FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Chambers, JE AF Chambers, JE TI Making more terrestrial planets SO ICARUS LA English DT Article DE accretion; planetary formation; Earth; terrestrial planets; extrasolar planets ID N-BODY SIMULATIONS; SOLAR NEBULA; NUMERICAL-SIMULATION; LATE-STAGE; STABILITY; ASTEROIDS; EMBRYOS; SYSTEM; FRAGMENTATION; PLANETESIMALS AB The results of 16 new 3D N-body simulations of the final stage of the formation of the terrestrial planets are presented. These N-body integrations begin with 150-160 lunar-to-Mars size planetary embryos, with semi-major axes 0.3 < a < 2.0 AU, and include perturbations from Jupiter and Saturn. Two initial mass distributions are examined: approximately uniform masses, and a bimodal distribution with a few large and many small bodies. In most of the integrations, systems of three or four terrestrial planets form within about 200 million years. These planets have orbital separations similar to the terrestrial planets, and the largest body contains 1/3-2/3 of the surviving mass. The final planets typically have larger eccentricities, e, and inclinations, i than the time-averaged values for Earth and Venus. However, the values of e and i are lower than in earlier N-body integrations which started with fewer embryos. The spin axes of the planets have approximately random orientations, unlike the terrestrial planets, and the high degree of mass concentration in the region occupied by Earth and Venus is not reproduced in any of the simulations. The principal effect of using an initially bimodal mass distribution is to increase the final number of planets. Each simulation ends with an object that is an approximate analogue of Earth in terms of mass and heliocentric distance. These Earth analogues reach 50% (90%) of their final mass with a median time of 20 (50) million years, and they typically accrete some material from all portions of the disk. (C) 2001 Academic Press. C1 Armagh Observ, Armagh BT61 9DG, North Ireland. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Chambers, JE (reprint author), Armagh Observ, Armagh BT61 9DG, North Ireland. NR 39 TC 281 Z9 287 U1 3 U2 12 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 AUG PY 2001 VL 152 IS 2 BP 205 EP 224 DI 10.1006/icar.2001.6639 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 457UC UT WOS:000170154400001 ER PT J AU Grogan, K Dermott, SF Durda, DD AF Grogan, K Dermott, SF Durda, DD TI The size-frequency distribution of the zodiacal cloud: Evidence from the solar system dust bands SO ICARUS LA English DT Article DE asteroids; dynamics; interplanetary dust; zodiacal light ID ASTEROID BELT; ORIGIN; EMISSION; MODELS; SEARCH; IRAS AB Recent observations of the size-frequency distribution of zodiacal cloud particles obtained from the cratering record on the LDEF satellite are the latest evidence for a significant large particle population (100-mum diameter or greater) near 1 AU. Our previous modeling of the Solar System dust bands, features of the zodiacal cloud associated with the comminution of Hirayama family asteroids, has been limited by the fact that only small particles (25-mum diameter or smaller) have been considered. This was due to the prohibitively large amount of computing power required to numerically analyze the dynamics of larger particles. The recent availability of inexpensive, fast processors has finally made this work possible. Models of the dust bands are created, built from individual dust particle orbits, taking into account a size-frequency distribution of the material and the dynamical history of the constituent particles. These models are able to match both the shapes and amplitudes of the dust band structures observed by IRAS in multiple wavebands. The size-frequency index, q, that best matches the observations is approximately 1.4, a distribution in which the surface area (and hence the infrared emission) is dominated by large particles. However, in order to successfully model the "ten degree" band, which is usually associated with collisional activity within the Eos family, we find that the mean proper inclination of the dust particle orbits has to be approximately 9.35 degrees, significantly different from the mean proper inclination of the Eos family (10.08 degrees). (C) 2001 Academic Press. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. SW Res Inst, Boulder, CO 80302 USA. RP Grogan, K (reprint author), NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 43 TC 63 Z9 63 U1 1 U2 2 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 AUG PY 2001 VL 152 IS 2 BP 251 EP 267 DI 10.1006/icar.2001.6638 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 457UC UT WOS:000170154400005 ER PT J AU Matcheva, KI Strobel, DF Flasar, FM AF Matcheva, KI Strobel, DF Flasar, FM TI Interaction of gravity waves with ionospheric plasma: Implications for Jupiter's ionosphere SO ICARUS LA English DT Article DE Jupiter; ionosphere; dynamics; aeronomy; planets ID TID RELATIONSHIP; THERMOSPHERE; ATMOSPHERE; MODEL; IONS; RECOMBINATION; CHEMISTRY; KINETICS; REGION; H-3(+) AB The J0-ingress radio occultation of the Galileo orbiter by Jupiter exhibits a system of well-defined, regularly spaced electron layers in the altitude range where the presence of gravity waves have been previously inferred. Based on the terrestrial analog of sporadic E and spread F ionospheric layers, we argue that the observed layers are a result of dynamical processes rather than chemistry. We consider the impact of upward propagating gravity waves on the plasma distribution in a H+ dominated ionosphere. The relevant physics is discussed and illustrated with an analytic, small-amplitude model. A time-dependent, 2D, large-amplitude model is developed to simulate the observed large excursions in the J0-electron density profile. We show that gravity waves with parameters consistent with the thermal structure of Jupiter's upper atmosphere are capable of creating large peaks in the electron density similar to the observed ones. The ionospheric response is extremely anisotropic with respect to the direction of wave propagation. We demonstrate that the location of the J0-ingress radio occultation on Jupiter favors large ionospheric response for waves propagating along the magnetic meridian. A wave driven plasma flux results in plasma removal above the altitude of maximum ionospheric response and plasma deposition in the region below, significantly modifying the initial steady state electron density profile. (C) 2001 Academic Press. C1 Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Matcheva, KI (reprint author), Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. RI Flasar, F Michael/C-8509-2012 NR 45 TC 20 Z9 20 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 AUG PY 2001 VL 152 IS 2 BP 347 EP 365 DI 10.1006/icar.2001.6631 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 457UC UT WOS:000170154400011 ER PT J AU Meadows, V Crisp, D Barnes, J Orton, G Spencer, J AF Meadows, V Crisp, D Barnes, J Orton, G Spencer, J TI AAT observations of the SL9 fragment C, D, G, K, N, R, V, and W impacts with Jupiter: Lightcurves and imaging SO ICARUS LA English DT Article DE comets, SL9; Jupiter; impact processes; infrared observations; photometry ID COMET SHOEMAKER-LEVY-9; INFRARED OBSERVATIONS; TELESCOPE; COLLISION AB We used the InfraRed Imaging Spectrometer (IRIS) on the Anglo-Australian Telescope to monitor the July 1994 impacts of Comet Shoemaker-Levy 9 with Jupiter. Spectral image cubes were obtained for the impacts of fragments C, D, G, K, R, and W. These data provide time sequences of spatially resolved spectra in K-band (1.98 to 2.40 mum), with a spectral resolution of 300 (lambda/Delta lambda) and a spatial sampling of 0.6 arcsec/pixel. Fast-rate 2.35-mum filter photometry was used to monitor the impacts of fragments N and V. Our imaging and spectral observations track the entire evolution of each impact, from the time the fragment entered the jovian atmosphere, until the impact site rotates into view. In this paper, we concentrate on photometry and imaging results. We present photometrically calibrated lightcurves for seven impacts, and an estimate of the peak brightness for the V impact. Each event we observed, with the exception of V, was first detected as a faint "precursor," which was followed 5-10 min later by a much brighter "main event." Precursor flashes for fragments G and K were first recorded about 30 and 90 s before an impact event was detected by instruments on the Galileo spacecraft. The precursor for the N impact was seen in our data 4 s before detection by the Galileo SSI, but may have occurred up to 30 s earlier due to gaps in our time sampling. The steady initial brightening of the lightcurves for fragments G and K indicates that these impacts may have been preceded by infalling dust. A radiative transfer model was used to determine the minimum vertical altitude at which the incoming meteor would have been directly visible to ground-based observers. The results indicate that the first precursor is most likely due to detection of impacting dust from each fragment's coma, rather than a bolide produced by the fragment itself. The onset of the main event and the first detection of high-temperature CO occur at times that are not a function of impactor energy. However, the time to reach peak brightness in the NIR lightcurves is a strong function of impactor energy, with lowest to highest energy impactors (N to K) taking from 2 to 8 min to reach peak flux after the onset of the main event. Very different peak impact brightnesses were found when comparing fragments from the main comet train with fragments with similar preimpact brightnesses that had been observed to travel displaced from the main train. These differences indicate compositional or structural differences between these two families of fragments. (C) 2001 Academic Press C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Dept Astron, Pasadena, CA 91125 USA. Lowell Observ, Flagstaff, AZ 86001 USA. RP Meadows, V (reprint author), CALTECH, Jet Prop Lab, MS183-900,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Barnes, Jason/B-1284-2009 OI Barnes, Jason/0000-0002-7755-3530 NR 30 TC 2 Z9 2 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 AUG PY 2001 VL 152 IS 2 BP 366 EP 383 DI 10.1006/icar.2001.6645 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 457UC UT WOS:000170154400012 ER PT J AU Lebonnois, S Toublanc, D Hourdin, F Rannou, P AF Lebonnois, S Toublanc, D Hourdin, F Rannou, P TI Seasonal variations of Titan's atmospheric composition SO ICARUS LA English DT Review DE Titan; photochemistry; atmospheres - composition; atmospheres - dynamics ID PHOTOABSORPTION CROSS-SECTIONS; RESOLVED ATOMIC RESONANCE; TEMPERATURE RATE COEFFICIENTS; GENERAL-CIRCULATION MODEL; EVALUATED KINETIC DATA; ABSOLUTE RATE-CONSTANT; X-RAY PHOTOABSORPTION; CN RADICAL REACTIONS; VACUUM ULTRA-VIOLET; OUTER SOLAR-SYSTEM AB In order to investigate seasonal variations of the composition of Titan's low stratosphere, we developed a two-dimensional (latitude-altitude) photochemical and transport model. Large-scale advection, hidden in the vertical eddy diffusion for one-dimensional models, is accounted for explicitly. Atmospheric dynamics is prescribed using results of independent numerical simulations of the atmospheric general circulation. Both the mean meridional transport and latitudinal mixing by transient planetary waves are taken into account. Chemistry is based on 284 reactions involving 40 hydrocarbons and nitriles. Photodissociation rates are based on a three-dimensional description of the ultraviolet flux. For most species, the model fits well the latitudinal variations observed by Voyager I giving for the first time a full and self-consistent interpretation of these observations. In particular, the enrichment of the high northern latitudes is attributed to subsidence during the winter preceeding the Voyager encounter. Discrepancies are observed for C2H4, HC3N, and C2N2 and are attributed to problems in the chemical scheme. Sensitivity to dynamical parameters is investigated. The vertical eddy diffusion coefficient keeps an important role for the upper atmosphere. The wind strength and horizontal eddy diffusion strongly control the latitudinal behavior of the composition in the low stratosphere, while mean concentrations appear to be essentially controlled by chemistry. (C) 2001 Academic Press. C1 Ctr Etud Spatiale Rayonnements, F-31028 Toulouse 04, France. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. CNRS, UMPC, Meteorol Dynam Lab, F-75252 Paris 05, France. CNRS, UMPC, Serv Aeron, F-75252 Paris 05, France. RP Lebonnois, S (reprint author), Ctr Etud Spatiale Rayonnements, 9 Av Col Roche,BP 4346, F-31028 Toulouse 04, France. RI RANNOU, Pascal/I-9059-2012; OI LEBONNOIS, SEBASTIEN/0000-0002-2390-8164 NR 146 TC 141 Z9 142 U1 0 U2 11 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 AUG PY 2001 VL 152 IS 2 BP 384 EP 406 DI 10.1006/icar.2001.6632 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 457UC UT WOS:000170154400013 ER PT J AU West, WC Whitacre, JF Brandon, EJ Ratnakumar, BV AF West, WC Whitacre, JF Brandon, EJ Ratnakumar, BV TI Lithium micro-battery development at the jet propulsion laboratory SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article AB Recent successes in the effort to miniaturize spacecraft components using MEMS technology, integrated passive components, and low power electronics have driven the need for very low power, low profile, low mass micro-power sources for micro/nanospacecraft applications. Recent work at JPL has focused upon developing thin film/micro-batteries compatible with temperature sensitive substrates. A process to prepare crystalline LiCoO2 films with RF sputtering and moderate (< 700 degreesC) annealing temperature has been developed. Thin film batteries with cathode films prepared with this process have specific capacities approaching the practical limit for LiCoO2, with acceptable rate capabilities and discharge voltage profiles. Solid-state micro-scale batteries have also been fabricated with feature sizes on the order of 50 microns. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP West, WC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 277-207, Pasadena, CA 91109 USA. NR 8 TC 16 Z9 16 U1 0 U2 7 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 AUG PY 2001 VL 16 IS 8 BP 31 EP 33 DI 10.1109/62.942217 PG 3 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA 464NY UT WOS:000170539700009 ER PT J AU Huang, J AF Huang, J TI The development of inflatable array antennas SO IEEE ANTENNAS AND PROPAGATION MAGAZINE LA English DT Article DE satellite antennas; antenna arrays; antenna mechanical factors; planar arrays; synthetic aperture radar; satellite communication; inflatable antennas; reflectarray ID MICROSTRIP AB Inflatable array antennas are being developed to significantly reduce the mass, the launch vehicle's stowage volume, and the cost of future spacecraft systems. Three inflatable array antennas, recently developed for spacecraft applications, are a 3.3 rn x 1.0 m L-band synthetic-aperture radar (SAR) array, a 1.0 m-diameter X-band telecom reflectarray, and a 3 m-diameter Ka-band telecom reflectarray. All three antennas are similar in construction, and each consists of an inflatable tubular frame that supports and tensions a multi-layer thin-membrane RF radiating surface with printed microstrip patches. The L-band SAR array achieved a bandwidth of 80 MHz, an aperture efficiency of 74%, and a total mass of 15 kg. The X-band reflectarray achieved an aperture efficiency of 37%, good radiation patterns, and a total mass of 1.2 kg (excluding the inflation system). The 3 m Ka-band reflectarray achieved a surface flatness of 0.1 mm RMS, good radiation patterns, and a total mass of 12.8 kg (excluding the inflation system). These antennas demonstrated that inflatable arrays are feasible across the microwave and millimeter-wave spectrums. Further developments of these antennas are deemed necessary, in particular, in the area of qualifying the inflatable structures for space-environment usage. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Huang, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM john.huang@jpl.nasa.gov NR 12 TC 25 Z9 29 U1 1 U2 8 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1045-9243 EI 1558-4143 J9 IEEE ANTENN PROPAG M JI IEEE Antennas Propag. Mag. PD AUG PY 2001 VL 43 IS 4 BP 44 EP 50 DI 10.1109/74.951558 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 474TD UT WOS:000171122200005 ER PT J AU Radisic, V Samoska, L Micovic, M Hu, M Janke, P Ngo, C Nguyen, L AF Radisic, V Samoska, L Micovic, M Hu, M Janke, P Ngo, C Nguyen, L TI 80 GHz MMIC HEMT VCO SO IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS LA English DT Article DE MMIC oscillators; MODFETs AB In this letter, a monolithic voltage-controlled oscillator (VCO) operating in the 77.5-83.5 GHz range is presented. InP HEMTs are used for both the active device and varactor. The VCO demonstrated a tuning range of 6 GHz and an output power better than 12.5 dBm in the entire tuning range. C1 HRL Labs LLC, Malibu, CA 90265 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Radisic, V (reprint author), HRL Labs LLC, Malibu, CA 90265 USA. NR 6 TC 2 Z9 2 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 1531-1309 J9 IEEE MICROW WIREL CO JI IEEE Microw. Wirel. Compon. Lett. PD AUG PY 2001 VL 11 IS 8 BP 325 EP 327 DI 10.1109/7260.941778 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 464HB UT WOS:000170526200001 ER PT J AU Simon, MK Alouini, MS AF Simon, MK Alouini, MS TI Multiple symbol differential detection with diversity reception SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article; Proceedings Paper CT IEEE Global Telecommunication Conference (GLOBECOM 00) CY NOV 27-DEC 01, 2000 CL SAN FRANCISCO, CALIFORNIA SP IEEE, IEEE, Commun Soc, Internet Soc, ICC GLOBECOM, Telesys Software, AT&T, SPIE, Opt Networks Magazine, Net Gen Learning Syst, MathWorks Inc, Kluwer Acad Publishers, John Wiley & Sons DE differential detection; diversity reception; fading channels; error probability performance ID GENERALIZED FADING CHANNELS; UNIFIED APPROACH; PERFORMANCE; ERROR; NONCOHERENT; FEEDBACK; SIGNALS; PHASE; MPSK AB In this letter, we first consider the maximum-likelihood sequence estimator for multiple symbol differential detection (MSDD) over the slow fading diversity channel. Since this optimum decision metric results in a complex receiver implementation whose average bit-error probability (BEP) performance is difficult (if not impossible) to obtain analytically, we then focus our attention on evaluating the average BEP for MSDD with diversity reception in the form of postdetection equal-gain combining (EGC) giving emphasis to its ability to bridge the gap between EGC of conventional differentially detected M-PSK and maximal-ratio combining of coherently detected M-PSK with differential encoding. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Minnesota, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA. RP Simon, MK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 23 Z9 23 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 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD AUG PY 2001 VL 49 IS 8 BP 1312 EP 1319 DI 10.1109/26.939840 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 460RG UT WOS:000170321900003 ER PT J AU Kory, CL AF Kory, CL TI Investigation of fully three-dimensional helical RF field effects on TWT beam/circuit interaction SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE helix; interaction model; MAFIA; 3-D PIC simulations; traveling-wave-tube AB A fully three-dimensional (3-D), time-dependent, helical traveling-wave tube (TWT) interaction model has been developed using the electromagnetic particle-in-cell (PIC) code MAFIA, The model includes a short section of helical slow-wave circuit with excitation fed by RF input/output couplers, and electron beam contained by periodic permanent magnet (PPM) focusing. All components of the model are simulated in three dimensions allowing the effects of the fully 3-D helical fields on RF circuit/beam interaction to be investigated for the first time. The development of the interaction model is presented, and predicted TWT performance using 2.5-D and 3-D models is compared to investigate the effect of conventional approximations used in TWT analysis. C1 Analex Corp, Glenn Res Ctr, NASA, Cleveland, OH 44135 USA. RP Kory, CL (reprint author), Analex Corp, Glenn Res Ctr, NASA, Cleveland, OH 44135 USA. NR 15 TC 10 Z9 11 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 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD AUG PY 2001 VL 48 IS 8 BP 1718 EP 1726 DI 10.1109/16.936694 PG 9 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 455WP UT WOS:000170051000034 ER PT J AU Hilland, JE Wessen, RR Porter, D Austin, RS AF Hilland, JE Wessen, RR Porter, D Austin, RS TI A market-based conflict resolution approach for satellite mission planning SO IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT LA English DT Article DE data acquisition; market-based planning; mission planning; synthetic aperture radar ID SAR; SYSTEMS AB A market-based system has been developed to assist in mission planning for an Earth orbiting synthetic aperture radar mission. This approach was chosen over more traditional systems based on a functional model used to compare the market-based system with human-expert, thematic and geometric approaches. The market-based system enables participants to signal demands for spacecraft resources needed for data acquisitions by establishing a currency and "worth" for a particular data acquisition request. We compared a serial draft approach to two market-based approaches; a simple market and a priority market. The market systems utilized a planning period which ended when the value of the time-ordered data acquisition plan did not increase by 10% of the value of the previous round. The market-based approaches were superior to a serial draft approach and that a priority market had a 2% greater value than a simple market. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Tucson, AZ 85721 USA. Fed Data Corp, Pasadena, CA 91107 USA. RP Hilland, JE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 24 TC 4 Z9 4 U1 0 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9391 J9 IEEE T ENG MANAGE JI IEEE Trans. Eng. Manage. PD AUG PY 2001 VL 48 IS 3 BP 272 EP 282 DI 10.1109/17.946526 PG 11 WC Business; Engineering, Industrial; Management SC Business & Economics; Engineering GA 468DG UT WOS:000170742400002 ER PT J AU Owe, M de Jeu, R Walker, J AF Owe, M de Jeu, R Walker, J TI A methodology for surface soil moisture and vegetation optical depth retrieval using the microwave polarization difference index SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE microwave radiometry; remote sensing; soil moisture; vegetation ID EMISSION; MODEL; GHZ; PARAMETERS; CANOPIES; FIELDS; COVER AB A methodology for retrieving surface soil moisture and vegetation optical depth from satellite microwave radiometer data is presented. The procedure is tested with historical 6.6 GHz H and V polarized brightness temperature observations from the scanning multichannel microwave radiometer (SMMR) over several test sites in Illinois. Results using only nighttime data are presented at this time due to the greater stability of nighttime surface temperature estimation. The methodology uses a radiative transfer model to solve for surface soil moisture and vegetation optical depth simultaneously using a nonlinear iterative optimization procedure. It assumes known constant values for the scattering albedo and roughness, and that vegetation optical depth for H-polarization is the same as for V-polarization. Surface temperature is derived by a procedure using high frequency V-polarized brightness temperatures. The methodology does not require any field observations of soil moisture or canopy biophysical properties for calibration purposes and may be applied to other wavelengths. Results compare well with field observations of soil moisture and satellite-derived vegetation index data from optical sensors. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. RP Owe, M (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. NR 41 TC 353 Z9 369 U1 6 U2 50 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 AUG PY 2001 VL 39 IS 8 BP 1643 EP 1654 DI 10.1109/36.942542 PG 12 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 467CG UT WOS:000170682500004 ER PT J AU Le Vine, DM Jackson, TJ Swift, CT Haken, M Bidwell, SW AF Le Vine, DM Jackson, TJ Swift, CT Haken, M Bidwell, SW TI ESTAR measurements during the Southern Great Plains experiment (SGP99) SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE microwave radiometry; moisture; remote sensing; soil; synthetic aperture radar ID APERTURE MICROWAVE RADIOMETER; SOIL-MOISTURE AB During the Southern Great Plains experiment (SGP99), the electronically scanned thinned array radiometer (ESTAR) mapped L-band brightness temperature over a swath about 50-km wide and 300 km long, extending west from Oklahoma City, OK, to El Reno, OK, and north from the Little Washita River watershed to the Kansas border. ESTAR flew on the NASA P-3B Orion aircraft at an altitude of 7.6 km, and maps were made on seven days between July 8-20, 1999. The brightness temperature maps reflect the patterns of soil moisture expected from rainfall and are consistent with values of soil moisture observed at the research sites within the SGP99 study area and with previous measurements in this area. The data add to the resources for hydrologic modeling in this area and are further validation of the technology represented by ESTAR as a potential path to a future mission to map soil moisture globally from space. C1 NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. USDA ARS, Hydrol & Remote Sensing Lab, Beltsville, MD 20705 USA. Univ Massachusetts, Dept Elect Engn, Amherst, MA 01003 USA. RP Le Vine, DM (reprint author), NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NR 19 TC 20 Z9 20 U1 4 U2 5 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 AUG PY 2001 VL 39 IS 8 BP 1680 EP 1685 DI 10.1109/36.942546 PG 6 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 467CG UT WOS:000170682500008 ER PT J AU Reichle, RH McLaughlin, DB Entekhabi, D AF Reichle, RH McLaughlin, DB Entekhabi, D TI Variational data assimilation of microwave radiobrightness observations for land surface hydrology applications SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE data assimilation; land surface hydrology; representer method; soil moisture ID SOIL-MOISTURE; TEMPERATURE; MODEL; PREDICTION; ADJOINT AB Our ability to accurately describe large-scale variations in soil moisture is severely restricted by process uncertainty and the limited availability of appropriate soil moisture data. Remotely sensed microwave radiobrightness observations can cover large scales but have limited resolution and are only indirectly related to the hydrologic variables of interest. We describe a four-dimensional (4-D) variational assimilation algorithm that makes best use of available information while accounting for both measurement and model uncertainty. The representer method used here is more efficient than a Kalman filter because it avoids explicit propagation of state error covariances. In a synthetic example, which is based on a field experiment, we demonstrate estimation performance by examining data residuals. Such tests provide a convenient way to check the statistical assumptions of the approach and to assess its operational feasibility. Internally computed covariances show that the estimation error decreases with increasing soil moisture. An adjoint analysis reveals that trends in model errors in the soil moisture equation can be estimated from daily L-band brightness measurements, whereas model errors in the soil and canopy temperature equations cannot be adequately retrieved from daily data alone. Nonetheless, state estimates obtained from the assimilation algorithm improve significantly on prior model predictions derived without assimilation of radiobrightness data. C1 Univ Maryland Baltimore Cty, Goddard Earth Sci & Technol Ctr, Baltimore, MD 21250 USA. MIT, Dept Civil & Environm Engn, Cambridge, MA 02139 USA. RP Reichle, RH (reprint author), Univ Maryland Baltimore Cty, Goddard Earth Sci & Technol Ctr, Baltimore, MD 21250 USA. RI Reichle, Rolf/E-1419-2012 NR 22 TC 96 Z9 101 U1 0 U2 13 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 AUG PY 2001 VL 39 IS 8 BP 1708 EP 1718 DI 10.1109/36.942549 PG 11 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 467CG UT WOS:000170682500011 ER PT J AU Johnson, WN Grove, JE Phlips, BF Ampe, J Singh, S Ponslet, E AF Johnson, WN Grove, JE Phlips, BF Ampe, J Singh, S Ponslet, E TI The construction and performance of the CsI hodoscopic calorimeter for the GLAST beam test engineering module SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article DE astronomical satellites; calorimetry; gamma rays; gamma-ray astronomy detectors; gamma-ray detectors; scintillation detectors AB We describe the design, construction, and performance of the CsI hodoscopic calorimeter of the GLAST beam test engineering module (BTEM), a full-size prototype of one of the 16 towers of the GLAST large-area telescope, approved by NASA to be launched in 2005. The calorimeter is composed of 80 CsI crystals organized in a hodoscopic arrangement with eight layers of ten crystals. The crystals are read out with PIN photodiodes at both ends. Light tapering along the length of the crystals produces an asymmetry in the light measured at the ends. The asymmetry is used for interaction positioning along the length of each crystal. The major design goals included the demonstration of a mechanical design to survive launch into space with minimal passive material, low power electronics with a dynamic range of similar to5 x 10(5), and digital data acquisition with < 20 mus dead time per event. We will describe the design and give results from the analysis of the beam test in winter 1999/2000 at the Stanford Linear Accelerator Center, where the BTEM was tested in gamma, positron, and hadron beams. C1 USN, Res Lab, Washington, DC 20375 USA. George Mason Univ, Fairfax, VA 22030 USA. Praxis Inc, Alexandria, VA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Hytec Inc, Los Alamos, NM 87544 USA. RP Johnson, WN (reprint author), USN, Res Lab, Washington, DC 20375 USA. RI Johnson, Neil/G-3309-2014 NR 3 TC 5 Z9 5 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD AUG PY 2001 VL 48 IS 4 BP 1182 EP 1189 DI 10.1109/23.958747 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 483XC UT WOS:000171660300046 ER PT J AU Liebe, CC AF Liebe, CC TI Charged particle-induced noise in camera systems SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article DE cameras; charge-coupled devices; radiation effects; space vehicle electronics; transient response ID ORBITAL ELECTRONS; DIFFUSION; RADIATION; DEVICES; SPECTRA; PROTON; NUCLEI AB When a camera system is operated in a flux of charged particles, it will generate transient signals. The charged particles will impinge on the focal plane array and generate tracks of ionized electron-hole pairs. The charge tracks will diffuse, and some of the charge will be collected as signal and the rest will recombine. Bremsstrahlung radiation will be generated in the structure around the camera, and the Bremsstrahlung photons will generate secondary electrons in the focal plane array. The radiation hits will look like small stars. The charged particles will also make the optics "glow" due to luminescence and Cerenkov radiation. This paper utilizes a charged particle flux found in the open literature for a future spacecraft called Europa Orbiter to show the effects of charged particles on a camera system. A simple focal plane model is constructed based on typical values, and simulations of the transient noise will be discussed. In this specific simulation, the radiation will generate average values of 3600 photoelectrons for impinging electrons, 6000 photoelectrons for Bremsstrahlung-generated secondary electrons in the focal plane, and 15 000 photoelectrons for impinging protons. These transient signals will make it difficult for the camera system to operate under low light conditions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liebe, CC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 37 TC 2 Z9 6 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 AUG PY 2001 VL 48 IS 4 BP 1541 EP 1549 DI 10.1109/23.958394 PN 3 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 483XK UT WOS:000171661000001 ER PT J AU Rushing, JA Ranganath, HS Hinke, TH Graves, SJ AF Rushing, JA Ranganath, HS Hinke, TH Graves, SJ TI Using association rules as texture features SO IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE LA English DT Article DE texture; segmentation; association rules; data mining ID IMAGE SEGMENTATION; DISCRIMINATION; CLASSIFICATION; FILTERS AB A new type of texture feature based on association rules is proposed in this paper. Association rules have been used in applications such as market basket analysis to capture relationships present among items in large data sets. It is shown that association rules can be adapted to capture frequently occurring local structures in images. Association rules capture both structural and statistical information, and automatically identifies the structures that occur most frequently and relationships that have significant discriminative power. Methods for classification and segmentation of textured images using association rules as texture features are described. Simulation results using images consisting of man made and natural textures show that association rule features perform well compared to other widely used texture features. It is shown that association rule features can distinguish texture pairs with identical first, second, and third order statistics, and texture pairs that are not easily discriminable visually. C1 Intel Corp, Santa Clara, CA 95052 USA. Univ Alabama, Dept Comp Sci, Huntsville, AL 35899 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Alabama, Informat Technol & Syst Ctr, Huntsville, AL 35899 USA. RP Rushing, JA (reprint author), Intel Corp, 2200 Miss Coll Blvd, Santa Clara, CA 95052 USA. EM john.a.rushing@intel.com; ranganat@cs.uah.edu; thinke@mail.arc.nasa.gov; sgraves@itsc.uah.edu NR 23 TC 33 Z9 35 U1 0 U2 6 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0162-8828 J9 IEEE T PATTERN ANAL JI IEEE Trans. Pattern Anal. Mach. Intell. PD AUG PY 2001 VL 23 IS 8 BP 845 EP 858 DI 10.1109/34.946988 PG 14 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 460AH UT WOS:000170283300005 ER PT J AU Havelund, K Lowry, M Penix, J AF Havelund, K Lowry, M Penix, J TI Formal analysis of a space-craft controller using SPIN SO IEEE TRANSACTIONS ON SOFTWARE ENGINEERING LA English DT Article DE program verification; concurrent programs; model checking; temporal logic; program abstraction; model extraction; space-craft software AB This paper documents an application of the finite state model checker SPIN to formally analyze a multithreaded plan execution module, The plan execution module is one component of NASA's New Millennium Remote Agent, an artificial intelligence-based space-craft control system architecture which launched in October of 1998 as part of the DEEP SPACE 1 mission. The bottom layer of the plan execution module architecture is a domain specific language, named ESL (Executive Support Language), implemented as an extension to multithreaded COMMON LISP. ESL supports the construction of reactive control mechanisms for autonomous robots and space-craft, For this case study, we translated the ESL services for managing interacting parallel goal-and-event driven processes into the PROMELA input language of SPIN, A total of five previously undiscovered concurrency errors were identified within the implementation of ESL. According to the Remote Agent programming team, the effort has had a major impact, locating errors that would not have been located otherwise and, in one case, identifying a major design flaw. In fact, in a different part of the system, a concurrency bug identical to one discovered by this study escaped testing and caused a deadlock during an in-flight experiment 96 million kilometers from earth. The work additionally motivated the introduction of procedural abstraction in terms of inline procedures into SPIN. C1 NASA, Ames Res Ctr, Kestrel Technol, Moffett Field, CA 94035 USA. RP Havelund, K (reprint author), NASA, Ames Res Ctr, Kestrel Technol, Moffett Field, CA 94035 USA. NR 11 TC 44 Z9 49 U1 0 U2 1 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0098-5589 J9 IEEE T SOFTWARE ENG JI IEEE Trans. Softw. Eng. PD AUG PY 2001 VL 27 IS 8 BP 749 EP 765 DI 10.1109/32.940728 PG 17 WC Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 461TA UT WOS:000170378500005 ER PT J AU Rokni, M Gatski, TB AF Rokni, M Gatski, TB TI Predicting turbulent convective heat transfer in fully developed duct flows SO INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW LA English DT Article ID LARGE-EDDY SIMULATION; LOW-REYNOLDS-NUMBER; SQUARE DUCT; NUMERICAL-SIMULATION; CROSS-SECTION; STRESS MODEL AB The performance of an explicit algebraic stress model (EASM) is assessed in predicting the turbulent flow and forced heat transfer in both straight and wavy ducts, with rectangular, trapezoidal and triangular cross-sections, under fully developed conditions. A comparison of secondary flow patterns, including velocity vectors and velocity and temperature contours, are shown in order to study the effect of waviness on flow dynamics, and comparisons between the hydraulic parameters, Fanning friction factor and Nusselt number, are also presented. In all cases, isothermal conditions are imposed on the duct walls, and the turbulent heat fluxes are modeled using gradient-diffusion type models. The formulation is valid for Reynolds numbers up to 10(5) and this minimizes the need for wall functions that have been used with mixed success in previous studies of complex duct flows. In addition, the present formulation imposes minimal demand on the number of grid points without any convergence or stability problems. Criteria in terms of heat transfer and friction factor needed to choose the optimal wavy duct cross-section for industrial applications among the ones considered are discussed. (C) 2001 Elsevier Science Inc. All rights reserved. C1 Lund Inst Technol, Div Heat Transfer, S-22100 Lund, Sweden. NASA, Langley Res Ctr, Computat Modeling & Simulat Branch, Hampton, VA 23681 USA. RP Rokni, M (reprint author), Lund Inst Technol, Div Heat Transfer, POB 118, S-22100 Lund, Sweden. NR 24 TC 15 Z9 15 U1 1 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0142-727X J9 INT J HEAT FLUID FL JI Int. J. Heat Fluid Flow PD AUG PY 2001 VL 22 IS 4 BP 381 EP 392 DI 10.1016/S0142-727X(01)00104-7 PG 12 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 456FQ UT WOS:000170072800001 ER PT J AU Kibria, AKMF Mo, YH Park, KS Nahm, KS Yun, MH AF Kibria, AKMF Mo, YH Park, KS Nahm, KS Yun, MH TI Electrochemical hydrogen storage behaviors of CVD, AD and LA grown carbon nanotubes in KOH medium SO INTERNATIONAL JOURNAL OF HYDROGEN ENERGY LA English DT Article ID EVOLUTION REACTION; NICKEL ELECTRODE; ADSORPTION; SORPTION; ALLOYS; ENERGY AB Carbon nanotubes (CNTs) were synthesized catalytically by both chemical vapor deposition (CVD) method in C2H2/H-2 atmosphere at 600 degreesC and arc-discharge (AD) method under helium atmosphere. The structure and morphology of CNTs was determined employing scanning electron microscopy (SEM) and FT-Raman spectroscopy. Hydrogen storage capacities were electrochemically measured for undoped and alkali metal (Li, Na and K) doped CVD, AD and laser ablation (LA) grown CNTs. The amounts of hydrogen stored were calculated from the measured discharge capacities. LA grown CNTs produced the highest hydrogen storage capacity of 1.6 wt%. The alkali metal-doped CNTs showed higher hydrogen storage capacities than un-doped CNTs. Although the hydrogen storage capacities of Li-doped CVD and AD grown CNTs were 6 times higher than that of un-doped CNTs, it is only 0.6 wt%. For Li-doped LA grown CNTs, the hydrogen storage capacity reached 2.4 wt%. The high hydrogen storage capacity of alkali metal-doped CNTs seems to be originated from increasing the hydrogen adsorption sites of CNTs due to introducing the doped metals in nanotube bundles and separating the tubes but not from their chemical effects. (C) 2001 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved. C1 Chonbuk Natl Univ, Sch Chem Engn & Technol, Chonju 561756, South Korea. NASA, JPL, Pasadena, CA 91109 USA. RP Chonbuk Natl Univ, Sch Chem Engn & Technol, Chonju 561756, South Korea. EM nahmks@moak.chonbuk.ac.kr NR 23 TC 59 Z9 60 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0360-3199 EI 1879-3487 J9 INT J HYDROGEN ENERG JI Int. J. Hydrog. Energy PD AUG PY 2001 VL 26 IS 8 BP 823 EP 829 DI 10.1016/S0360-3199(01)00007-6 PG 7 WC Chemistry, Physical; Electrochemistry; Energy & Fuels SC Chemistry; Electrochemistry; Energy & Fuels GA 456FW UT WOS:000170073300005 ER PT J AU Ambur, DR Jaunky, N Lawson, RE Knight, NF AF Ambur, DR Jaunky, N Lawson, RE Knight, NF TI Numerical simulations for high-energy impact of thin plates SO INTERNATIONAL JOURNAL OF IMPACT ENGINEERING LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 40th Structures, Structural Dynamics, and Materials Conference CY APR 12-15, 1999 CL ST LOUIS, MISSOURI SP Amer Inst Aeronaut & Astronaut, ASME, ASCE, AHS, ASC DE impact; penetration; LS-DYNA; finite elements AB New approaches to the design of advanced aerospace systems requires an evaluation of extreme loading conditions and assessment of different possible failures scenario. One such scenario involves the high-energy foreign-object impact on relatively thin plates used in fuselage and wing applications. This paper describes a series of LS-DYNA numerical simulations for studying the impact and penetration of thin plates by small fragment impactors. This work supported the development of a gas-actuated penetration device at NASA Langley Research Center for high-energy impact testing of structures. The high-energy impact testing device is used for experimental simulation of uncontained engine failures. Threshold velocities For different combinations of pitch and yaw angles of the impactor were obtained for the impactor-target test configuration in the numerical simulations. Complete penetration of the target plate was also simulated numerically. Finally, a comparison of numerical and experimental results is presented for a complete penetration test of the target by the impactor. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Eagle Aeronaut Inc, Newport News, VA 23606 USA. NASA, Langley Res Ctr, Mech & Durabil Branch, Hampton, VA 23681 USA. Newport News Shipbldg & Dry Dock Co, Newport News, VA 23607 USA. Veridian MRJ Technol Solut, Aerosp Syst Div, Fairfax, VA 22030 USA. RP Jaunky, N (reprint author), Eagle Aeronaut Inc, Newport News, VA 23606 USA. NR 19 TC 22 Z9 27 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 AUG PY 2001 VL 25 IS 7 BP 683 EP 702 DI 10.1016/S0734-743X(00)00073-7 PG 20 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 451BE UT WOS:000169780600005 ER PT J AU Gutman, H Laish-Farkash, A Risin, D Pellis, NR AF Gutman, H Laish-Farkash, A Risin, D Pellis, NR TI Locomotion of lymphocytes towards melanoma cells treated with tumor necrosis factor in a syngeneic in vitro model SO INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE LA English DT Article DE type I collagen; lymphocyte locomotion; tumor necrosis factor; melanoma; C3H mice; k1795p; in vitro; peripheral blood lymphocytes ID ISOLATED LIMB PERFUSION; FACTOR-ALPHA; ENDOTHELIAL-CELLS; TNF-ALPHA; COLLAGEN; RECEPTOR; MOTILITY; SARCOMA; MATRIX; ASSAY AB Tumor necrosis factor (TNF) causes cell necrosis in vivo by damaging the endothelium of the neovasculature. However, its mechanism of action is not well understood. We hypothesized that TNF affects the tumor microenvironment even before neovascularization occurs, thereby increasing lymphocyte locomotion through the peritumoral matrix, a crucial step in tumor cell killing. The effect of TNF on lymphocytes was tested with the type I rat-tail collagen mini-assay in peripheral blood lymphocytes (PBL) from normal donors, a non-migratory PBL cell line (HPB), and a C3H mice splenic lymphocytes. Melanoma cell line (k1735p) was treated with TNF alpha /TNF beta 10 or 20 pg/mul. The syngeneic splenic lymphocytes were layered on top of the collagen, and their migration into the collagen towards the tumor cells was assessed. Tumor cell viability was evaluated before and after TNF treatment. Paired two-tailed Student's t-test was used for statistical analysis. TNF alpha and TNF beta had no significant direct effect on locomotion of PBL or HPB. Lymphocyte locomotion was inhibited in the presence of untreated melanoma cells in 7 of 9 assays (statistically significant in four), and it was significantly increased towards TNF alpha- or beta -treated melanoma cells, compared to untreated condition, in 7 of 9 assays (p=0.05 to p=0.0001). The number of viable tumor cells was not significantly different before and after treatment. In conclusion, treatment of tumor cells with TNF alpha or TNF beta significantly enhances lymphocyte locomotion through the matrix. The effect of TNF is not the result of a direct influence on the lymphocytes, and is not associated with a decrease in the number of viable tumor cells. These findings suggest that TNF interaction with the cell microenvironment induces a change in lymphocyte locomotion. C1 Rabin Med Ctr, Dept Surg B, IL-49100 Petah Tiqwa, Israel. Univ Texas, MD Anderson Canc Ctr, Dept Surg Oncol, Houston, TX 77030 USA. Tel Aviv Univ, Sackler Fac Med, IL-69978 Tel Aviv, Israel. Wyle Life Sci Syst & Serv, Houston, TX USA. NASA, Lyndon B Johnson Space Ctr, Biotechnol Cell Sci Program, Houston, TX USA. RP Gutman, H (reprint author), Rabin Med Ctr, Dept Surg B, Beilinson Campus, IL-49100 Petah Tiqwa, Israel. RI tamam, shai/M-7262-2015 OI tamam, shai/0000-0002-0659-4378 NR 25 TC 0 Z9 0 U1 0 U2 0 PU PROFESSOR D A SPANDIDOS PI ATHENS PA 1, S MERKOURI ST, EDITORIAL OFFICE,, ATHENS 116 35, GREECE SN 1107-3756 J9 INT J MOL MED JI Int. J. Mol. Med. PD AUG PY 2001 VL 8 IS 2 BP 199 EP 203 PG 5 WC Medicine, Research & Experimental SC Research & Experimental Medicine GA 452RN UT WOS:000169872700014 PM 11445875 ER PT J AU Barut, A Madenci, E Heinrich, J Tessler, A AF Barut, A Madenci, E Heinrich, J Tessler, A TI Analysis of thick sandwich construction by a {3,2}-order theory SO INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES LA English DT Article DE sandwich; composites; higher-order plate theory ID PLATES; COMPOSITES; MODELS AB This study is an extension of the {1,2}-order plate theory to a higher order {3, 2} theory. Based on the equivalent single-layer assumptions, the in-plane and transverse displacement components are expressed as cubic and quadratic expansions through the thickness of the sandwich construction. Also, the transverse stress component is assumed to vary as a cubic function through the thickness. Utilizing Reissner's definitions for kinematics of thick plates, the displacement components at any point on the plate are approximated in terms of weighted-average quantities (displacements and rotations) that are functions of the in-plane coordinates. The undetermined coefficients defining the in-plane and transverse displacement fields are then expressed in terms of the weighted-average displacements and rotations and their derivatives by directly employing Reissner's definitions and enforcing the zero transverse-shear-stress conditions on the upper and lower surfaces of the sandwich panel. The coefficients defining the transverse stress component are obtained by requiring the transverse strain component, which is expressed in terms of the unknown coefficients of the transverse stress component from a mixed constitutive relation, to be the least-squares equivalent of the kinematic definition of the transverse strain component. The resulting expressions for the unknown coefficients of the transverse stress component are related to resultant strains and curvatures defined from kinematic relations. The equations of equilibrium and boundary conditions of the sandwich plate based on the {3, 2}-higher-order theory are derived by employing the principles of virtual displacements. The robustness and accuracy of this (3, 2)-order plate theory are established through comparisons with exact solutions available in the literature. The finite element implementation of the present (3, 2)-order plate theory is also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. NASA, Langley Res Ctr, Analyt & Computat Method Branch, Hampton, VA 23681 USA. RP Madenci, E (reprint author), Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. EM atila@u.arizona.edu; madenci@u.arizona.edu; heinrich@zeus.ame.arizona.edu; a.tessler@larc.nasa.gov RI Tessler, Alexander/A-4729-2009 NR 14 TC 34 Z9 35 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7683 EI 1879-2146 J9 INT J SOLIDS STRUCT JI Int. J. Solids Struct. PD AUG PY 2001 VL 38 IS 34-35 BP 6063 EP 6077 DI 10.1016/S0020-7683(00)00367-X PG 15 WC Mechanics SC Mechanics GA 451TA UT WOS:000169816300012 ER PT J AU Cassell, A Delzeit, L Nguyen, C Stevens, R Han, J Meyyappan, M AF Cassell, A Delzeit, L Nguyen, C Stevens, R Han, J Meyyappan, M TI Carbon nanotubes by CVD and applications SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 13th European Conference on Chemical Vapor Deposition (EUROCVD 13) CY AUG 26-31, 2001 CL GLYFADA, GREECE ID CHEMICAL-VAPOR-DEPOSITION; CATALYZED DECOMPOSITION; SINGLE-WALL; GROWTH; NUCLEATION; MICROSCOPY; ACETYLENE; HYDROGEN; DEVICES; STORAGE AB Carbon nanotube (CNT) exhibits extraordinary mechanical and unique electronic properties and offers significant potential for structural, sensor, and nanoelectronics applications. An overview of CNT, growth methods, properties and applications is provided. Single-wall, and multi-wall CNTs have been grown by chemical vapor deposition. Catalyst development and optimization has been accomplished using combinatorial optimization methods. CNT has also been grown from the tips of silicon cantilevers for use in atomic force microscopy. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Cassell, A (reprint author), NASA, Ames Res Ctr, Mailstop 229-3, Moffett Field, CA 94035 USA. NR 29 TC 9 Z9 9 U1 1 U2 5 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 1155-4339 J9 J PHYS IV JI J. Phys. IV PD AUG PY 2001 VL 11 IS PR3 BP 401 EP 409 PG 9 WC Physics, Multidisciplinary SC Physics GA 475AW UT WOS:000171140300052 ER PT J AU Masek, JG AF Masek, JG TI Stability of boreal forest stands during recent climate change: evidence from Landsat satellite imagery SO JOURNAL OF BIOGEOGRAPHY LA English DT Article DE climate change; boreal forests; remote sensing; forest-cover ID VEGETATION RESPONSE; WHITE SPRUCE; TERRESTRIAL ECOSYSTEMS; ENVIRONMENTAL-CHANGE; TREE-LINE; MODEL; CLASSIFICATION; RECONSTRUCTION; EXPANSION; DYNAMICS AB Aim To detect possible expansion of boreal forest stands in response to recent warming. Previous modelling studies have concluded that major shifts in vegetation patterns, including changes in boreal forest extent, could arise during the next two centuries under global warming scenarios. However, field investigations of tree stands at ecotones have so far revealed little indication of stand response to warming during the last 100 years. This study uses a c. 25-year record of Landsat satellite observations to quantify changes in forest stand extent in two areas of northern Canada. Location Two regions of northern Canada, near Richmond Gulf, Quebec, and Great Slave Lake, north-west Territories. Methods Normalized-difference vegetation index (NDVI) plots across forest-tundra boundaries were obtained from radiometrically corrected Landsat imagery acquired during the 1970s and 1990s. These curves were evaluated to look for changes over the c. 25-year period related to forest stand expansion. Results Although forest-tundra boundaries could be clearly mapped from the satellite data, no obvious change in forest boundaries was apparent during the duration of the image time series, constraining recent geographical expansion rates to <200-300 m per century. Also, no evidence for local expansion of forest stands (e.g. within sheltered valleys) was found. Main conclusions The results are consistent with field observations, and suggest that, at the moment, boreal forest extents remain basically stable. This may reflect inherent lags between forest response and climate change, or competitive pressures between tree stands and surrounding tundra and herbaceous vegetation. C1 Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Masek, JG (reprint author), NASA, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. RI Masek, Jeffrey/D-7673-2012 NR 41 TC 45 Z9 49 U1 8 U2 21 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0305-0270 J9 J BIOGEOGR JI J. Biogeogr. PD AUG PY 2001 VL 28 IS 8 BP 967 EP 976 DI 10.1046/j.1365-2699.2001.00612.x PG 10 WC Ecology; Geography, Physical SC Environmental Sciences & Ecology; Physical Geography GA 498YD UT WOS:000172540400003 ER PT J AU Rosenholtz, R AF Rosenholtz, R TI Visual search for orientation among heterogeneous distractors: Experimental results and implications for signal-detection theory models of search SO JOURNAL OF EXPERIMENTAL PSYCHOLOGY-HUMAN PERCEPTION AND PERFORMANCE LA English DT Article ID PREATTENTIVE VISION; SET-SIZE; ATTENTION; STIMULUS; SIMILARITY; PREDICTS; MOTION AB Three experiments tested a signal-detection theory (SDT) model of visual search (e.g., as described in J. Palmer, C. T. Ames, & D. T. Lindsey, 1993). In Experiment 1, participants searched for a 0 degrees line among distractors at (a) 30 degrees: (b) 1/3 at 30 degrees, 2/3 at 50 degrees; (c) 1/3 at 30 degrees, 50 degrees, and 70 degrees and (d) 1/3 at 30 degrees, 2/3 at 70 degrees. The SDT model predicts improved performance in the more heterogeneous conditions, as some distractors are more discriminable from the target. In contrast, in Experiment 1 human performance degraded in the more heterogeneous conditions (c and d). In Experiment 2, sparser displays improved the performance of the SDT model. In Experiment 3, search for theta degrees among homogeneous theta + 20 degrees distractors was compared with search for theta degrees among theta +/- 20 degrees distractors. Performance in the latter condition was often worse, relative to performance in the homogeneous condition, than predicted by the SDT model however, this depended greatly on the identity of the target. C1 Xerox Palo Alto Res Ctr, Palo Alto, CA 94304 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Rosenholtz, R (reprint author), Xerox Palo Alto Res Ctr, 3333 Coyote Hill Rd, Palo Alto, CA 94304 USA. NR 25 TC 34 Z9 34 U1 0 U2 5 PU AMER PSYCHOLOGICAL ASSOC PI WASHINGTON PA 750 FIRST ST NE, WASHINGTON, DC 20002-4242 USA SN 0096-1523 J9 J EXP PSYCHOL HUMAN JI J. Exp. Psychol.-Hum. Percept. Perform. PD AUG PY 2001 VL 27 IS 4 BP 985 EP 999 DI 10.1037//0096-1523.27.4.985 PG 15 WC Psychology; Psychology, Experimental SC Psychology GA 471TX UT WOS:000170945700016 PM 11518158 ER PT J AU Hallinan, TJ Kimball, J Stenbaek-Nielsen, HC Lynch, K Arnoldy, R Bonnell, J Kintner, P AF Hallinan, TJ Kimball, J Stenbaek-Nielsen, HC Lynch, K Arnoldy, R Bonnell, J Kintner, P TI Relation between optical emissions, particles, electric fields, and Alfven waves in a multiple rayed arc SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ION-ACCELERATION AB Velocities of rays in auroral arcs were used to infer the perpendicular electric fields above the acceleration region. Using rocket measurements of electron energy as a proxy for the high-altitude potential, the high-altitude perpendicular electric fields were calculated and found to be in good agreement with those derived from the ray motions. Additionally, a 0.6 Hz oscillating electric field at high altitude was postulated on the basis of the passing rays. Such a field was also calculated from the electron energy measurements and was found to be closely related to an Alfven wave measured on the payload following a delay of 0.8 s. The measured electron energy flux agreed well with the auroral luminosity down to scale sizes of about 10 km. The combination of ground-based imaging acid the measured energy flux also allowed a determination of the lower border altitude of the arcs. They were found to be somewhat higher (130 km) than expected on the basis of the electron energy. A tall rayed are with a lower border height of 170 km was associated with a burst of suprathermal electrons on the poleward edge of the aurora. C1 Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA. Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94704 USA. Cornell Univ, Sch Elect Engn, Ithaca, NY 14853 USA. RP Hallinan, TJ (reprint author), Univ Alaska Fairbanks, Inst Geophys, 903 Koyukuk Dr,POB 757320, Fairbanks, AK 99775 USA. NR 11 TC 17 Z9 17 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 AUG 1 PY 2001 VL 106 IS A8 BP 15445 EP 15454 DI 10.1029/2000JA000321 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400003 ER PT J AU Farrell, WM AF Farrell, WM TI Direct generation of O-mode emission in a dense, warm plasma: Applications to interplanetary type II emissions and others in its class SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID AURORAL KILOMETRIC RADIATION; RADIO EMISSIONS; BERNSTEIN WAVES; FREQUENCY; FORESHOCK; ELECTRONS; SHOCK AB A theory is presented that describes the direct generation of electromagnetic O-mode emission via mildly energetic electron beams in a highly dense and warm plasma. In previous theories, direct generation of O-mode emission from mildly energetic electron beams (1-10 keV) was considered unlikely because the Cerenkov wave phase speeds are much greater that the electron beam velocity, making the waves and electrons nonresonant. However, it is demonstrated that when cyclotron harmonic and relativistic effects are considered, resonance between particles and waves can occur under the conditions that omega be very near omega (p), and near (but not exactly at) m Omega (e), m being the cyclotron harmonic number. In this case, the calculated wave phase speeds can become very low (<2 x 10(7) m/s), thereby establishing resonance with the electrons. Such conditions do exist in regions where interplanetary type IT emission are generated, in the terrestrial foreshock region, and in planetary magnetospheres. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Farrell, WM (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 695, Greenbelt, MD 20771 USA. RI Farrell, William/I-4865-2013 NR 28 TC 12 Z9 12 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 AUG 1 PY 2001 VL 106 IS A8 BP 15701 EP 15709 DI 10.1029/2000JA000156 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400024 ER PT J AU Dewitte, S Joukoff, A Crommelynck, D Lee, RB Helizon, R Wilson, RS AF Dewitte, S Joukoff, A Crommelynck, D Lee, RB Helizon, R Wilson, RS TI Contribution of the Solar Constant (SOLCON) program to the long-term total solar irradiance observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOHO AB On long timescales the variation of the total solar irradiance (TSI) received by the Earth is believed to be one of the climate change drivers. Therefore accurate and time-stable measurements of the total solar irradiance are necessary. The Solar Constant (SOLCON) instrument made TSI measurements in April 1992 and during the International Extreme Ultraviolet Hitchhiker (IEH) 3 STS 95 shuttle flight in autumn 1998. We assume that the SOLCON instrument remained stable within 0.01 % in between those measurements, and we verify this assumption as well as possible. From the SOLCON measurements we conclude the following: (1) The 1998 Space Absolute Radiometric Reference (SARR) adjustment coefficient applicable to the Active Cavity Radiometer Irradiance Monitor II (ACRIM II) during the IEH 3 period is 1.000438 with a one sigma uncertainty of 18 ppm, compared to the 1993 SARR adjustment coefficient of 1.000258. (2) The solar monitor on the Earth Radiation Budget Satellite (ERBS), with a 1993 SARR adjustment coefficient of 1.000453, has not aged within a one sigma uncertainty level of 130 ppm; and (3) the 1998 SARR adjustment coefficients for the Variability of Solar Irradiance and Gravity Oscillations (VIRGO) radiometers have been determined with a one sigma uncertainty of 10 ppm: They are 1.000025 for the Differential Absolute Radiometer left channel (DIARAD-L) and 1.000279 for the version 1.2 data from the PMO6-VA radiometer. C1 Royal Metorol Inst Belgium, Sect Remote Sensing Space, B-1180 Brussels, Belgium. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23666 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. RP Dewitte, S (reprint author), Royal Metorol Inst Belgium, Sect Remote Sensing Space, Ringlaan 3, B-1180 Brussels, Belgium. NR 8 TC 5 Z9 6 U1 2 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 AUG 1 PY 2001 VL 106 IS A8 BP 15759 EP 15765 DI 10.1029/2000JA900160 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400028 ER PT J AU Ruzmaikin, A Feynman, J AF Ruzmaikin, A Feynman, J TI Strength and phase of the solar dynamo during the last 12 cycles SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GEOMAGNETIC-ACTIVITY; WIND; PREDICTION; ROTATION AB We use the nn index of geomagnetic activity recorded for 1.30 years to study the strength and phase properties of the solar dynamo. We split the monthly averaged cta into two pacts: one part proportional to the sunspot number and the other part proportional to the residual. We argue that the first part is a prosy for the solar dynamo's large-scale mean toroidal magnetic field. The residual has the same periodicity as the sunspot cycle and has closely related amplitude, but: is shifted in phase. WE relate this residual to the poloidal field generated from the toroidal field in the dynamo process. The changes in both components demonstrate that there was a long-term trend in the strength and relative phases of the toroidal and poloidal components of the mean-field dynamo. The changes in the relative phase of the toroidal and poloidal fields suggest that the distributions of the differential rotation and helicity within the Sun's convection zone have changed over timescales of 50 years. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ruzmaikin, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 9 Z9 9 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 AUG 1 PY 2001 VL 106 IS A8 BP 15783 EP 15789 DI 10.1029/2000JA000287 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400030 ER PT J AU Ness, NF Burlaga, LF AF Ness, NF Burlaga, LF TI Spacecraft studies of the interplanetary magnetic field SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Review ID SOLAR-WIND; VOYAGER-2 OBSERVATIONS; DISTANT HELIOSPHERE; SECTOR STRUCTURE; LATITUDES; MINIMUM; SHOCK; HOLES; AU AB In situ studies of the magnetic fields in space by spacecraft (S/C) began 4 decades ago. The experiments were initially difficult to perform and interpret accurately because of contamination by S/C-generated magnetic fields, partial measurements of the vector field, limited mass and power for the instrumentation, low-data-rate sampling, discontinuous or spotty data coverage, and sometimes unknown orientation or location of the S/C. As each of these challenges was overcome, an initial view of the macrostructure of the interplanetary magnetic field (IMF) emerged, substantiating the Archimedean spiral structure and solar origin of the IMF as proposed theoretically by E. N. Parker. An important mesoscale feature noted early on was the sectoring of the IMF into an ordered sequence of alternating polarities associated with solar sources. Subsequent studies catalogued the microscale magnetohydrodynamic structures: shock waves, and tangential and rotational discontinuities and fluctuations. Correlations with solar photospheric magnetic fields, coronal holes and in situ plasma, and energetic particles elaborated more completely on the structure and dynamics of the IMF. This paper will provide a brief historical summary of the study of the IMF or, as it is now more commonly referred to, the heliospheric magnetic field (HMF). C1 Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Ness, NF (reprint author), Univ Delaware, Bartol Res Inst, 217 Sharp Lab, Newark, DE 19716 USA. NR 70 TC 40 Z9 40 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 AUG 1 PY 2001 VL 106 IS A8 BP 15803 EP 15817 DI 10.1029/2000JA000118 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400034 ER PT J AU Smith, EJ AF Smith, EJ TI The heliospheric current sheet SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Review ID INTERPLANETARY MAGNETIC-FIELD; CORONAL MASS EJECTIONS; HEAT-FLUX DROPOUTS; SOLAR-WIND; ROTATIONAL DISCONTINUITIES; SMM OBSERVATIONS; SECTOR STRUCTURE; COSMIC-RAYS; MODULATION; STREAMERS AB The heliospheric current sheet (HCS) is the boundary between open oppositely directed magnetic field lines which commonly originate as the outward extension of the solar magnetic dipole. The dipole tilt, the rotation of the Sun, and the outward propagation of the solar wind cause peaks and valleys in the current sheet which spiral outward. The HCS extends throughout the heliosphere to the greatest distances reached by Pioneer and Voyager. It serves as a magnetic equator, and solar wind parameters including speed, temperature, density, and composition vary with distance from the HCS. Extrapolated back to the Sun, especially near solar minimum, the HCS corresponds to the low-latitude streamer belt. Both features are closely related to a neutral line obtained by extrapolating photospheric magnetic fields to a source surface at several solar radii. The current sheet and sector structure persist throughout the solar cycle including solar maximum. At 1 AU the width of the HCS is approximately 10,000 km while a surrounding plasma sheet is thicker by a factor of similar to 30. The field inside the HCS does not simply decrease to a null and then reappear with the opposite sense. Instead, the field rotates at nearly constant magnitude from one polarity to the other. In spite of theoretical expectations that fields on opposite sides of the HCS will merge or reconnect, there is little evidence that such is occurring. Many scientific questions remain unanswered. What are the global properties of the HCS near solar maximum, and how faithfully are they reproduced by source surface models? Are multiple HCS crossings caused by waves on the current sheet or by multiple current sheets? What is the effect of coronal mass ejections on the HCS and vice versa? C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Smith, EJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 169-506, Pasadena, CA 91109 USA. NR 60 TC 119 Z9 120 U1 1 U2 8 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 AUG 1 PY 2001 VL 106 IS A8 BP 15819 EP 15831 DI 10.1029/2000JA000120 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400035 ER PT J AU Liewer, PC Hall, JR De Jong, M Socker, DG Howard, RA Crane, PC Reiser, P Rich, N Vourlidas, A AF Liewer, PC Hall, JR De Jong, M Socker, DG Howard, RA Crane, PC Reiser, P Rich, N Vourlidas, A TI Determination of three-dimensional structure of coronal streamers and relationship to the solar magnetic field SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ACTIVE REGIONS; CURRENT SHEET; WIND; EVOLUTION; MINIMUM; MODELS; ORIGIN; SPEED; PHASE AB We have determined the location, in three dimensions, of eight quasi-stable coronal "streamers" from an analysis of Solar and Heliospheric Observatory (SOHO) Large-Angle and Spectrometric Coronagraph images acquired over approximately one solar rotation. We use the locations to attempt to determine the solar origin of the streamers. Comparison of the streamers' locations (longitude and latitude at the R approximate to 2.5 R-S source surface) with that of the current Sheet computed from a potential source surface model show that all of the streamers lie in or near the heliospheric current sheet, We assume that the streamers coincide with magnetic field lines and use a potential source surface magnetic model to map the location of the streamers from the source surface (R approximate to 2.5 R-S) to the photosphere, We find that many of the streamers are associated with strong magnetic field active regions, When a streamer and its associated active region are visible simultaneously, the active region is seen to be bright in the SOHO extreme ultraviolet imaging telescope (EIT) EW full disk images. This, and other evidence, leads us to conclude that many of the bright streamers are the result of scattering from regions of enhanced density associated with active region outflow, and not a result of line-of-sight viewing through folds in a warped current sheet with uniform density. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Interferometr Inc, Chantilly, VA 20151 USA. Naval Res Lab, Washington, DC 20375 USA. George Mason Univ, Sch Computat Sci, Ctr Earth Observing & Space Res, Fairfax, VA 22030 USA. RP Liewer, PC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Vourlidas, Angelos/C-8231-2009 OI Vourlidas, Angelos/0000-0002-8164-5948 NR 17 TC 27 Z9 29 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 AUG 1 PY 2001 VL 106 IS A8 BP 15903 EP 15915 DI 10.1029/2000JA000110 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400043 ER PT J AU Burlaga, LF AF Burlaga, LF TI Lognormal and multifractal distributions of the heliospheric magnetic field SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Review ID COSMIC-RAY MODULATION; SOLAR-WIND SPEED; FULLY-DEVELOPED TURBULENCE; MERGED INTERACTION REGIONS; LARGE-SCALE FLUCTUATIONS; VOYAGER 1; INTERMITTENT TURBULENCE; INTERPLANETARY MEDIUM; RECURRENT STREAMS; 1/F NOISE AB The heliospheric magnetic field strength B fluctuates appreciably over a large range of scales in the region from 1 AU to at least 30 AU and throughout the solar cycle. The fluctuations are often extreme and intermittent. For example, the distributions of hour averages of these parameters are usually lognormal to a good approximation, the long tail representing extreme events. The fluctuations can often be described by a multifractal distribution on scales from approximately 12 hours to 27 days or more, reflecting scaling symmetries of various moments of the fluctuations. Statistical variations, burstiness, extreme values, and clusters on various scales are ubiquitous in the time series describing the magnetic field. These properties can be described quantitatively, although not uniquely. Models of the solar wind should at least be consistent with these results. Ultimately, there is a need for physical models that can explain the statistical properties of the observed large-scale fluctuations. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Burlaga, LF (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Mail Code 692,Bldg 2,Room 127, Greenbelt, MD 20771 USA. EM burlaga@lepvax.gsfc.nasa.gov NR 84 TC 69 Z9 70 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 AUG 1 PY 2001 VL 106 IS A8 BP 15917 EP 15927 DI 10.1029/2000JA000107 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400044 ER PT J AU Crooker, NU Kahler, SW Gosling, JT Larson, DE Lepping, RP Smith, EJ De Keyser, J AF Crooker, NU Kahler, SW Gosling, JT Larson, DE Lepping, RP Smith, EJ De Keyser, J TI Scales of heliospheric current sheet coherence between 1 and 5 AU SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; PLANETARY SECTOR BOUNDARIES; SOLAR-WIND; STREAMER; POLARITIES; EVOLUTION; ELECTRONS; SURFACE AB The structure of the heliospheric current sheet (HCS) at Ulysses and at Wind is compared during the period of near-radial alignment in 1998. Electron heat flux and magnetic field data are used to determine true magnetic field polarity. During the solar rotation period surrounding alignment there was considerable disagreement between the HCS crossings at Wind and those predicted from the corresponding source surface map, both in number and in location, consistent with the disordered, temporally varying solar wind at this ascending phase of the solar cycle. Despite this complexity the four crossings closest to the time of radial alignment at Wind were successfully identified in Ulysses data with use of a one-dimensional hydrodynamic code. Further, minimum variance analysis for the first two crossings, which were separated by only 16 hours at Wind, indicated coherent propagation of a large-scale warp in the HCS. Analysis of the local structure of the HCS on the four crossings, however, revealed a high level of variability both from case to case and from one spacecraft to the other. For example, the third crossing at Wind was a single-sheet crossing adjacent to structures with fields folded back on themselves and a brief period of counterstreaming electrons implying a transient structure. At Ulysses multiple sheets were encountered. At the fourth crossings Wind passed through a counterstreaming event with a flux rope signature containing a south pointing axis, while Ulysses passed through a flux tube with little field rotation and northward pointing field. The results are consistent with the view that the heliospheric current sheet is coherent as a global structure but highly variable in local structure over angular distances of a few degrees. C1 Boston Univ, Ctr Space Phys, Boston, MA 02215 USA. Hanscom Air Force Base, Space Vehicles Directorate, Air Force Res Lab, Bedford, MA 01731 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Belgian Inst Space Aeron, Brussels, Belgium. RP Crooker, NU (reprint author), Boston Univ, Ctr Space Phys, 725 Commonwealth Ave, Boston, MA 02215 USA. NR 29 TC 7 Z9 7 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 AUG 1 PY 2001 VL 106 IS A8 BP 15963 EP 15971 DI 10.1029/2000JA000109 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400047 ER PT J AU Goldstein, ML Roberts, DA Burlaga, LF Siregar, E Deane, AE AF Goldstein, ML Roberts, DA Burlaga, LF Siregar, E Deane, AE TI North-south flows observed in the outer heliosphere at solar minimum: Vortex streets or corotating interaction regions? SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FLUX-CORRECTED TRANSPORT; PLASMA-FLOW; MERIDIONAL TRANSPORT; MAGNETIC-FLUX; WIND STREAMS; DYNAMICS; FLUCTUATIONS; PIONEER-10; HELIOS-1; MODEL AB During the last two solar minima in the distant heliosphere the equatorial heliospheric plasma velocity oscillated perpendicular to the ecliptic plane with an approximately 26-day period in the distant heliosphere. Two explanations have been proposed. compressive interactions between streams and velocity shear interactions that produce a Karman vortex street. The latter interpretation has been challenged on the basis that the velocity jumps are supersonic, thereby suppressing the Kelvin-Helmholtz (K-H) instability. Here we examine this issue using a time-dependent compressible magnetohydrodynamics code solved in spherical coordinates in the two-dimensional r - theta plane. We conclude that supersonic flow does suppress small-scale instabilities and that the classic Karman vortex street cannot be excited. Both velocity shear layers and stream interactions can, however, produce signatures in density, velocity, and magnetic field that resemble the observations. In particular, we find north-south variations of the flow velocity with a period that is approximately half that of the period of the variation in flow speed: a result insensitive to the thickness of the velocity shear layers. A depletion in density (and magnetic field magnitude) relative to the expected Parker value is predicted by the simulations that generate the north-south flow via velocity shear. The Voyager spacecraft observed a similar depletion in the outer heliosphere during the last two solar minima. When the effective tilt of the plasma sheet is increased, corotating interaction regions produce shock waves and other complex time-dependent evolution. We conclude that at solar minimum the observed north-south oscillations are a robust phenomenon that can form from either the interaction of fast and slow solar wind streams or from velocity shear. Which mechanism dominates is a consequence of the degree of tilt of the heliospheric current sheet, the magnitude of the velocity shear, and other physical parameters. However, the depletions seen in density and magnetic flux in the Voyager data suggest that velocity shear in the outer heliosphere at solar minimum may be the dominant cause of the observed north-south flow patterns. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Emergent Informat Technol, Largo, MD USA. Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. RP NASA, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. EM melvyn.goldstein@gsfc.nasa.gov; roberts@vayu.gsfc.nasa.gov; burlaga@lepvax.gsfc.nasa.gov; yses@puff.gsfc.nasa.gov RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 32 TC 11 Z9 11 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 2001 VL 106 IS A8 BP 15973 EP 15984 DI 10.1029/2000JA000106 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400048 ER PT J AU Collier, MR Szabo, A Farrell, WM Slavin, JA Lepping, RP Fitzenreiter, R Thompson, B Hamilton, DC Gloeckler, G Ho, GC Bochsler, P Larson, D Ofman, L AF Collier, MR Szabo, A Farrell, WM Slavin, JA Lepping, RP Fitzenreiter, R Thompson, B Hamilton, DC Gloeckler, G Ho, GC Bochsler, P Larson, D Ofman, L TI Reconnection remnants in the magnetic cloud of October 18-19, 1995: A shock, monochromatic wave, heat flux dropout, and energetic ion beam SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CORONAL MASS EJECTION; EARTHS BOW SHOCK; SOLAR-WIND; FIELD; UPSTREAM; EVENTS; SPACECRAFT; TOPOLOGY; MAGNETOSPHERE; OSCILLATIONS AB Evidence is presented that the Wind spacecraft observed particle and field signatures on October 18-19, 1995, due to reconnection near the foot points of a magnetic cloud (i.e., between 1 and 5 solar radii). These signatures include (1) an internal shock traveling approximately along the axis of the magnetic cloud, (2) a simple compression of the magnetic field consistent with the foot point magnetic fields being thrust outward at speeds much greater than the solar wind speed, (3) an electron heat flux dropout. occurring within minutes of the shock, indicating a topological change resulting from disconnection from the solar surface, (4) a very cold 5 keV proton beam, and (5) an associated monochromatic wave. We expect that given observations of enough magnetic clouds, Wind and other spacecraft will see signatures similar to the ones reported here indicating reconnection. However, these observations require the spacecraft to be fortuitously positioned to observe the passing shock and other signatures and will therefore be associated with only a small fraction of magnetic clouds. Consistent with this, a few magnetic clouds observed by Wind have been found to possess internal shock waves. C1 NASA, Goddard Space Flight Ctr, Space Sci Directorate, Greenbelt, MD 20771 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Raytheon Informat Technol & Sci Serv, Astron & Solar Phys Lab, Greenbelt, MD USA. RP Collier, MR (reprint author), NASA, Goddard Space Flight Ctr, Space Sci Directorate, Code 692, Greenbelt, MD 20771 USA. RI Slavin, James/H-3170-2012; Thompson, Barbara/C-9429-2012; Collier, Michael/I-4864-2013; Farrell, William/I-4865-2013; Ho, George/G-3650-2015; OI Slavin, James/0000-0002-9206-724X; Collier, Michael/0000-0001-9658-6605; Ho, George/0000-0003-1093-2066; Hamilton, Douglas/0000-0001-6103-8019 NR 65 TC 18 Z9 19 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 AUG 1 PY 2001 VL 106 IS A8 BP 15985 EP 16000 DI 10.1029/2000JA000101 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400049 ER PT J AU Zurbuchen, TH Hefti, S Fisk, LA Gloeckler, G Schwadron, NA Smith, CW Ness, NF Skoug, RM McComas, DJ Burlaga, LF AF Zurbuchen, TH Hefti, S Fisk, LA Gloeckler, G Schwadron, NA Smith, CW Ness, NF Skoug, RM McComas, DJ Burlaga, LF TI On the origin of microscale magnetic holes in the solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MIRROR-MODE STRUCTURES; ADVANCED-COMPOSITION-EXPLORER; FRACTIONATION; CORONA; FIELD AB Magnetic holes are sudden changes in the magnetic field intensity \B\ from typical interplanetary values (similar to 10 nT) to less than 1 nT in a matter of seconds. The intensity then recovers within seconds or up to similar to 30 min later. These \B\ dropouts can be seen daily. Less often observed, but even more dramatic, are magnetic field depletions that last for up to several hours. We use selected periods of magnetic flux dropouts observed with various sensors of the Advanced Composition Explorer (ACE), which has a unique combination of magnetic field, plasma, and composition experiments, to establish the origin of these peculiar objects. We conclude that these microscale magnetic holes very likely develop in the heliosphere and are not of direct solar origin. We also suggest a possible formation mechanism associated with magnetic reconnection close to the Sun. C1 Univ Michigan, Space Phys Res Lab, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Zurbuchen, TH (reprint author), Univ Michigan, Space Phys Res Lab, Dept Atmospher Ocean & Space Sci, 2455 Hayward St, Ann Arbor, MI 48109 USA. NR 28 TC 31 Z9 31 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 AUG 1 PY 2001 VL 106 IS A8 BP 16001 EP 16010 DI 10.1029/2000JA000119 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456HQ UT WOS:000170077400050 ER PT J AU Kim, J Benton, J McQuillen, J Vickerman, M AF Kim, J Benton, J McQuillen, J Vickerman, M TI Subcooled pool boiling heat transfer in microgravity and Hi-g SO JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Mechanical Engineering Congress CY NOV, 2000 CL ORLANDO, FLORIDA C1 Univ Maryland, College Pk, MD 20742 USA. NASA, Glen Res Ctr, Washington, DC USA. RP Kim, J (reprint author), Univ Maryland, College Pk, MD 20742 USA. NR 0 TC 6 Z9 7 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0022-1481 J9 J HEAT TRANS-T ASME JI J. Heat Transf.-Trans. ASME PD AUG PY 2001 VL 123 IS 4 BP 620 EP 620 DI 10.1115/1.1385891 PG 1 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 458XF UT WOS:000170220200004 ER PT J AU Walther, JH Koumoutsakos, P AF Walther, JH Koumoutsakos, P TI Molecular dynamics simulation of nanodroplet evaporation SO JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME LA English DT Article DE nanofluidics; nanodroplet; molecular dynamics simulation ID DROPLET COLLISION; LIQUID; CLUSTERS; VAPORIZATION; COMBUSTION; SURFACE; VAPOR; FLUID; ARGON; GAS AB Molecular dynamics simulations are used to study the sub-critical evaporation of a nanometer-size droplet at 300 K and 3 MPa. Classical molecular dynamics techniques are combined with an adaptive tree data structure for the construction of the neighbor lists, allowing efficient simulations using hundreds of thousands of molecules. We present a systematic convergence study of the method demonstrating its convergence for heat conduction problems in submicron scales. These high resolution simulations compute values of the evaporation coefficient that are in excellent agreement with. theoretical predictions. C1 ETH Zentrum, Inst Computat Sci, CH-8092 Zurich, Switzerland. NASA, CTR, Moffett Field, CA 94035 USA. RI Koumoutsakos, Petros/A-2846-2008; Walther, Jens/D-9549-2015 OI Koumoutsakos, Petros/0000-0001-8337-2122; Walther, Jens/0000-0001-8100-9178 NR 36 TC 36 Z9 38 U1 3 U2 23 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0022-1481 J9 J HEAT TRANS-T ASME JI J. Heat Transf.-Trans. ASME PD AUG PY 2001 VL 123 IS 4 BP 741 EP 748 DI 10.1115/1.1370517 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 458XF UT WOS:000170220200021 ER PT J AU Campbell, WF Salisbury, FB Bugbee, B Klassen, S Naegle, E Strickland, DT Bingham, GE Levinskikh, M Iljina, GM Veselova, TD Sytchev, VN Podolsky, I McManus, WR Bubenheim, DL Stieber, J Jahns, G AF Campbell, WF Salisbury, FB Bugbee, B Klassen, S Naegle, E Strickland, DT Bingham, GE Levinskikh, M Iljina, GM Veselova, TD Sytchev, VN Podolsky, I McManus, WR Bubenheim, DL Stieber, J Jahns, G TI Comparative floral development of Mir-grown and ethylene-treated, earth-grown Super Dwarf wheat SO JOURNAL OF PLANT PHYSIOLOGY LA English DT Article DE ethylene; micrcgravity; Mir; pollen; seed set; sterility; Super Dwarf; Svet; Triticum aestivum; wheat ID SPACEFLIGHT CONDITIONS; ARABIDOPSIS-THALIANA; SPACE-STATION; BARLEY; SENSITIVITY; ETHEPHON; POLLEN; ETHREL; PLANTS; FLIGHT AB To study plant growth in microgravity, we grew Super Dwarf wheat (Triticum aestivum L.) in the Svet growth chamber onboard the orbiting Russian space station, Mir, and in identical ground control units at the Institute of Biomedical Problems in Moscow, Russia. Seedling emergence was 56% and 73% in the two root-module compartments on Mir and 75% and 90% on earth. Growth was vigorous (produced ca. 1 kg dry mass), and individual plants produced 5 to 8 tillers on Mir compared with 3 to 5 on earth-grown controls. Upon harvest in space and return to earth, however, all inflorescences of the flight-grown plants were sterile. To ascertain if Super Dwarf wheat responded to the 1.1 to 1.7 mu mol . mol(-1) atmospheric levels of ethylene measured on the Mir prior to and during flowering, plants on earth were exposed to 0, 1, 3, 10, and 20 mu mol . mol(-1) of ethylene gas and 1200 mu mol . mol(-1) CO2 from 7d after emergence to maturity. As in our Mir wheat, plant height, awn length, and the flag leaf were significantly shorter in the ethylene-exposed plants than in controls; inflorescences also exhibited 100% sterility. Scanning-electron-microscopic (SEM) examination of florets from Mir-grown and ethyl ene-treated, earth-grown plants showed that development ceased prior to anthesis, and the anthers did not dehisce. Laser scanning confocal microscopic (LSCM) examination of pollen grains from Mir and ethyl ene-treated plants on earth exhibited zero, one, and occasionally two, but rarely three nuclei; pollen produced in the absence of ethylene was always trinucleate, the normal condition. The scarcity of trinucleate pollen, abrupt cessation of floret development prior to anthesis, and excess tillering in wheat plants on Mir and in ethylene-containing atmospheres on earth build a strong case for the ethylene on Mir as the agent for the induced male sterility and other symptoms, rather than microgravity. C1 Utah State Univ, Dept Plant Soils & Biometeorol, Logan, UT 84322 USA. Inst Biomed Problems, Moscow 123007, Russia. Moscow MV Lomonosov State Univ, Fac Biol, Moscow 119899, Russia. Utah State Univ, Dept Biol, Logan, UT 84322 USA. NASA, Moffett Field, CA 94035 USA. RP Campbell, WF (reprint author), Utah State Univ, Dept Plant Soils & Biometeorol, Logan, UT 84322 USA. RI bugbee, bruce/I-5008-2012 NR 59 TC 29 Z9 34 U1 0 U2 6 PU URBAN & FISCHER VERLAG PI JENA PA BRANCH OFFICE JENA, P O BOX 100537, D-07705 JENA, GERMANY SN 0176-1617 J9 J PLANT PHYSIOL JI J. Plant Physiol. PD AUG PY 2001 VL 158 IS 8 BP 1051 EP 1060 DI 10.1078/S0176-1617(04)70129-7 PG 10 WC Plant Sciences SC Plant Sciences GA 464UH UT WOS:000170549800011 PM 12033229 ER PT J AU Zakharova, NT Mishchenko, MI AF Zakharova, NT Mishchenko, MI TI Scattering by randomly oriented thin ice disks with moderate equivalent-sphere size parameters SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 5th Conference on Light Scattering by Nonspherical Particles CY AUG 28-SEP 01, 2000 CL DALHOUSIE UNIV, HALIFAX, CANADA SP USA Res Lab, Opt Soc Amer HO DALHOUSIE UNIV DE electromagnetic scattering; nonspherical particles; T-matrix method; remote sensing ID LIGHT-SCATTERING; NONSPHERICAL PARTICLES; CIRCULAR-CYLINDERS; ATMOSPHERES; JUPITER; TITAN AB We use the T-matrix method to compute the scattering matrix for randomly oriented circular ice cylinders with diameter-to-length ratios I and 20 and surface-equivalent-sphere size parameters up to 12. We show that wavelength-sized, sharp-edged ice plates with extreme diameter-to-length ratios possess the same scattering properties as smooth platelike spheroids: their phase functions are similar to those of surface-equivalent compact particles, whereas all other elements of the scattering matrix are typical of Rayleigh scattering. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 SGT Inc, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Zakharova, NT (reprint author), SGT Inc, 2880 Broadway, New York, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012 NR 22 TC 7 Z9 7 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD AUG-SEP PY 2001 VL 70 IS 4-6 BP 465 EP 471 DI 10.1016/S0022-4073(01)00023-1 PG 7 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 454ME UT WOS:000169975700008 ER PT J AU Yang, P Gao, BC Baum, BA Hu, YX Wiscombe, WJ Tsay, SC Winker, DM Nasiri, SL AF Yang, P Gao, BC Baum, BA Hu, YX Wiscombe, WJ Tsay, SC Winker, DM Nasiri, SL TI Radiative properties of cirrus clouds in the infrared (8-13 mu m) spectral region SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 5th Conference on Light Scattering by Nonspherical Particles CY AUG 28-SEP 01, 2000 CL DALHOUSIE UNIV, HALIFAX, CANADA SP USA Res Lab, Opt Soc Amer HO DALHOUSIE UNIV DE cirrus; crystal; infrared ID AIRBORNE SIMULATOR IMAGERY; DIFFERENCE TIME-DOMAIN; HEXAGONAL ICE CRYSTALS; ANOMALOUS DIFFRACTION THEORY; SINGLE-SCATTERING ALBEDO; LIGHT-SCATTERING; OPTICAL-PROPERTIES; NONSPHERICAL PARTICLES; EXTINCTION EFFICIENCY; CROSS-SECTIONS AB Atmospheric radiation in the infrared (IR) 8-13 mum spectral region contains a wealth of information that is very useful for the retrieval of ice cloud properties from aircraft or space-borne measurements. To provide the scattering and absorption properties of nonspherical ice crystals that are fundamental to the IR retrieval implementation, we use the finite-difference time-domain (FDTD) method to solve for the extinction efficiency, single-scattering albedo, and the asymmetry parameter of the phase function for ice crystals smaller than 40 mum. For particles larger than this size, the improved geometric optics method (IGOM) can be employed to calculate the asymmetry parameter with an acceptable accuracy, provided that we properly account for the inhomogeneity of the refracted wave due to strong absorption inside the ice particle. A combination of the results computed from the two methods provides the asymmetry parameter for the entire practical range of particle sizes between 1 and 10, 000 mum over the wavelengths ranging from 8 to 13 mum. For the extinction and absorption efficiency calculations, several methods including the IGOM, Mie solution for equivalent spheres (MSFES), and the anomalous diffraction theory (ADT) can lead to a substantial discontinuity in comparison with the FDTD solutions for particle sizes on the order of 40 mum. To overcome this difficulty, we have developed a novel approach called the stretched scattering potential method (SSPM), For the IR 8-13 mum spectral region, we show that SSPM is a more accurate approximation than ADT, MSFES, and IGOM. The SSPM solution can be further refined numerically. Through a combination of the FDTD and SSPM, the extinction and absorption efficiencies are computed for hexagonal ice crystals with sizes ranging from 1 to 10,000 mum at 12 wavelengths between 8 and 13 mum. Calculations of the cirrus bulk scattering and absorption properties are performed for 30 size distributions obtained from various field campaigns for midlatitude and tropical cirrus cloud systems. Ice crystals are assumed to be hexagonal columns randomly oriented in space. The bulk scattering properties are parameterized through the use of second-order polynomial functions for the extinction efficiency and the single-scattering albedo and a power-law expression for the asymmetry parameter. We note that the volume-normalized extinction coefficient can be separated into two parts: one is inversely proportional to effective size and is independent of wavelength, and the other is the wavelength-dependent effective extinction efficiency. Unlike conventional parameterization efforts, the present parameterization scheme is more accurate because only the latter part of the volume-normalized extinction coefficient is approximated in terms of an analytical expression. After averaging over size distribution, the single-scattering albedo is shown to decrease with an increase in effective size for wavelengths shorter than 10.0 mum whereas the opposite behavior is observed for longer wavelengths. The variation of the asymmetry parameter as a function of effective size is substantial when the effective size is smaller than 50 mum For effective sizes larger than 100 mum, the asymmetry parameter approaches its asymptotic value. The results derived in this study can be useful to remote sensing studies of ice clouds involving IR window bands. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD USA. Naval Res Lab, Remote Sensing Div, Washington, DC USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Univ Wisconsin, Cooperat Inst Meteorol Satellite Studies, Madison, WI USA. RP NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. EM pyang@climate.gsfc.nasa.gov RI Yang, Ping/B-4590-2011; Baum, Bryan/B-7670-2011; Nasiri, Shaima/C-8044-2011; Wiscombe, Warren/D-4665-2012; Tsay, Si-Chee/J-1147-2014; Hu, Yongxiang/K-4426-2012 OI Baum, Bryan/0000-0002-7193-2767; Wiscombe, Warren/0000-0001-6844-9849; NR 84 TC 65 Z9 69 U1 0 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 EI 1879-1352 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD AUG-SEP PY 2001 VL 70 IS 4-6 BP 473 EP 504 DI 10.1016/S0022-4073(01)00024-3 PG 32 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 454ME UT WOS:000169975700009 ER PT J AU Baran, AJ Francis, PN Havemann, S Yang, P AF Baran, AJ Francis, PN Havemann, S Yang, P TI A study of the absorption and extinction properties of hexagonal ice columns and plates in random and preferred orientation, using exact T-matrix theory and aircraft observations of cirrus SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 5th Conference on Light Scattering by Nonspherical Particles CY AUG 28-SEP 01, 2000 CL DALHOUSIE UNIV, HALIFAX, CANADA SP USA Res Lab, Opt Soc Amer HO DALHOUSIE UNIV ID INFRARED RADIATIVE PROPERTIES; LIGHT-SCATTERING; OPTICAL-PROPERTIES; SINGLE-SCATTERING; PARTICLES; CLOUDS; EFFICIENCY; SOLAR AB Absorption and extinction properties of the finite hexagonal ice column and hexagonal ice plate in random and preferred orientation are studied at the wavelength of 80 mum using a new implementation of exact T-matrix theory. For the case of random orientation at size parameters around two, it is shown that the hexagonal ice column and hexagonal ice plate absorption resonances are diminished relative to Mie theory, and the same behaviour is also noted for an aggregate particle consisting of eight hexagonal elements. The absorption properties of the aggregate particle have been calculated using the finite-difference time-domain method. It is also shown that extinction and absorption solutions for the hexagonal ice column and hexagonal ice plate can differ significantly if incidence occurs perpendicular or parallel to the cylindrical axis of the hexagon. For the case of perpendicular incidence on the edge of the hexagon, absorption solutions can exceed those of Mie theory, and for the case of parallel incidence, behaviour of the extinction solutions for hexagonal ice columns and hexagonal ice plates is shown to be similar to previously published work based on the prolate and oblate spheroid. Interference structure, associated with surface waves, is resolved on the hexagonal column extinction solution and the hexagonal plate absorption solution, thereby demonstrating that surface waves can exist on a non-axisymmetric geometry. The usefulness of assuming the hexagonal ice column in retrieval of ice crystal effective size is also investigated using aircraft based radiometric observations of semi-transparent cirrus at the wavelengths of 8.5 and 11 mum (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Met Off, Meteorol Res Flight, Farnborough, Hants, England. Univ Maryland Baltimore Cty, Goddard Earth Sci & Technol Ctr, Baltimore, MD 21228 USA. RP Baran, AJ (reprint author), Met Off, Meteorol Res Flight, Farnborough, Hants, England. RI Yang, Ping/B-4590-2011; Havemann, Stephan/D-1720-2010; Francis, Peter/H-9352-2013 OI Francis, Peter/0000-0002-5869-803X NR 22 TC 21 Z9 23 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD AUG-SEP PY 2001 VL 70 IS 4-6 BP 505 EP 518 DI 10.1016/S0022-4073(01)00025-5 PG 14 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 454ME UT WOS:000169975700010 ER PT J AU Hu, YX Winker, D Yang, P Baum, B Poole, L Vann, L AF Hu, YX Winker, D Yang, P Baum, B Poole, L Vann, L TI Identification of cloud phase from PICASSO-CENA lidar depolarization: a multiple scattering sensitivity study SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 5th Conference on Light Scattering by Nonspherical Particles CY AUG 28-SEP 01, 2000 CL DALHOUSIE UNIV, HALIFAX, CANADA SP USA Res Lab, Opt Soc Amer HO DALHOUSIE UNIV ID OPTICAL-PROPERTIES; AIRBORNE LIDAR; ICE CRYSTALS; RETURNS; LIGHT; MODIS AB A fast Monte Carlo simulation scheme is developed to assess the impact of multiple scattering on space-based lidar backscattering depolarization measurements. The specific application of our methodology is to determine cloud thermodynamic phase from satellite-based lidar depolarization measurements. Model results indicate that multiple scattering significantly depolarizes backscatter return from water clouds. Multiple scattering depolarization is less significant for non-spherical particles. There are sharp contrasts in the depolarization profile between a layer of spherical particles and a layer of non-spherical particles. Although it is not as obvious as ground-based lidar observations, it is likely that we can identify cloud phase not only for a uniform cloud layer, but also for overlapping cloud layers where one layer contains ice and the other water droplets. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Radiat & Aerosol Branch, Hampton, VA 23681 USA. NASA, GSFC, SSAI, Greenbelt, MD USA. RP Hu, YX (reprint author), NASA, Langley Res Ctr, Radiat & Aerosol Branch, MS 420, Hampton, VA 23681 USA. RI Baum, Bryan/B-7670-2011; Yang, Ping/B-4590-2011; Hu, Yongxiang/K-4426-2012 OI Baum, Bryan/0000-0002-7193-2767; NR 26 TC 53 Z9 59 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD AUG-SEP PY 2001 VL 70 IS 4-6 BP 569 EP 579 DI 10.1016/S0022-4073(01)00030-9 PG 11 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 454ME UT WOS:000169975700015 ER PT J AU Mishchenko, MI AF Mishchenko, MI TI Radiation force caused by scattering, absorption, and emission of light by nonspherical particles SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 5th Conference on Light Scattering by Nonspherical Particles CY AUG 28-SEP 01, 2000 CL DALHOUSIE UNIV, HALIFAX, CANADA SP USA Res Lab, Opt Soc Amer HO DALHOUSIE UNIV DE radiation force; electromagnetic scattering and emission; nonspherical particles ID PRESSURE; GRAINS AB General formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived. For randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory, whereas the average radiation force caused by emission vanishes. Published by Elsevier Science Ltd. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Mishchenko, MI (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012 NR 14 TC 32 Z9 32 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD AUG-SEP PY 2001 VL 70 IS 4-6 BP 811 EP 816 DI 10.1016/S0022-4073(01)00047-4 PG 6 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 454ME UT WOS:000169975700032 ER PT J AU Liu, L Mishchenko, MI AF Liu, L Mishchenko, MI TI Constraints on PSC particle microphysics derived from lidar observations SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 5th Conference on Light Scattering by Nonspherical Particles CY AUG 28-SEP 01, 2000 CL DALHOUSIE UNIV, HALIFAX, CANADA SP USA Res Lab, Opt Soc Amer HO DALHOUSIE UNIV DE scattering; depolarization; polar stratospheric clouds; remote sensing; nonspherical particles ID POLAR STRATOSPHERIC CLOUDS; AXIALLY-SYMMETRICAL PARTICLES; T-MATRIX COMPUTATIONS; LIGHT-SCATTERING; NONSPHERICAL PARTICLES; REFRACTIVE-INDEXES; LIQUID PARTICLES; ICE; SIZE; DEPOLARIZATION AB Based on extensive T-matrix computations of light scattering by polydispersions of randomly oriented, rotationally symmetric nonspherical particles, we analyze existing lidar observations of polar stratospheric clouds (PSCs) and derive several constraints on PSC particle microphysical properties. We show that sharp-edged nonspherical particles (finite circular cylinders) exhibit less variability of lidar backscattering characteristics with particle size and aspect ratio than particles with smooth surfaces (spheroids), For PSC particles significantly smaller than the wavelength, the backscatter color index alpha and the depolarization color index beta are essentially shape independent. Observations for type Ia PSCs can be reproduced by spheroids with aspect ratios larger than 1.2, oblate cylinders with diameter-to-length ratios greater than 1.6, and prolate cylinders with length-to-diameter ratios greater than 1.4. The effective equal-volume-sphere radius for type Ia PSCs is about 0.8 mum or larger. Type Ib PSCs are likely to be composed of spheres or nearly spherical particles with effective radii smaller than 0.8 mum. Observations for type II PSCs are consistent with large ice crystals (effective radius greater than 1 mum) modeled as cylinders or prolate spheroids, Published by Elsevier Science Ltd. C1 Columbia Univ, Dept Earth & Environm Sci, New York, NY 10025 USA. NASA GISS, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Columbia Univ, Dept Earth & Environm Sci, 2880 Broadway, New York, NY 10025 USA. EM crmim@giss.nasa.gov RI Mishchenko, Michael/D-4426-2012 NR 38 TC 29 Z9 29 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 EI 1879-1352 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD AUG-SEP PY 2001 VL 70 IS 4-6 BP 817 EP 831 DI 10.1016/S0022-4073(01)00048-6 PG 15 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 454ME UT WOS:000169975700033 ER PT J AU Whitlock, CH Brown, DE Chandler, WS DiPasquale, RC Ritchey, NA Gupta, SK Wilber, AC Kratz, DP Stackhouse, PW AF Whitlock, CH Brown, DE Chandler, WS DiPasquale, RC Ritchey, NA Gupta, SK Wilber, AC Kratz, DP Stackhouse, PW TI Global surface solar energy anomalies including El Nino and La Nina years SO JOURNAL OF SOLAR ENERGY ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT Annual Conference of the Solar Energy Division of the American-Society-of-Mechanical-Engineers CY APR 21-25, 2001 CL WASHINGTON, D.C. SP Amer Soc Mech Engineers, Solar Energy Div ID RADIATION AB Weather anomalies that increase clouds influence the reliability of both renewable energy and building environmental-control systems. Non-grid solar power systems may run out of capacity for such items as communications electronics, flood-warning stream gages, refrigerators, and small village power systems. This paper provides 1X1-degree resolution global maps that identify, those regions which experienced large abnormal solar energy during a 10-year period. A source is identified where specific values for maximum year-to-year variability can be obtained in regions where ground-site measurements do not exist. The information may aid in the selection of safety factors for solar power systems. C1 Sci Applicat Int Corp, Hampton, VA 23666 USA. Analyt Serv & Mat Inc, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Whitlock, CH (reprint author), Sci Applicat Int Corp, 1 Enterprise Pkwy,Suite 400, Hampton, VA 23666 USA. NR 4 TC 3 Z9 3 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0199-6231 J9 J SOL ENERG-T ASME JI J. Sol. Energy Eng. Trans.-ASME PD AUG PY 2001 VL 123 IS 3 BP 211 EP 215 DI 10.1115/1.1384570 PG 5 WC Energy & Fuels; Engineering, Mechanical SC Energy & Fuels; Engineering GA 461JJ UT WOS:000170360900008 ER PT J AU Juday, RD AF Juday, RD TI Generality of matched filtering and minimum Euclidean distance projection for optical pattern recognition SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID MODULATION; TARGET AB Matched filtering followed by a minimum Euclidean distance projection onto realizable filter values was previously shown to optimize the signal-to-noise ratio for single training images in optical correlation pattern recognition. The algorithm is now shown to solve the combination of(1) standard statistical pattern-recognition metrics with multiple training images, (2) additive input noise of known power spectral density and also additive detection noise that is irreducible by the filter, (3) the building of the filter on arbitrary subsets of the complex unit disk, and (4) the use of observable correlator outputs only. The criteria include the Fisher ratio, the Bayes error and Bayes cost, the Chernoff and Bhattacharyya bounds, the population entropy and expected information, versions of signal-to-noise ratio that use other than second power in their norm, and the area under the receiver operating characteristic curve. Different criteria are optimized by different complex scalar weights. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Juday, RD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 21 TC 11 Z9 11 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD AUG PY 2001 VL 18 IS 8 BP 1882 EP 1896 DI 10.1364/JOSAA.18.001882 PG 15 WC Optics SC Optics GA 455HK UT WOS:000170021300010 PM 11488492 ER PT J AU Yu, DH Lee, JH Chang, JS Ryu, JS Hahn, JW Danehy, PM AF Yu, DH Lee, JH Chang, JS Ryu, JS Hahn, JW Danehy, PM TI Effects of laser-beam temporal pulse shape on signal strength and spectral line shape of forward degenerate four-wave mixing SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID 2-LEVEL SATURABLE ABSORBERS; 4-WAVE-MIXING SPECTROSCOPY; 4-WAVE; SATURATION; GEOMETRY; INTENSITIES; SYSTEMS; FLAME AB We investigate the effects of the input laser beam's temporal pulse shape on a forward degenerate four-wave mixing (FDFWM) signal, assuming two-level saturable absorbers. Under conditions in which the coherence time is far shorter than the pulse-duration, we can calculate the signal easily in the time and frequency domains. From this result it is shown that, when the pulse duration is longer than ten times the population relaxation time, the calculated signal intensity is almost the same as that obtained by assuming a steady state throughout duration of the laser pulse, With this assumption, we obtain the signal by summing all the steady-state signals at each time-domain grid point during the pulse. The calculation is performed with three input beam temporal pulse shapes: square, Gaussian, and typical Q-switched pulses. After reaching a maximum, the signal intensity decreases. The rates of the signal increase and decrease depend strongly on the temporal shape of the input beam. For the same average power, the square-pulse input saturates the absorber faster than the other pulses. These results indicate that the weak part of the pulse input plays an important role in generating the signal, yielding differences in saturation behavior of the signal intensity and the spectral line shape. We compare the calculations with experiments by fitting the saturation curve of the FDFWM signal of argon atoms in a radio frequency inductively coupled plasma. Also, the spectral line shape of the DFWM signal is fitted with the calculation by use of published experimental data. (C) 2001 Optical Society of America. C1 Seoul Natl Univ, Sch Phys, Seoul 151742, South Korea. Korea Res Inst Stand & Sci, Div Opt Metrol, Laser Metrol Grp, Taejon 305600, South Korea. NASA, Langley Res Ctr, Instrumentat Syst Dev Branch, Hampton, VA 23681 USA. RP Yu, DH (reprint author), Seoul Natl Univ, Sch Phys, Seoul 151742, South Korea. EM jailee@phya.snu.ac.kr NR 23 TC 2 Z9 2 U1 0 U2 4 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 AUG PY 2001 VL 18 IS 8 BP 1111 EP 1118 DI 10.1364/JOSAB.18.001111 PG 8 WC Optics SC Optics GA 459YZ UT WOS:000170280200009 ER PT J AU DellaCorte, C AF DellaCorte, C TI Buddy, can you spare some change? SO LUBRICATION ENGINEERING LA English DT Editorial Material C1 NASA, Glenn Res Ctr, Washington, DC USA. RP DellaCorte, C (reprint author), NASA, Glenn Res Ctr, Washington, DC USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD AUG PY 2001 VL 57 IS 8 BP 3 EP 3 PG 1 WC Engineering, Mechanical SC Engineering GA 459QE UT WOS:000170261500001 ER PT J AU Gibson, H AF Gibson, H TI Lubrication of Space Shuttle main engine turbopump bearings SO LUBRICATION ENGINEERING LA English DT Article; Proceedings Paper CT 56th Annual Meeting of the Society-of-Tribologists-and-Lubrication-Engineers CY MAY 20-24, 2001 CL ORLANDO, FLORIDA SP Soc Tribologists Lubricat Engineers DE bearings; ceramic bearings; rolling element bearings; ball bearings; self-lubricating bearings AB The Space Shuttle has three main engines that are used for propulsion into orbit. These engines are fed propellants by four turbopumps on each engine. A main element in the turbopumps are the bearings supporting the rotor that spins the turbine blades and the pump impellers. These bearings are required to spin at very high speeds, support radial and thrust loads, and have high wear resistance without the benefit of lubrication. The liquid hydrogen and oxygen propellants flow through the bearings to cool the surfaces. The volatile nature Of the propellants excludes any conventional means of lubrication. Lubrication for these bearings is provided by, the ball separator inside the bearing. The separator is a composite material that supplies a transfer film of lubrication to the rings and balls. New lubrication schemes and materials have been investigated at Marshall Space Flight Center in a bearing test rig with promising results. Hybrid bearings with silicon nitride balls were also evaluated. The use of hybrid, silicon nitride ball bearings in conjunction with better separator materials has shown excellent results. The work that Mai-shall has done is being utilized in turbopumps flying on the space shuttle fleet and will be utilized in future space travel. The results of this work are valuable for all aerospace and commercial applications where high-speed bearings are used. C1 George C Marshall Space Flight Ctr, Huntsville, AL USA. RP Gibson, H (reprint author), George C Marshall Space Flight Ctr, Huntsville, AL USA. NR 3 TC 2 Z9 2 U1 0 U2 1 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD AUG PY 2001 VL 57 IS 8 BP 10 EP 12 PG 3 WC Engineering, Mechanical SC Engineering GA 459QE UT WOS:000170261500006 ER PT J AU Sandford, SA Bernstein, MP Dworkin, JP AF Sandford, SA Bernstein, MP Dworkin, JP TI Assessment of the interstellar processes leading to deuterium enrichment in meteoritic organics SO METEORITICS & PLANETARY SCIENCE LA English DT Review ID POLYCYCLIC AROMATIC-HYDROCARBONS; INTERPLANETARY DUST PARTICLES; LASER MASS-SPECTROMETRY; DENSE MOLECULAR CLOUDS; EARLY SOLAR-SYSTEM; 3 MICRON SPECTRA; H2O ICE BANDS; MURCHISON METEORITE; CARBONACEOUS CHONDRITES; INFRARED-EMISSION AB The presence of isotopic anomalies is the most unequivocal demonstration that meteoritic material contains circumstellar or interstellar components. In the case of organic compounds in meteorites and interplanetary dust particles (IDPs), the most useful isotopic tracer has been deuterium (D). We discuss four processes that are expected to lead to D enrichment in interstellar materials and describe how their unique characteristics can be used to assess their relative importance for the organics in meteorites. These enrichment processes are low-temperature gas phase ion-molecule reactions, low-temperature gas-grain reactions, gas phase unimolecular photodissociation, and ultraviolet photolysis in D-enriched ice mantles. Each of these processes is expected to be associated with distinct regiochemical signatures (D placement on the product molecules, correlation with specific chemical functionalities, etc.), especially in the molecular population of polycyclic aromatic hydrocarbons (PAHs). We describe these differences and discuss how they may be used to delineate the various interstellar processes that may have contributed to meteoritic D enrichments. We also briefly discuss how these processes may affect the isotopic distributions in C, O, and N in the same compounds. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SETI Inst, Mountain View, CA 94043 USA. RP Sandford, SA (reprint author), NASA, Ames Res Ctr, Mail Stop 245-6, Moffett Field, CA 94035 USA. EM ssandford@mail.arc.nasa.gov RI Dworkin, Jason/C-9417-2012 OI Dworkin, Jason/0000-0002-3961-8997 NR 109 TC 85 Z9 87 U1 0 U2 8 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 AUG PY 2001 VL 36 IS 8 BP 1117 EP 1133 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 465PN UT WOS:000170599300011 ER PT J AU MacKay, DDS Charnley, SB AF MacKay, DDS Charnley, SB TI Phosphorus in circumstellar envelopes SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE molecular processes; circumstellar matter; stars : individual : IRC+10 degrees 216; stars : late-type ID DENSE INTERSTELLAR CLOUDS; CARBON-BEARING MOLECULES; RICH; CHEMISTRY; ATMOSPHERES; HCN; PN AB We have investigated the chemistry of phosphorus-bearing compounds in the circumstellar envelopes of both oxygen-rich and carbon-rich evolved stars. In accordance with thermodynamic calculations of photospheric chemistry, we have assumed that the dominant forms of phosphorus in the inner circumstellar envelope (CSE) are PS and HCP in each case. In the C-rich case, we can reproduce the observed CP abundance reasonably well if it is the photodaughter of HCP In the O-rich case we find, for the same amount of P available in PS, that large abundances of atomic P are available for reaction but that a low abundance of PO can be produced. We have not extensively explored the effect of additional neutral processes since our results are partly compromised by the fact that neither HCP nor PS is detected in the three CSEs where searches have been made; our models predict column densities in excess of the published upper limits. Sensitive searches for these molecules at higher frequencies are required before their presence in circumstellar envelopes can definitely be ruled out. Dust condensation may incorporate all the available P into refractory grains and so we suggest that searches for P-bearing molecules may have the greatest opportunity for success in more evolved objects, such as protoplanetary nebulae, where P has been released from grains through the action of strong shock waves. C1 Univ Kent, Elect Engn Labs, Unit Space Sci & Astrophys, Canterbury CT2 7NT, Kent, England. NASA, Div Space Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. RP MacKay, DDS (reprint author), Univ Kent, Elect Engn Labs, Unit Space Sci & Astrophys, Canterbury CT2 7NT, Kent, England. RI Charnley, Steven/C-9538-2012 NR 30 TC 23 Z9 23 U1 0 U2 5 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 AUG 1 PY 2001 VL 325 IS 2 BP 545 EP 549 DI 10.1046/j.1365-8711.2001.04429.x PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 465BJ UT WOS:000170568100011 ER PT J AU Smith, JA Ballard, JR AF Smith, JA Ballard, JR TI Thermal infrared hot spot and dependence on canopy geometry SO OPTICAL ENGINEERING LA English DT Article DE remote sensing; thermal infrared; brightness temperature; directional anisotropy; hot spot; canopy geometry ID MODEL AB For simple homogeneous canopies, we predict canopy thermal infrared hot spot variations of 2 degreesC at the surface with respect to nadir viewing. Dependence on leaf size is weak as long as the ratio of leaf size to canopy height is maintained. However, the angular width of the hot spot increases as the ratio of leaf diameter to canopy height increases. Atmospheric effects minimize but do not eliminate the TIR hot spot at satellite altitudes. (C) 2001 society of Photo-Optical Instrumentation Engineers. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. USAE, Ctr Res & Dev, Environm Lab, Vicksburg, MS 39180 USA. RP Smith, JA (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NR 7 TC 9 Z9 9 U1 0 U2 0 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD AUG PY 2001 VL 40 IS 8 BP 1435 EP 1437 DI 10.1117/1.1387990 PG 3 WC Optics SC Optics GA 471ML UT WOS:000170933100003 ER PT J AU Crippen, RE Blom, RG AF Crippen, RE Blom, RG TI Unveiling the lithology of vegetated terrains in remotely sensed imagery SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID MULTISPECTRAL IMAGES; SOIL; NEVADA AB "Forced invariance" is a processing method that can subdue the expression of vegetation and enhance the expression of the underlying lithology in remotely sensed imagery. Data for each spectral band are altered in an empirically derived manner so as to produce a refined band that largely excludes contrasts attributable to variations in vegetation abundance. This is accomplished by (1) correcting the data for the effects of additive path radiance, (2) statistically characterizing the relationship between the band data and a vegetation index, and (3) multiplying the band data as a function of the index so that the average band value is generally invariant across all index values. Comparison of original and processed color composite displays confirms the method's utility in unveiling rock patterns consistent with nearby well-exposed bedrock and alluvial patterns downslope, especially in areas of open canopy vegetation such as in mixed and and semi-arid terrains. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Crippen, RE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-233, Pasadena, CA 91109 USA. NR 24 TC 15 Z9 18 U1 0 U2 1 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 USA SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD AUG PY 2001 VL 67 IS 8 BP 935 EP 943 PG 9 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 457CW UT WOS:000170120400009 ER PT J AU Gamba, P Houshmand, B AF Gamba, P Houshmand, B TI Integration of hyperspectral and IFSAR data for improved 3D urban profile reconstruction SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID INFORMATION; IMAGERY AB In this paper hyperspectral (AVIRIS) and radar (AIRSAR) aerial data acquired over urban environments are considered. The information available from each sensor was extracted and merged to improve the 3D profile reconstruction of builtup areas. Two classification schemes were evaluated for AVIRIS data clustering, while the effect of the radar view angle was considered in assessing the quality of the associated digital elevation models. A detailed analysis of what is possible to extract and to what extent these data are useful was also produced, considering precise 2D and 3D ground truth of the UCLA campus. C1 Univ Pavia, Dipartimento Elettron, I-27100 Pavia, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gamba, P (reprint author), Univ Pavia, Dipartimento Elettron, Via Ferrata 1, I-27100 Pavia, Italy. RI Gamba, Paolo/G-1959-2010 OI Gamba, Paolo/0000-0002-9576-6337 NR 20 TC 5 Z9 5 U1 0 U2 0 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 USA SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD AUG PY 2001 VL 67 IS 8 BP 947 EP 956 PG 10 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 457CW UT WOS:000170120400010 ER PT J AU Vasquez, RP Jung, CU Park, MS Kim, HJ Kim, JY Lee, SI AF Vasquez, RP Jung, CU Park, MS Kim, HJ Kim, JY Lee, SI TI X-ray photoemission study of MgB2 SO PHYSICAL REVIEW B LA English DT Article ID HIGH-TEMPERATURE SUPERCONDUCTORS; SPECTROSCOPY; SURFACE; SHIFTS AB A c-axis oriented thin film and a high-density sintered pellet of MgB2 have been studied by x-ray photoemission spectroscopy, and compared to measurements from MgO and MgF2 single crystals. The as-grown surface has a layer which is Mg-rich and oxidized, which is effectively removed by a nonaqueous etchant. The subsurface region of the pellet is Mg deficient. This nonideal near-surface region may explain varied scanning tunneling spectroscopy results. The MgB2 core level and Auger signals are similar to measurements from metallic Mg and transition-metal diborides, and the measured valence band is consistent with the calculated density of states. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. Pohang Univ Sci & Technol, Dept Phys, Pohang 790784, South Korea. Pohang Univ Sci & Technol, Natl Creat Res Initiat Ctr Superconduct, Pohang 790784, South Korea. RP Vasquez, RP (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. EM richard.p.vasquez@jpl.nasa.gov NR 27 TC 48 Z9 48 U1 1 U2 9 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 AUG 1 PY 2001 VL 64 IS 5 AR 052510 DI 10.1103/PhysRevB.64.052510 PG 4 WC Physics, Condensed Matter SC Physics GA 459TF UT WOS:000170267000024 ER PT J AU Ziemer, JK Choueiri, EY AF Ziemer, JK Choueiri, EY TI Scaling laws for electromagnetic, pulsed plasma thrusters SO PLASMA SOURCES SCIENCE & TECHNOLOGY LA English DT Article AB The scaling laws of pulsed plasma thrusters operating in the predominantly electromagnetic acceleration mode (EM-PPT) are investigated theoretically and experimentally using gas-fed pulsed plasma thrusters. A fundamental characteristic velocity that depends on the inductance per unit length and the square root of the capacitance to the initial inductance ratio is identified. An analytical model of the discharge current predicts scaling laws in which the propulsive efficiency is proportional to the EM-PPT performance scaling number, defined here as the ratio of the exhaust velocity to the EM-PPT characteristic velocity. The importance of the effective plasma resistance in improving the propulsive performance is shown. To test the validity of the predicted scaling relations, the performance of two gas-fed pulsed plasma thruster designs (one with coaxial electrodes and the other with parallel-plate electrodes), was measured under 70 different operating conditions using an argon plasma. The measurements demonstrate that the impulse bit scales linearly with the integral of the square of the discharge current as expected for an electromagnetic accelerator. The measured performance scaling is shown to be in good agreement with the theoretically predicted scaling. Normalizing the exhaust velocity and the impulse-to-energy ratio by the EM-PPT characteristic velocity collapses almost all the measured data onto single curves that uphold the general validity of these scaling laws. C1 Princeton Univ, Dept Mech & Aerosp Engn, Appl Phys Grp, Elect Propuls & Plasma Dynam Lab, Princeton, NJ 08544 USA. RP Ziemer, JK (reprint author), NASA, Jet Propuls Lab, Adv Propuls Technol Grp, M-S 125-109,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 25 TC 15 Z9 15 U1 2 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0963-0252 J9 PLASMA SOURCES SCI T JI Plasma Sources Sci. Technol. PD AUG PY 2001 VL 10 IS 3 BP 395 EP 405 DI 10.1088/0963-0252/10/3/302 PG 11 WC Physics, Fluids & Plasmas SC Physics GA 472KU UT WOS:000170983700002 ER PT J AU Dolan, JF AF Dolan, JF TI Dying pulse trains in Cygnus XR-1: Evidence for an event horizon? SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID NEUTRON-STARS; ORBITAL INCLINATION; BLACK-HOLES; ACCRETION AB The X-ray-emitting component in the Cyg XR-1/HDE 226868 system is a leading candidate for identification as a stellar-mass-sized black hole. The detection of an event horizon surrounding the point singularity in such a system would constitute a positive identification of a black hole as predicted by general relativity. One signature of such an event horizon would be the existence of dying pulse trains emitted by material spiraling into the event horizon from the last stable orbit around the black hole. We observed the Cyg XR-1 system at three different epochs in a 1400-3000 Angstrom bandpass with 0.1 ms time resolution using the Hubble Space Telescope's High Speed Photometer. Repeated excursions of the detected flux by more than 3 sigma above the mean are present in the UV flux with an FWHM of 1-10 ms. If any of these excursions are pulses of radiation produced in the system (and not just stochastic variability associated with the Poisson distribution of detected photon arrival times), then this short a timescale requires that the pulses originate in the accretion disk around Cyg XR-1. Two series of pulses with characteristics similar to those expected from dying pulse trains were detected in 3 hr of observation. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Dolan, JF (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NR 23 TC 5 Z9 5 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 AUG PY 2001 VL 113 IS 786 BP 974 EP 982 DI 10.1086/322917 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 459VC UT WOS:000170271300011 ER PT J AU Gonzalez-Zugasti, JP Otto, KN Baker, JD AF Gonzalez-Zugasti, JP Otto, KN Baker, JD TI Assessing value in platformed product family design SO RESEARCH IN ENGINEERING DESIGN-THEORY APPLICATIONS AND CONCURRENT ENGINEERING LA English DT Article DE platforms; options; value ID METRICS AB A platform is the set of elements and interfaces that are common to a family of products. In this paper, the design of a platform-based product family is formulated as an optimization problem. This optimization is then transformed into a two-step process amenable to industrial product design processes. The first step involves designing the technical aspects of the product family, optimizing an objective (or a set of objectives) subject to technical constraints, with external uncertain factors fixed. We have previously presented such a method for designing product families based on platforms that optimizes performance and cost metrics, using variables and a system model. That approach allows a team of engineers to design and evaluate candidate platforms, given perfect understanding of the designs and requirements. The second step is to quantify the value to the firm for each identified design alternative, while here accounting for external uncertain factors of the product family development. In this paper we present a model to perform this second step of the overall approach. Real options concepts are introduced to model the risks and delayed decision benefits present during product development due to uncertainty in technologies, funding, etc. We develop a quantitative measure of the value to the company for different family designs, and apply it to select the most appropriate design from the possible alternatives. An application to the design of platform-based families of spacecraft is shown. C1 MIT, Ctr Innovat Prod Dev, Cambridge, MA 02139 USA. CALTECH, Jet Prop Lab, Architecture Div, Pasadena, CA 91109 USA. RP Otto, KN (reprint author), MIT, Ctr Innovat Prod Dev, 3-449B,77 Massachusetts Ave, Cambridge, MA 02139 USA. NR 39 TC 74 Z9 76 U1 0 U2 6 PU SPRINGER-VERLAG LONDON LTD PI GODALMING PA SWEETAPPLE HOUSE CATTESHALL ROAD, GODALMING GU7 3DJ, SURREY, ENGLAND SN 0934-9839 J9 RES ENG DES JI Res. Eng. Design-Theory Appl. Concurrent Eng. PD AUG PY 2001 VL 13 IS 1 BP 30 EP 41 DI 10.1007/s001630100001 PG 12 WC Engineering, Multidisciplinary; Engineering, Industrial; Engineering, Manufacturing SC Engineering GA 610WB UT WOS:000178983600004 ER PT J AU Massom, RA Eicken, H Haas, C Jeffries, MO Drinkwater, MR Sturm, M Worby, AP Wu, XR Lytle, VI Ushio, S Morris, K Reid, PA Warren, SG Allison, I AF Massom, RA Eicken, H Haas, C Jeffries, MO Drinkwater, MR Sturm, M Worby, AP Wu, XR Lytle, VI Ushio, S Morris, K Reid, PA Warren, SG Allison, I TI Snow on Antarctic Sea ice SO REVIEWS OF GEOPHYSICS LA English DT Review ID SATELLITE PASSIVE MICROWAVE; WESTERN WEDDELL-SEA; THICKNESS DISTRIBUTION; SOUTHERN-OCEAN; THERMAL-CONDUCTIVITY; DRAG COEFFICIENTS; SEASONAL SNOW; PACK-ICE; STRUCTURAL CHARACTERISTICS; INTERANNUAL VARIABILITY AB Snow on Antarctic sea ice plays a complex and highly variable role in air-sea-ice interaction processes and the Earth's climate system. Using data collected mostly during, the past 10 years, this paper reviews the following topics: snow thickness and snow type and their geographical and seasonal variations; snow grain size, density, and salinity; frequency of occurrence of slush; thermal conductivity, snow surface temperature, and temperature gradients within snow; and the effect of snow thickness on albedo. Major findings include large regional and seasonal differences in snow properties and thicknesses; the consequences of thicker snow and thinner ice in the Antarctic relative to the Arctic (e.g., the importance of flooding and snow-ice formation); the potential impact of increasing snowfall resulting from global climate change; lower observed values of snow thermal conductivity than those typically used in models; periodic large-scale melt in winter; and the contrast in summer melt processes between the Arctic and the Antarctic. Both climate modeling and remote sensing would benefit by taking account of the differences between the two polar regions. C1 Univ Tasmania, Antarctic Cooperat Res Ctr, Hobart, Tas 7001, Australia. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. Alfred Wegener Inst Polar & Marine Res, D-27568 Bremerhaven, Germany. European Space Agcy, Estec, Oceans Sea Ice Unit, APP,FSO, NL-2200 AG Noordwijk, Netherlands. CALTECH, Jet Prop Lab, NASA, Pasadena, CA USA. USA, Cold Reg Res & Engn Lab, Ft Wainwright, AK 99703 USA. Australian Antarctic Div, Kingston, Tas, Australia. Natl Inst Polar Res, Itabashi Ku, Tokyo 173, Japan. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. RP Massom, RA (reprint author), Univ Tasmania, Antarctic Cooperat Res Ctr, GPO Box 252-80, Hobart, Tas 7001, Australia. RI Worby, Anthony/A-2373-2012; Haas, Christian/L-5279-2016; Eicken, Hajo/M-6901-2016; OI Haas, Christian/0000-0002-7674-3500; Drinkwater, Mark/0000-0002-9250-3806 NR 161 TC 142 Z9 150 U1 0 U2 47 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 AUG PY 2001 VL 39 IS 3 BP 413 EP 445 DI 10.1029/2000RG000085 PG 33 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 458WM UT WOS:000170218500005 ER PT J AU Blake, DF Jenniskens, P AF Blake, DF Jenniskens, P TI The ice of life SO SCIENTIFIC AMERICAN LA English DT Article C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Blake, DF (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 2 TC 4 Z9 4 U1 1 U2 6 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 AUG PY 2001 VL 285 IS 2 BP 44 EP + PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 455PE UT WOS:000170034600033 PM 11478001 ER PT J AU Hargrove, WW Hoffman, FM Sterling, T AF Hargrove, WW Hoffman, FM Sterling, T TI The do-it-yourself supercomputer SO SCIENTIFIC AMERICAN LA English DT Article C1 Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. CALTECH, Ctr Adv Comp Res, Pasadena, CA 91125 USA. Jet Propuls Lab, Pasadena, CA USA. RP Hargrove, WW (reprint author), Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. RI Hoffman, Forrest/B-8667-2012 OI Hoffman, Forrest/0000-0001-5802-4134 NR 3 TC 8 Z9 8 U1 0 U2 1 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 AUG PY 2001 VL 285 IS 2 BP 72 EP 79 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 455PE UT WOS:000170034600037 PM 11478005 ER PT J AU Okada, M Liou, NS Prakash, V Miyoshi, K AF Okada, M Liou, NS Prakash, V Miyoshi, K TI Tribology of high-speed metal-on-metal sliding at near-melt and fully-melt interfacial temperatures SO WEAR LA English DT Article DE high-speed friction; plate-impact; molten metal; dynamic viscosity; knoop-hardness; 7075-T6 Al; CH tool-steel ID TIME-RESOLVED FRICTION; PRESSURE-SHEAR IMPACT; SURFACE; SOLIDS; HEAT; WEAR; WAVE AB The present paper describes results of plate-impact friction experiments conducted to study time-resolved frictional characteristics of sliding interfaces under extreme conditions. By employing pressure-shear impact of tribo-pair materials comprising hard tool-steels against low melt-point metals such as 7075-T6 Al alloys, interfacial normal pressures ranging from 1 to 2 GPa and slip-speeds of approximately 100m/s have been obtained. The resulting relatively large friction-stresses (100-400 MPa) combined with high slip-speeds generate conditions conducive to interfacial temperatures approaching the near-melt and fully-melt temperature regime of the lower melt-point metal (aluminum alloy) comprising the tribo-pair. During the early part of frictional slip the coefficient of kinetic friction is observed to decrease with increasing slip-velocity while during the later part transition in interfacial slip occurs from near-melt to the fully-melt temperature regime of the 7075-T6 Al alloy. Under these fully-melt conditions, the interfacial resistance approaches the shear strength of the molten aluminum alloy under hydrostatic pressures of approximately 1-3 GPa and shear-strain rates of similar to 10(7) s(-1). The results of the study indicate that under these extreme conditions molten aluminum films maintain a shearing resistance as high as 100 MPa. Scanning electron microscopy (SEM) of the sliding surface reveal molten aluminum to be smeared on the tribo-pair interface. Results of energy dispersive X-ray spectroscopy shows appreciable amounts of material transfer between the tribo-pair surfaces. Knoop-hardness measurements in 7075-T6 Al alloy at various depths from the slip interface, indicate that the hardness increases approximately linearly with depth and reaches a plateau at approximately 40 mum from the surface. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Prakash, V (reprint author), Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. EM vxp18@po.cwru.edu NR 41 TC 12 Z9 15 U1 1 U2 9 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0043-1648 J9 WEAR JI Wear PD AUG PY 2001 VL 249 IS 8 BP 672 EP 686 DI 10.1016/S0043-1648(01)00698-6 PG 15 WC Engineering, Mechanical; Materials Science, Multidisciplinary SC Engineering; Materials Science GA 463GU UT WOS:000170469400005 ER PT J AU Millstein, J O'Clair, CE AF Millstein, J O'Clair, CE TI Comparison of age-length and growth-increment general growth models of the Schnute type in the Pacific Blue Mussel, Mytilus trossulus Gould SO JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY LA English DT Article DE aging; growth mussel; Mytilus trossulus; Schnute model; von Bertalanffy model ID SHELL GROWTH; EDULIS-L; POPULATION-STRUCTURE; MORTALITY-RATES; SEA; PARAMETERS; ALASKA; VARIABILITY; PATTERNS; BANDS AB Models of Mytilus growth, based mostly on length-at-age data, have typically taken the form exemplified by the von Bertalanffy or Gompertz formulations. These models require assumptions about the form of the growth curve. We used the Schnute general growth model to examine growth in the Pacific Blue Mussel, Mytilus trossulus, in Prince William Sound, AK. The Schnute model provides a convenient analytical method for selecting among all previously published growth models. Mussels were tagged with individually numbered tags at 13 sites in July 1997 and were collected in July 1998. Age was determined from surface growth rings on the shell, and shell length at maximum annulus was measured. Annual deposition of the growth rings was verified through radial sections of mussel valves, aided by acetate peels, in conjunction with in situ annual growth measurements. Growth was modeled with the Schnute general growth model for age-length data or with an analog of the Schnute model for growth-increment data. Bootstrap confidence intervals were obtained for all parameters of the model and for model predicted lengths at each annulus. Confidence intervals of the between-annuli growth-increment model overlapped those of the age-length model at all annuli when growth over the entire range of ages in the population was estimated. Differences in growth model parameters between the age-length model and the mark-recapture analog could be accounted for solely by inherent differences in age-based versus length-based models. Growth estimates generated from between-annuli measurements were equivalent to growth estimates obtained from mark-recapture measurements of annual growth. In general, mussel growth at our sites was best described by the von Bertalanffy submodel. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Natl Marine Fisheries Serv, Auke Bay Lab, Juneau, AK 99801 USA. Univ So Calif, Keck Sch Med, Div Biometry, Los Angeles, CA 90033 USA. RP O'Clair, CE (reprint author), Natl Marine Fisheries Serv, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 50 TC 9 Z9 9 U1 2 U2 18 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0981 J9 J EXP MAR BIOL ECOL JI J. Exp. Mar. Biol. Ecol. PD JUL 30 PY 2001 VL 262 IS 2 BP 155 EP 176 DI 10.1016/S0022-0981(01)00292-1 PG 22 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 454JG UT WOS:000169969000002 ER PT J AU Robertson, A Overpeck, J Rind, D Mosley-Thompson, E Zielinski, G Lean, J Koch, D Penner, J Tegen, I Healy, R AF Robertson, A Overpeck, J Rind, D Mosley-Thompson, E Zielinski, G Lean, J Koch, D Penner, J Tegen, I Healy, R TI Hypothesized climate forcing time series for the last 500 years SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ICE CORE; VOLCANIC-ERUPTIONS; ANTARCTIC ICE; ANTHROPOGENIC AEROSOLS; EXPLOSIVE VOLCANISM; OPTICAL-THICKNESS; SOLAR IRRADIANCE; ATMOSPHERIC CO2; 6 CENTURIES; RECORD AB A new compilation of annually resolved time series of atmospheric trace gas concentrations, solar irradiance, tropospheric aerosol optical depth, and stratospheric (volcanic) aerosol optical depth is presented for use in climate modeling studies of the period 1500 to 1999 A.D. Atmospheric CO2 CH4, and N2O concentrations over this period are well established on the basis of fossil air trapped in ice cores and instrumental measurements over the last few decades. Estimates of solar irradiance, ranging between 1364.2 and 1368.2 W/m(2), are presented using calibrated historical observations of the Sun back to 1610, along with cosmogenic isotope variations extending back to 1500. Tropospheric aerosol distributions are calculated by scaling the modern distribution of sulfate and carbonaceous aerosol optical depths back to 1860 using reconstructed regional CO2 emissions; prior to 1860 the anthropogenic tropospheric aerosol optical depths are assumed to be zero. Finally, the first continuous, annually dated record of zonally averaged stratospheric (volcanic) optical depths back to 1500 is constructed using sulfate flux data from multiple ice cores from both Greenland and Antarctica, in conjunction with historical and instrumental (satellite and pyrheliometric) observations. The climate forcings generated here are currently being used as input to a suite of transient (time dependent) paleoclimate model simulations of the past 500 years. These forcings are also available for comparison with instrumental and proxy paleoclimate data of the same period. C1 Univ Colorado, Inst Arctic & Alpine Res, Boulder, CO 80303 USA. Univ Colorado, Dept Geol Sci, Boulder, CO 80303 USA. Univ Arizona, Inst Study Planet Earth, Tucson, AZ 85721 USA. Univ Arizona, Dept Geosci, Tucson, AZ 85721 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. Univ Maine, Inst Quaternary Studies, Climate Studies Ctr, Orono, ME 04469 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. RP Univ Colorado, Inst Arctic & Alpine Res, 1560 30th St, Boulder, CO 80303 USA. RI Healy, Richard/J-9214-2015; OI Healy, Richard/0000-0002-5098-8921; Lean, Judith/0000-0002-0087-9639 NR 89 TC 108 Z9 111 U1 2 U2 12 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 JUL 27 PY 2001 VL 106 IS D14 BP 14783 EP 14803 DI 10.1029/2000JD900469 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700004 ER PT J AU Leblanc, T McDermid, IS AF Leblanc, T McDermid, IS TI Quasi-biennial oscillation signatures in ozone and temperature observed by lidar at Mauna Loa, Hawaii (19.5 degrees N, 155.6 degrees W) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID QBO; CYCLE; CIRCULATION; CLIMATOLOGY; TRANSPORT; ENSO AB Using nearly 6 years of nighttime differential absorption lidar ozone and Rayleigh/Raman lidar temperature measurements obtained by the Jet Propulsion Laboratory at Mauna Loa Observatory, Hawaii, the stratospheric quasi-biennial oscillation (QBO) signatures (.15-55 km) in ozone and temperature are revealed. Several clear QBO signatures have been observed in both temperature and ozone. The QBO signature in temperature maximizes at 35 km (5 K amplitude) and is seasonally synchronized (winter) and out of phase with the expected signature at the equator. Also, for the periods 1994-1996 and 1998-2000 the QBO is observable above 45 km, and near 24 km, with opposite phase to that observed at 35 km. The clearest QBO signature in stratospheric ozone maximizes near 31 km and is also seasonally synchronized in late winter-early spring and is out of phase with the expected equatorial ozone QBO anomaly. Other signatures are observed in winter-spring near 47 km, in summer near 26 km, and in winter-spring near 22 km, in phase, in phase, and out of phase, respectively, with the expected equatorial ozone QBO. These QBO anomalies identified in ozone and temperature are highly consistent with the previously observed and modeled QBO anomalies assuming that Hawaii is located in the subtropical branch of the asymmetrical QBO-induced meridional circulation. The observed temperature and ozone QBO were both strongly disturbed by the El Nino-Southern Oscillation below 25-27 km in 1997-1998. C1 CALTECH, Jet Prop Lab, Table Mtn Facil, Wrightwood, CA 92397 USA. RP Leblanc, T (reprint author), CALTECH, Jet Prop Lab, Table Mtn Facil, POB 367, Wrightwood, CA 92397 USA. NR 20 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 14869 EP 14874 DI 10.1029/2001JD900162 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700010 ER PT J AU Aires, F Prigent, C Rossow, WB Rothstein, M AF Aires, F Prigent, C Rossow, WB Rothstein, M TI A new neural network approach including first guess for retrieval of atmospheric water vapor, cloud liquid water path, surface temperature, and emissivities over land from satellite microwave observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NUMERICAL WEATHER PREDICTION; VARIATIONAL ASSIMILATION; SOUNDING RADIANCES; HUMIDITY PROFILE; SSM/I; ISCCP; TOVS; INFORMATION; VALIDATION; PROJECT AB The analysis of microwave observations over land to determine atmospheric and surface parameters is still limited due to the complexity of the inverse problem. Neural network techniques have already proved successful as the basis of efficient retrieval methods for nonlinear cases; however, first guess estimates, which are used in variational assimilation methods to avoid problems of solution nonuniqueness or other forms of solution irregularity, have up to now not been used with neural network methods. In this study, a neural network approach is developed that uses a first guess. Conceptual bridges are established between the neural network and variational assimilation methods. The new neural method retrieves the surface skin temperature, the integrated water vapor content, the cloud liquid water path and the microwave surface emissivities between 19 and 85 GHz over land from Special Sensor Microwave Imager observations. The retrieval, in parallel, of all these quantities improves the results for consistancy reasons. A database to train the neural network is calculated with a radiative transfer model and a global collection of coincident surface and atmospheric parameters extracted from the National Center for Environmental Prediction reanalysis, from the International Satellite Cloud Climatology Project data, and from microwave emissivity atlases previously calculated. The results of the neural network inversion axe very encouraging. The theoretical RMS error of the surface temperature retrieval over the globe is 1.3 K in clear-sky conditions and 1.6 K in cloudy scenes. Water vapor is retrieved with a theoretical RMS error of 3.8 kg m(-2) in clear conditions and 4.9 kg m(-2) in cloudy situations. The theoretical RMS error in cloud liquid water path is 0.08 kg m(-2). The surface emissivities are retrieved with an accuracy of better than 0.008 in clear conditions and 0.010 in cloudy conditions. Microwave land surface temperature retrieval presents a very attractive complement to the infrared estimates in cloudy areas: time record of land surface temperature will be produced. C1 Columbia Univ, NASA, Goddard Inst Space Studies, Dept Appl Phys, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, Sci Syst & Applicat Inc, New York, NY 10025 USA. RP Columbia Univ, NASA, Goddard Inst Space Studies, Dept Appl Phys, 2880 Broadway, New York, NY 10025 USA. EM faires@giss.nasa.gov; eprigent@giss.nasa.gov; wrossow@giss.nasa.gov; mrothstein@giss.nasa.gov RI Rossow, William/F-3138-2015 NR 48 TC 97 Z9 106 U1 4 U2 22 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 JUL 27 PY 2001 VL 106 IS D14 BP 14887 EP 14907 DI 10.1029/2001JD900085 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700012 ER PT J AU Formenti, P Andreae, MO Lange, L Roberts, G Cafmeyer, J Rajta, I Maenhaut, W Holben, BN Artaxo, P Lelieveld, J AF Formenti, P Andreae, MO Lange, L Roberts, G Cafmeyer, J Rajta, I Maenhaut, W Holben, BN Artaxo, P Lelieveld, J TI Saharan dust in Brazil and Suriname during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) - Cooperative LBA Regional Experiment (CLAIRE) in March 1998 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LONG-RANGE TRANSPORT; MARINE BOUNDARY-LAYER; AFRICAN DUST; OPTICAL-PROPERTIES; MINERAL DUST; SIZE DISTRIBUTION; UNITED-STATES; RADIATIVE PROPERTIES; CHEMICAL-COMPOSITION; TROPICAL ATLANTIC AB Advection of Saharan dust was observed via chemical and optical measurements during March 1998 in Brazil and Suriname during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA)-Cooperative LBA Airborne Regional Experiment (CLAIRE)-98 experiment. In Brazil the dust outbreak produced an increase of a factor of 3 in the daily mean mass concentration (up to 26 +/- 7 mug m(-3)) of particles smaller than 10 mum equivalent aerodynamic diameter (EAD), and in the daily mean aerosol particle scattering coefficient sigma (N) (up to 26 +/- 8 Mm(-1) STP, ambient humidity). Background levels of aerosol scattering (ambient) were sigma (s) similar to 10 Mm(-1). The effect of dust advection was evident for all major crustal elements (Al, Si, Ca, Ti, Mn, and Fe), as well as the sea-salt elements (Na, Cl, and S), as the dust layer was transported at low altitude (below 800 hPa). Coarse P and organic carbon (OC) concentrations were not influenced by the occurrence of dust, and were mainly emitted by the rain forest. The dry scattering mass efficiency of dust (particles smaller than 10 mum EAD) was estimated to be between 0.65 (+/- 0.06) and 0.89 (+/- 0.08) m(2) g(-1). Airborne profiles of aerosol scattering showed two distinct types of vertical structure in the dust layer over Suriname, either vertically uniform (15, 26 March), or plume-like (25 March). Dust layers extended generally up to 700 hPa, while scattering layers occasionally encountered at higher altitudes resulted from smoke emitted by biomass burning in Venezuela and Colombia, Observations in South America were supported by measurements in Israel and Tenerife (Canary Islands), where the dust outbreaks were also detected. C1 Max Planck Inst Chem, Biogeochem Dept, D-55020 Mainz, Germany. Univ Utrecht, IMAU, NL-3584 CC Utrecht, Netherlands. State Univ Ghent, Inst Nucl Sci, B-9000 Ghent, Belgium. Univ Sao Paulo, Inst Fis, BR-05389970 Sao Paulo, Brazil. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. RP Formenti, P (reprint author), Max Planck Inst Chem, Biogeochem Dept, POB 3060, D-55020 Mainz, Germany. RI Maenhaut, Willy/M-3091-2013; Andreae, Meinrat/B-1068-2008; Artaxo, Paulo/E-8874-2010; Lelieveld, Johannes/A-1986-2013 OI Maenhaut, Willy/0000-0002-4715-4627; Andreae, Meinrat/0000-0003-1968-7925; Artaxo, Paulo/0000-0001-7754-3036; NR 65 TC 88 Z9 88 U1 2 U2 17 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 14919 EP 14934 DI 10.1029/2000JD900827 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700014 ER PT J AU Platnick, S Li, JY King, MD Gerber, H Hobbs, PV AF Platnick, S Li, JY King, MD Gerber, H Hobbs, PV TI A solar reflectance method for retrieving the optical thickness and droplet size of liquid water clouds over snow and ice surfaces SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AIRBORNE SPECTRAL MEASUREMENTS; EFFECTIVE PARTICLE RADIUS; RADIATION MEASUREMENTS; ARCTIC CLOUDS; SEA-ICE; STRATOCUMULUS; ALBEDO; FIRE; SUSCEPTIBILITY; PRECIPITATION AB Cloud optical thickness and droplet effective radius retrievals from solar reflectance measurements are traditionally implemented using a combination of spectral channels that are absorbing and nonabsorbing for water particles. Reflectances in nonabsorbing channels (e.g., 0.67, 0.86, 1.2 mum spectral window bands) are largely dependent on cloud optical thickness, while longer-wavelength absorbing channels (1.6, 2.1, and 3.7 mum window bands) provide cloud particle size information. Cloud retrievals over ice and snow surfaces present serious difficulties. At the shorter wavelengths, ice is bright and highly variable, both characteristics acting, to significantly increase cloud retrieval uncertainty. In contrast, reflectances at the longer wavelengths are relatively small and may be comparable to that of dark open water. A modification to the traditional cloud retrieval technique is presented. The new algorithm uses only a combination of absorbing spectral channels for which the snow/ice albedo is relatively small. Using this approach, retrievals have been made with the MODIS airborne simulator (MAS) imager flown aboard the high-altitude NASA ER-2 from May to June 1998 during the Arctic FIRE-ACE field deployment. Data from several coordinated ER-2 and in situ University of Washington Convair-580 aircraft observations of liquid water stratus clouds are examined. MAS retrievals of optical thickness, droplet effective radius, and liquid water path are shown to be in good agreement with in situ measurements. The initial success of the technique has implications for future operational satellite cloud retrieval algorithms in polar and wintertime regions. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Baltimore, MD 21228 USA. Gerber Sci Inc, Reston, VA USA. Univ Washington, Seattle, WA 98195 USA. SM&A Corp, Vienna, VA 22180 USA. RP NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. EM platnick@climate.gsfc.nasa.gov RI King, Michael/C-7153-2011; Platnick, Steven/J-9982-2014 OI King, Michael/0000-0003-2645-7298; Platnick, Steven/0000-0003-3964-3567 NR 38 TC 52 Z9 52 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 JUL 27 PY 2001 VL 106 IS D14 BP 15185 EP 15199 DI 10.1029/2000JD900441 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700033 ER PT J AU Marchand, RT Ackerman, TP King, MD Moroney, C Davies, R Muller, JPAL Gerber, H AF Marchand, RT Ackerman, TP King, MD Moroney, C Davies, R Muller, JPAL Gerber, H TI Multiangle observations of Arctic clouds from FIRE ACE: June 3, 1998, case study SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID INSTRUMENT; RADIATION AB In May and June 1998 the Airborne Multiangle Imaging Spectroradiometer (AirMISR) participated in the FIRE Arctic Cloud Experiment (ACE). AirMISR is an airborne instrument for obtaining multiangle imagery similar to that of the satellite-borne MISR instrument. This paper presents a detailed analysis of the data collected on June 3, 1998. In particular, AirMISR radiance measurements are compared with measurements made by two other instruments, the Cloud Absorption Radiometer (CAR) and the MODIS airborne simulator (NIAS), as well as to plane-parallel radiative transfer simulations. It is found that the AirMSR radiance measurements and albedo estimates compare favorably both with the other instruments and with the radiative transfer simulations. In addition to radiance and albedo, the multiangle AirMISR data can be used to obtain estimates of cloud top height using stereoimaging techniques. Comparison of AirMISR retrieved cloud top height (using the complete MISR-based stereoimaging approach) shows excellent agreement with the measurements from the airborne Cloud Lidar System (CLS) and ground-based millimeterwave cloud radar. C1 Pacific NW Natl Lab, Richland, WA 99352 USA. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. Gerber Sci Inst, Reston, VA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. UCL, Dept Geomat Engn, London, England. RP Pacific NW Natl Lab, 902 Battelle Blvd,MSIN K9-24,POB 999, Richland, WA 99352 USA. EM roj@pnl.gov; thomas.ackerman@pnl.gov RI Davies, Roger/D-4296-2009; King, Michael/C-7153-2011 OI Davies, Roger/0000-0002-2991-0409; King, Michael/0000-0003-2645-7298 NR 19 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 EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 15201 EP 15214 DI 10.1029/2000JD900302 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700034 ER PT J AU Minnis, P Chakrapani, V Doelling, DR Nguyen, L Palikonda, R Spangenberg, DA Uttal, T Arduini, RF Shupe, M AF Minnis, P Chakrapani, V Doelling, DR Nguyen, L Palikonda, R Spangenberg, DA Uttal, T Arduini, RF Shupe, M TI Cloud coverage and height during FIRE ACE derived from AVHRR data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SATELLITE; PARAMETERS; SURFACE; SYSTEM; ISCCP AB Cloud cover and height are derived from NOAA-12 and NOAA-14 advanced very high resolution radiometer (AVHRR) data taken over the Arctic Ocean for an 8 degrees latitude by 30 degrees longitude domain centered on the Surface Heat Budget of the Arctic Ocean (SHEBA) ship Des Groseilliers. Multispectral thresholds were determined subjectively and applied to each image, providing excellent temporal coverage during the May-July 1998 First ISCCP Regional Experiment Arctic Clouds Experiment (FIRE ACE). Mean cloud amounts were near 70% for the entire period but varied regionally from 55 to 85%. On the basis of a limited climatology of ship observations, these values appear to be typical for this part of the Arctic, suggesting that most of FIRE ACE was conducted in representative cloud conditions. A diurnal cycle of mean cloud amount was found for the domain during June and July having a range of 10% with a middle-to-late morning maximum. The AVHRR-derived cloud amounts are in good agreement with visual and radar measurements taken from the Des Groseilliers, except for a few subvisual and low cloud cases. Average AVHRR-derived cloudiness differ from the mean values obtained at the surface by -1 to +3%; this represents a significant improvement over previous satellite retrievals. The satellite-derived cloud heights are very accurate for most of the low cloud cases. Higher cloud altitudes are less certain because cloud optical depths were not available to adjust the temperature observed for the optically thin high clouds, and the radiating temperature of many of the high clouds is representative of some altitude deep in the cloud rather than the highest altitude level of condensate. The development of a more accurate automated algorithm for detecting polar clouds at AVHRR wavelengths will require inclusion of variable thresholds to account for the angular dependence of the surface reflectance as well as the seasonally changing albedos of the ice pack. The use of a 1.6-mum channel on the AVHRR, or other complement of instruments, will greatly enhance the capabilities for detecting clouds over poles during summer. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. AS&M Inc, Hampton, VA 23666 USA. NOAA, ETL, Boulder, CO 80303 USA. SAIC, Hampton, VA 23666 USA. Sci & Technol Corp, Boulder, CO 80303 USA. RP Minnis, P (reprint author), NASA, Langley Res Ctr, MS 420, Hampton, VA 23681 USA. RI Shupe, Matthew/F-8754-2011; Minnis, Patrick/G-1902-2010 OI Shupe, Matthew/0000-0002-0973-9982; Minnis, Patrick/0000-0002-4733-6148 NR 25 TC 15 Z9 17 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 15215 EP 15232 DI 10.1029/2000JD900437 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700035 ER PT J AU Wang, JR Liu, G Spinhirne, JD Racette, P Hart, WD AF Wang, JR Liu, G Spinhirne, JD Racette, P Hart, WD TI Observations and retrievals of cirrus cloud parameters using multichannel millimeter-wave radiometric measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OCTOBER 1986 FIRE; WATER-VAPOR; MICROWAVE MEASUREMENTS; IMAGING RADIOMETER; ICE; SUCCESS; PRECIPITATION; SPECTROMETER; SENSITIVITY; CHANNELS AB The May 26, 1998, measurements by millimeter-wave imaging radiometer (MIR) onboard the NASA ER-2 aircraft over the arctic region north of Alaska are analyzed to study the characteristics of cirrus clouds. The brightness from the 1.88 and 10.4 mum channels of the MODIS airborne simulator (MAS) and the 1.064 Am backscatter from the cloud lidar system (CLS) are used to identify these clouds. The brightness temperature depressions derived from the 340 and 183.3 +/- 7 GHz measurements at 43 degrees incidence are compared with the results of radiative transfer calculations to arrive at an estimation of ice water path (IWP) and median equivalent mass sphere diameter (D-me) The measurements at a high incidence angle of 43 degrees are used to minimize the effect of surface emission. Two different particle size distributions are assumed in these calculations. The estimated average Dm values are similar to 270 and similar to 241 mum, and the average IWPs are similar to 174 and similar to 86 g/m(2) for the two distributions. The large difference in the estimated IWP values occurs in the domain of radiative transfer calculations at D-me less than or equal to 100 mum. There are also a number of pairs of 340 and 183.3 +/- 7 GHz brightness temperature depressions that occur in the same domain, and the estimation of IWP and D-me cannot be made. These difficulties are probably caused by the low sensitivity to cirrus cloud detection at 183.3 +/- 7 GHz. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. RP Wang, JR (reprint author), NASA, Goddard Space Flight Ctr, Code 975, Greenbelt, MD 20771 USA. RI Liu, Guosheng/D-3479-2011 OI Liu, Guosheng/0000-0001-7899-6125 NR 27 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 15251 EP 15263 DI 10.1029/2000JD900262 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700037 ER PT J AU Doelling, DR Minnis, P Spangenberg, DA Chakrapani, V Mahesh, A Pope, SK Valero, FPJ AF Doelling, DR Minnis, P Spangenberg, DA Chakrapani, V Mahesh, A Pope, SK Valero, FPJ TI Cloud radiative forcing at the top of the atmosphere during FIRE ACE derived from AVHRR data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BUDGET EXPERIMENT; SOLAR-RADIATION; SATELLITE DATA; EARTH; SURFACE; CLIMATE; FLUXES; CALIBRATION; RADIANCES; ISCCP AB Cloud radiative forcing at the top of the atmosphere is derived from narrowband visible and infrared radiances from NOAA-12 and NOAA-14 advanced very high resolution radiometer (AVHRR) data taken over the Arctic Ocean during the First ISCCP Regional Experiment Arctic Cloud Experiment (FIRE ACE) during spring and summer 1998. Shortwave and longwave fluxes at the top of the atmosphere (TOA) were computed using narrowband-to-broadband conversion formulae based on coincident Earth Radiation Budget Experiment (ERBE) broadband and AVHRR narrowband radiances. The NOAA-12/NOAA-14 broadband data were validated using model calculations and coincident broadband flux radiometer data from the Surface Heat Budget of the Arctic Ocean experiment and from aircraft data. The AVHRR TOA albedos agreed with the surface- and aircraft-based albedos to within one standard deviation of +/-0.029 on an instantaneous basis. Mean differences ranged from -0.012 to 0.023 depending on the radiometer and platform. AVHRR-derived longwave fluxes differed from the model calculations using aircraft- and surface-based fluxes by -0.2 to -0.3 W in-, on average, when the atmospheric profiles were adjusted to force agreement between the observed and the calculated downwelling fluxes. The standard deviations of the differences were less than 2%. Mean total TOA albedo for the domain between 72 degreesN and 80 degreesN and between 150 degreesW and 180 degreesW changed from 0.695 in May to 0.510 during July, while the longwave flux increased from 217 to 228 W m(-2). Net radiation increased from -89 to -2 W m-2 for the same period. Net cloud forcing varied from -15 W m(-2) in May to -31 W m(-2) during July, while longwave cloud forcing was nearly constant at similar to8 W m(-2). Shortwave cloud forcing dominated the cloud effect, ranging from -22 W m(-2) during May to -40 W m(-2) in July. The mean albedos and fluxes are consistent with previous measurements from the ERBE, except during May when the albedo and longwave flux were greater than the maximum ERBE values. The cloud-forcing results, while similar to some earlier estimates, are the most accurate values hitherto obtained for regions in the Arctic. When no significant melting was present, the clear-sky longwave flux showed a diurnal variation similar to that over land under clear skies. These data should be valuable for understanding, the Arctic energy budget and for constraining models of atmosphere and ocean processes in the Arctic. C1 AS&M Inc, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Scripps Inst Oceanog, Ctr Atmospher Sci, La Jolla, CA 92093 USA. RP Doelling, DR (reprint author), AS&M Inc, Hampton, VA 23666 USA. RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 37 TC 7 Z9 7 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 15279 EP 15296 DI 10.1029/2000JD900455 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700039 ER PT J AU Dong, XQ Mace, GG Minnis, P Young, DF AF Dong, XQ Mace, GG Minnis, P Young, DF TI Arctic stratus cloud properties and their effect on the surface radiation budget: Selected cases from FIRE ACE SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GROUND-BASED MEASUREMENTS; ATMOSPHERIC RADIATION; PARAMETERIZATIONS; TEMPERATURE; BALANCE; CLIMATE; OCEAN; SITE AB To study Arctic stratus cloud properties and their effect on the surface radiation balance during the spring transition season, analyses are performed using data taken during three cloud and two clear days in May 1998 as part of the First ISCCP Regional Experiment (FIRE) Arctic Cloud Experiment (ACE). Radiative transfer models are used in conjunction with surface- and satellite-based measurements to retrieve the layer-averaged microphysical and shortwave radiative properties. The surface-retrieved cloud properties in Cases 1 and 2 agree well with the in situ and satellite retrievals. Discrepancies in Case 3 are due to spatial mismatches between the aircraft and the surface measurements in a highly variable cloud field. Also, the vertical structure in the cloud layer is not fully characterized by the aircraft measurements. Satellite data are critical for understanding some of the observed discrepancies. The satellite- derived particle sizes agree well with the coincident surface retrievals and with the aircraft data when they were collocated. Optical depths derived from visible-channel data over snow backgrounds were overestimated in all three cases, suggesting that methods currently used in satellite cloud climatologies derive optical depths that are too large. Use of a near-infrared channel with a solar infrared channel to simultaneously derive optical depth and particle size appears to alleviate this overestimation problem. Further study of the optical depth retrieval is needed. The surface-based radiometer data reveal that the Arctic stratus clouds produce a net warming of 20 W m(-2) in the surface layer during the transition season suggesting that these clouds may accelerate the spring time melting of the ice pack. This surface warming contrasts with the net cooling at the top of the atmosphere (TOA) during the same period. An analysis of the complete FIRE ACE data sets will be valuable for understanding the role of clouds during the entire melting and refreezing process that occurs annually in the Arctic. C1 Univ Utah, Dept Meteorol, Salt Lake City, UT 84112 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Dong, XQ (reprint author), Univ Utah, Dept Meteorol, 819 Wm C Browning Bldg, Salt Lake City, UT 84112 USA. RI Minnis, Patrick/G-1902-2010; OI Minnis, Patrick/0000-0002-4733-6148; Dong, Xiquan/0000-0002-3359-6117 NR 24 TC 21 Z9 22 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 15297 EP 15312 DI 10.1029/2000JD900404 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700040 ER PT J AU Hutterli, MA McConnell, JR Stewart, RW Jacobi, HW Bales, RC AF Hutterli, MA McConnell, JR Stewart, RW Jacobi, HW Bales, RC TI Impact of temperature-driven cycling of hydrogen peroxide (H2O2) between air and snow on the planetary boundary layer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TO-FIRN TRANSFER; ATMOSPHERIC CHEMISTRY; ATOM CONCENTRATIONS; ARCTIC TROPOSPHERE; OZONE DEPLETION; SOUTH-POLE; ICE CORES; GREENLAND; GAS; SUMMIT AB Hydrogen peroxide (H2O2) contributes to the atmosphere's oxidizing capacity, which determines the lifetime of atmospheric trace species. Measured bidirectional summertime H2O2 fluxes from the snowpack at Summit, Greenland, in June 1996 reveal a daytime H2O2 release from the surface snow reservoir and a partial redeposition at night. The observations also provide the first direct evidence of a strong net summertime H2O2 release from the snowpack, enhancing average boundary layer H2O2 Concentrations approximately sevenfold and the OH and HO2 concentrations by 70% and 50%, respectively, relative to that estimated from photochemical modeling in the absence of the snowpack source. The total H2O2 release over a, 12-day period was of the order of 5x10(13) molecules m(-2) s(-1) and compares well with observed concentration changes in the top snow layer. Photochemical and air-snow interaction modeling indicate that the net snowpack release is driven by temperature-induced uptake and release of H2O2 as deposited snow, which is supersaturated with respect to ice-air partitioning, approaches equilibrium. The results show that the physical cycling of H2O2 and possibly other volatile species is a key to understanding snowpacks as complex physical-photochemical reactors and has far reaching implications for the interpretation of ice core records as well as or the photochemistry in polar regions and in the vicinity of snowpacks in general. C1 Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. Desert Res Inst, Water Resources Ctr, Reno, NV 89512 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hutterli, MA (reprint author), Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. NR 42 TC 53 Z9 53 U1 1 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 2001 VL 106 IS D14 BP 15395 EP 15404 DI 10.1029/2001JD900102 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 456YE UT WOS:000170109700049 ER PT J AU Oieroset, M Phan, TD Fujimoto, M Lin, RP Lepping, RP AF Oieroset, M Phan, TD Fujimoto, M Lin, RP Lepping, RP TI In situ detection of collisionless reconnection in the Earth's magnetotail SO NATURE LA English DT Article ID MAGNETIC-FIELD RECONNECTION; GEOTAIL OBSERVATIONS; MAGNETOPAUSE; PLASMA; MAGNETOSPHERE; SIMULATION; FLOWS AB Magnetic reconnection is the process by which magnetic field lines of opposite polarity reconfigure to a lower-energy state, with the release of magnetic energy to the surroundings. Reconnection at the Earth's dayside magnetopause and in the magnetotail allows the solar wind into the magnetosphere(1,2). It begins in a small `diffusion region', where a kink in the newly reconnected lines produces jets of plasma away from the region. Although plasma jets from reconnection have previously been reported(3-7), the physical processes that underlie jet formation have remained poorly understood because of the scarcity of in situ observations of the minuscule diffusion region. Theoretically, both resistive and collisionless processes can initiate reconnection(8-14), but which process dominates in the magnetosphere is still debated. Here we report the serendipitous encounter of the Wind spacecraft with an active reconnection diffusion region, in which are detected key processes predicted by models(8-13) of collisionless reconnection. The data therefore demonstrate that collisionless reconnection occurs in the magnetotail. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Tokyo Inst Technol, Dept Earth & Planetary Sci, Meguro Ku, Tokyo 152, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Oieroset, M (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NR 28 TC 286 Z9 298 U1 3 U2 20 PU MACMILLAN PUBLISHERS LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 26 PY 2001 VL 412 IS 6845 BP 414 EP 417 DI 10.1038/35086520 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 456DQ UT WOS:000170068200040 PM 11473310 ER PT J AU Bridges, NT Crisp, JA Bell, JF AF Bridges, NT Crisp, JA Bell, JF TI Characteristics of the Pathfinder APXS sites: Implications for the composition of Martian rocks and soils SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARS PATHFINDER; LANDING SITE; CHEMICAL-COMPOSITION; MAGNETIC-PROPERTIES; SURFACE; DUST; COATINGS; CALIBRATION; CONSTRAINTS; DEPOSITS AB An integrated study of spectral, elemental abundance, and image data from the Pathfinder alpha proton X-ray spectrometer (APXS) measurement sites has led to a better understanding of the nature of Martian surface materials. This rigorous analysis provides a new level of detail that forms the basis for the results reported here and that can be used by future scientists trying to understand rocks and soils on Mars. Each APXS site has been precisely located by analyzing stereo Imager for Mars Pathfinder (IMP) and rover camera images to determine the position of the APXS during deployment. Rover and IMP images are used to assess local geology, namely, the presence of pebbles, clods, and aeolian features in soils and surface textures and dust concentrations on rocks. IMP spectra using the latest calibrations for radiance and reflectance are analyzed at a number of different illumination geometries for each APXS site. The three-dimensional orientation of the sites has been determined and then used to compute the true sunlight (incidence) and viewing (emission) angles. Where suitable photometric coverage is available, reflectances are fit to the Hapke-Irvine function. This is then used to adjust spectral reflectances to a normalized illumination geometry common to all rocks and soils. Comparing all the data sets shows a positive correlation among red/blue reflectance ratio, SO, content, and dust abundance on rocks, indicating that rocks are coated with varying amounts of sulfur-rich, red dust. Other elements, such as silicon and iron, are poor tracers for dust because their abundances within soil are similar to those within rock. Rock APXS targets that are bluer, poorer in sulfur, and have minimal dust coverage face toward the northeast, the direction in which winds may be capable of efficiently removing loose material under current Martian conditions. The IMP spectral properties of the soils show poor correlations with APXS elemental abundances. On the basis of currently released APXS data, bulk soils at the Pathfinder landing site are richer in silica and sulfur than the Viking landing sites, suggesting a different composition. The APXS soils with the most apparent pebbles are the poorest in SiO2, indicating that either the pebbles are more mafic than the APXS rocks or the pebble-free soil component is inherently enriched in SiO2 compared to Viking soils. The mixture of materials at the APXS sites is a reflection of the overall complexity of Martian surface materials, a detailed understanding of which should drive the choice of future instruments and missions. C1 Jet Prop Lab, Pasadena, CA 91109 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. RP Bridges, NT (reprint author), Jet Prop Lab, MS 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Bridges, Nathan/D-6341-2016; Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 68 TC 5 Z9 5 U1 0 U2 11 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 JUL 25 PY 2001 VL 106 IS E7 BP 14621 EP 14665 DI 10.1029/2000JE001393 PG 45 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 455GE UT WOS:000170018500003 ER PT J AU Zent, AP Howard, DJ Quinn, RC AF Zent, AP Howard, DJ Quinn, RC TI H2O adsorption on smectites: Application to the diurnal variation of H2O in the Martian atmosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID BOUNDARY-LAYER MODEL; WATER-VAPOR; MARS; MONTMORILLONITE; IMMERSION; EXCHANGE; SURFACE AB Observations of the Martian planetary boundary layer lead to interpretations that are baffling and contradictory. In this paper we specifically address the question of whether or not water vapor finds a substantial diurnal reservoir in the Martian regolith. To address this issue, we have measured H2O adsorption kinetics on SWy-1, a Na-rich montmorillonite from Wyoming. The highest-temperature (273 K) data equilibrate rapidly. Data gathered at realistic H2O partial pressures and temperatures appropriate to early morning show two phenomena that preclude a significant role for smectites in diurnally exchanging a large column abundance. First, the equilibration timescale is longer than a sol. Second, the equilibrium abundances are a small fraction of that predicted by earlier adsorption isotherms. The explanation for this phenomenon is that smectite clay actually increases its surface area as a function of adsorptive coverage. At Mars-like conditions we show that the interlayer sites of smectites are likely to be unavailable. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. SETI Inst, Moffett Field, CA 94035 USA. RP Zent, AP (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. NR 22 TC 25 Z9 25 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-PLANET JI J. Geophys. Res.-Planets PD JUL 25 PY 2001 VL 106 IS E7 BP 14667 EP 14674 DI 10.1029/2000JE001394 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 455GE UT WOS:000170018500004 ER PT J AU Chillier, X Boulet, P Chermette, H Salama, F Weber, J AF Chillier, X Boulet, P Chermette, H Salama, F Weber, J TI Absorption and emission spectroscopy of matrix-isolated benzo[g,h,i]perylene: An experimental and theoretical study for astrochemical applications SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID POLYCYCLIC AROMATIC-HYDROCARBONS; DENSITY-FUNCTIONAL THEORY; UNIDENTIFIED INFRARED-EMISSION; CORRECT ASYMPTOTIC-BEHAVIOR; INHOMOGENEOUS ELECTRON-GAS; EXCITATION-ENERGIES; NAPHTHALENE CATION; EXCITED-STATE; BAND; APPROXIMATION AB The absorption and emission spectra of benzo[g,h,i]perylene, a six ring polycyclic aromatic hydrocarbon molecule (C22H12), embedded in a rare gas matrix are reported. Time dependent emission shows that this molecule exhibits sharp phosphorescence in the red. Supporting theoretical calculations using the recently developed time-dependent density-functional response theory formalism (TD-DFRT) allow a tentative assignment for the observed transitions. The astrochemical significance of the results is briefly discussed. (C) 2001 American Institute of Physics. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Geneva, Dept Chim Phys, CH-1211 Geneva 4, Switzerland. Univ Lyon 1, Lab Chim Phys Theor, F-69622 Villeurbanne, France. Inst Rech Catalyse, F-69626 Villeurbanne, France. RP Chillier, X (reprint author), NASA, Ames Res Ctr, Div Space Sci, M-S 245-6, Moffett Field, CA 94035 USA. RI Boulet, Pascal/A-1332-2011; Salama, Farid/A-8787-2009 OI Boulet, Pascal/0000-0001-8051-4287; Salama, Farid/0000-0002-6064-4401 NR 40 TC 20 Z9 20 U1 0 U2 4 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0021-9606 EI 1089-7690 J9 J CHEM PHYS JI J. Chem. Phys. PD JUL 22 PY 2001 VL 115 IS 4 BP 1769 EP 1776 DI 10.1063/1.1376632 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 451JY UT WOS:000169800000016 ER PT J AU Wilke, CO Adami, C AF Wilke, CO Adami, C TI Interaction between directional epistasis and average mutational effects SO PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES LA English DT Article DE epistasis; neutrality; RNA secondary; structure folding; digital organisms ID DELETERIOUS MUTATIONS; EVOLUTIONARY ADVANTAGE; SYNERGISTIC EPISTASIS; MULLERS RATCHET; RECOMBINATION; CANALIZATION; SELECTION; RNA; COMPLEXITY; ROBUSTNESS AB We investigate the relationship between the average fitness decay due to single mutations and the strength of epistatic interactions in genetic sequences. We observe that epistatic interactions between mutations are correlated to the average fitness decay, both in RNA secondary structure prediction as well as in digital organisms replicating in silico. This correlation implies that, during adaptation, epistasis and average mutational effect cannot be optimized independently. In experiments with RNA sequences evolving on a neutral network, the selective pressure to decrease the mutational load then leads to a reduction in the amount of sequences with strong antagonistic interactions between deleterious mutations in the population. C1 CALTECH, Digital Life Lab 13693, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wilke, CO (reprint author), CALTECH, Digital Life Lab 13693, Pasadena, CA 91125 USA. EM wilke@caltech.edu RI Adami, Christoph/A-5181-2009; Adami, Christoph/A-9675-2011; Wilke, Claus/B-4643-2008 OI Adami, Christoph/0000-0002-2915-9504; Wilke, Claus/0000-0002-7470-9261 NR 31 TC 76 Z9 78 U1 0 U2 5 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 0962-8452 J9 P ROY SOC B-BIOL SCI JI Proc. R. Soc. B-Biol. Sci. PD JUL 22 PY 2001 VL 268 IS 1475 BP 1469 EP 1474 PG 6 WC Biology; Ecology; Evolutionary Biology SC Life Sciences & Biomedicine - Other Topics; Environmental Sciences & Ecology; Evolutionary Biology GA 455AE UT WOS:000170003600006 PM 11454290 ER PT J AU Steinacker, A Shchekinov, YA AF Steinacker, A Shchekinov, YA TI The influence of gravitational acceleration on the supernova-driven Parker instability SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE instabilities; magnetic fields; MHD; ISM : bubbles; ISM : kinematics and dynamics; galaxies : haloes ID RADIATION MAGNETOHYDRODYNAMICS CODE; LINEAR-STABILITY ANALYSIS; ON SPIRAL GALAXIES; 2 SPACE DIMENSIONS; INTERSTELLAR-MEDIUM; GALACTIC DISK; ASTROPHYSICAL FLOWS; EXTRAPLANAR DUST; MAGNETIC-FIELD; MASS-LOSS AB Within a framework of 2D magnetohydrodynamic (MHD) simulations, we explore the dynamical regimes initiated by a supernova explosion in a magnetized stratified interstellar medium (ISM). We concentrate on the formation of large-scale magnetic structures and outflows connected with the Parker instability. For the sake of simplicity we only show models with a fixed explosion energy corresponding to a single supernova, (SN) occurring in host galaxies with different fixed values of the gravitational acceleration g and different ratios of specific heats. We show that in general, depending on these two parameters, three different regimes are possible: a slowly growing Parker instability on time-scales much longer than the galactic rotation period for small g; the Parker instability growing at roughly the rotation period, which for ratios of specific heats larger than one is accompanied by an outflow resulting from the explosion for intermediate g; and a rapidly growing instability and a strong blow-out flow for large g. By means of numerical simulations and analytical estimates we show that the explosion energy and gravitational acceleration which separate the three regimes scale as Eg(2) similar to constant in the 2D case. We expect that in the 3D case this scaling law is Eg(3) similar to constant. Our simulations demonstrate furthermore that a single SN explosion can lead to the growth of multiple Parker loops in the disc and large-scale magnetic field loops in the halo, extending over 2-3 kpc horizontally and up to 3 kpc vertically above the mid-plane of the disc. C1 Ruhr Univ Bochum, Inst Astron, D-44780 Bochum, Germany. Rostov State Univ, Dept Phys, Rostov Na Donu 344090, Russia. RP Steinacker, A (reprint author), NASA, Ames Res Ctr, Mailstop 245-3, Moffett Field, CA 94035 USA. RI Shchekinov, Yuri/M-8018-2015 OI Shchekinov, Yuri/0000-0002-3463-7339 NR 68 TC 2 Z9 2 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 JUL 21 PY 2001 VL 325 IS 1 BP 208 EP 220 DI 10.1046/j.1365-8711.2001.04411.x PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 458DT UT WOS:000170178500019 ER PT J AU Lyapustin, A Knyazikhin, Y AF Lyapustin, A Knyazikhin, Y TI Green's function method for the radiative transfer problem. I. Homogeneous non-Lambertian surface SO APPLIED OPTICS LA English DT Article ID MULTIPLE-SCATTERING; REFLECTANCE; MEDIA AB An application of the Green's function method to the one-dimensional radiative transfer problem with a non-Lambertian surface is described. This method separates atmospheric radiative transport from the lower boundary condition and allows expressing a solution analytically for an arbitrary surface reflectance. In the physical sense, the Green's function represents bidirectional atmospheric transmission for the unitary radiance source located at the bottom of the atmosphere. The boundary-value problem for the Green's function is adjoint to the problem for atmospheric path radiance, and therefore it can be solved by use of existing numerical methods by reversal of the direction of light propagation. From an analysis of an exact operator solution and extensive numerical study, we found two accelerating parameterizations for computing the surface-reflected radiance. The first one is a maximum-eigenvalue method that is comparable in accuracy with rigorous radiative transfer codes in calculations with realistic land-cover types. It requires a total of the first three orders of the surface-reflected radiance. The second one is based on the Lambertian approximation of multiple reflections. Designed for operational applications, it is much faster: Already the first-order reflected radiance ensures an average accuracy of better than 1%. (C) 2001 Optical Society of America. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Boston Univ, Dept Geog, Boston, MA 02215 USA. RP Lyapustin, A (reprint author), Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Mail Code 920, Greenbelt, MD 20771 USA. EM alyapust@pop900.gsfc.nasa.gov RI Lyapustin, Alexei/H-9924-2014 OI Lyapustin, Alexei/0000-0003-1105-5739 NR 25 TC 34 Z9 34 U1 0 U2 5 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 JUL 20 PY 2001 VL 40 IS 21 BP 3495 EP 3501 DI 10.1364/AO.40.003495 PG 7 WC Optics SC Optics GA 453TG UT WOS:000169932100008 PM 18360374 ER PT J AU Chandler, AM Koh, DT Lamb, RC Macomb, DJ Mattox, JR Prince, TA Ray, PS AF Chandler, AM Koh, DT Lamb, RC Macomb, DJ Mattox, JR Prince, TA Ray, PS TI A search for radio-quiet gamma-ray pulsars SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; pulsars : general ID EXPERIMENT TELESCOPE EGRET; MAGNETIZED NEUTRON-STARS; X-RAY; MILLISECOND PULSAR; SUPERNOVA-REMNANTS; EMISSION; CATALOG; GEMINGA; VARIABILITY; CALIBRATION AB Most Galactic point sources of gamma rays remain unidentified. The few (extrasolar) sources that have been identified are all young, rotation-powered pulsars, all but one of which were identified using radio ephemerides. The radio-quiet Geminga pulsar was identified only after pulsations were discovered in a coincident X-ray source. Observational evidence indicates that many of the unidentified Galactic sources are likely to be pulsars, and some theoretical models predict a potentially large population of radio-quiet gamma-ray pulsars. We present a new method for performing sensitive gamma-ray pulsar searches. We used this method to search several of the strongest EGRET sources for pulsations. This was a blind search for new pulsars, covering a frequency and a frequency-derivative phase space large enough to detect Crab-like pulsars as well as lower frequency, high magnetic field "magnetars." No new pulsars were discovered, and we report upper limits constraining the characteristics of any signals contained in the data sets searched. C1 CALTECH, Space Radiat Lab, Pasadena, CA 91125 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Boston Univ, Dept Astron, Boston, MA 02215 USA. USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. RP Chandler, AM (reprint author), CALTECH, Space Radiat Lab, MS 220-47, Pasadena, CA 91125 USA. EM amc@srl.caltech.edu; lamb@srl.caltech.edu; macomb@gsfc.nasa.gov; mattox@bu.edu; prince@srl.caltech.edu; paul.ray@nrl.navy.mil OI Ray, Paul/0000-0002-5297-5278 NR 49 TC 30 Z9 30 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 JUL 20 PY 2001 VL 556 IS 1 BP 59 EP 69 DI 10.1086/321573 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900007 ER PT J AU Smette, A Fruchter, AS Gull, TR Sahu, KC Petro, L Ferguson, H Rhoads, J Lindler, DJ Gibbons, R Hogg, DW Kouveliotou, C Livio, M Macchetto, D Metzger, MR Pedersen, H Pian, E Thorsett, SE Wijers, RAMJ Fynbo, JPU Gorosabel, J Hjorth, J Jensen, BL Levine, A Smith, DA Cline, T Hurley, K Trombka, J AF Smette, A Fruchter, AS Gull, TR Sahu, KC Petro, L Ferguson, H Rhoads, J Lindler, DJ Gibbons, R Hogg, DW Kouveliotou, C Livio, M Macchetto, D Metzger, MR Pedersen, H Pian, E Thorsett, SE Wijers, RAMJ Fynbo, JPU Gorosabel, J Hjorth, J Jensen, BL Levine, A Smith, DA Cline, T Hurley, K Trombka, J TI Hubble Space Telescope STIS observations of GRB 000301C: CCD imaging and near-ultraviolet MAMA spectroscopy SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts ID GAMMA-RAY BURST; LY-ALPHA ABSORBER; 28 FEBRUARY 1997; HIGH-REDSHIFT; OPTICAL COUNTERPART; HOST GALAXY; ABSORPTION; EMISSION; CLOUDS; DUST AB We present Space Telescope Imaging Spectrograph observations of the optical transient (OT) counterpart of the c-ray burster GRB 000301C obtained 5 days after the burst, on 2000 March 6. CCD clear-aperture imaging reveals a R similar or equal to 21.50 +/- 0.15 source with no apparent host galaxy. An 8000 s, 1150 Angstrom < < 2200 near-ultraviolet MAMA prism spectrum shows a flat or slightly rising continuum (in f(lambda)) between 2800 and 3300 Angstrom, with a mean flux of (8.7(-1.6)(+0.8) +/- 2.6) x 10(-18) ergs s(-1) cm(-2) Angstrom (-1), and a sharp break centered at 2797 +/- 25 Angstrom. We interpret this as the H I Lyman break at z = 2.067 +/- 0.025, indicating the presence of a cloud with an H I column density log N-HI(cm(2)) > 18 on the line of sight to the OT. This measured redshift is conservatively a lower limit to the GRB redshift. However, as all other GRBs that have deep Hubble Space Telescope images appear to lie on the stellar field of a host galaxy, and as the large H I column density measured here and in later ground-based observations is unlikely on a random line of sight, we believe we are probably seeing absorption from H I in the host galaxy. In any case, this represents the largest direct redshift determination of a c-ray burster to date. Our data are compatible with an OT spectrum represented by a power law with an intrinsic index alpha = 1.2 (f(nu) proportional to nu (-alpha)) and no extinction in the host galaxy, or with alpha = 0.5 and extinction by SMC-like dust in the OT rest frame with A(V) = 0.15. The large N-HI and the lack of a detected host are similar to the situation for damped Ly alpha absorbers at z > 2. C1 NASA, Adv Comp Concepts Inc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Fonds Natl Rech Sci, B-1050 Brussels, Belgium. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Inst Adv Study, Princeton, NJ 08540 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. European Space Agcy, Div Space Sci, Dept Astrophys, NL-2200 AG Noordwijk, Netherlands. CALTECH, Dept Astron, Pasadena, CA 91125 USA. Univ Copenhagen, Astron Observ, DK-2100 Copenhagen O, Denmark. CNR, Ist Tecnol & Studio Radiaz Extraterr, I-40129 Bologna, Italy. Univ Calif Santa Cruz, Dept Astron & Astrophys, Santa Cruz, CA 95064 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Aarhus Univ, Inst Phys & Astron, DK-8000 Aarhus C, Denmark. European So Observ, D-85748 Garching, Germany. Danish Space Res Inst, DK-2100 Copenhagen O, Denmark. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Smette, A (reprint author), NASA, Adv Comp Concepts Inc, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. RI Gull, Theodore/D-2753-2012; Hjorth, Jens/M-5787-2014; Jensen, Brian Lindgren/E-1275-2015; OI Gull, Theodore/0000-0002-6851-5380; Hjorth, Jens/0000-0002-4571-2306; Jensen, Brian Lindgren/0000-0002-0906-9771; Hogg, David/0000-0003-2866-9403; Pian, Elena/0000-0001-8646-4858 NR 62 TC 8 Z9 8 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 2001 VL 556 IS 1 BP 70 EP 76 DI 10.1086/321585 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900008 ER PT J AU Marcy, GW Butler, RP Fischer, D Vogt, SS Lissauer, JJ Rivera, EJ AF Marcy, GW Butler, RP Fischer, D Vogt, SS Lissauer, JJ Rivera, EJ TI A pair of resonant planets orbiting GJ 876 SO ASTROPHYSICAL JOURNAL LA English DT Article DE planetary systems; stars : individual (GJ 876) ID ECHELLE-SPECTROMETER; UPSILON-ANDROMEDAE; SOLAR-SYSTEM; M4 DWARF; PRECISION; COMPANIONS; HIPPARCOS; STARS AB Precise Doppler measurements during 6 yr from the Lick and Keck observatories reveal two planets orbiting GJ 876 (M4V). The orbital fit yields companion masses of M sin i = 0.56 and 1.89 M-J, orbital periods of P = 30.1 and 61.0 days, semimajor axes of a = 0.13 and 0.21 AU, and eccentricities of e = 0.28 and 0.10, respectively. The orbital periods are nearly in the ratio of 2: 1, unprecedented among major planets but common among moons and asteroids. Moreover, the axes of the elliptical orbits appear to be nearly aligned. The inner companion was not recognized previously owing to the 2: 1 ratio of periods, which allowed its signature to masquerade as added orbital eccentricity of the outer planet. Dynamical simulations show that the system is stable within a subset of the observed orbital parameters. The stability may be provided by a mean-motion resonance and the apparent alignment of the major axes. These planets pose unsolved questions about their formation and dynamical evolution, which brought them within 0.08 AU of each other and locked them in resonance. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95064 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. RP Marcy, GW (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. RI Butler, Robert/B-1125-2009; OI Fischer, Debra/0000-0003-2221-0861 NR 35 TC 236 Z9 241 U1 1 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 2001 VL 556 IS 1 BP 296 EP 301 DI 10.1086/321552 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900026 ER PT J AU Geballe, TR Saumon, D Leggett, SK Knapp, GR Marley, MS Lodders, K AF Geballe, TR Saumon, D Leggett, SK Knapp, GR Marley, MS Lodders, K TI Infrared observations and modeling of one of the coolest T dwarfs: Gliese 570D SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : abundances; stars : atmospheres; stars : individual (Gliese 570D); stars : low-mass, brown dwarfs ID DIGITAL SKY SURVEY; SURVEY COMMISSIONING DATA; METHANE BROWN DWARF; CHROMOSPHERIC EMISSION; MULTIPLE-SCATTERING; ATMOSPHERES; DISCOVERY; STARS; ABUNDANCES; 229B AB We have obtained a good-quality R similar to 400, 0.8-2.5 mum spectrum as well as accurate photometry of Gliese 570D, one of the coolest and least-luminous brown dwarfs currently known. The spectrum shows that Gl 570D has deeper absorptions in the strong water and methane bands at 1.12-1.17, 1.33-1.45, 1.62-1.88, and 2.20-2.45 mum and is both bluer at J-K and redder at K-L' than previously observed T dwarfs. Data analysis using model spectra coupled with knowledge of the well-understood primary implies that for the same surface gravity, Gl 570D is about 160 K cooler than Gl 229B. For an age range of 2-5 Gyr, Gl 570D has an effective temperature in the range 784-824 K, a surface gravity log g in the range 5.00-5.27 (cm (s-2)), and a luminosity in the range (2.88-2.98) x 10(-6) L-circle dot. C1 Gemini Observ, Hilo, HI 96720 USA. Vanderbilt Univ, Dept Phys & Astron, Nashville, TN 37235 USA. Joint Astron Ctr, Hilo, HI 96720 USA. Princeton Univ Observ, Princeton, NJ 08544 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. RP Geballe, TR (reprint author), Gemini Observ, 670 N Aohoku Pl, Hilo, HI 96720 USA. RI Marley, Mark/I-4704-2013; OI Leggett, Sandy/0000-0002-3681-2989 NR 45 TC 80 Z9 80 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 2001 VL 556 IS 1 BP 373 EP 379 DI 10.1086/321575 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900031 ER PT J AU Kaplan, DL Kulkarni, SR van Kerkwijk, MH Rothschild, RE Lingenfelter, RL Marsden, D Danner, R Murakami, T AF Kaplan, DL Kulkarni, SR van Kerkwijk, MH Rothschild, RE Lingenfelter, RL Marsden, D Danner, R Murakami, T TI Hubble Space Telescope observations of SGR 0526-66: New constraints on accretion and magnetar models SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; pulsars : individual (SGR 052-66); stars : neutron; X-rays : individual (SGR 0526-66); X-rays : stars ID GAMMA-RAY BURST; LARGE-MAGELLANIC-CLOUD; SUPERNOVA REMNANT N49; X-RAY; NEUTRON-STARS; 5 MARCH; REPEATER SGR1900+14; SPIN-DOWN; PULSAR; SGR-1806-20 AB Soft gamma -ray repeaters (SGRs) are among the most enigmatic sources known today. Exhibiting huge X-ray and gamma -ray bursts and flares, as well as soft quiescent X-ray emission, their energy source remains a mystery. Just as mysterious are the anomalous X-ray pulsars (AXPs), which share many of the same characteristics. Thanks to recent Chandra X-Ray Observatory observations, SGR 0526-66, the first SGR, now appears to be a transition object bridging the two classes, and therefore observations of it have implications for both SGRs and AXPs. The two most popular current models for their persistent emission are accretion of a fossil disk and decay of an enormous (similar to 10(15) G) magnetic field in a magnetar. We show how deep optical observations of SGR 0526-66, the only SGR with small enough optical extinction for meaningful observations, show no evidence of an optical counterpart. These observation place strong new constraints on both accretion disk and magnetar models and suggest that the spectral energy distribution may peak in the hard UV. Almost all accretion disks are excluded by the optical data, and a magnetar would require a similar to 10(15)-10(16) G field. C1 CALTECH 105 24, Dept Astron, Pasadena, CA 91125 USA. Univ Utrecht, Sterrekundig Inst, NL-3508 TA Utrecht, Netherlands. Univ Calif San Diego, Ctr Astrophys & Space Sci 0111, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. RP Kaplan, DL (reprint author), CALTECH 105 24, Dept Astron, Pasadena, CA 91125 USA. NR 63 TC 36 Z9 36 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 2001 VL 556 IS 1 BP 399 EP 407 DI 10.1086/323516 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900034 ER PT J AU Jura, M Velusamy, T Werner, MW AF Jura, M Velusamy, T Werner, MW TI What next for the likely presupernova HD 179821? SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; radio lines : stars; stars : mass loss; stars : winds, outflows; supernovae : general; supernova remnants ID KEPLERS SUPERNOVA REMNANT; LUMINOUS BLUE VARIABLES; ASYMPTOTIC GIANT BRANCH; MASS-LOSS RATES; X-RAY-SPECTRUM; PLANETARY-NEBULAE; CIRCUMSTELLAR ENVELOPES; INFRARED-SPECTROSCOPY; EXPANSION VELOCITIES; SOLAR NEIGHBORHOOD AB We have used the Owens Valley Radio Observatory Millimeter Array to obtain a map of the J =1 -->0 CO emission from the circumstellar shell around HD 179821, a highly evolved G-type star that will probably explode as a supernova in the next 10(5) yr. Very approximately, the gas presents as a circular ring with an inner diameter 3." 95 of an outer diameter of similar to 12 ", and azimuthal variations in the CO brightness of a factor of about 2. Until about 1600 years ago, the star was a red hypergiant, losing about 3 x 10(-4) M-circle dot yr(-1) at an average outflow speed of 32 km s(-1). We propose that when HD 179821 explodes as a supernova, it may resemble Kepler's supernova remnant, and thus some of the anisotropies in supernova remnants may be intrinsic. If the factors that cause the anisotropic mass loss in HD 179821 persist until the moment when the star explodes as a supernova, the newly born pulsar may receive a momentum "kick," leading to a space motion of close to 700 km s(-1). Independent of the angular asymmetries, the radially detached shell around HD 179821 may be representative of environments that produce dust echoes from gamma-ray bursts. 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 62 TC 15 Z9 15 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 2001 VL 556 IS 1 BP 408 EP 416 DI 10.1086/321553 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900035 ER PT J AU Cottin, H Gazeau, MC Benilan, Y Raulin, F AF Cottin, H Gazeau, MC Benilan, Y Raulin, F TI Polyoxymethylene as parent molecule for the formaldehyde extended source in comet Halley SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets : general; comets : individual (Halley); molecular processes ID O1 HALE-BOPP; ICE ANALOGS; INTERSTELLAR; IDENTIFICATION; DUST; CO AB Among unsolved questions raised by observations of comets is the origin of extended sources, i.e., the distribution of molecules in the coma which cannot be explained by a direct sublimation from the nucleus. Polyoxymethylene [formaldehyde polymer: (-CH(2)-O-)(n), also called POM] is sometimes invoked as a potential parent compound, the degradation of which could produce the required amount of H(2)CO across the coma, but no quantitative study has ever been undertaken with relevant parameters. From new experimental data, we are now able to consider multiphase chemistry: POM in the solid state on cometary grains slowly degrades by solar photons and heat and produces H(2)CO in the gaseous phase. This is a new approach to cometary organic chemistry. We show, by considering simple assumptions about the cometary environment, that the hypothesis of POM on grains leads to a very good agreement with Giotto observations if we assume that the cometary grains are similar to7% POM by mass at a temperature of 330 K. C1 Univ Paris 07, Lab Interuniv Syst Atmospher, CNRS, UMR 7583, F-94010 Creteil, France. Univ Paris 12, Lab Interuniv Syst Atmospher, CNRS, UMR 7583, F-94010 Creteil, France. RP Cottin, H (reprint author), NASA, Goddard Space Flight Ctr, Code 691, Greenbelt, MD 20771 USA. EM Cottin@lisa.univ-paris12.fr; Gazeau@lisa.univ-paris12.fr; Benilan@lisa.univ-paris12.fr; Raulin@lisa.univ-paris12.fr RI Cottin, Herve/H-5654-2013 OI Cottin, Herve/0000-0001-9170-5265 NR 26 TC 31 Z9 31 U1 0 U2 2 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 JUL 20 PY 2001 VL 556 IS 1 BP 417 EP 420 DI 10.1086/321579 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900036 ER PT J AU Pohjolainen, S Maia, D Pick, M Vilmer, N Khan, JI Otruba, W Warmuth, A Benz, A Alissandrakis, C Thompson, BJ AF Pohjolainen, S Maia, D Pick, M Vilmer, N Khan, JI Otruba, W Warmuth, A Benz, A Alissandrakis, C Thompson, BJ TI On-the-disk development of the halo coronal mass ejection on 1998 May 2 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : corona; Sun : coronal mass ejections (CMEs); Sun : flares; Sun : radio radiation; Sun : UV radiation; Sun : X-rays, gamma rays ID SOLAR-A MISSION; X-RAY TELESCOPE; INTERPLANETARY SHOCKS; SOHO/EIT OBSERVATIONS; RADIO; FLARE; ORIGIN; WAVES; EARTH; SIGNATURES AB A halo coronal mass ejection (CME) was observed at 15:03 UT on 1998 May 2 by the Solar and Heliospheric Observatory Large-Angle Spectrometric Coronagraph. The observation of the CME was preceded by a major soft X-ray flare in NOAA Active Region 8210, characterized by a delta spot magnetic configuration and some activity in region 8214. A large transequatorial interconnecting loop (TIL) seen in the soft X-rays connected AR 8210 to a faint magnetic field region in the periphery of region 8214. Smaller loop systems were also connecting AR 8210 to other fainter bipolar magnetic structures, the interconnecting loop (IL) east of AR 8210 being one of the most visible. We present here a multiwavelength analysis of the large- and small-scale coronal structures associated with the development of the flare and of the CME, with emphasis placed on radio-imaging data. In the early phases of the flare, the radio emission sources traced the propagation paths of electrons along the TIL and the IL, which are accelerated in the vicinity of AR 8210. Furthermore, jetlike flows were observed in soft X-rays and in H alpha in these directions. Significantly, the TIL and IL loop systems disappeared at least partially after the CME. An EUV Imaging Telescope (EIT) dimming region of similar size and shape to the soft X-ray TIL, but noticeably offset from it, was also observed. During the "flash" phase of the flare, new radio sources appeared, presenting signatures of destabilization and reconnection at discrete locations of the connecting loops. We interpret these as possible signatures of the CME liftoff on the disk. An H alpha Moreton wave (blast wave) and an "EIT wave" were also observed, originating from the flaring AR 8210. The signatures in radio, after the wave propagated high into the corona, include type II-like emissions in the spectra. The radio images link these emissions to fast-moving sources, presumably formed at locations where the blast wave encounters magnetic structures. The opening of the CME magnetic field is revealed by the radio observations, which show large and expanding moving sources overlying the later-seen EIT dimming region. C1 Observ Paris, DASOP, Meudon Sect, UMR 8645, F-92195 Meudon, France. Tuorla Observ, FIN-21500 Piikkio, Finland. UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. Sonnenobserv Kanzelhohe, A-9521 Treffen, Austria. ETH Zentrum, ETH Zurich, Inst Astron, CH-8092 Zurich, Switzerland. Univ Ioannina, GR-45110 Ioannina, Greece. NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD 20771 USA. RP Pohjolainen, S (reprint author), Observ Paris, DASOP, Meudon Sect, UMR 8645, Pl Jules Janssen, F-92195 Meudon, France. EM spo@astro.utu.fi RI Thompson, Barbara/C-9429-2012; OI Maia, Dalmiro/0000-0001-7855-1919 NR 42 TC 100 Z9 102 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 JUL 20 PY 2001 VL 556 IS 1 BP 421 EP 431 DI 10.1086/321577 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900037 ER PT J AU Bakes, ELO Tielens, AGGM Bauschlicher, CW AF Bakes, ELO Tielens, AGGM Bauschlicher, CW TI Theoretical modeling of infrared emission from neutral and charged polycyclic aromatic hydrocarbons. I. SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM; ISM : lines and bands; ISM : molecules; methods : analytical; molecular processes ID PHASE PAH MOLECULES; TEMPERATURE-FLUCTUATIONS; INTERSTELLAR GRAINS; ASTROPHYSICAL IMPLICATIONS; PHOTODISSOCIATION REGIONS; SPECTROSCOPY; CATIONS; SPECTRA; GAS; NAPHTHALENE AB Since the discovery of interstellar infrared emission features in the 3.3-12.7 mum wavelength range three decades ago, the carriers of these features have been the subject of much debate. Recent observational work with the Infrared Space Observatory, experimental work, and quantum chemical calculations concerning positively charged polycyclic aromatic hydrocarbon (PAH) molecules point to the infrared fluorescence of such species. This paper presents a model of the interstellar infrared emission between 3.3 and 12.7 mum from a population of symmetric, condensed polycyclic aromatic hydrocarbons composed of up to 54 carbon atoms. We describe the infrared emission intensity in terms of the size of the emitting molecule, its charge, and its temperature probability distribution function. The model takes the charge state (anion, neutral, cation of charge state up to +3) into account self-consistently, employing the most recent quantum chemically calculated infrared cross sections of such species. This paper provides an exploratory study to illustrate the dependence of the interstellar infrared emission on the polycyclic aromatic hydrocarbon charge distribution. We conclude that the charge state of the PAH has an important effect on the emitted infrared spectrum. The 3.3 mum stretching mode and, to a lesser extent, the 11-15 km C-H out-of-plane bending modes produce significant emission relative to the other infrared features and originate predominantly from neutral and anionic PAHs. The 6-8 mum emission from the C-C stretching modes, in contrast, originates mainly from charged PAHs with only a partial contribution from neutrals. For heavily ultraviolet irradiated regions such as the Orion Bar, multiply positively charged PAHs are the norm and contribute significantly in this wavelength region. However, because the total infrared emission is a sum over various charge states of different molecules, the ratios of the infrared emission bands do not vary much for G(o)/n(e) less than or equal to 10(3) cm(3). This range includes conditions relevant to both the diffuse interstellar medium and typical reflection nebulae. Larger variations in the interstellar infrared emission features can be expected from photodissociation regions associated with dense H II regions such as the Orion Bar (G(o)/n(e) similar to 10(4)). C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. RP Bakes, ELO (reprint author), NASA, Ames Res Ctr, SETI Inst, MS 245-3, Moffett Field, CA 94035 USA. EM bakes@shivakali.arc.nasa.gov NR 52 TC 99 Z9 99 U1 2 U2 12 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 2001 VL 556 IS 1 BP 501 EP 514 DI 10.1086/321501 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 460PN UT WOS:000170317900046 ER PT J AU Hoehler, TM Bebout, BM Des Marais, DJ AF Hoehler, TM Bebout, BM Des Marais, DJ TI The role of microbial mats in the production of reduced gases on the early Earth SO NATURE LA English DT Article ID OXYGEN; CYANOBACTERIA; FERMENTATION AB The advent of oxygenic photosynthesis on Earth may have increased global biological productivity by a factor of 100-1,000 (ref. 1), profoundly affecting both geochemical and biological evolution. Much of this new productivity probably occurred in microbial mats, which incorporate a range of photosynthetic and anaerobic microorganisms in extremely close physical proximity(2,3). The potential contribution of these systems to global biogeochemical change would have depended on the nature of the interactions among these mat microorganisms. Here we report that in modern, cyanobacteria-dominated mats from hypersaline environments in Guerrero Negro, Mexico, photosynthetic microorganisms generate H-2 and CO-gases that provide a basis for direct chemical interactions with neighbouring chemotrophic and heterotrophic microbes(4). We also observe an unexpected flux of CH4, which is probably related to H-2-based alteration of the redox potential within the mats. These fluxes would have been most important during the nearly 2-billion-year period during which photosynthetic mats contributed substantially to biological productivity(5) -and hence, to biogeochemistry-on Earth. In particular, the large fluxes of H-2 that we observe could, with subsequent escape to space, represent a potentially important mechanism for oxidation of the primitive oceans and atmosphere. C1 NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Exobiol Branch, MS 239-4, Moffett Field, CA 94035 USA. EM thoehler@mail.arc.nasa.gov NR 27 TC 136 Z9 147 U1 1 U2 38 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 EI 1476-4687 J9 NATURE JI Nature PD JUL 19 PY 2001 VL 412 IS 6844 BP 324 EP 327 DI 10.1038/35085554 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 453LW UT WOS:000169918200044 PM 11460161 ER PT J AU Wilke, CO Wang, JL Ofria, C Lenski, RE Adami, C AF Wilke, CO Wang, JL Ofria, C Lenski, RE Adami, C TI Evolution of digital organisms at high mutation rates leads to survival of the flattest SO NATURE LA English DT Article ID DELETERIOUS MUTATION; SELECTION BALANCE; COMPLEXITY; POPULATION; ROBUSTNESS AB Darwinian evolution favours genotypes with high replication rates, a process called 'survival of the fittest'. However, knowing the replication rate of each individual genotype may not suffice to predict the eventual survivor, even in an asexual population. According to quasi-species theory, selection favours the cloud of genotypes, interconnected by mutation, whose average replication rate is highest(1-5). Here we confirm this prediction using digital organisms that self-replicate, mutate and evolve(6-9). Forty pairs of populations were derived from 40 different ancestors in identical selective environments, except that one of each pair experienced a 4-fold higher mutation rate. In 12 cases, the dominant genotype that evolved at the lower mutation rate achieved a replication rate >1.5-fold faster than its counterpart. We allowed each of these disparate pairs to compete across a range of mutation rates. In each case, as mutation rate was increased, the outcome of competition switched to favour the genotype with the lower replication rate. These genotypes, although they occupied lower fitness peaks, were located in flatter regions of the fitness surface and were therefore more robust with respect to mutations. C1 CALTECH, Digital Life Lab, Pasadena, CA 91125 USA. Michigan State Univ, Ctr Biol Modeling, E Lansing, MI 48824 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wilke, CO (reprint author), CALTECH, Digital Life Lab, Mail Code 136-93, Pasadena, CA 91125 USA. EM wilke@caltech.edu RI Adami, Christoph/A-5181-2009; Adami, Christoph/A-9675-2011; Wilke, Claus/B-4643-2008; OI Adami, Christoph/0000-0002-2915-9504; Wilke, Claus/0000-0002-7470-9261; Lenski, Richard/0000-0002-1064-8375; Ofria, Charles/0000-0003-2924-1732 NR 28 TC 312 Z9 315 U1 2 U2 34 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 EI 1476-4687 J9 NATURE JI Nature PD JUL 19 PY 2001 VL 412 IS 6844 BP 331 EP 333 DI 10.1038/35085569 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 453LW UT WOS:000169918200046 PM 11460163 ER PT J AU Iga, I Sanches, IP Srivastava, SK Mangan, M AF Iga, I Sanches, IP Srivastava, SK Mangan, M TI Electron impact ionization of CHF3 SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY LA English DT Article ID SCATTERING CROSS-SECTIONS AB Electron impact production of ions from CHF, has been studied by a crossed electron beam-molecular beam geometry under single collision conditions for electron incident energies ranging from threshold of ionization to 1000 eV. Ions of CF3+ CHF2+, CF2+, CHF+, CF+, F+, CH+, and C+ are observed. Cross sections for their production have been measured by utilising the relative flow technique. At each impact energy, the cross sections for the production of individual ions have been summed up in order to yield total cross sections for the generation of all ions. These total cross sections are in good agreement with recent theoretical results of Kim [Proceedings of the 20th International Conference on the Physics of Electronic and Atomic Collisions, Vienna, Austria, July 1997, Vol. 1, p. WE 103] and experimental results of Jiao et al. [Chem. Phys. Lett. 269 (1997) 117] in the energy range where the comparison is made. However, there is a considerable disagreement between present results and previously published data and the recommended values of NIST. In addition, appearance energies for each ion have been measured and compared with previously published values. (C) 2001 Elsevier Science B.V. C1 Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Srivastava, SK (reprint author), Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil. RI Iga, Ione/C-1273-2015 NR 24 TC 9 Z9 9 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1387-3806 J9 INT J MASS SPECTROM JI Int. J. Mass Spectrom. PD JUL 18 PY 2001 VL 208 IS 1-3 BP 159 EP 167 DI 10.1016/S1387-3806(01)00391-8 PG 9 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 456UK UT WOS:000170100500017 ER PT J AU Ostraat, ML De Blauwe, JW Green, ML Bell, LD Brongersma, ML Casperson, J Flagan, RC Atwater, HA AF Ostraat, ML De Blauwe, JW Green, ML Bell, LD Brongersma, ML Casperson, J Flagan, RC Atwater, HA TI Synthesis and characterization of aerosol silicon nanocrystal nonvolatile floating-gate memory devices SO APPLIED PHYSICS LETTERS LA English DT Article ID CRYSTAL AB This letter describes the fabrication and structural and electrical characterization of an aerosol-nanocrystal-based floating-gate field-effect-transistor nonvolatile memory. Aerosol nanocrystal nonvolatile memory devices demonstrate program/erase characteristics comparable to conventional stacked-gate nonvolatile memory devices. Aerosol nanocrystal devices with 0.2 mum channel lengths exhibit large threshold voltage shifts (>3 V), submicrosecond program times, millisecond erase times, excellent endurance (> 10(5) program/erase cycles), and long-term nonvolatility (> 10(6) s) despite thin tunnel oxides (55-60 A). In addition, a simple aerosol fabrication and deposition process makes the aerosol nanocrystal memory device an attractive candidate for low-cost nonvolatile memory applications. (C) 2001 American Institute of Physics. C1 CALTECH, Pasadena, CA 91125 USA. Agere Syst, Murray Hill, NJ 07974 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ostraat, ML (reprint author), CALTECH, Pasadena, CA 91125 USA. RI Brongersma, Mark/R-6099-2016 NR 7 TC 135 Z9 137 U1 1 U2 33 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD JUL 16 PY 2001 VL 79 IS 3 BP 433 EP 435 DI 10.1063/1.1385190 PG 3 WC Physics, Applied SC Physics GA 451AA UT WOS:000169776000052 ER PT J AU Fleming, EL Jackman, CH Considine, DB Stolarski, RS AF Fleming, EL Jackman, CH Considine, DB Stolarski, RS TI Sensitivity of tracers and a stratospheric aircraft perturbation to two-dimensional model transport variations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDLATITUDE LOWER STRATOSPHERE; 2-DIMENSIONAL MODEL; MIDDLE ATMOSPHERE; TROPICAL STRATOSPHERE; NUMERICAL-MODEL; GRAVITY-WAVE; MEAN AGE; OZONE; AIR; EMISSIONS AB We examine the sensitivity of two-dimensional model simulations of stratospheric tracers to uncertainties in the model transport and explore how such uncertainties impact the simulation of a lower stratospheric perturbation due to highspeed civil transport (HSCT) aircraft emissions. To define the transport uncertainty, we vary the model transport fields so that the resulting tracer simulations roughly bracket the observations. This provides an estimate of the upper and lower limits on realistic transport rates in our two-dimensional (2-D) model, Increasing the advective residual circulation strength or the lower stratospheric vertical diffusion (K-zz) decreases the mean age and residence time of the HSCT emissions and diminishes the negative response in total column ozone globally. Increasing the stratospheric horizontal diffusion (K-yy) either globally or in the tropics only has the opposite effect of increasing the age and emission residence time and enhancing the negative total ozone response. Uncertainties in the mechanical eddy forcing derivation affect both K-yy and the residual circulation simultaneously, resulting in some cancellation of effects. This produces a smaller range of uncertainty in the tracer and perturbation simulations than given by uncertainties in the circulation or Kyy components separately. The model simulations in the lower and middle stratosphere are relatively insensitive to the strength of the mesospheric gravity wave effects and the magnitude of the horizontal diffusive transport across the tropopause. The base model transport compares most favorably with tracer data and gives a global and annual mean steady state HSCT perturbation response in total ozone of -0.62%, assuming a NOx emission index of 5 g/kg, 500 airplanes, and a 10% gas-to-particle conversion of the SO2 emission. For the range of transport uncertainty examined in this study, the global total ozone perturbation response ranges from -0.34% to -0.74%, with a mainly strong correlation between the total ozone response and mean age. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. RP Fleming, EL (reprint author), NASA, Goddard Space Flight Ctr, Code 916,Greenbelt Rd, Greenbelt, MD 20771 USA. RI Stolarski, Richard/B-8499-2013; Jackman, Charles/D-4699-2012 OI Stolarski, Richard/0000-0001-8722-4012; NR 49 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 16 PY 2001 VL 106 IS D13 BP 14245 EP 14263 DI 10.1029/2000JD900732 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 453EQ UT WOS:000169903900005 ER PT J AU Randel, WJ Wu, F Gettelman, A Russell, JM Zawodny, JM Oltmans, SJ AF Randel, WJ Wu, F Gettelman, A Russell, JM Zawodny, JM Oltmans, SJ TI Seasonal variation of water vapor in the lower stratosphere observed in Halogen Occultation Experiment data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPICAL STRATOSPHERE; UPPER TROPOSPHERE; TRANSPORT; CYCLE; DEHYDRATION; CLIMATOLOGY; AEROSOL; MASS; TROPOPAUSE; HYGROMETER AB The seasonal cycle of water vapor in the lower stratosphere is studied based on Halogen Occultation Experiment (HALOE) satellite observations spanning 1991-2000. The seasonal cycle highlights fast, quasi-horizontal transport between tropics and midlatitudes in the lowermost stratosphere (near isentropic levels similar to 380-420 K), in addition to vertical propagation above the equator (the tropical "tape recorder"). The rapid isentropic transport out of the tropics produces a layer of relatively dry air over most of the globe throughout the year, and the seasonal cycle in midlatitudes of both hemispheres land over the Arctic pole) follows that in the tropics. Additionally, the Northern Hemisphere summer monsoon has a dominant influence on hemispheric-scale constituent transport. Longitudinal structures in tropical water vapor and ozone identify regions of strong coupling to the troposphere; an intriguing result is that the solstice minima in water vapor and ozone are spatial separated from maximum convection and coldest tropical temperatures. Detailed comparisons with tropical aircraft measurements and the long record of balloon data from Boulder, Colorado, demonstrate the overall high quality of HALOE water vapor data. C1 Natl Ctr Atmospher Res, Boulder, CO 80305 USA. Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80305 USA. RP Randel, WJ (reprint author), Natl Ctr Atmospher Res, 1850 Table Mesa Dr, Boulder, CO 80305 USA. RI Randel, William/K-3267-2016 OI Randel, William/0000-0002-5999-7162 NR 59 TC 89 Z9 89 U1 1 U2 14 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 16 PY 2001 VL 106 IS D13 BP 14313 EP 14325 DI 10.1029/2001JD900048 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 453EQ UT WOS:000169903900010 ER PT J AU Kulikov, I AF Kulikov, I TI Thermodynamics of trapped fermions in gravitational field SO PHYSICS LETTERS A LA English DT Article ID BOSE-EINSTEIN CONDENSATION; HARMONIC TRAP; ATOMIC GAS AB Trapped non-interacting Fermi gas in an external gravitational field in Newtonian approximation is considered. Analytical equations for the internal energy, the number of particles are computed. The analytical expression for the specific heat of trapped Fermi gas in non-homogeneous gravitational field is found. (C) 2001 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Quantum Comp Technol Grp, Pasadena, CA 91109 USA. RP Kulikov, I (reprint author), CALTECH, Jet Prop Lab, Quantum Comp Technol Grp, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 0 Z9 0 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9601 J9 PHYS LETT A JI Phys. Lett. A PD JUL 16 PY 2001 VL 286 IS 1 BP 25 EP 29 DI 10.1016/S0375-9601(01)00390-5 PG 5 WC Physics, Multidisciplinary SC Physics GA 456RN UT WOS:000170096200005 ER PT J AU Alsdorf, D Birkett, C Dunne, T Melack, J Hess, L AF Alsdorf, D Birkett, C Dunne, T Melack, J Hess, L TI Water level changes in a large Amazon lake measured with spaceborne radar interferometry and altimetry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LANDERS EARTHQUAKE; DISCHARGE AB We demonstrate that interferometric processing of JERS-1 SAR data over an Amazon lake containing similar to 1500 islands yields centimeter-scale changes in the height of the water surface from February 14 to March 30, 1997. For the method to work, we qualitatively find that inundation of about one or two leafless trees per 25 m(2) multi-look SAR pixel is sufficient to return the radar pulse to the side-looking antenna. Validation is provided by multi-temporal TOPEX-POSEIDON altimetry profiles, which directly measure surface heights relative to a fixed datum. Because SAR provides an image, the water height changes (similar to 12 cm) can be converted to a net volume measurement (280 million m(3)) over the 44 days separating the JERS-1 acquisitions. Compared to historical gauge records, removal of this volume from the lake required a similar to 50% greater flow. C1 Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, USRA, Greenbelt, MD 20771 USA. Univ Calif Santa Barbara, Bren Sch Environm Sci & Mgt, Santa Barbara, CA 93106 USA. RP Alsdorf, D (reprint author), Univ Calif Los Angeles, Dept Geog, Los Angeles, CA 90024 USA. RI Dunne, Thomas/B-6374-2014 OI Dunne, Thomas/0000-0002-5281-6517 NR 13 TC 67 Z9 69 U1 3 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 JUL 15 PY 2001 VL 28 IS 14 BP 2671 EP 2674 DI 10.1029/2001GL012962 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 452GK UT WOS:000169849500001 ER PT J AU Allison, M Atkinson, DH AF Allison, M Atkinson, DH TI Galileo Probe Doppler residuals as the wave-dynamical signature of weakly stable, downward-increasing stratification in Jupiter's deep wind layer SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID COMET SHOEMAKER-LEVY-9; VERTICAL STRUCTURE; MOIST CONVECTION; HOT-SPOTS; ATMOSPHERE; INTERIORS; SATURN; MODEL AB Doppler radio tracking of the Galileo probe-to-orbiter relay, previously analyzed for its in situ measure of Jupiter's zonal wind at the equatorial entry site, also shows a record of significant residual fluctuations apparently indicative of varying vertical motions. Regular oscillations over pressure depth in the residual Doppler measurements of roughly 1-8 Hz (increasing upward), as filtered over a 134 sec window, are most plausibly interpreted as gravity waves, and imply a weak, but downward increasing static stability within the 5 - 20 bar region of Jupiter's atmosphere. A matched extension to deeper levels of an independent inertial stability constraint from the measured vertical wind shear at 1 - 4 bars is roughly consistent with a static stability of similar to 0.5 K/km near the 20 bar level, as independently detected by the probe Atmospheric Structure Instrument. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Idaho, Dept Elect Engn, Moscow, ID 83843 USA. RP Allison, M (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 25 TC 11 Z9 11 U1 1 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 JUL 15 PY 2001 VL 28 IS 14 BP 2747 EP 2750 DI 10.1029/2001GL012927 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 452GK UT WOS:000169849500020 ER PT J AU Oinas, V Lacis, AA Rind, D Shindell, DT Hansen, JE AF Oinas, V Lacis, AA Rind, D Shindell, DT Hansen, JE TI Radiative cooling by stratospheric water vapor: big differences in GCM results SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CLIMATE; TRENDS; OZONE; MODEL; ATMOSPHERE; MIDDLE AB The stratosphere has been cooling by about 2K/decade at 30-60 km over the past several decades and by lesser amounts toward the tropopause. Climate model calculations suggest that stratospheric water vapor is an important contributor to the observed stratospheric cooling, but there are large differences among recent GCM simulations for prescribed changes in stratospheric water vapor, which point to problems with the current GCM treatment of the absorption and emission by stratospheric water vapor. We show that the correlated k-distribution treatment with sufficient resolution is capable of simulating accurately cooling by stratospheric water vapor. We obtain equilibrium cooling of about 0.3K that extends From 20 km to the top of the atmosphere, and adjusted radiative forcing of 0.12 Wm(-2), for a stratospheric water vapor increase of 0.7 ppmv which has been estimated for the period 1979-1997. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Rutgers State Univ, Piscataway, NJ 08855 USA. RP Oinas, V (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Shindell, Drew/D-4636-2012; Lacis, Andrew/D-4658-2012 NR 24 TC 41 Z9 42 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 JUL 15 PY 2001 VL 28 IS 14 BP 2791 EP 2794 DI 10.1029/2001GL013137 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 452GK UT WOS:000169849500031 ER PT J AU Sparling, LC Bacmeister, JT AF Sparling, LC Bacmeister, JT TI Scale dependence of tracer microstructure: PDFs, intermittency and the dissipation scale SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FULLY-DEVELOPED TURBULENCE; TEMPERATURE INCREMENTS; LOWER STRATOSPHERE; ADVECTION; STATISTICS; DIFFUSION; TRANSPORT; SPECTRA; MODELS; TIME AB The statistics of tracer variability on small scales (< 200 km) is investigated using high resolution aircraft measurements of ozone in the northern winter middle/high latitudes. Conditioning based on potential temperature is used to isolate the statistics of filamentation on isentropic surfaces from spurious variability due to cross-isentropic motion of the platform. The distribution of isentropic increments Delta (r)chi in the tracer field chi across a horizontal scale r have non-Gaussian tails and are consistent with stretched exponential functions of the form P(Delta (r)chi) similar to exp(-a \ Delta (r)chi \ (p)), where a is a scale-dependent parameter and the exponent p increases overall with r. A scale break in the second order structure function suggests a dissipation scale r(d) similar to 20 km during northern winter 91-92, but the scale break is closer to 100 km during northern winter 88-89. Possible reasons for this are discussed. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21228 USA. Univ Maryland Baltimore Cty, Goddard Earth Sci & Technol Ctr, Baltimore, MD 21228 USA. RP Sparling, LC (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. NR 22 TC 25 Z9 25 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 JUL 15 PY 2001 VL 28 IS 14 BP 2823 EP 2826 DI 10.1029/2000GL012781 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 452GK UT WOS:000169849500039 ER PT J AU Toon, GC Blavier, JF Sen, B Drouin, BJ AF Toon, GC Blavier, JF Sen, B Drouin, BJ TI Atmospheric COCl2 measured by solar occultation spectrometry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INORGANIC CHLORINE; LOWER STRATOSPHERE; PHOSGENE; TROPOSPHERE; SPECTRA AB Vertical profiles of atmospheric COCl2 (phosgene, carbonyl dichloride) have been measured remotely by the JPL MkIV interferometer during recent balloon flights. The nu (5) band of COCl2 in the 830 to 860 cm(-1) spectral region was used for the analyses, despite its overlap with the stronger nu (4) band of CCl3F. Upper troposphere COCl2 volume mixing ratios of around 20 pptv were retrieved, increasing to 25 pptv by 15 km altitude, in good agreement with previous aircraft measurements made by in situ techniques. At mid-latitudes the COCl2 peaks at around 30 pptv at 22 km altitude, above which it rapidly drops, reaching zero by 28 km altitude. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toon, GC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 183-601, Pasadena, CA 91109 USA. NR 18 TC 12 Z9 12 U1 1 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 JUL 15 PY 2001 VL 28 IS 14 BP 2835 EP 2838 DI 10.1029/2000GL012156 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 452GK UT WOS:000169849500042 ER PT J AU Majumder, SB Jain, M Martinez, A Katiyar, RS Van Keuls, FW Miranda, FA AF Majumder, SB Jain, M Martinez, A Katiyar, RS Van Keuls, FW Miranda, FA TI Sol-gel derived grain oriented barium strontium titanate thin films for phase shifter applications SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID ELECTRICAL-PROPERTIES; DEPOSITION; CAPACITORS AB In the present work process methodology was optimized to synthesize oriented barium strontium titanate (BST) (50/50) and (60/40) thin films on strontium titanate (100) and lanthanum aluminate (LAO) (100) substrates by using the chemical solution deposition technique. These films were characterized in terms of their phase formation behavior and structural growth characteristics using x-ray diffraction and atomic force microscopy. A tentative mechanism of the epitaxial growth has been proposed. Films were also characterized in terms of their dielectric properties. The high tunability and low dielectric loss of these films make them attractive for fabricating tunable dielectric devices. Accordingly, we have fabricated eight element coupled microstrip phase shifters and tested them in terms of their degree of phase shift and insertion loss characteristics. An insertion loss of 8.435 dB, phase shift in the order of 320 degrees (2.6-14.5 V/mum) and kappa factor (phase shift/dB of loss) of about 38.0 degrees /dB was achieved in BST (60/40) films deposited on LAO (100) substrate which is comparable to the films grown by other film deposition techniques reported in the literature. The microstructure of the sol-gel derived films show surface porosity which may be responsible for the low dielectric strength of these films. Presently, we are studying the sintering mechanism and kinetics of these films in order to improve the density which is believed to further improve the phase shift and lower insertion loss to result in an improved tunability. (C) 2001 American Institute of Physics. C1 Univ Puerto Rico, Dept Phys, San Juan, PR 00931 USA. NASA, Glenn Res Ctr, Commun Technol Div, Cleveland, OH 44135 USA. RP Katiyar, RS (reprint author), Univ Puerto Rico, Dept Phys, POB 23343, San Juan, PR 00931 USA. OI Jain, Menka/0000-0002-2264-6895 NR 22 TC 82 Z9 88 U1 0 U2 19 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUL 15 PY 2001 VL 90 IS 2 BP 896 EP 903 DI 10.1063/1.1378811 PG 8 WC Physics, Applied SC Physics GA 448ZN UT WOS:000169660000054 ER PT J AU Bauschlicher, CW Ram, RS Bernath, PF Parsons, CG Galehouse, D AF Bauschlicher, CW Ram, RS Bernath, PF Parsons, CG Galehouse, D TI The A (6)Sigma(+)-X (6)Sigma(+) transition of CrH, Einstein coefficients, and an improved description of the A state SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID TRANSFORM EMISSION-SPECTROSCOPY; LASER MAGNETIC-RESONANCE; BASIS-SETS; ATOMS; HYDRIDE; SYSTEM AB The spectrum of CrH has been reinvestigated in the 9000-15 000 cm(-1) region using the Fourier transform spectrometer of the National Solar Observatory. The 1-0 and 1-1 bands of the A (6)Sigma (+)-X (6)Sigma (+) transition have been measured and improved spectroscopic constants have been determined. A value for the 2-0 band origin has been obtained from the band head using estimated spectroscopic constants. These data provide a set of much improved equilibrium vibrational and rotational constants for the A (6)Sigma (+) state. An accurate description of the A-X transition has been obtained using a multireference configuration interaction approach. The inclusion of both scalar relativity and Cr 3s3p correlation are required to obtain a good description of both states. The ab initio computed Einstein coefficients and radiative lifetimes are reported. (C) 2001 American Institute of Physics. C1 NASA, Ames Res Ctr, Space Technol Div, Moffett Field, CA 94035 USA. Univ Arizona, Dept Chem, Tucson, AZ 85721 USA. Univ Waterloo, Dept Chem, Waterloo, ON N2L 3G1, Canada. Univ Akron, Dept Phys, Akron, OH 44325 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Space Technol Div, Mail Stop 230-3, Moffett Field, CA 94035 USA. RI Bernath, Peter/B-6567-2012 OI Bernath, Peter/0000-0002-1255-396X NR 29 TC 37 Z9 37 U1 0 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD JUL 15 PY 2001 VL 115 IS 3 BP 1312 EP 1318 DI 10.1063/1.1377892 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 451AB UT WOS:000169776100019 ER PT J AU Chaban, GM Gerber, RB AF Chaban, GM Gerber, RB TI Anharmonic vibrational spectroscopy of the glycine-water complex: Calculations for ab initio, empirical, and hybrid quantum mechanics/molecular mechanics potentials SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID SELF-CONSISTENT-FIELD; INTRAMOLECULAR PROTON-TRANSFER; DENSITY-FUNCTIONAL THEORY; AQUEOUS-SOLUTION; POLYATOMIC-MOLECULES; OPTIMIZATION SCHEME; WAVE-FUNCTIONS; QM/MM METHODS; STATES; SURFACES AB Effects of intermolecular hydrogen bonding between glycine and one water molecule on the vibrational spectrum are investigated, using ab initio (at the level of second order Moller-Plesset perturbation theory), empirical (OPLS-AA), and mixed ab initio/empirical quantum mechanics/molecular mechanics (QM/MM) potentials. Vibrational spectroscopy is calculated using the correlation corrected vibrational self-consistent field method that accounts for anharmonicities and couplings between different vibrational normal modes. The intermolecular hydrogen bonding interactions are found to be very strong and to affect vibrational frequencies and infrared intensities of both the glycine and the water molecule to a very large extent. The predicted ab initio anharmonic spectra can be used to identify amino acids in complexes with water in experimental studies. The OPLS-AA potential is found to describe hydrogen bonding between glycine and water incorrectly, and to predict erroneous vibrational spectra. Hybrid (QM/MM) techniques can, however, be used to calculate more reliable vibrational spectra, in agreement with full ab initio treatment of the whole system, provided that the regions that contain hydrogen bonds are described by ab initio potentials. (C) 2001 American Institute of Physics. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. Hebrew Univ Jerusalem, Fritz Haber Res Ctr, IL-91904 Jerusalem, Israel. Hebrew Univ Jerusalem, Dept Chem Phys, IL-91904 Jerusalem, Israel. RP NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. EM chaban@pegasus.arc.nasa.gov NR 35 TC 59 Z9 59 U1 1 U2 8 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0021-9606 EI 1089-7690 J9 J CHEM PHYS JI J. Chem. Phys. PD JUL 15 PY 2001 VL 115 IS 3 BP 1340 EP 1348 DI 10.1063/1.1379040 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 451AB UT WOS:000169776100023 ER PT J AU Hakkinen, S AF Hakkinen, S TI Variability in sea surface height: A qualitative measure for the meridional overturning in the North Atlantic SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OCEAN; MODEL; CIRCULATION; TRANSPORT; PATTERNS; LEVEL AB Sea surface height (SSH) from altimeter observations (1992-2000) and modeling results are investigated to determine the modes of variability and the linkages to the state of oceanic circulation in the North Atlantic. Three different model experiments are used with climatological surface forcing appended by wind stress and/or buoyancy flux anomalies, The simulated SSH and gyre circulation and altimeter data are analyzed using the empirical orthogonal function analysis, It is shown that decadal variability in the leading SSH and gyre circulation mode originates from the basin-scale thermal forcing component, not from wind stress driving. This means that low-frequency variations of SSH along the Gulf Stream reflect predominantly overturning changes. The horizontal gyre circulation changes are also related to the overturning due to the topography which couples baroclinic and barotropic flows. SSH variability outside the western boundary current region, on the eastern side of the North Atlantic basin, is determined by local and remote (Rossby waves) wind stress forcing. The model simulations and altimeter data suggest that there was a large SSH change in 1995-1996 over the Gulf Stream which was associated with an abrupt weakening of the overturning. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hakkinen, S (reprint author), NASA, Goddard Space Flight Ctr, Code 971,Bldg 33,Room A221, Greenbelt, MD 20771 USA. RI Hakkinen, Sirpa/E-1461-2012 NR 21 TC 54 Z9 55 U1 0 U2 6 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 JUL 15 PY 2001 VL 106 IS C7 BP 13837 EP 13848 DI 10.1029/1999JC000155 PG 12 WC Oceanography SC Oceanography GA 452QW UT WOS:000169871100002 ER PT J AU Giudice, GF Kolb, EW Riotto, A AF Giudice, GF Kolb, EW Riotto, A TI Largest temperature of the radiation era and its cosmological implications SO PHYSICAL REVIEW D LA English DT Article ID NEUTRALINO-STAU COANNIHILATION; BIG-BANG NUCLEOSYNTHESIS; COLD DARK-MATTER; REHEATING TEMPERATURE; INFLATIONARY UNIVERSE; GRAVITINO PRODUCTION; MASSIVE PARTICLES; GRAND UNIFICATION; INVISIBLE AXION; STANDARD MODEL AB The thermal history of the universe before the epoch of nucleosynthesis is unknown. The maximum temperature in the radiation-dominated era, which we will refer to as the reheat temperature, may have been as low as 0.7 MeV. In this paper we show that a low reheat temperature has important implications for many topics in cosmology. We show that weakly interacting massive particles (WIMP's) may be produced even if the reheat temperature is much smaller than the freeze-out temperature of the WIMP, and that the dependence of the present abundance on the mass and the annihilation cross section of the WIMP differs drastically from familiar results. We reexamine predictions of the relic abundance and resulting model constraints of supersymmetric dark matter, axions, massive neutrinos, and other dark matter candidates, nucleosynthesis constraints on decaying particles, and leptogenesis by decay of superheavy particles. We find that the allowed parameter space of supersymmetric models is altered, removing the usual bounds on the mass spectrum; the cosmological bound on massive neutrinos is drastically changed, ruling out Dirac (Majorana) neutrino masses in, only in the range 33 keV less than or similar tom(nu)less than or similar to6 (5) MeV, which is significantly smaller from the standard disallowed range 94 eV less than or equal tom(nu)less than or similar to2 GeV (this implies that massive neutrinos may still play the role of either warm or cold dark matter); the cosmological upper bound on the Peccei-Quinn scale may be significantly increased to 10(16) GeV from the usually cited limit of about 10(12) GeV; and that efficient out-of-equilibrium grand unified theory GUT baryogenesis and/or leptogenesis can take place even if the reheat temperature is much smaller than the mass of the decaying superheavy particle. C1 CERN, Div Theory, CH-1211 Geneva 23, Switzerland. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Scuola Normale Super Pisa, I-56126 Pisa, Italy. Ist Nazl Fis Nucl, I-56127 Pisa, Italy. RP Giudice, GF (reprint author), CERN, Div Theory, CH-1211 Geneva 23, Switzerland. NR 67 TC 206 Z9 206 U1 2 U2 3 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 JUL 15 PY 2001 VL 64 IS 2 AR 023508 DI 10.1103/PhysRevD.64.023508 PG 20 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 453ZE UT WOS:000169947400018 ER PT J AU Hellings, RW AF Hellings, RW TI Elimination of clock jitter noise in spaceborne laser interferometers SO PHYSICAL REVIEW D LA English DT Article AB Space gravitational wave detectors employing laser interferometry between free-flying spacecraft differ in many ways from their laboratory counterparts. Among these differences is the fact that, in space, the end masses will be moving relative to each other. This creates a problem by inducing a Doppler shift between the incoming and outgoing frequencies. The resulting beat frequency is so high that its phase cannot be read to sufficient accuracy when referenced to state-of-the-art space-qualified clocks. This is the problem that is addressed in this paper. We introduce a set of time-domain algorithms in which the effects of clock jitter are exactly canceled. The method employs the two-color laser approach that has been previously proposed, but avoids the singularities that arise in the previous frequency-domain algorithms. In addition, several practical aspects of the laser and clock noise cancellation schemes are addressed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hellings, RW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 21 Z9 22 U1 1 U2 3 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 JUL 15 PY 2001 VL 64 IS 2 AR 022002 DI 10.1103/PhysRevD.64.022002 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 453ZE UT WOS:000169947400007 ER PT J AU Hoffman, MB Turner, NS AF Hoffman, MB Turner, NS TI Kinematic constraints to the key inflationary observables SO PHYSICAL REVIEW D LA English DT Article ID MICROWAVE BACKGROUND POLARIZATION; GRAVITATIONAL-WAVES; UNIVERSE; PERTURBATIONS; ANISOTROPY; RECONSTRUCTION; DETECTABILITY; RADIATION; SPECTRUM; SCALE AB The observables T/S and n-1 are key to testing and understanding inflation. (T, S, and n-1 respectively quantify the gravity-wave and density-perturbation contributions to CMB anisotropy and the deviation of the density perturbations from the scale-invariant form.) Absent a standard model, there is no definite prediction for, or relation between, T/S and n-1. By reformulating the equations for slow-roll inflation, we show that in the T/S-(n-1) plane there are excluded regions, regions in which the density perturbations are not well approximated by a power law, and regions in which models with a "featureless" potential must lie. C1 Univ Chicago, Dept Phys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Hoffman, MB (reprint author), Univ Chicago, Dept Phys, Chicago, IL 60637 USA. NR 35 TC 102 Z9 102 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 JUL 15 PY 2001 VL 64 IS 2 AR 023506 DI 10.1103/PhysRevD.64.023506 PG 5 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 453ZE UT WOS:000169947400016 ER PT J AU Akiyama, T Gautsch, S de Rooij, NF Staufer, U Niedermann, P Howald, L Muller, D Tonin, A Hidber, HR Pike, WT Hecht, MH AF Akiyama, T Gautsch, S de Rooij, NF Staufer, U Niedermann, P Howald, L Muller, D Tonin, A Hidber, HR Pike, WT Hecht, MH TI Atomic force microscope for planetary applications SO SENSORS AND ACTUATORS A-PHYSICAL LA English DT Article; Proceedings Paper CT Solid-State Sensors and Actuators Workshop CY JUN 04-08, 2000 CL HILTON HEAD ISL, SOUTH CAROLINA DE AFM; Mars; space; array ID MARS AB We have developed, built and tested an atomic force microscope (AFM) for planetary science applications, in particular for the study of Martian dust and soil. The system consists of a controller board, an electromagnetic scanner and a micro-fabricated sensor-chip. Eight cantilevers with integrated, piezoresistive deflection sensors are aligned in a row and are engaged one after the other to provide redundancy in case of tip or cantilever failure. Silicon and molded diamond tips are used for probing the sample. Images can be recorded in both, static and dynamic operation mode. In the latter case, excitation of the resonance frequencies of the cantilevers is achieved by vibrating the whole chip with a piezoelectric disk. (C) 2001 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Neuchatel, Inst Microtechnol, CH-2007 Neuchatel, Switzerland. CSEM, CH-2007 Neuchatel, Switzerland. Nanosurf AG, CH-4410 Liestal, Switzerland. Univ Basel, Inst Phys, CH-4056 Basel, Switzerland. RP Pike, WT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Gautsch, Sebastian/G-2561-2015; Staufer, Urs/J-6866-2016 OI Staufer, Urs/0000-0002-3519-6467 NR 5 TC 13 Z9 13 U1 1 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0924-4247 J9 SENSOR ACTUAT A-PHYS JI Sens. Actuator A-Phys. PD JUL 15 PY 2001 VL 91 IS 3 BP 321 EP 325 DI 10.1016/S0924-4247(01)00602-1 PG 5 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 454KA UT WOS:000169970700009 ER PT J AU Kanik, I Johnson, PV Das, MB Khakoo, MA Tayal, SS AF Kanik, I Johnson, PV Das, MB Khakoo, MA Tayal, SS TI Electron-impact studies of atomic oxygen: I. Differential and integral cross sections; experiment and theory SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID EXTREME-ULTRAVIOLET EMISSION; OSCILLATOR-STRENGTHS; MEDIUM-RESOLUTION; TRANSITION 1304; EXCITATION; SCATTERING; STATES; COLLISIONS; MOLECULES; HYDROGEN AB We report both experimental and theoretical differential and integral excitation cross sections of atomic oxygen corresponding to the 2s(2)2p(4) P-3 --> 3s S-3 (130.4 nm), 2s(2)2p(4) 3P --> 3d D-3 (102.7 nm), 2s(2)2p(4) P-3 --> 3s ' D-3 (98.9 nm) and 2s(2)2p(4) P-3 --> 3s " P-3 (87.8 nm) transitions at 30, 50, and 100 eV electron-impact energies. Experimental measurements have been made in the angular range from 0 degrees to 25 degrees with a conventional electrostatic electron energy-loss spectrometer. The atomic O differential cross sections (DCSs) were put on an absolute scale by normalization to the O-2 DCS values of Johnson and Kanik (2001). Extrapolation of the measured results to larger angles was performed using theoretical calculations as a guide, and integral cross sections were derived. Theoretical calculations based on the R-matrix method, along with other available experimental data, have been compared with the current experimental results. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92634 USA. Clark Atlanta Univ, Dept Phys, Atlanta, GA 30314 USA. RP Kanik, I (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Johnson, Paul/D-4001-2009 OI Johnson, Paul/0000-0002-0186-8456 NR 49 TC 28 Z9 28 U1 1 U2 7 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 JUL 14 PY 2001 VL 34 IS 13 BP 2647 EP 2665 DI 10.1088/0953-4075/34/13/308 PG 19 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 459GD UT WOS:000170241900010 ER PT J AU Noren, C Kanik, I Johnson, PV McCartney, P James, GK Ajello, JM AF Noren, C Kanik, I Johnson, PV McCartney, P James, GK Ajello, JM TI Electron-impact studies of atomic oxygen: II. Emission cross section measurements of the O I S-3(0) -> P-3 transition (130.4 nm) SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID EXCITATION; ULTRAVIOLET; DAYGLOW; CASCADE; STATE AB The optical excitation function of the O I S-3 degrees --> P-3 transition (130.4 nm), produced by electron-impact excitation of atomic oxygen, has been measured over an extended energy range from threshold to 1.0 keV Measurements were obtained in a crossed-beam experiment using both magnetically confined and electrostatically focused electrons in collision with atomic oxygen produced by a microwave discharge source. A 0.2 m vacuum ultraviolet monochromator system was used to measure the emitted O I radiation at 130.4 nm. The relative O I (130.4 nm) emission intensity corresponding to the S-3 degrees --> P-3 transition was then put on the absolute scale by normalization to the O I (130.4 nm) cross section produced by dissociative excitation of O-2 at 30 eV (Kanik et al 2000). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Noren, C (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Johnson, Paul/D-4001-2009 OI Johnson, Paul/0000-0002-0186-8456 NR 23 TC 17 Z9 17 U1 0 U2 5 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 JUL 14 PY 2001 VL 34 IS 13 BP 2667 EP 2677 DI 10.1088/0953-4075/34/13/309 PG 11 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 459GD UT WOS:000170241900011 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI On interpreting the photoelectron spectra of MgO- SO CHEMICAL PHYSICS LETTERS LA English DT Article ID CORRELATED MOLECULAR CALCULATIONS; GAUSSIAN-BASIS SETS; SYSTEMS; STATES AB The (2)Sigma (+) and (2)Pi states of MgO- and the (1)Sigma (+), (1)Pi, and (3)Pi states of MgO are studied using the ACPF approach. The computed spectroscopic constants are in good agreement with the available experimental. data. The computed Franck-Condon factors and photodetachment overlaps are compared with experiment. (C) 2001 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 12 TC 11 Z9 11 U1 0 U2 2 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 JUL 13 PY 2001 VL 342 IS 3-4 BP 441 EP 446 DI 10.1016/S0009-2614(01)00605-4 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 454NV UT WOS:000169979400030 ER PT J AU Melnick, GJ Neufeld, DA Ford, KES Hollenbach, DJ Ashby, MLN AF Melnick, GJ Neufeld, DA Ford, KES Hollenbach, DJ Ashby, MLN TI Discovery of water vapour around IRC+10216 as evidence for comets orbiting another star SO NATURE LA English DT Article ID WAVE-ASTRONOMY-SATELLITE; SUBMILLIMETER; MILLIMETER; MOLECULES; SPECTRUM; LINES; HCN AB Since 1995, planets with masses comparable to that of Jupiter have been discovered around approximately 60 stars(1). These planets have not been seen directly, but their presence has been inferred from the small reflex motions that they gravitationally induce on the star they orbit; these motions result in small periodic wavelength shifts in the stellar spectrum. The presence of analogues of the smaller bodies in our Solar System cannot, however, be determined using this technique, because the induced reflex motions are too small-so an alternative approach is needed. Here we report the observation of circumstellar water vapour around the ageing carbon star IRC+10216; water is not expected in measurable quantities around such a star. The only plausible explanation for this water is that the recent evolution of IRC+10216, which has been accompanied by a prodigious increase in its luminosity, is causing the vaporization of a collection of orbiting icy bodies-a process considered in an earlier theoretical study(2). C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Melnick, GJ (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. NR 18 TC 97 Z9 98 U1 0 U2 2 PU MACMILLAN PUBLISHERS LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 12 PY 2001 VL 412 IS 6843 BP 160 EP 163 DI 10.1038/35084024 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 451AJ UT WOS:000169778700044 PM 11449266 ER PT J AU Gladman, B Kavelaars, JJ Holman, M Nicholson, PD Burns, JA Hergenrother, CW Petit, JM Marsden, BG Jacobson, R Gray, W Grav, T AF Gladman, B Kavelaars, JJ Holman, M Nicholson, PD Burns, JA Hergenrother, CW Petit, JM Marsden, BG Jacobson, R Gray, W Grav, T TI Discovery of 12 satellites of Saturn exhibiting orbital clustering SO NATURE LA English DT Article ID JOVIAN-SATELLITES; ASTEROIDS; URANUS; STABILITY; CAPTURE; ORIGIN; PHOEBE; SYSTEM; MOONS AB The giant planets in the Solar System each have two groups of satellites. The regular satellites move along nearly circular orbits in the planet's orbital plane, revolving about it in the same sense as the planet spins. In contrast, the so-called irregular satellites are generally smaller in size and are characterized by large orbits with significant eccentricity, inclination or both. The differences in their characteristics suggest that the regular and irregular satellites formed by different mechanisms: the regular satellites are believed to have formed in an accretion disk around the planet, like a miniature Solar System, whereas the irregulars are generally thought to be captured planetesimals(1). Here we report the discovery of 12 irregular satellites of Saturn, along with the determinations of their orbits. These orbits, along with the orbits of irregular satellites of Jupiter and Uranus, fall into groups on the basis of their orbital inclinations. We interpret this result as indicating that most of the irregular moons are collisional remnants of larger satellites that were fragmented after capture, rather than being captured independently. C1 Observ Cote Azur, F-06304 Nice 4, France. McMaster Univ, Dept Phys & Astron, Hamilton, ON L8S 4M1, Canada. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Project Pluto, Bowdoinham, ME 04008 USA. Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway. RP Gladman, B (reprint author), Observ Cote Azur, BP 4229, F-06304 Nice 4, France. EM gladman@obs-nice.fr NR 36 TC 72 Z9 72 U1 0 U2 2 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 12 PY 2001 VL 412 IS 6843 BP 163 EP 166 DI 10.1038/35084032 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 451AJ UT WOS:000169778700045 PM 11449267 ER PT J AU Zahnle, K AF Zahnle, K TI Decline and fall of the martian empire SO NATURE LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Zahnle, K (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 15 TC 6 Z9 7 U1 0 U2 1 PU MACMILLAN PUBLISHERS LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 12 PY 2001 VL 412 IS 6843 BP 209 EP 213 DI 10.1038/35084148 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 451AJ UT WOS:000169778700059 PM 11449281 ER PT J AU Carr, MH Garvin, J AF Carr, MH Garvin, J TI Mars exploration SO NATURE LA English DT Editorial Material AB An international flotilla of spacecraft are to be sent to Mars over the next decade in an effort to understand the planet's geology and climate history, and to determine whether some form of life ever started there. At least two spacecraft will be sent at each launch opportunity, and at times up to four spacecraft may be operating simultaneously at the planet. C1 US Geol Survey, Menlo Park, CA 94025 USA. NASA Headquarters, Washington, DC 20546 USA. RP Carr, MH (reprint author), US Geol Survey, 345 Middlefield Rd, Menlo Park, CA 94025 USA. NR 15 TC 3 Z9 4 U1 0 U2 1 PU MACMILLAN PUBLISHERS LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 12 PY 2001 VL 412 IS 6843 BP 250 EP 253 DI 10.1038/35084200 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 451AJ UT WOS:000169778700065 PM 11449287 ER PT J AU Badhwar, GD O'Neill, PM AF Badhwar, GD O'Neill, PM TI Response of silicon-based linear energy transfer spectrometers: implication for radiation risk assessment in space flights SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article DE silicon dosimeter; Monte Carlo; LET spectrometer ID MODEL; SPECTRA; SHUTTLE; CASCADE; RANGE AB There is considerable interest in developing silicon-based telescopes because of their compactness and low power requirements. Three such telescopes have been flown on board the Space Shuttle to measure the linear energy transfer spectra of trapped, galactic cosmic ray, and solar energetic particles, Dosimeters based oil single silicon detectors have also been flown on the Mir orbital station. A comparison of the absorbed dose and radiation quality factors calculated from these telescopes with that estimated from measurements made with a tissue equivalent proportional counter show differences which need to be fully understood if these telescopes are to be used for astronaut radiation risk assessments. Instrument performance is complicated by a variety of factors. A Monte Carlo-based technique was developed to model the behavior of both single element detectors in a proton beam, and the performance of a two-element. wide-angle telescope, in the trapped belt proton field inside the Space Shuttle. The technique is based on: (1) radiation transport intranuclear-evaporation model that takes into account the charge and angular distribution of target fragments, (2) Landau-Vavilov distribution of energy deposition allowing for electron escape, (3) true detector geometry of the telescope, (4) coincidence and discriminator settings, (5) spacecraft shielding geometry, and (6) the external space radiation environment, including albedo protons. The value of such detailed modeling and its implications in astronaut risk assessment is addressed. (C) 2001 Elsevier Science B.V. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, SN,2101 NASA Rd 1, Houston, TX 77058 USA. NR 25 TC 13 Z9 14 U1 0 U2 3 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 JUL 11 PY 2001 VL 466 IS 3 BP 464 EP 474 DI 10.1016/S0168-9002(01)00285-6 PG 11 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 456UN UT WOS:000170100800005 PM 11858255 ER PT J AU Cambresy, L Reach, WT Beichman, CA Jarrett, TH AF Cambresy, L Reach, WT Beichman, CA Jarrett, TH TI The cosmic infrared background at 1.25 and 2.2 microns using DIRBE and 2MASS: A contribution not due to galaxies? SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; diffuse radiation; infrared : general ID EXPERIMENT SEARCH; COUNTS; FLUCTUATIONS; PHOTOMETRY; UNIVERSE; SPECTRUM; CLOUD; FIELD; LIGHT; MODEL AB Using the 2MASS second incremental data release and the zodiacal subtracted mission average maps of COBE/DIRBE, we estimate the cosmic background in the J (1.25 mum) and K (2.2 mum) bands using selected areas representing similar to 550 deg(2) of sky. We find a J background of 22.9 +/-7.0 kJy sr(-1) (54.0 +/- 16.8 nW m(-2) sr(-1)) and a K background of 20.4 +/-4.9 kJy sr(-1) (27.8 +/-6.7 nW m(-2) sr(-1)). This large-scale study shows that the main uncertainty comes from the residual zodiacal emission. The cosmic background we obtain is significantly higher than integrated galaxy counts (3.6 +/-0.8 kJy sr(-1) and 5.3 +/-1.2 kJy sr(-1) for J and K, respectively), suggesting either an increase of the galaxy luminosity function for magnitudes fainter than 30 mag or the existence of another contribution to the cosmic background from primeval stars, black holes, or relic particle decay. C1 CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Ctr Infrared Proc & Anal, M-S 100-22, Pasadena, CA 91125 USA. EM laurent@ipac.caltech.edu; reach@ipac.caltech.edu; chas@pop.jpl.nasa.gov; jarrett@ipac.caltech.edu RI Reach, William/C-4710-2008; OI Reach, William/0000-0001-8362-4094 NR 34 TC 114 Z9 115 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 JUL 10 PY 2001 VL 555 IS 2 BP 563 EP 571 DI 10.1086/321470 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200003 ER PT J AU Crenshaw, DM Kraemer, SB Bruhweiler, FC Ruiz, JR AF Crenshaw, DM Kraemer, SB Bruhweiler, FC Ruiz, JR TI Absorption and reddening in the Seyfert galaxy NGC 3227 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; galaxies : active; galaxies : individual (NGC 3227); galaxies : Seyfert; ultraviolet : galaxies ID ACTIVE GALACTIC NUCLEI; INTERNATIONAL-ULTRAVIOLET-EXPLORER; INTER-STELLAR EXTINCTION; LARGE MAGELLANIC CLOUD; NARROW-LINE REGION; SIZE DISTRIBUTION; 2175 ANGSTROM; WARM ABSORBER; DUST; EMISSION AB We have obtained low-dispersion spectra of NGC 3227 with the Space Telescope Imaging Spectrograph (STIS) to study the intrinsic UV absorption and the reddening of the nucleus in this Seyfert 1 galaxy. The UV spectra show a wealth of absorption lines at the systemic redshift that span a wide range in ionization state (Mg I to N V). The equivalent widths of the lines are consistent with our earlier prediction that a "lukewarm absorber" (T-e = 18,000 K at the ionized face) with a substantial column of gas (N-H = 2x 10(21) cm(-2)) is present and likely responsible for the reddening of the nucleus. The lukewarm absorber is also responsible for most of the absorption in the X-rays at energies less than 1 keV, although a more highly ionized "warm absorber" is needed to account for the O VII and O VIII ionization edges. In addition, we require a small column (N-H = 5x10(19) cm(-2)) of cold gas to match the strengths of the neutral and singly ionized lines in the UV spectra. NGC 3227 is the first Seyfert galaxy in which a strong link between the reddening and intrinsic UV absorption has been found. By comparing our STIS UV and optical spectra with those of the unreddened Seyfert galaxy NGC 4151, we have determined a reddening curve for the nuclear continuum source in NGC 3227 over the 1150-10200 Angstrom range. The reddening curve does not show a 2200 Angstrom bump and is steeper in the UV than reddening curves derived for the Galaxy, LMC, and SMC, suggesting a preponderance of small dust grains near the nucleus. C1 Catholic Univ Amer, Inst Astrophys & Computat Sci, Dept Phys, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Crenshaw, DM (reprint author), Catholic Univ Amer, Inst Astrophys & Computat Sci, Dept Phys, Washington, DC 20064 USA. NR 48 TC 55 Z9 56 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 2001 VL 555 IS 2 BP 633 EP 640 DI 10.1086/321522 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200009 ER PT J AU Malkan, MA Stecker, FW AF Malkan, MA Stecker, FW TI An empirically based model for predicting infrared luminosity functions, deep infrared galaxy counts, and the diffuse infrared background SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; galaxies : statistics; infrared : galaxies ID STAR-FORMATION HISTORY; MU-M; TENTATIVE DETECTION; IRAS GALAXIES; COBE FIRAS; EVOLUTION; REDSHIFT; UNIVERSE; MICRONS; LIMITS AB We predict luminosity functions and number counts for extragalactic infrared sources at various wavelengths using the framework of our empirically based model. Comparisons of our galaxy count results with existing data indicate that either galaxy luminosity evolution is not much stronger than Q = 3.1, where L proportional to (1 + z)(Q), or that this evolution does not continue beyond a redshift of 2. However, a derivation of the far-infrared background from COBE Diffuse Infrared Background Experiment data suggests a stronger evolution for the far-infrared emission, with Q>4 in the redshift range between 0 and 1. We discuss several interpretations of these results and also discuss how future observations can reconcile this apparent conflict. We also make predictions of the redshift distributions of extragalactic infrared sources at selected flux levels, which can be tested by planned detectors. Finally, we predict the fluxes at which various future surveys will become confusion-limited. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. EM malkan@astro.ucla.edu; stecker@lheapop.gsfc.nasa.gov RI Stecker, Floyd/D-3169-2012 NR 50 TC 75 Z9 75 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 JUL 10 PY 2001 VL 555 IS 2 BP 641 EP 649 DI 10.1086/321492 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200010 ER PT J AU Schmitt, HR Antonucci, RRJ Ulvestad, JS Kinney, AL Clarke, CJ Pringle, JE AF Schmitt, HR Antonucci, RRJ Ulvestad, JS Kinney, AL Clarke, CJ Pringle, JE TI Testing the unified model with an infrared-selected sample of Seyfert galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : interactions; galaxies : jets; galaxies : Seyfert; galaxies : statistics ID ACTIVE GALACTIC NUCLEI; POINT-SOURCE CATALOG; WARM IRAS SOURCES; STAR-FORMATION RATES; LINE IMAGING SURVEY; RADIO STRUCTURES; LIMITED SAMPLE; IONIZING-RADIATION; SPIRAL GALAXIES; JET DIRECTIONS AB We present a series of statistical tests done to a sample of 29 Seyfert 1 and 59 Seyfert 2 galaxies selected from mostly isotropic properties, their far-infrared fluxes and warm infrared colors. Such selection criteria provide a profound advantage over the criteria used by most investigators in the past, such as ultraviolet excess. These tests were done using ground-based high-resolution Very Large Array A-configuration 3.6 cm radio and optical B and I imaging data. From the relative number of Seyfert 1's and Seyfert 2's, we calculate that the torus half-opening angle is 48 degrees. We show that, as seen in previous papers, there is a lack of edge-on Seyfert 1 galaxies, suggesting that dust and gas along the host galaxy disk probably play an important role in hiding some nuclei from direct view. We find that there is no statistically significant difference in the distribution of host galaxy morphological types and radio luminosities of Seyfert 1's and Seyfert 2Is, suggesting that previous results showing the opposite may have been due to selection effects. The average extension of the radio emission of Seyfert 1's is smaller than that of Seyfert 2's by a factor of similar to2-3, as predicted by the unified model. A search for galaxies around our Seyferts allows us to put a lower and an upper limit on the possible number of companions around these galaxies of 19% and 28%, respectively, with no significant difference in the number of companion galaxies between Seyfert 1's and Seyfert 2's. We also show that there is no preference for the radio jets to be aligned closer to the host galaxy disk axis in late-type Seyferts, unlike results claimed by previous papers. These results, taken together, provide strong support for a uniDed model in which type 2 Seyferts contain a torus seen more edge-on than the torus in type 1 Seyferts. C1 Natl Radio Astron Observ, Socorro, NM 87801 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. NASA Headquarters, Washington, DC 20546 USA. Cambridge Observ, Inst Astron, Cambridge CB3 0HA, England. RP Schmitt, HR (reprint author), Natl Radio Astron Observ, POB O, Socorro, NM 87801 USA. NR 88 TC 70 Z9 71 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 2001 VL 555 IS 2 BP 663 EP 672 DI 10.1086/321505 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200012 ER PT J AU Boyd, PT Smale, AP Dolan, JF AF Boyd, PT Smale, AP Dolan, JF TI X-ray and ultraviolet orbital phase dependence in LMC X-3 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; black hole physics; stars : individual (LMC X-3); X-rays : stars ID LINEAR-POLARIZATION; MASS; DISCOVERY; BEHAVIOR; BINARIES; SPECTRA; STATE; NOISE AB The black hole binary LMC X-3 is known to be variable on timescales of days to years. We investigate X-ray and ultraviolet variability in the system as a function of the 1.7 day binary phase using a 6.4 day observation with the Rossi X-Ray Timing Explorer (RXTE) from 1998 December. An abrupt 14% flux decrease, lasting nearly an entire orbit, is followed by a return to previous flux levels. This behavior occurs twice, at nearly the same binary phase, but it is not present in consecutive orbits. When the X-ray flux is at lower intensity, a periodic amplitude modulation of 7% is evident in data folded modulo the orbital period. The higher intensity data show weaker correlation with phase. This is the first report of X-ray variability at the orbital period of LMC X-3. Archival RXTE observations of LMC X-3 during a high-flux state in 1996 December show similar phase dependence. An ultraviolet light curve obtained with the High-Speed Photometer on board the Hubble Space Telescope shows orbital modulation consistent with that in the optical, caused by the ellipsoidal variation of the spatially deformed companion. The X-ray spectrum of LMC X-3 can be acceptably represented by a phenomenological disk blackbody plus a power law. Changes in the spectrum of LMC X-3 during our observations are compatible with earlier observations during which variations in the 2-10 keV flux are tracked closely by the disk geometry spectral model parameter. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Astrophys, Baltimore, MD 21201 USA. RP Boyd, PT (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. RI Boyd, Patricia/D-3274-2012 NR 33 TC 9 Z9 9 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 2001 VL 555 IS 2 BP 822 EP 828 DI 10.1086/321511 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200023 ER PT J AU Levin, SM Langer, WD Velusamy, T Kuiper, TBH Crutcher, RM AF Levin, SM Langer, WD Velusamy, T Kuiper, TBH Crutcher, RM TI Measuring the magnetic field strength in L1498 with Zeeman-splitting observations of CCS SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : clouds; ISM : magnetic fields; ISM : molecules; magnetic fields; stars : formation ID CLOUDS; CORE AB We have measured the Zeeman splitting of the CCS J(N) = 3(2)-2(1) line at 33 GHz toward L1498, a dense preprotostellar core, in an effort to measure the line-of-sight component of its magnetic field. With approximately 35 hr of data on source (70 hr total) in good weather, the data suggest a line-of-sight component of the magnetic field in L1498 of 48 +/- 31 muG, yielding an upper limit of B-los < 100 G at the 95% confidence level. This upper limit provides some constraints on models. Our results show that the technique we have adopted to measure CCS Zeeman splitting holds great promise for determining magnetic field strengths in cloud cores using lower-frequency transitions, in particular the CCS J(N) = 1(0)-0(0) line at 11 GHz. At this transition, the frequency splitting per gauss is 3 times that at 33 GHz, the brightness temperature is comparable to the line, and receiver systems can be made more sensitive. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. RP Levin, SM (reprint author), CALTECH, Jet Prop Lab, M-S 169-506, Pasadena, CA 91109 USA. NR 12 TC 22 Z9 22 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 2001 VL 555 IS 2 BP 850 EP 854 DI 10.1086/321518 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200027 ER PT J AU Patat, F Cappellaro, E Danziger, J Mazzali, PA Sollerman, J Augusteijn, T Brewer, J Doublier, V Gonzalez, JF Hainaut, O Lidman, C Leibundgut, B Nomoto, K Nakamura, T Spyromilio, J Rizzi, L Turatto, M Walsh, J Galama, TJ van Paradijs, J Kouveliotou, C Vreeswijk, PM Frontera, F Masetti, N Palazzi, E Pian, E AF Patat, F Cappellaro, E Danziger, J Mazzali, PA Sollerman, J Augusteijn, T Brewer, J Doublier, V Gonzalez, JF Hainaut, O Lidman, C Leibundgut, B Nomoto, K Nakamura, T Spyromilio, J Rizzi, L Turatto, M Walsh, J Galama, TJ van Paradijs, J Kouveliotou, C Vreeswijk, PM Frontera, F Masetti, N Palazzi, E Pian, E TI The metamorphosis of SN 1998bw SO ASTROPHYSICAL JOURNAL LA English DT Review DE gamma rays : bursts; supernovae : general; supernovae : individual (SN 1998bw) ID GAMMA-RAY BURST; SUPERNOVA LIGHT CURVES; IB SUPERNOVAE; SPECTRAL EVOLUTION; UBVRI PHOTOMETRY; HYPERNOVA MODEL; STANDARD STARS; IA SUPERNOVAE; IC SUPERNOVAE; LATE PHASES AB We present and discuss the photometric and spectroscopic evolution of the peculiar SN 1998bw, associated with GRB 980425, through an analysis of optical and near-IR data collected at ESO-La Silla. The spectroscopic data, spanning the period from day -9 to day +376 (relative to B maximum), have shown that this supernova (SN) was unprecedented, although somewhat similar to SN 1997ef. Maximum expansion velocities as high as 3x10(4) km s(-1) to some extent mask its resemblance to other Type Ic SNe. At intermediate phases, between photospheric and fully nebular, the expansion velocities (similar to 10(4) km s(-1)) remained exceptionally high compared to those of other recorded core-collapse SNe at a similar phase. The mild linear polarization detected at early epochs suggests the presence of asymmetry in the emitting material. The degree of asymmetry, however, cannot be decoded from these measurements alone. The He I 1.083 and 2.058 mum lines are identified, and He is suggested to lie in an outer region of the envelope. The temporal behavior of the fluxes and profiles of emission lines of Mg I] lambda 4571, [O I] lambda lambda 6300, 6364, and a feature ascribed to Fe are traced to stimulate future modeling work. The uniqueness of SN 1998bw became less obvious once it entered the fully nebular phase (after 1 yr), when it was very similar to other Type Ib/c-IIb objects, such as the Type Ib SN 1996N and the Type IIb SN 1993J, even though SN 1998bw was 1.4 mag brighter than SN 1993J and 3 mag brighter than SN 1996N at a comparable phase. The late-phase optical photometry, which extends up to 403 days after B maximum, shows that the SN luminosity declined exponentially but substantially faster than the decay rate of Co-56. The ultraviolet-optical-infrared bolometric light curve, constructed using all available optical data and the early JHK photometry presented in this work, shows a slight flattening starting on about day +300. Since no clear evidence of ejecta-wind interaction was found in the late-time spectroscopy (see also the work of Sollerman and coworkers), this may be due to the contribution of the positrons since most gamma -rays escape thermalization at this phase. A contribution from the superposed H II region cannot, however, be excluded. C1 European So Observ, D-85748 Garching, Germany. Osserv Astron Padova, I-35122 Padua, Italy. Osserv Astron Trieste, I-34131 Trieste, Italy. Univ Tokyo, Res Ctr Early Universe, Bunkyo Ku, Tokyo 1130033, Japan. Univ Tokyo, Dept Astron, Bunkyo Ku, Tokyo 1130033, Japan. Stockholm Observ, S-13336 Saltsjobaden, Sweden. European So Observ, Santiago 19, Chile. Ecole Normale Super Lyon, Ctr Rech Astron Lyon, CNRS, UMR 5574, F-69364 Lyon 07, France. Univ Amsterdam, Astron Inst Anton Pannekoek, CHEAF, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. CNR, Ist Tecnol & Studio Radiaz Extraterr, I-40126 Bologna, Italy. RP European So Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany. EM fpatat@eso.org RI Gonzalez, Jean-Francois/B-7189-2008; Nomoto, Ken'ichi/A-4393-2011; Galama, Titus/D-1429-2014; Palazzi, Eliana/N-4746-2015; OI Gonzalez, Jean-Francois/0000-0001-9423-6062; Galama, Titus/0000-0002-1036-396X; Cappellaro, Enrico/0000-0001-5008-8619; Palazzi, Eliana/0000-0002-8691-7666; Turatto, Massimo/0000-0002-9719-3157; Pian, Elena/0000-0001-8646-4858 NR 107 TC 239 Z9 240 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 JUL 10 PY 2001 VL 555 IS 2 BP 900 EP 917 DI 10.1086/321526 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200032 ER PT J AU Font, AS Mitchell, GF Sandell, G AF Font, AS Mitchell, GF Sandell, G TI A submillimeter study of the star-forming region NGC 7129 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM : molecules; stars : formation; stars : individual (LkHa 234); stars : pre-main-sequence; submillimeter ID HERBIG-HARO OBJECTS; ISO-LWS OBSERVATIONS; PHOTODISSOCIATION REGIONS; CARBON-MONOXIDE; H2O MASERS; LKH-ALPHA-234; DUST; EMISSION; NGC-7129; JET AB New molecular ((CO)-C-13 J = 3-2) and dust continuum (450 and 850 mum) maps of the NGC 7129 star-forming region are presented. The maps include the Herbig Ae/Be star LkH alpha 234, the far-infrared source NGC 7129 FIRS 2, and several other prestellar sources embedded within the molecular ridge. The data are complemented with (CO)-O-18 J = 3-2 spectra at several positions within the mapped region. Both the submillimeter and the (CO)-C-13 emission show a similar morphology, displaying a sharp boundary toward the cavity. The submillimeter maps also reveal a second source, SMM 2, which is not clearly seen in any earlier data set. This is either a prestellar core or possibly a protostar. Also, the highest continuum peak emission is identified with the deeply embedded source IRS 6 a few arcseconds away from LkHa 234. These new 450 and 850 mum observations are combined with previous continuum observations of the three compact far-infrared sources in the field, in order to make fits to the spectral energy distributions and to obtain the source sizes, dust temperatures, luminosities, and masses. For nine positions where both (CO)-C-13 and (CO)-O-18 spectra are available, gas masses have been obtained and compared with masses derived from the continuum fluxes. The masses are found to be consistent, implying little or no CO depletion onto grains. The dust emissivity index is found to be low toward the dense compact sources, beta similar to1-1.6, and high, beta similar to 2.0, in the surrounding cloud. C1 St Marys Univ, Dept Phys & Astron, Halifax, NS B3H 3C3, Canada. NASA, Univ Space Res Assoc, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Sandell, G (reprint author), Univ Victoria, Dept Phys & Astron, POB 3055, Victoria, BC V8W 3P6, Canada. NR 47 TC 20 Z9 20 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 2001 VL 555 IS 2 BP 950 EP 960 DI 10.1086/321503 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200037 ER PT J AU Eviatar, A Strobel, DF Wolven, BC Feldman, PD McGrath, MA Williams, DJ AF Eviatar, A Strobel, DF Wolven, BC Feldman, PD McGrath, MA Williams, DJ TI Excitation of the Ganymede ultraviolet aurora SO ASTROPHYSICAL JOURNAL LA English DT Article DE planets and satellites : individual (Ganymede); plasmas; ultraviolet : solar system ID ELECTRON-IMPACT; MAGNETIC-FIELD; PLASMA; MAGNETOSPHERE; VOYAGER; JUPITER; O-2 AB We analyze the ultraviolet aurorae observed on Ganymede by means of the Hubble Space Telescope and compare them to similar phenomena on Earth. We find that the tenuous nature of Ganymede's atmosphere precludes excitation of the aurora by high-energy electrons and requires a local acceleration mechanism. We propose the following as plausible mechanisms for generating both the continuous background emission and the intense auroral bright spots: 1. Birkeland-type currents and associated magnetic field-aligned electric fields. 2. The stochastic heating of plasma electrons by the Landau damping of electron plasma oscillations generated by precipitated energetic electrons. We conclude that the electron density in the bright regions may attain local values as high as 10(5) cm(-3). C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20742 USA. RP Eviatar, A (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. NR 32 TC 24 Z9 24 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 2001 VL 555 IS 2 BP 1013 EP 1019 DI 10.1086/321510 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YR UT WOS:000169946200042 ER PT J AU Anyamba, A Tucker, CJ Eastman, JR AF Anyamba, A Tucker, CJ Eastman, JR TI NDVI anomaly patterns over Africa during the 1997/98 ENSO warm event SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID DIFFERENCE VEGETATION INDEX; NINO SOUTHERN OSCILLATION; SEA-SURFACE TEMPERATURE; EL-NINO; INTERANNUAL VARIABILITY; AVHRR DATA; TROPICAL ATLANTIC; INDIAN-OCEAN; EAST-AFRICA; NOAA AVHRR AB Normalized Difference Vegetation Index (NDVI) departure patterns for Africa during the 1997/98 El Nino/Southern Oscillation (ENSO) warm event show two dominant patterns. Over equatorial Eastern Africa, above normal NDVI anomalies persisted from October 1997 through the normal dry season (December-February) and into the long rains season in March-May. Over Southern Africa the spatial NDVI anomaly shows a dry western half and a relatively greener than normal eastern half. Correlations between the temporal NDVI anomalies with ENSO indices shows that the anomalous conditions over Eastern Africa were a direct result of anomalous warming of sea surface temperatures (similar to +3 degreesC) in the western equatorial Indian Ocean (WIO) and a lagged response to the warming in the eastern Pacific Ocean (+4 degreesC). We suggest that this anomalous warming of the WIO and the equatorial eastern Atlantic Ocean basin dampened the normal severe drought response pattern over Southern Africa where mild drought conditions were experienced. The overall continental response pattern shows a meridional dipole pattern, with above normal NDVI straddling the equator between 10 degrees N and 10 degrees S and normal to slightly below normal NDVI south of 15 degrees S, predominantly over south-western Africa. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Clark Univ, Grad Sch Geog, Worcester, MA 01610 USA. RP Anyamba, A (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923-0, Greenbelt, MD 20771 USA. NR 41 TC 75 Z9 80 U1 2 U2 11 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUL 10 PY 2001 VL 22 IS 10 BP 1847 EP 1859 PG 13 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 446FL UT WOS:000169502200001 ER PT J AU Baloga, SM Glaze, LS Peitersen, MN Crisp, JA AF Baloga, SM Glaze, LS Peitersen, MN Crisp, JA TI Influence of volatile loss on thickness and density profiles of active basaltic flow lobes SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID TERRESTRIAL LAVA FLOWS; MAUNA-LOA; FIELD-MEASUREMENTS; KILAUEA VOLCANO; DYNAMICS; MAGMA; CRYSTALLIZATION; EMPLACEMENT; RHEOLOGY; ERUPTION AB A bulk density increase due to degassing during emplacement may have a significant influence on the thickness of a lava flow and the rate at which it advances. We present a theoretical model of a lava flow that loses enough volatiles to cause density changes along the path of the flow. We assume that the flow is emplaced as a single, isolated unit and the bulk rheology (e.g., viscosity) is a function of distance from the vent. This type of model is applicable to solitary lobes of basaltic aa and isolated sheets of pahoehoe that advance as a fluid continuum with bulk lava density changes as a function of distance along the flow path. Equations for the flow thickness and the bulk density profiles are derived from mass and volume conservation. Formulas are tabulated for thickness and density profiles for various combinations of flow rates, theologic changes, and degassing rate functions. We also tabulate formulas for estimating parameters associated with the form and rate of degassing from field data. The Mauna Loa 1984 "1 flow" is a typical example of a flow showing evidence of a bulk density increase and is used to estimate the model parameters. Thickness and density profiles are then computed for a range of plausible lava densities, two different rate functions for the loss of volatiles, and two different models of viscosity change. Results indicate that the thickness profile of a lava flow can be significantly affected when there is a large difference between the density at the vent and at the flow front. For relatively high rates of degassing, the flow profile has a maximum thickness located progressively closer to the vent as the rate of degassing increases. For depth-dependent degassing, an increase in viscosity acts to thicken the flow, which increases the rate of degassing, thus mitigating the thickening influence of the increasing viscosity. Degassing while a flow is active can increase the duration of emplacement by as much as 60%. We find that the flow thickness profiles are sensitive to the choice of flow rate and the initial density, regardless of the form of the degassing function. The nature of the flow rate can significantly affect the shape of the profile as well as the flow front thickness. When the rate of volatile loss depends on the flow thickness, the density profile depends explicitly on the way the rheology changes along the flow path. In all cases, density increases during emplacement counter the tendency of a flow to thicken due to increases in viscosity or resistance to flow with distance. Thus the parameters that define the rate of degassing, and the consequent density change along the path of a flow, emerge as important variables for a quantitative understanding of flow emplacement. C1 Proxemy Res, Laytonville, MD 20882 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Baloga, SM (reprint author), Proxemy Res, 20528 Farcroft Lane, Laytonville, MD 20882 USA. EM steve@proxemy.com; ori@proxemy.com; matt@proxemy.com; joy@glassy.jpl.nasa.gov RI Glaze, Lori/D-1314-2012; Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 36 TC 13 Z9 13 U1 0 U2 3 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 JUL 10 PY 2001 VL 106 IS B7 BP 13395 EP 13405 DI 10.1029/2000JB900475 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 453FP UT WOS:000169906100010 ER PT J AU Andriotis, AN Menon, M Srivastava, D Chernozatonskii, L AF Andriotis, AN Menon, M Srivastava, D Chernozatonskii, L TI Ballistic switching and rectification in single wall carbon nanotube Y junctions SO APPLIED PHYSICS LETTERS LA English DT Article ID MOLECULAR-DYNAMICS; BRANCH SWITCH; TRANSPORT AB Transport properties of various semiconducting zig-zag carbon nanotube Y junctions are studied for the investigations of rectification and switching. Our results indicate that such junctions, when symmetric, can support both ballistic rectification and/or the ballistic switching operating modes. Although structural symmetry of the Y junction is found to be a necessary condition for rectification, it may not be sufficient in all cases. (C) 2001 American Institute of Physics. C1 Fdn Res & Technol Hellas, Inst Elect Struct & Laser, Heraklion 71110, Crete, Greece. Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. Univ Kentucky, Ctr Comp Sci, Lexington, KY 40506 USA. NASA, Ames Res Ctr, CSC, Moffett Field, CA 94035 USA. Russian Acad Sci, Inst Biochem Phys, Moscow 117977, Russia. RP Andriotis, AN (reprint author), Fdn Res & Technol Hellas, Inst Elect Struct & Laser, POB 1527, Heraklion 71110, Crete, Greece. RI Andriotis, Antonios/A-2848-2014 NR 18 TC 73 Z9 73 U1 0 U2 8 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD JUL 9 PY 2001 VL 79 IS 2 BP 266 EP 268 DI 10.1063/1.1385194 PG 3 WC Physics, Applied SC Physics GA 448ZJ UT WOS:000169659600042 ER PT J AU Anderson, JD Williams, JG AF Anderson, JD Williams, JG TI Long-range tests of the equivalence principle SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article; Proceedings Paper CT International Symposium on Testing the Equivalence Principle in Space CY SEP 04-07, 2000 CL GLASGOW, SCOTLAND SP Univ Stanford, Univ Strathclyde ID SOLAR GRAVITATIONAL DEFLECTION; PIONEER 10/11; ULYSSES DATA; ANOMALOUS ACCELERATIONS; PROSAIC EXPLANATION; DISTANT SPACECRAFT; MASSIVE BODIES; GALILEO; RELATIVITY; GRAVITY AB The equivalence principle can be tested using accurate tracking of the Moon, planets, and interplanetary spacecraft. Tests with solar system bodies probe the dependence of the equivalence principle on self-energy. Analysis of lunar laser ranges yields the difference in the ratio of the gravitational and inertial masses for the Earth and Moon of (-0.7 +/- 1.5) x 10(-13). In conjunction with laboratory tests of the equivalence principle and spacecraft and VLBI tests of PPN gamma, one derives /beta - 1/ less than or equal to 0.0005. Planetary tests are feasible, in particular tests using Mars. Improvements in Doppler accuracies under development may allow tests with interplanetary spacecraft. C1 CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Anderson, JD (reprint author), CALTECH, Jet Propuls Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM john.d.anderson@jpl.nasa.gov; james.g.williams@jpl.nasa.gov NR 30 TC 42 Z9 42 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD JUL 7 PY 2001 VL 18 IS 13 BP 2447 EP 2456 DI 10.1088/0264-9381/18/13/307 PG 10 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 455ZL UT WOS:000170057600008 ER PT J AU Kane, SM Caloz, F Leu, MT AF Kane, SM Caloz, F Leu, MT TI Heterogeneous uptake of gaseous N2O5 by (NH4)(2)SO4, NH4HSO4, and H2SO4 aerosols SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID METASTABILITY PHASE-DIAGRAMS; AMMONIUM-SULFATE AEROSOLS; SULFURIC-ACID; AQUEOUS AEROSOLS; HYDROLYSIS; TEMPERATURE; KINETICS; COEFFICIENTS; EQUILIBRIUM; DROPLETS AB The heterogeneous uptake of gaseous N2O5 by ammonium sulfate [(NH4)(2)SO4], ammonium bisulfate [NH4HSO4], and sulfuric acid [H2SO4] aerosols as a function of relative humidity has been investigated at room temperature and atmospheric pressure. Ammonium-containing aerosols were generated by a constant-output atomizer and conditioned by passing through a diffusion dryer. Sulfuric acid aerosols were produced by the homogeneous reaction of SO3 and H2O in a borosilicate vessel. Addition of a dry or wet N-2 flow controlled the relative humidity (RH) of these aerosol flows. Using a chemical ionization mass spectrometer (CIMS) for N2O5 concentration monitoring and a scanning mobility particle spectrometer (SMPS) for aerosol characterization, reaction probabilities (gamma) in the range of 0.001 to 0.1 for the uptake of N2O5 were determined as a function of RH. The results are expressed as follows: gamma[(NH4)(2)SO4] = 2.79 x 10(-4) + 1.30 x 10(-4) x (RH) - 3.43 x 10(-6) x (RH)(2) + 7.52 x 10(-8) x (RH)(3), gamma [NH4HSO4] = 2.07 x 10(-3) - 1.48 x 10(-4) x (RH) + 8.26 x 10(-6) x (RH)(2), and gamma [H2SO4] = 0.052 - 2.79 x 10(-4) x (RH). We suggest that the water content and phase in the ammonium-containing aerosols control the reactivity of N2O5 while liquid-phase ionic reactions primarily dominate the uptake in sulfuric acid aerosols. 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 27 TC 75 Z9 76 U1 3 U2 20 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 JUL 5 PY 2001 VL 105 IS 26 BP 6465 EP 6470 DI 10.1021/jp010490x PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 449YA UT WOS:000169713700024 ER PT J AU Wang, JJ Keyser, LF AF Wang, JJ Keyser, LF TI HCl yield from the OH plus ClO reaction at temperatures between 218 and 298 K SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID MAGNETIC-RESONANCE SPECTROSCOPY; ABSORPTION CROSS-SECTIONS; BRANCHING RATIO; RATE-CONSTANT; RATE COEFFICIENT; PRODUCT FORMATION; SELF-REACTION; KINETICS; HO2; DEPENDENCE AB The yield of HCl from the OH + ClO reaction has been determined at 1 Torr total pressure by using the discharge-laminar-flow technique with resonance fluorescence, infrared diode laser spectrometry, and ultraviolet absorption spectrometry detection methods. A known amount of OH is added to a large excess of ClO and the reaction is allowed to go to completion. Under these conditions, the yield is just the ratio of [HCl] produced to initial [OH]. The yield or branching ratio measurement reduces to a measurement of two concentrations; knowledge of the total rate constant or of the branching rate constants is not required. The results are 9.0 +/- 4.8% independent of temperature between 218 and 298 K. The errors given are two standard deviations. The results are also independent of the OH source: F + H(2)O or H + NO(2). Interference from secondary chemistry is minimized by extrapolating a plot of observed yields to zero initial [OH]. Numerical simulations are used only to check for interference from secondary chemistry and to validate the extrapolation procedure. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Keyser, LF (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. EM Leon.F.Keyser@jpl.nasa.gov NR 44 TC 9 Z9 9 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 JUL 5 PY 2001 VL 105 IS 26 BP 6479 EP 6489 DI 10.1021/jp0106449 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 449YA UT WOS:000169713700026 ER PT J AU Smith, GD Bell, R Borodin, O Jaffe, RL AF Smith, GD Bell, R Borodin, O Jaffe, RL TI A density functional theory study of the structure and energetics of zincate complexes SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID ALKALINE-SOLUTIONS; THERMOCHEMISTRY; HYDROXIDE; ATOMS; RAMAN; ZNO AB We have conducted a density functional theory (DFT) investigation of zincate species. The accuracy of the DFT/B3LYP method and the adequacy of the atomic basis sets employed were established through investigation of the ionization potentials of Zn, the geometry and bond energy of ZnO, and the geometries and energies of selected Zn-OH and Zn-H2O complexes. Our investigation revealed that the [Zn(OH)](+), Zn(OH)(2), and [Zn(OH)(3)](-) zincate complexes are stable in the gas phase. However, we found that dissociated [Zn(OH)(3)](-) + OH- is more stable than [Zn(OH)(4)](2-) in the gas phase and that the gas-phase geometry of [Zn(OH)(4)](2-) differs significantly from that gleaned from experimental studies of aqueous KOH/zincate solutions. We also investigated zincate complexes involving molecular water and K+ cations in order to better understand the influence of condensed phase effects in aqueous KOH solutions on the stability and geometry of the zincate complexes. We found that water does not si,significantly influence complex binding energies or the,geometries elf the underlying [Zn(OH)(n)](2-n) complexes for n = 1, 2, and 3. In contrast, for [Zn(OH)(4)](2-) the introduction of water strongly stabilizes the complex relative to the gas phase and results in a structure close to that observed experimentally. We were unable to find a stable [Zn(OH)(4)(H2O)(2)](2-) complex with a planar Zn(OH)(4) arrangement and close Zn-H2O coordination, corresponding to a Zn-O coordination of number of six, as has been suggested in some interpretations of experiments. We found through investigation of the K2Zn(OH)(4) complex that K+ cations are also effective in engendering a structure that is very close to experiment and that K+ ions are even more strongly bound to the [Zn(OH)(4)](2-) complex than water. Finally, we determined the structure and stability of [ZnO(OH)(2)](2-)(oxodihydroxozincate), a species that has been hypothesized to be important in water-poor zincates solutions. C1 Univ Utah, Dept Mat Sci & Engn, Salt Lake City, UT 84112 USA. Univ Utah, Dept Chem & Fuels Engn, Salt Lake City, UT 84112 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Smith, GD (reprint author), Univ Utah, Dept Mat Sci & Engn, 122 S Cent Campus Dr,Rm 304, Salt Lake City, UT 84112 USA. RI Borodin, Oleg/B-6855-2012 OI Borodin, Oleg/0000-0002-9428-5291 NR 30 TC 13 Z9 13 U1 1 U2 5 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 JUL 5 PY 2001 VL 105 IS 26 BP 6506 EP 6512 DI 10.1021/jp0100710 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 449YA UT WOS:000169713700029 ER PT J AU Navarro-Gonzalez, R McKay, CP Mvondo, DN AF Navarro-Gonzalez, R McKay, CP Mvondo, DN TI A possible nitrogen crisis for Archaean life due to reduced nitrogen fixation by lightning SO NATURE LA English DT Article ID EARTHS EARLY ATMOSPHERE; NITRIC-OXIDE; EVOLUTION; CARBON; ENERGY; OXYGEN AB Nitrogen is an essential element for life and is often the limiting nutrient for terrestrial ecosystems(1,2). As most nitrogen is locked in the kinetically stable form(3), N-2, in the Earth's atmosphere, processes that can fix N-2 into biologically available forms-such as nitrate and ammonia-control the supply of nitrogen for organisms. On the early Earth, nitrogen is thought to have been fixed abiotically, as nitric oxide formed during lightning discharge(4-6). The advent of biological nitrogen fixation suggests that at some point the demand for fixed nitrogen exceeded the supply from abiotic sources, but the timing and causes of the onset of biological nitrogen fixation remain unclear(7-11). Here we report an experimental simulation of nitrogen fixation by lightning over a range of Hadean (4.5-3.8 Gyr ago) and Archaean (3.8-2.5 Gyr ago) atmospheric compositions, from predominantly carbon dioxide to predominantly dinitrogen (but always without oxygen). We infer that, as atmospheric CO2 decreased over the Archaean period, the production of nitric oxide from lightning discharge decreased by two orders of magnitude until about 2.2 Gyr. After this time, the rise in oxygen (or methane) concentrations probably initiated other abiotic sources of nitrogen. Although the temporary reduction in nitric oxide production may have lasted for only 100 Myr or less, this was potentially long enough to cause an ecological crisis that triggered the development of biological nitrogen fixation. C1 Univ Nacl Autonoma Mexico, Inst Ciencias Nucl, Lab Quim Plasmas & Estud Planetarios, Mexico City 04510, DF, Mexico. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Navarro-Gonzalez, R (reprint author), Univ Nacl Autonoma Mexico, Inst Ciencias Nucl, Lab Quim Plasmas & Estud Planetarios, Circuito Exterior,Ciudad Univ,Apartado Postal 70-, Mexico City 04510, DF, Mexico. RI Gonzalez, Rafael/D-1748-2009 NR 30 TC 108 Z9 112 U1 9 U2 53 PU MACMILLAN PUBLISHERS LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 5 PY 2001 VL 412 IS 6842 BP 61 EP 64 DI 10.1038/35083537 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 448TB UT WOS:000169644900041 PM 11452304 ER PT J AU Digel, SW Grenier, IA Hunter, SD Dame, TM Thaddeus, P AF Digel, SW Grenier, IA Hunter, SD Dame, TM Thaddeus, P TI Egret observations of Monoceros: Diffuse gamma-ray emission in the outer Galaxy SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; ISM : molecules; radio lines : ISM ID MOLECULAR CLOUDS; MILKY-WAY; CO SURVEY; EXPERIMENT TELESCOPE; GALACTIC PLANE; SOLAR CIRCLE; COSMIC-RAY; HYDROGEN; CALIBRATION; ORION AB We present an analysis of the diffuse gamma-ray emission observed toward Monoceros by the Energetic Gamma-Ray Experiment Telescope (EGRET). The region studied, l = 210 degrees -250 degrees, b = -15 degrees to +20 degrees, has kinematically well-defined segments of the local and Perseus arms and is one of the best regions for the study of variations of cosmic-ray density across the outer Galaxy. The local gamma-ray emissivity is (1.81 +/- 0.17) x 10(-26) s(-1) sr(-1) for energies greater than 100 MeV. For energies greater than 300 MeV, the gamma-ray emissivity in Monoceros is consistent with that of other local clouds studied with EGRET, which suggests that the density of GeV cosmic-ray protons does not vary significantly on scales of less than 1 kpc. As with other local clouds studied with EGRET, an excess of emissivity is observed above 1 GeV relative to that predicted from the cosmic-ray spectrum at the Earth. The gamma-ray emissivity is apparently enhanced in the Perseus arm relative to the interarm regions, although to a much lesser degree than predicted by the model of Hunter et al. The molecular mass calibrating ratio, X = N(H(2))/W/(CO), is (1.64 +/- 0.31) x 10(20) cm(-2) (K km s(-1))(-1) in the local clouds and is apparently about the same (to within 50%) in Maddalena's cloud. An uncataloged, marginally significant (similar to4.5 sigma) unidentified point source near (215.degrees5, 0.degrees5) with a flux of (1.4 +/-0.5) x 10(-7) cm(-2) s(-1) (>100 MeV) is suggested by the data. C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. Univ Paris 07, F-75221 Paris 05, France. CE Saclay, Serv Astrophys, Gif Sur Yvette, France. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Digel, SW (reprint author), NASA, Goddard Space Flight Ctr, USRA, Code 661, Greenbelt, MD 20771 USA. RI Hunter, Stanley/D-2942-2012 NR 35 TC 22 Z9 22 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 JUL 3 PY 2001 VL 555 IS 1 BP 12 EP 22 DI 10.1086/321446 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XY UT WOS:000169944500003 ER PT J AU Sakai, S Madore, BF AF Sakai, S Madore, BF TI Observation of the halo of NGC 3077 near the "Garland" region using the Hubble Space Telescope SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : distances and redshifts; galaxies : individual (NGC 3077); galaxies : interactions; galaxies : stellar content ID RED GIANT BRANCH; GALAXY SEXTANS-A; DISTANCE INDICATOR; M81 GROUP; NGC-3077; STARS; TIP; REDDENINGS; PHOTOMETRY; DISCOVERY AB We report the detection of upper main-sequence stars and red giant branch stars in the halo of an amorphous galaxy, NGC 3077. The observations were made using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The red giant branch luminosity function in the I band shows a sudden discontinuity at I = 24.0 +/- 0.1 mag. Identifying this with the tip of the red giant branch (TRGB) and adopting the calibration provided by Lee, Freedman, & Madore and a foreground extinction of A(B) = 0.21 mag, we obtain a distance modulus of (m - M)(0) = 27.93 +/- 0.14(rand) +/- 0.16(sys). This value agrees well with the distance estimates of four other galaxies in the M81 Group. In addition to the RGB stars, we observe a concentration of upper main-sequence stars in the halo of NGC 3077, which coincides partially with a feature known as the "Garland." Using Padua isochrones, these stars are estimated to be less than 150 Myr old. Assuming that the nearest encounter between NGC 3077 and M81 occurred 280 Myr ago, as has been predicted by the numerical simulations of Yun, the observed upper main-sequence stars are likely the result of star formation triggered by the M81 + NGC 3077 tidal interaction. C1 Natl Opt Astron Observ, Kitt Peak Natl Observ, Tucson, AZ 85726 USA. Univ Calif Los Angeles, Div Astron & Astrophys, Los Angeles, CA 90095 USA. CALTECH, NASA, IPAC Extragalact Database, Pasadena, CA 91125 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. RP Sakai, S (reprint author), Natl Opt Astron Observ, Kitt Peak Natl Observ, Tucson, AZ 85726 USA. NR 40 TC 26 Z9 26 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP 280 EP 288 DI 10.1086/321459 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XY UT WOS:000169944500026 ER PT J AU Danchi, WC Green, WH Hale, DDS McElroy, K Monnier, JD Tuthill, PG Townes, CH AF Danchi, WC Green, WH Hale, DDS McElroy, K Monnier, JD Tuthill, PG Townes, CH TI Proper motions of dust shells surrounding NML Cygni SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; infrared : stars; stars : individual (NML Cygni); techniques : interferometric ID EVOLVED STARS; MASS-LOSS; OUTFLOW AB The distribution of dust emitted by the supergiant star NML Cygni has been resolved by interferometry at 11 mum wavelengths at various times over a period of 6 yr. Results show there are two discrete dust shells, which have both moved away from the star approximately the same amount during the 6 yr period. This allows determination of the time between ejection of material forming the two shells to be 65 +/- 14 yr. Assuming the radial outflow velocity can be derived from Doppler-measured velocities of masers surrounding the star, its distance can be calculated from the observed angular motion to be 1220 +/- 300 pc. This decreases the luminosity of the star by about 1 mag over that deduced from the distance 1900 pc previously assumed. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Danchi, WC (reprint author), NASA, Goddard Space Flight Ctr, Code 685, Greenbelt, MD 20771 USA. RI mcelroy, kyle/D-1816-2013 NR 16 TC 13 Z9 13 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP 405 EP 409 DI 10.1086/322237 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XY UT WOS:000169944500036 ER PT J AU Marcy, GW Butler, RP Vogt, SS Liu, MC Laughlin, G Apps, K Graham, JR Lloyd, J Luhman, KL Jayawardhana, R AF Marcy, GW Butler, RP Vogt, SS Liu, MC Laughlin, G Apps, K Graham, JR Lloyd, J Luhman, KL Jayawardhana, R TI Two substellar companions orbiting HD 168443 SO ASTROPHYSICAL JOURNAL LA English DT Article DE planetary systems; stars : individual (HD 168443) ID PLANETARY SYSTEMS; PROTOSTELLAR DISKS; ADAPTIVE OPTICS; GIANT PLANETS; SEARCH; STARS; PROTOPLANETS; PRECISION; MIGRATION; DIVERSITY AB Precise Doppler measurements during 4.4 yr from the Keck/HIRES spectrometer reveal two superimposed Keplerian velocity variations for HD 168443 (G6 IV). A simultaneous orbital Dt to both companions yields companion masses of M sin i = 7.7 and 17.2 M-JUP, orbital periods of P = 58 days and 4.8 yr, semimajor axes of a = 0.29 and 2.9 AU, and eccentricities of e = 0.53 and 0.20. An upper limit to the mass of the outer companion of 42 M-JUP is derived from the lack of astrometric wobble. The outer companion was not detected with Keck adaptive optics in the near-IR. Dynamical simulations show that the system is remarkably stable for all possible masses of both companions. The two orbiting companions have masses that are probably near and slightly above the upper end of the observed mass distribution of "planets" at 10 M-JUP. Formation in a protoplanetary disk seems plausible. But these objects present a puzzle about their formation and dynamical history, as well as about their possible kinship with planetary systems and triple-star systems. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95064 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Sussex, Brighton BN1 9QJ, E Sussex, England. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Marcy, GW (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. RI Butler, Robert/B-1125-2009; Lloyd, James/B-3769-2011 NR 32 TC 80 Z9 81 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP 418 EP 425 DI 10.1086/321445 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XY UT WOS:000169944500038 ER PT J AU Brosius, JW AF Brosius, JW TI Search for evidence of alpha-particle beams during a solar flare observed by the coronal diagnostic spectrometer aboard the Solar and Heliospheric Observatory SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : activity; Sun : corona; Sun : flares; Sun : UV radiation ID EXTREME-ULTRAVIOLET SPECTRUM; NONTHERMAL PROTON-BEAMS; IMPULSIVE PHASE; ATOMIC DATABASE; EMISSION-LINES; LY-ALPHA; IONIZATION; RADIATION; CHIANTI; IONS AB We observed NOAA Active Region 9090 (N13 degrees, W39 degrees) with the Coronal Diagnostic Spectrometer (CDS) and the Extreme-Ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory spacecraft between 18:17 and 21:09 UT on 2000 July 24 to search for evidence of alpha-particle beams during solar flares. Theoretically, an alpha-particle beam will manifest itself during the impulsive phase of a flare through an enhancement in the red wing of the He II Ly alpha (lambda 303.782) emission line without a corresponding blue wing enhancement. This enhancement is due to downstreaming nonthermal alpha particles undergoing charge-exchange with chromospheric neutral hydrogen atoms to form downstreaming nonthermal He II ions. Ly alpha radiation emitted from these downstreaming ions is Doppler-shifted into the red wing of the Ly alpha line. Our CDS observing program acquired high time resolution (9.7 s) 4 " x 4' slit spectra between 590 and 630 Angstrom where we observed He II Ly alpha in second , order (lambda 607.564). The CDS and EIT observations reveal that AR 9090 underwent significant intensity fluctuations prior to a sudden drastic increase (impulsive phase) around 20:00 UT. The GOES satellite reports a C3.8 event in this region from 19:57 to 20:05 UT. We fitted the spectral background and emission-line profiles for each CDS spectrum in our observed sequence. Density- and temperature-insensitive intensity ratios of O IV and Mg X lines generally agree with their theoretical values before and after the sudden intensity increase, which supports a reliable relative radiometric calibration for CDS, but differ significantly from their theoretical values during the flare impulsive phase. This may indicate line blending with unknown components, line blending with second-order C IV and Fe XV lines, or loss of ionization equilibrium. Most important, however, we find that although the red and blue wing backgrounds for He II Ly alpha remain relatively constant during most of our observation, the blue wing undergoes a more significant enhancement during the impulsive phase than does the red wing. This effect is opposite to that expected in the presence of an alpha-particle beam. Furthermore, blended spectral line features that mimic the expected nonthermal redshifted He II Ly alpha beam signal are understood in terms of well-known emission-line components. Thus, we find no evidence for the presence of alpha-particle beams in our observations. We estimate an upper limit of similar to 250 ergs cm(-2) s(-1) sr(-1) Angstrom (-1) for the non-thermal redshifted peak spectral intensity due to an alpha-particle beam prior to the impulsive phase. 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 18 TC 19 Z9 20 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP 435 EP 439 DI 10.1086/321438 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XY UT WOS:000169944500040 ER PT J AU McClintock, JE Haswell, CA Garcia, MR Drake, JJ Hynes, RI Marshall, HL Muno, MP Chaty, S Garnavich, PM Groot, PJ Lewin, WHG Mauche, CW Miller, JM Pooley, GG Shrader, CR Vrtilek, SD AF McClintock, JE Haswell, CA Garcia, MR Drake, JJ Hynes, RI Marshall, HL Muno, MP Chaty, S Garnavich, PM Groot, PJ Lewin, WHG Mauche, CW Miller, JM Pooley, GG Shrader, CR Vrtilek, SD TI Complete and simultaneous spectral observations of the black hole X-ray nova XTE J1118+480 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (XTE J1118+480); ultraviolet : stars; X-rays : stars ID INTERSTELLAR-MEDIUM; H-I; ULTRAVIOLET; TRANSIENT; STATE; MASS AB The X-ray nova XTE J1118+480 suffers minimal extinction (b = 62 degrees) and therefore represents an outstanding opportunity for multiwavelength studies. Hynes et al. conducted the first such study, which was centered on 2000 April 8 using UKIRT, EUVE, HST, and RXTE. On 2000 April 18, the Chandra X-Ray Observatory obtained data coincident with a second set of observations using all of these same observatories. A 30 ks grating observation using Chandra yielded a spectrum with high resolution and sensitivity covering the range 0.24-7 keV. Our near-simultaneous observations cover approximate to 80% of the electromagnetic spectrum from the infrared to hard X-rays. The UV/X-ray spectrum of XTE J1118+480 consists of two principal components. The Drst of these is an approximate to 24 eV thermal component that is caused by an accretion disk with a large inner disk radius : greater than or similar to 35R(Schw). The second is a quasi power-law component that was recorded with complete spectral coverage from 0.4 to 160 keV. A model for this twocomponent spectrum is presented in a companion paper by Esin et al. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Open Univ, Dept Phys & Astron, Milton Keynes MK7 6AA, Bucks, England. Univ Southampton, Dept Phys & Astron, Southampton SO17 1BJ, Hants, England. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Univ Cambridge, Cavendish Lab, Mullard Radio Astron Observ, Cambridge CB3 0HE, England. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP McClintock, JE (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. RI Groot, Paul/K-4391-2016; OI Groot, Paul/0000-0002-4488-726X; Chaty, Sylvain/0000-0002-5769-8601 NR 34 TC 107 Z9 107 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP 477 EP 482 DI 10.1086/321449 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XY UT WOS:000169944500046 ER PT J AU Loewenstein, M Mushotzky, RF Angelini, L Arnaud, KA Quataert, E AF Loewenstein, M Mushotzky, RF Angelini, L Arnaud, KA Quataert, E TI Chandra limits on X-ray emission associated with the supermassive black holes in three giant elliptical galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; galaxies : elliptical and lenticular; cD galaxies : nuclei; X-rays : galaxies ID ADVECTION-DOMINATED ACCRETION; GALACTIC NUCLEI; COOLING FLOWS; LUMINOSITY; CONVECTION AB Elliptical galaxy nuclei are the sites of the largest black holes known but typically show little or no nuclear activity. We investigate this extreme quiescence using Chandra X-Ray Observatory observations of the giant elliptical galaxies NGC 1399, NGC 4472, and NGC 4636. The unique Chandra imaging power enables us to place upper limits of 7.3, 15, and 28 x 10(-9)L(Edd) for the similar to 10(8)-10(9) M-circle dot black holes in NGC 1399, NGC 4472, and NGC 4636, respectively. The corresponding radiative efficiencies in this band are 4.1, 24, and 620 x 10(-6) using Bondi accretion rates derived from the Chandra hot interstellar gas surface brightness profiles. These limits are inconsistent with basic advection-dominated accretion flow models for NGC 1399 and NGC 4472, indicating accretion onto the black hole at less than or similar to 10% of the Bondi rate. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Adv Study, Sch Nat Sci, Princeton, NJ 08540 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. RP Loewenstein, M (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 37 TC 109 Z9 109 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP L21 EP L24 DI 10.1086/323157 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YL UT WOS:000169945700005 ER PT J AU Titarchuk, L Osherovich, V AF Titarchuk, L Osherovich, V TI Classification of power density spectrum features and estimation of the delta-invariant value for the Z source GX 340+0 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion; accretion disks; diffusion stars : individual (GX 340+0, Scorpius X-1, 4U 0614+09, 4U 1702-42, 4U 1728-34); stars : neutron; waves; X-rays : stars ID QUASI-PERIODIC OSCILLATIONS; X-RAY BINARIES; NEUTRON-STAR BINARIES; KEPLERIAN OSCILLATIONS; TIMING SPECTROSCOPY; MILLISECOND PULSAR; MODEL; FREQUENCIES; SYSTEM; FIELD AB We present a theoretical analysis of Rossi X-Ray Timing Explorer data of Z source GX 340+0 obtained by Jonker et al. In the frameworks of the recently formulated transition layer model, the delta -angle is an angle between the neutron star (NS) magnetospheric axis and the disk (presumably NS rotational) axis. We determine the angle, delta = 0.degrees3 +/-0.degrees3 which is a combination of the simultaneously observed kilohertz quasi-periodic and horizontal- branch oscillation frequencies. While these three frequencies change by a factor of 3 or more, their delta -combination stays almost constant. GX 340+0 is the fourth source (in addition to 4U 0614+09, Scorpius X-1, and 4U 1702-42) for which delta has been determined. With one (constrained) parameter, at most, we make a complete classification of six observed power spectral features, including the two kilohertz frequencies, the first and second harmonics of the horizontal- branch oscillation frequency, the low-frequency noise component, and the break frequencies. We demonstrate that a new component discovered by Jonker et al. in the GX 340+0 power spectrum is related to the viscous-frequency branch that has in fact been reported earlier in 4U 1728-34 by Ford & van der Klis. Finally, we reclassify several previously misidentified features in the power spectrum. C1 George Mason Univ, Ctr Earth Observing & Space Res, Fairfax, VA 22030 USA. USN, Res Lab, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Titarchuk, L (reprint author), George Mason Univ, Ctr Earth Observing & Space Res, Fairfax, VA 22030 USA. NR 31 TC 4 Z9 4 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP L55 EP L59 DI 10.1086/321725 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YL UT WOS:000169945700013 ER PT J AU Titarchuk, LG Bradshaw, CF Geldzahler, BJ Fomalont, EB AF Titarchuk, LG Bradshaw, CF Geldzahler, BJ Fomalont, EB TI Normal-branch quasi-periodic oscillations in scorpius X-1: Viscous oscillations of a spherical shell near the neutron star SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (Scorpius X-1); stars : magnetic fields; stars : neutron; X-rays : bursts ID BINARIES; FREQUENCY; BEHAVIOR; SPECTRA AB We present a comprehensive classification of all observed quasi-periodic oscillations (QPOs) within the framework of the transition layer model using a large set of Rossi X-Ray Timing Explorer data for Scorpius X-1. The model assumes an optically thin material along the observer's line of sight in the horizontal branch and an increasingly optically thick material while in the other two branches that is consistent with X-ray and radio observations and the disk transition layer model of QPOs. We identify the similar to6 Hz frequencies in the normal branch as acoustic oscillations of a spherical shell around the neutron star (NS) that is formed after radiation pressure near the Eddington accretion rate destroys the disk. The size of the shell is on the order of one NS radius from the NS. We also estimate the upper limit of Sco X-1's magnetic field to be 0.7 x 10(6) G at about one NS radius above the NS surface while in the horizontal X-ray branch. C1 George Mason Univ, Ctr Earth Observing & Space Res, Fairfax, VA 22030 USA. George Mason Univ, Sch Computat Sci, Fairfax, VA 22030 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. RP Bradshaw, CF (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 27 TC 8 Z9 8 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 3 PY 2001 VL 555 IS 1 BP L45 EP L48 DI 10.1086/323160 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453YL UT WOS:000169945700011 ER PT J AU Foster, DH Nascimento, SMC Amano, K Arend, L Linnell, KJ Nieves, JL Plet, S Foster, JS AF Foster, DH Nascimento, SMC Amano, K Arend, L Linnell, KJ Nieves, JL Plet, S Foster, JS TI Parallel detection of violations of color constancy SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article DE parallel processing; cone-excitation ratios; surface color; transient chromatic signals ID CONE-EXCITATION RATIOS; VISUAL-SEARCH; APPEARANCE DEPENDS; EARLY VISION; DISCRIMINATION; PERCEPTION; INTEGRATION; MODEL; ILLUMINATION; CONJUNCTIONS AB The perceived colors of reflecting surfaces generally remain stable despite changes in the spectrum of the illuminating light. This color constancy can be measured operationally by asking observers to distinguish illuminant changes on a scene from changes in the reflecting properties of the surfaces comprising it. It is shown here that during fast illuminant changes, simultaneous changes in spectral reflectance of one or more surfaces in an array of other surfaces can be readily detected almost independent of the numbers of surfaces, suggesting a preattentive, spatially parallel process. This process, which is perfect over a spatial window delimited by the anatomical fovea, may form an early input to a multistage analysis of surface color, providing the visual system with information about a rapidly changing world in advance of the generation of a more elaborate and stable perceptual representation. C1 Univ Manchester, Inst Sci & Technol, Dept Optometry & Neurosci, Visual & Computat Neurosci Grp, Manchester M60 1QD, Lancs, England. Univ Minho, Dept Phys, P-4710057 Braga, Portugal. NASA, Ames Res Ctr, Human Automat Integrat Res Branch, Moffett Field, CA 94035 USA. Univ Birmingham, Sch Psychol, Birmingham B15 2TT, W Midlands, England. Univ Granada, Dept Opt, E-18071 Granada, Spain. Univ Trieste, Dept Psychol, I-34123 Trieste, Italy. Kings Coll London, Div Physiol, London SE1 1RT, England. RP Foster, DH (reprint author), Univ Manchester, Inst Sci & Technol, Dept Optometry & Neurosci, Visual & Computat Neurosci Grp, Manchester M60 1QD, Lancs, England. EM d.h.forster@umist.ac.uk RI Foster, David H/A-1179-2011; Nieves, Juan Luis/L-1455-2014; Amano, Kinjiro/A-8263-2011; OI Foster, David H/0000-0003-2428-715X; Nieves, Juan Luis/0000-0002-3103-8322; Amano, Kinjiro/0000-0001-7992-9418; Nascimento, Sergio/0000-0002-2503-9003 NR 58 TC 31 Z9 31 U1 1 U2 5 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD JUL 3 PY 2001 VL 98 IS 14 BP 8151 EP 8156 DI 10.1073/pnas.141505198 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 450LK UT WOS:000169744200091 PM 11438751 ER PT J AU Danehy, PM Mere, P Gaston, MJ O'Byrne, S Palma, PC Houwing, AFP AF Danehy, PM Mere, P Gaston, MJ O'Byrne, S Palma, PC Houwing, AFP TI Fluorescence velocimetry of the hypersonic, separated flow over a cone SO AIAA JOURNAL LA English DT Article ID LASER-INDUCED FLUORESCENCE; INDUCED IODINE FLUORESCENCE; GAS-FLOWS; RAYLEIGH-SCATTERING; PLANAR MEASUREMENTS; VELOCITY; PRESSURE; TEMPERATURE; THERMOMETRY; NO AB Planar laser-induced fluorescence of nitric oxide is used to measure a component of the velocity field for the Mach 7 flow around a 30-deg half-angle, 50-mm-diam cone mounted to a long, 38-mm-diam shaft, or "sting" Transverse velocities are measured in the freestream, the shock layer, and the separated region at the junction between the cone and the sting. For most of the flowfield, the uncertainty of the measurements is between +/- 50 and +/- 100 m/s for velocities ranging from -300 to 1300 m/s, corresponding to a minimum uncertainty of +/-5%, The measurements are compared with the commercial computational fluid dynamics (CFD) code CFD-FASTRAN (TM). The agreement between the theoretical model and the experiment is reasonably good. CPD accurately predicts the size and shape of the shock layer and separated region behind the cone as well as the magnitude of the gas velocity near the reattachment shock. However, the magnitude of the velocity in the shock layer and gas expansion differ somewhat from that predicted by CFD. The discrepancies are attributed to a small systematic error associated with laser-beam attenuation and also to inexact modeling of the flowfield by CFD. C1 Australian Natl Univ, Dept Phys, Fac Sci, Canberra, ACT 0200, Australia. RP Danehy, PM (reprint author), NASA, Langley Res Ctr, Mail Stop 236, Hampton, VA 23681 USA. NR 27 TC 14 Z9 14 U1 0 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 JUL PY 2001 VL 39 IS 7 BP 1320 EP 1328 DI 10.2514/2.1450 PG 9 WC Engineering, Aerospace SC Engineering GA 449HY UT WOS:000169680000012 ER PT J AU Fox, JS O'Byrne, S Houwing, AFP AF Fox, JS O'Byrne, S Houwing, AFP TI Fluorescence visualization of hypersonic flow establishment over a blunt fin SO AIAA JOURNAL LA English DT Article ID BOUNDARY-LAYER INTERACTIONS; SHOCK-WAVE; GAS-FLOWS; TUNNEL AB Fluorescence imaging is used to investigate the separated flow upstream of a blunt fin in a hypersonic freestream with a transitional boundary layer. Images are presented to show the how development before, during, and after the test time of the free-piston shock tunnel used to generate the how These images indicate that the test time in this facility is long enough to achieve a steady how over the blunt fin. Thermocouple measurements are included to compare the surface heat flux upstream of the fin with that for flow along a flat plate with the same freestream conditions. The heat flux results are consistent with separation in a transitional boundary layer and show that the separated dow is oscillatory. C1 Australian Natl Univ, Aerophys & Laser Based Diagnost Res Lab, Dept Phys & Theoret Phys, Acton, ACT 0200, Australia. Univ New S Wales, Dept Aerosp & Mech Engn, Campbell, ACT, Australia. NASA, Langley Res Ctr, Instrumentat Syst Dev Branch, Hampton, VA 23681 USA. RP Fox, JS (reprint author), Australian Natl Univ, Aerophys & Laser Based Diagnost Res Lab, Dept Phys & Theoret Phys, Acton, ACT 0200, Australia. NR 43 TC 4 Z9 4 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 JUL PY 2001 VL 39 IS 7 BP 1329 EP 1337 DI 10.2514/2.1451 PG 9 WC Engineering, Aerospace SC Engineering GA 449HY UT WOS:000169680000013 ER PT J AU Bahadori, MY Zhou, L Stocker, DP Hegde, U AF Bahadori, MY Zhou, L Stocker, DP Hegde, U TI Functional dependence of flame flicker on gravitational level SO AIAA JOURNAL LA English DT Article ID JET DIFFUSION FLAME C1 Sci & Technol Dev Corp, Los Angeles, CA 90049 USA. Sci Applicat Int Corp, Torrance, CA 90501 USA. NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RP Bahadori, MY (reprint author), Sci & Technol Dev Corp, Los Angeles, CA 90049 USA. NR 11 TC 6 Z9 6 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 JUL PY 2001 VL 39 IS 7 BP 1404 EP 1406 DI 10.2514/2.1462 PG 3 WC Engineering, Aerospace SC Engineering GA 449HY UT WOS:000169680000023 ER PT J AU Rancourt, DG Fortin, D Pichler, T Thibault, PJ Lamarche, G Morris, RV Mercier, PHJ AF Rancourt, DG Fortin, D Pichler, T Thibault, PJ Lamarche, G Morris, RV Mercier, PHJ TI Mineralogy of a natural As-rich hydrous ferric oxide coprecipitate formed by mixing of hydrothermal fluid and seawater: Implications regarding surface complexation and color banding in ferrihydrite deposits SO AMERICAN MINERALOGIST LA English DT Review ID PAPUA-NEW-GUINEA; QUADRUPOLE SPLITTING DISTRIBUTIONS; NANOSCALE FEOOH PARTICLES; MOSSBAUER-SPECTROSCOPY; MAGNETIC-PROPERTIES; IRON-OXIDES; SUPERPARAMAGNETIC PARTICLES; REFLECTANCE SPECTROSCOPY; SYNTHETIC FERRIHYDRITE; LACUSTRINE SEDIMENTS AB We characterized the most As-rich natural hydrous ferric oxide (HFO) material ever reported using powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), X-ray fluorescence spectroscopy (XRF), light element analysis using gas chromatography (GC), visible-infrared (vis-IR) diffuse reflectivity, Fe-57 Mossbauer spectroscopy, and superconducting quantum interference device (SQUID) magnetometry. We find that the natural As-HFO material is very similar to synthetic coprecipitated As-HFO materials, but is: significantly different from all known natural and synthetic As-free HFO materials and ferrihydrite samples. The pXRD patterns show systematic differences with patterns for 2-line ferrihydrite, that are interpreted as evidence for significant populations of oxygen-coordinated Fe-As pairs. Observations by TEM, combined with energy dispersive spectroscopy (EDS) microanalysis, show agglomerations of nanophase primary particles and no evidence for other Fe- or As-bearing phases. Mossbauer spectroscopy shows octahedrally coordinated Fe3+, with a large fraction (similar to 20%) of the octahedral Fe environments that are significantly distorted by the presence of As, compared to the Fe local environments in As-free ferrihydrite and HFO samples. The loss on ignition (LOI) is quantitatively consistent with OH + H2O, measured by GC, which, in turn, is consistent with similar to1 nm diameter primary particles having all their surface cations (Fe3+, As5+, Si4+, C4+) coordinated on the free surface side by OH- and OH2. The banding into adjacent yellowish and reddish layers that occurs in the As-HFO deposits was studied by performing mineralogical analyses of the separated adjacent layers of two couplets of yellowish and reddish material. The yellowish samples were found not to contain secondary crystalline phases las did the reddish samples, in small amounts) and to be relatively As-rich, C- and Si-poor. The observed anticorrelations between As and Si and between As and inorganic C suggest that natural HFOs, which usually contain significant molar amounts of Si, may not be as efficient at surface complexing As land P) as their Si and C-free synthetic counterparts, unless formed by co-precipitation with the As (or P). The yellowish and reddish layers were also clearly resolved by both Mossbauer spectroscopy and magnetometry. Complexation of arsenate onto the HFO core was found to significantly increase the average quadrupole splitting (QS) obtained from Mossbauer spectroscopy by an amount that could not be explained by other chemical differences and that is consistent with an similar to1 nm diameter particle size and somewhat smaller HFO core. The Munsell hue YR index (5-10 YR) was found to be strongly correlated to the average QS, thereby establishing that the color differences, corresponding to the measured shifts of the main visible band edge, are due to the local distortions in the [6]Fe3+ environments that are induced by As complexation, via their influence on the relevant ligand field transitions. SQUID magnetometry allows the following observations. (1)The superparamagnetic to superferromagnetic transitions occur at 25 K and lower in As-HFO, compared to 55 K in synthetic 2-line ferrihydrite, suggesting a smaller magnetic primary particle (or core) size for As-HFO and inter-particle magnetic interaction reduction by surface complexed As, Si, and C. (2) The ratio of supermoment magnitude to magnetic particle size (m(2)/n, where m is the net number of Fe3+ atomic moments per supermoment and n is the number of Fe3+ cations per particle or HFO core) decreases with increasing As content in the sequence synthetic-HFO > reddish-As-HFO > yellowish-As-HFO. (3) The magnetic susceptibility magnitudes for As-HFO and synthetic 2-line ferrihydrite differ by a factor of 10 and suggest different supermoment formation mechanisms (m(2)/n < 1 vs, m(2)/n > 1, respectively) related to differences in intra-particle cationic and anionic disorder and magnetic particle size. C1 Univ Ottawa, Dept Phys, Ottawa, ON K1N 6N5, Canada. Univ Ottawa, Dept Earth Sci, Ottawa, ON K1N 6N5, Canada. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Rancourt, DG (reprint author), Univ Ottawa, Dept Phys, Ottawa, ON K1N 6N5, Canada. EM dgr@physics.uottawa.ca NR 113 TC 87 Z9 88 U1 1 U2 18 PU MINERALOGICAL SOC AMER PI CHANTILLY PA 3635 CONCORDE PKWY STE 500, CHANTILLY, VA 20151-1125 USA SN 0003-004X EI 1945-3027 J9 AM MINERAL JI Am. Miner. PD JUL-AUG PY 2001 VL 86 IS 7-8 BP 834 EP 851 PG 18 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA 451PG UT WOS:000169810000007 ER PT J AU Greene, TP AF Greene, TP TI Protostars - "Stellar embryology" takes a step forward with the first detailed look at the youngest Sun-like stars SO AMERICAN SCIENTIST LA English DT Article ID CLUSTER C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Greene, TP (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. NR 12 TC 0 Z9 0 U1 0 U2 1 PU SIGMA XI-SCI RES SOC PI RES TRIANGLE PK PA PO BOX 13975, RES TRIANGLE PK, NC 27709 USA SN 0003-0996 J9 AM SCI JI Am. Scientist PD JUL-AUG PY 2001 VL 89 IS 4 BP 316 EP 325 PG 10 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 440KE UT WOS:000169173800015 ER PT J AU Beegle, LW Kanik, I Matz, L Hill, HH AF Beegle, LW Kanik, I Matz, L Hill, HH TI Electrospray ionization nigh-resolution ion mobility spectrometry for the detection of organic compounds, 1. Amino acids SO ANALYTICAL CHEMISTRY LA English DT Article ID MASS-SPECTROMETRY AB Our aim in this investigation was to demonstrate the potential of the high-resolution electrospray ionization ion mobility spectrometry (ESI-IMS) technique as an analytical separation tool in analyzing biomolecular mixtures to pursue astrobiological objectives of searching for the chemical signatures of life during an in-situ exploration of solar system bodies. Because amino acids represent the basic building blocks of life, we used common amino acids to conduct the first part of our investigation, which is being reported here, to demonstrate the feasibility of using the ESI-IMS technique for detection of the chemical signatures of life. The ion mobilities of common amino acids were determined by electrospray ionization ion mobility spectrometry using three different drift gases (Nz, Ar, and CO2), We demonstrated that the selectivity can be vastly improved in ion mobility spectroscopy (IMS) in detecting organic molecules by using different drift gases. When a judicial choice of drift gas is made, a vastly improved separation of two different amino acid ions resulted. It was found that each of the studied amino acids could be uniquely identified from the others, with the exception of alanine and glycine, which were never separable by more then 0.1 ms. This unique identification is a result of the different polarizabilities of the various drift gases. In addition, a better separation was achieved by changing the drift voltage in successive experimental runs without significantly degrading the resolution. We also report the result of our analysis of liquid samples containing mixtures of amino acids. C1 CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. Washington State Univ, Dept Chem, Pullman, WA 99164 USA. RP Kanik, I (reprint author), CALTECH, Jet Propuls Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Beegle, Luther/A-6354-2010 NR 13 TC 51 Z9 53 U1 0 U2 15 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0003-2700 J9 ANAL CHEM JI Anal. Chem. PD JUL 1 PY 2001 VL 73 IS 13 BP 3028 EP 3034 DI 10.1021/ac001519g PG 7 WC Chemistry, Analytical SC Chemistry GA 448ZP UT WOS:000169660100038 PM 11467550 ER PT J AU Soding, A Neubauer, FM Tsurutani, BT Ness, NF Lepping, RP AF Soding, A Neubauer, FM Tsurutani, BT Ness, NF Lepping, RP TI Radial and latitudinal dependencies of discontinuities in the solar wind between 0.3 and 19 AU and -80 degrees and +10 degrees SO ANNALES GEOPHYSICAE LA English DT Article DE interplanetary physics; discontinuities; interplanetary magnetic fields; space plasma physics; discontinuities ID INTERPLANETARY-MAGNETIC-FIELD; HIGH HELIOGRAPHIC LATITUDES; ROTATIONAL DISCONTINUITIES; ALFVEN WAVES; ULYSSES OBSERVATIONS; TANGENTIAL DISCONTINUITIES; DIRECTIONAL DISCONTINUITIES; OUTER HELIOSPHERE; PLASMA-EXPERIMENT; PICKUP IONS AB Directional discontinuities (DD) from 5 missions at 7 different locations between 0.3 and 19 AU and -80 degrees and +10 degrees in the 3D heliosphere are investigated during minimum, solar activity. The data are surveyed using the identification criteria of Burlaga (1969) (B) and Tsurutani and Smith (1979) (TS). The rate of occurrence depends linearly on the solar wind velocity caused by the geometric effect of investigating a larger plasma volume if the solar wind velocity v(sw) increases. The radial dependence is proportional to r(-0.78) (TS criterion) and r(-1.28) (B criterion), respectively. This dependence is not only due to an increasing miss rate with increasing distance. The DDs must be unstable or some other physical effect must exist. After normalization of the daily rates to 400 km/s and 1 AU, no dependence on heliographic latitude or on solar wind structures is observable. This means that the DDs are uniformly distributed on a spherical shell. Normalizezd 64 DD per day are identified with both criteria. But large variations of the daily rate still occur, indicating that other influences must exist. The ratio of the rates of rotational (RDs) and tangential discontinuities (TDs) depends on the solar wind structures. In high speed streams, relatively more RDs exist than in low speed streams. In the inner heliosphere (r<10 AU), no radial or latitudinal dependence of the portions of the DD types occur. 55% clear RDs, 10% clear TDs and 33% EDs (either discontinuities) are observed, but the portions differ with regard to the criteria used. In the middle heliosphere (10 AU < r < 40 AU), the DD types are more uniformly distributed. The distribution of the directional change over the transition evolves to an increase of smaller omega with increasing distance from the sun. The evolution is yielded by the anisotropic RDs with small omega. The spatial thickness d(km) in kilometers increases with distance. The thickness d(rg) normalized to the proton gyro radius decreases by a factor of 50 between 0.3 and 19 AU, from 201.3 r(g) down to 4.3 r(g). In the middle heliosphere, the orientation of the normals relative to the local magnetic field is essentially uniform except for the parallel direction where no DDs occur. This indicates that RDs propagating parallel to B play a special role. In addition, in only a few cases is [v] parallel to [B/rho], which is required by the MHD theory for RDs. The DDs have strongly enhanced values of proton gyro radius r(g) for omega similar to 90 degrees. In contrast, in the inner heliosphere, only a small increase in r(g) with omega is observed. C1 Univ Cologne, Inst Geophys & Meteorol, D-5000 Cologne, Germany. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Delaware, Bartol Res Fdn, Newark, DE USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Soding, A (reprint author), Univ Cologne, Inst Geophys & Meteorol, D-5000 Cologne, Germany. NR 46 TC 10 Z9 10 U1 0 U2 2 PU EUROPEAN GEOPHYSICAL SOCIETY PI KATLENBURG-LINDAU PA MAX-PLANCK-STR 13, 37191 KATLENBURG-LINDAU, GERMANY SN 0992-7689 J9 ANN GEOPHYS JI Ann. Geophys. PD JUL PY 2001 VL 19 IS 7 BP 667 EP 680 PG 14 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA 468RU UT WOS:000170772600001 ER PT J AU Miller, SR Castenholz, RW AF Miller, SR Castenholz, RW TI Ecological physiology of Synechococcus sp strain SH-94-5, a naturally occurring cyanobacterium deficient in nitrate assimilation SO APPLIED AND ENVIRONMENTAL MICROBIOLOGY LA English DT Article ID P-II GLNB; ANACYSTIS-NIDULANS; NITROGEN ASSIMILATION; NTCA GENE; PCC-7942; TRANSCRIPTION; REDUCTASE; TRANSPORT; NITRITE; PHOSPHORYLATION AB Synechococcus sp. strain SH-94-5 is a nitrate assimilation-deficient cyanobacterium which was isolated from an ammonium-replete hot spring in central Oregon. While this clone could grow on ammonium and some forms of organic nitrogen as sole nitrogen sources, it could not grow on either nitrate or nitrite, even under conditions favoring passive diffusion, It was determined that this clone does not er;press functional nitrate reductase or nitrite reductase and that the lack of activity of either enzyme is not due to inactivation of the cyanobacterial nitrogen control protein NtcA. A few other naturally occurring cyanobacterial strains are also nitrate assimilation deficient, and phylogenetic analyses indicated that the ability to utilize nitrate has been independently lost at least four times during the evolutionary history of the cyanobacteria, This phenotype is associated with the presence of environmental ammonium, a negative regulator of nitrate assimilation gene expression, which may indicate that natural selection to maintain functional copies of nitrate assimilation genes has been relaxed in these habitats. These results suggest how the evolutionary fates of conditionally expressed genes might differ between environments and thereby effect ecological divergence and biogeographical structure in the microbial world. C1 Univ Oregon, Dept Biol, Eugene, OR 97403 USA. RP Miller, SR (reprint author), NASA, Ames Res Ctr, Mailstop 239-4, Moffett Field, CA 94305 USA. NR 47 TC 23 Z9 23 U1 0 U2 1 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1752 N ST NW, WASHINGTON, DC 20036-2904 USA SN 0099-2240 J9 APPL ENVIRON MICROB JI Appl. Environ. Microbiol. PD JUL PY 2001 VL 67 IS 7 BP 3002 EP 3009 DI 10.1128/AEM.67.7.3002-3009.2001 PG 8 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA 448AV UT WOS:000169605400017 PM 11425713 ER PT J AU Eder, W Jahnke, LL Schmidt, M Huber, R AF Eder, W Jahnke, LL Schmidt, M Huber, R TI Microbial diversity of the brine-seawater interface of the Kebrit Deep, Red Sea, studied via 16S rRNA gene sequences and cultivation methods SO APPLIED AND ENVIRONMENTAL MICROBIOLOGY LA English DT Article ID FATTY-ACID-COMPOSITION; GREAT-SALT-LAKE; ORCA BASIN; SP-NOV; ATLANTIS-II; ANAEROBIC BACTERIUM; REDUCING BACTERIUM; HYPERSALINE BASIN; METHYL STEROL; SP. NOV. AB The brine-seawater interface of the Kebrit Deep, northern Red Sea, was investigated for the presence of microorganisms using phylogenetic analysis combined with cultivation methods. Under strictly anaerobic culture conditions, novel halophiles were isolated. The ne,v rod-shaped isolates belong to the halophilic genus Halanaerobium and are the first representatives of the genus obtained from deep-sea, anaerobic brine pools. Within the genus Halanaerobium, they represent new species which grow chemoorganotrophically at NaCl concentrations ranging from 5 to 34%. The cellular fatty acid compositions are consistent with those of other Halanaerobium representatives, showing unusually large amounts of Delta7 and Delta 11 16:1 fatty acids. Phylogenetic analysis of the brine-seawater interface sample revealed the presence of various bacterial 16S rRNA gene sequences dominated by cultivated members of the bacterial domain, with the majority affiliated with the genus Halanaerobium. The new Halanaerobium 16S rRNA clone sequences showed the highest similarity (99.9%) to the sequence of isolate KT-8-13 from the Kebrit Deep brine. In this initial survey, our polyphasic approach demonstrates that novel halophiles thrive in the anaerobic, deep-sea brine pool of the Kebrit Deep, Red Sea. They may contribute significantly to the anaerobic degradation of organic matter enriched at the brine-seawater interface. C1 Univ Regensburg, Lehrstuhl Mikrobiol, D-93053 Regensburg, Germany. Univ Regensburg, Archaeenzentrum, D-93053 Regensburg, Germany. Univ Kiel, Inst Geowissensch, D-24098 Kiel, Germany. NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. RP Eder, W (reprint author), Univ Regensburg, Lehrstuhl Mikrobiol, Univ Str 31, D-93053 Regensburg, Germany. EM wolfgang.eder@biologie.uni-regensburg.de RI Schmidt, Mark/B-5230-2016 NR 72 TC 68 Z9 70 U1 3 U2 14 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1752 N ST NW, WASHINGTON, DC 20036-2904 USA SN 0099-2240 J9 APPL ENVIRON MICROB JI Appl. Environ. Microbiol. PD JUL PY 2001 VL 67 IS 7 BP 3077 EP 3085 DI 10.1128/AEM.67.7.3077-3085.2001 PG 9 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA 448AV UT WOS:000169605400029 PM 11425725 ER PT J AU Tsapin, AI Vandenberghe, I Nealson, KH Scott, JH Meyer, TE Cusanovich, MA Harada, E Kaizu, T Akutsu, H Leys, D Van Beeumen, JJ AF Tsapin, AI Vandenberghe, I Nealson, KH Scott, JH Meyer, TE Cusanovich, MA Harada, E Kaizu, T Akutsu, H Leys, D Van Beeumen, JJ TI Identification of a small tetraheme cytochrome c and a flavocytochrome c as two of the principal soluble cytochromes c in Shewanella oneidensis strain MR1 SO APPLIED AND ENVIRONMENTAL MICROBIOLOGY LA English DT Article ID FUMARATE REDUCTASE; PUTREFACIENS MR-1; OUTER-MEMBRANE; WOLINELLA-SUCCINOGENES; FRIGIDIMARINA NCIMB400; ANAEROBIC RESPIRATION; SEQUENCE; C(3); PURIFICATION; EXPRESSION AB Two abundant, low-redox-potential cytochromes c were purified from the facultative anaerobe Shewanella oneidensis strain MR1 grown anaerobically with fumarate, The small cytochrome was completely sequenced, and the genes coding for both proteins were cloned and sequenced. The small cytochrome c contains 91 residues and four heme binding sites. It is most similar to the cytochromes c from Shewanella frigidimarina (formerly Shewanella putrefaciens) NCIMB400 and the unclassified bacterial strain H1R (64 and 55% identity, respectively). The amount of the small tetraheme cytochrome is regulated by anaerobiosis, but not by fumarate, The larger of the two low-potential cytochromes contains tetraheme and flavin domains and is regulated by anaerobiosis and by fumarate and thus most nearly corresponds to the flavocytochrome c-fumarate reductase previously characterized from S. frigidimarina to which it is 59% identical. However, the genetic context of the cytochrome genes is not the same for the two Shewanella species, and they are not located in multicistronic operons, The small cytochrome c and the cytochrome domain of the flavocytochrome c are also homologous, showing 34% identity. Structural comparison shows that the Shewanella tetraheme cytochromes are not related to the Desulfovibrio cytochromes c, but define a new folding motif for small multiheme cytochromes c. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. State Univ Ghent, Dept Biochem Physiol & Microbiol, Lab Prot Biochem & Prot Engn, B-9000 Ghent, Belgium. Carnegie Inst Washington, Washington, DC 20015 USA. Univ Arizona, Dept Biochem & Mol Biophys, Tucson, AZ 85721 USA. Yokohama Natl Univ, Hodogaya Ku, Yokohama, Kanagawa 2408501, Japan. Osaka Univ, Inst Prot Res, Suita, Osaka 5650871, Japan. RP Van Beeumen, JJ (reprint author), CALTECH, Jet Prop Lab, MS 183-301,4800 Oak Grove Dr, Pasadena, CA 91109 USA. FU NIGMS NIH HHS [R01 GM021277, GM21277] NR 43 TC 33 Z9 36 U1 1 U2 12 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1752 N ST NW, WASHINGTON, DC 20036-2904 USA SN 0099-2240 J9 APPL ENVIRON MICROB JI Appl. Environ. Microbiol. PD JUL PY 2001 VL 67 IS 7 BP 3236 EP 3244 DI 10.1128/AEM.67.7.3236-3244.2001 PG 9 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA 448AV UT WOS:000169605400051 PM 11425747 ER PT J AU Johnson, LF Bosch, DF Williams, DC Lobitz, BM AF Johnson, LF Bosch, DF Williams, DC Lobitz, BM TI Remote sensing of vineyard management zones: Implications for wine quality SO APPLIED ENGINEERING IN AGRICULTURE LA English DT Article DE remote sensing; precision viticulture; management zones; vine vigor; image processing; geospatial technology ID YIELD AB High-spatial resolution multispectral imagery, was acquired at mid-season 1997 by, an airborne digital camera system and used to establish management zones within a 3-ha commercial wine vineyard in California Napa Valley. Image processing included off-axis brightness correction, band-to-band alignment, ground registration and conversion to a Vegetation Index to enhance sensitivity to canopy density. The image was then stratified by Vegetation Index and color-coded for visual discrimination. An output image was generated in TIFF-World format for input to mapping software on the grower's laptop computer The imagery was used to delineate low-, moderate-, and high-vigor zones within the study block. Supporting field measurements per zone then included canopy structure (woody biomass, canopy transmittance), vine physiology (leaf water potential, chlorophyll content), and fruit biochemistry. Grapes from each zone were fermented separately and the resulting wines were formally evaluated for difference and quality. The low- and high-vigor zones were clearly distinct from one another with respect to most measurements. Block subdivision enabled the production of a "reserve" (highest) quality, wine for the first time ever from this particular block. C1 NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA. Calif State Univ Monterey Bay, Inst Earth Syst Sci & Policy, Seaside, CA USA. Robert Mondavi Winery, Oakville, CA USA. RP Johnson, LF (reprint author), NASA, Ames Res Ctr, Div Earth Sci, MS242-4,Moffett Field, Moffett Field, CA 94035 USA. NR 12 TC 48 Z9 49 U1 3 U2 21 PU AMER SOC AGRICULTURAL ENGINEERS PI ST JOSEPH PA 2950 NILES RD, ST JOSEPH, MI 49085-9659 USA SN 0883-8542 J9 APPL ENG AGRIC JI Appl. Eng. Agric. PD JUL PY 2001 VL 17 IS 4 BP 557 EP 560 PG 4 WC Agricultural Engineering SC Agriculture GA 507VX UT WOS:000173052900021 ER PT J AU Ryaben'kii, VS Tsynkov, SV Turchaninov, VI AF Ryaben'kii, VS Tsynkov, SV Turchaninov, VI TI Long-time numerical computation of wave-type solutions driven by moving sources SO APPLIED NUMERICAL MATHEMATICS LA English DT Article DE wave equation; lacunae; finite-difference approximation; explicit numerical integration; arbitrarily long time intervals; non-accumulation of error; temporally uniform grid convergence; fixed expenses per time step ID BOUNDARY-CONDITIONS; DIFFERENCE AB We propose a methodology for calculating the solution of an initial-value problem for the three-dimensional wave equation over arbitrarily long time intervals. The solution is driven by moving sources that are compactly supported in space for any particular moment of time; the extent of the support is assumed bounded for all times. By a simple change of variables the aforementioned formulation obviously translates into the problem of propagation of waves across a medium in motion, which has multiple applications in unsteady aerodynamics, advective acoustics, and other areas. The algorithm constructed in the paper can employ any appropriate (i.e., consistent and stable) explicit finite-difference scheme for the wave equation. This scheme is used as a core computational technique and modified so that to allow for a non-deteriorating calculation of the solution for as long as necessary. Provided that the original underlying scheme converges in some sense, i.e., in suitable norms with a particular rate, we prove the grid convergence of the new algorithm in the same sense uniformly in time on arbitrarily long intervals. Thus, the new algorithm obviously does not accumulate error in the course of time; besides, it requires only a fixed nongrowing amount of computer resources (memory and processor time) per one time step: these amounts are linear with respect to the grid dimension and thus optimal. The algorithm is inherently three-dimensional; it relies on the presence of lacunae in the solutions of the wave equation in odd-dimension spaces. The methodology presented in the paper is, in fact, a building block for constructing the nonlocal highly accurate unsteady artificial boundary conditions to be used for the numerical simulrttion of waves propagating with finite speed over unbounded domains. (C) 2001 IMACS. Published by Elsevier Science B,V. All rights reserved. C1 Russian Acad Sci, MV Keldysh Appl Math Inst, Moscow 125047, Russia. NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. Tel Aviv Univ, Sch Math Sci, IL-69978 Tel Aviv, Israel. RP Tsynkov, SV (reprint author), N Carolina State Univ, Dept Math, Box 8205, Raleigh, NC 27695 USA. NR 12 TC 13 Z9 18 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD JUL PY 2001 VL 38 IS 1-2 BP 187 EP 222 DI 10.1016/S0168-9274(01)00038-1 PG 36 WC Mathematics, Applied SC Mathematics GA 442FB UT WOS:000169273600011 ER PT J AU Giles, S Adamovsky, G Rashidnia, N AF Giles, S Adamovsky, G Rashidnia, N TI Optical detection of small changes in refractive indices in water by single-beam scattering SO APPLIED OPTICS LA English DT Article ID LIGHT-SCATTERING AB We studied forward-scattered laser light that is produced when the light strikes an abrupt interface (air bubble in water) and when it passes unimpeded through diffused water layers caused by temperature gradients. Measured intensities of the scattered light indicated patterns that are due to both geometrical and physical optics. Distribution of intensities within the scattered beam changed with the average vertical temperature gradient. Shifts in locations of intensities indicated small changes in the index of refraction in the diffused scattering case. (C) 2001 Optical Society of America. C1 Univ Toledo, Dept Elect Engn & Comp Sci, Toledo, OH 43606 USA. NASA, Glenn Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. NASA, Glenn Res Ctr, Instrumentat & Control Grp, Cleveland, OH 44135 USA. RP Univ Toledo, Dept Elect Engn & Comp Sci, Toledo, OH 43606 USA. EM sgiles@uoft02.utoledo.edu NR 12 TC 0 Z9 0 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 JUL 1 PY 2001 VL 40 IS 19 BP 3190 EP 3195 PG 6 WC Optics SC Optics GA 446KE UT WOS:000169511800007 PM 11958258 ER PT J AU Howard, JM AF Howard, JM TI Optical design using computer graphics SO APPLIED OPTICS LA English DT Article ID SPHERICAL MIRRORS AB For decades the computer has been the primary tool used for optical design. Typical tasks include performing numerical calculations for ray tracing and analysis and rendering graphics for system drawings. As machines become faster with each new generation, the time needed for a particular design task has greatly reduced, allowing multiple assignments to be performed with little noticeable delay. This lets the designer modify a system and then immediately see the results rendered in graphics with a single motion. Such visual design methods are discussed here, where graphics of systems and plots relating to their performance are produced in real time, permitting the optical designer to design by pictures. Three examples are given: an educational tutorial for designing a simple microscope objective, an unobstructed reflective telescope composed of three spherical mirrors, and a modified Offner relay with an accessible pupil. (C) 2001 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Natl Res Council, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Natl Res Council, Code 551, Greenbelt, MD 20771 USA. EM Joseph.M.Howard@gsfc.nasa.gov NR 6 TC 11 Z9 11 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 JUL 1 PY 2001 VL 40 IS 19 BP 3225 EP 3231 DI 10.1364/AO.40.003225 PG 7 WC Optics SC Optics GA 446KE UT WOS:000169511800013 PM 11958264 ER PT J AU Zethson, T Gull, TR Hartman, H Johansson, S Davidson, K Ishibashi, K AF Zethson, T Gull, TR Hartman, H Johansson, S Davidson, K Ishibashi, K TI Sr II and [Sr II] emission in the ejecta of eta carinae SO ASTRONOMICAL JOURNAL LA English DT Article DE circumstellar matter; stars : individual (eta Carinae); stars : variables : other ID SPECTROSCOPY; STAR AB We have discovered four extremely surprising emission lines of strontium in ejecta near eta Carinae. Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) observations made in 1999 show two narrow features whose wavelengths correspond to the forbidden transitions of Sr II, and we have found no other plausible identification for these lines. The identifications are confirmed by new HST/STIS observations of the same stellar position, in which the Sr II resonance lines are observed. Moreover, [Ti II], [Ni II], [Mn II], and [Co II] lines are unusually strong relative to [Fe II] at the same position. C1 Univ Lund, Dept Phys, S-22100 Lund, Sweden. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. RP Zethson, T (reprint author), Univ Lund, Dept Phys, POB 118, S-22100 Lund, Sweden. RI Gull, Theodore/D-2753-2012; Hartman, Henrik/K-3113-2013 OI Gull, Theodore/0000-0002-6851-5380; NR 16 TC 24 Z9 24 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 2001 VL 122 IS 1 BP 322 EP 326 DI 10.1086/321119 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XK UT WOS:000169943300027 ER PT J AU Dempsey, RC Neff, JE Lim, J AF Dempsey, RC Neff, JE Lim, J TI Simultaneous observations of variability at all atmospheric levels of V824 Arae (HD 155555) SO ASTRONOMICAL JOURNAL LA English DT Article DE stars : activity; stars : chromospheres; stars : coronae; stars : individual (V824 Arae); stars : late-type ID HIGH-RESOLUTION SPECTROGRAPH; RS-CANUM-VENATICORUM; STELLAR SURFACE-STRUCTURE; MAIN-SEQUENCE BINARY; LATE-TYPE STARS; ROTATIONAL MODULATION; RADIO-EMISSION; TRANSITION REGION; SYSTEM HR-1099; AU-MICROSCOPII AB We conducted a multiwavelength campaign observing V824 Ara (HD 155555, G5 IV + K0 IV-V) continuously throughout one complete orbital cycle (similar to1.7 days) in early May of 1996. At the core of this campaign were observations using the GHRS on the Hubble Space Telescope (HST). In all, about 48,000 spectra, many in rapid readout mode, were obtained with the GHRS covering the C IV, Mg II, and Fe XXI wavelength regions at 11-15 separate phases. Simultaneous observations were made with the Extreme Ultraviolet Explorer (EUV E). Radio observations (3.5 and 6 cm) were conducted at the Australian Telescope, while ground-based visual spectroscopic and photometric observations were made at European Southern Observatory, Cerro Tololo Inter-American Observatory, the Anglo-Australian Telescope, and South African Astronomical Observatory. Additional ground-based observations were obtained before, during, and after the campaign. Our primary intent was to obtain a three-dimensional model of the atmosphere extending from the photosphere to the corona. Variability was clearly detected, including several flares observed in the HST, EUV E, and radio data. We present results from modeling the ultraviolet transition region lines using an anisotropic macroturbulence model. Previous studies of transition region lines in late-type active stars have used multiple Gaussians to fit the observed line profiles, adding broad components to account for the extended wings observed in several active systems, including V711 Tau (HR 1099). This broad component has been interpreted as arising from the continuous presence of microflaring. We demonstrate that anisotropic macroturbulence models can also explain the observed Mg II profiles. C1 Space Telescope Sci Inst, Comp Sci Corp, Astron Program, Baltimore, MD 21218 USA. Coll Charleston, Dept Phys & Astron, Charleston, SC 29424 USA. Acad Sinica, Inst Astron & Astrophys, Taipei 115, Taiwan. RP Dempsey, RC (reprint author), NASA, Lyndon B Johnson Space Ctr, NASA Rd 1,Mail Stop DF25, Houston, TX 77058 USA. NR 40 TC 5 Z9 5 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 2001 VL 122 IS 1 BP 332 EP 348 DI 10.1086/321102 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XK UT WOS:000169943300029 ER PT J AU Kenyon, SJ Proga, D Keyes, CD AF Kenyon, SJ Proga, D Keyes, CD TI The continuing slow decline of AG Pegasi SO ASTRONOMICAL JOURNAL LA English DT Article DE novae, cataclysmic variables; stars : evolution; stars : individual (AG Pegasi) ID LTE PHOTOIONIZATION MODELS; SYMBIOTIC BINARY STARS; COOL COMPONENTS; COLLIDING WINDS; EMISSION-LINES; Z-ANDROMEDAE; FE-VII; HM-SGE; COLLISION; NOVAE AB We analyze optical and ultraviolet observations of the symbiotic binary AG Pegasi acquired during 1992-1997. The bolometric luminosity of the hot component declined by a factor of 2-3 from 1980-1985 to 1997. Since 1992, the effective temperature of the hot component may have declined by 10%-20%, but this decline is comparable to the measurement errors. Optical observations of H beta and He I emission show a clear illumination effect, where high-energy photons from the hot component ionize the outer atmosphere of the red giant. Simple illumination models generally account for the magnitude of the optical and ultraviolet emission-line fluxes. High-ionization emission lines-[Ne V], [Mg V], and [Fe VII]-suggest mechanical heating in the outer portions of the photoionized red giant wind. This emission probably originates in a low-density region similar to 30-300 AU from the central binary. C1 Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Kenyon, SJ (reprint author), Smithsonian Astrophys Observ, 60 Garden St, Cambridge, MA 02138 USA. OI Kenyon, Scott/0000-0003-0214-609X NR 65 TC 13 Z9 13 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 2001 VL 122 IS 1 BP 349 EP 359 DI 10.1086/321107 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XK UT WOS:000169943300030 ER PT J AU Lu, WX Rucinski, SM Ogloza, W AF Lu, WX Rucinski, SM Ogloza, W TI Radial velocity studies of close binary stars. IV. SO ASTRONOMICAL JOURNAL LA English DT Article DE binaries : close; binaries : eclipsing; stars : variables : general ID LINE BROADENING FUNCTIONS; UMA-TYPE BINARIES; W-UMA; SPECTROSCOPIC BINARIES; LIGHT CURVES; SYSTEMS; HIPPARCOS; COMPONENTS; TODCOR AB Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for the fourth set of 10 close binary systems: 44 Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc (GSC 8-324), and HT Vir. All systems are double-lined spectroscopic binaries, with only two of them not being contact systems (SW Lyn and GSC 8-324) and five (FI Boo, V2150 Cyg, V899 Her, EX Leo, and V2377 Oph) being the recent photometric discoveries of the Hipparcos project. Five of the binaries are triple-lined systems (44 Boo, V899 Her, VZ Lib, SW Lyn, and HT Vir). Three (or possibly four) companions in the triple-lined systems show radial velocity changes during the span of our observations, suggesting that these are in fact quadruple systems. Several of the studied systems are prime candidates for combined light and radial velocity synthesis solutions. C1 Univ Toronto, David Dunlap Observ, Richmond Hill, ON L4C 4Y6, Canada. Cracow Pedagog Univ, Mt Suhora Observ, PL-30084 Krakow, Poland. N Copernicus Astron Ctr, PL-00716 Warsaw, Poland. RP Lu, WX (reprint author), NASA, Goddard Space Flight Ctr, Code 664,8800 Greenbelt Rd, Greenbelt, MD 20771 USA. NR 34 TC 61 Z9 61 U1 1 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 2001 VL 122 IS 1 BP 402 EP 412 DI 10.1086/321131 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XK UT WOS:000169943300035 ER PT J AU Douvion, T Lagage, PO Cesarsky, CJ Dwek, E AF Douvion, T Lagage, PO Cesarsky, CJ Dwek, E TI Dust in the Tycho, Kepler and Crab supernova remnants SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : supernova remnants; individual object : Kepler, Crab, Tycho ID CASSIOPEIA-A SUPERNOVA; X-RAY-SPECTRUM; HOT GAS; INFRARED-EMISSION; SIZE DISTRIBUTION; VLA OBSERVATIONS; NEBULA; SN-1987A; GRAINS; CONTINUUM AB SuperNova Remnants (SNR) have been extensively studied in radio, X-rays and optical, but barely in the InfraRed (IR). From IRAS observations, SNR are known to be IR emitters, but the origin of the emission is difficult to assess because of the limited angular and spectral resolution of IRAS observations. ISO follow-up observations of the Cassiopeia-A SNR have shown that the mid-IR radiation from this remnant was dominated by thermal emission from silicate condensates made from SN material. These condensates constitute a probe which can provide unique information about element mixing inside a SN. In this paper, we present ISOCAM observations of the three other young SNR's known in our galaxy: the Kepler SNR, the Tycho SNR and the Crab Nebula. The emission observed from the Kepler SNR is dominated by dust thermal emission. The dust at the origin of the IR emission is circumstellar, not from SN condensates. "Astronomical" silicates, collisionally heated to a temperature of 107 K, can account for both the mid-IR ISO data and the IRAS data. The IR emission from Tycho is probably also emitted by circumstellar or interstellar dust. In order to reproduce both the mid-IR ISO data and the IRAS data, a model with two dust components, one at a temperature of 107 K and the other at 55 K, is needed. The mid-IR emission from the Crab is dominated by synchrotron radiation; no dust is detected. C1 CEA Saclay, DSM, DAPNIA, Serv Astrophys, F-91191 Gif Sur Yvette, France. Supelec, Serv Mesures, F-91192 Gif Sur Yvette, France. European So Observ, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Douvion, T (reprint author), CEA Saclay, DSM, DAPNIA, Serv Astrophys, F-91191 Gif Sur Yvette, France. EM tdouvion@cea.fr; lagage@cea.fr NR 83 TC 47 Z9 48 U1 1 U2 3 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 JUL PY 2001 VL 373 IS 1 BP 281 EP 291 DI 10.1051/0004-6361:20010447 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 454HM UT WOS:000169967200029 ER PT J AU Fynbo, JU Gorosabel, J Dall, TH Hjorth, J Pedersen, H Andersen, MI Moller, P Holland, S Smail, I Kobayashi, N Rol, E Vreeswijk, P Burud, I Jensen, BL Thomsen, B Henden, A Vrba, F Canzian, B Ceron, JMC Castro-Tirado, AJ Cline, T Goto, M Greiner, J Hanski, MT Hurley, K Lund, N Pursimo, T Ostensen, R Solheim, J Tanvir, N Terada, H AF Fynbo, JU Gorosabel, J Dall, TH Hjorth, J Pedersen, H Andersen, MI Moller, P Holland, S Smail, I Kobayashi, N Rol, E Vreeswijk, P Burud, I Jensen, BL Thomsen, B Henden, A Vrba, F Canzian, B Ceron, JMC Castro-Tirado, AJ Cline, T Goto, M Greiner, J Hanski, MT Hurley, K Lund, N Pursimo, T Ostensen, R Solheim, J Tanvir, N Terada, H TI The optical afterglow and host galaxy of GRB 000926 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE cosmology : observations; gamma rays : bursts ID GAMMA-RAY BURST; LY-ALPHA ABSORBER; HUBBLE DEEP FIELD; 28 FEBRUARY 1997; HIGH-REDSHIFT; STAR-FORMATION; GRB 990123; LIGHT CURVES; EMISSION; DISCOVERY AB We present the discovery of the Optical Transient (OT) of the long-duration gamma-ray burst GRB 000926. The optical transient was detected independently with the Nordic Optical Telescope and at Calar Alto 22.2 hours after the burst. At this time the magnitude of the transient was R = 19.36. The transient faded with a decay slope of about 1.7 during the first two days after which the slope increased abruptly (within a few hours) to about 2.4. The light-curve started to flatten off after about a week indicating the presence of an underlying extended object. This object was detected in a deep image obtained one month after the GRB at R = 23.87 +/- 0.15 and consists of several compact knots within about 5 arcsec. One of the knots is spatially coincident with the position of the OT and hence most likely belongs to the host galaxy. Higher resolution imaging is needed to resolve whether all the compact knots belong to the host galaxy or to several independent objects. In a separate paper we present a discussion of the optical spectrum of the OT, and its inferred redshift (Moller et al., in prep.). C1 European So Observ, D-85748 Garching, Germany. Danish Space Res Inst, DK-2100 Copenhagen O, Denmark. Nord Opt Telescope, Santa Cruz De La Palma 38700, Spain. Aarhus Univ, Inst Phys & Astron, DK-8000 Aarhus C, Denmark. Univ Copenhagen, Astron Observ, DK-2100 Copenhagen O, Denmark. Univ Oulu, Div Astron, Oulu 90014, Finland. Univ Durham, Dept Phys, Durham DH1 3LE, England. Natl Astron Observ Japan, SUBARU Telescope, Hilo, HI 96720 USA. Univ Amsterdam, NL-1098 SJ Amsterdam, Netherlands. Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium. Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 USA. US Naval Observ, Univ Space Res Assoc, Flagstaff, AZ 86002 USA. Real Inst & Observ Armada, Secc Astron, Cadiz 11110, Spain. Inst Astrofis Andalucia, CSIC, E-18080 Granada, Spain. LAEFF, INTA, Madrid 28080, Spain. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Astrophys Inst Potsdam, D-14482 Potsdam, Germany. Univ Turku, Tuorla Observ, Piikkio 21500, Finland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Tromso, Dept Phys, Tromso, Norway. Univ Hertfordshire, Dept Phys Sci, Hatfield AL10 9AB, Herts, England. Kyoto Univ, Dept Phys, Sakyo Ku, Kyoto 6068502, Japan. RP Fynbo, JU (reprint author), European So Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany. EM jfynbo@eso.org RI Smail, Ian/M-5161-2013; Hjorth, Jens/M-5787-2014; Jensen, Brian Lindgren/E-1275-2015 OI Castro-Tirado, A. J./0000-0003-2999-3563; Smail, Ian/0000-0003-3037-257X; Hjorth, Jens/0000-0002-4571-2306; Jensen, Brian Lindgren/0000-0002-0906-9771 NR 63 TC 62 Z9 62 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 EI 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 2001 VL 373 IS 3 BP 796 EP 804 DI 10.1051/0004-6361:20010531 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 454MX UT WOS:000169977300009 ER PT J AU Grewe, V Brunner, D Dameris, M Grenfell, JL Hein, R Shindell, D Staehelin, J AF Grewe, V Brunner, D Dameris, M Grenfell, JL Hein, R Shindell, D Staehelin, J TI Origin and variability of upper tropospheric nitrogen oxides and ozone at northern mid-latitudes SO ATMOSPHERIC ENVIRONMENT LA English DT Article DE NOXAR; GCM; upper troposphere NOx and ozone; lightning NOx ID AIRCRAFT EMISSIONS; LOWER STRATOSPHERE; NOX; MODEL; DISTRIBUTIONS; IMPACT; PARAMETERIZATION; TROPOPAUSE; CHEMISTRY; TRANSPORT AB Year-long measurements of NOx and ozone performed during the NOXAR project are compared to results from the ECHAM4.L39(DLR)/CHEM (E39/C) and GISS coupled chemistry-climate models. The measurements were taken on flights between Europe and the eastern United States and between Europe and the Far East in the latitude range 40-65 degreesN. Our comparison concentrates on the upper troposphere and reveals strong longitudinal variations in seasonal mean NOx of more than 200 pptv, which both models are able to reproduce qualitatively. Vertical profiles show maximum NOx values 2-3 km below the tropopause ("E-shape") with a strong seasonal cycle. E39/C simulates a maximum located at the tropopause and with a reasonable seasonal cycle,The GISS model reproduces the seasonal cycle but not the profile's shape due to its coarser vertical resolution. A comparison of NOx frequency distributions reveals that both models are capable of reproducing the observed variability, except that E39/C shows no very high NOx mixing ratios. Both models show that lightning and surface NOx emissions contribute the most to the seasonal cycle of NOx at tropopause altitudes. The impact of lightning in the upper troposphere does not vary strongly with altitude, whereas the impact of surface emissions decreases with altitude. Among all sources, lightning contributes the most to the variability of NOx in the upper troposphere in northern mid-latitudes during summer. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Deutsch Zentrum Luft & Raumfahrt, DLR, Inst Phys Atmosphare, Oberpfaffenhofen, Germany. Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY USA. Columbia Univ, Ctr Climate Syst Res, New York, NY USA. ETH Zurich, Inst Atmospher Sci, Swiss Fed Inst Technol, Zurich, Switzerland. RP Grewe, V (reprint author), Deutsch Zentrum Luft & Raumfahrt, DLR, Inst Phys Atmosphare, Oberpfaffenhofen, Germany. RI Brunner, Dominik/A-1255-2009; Shindell, Drew/D-4636-2012; Grewe, Volker/A-6147-2011 OI Brunner, Dominik/0000-0002-4007-6902; Grewe, Volker/0000-0002-8012-6783 NR 35 TC 74 Z9 74 U1 2 U2 11 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1352-2310 J9 ATMOS ENVIRON JI Atmos. Environ. PD JUL PY 2001 VL 35 IS 20 BP 3421 EP 3433 DI 10.1016/S1352-2310(01)00134-0 PG 13 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 453VX UT WOS:000169938100006 ER PT J AU Miller, K Gadian, A Saunders, C Latham, J Christian, H AF Miller, K Gadian, A Saunders, C Latham, J Christian, H TI Modelling and observations of thundercloud electrification and lightning SO ATMOSPHERIC RESEARCH LA English DT Article DE thundercloud electrification; lightning; modelling; observations ID PRECIPITATION DEVELOPMENT; LIQUID WATER; THUNDERSTORM ELECTRIFICATION; MONTANA THUNDERSTORM; ICE; CLOUDS; STORM; CUMULONIMBUS; HAIL AB A two-dimensional lightning frequency model was applied to two case studies of thunderclouds: 9th July 1981, the CCOPE case, and 19th July 1991, the CaPE case. Factors influencing lightning activity were discussed. Although there was a strong link between updraft and lightning frequency, the relationship was not distinct; the initial environmental conditions, the updraft speed and more significantly the graupel number concentration were shown to have a large effect. The model computations suggested the importance of the 2-mm diameter graupel particles. No definite relationship between lightning frequency and cloud ice content could be established in this study. The results demonstrated the limitations of the current charge transfer parameterisation scheme used, with a more detailed structure being required. However, the model was capable of reproducing a realistic cloud structure and lightning activity using a relatively simple dynamical framework. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Univ Manchester, Inst Sci & Technol, Dept Phys, Manchester M60 1QD, Lancs, England. NCAR, Boulder, CO USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Gadian, A (reprint author), Univ Manchester, Inst Sci & Technol, Dept Phys, POB 88, Manchester M60 1QD, Lancs, England. NR 44 TC 8 Z9 12 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD JUL PY 2001 VL 58 IS 2 BP 89 EP 115 DI 10.1016/S0169-8095(01)00089-8 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 460RN UT WOS:000170322500002 ER PT J AU Asrar, G Kaye, JA Morel, P AF Asrar, G Kaye, JA Morel, P TI NASA research strategy for earth system science: Climate component SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SENSOR MICROWAVE IMAGER; GREENLAND ICE-SHEET; GLOBAL PRECIPITATION; GENERAL-CIRCULATION; SATELLITE ALTIMETRY; PROJECT; RAINFALL; BALANCE; MISSION; OCEAN AB This paper describes the principles adopted by the NASA Earth Science Enterprise in formulating a comprehensive 2002-2010 research strategy for earth system science, and outlines one component of this broad interdisciplinary program, focused on physical climate research. Before embarking upon topical discussions of each element of the program, the authors sketch NASA's overall strategy for climate research and organize the main research thrusts according to a logical progression from documenting climate variability and trends in relevant climate forcing factors, to the investigation of key climate responses and feedback mechanisms, consequences for weather and water resources, and climate prediction issues. The ultimate challenge for NASA's earth system science program, a major contribution to the U.S. Global Change Research Program, is to consolidate scientific findings in the different disciplines into an integrated representation of the coupled atmosphere, ocean, ice, land, and biosphere system. The hallmark of NASA programs is indeed the integration of observations, principally global observation from research and operational satellite and surface-based observation networks, into consistent global datasets to support its scientific research programs and the verification of earth system model predictions against observed phenomena. C1 Univ Maryland Baltimore Cty, GEST, Baltimore, MD 21250 USA. NASA, Off Earth Sci, Washington, DC 20546 USA. RP Morel, P (reprint author), Univ Maryland Baltimore Cty, GEST, 1000 Hilltop Circle, Baltimore, MD 21250 USA. EM morel@umbc.edu NR 48 TC 18 Z9 18 U1 0 U2 7 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 JUL PY 2001 VL 82 IS 7 BP 1309 EP 1329 DI 10.1175/1520-0477(2001)082<1309:NRSFES>2.3.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 451MH UT WOS:000169805500001 ER PT J AU Michaels, M Shepard, M Aberson, S Friedman, H Murphy, K AF Michaels, M Shepard, M Aberson, S Friedman, H Murphy, K TI Survey results of society membership: The face of our profession at the threshold of the new millennium SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article AB In the spring of 1999, the American Meteorological Society surveyed its membership in order to update demographic information on the Society and to gain a more detailed perspective on the workplace. The survey was sent out with the dues statement and was solicited on a separate form returned independently to protect privacy and maintain anonymity. The responses were captured in a newly employed, machine-readable format to provide an ease of statistical analysis and data compilation not available in prior survey analysis. This data collection and subsequent demographic analysis represents the first attempt to update information regarding the membership since the 1993 survey results were published by Zevin and Seitter. The format of the 1999 survey war, designed to logically follow and expand upon the historical data of the membership collected at varying intervals since 1975. The 1999 survey was broken into six parts. The sections on demographics, education, and current employment closely followed the previous surveys from 1993 and 1990 to facilitate direct comparisons between historical datasets whenever possible. The last three sections were reworked to elicit more declarative responses regarding personal circumstances, workplace circumstances, and additional issues concerning career choice and AMS membership, respectively. An additional space was provided for narrative comments regarding opportunities for women and minorities in the AMS-related sciences. Some 10 000 members were sent the 1999 dues statement and enclosed survey questionnaire. A total of 4669 members responded. The following is a detailed analysis of the data collected from the 1999 membership survey. C1 Weather Channel, Atlanta, GA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. AOML, Hurricane Res Div, Miami, FL USA. Ladue Jr High Sch, St Louis, MO USA. RP Michaels, M (reprint author), 955 Mass Ave,370, Cambridge, MA 02139 USA. RI Aberson, Sim/C-4891-2013; Friedman, Howard/B-1541-2017 OI Aberson, Sim/0000-0002-3670-0100; NR 8 TC 6 Z9 6 U1 0 U2 2 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 JUL PY 2001 VL 82 IS 7 BP 1331 EP 1352 DI 10.1175/1520-0477(2001)082<1331:SROSMT>2.3.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 451MH UT WOS:000169805500002 ER PT J AU Adler, RF Kidd, C Petty, G Morissey, M Goodman, HM AF Adler, RF Kidd, C Petty, G Morissey, M Goodman, HM TI Intercomparison of global precipitation products: The third Precipitation Intercomparison Project (PIP-3) SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID PROBABILITY-DISTRIBUTION FUNCTIONS; OCEANIC PRECIPITATION; RAINFALL RETRIEVAL; SSM/I; ALGORITHM; DATASET; CLOUD; MODEL; POLARIZATION; INDEXES AB A see of global, monthly rainfall products has been intercompared to understand the quality and utility of the estimates. The products include 25 observational (satellite based), four model, and two climatological products. The results of the intercomparison indicate a very large range (factor of 2 or 3) of values when all products are considered. The range of values is reduced considerably when the set of observational products is limited to those considered quasi-standard. The model products do significantly poorer in the Tropics, but are competitive with satellite-based fields in midlatitudes over land. Over ocean, products are compared to frequency of precipitation from ship observations. The evaluation of the observational products points to merged data products (including rain gauge information) as providing the overall best results. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Birmingham, Dept Geog, Birmingham B15 2TT, W Midlands, England. Univ Wisconsin, Dept Meteorol, Madison, WI 53706 USA. Univ Oklahoma, Coll Geosci, Norman, OK 73019 USA. NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35812 USA. RP Adler, RF (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Mail Code 912, Greenbelt, MD 20771 USA. RI Petty, Grant/E-3118-2012; Kidd, Christopher/H-9910-2014 NR 36 TC 194 Z9 205 U1 1 U2 19 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 JUL PY 2001 VL 82 IS 7 BP 1377 EP 1396 DI 10.1175/1520-0477(2001)082<1377:IOGPPT>2.3.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 451MH UT WOS:000169805500005 ER PT J AU Sigler, MF Lunsford, CR AF Sigler, MF Lunsford, CR TI Effects of individual quotas on catching efficiency and spawning potential in the Alaska sablefish fishery SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID ANOPLOPOMA-FIMBRIA; TAGGED SABLEFISH; PACIFIC; MOVEMENT; GROWTH AB Individual fishery quota (IFQ) management eliminates the race for fish and may improve economic efficiency, conservation, and safety in fisheries. Empirical information documenting these effects is limited, even though IFQs have been used since the late 1970s. We analyzed fishery data from the Alaska sablefish (Anoplopoma fimbria) longline fishery, which came under IFQ management in 1995. We compared the fishery data with fishery-independent survey data, which acted as a control to separate annual changes in population demographics from changes due to IFQ management. We found that IFQ management increased fishery catch rate and decreased harvest of immature fish. Catching efficiency increased 1.8 times with the change from an open-access to an IFQ fishery. The improved catching efficiency of the IFQ fishery reduced variable costs to catch the quota from 8 to 5% of landed value, a savings averaging $3.1 million US annually. Decreased harvest of immature fish improved the chance that individual fish will reproduce at least once. Spawning potential of sablefish, expressed as spawning biomass per recruit, increased 9% for the IFQ fishery. Switching from the open-access fishery's race for fish to IFQs provided two clear benefits that should be considered when evaluating management options for other open-access fisheries. C1 Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Sigler, MF (reprint author), Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 27 TC 25 Z9 25 U1 0 U2 4 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD JUL PY 2001 VL 58 IS 7 BP 1300 EP 1312 DI 10.1139/cjfas-58-7-1300 PG 13 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 451AG UT WOS:000169776600004 ER PT J AU Zhou, MF Andrews, L Bauschlicher, CW AF Zhou, MF Andrews, L Bauschlicher, CW TI Spectroscopic and theoretical investigations of vibrational frequencies in binary unsaturated transition-metal carbonyl cations, neutrals, and anions SO CHEMICAL REVIEWS LA English DT Review ID DENSITY-FUNCTIONAL CALCULATIONS; ELECTRON-SPIN-RESONANCE; MATRIX INFRARED-SPECTRA; POTENTIAL-ENERGY SURFACES; EXCIMER LASER PHOTOLYSIS; SEQUENTIAL BOND-ENERGIES; N = 1; PARAMAGNETIC-RES SPECTRUM; MAS-NMR-SPECTRA; ION PHOTOELECTRON-SPECTROSCOPY C1 Univ Virginia, Dept Chem, Charlottesville, VA 22904 USA. Fudan Univ, Dept Chem, Laser Chem Inst, Shanghai 200433, Peoples R China. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Andrews, L (reprint author), Univ Virginia, Dept Chem, Charlottesville, VA 22904 USA. NR 323 TC 300 Z9 303 U1 18 U2 98 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0009-2665 J9 CHEM REV JI Chem. Rev. PD JUL PY 2001 VL 101 IS 7 BP 1931 EP 1961 DI 10.1021/cr990102b PG 31 WC Chemistry, Multidisciplinary SC Chemistry GA 455TZ UT WOS:000170045000004 PM 11710236 ER PT J AU Srivastava, D Menon, M Cho, K AF Srivastava, D Menon, M Cho, K TI Computational nanotechnology with carbon nanotubes and fullerenes SO COMPUTING IN SCIENCE & ENGINEERING LA English DT Article ID MOLECULAR-DYNAMICS; DEVICES; SILICON; ELECTRONICS; JUNCTIONS; GEARS; WIRES AB The authors envision computational nanotechnology's role in developing the next generation of multifunctional materials and molecular-scale electronic and computing devices, sensors, actuators, and machines. They briefly review computational techniques and provide a few recent examples derived from computer simulations of carbon nanotube-based molecular nanotechnology. C1 NASA, Ames Res Ctr, Moffett Field, CA 95035 USA. Univ Kentucky, Ctr Computat Sci, Lexington, KY 40506 USA. Stanford Univ, Stanford, CA 94305 USA. RP NASA, Ames Res Ctr, Mail MS T27A-1, Moffett Field, CA 95035 USA. EM deepak@nas.nasa.gov; madhu@ccs.uky.edu; kjcho@stanford.edu NR 48 TC 72 Z9 73 U1 0 U2 13 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1521-9615 EI 1558-366X J9 COMPUT SCI ENG JI Comput. Sci. Eng. PD JUL-AUG PY 2001 VL 3 IS 4 BP 42 EP 55 DI 10.1109/5992.931903 PG 14 WC Computer Science, Interdisciplinary Applications SC Computer Science GA 446BB UT WOS:000169492100008 ER PT J AU Burke, MW Leardi, R Judge, RA Pusey, ML AF Burke, MW Leardi, R Judge, RA Pusey, ML TI Quantifying main trends in lysozyme nucleation: The effect of precipitant concentration, supersaturation, and impurities SO CRYSTAL GROWTH & DESIGN LA English DT Article ID EGG-WHITE LYSOZYME; CRYSTAL-GROWTH; QUANTITATIVE-ANALYSIS; PROTEIN CRYSTALS; IONIC-STRENGTH; TEMPERATURE; PH AB Full factorial experimental design incorporating multilinear regression analysis of the experimental data allows quick identification of main trends and effects using a limited number of experiments. In this study, we illustrate the usefulness of these techniques in macromolecule crystallization studies, by employing them to identify the effect of precipitant concentration, supersaturation, and the presence of an impurity, the physiological lysozyme dimer, on the nucleation and dimensions of chicken egg white lysozyme crystals. Decreasing precipitant concentration, increasing supersaturation, and increasing impurity were found to increase crystal numbers. The crystal axial ratio decreased with increasing precipitant concentration, independent of impurity. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Dipartimento Chim & Tecnol Farmaceut & Alimentari, I-16147 Genoa, Italy. RP Judge, RA (reprint author), NASA, George C Marshall Space Flight Ctr, Biophys SD48, Huntsville, AL 35812 USA. NR 18 TC 14 Z9 15 U1 0 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1528-7483 J9 CRYST GROWTH DES JI Cryst. Growth Des. PD JUL-AUG PY 2001 VL 1 IS 4 BP 333 EP 337 DI 10.1021/cg0155088 PG 5 WC Chemistry, Multidisciplinary; Crystallography; Materials Science, Multidisciplinary SC Chemistry; Crystallography; Materials Science GA 519CL UT WOS:000173707300011 ER PT J AU Davis, MW AF Davis, MW TI Behavioral responses of walleye pollock, Theragra chalcogramma, larvae to experimental gradients of sea water flow: implications for vertical distribution SO ENVIRONMENTAL BIOLOGY OF FISHES LA English DT Article DE current speed; feeding; gravity; light; orientation; swimming; turbulence ID SMALL-SCALE TURBULENCE; SHELIKOF-STRAIT; REEF FISH; LABORATORY CONDITIONS; POTENTIAL ROLE; ALASKA; PLANKTON; PATTERNS; SURVIVAL; PATCH AB Walleye pollock larvae under controlled laboratory conditions were exposed to vertical gradients of sea water flow in low and high light. Whether flow originated from the surface or the bottom, larvae responded by altering depth distribution, showing attraction to low flows, avoidance of higher flows and when flow was above a threshold level, loss of ability to orient, swim and feed. These results demonstrate that walleye pollock have the capability for responding to gradients of flow by adjusting their vertical distribution. Walleye pollock and many other pelagic fish larvae have weak swimming capabilities and are generally unable to directly control horizontal distributions in the sea by swimming in higher flow regimens. However, using vertical migration, larvae may select conditions of flow direction and speed which are favorable for feeding and predator avoidance and which indirectly allow them to control transport, aggregation and dispersion. C1 Natl Marine Fisheries Serv, Fisheries Behav Ecol Program, Alaska Fisheries Sci Ctr, Hatfield Marine Sci Ctr, Newport, OR 97365 USA. RP Davis, MW (reprint author), Natl Marine Fisheries Serv, Fisheries Behav Ecol Program, Alaska Fisheries Sci Ctr, Hatfield Marine Sci Ctr, Newport, OR 97365 USA. NR 42 TC 10 Z9 11 U1 0 U2 6 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0378-1909 J9 ENVIRON BIOL FISH JI Environ. Biol. Fishes PD JUL PY 2001 VL 61 IS 3 BP 253 EP 260 DI 10.1023/A:1010947621672 PG 8 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 448GK UT WOS:000169618900003 ER PT J AU Stunz, GW Levin, PS Minello, TJ AF Stunz, GW Levin, PS Minello, TJ TI Selection of estuarine nursery habitats by wild-caught and hatchery-reared juvenile red drum in laboratory mesocosms SO ENVIRONMENTAL BIOLOGY OF FISHES LA English DT Article DE habitat preference; habitat selection; predation; recruitment; Sciaenops ocellatus; fish ID TEMPERATE REEF FISH; STRUCTURAL COMPLEXITY; SCIAENOPS-OCELLATUS; DECAPOD CRUSTACEANS; ARTIFICIAL SEAGRASS; STOCK ENHANCEMENT; PREDATORY FISH; RECRUITMENT; PREY; FOOD AB We examined patterns of habitat selection in wild-caught and hatchery-reared early juvenile red drum, Sciaenops ocellatus, using mesocosm experiments. Experiments were performed in the presence and absence of a pinfish, Lagodon rhomboides. We hypothesized that newly recruited red drum would have distinct patterns of habitat selection, and these patterns could be influenced by the presence of a pinfish predator. Red drum were introduced to replicate mesocosms containing all possible pair-wise comparisons of four different habitat types: marsh Spartina alterniflora, non-vegetated bottom/sand, oyster reef Crassostrea virginica, and seagrass Halodule wrightii. Wild-caught and hatchery-reared red drum showed distinctively different patterns of habitat selection. In general, wild-caught red drum selected structured habitats, while hatchery-reared fish did not show strong selection for any habitat type. When a predator was present, wild-caught red drum either changed habitat selection or showed significant selection for other structured habitats. This predator effect was similar albeit weaker for hatchery-reared red drum, but as in the trials without a predator, overall habitat selection was reduced compared to wild-caught red drum. Our results suggest that in the absence of seagrass, other habitat types such as marshes and oyster reefs may be important recruitment habitat for red drum. Additionally, hatchery-dependent behaviors may need to be assessed in designing stock enhancement programs. C1 Natl Marine Fisheries Serv, Fishery Ecol Branch, SE Fisheries Sci Ctr, Galveston Lab, Galveston, TX 77551 USA. NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Seattle, WA 98112 USA. RP Stunz, GW (reprint author), Natl Marine Fisheries Serv, Fishery Ecol Branch, SE Fisheries Sci Ctr, Galveston Lab, 4700 Ave U, Galveston, TX 77551 USA. NR 56 TC 20 Z9 22 U1 0 U2 5 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0378-1909 J9 ENVIRON BIOL FISH JI Environ. Biol. Fishes PD JUL PY 2001 VL 61 IS 3 BP 305 EP 313 DI 10.1023/A:1010874629788 PG 9 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 448GK UT WOS:000169618900008 ER PT J AU Millet, C Custaud, MA Allevard, AM Zaouali-Ajina, M Monk, TH Arnaud, SB Claustrat, B Gharib, C Gauquelin-Koch, G AF Millet, C Custaud, MA Allevard, AM Zaouali-Ajina, M Monk, TH Arnaud, SB Claustrat, B Gharib, C Gauquelin-Koch, G TI Influence of head-down bed rest on the circadian rhythms of hormones and electrolytes involved in hydroelectrolytic regulation SO EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE circadian rhythms; human; hormones; head-down bed rest; urinary solutes ID GROWTH-HORMONE; SLEEP; SPACEFLIGHT; ALDOSTERONE; RESPONSES; EXERCISE; CORTISOL; SYSTEM AB We investigated in six men the impact of a 17-day head-down bed rest (HDBR) on the circadian rhythms of the hormones and electrolytes involved in hydroelectrolytic regulation. This HDBR study was designed to mimic an actual spaceflight. Urine samples were collected at each voiding before, during and after HDBR. Urinary excretion of aldosterone, arginine vasopressin (AV-P), cyclic guanosine monophosphate (cGMP), cortisol, electrolytes (Na+ and K+) and creatinine were determined. HDBR resulted in a significant reduction of body mass (P<0.01) and of caloric intake [mean (SEM) 2,778 (37) kcal.24 h(-1) to 2,450 (36) kcal.24 h(-1), where, 1 kcal.h(-1) = 1.163 J.s(-1) P<0.01]. There was a significant increase in diastolic blood pressure [71.8 (0.7) mmHg vs 75.6 (0.91) mmHg], with no significant changes in either systolic blood pressure or heart rate. The nocturnal hormonal decrease of aldosterone was clearly evident only before and after HDBR, but the day/night difference did not appear during HDBR. The rhythm of K+ excretion was unchanged during HDBR, whereas for Na excretion, a large decrease was shown during the night as compared to the day. The circadian rhythm of cortisol. persisted. These data suggest that exposure to a 17-day HDBR could induce an exaggeration of the amplitude of the Na+ rhythm and abolition of the aldosterone rhythm. C1 Fac Med, Lab Physiol Environm, GIP Exercice, F-69373 Lyon 08, France. Fac Med, Lab Physiol Environm, EA 645, F-69373 Lyon, France. Univ Pittsburgh, Med Ctr, Western Psychiat Inst & Clin, Sleep & Chronobiol Ctr, Pittsburgh, PA 15213 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Hop Neurol, Ctr Med Nucl, Serv Radioanal, F-69394 Lyon 03, France. Ctr Natl Etud Spatiales, F-75039 Paris 01, France. RP Gharib, C (reprint author), Fac Med, Lab Physiol Environm, GIP Exercice, Lyon Grange Blanche,8 Ave Rockefeller, F-69373 Lyon 08, France. RI Custaud, Marc-Antoine/K-1376-2015 NR 26 TC 3 Z9 4 U1 0 U2 4 PU SPRINGER-VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1439-6319 J9 EUR J APPL PHYSIOL JI Eur. J. Appl. Physiol. PD JUL PY 2001 VL 85 IS 1-2 BP 74 EP 81 DI 10.1007/s004210100446 PG 8 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 457DR UT WOS:000170122300011 PM 11513324 ER PT J AU Orlandi, P Carnevale, GF Lele, SK Shariff, K AF Orlandi, P Carnevale, GF Lele, SK Shariff, K TI Thermal perturbation of trailing vortices SO EUROPEAN JOURNAL OF MECHANICS B-FLUIDS LA English DT Article; Proceedings Paper CT Euromech Colloquium 396 CY JUN 22-25, 1999 CL CORTONA, ITALY ID SHORT-WAVE INSTABILITY; 3-DIMENSIONAL INSTABILITY; STRAINED VORTICES; VORTEX PAIR; FLUID AB The possibility of diminishing the danger of trailing vortices through thermal forcing is investigated. It is shown that heating the vortices would have two beneficial effects. First, it would cause the vortices to descend more rapidly thus clearing the flight path more quickly. Second, it would cause the vortices to draw closer together, thus greatly increasing the growth rate of the short-wave instabilities that can ultimately destroy the vortices through cross-diffusion. (C) 2001 Editions scientifiques et medicales Elsevier SAS. C1 Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. Univ Roma La Sapienza, Dipartimento Meccan & Aeronaut, I-00184 Rome, Italy. Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Carnevale, GF (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, 9500 Gilman Dr, La Jolla, CA 92093 USA. OI Shariff, Karim/0000-0002-7256-2497 NR 17 TC 0 Z9 0 U1 0 U2 0 PU GAUTHIER-VILLARS/EDITIONS ELSEVIER PI PARIS PA 23 RUE LINOIS, 75015 PARIS, FRANCE SN 0997-7546 J9 EUR J MECH B-FLUID JI Eur. J. Mech. B-Fluids PD JUL-AUG PY 2001 VL 20 IS 4 BP 511 EP 524 DI 10.1016/S0997-7546(01)01131-1 PG 14 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 476MM UT WOS:000171230900005 ER PT J AU Pappa, RS Giersch, LR Quagliaroli, JM AF Pappa, RS Giersch, LR Quagliaroli, JM TI Photogrammetry of a 5m inflatable space antenna with consumer-grade digital cameras SO EXPERIMENTAL TECHNIQUES LA English DT Article C1 NASA, Langley Res Ctr, Struct Dynam Branch, Hampton, VA 23665 USA. George Washington Univ, Dept Aerosp & Mech Engn, Hampton, VA USA. Univ Connecticut, Dept Mech Engn, Storrs, CT USA. RP Pappa, RS (reprint author), NASA, Langley Res Ctr, Struct Dynam Branch, Hampton, VA 23665 USA. NR 13 TC 22 Z9 24 U1 0 U2 1 PU SOC EXPERIMENTAL MECHANICS PI BETHEL PA 7 SCHOOL STREET, BETHEL, CT 06801 USA SN 0732-8818 J9 EXP TECHNIQUES JI Exp. Tech. PD JUL-AUG PY 2001 VL 25 IS 4 BP 21 EP 29 DI 10.1111/j.1747-1567.2001.tb00028.x PG 9 WC Engineering, Mechanical; Mechanics; Materials Science, Characterization & Testing SC Engineering; Mechanics; Materials Science GA 463XX UT WOS:000170503500006 ER PT J AU Wozniak, G Balasubramaniam, R Hadland, PH Subramanian, RS AF Wozniak, G Balasubramaniam, R Hadland, PH Subramanian, RS TI Temperature fields in a liquid due to the thermocapillary motion of bubbles and drops SO EXPERIMENTS IN FLUIDS LA English DT Article ID MARANGONI NUMBER; REDUCED GRAVITY; MIGRATION; MODERATE AB Experiments were performed on the motion of isolated air bubbles and drops of Fluorinert FC-75 moving in a Dow-Coming silicone oil under the action of an applied temperature gradient in a reduced gravity environment aboard the Space Shuttle in orbit. The disturbance of the imposed temperature field due to the motion of the objects was studied optically using a shearing interferometer with a Wollaston prism and the results of aa typical bubble run were compared with theoretical predictions. Also, the liquid velocity field surrounding the bubbles and drops has been qualitatively investigated in a few runs by the observation of tracer particles dispersed in the continuous phase fluid. The measurement techniques are described, and the results for the temperature and flow fields are presented and discussed. C1 Tu Freiberg, Inst Fluidmech & Fluidenergiemaschinen, D-09596 Freiberg, Germany. NASA, Glenn Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. Clarkson Univ, Dept Chem Engn, Potsdam, NY 13699 USA. RP Wozniak, G (reprint author), Tu Freiberg, Inst Fluidmech & Fluidenergiemaschinen, Lampadiusstr 2, D-09596 Freiberg, Germany. NR 10 TC 16 Z9 19 U1 0 U2 3 PU SPRINGER-VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD JUL PY 2001 VL 31 IS 1 BP 84 EP 89 DI 10.1007/s003480000262 PG 6 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 454DC UT WOS:000169956300010 ER PT J AU Jadaan, O Nemethm, N AF Jadaan, O Nemethm, N TI Transient reliability of ceramic structures SO FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES LA English DT Article DE failure; fatigue; reliability; transient; Weibull ID PREDICTION; COMPONENTS AB Present capabilities of the NASA Ceramic Analysis and Reliability Evaluation of Structures/Life (CARES/Life) code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (SCG) (stress corrosion), and cyclic fatigue failure modes. Currently, this code has the capability to compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in SCG type failure conditions CARES/Life can handle the cases of sustained and linearly increasing time-dependent loads, whereas for cyclic fatigue applications, it can account for various types of repetitive constant amplitude loads. In real applications applied loads are rarely that simple, but rather vary with time in more complex ways such as engine start up and shut down and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and/or thermal conditions, the material properties also vary with time. The objective of this paper is to demonstrate a methodology capable of predicting the time-dependent reliability of components subjected to transient thermomechanical loads that take into account the change in material response with time. In this article, the dominant delayed failure mechanism is assumed to be SCG. This capability has been added to the NASA CARES/Life code, which has also been modified to have the ability of interfacing with commercially available finite element analysis codes executed for transient load histories. An example involving a ceramic exhaust valve subjected to combustion cycle loads is presented to demonstrate the viability of this methodology and the CARES/Life program. C1 Univ Wisconsin, Coll Engn Math & Sci, Platteville, WI 53818 USA. NASA, Glenn Res Ctr, Cleveland, OH USA. RP Jadaan, O (reprint author), Univ Wisconsin, Coll Engn Math & Sci, Platteville, WI 53818 USA. NR 19 TC 10 Z9 10 U1 1 U2 4 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 8756-758X J9 FATIGUE FRACT ENG M JI Fatigue Fract. Eng. Mater. Struct. PD JUL PY 2001 VL 24 IS 7 BP 475 EP 487 DI 10.1046/j.1460-2695.2001.00419.x PG 13 WC Engineering, Mechanical; Materials Science, Multidisciplinary SC Engineering; Materials Science GA 469CR UT WOS:000170796400004 ER PT J AU Xirouchakis, D Hirschmann, MM Simpson, JA AF Xirouchakis, D Hirschmann, MM Simpson, JA TI The effect of titanium on the silica content and on mineral-liquid partitioning of mantle-equilibrated melts SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID SOLIDUS PERIDOTITE MELTS; T PHASE-RELATIONS; COORDINATION CHEMISTRY; DEPLETED PERIDOTITE; BASALTIC LIQUIDS; ALKALI BASALTS; RIDGE BASALTS; OLIVINE; PRESSURE; GLASSES AB High pressure, high temperature phase equilibria experiments were performed to investigate the effect of TiO2 on mineral-liquid equilibria fur near natural olivine + orthopyroxene-saturated mafic liquids. At 1.2 GPa and 1360 degreesC, and at 2.8 GPa and 1530 degreesC, near-natural picritic basaltic liquids with TiO2 concentrations ranging from 0.4 to 22 wt.% were forced to be in equilibrium with olivine (ol) + orthopyroxene (opx) by adding appropriate quantities of San Carlos olivine with increasing TiO2. Titanium enrichment of the ol + opx saturated mafic liquids results in nearly pressure-independent linear decreases in SiO2 amounting to 0.60 +/- 0.04 and 0.56 +/- 0.05 wt.% SiO2 per wt.% TiO2 at 1.2 and 2.8 GPa, respectively. Olivine-liquid Fe-Mg K-D decreases at 1.2 GPa from 0.33 at 0.4 wt.% TiO2 down to 0.22 at 19 wt.% TiO2. A similar trend, shifted to slightly higher K-D values, is observed at 2.8 Gpa. With increasing TiO2, the activity coefficient of SiO2 in the liquid increases owing to association of networking-modifying cations with Ti4+. Consequently, a smaller mole fraction of SiO2, X-SiO2(Liq), is required to maintain the silica activity imposed by the coexistence of olivine and orthopyroxene. Strong association between Ti and Fe in the liquid reduces a(FeO)(Liq) and gamma (Liq)(FeO), thereby causing olivine-liquid Fe-Mg K-D to decrease. These effects are expected to result in small decreases in SiO2 and very small increases in FeO in TiO2-enriched mantle-derived sources, such as those in OIB source regions derived from small degrees of melting of peridotite at high pressure. Stronger effects on the compositions of low-degree partial melts of more titanium-enriched rocks, such as pyroxenites, may he expected. Solubility of TiO2 in olivine under magmatic conditions and at modest (1.2-2.8 GPa) pressure is near 0.2 wt.%. For TiO2, partitioning between olivine and liquid is Henrian over the range of compositions studied, indicating constant activity coefficients: for liquids between 0-20 wt.