during the first field phase (FFP) of the international Indian Ocean Experiment. The FFP was conducted during February 20 to March 31, 1998. The results shown here are from the Kaashidhoo Climate Observatory (KCO), a new surface observatory established on the tiny island of Kaashidhoo (4.965 degrees N, 73.466 degrees E) in the Republic of Maldives. From simultaneous measurements of aerosol physical, chemical, and radiative properties and the vertical structure from lidar, we have developed an aerosol model which, in conjunction with a Monte Carlo radiative transfer model, successfully explains (within a few percent) the observed solar radiative fluxes at the surface and at the top of the atmosphere. This agreement demonstrates the fundamental importance of measuring aerosol physical and chemical properties for modeling radiative fluxes. KCO, during the northeast monsoon period considered here, is downwind of the Indian subcontinent and undergoes variations in the aerosol visible optical depth tau(v) from similar to 0.1 to 0.4, with a monthly mean of similar to 0.2. Lidar data suggest that the aerosol is confined largely to the first 3 kms. Sulfate and ammonium contribute similar to 29% to tau(v); sea-salt and nitrate contributes similar to 17%; mineral dust contributes similar to 15%; and the inferred soot, organics, and fly ash contribute 11%, 20%, and 8% respectively. We estimate that anthropogenic sources may contribute as much as 65% to the observed tau(v). We consider both an externally and an internally mixed aerosol model with very little difference between the two in the computed radiative forcing. The observed scattering coefficients are in the upper range of those reported for other oceanic regions, the single-scattering albedos are as low as 0.9, and the Angstrom wavelength exponents of similar to 1.2. indicate the abundance of submicron aerosols. In summary, the data and the model confirm the large impact of anthropogenic sources. The surface global fluxes (for overhead Sun) decrease by as much as 50 to 80 W m(-2) owing to the presence of the aerosols, and the top of the atmosphere fluxes increase by as much as 15 W m(-2), thus indicating that anthropogenic aerosols are having a large impact on the tropical Indian Ocean. C1 Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Miami, FL 33149 USA. RP Ramanathan, V (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, 9500 Gilman Dr, La Jolla, CA 92093 USA. EM ram@fiji.ucsd.edu OI Prospero, Joseph/0000-0003-3608-6160 NR 71 TC 194 Z9 197 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27421 EP 27440 DI 10.1029/1999JD900478 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700016 ER PT J AU Allen, DR Schoeberl, MR Herman, JR AF Allen, DR Schoeberl, MR Herman, JR TI Trajectory modeling of aerosol clouds observed by TOMS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE MAPPING SPECTROMETER; SATELLITE AB An aerosol trajectory model (ATM), which couples TOMS aerosol index (AI) measurements with multiple-level parcel trajectories, is presented for determining the three-dimensional (3-D) distribution of a tropospheric aerosol cloud. The ATM is illustrated with an idealized 2-D (height-longitude) cloud in linear vertical shear. The half width of the Vertical parcel distribution (an indicator of how well the cloud is resolved) is inversely proportional to time and to Vertical shear. The degree to which a cloud can be resolved is limited by an "uncertainty principle," whereby model precision improves with time, while accuracy degrades with time because of accumulating trajectory errors. ATM is applied to the ash cloud from the September 1992 eruption of Mount Spurr, Alaska. Disagreement in the predicted cloud structure occurs between 3-day ATM runs using United Kingdom Meteorological Office (UKMO) and National Centers for Environmental Prediction (NCEP) winds. This is due to significant differences in the UKMO and NCEP zonal wind speed near the tropopause, which cause large trajectory separations over 3 days. The UKMO-predicted cloud range (310-390 K) agrees well with radar and pilot observations of the ash cloud, while the NCEP-predicted range shows strong disagreement with observations in the region of the jet maximum. This indicates the potential (when independent observations are available) for using ATM to partially validate wind fields. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CNR, Washington, DC 20418 USA. RP Allen, DR (reprint author), Univ Chicago, Dept Geophys Sci, 5734 S Ellis Ave, Chicago, IL 60637 USA. EM drallen@bethel.uchicago.edu OI Herman, Jay/0000-0002-9146-1632 NR 23 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27461 EP 27471 DI 10.1029/1999JD900763 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700018 ER PT J AU Reid, JS Eck, TF Christopher, SA Hobbs, PV Holben, B AF Reid, JS Eck, TF Christopher, SA Hobbs, PV Holben, B TI Use of the Angstrom exponent to estimate the variability of optical and physical properties of aging smoke particles in Brazil SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AEROSOL CHARACTERIZATION; SATELLITE DATA; AMAZON BASIN; FOREST-FIRE; MODELS; EXTINCTION AB In situ airborne measurements from the Smoke, Clouds and Radiation-Brazil.(SCAR-B) study show that during aging over 1-4 days the physical and optical properties of smoke particles are correlated. Consequently, if one optical or physical property of the smoke particles is determined, other properties can be derived. This methodology is validated using multiwavelength Angstrom exponents determined from the ground-based Sun photometer measurements in SCAR-B. It is shown that the Angstrom exponent determined from Sun photometers for the wavelength intervals 339-437 nm and 437-669 nm are well correlated with particle size, single-scattering albedo, and the backscatter ratio (r(2) > 0.8). Therefore, when almucantar sky radiance data are not available and for remote sensing applications (such as MODIS), some of the uncertainties in the properties of smoke particles can be reduced by applying these relationships. Using this methodology, major oscillations were observed in smoke particle properties in Brazil on timescales of similar to 5-15 days, resulting in variations of the volume median diameter and single-scattering albedo of +/-0.04 mu m and +/-0.05, respectively. In comparison, the mean value of the dry smoke particle volume median diameter and single-scattering albedo over all of Brazil was 0.27 mu m and 0.86, respectively. A daily cycle in smoke particle properties was also observed. The weekly and seasonal variability in the single-scattering albedo is shown to have significant consequences for retrieving aerosol optical depths from satellite measurements. C1 Space & Naval Warfare Syst Ctr, Tropospher Branch D883, San Diego, CA 92152 USA. NASA, Goddard Space Flight Ctr, Raytheon RITSS Corp, Greenbelt, MD 20771 USA. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. Univ Alabama, Huntsville, AL 35899 USA. RP Reid, JS (reprint author), Space & Naval Warfare Syst Ctr, Tropospher Branch D883, 49170 Propagat Path, San Diego, CA 92152 USA. EM jreid@spawar.navy.mil RI Christopher, Sundar/E-6781-2011; ECK, THOMAS/D-7407-2012; Reid, Jeffrey/B-7633-2014 OI Reid, Jeffrey/0000-0002-5147-7955 NR 39 TC 148 Z9 150 U1 1 U2 13 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27473 EP 27489 DI 10.1029/1999JD900833 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700019 ER PT J AU Yue, GK AF Yue, GK TI A new approach to retrieval of aerosol size distributions and integral properties from SAGE II aerosol extinction spectra SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC AEROSOL; PINATUBO AEROSOL; INVERSION ALGORITHM; OZONE DEPLETION; MT-PINATUBO; SATELLITE; LIDAR; ERUPTION; MODEL; TEMPERATURE AB A new approach to the retrieval of aerosol size distributions and integral properties from Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction spectra is proposed. This method assumes that the aerosol size distribution can be approximated by a histogram of number density as a function of particle size. The retrieved number density in each bin is expressed as a linear combination of the SAGE II aerosol extinctions at four or fewer wavelengths. The coefficients in the weighted linear combination are obtained by minimizing the retrieval error averaged for a set of testing size distributions. The same method has been applied to retrieve aerosol surface area and volume densities from SAGE II aerosol extinctions. The retrieval accuracy was studied by calculating the aerosol surface area and volume densities for six aerosol size distributions retrieved by using the proposed linear minimizing error method. In general, the retrieval error increases with the decreasing number of wavelength-dependent extinction measurements available for retrieval. Besides accuracy, the proposed method has the advantage of not requiring an initial guess or a weighting function. Furthermore, it is very simple and fast. Another advantage is that the proposed method can still be applied to the case when the number of reliable aerosol extinction is less than four. The formulas presented in this paper can be used easily by investigators to retrieve surface area and volume densities from SAGE II aerosol extinction spectra at different altitudes for a variety of purposes. The proposed new method can also be extended to retrieve properties from other remote sensing systems. The application of the proposed method for instrument design is discussed. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Yue, GK (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, 100 NASA Rd, Hampton, VA 23681 USA. EM g.k.yue@larc.nasa.gov NR 40 TC 19 Z9 21 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27491 EP 27506 DI 10.1029/1999JD900455 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700020 ER PT J AU Mlynczak, MG AF Mlynczak, MG TI A new perspective on the molecular oxygen and hydroxyl airglow emissions SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR MESOSPHERE EXPLORER; LOWER THERMOSPHERE; MIDDLE ATMOSPHERE; SABER EXPERIMENT; ATOMIC-HYDROGEN; OZONE; MODEL; TEMPERATURE; INFERENCE; RATES AB The mesospheric molecular oxygen and hydroxyl airglow emissions have traditionally been measured in order to derive minor species abundances or to diagnose dynamical phenomena. We present a new interpretation of these airglow emissions and show them to be fundamental measures of energy deposition from which rates of atmospheric heating are readily derived. The heating rate due to absorption of ultraviolet radiation in the Hartley band of ozone may be derived from simultaneous measurements of the oxygen atmospheric band and infrared atmospheric band volume emission rates independent of knowledge of the ozone density, the solar irradiance, and the ozone absorption cross sections. The heating rates due to key exothermic reactions may be derived directly from appropriate airglow observations independent of the reactant concentrations and the temperature-dependent reaction rates. The accuracy of heating rates derived directly from airglow measurements is also inherently higher than that obtained in standard approaches. We suggest that heating rates derived in this manner be treated as data products and that they be compared with numerical model computations to enhance understanding of atmospheric thermodynamics. An initial comparison of airglow-derived energy deposition rates with deposition rates traditionally computed from numerical models shows agreement to within 20% for the Hartley band of ozone in the lower and upper mesosphere. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Mlynczak, MG (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 420, Hampton, VA 23681 USA. EM m.g.mlynczak@larc.nasa.gov RI Mlynczak, Martin/K-3396-2012 NR 26 TC 12 Z9 12 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27535 EP 27543 DI 10.1029/1999JD900839 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700024 ER PT J AU Douglass, AR Prather, MJ Hall, TM Strahan, SE Rasch, PJ Sparling, LC Coy, L Rodriguez, JM AF Douglass, AR Prather, MJ Hall, TM Strahan, SE Rasch, PJ Sparling, LC Coy, L Rodriguez, JM TI Choosing meteorological input for the global modeling initiative assessment of high-speed aircraft SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; DATA ASSIMILATION SYSTEM; MIDDLE ATMOSPHERE; 3-DIMENSIONAL MODEL; ANNUAL CYCLE; STRATOSPHERIC WINDS; SUPERSONIC AIRCRAFT; TRACER TRANSPORT; CARBON-DIOXIDE; CO2 AB The global modeling initiative (GMI) science team is developing a three-dimensional chemistry and transport model (CTM) for use in assessment of the atmospheric effects of aviation. This model must be documented, be validated against observations, use a realistic atmospheric circulation, and contain numerical transport and photochemical modules representing atmospheric processes. The model must retain computational efficiency for multiple scenarios and sensitivity studies. To meet these requirements, a facility model concept was developed in which the different components of the CTM: are evaluated separately. The assessment of the impact on the stratosphere of the exhaust of supersonic aircraft will depend strongly on the meteorological fields used by the CTM. Three data sets for the stratosphere were considered: the National Center for Atmospheric Research Community Climate Model (CCM2), the Goddard Earth Observing System data assimilation system, and the Goddard Institute for Space Studies general circulation model. Objective criteria were developed to identify the data set that provides the best representation of the stratosphere. Simulations of gases with simple chemical control were chosen to test various aspects of model transport. The data sets were evaluated and graded on their performance on these tests. The CCM2 meteorological data set has the highest score and was selected for GMI. This objective model evaluation establishes a physical basis for interpretation of differences between models and observations. Further, the method provides a quantitative basis for defining model errors, for discriminating between different models, and for ready reevaluation of improved models. This will lead to higher confidence in assessment calculations. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Irvine, Dept Earth Syst Sci, Irvine, CA 92717 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Gen Sci Corp, Laurel, MD USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Maryland Baltimore Cty, Joint Ctr Environm Technol, Baltimore, MD 21228 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Miami, FL 33149 USA. RP Douglass, AR (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. EM douglass@persephone.gsfc.nasa.gov; mprather@uci.edu; hall@giss.nasa.gov; sstrahan@dao.gsfc.nasa.gov; pjr@ncar.ucar.edu; sparling@dynarema.gsfc.nasa.gov; coy@demeter.gsfc.nasa.gov; jrodriguez@rsmas.miami.edu RI Douglass, Anne/D-4655-2012; Strahan, Susan/H-1965-2012; Rodriguez, Jose/G-3751-2013 OI Rodriguez, Jose/0000-0002-1902-4649 NR 55 TC 44 Z9 44 U1 1 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27545 EP 27564 DI 10.1029/1999JD900827 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700025 ER PT J AU Hall, FG AF Hall, FG TI Introduction to special section: BOREAS in 1999: Experiment and science overview SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material ID ATMOSPHERE INTERACTIONS; LAND-ATMOSPHERE; CARBON-DIOXIDE; HIGH-LATITUDES; FOREST; MODEL; CO2; NORTHERN; BALANCE; WATER AB The goal of BOREAS is to improve our understanding of the interactions between the boreal forest biome and the atmosphere in order to clarify their roles in global change. This overview briefly reviews the science background and motivations for the Boreal Ecosystem-Atmosphere Study (BOREAS). The findings of the 27 papers in this journal special issue are reviewed. Important scientific results of the project to date are summarized, and future research directions are identified. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hall, FG (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM FGHALL@ltpmail.gsfc.nasa.gov NR 31 TC 33 Z9 36 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27627 EP 27639 DI 10.1029/1999JD901026 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700032 ER PT J AU Potter, CS Coughlan, JC Brooks, V AF Potter, CS Coughlan, JC Brooks, V TI Investigations of BOREAS spatial data in support of regional ecosystem modeling SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CONTERMINOUS UNITED-STATES; NET PRIMARY PRODUCTION; CARBON-DIOXIDE; FOREST STANDS; ATMOSPHERE; VARIABILITY; EMISSIONS; EXCHANGE; METHANE; FIRE AB Simulation models are commonly used to scale up water, energy, and trace gas flux estimates from study plots to an entire region or biome, such as the North American boreal forest. As a means to validate ecosystem model predictions at the scale of the typical experimental area (100 m(2) to 1 km(2)), it is necessary to quantify potential errors in spatial data layers used as model inputs, independently from prediction errors resulting from incorrect model design or flawed process algorithms. Our analysis of land cover, hydrology, and soil maps generated as part of the Boreal Ecosystem-Atmosphere Study (BOREAS) suggests that coverages for plant functional types, derived from a combination of Landsat Thematic Mapper and the advanced very high resolution radiometer (AVHRR) satellite images, provide the highest quality information to define spatial model parameters. This information is critical for boreal ecosystem simulations of small patch types (e.g., dry conifer, fen, and disturbed sites), which are frequently obscured at l-km pixel resolution. We find that soil property information for the dominant class, as contained in the regional BOREAS soil maps, does not appear to be a highly consistent indicator of hydrologic dynamics for fen and other boreal wetlands at the study area level. It appears instead that accurate regional modeling analyses for methane and other biogenic trace gas fluxes will depend largely on relatively fine scale remote sensing to resolve the high level of undifferentiated pixel mixing Seen among boreal forest types and fen/bog areas in aggregated I-km AVHRR land cover data. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Johnson Controls World Serv Inc, Moffett Field, CA 94035 USA. RP Potter, CS (reprint author), NASA, Ames Res Ctr, Mail Stop 242-4, Moffett Field, CA 94035 USA. NR 39 TC 13 Z9 13 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27771 EP 27788 DI 10.1029/1999JD900166 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700043 ER PT J AU Kimball, JS Running, SW Saatchi, SS AF Kimball, JS Running, SW Saatchi, SS TI Sensitivity of boreal forest regional water flux and net primary production simulations to sub-grid-scale land cover complexity SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LEAF-AREA INDEX; CARBON-DIOXIDE; BLACK SPRUCE; JACK PINE; SEASONAL-VARIATION; PICEA-MARIANA; EXCHANGE; MODEL; PHOTOSYNTHESIS; VAPOR AB We use a general ecosystem process model (BIOME-BGC) coupled with remote sensing information to evaluate the sensitivity of boreal forest regional evapotranspiration (ET) and net primary production (NPP) to land cover spatial scale. Simulations were conducted over a 3 year period (1994-1996) at spatial scales ranging from 30 to 50 km within the BOREAS southern modeling subarea. Simulated fluxes were spatially complex, ranging from 0.1 to 3.9 Mg C ha(-1) yr(-1) and from 18 to 29 cm yr(-1). Biomass and leaf area index heterogeneity predominantly controlled this complexity, while biophysical differences between deciduous and coniferous vegetation were of secondary importance. Spatial aggregation of land cover characteristics resulted in mean monthly NPP estimation bias from 25 to 48% (0.11-0.20 g C m(-2) d(-1)) and annual estimation errors from 2 to 14% (0.04-0.31 Mg C ha(-1) yr(-1)). Error was reduced at longer time intervals because coarse scale overestimation errors during spring were partially offset by underestimation of fine scale results during summer and winter. ET was relatively insensitive to land cover spatial scale with an average bias of less than 5% (0.04 kg m(-2) d(-1)). Factors responsible for differences in scaling behavior between ET and NPP included compensating errors for ET calculations and boreal forest spatial and temporal NPP complexity. Careful consideration of landscape: spatial and temporal heterogeneity is necessary to identify and mitigate potential error sources when using plot scale information to understand regional scale patterns. Remote sensing data integrated within an ecological process model framework provides an efficient mechanism to evaluate scaling behavior, interpret patterns in coarse resolution data, and identify appropriate scales of operation for various processes. C1 Univ Montana, Sch Forestry, Numer Terradynam Simulatt Grp, Missoula, MT 59001 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kimball, JS (reprint author), Flathead Lake Biol Stn, 311 Biostn Lane, Polson, MT 59860 USA. EM johnk@ntsg.umt.edu NR 63 TC 36 Z9 40 U1 2 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27789 EP 27801 DI 10.1029/1999JD900085 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700044 ER PT J AU Frolking, S McDonald, KC Kimball, JS Way, JB Zimmermann, R Running, SW AF Frolking, S McDonald, KC Kimball, JS Way, JB Zimmermann, R Running, SW TI Using the space-borne NASA scatterometer (NSCAT) to determine the frozen and thawed seasons SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SPRUCE/MOSS BOREAL FOREST; CARBON-DIOXIDE; TAIGA FORESTS; IMAGING RADAR; ASPEN FOREST; WATER-VAPOR; ERS-1 SAR; CLASSIFICATION; PRODUCTIVITY; VARIABILITY AB We hypothesize that the strong sensitivity of radar backscatter to surface dielectric properties, and hence to the phase (solid or liquid) of any water near the surface should make space-borne radar observations a powerful tool for large-scale spatial monitoring of the freeze/thaw state of the land surface, and thus ecosystem growing season length. We analyzed the NASA scatterometer (NSCAT) backscatter from September 1996 to June 1997, along with temperature and snow depth observations and ecosystem modeling, for three BOREAS sites in central Canada. Because of its short wavelength (2.14 cm), NSCAT was sensitive to canopy and surface water. NSCAT had 25 km spatial resolution and approximately twice-daily temporal coverage at the BOREAS latitude. At the northern site the NSCAT signal showed strong seasonality, with backscatter around -8 dB in winter and -12 dB in early summer and fall. The NSCAT signal for the southern sites had less seasonality. At all three sites there was a strong decrease in backscatter during spring thaw (4-6 dB). At the southern deciduous site, NSCAT backscatter rose from -11 to -9.2 dB during spring leaf-out. All sites showed 1-2 dB backscatter shifts corresponding to changes in landscape water state coincident with brief midwinter thaws, snowfall, and extreme cold (T-max < -25 degrees C). Freeze/thaw detection algorithms developed for other radar instruments gave reasonable results for the northern site but were not successful at the two southern sites. We developed a change detection algorithm based on first differences of 5-day smoothed NSCAT backscatter measurements. This algorithm had some success in identifying the arrival of freezing conditions in the autumn and the beginning of thaw in the spring. Changes in surface freeze/thaw state generally coincided with the arrival and departure of the seasonal snow cover and with simulated shifts in the directions of net carbon exchange at each of the study sites. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Univ New Hampshire, Dept Earth Sci, Durham, NH 03824 USA. CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. Univ Montana, Sch Forestry, NTSG, Missoula, MT 59812 USA. Univ Bayreuth, D-95540 Bayreuth, Germany. RP Frolking, S (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Morse Hall, Durham, NH 03824 USA. NR 37 TC 41 Z9 44 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27895 EP 27907 DI 10.1029/1998JD200093 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700052 ER PT J AU Huemmrich, KF Black, TA Jarvis, PG McCaughey, JH Hall, FG AF Huemmrich, KF Black, TA Jarvis, PG McCaughey, JH Hall, FG TI High temporal resolution NDVI phenology from micrometeorological radiation sensors SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DIFFERENCE VEGETATION INDEX; NET PRIMARY PRODUCTION; CARBON-DIOXIDE FLUXES; BOREAL FOREST; SEASONAL-VARIATION; DECIDUOUS FOREST; SATELLITE DATA; WATER-VAPOR; SAIL MODEL; LEAF-AREA AB The boreal forest is a region characterized by wide swings in temperature and light levels over the course of a year. This seasonal variability strongly effects the vegetation of this biome. Normalized difference vegetation index (NDVI) Values were observed at daily timescales for key land cover types of the boreal forest, developing a more detailed description of seasonal changes in NDVI than could be produced from satellite data. NDVI Values were calculated from tower-mounted photosynthetically active radiation (PAR) and global solar sensors measuring both incoming and reflected radiation above the canopies at four Boreal Ecosystem-Atmosphere Study (BOREAS) sites. Comparisons were made between the tower-based broadband hemispherical NDVI values and the narrowband nadir-viewed NDVI values from helicopter modular multiband radiometer (MMR). The comparisons indicate that the tower NDVI values are close to the MMR NDVIs in value for the BOREAS sites, but the range in tower NDVIs is not so great as in the MMR NDVIs. In 1996, BOREAS towers operated from before thaw to freeze-up, allowing a complete picture of growing season NDVI for fen, young jack pine, black spruce, and aspen sites. The tower-based NDVI time series display different patterns for each vegetation type, showing the effects of snow cover and vegetation green-up and senescence. Changes in solar zenith angles are shown to have little effect on the seasonal NDVI patterns. C1 Univ Maryland, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ British Columbia, Dept Soil Sci, Vancouver, BC V6T 2A2, Canada. Univ Edinburgh, Inst Ecol & Resource Management, Edinburgh EH8 NYL, Midlothian, Scotland. Queens Univ, Dept Geog, Kingston, ON K7L 3N6, Canada. RP Huemmrich, KF (reprint author), Univ Maryland, NASA, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. EM Karl.Huemmrich@gsfc.nasa.gov NR 39 TC 75 Z9 77 U1 2 U2 17 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1999 VL 104 IS D22 BP 27935 EP 27944 DI 10.1029/1999JD900164 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 259BT UT WOS:000083874700055 ER PT J AU Jongen, T Gatski, TB AF Jongen, T Gatski, TB TI A unified analysis of planar homogeneous turbulence using single-point closure equations SO JOURNAL OF FLUID MECHANICS LA English DT Article ID REYNOLDS STRESS MODEL; EQUILIBRIUM STATES; FLOWS; EXPLICIT; ROTATION; STRAIN AB A unified approach for assessing and characterizing both the non-equilibrium and equilibrium states of planar homogeneous flows is analysed within the framework of single-point turbulence closure equations. The underlying methodology is based on the replacement of the modelled evolution equation for the Reynolds stress anisotropy tensor by an equivalent set of three equations for characteristic scalar invariants or state variables. For stress anisotropy evolution equations which use modelled pressure-strain rate correlations that are quasi-linear, this equivalence then leads to an analytic solution for the time evolution of the Reynolds stress anisotropy. With this analysis, the transient system characteristics can be studied, including the dependence on initial states, the occurrence of limit-cycle behaviour, and the system global stability. In the fixed-point asymptotic limit, these results are consistent with and unify previous equilibrium studies, and provide additional information allowing the resolution of some questions that could not be answered in the framework of previous developments. A new result on constraints applicable to the development of realizable pressure-strain rate models is obtained from a re-examination of the stress anisotropy invariant map. With the analytic solution for the transient behaviour, some recent non-equilibrium models, which incorporate relaxation effects, are evaluated in a variety of homogeneous flows in inertial and non-inertial frames. C1 Swiss Fed Inst Technol, CH-1015 Lausanne, Switzerland. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Jongen, T (reprint author), Unilever Res Labs Vlaardingen, POB 114, NL-3130 AC Vlaardingen, Netherlands. NR 37 TC 18 Z9 19 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD NOV 25 PY 1999 VL 399 BP 117 EP 150 DI 10.1017/S002211209900631X PG 34 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 260WX UT WOS:000083977400004 ER PT J AU Farmer, JD Des Marais, DJ AF Farmer, JD Des Marais, DJ TI Exploring for a record of ancient Martian life SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID THERMAL-SPRING DEPOSITS; MARS PATHFINDER MISSION; UREY PRIZE LECTURE; EXOBIOLOGICAL IMPLICATIONS; METEORITE ALH84001; ASTEROID IMPACTS; NORTHERN CHILE; DRUMMOND BASIN; LANDING SITE; HOT-SPRINGS AB The immediate task facing exopaleontology is to define a strategy to explore Mars for a fossil record during the decade-long exploration program that lies ahead. Consideration of the quality of paleontological information preserved under different geological conditions is important if we are to develop a strategy with broad applicability. The preservation of microbial fossils is strongly influenced by the physical, chemical, and biological factors of the environment which, acting together, determine the types of information that will be captured and retained in the rock record. In detrital sedimentary systems, preservation is favored by rapid burial in fine-grained, clay-rich sediments. In chemical sedimentary systems, preservation is enhanced by rapid entombment in fine-grained chemical precipitates. For long-term preservation, host rocks must be composed of stable minerals that are resistant to chemical weathering and that form an impermeable matrix and closed chemical system to protect biosignatures from alteration during subsequent diagenesis or metamorphism. In this context, host rocks composed of highly ordered, chemically stable mineral phases, like silica (e.g., cherts) or phosphate (e.g., phosphorites), are especially favored. Such lithologies tend to have very long crustal residence times and, along with carbonates and shales, are the most common host rocks for the Precambrian microfossil record on Earth. Although we make the defensible assumption that Mars was more like the Earth early in its history, clearly, the geological and historical differences between the two planets are many. Such differences must be carefully considered when adapting an Earth-based strategy to Mars. C1 Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Farmer, JD (reprint author), Arizona State Univ, Dept Geol, Box 871404, Tempe, AZ 85287 USA. EM jfarmer@asu.edu; desmarais@mail.arc.nasa.gov NR 185 TC 122 Z9 124 U1 5 U2 36 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1999 VL 104 IS E11 BP 26977 EP 26995 DI 10.1029/1998JE000540 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 258NE UT WOS:000083844600001 PM 11543200 ER PT J AU Hinson, DP Simpson, RA Twicken, JD Tyler, GL Flasar, FM AF Hinson, DP Simpson, RA Twicken, JD Tyler, GL Flasar, FM TI Initial results from radio occultation measurements with Mars Global Surveyor SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GENERAL-CIRCULATION MODEL; ORBITER LASER ALTIMETER; MARTIAN ATMOSPHERE; DUST STORMS; THERMAL TIDES; PRESSURE; TOPOGRAPHY; MARINER-9; MISSION; SURFACE AB A series of radio occultation experiments conducted with Mars Global Surveyor in early 1998 has yielded 88 vertical profiles of the neutral atmosphere. The measurements cover latitudes of 29 degrees N to 64 degrees S and local times from 0600 through midnight to 1800 during early summer in the southern hemisphere (L-s = 264 degrees-308 degrees). Retrieved profiles of pressure and temperature versus radius and geopotential extend from the surface to the 10-Pa pressure level. Near-surface uncertainties in temperature and pressure are about 1 K and 2 Pa, respectively, far smaller than in previous radio occultation measurements at Mars. The profiles resolve the radiative-convective boundary layer adjacent to the surface and also reveal gravity waves, particularly at northern and equatorial latitudes, which appear to be breaking in some cases. Distinctive meridional gradients of pressure and temperature indicate the presence of a low-altitude westerly jet st latitudes of 15 degrees-30 degrees S at southern summer solstice. This jet appears in predictions of general circulation models in connection with the strong, seasonal, cross-equatorial Hadley circulation. The pressure gradient at similar to 2 km altitude implies a wind speed of 33 m s(-1), stronger than predicted, which may help explain the occurrence of numerous local dust storms within this latitude band in late southern spring. These measurements also characterize the response of the atmosphere to stationary thermal forcing at midsouthern latitudes, where high terrain south of Tharsis and low terrain in Hellas Planitia produce large, zonal temperature variations in the lowest scale height above the surface. Pressure measured at constant geopotential decreases at an average rate of 0.13% per degree L-s, due primarily to condensation of CO2 at the North Pole. C1 Stanford Univ, Ctr Radar Astron, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hinson, DP (reprint author), Stanford Univ, Ctr Radar Astron, Stanford, CA 94305 USA. RI Flasar, F Michael/C-8509-2012 NR 58 TC 153 Z9 159 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1999 VL 104 IS E11 BP 26997 EP 27012 DI 10.1029/1999JE001069 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 258NE UT WOS:000083844600002 ER PT J AU Smrekar, S Catling, D Lorenz, R Magalhaes, J Moersch, J Morgan, P Murray, B Presley, M Yen, A Zent, A Blaney, D AF Smrekar, S Catling, D Lorenz, R Magalhaes, J Moersch, J Morgan, P Murray, B Presley, M Yen, A Zent, A Blaney, D TI Deep space 2: The Mars Microprobe Mission SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID POLAR LAYERED DEPOSITS; THERMAL-CONDUCTIVITY MEASUREMENTS; PARTICULATE MATERIALS; GENERAL-CIRCULATION; MAPPER OBSERVATIONS; WATER CYCLE; ALBEDO; MODEL; ATMOSPHERE; REGIONS AB The Mars Microprobe Mission will be the second of the New Millennium Program's technology development missions to planetary bodies. The mission consists of two penetrators that weigh 2.4 kg each and are being carried as a piggyback payload on the Mars Polar Lander cruise ring. The spacecraft arrive at Mars on December 3, 1999. The two identical penetrators will impact the surface at similar to 190 m/s and penetrate up to 0.6 m. They will land within 1 to 10 km of each other and similar to 50 km from the Polar Lander on the south polar layered terrain. The primary objective of the mission is to demonstrate technologies that will enable :future science missions and, in particular, network science missions. A secondary goal is to acquire science data. A subsurface evolved water experiment and a thermal conductivity experiment will estimate the water content and thermal properties of the regolith. The atmospheric density, pressure, and temperature will be derived using descent deceleration data. Impact accelerometer data will be used to determine the depth of penetration, the hardness of the regolith, and the presence or absence of 1.0 cm scale layers. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. No Arizona Univ, Dept Geol, Flagstaff, AZ 86011 USA. CALTECH, Dept Geol & Planetary Sci, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. RP Smrekar, S (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Moersch, Jeffrey/F-7189-2010; Catling, David/D-2082-2009; Lorenz, Ralph/B-8759-2016; OI Lorenz, Ralph/0000-0001-8528-4644; Catling, David/0000-0001-5646-120X NR 63 TC 30 Z9 30 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1999 VL 104 IS E11 BP 27013 EP 27030 DI 10.1029/1999JE001073 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 258NE UT WOS:000083844600003 ER PT J AU Yen, AS Murray, B Rossman, GR Grunthaner, FJ AF Yen, AS Murray, B Rossman, GR Grunthaner, FJ TI Stability of hydroxylated minerals on Mars: A study on the effects of exposure to ultraviolet radiation SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MAGNETIC-PROPERTIES; MARTIAN SOIL; WATER; SURFACE; PHOTOCHEMISTRY; REFLECTANCE; ADSORPTION; REGIONS; OXIDES AB The density and composition of the Martian atmosphere allow solar ultraviolet photons with wavelengths as short as 190 nm to reach the surface. We investigate the hypothesis that this UV radiation is capable of inducing the release of water from iron oxyhydroxide minerals resulting in the formation of oxide phases. These experiments, which utilize a quadrupole mass spectrometer to monitor the water vapor pressure above mineral samples during cyclic exposure to ultraviolet radiation, offer 5 to 6 orders of magnitude greater sensitivity than previous attempts to establish and quantify this process. We find no evidence that UV photons are capable of liberating OH from the crystal lattice of minerals, and we set a minimum ultraviolet radiation-induced dehydroxylation time of 10(8) years for removal of this structural OH from mineral particles at the Martian surface. The overturning timescales for surface fines are likely to be shorter than this lower limit for exposure time. Thus we conclude that UV-stimulated dehydroxylation is not a significant process at the Martian surface and that iron oxyhydroxides, if formed during an earlier water-rich environment, should still be found an Mars today. The lack of clear evidence for iron oxyhydroxides at the Martian surface further suggests that Mars' surface was never warm and wet for a long enough period of time for Earth-like weathering to have occurred. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Yen, AS (reprint author), CALTECH, Jet Prop Lab, Mail Code 302-306,4800 Oak Grove Dr, Pasadena, CA 91109 USA. OI Rossman, George/0000-0002-4571-6884 NR 36 TC 15 Z9 15 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1999 VL 104 IS E11 BP 27031 EP 27041 DI 10.1029/1999JE001065 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 258NE UT WOS:000083844600004 ER PT J AU Allen, CC Albert, FG Combie, J Banin, A Yablekovitch, Y Kan, I Bodnar, RJ Hamilton, VE Jolliff, BL Kuebler, K Wang, A Lindstrom, DJ Morris, PA Morris, RV Murray, RW Nyquist, LE Simpson, PD Steele, A Symes, SJ AF Allen, CC Albert, FG Combie, J Banin, A Yablekovitch, Y Kan, I Bodnar, RJ Hamilton, VE Jolliff, BL Kuebler, K Wang, A Lindstrom, DJ Morris, PA Morris, RV Murray, RW Nyquist, LE Simpson, PD Steele, A Symes, SJ TI Effects of sterilizing doses of gamma radiation on Mars analog rocks and minerals SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID INFRARED-EMISSION SPECTROSCOPY; ATMOSPHERE CONFINING PRESSURE; SYNTHETIC FLUID INCLUSIONS; DEINOCOCCUS RADIODURANS; METEORITES; QUARTZ; ENVIRONMENTS; PROTECTION; SURFACE; HISTORY AB Rock and soil samples from the planet Mars are due to be returned to Earth within a decade. Martian samples initially will be tested for evidence of life and biological hazard under strict biological containment. Wider distribution of samples for organic and inorganic analysis may occur only if neither evidence of life nor hazard is detected, or if the samples ate first sterilized. We subjected a range of Mars analog rocks and minerals to high doses of gamma radiation in order to determine the effects of gamma sterilization on the samples' isotopic, chemical, and physical properties. Gamma photons from Co-60 (1.17 and 1.33 MeV) in doses as high as 3 x 10(7) rads did not induce radioactivity in the samples and produced no measurable changes in their isotopic and chemical compositions. This level of irradiation also produced no measurable changes in the crystallographic structure of any sample, the surface areas of soil analogs, or the fluid inclusion homogenization temperature of quartz. The only detectable effects of irradiation were dose-dependent changes in the visible and near-infrared spectral region (e.g., discoloration and darkening of quartz and halite and an increase in albedo of carbonates) and increases in the thermoluminescence of quartz and plagioclase. If samples returned from Mars require biological sterilization, gamma irradiation provides a feasible option. C1 Lockheed Martin Space Operat, Houston, TX 77058 USA. Montana Biotech Corp, Belgrade, MT 59714 USA. Hebrew Univ Jerusalem, Dept Soil & Water Sci, IL-76100 Rehovot, Israel. Virginia Polytech Inst & State Univ, Dept Geol Sci, Blacksburg, VA 24061 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Houston, Dept Nat Sci, Houston, TX 77002 USA. Boston Univ, Dept Earth Sci, Boston, MA 02215 USA. Ctr Dis Control & Prevent, Atlanta, GA 30333 USA. Univ Portsmouth, Portsmouth P01 2DT, Hants, England. RP Allen, CC (reprint author), Lockheed Martin Space Operat, 2400 NASA Rd 1, Houston, TX 77058 USA. RI Bodnar, Robert/A-1916-2009 NR 62 TC 6 Z9 6 U1 2 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1999 VL 104 IS E11 BP 27043 EP 27066 DI 10.1029/1999JE001064 PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 258NE UT WOS:000083844600005 ER PT J AU McCord, TB Hansen, GB Shirley, JH Carlson, RW AF McCord, TB Hansen, GB Shirley, JH Carlson, RW TI Discussion of the 1.04-mu m water ice absorption band in the Europa NIMS spectra and a new NIMS calibration SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID INFRARED MAPPING SPECTROMETER; MU-M AB Measurements made by the Galileo Near Infrared Mapping Spectrometer (NIMS) have been used to calculate reflectance spectra for regions of Europa. Many of these spectra show features indicative of water ice. Others show asymmetric H2O absorption features suggesting hydrated non-ice constituents such as hydrated sulfates and carbonates. Often, both types of features are present. However, some previously published NIMS spectra with strongly developed ice features did not show the expected 1.04-mu m ice absorption band. This discrepancy has led to questions regarding earlier interpretations of Europa's spectral features. Recent work reveals that unexpected changes have occurred in the spectral range covered by each NIMS detector and that an additional calibration is required. Preliminary calibration values are given. When this new calibration is applied, the 1.04-mu m feature emerges clearly in those spectra where it was expected but absent previously, thereby resolving the 1.04-mu m band discrepancy. C1 Univ Hawaii, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP McCord, TB (reprint author), Univ Hawaii, Hawaii Inst Geophys & Planetol, 2525 Correa Rd, Honolulu, HI 96822 USA. NR 8 TC 14 Z9 14 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1999 VL 104 IS E11 BP 27157 EP 27162 DI 10.1029/1999JE001046 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 258NE UT WOS:000083844600013 ER PT J AU Farassat, F Farris, M AF Farassat, F Farris, M TI The mean curvature of the influence surface of wave equation with sources on a moving surface SO MATHEMATICAL METHODS IN THE APPLIED SCIENCES LA English DT Article ID FORMULATION; PREDICTION AB The mean curvature of the influence surface of the space-time point (x, t) appears in linear supersonic propeller noise theory and in the Kirchhoff formula for a supersonic surface. Both these problems are governed by the linear wave equation with sources on a moving surface. The influence surface is;also called the Sigma-surface in the aeroacoustic literature. This surface is the locus, in a frame fixed to the quiescent medium, of all the points of a radiating surface f (x, t) = 0 whose acoustic signals arrive simultaneously to an observer at position x and at the time t. Mathematically, the Sigma-surface is produced by the intersection of the characteristic conoid of the space-time point (x, t) and the moving surface. In this paper, we derive the expression for the local mean curvature of the Sigma-surface of the space-time point (x, t) for a moving rigid or deformable surface f (x, t) = 0. This expression is a complicated function of the geometric and kinematic parameters of the surface f(x, t) = 0. Using the results of this paper, the solution of the governing wave equation of high-speed propeller noise radiation as well;as the Kirchhoff formula for a supersonic surface can be written as very compact analytic expressions. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Midwestern State Univ, Wichita Falls, TX 76308 USA. RP Farassat, F (reprint author), NASA, Langley Res Ctr, Mail Stop 461, Hampton, VA 23681 USA. NR 25 TC 3 Z9 3 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0170-4214 J9 MATH METHOD APPL SCI JI Math. Meth. Appl. Sci. PD NOV 25 PY 1999 VL 22 IS 17 BP 1485 EP 1503 DI 10.1002/(SICI)1099-1476(19991125)22:17<1485::AID-MMA89>3.0.CO;2-8 PG 19 WC Mathematics, Applied SC Mathematics GA 254ET UT WOS:000083599500001 ER PT J AU Kremer, J Boezio, M Ambriola, ML Barbiellini, G Bartalucci, S Bellotti, R Bergstrom, D Bravar, U Cafagna, F Carlson, P Casolino, M Castellano, M Ciacio, F Circella, M De Marzo, C De Pascale, MP Francke, T Finetti, N Golden, RL Grimani, C Hof, M Menn, W Mitchell, JW Morselli, A Ormes, JF Papini, P Piccardi, S Picozza, P Ricci, M Schiavon, P Simon, M Sparvoli, R Spillantini, P Stephens, SA Stochaj, SJ Streitmatter, RE Suffert, M Vacchi, A Weber, N Zampa, N AF Kremer, J Boezio, M Ambriola, ML Barbiellini, G Bartalucci, S Bellotti, R Bergstrom, D Bravar, U Cafagna, F Carlson, P Casolino, M Castellano, M Ciacio, F Circella, M De Marzo, C De Pascale, MP Francke, T Finetti, N Golden, RL Grimani, C Hof, M Menn, W Mitchell, JW Morselli, A Ormes, JF Papini, P Piccardi, S Picozza, P Ricci, M Schiavon, P Simon, M Sparvoli, R Spillantini, P Stephens, SA Stochaj, SJ Streitmatter, RE Suffert, M Vacchi, A Weber, N Zampa, N TI Measurements of ground-level muons at two geomagnetic locations SO PHYSICAL REVIEW LETTERS LA English DT Article ID CAPRICE-RICH DETECTOR; ATMOSPHERIC NEUTRINOS; SEA-LEVEL; COSMIC-RAY; PERFORMANCE; SPECTROMETER; SPECTRUM; FLUX AB We report new measurements of the muon spectra and the muon charge ratio at ground level in the momentum range from 200 MeV/c to 120 GeV/c for two different geomagnetic locations. Above 0.9 GeV/c the absolute spectra measured in the two locations are in good agreement and are about 10% to 15% lower than previous experimental results. At lower momenta the data show latitude dependent geomagnetic effects. These observations are important for the understanding of the observed neutrino anomaly. C1 Univ Gesamthsch Siegen, D-57068 Siegen, Germany. Univ Bari, Dipartmento Fis, I-70126 Bari, Italy. Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Ist Nazl Fis Nucl, Sez Firenze, I-50125 Florence, Italy. Univ Florence, Dipartimento Fis, I-50125 Florence, Italy. Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. Univ Rome, Dipartimento Fis, I-00133 Rome, Italy. Ist Nazl Fis Nucl, Sez Roma, I-00133 Rome, Italy. Royal Inst Technol, S-10405 Stockholm, Sweden. Ctr Rech Nucl, F-67037 Strasbourg, France. Univ Trieste, Dipartimento Fis, I-34147 Trieste, Italy. Ist Nazl Fis Nucl, Sez Trieste, I-34147 Trieste, Italy. Univ Urbino, Dipartimento Fis, I-61029 Urbino, Italy. RP Kremer, J (reprint author), Univ Gesamthsch Siegen, D-57068 Siegen, Germany. RI Morselli, Aldo/G-6769-2011; Castellano, Marcello/J-3428-2012; Cafagna, Francesco/A-9299-2010; Vacchi, Andrea/C-1291-2010; OI Morselli, Aldo/0000-0002-7704-9553; Castellano, Marcello/0000-0002-4211-2903; Cafagna, Francesco/0000-0002-7450-4784; Vacchi, Andrea/0000-0003-3855-5856; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; Sparvoli, Roberta/0000-0002-6314-6117; Picozza, Piergiorgio/0000-0002-7986-3321; Papini, Paolo/0000-0003-4718-2895; Boezio, Mirko/0000-0002-8015-2981 NR 31 TC 92 Z9 95 U1 3 U2 10 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD NOV 22 PY 1999 VL 83 IS 21 BP 4241 EP 4244 DI 10.1103/PhysRevLett.83.4241 PG 4 WC Physics, Multidisciplinary SC Physics GA 256UV UT WOS:000083745600005 ER PT J AU Still, MD Steeghs, D Dhillon, VS Buckley, DAH AF Still, MD Steeghs, D Dhillon, VS Buckley, DAH TI Orbital period of the dwarf nova HL Canis Majoris SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; line : profiles; binaries : close; stars : individual : HL CMa; novae : cataclysmic variables; X-rays : stars ID DISK AB We present a small sample of time-resolved optical spectroscopy of the dwarf nova HL CMa during an outburst state. By combining radial velocity measurements with published data we show that the previously quoted value is not the only candidate for the orbital period of this system. We reduce the significance of daily aliasing but cannot distinguish between two periods at 0.2146 +/- 0.0004 and 0.2212 +/- 0.0005 d. We show that the low-excitation emission lines are composites from an accretion disc and the companion star, and that high-excitation emission originates in the disc or outflowing material associated with the accreting white dwarf. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ St Andrews, St Andrews KY16 9SS, Fife, Scotland. Univ Sheffield, Dept Phys & Astron, Sheffield S3 7RH, S Yorkshire, England. S African Astron Observ, ZA-7935 Cape Town, South Africa. Univ Space Res Assoc, Seabrook, MD 20706 USA. RP Still, MD (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. EM still@chunky.gsfc.nasa.gov; ds10@st-and.ac.uk; Vik.Dhillon@sheffield.ac.uk; dibnob@saao.ac.za RI Steeghs, Danny/C-5468-2009 OI Steeghs, Danny/0000-0003-0771-4746 NR 15 TC 1 Z9 1 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PY 1999 VL 310 IS 1 BP 39 EP 42 DI 10.1046/j.1365-8711.1999.02932.x PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264NU UT WOS:000084189000009 ER PT J AU Turner, TJ George, IM Netzer, H AF Turner, TJ George, IM Netzer, H TI Arakelian 564: An unusual component in the X-ray spectra of narrow-line Seyfert 1 galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (Arakelian 564); galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; ASCA OBSERVATIONS; EMISSION AB We present an ASCA observation of the narrow-line Seyfert 1 (NLSy1) galaxy Arakelian 564. The X-ray light curve shows rapid variability, but no evidence for energy dependence to these variations, within the 0.6-10 keV bandpass. A strong (EW similar to 70 eV) spectral feature is observed close to 1 keV. A similar feature has been observed in Ton S180, another member of the NLSy1 class of objects, but it has not been observed in broad-line Seyfert galaxies. The feature energy suggests a large contribution from Fe L-shell lines, but its intensity is difficult to explain in terms of emission and/or absorption from photoionized gas. The models that predict most emission at 1 keV are characterized by extreme values of column density, Fe abundance, and ionization parameter. Models based on gas in thermal equilibrium with kT similar to 1 keV provide an alternative parameterization of the soft spectrum. The latter may be interpreted as the hot intercloud medium, undergoing rapid cooling and producing strong Fe L-shell recombination lines. In all cases the physical conditions are rather different from those observed in broad-line Seyfert galaxies. The hard X-ray spectrum shows a broad and asymmetric Fe Ka line of large equivalent width (similar to 550 eV), suggestive of significant emission from the inner accretion disk. The profile can be explained by a neutral disk viewed at similar to 60 degrees to the line of sight, contrary to the hypothesis that NLSy1's are viewed pole-on. The large EW of this line, the strong 1 keV emission, and the strong optical Fe emission lines all suggest an extreme Fe abundance in this and perhaps other NLSy1's. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Baltimore, MD 21250 USA. Tel Aviv Univ, Sch Phys & Astron, IL-69978 Tel Aviv, Israel. Tel Aviv Univ, Wise Observ, IL-69978 Tel Aviv, Israel. RIKEN, Inst Phys & Chem Res, Wako, Saitama 3510198, Japan. RP Turner, TJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 660, Greenbelt, MD 20771 USA. NR 30 TC 30 Z9 30 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 52 EP 59 DI 10.1086/307995 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900006 ER PT J AU Sambruna, RM Eracleous, M Mushotzky, RF AF Sambruna, RM Eracleous, M Mushotzky, RF TI An X-ray spectral survey of radio-loud active galactic nuclei with ASCA SO ASTROPHYSICAL JOURNAL LA English DT Review DE galaxies : active; radiation mechanisms : nonthermal; surveys; X-rays : galaxies ID EARLY-TYPE GALAXIES; ADVECTION-DOMINATED ACCRETION; FAR-INFRARED PROPERTIES; WAVE CONTINUUM SOURCES; BRIGHT QUASAR SURVEY; MASSIVE BLACK-HOLE; C-IV ABSORPTION; COMPLETE SAMPLE; ELLIPTIC GALAXIES; CYGNUS-A AB We present a uniform and systematic analysis of the 0.6-10 keV X-ray spectra of radio-loud active galactic nuclei (AGNs) observed by ASCA. The sample, which is not statistically complete, includes 10 broad-line radio galaxies (BLRGs), five radio-loud quasars (QSRs), nine narrow-line radio galaxies (NLRGs), and 10 radio galaxies (RGs) of mixed FR I and FR II types. For several sources the ASCA data are presented here for the first time. The exposure times of the observations and the fluxes of the objects vary over a wide range; as a result, so does the signal-to-noise ratio of the individual X-ray spectra. At soft X-rays, about 50% of NLRGs and 100% of RGs exhibit thermal plasma emission components, with bimodal distributions of temperatures and luminosities. This indicates that the emission in such an object arises in hot gas either in a surrounding cluster or loose group or in a hot corona, consistent with previous ROSAT and optical results. At energies above 2 keV, a hard power-law component (photon index Gamma similar to 1.7-1.8) is detected in 90% of cases. The power-law photon indices and luminosities in BLRGs, QSRs, and NLRGs are similar. This is consistent with simple orientation-based unification schemes for lobe-dominated radio-loud sources in which BLRGs, QSRs, and NLRGs harbor the same type of central engine. Moreover, excess cold absorption in the range 10(21)-10(24) cm(-2) is detected in most (but not all) NLRGs, consistent with absorption by obscuring tori, as postulated by unification scenarios. The ASCA data provide initial evidence that the immediate gaseous environment of the X-ray source of BLRGs may be different than in Seyfert 1 galaxies: absorption edges of ionized oxygen, common in the latter, are detected in only one BLRG. Instead we detect large columns of cold gas in a fraction (similar to 44%-60%) of BLRGs and QSRs, comparable to the columns detected in NLRGs, which is puzzling. This difference hints at different physical and/or geometrical properties of the medium around the X-ray source in radio-loud AGNs compared to their radio-quiet counterparts, properties that can be explored further with future X-ray observations. For the full sample, the nuclear X-ray luminosity is correlated with the luminosity of the [O III] emission line, the FIR emission at 12 mu m, and the lobe radio power at 5 GHz. The Fe K alpha line is detected in 50% of BLRGs and in one QSR, with a large range of intrinsic widths and equivalent widths. In the handful of NLRGs where it is detected, the line is generally unresolved. Comparing the average power-law photon indices of the various classes of radio-loud AGNs to their radio-quiet counterparts from the literature, we find only a weak indication that the ASCA 2-10 keV spectra of BLRGs are flatter than those of Seyfert 1 galaxies of comparable X-ray luminosity. This result is at odds with evidence from samples studied by other authors suggesting that radio-loud AGNs have flatter spectra than radio-quiet ones. Rather, it supports the idea that a beamed synchrotron self-Compton component related to the radio source (jet) is responsible for the flatter slopes in those radio-loud AGNs. We argue that, because of the way those samples were constructed, beamed X-ray emission from the radio jets probably contributed to the observed X-ray spectra. The sample studied here includes six weak-line radio galaxies (WLRGs), powerful radio galaxies characterized by [O III] 4569 and 5007 Angstrom of unusually low luminosity and by unusually high [O II]/[O III] line ratios. The ASCA spectra of WLRGs can be generally decomposed into a soft thermal component with kT similar to keV, plus a hard component, described either by a flat ([Gamma]= 1.5) absorbed power law or by a very hot (kT similar to 100 keV) thermal bremsstrahlung model. Their intrinsic luminosities are in the range L2-10 keV similar to 10(40)-10(42) ergs s(-1), 2 orders of magnitude lower than in other sources in our sample. If the hard X-ray emission is attributed to a low-luminosity AGN, an interesting possibility is that WLRGs represent an extreme population of radio galaxies in which the central black hole is accreting at a rate well below the Eddington rate. C1 Penn State Univ, Dept Astron & Astrophys, State Coll, PA 16802 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sambruna, RM (reprint author), Penn State Univ, Dept Astron & Astrophys, 525 Davey Lab, State Coll, PA 16802 USA. NR 232 TC 173 Z9 174 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 60 EP 96 DI 10.1086/307981 PN 1 PG 37 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900007 ER PT J AU Sturner, SJ Naya, JE AF Sturner, SJ Naya, JE TI On the nature of the high-velocity Al-26 near the Galactic center SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; dust, extinction; Galaxy : center; gamma rays : observations; ISM : kinematics and dynamics ID INTERSTELLAR-MEDIUM; SUPERNOVA-REMNANTS; SIZE DISTRIBUTION; DUST; EMISSION; GRAINS; EVOLUTION; SN-1987A; GAS AB Recent observations of the Galactic center region by the GRIS balloon-borne germanium spectrometer have determined that the diffuse 1809 keV emission resulting from the decay of Al-26 has intrinsic width of 5.4 keV FWHM. This line width indicates that the Al-26 either is at a temperature of similar to 4.5 x 10(8) K or has a nonthermal velocity of similar to 500 km s(-1). Previous authors have suggested that the Al-26 must be trapped within dust grains in the interstellar medium (ISM) in order for these conditions to persist over the 10(6) yr lifetime of the aluminum. We discuss the results of our model, in which Al-26 dust grains are produced in Type II supernovae and are subsequently reaccelerated in the ISM by ambient supernova remnant (SNR) shocks. Our results show that dust grains can be maintained at a velocity sufficient to explain the GRIS observation for ISM densities of similar to 0.2 cm(-3), dust-grain sizes near 10(-5) cm, and distances between SNR shocks in the ISM of 100-200 pc. C1 Univ Space Res Assoc, Seabrook, MD 20706 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Sturner, SJ (reprint author), Univ Space Res Assoc, 7501 Forbes Blvd,Suite 206, Seabrook, MD 20706 USA. NR 33 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 200 EP 206 DI 10.1086/307979 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900015 ER PT J AU Fixsen, DJ Bennett, CL Mather, JC AF Fixsen, DJ Bennett, CL Mather, JC TI COBE Far Infrared Absolute Spectrophotometer observations of Galactic lines SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; Galaxy : center; ISM : molecules; line : identification ID MICROWAVE BACKGROUND SPECTRUM; FIRAS INSTRUMENT; NGC-7027; EMISSION; REGIONS; CLOUDS; GALAXY AB The COBE Far Infrared Absolute Spectrophotometer (FIRAS) observations constitute an unbiased survey over the wavelength range from 100 mu m to 1 cm over 99% of the sky. Improved calibration of the FIRAS instrument and the inclusion of all of the FIRAS data allow an improved signal-to-noise ratio determination of the spectral lines by a factor of similar to 2 over our previous results. The resolution is low (0.45 cm(-1)), so only the strongest lines are observable. The CO chain from J = 1-0 to J = 8-7 is observed toward the Galactic center. The line ratios are roughly consistent with a 40 K excitation temperature. The 157.7 mu m C II and 205.3 mu m N II lines are observable over most of the sky. The 370.4 and 609.1 mu m lines of C I and the 121.9 mu m line of N II are observed in the Galactic plane. The line ratios at the Galactic center are consistent with a density of n(0) similar to 30 cm(-3) and a UV flux of G(0), approximate to 15 mu W m(-2) sr(-1) (10 Habing units). The 269 mu m H2O line is observed toward the Galactic center in absorption. C1 NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Infrared Astrophys Branch, Greenbelt, MD 20771 USA. RP Fixsen, DJ (reprint author), NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Code 685, Greenbelt, MD 20771 USA. RI Bennett, Charles/C-2050-2008 NR 26 TC 128 Z9 128 U1 1 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 207 EP 214 DI 10.1086/307962 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900016 ER PT J AU Nittler, LR Alexander, CMO AF Nittler, LR Alexander, CMO TI Can stellar dynamics explain the metallicity distributions of presolar grains? SO ASTROPHYSICAL JOURNAL LA English DT Article DE celestial mechanics, stellar dynamics; dust, extinction; galaxies : evolution; ISM : abundances; nuclear reactions, nucleosynthesis, abundances stars : AGB and post-AGB ID SILICON-CARBIDE GRAINS; CHEMICAL EVOLUTION; GALACTIC DISK; SOLAR NEIGHBORHOOD; SIC GRAINS; METEORITES; ABUNDANCE; OXYGEN; STARS; NUCLEOSYNTHESIS AB The majority of presolar circumstellar SiC and Al2O3 grains found in meteorites are inferred to have originated in asymptotic giant branch (AGB) stars that were more metal-rich than the Sun despite being much older than the Sun. We test the suggestion of Clayton that this reflects the overwhelming diffusion of AGB stars from the more metal-rich inner Galaxy to the protosolar cloud. Weighting the orbital diffusion model of Wielen, Fuchs, & Dettbarn to take into account the higher density of AGE stars and molecular clouds in the inner Galaxy, we find that most parent stars of presolar grains should have diffused to the presolar cloud from their birthplaces at smaller Galactocentric radii. However, the majority of these stars are expected to have had subsolar metallicities, in conflict with the grain data. The self-consistency of the diffusion model is discussed in the context of stellar abundance data in the solar neighborhood. The disagreement between the model predictions and the observations might indicate that the inferred metallicities of presolar grain parent stars are wrong, that the adopted diffusion parameters are incorrect, and/or that stellar orbital diffusion is not the correct explanation for the grain data. C1 Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. RP Nittler, LR (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 691, Greenbelt, MD 20771 USA. RI Alexander, Conel/N-7533-2013 OI Alexander, Conel/0000-0002-8558-1427 NR 36 TC 6 Z9 6 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 249 EP 256 DI 10.1086/307968 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900020 ER PT J AU Salama, F Galazutdinov, GA Krelowski, J Allamandola, LJ Musaev, FA AF Salama, F Galazutdinov, GA Krelowski, J Allamandola, LJ Musaev, FA TI Polycyclic aromatic hydrocarbons and the diffuse interstellar bands: A survey SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM : abundances; line : identification; methods : laboratory ID ELECTRONIC ABSORPTION-SPECTROSCOPY; HIGH-RESOLUTION OBSERVATIONS; CARRIERS; EXTINCTION; CATIONS; FAMILIES; CORONENE; FEATURES; SPECTRUM; OVALENE AB We discuss the proposal relating the origin of some of the diffuse interstellar bands (DIBs) to neutral and ionized polycyclic aromatic hydrocarbons (PAHs) present in interstellar clouds. Laboratory spectra of several PAHs, isolated at low temperature in inert gas matrices, are compared with the spectra of five reddened early-type stars selected from an extensive set of astronomical spectra. From this comparison, it is concluded that PAH ions are good candidates to explain some of the DIBs. Unambiguous assignments are difficult, however, because of the shift in:wavelengths and the band broadening induced in the laboratory spectra by the solid matrix. This situation is illustrated by a comparison with the gas-phase spectra made available recently for two PAH ions. Definitive band assignments and, ultimately, the test of the proposal that PAH ions carry some of the DIBs must await the availability of a larger set of gas-phase measurements in the laboratory. The present assessment offers a guideline for future laboratory experiments by allowing the preselection of promising PAH molecules to be studied in jet expansions. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Special Astrophys Observ, Nizhni Arkhyz 357147, Russia. Nicholas Copernicus Univ, Ctr Astron, PL-87100 Torun, Poland. RP Salama, F (reprint author), NASA, Ames Res Ctr, Div Space Sci, Mail Stop 245-6, Moffett Field, CA 94035 USA. RI Salama, Farid/A-8787-2009 OI Salama, Farid/0000-0002-6064-4401 FU NINDS NIH HHS [MEN/NSF-94-196] NR 56 TC 142 Z9 142 U1 3 U2 24 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 265 EP 273 DI 10.1086/307978 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900022 PM 11543306 ER PT J AU Bell, KR AF Bell, KR TI Reprocessing in luminous disks SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : pre-main-sequence; stars : variables : other (FU Orionis) ID T-TAURI STARS; YOUNG STELLAR OBJECTS; SPECTRAL ENERGY-DISTRIBUTIONS; FU ORIONIS VARIABLES; PROTOSTELLAR ACCRETION DISKS; CIRCUMSTELLAR DISKS; VERTICAL STRUCTURE; INFRARED-SPECTRA; EVOLUTION; MODELS AB We develop and investigate a procedure that accounts for disk reprocessing of photons that originate in the disk itself. Surface temperatures and simple, blackbody spectral energy distributions (SEDs) of protostellar disks are calculated. In disks that flare with radius, reprocessing of stellar photons results in temperature profiles that are not power-law at all radii but are consistently shallower than r(-3/4). Including the disk as a radiation source (as in the case of active accretion) along with the stellar source further flattens the temperature profile. Disks that flare strongly near the star and then smoothly curve over and become shadowed at some distance (" decreasing curvature" disks) exhibit nearly power-law temperature profiles that result in power-law infrared SEDs with slopes in agreement with typical observations of young stellar objects. Disk models in which the photospheric thickness is controlled by the local opacity and in which the temperature decreases with radius naturally have this shape. Uniformly flaring models do not match observations as well; progressively stronger reprocessing at larger radii leads to SEDs that flatten toward the infrared or even have a second peak at the wavelength corresponding (through the Wien law) to the temperature of the outer edge of the disk. In FU Orionis outbursting systems, the dominant source of energy is the inner disk. Reprocessing throughout the disk depends sensitively on the inner disk shape and emitted temperature profile. We show that the thermal instability outburst models of Bell & Lin reproduce trends in the observed SEDs of FU Ori systems with T proportional to r(-3/4) in the inner disk (r less than or similar to 0.25 AU corresponding to lambda less than or similar to 10 mu m) and T proportional to r(-1/2) in the outer disk. Surface irradiation during outburst and quiescence is compared in the region of planet formation (1-10 AU). The contrast between the two phases is diminished by the importance of the reprocessing of photons from the relatively high mass flux, outer disk ((M) over dot = 10(-5) M. yr(-1)), which is present during both outburst and quiescence. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Bell, KR (reprint author), NASA, Ames Res Ctr, Div Space Sci, Bldg 245,Room 280K,MS 245-3, Moffett Field, CA 94035 USA. NR 54 TC 30 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 411 EP 434 DI 10.1086/307988 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900036 ER PT J AU Belien, AJC Martens, PCH Keppens, R AF Belien, AJC Martens, PCH Keppens, R TI Coronal heating by resonant absorption: The effects of chromospheric coupling SO ASTROPHYSICAL JOURNAL LA English DT Article DE methods : numerical; MHD; Sun : chromosphere; Sun : corona; Sun : transition region; waves ID POLARIZED FOOTPOINT MOTIONS; MAGNETIC-FLUX TUBES; REBOUND SHOCK MODEL; ALFVEN WAVES; SOLAR ATMOSPHERE; MAGNETOHYDRODYNAMIC WAVES; DISSIPATIVE MHD; SCALING LAWS; STATIONARY BEHAVIOR; CORRECTED TRANSPORT AB We present the first 2.5 dimensional numerical model calculations of the nonlinear wave dynamics and heating by resonant absorption in coronal loops with thermal structuring of the transition region and higher chromosphere. The numerical calculations were done with the Versatile Advection Code. The transition region can move freely and is transparent for mass motions from chromosphere to corona. The loops are excited at the chromospheric level by linearly polarized monochromatic Alfven waves. We find that the efficiency of resonant absorption can be much lower than in equivalent line-tied coronal loop models. The inefficiency is due to the fast rate at which slow magnetosonic waves are nonlinearly generated in the chromosphere and transition region. This leads to considerable transfer of energy from the Alfven wave to the magnetosonic waves. Consequently, only a relatively small fraction of the Poynting flux that is injected into the loop system at the chromospheric level is available at the coronal level. Cavity leakage and detuning also have a negative impact on the efficiency, but less so than the nonlinear energy transfer. Inclusion of radiative and conductive losses improves the efficiency of resonant absorption. While the efficiency of resonant absorption heating is low, our results indicate that heating by compression and dissipation of the slow magnetosonic waves and shocks can easily lead to a temperature rise of a few percent, and for larger driver amplitudes even to a rise over 10%. Hence, our results support the idea of indirect coronal heating through the nonlinear generation of magnetosonic waves that was put forward more than 20 yr ago. Furthermore, the large transition region and coronal density oscillations that are associated with the slow magnetosonic waves provide an explanation for some observed coronal and transition region loop extreme-ultraviolet intensity variations. C1 NASA, Goddard Space Flight Ctr, Dept Space Sci, ESA,Solar Syst Div, Greenbelt, MD 20771 USA. EURATOM, FOM, Inst Plasma Phys Rijnhuizen, NL-3430 BE Nieuwegein, Netherlands. RP EURATOM, FOM, Inst Plasma Phys Rijnhuizen, POB 1207, NL-3430 BE Nieuwegein, Netherlands. EM belien@rijnh.nl; martens@mithra.physics.montana.edu OI keppens, rony/0000-0003-3544-2733 NR 69 TC 29 Z9 29 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 478 EP 493 DI 10.1086/307980 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900042 ER PT J AU Brosius, JW Thomas, RJ Davila, JM AF Brosius, JW Thomas, RJ Davila, JM TI SERTS-95 measurements of wavelength shifts in coronal emission lines across a solar active region SO ASTROPHYSICAL JOURNAL LA English DT Article DE instrumentation : spectrographs; Sun : activity; Sun : corona; Sun : UV radiation ID DIAGNOSTIC SPECTROMETER CDS; EXTREME-ULTRAVIOLET-SPECTRA; TRANSITION REGION; QUIET-SUN; OBSERVED REDSHIFTS; FLOWS; CHROMOSPHERE; SOHO AB We used slit spectra from the 1995 flight of Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-95) to measure wavelength shifts of coronal emission lines in the core of NOAA active region 7870 relative to its immediate surroundings (its "edge"). This method circumvents the unavailability of reliable laboratory rest wavelengths for the observed lines by using wavelengths from the edge spectrum as references. We derived the SERTS-95 wavelength calibration from measurements of a post-flight laboratory spectrum containing 28 He II and Ne Ir EUV standard wavelengths known to high accuracy. Wavelength measurements for lines of He I, Ne III, and additional lines of Ne II in the laboratory calibration spectrum provide more accurate values than were previously available, enabling these lines also to serve as future calibration standards. Six solar lines were chosen for this study, namely, He II. at 303.78 Angstrom Fe XII. at 193.51 Angstrom Fe XIII at 202.05 Angstrom, Fe XIV at 211.33 Angstrom, Fe XV at 284.15 Angstrom, and Fe XVI at 335.41 Angstrom. Because these lines are free from known blends in the SERTS-95 spectra and are either intrinsically strong or near the SERTS-95 peak sensitivity, they are our most reliable lines for measuring relative wavelength shifts in the spatially resolved active-region core spectra. The iron ions are the hottest ions ever used for this type of analysis. Ail six lines reveal statistically significant spatial variations in their measured relative wavelength shifts in the active-region core, including mixtures of blueshifts and redshifts (each with maximum values corresponding to relative Doppler velocities similar to 15 km s(-1)), indicating a dynamic, turbulent corona. For each of these lines we calculated weighted-average relative Doppler velocities from the wavelength shifts in the spatially resolved core spectra by weighting the shifts in the individual spatial pixels with their respective measurement uncertainties. This yields velocities of 3.3 +/- 1.1 km s(-1) for He II, 5.2 +/- 1.6 km s(-1) for Fe XII, 0.7 +/- 1.5 km s(-1) for Fe XIII, -2.1 +/- 1.4 km s(-1) for Fe XIV, 1.0 +/- 1.1 km s(-1) for Fe XV, and - 1.1 +/- 0.8 km s(-1) for Fe XVI. We also calculated intensity-weighted relative Doppler velocities from the wavelength shifts in the spatially averaged core spectrum, obtaining corresponding values of 5.8 +/- 0.6 km s(-1), 5.7 +/- 0.9 km s(-1), 0.4 +/- 0.7 km s(-1), - 2.1 +/- 1.0 km s(-1), 0.8 +/- 0.8 km s(-1), and - 1.1 +/- 0.5 km s(-1). Combining the above six lines with several additional ones that are strong enough in both the edge and average core spectra to provide reliable centroid measurements, we find statistically significant net relative redshifts for lines of He II, Fe X, Fe XI, and Fe XII; lines of Fe XIII and Fe XV show no significant shift while lines of Si XI, Fe XIV, and Fe XVI show a small net relative blueshift. Where multiple lines are available for a given ion, the directions (red or blue) and magnitudes (except for Fe XI) of the relative shifts are mutually consistent. The net relative blueshift observed in the hottest active-region coronal lines in our sample, combined with the net relative redshift observed in the cooler active-region coronal lines, suggests a net upflow of heated material cospatially and cotemporally with a net downflow of cooler material. