FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Cassen, P AF Cassen, P TI Models for the fractionation of moderately volatile elements in the solar nebula SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID ACCRETION; DISKS; CHONDRITES; METEORITES; EVOLUTION; ORIGIN; SYSTEM; EARTH AB We test the validity of the idea that the abundances of moderately volatile elements in chondritic meteorites reflect global condensation and coagulation in an evolving solar nebula and explore what constraints these abundances might place on nebular parameters. The abundances of moderately volatile elements were identified as particularly suitable for modeling the nebula because the data represent a simple pattern explicable in terms of a straightforward hypothesis which has implications for global evolution. The models incorporate a correspondingly simple prescription, derived from theory, for the rate at which condensible material is decoupled from the evolving nebular gas to become part of the surviving planetary system. It is concluded from model results that cooling, diminishing nebular mass and coagulation of solids, through their mutual dependences on accretion rate and opacity, lead naturally to the chondritic depletion patterns of moderately volatile elements. In particular, the trends found in CO and CV meteorites are readily and accurately produced; those of the CM meteorites are less so. The CM meteorites and ordinary chondrite patterns may require a more complicated model, but the full range of possible results from even the simplest model has yet to be completely determined. RP Cassen, P (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 43 TC 57 Z9 57 U1 1 U2 7 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1996 VL 31 IS 6 BP 793 EP 806 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VY468 UT WOS:A1996VY46800011 ER PT J AU Christoffersen, R Keller, LP McKay, DS AF Christoffersen, R Keller, LP McKay, DS TI Microstructure, chemistry, and origin of grain rims on ilmenite from the lunar soil finest fraction SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID BEAM-INDUCED AMORPHIZATION; VAPOR DEPOSITS; RECOIL IMPLANTATION; ALLOY SURFACES; REGOLITH; DIFFUSION AB Analytical transmission electron microscope (TEM) observations reveal that ilmenite grains sampled from the sub-10 mu m size fraction of Apollo 11 (10084) and Apollo 16 (61221, 67701) soils have rims 10-300 nm thick that are chemically and microstructurally distinct from the host ilmenite. The rims have a thin outer sublayer 10-50 nm thick that contains the ilmenite-incompatible elements Si, Al, Ca and S. This overlies a relatively thicker (50-250 nm) inner sublayer of nanocrystalline Ti-oxide precipitates in a matrix of single-crystal ilmenite that is structurally continuous with the underlying host grain. Microstructural information, as well as data from x-ray spectrometry (EDS) and electron energy loss spectrometry (EELS) analysis of the inner sublayer, suggest that both the inner and outer sublayer assemblages are reduced and that the inner layer is depleted in Fe relative to the underlying ilmenite. The chemistry of the outer sublayer suggests that it is a surface deposit of sputtered or impact-vaporized components from the bulk lunar soil. The inner sublayer is part of the original host grain that has been physically and chemically processed, but not amorphized, by solar ion irradiation and possibly some subsolidus heating. The fact that the deposited outer sublayer is consistently much thinner than the radiation-altered inner sublayer indicates that only a minor fraction of the total rim volume is a product of vapor or sputter deposition. This finding is in contrast to recent descriptions of thick deposited layers on one-third of regolith silicate grains and indicates that ilmenite and silicate rims as a group are different in the fraction of deposited material that they contain. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. MVA ASSOCIATES,NORCROSS,GA 30093. NR 71 TC 16 Z9 21 U1 1 U2 4 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1996 VL 31 IS 6 BP 835 EP 848 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VY468 UT WOS:A1996VY46800014 ER PT J AU Nguyen, H Kunath, R AF Nguyen, H Kunath, R TI Fabrication of a low-loss microstrip-coplanar transition with the use of a diffraction photolithographic technique SO MICROWAVE AND OPTICAL TECHNOLOGY LETTERS LA English DT Article DE microstrip/coplanar waveguide; diffraction; reactive ion etching; polymer ID WAVE AB A new fabrication technique that yields a smoothly sloped side wall at the transition region between microstrip and coplanar waveguides on thermally cross-linked Ultradel 9020D polymer substrates is reported. The process uses a diffraction photolithography method followed by a simple, wet chemical development to etch through polymer layers of more than 6-mu m thickness. The method reduces interline coupling in waveguides and is applicable on thick substrates without via holes. Measured microwave loses of sample transitions are presented, and results show this technique to be as good as reactive ion etching techniques, which re of considerably higher cost. (C) 1996 John Wiley & Sons, Inc. RP Nguyen, H (reprint author), NASA,LEWIS RES CTR,SPACE COMMUN DIV,MAIL STOP 54-8,21000 BROOKPARK RD,CLEVELAND,OH 44135, USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0895-2477 J9 MICROW OPT TECHN LET JI Microw. Opt. Technol. Lett. PD NOV PY 1996 VL 13 IS 4 BP 182 EP 184 DI 10.1002/(SICI)1098-2760(199611)13:4<182::AID-MOP2>3.0.CO;2-I PG 3 WC Engineering, Electrical & Electronic; Optics SC Engineering; Optics GA VL891 UT WOS:A1996VL89100002 ER PT J AU Israelian, G deGroot, M Parker, JW Sterken, C AF Israelian, G deGroot, M Parker, JW Sterken, C TI The variable mass loss of the peculiar supergiant P Cygni SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE line, identification; line, profiles; stars, early-type; stars, individual, P Cygni; stars, mass-loss; supergiants ID STELLAR WIND; SPECTRAL ATLAS; O-STARS; LINE AB The study of iron lines from 49 high-resolution IUE spectra observed in the period of 1985-1991 allowed us to find a repetition time between two successive shells of the order of six months. We found that absorption lines of Fe III often have two components while Fe II lines can have three. PCygni is the only luminous blue variable (LBV) that does not show photometric variability on the scale of 1-2 mag and the only one whose shell phenomena have been followed for some considerable time, The recent disappearance of shell components observed in Si, O and N lines during the last decades is possibly a new unique phenomenon. C1 FREE UNIV BRUSSELS,ASTRON GRP,B-1050 BRUSSELS,BELGIUM. FREE UNIV BRUSSELS,FAC SCI,B-1050 BRUSSELS,BELGIUM. ARMAGH OBSERV,ARMAGH BT61 9DG,NORTH IRELAND. NASA,GODDARD SPACE FLIGHT CTR,LASP,GREENBELT,MD 20771. NR 42 TC 10 Z9 10 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 1 PY 1996 VL 283 IS 1 BP 119 EP 136 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR110 UT WOS:A1996VR11000015 ER PT J AU Baugh, CM Gardner, JP Frenk, CS Sharples, RM AF Baugh, CM Gardner, JP Frenk, CS Sharples, RM TI A wide-field K-band survey .2. Galaxy clustering SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE surveys; galaxies, clusters, general; cosmology, observations; largescale structure of Universe; infrared, galaxies ID ANGULAR-CORRELATION FUNCTION AB We present the first measurement of the angular correlation function in a K-selected galaxy survey, from two fields covering almost 10 deg(2). The angular correlation function at small angles is well described by a theta(-0.8) power law, as for optically selected samples. The clustering amplitude is reduced by a factor of similar to 4 between galaxies with K <15 and a fainter magnitude slice with 15 , would be the relic R-odd species. For the photino masses-considered here, previous calculations resulted in an unacceptable photino relic abundance. But we point out that processes other than photino self-annihilation determine the relic abundance when the photino and R(0) are close in mass. We find that the photino relic abundance is most sensitive to the R(0)-to-<(gamma)over tilde> mass ratio, and within model uncertainties, a critical density in photinos may be obtained for an R(0)-to-<(gamma)over tilde> mass ratio in the range 1.2 to 2.2. We propose photinos in the mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a strategy to test the hypothesis. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RP Farrar, GR (reprint author), RUTGERS STATE UNIV,DEPT PHYS & ASTRON,POB 849,PISCATAWAY,NJ 08855, USA. NR 2 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0550-3213 J9 NUCL PHYS B JI Nucl. Phys. B PD NOV PY 1996 SU 51B BP 188 EP 195 DI 10.1016/S0920-5632(96)00509-9 PG 8 WC Physics, Particles & Fields SC Physics GA VY665 UT WOS:A1996VY66500029 ER PT J AU Stecker, FW AF Stecker, FW TI Gamma-rays and neutrinos from dark matter SO NUCLEAR PHYSICS B LA English DT Article; Proceedings Paper CT 2nd Symposium on Dark Matter in the Universe CY FEB 14-16, 1996 CL SANTA MONICA, CA SP UCLA ID LARGE-SCALE STRUCTURE; INTERACTING MASSIVE PARTICLES; ASTROPHYSICAL IMPLICATIONS; ANNIHILATION; ANTIPROTONS; UNIVERSE; SPECTRA; GALAXY; SUN; OBSERVABILITY AB High energy astrophysical gamma-rays and neutrinos can be produced both by the annihilation and possible slow decay of dark matter particles. We discuss the fluxes and spectra of such secondaries produced by dark matter particles in the universe and their observability in competition with Other astrophysical gamma-ray signals and with atmospheric neutrinos. To do this, we work within the assumption that the dark matter particles are neutralinos with are the lightest supersymmetric particles (LSPs) predicted by supersymmetry theories. RP Stecker, FW (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Stecker, Floyd/D-3169-2012 NR 35 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0550-3213 J9 NUCL PHYS B JI Nucl. Phys. B PD NOV PY 1996 SU 51B BP 199 EP 203 DI 10.1016/S0920-5632(96)00511-7 PG 5 WC Physics, Particles & Fields SC Physics GA VY665 UT WOS:A1996VY66500030 ER PT J AU Streitmatter, RE AF Streitmatter, RE TI Antimatter in the Universe SO NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA C-GEOPHYSICS AND SPACE PHYSICS LA English DT Article; Proceedings Paper CT XXIV International Cosmic-Ray Conference CY AUG 28-SEP 08, 1995 CL ROME, ITALY ID ANTIPROTON PROTON RATIO; NUMBER DOMAIN-STRUCTURE; COSMIC-RAY; BARYON ASYMMETRY; RADIATION; SPECTRUM; EXISTENCE; GALAXY; LIMITS; SCALE AB The evidence for cosmologically significant amounts of antimatter in the Universe is reviewed. There is no compelling evidence, either theoretical or experimental, for a baryon-symmetric. Universe. The possibility is not completely ruled out, however. RP Streitmatter, RE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 68 TC 2 Z9 2 U1 0 U2 2 PU EDITRICE COMPOSITORI BOLOGNA PI BOLOGNA PA VIA STALINGRADO 97/2, I-40128 BOLOGNA, ITALY SN 0390-5551 J9 NUOVO CIMENTO C JI Nuovo Cimento Soc. Ital. Fis. C-Geophys. Space Phys. PD NOV-DEC PY 1996 VL 19 IS 6 BP 835 EP 845 DI 10.1007/BF02508124 PG 11 GA XA659 UT WOS:A1996XA65900003 ER PT J AU Yan, JC Sarukkai, SR AF Yan, JC Sarukkai, SR TI Analyzing parallel program performance using normalized performance indices and trace transformation techniques SO PARALLEL COMPUTING LA English DT Article DE benchmark; performance; tuning tool; monitoring system; communication; optimization ID SCALABILITY AB In this paper we describe how a performance tuning tool-set, AIMS, guides the user towards developing efficient and scalable production-level parallel programs by locating performance improvement opportunities and determining optimization benefits. AIMS's Xisk helps identify potential optimizations by computing various pre-defined normalized performance indices from program traces. Inspection of these index point to specific optimizations that may benefit program performance. After identifying and characterizing performance problems, AIMS's MK can provide quantitative estimates of performance benefits to help the user avoid arduous optimizations that may not lead to expected performance improvements by. MK also helps identify potential pitfalls or benefits of changing any of various system parameters. Based on MK's performance projection, an informed decision regarding the most beneficial program optimizations or upgrades in execution environments can be chosen. RP Yan, JC (reprint author), NASA,AMES RES CTR,MS T2TA-I,MOFFETT FIELD,CA 94035, USA. NR 23 TC 15 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8191 J9 PARALLEL COMPUT JI Parallel Comput. PD NOV PY 1996 VL 22 IS 9 BP 1215 EP 1237 DI 10.1016/S0167-8191(96)00032-4 PG 23 WC Computer Science, Theory & Methods SC Computer Science GA VV473 UT WOS:A1996VV47300003 ER PT J AU Lewis, BR Dooley, PM England, JP Waring, K Gibson, ST Baldwin, KGH Partridge, H AF Lewis, BR Dooley, PM England, JP Waring, K Gibson, ST Baldwin, KGH Partridge, H TI Observation of the second (3)Pi(u) valence state of O-2 SO PHYSICAL REVIEW A LA English DT Article ID SCHUMANN-RUNGE BANDS; REGION 175-205 NM; ABSORPTION-BANDS; PREDISSOCIATION LINEWIDTH; DIATOMIC-MOLECULES; O2; CONSTANTS; OXYGEN; PHOTODISSOCIATION; PARAMETERS