% TiO2 and for olivine between 0-0.23 wt.%. Orthopyroxene/liquid partitioning of TiO2 is variable, presumably owing to complex interactions between Al and Ti in orthopyroxene. Olivine/liquid partitioning of Al2O3 is nearly constant, but partitioning of Al2O3 between orthopyroxene and liquid is variable, owing to the aforementioned interactions between Al and Ti. Olivine/liquid and orthopyroxene/liquid partitioning of CaO diminish with increasing TiO2, suggesting stabilization of CaO in silicate liquids by formation of CaO-TiO2 complexes. At 1.2 GPa, saturation in aluminous armalcolite is found for liquids at 19.2 wt.% TiO2, in contrast, at 2.8 GPa, Ti-rich oxide saturation is not encountered for Liquids with as much as 21.8 wt.% TiO2. The large TiO2 enrichment in the liquid required for oxide saturation in the presence of olivine + orthopyroxene at these pressures suggests that near-solidus liquids generated by melting of Ti-rich oxide-bearing peridotite would have greater than or equal to 20 wt.% TiO2. The general absence of such Ti-rich primitive terrestrial lavas either precludes magmas from such source assemblages or indicates that they are strongly diluted by other magmas. Our results also suggest that armalcolite may be a significant phase in the Ti-enriched portions of the lunar mantle. Copyright (C) 2000 Elsevier Science Ltd. C1 Univ Minnesota, Dept Geol & Geophys, Minneapolis, MN 55455 USA. RP Xirouchakis, D (reprint author), NASA, Lyndon B Johnson Space Ctr, Div Earth Sci & Solar Syst Explorat, Mail Code SN2, Houston, TX 77058 USA. RI Hirschmann, marc/B-9455-2016 OI Hirschmann, marc/0000-0003-1213-6645 NR 97 TC 56 Z9 56 U1 0 U2 5 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 JUL PY 2001 VL 65 IS 14 BP 2201 EP 2217 DI 10.1016/S0016-7037(00)00549-4 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 451ZM UT WOS:000169832700001 ER PT J AU Chao, BF O'Connor, WP Zeng, D Au, AY AF Chao, BF O'Connor, WP Zeng, D Au, AY TI Reply to comment by C. Wunsch on 'Wind stress forcing of the North Sea "pole tide"' SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Letter C1 NASA, Space Geodesy Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, NOS Coast Survey Dev Lab, Silver Spring, MD 20910 USA. Chinese Acad Sci, Shanghai Astron Observ, Shanghai 200030, Peoples R China. Raytheon ITSS, Lanham, MD 20706 USA. RP Chao, BF (reprint author), NASA, Space Geodesy Branch, Goddard Space Flight Ctr, Code 926, Greenbelt, MD 20771 USA. RI Chao, Benjamin Fong/N-6156-2013 NR 5 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 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD JUL PY 2001 VL 146 IS 1 BP 266 EP 266 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 447HM UT WOS:000169565900021 ER PT J AU Brittnacher, M Kang, J Parks, G Elsen, R Germany, G Spann, J Fox, N Puetter, RC Yahil, A AF Brittnacher, M Kang, J Parks, G Elsen, R Germany, G Spann, J Fox, N Puetter, RC Yahil, A TI Far-ultraviolet observations of the neutral comae of Comet Hale-Bopp (C/1995 01) near perihelion SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TERRESTRIAL PHYSICS MISSION; SPECTROSCOPY; NUCLEUS; CARBON; IMAGER; O1 AB The Ultraviolet Imager on the Polar spacecraft observed the neutral oxygen and carbon comae of Comet Hale-Bopp (C/1995 01) at far-ultraviolet wavelengths near perihelion on March 31 and April 2, 1997. The OI (1304) coma was circularly symmetric with a diameter of about 5 million km. The coma was smaller in the longer wavelength (1400-1600 Angstrom and 1600-1800 Angstrom) bands, which is probably due to fluorescence of neutral carbon at 1561 Angstrom and 1657 Angstrom. The production rate for O calculated from the observed OI (1304) flux was (9.8 +/- 2.5) x 10(30). Using this value the estimated production rate for OH was (8.9 +/-2.5) x 10(30) and for H2O was (1.0 +/- 0.3) x 10(31). C1 Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 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 Brittnacher, M (reprint author), Univ Washington, Geophys Program, Box 351650, Seattle, WA 98195 USA. RI Fox, Nicola/P-6692-2016 OI Fox, Nicola/0000-0003-3411-4228 NR 19 TC 3 Z9 3 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 JUL 1 PY 2001 VL 28 IS 13 BP 2561 EP 2564 DI 10.1029/2000GL012567 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 446BU UT WOS:000169493700020 ER PT J AU Richardson, IG Cliver, EW Cane, HV AF Richardson, IG Cliver, EW Cane, HV TI Sources of geomagnetic storms for solar minimum and maximum conditions during 1972-2000 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CORONAL MASS EJECTIONS; CYCLE; WIND AB We determine the solar wind structures (coronal mass ejection (CME) - related, corotating high-speed streams, and slow solar wind) driving geomagnetic storms of various strength over nearly three solar cycles (1972-2000). The most intense storms (defined by Kp) at both solar minimum and solar maximum are almost all (similar to 97%) generated by transient structures associated with CMEs. Weaker storms are preferentially associated with streams at solar minimum and with CMEs at solar maximum, reflecting the change in the structure of the solar wind between these phases of the solar cycle. Slow solar wind generates a small fraction of the weaker storms at solar minimum and maximum. We also determine the size distributions of Kp for each solar wind component. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. USAF, Space Vehicles Directorate, Hanscom AFB, MA 01731 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Tasmania, Sch Math & Phys, Hobart, Tas, Australia. RP Richardson, IG (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. OI Richardson, Ian/0000-0002-3855-3634 NR 14 TC 116 Z9 118 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 JUL 1 PY 2001 VL 28 IS 13 BP 2569 EP 2572 DI 10.1029/2001GL013052 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 446BU UT WOS:000169493700022 ER PT J AU Manney, GL Sabutis, JL Swinbank, R AF Manney, GL Sabutis, JL Swinbank, R TI A unique stratospheric warming event in November 2000 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WINTER STRATOSPHERE; INTERANNUAL VARIABILITY AB Stratospheric sudden warmings frequently influence temperatures and circulation in the Arctic winter stratosphere. A unique stratospheric warming in Nov 2000 was characterized by wave 1 amplification with little phase tilt with height, a large displacement of the vortex off the pole, a warm pool at high latitudes, and a modest polar temperature increase, all of which are characteristic of early winter "Canadian" warmings. Unlike most Canadian warmings, the Nov 2000 event led to a strong zonal mean wind reversal for similar to9 days in the mid and lower stratosphere. Wind reversals during Canadian warmings occurred only three times before in the last 23 years. Midstratospheric minimum temperatures continued to decrease during the warming, but lower stratospheric temperatures increased substantially. The Nov 2000 warming was unique in its timing, intensity and duration, and in its impact on the development of the polar vortex, especially in the lower stratosphere. C1 New Mexico Highlands Univ, Dept Phys, Las Vegas, NM 87701 USA. Meteorol Off, Bracknell RG12 2SZ, Berks, England. CALTECH, Jet Propuls Lab, Pasadena, CA 91125 USA. RP Manney, GL (reprint author), New Mexico Highlands Univ, Dept Phys, Las Vegas, NM 87701 USA. NR 14 TC 8 Z9 10 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 JUL 1 PY 2001 VL 28 IS 13 BP 2629 EP 2632 DI 10.1029/2001GL012973 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 446BU UT WOS:000169493700037 ER PT J AU Young, RE Magalhaes, JA AF Young, RE Magalhaes, JA TI In memoriam - Alvin Seiff (1922-2000) SO ICARUS LA English DT Biographical-Item C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Young, RE (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 1 Z9 1 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 JUL PY 2001 VL 152 IS 1 BP 1 EP 3 DI 10.1006/icar.2001.6642 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 451WK UT WOS:000169825200001 ER PT J AU Espresate, J Lissauer, JJ AF Espresate, J Lissauer, JJ TI Resonant satellite torques on low optical depth particulate disks - II. Numerical simulations SO ICARUS LA English DT Article DE planetary rings; resonances; planetesimals ID RINGS AB This paper presents the results of numerical simulations of collisionless and collisional annuli of test particles centered at the 2: 1 inner Lindblad resonance of a small satellite. We discuss the role of the physical width W ' (around the resonance) in the value of the initial transient torque for both collisionless and collisional systems. We demonstrate analytically as well as numerically that the torque over the collisionless particulate annuli (before the problem becomes nonlinear) is a function that depends exclusively on the product W 't ', where t ' is the time. For the collisional case, the secular torque after the first transient depends on both the mean time between collisions, t ' (coll), and the physical width of the annulus. Under certain restrictions on the value of t ' (coll), the secular torque for t ' > t ' (coll) depends exclusively on the product W 't ' (coll), in the same form as for the collisionless case. (C) 2001 Academic Press. C1 Inst Astron, Mexico City 04510, DF, Mexico. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Espresate, J (reprint author), Inst Astron, Ciudad Univ, Mexico City 04510, DF, Mexico. NR 12 TC 3 Z9 3 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 JUL PY 2001 VL 152 IS 1 BP 29 EP 47 DI 10.1006/icar.2000.6585 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 451WK UT WOS:000169825200003 ER PT J AU Showman, AP AF Showman, AP TI Hydrogen halides on Jupiter and Saturn SO ICARUS LA English DT Article DE atmospheric abundances; atmospheric composition; Jupiter; Saturn; spectroscopy ID AMMONIUM-NITRATE AEROSOLS; HOMOGENEOUS NUCLEATION; CLOUD STRUCTURE; GIANT PLANETS; JOVIAN ATMOSPHERE; VAPOR-PHASE; PHOTOCHEMISTRY; CHLORIDE; IONOSPHERE; CHEMISTRY AB The quest to detect gaseous HCl, HBr, and I-IF in the atmospheres of Jupiter and Saturn has led to a tentative detection of 1 ppb HCl near Saturn's cloud deck. The detection is puzzling because, while these hydrogen halides may be present several scale heights below the clouds, they are expected to react with ammonia to form solid ammonium halide salts in the upper troposphere. I show that the loss timescale for condensation of gaseous hydrogen halides onto particles is similar to 10(3)-10(5) s for realistic cloud densities and particle sizes, which is much less than the similar to 10(8) s residence time of upper tropospheric air. The hydrogen halides can only survive transport up to the cloud layer if less than 1 in 10(6) of their collisions with particle surfaces leads to condensation, which is unlikely. Even in the absence of foreign particles, homogeneous nucleation would probably prevent supersaturations in excess of a few hundred, which is similar to 10(20)-10(40) times too low to explain the observation. These calculations therefore suggest that hydrogen halides cannot exist at part-per-billion levels in the upper troposphere. The interplanetary source of halogens is also too low to produce detectable quantities of hydrogen halides except perhaps at pressures less than 1 mbar. A possible detection of chlorine by the Galileo probe at pressures exceeding 9 bars on Jupiter may be consistent with the equilibrium abundance of gaseous HCl or NH4Cl. (C) 2001 Academic Press. C1 NASA, Ames Res Ctr, Natl Res Council, Moffett Field, CA 94035 USA. RP Showman, AP (reprint author), NASA, Ames Res Ctr, Natl Res Council, Mail Stop 245-3, Moffett Field, CA 94035 USA. NR 77 TC 9 Z9 9 U1 0 U2 3 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 JUL PY 2001 VL 152 IS 1 BP 140 EP 150 DI 10.1006/icar.2001.6614 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 451WK UT WOS:000169825200012 ER PT J AU Ajello, JM Shemansky, DE Pryor, WR Stewart, AI Simmons, KE Majeed, T Waite, JH Gladstone, GR Grodent, D AF Ajello, JM Shemansky, DE Pryor, WR Stewart, AI Simmons, KE Majeed, T Waite, JH Gladstone, GR Grodent, D TI Spectroscopic evidence for high-altitude Aurora at Jupiter from Galileo Extreme Ultraviolet Spectrometer and Hopkins Ultraviolet Telescope observations SO ICARUS LA English DT Article DE Jupiter; aurorae; spectroscopy ID HUBBLE-SPACE-TELESCOPE; ELECTRON-IMPACT EXCITATION; JOVIAN AURORA; MOLECULAR-HYDROGEN; UPPER-ATMOSPHERE; ION PRECIPITATION; CROSS-SECTIONS; BAND SYSTEMS; UV AURORA; H-2 LYMAN AB The Galileo Extreme Ultraviolet Spectrometer (EUVS) and the Hopkins Ultraviolet Telescope (HUT) acquired UV spectra of Jupiter Aurora in the period from 1995 through 1997, The EUVS spectra spanned the wavelength range 540-1280 Angstrom and the HUT spectra measured the extreme ultraviolet and far ultraviolet (EUV + FUV) wavelength range 830-1850 Angstrom. Both sets of spectra present evidence of high-altitude, optically thin H-2 band emissions from the exobase region, The analysis of the UV spectra with a two-stream electron transport model and a jovian model auroral atmosphere indicates that the primary electron flux is composed of both soft and hard electrons with characteristic energies in the soft electron energy range of 20-200 eV and the hard electron range of 5-100 keV, The soft electron flux causes enhanced EUV emission intensities below 1100 Angstrom. The soft electron flux may explain the high temperature of the upper atmosphere above the homopause as measured from Il: rovibrational temperatures in the IR. For the deep aurora, a high primary characteristic energy above 5 keV is known to be present. The Galileo Energetic Particle Detector (EPD) has measured the electron distribution functions for energies above 15 keV in the middle magnetosphere. The high-energy distribution functions can be modeled by a combination of Maxwellian and kappa distributions. However, the EUV (800-1200 Angstrom) portion of the HUT spectrum cannot be modeled with a single distribution of hard electrons as was possible in the past for the FUV (1200-1650 Angstrom) spectrum measured by itself, The combination of EUV and FUV spectral observations by HUT serves to identify the amount of soft electron flux relative to the hard primary flux required to produce the high-altitude aurora in the neighborhood of the exobase, (C) tool academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ So Calif, Los Angeles, CA 90089 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. SW Res Inst, San Antonio, TX 78228 USA. Univ Liege, Lab Phys Atmospher & Planetaire, Liege, Belgium. RP Ajello, JM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 60 TC 19 Z9 19 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 JUL PY 2001 VL 152 IS 1 BP 151 EP 171 DI 10.1006/icar.2001.6619 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 451WK UT WOS:000169825200013 ER PT J AU Hoffman, JP Steffes, PG DeBoer, DR AF Hoffman, JP Steffes, PG DeBoer, DR TI Laboratory measurements of the microwave opacity of phosphine: Opacity formalism and application to the atmospheres of the outer planets SO ICARUS LA English DT Article ID NEPTUNE; SATURN; AMMONIA; SUBMILLIMETER; MILLIMETER; URANUS; LINES; H2S; PH3 AB Preliminary room-temperature measurements of the microwave opacity of phosphine (Hoffman and Steffes 1999). Icarus 140, 235-238, suggested that phosphine (PH3) may contribute significantly to the microwave emission spectrum of Neptune, and to the centimeter-wavelength opacity measured by the Voyager 2 spacecraft at Neptune and Saturn. As a result, new laboratory measurements of the microwave opacity of PH3 in an H-2/He atmosphere have been conducted at frequencies (wavelengths) of 1.5 GHz (20 cm), 2.2 GHz (13.3 cm) 8.3 GHz (3.6 cm), 13.3, GHz (2.3 cm), 21.6 GHz (1.4 cm), and 27 GHz (1.1 cm) over a range of temperatures (175-298 K) and pressures (1-6 bars). A measurement-based centimeter-wavelength opacity formalism for phosphine has been developed and provides an order of magnitude improvement over previous models. The resulting model is applied to results from the Voyager 2 radio science experiments at Saturn and Neptune and to disk-averaged, centimeter-wavelength observations of Neptune and Saturn. Future uses will include application to spatially resolved microwave images of the outer planets from radio telescopes and spacecraft radiometry and to future radio occultation measurements, including Cassini-Saturn. (C) 2001 Academic Press. C1 Georgia Inst Technol, Sch Elect & Comp Engn, Atlanta, GA 30332 USA. SETI Inst, Mt View, CA 94043 USA. RP Hoffman, JP (reprint author), Jet Prop Lab, M-S 300-241,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 35 TC 11 Z9 11 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 JUL PY 2001 VL 152 IS 1 BP 172 EP 184 DI 10.1006/icar.2001.6622 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 451WK UT WOS:000169825200014 ER PT J AU Ostro, SJ Nolan, MC Margot, JL Magri, C Harris, AW Giorgini, JD AF Ostro, SJ Nolan, MC Margot, JL Magri, C Harris, AW Giorgini, JD TI Radar observations of asteroid 288 Glauke SO ICARUS LA English DT Article DE asteroids; radar ID PHYSICAL MODEL; SPIN-STATE; SHAPE; IMAGES; LIGHTCURVE; TOUTATIS; ROTATION AB The combination of Arecibo radar echoes and available vis/IR data indicates that 288 Glauke is an S-class object slightly smaller and less elongated than 243 Ida, with radar surface properties near the average for S asteroids in the main belt, in an extraordinarily slow (similar to 50-d) rotation state. (C) 2001 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Astron & Ionosphere Ctr, Arecibo Observ, Arecibo, PR 00612 USA. Univ Maine, Farmington, ME 04938 USA. RP Ostro, SJ (reprint author), CALTECH, Jet Prop Lab, 300-233, Pasadena, CA 91109 USA. RI Margot, Jean-Luc/A-6154-2012; Nolan, Michael/H-4980-2012 OI Margot, Jean-Luc/0000-0001-9798-1797; Nolan, Michael/0000-0001-8316-0680 NR 25 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 0019-1035 J9 ICARUS JI Icarus PD JUL PY 2001 VL 152 IS 1 BP 201 EP 204 DI 10.1006/icar.2001.6636 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 451WK UT WOS:000169825200016 ER PT J AU Ma, ZQ Mohammadi, S Lu, LH Bhattacharya, P Katehi, LPB Alterovitz, SA Ponchak, GE AF Ma, ZQ Mohammadi, S Lu, LH Bhattacharya, P Katehi, LPB Alterovitz, SA Ponchak, GE TI An X-band high-power amplifier using SiGe/Si HBT and lumped passive components SO IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS LA English DT Article DE lumped passives; MMIC power amplifier; SiGe/Si HBT AB We report the design and fabrication of a compact microwave monolithic integrated circuit (MMIC) amplifier, which demonstrates high output power at X-Band, A single-stage power amplifier is demonstrated, with a double-mesa type SiGe/Si HBT as the active device and spiral inductors and MIM capacitors as lumped passive components. At 8.4 GHz, a linear gain of 8.7 dB, an output power at peak efficiency of 23 dBm, and a saturated output power P-sat of 25 dBm, are measured. To our knowledge, this is the first MMIC X-Band power amplifier using SiGe/Si HBTs. C1 Univ Michigan, Dept Elect Engn & Comp Sci, Ann Arbor, MI 48109 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Ma, ZQ (reprint author), Univ Michigan, Dept Elect Engn & Comp Sci, Ann Arbor, MI 48109 USA. NR 6 TC 6 Z9 7 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 1531-1309 J9 IEEE MICROW WIREL CO JI IEEE Microw. Wirel. Compon. Lett. PD JUL PY 2001 VL 11 IS 7 BP 287 EP 289 DI 10.1109/7260.933773 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 452TE UT WOS:000169874400002 ER PT J AU Caplin, J Ray, A Joshi, SM AF Caplin, J Ray, A Joshi, SM TI Damage-mitigating control of aircraft for enhanced structural durability SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Article ID ROBUST MULTIVARIABLE CONTROL; LIFE-EXTENDING CONTROL; GUST LOAD ALLEVIATION; ROCKET ENGINE; SYSTEMS; FLIGHT; ROTORCRAFT; MODEL AB The concept and a design methodology for robust damage-mitigating control (DMC) of aircraft is presented. The goal of DMC is to simultaneously achieve high performance and structural durability and the design procedure is based on damage mitigation at critical structures and retention of the flight performance. An aeroelastic model of the wings has been formulated and is incorporated into a nonlinear rigid-body model of aircraft flight-dynamics. Robust damage-mitigating controllers are then designed using the H-infinity-based structured singular value (mu) synthesis method based on a linearized model of the aircraft. In addition to penalizing the error between the ideal performance and the actual performance of the aircraft, frequency-dependent weights are placed on the strain amplitude at the root of each wing. Using each controller in turn, the control system is put through an identical sequence of maneuvers, and the resulting (varying amplitude cyclic) stress profiles are analyzed using a fatigue crack growth model that incorporates the effects of varying-amplitude cyclic loading. Comparisons are made to determine the impact of different strain-amplitude weights on the resulting flight performance and fatigue crack damage in the wings. The results of simulation experiments show significant savings in fatigue life of the wings while retaining the dynamic performance of the aircraft. C1 Penn State Univ, Dept Mech Engn, University Pk, PA 16802 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Caplin, J (reprint author), Penn State Univ, Dept Mech Engn, University Pk, PA 16802 USA. NR 34 TC 4 Z9 4 U1 1 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9251 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD JUL PY 2001 VL 37 IS 3 BP 849 EP 862 DI 10.1109/7.953241 PG 14 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 477VQ UT WOS:000171305300007 ER PT J AU Berner, JB Layland, JM Kinman, PW AF Berner, JB Layland, JM Kinman, PW TI Flexible loop filter design for spacecraft phase-locked receivers SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Article AB A flexible loop filter design for spacecraft phase-locked receivers Is proposed. The loop filter is implemented as digital hardware with coefficients that are set by registers. Either a perfect or an imperfect integrating loop filter can be effected. This flexibility is important since no one type of loop filter is preferred for all circumstances. An imperfect integrator is preferred when, as is often the case for spacecraft receivers, it is important to minimize the best-lock frequency drift of an idling loop. A perfect integrator is preferred when the tracking performance of the loop is the most important consideration. C1 Jet Prop Lab, Pasadena, CA 91109 USA. Case Western Reserve Univ, EECS Dept, Cleveland, OH 44106 USA. RP Berner, JB (reprint author), Jet Prop Lab, MS 238-737,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 2 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 0018-9251 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD JUL PY 2001 VL 37 IS 3 BP 957 EP 964 DI 10.1109/7.953249 PG 8 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 477VQ UT WOS:000171305300015 ER PT J AU Greenhall, CA AF Greenhall, CA TI Comments on a study of drift in cesium frequency standards SO IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL LA English DT Letter AB This letter comments on a recent study of the drift rate of 115 cesium standards. The conclusion here is that, no aging effect is visible in the results of the study. C1 CALTECH, Jet Propuls Lab, CIT, Pasadena, CA 91109 USA. RP Greenhall, CA (reprint author), CALTECH, Jet Propuls Lab, CIT, Pasadena, CA 91109 USA. NR 6 TC 1 Z9 1 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 0885-3010 J9 IEEE T ULTRASON FERR JI IEEE Trans. Ultrason. Ferroelectr. Freq. Control PD JUL PY 2001 VL 48 IS 4 BP 860 EP 860 DI 10.1109/58.935700 PG 1 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 452RX UT WOS:000169873500002 PM 11477775 ER PT J AU Wu, H Durante, M Lucas, JN AF Wu, H Durante, M Lucas, JN TI Relationship between radiation-induced aberrations in individual chromosomes and their DNA content: effects of interaction distance SO INTERNATIONAL JOURNAL OF RADIATION BIOLOGY LA English DT Article ID IN-SITU HYBRIDIZATION; INDUCED STRUCTURAL-ABERRATIONS; IONIZING-RADIATION; INTERPHASE; FREQUENCY; INVOLVEMENT; LYMPHOCYTES; EXPOSURE; GEOMETRY; DOMAINS AB Purpose: To study the effect of the interaction distance on the frequency of inter- and intrachromosome exchanges in individual chromosomes with respect to their DNA content. Assumptions: Chromosome exchanges are formed by misrejoining of tw DNA double-strand breaks (DSB) induced within an interaction distance, d. It is assumed that chromosomes in G(o)/G(1) phase of the cell cycle occupy a spherical domain in a cell nucleus, with no spatial overlap between individual chromosome domains. Results: Formulae are derived for the probability of formation of inter-, as well as intra-, chromosome exchanges relating to the DNA content of the chromosome for a given interaction distance. For interaction distances <1 m, the relative frequency of interchromosome exchanges predicted by the present model is similar to that by Cigarran et al. (1998) based of the assumption that the probability of interchromosome exchanges is proportional to the 'surface area' of the chromosome territory. The 'surface area' assumption is shown to be a limiting case of d-->0 in the present model. The present model also predicts that the probability of intrachromosome exchanges occurring in individual chromosomes is proportional to their DNA content with correction terms. Conclusion: When the interaction distance is small, the 'surface area' distribution for chromosome participation in interchromosome exchanges has been expected. However, the present model shows that for the interaction distance as large as 1 mum, the predicted probability of interchromosome exchange formation is still close to the surface area distribution. Therefore, this distribution does not necessarily rule out the formation of complex chromosomal aberrations by long-range misrejoining of DSB. C1 NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Kelsey Seybold Clin, Houston, TX 77058 USA. Univ Naples, Dept Phys, Naples, Italy. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. RP Wu, H (reprint author), NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Mail Code SD23, Houston, TX 77058 USA. RI Durante, Marco/K-1315-2014; OI Durante, Marco/0000-0002-4615-553X NR 23 TC 14 Z9 14 U1 1 U2 3 PU TAYLOR & FRANCIS LTD PI LONDON PA 11 NEW FETTER LANE, LONDON EC4P 4EE, ENGLAND SN 0955-3002 J9 INT J RADIAT BIOL JI Int. J. Radiat. Biol. PD JUL PY 2001 VL 77 IS 7 BP 781 EP 786 PG 6 WC Biology; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging GA 450PE UT WOS:000169751700003 PM 11454278 ER PT J AU Mital, SK Murthy, PLN Chamis, CC AF Mital, SK Murthy, PLN Chamis, CC TI Simplified micromechanics of plain weave composites SO JOURNAL OF ADVANCED MATERIALS LA English DT Article AB A micromechanics based methodology to simulate the complete hygro-thermomechanical behavior of plain weave composites is developed This methodology is based on micromechanics and the classical laminate theory It predicts a complete set of thermal, hygral and mechanical properties of plain woven composites, generates necessary data for use in a finite element structural analysis, and predicts stresses from laminate to the constituent level. This methodology is used in conjunction with a composite mechanics code to analyze and predict the properties/response of a generic graphite/epoxy plain weave textile composite and a plain weave ceramic matrix composite. The fiber architecture, including the fiber waviness and fiber end distributions through the thickness, is properly accounted. Predicted results compare reasonably well with those from detailed three-dimensional finite element analyses as well as available experimental data. C1 Univ Toledo, Toledo, OH 43606 USA. NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. RP Mital, SK (reprint author), Univ Toledo, 2801 W Bancroft St, Toledo, OH 43606 USA. NR 13 TC 2 Z9 2 U1 2 U2 6 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER-COVINA JI J. Adv. Mater. PD JUL PY 2001 VL 33 IS 3 BP 10 EP 17 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA 509KC UT WOS:000173146100003 ER PT J AU Hou, TH Grimsley, BW Peterson, KE AF Hou, TH Grimsley, BW Peterson, KE TI Processability of B-Staged IM7/PETI composites SO JOURNAL OF ADVANCED MATERIALS LA English DT Article ID POLYIMIDE COMPOSITES AB The fabrication of composites from polyimides that involve condensation reactions often requires, the depletion of volatiles (solvent and reaction by-products) prior to consolidation in order to achieve a void-free laminate. However volatile removal during the B-stage period involves imidization that causes resin viscosity to increase and the composite processability to suffer The residual processability becomes a serious issue, especially in the fabrication of large structural parts using an autoclave where temperature non-uniformity is commonly experienced. In this study, the residual processability of B-staged IM7/PETI (phenylethynyl terminated imide) prepreg was characterized rising the Parallel-Plate Plastometer (PPP). Prepregs were B-staged at temperatures between 225 and 300degreesC with duration times between 0.5 and 4 hrs. The residual processability was defined by the percent deformation of the test specimen by the PPP. Significant reductions in the percent deformation were measured for specimens B-staged at 300degreesC for duration times longer than two hrs. B-staged specimens with poorer residual processability were also shown to exhibit lower densities and higher void contents. Because of the inherent limitation on specimen sizes, the PPP measurements were shown to over-estimate the residual processability of the B-staged prepregs. In conjunction with the PPP experiments, rheological measurements were also conducted. Different rheological behaviors were obtained and interpreted with the aid of thermal analyses, which revealed the crystallization behavior of PETI prepregs under different B-stage conditions and its effect on the residual processability. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Boeing Commercial Airplane Grp, Seattle, WA USA. RP Hou, TH (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 11 TC 0 Z9 0 U1 0 U2 1 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER-COVINA JI J. Adv. Mater. PD JUL PY 2001 VL 33 IS 3 BP 52 EP 60 PG 9 WC Materials Science, Multidisciplinary SC Materials Science GA 509KC UT WOS:000173146100009 ER PT J AU Burner, AW Liu, TS AF Burner, AW Liu, TS TI Videogrammetric model deformation measurement technique SO JOURNAL OF AIRCRAFT LA English DT Article ID CALIBRATION; ACCURACY AB The theory, methods, and applications of the videogrammetric model deformation (VMD) measurement technique used at NASA for wind-tunnel testing are presented. The VMD technique, based on nontopographic photogrammetry, can determine static and dynamic aeroelastic deformation and attitude of a wind-tunnel model. Hardware of the system includes a video-rate charge-coupled device camera, a computer with an image acquisition frame grabber board, illumination lights, and retroreflective or painted targets on a wind-tunnel model. Custom software includes routines for image acquisition, target-tracking/identification, target centroid calculation, camera calibration, and deformation calculations. Applications of the VMD technique at five large NASA wind tunnels are discussed. C1 NASA, Langley Res Ctr, Instrumentat Syst Dev Branch, Hampton, VA 23681 USA. RP Burner, AW (reprint author), NASA, Langley Res Ctr, Instrumentat Syst Dev Branch, MS 236, Hampton, VA 23681 USA. NR 32 TC 33 Z9 40 U1 1 U2 4 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 JUL-AUG PY 2001 VL 38 IS 4 BP 745 EP 754 DI 10.2514/2.2826 PG 10 WC Engineering, Aerospace SC Engineering GA 461AX UT WOS:000170343700019 ER PT J AU Sanghadasa, M Shin, IS Clark, RD Guo, H Penn, BG AF Sanghadasa, M Shin, IS Clark, RD Guo, H Penn, BG TI Optical limiting behavior of octa-decyloxy metallo-phthalocyanines SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID THIN-FILMS; ABSORPTION; REFRACTION AB One of the key issues involved in the development of passive optical power limiters is the search for appropriate materials that show effective reverse saturable absorption. Metallo-phthalocyanines seem to be good candidates for such applications because of their high optical nonlinearity and their unique electronic absorption characteristics. A series of 1,4,8,11,15,18,22,25-octa-decyloxy metallo-phthalocyanines containing palladium, nickel, cobalt, copper, and zinc as central metal atoms were characterized for their nonlinear absorptive properties to evaluate their suitability to function as reverse saturable absorbers. Nonlinear transmission measurements were analyzed in terms of a five-state model and a simple model based on the effective excited-state absorption cross sections without ascribing their origin to the states involved. Optical limiting thresholds were also estimated and compared with the absorption cross sections. (C) 2001 American Institute of Physics. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. New Mexico Highlands Univ, Dept Phys Sci, Las Vegas, NV USA. NASA, George C Marshall Space Flight Ctr, Micrograv Sci & Applicat Dept, Huntsville, AL 35812 USA. RP Sanghadasa, M (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 16 TC 21 Z9 22 U1 0 U2 2 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUL 1 PY 2001 VL 90 IS 1 BP 31 EP 37 DI 10.1063/1.1371280 PG 7 WC Physics, Applied SC Physics GA 443UY UT WOS:000169361100003 ER PT J AU Ning, CZ Goorjian, P AF Ning, CZ Goorjian, P TI Ultrafast directional beam switching in coupled vertical-cavity surface-emitting lasers SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID SEMICONDUCTOR-LASERS; PHASED-ARRAY AB We propose a strategy to performing ultrafast directional beam switching using two coupled vertical-cavity surface-emitting lasers (VCSELs). The proposed strategy is demonstrated for two VCSELs of 5.6 mum in diameter placed about 1 mum apart from the edges, showing a switching speed of 42 GHz with a maximum far-field angle span of about 10 degrees. (C) 2001 American Institute of Physics. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ning, CZ (reprint author), NASA, Ames Res Ctr, Mail Stop T27A-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 10 TC 5 Z9 5 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUL 1 PY 2001 VL 90 IS 1 BP 497 EP 499 DI 10.1063/1.1377298 PG 3 WC Physics, Applied SC Physics GA 443UY UT WOS:000169361100078 ER PT J AU Smorawinski, J Nazar, K Kaciuba-Uscilko, H Kaminska, E Cybulski, G Kodrzycka, A Bicz, B Greenleaf, JE AF Smorawinski, J Nazar, K Kaciuba-Uscilko, H Kaminska, E Cybulski, G Kodrzycka, A Bicz, B Greenleaf, JE TI Effects of 3-day bed rest on physiological responses to graded exercise in athletes and sedentary men SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE exercise tolerance; blood lactate threshold; catecholamines; hormones; plasma renin activity ID HEAD-DOWN TILT; SIMULATED MICROGRAVITY; PLASMA-CATECHOLAMINE; GROWTH-HORMONE; OXYGEN-UPTAKE; HUMANS; THRESHOLD; ENDURANCE; BEDREST AB To test the hypotheses that short-term bed-rest (BR) deconditioning influences metabolic, cardiorespiratory, and neurohormonal responses to exercise and that these effects depend on the subjects' training status, 12 sedentary men and 10 endurance- and 10 strength-trained athletes were submitted to 3-day BR. Before and after BR they performed incremental exercise test until volitional exhaustion. Respiratory gas exchange and heart rate (HR) were recorded continuously, and stroke volume (SV) was measured at submaximal loads. Blood was taken for lactate concentration ([LA]), epinephrine concentration ([Epi]), norepinephrine concentration ([NE]), plasma renin activity (PRA), human growth hormone concentration ([hGH]), testosterone, and cortisol determination. Reduction of peak oxygen uptake ((V) over dot O-2 peak) after BR was greater in the endurance athletes than in the remaining groups (17 vs. 10%). Decrements in (V) over dot O-2 peak correlated positively with the initial values (r = 0.73, P < 0.001). Resting and exercise respiratory exchange ratios were increased in athletes. Cardiac output was unchanged by BR in all groups, but exercise HR was increased and SV diminished in the sedentary subjects. The submaximal [LA] and [LA] thresholds were decreased in the endurance athletes from 71 to 60% (V) over dot O-2 peak (P < 0.001); they also had an earlier increase in [NE], an attenuated increase in [hGH], and accentuated PRA and cortisol elevations during exercise. These effects were insignificant in the remaining subjects. In conclusion, reduction of exercise performance and modifications in neurohormonal response to exercise after BR depend on the previous level and mode of physical training, being the most pronounced in the endurance athletes. C1 Polish Acad Sci, Med Res Ctr, Dept Appl Physiol, PL-02106 Warsaw, Poland. Acad Phys Educ, Dept Sport Med, PL-61871 Poznan, Poland. NASA, Ames Res Ctr, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. RP Kaciuba-Uscilko, H (reprint author), Polish Acad Sci, Med Res Ctr, Dept Appl Physiol, 5 Pawinskiego Str, PL-02106 Warsaw, Poland. NR 36 TC 32 Z9 33 U1 1 U2 15 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD JUL PY 2001 VL 91 IS 1 BP 249 EP 257 PG 9 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 445RT UT WOS:000169471700032 PM 11408437 ER PT J AU Ray, RD AF Ray, RD TI Comparisons of global analyses and station observations of the S-2 barometric tide SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article DE atmospheric tides; barometric tides; S-2; tides ID PRESSURE AB The semidiurnal atmospheric pressure oscillation - the S-2(p) tide - is deduced from Mo global meteorological reanalysis products: the NCEP/NCAR and GEOS-1 products. S-2 is deduced from the NCEP surface pressure product by using a special temporal interpolation devised by Van den Dool et al. The tide is deduced from the GEOS-1 product by directly analyzing six years of 3-h surface pressure fields. Two extensive collections of "ground-truth" stations are used to test the results; these are stations where the tides have been previously estimated from long time series of pressure measurements. Neither reanalysis product gives a completely adequate description of the semidiurnal tide. A new spherical harmonic expansion of St is developed directly from one of the station datasets. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Ray, RD (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Code 926, Greenbelt, MD 20771 USA. RI Ray, Richard/D-1034-2012 NR 24 TC 17 Z9 18 U1 0 U2 3 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 JUL PY 2001 VL 63 IS 10 BP 1085 EP 1097 DI 10.1016/S1364-6826(01)00018-9 PG 13 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 448VZ UT WOS:000169651800011 ER PT J AU Lansford, R Bearman, G Fraser, SE AF Lansford, R Bearman, G Fraser, SE TI Resolution of multiple green fluorescent protein color variants and dyes using two-photon microscopy and imaging spectroscopy SO JOURNAL OF BIOMEDICAL OPTICS LA English DT Article DE microscopy; tissues; tunable filters ID CELLS AB The imaging of living cells and tissues using laser-scanning microscopy is offering dramatic insights into the spatial and temporal controls of biological processes. The availability of genetically encoded labels such as green fluorescent protein (GFP) offers unique opportunities by which to trace cell movements, cell signaling or gene expression dynamically in developing embryos. Two-photon laser scanning microscopy (TPLSM) is ideally suited to imaging cells in vivo due to its deeper tissue penetration and reduced phototoxicity; however, in TPLSM the excitation and emission spectra of GFP and its color variants [e.g., CyanFP (CFP); yellowFP (YFP)] are insufficiently distinct to be uniquely imaged by conventional means. To surmount such difficulties, we have combined the technologies of TPLSM and imaging spectroscopy to unambiguously identify CFP, GFP, YFP, and redFP (RFP) as well as conventional dyes, and have tested the approach in cell lines. In our approach, a liquid crystal tunable filter was used to collect the emission spectrum of each pixel within the TPLSM image. Based on the fluorescent emission spectra, supervised classification and linear unmixing analysis algorithms were used to identify the nature and relative amounts of the fluorescent proteins expressed in the cells. In a most extreme case, we have used the approach to separate GFP and fluorescein, separated by only 7 nm, and appear somewhat indistinguishable by conventional techniques. This approach offers the needed ability to concurrently image multiple colored, spectrally overlapping marker proteins within living cells. (C) 2001 Society of Photo-Optical Instrumentation Engineers. C1 CALTECH, Beckman Inst, Biol Imaging Ctr, Div Biol, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lansford, R (reprint author), CALTECH, Beckman Inst, Biol Imaging Ctr, Div Biol, 139-74, Pasadena, CA 91125 USA. RI Lansford, Rusty/C-6956-2014 NR 19 TC 128 Z9 131 U1 1 U2 16 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225 USA SN 1083-3668 J9 J BIOMED OPT JI J. Biomed. Opt. PD JUL PY 2001 VL 6 IS 3 BP 311 EP 318 DI 10.1117/1.1383780 PG 8 WC Biochemical Research Methods; Optics; Radiology, Nuclear Medicine & Medical Imaging SC Biochemistry & Molecular Biology; Optics; Radiology, Nuclear Medicine & Medical Imaging GA 462DR UT WOS:000170405900007 PM 11516321 ER PT J AU Cohen, D Chuck, R Bearman, G McDonnell, P Grundfest, W AF Cohen, D Chuck, R Bearman, G McDonnell, P Grundfest, W TI Ablation spectra of the human cornea SO JOURNAL OF BIOMEDICAL OPTICS LA English DT Article DE cornea; fluorescence; lasers; ablation ID PHOTOREFRACTIVE KERATECTOMY; FLUORESCENCE AB Ablation of human corneal tissue with 193 nm excimer laser energy generates fluorescence in the near ultraviolet and visible regions of the spectrum. The fluorescence spectra from five human corneas were collected during ablation in vitro. We find that the fluorescence spectrum changes continuously as the cornea is ablated from the epithelial surface towards the endothelium. We reduced the dimensionality of the large data set resulting from each cornea by a principal components analysis. The three most significant principal component eigenvectors suffice to describe the observed spectral evolution, and independent analysis of each tissue sample produces a similar set of eigenvectors. The evolution of the calculated eigenvector weighting factors during ablation then corresponds to the observed spectral evolution. In fact, this evolution is qualitatively consistent between corneas. We suggest that this spectral evolution offers promise as a real-time surgical feedback tool. (C) 2001 Society of Photo-Optical Instrumentation Engineers. C1 Univ Calif Los Angeles, Cedars Sinai Med Ctr, Laser Lab, Dept Biomed Engn, Los Angeles, CA 90048 USA. Univ Calif Irvine, Dept Ophthalmol, Irvine, CA USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bearman, G (reprint author), ANE Image, 974 E Elizabeth, Pasadena, CA USA. NR 12 TC 12 Z9 14 U1 0 U2 1 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225 USA SN 1083-3668 J9 J BIOMED OPT JI J. Biomed. Opt. PD JUL PY 2001 VL 6 IS 3 BP 339 EP 343 DI 10.1117/1.1380670 PG 5 WC Biochemical Research Methods; Optics; Radiology, Nuclear Medicine & Medical Imaging SC Biochemistry & Molecular Biology; Optics; Radiology, Nuclear Medicine & Medical Imaging GA 462DR UT WOS:000170405900011 PM 11516325 ER PT J AU Martinez, DM Ferguson, FT Heist, RH Nuth, JA AF Martinez, DM Ferguson, FT Heist, RH Nuth, JA TI Application of scaled nucleation theory to metallic vapor condensation SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID CORRESPONDING STATES CORRELATION; ONSET SUPERSATURATION RATIOS; HOMOGENEOUS NUCLEATION; REFRACTORY COMPOUNDS; PHASE NUCLEATION; CESIUM VAPOR; SCALING LAW; TEMPERATURE; MOLECULES; CH3CN AB In this paper we report that scaled nucleation theory (SNT) can describe moderately well the observed nucleation behavior of a significant number of refractory materials if a more appropriate value of a quantity commonly referred to as the excess surface entropy is used. With the availability of more reliable critical point and liquid property data, we are better able to calculate this quantity and we find that for refractory materials it can be as small as one half to one third the quantity traditionally used in its approximation. As a result of using more accurate values, we find considerably better agreement between SNT and experiment than what was originally determined. We also explain why using surface tension slope information to determine the excess surface entropy can lead to substantial errors in the SNT supersaturation prediction. (C) 2001 American Institute of Physics. C1 Univ Rochester, Dept Chem Engn, Rochester, NY 14627 USA. Catholic Univ Amer, Dept Chem, Washington, DC 20064 USA. Manhattan Coll, Nucleat Lab, Bronx, NY 10471 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Martinez, DM (reprint author), Univ Rochester, Dept Chem Engn, Rochester, NY 14627 USA. RI Ferguson, Frank/C-9493-2012; Nuth, Joseph/E-7085-2012 NR 37 TC 11 Z9 11 U1 0 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD JUL 1 PY 2001 VL 115 IS 1 BP 310 EP 316 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 444ED UT WOS:000169385300036 ER PT J AU Odegard, G Armentrout, D Searles, K Kumosa, L Sutter, JK Kumosa, M AF Odegard, G Armentrout, D Searles, K Kumosa, L Sutter, JK Kumosa, M TI Failure analysis of +/- 45 degrees off-axis woven fabric composite specimens SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE woven fabric composites; off-axis testing; FEM; graphite/PMR-15 AB The purpose of this research is to evaluate the mechanical response of eight harness satin woven graphite/polyimide composite specimens using the +/- 45 degrees test. A series of tensile tests have been conducted at room temperature to evaluate the effect of specimen width as well as monotonic, progressive, and multiple loadings on the response of the composite specimens. Acoustic emission techniques have been employed to monitor damage initiation and progression in the specimens at different stages of loading. In addition, nonlinear finite element computations have been conducted to determine stress distributions in the +/- 45 degrees fabric specimens. It has been shown that the specimen width effect is strong and should not be ignored in a failure analysis of the fabric composite using the +/- 45 degrees test. The shear strength of the composite determined from the maximum loads increases substantially with the width of the specimen. It has also been shown in this research that the initiation of intralaminar damage in the graphite/polyimide composite can be monitored using acoustic emission. The initiation of interlaminar damage can be determined either from the characteristic knees on the load/displacement diagrams or from the acoustic emission data. C1 Univ Denver, Dept Engn, Ctr Adv Mat & Struct, Denver, CO 80208 USA. Oregon Grad Inst Sci & Technol, Dept Mat Sci & Engn, Portland, OR 97291 USA. NASA, Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. RP Odegard, G (reprint author), Univ Denver, Dept Engn, Ctr Adv Mat & Struct, 2390 S York St, Denver, CO 80208 USA. NR 9 TC 9 Z9 9 U1 1 U2 4 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 USA SN 0884-6804 J9 J COMPOS TECH RES JI J. Compos. Technol. Res. PD JUL PY 2001 VL 23 IS 3 BP 205 EP 224 PG 20 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA 490KY UT WOS:000172052100005 ER PT J AU Yamaleev, NK AF Yamaleev, NK TI Minimization of the truncation error by grid adaptation SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE truncation error; grid adaptation criterion; finite difference approximation; error equidistribution ID BOUNDARY-VALUE PROBLEMS; FLUID-DYNAMICS; MESHES AB A new grid adaptation strategy, which minimizes the truncation error of a pth-order finite difference approximation. is proposed. The main idea of the method is based on the observation that the global truncation error associated with discretization on nonuniform meshes can be minimized if the interior grid points are redistributed in an optimal sequence. The method does not explicitly require the truncation error estimate, and at the same time, it allows one to increase the design order of approximation globally by one, so that the same finite difference operator reveals superconvergence properties on the optimal grid. Another very important characteristic of the method is that if the differential operator and the metric coefficients are evaluated identically by some hybrid approximation. then the single optimal grid generator can be employed in the entire computational domain independently of points where the hybrid discretization switches from one approximation to another. Generalization of the present method to multiple dimensions is presented. Numerical calculations of several one-dimensional and one two-dimensional test examples demonstrate the performance of the method and corroborate the theoretical results. (C) 2001 Academic Press. C1 NASA, Langley Res Ctr, Hampton, VA 23666 USA. RP Yamaleev, NK (reprint author), NASA, Langley Res Ctr, Mail Stop 128, Hampton, VA 23666 USA. NR 19 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 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD JUL 1 PY 2001 VL 170 IS 2 BP 459 EP 497 DI 10.1006/jcph.2001.6745 PG 39 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 454HP UT WOS:000169967400001 ER PT J AU Fox, NJ Cowley, SWH Davies, JA Greenwald, RA Lester, M Lockwood, M Luhr, H AF Fox, NJ Cowley, SWH Davies, JA Greenwald, RA Lester, M Lockwood, M Luhr, H TI Ionospheric ion and electron heating at the poleward boundary of a poleward expanding substorm-disturbed region SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID F-REGION; EISCAT; FIELDS AB We present observations of a poleward propagating substorm-disturbed region which was observed by the European Incoherent SCATter (EISCAT) radar and the Svalbard International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometers in the postmidnight sector. The expansion of the disturbance was launched by a substorm intensification which started similar to 25 min after the initial onset, and similar to 10 min before the disturbance arrived over Svalbard. In association with the magnetic disturbance, a poleward expanding enduring enhancement in the F region electron temperature was observed, indicative of soft electron precipitation, with a narrow band of enhanced ion temperature straddling its poleward edge, indicative of fast ion flows and ion-neutral collisional heating. This electron temperature boundary was coincident with the poleward propagating electrojet current system detected by the high-latitude IMAGE magnetometer stations and is taken to be a proxy for the observation of a substorm auroral bulge. The electron temperature boundary is inferred to have a width comparable or less than one radar range gate (similar to 60 km transverse to the magnetic field), while the region of high ion temperature was found to be approximately three gates wide, extending approximately two gates (similar to 120 km) poleward of the electron temperature boundary, and approximately one gate (similar to 60 km) equatorward. The two-beam radar line-of-sight velocity data are found to be consistent with the existence of a layer of high-speed flow in the boundary, peaking at values similar to1.5-3 km s(-1), roughly consistent with the ion temperature data. The flow is directed either east or west along the boundary depending on the direction of the flow in the poleward region. We infer that the flow is deflected along and around the boundary of the substorm-disturbed region due to the high conductivity of the latter. Variations in the flow poleward of the boundary produced no discernible magnetic effects on the ground, confirming the low conductivity of the preboundary ionosphere. C1 Johns Hopkins Univ, Appl Phys Lab, SRA Grp, Laurel, MD 20723 USA. Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Fox, NJ (reprint author), Johns Hopkins Univ, Appl Phys Lab, SRA Grp, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA. RI Lockwood, Mike/G-1030-2011; Fox, Nicola/P-6692-2016; OI Lockwood, Mike/0000-0002-7397-2172; Fox, Nicola/0000-0003-3411-4228; Greenwald, Raymond/0000-0002-7421-5536 NR 18 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 JUL 1 PY 2001 VL 106 IS A7 BP 12845 EP 12862 DI 10.1029/1999JA000387 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 446VT UT WOS:000169535400009 ER PT J AU Gjerloev, JW Hoffman, RA AF Gjerloev, JW Hoffman, RA TI The convection electric field in auroral substorms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WESTWARD TRAVELING SURGE; HEIGHT-INTEGRATED CONDUCTIVITY; TWO-DIMENSIONAL OBSERVATIONS; NIGHTTIME SECTOR; ZONE CURRENTS; MODELS; FLOW AB Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained by DE 1. The selected passes, which occurred during substorm expansion phase, maximum, or early recovery phase, cover the entire nighttime substorm. The organization of the data used the method developed by Fujii et al. [1994], which divided the data into six local time sectors covering the nighttime substorm region. Following the procedures employed in the paper by Gjerloev and Hoffman [2000b], the latitudinal width and location of each auroral oval crossing was then adjusted to fit the sector average. In addition to the detailed study of the characteristics of the field within each sector this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection channel is coincident with the highest conductances located just poleward of the Harang region. This channel drives the substorm current wedge component of the westward electrojet in the surge and middle surge sectors. It is present in all premidnight passes and consequently is an integral part of the three-dimensional substorm current wedge system. C1 Danish Space Res Inst, DK-2100 Copenhagen, Denmark. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Gjerloev, JW (reprint author), Danish Space Res Inst, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark. NR 35 TC 16 Z9 16 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 JUL 1 PY 2001 VL 106 IS A7 BP 12919 EP 12931 DI 10.1029/1999JA000240 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 446VT UT WOS:000169535400014 ER PT J AU Samir, U Israelevich, P Wright, KH Stone, NH AF Samir, U Israelevich, P Wright, KH Stone, NH TI Ion temperature enhancement in the wakes of ionospheric spacecraft SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SATELLITE; SHUTTLE; STREAMS; THERMALIZATION; VICINITY; TSS-1 AB Enhancements of the temperature of electrons in spacecraft plasma wakes have been reported for numerous cases [Samir and Wrenn, 1972; Troy et al., 1975; Oran et al., 1975], and this phenomenon has been discussed both empirically [Samir and Stone, 1986; Stone ann Samir, 1986] and theoretically [Singh et al., 1987]. However, very few measurements seem to have been made of the ion temperature within plasma wakes, possibly because the great majority of ion measurements were focused on obtaining geophysical parameters and hence were confined to the region ahead of the spacecraft. Recently, however, an enhancement of the temperature of ions was discovered in data obtained in the wake of the space shuttle during the Spacelab 2 mission [Sorensen et al., 1997]. At the time of that publication this was the only known observation of this type. Herein we report an additional case of ion temperature enhancement in a plasma wake. The data were taken during the tethered satellite system reflight (TSS-1R) mission in the wake of the tethered satellite during passive (no current flow) operations. The measurements were obtained with the Differential Ion Flux Probe. C1 Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. NASA, George C Marshall Space Flight Ctr, Sci Directorate, Huntsville, AL 35812 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. RP Samir, U (reprint author), Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. NR 28 TC 2 Z9 2 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 JUL 1 PY 2001 VL 106 IS A7 BP 12963 EP 12968 DI 10.1029/2000JA000198 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 446VT UT WOS:000169535400017 ER PT J AU Vaisberg, OL Smirnov, VN Avanov, LA Waite, JH Burch, JL Gallagher, DL Borodkova, NL AF Vaisberg, OL Smirnov, VN Avanov, LA Waite, JH Burch, JL Gallagher, DL Borodkova, NL TI Different types of low-latitude boundary layer as observed by Interball Tail probe SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; FLUX-TRANSFER EVENTS; CONVECTION ELECTRIC-FIELDS; NEAR-EARTH MAGNETOTAIL; DAYSIDE MAGNETOPAUSE; AMPTE/IRM OBSERVATIONS; SUBSOLAR MAGNETOPAUSE; GEOTAIL OBSERVATIONS; ISEE OBSERVATIONS; NORTHWARD IMF AB Interball Tail probe crossed dayside magnetopause during late winter to middle autumn months. The high-latitude magnetopause was crossed outbound orbit, while the low-latitude magnetopause was crossed inbound. We analyze 31 low-latitude magnetopause/low-latitude boundary layer (LLBL) crossings recorded in 1996 in the fast mode of SCA-1 ion spectrometer. Data from the MIF/FM-3 magnetometers and ELECTRON spectrometer are also used. The majority of magnetopause/LLBL crossings fall into two categories: (1) highly structured LLBL (14 cases) and (2) weakly structured LLBL (9 cases). The highly structured LLBL usually consists of short-time (0.5-5 min) transients including fast-moving (of an order of magnetosheath velocity) plasma as well as density transients that are nearly stationary relative to the magnetospheric plasma. The observed ensemble of transients shows evolution of plasma parameters from magnetosheath-like to magnetosphere-like. Fast-moving transients frequently have flux transfer event (FTE) magnetic signatures. This type of LLBL is usually accompanied by various reconnection signatures and is more frequently observed when the interplanetary magnetic field (IMF) and/or magnetosheath magnetic field has a negative B, component. The weakly structured LLBL shows a significantly smaller variation of number density and hotter plasma temperature. Strong velocity shear is frequently observed at the magnetopause in the weakly structured case. Dispersed ion signatures are often seen within this type of LLBL. The ion and electron temperatures within the weakly structured LLBL are more elevated in respect to the magnetosheath values compared to the highly structured LLBL. The weakly structured LLBL has a tendency to occur at positive IMF and/or magnetosheath magnetic field B,. The cause of significant differences between the two kinds of LLBL lies, apparently, in the significantly larger distance of the plasma entry site from the observation point, for weakly structured LLBL, as opposed to highly structured LLBL. While the highly structured LLBL originates at low latitudes, the weakly structured LLBL is most probably formed at high latitudes. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Russian Acad Sci, Inst Space Res, Moscow 117810, Russia. SW Res Inst, San Antonio, TX 78228 USA. RP Vaisberg, OL (reprint author), NASA, Goddard Space Flight Ctr, Interplanetary Phys Branch, Greenbelt, MD 20771 USA. NR 75 TC 15 Z9 16 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 JUL 1 PY 2001 VL 106 IS A7 BP 13067 EP 13090 DI 10.1029/2000JA000154 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 446VT UT WOS:000169535400027 ER PT J AU Benson, RF Osherovich, VA Fainberg, J Vinas, AF Ruppert, DR AF Benson, RF Osherovich, VA Fainberg, J Vinas, AF Ruppert, DR TI An interpretation of banded magnetospheric radio emissions SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID DIFFUSE PLASMA RESONANCES; AURORAL KILOMETRIC RADIATION; CYCLOTRON-HARMONIC-WAVES; FREE ELECTROMAGNETIC-FIELDS; ELECTRON-DENSITY; CYLINDRICAL OSCILLATIONS; PHYSICAL NATURE; AMPTE IRM; IONOSPHERE; TORUS AB Recently published Active Magnetospheric Particle Tracer Explorers/Ion Release Module (AMPTE/IRM) banded magnetospheric emissions, commonly referred to as "(n + 1/2)f(ce)" emissions, where f(ce) is the electron gyrofrequency, are analyzed by treating them as analogous to sounder-stimulated ionospheric emissions. We show that both individual spectra of magnetospheric banded emissions and a statistically derived spectra observed over the 2-year lifetime of the mission can be interpreted in a self-consistent manner. The analysis, which predicts all spectral peaks within 4% of the observed peaks, interprets the higher-frequency emissions as due to low group velocity Bernstein-mode waves and interprets the lower-frequency emissions as eigenmodes of cylindrical-electromagnetic plasma oscillations. The demarcation between these two classes of emissions is the electron plasma frequency f(pe) where an emission is often observed. This f(pe) emission is not necessarily the strongest. None of the observed banded emissions were attributed to the upper hybrid frequency. We present Alouette 2 and ISIS 1 plasma resonance data and model electron temperature (T,) values to support the argument that the frequency spectrum of ionospheric sounder-stimulated emissions is not strongly temperature dependent and thus that the interpretation of these emissions in the ionosphere is relevant to other plasmas (such as the magnetosphere) where N-e and T-e can be quite different but where the ratio f(pe)/f(ce) is identical. The N-e values deduced from the spectral interpretation do not agree with the values determined from the AMPTE/IRM three-dimensional plasma instrument. The latter, which represent a lower bound, are found to be higher than the former by a factor of 3.2 - 3.5. All values were less than 1 cm, a domain known for measurement difficulties. One possible explanation is that the wave and plasma techniques respond to different components of a non-Maxwellian magnetospheric electron distribution. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Emergent, Largo, MD USA. RP Benson, RF (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 692, Greenbelt, MD 20771 USA. NR 68 TC 17 Z9 17 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 JUL 1 PY 2001 VL 106 IS A7 BP 13179 EP 13190 DI 10.1029/2000JA000162 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 446VT UT WOS:000169535400034 ER PT J AU Nelson, ML AF Nelson, ML TI A new digital library technology for preserving NASA research SO JOURNAL OF GOVERNMENT INFORMATION LA English DT Article DE digital libraries; digital preservation; intelligent agents; scientific and technical information; smart objects, dumb archives; open archives initiative ID SERVER; DOCUMENTS; INTERNET; SCIENCE; POLICY AB A fundamental task of research organizations is the preservation and dissemination of their intellectual output. Historically, this has been accomplished with hard copy formats through a multitiered approach of using the open literature, self-publishing, and an array of cooperative libraries and depositories. It can be argued that the historical approach is less than optimal with respect to results achieved and resources expended. However, there have been recent advances in the area of digital libraries (DLs) that address some of the shortcomings of traditional hard copy preservation and dissemination. One of these technologies is "buckets," an aggregative, intelligent construct for publishing. Buckets exist within the "Smart Object, Dumb Archive" (SODA) DL model, which can be summarized as promoting the importance and responsibility of individual information objects and reducing the role of traditional archives and database systems. The goal is that smart objects will be independent of and more resilient to the transient nature of information systems. This paper examines the motivation for buckets and SODA, as well as discussing some initial experiences in using these DL technologies in some US government research laboratories in NASA, the Air Force, and the Department of Energy. (C) 2002 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Nelson, ML (reprint author), NASA, Langley Res Ctr, MS 158, Hampton, VA 23681 USA. EM m.l.nelson@larc.nasa.gov OI Nelson, Michael/0000-0003-3749-8116 NR 58 TC 2 Z9 2 U1 0 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1352-0237 J9 J GOV INFORM JI J. Gov. Inf. PD JUL-AUG PY 2001 VL 28 IS 4 BP 369 EP 394 AR PII S1352-0237(01)00322-7 DI 10.1016/S1352-0237(01)00322-7 PG 26 WC Information Science & Library Science SC Information Science & Library Science GA 534BH UT WOS:000174564400001 ER PT J AU Windhorst, R Ardema, M Kinney, D AF Windhorst, R Ardema, M Kinney, D TI Fixed-range optimal trajectories of supersonic aircraft by first-order expansions SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID FLIGHT AB A near-optimal guidance law that generates minimum-fuel, minimum-time, or direct operating cost fixed-range trajectories for supersonic transport aircraft is developed. The approach uses singular perturbation techniques to timescale decouple the equations of motion into three sets of dynamics, two of which are studied here: weight/range and energy The two-point boundary-value problems obtained by application of the maximum principle to the dynamic systems are solved using the method of matched asymptotic expansions. Both the weight/range and the energy dynamic solutions are carried out to first order. The two solutions are combined using the matching principle to form a uniformly valid approximation of the full fixed-range trajectory, Results show that the minimum-fuel trajectory has three segments: a minimum-fuel energy climb, a cruise climb, and a minimum-drag glide. The minimum-time trajectory also has three segments: a maximum dynamic pressure climb, a constant altitude cruise, and a maximum dynamic pressure descent. The minimum direct operating cost trajectory is an optimal combination of the preceding two trajectories. It is shown that for representative costs of fuel and flight time, the minimum direct operating cost trajectory is very similar to the minimum-fuel trajectory. C1 Santa Clara Univ, Dept Mech Engn, Santa Clara, CA 95053 USA. NASA, Ames Res Ctr, Syst Anal Branch, Moffett Field, CA 94035 USA. RP Windhorst, R (reprint author), Santa Clara Univ, Dept Mech Engn, Santa Clara, CA 95053 USA. NR 23 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 2001 VL 24 IS 4 BP 700 EP 709 DI 10.2514/2.4797 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 451KB UT WOS:000169800300008 ER PT J AU Jardin, MR Bryson, AE AF Jardin, MR Bryson, AE TI Neighboring optimal aircraft guidance in winds SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB The technique of neighboring optimal control is extended to handle cases of parameter change in the system dynamic model. This extension is used to develop an algorithm for optimizing horizontal aircraft trajectories in general wind fields using time-varying linear feedback gains. The minimum-time problem far an airplane traveling horizontally between two points in a variable wind field (a type of Zermelo problem) is used to illustrate how perturbations in system parameters can be accounted for by augmenting the dynamic model with additional bias states. For the special case of a constant wind shear in the cross-track direction, analytical and numerical results are derived for bias perturbations, Numerical simulations are presented to demonstrate the performance of the proposed state-augmentation technique. An additional example is used to demonstrate an algorithm to compute near-optimal trajectories in general wind fields, The algorithm is based on nondimensionalizing the neighboring optimal control solutions and using piecewise linearly,varying wind and horizontal wind shear parameters. One proposed application of this technique is to the computation and real-time update of time-optimal trajectories in mind fields by onboard flight management systems and by ground-based air traffic management automation tools. C1 NASA, Ames Res Ctr, Automat Concepts Res Branch, Moffett Field, CA 94035 USA. Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. RP Jardin, MR (reprint author), NASA, Ames Res Ctr, Automat Concepts Res Branch, MS 210-10, Moffett Field, CA 94035 USA. NR 9 TC 25 Z9 25 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 2001 VL 24 IS 4 BP 710 EP 715 DI 10.2514/2.4798 PG 6 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 451KB UT WOS:000169800300009 ER PT J AU Scheeres, DJ Guman, MD Villac, BF AF Scheeres, DJ Guman, MD Villac, BF TI Stability analysis of planetary satellite orbiters: Application to the Europa orbiter SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID ASTEROIDS; DYNAMICS AB The stability of orbit dynamics around a planetary satellite is studied using analytical and numerical techniques, The Europa orbiter mission is used to motivate our analysis and to provide specific numerical data for verification of our analytical results. After verification, the results are applied to a large number of planetary satellites in the solar system, The motivation is that numerically integrated, low-altitude spacecraft orbits shout Europa often impact on that moon's surface after a short period of a few days to weeks. Numerical integrations indicate that these impact orbits only occur for inclinations within similar to 45 deg of a polar orbit. An analytical study of this problem using averaging theory, which results in an approximate, closed-form solution for the orbiter dynamics, is described. The solution includes the effect of the planet gravity and the planetary satellite oblateness, with the assumption that the eccentricity of the nominal orbit is small. This solution is used to compute limits for impacting and nonimpacting orbits at Europa and provides good agreement with numerical computations of these limits performed with high-precision numerical integrations of the motion. The analytical result predicts a set of initial conditions that can postpone impact with the planetary surface for considerable lengths of time. C1 Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA. CALTECH, Jet Prop Lab, Navigat & Miss Design Sect, Pasadena, CA 91109 USA. RP Scheeres, DJ (reprint author), Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA. NR 13 TC 79 Z9 80 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 2001 VL 24 IS 4 BP 778 EP 787 DI 10.2514/2.4778 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 451KB UT WOS:000169800300017 ER PT J AU Nitzshe, F Zimcik, DG Ryall, TG Moses, RW Henderson, DA AF Nitzshe, F Zimcik, DG Ryall, TG Moses, RW Henderson, DA TI Closed-loop control for vertical fin buffeting alleviation using strain actuation SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article C1 Carleton Univ, Dept Mech & Aerosp Engn, Ottawa, ON K1S 5B6, Canada. Natl Res Council Canada, Inst Aerosp Res, Aeroacoust & Struct Dynam Grp, Ottawa, ON K1A 0R6, Canada. Aeronautical & Maritime Res Lab, Airframe & Engines Div, Melbourne, Vic 3001, Australia. NASA, Langley Res Ctr, Aeroelastic Branch, Hampton, VA 23681 USA. USAF, Res Lab, Wright Patterson AFB, OH 45433 USA. RP Nitzshe, F (reprint author), Carleton Univ, Dept Mech & Aerosp Engn, Ottawa, ON K1S 5B6, Canada. NR 7 TC 7 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 2001 VL 24 IS 4 BP 855 EP 857 DI 10.2514/2.4788 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 451KB UT WOS:000169800300028 ER PT J AU Hilico, JC Robert, O Loete, M Toumi, S Pine, AS Brown, LR AF Hilico, JC Robert, O Loete, M Toumi, S Pine, AS Brown, LR TI Analysis of the interacting Octad system of (CH4)-C-12 SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID METHANE LINE PARAMETERS; TETRAHEDRAL MOLECULES; DIPOLE-MOMENT; NU-4 BANDS; MU-M; STRENGTHS; SPECTRUM; SPECTROSCOPY; INTENSITIES; (CH4)C-12 AB The octad system of methane (CH4)-C-12 has been analyzed with a fourth-order (459 parameters) Hamiltonian for energy levels and a third-order (28 parameters) dipole moment expansion for infrared intensities. Nearly 8000 assigned positions and 2500 measured line intensities (obtained with the Fourier transform spectrometer located at Kitt Peak National Observatory/National Solar Observatory) have been considered in the modeling. Infrared (Octad-Ground State) and hot bands (Octad-Dyad) data have been used, While the model does not reproduce the measurements at their inherent experimental precisions, it has been sufficient to interpret and substantially assign this spectral region of methane for the first time in over 30 years of investigation, (C) 2001 Academic Press. C1 Univ Bourgogne, Phys Lab, F-21078 Dijon, France. Univ Badji Mokhtar, Fac Sci Ingn, Dept Elect, Annaba 23000, Algeria. Alpine Technol, Germantown, MD 20874 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Loete, M (reprint author), Univ Bourgogne, Phys Lab, 9 Av A Savary,BP 47870, F-21078 Dijon, France. NR 36 TC 46 Z9 48 U1 0 U2 1 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 JUL PY 2001 VL 208 IS 1 BP 1 EP 13 DI 10.1006/jmsp.2001.8364 PG 13 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 455TE UT WOS:000170043200001 ER PT J AU Petkie, DT Goyette, TM Helminger, P Pickett, HM De Lucia, FC AF Petkie, DT Goyette, TM Helminger, P Pickett, HM De Lucia, FC TI The energy levels of the nu 5/2 nu(9) dyad of HNO3 from millimeter and submillimeter rotational spectroscopy SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article DE nitric acid; nu(5); 2 nu(9); HNO3; millimeter; infrared; spectra; spectroscopy ID NITRIC-ACID; SPECTRUM; BAND; 2-NU-9; NU-5; 2-NU(9); NU(5) AB In this paper we show that the rotational structure of the nu (5)/2 nu (9) infrared band near 11 mum can be synthesized to high accuracy from pure rotational measurements in the millimeter- and submillimeter-wave region. The analysis uses an internal axis system Hamiltonian that accounts for the rotational dependence of the torsional splitting in 2 nu (9), the induced torsional splitting in nu (5), and all of the infrared line positions, including those in the regions of strongest mixing and of highest excitation. This model also predicts the strength of the 2 nu (9) infrared band due to the strong Fermi mixing with nu (5). The analysis is based on the 2317 millimeter/submillimeter lines and uses the well-documented SPFIT routines of JPL. (C) 2001 Academic Press. C1 Ohio No Univ, Dept Phys, Ada, OH 45810 USA. Univ Lowell, Dept Phys, Lowell, MA 01854 USA. Univ S Alabama, Dept Phys, Mobile, AL 36688 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. RP Petkie, DT (reprint author), Ohio No Univ, Dept Phys, Ada, OH 45810 USA. NR 17 TC 27 Z9 27 U1 0 U2 4 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 JUL PY 2001 VL 208 IS 1 BP 121 EP 135 DI 10.1006/jmsp.2001.8367 PG 15 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 455TE UT WOS:000170043200016 ER PT J AU Smith, SM Davis-Street, JE Rice, BL Nillen, JL Gillman, PL Block, G AF Smith, SM Davis-Street, JE Rice, BL Nillen, JL Gillman, PL Block, G TI Nutritional status assessment in semiclosed environments: Ground-based and space flight studies in humans SO JOURNAL OF NUTRITION LA English DT Article; Proceedings Paper CT Experimental Biology 99 Meeting CY APR 17-21, 1999 CL WASHINGTON, D.C. DE weightlessness; food-frequency questionnaire; dietary intake; humans ID SPACEFLIGHT; METABOLISM; IRON AB Adequate nutrition is critical during long-term spaceflight, as is the ability to easily monitor dietary intake. A comprehensive nutritional status assessment profile was designed for use before, during and after flight. It included assessment of both dietary intake and biochemical markers of nutritional status. A spaceflight food-frequency questionnaire (FFQ) was developed to evaluate intake of key nutrients during spaceflight. The nutritional status assessment protocol was evaluated during two ground-based closed-chamber studies (60 and 91 d; n = 4/study), and was implemented for two astronauts during 4-mo stays on the Mir space station. Ground-based studies indicated that the FFQ, administered daily or weekly, adequately estimated intake of key nutrients. Chamber subjects maintained prechamber energy intake and body weight. Astronauts tended to eat 40-50% of WHO-predicted energy requirements, and lost > 10% of preflight body mass. Serum ferritin levels were lower after the chamber stays, despite adequate iron intake. Red blood cell folate concentrations were increased after the chamber studies, Vitamin D stores were decreased by > 40% on chamber egress and after spaceflight. Mir crew members had decreased levels of most nutritional indices, but these are difficult to interpret given the insufficient energy intake and loss of body mass. Spaceflight food systems can provide adequate intake of macronutrients, although, as expected, micronutrient intake is a concern for any closed or semiclosed food system, These data demonstrate the utility and importance of nutritional status assessment during spaceflight and of the FFQ during extended-duration spaceflight. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Enterprise Advisory Serv Inc, Houston, TX 77058 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. RP Smith, SM (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. RI Block, Gladys/E-3304-2010 NR 24 TC 46 Z9 47 U1 0 U2 7 PU AMER INST NUTRITION PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 0022-3166 J9 J NUTR JI J. Nutr. PD JUL PY 2001 VL 131 IS 7 BP 2053 EP 2061 PG 9 WC Nutrition & Dietetics SC Nutrition & Dietetics GA 452BH UT WOS:000169836900030 PM 11435529 ER PT J AU Marsh, RA Vukson, S Surampudi, S Ratnakumar, BV Smart, MC Manzo, M Dalton, PJ AF Marsh, RA Vukson, S Surampudi, S Ratnakumar, BV Smart, MC Manzo, M Dalton, PJ TI Li ion batteries for aerospace applications SO JOURNAL OF POWER SOURCES LA English DT Article; Proceedings Paper CT 10th International Meeting on Lithium Batteries CY MAY 28-JUN 02, 2000 CL COMO, ITALY DE geosynchronous earth orbit; Li ion batteries; low earth orbit AB Rechargeable Li ion batteries are perceived as likely substitutes for conventional nickel systems in an effort to minimize the mass and volume of the power subsystems in aerospace applications. The on-going consortium of NASA and DoD, after 2 years of existence, has propelled the advancement of aerospace Li ion technology in the US. Prototype cells of different sizes have been built by domestic manufacturers and are being evaluated both by NASA and Air Force. The early versions of these prototypes catered to needs of imminent NASA missions, i.e. Mars landers and revers. Developmental efforts are underway to further improve the technology to meet the demands of long calendar life, as in the geosynchronous earth orbit (GEO) and the outer planets missions, and long cycle life as in the low earth orbit (LEO) missions. In this paper, we will briefly describe the objective and progress of this joint effort. (C) 2001 Published by Elsevier Science B.V. C1 USAF, Res Lab, PR PB, Wright Patterson AFB, OH USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Glen Res Ctr, Cleveland, OH USA. RP Marsh, RA (reprint author), USAF, Res Lab, PR PB, 1950 5th St,Bldg 18, Wright Patterson AFB, OH USA. NR 0 TC 54 Z9 55 U1 0 U2 20 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0378-7753 J9 J POWER SOURCES JI J. Power Sources PD JUL PY 2001 VL 97-8 SI SI BP 25 EP 27 DI 10.1016/S0378-7753(01)00584-5 PG 3 WC Chemistry, Physical; Electrochemistry; Energy & Fuels; Materials Science, Multidisciplinary SC Chemistry; Electrochemistry; Energy & Fuels; Materials Science GA 452AY UT WOS:000169836000006 ER PT J AU Ratnakumar, BV Smart, MC Surampudi, S AF Ratnakumar, BV Smart, MC Surampudi, S TI Effects of SEI on the kinetics of lithium intercalation SO JOURNAL OF POWER SOURCES LA English DT Article; Proceedings Paper CT 10th International Meeting on Lithium Batteries CY MAY 28-JUN 02, 2000 CL COMO, ITALY DE SEI; lithium intercalation; carbon anode ID BATTERIES; ELECTROLYTES; CARBONATES; GRAPHITE AB The electrochemical stability of electrolytes at lithium, or lithium-intercalating anodes, is achieved via ionically conducting surface films termed as solid electrolyte interphase (SEI). Since the lithium deposition or intercalation process occurs on the electrode covered with the SEI, the characteristics of the SEI determine the kinetics of lithiation/delithiation, stability of the interface, and thus, the overall cell performance, especially at low temperatures. In this paper, we have reiterated the significance of the SEI characteristics over the solution properties, using a few illustrative examples from our research on low temperature Li ion battery electrolytes at JPL. The examples specifically include the beneficial aspects of a ternary carbonate mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) compared to the binary mixtures (of EC and either DMC or DEC) and quaternary solutions with appropriate co-solvents, such as alkyl esters. Published by Elsevier Science B.V. C1 CALTECH, Jet Prop Lab, Electrochem Technol Grp, Pasadena, CA 91109 USA. RP Ratnakumar, BV (reprint author), CALTECH, Jet Prop Lab, Electrochem Technol Grp, 4800 Oak Grove Dr,M-S 277-207, Pasadena, CA 91109 USA. NR 8 TC 51 Z9 56 U1 4 U2 55 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0378-7753 J9 J POWER SOURCES JI J. Power Sources PD JUL PY 2001 VL 97-8 SI SI BP 137 EP 139 DI 10.1016/S0378-7753(01)00682-6 PG 3 WC Chemistry, Physical; Electrochemistry; Energy & Fuels; Materials Science, Multidisciplinary SC Chemistry; Electrochemistry; Energy & Fuels; Materials Science GA 452AY UT WOS:000169836000029 ER PT J AU Dyer, K Yankura, G Acosta, J AF Dyer, K Yankura, G Acosta, J TI Low mass components for Mars ascent propulsion SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 35th Joint Propulsion Conference CY JUN 20-24, 1999 CL LOS ANGELES, CALIFORNIA SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE AB The Jet Propulsion Laboratory is planning a sample return mission for early in the next century. To accomplish this, the Mars ascent stage must be landed on the Martian surface and then, after actuation, ascend to Mars orbit. Given this mission profile it is necessary to develop propulsion components of substantially lower mass than were previously available for spacecraft applications. Low mass is especially critical to the Mars ascent stage because mass reduction of this stage affords the greatest leverage for the reduction of the total mission system mass at Earth liftoff. In addition to very low mass, these components must be rugged, reliable, and compatible with fuel, oxidizer, pressurant gas, and environmental extremes. Three separate components were developed for a liquid bipropellant baseline stage propulsion system: A high-flow etched-disk filter with a mass under 90 g, an all-metal miniature fill and drain/vent valve with a mass under 9 g, and a miniature high-flow check valve with a mass under 20 g, The design and development of these components as well as test data are summarized. C1 VACCO Ind, Dept Engn, S El Monte, CA 91733 USA. CALTECH, Jet Prop Lab, Prop Flight Syst Grp, Pasadena, CA 91109 USA. RP Dyer, K (reprint author), VACCO Ind, Dept Engn, S El Monte, CA 91733 USA. NR 3 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 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 2001 VL 17 IS 4 BP 758 EP 761 DI 10.2514/2.5822 PG 4 WC Engineering, Aerospace SC Engineering GA 454BN UT WOS:000169952700002 ER PT J AU Eckman, R Byrne, L Gatsonis, NA Pencil, EJ AF Eckman, R Byrne, L Gatsonis, NA Pencil, EJ TI Triple Langmuir probe measurements in the plume of a pulsed plasma thruster SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB An experimental apparatus using triple langmuir probes was designed to obtain electron temperature and density in the plume of a laboratory-model pulsed plasma thruster (PPT) operating at discharge energy levels of 5, 20, and 40 J. Electron temperature and density were obtained on two planes parallel and perpendicular to the thruster electrodes passing through the thruster's centerline, Measurements were obtained fur radial distances of 6, 10, 12, 14, 16, 18, and 20 cm and for polar angles of 10, 20, 30, and 45 deg with respect to the center of the Teflon (R) propellant face. Plume properties show large angular variation on the perpendicular to the electrodes plane hut small variation on the parallel plane confirming the asymmetry of the PPT plume, Electron density and temperature decrease with increasing radial distance from the Teflon surface. The average maximum temperature is between 2 and 4 eV for all discharge energy levels considered. The average maximum electron density is 1.6 x 10(20), 1.6 x 10(21), and 1.8 x 10(21) m(-3) for the 5-, 20-, and 40-J discharge, The time average electron density increases with increasing discharge energy and is in the range between 10(19) and 2 x 10(20) m(-3) for 5 J, 3 x 10(19) and 10(21) m(-3) for 20 J, and 5 x 10(19) and 1,4 x 10(21) m(-3) for 40 J. C1 Worcester Polytech Inst, Dept Engn Mech, Worcester, MA 01609 USA. NASA, John H Glenn Res Ctr, Cleveland, OH 44135 USA. RP Eckman, R (reprint author), Gen Elect Aircraft Engines, 1000 Western Ave, Lynn, MA 01910 USA. NR 28 TC 18 Z9 20 U1 1 U2 12 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 2001 VL 17 IS 4 BP 762 EP 771 DI 10.2514/2.5831 PG 10 WC Engineering, Aerospace SC Engineering GA 454BN UT WOS:000169952700003 ER PT J AU Moreau, G Boissoles, J Le Doucen, R Boulet, C Tipping, RH Ma, Q AF Moreau, G Boissoles, J Le Doucen, R Boulet, C Tipping, RH Ma, Q TI Metastable dimer contributions to the collision-induced fundamental absorption spectra of N-2 and O-2 pairs SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article DE collision-induced absorption; metastable dimers; fundamental absorption of N-2 and O-2 ID STRATOSPHERIC MEASUREMENTS; INFRARED-SPECTRUM; N2-N2 PAIRS; TEMPERATURES; MOLECULES; STATES; OXYGEN; (N2)2; VAN AB The contributions of dimer transitions to the low-temperature collision-induced fundamental spectra of N-2 and O-2 have been observed in many earlier studies. However, recent measurements made at high resolution have shown the existence of periodic structures superposed on the smooth collision-induced envelope which persist to room temperatures. In a series of recent papers, we have compared theoretical calculations with experimental data for N-2-N-2, O-2-O-2, N-2-O-2 and O-2-N-2 pairs and have concluded that the observed structure was not due to either collisional line mixing or intercollisional interference. In the present paper, we show that one can get both qualitative and quantitative agreement between theory and experiment by including the contributions due to metastable dimers that are expected to be present at the few percent level, (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Univ Alabama, Coll Arts & Sci, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. Univ Rennes 1, Unite Mixte Rech PALMS, F-35042 Rennes, France. Univ Paris Sud, CNRS, Photophys Mol Lab, F-91405 Orsay, France. Columbia Univ, Dept Appl Phys, New York, NY 10025 USA. Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Tipping, RH (reprint author), Univ Alabama, Coll Arts & Sci, Dept Phys & Astron, 206 Gallalee,Box 870324, Tuscaloosa, AL 35487 USA. NR 24 TC 9 Z9 9 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUL 1 PY 2001 VL 70 IS 1 BP 99 EP 113 DI 10.1016/S0022-4073(00)00125-4 PG 15 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 438GF UT WOS:000169044700009 ER PT J AU Blanchard, RC Wilmoth, RG Glass, CE Merski, NR Berry, SA Bozung, TJ Tietjen, A Wendt, J Dawson, D AF Blanchard, RC Wilmoth, RG Glass, CE Merski, NR Berry, SA Bozung, TJ Tietjen, A Wendt, J Dawson, D TI Infrared sensing aeroheating flight experiment: STS-96 flight results SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Major elements of an experiment called the infrared sensing aeroheating flight experiment are discussed. The primary experimental goal is to provide reentry global temperature images from infrared measurements. These measurements are used to define the characteristics of hypersonic boundary-layer transition during flight. Specifically, the experiment is to identify, monitor, and quantify hypersonic boundary-layer windward surface transition of the X-33 vehicle during flight. In addition, the flight data will serve as a calibration and validation of current boundary-layer transition prediction techniques; provide benchmark laminar, transitional, and fully turbulent global aeroheating data to validate existing wind-tunnel and computational results; and advance aeroheating technology. Shuttle Orbiter data from STS-96 are used to validate the data acquisition, and data reduction to global temperatures, to mitigate the experiment risks before the maiden flight of the X-33, is discussed. STS-96 reentry midwave (3-5 mum) infrared data were collected at the Ballistic Missile Defense Organization/Innovative Sciences and Technology Experimentation Facility site at NASA Kennedy Space Center and subsequently mapped into global temperature contours using ground calibrations only. A series of image mapping techniques have been developed to compare each frame of infrared data with thermocouple data collected during the flight. Comparisons of the ground calibrated global temperature images with the corresponding thermocouple data are discussed. The differences are shown to be generally less than about 5%, which is comparable to the expected accuracy of both types of aeroheating measurements. C1 NASA Langley Res Ctr, Aerothermodynam Branch, Aerodynam Aerothermodynam & Acoust Competency, Hampton, VA 23681 USA. George Washington Univ, Joint Inst Advancement Flight Sci, Hampton, VA 23681 USA. Comp Sci Corp, Ballist Missile Def Org, Innovat Sci & Technol Expt Facil, Kennedy Space Ctr, FL 32899 USA. RP Blanchard, RC (reprint author), NASA Langley Res Ctr, Aerothermodynam Branch, Aerodynam Aerothermodynam & Acoust Competency, Hampton, VA 23681 USA. NR 11 TC 3 Z9 5 U1 2 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 JUL-AUG PY 2001 VL 38 IS 4 BP 465 EP 472 DI 10.2514/2.3713 PG 8 WC Engineering, Aerospace SC Engineering GA 461TQ UT WOS:000170379900001 ER PT J AU Chen, YK Milos, FS AF Chen, YK Milos, FS TI Two-dimensional implicit thermal response and ablation program for charring materials SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 38th Aerospace Sciences Meeting and Exhibit CY JAN 10-15, 2000 CL RENO, NEVADA SP Amer Inst Aeronatu & Astronaut AB The TITAN program for predicting charring material ablation and shape change of thermal protection materials is presented. The governing equations include energy conservation and a three-component decomposition model. The surface energy balance condition is solved with a moving grid to calculate the shape change due to surface recession. The governing equations are discretized with a finite volume approximation with a general body-fitted coordinate system. A time-accurate solution is achieved by an implicit time-marching technique with Gauss-Seidel line relaxation with alternating sweeps. Benchmark solutions are calculated and compared with available solutions to check code consistency and accuracy. For fully coupled solid-fluid simulation, this technique has been directly integrated with both a high-fidelity Navier-Stokes solver and an aerothermal flowfield engineering correlation code. Representative computations, including a slender hypersonic reentry vehicle and a flat-faced cylinder model in an arcjet test, are presented and discussed in detail. C1 NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. RP Chen, YK (reprint author), NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, MS 234-1, Moffett Field, CA 94035 USA. NR 19 TC 28 Z9 35 U1 1 U2 5 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 JUL-AUG PY 2001 VL 38 IS 4 BP 473 EP 481 DI 10.2514/2.3724 PG 9 WC Engineering, Aerospace SC Engineering GA 461TQ UT WOS:000170379900002 ER PT J AU Woll, SLB Loebs, VA Phelps, CS Pippin, HG Crandall, DG Kinard, WH AF Woll, SLB Loebs, VA Phelps, CS Pippin, HG Crandall, DG Kinard, WH TI Study of long duration exposure facility contaminated chromic-acid-anodized surfaces SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID SPACECRAFT AB Contamination plumes that were visible postflight on chromic-acid-anodized experiment tray panels flown on the Long Duration Exposure Facility were examined for content, thickness, and optical property values as a function of location on the panel. The source of the contamination was determined to be a mixture of methyl silicone that was suspected to have outgassed from a tray cover gasket during preflight storage and polyurethane that outgassed from Z306 black paint both preflight and on orbit. Contamination depths on the panels ranged from 40 to 36,000 Angstrom. Changes in solar absorptance and thermal emittance were mathematically modeled as functions of atomic oxygen fluence, solar exposure, and contaminant thickness. Very high correlation was found between discoloration and atomic oxygen exposure. Little correlation was found between discoloration and solar exposure. The atomic oxygen coefficients for the panel models indicated that the optical properties of the contaminated, anodized panels degraded twice as much as the contaminated, untreated brackets. The change in solar absorptance was approximately 0.06 per 1000 Angstrom. This change is less than the rate derived from earlier linear degradation models using temperature data telemetered from operational satellites, which have reported solar absorptance changes of 0.01 per 100 Angstrom. C1 Boeing Phantom Works, Nonmet Mat Technol, Seattle, WA 98124 USA. AZ Technol, Huntsville, AL 35806 USA. NASA Langley Res Ctr, Hampton, VA 23681 USA. RP Woll, SLB (reprint author), Boeing Phantom Works, Nonmet Mat Technol, MS 82-94 POB 3707, Seattle, WA 98124 USA. NR 14 TC 0 Z9 1 U1 3 U2 5 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 JUL-AUG PY 2001 VL 38 IS 4 BP 569 EP 577 DI 10.2514/2.3718 PG 9 WC Engineering, Aerospace SC Engineering GA 461TQ UT WOS:000170379900014 ER PT J AU Newman, DJ Amir, AR Beck, SM AF Newman, DJ Amir, AR Beck, SM TI Astronaut-induced disturbances to the microgravity environment of the Mir space station SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB In preparation for the International Space Station, the Enhanced Dynamic Load Sensors Space Flight Experiment measured the forces and moments astronauts exerted on the Mir Space Station during their daily on-orbit activities to quantify the astronaut-induced disturbances to the microgravity environment during a long-duration space mission. An examination of video recordings of the astronauts moving in the modules and using the instrumented crew restraint and mobility load sensors led to the identification of several typical astronaut motions and the quantification of the associated forces and moments exerted on the spacecraft. For 2806 disturbances recorded by the foot restraints and hand-hold sensor, the highest force magnitude was 137 N. For about 96 % of the time, the maximum force magnitude was below 60 N, and for about 99 % of the time the maximum force magnitude was below 90 N. For 95 % of the astronaut motions, the rills force level was below 9.0 N. It can be concluded that expected astronaut-induced loads from usual intravehicular activity are considerably less than previously thought and will not significantly disturb the microgravity environment. C1 MIT, Dept Aeronaut, Man Vechicle Lab, Cambridge, MA 02139 USA. NASA Langley Res Ctr, Hampton, VA 23681 USA. RP MIT, Dept Aeronaut, Man Vechicle Lab, 77 Massachusetts Ave, Cambridge, MA 02139 USA. NR 22 TC 11 Z9 13 U1 0 U2 1 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0022-4650 EI 1533-6794 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 2001 VL 38 IS 4 BP 578 EP 583 DI 10.2514/2.3719 PG 6 WC Engineering, Aerospace SC Engineering GA 461TQ UT WOS:000170379900015 PM 12033220 ER PT J AU Bilen, SG Domonkos, MT Gallimore, AD AF Bilen, SG Domonkos, MT Gallimore, AD TI Simulating ionospheric plasma with a hollow cathode in a large vacuum chamber SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID CONTACTORS; DISCHARGES; FIELD AB A plasma environment closely approximating the ionosphere can be generated by a hollow cathode assembly in a large vacuum chamber. This capability allows examinations of ionospheric-plasma phenomena in a controlled setting without, in most cases, relying on scaling techniques. The hollow cathode provides a low-temperature, low-density, fairly uniform plasma in its far field, and the large chamber provides ample room such that the effects of plasma confinement are reduced to a minimum. Most previous studies of hollow cathodes have concentrated on their plasma environment in the near field, i.e., within a few tens of centimeters. This work, however, examines their farfield plasma environment, i.e., 1-2m. This characterization shows that the hollow cathode provides, in the far field, a fairly uniform ionospheric-level plasma environment. The hollow cathode was operated at nine different operating conditions consisting of three different gases (argon, krypton, and xenon) each at three different flow rates. Results from these nine operating conditions are summarized, and the corresponding far-field plasma environments are analyzed. Comparison of the hollow cathode's plasma environment parameters with typical ionospheric values is presented. Uses of the facility, such as full-scale scientific instrument verification, are presented. C1 Penn State Univ, University Pk, PA 16802 USA. NASA, John H Glenn Res Ctr Lewis Field, Onboard Prop Branch, Cleveland, OH 44135 USA. Univ Michigan, Ann Arbor, MI 48109 USA. RP Penn State Univ, University Pk, PA 16802 USA. RI Bilen, Sven/F-4329-2011 OI Bilen, Sven/0000-0002-5416-7039 NR 24 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0022-4650 EI 1533-6794 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 2001 VL 38 IS 4 BP 617 EP 621 DI 10.2514/2.3726 PG 5 WC Engineering, Aerospace SC Engineering GA 461TQ UT WOS:000170379900021 ER PT J AU Schroeder, JA Chung, WW AF Schroeder, JA Chung, WW TI Simulation motion requirements for coordinated maneuvers SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 53rd Annual Forum of the American-Helicopter-Society CY APR 29-MAY 01, 1997 CL VIRGINIA BEACH, VIRGINIA SP Amer Helicopter Soc AB When no apparent lateral acceleration is present on a pilot, the maneuver is coordinated. To represent these maneuvers accurately in a moving-based simulation, the motion platform must translate laterally when it rolls. Typical platform lateral displacement limits prevent an accurate representation of such maneuvers. The result is that the pilot receives an uncoordinated lateral specific force (ball not centered). This study examined the effects of these false uncoordinated roll-lateral motion cues. The vehicle model represented a typical helicopter with satisfactory handling qualities in the roll-lateral axes. The task was a two-degree-of-freedom sidestep, in which the pilot controlled lateral position with roll attitude. Two gains varied in the motion platform control. One gain controlled the ratio between platform roll angle and math model (and thus visual) roll angle. The other gain controlled the amount of lateral platform movement, relative to the amount needed, to keep the apparent gravity vector aligned vertically about the pilot. Both gains varied from zero to one. With both gains equal to one, pilots evaluated the true 1:1 motion case, in which the motion cues matched the visual cues. The results showed that, as the motion cues degraded, both objective and subjective evaluations worsened. These effects were found to be reasonably predicted by a combination of previously developed motion fidelity criteria. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SYRE Logicon, Moffett Field, CA USA. RP Schroeder, JA (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 2001 VL 46 IS 3 BP 175 EP 181 PG 7 WC Engineering, Aerospace SC Engineering GA 466UT UT WOS:000170665100001 ER PT J AU Nguyen, K Betzina, M Kitaplioglu, C AF Nguyen, K Betzina, M Kitaplioglu, C TI Full-scale demonstration of higher harmonic control for noise and vibration reduction on the XV-15 rotor SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 56th Annual Forum of the American-Helicopter-Society CY MAY, 2000 CL VIRGINIA BEACH, VIRGINIA SP Amer Helicopter Soc AB A higher harmonic control (HHC) investigation was conducted on a full-scale, isolated XV-15 rotor in helicopter mode in the NASA Ames 80- by 120-Foot Wind Tunnel to independently control noise and vibration. The higher harmonic blade pitch was generated using swashplate oscillations. The radiated blade-vortex interaction (BVI) noise footprint was measured on a plane beneath the rotor with an acoustic traverse. Test results showed that HHC is highly effective in reducing BVI noise, achieving a 12 dB reduction in peak noise level within the noise footprint. Noise reduction with HHC remains effective even with perturbations in rotor trim and flight conditions. Blade pressure feedback was demonstrated to be a viable method for closed-loop noise control. Some noise reduction was achieved with no increase in vibratory hub loads. Increases in control loads due to HHC generally limited further noise reduction. The vibration controller achieved about 50 percent reduction in vibratory hub loads with control loads limiting the HHC amplitude. C1 NASA, Ames Res Ctr, Army NASA Rotorcraft Div, Moffett Field, CA 94035 USA. RP Nguyen, K (reprint author), NASA, Ames Res Ctr, Army NASA Rotorcraft Div, Moffett Field, CA 94035 USA. NR 23 TC 11 Z9 11 U1 0 U2 1 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 2001 VL 46 IS 3 BP 182 EP 191 PG 10 WC Engineering, Aerospace SC Engineering GA 466UT UT WOS:000170665100002 ER PT J AU Mesbahi, M Hadaegh, FY AF Mesbahi, M Hadaegh, FY TI Mode and logic-based switching for the formation flying control of multiple spacecraft SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article ID SYSTEMS AB Mode and logic-based switching for formation flying control is motivated and addressed in the context of separated spacecraft optical interferometry. In this venue, we show that logic-based switching is an attractive approach for satisfying multiple performance criteria during the different phases of a representative formation flying mission. Simulation results are provided to demonstrate the viability of the proposed methodology. C1 Univ Minnesota, Dept Aerosp Engn & Mech, Minneapolis, MN 55455 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Mesbahi, M (reprint author), Univ Minnesota, Dept Aerosp Engn & Mech, Minneapolis, MN 55455 USA. EM mesbahi@aem.umn.edu; fred.y.hadaegh@jpl.nasa.gov NR 25 TC 3 Z9 3 U1 0 U2 0 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD JUL-SEP PY 2001 VL 49 IS 3 BP 443 EP 468 PG 26 WC Engineering, Aerospace SC Engineering GA 551PB UT WOS:000175569100005 ER PT J AU Cope, JCW Watts, AB McKerrow, WS Fielding, E AF Cope, JCW Watts, AB McKerrow, WS Fielding, E TI Discussion on lithospheric flexure, uplift, and landscape evolution in south-central England - Journal, Vol. 157, 2000, 1169-1177 SO JOURNAL OF THE GEOLOGICAL SOCIETY LA English DT Editorial Material ID VALLEY C1 Cardiff Univ, Dept Earth Sci, Cardiff CF10 3YE, S Glam, Wales. Dept Earth Sci, Oxford OX1 3PR, England. Jet Propuls Lab, Pasadena, CA USA. RP Cope, JCW (reprint author), Cardiff Univ, Dept Earth Sci, POB 914, Cardiff CF10 3YE, S Glam, Wales. RI Fielding, Eric/A-1288-2007 OI Fielding, Eric/0000-0002-6648-8067 NR 14 TC 0 Z9 0 U1 0 U2 1 PU GEOLOGICAL SOC PUBL HOUSE PI BATH PA UNIT 7, BRASSMILL ENTERPRISE CENTRE, BRASSMILL LANE, BATH BA1 3JN, AVON, ENGLAND SN 0016-7649 J9 J GEOL SOC LONDON JI J. Geol. Soc. PD JUL PY 2001 VL 158 BP 725 EP 727 PN 4 PG 3 WC Geosciences, Multidisciplinary SC Geology GA 447PP UT WOS:000169581900014 ER PT J AU Teng, S Han, JC Poinsatte, PE AF Teng, S Han, JC Poinsatte, PE TI Effect of film-hole shape on turbine-blade heat-transfer coefficient distribution SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 38th Aerospace Sciences Meeting and Exhibit CY JAN 10-15, 2000 CL RENO, NEVADA SP Amer Inst Aeronatu & Astronaut ID UNSTEADY WAKE; GAS; EDGE AB Detailed heat transfer coefficient distributions on the suction side of a gas turbine blade were measured using a transient liquid crystal image method. The blade has only one row of film holes near the gill-hole portion on the suction side of the blade. Studies on three different kinds of film-cooling hole shapes were presented. The hole geometries studied include standard cylindrical holes and holes with a diffuser-shaped exit portion (i.e., fan-shaped holes and laidback fan-shaped holes). Tests were performed on a five-blade Linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on the cascade exit velocity was 5.3 x 10(5). Upstream unsteady wakes were simulated using a spoke wheel-ape wake generator. The wake Strouhal number was kept at 0 and 0.1. The coolant-to-mainstream blowing ratio was varied from 0.4 to 1.2. The results show that unsteady wake generally tends to induce earlier boundary-layer transition and enhance the surface heat-transfer coefficients. When compared to the cylindrical hole case, both the expanded hole injections have much lower heat-transfer coefficients over the surface downstream of the injection location, particularly at high blowing ratios. However, the expanded hole injections induce earlier boundary-layer transition to turbulence and enhance heat-transfer coefficients at the latter part of the blade suction surface. C1 Texas A&M Univ, Dept Mech Engn, Turbine Heat Transfer Lab, College Stn, TX 77843 USA. NASA, John H Glenn Res Ctr Lewis Field, Turbomachinery & Prop Syst Div, Cleveland, OH 44135 USA. RP Teng, S (reprint author), Heat Transfer Res Inc, College Stn, TX 77845 USA. NR 24 TC 16 Z9 20 U1 2 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 2001 VL 15 IS 3 BP 249 EP 256 DI 10.2514/2.6610 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 454RT UT WOS:000169986100001 ER PT J AU Teng, S Han, JC Poinsatte, PE AF Teng, S Han, JC Poinsatte, PE TI Effect of film-hole shape on turbine-blade film-cooling performance SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID HEAT-TRANSFER; UNSTEADY WAKE; GAS; EDGE AB Detailed coolant jet temperature profiles and film effectiveness distributions on the suction side of a gas turbine blade are measured using a thermocouple probe and a transient liquid crystal image method, respectively. The blade has only one row of film holes near the gill-hole portion on the suction side of the blade. The hole geometries studied include standard cylindrical holes and holes with diffuser-shaped exit portion (i.e,, fan-shaped holes and laidback fan-shaped holes). Tests are performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity is 5.3 x 10(5). Upstream unsteady wakes are simulated using a spoke-wheel-type wake generator, The wake Strouhal number is kept at 0 or 0.1. Coolant blowing ratio is varied from 0.4 to 1.2. Results show that both expanded holes have significantly improved thermal protection over the surface downstream of the ejection location, particularly at high blowing ratios. In general, the unsteady wake tends to reduce film-cooling effectiveness. C1 Texas A&M Univ, Dept Mech Engn, Turbine Heat Transfer Lab, College Stn, TX 77843 USA. NASA, John H Glenn Res Ctr Lewis Field, Turbomachinery & Prop Syst Div, Cleveland, OH 44135 USA. RP Teng, S (reprint author), Heat Transfer Res Inc, College Stn, TX 77845 USA. NR 25 TC 19 Z9 20 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 2001 VL 15 IS 3 BP 257 EP 265 DI 10.2514/2.6621 PG 9 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 454RT UT WOS:000169986100002 ER PT J AU Zhang, NL Chao, DF Yang, WJ AF Zhang, NL Chao, DF Yang, WJ TI Enhancements of nucleate boiling and critical heat flux under microgravity conditions SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 38th Aerospace Sciences Meeting and Exhibit CY JAN 10-15, 2000 CL RENO, NEVADA SP Amer Inst Aeronatu & Astronaut ID POOL; GRAVITY; MIXTURES AB Two means are presented for enhancing nucleate boiling and critical heat flux under microgravity conditions: using microconfigured metal-graphite composites as the boiling surface and using dilute aqueous solutions of long-chain alcohols as the working fluid. In the former, thermocapillary force induced by the temperature difference between the graphite-fiber tips and the metal matrix plays an important role in bubble detachment. Thus, boiling heat transfer performance does not deteriorate in a reduced-gravity environment. In the latter case, the surface-tension-temperature gradient of the long-chain alcohol solutions turns positive as the temperature exceeds a certain value. Consequently, the Marangoni effect does not impede, but rather aids in bubble departure from the heating surface. This feature is most favorable in microgravity conditions. As a result, the bubble size of departure is substantially reduced at higher frequencies, Based on the existing experimental data, and a two tier theoretical model, correlation formulas are derived for nucleate boiling on the copper-graphite and aluminum-graphite composite surfaces, in both the isolated and coalesced bubble regimes, In addition, performance equations for nucleate boiling and critical heat flux in dilute aqueous solutions of long chain alcohols are obtained. C1 Ohio Aerosp Inst, Dept Work Force Enhancement, Cleveland, OH 44142 USA. NASA, Micrograv Fluid Phys Branch, John H Glenn Res Ctr Lewis Field, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. Univ Michigan, Dept Mech Engn & Appl Mech, Ann Arbor, MI 48109 USA. RP Zhang, NL (reprint author), NASA, Micrograv Fluid Phys Branch, John H Glenn Res Ctr Lewis Field, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. NR 41 TC 5 Z9 5 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 2001 VL 15 IS 3 BP 326 EP 332 DI 10.2514/2.6611 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 454RT UT WOS:000169986100010 ER PT J AU Spakovszky, ZS Paduano, JD Larsonneur, R Traxler, A Bright, MM AF Spakovszky, ZS Paduano, JD Larsonneur, R Traxler, A Bright, MM TI Tip clearance actuation with magnetic bearings for high-speed compressor stall control SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 45th International Gas Turbine and Aeroengine Congress and Exhibition CY MAY 08-11, 2000 CL MUNICH, GERMANY ID FLOW AB Magnetic bearings are widely used as active suspension devices in rotating machinery mainly for active vibration control purposes. The concept of active tip-clearance control suggests a new application of magnetic bearings as servo-actuators to stabilize rotating stall in axial compressors. This paper presents a first-of-a-kind feasibility study of an active stall control experiment with a magnetic bearing servo-actuator in the NASA Glenn high-speed single-stage compressor test facility. Together with CFD and experimental data a two-dimensional, incompressible compressor stability model was used in a stochastic estimation and control analysis to determine the required magnetic bearing performance for compressor stall control. The resulting requirements introduced new challenges to the magnetic bearing actuator design. A magnetic bearing servo-actuator was designed that fulfilled the performance specifications. Control laws were then developed to stabilize the compressor shaft. In a second control loop, a constant gain controller was implemented to stabilize rotating stall. A detailed closed loop simulation tit 100 percent corrected design speed resulted in a 2.3 percent reduction of stalling mass flow, which is comparable to results obtained in the same compressor by Weigl et ell. (1998. ASME J. Turbomach. 120, 625-636) using unsteady air injection. The design and simulation results presented here establish the viability Of magnetic bearings for stall control in aeroengine high-speed compressors. Furthermore, the paper outlines a general design procedure to develop magnetic bearing servo-actuators for high-speed turbomachinery. C1 MIT, Dept Aeronaut & Astronaut, Cambridge, MA 02139 USA. MECOS Traxler AG, CH-8404 Winterthur, Switzerland. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Spakovszky, ZS (reprint author), MIT, Dept Aeronaut & Astronaut, 77 Massachusetts Ave, Cambridge, MA 02139 USA. NR 16 TC 6 Z9 6 U1 0 U2 5 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD JUL PY 2001 VL 123 IS 3 BP 464 EP 472 DI 10.1115/1.1370163 PG 9 WC Engineering, Mechanical SC Engineering GA 457YX UT WOS:000170167500006 ER PT J AU Lepicovsky, J Chima, RV McFarland, ER Wood, JR AF Lepicovsky, J Chima, RV McFarland, ER Wood, JR TI On flowfield periodicity in the NASA transonic flutter cascade SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 45th International Gas Turbine and Aeroengine Congress and Exhibition CY MAY 08-11, 2000 CL MUNICH, GERMANY ID OSCILLATING CASCADE AB A combined experimental and numerical program was carried out to improve the flow uniformity and periodicity in the NASA transonic flutter cascade. The objectives of the program were to improve the periodicity of the cascade and to resolve discrepancies between measured and computed flow incidence angles and exit pressures. Previous experimental data and some of the discrepancies with computations are discussed. In the present work surface pressure taps, boundary layer probes, shadowgraphs, and pressure-sensitive paints were used to measure the effects of boundary layer bleed and tailboard settings on flowfield periodicity. These measurements are described in detail. Two numerical methods were used to analyze the cascade. A multibody panel code was used to analyze the entire cascade and a quasi-three-dimensional viscous code was used to analyze the isolated blades. The codes are described and the results are compared to the measurements. The measurements and computations both showed that the operation of the cascade was heavily dependent on the endwall configuration. The endwalls were redesigned to approximate the midpassage streamlines predicted using the viscous code, and the measurements were repeated. The results of the program were that: (1) Boundary layer bleed does not improve the cascade flow periodicity. (2) Tunnel endwalls must be shaped like predicted cascade streamlines. (3) The actual flow, incidence must be measured for each cascade configuration rather than using the tunnel geometry. (4) The redesigned cascade exhibits excellent periodicity over six of the nine blades. C1 QSS Grp Inc, Cleveland, OH 44135 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Lepicovsky, J (reprint author), QSS Grp Inc, Cleveland, OH 44135 USA. NR 16 TC 3 Z9 4 U1 0 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA THREE PARK AVE, NEW YORK, NY 10016-5990 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD JUL PY 2001 VL 123 IS 3 BP 501 EP 509 DI 10.1115/1.1378300 PG 9 WC Engineering, Mechanical SC Engineering GA 457YX UT WOS:000170167500010 ER PT J AU Bronikowski, MJ Willis, PA Colbert, DT Smith, KA Smalley, RE AF Bronikowski, MJ Willis, PA Colbert, DT Smith, KA Smalley, RE TI Gas-phase production of carbon single-walled nanotubes from carbon monoxide via the HiPco process: A parametric study SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A LA English DT Article; Proceedings Paper CT 47th International Symposium of AVS CY OCT 02-06, 2000 CL BOSTON, MA SP AVS ID VAPOR-PHASE; CATALYZED GROWTH; METAL PARTICLES; FIBERS; HYDROCARBONS; DIAMETER; IRON AB We have demonstrated large-scale production (10 g/day) of high-purity carbon single-walled nanotubes (SWNTs) using a gas-phase chemical-vapor-deposition process we call the HiPco process. SWNTs grow in high-pressure (30-50 atm), high-temperature (900-1100 degreesC) flowing CO on catalytic clusters of iron. The clusters are formed in situ: Fe is added to the gas flow in the form of Fe(CO)(5). Upon heating, the Fe(CO)(5) decomposes and the iron atoms condense into clusters. These clusters serve as catalytic particles upon which SWNT nucleate and grow (in the gas phase) via CO disproportionation: CO + CO==>CO2 + C(SWNT). SWNT material of up to 97 mol % purity has been produced at rates of up to 450 mg/h. The HiPco process has been studied and optimized with respect to a number of process parameters including temperature, pressure, and catalyst concentration. The behavior of the SWNT yield with respect to various parameters sheds light on the processes that currently limit SWNT production, and suggests ways that the production rate can be increased still further. (C) 2001 American Vacuum Society. C1 Rice Univ, Ctr Nanoscale Sci & Technol, Houston, TX 77005 USA. RP Bronikowski, MJ (reprint author), Jet Prop Lab, MS 302-231,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM bronikow@mail2.jpl.nasa.gov RI Willis, Peter/I-6621-2012 NR 24 TC 478 Z9 479 U1 8 U2 102 PU A V S AMER INST PHYSICS PI MELVILLE PA STE 1 NO 1, 2 HUNTINGTON QUADRANGLE, MELVILLE, NY 11747-4502 USA SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A PD JUL-AUG PY 2001 VL 19 IS 4 BP 1800 EP 1805 DI 10.1116/1.1380721 PN 2 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 456YV UT WOS:000170111100046 ER PT J AU Work, TM Rameyer, RA Balazs, GH Cray, C Chang, SP AF Work, TM Rameyer, RA Balazs, GH Cray, C Chang, SP TI Immune status of free-ranging green turtles with fibropapillomatosis from Hawaii SO JOURNAL OF WILDLIFE DISEASES LA English DT Article DE cell proliferation assay; Chelonia mydas; fibropapillomatosis; green turtle; hematology; immunology; protein electrophoresis ID CHELONIA-MYDAS; MARINE TURTLES; CELLS; RESPONSES; PHYLOGENY; STRESS; BLOOD AB Cell-mediated and humoral immune status of free-ranging green turtles (Chelonia,mydas) in Hawaii (USA) with and without fibropapillomatosis (FP) were assessed. Tumored and non-tumored turtles from Kaneohe Bay (KB) on the island of Oahu and from FP-free areas on the west (Kona/Kohala) coast of the island of Hawaii were sampled from April 1998 through February 1999. Turtles on Oahu were grouped (0-3) for severity of tumors with 0 for absence of tumors, 1 for light, 2 for moderate, and 3 for most severe. Turtles were weighed, straight carapace length measured and the regression slope of weight to straight carapace length compared between groups (KB0, KB1, KB2, KB3, Kona). Blood was assayed for differential white blood cell count, hematocrit, in vitro peripheral blood mononuclear cell (PBMC) proliferation in the presence of concanavalin A (Con-A) and phytohaemagglutinin (PHA), and protein electrophoresis. On Oahu, heterophil/lymphocyte ratio increased while eosinophil/monacyte ratio decreased with increasing tumors score. Peripheral blood mononuclear cell proliferation indices for ConA and PRA were significantly lower for turtles with tumor scores 2 and 3. Tumor score 3 turtles (KB3) had significantly lower hematocrit, total protein, alpha 1, alpha 2, and gamma globulins than the other four groups. No significant differences in immune status were seen between non-tumored (or KB1.) turtles from Oahu and Hawaii. There was no significant difference between groups in regression slopes of body condition to carapace length. We conclude that turtles with severe FP are imunosuppressed. Furthermore, the lack of significant difference in immune status between non-tumored (and KB1) turtles from Oahu and Kona/Kohala indicates that immunosuppression may not be a prerequisite for development of FP. C1 US Geol Survey, Natl Wildlife Hlth Ctr, Honolulu Field Stn, Honolulu, HI 96850 USA. Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. Univ Miami, Div Comparat Pathol, Miami, FL 33152 USA. Univ Hawaii, Dept Trop Med, Honolulu, HI 96822 USA. RP Work, TM (reprint author), US Geol Survey, Natl Wildlife Hlth Ctr, Honolulu Field Stn, Honolulu, HI 96850 USA. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 NR 41 TC 44 Z9 50 U1 0 U2 5 PU WILDLIFE DISEASE ASSN, INC PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044-8897 USA SN 0090-3558 J9 J WILDLIFE DIS JI J. Wildl. Dis. PD JUL PY 2001 VL 37 IS 3 BP 574 EP 581 PG 8 WC Veterinary Sciences SC Veterinary Sciences GA 459AH UT WOS:000170227300017 PM 11504232 ER PT J AU Van Mooy, B MacGregor, B Hollander, D Nealson, K Stahl, D AF Van Mooy, B MacGregor, B Hollander, D Nealson, K Stahl, D TI Evidence for tight coupling between active bacteria and particulate organic carbon during seasonal stratification of Lake Michigan SO LIMNOLOGY AND OCEANOGRAPHY LA English DT Article ID SUBSTRATE LIMITATION; GROWTH-RATE; RNA-CONTENT; BACTERIOPLANKTON; DYNAMICS; PHYTOPLANKTON; CHLOROPHYLL; COMMUNITIES; PHOSPHORUS AB Suspended particulate organic matter (POM) plays a critical role in the planktonic ecology of Lake Michigan during seasonal thermal stratification. We show, based on stable isotope and ribosomal RNA (rRNA) data, that the relationship between suspended POM and active biomass changes as thermal stratification persists. Stable isotope data indicated that sources of suspended POM change between July and October, moving from primary production at a deep chlorophyll layer to recycling-based production in surface waters. Concomitant change in the distribution of active bacterial and eukaryotic biomass was observed as indicated by rRNA abundances. Active bacterial and eukaryotic biomass were highly correlated throughout the year. However, the correlation be tween suspended POM and active bacterial biomass varied seasonally and reflected the transitions in planktonic ecology. Suspended POM from depths > 60 m was primarily of sedimentary origin. The combined application of stable isotope and rRNA analysis of suspended POM indicated a dynamic relationship between the bulk POM reservoir and living planktonic biomass. C1 Northwestern Univ, Dept Geol Sci, Evanston, IL 60208 USA. Northwestern Univ, Dept Civil Engn, Evanston, IL 60208 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Van Mooy, B (reprint author), Univ Washington, Sch Oceanog, Seattle, WA 98125 USA. RI MacGregor, Barbara/D-9911-2013 OI MacGregor, Barbara/0000-0003-1238-5799 NR 26 TC 6 Z9 6 U1 0 U2 10 PU AMER SOC LIMNOLOGY OCEANOGRAPHY PI WACO PA 5400 BOSQUE BLVD, STE 680, WACO, TX 76710-4446 USA SN 0024-3590 J9 LIMNOL OCEANOGR JI Limnol. Oceanogr. PD JUL PY 2001 VL 46 IS 5 BP 1202 EP 1208 PG 7 WC Limnology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 453JX UT WOS:000169913700021 ER PT J AU DellaCorte, C AF DellaCorte, C TI Where did all the physicists go? SO LUBRICATION ENGINEERING LA English DT Editorial Material C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP DellaCorte, C (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD JUL PY 2001 VL 57 IS 7 BP 3 EP 3 PG 1 WC Engineering, Mechanical SC Engineering GA 451ZQ UT WOS:000169833000001 ER PT J AU Radil, K AF Radil, K TI The influence of honing on the wear of ceramic coated piston rings and cylinder liners SO LUBRICATION ENGINEERING LA English DT Article DE engines; surface modification; coatings; friction AB Reciprocating wear tests were performed to investigate the effects of honing an the wear of ceramic coated piston rings and cylinder liners. The baseline or control cases consisted of testing ceramic coated rings against ceramic coated liner specimens whose surfaces were ground and lapped smooth. A second series of tests were performed with liner specimens with base and plateau honed surfaces. Test conditions were chosen to simulate the temperatures, pressures, and boundary lubricated conditions present at top ring reversal in a conventional diesel engine. Wear factor comparisons between the baseline cases and the rests with the honed liner specimens indicate that honing alone is not sufficient to ensure an improvement in ring and liner wear. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Radil, K (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD JUL PY 2001 VL 57 IS 7 BP 10 EP 14 PG 5 WC Engineering, Mechanical SC Engineering GA 451ZQ UT WOS:000169833000004 ER PT J AU Rooker, JR Zdanowicz, VS Secor, DH AF Rooker, JR Zdanowicz, VS Secor, DH TI Chemistry of tuna otoliths: assessment of base composition and postmortem handling effects SO MARINE BIOLOGY LA English DT Article ID TRACE-ELEMENT ANALYSIS; LASER-ABLATION ICPMS; FISH OTOLITHS; STOCK IDENTIFICATION; PROBE MICROANALYSIS; MICROCHEMISTRY; STRONTIUM; WATER; TEMPERATURE; RECRUITMENT AB Protocols used to collect and prepare otoliths for chemical analysis may result in either contamination or loss of elements, thus biasing population studies in unknown ways. We evaluated precision and bias associated with collection and cleaning procedures for three Atlantic tuna species: Atlantic bluefin tuna (Thunnus thynnus), yellowfin tuna (T. albacares), and blackfin tuna (T. atlanticus). Elemental concentrations were measured using solution-based inductively coupled plasma mass spectrometry and atomic absorption spectrophotometry. Seven elements were present above detection limits in all samples (Na, Mg, K, Ca, Mn, Sr, Ba). Mean concentrations of all seven elements were statistically indistinguishable in fresh pairs of otoliths of T. thynnus (mean error 5%, range 2-8%) and T. albacares (mean error 5%, range 3-7%); no indication of a left versus right otolith effect was observed. Otolith elemental concentrations were size dependent and significant inverse relationships were observed for Mg, Na, and K. Deliberate contamination of previously cleaned samples using a 10-ppm solution of a mixture of elements demonstrated that otoliths easily acquire surface contamination. Recleaning contaminated otoliths restored elemental concentrations to levels similar to control otoliths. Precision of paired comparisons between cleaned otoliths and those exposed to contamination and recleaned was high (mean error 6%). The effects of storage at two temperatures (7 days at -20 degreesC, 3 days at 1 degreesC) were investigated. For K, Ca, Sr, Mn, and Ba, variation between control (removed immediately) and treatment otoliths (in situ freezing or chilling) was similar to variation observed within fresh otolith pairs (mean error: fresh vs frozen 5%, fresh vs iced 5%). Statistically significant but small ( <10%) postmortem storage effects were observed for Na and Mg. Estimates of error indexed to natural ranges in otolith chemistry of T. thynnus and T. albacares from different geographic regions in the Atlantic and Pacific showed that error values of several elements (Mg, Mn, Ba, Na, K) accounted for a small proportion of the natural range, suggesting levels of precision achieved in this study are suitable for the purpose of stock delineation. C1 Texas A&M Univ, Dept Marine Biol, Galveston, TX 77551 USA. NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. Univ Maryland, Ctr Environm Sci, Chesapeake Biol Lab, Solomons, MD 20688 USA. RP Rooker, JR (reprint author), Texas A&M Univ, Dept Marine Biol, 5007 Ave U, Galveston, TX 77551 USA. RI Secor, D/D-4367-2012; Rooker, Jay/M-3197-2013 OI Secor, D/0000-0001-6007-4827; Rooker, Jay/0000-0002-5934-7688 NR 33 TC 44 Z9 44 U1 1 U2 17 PU SPRINGER-VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0025-3162 J9 MAR BIOL JI Mar. Biol. PD JUL PY 2001 VL 139 IS 1 BP 35 EP 43 PG 9 WC Marine & Freshwater Biology SC Marine & Freshwater Biology GA 461AH UT WOS:000170342400005 ER PT J AU Henderson, JR AF Henderson, JR TI A pre- and post-MARPOL Annex V summary of Hawaiian monk seal entanglements and marine debris accumulation in the northwestern Hawaiian Islands, 1982-1998 SO MARINE POLLUTION BULLETIN LA English DT Article DE pinniped; Monachus; monk seal; marine debris; entanglement; MARPOL ID FUR SEALS; ENVIRONMENT AB Entanglements of Hawaiian monk seals, Monachus schauinslandi, were documented in the northwestern Hawaiian Islands (NWHI) from 1982 to 1998, and debris which presented a threat of entanglement was inventoried and removed from 1987 to 1996. A total of 173 entanglements was documented. The number of entanglements did not change after implementation of MARPOL Annex V in 1989. Pups and juvenile seals were more likely to become entangled than older seals, and became entangled primarily in nets, whereas entanglement of subadults and adults was more likely to involve line. The subpopulation of seals at Lisianski Island experienced the most entanglements, although Lisianski did not accumulate the most debris. Localized high entanglement rates may gravely affect individual monk seal subpopulations. Accumulation of debris has not diminished since implementation of Annex V, nor has occurrence of derelict drift nets abated since a 1989 moratorium. Debris washing ashore has likely been circulating in the North Pacific Ocean for some time. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, 2570 Dole St, Honolulu, HI 96822 USA. EM john.r.henderson@noaa.gov NR 21 TC 53 Z9 57 U1 3 U2 12 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0025-326X EI 1879-3363 J9 MAR POLLUT BULL JI Mar. Pollut. Bull. PD JUL PY 2001 VL 42 IS 7 BP 584 EP 589 DI 10.1016/S0025-326X(00)00204-6 PG 6 WC Environmental Sciences; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 457RJ UT WOS:000170150300018 PM 11488238 ER PT J AU Scott, ERD Haack, H Love, SG AF Scott, ERD Haack, H Love, SG TI Formation of mesosiderites by fragmentation and reaccretion of a large differentiated asteroid SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID THERMAL HISTORY; SOLAR-SYSTEM; PARENT BODY; ORDINARY CHONDRITES; PLANET FORMATION; IRON-METEORITES; IMPACT; METAMORPHISM; ORIGIN; CLASTS AB We propose that mesosiderites formed when a 200-400 km diameter asteroid with a molten core was disrupted by a 50-150 km diameter projectile. To test whether impacts can excavate core iron and mix it with crustal material, we used a low-resolution, smoothed-particle hydrodynamics computer simulation. For 50-300 km diameter differentiated targets, we found that significant proportions of scrambled core material (and hence potential mesosiderite metal material) could be generated. For near-catastrophic impacts that reduce the target to 80% of its original diameter and about half of its original mass, the proportion of scrambled core material would be about 5 vol%, equivalent to similar to 10 vol% of mesosiderite-like material. The paucity of olivine in mesosiderites and the lack of metal-poor or troilite-rich meteorites from the mesosiderite body probably reflect biased sampling. Mesosiderites may be olivine-poor because mantle material was preferentially excluded from the metal-rich regions of the reaccreted body. Molten metal globules probably crystallized around small, cool fragments of crust hindering migration of metal to the core. If mantle fragments were much hotter and larger than crustal fragments, little metal would have crystallized around the mantle fragments allowing olivine and molten metal to separate gravitationally. The rapid cooling rates of mesosiderites above 850 degreesC can be attributed to local thermal equilibration between hot and cold ejecta. Very slow cooling below 400 degreesC probably reflects the large size of the body and the excellent thermal insulation provided by the reaccreted debris. We infer that our model is more plausible than an earlier model that invoked an impact at similar to1 km/s to mix projectile metal with target silicates. If large impacts cannot effectively strip mantles from asteroidal cores, as we infer, we should expect few large eroded asteroids to have surfaces composed purely of mantle or core material. This may help to explain why relatively few olivine-rich (A-type) and metal-rich asteroids (M-type) are known. Some S-type asteroids may be scrambled differentiated bodies. C1 Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Scott, ERD (reprint author), Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. EM escott@higp.hawaii.edu RI Haack, Henning/A-4807-2013 OI Haack, Henning/0000-0002-4618-3178 NR 67 TC 42 Z9 45 U1 0 U2 1 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 JUL PY 2001 VL 36 IS 7 BP 869 EP 881 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 457RZ UT WOS:000170151800003 ER PT J AU Pizzarello, S Cooper, GW AF Pizzarello, S Cooper, GW TI Molecular and chiral analyses of some protein amino acid derivatives in the Murchison and Murray meteorites SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID MASS-SPECTROMETRY; ENANTIOMERS AB The varied organic suite extracted from the Murchison meteorite contains several amino acids that are common to the biosphere. Some of these have been found to be non-racemic, but the indigenous nature of their L-enantiomeric excesses has been subject to debate in view of possible terrestrial contamination. We have investigated two amino acids of common terrestrial and meteoritic occurrence, alanine and glutamic acid, and assessed their indigenous enantiomeric ratios in the Murchison and Murray meteorites through the ratios of some of their derivatives. Analyzed were N-acetyl alanine, alpha-imino propioacetic acid, N-acetyl glutamic acid and pyroglutamic acid. Both alanine derivatives were found to be racemic, while those of glutamic acid showed L-enantiomeric excesses varying from 16% to 47.2% for pyroglutamic acid, and from 8.6% to 41% for N-acetyl glutamic acid. The delta C-13 was determined for the two enantiomers of Murchison pyroglutamic acid both before and after acid hydrolysis to glutamic acid. The values of +27.7 parts per thousand (D-pyro), +10.0 parts per thousand (L-pyro), +32.2 parts per thousand (D-glu) and +14.6 parts per thousand (L-glu) were obtained. The racemic nature of alanine derivatives strongly suggests that alanine itself, as indigenous to the meteorite, is racemic. The explanation of the L-enantiomeric excesses found for glutamic acid derivatives is less direct; however, the variability of the enantiomeric ratios for these compounds and the distinctly lower delta C-13 values determined for pyroglutamic L-enantiomer point to a terrestrial contamination, possibly dating to the time of fall. C1 Arizona State Univ, Dept Biochem & Chem, Tempe, AZ 85287 USA. NASA, Ames Res Ctr, Exobiol Div, Moffett Field, CA 94035 USA. RP Pizzarello, S (reprint author), Arizona State Univ, Dept Biochem & Chem, Tempe, AZ 85287 USA. NR 28 TC 37 Z9 40 U1 1 U2 9 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 JUL PY 2001 VL 36 IS 7 BP 897 EP 909 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 457RZ UT WOS:000170151800005 ER PT J AU Nyquist, L Lindstrom, D Mittlefehldt, D Shih, CY Wiesmann, H Wentworth, S Martinez, R AF Nyquist, L Lindstrom, D Mittlefehldt, D Shih, CY Wiesmann, H Wentworth, S Martinez, R TI Manganese-chromium formation intervals for chondrules from the Bishunpur and Chainpur meteorites SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID EARLY SOLAR-SYSTEM; ANGRA-DOS-REIS; CARBONACEOUS CHONDRITES; SEMARKONA CHONDRULES; PRIMITIVE METEORITES; LUNAR SPHERULES; IODINE-XENON; AL-26; ORIGIN; FRACTIONATION AB Whole-chondrule Mn-Cr isochrons are presented for chondrules separated from the Chainpur (LL3.4) and Bishunpur (LL3.1) meteorites. The chondrules were initially surveyed by instrumental neutron activation analysis. LL-chondrite-normalized Mn/Cr, Mn/Fe, and Sc/Fe served to identify chondrules with unusually high or low Mn/Cr ratios, and to correlate the abundances of other elements to Sc, the most refractory element measured. A subset of chondrules from each chondrite was chosen for analysis by a scanning electron microscope equipped with an energy dispersive x-ray spectrometer prior to high-precision Cr-isotopic analyses. Cr-53/Cr-52 correlates with Mn-55/Cr-52 to give initial (Mn-53/Mn-55)(I) = (9.4 +/- 1.7) x 10(-6) for Chainpur chondrules and (Mn-53/Mn-55)(I) = (9.5 +/- 3.1) x 10(-6) for Bishunpur chondrules. The corresponding chondrule formation intervals are, respectively, Deltat(LEW) = -10 +/- 1 Ma for Chainpur and -10 +/- 2 Ma for Bishunpur relative to the time of igneous crystallization of the Lewis Cliff (LEW) 86010 angrite. Because Mn/Sc correlates positively with Mn/Cr for both the Chainpur and Bishunpur chondrules, indicating dependence of the Mn/Cr ratio on the relative volatility of the elements, we identify the event dated by the isochrons as volatility-driven elemental fractionation for chondrule precursors in the solar nebula. Thus, our data suggest that the precursors to LL chondrules condensed from the nebula 5.8 +/- 2.7 Ma after the time when initial (53Mn/55Mn)(I) = (2.8 +/- 0.3) x 10(-5) for calcium-aluminum-rich inclusions (CAIs), our preferred value, determined from data for (a) mineral separates of type B Allende CAI BR1, (b) spinels from Efremovka CAI E38, and (c) bulk chondrites. Mn-Cr formation intervals for meteorites are presented relative to average I(Mn) = (53Mn/55Mn)Ch 9.46 x 10(-6) for chondrules. Mn/Cr ratios for radiogenic growth of Cr-53 in the solar nebula and later reservoirs are calculated relative to average (I(Mn), epsilon(Cr-53)(I)) = ((9.46 +/- 0.08) x 10(-6), -0.23 +/- 0.08) for chondrules. Inferred values of Mn/Cr lie within expected ranges. Thus, it appears that evolution of the Cr-isotopic composition can be traced from condensation of CAls via condensation of the ferromagnesian precursors of chondrules to basalt generation on differentiated asteroids. Measured values of epsilon(Cr-53) for individual chondrules exhibit the entire range of values that has been observed as initial 6(53Cr) values for samples from various planetary objects, and which has been attributed to radial heterogeneity in initial 53Mn/55Mn in the early solar system. Estimated Mn-55/Cr-52 = 0.42 +/- 0.05 for the bulk Earth, combined with epsilon(Cr-53) = 0 for the Earth, plots very close to the chondrule isochrons, so that the Earth appears to have the Mn-Cr systematics of a refractory chondrule. Thus, the Earth apparently formed from material that had been depleted in Mn relative to Cr contemporaneously with condensation of chondrule precursors. If, as seems likely, the Earth's core formed after complete decay of Mn-53, there must have been little differential partitioning of Mn and Cr at that time. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin Space Mission Syst & Serv Co, Houston, TX 77058 USA. RP Nyquist, L (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN2, Houston, TX 77058 USA. NR 83 TC 44 Z9 46 U1 0 U2 6 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 JUL PY 2001 VL 36 IS 7 BP 911 EP 938 PG 28 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 457RZ UT WOS:000170151800006 ER PT J AU Reimer, O Brazier, KTS Carraminana, A Kanbach, G Nolan, PL Thompson, DJ AF Reimer, O Brazier, KTS Carraminana, A Kanbach, G Nolan, PL Thompson, DJ TI Multifrequency studies of the enigmatic gamma-ray source 3EG: J1835+5918 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE gamma-rays : observations; X-rays : stars ID PULSAR PSR J0218+4232; NEUTRON-STARS; POINT SOURCES; EMISSION; EGRET; BLAZARS AB The EGRET telescope aboard the NASA Compton Gamma-Ray Observatory (CGRO) has repeatedly detected 3EG J1835+5918, a bright and steady source of high-energy gamma-ray emission which has not yet been identified. The absence of any likely counterpart for a bright gamma-ray source located 25 degrees off the Galactic plane initiated several attempts of deep observations at other wavelengths. We report on counterparts in X-rays on a basis of a 60-ks ROSAT HRI image. In older to conclude on the plausibility of the X-ray counterparts, we reanalysed data from EGRET at energies above 100 MeV and above 1 GeV, including data up to CGRO observation cycle 7. The gamma-ray sauce location represents the latest and probably the final positional assessment based on EGRET data. We especially address the question of flux and spectral variability, here discussed using the largest and most homogeneous data set available at high-energy gamma-rays for many years. The results from X-ray and gamma-ray observations were used in a follow-up optical identification campaign at the 2.2-m Guillermo Hare Telescope at Cananea, Mexico. VRI imaging. has been performed at the positions of all of the X-ray counterpart candidates, and spectra were taken where applicable. The results of the multifrequency identification campaign toward this enigmatic unidentified gamma-ray source are given, especially on the one object which might be associated with the gamma-ray source 3EG J1835+5918. This object has the characteristics of an isolated neutron star and possibly of a radio-quiet pulsar. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Durham, Durham DH1 3LE, England. Inst Nacl Astrofis Opt & Elect, Tonantzintla, Mexico. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. RP Reimer, O (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. RI Nolan, Patrick/A-5582-2009; Thompson, David/D-2939-2012; Reimer, Olaf/A-3117-2013 OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385 NR 38 TC 35 Z9 35 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 JUL 1 PY 2001 VL 324 IS 3 BP 772 EP 780 DI 10.1046/j.1365-8711.2001.04397.x PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 452ZX UT WOS:000169890700028 ER PT J AU Primas, F Rebull, LM Duncan, DK Hobbs, LM Truran, JW Beers, TC AF Primas, F Rebull, LM Duncan, DK Hobbs, LM Truran, JW Beers, TC TI A new study of oxygen abundances derived from the OI triplet SO NEW ASTRONOMY REVIEWS LA English DT Article; Proceedings Paper CT 24th General Assembly of the International-Astronomical-Union CY AUG 07-18, 2000 CL MANCHESTER, ENGLAND SP Int Astron Union ID METAL-POOR STARS; LIGHT-ELEMENTS; STELLAR AB Despite being the most abundant element in the Galaxy and the fact that the first determinations of its abundance in large samples of stars date back to the 60s, the evolution of oxygen along the Galactic history is still quite puzzling. In short, the results obtained by analyzing different oxygen abundance indicators (the O I triplet, the forbidden [O I] lines, the near-UV and IR OH molecular lines) are discrepant and prevent us from achieving a satisfactory interpretation of the oxygen evolutionary trend (e.g., [O/Fe] vs. [Fe/H]). Here, we present the preliminary results of a new analysis of the O I triplet in a large sample of halo and disk stars. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Observ Midi Pyrenees, Astrophys Lab, F-31400 Toulouse, France. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Yerkes Observ, Williams Bay, WI 53191 USA. Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. RP Primas, F (reprint author), European So Observ, Karl Schwarzschildstr 2, D-85748 Garching, Germany. EM fprimas@eso.org OI Rebull, Luisa/0000-0001-6381-515X NR 17 TC 4 Z9 4 U1 0 U2 2 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 1387-6473 J9 NEW ASTRON REV JI New Astron. Rev. PD JUL PY 2001 VL 45 IS 8 BP 541 EP 543 DI 10.1016/S1387-6473(01)00121-X PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 457JY UT WOS:000170134800009 ER PT J AU Ramaty, R Lingenfelter, RE Kozlovsky, B AF Ramaty, R Lingenfelter, RE Kozlovsky, B TI Oxygen and Fe evolution: the effect of refractory element deposition delays SO NEW ASTRONOMY REVIEWS LA English DT Article; Proceedings Paper CT 24th General Assembly of the International-Astronomical-Union CY AUG, 2000 CL MANCHESTER, ENGLAND SP Int Astron Union AB The delay of Fe deposition relative to O, due to the incorporation of supernova ejecta refractories in high velocity grains, can account for the possible rise of [O/Fe]. The predicted behavior of alpha elements, refractory Mg, Si, Ca and Ti, and volatile S, appears to be consistent with this model. (C) 2001 Published by Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif San Diego, CASS, 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 7 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 1387-6473 J9 NEW ASTRON REV JI New Astron. Rev. PD JUL PY 2001 VL 45 IS 8 BP 587 EP 588 DI 10.1016/S1387-6473(01)00133-6 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 457JY UT WOS:000170134800022 ER PT J AU M'Closkey, RT Vakakis, A Gutierrez, R AF M'Closkey, RT Vakakis, A Gutierrez, R TI Mode localization induced by a nonlinear control loop SO NONLINEAR DYNAMICS LA English DT Article DE nonlinear localization; nonlinear control; automatic gain control; vibratory gyroscope ID COUPLED BEAMS; SYSTEM AB We present the analysis of a nonlinear control system that is used to excite and maintain a specified amplitude of oscillation in the Jet Propulsion Laboratory vibratory gyroscope. This experimental application shows that nonlinear localization through active means can be implemented in a practical system when it is desirable to confine the response to a favorable mode. The closed-loop system response predicted by the model shows very close agreement with the experimental results for a significant range of controller parameters. We also experimentally demonstrate that the actively localized motion is eliminated through bifurcation, similar to what was observed in previous passive localization studies applied to extended flexible oscillators. C1 Univ Calif Los Angeles, Los Angeles, CA 90095 USA. Univ Illinois, Urbana, IL 61801 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP M'Closkey, RT (reprint author), Univ Calif Los Angeles, Los Angeles, CA 90095 USA. NR 14 TC 22 Z9 22 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0924-090X J9 NONLINEAR DYNAM JI Nonlinear Dyn. PD JUL PY 2001 VL 25 IS 1-3 BP 221 EP 236 DI 10.1023/A:1012934112137 PG 16 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 496EV UT WOS:000172384000013 ER PT J AU Moles, A Scott, R AF Moles, A Scott, R TI Effect of entry timing and salinity on overwinter growth of sockeye salmon fry in seawater SO NORTH AMERICAN JOURNAL OF AQUACULTURE LA English DT Article ID ONCORHYNCHUS-NERKA; FRESH-WATER; NET-PENS; SURVIVAL; SALAR; SMOLTIFICATION; ADAPTATION; KISUTCH; HORMONE; STOCKS AB Groups of sockeye salmon Oncorhynchus nerka (approximately 2 g in weight) were introduced into seawater tanks at three distinct times, 3 weeks before the fall equinox, at the equinox, and 3 weeks after the equinox. All groups were reared for 8 months (September-May) in those tanks to determine the relative effects of seawater entry timing and salinity (20 parts per thousand and 30 parts per thousand) on overwinter growth in seawater. The growth rates in all groups declined from more than 2% of body weight per day (BWD) to less than 0.5% of BWD following the equinox. Growth rates did not differ significantly between fish transferred to seawater before the autumnal equinox and those transferred after the equinox. Fish transferred to water with reduced salinity (20 parts per thousand) had significantly better initial growth than those transferred directly to full-strength seawater (30 parts per thousand) at the same time. This difference did not persist past the winter solstice, however. These data suggest that managers can successfully rear sockeye salmon fry as small as 1.5 g in seawater if water with 20 parts per thousand salinity is initially used. C1 Natl Marine Fisheries Serv, Auke Bay Fisheries Lab, Juneau, AK 99801 USA. Alaska Dept Fish & Game, Juneau, AK 99801 USA. RP Moles, A (reprint author), Natl Marine Fisheries Serv, Auke Bay Fisheries Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 17 TC 0 Z9 0 U1 1 U2 1 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 1522-2055 J9 N AM J AQUACULT JI N. Am. J. Aqualcult. PD JUL PY 2001 VL 63 IS 3 BP 222 EP 228 DI 10.1577/1548-8454(2001)063<0222:EOETAS>2.0.CO;2 PG 7 WC Fisheries SC Fisheries GA 457MB UT WOS:000170140200006 ER PT J AU Martin, RM Wertheimer, AC Thrower, F Joyce, JE AF Martin, RM Wertheimer, AC Thrower, F Joyce, JE TI Growth and survival of Alaska stream-type Chinook salmon cultured in estuarine net-pens or freshwater raceways SO NORTH AMERICAN JOURNAL OF AQUACULTURE LA English DT Article ID 2 SMOLT RELEASES; COHO SALMON; ONCORHYNCHUS-KISUTCH; MARINE SURVIVAL; RETURNS; ADULTS; SIZE AB The overwinter survival and growth and the subsequent marine survival of stream-type chinook salmon Oncorhynchus tshawytscha were compared between fish cultured in marine net-pens and their siblings cultured in freshwater. The net-pens were suspended in a stratified estuary with a low-salinity lens; the lens provided osmotic relief to the fish, and its depth and salinity varied seasonally. The median overwinter survival for chinook salmon from six brood years was 89.1% for the net-pen groups, significantly (P = 0.009) less than the median survival of 99.0% in freshwater. The median overwinter growth rate was 0.5% of body weight/d for the net-pen groups, significantly (P = 0.013) higher than the median growth rate of 0.2% for freshwater groups. The median marine survival of smolts from net-pen and freshwater groups was similar, 5.6% and 5.3%, respectively. These results demonstrate that juvenile stream-type chinook salmon can be cultured successfully over winter from the subyearling to smolt stage in marine net-pens suspended in a highly stratified estuary but that overwinter survival will be lower than in freshwater raceways. C1 Natl Marine Fisheries Serv, Auke Bay Lab, Alaska Fisheries Sci Ctr, Juneau, AK 99801 USA. RP Wertheimer, AC (reprint author), Natl Marine Fisheries Serv, Auke Bay Lab, Alaska Fisheries Sci Ctr, 11305 Glacier Highway, Juneau, AK 99801 USA. EM alex.wertheimer@noaa.gov NR 22 TC 2 Z9 2 U1 0 U2 0 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 1522-2055 J9 N AM J AQUACULT JI N. Am. J. Aqualcult. PD JUL PY 2001 VL 63 IS 3 BP 256 EP 261 DI 10.1577/1548-8454(2001)063<0256:GASOAS>2.0.CO;2 PG 6 WC Fisheries SC Fisheries GA 457MB UT WOS:000170140200013 ER PT J AU Chai, JC Moder, JP Karki, KC AF Chai, JC Moder, JP Karki, KC TI A procedure for view factor calculation using the finite-volume method SO NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS LA English DT Article ID RADIATION HEAT-TRANSFER; CYLINDRICAL ENCLOSURES; IRREGULAR GEOMETRIES AB This article presents a finite-volume method to calculate view factors between surfaces of control volumes. A simple approach, which does not lead to the increase in memory requirement with increasing angular grid, is used. The spatial and angular resolution errors are resolved by grid refinements. The procedure can handle straight-edged, inclined, and curved boundaries. Blockages due to internal obstructions and boundaries can also be accommodated. Five problems are examined and the exact solutions are reproduced. C1 Nanyang Technol Univ, Sch Mech & Prod Engn, Singapore 639798, Singapore. NASA, Glenn Res Ctr, Cleveland, OH USA. Innovat Res Inc, Plymouth, MN USA. RP Chai, JC (reprint author), Nanyang Technol Univ, Sch Mech & Prod Engn, Nanyang Ave, Singapore 639798, Singapore. RI Chai, John/A-3764-2010 NR 12 TC 11 Z9 11 U1 1 U2 2 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 USA SN 1040-7790 J9 NUMER HEAT TR B-FUND JI Numer Heat Tranf. B-Fundam. PD JUL PY 2001 VL 40 IS 1 BP 23 EP 35 PG 13 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA 453GJ UT WOS:000169907900002 ER PT J AU Kaminskii, AA Ueda, K Eichler, HJ Kuwano, Y Kouta, H Bagaev, SN Chyba, TH Barnes, JC Gad, GMA Murai, T Lu, JR AF Kaminskii, AA Ueda, K Eichler, HJ Kuwano, Y Kouta, H Bagaev, SN Chyba, TH Barnes, JC Gad, GMA Murai, T Lu, JR TI Tetragonal vanadates YVO4 and GdVO4 - new efficient chi((3))-materials for Raman lasers SO OPTICS COMMUNICATIONS LA English DT Article DE stimulated Raman scattering; rare-earth vanadates; laser crystals ID DIODE; OPERATION AB Efficient room temperature multiple Stokes and anti-Stokes picosecond generation in tetragonal YVO4 and GdVO4 host crystals for lasing trivalent lanthanides (Ln(3+)) has been observed for the first time. All measured stimulated Raman scattering (SRS) wavelengths in the visible and near infrared are identified and attributed to the SRS-active vibration modes of these vanadates. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Univ Electrocommun, Inst Laser Sci, Chofu, Tokyo 1828585, Japan. Russian Acad Sci, Inst Crystallog, Moscow 117333, Russia. Tech Univ Berlin, Inst Opt, D-10623 Berlin, Germany. NEC Corp Ltd, Funct Mat Dept Ctr, Miyamae Ku, Kawasaki, Kanagawa 2168555, Japan. Russian Acad Sci, Inst Laser Phys, Novosibirsk 630090, Russia. Hampton Univ, Res Ctr Opt Phys, Dept Phys, Hampton, VA 23688 USA. NASA, Langley Res Ctr, Laser Syst Branch, Hampton, VA 23681 USA. RP Ueda, K (reprint author), Univ Electrocommun, Inst Laser Sci, 1-5-1 Chofugaoka, Chofu, Tokyo 1828585, Japan. RI Bagayev, Sergei/R-7942-2016 OI Bagayev, Sergei/0000-0003-4470-2779 NR 17 TC 219 Z9 238 U1 6 U2 42 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0030-4018 J9 OPT COMMUN JI Opt. Commun. PD JUL 1 PY 2001 VL 194 IS 1-3 BP 201 EP 206 DI 10.1016/S0030-4018(01)01274-3 PG 6 WC Optics SC Optics GA 448XW UT WOS:000169656100022 ER PT J AU Klimeck, G AF Klimeck, G TI Indirect bandgap-like current flow in direct bandgap electron resonant tunneling diodes SO PHYSICA STATUS SOLIDI B-BASIC RESEARCH LA English DT Article; Proceedings Paper CT 2nd Motorola Workshop on Computational Materials and Electronics CY NOV 09-10, 2000 CL TEMPE, ARIZONA ID CURRENT-VOLTAGE CALCULATIONS; INTERFACE ROUGHNESS; SIMULATION; SCATTERING; TRANSPORT; DEVICES; FORMULA; MODELS AB The current turn-on and turn-off in a resonant tunneling diode (RTD) is determined by the crossing of the central resonance subband with the Fermi level in the emitter, the subbands of quasi bound states in the emitter and the conduction band edge in the emitter. In a typical RTD the subbands in the central well and the emitter are similar, resulting in a simple resonant current now for almost all transverse momenta. Since most of the electrons have zero transverse momentum, one therefore observes that most of the carriers travel straight through the structure. This paper presents a mechanism that can generate off-zone-center current now in electron resonant tunneling diodes, where most of the carriers travel through the structure at an angle for a certain bias range. The basic idea is that if the effective mass in the RTD well is much smaller than the effective mass in the emitter, subband crossings will occur outside the zone center, resulting in this unintuitive distribution of the current as a function of transverse momentum. This mechanism is shown to increase the valley current within a single band approximation without non-parabolicity. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Klimeck, G (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Klimeck, Gerhard/A-1414-2012 OI Klimeck, Gerhard/0000-0001-7128-773X NR 25 TC 3 Z9 3 U1 0 U2 1 PU WILEY-V C H VERLAG GMBH PI BERLIN PA PO BOX 10 11 61, D-69451 BERLIN, GERMANY SN 0370-1972 J9 PHYS STATUS SOLIDI B JI Phys. Status Solidi B-Basic Res. PD JUL PY 2001 VL 226 IS 1 BP 9 EP 19 PG 11 WC Physics, Condensed Matter SC Physics GA 455QG UT WOS:000170037800007 ER PT J AU Mingo, N Yang, L Han, J Anantram, MP AF Mingo, N Yang, L Han, J Anantram, MP TI Resonant versus anti-resonant tunneling at carbon nanotube A-B-A heterostructures SO PHYSICA STATUS SOLIDI B-BASIC RESEARCH LA English DT Article; Proceedings Paper CT 2nd Motorola Workshop on Computational Materials and Electronics CY NOV 09-10, 2000 CL TEMPE, ARIZONA ID TRANSMISSION; TRANSPORT; JUNCTIONS AB Narrow antiresonances going to zero transmission are found to occur for general (2n, 0) (n, n) (2n, 0) carbon nanotube heterostructures, whereas the complementary configuration, (n,n)(2n,0)(n,n), displays simple resonant tunneling behavior. We compute examples for different cases, and give a simple explanation for the appearance of antiresonances in one case but not in the other. Conditions and ranges for the occurrence of these different behaviors are stated. The phenomenon of anti-resonant tunneling, which has passed unnoticed in previous studies of nanotube hetero-structures, adds up to the rich set of behaviors available to nanotube based quantum effect devices. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Han, J (reprint author), NASA, Ames Res Ctr, Mail Stop T27A-1, Moffett Field, CA 94035 USA. NR 20 TC 11 Z9 11 U1 0 U2 2 PU WILEY-V C H VERLAG GMBH PI BERLIN PA PO BOX 10 11 61, D-69451 BERLIN, GERMANY SN 0370-1972 J9 PHYS STATUS SOLIDI B JI Phys. Status Solidi B-Basic Res. PD JUL PY 2001 VL 226 IS 1 BP 79 EP 85 DI 10.1002/1521-3951(200107)226:1<79::AID-PSSB79>3.0.CO;2-5 PG 7 WC Physics, Condensed Matter SC Physics GA 455QG UT WOS:000170037800014 ER PT J AU Riley, N Trinh, EH AF Riley, N Trinh, EH TI Steady streaming in an oscillatory inviscid flow SO PHYSICS OF FLUIDS LA English DT Article AB Steady streaming, arising within a fluctuating flow field, is commonly associated with attenuation due to viscosity. In this paper we show that such streaming may be induced within an inviscid fluid when the underlying fluctuating flow is the result of a nonconservative body force. In such a situation the induced streaming is significantly greater than that in a viscous fluid brought about by a fluctuating conservative body force. The vehicle we choose to illustrate this is a unidirectional buoyancy force, otherwise known as g-jitter. In particular the flow about a heated sphere in an otherwise gravity-free environment is analyzed. The relationship with the analogous viscous-flow problem is investigated. (C) 2001 American Institute of Physics. C1 Univ E Anglia, Sch Math, Norwich NR4 7TJ, Norfolk, England. NASA Headquarters, Washington, DC 20546 USA. RP Riley, N (reprint author), Univ E Anglia, Sch Math, Norwich NR4 7TJ, Norfolk, England. NR 7 TC 5 Z9 5 U1 1 U2 2 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD JUL PY 2001 VL 13 IS 7 BP 1956 EP 1960 DI 10.1063/1.1369127 PG 5 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 443KQ UT WOS:000169340700012 ER PT J AU Levine, LH Heyenga, AG Levine, HG Choi, JW Davin, LB Krikorian, AD Lewis, NG AF Levine, LH Heyenga, AG Levine, HG Choi, JW Davin, LB Krikorian, AD Lewis, NG TI Cell-wall architecture and lignin composition of wheat developed in a microgravity environment SO PHYTOCHEMISTRY LA English DT Article; Proceedings Paper CT Symposium of the American-Chemical-Society CY MAR 26-29, 2000 CL SAN FRANCISCO, CALIFORNIA SP Amer Chem Soc DE Triticum aestivum L.; wheat; gramineae; space flight; microfibrils; secondary wall; lignin; microgravity ID TRACHEARY ELEMENTS; MICROFIBRIL ORIENTATION; CELLULOSE MICROFIBRILS; MAIZE ROOTS; GROWTH; PLANTS; MICROTUBULES; MORPHOGENESIS; CYTOSKELETON; SPACEFLIGHT AB The microgravity environment encountered during space-flight has long been considered to affect plant growth and developmental processes, including cell wall biopolymer composition and content. As a prelude to studying how microgravity is perceived - and acted upon - by plants, it was first instructive to investigate what gross effects on plant growth and development occurred in microgravity. Thus, wheat seedlings were exposed to microgravity on board the space shuttle Discovery (STS-51) for a 10 day duration, and these specimens were compared with their counterparts grown on Earth under the same conditions (e.g. controls). First, the primary roots of the wheat that developed under both microgravity and 1 g on Earth were examined to assess the role of gravity on cellulose microfibril (CMF) organization and secondary wall thickening patterns. Using a quick freeze/deep etch technique, this revealed that the cell wall CMFs of the space-grown wheat maintained the same organization as their 1 g-grown counterparts. That is, in all instances. CMFs were randomly interwoven with each other in the outermost layers (farthest removed from the plasma membrane), and parallel to each other within the individual strata immediately adjacent to the plasma membranes. The CMF angle in the innermost stratum relative to the immediately adjacent stratum was ra 80 degrees in both the space and Earth-grown plants. Second, all plants grown in microgravity had roots that grew downwards into the agar; they did not display "wandering" and upward growth as previously reported by others, Third, the space-grown wheat also developed normal protoxylem and metaxylem vessel elements with secondary thickening patterns ranging from spiral to regular pit to reticulate thickenings. Fourthly, both the space- and Earth-grown plants were essentially of the same size acid height, and their lignin analyses revealed no substantial differences in their amounts and composition regardless of the gravitational held experienced, i.e. for the purposes of this study, all plants were essentially identical. These results suggest that the microgravity environment itself at best only slightly affected either cell wall biopolymer synthesis or the deposition of CMFs, in contrast to previous assertions. (C) 2001 Published by Elsevier Science Ltd. All rights reserved. C1 Dynamac Corp, Kennedy Space Ctr, FL 32899 USA. NASA, Ames Res Ctr, Space Technol Div, Moffett Field, CA 94035 USA. Washington State Univ, Inst Biol Chem, Pullman, WA 99164 USA. SUNY Stony Brook, Dept Biochem & Cell Biol, Stony Brook, NY 11794 USA. RP Levine, LH (reprint author), Dynamac Corp, DYN-3, Kennedy Space Ctr, FL 32899 USA. NR 37 TC 28 Z9 31 U1 1 U2 8 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0031-9422 J9 PHYTOCHEMISTRY JI Phytochemistry PD JUL PY 2001 VL 57 IS 6 BP 835 EP 846 DI 10.1016/S0031-9422(01)00148-0 PG 12 WC Biochemistry & Molecular Biology; Plant Sciences SC Biochemistry & Molecular Biology; Plant Sciences GA 451MC UT WOS:000169805000005 PM 11423135 ER PT J AU Xu, KM Randall, DA AF Xu, KM Randall, DA TI Explicit simulation of cumulus ensembles with the GATE phase III data: Budgets of a composite easterly wave SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE cloud-resolving simulations; easterly waves; GATE convection ID SYNOPTIC-SCALE DISTURBANCES; GENERAL-CIRCULATION MODEL; NUMERICAL-SIMULATION; MACROSCOPIC BEHAVIOR; TROPICAL CONVECTION; MESOSCALE PROCESSES; CLOUD ENSEMBLE; AFRICAN WAVES; PARAMETERIZATION; MASS AB The mass, heat and moisture budgets of a composite easterly wave over the eastern tropical Atlantic are analysed from simulations of a convection-resolving model (CRM). The large-scale data from the GARP (Global Atmospheric Research Program) Atlantic Tropical Experiment (GATE) phase III are used to drive the CRM simulations. The simulated, composite easterly wave is reasonably comparable with the observed, except for the lack of shallow convection embedded in the simulated easterly waves. The mesoscale stratiform precipitation processes are found to be an inseparable component of cumulus convection embedded in the easterly waves. Their main differences from convective processes are twofold: (1) the distinct vertical structures of the budget components due to mesoscale updraughts and downdraughts, and (2) the phase lags relative to the convective processes in the temporal evolution of the easterly waves. Thus, theoretical studies should include both convective and mesoscale stratiform precipitation processes in order to further understanding of diabatic processes in the dynamics of the easterly waves and possibly other waves in the tropics. In addition, the budget analysis presented in this study also provides some details for improving parametrizations of cumulus convection. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Colorado State Univ, Ft Collins, CO 80523 USA. RP Xu, KM (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23681 USA. RI Xu, Kuan-Man/B-7557-2013; Randall, David/E-6113-2011 OI Xu, Kuan-Man/0000-0001-7851-2629; Randall, David/0000-0001-6935-4112 NR 60 TC 4 Z9 5 U1 0 U2 0 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING RG1 7LJ, BERKS, ENGLAND SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD JUL PY 2001 VL 127 IS 575 SI A BP 1571 EP 1591 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 461YH UT WOS:000170391100005 ER PT J AU Riishojgaard, LP AF Riishojgaard, LP TI Deterministic prediction of the ensemble variance for a barotropic vorticity-equation model SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE data assimilation; forecast error variance; Kalman filter ID DATA ASSIMILATION; ERROR AB The problem of estimating the error variance of a meteorological forecast is important both for data assimilation purposes and in order to increase the value of the forecast to the end user. Current data assimilation systems have no-or at best a severely limited-capability to estimate this quantity. In principle, the prognostic equation for the forecast error covariance is known from the Kalman filter. However, in its full form this equation is prohibitively expensive to implement and solve. In this article, the possibility of evolving a variance-only estimate is explored. It is shown that for a barotropic vorticity-equation model, an approximate equation for the error variance evolution can be written in a closed form under certain assumptions. The cost of solving this equation is comparable to that of solving the model equation itself. Through a demonstration experiment, it is shown that the approximate equation tracks the actual variance of a model run-represented by the variance over a randomly perturbed ensemble of forecasts generated by the model-remarkably well, qualitatively as well as quantitatively. C1 Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. Univ Maryland, College Pk, MD 20742 USA. RP Riishojgaard, LP (reprint author), Goddard Space Flight Ctr, Data Assimilat Off, Code 910-3, Greenbelt, MD 20771 USA. NR 10 TC 1 Z9 1 U1 0 U2 0 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING RG1 7LJ, BERKS, ENGLAND SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD JUL PY 2001 VL 127 IS 575 SI A BP 1761 EP 1773 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 461YH UT WOS:000170391100014 ER PT J AU Alexander, MA Le, TT Hill, DJT Connell, JW Watson, KA AF Alexander, MA Le, TT Hill, DJT Connell, JW Watson, KA TI The behaviour of phenylphosphine oxide containing polyimides in a water plasma following gamma-radiolysis SO RADIATION PHYSICS AND CHEMISTRY LA English DT Article; Proceedings Paper CT Pacifichem 2000 Meeting CY DEC 14-19, 2000 CL HONOLULU, HAWAII DE polyimide; phenylphosphine oxide; water plasma and gamma radiolysis (XPS) ID ATOMIC OXYGEN; DEGRADATION; RADIATION AB The surface oxidation of two polyimides containing fluorinated phenylphosphine oxide units, TOR-RC and TOR-RC ODPA, have been studied by (XPS) spectroscopy following gamma -radiolysis under vacuum or in air and subsequent treatment in a water plasma. The changes in the O 1s/C 1s ratios obtained from (XPS) analysis showed that on exposure to the water plasma the ratio increases and then levels to a constant value which is similar to that found for exposure to the plasma without prior gamma -radiation treatment. Evidence for the formation of phosphate species was also obtained from the (XPS) analyses. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Univ Queensland, Dept Chem, Polymer Mat & Radiat Grp, Ctr Magnet Resonance, Brisbane, Qld 4072, Australia. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Hill, DJT (reprint author), Univ Queensland, Dept Chem, Polymer Mat & Radiat Grp, Ctr Magnet Resonance, Brisbane, Qld 4072, Australia. NR 18 TC 2 Z9 2 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0969-806X J9 RADIAT PHYS CHEM JI Radiat. Phys. Chem. PD JUL PY 2001 VL 62 IS 1 BP 171 EP 177 DI 10.1016/S0969-806X(01)00435-2 PG 7 WC Chemistry, Physical; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical SC Chemistry; Nuclear Science & Technology; Physics GA 474BG UT WOS:000171084000023 ER PT J AU Devasahayam, S Hill, DJT Connell, JW AF Devasahayam, S Hill, DJT Connell, JW TI A comparative study of the radiation resistance of four optically transparent polyimides SO RADIATION PHYSICS AND CHEMISTRY LA English DT Article; Proceedings Paper CT Pacifichem 2000 Meeting CY DEC 14-19, 2000 CL HONOLULU, HAWAII DE transparent polyimides; radiation sensitivity; UV spectroscopy; ESR spectroscopy; radical yields AB A comparative study of the high energy radiation resistance to formation of radicals in two pairs of polymers is reported. In one pair of polymers the phenyl groups containing the imide rings are separated by an ether linkage and in the other pair they are separated by an hexafluoroisopropylidine group. Two of the polymers contained aromatic amine units linked through an ether linkage and the other two polymers contained a trifluoromethyl biphenyl diamine. The polymers were shown to retain a high level of transparency in the visible region following radiolysis to doses as high as 8 Gy. ESR studies of the resistance to radical formation on radiolysis. at 77 K revealed that the polymers containing ether linkages were more stable than their fluorinated analogues, but all were less stable than Kapton (R). (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Univ Queensland, Dept Chem, Polymer Mat & Radiat Grp, Ctr Magnet Resonance, Brisbane, Qld 4072, Australia. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Hill, DJT (reprint author), Univ Queensland, Dept Chem, Polymer Mat & Radiat Grp, Ctr Magnet Resonance, Brisbane, Qld 4072, Australia. NR 10 TC 9 Z9 9 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0969-806X J9 RADIAT PHYS CHEM JI Radiat. Phys. Chem. PD JUL PY 2001 VL 62 IS 1 BP 189 EP 194 DI 10.1016/S0969-806X(01)00437-6 PG 6 WC Chemistry, Physical; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical SC Chemistry; Nuclear Science & Technology; Physics GA 474BG UT WOS:000171084000025 ER PT J AU Karnieli, A Kaufman, YJ Remer, L Wald, A AF Karnieli, A Kaufman, YJ Remer, L Wald, A TI AFRI - aerosol free vegetation index SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID THEMATIC MAPPER DATA; SATELLITE DATA; FOREST DAMAGE; SPECTRAL REFLECTANCE; AVHRR DATA; MODIS; LAND; LEAVES; WATER; SPACE AB Aircraft measurements using a field spectrometer over variety of ground surfaces in Israel reveals that under clear sky conditions the shortwave infrared (SWIR) spectral bands around 1.6 and 2.1 mum are highly correlated with the visible-blue, green, and red- spectral bands. Empirical linear relationships, such as rho (0.469) = 0.25(rho2.1); rho (0.555) = 0.33(rho2.1); rho (0.645) = 0.5(rho2.1); and rho (0.645) = 0.66(rho1.6), were found to be statistically significant and consistent with previous findings. Based on the above relationships, a modified vegetation index (VI) is proposed and named Aerosol Free Vegetation Index (AFRI). Two versions of this VI are formulated as: AFRI(1.6) = (rho (NIR) - 0 66 rho (1.6))/(rho (NIR) + 0.66 rho (1.6)) and AFRI(2.1) = (rho (NIR) - 0.5 rho (2.1))/(rho (NIR) + 0.5 rho (2.1)). It is shown that under clear sky conditions, the AFRIs (and especially AFRI(2.1)) closely resemble the Normalized Difference Vegetation Index (NDVI) and their values are almost identical. The advantage of the derived AFRIs, based on the ability of the SWIR bands is to penetrate the atmospheric column even when aerosols such as smoke or sulfates exist. Consequently, these indices have a major application in assessing vegetation in the presence of smoke, anthropogenic pollution, or volcanic plumes. This was demonstrated by applying the AFRI for a biomass burned forest in Brazil. Limited success of these indices is expected in case of dust due to presence of larger particles that are of similar size to the wavelength and therefore not transparent at 2.1 mum. The AFRIs can be implemented to data from any sensor that has the SWIR bands. Currently the most commonly used of such instruments are the Landsat-Thematic Mapper (TM) and Advanced Thematic Mapper Plus (ETM+), Moderate Resolution Imaging Spectrometer (MODIS), Advanced Spaceborne Thermal Emission and Reflection (ASTER), and Japanese Earth Resources Satellite-Optical System (JERS-OPS). Although the AFRI(2.1) was demonstrated to perform better than the AFRI(1.6), the latter still can be used for the same application in conjunction with instruments that have onboard only the 1.6-mum band, such as Systeme Probatoire d'Observation del la Terre (SPOT4)-VEGETATION, Indian Remote Sensing (IRS-IC/D), and Resource-21. (C) 2001 Elsevier Science Inc. All rights reserved. C1 Ben Gurion Univ Negev, Jacob Blaustein Inst Desert Res, Remote Sensing Lab, IL-84990 Sede Boqer, Israel. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SAIC, Chantilly, VA 20151 USA. RP Karnieli, A (reprint author), Ben Gurion Univ Negev, Jacob Blaustein Inst Desert Res, Remote Sensing Lab, Sede Boker Campus, IL-84990 Sede Boqer, Israel. NR 38 TC 79 Z9 83 U1 4 U2 15 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 JUL PY 2001 VL 77 IS 1 BP 10 EP 21 DI 10.1016/S0034-4257(01)00190-0 PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 454CT UT WOS:000169955400002 ER PT J AU Giglio, L Kendall, JD AF Giglio, L Kendall, JD TI Application of the Dozier retrieval to wildfire characterization - A sensitivity analysis SO REMOTE SENSING OF ENVIRONMENT LA English DT Article DE Dozier retrieval; fire; fire detection; fire temperature; fire area; sensitivity analysis ID SATELLITE DETECTION; FIRE; AVHRR; IDENTIFICATION; RESOLUTION; SAVANNA; BRAZIL; MODIS AB The demand for improved information on regional and global fire activity in the context of land use/land cover change, ecosystem disturbance, climate modeling, and natural hazards has increased efforts in recent years to improve earth-observing satellite sensors and associated methods for fire information retrieval. While sensor development has made considerable headway for fire monitoring with the recent launch of Terra in late 1999 and upcoming missions such as bispectral infrared detection (BIRD), FOCUS, and the National Polar-Orbiting Operational Environmental Satellite System (NPOESS), the retrieval of fire properties from satellite observations remains problematic. Current methods for determining properties of actively burning fires, for example, continue to be based on a simple two-component model developed by Dozier in 1981 [Remote Sens. Environ. 11 (1981) 221.]. Its limitations in terms of reliable operational fire property retrieval have been known for some time, although not examined in derail to date. With new measurements from recently deployed and evolving satellite systems. which offer kev advantages for fire remote sensing, it is appropriate now to more comprehensively examine the heritage methodology for fire property retrieval. The results of a sensitivity analysis indicate that under realistic conditions the random errors in fire temperature and area retrieved using Dozier's method are +/- 100 K and +/- 50% at one standard deviation, respectively, for fires occupying a pixel fraction greater than 0.005 (this corresponds to a 5000-m(2) fire within a 1-km pixel). For smaller active fires, larger random and systematic errors are likely to occur. (C) 2001 Elsevier Science inc. All rights reserved. C1 Sci Syst & Applicat Inc, Lanham, MD USA. RP Giglio, L (reprint author), NASA, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. NR 25 TC 86 Z9 86 U1 0 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 JUL PY 2001 VL 77 IS 1 BP 34 EP 49 DI 10.1016/S0034-4257(01)00192-4 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 454CT UT WOS:000169955400004 ER PT J AU Fixsen, DJ Cheng, ES Crawford, TM Meyer, SS Wilson, GW Oh, ES Sharp, EH AF Fixsen, DJ Cheng, ES Crawford, TM Meyer, SS Wilson, GW Oh, ES Sharp, EH TI Lightweight long-hold-time Dewar SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID HE-3 REFRIGERATOR; SPACE AB We describe the design, operation, and performance of a light-weight, long-hold-time He-3 cryostat used to cool the bolometric detectors of a far-infrared radiometer. A small internally pumped He-3 reservoir, supported by He-4 and liquid-nitrogen baths, is maintained at 0.25 K for more than a week. The cryostat has a total volume of 30 l and weights 10 kg. (C) 2001 American Institute of Physics. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Chicago, Chicago, IL 60637 USA. NASA, Goddard Space Flight Ctr, Global Sci & Technol, Greenbelt, MD 20771 USA. RP Fixsen, DJ (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Raytheon ITSS Code 685, Greenbelt, MD 20771 USA. NR 7 TC 7 Z9 7 U1 0 U2 5 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUL PY 2001 VL 72 IS 7 BP 3112 EP 3120 DI 10.1063/1.1379964 PG 9 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 449BB UT WOS:000169663500040 ER PT J AU Ovcharenko, AA Shkuratov, YG Nelson, RM AF Ovcharenko, AA Shkuratov, YG Nelson, RM TI Characteristics of light scattering at small phase angles by surfaces consisting of spherical particles SO SOLAR SYSTEM RESEARCH LA English DT Article AB We present the results of measurements of the phase dependences of brightness and of the polarization and depolarization characteristics for surfaces consisting of spherical glass particles in the phase-angle range from 0.1 degrees to 5.0 degrees. The measurements are performed using the laboratory photometer/polarimeter of Kharkov Astronomical Observatory and the photometer of Jet Propulsion Laboratory. An optically thick layer of transparent-glass spheres with mean size of about 57 mum and refractive index of 1.44 exhibits a strong opposition effect due to single scattering. The contribution of interparticle scattering is nearly independent of the phase angle. At an angle of 0.4 degrees, the spheres exhibit a glory ring that manifests itself in the phase behavior of all characteristics investigated. Small details are seen on the curves when a monochromatic radiation source is used for measurements. Their occurrence is confirmed by calculations based on the Mie theory. The unusual behavior of the phase dependences of reflectivity, degree of polarization, and color index for layers composed of spherical particles can be used to search for sites of possible deposits of spherical glass (or ice) particles in regoliths of atmosphereless celestial bodies. C1 Kharkov AM Gorkii State Univ, Astron Observ, UA-210022 Kharkov, Ukraine. NASA, Jet Propuls Lab, Pasadena, CA USA. RP Ovcharenko, AA (reprint author), Kharkov AM Gorkii State Univ, Astron Observ, Sumskaya Ul 35, UA-210022 Kharkov, Ukraine. NR 13 TC 5 Z9 5 U1 0 U2 2 PU MAIK NAUKA/INTERPERIODICA PI NEW YORK PA C/O KLUWER ACADEMIC-PLENUM PUBLISHERS, 233 SPRING ST, NEW YORK, NY 10013-1578 USA SN 0038-0946 J9 SOLAR SYST RES+ JI Solar Syst. Res. PD JUL-AUG PY 2001 VL 35 IS 4 BP 291 EP 298 DI 10.1023/A:1010559401148 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 473YX UT WOS:000171078300004 ER PT J AU Wang, WF Stevenson, A Reuter, DC Sirota, JM AF Wang, WF Stevenson, A Reuter, DC Sirota, JM TI Absolute band intensities of acetone ((CH3)(2)CO) in the infrared region of 830-3200 cm(-1) at low and room temperatures SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE acetone (CH3)(2)CO spectra; band intensity; infrared; low temperature AB Absolute integrated band intensities of acetone (CII,),CO in the region of 830-3200 cm(-1) have been measured near the temperatures of 233, 260 and 293 K. The spectra were recorded with a Fourier transform infrared (FTIR) spectrometer. The investigated region encompasses a total of 15 fundamental bands. At 293 K, for example, the band intensities range from 16.8 to 554.3 cm(-2) atm(-1) (at 300 K). The intensities have uncertainties of about 5%. All the band intensities increase with decreasing temperature. An empirical formulation was introduced which fit this temperature dependence well and which can be used to predict other unmeasured band intensities in the temperature region of similar to 200-300 K. The 295 K intensities reported here agree to within similar to 10% of previously published values, with lower estimated uncertainties. Low temperature intensity measurements are not available in the literature. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. Univ Alabama, Ctr Space Plasma Aeron & Astrophys Res, Huntsville, AL 35899 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. OI Stevenson, Benjamin/0000-0001-9918-1240 NR 10 TC 9 Z9 9 U1 0 U2 7 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD JUL PY 2001 VL 57 IS 8 BP 1603 EP 1610 DI 10.1016/S1386-1425(01)00393-6 PG 8 WC Spectroscopy SC Spectroscopy GA 450DE UT WOS:000169725600007 PM 11471712 ER PT J AU Smialek, JL AF Smialek, JL TI Advances in the oxidation resistance of high-temperature turbine materials SO SURFACE AND INTERFACE ANALYSIS LA English DT Article DE oxidation; alumina scales; surface analyses ID FE-CR-AL; OXIDE GRAIN MORPHOLOGY; SULFUR SEGREGATION; GROWTH MECHANISMS; SCALE ADHERENCE; ALUMINA SCALES; NICRAL ALLOYS; BETA-NIAL+ZR; Y ALLOYS; ALPHA-AL2O3 AB This overview highlights some of the key factors in understanding the protective ability of aluminum oxide scales for current gas turbine engine alloys and coatings. Dense, phase-pure, slow-growing and adherent scales are required. In most cases, solutions have been found through educated empiricism, with more complete understanding often lagging by decades. Nevertheless, the relentless application of new techniques to answer old questions has often provided radically different viewpoints and pointed the way to new engineering developments. Equally important, this understanding prevents prior misconceptions from taking too strong a hold and maintaining a limited perspective. The microstructure, kinetics, short-circuit diffusion, phase transformation, growth and residual stresses, interfacial segregation and adhesion provide a richness of topics for this singular and effective system. Copyright (C) 2001 John Wiley & Sons, Ltd. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Smialek, JL (reprint author), NASA, Glenn Res Ctr, Mail Stop 106-1,21000 Brookpk Rd, Cleveland, OH 44135 USA. EM james.L.Smialek@grc.nasa.gov NR 53 TC 15 Z9 16 U1 0 U2 2 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0142-2421 J9 SURF INTERFACE ANAL JI Surf. Interface Anal. PD JUL PY 2001 VL 31 IS 7 BP 582 EP 592 DI 10.1002/sia.1085 PG 11 WC Chemistry, Physical SC Chemistry GA 456WV UT WOS:000170106500008 ER PT J AU Venkateswaran, K Satomi, M Chung, S Kern, R Koukol, R Basic, C White, D AF Venkateswaran, K Satomi, M Chung, S Kern, R Koukol, R Basic, C White, D TI Molecular microbial diversity of a spacecraft assembly facility SO SYSTEMATIC AND APPLIED MICROBIOLOGY LA English DT Article DE Spacecraft Assembly Facility; thermo-tolerance; Bacillus spores; 16S rDNA analysis; RFLP analysis; phylogeny ID VIBRIO AB In ongoing investigations to map and archive the microbial footprints in various components of the spacecraft and its accessories, we have examined the microbial populations of the Jet Propulsion Laboratory's Spacecraft Assembly Facility (JPL-SAF). Witness plates made up of spacecraft materials, some painted with spacecraft qualified paints, were exposed for similar to7 to 9 months at JPL-SAF and examined the particulate materials collected for the incidence of total cultivable aerobic heterotrophs and heat-tolerant (80 degreesC for 15-min.) spore-formers. The results showed that the witness plates coated with spacecraft qualified paints attracted more dust particles than the non-coated stainless steel witness plates. Among the four paints tested, witness plates coated with NS43G accumulated the highest number of particles, and hence attracted more cultivable microbes. The conventional microbiological examination revealed that the JPL-SAF harbors mainly Gram-positive microbes and mostly spore-forming Bacillus species. Most of the isolated microbes were heat resistant to 80 degreesC and proliferate at 60 degreesC. The phylogenetic relationships among 23 cultivable heat-tolerant microbes were examined using a battery of morphological, physiological, molecular and chemotaxonomic characterizations. By 16S rDNA sequence analysis, the isolates fell into seven clades: Bacillus licheniformis, B. pumilus, B. cereus, B. circulans, Staphylococcus capitis, Planococcus sp. and Micrococcus lylae. In contrast to the cultivable approach, direct DNA isolation, cloning and 16S rDNA sequencing analysis revealed equal representation of both Gram-positive and Gram-negative microorganisms. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Res Inst Fisheries Sci, Div Food Proc, Kanazawa Ku, Yokohama, Kanagawa 2368648, Japan. RP Venkateswaran, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 18 TC 99 Z9 99 U1 2 U2 7 PU URBAN & FISCHER VERLAG PI JENA PA BRANCH OFFICE JENA, P O BOX 100537, D-07705 JENA, GERMANY SN 0723-2020 J9 SYST APPL MICROBIOL JI Syst. Appl. Microbiol. PD JUL PY 2001 VL 24 IS 2 BP 311 EP 320 DI 10.1078/0723-2020-00018 PG 10 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA 462ME UT WOS:000170423200021 PM 11518337 ER PT J AU Zhao, CY So, RMC Gatski, TB AF Zhao, CY So, RMC Gatski, TB TI Turbulence modeling effects on the prediction of equilibrium states of buoyant shear flows SO THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS LA English DT Article ID REYNOLDS-STRESS CLOSURES; HOMOGENEOUS TURBULENCE; DISSIPATION RATE; SCALAR FLUX; TEMPERATURE VARIANCE; NUMERICAL-SIMULATION; STRATIFIED FLUID; ALGEBRAIC MODEL; EVOLUTION; DIFFUSION AB The effects of turbulence modeling on the prediction of equilibrium states of turbulent buoyant shear flows were investigated. The velocity field models used include a two-equation closure, a Reynolds-stress closure assuming two different pressure-strain models and three different dissipation rate tensor models. As for the thermal field closure models, two different pressure-scrambling models and nine different temperature variance dissipation rate (epsilon (theta)) equations were considered. The emphasis of this paper is focused on the effects of the epsilon (theta)-equation, of the dissipation rate models, of the pressure-strain models and of the pressure-scrambling models on the prediction of the approach to equilibrium turbulence. Equilibrium turbulence is defined by the time rate of change of the scaled Reynolds stress anisotropic tensor and heat flux vector becoming zero. These conditions lead to the equilibrium state parameters, given by (P) over tilde/epsilon, (P) over tilde (theta)/epsilon (theta), R = (<((2))over bar>/2 epsilon (theta))/(k/epsilon), Sk/epsilon and G/epsilon, becoming constant. Here, (P) over tilde and (P) over tilde (theta) are the production of turbulent kinetic energy k and temperature variance <((2))over bar>, respectively, epsilon and epsilon (theta) are their respective dissipation rates, R is the mixed time scale ratio, G is the buoyant production of k and S is the mean shear gradient. Calculations show that the epsilon (theta)-equation has a significant effect on the prediction of the approach to equilibrium turbulence. For a particular epsilon (theta)-equation, all velocity closure models considered give an equilibrium state if anisotropic dissipation is accounted for in one form or another in the dissipation rate tensor or in the epsilon -equation. It is further found that the models considered for the pressure-strain tensor and the pressure-scrambling vector have little or no effect on the prediction of the approach to equilibrium turbulence. C1 Hong Kong Polytech Univ, Dept Mech Engn, Kowloon, Hong Kong, Peoples R China. NASA, Langley Res Ctr, Computat Modeling & Simulat Branch, Hampton, VA 23681 USA. RP Zhao, CY (reprint author), Hong Kong Polytech Univ, Dept Mech Engn, Kowloon, Hong Kong, Peoples R China. RI So, Ronald/B-6698-2008 NR 47 TC 11 Z9 12 U1 0 U2 3 PU SPRINGER-VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0935-4964 J9 THEOR COMP FLUID DYN JI Theor. Comput. Fluid Dyn. PD JUL PY 2001 VL 14 IS 6 BP 399 EP 422 DI 10.1007/s001620100036 PG 24 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 457GT UT WOS:000170129300003 ER PT J AU Wertheimer, AC Smoker, WW Joyce, TL Heard, WR AF Wertheimer, AC Smoker, WW Joyce, TL Heard, WR TI Comment: A review of the hatchery programs for pink salmon in Prince William Sound and Kodiak Island, Alaska SO TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY LA English DT Editorial Material ID VALDEZ OIL-SPILL; PACIFIC SALMON; FISH; MORTALITY; CAPACITY; CLIMATE; DAMAGE C1 Natl Marine Fisheries Serv, Auke Bay Lab, Juneau, AK 99801 USA. Univ Alaska, Juneau Ctr Fisheries & Ocean Sci, Juneau, AK 99801 USA. Alaska Dept Fish & Game, Commercial Fisheries Div, Cordova, AK 99574 USA. RP Wertheimer, AC (reprint author), Natl Marine Fisheries Serv, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 30 TC 27 Z9 29 U1 0 U2 2 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 0002-8487 J9 T AM FISH SOC JI Trans. Am. Fish. Soc. PD JUL PY 2001 VL 130 IS 4 BP 712 EP 720 DI 10.1577/1548-8659(2001)130<0712:CAROTH>2.0.CO;2 PG 9 WC Fisheries SC Fisheries GA 452HR UT WOS:000169852700017 ER PT J AU Hazeltine, E AF Hazeltine, E TI Ipsilateral sensorimotor regions and motor sequence learning SO TRENDS IN COGNITIVE SCIENCES LA English DT Review ID MOVEMENT AB Recently, Boyd and Winstein tested three groups of individuals with damage to unilateral sensorimotor areas on a version of the serial reaction time task performed with the ipsilesional hand. Only when the individuals were provided in advance with explicit knowledge of the motor sequence were they able to benefit behaviorally from the sequence. Despite aspects of the experimental procedure and the subject selection that make it difficult to draw strong conclusions, these results add to growing evidence that sensorimotor structures contribute to the formation of abstract representations that affect more than ipsilateral effectors. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hazeltine, E (reprint author), NASA, Ames Res Ctr, Mail Stop 262-4, Moffett Field, CA 94035 USA. NR 7 TC 2 Z9 2 U1 0 U2 0 PU ELSEVIER SCIENCE LONDON PI LONDON PA 84 THEOBALDS RD, LONDON WC1X 8RR, ENGLAND SN 1364-6613 J9 TRENDS COGN SCI JI TRENDS COGN. SCI. PD JUL PY 2001 VL 5 IS 7 BP 281 EP 282 DI 10.1016/S1364-6613(00)01702-2 PG 2 WC Behavioral Sciences; Neurosciences; Psychology, Experimental SC Behavioral Sciences; Neurosciences & Neurology; Psychology GA 450VF UT WOS:000169765000001 ER PT J AU Benner, SA Gaucher, EA AF Benner, SA Gaucher, EA TI Evolution, language and analogy in functional genomics SO TRENDS IN GENETICS LA English DT Article ID PROTEIN FAMILIES; MOLECULAR ADAPTATION; STATISTICAL-METHODS; DATABASE; CLONING; HISTORY; IMPACT; GENES; MODEL AB Almost a century ago, Wittgenstein pointed out that theory in science is intricately connected to language. This connection is not a frequent topic in the genomics literature. But a case can be made that functional genomics is today hindered by the paradoxes that Wittgenstein identified. If this is true, until these paradoxes are recognized and addressed, functional genomics will continue to be limited in its ability to extrapolate information from genomic sequences. C1 Univ Florida, Dept Chem, NASA, Astrobiol Inst, Gainesville, FL 32611 USA. RP Benner, SA (reprint author), Univ Florida, Dept Chem, NASA, Astrobiol Inst, Gainesville, FL 32611 USA. RI Gaucher, Eric/I-7313-2013 NR 38 TC 16 Z9 18 U1 1 U2 2 PU ELSEVIER SCIENCE LONDON PI LONDON PA 84 THEOBALDS RD, LONDON WC1X 8RR, ENGLAND SN 0168-9525 J9 TRENDS GENET JI Trends Genet. PD JUL PY 2001 VL 17 IS 7 BP 414 EP 418 DI 10.1016/S0168-9525(01)02320-4 PG 5 WC Genetics & Heredity SC Genetics & Heredity GA 449GA UT WOS:000169674900011 PM 11418223 ER PT J AU Pinel, SI Signer, HR Zaretsky, EV AF Pinel, SI Signer, HR Zaretsky, EV TI Comparison between oil-mist and oil-jet lubrication of high-speed, small-bore, angular-contact ball bearings SO TRIBOLOGY TRANSACTIONS LA English DT Article DE rolling-element bearings; ball bearings; life prediction; lubrication; oil-jet lubrication; air-oil mist lubrication AB Parametric rests were conducted with an optimized 35-mm-bore-angular-contact ball bearing on a high-speed, high-temperature bearing tester. Results from both air-oil mist lubrication and oil-jet lubrication systems used to lubricate the bearing were compared to speeds of 2.5Y10(6) DN. The maximum obtainable speed with air-oil mist lubrication is 2.5Y10(6) DN. Lower bearing temperatures and higher power losses are obtained with oil-jet lubrication than with air-oil mist lubrication. Bearing power loss is a direct function of oil flow to the bearing and independent of oil delivery system. For a given oil-flow rate, hearing temperature and power loss increase with increases in speed. Bearing life is an inverse function of temperature, the difference in temperature between the individual bearing ring components, and the resultant elastohydrodynamic (EHD)film thicknesses. Bearing life is independent of the oil delivery system except as it affects rs temperature. Cage slip increased with increases in speed. Cage slip as high as 7 per-cent was measured and was generally higher with air-oil mist lubrication than with oil-jet lubrication. C1 Pinel Engn, Fullerton, CA USA. Signer Tech Serv, Fullerton, CA USA. NASA, Glenn Res Ctr, Cleveland, OH USA. RP Pinel, SI (reprint author), Pinel Engn, Fullerton, CA USA. NR 15 TC 7 Z9 11 U1 3 U2 12 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD JUL PY 2001 VL 44 IS 3 BP 327 EP 338 DI 10.1080/10402000108982465 PG 12 WC Engineering, Mechanical SC Engineering GA 452HN UT WOS:000169852400001 ER PT J AU Poplawski, JV Peters, SM Zaretsky, EV AF Poplawski, JV Peters, SM Zaretsky, EV TI Effect of roller profile on cylindrical roller bearing life prediction - Part I: Comparison of bearing life theories SO TRIBOLOGY TRANSACTIONS LA English DT Article DE rolling-element bearings; life prediction methods; rolling-element fatigue; stress analysis ID ROLLING-ELEMENT BEARINGS; RELIABILITY AB Four rolling-element bearing life theories were chosen for analysis and compared for a simple roller-race geometry model. The life theories were those of Weibull; Lundberg and Palmgren; loannides and Harris; and Zaretsky. The analysis without a fatigue limit of loannides and Harris is identical to the Lundberg and Palmgren analysis, and the Weibull analysis is similar to that of Zaretsky if the exponents are chosen to be identical. The resultant predicted life at each stress condition not only depends on the life equation used but also on the Weibull slope assumed. The least variation in predicted life with Weibull slope comes with the Zaretsky equation. Except for a Weibull slope of 1.11, at which the Weibull equation predicts the highest lives, the highest lives are predicted by the Zaretsky equation. For Weibull slopes of 1.5 and 2, both the Lundberg-Palmgren and Ioannides-Harris (where tau (u) equals 0) equations predict lower lives than the ANSI/ABMA/ISO standard. Based upon the Hertz stresses for line contact, the accepted load-life exponent of 10/3 results in a maximum Hertz stress-life exponent equal to 6.6. This value is inconsistent with that experienced in the field. The assumption of a shear stress fatigue limit tau (u), results in Hertz sb ess-life exponents greater than are experimentally verifiable. C1 JV Poplawski & Associates, Bethlehem, PA USA. NASA, Glenn Res Ctr, Cleveland, OH USA. RP Poplawski, JV (reprint author), JV Poplawski & Associates, Bethlehem, PA USA. NR 25 TC 20 Z9 26 U1 1 U2 11 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD JUL PY 2001 VL 44 IS 3 BP 339 EP 350 DI 10.1080/10402000108982466 PG 12 WC Engineering, Mechanical SC Engineering GA 452HN UT WOS:000169852400002 ER PT J AU Poplawski, JV Peters, SM Zaretsky, EV AF Poplawski, JV Peters, SM Zaretsky, EV TI Effect of roller profile on cylindrical roller bearing life prediction - Part II comparison of roller profiles SO TRIBOLOGY TRANSACTIONS LA English DT Article DE rolling-element bearings; life prediction methods; rolling-element fatigue; stress analysis ID ROLLING-ELEMENT BEARINGS; RELIABILITY AB Four roller profiles used in cylindrical roller bearing design and manufacture were analyzed using both a closed form solution and finite element analysis (FEA)for stress and life. The analyzed roller profiles were flat, end tapered, aerospace, and fully crowned and loaded against a flat raceway. Four rolling-element bearing life models were chosen for this analysis: those of Weibull; Lundberg and Palmgren; loannides and Harris; and Zaretsky. The flat roller profile without edge loading has the longest predicted life. However, edge loading ran reduce life by as much as 98 percent. The end-tapered profile produced the highest lives, but not significantly higher than those produced by the aerospace profile. The fully crowned profile produced the lowest lives. Except for the flat roller profile, the predicted lives with the FEA method exceed those with the closed form solution. The fatigue limit proposed by loannides and Harris equates to one-half the value of a compressive residual stress that may exist in a rolling bearing steel. C1 JV Poplawski & Associates, Bethlehem, PA USA. NASA, Gless Res Ctr, Cleveland, OH USA. RP Poplawski, JV (reprint author), JV Poplawski & Associates, Bethlehem, PA USA. NR 22 TC 16 Z9 21 U1 1 U2 7 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD JUL PY 2001 VL 44 IS 3 BP 417 EP 427 DI 10.1080/10402000108982476 PG 11 WC Engineering, Mechanical SC Engineering GA 452HN UT WOS:000169852400012 ER PT J AU Howard, SA Dellacorte, C Valco, MJ Prahl, JM Heshmat, H AF Howard, SA Dellacorte, C Valco, MJ Prahl, JM Heshmat, H TI Steady-state stiffness of foil air journal bearings at elevated temperatures SO TRIBOLOGY TRANSACTIONS LA English DT Article DE fluid film compliant bearings; foil bearings; gas bearings; turbomachinery ID LOAD AB A previously developed test method for measuring steady-state stiffness of foil air journal bearings is extended to measure trends in bearing stiffness at high temperature. Steady-state stiffness of the tested foil bearing is found to decrease in general as the temperature increases from 25 degrees to 538 degreesC. The magnitude of stiffness change observed is roughly a factor of two, which is important information for the design of future high speed turbomachinery. it is expected that damping in foil bearings may also be affected by changes in temperature necessitating future resting to evaluate the trends in dynamic bearing characteristics. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. USA, Res Lab, Vehicle Technol Ctr, Cleveland, OH USA. Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. Mohawk Innovat Technol Inc, Albany, NY USA. RP Howard, SA (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 19 TC 25 Z9 28 U1 0 U2 1 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD JUL PY 2001 VL 44 IS 3 BP 489 EP 493 DI 10.1080/10402000108982486 PG 5 WC Engineering, Mechanical SC Engineering GA 452HN UT WOS:000169852400022 ER PT J AU Curtis, S Adler, R Huffman, G Nelkin, E Bolvin, D AF Curtis, S Adler, R Huffman, G Nelkin, E Bolvin, D TI Evolution of tropical and extratropical precipitation anomalies during the 1997-1999 ENSO cycle SO INTERNATIONAL JOURNAL OF CLIMATOLOGY LA English DT Article DE El Nino; ENSO; La Nina; precipitation; tropics ID 1997-98 EL-NINO; SOUTHERN OSCILLATION; CLIMATE ASSESSMENT; TEMPERATURE; PACIFIC; DATASET; SURFACE; PATTERNS; PROJECT; EVENT AB The 1997-1999 El Nino-Southern Oscillation (ENSO) period was very powerful, but also well observed. Multiple satellite rainfall estimates combined with gauge observations allow for a quantitative analysis of precipitation anomalies in the tropics and elsewhere accompanying the 1997-1999 ENSO cycle. An examination of the evolution of the El Nino and accompanying precipitation anomalies revealed that a dry Maritime Continent (MC) preceded the formation of positive sea-surface temperature (SST) anomalies in the eastern Pacific Ocean. Thirty- to sixty-day oscillations in the winter of 1996-1997 may have contributed to this lag relationship. Furthermore, westerly wind burst events may have maintained the drought over the MC. The warming of the equatorial pacific was then followed by an increase in convection. A rapid transition from El Nino to La Nino occurred in May 1998, but as early as October-November 1997, precipitation indices captured substantial changes in Pacific rainfall anomalies. The global precipitation patterns for this event were in good agreement with the strong consistent ENSO-related precipitation signals identified in earlier studies. Differences included a shift in precipitation anomalies over Africa during the 1997-1998 El Nino and unusually wet conditions over northeast Australia during the later stages of the Fl Nino. Also, the typically wet region in the north tropical Pacific was mostly dry during the 1998-1999 La Nina. Reanalysis precipitation was compared with observations during this time period and substantial differences were noted. In particular, the model had a bias towards positive precipitation anomalies and the magnitudes of the anomalies in the equatorial Pacific were small compared with the observations. Also, the evolution of the precipitation field, including the drying of the MC and eastward progression of rainfall in the equatorial Pacific, was less pronounced for the model compared with the observations. Copyright (C) 2001 Royal Meteorological Society. C1 Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Joint Ctr Earth Syst Technol,Lab Atmospheres, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Sci Syst Applicat Inc, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Curtis, S (reprint author), Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Joint Ctr Earth Syst Technol,Lab Atmospheres, Code 912, Greenbelt, MD 20771 USA. RI Curtis, Scott/C-1115-2013; Huffman, George/F-4494-2014; OI Huffman, George/0000-0003-3858-8308; Curtis, Scott/0000-0001-9065-8639 NR 27 TC 22 Z9 22 U1 1 U2 9 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0899-8418 J9 INT J CLIMATOL JI Int. J. Climatol. PD JUN 30 PY 2001 VL 21 IS 8 BP 961 EP 971 DI 10.1002/joc.643 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 451ZB UT WOS:000169831700003 ER PT J AU Kuntz, KD Snowden, SL AF Kuntz, KD Snowden, SL TI On the contribution of unresolved Galactic stars to the diffuse soft X-ray background SO ASTROPHYSICAL JOURNAL LA English DT Article DE X-rays : diffuse background; X-rays : ISM; X-rays : stars ID ALL-SKY SURVEY; ROSAT DEEP SURVEY; OPTICAL IDENTIFICATIONS; STATISTICAL-ANALYSIS; COMPLETE SAMPLE; CATALOG; SPECTRUM; CLUSTER; FIELD; GALAXY AB Using stellar luminosity functions derived from ROSAT data, the contributions of Galactic stars to the diffuse X-ray background are calculated for ROSAT PSPC energy bands. The model follows that of Guillout and coworkers but uses ROSAT rather than Einstein data to determine the intrinsic luminosity distributions. The model adequately predicts the numbers of stellar sources observed in deep ROSAT surveys. The contribution of unresolved stellar sources to the ROSAT All-Sky Survey at the Galactic poles is 6.85, 4.76, and 4.91 x 10(-6) counts s(-1) arcmin(-2) in bands R12 (1/4 keV), R45 (3/4 keV), and R67 (1.5 keV), respectively, which is equivalent to 4.66, 31.3, and 26.9 x 10(-14) ergs cm(-2) s(-1) deg(-2). C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Kuntz, KD (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. RI Snowden, Steven/D-5292-2012 NR 45 TC 23 Z9 23 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP 684 EP 693 DI 10.1086/321421 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XL UT WOS:000169943400005 ER PT J AU Nandra, K Papadakis, IE AF Nandra, K Papadakis, IE TI Temporal characteristics of the X-ray emission of NGC 7469 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : activegalaxies : individual (NGC 7469); galaxies : nuclei; galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; ACCRETING COMPACT SOURCES; BROAD-LINE REGION; SEYFERT-GALAXIES; ULTRAVIOLET-SPECTRUM; TIME VARIABILITY; MAGNETIC FLARES; POWER SPECTRA; BLACK-HOLES; CYGNUS X-1 AB We present a study of the time variability of the Seyfert 1 galaxy NGC 7469, based on a similar to 30 day RXTE/PCA observation. Variability is seen across the X-ray band, and spectral changes are observed. The softness ratio is correlated with the ultraviolet flux but appears to show more rapid variability. The rms variability parameter calculated on similar to1 day timescales is significantly variable, and sharp increases are seen close to the periods during which the spectrum is hardest. Cross correlation of 2-4, 4-10, and 10-15 keV light curves show a peak at zero delay, but the CCFs are skewed toward positive lags (i.e., the soft leading the hard), with an apparent time lag of about 0.5 days. The power spectral density (PSD) function in the 2-10 keV band shows no clear features-for example periodicities or breaks-but a power law is a rather poor Dt, particularly to the high-frequency spectrum. The normalized PSD in the soft X-ray band shows a larger amplitude of variability on long timescales, but the hard X-ray PSD is flatter and shows more power on timescales less than about 1 day. Our data broadly support the idea that the X-rays are produced by Compton upscattering of lower energy seed photons, as had been previously concluded. They are difficult to reconcile with models in which the sole source of variability is the seed photons, and more likely suggest a variability process intrinsic to the X-ray corona. Our interpretation for these results is that the low-frequency variability in NGC 7469 does arise via variations in the Compton seed photons but that the high-frequency variability arises from the coronal heating mechanism. Both induce spectral variations. A patchy corona is implied, and one interpretation consistent with the data is that hotter blobs exist closer to the central black hole, responsible for the most rapid variations in the hard X-rays. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. Univ Crete, Dept Phys, Heraklion 71003, Greece. RP Nandra, K (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. RI Papadakis, Iossif/C-3235-2011 NR 68 TC 43 Z9 43 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP 710 EP 724 DI 10.1086/321423 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XL UT WOS:000169943400007 ER PT J AU Lister, ML Tingay, SJ Murphy, DW Piner, BG Jones, DL Preston, RA AF Lister, ML Tingay, SJ Murphy, DW Piner, BG Jones, DL Preston, RA TI The Pearson-Readhead survey of compact extragalactic radio sources from space. I. The images SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : jets; quasars : general; radio continuum : galaxies; techniques : high angular resolution; techniques : interferometric ID COMPLETE SAMPLE; VLBI; GHZ; TELESCOPE; MAPS AB We present images from a space-VLBI survey using the facilities of the VLBI Space Observatory Programme (VSOP), drawing our sample from the well-studied Pearson-Readhead survey of extragalactic radio sources. Our survey has taken advantage of long space-VLBI baselines and large arrays of ground antennas, such as the Very Long Baseline Array and European VLBI Network, to obtain high-resolution images of 27 active galactic nuclei and to measure the core brightness temperatures of these sources more accurately than is possible from the ground. A detailed analysis of the source properties is given in accompanying papers. We have also performed an extensive series of simulations to investigate the errors in VSOP images caused by the relatively large holes in the (u, v)-plane when sources are observed near the orbit normal direction. We find that while the nominal dynamic range (defined as the ratio of map peak to off-source error) often exceeds 1000:1, the true dynamic range (map peak to on-source error) is only about 30:1 for relatively complex core-jet sources. For sources dominated by a strong point source, this value rises to approximately 100:1. We find the true dynamic range to be a relatively weak function of the difference in position angle (P.A.) between the jet P.A. and u-v coverage major axis P.A. For regions with low signal-to-noise ratios, typically located down the jet away from the core, large errors can occur, causing spurious features in VSOP images that should be interpreted with caution. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Whittier Coll, Dept Phys, Whittier, CA 90608 USA. RP Lister, ML (reprint author), Natl Radio Astron Observ, 520 Edgemont Rd, Charlottesville, VA 22903 USA. EM mlister@nrao.edu RI Tingay, Steven/B-5271-2013 NR 21 TC 27 Z9 27 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 JUN 29 PY 2001 VL 554 IS 2 BP 948 EP 963 DI 10.1086/321429 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XL UT WOS:000169943400022 ER PT J AU Lister, ML Tingay, SJ Preston, RA AF Lister, ML Tingay, SJ Preston, RA TI The Pearson-Readhead survey of compact extragalactic radio sources from space. II. Analysis of source properties SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : jets; methods : statistical; quasars : general; radio continuum : galaxies ID BL-LACERTAE OBJECTS; ACTIVE GALACTIC NUCLEI; CORE-DOMINATED QUASARS; PARSEC-SCALE JET; RANGE VLA OBSERVATIONS; X-RAY-SPECTRA; COMPLETE SAMPLE; INTRADAY VARIABILITY; OPTICAL POLARIZATION; SUPERLUMINAL QUASAR AB We have performed a multidimensional correlation analysis on the observed properties of a statistically complete core-selected sample of compact radio-loud active galactic nuclei based on data from the VLBI Space Observing Programme (Paper I) and previously published studies. Our sample is drawn from the well-studied Pearson-Readhead (PR) survey and is ideally suited for investigating the general effects of relativistic beaming in compact radio sources. In addition to confirming many previously known correlations, we have discovered several new trends that lend additional support to the beaming model. These trends suggest that the most highly beamed sources in core-selected samples tend to have (1) high optical polarizations; (2) large parsec- kiloparsec-scale jet misalignments; (3) prominent VLBI core components; (4) one-sided, core, or halo radio morphology on kiloparsec scales; (5) narrow emission line equivalent widths; and (6) a strong tendency for intraday variability at radio wavelengths. We have used higher resolution space and ground-based VLBI maps to confirm the bimodality of the jet misalignment distribution for the PR survey and find that the sources with aligned parsec- and kiloparsec-scale jets generally have arcsecond-scale radio emission on both sides of the core. The aligned sources also have broader emission line widths. We find evidence that the BL Lacertae objects in the PR survey are all highly beamed and have very similar properties to the high optically polarized quasars, with the exception of smaller redshifts. A cluster analysis on our data shows that after partialing out the effects of redshift, the luminosities of our sample objects in various wave bands are generally well correlated with each other but not with other source properties. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. RP Lister, ML (reprint author), Natl Radio Astron Observ, 520 Edgemont Rd, Charlottesville, VA 22903 USA. RI Tingay, Steven/B-5271-2013 NR 99 TC 26 Z9 27 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP 964 EP 980 DI 10.1086/321430 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XL UT WOS:000169943400023 ER PT J AU Francis, PJ Williger, GM Collins, NR Palunas, P Malumuth, EM Woodgate, BE Teplitz, HI Smette, A Sutherland, RS Danks, AC Hill, RS Lindler, D Kimble, RA Heap, SR Hutchings, JB AF Francis, PJ Williger, GM Collins, NR Palunas, P Malumuth, EM Woodgate, BE Teplitz, HI Smette, A Sutherland, RS Danks, AC Hill, RS Lindler, D Kimble, RA Heap, SR Hutchings, JB TI A pair of compact red galaxies at redshift 2.38, immersed in a 100 kiloparsec scale Ly alpha nebula SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : evolution; galaxies : formation; galaxies : high-redshift; galaxies : interactions ID STAR-FORMING GALAXIES; EMISSION; RADIATION; DEEP; Z-GREATER-THAN-3; SPECTROGRAPH; ULTRAVIOLET; EXTINCTION; DISCOVERY; WFPC2 AB We present Hubble Space Telescope and ground-based observations of a pair of galaxies at a redshift of 2.38, which are collectively known as 2142-4420 B1. Both galaxies are luminous extremely red objects (EROs) and are separated by 0."8. They are embedded within a 100 kpc scale diffuse Ly alpha nebula (or blob) of luminosity similar to 10(44) ergs s(-1). The radial profiles and colors of both red objects are most naturally explained if they are young elliptical galaxies, the most distant galaxies of this type found to date. It is not possible, however, to rule out a model in which they are abnormally compact, extremely dusty starbursting disk galaxies. If they are elliptical galaxies, their stellar populations have inferred masses of similar to 10(11) and ages of similar to7 x 10(8) yr. Both galaxies have color gradients : their centers are significantly bluer than their outer regions. The surface brightness of both galaxies is roughly 1 order of magnitude greater than would be predicted by the Kormendy relation. A chain of diffuse star formation extending 1" from the galaxies may be evidence that they are interacting or merging. The Ly alpha nebula surrounding the galaxies shows apparent velocity substructure of amplitude similar to 700 km s(-1). We propose that the Ly alpha emission from this nebula may be produced by fast shocks that are powered either by a galactic superwind or by the release of gravitational potential energy. C1 Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia. Australian Natl Univ, Fac Sci, Dept Phys, Canberra, ACT 0200, Australia. NASA, Natl Opt Astron Observ, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Raytheon ITSS, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Raytheon RPSC, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Adv Comp Concepts Inc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. RP Francis, PJ (reprint author), Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia. RI Woodgate, Bruce/D-2970-2012 NR 67 TC 85 Z9 85 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP 1001 EP 1011 DI 10.1086/321417 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XL UT WOS:000169943400025 ER PT J AU Lissauer, JJ Rivera, EJ AF Lissauer, JJ Rivera, EJ TI Stability analysis of the planetary system orbiting nu Andromedae. II. Simulations using new lick observatory fits SO ASTROPHYSICAL JOURNAL LA English DT Article DE celestial mechanics, stellar dynamics; methods : n-body simulations; planetary systems; stars : individual (nu Andromedae) ID UPSILON-ANDROMEDAE; DYNAMICS; STARS AB We present results of long-term numerical orbital integrations designed to test the stability of the three-planet system orbiting upsilon Andromedae and short-term integrations to test whether mutual perturbations among the planets can be used to determine planetary masses. Our initial conditions are based on recent fits to the radial velocity data obtained by the planet search group at Lick Observatory. The new fits result in significantly more stable systems than did the initially announced planetary parameters. Our integrations using the 2000 February parameters show that if the system is nearly planar, then it is stable for at least 100 Myr for m(f) equivalent to 1/sin i less than or equal to4. In some stable systems, the eccentricity of the inner planet experiences large oscillations. The relative periastra of the outer two planets' orbits librate about 0 degrees in most of the stable systems; if future observations imply that the periastron longitudes of these planets are very closely aligned at the present epoch, dynamical simulations may provide precise estimates for the masses and orbital inclinations of these two planets. C1 NASA, Ames Res Ctr, Div Space Sci 2453, Moffett Field, CA 94035 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. RP Lissauer, JJ (reprint author), NASA, Ames Res Ctr, Div Space Sci 2453, Moffett Field, CA 94035 USA. NR 19 TC 49 Z9 49 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP 1141 EP 1150 DI 10.1086/321426 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XL UT WOS:000169943400038 ER PT J AU Kehoe, R Akerlof, C Balsano, R Barthelmy, S Bloch, J Butterworth, P Casperson, D Cline, T Fletcher, S Gisler, G Hurley, K Kippen, M Lee, B Marshall, S McKay, T Rykoff, E Smith, D Vestrand, T Wren, J AF Kehoe, R Akerlof, C Balsano, R Barthelmy, S Bloch, J Butterworth, P Casperson, D Cline, T Fletcher, S Gisler, G Hurley, K Kippen, M Lee, B Marshall, S McKay, T Rykoff, E Smith, D Vestrand, T Wren, J TI A search for early optical emission from short- and long-duration gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; gamma rays : observations ID CATALOG; IDENTIFICATION AB Gamma-ray bursts of short duration may harbor vital clues to the range of phenomena producing bursts. However, recent progress from the observation of optical counterparts has not benefited the study of short bursts. We have searched for early optical emission from six gamma-ray bursts using the telephoto array on the Robotic Optical Transient Search Experiment I. Three of these events were of short duration, including GRB 980527, which is among the brightest short bursts yet observed. The data consist of unfiltered CCD optical images taken in response to Burst and Transient Source Experiment triggers delivered via the GRB Coordinates Network. For the first time, we have analyzed the entire 16 degrees x 16 degrees field covered for five of these bursts. In addition, we discuss a search for the optical counterpart to GRB 000201, a well-localized long burst. Single-image sensitivities range from 13th to 14th magnitude around 10 s after the initial burst detection and from 14 to 15.8 mag 1 hr later. No new optical counterparts were discovered in this analysis suggesting short-burst optical and gamma-ray fluxes are uncorrelated. C1 Univ Michigan, Dept Phys, Randall Lab, Ann Arbor, MI 48109 USA. Los Alamos Natl Lab, NIS Div 2, Los Alamos, NM 87545 USA. Lawrence Livermore Natl Lab, IGPP Div, Livermore, CA 94550 USA. Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35805 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA. RP Kehoe, R (reprint author), Univ Michigan, Dept Phys, Randall Lab, 500 E Univ, Ann Arbor, MI 48109 USA. RI Barthelmy, Scott/D-2943-2012; McKay, Timothy/C-1501-2009 OI McKay, Timothy/0000-0001-9036-6150 NR 21 TC 39 Z9 40 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 JUN 29 PY 2001 VL 554 IS 2 BP L159 EP L162 DI 10.1086/321719 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XN UT WOS:000169943600008 ER PT J AU Papadakis, IE Nandra, K Kazanas, D AF Papadakis, IE Nandra, K Kazanas, D TI Dependent time lags in the X-ray emission of the Seyfert galaxy NGC 7469 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 7469); galaxies : nuclei; X-rays : galaxies ID ACCRETING COMPACT SOURCES; CYGNUS X-1; SPECTRUM; VARIABILITY; RADIATION; CORONAE; FLARES; STATE AB We report the discovery of time lags in the cross spectra of the X-ray light curves of the Seyfert galaxy NGC 7469. This behavior is common in Galactic black hole and neutron star binaries and is in the sense that harder Xrays are delayed with respect to softer X-rays, with a time lag approximately proportional to the Fourier period. At the longest period probed by our observation (similar to6 days), we find a time lag of approximately 3.5 hr between the 2-4 and 4-10 keV X-rays. A similar lag and period dependence are found by comparing the 2-4 and 10-15 keV light curves, albeit with less significance. We find the coherence function of the light curves to be close to 1 in the frequency range between 10(-5.5) and 10(-3.5) Hz. The implications of these results for the X-ray production mechanism in active galactic nuclei are discussed. C1 Univ Crete, Dept Phys, Heraklion 71003, Greece. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. RP Papadakis, IE (reprint author), Univ Crete, Dept Phys, POB 2208, Heraklion 71003, Greece. RI Papadakis, Iossif/C-3235-2011 NR 29 TC 39 Z9 39 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP L133 EP L137 DI 10.1086/321722 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XN UT WOS:000169943600002 ER PT J AU Strohmayer, TE AF Strohmayer, TE TI Discovery of a second high-frequency quasi-periodic oscillation from the microquasar GRS 1915+105 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; stars : individual (GRS 1915+105) stars : oscillations; X-rays : stars ID X-RAY BINARIES; RXTE OBSERVATIONS; BLACK-HOLES; GRS-1915+105; PRECESSION; EMISSION; MODEL AB We report the discovery in archival Rossi X-Ray Timing Explorer data of a similar to 40 Hz quasi-periodic oscillation (QPO) in the hard X-ray flux from the Galactic microquasar GRS 1915+105. The QPO is detected only in the hard X-ray band above similar to 13 keV and was discovered in observations in which the previously known 67 Hz QPO is present. The 40 Hz QPO has a typical rms amplitude of similar to2% in the 13-27 keV band and a width of similar to5.5 Hz (FWHM). We show that the 67 and 40 Hz QPOs are detected in the same observations in 1997 July and November. However, the QPO is not detected in observations from 1996 April, May, and June in which the 67 Hz QPO was first discovered. The frequency of the 67 Hz QPO is significantly higher in the 1997 observations by about 5% compared with the 1996 data. The identification of the 40 Hz QPO makes GRS 1915+105 the second black hole binary to show a pair of simultaneous high-frequency QPOs (the other being GRO J1655-40). The similarities between the properties of the 67 Hz QPO in GRS 1915+105 and the recently discovered 450 Hz QPO in GRO J1655-40 suggest that the pairs of frequencies in these systems may be produced by the same physical mechanism, with the frequency differences between the two being likely due to different black hole masses in the two systems. We discuss the implications of our result for the mass and spin of GRS 1915+105 as well as for models of X-ray variability in black holes and neutron stars. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Strohmayer, TE (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 29 TC 91 Z9 91 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP L169 EP L172 DI 10.1086/321720 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XN UT WOS:000169943600010 ER PT J AU Tennant, AF Becker, W Juda, M Elsner, RF Kolodziejczak, JJ Murray, SS O'Dell, SL Paerels, F Swartz, DA Shibazaki, N Weisskopf, MC AF Tennant, AF Becker, W Juda, M Elsner, RF Kolodziejczak, JJ Murray, SS O'Dell, SL Paerels, F Swartz, DA Shibazaki, N Weisskopf, MC TI Discovery of X-ray emission from the crab pulsar at pulse minimum SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (Crab Nebula) pulsars : individual (Crab Pulsar) radiation mechanisms : nonthermal stars : neutron; X-rays : general ID COOLING NEUTRON-STARS; ACCRETED ENVELOPES; THERMAL EVOLUTION; CASSIOPEIA; RADIATION; NEBULA AB The Chandra X-Ray Observatory observed the Crab pulsar using the Low-Energy Transmission Grating with the High-Resolution Camera. Time-resolved zeroth-order images reveal that the pulsar emits X-rays at all pulse phases. Analysis of the flux at minimum-most likely nonthermal in origin-places an upper limit (T(infinity) < 2.1 MK) on the surface temperature of the underlying neutron star. In addition, analysis of the pulse profile establishes that the error in the Chandra-determined absolute time is quite small, -0.2 +/- 0.1 ms. C1 NASA, Dept Space Sci, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. NASA, Univ Space Res Assoc, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Rikkyo Univ, Tokyo 1718501, Japan. RP Tennant, AF (reprint author), NASA, Dept Space Sci, George C Marshall Space Flight Ctr, SD50, Huntsville, AL 35812 USA. OI O'Dell, Stephen/0000-0002-1868-8056; Juda, Michael/0000-0002-4375-9688 NR 26 TC 45 Z9 45 U1 0 U2 2 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 JUN 29 PY 2001 VL 554 IS 2 BP L173 EP L176 DI 10.1086/321718 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XN UT WOS:000169943600011 ER PT J AU Zhang, W Marshall, FE Gotthelf, EV Middleditch, J Wang, QD AF Zhang, W Marshall, FE Gotthelf, EV Middleditch, J Wang, QD TI A phase-connected braking index measurement for the Large Magellanic Cloud pulsar PSR B0540-69 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (PSR B0540-69) stars : neutron; X-rays : stars ID GINGA OBSERVATIONS; SPIN-DOWN; DISCOVERY; PSR-0540-69 AB We report the results of an extensive monitoring campaign of PSR B0540-69, the 50 ms pulsar in the Large Magellanic Cloud, using data acquired with the Rossi X-Ray Timing Explorer. A set of 45 pointed X-ray observations spanning 1.2 yr reveals a steady spin-down interrupted by a single glitch event, the first recorded for this young, rotation-powered pulsar. The quality of the data allowed us to perform a pulse-timing analysis that successfully maintains cycle count between observations, after allowing for the observed glitch. The glitch event occurred on MJD 51,325 +/- 45 (90% CL error) and is characterized by a change in frequency of Delta nu/nu = 1.90 +/- 0.04 x 10(-9) and in frequency derivative of. By phase-linking the data set we provide a definitive measurement of the spin frequency of the pulsar and its first and second derivatives. These translate into a braking index of n = 1.81 +/- 0.07, significantly lower than reported previously for this source using measurements that could not be phase-linked unambiguously. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Massachusetts, Dept Astron, Amherst, MA 01003 USA. RP Zhang, W (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 19 TC 33 Z9 33 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 29 PY 2001 VL 554 IS 2 BP L177 EP L180 DI 10.1086/321703 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 453XN UT WOS:000169943600012 ER PT J AU Sun, JL Vandemark, D Mahrt, L Vickers, D Crawford, T Vogel, C AF Sun, JL Vandemark, D Mahrt, L Vickers, D Crawford, T Vogel, C TI Momentum transfer over the coastal zone SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SURFACE WIND STRESS; HEAT-FLUX; ATMOSPHERIC STABILITY; DRAG COEFFICIENTS; BOUNDARY-LAYER; SEA STATE; DEPENDENCE; WAVES; OCEAN; ROUGHNESS AB Spatial variations of surface stress over the coastal shoaling zone are studied offshore of Duck, North Carolina, by the LongEZ research aircraft, equipped to measure both atmospheric turbulence and oceanic waves. We find that the spatial variation of the friction velocity with offshore distance is much larger with offshore flow than with onshore flow. In general, the mean square slope of the short waves (wavelength shorter than 2 m) decreases with offshore distance, while the mean square slope of the long waves (wavelength longer than 2 m) increases with offshore distance. With onshore flow the friction velocity is strongly correlated with surface waves. In addition, the variation of the neutral drag coefficient is well correlated with the atmospheric bulk Richardson number. With offshore flow the observed momentum flux significantly decreases with offshore distance. Within the first few kilometer offshore, the relationship between the friction velocity and the mean square slope of the short waves and the relationship between the neutral drag coefficient and the atmospheric bulk Richardson number are obscured by the direct influence of the upstream land surface on the measured turbulence. These relationships for offshore flow agree well with those for onshore flow if the fetch is beyond the immediate influence of the land surface. The results in this study suggests that the effects of the strong turbulence advected from over the nearby land surface in offshore flow may lead to ambiguous physical interpretation of the correlation between the momentum flux and the wave state. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NOAA, FRD, Idaho Falls, ID 83402 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. NASA, Goddard Space Flight Ctr, Wallops Isl, VA 23337 USA. NOAA, ATDD, Oak Ridge, TN 37831 USA. Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. RP Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA. EM jsun@ucar.edu; vandemark@gsfc.nasa.gov; mahrt@oce.orst.edu; vickers@oce.orst.edu; tim.crawford@noaa.gov; vogel@atdd.noaa.gov RI Sun, Jielun/H-6576-2015 OI Sun, Jielun/0000-0003-3271-7914 NR 47 TC 23 Z9 23 U1 1 U2 7 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 JUN 27 PY 2001 VL 106 IS D12 BP 12437 EP 12448 DI 10.1029/2000JD900696 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 447FB UT WOS:000169559800006 ER PT J AU Wang, PH Veiga, RE Vann, LB Minnis, P Kent, GS AF Wang, PH Veiga, RE Vann, LB Minnis, P Kent, GS TI A further study of the method for estimation of SAGE II opaque cloud occurrence SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GAS EXPERIMENT-II; STRATOSPHERIC AEROSOL; VERTICAL STRUCTURE; CIRCULATION; SATELLITE; FREQUENCY; DATASET; CIRRUS; MODEL AB Information on vertical cloud distribution is important to atmospheric radiative calculation, general circulation modeling, and climate study. The method used for estimating the vertical structure of opaque cloud occurrence from the solar occultation observations obtained by the Stratospheric Aerosol and Gas Experiment (SAGE) II has been reviewed for further understanding of the nature of the derived cloud statistics. Most importantly, based on the SAGE II tropical observations (1985-1998), the present study illustrates that the derived opaque cloud occurrence at a given altitude is generally independent of the cloud occurrence at other altitudes, except for some anticorrelation between high-level (12.5 km) and low-level (1-3 km) clouds. This feature of the layer cloud frequency independence is also evident when regional data over the Pacific warm pool and the eastern Pacific are examined. The independent information of the layer cloud frequency is significant and makes it possible to use the derived vertical distribution of cloud occurrence to estimate the probability of multilayer clouds. The limitation is that it is difficult to determine how frequently the multilayer clouds are actually overlapping or how frequently thick cloud (> 1 km) really occurs based on the SAGE II observations alone. A discussion of the SAGE II tropical opaque cloud occurrence in relation to the cloud climatology based on visual observations from surface stations and ships, the International Satellite Cloud Climatology Project data, and the cloud statistics using rawinsonde records is also provided. C1 Sci & Technol Corp, Hampton, VA 23666 USA. Sci Applicat Int Corp, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Wang, PH (reprint author), Sci & Technol Corp, Hampton, VA 23666 USA. RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 29 TC 10 Z9 10 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 27 PY 2001 VL 106 IS D12 BP 12603 EP 12613 DI 10.1029/2001JD900138 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 447FB UT WOS:000169559800018 ER PT J AU Dohm, JM Anderson, RC Baker, VR Ferris, JC Rudd, LP Hare, TM Rice, JW Casavant, RR Strom, RG Zimbelman, JR Scott, DH AF Dohm, JM Anderson, RC Baker, VR Ferris, JC Rudd, LP Hare, TM Rice, JW Casavant, RR Strom, RG Zimbelman, JR Scott, DH TI Latent outflow activity for western Tharsis, Mars: Significant flood record exposed SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID PATHFINDER LANDING SITE; MARTIAN NORTHERN PLAINS; TECTONIC HISTORY; ANCIENT OCEANS; CHANNELS; REGION; ICE; GEOLOGY; GENERATION; EVOLUTION AB Observations permitted by the newly acquired Mars Observer Laser Altimeter data have revealed a system of gigantic valleys northwest of the huge Martian shield volcano, Arsia Mons, in the western hemisphere of Mars (northwestern slope valleys (NSVs)). These features, which generally correspond spatially to gravity lows, are obscured by veneers of materials including volcanic lava flows, air fall deposits, and eolian materials. Geologic investigations of the Tharsis region suggest that the system of gigantic valleys predates the construction of Arsia Mons and its extensive associated lava flows of mainly late Hesperian and Amazonian age and coincides stratigraphically with the early development of the outflow channels that debouch into Chryse Planitia. Similar to the previously identified outflow channels, which issued tremendous volumes of water into topographic lows such as Chryse Planitia, the NSVs potentially represent flooding of immense magnitude and, as such, a source of water for a northern plains ocean. C1 Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. Jet Prop Lab, Pasadena, CA 91109 USA. US Geol Survey, Flagstaff, AZ 86001 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Smithsonian Inst, Natl Air & Space Museum, Washington, DC 20560 USA. RP Dohm, JM (reprint author), Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. RI Dohm, James/A-3831-2014; OI Hare, Trent/0000-0001-8842-389X NR 77 TC 42 Z9 42 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 JUN 25 PY 2001 VL 106 IS E6 BP 12301 EP 12314 DI 10.1029/2000JE001352 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 445ZJ UT WOS:000169488200002 ER PT J AU Nimmo, F Gilmore, MS AF Nimmo, F Gilmore, MS TI Constraints on the depth of magnetized crust on Mars from impact craters SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID THERMAL EVOLUTION; BASINS; TOPOGRAPHY AB Large (diameter greater than similar to 500 km) Martian impact basins are associated with observed magnetic fields which are statistically distinct from, and smaller than, fields associated with smaller craters. We suggest that this effect arises because impacts cause shock, heating, and excavation, reducing the magnetization of previously magnetized crust. For a simple, uniformly magnetized model the magnetic field at 100 km altitude is reduced by similar to 50% when a crater-shaped demagnetization zone reaches the base of the magnetized layer. By analogy with terrestrial data, we assume that in Martian craters the zone of demagnetization extends to a depth of 0.04-0.15 crater diameters. On the basis of this assumption, the data suggest that the depth to the base of the magnetized layer on Mars, if uniform, is similar to 35 km, with lower and upper bounds of 10 and 100 km, respectively. These bounds imply magnetizations of 5-40 A m(-1) and are consistent with likely Mars geotherms at 4 Gyr B.P. C1 CALTECH, Pasadena, CA 91125 USA. Jet Prop Lab, Pasadena, CA USA. RP Nimmo, F (reprint author), Bullard Labs, Madingley Rd, Cambridge CB3 0EZ, England. RI Gilmore, Martha/G-5856-2011; OI Nimmo, Francis/0000-0003-3573-5915 NR 33 TC 51 Z9 52 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 JUN 25 PY 2001 VL 106 IS E6 BP 12315 EP 12323 DI 10.1029/2000JE001325 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 445ZJ UT WOS:000169488200003 ER PT J AU Pearl, JC Smith, MD Conrath, BJ Bandfield, JL Christensen, PR AF Pearl, JC Smith, MD Conrath, BJ Bandfield, JL Christensen, PR TI Observations of Martian ice clouds by the Mars Global Surveyor Thermal Emission Spectrometer: The First Martian year SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID HUBBLE-SPACE-TELESCOPE; WATER-VAPOR; GENERAL-CIRCULATION; VERTICAL STRUCTURE; TES OBSERVATIONS; ATMOSPHERE; SURFACE; VIKING; MISSION; TEMPERATURES AB Successful operation of the Mars Global Surveyor spacecraft, beginning in September 1997 (L-s 184 degrees), has permitted extensive observations over more than a Martian year. Initially, thin (normal optical depth <0.06 at 825 cm(-1)) ice clouds and hazes were widespread, showing a distinct latitudinal gradient. With the onset of a regional dust storm at L-s = 224 degrees, ice clouds vanished in the southern hemisphere, to reappear gradually after the decay of the storm. The zonally averaged cloud opacities show little difference between the beginning and end of the first Martian year. A broad low-latitude cloud belt: with considerable longitudinal structure was present in early northern summer. Apparently characteristic of the northern summer season, it vanished between L-s = 140 degrees and 150 degrees. The latitudinal extent of this feature is apparently controlled by the ascending branch of the Hadley circulation. The most opaque clouds (optical depth similar to0.6) were found above the summits of major volcanic features; these showed spatial structure possibly associated with wave activity. Variety among low-lying late morning clouds suggests localized differences in circulation and microclimates. Limb observations showed extensive optically thin (optical depth <0.04) stratiform clouds at altitudes up to 55 km. Considerable latitude and altitude variations were evident in ice clouds in early northern spring (L-s = 25 degrees); near 30 km, thin clouds extended from just north of the equator to similar to 45 degreesN, nearly to the north polar vortex. A water ice haze was present in the north polar night (L-s = 30 degrees) at altitudes up to 40 km. Because little dust was present this probably provided heterogeneous nucleation sites for the formation of CO2 clouds and snowfall at altitudes below similar to 20 km, where atmospheric temperatures dropped to the CO2 condensation point. The relatively invariant spectral shape of the water ice cloud feature over space and time indicates that ice particle radii are generally between 1 and 4 mum. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. RP Pearl, JC (reprint author), NASA, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. RI Smith, Michael/C-8875-2012 NR 69 TC 92 Z9 93 U1 0 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 JUN 25 PY 2001 VL 106 IS E6 BP 12325 EP 12338 DI 10.1029/1999JE001233 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 445ZJ UT WOS:000169488200004 ER PT J AU Lawrence, JK Cadavid, AC Ruzmaikin, A Berger, TE AF Lawrence, JK Cadavid, AC Ruzmaikin, A Berger, TE TI Spatiotemporal scaling of solar surface flows SO PHYSICAL REVIEW LETTERS LA English DT Article ID ANOMALOUS DIFFUSION; PAIR DISPERSION; TURBULENCE; GRANULATION; DYNAMICS AB The sun provides an excellent natural laboratory for nonlinear phenomena. We use motions of magnetic bright points on the solar surface, at the smallest scales yet observed, to study the small scale dynamics of the photospheric plasma. The paths of the bright points are analyzed within a continuous time random walk framework. Their spatial and temporal scaling suggests that the observed motions are the walks of imperfectly correlated tracers on a turbulent fluid flow in the lanes between granular convection cells. C1 Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA. CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. Lockheed Martin Space & Astrophys Lab, Palo Alto, CA 94304 USA. RP Lawrence, JK (reprint author), Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA. NR 16 TC 20 Z9 20 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 JUN 25 PY 2001 VL 86 IS 26 BP 5894 EP 5897 DI 10.1103/PhysRevLett.86.5894 PG 4 WC Physics, Multidisciplinary SC Physics GA 445XQ UT WOS:000169484200013 PM 11415388 ER PT J AU Segre, PN Prasad, V Schofield, AB Weitz, DA AF Segre, PN Prasad, V Schofield, AB Weitz, DA TI Glasslike kinetic arrest at the colloidal-gelation transition SO PHYSICAL REVIEW LETTERS LA English DT Article ID DYNAMIC LIGHT-SCATTERING; MODE-COUPLING-THEORY; VISCOELASTIC PROPERTIES; SUSPENSIONS; GELS; DISPERSIONS; RELAXATION AB We show that gelation of weakly attractive colloids is remarkably similar to the colloidal glass transition. Like the glass transition, dynamic light scattering functions near gelation scale with scattering vector, and exhibits a two-step decay with a power-law divergence of the final decay time. Like the glass transition, static light scattering does not change upon gelation. These results suggest that, like the glass transition, gelation results from kinetic arrest due to crowding of clusters, and that both gelation and the glass transition are manifestations of a more general jamming transition. C1 Harvard Univ, Dept Phys, Cambridge, MA 02138 USA. Univ Edinburgh, Dept Phys & Astron, Edinburgh EH9 3JZ, Midlothian, Scotland. RP Segre, PN (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 25 TC 274 Z9 275 U1 5 U2 57 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 JUN 25 PY 2001 VL 86 IS 26 BP 6042 EP 6045 DI 10.1103/PhysRevLett.86.6042 PG 4 WC Physics, Multidisciplinary SC Physics GA 445XQ UT WOS:000169484200050 PM 11415424 ER PT J AU Yamaoka, K Ueda, Y Inoue, H Nagase, F Ebisawa, K Kotani, T Tanaka, Y Zhang, SN AF Yamaoka, K Ueda, Y Inoue, H Nagase, F Ebisawa, K Kotani, T Tanaka, Y Zhang, SN TI ASCA observation of the superluminal jet source GRO J1655-40 in the 1997 outburst SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (GRO J1655-40); X-rays : stars ID ABSORPTION-LINE FEATURES; GAS IMAGING SPECTROMETER; BLACK-HOLE; BOARD ASCA; RAY; SATELLITE; SPECTRA; PERFORMANCE; RATES; MASS AB We report on the results of an ASCA observation of the Galactic jet source GRO J1655-10 performed from 1997 February 25 to February 28 covering a full orbital period (2.62 d). The averaged 2-10 keV flux was about 1.1 Crab. An absorption line feature centered at 6.8 keV was detected both in the GIS and SIS spectra. We interpret this as a blend of two resonance-absorption K alpha, lines from H-like and He-like iron ions. We can consistently explain both the ASCA spectra and the simultaneous RXTE/PCA spectrum by a combination of K-absorption lines and Ii-absorption edges of iron ions. The fact that the absorption line is stably present over the whole orbital phase implies that the distribution of the highly ionized plasma is not affected by the companion star, which is consistent with its presence around the black hole. A curve of growth analysis shows that the plasma contains velocity dispersion along the line-of-sight larger than 300 km s(-1) attributed to bulk motions. It is probably a part of a geometrically thick accretion flow in turbulent motions with velocities of 500-1600 km s(-1) at an estimated radius of similar to 10(10) cm. C1 Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Inst Space & Astronaut Sci, 3-1-1 Yoshinodai, Kanagawa 2298510, Japan. EM yamaoka@astro.isas.ac.jp NR 37 TC 43 Z9 43 U1 0 U2 0 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0004-6264 EI 2053-051X J9 PUBL ASTRON SOC JPN JI Publ. Astron. Soc. Jpn. PD JUN 25 PY 2001 VL 53 IS 2 BP 179 EP 188 DI 10.1093/pasj/53.2.179 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 426EH UT WOS:000168336500003 ER PT J AU Lazzarotto, B Frioud, M Larcheveque, G Mitev, V Quaglia, P Simeonov, V Thompson, A van den Bergh, H Calpini, B AF Lazzarotto, B Frioud, M Larcheveque, G Mitev, V Quaglia, P Simeonov, V Thompson, A van den Bergh, H Calpini, B TI Ozone and water-vapor measurements by Raman lidar in the planetary boundary layer: error sources and field measurements SO APPLIED OPTICS LA English DT Article ID DIFFERENTIAL ABSORPTION LIDAR; PHOTOMULTIPLIER TUBE; TROPOSPHERIC OZONE; CROSS-SECTIONS; CAMPAIGN; FLUXES; UV AB A new lidar instrument has been developed to measure tropospheric ozone and water vapor at low altitude. The lidar uses Raman scattering of an UV beam from atmospheric nitrogen, oxygen, and water vapor to retrieve ozone and water-vapor vertical profiles. By numerical simulation we investigate the sensitivity of the method to both atmospheric and device perturbations. The aerosol optical effect in the planetary boundary layer, ozone interference in water-vapor retrieval, statistical error, optical cross talk between Raman-shifted channels, and optical cross talk between an elastically backscattered signal in Raman-shifted signals and an afterpulse effect are studied in detail. In support of the main conclusions of this model study, time series of ozone and water vapor obtained at the Swiss Federal Institute of Technology in Lausanne and during a field campaign in Crete are presented. They are compared with point monitor and balloon sounding measurements for daytime and nighttime conditions. (C) 2001 Optical Society of America. C1 Ecole Polytech Fed Lausanne, Lab Air Pollut, CH-1015 Lausanne, Switzerland. Observ Neuchatel, CH-2000 Neuchatel, Switzerland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ecole Polytech Fed Lausanne, Lab Air Pollut, CH-1015 Lausanne, Switzerland. EM bertrand.calpini@epfl.ch RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 31 TC 9 Z9 11 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 JUN 20 PY 2001 VL 40 IS 18 BP 2985 EP 2997 DI 10.1364/AO.40.002985 PG 13 WC Optics SC Optics GA 442ZP UT WOS:000169315100006 PM 18357316 ER PT J AU Eldering, A Irion, FW Chang, AY Gunson, MR Mills, FP Steele, HM AF Eldering, A Irion, FW Chang, AY Gunson, MR Mills, FP Steele, HM TI Vertical profiles of aerosol volume from high-spectral-resolution infrared transmission measurements. I. Methodology SO APPLIED OPTICS LA English DT Article ID DEPENDENT OPTICAL-CONSTANTS; STRATOSPHERIC AEROSOL; SULFURIC-ACID; RADIATIVE CHARACTERISTICS; SULFATE AEROSOLS; PINATUBO AEROSOL; SURFACE-AREA; TEMPERATURE; EXTINCTION; CLOUDS AB The wavelength-dependent aerosol extinction in the 800-1250-cm(-1) region has been derived from ATMOS (atmospheric trace molecule spectroscopy) high-spectral-resolution IR transmission measurements. Using models of aerosol and cloud extinction, we have performed weighted nonlinear least-squares fitting to determine the aerosol-volume columns and vertical profiles of stratospheric sulfate aerosol and cirrus cloud volume. Modeled extinction by use of cold-temperature aerosol optical constants for a 70-80% sulfuric-acid-water solution shows good agreement with the measurements, and the derived aerosol volumes for a 1992 occultation are consistent with data from other experiments after the eruption of Nit. Pinatubo. The retrieved sulfuric acid aerosol-volume profiles are insensitive to the aerosol-size distribution and somewhat sensitive to the set of optical constants used. Data from the nonspherical cirrus extinction model agree well with a 1994 mid-latitude measurement indicating the presence of cirrus clouds at the tropopause. (C) 2001 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91101 USA. Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. Calif State Univ Northridge, Dept Geog, Northridge, CA 91330 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91101 USA. EM annmarie.eldering@jpl.nasa.gov NR 39 TC 17 Z9 18 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 JUN 20 PY 2001 VL 40 IS 18 BP 3082 EP 3091 DI 10.1364/AO.40.003082 PG 10 WC Optics SC Optics GA 442ZP UT WOS:000169315100019 PM 18357329 ER PT J AU Gupta, KK Lawson, CL AF Gupta, KK Lawson, CL TI On a progressive simultaneous iteration method for vibration analysis of gyroscopic systems SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE vibrations; finite elements; spinning structures AB This paper presents details of an eigenproblem solution procedure for the efficient and accurate free vibration analysis of gyroscopic systems such as spinning structures. The procedure enables computation of the first few roots and vectors without having to compute any other. While structural discretization is achieved by the standard finite element method, eigenproblem solution of the resulting equations is effected by a newly developed progressive simultaneous iterative (PSI) method. Numerical solution of relevant example problems are presented which are compared to those obtained by other existing analysis techniques, testifying to substantial gains in the efficacy of the newly developed solution algorithm. Copyright (C) 2001 John Wiley & Sons, Ltd. C1 NASA, Dryden Flight Res Ctr, Edwards, CA 93523 USA. RP Gupta, KK (reprint author), NASA, Dryden Flight Res Ctr, POB 273, Edwards, CA 93523 USA. NR 7 TC 2 Z9 2 U1 0 U2 1 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD JUN 20 PY 2001 VL 51 IS 5 BP 609 EP 617 DI 10.1002/nme.180.abs PG 9 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA 433WW UT WOS:000168784500005 ER PT J AU Mingo, N Makoshi, K Mii, T Ueba, H AF Mingo, N Makoshi, K Mii, T Ueba, H TI Theory of the relation between inelastic scanning tunneling spectroscopy of adsorbates and their vibrational deexcitation SO SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 19th European Conference on Surface Science (ECOSS-19) CY SEP 05-08, 2000 CL MADRID, SPAIN SP Univ Autonoma Madrid, Dept Fis Mat Condensada, European Phys Soc, Surface & Interface Div, Int Union Vacuum Sci, Techni & Applicat, Surface Div DE Green's function methods; tunneling; vibrations of adsorbed molecules; carbon monoxide; metallic surfaces; surface electronic phenomena (work function; surface potential, surface states, etc.) ID CO; EXCITATION; MOLECULE; CU(100); MICROSCOPY; MODES AB We show how the rate for controlled excitation of adsorbate vibrational modes by scanning tunneling microscope can be quantitatively related to the lifetimes of these modes when deexciting by electron-hole pair mechanism. To this end we present a Green function formalism that accounts for the two processes in a unified way, A model calculation for an adsorbate like CO is studied and compared with existing experimental results. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Himeji Inst Technol, Fac Sci, Kamigori, Hyogo 6781297, Japan. Toyama Univ, Dept Elect & Informat Engn, Toyama 930, Japan. RP Mingo, N (reprint author), NASA, Ames Res Ctr, Mailstop T27A-1, Moffett Field, CA 94035 USA. NR 15 TC 6 Z9 6 U1 0 U2 5 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD JUN 20 PY 2001 VL 482 BP 96 EP 100 DI 10.1016/S0039-6028(01)00736-1 PN 1 PG 5 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 460HL UT WOS:000170302100018 ER PT J AU Garces, JE Bozzolo, G Mosca, HO Abel, PS AF Garces, JE Bozzolo, G Mosca, HO Abel, PS TI Surface alloys of Pd and Cu via atomistic modeling SO SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 19th European Conference on Surface Science (ECOSS-19) CY SEP 05-08, 2000 CL MADRID, SPAIN SP Univ Autonoma Madrid, Dept Fis Mat Condensada, European Phys Soc, Surface & Interface Div, Int Union Vacuum Sci, Techni & Applicat, Surface Div DE alloys; semi-empirical models and model calculations; computer simulations; surface defects ID GROWTH; PD(110); CU(100); AU AB Atomistic modeling using parameter-dependent approximate methods has become a useful tool for the understanding of the basic features and mechanisms of complex surface processes. In most cases, however, the inadequate transferability of the input parameters results in their becoming specific to each particular application. Unlike other methods, the BFS method for alloys is a quantum approximate formalism with the advantage that all the needed parameters, computed via first-principles calculations or from experimental input, are transferable, in the sense that both surface and bulk problems are dealt with using the same set of parameters with no loss in accuracy. This characteristic of the BFS method is highlighted in the study of Cu-Pd surface alloys presented in this work, focusing on the deposition of Pd on Cu(100) and Cu(110), and Cu on Pd(110), showing excellent agreement with experiment in all cases: (a) Pd/Cu(100) exhibits a c(2 x 2) structure for low Pd coverages, (b) Pd/Cu(110) shows the formation of Pd-Cu chains, resulting into a Cu3Pd one-layer surface alloy and (c) Cu/Pd(110) displays the formation of mono-atomic linear chains oriented in the [110] direction for low Cu coverage. This work shows that such a wide range of results can be obtained from the same set of parameters, thus enhancing the predictive power and reliability of this technique. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Ohio Aerosp Inst, Cleveland, OH 44142 USA. Comis Nacl Energia Atom, Ctr Atom Bariloche, RA-8400 Bariloche, Rio Negro, Argentina. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Comis Nacl Energia Atom, Ctr Atom Constituyentes, RA-1429 Buenos Aires, DF, Argentina. Univ Buenos Aires, Fac Ingn, Dept Ingn Mecan & Naval, RA-1428 Buenos Aires, DF, Argentina. RP Bozzolo, G (reprint author), Ohio Aerosp Inst, 22800 Cedar Point Rd, Cleveland, OH 44142 USA. NR 15 TC 5 Z9 5 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD JUN 20 PY 2001 VL 482 BP 776 EP 783 DI 10.1016/S0039-6028(01)00712-9 PN 2 PG 8 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 460HM UT WOS:000170302200002 ER PT J AU Mingo, N Han, J Anantram, MP Yang, L AF Mingo, N Han, J Anantram, MP Yang, L TI Potential drop along carbon nanotube devices with current flow SO SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 19th European Conference on Surface Science (ECOSS-19) CY SEP 05-08, 2000 CL MADRID, SPAIN SP Univ Autonoma Madrid, Dept Fis Mat Condensada, European Phys Soc, Surface & Interface Div, Int Union Vacuum Sci, Techni & Applicat, Surface Div DE Green's function methods; computer simulations; conductivity; electrical transport (conductivity, resistivity; mobility, etc.); surface electronic phenomena (work function; surface potential, surface states, etc.); carbon ID SURFACES AB Electronic transport in carbon nanotube devices is calculated self-consistently and characterized by potential profile, using a non-equilibrium Green function approach. We study the potential drop along structures with two types of scatters: randomly disordered, and nanotube 'heterojunctions'. While perfectly conducting tubes have a flat potential along the tube axis, all the potential drop taking place at the contacts, highly disordered tubes display a linear potential drop profile, showing diffusive conducting behavior. For a heterojunction in which three metallic tubes arc connected by topological defects, the potential drop takes place also at the defect located interfaces. Reference is also made to experimental results and applications. (C) 2001 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC USA. RP Mingo, N (reprint author), NASA, Ames Res Ctr, Mailstop T27A-1, Moffett Field, CA 94035 USA. NR 12 TC 5 Z9 5 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD JUN 20 PY 2001 VL 482 BP 1130 EP 1134 DI 10.1016/S0039-6028(01)00734-8 PN 2 PG 5 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 460HM UT WOS:000170302200062 ER PT J AU Krotkov, NA Herman, JR Bhartia, PK Fioletov, V Ahmad, Z AF Krotkov, NA Herman, JR Bhartia, PK Fioletov, V Ahmad, Z TI Satellite estimation of spectral surface UV irradiance 2. Effects of homogeneous clouds and snow SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ACTIVE ULTRAVIOLET-RADIATION; TOTAL OZONE; SOLAR-RADIATION; EARTHS SURFACE; ATMOSPHERIC TRANSMISSION; TROPOSPHERIC OZONE; AEROSOLS; ABSORPTION; SCATTERING; TOMS AB This paper extends the theoretical analysis of the estimation of the surface UV irradiance from satellite ozone and reflectivity data from a clear-sky case to a cloudy atmosphere and snow-covered surface. Two methods are compared for the estimation of cloud-transmission factor C-T, the ratio of cloudy to clear-sky surface irradiance: (1) the Lambert equivalent reflectivity (LER) method and (2) a method based on radiative transfer calculations for a homogeneous (plane parallel) cloud embedded into a molecular atmosphere with ozone absorption. The satellite-derived C-T from the NASA Total Ozone Mapping Spectrometer (TOMS) is compared with ground-based C-T estimations from the Canadian network of Brewer spectrometers for the period 1989-1998. For snow-free conditions the TOMS derived C, at 324 nm approximately agrees with Brewer data with a correlation coefficient of similar to0.9 and a standard deviation of similar to0.1. The key source of uncertainty is the different size of the TOMS FOV (similar to 100 km field of view) and the much smaller ground instrument FOV, As expected, the standard deviations of weekly and monthly C-T averages were smaller than for daily values. The plane-parallel cloud method produces a systematic C-T bias relative to the Brewer data (+7% at low solar zenith angles to -10% at large solar zenith angles). The TOMS algorithm can properly account for conservatively scattering clouds and snow/ice if the regional snow albedo R-S is known from outside data. Since R-S varies on a daily basis, using a climatology will result in additional error in the satellite-estimated C-T. The C-T error has the same sign as the R-S error and increases over highly reflecting surfaces. Finally, clouds polluted with absorbing aerosols transmit less radiation to the ground than conservative clouds for the same satellite reflectance and flatten spectral dependence of C-T. Both effects reduce C-T compared to that estimated assuming conservative cloud scattering. The error increases if polluted clouds are over snow. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Meteorol Serv Canada, Downsview, ON M3H 5T4, Canada. Sci & Data Syst, Silver Spring, MD 20906 USA. Univ Maryland Baltimore Cty, Goddard Earth Sci & Technol Ctr, Baltimore, MD 21228 USA. RP Krotkov, NA (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916,Bldg 33,Room E411, Greenbelt, MD 20771 USA. RI Krotkov, Nickolay/E-1541-2012; Bhartia, Pawan/A-4209-2016; OI Krotkov, Nickolay/0000-0001-6170-6750; Fioletov, Vitali/0000-0002-2731-5956; Bhartia, Pawan/0000-0001-8307-9137; Herman, Jay/0000-0002-9146-1632 NR 74 TC 90 Z9 90 U1 1 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 11743 EP 11759 DI 10.1029/2000JD900721 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200001 ER PT J AU Walker, JP Houser, PR AF Walker, JP Houser, PR TI A methodology for initializing soil moisture in a global climate model: Assimilation of near-surface soil moisture observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC DATA ASSIMILATION; CATCHMENT-BASED APPROACH; KALMAN FILTER; BOUNDARY-CONDITIONS; UNITED-STATES; LAND; CIRCULATION; VARIABILITY; EVAPORATION; BALANCE AB Because of its long-term persistence, accurate initialization of land surface soil moisture in fully coupled global climate models has the potential to greatly increase the accuracy of climatological and hydrological prediction. To improve the initialization of soil moisture in the NASA Seasonal-to-Interannual Prediction Project (NSIPP), a one-dimensional Kalman filter has been developed to assimilate near-surface soil moisture observations into the catchment-based land surface model used by NSIPP. A set of numerical experiments was performed using an uncoupled version of the NSIPP land surface model to evaluate the assimilation procedure. In this study, "true" land surface data were generated by spinning-up the land surface model for 1987 using the International Satellite Land Surface Climatology Project (ISLSCP) forcing data sets. A degraded simulation was made for 1987 by setting the initial soil moisture prognostic variables to arbitrarily wet values uniformly throughout North America. The final simulation run assimilated the synthetically generated near-surface soil moisture "observations" from the true simulation into the degraded simulation once every 3 days. This study has illustrated that by assimilating near-surface soil moisture observations, as would be available from a remote sensing satellite, errors in forecast soil moisture profiles as a result of poor initialization may be removed and the resulting predictions of runoff and evapotranspiration improved. After only 1 month of assimilation the root-mean-square error in the profile storage of soil moisture was reduced to 3% vol/vol, while after 12 months of assimilation, the root-mean-square error in the profile storage was as low as 1% vol/vol. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Goddard Earth Sci & Technol Ctr, Greenbelt, MD USA. RP Walker, JP (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Mail Code 974, Greenbelt, MD 20771 USA. EM cejpw@land.gsfc.nasa.gov RI Houser, Paul/J-9515-2013 OI Houser, Paul/0000-0002-2991-0441 NR 33 TC 132 Z9 141 U1 0 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 11761 EP 11774 DI 10.1029/2001JD900149 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200002 ER PT J AU Lyapustin, AI Kaufman, YJ AF Lyapustin, AI Kaufman, YJ TI Role of adjacency effect in the remote sensing of aerosol SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB Adjacency effect is known to reduce apparent surface contrast by decreasing the top of the atmosphere radiance over bright pixels and increasing the brightness of the dark pixels. This effect is systematic and thus becomes important for the land remote sensing applications developed for use with either dark or bright targets. In this paper we trace the error caused by adjacency effect in the data processing chain from aerosol retrieval over dark targets to the atmospheric correction of the top of the atmosphere radiance. A systematic overestimation of the retrieved aerosol optical thickness and underestimation of surface albedo is demonstrated in accurate numeric simulations for a variety of atmospheric conditions and surface models. Results obtained suggest that 3-D radiation effects should be taken into account not only in the atmospheric correction algorithms but also in the aerosol retrieval over land at a high-to-medium (up to 1 km) resolution of sensor. C1 Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Joint Ctr Earth Syst Technol, Greenbelt, MD 20771 USA. RP Lyapustin, AI (reprint author), Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Joint Ctr Earth Syst Technol, Mail Code 920, Greenbelt, MD 20771 USA. RI Lyapustin, Alexei/H-9924-2014 OI Lyapustin, Alexei/0000-0003-1105-5739 NR 13 TC 24 Z9 29 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 11909 EP 11916 DI 10.1029/2000JD900647 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200015 ER PT J AU Pinty, B Gobron, N Widlowski, JL Gerstl, SAW Verstraete, MM Antunes, M Bacour, C Gascon, F Gastellu, JP Goel, N Jacquemoud, S North, P Qin, WH Thompson, R AF Pinty, B Gobron, N Widlowski, JL Gerstl, SAW Verstraete, MM Antunes, M Bacour, C Gascon, F Gastellu, JP Goel, N Jacquemoud, S North, P Qin, WH Thompson, R TI Radiation transfer model intercomparison (RAMI) exercise SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CANOPY REFLECTANCE; LIGHT-SCATTERING; VEGETATION; FOREST; MEDIA AB The community involved in modeling radiation transfer over terrestrial surfaces designed and implemented the first phase of a radiation transfer model intercomparison (RAMI) exercise. This paper discusses the rationale and motivation for this endeavor, presents the intercomparison protocol as well as the evaluation procedures, and describes the principal results. Participants were asked to simulate the transfer of radiation for a variety of precisely defined terrestrial environments and illumination conditions. These were abstractions of typical terrestrial systems and included both homogeneous and heterogeneous scenes. The differences between the results generated by eight different models, including both one-dimensional and three-dimensional approaches, were then documented and analyzed. RAMI proposed a protocol to quantitatively assess the consequences of the model discrepancies with respect to application, such as those motivating the development of physically based inversion procedures. This first phase of model intercomparison has already proved useful in assessing the ability of the modeling community to generate similar radiation fields despite the large panoply of models that were tested. A detailed analysis of the results also permitted to identify apparent "outliers" and their main deficiencies. Future undertakings in this intercomparison framework must be oriented toward an expansion of RAMI into other and more complex geophysical systems as well as the focusing on actual inverse problems. C1 EC Joint Res Ctr, SAI, Global Vegetat Monitoring Unit, I-21020 Ispra, VA, Italy. Inst Nacl Pesquisas Espaciais, BR-12201 Sao Jose Dos Campos, Brazil. Univ Paris 07, Lab Environm & Dev, F-75251 Paris, France. Ctr Etud Spatiale Biosphere, F-31055 Toulouse, France. Wayne State Univ, Dept Comp Sci, Detroit, MI 48202 USA. NERC, Ctr Ecol & Hydrol ITE, Monks Wood PE28 2LS, Cambs, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Alachua Res Inst, Alachua, FL 32616 USA. RP Pinty, B (reprint author), EC Joint Res Ctr, SAI, Global Vegetat Monitoring Unit, TP 440,Via E Fermi, I-21020 Ispra, VA, Italy. RI North, Peter/A-1616-2009; Jacquemoud, Stephane/F-8842-2010; OI North, Peter/0000-0001-9933-6935; Verstraete, Michel/0000-0003-0968-8721 NR 23 TC 87 Z9 89 U1 1 U2 20 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 11937 EP 11956 DI 10.1029/2000JD900493 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200018 ER PT J AU Abdou, WA Helmlinger, MC Conel, JE Bruegge, CJ Pilorz, SH Martonchik, JV Gaitley, BJ AF Abdou, WA Helmlinger, MC Conel, JE Bruegge, CJ Pilorz, SH Martonchik, JV Gaitley, BJ TI Ground measurements of surface BRF and HDRF using PARABOLA III SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; REMOTELY-SENSED DATA; IMAGING SPECTRORADIOMETER; INSTRUMENT DESCRIPTION; PHYSICAL MODEL; RETRIEVAL; BRDF AB The ground-based Portable Apparatus for Rapid Acquisition of Bidirectional Observations of Land and Atmosphere (PARABOLA), version 3, provides multiangle measurements of sky and ground radiances on a spherical grid of 5 degrees in the zenith-to-nadir and azimuthal planes in eight spectral channels. The hemispherical directional reflectance factor (HDRF) can be measured directly by comparing the radiance reflected by the surface in given direction to that reflected from a reference surface simultaneously observed by the PARABOLA 3. The surface bidirectional reflectance factor (BRF) cannot be measured directly, however, because of the presence of the sky diffuse illumination. The contribution of the diffuse sky radiance to the radiance reflected by the natural target surface is computed, and removed, using an iterative technique. Two approaches are employed: the first requires knowledge of the atmospheric optical depth, and the second requires the simultaneous measurements of the radiance reflected by a standard surface panel under the same atmospheric and illumination conditions. Ground measurements of the BRF and HDRF for dry lake surfaces were obtained from the PARABOLA 3 observations with better than +/- 10% accuracy. The results described in this work are used primarily for the vicarious calibration of the Multiangle Imaging Spectroradiometer (MISR) onboard the Earth Observing System (EOS) Terra platform and for validation of MISR BRF retrievals of selected Earth surface targets. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Abdou, WA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 25 TC 7 Z9 7 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 11967 EP 11976 DI 10.1029/2000JD900654 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200020 ER PT J AU Kahn, R Banerjee, P McDonald, D Martonchik, J AF Kahn, R Banerjee, P McDonald, D Martonchik, J TI Aerosol properties derived from aircraft multiangle imaging over Monterey Bay SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GEOPHYSICAL RETRIEVALS; INSTRUMENT DESCRIPTION; OPTICAL-PROPERTIES; MISR; SPECTRORADIOMETER; SENSITIVITY; OCEAN; REFLECTANCE; THICKNESS; SATELLITE AB The first generic and climatological aerosol retrievals using AirMISR data are presented. Multiangle observations at 672 and 867 nm, in a cloud-free region over dark water in Monterey Bay on June 29, 1999, yield complementary generic and climatological results. The generic retrieval produces cross-section-weighted, column-mean aerosol properties: midvisible aerosol optical depth between 0.05 and 0.10, with a preference for values on the low side of the range, particle number-mean characteristic radius between 0.25 and 0.45 mum, and imaginary index of refraction <0.004, with 0.0 as the most likely value. These properties correspond to a "medium-to-large, spherical'' column-average particle. The climatological retrieval identifies a maritime air mass, having a total aerosol optical depth about 0.1, and mixing ratio for sea-salt particles (large, spherical) of 50%, based on optical depth in MISR Band 2, and 40% for the sulfate plus carbonaceous (medium, spherical) components, to an accuracy of about +/- 15%. These results are in good agreement with the limited nearby surface-based and aircraft observations available. The analysis also shows that over dark water, pixel-to-pixel scene variability can contribute more to the retrieval uncertainty than camera calibration and that high spatial variance of the reflectance, in addition to geometric considerations, is a better indicator of Sun glint contamination than geometry alone. This work represents an early step toward the goal of using MISR multiangle data to add spatial detail and information about temporal variability to the global aerosol climatology. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kahn, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kahn, Ralph/D-5371-2012 OI Kahn, Ralph/0000-0002-5234-6359 NR 35 TC 15 Z9 15 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 11977 EP 11995 DI 10.1029/2000JD900740 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200021 ER PT J AU Holben, BN Tanre, D Smirnov, A Eck, TF Slutsker, I Abuhassan, N Newcomb, WW Schafer, JS Chatenet, B Lavenu, F Kaufman, YJ Castle, JV Setzer, A Markham, B Clark, D Frouin, R Halthore, R Karneli, A O'Neill, NT Pietras, C Pinker, RT Voss, K Zibordi, G AF Holben, BN Tanre, D Smirnov, A Eck, TF Slutsker, I Abuhassan, N Newcomb, WW Schafer, JS Chatenet, B Lavenu, F Kaufman, YJ Castle, JV Setzer, A Markham, B Clark, D Frouin, R Halthore, R Karneli, A O'Neill, NT Pietras, C Pinker, RT Voss, K Zibordi, G TI An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NORTHEASTERN TROPICAL ATLANTIC; LONG-RANGE TRANSPORT; MAUNA-LOA; ATMOSPHERIC TURBIDITY; STRATOSPHERIC AEROSOL; PRECIPITABLE WATER; SOUTHERN AFRICA; DESERT AEROSOL; DUST; NORTH AB Long-term measurements by the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into an aerosol optical properties climatology. Quality assured monthly means are presented and described for 9 primary sites and 21 additional multiyear sites with distinct aerosol regimes representing tropical biomass burning, boreal forests, midlatitude humid climates, midlatitude dry climates, oceanic sites, desert sites, and background sites. Seasonal trends for each of these nine sites are discussed and climatic averages presented. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Univ Lille 1, Ctr Hyperfrequences & Semicond, CNRS, Opt Atmospher Lab, F-59655 Villeneuve Dascq, France. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. Raytheon STX Corp, Lanham, MD USA. Univ Paris 07, Lab Interuniv Syst Atmospher, F-94010 Creteil, France. Univ Paris 12, F-94010 Creteil, France. CNRS, CESBIO, Toulouse, France. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. Univ New Mexico, Albuquerque, NM 87106 USA. Inst Pesquisas Espaciais, Sao Jose Dos Campos, San Paolo, Brazil. NOAA, Silver Spring, MD 20746 USA. Scripps Inst Oceanog, La Jolla, CA 92093 USA. Brookhaven Natl Lab, Dept Appl Sci, Upton, NY 11973 USA. Ben Gurion Univ Negev, IL-84990 Sede Boqer, Israel. Univ Sherbrooke, CARTEL, Sherbrooke, PQ J1K 2R1, Canada. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SAIC, GSC, Beltsville, MD USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Miami, Dept Phys, Miami, FL 33124 USA. Commiss European Communities, Joint Res Ctr, Space Applicat Inst, I-21020 Ispra, Italy. RP Holben, BN (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. RI Pinker, Rachel/F-6565-2010; Schafer, Joel/A-3978-2010; Smirnov, Alexander/C-2121-2009; ECK, THOMAS/D-7407-2012; Voss, Kenneth /A-5328-2013; Markham, Brian/M-4842-2013 OI Smirnov, Alexander/0000-0002-8208-1304; Voss, Kenneth /0000-0002-7860-5080; Markham, Brian/0000-0002-9612-8169 NR 77 TC 966 Z9 999 U1 8 U2 73 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 12067 EP 12097 DI 10.1029/2001JD900014 PG 31 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200027 ER PT J AU Wen, GY Cahalan, RF Tsay, SC Oreopoulos, L AF Wen, GY Cahalan, RF Tsay, SC Oreopoulos, L TI Impact of cumulus cloud spacing on Landsat atmospheric correction and aerosol retrieval SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RADIATIVE-TRANSFER; FIELDS; MODIS AB A Landsat 7 Enhanced Thematic Mapper Plus (ETM+) image acquired over the Southern Great Plains site of Department of Energy's Atmospheric Radiation Measurement Program during the Atmospheric Radiation Measurement Enhanced Shortwave Experiment II is used to study the effect of clouds on reflected radiation in clear gaps in a cumulus cloud field. A technique using the spectral information of background and clouds is applied to identify clouds. The path radiance technique is used to extract the apparent path radiance in a clear region of the cumulus cloud field. The result shows that the apparent path radiance is enhanced by nearby clouds in both band 1 (blue) and band 3 (red) of ETM+. More importantly, the magnitude of the enhancement depends on the mean cloud-free distance in the clear patches. For cloud-free distances <0.5 km the enhancement of apparent path radiance is more than 0.025 and 0.015 (reflectance units) in band 1 and band 3, respectively, which corresponds to an enhancement of apparent aerosol optical thickness of similar to0.25 and similar to0.15. Neglecting of the three-dimensional cloud effect would lead to underestimates of surface reflectance of similar to0.025 and similar to0.015 in the blue and red band, respectively, if the true aerosol optical thickness is 0.2 and the surface reflectance is 0.05, The enhancement decreases exponentially with mean cloud-free distance, reaching asymptotic values of 0.09 for band 1 and 0.027 for band 3 at a mean cloud-free distance about 2 km. The asymptotic values are slightly larger than the mean path radiances retrieved from a completely clear region: 0.086 and 0.024 for the blue and red bands, respectively. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syt Technol, Catonsville, MD USA. RP Wen, GY (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. 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 19 TC 24 Z9 24 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 12129 EP 12138 DI 10.1029/2001JD900159 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200030 ER PT J AU Johnson, DG Jucks, KW Traub, WA Chance, KV AF Johnson, DG Jucks, KW Traub, WA Chance, KV TI Isotopic composition of stratospheric water vapor: Measurements and photochemistry SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID INFRARED SOLAR SPECTRA; TRANSITION FREQUENCIES; PLANETARY-ATMOSPHERES; HYDROGEN BUDGET; METHANE; OZONE; FRACTIONATION; ABUNDANCES; DEUTERIUM; STRENGTHS AB We present a photochemical model describing the changes in the isotopic composition of stratospheric water vapor that result from methane oxidation and reactions with O(D-1). We then compare model calculations with measurements made with the Smithsonian Astrophysical Observatory far-infrared spectrometer during seven balloon flights that took place between 1989 and 1997. The agreement between the model calculations and measurements establishes the validity of the model and the internal consistency of the data set. Finally, we use the model and measurements together to estimate the mixing ratio and isotopic composition of water vapor entering the stratosphere and find that the average over all flights of the water vapor mixing ratio, deltaD, delta O-18, and delta O-17 are 3.48 +/- 0.15 parts per million by volume, -679 +/- 20 parts per thousand, -128 +/- 31 parts per thousand, and -84 +/- 31 parts per thousand, respectively, where the errors indicate the estimated accuracy. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Johnson, DG (reprint author), NASA, Langley Res Ctr, MS 468, Hampton, VA 23681 USA. EM d.g.johnson@larc.nasa.gov; kjucks@cfa.harvard.edu; wtraub@cfa.harvard.edu; kchance@cfa.harvard.edu RI Johnson, David/F-2376-2015; OI Johnson, David/0000-0003-4399-5653; Chance, Kelly/0000-0002-7339-7577 NR 36 TC 32 Z9 32 U1 0 U2 4 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 JUN 16 PY 2001 VL 106 IS D11 BP 12211 EP 12217 DI 10.1029/2000JD900763 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200036 ER PT J AU Johnson, DG Jucks, KW Traub, WA Chance, KV AF Johnson, DG Jucks, KW Traub, WA Chance, KV TI Isotopic composition of stratospheric water vapor: Implications for transport SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERE; DEUTERIUM; TROPOPAUSE; PACIFIC AB We develop a series of models of transport in the upper tropical troposphere in order to explain the observed abundance and isotopic composition of stratospheric water vapor. We start with the Rayleigh fractionation process and add the effects of mixing and recirculation of stratospheric air through the upper troposphere. We compare our measurements with model calculations for a range of input parameters and find that the observations are best explained by a model that mixes vapor from roughly 11 km (carried aloft either as condensate or through radiative heating and uplift) with air that has been dehydrated (in a large convective system) to a mixing ratio substantially below the saturation mixing ratio of the mean tropical tropopause. The result is that while most of the moisture comes from convective outflow near ii km, most of the air in the upper troposphere consists of dehydrated air from convective systems with cloud top temperatures below that of the mean tropical tropopause. We also find that the water vapor mixing ratio in the stratosphere is determined not only by the temperature of the tropical tropopause but also by the relative importance of radiative heating, recirculation of stratospheric air, and deep convection in supplying air to the upper troposphere. Our results show that water vapor isotope ratios are a powerful diagnostic tool for testing the results of general circulation models. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Johnson, DG (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. RI Johnson, David/F-2376-2015; OI Johnson, David/0000-0003-4399-5653; Chance, Kelly/0000-0002-7339-7577 NR 21 TC 38 Z9 38 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 12219 EP 12226 DI 10.1029/2000JD900764 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200037 ER PT J AU Cordero, EC Kawa, SR AF Cordero, EC Kawa, SR TI Ozone and tracer transport variations in the summer Northern Hemisphere stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DIABATIC CIRCULATION; TEMPORAL VARIANCE; DATA ASSIMILATION; MODEL; HALOE; CH4; PHOTOCHEMISTRY; SPECTROMETER; SATELLITE; LATITUDES AB Constituent observations from the Upper Atmosphere Research Satellite (UARS) in combination with estimates of the residual circulation are used to examine the transport and chemical. budgets of HF, CH4 and O-3 in the summer Northern Hemisphere. Budget calculations of HF, CH4 and O-3 show that the transport tendency due to the residual circulation increases in magnitude and is largely opposed by eddy motions through the summer months. Ozone budget analyses show that between 100 and 31 hPa, the magnitudes of the mean circulation and eddy transport terms increase through the summer months, producing tendencies that are factors of 2 to 3 times larger than the observed ozone change in the stratosphere. Chemical loss dominates the observed ozone decrease only at the highest latitudes, poleward of about 70 degreesN. A comparison of observations from the Total Ozone Mapping Spectrometer with UARS-calculated total ozone suggests that poleward of 50 degreesN, between 35% and 55% of the seasonal ozone decline during the summer occurs at altitudes below 100 hPa. The overall uncertainties, associated primarily with calculations of the residual circulation and eddy transport, are relatively large, and thus prevent accurate and useful constraints on the ozone chemical rate in the lower stratosphere. C1 Monash Univ, Dept Math & Stat, Clayton, Vic 3168, Australia. NASA, Goddard Space Flight Ctr, Atmospher Chem & Dynam Branch, Greenbelt, MD 20771 USA. RP Cordero, EC (reprint author), Monash Univ, Dept Math & Stat, Clayton, Vic 3168, Australia. RI Kawa, Stephan/E-9040-2012 NR 43 TC 8 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 16 PY 2001 VL 106 IS D11 BP 12227 EP 12239 DI 10.1029/2001JD900004 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 442TC UT WOS:000169300200038 ER PT J AU Kostiuk, T Fast, KE Livengood, TA Hewagama, T Goldstein, JJ Espenak, F Buhl, D AF Kostiuk, T Fast, KE Livengood, TA Hewagama, T Goldstein, JJ Espenak, F Buhl, D TI Direct measurement of winds on Titan SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ETHANE; ATMOSPHERE; TEMPERATURE; PLANETS; SURFACE C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Challenger Ctr Space Sci Educ, Alexandria, VA 22314 USA. RP Kostiuk, T (reprint author), NASA, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. RI Hewagama, T/C-8488-2012; Livengood, Timothy/C-8512-2012; Kostiuk, Theodor/A-3077-2014 NR 28 TC 71 Z9 71 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 JUN 15 PY 2001 VL 28 IS 12 BP 2361 EP 2364 DI 10.1029/2000GL012617 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 472WT UT WOS:000171008500018 ER PT J AU Haywood, JM Francis, PN Geogdzhayev, I Mishchenko, M Frey, R AF Haywood, JM Francis, PN Geogdzhayev, I Mishchenko, M Frey, R TI Comparison of Saharan dust aerosol optical depths retrieved using aircraft mounted pyranometers and 2-channel AVHRR algorithms. SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SULFATE; MODEL AB The 0.55 mum optical depth of the Saharan dust aerosol plume is determined from C-130 pyranometer data for two different days and the results compared to those from a 2-channel Advanced Very High Resolution Radiometer (AVHRR) retrieval algorithm. When the time difference between the C-130 and AVHRR overpasses is small, the geographic distribution of the aerosol optical depths are similar and differ by less than +/- 0.1 despite the different refractive indices, size distributions and atmospheric profiles implicit in each method. The pyranometer derived optical depth at 0.55 mum exceeds a value of I on one of the days, which exceeds the cloud threshold used in many satellite retrieval algorithms with implications for the accuracy of satellite derived aerosol optical depths. The difficulties in making extensive geographical comparisons between satellite and aircraft measurements owing to the differential speed of the observing platforms are also highlighted. C1 DERA, Met Off, Farnborough GU14 0LX, Hants, England. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Wisconsin, Madison, WI 53706 USA. Columbia Univ, New York, NY 10027 USA. RP Haywood, JM (reprint author), DERA, Met Off, Y46 Bldg, Farnborough GU14 0LX, Hants, England. RI Francis, Peter/H-9352-2013; Mishchenko, Michael/D-4426-2012 OI Francis, Peter/0000-0002-5869-803X; NR 16 TC 26 Z9 25 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 JUN 15 PY 2001 VL 28 IS 12 BP 2393 EP 2396 DI 10.1029/2000GL012625 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 472WT UT WOS:000171008500026 ER PT J AU Gao, RS Del Negro, LA Swartz, WH Salawitch, RJ Lloyd, SA Proffitt, MH Fahey, DW Donnelly, SG Neuman, JA Stimpfle, RM Bui, TP AF Gao, RS Del Negro, LA Swartz, WH Salawitch, RJ Lloyd, SA Proffitt, MH Fahey, DW Donnelly, SG Neuman, JA Stimpfle, RM Bui, TP TI Jno(2) at high solar zenith angles in the lower stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID REACTIVE NITROGEN; POLARIS; CLO AB In situ measurements of NO, NO2, O-3, HO2, ClO, pressure, and temperature have been made at high solar zenith angles (SZA, 70 degrees - 93 degrees) in the lower stratosphere. These measurements are used to derive the photolysis rate of NO2, J(NO2),, using a time-dependent method. The resultant J(NO2) values and the results of a multiple-scattering actinic flux model show a linear relationship throughout the SZA range. The difference of the two sets of J(NO2) values of about 11% suggests that the model scattering calculation is very accurate at high SZA conditions near sunrise and sunset. C1 NOAA, Aeron Lab, Boulder, CO 80305 USA. Middlebury Coll, Dept Chem & Biochem, Middlebury, VT 05753 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Natl Ctr Atmospher Res, Boulder, CO 80303 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. NASA, Ames Res Ctr, Moffett Field, CA 94305 USA. RP Gao, RS (reprint author), NOAA, Aeron Lab, 325 Broadway R-AL6, Boulder, CO 80305 USA. RI Neuman, Andy/A-1393-2009; Salawitch, Ross/B-4605-2009; Swartz, William/A-1965-2010; Gao, Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013 OI Neuman, Andy/0000-0002-3986-1727; Salawitch, Ross/0000-0001-8597-5832; Swartz, William/0000-0002-9172-7189; Fahey, David/0000-0003-1720-0634 NR 10 TC 5 Z9 5 U1 1 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 JUN 15 PY 2001 VL 28 IS 12 BP 2405 EP 2408 DI 10.1029/2000GL012615 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 472WT UT WOS:000171008500029 ER PT J AU Hirose, N Fukumori, I Ponte, RM AF Hirose, N Fukumori, I Ponte, RM TI A non-isostatic global sea level response to barometric pressure near 5 days SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NORMAL-MODES; WORLD OCEAN; TIDES; VARIABILITY; PACIFIC; WAVES AB Changes in surface atmospheric pressure usually induce an isostatic response in the ocean characterized by an adjustment in sea level at the rate of approximately -1cm/hPa. Nonisostatic signals are, however, observed at many tropical tide gauges at periods near 5 days. Our analysis of satellite observations reveals the global nature of these signals, involving nonisostatic sea level fluctuations with nearly uniform phase within separate basins and an out-of-phase oscillation between the Atlantic and Pacific Oceans. Comparisons with a barotropic model further link the observed signals to forcing by a large scale pressure wave in the atmosphere and show that constrictions between basins prevent an isostatic response from being established. The apparent forced, nonresonant nature of the nonisostatic response contrasts with the predominantly resonant ocean dynamics at higher frequencies and may be relevant to explain the behavior of the long period tides. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Atmospher & Environm Res Inc, Lexington, MA 02421 USA. RP Hirose, N (reprint author), CALTECH, Jet Prop Lab, MS 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. OI Hirose, Naoki/0000-0001-6234-8676; Ponte, Rui/0000-0001-7206-6461 NR 15 TC 14 Z9 14 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 JUN 15 PY 2001 VL 28 IS 12 BP 2441 EP 2444 DI 10.1029/2001GL012907 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 472WT UT WOS:000171008500039 ER PT J AU Palko, JW Kriven, WM Sinogeikin, SV Bass, JD Sayir, A AF Palko, JW Kriven, WM Sinogeikin, SV Bass, JD Sayir, A TI Elastic constants of yttria (Y2O3) monocrystals to high temperatures SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID BRILLOUIN SPECTROSCOPY; CUBIC MATERIALS; DEPENDENCE; SCATTERING; PRESSURE; CORUNDUM; DIAMOND; GARNET; MODULI; FIBERS AB The single-crystal elastic moduli of yttria have been measured by Brillouin spectroscopy up to 1200 degreesC. The room temperature values obtained are C-11 = 223.7 +/-0.6 GPa, C-44 = 74.6 +/-0.7 GPa, and C-12 = 112.4 +/-1.1 GPa. The resulting bulk and (Voigt-Reuss-Hill) shear moduli are K = 149.5 +/-1.0 GPa and G(VRH) = 66.3 +/-0.8 GPa, respectively. These agree much more closely with experimental values reported for polycrystalline samples than do previous single-crystal measurements. Linear least squares regressions to the variation of bulk and shear moduli with temperature result in derivatives of dK/dT = -17 +/-2 MPa/degreesC and dG(VRH)/dT = -8 +/-2 MPa/degreesC. Elastic anisotropy was found to remain essentially constant over the temperature range studied. (C) 2001 American Institute of Physics. C1 Univ Illinois, Dept Mat Sci & Engn, Urbana, IL 61801 USA. Univ Illinois, Dept Geol, Urbana, IL 61801 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Case Western Reserve Univ, Cleveland, OH 44135 USA. RP Univ Illinois, Dept Mat Sci & Engn, 1304 W Green St, Urbana, IL 61801 USA. EM palko@uiuc.edu RI Bass, Jay/G-2599-2013 NR 60 TC 36 Z9 36 U1 1 U2 9 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0021-8979 EI 1089-7550 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 15 PY 2001 VL 89 IS 12 BP 7791 EP 7796 DI 10.1063/1.1369395 PG 6 WC Physics, Applied SC Physics GA 440PM UT WOS:000169183500015 ER PT J AU Hagan, DE Nalli, NR AF Hagan, DE Nalli, NR TI Tropical water vapor correction for remotely sensed sea surface temperature: Results using narrowband window radiance profiles from TOGA COARE SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID TRACK SCANNING RADIOMETER; SATELLITE; OCEAN; RETRIEVALS; VALIDATION; ALGORITHMS AB This paper describes sea surface skin temperatures (SST) derived from unique aircraft-based measurements and a physical multispectral retrieval technique. The aircraft data were acquired under moist atmospheric conditions over the western and eastern tropical Pacific Ocean during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment and the Central Equatorial Pacific Experiment. Radiometric profiles were obtained in four contiguous channels over the spectral window region 800-1000 cm(-1) during aircraft ascents from 0.03 through 4.6 km altitude. These bands subdivide the "split window" of present satellite radiometers used for measurements of SST. The use of four channels in the measurement approach was motivated by theoretical studies that suggest the need for three independent pieces of information to separate atmospheric and surface components of upwelling radiance in moist atmospheres. The analyses were unusual in that the absorption path length differed for each multispectral set of nadir observations made at discrete altitudes. The mean accuracy for retrievals at all altitudes was less than or similar to1 K and was relatively insensitive to the guess profiles used for the simple forward radiance model. Simulated four-channel retrievals demonstrate an rms accuracy of similar or equal to0.3 K with negligible bias for global maritime profile conditions, which include extreme moisture-laden samples. The results demonstrate that the combination of high-precision measurements with a robust retrieval method can provide SST (instantaneous, global, day, or night) that meet the World Climate Research Programme accuracy objectives. C1 CALTECH, Jet Prop Lab, Natl Aernaut Space Adm, Pasadena, CA 91109 USA. Univ Wisconsin, Dept Atmospher & Ocean Sci, Madison, WI USA. RP Hagan, DE (reprint author), CALTECH, Jet Prop Lab, Natl Aernaut Space Adm, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Nalli, Nicholas/F-6731-2010 OI Nalli, Nicholas/0000-0002-6914-5537 NR 33 TC 2 Z9 2 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 JUN 15 PY 2001 VL 106 IS C6 BP 11423 EP 11436 DI 10.1029/1999JC000143 PG 14 WC Oceanography SC Oceanography GA 442TU UT WOS:000169301700003 ER PT J AU Blanco, JL Thomas, AC Carr, ME Strub, PT AF Blanco, JL Thomas, AC Carr, ME Strub, PT TI Seasonal climatology of hydrographic conditions in the upwelling region off northern Chile SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID CALIFORNIA CURRENT SYSTEM; ATLANTIC CURRENT; CIRCULATION; VARIABILITY; PACIFIC; TEMPERATURE; COAST; SEA AB Over 30 years of hydrographic data from the northern Chile (18 degreesS-24 degreesS) upwelling region are used to calculate the surface and subsurface seasonal climatology extending 400 km offshore. The data are interpolated to a grid with sufficient spatial resolution to preserve cross-shelf gradients and then presented as means within four seasons: austral winter (July-September), spring (October-December), summer (January-March), and fall (April-June). Climatological monthly wind forcing, surface temperature, and sea level from three coastal stations indicate equatorward (upwelling favorable) winds throughout the year, weakest in the north. Seasonal maximum alongshore wind stress is in late spring and summer (December-March). Major water masses of the region are identified in climatological T-S plots and their sources and implied circulation discussed. Surface fields and vertical transects of temperature and salinity confirm that upwelling occurs year-round, strongest in summer and weakest in winter, bringing relatively fresh water to the surface nearshore. Surface geostrophic flow nearshore is equatorward throughout the year. During summer, an anticyclonic circulation feature in the north which extends to at least 200 m depth is evident in geopotential anomaly and in both temperature and geopotential variance fields. Subsurface fields indicate generally poleward flow throughout the year, strongest in an undercurrent near the coast. This undercurrent is strongest in summer and most persistent and organized in the south (south of 21 degreesS), A subsurface oxygen minimum, centered at similar to 250 m, is strongest at lower latitudes. Low-salinity subsurface water intrudes into the study area near 100 m, predominantly in offshore regions, strongest during summer and fall and in the southernmost portion of the region. The climatological fields are compared to features off Baja within the somewhat analogous California Current and to measurements from higher latitudes within the Chile-Peru Current system. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91009 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. Univ Maine, Sch Marine Sci, Orono, ME 04469 USA. Inst Fomento Pesquero, Valparaiso, Chile. RP Blanco, JL (reprint author), Old Dominion Univ, Dept Ocean Earth & Atmospher Sci, Norfolk, VA 23529 USA. NR 47 TC 90 Z9 92 U1 0 U2 11 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 JUN 15 PY 2001 VL 106 IS C6 BP 11451 EP 11467 DI 10.1029/2000JC000540 PG 17 WC Oceanography SC Oceanography GA 442TU UT WOS:000169301700005 ER PT J AU Exton, RJ AF Exton, RJ TI Correlation of Cs/foreign gas diffuse bands with theoretical interaction potentials SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article DE satellites; cesium; fluorescence; potentials ID COLLISIONS AB Fluorescence excitation is employed to survey diffuse spectral bands in mixtures of Cs with He, Ne, Ar, Kr, Xe, or N-2 over the wavelength range 430-470 nm. Direct fluorescence and sensitized fluorescence at low pressures are also utilized to associate various diffuse bands with their respective atomic parent lines. The line-band associations, along with the positions and strengths of the bands, are then correlated with theoretical potentials for the collision pairs. The potentials exhibit a rich structure in the excited state which qualitatively describes many of the diffuse band characteristics and lead to the following conclusions: (1) red satellite bands are correlated with long-range (20-30 a.u.) shallow potential wells in the excited state, (2) violet satellite bands are correlated with maxima in the excited state potentials in the range 10-20 a.u., and (3) detached bands are formed near avoided crossings in the range 6-10 a.u. A diagnostic technique for foreign gas density is also demonstrated for N-2 and He. Published by Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Adv Measurement & Diagnost Branch, Hampton, VA 23681 USA. RP Exton, RJ (reprint author), NASA, Langley Res Ctr, Adv Measurement & Diagnost Branch, Hampton, VA 23681 USA. NR 31 TC 1 Z9 1 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUN 15 PY 2001 VL 69 IS 6 BP 723 EP 743 DI 10.1016/S0022-4073(00)00109-6 PG 21 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 430KR UT WOS:000168573500003 ER PT J AU Bahoura, M Clairon, A AF Bahoura, M Clairon, A TI Diode-laser noise conversion in an optically dense atomic sample SO OPTICS LETTERS LA English DT Article ID PHASE NOISE; SPECTROSCOPY; FLUCTUATIONS; VAPOR AB We report on oscillating complex noise spectra obtained when a diode-laser beam passes through a resonant dense Doppler-broadened cesium-vapor cell. Atomic coherence converts the laser phase noise into amplitude noise in the transmitted beam. We have found that the level of amplitude noise is orders of magnitude above the intrinsic laser noise. As a function of laser detuning, this noise extends over several inhomogeneous widths, depending on the spectral frequency. Numerical calculations based on a simple theory remarkably mimic the details of the experimental noise spectra. (C) 2001 Optical Society of America C1 NASA, Langley Res Ctr, Aerosp Elect Syst Div, Hampton, VA 23681 USA. Observ Paris, Lab Primaire Temps & Frequences, F-75014 Paris, France. RP Bahoura, M (reprint author), NASA, Langley Res Ctr, Aerosp Elect Syst Div, Hampton, VA 23681 USA. NR 14 TC 12 Z9 12 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD JUN 15 PY 2001 VL 26 IS 12 BP 926 EP 928 DI 10.1364/OL.26.000926 PG 3 WC Optics SC Optics GA 440QN UT WOS:000169185900022 PM 18040494 ER PT J AU Boykin, TB Bowen, RC Klimeck, G AF Boykin, TB Bowen, RC Klimeck, G TI Electromagnetic coupling and gauge invariance in the empirical tight-binding method SO PHYSICAL REVIEW B LA English DT Article ID RESONANT MAGNETOTUNNELING SPECTROSCOPY; QUANTUM-WELLS; MAGNETIC-FIELD; OPTICAL-PROPERTIES; TUNNELING DIODES; EFFECTIVE MASSES; SPIN-ORBIT; DISPERSION; ANISOTROPY; MODELS AB We examine the requirements placed upon the Hamiltonian under the demand of gauge invariance. From these requirements we derive the gauge-invariant form of the tight-binding Hamiltonian with electromagnetic coupling. In our derivation we do not make recourse to a Peierls substitution and hence avoid introducing any ambiguities of path. Our expression transparently reduces to the familiar expression in a complete basis. We apply this Hamiltonian to study resonant magnetotunneling spectroscopy using a simple tight-binding model. C1 Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. Univ Alabama, LICOS, Huntsville, AL 35899 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Boykin, TB (reprint author), Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. RI Klimeck, Gerhard/A-1414-2012 OI Klimeck, Gerhard/0000-0001-7128-773X NR 37 TC 68 Z9 68 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 JUN 15 PY 2001 VL 63 IS 24 AR 245314 DI 10.1103/PhysRevB.63.245314 PG 17 WC Physics, Condensed Matter SC Physics GA 446TX UT WOS:000169531200053 ER PT J AU Xie, SP Liu, WT Liu, QY Nonaka, M AF Xie, SP Liu, WT Liu, QY Nonaka, M TI Far-reaching effects of the Hawaiian islands on the Pacific Ocean-atmosphere system SO SCIENCE LA English DT Article ID NORTH PACIFIC; WAKE; MODEL; GCM AB Using satellite data, we detected a wind wake trailing westward behind the Hawaiian Islands for 3000 kilometers, a length many times greater than observed anywhere else on Earth, This wind wake drives an eastward ocean current that draws warm water from the Asian coast 8000 kilometers away, leaving marked changes in surface and subsurface ocean temperature. Standing in the path of the steady trade winds, Hawaii triggers an air-sea interaction that provides the feedback to sustain the influence of these small islands over a long stretch of the Pacific Ocean. C1 Univ Hawaii, Sch Ocean & Earth Sci & Technol, Int Pacific Res Ctr, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Ocean Univ Qingdao, Phys Oceanog Lab, Qingdao 266003, Peoples R China. Frontier Res Syst Global Change, Yokohama, Kanagawa 2360001, Japan. RP Xie, SP (reprint author), Univ Hawaii, Sch Ocean & Earth Sci & Technol, Int Pacific Res Ctr, 2525 Correa Rd, Honolulu, HI 96822 USA. EM de@soest.hawaii.edu RI Xie, Shang-Ping/C-1254-2009; Nonaka, Masami/G-3417-2014 OI Xie, Shang-Ping/0000-0002-3676-1325; NR 26 TC 149 Z9 159 U1 1 U2 15 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 JUN 15 PY 2001 VL 292 IS 5524 BP 2057 EP 2060 DI 10.1126/science.1059781 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 442KP UT WOS:000169284700041 PM 11408652 ER PT J AU Peebles, PJE Phelps, SD Shaya, EJ Tully, RB AF Peebles, PJE Phelps, SD Shaya, EJ Tully, RB TI Radial and transverse velocities of nearby galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; galaxies : distances and redshifts; large-scale structure of universe; Local Group ID DISTANCES; CLUSTER; ORBITS; SPACE; MASS; M81 AB Analysis of the peculiar velocities of the galaxies should take account of the uncertainties in both redshifts and distances. We show how this can be done by a numerical application of the action principle. The method is applied to an improved catalog of the galaxies and tight systems of galaxies within 4h(75)(-1) Mpc, supplemented with a coarser sample of the major concentrations at 4h(75)(-1) Mpc to 20h(75)(-1) Mpc distance. Inclusion of this outer zone improves the fit of the mass tracers in the inner zone to their measured redshifts and distances, yielding best fits with reduced chi (2) in redshift and distance in the range 1.5-2. These solutions are based on the assumption that the galaxies in and near the Local Group trace the mass, and a powerful test would be provided by observations of proper motions of the nearby galaxies. Predicted transverse galactocentric velocities of some of the nearby galaxies are confined to rather narrow ranges of values, and are on the order of 100 km s(-1), large enough to be detected and tested by the proposed SIM and GAIA satellite missions. C1 Princeton Univ, Joseph Henry Labs, Princeton, NJ 08544 USA. Raytheon ITSS, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Phys, College Pk, MD 20743 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. RP Peebles, PJE (reprint author), Princeton Univ, Joseph Henry Labs, Princeton, NJ 08544 USA. NR 23 TC 44 Z9 45 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 104 EP 113 DI 10.1086/321326 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800011 ER PT J AU Bregman, JD Temi, P AF Bregman, JD Temi, P TI Gas-phase polycyclic aromatic hydrocarbons in absorption toward protostellar sources? SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM : lines and bands; ISM : molecules; stars : individual (AFGL 989, AFGL 2591, Elias 29, S140) ID DIFFUSE INTERSTELLAR-MEDIUM; H2O ICE BANDS; INFRARED-SPECTROSCOPY; PAH MOLECULES; MONOCEROS R2/IRS-3; MICRON SPECTRA; DUST; EMISSION; EXTINCTION; CLOUDS AB One of the major criticisms of identifying the infrared emission bands with polycyclic aromatic hydrocarbon (PAH) molecules has been the lack of a match between laboratory spectra of individual PAHs and the emission features. Part of the difficulty arises from the complexity of modeling the emission mechanism with an a priori unknown mixture of ionized and neutral PAHs. A direct comparison between laboratory spectra of PAHs and astronomical sources is possible for absorption spectra. However, because of poor atmospheric transmission, ground-based spectra of the PAH absorption band in the C-H stretch region are too noisy to make a detailed comparison with laboratory spectra. In this paper we show that ISO Short Wavelength Spectrometer spectra of a few protostars that show a 3.25 mum absorption band can be well matched by laboratory absorption spectra of a mixture of isolated PAHs. C1 NASA, Ames Res Ctr, Astrophys Branch, Stanford, CA 94305 USA. SETI Inst, Mt View, CA 94043 USA. RP Bregman, JD (reprint author), NASA, Ames Res Ctr, Astrophys Branch, MS 245-6, Stanford, CA 94305 USA. NR 33 TC 23 Z9 23 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 126 EP 131 DI 10.1086/321347 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800013 ER PT J AU Kaspi, S Brandt, WN Netzer, H George, IM Chartas, G Behar, E Sambruna, RM Garmire, GP Nousek, JA AF Kaspi, S Brandt, WN Netzer, H George, IM Chartas, G Behar, E Sambruna, RM Garmire, GP Nousek, JA TI High-resolution X-ray spectroscopy and modeling of the absorbing and emitting outflow in NGC 3783 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 3783); galaxies : nuclei; galaxies : Seyfert; techniques : spectroscopic; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; SEYFERT-GALAXY NGC-3783; BROAD-LINE REGION; ABSORPTION LINES; ULTRAVIOLET; IRON; DISCOVERY; EMISSION; NGC-5548; SPECTRUM AB The high-resolution X-ray spectrum of NGC 3783 shows several dozen absorption lines and a few emission lines from the H-like and He-like ions of O, Ne, Mg, Si, and S, as well as from Fe XVII-Fe XXIII L-shell transitions. We have reanalyzed the Chandra HETGS spectrum using better flux and wavelength calibrations, along with more robust methods. Combining several lines from each element, we clearly demonstrate the existence of the absorption lines and determine that they are blueshifted relative to the systemic velocity by -610 +/- 130 km s(-1). We find the Ne absorption lines in the High-Energy Grating spectrum to be resolved with FWHM = 840(-360)(+490) km s(-1): no other lines are resolved. The emission lines are consistent with being at the systemic velocity. We have used regions in the spectrum where no lines are expected to determine the X-ray continuum, and we model the absorption and emission lines using photoionized-plasma calculations. The model consists of two absorption components, with different covering factors, which have an order-of-magnitude difference in their ionization parameters. The two components are spherically outflowing from the active galactic nucleus, and thus contribute to both the absorption and the emission via P Cygni profiles. The model also clearly requires O VII and O VIII absorption edges. The low-ionization component of our model can plausibly produce UV absorption lines with equivalent widths consistent with those observed from NGC 3783. However, we note that this result is highly sensitive to the unobservable UV to X-ray continuum, and the available UV and X-ray observations cannot firmly establish the relationship between the UV and X-ray absorbers. We find good agreement between the Chandra spectrum and simultaneous ASCA and RXTE observations. The 1 keV deficit previously found when modeling ASCA data probably arises from iron L-shell absorption lines not included in previous models. We also set an upper limit on the FWHM of the narrow Fe K alpha emission line of 3250 km s(-1). This is consistent with this line originating outside the broad-line region, possibly from a torus. C1 Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA. Tel Aviv Univ, Raymond & Beverly Sackler Fac Exact Sci, Sch Phys & Astron, IL-69978 Tel Aviv, Israel. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Astrophys, Baltimore, MD 21250 USA. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. George Mason Univ, Dept Phys & Astron, Fairfax, VA 22030 USA. George Mason Univ, Sch Computat Sci, Fairfax, VA 22030 USA. RP Kaspi, S (reprint author), Penn State Univ, Dept Astron & Astrophys, 525 Davey Lab, University Pk, PA 16802 USA. RI Brandt, William/N-2844-2015 OI Brandt, William/0000-0002-0167-2453 NR 54 TC 132 Z9 132 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 216 EP 232 DI 10.1086/321333 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800020 ER PT J AU Alcock, C Allsman, RA Alves, DR Axelrod, TS Becker, A Bennett, DP Clayton, GC Cook, KH Dalal, N Drake, AJ Freeman, KC Geha, M Gordon, KD Griest, K Kilkenny, D Lehner, MJ Marshall, SL Minniti, D Misselt, KA Nelson, CA Peterson, BA Popowski, P Pratt, MR Quinn, PJ Stubbs, CW Sutherland, W Tomaney, A Vandehei, T Welch, DL AF Alcock, C Allsman, RA Alves, DR Axelrod, TS Becker, A Bennett, DP Clayton, GC Cook, KH Dalal, N Drake, AJ Freeman, KC Geha, M Gordon, KD Griest, K Kilkenny, D Lehner, MJ Marshall, SL Minniti, D Misselt, KA Nelson, CA Peterson, BA Popowski, P Pratt, MR Quinn, PJ Stubbs, CW Sutherland, W Tomaney, A Vandehei, T Welch, DL CA MACHO Collaboration TI The MACHO project LMC variable star inventory. X. The R Coronae Borealis stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE Magellanic Clouds; stars : evolution; stars : variables : other ID LARGE-MAGELLANIC-CLOUD; DEFICIENT CARBON STARS; INFRARED OBSERVATIONS; SAKURAIS OBJECT; WHITE-DWARFS; RCB STARS; EVOLUTION; DUST; PHOTOMETRY; SUPERGIANTS AB We report the discovery of eight new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The discovery of these new stars increases the number of known RCB stars in the LMC to thirteen. We have also discovered four stars similar to the Galactic variable DY Per. These stars decline much more slowly and are cooler than the RCB stars. The absolute luminosities of the Galactic RCB stars are unknown since there is no direct measurement of the distance to any Galactic RCB star. Hence, the importance of the LMC RCB stars. We find a much larger range of absolute magnitudes (M-V = -2.5 to -5 mag) than inferred from the small pre-MACHO sample of LMC RCB stars. It is likely that there is a temperature-M, relationship with the cooler stars being intrinsically fainter. Cool (similar to 5000 K) RCB stars are much more common than previously thought based on the Galactic RCB star sample. Using the fairly complete sample of RCB stars discovered in the MACHO fields, we have estimated the likely number of RCB stars in the Galaxy to be similar to 3200. The SMC MACHO fields were also searched for RCB stars, but none were found. C1 Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Univ Calif Berkeley, Ctr Particle Astrophys, Berkeley, CA 94720 USA. Australian Natl Univ, Supercomp Facil, Canberra, ACT 0200, Australia. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Res Sch Astron & Astrophys, Weston Creek, ACT 2611, Australia. Univ Washington, Dept Astron, Seattle, WA 98195 USA. Univ Washington, Dept Phys, Seattle, WA 98195 USA. Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 USA. Louisiana State Univ, Dept Phys & Astron, Baton Rouge, LA 70803 USA. Univ Calif San Diego, Dept Phys, San Diego, CA 92093 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. S African Astron Observ, ZA-7935 Observatory, South Africa. Univ Sheffield, Dept Phys, Sheffield S3 7RH, S Yorkshire, England. Pontificia Univ Catolica Chile, Dept Astron, Santiago 22, Chile. NASA, Infrared Astrophys Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. European So Observ, D-85748 Garching, Germany. Univ Oxford, Dept Phys, Oxford OX1 3RH, England. McMaster Univ, Hamilton, ON L8S 4M1, Canada. RP Alcock, C (reprint author), Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. RI Stubbs, Christopher/C-2829-2012; Quinn, Peter/B-3638-2013 OI Stubbs, Christopher/0000-0003-0347-1724; NR 81 TC 65 Z9 65 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 298 EP 315 DI 10.1086/321369 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800028 ER PT J AU Franco, LM AF Franco, LM TI The effect of the mass accretion rate on the burst oscillations in 4U 1728-34 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (4U 1728-34); stars : neutron; X-rays : bursts ID X-RAY-BURSTS; QUASI-PERIODIC OSCILLATIONS; MILLISECOND OSCILLATIONS; COHERENT OSCILLATIONS; SAX J1808.4-3658; TIMING-EXPLORER; SHELL FLASHES; NEUTRON-STARS; KS 1731-260; BINARY AB We present a comprehensive study of the properties of nearly coherent brightness oscillations in a large sample of type I X-ray bursts observed from the low-mass X-ray binary 4U 1728-34. We have analyzed 547 ks of data of this source obtained with the Rossi X-Ray Timing Explorer over a 3 yr span from 1996 to 1999. The data contain 38 bursts, 16 of which show oscillations. We find no burst oscillations present when the inferred mass accretion rate of the system is lowest. Furthermore, we define a measure of the strength of the oscillations and find that this integrated strength increases with increasing mass accretion rate. This correlation is particularly evident within bursts detected only a few weeks apart and becomes less clear for bursts separated in time by several months to years. The correlation we find for 4U 1728-34 between the burst oscillations and the inferred accretion rate of the system is similar to that found for KS 1731-260 by Muno and coworkers, where the burst oscillations are only present at relatively high mass accretion rates. However, unlike the case for KS 1731-260, we find an anticorrelation in the bursts of 4U 1728-34 between the existence of episodes of photospheric radius expansion and the inferred mass accretion rate of the system. Moreover, we distinguish between burst oscillations present in the rise and in the decay phases of the burst and find that the bursts with oscillations only in the decay phase occur at intermediate accretion rates while those with oscillations in both the rise and the decay phases are concentrated at high inferred mass accretion rates. We discuss these results in the context of the theory of thermonuclear bursts and propose intrinsic differences in the neutron stars in KS 1731-260 and 4U 1728-34 as the origin of the different behaviors. C1 Univ Chicago, Chicago, IL 60637 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Univ Chicago, 5640 S Ellis Ave, Chicago, IL 60637 USA. EM lucia@oddjob.uchicago.edu NR 39 TC 18 Z9 18 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 JUN 10 PY 2001 VL 554 IS 1 BP 340 EP 351 DI 10.1086/321341 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800031 ER PT J AU Still, M O'Brien, K Horne, K Boroson, B Titarchuk, LG Engle, K Vrtilek, SD Quaintrell, H Fiedler, H AF Still, M O'Brien, K Horne, K Boroson, B Titarchuk, LG Engle, K Vrtilek, SD Quaintrell, H Fiedler, H TI Atmospheric reflection during an anomalous low state of Hercules X-l SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; binaries : eclipsing; pulsars : individual (Hercules X-1) radiative transfer; stars : neutron; X-rays : stars ID ABSORPTION CROSS-SECTIONS; ACTIVE GALACTIC NUCLEI; RAY-TIMING-EXPLORER; ACCRETION DISKS; SPECTRA; X-1; RADIATION; BINARIES; BEPPOSAX; LINES AB We present RXTE observations of the eclipsing X-ray binary Hercules X-l during an anomalous low state. Data reduction reveals a light curve over 2.7 orbital cycles remarkably similar to optical and UV light curves dominated by the companion star. Count rates are modulated close to the orbital period, attaining a maximum when the inner face of the companion star, irradiated by X-rays from the compact source, is most visible. Cold reflection provides an acceptable fit to the energy spectrum. Employing binary geometry to scale the model and assuming companion-star reflection, we are able to reconstruct the incident X-rays that are removed from our direct line of sight (presumably by the accretion disk). We find the flux of the hidden source to be identical to the observed flux of Her X-l at the peak of its main high state. Consequently, Her X-l is emitting a reflected spectrum, largely uncontaminated by direct X-rays in the anomalous low state. The spectral energy distribution, period, amplitude, and phasing of the modulation are all consistent with a companion-star origin. Since this source occurs in a well-understood binary environment, it provides an excellent case study for more sensitive experiments in the future. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Open Univ, Dept Phys, Milton Keynes MK7 6AA, Bucks, England. Univ Munich, Inst Astron & Astrophys, D-81679 Munich, Germany. RP Still, M (reprint author), Univ Space Res Assoc, Columbia, MD 21044 USA. NR 42 TC 12 Z9 12 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 352 EP 361 DI 10.1086/321337 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800032 ER PT J AU Robinson, RD Linsky, JL Woodgate, BE Timothy, JG AF Robinson, RD Linsky, JL Woodgate, BE Timothy, JG TI Far-ultraviolet observations of flares on the dMOe star AU Microscopii SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : activity; stars : flare; stars : late-type; ultraviolet : stars ID NONTHERMAL PROTON-BEAMS; RS-CANUM-VENATICORUM; YZ-CANIS-MINORIS; STELLAR FLARES; TRANSITION REGION; AD LEONIS; MICROFLARING ACTIVITY; IMPULSIVE PHASE; EMISSION; SOLAR AB We report on far-ultraviolet (FUV) observations of flares on the dMOe star AU Microscopii obtained on 1998 September 6 with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The data consist of medium-resolution echelle spectra covering the wavelength region from 1170 to 1730 Angstrom with a spectral resolution of lambda/Delta lambda = 45,800. The observations were obtained using the TIME-TAG observing mode in which the time and position of each detected photon is recorded. This allows a study of variability that is constrained only by counting statistics. During a total on-source time of 10,105 s, we observed numerous microflare bursts as well as four well-defined flare events. These flares lasted between 10 s and 3 minutes and were most easily detected in the FUV continuum and the Si Iv and C IV resonance lines. Variations in both the cooler (e.g., Ly alpha, C II, O I) and hotter (O V, N V, Fe XXI) emission lines were much less pronounced. We examined the physical characteristics of the flare events, including the time history of the wavelength-integrated fluxes in the continuum and the various emission lines. In particular, we searched for, but did not find, evidence for increased emission in the red wing of the Ly alpha line, which would indicate the presence of moderately energetic proton beams. We integrated the emission over the entire time of major flare activity to investigate the average line and continuum properties of the time-averaged spectrum, including flows and turbulence as a function of temperature. We also considered the shape of the FUV continuum, which may actually be caused by the enhancement of numerous weak emission lines. Unfortunately, none of the events were strong enough to allow a detailed examination of line profiles as a function of time. C1 Comp Sci Corp, Civil Grp, Cincinnati, OH 45202 USA. Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Nightsen Inc, Warwick, RI 02886 USA. RP Robinson, RD (reprint author), Comp Sci Corp, Civil Grp, Cincinnati, OH 45202 USA. RI Woodgate, Bruce/D-2970-2012 NR 34 TC 29 Z9 29 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 368 EP 382 DI 10.1086/321379 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800034 ER PT J AU Pravdo, SH Ghosh, P AF Pravdo, SH Ghosh, P TI An orbital light-curve model for GX 301-2 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (GX 301-2); stars : individual (GX 301-2); stars : neutron; X-rays : stars ID RAY PULSAR GX-301-2; ACCRETION DISKS; BINARY-SYSTEMS; NEUTRON-STARS; STELLAR WIND; BLACK-HOLES; ASCA AB We present the results of X-ray observations of CX 301-2 with instruments aboard the ASCA and RXTE spacecraft, as well as analysis of archival data from BATSE/CGRO and the All-Sky Monitor on RXTE. We discuss evidence that (1) GX 301-2 has changed its spin state, perhaps entering a stochastic spin state similar to 1974-1984; (2) epochal changes occur in the constant and flaring components of the orbital light curve-a 25% increase in the overall luminosity is coincident with the changed spin state and is due to an increase in the constant component accompanied by a decrease in the near-apastron flare; and (3) the orbital light curve, in general, and timing of the preperiastron flare, in particular, can be understood as a latency effect in the GX 301-2 accretion disk. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, Mail Stop 306-438, Pasadena, CA 91109 USA. EM spravdo@jpl.nasa.gov; pranab@tifr.res.in NR 30 TC 28 Z9 28 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 JUN 10 PY 2001 VL 554 IS 1 BP 383 EP 390 DI 10.1086/321350 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800035 ER PT J AU Qiu, J Ding, MD Wang, HM Gallagher, PT Sato, J Denker, C Goode, PR AF Qiu, J Ding, MD Wang, HM Gallagher, PT Sato, J Denker, C Goode, PR TI Asymmetric behavior of H alpha footpoint emission during the early phase of an impulsive flare SO ASTROPHYSICAL JOURNAL LA English DT Article DE sun : activity; sun : flares; sun : magnetic fields ID LOOP RADIATIVE HYDRODYNAMICS; SOLAR-FLARES; ELECTRIC CURRENTS; REGIONS AB We study the impulsive phase of a C9.0 solar flare using high temporal and spatial resolution H alpha images from Big Bear Solar Observatory (BBSO) in conjunction with high-cadence hard X-ray (HXR) observations from Yohkoh. During the early impulsive phase, HXR emission emerged from two kernels K1 and K2 which were connected by coronal loops observed in soft X-ray (SXR) images from Yohkoh. In H alpha, the initial rise was observed in one flare kernel K2, which was followed within 10 s by enhanced emission in the associated kernel K1. Such a significant asymmetry was not observed at HXR wavelengths. Our analysis shows that the asymmetric H alpha footpoint emission cannot be explained by the magnetic mirroring effect in which strong field footpoints show lower precipitation rates. Instead, we study this phenomenon by investigating the atmospheric response of the lower chromosphere to nonthermal beam heating. From numerical simulations, it is suggested that a cool atmosphere does not respond rapidly to beam impact, which may explain the missing H alpha emission at K1 during the early impulsive phase. At K2, the early-phase atmosphere may be preferentially heated resulting in the H alpha emission rapidly following the HXR emission. This is due to the fact that K2 is a compact source which received persistent energy deposition and consequent heating in a confined area during the early phase. K1, on the other hand, is a diffused source which therefore experienced a lower heating rate per unity area. We propose a scenario in which the flare loop consists of multiple magnetic "threads" connecting the compact footpoint K2 with the diffuse footpoint K1. C1 New Jersey Inst Technol, Big Bear Solar Observ, Big Bear City, CA 92314 USA. Nanjing Univ, Dept Astron, Nanjing 210093, Jiangsu, Peoples R China. NASA, Natl Res Council, Goddard Space Flight Ctr, Branch 682, Greenbelt, MD 20771 USA. RP Qiu, J (reprint author), New Jersey Inst Technol, Big Bear Solar Observ, 40386 N Shore Lane, Big Bear City, CA 92314 USA. RI Ding, Mingde/C-7787-2009; Gallagher, Peter/C-7717-2011 OI Gallagher, Peter/0000-0001-9745-0400 NR 19 TC 11 Z9 11 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 445 EP 450 DI 10.1086/321361 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800040 ER PT J AU Rilee, ML Doschek, GA AF Rilee, ML Doschek, GA TI Solar flare Doppler blueshifted soft X-ray emission and hard X-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE sun : flares; sun : X-rays, gamma rays ID BRAGG CRYSTAL SPECTROMETER; THERMAL NONTHERMAL MODEL; CA-XIX; YOHKOH; LOOP; HOT; ACCELERATION; MISSION AB Hard X-ray emission and the dynamics of soft X-ray emitting plasma are among the most immediate manifestations of solar flare energy release. To understand better the early impulsive phase of solar flare energy release, we have examined Ca XIX and Fe XXV soft X-ray resonance line spectra that exhibit strong blue-wing asymmetries from 32 flares. These spectra were obtained with the Bragg Crystal Spectrometer on the Japanese Yohkoh spacecraft, which is up to 10 times more sensitive than previously flown crystal spectrometers. The increased sensitivity allowed the comparison of Doppler blueshifted X-ray emission to hard X-ray emission observed with the Compton Gamma Ray Observatory's Burst and Transient Source Experiment, the Yohkoh Wide Band Spectrometer, and Yahkoh Hard X-Ray Telescope. We found that (I) hard X-ray burst light curves and resonance line blue-wing light curves are similar for most flares that exhibit strong blueshifts; (2) the time evolution of the intensity ratio of the blue wing to the peak unshifted spectral component resembles higher energy hard X-ray emission more closely than the blue-wing light curve alone; (3) though many flares had blue-wing/resonance peak ratios that resembled or peaked at the same time as the hard X-ray burst, nearly one-third of the flares exhibited ratio curves that either were nonzero before the detection of burst hard X-rays or peaked before the hard X-ray burst peaked-a few of these hares exhibited small blueshifted line profiles before the detection of hard X-ray emission; (4) a few flares with strong blueshifts had little or no detectable emission above 30 keV; and (5) the time derivative of the resonance peak emission usually resembles the blue-wing light curve. The implication of these results for current flare models is discussed. C1 NASA, Emergent IT, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. Cornell Univ, Ithaca, NY 14853 USA. RP Rilee, ML (reprint author), NASA, Emergent IT, Goddard Space Flight Ctr, Bldg 28-S207, Greenbelt, MD 20771 USA. NR 37 TC 0 Z9 0 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 464 EP 473 DI 10.1086/321384 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800042 ER PT J AU Linfield, RP Colavita, MM Lane, BF AF Linfield, RP Colavita, MM Lane, BF TI Atmospheric turbulence measurements with the Palomar Testbed Interferometer SO ASTROPHYSICAL JOURNAL LA English DT Article DE atmospheric effects; techniques : interferometric; turbulence ID OUTER SCALE; WILSON AB Data from the Palomar Testbed Interferometer, with a baseline length of 110 m and an observing wavelength of 2.2 mum, were used to derive information on atmospheric turbulence on 64 nights in 1999. The measured two-aperture variance coherence times at 2.2 mum ranged from 25 to 415 ms (the lower value was set by instrumental limitations-the interferometer could not operate when the coherence time was lower than this). On all nights, the spectrum of the short-timescale (less than 600 ms) delay fluctuations had a shallower spectrum than the theoretical Kolmogorov value of 5/3. On most nights, the mean value of the power-law slope was between 1.40 and 1.50. Such a sub-Kolmogorov slope will result in the seeing improving as the approximate to0.4 power of wavelength, rather than the slower 0.2 power predicted by Kolmogorov theory. On four nights, the combination of delay and angle-tracking measurements allowed a derivation of the (multiple) wind velocities of the turbulent layers, for a frozen-flow model. The derived wind velocities were all less than or equal to4 m s(-1), except for a small 10 m s(-1) component on one night. The combination of measured coherence time, turbulence spectral slope, and wind velocity for the turbulent layer(s) allowed a robust solution for the outer scale size (beyond which the fluctuations do not increase). On the four nights with angle-tracking data, the outer scale varied from 6 to 54 m, with most values in the 10-25 m range. Such small outer scale values cause some components of visibility and astrometric errors to average down rapidly. C1 CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Dept Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Linfield, RP (reprint author), CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. NR 16 TC 27 Z9 27 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP 505 EP 513 DI 10.1086/321372 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MV UT WOS:000169690800046 ER PT J AU Gorjian, V Turner, JL Beck, SC AF Gorjian, V Turner, JL Beck, SC TI Infrared emission from the radio supernebula in NGC 5253. A proto-globular cluster? SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : dwarf; galaxies : individual (NGC 5253); galaxies : starburst; galaxies : star clusters ID STARBURST GALAXY NGC-5253; STAR-FORMATION; SUPERNOVA-REMNANTS; ANTENNAE GALAXIES; HII-REGIONS; RESOLUTION; NGC-253; SPECTROSCOPY; NUCLEI; YOUNG AB Hidden from optical view in the starburst region of the dwarf galaxy NGC 5253 lies an intense radio source with an unusual spectrum, which could be interpreted variously as nebular gas ionized by a young stellar cluster or nonthermal emission from a radio supernova or an active galactic nucleus. We have obtained 11.7 and 18.7 mum images of this region at the Keck telescope and find that it is an extremely strong mid-infrared emitter. The infrared-to-radio flux ratio rules out a supernova and is consistent with an H II region excited by a dense cluster of young stars. This "supernebula" provides at least 15% of the total bolometric luminosity of the galaxy. Its excitation requires 10(5)-10(6) stars, giving it the total mass and size (1-2 pc diameter) of a globular cluster. However, its high obscuration, small size, and high gas density all argue that it is very young, no more than a few hundred thousand years old. This may be the youngest globular cluster yet observed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Tel Aviv Univ, Dept Phys & Astron, Ramat Aviv, Israel. Tel Aviv Univ, Wise Observ, Ramat Aviv, Israel. RP Gorjian, V (reprint author), CALTECH, Jet Prop Lab, MS 169-327,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 28 TC 57 Z9 57 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP L29 EP L32 DI 10.1086/320923 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MW UT WOS:000169690900007 ER PT J AU Hollis, JM Vogel, SN Snyder, LE Jewell, PR Lovas, FJ AF Hollis, JM Vogel, SN Snyder, LE Jewell, PR Lovas, FJ TI The spatial scale of glycolaldehyde in the galactic center SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : abundances; ISM : clouds; ISM : individual (Sagittarius B2); ISM : molecules; radio lines : ISM ID INTERSTELLAR AB We previously reported the spectral detection of the first interstellar sugar, which is known as glycolaldehyde (CH2OHCHO), by observing six separate millimeter-wave rotational transitions with the NRAO 12 m telescope while pointed toward the Sagittarius B2 North hot core source known as the Large Molecule Heimat (LMH) source. In the present BIMA array work, we have spatially mapped Sgr B2 using the 8(08)-7(17) transition of glycolaldehyde at 82.4 GHz. We find that glycolaldehyde has a spatial scale of greater than or equal to 60" unlike its isomers methyl formate and acetic acid, which are concentrated in the LMH source that has a spatial scale of less than or equal to5". We estimate that the relative abundance ratios of (acetic acid): (glycolaldehyde) :(methyl formate) are similar to1 :0.5:26 within the LMH source. It is likely that the conditions of the LMH source favor the chemically reactive nature of glycolaldehyde over its isomers and other large molecules such as dimethyl ether. The ensuing chemistry leads to glycolaldehyde destruction in the LMH source and glycolaldehyde survival outside of the LMH source in extended cloud extremities. This scenario is supported by comparison of line widths. which shows that glycol aldehyde possesses a factor of 2-3 greater line width than those of other complex molecules that are confined largely to the LMH source. C1 NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. Natl Radio Astron Observ, Green Bank, WV 24944 USA. RP Hollis, JM (reprint author), NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Code 930, Greenbelt, MD 20771 USA. NR 12 TC 79 Z9 79 U1 0 U2 13 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP L81 EP L85 DI 10.1086/320930 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MW UT WOS:000169690900020 ER PT J AU Smith, DM Heindl, WA Markwardt, CB Swank, JH AF Smith, DM Heindl, WA Markwardt, CB Swank, JH TI A transition to the soft state in GRS 1758-258 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; stars : individual (GRS 1758-258); X-rays : stars ID X-RAY SOURCE; CYGNUS X-1; SOURCE GRS-1758-258; INTERMEDIATE STATE; TIMING EXPLORER; GX-339-4; 1E-1740.7-2942; SPECTRUM; RXTE AB Near the end of 2001 February, the black hole candidate (BHC) GRS 1758-258 made an abrupt transition from a standard hard (low) state to a soft state. Unlike Cygnus X-1 and other BHCs, whose luminosity increases during this transition, GRS 1758-258 was dimmer after the transition. We present observations with the Proportional Counter Array on the Rossi X-Ray Timing Explorer and interpret the phenomenon in the context of a "dynamical" soft-state model. Using this model, we predicted that mass transfer from the companion had ceased and that the luminosity should decay on a timescale of a few weeks. The most recent data support this prediction, being consistent with a decay time of 28 days. The current state is consistent with the "off" state of GRS 1758-258 reported by SIGMA/Granat in 1991-1992. 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. RP Smith, DM (reprint author), Univ Calif Berkeley, Space Sci Lab, Centennial & Grizzly Peak Blvd, Berkeley, CA 94720 USA. RI Swank, Jean/F-2693-2012 NR 29 TC 51 Z9 51 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 2001 VL 554 IS 1 BP L41 EP L44 DI 10.1086/320928 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449MW UT WOS:000169690900010 ER PT J AU Lu, HI Robertson, FR AF Lu, HI Robertson, FR TI Retrieving the balanced winds on the globe as a generalized inverse problem SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE linear balance equation; vorticity budget equation; chi problem; tropical singularities; generalized inversion; pseudo inversion; minimum-length solution; constrained linear inversion; similarity transformation ID CHI-PROBLEM; BUDGET AB A generalized inverse technique is applied to retrieve two types of balanced winds that characterize the large-scale dynamics of the atmosphere: rotational winds based upon the linear balance equation and divergent winds based upon the vorticity budget equation. Both balance equations are singular at or near the equator. The balance equations are transformed in spherical harmonic function space to an underdetermined system, for which the scale-weighted, least-squares solution consists of a sum of principal and singular components. The principal components represent the response to the source function for the regular eigenmodes, while the singular components are determined by the projection of an independent measurement on the singular eigenmodes. The method was tested with the NCEP/NCAR reanalysis data in which a quasi-balance condition exists. A realistic balanced wind field is retrievable when the singular components are computed based upon the reanalyzed wind data. (C) 2001 Academic Press. C1 George C Marshall Space Flight Ctr, Huntsville, AL USA. Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Lu, HI (reprint author), Global Hydrol & Climate Ctr, 320 Sparkman Dr, Huntsville, AL 35805 USA. NR 23 TC 0 Z9 0 U1 0 U2 0 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 JUN 10 PY 2001 VL 170 IS 1 BP 299 EP 319 DI 10.1006/jcph.2001.6738 PG 21 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 453YT UT WOS:000169946300013 ER PT J AU Miller, RS Harstad, KG Bellan, J AF Miller, RS Harstad, KG Bellan, J TI Direct numerical simulations of supercritical fluid mixing layers applied to heptane-nitrogen SO JOURNAL OF FLUID MECHANICS LA English DT Article ID SHEAR-LAYER; ENTRAINMENT; STABILITY; MIXTURES; FLOWS AB Direct numerical simulations (DNS) are conducted of a model hydrocarbon-nitrogen mixing layer under supercritical conditions. The temporally developing mixing layer configuration is studied using heptane and nitrogen supercritical fluid streams at a pressure of 60 atm as a model system related to practical hydrocarbon-fuel/air systems. An entirely self-consistent cubic Peng-Robinson equation of state is used to describe all thermodynamic mixture variables, including the pressure, internal energy, enthalpy, heat capacity, and speed of sound along with additional terms associated with the generalized heat and mass transport vectors. The Peng-Robinson formulation is based on pure-species reference states accurate to better than 1% relative error through comparisons with highly accurate state equations over the range of variables used in this study (600 less than or equal to T less than or equal to 1100 K, 40 less than or equal to p less than or equal to 80 atm) and is augmented by an accurate curve fit to the internal energy so as not to require iterative solutions. The DNS results of two-dimensional and three-dimensional layers elucidate the unique thermodynamic and mixing features associated with supercritical conditions. Departures from the perfect gas and ideal mixture conditions are quantified by the compression factor and by the mass diffusion factor, both of which show reductions from the unity value. It is found that the qualitative aspects of the mixing layer may be different according to the specification of the thermal diffusion factors whose value is generally unknown, and the reason for this difference is identified by examining the second-order statistics: the constant Bearman-Kirkwood (BK) thermal diffusion factor excites fluctuations that the constant Irwing-Kirkwood (IK) one does not, and thus enhances overall mixing. Combined with the effect of the mass diffusion factor, constant positive large BK thermal diffusion factors retard diffusional mixing, whereas constant moderate IK factors tend to promote diffusional mixing. Constant positive BK thermal diffusion factors also tend to maintain density gradients, with resulting greater shear and vorticity. These conclusions about IK and BK thermal diffusion factors are species-pair dependent, and therefore are not necessarily universal. Increasing the temperature of the lower stream to approach that of the higher stream results in increased layer growth as measured by the momentum thickness. The three-dimensional mixing layer exhibits slow formation of turbulent small scales, and transition to turbulence does not occur even for a relatively long non-dimensional time when compared to a previous, atmospheric conditions study. The primary reason for this delay is the initial density stratification of the how, while the formation of strong density gradient regions both in the braid and between-the-braid planes may constitute a secondary reason for the hindering of transition through damping of emerging turbulent eddies. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bellan, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 38 TC 62 Z9 63 U1 1 U2 10 PU CAMBRIDGE UNIV PRESS PI PORT CHESTER PA 110 MIDLAND AVE, PORT CHESTER, NY 10573-9863 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD JUN 10 PY 2001 VL 436 BP 1 EP 39 PG 39 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 445CT UT WOS:000169441100001 ER PT J AU Cohen, SC Freymueller, JT AF Cohen, SC Freymueller, JT TI Crustal uplift in the south central Alaska subduction zone: New analysis and interpretation of tide gauge observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID WILLIAM-SOUND EARTHQUAKE; KENAI PENINSULA; ADJACENT REGIONS; TENSILE FAULTS; HALF-SPACE; DEFORMATION; TIME; PLATE; MOTIONS; SHEAR AB We have examined tide gauge measurements of apparent sea level height in south central Alaska to determine the history of crustal uplift subsequent to the 1964 Prince William Sound earthquake. There are spatial and temporal variations in the uplift rate since the 1994 earthquake that depend on the location of the tide gauge relative to the coseismic rupture features. At Seward, on the eastern side of the Kenai Peninsula, we find slow uplift that is consistent with elastic strain accumulation at the locked North American-Pacific Plate boundary. Conversely, at Seldovia and Nikiski, on the western side of the Kenai Peninsula, we find persistent rapid uplift of similar to 10 mm yr(-1) that may be longterm transient response to the earthquake but that cannot be sustained over the entire several hundred year recurrence interval for a great earthquake. Farther to the southwest, at Kodiak, the rate of uplift is several millimeters per year but has slowed significantly over the past three and a half decades. To the east of the Kenai Peninsula we find subsidence at Cordova and an uncertain behavior at Valdez. AT Cordova, and to a lesser extent Valdez, there is a mathematically significant time dependence, although the evidence for the time dependence is less compelling than at Kodiak. At Anchorage, there is little evidence of vertical motion since the earthquake. The along-strike spatial variability in the relaxation time of the rates of vertical motion since the 1964 earthquake may be related to variations in the updip coseismic slip during the megathrust event. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. RP Cohen, SC (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. EM scohen@carnoustie.gsfc.nasa.gov; jeff@giseis.alaska.edu NR 28 TC 15 Z9 15 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 JUN 10 PY 2001 VL 106 IS B6 BP 11259 EP 11270 DI 10.1029/2000JB900419 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 440DG UT WOS:000169160200021 ER PT J AU Johnson, TJ Wilson, CR Chao, BF AF Johnson, TJ Wilson, CR Chao, BF TI Nontidal oceanic contributions to gravitational field changes: Predictions of the Parallel Ocean Climate Model SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID ATMOSPHERIC MASS REDISTRIBUTION; SEA-LEVEL VARIATIONS; GLOBAL OCEAN; SEASONAL-VARIATIONS; GEOCENTER VARIATIONS; EARTHS ROTATION; LAGEOS; WATER; CIRCULATION; EXCITATION AB This study examines the nontidal contributions of the oceans to the Earth's gravitational field variations as predicted by a global ocean general circulation model: the Parallel Ocean Climate Model. Such variations in the gravitational field Stokes coefficient are determined up to spherical harmonic degree and order 20 and compared with satellite laser ranging (SLR) data from LAGEOS I and LAGEOS II. For most Stokes coefficients except the lowest-degree ones, this investigation indicates that the application of sea level adjustment to reduce the effects of the model's lack of mass conservation due to the Boussinesq approximation has a negligible effect on timescales less than a few years. Predicted gravitational changes show strong seasonal variability and account for a portion of the variations estimated from SLR. We conclude that, in addition to the atmosphere, the oceans are an important contributor to the temporal variations in the Earth's gravitational field. The Stokes coefficients are useful in examining oceanic mass transport between hemispheres and ocean basins. The estimated oceanic power spectrum has a spectral shape similar to the atmosphere and is well above the noise level of planned satellite missions like the Gravity Recovery and Climate Experiment (GRACE). C1 USN Observ, Earth Orientat Dept, Washington, DC 20392 USA. NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. Univ Texas, Dept Geol Sci, Floor Fac 2, Austin, TX 78723 USA. Univ Texas, Inst Geophys, Austin, TX 78723 USA. Univ Texas, Space Res Ctr, Austin, TX 78723 USA. RP Johnson, TJ (reprint author), USN Observ, Earth Orientat Dept, Washington, DC 20392 USA. EM johnson.thomas@usno.navy.mil RI Chao, Benjamin Fong/N-6156-2013 NR 48 TC 11 Z9 12 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 JUN 10 PY 2001 VL 106 IS B6 BP 11315 EP 11334 DI 10.1029/2000JB900438 PG 20 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 440DG UT WOS:000169160200024 ER PT J AU Newman, JA Ferrarese, L Stetson, PB Maoz, E Zepf, SE Davis, M Freedman, WL Madore, BF AF Newman, JA Ferrarese, L Stetson, PB Maoz, E Zepf, SE Davis, M Freedman, WL Madore, BF TI A revised Cepheid distance to NGC 4258 and a test of the distance scale SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; cosmological parameters; distance scale; galaxies : individual (NGC 4258) ID HUBBLE-SPACE-TELESCOPE; LARGE-MAGELLANIC-CLOUD; KEY PROJECT; GALAXY NGC4258; METALLICITY; PHOTOMETRY; DISCOVERY; WFPC2; CALIBRATION; PROGRAM AB In a previous paper we reported a Hubble Space Telescope (HST) Cepheid distance to the galaxy NGC 4258 obtained using the calibrations and methods then standard for the Key Project. Here we reevaluate the Cepheid distance using the recently revised Key Project procedures. These revisions alter the zero points and slopes of the Cepheid period-luminosity (P-L) relations derived at the Large Magellanic Cloud (LMC), the calibration of the HST WFPC2 camera, and the treatment of metallicity differences. We also provide herein full information on the Cepheids described in the previous paper. Using the refined Key Project techniques and calibrations, we determine the distance modulus of NGC 4258 to be 29.47 +/- 0.09 (unique to this determination) +/-0.15 mag (systematic uncertainties in Key Project distances), corresponding to a metric distance of 7.8 +/- 0.3 +/- 0.5 Mpc and 1.2 sigma from the maser distance of 7.2 +/- 0.5 Mpc. Additionally, we place weak limits upon the distance to the LMC and upon the effect of metallicity in Cepheid distance determinations. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Rutgers State Univ, Piscataway, NJ 08854 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Yale Univ, Dept Astron, New Haven, CT 06520 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. CALTECH, Jet Prop Lab, Infrared Proc & Anal Ctr, NASA IPAC Extragalact Database, Pasadena, CA 91125 USA. RP Newman, JA (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. NR 37 TC 44 Z9 44 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 562 EP 574 DI 10.1086/320969 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100008 ER PT J AU Rodgers, SD Charnley, SB AF Rodgers, SD Charnley, SB TI Gas-phase production of NHD2 in L134N SO ASTROPHYSICAL JOURNAL LA English DT Article DE astrochemistry; ISM : individual (L134N); molecular processes ID DENSE INTERSTELLAR CLOUDS; HOT MOLECULAR CORES; DISSOCIATIVE RECOMBINATION; DEUTERIUM FRACTIONATION; DARK CLOUDS; SURFACE-CHEMISTRY; FORMALDEHYDE; AMMONIA; H2D+; ION AB We show analytically that large abundances of NH2D and NHD2 can be produced by gas-phase chemistry in the interiors of cold dense clouds. The calculated fractionation ratios are in good agreement with the values that have been previously determined in L134N and suggest that triply deuterated ammonia could be detectable in dark clouds. Grain-surface reactions may lead to similar NH2D and NHD2 enhancements but, we argue, are unlikely to contribute to the deuteration observed in L134N. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Rodgers, SD (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. RI Charnley, Steven/C-9538-2012 NR 47 TC 52 Z9 52 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 613 EP 617 DI 10.1086/320987 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100013 ER PT J AU Hartman, RC Bottcher, M Aldering, G Aller, H Aller, M Backman, DE Balonek, TJ Bertsch, DL Bloom, SD Bock, H Boltwood, P Carini, MT Collmar, W De Francesco, G Ferrara, EC Freudling, W Gear, WK Hall, PB Heidt, J Hughes, P Hunter, SD Jogee, S Johnson, WN Kanbach, G Katajainen, S Kidger, M Kii, T Koskimies, M Kraus, A Kubo, H Kurtanidze, O Lanteri, L Lawson, A Lin, YC Lisenfeld, U Madejski, G Makino, F Maraschi, L Marscher, AP McFarland, JP McHardy, I Miller, HR Nikolashvili, M Nilsson, K Noble, JC Nucciarelli, G Ostorero, L Pian, E Pursimo, T Raiteri, CM Reich, W Rekola, R Richter, GM Robson, EI Sadun, A Savolainen, T Sillanpaa, A Smale, A Sobrito, G Sreekumar, P Stevens, JA Takalo, LO Tavecchio, F Terasranta, H Thompson, DJ Tornikoski, M Tosti, G Ungerechts, H Urry, CM Valtaoja, E Villata, M Wagner, SJ Wehrle, AE Wilson, JW AF Hartman, RC Bottcher, M Aldering, G Aller, H Aller, M Backman, DE Balonek, TJ Bertsch, DL Bloom, SD Bock, H Boltwood, P Carini, MT Collmar, W De Francesco, G Ferrara, EC Freudling, W Gear, WK Hall, PB Heidt, J Hughes, P Hunter, SD Jogee, S Johnson, WN Kanbach, G Katajainen, S Kidger, M Kii, T Koskimies, M Kraus, A Kubo, H Kurtanidze, O Lanteri, L Lawson, A Lin, YC Lisenfeld, U Madejski, G Makino, F Maraschi, L Marscher, AP McFarland, JP McHardy, I Miller, HR Nikolashvili, M Nilsson, K Noble, JC Nucciarelli, G Ostorero, L Pian, E Pursimo, T Raiteri, CM Reich, W Rekola, R Richter, GM Robson, EI Sadun, A Savolainen, T Sillanpaa, A Smale, A Sobrito, G Sreekumar, P Stevens, JA Takalo, LO Tavecchio, F Terasranta, H Thompson, DJ Tornikoski, M Tosti, G Ungerechts, H Urry, CM Valtaoja, E Villata, M Wagner, SJ Wehrle, AE Wilson, JW TI Multiepoch multiwavelength spectra and models for blazar 3C 279 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; quasars : individual (3C 279) ID EXTRAGALACTIC RADIO-SOURCES; RAY ASTRONOMY SATELLITE; MILLIMETER CONTINUUM MEASUREMENTS; ENERGY CONCENTRATOR SPECTROMETER; ACTIVE GALACTIC NUCLEI; BL LACERTAE OBJECTS; 3C 279; GAMMA-RAYS; QUASAR 3C-279; INSTRUMENT DESCRIPTION AB Of the blazars detected by EGRET in GeV gamma -rays, 3C 279 is not only the best observed by EGRET but also one of the best monitored at lower frequencies. We have assembled 11 spectra, from GHz radio through GeV gamma -rays, from the time intervals of EGRET observations. Although some of the data have appeared in previous publications, most are new, including data taken during the high states in early 1999 and early 2000. All of the spectra show substantial gamma -ray contribution to the total luminosity of the object; in a high state, the gamma -ray luminosity dominates over that at all other frequencies by a factor of more than 10. There is no clear pattern of time correlation; different bands do not always rise and fall together, even in the optical, X-ray, and gamma -ray bands. The spectra are modeled using a leptonic jet, with combined synchrotron self-Compton plus external Compton gamma -ray production. Spectral variability of 3C 279 is consistent with variations of the bulk Lorentz factor of the jet, accompanied by changes in the spectral shape of the electron distribution. Our modeling results are consistent with the UV spectrum of 3C 279 being dominated by accretion disk radiation during times of low gamma -ray intensity. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. Franklin & Marshall Coll, Dept Phys & Astron, Lancaster, PA 17604 USA. Colgate Univ, Dept Phys & Astron, Hamilton, NY 13346 USA. Hampden Sydney Coll, Hampden Sydney, VA 23943 USA. Landessternwarte Konigstuhl, D-69117 Heidelberg, Germany. Western Kentucky Univ, Dept Phys & Astron, Bowling Green, KY 42104 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Osserv Astron Torino, I-10025 Pino Torinese, Italy. Georgia State Univ, Dept Phys & Astron, Atlanta, GA 30303 USA. European So Observ, D-85748 Munich, Germany. Space Telescope European Coordinating Facil, D-85748 Munich, Germany. Cardiff Univ, Dept Phys & Astron, Cardiff CF2 3YB, S Glam, Wales. Pontificia Univ Catolica Chile, Fac Fis, Dept Astron & Astrofis, Santiago 22, Chile. Princeton Univ Observ, Princeton, NJ 08544 USA. CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. USN, Res Lab, Washington, DC 20375 USA. Tuorla Observ, FIN-21500 Piikkio, Finland. Inst Astrofis Canarias, E-38200 San Cristobal la Laguna, Tenerife, Spain. Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. Max Planck Inst Radioastron, D-53121 Bonn, Germany. Kyoto Univ, Fac Sci, Dept Phys, Kyoto 6068502, Japan. Astrophys Inst Potsdam, D-14482 Potsdam, Germany. Univ Southampton, Dept Phys & Astron, Southampton SO17 1BJ, Hants, England. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Inst Radioastron Millimetr, E-18012 Granada, Spain. Stanford Linear Accelerator Ctr, GLAST Grp, Menlo Pk, CA 94025 USA. Osserv Astron Brera, I-20121 Milan, Italy. Boston Univ, Inst Astrophys Res, Boston, MA 02215 USA. Abastumani Observ, GE-383762 Abastumani, Rep of Georgia. Osservatorio Astron Perugia, I-06123 Perugia, Italy. Astron Observ Trieste, I-34131 Trieste, Italy. Joint Astron Ctr, Hilo, HI 96720 USA. Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. Univ Colorado, Dept Phys, Denver, CO 80217 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Indian Space Res Org, Satellite Ctr, Control & Mission Area, Bangalore 560017, Karnataka, India. UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. Aalto Univ, Metsahovi Radio Observ, Kylmala 02540, Finland. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Turku, Dept Phys, SF-20500 Turku, Finland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. EM rch@egret.gsfc.nasa.gov RI Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; Tosti, Gino/E-9976-2013; Urry, Claudia/G-7381-2011; Johnson, Neil/G-3309-2014; Kurtanidze, Omar/J-6237-2014; Lisenfeld, Ute/A-1637-2015; OI Thompson, David/0000-0001-5217-9135; Urry, Claudia/0000-0002-0745-9792; Lisenfeld, Ute/0000-0002-9471-5423; Ostorero, Luisa/0000-0003-3983-5980 NR 79 TC 112 Z9 114 U1 0 U2 4 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 JUN 8 PY 2001 VL 553 IS 2 BP 683 EP 694 DI 10.1086/320970 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100019 ER PT J AU Still, M O'Brien, K Horne, K Hudson, D Boroson, B Vrtilek, SD Quaintrell, H Fiedler, H AF Still, M O'Brien, K Horne, K Hudson, D Boroson, B Vrtilek, SD Quaintrell, H Fiedler, H TI RXTE observations of Hercules X-1 during the 1998 July short high state SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; binaries : eclipsing; stars : individual (Hercules X-1); stars : neutron; X-rays : stars ID RAY-TIMING-EXPLORER; ALL-SKY MONITOR; NEUTRON-STAR; PRE-ECLIPSE; ACCRETION; DIPS; MASS; BEPPOSAX; UHURU; DISCS AB We present RXTE monitoring of the eclipsing X-ray binary Hercules X-1 conducted over the short high state of 1998 July. This was one of the last major short high states before the source entered an anomalous low state of activity. A comparison with previous epochs Dnds no evidence for special behavior during these observations. We determine orbital and pulsar spin periods to facilitate measurements of (P)over dot(spin) and (P)over dot(orb) during the subsequent anomalous low state and the next epoch of high-state activity. Spectrally, the decay of the short high state and concurrent pre-eclipse dips are consistent with obscuration of a central X-ray source by a cloud of nonuniform column density. The standard model of a warped accretion disk of finite vertical scale height fits the characteristics of this absorber well. Pre-eclipse dips have durations a factor of a few longer than the characteristic durations of dips during main high states. Pulse profile structure increases in complexity toward the tail of the short high state, suggesting changes in accretion curtain geometry. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland. Univ Texas, Dept Astron, Austin, TX 78712 USA. Harvard Smithsonian Ctr Astrophys, High Energy Astrophys Div, Cambridge, MA 02138 USA. Open Univ, Dept Phys & Astron, Milton Keynes MK7 6AA, Bucks, England. Univ Munich, Inst Astron & Astrophys, D-81679 Munich, Germany. RP Still, M (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 42 TC 11 Z9 12 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 776 EP 787 DI 10.1086/320951 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100027 ER PT J AU Seward, FD Butt, YM Karovska, M Prestwich, A Schlegel, EM Corcoran, M AF Seward, FD Butt, YM Karovska, M Prestwich, A Schlegel, EM Corcoran, M TI Early Chandra X-ray observations of eta Carinae SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : early-type; stars : individual (eta Carinae); X-rays : stars ID VARIABLES; SPECTRUM AB Subarcsecond-resolution Chandra observations of eta Carinae reveal a 40" x 70" ring or partial shell of X-ray emission surrounding an unresolved bright central source. The spectrum of the central source is strongly absorbed and can be fitted with a high-temperature thermal continuum and emission lines. The surrounding shell is well outside the optical/infrared bipolar nebula and is coincident with the outer shell of eta Car. The X-ray spectrum of the shell is much softer than that of the central source. The X-ray shell is irregular and only correlates well with optical features in which a bright X-ray knot coincides with a bright feature of the outer shell. Implications for the binary model of the central source are discussed. C1 Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Seward, FD (reprint author), Smithsonian Astrophys Observ, 60 Garden St, Cambridge, MA 02138 USA. NR 25 TC 36 Z9 36 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 832 EP 836 DI 10.1086/320961 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100034 ER PT J AU Hillier, DJ Davidson, K Ishibashi, K Gull, T AF Hillier, DJ Davidson, K Ishibashi, K Gull, T TI On the nature of the central source in eta Carinae SO ASTROPHYSICAL JOURNAL LA English DT Review ID WOLF-RAYET STARS; PHOTOIONIZATION CROSS-SECTIONS; LUMINOUS BLUE VARIABLES; HUBBLE-SPACE-TELESCOPE; ATOMIC DATA; OPACITY CALCULATIONS; IRON-PROJECT; ISOELECTRONIC SEQUENCE; OSCILLATOR-STRENGTHS; MASSIVE STARS AB Long-slit spectroscopic observations of eta Carinae and its Homunculus have recently been obtained using STIS on the Hubble Space Telescope (HST). We have extracted the spectrum of the central source using a 0.1" x 0.13 aperture. As expected, the spectrum is very different from ground-based spectra obtained under normal seeing conditions (i.e., 1")-the HST observed spectrum exhibits primarily broad permitted emission lines (v(FWHM) approximate to 500 km s(-1)), while ground-based spectra show strong narrow (v(FWHM) approximate to 40 km s(-1)) permitted and forbidden lines (primarily [Fe II], Fe II, and H I) superimposed on a broad emission-line spectrum. In the optical, the spectrum shows strong H I, He I, and Fe II emission lines, many exhibiting P Cygni absorption components. Emission features due to N I, Si II, Na I, Mg II, Ca II, and Al II can also be identified. Only a few weak broad lines of [Fe II] are seen. The spectrum is qualitatively similar to a much less luminous object, the extreme P Cygni star HDE 316285. We have performed a detailed analysis of the spectrum using the non-LTE line blanketed wind code of Hillier & Miller. Despite the complexity of eta Carinae, we are able to obtain a good fit to the optical emission line spectrum using a model with a mass-loss rate of 10(-3) M-. yr(-1). The weakness of the electron-scattering wings indicates that the wind is clumped, with a volume filling factor of approximately 0.1. Because of the parameter range and the extremely dense wind associated with the central star, our best-fit model is not unique. As is the case for HDE 316285, there is a strong coupling between the derived mass-loss rate and the derived N(H)/N(He) abundance ratio. In addition, the wind is so dense that the star's surface cannot be observed. Consequently, the effective temperature of the underlying star is not well determined. Because of the rich emission-line spectrum we are able to place limits on many abundances: Mass fractions of species such as Fe and Mg (and perhaps Ca, Si, and Al) are solar to within a factor of 2. In accord with standard evolutionary scenarios, Na is slightly enhanced, the N mass fraction is at least a factor of 10 over solar, while C and O show substantial depletions. The adopted luminosity of 5 x 10(6) L-. is based on the observed IR flux and an assumed distance of 2.3 kpc. Thus, based on the Eddington limit, the minimum mass of the system is approximately 120 (L/5 x 10(6) L-.) M-. [for N(H)/ N(He) = 5]. While eta Carinae may be a binary, recent evidence suggests that the purported secondary star has a mass less than 30 M-.. Thus the primary star is currently more massive than 90 M-., and the initial mass of the star should conservatively have been in excess of 150 (L/5 x 10(6)) M-.. C1 Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. Univ Minnesota, Dept Phys & Astron, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, Lab Astron & Space Phys, Greenbelt, MD 20771 USA. RP Hillier, DJ (reprint author), Univ Pittsburgh, Dept Phys & Astron, 3941 OHara St, Pittsburgh, PA 15260 USA. RI Gull, Theodore/D-2753-2012 OI Gull, Theodore/0000-0002-6851-5380 NR 114 TC 207 Z9 207 U1 0 U2 6 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 837 EP 860 DI 10.1086/320948 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100035 ER PT J AU Akmal, A Raymond, JC Vourlidas, A Thompson, B Ciaravella, A Ko, YK Uzzo, M Wu, R AF Akmal, A Raymond, JC Vourlidas, A Thompson, B Ciaravella, A Ko, YK Uzzo, M Wu, R TI SOHO observations of a coronal mass ejection SO ASTROPHYSICAL JOURNAL LA English DT Article DE solar wind; Sun : activity; Sun : Corona; Sun : coronal mass ejections (CMEs) ID BE-LIKE IONS; COLLISION STRENGTHS; SOLAR; SPECTROMETER; PROMINENCE; EMISSION; ANGSTROM; LASCO; SUN AB We describe a coronal mass ejection (CME) observed on 1999 April 23 by the Ultraviolet Coronagraph Spectrometer (UVCS), the Extreme-Ultraviolet Imaging Telescope (EIT), and the Large-Angle and Spectrometric Coronagraphs (LASCO) aboard the Solar and Heliospheric Observatory (SOHO). In addition to the O VI and C III lines typical of UVCS spectra of CMEs, this 480 km s(-1) CME exhibits the forbidden and intercombination lines of O V at lambda lambda 1213.8 and 1218.4. The relative intensities of the O V lines represent an accurate electron density diagnostic not generally available at 3.5 R-.. By combining the density with the column density derived from LASCO, we obtain the emission measure of the ejected gas. With the help of models of the temperature and time-dependent ionization state of the expanding gas, we determine a range of heating rates required to account for the UV emission lines. The total thermal energy deposited as the gas travels to 3.5 R-. is comparable to the kinetic and gravitational potential energies. We note a core of colder material radiating in C III, surrounded by hotter material radiating in the O V and O VI lines. This concentration of the coolest material into small regions may be a common feature of CMEs. This event thus represents a unique opportunity to describe the morphology of a CME, and to characterize its plasma parameters. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. USN, Res Lab, Washington, DC 20375 USA. George Mason Univ, Inst Computat Sci, Ctr Earth Observing & Space Res, Fairfax, VA 22030 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Akmal, A (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. RI Vourlidas, Angelos/C-8231-2009; Thompson, Barbara/C-9429-2012 OI Vourlidas, Angelos/0000-0002-8164-5948; NR 34 TC 63 Z9 66 U1 1 U2 7 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 922 EP 934 DI 10.1086/320971 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100040 ER PT J AU Ofman, L Davila, JM AF Ofman, L Davila, JM TI Three-fluid 2.5-dimensional magnetohydrodynamic model of the effective temperature in coronal holes SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun : corona; Sun : magnetic fields; waves ID SOLAR-WIND ACCELERATION; SOLITARY WAVES; CHARGE STATES; MINOR IONS; HELIUM AB Recent SOHO Ultraviolet Coronagraph Spectrometer (UVCS) observations show that protons and minor ions are hot (T-p > 10(6) K, T-i > 10(7) K) and anisotropic in coronal holes. A possible cause of the large perpendicular motions is unresolved fluctuations in the solar wind. Using the three-fluid Alfvenic 2.5-dimensional MHD model, we have shown that the unresolved fluctuations lead to apparent Alfvenic proton temperature and anisotropy consistent with UVCS observations. However, waves with Alfven realistic amplitudes cannot reproduce the O5+ perpendicular temperature and anisotropy deduced from UVCS observations. This suggests that the minor ions are heated by a different mechanism than protons. C1 Raytheon ITSS, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ofman, L (reprint author), Raytheon ITSS, Code 682, Greenbelt, MD 20771 USA. NR 31 TC 21 Z9 21 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 935 EP 940 DI 10.1086/320960 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100041 ER PT J AU Jones, DL Wehrle, AE Piner, BG Meier, DL AF Jones, DL Wehrle, AE Piner, BG Meier, DL TI In the shadow of the accretion disk: Higher resolution imaging of the central parsec in NGC 4261 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies : active; galaxies : individual (NGC 4261, 3C 270); galaxies : jets; galaxies : nuclei; radio continuum : galaxies ID SPACE-TELESCOPE IMAGES; RADIO GALAXIES; BLACK-HOLE; NGC-4261; JETS; SPECTRA; CATALOG; FLOW AB The physical conditions in the inner parsec of accretion disks believed to orbit the central black holes in active galactic nuclei can be probed by imaging the absorption (by ionized gas in the disk) of background emission from a radio counterjet. We report high angular resolution VLBI observations of the nearby (similar to 40 Mpc) radio galaxy NGC 4261 that confirm free-free absorption of radio emission from a counterjet by a geometrically thin, nearly edge-on disk at 1.6, 4.8, and 8.4 GHz. The angular width and depth of the absorption appears to increase with decreasing frequency, as expected. We derive an average electron density of similar to 10(4) cm(-3) at a disk radius of about 0.2 pc, assuming that the inner disk inclination and opening angles are the same as at larger radii. Pressure balance between the thermal gas and the magnetic field in the disk implies an average field strength of 10(-4) G at a radius of 0.2 pc. These are the closest in free-free absorption measurements to date of the conditions in an extragalactic accretion disk orbiting a black hole with a well-determined mass. If a standard advection-dominated accretion flow exists in the disk center, then the transition between thin and thick disk regions must occur at a radius less than 0.2 pc (4000 Schwarzschild radii). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Whittier Coll, Dept Phys & Astron, Whittier, CA 90608 USA. RP Jones, DL (reprint author), CALTECH, Jet Prop Lab, Mail Code 238-332,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 21 TC 28 Z9 28 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 968 EP 977 DI 10.1086/320979 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100046 ER PT J AU Wiedner, MC Hills, RE Carlstrom, JE Lay, OP AF Wiedner, MC Hills, RE Carlstrom, JE Lay, OP TI Interferometric phase correction using 183 GHz water vapor monitors SO ASTROPHYSICAL JOURNAL LA English DT Article DE atmospheric effects; instrumentation : adaptive optics; site testing; techniques : interferometric ID PATH-LENGTH; RADIOMETRY; FLUCTUATIONS; ARRAY AB The angular resolution that can be obtained by ground-based aperture synthesis telescopes at millimeter and submillimeter wavelengths is limited by phase fluctuations caused by water vapor in the Earth's atmosphere. We describe here the successful correction of such fluctuations during observations at 0.85 mm wavelength with an interferometer consisting of the James Clark Maxwell Telescope and the Caltech Submillimeter Observatory. This was achieved by using two 183 GHz heterodyne radiometers to measure the water vapor content along the line of sight of each telescope. Further development of such techniques will enable future telescopes, such as the Submillimeter Array and the Atacama Large Millimeter Array, to reach their full capability, providing a resolution of up to 0."01. C1 Univ Cambridge, Cavendish Lab, Mullard Radio Astron Observ, Cambridge CB3 0HE, England. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wiedner, MC (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. NR 30 TC 32 Z9 32 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP 1036 EP 1041 DI 10.1086/320943 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YX UT WOS:000169429100052 ER PT J AU Contreras, CS Sahai, R AF Contreras, CS Sahai, R TI A 2000 kilometer per second "pristine" post-asymptotic giant branch wind in the proto-planetary nebula He 3-1475 SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; planetary nebulae : individual (He 3-1475) reflection nebulae stars : AGB and post-AGB; stars : mass loss; stars : winds; outflows ID JETS AB We analyze (archival) Space Telescope Imaging Spectrograph long-slit H alpha spectra of the proto-planetary nebula He 3-1475. We find two remarkable blueshifted absorption features arising from the inner cm similar to5 x 10(16) cm of the nebula, revealing the presence of two different winds outflowing at high velocity from the central star. The kinematic age of these winds is only tens of years. We find that the fast wind is flowing with velocities in the range similar to 150-1200 km s(-) whereas the ultrafast wind is moving much faster (up to 2300 km s(-1)). The latter is highly collimated (length/width greater than or similar to7) close to the central star (similar to 10(16) cm) along a direction different from previous mass ejection axes and shows a radially increasing velocity. We identify the ultrafast wind with a "pristine" post-asymptotic giant branch (post-AGB) outflow that has not been (strongly) altered by its interaction with the AGB envelope. We discuss the implications of the spatiokinematic structure of this wind for current theories of the formation and shaping of planetary nebulae. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Contreras, CS (reprint author), CALTECH, Jet Prop Lab, MS 183-900,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Sanchez-Contreras, Carmen/N-3718-2015 OI Sanchez-Contreras, Carmen/0000-0002-6341-592X NR 11 TC 25 Z9 25 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP L173 EP L176 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YY UT WOS:000169430800020 ER PT J AU Haisch, KE Lada, EA Lada, CJ AF Haisch, KE Lada, EA Lada, CJ TI Disk frequencies and lifetimes in young clusters SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : stars; open clusters and associations : general; planetary systems : protoplanetary disks; stars : formation ID MAIN-SEQUENCE STARS; CIRCUMSTELLAR DISKS; TRAPEZIUM CLUSTER; PLANET FORMATION; MOLECULAR CLOUD; SOLAR NEBULA; EVOLUTION; PHOTOMETRY; IC-348; FIELD AB We report the results of the first sensitive L-band survey of the intermediate-age (2.5-30 Myr) clusters NGC 2264, NGC 2362, and NGC 1960. We use JHKL colors to obtain a census of the circumstellar disk fractions in each cluster. We find disk fractions of,, and for the three clusters, respectively. 52% +/- 10% 12% +/- 4% 3% +/- 3% Together with our previously published JHKL investigations of the younger NGC 2024, Trapezium, and IC 348 clusters, we have completed the first systematic and homogeneous survey for circumstellar disks in a sample of young clusters that both span a significant range in age (0.3-30 Myr) and contain statistically significant numbers of stars whose masses span nearly the entire stellar mass spectrum. Analysis of the combined survey indicates that the cluster disk fraction is initially very high (greater than or equal to 80%) and rapidly decreases with increasing cluster age, such that one-half the stars within the clusters lose their disks in less than or similar to3 Myr. Moreover, these observations yield an overall disk lifetime of similar to6 Myr in the surveyed cluster sample. This is the timescale for essentially all the stars in a cluster to lose their disks. This should set a meaningful constraint for the planet-building timescale in stellar clusters. The implications of these results for current theories of planet formation are briefly discussed. C1 Univ Florida, Dept Astron, Gainesville, FL 32611 USA. Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. RP Haisch, KE (reprint author), NASA, Ames Res Ctr, Mail Stop 245-6, Moffett Field, CA 94035 USA. NR 37 TC 672 Z9 676 U1 2 U2 12 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 JUN 8 PY 2001 VL 553 IS 2 BP L153 EP L156 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YY UT WOS:000169430800015 ER PT J AU Jensen, JM Duvall, TL Jacobsen, BH Christensen-Dalsgaard, J AF Jensen, JM Duvall, TL Jacobsen, BH Christensen-Dalsgaard, J TI Imaging an emerging active region with helioseismic tomography SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : helioseismology; sunspots ID TIME-DISTANCE HELIOSEISMOLOGY; SENSITIVITY KERNELS; INVERSION AB The wave-speed structure beneath an emerging active region is derived from helioseismic time-distance data using inversion techniques developed in geophysics. We use Fresnel zone-based sensitivity kernels along with a Fourier domain-based regularized least-squares inversion technique. The results show that wave-speed anomalies extend down to 20 Mm below active regions. We also see some evidence of deeper anomalies that appear around 16-20 hr after the emergence of an active region and then disappear within 8 hr. These anomalies could be the signature of a change in the subsurface structure of the active region. C1 Danish Natl Res Fdn, Theoret Astrophys Ctr, DK-8000 Aarhus C, Denmark. Aarhus Univ, Dept Earth Sci, DK-8000 Aarhus C, Denmark. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Aarhus Univ, Inst Phys & Astron, DK-8000 Aarhus C, Denmark. RP Jensen, JM (reprint author), Danish Natl Res Fdn, Theoret Astrophys Ctr, DK-8000 Aarhus C, Denmark. RI Jacobsen, Bo Holm/A-4854-2012; Duvall, Thomas/C-9998-2012 NR 13 TC 52 Z9 52 U1 0 U2 2 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 JUN 8 PY 2001 VL 553 IS 2 BP L193 EP L196 DI 10.1086/320677 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YY UT WOS:000169430800025 ER PT J AU Man in't Zand, JJ Corbet, RHD Marshall, FE AF Man in't Zand, JJ Corbet, RHD Marshall, FE TI Discovery of a 75 day orbit in XTE J1543-568 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : general; pulsars : individual (XTE J1543-568); X-rays : stars AB Dedicated monitoring of the transient X-ray pulsar XTE J1543-568 during the first year after its discovery has revealed the unambiguous detection of a binary orbit. The orbital period is days, and the 75.56 +/- 0.25 projected semimajor axis is 353 +/- 8 lt-s. The mass function and position in the pulse period versus orbital period diagram are consistent with XTE J1543-568 being a Be X-ray binary. The eccentricity of less than 0.03 (2 sigma) is among the lowest for the 12 Be X-ray binaries whose orbits have now been measured. This confirms the suspicion that small kick velocities of neutron stars during supernovae are more common than expected. The distance is estimated to be larger than 10 kpc and the luminosity at least 10(37) ergs s(-1). C1 Univ Utrecht, Astron Inst, NL-3508 TA Utrecht, Netherlands. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Space Res Org Netherlands, Utrecht, Netherlands. Univ Space Res Assoc, Columbia, MD 21044 USA. RP Man in't Zand, JJ (reprint author), Univ Utrecht, Astron Inst, POB 80000, NL-3508 TA Utrecht, Netherlands. NR 17 TC 13 Z9 13 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP L165 EP L168 DI 10.1086/320688 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YY UT WOS:000169430800018 ER PT J AU Masi, S Ade, PAR Bock, JJ Boscaleri, A Crill, BP de Bernardis, P Giacometti, M Hivon, E Hristov, VV Lange, AE Mauskopf, PD Montroy, T Netterfield, CB Pascale, E Piacentini, F Prunet, S Ruhl, J AF Masi, S Ade, PAR Bock, JJ Boscaleri, A Crill, BP de Bernardis, P Giacometti, M Hivon, E Hristov, VV Lange, AE Mauskopf, PD Montroy, T Netterfield, CB Pascale, E Piacentini, F Prunet, S Ruhl, J TI High-latitude galactic dust emission in the BOOMERANG maps SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; dust, extinction; infrared : ISM : continuum; submillimeter ID MICROWAVE BACKGROUND-RADIATION; INFRARED CIRRUS; ARGO 1993; SKY MAPS; ANISOTROPY; COBE; FOREGROUNDS; SCALES AB We present millimeter-wave observations obtained by the BOOMERANG (Balloon Observations Of Millimetric Extragalactic Radiation ANd Geophysics) experiment of Galactic emission at intermediate and high (b < -20) Galactic latitudes. We find that this emission is well correlated with extrapolated dust maps and is spectrally consistent with thermal emission from interstellar dust (ISD). The ISD brightness in the 410 GHz map has an angular power spectrum c(l) similar to l(-beta) with 2 less than or similar to beta less than or similar to 3. At 150 GHz and at multipoles l similar to 200, the angular power spectrum of the IRAS- correlated dust signal is estimated to be l/(l + 1)c(l)/2 pi = 3.7 +/- 2.9 muK(2). This is negligible with respect to the cosmic microwave background (CMB) signal measured by the same experiment l(l + 1)c(l)/2 pi = 4700 +/- 540 muK(2). For the uncorrelated dust signal, we set an upper limit to the contribution to the CMB power at 150 GHz and of l similar to 200 l(l + l)c(l)/2 pi < 3 K-2 at 95% CL. C1 Univ La Sapienza, Dipartimento Fis, I-00185 Rome, Italy. Univ London Queen Mary & Westfield Coll, Dept Phys, London E1 4NS, England. CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CNR, IROE, I-50127 Florence, Italy. Cardiff Univ, Dept Phys & Astron, Cardiff CF2 3YB, S Glam, Wales. Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. Univ Toronto, Dept Phys & Astron, Toronto, ON M5S 1A1, Canada. RP Masi, S (reprint author), Univ La Sapienza, Dipartimento Fis, Piazza Le Aldo Moro 2, I-00185 Rome, Italy. OI Masi, Silvia/0000-0001-5105-1439; de Bernardis, Paolo/0000-0001-6547-6446; Piacentini, Francesco/0000-0002-5444-9327; Hivon, Eric/0000-0003-1880-2733 NR 31 TC 45 Z9 45 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP L93 EP L96 DI 10.1086/320679 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YY UT WOS:000169430800001 ER PT J AU Nayakshin, S Kazanas, D AF Nayakshin, S Kazanas, D TI Narrow moving FeK alpha lines from magnetic flares in active galactic nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; line : formation; radiative transfer; X rays : general ID HOLE ACCRETION DISKS; INNERMOST STABLE ORBIT; CORONAE; REVERBERATION; MODEL AB We show that luminous magnetic flares, thought to occur in standard accretion disks in active galactic nuclei, cannot be located much higher than a few pressure scale heights above the disk. Using this fact, we estimate the fraction of the disk surface illuminated by a typical flare to be very small for geometrically thin disks, which implies that the instantaneous Fe K alpha emission line from a specific magnetic flare is narrow. The line is red- or blueshifted depending on the position of the observer relative to the flare and sweeps across the line band with time. We present several examples of theoretical time-resolved line profiles from such flares for Schwarzschild geometry. Search for such moving features with future X-ray telescopes will present a powerful test of the accretion disk geometry; if observed, these features may let us test general relativity in the strong field limit. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. RP Nayakshin, S (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 19 TC 28 Z9 28 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 8 PY 2001 VL 553 IS 2 BP L141 EP L144 DI 10.1086/320684 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444YY UT WOS:000169430800012 ER PT J AU Ma, Z Mohammadi, S Bhattacharya, P Katehi, LPB Alterovitz, SA Ponchak, GE AF Ma, Z Mohammadi, S Bhattacharya, P Katehi, LPB Alterovitz, SA Ponchak, GE TI High power X-band (8.4 GHz) SiGe/Si heterojunction bipolar transistor SO ELECTRONICS LETTERS LA English DT Article ID HBTS AB A high-performance double-mesa type Si/SiGe/Si power HBT at X-band (8.4GHz) frequency is demonstrated. Under continuous wave operation, a single 20-finger common-base Si/Si0.75Ge0.25/Si (2 x 10 mum(2) of each emitter finger) HBT has an output power of 27.4dBm and an associated power gain of 7dB at peak PAE of 32.3%. These parametric values represent the state-of-the-art power performance of SiGe-based HBTs. C1 Univ Michigan, Dept Elect Engn & Comp Sci, Ann Arbor, MI 48109 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Ma, Z (reprint author), Univ Michigan, Dept Elect Engn & Comp Sci, Ann Arbor, MI 48109 USA. NR 6 TC 7 Z9 7 U1 0 U2 1 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 0013-5194 J9 ELECTRON LETT JI Electron. Lett. PD JUN 7 PY 2001 VL 37 IS 12 BP 790 EP 791 DI 10.1049/el:20010514 PG 2 WC Engineering, Electrical & Electronic SC Engineering GA 444ZX UT WOS:000169433400043 ER PT J AU Hu, ZW Thomas, BR Chernov, AA AF Hu, ZW Thomas, BR Chernov, AA TI Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID EGG-WHITE LYSOZYME; DIFFRACTION ANALYSES; TETRAGONAL LYSOZYME; RESOLUTION; CRYSTALLIZATION; MICROGRAVITY; SCATTERING; MOSAICITY; GROWTH; WAVE AB Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Alabama, Ctr Micrograv Mat Res, Huntsville, AL 35899 USA. RP Hu, ZW (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. EM zhengwei.hu@msfc.nasa.gov NR 39 TC 15 Z9 15 U1 0 U2 0 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0907-4449 EI 1399-0047 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD JUN PY 2001 VL 57 BP 840 EP 846 DI 10.1107/S0907444901005832 PN 6 PG 7 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA 446UV UT WOS:000169533300009 PM 11375503 ER PT J AU Walker, JP Willgoose, GR Kalma, JD AF Walker, JP Willgoose, GR Kalma, JD TI One-dimensional soil moisture profile retrieval by assimilation of near-surface observations: a comparison of retrieval algorithms SO ADVANCES IN WATER RESOURCES LA English DT Article ID UNSATURATED FLOW; MODEL; HEAT; TEMPERATURE AB This paper investigates the ability to retrieve the true soil moisture and temperature profiles by assimilating near-surface soil moisture and surface temperature data into a soil moisture and heat transfer model. The direct insertion and Kalman filter assimilation schemes have been used most frequently in assimilation studies, but no comparisons of these schemes have been made. This study investigates which of these approaches is able to retrieve the soil moisture and temperature profiles the fastest, over what depth soil moisture observations are required, and the effect of update interval on profile retrieval. These questions are addressed by a desktop study using synthetic data. The study shows that the Kalman filter assimilation scheme is superior to the direct insertion assimilation scheme, with retrieval of the soil moisture profile being achieved in 12 h as compared to 8 days or more, depending on observation depth, for hourly observations. It was also found that profile retrieval could not be realised for direct insertion of the surface node alone, and that observation depth does not have a significant effect on profile retrieval time for the Kalman filter. The observation interval was found to be unimportant for profile retrieval with the Kalman filter when the forcing data is accurate, whilst for direct insertion the continuous Dirichlet boundary condition was required for an increasingly longer period of time. It was also found that the Kalman filter assimilation scheme was less susceptible to unstable updates if volumetric soil moisture was modelled as the dependent state rather than matric head, because the volumetric soil moisture state is more linear in the forecasting model. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Univ Newcastle, Dept Civil Surveying & Environm Engn, Callaghan, NSW 2308, Australia. RP Walker, JP (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Rm B309,Bldg 33,Mail Code 974, Greenbelt, MD 20771 USA. EM cejpw@land.gsfc.nasa.gov RI Willgoose, Garry/A-1492-2008 OI Willgoose, Garry/0000-0001-5175-4935 NR 41 TC 113 Z9 135 U1 1 U2 11 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0309-1708 J9 ADV WATER RESOUR JI Adv. Water Resour. PD JUN PY 2001 VL 24 IS 6 BP 631 EP 650 DI 10.1016/S0309-1708(00)00043-9 PG 20 WC Water Resources SC Water Resources GA 440UB UT WOS:000169192100005 ER PT J AU Shirinzadeh, B Herring, GC Exton, RJ AF Shirinzadeh, B Herring, GC Exton, RJ TI Examination of anomalous shock velocities in weakly ionized gases SO AIAA JOURNAL LA English DT Article C1 NASA, Langley Res Ctr, Adv Measurement Diagnost Branch, Hampton, VA 23681 USA. RP Shirinzadeh, B (reprint author), NASA, Langley Res Ctr, Adv Measurement Diagnost Branch, M-S 493, Hampton, VA 23681 USA. NR 11 TC 4 Z9 4 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 JUN PY 2001 VL 39 IS 6 BP 1210 EP 1212 DI 10.2514/2.1438 PG 3 WC Engineering, Aerospace SC Engineering GA 439UW UT WOS:000169136800029 ER PT J AU Conley, CA AF Conley, CA TI Leiomodin and tropomodulin in smooth muscle SO AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY LA English DT Article DE actin cytoskeleton; tropomyosin binding protein; contraction bands; human 64-kDa autoantigen D1 ID PROTEIN-KINASE-C; DROSOPHILA-MELANOGASTER; SKELETAL-MUSCLE; POINTED ENDS; TROPOMYOSIN-BINDING; MOUSE EMBRYOGENESIS; ACTIN-FILAMENTS; TROPONIN-H; CELLS; EXPRESSION AB Evidence is accumulating to suggest that actin filament remodeling is critical for smooth muscle contraction, which implicates actin filament ends as important sites for regulation of contraction. Tropomodulin (Tmod) and smooth muscle leiomodin (SM-Lmod) have been found in many tissues containing smooth muscle by protein immunoblot and immunofluorescence microscopy. Both proteins cofractionate with tropomyosin in the Triton-insoluble cytoskeleton of rabbit stomach smooth muscle and are solubilized by high salt. SM-Lmod binds muscle tropomyosin, a biochemical activity characteristic of Tmod proteins. SM-Lmod staining is present along the length of actin filaments in rat intestinal smooth muscle, while Tmod stains in a punctate pattern distinct from that of actin filaments or the dense body marker alpha -actinin. After smooth muscle is hypercontracted by treatment with 10 mM Ca2+, both SM-Lmod and Tmod are found near alpha -actinin at the periphery of actin-rich contraction bands. These data suggest that SM-Lmod is a novel component of the smooth muscle actin cytoskeleton and, furthermore, that the pointed ends of actin filaments in smooth muscle may be capped by Tmod in localized clusters. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Conley, CA (reprint author), NASA, Ames Res Ctr, MS 239-11, Moffett Field, CA 94035 USA. NR 64 TC 26 Z9 27 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 0363-6143 J9 AM J PHYSIOL-CELL PH JI Am. J. Physiol.-Cell Physiol. PD JUN PY 2001 VL 280 IS 6 BP C1645 EP C1656 PG 12 WC Cell Biology; Physiology SC Cell Biology; Physiology GA 432DF UT WOS:000168675500033 PM 11350761 ER PT J AU Landis, GA AF Landis, Geoffrey A. TI Martian Water: Are There Extant Halobacteria on Mars? SO ASTROBIOLOGY LA English DT Article DE Mars; Halobacteria; Halophiles; Salt AB On Earth, life exists in all niches where water exists in liquid form for at least a portion of the year. On Mars, any liquid water would have to be a highly concentrated brine solution. It is likely, therefore, that any present-day Martian microorganisms would be similar to terrestrial halophiles. Even if present-day life does not exist on Mars, it is an interesting speculation that ancient bacteria preserved in salt deposits could be retrieved from an era when the climate of Mars was more conducive to life. C1 NASA, John Glenn Res Ctr, Cleveland, OH 44135 USA. RP Landis, GA (reprint author), NASA, John Glenn Res Ctr, Mailstop 302 1,21000 Brookpk Rd, Cleveland, OH 44135 USA. EM geoffrey.landis@grc.nasa.gov NR 45 TC 28 Z9 31 U1 0 U2 5 PU MARY ANN LIEBERT, INC PI NEW ROCHELLE PA 140 HUGUENOT STREET, 3RD FL, NEW ROCHELLE, NY 10801 USA SN 1531-1074 EI 1557-8070 J9 ASTROBIOLOGY JI Astrobiology PD JUN PY 2001 VL 1 IS 2 BP 161 EP 164 DI 10.1089/153110701753198927 PG 4 WC Astronomy & Astrophysics; Biology; Geosciences, Multidisciplinary SC Astronomy & Astrophysics; Life Sciences & Biomedicine - Other Topics; Geology GA V38SL UT WOS:000209363000004 PM 12467119 ER PT J AU Wynn-Williams, DD Cabrol, NA Grin, EA Haberle, RM Stoker, CR AF Wynn-Williams, David D. Cabrol, Nathalie A. Grin, Edmond A. Haberle, Robert M. Stoker, Carol R. TI Brines in Seepage Channels as Eluants for Subsurface Relict Biomolecules on Mars? SO ASTROBIOLOGY LA English DT Article DE Biomolecules; Brines; Fluvial erosion; Mars; Microbes; Salinity; Water AB Water, vital for life, not only maintains the integrity of structural and metabolic biomolecules, it also transports them in solution or colloidal suspension. Any flow of water through a dormant or fossilized microbial community elutes molecules that are potentially recognizable as biomarkers. We hypothesize that the surface seepage channels emanating from crater walls and cliffs in Mars Orbiter Camera images result from fluvial erosion of the regolith as low-temperature hypersaline brines. We propose that, if such flows passed through extensive subsurface catchments containing buried and fossilized remains of microbial communities from the wet Hesperian period of early Mars (similar to 3.5 Ga ago), they would have eluted and concentrated relict biomolecules and delivered them to the surface. Life-supporting low-temperature hypersaline brines in Antarctic desert habitats provide a terrestrial analog for such a scenario. As in the Antarctic, salts would likely have accumulated in water-filled depressions on Mars by seasonal influx and evaporation. Liquid water in the Antarctic cold desert analogs occurs at -80 degrees C in the interstices of shallow hypersaline soils and at -50 degrees C in salt-saturated ponds. Similarly, hypersaline brines on Mars could have freezing points depressed below -50 degrees C. The presence of hypersaline brines on Mars would have extended the amount of time during which life might have evolved. Phototrophic communities are especially important for the search for life because the distinctive structures and longevity of their pigments make excellent biomarkers. The surface seepage channels are therefore not only of geomorphological significance, but also provide potential repositories for biomolecules that could be accessed by landers. C1 [Wynn-Williams, David D.] British Antarctic Survey, Nat Environm Res Council, Cambridge CB3 OET, England. [Cabrol, Nathalie A.; Grin, Edmond A.] SETI Inst, Mountain View, CA 94043 USA. [Cabrol, Nathalie A.; Grin, Edmond A.; Haberle, Robert M.; Stoker, Carol R.] NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Wynn-Williams, DD (reprint author), British Antarctic Survey, Antarctic Astrobiol, High Cross, Madingley Rd, Cambridge CB3 0ET, England. EM ddww@bas.ac.uk FU SETI/NASA Ames Research Center [NCC2-1064]; British Antarctic Survey FX The authors thanks Jeff Kargel and an anonymous reviewer for the valued criticisms and the time and care they have allocated to review our manuscript. This study is supported through SETI/NASA Ames Research Center cooperative agreements NCC2-1064 for Nathalie Cabrol and Edmond Grin. D.D. Wynn-Williams thanks the British Antarctic Survey for supporting this research, Susan Chambers for many years of extensive bibliographic work, and NZARP and USAP for field logistic support in the Ross Dependency. MOC imagery is used courtesy of M.C. Malin et al. (NASA's Planetary Photojournal, http://photojournal.jpl.nasa.gov). NR 118 TC 13 Z9 13 U1 1 U2 4 PU MARY ANN LIEBERT, INC PI NEW ROCHELLE PA 140 HUGUENOT STREET, 3RD FL, NEW ROCHELLE, NY 10801 USA SN 1531-1074 EI 1557-8070 J9 ASTROBIOLOGY JI Astrobiology PD JUN PY 2001 VL 1 IS 2 BP 165 EP 184 DI 10.1089/153110701753198936 PG 20 WC Astronomy & Astrophysics; Biology; Geosciences, Multidisciplinary SC Astronomy & Astrophysics; Life Sciences & Biomedicine - Other Topics; Geology GA V38SL UT WOS:000209363000005 PM 12467120 ER PT J AU Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Snow, M Ake, TB AF Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Snow, M Ake, TB TI Goddard high resolution spectrograph observations of NGC 4151 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 4151); galaxies : Seyfert AB Goddard High Resolution Spectrograph observations of the nucleus of the bright, nearby Seyfert galaxy NGC 4151 are briefly described. The reduced spectra are made available electronically. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Univ New Mexico, Dept Phys & Astron, Inst Astrophys, Albuquerque, NM 87131 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. Ball Aerosp & Technol Corp, Boulder, CO 80306 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. Natl Inst Stand & Technol, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Space Sci Directorate, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Anat, Madison, WI 53706 USA. Univ Texas, McDonald Observ, Austin, TX 78712 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. NASA, Goddard Space Flight Ctr, Comp Sci Corp, Sci Programs, Greenbelt, MD 20771 USA. RP Brandt, JC (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA. RI heap, sara/E-2237-2012; Carpenter, Kenneth/D-4740-2012; OI SNOW, MARTIN/0000-0001-9106-1332 NR 4 TC 3 Z9 3 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUN PY 2001 VL 121 IS 6 BP 2999 EP 3000 DI 10.1086/321070 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444FC UT WOS:000169387500009 ER PT J AU Snowden, SL Mukai, K Pence, W Kuntz, KD AF Snowden, SL Mukai, K Pence, W Kuntz, KD TI Reconsidering the identification of M101 hypernova remnant candidates SO ASTRONOMICAL JOURNAL LA English DT Article DE binaries : general; galaxies : individual (M101); supernova remnants; X-rays ID RAY; AXAF AB Using a deep Chandra AO-1 observation of the face-on spiral galaxy M101, we examine three of five previously optically identified X-ray sources that are spatially correlated with optical supernova remnants (MF 54, MF 57, and MF 83). The X-ray fluxes from these objects, if due to diffuse emission from the remnants, are bright enough to require a new class of objects, with the possible attribution by Wang to diffuse emission from hypernova remnants. Of the three, MF 83 was considered the most likely candidate for such an object because of its size, nature, and close positional coincidence. However, we find that MF 83 is clearly ruled out as a hypernova remnant by both its temporal variability and spectrum. The bright X-ray sources previously associated with MF 54 and MF 57 are seen by Chandra to be clearly offset from the optical positions of the supernova remnants by several arcseconds, confirming a result suggested by the previous work. MF 54 does have a faint X-ray counterpart, however, with a luminosity and temperature consistent with a normal supernova remnant of its size. The most likely classifications of the sources are as X-ray binaries. Although counting statistics are limited, over the 0.3-5.0 keV spectral band the data are well fitted by simple absorbed power laws with luminosities in the 10(38)-10(39) ergs s(-1) range. The power-law indices are softer than those of Milky Way low-mass X-ray binaries of similar luminosities and are more consistent with those of the Large Magellanic Cloud. Both the high luminosity and the soft spectral shape favor these being accreting black hole binaries in high soft states. C1 NASA, Goddard Space Flight Ctr, High Energy Phys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Astrophys, Baltimore, MD 21250 USA. RI Snowden, Steven/D-5292-2012 NR 16 TC 11 Z9 11 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUN PY 2001 VL 121 IS 6 BP 3001 EP 3006 DI 10.1086/321083 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 444FC UT WOS:000169387500010 ER PT J AU Pap, J Rozelot, JP Godier, S Varadi, F AF Pap, J Rozelot, JP Godier, S Varadi, F TI On the relation between total irradiance and radius variations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun : general; Sun : fundamental parameters ID SOLAR DIAMETER MEASUREMENTS; SINGULAR-SPECTRUM ANALYSIS; SURFACE-TEMPERATURE; VARIABILITY; SUN; ASTROLABE; LUMINOSITY; SANTIAGO; BRIGHTNESS; CYCLE AB We use Singular Spectrum Analysis (SSA) to analyze total solar irradiance variations and CERGA radius measurements. Total solar irradiance has been monitored from space for more than two decades, whilst ground-based radius measurements are available as a coherent time series from 1975. We compare these indicators to try to understand the origin of energy production inside the Sun. One of the main objectives was to assess the reality of the observed variations of the Sun's radius by distinguishing the signal from the noise. Two approaches were used: one using SSA on ground-based data averaged over 90 days, in order to smooth the signal (especially over periods when no data were obtained, mainly in winter time); the second repeats the analysis on individual measurements corrected by reporting data to the zenith. As expected, the level of noise is higher in the first case and the reconstructed noise level, which is large, indicates the difficulty in ascertaining the solar origin in the apparent variability of the solar radius. It is shown from the reconstructed components that the main variation in amplitude (over 930 days) is pronounced during the first part of the measurements and seems to disappear after 1988. There is also a variation with a periodicity of 1380 days, of lower amplitude than that of the shorter component. In both cases, these variations disappear during the rising portion of cycle 23. The first reconstructed component shows that total irradiance varies in parallel with the solar cycle, being higher during maximum activity conditions. The reconstructed radius trend indicates that the solar radius was higher during the minimum of solar cycle 21, but its decrease with the rising activity of cycle 23 is less obvious. The observed value of the solar radius increased by about 0.11 arcsec from the maximum of cycle 21 to the minimum between cycles 21 and 22. Most importantly, we report a long-term radius variation which increased from the maximum of cycle 21 to minimum by about 0.015%, while a smaller decrease (around 0.01%) is seen from the minimum of cycle 21 to the maximum of cycle 22. This study indicates need for measurements of the degree of the radius changes taken from space, together with total irradiance measurements to establish the phase relation between these two quantities. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. OCA CERGA, F-06130 Grasse, France. Univ Calif Los Angeles, Dept Phys, Los Angeles, CA 90095 USA. RP Rozelot, JP (reprint author), NASA, Goddard Space Flight Ctr, Code 680-0, Greenbelt, MD 20771 USA. EM rozelot@obs-azur.fr NR 74 TC 22 Z9 22 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 JUN PY 2001 VL 372 IS 3 BP 1005 EP 1018 DI 10.1051/0004-6361 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 454HF UT WOS:000169966600034 ER PT J AU Nakariakov, VM Ofman, L AF Nakariakov, VM Ofman, L TI Determination of the coronal magnetic field by coronal loop oscillations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE magnetohydrodynamics (MHD); waves; Sun : corona; Sun : activity; Sun : oscillations; Sun : UV; radiation ID SOLAR CORONA; REGION; PHOTOSPHERE; PLASMA AB We develop a new method for the determination of the absolute value of the magnetic field strength in coronal closed magnetic structures, based on the analysis of flare-generated oscillations of coronal loops. Interpretation of the oscillations observed in terms of global standing kink waves allows to connect the period of the oscillations and the loops length with the magnetic field strength in the loops. For loop oscillations observed with TRACE on 14th July 1998 and 4th July 1999, we estimate the magnetic field strength as 4-30 G. Using TRACE 171 Angstrom and 195 Angstrom images of the loop, taken on 4th July 1999 to determine the plasma density, we estimate the magnetic field in the loop as 13 +/- 9 G. Improved diagnostic of the loop length, the oscillation period, and the plasma density in the loop will significantly improve the method's precision. C1 Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England. NASA, Goddard Space Flight Ctr, CUA, Greenbelt, MD 20771 USA. RP Nakariakov, VM (reprint author), Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England. EM valery@astro.warwick.ac.uk; leon.ofman@gsfc.nasa.gov RI Nakariakov, Valery/E-2375-2013; Lee, SungHwan/O-2563-2013 OI Nakariakov, Valery/0000-0001-6423-8286; NR 15 TC 283 Z9 284 U1 1 U2 7 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 JUN PY 2001 VL 372 IS 3 BP L53 EP L56 DI 10.1051/0004-6361:20010607 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 454HF UT WOS:000169966600004 ER PT J AU Jorstad, SG Marscher, AP Mattox, JR Wehrle, AE Bloom, SD Yurchenko, AV AF Jorstad, SG Marscher, AP Mattox, JR Wehrle, AE Bloom, SD Yurchenko, AV TI Multiepoch Very Long Baseline Array observations of egret-detected quasars and BL lacertae objects: Superluminal motion of gamma-ray bright blazars SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Review DE BL Lacertae objects : general; galaxies : jets; gamma rays : observations; quasars : general; radio continuum : galaxies ID ACTIVE GALACTIC NUCLEI; COMPACT RADIO-SOURCES; SCALE POLARIZATION STRUCTURE; SPACE VLBI OBSERVATIONS; REFERENCE FRAME SOURCES; FLUX-LIMITED SAMPLES; RELATIVISTIC JETS; 43 GHZ; X-RAY; MILLIARCSECOND STRUCTURE AB We present the results of a program to monitor the structure of the radio emission in 42 gamma -ray bright blazars (31 quasars and 11 BL Lac objects) with the Very Long Baseline Array (VLBA) at 43, 22, and occasionally 15 and 8.4 GHz, over the period from 1993 November to 1997 July. We determine proper motions in 33 sources and find that the apparent superluminal motions in gamma -ray sources are much faster than for the general population of bright compact radio sources. This follows the strong dependence of the gamma -ray flux on the level of relativistic beaming for both external radiation Compton and synchrotron self-Compton emission. There is a positive correlation (correlation coefficient r = 0.45) between the flux density of the VLBI core and the gamma -ray flux and a moderate correlation (partial correlation coefficient r = 0.31) between gamma -ray apparent luminosity and superluminal velocities of jet components, as expected if the gamma -ray emission originates in a very compact region of the relativistic jet and is highly beamed. In 43% of the sources the jet bends by more than 20 degrees on parsec scales, which is consistent with amplification by projection effects of modest actual changes in position angle. In 27 of the sources in the sample there is at least one non-core component that appears to be stationary during our observations. Different characteristics of stationary features close to and farther from the core lead us to suggest two different classes of stationary components: those within about 2 mas of the core, probably associated with standing hydrodynamical compressions, and those farther down the jet, which tend to be associated with bends in the jet. C1 Boston Univ, Inst Astrophys Res, Boston, MA 02215 USA. St Petersburg State Univ, Astron Inst, St Petersburg 198904, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Hampden Sydney Coll, Hampden Sydney, VA 23943 USA. RP Jorstad, SG (reprint author), Boston Univ, Inst Astrophys Res, 725 Commonwealth Ave, Boston, MA 02215 USA. RI Jorstad, Svetlana/H-6913-2013 OI Jorstad, Svetlana/0000-0001-9522-5453 NR 116 TC 290 Z9 295 U1 2 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUN PY 2001 VL 134 IS 2 SU S BP 181 EP 240 DI 10.1086/320858 PG 60 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JD UT WOS:000169280700001 ER PT J AU Kommers, JM Lewin, WHG Kouveliotou, C van Paradus, J Pendleton, GN Meegan, CA Fishman, GJ AF Kommers, JM Lewin, WHG Kouveliotou, C van Paradus, J Pendleton, GN Meegan, CA Fishman, GJ TI A nontriggered burst supplement to the BATSE gamma-ray burst catalogs SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE catalogs; gamma rays : bursts ID INTENSITY DISTRIBUTION; SEARCH AB The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory detects gamma-ray bursts (GRBs) with a real-time burst detection (or "trigger") system running onboard the spacecraft. Under some circumstances, however, a GRB may not activate the on-board burst trigger. For example, the burst may be too faint to exceed the on-board detection threshold, or it may occur while the on-board burst trigger is disabled for technical reasons. This paper describes a catalog of 873 "nontriggered" GRBs that were detected in a search of the archival continuous data from BATSE recorded between 1991 December 9.0 and 1997 December 17.0. For each burst, the catalog gives an estimated source direction, duration, peak flux, and fluence. Similar data are presented for 50 additional bursts of unknown origin that were detected in the 25-50 keV range; these events may represent the low-energy "tail" of the GRB spectral distribution. This catalog increases the number of GRBs detected with BATSE by 48% during the time period covered by the search. C1 MIT, Dept Phys, Cambridge, MA 02139 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Space Res Assoc, Huntsville, AL 35800 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35812 USA. Univ Amsterdam, Amsterdam, Netherlands. RP Kommers, JM (reprint author), MIT, Dept Phys, Cambridge, MA 02139 USA. NR 23 TC 17 Z9 17 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUN PY 2001 VL 134 IS 2 SU S BP 385 EP 454 DI 10.1086/320856 PG 70 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JD UT WOS:000169280700010 ER PT J AU Ramakrishna, V Hunt, LR Meyer, G AF Ramakrishna, V Hunt, LR Meyer, G TI Parameter variations, relative degree, and stable inversion SO AUTOMATICA LA English DT Article DE parameter variations; relative degree; stable inversion; Picard process ID NONLINEAR-SYSTEMS; OUTPUT TRACKING; DYNAMICS AB Motivated by our prior research on automatic: aircraft guidance, we address stable inversion for output tracking and prove that this process is continuous with respect to parameter variations, even when these variations cause a change in relative degree. Our earlier simulations indicated that the stable inversion process is extremely accurate and that only a linear regulator about the desired trajectory is required in the face of reasonable modeling error. The principal novelty in our technique is that a differential equations point of view is taken as opposed to a state-space approach on the (driven) zero dynamics of the system. This is the situation that arises in many applications and it also enables handling the question of changes in relative degree, without having to be encumbered by the change in state space dimension as the parameters change. Linear systems are first studied, since the corresponding result is unknown. Next, a corresponding theorem for nonlinear systems proved by using the Picard process in conjunction with the result for the linear case. The principal contribution of this paper is a result concerning the continuous dependence of a generalized steady state solution of nonlinear driven differential equations, with respect to parameter variations which cause the order of the differential equation to change. Since the notion of steady state is of paramount importance to innumerable engineering situations, the contents of this paper have wider scope. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Univ Texas, Dept Math Sci, Richardson, TX 75083 USA. Univ Texas, Ctr Signals Syst & Telecommun, Richardson, TX 75083 USA. Univ Texas, Ctr Signals Syst & Telecommun, Richardson, TX 75083 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ramakrishna, V (reprint author), Univ Texas, Dept Math Sci, EC 35,POB 830688, Richardson, TX 75083 USA. NR 12 TC 9 Z9 9 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0005-1098 J9 AUTOMATICA JI Automatica PD JUN PY 2001 VL 37 IS 6 BP 871 EP 880 DI 10.1016/S0005-1098(01)00029-2 PG 10 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA 428ZT UT WOS:000168492100007 ER PT J AU Greenleaf, JE Hinghofer-Szalkay, H Rossler, A Farrell, PA Loomis, JL Fedele, MJ West, J Cowell, SA AF Greenleaf, JE Hinghofer-Szalkay, H Rossler, A Farrell, PA Loomis, JL Fedele, MJ West, J Cowell, SA TI Plasma sodium-osmotic dissociation and hormonal interaction with drinking-induced hypervolemia at 2800 m altitude SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE flight fatigue; fluid intake; flight; stress ID FLUID REPLACEMENT; EXERCISE; VOLUME; REHYDRATION; MEN; OSMOLALITY; BEVERAGES; VASOPRESSIN; STRESS; HUMANS AB Purpose: To study hormonal factors that may account for the dissociation between beverage -induced plasma sodium p[Na+] and osmotic p[Osm] concentrations that appear to refute the high theoretical correlation between pINa(+)] and p[Osm]. Methods: Ten men (24 +/- SD 3 yr of age) sat reclining (head up) for 12 h in a chamber (21-23 degreesC dry bulb, 25-33% relative humidity) at 2800 m (9184 ft, 539 mm Hg) altitude (ALT), and at 321 m (1053 it, 732 mm Hg) on the ground (CND). During 1000-1030 hours they consumed 3 fluids (12 mi . kg(-1),(X) over bar = 948 mi . d(-1)) with large differences in sodium and osmotic contents: AstroAde (AA) with 185 mEq . L-1 Na+ and 283 mOsm . kg(-1), Performance 1(TM) (Shaklee) (P1) with 22 mEq . L-1 Na+ and 3G5 mOsm . kg(-1), or H2O at ALT; and only H2O on the GND. Results: After drinking: plasma volume (PV) increased at 1200 hours by 8.3% (p < 0.05) with AA but was not significantly (NS) changed in the other sessions (<(X)over bar>Delta = +0.9%, range -0.3 to 2.8%); p[Na+] and p[Osm) were unchanged. Urinary rates and free-water clearances were attenuated with AA and Pl vs. those with H2O. Correlations between and among p[Na+] and p[Osm] suggest that the pNa(+) ion is more tightly controlled than pOsm; and that there was no clear hormonal response that could account for this dissociation from theoretical considerations. Conclusions: There is significant dissociation between plasma sodium and osmotic concentrations after fluid intake. Induction and maintenance of hypervolemia requires increased (near isotonic) drink Na+ osmols rather than increased non-ionic osmols. C1 Penn State Univ, Noll Physiol Res Ctr, University Pk, PA 16802 USA. Austrian Soc Aerosp Med, Inst Adapt & Spaceflight Physiol, A-8010 Graz, Austria. Graz Univ, Inst Physiol, Graz, Austria. NASA, Ames Res Ctr, Gravitat Res Branch 221A 2, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. RP Greenleaf, JE (reprint author), NASA, Ames Res Ctr, Gravitat Res Branch 221A 2, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. RI Roessler, Andreas/A-5751-2008 NR 27 TC 5 Z9 5 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 JUN PY 2001 VL 72 IS 6 BP 522 EP 528 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 436JU UT WOS:000168933400003 PM 11396557 ER PT J AU Lenihan, HS Peterson, CH Byers, JE Grabowski, JH Thayer, GW Colby, DR AF Lenihan, HS Peterson, CH Byers, JE Grabowski, JH Thayer, GW Colby, DR TI Cascading of habitat degradation: Oyster reefs invaded by refugee fishes escaping stress SO ECOLOGICAL APPLICATIONS LA English DT Article DE cascading interactions; Crassostrea virginica; ecosystem management; essential fish habitat; fish use of restored oyster reefs; habitat structure; hypoxia effects; Neuse River estuary, North Carolina, USA; oyster reefs; reef habitat, biogenic; refugee species; restored habitat ID CHESAPEAKE BAY; NORTH-CAROLINA; RIVER ESTUARY; SEA OTTERS; FOOD WEBS; HYPOXIA; EUTROPHICATION; DISTURBANCE; ECOSYSTEMS; RECRUITMENT AB Mobile consumers have potential to cause a cascading of habitat degradation beyond the region that is directly stressed, by concentrating in refuges where they intensify biological interactions and can deplete prey resources. We tested this hypothesis on structurally complex, species-rich biogenic reefs created by the eastern oyster, Crassostrea virginica, in the Neuse River estuary, North Carolina, USA. We (1) sampled fishes and invertebrates on natural and restored reefs and on sand bottom to compare fish utilization of these different habitats and to characterize the trophic relations among large reef-associated fishes and benthic invertebrates, and (2) tested whether bottom-water hypoxia and fishery-caused degradation of reef habitat combine to induce mass emigration of fish that then modify community composition in refuges across an estuarine seascape. Experimentally restored oyster reefs of two heights (1 m tall "degraded" or 2 m tall "natural" reefs) were constructed at 3 and 6 m depths. We sampled hydrographic conditions within the estuary over the summer to monitor onset and duration of bottom-water hypoxia/anoxia, a disturbance resulting from density stratification and anthropogenic eutrophication. Reduction of reef height caused by oyster dredging exposed the reefs located in deep water to hypoxia/anoxia for >2 wk, killing reef-associated invertebrate prey and forcing mobile fishes into refuge habitats. Refugee fishes accumulated at high densities on reefs in oxygenated shallow water, where they depleted epibenthic crustacean prey populations. Thus, physical disturbances can impact remote, undisturbed refuge habitats through the movement and abnormal concentration of refugee organisms that have subsequent strong trophic impacts. These results have implications for the design of Marine Protected Areas (MPAs), showing that reserves placed in proximity to disturbed areas may be impacted indirectly but may serve a critical refuge function on a scale that matches the mobility of consumers. C1 NOAA, Natl Ocean Serv, Ctr Coastal Fisheries & Habitat Res, Beaufort, NC 28516 USA. RP Lenihan, HS (reprint author), NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Newport, OR 97365 USA. RI Ross, Donald/F-7607-2012 OI Ross, Donald/0000-0002-8659-3833 NR 63 TC 138 Z9 139 U1 6 U2 50 PU ECOLOGICAL SOC AMER PI WASHINGTON PA 1707 H ST NW, STE 400, WASHINGTON, DC 20006-3915 USA SN 1051-0761 J9 ECOL APPL JI Ecol. Appl. PD JUN PY 2001 VL 11 IS 3 BP 764 EP 782 DI 10.2307/3061115 PG 19 WC Ecology; Environmental Sciences SC Environmental Sciences & Ecology GA 445KP UT WOS:000169456900011 ER PT J AU Steininger, MK Tucker, CJ Townshend, JRG Killeen, TJ Desch, A Bell, V Ersts, P AF Steininger, MK Tucker, CJ Townshend, JRG Killeen, TJ Desch, A Bell, V Ersts, P TI Tropical deforestation in the Bolivian Amazon SO ENVIRONMENTAL CONSERVATION LA English DT Article DE deforestation; Bolivia; Amazon; tropical forest; landsat ID BRAZILIAN AMAZON; FOREST FRAGMENTS; SATELLITE DATA; SANTA-CRUZ; CARBON; BIOMASS; BIODIVERSITY; COMMUNITIES; VEGETATION; REGROWTH AB The distributions of forest and deforestation throughout the tropics are poorly known despite their importance to regional biodiversity and global climate and biodiversity. Deforestation estimates based on surveys or sampling have large errors, and high-resolution, wall-to-wall mapping of tropical forests is necessary to assess the impacts of fragmentation. Landsat satellite images from the mid-1980s and early 1990s were thus used to map closed-canopy tropical forest extent and anthropogenic deforestation in an approximately 700 000 km(2) area of Amazonian Bolivia with precipitation > 1000mm yr(-1). Total potential forest cover extent, including tropical deciduous forest, was 448 700 km(2), while the area of natural non-forest formations was 245 100 km(2). The area deforested was 15 500 km(2) in the mid-1980s and 24 700 km(2) by the early 1990s. The rate of tropical deforestation in the forest zone of Bolivia with > 1000 mm yr(-1) precipitation below 1500 m elevation and north of 19 degrees S, was 1529 km(2) yr(-1) from 1985-1986 to 1992-1994. Our estimates of deforestation are significantly lower than those reported by the Food and Agriculture Organization of the United Nations (FAO). We document a spatially-concentrated 'deforestation zone' in Santa Cruz where > 60% of the Bolivian deforestation has occurred. These results indicate that the rate of deforestation in Bolivia has been rapid despite a relatively small human population, and, as in Brazil, clearance has concentrated in the more deciduous forests. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NASA, Landsat Pathfinder Trop Deforestat Project, College Pk, MD 20742 USA. Missouri Bot Garden, St Louis, MO 63166 USA. Museu Hist Nat Noel Kempff Mercado, Santa Cruz, Bolivia. RP Steininger, MK (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NR 82 TC 110 Z9 119 U1 5 U2 26 PU CAMBRIDGE UNIV PRESS PI PORT CHESTER PA 110 MIDLAND AVE, PORT CHESTER, NY 10573-9863 USA SN 0376-8929 J9 ENVIRON CONSERV JI Environ. Conserv. PD JUN PY 2001 VL 28 IS 2 BP 127 EP 134 PG 8 WC Biodiversity Conservation; Environmental Sciences SC Biodiversity & Conservation; Environmental Sciences & Ecology GA 458WV UT WOS:000170219200005 ER PT J AU Bock, O Schneider, S Bloomberg, J AF Bock, O Schneider, S Bloomberg, J TI Conditions for interference versus facilitation during sequential sensorimotor adaptation SO EXPERIMENTAL BRAIN RESEARCH LA English DT Article DE humans; sensorimotor integration; motor learning; sensorimotor adaptation; tracking ID MOTOR; MOVEMENTS; MEMORY; GAIN AB We investigated how sensorimotor adaptation acquired during one experimental session influenced the adaptation in a subsequent session. The subjects' task was to track a visual target using a joystick-controlled cursor, while the relationship between joystick and cursor position was manipulated to introduce a sensorimotor discordance. Each subject participated in two sessions, separated by a pause of 2 min to 1 month duration. We found that adaptation was achieved within minutes, and persisted in the memory for at least a month, with only a small decay (experiment A). When the discordances administered in the two sessions were in mutual conflict, we found evidence for task interference (experiment B). However, when the discordances were independent, we found facilitation rather than interference (experiment C); the latter finding could not be explained by the use of an "easier" discordance in the second session (experiment D). We conclude that interference is due to an incompatibility between task requirements, and not to a competition of tasks for short-term memory. We further conclude that the ability to adapt to a sensorimotor discordance can be improved by practicing with an unrelated discordance. C1 German Sport Univ, Inst Physiol, D-50927 Cologne, Germany. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Bock, O (reprint author), German Sport Univ, Inst Physiol, D-50927 Cologne, Germany. NR 21 TC 87 Z9 88 U1 0 U2 5 PU SPRINGER-VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0014-4819 J9 EXP BRAIN RES JI Exp. Brain Res. PD JUN PY 2001 VL 138 IS 3 BP 359 EP 365 DI 10.1007/s002210100704 PG 7 WC Neurosciences SC Neurosciences & Neurology GA 442UH UT WOS:000169303000009 PM 11460774 ER PT J AU Hare, JA Fahay, MP Cowen, RK AF Hare, JA Fahay, MP Cowen, RK TI Springtime ichthyoplankton of the slope region off the north-eastern United States of America: larval assemblages, relation to hydrography and implications for larval transport SO FISHERIES OCEANOGRAPHY LA English DT Article DE continental slope; Gulf Stream; larval assemblages; larval transport ID MIDDLE ATLANTIC BIGHT; BLUEFISH POMATOMUS-SALTATRIX; CORAL-REEF FISHES; GULF-STREAM; CONTINENTAL-SHELF; SPAWNING SEASONALITY; UROPHYCIS-TENUIS; PELAGIC STAGES; SCOTIAN SHELF; FLORIDA-KEYS AB Larval transport in the slope region off north-eastern North America influences recruitment to juvenile habitats for a variety of fishes that inhabit the continental shelf. In this study, collections of larval fishes were made during springtime over the continental slope to provide insights into larval distributions and transport. Ichthyoplankton composition and distribution mirrored the physical complexity of the region. Three larval fish assemblages were defined, each with different water mass distributions. A Gulf Stream assemblage was found predominantly in the Gulf Stream and associated with filaments of discharged Gulf Stream water in the Slope Sea. Larvae of this assemblage originated from oceanic and shelf regions south of Cape Hatteras. Several members of this assemblage utilize habitats in the Middle Atlantic Bight (MAB) as juveniles (Pomatomus saltatrix, Peprilus triacanthus) and other members of the assemblage may share this life cycle (Mugil curema, Sphyraena borealis, Urophycis regia). A Slope Sea assemblage was found in all water masses, and was composed of epi- and mesopelagic fish larvae, as well as larvae of benthic shelf/slope residents. Larvae of one member of this assemblage (U. tenuis) are spawned in the Slope Sea but cross the shelf-slope front and use nearshore habitats for juvenile nurseries. A MAB shelf assemblage was found in MAB shelf water and was composed of larvae that were spawned on the shelf. Some of these species may cross into the Slope Sea before returning to MAB shelf habitats (e.g. Enchelyopus cimbrius, Glyptocephalus cynoglossus). Previous studies have examined the effect of warm-core rings on larval distributions, but this study identifies the importance of smaller-scale features of the MAB shelf/slope front and of filaments associated with Gulf Stream meanders. In combination with these advective processes, the dynamic nature of larval distributions in the Slope Sea appears to be influenced, to varying degrees, by both vertical and horizontal behaviour of larvae and pelagic juveniles themselves. C1 NOAA, Natl Ocean Serv, Ctr Coastal Fisheries & Habitat Res, Beaufort, NC 28516 USA. NOAA, Natl Marine Fisheries Serv, Sandy Hook Lab, Highlands, NJ 07732 USA. SUNY Stony Brook, Marine Sci Res Ctr, Stony Brook, NY 11794 USA. RP Hare, JA (reprint author), NOAA, Natl Ocean Serv, Ctr Coastal Fisheries & Habitat Res, 101 Pivers Isl Rd, Beaufort, NC 28516 USA. NR 81 TC 39 Z9 42 U1 0 U2 4 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 JUN PY 2001 VL 10 IS 2 BP 164 EP 192 DI 10.1046/j.1365-2419.2001.00168.x PG 29 WC Fisheries; Oceanography SC Fisheries; Oceanography GA 464YE UT WOS:000170560300003 ER PT J AU Li, J Agee, CB AF Li, J Agee, CB TI The effect of pressure, temperature, oxygen fugacity and composition on partitioning of nickel and cobalt between liquid Fe-Ni-S alloy and liquid silicate: Implications for the Earth's core formation SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID TERRESTRIAL MAGMA OCEAN; SIDEROPHILE ELEMENTS; LOWER-MANTLE; PHASE-DIAGRAM; ALLENDE METEORITE; MASS-SPECTROMETRY; METAL; CONSTRAINTS; MELTS; DIFFERENTIATION AB Experiments have been conducted with a multi-anvil apparatus on two natural chondrites in four different sample containers. Partition coefficients for Ni and Co between liquid Fe-Ni-S-alloy and liquid silicate (D-Ni(LA/LS) and D-Co(LA/LS)) were determined over a pressure range between 2 and 25 GPa and a temperature range between 2100 and 2623 K. Multi-variable linear regression analysis was performed on the measured D-Ni(LA/LS) and D-Co(LA/LS) using a formula that is partially based on thermodynamics and partially empirical relationships. The results from the experiments with non-graphite capsules revealed that the effects of oxygen fugacity are roughly consistent with Ni and Co being divalent ions in liquid silicate. Within the experimental pressure and temperature ranges, both Ni and Co become less siderophile with increasing pressure and temperature. The effect of pressure is more pronounced for Ni while the effect of temperature is more pronounced for Co. Furthermore, both effects become smaller at higher pressures and higher temperatures, Nickel and Co are less soluble in liquid silicate with higher degree of polymerization. The presence of S in liquid Fe-alloy enhances the siderophile behavior of Ni and Co. However, for a given relative proportion of Fe, Ni and Co in the Fe-alloy, D-Ni(LA/LS) and D-Co(LA/LS) are larger for the Fe-alloy with a smaller S content. Applying the observed effects of pressure, temperature, oxygen fugacity and composition on D-Ni(LA/LS) and D-Co(LA/LS). we found that the observed partitioning of Ni and Co between core and mantle (D-Ni(core/mantle) and D-Co(core/mantle)) can be matched at high pressures and high temperatures. The pressure-temperature range corresponds to that in the current midmantle (about 1200-1450 km in depth). Therefore, the observed high abundances and near-chondritic ratio of Ni and Co in the Earth's upper mantle can be explained by chemical equilibrium between liquid Fe-Ni-S-alloy and liquid silicate in a deep magma ocean. Copyright (C) 2001 Elsevier Science Ltd. C1 Carnegie Inst Washington, Washington, DC 20015 USA. Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Li, J (reprint author), Carnegie Inst Washington, 5251 Broad Branch Rd NW, Washington, DC 20015 USA. NR 60 TC 113 Z9 116 U1 3 U2 34 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 JUN PY 2001 VL 65 IS 11 BP 1821 EP 1832 DI 10.1016/S0016-7037(00)00613-X PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 440AM UT WOS:000169150900010 ER PT J AU Richard, EC Aikin, KC Andrews, AE Daube, BC Gerbig, C Wofsy, SC Romashkin, PA Hurst, DF Ray, EA Moore, FL Elkins, JW Deshler, T Toon, GC AF Richard, EC Aikin, KC Andrews, AE Daube, BC Gerbig, C Wofsy, SC Romashkin, PA Hurst, DF Ray, EA Moore, FL Elkins, JW Deshler, T Toon, GC TI Severe chemical ozone loss inside the Arctic polar vortex during winter 1999-2000 inferred from in situ airborne measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LOWER STRATOSPHERE; DEPLETION; ANTARCTICA; TRANSPORT; TRENDS; MODEL; N2O AB Lower stratospheric in situ observations are used to quantify both the accumulated ozone loss and the ozone chemical loss rates in the Arctic polar vortex during the 1999-2000 winter. Multiple long-lived trace gas correlations are used to identify parcels in the inner Arctic vortex whose chemical loss rates are unaffected by extra-vortex intrusions. Ozone-tracer correlations are then used to calculate ozone chemical loss rates. During the late winter the ozone chemical loss rate is found to be -46 +/- 6 (1 sigma) ppbv/day. By mid-March 2000, the accumulated ozone chemical loss is 58 +/- 4 % in the lower stratosphere near 450 K potential temperature (similar to 19 km altitude). C1 NOAA, Aeron Lab, Boulder, CO 80309 USA. Univ Colorado, CIRES, Boulder, CO 80309 USA. Harvard Univ, Div Appl Sci, Cambridge, MA 02138 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Univ Wyoming, Dept Atmospher Sci, Laramie, WY 82071 USA. Jet Prop Lab, Pasadena, CA USA. RP Richard, EC (reprint author), NOAA, Aeron Lab, 325 Broadway, Boulder, CO 80309 USA. RI Ray, Eric/D-5941-2013; Aikin, Kenneth/I-1973-2013; Gerbig, Christoph/L-3532-2013; Hurst, Dale/D-1554-2016 OI Ray, Eric/0000-0001-8727-9849; Gerbig, Christoph/0000-0002-1112-8603; Hurst, Dale/0000-0002-6315-2322 NR 24 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 JUN 1 PY 2001 VL 28 IS 11 BP 2197 EP 2200 DI 10.1029/2001GL012878 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 434TB UT WOS:000168831000015 ER PT J AU Polito, PS Ryan, JP Liu, WT Chavez, FP AF Polito, PS Ryan, JP Liu, WT Chavez, FP TI Oceanic and atmospheric anomalies of tropical instability waves SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EQUATORIAL PACIFIC-OCEAN; ENERGETICS AB Tropical instability waves (TIWs) are detected in remotely-sensed sea surface height (SSH), temperature (SST), and wind records of the eastern equatorial Pacific. Analyses of TIW anomaly relationships reveal strong dynamical influence of TIWs within approximately 5 degrees of the equator. The first influence is advective heat flux. The primary forcing of TIW SST anomalies is advection of the meridional temperature gradient by TIW currents. The second influence is modification of the wind stress and Ekman pumping fields by TIW surface ocean currents. By affecting surface stress and hence roughness, TIW currents in this low-wind region introduce a significant bias in scatterometer vector wind measurement. This bias is evident in both NSCAT and QuikSCAT winds. The difference between wind measurements from TAO moorings and scatterometers is phase-locked with TIW SST oscillations. These results have important implications for scatterometry and for understanding tropical dynamics, thermodynamics and biogeochemistry. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Monterey Bay Aquarium Res Inst, Moss Landing, CA 95039 USA. RP Polito, PS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-323, Pasadena, CA 91109 USA. RI Polito, Paulo/F-3040-2013 OI Polito, Paulo/0000-0003-2217-3853 NR 16 TC 41 Z9 42 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 JUN 1 PY 2001 VL 28 IS 11 BP 2233 EP 2236 DI 10.1029/2000GL012400 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 434TB UT WOS:000168831000024 ER PT J AU Wu, XP Bar-Sever, YE Folkner, WM Williams, JG Zumberge, JF AF Wu, XP Bar-Sever, YE Folkner, WM Williams, JG Zumberge, JF TI Probing Europa's hidden ocean from tidal effects on orbital dynamics SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GALILEO AB Recent observations of Europa suggest that the Jovian satellite may have a liquid ocean underneath its icy surface. Geophysical models indicate that the tidal Love number k(2) has a strong dependence on the presence or absence of an ocean. The k(2) dependence on the ice shell thickness is also significant. Measurements of the static and tidal gravity fields through their dynamic effects on the trajectory of a low Europan orbiter can be essential in the detection of an ocean and inference of other internal structures. Covariance analyses have been carried out to assess accuracies using simulated Doppler tracking data. With 15 days of tracking from 2 Earth stations, the uncertainties for k(2), mantle libration amplitude and the epoch radial position of the spacecraft are expected to be 0.0004, 2.8 arcsec and 5.7 m, respectively. These tight constraints will strongly contribute to ocean detection and ice thickness determination when combined with altimeter measurements. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wu, XP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 24 Z9 24 U1 1 U2 11 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 JUN 1 PY 2001 VL 28 IS 11 BP 2245 EP 2248 DI 10.1029/2000GL012814 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 434TB UT WOS:000168831000027 ER PT J AU Binzel, RP Harris, AW Bus, SJ Burbine, TH AF Binzel, RP Harris, AW Bus, SJ Burbine, TH TI Spectral properties of near-earth objects: Palomar and IRTF results for 48 objects including spacecraft targets (9969) Braille and (10302) 1989 ML SO ICARUS LA English DT Article DE asteroids; composition; meteorites; surfaces; asteroids ID ORDINARY CHONDRITE METEORITES; MAIN-BELT; ASTEROIDS; DISCOVERY AB We present results of visible wavelength spectroscopic measurements for 48 near-Earth objects (NEOs) obtained with the 5-m telescope at Palomar Mountain Observatory during 1998, 1999, and early 2000. The compositional interpretations for 15 of these objects have been enhanced by the addition of near-infrared spectra obtained with the NASA Infrared Telescope Facility, One-third of our sampled objects fall in the Sq and Q classes and resemble ordinary chondrite meteorites. Overall our sample shows a cleat transition between S-type and Q-type compositional classes over visible and near-infrared wavelengths. Taken together these results point toward an abundance of near-Earth asteroids capable of providing sources for ordinary chondrite meteorites. Our sampling strategy favors targeting the smallest observable objects and we report results for the 15-m diameter object 1998 BT13, the smallest spectroscopically measured NEO to date. NEOs show a greater spectral diversity than main-belt asteroids, and our small sample includes objects falling in the rare categories of K, L, O, and V classes. The K-class object 1999 JD6 is found to match CV chondrite meteorites. Potential spacecraft targets received top priority for observation, with the ordinary chondrite-like composition of (9969) Braille being reported prior to the Deep Space-1 encounter. The relatively accessible asteroid (10302) 1989 ML displays a neutral spectrum that may be interpreted as a shock-darkened ordinary chondrite. (C) 2001 Academic Press. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. Jet Prop Lab, Pasadena, CA 91109 USA. Smithsonian Inst, Natl Museum Nat Hist, Dept Mineral Sci, Washington, DC 20560 USA. RP Binzel, RP (reprint author), MIT, Dept Earth Atmospher & Planetary Sci, 77 Massachusetts Ave, Cambridge, MA 02139 USA. NR 20 TC 84 Z9 84 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 JUN PY 2001 VL 151 IS 2 BP 139 EP 149 DI 10.1006/icar.2001.6613 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441PX UT WOS:000169239700001 ER PT J AU Milani, A Sansaturio, ME Chesley, SR AF Milani, A Sansaturio, ME Chesley, SR TI The asteroid identification problem IV: Attributions SO ICARUS LA English DT Article AB Existing archives of asteroid observations contain many objects with very short observed arcs, In this paper we present a method that we have used with considerable success to attribute these short are "discoveries" to other objects with better defined orbits. The method consists of a three-stage filtering process whereby several billion possible attribution/orbit pairs are systematically analyzed with more and more exact algorithms, at each stage rejecting improbable cases. The first stage compares an attributable, by definition a synthetic observation representative of all the observations over a short are, with the predicted observation for each available orbit. The second stage compares the proposed attributable observations with predicted positions from the known orbit using conventional linear covariance techniques, considering both the position and motion on the celestial sphere. In the final filter we attempt to compute a best-fitting orbit by differential corrections using the combined dataset, With this algorithm we have found 1675 attributions in approximately one year of operations, in addition to 902 identifications found with another algorithm. We discuss the lessons learned from this one-year experiment and the possibilities of further improvement and automation of the procedure. (C) 2001 Academic Press. C1 Univ Pisa, Dipartimento Matemat, I-56127 Pisa, Italy. Univ Valladolid, ETS Ingn Ind, E-47011 Valladolid, Spain. Jet Prop Lab, Navigat & Miss Design Sect, Pasadena, CA 91109 USA. RP Milani, A (reprint author), Univ Pisa, Dipartimento Matemat, Via Buonarroti 2, I-56127 Pisa, Italy. NR 6 TC 25 Z9 24 U1 0 U2 2 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 JUN PY 2001 VL 151 IS 2 BP 150 EP 159 DI 10.1006/icar.2001.6594 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441PX UT WOS:000169239700002 ER PT J AU Black, GJ Campbell, DB Ostro, SJ AF Black, GJ Campbell, DB Ostro, SJ TI Icy Galilean satellites: 70 cm radar results from Arecibo SO ICARUS LA English DT Article DE satellites of Jupiter; radar; Europa; Ganymede; Callisto AB The radar scattering properties of Europa, Ganymede, and Callisto are unlike those of any other object observed with planetary radars. At wavelengths of 3.5 cm and 13 cm most inner Solar System targets have low reffectivities on the order of 0.1, while the icy Galilean satellites are strongly backscattering with specific radar cross sections that can exceed unity (Campbell et al. 1978, Icarus 34, 254-267, Ostro et al. 1992, J. Geophys. Res. 97, 18227-18244). Their polarization ratios are also high, similar to1.5, indicative of multiple scattering, and the echoes follow a diffuse scattering law at all incident angles with no indication of the quasi-specular reflections characteristic of terrestrial planets and the Moon. We present observations that were made in 1988 and 1990 with the Arecibo radar at a much longer wavelength, 70 cm. The total cross sections measured at this wavelength are much lower than those measured at the shorter wavelengths. At 0.62 +/- 0.20 and 0.15 +/- 0.09, respectively, Ganymede's and Callisto's total normalized cross sections are a factor of 3 lower than their values at the short wavelengths. However, their 70-cm polarization ratios are greater than unity and consistent with those at the shorter wavelengths. Europa was not reliably detected at 70 cm and hence an upper limit on its total cross section is placed at 0.34, which is almost a factor of 10 lower than at the short wavelengths. Although all the 70-cm echoes are fairly weak and carry relatively large uncertainties, it appears unlikely that single reflections from the vacuum-surface interface are contributing significantly to the reflections, and hence the mechanism responsible for the radar scattering properties at 3.5 cm and 13 cm is still active at 70 cm, but apparently not operating as efficiently. (C) 2001 Academic Press. C1 NRAO, Green Bank, WV 24944 USA. Cornell Univ, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Black, GJ (reprint author), NRAO, POB 2, Green Bank, WV 24944 USA. NR 12 TC 16 Z9 16 U1 1 U2 3 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 JUN PY 2001 VL 151 IS 2 BP 160 EP 166 DI 10.1006/icar.2001.6615 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441PX UT WOS:000169239700003 ER PT J AU Rafkin, SCR Haberle, RM Michaels, TI AF Rafkin, SCR Haberle, RM Michaels, TI TI The Mars regional atmospheric modeling system: Model description and selected simulations SO ICARUS LA English DT Article DE Mars, atmosphere; atmospheres, dynamics; atmospheres, structure; Mars, surface ID GENERAL-CIRCULATION MODEL; CONVECTIVE BOUNDARY-LAYER; PATHFINDER LANDING SITE; LARGE-EDDY SIMULATIONS; MARTIAN SLOPE WINDS; GLOBAL DUST STORMS; SURFACE; DYNAMICS; TURBULENCE; VORTICES AB The Mars regional atmospheric modeling system (MRAMS) is introduced, and selected model results are presented and compared with landed meteorological data when possible. MRAMS is descended from a nonhydrostatic Earth mesoscale and cloud-scale model that is widely used for forecasting weather and simulating atmospheric systems over complex terrain. Mesoscale models such as MRAMS are ideal tools for making use of the high-resolution data sets arriving from Mars Global Surveyor experiments. Simulation of the Mars Pathfinder (MPF) landing site at L-s = 142 using 1/2 degree Mars orbiter laser altimeter (MOLA)-derived topography and thermal emission spectrometer thermal inertia is shown to be in good agreement with observed near-surface temperature, pressure, and wind direction. Simulations of topographically induced thermal circulations and mountain-induced gravity waves are shown to be consistent with theory and earlier studies that tie large-amplitude mountain waves to strong winds capable of producing dust streaks and local dust-lifting events. A large eddy simulation of the convective boundary layer provides estimates of vertical profiles of heat flux, momentum flux, turbulent kinetic energy, and vertical velocity variance. The model results suggest that the martian atmosphere is roughly two to three times more turbulent than the terrestrial atmosphere during the afternoon, but fluxes are roughly an order of magnitude smaller due to the lower density. Dust-devil-like circulations are also predicted in the large eddy simulation. Finally, a simulation that examines atmosphere-surface interactions near Big Crater is discussed. Predicted surface wind stress patterns are consistent with aeolian processes inferred through Mars Orbiter Camera imagery of Big Crater, located near the MPF landing site. (C) 2001 Academic Press. C1 San Jose State Univ, Dept Meteorol, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Rafkin, SCR (reprint author), San Jose State Univ, Dept Meteorol, 1 Washington Sq, San Jose, CA 95192 USA. NR 59 TC 125 Z9 124 U1 1 U2 8 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 JUN PY 2001 VL 151 IS 2 BP 228 EP 256 DI 10.1006/icar.2001.6605 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441PX UT WOS:000169239700009 ER PT J AU Stratman, PW Showman, AP Dowling, TE Sromovsky, LA AF Stratman, PW Showman, AP Dowling, TE Sromovsky, LA TI EPIC simulations of bright companions to Neptune's great dark spots SO ICARUS LA English DT Article DE atmospheric dynamics; atmospheric structure; meteorology; Neptune; atmosphere ID RED SPOT; CLOUD STRUCTURE; MODELS; METHANE; COORDINATE; ATMOSPHERE; ABUNDANCE; DYNAMICS; SYSTEM AB We present a three-dimensional model of the bright companion clouds associated with Neptune's Great Dark Spots (GDSs). Our results support the hypothesis that the bright companions of the southern-hemisphere GDS discovered in 1989 and of the northern-hemisphere GDS discovered in 1994 are methane clouds that form at or just below the tropopause and that they are caused by lifting in a manner analogous to the formation of orographic clouds. We vary the vertical position of the GDS and find that the companion cloud is a robust feature except when the anticyclone itself does not survive. When a GDS is started with its top in the stratosphere it drifts much too rapidly toward the equator and quickly disperses. On the other hand, if its top is well below the tropopause there is a tendency for the companion clouds to be too large. Hence the top of a GDS is probably at the tropopause. Along an open streamline that threads a bright companion, the typical pressure and temperature drops are about 3 mb and 1 R, respectively, corresponding to a lift of about half a kilometer or 4% of the pressure scale height, and the relative horizontal wind speed is about 45 m s(-1) eastward through the cloud. (C) 2001 Academic Press. C1 Univ Louisville, Comparat Planetol Lab, Louisville, KY 40292 USA. NASA, Ames Res Ctr, Natl Res Council, Moffett Field, CA 94035 USA. Univ Wisconsin, Ctr Space Sci & Engn, Madison, WI 53706 USA. RP Stratman, PW (reprint author), Univ Louisville, Comparat Planetol Lab, Louisville, KY 40292 USA. EM dowling@louisville.edu RI Dowling, Timothy/J-4537-2013 OI Dowling, Timothy/0000-0002-7400-2274 NR 30 TC 20 Z9 20 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 J9 ICARUS JI Icarus PD JUN PY 2001 VL 151 IS 2 BP 275 EP 285 DI 10.1006/icar.2001.6603 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441PX UT WOS:000169239700011 ER PT J AU Levison, HF Dones, L Chapman, CR Stern, SA Duncan, MJ Zahnle, K AF Levison, HF Dones, L Chapman, CR Stern, SA Duncan, MJ Zahnle, K TI Could the lunar "Late heavy bombardment" have been triggered by the formation of Uranus and Neptune? SO ICARUS LA English DT Review ID SHORT-PERIOD COMETS; OUTER SOLAR-SYSTEM; FRONT FACE BASINS; ASTEROID BELT; ICE DEPOSITS; KUIPER-BELT; COLLISIONAL EVOLUTION; PLANETARY MIGRATION; OBLIQUE IMPACTS; ABSOLUTE AGES AB We investigate the hypothesis that the so-called Late Heavy Bombardment (LHB) of the Moon was triggered by the formation of Uranus and Neptune. As Uranus and Neptune formed, which we assume occurred at the epoch of the LHB, they scattered neighboring icy planetesimals throughout the Solar System. Some of these objects hit the Moon. Our integrations show that the Moon would have accreted about 6 x 10(21) g, if we assume that the Uranus-Neptune region initially contained 5 times the current mass of these planets in the form of small solid objects. In addition, Mars would have accumulated similar to6 x 10(22) g of icy material, which could have supplied its putative early massive atmosphere. However, Earth would likely have accreted only similar to7 x 10(22) g of water, or similar to5% of its oceans, through the mechanisms studied here. The numerical experiment that we have performed on the behavior of Uranus-Neptune planetesimals shows very good agreement with current constraints on the LHB. The influx of Uranus-Neptune planetesimals onto the Moon could have lasted for a time as short as 10 or 20 million years. The dynamical transport of the Uranus-Neptune planetesimals during this process would have caused Jupiter and Saturn to migrate. This migration, in turn, would have destabilized objects in the jovian Trojan swarms and the asteroid belt. Thus, not only would Uranus and Neptune planetesimals have struck the Moon, but asteroids would have as well. We find that the Trojan asteroids of Jupiter could not have contributed a large percentage of material to the LHB, but the asteroid belt could, in principle, have contributed to, or even dominated, the LHB, Although this model appears to explain the LHB well, it requires that fully formed Uranus and Neptune not appear in the trans-saturnian region until some 700 million years after the formation of the Earth. (C) 2001 Academic Press. C1 SW Res Inst, Space Studies Dept, Boulder, CO 80302 USA. Queens Univ, Dept Phys, Kingston, ON K7L 3N6, Canada. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Levison, HF (reprint author), SW Res Inst, Space Studies Dept, Boulder, CO 80302 USA. EM hal@gort.boulder.swri.edu RI Levison, Harold/C-6061-2013 OI Levison, Harold/0000-0001-5847-8099 NR 134 TC 113 Z9 113 U1 1 U2 10 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 JUN PY 2001 VL 151 IS 2 BP 286 EP 306 DI 10.1006/icar.2001.6608 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441PX UT WOS:000169239700012 ER PT J AU Pryor, WR Stewart, AIF Simmons, KE Ajello, JM Tobiska, WK Clarke, JT Gladstone, GR AF Pryor, WR Stewart, AIF Simmons, KE Ajello, JM Tobiska, WK Clarke, JT Gladstone, GR TI Detection of rapidly varying H-2 emissions in Jupiter's aurora from the Galileo orbiter SO ICARUS LA English DT Article DE Jupiter, atmosphere; Jupiter, magnetosphere; aurorae ID ULTRAVIOLET SPECTROMETER; JOVIAN AURORA; SPECTRUM AB H-2 band emissions in Jupiter's northern auroral region at 1240 Angstrom were highly variable on time scales of a few seconds in Galileo ultraviolet spectrometer (UVS) recorded data from November 5, 1996 (7:25:29 to 7:34:30 spacecraft event time (SCET)) during orbit Callisto-3 (C3), Emission at 1611 Angstrom varied in phase with 1240 Angstrom emission, but was much weaker. The 1240 and 1611 Angstrom variability are evidence that the precipitating particles have a highly variable flux, The estimated 1611 Angstrom /1240 Angstrom photon flux ratio of 1.82 +/- 0.07 (after background subtraction) is consistent with auroral penetration of a slant column depth in CH4 of (3.5 +/- 0.2) x 10(16) cm(-2). UVS observed both the main auroral are and the polar cap region on the day side. The slit-averaged brightness at 1240 and 1611 Angstrom increased by almost a factor of 2 on two occasions with durations (full-width at half-maximum) of order 100 s. A similar observation of the south polar aurora near the dawn terminator during Galileo orbit Ganymede-8 on May 6, 1997 (13:16:32 to 13:32:42 SCET) found both the 1240 and 1611 Angstrom emissions to be more steady and gradually increasing. The variable 1240 and 1611 Angstrom emissions seen on orbit C3 may be similar to variable polar cap "flares" reported in recent Hubble Space Telescope (HST) ultraviolet images of Jupiter from the new Space Telescope imaging spectrograph. (C) 2001 Academic Press. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Jet Prop Lab, Pasadena, CA 91109 USA. Fed Data Corp, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. SW Res Inst, San Antonio, TX 78228 USA. RP Pryor, WR (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80303 USA. RI Clarke, John/C-8644-2013 NR 19 TC 8 Z9 8 U1 0 U2 2 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 JUN PY 2001 VL 151 IS 2 BP 314 EP 317 DI 10.1006/icar.2001.6604 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441PX UT WOS:000169239700014 ER PT J AU Otoshi, TY Rahmat-Samii, Y Cirillo, R Sosnowski, J AF Otoshi, TY Rahmat-Samii, Y Cirillo, R Sosnowski, J TI Noise temperature and gain loss due to paints and primers: A case study of DSN antennas SO IEEE ANTENNAS AND PROPAGATION MAGAZINE LA English DT Article DE coatings; paints; primers; non-homogeneous media; reflector antennas; multi-reflector antennas; polarization; noise temperature; excess noise temperature; gain loss; antenna gain; gain measurement ID REFLECTOR AB in achieving high performance for reflector antennas, it has been noted that it is essential to carefully assess the roles of surface paints and primers. A thorough literature search has revealed that not much has been reported on this very important engineering-implementation topic. It is one of the main objectives of this feature article to provide a detailed study on the effects of paints and primers on reflector-antenna performance. In particular, as a case study, this paper presents excess-noise-temperature and added-gain loss data at 32 GHz for various combinations of paints and primers currently being studied for use on DSN (Deep Space Network) antenna reflector surfaces. It is shown that 500FHR6 acrylic urethane-based paint has the lowest excess-noise-temperature contribution. Recently, it has been recommended that this paint be used for all new DSN beam-waveguide antennas being constructed, and for all those 34-m and 70-m antennas with reflector surfaces that need repainting. The results, methodologies, and observations presented in this article are also applicable to other reflector-antenna configurations. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90094 USA. RP Otoshi, TY (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM tyo@jpl.nasa.gov; Rahmat-Samii@jpl.nasa.gov; Richard.Cirillo@jpl.nasa.gov; John.B.Sosnowski@jpl.nasa.gov NR 24 TC 1 Z9 1 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1045-9243 EI 1558-4143 J9 IEEE ANTENN PROPAG M JI IEEE Antennas Propag. Mag. PD JUN PY 2001 VL 43 IS 3 BP 11 EP 28 DI 10.1109/74.934900 PG 18 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 451BL UT WOS:000169781200002 ER PT J AU Lau, WC Alouini, MS Simon, MK AF Lau, WC Alouini, MS Simon, MK TI Optimum spreading bandwidth for selective RAKE reception over Rayleigh fading channels SO IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS LA English DT Article DE diversity combining; generalized selection combining; hybrid SC/MRC; maximal ratio combining; RAKE reception; Rayleigh fading; selection combining; spreading bandwidth; ultrawideband radio ID DENSE MULTIPATH CHANNELS; DIVERSITY COMBINING TECHNIQUES; PERFORMANCE ANALYSIS AB Building on the recent developments in the performance analysis of generalized selection combining (GSC), this paper examines the optimum spreading bandwidth for a fixed-complexity GSC diversity receiver operating over independent identically distributed Rayleigh paths. For this purpose, the study considers three performance criteria: 1) average combined signal-to-noise ratio (SNR) at the GSC output; 2) average bit error probability (BEP); and 3) outage probability of the instantaneous combined SNR at the GSC output. For the average BEP criterion, results are presented for both coherent and noncoherent combining. For the average combined SNR and some instances of the average BEP optimization problem, an accurate approximate estimate of this optimum bandwidth in the form of a solution of a transendental equation is provided. In other cases, where the optimization is not easily tractable in an analytic fashion, a numeric-search procedure is used to find this optimum bandwidth for different performance criteria and system parameters of interest, Finally, simplified rule-of-thumb-type formulas are also presented as a good reference for picking the optimum spreading bandwidth given a set of system parameters and a particular performance criterion of interest. C1 Univ Minnesota, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA. Jet Prop Lab, Pasadena, CA 91109 USA. RP Lau, WC (reprint author), Univ Minnesota, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA. NR 29 TC 15 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 0733-8716 J9 IEEE J SEL AREA COMM JI IEEE J. Sel. Areas Commun. PD JUN PY 2001 VL 19 IS 6 BP 1080 EP 1089 PG 10 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 439PQ UT WOS:000169126600010 ER PT J AU Radisic, V Micovic, M Hu, M Janke, P Ngo, C Nguyen, L Samoska, L Morgan, M AF Radisic, V Micovic, M Hu, M Janke, P Ngo, C Nguyen, L Samoska, L Morgan, M TI 164-GHz MMIC HEMT doubler SO IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS LA English DT Article DE MMIC frequency converters; MODFETs AB In this letter, a MMIC frequency doubler based on InP HEMT and grounded CPW (GCPW) technology is reported. The doubler demonstrated a conversion loss of only 2 dB and output power of 5 dBm at 164 GHz, The 3-dB output power bandwidth is 14 GHz, or 8,5%, This is the best reported result for a MMIC HEMT doubler above 100 GHz. C1 HRL Labs LLC, Malibu, CA 90265 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Pasadena, CA 91125 USA. RP Radisic, V (reprint author), HRL Labs LLC, Malibu, CA 90265 USA. NR 5 TC 22 Z9 23 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 1531-1309 J9 IEEE MICROW WIREL CO JI IEEE Microw. Wirel. Compon. Lett. PD JUN PY 2001 VL 11 IS 6 BP 241 EP 243 DI 10.1109/7260.928925 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 443YA UT WOS:000169370100001 ER PT J AU Koppen, M Wolpert, DH Macready, WG AF Koppen, M Wolpert, DH Macready, WG TI Remarks on a recent paper on the '' No free lunch '' theorems SO IEEE TRANSACTIONS ON EVOLUTIONARY COMPUTATION LA English DT Letter DE algorithms; genetic algorithms; knowledge representation; learning systems AB This letter discusses the recent paper "Some technical remarks on the proof of the 'No Free Lunch' theorem," In that paper, some technical issues related to the formal proof of the no free lunch (NFL) theorem for search were given by Wolpert and Macready (1995 and 1997). As a result of a discussion among the authors, this letter explores the issues raised in that paper more thoroughly. This includes the presentation of a simpler version of the NFL proof in accord with a suggestion made explicitly by Koppen (2000) and implicitly by Wolpert and Macready (1997). It also includes the correction of an incorrect claim made by Koppen (2000) of a limitation of the NFL theorem. Finally, some thoughts on future research directions for research into algorithm performance are given. C1 Fraunhofer IPK, D-10587 Berlin, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Bios Grp Inc, Santa Fe, NM 87501 USA. RP Koppen, M (reprint author), Fraunhofer IPK, D-10587 Berlin, Germany. RI Koppen, Mario/I-2749-2012 NR 6 TC 21 Z9 23 U1 1 U2 11 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1089-778X J9 IEEE T EVOLUT COMPUT JI IEEE Trans. Evol. Comput. PD JUN PY 2001 VL 5 IS 3 BP 295 EP 296 DI 10.1109/4235.930318 PG 2 WC Computer Science, Artificial Intelligence; Computer Science, Theory & Methods SC Computer Science GA 445ND UT WOS:000169463200009 ER PT J AU McClamroch, NH Sridhar, B AF McClamroch, NH Sridhar, B TI Guest editorial - Special issue on automated air traffic control systems SO IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS LA English DT Editorial Material C1 Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP McClamroch, NH (reprint author), Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA. NR 0 TC 2 Z9 2 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 1524-9050 J9 IEEE T INTELL TRANSP JI IEEE Trans. Intell. Transp. Syst. PD JUN PY 2001 VL 2 IS 2 BP 37 EP 38 AR PII S1524-9050(01)04971-7 PG 2 WC Engineering, Civil; Engineering, Electrical & Electronic; Transportation Science & Technology SC Engineering; Transportation GA 529GW UT WOS:000174292500001 ER PT J AU Cheng, VHL Sharma, V Foyle, DC AF Cheng, VHL Sharma, V Foyle, DC TI A study of aircraft taxi performance for enhancing airport surface traffic control SO IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS LA English DT Article DE active-runway crossing; aircraft taxi control; air traffic management; nonlinear control; runway incursion; surface movement ID HELICOPTER AB In view of the ever-increasing air traffic, much attention in air traffic management research has been given to improving arrival and departure efficiency. As air traffic begins and ends at the airport, the issues of taxi delays and ground incursions are becoming more evident. This paper considers the surface-traffic problem at major airports and envisions a collaborative traffic and aircraft control environment where a surface traffic automation system will help coordinate surface traffic movements. Specifically, this paper studies the performance potential of high-precision tax! toward the realization of such an environment. A state-of-the-art nonlinear control system based on feedback linearization is designed for a detailed B-737 aircraft taxi model. The simulation model with the nonlinear control system is evaluated extensively in a scenario representing the demanding situation of an arrival aircraft crossing an adjacent active runway immediately following its own landing. The evaluation establishes the potential of an automated system to achieve high-precision taxi control, including the ability to comply with taxi clearances with tight time margins. Such a high-precision taxi capability reduces the time margin required for clearing taxiing aircraft to cross active runways, thus increasing the opportunity for issuing such clearances, which in turn reduces the need for aircraft to hold short at the runways to wait for the opportunity for crossing. The results from the analyses provide insight into future aircraft operational capabilities toward the design of the envisioned surface traffic automation system. Moreover, the nonlinear control design serves as a preliminary study for future auto-taxi functional development. C1 Opt Synth Inc, Los Altos, CA 94022 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Cheng, VHL (reprint author), Opt Synth Inc, Los Altos, CA 94022 USA. NR 31 TC 30 Z9 36 U1 2 U2 9 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1524-9050 J9 IEEE T INTELL TRANSP JI IEEE Trans. Intell. Transp. Syst. PD JUN PY 2001 VL 2 IS 2 BP 39 EP 54 AR PII S1524-9050(01)04966-3 DI 10.1109/6979.928715 PG 16 WC Engineering, Civil; Engineering, Electrical & Electronic; Transportation Science & Technology SC Engineering; Transportation GA 529GW UT WOS:000174292500002 ER PT J AU Mao, ZH Feron, E Bilimoria, K AF Mao, ZH Feron, E Bilimoria, K TI Stability and performance of intersecting aircraft flows under decentralized conflict avoidance rules SO IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS LA English DT Article ID RESOLUTION; MANAGEMENT AB This paper considers the problem of two intersecting aircraft flows under decentralized conflict resolution rules. Considering aircraft flowing through a fixed control volume, new air traffic control models and scenarios are defined that enable the study or long-term aircraft flow stability. For a class or two intersecting aircraft flows, this paper considers conflict scenarios involving arbitrary encounter angles. It is shown that aircraft flow stability, defined both in terms of safety and performance, is preserved under the decentralized conflict resolution algorithm considered in this paper. It is shown that the lateral deviations experienced by aircraft in each now are bounded. C1 MIT, Informat & Decis Syst Lab, Dept Aeronaut & Astronaut, Int Ctr Air Transportat, Cambridge, MA 02139 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Mao, ZH (reprint author), MIT, Informat & Decis Syst Lab, Dept Aeronaut & Astronaut, Int Ctr Air Transportat, 77 Massachusetts Ave, Cambridge, MA 02139 USA. EM feron@mit.edu; kbilimoria@mail.arc.nasa.gov NR 24 TC 25 Z9 31 U1 1 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1524-9050 J9 IEEE T INTELL TRANSP JI IEEE Trans. Intell. Transp. Syst. PD JUN PY 2001 VL 2 IS 2 BP 101 EP 109 AR PII S1524-9050(01)04968-7 DI 10.1109/6979.928721 PG 9 WC Engineering, Civil; Engineering, Electrical & Electronic; Transportation Science & Technology SC Engineering; Transportation GA 529GW UT WOS:000174292500008 ER PT J AU Zhang, LYY Zhu, KJJ Zhu, RY Liu, DT AF Zhang, LYY Zhu, KJJ Zhu, RY Liu, DT TI Monitoring light source for CMS lead tungstate crystal calorimeter at LHC SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT Annual Nuclear Science Symposium (NSS) CY OCT 15-20, 2000 CL LYON, FRANCE SP IEEE, CEA, IN2P3, CERN DE calibration; crystal; laser; monitoring; radiation damage ID RADIATION-DAMAGE; SCINTILLATING CRYSTALS AB Light monitoring will serve as an intercalibration for compact muon solenoid (CMS) lead tuna tate crystals in situ at the large hadronic collider, which is crucial for maintaining crystal calorimeter's subpercent constant term in the energy resolution. This paper presents the design of the CMS electromagnetic calorimeter monitoring light source and high-level distribution system. The correlations between variations of the light output and the transmittance for the CMS choice of yttrium-doped PbWO4 crystals were investigated and were used to study monitoring linearity and sensitivity as a function of wavelength. The monitoring wavelength was determined so that a good linearity as well as adequate sensitivity can be achieved. The performance of a custom manufactured tunable laser system is presented. Issues related to monitoring precision are discussed. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zhang, LYY (reprint author), CALTECH, Pasadena, CA 91125 USA. NR 12 TC 16 Z9 16 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 JUN PY 2001 VL 48 IS 3 BP 372 EP 378 DI 10.1109/23.940083 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 465EG UT WOS:000170576200028 ER PT J AU Ting, DZY Bandara, SV Gunapala, SD Liu, JK Rafol, SB Mumolo, JM AF Ting, DZY Bandara, SV Gunapala, SD Liu, JK Rafol, SB Mumolo, JM TI Wave function engineering for normal incidence intersubband infrared detection SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab DE intersubband; quantum well; infrared detector; normal incidence; submonolayer insertion ID HIGH-INDEX SURFACES; OPTICAL CHARACTERIZATION; GAAS MATRIX; SUBMONOLAYER AB We propose a new intersubband infrared photodetector concept, the island insertion infrared detector ((ID)-D-3), with the aim of achieving improved normal incidence absorption characteristics over the quantum well infrared photo-detector (QWIP). The lack of normal incidence absorption in typical QWIP structures is the direct consequence of the in-plane translational symmetry of the quantum well. The active region of our proposed detector structure consists of a quantum well as in QWIPs, but inserted with submonolayers (SMLs) of a lattice mismatched semiconductor. The insertion of SMLs should not disrupt epitaxial growth, while the presence of strain would promote the formation of embedded islands. The embedded islands introduce lateral (in-plane) variations in the quantum well wave function, which in turn enhance inter-conduction-subband absorption of normal incidence radiation. Specific implementations include the insertion of SMLs of InAs, InSb, GaSb, AlSb, or AlAs in GaAs quantum wells. Results of preliminary model calculations show that InAs island insertions can indeed induce substantial lateral variations in GaAs quantum well wave functions, provided that the island sizes are comparable to or larger than the electron deBroglie wavelength. Our results also suggest that optimization of normal incidence absorption would likely require the use of multiple SML insertions at different positions along the quantum well. These promising initial results suggest that the island insertion infrared detector concept merits further theoretical and experimental investigations. (C) 2001 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ting, DZY (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 3 Z9 3 U1 1 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 205 EP 210 DI 10.1016/S1350-4495(01)00078-0 PG 6 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200013 ER PT J AU Bandara, S Gunapala, S Rafol, S Ting, D Liu, J Mumolo, J Trinh, T Liu, AWK Fastenau, JM AF Bandara, S Gunapala, S Rafol, S Ting, D Liu, J Mumolo, J Trinh, T Liu, AWK Fastenau, JM TI Quantum well infrared photodetectors for low background applications SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab DE long wavelength infrared; detectors; quantum wells; imaging ID TEMPERATURE DARK CURRENT; MODEL; GAIN AB Quantum well infrared photodetectors (QWIPs) afford greater flexibility than the usual extrinsically doped semiconductor IR detectors. The wavelength of the peak response and cutoff can be continuously tailored over any wavelength range between 6-20 mum. The spectral band width of these detectors can be tuned from narrow (Delta lambda/lambda similar to 10%) to wide (Delta lambda/lambda similar to 40%) allowing various applications. Also, QWIP device parameters can be optimized to achieve extremely high performances at high back ground at lower operating temperatures (similar to 30 K). However, for low-background irradiance levels at low operating temperatures, high resistivity of the active region could leads to nonlinear responsivity behavior. A new structure with a photosensitive superlattice and a thick blocking barrier has been tested, and is expected to avoid anomalous behavior under low backgrounds at low temperatures. (C) 2001 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. IEQ Inc, Bethlehem, PA 18015 USA. RP Bandara, S (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 8 Z9 8 U1 0 U2 1 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 237 EP 242 DI 10.1016/S1350-4495(01)00081-0 PG 6 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200016 ER PT J AU Gunapala, SD Bandara, SV Liu, JK Luong, EM Rafol, SB Mumolo, JM Ting, DZ Bock, JJ Ressler, ME Werner, MW LeVan, PD Chehayeb, R Kukkonen, CA Levy, M LeVan, P Fauci, MA AF Gunapala, SD Bandara, SV Liu, JK Luong, EM Rafol, SB Mumolo, JM Ting, DZ Bock, JJ Ressler, ME Werner, MW LeVan, PD Chehayeb, R Kukkonen, CA Levy, M LeVan, P Fauci, MA TI Quantum well infrared photodetector research and development at Jet Propulsion Laboratory SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab DE infrared detectors; long-wavelength infrared; multi-quantum well; multi-color; focal plane arrays ID FOCAL-PLANE ARRAY; QWIP ARRAY; CAMERA; FABRICATION AB One of the simplest device realizations of the classic particle-in-the-box problem of basic quantum mechanics is the quantum well infrared photodetector (QWIP). In this paper, we discuss the effect of focal plane array nonuniformity on the performance, optimization of the detector design, material growth and processing that has culminated in realization of large format long-wavelength QWIP cameras, holding forth great promise for many applications in 6-18 mum wavelength range in science, medicine, defense and industry, In addition, we present the recent developments in long-wavelength/very long-wavelength dualband QWIP imaging camera for various applications. (C) 2001 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. USAF, Res Lab, Kirtland AFB, NM 87117 USA. Univ So Calif Hosp, Los Angeles, CA 90027 USA. QWIP Technol, Altadena, CA 91001 USA. OmniCorder Technol Inc, Stony Brook, NY 11790 USA. RP Gunapala, SD (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, M-S 302-306, Pasadena, CA 91109 USA. EM sarah.d.gunapala@jpl.nasa.gov NR 29 TC 22 Z9 26 U1 1 U2 4 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 267 EP 282 DI 10.1016/S1350-4495(01)00085-8 PG 16 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200020 ER PT J AU Fauci, MA Breiter, R Cabanski, W Fick, W Koch, R Ziegler, J Gunapala, SD AF Fauci, MA Breiter, R Cabanski, W Fick, W Koch, R Ziegler, J Gunapala, SD TI Medical infrared imaging - differentiating facts from fiction, and the impact of high precision quantum well infrared photodetector camera systems, and other factors, in its reemergence SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab ID BREAST THERMOGRAPHY; CANCER AB Through most of the 1970s infrared medical imaging was viewed as an exciting and very promising new imaging technology, for a variety of potential diagnostic applications, by the US clinical community. Infrared technology subsequently disappeared from US medical practice. This was due to a number of reasons including inflated expectations, technical immaturity as well as substantial amount of misinformation. But new technical developments, such as high precision quantum well infrared photodetector camera systems, and the changing commercial and political environment, are ushering in a renaissance of medical infrared imaging. (C) 2001 Published by Elsevier Science B.V. C1 OmniCorder Technol Inc, Stony Brook, NY 11790 USA. AEG Infrarot Module GmbH, D-74072 Heilbronn, Germany. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Fauci, MA (reprint author), OmniCorder Technol Inc, 25 E Loop Rd, Stony Brook, NY USA. NR 16 TC 17 Z9 17 U1 0 U2 1 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 337 EP 344 DI 10.1016/S1350-4495(01)00093-7 PG 8 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200028 ER PT J AU Reininger, FM AF Reininger, FM TI The application of large format, broadband quantum well infrared photodetector arrays to spatially modulated prism interferometers SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab ID FOURIER-TRANSFORM SPECTROMETER; IMAGING SPECTROMETER; PHOTODIODE ARRAY; CAMERA; MARS AB The spatially modulated prism interferometer (SMPI) is a new type of imaging interferometer that has double the efficiency of conventional interferometers and only a fraction of the mass and volume. Its spectral resolution is independent of wavelength and slit width, an attribute made possible by generating interferograms at a pupil plane. It uses a large format, broadband quantum well infrared photodetector array to scan the interferograms digitally without moving any optical components. This enables the interferometer to make accurate measurements of target scenes that fluctuate during the scan period. Applications include detecting water sources on Mars, monitoring global warming and ozone depletion on Earth, monitoring pollution in cities, detecting chemical agents on the battlefield, and warning commercial aircraft of volcanic eruptions. (C) 2001 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Reininger, FM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 21 TC 14 Z9 14 U1 0 U2 3 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 345 EP 362 DI 10.1016/S1350-4495(01)00094-9 PG 18 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200029 ER PT J AU Jhabvala, M AF Jhabvala, M TI Applications of GaAs quantum well infrared photoconductors at the NASA/Goddard Space Flight Center SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab AB Prior to 1990 large format, hybridized GaAs quantum well infrared photoconductors (QWIP) arrays had not been fabricated. In a unique collaboration between the Goddard Space Flight Center, ATT/Bell Labs and the Rockwell Science Center we designed and built a 128 x 128 element GaAs/AlGaAs QWIP array, developed a continuous flow liquid helium cooler/camera system and successfully performed airborne imaging test flights over the Wallops Flight Facility. As a result of work performed at Lockheed Martin of Dallas, Texas a 256 x 256 QWIP was developed and Goddard obtained a unit for a second-generation camera system. A more compact imaging system was developed which could operate with a liquid nitrogen dewar. This instrument was used as part of the joint NASA/Southern African Fire-Atmosphere Research Initiative campaign to gather airborne terrestrial science information. This system was also used to evaluate the emission/reflectance properties of commercially available pyrgeometers and pyranometers. These radiometers rely on constants for the filter dome and the detector which are key in making absolute measurements. In an effort to improve the optical coupling efficiency and also to develop QWIPs with sensitivity beyond 11 mum a partnership has been established between Goddard and the Army Research Laboratory (ARL). By corrugating the surface of the QWIP array, normal incidence radiation is deflected almost horizontally allowing for absorption in the quantum wells. Most recently, a joint Goddard/Jet Propulsion Laboratory/ARL proposal to develop a four band, hyperspectral, 512 x 640 QWIP array has been funded by the Earth Science Technology Office of NASA. This three year effort will focus on expanding the integrated QWIP spectral imaging capability, utilizing a new Sunpower, Inc. cryocooler and developing a linear variable etalon to produce the hyperspectral image from 3 to 15.4 mum. The four IR bands are (1) 3-5 mum, (2) 8.5-10 mum, (3) 10-12 mum and (4) 14-15.4 mum. These four bands are spectrally subdivided into approximately 200 bands. This paper will discuss these efforts in general with an emphasis on the system performance. (C) 2001 Published by Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Instrument Technol Ctr, Greenbelt, MD 20771 USA. RP Jhabvala, M (reprint author), NASA, Goddard Space Flight Ctr, Instrument Technol Ctr, Greenbelt, MD 20771 USA. NR 10 TC 15 Z9 15 U1 0 U2 1 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 363 EP 376 DI 10.1016/S1350-4495(01)00095-0 PG 14 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200030 ER PT J AU Ressler, ME Bock, JJ Bandara, SV Gunapala, SD Werner, MW AF Ressler, ME Bock, JJ Bandara, SV Gunapala, SD Werner, MW TI Astronomical imaging with quantum well infrared photodetectors SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab DE Astronomical instruments; Mid-infrared detectors AB Quantum well infrared photodetectors (QWIPs) are attractive for use in astronomy because they offer good sensitivity, are very stable, are easily manufactured in large sizes, and have (comparatively) warm operating temperatures. We describe an astronomical camera based on an 8.5 muM QWIP array which built at the Jet Propulsion Laboratory and is operated at the Palomar 5-m telescope. We highlight some science results obtained with this instrument, then discuss the prospects for QWIP arrays in future NASA astronomy missions. (C) 2001 Published by Elsevier Science B.V. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ressler, ME (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 5 TC 8 Z9 8 U1 0 U2 1 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 377 EP 383 DI 10.1016/S1350-4495(01)00096-2 PG 7 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200031 ER PT J AU Kenny, JT Pollock, HR AF Kenny, JT Pollock, HR TI STRV-1d QWIP technology validation in space flight SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab AB New technologies are arriving on the scene that promise enhancement or new capabilities. Some of these technologies have potential for NASA and DOD space-based applications. In these cases, the technology must be demonstrated and Validated to a degree that risk may be balanced for the space mission roles. Quantum well infrared photo-detector (QWIP) is one of these technologies. QWIP has a variety of space-based applications in the 8 to 16 mum wavelength range. Radiation tolerance and higher operating temperature are potentially significant benefits for long duration missions. In this paper, we describe the selection of and preparation for a mission that provides the opportunity to demonstrate and validate QWIP focal plane arrays in the natural, space radiation environment. We discuss the objectives of this demonstration opportunity, and the development and test steps required to deliver the QWIP experiment to space. (C) 2001 Published by Elsevier Science B.V. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kenny, JT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 2 TC 2 Z9 2 U1 0 U2 1 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 385 EP 390 DI 10.1016/S1350-4495(01)00097-4 PG 6 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200032 ER PT J AU Kukkonen, CA Sirangelo, MN Chehayeb, R Kaufmann, M Liu, JK Rafol, SB Gunapala, SD AF Kukkonen, CA Sirangelo, MN Chehayeb, R Kaufmann, M Liu, JK Rafol, SB Gunapala, SD TI Commercialization of quantum well infrared photodetector focal plane arrays SO INFRARED PHYSICS & TECHNOLOGY LA English DT Article; Proceedings Paper CT Workshop on Quantum Well Infrared Photodetectors (QWIP 2000) CY JUL 27-29, 2000 CL DANA POINT, CALIFORNIA SP NASA Breakthrough Sensors, Instrument Component Technol Thrust, Jet Propulsion Lab Ctr, Integrat Space Microsyst, Air Force Res Lab, Army Res Lab ID CAMERA AB Many commercial and government applications need high performance, large format, long-wavelength infrared (LWIR) detector arrays in the range of 6-20 mum NASA and the ballistic missile defense organization (BMDO) have devoted a significant effort to develop highly sensitive infrared (IR) detectors and large format focal plane arrays (FPAs) based on novel 'artificial low effective bandgap semiconductor material systems such as GaAs/AlGaAs. Caltech's Jet propulsion laboratory (JPL) under contract from NASA and BMDO has extensively pursued GaAs/AlGaAs based multi-quantum wells (MQWs) for IR radiation detection. Optimization of the detector design, light coupling schemes, large format FPA fabrication and packaging techniques have culminated in the realization of portable LWIR cameras with a mid format (256 x 256 pixel) FPA of QWIP detectors and the demonstration of TV format (i.e., 640 x 486) QWIP camera. QWIP technologies LLC, under an exclusive agreement with Caltech is currently manufacturing the QWIP-Chip(TM), a 320 x 256 element FPA. In this, presentation, we will discuss the advantages of MQW technology and our experience in the commercialization of QWIP FPAs. (C) 2001 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Microelect Technol, Pasadena, CA 91109 USA. QWIP Technol, Altadena, CA 91001 USA. RP Kukkonen, CA (reprint author), CALTECH, Jet Prop Lab, Microelect Technol, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 8 Z9 10 U1 0 U2 3 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 JUN-OCT PY 2001 VL 42 IS 3-5 BP 397 EP 405 DI 10.1016/S1350-4495(01)00099-8 PG 9 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 444KG UT WOS:000169398200034 ER PT J AU Sterling, T AF Sterling, T TI An introduction to PC clusters for high performance computing SO INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS LA English DT Editorial Material C1 CALTECH, Ctr Adv Comp Res, Pasadena, CA 91125 USA. NASA, Jet Prop Lab, Washington, DC 20546 USA. RP Sterling, T (reprint author), CALTECH, Ctr Adv Comp Res, Pasadena, CA 91125 USA. NR 0 TC 5 Z9 5 U1 0 U2 0 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 1094-3420 J9 INT J HIGH PERFORM C JI Int. J. High Perform. Comput. Appl. PD SUM PY 2001 VL 15 IS 2 SI SI BP 92 EP 101 DI 10.1177/109434200101500202 PG 10 WC Computer Science, Hardware & Architecture; Computer Science, Interdisciplinary Applications; Computer Science, Theory & Methods SC Computer Science GA 424HE UT WOS:000168226200002 ER PT J AU Katz, DS Kepner, J AF Katz, DS Kepner, J TI Embedded/real-time systems SO INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS LA English DT Article C1 CALTECH, Jet Prop Lab, Remote Explorat & Experimentat Project, Pasadena, CA 91125 USA. MIT, Lincoln Lab, Cambridge, MA 02139 USA. RP Katz, DS (reprint author), CALTECH, Jet Prop Lab, Remote Explorat & Experimentat Project, Pasadena, CA 91125 USA. OI Katz, Daniel S./0000-0001-5934-7525 NR 4 TC 0 Z9 0 U1 0 U2 0 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 1094-3420 J9 INT J HIGH PERFORM C JI Int. J. High Perform. Comput. Appl. PD SUM PY 2001 VL 15 IS 2 SI SI BP 186 EP 190 DI 10.1177/109434200101500212 PG 5 WC Computer Science, Hardware & Architecture; Computer Science, Interdisciplinary Applications; Computer Science, Theory & Methods SC Computer Science GA 424HE UT WOS:000168226200012 ER PT J AU Chow, PL Maestrello, L AF Chow, PL Maestrello, L TI Vibrational control of a non-linear elastic panel SO INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS LA English DT Article DE vibrational control; non-linear panel oscillation; method of averaging AB The paper is concerned with the stabilization of the non-linear panel oscillation by an active control. The control is actuated by a combination of additive and parametric vibrational forces. A general method of vibrational control is presented for stabilizing panel vibration satisfying a non-linear beam equation. To obtain analytical results, a perturbation technique is used in the case of weak non-linearity. Possible application to the other type of problems is briefly discussed. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Wayne State Univ, Dept Math, Detroit, MI 48202 USA. NASA, Langley Res Ctr, Acoust Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23665 USA. RP Chow, PL (reprint author), Wayne State Univ, Dept Math, Detroit, MI 48202 USA. NR 11 TC 4 Z9 4 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7462 J9 INT J NONLINEAR MECH JI Int. J. Non-Linear Mech. PD JUN PY 2001 VL 36 IS 4 BP 709 EP 718 DI 10.1016/S0020-7462(00)00038-X PG 10 WC Mechanics SC Mechanics GA 406PP UT WOS:000167224600015 ER PT J AU Bose, D Govindan, TR Meyyappan, M AF Bose, D Govindan, TR Meyyappan, M TI Semianalytical ion current model for radio-frequency driven collisionless sheaths SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID PLASMA SHEATHS; RF DISCHARGES; DYNAMICS; REACTORS AB We propose a semianalytical ion dynamics model for a collisionless radio-frequency biased sheath. The model uses bulk plasma and electrode boundary conditions to predict the ion impact energy distribution and electrical properties of the sheath. The proposed model accounts for ion inertia and ion current modulation at bias frequencies that are of the same order of magnitude as the ion plasma frequency. A relaxation equation for ion current oscillations is derived, which is coupled with a damped potential equation in order to model ion inertia effects. We find that inclusion of ion current modulation in the sheath model shows marked improvements in the predictions of the sheath electrical properties and ion energy distribution function. (C) 2001 American Institute of Physics. C1 NASA, Ames Res Ctr, Eloret Corp, Moffett Field, CA 94035 USA. RP Bose, D (reprint author), NASA, Ames Res Ctr, Eloret Corp, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 11 TC 4 Z9 4 U1 0 U2 1 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 1 PY 2001 VL 89 IS 11 BP 5932 EP 5938 DI 10.1063/1.1365436 PN 1 PG 7 WC Physics, Applied SC Physics GA 440AC UT WOS:000169149900010 ER PT J AU Ramsdell, CD Mullen, TJ Sundby, GH Rostoft, S Sheynberg, N Aljuri, N Maa, M Mukkamala, R Sherman, D Toska, K Yelle, J Bloomfield, D Williams, GH Cohen, RJ AF Ramsdell, CD Mullen, TJ Sundby, GH Rostoft, S Sheynberg, N Aljuri, N Maa, M Mukkamala, R Sherman, D Toska, K Yelle, J Bloomfield, D Williams, GH Cohen, RJ TI Midodrine prevents orthostatic intolerance associated with simulated spaceflight SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE cardiovascular system; vasovagal syncope ID SHORT-DURATION SPACEFLIGHT; ARTERIAL-PRESSURE; VASOVAGAL SYNCOPE; HYPOTENSION; MECHANISMS; HUMANS AB Many astronauts after being weightless in space become hypotensive and presyncopal when they assume an upright position. This phenomenon, known as orthostatic intolerance, may interfere with astronaut function during reentry and after spaceflight and may limit the ability of an astronaut to exit a landed spacecraft unaided during an emergency. Orthostatic intolerance is more pronounced after long-term spaceflight and is a major concern with respect to the extended flights expected aboard the International Space Station and for interplanetary exploration class missions, such as a human mission to Mars. Fully effective countermeasures to this problem have not yet been developed. To test the hypothesis that alpha -adrenergic stimulation might provide an effective countermeasure, we conducted a 16-day head-down-tilt bedrest study (an analog of weightlessness) using normal human volunteers and administered the alpha (1)-agonist drug midodrine at the end of the bed-rest period. Midodrine was found to significantly ameliorate excessive decreases in blood pressure and presyncope during a provocative tilt test. We conclude that midodrine may be an effective countermeasure for the prevention of orthostatic intolerance following spaceflight. C1 MIT, Harvard MIT Div Hlth Sci & Technol, NASA Ctr Quantitat Cardiovasc Physiol, Cambridge, MA 02139 USA. Brigham & Womens Hosp, Div Endocrine Hypertens, Boston, MA 02115 USA. Massachusetts Gen Hosp, Dept Anesthesia & Crit Care, Boston, MA 02114 USA. Royal Norwegian Air Force, Inst Aviat Med, N-0313 Oslo, Norway. Univ Oslo, Dept Physiol, N-0317 Oslo, Norway. NASA, Lyndon B Johnson Space Ctr, Cardiovasc Lab, Houston, TX 77058 USA. Columbia Univ, New York, NY 10032 USA. RP Cohen, RJ (reprint author), MIT, Harvard MIT Div Hlth Sci & Technol, NASA Ctr Quantitat Cardiovasc Physiol, 45 Carlton St,Rm E25-335A, Cambridge, MA 02139 USA. FU NCRR NIH HHS [RR-02635] NR 18 TC 30 Z9 32 U1 1 U2 3 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD JUN PY 2001 VL 90 IS 6 BP 2245 EP 2248 PG 4 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 436WC UT WOS:000168958000030 PM 11356789 ER PT J AU Sobral, JHA Abdu, MA Yamashita, CS Gonzalez, WD de Gonzalez, AC Batista, IS Zamlutti, CJ Tsurutani, BT AF Sobral, JHA Abdu, MA Yamashita, CS Gonzalez, WD de Gonzalez, AC Batista, IS Zamlutti, CJ Tsurutani, BT TI Responses of the low-latitude ionosphere to very intense geomagnetic storms SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article; Proceedings Paper CT Meeting of the International-Union-of-Geodesy-and-Geophysics (IUGG) CY JUL 27-28, 1999 CL UNIV BIRMINGHAM, BIRMINGHAM, ENGLAND SP Int Union Geodesy & Geophys HO UNIV BIRMINGHAM DE geomagnetic storms; storm effects; substorms; low latitude ionosphere; ionospheric drifts ID ELECTRIC-FIELDS; EQUATORIAL IONOSPHERE; DISTURBANCE DYNAMO; PENETRATION; SYSTEM; SECTOR AB In this work, we investigate the ionospheric responses to exceptionally high-intensity and long-duration magnetic storms over Brazil. Disturbed ionospheric F-region vertical drifts and peak electron density changes observed at the equatorial station Fortaleza - Fz (3 degrees 55'S; 38 degrees 25'W; dip - 3.5 degrees) and the low-latitude station Cachoeira Paulista - CP (22 degrees 41'S; 45 degrees 00'W; dip 24 degreesS), for three magnetospheric storm events that occurred in December 1980, April 1981 and September 1982, are analyzed. These storms had minimum Dst indexes -240, -311 and -289 nT, respectively. The interplanetary magnetic field (Bz) data from the ISEE-3 satellite, the auroral activity index AE, and the ring current index Dst are used as indicators of the magnetospheric conditions. The ionospheric response features are analyzed using the F-layer critical parameters h'F, hpF2 and foF2, from ionograms obtained at Fz and CP. The Bz and the AE index variations were much higher than those in many previous studies. Therefore, many of the observations reported here either have not been observed or are not readily explained by current models for predicting the penetration/dynamo disturbance electric fields. The altitude of the nocturnal ionospheric F-layer at low latitudes may undergo significant variations during storm-time, caused by magnitude variations on the local zonal component of the F-region electric field intensity. During the period studied here, clear association of the F-layer rise (vertical velocity and altitude) and spread-F occurrence is observed. It is shown that the storm-time layer rise has a dominant role on the equatorial spread-F. An attempt is made to identify the origin of electric fields responsible for the disturbed F-layer alterations. The main conclusions of this study are that (a) some effects on the F-layer height and peak electron concentrations are consistent with model predictions. Some others are in discrepancy or have not been either predicted by model studies or experimentally detected, (b) the F-layer rise over Fz played a major role in the generation of spread-F, (c) the maximum disturbance electric field intensity observed was about 1.09 mV m s(-1), (d) in some cases, foF2 increases (decreases) over CP were seen to be related to increases (decreases), in the fountain effect mechanism, (e) storm-time-induced h'F post-sunset height rise inhibitions over Fz may extend for at least 4 days, as observed, (f) daytime foF2 depressions of amplitude up to -9 MHz are observed over Fz, (g) in particular, a rather unexpected disturbance rise in h'F over Fortaleza, on September 8 at 08 LT, does not seem directly associated with either disturbance winds or penetration electric fields with origin at high latitude, where the convection remained low during the preceding 10h. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Inst Nacl Pesquisas Espaciais, BR-12201970 Sao Jose Dos Campos, Brazil. Jet Prop Lab, Pasadena, CA USA. RP Sobral, JHA (reprint author), Inst Nacl Pesquisas Espaciais, CP 515, BR-12201970 Sao Jose Dos Campos, Brazil. RI Batista, Inez/F-2899-2012 NR 21 TC 53 Z9 54 U1 1 U2 4 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 JUN PY 2001 VL 63 IS 9 BP 965 EP 974 DI 10.1016/S1364-6826(00)00197-8 PG 10 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 440KK UT WOS:000169174300018 ER PT J AU Jacobson, N AF Jacobson, N TI Use of tabulated thermochemical data for pure compounds SO JOURNAL OF CHEMICAL EDUCATION LA English DT Article ID ELEMENTS C1 NASA, John Glenn Res Ctr, Cleveland, OH 44135 USA. RP Jacobson, N (reprint author), NASA, John Glenn Res Ctr, 21000 Brookpk Rd, Cleveland, OH 44135 USA. RI Jacobson, Nathan/A-9411-2009 NR 37 TC 9 Z9 9 U1 0 U2 6 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0021-9584 J9 J CHEM EDUC JI J. Chem. Educ. PD JUN PY 2001 VL 78 IS 6 BP 814 EP 819 PG 6 WC Chemistry, Multidisciplinary; Education, Scientific Disciplines SC Chemistry; Education & Educational Research GA 432LW UT WOS:000168694100031 ER PT J AU Campbell, TA Schweizer, M Dold, P Croll, A Benz, KW AF Campbell, TA Schweizer, M Dold, P Croll, A Benz, KW TI Float zone growth and characterization of Ge1-xSix (x <= 10 at%) single crystals SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE computer simulation; convection; morphological stability; segregation; solutocapillary convection; thermocapillary convection; floating zone technique; germanium silicon alloys ID THERMOCAPILLARY CONVECTION; SILICON-GERMANIUM; DENSITY; MELT AB Ge1-xSix (x less than or equal to 10 at%) single crystals were grown with the float zone technique using a monoellipsoid mirror furnace. The feed rod consisted of pre-synthesized Ge0.95Si0.05 polycrystalline material with an initial composition of pure germanium. Several boron-doped (1-2 x 10(17) at cm (-3)) crystals were grown using (1 0 0) Ge seeds. Taking advantage of the pre-synthesized feed rods, a defined macrosegregation could be achieved in the grown crystals with a linear slope at the beginning (approximate to 0.5 at% mm (-1)) followed by a plateau region with a constant silicon distribution (Si concentration up to 10 at%, fluctuation rate: less than or equal to +/-0.3 at%). The etch pit density was in the range of 7 x 10(3)-2 x 10(4)cm(-2) Micrographs of the etched crystals show sharp changes in interface curvature at the crystal edges. These distortions of the interface morphology are a direct function of the Si concentration; they are considered to be caused by solutal Marangoni convection. Theoretical considerations show that the flow direction and strength vary significantly from a solutal Marangoni convection regime directly in front of the solid-liquid interface to a thermal Marangoni convection regime within the bulk melt. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Univ Freiburg, Inst Kristallog, D-79104 Freiburg, Germany. Tech Univ Freiberg, Inst NE Met & Reinststoffe, D-09599 Freiberg, Germany. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Dold, P (reprint author), Univ Freiburg, Inst Kristallog, Hebelstr 25, D-79104 Freiburg, Germany. RI Croell, Arne/A-2480-2013 OI Croell, Arne/0000-0002-8673-9994 NR 35 TC 44 Z9 47 U1 1 U2 13 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 JUN PY 2001 VL 226 IS 2-3 BP 231 EP 239 DI 10.1016/S0022-0248(01)01394-X PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 446VP UT WOS:000169535100009 ER PT J AU Velicu, S Badano, G Selamet, Y Grein, CH Faurie, JP Sivananthan, S Boieriu, P Rafol, D Ashokan, R AF Velicu, S Badano, G Selamet, Y Grein, CH Faurie, JP Sivananthan, S Boieriu, P Rafol, D Ashokan, R TI HgCdTe/CdTe/Si infrared photodetectors grown by MBE for near-room temperature operation SO JOURNAL OF ELECTRONIC MATERIALS LA English DT Article; Proceedings Paper CT 19th US Workshop on the Physics and Chemistry of II-VI Materials CY OCT 30-NOV 02, 2000 CL ALBUQUERQUE, NEW MEXICO SP USA SMDC, USA, Res Lab, Off Naval Res, Air Force Res Lab, Minerals, Metals & Materials Soc DE HgCdTe; infrared detectors; MBE ID HG1-XCDXTE; LIFETIME; DIODES AB Conventional HgCdTe infrared detectors need significant cooling in order to reduce noise and leakage currents resulting from thermal generation and recombination processes. Although the need for cooling has long been thought to be fundamental and inevitable, it has been recently suggested that Auger recombination and generation rates can be reduced by using the phenomena of exclusion and extraction to produce nonequilibrium carrier distributions. The devices with Auger suppressed operation requires precise control over the composition, and donor and acceptor doping. The successful development of the molecular beam epitaxy (MBE) growth technique for multi-layer HgCdTe makes it possible to grow these device structures. Theoretical calculations suggest that the p pin+ layer sequence is preferable for near-room temperature operation due to longer minority carrier lifetime in lightly doped p-HgCdTe absorber layers. However, because the low doping required for absorption and nonequilibrium operation is easier to achieve in n-type materials, and because Shockley-Read centers should be minimized in order to obtain the benefits of Auger suppression, we have focused on p(+)vn structures. Planar photodiodes vr ere formed on CdTe/ Si (211) composite substrates by As implantation followed by a three step annealing sequence. Three inch diameter Si substrates were employed since they are of high quality, low cost, and available in large areas. Due to this development, large area focal plane arrays (FPAs) operated at room temperature are possible in the near future. The structures were characterized by FTIR, x-ray diffraction, temperature dependent Hall measurements minority carrier lifetimes by photoconductive decay, and in-situ ellipsometry. To study the relative influence of bulk and surface effects, devices with active areas from 1.6 x 10(-5) cm(2) to 10(-3) cm(2) were fabricated. The smaller area devices show better performance in terms of reverse bias characteristics indicating that the bulk quality could be further improved. At 80 K, the zero bias leakage current for a 40 mum x 40 mum diode with 3.2 mum cutoff wavelength is 1 pA, the R(o)A product is 1.1 x 10(4) Omega -cm(2) and the breakdown voltage is in excess of 500 mV. The device shows a responsivity of 1.3 x 10(7) V/W and a 80 K detectivity of 1.9 x 10(11) cm-Hz(1/2)/W. At 200 K, the zero bias leakage current is 5 nA and the R(o)A product 2.03 Omega -cm(2), while the breakdown voltage decreases to 40 mV. C1 Univ Illinois, Dept Phys, Microphys Lab, Chicago, IL 60607 USA. EPIR Ltd, Bolingbrook, IL 60440 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Smart Pixel Inc, Bolingbrook, IL 60440 USA. RP Velicu, S (reprint author), Univ Illinois, Dept Phys, Microphys Lab, Chicago, IL 60607 USA. NR 11 TC 10 Z9 11 U1 1 U2 7 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 184 THORN HILL RD, WARRENDALE, PA 15086 USA SN 0361-5235 J9 J ELECTRON MATER JI J. Electron. Mater. PD JUN PY 2001 VL 30 IS 6 BP 711 EP 716 DI 10.1007/BF02665860 PG 6 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA 445EE UT WOS:000169444500027 ER PT J AU Kirschman, RK Sokolowski, WM Kolawa, EA AF Kirschman, RK Sokolowski, WM Kolawa, EA TI Die attachment for-120 degrees C to+20 degrees C thermal cycling of microelectronics for future mars rovers - An overview SO JOURNAL OF ELECTRONIC PACKAGING LA English DT Article ID LIQUID-NITROGEN; EUTECTIC ALLOY; CERAMIC PACKAGES; AU-SN; TECHNOLOGY; INDIUM; GOLD; TEMPERATURES; SUBSTRATE; STRENGTH AB Active thermal control for electronics on Mars rovers imposes a serious penalty in weight, volume, power consumption, and reliability. Thus, we propose that thermal control be eliminated for future lovers. From a functional standpoint there is no reason that the electronics could not operate over the entire temperature range of the Martian environment, which can vary from a low of approximate to -90 degrees C to a high of approximate to +20 degrees C during the Martian night and day. The upper end of this range is well within that for conventional electronics. Although the lower end is considerably below that for which conventional-even high-reliability-electronics is designed of tested, it is well established that electronic devices can operate to such low temperatures. The primary concern is reliability of the overall electronic system, especially in regard To the numerous daily temperature cycles that it would experience over the duration of a mission on Mars. Accordingly, key reliability issues have been identified for elimination of thermal control on future Mars rovers. One of these is attachment of semiconductor die onto substrates and into packages. Die attachment is critical since it forms a mechanical, thermal, and electrical interface between the electronic device and the substrate or package. This paper summarizes our initial investigation of existing information related to this issue, in order to form an opinion whether die attachment techniques exist, or could be developed with reasonable effort, to withstand the Mars thermal environment for a mission;duration of approximately one earth year: Our conclusion, from a review of literature and personal contacts, is that die attachment can be made sufficiently reliable to satisfy the requirements of future Mars rovers. Moreover it appears that there are several possible techniques from which to choose and that the requirements could be met by judicious selection from existing methods using hard solders, soft solders, or organic adhesives. Thus die attachment does not appear to be a roadblock to eliminating thermal control for rover electronics. We recommend that this be further investigated and verified for the specific hardware and thermal conditions appropriate to Mars revers. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM ExtElect@aol.com; Witold.M.Sokolowski@jpl.nasa.gov; Elizabeth.A.Kolawa@jpl.nasa.gov NR 64 TC 5 Z9 5 U1 0 U2 3 PU ASME PI NEW YORK PA TWO PARK AVE, NEW YORK, NY 10016-5990 USA SN 1043-7398 EI 1528-9044 J9 J ELECTRON PACKAGING JI J. Electron. Packag. PD JUN PY 2001 VL 123 IS 2 BP 105 EP 111 DI 10.1115/1.1347996 PG 7 WC Engineering, Electrical & Electronic; Engineering, Mechanical SC Engineering GA 440ZE UT WOS:000169205900002 ER PT J AU Anderson, CJ Glassman, M McAfee, RB Pinelli, T AF Anderson, CJ Glassman, M McAfee, RB Pinelli, T TI An investigation of factors affecting how engineers and scientists seek information SO JOURNAL OF ENGINEERING AND TECHNOLOGY MANAGEMENT LA English DT Article DE information seeking; task; user; carrier ID TECHNICAL COMMUNICATION; PROJECT; PERFORMANCE; UNCERTAINTY; PATTERNS; MODEL; ACCESSIBILITY; ORGANIZATION; INNOVATION; IMPACT AB This study investigated how 872 US aerospace scientists and engineers select information carriers. When considering oral and written information carriers, the principle of least effort was supported with a strong preference for oral communication over written communication. In examining how the respondents select written carriers, the decision to use or not to use a written carrier was found to be primarily a function of the perceived importance of the carrier's information to a person's work. Task uncertainty and task complexity were found to be significant, but not the primary nor a totally consistent criteria. The perceived quality and accessibility of written carriers were not found significant. The findings reinforce the need for firms to hire knowledgeable employees, to provide them with comprehensive training programs, and to develop formal and informal communication networks. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Old Dominion Univ, Dept Mkt, Coll Business & Publ Adm, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Norfolk, VA 23529 USA. RP Glassman, M (reprint author), Old Dominion Univ, Dept Mkt, Coll Business & Publ Adm, Norfolk, VA 23529 USA. NR 71 TC 86 Z9 87 U1 6 U2 24 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0923-4748 J9 J ENG TECHNOL MANAGE JI J. Eng. Technol. Manage. PD JUN PY 2001 VL 18 IS 2 BP 131 EP 155 DI 10.1016/S0923-4748(01)00032-7 PG 25 WC Business; Engineering, Industrial; Management SC Business & Economics; Engineering GA 431CB UT WOS:000168613400002 ER PT J AU Ortiz, RM AF Ortiz, RM TI Osmoregulation in marine mammals SO JOURNAL OF EXPERIMENTAL BIOLOGY LA English DT Review DE kidney; urine; water; feeding; fasting; diving; salinity; drinking; aldosterone; vasopressin; angiotensin ID ELEPHANT SEAL PUPS; MANATEES TRICHECHUS-MANATUS; GLOMERULAR-FILTRATION RATE; WATER FLUX; MIROUNGA-ANGUSTIROSTRIS; PLASMA VASOPRESSIN; PHOCA-GROENLANDICA; POSTWEANING FAST; BLOOD-FLOW; NASAL HEAT AB Osmoregulation in marine mammals has been investigated for over a century; however, a review of recent advances in our understanding of water and electrolyte balance and of renal function in marine mammals is warranted. The following topics are discussed: (i) kidney structure and urine concentrating ability, (ii) sources of water, (iii) the effects of feeding, fasting and diving, (iv) the renal responses to infusions of varying salinity and (v) hormonal regulation. The kidneys of pinnipeds and cetaceans are reniculate in structure, unlike those of terrestrial mammals (except bears), but this difference does not confer any greater concentrating ability. Pinnipeds, cetaceans, manatees and sea otters can concentrate their urine above the concentration of sea water, but only pinnipeds and otters have been shown to produce urine concentrations of Na+ and Cl- that are similar to those in sea water. This could afford them the capacity to drink sea water and not lose fresh water. However, with few exceptions, drinking is not a common behavior in pinnipeds and cetaceans, Water balance is maintained in these animals via metabolic and dietary water, while incidental ingestion and dietary salt may help maintain electrolyte homeostasis, Unlike most other aquatic mammals, sea otters commonly drink sea water and manatees frequently drink fresh water. Among the various taxonomic groups of marine mammals, the sensitivity of the renin-angiotensin-aldosterone system appears to be influenced by the availability of Na+. The antidiuretic role of vasopressin remains inconclusive in marine mammals, while the natriuretic function of atrial natriuretic peptide has yet to be examined. Ideas on the direction of future studies are presented. C1 Univ Calif Santa Cruz, Dept Biol, Santa Cruz, CA 95064 USA. NASA, Ames Res Ctr, Div Life Sci, Neuroendocrinol Lab, Moffett Field, CA 94035 USA. RP Ortiz, RM (reprint author), Univ Calif Santa Cruz, Dept Biol, A316 Earth & Marine Sci, Santa Cruz, CA 95064 USA. FU NIGMS NIH HHS [GM 58903-01] NR 94 TC 76 Z9 80 U1 10 U2 56 PU COMPANY OF BIOLOGISTS LTD PI CAMBRIDGE PA BIDDER BUILDING CAMBRIDGE COMMERCIAL PARK COWLEY RD, CAMBRIDGE CB4 4DL, CAMBS, ENGLAND SN 0022-0949 J9 J EXP BIOL JI J. Exp. Biol. PD JUN PY 2001 VL 204 IS 11 BP 1831 EP 1844 PG 14 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 443YJ UT WOS:000169370900001 PM 11441026 ER PT J AU Thio, YCF Knapp, CE Kirkpatrick, RC Siemon, RE Turchi, PJ AF Thio, YCF Knapp, CE Kirkpatrick, RC Siemon, RE Turchi, PJ TI A physics exploratory experiment on plasma liner formation SO JOURNAL OF FUSION ENERGY LA English DT Article DE magnetized target fusion; plasma liner; plasma jets; plasma acceleration; plasma gun ID FUSION AB Momentum flux for imploding a target plasma in magnetized target fusion (MTF) may be delivered by an array of plasma guns launching plasma jets that would merge to form an imploding plasma shell (liner). In this paper, we examine what would be a worthwhile experiment to explore the dynamics of merging plasma jets to form a plasma liner as a first step in establishing an experimental database for plasma-jets-driven magnetized target fusion (PJETS-MTF). Using past experience in fusion energy research as a model, we envisage a four-phase program to advance the art of PJETS-MTF to fusion breakeven (Q similar to 1). The experiment (PLX) described in this paper serves as Phase 1 of this four-phase program. The logic underlying the selection of the experimental parameters is presented. The experiment consists of using 12 plasma guns arranged in a circle, launching plasma jets toward the center of a vacuum chamber. The velocity of the plasma jets chosen is 200 km/s, and each jet is to carry a mass of 0.2 mg to 0.4 mg. A candidate plasma accelerator for launching these jets consists of a coaxial plasma gun of the Marshall type. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Los Alamos Natl Lab, Los Alamos, NM 87545 USA. USAF, Res Lab, Kirtland AFB, NM 87185 USA. RP Thio, YCF (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RI Thio, Yong Chia/G-5442-2014 OI Thio, Yong Chia/0000-0003-3615-643X NR 24 TC 40 Z9 40 U1 1 U2 9 PU KLUWER ACADEMIC/PLENUM PUBL PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0164-0313 J9 J FUSION ENERG JI J. Fusion Energy PD JUN PY 2001 VL 20 IS 1-2 BP 1 EP 11 AR UNSP 0164-0313/01/0600-001/0 DI 10.1023/A:1019813528507 PG 11 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 585TW UT WOS:000177541500001 ER PT J AU Khazanov, GV Stone, NH Krivorutsky, EN Gamayunov, KV Liemohn, MW AF Khazanov, GV Stone, NH Krivorutsky, EN Gamayunov, KV Liemohn, MW TI Current-induced magnetic field effects on bare tether current collection: A parametric study SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CYLINDRICAL LANGMUIR PROBES AB The physical process of current collection by a "bare wire" electrodynamic tether in space is considered. The study uses an improved model that takes into account the resistance of the wire and the magnetic shielding induced by current flow in the tether. The plasma density, n(e), electron temperature, T-e, tether length, L, tether radius, r(w), and the angle of the geomagnetic field to the tether (90 degrees-alpha) were all used as parameters. It is shown, for certain tether configurations and parameter values, that magnetic shielding reduces the collected current. In general, any parametric change that increases tether current, and hence, the strength of the current-induced magnetic field relative to the strength of the electric field between the tether and the ambient plasma, will increase the shielding effect. Tether current is increased directly with tether collection area (which depends on L and r(w)), plasma conductivity (which depends on n(e) and T-e), and the motional emf along the tether (which increases with L and the angle 90 degrees-alpha). It turns out that, as any of these parameters change so as to cause the overall tether current to increase, the overestimate of current that results from ignoring the magnetic shielding effect becomes correspondingly greater. Moreover, it is shown that a tether system in the thruster (or motor) mode suffers greater current reduction from magnetic shielding than does the same tether deployed in the generator mode. Finally, it is shown that, for certain tether system configurations combined with particular values of the governing plasma parameters, current-induced magnetic shielding can significantly reduce the collected current and, therefore, system efficiency. For example, in the case of an electrodynamic tether system in the thruster mode under conditions of n(e)=1.67x10(6) cm(-3), alpha =60 degrees, r(w)=2.5 mm, and E-m=34 V/km, magnetic shielding will reduce the collected current 10% at a point L=0.65 km along the tether (4.3 A instead of 4.8 A) and this increases to more than 40% at L=1.3km (9.6 A instead of 13.4 A). C1 Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Khazanov, GV (reprint author), Univ Alaska, Inst Geophys, 903 Koyukuk Dr,POB 75720, Fairbanks, AK 99775 USA. RI Gamayunov, Konstantin/A-8505-2009; Liemohn, Michael/H-8703-2012 OI Gamayunov, Konstantin/0000-0002-8768-8527; Liemohn, Michael/0000-0002-7039-2631 NR 7 TC 10 Z9 10 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-SPACE JI J. Geophys. Res-Space Phys. PD JUN 1 PY 2001 VL 106 IS A6 BP 10565 EP 10579 DI 10.1029/2000JA000345 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 435WP UT WOS:000168905400009 ER PT J AU Gary, SP Yin, L Winske, D Ofman, L AF Gary, SP Yin, L Winske, D Ofman, L TI Electromagnetic heavy ion cyclotron instability: Anisotropy constraint in the solar corona SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TEMPERATURE ANISOTROPY; INVERSE CORRELATION; MAGNETOSHEATH; WIND; PROTON; MODEL; WAVES; ACCELERATION; RESONANCE; DRIVEN AB The electromagnetic proton cyclotron anisotropy instability is driven by T-perpendicular top/T-parallel top > 1 where p represents protons and the directional subscripts denote directions relative to the background magnetic field. Fluctuating field growth leads to wave-particle scattering, which in turn imposes an upper bound on the anisotropy of the form T-perpendicular top/T-parallel top - 1 = S-p/beta (alphap)(parallel top),where beta (parallel top) equivalent to 8 pin(p)k(B)T(parallel top)/B-0(2), and the fitting parameters S-p less than or similar to 1 and alpha (p) similar or equal to 0.4 Recent SOHO observations indicate that minority heavy ions are substantially hotter and more anisotropic than protons in the solar corona. Here linear theory and hybrid simulations have been carried out in a model of a homogeneous, magnetized, collisionless plasma with anisotropic minority oxygen ions (denoted by subscript O). These calculations show that the electromagnetic oxygen ion cyclotron anisotropy instability also leads to wave-particle scattering, which constrains that anisotropy by the form T-perpendicular toO/T-parallel toO - 1 = S-O/[(m(p)/m(O))<()over bar>(parallel toO)](alphaO) where <()over bar>(parallel toO) equivalent to 8 pin(e)k(B)T(parallel toO)/B-o(2), S-O similar to 10 and alpha (O) similar to 0.4. This constraint should be observable in the solar corona. C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gary, SP (reprint author), Univ Calif Los Alamos Natl Lab, MS D466, Los Alamos, NM 87545 USA. NR 46 TC 32 Z9 32 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 JUN 1 PY 2001 VL 106 IS A6 BP 10715 EP 10722 DI 10.1029/2000JA000406 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 435WP UT WOS:000168905400021 ER PT J AU Smith, DD Snow, LA Sibille, L Ignont, E AF Smith, DD Snow, LA Sibille, L Ignont, E TI Tunable optical properties of metal nanoparticle sol-gel composites SO JOURNAL OF NON-CRYSTALLINE SOLIDS LA English DT Article; Proceedings Paper CT 6th International Symposium on Aerogels (ISA-6) CY OCT 08-11, 2000 CL ALBUQUERQUE, NEW MEXICO SP NanoPore Inc, Cabot Corp, Lawrence Livermore Natl Lab ID PHOTONIC-BAND-GAP; AEROGELS; SUSCEPTIBILITY; ENHANCEMENT; NANOSHELLS; MONOLAYERS; ABSORPTION AB We demonstrate that the linear and non-linear optical properties of sol-gels containing metal nanoparticles are highly tunable with porosity. Moreover, we extend the technique of immersion spectroscopy to inhomogeneous hosts, such as aerogels, and determine rigorous bounds for the average fractional composition of each component, i.e., the porosity of the aerogel, or equivalently, for these: materials, the catalytic dispersion. Sol-gels containing noble metal nanoparticles were fabricated and a significant blue-shift in the surface plasmon resonance (SPR) was observed upon formation of an aerogel, as a result of the decrease in the dielectric constant of the matrix upon supercritical extraction of the solvent. However, as a result of chemical interface damping and aggregation this blue-shift does not strictly obey standard effective medium theories. Mitigation of these complications is achieved by avoiding the use of alcohol rind by annealing the samples in a reducing atmosphere. (C) 2001 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Micrograv Sci & Applicat Dept, Huntsville, AL 35812 USA. Univ Alabama, Dept Mat Sci, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Smith, DD (reprint author), NASA, George C Marshall Space Flight Ctr, Micrograv Sci & Applicat Dept, SD-48, Huntsville, AL 35812 USA. NR 31 TC 31 Z9 31 U1 1 U2 13 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-3093 J9 J NON-CRYST SOLIDS JI J. Non-Cryst. Solids PD JUN 1 PY 2001 VL 285 IS 1-3 BP 256 EP 263 DI 10.1016/S0022-3093(01)00464-1 PG 8 WC Materials Science, Ceramics; Materials Science, Multidisciplinary SC Materials Science GA 444QJ UT WOS:000169410800040 ER PT J AU Subbarao, GV Wheeler, RM Levine, LH Stutte, GW AF Subbarao, GV Wheeler, RM Levine, LH Stutte, GW TI Glycine betaine accumulation, ionic and water relations of red-beet at contrasting levels of sodium supply SO JOURNAL OF PLANT PHYSIOLOGY LA English DT Article DE Beta vulgaris (L.); chlorophyll fluorescence; glycine betaine; hydroponics; osmotic potential; photosynthetic rate; potassium; red-beet; sodium ID QUATERNARY AMMONIUM; SUAEDA-MARITIMA; PROLINE ANALOGS; PHOTOSYSTEM-II; SALT TOLERANCE; CHLOROPLASTS; STRESS; PLANTS; LOCALIZATION; CARBOXYLASE AB Exposure of plants to sodium (Na) and salinity may increase glycine betaine accumulation in tissues. To study this, red-beet cvs. Scarlet Supreme and Ruby Queen, were grown for 42 days in a growth chamber using a re-circulating nutrient film technique with 0.25 mmol/L K and either 4.75 mmol/L (control) or 54.75 mmol/L (saline) Na (as NaCl). Plants were harvested at weekly intervals and measurements were taken on leaf water relations, leaf photosynthetic rates, chlorophyll fluorescence, chlorophyll levels, glycine betaine levels, and tissue elemental composition. Glycine betaine accumulation increased under salinity and this accumulation correlated with higher tissue levels of Na in both cultivars. Na accounted for 80 to 90% of the total cation uptake under the saline treatment. At final harvest (42 days), K concentrations in laminae ranged from similar to 65-95 mu mol g(-1) dry matter (DM), whereas Na in shoot tissue ranged from similar to 3000-4000 mu mol g(-1). Leaf sap osmotic potential at full turgor (psi (S) (100)) increased as lamina Na content increased. glycine betaine levels of leaf laminae showed a linear relationship with leaf sap psi (S) (100) Chlorophyll levels, leaf photosynthetic rates, and chlorophyll fluorescence were not affected by Na levels. These results suggest that the metabolic tolerance to high levels of tissue Na in red-beet could be due to its ability to synthesize and regulate glycine betaine production, and to control partitioning of Na and glycine betaine between the vacuole and the cytoplasm. C1 Dynamac Corp, Kennedy Space Ctr, FL 32899 USA. NASA, Biomed Off, Kennedy Space Ctr, FL 32899 USA. RP Wheeler, RM (reprint author), NASA, Biomed Off, Kennedy Space Ctr, FL 32899 USA. NR 43 TC 39 Z9 47 U1 1 U2 10 PU URBAN & FISCHER VERLAG PI JENA PA BRANCH OFFICE JENA, P O BOX 100537, D-07705 JENA, GERMANY SN 0176-1617 J9 J PLANT PHYSIOL JI J. Plant Physiol. PD JUN PY 2001 VL 158 IS 6 BP 767 EP 776 DI 10.1078/0176-1617-00309 PG 10 WC Plant Sciences SC Plant Sciences GA 448PH UT WOS:000169635500011 PM 12033231 ER PT J AU Braak, CJ de Haan, JF van der Mee, CVM Hovenier, JW Travis, LD AF Braak, CJ de Haan, JF van der Mee, CVM Hovenier, JW Travis, LD TI Parameterized scattering matrices for small particles in planetary atmospheres SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID POLARIZED-LIGHT; MULTIPLE-SCATTERING; AEROSOL PROPERTIES; ASYMMETRY PARAMETERS; SATELLITE RETRIEVAL; REFLECTED SUNLIGHT; PHASE FUNCTION; POLARIMETRY; PHOTOMETRY; VENUS AB Parameterized matrices are discussed that may be used as (single) scattering matrices for interpretations of the brightness and polarization of planetary atmospheres containing randomly oriented small particles. A number of guidelines are developed for the construction of such matrices. These guidelines are based on (i) physical conditions for the elements of a natural scattering matrix, some holding for arbitrary scattering angles and some for the exact forward and backward scattering directions only, as well as (ii) theorems for the asymptotic behavior of coefficients in expansions of the matrix elements in generalized spherical functions of the scattering angle. A set of parameterized matrices is introduced and assessed according to these guidelines. These particular parameterizations are especially useful for scattering by particles that are not large compared to the wavelength, particles in the Rayleigh-Gans domain and for a variety of irregularly shaped particles in the visible part of the spectrum. The use of parameterized matrices as scattering matrices is illustrated by deriving their elements as functions of the scattering angle from simulated measurements of the brightness and polarization of light reflected by plane-parallel atmospheres containing aggregated or spheroidal particles. In both cases, the scattering angle dependences of the original elements are retrieved in fair approximation. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Free Univ Amsterdam, Dept Phys & Astron, NL-1081 HV Amsterdam, Netherlands. Univ Cagliari, Dipartimento Matemat, I-09124 Cagliari, Italy. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Hovenier, JW (reprint author), Free Univ Amsterdam, Dept Phys & Astron, Boelelaan 1081, NL-1081 HV Amsterdam, Netherlands. NR 44 TC 16 Z9 16 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUN 1 PY 2001 VL 69 IS 5 BP 585 EP 604 DI 10.1016/S0022-4073(00)00103-5 PG 20 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 425JR UT WOS:000168287900005 ER PT J AU Sogard, SM Able, KW Hagan, SM AF Sogard, SM Able, KW Hagan, SM TI Long-term assessment of settlement and growth of juvenile winter flounder (Pseudopleuronectes americanus) in New Jersey estuaries SO JOURNAL OF SEA RESEARCH LA English DT Article; Proceedings Paper CT 4th International Symposium on Flatfish Ecology CY OCT 18-23, 1999 CL ATLANTIC BEACH, NORTH CAROLINA SP Netherlands Inst Sea Res, Marine Fisheries, N Carolina Div, N Carolina Sea Grant, N Carolina State Univ DE growth; winter flounders; metamorphosis; settlement; temperature ID PLAICE PLEURONECTES-PLATESSA; SOLEA-SOLEA L; OTOLITH MICROSTRUCTURE; HABITAT QUALITY; WADDEN SEA; NORTH-SEA; FISHES; RECRUITMENT; SIZE; PREDATION AB We examined patterns of metamorphosis, settlement, and growth for young-of-the-year winter flounder over a ten year period (1990-1999) in four estuaries spanning the coast of New Jersey, USA, with the objective to determine the spatial and temporal coherence in these processes. We hypothesised that these processes could be influenced by large-scale climatic factors such as temperature and small-scale, local factors such as predator and prey abundances and differences associated with the localised population structure of winter flounder. Newly settled juveniles were collected in late May/early June each year. Increment counts on sagittal otoliths were used to determine the date of metamorphosis, and increment widths were used to estimate growth rates at two times, just after settlement and just prior to capture. A high level of consistency in spatial patterns among four individual estuaries was evident, and was largely driven by the northernmost site, Sandy Hook, which had higher fish densities and later metamorphosis than the three other sites, and faster growth rates than the two mid-coast sites (Barnegat Bay and Great Bay). In contrast to spatial patterns, consistent temporal patterns were evident only in the timing of metamorphosis, which was delayed in colder years at all sites. Weekly plankton sampling over the same ten year period at one site (Great Bay) yielded winter flounder larvae during a relatively narrow period in spring, with a later peak of abundance in colder years, in agreement with back-calculated dates of metamorphosis for settled juveniles. These patterns suggest that the timing of settlement is driven by large-scale climatic factors that influence the timing of spawning and/or larval development. Interannual variability in densities and growth rates, however, appeared to be independent at each site, indicating control by local environmental factors or genetic differences among local populations. The spatial consistency of growth rates suggests that appropriate nursery areas can be readily identified for juvenile winter flounder. However, subsequent recruitment needs to be verified at the level of local populations to identify contributing source habitats. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Newport, OR 97365 USA. Rutgers State Univ, Marine Field Stn, Tuckerton, NJ 08087 USA. RP Sogard, SM (reprint author), Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, 2030 Marine Sci Dr, Newport, OR 97365 USA. NR 49 TC 42 Z9 43 U1 0 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1385-1101 J9 J SEA RES JI J. Sea Res. PD JUN PY 2001 VL 45 IS 3-4 BP 189 EP 204 DI 10.1016/S1385-1101(01)00048-X PG 16 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 467HN UT WOS:000170696500002 ER PT J AU Chambers, RC Witting, DA Lewis, SJ AF Chambers, RC Witting, DA Lewis, SJ TI Detecting critical periods in larval flatfish populations SO JOURNAL OF SEA RESEARCH LA English DT Article; Proceedings Paper CT 4th International Symposium on Flatfish Ecology CY OCT 18-23, 1999 CL ATLANTIC BEACH, NORTH CAROLINA SP Netherlands Inst Sea Res, Marine Fisheries, N Carolina Div, N Carolina Sea Grant, N Carolina State Univ DE critical periods; fish larvae; mortality; Pseudopleuronectes americanus; survival models; temperature effects; Northwest Atlantic; Mid-Atlantic Bight ID FLOUNDER PSEUDOPLEURONECTES-AMERICANUS; PACIFIC HERRING LARVAE; PARALICHTHYS DENTATUS; MALLOTUS-VILLOSUS; ANCHOA-MITCHILLI; ENGRAULIS-MORDAX; SUMMER FLOUNDER; CLUPEA-HARENGUS; CHESAPEAKE-BAY; MARINE FISHES AB We evaluate the time-course of deaths and evidence of periods of increased mortality (i.e., critical periods) in laboratory populations of larval flatfish. First, we make the distinction between age-at-death and abundance-at-time data for fish larvae, the latter being typical in studies of natural populations. Next, we describe an experimental investigation of age-and temperature-dependent mortality in larval winter flounder, Pseudopleuronectes americanus. The survivorship curves of these populations differed significantly in both the magnitude and time-course of mortality among the four water temperatures evaluated (7, 10, 13, and 16 degreesC). Mortality was highest in the cooler temperatures and concentrated in the third quarter of larval life, largely concurrent with settlement of surviving members of the cohort. Among the statistical methods for analysing survival data, the proportional-hazards model with time-varying covariates proved best at capturing the patterns of age-specific mortalities. We conclude that fair appraisals of recruitment hypotheses which are predicated on periods of high, age-specific mortality that vary with environmental conditions (e.g., Hjort's critical period hypothesis) will require: (1) data that are based on age, not time; (2) data that are of higher temporal resolution than commonly available at present and (3) analytical methods that are sensitive to irregularities in survivorship curves. We suggest four research approaches for evaluating critical periods in nature. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Natl Marine Fisheries Serv, Howard Marine Sci Lab, Highlands, NJ 07732 USA. RP Chambers, RC (reprint author), Natl Marine Fisheries Serv, Howard Marine Sci Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 50 TC 14 Z9 14 U1 0 U2 12 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1385-1101 J9 J SEA RES JI J. Sea Res. PD JUN PY 2001 VL 45 IS 3-4 BP 231 EP 242 DI 10.1016/S1385-1101(01)00058-2 PG 12 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 467HN UT WOS:000170696500005 ER PT J AU Canuto, VM Cheng, Y Howard, A AF Canuto, VM Cheng, Y Howard, A TI New third-order moments for the convective boundary layer SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID TRANSPORT; CLOSURES AB Turbulent convection is inherently a nonlocal phenomenon and a primary condition for a successful treatment of the convective boundary layer is a reliable model of nonlocality. In the dynamic equations governing the convective flux, the turbulent kinetic energy, etc., nonlocality is represented by the third-order moments (TOMs). Since the simplest form, the so-called down gradient approximation (DGA), severely underestimates the TOMs (up to an order of magnitude), a more physical model is needed. In 1994, an analytical model was presented that was derived directly from the dynamical equations for the TOMs. It considerably improved the DGA but was a bit cumbersome to use and, more importantly, it was based on the quasi-normal (QN) approximation for the fourth-order moments. Here, we present a new analytic expression for the TOMs that is structurally simpler than the 1994 expression and avoids the QN approximation. The resulting fit to the LES data is superior to that of the 1994 model. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 5 TC 39 Z9 39 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUN PY 2001 VL 58 IS 9 BP 1169 EP 1172 DI 10.1175/1520-0469(2001)058<1169:NTOMFT>2.0.CO;2 PG 4 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 430EY UT WOS:000168562600015 ER PT J AU Burbine, TH Buchanan, PC Binzel, RP Bus, SJ Hiroi, T Hinrichs, JL Meibom, A McCoy, TJ AF Burbine, TH Buchanan, PC Binzel, RP Bus, SJ Hiroi, T Hinrichs, JL Meibom, A McCoy, TJ TI Vesta, Vestoids, and the howardite, eucrite, diogenite group: Relationships and the origin of spectral differences SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID ASTEROID 4 VESTA; MAIN-BELT; PARENT BODY; METEORITES; PYROXENE; SURFACE; EVOLUTION; BODIES; SIZE; CHONDRITES AB Spectra of asteroid 4 Vesta and 21 small (estimated diameters less than 10 km) asteroids with Vesta-like spectral properties (Vestoids) were measured at visible and near-infrared wavelengths (similar to0.44 to similar to1.65 mum). All of the measured small asteroids (except for 2579 Spartacus) have reflectance spectra consistent with surface compositions similar to eucrites and howardites and consistent with all being derived from Vesta. None of the observed asteroids have spectra similar to diogenites. We find no spectral distinction between the 15 objects tabulated as members of the Vesta dynamical family and 6 of the 7 sampled "non-family" members that reside just outside the semi-major axis (a), eccentricity (e), and inclination (i) region of the family. The spectral consistency and close orbital (a-e-i) match of these "non-family" objects to Vesta and the Vesta family imply that the true bounds of the family extend beyond the subjective cut-off for membership. Asteroid 2579 Spartacus has a spectrum consistent with a mixture of eucritic material and olivine. Spartacus could contain olivine-rich material from Vesta's mantle or may be unrelated to Vesta altogether. Laboratory measurements of the spectra of eucrites show that samples having nearly identical compositions can display a wide range of spectral slopes. Finer particle sizes lead to an increase in the slope, which is usually referred to as reddening. This range of spectral variation for the best-known meteoritic analogs to the Vestoids, regardless of whether they are actually related to each other, suggests that the extremely red spectral slopes for some Vestoids can be explained by very fine-grained eucritic material on their surfaces. C1 Smithsonian Inst, Natl Museum Nat Hist, Dept Mineral Sci, Washington, DC 20560 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Univ Hawaii Manoa, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. RP Burbine, TH (reprint author), Smithsonian Inst, Natl Museum Nat Hist, Dept Mineral Sci, Washington, DC 20560 USA. NR 74 TC 114 Z9 115 U1 0 U2 6 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 JUN PY 2001 VL 36 IS 6 BP 761 EP 781 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 454VD UT WOS:000169991700002 ER PT J AU Paulin, MG Hoffman, LF AF Paulin, MG Hoffman, LF TI State-space receptive fields of semicircular canal afferent neurons in the bullfrog SO NEUROCOMPUTING LA English DT Article; Proceedings Paper CT 9th Annual Computational Neuroscience Meeting (CNS*00) CY JUL, 2000 CL BRUGGE, BELGIUM DE neural models; neural coding, vestibular, spike train analysis AB Receptive fields are commonly used to describe spatial characteristics of sensory neuron responses. They can be extended to characterize temporal or dynamical aspects by mapping neural responses in dynamical state spaces. The state-space receptive field of a neuron is the probability distribution of the dynamical state of the stimulus-generating system conditioned upon the occurrence of a spike. We have computed state-space receptive fields for semicircular canal afferent neurons in the bullfrog (Rana catesbeiana). We recorded spike times during broad-band Gaussian noise rotational velocity stimuli, computed the frequency distribution of head states at spike times, and normalized these to obtain conditional pdfs for the state. These state-space receptive fields quantify what the brain can deduce about the dynamical state of the head when a single spike arrives from the periphery. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Univ Otago, Dept Zool, Dunedin, New Zealand. Univ Otago, Ctr Neurosci, Dunedin, New Zealand. Univ Calif Los Angeles, Sch Med, Div Head & Neck Surg, Los Angeles, CA 90024 USA. NASA, Ames Res Ctr, Vestibular Res Facil, Mt View, CA USA. RP Paulin, MG (reprint author), Univ Otago, Dept Zool, POB 56, Dunedin, New Zealand. NR 10 TC 4 Z9 4 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-2312 J9 NEUROCOMPUTING JI Neurocomputing PD JUN PY 2001 VL 38 BP 293 EP 298 DI 10.1016/S0925-2312(01)00448-9 PG 6 WC Computer Science, Artificial Intelligence SC Computer Science GA 439QU UT WOS:000169129200040 PM 12194188 ER PT J AU Krukowski, AE Troyer, TW Miller, KD AF Krukowski, AE Troyer, TW Miller, KD TI A model of visual cortical temporal frequency tuning SO NEUROCOMPUTING LA English DT Article; Proceedings Paper CT 9th Annual Computational Neuroscience Meeting (CNS*00) CY JUL, 2000 CL BRUGGE, BELGIUM DE NMDA; LGN; striate cortex; inhibition; cat ID LATERAL GENICULATE-NUCLEUS; CELL RECEPTIVE-FIELDS; NMDA RECEPTORS; RAT NEOCORTEX; CORTEX; CAT; RESPONSES; NEURONS; INPUT AB There are several response properties that distinguish cortical simple cells of cat Vf. layer 4 from the geniculate cells that provide their input. We have recently demonstrated that a developmentally motivated pattern of intracortical inhibition, in conjunction with the observed pattern of geniculocortical connections, can robustly account for the contrast-invariance of simple cell orientation tuning. We now show that this same model circuit unexpectedly accounts for the low-pass shift in the temporal frequency tuning curves of cortical cells relative to geniculate cells. This arises when NMDA-mediated excitatory conductances are included in the thalamocortical synapses, at levels observed experimentally. (C) 2001 Published by Elsevier Science B.V. C1 Univ Calif San Francisco, WM Keck Ctr Integrat Neurosci, Sloan Ctr Theoret Neurobiol, Dept Physiol,Grad Grp Biophys, San Francisco, CA 94143 USA. RP Krukowski, AE (reprint author), NASA, Ames Res Ctr, Mail Stop 262-2, Moffett Field, CA 94035 USA. RI Troyer, Todd/C-2817-2011 OI Troyer, Todd/0000-0002-2037-219X NR 18 TC 2 Z9 2 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-2312 J9 NEUROCOMPUTING JI Neurocomputing PD JUN PY 2001 VL 38 BP 1379 EP 1383 DI 10.1016/S0925-2312(01)00499-4 PG 5 WC Computer Science, Artificial Intelligence SC Computer Science GA 439QU UT WOS:000169129200181 ER PT J AU Lewis, MA Hartmann, MJ Etienne-Cummings, R Cohen, AH AF Lewis, MA Hartmann, MJ Etienne-Cummings, R Cohen, AH TI Control of a robot leg with an adaptive aVLSI CPG chip SO NEUROCOMPUTING LA English DT Article DE neuromorphic engineering; locomotion; central pattern generator; sensorimotor integration; adaptive control ID MODEL; ADAPTATION; LOCOMOTION AB The rhythmic locomotion of animals, such as walking, swimming, and flying, is controlled by groups of neurons called central pattern generators (CPGs). CPGs can autonomously produce rhythmic output, but under normal biological conditions make extensive use of peripheral sensory feedback. Models of CPGs have been used to control robot locomotion, but none of these models have incorporated sensory feedback adaptation. We have constructed an adaptive CPG in an analog VLSI chip, and have used the chip to control a running robot leg. We show that adaptation based on sensory feedback permits a stable gait even in an underactuated condition: the leg can be driven using a hip actuator alone while the knee is purely passive. (C) 2001 Elsevier Science B.V, All rights reserved. C1 Iguana Robot Inc, Mohomet, IL 61853 USA. Caltech MC 303 300 4800, Jet Prop Lab, Pasadena, CA 91109 USA. Johns Hopkins Univ, Dept Elect & Comp Engn, Baltimore, MD 21218 USA. Univ Maryland, Dept Biol Neurosci & Cognit Sci, College Pk, MD 20742 USA. RP Lewis, MA (reprint author), Iguana Robot Inc, POB 628, Mohomet, IL 61853 USA. EM tlewis@iguana-robotics.com; hartmann@brain.jpl.nasa.gov; etienne@ece.jhu.edu; ac61@umail.umd.edu RI Hartmann, Mitra/A-8150-2008; Hartmann, Mitra/B-6766-2009; Etienne-Cummings, Ralph/A-3227-2010 NR 16 TC 19 Z9 19 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-2312 J9 NEUROCOMPUTING JI Neurocomputing PD JUN PY 2001 VL 38 BP 1409 EP 1421 DI 10.1016/S0925-2312(01)00506-9 PG 13 WC Computer Science, Artificial Intelligence SC Computer Science GA 439QU UT WOS:000169129200185 ER PT J AU Mazzei, P Aussel, H Xu, C Salvo, M De Zotti, G Franceschini, A AF Mazzei, P Aussel, H Xu, C Salvo, M De Zotti, G Franceschini, A TI ISOCAM observations of the deep IRAS 60 micron sample in the NEP region - II. Comparison of ISO and IRAS galaxy counts SO NEW ASTRONOMY LA English DT Article DE galaxies : starburst; galaxies : photometry; infrared; surveys ID LUMINOSITY FUNCTION; STATISTICAL-METHODS; ASTRONOMICAL DATA; UPPER LIMITS; EVOLUTION; ISOPHOT AB We have determined IRAS flux densities at positions of sources detected by our ISOCAM LW3 observations of the IRAS deep survey sample in the north ecliptic polar region [ApJS 63 (1987) 311]. Exploiting the higher angular resolution of ISOCAM to deal with confusion effects and properly correcting the fluxes for observational biases, we show that 60 mum counts can be reliably determined only above 80 mJy. We have also derived the distributions of 15 to 60 mum and of 100 to 60 mum flux density ratios for the sample and used them to extrapolate the 60 mum counts of galaxies to the ISOCAM LW3 15 mm and to the ISOPHOT C100 90 mm bands. Our results cover a flux density range intermediate between those of the European Large Area ISO Survey and the IRAS Faint Source Survey, hence allowing to establish a direct link between ISO and IRAS surveys. The present estimate has the further advantage of being automatically rid of the stellar contamination to the galaxy counts and provides a crucial boundary to constrain evolutionary properties of faint mid- and far-IR sources. (C) 2001 Published by Elsevier Science B. V. C1 Dipartimento Astron, I-35122 Padua, Italy. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Australian Natl Univ, Mt Stromlo Observ, RSAA, Weston, ACT 2611, Australia. Osservatorio Astron Padova, I-35122 Padua, Italy. RP Franceschini, A (reprint author), Dipartimento Astron, Vicolo Osservatorio 5, I-35122 Padua, Italy. OI Mazzei, Paola/0000-0002-8004-1034 NR 34 TC 15 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1384-1092 J9 NEW ASTRON JI New Astron. PD JUN PY 2001 VL 6 IS 5 BP 265 EP 276 DI 10.1016/S1384-1076(01)00052-5 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 449XV UT WOS:000169713200001 ER PT J AU Gunapala, SD Bandara, SV Liu, JK Luong, EM Rafol, SB Mumolo, JM Ting, DZ Bock, JJ Ressler, ME Werner, MW Levan, PD Chehayeb, R Kukkonen, CA Levy, M Levan, P Fauci, MA AF Gunapala, SD Bandara, SV Liu, JK Luong, EM Rafol, SB Mumolo, JM Ting, DZ Bock, JJ Ressler, ME Werner, MW Levan, PD Chehayeb, R Kukkonen, CA Levy, M Levan, P Fauci, MA TI Recent developments and applications of quantum well infrared photodetector focal plane arrays SO OPTO-ELECTRONICS REVIEW LA English DT Article; Proceedings Paper CT 2nd International Conference on Solid State Crystals 2000 (ICSSC 2000) CY OCT 09-13, 2000 CL ZAKOPANE, POLAND SP Military Univ Technol, Inst Appl Phys, Polish Soc Crystal Growth, SPIE, State Comm Sci Res, European Off Aerosp Res & Dev, Tech Univ Lodz, Inst Phys, Wroclaw Univ Technol, Inst Phys DE infrared detectors; long-wavelength infrared; multi quantum well; multi-colour; focal plane arrays ID QWIP ARRAY; CAMERA; FABRICATION AB One of the simplest device realisations of the classic particle-in-the-box problem of basic quantum mechanics is the quantum well infrared photodetector (QWIP). In this paper we discuss the effect of focal plane array non uniformity on the performance, optimisation of the detector design, material growth and processing that has culminated in realisation of large format long-wavelength QWIP cameras, holding forth great promise for many applications in 6-18 micron wavelength range in science, medicine, defence and industry. In addition, we present the recent developments in long-wavelength/very long-wavelength dualband QWIP imaging camera for various applications. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. USAF, Res Lab, Kirtland AFB, NM 87117 USA. QWIP Technol, Altadena, CA 91001 USA. Univ So Calif Hosp, Los Angeles, CA 90027 USA. OmniCorder Technol Inc, Stony Brook, NY 11790 USA. RP Gunapala, SD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM gunapala@mail1.jpl.nasa.gov NR 29 TC 7 Z9 7 U1 0 U2 0 PU VERSITA PI WARSAW PA SOLIPSKA 14A-1, 02-482 WARSAW, POLAND SN 1230-3402 J9 OPTO-ELECTRON REV JI Opto-Electron. Rev. PD JUN PY 2001 VL 9 IS 2 BP 150 EP 163 PG 14 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA 445NY UT WOS:000169465200009 ER PT J AU Weber, AL AF Weber, AL TI The sugar model: Catalytic flow reactor dynamics of pyruvaldehyde synthesis from triose catalyzed by poly-L-lysine contained in a dialyzer SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article DE catalysis; flow reactor; glyceraldehyde; molecular evolution; origin of life; prebiotic synthesis; pyruvaldehyde; sugar dehydration; triose ID SELF-REPLICATING PEPTIDE; GLYCERALDEHYDE; FORMALDEHYDE; THIOESTERS; KINETICS; PHASE; THIOL AB The formation of pyruvaldehyde from triose sugars was catalyzed by poly-L-lysine contained in a small dialyzer with a 100 molecular weight cut off (100 MWCO) suspended in a much larger triose substrate reservoir at pH 5.5 and 40 degreesC. The polylysine confined in the dialyzer functioned as a catalytic flow reactor that constantly brought in triose from the substrate reservoir by diffusion to offset the drop in triose concentration within the reactor caused by its conversion to pyruvaldehyde. The catalytic polylysine solution (400 mM, 0.35 mL) within the dialyzer generated pyruvaldehyde with a synthetic intensity (rate/volume) that was 3400 times greater than that of the triose substrate solution (12 mM, 120 mL) outside the dialyzer. Under the given conditions the final yield of pyruvaldehyde was greater than twice the weight of the polylysine catalyst. During the reaction the polylysine catalyst was poisoned presumably by reaction of its amino groups with aldehyde reactants and products. Similar results were obtained using a dialyzer with a 500 MWCO. The dialyzer method of catalyst containment was selected because it provides a simple and easily manipulated experimental system for studying the dynamics and evolutionary development of confined autocatalytic processes related to the origin of life under anaerobic conditions. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP Weber, AL (reprint author), NASA, Ames Res Ctr, SETI Inst, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 36 TC 11 Z9 11 U1 1 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD JUN PY 2001 VL 31 IS 3 BP 231 EP 240 DI 10.1023/A:1010642016903 PG 10 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 430CK UT WOS:000168555800003 PM 11434102 ER PT J AU Jacobson, NS Myers, DL Zhu, D Humphrey, DL AF Jacobson, NS Myers, DL Zhu, D Humphrey, DL TI Rhenium/oxygen interactions at elevated temperatures SO OXIDATION OF METALS LA English DT Article DE oxidation; rhenium; gas/solid reactions; refractory metals AB The oxidation of pure rhenium was examined from 600 to 1400 degreesC in oxygen/argon mixtures. Linear weight-loss kinetics were observed. Gas pressures, flow rates, and temperatures were methodically varied to determine the rate-controlling steps. The reaction at 600 and 800 degreesC appeared to be controlled by a chemical-reaction step at the surface; whereas the higher-temperature reactions appeared to be controlled by gas-phase diffusion of oxygen to the rhenium surface. Attack of the rhenium appeared along grain boundaries and crystallographic planes. C1 NASA, Glenn Res Ctr, Ohio Aerosp Inst, Cleveland, OH 44135 USA. E Cent Univ, Dept Chem, Ada, OK 74820 USA. RP Jacobson, NS (reprint author), NASA, Glenn Res Ctr, Ohio Aerosp Inst, Cleveland, OH 44135 USA. RI Jacobson, Nathan/A-9411-2009 NR 11 TC 4 Z9 4 U1 1 U2 2 PU KLUWER ACADEMIC/PLENUM PUBL PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0030-770X J9 OXID MET JI Oxid. Met. PD JUN PY 2001 VL 55 IS 5-6 BP 471 EP 480 DI 10.1023/A:1010355714642 PG 10 WC Metallurgy & Metallurgical Engineering SC Metallurgy & Metallurgical Engineering GA 428CX UT WOS:000168444500004 ER PT J AU Olson, CF AF Olson, CF TI Locating geometric primitives by pruning the parameter space SO PATTERN RECOGNITION LA English DT Article DE geometric primitive extraction; parameter estimation; divide-and-conquer search; robust error modeling; randomized algorithms ID HOUGH TRANSFORM; VISION AB This paper examines the detection of geometric primitives using 2D edge pixels or 3D range points. The geometric primitives are described by parametric equations in the image space. An explicit error model allows the primitives to be extracted robustly, while a hierarchical search of the parameter space with conservative pruning allows the primitives to be located efficiently. The result is an efficient search strategy that is robust to distracters, missing data and noise, and that does not require an initial estimate of the positions of the geometric primitives. We apply these techniques to circle detection, for locating craters on planetary bodies and analyzing engineering drawings, and to cylinder detection, for finding unexploded ordnance in test ranges. (C) 2001 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Olson, CF (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 125-209, Pasadena, CA 91109 USA. NR 16 TC 13 Z9 13 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 JUN PY 2001 VL 34 IS 6 BP 1247 EP 1256 PG 10 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 424AD UT WOS:000168209200011 ER PT J AU Greenwood, JB Williams, ID Smith, SJ Chutjian, A AF Greenwood, JB Williams, ID Smith, SJ Chutjian, A TI Experimental investigation of the processes determining x-ray emission intensities from charge-exchange collisions SO PHYSICAL REVIEW A LA English DT Article ID SELECTIVE ELECTRON-CAPTURE; LOW-ENERGY COLLISIONS; EXTREME-ULTRAVIOLET EMISSION; CROSS-SECTIONS; SOLAR-WIND; SLOW COLLISIONS; COMET HYAKUTAKE; SINGLE-ELECTRON; IONS; HE AB Absolute cross sections have been measured for single and double charge exchange and x-ray line emission for highly charged ions of C, N, 0, and Ne colliding with He, H-2 CO2, and H2O at collisions energies of 7q keV. Present results of charge exchange in He and H-2 compare favorably with previous results. For CO2 and H2O, where prior work is scarce, the classical overbarrier model is found to overestimate results by up to a factor of 3. An analysis of the relative intensities of the observed Lyman x-ray transitions indicates that capture into l states is not statistical, as collision velocities are insufficient to populate the highest angular-momentum states. The importance of autoionization following multiple capture is highlighted, and enhanced radiative stabilization following double capture is observed and compared to other studies. Present results are also discussed in terms of mechanisms likely to generate x-ray emission in comets. C1 Queens Univ Belfast, Dept Phys, Belfast BT7 1NN, Antrim, North Ireland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Greenwood, JB (reprint author), Queens Univ Belfast, Dept Phys, Belfast BT7 1NN, Antrim, North Ireland. EM j.greenwood@qub.ac.uk; i.williams@qub.ac.uk; steven.j.smith@jpl.nasa.gov; ara.chutjian@jpl.nasa.gov RI Greenwood, Jason/L-4799-2014 NR 54 TC 81 Z9 81 U1 1 U2 3 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 JUN PY 2001 VL 63 IS 6 AR 062707 DI 10.1103/PhysRevA.63.062707 PG 9 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 439TZ UT WOS:000169134800038 ER PT J AU Kok, P Boto, AN Abrams, DS Williams, CP Braunstein, SL Dowling, JP AF Kok, P Boto, AN Abrams, DS Williams, CP Braunstein, SL Dowling, JP TI Quantum-interferometric optical lithography: Towards arbitrary two-dimensional patterns SO PHYSICAL REVIEW A LA English DT Article ID LIMIT AB As demonstrated by Boto et al. [Phys. Rev. Lett. 85, 2733 (2000)], quantum lithography offers an increase in resolution below the diffraction limit. Here, we generalize this procedure in order to create patterns in one and two dimensions. This renders quantum lithography a potentially useful tool in nanotechnology. C1 Bangor Univ, Bangor LL57 1UT, Gwynedd, Wales. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kok, P (reprint author), Bangor Univ, Bangor LL57 1UT, Gwynedd, Wales. EM pieter@sees.bangor.ac.uk RI Braunstein, Samuel/A-5501-2009; Kok, Pieter/B-1658-2010; DOWLING, JONATHAN/L-2749-2013 NR 12 TC 99 Z9 99 U1 0 U2 3 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 JUN PY 2001 VL 63 IS 6 AR 063407 DI 10.1103/PhysRevA.63.063407 PG 8 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 439TZ UT WOS:000169134800066 ER PT J AU Shertzer, J Temkin, A AF Shertzer, J Temkin, A TI Direct calculation of the scattering amplitude without partial-wave analysis SO PHYSICAL REVIEW A LA English DT Article AB Two developments in scattering theory are reported. We show, in a practical way, how one can calculate the scattering amplitude without invoking a partial-wave expansion. First, the integral expression for the scattering amplitude f(theta) is simplified by an analytic integration over the azimuthal angle. Second, the full scattering wave function that appears in the integral expression for f(theta) is obtained by solving the Schrodinger equation with the finite element method. As an example, we calculate electron scattering from static hydrogen (the Hartree potential). With minimal computational effort, we obtain accurate and stable results for the scattering amplitude. C1 Coll Holy Cross, Dept Phys, Worcester, MA 01610 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Shertzer, J (reprint author), Coll Holy Cross, Dept Phys, Worcester, MA 01610 USA. NR 8 TC 7 Z9 7 U1 0 U2 0 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 JUN PY 2001 VL 63 IS 6 AR 062714 DI 10.1103/PhysRevA.63.062714 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 439TZ UT WOS:000169134800045 ER PT J AU Bridges, F Booth, CH Anderson, M Kwei, GH Neumeier, JJ Snyder, J Mitchell, J Gardner, JS Brosha, E AF Bridges, F Booth, CH Anderson, M Kwei, GH Neumeier, JJ Snyder, J Mitchell, J Gardner, JS Brosha, E TI Mn K-edge XANES studies of La(1-x)A(x)MnO(3) systems (A = Ca, Ba, Pb) SO PHYSICAL REVIEW B LA English DT Article ID X-RAY-ABSORPTION; FERROMAGNETIC KONDO MODEL; COLOSSAL-MAGNETORESISTANCE; ELECTRONIC-STRUCTURE; LOCAL-STRUCTURE; LA1-XCAXMNO3 SYSTEM; PEROVSKITE OXIDES; PHASE-DIAGRAM; THIN-FILMS; T-C AB We present Mn K-edge x-ray absorption near-edge structure (XANES) data for a number of manganite systems as a function of temperature. The 1s absorption edge for the Ca-substituted samples is very sharp, almost featureless, and shifts uniformly upwards with increasing Ca content. The interpretation of this result is controversial because the lack of structure appears difficult to reconcile with a mixture of Mn+3 and Mn+4 ions or with several different Mn-O bond lengths at high T. We propose a possible solution in terms of covalency and considerable overlap of the Mn p states (mostly Mn 4p). The manganite preedge structure is quite similar to that for a large number of other Mn compounds, with two or three small peaks that are ascribed to 1s-3d weakly allowed dipole transitions plus possibly a small quadrupole component. The weak dipole transitions are explained as arising from a hybridization of the Mn 4p stale of the excited atom with an odd symmetry combination of Mn 3d states on adjacent Mn atoms. The first preedge peak A(1) has a small shift to higher energy with increasing valence while the next peak A(2) is nearly independent of dopant concentration at 300 K. However, for the colossal magnetoresistance (CMR) samples the A(2) preedge peak shifts to a lower energy below the ferromagnetic transition temperature T-c, resulting in a decrease in the A(2)-A(1) splitting by similar to 0.4 eV. This indicates a change in the higher-energy 3d bands, most likely the minority spin e(g) , plus some change in covalency. In addition, the amplitudes are temperature dependent for the CMR materials, with the change in A(1), A(2) correlated with the change in sample magnetization. For the charge ordered (CO) sample, the analysis suggests that the change in the preedge is produced by a distortion that increases below T-CO. We discuss these results in terms of some of the theoretical models that have been proposed and other recent XANES studies. C1 Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Florida Atlantic Univ, Dept Phys, Boca Raton, FL 33431 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Argonne Natl Lab, Argonne, IL 60439 USA. RP Bridges, F (reprint author), Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. RI Gardner, Jason/A-1532-2013; Booth, Corwin/A-7877-2008 NR 56 TC 77 Z9 77 U1 2 U2 18 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 JUN 1 PY 2001 VL 63 IS 21 AR 214405 DI 10.1103/PhysRevB.63.214405 PG 14 WC Physics, Condensed Matter SC Physics GA 438NV UT WOS:000169060700042 ER PT J AU Rubincam, DP Lowman, PD Chovitz, B AF Rubincam, DP Lowman, PD Chovitz, B TI John Aloysius O'Keefe - Obituary SO PHYSICS TODAY LA English DT Biographical-Item C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Rubincam, DP (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Rubincam, David/D-2918-2012 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD JUN PY 2001 VL 54 IS 6 BP 76 EP 77 DI 10.1063/1.1387605 PG 2 WC Physics, Multidisciplinary SC Physics GA 436BV UT WOS:000168917400022 ER PT J AU Titarchuk, L Shrader, C AF Titarchuk, L Shrader, C TI Black hole candidates weigh in SO PHYSICS TODAY LA English DT Letter ID SPECTRA C1 George Mason Univ, Fairfax, VA 22030 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Titarchuk, L (reprint author), George Mason Univ, Fairfax, VA 22030 USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD JUN PY 2001 VL 54 IS 6 BP 82 EP 83 DI 10.1063/1.1387615 PG 2 WC Physics, Multidisciplinary SC Physics GA 436BV UT WOS:000168917400032 ER PT J AU Encrenaz, T Coradini, A Beaudin, G Crovisier, J Drossart, P Erard, S Germain, B Gulkis, S Langevin, Y Lellouch, E AF Encrenaz, T Coradini, A Beaudin, G Crovisier, J Drossart, P Erard, S Germain, B Gulkis, S Langevin, Y Lellouch, E TI The Mars flyby of ROSETTA: an opportunity for infrared and microwave high-resolution sounding SO PLANETARY AND SPACE SCIENCE LA English DT Article ID WATER-VAPOR; VERTICAL-DISTRIBUTION; MARTIAN ATMOSPHERE; IMAGING SPECTROMETER; MIDDLE ATMOSPHERE; MU-M; SPECTRA; SPECTROSCOPY; ISM; TEMPERATURE AB The Mars flyby of ROSETTA will provide a valuable opportunity for sounding, at high spatial resolution, the Mars atmosphere and surface in the infrared and microwave range. The VIRTIS infrared imaging spectrometer should be able to determine the surface mineralogy and temperature of the observed areas, the abundances of minor constituents (H2O, CO), and possibly to study the atmospheric thermal profile. VIRTIS will complement the OMEGA and PFS infrared spectrometers on-board the Mars Express mission, expected to operate in Mars orbit at the time of the ROSETTA flyby. The MIRO microwave spectrometer is expected to provide information on the thermal profile, the H2O vertical distribution, the temperature of the subsurface, and possibly the atmospheric winds. In addition, the Mars flyby of ROSETTA will provide the first opportunity for testing the VIRTIS and MIRO instruments, in particular for wavelength/frequency and phstometry/radiometry calibration. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Observ Paris, DESPA, F-92195 Meudon, France. CNR, Inst Astrofis Spaziale, I-00133 Rome, Italy. Observ Paris, DEMIRM, F-75014 Paris, France. Observ Paris, ARPEGES, F-75014 Paris, France. Inst Astrophys Spatiale, F-91405 Orsay, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Encrenaz, T (reprint author), Observ Paris, DESPA, F-92195 Meudon, France. NR 35 TC 8 Z9 8 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 JUN PY 2001 VL 49 IS 7 BP 673 EP 687 DI 10.1016/S0032-0633(01)00010-1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441CT UT WOS:000169214000002 ER PT J AU Encrenaz, T Lellouch, E Paubert, G Gulkis, S AF Encrenaz, T Lellouch, E Paubert, G Gulkis, S TI The water vapor vertical distribution on mars from millimeter transitions of HDO and (H2O)-O-18 SO PLANETARY AND SPACE SCIENCE LA English DT Article ID MARTIAN ATMOSPHERE; INTERANNUAL VARIABILITY; ABUNDANCE; SURFACE; ISM; TEMPERATURES; BEHAVIOR; SEASON; LINES AB Millimeter observations of Mars were performed in April 1997, near opposition, using heterodyne spectroscopy with the IRAM 30-m antenna at Pico Veleta (Spain). During the observations, the northern latitude of the sub-Earth point was about 24 degrees. The planetocentric longitude of the Sun (L,) was close to 100 degrees, which corresponds to the beginning of Martian northern summer, when the water vapor abundance is expected to be maximum at high northern latitudes. A strong emission was detected in the 226 GHz transition of HDO at the disk center (latitude = +24 degrees) and around the north pole. The 203 GHz transition of (H2O)-O-18 was also unambiguously detected. The thermal profile was retrieved from the simultaneous observation of (CO)-C-12(2-1) at 230 GHz, (CO)-C-13(2-1) at 220 GHz and (CO)-C-12(1-0) at 115 GHz. Using both HDO and (H2O)-O-18 transitions, we derive a water vapor content of 52 (+34, -23) pr mum at the disk center and 85 (+30, -33) pr mum at the north pole. These high values are consistent with the seasonal water cycle found by the MAWD Viking data (Jakosky, Kaberle, in: H.H. Kieffer, B.M. Jakosly, C.N. Synder, M.S. Mathews (Eds.), Mars, University of Arizona Press, 1992.) in the case of the northern region, but higher than the Viking estimates at low latitude. The water vapor profile was found to be saturated at a level of 9 (+5/-4) km at the disk center and 5 (+3, -2) km at the north pole. These saturation levels are consistent with MAWD Viking data (H.M. Hart, Seasonal changes in the abundance and vertical distribution of water vapor in the atmosphere of Mars, Ph.D. Thesis, University of Colorado, 1989) and with millimeter measurements performed by Clancy et al. (Icarus 122 (1996) 36); they confirm that water is confined to the lower troposphere near aphelion. The quality of our data did not allow us to derive a precise determination of the D/H Martian ratio, which is found to be, within a factor of 2, equal to 6 times the terrestrial ratio, in agreement with previous measurements. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Observ Paris, DESPA, F-92195 Meudon, France. IRAM, E-18012 Granada, Spain. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Encrenaz, T (reprint author), Observ Paris, DESPA, F-92195 Meudon, France. NR 39 TC 25 Z9 25 U1 1 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 JUN PY 2001 VL 49 IS 7 BP 731 EP 741 DI 10.1016/S0032-0633(01)00009-5 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441CT UT WOS:000169214000005 ER PT J AU Watters, TR Konopliv, AS AF Watters, TR Konopliv, AS TI The topography and gravity of Mare Serenitatis: implications for subsidence of the mare surface SO PLANETARY AND SPACE SCIENCE LA English DT Article ID WRINKLE RIDGES; CLEMENTINE MISSION; LUNAR; MOON; ORIGIN; BASINS; EVOLUTION; TECTONICS; ALTIMETRY; RADAR AB The long wavelength topography of Mare Serenitatis was analyzed using topographic data obtained by the Clementine laser ranging instrument (LIDAR). The topography shows that the lowest elevations in the mare surface occur near the margins of the basin. The present mare surface reflects a long period of volcanism, subsidence, and deformation. Subsidence is generally attributed to a Gaussian-shaped, superisostatic load from the mare basalts that results in flexure of the lunar lithosphere. Gravity data from Lunar Prospector suggest that the basalt sequence in the interior of Serenitatis is generally uniform in thickness and thins rapidly at the margins. This suggests that the topographic lows in the basin do not coincide with areas where the mare basalts are thick but rather occur where the basalts thin. The topographic lows also do not appear to coincide with accumulations of the youngest mare basalt units. The long wavelength topography of Mare Serenitatis may reflect subsidence influenced by pre-mare basalt basin topography and preexisting zones of lithospheric weakness. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Smithsonian Inst, Natl Air & Space Museum, Ctr Earth & Planetary Studies, Washington, DC 20560 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Watters, TR (reprint author), Smithsonian Inst, Natl Air & Space Museum, Ctr Earth & Planetary Studies, Washington, DC 20560 USA. NR 51 TC 9 Z9 10 U1 1 U2 2 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 JUN PY 2001 VL 49 IS 7 BP 743 EP 748 DI 10.1016/S0032-0633(01)00007-1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 441CT UT WOS:000169214000006 ER PT J AU Lincoln, JE Morgan, RJ Shin, EE AF Lincoln, JE Morgan, RJ Shin, EE TI Fundamental investigation of cure-induced microcracking in carbon fiber/bismaleimide cross-ply laminates SO POLYMER COMPOSITES LA English DT Article ID DYNAMIC-MECHANICAL ANALYSIS; POLYMER-MATRIX COMPOSITES; BISMALEIMIDE PMR-15 COMPOSITES; FIBER REINFORCED COMPOSITES; TRANSVERSE CRACKING; THERMAL STRAINS; INTERFACIAL MICROCRACKING; STIFFNESS REDUCTION; EPOXY-RESIN; STRESS AB Transverse microcracks are present in carbon fiber/bismaleimide (BMI) cross-ply composite laminates composed of 4.4'-bismaleimidodiphenylmethane (BMPM)/ 0,0'-diallyl bisphenol A (DABPA) matrices after standard cure and fabrication conditions, and grow in width upon subsequent postcure. This investigation characterizes cure-induced microcracking in terms of the critical fundamental macroscopic, microscopic, and molecular damage mechanisms and thresholds, and a cure cycle modification that prevents microcrack formation under standard processing conditions for [0 degrees /90 degrees](S) laminates is examined. A unique in-situ technique is utilized in which cure of the laminate is performed inside the chamber of an environmental scanning electron microscope (ESEM), allowing for (i) physical observation of microcrack growth and formation mechanisms and (ii) characterization of microcracking onset time-temperature thresholds. The cure cycle modification that prevents microcracking is an extended initial cure time at 177 degreesC prior to higher temperature cure regimes. Effects of this modification are examined through network structure-property-processing interrelationships by way of (i) dynamic mechanical analysis (DMA), (ii) optical and electron microscopy, (iii) differential scanning calorimetry (DSC), and (iv) our previous work on carbon fiber/bismaleimide composites. From the aforementioned analysis it was concluded that an extended initial cure time at 177 degreesC prior to higher temperature cure steps prevents microcracking under standard fabrication postcure conditions for [0 degrees /90 degrees](S) laminates: no microcracking was observed until an additional postcure of 6 h at 300 degreesC. This microcrack resistance was independent of initial BMPM:DABPA monomer stoichiometry for the two monomer ratios examined and associated with an improved fiber-matrix interface and lower composite residual stress. C1 Michigan State Univ, Dept Mat Sci & Mech, E Lansing, MI 48824 USA. Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NASA, Glenn Res Ctr, Ohio Aerosp Inst, Cleveland, OH 44135 USA. RP Lincoln, JE (reprint author), Michigan State Univ, Dept Mat Sci & Mech, E Lansing, MI 48824 USA. NR 84 TC 12 Z9 12 U1 0 U2 13 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0272-8397 EI 1548-0569 J9 POLYM COMPOSITE JI Polym. Compos. PD JUN PY 2001 VL 22 IS 3 BP 397 EP 419 DI 10.1002/pc.10547 PG 23 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA 445GT UT WOS:000169450300007 ER PT J AU Yau, ST Thomas, BR Galkin, O Gliko, O Vekilov, PG AF Yau, ST Thomas, BR Galkin, O Gliko, O Vekilov, PG TI Molecular mechanisms of microheterogeneity-induced defect formation in ferritin crystallization SO PROTEINS-STRUCTURE FUNCTION AND GENETICS LA English DT Article ID ATOMIC-FORCE MICROSCOPY; EGG-WHITE LYSOZYME; PROTEIN CRYSTALLIZATION; MACROMOLECULAR CRYSTALLIZATION; APOFERRITIN MOLECULES; SURFACE-MORPHOLOGY; GROWTH-KINETICS; CRYSTAL-GROWTH; TAPPING MODE; HUMAN-H AB We apply in situ atomic force microscopy to the crystallization of ferritins from solutions containing approximate to5% (w/w) of their inherent molecular dimers. Molecular resolution imaging shows that the dimers consist of two bound monomers. The constituent monomers are likely partially denatured, resulting in increased hydrophobicity of the dimer surface. Correspondingly, the dimers strongly adsorb on the crystal surface. The adsorbed dimers hinder step growth and on incorporation by the crystal initiate stacks of up to 10 triple and single vacancies in the subsequent crystal layers. The molecules around the vacancies are shifted by approximate to0.1 molecular dimensions from their crystallographic positions. The shifts strain the lattice and, as a consequence, at crystal sizes > 200 mum, the accumulated strain is resolved by a plastic deformation whereupon the crystal breaks into mosaic blocks 20-50 mum in size. The critical size for the onset of mosaicity is similar for ferritin and apoferritin and close to the value for a third protein, lysozyme; it also agrees with theoretical predictions. Trapped microcrystals in ferritin and apoferritin induce strain with a characteristic length scale equal to that of a single point defect, and, as a consequence, trapping does not contribute to the mosaicity. The sequence of undesired phenomena that include heterogeneity generation, adsorption, incorporation, and the resulting lattice strain and mosaicity in this and other proteins systems, could be avoided by improved methods to separate similar proteins species (microheterogeneity) or by increasing the biochemical stability of the macromolecules against oligomerization. Proteins 2001;43:343-352, (C) 2001 Wiley-Liss, Inc. C1 Univ Alabama, Dept Chem, Huntsville, AL 35899 USA. Univ Alabama, Ctr Micrograv & Mat Res, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Vekilov, PG (reprint author), Univ Alabama, Dept Chem, Von Braun Res Hall D-9, Huntsville, AL 35899 USA. FU NHLBI NIH HHS [HL 58038] NR 60 TC 31 Z9 32 U1 1 U2 5 PU WILEY-LISS PI NEW YORK PA DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0887-3585 J9 PROTEINS JI Proteins PD JUN 1 PY 2001 VL 43 IS 4 BP 343 EP 352 DI 10.1002/prot.1047 PG 10 WC Biochemistry & Molecular Biology; Biophysics SC Biochemistry & Molecular Biology; Biophysics GA 436DJ UT WOS:000168921000001 PM 11340651 ER PT J AU Francis, PJ Wilson, GM Woodgate, BE AF Francis, PJ Wilson, GM Woodgate, BE TI On the gas surrounding high-redshift galaxy clusters SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF AUSTRALIA LA English DT Article DE galaxies : clusters : individual (2142-4420); galaxies : distances and redshifts; quasars : absorption lines ID LYMAN-BREAK GALAXIES; 2-POINT CORRELATION-FUNCTION; LY-ALPHA EMISSION; ABSORPTION SYSTEMS; STAR-FORMATION; EVOLUTION; CLOUDS; Z-SIMILAR-TO-3; KINEMATICS; TELESCOPE AB Francis & Hewett (1993) identified two 10 Mpc-scale regions of the high-redshift universe that were seemingly very overdense in neutral hydrogen. Subsequent observations showed that at least one of these gas-rich regions enveloped a cluster of galaxies at redshift 2.38. We present improved observations of the three background QSOs with sightlines passing within a few Mpc of this cluster of galaxies. All three QSOs show strong neutral hydrogen absorption at the cluster redshift, suggesting that this cluster (and perhaps all high-redshift clusters) may be surrounded by a similar to5 Mpc-scale region containing similar to 10(12) M-. of neutral gas. We show that if most high-redshift clusters are surrounded by such regions, the gas must be in the form of many small (<1 kpc), dense ( >0.03 cm(-3)) clouds, each of mass < 10(6) M-.). These clouds are themselves probably gathered into >20 kpc-sized clumps, which may be galaxy halos or protogalaxies. If this gas exists. it will be partially photoionised by the UV background. We predict the diffuse Ly alpha flux from this photoionisation, and place observational limits on its intensity. C1 Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Francis, PJ (reprint author), Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia. RI Woodgate, Bruce/D-2970-2012 NR 70 TC 11 Z9 11 U1 0 U2 1 PU C S I R O PUBLISHING PI COLLINGWOOD PA 150 OXFORD ST, PO BOX 1139, COLLINGWOOD, VICTORIA 3066, AUSTRALIA SN 1323-3580 J9 PUBL ASTRON SOC AUST JI Publ. Astron. Soc. Aust. PD JUN PY 2001 VL 18 IS 1 BP 64 EP 75 DI 10.1071/AS01005 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 465MD UT WOS:000170592000005 ER PT J AU Badhwar, G Benton, EV AF Badhwar, G Benton, EV TI Prediction and measurements of secondary neutrons in space - Preface SO RADIATION MEASUREMENTS LA English DT Editorial Material C1 NASA, Johnson Spacecraft Ctr, Houston, TX 77058 USA. Univ San Francisco, San Francisco, CA 94117 USA. RP Badhwar, G (reprint author), NASA, Johnson Spacecraft Ctr, SN,2101 NASA Rd 1, Houston, TX 77058 USA. NR 0 TC 6 Z9 7 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 2001 VL 33 IS 3 SI SI BP 227 EP 227 DI 10.1016/S1350-4487(01)00046-4 PG 1 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 439EW UT WOS:000169098700001 ER PT J AU Badhwar, GD Keith, JE Cleghorn, TF AF Badhwar, GD Keith, JE Cleghorn, TF TI Neutron measurements onboard the space shuttle SO RADIATION MEASUREMENTS LA English DT Article ID LOW EARTH ORBIT AB The radiation environment inside a shielded volume is highly complex, consisting of both charged and neutral particles. Since the inception of human space flights, the charged particle component has received virtually all of the attention. There is however, a significant production of secondary neutrons, particularly from the aluminum structure in low earth orbiting spacecrafts. The interactions of galactic cosmic rays (GCR), and solar energetic particles with the earth's atmosphere produce a non-isotropic distribution of albedo neutrons. Inside any reasonable habitable module, the average radiation quality factor of neutrons is about 4-5 times larger than the corresponding average quality factor of charged particles. The measurement of neutrons and their energy spectra is a difficult problem due the intense sources of charged particles. This paper reviews the results of Shuttle flight experiments (made during both solar maximum and solar minimum) to measure the contribution of neutrons to the dose equivalent, as well as theoretical calculations to estimate the appropriate range of neutron energies that contribute most to the dose equivalent. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, SN 2101 NASA Rd 1, Houston, TX 77058 USA. NR 22 TC 21 Z9 22 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 2001 VL 33 IS 3 SI SI BP 235 EP 241 DI 10.1016/S1350-4487(00)00159-1 PG 7 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 439EW UT WOS:000169098700003 PM 11852943 ER PT J AU Braby, LA Badhwar, GD AF Braby, LA Badhwar, GD TI Proportional counter as neutron detector SO RADIATION MEASUREMENTS LA English DT Article DE neutron dosimetry; proportional counter AB A technique to separate out the dose, and lineal energy spectra of neutrons and charged particles is described. It is based on using two proportional counters, one with a tissue equivalent wall, and the other with similar characteristics but wall made from a non-hydrogen containing material. Results of a calibration in a neutron field are also shown. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Texas A&M Univ, Dept Phys, College Stn, TX 77843 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77059 USA. RP Braby, LA (reprint author), Texas A&M Univ, Dept Phys, College Stn, TX 77843 USA. NR 3 TC 4 Z9 5 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 2001 VL 33 IS 3 SI SI BP 265 EP 267 DI 10.1016/S1350-4487(00)00160-8 PG 3 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 439EW UT WOS:000169098700006 PM 11855407 ER PT J AU Shavers, MR Cucinotta, FA Wilson, JW AF Shavers, MR Cucinotta, FA Wilson, JW TI HZETRN: neutron and proton production in quasi-elastic scattering of GCR heavy-ions SO RADIATION MEASUREMENTS LA English DT Article ID COLLISIONS AB The development of transport models for radiation shielding design and evaluation has provided a series of deterministic computer codes that describe galactic cosmic radiation (GCR), solar particle events, and experimental beams at particle accelerators. These codes continue to be modified to accommodate new theory and improvements to the particle interaction database (Cucinotta ct al., 1994, NASA Technical Paper 3472, US Government Printing Office, Washington DC). The solution employed by the heavy-ion transport code HZETRN was derived with the assumption that nuclear fragments are emitted with the same velocity as the incident ion through velocity conserving nuclear interactions. This paper presents a version of the HZETRN transport code that provides a more realistic distribution of the energy of protons and neutrons emitted from GCR interactions in shields. This study shows that the expected GCR dose equivalent is lower than previously calculated for water shields that are less than 110 g cm(-2) thick. Calculations of neutron energy spectra in low Earth orbit indicate substantial contributions from relativistic neutrons. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Loma Linda Univ, Radiobiol Program, Loma Linda, CA 92354 USA. NASA, Lyndon B Johnson Space Ctr, SN3, Houston, TX 77058 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Shavers, MR (reprint author), Loma Linda Univ, Radiobiol Program, 11175 Campus St,CSP A-1010, Loma Linda, CA 92354 USA. NR 19 TC 1 Z9 1 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 2001 VL 33 IS 3 SI SI BP 347 EP 353 DI 10.1016/S1350-4487(01)00048-8 PG 7 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 439EW UT WOS:000169098700016 PM 11855417 ER PT J AU Singleterry, RC Badavi, FF Shinn, JL Cucinotta, FA Badhwar, GD Clowdsley, MS Heinbockel, JH Wilson, JW Atwell, W Beaujean, R Kopp, J Reitz, G AF Singleterry, RC Badavi, FF Shinn, JL Cucinotta, FA Badhwar, GD Clowdsley, MS Heinbockel, JH Wilson, JW Atwell, W Beaujean, R Kopp, J Reitz, G TI Estimation of neutron and other radiation exposure components in low earth orbit SO RADIATION MEASUREMENTS LA English DT Article DE neutron; exposure; extraterrestrial radiation; damage; astronauts; risk ID EQUIVALENT; SHUTTLE AB The interaction of high-energy space radiation with spacecraft materials generates a host of secondary particles, some, such as neutrons, are more biologically damaging and penetrating than the original primary particles. Before committing astronauts to long term exposure in such high radiation environments, a quantitative understanding of the exposure and estimates of the associated risks are required. Energetic neutrons are traditionally difficult to measure due to their neutral charge. Measurement methods have been limited by mass and weight requirements in space to nuclear emulsion, activation foils, a limited number of Bonner spheres, and TEPCs. Such measurements have had limited success in quantifying the neutron component relative to the charged components. We will show that a combination of computational models and experimental measurements can be used as a quantitative tool to evaluate the radiation environment within the Shuttle, including neutrons. Comparisons with space measurements are made with special emphasis on neutron sensitive and insensitive devices. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Christopher Newport Univ, Newport News, VA 23606 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Old Dominion Univ, Norfolk, VA 23529 USA. Boeing N Amer, Seattle, WA USA. Univ Kiel, D-24098 Kiel, Germany. DLR, D-5000 Cologne, Germany. RP Singleterry, RC (reprint author), NASA, Langley Res Ctr, 8 W Taylor St,MS 188B, Hampton, VA 23681 USA. NR 7 TC 4 Z9 4 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 2001 VL 33 IS 3 SI SI BP 355 EP 360 DI 10.1016/S1350-4487(01)00049-X PG 6 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 439EW UT WOS:000169098700017 PM 11855418 ER PT J AU Badhwar, GD Truong, AG O'Neill, PM Choutko, V AF Badhwar, GD Truong, AG O'Neill, PM Choutko, V TI Validation of the galactic cosmic ray and geomagnetic transmission models SO RADIATION MEASUREMENTS LA English DT Article AB A very high-momentum resolution particle spectrometer called the Alpha Magnetic Spectrometer (AMS) was flown in the payload bay of the Space Shuttle in a 51.65 degrees x 380-km orbit during the last solar minimum. This spectrometer has provided the first high statistics data set for galactic cosmic radiation protons, and helium, as well as limited spectral data on carbon and oxygen nuclei in the International Space Station orbit. First measurements of the albedo protons at this inclination were also made. Because of the high-momentum resolution and high statistics, the data can be separated as a function of magnetic latitude. A related investigation, the balloon borne experiment with a superconducting solenoid spectrometer (BESS), has been flown from Lynn Lake, Canada and has also provided excellent high-resolution data on protons and helium. These two data sets have been used here to study the validity of two galactic cosmic ray models and the geomagnetic transmission function developed from the 1990 geomagnetic reference field model. The predictions of both the CREME96 and NASA/JSC models are in good agreement with the AMS data. The shape of the AMS measured albedo proton spectrum, up to 2 GeV, is in excellent agreement with the previous balloon and satellite observations. A new LIS spectrum was developed that is consistent with both previous and new BESS He-3 observations. Because the astronaut radiation exposures onboard ISS will be highest around the time of the solar minimum, these AMS measurements and these models provide important benchmarks for future radiation studies. AMS-02 slated for launch in September 2003, will provide even better momentum resolution and higher statistics data. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. CERN, CH-1211 Geneva 23, Switzerland. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, SN,2101 NASA Rd 1, Houston, TX 77058 USA. NR 14 TC 4 Z9 4 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 2001 VL 33 IS 3 SI SI BP 361 EP 367 DI 10.1016/S1350-4487(00)00166-9 PG 7 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 439EW UT WOS:000169098700018 PM 11855419 ER PT J AU Badhwar, GD Watts, J Cleghorn, TE AF Badhwar, GD Watts, J Cleghorn, TE TI Radiation dose from reentrant electrons SO RADIATION MEASUREMENTS LA English DT Article AB In estimating the crew exposures during an extra vehicular activity (EVA), the contribution of reentrant electrons has always been neglected. Although the flux of these electrons is small compared to the flux of trapped electrons, their energy spectrum extends to several GeV compared to about 7 MeV for trapped electrons. This is also true of splash electrons. Using the measured reentrant electron energy spectra, it is shown that the dose contribution of these electrons to the blood forming organs (BFO) is more than 10 times greater than that from the trapped electrons. The calculations also show that the dose-depth response is a very slowly changing function of depth, and thus adding reasonable amounts of additional shielding would not significantly lower the dose to BFO. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, SBm2191 NASA Rd 1, Houston, TX 77058 USA. NR 14 TC 2 Z9 2 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 2001 VL 33 IS 3 SI SI BP 369 EP 372 DI 10.1016/S1350-4487(00)00150-5 PG 4 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 439EW UT WOS:000169098700019 PM 11855420 ER PT J AU Kuvvetli, I Budtz-Jorgensen, C Gerward, L Stahle, CM AF Kuvvetli, I Budtz-Jorgensen, C Gerward, L Stahle, CM TI Response of CZT drift-strip detector to X- and gamma rays SO RADIATION PHYSICS AND CHEMISTRY LA English DT Article; Proceedings Paper CT 8th International Symposium on Radiation Physics (ISRP-8) CY JUN 05-09, 2000 CL PRAGUE, CZECH REPUBLIC SP Int Radiat Phys Soc, Czech Tech Univ, Fac Nucl Sci & Phys Engn, Czech Energy Co DE CdZnTe detector; drift-strip detector; detector response AB The drift-strip method for improving the energy response of a CdZnTe (CZT) detector to hard X- and gamma rays is discussed. Results for a 10 x 10 x 3 mm(3) detector crystal demonstrate a remarkable improvement of the energy resolution. The full width at half maximum (FWHM) is 2.18 keV (3.6%), 2.45 keV (3.0%), 2.86 keV (0.8 %) and 3.89 keV (0.6%) at 60, 80, 356 and 661 keV, respectively. The resolution is limited by electronic noise below 100 keV. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark. DSRI, Copenhagen, Denmark. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gerward, L (reprint author), Tech Univ Denmark, Dept Phys, Bldg 307, DK-2800 Lyngby, Denmark. RI Gerward, Leif/A-7843-2011 NR 3 TC 13 Z9 13 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0969-806X J9 RADIAT PHYS CHEM JI Radiat. Phys. Chem. PD JUN PY 2001 VL 61 IS 3-6 BP 457 EP 460 DI 10.1016/S0969-806X(01)00299-7 PG 4 WC Chemistry, Physical; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical SC Chemistry; Nuclear Science & Technology; Physics GA 464HF UT WOS:000170526600061 ER PT J AU Ramsey, B Sharma, D Sipila, H Gostilo, V Loupilov, A AF Ramsey, B Sharma, D Sipila, H Gostilo, V Loupilov, A TI Gas filled prototype of a CdZnTe pixel detector SO RADIATION PHYSICS AND CHEMISTRY LA English DT Article; Proceedings Paper CT 8th International Symposium on Radiation Physics (ISRP-8) CY JUN 05-09, 2000 CL PRAGUE, CZECH REPUBLIC SP Int Radiat Phys Soc, Czech Tech Univ, Fac Nucl Sci & Phys Engn, Czech Energy Co DE Cdznte; pixel; imaging detectors AB CdZnTe pixel structures are currently the most promising detectors for the focal planes of hard X-ray telescopes, for astronomical observation in the range 5-100keV. In Sharma et al. (Proc. SPIE 3765 (1999) 822) and Ramsey et al. (Nucl. Instrum. Methods A 458 (2001) 55) we presented preliminary results on the development of prototype 4 x 4 CdZnTe imaging detectors operated under vacuum. These pixel detectors were installed inside vacuum chambers on three-stage Peltier coolers providing detector temperatures down to -40 degreesC. A miniature sputter ion pump inside each chamber maintained the necessary vacuum of 10(-5)Torr. At a temperature of -20 degreesC we achieved an FWHM energy resolution of between 2% and 3% at 60 keV and approximate to 15% at 5.9 keV; however, the dependency on temperature was weak and at +20 degreesC the respective resolutions were 3% and 20%. As the detectors could be operated at room temperature without loss of their good characteristics it was possible to exclude the sputter ion pump and fill the chamber with dry nitrogen instead. We have tested a nitrogen-filled CdZnTe (5 x 5 x 1 mm(3)) prototype having 0.65 x 0.65 mm(2) readout pads on a 0.75 mm. pitch. The interpixel resistance at an applied voltage of 10 V was higher than 50 G Omega and the pixel leakage currents at room temperature with a bias of 200 V between each pad and the common electrode did not exceed 0.8 nA. The pixel detector inside the microassembly, which also contained the input stages of the preamplifiers, was installed on a Peltier cooler to maintain the detector temperature at +20 degreesC. To define real leakage currents of the pixels in their switched-on state we have checked the voltage on the preamplifiers feedback resistors. The resulting currents were 10-50 pA at a detector bias of 500 V. Under test, the typical energy resolution per pixel at +20 degreesC was approximate to3% at energy 59.6 keV and approximate to 20% at energy 5.9 keV, which are similar to the values obtained in the vacuum prototype at room temperature (Nucl. Instrum. Methods A 458 (2001) 55). Using the three stage Peltier cooler it is possible to cool the pixel detector in the nitrogen atmosphere to 0 degreesC which would slightly improve these spectrometrical characteristics. Thus the conclusion here is that the use of a nitrogen environment instead of a vacuum one did not cause any deterioration of the characteristics of the CdZnTe imaging detector. (C) 2001 Elsevier Science Ltd. All rights reserved. C1 Baltic Sci Instrument, LV-1005 Riga, Latvia. Metorex Int Oy, FIN-02631 Espoo, Finland. George C Marshall Space Flight Ctr, Dept Space Sci, Huntsville, AL 35812 USA. RP Gostilo, V (reprint author), Baltic Sci Instrument, Ganibu Dambis 26,POB 33, LV-1005 Riga, Latvia. NR 3 TC 0 Z9 0 U1 2 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0969-806X J9 RADIAT PHYS CHEM JI Radiat. Phys. Chem. PD JUN PY 2001 VL 61 IS 3-6 BP 663 EP 664 DI 10.1016/S0969-806X(01)00365-6 PG 2 WC Chemistry, Physical; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical SC Chemistry; Nuclear Science & Technology; Physics GA 464HF UT WOS:000170526600126 ER PT J AU Harding, DJ Lefsky, MA Parker, GG Blair, JB AF Harding, DJ Lefsky, MA Parker, GG Blair, JB TI Laser altimeter canopy height profiles - Methods and validation for closed-canopy, broadleaf forests SO REMOTE SENSING OF ENVIRONMENT LA English DT Article DE laser; altimeter; forest; canopy; structure; height; broadleaf; lidar; altimetry; waveform; SLICER ID LEAF-AREA INDEX; RADAR BACKSCATTER; AIRBORNE LIDAR; SAR INTERFEROMETRY; DECIDUOUS FORESTS; WAVE-FORMS; VEGETATION; BIOMASS; TOPOGRAPHY; MODEL AB Waveform-recording laser altimeter observations of vegetated landscapes provide a time-resolved measure of laser pulse backscatter energy from canopy surfaces and the underlying ground. Airborne laser altimeter waveform data was acquired using the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) for a successional sequence of four, closed-canopy, deciduous forest stands in eastern Maryland. The four stands were selected so as to include a range of canopy structures of importance to forest ecosystem function, including variation in the height and roughness of the outermost canopy surface and the vertical organization of canopy stories and gaps. The character of the SLICER backscatter signal is described and a method is developed that accounts for occlusion of the laser energy by canopy surfaces, transforming the backscatter signal to a canopy height profile (CHP) that quantitatively represents the relative vertical distribution of canopy surface area. The transformation applies increased weighting to the backscatter amplitude as a function of closure through the canopy and assumes a horizontally random distribution of the canopy components. SLICER CHPs, averaged over areas of overlap where altimeter ground tracks intersect, are shown to be highly reproducible. CHP transects across the four stands reveal spatial variations in vegetation, at the scale of the individual 10-m-diameter laser footprints, within and between stands. Averaged SLICER CHPs are compared to analogous height profile results derived from ground-based sightings to plant intercepts measured on plots within the four stands. The plots were located on the segments of the altimeter ground tracks from which averaged SLICER CHPs were derived, and the ground observations were acquired within 2 weeks of the SLICER data acquisition to minimize temporal change. The differences in canopy structure between the four stands is similarly described by the SLICER and ground-based CHP results. However, a chi-square test of similarity documents differences that are statistically significant. The differences are discussed in terms of measurement properties that define the smoothness of the resulting CHPs and canopy properties that may vertically bias the CHP representations of canopy structure. The statistical differences are most likely due to the more noisy character of the ground-based CHPs, especially high in the canopy where ground-based sightings are rare resulting in an underestimate of canopy surface area and height, and to departures from assumptions of canopy uniformity, particularly regarding lack of clumping and vertically constant canopy reflectance, which bias the CHPs. The results demonstrate that the SLICER observations reliably provide a measure of canopy structure that reveals ecologically interesting structural variations such as those characterizing a successional sequence of closed-canopy, broadleaf forest stands. (C) 2001 Elsevier Science Inc. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. US Forest Serv, USDA, Forest Sci Lab, Pacific NW Res Stn, Corvallis, OR 97331 USA. Smithsonian Environm Res Ctr, Edgewater, MD 21037 USA. RP Harding, DJ (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Mail Code 924, Greenbelt, MD 20771 USA. RI Lefsky, Michael/A-7224-2009; Blair, James/D-3881-2013; Beckley, Matthew/D-4547-2013; Harding, David/F-5913-2012; OI Parker, Geoffrey/0000-0001-7055-6491 NR 55 TC 225 Z9 240 U1 6 U2 47 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 JUN PY 2001 VL 76 IS 3 BP 283 EP 297 DI 10.1016/S0034-4257(00)00210-8 PG 15 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 439FL UT WOS:000169100100001 ER PT J AU Parker, GG Lefsky, MA Harding, DJ AF Parker, GG Lefsky, MA Harding, DJ TI Light transmittance in forest canopies determined using airborne laser altimetry and in-canopy quantum measurements SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID OPTICAL-PROPERTIES; DECIDUOUS FORESTS; VEGETATION; LIDAR; TERRESTRIAL; TOPOGRAPHY; MARYLAND; BIOMASS; VOLUME; STANDS AB The vertical distribution of light transmittance was derived from field and laser altimeter observations taken in the same canopies of five forests of several ages (young to mature) and canopy types (eastern broadleaved and western tall conifer). Vertical transmittances were derived remotely from the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) laser altimeter and in the field from measurements of Photosynthetically Active Radiation (PAR) made within the canopy using quantum sensors suspended from the gondola of a tower crane or atop small balloons. Derived numerical characteristics of mean transmittance profiles (the rate of attenuation, whole canopy transmittance, and the radiation-effective height) were similar for both methods across the sites. Measures of the variance and skewness of transmittance also showed similar patterns far corresponding heights between methods. The two methods exhibited greater correspondence in the eastern stands than in the western ones; differences in the interaction between canopy organization and the sensor characteristics between the stand types might explain this. The narrower, more isolated crowns of the western stands permit a deeper penetration into the canopy of nadir-directed laser light than of direct solar radiation from typical elevation angles. Transects of light transmittance in two stands demonstrate that the SLICER sensor can capture meaningful functional variation. Additionally, for one stand with numerous overlapping transects we constructed a three-dimensional View of the transmittance field. Using geostatistics, we demonstrated that the spatial covariance measured in the horizontal plane varied as a function of height. These results suggest a means to remotely assess an important functional characteristic of vegetation, providing a capacity for process-based ecological studies at large scales. (C) 2001 Elsevier Science Inc. All rights reserved. C1 Smithsonian Environm Res Ctr, Edgewater, MD 21037 USA. Pacific NW Expt Stn, Corvallis, OR 97331 USA. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Parker, GG (reprint author), Smithsonian Environm Res Ctr, POB 28, Edgewater, MD 21037 USA. RI Lefsky, Michael/A-7224-2009; Harding, David/F-5913-2012; OI Parker, Geoffrey/0000-0001-7055-6491 NR 55 TC 60 Z9 64 U1 3 U2 21 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 JUN PY 2001 VL 76 IS 3 BP 298 EP 309 DI 10.1016/S0034-4257(00)00211-X PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 439FL UT WOS:000169100100002 ER PT J AU Curran, PJ Dungan, JL Peterson, DL AF Curran, PJ Dungan, JL Peterson, DL TI Estimating the foliar biochemical concentration of leaves with reflectance spectrometry testing the Kokaly and Clark methodologies SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID LEAF OPTICAL-PROPERTIES; RADIATIVE-TRANSFER MODEL; SLASH PINE; CHLOROPHYLL CONTENT; FOREST CANOPY; BIOPHYSICAL PARAMETERS; QUANTITATIVE-ANALYSIS; ABSORPTION FEATURES; OREGON TRANSECT; REMOTE AB Zn an effort to further develop the methods needed to remotely sense the biochemical concentration of plant canopies, we report the results of an experiment to estimate the concentration of 12 foliar biochemicals (chlorophyll a, chlorophyll b, total chlorophyll, lignin, nitrogen, cellulose, water, phosphorous, protein, amino acids, sugar, starch) from reflectance spectra of dried and ground slash pine needles. The three methodologies employed used stepwise regression and either of the following: (i) standard first derivative reflectance spectra (FDS), (ii) absorption band depths, following continuum removal and normalisation against band depth at the centre of the absorption feature (BNC) or (iii) absorption band depths, following continuum removal and normalisation against the area of the absorption feature (BNA). These latter two methodologies have been proposed in this journal [Remote Sens. Environ., 67 (1999) 267.] on the basis of an experiment using reflectance spectra of dried and ground tree leaves and the concentration of three foliar biochemicals: nitrogen, lignin and cellulose. All three methodologies were implemented on a spectra/biochemical data set from early in the growing season and tested on a similar data set from late in the growing season. The accuracy with which foliar biochemical concentration could be estimated: while high for all methodologies, was highest when using the two proposed by Kokaly and Clark. At an illustrative R-2 threshold of .85 (between estimated and observed biochemical concentration), all three methodologies could be used to estimate total chlorophyll, nitrogen, cellulose and sugar; in addition, the BNC methodology could be used to estimate chlorophyll a and b, and in addition to this, the BNA methodology could be used to estimate lignin and water. Given the advantages offered by the Kokaly and Clark methodologies lover and above the standard methodology) for a wide range of foliar biochemicals, it is recommended that their utility is investigated for the estimation of foliar biochemical concentration from field, airborne and spaceborne spectra. (C) 2001 Elsevier Science Inc. All rights reserved. C1 Univ Southampton, Dept Geog, Southampton SO17 1BJ, Hants, England. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Univ Southampton, Dept Geog, Southampton SO17 1BJ, Hants, England. EM p.curran@soton.ac.uk RI Dungan, Jennifer/G-9921-2016 OI Dungan, Jennifer/0000-0002-4863-1616 NR 69 TC 226 Z9 288 U1 8 U2 41 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0034-4257 EI 1879-0704 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD JUN PY 2001 VL 76 IS 3 BP 349 EP 359 DI 10.1016/S0034-4257(01)00182-1 PG 11 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 439FL UT WOS:000169100100006 ER PT J AU Csiszar, I Gutman, G Romanov, P Leroy, M Hautecoeur, O AF Csiszar, I Gutman, G Romanov, P Leroy, M Hautecoeur, O TI Using ADEOS/POLDER data to reduce angular variability of NOAA/AVHRR reflectances SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID NOAA-AVHRR DATA; BIDIRECTIONAL REFLECTANCES; VEGETATION INDEXES; SURFACE; POLDER/ADEOS; RETRIEVAL; MODELS; LAND AB Time series of National Oceanic and Atmospheric Administration (NOAA)/Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) data, collected daily over two 50-km targets during March-June 1997 in Hungary, were corrected for angular effects using coincident multiangle Polarization and Directionality of the Earth's Reflectance (POLDER) Level-2 Land Surface data products. The POLDER data used consisted of narrow-band 0.67- and 0.765-mum reflectances corrected for ozone and water vapor absorption and Rayleigh scattering effects. The AVHRR visible (0.55-0.75 mum) and near-IR (0.68-1.05 mum) data were converted to reflectances, screened for clouds, and corrected for the same atmospheric effects as the POLDER data. Neither POLDER nor AVHRR data were collected for aerosol effects. POLDER reflectances were used to derive bidirectional reflectance distribution function (BRDF) for each 6-km(2) POLDER grid box. The BRDFs were normalized to the near-nadir values at 45 degrees solar zenith angle, resulting in the anisotropic factors, which were derived for each month for each grid box. Thus, seasonal variability of local anisotropy for each POLDER, grid box in the target areas was established. The anisotropic factors were then applied to the AVHRR/GAC visible and near-IR reflectances mapped into the POLDER grid. The anisotropy-corrected AVHRR reflectances exhibit less fluctuation than the original uncorrected values, thus, facilitating the interpretation of short-term variability in surface conditions. Application of the POLDER BRDFs to AVHRR data is especially advantageous for processing AVHRR temporal composites because of the scarce angular statistics in the areas of frequent clouds, which hampers derivation of BRDFs from AVHRR data itself. Assuming that the local BRDF does not substantially vary from year to year, this approach could be extended to data from the growing seasons of other years. Ultimately, the multiyear time series could be corrected so that the variability, related to angular effects, inherent to AVHRR time series, is reduced. The current approach suggests a paradigm for a synergistic use of TERRA/EOS Multiangle Imaging SpectroRadiometer (MISR)/MODerate resolution Imaging Spectrometer (MODIS) data stream. (C) 2001 Elsevier Science Inc. All rights reserved. C1 NOAA, NESDIS, Off Res & Applicat, Washington, DC USA. Cooperat Inst Res Atmosphere, Ft Collins, CO 80523 USA. NASA Headquarters, Washington, DC 20546 USA. CESBIO, UMR CNES CNR IPS, Toulouse, France. RP Csiszar, I (reprint author), NOAA, NESDIS, Off Res & Applicat, Cooperat Inst Res Atmospher, E-RAI WWBG 712,5200 Auth Rd, Camp Springs, MD 20746 USA. RI Romanov, Peter/F-5622-2010; Csiszar, Ivan/D-2396-2010 OI Romanov, Peter/0000-0002-2153-8307; NR 18 TC 19 Z9 25 U1 2 U2 5 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 JUN PY 2001 VL 76 IS 3 BP 399 EP 409 DI 10.1016/S0034-4257(01)00188-2 PG 11 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 439FL UT WOS:000169100100010 ER PT J AU Oh, ES Sharp, EH Fixsen, DJ Cheng, ES Inman, CA Silver, C AF Oh, ES Sharp, EH Fixsen, DJ Cheng, ES Inman, CA Silver, C TI A low noise cryogenic preamplifier for the cosmic microwave background radiation anisotropy experiment SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB A cryogenic stage preamplifier for the TopHat experiment is built with InterFet NJ132L junction field effect transistors. We describe the testing procedure, screening, and fabrication of the six-channel preamplifier. It is attached to the LN2 shield and self-heats to 110 K with 20 mW total dissipation. The noise performance with grounded input is 7 nV root-mean-square (rms)/root Hz at 1.5 Hz and 1 nV rms/root Hz at 50 Hz. (C) 2001 American Institute of Physics. C1 NASA, GSFC, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Oh, ES (reprint author), NASA, GSFC, Astron & Solar Phys Lab, Raytheon ITSS Code 685, Greenbelt, MD 20771 USA. NR 8 TC 2 Z9 2 U1 0 U2 2 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUN PY 2001 VL 72 IS 6 BP 2735 EP 2737 DI 10.1063/1.1372167 PG 3 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 435EJ UT WOS:000168864200033 ER PT J AU Tracey, N Penix, J Visser, W AF Tracey, N Penix, J Visser, W TI The First International Workshop on Automated Program Analysis, Testing and Verification (WAPATV 2000) SO SOFTWARE TESTING VERIFICATION & RELIABILITY LA English DT Editorial Material C1 NASA, Ames Res Ctr, Computat Sci Div, Automated Software Engn Grp, Moffett Field, CA 94035 USA. Univ York, Dept Comp Sci, York YO10 5DD, N Yorkshire, England. RP Tracey, N (reprint author), Innovat Ctr, York Sci Pk, York YO10 5DG, N Yorkshire, England. NR 0 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0960-0833 J9 SOFTW TEST VERIF REL JI Softw. Test. Verif. Reliab. PD JUN PY 2001 VL 11 IS 2 BP 63 EP 64 DI 10.1002/stvr.227 PG 2 WC Computer Science, Software Engineering SC Computer Science GA 449BC UT WOS:000169663600001 ER PT J AU Watanabe, T Sterling, AC Hudson, HS Harra, LK AF Watanabe, T Sterling, AC Hudson, HS Harra, LK TI Energetics of an active region observed from helium-like sulphur lines SO SOLAR PHYSICS LA English DT Article ID CORONAL DIAGNOSTIC SPECTROMETER; BRAGG CRYSTAL SPECTROMETER; X-RAY TELESCOPE; TEMPERATURE STRUCTURE; SOLAR-FLARES; YOHKOH; NANOFLARES; SOHO; CDS; SPECTRUM AB We report temperature diagnostics derived from helium-like ions of sulphur for an active region NOAA 7978 obtained with Bragg Crystal Spectrometer (BCS) on board the Yohkoh satellite. For the same region we estimate conductive flux downward to the chromosphere by the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO) satellite. This region appeared as a region of soft X-ray enhancement in May 1996, underwent a period of enhanced activity coinciding with flux emergence between 6 July and 12 July, and then continued to exist in a nearly flareless state for several solar rotations until November 1996. Energy balance of the non-flaring active region is basically consistent with a model of an arcade of coronal loops having an average loop-top temperature of 4x10(6) K. Energy from flare activity during a period of flux emergence is comparable to the energy requirements of the non-flaring active region. However, the non-flaring energy is roughly constant for the subsequent solar rotations following the birth of the active region even after the flare activity essentially subsided. Energy partition between flare activity and steady active-region heating thus varies significantly over the lifetime of the active region, and active-region emission cannot always be identified with flaring. C1 Natl Astron Observ, Tokyo 1818588, Japan. NASA, George C Marshall Space Flight Ctr, Space Sci Dept SD50, Huntsville, AL 35812 USA. Solar Phys Res Corp, Tucson, AZ 85718 USA. UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. RP Natl Astron Observ, 2-21-1 Osawa Mitaka, Tokyo 1818588, Japan. EM WATANABE@uvlab.mtk.nao.ac.jp OI Harra, Louise/0000-0001-9457-6200 NR 42 TC 2 Z9 2 U1 0 U2 0 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 JUN PY 2001 VL 201 IS 1 BP 71 EP 91 DI 10.1023/A:1010311814904 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456DL UT WOS:000170067800006 ER PT J AU Share, GH Murphy, RJ Newton, EK AF Share, GH Murphy, RJ Newton, EK TI Limits on radiative capture gamma-ray lines and implications for energy content in flare-accelerated protons SO SOLAR PHYSICS LA English DT Article ID SOLAR-FLARES; H-ALPHA; NONTHERMAL PROTONS; IMPULSIVE PHASE; ABUNDANCES; SPECTRA; EMISSION; BEAM; SPECTROSCOPY; ATMOSPHERE AB Measurements of radiative-capture gamma -ray lines can provide information on both the energy content of nonthermal protons below 1 MeV and the temperature in the region where they interact. We have derived upper limits on the fluences in three proton-capture lines of C-12 and C-13 in the flare-averaged gamma-ray spectrum from 19 X-class flares observed with the Solar Maximum Mission (SMM). The most significant limit comes from the 2.37 MeV line that is excited by 0.46 MeV protons. We estimate an upper limit on the energy content in the accelerated protons by extrapolating the power-law spectruzm derived at higher energies down to the resonant energy. The derived upper limit on the temperature, similar to 5-10x10(7) K, is higher thazn measured in the flaring region with other techniques, even for this optimistic energy content. It is possible that NASA's High Energy Solar Spectroscopic Imager (HESSI) will be sensitive enough to detect the 2.37 MeV line if temperatures exceed similar to 2x10(7) K. C1 USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. NASA, Sci Directorate, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Share, GH (reprint author), USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. NR 33 TC 5 Z9 5 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 JUN PY 2001 VL 201 IS 1 BP 191 EP 200 DI 10.1023/A:1010333807867 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 456DL UT WOS:000170067800013 ER PT J AU Jensen, KL Marrese, CM AF Jensen, KL Marrese, CM TI Special issue on vacuum microelectronics - Preface SO SOLID-STATE ELECTRONICS LA English DT Editorial Material ID FIELD C1 USN, Res Lab, Div Elect Sci & Technol, Vacuum Elect Branch, Washington, DC 20375 USA. CALTECH, Jet Propuls Lab, Thermal & Propuls Engn Sect 333, Adv Propuls Technol Grp, Pasadena, CA 91109 USA. RP Jensen, KL (reprint author), USN, Res Lab, Div Elect Sci & Technol, Vacuum Elect Branch, Code 6841,4555 Overlook Ave SW, Washington, DC 20375 USA. RI Jensen, Kevin/I-1269-2015 OI Jensen, Kevin/0000-0001-8644-1680 NR 8 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0038-1101 J9 SOLID STATE ELECTRON JI Solid-State Electron. PD JUN PY 2001 VL 45 IS 6 BP 777 EP 778 DI 10.1016/S0038-1101(01)00181-2 PG 2 WC Engineering, Electrical & Electronic; Physics, Applied; Physics, Condensed Matter SC Engineering; Physics GA 461VW UT WOS:000170385000001 ER PT J AU Kincaid, RK Weber, M Sobieszczanski-Sobieski, J AF Kincaid, RK Weber, M Sobieszczanski-Sobieski, J TI Performance of a bell-curve based evolutionary optimization algorithm SO STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION LA English DT Article DE evolutionary algorithm; heuristic; optimization; applications AB An evolutionary search strategy utilizing two normal distributions to generate children is presented. This Bell-Curve Based (BCB) evolutionary algorithm is similar in spirit to (mu+mu) evolutionary strategies but with fewer parameters to adjust. Extensive tests regarding the sensitivity of BCB parameters to performance are provided. The test suite includes continuous variable constrained hub design problems, mixed discrete and continuous variable constrained hub design problems, and an unconstrained highly multimodal discrete optimization problem. C1 Coll William & Mary, Dept Math, Williamsburg, VA 23187 USA. Coll William & Mary, Dept Comp Sci, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Kincaid, RK (reprint author), Coll William & Mary, Dept Math, Williamsburg, VA 23187 USA. NR 14 TC 2 Z9 2 U1 0 U2 1 PU SPRINGER-VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1615-147X J9 STRUCT MULTIDISCIP O JI Struct. Multidiscip. Optim. PD JUN PY 2001 VL 21 IS 4 BP 261 EP 271 PG 11 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary; Mechanics SC Computer Science; Engineering; Mechanics GA 448MW UT WOS:000169631500001 ER PT J AU Hsieh, WW Tang, B AF Hsieh, WW Tang, B TI Interannual variability of accumulated snow in the Columbia basin, British Columbia SO WATER RESOURCES RESEARCH LA English DT Article ID SEA-SURFACE TEMPERATURES; WESTERN UNITED-STATES; SOUTHERN OSCILLATION; EL-NINO; TELECONNECTIONS; PATTERNS; CLIMATE; COVER AB Snow water equivalent anomalies (SWEA) measured around April 1 by stations in the Columbia basin area in British Columbia, Canada, were studied for their interannual variability during the period 1950-1999, particularly in relation to El Nino/La Nina events and to high and low Pacific-North American (PNA) atmospheric circulation patterns. Composites of the SWEA showed that SWEA were negative during El Nino years, positive during La Nina years, negative during high PNA years, and positive during low PNA years. High PNA appeared to have the most impact on the SWEA, followed by La Nina, El Nino, and low PNA. In the Columbia basin area, La Nina effects (relative to El Nino effects) on SWEA decrease northward and eastward but strengthen with elevation. Composites of the Pacific sea surface temperature anomalies (SSTA) during the 10 lowest SWEA years revealed weak signals, with El Nino warm SSTA present only during spring and early summer in the preceding year and the SSTA pattern consistent with a high PNA present by fall and winter. In contrast, composites of the SSTA during the 10 highest SWEA years showed strong La Nina cool SSTA starting around May in the preceding year and lasting onto winter. C1 Univ British Columbia, Dept Earth & Ocean Sci, Vancouver, BC V6T 1Z4, Canada. CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Hsieh, WW (reprint author), Univ British Columbia, Dept Earth & Ocean Sci, Vancouver, BC V6T 1Z4, Canada. RI Hsieh, William/G-8380-2011 OI Hsieh, William/0000-0003-2654-392X NR 12 TC 26 Z9 26 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0043-1397 J9 WATER RESOUR RES JI Water Resour. Res. PD JUN PY 2001 VL 37 IS 6 BP 1753 EP 1759 DI 10.1029/2000WR900410 PG 7 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 434ZF UT WOS:000168845200019 ER PT J AU Goldsby, JC AF Goldsby, JC TI Micro-mechanical and electrical properties of monolithic aluminum nitride at high temperatures SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article DE electronic materials; aluminum nitride high temperature properties; internal friction high temperature dielectric measurements; functional ceramics high temperatures ID POLYCRYSTALLINE SOLID ELECTROLYTES; CONDUCTIVITY; BEHAVIOR AB Micromechanical spectroscopy of aluminum nitride reveals it to possess extremely low background internal friction at less than 1X10(-4) logarithmic decrement (log dec.) from 20 to 1200 degreesC. Two mechanical loss peaks were observed, the first at 350 degreesC approximating a single Debye peak with a peak height of 60x10(-4) log dec. The second peak was seen at 950 degreesC with a peak height of 20x10(-4) log dec. and extended from 200 to over 1200 degreesC. These micromechanical observations manifested themselves in the electrical behavior of these materials. Electrical conduction processes were predominately intrinsic. Both mechanical and electrical relaxations appear to be thermally activated processes, with activation energies of 0.78 and 1.32 eV, respectively. (C) 2001 Elsevier Science B.V. All rights reserved. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Goldsby, JC (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 12 TC 5 Z9 5 U1 1 U2 1 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 MAY 31 PY 2001 VL 321 IS 1 BP 67 EP 71 DI 10.1016/S0925-8388(01)00953-7 PG 5 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 433RT UT WOS:000168774100012 ER PT J AU Stunz, GW Minello, TJ AF Stunz, GW Minello, TJ TI Habitat-related predation on juvenile wild-caught and hatchery-reared red drum Sciaenops ocellatus (Linnaeus) SO JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY LA English DT Article DE estuaries; habitat; hatchery fish; mesocosms; mortality; Sciaenops ocellatus ID CHESAPEAKE BAY; STOCK ENHANCEMENT; AQUATIC HABITATS; SEAGRASS MEADOWS; ESTUARINE FISH; MARINE FISHES; LIFE-HISTORY; RECRUITMENT; SURVIVAL; FOOD AB We examined the patterns of habitat-specific mortality for newly settled red drum (Sciaenops ocellatus) using an experimental mesocosm approach. Experiments were designed to analyze prey vulnerability and fish rearing-type (wild-caught or hatchery-reared) in estuarine habitats of varying structural complexity including marsh (Spartina alterniflora Loisel), oyster reef (Crassostrea virginica Gmelin), seagrass (Halodule wrightii Aschers), and nonvegetated sand bottom. We used two different predators, pinfish (Lagodon rhomboides Linnaeus) and spotted seatrout (Cynoscion nebulosus Cuvier). For both predators, vulnerability of wild-caught red drum was significantly lower in structurally complex habitats such as seagrass and oyster reef; the highest vulnerability was associated with the nonvegetated bottom. This habitat effect was not apparent for hatchery-reared prey. In trials using a combination of both rearing-types, there was no significant habitat effect on prey selection, but hatchery-reared red drum suffered higher overall mortality than wild-caught fish from pinfish predators. In these trials, spotted seatrout did not select for either prey type. Differences we observed in prey vulnerability were likely caused by behavioral differences between wild-caught and hatchery-reared red drum. Our results reinforce the conclusion that structural complexity in estuarine habitats increases survival of newly settled fishes. Our data also suggest that hatchery-reared red drum may be more vulnerable to predation than natural fishes, and that survival of stocked fish may be enhanced through habitat-related behavior modification. Published by Elsevier Science B.V. C1 Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, Galveston Lab, Fishery Ecol Branch, Galveston, TX 77551 USA. RP Stunz, GW (reprint author), Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, Galveston Lab, Fishery Ecol Branch, 4700 Ave U, Galveston, TX 77551 USA. NR 61 TC 72 Z9 75 U1 3 U2 14 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0981 J9 J EXP MAR BIOL ECOL JI J. Exp. Mar. Biol. Ecol. PD MAY 31 PY 2001 VL 260 IS 1 BP 13 EP 25 DI 10.1016/S0022-0981(01)00248-9 PG 13 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 439DL UT WOS:000169095500002 ER PT J AU Wang, WF Sirota, JM Reuter, DC AF Wang, WF Sirota, JM Reuter, DC TI Ab initio calculation of the structure and infrared spectra of the van der Waals complex H2O center dot F-2 SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM LA English DT Article DE H2O.F-2; van der Waals complex; vibrational modes; barrier; rotational and distortion constants ID ROTATIONAL SPECTRUM; FLUORINE; PHOTOCHEMISTRY; STRATOSPHERE; WATER AB The equilibrium structures, binding energies and infrared spectra were computed using the ab initio molecular orbital theory for the weakly bonded van der Waals complex H2O .F-2 The most stable state was found to possess an effectively planar las defined by Cooke et al. (Angew. Chem., Int. Ed. Engl., 36 (1997) 129)) C-s structure with the monomers bonded through the Lewis acid-base type interaction. The zero-point HHO inverting motion could overcome the low barrier of a planar configuration and as a result, produces the spectroscopic features observed in the previous microwave measurement. Several intense far infrared vibrational modes were predicted. A considerable uncertainty, arising from the ill-represented harmonic force field presumed by the ab initio theory, was identified for the vibrational analysis. Finally, the quartic centrifugal distortion constants were estimated. Published by Elsevier Science B.V. 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 20 TC 1 Z9 1 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0166-1280 J9 J MOL STRUC-THEOCHEM JI Theochem-J. Mol. Struct. PD MAY 31 PY 2001 VL 541 BP 31 EP 37 DI 10.1016/S0166-1280(00)00756-9 PG 7 WC Chemistry, Physical SC Chemistry GA 427CJ UT WOS:000168387000004 ER PT J AU Walch, SP Dateo, CE AF Walch, SP Dateo, CE TI Thermal decomposition pathways and rates for dimethylaluminum hydride SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID CONFIGURATION-INTERACTION CALCULATIONS; AB-INITIO; REACTION-MECHANISM; MOLECULES AB Calculations have been carried out for the thermal decomposition of dimethylaluminum hydride (DMAlH), For each decomposition pathway, the stationary point geometries and harmonic frequencies were characterized using complete active space self-consistent field (CASSCF)/derivative methods and the correlation consistent polarized valence double-zeta; (cc-pVDZ) basis set. Accurate energetics were obtained by combining the coupled cluster singles and doubles with perturbational estimate of triples [CCSD(T)] results using the cc-pVTZ basis set with an extrapolation to the basis set limit using the cc-pVDZ, cc-pVTZ, and cc-pVQZ basis sets at the Moller-Plesset second-order perturbation theory (MP2) level. The geometries, energetics, and harmonic frequencies were used to obtain rate constants using conventional transition state theory. It was found that the lowest energy pathway leads to CH3AlCH2 + H-2 with a barrier of 71.1 kcal/mol, which is below the first product resulting from direct bond breaking (CH3Al + CH3 at 82.2 kcal/mol). Decomposition of DMAlH dimer was also considered. The rate-limiting step here is elimination of Hz from the DMAlH dimer, and the best estimate of the barrier for this process is 80 kcal/mol [from CCSD(T) calculations with the cc-pVDZ basis set]. This barrier is too large for this pathway to play a major role in Al chemical vapor deposition. C1 NASA, Ames Res Ctr, Eloret Corp, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Eloret Corp, MS 230-3, Moffett Field, CA 94035 USA. NR 24 TC 1 Z9 1 U1 1 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 MAY 31 PY 2001 VL 105 IS 21 BP 5260 EP 5265 DI 10.1021/jp0042462 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 438CX UT WOS:000169037100024 ER PT J AU Salama, F AF Salama, F TI Molecular spectroscopy in astrophysics: the case of polycyclic aromatic hydrocarbons SO JOURNAL OF MOLECULAR STRUCTURE LA English DT Article DE PAHs; electronic; spectroscopy; diffuse interstellar medium ID DIFFUSE INTERSTELLAR BANDS; ELECTRONIC ABSORPTION-SPECTROSCOPY; INFRARED-EMISSION; CATIONS; EXTINCTION; CORONENE; SPECTRA; OVALENE; SEARCH; C10H8+ AB The role of molecular spectroscopy in astrophysics and astrochemistry is discussed in the context of the study of larger complex, carbon-bearing molecules, namely. polycyclic aromatic hydrocarbons (PAHs). These molecular species are now thought to be widespread in the interstellar medium in their neutral and ionized forms. Identifying the carriers responsible for unidentified interstellar spectral bands will allow to derive important information on cosmic elemental abundance as well as information on the physical conditions (density, temperature) reigning in specific interstellar environments. These, in turn, are key elements for a correct understanding of the energetic mechanisms that govern the origin and the evolution of the interstellar medium. A multidisciplinary approach - combining astronomical observations with laboratory simulations and theoretical modeling - is required to address these complex issues. Laboratory spectra of several PAHs, isolated at low temperature in inert gas matrices or seeded in a supersonic jet expansion, are discussed here and compared to the astronomical spectra of reddened. early type, stars. The electronic spectroscopy of PAHs in the ultraviolet, visible and near-infrared domains is reviewed and an assessment of the potential contribution of PAHs to the interstellar extinction in the ultraviolet and in the visible is discussed. (C) 2001 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Salama, F (reprint author), NASA, Ames Res Ctr, Div Space Sci, Mail Stop 245-6, Moffett Field, CA 94035 USA. EM fsalama@mail.arc.nasa.gov RI Salama, Farid/A-8787-2009 OI Salama, Farid/0000-0002-6064-4401 NR 34 TC 11 Z9 11 U1 2 U2 8 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-2860 J9 J MOL STRUCT JI J. Mol. Struct. PD MAY 28 PY 2001 VL 563 SI SI BP 19 EP 26 DI 10.1016/S0022-2860(00)00952-2 PG 8 WC Chemistry, Physical SC Chemistry GA 439UP UT WOS:000169136200004 ER PT J AU Wu, MLC Schubert, S Lin, CI Stajner, I AF Wu, MLC Schubert, S Lin, CI Stajner, I TI A method for assessing the quality of model-based estimates of ground temperature and atmospheric moisture using satellite data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CLIMATE MODELS; SYSTEM AB A method is developed for validating model-based estimates of atmospheric moisture and ground temperature using satellite data. The approach relates errors in estimates of clear-sky longwave fluxes at the top of the Earth-atmosphere system to errors in geophysical parameters. The fluxes include clear-sky outgoing longwave radiation (CLR) and radiative flux in the window region between 8 and 12 mum (RadWn). The approach capitalizes on the availability of satellite estimates of CLR and RadWn and other auxiliary satellite data, and multiple global four-dimensional data assimilation (4-DDA) products. The basic methodology employs off-line forward radiative transfer calculations to generate synthetic clear-sky longwave fluxes from two different 4-DDA data sets. Simple linear regression is used to relate the clear-sky longwave flux discrepancies to discrepancies in ground temperature (deltaT(g)) and broad-layer integrated atmospheric precipitable water (delta pw). The slopes of the regression lines define sensitivity parameters which can be exploited to help interpret mismatches between satellite observations and model-based estimates of clear-sky longwave fluxes. For illustration we analyze the discrepancies in the clear-sky longwave fluxes between an early implementation of the Goddard Earth Observing System Data Assimilation System (GEOS2) and a recent operational version of the European Centre for Medium-Range Weather Forecasts data assimilation system. The analysis of the synthetic clear-sky flux data shows that simple linear regression employing deltaT(g) and broad layer delta pw provides a good approximation to the full radiative transfer calculations, typically explaining more than 90% of the 6 hourly variance in the flux differences. These simple regression relations can be inverted to "retrieve" the errors in the geophysical parameters. Uncertainties (normalized by standard deviation) in the monthly mean retrieved parameters range from 7% for deltaT(g) to similar to 20% for the lower tropospheric moisture between 500 hPa and surface. The regression relationships developed from the synthetic flux data, together with CLR and RadWn observed with the Clouds and Earth Radiant Energy System instrument, are used to assess the quality of the CEOS2 T-g and pw. Results showed that the GEOS2 T-g is too cold over land, and pw in upper layers is too high over the tropical oceans and too low in the lower atmosphere. C1 NASA, Goddard Space Flight Ctr, Goddard Lab Atmospheres, Data Assimilat Off, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Gen Sci Corp, Greenbelt, MD 20771 USA. RP Wu, MLC (reprint author), NASA, Goddard Space Flight Ctr, Goddard Lab Atmospheres, Data Assimilat Off, Code 910-3, Greenbelt, MD 20771 USA. RI Stajner, Ivanka/B-5228-2009 OI Stajner, Ivanka/0000-0001-6103-3939 NR 23 TC 1 Z9 1 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 2001 VL 106 IS D10 BP 10129 EP 10144 DI 10.1029/2000JD900478 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 434WY UT WOS:000168839900001 ER PT J AU Hashizume, H Xie, SP Liu, WT Takeuchi, K AF Hashizume, H Xie, SP Liu, WT Takeuchi, K TI Local and remote atmospheric response to tropical instability waves: A global view from space SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SEA-SURFACE TEMPERATURE; EASTERN EQUATORIAL PACIFIC; OCEAN; PROPAGATION; WIND; VARIABILITY; GRADIENTS; ASYMMETRY; MODEL; FRONT AB A La Nina took place in the equatorial Pacific in 1999, and strong tropical instability waves (TIWs) developed, causing large meanders of a sea surface temperature (SST) front between the equator and 3 degreesN. High-resolution satellite measurements are used to describe the variability of SST, surface wind velocity, column-integrated water vapor, cloud liquid water, and precipitation associated with these strong TIWs in 1999. Coherent ocean-atmosphere patterns emerge in both the Pacific and Atlantic, revealing rich regional characteristics. In the far eastern Pacific, southeasterly trades strengthen (weaken) over positive (negative) SST anomalies, apparently due to enhanced (reduced) mixing with high-speed winds aloft. In the central Pacific we find evidence that SST-induced sea level pressure changes also contribute substantially to wind fluctuations. Similar SST-wind covariability also exists in the Southern Hemisphere along 2 degreesS, but the wind variability induced by unit SST anomaly is much larger than that north of the equator. In the central Pacific where the equatorial front is broad, the northern SST pattern has a large meridional scale and reaches as far north as 6 degreesN. Further to the north in the Intertropical Convergence Zone (ITCZ) where local SST anomalies are small, significant variability is found in clouds and precipitation, which is further correlated with surface wind convergence. In the Atlantic, TIW signals in SST are strongly trapped near the equator, but they induce significant remote response in the ITCZ, which takes a more southern position than its Pacific counterpart and thus more susceptible to TIW influence. C1 Hokkaido Univ, Grad Sch Environm Earth Sci, Sapporo, Hokkaido 0600810, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Hokkaido Univ, Inst Low Temp Sci, Sapporo, Hokkaido 0600819, Japan. Univ Hawaii, Int Pacific Res Ctr, Honolulu, HI 96822 USA. Univ Hawaii, Dept Meteorol, Honolulu, HI 96822 USA. RP Hashizume, H (reprint author), Hokkaido Univ, Grad Sch Environm Earth Sci, Sapporo, Hokkaido 0600810, Japan. RI Xie, Shang-Ping/C-1254-2009 OI Xie, Shang-Ping/0000-0002-3676-1325 NR 26 TC 106 Z9 111 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 2001 VL 106 IS D10 BP 10173 EP 10185 DI 10.1029/2000JD900684 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 434WY UT WOS:000168839900004 ER PT J AU Andrews, AE Boering, KA Wofsy, SC Daube, BC Jones, DB Alex, S Loewenstein, M Podolske, JR Strahan, SE AF Andrews, AE Boering, KA Wofsy, SC Daube, BC Jones, DB Alex, S Loewenstein, M Podolske, JR Strahan, SE TI Empirical age spectra for the midlatitude lower stratosphere from in situ observations of CO2: Quantitative evidence for a subtropical "barrier" to horizontal transport SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LOWER TROPICAL STRATOSPHERE; CARBON-DIOXIDE; 2-DIMENSIONAL MODEL; SEASONAL CYCLE; WATER-VAPOR; GENETIC ALGORITHMS; UPPER TROPOSPHERE; PIPE MODEL; MEAN AGE; TRACERS AB Empirical age spectra for the northern midlatitude lower stratosphere were derived using a genetic algorithm constrained by in situ observations of CO2 and N2O. An age spectrum is the probability distribution function describing the ensemble of transit times between the tropical tropopause and a point in the stratosphere. Age spectra with two distinct maxima fit observed CO2 mixing ratios significantly better than age spectra consisting of a single peak. The mean transit time (mean age) of the younger peak increased with altitude from the tropopause to similar to1 year at 19.5 km, while the mean age of the older peak was 5.4 +/- 0.4 years throughout this altitude region. Near the tropopause, similar to 10% of the air was represented by the older peak, increasing to similar to 50% at 19.5 km. We argue that the younger peak represents rapid quasihorizontal transport of air from the tropics, while the older peak represents downwelling of air from higher altitudes in the mean meridional circulation. Mean ages for the younger and older peaks provide estimates of the residence times fur air in the lower and middle stratosphere, respectively. The clear separation of the peaks implies a significant altitude region where there is little meridional exchange between midlatitudes and the tropics. 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 Earth & Planetary Sci, Berkeley, CA 94720 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Gen Sci Corp, Beltsville, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Andrews, AE (reprint author), NASA, Goddard Space Flight Ctr, Mailstop 916-0, Greenbelt, MD 20771 USA. EM andrews@code916.gsfc.nasa.gov RI Strahan, Susan/H-1965-2012; Andrews, Arlyn/K-3427-2012; Jones, Dylan/O-2475-2014 OI Jones, Dylan/0000-0002-1935-3725 NR 71 TC 44 Z9 45 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 2001 VL 106 IS D10 BP 10257 EP 10274 DI 10.1029/2000JD900703 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 434WY UT WOS:000168839900010 ER PT J AU Keil, M Heun, M Austin, J Lahoz, W Lou, GP O'Neill, A AF Keil, M Heun, M Austin, J Lahoz, W Lou, GP O'Neill, A TI The use of long-duration balloon data to determine the accuracy of stratospheric analyses and forecasts SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DATA ASSIMILATION; OZONE DEPLETION; UNIFIED MODEL; ARCTIC WINTER; VALIDATION; PROJECT; WIND AB Wind velocity data from seven high-altitude long-duration balloon flights are compared with stratospheric analyses and forecasts produced by the U.K. Meteorological Office (UKMO) and the Data Assimilation Office (DAO). The results suggest that biases in both the UKMO and DAO analyses arise from the displacement of the polar night jet to higher latitudes in the winter and from a cold bias in the stratosphere in the summer. At high latitudes the DAO analysis performs better than the UKMO analyses, with the use of a rotated pole in the DAO system the most likely cause of the improvement. The trajectories for each flight were simulated using UKMO and DAO 5-day forecasts and by using simple persistence techniques. It is shown that UKMO and DAO forecasts based on better initial analyses produced trajectories that were more accurate. On the 1-day forecast timescale there is little difference between the techniques, but on the 2-to 5-day range the trajectories based on forecasts generally :performed significantly better than persistence. The results demonstrate the usefulness of stratospheric balloon data for validating both analyses and forecasts. C1 Univ Reading, Dept Meteorol, Reading RG6 6BB, Berks, England. NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. UK Meteorol Off, Bracknell RG12 2SZ, Berks, England. Global Aerosp Corp, Beverly, MA 01915 USA. RP Keil, M (reprint author), UK Meteorol Off, London Rd, Bracknell RG12 2SZ, Berks, England. NR 28 TC 6 Z9 6 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 2001 VL 106 IS D10 BP 10299 EP 10312 DI 10.1029/2000JD900420 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 434WY UT WOS:000168839900013 ER PT J AU Potter, C Klooster, S de Carvalho, CR Genovese, VB Torregrosa, A Dungan, J Bobo, M Coughlan, J AF Potter, C Klooster, S de Carvalho, CR Genovese, VB Torregrosa, A Dungan, J Bobo, M Coughlan, J TI Modeling seasonal and interannual variability in ecosystem carbon cycling for the Brazilian Amazon region SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NET PRIMARY PRODUCTION; LAND-COVER CLASSIFICATIONS; TRACE-GAS EMISSIONS; NDVI DATA SET; CLIMATE VARIABILITY; RAIN-FOREST; AVHRR DATA; BIOMASS ALLOCATION; SOLAR-RADIATION; SOIL-MOISTURE AB Previous field measurements have implied that undisturbed Amazon forests may represent a substantial terrestrial sink for atmospheric carbon dioxide. We investigated this hypothesis using a regional ecosystem model for net primary production (NPP) and soil biogeochemical cycling. Seasonal and interannual controls on net ecosystem production (NEP) were studied with integration of high-resolution (8-km) multiyear satellite data to characterize Amazon land surface properties over time. Background analysis of temporal and spatial relationships between regional rainfall patterns and satellite observations (for vegetation land cover, fire counts, and smoke aerosol effects) reveals several notable patterns in the model driver data. Autocorrelation analysis for monthly vegetation "greenness" index (normalized difference vegetation index, NDVI) from the advanced very high resolution radiometer (AVHRR) and monthly rainfall indicates a significant lag time correlation of up to 12 months. At lag times approaching 36 months, autocorrelation function (ACF) values did not exceed the 95% confidence interval at locations west of about 47 degreesW, which is near the transition zone of seasonal tropical forest and other (nonforest) vegetation types. Even at lag times of 12 months or less, the location near Manaus (approximately 60 degreesW) represents the farthest western point in the Amazon region where seasonality of rainfall accounts significantly for monthly variations in forest phenology, as observed using NDVI. Comparisons of NDVI seasonal profiles in areas of the eastern Amazon widely affected by fires (as observed from satellite) suggest that our adjusted AVHRR-NDVI captures year-to-year variation in land cover greenness with minimal interference from small fires and smoke aerosols. Ecosystem model results using this newly generated combination of regional forcing data from satellite suggest that undisturbed Amazon forests can be strong net sinks for atmospheric carbon dioxide, particularly during wet (non El Nino) years. However, drought effects during El Nino years can reduce NPP in primary forests of the eastern Amazon by 10-20%, compared to long-term average estimates of regional productivity. Annual NEP for the region is predicted to range from -0.4 Pg C yr(-1) (net CO2 source) to 0.5 Pg C yr (-1) (net CO2 sink), with large interannual variability over the states of Para, Maranhao, and Amazonas. As in the case of predicted NPP, it appears that periods of relatively high solar surface irradiance combined with several months of adequate rainfall are required to sustain the forest carbon sink for positive yearly NEP estimates. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EMBRAPA Amazonia Ocidental, Lab Ecofisiol Vegetal, Belem, Para, Brazil. Calif State Univ Monterey Bay, Seaside, CA 93955 USA. NASA, Johnson Controls World Serv, Moffett Field, CA 94035 USA. RP Potter, C (reprint author), NASA, Ames Res Ctr, Mail Stop 242-4, Moffett Field, CA 94035 USA. RI Dungan, Jennifer/G-9921-2016; OI Dungan, Jennifer/0000-0002-4863-1616; Torregrosa, Alicia/0000-0001-7361-2241 NR 93 TC 46 Z9 49 U1 4 U2 21 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0747-7309 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 2001 VL 106 IS D10 BP 10423 EP 10446 DI 10.1029/2000JD900563 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 434WY UT WOS:000168839900023 ER PT J AU Crenshaw, DM AF Crenshaw, DM TI Astrophysics - Mass outflow in active galactic nuclei SO SCIENCE LA English DT Editorial Material ID X-RAY-ABSORPTION; LINE; DYNAMICS; NGC-5548 C1 Catholic Univ Amer, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Crenshaw, DM (reprint author), Catholic Univ Amer, Code 681, Greenbelt, MD 20771 USA. NR 13 TC 2 Z9 2 U1 0 U2 0 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 MAY 25 PY 2001 VL 292 IS 5521 BP 1500 EP 1501 DI 10.1126/science.1061145 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 436YQ UT WOS:000168963800032 PM 11379632 ER PT J AU Hadjiev, VG Iliev, MN Arepalli, S Nikolaev, P Files, BS AF Hadjiev, VG Iliev, MN Arepalli, S Nikolaev, P Files, BS TI Raman scattering test of single-wall carbon nanotube composites SO APPLIED PHYSICS LETTERS LA English DT Article ID SPECTROSCOPY; PRESSURE; ROPES AB Raman spectroscopy is used to infer elastic properties of single-wall carbon nanotubes (SWNTs) in composites. This letter presents strain-induced frequency shift of tangential Raman active modes of SWNTs embedded in epoxy resin subjected to bending. Epoxy curing and sample extension in the tensile strength test are found to create residual strains on the SWNT ropes. We demonstrate that specimen compression in combination with the Raman microprobe technique provides a means for determining of these strains and hence load transfer effectiveness. (C) 2001 American Institute of Physics. C1 Univ Houston, Inst Space Syst Operat, Houston, TX 77204 USA. Univ Houston, Texas Ctr Superconduct, Houston, TX 77204 USA. GB Tech Lockheed Martin, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Hadjiev, VG (reprint author), Univ Houston, Inst Space Syst Operat, Houston, TX 77204 USA. RI ILIEV, MILKO/A-5941-2008; Arepalli, Sivaram/A-5372-2010; Nikolaev, Pavel/B-9960-2009; Hadjiev, Viktor/A-7069-2008 OI ILIEV, MILKO/0000-0002-9685-542X; Hadjiev, Viktor/0000-0001-8579-9357 NR 14 TC 113 Z9 115 U1 0 U2 23 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAY 21 PY 2001 VL 78 IS 21 BP 3193 EP 3195 DI 10.1063/1.1373405 PG 3 WC Physics, Applied SC Physics GA 432XN UT WOS:000168721200011 ER PT J AU Walsh, P Li, W Kalia, RK Nakano, A Vashishta, P Saini, S AF Walsh, P Li, W Kalia, RK Nakano, A Vashishta, P Saini, S TI Structural transformation, amorphization, and fracture in nanowires: A multimillion-atom molecular dynamics study SO APPLIED PHYSICS LETTERS LA English DT Article ID SILICON; INDENTATION; GLASS; PHASE; NANOTUBES; MEMORY; ALPO4 AB Multimillion-atom molecular dynamics simulations of silicon diselenide nanowires are used to study mechanical properties and changes in nanowire structure under strain. The nanowires transform from a body-centered orthorhombic structure to a body-centered tetragonal structure under uniaxial strain, which causes an unexpected elongation in one of the transverse directions. For larger strains, the nanowires undergo a process of local amorphization, followed by fracture at one of the resulting crystalline-amorphous interfaces. The critical strain for fracture is 15%. Local temperature and stress distributions after failure are interpreted in terms of the local amorphization. (C) 2001 American Institute of Physics. C1 Louisiana State Univ, Concurrent Comp Lab Mat Simulat, Baton Rouge, LA 70803 USA. Louisiana State Univ, Biol Computat & Visualizat Ctr, Dept Phys & Astron, Baton Rouge, LA 70803 USA. Louisiana State Univ, Dept Comp Sci, Baton Rouge, LA 70803 USA. NASA, Ames Res Ctr, Numer Aerosp Simulat Facil, Moffett Field, CA 94035 USA. RP Walsh, P (reprint author), Louisiana State Univ, Concurrent Comp Lab Mat Simulat, Baton Rouge, LA 70803 USA. NR 18 TC 31 Z9 32 U1 0 U2 8 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAY 21 PY 2001 VL 78 IS 21 BP 3328 EP 3330 DI 10.1063/1.1374237 PG 3 WC Physics, Applied SC Physics GA 432XN UT WOS:000168721200056 ER PT J AU Roth, M Cowan, TE Brown, C Christl, M Fountain, W Hatchett, S Johnson, J Key, MH Pennington, DM Perry, MD Phillips, TW Sangster, TC Singh, M Snavely, R Stoyer, M Takahashi, Y Wilks, SC Yasuike, K AF Roth, M Cowan, TE Brown, C Christl, M Fountain, W Hatchett, S Johnson, J Key, MH Pennington, DM Perry, MD Phillips, TW Sangster, TC Singh, M Snavely, R Stoyer, M Takahashi, Y Wilks, SC Yasuike, K TI Intense ion beams accelerated by Petawatt-class lasers SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 13th International Symposium on Heavy IOn Inertial Fusion CY MAR 13-17, 2000 CL SAN DIEGO, CALIFORNIA SP Lawrence Berkeley Natl Lab, Fusion Power Associates, US DOE, Off Fus Energy Sci ID ELECTRONS AB The LLNL Petawatt Laser has achieved focussed intensities up to 6 x 10(20)W/cm(2), which has opened a new, higher energy regime of relativistic laser-plasma interactions in which the quiver energy of target electrons exceeds several MeV. Recent experiments revealed an intense, collimated beam of high-energy protons emitted normal to the rear surface of thin, solid targets. Up to 10(13) particles were emitted in a pulse less than 10 ps resulting in a current in the MA regime. With an overall energy content of 30 J, up to 7% of the incident laser energy is converted into protons. The beam shows a broad particle energy spectrum with a sharp cut off above 55 MeV. Based on our current understanding of the accelerating process, it may be possible to shape and focus the ion beam by using special target geometries. With their short pulse duration, high particle energy and large luminosity these beams are promising candidates in numerous applications, such as short-pulse injectors for large accelerators or as the ignitor for fast ignition ICF. Using intense proton beams the fast ignitor concept may become more attractive in heavy-ion fusion due to the possibility to work with indirectly driven targets. Finally, the acceleration is not restricted to protons and using tailored target surfaces may allow acceleration of more massive ions to similar energy per nucleon. (C) 2001 Elsevier Science B.V. All rights reserved. C1 Gesell Schwerionenforsch GmbH, D-64291 Darmstadt, Germany. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35812 USA. Osaka Univ, Inst Laser Engn, Suita, Osaka 565, Japan. RP Roth, M (reprint author), Gesell Schwerionenforsch GmbH, D-64291 Darmstadt, Germany. RI Cowan, Thomas/A-8713-2011 OI Cowan, Thomas/0000-0002-5845-000X NR 11 TC 6 Z9 6 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 MAY 21 PY 2001 VL 464 IS 1-3 BP 201 EP 205 DI 10.1016/S0168-9002(01)00189-9 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 444XC UT WOS:000169424500030 ER PT J AU Fryxell, B Zingale, M Timmes, FX Lamb, DQ Olson, K Calder, AC Dursi, LJ Ricker, P Rosner, R Truran, JW MacNeice, P Tufo, H AF Fryxell, B Zingale, M Timmes, FX Lamb, DQ Olson, K Calder, AC Dursi, LJ Ricker, P Rosner, R Truran, JW MacNeice, P Tufo, H TI Numerical simulations of thermonuclear flashes on neutron stars SO NUCLEAR PHYSICS A LA English DT Article; Proceedings Paper CT 6th International Conference on Nuclei in the Cosmos CY JUN 27-JUL 01, 2000 CL UNIV AARHUS, AARHUS, DENMARK HO UNIV AARHUS ID NUCLEAR AB Helium accreting slowly onto the surface of a neutron star accumulates in a thin surface layer. After reaching a depth of approximately 100 m and a density of about 2 x 10(8) gm cm(-3), the helium layer becomes unstable and a thermonuclear runaway initiates at its base. Since the runaway time scale is much shorter than the accretion time scale, it is likely that ignition will occur at a single point instead of simultaneously over the entire surface. This conclusion is supported by observations of brightness oscillations in X-ray bursts. In this case, a burning front will propagate across the surface, eventually consuming the entire layer. This paper describes high-resolution two-dimensional simulations of the propagation of a helium detonation across the surface of a neutron star. C1 Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Chicago, Dept Comp Sci, Chicago, IL 60637 USA. RP Fryxell, B (reprint author), Univ Chicago, Enrico Fermi Inst, 5640 S Ellis Ave, Chicago, IL 60637 USA. RI Calder, Alan/E-5348-2011 NR 12 TC 2 Z9 2 U1 0 U2 0 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 MAY 21 PY 2001 VL 688 IS 1-2 BP 172C EP 176C PG 5 WC Physics, Nuclear SC Physics GA 434DF UT WOS:000168799300036 ER PT J AU Braunstein, SL Cerf, NJ Iblisdir, S van Loock, P Massar, S AF Braunstein, SL Cerf, NJ Iblisdir, S van Loock, P Massar, S TI Optimal cloning of coherent states with a linear amplifier and beam splitters SO PHYSICAL REVIEW LETTERS LA English DT Article ID CONTINUOUS QUANTUM VARIABLES; UNIVERSAL; BIT AB A transformation achieving the optimal symmetric N --> M cloning of coherent states is presented. Its implementation requires only a phase-insensitive linear amplifier and a network of beam splitters. An experimental demonstration of this continuous-variable cloner should therefore he in the scope of current technology. The link between optimal quantum cloning and optimal amplification of quantum states is also pointed out. C1 Bangor Univ, Bangor LL57 1UT, Gwynedd, Wales. Free Univ Brussels, Ecole Polytech, B-1050 Brussels, Belgium. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Free Univ Brussels, Serv Phys Theor, B-1050 Brussels, Belgium. RP Braunstein, SL (reprint author), Bangor Univ, Bangor LL57 1UT, Gwynedd, Wales. RI Braunstein, Samuel/A-5501-2009 NR 23 TC 104 Z9 104 U1 0 U2 3 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 MAY 21 PY 2001 VL 86 IS 21 BP 4938 EP 4941 DI 10.1103/PhysRevLett.86.4938 PG 4 WC Physics, Multidisciplinary SC Physics GA 435DH UT WOS:000168861800055 PM 11384386 ER PT J AU Beer, R Glavich, TA Rider, DM AF Beer, R Glavich, TA Rider, DM TI Tropospheric emission spectrometer for the Earth Observing System's Aura Satellite SO APPLIED OPTICS LA English DT Article ID INFRARED-SPECTROSCOPY; SPACE AB The Tropospheric Emission Spectrometer (TES) is an imaging infrared Fourier-transform spectrometer scheduled to be launched into polar Sun-synchronous orbit aboard the Earth Observing System's Aura satellite in June 2003. The primary objective of the TES is to make global three-dimensional measurements of tropospheric ozone and of the physical-chemical factors that control its formation, destruction, and distribution. Such an ambitious goal requires a highly sophisticated cryogenic instrument operating over a wide frequency range, which, in turn, demands state-of-the-art infrared detector arrays. in addition, the measurements require an instrument that can operate in both nadir and limb-sounding modes with a precision pointing system. The way in which these mission objectives flow down to the specific science and measurement requirements and in turn are implemented in the flight hardware are described. A brief overview of the data analysis approach is provided. (C) 2001 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Beer, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-301, Pasadena, CA 91109 USA. EM reinhard.beer@jpl.nasa.gov NR 14 TC 229 Z9 236 U1 1 U2 14 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 MAY 20 PY 2001 VL 40 IS 15 BP 2356 EP 2367 DI 10.1364/AO.40.002356 PG 12 WC Optics SC Optics GA 433KQ UT WOS:000168758900002 PM 18357244 ER PT J AU O'Neill, NT Dubovik, O Eck, TF AF O'Neill, NT Dubovik, O Eck, TF TI Modified angstrom ngstrom exponent for the characterization of submicrometer aerosols SO APPLIED OPTICS LA English DT Article ID AERONET AB The classical Angstrom exponent is an operationally robust optical parameter that contains size information on all optically active aerosols in the field of view of a sunphotometer. Assuming that the optical effects of a typical (radius) size distribution can be approximated by separate submicrometer and supermicrometer components, we show that one can exploit the spectral curvature information in the measured optical depth to permit a direct estimation of a fine-mode (submicrometer) Angstrom exponent (alpha (f)) as well as the optical fraction of fine-mode particles (eta) Simple expressions that enable the estimation of these parameters are presented and tested by use of simulations and measurements. (C) 2001 Optical Society of America. C1 Sci Syst & Applicat Inc, Lanham, MD 20706 USA. Univ Maryland Baltimore Cty, Goddard Earth Sci & Technol Ctr, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Dubovik, Oleg/A-8235-2009; ECK, THOMAS/D-7407-2012 OI Dubovik, Oleg/0000-0003-3482-6460; NR 17 TC 86 Z9 95 U1 1 U2 2 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 MAY 20 PY 2001 VL 40 IS 15 BP 2368 EP 2375 DI 10.1364/AO.40.002368 PG 8 WC Optics SC Optics GA 433KQ UT WOS:000168758900003 PM 18357245 ER PT J AU Freedman, WL Madore, BF Gibson, BK Ferrarese, L Kelson, DD Sakai, S Mould, JR Kennicutt, RC Ford, HC Graham, JA Huchra, JP Hughes, SMG Illingworth, GD Macri, LM Stetson, PB AF Freedman, WL Madore, BF Gibson, BK Ferrarese, L Kelson, DD Sakai, S Mould, JR Kennicutt, RC Ford, HC Graham, JA Huchra, JP Hughes, SMG Illingworth, GD Macri, LM Stetson, PB TI Final results from the Hubble Space Telescope key project to measure the Hubble constant SO ASTROPHYSICAL JOURNAL LA English DT Review DE cepheids; cosmology : observations; distance scale; galaxies : distances and redshifts ID EXTRAGALACTIC DISTANCE SCALE; TULLY-FISHER RELATION; GRAVITATIONAL LENSING EXPERIMENT; MICROWAVE BACKGROUND-RADIATION; EXPANDING PHOTOSPHERE METHOD; CHARGE-TRANSFER EFFICIENCY; PERIOD-LUMINOSITY RELATION; VELOCITY-WIDTH RELATION; LARGE-MAGELLANIC-CLOUD; BVRI CCD PHOTOMETRY AB We present here the final results of the Hubble Space Telescope (HST) Key Project to measure the Hubble constant. We summarize our method, the results, and the uncertainties, tabulate our revised distances, and give the implications of these results for cosmology. Our results are based on a Cepheid calibration of several secondary distance methods applied over the range of about 60-400 Mpc. The analysis presented here benefits from a number of recent improvements and refinements, including (1) a larger LMC Cepheid sample to define the fiducial period-luminosity (PL) relations, (2) a more recent HST Wide Field and Planetary Camera 2 (WFPC2) photometric calibration, (3) a correction for Cepheid metallicity, and (4) a correction for incompleteness bias in the observed Cepheid PL samples. We adopt a distance modulus to the LMC (relative to which the more distant galaxies are measured) of mu (o)(LMC) = 18.50 +/- 0.10 mag, or 50 kpc. New, revised distances are given for the 18 spiral galaxies for which Cepheids have been discovered as part of the Key Project, as well as for 13 additional galaxies with published Cepheid data. The new calibration results in a Cepheid distance to NGC 4258 in better agreement with the maser distance to this galaxy. Based on these revised Cepheid distances, we find values (in km s(-1) Mpc(-1)) of H-o = 71 +/- 2 (random) +/- 6 (systematic) (Type Ia supernovae), H-o = 71 +/- 3 +/- 7 (Tully-Fisher relation), H-o = 70 +/- 5 +/- 6 (surface brightness fluctuations), H-o = 72 +/- 9 +/- 7 (Type II supernovae), and H-o = 82 +/- 6 +/- 9 (fundamental plane). We combine these results for the different methods with three different weighting schemes, and find good agreement and consistency with H-o = 72 +/- 8 km s(-1) Mpc(-1). Finally, we compare these results with other, global methods for measuring H-o. C1 Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. CALTECH, NASA IPAC Extragalact Database, Pasadena, CA 91125 USA. Swinburne Univ Technol, Ctr Astrophys & Supercomp, Hawthorn, Vic 3122, Australia. Rutgers State Univ, Piscataway, NJ 08854 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 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. Natl Res Council Canada, Herzberg Inst Astrophys, Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. RP Freedman, WL (reprint author), Carnegie Inst Washington Observ, 813 Santa Barbara St, Pasadena, CA 91101 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 165 TC 2122 Z9 2131 U1 3 U2 37 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 2001 VL 553 IS 1 BP 47 EP 72 DI 10.1086/320638 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JA UT WOS:000169280400006 ER PT J AU Henriksen, M Mushotzky, R AF Henriksen, M Mushotzky, R TI X-ray measurements of nonthermal emission from the Abell 1367 galaxy cluster using the Rossi X-ray Timing Explorer SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : clusters : individual (Abell 1367); galaxies : magnetic fields; intergalactic medium; X-rays : galaxies ID MAGNETIC-FIELDS; COMA-CLUSTER; RADIO; CONSTRAINTS; RADIATION; SPECTRUM; A2256; A1367 AB Observations with the Rossi X-Ray Timing Explorer (RXTE), the Advanced Satellite for Astrophysics and Cosmology, and ROSAT have been used to search for X-ray emission produced by the inverse Compton process in the Abell 1367 galaxy cluster. The three data sets provide a high-quality spectrum which extends from 0.4 to 20 keV, allowing accurate separation of thermal and nonthermal components. In the cases of both the duster's radio halo relic and radio galaxy 3C 264 the detection of nonthermal emission is model dependent. Nonthermal emission from the relic is detected using the RXTE Proportional Counter Array with a flux of similar to0.010-0.019 photons cm(-2) keV(-1) s(-1) at 1 keV, when the thermal emission is modeled with a single thermal component. However, modeling the thermal emission with two thermal components provides a better fit to the data and obviates the need for a nonthermal power-law component. We also find that thermal emission is a physically plausible origin for the second component. Using two thermal components to model the spectrum gives an upper limit of 3.3 x 10(-3) photons cm(-2) keV(-1) s(-1) on nonthermal X-ray emission from the radio relic region. We derive an average intracluster magnetic field of greater than or equal to0.84 muG for this region. This value is consistent with the radial field derived from Faraday rotation studies of noncooling flow clusters. For the central region of the intracluster medium, we find an upper limit of 1.08 x 10(-3) photons cm(-2) keV(-1) s(-1) at 1 keV for nonthermal emission. Joint fitting of the data sets gives a detection of nonthermal emission for 3C 264 of 1.21 x 10(-4) to 2.45 x 10(-4) photons cm(-2) keV(-1) s(-1) at 1 keV, using a single thermal component. However, as with the radio relic region, two thermal components provide a much better fit to the spectrum and give an upper limit of less than 5.3 x 10(-5) photons cm(-2) keV(-1) s(-1) at 1 keV. Combining the X-ray upper limit with the radio spectrum gives an average magnetic field greater than 0.41 muG. C1 Univ Maryland, Dept Phys, Joint Ctr Astrophys, Baltimore, MD 21250 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Henriksen, M (reprint author), Univ Maryland, Dept Phys, Joint Ctr Astrophys, 1000 Hilltop Circle, Baltimore, MD 21250 USA. NR 23 TC 9 Z9 9 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 2001 VL 553 IS 1 BP 84 EP 89 DI 10.1086/320646 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JA UT WOS:000169280400009 ER PT J AU Hunter, DA Kaufman, M Hollenbach, DJ Rubin, RH Malhotra, S AF Hunter, DA Kaufman, M Hollenbach, DJ Rubin, RH Malhotra, S TI The interstellar medium of star-forming irregular galaxies: The view with ISO SO ASTROPHYSICAL JOURNAL LA English DT Review DE galaxies : individual (IC 10, IC 4662, NGC 1156, NGC 1569, NGC 2366, NGC 6822); galaxies : irregular; galaxies : ISM; galaxies : stellar content; infrared : galaxies ID FAR-INFRARED SPECTROSCOPY; GIANT MOLECULAR CLOUDS; LARGE-MAGELLANIC-CLOUD; C-II LINE; FORMATION HISTORY; IRAS OBSERVATIONS; LOW-METALLICITY; DWARF GALAXIES; HII-REGIONS; CONVERSION FACTOR AB We present mid-infrared imaging and far-infrared (FIR) spectroscopy of five IBm galaxies observed by ISO as part of our larger study of the interstellar medium of galaxies. Most of the irregulars in our sample are very actively forming stars, and one is a starburst system. Thus, most are not typical Im galaxies. The mid-infrared imaging was in a band centered at 6.75 mum that is dominated by polycyclic aromatic hydrocarbons (PAHs) and in a band centered at 15 mum that is dominated by small dust grains. The spectroscopy of three of the galaxies includes [C II] lambda 158 mum and [O I] lambda 63 mum, important coolants of photodissociation regions (PDRs), and [O III] lambda 88 mum and [N II] lambda 122 mum, which come from ionized gas. [O I] lambda 145 mum and [O III] lambda 52 mum were measured in one galaxy as well. These data are combined with PDR and H II region models to deduce properties of the interstellar medium of these galaxies. We find a decrease in PAH emission in our irregulars relative to small grain, FIR, and Her emissions for increasing FIR color temperature, which we interpret as an increase in the radiation field due to star formation resulting in a decrease in PAH emission. The f(15)/f(H alpha) ratio is constant for our irregulars, and we suggest that the 15 mum emission in these irregulars is being generated by the transient heating of small dust grains by single-photon events, possibly Ly alpha photons trapped in H II regions. The low f(15)/f(H alpha) ratio, as well as the high f([C II])/f(15) ratio, in our irregulars compared to spirals may be due to the lower overall dust content, resulting in fewer dust grains being, on average, near heating sources. We find that, as in spirals, a large fraction of the [C II] emission comes from PDRs. This is partly a consequence of the high average stellar effective temperatures in these irregulars. However, our irregulars have high [C II] emission relative to FIR, PAH, and small grain emission compared to spirals. If the PAHs that produce the 6.75 mum emission and the PAHs that heat the PDR are the same, then the much higher f([C II])/f(6.75) ratio in irregulars would require that the PAHs in irregulars produce several times more heat than the PAHs in spirals. Alternatively, the carrier of the 6.75 mum feature tracks, but contributes only a part of, the PDR heating, that is due mostly to small grains or other PAHs. In that case, our irregulars would have a higher proportion of the PAHs that heat the PDRs compared to the PAHs that produce the 6.75 mum feature. The high f([O III])/f([C II]) ratio may indicate a smaller solid angle of optically thick PDRs outside the H II regions compared to spirals. The very high L-[C II]/L-CO ratios among our sample of irregulars could be accounted for by a very thick [C II] shell around a tiny CO core in irregulars, and PDR models for one galaxy are consistent with this. The average densities of the PDRs and far-ultraviolet stellar radiation fields hitting the PDRs are much higher in two of our irregulars than in most normal spirals; the third irregular has properties like those in typical spirals. We deduce the presence of several molecular clouds in each galaxy with masses much larger than typical GMCs. C1 Lowell Observ, Flagstaff, AZ 86001 USA. San Jose State Univ, Dept Phys, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Johns Hopkins Univ, Bloomberg Ctr, Baltimore, MD 21210 USA. CALTECH, IPAC, Pasadena, CA 91125 USA. RP Hunter, DA (reprint author), Lowell Observ, 1400 W Mars Hill Rd, Flagstaff, AZ 86001 USA. NR 112 TC 63 Z9 62 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 2001 VL 553 IS 1 BP 121 EP 145 DI 10.1086/320654 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JA UT WOS:000169280400012 ER PT J AU Turnshek, DA Rao, S Nestor, D Lane, W Monier, E Bergeron, J Smette, A AF Turnshek, DA Rao, S Nestor, D Lane, W Monier, E Bergeron, J Smette, A TI The z=0.0912 and z=0.2212 damped Ly alpha galaxies along the sight line toward the quasar OI 363 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : formation; quasars : absorption lines; quasars : individual (OI 363) ID LUMINOSITY FUNCTION; ABSORPTION; SYSTEMS; SPECTROSCOPY; ABSORBERS; EVOLUTION; DISCOVERY AB New optical and infrared observations along the sight line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding quasars selectively observed because they were known to be located behind gas-rich galaxies and systems which lack confirming UV spectroscopic observations of the actual Ly alpha Line, this sight line presently contains the two lowest redshift classical damped Lya (DLA) quasar absorption-line systems found in survey mode (i.e., with N-H I >2 x 10(20) atoms cm(-2)), one at z(abs) = 0.0912 and the other at z(abs) = 0.2212. Our new observations suggest identfications for the DLA galaxy counterparts of these absorption-line systems. The z = 0.09 DLA galaxy appears to be an extended low surface brightness galaxy which is easily visible only in infrared images and shows possible rich morphological structure. Assuming there is no contribution from the quasar host galaxy, we place an upper limit on the K-band luminosity of the z = 0.09 DLA galaxy of L-K less than or equal to 0.13L*(K) (for a cosmology with H-0 = 65 km s(-1) Mpc(-1), Omega = 1, and Lambda = 0). More realistically, a subtraction of the quasar nuclear and host light yields L(K)approximate to0.08L*(K). The impact parameter between the galaxy and quasar sight line is very small, b < 3.6 kpc(<2"), which makes measurements difficult. The z = 0.22 DLA galaxy is an early-type dwarf with a K-band luminosity of L(K)approximate to 0.1L*(K) at impact parameter b = 20 kpc. Its colors are neutral and consistent with star formation models, suggesting its formation epoch was less than a few Gyr ago (i.e., z(f) approximate to 0.3-0.9). Thus, it is conceivable that its progenitor originated from the population of "faint blue galaxies" seen at moderate redshifts. In general, these results serve to support mounting evidence that DLA galaxies are drawn from a wide variety of gas-rich galaxy types. C1 Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. ESO, D-85748 Garching, Germany. Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium. RP Turnshek, DA (reprint author), Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. EM turnshek@quasar.phyast.pitt.edu; rao@everest.phyast.pitt.edu; dbn@phyast.pitt.edu; lane@rsd.nrl.navy.mil; monier@astronomy.ohio-state.edu; jbergero@eso.org; smette@astro.ulg.ac.be NR 40 TC 56 Z9 56 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 2001 VL 553 IS 1 BP 288 EP 298 DI 10.1086/320660 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JA UT WOS:000169280400025 ER PT J AU Jonker, PG van der Klis, M Homan, J Mendez, M van Paradijs, J Belloni, T Kouveliotou, C Lewin, W Ford, EC AF Jonker, PG van der Klis, M Homan, J Mendez, M van Paradijs, J Belloni, T Kouveliotou, C Lewin, W Ford, EC TI Discovery of a kilohertz quasi-periodic oscillation in 2S 0918-549 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (2S 0918-549); stars : neutron; stars : oscillations; X-rays : stars ID X-RAY BINARIES; LUMINOSITY AB We report the discovery of a kilohertz quasi-periodic oscillation (kHz QPO) in the low-mass X-ray binary (LMXB) 2S 0918-549. The kHz QPO has a frequency of 1156 +/- 9 Hz, an FWHM of 70 +/- 20 Hz, and a fractional rms amplitude of 18% +/- 2%. We also detected for the first time a type I X-ray burst in this source. The compact object must therefore be a neutron star. Finally, we were able to classify the source as an atoll source exhibiting the full complement of spectral/timing states of this class (island and banana). From the peak burst flux, an upper limit on the persistent luminosity can be derived of 0.5% of the Eddington luminosity, making 2S 0918-549 one of the least luminous LMXBs showing a kHz QPO. We compare the fractional rms amplitudes of the upper kHz QPO across the ensemble of LMXBs. We find a strong anticorrelation with luminosity. In LMXBs with luminosities similar to 100 times lower than those of Z sources, the fractional rms amplitude is a factor similar to 10 larger. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Natl Univ La Plata, Fac Ciencias Astron & Geofis, RA-1900 La Plata, Argentina. Osservatorio Astron Brera, I-23807 Merate, Italy. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35899 USA. MIT, Dept Phys, Cambridge, MA 02139 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. RP Jonker, PG (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Mendez, Mariano/C-8011-2012 OI Mendez, Mariano/0000-0003-2187-2708 NR 46 TC 26 Z9 27 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 2001 VL 553 IS 1 BP 335 EP 340 DI 10.1086/320659 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JA UT WOS:000169280400029 ER PT J AU Feng, YX Zhang, SN Sun, X Durouchoux, P Chen, W Cui, W AF Feng, YX Zhang, SN Sun, X Durouchoux, P Chen, W Cui, W TI Evolution of iron K alpha line emission in the black hole candidate GX 339-4 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; black hole physics; stars : individual (GX 339-4); X-rays : stars ID X-RAY-EMISSION; SOURCE GX-339-4; GALACTIC RIDGE; STATE; ASCA; SPECTRA; JET AB GX 339-4 was regularly monitored with the Rossi X-Ray Timing Explorer during a period (in 1999) when its X-ray flux decreased significantly (from 4.2 x 10(-10) to 7.6 x 10(-12) ergs cm(-2) s(-1) in the 3-20 keV band), as the source settled into the "off state." Our spectral analysis revealed the presence of a prominent iron Kcl line in the observed spectrum of the source for all observations. The line shows an interesting evolution: it is centered at similar to6.4 keV when the measured flux is above 5 x 10(-11) ergs cm(-2) s(-1) but is shifted to similar to6.7 keV at lower fluxes. The equivalent width of the line appears to increase significantly toward lower fluxes, although it is likely to be sensitive to calibration uncertainties. While the fluorescent emission of neutral or mildly ionized iron atoms in the accretion disk can perhaps account for the 6.4 keV Line, as is often invoked for black hole candidates, it seems difficult to understand the 6.7 keV line with this mechanism because the disk should be less ionized at lower fluxes (unless its density changes drastically). On the other hand, the 6.7 keV line might be due to a recombination cascade of hydrogen- or helium-like iron ions in an optically thin, highly ionized plasma. We discuss the results in the context of proposed accretion models. C1 Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. CE Saclay, DSM, DAPNIA, Serv Astrophys, Gif Sur Yvette, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Feng, YX (reprint author), Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA. OI Cui, Wei/0000-0002-6324-5772 NR 25 TC 10 Z9 10 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 2001 VL 553 IS 1 BP 394 EP 398 DI 10.1086/320634 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 442JA UT WOS:000169280400035 ER EF