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Brosius, JW (reprint author), Raytheon ITSS, 4400 Forbes Blvd, Lanham, MD 20706 USA. NR 21 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 494 EP 504 DI 10.1086/307987 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900043 ER PT J AU Moore, RL Falconer, DA Porter, JG Suess, ST AF Moore, RL Falconer, DA Porter, JG Suess, ST TI On heating the sun's corona by magnetic explosions: Feasibility in active regions and prospects for quiet regions and coronal holes SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun : corona; Sun : magnetic fields; Sun : X-rays, gamma rays ID SOLAR-FLARE MYTH; X-RAY TELESCOPE; MASS EJECTIONS; TEMPERATURE STRUCTURE; FILAMENT ERUPTIONS; TRANSITION REGION; ENERGY-RELEASE; NETWORK; RECONNECTION; EVENTS AB We build a case for the persistent strong coronal heating in active regions and the pervasive quasisteady heating of the corona in quiet regions and coronal holes being driven in basically the same way as the intense transient heating in solar hares: by explosions of sheared magnetic fields in the cores of initially closed bipoles. We begin by summarizing the observational case for exploding sheared core fields being the drivers of a wide variety of flare events, with and without coronal mass ejections. We conclude that the arrangement of an event's hare heating, whether there is a coronal mass ejection, and the time and place of the ejection relative to the flare heating are all largely determined by four elements of the form and action of the magnetic field: (1) the arrangement of the impacted, interacting bipoles participating in the event, (2) which of these bipoles are active (have sheared core fields that explode) and which are passive (are heated by injection from impacted active bipoles), (3) which core held explodes first, and (4) which core-field explosions are confined within the closed field of their bipoles and which ejectively open their bipoles. We then apply this magnetic-configuration framework for flare heating to the strong coronal heating observed by the Yohkoh Soft X-ray Telescope in an active region with strongly sheared core fields observed by the Marshall Space Flight Center vector magnetograph. All of the strong coronal heating is in continually microflaring sheared core fields or in extended loops rooted against these active core fields. Thus, the strong heating occurs in field configurations consistent with the heating being driven by frequent core-held explosions that are smaller than but similar to those in confined flares and flaring arches. From analysis of the thermal and magnetic energetics of two selected core-field microflares and a bright extended loop, we find that (1) it is energetically feasible for the sheared core fields to drive all of the coronal heating in the active region via a staccato of magnetic microexplosions, (2) the microflares at the feet of the extended loop behave as the flares at the feet of flaring arches in that more coronal heating is driven within the active bipole than in the extended loop, (3) the filling factor of the X-ray plasma in the core field microflares and in the extended loop is similar to 0.1, and (4) to release enough magnetic energy for a typical microflare (10(27)-10(28) ergs), a microflaring strand of sheared core field need expand and/or untwist by only a few percent at most. Finally, we point out that (1) the field configurations for strong coronal heating in our example active region (i.e., neutral-line core fields, many embedded in the feet of extended loops) are present in abundance in the magnetic network in quiet regions and coronal holes, and (2) it is known that many network bipoles do microflare and that many produce detectable coronal heating. We therefore propose that exploding sheared core fields are the drivers of most of the heating and dynamics of the solar atmosphere, ranging from the largest and most powerful coronal mass ejections and flares, to the vigorous microflaring and coronal heating in active regions, to the multitude of fine-scale explosive events in the magnetic network, which drive microflares, spicules, global coronal heating, and, consequently, the solar wind. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Moore, RL (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, SD5O, Huntsville, AL 35812 USA. NR 64 TC 41 Z9 42 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP 505 EP 522 DI 10.1086/307969 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XA UT WOS:000083863900044 ER PT J AU Gaensler, BM Gotthelf, EV Vasisht, G AF Gaensler, BM Gotthelf, EV Vasisht, G TI A new supernova remnant coincident with the slow X-ray pulsar AX J1845-0258 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (G29.6+0.1); pulsars : individual (AX J1845-0258); radio continuum : ISM; stars : neutron; supernova remnants; X-rays : stars ID MILKY-WAY; VELOCITIES; DISCOVERY; LIFETIME; NEBULA; BIRTH AB We report on Very Large Array observations in the direction of the recently discovered slow X-ray pulsar AX J1845-0258. In the resulting images, we find a 5' shell of radio emission; the shell is linearly polarized with a nonthermal spectral index. We classify this source as a previously unidentified, young (<8000 yr) supernova remnant (SNR), G29.6+0.1, which we propose is physically associated with AX J1845-0258. The young age of G29.6+0.1 is then consistent with the interpretation that anomalous X-ray pulsars (AXPs) are isolated, highly magnetized neutron stars ("magnetars"). Three of the six known AXPs can now be associated with SNRs; we conclude that AXPs are young (less than or equal to 10,000 yr) objects and that they are produced in at least 5% of core-collapse supernovae. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gaensler, BM (reprint author), MIT, Ctr Space Res, 70 Vassar St, Cambridge, MA 02139 USA. RI Gaensler, Bryan/F-8655-2010 NR 40 TC 57 Z9 57 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1999 VL 526 IS 1 BP L37 EP L40 DI 10.1086/312362 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258XE UT WOS:000083864300010 ER PT J AU Descloitres, J AF Descloitres, J TI SeaWiFS global data represented in MODIS land projections SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article C1 Univ Maryland, Dept Geog, NASA, GSFC, Greenbelt, MD 20771 USA. RP Descloitres, J (reprint author), Univ Maryland, Dept Geog, NASA, GSFC, Code 922, Greenbelt, MD 20771 USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD NOV 20 PY 1999 VL 20 IS 17 BP 3243 EP 3244 DI 10.1080/014311699211282 PG 2 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 247UN UT WOS:000083238900001 ER PT J AU Chang, SC Wang, XY Chow, CY AF Chang, SC Wang, XY Chow, CY TI The space-time conservation element and solution element method: A new high-resolution and genuinely multidimensional paradigm for solving conservation laws SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE space-time; flux conservation; conservation element; solution element; shocks; contact discontinuities ID EULER EQUATIONS; SIMULATION AB A new high-resolution and genuinely multidimensional numerical method for solving conservation laws is being developed. It was designed to avoid the limitations of the traditional methods and was built from ground zero with extensive physics considerations. Nevertheless, its foundation is mathematically simple enough that one can build from it a coherent, robust, efficient, and accurate numerical framework. Two basic beliefs that set the new method apart from the established methods are at the core of its development. The first belief is that, in order to capture physics more efficiently and realistically, the modeling focus should be placed on the original integral form of the physical conservation laws, rather than the differential form. The latter form follows from the integral form under the additional assumption that the physical solution is smooth, an assumption that is difficult to realize numerically in a region of rapid change, such as a boundary layer or a shock. The second belief is that, with proper modeling of the integral and differential forms themselves, the resulting numerical solution should automatically be consistent with the properties derived from the integral and differential forms, e.g., the jump conditions across a shock and the properties of characteristics. Therefore a much simpler and more robust method can be developed by avoiding the explicit use of the above derived properties. Specifically, to capture physics as fully as possible, the method requires that: (i) space and time be unified and treated as a single entity; (ii) both local and global flux conservation in space and time be enforced; and (iii) a multidimensional scheme be constructed without using the dimensional-splitting approach, such that multidimensional effects and source terms (which an scalars) can be modeled more realistically. To simplify mathematics and broaden its applicability as much as possible, the method attempts to use the simplest logical structures and approximation techniques. Specifically, (i) it uses a staggered space-time mesh such that Aux at any interface separating two conservation elements can be evaluated internally in a simpler and more consistent manner, without using a separate flux model; (ii) it avoids the use of many well-established techniques such as Riemann solvers, flux splittings, and monotonicity constraints such that the complications and possibly even the limitations associated with them may be avoided; and (iii) it avoids tho use of special techniques that are not applicable to more general problems. Furthermore, triangles in 2D space and tetrahedrons in 3D space are used as the basic building blocks of the spatial meshes, such that the method (i) can be used to construct 2D and 3D nondissipative schemes in a natural manner; and (ii) is compatible with the simplest unstructured meshes. Note that while numerical dissipation is required for shock capturing, it may also result in annihilation of small disturbances such as sound waves and, in the case of flow with a large Reynolds number, may overwhelm physical dissipation. To overcome this difficulty, two different and mutually complementary types of adjustable numerical dissipation are introduced in the present development. (C) 1999 Academic Press. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Taitech Inc, Cleveland, OH 44135 USA. Univ Colorado, Dept Aerosp Engn Sci, Boulder, CO 80309 USA. RP NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. EM sin-chung.chang@grc.nasa.gov; wangxy@turbot.grc.nasa.gov; chow@rastro.colorado.edu NR 38 TC 122 Z9 126 U1 0 U2 9 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 EI 1090-2716 J9 J COMPUT PHYS JI J. Comput. Phys. PD NOV 20 PY 1999 VL 156 IS 1 BP 89 EP 136 DI 10.1006/jcph.1999.6354 PG 48 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 258NA UT WOS:000083844200004 ER PT J AU Pougatchev, NS Sachse, GW Fuelberg, HE Rinsland, CP Chatfield, RB Connors, VS Jones, NB Notholt, J Novelli, PC Reichle, HG AF Pougatchev, NS Sachse, GW Fuelberg, HE Rinsland, CP Chatfield, RB Connors, VS Jones, NB Notholt, J Novelli, PC Reichle, HG TI Pacific Exploratory Mission-Tropics carbon monoxide measurements in historical context SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOUTH-ATLANTIC OCEAN; SPECTROSCOPIC MEASUREMENTS; KITT PEAK; TRACE-A; CHEMICAL CHARACTERISTICS; VERTICAL-DISTRIBUTION; EARTHS ATMOSPHERE; MIXING RATIOS; CO; HEMISPHERE AB The three-dimensional (3-D) distribution of carbon monoxide (CO) over the southern Pacific during the NASA Global Tropospheric Experiment Pacific Exploratory Mission-Tropics (PEM-T) (August-October 1996) has been analyzed in comparison to other CO measurements. The following data sets have been used in the study: National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostic Laboratory surface level sampling; Commonwealth Scientific and Industrial Research Organization aircraft measurements over Cape Grim, Tasmania; solar spectroscopic measurements at Lauder, New Zealand; and data from two spaceborne Measurement of Air Pollution From Satellite experiments. For the PEM-T mission back trajectories analysis and 3-D modeling of the CO transport have been performed. It has been demonstrated that CO measurements obtained by different in situ and remote techniques can be used to build the picture of the CO climatology over the large geographical area. The structure of the CO distribution over the western part of the southern Pacific during the austral spring is mainly controlled by emission from biomass burning in Australia and Africa and subsequent long-range transport. The prevailing westerly transport occurs in the middle and upper troposphere, whereas the marine boundary layer remains relatively clean and uniform. Barriers in the form of the Intertropical Convergence Zone and South Pacific Convergence Zone protect the equatorial area (equator to 10 degrees S) from direct impact of biomass burning plumes from north and southwest. Consistency between the measurements taken in different years and modeling results indicates that the observed feature is a stable phenomenon. Outside the equatorial area the CO vertical distribution has a broad distinctive maximum at the altitude range 5-8 km and latitudes between 20 degrees S and 30 degrees S. This maximum is a stable feature, and its location indicates the area where the most intensive westerly transport occurs. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Natl Inst Water & Atmospher Res, Central Otago, New Zealand. Alfred Wegener Inst Polar & Marine Res, Potsdam, Germany. NOAA, CMDL, Boulder, CO 80303 USA. N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27695 USA. RP Pougatchev, NS (reprint author), NASA, Langley Res Ctr, MS 472, Hampton, VA 23681 USA. EM n.s.pougatchev@larc.nasa.gov; rinsland@mipsbox.larc.nasa.gov; chatfield@clio.arc.nasa.gov; vickie@stormy.larc.nasa.gov; jones@kea.lauder.cri.nz; jnotholt@awi-potsdam.de; pnovelli@cmdl.noaa.gov; henry_reichle@ncsu.edu RI Jones, Nicholas/G-5575-2011; Notholt, Justus/P-4520-2016 OI Jones, Nicholas/0000-0002-0111-2368; Notholt, Justus/0000-0002-3324-885X NR 58 TC 11 Z9 11 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26195 EP 26207 DI 10.1029/1999JD900465 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200010 ER PT J AU Logan, JA Megretskaia, IA Miller, AJ Tiao, GC Choi, D Zhang, L Stolarski, RS Labow, GJ Hollandsworth, SM Bodeker, GE Claude, H De Muer, D Kerr, JB Tarasick, DW Oltmans, SJ Johnson, B Schmidlin, F Staehelin, J Viatte, P Uchino, O AF Logan, JA Megretskaia, IA Miller, AJ Tiao, GC Choi, D Zhang, L Stolarski, RS Labow, GJ Hollandsworth, SM Bodeker, GE Claude, H De Muer, D Kerr, JB Tarasick, DW Oltmans, SJ Johnson, B Schmidlin, F Staehelin, J Viatte, P Uchino, O TI Trends in the vertical distribution of ozone: A comparison of two analyses of ozonesonde data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERE; TROPOSPHERE; CANADA AB We present the results of two independent analyses of trends in the vertical distribution of ozone. For most of the ozonesonde stations we use data that were recently reevaluated and reprocessed to improve their quality and internal consistency. The two analyses give similar results for trends in ozone. We attribute differences in results primarily to differences in data selection criteria, rather than in statistical trend models. We find significant decreases in stratospheric ozone at all stations in middle and high latitudes of the Northern Hemisphere from 1970 to 1996, with the largest decreases located between 12 and 2i km, and trends of -3 to -10 %/decade near 17 km. The decreases are largest at the Canadian and the most northerly Japanese station and are smallest at the European stations and at Wallops Island. The mean midlatitude trend is largest, -7 %/decade, from 12 to 18 km for 1970-1996, and the decrease in ozone is significant from 10.5 to 25 km. For 1980-1996, the decrease is more negative by 1-2 %/decade, with a maximum trend of -9%/decade in the lowermost stratosphere. The trends vary seasonally from about 10 to 17 km, with largest ozone decreases in winter and spring. Trends in tropospheric ozone are highly variable and depend on the region. There are decreases or zero trends at the Canadian stations for 1970-1996, and decreases of -2 to -8 %/decade for the mid-troposphere for 1980-1996; the three European stations show increases for 1970-1996, but trends are close to zero for two stations for 1980-1996 and positive for one; there are increases in ozone for the three Japanese stations for 1970-1996, but trends are either positive or zero for 1980-1996. The United States stations show zero or slightly negative trends in tropospheric ozone after 1980. It is not possible to define reliably a mean tropospheric ozone trend for northern midlatitudes, given the small number of stations and the large variability in trends. The integrated column trends derived from the sonde data are consistent with trends derived from both surface-based and satellite measurements of the ozone column. C1 Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Natl Inst Water & Atmospher Res, Central Otago, New Zealand. Univ Chicago, Grad Sch Business, Chicago, IL 60637 USA. Meteorol Observ Hohenpeissenberg, Deutsch Wetterdienst, D-82383 Hohenpeissenberg, Germany. Royal Meteorol Inst Belgium, B-1180 Brussels, Belgium. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Atmospher Environm Serv, Toronto, ON M3H 5T4, Canada. NOAA, Natl Weather Serv, Climate Predict Ctr, Washington, DC 20233 USA. NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA. ETH Honggerberg, Inst Atmospher Sci, CH-8093 Zurich, Switzerland. Japan Meteorol Agcy, Div Atmospher Environm, Chiyoda Ku, Tokyo 1008122, Japan. Swiss Meteorol Inst, Aerol Stn, CH-1530 Payerne, Switzerland. Raytheon STX, Lanham, MD USA. RP Logan, JA (reprint author), Harvard Univ, Dept Earth & Planetary Sci, 29 Oxford St, Cambridge, MA 02138 USA. RI Bodeker, Greg/A-8870-2008; Stolarski, Richard/B-8499-2013; OI Bodeker, Greg/0000-0003-1094-5852; Stolarski, Richard/0000-0001-8722-4012; Tarasick, David/0000-0001-9869-0692 NR 33 TC 143 Z9 148 U1 2 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26373 EP 26399 DI 10.1029/1999JD900300 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200021 ER PT J AU Michelsen, HA Webster, CR Manney, GL Scott, DC Margitan, JJ May, RD Irion, FW Gunson, MR Russell, JM Spivakovsky, CM AF Michelsen, HA Webster, CR Manney, GL Scott, DC Margitan, JJ May, RD Irion, FW Gunson, MR Russell, JM Spivakovsky, CM TI Maintenance of high HCl/Cl-y and NOx/NOy in the Antarctic vortex: A chemical signature of confinement during spring SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC POLAR VORTEX; HALOGEN OCCULTATION EXPERIMENT; ARCTIC STRATOSPHERE; HYDROGEN-CHLORIDE; SULFURIC-ACID; OZONE LOSS; ATMOS/ATLAS-3 MEASUREMENTS; POTENTIAL VORTICITY; WINTER STRATOSPHERE; INSTRUMENTS ABOARD AB Observations made in the 1994 Antarctic vortex show that Cl-y recovered completely into HCl following conversion of Cl-y reservoir species to active radicals, and NOx constituted a 4-5 times higher fraction of NOy inside the vortex than outside. Measurements made in October and November from the Airborne Southern Hemisphere Ozone Expedition/Measurements of the Atmospheric Effects of Stratospheric Aircraft (ASHOE/MAESA) ER-2 aircraft mission, the third Atmospheric Laboratory for Applications and Science (ATLAS-3) space shuttle mission, and the Upper Atmosphere Research Satellite (UARS) demonstrate that this unusual partitioning of Cl-y and NOy was maintained for at least 4 weeks in the springtime vortex. In response to severe ozone loss, abundances of HCl and NOx remained high despite temperatures low enough to reactivate Cl-y and convert NOx to HNO3 via heterogeneous processes. Thus, under severely ozone depleted conditions, high HCl and NOx abundances in the vortex are maintained until the vortex breaks up or an influx of ozone-rich extravortex air is entrained into the vortex. These observations suggest that the flux of extravortex air entering the core of the lower stratospheric vortex was small or negligible above similar to 400 K during late spring, despite weakening of the vortex during this time period. Results of a photochemical model constrained by the measurements suggest that extravortex air entrained into the vortex during October and early November made up less than 5% of the vortex core air at 409 K. The model results also show that heterogeneous chemistry has little effect on the Cl-y and NOy partitioning once high abundances of HCl have been attained under ozone depleted conditions, even when aerosol loading is high. C1 Sandia Natl Labs, Livermore, CA 94551 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Atmospher & Environm Res Inc, San Ramon, CA USA. RP Michelsen, HA (reprint author), Sandia Natl Labs, MS 9055,POB 969, Livermore, CA 94551 USA. EM hamiche@ca.sandia.gov; chris.r.webster@jpl.nasa.gov; manney@mls.jpl.nasa.gov; dcscott@alpha1.jpl.nasa.gov; jjm@mark4sun.jpl.nasa.gov; rmay@alpha1.jpl.nasa.gov; fwi@caesar.jpl.nasa.gov; mrg@caesar.jpl.nasa.gov; jmr@lcas.hamptonu.edu; cms@io.harvard.edu NR 100 TC 28 Z9 28 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26419 EP 26436 DI 10.1029/1999JD900473 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200023 ER PT J AU Aikin, AC Smith, HJP AF Aikin, AC Smith, HJP TI Mesospheric constituent variations during electron precipitation events SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE; WATER-VAPOR; LOWER THERMOSPHERE; OZONE; RADIOMETRY; H2O AB The response of mesospheric constituents to energetic electron deposition events is modeled on a diurnal scale for two precipitation scenarios. In the first example, upper limit electron fluxes representative of diffuse aurora are employed. The other case considers the 10-day precipitation event of May 1992 observed by the Upper Atmosphere Research satellite Particle Environment Monitor (UARS/PEM). Since the UARS Halogen Occultation Experiment (UARS/HALOE) water vapor measurements indicate large variability from day to day as well as at different longitudes on the same day, water is used as a parameter in studying the diurnal response of different species to particle precipitation. Water amount affects the diurnal variation of ozone by changing the concentration of hydrogen radicals, creating a water-dependent temporal response of the depletion of ozone by precipitating ionizing energetic electrons and protons. For constant particle fluxes, ozone depletion at a given altitude varies throughout the day at variance with model results where the Sun is assumed to have an average solar zenith angle throughout the day. At night, ozone depletion remains nearly constant and different from daylight values. Nighttime and twilight OH and HO2 are significantly enhanced during electron precipitation, Since precipitation often occurs between L = 3 and L = 6, where L is the distance in earth radii from the center of the Earth dipole to the equatorial crossing of the field line in question, as far south as 35 degrees N in the North American longitude zone, particle precipitation is one of the factors determining OH and HO2 concentrations within this latitude range, particularly when the magnetic index Ap is enhanced. Because of the large diurnal changes associated with the amount of particle-related ozone depletion, fixed microwave sites measuring ozone and water will be better able to determine the atmospheric effects of particle precipitation than satellite measurements of ozone. Diurnally averaged models are inadequate for predicting the detailed ozone response to charged particle precipitation. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. TPE Associates, Chestnut Hill, MA 02467 USA. RP Aikin, AC (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. EM aikin@chapman.gsfc.nasa.gov; hjpsmith@earthlink.net NR 33 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26457 EP 26471 DI 10.1029/1999JD900752 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200025 ER PT J AU Newman, PA Fahey, DW Brune, WH Kurylo, MJ AF Newman, PA Fahey, DW Brune, WH Kurylo, MJ TI Including special sections - Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) CACGP/IGAC 1998 Symposium (CACGP/IGAC) - Preface SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material ID TROPOSPHERE EXCHANGE PROJECT; DIODE-LASER SPECTROMETER; LOWER STRATOSPHERE; NASA ER-2; TROPICAL TROPOPAUSE; MODEL-CALCULATIONS; AIRCRAFT; N2O; INSTRUMENT; PARTICLES C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD USA. NOAA, Aeron Lab, Boulder, CO USA. Penn State Univ, Dept Meteorol, University Pk, PA USA. NIST, Gaithersburg, MD USA. NASA, Washington, DC USA. RP Newman, PA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD USA. RI Newman, Paul/D-6208-2012; Kurylo, Michael/H-2201-2012; Fahey, David/G-4499-2013 OI Newman, Paul/0000-0003-1139-2508; Fahey, David/0000-0003-1720-0634 NR 101 TC 29 Z9 29 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26481 EP 26496 DI 10.1029/1999JD900832 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200027 ER PT J AU Toon, GC Blavier, JF Sen, B Salawitch, RJ Osterman, GB Notholt, J Rex, M McElroy, CT Russell, JM AF Toon, GC Blavier, JF Sen, B Salawitch, RJ Osterman, GB Notholt, J Rex, M McElroy, CT Russell, JM TI Ground-based observations of Arctic O-3 loss during spring and summer 1997 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LOWER STRATOSPHERE; OZONE DEPLETION; SEASONAL-VARIATIONS; HALOE OBSERVATIONS; TRACE GASES; VORTEX; WINTER; LATITUDE; DECLINE AB Ground-based solar absorption spectra were measured from Fairbanks, Alaska (65-degrees N, 148-degrees W) from March to September 1997 by the Jet Propulsion Laboratory (JPL) MkIV Fourier transform infrared (FTIR) spectrometer. The derived column abundances of O-3 declined by 35% over this period (20% in April and May, and 15% during the summer), whereas those of HF, a long-lived tracer, changed by less than 5%. High-latitude, summertime balloon observations reveal similar shapes for the volume mixing ratio profiles of O-3 and HF in the lower stratosphere, where most of their column abundance resides. Vertical transport should therefore have similar effects on the column abundances of O-3 and HF. Data from the Halogen Occultation Experiment (HALOE) show a poleward decrease in the O-3/HF ratio at all stratospheric altitudes, so that any reductions in column O-3 due to horizontal meridional transport would have been accompanied by even larger reductions in column HF. Therefore the observed column O-3 decrease must be the result of chemical loss processes. Column measurements of other atmospheric gases show a summertime maximum in the NOx/NOy column ratio and little change in the chlorine partitioning. We conclude that most of the reduction in column O-3 over Fairbanks from March to September 1997 was likely driven by NOx chemistry. These conclusions are supported by the similar behavior of column abundances measured by another ground-based FTIR spectrometer based in Ny Alesund, Spitsbergen (79-degrees N, 12-degrees E). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Environm Canada, Atomospher Environm Serv, Downsview, ON M3H 5T4, Canada. Alfred Wegener Inst Polar & Marine Res, D-14401 Potsdam, Germany. Hampton Univ, Hampton, VA 23668 USA. RP Toon, GC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM toon@mark4sun.upl.nasa.gov RI Rex, Markus/A-6054-2009; Salawitch, Ross/B-4605-2009; Notholt, Justus/P-4520-2016 OI Rex, Markus/0000-0001-7847-8221; Salawitch, Ross/0000-0001-8597-5832; Notholt, Justus/0000-0002-3324-885X NR 35 TC 22 Z9 22 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26497 EP 26510 DI 10.1029/1999JD900745 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200028 ER PT J AU Pierce, RB Al-Saadi, JA Fairlie, TD Olson, JR Eckman, RS Grose, WL Lingenfelser, GS Russell, JM AF Pierce, RB Al-Saadi, JA Fairlie, TD Olson, JR Eckman, RS Grose, WL Lingenfelser, GS Russell, JM TI Large-scale stratospheric ozone photochemistry and transport during the POLARIS Campaign SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; MODEL; ATMOSPHERE; VORTEX; AIR; NO2 AB Measurements from the Halogen Occultation Experiment (HALOE) on board the UARS satellite and assimilated winds, temperatures, and diabatic heating rates from the NASA Goddard data assimilation office (DAO) are used with the NASA Langley Research Center (LaRC) Lagrangian photochemical model to compute 3-D air parcel trajectories with photochemistry for all Northern Hemisphere HALOE observations during the period March-September 1997. Results from ensemble means of the photochemical trajectory calculations provide a global perspective for the interpretation of constituent measurements made from the ER-2 and balloon platforms during the POLARIS aircraft campaign. Lagrangian photochemical predictions are shown to compare favorably with ER-2, balloon, Total Ozone Mapping Spectometer (TOMS), and subsequent coincident HALOE observations. Model predictions show large-scale photochemical ozone loss in high latitudes at ER-2 flight altitudes of over 10% per month in June and July, in good agreement with steady state photochemical calculations constrained with ER-2 observations of radical and long-lived species. Largest summertime photochemical ozone losses (over 1.4 ppmv/month) are found to occur poleward of 60 degrees N above 30 mbar, in good agreement with steady state photochemical calculations constrained with observations from the balloon-borne Fourier transform infrared solar absorption spectrometer (MkIV) instrument. Summertime polar photochemical ozone losses are driven largely by NOx chemistry and are largest for air parcels with high NOx/NOy ratios that have experienced continuous sunlight for several days. Differences between predicted net changes in ozone and changes due to photochemistry are used to estimate residual changes due to transport processes. Photochemical and residual transport tendencies tend to be of similar magnitude but opposite sign. Photochemical loss of ozone tends to outweigh positive transport tendencies in high latitudes, while upwelling of low ozone below the tropical ozone maximum moderates photochemical production there. The estimated transport tendencies are generally consistent with expectations based on transformed Eulerian circulation derived from the DAO assimilated data and the mean ozone distribution. A net (photochemical plus transport) ozone decrease of over 0.2 ppmv/month is predicted throughout the middle and lower stratosphere poleward of 70 degrees N during the summer months. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci & Technol Corp, Hampton, VA 23666 USA. Sci Applicat Int Corp, Hampton, VA 23669 USA. Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. RP Pierce, RB (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 36 TC 16 Z9 17 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26525 EP 26545 DI 10.1029/1999JD900395 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200030 ER PT J AU Andrews, AE Boering, KA Daube, BC Wofsy, SC Hintsa, EJ Weinstock, EM Bui, TP AF Andrews, AE Boering, KA Daube, BC Wofsy, SC Hintsa, EJ Weinstock, EM Bui, TP TI Empirical age spectra for the lower tropical stratosphere from in situ observations of CO2: Implications for stratospheric transport SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CARBON-DIOXIDE; WATER-VAPOR; TROPOSPHERE; CIRCULATION; AIR; CH4; MIDLATITUDES; FOUNTAIN; N2O AB Empirical age spectra for the lower tropical stratosphere (from the tropopause to similar to 19.5 km) have been derived from in situ measurements of CO2, using information provided by the vertical propagation of the tropospheric seasonal cycle and long-term positive trend. Our method provides accurate and unambiguous mean ages for this region which are difficult to obtain by simple analysis of lag times from tracer measurements. We find that the air is 30-40% younger in northern spring than in autumn. For example, at 460 K the mean age (relative to the tropical tropopause) was 0.4 years in March and 0.6 years in September. The phase lag times and attenuation of CO2 seasonal extrema in the stratosphere are shown to depend on seasonal variations in transport rates and on the presence of harmonics in the CO2 boundary condition with frequencies higher than 2 pi/yr. Profiles of stratospheric water vapor, generated from the derived age spectra with a stratospheric boundary condition based on observed tropical tropopause temperatures, are consistent with in situ observations of H2O. Comparison of the predicted water vapor seasonal cycle with satellite observations suggests that satellite-borne instruments underestimate the amplitude near the tropical tropopause. We relate the empirical age spectra to the analytic solution for the 1-D advection-diffusion tracer continuity equation to obtain seasonally resolved estimates of the ascent rate and the vertical diffusion coefficient. The derived age spectra provide a unique observation-based diagnostic for evaluating the simulation of tracer transport in models. C1 Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Harvard Univ, Div Engn & Appl Sci, Cambridge, MA 02138 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Univ Calif Berkeley, Dept Geol & Geog, Berkeley, CA 94720 USA. Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Andrews, AE (reprint author), Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. EM aea@io.harvard.edu; boering@cchem.berkeley.edu; bcd@io.harvard.edu; scw@io.harvard.edu; ehintsa@whoi.edu; weinstock@huarp.harvard.edu; pbui@mail.arc.nasa.gov RI Andrews, Arlyn/K-3427-2012 NR 39 TC 68 Z9 68 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26581 EP 26595 DI 10.1029/1999JD900150 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200033 ER PT J AU Fairlie, TD Pierce, RB Al-Saadi, JA Grose, WL Russell, JM Proffitt, MH Webster, CR AF Fairlie, TD Pierce, RB Al-Saadi, JA Grose, WL Russell, JM Proffitt, MH Webster, CR TI The contribution of mixing in Lagrangian photochemical predictions of polar ozone loss over the Arctic in summer 1997 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VORTEX; CONSTITUENTS; STRATOSPHERE; ADVECTION; TRANSPORT; AIRCRAFT; MODEL; FLOW AB Measurements from the Halogen Occultation Experiment, together with assimilated winds, temperatures, and diabatic heating rates from the NASA Goddard data assimilation office, are used in the NASA Langley Research Center trajectory-photochemical model to compute photochemistry along three-dimensional air parcel trajectories for the Northern Hemisphere for the period March through September 1997. These calculations provide a global perspective for the interpretation of constituent measurements made fram the ER-2 platform during the Photochemistry of Ozone Loss in the Arctic Region in Summer aircraft campaign. An important component of the model is a parameterization of sub-grid-scale diffusive mixing. The parameterization uses an "n-member mixing" approach which includes an efficiency factor that enhances the mixing in regions where strain dominates the large-scale flow. Model predictions of O-3 and CH4 are compared with in situ measurements made from the ER-2. Comparison of the in situ data with model predictions, conducted with and without diffusive mixing, illustrates the contribution that irreversible mixing makes in establishing observed tracer-tracer correlations. Comparisons made for an ER-2 flight in late April 1997 show that irreversible mixing was important in establishing observed tracer-tracer correlations during spring 1997. Comparisons made in late June 1997, when filaments of very low N2O and CH4 were observed, indicate that remnants of air from the polar vortex survived unmixed in the low stratosphere 6 weeks after the breakup of the polar vortex in May. The results demonstrate that the sub-grid-scale mixing parameterization used in the model is effective not only for strong mixing conditions in late winter and early spring, but also for relatively weak mixing conditions that prevail in summer. C1 Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fairlie, TD (reprint author), NASA, Langley Res Ctr, Mail Stop 401B, Hampton, VA 23681 USA. EM t.d.fairlie@larc.nasa.gov; r.b.pierce@larc.nasa.gov; j.a.alsaadi@larc.nasa.gov; w.l.grose@larc.nasa.gov; jmr@cas.hamptonu.edu; proffitt@al.noaa.gov; cwebster@alpha1.jpl.nasa.gov RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 25 TC 26 Z9 26 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26597 EP 26609 DI 10.1029/1999JD900111 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200034 ER PT J AU Rex, M Salawitch, RJ Toon, GC Sen, B Margitan, JJ Osterman, GB Blavier, JF Gao, RS Donnelly, S Keim, E Neuman, J Fahey, DW Webster, CR Scott, DC Herman, RL May, RD Moyer, EJ Gunson, MR Irion, FW Chang, AY Rinsland, CP Bui, TP AF Rex, M Salawitch, RJ Toon, GC Sen, B Margitan, JJ Osterman, GB Blavier, JF Gao, RS Donnelly, S Keim, E Neuman, J Fahey, DW Webster, CR Scott, DC Herman, RL May, RD Moyer, EJ Gunson, MR Irion, FW Chang, AY Rinsland, CP Bui, TP TI Subsidence, mixing, and denitrification of Arctic polar vortex air measured During POLARIS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MICROWAVE LIMB SOUNDER; OZONE DEPLETION; REACTIVE NITROGEN; STRATOSPHERIC CLOUD; ER-2 AIRCRAFT; WINTER; HNO3; N2O; ATMOS; CH4 AB We determine the degree of denitrification that occurred during the 1996-1997 Arctic winter using a technique that is based on balloon and aircraft borne measurements of NOy, N2O, and CH4. The NOy/N2O relation can undergo significant change due to isentropic mixing of subsided vortex air masses with extravortex air due to the high nonlinearity of the relation. These transport related reductions in NOy can be difficult to distinguish from the effects of denitrification caused by sedimentation of condensed HNO3. In this study, high-altitude balloon measurements are used to define the properties of air masses that later descend in the polar vortex to altitudes sampled by the ER-2 aircraft (i.e., similar to 20 km) and mix isentropically with extravortex air. Observed correlations of CH4 and N2O are used to quantify the degree of subsidence and mixing for individual air masses. on the basis of these results the expected mixing ratio of NOy resulting from subsidence and mixing, defined here as NOy**, is calculated and compared with the measured mixing ratio of NOy. Values of NOy and NOy** agree well during most parts of the flights. A slight deficit of NOy versus NOy** is found only for a limited region during the ER-2 flight on April 26, 1997. This deficit is interpreted as indication for weak denitrification (similar to 2-3 ppbv) in that air mass. The small degree of denitrification is consistent with the general synoptic-scale temperature history of the sampled air masses, which did not encounter temperatures below the frostpoint and had relatively brief encounters with temperatures below the nitric acid trihydrate equilibrium temperature. Much larger degrees of denitrification would have been inferred if mixing effects had been ignored, which is the traditional approach to diagnose denitrification. Our analysis emphasizes the importance of using other correlations of conserved species to be able to accurately interpret changes in the NOy/N2O relation with respect to denitrification. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Rex, M (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Neuman, Andy/A-1393-2009; Rex, Markus/A-6054-2009; Salawitch, Ross/B-4605-2009; Herman, Robert/H-9389-2012; Gao, Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013 OI Neuman, Andy/0000-0002-3986-1727; Rex, Markus/0000-0001-7847-8221; Salawitch, Ross/0000-0001-8597-5832; Herman, Robert/0000-0001-7063-6424; Fahey, David/0000-0003-1720-0634 NR 46 TC 42 Z9 41 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26611 EP 26623 DI 10.1029/1999JD900463 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200035 ER PT J AU Flocke, F Herman, RL Salawitch, RJ Atlas, E Webster, CR Schauffler, SM Lueb, RA May, RD Moyer, EJ Rosenlof, KH Scott, DC Blake, DR Bui, TP AF Flocke, F Herman, RL Salawitch, RJ Atlas, E Webster, CR Schauffler, SM Lueb, RA May, RD Moyer, EJ Rosenlof, KH Scott, DC Blake, DR Bui, TP TI An examination of chemistry and transport processes in the tropical lower stratosphere using observations of long-lived and short-lived compounds obtained during STRAT and POLARIS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; UPPER TROPOSPHERE; OZONE DEPLETION; N2O; CH4; AIRCRAFT; ABSORPTION; CHLORINE; RADICALS; CIRCULATION AB A suite of compounds with a wide range of photochemical lifetimes (3 months to several decades) was measured in the tropical and midlatitude upper troposphere and lower stratosphere during the Stratospheric Tracers of Atmospheric Transport (STRAT) experiment (fall 1995 and winter, summer, and fall 1996) and the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) deployment in late summer 1997. These species include various chlorofluorocarbons, hydrocarbons, halocarbons, and halons measured in whole air samples and CO measured in situ by tunable diode laser spectroscopy. Mixing ratio profiles of long-lived species in the tropical lower stratosphere are examined using a one-dimensional (1-D) photochemical model that includes entrainment from the extratropical stratosphere and is constrained by measured concentrations of OH. Profiles of tracers found using the 1-D model agree well with all the observed tropical profiles for an entrainment time scale of 85(-4)(+6) months, independent of altitude between potential temperatures of 370 and 500 K. The tropical profile of CO is used to show that the annually averaged ascent rate profile, on the basis of a set of radiative heating calculations, is accurate to approximately +/-44%, a smaller uncertainty than found by considering the uncertainties in the radiative model and its inputs. Tropical profiles of ethane and C2Cl4 reveal that the concentration of C1 is higher than expected on the basis of photochemical model simulations using standard gas phase kinetics and established relationships between total inorganic chlorine and CFC-11. Our observations suggest that short-lived organic chlorinated compounds and HCl carried across the tropical tropopause may provide an important source of inorganic chlorine to the tropical lower stratosphere that has been largely unappreciated in previous studies. The entrainment timescale found here is considerably less than the value found by a similar study that focused on observations obtained in the lower stratosphere during 1994. Several possible explanations for this difference are discussed. C1 Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. CALTECH, Jet Prop Lab, NASA, Pasadena, CA 91109 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Flocke, F (reprint author), Natl Ctr Atmospher Res, Div Atmospher Chem, POB 3000, Boulder, CO 80307 USA. EM ffl@ucar.edu RI Salawitch, Ross/B-4605-2009; Herman, Robert/H-9389-2012; Rosenlof, Karen/B-5652-2008; Atlas, Elliot/J-8171-2015 OI Salawitch, Ross/0000-0001-8597-5832; Herman, Robert/0000-0001-7063-6424; Rosenlof, Karen/0000-0002-0903-8270; NR 74 TC 45 Z9 45 U1 0 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26625 EP 26642 DI 10.1029/1999JD900504 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200036 ER PT J AU Sen, B Osterman, GB Salawitch, RJ Toon, GC Margitan, JJ Blavier, JF Chang, AY May, RD Webster, CR Stimpfle, RM Bonne, GP Voss, PB Perkins, KK Anderson, JG Cohen, RC Elkins, JW Dutton, GS Hurst, DF Romashkin, PA Atlas, EL Schauffler, SM Loewenstein, M AF Sen, B Osterman, GB Salawitch, RJ Toon, GC Margitan, JJ Blavier, JF Chang, AY May, RD Webster, CR Stimpfle, RM Bonne, GP Voss, PB Perkins, KK Anderson, JG Cohen, RC Elkins, JW Dutton, GS Hurst, DF Romashkin, PA Atlas, EL Schauffler, SM Loewenstein, M TI The budget and partitioning of stratospheric chlorine during the 1997 Arctic summer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SULFATE AEROSOLS; ANTARCTIC OZONE; NITROUS-OXIDE; SULFURIC-ACID; ATMOS; ABSORPTION; AIRCRAFT; N2O; ABUNDANCE; DEPLETION AB Volume mixing ratio profiles of HCl, HOCl, ClNO3, CH3Cl, CFC-12, CFC-11, CCl4, HCFC-22, and CFC-113, were measured simultaneously from 9 to 38 km by the Jet Propulsion Laboratory MkIV Fourier Transform Infrared solar absorption spectrometer during two balloon flights from Fairbanks, Alaska (64.8 degrees N), on May 8 and July 8, 1997. The altitude variation of total organic chlorine (CCly), total inorganic chlorine (Cl-y), and the nearly constant value (3.7 +/- 0.2 ppbv) of their sum (Cl-TOT) demonstrates that the stratospheric chlorine species available to react with O-3 are supplied by the decomposition of organic chlorinated compounds whose abundances are well quantified. Measured profiles of HCL and ClNO3 agree well with profiles found by photochemical model (differences < 10% for altitudes below 35 km) constrained by various other constituents measured by MkIV. The production of HCl by ClO + OH plays a relatively small role in the partitioning of HCl and ClNO3 for the sampled air masses. However, better agreement with the measured profiles of HCl and ClNO3 is obtained when this source of HCl is included in the model. Both the measured and calculated [ClNO3]/[HCl] ratios exhibit the expected near linear variation with [O-3](2)/[CH4] over a broad range of altitudes. MkIV measurements of HCl, ClNO3, and CCly agree well with ER-2 in situ observations of these quantities for directly comparable air masses. These results demonstrate good understanding of the budget of stratospheric chlorine and that the partitioning of inorganic chlorine is accurately described by photochemical models that employ JPL97 reaction rates and production of HCl from ClO + OH for the environmental conditions encountered: relatively warm temperatures, long periods of solar illumination, and relatively low aerosol surface areas. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Univ Calif Berkeley, Dept Geol & Geophys, Berkeley, CA 94720 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Natl Ctr Atmospher Res, Cooperat Inst Res Environm Sci, Boulder, CO 80303 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Sen, B (reprint author), CALTECH, Jet Prop Lab, MS 183-601, Pasadena, CA 91109 USA. EM bhaswar.sen@jpl.nasa.gov RI Salawitch, Ross/B-4605-2009; Cohen, Ronald/A-8842-2011; Atlas, Elliot/J-8171-2015; Hurst, Dale/D-1554-2016 OI Salawitch, Ross/0000-0001-8597-5832; Cohen, Ronald/0000-0001-6617-7691; Hurst, Dale/0000-0002-6315-2322 NR 44 TC 22 Z9 22 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26653 EP 26665 DI 10.1029/1999JD900245 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200038 ER PT J AU Del Negro, LA Fahey, DW Gao, RS Donnelly, SG Keim, ER Neuman, JA Cohen, RC Perkins, KK Koch, LC Salawitch, RJ Lloyd, SA Proffitt, MH Margitan, JJ Stimpfle, RM Bonne, GP Voss, PB Wennberg, PO McElroy, CT Swartz, WH Kusterer, TL Anderson, DE Lait, LR Bui, TP AF Del Negro, LA Fahey, DW Gao, RS Donnelly, SG Keim, ER Neuman, JA Cohen, RC Perkins, KK Koch, LC Salawitch, RJ Lloyd, SA Proffitt, MH Margitan, JJ Stimpfle, RM Bonne, GP Voss, PB Wennberg, PO McElroy, CT Swartz, WH Kusterer, TL Anderson, DE Lait, LR Bui, TP TI Comparison of modeled and observed values of NO2 and JNO(2) during the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) mission SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; LOWER STRATOSPHERE; ER-2 AIRCRAFT; REACTIVE NITROGEN; CHLORINE RADICALS; UPPER TROPOSPHERE; AMORPHOUS-CARBON; TEMPERATURE; O-3; ACTIVATION AB Stratospheric measurements of NO, NO2, O-3, ClO, and HO2 were made during spring, early summer, and late summer in the Arctic region during 1997 as part of the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) field campaign. In the sunlit atmosphere, NO2 and NO are in steady state through NO2 photolysis and reactions involving O-3, ClO, BrO, and HO2. By combining observations of O-3, ClO, and HO2, observed and modeled values of the NO2 photolysis rate coefficient ((NO2)-N-J), and model estimates of BrO, several comparisons are made between steady state and measured values of both NO2 and (NO2)-N-J An apparent seasonal dependence in discrepancies between calculated and measured values was found; however, a source for this dependence could not be identified. Overall, the mean linear fits in the various comparisons show agreement within 19%, well within the combined uncertainties (+/-50 to 70%). These results suggest that photochemistry controlling the NO2/NO abundance ratio is well represented throughout much of the sunlit lower stratosphere. A reduction in the uncertainty of laboratory determinations of the rate coefficient of NO + O-3 --> NO2 + O-2 would aid future analyses of these or similar atmospheric observations. C1 NOAA, Aeron Lab, Boulder, CO 80303 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Univ Colorado, Dept Chem & Biochem, Boulder, CO 80309 USA. Aerosp Corp, Space & Environm Technol Ctr, Los Angeles, CA 90009 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Johns Hopkins Univ, Appl Phys Lab, Atomospher Remote Sensing Grp, Laurel, MD 20723 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Environm Canada, Atomospher Environm Serv, Downsview, ON M3H 5T4, Canada. Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Del Negro, LA (reprint author), NOAA, Climate Monitoring & Diagnost Lab, R-E-CG1,325 Broadway, Boulder, CO 80303 USA. EM ldelnegro@cmdl.noaa.gov RI Fahey, David/G-4499-2013; Neuman, Andy/A-1393-2009; Salawitch, Ross/B-4605-2009; Cohen, Ronald/A-8842-2011; Wennberg, Paul/A-5460-2012; Swartz, William/A-1965-2010; Gao, Ru-Shan/H-7455-2013 OI Fahey, David/0000-0003-1720-0634; Neuman, Andy/0000-0002-3986-1727; Salawitch, Ross/0000-0001-8597-5832; Cohen, Ronald/0000-0001-6617-7691; Swartz, William/0000-0002-9172-7189; NR 40 TC 27 Z9 27 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26687 EP 26703 DI 10.1029/1999JD900246 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200040 ER PT J AU Stimpfle, RM Cohen, RC Bonne, GP Voss, PB Perkins, KK Koch, LC Anderson, JG Salawitch, RJ Lloyd, SA Gao, RS Del Negro, LA Keim, ER Bui, TP AF Stimpfle, RM Cohen, RC Bonne, GP Voss, PB Perkins, KK Koch, LC Anderson, JG Salawitch, RJ Lloyd, SA Gao, RS Del Negro, LA Keim, ER Bui, TP TI The coupling of ClONO2, ClO, and NO2 in the lower stratosphere from in situ observations using the NASA ER-2 aircraft SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CHLORINE NITRATE; HCL; ATMOSPHERE; SPECTROSCOPY; NITROGEN; GASES AB The first in situ measurements of ClONO2 in the lower stratosphere, acquired using the NASA ER-2 aircraft during the Polar Ozone Loss in the Arctic Region in Summer (POLARIS) mission, are combined with simultaneous measurements of ClO, NO2, temperature, pressure, and the calculated photolysis rate coefficient (J(CLONO2)) to examine the balance between production and loss of ClONO2. The observations demonstrate that the ClONO2 photochemical steady state approximation, [ClONO2](PSS) = k x [ClO] x [NO2] / J(ClONO2) is in good agreement with the direct measurement, [ClONO2](MEAS). For the bulk of the data (80%), where T > 220 K and latitudes > 45 degrees N, [ClONo2](PSS) = 1.15 +/- 0.36 (1 sigma) x [ClONO2](MEAS), while for T < 220 K and latitudes < 45 degrees N the result is somewhat less at 1.01 +/- 0.30. The cause of the temperature and/or latitude trend is unidentified. These results are independent of solar zenith angle and air density, thus there is no evidence in support of a pressure-dependent quantum yield for photodissociation of ClONO2 at wavelengths >300 nm. These measurements confirm the mechanism by which active nitrogen (NOx = NO + NO2) controls the abundance of active chlorine (Cl-x = ClO + Cl) in the stratosphere. C1 Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Univ Colorado, Dept Chem, Boulder, CO 80302 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Stimpfle, RM (reprint author), Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. EM stimpfle@huarp.harvard.edu RI Salawitch, Ross/B-4605-2009; Cohen, Ronald/A-8842-2011; Gao, Ru-Shan/H-7455-2013 OI Salawitch, Ross/0000-0001-8597-5832; Cohen, Ronald/0000-0001-6617-7691; NR 37 TC 29 Z9 29 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26705 EP 26714 DI 10.1029/1999JD900288 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200041 ER PT J AU Jucks, KW Johnson, DG Chance, KV Traub, WA Salawitch, RJ AF Jucks, KW Johnson, DG Chance, KV Traub, WA Salawitch, RJ TI Nitric acid in the middle stratosphere as a function of altitude and aerosol loading SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOS MEASUREMENTS; N2O; NITROGEN; ABUNDANCES; TRANSPORT; RADIATION; AIRCRAFT; O-3; CH4; NM AB We present remote-sensing measurements of the abundance of nitric acid (HNO3) in the lower and middle stratosphere (between 16 and 40 km) covering the period 1989-1997. The measurements were made with the Smithsonian Astrophysical Observatory Far-Infrared Spectrometer (FIRS-2) under a wide range of aerosol surface area density. We compare our measurements with the results of a photochemical steady state model to test our understanding of the chemistry of HNO3 under a variety of conditions. We find that HNO3 is significantly overestimated by the model at altitudes above 22 km, with the difference increasing with increasing altitude and decreasing aerosol surface area density. The agreement between modeled and measured HNO3 can be improved by either decreasing the rate of OH + NO2 by 35% or by using newly measured rate constants for the reactions OH + NO2 and OH + HNO3, but significant differences remain. We discuss these observations in the context of possible uncertainties in the calculated photolysis rate of HNO3 at wavelengths near 200 nm, uncertainties in the observations, errors caused by the use of constrained steady state models, and possible missing sink reactions for HNO3. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Jucks, KW (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. EM jucks@cfa.harvard.edu RI Salawitch, Ross/B-4605-2009; Johnson, David/F-2376-2015; OI Salawitch, Ross/0000-0001-8597-5832; Johnson, David/0000-0003-4399-5653; Chance, Kelly/0000-0002-7339-7577 NR 33 TC 17 Z9 17 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26715 EP 26723 DI 10.1029/1999JD900330 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200042 ER PT J AU Drdla, K Pueschel, RF Strawa, AW Cohen, RC Hanisco, TF AF Drdla, K Pueschel, RF Strawa, AW Cohen, RC Hanisco, TF TI Microphysics and chemistry of sulphate aerosols at warm stratospheric temperatures SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SULFURIC-ACID-SOLUTIONS; HETEROGENEOUS CHEMISTRY; CHLORINE RADICALS; SULFATE AEROSOLS; OZONE DEPLETION; POLAR VORTEX; HONO; FORMALDEHYDE; SURFACES; AIRCRAFT AB Observations of high NOx/NOy ratios (overall 40% larger than modelled values) during the Polar Ozone Loss in the Arctic Region in Summer campaign have led us to re-examine the heterogeneous chemistry of stratospheric aerosol particles during the polar summer period, using the Integrated MicroPhysics and Aerosol Chemistry on Trajectories model. The warm summer temperatures (up to 235 K) imply very concentrated sulphuric acid solutions (80 wt %). On the one hand, these solutions are more likely to freeze, into sulphuric acid monohydrate (SAM), reducing the efficiency of the N2O5 hydrolysis reaction. Including this freezing process increases NOx/NOy, ratios but does not improve model/measurement agreement: in polar spring, SAM formation causes the NOx/NOy ratio to be overpredicted whereas freezing has a much smaller effect on nitrogen chemistry during the continuous solar exposure of polar summer. On the other hand, if sulphate aerosols remain liquid, the high acidity may promote acid-catalysed reactions. The most important reaction is CH2O+HNO3, which effectively increases NOx/NOy ratios across a wide range of conditions, improving agreement with measurements. Furthermore, the production of HONO can either enhance gas-phase OH concentrations or promote secondary liquid reactions, including HONO+HNO3 and HONO+HCl. Primary uncertainties include the uptake coefficient of CH2O relevant to reaction with HNO3, the amount of HONO available for secondary reaction, and the relative rates of HONO reaction with HNO3 and HCl. The fate of the formic acid product, whose presence in the stratosphere may be an indicator for the CH2O reaction, and the impact on the stratospheric hydrogen budget are also discussed. C1 NASA, Ames Res Ctr, Atmospher Phys Branch, Moffett Field, CA 95006 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. RP Drdla, K (reprint author), NASA, Ames Res Ctr, Atmospher Phys Branch, Moffett Field, CA 95006 USA. EM katja@aerosol.arc.nasa.gov; rpueschel@mail.arc.nasa.gov; astrawa@mail.arc.nasa.gov; rccohen@cchem.berkeley.edu; tom@huarp.harvard.edu RI Cohen, Ronald/A-8842-2011 OI Cohen, Ronald/0000-0001-6617-7691 NR 58 TC 8 Z9 8 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26737 EP 26751 DI 10.1029/1999JD900406 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200044 ER PT J AU Strawa, AW Drdla, K Ferry, GV Verma, S Pueschel, RF Yasuda, M Salawitch, RJ Gao, RS Howard, SD Bui, PT Loewenstein, M Elkins, JW Perkins, KK Cohen, R AF Strawa, AW Drdla, K Ferry, GV Verma, S Pueschel, RF Yasuda, M Salawitch, RJ Gao, RS Howard, SD Bui, PT Loewenstein, M Elkins, JW Perkins, KK Cohen, R TI Carbonaceous aerosol (Soot) measured in the lower stratosphere during POLARIS and its role in stratospheric photochemistry SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; FRACTAL DIMENSION; UPPER TROPOSPHERE; AMORPHOUS-CARBON; BLACK CARBON; REACTION-KINETICS; OZONE DEPLETION; EXHAUST PLUMES; HEXANE SOOT; PARTICLES AB This paper describes recent measurements of carbonaceous aerosol made by wire impactors during the Photochemistry Ozone Loss in the Arctic Region in Summer (POLARIS) campaign and assesses their role in stratospheric photochemistry. Ninety-five percent of the carbonaceous aerosol collected during this campaign was in the form of b lack carbon aerosol (BCA), or soot. A new method of analyzing impactor samples is described that accounts for particle bounce and models the BCA as fractal aggregates to modify the aerodynamic collection efficiency and determine particle surface area. Results are compared to previously used methods. The new method results in an increase in the measured BCA number density of 4 times, surface area density of similar to 15 times, and an increase in mass loading of 6.15 times over one previously used approach, Average values of number, surface area, and mass densities are 0.06 no./cm(3), 0.03 mu m(2)/cm(3), and 0.64 ng/m(3), respectively. BCA number densities are similar to 1% of total aerosol number density, and BCA surface area density is similar to 10% of the measured sulfuric acid aerosol surface area. Including heterogeneous reactions on BCA in a photochemical model can affect photochemistry leading to renoxification and increased ozone depletion. However, these predicted effects are not supported by the POLARIS observations, in particular, the NOx/NOy ratios, The laboratory data is not conclusive enough to determine to what extent the heterogeneous reaction is catalytic or carbon consuming. Including catalytic reactions on BCA does not statistically improve the agreement between model and measurement in any of the several scenarios considered. Furthermore, if the reactions cause even partial carbon oxidation, the BCA would be consumed at a rate inconsistent with POLARIS observations. These inconsistencies lead us to conclude that the presence of BCA in the stratosphere did not affect stratospheric photochemistry during POLARIS. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Sci Syst & Applicat Inc, Moffett Field, CA USA. San Jose State Univ, San Jose, CA 95192 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Symtek, Moffett Field, CA USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. RP Strawa, AW (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM astrawa@mail.arc.nasa.gov RI Salawitch, Ross/B-4605-2009; Cohen, Ronald/A-8842-2011; Gao, Ru-Shan/H-7455-2013 OI Salawitch, Ross/0000-0001-8597-5832; Cohen, Ronald/0000-0001-6617-7691; NR 64 TC 34 Z9 35 U1 3 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26753 EP 26766 DI 10.1029/1999JD900453 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200045 ER PT J AU Lloyd, S Swartz, WH Kusterer, T Anderson, D McElroy, CT Midwinter, C Hall, R Nassim, K Jaffe, D Simpson, W Kelley, J Nicks, D Griffin, D Johnson, B Evans, R Quincy, D Oltmans, S Newman, P McPeters, R Labow, G Moy, L Seftor, C Toon, G Sen, B Blavier, JF AF Lloyd, S Swartz, WH Kusterer, T Anderson, D McElroy, CT Midwinter, C Hall, R Nassim, K Jaffe, D Simpson, W Kelley, J Nicks, D Griffin, D Johnson, B Evans, R Quincy, D Oltmans, S Newman, P McPeters, R Labow, G Moy, L Seftor, C Toon, G Sen, B Blavier, JF TI Intercomparison of total ozone observations at Fairbanks, Alaska, during POLARIS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID COLUMN AB The pattern of seasonal ozone loss over Fairbanks, Alaska (AK), during the NASA Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) campaign in the spring and summer of 1997 is defined. Five independent data sets of total ozone observations at Fairbanks are presented, from the Earth Probe and ADEOS Total Ozone Mapping Spectrometer (TOMS) satellite instruments, balloon-borne electrochemical concentration cell ozonesondes, and ground-based (Brewer spectroradiometer, Dobson spectrophotometer, and the Jet Propulsion Laboratory MkIV infrared interferometer) instruments. The excellent agreement between different observational techniques lends confidence to the observed rate of summertime loss of total ozone at high latitudes. In addition, the small offsets between the data sets are well understood. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Maryland, Dept Chem, College Pk, MD 20742 USA. Environm Canada, Atmospher Environm Serv, Downsview, ON, Canada. Univ Washington, Inst Geophys, Bothell, WA USA. Univ Alaska, Dept Chem, Fairbanks, AK 99775 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon Informat Technol & Sci Serv, Lanham, MD USA. Jet Propuls Lab, Pasadena, CA USA. RP Lloyd, S (reprint author), Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA. EM Steven.Lloyd@jhuapl.edu RI Newman, Paul/D-6208-2012; Swartz, William/A-1965-2010; McPeters, Richard/G-4955-2013; Simpson, William/I-2859-2014 OI Newman, Paul/0000-0003-1139-2508; Swartz, William/0000-0002-9172-7189; McPeters, Richard/0000-0002-8926-8462; Simpson, William/0000-0002-8596-7290 NR 14 TC 8 Z9 8 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26767 EP 26778 DI 10.1029/1999JD900468 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200046 ER PT J AU Toon, GC Blavier, JF Sen, B Margitan, JJ Webster, CR May, RD Fahey, D Gao, R Del Negro, L Proffitt, M Elkins, J Romashkin, PA Hurst, DF Oltmans, S Atlas, E Schauffler, S Flocke, F Bui, TP Stimpfle, RM Bonne, GP Voss, PB Cohen, RC AF Toon, GC Blavier, JF Sen, B Margitan, JJ Webster, CR May, RD Fahey, D Gao, R Del Negro, L Proffitt, M Elkins, J Romashkin, PA Hurst, DF Oltmans, S Atlas, E Schauffler, S Flocke, F Bui, TP Stimpfle, RM Bonne, GP Voss, PB Cohen, RC TI Comparison of MkIV balloon and ER-2 aircraft measurements of atmospheric trace gases SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC MEASUREMENTS; INSTRUMENTS ABOARD; REACTIVE NITROGEN; ATMOS; OZONE; SPECTROMETER; WATER; OXIDE; N2O; CH4 AB On May 8, 1997, vertical profiles of over 30 different gases were measured remotely in solar occultation by the Jet Propulsion Laboratory MkIV Interferometer during a balloon flight launched from Fairbanks, Alaska. These gases included H2O, N2O, CH4, CO, NOx, NOy, HCl, ClNO3, CCl2F2, CCl3F, CCl4, CHClF2, CClF2CCl2F, SF6, CH3Cl, and C2H6, all of which were also measured in situ by instruments on board the NASA ER-2 aircraft, which was making flights from Fairbanks during this same early May time period as part of the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) experiment. A comparison of the gas volume mixing ratios in the upper troposphere and lower stratosphere reveals agreement better than 5% for most gases. The three significant exceptions to this are SF6 and CCl4 for which the remote measurements exceed the in situ observations by 15-20% at all altitudes, and H2O for which the remote measurements are up to 30% smaller than the in situ observations near the hygropause. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Ocean & Atmospher Adm, Aeron Lab, Boulder, CO USA. Natl Ocean & Atmospher Adm, Climate Monitoring & Diagnost Lab, Boulder, CO USA. Univ Colorado, CIRES, Boulder, CO 80309 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Harvard Univ, Cambridge, MA 02138 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. RP Toon, GC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM toon@mark4sun.jpl.nasa.gov RI Cohen, Ronald/A-8842-2011; Atlas, Elliot/J-8171-2015; Hurst, Dale/D-1554-2016; Fahey, David/G-4499-2013 OI Cohen, Ronald/0000-0001-6617-7691; Hurst, Dale/0000-0002-6315-2322; Fahey, David/0000-0003-1720-0634 NR 22 TC 79 Z9 79 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26779 EP 26790 DI 10.1029/1999JD900379 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200047 ER PT J AU Thompson, AM Hudson, RD AF Thompson, AM Hudson, RD TI Tropical tropospheric ozone (TTO) maps from Nimbus 7 and Earth Probe TOMS by the modified-residual method: Evaluation with sondes, ENSO signals, and trends from Atlantic regional time series SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article; Proceedings Paper CT Joint Symposium on Atmospheric Chemistry and Climate Change CY AUG 19-25, 1998 CL UNIV WASHINGTON, SEATTLE, WA SP Univ Washington Joint Inst Study Atmoshere & Ocean, NOAA Pacific Marine Environm Lab, European Commiss, US DOE, NASA, US Natl Sci Fdn, World Meteorol Org, Int Assoc Meteorol & Atmospher Sci, Commiss Atmospher Chem & Global Pollut, Int Global Atmospher Chem Project HO UNIV WASHINGTON ID GAS EXPERIMENT DATA; TRACE-A; MAPPING SPECTROMETER; COLUMN OZONE; TOMS/SBUV MEASUREMENTS; STRATOSPHERIC AEROSOL; VERTICAL-DISTRIBUTION; SOUTH-AMERICA; PACIFIC-OCEAN; EL-NINO AB The modified-residual (MR) method for retrieving time-averaged stratospheric ozone and tropospheric ozone column amounts from the Total Ozone Mapping Spectrometer (TOMS) is applied to the 14 complete calendar years of Nimbus 7 observations (1979-1992). These are available as digital data at http://metosrv2.umd.edu/ similar to tropo/14y_data.d. The MR method has also been used to produce real-time maps of tropical tropospheric ozone (TTTO) from TOMS on the Earth-Probe (1996-present) and ADEOS platforms (1996-1997). Evaluation of the TTO time series for 1979-1990 and 1997-1995 is presented here; it is limited to the few tropical ozonesonde stations operational during those years (Ascension Island; Natal, Brazil; Brazzaville). The standard deviation of the differences between TTO and the sondes is +/-(6-7) Dobson units (DU), depending on location. Stratospheric column ozone, which is also derived by the modified-residual method, compares favorably with sondes (to within 6-9 DU) and with stratospheric ozone inferred from other satellites (usually 8-15 DU lower than the latter). TTO time series and the magnitude of the tropospheric wave-one pattern show El Nino-Southern Oscillation (ENSO) signals during the period from 1979-1992. During 1997 the ENSO stands out at some stations, but not at others. Between 12 degrees N and 12 degrees S, zonally averaged TTO shows no significant trend from 1980-1990. Trends are also not significant during this period in localized regions, for example, from just west of South America across to southern Africa. This is consistent with the ozonesonde record at Natal, Brazil (the only tropical ozone data publicly available for the 1980s), which shows no significant trend. The lack of trend in tropospheric ozone agrees with a statistical analysis based on another method for deriving TTO from TOMS, the convective-cloud-differential approach of Ziemke er al. [1998]. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Lab Atmospheres, Greenbelt, MD 20771 USA. RP Thompson, AM (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM anne.m.thompson@gsfc.nasa.gov RI Hudson, Robert/F-4506-2010; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 41 TC 65 Z9 66 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1999 VL 104 IS D21 BP 26961 EP 26975 DI 10.1029/1999JD900470 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 257KN UT WOS:000083781200062 ER PT J AU Kuga, Y Ishimaru, A Catton, JA Le, CTC AF Kuga, Y Ishimaru, A Catton, JA Le, CTC TI Detection of slowly moving targets using angular- and frequency-correlation techniques SO MICROWAVE AND OPTICAL TECHNOLOGY LETTERS LA English DT Article DE radar; MTI; correlation function; target detection; Doppler shift AB To accurately detect slow-moving vehicles, we have developed a new correlation technique which employs multiple sensors (two sensors with an along-track orientation and two sensors with an across-track orientation). Unlike conventional MTI (moving target indicator) radar, our technique makes use of the Doppler-shifted phase of the correlation of the scattered waves. (C) 1999 John Wiley & Sons, Inc. C1 Univ Washington, Dept Elect Engn, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA 96109 USA. RP Kuga, Y (reprint author), Univ Washington, Dept Elect Engn, Seattle, WA 98195 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0895-2477 J9 MICROW OPT TECHN LET JI Microw. Opt. Technol. Lett. PD NOV 20 PY 1999 VL 23 IS 4 BP 197 EP 200 PG 4 WC Engineering, Electrical & Electronic; Optics SC Engineering; Optics GA 250TR UT WOS:000083404700001 ER PT J AU Zaman, AJ Lee, RQ Simons, RN AF Zaman, AJ Lee, RQ Simons, RN TI A new design approach for a patch antenna with a notch feed SO MICROWAVE AND OPTICAL TECHNOLOGY LETTERS LA English DT Article DE patch antenna; antenna feed; coplanar waveguide AB A grounded CPW model for the notch region of a patch antenna feed is presented. The model is validated by measuring the input impedance for a wide range of substrate thickness and frequency using an accurate de-embedding technique. Based on these results, new design guidelines for a notch feed that assure impedance matching to a 50 Omega microstrip line are given. (C) 1999 John Wiley & Sons, Inc. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Zaman, AJ (reprint author), NASA, Glenn Res Ctr, Lewis Field, Cleveland, OH 44135 USA. NR 9 TC 4 Z9 4 U1 1 U2 1 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0895-2477 J9 MICROW OPT TECHN LET JI Microw. Opt. Technol. Lett. PD NOV 20 PY 1999 VL 23 IS 4 BP 236 EP 238 DI 10.1002/(SICI)1098-2760(19991120)23:4<236::AID-MOP14>3.0.CO;2-5 PG 3 WC Engineering, Electrical & Electronic; Optics SC Engineering; Optics GA 250TR UT WOS:000083404700014 ER PT J AU Zeng, N Neelin, JD Lau, KM Tucker, CJ AF Zeng, N Neelin, JD Lau, KM Tucker, CJ TI Enhancement of interdecadal climate variability in the Sahel by vegetation interaction SO SCIENCE LA English DT Article ID LAND-SURFACE PROCESSES; TROPICAL NORTH-AFRICA; SUMMER RAINFALL; MODEL; DYNAMICS; DESERTS; GCM AB The role of naturally varying vegetation in influencing the climate variability in the West African Sahel is explored in a coupled atmosphere-land-vegetation model. The Sahel rainfall variability is influenced by sea-surface temperature variations in the oceans. Land-surface feedback is found to increase this variability both on interannual and interdecadal time scales. Interactive vegetation enhances the interdecadal variation substantially but can reduce year-to-year variability because of a phase lag introduced by the relatively slow vegetation adjustment time. Variations in vegetation accompany the changes in rainfall in particular the multidecadal drying trend from the 1950s to the 1980s. C1 Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Zeng, N (reprint author), Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. RI Zeng, Ning/A-3130-2008; Neelin, J. David/H-4337-2011; Lau, William /E-1510-2012 OI Zeng, Ning/0000-0002-7489-7629; Lau, William /0000-0002-3587-3691 NR 31 TC 327 Z9 341 U1 4 U2 34 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD NOV 19 PY 1999 VL 286 IS 5444 BP 1537 EP 1540 DI 10.1126/science.286.5444.1537 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 257DZ UT WOS:000083768300050 ER PT J AU Kane, SM Timonen, RS Leu, MT AF Kane, SM Timonen, RS Leu, MT TI Heterogeneous chemistry of acetone in sulfuric, acid solutions: Implications for the upper troposphere SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID LOWER STRATOSPHERE; HYDROGEN RADICALS; UNITED-STATES; WATER; COEFFICIENTS; ACETONITRILE; HYDROCARBONS; TEMPERATURES; SURFACES; GAS AB The uptake of acetone vapor by liquid sulfuric acid has been investigated over the range of 40-87 wt % H(2)SO(4) and between the temperatures 198 and 300 K. Studies were performed with a flow-tube reactor, using a quadrupole mass spectrometer for detection. At most concentrations studied (40-75 wt %), acetone was physically absorbed by sulfuric acid without undergoing irreversible reaction. However, at acid concentrations at or above 80 wt %, reactive uptake of acetone was observed, leading to products such as mesityl oxide and/or mesitylene, From time-dependent uptake data and liquid-phase diffusion coefficients calculated from molecular viscosity, the effective Henry's law solubility constant (H*) was determined, The solubility of acetone in liquid sulfuric acid was found to increase with increasing acid concentration and decreasing temperature. In the 75 wt % and 230 K range, the value for H* was found to be similar to 2 x 10(6) M/atm. This value suggests that acetone primarily remains in the gas phase:rather than absorbing into sulfate aerosols under atmospheric conditions. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Leu, MT (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. NR 36 TC 33 Z9 34 U1 1 U2 7 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD NOV 18 PY 1999 VL 103 IS 46 BP 9259 EP 9265 DI 10.1021/jp9926692 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 260XL UT WOS:000083978700013 ER PT J AU Owen, T Mahaffy, P Niemann, HB Atreya, S Donahue, T Bar-Nun, A de Pater, I AF Owen, T Mahaffy, P Niemann, HB Atreya, S Donahue, T Bar-Nun, A de Pater, I TI A low-temperature origin for the planetesimals that formed Jupiter SO NATURE LA English DT Article ID SOLAR NEBULA; WAVELENGTHS; CHEMISTRY; MODELS AB The four giant planets in the Solar System have abundances of 'metals' (elements heavier than helium), relative to hydrogen, that are much higher than observed in the Sun. In order to explain this, all models for the formation of these planets rely on an influx of solid planetesimals(17). It is generally assumed that these planetesimals were similar, if not identical, to the comets from the Oort cloud that we see today. Comets that formed in the region of the giant planets should not have contained much neon, argon and nitrogen, because the temperatures were too high for these volatile gases to be trapped effectively in ice. This means that the abundances of those elements on the giant planets should be approximately solar. Here we show that argon, krypton and xenon in Jupiter's atmosphere are enriched to the same extent as the other heavy elements, which suggests that the planetesimals carrying these elements must have formed at temperatures lower than predicted by present models of giant-planet formation. C1 Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Michigan, Ann Arbor, MI 48109 USA. Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. RP Owen, T (reprint author), Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA. EM owen@ifa.hawaii.edu RI Mahaffy, Paul/E-4609-2012 NR 24 TC 172 Z9 172 U1 0 U2 6 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD NOV 18 PY 1999 VL 402 IS 6759 BP 269 EP 270 DI 10.1038/46232 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 257ZP UT WOS:000083813700041 PM 10580497 ER PT J AU Khan, MA Yang, JW Simin, G zur Loye, H Bicknell-Tassius, R Gaska, R Shur, MS Tamulaitis, G Zukauskas, A AF Khan, MA Yang, JW Simin, G zur Loye, H Bicknell-Tassius, R Gaska, R Shur, MS Tamulaitis, G Zukauskas, A TI Energy band/lattice mismatch engineering in quaternary AlInGaN/GaN heterostructure SO PHYSICA STATUS SOLIDI A-APPLIED RESEARCH LA English DT Article; Proceedings Paper CT 3rd International Conference on Nitride Semiconductors (ICNS 99) CY JUL 05-09, 1999 CL MONTPELLIER, FRANCE SP ICNS ID FIELD-EFFECT TRANSISTORS; ALGAN/GAN AB We discuss structural, optical and electrical properties of AlxInyGai-x-yN/GaN heterostructures grown on sapphire and GH-SIC substrates. The incorporation of In reduces the lattice mismatch in a much stronger way than the energy gap discontinuity. An In to Al ratio close to 1:5 should result in nearly strain-free heterostructures. The incorporation of In and resulting changes in the built-in strain in AlInGaN/GaN heterostructures strongly affect the transport properties of the two-dimensional (2D) electron gas at the heterointerface. Using the incorporation of In in order to increase the Al molar fraction preserving the same value of strain should allow us to greatly enhance the sheet carrier density at the AlGaInN/GaN heterointerface. Further work on improving In incorporation techniques is needed in order to meet these expectations. C1 Univ S Carolina, Dept ECE, Columbia, SC 29208 USA. Univ S Carolina, Dept Chem, Columbia, SC 29208 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Rensselaer Polytech Inst, Dept ECSE, Troy, NY 12180 USA. Vilnius State Univ, Inst MSAR, LT-2006 Vilnius, Lithuania. RP Khan, MA (reprint author), Univ S Carolina, Dept ECE, Columbia, SC 29208 USA. RI Shur, Michael/A-4374-2016; OI Shur, Michael/0000-0003-0976-6232; zur Loye, Hans-Conrad/0000-0001-7351-9098 NR 10 TC 18 Z9 19 U1 0 U2 12 PU WILEY-V C H VERLAG GMBH PI BERLIN PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY SN 0031-8965 J9 PHYS STATUS SOLIDI A JI Phys. Status Solidi A-Appl. Res. PD NOV 16 PY 1999 VL 176 IS 1 BP 227 EP 230 PG 4 WC Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 261WA UT WOS:000084032200043 ER PT J AU Hirata, S Lee, TJ Head-Gordon, M AF Hirata, S Lee, TJ Head-Gordon, M TI Time-dependent density functional study on the electronic excitation energies of polycyclic aromatic hydrocarbon radical cations of naphthalene, anthracene, pyrene, and perylene SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID DIFFUSE INTERSTELLAR BANDS; VIBRONIC ABSORPTION-SPECTRA; MATRIX-ISOLATED NAPHTHALENE; SOLID ARGON; VIBRATIONAL-SPECTRA; INFRARED-SPECTRUM; RESPONSE THEORY; SPECTROSCOPY; IONIZATION; APPROXIMATION AB Time-dependent density functional theory (TDDFT) and its modification, the Tamm-Dancoff approximation to TDDFT, are employed to calculate the electronic excitation energies and oscillator strengths for a series of polycyclic aromatic hydrocarbon radical cations. For the radical cations of naphthalene and anthracene, TDDFT using the Becke-Lee-Yang-Parr functional and the 6-31G** basis set provides the excitation energies that are roughly within 0.3 eV of the experimental data. The assignments of the electron transitions proposed by TDDFT accord with the previous assignments made by accurate ab initio calculations, except that TDDFT indicates the existence of a few additional transitions of pi*<--sigma character among the several low-lying transitions. The calculated energies for these pi*<--sigma transitions are found to be consistent with the onset of a sigma electron ionization manifold in the photoelectron spectra. For the pyrene radical cation, TDDFT supports the previous assignments made by semiempirical calculations, whereas for the perylene radical cation, TDDFT suggests the energy ordering of the three lowest-lying excited states be changed from those of the semiempirical results. (C) 1999 American Institute of Physics. [S0021-9606(99)30542-0]. C1 Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Head-Gordon, M (reprint author), Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. RI Lee, Timothy/K-2838-2012 NR 54 TC 186 Z9 187 U1 4 U2 59 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD NOV 15 PY 1999 VL 111 IS 19 BP 8904 EP 8912 DI 10.1063/1.480235 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 251GQ UT WOS:000083437400020 ER PT J AU Fukumori, I Raghunath, R Fu, LL Chao, Y AF Fukumori, I Raghunath, R Fu, LL Chao, Y TI Assimilation of TOPEX/Poseidon altimeter data into a global ocean circulation model: How good are the results? SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID TROPICAL PACIFIC-OCEAN; GULF-STREAM MODEL; SEA-SURFACE; KALMAN FILTER; WIND-STRESS; VARIABILITY; HEIGHT AB The feasibility of assimilating satellite altimetry data into a global ocean general circulation model is studied. Three years of TOPEX/Poseidon data are analyzed using a global, three-dimensional, nonlinear primitive equation model. The assimilation's success is examined by analyzing its consistency and reliability measured by formal error estimates with respect to independent measurements. Improvements in model solution are demonstrated, in particular, properties not directly measured. Comparisons are performed with sea level measured by tide gauges, subsurface temperatures and currents from moorings, and bottom pressure measurements. Model representation errors dictate what can and cannot be resolved by assimilation, and its identification is emphasized. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fukumori, I (reprint author), CALTECH, Jet Prop Lab, Mail Stop 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 37 TC 78 Z9 80 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1999 VL 104 IS C11 BP 25647 EP 25665 DI 10.1029/1999JC900193 PG 19 WC Oceanography SC Oceanography GA 255DC UT WOS:000083653400002 ER PT J AU Kwok, R Cunningham, GF Yueh, S AF Kwok, R Cunningham, GF Yueh, S TI Area balance of the Arctic Ocean perennial ice zone: October 1996 to April 1997 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-ICE; PASSIVE MICROWAVE; BEAUFORT SEA; COVER; IDENTIFICATION AB We use National Aeronautics and Space Administration scatterometer (NSCAT), RADARSAT, and ice motion data to examine the perennial ice zone (PIZ) of the Arctic Ocean between October 1996 and April 1997. The PIZ is identified by a simple backscatter-based classification of the gridded NSCAT backscatter fields. The area of the PIZ at the beginning of October occupies an area of 5.32 x 10(6) km(2), similar to 76% of the Arctic Ocean. By the first of May, only 4.54 x 10(6) km(2) of that area remains, a decrease of 0.78 x 10(6) km(2) over the 7-month period. This area loss can be explained almost entirely Ocean. 0.78 x 10(6) km(2) over the 7-month period. This area loss can be explained almost by ice export. Over this period the total area flux of sea ice through Fram Strait, estimated using satellite passive microwave ice motion, is 0.80 x 10(6) km2 or 12% of the Arctic Ocean. Approximately 0.70 x 10(6) km(2) or 88% of the exported area is from the PIZ Nares Strait outflow is small at 34,000 km(2) and is estimated by summing the high backscatter areas exported into northern Baffin Bay. After accounting for the outflow through the Fram and Nares Straits an unexplained residual of 46,000 km(2) remains. We attribute this residual to errors in our estimation process, the unaccounted for ice flux through the: Canadian Archipelago, and the net divergence and convergence of the PIZ over the period. Our interpretation of the radiometry seems to be sound on the basis of the area balance arguments provided here. This study shows that (1) the PIZ converage of the Arctic Ocean can be derived from NSCAT backscatter fields and (2) the decrease in PIZ area over the winter is a good estimate of the PIZ net ice area exported through Fram Strait. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kwok, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 23 TC 18 Z9 18 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1999 VL 104 IS C11 BP 25747 EP 25759 DI 10.1029/1999JC900234 PG 13 WC Oceanography SC Oceanography GA 255DC UT WOS:000083653400009 ER PT J AU Barber, DG Nghiem, SV AF Barber, DG Nghiem, SV TI The role of snow on the thermal dependence of microwave backscatter over sea ice SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID STRONG PERMITTIVITY FLUCTUATIONS; COMPLEX-DIELECTRIC-CONSTANT; LAYERED MEDIA; MODEL; SCATTERING; FREQUENCIES; ENERGY; SIGNATURES; PROFILE; BRINE AB Our understanding of snow distribution in the polar regions is severely restricted owing to the heterogeneity, both in space and time, of this solid precipitate. Processes such as vapor and mass fluxes across the interface are, to a large extent, controlled by the presence and geophysical state of the snow cover on sea ice. Numerous studies have shown the importance of snow cover in ecosystem processes and particularly in photosynthetically active radiation extinction. Researchers are currently exploiting developments in electromagnetic interaction theory in an attempt to measure snow thickness distributions remotely. In this paper, we investigate the dependence of radar backscatter on snow thickness over smooth first-year ice. We use data from the Seasonal Sea Ice Monitoring and Modeling Site located in the Canadian Archipelago. Results show that the thermodynamics of the snow cover affect wave propagation, attenuation, and scattering through the control that brine volume exerts on interfacial characteristics of the snow and ice layers. The effect is subtle and specific to certain ranges of salinity, surface roughness and thickness of sea ice. We describe the phenomenon responsible for this effect using a microwave model consistently for both complex effective permittivities and backscatter coefficients coupled to a one-dimensional model. We validate the physical principles using in situ field data. We then discuss the potential of synthetic aperture radar in estimating snow thickness distributions under these specific conditions using both observed and modeled microwave scattering. C1 Univ Manitoba, Dept Geog, Ctr Earth Observat Sci, Winnipeg, MB R3T 2N2, Canada. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Barber, DG (reprint author), Univ Manitoba, Dept Geog, Ctr Earth Observat Sci, Winnipeg, MB R3T 2N2, Canada. NR 40 TC 53 Z9 53 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1999 VL 104 IS C11 BP 25789 EP 25803 DI 10.1029/1999JC900181 PG 15 WC Oceanography SC Oceanography GA 255DC UT WOS:000083653400011 ER PT J AU Yang, L Anantram, MP Han, J Lu, JP AF Yang, L Anantram, MP Han, J Lu, JP TI Band-gap change of carbon nanotubes: Effect of small uniaxial and torsional strain SO PHYSICAL REVIEW B LA English DT Article ID ELECTRONIC-STRUCTURE; TUBULES AB We use a simple picture based on the pi electron approximation to study the band-gap variation of carbon nanotubes with uniaxial and torsional strain. We find (i) that the magnitude of slope of band gap versus strain has an almost universal behavior that depends on the chiral angle, (ii) that the sign of slope depends on the value of (n - m) mod 3, and (iii) a novel change in sign of the slope of band gap versus uniaxial strain arising from a change in the value of the quantum number corresponding to the minimum band gap. Four orbital calculations are also presented to show that the pi orbital results are valid. [S0163-1829(99)00841-9]. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. Univ N Carolina, Chapel Hill, NC 27599 USA. RP Anantram, MP (reprint author), NASA, Ames Res Ctr, Mail Stop T27A-1, Moffett Field, CA 94035 USA. EM anant@nas.nasa.gov NR 19 TC 319 Z9 321 U1 1 U2 32 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD NOV 15 PY 1999 VL 60 IS 19 BP 13874 EP 13878 DI 10.1103/PhysRevB.60.13874 PG 5 WC Physics, Condensed Matter SC Physics GA 260GD UT WOS:000083940400091 ER PT J AU Zetner, PW Trajmar, S Kanik, I Wang, S Csanak, G Clark, REH Abdallah, J Fursa, D Bray, I AF Zetner, PW Trajmar, S Kanik, I Wang, S Csanak, G Clark, REH Abdallah, J Fursa, D Bray, I TI Differential cross sections for electron-impact excitation out of the metastable levels of the barium atom SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID LASER-EXCITED BARIUM; COHERENCE PARAMETERS; SCATTERING; ...6S5D(1)D(2); TRANSITION; IONS AB We report an experimental and theoretical investigation of low-energy electron scattering from Ba-138 atoms prepared in the metastable D-3(2) and D-1(2) levels by laser-optical pumping. Differential cross sections were measured for excitation out of these metastable levels to a variety of higher-lying levels at electron-impact energies of 10, 20 and 36.7 eV. A comparison of experimental data with the results of theoretical approaches using the unitarized distorted-wave approximation and the convergent close-coupling scheme is given. C1 Univ Manitoba, Dept Phys & Astron, Winnipeg, MB R3T 2N2, Canada. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA. Flinders Univ S Australia, Sch Phys Sci, Adelaide, SA 5001, Australia. RP Zetner, PW (reprint author), Univ Manitoba, Dept Phys & Astron, Winnipeg, MB R3T 2N2, Canada. RI Fursa, Dmitry/C-2301-2009; Bray, Igor/B-8586-2009 OI Fursa, Dmitry/0000-0002-3951-9016; Bray, Igor/0000-0001-7554-8044 NR 40 TC 15 Z9 15 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD NOV 14 PY 1999 VL 32 IS 21 BP 5123 EP 5146 DI 10.1088/0953-4075/32/21/306 PG 24 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 259VE UT WOS:000083914000009 ER PT J AU Dunn, MH Tweed, J Farassat, F AF Dunn, MH Tweed, J Farassat, F TI The application of a boundary integral equation method to the prediction of ducted fan engine noise SO JOURNAL OF SOUND AND VIBRATION LA English DT Article AB The prediction of ducted fan engine noise using a boundary integral equation method (BIEM) is considered. Governing equations for the BIEM are based on linearized acoustics and describe the scattering of incident sound by a thin, finite-length cylindrical duct in the presence of a uniform axial inflow. A classical boundary value problem (BVP) is derived that includes an axisymmetric, locally reacting liner on the duct interior. Using potential theory, the BVP is recast as a system of hypersingular boundary integral equations with subsidiary conditions. We describe the integral equation derivation and solution procedure in detail. The development of the computationally efficient ducted fan noise prediction program TBIEM3D, which implements the BIEM, and its utility in conducting parametric noise reduction studies are discussed. Unlike prediction methods based on spinning mode eigenfunction expansions, the BIEM does not require the decomposition of the interior acoustic field into its radial and axial components which, for the liner case, avoids the solution of a difficult complex eigenvalue problem. Numerical spectral studies are presented to illustrate the nexus between the eigenfunction expansion representation and BIEM results. We demonstrate BIEM liner capability by examining radiation patterns for several cases of practical interest. (C) 1999 Academic Press. C1 Old Dominion Univ, Norfolk, VA 23508 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Dunn, MH (reprint author), Old Dominion Univ, Norfolk, VA 23508 USA. NR 28 TC 16 Z9 33 U1 1 U2 4 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD NOV 11 PY 1999 VL 227 IS 5 BP 1019 EP 1048 DI 10.1006/jsvi.1999.2394 PG 30 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 259TQ UT WOS:000083910400010 ER PT J AU Brocksopp, C Fender, RP Larionov, V Lyuty, VM Tarasov, AE Pooley, GG Paciesas, WS Roche, P AF Brocksopp, C Fender, RP Larionov, V Lyuty, VM Tarasov, AE Pooley, GG Paciesas, WS Roche, P TI Orbital, precessional and flaring variability of Cygnus X-1 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars : activity; binaries : general; stars : individual : Cygnus X-1; infrared : stars; radio continuum : stars; X-rays : stars ID X-RAY BINARIES; BLACK-HOLE; PERIOD; DISCOVERY; MODEL; DISKS; MASS AB We present the results of a 2.5-yr multiwavelength monitoring programme of Cygnus X-l, making use of hard and soft X-ray data, optical spectroscopy, UBVJHK photometry and radio data. In particular, we confirm that the 5.6-d orbital period is apparent in all wavebands, and note the existence of a wavelength dependence to the modulation, in the sense that higher energies reach minimum first. We also find a strong modulation at a period of 142 +/- 7 d, which we suggest is caused by precession and/or radiative warping of the accretion disc. Strong modulation of the hard and soft X-lay flux at this long period may not be compatible with simple models of an optically thin accretion flow and corona in the low state. We present the basic components required for more detailed future modelling of the system - including a partially optically thick jet, quasi-continuous in the low state, the base of which acts as the Comptonizing corona. In addition, we find that there are a number of flares that appear to be correlated in at least two wavebands and generally in more. We choose two of these flares to study in further detail, and find that the hard and soft X-rays are well correlated in the first, and that the soft X-rays and radio are correlated in the second. In general, the optical and infrared show similar behaviour to each other, but are not correlated with the X-rays or radio. C1 Univ Sussex, Ctr Astron, CPES, Brighton BN1 9QJ, E Sussex, England. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Amsterdam, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. St Petersburg State Univ, Astron Inst, St Petersburg 198904, Russia. Moscow MV Lomonosov State Univ, Sternberg Astron Inst, Moscow 119899, Russia. Crimean Astrophys Observ, UA-334413 Nauchnyi, Crimea, Ukraine. Univ Cambridge, Cavendish Lab, Mullard Radio Astron Observ, Cambridge CB3 0HE, England. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Brocksopp, C (reprint author), Univ Sussex, Ctr Astron, CPES, Brighton BN1 9QJ, E Sussex, England. EM cb@star.cpes.susx.ac.uk OI Larionov, Valeri/0000-0002-4640-4356 NR 58 TC 111 Z9 115 U1 1 U2 3 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 11 PY 1999 VL 309 IS 4 BP 1063 EP 1073 DI 10.1046/j.1365-8711.1999.02919.x PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258KZ UT WOS:000083839500026 ER PT J AU Koekemoer, AM O'Dea, CP Sarazin, CL McNamara, BR Donahue, M Voit, GM Baum, SA Gallimore, JF AF Koekemoer, AM O'Dea, CP Sarazin, CL McNamara, BR Donahue, M Voit, GM Baum, SA Gallimore, JF TI The extended blue continuum and line emission around the central radio galaxy in Abell 2597 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : clusters : individual (A2597); galaxies : elliptical and lenticular, cD; galaxies : structure; radio continuum : galaxies; stars : formation ID CENTRAL CLUSTER GALAXIES; KINEMATICALLY DISTINCT CORES; HUBBLE-SPACE-TELESCOPE; RAY LUMINOUS CLUSTERS; COOLING FLOW GALAXIES; STAR-FORMATION; SURFACE PHOTOMETRY; MOLECULAR GAS; MINOR MERGERS; DARK MATTER AB We present results from detailed imaging of the centrally dominant radio elliptical galaxy in the cooling-flow cluster Abell 2597, using data obtained with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). This object is one of the archetypal "blue-lobed" cooling-flow radio elliptical galaxies, also displaying a luminous emission-line nebula, a compact radio source, and a significant dust lane and evidence of molecular gas in its center. We show that the radio source is surrounded by a complex network of emission-line filaments, some of which display a close spatial association with the outer boundary of the radio lobes. We present a detailed analysis of the physical properties of ionized and neutral gas associated with the radio lobes, and show that their properties are strongly suggestive of direct interactions between the radio plasma and ambient gas. We resolve the blue continuum emission into a series of knots and clumps, and present evidence that these are most likely due to regions of recent star formation. We investigate several possible triggering mechanisms for the star formation, including direct interactions with the radio source, filaments condensing from the cooling flow, or the result of an interaction with a gas-rich galaxy, which may also have been responsible for fueling the active nucleus. We propose that the properties of the source are plausibly explained in terms of accretion of gas by the cD during an interaction with a gas-rich galaxy, which, combined with the fact that this object is located at the centre of a dense, high-pressure intracluster medium, can account for the high rates of star formation and the strong confinement of the radio source. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. RP Koekemoer, AM (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. EM koekemoe@stsci.edu; odea@stsci.edu; cls7i@coma.astro.virginia.edu; brm@head-cfa.harvard.edu; donahue@stsci.edy; voit@stsci.edu; sbaum@stsci.edu; jgallimo@nrao.edu RI Donahue, Megan/B-5361-2012; OI Koekemoer, Anton/0000-0002-6610-2048 NR 87 TC 37 Z9 37 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP 621 EP 637 DI 10.1086/307911 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HP UT WOS:000083776700007 ER PT J AU Simpson, C Eisenhardt, P Armus, L Chokshi, A Dickinson, M Djorgovski, SG Elston, R Jannuzi, BT McCarthy, PJ Pahre, MA Soifer, BT AF Simpson, C Eisenhardt, P Armus, L Chokshi, A Dickinson, M Djorgovski, SG Elston, R Jannuzi, BT McCarthy, PJ Pahre, MA Soifer, BT TI Young stars and nonstellar emission in the aligned radio galaxy 3C 256 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (3C 256); galaxies : nuclei; galaxies : photometry; galaxies : stellar ID INFRARED STANDARD STARS; LUMINOSITY DEPENDENCE; REDSHIFT; ULTRAVIOLET; SCATTERING; ALIGNMENTS; 3C-256; MODELS; LINE; DUST AB We present ground-based images of the z=1.824 radio galaxy 3C 256 in the standard BVRIJHK filters and an interference filter centered at 8800 Angstrom, a Hubble Space Telescope image in a filter dominated by Ly alpha emission (F336W), and spectra covering rest-frame wavelengths from Lya to [O III] lambda 5007. Together with published polarimetry observations, we use these to decompose the overall spectral energy distribution into nebular continuum emission, scattered quasar light, and stellar emission. The nebular continuum and scattered light together comprise half (one-third) of the V-band (K-band) light within a 4 " aperture and are responsible for the strong alignment between the optical/near-infrared light and the radio emission. The stellar emission is dominated by a population estimated to be 100-200 Myr old (assuming a Salpeter IMF) and formed in a short burst with a peak star formation rate of 1-4 x 10(3) M. yr(-1). The total stellar mass is estimated to be no mote than 2 x 10(11) M., which is far less than other luminous radio galaxies at similar redshifts, and suggests that 3C 256 will undergo further star formation or mergers. C1 Natl Astron Observ Japan, Subaru Telescope, Hilo, HI 96720 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, SIRTF Sci Ctr, Pasadena, CA 91125 USA. CALTECH, Palomar Observ, Pasadena, CA 91125 USA. Indian Inst Astrophys, Bangalore 560034, Karnataka, India. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Simpson, C (reprint author), Natl Astron Observ Japan, Subaru Telescope, 650 N Aohoku Pl, Hilo, HI 96720 USA. NR 64 TC 7 Z9 7 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP 659 EP 672 DI 10.1086/307926 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HP UT WOS:000083776700010 ER PT J AU Figer, DF Kim, SS Morris, M Serabyn, E Rich, RM McLean, IS AF Figer, DF Kim, SS Morris, M Serabyn, E Rich, RM McLean, IS TI Hubble Space Telescope/NICMOS observations of massive stellar clusters near the Galactic center SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy : center; Galaxy : stellar content; open clusters and associations : general; stars : evolution; stars : formation; stars : luminosity function, mass function ID STAR-FORMATION; MILKY-WAY; DISCOVERY; GALAXY; YOUNG AB We report Nubble Space Telescope (HST) Near-Infrared Camera and Multiobject Spectrometer (NICMOS) observations of the Arches and Quintuplet clusters, two extraordinary young clusters near the Galactic center. For the first time, we have identified main-sequence stars in the Galactic center with initial masses well below 10 M.. We present the first determination of the initial mass function (IMF) for any population in the Galactic center, finding an IMF slope that is significantly more positive (Gamma approximate to -0.65) than the average for young clusters elsewhere in the Galaxy (Gamma approximate to -1.4). The apparent turn-offs in the color-magnitude diagrams suggest cluster ages that are consistent with the ages implied by the mixture of spectral types in the clusters; we find tau(age) similar to 2 +/- 1 Myr for the Arches cluster and tau(age) similar to 4 +/- 1 Myr for the Quintuplet. We estimate total cluster masses by adding the masses of observed stars down to the 50% completeness limit and then extrapolating down to a lower mass cutoff of 1 M.. Using this method, we find greater than or similar to 10(4) M. for the total mass of the Arches cluster. Such a determination for the Quintuplet cluster is complicated by the double-valued mass-magnitude relationship for clusters with ages greater than or similar to 3 Myr. We find a lower limit of 6300 M. for the total cluster mass and suggest a best estimate of twice this value, which accounts for the outlying members of the cluster. Both clusters have masses that place them as the two most massive young clusters in the Galaxy. C1 Univ Calif Los Angeles, Div Astron, Dept Phys & Astron, Los Angeles, CA 90095 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Korea Adv Inst Sci & Technol, Dept Phys, Space Sci Lab, Taejon 305701, South Korea. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Figer, DF (reprint author), Univ Calif Los Angeles, Div Astron, Dept Phys & Astron, Los Angeles, CA 90095 USA. RI Kim, Sungsoo/A-8601-2011 OI Kim, Sungsoo/0000-0002-5570-2160 NR 23 TC 309 Z9 310 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP 750 EP 758 DI 10.1086/307937 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HP UT WOS:000083776700019 ER PT J AU Figer, DF Morris, M Geballe, TR Rich, RM Serabyn, E McLean, IS Puetter, RC Yahil, A AF Figer, DF Morris, M Geballe, TR Rich, RM Serabyn, E McLean, IS Puetter, RC Yahil, A TI High-resolution infrared imaging and spectroscopy of the Pistol nebula: Evidence for ejection SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy : center; infrared : ISM : continuum; infrared : ISM : lines and bands; ISM : individual (G0.15-0.05) ID LUMINOUS BLUE VARIABLES; WOLF-RAYET STARS; GALACTIC-CENTER; INTERSTELLAR-MEDIUM; ETA-CARINAE; G0.18-0.04; ARC; RECONSTRUCTION; FILAMENTS; PICTURE AB We present new infrared images, obtained with the Hubble Space Telescope (HST) Near-Infrared Camera and Multiobject Spectrometer (NICMOS), and Br alpha (4.05 mu m) spectroscopy, obtained using CGS4 on UKIRT, of the Pistol Star and its associated nebula. We find strong evidence to support the hypothesis that the Pistol Nebula was ejected from the Pistol Star. The Pa alpha (1.87 mu m) NICMOS image shows that the nebula completely surrounds the Pistol Star, although the line intensity is much stronger on its northern and western edges. The Br alpha CGS4 spectra show the classical ringlike signature of quasi-spherical expansion. The blueshifted emission (V(max) approximate to -60 km s(-1)) is much weaker than the redshifted emission (V(max) approximate to + 10 km s(-1)), where the velocities are with respect to the velocity of the Pistol Star; further, the redshifted emission spans a very narrow range of velocities, i.e., it appears "flattened" in the position-velocity diagram. These data suggest that the nebula was ejected from the star several thousand years ago, with a velocity between the current terminal velocity of the stellar wind (95 km s(-1)) and the present expansion velocity of gas in the outer shell of the nebula (60 km s(-1)). The Pa alpha image reveals several emission-line stars in the region, including two newly identified emission-line stars north of the Pistol Star, both of which are likely to be the hottest known stars in the Galactic center with spectral types earlier than WC8 and T(eff) > 50,000 K). The presence of these stars, the morphology of the Pa alpha emission, and the velocity field in the gas suggest that the side of the nebula farthest from us is approaching, and being ionized by, the hot stars of the Quintuplet and that the highest velocity redshifted gas has been decelerated by winds from the Quintuplet stars. We also discuss the possibility that the nebular gas might be magnetically confined by the ambient magnetic field delineated by the nearby nonthermal filaments. C1 Univ Calif Los Angeles, Dept Phys & Astron, Div Astron, Los Angeles, CA 90095 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Inst Astrophys, F-75014 Paris, France. Gemini Observ, Hilo, HI 96720 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. RP Figer, DF (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Div Astron, 405 Hilgard Ave, Los Angeles, CA 90095 USA. EM figer@astro.ucla.edu; morris@astro.ucla.edu; tgeballe@gemini.edu; rmr@astro.ucla.edu; eserabyn@huey.jpl.nasa.gov; mclean@astro.ucla.edu; rpuetter@ucsd.edu; Amos.Yahil@sunysb.edu NR 39 TC 43 Z9 43 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP 759 EP 771 DI 10.1086/307927 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HP UT WOS:000083776700020 ER PT J AU Feibelman, WA AF Feibelman, WA TI The IUE spectra of the OVI sequence planetary nebulae NGC 2452, NGC 7026, M3-30, and LO 4 SO ASTROPHYSICAL JOURNAL LA English DT Article DE planetary nebulae : individual (NGC 2452, NGC 7026, M3-30, Lo 4); ultraviolet : ISM ID CENTRAL STAR; PULSATING NUCLEUS AB We present emission-line fluxes for NGC 2452, NGC 7026, M3-30, and Lo 4 from IUE low-dispersion spectra that have been processed by the New Spectral Image Processing System (NEWSIPS). For NGC 2452, a terminal wind velocity of - 4200 +/- 300 km s(-1) was determined from the C IV lambda 1549 P Cygni profile, while that of NGC 7026 is - 4600 +/- 300 km s(-1), and - 4800 +/- 400 km s(-1) for M3-30. The spectrum of Lo 4 is a stellar continuum with some absorptions and a questionable C IV lambda 1549 feature. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. EM feibelman@stars.gsfc.nasa.gov NR 51 TC 3 Z9 3 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP 863 EP 870 DI 10.1086/307943 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HP UT WOS:000083776700030 ER PT J AU Main, DS Smith, DM Heindl, WA Swank, J Leventhal, M Mirabel, IF Rodriguez, LF AF Main, DS Smith, DM Heindl, WA Swank, J Leventhal, M Mirabel, IF Rodriguez, LF TI Long-term X-ray monitoring of 1E 1740.7-2942 and GRS 1758-258 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; stars : individual (1E 1740.7-2942, GRS 1758-258); X-rays : stars ID BLACK-HOLE; SOURCE GRS-1758-258; MOLECULAR CLOUD; ACCRETION DISKS; CYGNUS X-1; 1E-1740.7-2942; 1E1740.7-2942; VARIABILITY; TRANSIENT; GRANAT AB We report on long-term observations of the Galactic bulge black hole candidates 1E 1740.7-2942 and GRS 1758-258 made with the Rossi X-Ray Timing Explorer; 1E 1740.7-2942 has been observed 77 times and GRS 1758-258 has been observed 82 times over the past 1000 days. The flux of each object has varied by no more than a factor of 2.5 during this period, and the indices of the energy spectra have varied by no more than 0.4. The power spectra ape similar to other black hole candidates: flat-topped noise, breaking to a power law. Each object has exhibited a brightening that lasted for several months, and we have a found a time lag between the photon power-law index and the count rate. In both sources, the spectrum is softest during the decline from the brightening. This behavior can be understood in the context of thin-disk and advection-dominated accretion flows coexisting over a wide range of radii, with the implication that both sources have low-mass companions and accrete via Roche lobe overflow. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. CEA Saclay, CEN, Serv Astrophys, F-91191 Gif Sur Yvette, France. Natl Autonomous Univ Mexico, Inst Astron, Mexico City 04510, DF, Mexico. RP Main, DS (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Swank, Jean/F-2693-2012 NR 41 TC 29 Z9 29 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP 901 EP 908 DI 10.1086/307935 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HP UT WOS:000083776700034 ER PT J AU Harding, AK Contopoulos, I Kazanas, D AF Harding, AK Contopoulos, I Kazanas, D TI Magnetar spin-down SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; magnetic fields; stars : neutron; stars : winds, outflows ID RAY REPEATER 1806-20; SOFT GAMMA-REPEATERS; X-RAY; NEUTRON-STARS; RADIO NEBULA; PULSAR; EMISSION; BURSTS AB We examine the effects of a relativistic wind on the spin-down of a neutron star and apply our results to the study of soft gamma repeaters (SGRs), which are thought to be neutron stars with magnetic fields greater than 10(14) G. We derive a spin-down formula that includes torques from both dipole radiation and episodic or continuous particle winds. We find that if SGR 1806-20 puts out a continuous particle wind of 10(37) ergs s(-1), then the pulsar age is consistent with that of the supernova remnant, but the derived surface dipole magnetic field is only 3 x 10(13) G, in the range of normal radio pulsars. If instead the particle wind flows are episodic with small duty cycle, then the observed period derivatives imply magnetar-strength fields, while still allowing characteristic ages within a factor of 2 of the estimated supernova remnant age. Close monitoring of the periods of SGRs will allow us to establish or place limits on the wind duty cycle and thus the magnetic field and age of the neutron star. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Harding, AK (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Harding, Alice/D-3160-2012 NR 23 TC 96 Z9 96 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP L125 EP L128 DI 10.1086/312339 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HQ UT WOS:000083776800015 ER PT J AU Jura, M Werner, MW AF Jura, M Werner, MW TI The detached dust shell around the massive star HD 179821 SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; stars : mass loss; stars : winds, outflows ID PROTO-PLANETARY-NEBULAE; ASYMPTOTIC GIANT BRANCH; CIRCUMSTELLAR ENVELOPES; PROTOPLANETARY NEBULAE; CONTINUUM EMISSION; EVOLVED STARS; HD-179821; OBJECTS; SUPERGIANTS; TRANSITION AB We have used the Keek I telescope to resolve at three mid-IR wavelengths the emission from HD 179821 (= RAFGL 2343), a G-type supergiant of perhaps 30 M. with a detached dust shell. The shell is very approximately circular in shape with an inner diameter of similar to 3 ".3, corresponding to 3.0 x 10(17) cm. We estimate that the star was losing similar to 4 x 10(-4) M. yr(-1) until about 1800 yr ago, when the mass loss slowed dramatically. During the past similar to 10(4) yr, the star has lost similar to 10% of its initial mass. The star lies about 0 ".35 off center and is closer to the brighter, northern hemisphere of the nebula, which can be explained if the outflow velocity V-infinity deviates by +20% from the average in the southern hemisphere and -20% from the average in the northern hemisphere. The mass-loss rate (M) over dot (theta) may have been inversely correlated with the outflow velocity so that the momentum outflow p was isotropic during the mass-loss phase. It also seems that MtotalVinfinity was within a factor of 2 of L-*/c, where L-* is the current luminosity of the star; the mass loss may have been driven by radiation pressure. These results may help characterize the asymmetric circumstellar winds into which supernova explosions propagate. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Jura, M (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NR 38 TC 33 Z9 33 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP L113 EP L116 DI 10.1086/312344 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HQ UT WOS:000083776800012 ER PT J AU Titarchuk, L Osherovich, V Kuznetsov, S AF Titarchuk, L Osherovich, V Kuznetsov, S TI Timing spectroscopy of quasi-periodic oscillations in the low-mass X-ray neutron star binaries SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (4U 1728-34, Scorpius X-1); stars : neutron; X-rays : bursts AB Precise simultaneous measurements of the frequencies of the two kilohertz quasi-periodic oscillations (referred in the literature as upper and lower kHz QPOs) cast doubts on the validity of the simple beat-frequency interpretation and some of the modifications introduced to explain the results of the varying frequency difference. A new model explains the variation of the frequency difference, suggesting that the upper Wt QPO, namely v(h), is an upper hybrid frequency of the Keplerian oscillator under the influence of the Coriolis force and the lower kHz QPO is the Keplerian frequency v(K). Such an oscillator has two branches characterized by a high frequency v(h) (similar to 1 kHz) and by a low frequency v(L) (similar to 50 Hz). The frequency v(L) depends strongly on the angle delta between the normal to the neutron star disk and Omega-the angular velocity of the magnetosphere surrounding the neutron star In the lower part of the QPO spectrum (similar to 10 Hz), this model identifies the frequency of radial viscous oscillations v(V) (previously called ''extra noise component") and the break frequency v(b), which is associated with the diffusive process in the transition region (the innermost part of the disk). According to this model, all frequencies (namely v(h), y(L), y(b), and v(V)) have specific dependences on v,. This Letter focuses on the verification of the predicted relations. For the source 4U 1728-34, the best theoretical fit is obtained for delta = 8 degrees.3 +/- 1 degrees.0, which is slightly larger than the value of delta = 5 degrees.5 +/- 0 degrees.5 previously found for Scorpius X-1. In addition, we show that the theoretically derived power-law relation v(b) proportional to v(V)(1.61) is consistent with the recent observations of other atoll and Z-sources. C1 NASA, Goddard Space Flight Ctr, RITSS, Greenbelt, MD 20771 USA. George Mason Univ, CSI, Fairfax, VA 22030 USA. Russian Acad Sci, Inst Space Res, High Energy Astrophys Dept, Moscow 117810, Russia. RP Titarchuk, L (reprint author), NASA, Goddard Space Flight Ctr, RITSS, Greenbelt, MD 20771 USA. NR 19 TC 38 Z9 39 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1999 VL 525 IS 2 BP L129 EP L132 DI 10.1086/312341 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 257HQ UT WOS:000083776800016 ER PT J AU Johnson, TJ Wilson, CR Chao, BF AF Johnson, TJ Wilson, CR Chao, BF TI Oceanic angular momentum variability estimated from the Parallel Ocean Climate Model, 1988-1998 SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID POLAR MOTION; CIRCULATION MODEL; EARTH; ROTATION; FLUCTUATIONS; ORIENTATION; EXCITATION; SIGNALS; LENGTH AB This paper describes the use of a global numerical model of the oceans to estimate variations in both the equatorial and axial components of angular momentum resulting from oceanic mass redistribution and circulation. The Parallel Ocean Climate Model, driven by daily wind fields and monthly heat fluxes from the European Gentle for Medium-Range Weather Forecasts for 1988-1998, provides insight into variations in the transport and exchange of angular momentum, a quantity which is essentially conserved within the Earth system. Exchange of angular momentum between the oceans and tl-Le solid Earth should be manifest as changes in the Earth's rotation (both polar motion and length of day), and it is possible to compare predicted Earth rotation changes with actual geodetic observations. Using an inverted barometer assumption for oceans, the numerical model predictions of rotation change agree in sign and magnitude and are significantly correlated with observed polar motion and length of day variations after subtracting the dominant atmospheric contributions. The correlation has a seasonal variation which suggests that the role of the oceans in the excitation polar motion is more important during the Northern Hemisphere summer. Our results indicate that the oceans, to a different extent, account for a significant part of the nonatmospheric angular momentum budget for the Earth, and its fluid envelopes on interannual to submonthly timescales. C1 Univ Texas, Dept Geol Sci, Ctr Space Res, Austin, TX USA. NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. NASA Headquarters, Washington, DC USA. RP Johnson, TJ (reprint author), USN Observ, Earth Orientat Dept, Washington, DC 20392 USA. EM tj@CasA.usno.navy.mil RI Chao, Benjamin Fong/N-6156-2013 NR 36 TC 52 Z9 54 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD NOV 10 PY 1999 VL 104 IS B11 BP 25183 EP 25195 DI 10.1029/1999JB900231 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 255DE UT WOS:000083653600002 ER PT J AU Liu, HS AF Liu, HS TI Insolation changes caused by combination of amplitude and frequency modulation of the obliquity SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID SOLAR-RADIATION VARIATIONS; GLACIAL CYCLES; STOCHASTIC RESONANCE; ORBITAL INCLINATION; CLIMATE MODELS; EARTHS ORBIT; TIME-SERIES; ICE AGES; PLEISTOCENE; EVOLUTION AB A forcing function is derived from the insolation signal with a bipolar pulse modulation train that is a function of Earth's obliquity. From this obliquity-forced insolation, there is a calculated variation of about +/-9% in the energy flux at the top of the atmosphere. Pulsations in the incoming solar radiation, induced by the amplitude-frequency coupling effect of the obliquity, correlate well with continental biogenic silica data and the marine oxygen isotope record. The theory lends a new perspective to the physical mechanism invoking climate change studies. Particularly, it provides a physical explanation of the 100-kyr cycle in glaciation, which Is distinct from the commonly considered variations in orbital ecentricity. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP Liu, HS (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. EM hanshou@denali.gsfs.nasa.gov NR 57 TC 7 Z9 8 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD NOV 10 PY 1999 VL 104 IS B11 BP 25197 EP 25206 DI 10.1029/1999JB900246 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 255DE UT WOS:000083653600003 ER PT J AU Hager, BH Lyzenga, GA Donnellan, A Dong, D AF Hager, BH Lyzenga, GA Donnellan, A Dong, D TI Reconciling rapid strain accumulation with deep seismogenic fault planes in the Ventura basin, California SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID WESTERN TRANSVERSE RANGES; LANDERS EARTHQUAKE SEQUENCE; 1994 NORTHRIDGE EARTHQUAKE; OAK-RIDGE FAULT; SOUTHERN-CALIFORNIA; CRUSTAL DEFORMATION; COSEISMIC DISPLACEMENTS; GEODETIC MEASUREMENT; KINEMATIC MODEL; SPACE AB Global Positioning System measurements across the east central Ventura basin, Transverse Ranges, southern California, before the nearby 1994 Northridge earthquake show high strain rates. Interpreting this rapid strain accumulation using the usual model of deep slip on a dislocation in a uniform elastic half-space requires slip to extend to within 5 km of the surface. Such shallow slip is difficult to reconcile with the substantial coseismic displacement at depths from 7 to 19 km during the Northridge earthquake. Here we model the displacement and velocity fields throughout the earthquake cycle using a two-dimensional finite element model with a viscoelastic theology. Displacements are driven by far-field and basal velocity boundary conditions and by imposed periodic earthquakes on the thrust faults bounding the basin. The thrust faults rupture through an elastic upper crust to a depth of 15 km. After a transient stage, during which stresses and strains build up to quasi-equilibrium values, the behavior of the model becomes periodic. The sum of the coseismic displacement divided by the repeat interval, plus the average interseismic velocity, is equal to the geologic velocity. The temporal variation in surface velocity depends mainly on the Elsasser relaxation time (proportional to the product of the Maxwell time of the lower crust and the ratio of the thicknesses of the entire crust and viscoelastic lower crust). We are able to match the observed high strain rate only if we include the observed variations in elastic modulus associated with the deep basin sediments. The model reconciles geologic, geodetic, and seismological observations of deformation. There are trade-offs among the far-field convergence rate, the Elsasser time, the earthquake repeat time, and the time into the earthquake cycle. Acceptable convergence rates range from 8 mm/yr, for a relaxation time of the lower crust of 300 years, to 12 mm/yr, for a 30-year relaxation time. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvey Mudd Coll, Dept Phys, Claremont, CA 91711 USA. RP Hager, BH (reprint author), MIT, Dept Earth Atmospher & Planetary Sci, 54-620, Cambridge, MA 02139 USA. EM brad@wegener.mit.edu; lyzenga@thuban.ac.hmc.edu; andrea@cobra.jpl.nasa.gov; dong@cobra.jpl.nasa.gov NR 43 TC 37 Z9 38 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD NOV 10 PY 1999 VL 104 IS B11 BP 25207 EP 25219 DI 10.1029/1999JB900184 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 255DE UT WOS:000083653600004 ER PT J AU Heinemann, J Stock, J Clayton, R Hafner, K Cande, S Raymond, C AF Heinemann, J Stock, J Clayton, R Hafner, K Cande, S Raymond, C TI Constraints on the proposed Marie Byrd Land-Bellingshausen plate boundary from seismic reflection data SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID TECTONIC HISTORY; SPREADING RATE; SEA-FLOOR; PACIFIC; ROUGHNESS; MOTION AB Single-channel and multichannel marine seismic data off the coast of West Antarctica collected during two Nathaniel B. Palmer cruises (NP92-8 and NP96-2) in the vicinity of 65 degrees S to 71 degrees S, 220 degrees E to 250 degrees E, reveal a NNW trending graben. We interpret this graben to be part of the paleodivergent plate boundary between the Marie Byrd Land and Bellingshausen plates. This graben coincides with a -520 nT magnetic anomaly to the NNW and a -720 nT anomaly to the SSE, as well as a 20 mGal negative gravity anomaly. Seismic profiles subparallel to the graben (22 km/Ma half-spreading rate) reveal greater seafloor roughness to the NE, where seafloor spreading was slower, than to the SW (27 km/Ma half-spreading rate). These data allow the position of the Marie Byrd Land-Bellingshausen plate boundary to be constrained more precisely than has previously been possible, with a trend of N17 degrees W from 68.52 degrees S, 233.65 degrees E to 68.41 degrees S, 233.56 degrees E. The sediment-filled graben has normal separation of sedimentary layers varying from 740 +/- 30 m to 580 +/- 20 m imaged in seafloor of age A33y (74 Ma). C1 CALTECH, Dept Geol & Geophys, Pasadena, CA 91125 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Heinemann, J (reprint author), CALTECH, Dept Geol & Geophys, 252-21 Wilson Ave, Pasadena, CA 91125 USA. EM jstock@gps.caltech.edu NR 22 TC 11 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD NOV 10 PY 1999 VL 104 IS B11 BP 25321 EP 25330 DI 10.1029/1998JB900079 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 255DE UT WOS:000083653600010 ER PT J AU Hulbe, CL MacAyeal, DR AF Hulbe, CL MacAyeal, DR TI A new numerical model of coupled inland ice sheet, ice stream, and ice shelf flow and its application to the West Antarctic Ice Sheet SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID MASS-BALANCE; DYNAMICS; VELOCITY; SENSITIVITY; DRAG AB We have developed a dynamic/thermodynamic finite element numerical model that couples inland ice sheet, ice stream, and ice shelf dynamics. This new model stands apart from other whole ice sheet models in its explicit treatment of ice stream flow. Additionally, the model accounts for both horizontal and vertical advection and diffusion of temperature in the flowing ice. In present day simulations of the West Antarctic Ice Sheet (WAIS), modeled ice velocity agrees well with observed ice flow. In particular, the model reproduces the pattern of speed variation across ice streams although the continuous downstream speed up of ice flow cannot be reproduced without concurrent downstream variation in basal friction. Model thermodynamics, evaluated qualitatively by model prediction of the spatial distribution of basal melting and quantitatively by comparison with ice temperature measured in boreholes at several locations, are sound. In particular, the model reproduces the broad pattern of frozen-bed inter-ice stream ridges and melted-bed ice streams. Model initialization for long-time simulations is somewhat limited by computation time and by a thermodynamic feedback at sites of large viscous heating that can be a problem in heat balance only model initializations. Methods for averting those initialization problems are discussed. The new model can accommodate a variety of boundary conditions (such as various bed rheologies) and is well-suited to investigate the origin and evolution of WAIS ice streams within the context of the whole ice sheet system. C1 Univ Chicago, Dept Geophys Sci, Chicago, IL 60637 USA. RP Hulbe, CL (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. EM chulbe@ice.gsfc.nasa.gov; drm7@midway.uchi-cago.edu NR 43 TC 45 Z9 46 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD NOV 10 PY 1999 VL 104 IS B11 BP 25349 EP 25366 DI 10.1029/1999JB900264 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 255DE UT WOS:000083653600012 ER PT J AU Mack, WJ Selzer, RH Lee, Z Li, YJ Hodis, HN AF Mack, WJ Selzer, RH Lee, Z Li, YJ Hodis, HN TI Vascular stiffness is adversely affected by passive smoke exposure in nonsmoking healthy adults SO CIRCULATION LA English DT Meeting Abstract C1 Univ So Calif, Los Angeles, CA USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 0009-7322 J9 CIRCULATION JI Circulation PD NOV 2 PY 1999 VL 100 IS 18 SU S MA 3560 BP 675 EP 676 PG 2 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA 250YD UT WOS:000083417103555 ER PT J AU Hodis, HN Mack, WJ Selhub, J LaBree, L Seizer, RH Liu, CR Li, YJ Lee, ZA Liu, CH Mahrer, PR AF Hodis, HN Mack, WJ Selhub, J LaBree, L Seizer, RH Liu, CR Li, YJ Lee, ZA Liu, CH Mahrer, PR TI Pasting total plasma homocysteine levels correlate with progression of subclinical atherosclerosis in healthy individuals without cardiovascular symptoms SO CIRCULATION LA English DT Meeting Abstract C1 Univ So Calif, Los Angeles, CA USA. Tufts Univ, USDA, Human Nutr Res Ctr Aging, Boston, MA 02111 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Kaiser Permanente Med Ctr, Los Angeles, CA 90034 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 0009-7322 J9 CIRCULATION JI Circulation PD NOV 2 PY 1999 VL 100 IS 18 SU S MA 4586 BP 869 EP 869 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA 250YD UT WOS:000083417104576 ER PT J AU Kinzie, KW McLaughlin, DK AF Kinzie, KW McLaughlin, DK TI Measurements of supersonic helium/air mixture jets SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/CEAS 4th Aeroacoustics Conference CY JUN 02-04, 1998 CL TOULOUSE, FRANCE SP AIAA, CEAS ID TURBULENT AB An enhanced method of using helium/air mixture jets to simulate the aeroacoustic properties of hot jets is presented. By using helium to reduce the jet density and to increase the jet acoustic speed, unheated nominal Mach 1.5 jets are tested that have jet-to-ambient density and acoustic speed ratios that approximately match those from a hot jet with a jet to-ambient static temperature ratio of 1.2. The jets are operated at a reduced Reynolds number (approximately 2.7 x 10(4)), which allows the use of diagnostic measurement tools such as hot-wire anemometry and active control via glow discharge excitation. Mean and fluctuating flowfield and acoustic measurements from a near perfectly expanded Mach 1.5 elliptic and round jet are presented. Direct comparisons of the cold and simulated heated jets are made. Compared to the pure air jets, the helium/air mixture jets showed increased instability wave phase speeds near or exceeding the ambient acoustic speed, increased noise levers, and increased coupling between the flowfield fluctuations and the radiated acoustic field. These features are consistent with the theory of Mach wave radiation, the dominant noise source in high-speed jets. The data presented show that the helium/air simulation is able to capture the dominant noise characteristics of actual heated jets. The use of this group of diagnostic measurement techniques is an added benefit of the simulation that is not available in conventional heated jet experiments. C1 GE, Aircraft Engines, Installat Aero Technol, Cincinnati, OH 45215 USA. Penn State Univ, Dept Aerosp Engn, University Pk, PA 16802 USA. RP Kinzie, KW (reprint author), NASA, Langley Res Ctr, Aerocoust Branch, MS 166, Hampton, VA 23681 USA. NR 14 TC 18 Z9 18 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1999 VL 37 IS 11 BP 1363 EP 1369 DI 10.2514/2.634 PG 7 WC Engineering, Aerospace SC Engineering GA 255AM UT WOS:000083647400003 ER PT J AU Niu, YY Liou, MS AF Niu, YY Liou, MS TI Numerical simulation of dynamic stall using an improved advection upwind splitting method SO AIAA JOURNAL LA English DT Article ID TURBULENCE AB In this study a dual-time integration method with the advection upwind splitting method based on nut difference (AUSMD) scheme is demonstrated with simplicity, robustness, and accuracy in solving the time-dependent full Navier-Stoke equations for aerodynamic analysis of stationary and oscillating airfoils. A pseudotime is introduced as an iteration strategy so that time accuracy Par solving the unsteady equations can be preserved for long time. A second-order, time-accurate, Euler backward implicit discretization is made at the physical time level. A two-stage Runge-Kutta scheme is used in the pseudotime iteration, in combination with acceleration enhancement procedures, the local time stepping, and residual smoothing. The recent AUSMD flux scheme with a slight modification is applied for approximating the inviscid terms. This modification has been Pound necessary to provide robust and accurate solutions far the study of dynamic stall. Meanwhile, the renormalization group theory model is chosen to evaluate the turbulence eddy viscosity. Both light and deep dynamic stall cases were calculated, along with grid refinement and time stepping size studies. Results of unsteady airload hysteresis curves and instantaneous flow pictures are analyzed and compared with measured data. C1 Chung Hua Univ, Dept Engn Mech, Hsinchu 30067, Taiwan. NASA, John H Glenn Res Ctr, Cleveland, OH 44135 USA. RP Niu, YY (reprint author), Chung Hua Univ, Dept Engn Mech, Hsinchu 30067, Taiwan. NR 29 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1999 VL 37 IS 11 BP 1386 EP 1392 PG 7 WC Engineering, Aerospace SC Engineering GA 255AM UT WOS:000083647400006 ER PT J AU Byun, C Farhangnia, M Guruswamy, GP AF Byun, C Farhangnia, M Guruswamy, GP TI Aerodynamic influence coefficient computations using Euler/Navier-Stokes equations on parallel computers SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 38th Structures, Structural Dynamics, and Materials Conference CY APR 07-10, 1997 CL KISSIMMEE, FLORIDA SP Amer Inst Aeronaut & Astronaut, ASME, ASCE, AHS, ASC ID UNSTEADY TRANSONIC-FLOWS AB An efficient procedure to compute aerodynamic influence coefficients (AICs), using high-fidelity how equations such as Euler/Navier-Stokes equations, is presented. The AICs are computed by perturbing structures using mode shapes. The procedure is developed on a multiple-instruction, multiple data parallel computer. In addition to discipline parallelization and coarse-grain parallelization of the flow domain, embarrassingly parallel implementation of ENSAERO code demonstrates linear speedup for a large number of processors. Demonstration of the AIC computation for static aeroelasticity analysis is made on an arrow wing-body configuration. Validation of the current procedure is made on a straight wing with arc airfoil at a subsonic region. The present flutter speed and frequency of the wing show excellent agreement with those results obtained by experiment and NASTRAN. The demonstrated linear scalability for multiple concurrent analyses shows that the three-level parallelism in the code is well suited for the computation of the AICs. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Byun, C (reprint author), Sun Microsyst Inc, Market Dev Engn, 901 San Antonio Rd, Palo Alto, CA 94303 USA. NR 28 TC 2 Z9 2 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1999 VL 37 IS 11 BP 1393 EP 1400 DI 10.2514/2.638 PG 8 WC Engineering, Aerospace SC Engineering GA 255AM UT WOS:000083647400007 ER PT J AU Nielsen, EJ Anderson, WK AF Nielsen, EJ Anderson, WK TI Aerodynamic design optimization on unstructured meshes using the Navier-Stokes equations SO AIAA JOURNAL LA English DT Article ID TURBULENT FLOWS; GRIDS; ALGORITHM AB A discrete adjoint method is developed and demonstrated for aerodynamic design optimization an unstructured grids. The governing equations are the three-dimensional Reynolds-averaged Navier-Stokes equations coupled with a one-equation turbulence model. A discussion of the numerical implementation of the flow and adjoint equations is presented. Both compressible and incompressible solvers are differentiated and the accuracy of the sensitivity derivatives is verified by comparing with gradients obtained using finite differences. several simplifying approximations to the complete linearization of the residual are also presented, and the resulting accuracy of the derivatives is examined. Demonstration optimizations for both compressible and incompressible flows are given. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Nielsen, EJ (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 35 TC 59 Z9 63 U1 1 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1999 VL 37 IS 11 BP 1411 EP 1419 DI 10.2514/2.640 PG 9 WC Engineering, Aerospace SC Engineering GA 255AM UT WOS:000083647400009 ER PT J AU Tucker, CJ Nicholson, SE AF Tucker, CJ Nicholson, SE TI Variations in the size of the Sahara Desert from 1980 to 1997 SO AMBIO LA English DT Article; Proceedings Paper CT World Conference on Science CY JUN 26, 1999 CL BUDAPEST, HUNGARY SP UNESCO, ICSU ID CANOPY REFLECTANCE; AVHRR DATA; SAHEL; VEGETATION; RAINFALL; DESERTIFICATION; PRODUCTIVITY; CALIBRATION; DROUGHT; INDEX AB Satellite data and ground rainfall measurements have been used to study variations in the size of the Sahara Desert from 1980 to 1997. Through a combination of the satellite and ground data, the 200 mm yr(-1) precipitation boundary was mapped for the Saharan-Sahelian region by year. Although highly significant year-to-year variation in the size of the Sahara Desert has occurred, no systematically increasing or decreasing trend from 1980 to 1997 was evident, The area of the Sahara Desert varied from 9 980 000 km(2) in 1984 to km(2) in 8 600 000 1994 and had an average 1980-1997 area of 9 150 000 km(2). C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32308 USA. RP Tucker, CJ (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Code 923, Greenbelt, MD 20771 USA. NR 47 TC 105 Z9 112 U1 0 U2 22 PU ROYAL SWEDISH ACAD SCIENCES PI STOCKHOLM PA PUBL DEPT BOX 50005, S-104 05 STOCKHOLM, SWEDEN SN 0044-7447 J9 AMBIO JI Ambio PD NOV PY 1999 VL 28 IS 7 BP 587 EP 591 PG 5 WC Engineering, Environmental; Environmental Sciences SC Engineering; Environmental Sciences & Ecology GA 267KM UT WOS:000084357200004 ER PT J AU Fox, NJ Cowley, SWH Davda, VN Enno, G Friis-Christensen, E Greenwald, RA Hairston, MR Lester, M Lockwood, M Luhr, H Milling, DK Murphree, JS Pinnock, M Reeves, GD AF Fox, NJ Cowley, SWH Davda, VN Enno, G Friis-Christensen, E Greenwald, RA Hairston, MR Lester, M Lockwood, M Luhr, H Milling, DK Murphree, JS Pinnock, M Reeves, GD TI A multipoint study of a substorm occurring on 7 December, 1992, and its theoretical implications SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Article DE ionosphere (auroral ionosphere; plasma; convection); magnetospheric physics (storms and substorms) ID ENERGETIC PARTICLE MEASUREMENTS; CONVECTION PATTERNS; MAGNETOSPHERE; IONOSPHERE; 6.6-RE; RADARS AB On 7 December 1992, a moderate substorm was observed by a variety of satellites and ground-based instruments. Ionospheric flows were monitored near dusk by the Goose Bay HF radar and near midnight by the EISCAT radar. The observed flows are compared here with magnetometer observations by the IMAGE array in Scandinavia and the two Greenland chains, the auroral distribution observed by Freja and the substorm cycle observations by the SABRE radar, the SAMNET magnetometer array and LANL geosynchronous satellites. Data from Galileo Earth-encounter II are used to estimate the IMF B-z component. The data presented show that the substorm onset electrojet at midnight was confined to closed field lines equatorward of the preexisting convection reversal boundaries observed in the dusk and midnight regions. No evidence of substantial closure of open flux was detected following this substorm onset. Indeed the convection reversal boundary on the duskside continued to expand equatorward after onset due to the continued presence of strong southward IMF, such that growth and expansion phase features were simultaneously present. Clear indications of closure of open flux were not observed until a subsequent substorm intensification 25 min after the initial onset. After this time, the substorm auroral bulge in the nightside hours propagated well poleward of the pre-existing convection reversal boundary, and strong flow perturbations were observed by the Goose Bay radar, indicative of flows driven by reconnection in the tail. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Leicester, Dept Phys, Leicester LE1 7RH, Leics, England. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. Univ Calgary, Dept Phys & Astron, Calgary, AB T2N 1N4, Canada. Danish Space Res Inst, DK-2100 Copenhagen, Denmark. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Texas, Richardson, TX 75080 USA. Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany. Univ York, Dept Phys, York YO1 5DD, N Yorkshire, England. British Antarctic Survey, Cambridge CB3 0ET, England. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Fox, NJ (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Lockwood, Mike/G-1030-2011; Reeves, Geoffrey/E-8101-2011; Fox, Nicola/P-6692-2016; OI Lockwood, Mike/0000-0002-7397-2172; Reeves, Geoffrey/0000-0002-7985-8098; Fox, Nicola/0000-0003-3411-4228; Hairston, Marc/0000-0003-4524-4837; Greenwald, Raymond/0000-0002-7421-5536 NR 31 TC 14 Z9 14 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0992-7689 J9 ANN GEOPHYS-ATM HYDR JI Ann. Geophys.-Atmos. Hydrospheres Space Sci. PD NOV PY 1999 VL 17 IS 11 BP 1369 EP 1384 DI 10.1007/s005850050863 PG 16 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA 259DE UT WOS:000083878000002 ER PT J AU White, RA Bliton, H Bhavsar, SP Bornmann, P Burns, JO Ledlow, MJ Loken, C AF White, RA Bliton, H Bhavsar, SP Bornmann, P Burns, JO Ledlow, MJ Loken, C TI A catalog of nearby poor clusters of galaxies SO ASTRONOMICAL JOURNAL LA English DT Article DE catalogs; galaxies : clusters : general ID RICH CLUSTERS; CD GALAXIES AB A catalog of 732 optically selected, nearby poor clusters of galaxies covering the entire sky north of -3 degrees declination is presented. The poor clusters, called WBL clusters, were identified as concentrations of three or more galaxies with photographic magnitudes brighter than 15.7, possessing a galaxy surface overdensity of 10(4/3). These criteria are consistent with those used in the identification of the original Yerkes poor clusters, and this new catalog substantially increases the sample size of such objects. These poor clusters cover the entire range of galaxy associations up to and including Abell clusters, systematically including poor and rich galaxy systems spanning over 3 orders of magnitude in the cluster mass function. As a result, this new catalog contains a greater diversity of richness and structures than other group catalogs, such as the Hickson and Yerkes catalogs. The information on individual galaxies includes redshifts and cross-references to other galaxy catalogs. The entries for the clusters include redshift (where available) and cross-references to other group and cluster catalogs. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. Univ Missouri, Dept Phys & Astron, Columbia, MO 65211 USA. Univ New Mexico, Dept Phys & Astron, Albuquerque, NM 87131 USA. RP White, RA (reprint author), NASA, Goddard Space Flight Ctr, Code 631, Greenbelt, MD 20771 USA. NR 21 TC 58 Z9 58 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1999 VL 118 IS 5 BP 2014 EP 2037 DI 10.1086/301103 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264LB UT WOS:000084182800009 ER PT J AU Dale, DA Helou, G Silbermann, NA Contursi, A Malhorta, S Rubin, RH AF Dale, DA Helou, G Silbermann, NA Contursi, A Malhorta, S Rubin, RH TI Toward an understanding of the mid-infrared surface brightness of normal galaxies SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : individual (IC 10, NGC 1313, NGC 6946); galaxies : ISM ID INTERSTELLAR MATTER; ISOCAM OBSERVATIONS; SPIRAL GALAXIES; LOCAL GROUP; H-I; EMISSION; IC-10; NGC-6946; NGC-1313; TRANSITION AB We report a mid-infrared color and surface brightness analysis of IC 10, NGC 1313, and NGC 6946, three of the nearby galaxies studied under the Infrared Space Observatory Key Project on Normal Galaxies. Images with less than 9 " (170 pc) resolution of these nearly face-on, late-type galaxies were obtained using the LW2 (6.75 mu m) and LW3 (15 mu m) ISOCAM filters. Although their global flux ratios are similar and typical of normal galaxies, they show distinct trends of this color ratio with mid-infrared surface brightness. We find that I-v(6.75 mu m)/I-v(15 mu m) less than or similar to 1 only occurs for regions of intense heating activity where the continuum rises at 15 mu m and where polycyclic aromatic hydrocarbon destruction can play an important role. The shape of the color-surface brightness trend also appears to depend, to the second order, on the hardness of the ionizing radiation. We discuss these findings in the context of a two-component model for the phases of the interstellar medium and suggest that star formation intensity is largely responsible for the mid-infrared surface brightness and colors within normal galaxies, whereas differences in dust column density are the primary drivers of variations in the mid-infrared surface brightness between the disks of normal galaxies. C1 CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Kitt Peak Natl Observ, Natl Opt Astron Observ, Tucson, AZ 85726 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dale, DA (reprint author), CALTECH, Ctr Infrared Proc & Anal, MS 100-22, Pasadena, CA 91125 USA. NR 53 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1999 VL 118 IS 5 BP 2055 EP 2064 DI 10.1086/301110 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264LB UT WOS:000084182800011 ER PT J AU Hutchings, JB Crenshaw, DM Danks, AC Gull, TR Kraemer, SB Nelson, CH Weistrop, D Kaiser, ME Joseph, CL AF Hutchings, JB Crenshaw, DM Danks, AC Gull, TR Kraemer, SB Nelson, CH Weistrop, D Kaiser, ME Joseph, CL TI High-velocity line emission in the narrow-line region of NGC 4151 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 4151); galaxies : Seyfert AB Narrowband imaging of the nuclear region of NGC 4151 with the Hubble Space Telescope is presented. The filter bandpasses isolate line emission in various high-velocity ranges in several ions. Slitless and long-slit spectra of the region with the Space Telescope Imaging Spectrograph also indicate the locations of high-velocity gas. These emission regions are faint and interspersed among the bright emission clouds seen in direct images. They have radial velocities up to 1400 km s(-1) relative to the nucleus and are found in both approach and recession on both sides of the nucleus. This contrasts strongly with the bright emission-line clouds, which have been discussed previously as showing bidirectional outflow with velocities within 400 km s(-1) of the nucleus. We discuss the possible connections of the high-velocity material with the radio jet and the nuclear radiation. C1 Natl Res Council Canada, Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Nevada, Dept Phys, Las Vegas, NV 89154 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RP Hutchings, JB (reprint author), Natl Res Council Canada, Dominion Astrophys Observ, 5071 W Saanich Rd, Victoria, BC V8X 4M6, Canada. RI Gull, Theodore/D-2753-2012 OI Gull, Theodore/0000-0002-6851-5380 NR 11 TC 23 Z9 23 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1999 VL 118 IS 5 BP 2101 EP 2107 DI 10.1086/301076 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264LB UT WOS:000084182800014 ER PT J AU Holtzman, JA Gallagher, JS Cole, AA Mould, JR Grillmair, CJ Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Griffiths, RE Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Watson, AM AF Holtzman, JA Gallagher, JS Cole, AA Mould, JR Grillmair, CJ Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Griffiths, RE Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Watson, AM TI Observations and implications of the star formation history of the large magellanic cloud SO ASTRONOMICAL JOURNAL LA English DT Article DE magellanic clouds ID STELLAR POPULATIONS; LOCAL GROUP; AGE; GALAXIES; CLUSTERS; PERFORMANCE; CALIBRATION; MODELS; WFPC2; OLD AB We present derivations of star formation histories based on color-magnitude diagrams of three fields in the LMC from HST/WFPC2 observations. One held is located in the LMC bar and the other two are in the outer disk. We find that a significant component of stars older than 4 Gyr is required to match the observed color-magnitude diagrams. Models with a dispersion-free age-metallicity relation are unable to reproduce the width of the observed main sequence; models with a range of metallicity at a given age provide a much better fit. Such models allow us to construct complete "population boxes" for the LMC based entirely on color-magnitude diagrams; remarkably, these qualitatively reproduce the age-metallicity relation observed in LMC clusters. We discuss some of the uncertainties in deriving star formation histories by our method and suggest that improvements and confidence in the method will be obtained by independent metallicity determinations. We find, independently of the models, that the LMC bar held has a larger relative component of older stars than the outer fields. The main implications suggested by this study are: (1) The star formation history of field stars appears to differ from the age distribution of clusters. (2) There is no obvious evidence for bursty star formation, but our ability to measure bursts shorter in duration than about 25% of any given age is limited by the statistics of the observed number of stars. (3) There may be some correlation of the star formation rate with the last close passage of the LMC/SMC/Milky Way, but there is no dramatic effect. (4) the derived star formation history is probably consistent with observed abundances, based on recent chemical evolution models. C1 New Mexico State Univ, Dept Astron, Dept 4500, Las Cruces, NM 88003 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. CALTECH, SIRTF Sci Ctr, Pasadena, CA 91125 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. European Space Agcy, Div Space Sci, Div Astrophys, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. RP Holtzman, JA (reprint author), New Mexico State Univ, Dept Astron, Dept 4500, POB 30001, Las Cruces, NM 88003 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013; OI Cole, Andrew/0000-0003-0303-3855 NR 32 TC 143 Z9 144 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1999 VL 118 IS 5 BP 2262 EP 2279 DI 10.1086/301097 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264LB UT WOS:000084182800025 ER PT J AU Creech-Eakman, MJ Kulkarni, SR Pan, XP Shaklan, SB AF Creech-Eakman, MJ Kulkarni, SR Pan, XP Shaklan, SB TI Photometric measurements of the fields of more than 700 nearby stars SO ASTRONOMICAL JOURNAL LA English DT Article DE surveys; techniques : interferometric; techniques : photometric AB In preparation for optical/IR interferometric searches for substellar companions of nearby stars, we undertook to characterize the fields of all nearby stars visible from the Northern Hemisphere to determine suitable companions for interferometric phase referencing. Because the Keck Interferometer in particular will be able to phase-reference on companions within the isoplanatic patch (30 ") to about 17th magnitude at K, we took images at V, r, and i that were deep enough to determine if field stars were present to this magnitude around nearby stars using a spot-coated CCD. We report on 733 fields containing 10,629 measurements in up to three filters (Gunn i, r and Johnson V) of nearby stars down to about 13th magnitude at V. C1 CALTECH, Dept Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Dept Astron, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Creech-Eakman, MJ (reprint author), CALTECH, Dept Geol & Planetary Sci, Mail Stop 150-21, Pasadena, CA 91125 USA. NR 11 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1999 VL 118 IS 5 BP 2483 EP 2487 DI 10.1086/301094 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 264LB UT WOS:000084182800043 ER PT J AU Moehler, S Sweigart, AV Catelan, M AF Moehler, S Sweigart, AV Catelan, M TI Blue horizontal branch stars in metal-rich globular clusters I. NGC 6388 and NGC 6441 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : early-type; stars : fundamental parameters; stars : horizontal-branch; Galaxy : globular clusters : individual : NGC 6388; Galaxy : globular clusters : individual : NGC 6441 ID ELLIPTIC GALAXIES; ULTRAVIOLET UPTURN; WHITE-DWARFS; PARAMETERS; EVOLUTION; AGES AB We report the first results of an ongoing spectroscopic survey of blue horizontal branch stars in the metal-rich ([Fe/H] similar or equal to -0.5) globular clusters NGC 6388 and NGC 6441. Based on data obtained with the ESO-New Technology Telescope (NTT), we provide gravities and temperatures for four stars in NGC 6388 and three stars in NGC 6441. These results are marginally inconsistent with the predictions of canonical evolutionary theory, but disagree strongly with all non-canonical scenarios that explain the sloped horizontal branches seen in the colour-magnitude diagrams of these clusters. C1 Univ Erlangen Nurnberg, Astron Inst, D-96049 Bamberg, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Moehler, S (reprint author), Univ Erlangen Nurnberg, Astron Inst, Sternwartstr 7, D-96049 Bamberg, Germany. EM ai13@sternwarte.uni-erlangen.de; sweigart@bach.gsfc.nasa.gov; catelan@virginia.edu NR 37 TC 28 Z9 28 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1999 VL 351 IS 2 BP 519 EP 525 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 260UU UT WOS:000083972500017 ER PT J AU Fioc, M Rocca-Volmerange, B AF Fioc, M Rocca-Volmerange, B TI A statistical study of nearby galaxies - I. NIR growth curves and optical-to-NIR colors as a function of type, luminosity and inclination SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE galaxies : evolution; galaxies : fundamental parameters; galaxies : photometry; galaxies : statistics; infrared : galaxies; ISM : dust, extinction ID BAND SURFACE PHOTOMETRY; DISK DOMINATED GALAXIES; MAGNITUDE RELATION; SPIRAL GALAXIES; ELLIPTIC GALAXIES; BRIGHT GALAXIES; EVOLUTION; STELLAR; REDUCTION; CLUSTERS AB Growth curves of the near-infrared (NIR) magnitude as a function of the aperture have been built and used to derive NIR total magnitudes from aperture data taken from the literature. By cross-correlating with optical and redshift data, absolute magnitudes and optical-to-NIR colors have been computed for some 1000 galaxies of different types. Significant color gradients are observed, underlining that small aperture colors may lead to a biased picture of the stellar populations of galaxies. A statistical analysis, using various estimators taking into account the intrinsic scatter, has been performed to establish relations between the colors, the morphological type, the inclination or the shape, and the intrinsic luminosity. The combination of the optical and the NIR should obviously improve our understanding of the evolution of galaxies. Despite the intrinsic scatter, especially among star-forming galaxies, optical-to-NIR colors show a very well defined sequence with type, blueing by 1.35 mag from ellipticals to irregulars. The colors of spiral galaxies strongly redden with increasing inclination and put new constraints on the modeling of the extinction. No such effect is observed for lenticular galaxies. We also find that rounder ellipticals tend to be redder. A color-absolute magnitude relation is observed inside each type, with a slept significantly steeper for early and intermediate spirals than for ellipticals or late spirals. This stresses the importance of considering both the mass and the type to study the star formation history of galaxies. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CNRS, Inst Astrophys Paris, F-75014 Paris, France. Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. RP Fioc, M (reprint author), NASA, Goddard Space Flight Ctr, Code 685, Greenbelt, MD 20771 USA. EM fioc@zardoz.gsfc.nasa.gov NR 62 TC 63 Z9 63 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1999 VL 351 IS 3 BP 869 EP 882 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 262LG UT WOS:000084068300013 ER PT J AU Oosterbroek, T Orlandini, M Parmar, AN Angelini, L Israel, GL Dal Fiume, D Mereghetti, S Santangelo, A Cusumano, G AF Oosterbroek, T Orlandini, M Parmar, AN Angelini, L Israel, GL Dal Fiume, D Mereghetti, S Santangelo, A Cusumano, G TI Discovery of a faint 437 s X-ray pulsar 1SAXJ1452.8-5949 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE X-rays : stars; stars : individual : 1SAXJ1452.8-5939; stars : neutron; stars : binaries : close; accretion, accretion disks C1 European Space Agcy, Estec, Dept Space Sci, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. CNR, Ist Tesre, I-40129 Bologna, Italy. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Osservatorio Astron Roma, I-00040 Monte Porzio Catone, Italy. CNR, Ist Fis Cosm G Occhialini, I-20133 Milan, Italy. CNR, IFCAI, I-90146 Palermo, Italy. RP Oosterbroek, T (reprint author), European Space Agcy, Estec, Dept Space Sci, Div Astrophys, Postbus 299, NL-2200 AG Noordwijk, Netherlands. RI Orlandini, Mauro/H-3114-2014 OI Orlandini, Mauro/0000-0003-0946-3151 NR 21 TC 11 Z9 11 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1999 VL 351 IS 3 BP L33 EP L36 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 262LG UT WOS:000084068300001 ER PT J AU Alcolea, J Pardo, JR Bujarrabal, V Bachiller, R Barcia, A Colomer, F Gallego, JD Gomez-Gonzalez, J del Pino, A Planesas, P del Rio, S Rodriguez-Franco, A del Romero, A Tafalla, M de Vicente, P AF Alcolea, J Pardo, JR Bujarrabal, V Bachiller, R Barcia, A Colomer, F Gallego, JD Gomez-Gonzalez, J del Pino, A Planesas, P del Rio, S Rodriguez-Franco, A del Romero, A Tafalla, M de Vicente, P TI Six years of short-spaced monitoring of the v=1 and v=2, J=1-0 (SiO)-Si-28 maser emission in evolved stars SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE masers; stars : AGB; circumstellar matter; stars : late-type; stars : variables; radio-lines : stars ID POLARIZATION PROPERTIES; OMICRON-CETI; VARIABLES; ENVELOPES; ORION AB We present the results from a monitoring of the upsilon = 1 and upsilon = 2, J = 1-0 (SiO)-Si-28 maser emission in 21 objects, covering all types of known SiO maser emitters: 13 Mira variables, 2 long period semiregulars (SRGs), 3 variable supergiants (SGs), 2 OH/IR stars, and one young stellar object. This study has been carried out with the 13.7 meter radiotelescope of the Centro Astronomico de Yebes (Guadalajara, Spain), from July 1984 to May 1990, and represents the longest and most tightly sampled monitoring of SiO masers ever published. Our data show that for Mira-type (i.e. regular) variables, the SiO and optical light curves agree in period, and that the maxima of the SiO emission lag the optical ones by about 0.1 - 0.2 periods. Since a similar lag characterizes the near infrared (NIR) emission variability from these stars, we conclude that for regular variables SiO and NIR vary in phase. This result was confirmed in three objects for which NIR variability curves are available. For SRGs and SGs, we found a less systematic behavior, but when the SiO emission is periodic, its variability curve agrees with the optical one, also showing a lag between maximum epochs similar to that of Mira-type stars. The data clearly reveal other interesting details on the SiO maser variability, such as the strong intensity differences between different maxima and changes in the velocity distribution of the emission. Finally the SiO masers associated to the young stellar object Orion IRc2 showed a double peaked spectrum with low amplitude, aperiodic variations. C1 Observ Astron Nacl, E-28800 Alcala De Henares, Spain. Observ Paris Meudon, DEMIRM, F-75014 Paris, France. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Complutense Madrid, Escuela Univ Opt, Secc Dept Opt, Dept Matemat Aplicad Biomatemat 2, E-28037 Madrid, Spain. Univ Alcala de Henares, Dept Fis, E-28871 Alcala De Henares, Spain. RP Alcolea, J (reprint author), Observ Astron Nacl, Apartado 1143, E-28800 Alcala De Henares, Spain. RI Planesas, Pere/G-7950-2015 OI Planesas, Pere/0000-0002-7808-3040 NR 22 TC 34 Z9 34 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD NOV PY 1999 VL 139 IS 3 BP 461 EP 482 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 259MP UT WOS:000083897900003 ER PT J AU Prosser, CF Kennicutt, RC Bresolin, F Saha, A Sakai, S Freedman, WL Mould, JR Ferrarese, L Ford, HC Gibson, BK Graham, JA Hoessel, JG Huchra, JP Hughes, SM Illingworth, GD Kelson, DD Macri, L Madore, BF Silbermann, NA Stetson, PB AF Prosser, CF Kennicutt, RC Bresolin, F Saha, A Sakai, S Freedman, WL Mould, JR Ferrarese, L Ford, HC Gibson, BK Graham, JA Hoessel, JG Huchra, JP Hughes, SM Illingworth, GD Kelson, DD Macri, L Madore, BF Silbermann, NA Stetson, PB TI The Hubble Space Telescope key project on the extragalactic distance scale. XXII. The discovery of Cepheids in NGC 1326A SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies : distances and redshifts; galaxies : individual (NGC 1326A) ID FORNAX CLUSTER; PHOTOMETRY; GALAXIES; PERFORMANCE; CALIBRATION; EXTINCTION; WFPC2 AB We report on the detection of Cepheids and the first distance measurement to the spiral galaxy NGC 1326A, a member of the Fornax Cluster of galaxies. We have employed data obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Over a 49 day interval, a total of 12 V-band (F555W) and eight I-band (F814W) epochs of observation were obtained. Two photometric reduction packages, ALLFRAME and DoPHOT, have been employed to obtain photometry measures from the three Wide Field CCDs. Variability analysis yields a total of 17 Cepheids in common with both photometry data sets, with periods ranging between 10 and 50 days. Of these, 14 Cepheids with high-quality light curves are used to fit the V and I period-luminosity relations and derive apparent distance moduli, assuming a Large Magellanic Cloud distance modulus mu(LMC) = 18.50 +/- 0.10 mag and color excess E(B-V) = 0.10 mag. Assuming A(V)/E(V-I) = 2.45, the DoPHOT data yield a true distance modulus to NGC 1326A of mu(0) = 31.36 +/- 0.17(random) +/- 0.13(systematic) mag, corresponding to a distance of 18.7 +/- 1.5(random) +/- 1.2(systematic) Mpc. The derived distance to NGC 1326A is in good agreement with the distance derived previously to NGC 1365, another spiral galaxy member of the Fornax Cluster. However, the distances to both galaxies are significantly lower than that to NGC 1425, a third Cepheid calibrator in the outer parts of the cluster. C1 Natl Opt Astron Observ, Tucson, AZ 85726 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. European So Observ, D-8046 Garching, Germany. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia. CALTECH, Dept Astron, Pasadena, CA 91125 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. CALTECH, Pasadena, CA 91125 USA. NASA IPAC Extragalact Database, Pasadena, CA 91125 USA. CALTECH, IPAC, Pasadena, CA 91125 USA. Natl Res Council Canada, Herzberg Inst Astrophys, Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 37 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 80 EP 104 DI 10.1086/307899 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900008 ER PT J AU Ho, LC Ptak, A Terashima, Y Kunieda, H Serlemitsos, PJ Yaqoob, T Koratkar, AP AF Ho, LC Ptak, A Terashima, Y Kunieda, H Serlemitsos, PJ Yaqoob, T Koratkar, AP TI X-ray properties of the weak Seyfert 1 nucleus in NGC 4639 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NCC4639); galaxies : nuclei; galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; H-ALPHA EMISSION; ASCA OBSERVATIONS; GALAXIES; VARIABILITY; SEARCH; SPECTRUM; QUASARS; LINES; AGN AB Low-luminosity active galactic nuclei (AGNs), of which NGC 4639 is a good example, constitute an important but poorly understood constituent of the nearby galaxy population. We obtained observations of NGC 4639 with ASCA in order to investigate its mildly active Seyfert 1 nucleus at hard X-ray energies. Koratkar et al. have previously shown that the nucleus is a pointlike source in the ROSAT soft X-ray band. We detected in the 2-10 keV band a compact central source with a luminosity of 8.3 x 10(40) ergs s(-1) (for an adopted distance of 25.1 Mpc). Comparison of the ASCA data with archival data taken with the Einstein and ROSAT satellites shows that the nucleus varies on timescales of months to years. The variability could be intrinsic, or it could be caused by variable absorption. More rapid variability, on a timescale of similar to 10(4) s, may be present in the ASCA data. The spectrum from 0.5 to 10 keV is well described by a model consisting of a lightly absorbed (N-H = 7.3 x 10(20) cm(-2)) power law with a photon index of Gamma = 1.68 +/- 0.12. We find no evidence far significant emission from a thermal plasma; if present, it can account for no more than similar to 25% of the flux in the 0.5-2.0 keV band. The limited photon statistics of our data do not allow us to place significant limits on the presence of iron K emission. Despite its low luminosity, the X-ray properties of the nucleus of NGC 4639 appear quite normal compared with those of more luminous AGNs. The strength of its broad H alpha line follows the correlation between broad H alpha luminosity and hard X-ray luminosity that was previously known for luminous objects. Images taken with the Hubble Space Telescope detected the nucleus in the ultraviolet at a strength relative to the X-ray band that appears to be quite typical of that found in other AGNs. NGC 5033, another low-luminosity Seyfert 1 galaxy with optical characteristics that closely resemble those of NGC 4639, has also been studied recently with ASCA, and we highlight some of the similarities between these two objects. C1 Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Nagoya Univ, Dept Astrophys, Nagoya, Aichi 46401, Japan. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Ho, LC (reprint author), Carnegie Inst Washington Observ, 813 Santa Barbara St, Pasadena, CA 91101 USA. NR 44 TC 14 Z9 14 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 168 EP 175 DI 10.1086/307898 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900013 ER PT J AU Piner, BG Unwin, SC Wehrle, AE Edwards, PG Fey, AL Kingham, KA AF Piner, BG Unwin, SC Wehrle, AE Edwards, PG Fey, AL Kingham, KA TI VSOP and ground-based VLBI imaging of the TeV blazar Markarian 421 at multiple epochs SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (Markarian 421); galaxies : active; galaxies : jets; radiation mechanisms : nonthermal; radio continuum : galaxies techniques : interferometric ID ACTIVE GALACTIC NUCLEI; LACERTAE OBJECT MARKARIAN-421; RADIO REFERENCE FRAME; GAMMA-RAY EMISSION; SELF-COMPTON MODEL; BL-LACERTAE; X-RAY; MILLIARCSECOND STRUCTURE; GALAXY MARKARIAN-421; SUPERLUMINAL MOTION AB We present 30 VLBI images of the TeV blazer Markarian 421 (1101 + 384) at 15 epochs spanning the time range 1994-1997 and at six different frequencies from 2.3 to 43 GHz. The imaged observations include a high-resolution 5 GHz VLBI Space Observatory Programme (VSOP) observation with the HALCA satellite on 1997 November 14; full-track Very Long Base Array (VLBA) observations from 1994 April, 1996 November, and 1997 May at frequencies between 5 and 43 GHz; six epochs of VLBA snapshot observations at frequencies between 2 and 15 GHz from Radio Reference Frame studies; and five geodetic VLBI observations at 2 and 8 GHz from the archive of the Washington VLBI Correlator Facility located at the US Naval Observatory. The dense time coverage of the images allows us to track components unambiguously in the parsec-scale jet over the observed time range. We measure the speeds of three inner jet components located between 0.5 and 5 mas from the core (0.3-3 pc projected linear distance) to be 0.19 +/- 0.27c, 0.30 +/- 0.07c, and -0.07 +/- 0.07c (H-0 = 65 km s(-1) Mpc(-1)). If the sole 43 GHz image is excluded, all measured speeds are consistent with no motion. These speeds differ from tentative superluminal speeds measured by Zhang & Baath from three epochs of data from the early 1980s. Possible interpretations of these subluminal speeds in terms of the high Doppler factor demanded by the TeV variability of this source are discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. USN Observ, Earth Orientat Dept, Washington, DC 20392 USA. RP Piner, BG (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 71 TC 44 Z9 45 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 176 EP 190 DI 10.1086/307905 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900014 ER PT J AU Lin, YC Bertsch, DL Bloom, SD Esposito, JA Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Mayer-Hasselwander, HA Michelson, PF Mukherjee, R Mucke, A Nolan, PL Pohl, M Reimer, O Schneid, EJ Thompson, DJ Tompkins, WF AF Lin, YC Bertsch, DL Bloom, SD Esposito, JA Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Mayer-Hasselwander, HA Michelson, PF Mukherjee, R Mucke, A Nolan, PL Pohl, M Reimer, O Schneid, EJ Thompson, DJ Tompkins, WF TI EGRET spectral index and the low-energy peak position in the spectral energy distribution of EGRET-detected blazars SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; gamma rays : theory; radiation mechanisms : nonthermal; X-rays : galaxies ID BL-LACERTAE; MULTIWAVELENGTH OBSERVATIONS; GAMMA-RAYS; FLARE AB In current theoretical models of the blazar subclass of active galaxies, the broadband emission consists of two components: a low-frequency synchrotron component with a peak in the IR to X-ray band and a high-frequency inverse Compton component with a peak in the gamma-ray band. In such models, the gamma-ray spectral index should be correlated with the location of the low-energy peak, with flatter gamma-ray spectra expected for blazars with synchrotron peaks at higher photon energies and vice versa. Using the EGRET-detected blazars as al sample, we examine this correlation and possible uncertainties in its construction. C1 Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Res & Data Syst Corp, Lanham, MD 20706 USA. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. Hampden Sydney Coll, Dept Phys, Hampden Sydney, VA 23943 USA. Columbia Univ Barnard Coll, New York, NY 10027 USA. Univ Adelaide, Dept Phys & Math Phys, Adelaide, SA 5005, Australia. Ruhr Univ Bochum, Inst Theoret Phys 4, D-44780 Bochum, Germany. Northrop Grumman Aerosp Corp, Bethpage, NY 11714 USA. RP Lin, YC (reprint author), Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. EM lin@egret0.stanford.edu RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; Reimer, Olaf/A-3117-2013 OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385 NR 26 TC 18 Z9 19 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 191 EP 194 DI 10.1086/307897 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900015 ER PT J AU Hyung, S Aller, LH Feibelman, WA AF Hyung, S Aller, LH Feibelman, WA TI Chemical abundances of the planetary nebula IC 4634 and its central star SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : abundances; planetary nebulae : individual (IC 4634) ID MASS-LOSS; WINDS; EVOLUTION; SPECTRUM; CATALOG; SAMPLE; LINES AB We have measured the spectral line intensities of the metal-poor planetary nebula IC 4634. Using a photoionization model calculation, we try to fit the optical and UV region spectra, i.e., Hamilton echelle and IUE observations. From direct images, one expects complicated density variations, but the model predicts a range in densities that may be smaller than actually exist. We find N-epsilon similar to 5000 cm(-3). In spite of the geometrical complexity of the S-shaped double-lobed structure, the simple photoionization model with a spherical symmetry can fit most emission lines fairly well. The derived chemical composition has been compared with previous estimates and also with the Sun. The metallicity in IC 4634 appears to be lower than in the Sun or the average planetary nebula. The most likely temperature of the central ionizing source of IC 4634 appears to be similar to 55,000 K. We find a central star mass of similar to 0.55 M. from comparison with theoretical evolutionary tracks. C1 Korea Astron Observ, Taejon 305348, South Korea. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Hyung, S (reprint author), Korea Astron Observ, San 36-1,Hwaam Dong, Taejon 305348, South Korea. NR 43 TC 16 Z9 16 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 294 EP 304 DI 10.1086/307903 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900023 ER PT J AU Yorke, HW Bodenheimer, P AF Yorke, HW Bodenheimer, P TI The formation of protostellar disks. III. The influence of gravitationally induced angular momentum transport on disk structure and appearance SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; ISM : clouds; radiative transfer; stars : formation ID MOLECULAR CLOUD CORES; YOUNG STELLAR OBJECTS; STAR-FORMATION; CIRCUMSTELLAR DISKS; ACCRETION DISKS; AMBIPOLAR DIFFUSION; INITIAL CONDITIONS; ISOTHERMAL CLOUDS; GASEOUS DISK; EVOLUTION AB Hydrodynamical two-dimensional calculations are presented for the evolution of collapsing, rotating protostars, including the effects of radiative acceleration and angular momentum transport. The initial cloud is assumed to be a uniformly rotating centrally condensed sphere with rho proportional to r(-2). Results are presented for masses of 1, 2, and 10 M., over times comparable to protostellar lifetimes. The calculations show how a warm, quasi-hydrostatic disk surrounding a central unresolved core forms, grows in mass and size, and accretes onto the central object. As a result of the accretion of material from the parent cloud, the disk is encased in one or two accretion shock fronts, located several scale heights above the equatorial plane. During accretion, the disks grow radially due to the effects of angular momentum transport, which according to our model arises from tidally induced gravitational torques. In this manner, quasi-static disks in excess of several thousand AU in radius can be produced. Accretion onto the central object slows down, however, and rather long timescales (M/(M) over dot greater than or equal to 10(7) yr) are reached while an appreciable fraction of the total mass (approximate to 35%) is still in the disk. In order to further reduce the disk mass on a shorter timescale, processes not considered here must be invoked. Alternatively, if the initially selected angular momentum is significantly lower, smaller disk sizes would result. Frequency-dependent radiative transfer calculations at selected ages, including the effects of scattered radiation in the infrared and optical spectral regimes, show how the continuum spectra of the structure depend on the disk's orientation and age and how the observed isophotal contours vary with wavelength and viewing angle. Because of the strong dependence on viewing angle, continuum spectra alone should not be used to estimate the evolutionary stage of development of these objects. The infrared flux at similar to 10 mu m can vary by orders of magnitude between pole-on and edge-on views, and the inferred total bolometric luminosity will vary by up to a factor of greater than or similar to 30 as a function of viewing angle during much of the lifetime of accreting circumstellar disks. We conclude that near- and mid-infrared searches for disks will be strongly biased toward pole-on orientations because of this "flashlight" effect. C1 Astron Inst, D-97074 Wurzburg, Germany. Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Board Studies Astron & Astrophys, Santa Cruz, CA 95064 USA. RP Yorke, HW (reprint author), CALTECH, Jet Prop Lab, MS 169-506, Pasadena, CA 91109 USA. NR 70 TC 98 Z9 98 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 330 EP 342 DI 10.1086/307867 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900026 ER PT J AU Reynolds, SP Keohane, JW AF Reynolds, SP Keohane, JW TI Maximum energies of shock-accelerated electrons in young shell supernova remnants SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; shock waves; supernova remnants; supernovae : general; X-rays : ISM ID COSMIC-RAY ORIGIN; PARTICLE-ACCELERATION; GAMMA-RAYS; X-RAYS; SN-1006; MODELS; TEV AB Young supernova remnants (SNRs) are often assumed to be the source of cosmic rays up to energies approaching the slight steepening in the cosmic-ray spectrum at around 1000 TeV, known as the "knee." We show that the observed X-ray emission of 14 radio-bright shell remnants, including all live historical shells, can be used to put limits on E-max, the energy at which the electron energy distribution must steepen from its slope at radio-emitting energies. Most of the remnants show thermal spectra, so any synchrotron component must fall below the observed X-ray fluxes. We obtain upper limits on E-max by considering the most rapid physically plausible cutoff in the relativistic electron distribution, an exponential, which is as sharp or sharper than found in any more elaborate models. This maximally curved model then gives us the highest possible E-max consistent with not exceeding observed X-rays. Our results are thus independent of particular models for the electron spectrum in SNRs. Assuming homogeneous emitting volumes with a constant magnetic field strength of 10 mu G, no object could reach 1000 TeV, and only one, Kes 73, has an upper limit on E-max above 100 TeV. All the other remnants have limits at or below 80 TeV. E-max is probably set by the finite remnant lifetime rather than by synchrotron losses for remnants younger than a few thousand years, so that an observed electron steepening should be accompanied by steepening at the same energy for protons. More complicated, inhomogeneous models could allow higher values of E-max in parts of the remnant, but the emission-weighted average value, that characteristic of typical electrons, should obey these limits. The young remnants are not expected to improve much over their remaining lives at producing the highest energy Galactic cosmic rays; if they cannot, this picture of cosmic-ray origin may need major alteration. C1 N Carolina State Univ, Dept Phys, Raleigh, NC 27695 USA. N Carolina Sch Sci & Math, Durham, NC 27715 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Minneapolis, MN 55455 USA. RP Reynolds, SP (reprint author), N Carolina State Univ, Dept Phys, Raleigh, NC 27695 USA. NR 35 TC 155 Z9 156 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 368 EP 374 DI 10.1086/307880 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900029 ER PT J AU Ragot, BR AF Ragot, BR TI On the quasi-linear transport of magnetic field lines SO ASTROPHYSICAL JOURNAL LA English DT Article DE chaos; diffusion; interplanetary medium; magnetic fields; solar wind; turbulence ID PLASMA HEAT-CONDUCTIVITY; SOLAR-WIND FLUCTUATIONS; PERCOLATION; TURBULENCE; MODEL; LIMIT AB Under the assumption that a finite correlation length, L-c, exists and is much smaller than the size of the system, the quasi-linear theory for weak magnetic turbulence predicts, beyond L-c, a linear spreading of the magnetic field lines, , as a function of the elapsed distance z along the main magnetic field, B-0. When the power spectrum of the turbulence flattens at low wavenumbers, as was deduced from early observations of the interplanetary turbulence and is expected for an isotropic turbulence, the correlation length can be estimated as the Alfven speed times the reciprocal of the upper frequency in the Bat spectrum. However, more recent measurements of the solar wind magnetic power spectrum indicate a more complex spectrum at low frequencies. The field-lines' spreading in the quasi-linear regime of turbulence is derived here as a function of z for a general power spectrum. The transport exponent alpha, defined by [Delta r(perpendicular to)(2)] proportional to z(alpha), can be deduced from the projection along B-0 of the spectrum. Normal (alpha = 1), supradiffusive (alpha > 1), and subdiffusive (alpha < 1) predictions are made, depending on the shape at low wavenumbers assumed for the projected spectrum, which is related to the anisotropy and \k\-form of the three-dimensional spectrum. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Ragot, BR (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 22 TC 23 Z9 23 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP 524 EP 532 DI 10.1086/307875 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MR UT WOS:000083449900041 ER PT J AU Weinberger, AJ Becklin, EE Schneider, G Smith, BA Lowrance, PJ Silverstone, MD Zuckerman, B Terrile, RJ AF Weinberger, AJ Becklin, EE Schneider, G Smith, BA Lowrance, PJ Silverstone, MD Zuckerman, B Terrile, RJ TI The circumstellar disk of HD 141569 imaged with NICMOS SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; stars : emission-line, Be; stars : individual (HD 141569) ID PLANET FORMATION; STARS; SYSTEMS AB Coronagraphic imaging with the Near-Infrared Camera and Multiobject Spectrometer on the Hubble Space Telescope reveals a large, similar to 400 AU (4") radius, circumstellar disk around the Herbig Ac/Be star HD 141569. A reflected light image at 1.1 Ccm shows the disk oriented at a position angle of 356 degrees +/- 5 degrees and inclined to our line of sight by 51 degrees +/- 3 degrees; the intrinsic scattering function of the dust in the disk makes the side inclined toward us, the eastern side, brighter. The disk flux density peaks 185 AU (1".85) from the star and falls off to both larger and smaller radii. A region of depleted material, or a gap, in the disk is centered 250 AU from the star. The dynamical effect of one or more planets may be necessary to explain this morphology. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Weinberger, AJ (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Box 156205, Los Angeles, CA 90095 USA. OI Weinberger, Alycia/0000-0001-6654-7859 NR 25 TC 103 Z9 103 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP L53 EP L56 DI 10.1086/312334 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MT UT WOS:000083450000014 ER PT J AU Yaqoob, T George, IM Nandra, K Turner, TJ Zobair, S Serlemitsos, PJ AF Yaqoob, T George, IM Nandra, K Turner, TJ Zobair, S Serlemitsos, PJ TI A highly Doppler blueshifted Fe-K emission line in the high-redshift QSO PKS 2149-306 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; quasars : emission lines; quasars : individual (PKS 0637-752, PKS 2149-306); X-rays : galaxies ID ASCA OBSERVATIONS; PROFILES; QUASARS AB We report the results from an ASCA observation of the high-luminosity, radio-loud quasar PKS 2149-306 (redshift 2.345), covering the similar to 1.7-30 keV band in the quasar frame. We find the source to have a luminosity similar to 6 x 10(47) ergs s(-1) in the 2-10 keV band (quasar frame). We detect an emission line centered at similar to 17 keV in the quasar frame. Line emission at this energy has not been observed in any other active galaxy or quasar to date. We present evidence rejecting the possibility that this line is the result of instrumental artifacts or a serendipitous source. The most likely explanation is blueshifted Fe-K emission (the equivalent width is EW 300 +/- 200 eV, quasar frame). Bulk velocities of the order of 0.75c are implied by the data. We show that Fe-K line photons originating in an accretion disk and Compton scattering off a leptonic jet aligned along the disk axis can account for the emission line. Curiously, if the emission-line feature recently discovered in another quasar (PKS 0637-752, z = 0.654) at 1.6 keV in the quasar frame is due to blueshifted O VII emission, the Doppler blueshifting factor in both quasars is similar (similar to 2.7-2.8). C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 17 TC 28 Z9 28 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1999 VL 525 IS 1 BP L9 EP L12 DI 10.1086/312327 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251MT UT WOS:000083450000003 ER PT J AU Ortiz, RM Wang, TJ Wade, CE AF Ortiz, RM Wang, TJ Wade, CE TI Urea and osmotic excretion in rats exposed to chronic centrifugation SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE aldosterone; GFR; hypergravity; osmotic diuresis; sodium excretion ID ALDOSTERONE; STARVATION; METABOLISM; DOG AB Background: A reduction in vasopressin was attributed to the initial diuresis reported in rats exposed to chronic centrifugation. However, it was suggested that urea may also contribute an osmotic component to this observed diuresis. Hypothesis: increased urea excretion will contribute to osmotic excretion during chronic centrifugation, which may be partly responsible for the initial diuresis previously observed. Methods: Eight Sprague-Dawley rats were centrifuged (12 d at -2Gx) and eight were used as a control group. Daily urine samples were collected and an aliquot measured for excreted solutes and aldosterone. Results: Urine volume was elevated over the first 7 d of centrifugation with a peak on day 4. Urea and osmotic excretion were elevated over the first 5 d. Excreted Na+ was elevated on days 1 and 2, which coincided with an increase in excreted aldosterone over the first 3 d of centrifugation. Urea excretion accounted for up to 54% of the increase in osmotic excretion during the initial portion of centrifugation suggesting that urea was, in part, responsible for the observed increase in urine output despite a reduction in water consumption. Following the first day of centrifugation, aldosterone appears to regulate Na+ as suggested by the reduction in Na+ excretion between days 2 and 3 when aldosterone excretion was elevated. Conclusions: It would appear that centrifugation induced an acute increase in protein catabolism as indicated by the increase in urea excretion which resulted in an increase in obligatory water loss. This increased diuresis may have acute consequences on the hydration state of centrifuged rats. C1 NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. RP Ortiz, RM (reprint author), Univ Calif Santa Cruz, Dept Biol, EMS A316, Santa Cruz, CA 95064 USA. NR 25 TC 7 Z9 7 U1 0 U2 2 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD NOV PY 1999 VL 70 IS 11 BP 1089 EP 1095 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 251KP UT WOS:000083445100006 PM 10608606 ER PT J AU Diner, DJ Asner, GP Davies, R Knyazikhin, Y Muller, JP Nolin, AW Pinty, B Schaaf, CB Stroeve, J AF Diner, DJ Asner, GP Davies, R Knyazikhin, Y Muller, JP Nolin, AW Pinty, B Schaaf, CB Stroeve, J TI New directions in earth observing: Scientific applications of multiangle remote sensing SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Review ID GREENLAND ICE-SHEET; LEAF-AREA INDEX; SURFACE PARAMETERIZATION SCHEMES; AEROSOL OPTICAL-PROPERTIES; RADIATION BUDGET; SNOW COVER; IMAGING SPECTRORADIOMETER; BIDIRECTIONAL REFLECTANCE; AVHRR DATA; EOS-MODIS AB The physical interpretation of simultaneous multiangle observations represents a relatively new approach to remote sensing of terrestrial geophysical and biophysical parameters. Multiangle measurements enable retrieval of physical scene characteristics, such as aerosol type, cloud morphology and height, and land cover (e.g., vegetation canopy type), providing improved albedo accuracies as well as compositional, morphological, and structural information that facilitates addressing many key climate, environmental, and ecological issues. While multiangle data from wide field-of-view scanners have traditionally been used to build up directional "signatures" of terrestrial scenes through multitemporal compositing, these approaches either treat the multiangle variation as a problem requiring correction or normalization or invoke statistical assumptions that may not apply to specific scenes. With the advent of a new generation of global imaging spectroradiometers capable of acquiring simultaneous visible/near-IR multiangle observations, namely, the Along Track Scanning Radiometer-2, the Polarization and Directionality of the Earth's Reflectances instrument, and the Multiangle imaging SpectroRadiometer, both qualitatively new approaches as well as quantitative improvements in accuracy are achievable that exploit the multiangle signals as unique and rich sources of diagnostic information. This paper discusses several applications of this technique to scientific problems in terrestrial atmospheric and surface geophysics and biophysics. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Stanford Univ, Stanford, CA 94305 USA. Univ Arizona, Tucson, AZ USA. Boston Univ, Boston, MA 02215 USA. UCL, London, England. Univ Colorado, Boulder, CO 80309 USA. Commiss European Communities, Joint Res Ctr, I-21020 Ispra, Italy. RP Diner, DJ (reprint author), CALTECH, Jet Prop Lab, Mail Stop 169-237,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM djd@jord.jpl.nasa.gov RI Stroeve, Julienne/D-1525-2010; Davies, Roger/D-4296-2009; Asner, Gregory/G-9268-2013 OI Davies, Roger/0000-0002-2991-0409; Asner, Gregory/0000-0001-7893-6421 NR 143 TC 147 Z9 155 U1 1 U2 24 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 EI 1520-0477 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD NOV PY 1999 VL 80 IS 11 BP 2209 EP 2228 DI 10.1175/1520-0477(1999)080<2209:NDIEOS>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 253NG UT WOS:000083562200004 ER PT J AU King, MD Kaufman, YJ Tanre, D Nakajima, T AF King, MD Kaufman, YJ Tanre, D Nakajima, T TI Remote sensing of tropospheric aerosols from space: Past, present, and future SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Review ID MULTIANGLE IMAGING SPECTRORADIOMETER; MT-PINATUBO ERUPTION; SCALE AIR-POLLUTION; OPTICAL-THICKNESS; SATELLITE MEASUREMENTS; WATER-VAPOR; AVHRR DATA; SIZE DISTRIBUTIONS; STRATOSPHERIC AEROSOL; PHASE FUNCTION AB Tropospheric aerosol particles originate from man-made sources such as urban/industrial activities, biomass burning associated with land use processes, wind-blown dust, and natural sources. Their interaction with sunlight and their effect on cloud microphysics form a major uncertainty in predicting climate change. Furthermore, the lifetime of only a few days causes high spatial variability in aerosol optical and radiative properties that requires global observations from space. Remote sensing of tropospheric aerosol properties from space is reviewed both for present and planned national and international satellite sensors. Techniques that are being used to enhance our ability to characterize the global distribution of aerosol properties include well-calibrated multispectral radiometers, multispectral polarimeters, and multiangle spectroradiometers. Though most of these sensor systems rely primarily on visible to near-infrared spectral channels, the availability of thermal channels to aid in cloud screening is an important additional piece of information that is not always incorporated into the sensor design. In this paper, the various satellite sensor systems being developed by Europe, Japan, and the United States are described, and the advantages and disadvantages of each of these systems for aerosol applications are highlighted. An important underlying theme is that the remote sensing of aerosol properties, especially aerosol size distribution and single scattering albedo, is exceedingly difficult. As a consequence, no one sensor system is capable of providing totally unambiguous information, and hence a careful intercomparison of derived products from different sensors, together with a comprehensive network of ground-based sunphotometer and sky radiometer systems, is required to advance our quantitative understanding of global aerosol characteristics. C1 NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. Univ Sci & Tech Lille Flandres Artois, Natl Ctr Sci Res, Villeneuve Dascq, France. Univ Tokyo, Ctr Climate Syst Res, Tokyo, Japan. RP King, MD (reprint author), NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Code 900, Greenbelt, MD 20771 USA. EM king@climate.gsfc.nasa.gov RI King, Michael/C-7153-2011; Nakajima, Teruyuki/H-2370-2013 OI King, Michael/0000-0003-2645-7298; Nakajima, Teruyuki/0000-0002-9042-504X NR 111 TC 490 Z9 535 U1 14 U2 110 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD NOV PY 1999 VL 80 IS 11 BP 2229 EP 2259 DI 10.1175/1520-0477(1999)080<2229:RSOTAF>2.0.CO;2 PG 31 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 253NG UT WOS:000083562200005 ER PT J AU Rossow, WB Schiffer, RA AF Rossow, WB Schiffer, RA TI Advances in understanding clouds from ISCCP SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Review ID MESOSCALE CONVECTIVE COMPLEXES; CLIMATOLOGY-PROJECT ISCCP; BOUNDARY-LAYER CLOUDS; LIQUID WATER PATH; HIGH-LEVEL CLOUDS; ICE CRYSTALS; RADIATIVE PROPERTIES; OPTICAL-THICKNESS; SATELLITE MEASUREMENTS; AVHRR DATA AB This progress report on the International Satellite Cloud Climatology Project (ISCCP) describes changes made to produce new cloud data products (D data), examines the evidence that these changes are improvements over the previous version (C data), summarizes some results, and discusses plans for the ISCCP through 2005. By late 1999 all datasets will be available for the period from July 1983 through December 1997. The most significant changes in the new D-series cloud datasets are 1) revised radiance calibrations to remove spurious changes in the long-term record, 2) increased cirrus detection sensitivity over land, 3) increased low-level cloud detection sensitivity in polar regions, 4) reduced biases in cirrus cloud properties using an ice crystal microphysics model in place of a liquid droplet microphysics model, and 5) increased detail about the variations of cloud properties. The ISCCP calibrations are now the most complete and self-consistent set of calibrations available for all the weather satellite imaging radiometers: total relative uncertainties in the radiance calibrations are estimated to be less than or similar to 5% for visible and less than or similar to 2% for infrared; absolute uncertainties are < 10% and < 3%, respectively. Biases in (detectable) cloud amounts have been reduced to less than or similar to 0.05, except in the summertime polar regions where the bias may still be similar to 0.10. Biases in cloud-top temperatures have been reduced to less than or similar to 2 K for lower-level clouds and less than or similar to 4 K for optically thin, upper-level clouds, except when they occur over lower-level clouds. Using Liquid and ice microphysics models reduces the biases in cloud optical thicknesses to less than or similar to 10%, except in cases of mistaken phase identification; most of the remaining bias is caused by differences between actual and assumed cloud particle sizes and the small effects of cloud variations at scales < 5 km. Global mean cloud properties averaged over the period July 1983-June 1994 are the following: cloud amount = 0.675 +/- 0.012; cloud-top temperature = 261.5 +/- 2.8 K; and cloud optical thickness = 3.7 +/- 0.3, where the plus-minus values are the rms deviations of global monthly mean values from their long-term average. Long-term, seasonal, synoptic, and diurnal cloud variations are illustrated. The ISCCP dataset quantifies the variations of cloud properties at mesoscale resolution (3 h, 30 km) covering the whole globe for more than a decade, making it possible to study cloud system evolution over whole life cycles, watching interactions with the atmospheric general circulation. Plans for the next decade of the World Climate Research Programme require continuing global observations of clouds and the most practical way to fulfill this requirement is to continue ISCCP until it can be replaced by a more capable system with similar time resolutions and global coverage. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NASA, Washington, DC 20546 USA. RP Rossow, WB (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Rossow, William/F-3138-2015 NR 121 TC 1291 Z9 1348 U1 7 U2 88 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD NOV PY 1999 VL 80 IS 11 BP 2261 EP 2287 DI 10.1175/1520-0477(1999)080<2261:AIUCFI>2.0.CO;2 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 253NG UT WOS:000083562200006 ER PT J AU Nguyen, CV Carter, KR Hawker, CJ Hedrick, JL Jaffe, RL Miller, RD Remenar, JF Rhee, HW Rice, PM Toney, MF Trollsas, M Yoon, DY AF Nguyen, CV Carter, KR Hawker, CJ Hedrick, JL Jaffe, RL Miller, RD Remenar, JF Rhee, HW Rice, PM Toney, MF Trollsas, M Yoon, DY TI Low-dielectric, nanoporous organosilicate films prepared via inorganic/organic polymer hybrid templates SO CHEMISTRY OF MATERIALS LA English DT Article ID MESOPOROUS SILICA; STAR AB Dielectric insulator materials containing nanometer-scale closed-cell pores with low dielectric constants (k < 2.2), good mechanical properties, and high dielectric breakdown strengths are required for future semiconductor devices. In this paper we present a novel method for preparing nanoporous polyorganosilicate films, which promise to satisfy the key requirements, via inorganic/organic polymer hybrid templating. The nanometer-scale inorganic/organic polymer hybrids are generated in situ upon heating mixtures of methylsilsesquioxane (MSSQ) prepolymer with star-shaped hydroxy-terminated poly(epsilon-caprolactone) (PCL) to similar to 250 degrees C, causing chain extension and cross-linking of MSSQ. Subsequent heating to 430 degrees C results in the thermal decomposition and volatilization of PCL components from the vitrified poly(methylsilsesquioxane) (PMSSQ) matrix;, leaving behind porous PMSSQ films with pores with the size and shape of the original hybrid morphology. A dielectric constant as low as 2.1 has been achieved for closed-cell nanoporous PMSSQ films with hydrophobic surfaces and excellent breakdown strengths close to that of SiO2. Moreover, conductance measurements on inorganic/organic polymer hybrids offer insight into the development of interconnected PCL domains as the PCL content is increased above similar to 25%. C1 Seoul Natl Univ, Dept Chem, Seoul 151742, South Korea. IBM Corp, Almaden Res Ctr, Div Res, San Jose, CA 95120 USA. ELORET Inc, Sunnyvale, CA 94087 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Sogang Univ, Dept Chem Engn, Seoul 121742, South Korea. RP Yoon, DY (reprint author), Seoul Natl Univ, Dept Chem, Seoul 151742, South Korea. RI Hawker, Craig/G-4971-2011; Carter, Kenneth/G-2594-2015 OI Hawker, Craig/0000-0001-9951-851X; Carter, Kenneth/0000-0002-7081-2296 NR 23 TC 189 Z9 191 U1 3 U2 45 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0897-4756 J9 CHEM MATER JI Chem. Mat. PD NOV PY 1999 VL 11 IS 11 BP 3080 EP 3085 DI 10.1021/cm990114d PG 6 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA 257HG UT WOS:000083776000014 ER PT J AU Reeves, GE AF Reeves, GE TI Priority inversion: How we found it, how we fixed it SO DR DOBBS JOURNAL LA English DT Article C1 JPL, Miss Data Syst Project, Pasadena, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MILLER FREEMAN, INC PI SAN FRANCISCO PA 600 HARRISON ST,, SAN FRANCISCO, CA 94107 USA SN 1044-789X J9 DR DOBBS J JI Dr. Dobbs J. PD NOV PY 1999 VL 24 IS 11 BP 24 EP + PG 2 WC Computer Science, Software Engineering SC Computer Science GA 247HE UT WOS:000083214700018 ER PT J AU Paulson, AJ Balistrieri, L AF Paulson, AJ Balistrieri, L TI Modeling removal of Cd, Cu, Pb, and Zn in acidic groundwater during neutralization by ambient surface waters and groundwaters SO ENVIRONMENTAL SCIENCE & TECHNOLOGY LA English DT Article ID MINE DRAINAGE; HUMIC SUBSTANCES; MINING DISTRICT; ORGANIC-MATTER; IRON-OXIDES; ADSORPTION; TRANSPORT; SEDIMENTS; SORPTION; COLORADO AB Removal of Pb, Cu, Zn, and Cd during neutralization of acid rock drainage is examined using model simulations of field conditions and laboratory experiments involving mixing of natural drainage and surface waters or groundwaters. The simulations consider sorption onto hydrous Fe and Al oxides and particulate organic carbon, mineral precipitation, and organic and inorganic solution complexation of metals for two physical systems where newly formed oxides and particulate organic matter are either transported or retained along the chemical pathway. The calculations indicate that metal removal is a strong function of the physical system. Relative to direct discharge of ARD into streams, lower metal removals are observed where ARD enters streamwaters during the latter sta ges of neutralization by ambient groundwater after most of the Fe has precipitated and been retained in the soils. The mixing experiments, which represent the field simulations, also demonstrated the importance of dissolved metal to particle Fe ratios in controlling dissolved metal removal along the chemical pathway. Finally, model calculations indicate that hydrous Fe oxides and particulate organic carbon are more important than hydrous Al oxides in removing metals and that both inorganic and organic complexation must be considered when modeling metal removal from aquatic systems that are impacted by sulfide oxidation. C1 NOAA, Natl Marine Fisheries Serv, NEFSC, James J Howard Lab, Highlands, NJ 07732 USA. Univ Washington, US Geol Survey, Sch Oceanog, Seattle, WA 98195 USA. RP Paulson, AJ (reprint author), NOAA, Natl Marine Fisheries Serv, NEFSC, James J Howard Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 31 TC 35 Z9 36 U1 0 U2 12 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0013-936X J9 ENVIRON SCI TECHNOL JI Environ. Sci. Technol. PD NOV 1 PY 1999 VL 33 IS 21 BP 3850 EP 3856 DI 10.1021/es9900454 PG 7 WC Engineering, Environmental; Environmental Sciences SC Engineering; Environmental Sciences & Ecology GA 251RN UT WOS:000083458800039 ER PT J AU Hashemi, BB Penkala, JE Vens, C Huls, H Cubbage, M Sams, CF AF Hashemi, BB Penkala, JE Vens, C Huls, H Cubbage, M Sams, CF TI T cell activation responses are differentially regulated during clinorotation and in spaceflight SO FASEB JOURNAL LA English DT Article DE microgravity culture; clinostat; DNA synthesis; CD69; CD25 ID PROTEIN-KINASE-C; ANTIGEN-RECEPTOR COMPLEX; LYMPHOCYTES-T; SIGNAL-TRANSDUCTION; INTERLEUKIN-2 PRODUCTION; MESSENGER-RNA; MICROGRAVITY; STIMULATION; EXPRESSION; INDUCTION AB Studies of T lymphocyte activation with mitogenic lectins during spaceflight have shown a dramatic inhibition of activation as measured by DNA synthesis at 72 h, but the mechanism of this inhibition is unknown. We have investigated the progression of cellular events during the first 24 h of activation using both spaceflight microgravity culture and a groundbased model system that relies on the low shear culture environment of a rotating clinostat (clinorotation). Stimulation of human peripheral blood mononuclear cells (PBMCs) with soluble anti-CD3 (Leu4) in clinorotation and in microgravity culture shows a dramatic reduction in surface expression of the receptor for IL-2 (CD25) and CD69. An absence of bulk RNA synthesis in clinorotation indicates that stimulation with soluble Leu4 does not induce transition of T cells from G0 to the G1 stage of the cell cycle. However, internalization of the TCR by T cells and normal levels of IL-1 synthesis by monocytes indicate that intercellular interactions that are required for activation occur during clinorotation. Complementation of TCR-mediated signaling by phorbol ester restores the ability of PBMCs to express CD25 in clinorotation, indicating that a PKC associated pathway may be compromised under these conditions. Bypassing the TCR by direct activation of intracellular pathways with a combination of phorbol ester and calcium ionophore in clinorotation resulted in full expression of CD25; however, only partial expression of CD25 occurred in microgravity culture. Though stimulation of purified T cells with Bead-Leu4 in microgravity culture resulted in the engagement and internalization of the TCR, the cells still failed to express CD25. When T cells were stimulated with Bead-Leu4 in microgravity culture, they were able to partially express CD69, a receptor that is constitutively stored in intracellular pools and can be expressed in the absence of new gene expression. Our results suggest that the inhibition of T cell proliferative response in microgravity culture is a result of alterations in signaling events within the first few hours of activation, which are required for the expression of important regulatory molecules.-Hashemi, B. B., Penkala, J. E., Vens, C., Huls, H., Cubbage, M., Sams, C. F. T cell activation responses are differentially regulated during clinorotation and in spaceflight. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. RP Sams, CF (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, SD3, Houston, TX 77058 USA. NR 50 TC 64 Z9 72 U1 1 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD NOV PY 1999 VL 13 IS 14 BP 2071 EP 2082 PG 12 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 255GG UT WOS:000083660700019 PM 10544190 ER PT J AU Dean, BH AF Dean, BH TI Phase-plane analysis of periastron precession about a Reissner-Nordstrom black hole SO GENERAL RELATIVITY AND GRAVITATION LA English DT Article DE Reissner-Nordstrom; periastron precession; phase-plane analysis AB Periastron precession in the Reissner-Nordstrom spacetime is analyzed using the phase-plane and bifurcation techniques. Earlier calculations are generalized to include a bifurcation point of the dynamics which corresponds physically to timelike orbits about a naked singularity. A numerical solution at these parameter values illustrates that such orbits typically yield a larger precession Value when compared to the standard value for timelike precession. A transcritical bifurcation point is identified at the parameter values corresponding to photon orbits about a naked singularity. Finally, the "acausal" geodesics considered by Brigman are discussed and their precession value is calculated. A review of the previous literature is also given. C1 W Virginia Univ, Dept Phys, Morgantown, WV 26506 USA. RP Dean, BH (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 28 TC 0 Z9 0 U1 0 U2 0 PU KLUWER ACADEMIC/PLENUM PUBL PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0001-7701 J9 GEN RELAT GRAVIT JI Gen. Relativ. Gravit. PD NOV PY 1999 VL 31 IS 11 BP 1727 EP 1741 DI 10.1023/A:1026714200725 PG 15 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 255PB UT WOS:000083677400007 ER PT J AU Kostka, JE Wu, J Nealson, KH Stucki, JW AF Kostka, JE Wu, J Nealson, KH Stucki, JW TI The impact of structural Fe(III) reduction by bacteria on the surface chemistry of smectite clay minerals SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID ORGANIC-CARBON OXIDATION; MICROBIAL REDUCTION; FERRIC IRON; EXTRACTION TECHNIQUES; ANAEROBIC SEDIMENTS; OXIDE REDUCTION; NONTRONITE; REOXIDATION; MANGANESE; SOILS AB Although clay mineral reduction is thought to occur primarily as a result of the activity of indigenous microorganisms in soil, most research has focused on chemical mechanisms of Fe reduction within clay minerals. Here we show that bacteria isolated from soils and sediments catalyze the rapid reduction of structural Fe(III) in the smectite clay minerals. The extent of Fe(III) reduction is large, from 46% to >90%. Furthermore, the effects of structural Fe(III) reduction by bacteria on the surface chemistry of smectites are dramatic. Swelling pressure, as measured by water content, was shown to decrease by 40% to 44% in smectites reduced by bacteria as compared to unaltered or reoxidized smectites. Particle surface area decreased by 26% to 46% in response to bacterial reduction, and the surface charge density as measured by the ratio of cation exchange capacity to specific surface area increased over the same scale. Measurements of swelling pressure in smectite saturated with the organic cation trimethylphenylammonium (TMPA) indicated that the hydrophilic character of the clay mineral surface was enhanced upon reduction. The valence state of Fe in the octahedral layer of smectite, as revealed through reflectance spectra, correlated to the amount of Fe(III) reduced in bacterial cultures, providing information on the mechanism of intervalence electron transfer in bacterially reduced clay minerals. The extent of reduction and surface chemical effects catalyzed by bacteria in this study are similar in magnitude to those observed previously for potent inorganic reductants. Given that clay minerals dominate the solid phase of porous media and that Fe(III)-reducing bacteria are abundant in soils and aquatic sediments, these data suggest that bacterial clay mineral reduction may play an important role in soil biogeochemistry, affecting processes such as nutrient cycles and the fate of organic contaminants. Copyright (C) 1999 Elsevier Science Ltd. C1 Skidaway Inst Oceanog, Savannah, GA 31411 USA. Univ Illinois, Nat Resources & Environm Sci Dept, Urbana, IL 61801 USA. CALTECH, Jet Prop Lab, Div Earth & Space Sci, Engn & Sci Directorate, Pasadena, CA 91109 USA. RP Kostka, JE (reprint author), Florida State Univ, Dept Oceanog, Tallahassee, FL 32306 USA. NR 53 TC 120 Z9 130 U1 6 U2 38 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD NOV PY 1999 VL 63 IS 22 BP 3705 EP 3713 DI 10.1016/S0016-7037(99)00199-4 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 264JU UT WOS:000084178000001 ER PT J AU Des Marais, DJ AF Des Marais, DJ TI Alfred E. Treib Award - Introduction of John M. Hayes for the 1998 Alfred E. Treibs Award SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Biographical-Item C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Des Marais, DJ (reprint author), NASA, Ames Res Ctr, Div Space Sci, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD NOV PY 1999 VL 63 IS 22 BP 3935 EP 3936 DI 10.1016/S0016-7037(99)00159-3 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 264JU UT WOS:000084178000016 ER PT J AU Tackman, GE Bills, BG James, TS Currey, DR AF Tackman, GE Bills, BG James, TS Currey, DR TI Lake-gauge evidence for regional postglacial tilting in southern Manitoba SO GEOLOGICAL SOCIETY OF AMERICA BULLETIN LA English DT Article ID LAST GLACIAL MAXIMUM; LAURENTIDE ICE-SHEET; NUMERICAL RECONSTRUCTION; GREAT-LAKES; PREDICTIONS; SPECTRA; UPLIFT AB The network of lake-level gauges in place for Lake Winnipeg, Lake Winnipegosis, Lake Manitoba, and Lake of the Woods presents an opportunity to study the contemporary pattern of postglacial rebound in a North American continental-interior region. We used a regional trend-surface model based on mean winter-season differences of lake level between pairs of gauges to extract the postglacial rebound signature recorded in the lake-gauge data. The results from a best-fitting planar model indicate that tilting is up to the northeast with a bearing of N(42.7 +/- 11.8)degrees E and a rate of (10.7 +/- 2.2) x 10(-9) rad.yr(-1). In spite of the fact that both the ICE-3G and ICE-4G load models are derived from the inversion of relative sea-level histories obtained from marine coastal sites, the pattern of rebound that we computed from these two ice models for this continental-interior region agrees reasonably wed with the pattern derived from the lake-gauge data. Rates computed from an ICE-3G load are in close agreement with those computed from the lake gauges, whereas rates derived from ICE-4G are 50% too slow When the planar pattern of postglacial rebound derived from the lake gauges in southern Manitoba and Lake of the Woods is linked to the lake-gauge-derived pattern of rebound over the Great Lakes region, the two-region pattern suggests influential source regions of rebound that include southern and southwestern Hudson Bay as wed as more local sources En western Ontario. It is possible that the spatial arrangement of ice domes predicted in the multidomed paleotopography of ICE-4G could explain the two-region pattern of rebound if more ice were added to Ontario in the model, or if Earth structure assumptions could be modified, or both. As postglacial tilting continues to shift the region's lakes to the southwest, there is an increased risk of flooding and wave erosion along the south shores over the long term. In addition, postglacial tilting deforms the datums to which the lake-level gauges are referenced. Thus, where and how the levels of these lakes are measured is an important operational issue. These Factors present challenges to water-resource managers who are responsible for monitoring the levels and controlling the outflows of these lakes. C1 Univ Utah, Limneotecton Lab, Salt Lake City, UT 84112 USA. Univ Calif San Diego, Scripps Inst Oceanog, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. Geol Survey Canada, Sidney, BC V8L 4B2, Canada. RP Tackman, GE (reprint author), Univ Utah, Limneotecton Lab, 270 OSH, Salt Lake City, UT 84112 USA. RI Bills, Bruce/C-1156-2008; James, Thomas/D-9301-2013 OI James, Thomas/0000-0001-7321-047X NR 33 TC 7 Z9 7 U1 2 U2 2 PU ASSOC ENGINEERING GEOLOGISTS GEOLOGICAL SOCIETY AMER PI COLLEGE STN PA TEXAS A & M UNIV, DEPT GEOLOGY & GEOPHYSICS, COLLEGE STN, TX 77843-3115 USA SN 0016-7606 J9 GEOL SOC AM BULL JI Geol. Soc. Am. Bull. PD NOV PY 1999 VL 111 IS 11 BP 1684 EP 1699 DI 10.1130/0016-7606(1999)111<1684:LGEFRP>2.3.CO;2 PG 16 WC Geosciences, Multidisciplinary SC Geology GA 252AB UT WOS:000083477600006 ER PT J AU Rao, MN Borg, LE McKay, DS Wentworth, SJ AF Rao, MN Borg, LE McKay, DS Wentworth, SJ TI Martian soil component in impact glasses in a Martian meteorite SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SHERGOTTITE METEORITES; NOBLE-GASES; PETROGENESIS; ORIGIN AB Chemical compositions of impact melt glass veins, called Lithology C (Lith C) in Martian meteorite EET79001 were determined by electron microprobe analysis. A large enrichment of S, and significant enrichments of Al, Ca, and Na were observed in Lith C glass compared to Lithology A (Lith A). The S enrichment is due to mixing of plagioclase- enriched Lith A material with Martian soil, either prior to or during impact on Mars. A mixture of 87% Lith A, 7% plagioclase, and 6% Martian soil reproduces the average elemental abundances observed in Lith C. Shock melting of such a mixture of plagioclase-enriched, fine-grained Lith A host rock and Martian soil could yield large excesses of S (observed in this study) and Martian atmospheric noble gases (found by Bogard ct al., 1983) in Lith C. These mixing proportions can be used to constrain the elemental abundance of phosphorus in Martian soil. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. RP Rao, MN (reprint author), NASA, Lyndon B Johnson Space Ctr, SN2, Houston, TX 77058 USA. NR 12 TC 28 Z9 28 U1 2 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1999 VL 26 IS 21 BP 3265 EP 3268 DI 10.1029/1999GL005388 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 252DM UT WOS:000083485500015 PM 11543347 ER PT J AU Hauglustaine, DA Brasseur, GP Levine, JS AF Hauglustaine, DA Brasseur, GP Levine, JS TI A sensitivity simulation of tropospheric ozone changes due to the 1997 Indonesian fire emissions SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CHEMICAL-TRANSPORT MODEL; MOZART AB A global chemical transport model, called MOZART, is used to investigate the photochemical impact of the 1997 Indonesian fires on tropospheric ozone and its precursors in the tropics. Due to the high release of carbon monoxide by peat fires, CO increases by up to 1000 ppbv in the free troposphere over Indonesia. As a consequence of increased photochemical production, ozone is significantly perturbed over source regions (Sumatra and Kalimantan). The tropospheric O-3 column increases by 20-25 DU and the ozone mixing ratio reaches 50 ppbv in the mid-troposphere in November. South of the source region, low ozone mixing ratios of 20-25 ppbv are calculated in the boundary layer due to marine air influence and reduced photochemical activity in presence of biomass burning aerosols. The particular transport regime prevailing during the 1997 El Nino event is not considered in our calculations. This limitation precludes any definitive conclusion regarding the relative role played by photochemistry and transport processes on the distribution of species during the 1997 fires. C1 Univ Paris 06, CNRS, Serv Aeron, F-75252 Paris 05, France. Natl Ctr Atmospher Res, Boulder, CO 80303 USA. NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. RP Hauglustaine, DA (reprint author), Univ Paris 06, CNRS, Serv Aeron, 4 Pl Jussieu, F-75252 Paris 05, France. NR 13 TC 33 Z9 35 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1999 VL 26 IS 21 BP 3305 EP 3308 DI 10.1029/1999GL900610 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 252DM UT WOS:000083485500025 ER PT J AU Potter, CS Klooster, SA AF Potter, CS Klooster, SA TI Dynamic global vegetation modelling for prediction of plant functional types and biogenic trace gas fluxes SO GLOBAL ECOLOGY AND BIOGEOGRAPHY LA English DT Article; Proceedings Paper CT Joint Open Science Conference of the IGBP Core Project Global Change and Terrestrial Ecosystems/IGBP IHDP Core Project Land Use and Cover Change CY MAR 14-18, 1998 CL BARCELONA, SPAIN SP Int Geosphere Biosphere Programme, Int Human Dimensions Programme DE dynamic vegetation; global modelling; remote sensing; NDVI; net primary production; plant biomass; biogenic trace gases; climate change ID TERRESTRIAL BIOSPHERE MODEL; BIOMASS ALLOCATION; SOLAR-RADIATION; LAND-SURFACE; NITROGEN; CLIMATE; AVAILABILITY; COMPETITION; FORESTS; CARBON AB 1. A Dynamic Global Vegetation Model (DGVM) has been developed as a new feature of the NASA-CASA (Carnegie Ames Stanford Approach) ecosystem production and trace gas model. This DGVM includes seasonal phenology algorithms calibrated using historical interannual data sets derived from the Advanced Very High Resolution (AVHRR) satellite 'greenness' index. 2. The coupled CASA-DGVM design is based conceptually on two main elements of Tilman's resource-ratio hypothesis of vegetation change, namely: 1) plant competition for resources (water and light) over relatively short time periods of months and seasons; and 2) the long-term pattern in the supply of growth-limiting resources such as water and nutrients, i.e. the resource-supply trajectory. This simulation model generates global gridded estimates of primary production, above and below ground biomass, leaf area index (LAI), and trace gas fluxes from soil. 3. Eight distributed rest locations for the DGVM were evaluated initially to represent a variety of climate conditions ranging from Arctic (64 degrees N Alaska) to tropical and subtropical (24 degrees S southern Africa) latitude zones. At all test locations, the predicted plant functional type (PFT) matched closely with the actual reported PFT. 4. In the process of running the model to steady state PFTs, most forest locations showed a rapid progression of transient stales, from bare ground to grassland, to grasses with shrub cover, and finally to the forest PFT. From this first global application. the DGVM correctly predicts the presence of forest classes in approximately 75-95% of all cases worldwide, and grasslands in approximately 58% of all cases. 5. The effects of two hypothetical climate change scenarios were evaluated. Scenario I was set by warming air surface temperatures linearly to 4 degrees C above average over a 25-year simulation period. Scenario II was set by decreasing annual rainfall amounts linearly to 50% below average over a 25-year simulation period. 6. The warming scenario I resulted in PFT at high latitude forest and boreal forest sites changing to mixed coniferous forest, accompanied by increase in canopy LAI. The drought scenario II resulted in PFT at the boreal forest and savanna sites changing to grasslands. At locations where PFT did not change with climate, however, soil water and canopy LAI were predicted to decline progressively under the warming scenario, beginning from steady-state temperate and tropical zone PFTs. They also declined under the drought scenario beginning from practically any steady slate PFT. C1 NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Moffett Field, CA 94035 USA. Calif State Univ Monterey Bay, Seaside, CA 93955 USA. RP Potter, CS (reprint author), NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Moffett Field, CA 94035 USA. NR 46 TC 29 Z9 31 U1 1 U2 23 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0960-7447 J9 GLOBAL ECOL BIOGEOGR JI Glob. Ecol. Biogeogr. PD NOV PY 1999 VL 8 IS 6 BP 473 EP 488 DI 10.1046/j.1365-2699.1999.00152.x PG 16 WC Ecology; Geography, Physical SC Environmental Sciences & Ecology; Physical Geography GA 286TF UT WOS:000085461200005 ER PT J AU Cabrol, NA Grin, EA AF Cabrol, NA Grin, EA TI Distribution, classification, and ages of martian impact crater lakes SO ICARUS LA English DT Article DE Mars; Mars surface; exobiology ID MARS; SEDIMENTATION; CARBONATES; SEARCH; SYSTEM; BASINS; MODEL; VIEW; LIFE AB Paleolakes in impact craters on Mars are characterized at global scale using the Viking Orbiter data. We identified 179 paleolakes in impact structures formed by the influx of water and sediment derived from valley networks and channels that can be classified into three different fluviolacustrine systems: closed, open, and lake-chain systems. We show the hydrogeologic implications for each of the three systems and their significance in terms of duration of fluviolacustrine activity. This study provides a catalog of areographic, physical, and physiographic data for each of the studied impact crater lakes, associated with the description of the sedimentary structures observed. It also identifies environments where life and/or precursors to life could have found favorable conditions to evolve. (C) 1999 Academic Press. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP Cabrol, NA (reprint author), NASA, Ames Res Ctr, SETI Inst, MS 239-20, Moffett Field, CA 94035 USA. NR 49 TC 172 Z9 175 U1 0 U2 7 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1999 VL 142 IS 1 BP 160 EP 172 DI 10.1006/icar.1999.6191 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 259YD UT WOS:000083920800017 ER PT J AU Harris, AW Young, JW Bowell, E Tholen, DJ AF Harris, AW Young, JW Bowell, E Tholen, DJ TI Asteroid lightcurve observations from 1981 to 1983 SO ICARUS LA English DT Article DE asteroids; rotation; photometry ID NEAR-EARTH ASTEROIDS; MAIN-BELT ASTEROIDS; PHOTOELECTRIC PHOTOMETRY; POLE DETERMINATIONS; PHASE-RELATIONS; MINOR PLANETS; ROTATION; SPIN; SHAPE; ORIENTATION AB We present observations of 40 asteroids taken mostly from Table Mountain Observatory, mostly from 1982, but with a few observations from late 1981 and early 1983. Several new or substantially revised periods are reported. Perhaps most interesting are observations of two asteroids, 288 Glauke and 3288 Seleucus, which are in "tumbling," or nonprincipal axis rotation, states. Glauke has the longest rotation period known, similar to 1200 h. Absolute photometry was performed on most objects, allowing us to derive phase relations and absolute magnitudes, For objects where these results are superior to previous values, we have revised the IRAS albedos using our absolute magnitude (H) values. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lowell Observ, Flagstaff, AZ 86001 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. RP Harris, AW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 70 TC 30 Z9 30 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1999 VL 142 IS 1 BP 173 EP 201 DI 10.1006/icar.1999.6181 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 259YD UT WOS:000083920800018 ER PT J AU Sheehan, DP Davis, SS Cuzzi, JN Estberg, GN AF Sheehan, DP Davis, SS Cuzzi, JN Estberg, GN TI Rossby wave propagation and generation in the protoplanetary nebula SO ICARUS LA English DT Article DE planetary formation; origin; solar system; accretion ID GREAT RED SPOT; ANGULAR-MOMENTUM TRANSPORT; PRIMORDIAL SOLAR NEBULA; LOCAL SHEAR INSTABILITY; WEAKLY MAGNETIZED DISKS; ACCRETION DISKS; NUMERICAL SIMULATIONS; TURBULENT CONVECTION; BETA-PLANE; 2-DIMENSIONAL TURBULENCE AB The protoplanetary nebular analog to the planetary Rossby wave is developed, Linear dispersion relations are derived. It is found that the nebular Rossby wave propagates freely in the nebular azimuthal direction and slowly grows in the radial direction. Possible ramifications for the nebula are raised for the reverse transition of turbulence into Rossby waves and zonal jets via the Rhines mechanism (P. B, Rhines 1975, J. Fluid Mech, 69, 417-443), specifically, the formation of long-lived vortices and the accretion of solid bodies. (C) 1999 Academic Press. C1 Univ San Diego, Dept Phys, San Diego, CA 92110 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Univ San Diego, Dept Phys, San Diego, CA 92110 USA. EM dsheehan@acusd.edu NR 87 TC 8 Z9 8 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 EI 1090-2643 J9 ICARUS JI Icarus PD NOV PY 1999 VL 142 IS 1 BP 238 EP 248 DI 10.1006/icar.1999.6200 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 259YD UT WOS:000083920800021 ER PT J AU Smart, MC Ratnakumar, BV Whitcanack, L Surampudi, S Byers, J Marsh, R AF Smart, MC Ratnakumar, BV Whitcanack, L Surampudi, S Byers, J Marsh, R TI Performance characteristics of lithium-ion cells for NASA's Mars 2001 Lander application SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article AB NASA requires lightweight rechargeable batteries for future missions to Mars and the outer planets that are capable of operating over a wide range of temperatures, with high specific energy and energy densities. Due to the attractive performance characteristics, lithium-ion batteries have been identified as the battery chemistry of choice for a number of future applications, including Mars revers and landers. The Mars 2001 Lander (Mars Surveyor Program MSP 01) will be one of the first missions which will utilize lithium-ion technology. This application will require two lithium-ion batteries, each being 28 V (eight cells), 25 Ah and 8 kg. In addition to the requirement of being able to supply at least 200 cycles and 90 days of operation on the surface of Mars, the battery must be capable of operation (both charge and discharge) at temperatures as low as -20 degrees C. To assess the viability of lithium-ion cells for these applications, a number of performance characterization tests have been performed, including: assessing the room temperature cycle life, low temperature cycle life (-20 degrees C), rate capability as a function of temperature, pulse capability, self-discharge and storage characteristics, as well as mission profile capability, This paper will describe the Mars 2001 Lander mission battery requirements and will contain results of the cell testing conducted to-date in support of the mission. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lockheed Martin Astronaut Corp, Denver, CO USA. USAF, Res Lab, Wright Patterson AFB, OH 45433 USA. RP Smart, MC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 12 Z9 12 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD NOV PY 1999 VL 14 IS 11 BP 36 EP 42 DI 10.1109/62.809207 PG 7 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA 262TB UT WOS:000084081600007 ER PT J AU Filman, R AF Filman, R TI Blanket security SO IEEE INTERNET COMPUTING LA English DT Editorial Material C1 NASA, Ames Res Ctr, Caelum Res Corp, Moffett Field, CA 94035 USA. RP Filman, R (reprint author), NASA, Ames Res Ctr, Caelum Res Corp, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1089-7801 J9 IEEE INTERNET COMPUT JI IEEE Internet Comput. PD NOV-DEC PY 1999 VL 3 IS 6 BP 73 EP 74 PG 2 WC Computer Science, Software Engineering SC Computer Science GA 258NJ UT WOS:000083845000011 ER PT J AU Chattopadhyay, G Rice, F Miller, D LeDuc, HG Zmuidzinas, J AF Chattopadhyay, G Rice, F Miller, D LeDuc, HG Zmuidzinas, J TI A 530-GHz balanced mixer SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article DE balanced mixer; low noise; superconductor-insulator-superconductor; (SIS) junctions ID MILLIMETER AB We report on the design and performance of a 530-GHz balanced SIS mixer, the first balanced mixer in this frequency range. This quasi-optical balanced mixer utilizes a cross-slot antenna on a hyperhemispherical substrate lens with eight superconductor-insulator-superconductor (SIS) junctions and a 180 degrees lumped element IF hybrid circuit. The local oscillator (LO) and the radio frequency (RF) signal, orthogonal in polarization to each other, are coupled to the mixer using a wire-grid polarizer, The noise performance of the mixer is excellent, giving an uncorrected receiver noise temperature of 105 K (DSB) at 528 GHz. C1 CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. CALTECH, George Downs Lab Phys, Dept Phys, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab 320 231, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Chattopadhyay, G (reprint author), CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. NR 9 TC 15 Z9 15 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD NOV PY 1999 VL 9 IS 11 BP 467 EP 469 DI 10.1109/75.808038 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 262RU UT WOS:000084080900010 ER PT J AU Asenov, A Brown, AR Davies, JH Saini, S AF Asenov, A Brown, AR Davies, JH Saini, S TI Hierarchical approach to "atomistic" 3-D MOSFET simulation SO IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS LA English DT Article DE deep submicron; device models; modeling; simulation; very large scale integration (VLSI) ID THRESHOLD VOLTAGE; FLUCTUATIONS; TRANSISTORS AB We present a hierarchical approach to the "atomistic" simulation of aggressively scaled sub-0.1-mu m MOSFET's, These devices are so small that their characteristics depend on the precise location of dopant atoms within them, not just on their average density. A full-scale three-dimensional drift-diffusion atomistic simulation approach is first described and used to verify more economical, but restricted, options, To reduce processor time and memory requirements at high drain voltage, we have developed a self-consistent option based on a solution of the current continuity equation restricted to a thin slab of the channel. This is coupled to the solution of the Poisson equation in the whole simulation domain in the Gummel iteration cycles. The accuracy of this approach is investigated in comparison to the full self-consistent solution. At low drain voltage, a single solution of the nonlinear Poisson equation is sufficient to extract the current with satisfactory accuracy. In this case, the current is calculated by solving the current continuity equation in a drift approximation only, also in a thin slab containing the MOSFET channel. The regions of applicability for the different components of this hierarchical approach are illustrated in example simulations covering the random dopant-induced threshold voltage fluctuations, threshold voltage lowering, threshold voltage asymmetry, and drain current fluctuations. C1 Univ Glasgow, Dept Elect & Elect Engn, Glasgow G12 8LT, Lanark, Scotland. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Asenov, A (reprint author), Univ Glasgow, Dept Elect & Elect Engn, Glasgow G12 8LT, Lanark, Scotland. NR 24 TC 64 Z9 65 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0278-0070 J9 IEEE T COMPUT AID D JI IEEE Trans. Comput-Aided Des. Integr. Circuits Syst. PD NOV PY 1999 VL 18 IS 11 BP 1558 EP 1565 DI 10.1109/43.806802 PG 8 WC Computer Science, Hardware & Architecture; Computer Science, Interdisciplinary Applications; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 261VU UT WOS:000084031600003 ER PT J AU Bunting, CF Moeller, KJ Reddy, CJ Scearce, SA AF Bunting, CF Moeller, KJ Reddy, CJ Scearce, SA TI A two-dimensional finite-element analysis of reverberation chambers SO IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY LA English DT Article DE finite elements; mode-stirred chambers; reverberation chambers; statistical electromagnetics ID MODE AB A two-dimensional (2-D) analysis of reverberation chambers is performed at cutoff,The structure considered is lossless and corresponds to an infinite quality factor (Q) chamber. The concept of frequency stirring is used to generate field data for a discrete set of modes and the resulting statistics are analyzed. The field statistics are examined for TE and TM modes, This analysis yields statistics similar to the expected reverberation chamber statistics for the fields, Mechanical stirring is also examined and a connection to the peak-frequency deviation is presented. C1 Old Dominion Univ, Dept Engn Technol, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Electromagnet Res Branch, Hampton, VA 23681 USA. Hampton Univ, Dept Elect Engn, Hampton, VA 23668 USA. Old Dominion Univ, Dept Elect Engn, Norfolk, VA 23529 USA. RP Bunting, CF (reprint author), Old Dominion Univ, Dept Engn Technol, Norfolk, VA 23529 USA. NR 11 TC 18 Z9 20 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9375 J9 IEEE T ELECTROMAGN C JI IEEE Trans. Electromagn. Compat. PD NOV PY 1999 VL 41 IS 4 BP 280 EP 289 DI 10.1109/15.809794 PN 1 PG 10 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 266RX UT WOS:000084314800002 ER PT J AU Smith, JA Goltz, SM AF Smith, JA Goltz, SM TI Simple forest canopy thermal-exitance model SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE brightness temperature; canopy model; surface energy balance; thermal infrared ID BALANCE MODEL AB We describe a simple model to calculate brightness temperature and surface-energy balance for a forest-canopy system. The root mean-square (RMS) error in brightness temperature was 2.5 degrees C. The corresponding RMS errors for net radiation, latent, and sensible heat were 38.9, 30.7, and 41.4 m(-2) respectively. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maine, Orono, ME 04469 USA. RP Smith, JA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 14 TC 1 Z9 1 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD NOV PY 1999 VL 37 IS 6 BP 2733 EP 2736 DI 10.1109/36.803422 PG 4 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 257RY UT WOS:000083796600012 ER PT J AU Smith, JO Abel, JS AF Smith, JO Abel, JS TI Bark and ERB bilinear transforms SO IEEE TRANSACTIONS ON SPEECH AND AUDIO PROCESSING LA English DT Article DE bark; bilinear transform; ERB; filter design; frequency warping ID AUDITORY FILTER SHAPES; TIME-DOMAIN; FREQUENCY; HEARING AB Use of a bilinear conformal map to achieve a frequency warping nearly identical to that of the Bark frequency scale is described. Because the map takes the unit circle to itself, its form is that of the transfer function of a first-order allpass filter, Since it is a first-order map, it preserves the model order of rational systems, making it a valuable frequency warping technique for use in audio filter design. A closed-form weighted-equation-error method is derived that computes the optimal mapping coefficient as a function of sampling rate, and the solution is shown to be generally indistinguishable from the optimal least-squares solution. The optimal Chebyshev mapping is also found to be essentially identical to the optimal least-squares solution. The expression 0.8517 [arctan (0.06583f(s))](1/2) - 0.916 is shown to accurately approximate the optimal allpass coefficient as a function of sampling rate f(s) in kHz for sampling rates greater than 1 kHz, A filter design example is included that illustrates improvements due to carrying out the design over a Bark scale. Corresponding results are also given and compared for approximating the related "equivalent rectangular bandwidth (ERB) scale" of Moore and Glasberg using a first-order allpass transformation. Due to the higher frequency resolution called for by the ERB scale, particularly at low frequencies, the first-order conformal map is less able to follow the desired mapping, and the error is two to three times greater than the Bark-scale case, depending on the sampling rate. C1 Stanford Univ, Ctr Comp Res Mus & Acoust, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Human Factors Res Div, Moffett Field, CA 94035 USA. RP Smith, JO (reprint author), Stanford Univ, Ctr Comp Res Mus & Acoust, Stanford, CA 94305 USA. NR 43 TC 114 Z9 122 U1 1 U2 7 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1063-6676 J9 IEEE T SPEECH AUDI P JI IEEE Trans. Speech Audio Process. PD NOV PY 1999 VL 7 IS 6 BP 697 EP 708 DI 10.1109/89.799695 PG 12 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 252HZ UT WOS:000083497200009 ER PT J AU Zhang, NL Chao, DF AF Zhang, NL Chao, DF TI Mechanisms of convection instability in thin liquid layers induced by evaporation SO INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER LA English DT Article ID DEFORMABLE FREE-SURFACE; STABILITY AB Available theories, including those of Rayleigh and Pearson, successfully explain convection in a thin liquid layer heated from below. However, the theories are unable to explain convection in an evaporating liquid layer heated/cooled from below. In this paper new mechanisms for convection instabilities in evaporating liquid layers are described from a physical viewpoint. Circulating flows in evaporating layers are shown to differ from the flow in layers heated from below without evaporation. Modified Marangoni and Rayleigh numbers are proposed to gauge the convection stability status in both evaporating layers and in liquid layers heated from below without evaporation. (C) 1999 Elsevier Science Ltd. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Zhang, NL (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 15 TC 27 Z9 29 U1 1 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0735-1933 J9 INT COMMUN HEAT MASS JI Int. Commun. Heat Mass Transf. PD NOV PY 1999 VL 26 IS 8 BP 1069 EP 1080 DI 10.1016/S0735-1933(99)00098-6 PG 12 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA 258ZG UT WOS:000083869100003 ER PT J AU Zhang, NL Chao, DF AF Zhang, NL Chao, DF TI Models for enhanced boiling heat transfer by unusual, Marangoni effects under microgravity conditions SO INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER LA English DT Article ID POOL AB A new approach is suggested to enhance boiling heat transfer through introduction of unusual surface tension effects. The surface tension of aqueous solutions of alcohols with a chain length longer than four carbon atoms offers a positive gradient with temperature when the temperature exceeds a certain value. Moreover, the positive gradient near the boiling point has avery large value. This will generate a considerable driving force for bubble departure. As a result, in the nucleate boiling of these solutions, the Marangoni effect around the bubble surface will not impede the bubble detachment from the heater surface but rather will provide an additional driving force for the bubble departure. This effect combines with the buoyancy under normal gravity and acts as a main driving force of bubble departure in microgravity. Models for predictions of the bubble detachment diameters, the nucleate boiling heat transfer coefficient, and the critical heat flux are developed. (C) 1999 Elsevier Science Ltd. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Zhang, NL (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 24 TC 17 Z9 17 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0735-1933 J9 INT COMMUN HEAT MASS JI Int. Commun. Heat Mass Transf. PD NOV PY 1999 VL 26 IS 8 BP 1081 EP 1090 DI 10.1016/S0735-1933(99)00099-8 PG 10 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA 258ZG UT WOS:000083869100004 ER PT J AU Skitka, LJ Mosier, KL Burdick, M AF Skitka, LJ Mosier, KL Burdick, M TI Does automation bias decision-making? SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Article AB Computerized system monitors and decision aids are increasingly common additions to critical decision-making contexts such as intensive care units, nuclear power plants and aircraft cockpits. These aids are introduced with the ubiquitous goal of "reducing human error". The present study compared error rates in a simulated flight task with and without a computer that monitored system states and made decision recommendations. Participants in non-automated settings out-performed their counterparts with a very but not perfectly reliable automated aid on a monitoring task. Participants with an aid made errors of omission (missed events when not explicitly prompted about them by the aid) and commission (did what an automated aid recommended, even when it contradicted their training and other 100% valid and available indicators). Possible causes and consequences of automation bias are discussed (C) 1999 Academic Press. C1 Univ Illinois, Dept Psychol, Chicago, IL 60607 USA. San Francisco State Univ, San Francisco, CA USA. NASA, San Jose State Univ Fdn, Ames Res Ctr, Moffett Field, CA USA. RP Skitka, LJ (reprint author), Univ Illinois, Dept Psychol, 1007 W Harrison St, Chicago, IL 60607 USA. OI Skitka, Linda/0000-0002-7078-0650 NR 33 TC 70 Z9 70 U1 0 U2 7 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1071-5819 J9 INT J HUM-COMPUT ST JI Int. J. Hum.-Comput. Stud. PD NOV PY 1999 VL 51 IS 5 BP 991 EP 1006 DI 10.1006/ijhc.1999.0252 PG 16 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA 253QN UT WOS:000083567400006 ER PT J AU Dukhan, N Masiulaniec, KC De Witt, KJ Van Fossen, GJ AF Dukhan, N Masiulaniec, KC De Witt, KJ Van Fossen, GJ TI Experimental heat transfer coefficients from ice-roughened surfaces for aircraft deicing design SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 34th Aerospace Sciences Meeting and Exhibit CY JAN 15-19, 1996 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID NACA-0012 AIRFOIL AB Experimental Stanton numbers are presented for seven aluminum model castings of ice-roughened surfaces in parallel air flow for Re-x ranging from 5.3 x 10(4) to 1.3 x 10(6). The Stanton numbers were generally higher than those far previous studies with hemispherical and truncated cone roughness elements, and the majority of the data were in the fully turbulent regime, In general, the rime feather ice roughness produced the highest rate of heat transfer, followed by the rough glaze roughness, the smooth rime roughness, and the smooth glaze roughness, respectively. in the fully developed turbulent regime the! local Stanton number could be described by a power law of the form St(x) = a Re-x(m) Pr-0.4 where a and m correlated well with the newly defined Index of Random Roughness and the roughness height, respectively. This work provides a set of measured values of the Stanton number, specific to the case of stochastically accreted ice on aircraft surfaces, needed for the effective design of in-flight design systems. C1 John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. Univ Toledo, Dept Mech Ind & Mfg Engn, Toledo, OH 43606 USA. Univ Toledo, Dept Chem Engn, Toledo, OH 43606 USA. RP Dukhan, N (reprint author), RELTEC Corp, 4350 Weaver Pkwy, Warrenville, IL 60555 USA. NR 24 TC 5 Z9 5 U1 0 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1999 VL 36 IS 6 BP 948 EP 956 DI 10.2514/2.2556 PG 9 WC Engineering, Aerospace SC Engineering GA 264NF UT WOS:000084187800008 ER PT J AU Anders, JB Anderson, WK Murthy, AV AF Anders, JB Anderson, WK Murthy, AV TI Transonic similarity theory applied to a supercritical airfoil in heavy gas SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 20th Advanced Measurement and Ground Testing Technology Conference CY JUN 15-18, 1998 CL ALBUQUERQUE, NEW MEXICO SP Amer Inst Aeronaut & Astronaut AB The use of a high-molecular-weight test gas to increase the Reynolds number range of transonic wind tunnels is explored experimentally. Modifications to a transonic wind tunnel for heavy-gas operation are described, and the real-gas properties of the example heavy gas (sulfur hexafluoride) are discussed. Sulfur hexafluoride is shown to increase the test Reynolds number by a factor of more than 2 over air at the same stagnation conditions and test section Mach number. Experimental and computational pressure distributions on an advanced supercritical airfoil at Mach numbers of 0.7 and 0.72 in both sulfur hexafluoride and nitrogen are presented. Transonic similarity theory is shown to be successful in transforming the heavy-gas results to equivalent nitrogen (air) results, provided the correct definition of gamma is used and viscous effects are not dominant. When strong shocks are present on the airfoil upper surface, transonic similarity theory is shown to be less successful in the shock-boundary-layer interaction region, in agreement with computational predictions. C1 NASA, Langley Res Ctr, Flow Modeling & Control Branch, Hampton, VA 23681 USA. Aerotech Inc, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Aerodyanm & Acoust Methods Branch, Hampton, VA 23681 USA. RP Anders, JB (reprint author), NASA, Langley Res Ctr, Flow Modeling & Control Branch, MS 170, Hampton, VA 23681 USA. NR 19 TC 6 Z9 7 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1999 VL 36 IS 6 BP 957 EP 964 DI 10.2514/2.2557 PG 8 WC Engineering, Aerospace SC Engineering GA 264NF UT WOS:000084187800009 ER PT J AU Mavriplis, DJ Pirzadeh, S AF Mavriplis, DJ Pirzadeh, S TI Large-scale parallel unstructured mesh computations for three-dimensional high-lift analysis SO JOURNAL OF AIRCRAFT LA English DT Article ID EQUATIONS; SOLVER; GRIDS AB A complete geometry to drag polar analysis capability for three-dimensional high-lift configurations is described. The approach is based on the use of unstructured meshes to enable rapid turnaround for complicated geometries that arise in high-lift configurations. Special attention is devoted to creating a capability for enabling analyses on highly resolved grids. Unstructured meshes of several million vertices are initially generated on a workstation and subsequently are refined on a supercomputer. The Row is solved on these refined meshes on large parallel computers using an unstructured agglomeration multigrid algorithm. Good prediction of lift and drag throughout the range of incidences is demonstrated on a transport takeoff configuration using up to 24.7 x 10(6) grid points. The feasibility of using this approach in a production environment on existing parallel machines is demonstrated, as well as the scalability of the solver on machines using up to 1450 processors. C1 NASA, Langley Res Ctr, Configurat Aerodynam Branch, Hampton, VA 23681 USA. NR 36 TC 27 Z9 28 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1999 VL 36 IS 6 BP 987 EP 998 DI 10.2514/2.2540 PG 12 WC Engineering, Aerospace SC Engineering GA 264NF UT WOS:000084187800013 ER PT J AU Schairer, ET Hand, LA AF Schairer, ET Hand, LA TI Measurements of unsteady aeroelastic model deformation by stereo photogrammetry SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 15th Applied Aerodynamics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut AB Stereo photogrammetry measurements of the deformation of simple, hat-plate, clipped delta wings that were undergoing aeroelastic oscillations in transonic flow are described. The measurements were made in High Reynolds number Channel 2 at NASA Ames Research Center. Two types of aeroelastic responses were measured: 1) highly damped responses in which the tip of the model was deflected and then released at subcritical dynamic pressures; and 2) responses excited by perturbations in the flow as the dynamic pressure was slowly increased until the model became unstable. The model was imaged by three synchronized black-and-white video cameras, and the data were recorded on videotape. Correlated images from two of these cameras were used to estimate the space coordinates of reference marks on the model at each instant, and the motion of each mark was estimated by fitting the deflection data with a damped sinusoid. The resulting estimates of the frequency and damping of the first-bending-mode oscillations compared favorably with strain-gauge measurements. A large increase in the phase difference between motions of the leading and the trailing edges was observed just before the models became unstable. C1 NASA, Ames Res Ctr, Expt Phys Branch, Moffett Field, CA 94035 USA. RP Schairer, ET (reprint author), NASA, Ames Res Ctr, Expt Phys Branch, Moffett Field, CA 94035 USA. NR 25 TC 12 Z9 16 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1999 VL 36 IS 6 BP 1033 EP 1040 DI 10.2514/2.2545 PG 8 WC Engineering, Aerospace SC Engineering GA 264NF UT WOS:000084187800018 ER PT J AU Jegley, DC AF Jegley, DC TI Parametric study of the behavior of graphite/epoxy panels with stiffener terminations SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/ASME/ASC/AHS 40th Structures, Structural dynamics, and Materials Conference CY APR 12-15, 1999 CL ST LOUIS, MISSOURI SP Amer Inst Aeronaut & Astronaut, ASME, ASC, AHS AB The results of a parametric study examining six types of stiffener terminations for stiffened graphite/epoxy panels are presented. Stiffener blades are terminated by attaching to another blade, by tapering the stiffener height, by tapering the stiffener thickness, or by a combination of these methods. Stiffener flanges are also terminated abruptly or by tapering their thickness. Flange length is also varied. Both thin-skin panels and thick-skin panels art? considered. Panels were analyzed with a nonlinear finite element analysis code to determine panel response and failure modes. Midplane axial and shear strains, surface strains, interlaminar strains, and failure predictions for the panels are discussed, These results indicate that the mechanism initiating failure is dependent on the stringer configuration of the panel. Interlaminar stresses and bending must be considered to predict the failure of thin-skin panels, and interlaminar stress, in-plane shear strains, and axial strains must be considered to predict the failure of thick-skin panels. C1 NASA, Langley Res Ctr, Struct Mech Branch, Struct & Mat Competency, Hampton, VA 23681 USA. RP Jegley, DC (reprint author), NASA, Langley Res Ctr, Struct Mech Branch, Struct & Mat Competency, Mail Stop 190, Hampton, VA 23681 USA. NR 6 TC 1 Z9 3 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1999 VL 36 IS 6 BP 1048 EP 1054 DI 10.2514/2.2548 PG 7 WC Engineering, Aerospace SC Engineering GA 264NF UT WOS:000084187800020 ER PT J AU Anagnostou, EN Negri, AJ Adler, RF AF Anagnostou, EN Negri, AJ Adler, RF TI Statistical adjustment of satellite microwave monthly rainfall estimates over Amazonia SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID ERRORS; SPACE; MODEL AB A technique is described for quantifying nonlinear adjustment to the half-degree monthly rainfall estimates over land, derived from the Special Sensor Microwave Imager (SSM/I) observations. The technique uses a function that represents the distortion between the probability distributions of SSM/I and rain gauge half-degree monthly rainfall. The proposed adjustment procedure is assessed and evaluated with a 10-yr period (1988-97) of SSM/I observations over the northern South America region (15 degrees N-15 degrees S, 80 degrees-35 degrees W), which includes the Amazon basin. The rain estimates are derived from the National Aeronautics and Space Administration's Goddard Profiling (GPROF) algorithm instantaneous rain-rate retrievals, averaged in half-degree areas and aggregated into monthly accumulations. Monthly rain accumulations from a network of 650 rain gauges distributed across the Amazon basin and the state of Ceara in northeastern Brazil are used for calibration and validation, respectively. Assessment of the adjustment relationship with the validation dataset shows an overall 45% GPROF-gauge root-mean-square (rms) difference reduction with respect to no adjustment, which is due mainly to elimination of the mean bias, and a respective 10% increase in the GPROF-gauge correlation. The rms difference between 5 degrees gridbox monthly rain averages of adjusted GPROF and rain gauges is 23% of the mean rain, and the corresponding correlation coefficient is 0.94. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Anagnostou, EN (reprint author), Univ Connecticut, Dept Civil & Environm Engn, Storrs, CT 06269 USA. NR 11 TC 18 Z9 18 U1 0 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD NOV PY 1999 VL 38 IS 11 BP 1590 EP 1598 DI 10.1175/1520-0450(1999)038<1590:SAOSMM>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 258MD UT WOS:000083842200003 ER PT J AU Damayanthi, P Joshi, RP McAdoo, JA AF Damayanthi, P Joshi, RP McAdoo, JA TI Electron mobility and drift velocity calculations for bulk GaSb material SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID BEAM EPITAXIAL-GROWTH; GALLIUM ANTIMONIDE; INAS/GASB SUPERLATTICES; TEMPERATURE; PARAMETERS; PRESSURE; WELL; GAAS AB Electron mobility and drift velocity simulation results are presented for bulk GaSb based on a many-valley, anisotropic Monte Carlo model. Our mobility results at 300 K are in good agreement with available experimental data. Values close to the room temperature GaAs mobility have been predicted. Transient drift velocities are demonstrated to be higher than for GaAs and the negative differential velocity regime is shown to occur at much lower electric fields of about 1 kV/cm. The material could be useful as a low voltage oscillator or in high speed photodetection. (C) 1999 American Institute of Physics. [S0021- 8979(99)00321-7]. C1 Old Dominion Univ, Dept Elect & Comp Engn, Norfolk, VA 23529 USA. NASA, Electroopt Branch, Aerosp Elect Syst Div, Langley Res Ctr, Hampton, VA 23681 USA. RP Damayanthi, P (reprint author), Old Dominion Univ, Dept Elect & Comp Engn, Norfolk, VA 23529 USA. NR 36 TC 6 Z9 6 U1 1 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD NOV 1 PY 1999 VL 86 IS 9 BP 5060 EP 5064 DI 10.1063/1.371479 PG 5 WC Physics, Applied SC Physics GA 246XA UT WOS:000083189100050 ER PT J AU Zibordi, G Doyle, JP Hooker, SB AF Zibordi, G Doyle, JP Hooker, SB TI Offshore tower shading effects on in-water optical measurements SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID IRRADIANCE MEASUREMENTS; SIMULATIONS; OCEAN AB A field campaign was performed to estimate the shading effect induced on in-water irradiance and radiance measurements taken in the immediate vicinity of the Acqua Alta Oceanographic Tower (AAOT), located in the northern Adriatic Sea, which is regularly used to support ocean color validation activities; Sequences of downwelling irradiance and upwelling radiance profiles were collected at varying distances from the tower to evaluate the shading effects during clear-sky conditions as a function of the deployment distance. The experimental data, as well as Monte Carlo simulations, indicate that the shading effect is negligible for both downwelling irradiances and upwelling radiances at deployment distances greater than 15 and 20 m, respectively. At closer distances, for example, at the 7.5-m deployment distance regularly used at the AAOT for the collection of underwater optical measurements, the shading effect is remarkable: both field and simulated data at a depth of 7 m and a wavelength of 443 nm show that, with a relatively low sun zenith angle of 22 degrees, the shading effect is within 3% for downwelling irradiance and within 8% for upwelling radiance. Monte Carlo simulations at 443, 555, and 665 nm, computed at a depth of 0(-) m and with values of seawater inherent optical properties representative of the AAOT site, are used to extend considerations on shading effects to measurements taken during different illumination conditions at the 7.5-m deployment distance. Simulations for ideal clear-sky conditions (i.e., in the absence of atmospheric aerosols) show that errors induced by AAOT perturbations significantly vary as a function of wavelength and sun zenith angle. The highest values are observed at 443 nm where, with the sun zenith angle ranging from 20 degrees to 70 degrees, errors vary from 2.4% to approximately 6.2% for downwelling irradiance and from a minimum of 3.0% (occurring at 30 degrees) to almost 6.6% for upwelling radiance. Simulations also show that thr shading error can be as high as approximately 20% for both irradiance and radiance measurements taken during overcast sky conditions. C1 Commiss European Communities, Joint Res Ctr, Space Applicat Inst, Marine Environm Unit, I-21020 Ispra, VA, Italy. Univ London Imperial Coll Sci Technol & Med, Environm Technol Ctr, Dept Phys, London, England. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Zibordi, G (reprint author), Joint Res Ctr, Inst Delle Appl Spaziali, SAI-TP 272, I-21020 Ispra, VA, Italy. RI Hooker, Stanford/E-2162-2012 NR 28 TC 17 Z9 17 U1 1 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD NOV PY 1999 VL 16 IS 11 BP 1767 EP 1779 DI 10.1175/1520-0426(1999)016<1767:OTSEOI>2.0.CO;2 PN 2 PG 13 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 258VH UT WOS:000083859600009 ER PT J AU Iijima, BA Harris, IL Ho, CM Lindqwister, UJ Mannucci, AJ Pi, X Reyes, MJ Sparks, LC Wilson, BD AF Iijima, BA Harris, IL Ho, CM Lindqwister, UJ Mannucci, AJ Pi, X Reyes, MJ Sparks, LC Wilson, BD TI Automated daily process for global ionospheric total electron content maps and satellite ocean altimeter ionospheric calibration based on Global Positioning System data SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article; Proceedings Paper CT 2nd Annual Workshop on Ionospheric Determination for Ocean Altimetry and GPS Surface Reflection CY DEC 01-03, 1998 CL ARCADIA, CALIFORNIA SP NASA, USN, Jet Propuls Lab ID GPS; BIASES; TOPEX AB The accuracy of single-frequency ocean altimeters benefits from calibration of the total electron content (TEC) of the ionosphere below the satellite. Data from a global network of Global Positioning System (GPS) receivers provides timely, continuous, and globally well-distributed measurements of ionospheric electron content. For several months we have been running a daily automatic Global Ionospheric Map process which inputs global GPS data and climatological ionosphere data into a Kalman filter, and produces global ionospheric TEC maps and ocean altimeter calibration data within 24 h of the end-of-day. Other groups have successfully applied this output to altimeter data from the GFO satellite and in orbit, determination for the TOPEX/Poseidon satellite. Daily comparison of the global TEC maps with independent TEC data from the TOPEX altimeter is performed as a check on the calibration whenever the TOPEX data are available. Comparisons of the global TEC maps against TOPEX data will be discussed. Accuracy is best at mid-to-high absolute latitudes (\latitude\ > 30 degrees) due to the better geographic distribution of GPS receivers and the relative simplicity of the ionosphere, Our highly data-driven technique is relatively less accurate at low latitudes and especially during ionospheric storm periods, due to the relative scarcity of GPS receivers and the structure and volatility of the ionosphere. However, it is still significantly more accurate than climatological models. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Iijima, BA (reprint author), CALTECH, Jet Prop Lab, M-S 138-308,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 22 TC 76 Z9 84 U1 1 U2 6 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD NOV PY 1999 VL 61 IS 16 BP 1205 EP 1218 DI 10.1016/S1364-6826(99)00067-X PG 14 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 282HH UT WOS:000085211900003 ER PT J AU Mannucci, AJ Iijima, B Sparks, L Pi, XQ Wilson, B Lindqwister, U AF Mannucci, AJ Iijima, B Sparks, L Pi, XQ Wilson, B Lindqwister, U TI Assessment of global TEC mapping using a three-dimensional electron density model SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article; Proceedings Paper CT 2nd Annual Workshop on Ionospheric Determination for Ocean Altimetry and GPS Surface Reflection CY DEC 01-03, 1998 CL ARCADIA, CALIFORNIA SP NASA, USN, Jet Propuls Lab ID POSITIONING SYSTEM; IONOSPHERIC MAPS; GPS TOMOGRAPHY; RADAR; OCCULTATIONS; BIASES; DELAY AB Dual-frequency transmissions from the Global Positioning System satellites can be used to measure and map ionospheric total electron content (TEC) on global scales, Using data exclusively from ground-based GPS networks, global ionosphere mapping has been successfully applied using either two- or three-dimensional techniques. Two-dimensional TEC maps retrieve a horizontally-varying distribution of total electron content, assuming a fixed vertical electron density profile. In three-dimensional mapping, both the horizontal and vertical distribution density are adjusted to fit the data. We describe a three-dimensional TEC mapping algorithm that uses three independent constant-density slabs stacked vertically to model the electron density, and compare with a more conventional two-dimensional approach using a single slab. One apparent benefit of the new method is reduction in a level error of the TEC maps, which decreased by 1.7 TECU using the three-dimensional retrieval on simulated data (1 TEC Unit corresponds to 10(16) electrons/m(2)). Another benefit of the multilayer approach is improved slant TEC modeling, Using actual data from an equatorial site at Cocos Islands (96.8E, 12.2 S), three slab modeling improved estimates of slant TEC by a factor of 2 for elevation angles between 10 and 20 degrees (9 versus 4.4 TECU, root-mean-square). However, the global structure of the vertical TEC retrievals we analyzed did not improve using three-dimensional modeling. This may be due to a critical approximation shared by both techniques that TEC persists unchanged at a given local time. This assumption is required to produce global maps from observations acquired from widely scattered ground receivers, Further improving the retrieval of global TEC structure with ground-based data probably requires improved dynamical models of TEC behavior. New data available from GPS receivers in low Earth orbit is also promising. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mannucci, AJ (reprint author), CALTECH, Jet Prop Lab, Mail Stn 138-308,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 24 TC 24 Z9 28 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD NOV PY 1999 VL 61 IS 16 BP 1227 EP 1236 DI 10.1016/S1364-6826(99)00053-X PG 10 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 282HH UT WOS:000085211900005 ER PT J AU Wilson, RM AF Wilson, RM TI Variation of surface air temperatures in relation to El Nino and cataclysmic volcanic eruptions, 1796-1882 SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID GREENLAND ICE CORE; SOUTHERN OSCILLATION; EXPLOSIVE VOLCANISM; SUMMER TEMPERATURE; PINATUBO; RECORD; SHEET; SULFUR; EVENTS; NUMBER AB During the contemporaneous interval of 1796-1882 a number of significant decreases in temperature are found in the records of Central England and Northern Ireland. These decreases appear to be related to the occurrences of El Nino and/or cataclysmic volcanic eruptions. For example, a composite of residual Central England temperatures, centering temperatures on the yearly onsets of 20 El Nino events of moderate to stronger strengths, shows that, on average, the change in temperature varied by about +/- 0.3 degrees C from normal, being warmer during the boreal fall-winter leading up to the El Nino year and cooler during the spring-summer of the El Nino year. Also, the influence of El Nino on Central England temperatures appears to have lasted about 1-2 years. Similarly, a composite of residual Central England temperatures, centering temperatures on the month of eruption for 26 cataclysmic volcanic eruptions, shows that, on average, the temperature decreased by about 0.1-0.2 degrees C, typically, 1-2 years after the eruption; although for specific events, like Tambora, the decrease was considerably greater. Additionally, tropical eruptions appear to have produced greater cooling than extratropical eruptions, and eruptions occurring in boreal spring-summer appear to have produced greater cooling than those occurring in fall-winter. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Sci Directorate, Huntsville, AL 35812 USA. RP Wilson, RM (reprint author), NASA, George C Marshall Space Flight Ctr, Sci Directorate, SD50, Huntsville, AL 35812 USA. NR 53 TC 5 Z9 6 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD NOV PY 1999 VL 61 IS 17 BP 1307 EP 1319 DI 10.1016/S1364-6826(99)00055-3 PG 13 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 285KN UT WOS:000085388400007 ER PT J AU Ferguson, FT Nuth, JA AF Ferguson, FT Nuth, JA TI The influence of buoyant convection on the operation of the upward thermal diffusion cloud nucleation chamber SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID HOMOGENEOUS NUCLEATION; SUPERSATURATED VAPOR; BACKGROUND GASES; 2-DIMENSIONAL TRANSPORT; CONDENSATION; PRESSURE; IONS AB Recently, the stable operation of the upward thermal diffusion cloud chamber with respect to buoyancy-induced convection has become a concern in obtaining reliable nucleation data. During chamber operation, evidence of strong convective currents are clearly visible due to the curved trajectories of entrained droplets. A potential problem exists when these flows are much smaller in magnitude; there is no visible evidence of convection, yet these minute flows may result in systematic errors in the nucleation data calculated via 1D diffusive models of the transport mechanisms within the chamber. To examine whether such flows are possible and the characteristics of these flows we have developed an extension to recent 2D modeling of the nucleation chamber which includes buoyancy-induced, convective motion. We have examined both wet and dry chamber operation with an example case of 1-propanol in helium at a pressure of 1.18 bar. In addition, for the dry wall case we examined the effect of overheating the chamber wall and varying the chamber diameter. Results indicate that, for the representative cases investigated, very subtle convective flows can exist and that these minute flows can affect the maximum attainable supersaturation along the chamber centerline. Finally, a list of general recommendations are given for minimizing the possibility of such flows within the cloud chamber. (C) 1999 American Institute of Physics. [S0021-9606(99)51833-3]. C1 Catholic Univ Amer, Dept Chem, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ferguson, FT (reprint author), Catholic Univ Amer, Dept Chem, Washington, DC 20064 USA. RI Ferguson, Frank/C-9493-2012; Nuth, Joseph/E-7085-2012 NR 19 TC 18 Z9 18 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD NOV 1 PY 1999 VL 111 IS 17 BP 8013 EP 8021 DI 10.1063/1.480274 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 245LX UT WOS:000083111400036 ER PT J AU Prabhakara, C Iacovazzi, R AF Prabhakara, C Iacovazzi, R TI Comments on "Analysis of the merging procedure for the MSU daily temperature time series" SO JOURNAL OF CLIMATE LA English DT Article ID TRENDS; RECORDS C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon ITSS Corp, Greenbelt, MD USA. RP Prabhakara, C (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. RI Iacovazzi Jr, Robert/G-3867-2010 NR 8 TC 5 Z9 5 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD NOV PY 1999 VL 12 IS 11 BP 3331 EP 3334 DI 10.1175/1520-0442(1999)012<3331:COAOTM>2.0.CO;2 PG 4 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 250KX UT WOS:000083388500011 ER PT J AU Mei, RW Luo, LS Shyy, W AF Mei, RW Luo, LS Shyy, W TI An accurate curved boundary treatment in the lattice Boltzmann method SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID NAVIER-STOKES EQUATION; ANALYTIC SOLUTIONS; GAS AUTOMATA; SIMPLE FLOWS; BGK MODELS; SIMULATIONS AB The lattice Boltzmann equation (LBE) is an alternative kinetic method capable of solving hydrodynamics for various systems. Major advantages of the method are due to the fact that the solution for the particle distribution functions is explicit, easy to implement, and natural to parallelize. Because the method often uses uniform regular Cartesian lattices in space, curved boundaries are often approximated by a series of stairs that leads to reduction in computational accuracy. In this work, a second-order accurate treatment of the boundary condition in the LEE method is developed for a curved boundary. The proposed treatment of the curved boundaries is an improvement of a scheme due to O. Filippova and D. Hanel (1998, J. Comput. Phys. 147, 219). The proposed treatment for curved boundaries is tested against several flow problems: 2-D channel flows with constant and oscillating pressure gradients for which analytic solutions are known, flow due to an impulsively started wall, lid-driven square cavity flow, and uniform flow over a column of circular cylinders. The second-order accuracy is observed with a solid boundary arbitrarily placed between lattice nodes. The proposed boundary condition has well-behaved stability characteristics when the relaxation time is close to 1/2, the zero limit of viscosity. The improvement can make a substantial contribution toward simulating practical fluid flow problems using the lattice Boltzmann method. (C) 1999 Academic Press. C1 Univ Florida, Dept Aerosp Engn Mech & Engn Sci, Gainesville, FL 32611 USA. ICASE, NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Mei, RW (reprint author), Univ Florida, Dept Aerosp Engn Mech & Engn Sci, Gainesville, FL 32611 USA. RI Luo, Li-Shi/A-4561-2011 OI Luo, Li-Shi/0000-0003-1215-7892 NR 33 TC 310 Z9 340 U1 4 U2 40 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD NOV 1 PY 1999 VL 155 IS 2 BP 307 EP 330 DI 10.1006/jcph.1999.6334 PG 24 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 254AX UT WOS:000083590300004 ER PT J AU Su, CH Feth, S Volz, MP Matyi, R George, MA Chattopadhyay, K Burger, A Lehoczky, SL AF Su, CH Feth, S Volz, MP Matyi, R George, MA Chattopadhyay, K Burger, A Lehoczky, SL TI Vapor growth and characterization of Cr-doped ZnSe crystals SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE Cr-doped ZnSe crystals; vapor growth; HRTXD; AFM ID TRANSPORT AB Cr-doped ZnSe single crystals were grown by a self-seeded physical vapor transport technique in both vertical (stabilized) and horizontal configurations. The source materials were mixtures of ZnSe and CrSe. Growth temperatures were in the range of 1140-1150 degrees C and the furnace translation rates were 1.9-2.2 mm/day. The surface morphology of the as-grown crystals was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Different features of the as-grown surface of the vertically and horizontally grown crystals suggest that different growth mechanisms were involved in the two growth configurations. The [Cr] doping levels were determined to be in the range of 1.8-8.3 x 10(19) cm(-3) from optical absorption measurements. The crystalline quality of the grown crystals were examined by high-resolution triple-crystal X-ray diffraction (HRTXD) analysis. (C) 1999 Published by Elsevier Science B.V. C1 NASA, George C Marshall Space Flight Ctr, Micrograv Sci & Applicat Dept, Sci Directorate, Huntsville, AL 35812 USA. Univ Wisconsin, Dept Mat Sci & Engn, Madison, WI 53706 USA. Univ Alabama, Dept Chem, Ctr Mat & Surface Sci, Huntsville, AL 35899 USA. Fisk Univ, Dept Phys, NASA, Fisk Ctr Photon Mat & Devices, Nashville, TN 37208 USA. RP Su, CH (reprint author), NASA, George C Marshall Space Flight Ctr, Micrograv Sci & Applicat Dept, Sci Directorate, SD 47, Huntsville, AL 35812 USA. RI Feth, Shari/F-6302-2013 OI Feth, Shari/0000-0003-3545-5649 NR 9 TC 33 Z9 35 U1 4 U2 9 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD NOV PY 1999 VL 207 IS 1-2 BP 35 EP 42 DI 10.1016/S0022-0248(99)00358-9 PG 8 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 254CT UT WOS:000083594900007 ER PT J AU Bell, GW Buckel, JA Stoner, AW AF Bell, GW Buckel, JA Stoner, AW TI Effects of alternative prey on cannibalism in age-1 bluefish SO JOURNAL OF FISH BIOLOGY LA English DT Article DE selectivity; switching; cannibalism; alternative prey; density dependent; bluefish; Pomatomus salatrix; Atlantic silverside; Menidia menidia ID THE-YEAR BLUEFISH; POLLOCK THERAGRA-CHALCOGRAMMA; EASTERN BERING SEA; POMATOMUS-SALTATRIX; WALLEYE POLLOCK; JUVENILE BLUEFISH; CAPTURE SUCCESS; SIZE-SELECTION; PREDATION; RECRUITMENT AB Age-1 bluefish Pomatomus saltatrix were offered both age-0 bluefish and age-1 Atlantic silversides Menidia menidia in the following proportions: 0 : 1.0, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, 1.0 : 0. Atlantic silversides were consumed in greater proportion than offered throughout all treatments suggesting strong selection for silversides. There was no evidence of prey-m itching. The behavioral processes leading to age-1 bluefish selection of Atlantic silversides was investigated. The proportion of attacks on each prey species was distributed randomly, or slightly higher on age-0 bluefish; however, capture success was greater on silversides than on age-0 bluefish prey. Therefore, age-1 bluefish did not actively select for silversides and the observed selection pattern is a result of passive processes. These findings suggest that prey snitching between age-0 bluefish and an alternative prey probably does not act as a stabilizing mechanism in the bluefish population and confirm the importance of capture success in determining piscivore selectivity patterns. (C) 1999 The Fisherics Society of the British Isles. C1 NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. RP Buckel, JA (reprint author), NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 33 TC 10 Z9 10 U1 0 U2 2 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-1112 J9 J FISH BIOL JI J. Fish Biol. PD NOV PY 1999 VL 55 IS 5 BP 990 EP 1000 DI 10.1006/jfbi.1999.1102 PG 11 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 256RJ UT WOS:000083739100006 ER PT J AU Goolish, EM Okutake, K AF Goolish, EM Okutake, K TI Lack of gas bladder inflation by the larvae of zebrafish in the absence of an air-water interface SO JOURNAL OF FISH BIOLOGY LA English DT Article DE fish larvae; swimbladder; gas phase; lordosis; buoyancy; growth; survivorship ID UNINFLATED SWIM BLADDERS; DICENTRARCHUS-LABRAX; SPARUS-AURATUS; SWIMBLADDER; VERTEBRATE; BIOLOGY; BASS AB Compared to a control gas bladder inflation rate of 95.1 +/- 1.9%, zebrafish Danio rerio larvae 72 h post-fertilization maintained in closed chambers had an inflation rate of just 19.1 +/- 7.7%. Larval survivorship through 10 days in closed chambers (32%) was significantly less than that in open chambers (76%), and the extent of spinal curvature was significantly higher among larvae maintained in closed chambers. Larvae which failed to inflate their gas bladder showed very little change in body length, and had a final dry weight c. 14% of that for control larvae. The small number of larvae with inflated gas bladders found in closed chambers might be attributed to the inadvertent introduction of small bubbles into two replicates. These results indicate that access to an ah-water interface is critical for the normal development of zebrafish larvae. but also that a small, submerged, spherical gas volume may to a limited extent be used for initial gas bladder inflation. (C) 1999 The Fisheries Society of the British Isles. C1 NASA, Ames Res Ctr, Space Stn Biol Res Project, Lockheed Martin Space Operat, Moffett Field, CA 94035 USA. RP Goolish, EM (reprint author), NASA, Ames Res Ctr, Space Stn Biol Res Project, Lockheed Martin Space Operat, T20G, Moffett Field, CA 94035 USA. NR 25 TC 32 Z9 34 U1 2 U2 13 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-1112 J9 J FISH BIOL JI J. Fish Biol. PD NOV PY 1999 VL 55 IS 5 BP 1054 EP 1063 DI 10.1006/jfbi.1999.1110 PG 10 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 256RJ UT WOS:000083739100012 ER PT J AU Wang, JJ Gary, SP Liewer, PC AF Wang, JJ Gary, SP Liewer, PC TI Electromagnetic heavy-ion/proton instabilities SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ION-BEAM INSTABILITIES; SOLAR-WIND; COMPUTER-SIMULATIONS; DRIVEN; SPACE; WAVES AB Ion/ion instabilities are driven by the relative velocity v(o) of two distinct ion components. This manuscript reports linear theory and simulation studies of electromagnetic ion/ion instabilities for a warm proton component streaming against a cool, heavy ion component in a homogeneous, magnetized, collisionless plasma in which v(o) is parallel or antiparallel to the background magnetic field. Under these conditions linear Vlasov dispersion theory predicts that the fastest growing mode is usually the right-hand polarized proton resonant instability. Two-dimensional initial value hybrid simulations of this growing mode are carried out, yielding scaling relations for the maximum fluctuating magnetic field energy density and the proton pickup time. The latter is proportional to the inverse of the maximum growth rate for a wide range of plasma parameters. C1 Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Wang, JJ (reprint author), Jet Prop Lab, Mail Stop 125-109, Pasadena, CA 91109 USA. NR 18 TC 1 Z9 1 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24807 EP 24818 DI 10.1029/1999JA900333 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700018 ER PT J AU Bhattacharjee, A Ng, CS Ghosh, S Goldstein, ML AF Bhattacharjee, A Ng, CS Ghosh, S Goldstein, ML TI A comparative study of four-field and fully compressible magnetohydrodynamic turbulence in the solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INCOMPRESSIBLE MAGNETOHYDRODYNAMICS; FLUCTUATIONS; WAVES; EVOLUTION; TEMPERATURE; EQUATIONS; FLUIDS AB A four-field system of equations has been recently derived from the compressible magnetohydrodynamic (MHD) equations to describe turbulence in the solar wind. These equations apply to a plasma permeated by a spatially varying mean magnetic field when the plasma, beta is of the order unity or less. In the presence of spatial inhomogeneities, the four-field equations predict pressure fluctuations df the order of the Mach number of the turbulence, as observed by Helios 1 and 2. It is shown that inhomogeneities that occur only in the form of pressure-balanced structures cannot account for density fluctuations as large as the Mach number of the turbulence. Numerical predictions from the four-field and compressible MHD equations are compared using the same initial condition. The comparison shows that the predictions of the four-field model are qualitatively consistent with the predictions of the compressible MHD model and suggests that the four-field model is a viable model of compressible turbulence in the solar wind. C1 Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Bhattacharjee, A (reprint author), Univ Iowa, Dept Phys & Astron, 203 Van Allen Hall, Iowa City, IA 52242 USA. RI Ng, Chung-Sang/F-2980-2011; Goldstein, Melvyn/B-1724-2008 OI Ng, Chung-Sang/0000-0003-1861-5356; NR 31 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24835 EP 24843 DI 10.1029/1999JA900327 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700020 ER PT J AU Verheest, F Lakhina, GS Tsurutani, BT AF Verheest, F Lakhina, GS Tsurutani, BT TI Intermediate electromagnetic turbulence at comets SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FREQUENCY PLASMA TURBULENCE; MAGNETIC-FIELD OBSERVATIONS; ION-BEAM INSTABILITIES; WATER GROUP IONS; SOLAR-WIND; BOW SHOCK; GIACOBINI-ZINNER; GRIGG-SKJELLERUP; HALLEY; P/HALLEY AB Low-frequency electromagnetic turbulence observed in cometary environments mostly peaks at the gyrofrequency of the water-group ions of cometary origin, because of cyclotron resonance fueled by relative drifts parallel to the interplanetary magnetic field. Nevertheless, some of the observations point to pickup proton cyclotron turbulence, to single-cycle magnetic pulses or solitary waves at the proton gyrofrequency, and also to intermediate frequencies between the water-group and the proton gyrofrequencies. The generation of turbulence at such frequencies has been attributed to cascade via wave-wave interactions, but here an alternative and direct mechanism for the generation of these waves is suggested in an unstable wavelength band when the solar wind is sufficiently mass-loaded by cometary material. It is shown, for average parameters near comet 1P/Halley, that unstable modes of the intermediate frequency kind can indeed occur up to several million kilometers from the cometary nucleus and are easier to excite in higher-velocity solar wind flows. C1 State Univ Ghent, Sterrenkundig Observ, B-9000 Ghent, Belgium. Indian Inst Geomagnetism, Colaba 400005, Mumbai, India. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Verheest, F (reprint author), State Univ Ghent, Sterrenkundig Observ, Krijgslaan 281, B-9000 Ghent, Belgium. RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 31 TC 1 Z9 1 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24863 EP 24867 DI 10.1029/1999JA900331 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700022 ER PT J AU Kessel, RL Quintana, E Peredo, M AF Kessel, RL Quintana, E Peredo, M TI Local variations of interplanetary magnetic field at Earth's bow shock SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID QUASI-PARALLEL SHOCKS; IONS UPSTREAM; PROPAGATION; ISEE-1 AB We present interplanetary magnetic field (IMF) observations from Geotail and Wind in which the IMF was not uniform over spatial scales relevant to the magnetosphere. Geotail, at the dawn flank of the Earth's bow shock, measured magnetic field directions 60 degrees to 120 degrees different from the magnetic field measured by Wind on the duskside similar to 30 R-E upstream, during a 2-hour interval. If there is a global connection between these observations, one possible explanation is a kink in the magnetic field near the Sun-Earth line. The different orientations of IMF at Wind and Geotail land thus the kink) change during the 2-hour interval. Multiple shock crossings may have resulted from the changing orientations driving small surface waves on the shock surface. During this interval the bow shock does not fit a standard dawnside-quasi-parallel-duskside-quasi-picture. Instead, both sides of the bow shock may have been locally quasi-perpendicular, The question of where a quasi-parallel bow shock and/or foreshock could form needs to be explored, Both before and after the 2-hour time interval, the IMF was close to uniform as measured by Wind, Geotail, and IMP8. C1 NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20770 USA. RP NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20770 USA. EM mona.kessel@gsfc.nasa.gov NR 23 TC 3 Z9 3 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24869 EP 24878 DI 10.1029/1999JA900230 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700023 ER PT J AU Kanekal, SG Baker, DN Blake, JB Klecker, B Mewaldt, RA Mason, GM AF Kanekal, SG Baker, DN Blake, JB Klecker, B Mewaldt, RA Mason, GM TI Magnetospheric response to magnetic cloud (coronal mass ejection) events: Relativistic electron observations from SAMPEX and Polar SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GEOMAGNETIC STORMS; SOLAR; ACCELERATION; ISTP; WIND; PARTICLES; INNER AB In this paper we report on relativistic electron (energies of greater than or similar to 2 MeV) observations using detectors onboard SAMPEX and Polar satellites. The spacecraft orbits are such that a global view of the outer zone is obtained covering a wide range of energy and pitch angle. We have examined the magnetospheric electron effects of nine magnetic cloud events identified using sensors onboard the Wind spacecraft. It is confirmed, as suspected from earlier, more limited work, that the relativistic electron Aux enhancements in outer zone show a high degree of coherence that is largely independent of pitch angle, L shell and energy. Furthermore, the flux enhancements occur over a broad range of L values. The observations imply that the underlying acceleration mechanism(s) are of a global nature operating simultaneously over much of the outer zone. C1 Raytheon Informat Technol & Sci Serv, Lanham, MD 20706 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Aerosp Corp, Space & Environm Technol Ctr, Dept Space Sci, Los Angeles, CA 90009 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. CALTECH, Downs Lab, Pasadena, CA 91125 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kanekal, SG (reprint author), Raytheon Informat Technol & Sci Serv, Lanham, MD 20706 USA. NR 23 TC 33 Z9 33 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24885 EP 24894 DI 10.1029/1999JA900239 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700025 ER PT J AU Tsyganenko, NA Russell, CT AF Tsyganenko, NA Russell, CT TI Magnetic signatures of the distant polar cusps: Observations by Polar and quantitative modeling SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID DIPOLE TILT ANGLE; BOUNDARY-LAYER; FIELD; CLEFT; PRECIPITATION; MAGNETOSPHERE; MAGNETOMETER; WIND AB Polar cusps are an essential element of the magnetospheric topology. In the outermost regions of the cusp the magnetosheath plasma becomes entrained on magnetospheric field lines and penetrates to low altitudes along held lines on the dayside, causing a significant local depression of B, clearly visible in magnetometer data taken at high latitudes. This study addresses the spatial distribution of the magnetic depression associated with the polar cusp, as derived from a large set of Polar magnetometer data taken in 1996-1998. The depression Delta B was derived as the difference between the total. magnitude of the observed field and the one calculated from the International Geomagnetic Reference Field model of the internal held, combined with an external field model. In the noon sector the cusp depression is clearly visible in plots of Delta B versus solar magnetic latitude as a relatively narrow region of large negative Delta B (down to similar to -80 nT), extending from R similar to 8 - 9 R-E (Polar apogee) to R similar to 5 - 6 R-E. At closer geocentric distances the cusp depression fades out because of a rapid increase of the geomagnetic field toward Earth. The cusp depression also shallows as one moves away from the noon meridian and completely disappears at solar magnetic longitudes +/-40 - 60 degrees. The second part of the paper deals with a mathematical representation of the observed polar cusp depression in quantitative models of the geomagnetic field. A method is suggested on the basis of the field deformation technique, making it possible to incorporate a realistic structure of the polar cusps in global models of the magnetosphere. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Inst Geophys, Los Angeles, CA USA. Raytheon ITSS Corp, Lanham, MD USA. RP Tsyganenko, NA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 690-2, Greenbelt, MD 20771 USA. RI Tsyganenko, Nikolai/J-7377-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579 NR 33 TC 35 Z9 36 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24939 EP 24955 DI 10.1029/1999JA900279 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700029 ER PT J AU Vassiliadis, D Klimas, AJ Valdivia, JA Baker, DN AF Vassiliadis, D Klimas, AJ Valdivia, JA Baker, DN TI The D-st geomagnetic response as a function of storm phase and amplitude and the solar wind electric field SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID DATA-DERIVED ANALOGS; RING-CURRENT; MAGNETOSPHERIC DYNAMICS; SUBSTORM RELATION; MAGNETIC STORMS; NEURAL NETWORKS; DST FIELD; PREDICTION; DISTURBANCE; DECAY AB We examine the dependence of the D-st timescales on storm conditions and its implications for the storm-substorm relationship. The growth, decay and oscillation timescales are expressed as functions of the storm magnitude and phase, and the solar wind electric-field input VBs. Nonlinear, second-order autoregressive moving average (ARMA) models are fit to 5-min data and yield two timescales? an exponential decay with an average e-folding time tau(1) -4.69 hours (-7.26 hours for the pressure-corrected D-st((0))) and an inductive time tau(2) = -0.81 hours (-0.05 hours for D-st((0))). Around these average values there is a systematic variation: (1) For most of the storm duration, tau(1) is negative representing the rapid adjustment of the inner magnetosphere to the imposed electric field. (2) In the early main phase, however, tau(1) = 5.29 hours (1.76 hours for D-st((0))), so the disturbance grows as a slow exponential. (3) During commencement and main phase, the timescales are complex conjugate and the response is oscillatory. Fast oscillations during storm commencement (period 1.13 hours; 8.48 min for D-st((0))) are a "ringing" response to interplanetary pressure enhancements. Slow oscillations in the main phase have an average period of 1.96 hours (1.55 hours for D-st((0))) and coincide with AL intensifications. The main phase can be separated into periods of oscillatory, fast decay (coincident with AL activity and probably due to injections) and monotonic slow decay (regular convection). (4) All timescales decrease with increasing interplanetary activity because high activity involves acceleration and loss of heavy ions with shorter lifetimes than protons. (5) Also, decay times are about twice as long during recovery than during main phase. (6) Similar dependences are found for the solar wind coupling coefficients. The models are similar to linear models in predictability and are stable with respect to perturbation in the initial conditions. C1 Univ Space Res Assoc, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Natl Res Council, Greenbelt, MD 20771 USA. RP Vassiliadis, D (reprint author), Univ Space Res Assoc, NASA, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 47 TC 38 Z9 38 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24957 EP 24976 DI 10.1029/1999JA900185 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700030 ER PT J AU Baumjohann, W Hesse, M Kokubun, S Mukai, T Nagai, T Petrukovich, AA AF Baumjohann, W Hesse, M Kokubun, S Mukai, T Nagai, T Petrukovich, AA TI Substorm dipolarization and recovery SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOTAIL DYNAMICS; CURRENT DISRUPTION; CURRENT WEDGE; PLASMA SHEET; TAIL; EXPANSION; PHASE; FLOWS AB On the basis of similar to 2 years of Geotail data, we use a superposed epoch approach to study the average behavior of plasma and magnetic fields at different radial distances, between 11 and 31 R-E, during 66 substorms in the premidnight sector. Magnetic field dipolarization is first seen in the innermost region (11-16 R-E) around substorm onset and subsequently moves tailward at a rate of 35 km/s. Fast earthward and tailward ion bulk flows in the central plasma sheet indicate that during substorm expansion the near-Earth neutral line is located between 21 and 26 R-E, With a tendency to be closer to 21 R-E near substorm onset. About 45 min after onset, the tailward moving dipolarization front reaches the distance range where the near-Earth neutral line is located. Thereafter the near-Earth neutral line disappears beyond 31 R-E. This is the classical signature of the start of the recovery phase. We conclude that substorm recovery sets in when the tailward moving dipolarization front reaches the near-Earth neutral line, because the near-Earth neutral line cannot operate in a dipolar field geometry. C1 Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Solar Terr Environm Lab, Toyokawa, Aici 4428507, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Tokyo Inst Technol, Tokyo 1528551, Japan. Moscow Space Res Inst, Moscow 117810, Russia. RP Baumjohann, W (reprint author), Max Planck Inst Extraterr Phys, Postfach 1603, D-85740 Garching, Germany. RI Hesse, Michael/D-2031-2012; Baumjohann, Wolfgang/A-1012-2010; Petrukovich, Anatoly/G-8764-2011 OI Baumjohann, Wolfgang/0000-0001-6271-0110; Petrukovich, Anatoly/0000-0002-5344-2967 NR 20 TC 166 Z9 172 U1 2 U2 13 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 24995 EP 25000 DI 10.1029/1999JA900282 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700032 ER PT J AU Rastatter, L Hesse, M AF Rastatter, L Hesse, M TI Patchy reconnection and evolution of multiple plasmoids in the Earth's magnetotail: Effects on near-Earth current system SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID THIN CURRENT SHEETS; BURSTY BULK FLOWS; MAGNETIC RECONNECTION; GROWTH-PHASE; SUBSTORM; TAIL; SIMULATIONS; GEOTAIL; CONVECTION; DIVERSION AB Reconnection during substorms in the near-Earth magnetotail occurs in a complicated way. Local instabilities can trigger anomalous resistivity in several spatial regions, which may initially be well separated from each other. As time progresses, the resulting plasmoids grow larger until they reach the dimension of the entire system and start to interact with each other. Satellite observations show that this expansion occurs rapidly during the downtail travel after plasmoid development when -10 R-E > X-GSM > -30 R-E [leda et a., 1998]. In this paper we study the interaction of two and three plasmoids and their coalescence, as well as the current system seen. near the Earth brought about by the reconnection regions. In the numerical experiments, resistivity is prescribed at localized patches which, are placed at different downtail locations. We compare the magnitude of the influence the reconnection sites have on the near-Earth current system. We find that not only the relative position of the resistivity patches but also the absolute distance from the Earth play roles in the relative amplitude of the held-aligned currents associated with the individual reconnection events. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Rastatter, L (reprint author), NASA, Goddard Space Flight Ctr, Code 696, Greenbelt, MD 20771 USA. RI Hesse, Michael/D-2031-2012; Rastaetter, Lutz/D-4715-2012 OI Rastaetter, Lutz/0000-0002-7343-4147 NR 27 TC 4 Z9 4 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1999 VL 104 IS A11 BP 25011 EP 25020 DI 10.1029/1999JA900375 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 250XC UT WOS:000083414700034 ER PT J AU Dowling, JP AF Dowling, JP TI Dipole emission in finite photonic bandgap structures: An exactly solvable one-dimensional model SO JOURNAL OF LIGHTWAVE TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Electromagnetic Crystal Structures CY JAN 04-06, 1999 CL LAGUNA BEACH, CALIFORNIA DE dipole antennas; distributed Bragg reflector lasers; electromagnetic interference; emission; frequency selective surfaces; laser resonators; photon radiation effects ID INHIBITED SPONTANEOUS EMISSION; QUANTUM ELECTRODYNAMICS; LOCALIZED LIGHT; GAP STRUCTURES; CAVITY; ATOMS; MICROCAVITIES; SCATTERING; PARTICLES; RADIATION AB This paper considers an exact model of atomic spontaneous dipole emission and classical dipole radiation in a finite photonic bandgap (PEG) structure. The full three-dimensional (3-D) or two-dimensional (2-D) problem is reduced to a finite one-dimensional (1-D) model, which then is solved for analytically using algebraic matrix transfer techniques. The results give insight to the electromagnetic emission process in periodic dielectrics, quantitative predictions for emission in 1-D dielectric stacks, and qualitative formulas for the 2-D and 3-D problem. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Dowling, JP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI DOWLING, JONATHAN/L-2749-2013 NR 43 TC 31 Z9 33 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0733-8724 J9 J LIGHTWAVE TECHNOL JI J. Lightwave Technol. PD NOV PY 1999 VL 17 IS 11 BP 2142 EP 2151 DI 10.1109/50.803005 PG 10 WC Engineering, Electrical & Electronic; Optics; Telecommunications SC Engineering; Optics; Telecommunications GA 255NB UT WOS:000083675100030 ER PT J AU Croat, TK Kelton, KF Holland-Moritz, D Rathz, TJ Robinson, MB AF Croat, TK Kelton, KF Holland-Moritz, D Rathz, TJ Robinson, MB TI Containerless solidification studies of the alpha-1/1 crystal approximant in Ti-Cr-Si-O alloys SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID ICOSAHEDRAL PHASE AB The nucleation behavior of alpha(TiCrSiO), a 1/1 Fibonacci crystal approximant phase, was investigated in alloys made near the stoichiometric composition. Containerless solidification studies were made with electromagnetic radio-frequency levitation and the 105-m NASA Drop Tube. The solidification microstructures indicate that the alpha-Ti hexagonal solid solution was the primary crystallizing phase in these alloys, growing dendritically, The alpha(TiCrSiO) phase nucleated in the remaining liquid. The competition between these two phases resulted from the high oxygen concentration needed to form alpha(TiCrSiO), which also stabilized the hexagonal-close-packed alpha-Ti phase. C1 Washington Univ, Dept Phys, St Louis, MO 63130 USA. Deutsch Zentrum Luft & Raumfahrt, Inst Raumsimulat, D-51147 Cologne, Germany. Harvard Univ, Gordon Mckay Lab, Div Engn & Appl Sci, Cambridge, MA 02138 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Croat, TK (reprint author), Washington Univ, Dept Phys, Box 1105, St Louis, MO 63130 USA. NR 10 TC 0 Z9 0 U1 1 U2 3 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD NOV PY 1999 VL 14 IS 11 BP 4208 EP 4213 DI 10.1557/JMR.1999.0570 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA 257FC UT WOS:000083771000015 ER PT J AU Ogbuji, LUJT AF Ogbuji, LUJT TI Identification of carbon sublayer in a Hi-Nicalon/BN/SiC composite SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article ID CERAMIC-MATRIX COMPOSITES; FIBER; CHEMISTRY C1 Dynacs Engn Co, NASA Glenn Res Ctr, Cleveland, OH 44135 USA. RP Ogbuji, LUJT (reprint author), Dynacs Engn Co, NASA Glenn Res Ctr, Lewis Field, Cleveland, OH 44135 USA. NR 9 TC 6 Z9 6 U1 0 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0261-8028 J9 J MATER SCI LETT JI J. Mater. Sci. Lett. PD NOV PY 1999 VL 18 IS 22 BP 1825 EP 1827 DI 10.1023/A:1006695105463 PG 3 WC Materials Science, Multidisciplinary SC Materials Science GA 247PY UT WOS:000083230200009 ER PT J AU Yasuda, H AF Yasuda, H TI Glow curve analyses of (LiF)-Li-6 : Mg, Ti (TLD-600) and (LiF)-Li-7 : Mg, Ti (TLD-700) exposed to high-energy heavy ions SO JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY LA English DT Article DE thermoluminescent dosemeters; glow curve; lithium fluorides; TLD-600; TLD-700; relative efficiency; high-energy heavy ions; NIRS-HIMAC; space radiation ID DOSE MEASUREMENT; FLIGHT; SPACE; TLDS C1 Natl Inst Radiol Sci, Inage Ku, Chiba 2638555, Japan. RP NASA, Lyndon B Johnson Space Ctr, Mail Code SN3, Houston, TX 77058 USA. EM h_yasuda@nirs.go.jp NR 13 TC 2 Z9 2 U1 2 U2 2 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0022-3131 EI 1881-1248 J9 J NUCL SCI TECHNOL JI J. Nucl. Sci. Technol. PD NOV PY 1999 VL 36 IS 11 BP 1105 EP 1107 DI 10.1080/18811248.1999.9726304 PG 3 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 272CF UT WOS:000084632400016 ER PT J AU Lazar, A Madec, G Delecluse, P AF Lazar, A Madec, G Delecluse, P TI The deep interior downwelling, the Veronis effect, and mesoscale tracer transport parameterizations in an OGCM SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID GENERAL-CIRCULATION MODEL; EDDY-INDUCED ADVECTION; OCEAN CLIMATE MODELS; WORLD OCEAN; MIXING PARAMETERIZATION; ABYSSAL CIRCULATION; ATLANTIC-OCEAN; SENSITIVITY; SCHEMES; DISTRIBUTIONS AB Numerous numerical simulations of basin-scale ocean circulation display a vast interior downwelling and a companion intense western boundary layer upwelling at midlatitude below the thermocline. These features, related to the so-called Veronis effect, are poorly rationalized and depart strongly from the classical vision of the deep circulation where upwelling is considered to occur in the interior Furthermore, they significantly after results of ocean general circulation models (OGCMs) using horizontal Laplacian diffusion. Recently, some studies showed that the parameterization for mesoscale eddy effects formulated by Cent and McWilliams allows integral quantities like the streamfunction and meridional heat transport to be free of these undesired effects. In this paper, an idealized OGCM is used to validate an analytical rationalization of the processes at work and help understand the physics. The results show that the features associated with the Veronis effect can be related quantitatively to three different width scales that characterize the baroclinic structure of the deep western boundary current. In addition, since one of these scares may be smaller than the Munk barotropic layer, usually considered to determine the minimum resolution and horizontal viscosity for numerical models, the authors recommend that it be taken into account. Regarding the introduction of the new parameterization, diagnostics in terms of heat balances underline some interesting similarities between local heat fluxes by eddy-induced velocities and horizontal diffusion at low and midlatitudes when a common large diffusivity (here 2000 m(2) s(-1)) is used. The near-quasigeostrophic character of the flow explains these results. As a consequence, the response of the Eulerian-mean circulation is locally similar for runs using either of the two parameterizations. However, it is shown that the advective nature of the eddy-induced heat fluxes results in a very different effective circulation. which is the one felt by tracers. C1 Univ Paris 06, Lab Oceanog Dynam & Climatol, Unite Mixte Rech CNRS ORSTOM UPMC, Paris, France. RP Lazar, A (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Code 970, Greenbelt, MD 20771 USA. RI madec, gurvan/E-7825-2010; lazar, alban/B-7290-2013 OI madec, gurvan/0000-0002-6447-4198; NR 49 TC 20 Z9 21 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD NOV PY 1999 VL 29 IS 11 BP 2945 EP 2961 DI 10.1175/1520-0485(1999)029<2945:TDIDTV>2.0.CO;2 PG 17 WC Oceanography SC Oceanography GA 258ZA UT WOS:000083868500012 ER PT J AU Turk, MJ Ansari, AS Alston, WB Gahn, GS Frimer, AA Scheiman, DA AF Turk, MJ Ansari, AS Alston, WB Gahn, GS Frimer, AA Scheiman, DA TI Evaluation of the thermal oxidative stability of polyimides via TGA techniques SO JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY LA English DT Article DE thermogravimetric analysis (TGA); TGA-FTIR; activation energy (E-a); polyimides; kinetic methods; thermooxidative stability (TOS); decomposition onset temperature (T-d) ID THERMOOXIDATIVE STABILITY; FLUORINATED POLYIMIDES; THERMOGRAVIMETRIC DATA; DEGRADATION; 371-DEGREES-C AB Thermogravimetric analysis (TGA) has been used for many years to evaluate polymer thermal stability. The objective of this study is to determine if weight-loss curves from TGA and isothermal TGA (IGA) can be used to determine degradation activation energies and thus rank the thermal stability (TS) and thermooxidative stability (TOS) for selected polyimides. Two high-temperature stable addition-cured polyimides and two aromatic condensation polyimides, all four containing fluorinated connecting linkages in the dianhydride monomers, were compared. Three TGA kinetic methods (Coats/Redfern, Ingraham/Marier, Horowitz/Metzger) were used to determine the activation energy for decomposition in air. The results were then used to rank polyimide stability compared to more traditional rankings based on long-term isothermal air aging weight-loss (IWL) studies and thermal decomposition temperatures (T-d) from TGA data. Use of TGA coupled to a Fourier transform infrared (TGA-FTIR) spectrophotometer allowed for the simultaneous identification and relative quantification of evolved decomposition products (CO2, CO, ArNCO, and CHF3) of the four polyimides degraded in air or nitrogen. Isothermal TGA-FTIR (IGA-FTIR) was also done in air to determine the relative rate of product evolution at a constant temperature. Activation energies using TGA and ICA data were determined and then compared with IWL values for the degradation of the polyimide to examine for correlations of real-life thermal oxidative aging to accelerated aging techniques. The Coats/Redfern method and T-d were found to best reproduce stability rankings of those from long-term, high-temperature IWL studies. Together, they may provide a time-saving technique to evaluate polyimide thermal oxidative stability. (C) 1999 John Wiley & Sons, Inc. C1 Dynacs Eng Inc, Glenn Res Ctr, Brookpark, OH 44142 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. USA, Res Lab, Glenn Res Ctr, Cleveland, OH 44135 USA. Bar Ilan Univ, Ethel & David Resnick Chair Act Oxygen Chem, IL-52900 Ramat Gan, Israel. RP Scheiman, DA (reprint author), Dynacs Eng Inc, Glenn Res Ctr, Brookpark, OH 44142 USA. NR 44 TC 31 Z9 32 U1 2 U2 33 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0887-624X J9 J POLYM SCI POL CHEM JI J. Polym. Sci. Pol. Chem. PD NOV 1 PY 1999 VL 37 IS 21 BP 3943 EP 3956 DI 10.1002/(SICI)1099-0518(19991101)37:21<3943::AID-POLA10>3.0.CO;2-5 PG 14 WC Polymer Science SC Polymer Science GA 252FB UT WOS:000083490500010 ER PT J AU Wang, TS AF Wang, TS TI Analysis of linear aerospike plume-induced X-33 base-heating environment SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA/ASME 7th Joint Thermophysics and Heat Transfer Conference CY JUN 15-18, 1998 CL ALBUQUERQUE, NEW MEXICO SP AIAA, ASME ID CLUSTERED NOZZLE CONFIGURATION; FLOWFIELD AB Computational analysis is conducted to study the effect of a linear aerospike engine plume on the X-33 base-heating environment during ascent flight. To properly account for the freestream-body interaction and to allow for potential plume-induced flow separation, the thermo flowfield of the entire vehicle at several trajectory points is computed. A sequential grid-refinement technique is used in conjunction with solution-adaptive, patched, and embedded grid methods to limit the model to a manageable size. The computational methodology is based on a three-dimensional, finite difference, viscous flow, chemically reacting, pressure-based computational fluid dynamics formulation, and a three-dimensional, finite volume, spectral-line-based weighted-sum of gray gases absorption, computational radiation heat transfer formulation. The computed forebody and afterbody surface pressure coefficients and base pressure characteristic curves are compared with those of a cold flow test. The predicted convective and radiative base-heat fluxes, the effect of base bleed, and the potential for plume induced Row separation are presented and discussed. C1 NASA, George C Marshall Space Flight Ctr, Appl Fluid Dynam Anal Grp, Huntsville, AL 35812 USA. RP Wang, TS (reprint author), NASA, George C Marshall Space Flight Ctr, Appl Fluid Dynam Anal Grp, Mail Stop TD64, Huntsville, AL 35812 USA. NR 21 TC 12 Z9 16 U1 1 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 777 EP 783 DI 10.2514/2.3502 PG 7 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400001 ER PT J AU Nemeth, MP Britt, VO Young, RD Collins, TJ Starnes, JH AF Nemeth, MP Britt, VO Young, RD Collins, TJ Starnes, JH TI Nonlinear behavior of Space Shuttle superlightweight liquid-oxygen tank under prelaunch loads SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The new Space Shuttle superlightweight external fuel tank flew for the first time on 2 June 1998 (Space Trans portation System-mission 91). We present results of elastic linear-bifurcation buckling and nonlinear analyses of one of its major components; that is, the liquid-oxygen tank. The contents include an overview of the structure and a brief description of the finite element code that was used to conduct the analyses, Results are presented that illustrate three distinctly different types of nonlinear response phenomena for thin-walled shells that are subjected to combined mechanical and thermal loads that launch-vehicle shell designers may encounter. A procedure is demonstrated that can be used by structural analysts and designers to obtain reasonable, conservative estimates of linear-bifurcation, buckling-load knockdown factors for shells that are subjected to complex loading conditions or to characterize the effects of initial geometric imperfections on nonlinear shell response phenomena. Results an: also presented that show that the superlightweight liquid-oxygen tank can carry loads in excess of twice the values of the operational prelaunch loads considered and that a fluid-filled launch-vehicle shell can be highly sensitive to initial geometric imperfections. C1 NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, Hampton, VA 23681 USA. RP Nemeth, MP (reprint author), NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, Hampton, VA 23681 USA. NR 11 TC 5 Z9 5 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 788 EP 803 DI 10.2514/2.3517 PG 16 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400004 ER PT J AU Young, RD Rankin, CC AF Young, RD Rankin, CC TI Modeling and nonlinear structural analysis of a large-scale launch vehicle SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Advanced modeling and analysis capabilities of a state-of-the-art general purpose finite element code, developed for nonlinear structural analysis of launch vehicles, are described. In particular, the application of these capabilities to nonlinear analyses of the new Space Shuttle superlightweight external liquid oxygen tank are presented that can be used as a guide for conducting similar analyses on future launch vehicles. A typical prelaunch leading condition Kith combined thermal and mechanical loads is considered, and applications of the advanced modeling and analysis capabilities to linear bifurcation buckling and nonlinear static analyses an! presented, The results for this problem illustrate a localized short-wavelength bending response, and that a high fidelity model is required to represent accurately the behavior. A mesh refinement strategy is presented that is based on the linear bifurcation buckling analyses and does not require respecification of the shell wall properties and loads, Specifically mesh refinement is simplified by using user-written subroutines to describe the spatial distribution of complex shell wall properties and loading conditions. In addition, a procedure for assessing the sensitivity to initial shell walt geometric imperfections is presented. For the prelaunch load condition considered, the deformations from a nonlinear analysis using these capabilities are found to be similar in shape to the linear bifurcation buckling mode shape and insensitive to Initial geometric imperfections. Recommended solution procedures for large-scale nonlinear analysis include using an are-length projection method, and a combination of modified and true Newton refactoring schemes to balance computational efficiency and robustness, with careful monitoring of the stability of the obtained solutions. C1 Lockheed Missiles & Space Co Inc, Mat & Struct Technol Dept, Palo Alto, CA 94304 USA. Lockheed Martin Engn & Sci Serv, Struct & Acoust Dept, Hampton, VA 23681 USA. RP Young, RD (reprint author), NASA, Langley Res Ctr, Mech & Durabil Branch, Hampton, VA 23681 USA. NR 11 TC 5 Z9 5 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 804 EP 811 DI 10.2514/2.3518 PG 8 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400005 ER PT J AU Nemeth, MP Young, RD Collins, TJ Starnes, JH AF Nemeth, MP Young, RD Collins, TJ Starnes, JH TI Effects of welding-induced imperfections on behavior of Space Shuttle superlightweight tank SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Results of linear-bifurcation buckling and nonlinear analyses of the Space Shuttle superlightweight external liquid-oxygen tank are presented for an important prelaunch loading condition. These results show the effects of actual, measured welding-induced initial geometric imperfections on an important response mode for thin-walled shells that are subjected to combined mechanical and thermal loads. This type of initial geometric imperfection may be Encountered in the design of other Liquid-fuel launch vehicles, Results are presented that show that the liquid-oxygen tank will buckle in the barrel section, but at load levels nearly four times the magnitude of the operational load level, and will exhibit stable postbuckling behavior, The actual measured imperfections are located in this section of the tank. Results of imperfection sensitivity analyses are presented that show that the largest degradation in the apparent membrane stiffnesses of the Liquid-oxygen tank barrel section is caused by an imperfection shape that is in the form of the linear-bifurcation buckling mode with a relatively small amplitude. These results also show that the effect of the relatively large-amplitude measured imperfection is benign. C1 NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, Hampton, VA 23681 USA. RP Nemeth, MP (reprint author), NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, Hampton, VA 23681 USA. NR 7 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 812 EP 819 DI 10.2514/2.3519 PG 8 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400006 ER PT J AU Young, RD Nemeth, MP Collins, TJ Starnes, JH AF Young, RD Nemeth, MP Collins, TJ Starnes, JH TI Nonlinear behavior of Space Shuttle superlightweight tank under booster ascent loads SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Results of linear-bifurcation and nonlinear analyses of the Space Shuttle superlightweight (SLWT) external liquid-oxygen (LO2) tank for an important early booster ascent lending condition are presented. These results for thin-walled linear elastic shells that are subjected to combined mechanical and thermal loads illustrate an important type of response mode that may be encountered in the design of ether liquid-fuel launch vehicles, Linear-bifurcation analyses are presented that predict several nearly equal eigenvalues that correspond to local bucking modes in the forward ogive section of the LO2 tank. In contrast, the nonlinear response phenomenon is shown to consist of short-wavelength bending deformations in the forward-ogive and barrel sections of the LO2 tank that grow in amplitude in a stable manner with increasing load. Imperfection sensitivity analyses are presented that show that the presence of several nearly equal eigenvalues does not lead to a premature general instability mode for the forward-ogive section. For the linear-bifurcation and nonlinear analyses, the results show that accurate predictions of the response of the shell generally require a large scale, high-fidelity, finite element model, and that a design based on a linear-bifurcation buckling analysis and a buckling load knockdown factor is overly conservative, Results are presented that show that the SLWT LO2 tank can support loads in excess of approximately 2.6 times the values of the operational loads considered, In addition, results are presented that show that local bending deformations may cause failure of the thermal protection system (TPS) It load levels less than the load level corresponding to structural collapse. Results are presented that can be used to estimate the load level at which TPS failure is likely to occur. C1 NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. RP Young, RD (reprint author), NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. NR 6 TC 3 Z9 3 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 820 EP 827 DI 10.2514/2.3520 PG 8 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400007 ER PT J AU Nemeth, MP Young, RD Collins, TJ Starnes, JH AF Nemeth, MP Young, RD Collins, TJ Starnes, JH TI Nonlinear behavior of Space Shuttle superlightweight tank under end-of-flight loads SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Results of elastic, linear-bifurcation buckling and nonlinear analyses of the new Space Shuttle superlightweight external liquid-oxygen tank are presented for an important end of-flight loading condition. These results illustrate an important type of response mode for thin-walled shells subjected to combined mechanical and thermal loads that may be encountered in the design of other liquid-fuel launch vehicles. Linear-bifurcation buckling analyses are presented that predict several nearly equal eigenvalues that correspond to local buckling modes in the aft dome of the liquid-oxygen tank. In contrast, the nonlinear response phenomenon is shown to consist of a short-wavelength bending deformation in the aft elliptical dome of the liquid-oxygen tank that grows in amplitude in a stable manner with increasing load. Imperfection sensitivity analyses are presented that show that the presence of several nearly equal eigenvalues does not lead to a premature general instability mode for the aft dome. For the linear-bifurcation and nonlinear analyses, the results show that accurate predictions of the response of the shell generally require a large-scale, high-fidelity, finite element model, and that a design based on a linear bifurcation buckling analysis and a buckling-load knockdown factor is overly conservative, Results are also presented that show that the superlightweight liquid-oxygen tank can support loads in excess of approximately 1.9 times the values of the operational loads considered. C1 NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, Hampton, VA 23681 USA. RP Nemeth, MP (reprint author), NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, Hampton, VA 23681 USA. NR 6 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 828 EP 835 DI 10.2514/2.3521 PG 8 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400008 ER PT J AU Palmer, G Kontinos, D Sherman, B AF Palmer, G Kontinos, D Sherman, B TI Surface heating effects of X-33 vehicle thermal-protection-system panel bowing SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB The thermal protection system on the windward side of the Lockheed Martin X-33 technology demonstrator vehicle consists largely of metallic panels. As the vehicle travels through the Earth's atmosphere at hypersonic speeds, thermal gradients between the top and bottom face sheets of the honeycomb panels cause them to bow. This study uses Navier-Stokes flow analysis to assess the effects of panel bowing on the surface heating of the vehicle, Analysis is performed at keg locations on the design trajectory. A series of surface heating augmentation factors an! presented that provide the increase or decrease in heating rate as a function of bow height. The existence of reverse flow at the panel interfaces because of panel bowing is demonstrated. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Thermosci Inst, Moffett Field, CA 94035 USA. BF Goodrich Co, Chula Vista, CA 91910 USA. RP Palmer, G (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 21 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 836 EP 841 DI 10.2514/2.3522 PG 6 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400009 ER PT J AU Kontinos, DA Palmer, G AF Kontinos, DA Palmer, G TI Numerical simulation of metallic thermal protection system panel bowing SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB Numerical simulation of the thermoelastic response of metallic thermal protection panel is presented. The panels, which ate being designed for use on the windward surface of the X-33 flight test vehicle, deform into convex and concave bowed surfaces due to thermal gradients caused by aerodynamic heating. Three numerical models, for the flowfield, for the in-depth heat transfer, and for the thermoelastic deformation, are coupled in sequence to yield the transient response of the metallic panel. The aerothermal loads are derived from computational fluid dynamic solutions and are prescribed as a distribution function with maximum bow height as the governing parameter Finite element models are used to simulate the thermal and structural responses. The coupled simulation is compared to a single-pass uncoupled solution. Results show negligible feedback between the structural deformation and the deformation-induced perturbation of the aerothermal heat load. Nevertheless, significant temperature variations on the surface of the panel are produced. The deformations induce lateral temperature gradients that increase the thermal stress within the panel. Finally, it is shown that panel bowing does not appreciably alter the trajectory integrated heat load. C1 NASA, Ames Res Ctr, Eloret Thermosci Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Reacting Flow Environm Branch, Moffett Field, CA 94035 USA. RP Kontinos, DA (reprint author), NASA, Ames Res Ctr, Eloret Thermosci Inst, Moffett Field, CA 94035 USA. NR 17 TC 6 Z9 6 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 842 EP 849 DI 10.2514/2.3523 PG 8 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400010 ER PT J AU Chuang, JCH Goodson, TD Hanson, J AF Chuang, JCH Goodson, TD Hanson, J TI Multiple-burn families of optimal low- and medium-thrust orbit transfers SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A new procedure for improving fuel- and time-optimal orbit transfers through burn additions is introduced and analyzed in terms of physical characteristics; results of its use are presented. The procedure is based on a property of the switching function for the optimal control problem. Criteria am given that may be used to determine whether other optimal control problems exhibit this property. This property and other properties of fuel-optimal orbit transfers related to number of burns and burn placement are examined. The orbit transfer problem formulation is given for final mass maximization allowing for second-harmonic oblateness effects, atmospheric drag effects, and three-dimensional, noncoplanar, nonaligned elliptic terminal orbits. A set BE extremal solutions parameterized by transfer time, referred to as a Family, are obtained using a combination of the new procedure, homotopy, and other numerical methods. Notably, this family exhibits multiplicity in solutions; that is, terminal orbits, transfer times, and numbers of burns are identically specified, but the resulting transfer trajectories and costs are different. Reasons am suggested why one transfer is favored over the other, using physical rationale. Effects of the drag and oblateness terms are discussed. C1 Lockheed Martin Vought Syst Corp, Guidance & Navigat, Dallas, TX 75051 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Chuang, JCH (reprint author), Lockheed Martin Vought Syst Corp, Guidance & Navigat, Dallas, TX 75051 USA. NR 19 TC 5 Z9 7 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 866 EP 874 DI 10.2514/2.3505 PG 9 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400013 ER PT J AU Lauriente, M Vampola, AL Koga, R Hosken, R AF Lauriente, M Vampola, AL Koga, R Hosken, R TI Analysis of spacecraft anomalies due to the radiation environment SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB Various space-environment-induced anomalies are discussed and new tools under development are demonstrated that are now or soon will be available to the spacecraft designer to mitigate the effects of the space environment on space systems. Two-dimensional cross correlations between spacecraft anomalies and trapped particle models provide information on the energy of the particles that cause the anomalies and are also used to evaluate the accuracy of energetic proton models. Results of studies using anomalies and background effects in satellite sensors to evaluate the BPS trapped radiation model and an update to it are also presented. C1 NASA, Goddard Space Flight Ctr, EnviroNET, Greenbelt, MD 20771 USA. Univ Res Fdn, Greenbelt, MD 20771 USA. Aerospace Corp, Dept Space Sci, El Segundo, CA 90245 USA. Aerospace Corp, Comp Syst Dept, El Segundo, CA 90245 USA. RP Lauriente, M (reprint author), NASA, Goddard Space Flight Ctr, EnviroNET, Code 730, Greenbelt, MD 20771 USA. NR 14 TC 9 Z9 12 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 902 EP 906 DI 10.2514/2.3509 PG 5 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400017 ER PT J AU Glass, DE Camarda, CJ Merrigan, MA Sena, JT Reid, RS AF Glass, DE Camarda, CJ Merrigan, MA Sena, JT Reid, RS TI Fabrication and testing of a leading-edge-shaped heat pipe SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 Analyt Serv & Mat Inc, Hampton, VA 23666 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Glass, DE (reprint author), NASA, Langley Res Ctr, Met & Thermal Struct Branch, Mail Stop 396, Hampton, VA 23681 USA. NR 4 TC 3 Z9 3 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1999 VL 36 IS 6 BP 921 EP 923 DI 10.2514/2.3515 PG 3 WC Engineering, Aerospace SC Engineering GA 269GB UT WOS:000084467400022 ER PT J AU Lissenden, CJ Gil, CM Lerch, BA AF Lissenden, CJ Gil, CM Lerch, BA TI A methodology for determining rate-dependent flow surfaces for inconel 718 SO JOURNAL OF TESTING AND EVALUATION LA English DT Article DE Inconel 718; flow surfaces; aeronautics ID DEFORMATION; METALS AB A detailed set of experiments has been conducted in an attempt to characterize the inelastic flow behavior of materials used in aeronautics applications. These experiments have shown that aged (precipitate-hardened) Inconel 718 exhibits an initial nonlinear elastic behavior as well as a strength differential in tension and compression at room temperature. This nonlinear elastic behavior correlates reasonably well with a second order stress-strain law that was developed to account for interactions between dislocations and interstitial solute atoms. Flow loci in the axial-shear stress plane at 25 and 650 degrees C have been determined from yield locus data using both inelastic power and equivalent inelastic strain definitions of flow. Flow loci are more theoretically meaningful than yield loci for describing the time-dependent material response. These Row loci are especially important if they are proportional to the dissipation potential since the normality rule is associated with dissipation and not necessarily with a particular yield or flow definition employed in an experiment. A threshold function that depends only on the second deviatoric stress invariant, J(2), is inadequate for predicting the threshold surface (initial yield locus) for Inconel 718 due to the difference in flow behavior in tension and compression. Threshold functions including all three stress invariants (I-1, J(2), and J(3)) with each term having units of stress raised to the first or third power were equally successful in fitting thr initial flow locus. Additionally, both F = aI(1) + bJ(2)(1/2) - 1 and F = b(3)J(2)(3/2) + c(3)J(3) - 1 are shown to represent the data very well. The outward normals for these two representations of the threshold surface are consistent with experimentally determined directions of the inelastic strain rate vectors. C1 Penn State Univ, University Pk, PA 16802 USA. Boeing Corp, Huntington Beach, CA USA. NASA, Glenn Res Ctr, Cleveland, OH USA. RP Lissenden, CJ (reprint author), Penn State Univ, University Pk, PA 16802 USA. NR 14 TC 4 Z9 4 U1 1 U2 3 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 USA SN 0090-3973 J9 J TEST EVAL JI J. Test. Eval. PD NOV PY 1999 VL 27 IS 6 BP 402 EP 411 PG 10 WC Materials Science, Characterization & Testing SC Materials Science GA 287YT UT WOS:000085535600007 ER PT J AU Hoyer, JR Pietrzyk, RA Liu, HY Whitson, PA AF Hoyer, JR Pietrzyk, RA Liu, HY Whitson, PA TI Effects of microgravity on urinary osteopontin SO JOURNAL OF THE AMERICAN SOCIETY OF NEPHROLOGY LA English DT Article ID INHIBITION; UROPONTIN; PHOSPHOPROTEINS; PURIFICATION; AFFINITY AB Increased risk of renal stone formation during space flight has been linked primarily to increased calcium excretion from bone demineralization induced by space flight. Other factors contributing to increased risk include increased urinary calcium oxalate supersaturation, while urinary citrate, magnesium and volume are all decreased. The aim of this study was to increase the predictive value of stone risk profiles for crew members during space flight by evaluating the excretion of urinary protein inhibitors of calcium crystallization so that more comprehensive stone risk profiles could relate mineral saturation to the concentrations of inhibitor proteins. Levels of urinary osteopontin (uropontin) are reported in a series of 14 astronauts studied before, during, and after space flights. During space flight, a compensatory increase in uropontin excretion was not observed. However, the uropontin excretion of a majority of astronauts was increased during the period after space flight and was maximal at 2 wk after landing. The downward shift in the molecular size of uropontin observed in samples obtained during space flight was shown to result from storage at ambient temperature during flight, rather than an effect of microgravity on uropontin synthesis. C1 Childrens Hosp Philadelphia, Abramson Res Ctr 1107, Philadelphia, PA 19104 USA. Univ Penn, Dept Pediat, Philadelphia, PA 19104 USA. Univ Penn, Dept Med, Philadelphia, PA 19104 USA. Wyle Labs, Houston, TX USA. NASA, Lyndon B Johnson Space Ctr, Div Med Sci, Houston, TX 77058 USA. RP Hoyer, JR (reprint author), Childrens Hosp Philadelphia, Abramson Res Ctr 1107, Philadelphia, PA 19104 USA. FU NIDDK NIH HHS [R01 DK33501] NR 13 TC 10 Z9 10 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 1046-6673 J9 J AM SOC NEPHROL JI J. Am. Soc. Nephrol. PD NOV PY 1999 VL 10 SU 14 BP S389 EP S393 PG 5 WC Urology & Nephrology SC Urology & Nephrology GA 250WG UT WOS:000083411800016 PM 10541270 ER PT J AU Smart, MC Ratnakumar, BV Surampudi, S Wang, Y Zhang, X Greenbaum, SG Hightower, A Ahn, CC Fultz, B AF Smart, MC Ratnakumar, BV Surampudi, S Wang, Y Zhang, X Greenbaum, SG Hightower, A Ahn, CC Fultz, B TI Irreversible capacities of graphite in low-temperature electrolytes for lithium-ion batteries SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID SOLVENT; CARBON; NMR; ELECTRODES; INSERTION; BEHAVIOR; SYSTEMS; ANODES; LI-6 AB Carbonaceous anode materials in lithium-ion rechargeable cells exhibit irreversible capacity, mainly due to reaction of lithium during the formation of passive surface films. The stability and kinetics of lithium intercalation into mt carbon anodes are determined by these films. The nature, thickness, and morphology of these films are in turn affected by the electrolyte components, primarily the solvent constituents. In this work, the films formed on graphite anodes in low-temperature electrolytes, i.e.. solutions with different mixtures of alkyl carbonates and low-viscosity solvent additives, are examined using electrochemical impedance spectroscopy (EIS) and solid-stare Li-7 nuclear magnetic resonance techniques. Tn addition, other ex situ studies such as X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy were carried out on the graphite anodes to under stand their microstructures. (C) 1999 The Electrochemical Society. S0013-4651(99)02-078-9. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CUNY Hunter Coll, Dept Phys, New York, NY 10021 USA. CALTECH, Div Engn & Appl Sci, Pasadena, CA 91125 USA. RP Smart, MC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 34 TC 93 Z9 102 U1 9 U2 74 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 65 SOUTH MAIN STREET, PENNINGTON, NJ 08534 USA SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD NOV PY 1999 VL 146 IS 11 BP 3963 EP 3969 DI 10.1149/1.1392577 PG 7 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA 253HT UT WOS:000083551500004 ER PT J AU Ning, CZ Goorjian, PM AF Ning, CZ Goorjian, PM TI Microscopic modeling and simulation of transverse-mode dynamics of vertical-cavity surface-emitting lasers SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID SEMICONDUCTOR-LASERS; LASING MODES; VCSELS; DIODES; MODULATION; INSTABILITIES; AMPLIFIERS; FEEDBACK; ARRAYS AB The dynamics of transverse modes of vertical-cavity surface-emitting lasers were simulated by use of a model that incorporates microscopically computed gain and refractive index with many-body effects. The model equations were solved by finite-difference methods in two-dimensional space and time domains without any a priori assumptions of symmetry of solutions or types and number of modes. Simulation was carried out for devices with and without index guiding at various pumping levels. We show that index-guided vertical-cavity surface-emitting lasers involve more transverse modes than purely gain-guided devices at the same pumping level. Both time-resolved and time-averaged near-field patterns over several time scales are investigated. Complicated spatial and temporal dynamic behaviors occur at higher pumping levels that include azimuthal rotating waves and intensity oscillations owing to dynamic competition between modes of the same order and those of different orders. (C) 1999 Optical Society of America [S0740-3224(99)00311-2]. C1 NASA, Ames Res Ctr, Computat Quantum Optoelect, Moffett Field, CA 94035 USA. RP Ning, CZ (reprint author), NASA, Ames Res Ctr, Computat Quantum Optoelect, N229-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 57 TC 31 Z9 31 U1 1 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD NOV PY 1999 VL 16 IS 11 BP 2072 EP 2082 DI 10.1364/JOSAB.16.002072 PG 11 WC Optics SC Optics GA 252TV UT WOS:000083519100030 ER PT J AU Dulchavsky, SA Hamilton, DR Diebel, LN Sargsyan, AE Billica, RD Williams, DR AF Dulchavsky, SA Hamilton, DR Diebel, LN Sargsyan, AE Billica, RD Williams, DR TI Thoracic ultrasound diagnosis of pneumothorax SO JOURNAL OF TRAUMA-INJURY INFECTION AND CRITICAL CARE LA English DT Article C1 Wayne State Univ, Sch Med, Dept Surg, Detroit, MI 48201 USA. NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Directorate, Houston, TX 77058 USA. RP Dulchavsky, SA (reprint author), Detroit Receiving Hosp, Dept Surg, 4201 St Antoine, Detroit, MI 48201 USA. NR 6 TC 45 Z9 46 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 1079-6061 J9 J TRAUMA JI J. Trauma-Injury Infect. Crit. Care PD NOV PY 1999 VL 47 IS 5 BP 970 EP 971 DI 10.1097/00005373-199911000-00029 PG 2 WC Critical Care Medicine; Surgery SC General & Internal Medicine; Surgery GA 254QM UT WOS:000083623700030 PM 10568732 ER PT J AU Bielitzki, JT AF Bielitzki, JT TI Globalizing animal care and use: Making the dream a reality SO LAB ANIMAL LA English DT Article AB What will drive the globalization of animal care in the 21(st) century? Will targeted concerns from privately funded groups be the motivating factors? Will the threat of disease, and the concomitant hue and cry from a threatened public, be responsible for bringing nations together to collaborate on rules and regulations? The author, who is responsible for the animal use protocols on NASA's space station, explains why globalization on Planet Earth may be guided by what happens in outer space. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bielitzki, JT (reprint author), NASA, Ames Res Ctr, Mail Stop 261-1, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU NATURE AMERICA INC PI NEW YORK PA 345 PARK AVE SOUTH, NEW YORK, NY 10010-1707 USA SN 0093-7355 J9 LAB ANIMAL JI Lab Anim. PD NOV PY 1999 VL 28 IS 10 BP 24 EP 27 PG 4 WC Veterinary Sciences SC Veterinary Sciences GA 252LM UT WOS:000083503000007 PM 11543431 ER PT J AU Clarke, MSF Prendergast, MA Terry, AV AF Clarke, MSF Prendergast, MA Terry, AV TI Plasma membrane ordering agent pluronic F-68 (PF-68) reduces neurotransmitter uptake and release and produces learning and memory deficits in rats SO LEARNING & MEMORY LA English DT Article ID ARTERIAL SMOOTH-MUSCLE; FLUIDITY ALTERATIONS; CHOLESTEROL CONTENT; INSULIN-RESISTANCE; ALZHEIMERS-DISEASE; CELL-MEMBRANE; WATER-MAZE; INHIBITION; BRAIN; SENSITIVITY AB A substantial body of evidence indicates that aged-related changes in the fluidity and Lipid composition of the plasma membrane contribute to cellular dysfunction in humans and other mammalian species. Ln the CNS, reductions in neuronal plasma membrane order (PMO) (i.e., increased plasma membrane fluidity) have been attributed to age as well as the presence of the beta-amyloid peptide-25-35, known to play an important role in the neuropathology of Alzheimer's disease (AD). These PMO increases may influence neurotransmitter synthesis, receptor binding, and second messenger systems as well as signal transduction pathways. The effects of neuronal PMO on learning and memory processes have not been adequately investigated, however. Based on the hypothesis that an increase in PMO may alter a number of aspects of synaptic transmission, we investigated several neurochemical and behavioral effects of the membrane ordering agent, PF-68. In cell culture, PF-68 (nmoles/mg SDS extractable protein) reduced [H-3]norepinephrine (NE) uptake into differentiated PC-12 cells as well as reduced nicotine stimulated [H-3]NE release. The compound (800-2400 mu g/kg, i.p., resulting in nmoles/mg SDS extractable protein in the brain) decreased step-through latencies and increased the frequencies of crossing into the unsafe side of the chamber in inhibitory avoidance training. In the Morris water maze, PF-68 increased the latencies and swim distances required to locate a hidden platform and reduced the time spent and distance swam in the previous target quadrant during transfer (probe) trials. PF-68 did not impair performance of a well-learned working memory task, the rat delayed stimulus discrimination task (DSDT), however. Studies with C-14-labeled PF-68 indicated that significant (pmoles/mg wet tissue) levels of the compound entered the brain from peripheral (i.p.) injection. No PF-68 related changes were observed in swim speeds or in visual acuity tests in water maze experiments, rotorod performance, or in tests of general locomotor activity. Furthermore, latencies to select a lever in the DSDT were not affected. These results suggest that PF-68 induced deficits in learning and memory without confounding peripheral motor, sensory, or motivational effects at the tested doses. Furthermore, none of the doses induced a conditioned taste aversion to a novel 0.1% saccharin solution indicating a lack of nausea or gastrointestinal malaise induced by the compound. The data indicate that increases in neuronal plasma membrane order may have significant effects on neurotransmitter function as well as learning and memory processes. Furthermore, compounds such as PF-GS may also offer novel tools for studying the role of neuronal PMO in mnemonic processes and changes in PMO resulting from age-related disorders such as AD. C1 NASA, Lyndon B Johnson Space Ctr, Univ Space Res Assoc, Div Space Life Sci, Houston, TX 77058 USA. Univ Kentucky, Tobacco & Hlth Res Inst, Lexington, KY 40645 USA. Univ Georgia, Med Coll Georgia, Coll Pharm, Augusta, GA 30912 USA. Med Coll Georgia, Alzheimers Res Ctr, Augusta, GA 30912 USA. Med Coll Georgia, Dept Pharmacol & Toxicol, Augusta, GA 30912 USA. Vet Affairs Med Ctr, Augusta, GA 30910 USA. RP Clarke, MSF (reprint author), NASA, Lyndon B Johnson Space Ctr, Univ Space Res Assoc, Div Space Life Sci, Houston, TX 77058 USA. OI Terry, Alvin/0000-0003-2071-4767 NR 55 TC 26 Z9 26 U1 1 U2 4 PU COLD SPRING HARBOR LAB PRESS PI PLAINVIEW PA 1 BUNGTOWN RD, PLAINVIEW, NY 11724 USA SN 1072-0502 J9 LEARN MEMORY JI Learn. Mem. PD NOV-DEC PY 1999 VL 6 IS 6 BP 634 EP 649 DI 10.1101/lm.6.6.634 PG 16 WC Neurosciences; Psychology, Experimental SC Neurosciences & Neurology; Psychology GA 270RC UT WOS:000084548900007 PM 10641767 ER PT J AU Goldin, DS Venneri, SL Noor, AK AF Goldin, DS Venneri, SL Noor, AK TI Ready for the future? NASA explores virtual environments that can bring work, creativity, and distant expertise closer together than ever before. SO MECHANICAL ENGINEERING LA English DT Article C1 NASA, Washington, DC 20546 USA. RP Goldin, DS (reprint author), NASA, Washington, DC 20546 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0025-6501 J9 MECH ENG JI Mech. Eng. PD NOV PY 1999 VL 121 IS 11 BP 60 EP 66 PG 7 WC Engineering, Mechanical SC Engineering GA 254AA UT WOS:000083588300030 ER PT J AU Li, D Herlach, DM AF Li, D Herlach, DM TI Discussion of "Dendrite growth processes of silicon and germanium from highly undercooled melts" SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID GRAIN-STRUCTURE; CRYSTAL-GROWTH; MICROSTRUCTURES; SOLIDIFICATION; LEVITATION; ALLOYS C1 NASA, George C Marshall Space Flight Ctr, Drop Facil SD47, Huntsville, AL 35812 USA. DLR, Inst Space Simulat, D-51170 Cologne, Germany. RP Li, D (reprint author), NASA, George C Marshall Space Flight Ctr, Drop Facil SD47, Huntsville, AL 35812 USA. NR 26 TC 1 Z9 1 U1 1 U2 2 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD NOV PY 1999 VL 30 IS 11 BP 3011 EP 3013 DI 10.1007/s11661-999-0139-0 PG 3 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 258CZ UT WOS:000083821700030 ER PT J AU Rao, MN Wentworth, SJ Basu, A Garrison, DH McKay, DS AF Rao, MN Wentworth, SJ Basu, A Garrison, DH McKay, DS TI Properties and mixing of soil components in Apollo 17 double-drive tube 79001/2 SO METEORITICS & PLANETARY SCIENCE LA English DT Article AB Previous studies of Apollo 17 double-drive tube 79001/2 showed that portions of this lunar regolith segment have some unusual properties, such as very high I-s/FeO values (Morris ed al., 1989) and N contents (Stone and Clayton, 1989). To understand the geologic significance of these features in this core, we determined the grain-size distribution and modal abundance of the petrographic constituents for samples from 12 different depths of the core. Also, we measured the elemental and isotopic compositions of noble gases in the coarse-grained (150-250 mu m) and fine-grained (<20 mu m) sample fractions ti om four depths of this core. The agglutinate abundance and Ar-36 contents show depth-related variations similar to those observed for I-s/FeO and N in this core. Samples from the top (similar to 0.5 cm depth) and the bottom (similar to 45 cm depth) of the drive tube are related to Apollo 17 submature soils with about 250-300 Ma galactic cosmic-ray (GCR) exposure age. But the soil at the top of the drive tube received additional surface irradiation for similar to 2 Ma after deposition at Van Serg. The samples at intermediate depths (i.e., similar to 7 cm (upper zone) and similar to 20 cm (lower zone) of the 79001/2 core) show features characteristic of mixtures of Apollo 17 mature soils and finely comminuted regolith breccias having about 600-800 Ma GCR exposure age. The mixing ratios between the coarse and fine fractions of the intermediate-depth samples are similar to each other. Though the mixing ratios for the samples from the top and the bottom of the core are also similar to each other, they differ significantly from the ratios at intermediate depths. The results presented here are consistent with the two-component Van Serg core model proposed by Stone and Clayton (1989) and McKay et al. (1988). C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. Indiana Univ, Dept Geol Sci, Bloomington, IN 47405 USA. RP Rao, MN (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 13 TC 2 Z9 2 U1 1 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1999 VL 34 IS 6 BP 853 EP 859 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 259FZ UT WOS:000083885000005 ER PT J AU Woolum, DS Cassen, P AF Woolum, DS Cassen, P TI Astronomical constraints on nebular temperatures: Implications for planetesimal formation SO METEORITICS & PLANETARY SCIENCE LA English DT Review ID T-TAURI STARS; EARLY SOLAR-SYSTEM; PROTOSTELLAR DISK MODELS; CHONDRITE PARENT BODIES; YOUNG STELLAR OBJECTS; ACCRETION DISKS; HL-TAURI; CARBONACEOUS CHONDRITE; PRIMITIVE METEORITES; PROTOPLANETARY DISKS AB Motivated by recent observations of T-Tauri stars and the interpretation of these observations in terms of the properties of circumstellar disks, we derive internal (midplane) temperatures for disks around mature (age similar to 1 Ma) T-Tauri stars. The estimates are obtained by combining published results for disk masses, sizes, accretion rates, and surface temperatures. For 26 stars (for which adequate data are available), we derive midplane temperatures at 1 AU primarily in the range 200-800 K, and 100-400 K at 2.5 AU. It is likely that the solar nebula, at the same stage of evolution, contained planetesimals and objects destined to become meteorite parent bodies. Observations of young stellar objects at earlier stages of evolution (age similar to 0.1 Ma) imply that accretion rates were, on the average, at least two orders of magnitude greater than the 10(-8) M./year rates typical for mature T-Tauri stars. Such high values would result in midplane temperatures at or near the silicate vaporization temperature in the terrestrial planet region. If cooling of the solar nebula from such a hot epoch was responsible for establishing the pervasive elemental fractionation patterns found in chondritic meteorites, then objects in the asteroid belt must have grown rapidly (within 0.1 Ma) to sizes of similar to 1 km, a conclusion consistent with current theories of planetesimal formation. However, the fact that primitive meteorite parent bodies escaped being melted by the decay of Al-26 then implies that further growth of at least some objects was essentially delayed for 2 Ma or more. Such a diminished growth rate appears to be consistent with simulations of the dynamics of solid bodies in the asteroid belt. Other hypotheses seem less attractive. One might assume that the final cooling occurred only after the decay of Al-26 (i.e., more than a million years after calcium-aluminum rich inclusion formation), or that Al-26 was not ubiquitous in the early solar system. But the first of these conjectures is incompatible with astronomical observations of T-Tauri systems, and the second appears to be contradicted by the evidence for Al-26 in diverse meteoritic components. The remaining alternative would then appear to be that, despite a lack of supporting evidence, chondritic fractionation patterns reflect the net effect of many local heating and cooling events and have nothing to do with global nebular cooling. We conclude that the most plausible hypothesis is that both nebular cooling and coagulation of solids to kilometer-sized objects occurred rapidly and that a substantial number of planetesimals in the asteroid belt remained smaller than a few kilometers in radius for at least 2 Ma. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92834 USA. RP Woolum, DS (reprint author), NASA, Ames Res Ctr, 245-3, Moffett Field, CA 94035 USA. NR 105 TC 42 Z9 41 U1 0 U2 4 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1999 VL 34 IS 6 BP 897 EP 907 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 259FZ UT WOS:000083885000010 ER PT J AU Jenniskens, P Butow, SJ AF Jenniskens, P Butow, SJ TI The 1998 Leonid multi-instrument aircraft campaign - an early review SO METEORITICS & PLANETARY SCIENCE LA English DT Article; Proceedings Paper CT Workshop on the Leonid Multi-Instrument Aircraft Campaign CY APR 12-15, 1999 CL MOFFETT FIELD, CA ID METEOR STREAM ACTIVITY; COMETARY DUST TRAILS; AIRBORNE LIDAR; TEMPEL-TUTTLE; STORMS; DYNAMICS; SPECTRA; DANGER; SHOWER; ORBITS AB The 1998 return of the Leonid shower was the target of the Leonid multi-instrument aircraft campaign (Leonid MAC), an unusual two-aircraft astronomical research mission executed near Okinawa, Japan. The prospect of a meteor storm brought 28 researchers of 7 nationalities together in a concerted effort to observe the shower by imaging, spectroscopic, and ranging techniques. This paper is a review of the major science issues that are behind the deployment of each of the present array of instruments and describes the interconnection of the various experiments. This was NASA's first astrobiology mission. The mission also aimed to study contemporary issues in planetary astronomy, in atmospheric sciences, and concerning the satellite impact hazard. First results of the participating observers are discussed and put in context, in preparation for the deployment of a planned second mission in November of 1999. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. USAF, RQS ACC 129, Calif Air Natl Guard, Moffett Fed Airfield, Moffett Field, CA 94035 USA. RP Jenniskens, P (reprint author), NASA, Ames Res Ctr, SETI Inst, Mail Stop 239-4, Moffett Field, CA 94035 USA. EM peter@max.arc.nasa.gov NR 79 TC 49 Z9 49 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1999 VL 34 IS 6 BP 933 EP 943 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 259FZ UT WOS:000083885000013 ER PT J AU Pawlowski, JF AF Pawlowski, JF TI Johnson Space Center's Leonids optical observations SO METEORITICS & PLANETARY SCIENCE LA English DT Article; Proceedings Paper CT Workshop on the Leonid Multi-Instrumetn Aircraft Campaign CY APR 12-15, 1999 CL MOFFETT FIELD, CALIFORNIA AB The 1998 Leonid meteor shower was videotaped by NASA Johnson Space Center (JSC) personnel, Jim Pawlowski and Jerry Winkler, at Houston, Texas, and Anna Scott at Cloudcroft, New Mexico. The videotapes were screened and the Leonid meteors in the videotapes were analyzed. The out:come of this effort was tables of counts per hour over the viewing period and a comparison to the Leonids meteors mass distribution model (Matney, 1998, unpubl. data) used for risk assessment calculations associated with space shuttle missions. The comparison exhibited a difference between. the observed data and the model. Perhaps this difference can be resolved when observations from other parts of the Earth are assimilated with JSC observations. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Pawlowski, JF (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 1 TC 4 Z9 4 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1999 VL 34 IS 6 BP 945 EP 947 PG 3 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 259FZ UT WOS:000083885000014 ER PT J AU Murray, IS Hawkes, RL Jenniskens, P AF Murray, IS Hawkes, RL Jenniskens, P TI Airborne intensified charge-coupled device observations of the 1998 Leonid shower SO METEORITICS & PLANETARY SCIENCE LA English DT Article; Proceedings Paper CT Workshop on the Leonid Multi-Instrumetn Aircraft Campaign CY APR 12-15, 1999 CL MOFFETT FIELD, CALIFORNIA ID METEORS; RADAR AB We have used dual coaxial microchannel plate image-intensified monochrome charge-coupled device (CCD) detectors run at standard NTSC frame rates (30 frames per second, fps) to study the Leonid meteor shower on 1998 November 17 fi-om an airborne platform at an altitude of similar to 13 km. These observations were part of NASA's 1998 Leonid multi-instrument aircraft campaign(MAC). The observing systems had fields of view (width) of 16.3 degrees and 9.5 degrees, and limiting stellar sensitivities of +8.3(m) and +8.9(m). During 12 h of recording, 230 meteors were detected, of which 65 were Leonid meteors. Light curves are presented for 53 of these meteors. The magnitudes at peak brightness of the meteors investigated were generally in the range from +4.0(m) to +6.0(m) The mass distribution indices for the two samples are 1.67 and 1.44, with the former being based on the wider field of view dataset. The light curves were skewed with the brightest point towards the beginning of the meteor trail. The F parameter for points one magnitude below maximum luminosity had a mean value of 0.47 for the wider field system and 0.37 far the more sensitive narrower field system. We provide leading and trailing edge light curve slopes for each meteor as another indication of light curve shape. There were few obvious flares on the light curves, indicating that in-flight fragmentation into a large number of grains is not common. There is variability in light curve shape from meteor to meteor. The light curves are inconsistent with single, compact body meteor theory, and we interpret the data as indicative of a two-component dustball model with metal or silicate grains bonded by a lower boiling point, possibly organic, substance. The variation in light curve shape may be indicative of differences in mass distribution of the constituent grains. We provide trail length vs. magnitude data. There is only a slight hint of a bend at +5(m) in the data, representing the difference between meteors that have broken into a cluster of grains prior to grain ablation, and those that continue to fragment during the grain ablation phase. Two specific meteors show interesting light curve features. One meteor is nebulous in appearance, with significant transverse width. The apparent light production region extends fbr 450 m from the center of the meteor path. Another meteor has several main fragments, and evidence of significant separated fragments. We offer several suggestions for improvements for the 1999 Leonid MAC light curve experiment. C1 Mt Allison Univ, Dept Phys, Sackville, NB E4L 1E6, Canada. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP Hawkes, RL (reprint author), Mt Allison Univ, Dept Phys, 67 York St, Sackville, NB E4L 1E6, Canada. NR 27 TC 53 Z9 53 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1999 VL 34 IS 6 BP 949 EP 958 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 259FZ UT WOS:000083885000015 ER PT J AU Jenniskens, P AF Jenniskens, P TI Activity of the 1998 Leonid shower from video records SO METEORITICS & PLANETARY SCIENCE LA English DT Article; Proceedings Paper CT Workshop on the Leonid Multi-Instrumetn Aircraft Campaign CY APR 12-15, 1999 CL MOFFETT FIELD, CALIFORNIA ID METEOR STREAM ACTIVITY; IMPACT PROBABILITIES; RADAR AB Video observations of the Leonid shower aboard two aircraft in the 1998 Leonid multi-instrument aircraft campaign and from ground locations in China are presented. Observing at altitude proved particularly effective, with four times higher rates due to low extinction and low angular velocity at the horizon. The rates, derived from a total of 2500 Leonid meteors, trace at least two distinct dust components. One dominated the night of 1998 November 16/17. This two-day wide component was rich in bright meteors with r = N (m + 1)/N (m) approximate to 1.5 (s = 1.4) and peaked at an influx of 3.1 +/- 0.4 x 10(-12) m(-2) s(-1) (for particles of mass <7 x 10(-5) g) at solar longitude lambda(o) approximate to 234.52 (Eq. J2000). The other more narrow component peaked on 1998 November 17/18 at lambda(o) = 235.31 +/- 0.01. Rates were elevated above the broad component between lambda(o) = 235.15 and 235.40, symmetric around the current node of the parent comet 55P/Tempel-Tuttle, peaking at 5.1 +/- 0.2 x 10(-12) m(-2) s(-1). The population index was higher, r = 1.8 +/- 0.1 (s = 1.7), but not as high as in past Leonid storms (r = 3.0). The flux profile of this component has an unusual asymmetric shape, which implies a blend of contributions from at least two different but relatively recent epochs of ejection. The variation of r across the profile might be due to mass-dependent ejection velocities of the narrowest component. High rates of faint meteors occurred only in an isolated five-minute interval at lambda(o) = 235.198, which is likely the result of a single meteoroid breakup in space. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP Jenniskens, P (reprint author), NASA, Ames Res Ctr, SETI Inst, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 27 TC 22 Z9 22 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1999 VL 34 IS 6 BP 959 EP 968 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 259FZ UT WOS:000083885000016 ER PT J AU Betlem, H Jenniskens, P van't Leven, J ter Kuile, C Johannink, C Zhao, HB Lei, CM Li, GY Zhu, J Evans, S Spurny, P AF Betlem, H Jenniskens, P van't Leven, J ter Kuile, C Johannink, C Zhao, HB Lei, CM Li, GY Zhu, J Evans, S Spurny, P TI Very precise orbits of 1998 Leonid meteors SO METEORITICS & PLANETARY SCIENCE LA English DT Article; Proceedings Paper CT Workshop on the Leonid Multi-Instrumetn Aircraft Campaign CY APR 12-15, 1999 CL MOFFETT FIELD, CALIFORNIA ID OUTBURST AB Seventy-five orbits of Leonid meteors obtained during the 1998 outburst are presented. Thirty-eight are precise enough to recognize significant dispersion in orbital elements. Results from the nights of 1998 November 16/17 and 17/18 differ, in agreement with the dominant presence of different dust components. The shower rate profile of 1998 November 16/17 was dominated by a broad component, rich in bright meteors. The radiant distribution is compact. The semimajor axis is confined to values close to that of the parent comet, whereas the distribution of inclination has a central condensation in a narrow range. On the other hand, 1998 November 17/18 was dominated by dust responsible for a more narrow secondary peak in the flux curve. The declination of the radiant and the inclination of the orbit are more widely dispersed. The argument of perihelion, inclination, and the perihelion distance are displaced. These data substantiate the hypothesis that trapping in orbital resonances is important for the dynamical evolution of the broad component. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. Dutch Meteor Soc, NL-2318 NB Leiden, Netherlands. Purple Mt Observ, Nanjing 210008, Peoples R China. Chinese Acad Sci, Beijing Astron Observ, Beijing 100080, Peoples R China. BAA Meteor Sect, Haverhill CB9 7HY, Suffolk, England. Ondrejov Observ, Astron Inst, Ondrejov 25165, Czech Republic. RP Jenniskens, P (reprint author), NASA, Ames Res Ctr, SETI Inst, Mail Stop 239-4, Moffett Field, CA 94035 USA. RI Spurny, Pavel/G-9044-2014 NR 16 TC 34 Z9 34 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1999 VL 34 IS 6 BP 979 EP 986 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 259FZ UT WOS:000083885000019 ER PT J AU Lloyd, JR Clemens, J Snede, R AF Lloyd, JR Clemens, J Snede, R TI Copper metallization reliability SO MICROELECTRONICS RELIABILITY LA English DT Article ID ELECTROMIGRATION; ENERGY; FILMS AB The electromigration performance of Cu metalization has been reviewed with an explanation as to why the advantage of Cu over Al alloys in the fine line regime is not as great as anticipated. Cu metalization testing procedures are described and the dangers of "overstressing" are explained in some detail. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Aetrium Inc, St Paul, MN USA. RP Lloyd, JR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 21 TC 108 Z9 111 U1 0 U2 7 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0026-2714 J9 MICROELECTRON RELIAB JI Microelectron. Reliab. PD NOV PY 1999 VL 39 IS 11 BP 1595 EP 1602 DI 10.1016/S0026-2714(99)00177-8 PG 8 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA 266NA UT WOS:000084305000009 ER PT J AU Conley, CA Fowler, VM AF Conley, CA Fowler, VM TI The human 64kD autoantigen D1 is expressed in slow fibers of eye muscle. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Scripps Res Inst, La Jolla, CA 92037 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1999 VL 10 SU S MA 1421 BP 245A EP 245A PG 1 WC Cell Biology SC Cell Biology GA 255MW UT WOS:000083673501422 ER PT J AU Clarke, MSF Vanderburg, CR Carpenter, J Howerte, C Abbasi, T Feeback, DL AF Clarke, MSF Vanderburg, CR Carpenter, J Howerte, C Abbasi, T Feeback, DL TI Macromolecular loading and transfection of adherent cells utilizing a navel hypergravity-assisted impact-mediated loading device. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 Univ Space Res Assoc, Houston, TX 77058 USA. Massachusetts Gen Hosp, Boston, MA 02114 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1999 VL 10 SU S MA 1566 BP 270A EP 270A PG 1 WC Cell Biology SC Cell Biology GA 255MW UT WOS:000083673501567 ER PT J AU Risin, D Sundaresan, A Pellis, NR AF Risin, D Sundaresan, A Pellis, NR TI PKC isoforms expression in modeled microgravity. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 Wyle Labs, Houston, TX 77058 USA. NASA, Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1999 VL 10 SU S MA 1922 BP 332A EP 332A PG 1 WC Cell Biology SC Cell Biology GA 255MW UT WOS:000083673501921 ER PT J AU Sundaresan, A Risin, D Pellis, NR AF Sundaresan, A Risin, D Pellis, NR TI Locomotion In lymphocytes is altered by differential PKC isoform expression. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 Wyle Labs, El Segundo, CA 90245 USA. NASA, Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1999 VL 10 SU S MA 1923 BP 332A EP 332A PG 1 WC Cell Biology SC Cell Biology GA 255MW UT WOS:000083673501924 ER PT J AU DelSole, T Hou, AY AF DelSole, T Hou, AY TI Empirical correction of a dynamical model. Part I: Fundamental issues SO MONTHLY WEATHER REVIEW LA English DT Article ID DATA ASSIMILATION; ERROR; PREDICTION; ATMOSPHERE AB The possibility of empirically correcting a nonlinear dynamical model is examined. The empirical correction is constructed by fitting a first-order Markov model to the forecast errors using initial conditions as predictors. The dynamical operator of the Markov model can then be subtracted from the original forecast model to correct the forecast. The procedure is based an an earlier work by Leith, suitably modified for practical applications. The effects of analysis errors and finite difference approximations are analyzed. It is shown that uncorrelated analysis errors produce spurious terms in the empirical correction operator that act to damp eddy variance at a rate inversely proportional to the lead time used to estimate the Markov model. The finite difference approximation is appropriate as long as the forecast errors grow linearly with lead time. These restrictions can be interpreted as setting lower and upper limits on the lead time, respectively, and can be checked without knowing the true state exactly. The procedure is sensitive to sampling errors, but this problem was not explored. These formal conclusions are tested on a nonlinear quasigeostrophic model in which model error is created by changing the model parameters. A "systematic error" correction, which does not depend on state and is herd constant throughout the integration, does not improve the forecast skin of the model because the contrived error is primarily state dependent. However, an empirical correction, which depends on instantaneous state, improves the forecast skill of the model by 10 days, and further iterations extend the skill to the limit imposed by observation error (about 20 days in this example). C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. RP DelSole, T (reprint author), Ctr Ocean Land Atmophere Studies, Suite 302,4041 Powder Mill Rd, Beltsville, MD 20705 USA. RI Hou, Arthur/D-8578-2012 NR 23 TC 25 Z9 29 U1 2 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD NOV PY 1999 VL 127 IS 11 BP 2533 EP 2545 DI 10.1175/1520-0493(1999)127<2533:ECOADM>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 250TG UT WOS:000083403800001 ER PT J AU Parikh, JA DaPonte, JS Vitale, JN Tselioudis, G AF Parikh, JA DaPonte, JS Vitale, JN Tselioudis, G TI An evolutionary system for recognition and tracking of synoptic-scale storm systems SO PATTERN RECOGNITION LETTERS LA English DT Article DE cloud tracking; evolutionary computation; optical flow; self-organizing maps; k-nearest neighbor analysis ID OPTICAL-FLOW; FRAMEWORK; ALGORITHM AB An evolutionary system was developed for generation of complete tracks of northern midlatitude synoptic-scale storm systems based on optical flow and cloud motion analyses of global satellite-based datasets produced by the International Satellite Cloud Climatology Project (ISCCP). The tracking results were compared with low sea level pressure anomaly (SLPA) tracks obtained from the NASA Goddard Institute for Space Studies (GISS). The SLPA tracks were produced at GISS by analysis of meteorological, ground-based National Center for Environmental Prediction (NCEP) datasets. Results from the evolutionary system were also compared with results from using (a) the k-nearest neighbor rule (K-NN) and (b) self-organizing maps (SOM) to determine correspondences between consecutive locations within a track. The consistency of our evolutionary storm tracking results with the behavior of the low sea level pressure anomaly tracks, the ability of our evolutionary system to generate and evaluate complete tracks, and the close comparison between the results obtained by the evolutionary, k-NN, and SOM analyses of the ISCCP-derived datasets at tracking steps in which proximity or optical flow information sufficed to determine movement, demonstrate the applicability and the potential of evolutionary systems for tracking midlatitude storm systems through low-resolution ISCCP cloud product datasets. (C) 1999 Elsevier Science B.V. All rights reserved. C1 So Connecticut State Univ, Dept Comp Sci, New Haven, CT 06515 USA. Columbia Univ, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Parikh, JA (reprint author), So Connecticut State Univ, Dept Comp Sci, New Haven, CT 06515 USA. NR 18 TC 7 Z9 7 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8655 J9 PATTERN RECOGN LETT JI Pattern Recognit. Lett. PD NOV PY 1999 VL 20 IS 11-13 BP 1389 EP 1396 DI 10.1016/S0167-8655(99)00110-5 PG 8 WC Computer Science, Artificial Intelligence SC Computer Science GA 263YF UT WOS:000084152300037 ER PT J AU Vega, AJ Rohli, RV Sui, CH AF Vega, AJ Rohli, RV Sui, CH TI Climatic relationships to Chesapeake Bay salinity during southern oscillation extremes SO PHYSICAL GEOGRAPHY LA English DT Article DE El Nino; La Nina; Chesapeake Bay (CB); salinity; North Atlantic Oscillation (NAO); climatic variability; change ID AMERICAN TELECONNECTION PATTERN; ATMOSPHERIC CIRCULATION PATTERNS; UNITED-STATES CLIMATE; EL-NINO; PRECIPITATION EVENTS; NORTHERN HEMISPHERE; TEMPERATURE; PACIFIC; VARIABILITY; TOLERANCE AB Monthly cool-season salinity over the 1958 to 1991 period is analyzed for the Chesapeake Bay (CB), and the salinity variations are associated with low-frequency 500 hPa flow variations and with extremes of the Southern Oscillation (SO). Results identify a significant decrease in mean CB surface salinity, which is supported by similar trends in individual salinity subbasins occupying the northern extremes of the bay. Zonal (meridional) flow associated with the North Atlantic Oscillation (NAO) seems to be linked to below-(above-) normal CB salinity, while the Southern Oscillation Index (SOI) seems to be negatively correlated with CB salinity. Principal components analysis (PCA) reveals that the Pacific/North American (PNA) pattern is related to CB salinity, even though the PNA index is not. Within extreme El Nino months, the strongest association between CB salinity and PCA-derived circulation suggests that 500 hPa height features over the Great Plains may be linked to surface salinity in CB. By contrast, during La Nina months, height features over the Desert Southwest appear to be linked more directly to surface CB salinity. The results also suggest that 500 hPa flow patterns conducive to extreme precipitation in the northeastern United States are related to salinity variations in the northern bay. However, for the bay as a whole, and especially the southern portions of the bay, flow patterns favoring mean advective processes of CB and oceanic surface waters may be more important than those patterns relating to precipitation in contributing drainage basin areas. Results may be useful to environmental planners in the CB region. C1 Clarion Univ Pennsylvania, Dept Anthropol Geog & Earth Sci, Clarion, PA 16214 USA. Kent State Univ, Dept Geog, Kent, OH 44242 USA. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Vega, AJ (reprint author), Clarion Univ Pennsylvania, Dept Anthropol Geog & Earth Sci, Clarion, PA 16214 USA. OI SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 44 TC 7 Z9 7 U1 1 U2 2 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0272-3646 EI 1930-0557 J9 PHYS GEOGR JI Phys. Geogr. PD NOV-DEC PY 1999 VL 20 IS 6 BP 468 EP 490 PG 23 WC Environmental Sciences; Geography, Physical; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Physical Geography; Geology; Meteorology & Atmospheric Sciences GA 318KC UT WOS:000087282100003 ER PT J AU Smith, SJ Chutjian, A Greenwood, JB AF Smith, SJ Chutjian, A Greenwood, JB TI Lifetimes of the 2s(2)2p P-2(o)-2s2p(2) P-4 intercombination transitions of C+ SO PHYSICAL REVIEW A LA English DT Article ID HUBBLE-SPACE-TELESCOPE; EMISSION AB Radiative lifetimes have been measured for fine-structure transitions in the intercombination 2s2p(24)P -->2s(2)2p(2) P-o decay in C+. Use was made of a Kingdon ion trap installed on a beam line for highly charged ions. The radiative rates A(J) derived from the lifetime measurements are 130.0+/-5.5 s(-1) for the P-4(1/2) sublevel, 9.0+/-1.0 s(-1) for the P-4(3/2) sublevel, and 50.0+/-2.5 s(-1) for the P-4(5/2) sublevel. Comparisons with other measurements and results of theories are given. [S1050-2947(99)06910-3]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Greenwood, Jason/L-4799-2014 NR 20 TC 16 Z9 16 U1 0 U2 1 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2469-9926 EI 2469-9934 J9 PHYS REV A JI Phys. Rev. A PD NOV PY 1999 VL 60 IS 5 BP 3569 EP 3574 DI 10.1103/PhysRevA.60.3569 PG 6 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 257ED UT WOS:000083768800036 ER PT J AU Wu, JS Derrickson, JH Parnell, TA Strayer, MR AF Wu, JS Derrickson, JH Parnell, TA Strayer, MR TI Screening effect in electromagnetic production of electron-positron pairs in relativistic nucleus-atom collisions SO PHYSICAL REVIEW A LA English DT Article ID HEAVY-ION COLLISIONS; COULOMB COLLISIONS; SULFUR IONS; FIXED TARGETS; FIELDS AB We study the screening effects of the atomic electrons in the electromagnetic production of electron-positron pairs in relativistic nucleus-atom collisions for fixed target experiments. Our results are contrasted with those obtained in bare collisions, with particular attention given to its dependence on the beam energy and the target atom. [S1050-2947(99)06311-8]. C1 Fayetteville State Univ, Dept Nat Sci, Fayetteville, NC 28301 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Oak Ridge Natl Lab, Div Phys, Oak Ridge, TN 37831 USA. RP Wu, JS (reprint author), Fayetteville State Univ, Dept Nat Sci, Fayetteville, NC 28301 USA. NR 30 TC 4 Z9 4 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD NOV PY 1999 VL 60 IS 5 BP 3722 EP 3726 DI 10.1103/PhysRevA.60.3722 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 257ED UT WOS:000083768800054 ER PT J AU Stoev, K Rame, E Garoff, S AF Stoev, K Rame, E Garoff, S TI Effects of inertia on the hydrodynamics near moving contact lines SO PHYSICS OF FLUIDS LA English DT Article ID SOLID-SURFACES; BOUNDARY-CONDITIONS; MOLECULAR-DYNAMICS; FLUID INTERFACE; LIQUIDS; ANGLES; FLOW AB We investigate the effects of inertia on the hydrodynamics in the microscopic vicinity of moving contact lines. These hydrodynamics control the macroscopic shape and spreading of fluid bodies across solid surfaces. We perform experiments at low capillary number (Ca < 0.1) and negligible (10(-4)) to moderate (Re similar to 1) Reynolds number. On a microscopic scale, inertia decreases the dynamic curvature of the free surface near the contact line compared to the case with Re=0 at the same Ca. On a macroscopic scale, inertia lowers the apparent contact angle of the static-like macroscopic interface compared to the situations with the same Ca but negligible Re. (C) 1999 American Institute of Physics. [S1070-6631(99)02611-2]. C1 Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Carnegie Mellon Univ, Colloids Surfaces & Polymers Program, Pittsburgh, PA 15213 USA. NASA, Glenn Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RP Stoev, K (reprint author), Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. RI Garoff, Stephen/P-7629-2014 OI Garoff, Stephen/0000-0001-8148-8535 NR 36 TC 28 Z9 28 U1 1 U2 10 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD NOV PY 1999 VL 11 IS 11 BP 3209 EP 3216 DI 10.1063/1.870182 PG 8 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 244LN UT WOS:000083052700004 ER PT J AU Vassiliadis, D Baker, DN Lundstedt, H Davidson, RC AF Vassiliadis, D Baker, DN Lundstedt, H Davidson, RC TI Special topic: Nonlinear Methods in Space Plasma Physics Papers Presented at the 1998 Fall Meeting of the American Geophysical Union - Foreword SO PHYSICS OF PLASMAS LA English DT Editorial Material C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. Univ Colorado, Lab Astrophys & Space Phys, Boulder, CO 80309 USA. Univ Lund, Dept Astron, Lund, Sweden. Princeton Univ, Princeton Plasma Phys Lab, Princeton, NJ 08543 USA. RP Vassiliadis, D (reprint author), NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD NOV PY 1999 VL 6 IS 11 BP III EP IV PG 2 WC Physics, Fluids & Plasmas SC Physics GA 246XN UT WOS:000083190300001 ER PT J AU Goldstein, ML Roberts, DA AF Goldstein, ML Roberts, DA TI Magnetohydrodynamic turbulence in the solar wind SO PHYSICS OF PLASMAS LA English DT Article; Proceedings Paper CT Fall Meeting of the American-Geophysical-Union CY DEC 06-10, 1998 CL SAN FRANCISCO, CA SP Amer Geophys Union ID MAGNETIC-FIELD CORRELATION; MHD TURBULENCE; RADIAL EVOLUTION; ALFVEN WAVES; INCOMPRESSIBLE MAGNETOHYDRODYNAMICS; OBSERVATIONAL CONSTRAINTS; HELIOCENTRIC DISTANCE; INNER HELIOSPHERE; STREAM STRUCTURE; CROSS-HELICITY AB Low frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much so that the fluctuations may be thought of as originating near the Sun as nearly perfect Alfven waves. Power spectra of these fluctuations from 10(-7) Hz to several Hz to suggest that the medium is turbulent. Near 1 AU, fluctuations below 10(-5) Hz have a relatively flat slope (similar to-1) and contain most of the energy in the fluctuating fields. From 10(-5) Hz to similar to 0.1 Hz, the spectra exhibit a power law inertial range similar to that seen in ordinary fluid turbulence. At the highest frequencies, the rapid fall-off of the power suggests that strong dissipation is occurring. From in situ measurements, it is clear that the fluctuations emanate from the solar corona. The turbulent cascade appears to evolve most rapidly in the vicinity of velocity shears and current sheets. Numerical solutions of both the compressible and incompressible equations of magnetohydrodynamics in both Cartesian and spherical geometry corroborate this interpretation. There are conflicting interpretations of observations suggesting that much of the power in magnetic field fluctuations resides in quasi-two-dimensional structures and simulations have helped to elucidate some of these issues. (C) 1999 American Institute of Physics. [S1070-664X(99)02811-6]. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 93 TC 114 Z9 115 U1 0 U2 6 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 1070-664X EI 1089-7674 J9 PHYS PLASMAS JI Phys. Plasmas PD NOV PY 1999 VL 6 IS 11 BP 4154 EP 4160 DI 10.1063/1.873680 PG 7 WC Physics, Fluids & Plasmas SC Physics GA 246XN UT WOS:000083190300004 ER PT J AU Valdivia, JA Vassiliadis, D Klimas, A Sharma, AS AF Valdivia, JA Vassiliadis, D Klimas, A Sharma, AS TI Modeling the spatial structure of the high latitude magnetic perturbations and the related current systems SO PHYSICS OF PLASMAS LA English DT Article; Proceedings Paper CT Fall Meeting of the American-Geophysical-Union CY DEC 06-10, 1998 CL SAN FRANCISCO, CALIFORNIA SP Amer Geophys Union ID DATA-DERIVED ANALOGS; MAGNETOSPHERIC DYNAMICS; IONOSPHERE; PREDICTION AB Previous input-output analysis of the electrojet indices has been generalized to a spatio-temporal dynamical model of the high latitude magnetic perturbation (HLMP) by using the spatially dependent measurements that can be provided by a ground magnetometer array of latitudinal coverage. A technique that utilizes the daily rotation of the Earth as a longitudinal, or local time, sampling mechanism is used to construct a two-dimensional representation of the high latitude magnetic perturbations, both in magnetic latitude and local time, from the single latitudinal chain of magnetometers. Two-dimensional static, linear dynamical and nonlinear dynamical models for the evolution of the spatial structure of the HLMP are constructed by including a coupling to the solar wind as the energy input. The nonlinear spatial model of the HLMP produces better predictions than the linear one, reducing the average error from 65 to 50 nT for the H-x component. This can be taken as an indication that during intense activity, the HLMP and related current system evolves in a nonlinear fashion. (C) 1999 American Institute of Physics. [S1070-664X(99)03211-5]. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Valdivia, JA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 17 TC 26 Z9 26 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD NOV PY 1999 VL 6 IS 11 BP 4185 EP 4194 DI 10.1063/1.873684 PG 10 WC Physics, Fluids & Plasmas SC Physics GA 246XN UT WOS:000083190300008 ER PT J AU Baker, DN Kanekal, SG Klimas, AJ Vassiliadis, D Pulkkinen, TI AF Baker, DN Kanekal, SG Klimas, AJ Vassiliadis, D Pulkkinen, TI TI Collective phenomena in the inner magnetosphere SO PHYSICS OF PLASMAS LA English DT Article; Proceedings Paper CT Fall Meeting of the American-Geophysical-Union CY DEC 06-10, 1998 CL SAN FRANCISCO, CALIFORNIA SP Amer Geophys Union ID DYNAMICS; MODEL AB The Earth's magnetosphere exhibits substantial complexity in many of its physical properties. Particle populations wax and wane and magnetic fields fluctuate on virtually all observed time scales, from less than 1 minute to many days. Much of the variability of the magnetosphere and its interaction with the ionosphere can be ascribed to the phenomena termed "substorms" and "storms." Ample evidence is found that these geospace disturbances, though exhibiting event-to-event differences, are remarkably repetitive and have basic underlying similarities. The ring current development, radiation belt particle changes, and basic substorm patterns suggest a high degree of coherence in the phenomena. Observations, modeling, and basic physical properties are discussed here that point to a relatively ordered, low-dimensional underlying dynamics in the magnetosphere. These results suggest that nonlinear processes and couplings introduce much of the observed complexity in magnetospheric particle and field changes. (C) 1999 American Institute of Physics. [S1070-664X(99)03311-X]. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. RP Baker, DN (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Campus Box 590, Boulder, CO 80309 USA. RI Pulkkinen, Tuija/D-8403-2012 OI Pulkkinen, Tuija/0000-0002-6317-381X NR 12 TC 8 Z9 8 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD NOV PY 1999 VL 6 IS 11 BP 4195 EP 4199 DI 10.1063/1.873685 PG 5 WC Physics, Fluids & Plasmas SC Physics GA 246XN UT WOS:000083190300009 ER PT J AU Monkiewicz, J Mould, JR Gallagher, JS Clarke, JT Trauger, JT Grillmair, C Ballester, GE Burrows, CJ Crisp, D Evans, R Griffiths, R Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Meadows, V Scowen, PA Stapelfeldt, KR Sahai, R Watson, A AF Monkiewicz, J Mould, JR Gallagher, JS Clarke, JT Trauger, JT Grillmair, C Ballester, GE Burrows, CJ Crisp, D Evans, R Griffiths, R Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Meadows, V Scowen, PA Stapelfeldt, KR Sahai, R Watson, A TI The age of the Sculptor dwarf spheroidal galaxy from imaging with WFPC2 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID GALACTIC GLOBULAR-CLUSTERS; INFRARED PHOTOMETRY; STELLAR CONTENT; LOCAL GROUP; STARS; COMPANIONS; M31; SMC AB From images taken with the Hubble Space Telescope's WFPC2, we have obtained photometry of a field in the Sculptor dwarf spheroidal galaxy to 3 mag below the main-sequence turnoff. We determine an age equal to that of the earliest globular clusters for the bulk of the stars in our field of view. We attempt to constrain the star formation history of the Sculptor dwarf by examining the main-sequence luminosity function. The presence of a half-dozen blue straggler candidates blueward of the turnoff points to a possibly complex star formation history. However, the contribution of any intermediate-age population is difficult to measure conclusively, because of the uncertain origin of blue stragglers and the sparseness of the photometric sample. C1 Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Jet Propuls Lab, Pasadena, CA 91109 USA. CALTECH, IPAC, Pasadena, CA 91125 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Univ Nacl Autonoma Mexico, Astron Inst, Morelia 58090, Michoacan, Mexico. RP Monkiewicz, J (reprint author), Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Res Sch Astron & Astrophys, Private Bag,Weston Creek Post Off, Weston, ACT 2611, Australia. EM jrm@mso.anu.edu.au; jsg@astro.wisc.edu RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 36 TC 41 Z9 42 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD NOV PY 1999 VL 111 IS 765 BP 1392 EP 1397 DI 10.1086/316447 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 258DY UT WOS:000083823900005 ER PT J AU Mortensen, MD Linfield, RP Kursinski, ER AF Mortensen, MD Linfield, RP Kursinski, ER TI Vertical resolution approaching 100 m for GPS occultations of the Earth's atmosphere SO RADIO SCIENCE LA English DT Article ID RADIO OCCULTATION; JUPITERS IONOSPHERE; VOYAGER-2; PROFILES; SYSTEM; VENUS AB Vertical resolution is a fundamental aspect of any atmospheric remote sensing technique. Occultations using the Global Positioning System (GPS) signals provide inherently high vertical resolution. The phase coherence of the GPS signals allows improvement beyond the resolution limit set by Fresnel diffraction and the viewing geometry. We have characterized this improvement by simulating the forward propagation of GPS signals through the atmosphere to the GPS receiver. The signals are then back-propagated to a position closer to the atmosphere, thereby reducing the effects of diffraction. Comparison between the direct and the back-propagated results indicates that the resolution is improved by a factor of several, down to similar to 100 m. C1 Danish Meteorol Inst, Atmosphere Ionosphere Res Div, DK-2100 Copenhagen 0, Denmark. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mortensen, MD (reprint author), Danish Meteorol Inst, Atmosphere Ionosphere Res Div, Lyngbyvej 100, DK-2100 Copenhagen 0, Denmark. NR 26 TC 15 Z9 15 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD NOV-DEC PY 1999 VL 34 IS 6 BP 1475 EP 1484 DI 10.1029/1999RS900093 PG 10 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 258EC UT WOS:000083824300011 ER PT J AU Reinisch, BW Sales, GS Haines, DM Fung, SF Taylor, WWL AF Reinisch, BW Sales, GS Haines, DM Fung, SF Taylor, WWL TI Radio wave active Doppler imaging of space plasma structures: Arrival angle, wave polarization, and Faraday rotation measurements with the radio plasma imager SO RADIO SCIENCE LA English DT Article AB Radio sounding in the magnetosphere by the radio plasma imager on the IMAGE spacecraft will determine the dimensions and shape of the cavity between the magnetopause and the plasmapause. Omnidirectional transmission of pulsed radio signals results in echoes arriving from many directions. Quadrature sampling and Doppler analysis of the signals received on three orthogonal antennas will make it possible to determine the angles of arrival of the echoes, their polarization ellipses, and the Faraday rotation. Decomposition of the echo signals into the two characteristic waves is used to identify the O- and X-wave components. C1 Univ Lowell, Ctr Atmospher Res, Lowell, MA 01854 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Raytheon Informat & Sci Serv, Greenbelt, MD 20771 USA. RP Reinisch, BW (reprint author), Univ Lowell, Ctr Atmospher Res, 600 Suffolk St, Lowell, MA 01854 USA. RI Fung, Shing/F-5647-2012 NR 22 TC 13 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD NOV-DEC PY 1999 VL 34 IS 6 BP 1513 EP 1524 DI 10.1029/1999RS900075 PG 12 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 258EC UT WOS:000083824300015 ER PT J AU Ganapol, BD Johnson, LF Hlavka, CA Peterson, DL Bond, B AF Ganapol, BD Johnson, LF Hlavka, CA Peterson, DL Bond, B TI LCM2: A coupled leaf/canopy radiative transfer model SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID REFLECTANCE SPECTRA; FN METHOD; LEAF; SCATTERING; CANOPIES; PROSPECT; NITROGEN AB Two radiative transfer models have been coupled to generate vegetation canopy reflectance as a function of leaf chemistry, leaf morphology (as represented by leaf scattering properties), leaf thickness, soil reflectance, and canopy architecture. A model of radiative transfer within a leaf, called LEAFMOD, treats the radiative transfer equation for a slab of optically uniform leaf material, providing an estimate of leaf hemispherical reflectance and transmittance as well as the radiance exiting the leaf surfaces. The canopy model then simulates radiative transfer within a mixture of leaves, with each having uniform optical properties as determined by LEAFMOD, assuming a bi-Lambertian leaf scattering phase function. The utility of the model, called LCM2 (Leaf/Canopy Model version 2), is demonstrated through predictions of radiometric measurements of canopy reflectance and sensitivity to leaf chlorophyll and moisture content. (C)Elsevier Science Inc., 1999. C1 Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. Calif State Univ Monterey Bay, Inst Earth Syst Sci & Policy, Seaside, CA USA. NASA, Ecosyst Sci & Technol Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. Oregon State Univ, Dept Forest Sci, Corvallis, OR 97331 USA. RP Ganapol, BD (reprint author), Univ Arizona, Dept Aerosp & Mech Engn, Aero Bldg 16, Tucson, AZ 85721 USA. NR 23 TC 30 Z9 32 U1 1 U2 6 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD NOV PY 1999 VL 70 IS 2 BP 153 EP 166 DI 10.1016/S0034-4257(99)00030-9 PG 14 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 256MY UT WOS:000083730200003 ER PT J AU Abuelgasim, AA Ross, WD Gopal, S Woodcock, CE AF Abuelgasim, AA Ross, WD Gopal, S Woodcock, CE TI Change detection using adaptive fuzzy neural networks: Environmental damage assessment after the Gulf War SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID MAXIMUM-LIKELIHOOD CLASSIFICATION; RESOLUTION SATELLITE DATA; REMOTELY-SENSED DATA; MIXED PIXELS; LANDSAT TM; FEATURES; MAPS AB This article introduces an adaptive fuzzy neural network classifier for environmental change detection and classification applied to monitor landcover changes resulting from the Gulf War. In this study, landcover change is treated as a qualitative shift between landcover categories. The Change Detection Adaptive Fuzzy (CDAF) network learns fuzzy membership functions for each landcover class present at the first image date based on a sample of the image data. An image from a later date is then classified using this network to recognize change among familiar classes as well as change to unfamiliar landcover classes. The CDAF network predicts landcover change with 86% accuracy representing an improvement over both a standard multidate K-means technique which performed at 70% accuracy and a hybrid approach using a maximum likelihood classifier (MLC)/K-means which achieved 65% accuracy. In this study, we developed a hybrid classified based on conventional statistical methods (MLC/K-means classifier) for comparison purposes to help evaluate the performance of the CDAF network. The CDAF compared with existing change detection methodology has two features that lead to significant performance improvements: 1) new landcover types created by a change event automatically lead to the establishment of new landcover categories through an unsupervised learning strategy, and 2) for each pixel the distribution of fuzzy membership values across possible categories are compared to determine whether a significant change has occurred. (C)Elsevier Science Inc., 1999. C1 Boston Univ, Dept Geog, Boston, MA 02215 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. MIT, Cambridge, MA 02139 USA. RP Gopal, S (reprint author), Boston Univ, Dept Geog, 675 Commonwealth Ave, Boston, MA 02215 USA. RI Lukes, Petr/B-1771-2010 NR 27 TC 42 Z9 44 U1 2 U2 4 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD NOV PY 1999 VL 70 IS 2 BP 208 EP 223 DI 10.1016/S0034-4257(99)00039-5 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 256MY UT WOS:000083730200007 ER PT J AU Allen, JE Nelson, RN Harris, BC AF Allen, JE Nelson, RN Harris, BC TI Apparatus for measuring thermodynamic properties at low temperatures SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID JUPITER AB An apparatus has been constructed to provide thermodynamic data for models of planetary atmospheres. Often these data are needed at low temperatures, especially for the outer planets and their satellites, but are not readily available in the literature. The vapor pressure of propane was measured from 85 to 240 K to demonstrate one application of the apparatus for the acquisition of these types of data and to assess the performance of the system. This molecule was chosen because it is available in high purity, it has a well-established vapor-pressure curve, and it exhibits only one phase change over this temperature range. Our results compare favorably with the values available in the literature. The major components of the system include several types of pressure measuring instruments (1000 and 1 Torr capacitance manometers, spinning-rotor gauge), a residual gas analyzer to monitor sample purity in situ, and a helium closed-cycle refrigerator for cooling. The gas-handling manifold was constructed using materials and techniques adapted from the semiconductor production industry to minimize sample impurities which constitute a significant source of error in these types of measurements. Several unique design features were also incorporated in the construction of the sample cell to facilitate proper correction for thermal transpiration-an important factor for pressure measurements at low temperatures-and to ensure that the temperature sensor accurately reflected the sample temperature. The operational temperature and pressure limits are 62-240 K and 3 x 10(-6)-10(3) Torr, respectively. The lowest achievable temperature is governed by the no-load temperature of the first stage of the refrigerator and vertical thermal gradients along the sample cell walls, while the minimum obtainable pressure is set by the base pressure of the manifold and a slight outgassing rate. (C) 1999 American Institute of Physics. [S0034-6748(99)01711-6]. C1 NASA, Astrochem Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Georgia So Univ, Dept Chem, Statesboro, GA 30460 USA. NASA, Machining Technol Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Allen, JE (reprint author), NASA, Astrochem Branch, Goddard Space Flight Ctr, Code 691, Greenbelt, MD 20771 USA. NR 9 TC 3 Z9 3 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD NOV PY 1999 VL 70 IS 11 BP 4283 EP 4294 DI 10.1063/1.1150093 PG 12 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 251NQ UT WOS:000083452100026 ER PT J AU Tsurutani, BT Ho, CM AF Tsurutani, BT Ho, CM TI A review of discontinuities and Alfven waves in interplanetary space: Ulysses results SO REVIEWS OF GEOPHYSICS LA English DT Review ID IMBEDDED ROTATIONAL DISCONTINUITIES; HIGH HELIOGRAPHIC LATITUDES; MIRROR-MODE STRUCTURES; SOLAR-WIND; MAGNETIC-FIELD; TANGENTIAL DISCONTINUITIES; INTERACTION REGIONS; SLOW SHOCK; PLASMA; HOLES AB The Ulysses mission is the first to explore our heliosphere at all latitudes up to +/- 80 degrees and therefore is an ideal mission to study potential gradients in heliolatitude land radial distance) of discontinuity occurrence rates and types. Directional discontinuities (DDs) are shown to be dependent on the type of solar wind streams that they are embedded in. The occurrence rate of DDs is 5-10 times higher in high-speed streams than in slow streams. The explanation is that nonlinear Alfven waves dominate the high-speed streams and rotational discontinuities are the phase-steepened edges of the Alfven waves. Dissipation at these phase-steepened Alfven waves have been sought but not found. An e(-(R-1)/5) decrease in discontinuity rate with increasing radial distance (R in units of AU) is partially an artifact of the selection criteria (discontinuity thickening), but dissipation at a relatively slow rate cannot be ruled out at this time. There is no obvious latitudinal gradients in discontinuity types or occurrence rates. Somewhat surprisingly, tangential discontinuities are detected at high latitudes. These have been associated with the edges of local small-scale magnetic decreases. A pair of slow shocks were detected at 5.3 AU. The speeds are similar to fast mode shock speeds. When Alfven waves in highspeed streams impinge upon the Earth's magnetosphere, near-continuous substorms (called HILDCAAs) occur, leading to the pumping of an extraordinary amount of energy into the nightside ionosphere. Current discontinuity and Alfven wave research problems are discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Tsurutani, BT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 54 TC 78 Z9 80 U1 2 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 8755-1209 J9 REV GEOPHYS JI Rev. Geophys. PD NOV PY 1999 VL 37 IS 4 BP 517 EP 541 DI 10.1029/1999RG900010 PG 25 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 252WN UT WOS:000083525400005 ER PT J AU Ramaty, R Higdon, JC Lingenfelter, RE Kozlovsky, B AF Ramaty, R Higdon, JC Lingenfelter, RE Kozlovsky, B TI Rain of fire - Cosmic rays, spewed in all directions by cataclysmic stellar explosions, encode rich information about the violent history of the Milky Way SO SCIENCES-NEW YORK LA English DT Article C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Claremont Coll, Claremont, CA 91711 USA. Univ Calif San Diego, La Jolla, CA 92093 USA. Tel Aviv Univ, IL-69978 Tel Aviv, Israel. RP Ramaty, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU NEW YORK ACAD SCIENCES PI NEW YORK PA 2 E 63RD ST, NEW YORK, NY 10021 USA SN 0036-861X J9 SCIENCES JI Sci.-New York PD NOV-DEC PY 1999 VL 39 IS 6 BP 24 EP 29 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 251RG UT WOS:000083458200012 ER PT J AU Smith, IS Cutts, JA AF Smith, IS Cutts, JA TI Floating in space SO SCIENTIFIC AMERICAN LA English DT Article C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Cambridge, Cambridge CB2 1TN, England. CALTECH, Pasadena, CA 91125 USA. RP Smith, IS (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 2 TC 2 Z9 2 U1 0 U2 0 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 USA SN 0036-8733 J9 SCI AM JI Sci.Am. PD NOV PY 1999 VL 281 IS 5 BP 98 EP 103 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 249PN UT WOS:000083341600027 ER PT J AU Addy, E Mili, A Yacoub, S AF Addy, E Mili, A Yacoub, S TI A case study in software reuse SO SOFTWARE QUALITY JOURNAL LA English DT Article DE software reuse; domain engineering; domain architecture; COCOMO; reuse metrics and waiting queues simulations ID SPECIFICATION; VERIFICATION AB We report on a term project to conduct domain engineering followed by application engineering for a specific set of applications. We discuss some of the observations we have made on this project, as well some of the lessons we have learned. C1 NASA IV & Facil, Fairmont, WV USA. W Virginia Univ, Dept CS & EE, Morgantown, WV 26506 USA. RP Addy, E (reprint author), NASA IV & Facil, 100 Univ Dr, Fairmont, WV USA. NR 19 TC 1 Z9 1 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0963-9314 J9 SOFTWARE QUAL J JI Softw. Qual. J. PD NOV PY 1999 VL 8 IS 3 BP 169 EP 196 DI 10.1023/A:1008963424886 PG 28 WC Computer Science, Software Engineering SC Computer Science GA 349PA UT WOS:000089053800001 ER PT J AU Harrison, W Raffo, D Settle, J Eickelmann, N AF Harrison, W Raffo, D Settle, J Eickelmann, N TI Technology review: Adapting financial measures: Making a business case for software process improvement SO SOFTWARE QUALITY JOURNAL LA English DT Review DE return on investment; business case for SPI; process improvement; ROI AB Software firms invest in process improvements in order to benefit from decreased costs and/or increased productivity sometime in the future. Such efforts are seldom cheap, and they typically require making a business case in order to obtain funding. We review some of the main techniques from financial theory for evaluating the risk and returns associated with proposed investments and apply them to process improvement programs for software development. We also discuss significant theoretical considerations as well as robustness and correctness issues associated with applying each of the techniques to software development and process improvement activities. Finally we introduce a present value technique that incorporates both risk and return that has many applications to software development activities and is recommended for use in a software process improvement context. C1 Portland State Univ, Dept Comp Sci, Portland, OR 97207 USA. Portland State Univ, Sch Business Adm, Portland, OR 97207 USA. NASA IV & V Facil, WVU Software Res Lab, Fairmont, WV 26554 USA. RP Harrison, W (reprint author), Portland State Univ, Dept Comp Sci, Portland, OR 97207 USA. NR 22 TC 4 Z9 4 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0963-9314 J9 SOFTWARE QUAL J JI Softw. Qual. J. PD NOV PY 1999 VL 8 IS 3 BP 211 EP 231 DI 10.1023/A:1008971726703 PG 21 WC Computer Science, Software Engineering SC Computer Science GA 349PA UT WOS:000089053800003 ER PT J AU Karasik, BS McGrath, WR LeDuc, HG Gershenson, ME AF Karasik, BS McGrath, WR LeDuc, HG Gershenson, ME TI A hot-electron direct detector for radioastronomy SO SUPERCONDUCTOR SCIENCE & TECHNOLOGY LA English DT Article; Proceedings Paper CT International Superconductive Electronics Conference CY JUN 21-25, 1999 CL BERKELEY, CALIFORNIA ID BOLOMETER AB A hot-electron transition-edge superconducting bolometer with adjustable thermal relaxation speed is proposed. The bolometer contacts are made from a superconductor with high critical temperature which blocks the thermal diffusion of hot carriers into the contacts. Thus electron-phonon interaction is the only mechanism for heat removal. The speed of thermal relaxation for hot electrons in a nanometre-size superconducting bolometer with T-c = 100-300 mK is controlled by the elastic electron mean free path l. The relaxation rate behaves as T(4)l at subkelvin temperatures and can be reduced by a factor of 10-100 by decreasing l. Then an antenna- or waveguide-coupled bolometer with a time constant similar to 10(-3)-10(-4) s will exhibit photon-noise-limited performance at millimetre and submillimetre wavelengths. The bolometer will have a figure of merit NEP tau(1/2) = 10(-23)-10(-22) J(-1) at 100 mK which is 10(3)-10(4) times better (i.e. smaller) than that of a state-of-the-art bolometer. A tremendous increase in speed and sensitivity will have a significant impact for observational mapping applications. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08854 USA. RP Karasik, BS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Karasik, Boris/C-5918-2011 NR 15 TC 28 Z9 28 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-2048 J9 SUPERCOND SCI TECH JI Supercond. Sci. Technol. PD NOV PY 1999 VL 12 IS 11 BP 745 EP 747 DI 10.1088/0953-2048/12/11/316 PG 3 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 260KH UT WOS:000083948400016 ER PT J AU Chen, TC Finkbeiner, FM Bier, A DiCamillo, B AF Chen, TC Finkbeiner, FM Bier, A DiCamillo, B TI Molybdenum-gold proximity bilayers as transition edge sensors for microcalorimeters and bolometers SO SUPERCONDUCTOR SCIENCE & TECHNOLOGY LA English DT Article; Proceedings Paper CT International Superconductive Electronics Conference CY JUN 21-25, 1999 CL BERKELEY, CALIFORNIA ID RAY AB Mo/Au proximity bilayers as transition edge sensors (TESs) are promising candidates for low-temperature thermometry. The transition temperature of the bilayers can be easily tuned between 50 and 600 mK, yielding sensors which can be used in a variety of calorimetric and bolometric applications. With phase transition widths of less than 1 mK, Mo/An TESs show very high temperature sensitivity (d(log R)/d(log T) similar to 2500). Also, Mo/Au TESs show improved thermal and chemical stability compared to most other bilayer configurations. Fabrication issues and detector performance of Mo/Au TESs on Si3N4 membranes are discussed. C1 Global Sci & Technol Inc, Greenbelt, MD 20770 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Chen, TC (reprint author), Global Sci & Technol Inc, Greenbelt, MD 20770 USA. NR 4 TC 4 Z9 4 U1 1 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-2048 J9 SUPERCOND SCI TECH JI Supercond. Sci. Technol. PD NOV PY 1999 VL 12 IS 11 BP 840 EP 842 DI 10.1088/0953-2048/12/11/344 PG 3 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 260KH UT WOS:000083948400044 ER PT J AU Harnack, O Karasik, B McGrath, W Kleinsasser, A Barner, J AF Harnack, O Karasik, B McGrath, W Kleinsasser, A Barner, J TI Submicron-long HTS hot-electron mixers SO SUPERCONDUCTOR SCIENCE & TECHNOLOGY LA English DT Article; Proceedings Paper CT International Superconductive Electronics Conference CY JUN 21-25, 1999 CL BERKELEY, CALIFORNIA ID PHOTORESPONSE; RADIATION; FILMS; NONEQUILIBRIUM AB We have measured the device length and temperature dependence of the intermediate frequency (IF) bandwidth and noise of hot-electron bolometer (HEB) mixers made from a high-T-c superconductor. Mixer devices with lengths (L) between 50 nm and 1 mu m were fabricated from 25-35 nm thick YBCO films on MgO and sapphire substrates. Bandwidth measurements were made using signal and local oscillator (LO) frequencies in the range 1-20 GHz. At low operation temperatures the IF bandwidths were about 100 MHz and several hundred MHz for devices on MgO and sapphire, respectively. At higher operation temperatures, where self-heating disappeared and flux-flow effects define the shape of the l-V characteristic, the measured IF bandwidth increased significantly. The temperature and IF dependence of absolute conversion efficiencies determined from noise measurements are in good agreement with the bandwidth data. At 2.7 GHz LO frequency the single-side-band mixer noise temperature of a 50 nm long HEB on MgO was about 8000 K. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Harnack, O (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RI Karasik, Boris/C-5918-2011 NR 8 TC 5 Z9 5 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-2048 J9 SUPERCOND SCI TECH JI Supercond. Sci. Technol. PD NOV PY 1999 VL 12 IS 11 BP 850 EP 852 DI 10.1088/0953-2048/12/11/347 PG 3 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 260KH UT WOS:000083948400047 ER PT J AU Wu, RLC Miyoshi, K Lanter, WC Wrbanek, JD DeJoseph, CA AF Wu, RLC Miyoshi, K Lanter, WC Wrbanek, JD DeJoseph, CA TI Growth and tribological properties of amorphous hydrogenated carbon nitride produced by ion-beam technique SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 26th International Conference on Metallurgical Coating and Thin Films CY APR 12-15, 1999 CL SAN DIEGO, CALIFORNIA SP Div Amer Vacuum Soc, Vacuum Metallurgy & Thin Films DE carbon nitride; ion-beam technique; tribology ID DIAMOND; COATINGS AB Hydrogenated carbon nitride (H-CNx) films have been deposited on a variety of substrates using a 20 cm diameter r.f.-excited (13.56 MHz) ion gun and a four-axis substrate scanner. Mixtures of methane and nitrogen were used to generate various hydrocarbon and nitrogen-containing ions. The effects of r.f. power (99-600 W), N-2/CH4 gas mixture (0.2-3), total pressure, and ion energy (200-1750 eV) on the film deposition rate, chemical composition, and tribological properties have been systematically investigated. A quadrupole mass spectrometer and a total ion current measuring device were utilized to monitor the ion compositions of the gas mixtures of N-2/CH4 during the deposition for quality control and process optimization. The predominate ion species in the gas mixture of N-2/CH4 is CH3+, and as more nitrogen was added into the iron source with CH4, the ionic species of N-2(+), N+, NH4+, NH3+, NH2+, HCN+, CN+, and N2H2+ were relatively increased. RES and proton recoil techniques were used to analyze the as-deposited films. Unidirectional sliding friction experiments in UHV, humid air, and dry nitrogen were conducted to measure the coefficient of friction and wear behavior of these films. The tribological properties of H-CNx films were compared with those of polycrystalline diamond (PCD) and diamond-like carbon (DLC) films studied previously. The correlation between the deposition parameters on the amorphous H-CNx film growth rate, nitrogen content, and tribological properties is discussed. (C) 1999 Elsevier Science S.A. All rights reserved. C1 K Syst Corp, Beavercreek, OH 45432 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. USAF, Res Lab, Wright Patterson AFB, OH 45433 USA. RP Wu, RLC (reprint author), K Syst Corp, 1522 Marsetta Dr, Beavercreek, OH 45432 USA. EM rlwu@aol.com NR 7 TC 4 Z9 4 U1 1 U2 3 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD NOV PY 1999 VL 120 BP 573 EP 578 DI 10.1016/S0257-8972(99)00447-8 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 262ED UT WOS:000084051900089 ER PT J AU Murakawa, M Komori, T Takeuchi, S Miyoshi, K AF Murakawa, M Komori, T Takeuchi, S Miyoshi, K TI Performance of a rotating gear pair coated with an amorphous carbon film under a loss-of-lubrication condition SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 26th International Conference on Metallurgical Coating and Thin Films CY APR 12-15, 1999 CL SAN DIEGO, CALIFORNIA SP Div Amer Vacuum Soc, Vacuum Metallurgy & Thin Films DE amorphous carbon film; gear box; loss of lubrication ID DIAMOND-LIKE CARBON AB The ability of gear boxes to complete their missions following loss of lubrication is an important parameter in design criteria for various machines. This paper shows the results of the actual gear performance test conducted using a gear testing machine that was subjected to a loss-of-lubrication condition immediately after a short operating period under fully lubricated conditions. The result showed that a gear pair subjected to an initial shot peening process and a subsequent PVD process to deposit an amorphous carbon film (WC/C film) could endure the conditions for a very long time before it failed or seized even under a very severe loading condition, thus demonstrating the utility of gears coated with an amorphous carbon film. (C) 1999 Elsevier Science S.A. All rights reserved. C1 Nippon Inst Technol, Dept Mech Engn, Miyashiro, Saitama 3458501, Japan. Kyouiku Gear Mfg Co Ltd, Dev Sect, Kasukab, Saitama 3440057, Japan. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Murakawa, M (reprint author), Nippon Inst Technol, Dept Mech Engn, 4-1 Gakuendai, Miyashiro, Saitama 3458501, Japan. EM mura@nit.ac.jp NR 6 TC 29 Z9 30 U1 1 U2 8 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD NOV PY 1999 VL 120 BP 646 EP 652 DI 10.1016/S0257-8972(99)00437-5 PG 7 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 262ED UT WOS:000084051900102 ER PT J AU Halicioglu, T Barnett, DM AF Halicioglu, T Barnett, DM TI Formation and migration energies of interstitials in silicon under strain conditions SO SURFACE SCIENCE LA English DT Article DE computer simulations; diffusion and migration; silicon; surface diffusion ID AB-INITIO; DIFFUSION; PRESSURE; SI; SURFACE AB Simulation calculations are conducted for Si substrates to analyze the formation and diffusion energies of interstitials under strain condition using statics methods based on a Stillinger-Weber-type potential function. Defects in the vicinity of the surface region and in the bulk are examined, and the role played by compressive and tensile strains on the energetics of interstitials is investigated. The results indicate that strain alters defect energetics, which, in turn, modifies their diffusion characteristics. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA. RP Halicioglu, T (reprint author), NASA, Ames Res Ctr, Thermosci Inst, M-S 230-3, Moffett Field, CA 94035 USA. NR 11 TC 4 Z9 4 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD NOV 1 PY 1999 VL 441 IS 2-3 BP 265 EP 269 DI 10.1016/S0039-6028(99)00721-9 PG 5 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 253RW UT WOS:000083570400008 ER PT J AU Miyoshi, K AF Miyoshi, K TI Considerations in vacuum tribology (adhesion, friction, wear, and solid lubrication in vacuum) SO TRIBOLOGY INTERNATIONAL LA English DT Editorial Material DE adhesion; solid lubrication; vacuum tribology ID SURFACE ENERGIES; METALS; DIAMOND; FILMS AB The success of many tribological products used or tribological systems operated in vacuum depends on adequate control of adhesion between two or more materials. Adhesion (e.g., in adhesive bonding) is the mechanical force or strength required to separate the surfaces in contact. This foreword is concerned with adhesion, which has greatly contributed, and should continue to contribute, to tribological problems, such as high friction, solid-state welding, scuffing or scoring, high wear, and a short lubricant life, in vacuum. Published by Elsevier Science Ltd. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Miyoshi, K (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 16 TC 34 Z9 38 U1 1 U2 19 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0301-679X J9 TRIBOL INT JI Tribol. Int. PD NOV PY 1999 VL 32 IS 11 BP 605 EP 616 DI 10.1016/S0301-679X(99)00093-6 PG 12 WC Engineering, Mechanical SC Engineering GA 304JG UT WOS:000086479600001 ER PT J AU Miyoshi, K AF Miyoshi, K TI Aerospace mechanisms and tribology technology - Case study SO TRIBOLOGY INTERNATIONAL LA English DT Article DE aerospace mechanisms; space-vacuum technology; solid lubrication AB This paper focuses attention on tribology technology practice related to vacuum tribology. A case study describes an aspect of a real problem in sufficient detail for the engineer and scientist to understand the tribological situation and the failure. The nature of the problem is analyzed and the tribological properties are examined. (C) 2000 Elsevier Science Ltd. All rights reserved. C1 NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. RP Miyoshi, K (reprint author), NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. NR 6 TC 18 Z9 19 U1 1 U2 6 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0301-679X J9 TRIBOL INT JI Tribol. Int. PD NOV PY 1999 VL 32 IS 11 BP 673 EP 685 DI 10.1016/S0301-679X(99)00092-4 PG 13 WC Engineering, Mechanical SC Engineering GA 304JG UT WOS:000086479600007 ER PT J AU Herbst, LH Jacobson, ER Klein, PA Balazs, GH Moretti, R Brown, T Sundberg, JP AF Herbst, LH Jacobson, ER Klein, PA Balazs, GH Moretti, R Brown, T Sundberg, JP TI Comparative pathology and pathogenesis of spontaneous and experimentally induced fibropapillomas of green turtles (Chelonia mydas) SO VETERINARY PATHOLOGY LA English DT Article DE Chelonia mydas; dermatitis; fibropapilloma; green turtles; herpesvirus; immunohistochemistry; tumor ID HUMAN-IMMUNODEFICIENCY-VIRUS; HERPES-SIMPLEX VIRUSES; CUTANEOUS FIBROPAPILLOMAS; HAWAIIAN-ISLANDS; GENE-EXPRESSION; RUN MECHANISM; SKIN-LESIONS; SEA TURTLES; INFECTION; SPIRORCHIDAE AB Tumor biopsy samples from 25 Floridian and 15 Hawaiian green turtles (Chelonia mydas) with spontaneous green turtle fibropapillomatosis (GTFP) and from 27 captive-reared,green turtles with experimentally induced GTFP were examined microscopically to differentiate the histologic features that result from GTFP pathogenesis and those that result from incidental factors that may vary according to geographic region. Common histologic features for spontaneous and experimentally induced tumors included fibroblast proliferation in the superficial dermis, epidermal acanthosis and hyperkeratosis, epidermal basal cell degeneration with dermal-epidermal cleft formation, spinous layer degeneration with intraepidermal vesicle and pustule formation, and ulceration. Visceral tumors, found in eight of 10 (80%) free-ranging turtles with cutaneous disease that were examined after death, had extensive interstitial fibrous proliferation. The presence of spirorchid trematode eggs and associated foreign body granulomas, common secondary findings within spontaneous tumors, varied by geographic location, and these findings were not observed in experimentally induced tumors. Eosinophilic intranuclear inclusions and intranuclear herpesvirus-associated antigen immunoreactivity were found in 18 of 38 (47%) experimentally induced cutaneous tumors and nine of 119 (7.5%) spontaneous tumors from Floridian but not Hawaiian turtles. The possible involvement of GTFP-associated herpesvirus in the pathogenesis of epidermal degenerative changes and GTFP pathogenesis is discussed. C1 Albert Einstein Coll Med, Inst Anim Studies, Dept Pathol, Bronx, NY 10461 USA. Univ Florida, Dept Small Anim Clin Sci, Gainesville, FL USA. Univ Florida, Dept Pathol & Lab Med, Gainesville, FL USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. Turtle Hosp, Marathon, FL USA. Jackson Lab, Bar Harbor, ME 04609 USA. RP Herbst, LH (reprint author), Albert Einstein Coll Med, Inst Anim Studies, Dept Pathol, Room 1005 Ullman,1300 Morris Pk Ave, Bronx, NY 10461 USA. FU NCRR NIH HHS [RR07001] NR 66 TC 42 Z9 43 U1 0 U2 8 PU AMER COLL VET PATHOLOGIST PI LAWRENCE PA 810 EAST 10TH STREET, LAWRENCE, KS 66044 USA SN 0300-9858 J9 VET PATHOL JI Vet. Pathol. PD NOV PY 1999 VL 36 IS 6 BP 551 EP 564 DI 10.1354/vp.36-6-551 PG 14 WC Pathology; Veterinary Sciences SC Pathology; Veterinary Sciences GA 283NH UT WOS:000085281300004 PM 10568436 ER PT J AU Ichoku, C Andreae, MO Andreae, TW Meixner, FX Schebeske, G Formenti, P Maenhaut, W Cafmeyer, J Ptasinski, J Karnieli, A Orlovsky, L AF Ichoku, C Andreae, MO Andreae, TW Meixner, FX Schebeske, G Formenti, P Maenhaut, W Cafmeyer, J Ptasinski, J Karnieli, A Orlovsky, L TI Interrelationships between aerosol characteristics and light scattering during late winter in an Eastern Mediterranean arid environment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID METEOSAT ISCCP-B2 DATA; LONG-RANGE TRANSPORT; SAHARAN DUST LOAD; OPTICAL-PROPERTIES; GREENHOUSE GASES; PARTICLE-SIZE; SOOT CARBON; ABSORPTION; APPORTIONMENT; NEPHELOMETER AB An intensive field campaign involving measurement of various aerosol physical, chemical, and radiative properties was conducted at Sde Boker (also written as Sede Boqer) in the Negev Desert of Israel, from is February to 15 March 1997, Nephelometer measurements gave average background scattering coefficient values of about 25 Mm(-1) at 550 nm wavelength, but strong dust events caused the value of this parameter to rise up to about 800 Mm(-1). Backscattering fractions did not depend on aerosol loading and generally fell in the range of 0.1 to 0,25, comparable to values reported for marine and Arctic environments. Chemical analysis of the aerosol revealed that in the coarse size range (2-10 mu m equivalent aerodynamic diameter (EAD)), calcium (Ca) was by far the most abundant element followed by silicon (Si), both of which are indicators for mineral dust. In the fine size fraction (<2 mu m EAD), sulfur (S) generally was the dominant element, except during high dust episodes when Ca and Si were again the most abundant. Furthermore, fine black carbon (BC) correlates with S, suggesting that they may have originated from the same sources or source regions, An indication of the shortterm effect of aerosol loading on radiative forcing was provided by measurements of global and diffuse solar radiation, which showed that during high-turbidity periods (strong dust events), almost all of the solar radiation reaching the area is scattered or absorbed. C1 Max Planck Inst Chem, Biogeochem Dept, D-55020 Mainz, Germany. Univ Ghent, Inst Nucl Sci, B-9000 Ghent, Belgium. Ben Gurion Univ Negev, Jacob Blaustein Inst Desert Res, Microalgal Biotechnol Lab, IL-84990 Sede Boqer, Israel. RP Ichoku, C (reprint author), NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Climate & Radiat Branch, Code 913, Greenbelt, MD 20771 USA. EM ichoku@climate.gsfc.nasa.gov; moa@mpch-mainz.mpg.de; maenhaut@inwchem.rug.ac.be; karnieli@bgumail.bg.ac.il RI Ichoku, Charles/E-1857-2012; Maenhaut, Willy/M-3091-2013; Andreae, Meinrat/B-1068-2008 OI Ichoku, Charles/0000-0003-3244-4549; Maenhaut, Willy/0000-0002-4715-4627; Andreae, Meinrat/0000-0003-1968-7925 NR 47 TC 34 Z9 34 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 27 PY 1999 VL 104 IS D20 BP 24371 EP 24393 DI 10.1029/1999JD900781 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 249KN UT WOS:000083332400011 ER PT J AU Zuffada, C Hajj, GA Kursinski, ER AF Zuffada, C Hajj, GA Kursinski, ER TI A novel approach to atmospheric profiling with a mountain-based or airborne GPS receiver SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GLOBAL-POSITIONING-SYSTEM; RADIO OCCULTATION; EARTHS ATMOSPHERE; ADJOINT MODEL; ASSIMILATION; RETRIEVAL AB The delay induced by the Earth's atmosphere on the Global Positioning System (GPS) signal has been exploited in the last decade for atmospheric remote sensing. Ground-based GPS measurements are traditionally used to derive columnar water vapor content, while space-based GPS measurements, obtained by a receiver in a low-Earth orbit tracking GPS satellites occulting behind the Earth's atmosphere, yield accurate, high-resolution profiles of refractivity, temperature, and water vapor. A GPS receiver on a mountain top or an airplane with a "downward looking" field of view toward the Earth's limb is a novel concept presented here. We describe a generalized ray-tracing inversion scheme where spherical symmetry is assumed for the atmosphere, and the refractivity is modeled as piecewise exponential, with scale height changing from one atmospheric layer to the next. Additional refractivity data, derived from a model, might be introduced above the receiver as an a priori constraint, and are treated as properly weighted additional measurements. The exponential scale heights and a normalizing value of refractivity are retrieved by minimizing, in a least squares sense, the residuals between measured bending angles and refractivity and those calculated on the basis of the exponential model and ray-tracing. As a first validation step, we illustrate results comparing refractivity and temperature profiles obtained by this generalized ray-tracing scheme against those derived via the Abel inversion for the GPS/MET experiment. Additionally, we present results for a hypothetical situation where the receiver is located within the atmosphere at a height of 5 km. For the last case we investigate the accuracy of the retrieval both below and above the receiver at a set of locations in the atmosphere ranging from middle to tropical latitudes. The main objective is that of establishing whether the bending measurements have sufficient strength to allow for retrieval of refractivity below and possibly above the receiver location. Our findings suggest that accurate profiles of refractivity at heights ranging from the Earth's surface to slighly above the receiver location can be derived by GPS data collected from within the atmosphere. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zuffada, C (reprint author), CALTECH, Jet Prop Lab, MS 238-600,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM cinzia@cobra.jpl.nasa.gov NR 23 TC 39 Z9 46 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 27 PY 1999 VL 104 IS D20 BP 24435 EP 24447 DI 10.1029/1999JD900766 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 249KN UT WOS:000083332400015 ER PT J AU Frey, RA Baum, BA Menzel, WP Ackerman, SA Moeller, CC Spinhirne, JD AF Frey, RA Baum, BA Menzel, WP Ackerman, SA Moeller, CC Spinhirne, JD TI A comparison of cloud top heights computed from airborne lidar and MAS radiance data using CO2 slicing SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RADIATION BUDGET; CIRRUS CLOUDS; CLIMATE; SENSITIVITY; PARAMETERS; SOUNDER; VAS AB Data from two instruments onboard the National Aeronautics and Space Administration (NASA) ER-2 high-altitude aircraft have been utilized in the largest validation study to date in assessing the accuracy of the CO2-slicing cloud height algorithm. Infrared measurements of upwelling radiance from the MODIS (Moderate-Resolution Imaging Spectroradiometer) airborne simulator (MAS) were used to generate cloud top heights and then compared to those derived from the Cloud Lidar System (CLS), operating with dual polarization at 0.532 mu m. The comparisons were performed for 10 flight days during the Subsonic Aircraft Contrail and Cloud Effects Special Study (SUCCESS) field experiment during April and May 1996 which included various singlelayer and multilayer cloud conditions. Overall, the CO2-slicing method retrieved cloud heights to within +/-500 m and to within +/-1500 m of the lidar heights in 32 and 64% of the cases, respectively, From a simulation of cloud height errors as a function of various error sources in the CO2-slicing algorithm: it was concluded that the problem of multilayer clouds is secondary to that of proper specification of clear-sky radiances. C1 Univ Wisconsin, Ctr Space Sci & Engn, Madison, WI 53706 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. NOAA, NESDIS, Satellite Applicat Lab, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Frey, RA (reprint author), Univ Wisconsin, Ctr Space Sci & Engn, 1225 W Dayton St,Room 219, Madison, WI 53706 USA. EM richard.frey@ssec.wisc.edu RI Menzel, W. Paul/B-8306-2011; Ackerman, Steven/G-1640-2011; Baum, Bryan/B-7670-2011 OI Menzel, W. Paul/0000-0001-5690-1201; Ackerman, Steven/0000-0002-4476-0269; Baum, Bryan/0000-0002-7193-2767 NR 25 TC 45 Z9 47 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 27 PY 1999 VL 104 IS D20 BP 24547 EP 24555 DI 10.1029/1999JD900796 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 249KN UT WOS:000083332400023 ER PT J AU Nikzad, S Croley, D Elliott, ST Cunningham, TJ Proniewicz, WK Murphy, GB Jones, TJ AF Nikzad, S Croley, D Elliott, ST Cunningham, TJ Proniewicz, WK Murphy, GB Jones, TJ TI Single-event keV proton detection using a delta-doped charge-coupled device SO APPLIED PHYSICS LETTERS LA English DT Article ID QUANTUM EFFICIENCY; ULTRAVIOLET; ELECTRONS; WINDOWS AB Using a delta-doped charge-coupled device (CCD), we have demonstrated an order-of-magnitude improvement in the low-energy cutoff for particle detection compared to conventional solid-state detectors. Individual protons with energies in the 1.2-12 keV range were successfully detected using a delta-doped, back-illuminated CCD. Moreover, it is shown that, by measuring the charge generated by the proton, it is potentially possible to use delta-doped CCDs to determine the energy of the incoming particle. (C) 1999 American Institute of Physics. [S0003-6951(99)03943-1]. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Nikzad, S (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. NR 16 TC 6 Z9 6 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD OCT 25 PY 1999 VL 75 IS 17 BP 2686 EP 2688 DI 10.1063/1.125118 PG 3 WC Physics, Applied SC Physics GA 246VQ UT WOS:000083185900056 ER PT J AU Watmuff, JH AF Watmuff, JH TI Evolution of a wave packet into vortex loops in a laminar separation bubble SO JOURNAL OF FLUID MECHANICS LA English DT Article ID BOUNDARY-LAYER; 2-DIMENSIONAL SEPARATION; TURBULENT; INSTABILITIES; ENTRAINMENT AB A laminar boundary layer develops in a favourable pressure gradient where the velocity profiles asymptote to the Falkner & Skan similarity solution. Flying-hot-wire measurements show that the layer separates just downstream of a subsequent region of adverse pressure gradient, leading to the formation of a thin separation bubble. In an effort to gain insight into the nature of the instability mechanisms, a small-magnitude impulsive disturbance is introduced through a hole in the test surface at the pressure minimum. The facility and all operating procedures are totally automated and phase-averaged data are acquired on unprecedently large and spatially dense measurement grids. The evolution of the disturbance is tracked all the way into the reattachment region and beyond into the fully turbulent boundary layer. The spatial resolution of the data provides a level of detail that is usually associated with computations. Initially, a wave packet develops which maintains the same bounded shape and form, while the amplitude decays exponentially with streamwise distance. Following separation, the rate of decay diminishes and a point of minimum amplitude is reached, where the wave packet begins to exhibit dispersive characteristics. The amplitude then grows exponentially and there is an increase in the number of waves within the packet. The region leading up to and including the reattachment has been measured with a cross-wire probe and contours of spanwise vorticity in the centreline plane clearly show that the wave packet is associated with the cat's eye pattern that is a characteristic of Kelvin-Helmholtz instability. Further streamwise development leads to the formation of roll-ups and contour surfaces of vorticity magnitude show that they are three-dimensional. Beyond this point, the behaviour is nonlinear and the roll-ups evolve into a group of large-scale vortex loops in the vicinity of the reattachment. Closely spaced cross-wire measurements are continued in the downstream turbulent boundary layer and Taylor's hypothesis is applied to data on spanwise planes to generate three-dimensional velocity fields. The derived vorticity magnitude distribution demonstrates that the second vortex loop, which emerges in the reattachment region, retains its identity in the turbulent boundary layer and it persists until the end of the test section. C1 NASA, Ames Res Ctr, MCAT Inc, Moffett Field, CA 94035 USA. RP Watmuff, JH (reprint author), NASA, Ames Res Ctr, MCAT Inc, Moffett Field, CA 94035 USA. NR 36 TC 122 Z9 124 U1 0 U2 5 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD OCT 25 PY 1999 VL 397 BP 119 EP 169 DI 10.1017/S0022112099006138 PG 51 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 250FT UT WOS:000083378900006 ER PT J AU Pappalardo, RT Belton, MJS Breneman, HH Carr, MH Chapman, CR Collins, GC Denk, T Fagents, S Geissler, PE Giese, B Greeley, R Greenberg, R Head, JW Helfenstein, P Hoppa, G Kadel, SD Klaasen, KP Klemaszewski, JE Magee, K McEwen, AS Moore, JM Moore, WB Neukum, G Phillips, CB Prockter, LM Schubert, G Senske, DA Sullivan, RJ Tufts, BR Turtle, EP Wagner, R Williams, KK AF Pappalardo, RT Belton, MJS Breneman, HH Carr, MH Chapman, CR Collins, GC Denk, T Fagents, S Geissler, PE Giese, B Greeley, R Greenberg, R Head, JW Helfenstein, P Hoppa, G Kadel, SD Klaasen, KP Klemaszewski, JE Magee, K McEwen, AS Moore, JM Moore, WB Neukum, G Phillips, CB Prockter, LM Schubert, G Senske, DA Sullivan, RJ Tufts, BR Turtle, EP Wagner, R Williams, KK TI Does Europa have a subsurface ocean? Evaluation of the geological evidence SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID DIFFERENTIATED INTERNAL STRUCTURE; CONAMARA CHAOS REGION; OUTER SOLAR-SYSTEM; GALILEAN SATELLITES; ICE SHELL; NONSYNCHRONOUS ROTATION; HYDROTHERMAL VENTS; LAPLACE RESONANCE; WATER VOLCANISM; TIDAL STRESSES AB It has been proposed that Jupiter's satellite Europa currently possesses a global subsurface ocean of liquid water. Galileo gravity data verify that the satellite is differentiated into an outer H(2)O layer about 100 km thick but cannot determine the current physical state of this layer (liquid or solid). Here we summarize the geological evidence regarding an extant subsurface ocean, concentrating on Galileo imaging data. We describe and assess nine pertinent lines of geological evidence: impact morphologies, lenticulae, cryovolcanic features, pull-apart bands, chaos, ridges, surface frosts, topography, and global tectonics. An internal ocean would be a simple and comprehensive explanation for a broad range of observations; however, we cannot rule out the possibility that all of the surface morphologies could be due to processes in warm, soft ice with only localized or partial melting. Two different models of impact flux imply very different surface ages for Europa; the model favored here indicates an average age of similar to 50 Myr. Searches for evidence of current geological activity on Europa, such as plumes or surface changes, have yielded negative results to date. The current existence of a global subsurface ocean, while attractive in explaining the observations, remains inconclusive. Future geophysical measurements are essential to determine conclusively whether or not there is a liquid water ocean within Europa today. C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. US Geol Survey, Menlo Pk, CA 94025 USA. SW Res Inst, Boulder, CO USA. DLR, Inst Planetenerkundung, Berlin, Germany. Univ Arizona, Lunar & Planetary Lab, Tempe, AZ USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Sterling Software, Pasadena, CA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA. RP Pappalardo, RT (reprint author), Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. EM pappalardo@brown.edu RI Turtle, Elizabeth/K-8673-2012; Fagents, Sarah/B-3983-2014 OI Turtle, Elizabeth/0000-0003-1423-5751; NR 202 TC 207 Z9 210 U1 4 U2 40 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1999 VL 104 IS E10 BP 24015 EP 24055 DI 10.1029/1998JE000628 PG 41 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 248AL UT WOS:000083253100001 ER PT J AU Haldemann, AFC Muhleman, DO AF Haldemann, AFC Muhleman, DO TI Circular-polarization radar properties of high-altitude ice: Western Kunlun Shan and central Andes SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID COHERENT-BACKSCATTER; SURFACE-PROPERTIES; POLAR ANOMALIES; SHEET; MERCURY; IMAGES; SATELLITES; CALIBRATION; STABILITY; GANYMEDE AB Full polarization synthetic aperture radar images of high-altitude glaciers and ice fields in the Western Kunlun Shan of Tibet and the central Andes near Santiago, Chile, made with the shuttle imaging radar, display regions with circular-polarization ratios, mu(c), in excess of unity. The mountainous topography at both locales allows reconstruction of the angular scattering behavior. The behavior is very similar to that displayed by Greenland's percolation zone. Glaciologic evidence from the Tibetan site confirms ice pipes and lenses embedded in the firn, which have been identified as the scatterers producing mu(c)>1 in Greenland. This demonstrates that the cold snow percolation facies radar signature exists outside of Greenland. The Greenland radar behavior had been suggested as an analogue for that of the icy Galilean satellites. We, like previous workers, find that the near-nadir backscatter is too specular to be considered analogous to that of the Jovian moons. We also present a crevasse region in Tibet that exhibits mu(c)>1 and a possible detection of the ice substrate of a rock-covered glacier in the Andes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Div Geol Sci, Pasadena, CA 91125 USA. RP Haldemann, AFC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 65 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1999 VL 104 IS E10 BP 24075 EP 24094 DI 10.1029/1999JE900023 PG 20 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 248AL UT WOS:000083253100003 ER PT J AU Poulet, F Karoschka, E Sicardy, B AF Poulet, F Karoschka, E Sicardy, B TI Spectrophotometry of Saturn's small satellites and rings from Hubble Space Telescope images SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID F-RING; VOYAGER OBSERVATIONS; PARTICLE PROPERTIES; PLANE CROSSINGS; PHOTOMETRY; SPECTRA; PROMETHEUS; ASTEROIDS; DYNAMICS; MIRANDA AB We investigate the photometric properties of four of Saturn's inner satellites (Prometheus, Pandora, Janus, and Epimetheus) and five ring regions (the A, B, and C rings; the Cassini division; and the F ring). We have used Hubble Space Telescope images taken in July 1991 and during the Saturn's ring plane crossings by the Earth (August 1995) and the Sun (November 1995). The spectral range of this study is similar to 0.30-0.95 mu m. We confirm qualitatively but not quantitatively several interesting color properties of the main rings already derived by Estrada and Cuzzi [1996]. The derived albedos of Prometheus and Pandora are consistent with the lower limits based on Voyager images [Thomas et al., 1983], The albedos of the coorbital satellites Janus and Epimetheus are smaller than previously determined. The colors of Janus and Pandora are similar to those of the main rings, indicating the presence of ices altered by red contaminants. Epimetheus is more neutral, with spectral shape similar to that of the G ring. Our data for Prometheus are fragmentary in terms of wavelength coverage; otherwise, the satellite looks like the F ring, which is neutral or slightly blue. This unusual color could be explained if there is an inward migration of the F ring particles through Poynting-Robertson drag, which subsequently sandblast the surface of the satellite. We find a correlation of color with the distance from Saturn. This indicates that the inner satellites are spectrally closer to the main rings than to the major Saturnian satellites. The implications for the origin of the inner satellites are discussed. C1 Observ Paris, Dept Rech Spatiale, Meudon, France. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Poulet, F (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 41 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1999 VL 104 IS E10 BP 24095 EP 24110 DI 10.1029/1998JE000621 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 248AL UT WOS:000083253100004 ER PT J AU Sakimoto, SEH Frey, HV Garvin, JB Roark, JH AF Sakimoto, SEH Frey, HV Garvin, JB Roark, JH TI Topography, roughness, layering, and slope properties of the Medusae Fossae Formation from Mars Orbiter Laser Altimeter (MOLA) and Mars Orbiter Camera (MOC) data SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GLOBAL SURVEYOR; HEMISPHERE AB The enigmatic Medusae Fossae Formation (MFF) is one of the youngest surficial deposits on Mars. Previously proposed modes of origin include pyroclastic volcanism, eolian mantling, polar sedimentation, carbonate platform, and paleoshorelines. In order to assess mapped member boundaries and constrain likely origin processes we analyze five topographic transects from the Mars Orbiter Laser Altimeter (MOLA) collected during the aerobraking hiatus orbit period of the Mars Global Surveyor (MGS) mission together with several simultaneously acquired Mars Orbiter Camera (MOC) images to examine the regional and local variations in the relief, slopes, vertical roughness, and relative elevations of mapped MFF members. We find that the members are not particularly flat or level but have average thicknesses of many hundreds of meters and substantially more internal relief than previously thought. Locally, the MFF members are sometimes distinguishable by slope, elevation, and surface roughness characteristics, but no unique formation-wide characteristics are apparent in this analysis of the limited initial data. The relative elevations of the mapped members are not consistent with undeformed planar horizontal layers but may be consistent with layers draped over preexisting topography with subsequent partial removal. Analysis of the initial coincident MOC and MOLA hiatus data suggests the possible presence of local layers, as well as the mislocation of at least a few MFF member and formation boundaries. We conclude that carbonate and shoreline deposit origins are not as well supported in the initial MGS data as they were in the Viking data and that the MFF formation and member boundaries should be reexamined in conjunction with the incoming new MGS data. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD USA. RP Sakimoto, SEH (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NR 25 TC 24 Z9 24 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1999 VL 104 IS E10 BP 24141 EP 24154 DI 10.1029/1999JE001044 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 248AL UT WOS:000083253100007 ER PT J AU Thorn, RP Stief, LJ Buckley, TJ Johnson, RD Monks, PS Klemm, RB AF Thorn, RP Stief, LJ Buckley, TJ Johnson, RD Monks, PS Klemm, RB TI Photoionization efficiency spectrum and ionization energy of OBrO SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID BROMINE DIOXIDE; THERMOCHEMISTRY; STRATOSPHERE; SYSTEM; BR2O; HEAT AB The photoionization efficiency (PIE) spectrum of OBrO was measured over the wavelength range lambda = 86-126 nm using a discharge flow-photoionization mass spectrometer (DF-PIMS) apparatus coupled to a VUV synchrotron radiation source. Bromine dioxide was generated in a flow tube reactor by first forming BrO via the reaction O(P-3) + Br-2 and then allowing the BrO to react on the cold flow tube wall. The PIE spectrum of the BrO reactant was obtained and the photoionization threshold evaluated from the half-rise point of the step at threshold. This remeasurement yields IE(BrO) = 10.48 +/- 0.02 eV, which supersedes our previous result. The PIE spectrum of OBrO displayed steplike behavior near threshold. A value of 10.29 +/- 0.03 eV was obtained for the adiabatic ionization energy (IE) of OBrO from analysis of the photoionization threshold at lambda = 120.5 nn. An ab initio determination of the IE of OBrO using the CCSD(T)/6-311+G(3dF)//CCD/6-311+G(3df) level of theory gives a value of 10.26 +/- 0.06 eV, which is in excellent agreement with the experimental result. The results are compared with previous determinations of the IE for both halogen monoxides, XO, and halogen dioxides, OXO (X = Cl, Br, I). C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Natl Inst Stand & Technol, Phys & Chem Properties Div, Gaithersburg, MD 20899 USA. Univ Leicester, Dept Chem, Leicester LE1 7RH, Leics, England. Brookhaven Natl Lab, Upton, NY 11973 USA. RP Thorn, RP (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Monks, Paul/H-6468-2016 OI Monks, Paul/0000-0001-9984-4390 NR 33 TC 9 Z9 9 U1 1 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD OCT 21 PY 1999 VL 103 IS 42 BP 8384 EP 8388 DI 10.1021/jp991555n PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 251DT UT WOS:000083429900006 ER PT J AU Amendola, L Frieman, JA Waga, I AF Amendola, L Frieman, JA Waga, I TI Weak gravitational lensing by voids SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE cosmology : theory; gravitational lensing ID LUMINOSITY FUNCTION; MASS FLUCTUATIONS; POWER SPECTRUM; GALAXIES; UNIVERSE; STATISTICS; BUBBLES AB We consider the prospects for detecting weak gravitational lensing by underdensities (voids) in the large-scale matter distribution. We derive the basic expressions for magnification and distortion by spherical voids. Clustering of the background sources and cosmic variance are the main factors that limit in principle the detection of lensing by voids. We conclude that only voids with radii larger than similar to 100 h(-1) Mpc have lensing signal-to-noise ratio larger than unity. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Osservatorio Astron Roma, I-00136 Rome, Italy. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Fed Univ Rio De Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, Brazil. RP Amendola, L (reprint author), NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. RI Waga, Ioav/B-6288-2014 NR 27 TC 14 Z9 14 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD OCT 21 PY 1999 VL 309 IS 2 BP 465 EP 473 DI 10.1046/j.1365-8711.1999.02841.x PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251VK UT WOS:000083466900022 ER PT J AU Gierlinski, M Zdziarski, AA Poutanen, J Coppi, PS Ebisawa, K Johnson, WN AF Gierlinski, M Zdziarski, AA Poutanen, J Coppi, PS Ebisawa, K Johnson, WN TI Radiation mechanisms and geometry of Cygnus X-1 in the soft state SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; radiation mechanisms : non-thermal; stars : individual : Cygnus X-1; gamma-rays : observations; gamma-rays : theory; X-rays : stars ID ACTIVE GALACTIC NUCLEI; X-RAY-EMISSION; ACCRETION DISKS; BLACK-HOLE; HDE 226868; CROSS-SECTIONS; PAIR PLASMAS; MASS; ABSORPTION; SPECTRUM AB We present X-ray/gamma-ray spectra of Cyg X-1 observed during the transition from the hard to the soft state and in the soft state by ASCA, RXTE and CGRO/OSSE in 1996 May and June. The spectra consist of a dominant soft component below similar to 2keV and a power-law-like continuum extending to at least similar to 800 keV. We interpret them as emission from an optically thick, cold accretion disc and from an optically thin, non-thermal corona above the disc, A fraction f greater than or similar to 0.5 of total available power is dissipated in the corona, We model the soft component by multicolour blackbody disc emission taking into account the torque-free inner-boundary condition. If the disc extends down to the minimum stable orbit, the ASCA/RXTE data yield the most probable black hole mass of M-X approximate to 10 M-circle dot and an accretion rate, (M) over dot approximate to 0.5L(E)/c(2), locating Cyg X-l in the soft state in the upper part of the stable, gas-pressure-dominated, accretion-disc solution branch. The spectrum of the corona is well modelled by repeated Compton scattering of seed photons from the disc off electrons with a hybrid, thermal/non-thermal distribution. The electron distribution can be characterized by a Maxwellian with an equilibrium temperature of kT(e) similar to 30-50 keV, a Thomson optical depth of tau similar to 0.3 and a quasi-power-law tail, The compactness of the corona is 2 less than or similar to l(h) less than or similar to 7, and a presence of a significant population of electron-positron pairs is ruled out, We find strong signatures of Compton reflection from a cold and ionized medium, presumably an accretion disc, with an apparent reflector solid angle, Omega/2 pi similar to 0.5-0.7. The reflected continuum is accompanied by a broad iron K alpha line. C1 Jagiellonian Univ, Astron Observ, PL-30244 Krakow, Poland. N Copernicus Astron Ctr, PL-00716 Warsaw, Poland. Stockholm Observ, SE-13336 Saltsjobaden, Sweden. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Yale Univ, Dept Astron, New Haven, CT 06511 USA. RP Gierlinski, M (reprint author), Jagiellonian Univ, Astron Observ, Orla 171, PL-30244 Krakow, Poland. RI Johnson, Neil/G-3309-2014; Poutanen, Juri/H-6651-2016; OI Poutanen, Juri/0000-0002-0983-0049; Gierlinski, Marek/0000-0001-9149-3514 NR 87 TC 319 Z9 322 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD OCT 21 PY 1999 VL 309 IS 2 BP 496 EP 512 DI 10.1046/j.1365-8711.1999.02875.x PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 251VK UT WOS:000083466900025 ER PT J AU Stahle, CM Parker, BH Parsons, AM Barbier, LM Barthelmy, SD Gehrels, NA Palmer, DM Snodgrass, SJ Tueller, J AF Stahle, CM Parker, BH Parsons, AM Barbier, LM Barthelmy, SD Gehrels, NA Palmer, DM Snodgrass, SJ Tueller, J TI CdZnTe and CdTe detector arrays for hard X-ray and gamma-ray astronomy SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 7th International Conference on Solid State Detectors CY DEC 04-06, 1998 CL NARA, JAPAN SP Crest, Japan Sci & Technol Corp DE CdZnTe; CdTe; X-ray; gamma ray; astronomy detector array AB A variety of CdZnTe and CdTe detector arrays were fabricated at NASA/GSFC for use in hard X-ray and gamma-ray astronomy. Mosaic, pixel, and 3-D position-sensitive detector arrays were built to demonstrate the capabilities for high-resolution imaging and spectroscopy for 10 to 2 MeV. This paper will summarize the different arrays and their applications for instruments being developed at NASA/GSFC. Specific topics to be addressed include materials characterization, fabrication of detectors, ASIC readout electronics, and imaging and spectroscopy tests. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD 20771 USA. Raytheon STX, Greenbelt, MD 20771 USA. RP Stahle, CM (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Tueller, Jack/D-5334-2012; Barthelmy, Scott/D-2943-2012; Parsons, Ann/I-6604-2012 NR 15 TC 27 Z9 28 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD OCT 21 PY 1999 VL 436 IS 1-2 BP 138 EP 145 DI 10.1016/S0168-9002(99)00610-5 PG 8 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 241TD UT WOS:000082897900020 ER PT J AU White, NE Tananbaum, H AF White, NE Tananbaum, H TI The Constellation X-ray mission SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 7th International Conference on Solid State Detectors CY DEC 04-06, 1998 CL NARA, JAPAN SP Crest, Japan Sci & Technol Corp DE X-ray astronomy; X-ray spectroscopy AB The Constellation-X mission is a large collecting area X-ray facility, emphasizing observations at high spectral resolution (E/Delta E similar to 300-3000) while covering a broad energy band (0.25-40 keV). By increasing the telescope aperture and utilizing efficient spectrometers the mission will achieve a factor of 100 increased sensitivity over current high-resolution X-ray spectroscopy missions. The use of focussing optics across the 10-40 keV band will provide a similar factor of 100 increased sensitivity in this band. Key technologies under development for the mission include lightweight high throughput X-ray optics, multilayer coatings to enhance the hard X-ray performance of X-ray optics, microcalorimeter spectrometer arrays with 2 eV resolution, low-power and low-weight CCD arrays, lightweight gratings and hard X-ray detectors. When observations commence towards the end of the next decade, Constellation-X will address many pressing questions concerning the extremes of gravity and the evolution of the Universe. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP White, NE (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 8 TC 3 Z9 5 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD OCT 21 PY 1999 VL 436 IS 1-2 BP 201 EP 204 DI 10.1016/S0168-9002(99)00621-X PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 241TD UT WOS:000082897900031 ER PT J AU McCammon, D Almy, R Apodaca, E Deiker, S Galeazzi, M Han, SI Lesser, A Sanders, W Kelley, RL Moseley, SH Porter, FS Stahle, CK Szymkowiak, AE AF McCammon, D Almy, R Apodaca, E Deiker, S Galeazzi, M Han, SI Lesser, A Sanders, W Kelley, RL Moseley, SH Porter, FS Stahle, CK Szymkowiak, AE TI High-resolution calorimetry: limitations of doped semiconductor thermometers SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 7th International Conference on Solid State Detectors CY DEC 04-06, 1998 CL NARA, JAPAN SP Crest, Japan Sci & Technol Corp DE X-ray; detectors; calorimeters; bolometers; 1/f noise; X-ray spectroscopy AB Small thermal calorimeters operating at cryogenic temperatures have achieved an energy resolution for single X-ray photons that is a factor of 20 better than the theoretical limit for a silicon ionization detector. To determine the potential for further improvements and decide on likely routes for achieving them, we discuss detector design optimization, first for an ideal calorimeter, and then for the case where components exhibit non-ideal behavior. Two serious non-ideal properties of doped semiconductor thermometers are electron-phonon decoupling and excess noise. These have been characterized over a range of sensitivity and operating temperature, and their effects on design optimization and ultimate performance can be evaluated. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP McCammon, D (reprint author), Univ Wisconsin, Dept Phys, 1150 Univ Ave, Madison, WI 53706 USA. RI Porter, Frederick/D-3501-2012; Moseley, Harvey/D-5069-2012; Kelley, Richard/K-4474-2012 OI Porter, Frederick/0000-0002-6374-1119; NR 4 TC 10 Z9 10 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD OCT 21 PY 1999 VL 436 IS 1-2 BP 205 EP 211 DI 10.1016/S0168-9002(99)00622-1 PG 7 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 241TD UT WOS:000082897900032 ER PT J AU Mitsuda, K Kelley, R AF Mitsuda, K Kelley, R TI The XRS system - the first cryogenic X-ray detector in orbit SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 7th International Conference on Solid State Detectors CY DEC 04-06, 1998 CL NARA, JAPAN SP Crest, Japan Sci & Technol Corp DE X-ray micro calorimeters; cryogenics; ASTRO-E ID SPECTROMETER XRS; MISSION; INSTRUMENT AB The X-ray Spectrometer, XRS on board the ASTRO-E Satellite is a cryogenic X-ray detector system utilizing a micro calorimeter array of 32 pixels operating at 60 mK. An energy resolution of about 12 eV (FWHM) has been obtained across the array in the ground calibration measurements. We adopted a unique three-stage cryogenic system consisting of solid neon, liquid helium, and an adiabatic de-magnetization refrigerator to obtain a long cryogenic lifetime in orbit, The design of the neon tank was optimized to obtain about 2 yr of the neon lifetime, which determines the lifetime of the whole cryogenic system. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298150, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mitsuda, K (reprint author), Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298150, Japan. RI Mitsuda, Kazuhisa/C-2649-2008; Kelley, Richard/K-4474-2012 NR 9 TC 14 Z9 14 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD OCT 21 PY 1999 VL 436 IS 1-2 BP 212 EP 217 DI 10.1016/S0168-9002(99)00623-3 PG 6 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 241TD UT WOS:000082897900033 ER PT J AU Stahle, CK Brekosky, RP Dutta, SB Gendreau, KC Kelley, RL McCammon, D McClanahan, RA Moseley, SH Mott, DB Porter, FS Szymkowiak, AE AF Stahle, CK Brekosky, RP Dutta, SB Gendreau, KC Kelley, RL McCammon, D McClanahan, RA Moseley, SH Mott, DB Porter, FS Szymkowiak, AE TI The physics and the optimization of the XRS calorimeters an Astro-E SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 7th International Conference on Solid State Detectors CY DEC 04-06, 1998 CL NARA, JAPAN SP Crest, Japan Sci & Technol Corp DE XRS; Astro-E; microcalorimeter; X-ray spectroscopy ID X-RAYS; THERMALIZATION; TRANSITION; SILICON; TIN AB The X-Ray Spectrometer (XRS) instrument, scheduled to be launched as part of the Japanese X-ray astronomy satellite Astro-E in February 2000, has an array of 32 microcalorimeters at the focal plane. These calorimeters consist of ion-implanted silicon thermistors and HgTe thermalizing X-ray absorbers. These devices provide spectral resolution of 9 eV at 3 keV and 11 eV at 6 keV. The process of determining the detector parameters for this instrument will be discussed. This will include discussion of the array layout, thermal conductance of the link to the heat sink, operating temperature, thermistor size, absorber choice, and means of attaching the absorber to the thermistor bearing element. We: consider the XRS calorimeters to be operating in a local optimum, with the absolute optimization yet to be performed, thus we will discuss directions for future development of this sensor technology. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Swales & Associates Inc, Beltsville, MD 20705 USA. Hughes STX Corp, Lanham, MD 20706 USA. Univ Maryland, College Pk, MD 20706 USA. Univ Wisconsin, Madison, WI 53706 USA. RP Stahle, CK (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Porter, Frederick/D-3501-2012; Moseley, Harvey/D-5069-2012; Kelley, Richard/K-4474-2012 OI Porter, Frederick/0000-0002-6374-1119; NR 13 TC 10 Z9 11 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD OCT 21 PY 1999 VL 436 IS 1-2 BP 218 EP 225 DI 10.1016/S0168-9002(99)00624-5 PG 8 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 241TD UT WOS:000082897900034 ER PT J AU Godin, S Carswell, AI Donovan, DP Claude, H Steinbrecht, W McDermid, IS McGee, TJ Gross, MR Nakane, H Swart, DPJ Bergwerff, HB Uchino, O von der Gathen, P Neuber, P AF Godin, S Carswell, AI Donovan, DP Claude, H Steinbrecht, W McDermid, IS McGee, TJ Gross, MR Nakane, H Swart, DPJ Bergwerff, HB Uchino, O von der Gathen, P Neuber, P TI Ozone differential absorption lidar algorithm intercomparison SO APPLIED OPTICS LA English DT Article ID STRATOSPHERIC OZONE; AEROSOLS AB An intercomparison of ozone differential absorption lidar algorithms was performed in 1996 within the framework of the Network for the Detection of Stratospheric Changes (NDSC) lidar working group. The objective of this research was mainly to test the differentiating techniques used by the various lidar teams involved in the NDSC for the calculation of the ozone number density from the lidar signals. The exercise consisted of processing synthetic lidar signals computed from simple Rayleigh scattering and three initial ozone profiles. Two of these profiles contained perturbations in the low and the high stratosphere to test the vertical resolution of the various algorithms. For the unperturbed profiles the results of the simulations show the correct behavior of the lidar processing methods in the low and the middle stratosphere with biases of less than 1% with respect to the initial profile to as high as 30 km in most cases. In the upper stratosphere, significant biases reaching 10% at 45 km for most of the algorithms are obtained. This bias is due to the decrease in the signal-to-noise ratio with altitude, which makes it necessary to increase the number of points of the derivative low-pass filter used for data processing. As a consequence the response of the various retrieval algorithms to perturbations in the ozone profile is much better in the lower stratosphere than in the higher range. These results show the necessity of limiting the vertical smoothing in the ozone lidar retrieval algorithm and questions the ability of current lidar systems to detect long-term ozone trends above 40 km. Otherwise the simulations show in general a correct estimation of the ozone profile random error and, as shown by the tests involving the perturbed ozone profiles, some inconsistency in the estimation of the vertical resolution among the lidar teams involved in this experiment. (C) 1999 Optical Society of America. C1 Univ Paris 06, CNRS, Serv Aeron, F-75252 Paris 05, France. York Univ, Inst Space & Terr Sci, Downsview, ON M3J 3K1, Canada. York Univ, Dept Phys & Astron, Downsview, ON M3J 3K1, Canada. Deutsch Wetterdienst, D-82383 Hohenpeissenberg, Germany. Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Inst Environm Studies, Tsuchiura, Ibaraki 305, Japan. Natl Inst Publ Hlth & Environm Protect, NL-3720 BA Bilthoven, Netherlands. Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan. Alfred Wagner Inst Polar & Marine Res, D-14473 Potsdam, Germany. RP Godin, S (reprint author), Univ Paris 06, CNRS, Serv Aeron, F-75252 Paris 05, France. EM sophie.godin@aero.jussieu.fr RI Steinbrecht, Wolfgang/G-6113-2010; von der Gathen, Peter/B-8515-2009; McGee, Thomas/G-4951-2013; OI Steinbrecht, Wolfgang/0000-0003-0680-6729; von der Gathen, Peter/0000-0001-7409-1556; Nakane, Hideaki/0000-0002-9032-6105 NR 21 TC 46 Z9 49 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1999 VL 38 IS 30 BP 6225 EP 6236 DI 10.1364/AO.38.006225 PG 12 WC Optics SC Optics GA 249BA UT WOS:000083311200001 PM 18324146 ER PT J AU Wan, ZM Zhang, YL Ma, XL King, MD Myers, JS Li, XW AF Wan, ZM Zhang, YL Ma, XL King, MD Myers, JS Li, XW TI Vicarious calibration of the Moderate-Resolution Imaging Spectroradiometer Airborne Simulator thermal-infrared channels SO APPLIED OPTICS LA English DT Article ID RADIOMETRIC CALIBRATION; SURFACE TEMPERATURE; OPTICAL-CONSTANTS; WATER-VAPOR; MODIS; SPECTROMETER; EMISSIVITY; ALGORITHM; AEROSOL; SYSTEM AB We made an experimental vicarious calibration of the Moderate Resolution imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) thermal infrared (TIR) channel data acquired in the field campaign near Mono Lake, Calif. on 10 March 1998 to demonstrate the advantage of using high-elevation sites in dry atmospheric conditions for vicarious calibration. With three lake-surface sites and one snow-field site, we estimated the MAS noise-equivalent temperature difference as 0.7-1.0 degrees C for bands 30-32 in the 3.68-4.13-mu m region and 0.1-0.5 degrees C for bands 42, 45, 46, and 48 in the 8-13.5-mu m region. This study shows that the MAS calibration error is within +/-0.4 degrees C in the split-window channels (at 11 and 12 mu m) and larger in other TIR channels based on the MAS data over Mono Lake and in situ measurement data over the snow-field site. (C) 1999 Optical Society of America. C1 Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Boston Univ, Ctr Remote Sensing, Boston, MA 02215 USA. RP Wan, ZM (reprint author), Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. EM wan@icess.ucsb.edu RI King, Michael/C-7153-2011 OI King, Michael/0000-0003-2645-7298 NR 20 TC 15 Z9 16 U1 0 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1999 VL 38 IS 30 BP 6294 EP 6306 DI 10.1364/AO.38.006294 PG 13 WC Optics SC Optics GA 249BA UT WOS:000083311200011 PM 18324156 ER PT J AU Haner, DA McGuckin, BT Bruegge, CJ AF Haner, DA McGuckin, BT Bruegge, CJ TI Polarization characteristics of Spectralon illuminated by coherent light SO APPLIED OPTICS LA English DT Article ID IMAGING SPECTRORADIOMETER MISR; EARTH-ORBITING SENSORS; IN-FLIGHT CALIBRATION; BIDIRECTIONAL REFLECTANCE AB The Multiangle Imaging Spectroradiometer makes use of an onboard calibration system that includes two Spectralon panels that are used to reflect sunlight into the cameras. During preflight testing, these panels were quantified in terms of their bidirectional reflectance distribution function, which was measured as a function of the source-incident and detector view angles and at laser wavelengths of 442.0, 632.8, and 859.9 nm. Principal plane measurements are presented in which polarizations of the source and detector are analyzed. These data are unique and valuable in modeling Spectralon reflectance properties and for experiments in which polarization sensitivities are important. (C) 1999 Optical Society of America. C1 Calif State Polytech Univ Pomona, Dept Chem, Pomona, CA 91768 USA. Capital City Lasers, S Edinburgh EH14 4YG, Scotland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Haner, DA (reprint author), Calif State Polytech Univ Pomona, Dept Chem, Pomona, CA 91768 USA. EM carol.bruegge@jpl.nasa.gov NR 17 TC 31 Z9 31 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1999 VL 38 IS 30 BP 6350 EP 6356 DI 10.1364/AO.38.006350 PG 7 WC Optics SC Optics GA 249BA UT WOS:000083311200019 PM 18324164 ER PT J AU Balin, YS Samoilova, SV Krekova, MM Winker, DM AF Balin, YS Samoilova, SV Krekova, MM Winker, DM TI Retrieval of cloud optical parameters from space-based backscatter lidar data SO APPLIED OPTICS LA English DT Article ID EXTINCTION RATIOS; SCATTERING; INVERSION AB We present an approach to estimating the multiple-scattering (MS) contribution to lidar return signals from clouds recorded from space that enables us to describe in more detail the return formation at the depth where first orders of scattering dominate. Estimates made have enabled us to propose a method for correcting solutions of single-scattering lidar equations for the MS contribution. We also describe an algorithm for reconstructing the profiles of the cloud scattering coefficient and the optical thickness tau under conditions of a priori uncertainties. The approach proposed is illustrated with results for optical parameters of cirrus and stratiform clouds determined from return signals calculated by the Monte Carlo method as well as from return signals acquired with the American spaceborne lidar during the Lidar In-Space Technology Experiment (LITE). (C) 1999 Optical Society of America. C1 Russian Acad Sci, Inst Atmospher Opt, Siberian Branch, Tomsk 634055, Russia. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Balin, YS (reprint author), Russian Acad Sci, Inst Atmospher Opt, Siberian Branch, 1 Acad Skii Ave, Tomsk 634055, Russia. EM balin@losa.iao.tomsk.ru NR 26 TC 9 Z9 10 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1999 VL 38 IS 30 BP 6365 EP 6373 DI 10.1364/AO.38.006365 PG 9 WC Optics SC Optics GA 249BA UT WOS:000083311200021 PM 18324166 ER PT J AU Gudimetla, VSR Kavaya, MJ AF Gudimetla, VSR Kavaya, MJ TI Special relativity corrections for space-based lidars SO APPLIED OPTICS LA English DT Article ID COHERENT LASER-RADAR; DOPPLER LIDAR; PERFORMANCE; TECHNOLOGY; WINDS AB The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. However, the ray that enters the receiver does not correspond to a retroreflected ray by the target. For the retroreflection case there is misalignment between the transmitted ray and the received ray. In addition, the Doppler shift in the frequency and the amount of tip for the receiver aperture when needed are calculated. The error in estimating wind because of the Doppler shift in the frequency due to special relativity effects is examined. The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system. (C) 1999 Optical Society of America. C1 Oregon Grad Inst, Dept Elect & Comp Engn, Portland, OR 97291 USA. NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35812 USA. RP Gudimetla, VSR (reprint author), Ansoft Corp, 669 River Dr,Suite 200, Elmwood Pk, NJ 07407 USA. EM gudimetla@comsoft.com NR 37 TC 4 Z9 4 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1999 VL 38 IS 30 BP 6374 EP 6382 DI 10.1364/AO.38.006374 PG 9 WC Optics SC Optics GA 249BA UT WOS:000083311200022 PM 18324167 ER PT J AU McGill, MJ Hart, WD McKay, JA Spinhirne, JD AF McGill, MJ Hart, WD McKay, JA Spinhirne, JD TI Modeling the performance of direct-detection Doppler lidar systems including cloud and solar background variability SO APPLIED OPTICS LA English DT Article ID ATMOSPHERIC WIND SENSOR; OCTOBER 1986 FIRE; EDGE TECHNIQUE; BACKSCATTER; EXTINCTION; AEROSOL; TROPOSPHERE; PARAMETERS AB Previous modeling of the performance of spaceborne direct-detection Doppler lidar systems assumed extremely idealized atmospheric models. Here we develop a technique for modeling the performance of these systems in a more realistic atmosphere, based on actual airborne lidar observations. The resulting atmospheric model contains cloud and aerosol variability that is absent in other simulations of spaceborne Doppler lidar instruments. To produce a realistic simulation of daytime performance, we include solar radiance values that are based on actual measurements and are allowed to vary as the viewing scene changes. Simulations are performed for two types of direct-detection Doppler lidar system: the double-edge and the multichannel techniques. Both systems were optimized to measure winds from Rayleigh backscatter at 355 nm. Simulations show that the measurement uncertainty during daytime is degraded by only approximately 10-20% compared with nighttime performance, provided that a proper solar filter is included in the instrument design. (C) 1999 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Sci Syst Applicat Inc, Lanham, MD 20706 USA. LLC, Remote Sensing Concepts, Washington, DC 20010 USA. RP McGill, MJ (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. EM mcgill@virl.gsfc.nasa.gov RI McGill, Matthew/D-8176-2012 NR 34 TC 14 Z9 17 U1 0 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1999 VL 38 IS 30 BP 6388 EP 6397 DI 10.1364/AO.38.006388 PG 10 WC Optics SC Optics GA 249BA UT WOS:000083311200024 PM 18324169 ER PT J AU Turner, TJ George, IM Nandra, K Turcan, D AF Turner, TJ George, IM Nandra, K Turcan, D TI On X-ray variability in Seyfert galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : nuclei; galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; BROAD-LINE REGION; IMAGING SPECTROMETER; ASCA OBSERVATIONS; EMISSION; SPECTROPHOTOMETRY; PROFILES; ATLAS; ALPHA AB This paper presents a quantification of the X-ray variability amplitude for 79 ASCA observations of 36 Seyfert 1 galaxies. We find that consideration of sources with the narrowest permitted lines in the optical band introduces scatter into the established correlation between X-ray variability and nuclear luminosity. Consideration of the X-ray spectral index and variability properties together shows distinct groupings in parameter space for broad- and narrow-line Seyfert 1 galaxies, confirming previous studies. A strong correlation is found between hard X-ray variability and FWHM H beta. A range of nuclear mass and accretion rate across the Seyfert population can explain the differences observed in X-ray and optical properties. An attractive alternative model, which does not depend on any systematic difference in central mass, is that the circumnuclear gas of narrow-line Seyfert 1 galaxies is different from broadline Seyfert 1 galaxies in temperature, optical depth, density, or geometry. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Baltimore, MD 21250 USA. Univ Maryland, College Pk, MD 20742 USA. RP Turner, TJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 660, Greenbelt, MD 20771 USA. NR 41 TC 126 Z9 128 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 667 EP 673 DI 10.1086/307834 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300015 ER PT J AU Reid, MJ Readhead, ACS Vermeulen, RC Treuhaft, RN AF Reid, MJ Readhead, ACS Vermeulen, RC Treuhaft, RN TI The proper motion of Sagittarius A*. I. First VLBA results SO ASTROPHYSICAL JOURNAL LA English DT Article DE astrometry; black hole physics; Galaxies : fundamental parameters Galaxy : center; Galaxy : kinematics and dynamics ISM : individual (Sagittarius A*) ID GALAXY AB We observed Sgr A* and two extragalactic radio sources nearby in angle with the VLBA over a period of 2 yr and measured relative positions with an accuracy approaching 0.1 mas. The apparent proper motion of Sgr A* relative to J1745-283 is 5.90 +/- 0.4 mas yr(-1), almost entirely in the plane of the Galaxy. The effects of the orbit of the Sun around the Galactic center can account for this motion, and any residual proper motion of Sgr A*, with respect to extragalactic sources, is less than about 20 km s(-1). Assuming that Sgr A* is at rest at the center of the Galaxy, we estimate that the circular rotation speed in the Galaxy at the position of the Sun, Theta(0) is 219 +/- 20 km s(-1), scaled by R-0/8.0 kpc. Current observations are consistent with Sgr A* containing all of the nearly 2.6 x 10(6) M-circle dot deduced from stellar proper motions, in the form of a massive black hole. While the low luminosity of Sgr A*, for example, might possibly have come from a contact binary containing of order 10 M-circle dot the lack of substantial motion rules out a "stellar" origin for Sgr A*. The very slow speed of Sgr A* yields a lower limit to the mass of Sgr A* of about 1000 M-circle dot, Even for this mass, Sgr A* appears to be radiating at less than 0.1% of its Eddington limit. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Reid, MJ (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. NR 22 TC 184 Z9 187 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 816 EP 823 DI 10.1086/307855 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300025 ER PT J AU Suttner, G Yorke, HW Lin, DNC AF Suttner, G Yorke, HW Lin, DNC TI Dust coagulation in infalling protostellar envelopes. I. Compact grains SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; dust, extinction; hydrodynamics; radiative transfer; stars : formation ID PROTOPLANETARY ACCRETION DISKS; PRIMORDIAL SOLAR NEBULA; SIZE DISTRIBUTION; EVOLUTION; CLOUDS; AGGREGATION; GROWTH AB Dust plays a key role in the optical, thermodynamic, and gasdynamical behavior of collapsing molecular cores. Because of relative velocities of the individual dust grains, coagulation and shattering can modify the grain size distribution and-because of corresponding changes in the medium's opacity-significantly influence the evolution during early phases of star formation. In order to study relevant timescales and possible consequences for intermediate-mass stars, we examine the dust evolution in spherical protostellar envelopes that evolve from cloud clumps of masses 3, 5, and 10 M.. At first the collapse proceeds in the well-known nonhomologous manner until a central hydrostatic core is formed. During the non-steady state accretion the accretion luminosity of the central core reaches high values (approximate to 10(4) L.). Thus, differential radiative acceleration provides an important contribution to the relative velocities of the grains. In turn, the mass accretion rate, which determines the central core's accretion luminosity (and ultimately the final mass of the central object), depends strongly on the opacity distribution in the enshrouding envelope. We find that coagulation and shattering can lead to significant modifications of the dust size distribution and the opacity during early collapse phases. The visible and ultraviolet extinction is most strongly affected. C1 Univ Wurzburg, Astron Inst, D-97074 Wurzburg, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Cruz, Lick Observ, UCO, Santa Cruz, CA USA. RP Suttner, G (reprint author), Univ Wurzburg, Astron Inst, D-97074 Wurzburg, Germany. NR 28 TC 14 Z9 14 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 857 EP 866 DI 10.1086/307825 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300029 ER PT J AU Miesch, MS Scalo, J Bally, J AF Miesch, MS Scalo, J Bally, J TI Velocity field statistics in star-forming regions. I. Centroid velocity observations SO ASTROPHYSICAL JOURNAL LA English DT Review DE ISM : clouds; ISM : kinematics and dynamics; ISM : molecules; stars : formation; turbulence ID HERBIG-HARO OBJECTS; PROBABILITY-DISTRIBUTION FUNCTIONS; REYNOLDS-NUMBER TURBULENCE; L1551 MOLECULAR OUTFLOW; NON-GAUSSIAN STATISTICS; HL TAURI REGION; INFRARED OBSERVATIONS; CARBON-MONOXIDE; MONOCEROS R2; DARK CLOUDS AB The probability density functions (pdfs) of molecular line centroid velocity fluctuations, and of line centroid velocity fluctuation differences at different spatial lags, are estimated for several nearby molecular clouds with active internal star formation. The data consist of over 75,000 (13)CO line profiles divided among 12 spatially and/or kinematically distinct regions. These regions range in size from less than 1 to more than 40 pc and are all substantially supersonic, with centroid fluctuation Mach numbers ranging from about 1.5 to 7. The centroid pdfs are constructed using three different types of estimators. Although three regions (all in Mon R2) exhibit nearly Gaussian centroid pdfs, the other regions show strong evidence for non-Gaussian pdfs, often nearly exponential, with possible evidence for power-law contributions in the far tails. Evidence for nearly exponential centroid pdfs in the neutral H I component of the interstellar medium is also presented, based on older published data for optical absorption lines and H I emission and absorption lines. These strongly non-Gaussian pdfs disagree with the nearly Gaussian behavior found for incompressible turbulence (except possibly shear flow turbulence) and simulations of decaying mildly supersonic turbulence. Spatial images of the largest magnitude centroid velocity differences for the star-forming regions appear less filamentary than predicted by decay simulations dominated by vortical interactions. No evidence for the scaling of difference pdf kurtosis with Reynolds number, as found in incompressible turbulence experiments and simulations, is found. We conclude that turbulence in both star-forming molecular clouds and diffuse H I regions involves physical processes that are not adequately captured by incompressible turbulence or by mildly supersonic decay simulations. The variation with lag of the variance and kurtosis of the difference pdfs is presented as a constraint on future simulations, and we evaluate and discuss the implications of the large scale and Taylor scale Reynolds numbers for the regions studied here. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. RP Miesch, MS (reprint author), Univ Cambridge, Dept Appl Math & Theoret Phys, Silver St, Cambridge CB3 9EW, England. EM miesch@ktaadn.gsfc.nasa.gov; parrot@astro.as.utexas.edu; bally@casa.colorado.edu RI Miesch, Mark/B-1104-2008; OI Miesch, Mark/0000-0003-1976-0811 NR 164 TC 53 Z9 53 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 895 EP 922 DI 10.1086/307824 PN 1 PG 28 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300032 ER PT J AU Nelson, RP Langer, WD AF Nelson, RP Langer, WD TI On the stability and evolution of isolated Bok globules SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; ISM : clouds; ISM : kinematics and dynamics; ISM : molecules ID YOUNG STELLAR OBJECTS; SMALL MOLECULAR CLOUDS; SMALL DARK CLOUDS; STAR-FORMATION; PROTOSTELLAR CORES; THERMAL BALANCE; EMISSION; MILLIMETER; CHEMISTRY; PHOTODISSOCIATION AB We present the results of three-dimensional hydrodynamic simulations of evolving isolated low-mass clouds and Bok globules, where the interstellar radiation field plays an important role in the chemical and thermal evolution. We consider two classes of cloud models: (1) clouds that are initially supported against gravitational collapse by thermal pressure alone, and (2) clouds that are initially supported by a mildly supersonic, complex internal velocity held ("turbulence"). The models are based on our earlier work with a smoothed particle hydrodynamics code, but upgraded to include a larger chemical network, refined chemical and dust properties, and different boundary conditions. The chemical network predicts the abundances of several key tracers of cloud structure and evolution, including C(+), C I, and CO. There are two main purposes of this work. The first is to calculate the effective Jeans masses of isolated and externally heated clouds under a range of initial conditions, in order to delineate the physical parameters necessary for gravitational collapse and star formation to occur. The second is to calculate density, temperature, and chemical species profiles for comparison with observations. We consider clouds with masses in the range 8 less than or equal to M less than or equal to 70 M., radii in the range 0.34 less than or equal to R less than or equal to 1.8 pc, and initial number densities in the range 50 less than or equal to n less than or equal to 1000 cm(-3), corresponding to low-mass Bok globules. We examine the evolution of both uniform-density and centrally condensed clouds, and clouds with and without a turbulent velocity held. The main results of our calculations are: 1. Clouds that proved to be gravitationally unstable collapsed to form cold, dense molecular cores, surrounded by warm, thermally supported, tenuous halos in which the trace species were in ionic or atomic form. 2. The evolution of the thermally supported clouds is driven in the first instance by a pressure gradient through the cloud that arises because of the attenuation of the interstellar radiation field. Subsequent thermal evolution leads to cooling of the gas, which can induce gravitational instability. 3. Initially turbulent clouds evolve through the dissipation of their internal kinetic energy and then follow evolutionary paths similar to those of the thermally supported clouds. The effect of the turbulence is to delay the collapse of the clouds until the turbulence decays, which occurs on a rapid timescale through shock dissipation, and to increase the stability of the cloud models by a small amount. 4. The collapsing dense cores that arise in the simulations have masses in the range 3 less than or similar to M less than or similar to 20 M., radii in the range 0.1 less than or similar to R less than or similar to 0.2 pc, and temperatures in the range 8 less than or similar to T less than or similar to 12 K. These align closely with the observationally derived properties of Bok globule cores. 5. The characteristics of the collapsing dense cores are similar to those of collapsing isothermal spheres, since the gas evolves toward a constant temperature of 10 K before collapse ensues, because of gas-dust thermal coupling. C1 Queen Mary Univ London, Sch Math Sci, Astron Unit, London E1 4NS, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Nelson, RP (reprint author), Queen Mary Univ London, Sch Math Sci, Astron Unit, Mile End Rd, London E1 4NS, England. EM R.P.Nelson@qmw.ac.uk; langer@nimba.jpl.nasa.gov NR 42 TC 41 Z9 41 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 923 EP 946 DI 10.1086/307823 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300033 ER PT J AU Roby, SW Leckrone, DS Adelman, SJ AF Roby, SW Leckrone, DS Adelman, SJ TI Abundances of the elements in sharp-lined early-type stars from IUE high-dispersion spectrograms. II. The nitrogen deficiency in mercury-manganese stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : abundances; stars : early-type; stars : peculiar; ultraviolet : stars ID COADDED DAO SPECTROGRAMS; TRANSITION-PROBABILITIES; VACUUM ULTRAVIOLET; NEUTRAL NITROGEN; SPECTRAL-LINES; MAIN-SEQUENCE; SOLAR; DIFFUSION; CANCRI; CARBON AB We determine nitrogen abundances from co-added IUE high-dispersion SWP spectrograms of four HgMn stars and five normal or superficially normal main-sequence B and A stars. We find N deficiencies in the HgMn stars greater than previously reported (depletion factors of 135-400 relative to the Sun). N abundance discrepancies from UV and IR studies of normal stars are discussed in light of possible non-LTE effects. Our data set for our sample of HgMn stars (observed with a consistent strategy to maximize the benefits of co-additions) is an improvement over the single or few images previously used to derive N abundances for most of these stars. C1 SUNY Coll Oswego, Dept Earth Sci, Oswego, NY 13126 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. The Citadel, Dept Phys, Charleston, SC 29409 USA. RP Roby, SW (reprint author), SUNY Coll Oswego, Dept Earth Sci, Oswego, NY 13126 USA. NR 36 TC 12 Z9 12 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 974 EP 982 DI 10.1086/307815 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300037 ER PT J AU Ishibashi, K Corcoran, MF Davidson, K Swank, JH Petre, R Drake, SA Damineli, A White, S AF Ishibashi, K Corcoran, MF Davidson, K Swank, JH Petre, R Drake, SA Damineli, A White, S TI Recurrent X-ray emission variations of eta carinae and the binary hypothesis SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : early-type; stars : individual (eta Carinae); X-rays : stars ID LONG-PERIOD BINARY; EARLY-TYPE STARS; VARIABILITY; OUTBURSTS; SPECTRUM; NEBULA; WINDS AB Recent studies by Damineli and coworkers suggest that the supermassive star eta Carinae may have a massive stellar companion, although the dense ejecta surrounding the star make this claim hard to test using conventional methods. Settling this question is critical for determining the current evolutionary state and future evolution of the star. We address this problem by an unconventional method: If eta Carinae is a binary, X-ray emission should be produced in shock waves generated by wind-wind collisions in the region between eta Carinae and its companion. Detailed X-ray monitoring of eta Carinae for more than 2 years shows that the observed emission generally resembles colliding-wind X-ray emission, but with some significant discrepancies. Briefly, the presence of enhanced absorbing material-such as a circumstellar disk-has been examined to explain the discrepancies. Furthermore, periodic X-ray "flaring" may provide an additional clue to determine the presence of a companion star and for atmospheric pulsation in eta Carinae. C1 Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. Univ Sao Paulo, Inst Astron & Geofis, BR-04301904 Sao Paulo, Brazil. Univ Maryland, Dept Agron, College Pk, MD 20742 USA. RP Ishibashi, K (reprint author), Univ Minnesota, Dept Astron, 116 Church St SE, Minneapolis, MN 55455 USA. RI Damineli, Augusto/D-8210-2012; Swank, Jean/F-2693-2012 OI Damineli, Augusto/0000-0002-7978-2994; NR 28 TC 106 Z9 106 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 983 EP 987 DI 10.1086/307859 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300038 ER PT J AU Oluseyi, HM Walker, ABC Porter, J Hoover, RB Barbee, TW AF Oluseyi, HM Walker, ABC Porter, J Hoover, RB Barbee, TW TI Observation and modeling of the solar transition region. I. Multi-spectral solar telescope array observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : chromosphere; Sun : transition region; Sun : UV radiation ID UNRESOLVED FINE-STRUCTURES; RAY BRIGHT POINTS; ENERGY-BALANCE; CORONAL LOOPS; POLAR PLUMES; QUIET SUN; TEMPERATURE REGION; MAGNETIC-STRUCTURE; ACTIVE REGIONS; SCALING LAW AB We report on observations of the solar atmosphere in several extreme-ultraviolet and far-ultraviolet bandpasses obtained by the Multi-Spectral Solar Telescope Array, a rocket-borne spectroheliograph, on flights in 1987, 1991, and 1994, spanning the last solar maximum. Quiet-Sun emission observed in the 171-175 Angstrom bandpass, which includes lines of O V, O VI, Fe rx, and Fe X, has been analyzed to test models of the temperatures and geometries of the structures responsible for this emission. Analyses of intensity variations above the solar limb reveal scale heights consistent with a quiet-Sun plasma temperature of 500,000 less than or equal to T-e less than or equal to 800,000 K. The structures responsible for the quiet-Sun EUV emission are modeled as small quasi-static loops. We submit our models to several tests. We compare the emission our models would produce in the bandpass of our telescope to the emission we have observed. We find that the emission predicted by loop models with maximum temperatures between 700,000 and 900,000 K are consistent with our observations. We also compare the absolute flux predicted by our models in a typical upper transition region line to the flux measured by previous observers. Finally, we present a preliminary comparison of the predictions of our models with diagnostic spectral line ratios from previous observers. Intensity modulations in the quiet Sun are observed to occur on a scale comparable to the supergranular scale. We discuss the implications that a distribution of loops of the type we model here would have for heating the local network at the loops' footpoints. C1 Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Stanford Univ, Ctr Space Sci & Astrophys, Stanford, CA 94305 USA. Stanford Univ, Dept Appl Phys, Stanford, CA 94305 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Lawrence Livermore Natl Lab, Dept Chem & Mat Sci, Livermore, CA 94550 USA. RP Stanford Univ, Dept Phys, Stanford, CA 94305 USA. EM Hakeem@banneker.stanford.edu; walker@banneker.stanford.edu; Jason.Porter@msfc.nasa.gov; Richard.Hoover@msfc.nasa.gov; barbee2@llnl.gov NR 89 TC 9 Z9 9 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP 1105 EP 1121 DI 10.1086/307830 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YB UT WOS:000083135300048 ER PT J AU Sahai, R AF Sahai, R TI Discovery of a remarkable point-symmetric proto-planetary nebula: Hubble Space Telescope imaging of IRAS 04296+3429 SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; planetary nebulae : general; stars : AGB and post-AGB; stars : mass loss ID POST-AGB STARS; CIRCUMSTELLAR ENVELOPES; PROTOPLANETARY NEBULAE; MASS-LOSS; JETS; COLLIMATION; EVOLUTION; EMISSION; OUTFLOWS; BUBBLES AB We present images of the proto-planetary nebula (PPN) IRAS 04296+3429 thereafter I04296) taken with the Hubble Space Telescope Wide Field Planetary Camera 2 in two wide-band filters centered at 0.56 and 0.81 mu m. We find that this object, which belongs to a class of carbon-rich PPNs with a peculiar 21 mu m dust emission feature, has a striking point-symmetric morphology, with a pair of long, well-collimated lobes oriented at about 70 degrees to an equatorial elliptical "disklike" structure. Although dense disklike regions have been inferred from the presence of dark lanes separating the bipolar lobes of post-asymptotic giant branch (AGB) objects, I04296 is the first to show a bounded disk directly in scattered light. The lobes and the disk appear embedded in a roughly round, faint halo with a radius at least as large as 2."8. The bipolar lobes probably result from the interaction of a collimated high-velocity bipolar outflow with the spherical progenitor AGE circumstellar envelope, which is seen as the halo. The internal structure of the lobes suggests that the bipolar outflow changes its direction with time. A simple single-scattering model of a spherical inverse-square density envelope with a dust mass-loss rate of 4 x 10(-8) M-. yr(-1) provides a good fit to the scattered light in the halo at both wavelengths. The collimated lobes and point-symmetric structure in 104296 provide strong support for the jet-driven formation of aspherical planetary nebulae. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sahai, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 35 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP L125 EP L128 DI 10.1086/312307 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YM UT WOS:000083136300012 ER PT J AU Schaefer, BE Snyder, JA Hernandez, J Roscherr, B Deng, M Ellman, N Bailyn, C Rengstorf, A Smith, D Levine, A Barthelmy, S Butterworth, P Hurley, K Cline, T Meegan, C Kouveliotou, C Kippen, RM Park, HS Williams, GG Porrata, R Bionta, R Hartmann, D Band, D Frail, D Kulkarni, S Bloom, J Djorgovski, S Sadava, D Chaffee, F Harris, F Abad, C Adams, B Andrews, P Baltay, C Bongiovanni, A Briceno, C Bruzual, G Coppi, P Della Prugna, F Dubuc, A Emmet, W Ferrin, I Fuenmayor, F Gebhard, M Herrera, D Honeycutt, K Magris, G Mateu, J Muffson, S Musser, J Naranjo, O Oemler, A Pacheco, R Paredes, G Rengel, M Romero, L Rosenzweig, P Sabbey, C Sanchez, G Sanchez, G Schenner, H Shin, J Sinnott, J Sofia, S Stock, J Suarez, J Telleria, D Vicente, B Vieira, K Vivas, K AF Schaefer, BE Snyder, JA Hernandez, J Roscherr, B Deng, M Ellman, N Bailyn, C Rengstorf, A Smith, D Levine, A Barthelmy, S Butterworth, P Hurley, K Cline, T Meegan, C Kouveliotou, C Kippen, RM Park, HS Williams, GG Porrata, R Bionta, R Hartmann, D Band, D Frail, D Kulkarni, S Bloom, J Djorgovski, S Sadava, D Chaffee, F Harris, F Abad, C Adams, B Andrews, P Baltay, C Bongiovanni, A Briceno, C Bruzual, G Coppi, P Della Prugna, F Dubuc, A Emmet, W Ferrin, I Fuenmayor, F Gebhard, M Herrera, D Honeycutt, K Magris, G Mateu, J Muffson, S Musser, J Naranjo, O Oemler, A Pacheco, R Paredes, G Rengel, M Romero, L Rosenzweig, P Sabbey, C Sanchez, G Sanchez, G Schenner, H Shin, J Sinnott, J Sofia, S Stock, J Suarez, J Telleria, D Vicente, B Vieira, K Vivas, K TI Discovery of the optical transient of GRB 990308 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts ID GAMMA-RAY BURSTS; 28 FEBRUARY 1997; EMISSION; GRB-970508; EVOLUTION; GALAXIES AB The optical transient of the faint gamma-ray burst GRB 990308 was detected by the QUEST camera on the Venezuelan 1 m Schmidt telescope starting 3.28 hr after the burst. Our photometry gives V = 18.32 +/- 0.07, R = 18.14 +/- 0.06, B = 18.65 +/- 0.23, and R = 18.22 +/- 0.05 for times ranging from 3.28 to 3.47 hr after the burst. The colors correspond to a spectral slope of close to f(v) proportional to nu(1/3). Within the standard synchrotron fireball model, this requires that the external medium be less dense than 10(4) cm(-3), the electrons contain more than 20% of the shock energy, and the magnetic field energy be less than 24% of the energy in the electrons for normal interstellar or circumstellar densities. We also report upper limits of V> 12.0 at 132 s (with LOTIS), V > 13.4 from 132 to 1029 s (with LOTIS), V>15.3 at 28.2 minutes (with Super-LOTIS), and a 8.5 GHz flux of less than 114 mu Jy at 110 days (with the Very Large Array). Wisconsin-Indiana-Yale-NOAO 3.5 m and Keck 10 m telescopes reveal this location to be empty of any host galaxy to R > 25.7 and K> 23.3. The lack of a host galaxy likely implies that it is either substantially subluminous or more distant than a redshift of similar to 1.2. C1 Yale Univ, Dept Phys, New Haven, CT 06520 USA. Yale Univ, Dept Astron, New Haven, CT 06520 USA. CIDA, Merida 5101, Venezuela. Univ Los Andes, Dept Fis, Merida 5101, Venezuela. Indiana Univ, Dept Astron, Bloomington, IN 47405 USA. MIT, Dept Phys, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Clemson Univ, Dept Phys & Astron, Kinard Lab, Clemson, SC 29634 USA. Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Natl Radio Astron Observ, Socorro, NM 87801 USA. WM Keck Observ, Kamuela, HI 96743 USA. USN Observ, Flagstaff, AZ 86002 USA. Cent Univ Venezuela, Dept Fis, Caracas 1042, Venezuela. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. RP Schaefer, BE (reprint author), Yale Univ, Dept Phys, POB 208121, New Haven, CT 06520 USA. RI Barthelmy, Scott/D-2943-2012; Bongiovanni, Angel/J-6176-2012 NR 33 TC 24 Z9 25 U1 3 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1999 VL 524 IS 2 BP L103 EP L106 DI 10.1086/312318 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 245YM UT WOS:000083136300007 ER PT J AU Koch, D Jacob, D Tegen, I Rind, D Chin, M AF Koch, D Jacob, D Tegen, I Rind, D Chin, M TI Tropospheric sulfur simulation and sulfate direct radiative forcing in the Goddard Institute for Space Studies general circulation model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VERTICAL TRANSPORT; GLOBAL SIMULATION; GREENHOUSE GASES; ATMOSPHERIC SULFUR; AEROSOLS; CHEMISTRY; CYCLE; PARAMETERIZATION; DIMETHYLSULFIDE; SENSITIVITY AB Global simulations of tropospheric sulfur are performed in the Goddard Institute for Space Studies (GISS) general circulation model (GCM) and used to calculate anthropogenic sulfate direct radiative forcing, Prognostic species are in cloud oxidant H2O2, dimethylsulfide (DMS), methanesulfonic acid (MSA), SO2 and sulfate, Compared with most previous models (except others with prognostic H2O2), this model has relatively high anthropogenic SO2 and sulfate burden, We show that this is due partly to the depletion of the prognostic H2O2 and that moist convection delivers significant levels of SO2 to the free troposphere in polluted regions. Model agreement with surface observations is not remarkably different from previous studies. Following some previous studies, we propose that an additional in-cloud or heterogeneous oxidant is Likely to improve the simulation near the surface. Our DMS source is lower than sources in previous studies, and sulfur values in remote regions are generally lower than those observed. Because of the high flux of SO2 to the free troposphere and the relatively low natural source, our model indicates a larger global anthropogenic contribution to the sulfate burden (77%) than was estimated by previous global models. Additional high-altitude observations of the sulfur species are needed for model validation and resolution of this issue. Direct radiative forcing calculations give an annual average anthropogenic sulfate forcing of -0.67 W/m(2) We compare the radiative forcings due to online (hourly varying) versus offline (monthly average) sulfate and find Little difference on a global average, but we do find differences as great as 10% in some regions, Thus, for example, over some polluted continental regions the forcing due to offline sulfate exceeds that of online sulfate, while over some oceanic regions the online sulfate forcing is larger, We show that these patterns are probably related to the correlation between clouds and sulfate, with positive correlations occuring over some polluted continental regions and negative correlations over high-latitude oceanic regions. C1 Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Koch, D (reprint author), Columbia Univ, NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM dkoch@giss.nasa.gov RI Chin, Mian/J-8354-2012 NR 57 TC 171 Z9 174 U1 1 U2 16 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1999 VL 104 IS D19 BP 23799 EP 23822 DI 10.1029/1999JD900248 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 246WT UT WOS:000083188400015 ER PT J AU Wong, S Prather, MJ Rind, DH AF Wong, S Prather, MJ Rind, DH TI Seasonal and interannual variability of the budgets of N3O and CCI3F SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE MODEL; ANTARCTIC OZONE HOLE; 3-DIMENSIONAL SIMULATIONS; TRACE CONSTITUENTS; STRATOSPHERIC N2O; DOWNWARD CONTROL; PLANETARY-WAVES; CLIMATE CHANGE; ANNUAL CYCLE; TRANSPORT AB The 6-year wind archives from the Goddard Institute for Space Studies/Global Climate-Middle Atmosphere Model (GISS/GCMAM) were input to the GISS/Harvard/Irvine Chemical Transport Model (G/H/I CTM) to study the seasonal and interannual variability of the budgets and distributions of nitrous oxide (N2O) and trichlorofluoromethane (CCl3F), with the corresponding chemical loss frequencies recycled and boundary conditions kept unchanged from year to year. The effects of ozone feedback and quasibiennial oscillation (QBO) were not included. However, the role of circulation variation in driving the lifetime variability is investigated. It was found that the global loss rates of these tracers are related to the extratropical planetary wave activity, which drives the tropical upward mass flux. For N2O a semiannual signal in the loss rate variation is associated with the interhemispheric asymmetry in the upper stratospheric wave activity. For CCl3F the semiannual signal is weaker, associated with the comparatively uniform wave episodes in the lower stratosphere. The loss rates lag behind the wave activity by about 1-2 months. The interannual variation of the general circulation model generated winds drives the interannual variation of the annually averaged lifetime. The year-to-year variations of the annually averaged lifetimes can be about 3% for N2O and 4% for CCl3F. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. Univ Calif Irvine, Dept Earth Syst Sci, Irvine, CA 92717 USA. Columbia Univ, Dept Phys, New York, NY 10027 USA. RP Wong, S (reprint author), SUNY Albany, Atmospher Sci Res Ctr, 251 Fuller Rd, Albany, NY 12203 USA. EM wong@climate.cestm.albany.edu; prather@halo.ps.uci.edu; drind@giss.nasa.gov NR 36 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1999 VL 104 IS D19 BP 23899 EP 23909 DI 10.1029/1999JD900776 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 246WT UT WOS:000083188400021 ER PT J AU Fleming, EL Jackman, CH Stolarski, RS Considine, DB AF Fleming, EL Jackman, CH Stolarski, RS Considine, DB TI Simulation of stratospheric tracers using an improved empirically based two-dimensional model transport formulation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SULFUR-HEXAFLUORIDE SF6; GRAVITY-WAVE BREAKING; PARABOLIC METHOD PPM; MIDDLE ATMOSPHERE; NUMERICAL-MODEL; 2-DIMENSIONAL MODEL; UPPER TROPOSPHERE; POLAR VORTEX; ANNUAL CYCLE; DYNAMICS AB We have developed a new empirically based transport formulation for use in our Goddard Space Flight Center (GSFC) two-dimensional chemistry and transport model. In this formulation, we consider much of the information about atmospheric transport processes available from existing data sets. This includes zonal mean temperature, zonal wind, net heating rates, and Eliassen-Palm flux diagnostics for planetary and synoptic-scale waves. We also account for the effects of gravity waves and equatorial Kelvin waves by utilizing previously developed parameterizations in which the zonal mean flow is constrained to observations. This scheme utilizes significantly more information compared to our previous formulation and results in simulations that are in substantially better agreement with observations. The new model transport captures much of the qualitative structure and seasonal variability observed in stratospheric long lived tracers, such as isolation of the tropics and the southern hemisphere winter polar vortex, the well-mixed surf-zone region of the winter subtropics and midlatitudes, and the latitudinal and seasonal variations of total ozone. Model simulations of carbon 14 and strontium 90 are in good agreement with observations, capturing the peak in mixing ratio at 20-25 km and the decrease with altitude in mixing ratio above 25 km. We also find mostly good agreement between modeled and observed age of air determined from SF6 outside of the northern hemisphere polar vortex. However, inside the vortex, the model simulates significantly younger air compared to observations. This is consistent with the model deficiencies in simulating CH4 in this region and illustrates the limitations of the current climatological zonal mean model formulation. The model correctly propagates the phase of the lower stratospheric seasonal cycles in 2CH(4)+H2O and CO2. The model also qualitatively captures the observed decrease in the amplitude of the stratospheric CO2 seasonal cycle between the tropics and midlatitudes. However, the simulated seasonal amplitudes were attenuated too rapidly with altitude in the tropics. The generally good model-measurement agreement of these tracer simulations demonstrate that a successful formulation of zonal mean transport processes can be constructed from currently available atmospheric data sets. C1 Steven Myers & Associates Corp, Arlington, VA USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Fleming, EL (reprint author), NASA, Goddard Space Flight Ctr, Code 916,Greenbelt Rd, Greenbelt, MD 20771 USA. EM flem-ing@kahuna.gsfc.nasa.gov RI Stolarski, Richard/B-8499-2013; Jackman, Charles/D-4699-2012 OI Stolarski, Richard/0000-0001-8722-4012; NR 63 TC 54 Z9 54 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1999 VL 104 IS D19 BP 23911 EP 23934 DI 10.1029/1999JD900332 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 246WT UT WOS:000083188400022 ER PT J AU Martin, JML Baldridge, KK Lee, TJ AF Martin, JML Baldridge, KK Lee, TJ TI Accurate ab initio anharmonic force field and heat of formation for silane SO MOLECULAR PHYSICS LA English DT Article ID BASIS-SET CONVERGENCE; CHEMICAL-VAPOR-DEPOSITION; CORRELATED MOLECULAR CALCULATIONS; VANVLECK PERTURBATION-THEORY; TOTAL ATOMIZATION ENERGIES; SMALL POLYATOMIC-MOLECULES; COUPLED-CLUSTER THEORY; GAUSSIAN-BASIS SETS; VIBRATIONAL FREQUENCIES; WAVE-FUNCTIONS AB From large basis set coupled cluster calculations and a minor empirical adjustment, an anharmonic force field for silane has been derived that is consistently of spectroscopic quality (+/-1 cm(-1) on vibrational fundamentals) for all isotopomers of silane studied. Inner-shell polarization functions have an appreciable effect on computed properties and even on anharmonic corrections. From large basis set coupled cluster calculations and extrapolations to the infinite-basis set limit, we obtain TAE(0) = 303.80 +/- 0.18 kcal mol(-1), which includes an anharmonic zero-point energy (19.59 kcal mol(-1)), inner-shell correlation (-0.36 kcal mol(-1)), scalar relativistic corrections (-0.70 kcal mol(-1)) and atomic spin-orbit corrections (-0.43 kcal mol(-1)). In combination with the recently revised Delta H<((f))over circle>,(0)[Si(g)], we obtain Delta H<((f))over circle>,(0)[SiH4(g)] = 9.9 +/- 0.4 kcal mol(-1) in between the two established experimental values. C1 Weizmann Inst Sci, Dept Organ Chem, IL-76100 Rehovot, Israel. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif San Diego, San Diego Supercomp Ctr MC0505, La Jolla, CA 92093 USA. RP Martin, JML (reprint author), Weizmann Inst Sci, Dept Organ Chem, Kimmelman Bldg,Room 262, IL-76100 Rehovot, Israel. EM comartin@wicc.weizmann.ac.il RI Baldridge, Kim/E-6422-2011; Lee, Timothy/K-2838-2012; Martin, Jan/A-7457-2008 OI Baldridge, Kim/0000-0001-7171-3487; Martin, Jan/0000-0002-0005-5074 NR 92 TC 27 Z9 27 U1 0 U2 6 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0026-8976 EI 1362-3028 J9 MOL PHYS JI Mol. Phys. PD OCT 20 PY 1999 VL 97 IS 8 BP 945 EP 953 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 251ZV UT WOS:000083477000003 ER PT J AU Wright, TJ Parsons, BE Jackson, JA Haynes, M Fielding, EJ England, PC Clarke, PJ AF Wright, TJ Parsons, BE Jackson, JA Haynes, M Fielding, EJ England, PC Clarke, PJ TI Source parameters of the 1 October 1995 Dinar (Turkey) earthquake from SAR interferometry and seismic bodywave modelling SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE earthquakes; SAR; interferometry; seismic migration; body waves; models ID POSITIONING SYSTEM MEASUREMENTS; MOMENT TENSOR SOLUTIONS; LOMA-PRIETA EARTHQUAKE; COSEISMIC DEFORMATION; RADAR INTERFEROMETRY; LANDERS EARTHQUAKE; GREECE EARTHQUAKE; ACTIVE TECTONICS; EUREKA VALLEY; AEGEAN SEA AB The 1 October 1995, M-s = 6.1 Dinar earthquake ruptured a 10 km section of the NW-SE Dinar-Civril fault. There are discrepancies between the published source parameters from seismic data, with seismic moments in disagreement by over a factor of two. We use both SAR interferometry and seismic bodywave modelling to determine earthquake source parameters. An interferogram generated from ERS-1/2 SAR imagery spanning the event, and separated by 5 months, is used to derive source parameters by a downhill simplex inversion with multiple Monte-Carlo restarts. We model the displacements in the satellite line of sight, initially using uniform slip on a rectangular dislocation in an elastic half-space. The resultant model fault plane agrees in strike and location with the observed surface break, but systematic residuals exist in the line-of-sight deformation field, resulting in a r.m.s. residual of 20 mm in the interferogram. The residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane. Our best-fitting solution? with a r.m.s. misfit of 8 mm, reveals two distinct areas of slip on the fault plane (strike 145 degrees, dip 49 degrees, rake 270 degrees): a main rupture slipping by 1.44 m between depths of 1 and 8 km, becoming deeper to the SE and matching the observed surface rupture, and an along-strike continuation to the NW of the same fault plane, but between depths of 8 and 13 km and not associated with a surface break. The total geodetic moment (4.5 +/- 0.1 x 10(18) Nm) is more than twice as large as published seismic moments based on the inversion of P-waveforms alone, but close to the Harvard CMT moment (4.7 x 10(18) Nm). We use SH-waveforms, in addition to the P-waves used previously, to determine an alternative seismic source mechanism. SH-waves constrain the depth to be shallower than solutions based on P-waves alone, agreeing with the depths from the interferometric inversion and resulting in a larger moment (3.1 +/- 0.4 x 10(18) Nm) than the previous bodywave estimates (2, 2.1 x 10(18) Nm). The CMT moment reduces in magnitude to a similar size (3.3 x 10(18) Nm) if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry. Thus, the geodetic moment is 40% bigger than the moment determined from seismology. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Oxford, Dept Earth Sci, Parks Rd, Oxford OX1 3PR, England. Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ, England. Nigel Press Associates, Edenbridge TN8 6SR, Kent, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wright, TJ (reprint author), Univ Oxford, Dept Earth Sci, Parks Rd, Oxford OX1 3PR, England. RI Clarke, Peter/B-1783-2008; Wright, Tim/A-5892-2011; Parsons, Barry/K-4716-2012; England, Philip/A-1920-2010; Fielding, Eric/A-1288-2007 OI Clarke, Peter/0000-0003-1276-8300; Wright, Tim/0000-0001-8338-5935; England, Philip/0000-0002-9024-8901; Fielding, Eric/0000-0002-6648-8067 NR 46 TC 99 Z9 103 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD OCT 15 PY 1999 VL 172 IS 1-2 BP 23 EP 37 DI 10.1016/S0012-821X(99)00186-7 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 252XL UT WOS:000083527500003 ER PT J AU Singh, HB Thompson, AM Schlager, H AF Singh, HB Thompson, AM Schlager, H TI SONEX airborne mission and coordinated POLINAT-2 activity: overview and accomplishments SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EMISSIONS; AIRCRAFT AB The SASS (Subsonic Assessment) Ozone and NOX Experiment (SONEX) was an airborne field campaign conducted in October-November 1997 in the vicinity of the North Atlantic Flight Corridor to study the impact of aircraft emissions on NOX and ozone (O-3). A fully instrumented NASA DC-8 aircraft was used as the primary SONEX platform. SONEX activities were closely coordinated with the European POLINAT-2 (Pollution from Aircraft Emissions in the North Atlantic Flight Corridor) program, which used a Falcon-20 aircraft. Both campaigns focused on the upper troposphere/"lowermost" stratosphere (UT/LS) as the region of greatest interest. Specific sampling goals were achieved with the aid of a state-of-the art modeling and meteorological support system, which allowed targeted sampling of air parcels with desired characteristics. A substantial impact of aircraft emissions on NOX, O-3, and CN in the UT/LS of the study region is shown to be present. This mission provided direct support for the highly nonlinear nature of the NOX-O-3 chemistry. The results are being published in Special Sections of GRL and JGR. This overview provides a context within which these publications can be understood. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. DLR, D-82230 Wessling, Germany. RP Singh, HB (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 11 TC 47 Z9 48 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3053 EP 3056 DI 10.1029/1999GL900588 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000001 ER PT J AU Talbot, RW Dibb, JE Scheuer, EM Kondo, Y Koike, M Singh, HB Salas, LB Fukui, Y Ballenthin, JO Meads, RF Miller, TM Hunton, DE Viggiano, AA Blake, DR Blake, NJ Atlas, E Flocke, F Jacob, DJ Jaegle, L AF Talbot, RW Dibb, JE Scheuer, EM Kondo, Y Koike, M Singh, HB Salas, LB Fukui, Y Ballenthin, JO Meads, RF Miller, TM Hunton, DE Viggiano, AA Blake, DR Blake, NJ Atlas, E Flocke, F Jacob, DJ Jaegle, L TI Reactive nitrogen budget during the NASA SONEX mission SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CATALYTIC REDUCTION TECHNIQUE; PEROXYACETYL NITRATE PAN; NOY; TROPOSPHERE; ATMOSPHERE AB The SASS Ozone and Nitrogen Oxides Experiment (SONEX) over the North Atlantic during October/November 1997 offered an excellent opportunity to examine the budget of reactive nitrogen in the upper troposphere (8 - 12 km altitude). The median measured total reactive nitrogen (NO,) mixing ratio was 425 parts per trillion by volume (pptv). A data set merged to the HNO3 measurement time resolution was used to calculate NOy (NOy sum) by summing the reactive nitrogen species (a combination of measured plus modeled results) and comparing it to measured NOy (NOy meas.). Comparisons were done for tropospheric air (O-3 <100 parts per billion by volume (ppbv)) and stratospherically influenced air (O-3 > 100 ppbv) with both showing good agreement between NOy sum and NOy meas. (slope >0.9 and r(2) approximate to 0.9). The total reactive nitrogen budget in the upper troposphere over the North Atlantic appears to be dominated by a mixture of NOx (NO + NO2), HNO3, and PAN. In tropospheric air median values of NOx/NOy were approximate to 0.25, HNO3/NOy approximate to 0.35 and PAN/NOy approximate to 0.17. Particulate NO3- and alkyl nitrates together composed <10% of NOy, while model estimated HNO4 averaged 12%. For the air parcels sampled during SONEX, there does not appear to be a large reservoir of unidentified NOy compounds. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. USAF, Res Lab, VSBP, Hanscom AFB, MA 01731 USA. Univ Calif Irvine, Dept Chem, Irvine, CA USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Talbot, RW (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. RI Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012; Atlas, Elliot/J-8171-2015 NR 18 TC 41 Z9 42 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3057 EP 3060 DI 10.1029/1999GL900589 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000002 ER PT J AU Kondo, Y Koike, M Ikeda, H Anderson, BE Brunke, KE Zhao, Y Kita, K Sugita, T Singh, HB Liu, SC Thompson, A Gregory, GL Shetter, R Sachse, G Vay, SA Browell, EV Mahoney, MJ AF Kondo, Y Koike, M Ikeda, H Anderson, BE Brunke, KE Zhao, Y Kita, K Sugita, T Singh, HB Liu, SC Thompson, A Gregory, GL Shetter, R Sachse, G Vay, SA Browell, EV Mahoney, MJ TI Impact of aircraft emissions on NOx in the lowermost stratosphere at northern midlatitudes SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIRBORNE OBSERVATIONS; TROPOSPHERE AB Airborne measurements of NOx, total reactive nitrogen (NOy), O-3, and condensation nuclei (CN) were made within air traffic corridors over the U.S. and North Atlantic regions (35-60 degrees N) in the fall of 1997. NOx and NOy data obtained in the lowermost stratosphere (LS) were examined using the calculated increase in NOy (Delta NOy) along five-day back trajectories as a parameter to identify possible effects of aircraft on reactive nitrogen. It is very likely that aircraft emissions had a significant impact on the NOx levels in the LS inasmuch as the NOx mixing ratios at 8.5-12 km were significantly correlated with the independent parameters of aircraft emissions, i.e., Delta NOy levels and CN values. In order to estimate quantitatively the impact of aircraft emissions on NOx and CN, the background levels of CN and NOx at O-3 = 100-200 ppbv were derived from the correlations of these quantities with Delta NOy. On average, the aircraft emissions are estimated to have increased the NOx and CN values by 130 pptv and 400 STP cm(-3), respectively, which corresponds to 70+/-30 % and 30+/-20 % of the observed median values. C1 Nagoya Univ, Solar Terr Environm Lab, Aichi 448507, Japan. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Christopher Newport Univ, Newport News, VA 23606 USA. Univ Tokyo, Tokyo, Japan. Natl Inst Environm Studies, Tsukuba, Ibaraki, Japan. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Georgia Inst Technol, Atlanta, GA 30332 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Kondo, Y (reprint author), Nagoya Univ, Solar Terr Environm Lab, 3-13 Honohara, Aichi 448507, Japan. RI Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012; Thompson, Anne /C-3649-2014; OI Thompson, Anne /0000-0002-7829-0920; Sugita, Takafumi/0000-0002-0508-7040 NR 13 TC 7 Z9 7 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3065 EP 3068 DI 10.1029/1999GL900376 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000004 ER PT J AU Anderson, BE Cofer, WR Crawford, J Gregory, GL Vay, SA Brunke, KE Kondo, Y Koike, M Schlager, H Baughcum, SL Jensen, E Zhao, YJ Kita, K AF Anderson, BE Cofer, WR Crawford, J Gregory, GL Vay, SA Brunke, KE Kondo, Y Koike, M Schlager, H Baughcum, SL Jensen, E Zhao, YJ Kita, K TI An assessment of aircraft as a source of particles to the upper troposphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ULTRAFINE AEROSOL-PARTICLES; AIRBORNE OBSERVATIONS; EXHAUST PLUMES; LOWER STRATOSPHERE; EMISSIONS AB Condensation nuclei measurements are examined in conjunction with measurements of reactive nitrogen species (NO(y)) to identify aircraft plumes in primary air traffic corridors over the North Atlantic. Several hundred plumes exhibiting greater than or equal to 100 pptv enhancements in NO(y) mixing ratio were observed. The plumes were typically a few hundred meters wide, exhibited high NO/NO(y) ratios, and ranged in age from similar to 10 minutes to similar to 10 hours. Assuming the sampled aircraft emitted similar to 12 g NO(x) (as NO(2)) kg(-1) fuel burned and that the loss of NO, to the particle phase was negligible, we calculate median aerosol emission indices in terms of number of particles kg(-1) of fuel burned of similar to 120 x 10(15) for CN greater than or equal to 8 nm in size; similar to 50 x 10(15) for CN greater than or equal to 17 nm; and similar to 3 x 10(15) for the nonvolatile CN greater than or equal to 17 nm. Using published fuel burn statistics, background aerosol concentrations, and a 10 day particle lifetime, we conclude that present aviation sources enhance global averaged upper-tropospheric fine and nonvolatile aerosol number densities by similar to 6% and similar to 3%, respectively. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Christopher Newport Univ, Newport News, VA 23606 USA. Nagoya Univ, Nagoya, Aichi, Japan. DLR, Oberpfaffenhofen, Germany. Boeing Co, Seattle, WA 98124 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Tokyo, Tokyo, Japan. RP Anderson, BE (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. EM B.E.Anderson@larc.nasa.gov RI Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012; Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 21 TC 21 Z9 21 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3069 EP 3072 DI 10.1029/1999GL900276 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000005 ER PT J AU Thompson, AM Sparling, LC Kondo, Y Anderson, BE Gregory, GL Sachse, GW AF Thompson, AM Sparling, LC Kondo, Y Anderson, BE Gregory, GL Sachse, GW TI Perspectives on NO, NOy and fine aerosol sources and variability during SONEX SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Distributions of upper tropospheric tracer data on each of the 14 science flights of SONEX (SASS [Subsonics Assessment] Ozone and Nitrogen Oxides Experiment) provide a statistical overview of NO, NOy and fine aerosol variability during SONEX tan aircraft mission conducted in October and November 1997). The wide range of variability of NO from all sources provides a perspective on the aircraft perturbation. Background distributions of NOy are somewhat elevated inside flight corridors relative to outside; fine aerosol and NO/NOy in and out of corridors are similar. The potential vorticity of air sampled during SONEX is low relative to the NAFC (North Atlantic Flight Corridor) as a whole, due either to advection of lower latitude air into the corridor or biases in sampling to avoid the stratosphere. High NO/NOy (>0.4) from fresh lightning acid aircraft sources was usually associated with pv much lower than the NAFC as a whole. Air masses identified as tropospheric by a low ozone criterion nevertheless have high pv, a marker for stratospheric air. Thus, stratospheric and surface sources also contribute to overall variability. A statistically robust assessment of the relative aircraft NO contribution during SONEX, based on data alone, is unlikely, given the mixture of other NO sources within which the aircraft signal is embedded. This underscores the need for more data and modeling studies. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. Nagoya Univ, Solar Terr Lab, Toyakawa, Japan. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Thompson, AM (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916, Greenbelt, MD 20771 USA. RI Kondo, Yutaka/D-1459-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 5 TC 26 Z9 26 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3073 EP 3076 DI 10.1029/1999GL900581 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000006 ER PT J AU Brune, WH Tan, D Faloona, IF Jaegle, L Jacob, DJ Heikes, BG Snow, J Kondo, Y Shetter, R Sachse, GW Anderson, B Gregory, GL Vay, S Singh, HB Davis, DD Crawford, JH Blake, DR AF Brune, WH Tan, D Faloona, IF Jaegle, L Jacob, DJ Heikes, BG Snow, J Kondo, Y Shetter, R Sachse, GW Anderson, B Gregory, GL Vay, S Singh, HB Davis, DD Crawford, JH Blake, DR TI OH and HO2 chemistry in the North Atlantic free troposphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Interactions between atmospheric hydrogen oxides and aircraft nitrogen oxides determine the impact of aircraft exhaust on atmospheric chemistry. To study these interactions, the Subsonic Assessment: Ozone and Nitrogen Oxide Experiment (SONEX) assembled the most complete measurement complement to date for studying HOx (OH and HO2) chemistry in the free troposphere. Observed and modeled HOx agree on average to within experimental uncertainties (+/-40%). However, significant discrepancies occur as a function of NO and at solar zenith angles >70 degrees. Some discrepancies appear to be removed by model adjustments to HOx-NOx chemistry, particularly by reducing HO2NO2 (PNA) and by including heterogeneous reactions on aerosols and cirrus clouds. C1 Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, England. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi, Japan. NCAR, Div Atmospher Chem, Boulder, CO USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Georgia Inst Technol, Sch Geophys Sci, Atlanta, GA 30332 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. RP Brune, WH (reprint author), Penn State Univ, Dept Meteorol, 503 Walker Bldg, University Pk, PA 16802 USA. RI Kondo, Yutaka/D-1459-2012; Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 12 TC 55 Z9 55 U1 1 U2 16 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3077 EP 3080 DI 10.1029/1999GL900549 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000007 ER PT J AU Jaegle, L Jacob, DJ Brune, WH Faloona, IC Tan, D Kondo, Y Sachse, GW Anderson, B Gregory, GL Vay, S Singh, HB Blake, DR Shetter, R AF Jaegle, L Jacob, DJ Brune, WH Faloona, IC Tan, D Kondo, Y Sachse, GW Anderson, B Gregory, GL Vay, S Singh, HB Blake, DR Shetter, R TI Ozone production in the upper troposphere and the influence of aircraft during SONEX: Approach of NOx-saturated conditions SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HO2; OH AB During October/November 1997, simultaneous observations of NO, HO2 and other species were obtained as part of the SONEX campaign in the upper troposphere. We use these observations, over the North Atlantic (40-60 degrees N), to derive ozone production rates, P(O-3), and to examine the relationship between P(O-3) and the concentrations of NOx (= NO + NO2) and HOx (= OH + peroxy) radicals. A positive correlation is found between P(O-3) and NOx over the entire data set, which reflects the association of elevated HOx with elevated NOx injected by deep convection and lightning. By filtering out this association we find that for NOx>70 pptv, P(O-3) is nearly independent of NOx, showing the approach of NOx-saturated conditions. Predicted doubling of aircraft emissions in the future will result in less than doubling of the aircraft contribution to ozone over the North Atlantic in the fall. Greater sensitivity to aircraft emissions would be expected in the summer. C1 Harvard Univ, Div Engn & Appl Sci, Cambridge, MA 02138 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi, Japan. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Jaegle, L (reprint author), Harvard Univ, Div Engn & Appl Sci, 29 Oxford St,Pierce Hall, Cambridge, MA 02138 USA. RI Kondo, Yutaka/D-1459-2012 NR 11 TC 41 Z9 41 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3081 EP 3084 DI 10.1029/1999GL900451 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000008 ER PT J AU Stachnik, RA Salawitch, R Engel, A Schmidt, U AF Stachnik, RA Salawitch, R Engel, A Schmidt, U TI Measurements of chlorine partitioning in the winter Arctic stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID POLAR VORTEX; EVOLUTION; OZONE; CLO; HCL AB Measurements of the concentration profiles of key stratospheric reactive, reservoir and source gases, ClO, O-3, HCl, N2O and CCl2F2, were made during two balloon flights in the Arctic on 27 January and 08 March 1995 that were part of the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME). On 27 January, low abundances of HCl (similar to 250 ppt at 50 hPa) were measured in air parcels that had been at temperatures below the type I PSC existence threshold accompanied by high concentrations of ClO (1.6 ppb at 50 hPa). Calculations using the currently recommended photochemical data yield a ratio of [ClO]+2[Cl2O2]+[HCl] to [Cl-y] near unity in these air parcels. The 08 March flight sampled warm stratospheric conditions outside the vortex with normal mid-latitude ClO (<100ppt at 50 hPa) and HCl abundances comprising about half of the available chlorine at 50 hPa. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Frankfurt, Inst Meteorol & Geophys, D-60325 Frankfurt, Germany. RP Stachnik, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Salawitch, Ross/B-4605-2009; Engel, Andreas/E-3100-2014 OI Salawitch, Ross/0000-0001-8597-5832; Engel, Andreas/0000-0003-0557-3935 NR 16 TC 14 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3093 EP 3096 DI 10.1029/1999GL010817 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000011 ER PT J AU Signorini, SR McClain, CR Dandonneau, Y AF Signorini, SR McClain, CR Dandonneau, Y TI Mixing and phytoplankton bloom in the wake of the Marquesas Islands SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EQUATORIAL PACIFIC-OCEAN AB A persistent phytoplankton bloom was observed during August-December 1998 around the Marquesas Islands in the South Pacific using a spaceborne ocean color sensor. The enhancement of the phytoplankton production is attributed to the island mass effect. The effect consists of a combination of turbulent mixing and advection from the south equatorial current flowing through and around the islands, and iron-enriched waters originating from land drainage and hydrothermal fluxes through old volcanic formations. The enhanced phytoplankton production effects are noticeable a large distance downstream from the island (500 to 1000 km). This island mass effect is an important contributor to the productivity of the region and therefore potentially important for fisheries in the area. C1 SAIC Gen Sci Corp, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Sea WiFS Project, Greenbelt, MD 20771 USA. Univ Paris 06, CNRS, Lab Oceanog Dinam & Climatol, F-75252 Paris, France. RP Signorini, SR (reprint author), SAIC Gen Sci Corp, 4600 Powder Mill Rd, Beltsville, MD 20705 USA. NR 19 TC 43 Z9 44 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3121 EP 3124 DI 10.1029/1999GL010470 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000018 ER PT J AU Cummer, SA Stanley, M AF Cummer, SA Stanley, M TI Submillisecond resolution lightning currents and sprite development: Observations and implications SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ELF RADIATION; RED SPRITES AB We analyze synchronized high speed video images and ELF-VLF radio emissions from 11 sprite clusters observed on 6 October 1997. Quantitative analysis shows that vertical lightning charge moment changes of 150-1100 C.km occurred before the optical emissions reached their peak with delays of 2-11 ms from the lightning discharge. This threshold unexpectedly decreases with increasing delay from parent lightning to peak emissions. We also find that sprite charge moment change and minimum sprite altitude are not well correlated with the vertical charge moment change in the parent discharge. These observations do not agree well with present sprite generation models, and we suggest that streamer development and horizontal lightning charge motion can play a significant role in sprite generation. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. New Mexico Tech, Dept Phys, Socorro, NM 87801 USA. RP Cummer, SA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 690, Greenbelt, MD 20771 USA. RI Cummer, Steven/A-6118-2008 OI Cummer, Steven/0000-0002-0002-0613 NR 12 TC 26 Z9 27 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1999 VL 26 IS 20 BP 3205 EP 3208 DI 10.1029/1999GL003635 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 246JE UT WOS:000083160000039 ER EF