AB Rotational perturbations in the B (3) Sigma(u)(-) state of molecular oxygen are studied by measuring high-resolution vacuum ultraviolet laser photoabsorption cross sections of the (16,0)-(18,0) B (3) Sigma(u)(-) <-- X (3) Sigma(g)(-) Schumann-Runge bands of O-16(2). The observation of numerous extra lines in the spectrum, together with ab initio calculations of relevant potential-energy curves, enables the perturbing state to be assigned as the second valence state of (3) Pi(u), symmetry. This weakly bound state, which we name C'(3) Pi(u), is also likely to be principally responsible for the well-known rapid increase in the magnitudes of the B-state triplet-splitting constants lambda(upsilon) and gamma(upsilon) as the dissociation limit is approached. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Lewis, BR (reprint author), AUSTRALIAN NATL UNIV,RES SCH PHYS SCI & ENGN,CANBERRA,ACT 0200,AUSTRALIA. RI Baldwin, Kenneth/A-4928-2008 OI Baldwin, Kenneth/0000-0002-2043-5330 NR 36 TC 13 Z9 13 U1 0 U2 6 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD NOV PY 1996 VL 54 IS 5 BP 3923 EP 3938 DI 10.1103/PhysRevA.54.3923 PG 16 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA VT673 UT WOS:A1996VT67300034 ER PT J AU Rubinstein, R Zhou, Y AF Rubinstein, R Zhou, Y TI Analytical theory of the destruction terms in dissipation rate transport equations SO PHYSICS OF FLUIDS LA English DT Article ID ISOTROPIC TURBULENCE; ROTATION AB Modeled dissipation rate transport equations are often derived by invoking various hypotheses to close correlations in the corresponding exact equations. D. C. Leslie [Modern Developments in the Theory of Turbulence (Oxford University, Oxford, 1972)] suggested that these models might be derived instead from Kraichnan's [J. Fluid Mech. 47 (1971)] wavenumber space integrals for inertial range transport Stower. This suggestion is applied to the destruction terms in the dissipation rate equations for incompressible turbulence, buoyant turbulence, rotating incompressible turbulence, and rotating buoyant turbulence. Model constants like C-epsilon 2 are expressed as integrals; convergence of these integrals implies the absence of Reynolds number dependence ii the corresponding destruction term. The dependence of C-epsilon 2 on rotation rate emerges naturally; sensitization of the modeled dissipation rats equation to rotation is not required. A buoyancy related effect which is absent in the exact transport equation for temperature variance dissipation, but which sometimes improves computational predictions; also arises naturally, The time scale in the modeled transport equation depends on whether Bolgiano or Kulmogorov inertial range scaling applies. A simple extension af these methods leads to a preliminary dissipation rate equation for rotating buoyant turbulence. (C) 1996 American Institute of Physics. RP Rubinstein, R (reprint author), NASA,LANGLEY RES CTR,INST COMP APPL SCI & ENGN,MS 403,HAMPTON,VA 23681, USA. NR 28 TC 14 Z9 14 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD NOV PY 1996 VL 8 IS 11 BP 3172 EP 3178 DI 10.1063/1.869090 PG 7 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA VP367 UT WOS:A1996VP36700032 ER PT J AU Lognonne, P Beyneix, JG Banerdt, WB Cacho, S Karczewski, JF Morand, M AF Lognonne, P Beyneix, JG Banerdt, WB Cacho, S Karczewski, JF Morand, M TI Ultra broad band seismology on InterMarsNet SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy ID TERRESTRIAL FREE OSCILLATIONS; TAPER SPECTRAL-ANALYSIS; EARTH; RETRIEVAL; MARS AB Very broad band seismometers, which are included in the baseline of the InterMarsNet payload cover the whole frequency band from tidal frequencies up to 50 Hz. By using the results of field tests performed on Earth with the deployment scenario of the InterMarsNet seismic experiment, it is shown that it should probably be possible to reach very low micro-seismic noise level, possibly less than a spectral amplitude of 10(-9) ms(-2) Hz(-1/2) on the vertical component. Despite the fact that only three stations will be available for the network, sufficient information should be available in the three-component short period records to determine the location of Marsquake foci and the origin time to a level that will enable studies of the seismicity, interior velocity structure, and tectonic activity of the planet. Despite the fact that the most current signals will be recorded in the frequency band 10 mHz-10 Hz, it is shown that the detection of a quake of moment 10(18) N m, or the stack of the InterMarsNet records of quakes with a moment greater than 10(17) N m will allow normal mode frequency measurement in the range 5-20 mHz for a noise amplitude of 10(-9) m s(-2) Hz(-1/2) Observation in the range 3-5 mHz cannot also be ruled out. These normal mode frequencies will have a high scientific return for determining the deep Mars structure. At longer periods, the detection of the tides of Phobos will provide information on the deep internal structure even if no strong quakes are recorded. It is shown that the amplitude of the Phobos tide fundamental after the analysis of a 2 year time series from a single station, for a realistic and conservative estimate of the long period noise may be measured with a precision of 1%. For less noise scenario, and/or by using the stack of all the records, information from the higher Phobos tidal harmonics will also be obtained. Copyright (C) 1996 Published by Elsevier Science Ltd C1 CALTECH,JET PROP LAB,PASADENA,CA. INSU,DT,ST MAUR FOSSES,FRANCE. RP Lognonne, P (reprint author), INST PHYS GLOBE,URA 195 CNRS,4 PL JUSSIEU,PARIS,FRANCE. RI Gagnepain-Beyneix, Jeannine/A-5738-2011; Lognonne, Philippe/F-8846-2010 NR 33 TC 26 Z9 26 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1237 EP & DI 10.1016/S0032-0633(96)00083-9 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000004 ER PT J AU Klingelhofer, G Fegley, B Morris, RV Kankeleit, E Held, P Evlanov, E Priloutskii, O AF Klingelhofer, G Fegley, B Morris, RV Kankeleit, E Held, P Evlanov, E Priloutskii, O TI Mineralogical analysis of Martian soil and rock by a miniaturized backscattering Mossbauer spectrometer SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy ID HAWAIIAN PALAGONITIC SOIL; MAGNETIC-PROPERTIES; IRON-OXIDES; MARS; SPECTROSCOPY; HEMATITE; SURFACE; OXIDATION; NANOPHASE; SPECTRA AB The general scientific objectives of an in situ experiment employing a Mossbauer spectrometer on a Martian lander are, for both rock and soil samples, identification and relative abundance of iron-bearing minerals (including carbonates, phyllosilicates (clays), hydroxyoxides, phosphates, oxides, silicates, sulfides, sulfates), measurement of the ferric (Fe3+) to ferrous (Fe2+) ratio, determination of the properties of magnetic phases including the size distribution of magnetic particles (nanophase versus larger particles) in the Martian soil. These data provide information about the nature and extent of atmosphere-surface chemical and physical weathering processes involving Fe-bearing phases. These objectives are directly relevant to studying the evolution of volatiles and climate over time on Mars because surface materials are major volatile sinks. In fact one of the major problems associated with understanding the evolution of volatiles on Mars is understanding the processes in the past and/or present that are responsible for oxidizing the red planet. A miniaturized backscattering Mossbauer spectrometer, developed at the Technical University of Darmstadt, is reported on which is a flight prototype of an instrument that could be used for in situ analysis as part of a payload of a Martian lander. Its critical instrument parameters are < 300 g mass, 250 cm(3) volume, about 0.4 W power, and about 300 mCi (at launch) Co-57 radiation source. Results of test measurements on Mars sample analogues will be presented. As an example for laboratory weathering studies on Fe-bearing phases, which are important for analysis and interpretation of returned data from Mars, first results of the study of weathering of basalt under CO2 and CO2-O-2 atmospheres will be presented and discussed. Copyright (C) 1996 Elsevier Science Ltd C1 UNIV WASHINGTON,DEPT EARTH & PLANETARY SCI,ST LOUIS,MO. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. MOSCOW SPACE RES INST,MOSCOW,RUSSIA. RP Klingelhofer, G (reprint author), TH DARMSTADT,INST KERNPHYS,SCHLOSSGARTENSTR 9,D-64289 DARMSTADT,GERMANY. NR 71 TC 40 Z9 40 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1277 EP & DI 10.1016/S0032-0633(96)00020-7 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000007 ER PT J AU Menvielle, M Kuhnke, F Musmann, G Tsurutani, B Karczewski, JK AF Menvielle, M Kuhnke, F Musmann, G Tsurutani, B Karczewski, JK TI Contribution of surface magnetic recordings to planetary exploration SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy ID ELECTRICAL-CONDUCTIVITY; UPPER-MANTLE; MAGSAT DATA; SOLAR-WIND; MARS; FIELD; SOUNDINGS; FLOW AB The transient variations of the magnetic field at the surface of a planet have a primary external source, the interaction between the environment of the planet and solar radiation, and a secondary source, the electric currents induced in the conductive planet. The continuous recording of the time variations of the magnetic fields at the surface of Mars by means of three-component magnetometers installed on board landers would therefore allow study of both the internal structure of Mars and the dynamic of its ionized environment. The depth of penetration of an electromagnetic wave in a conductive medium depends on both the period of the wave and the electrical resistivity of the medium. The larger the period and the resistivity, the greater the depth of penetration (skin effect). The high frequency spectrum will therefore enable one to estimate the resistivity in the uppermost kilometres of the planet, and to give information about the presence (or absence) of liquid water under the permafrost. The low frequency spectrum of the transient variations will give information on the presence (or absence) of sharp variations in the resistivity in the uppermost hundreds of kilometres of Mars, and thus on the thermodynamic conditions within the upper mantle of this planet. Averages of the measurements made during ''quiet time measurements'' would provide a very good estimate of the field of internal origin at the locations of the surface stations. If in addition a total duration of one year or more for the mission can be expected, and a drift on the order of 1 nT per year for the ground-based magnetometer, it might even be possible to detect some dynamo-related secular variation. In addition to the map of the Martian magnetic field which will be produced by the Mars Surveyor 1 orbiter, these ground-based local main field measurements will provide original information on the present and past magnetic field of Mars, and then on its present and past core dynamics. As is the case for the Earth, different possible controlling plasma processes will lead to different convection patterns inside the magnetosphere and therefore different magnetic signatures at the planetary 1 surface. Continuous recordings of the transient variations of the magnetic field on board landers will then provide constraints on the convection within the Martian magnetosphere, that is a small magnetosphere where the ionosphere lies at great heights relative to the dimensions of the magnetospheric cavity. Copyright (C) 1996 Elsevier Science Ltd C1 INST METEOROL & GEOPHYS,D-38106 BRAUNSCHWEIG,GERMANY. CALTECH,JET PROP LAB,PASADENA,CA 91109. INSU,DIV TECHNIQUE,F-94100 ST MAUR FOSSES,FRANCE. RP Menvielle, M (reprint author), UNIV PARIS 11,EQUIPE PHYS TERRE & PLANETES,URA 1369,BAT 504,F-91405 ORSAY,FRANCE. NR 52 TC 10 Z9 10 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1289 EP 1302 DI 10.1016/S0032-0633(96)00132-8 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000008 ER PT J AU Taylor, FW Calcutt, SB Irwin, PGJ McCleese, DJ Schofield, JT Muhleman, DO Clancy, RT Leovy, CB AF Taylor, FW Calcutt, SB Irwin, PGJ McCleese, DJ Schofield, JT Muhleman, DO Clancy, RT Leovy, CB TI Remote sounding of the Martian atmosphere in the context of the InterMarsNet mission: General circulation and meteorology SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy ID MARINER-9 AB A concept has been developed for a remote sensing experiment to investigate the physics of the Martian atmosphere from a spin-stabilized orbiter, like that planned for the InterMarsNet mission. Using coincident infrared and microwave channels and limb-to-limb scanning, it can map the planet much more extensively than previously in temperature atmospheric dust loading, and humidity. When combined with one or more surface stations measuring the same variables, the sounder experiment can contribute to major progress in understanding the general circulation and dust and water cycles of the atmosphere of Mars, and the characterization of medium-scale meteorological systems. Copyright (C) 1996 Elsevier Science Ltd C1 CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. UNIV WASHINGTON,DEPT ATMOSPHER SCI,SEATTLE,WA 98195. RP Taylor, FW (reprint author), UNIV OXFORD,CLARENDON LAB,DEPT PHYS ATMOSPHER OCEAN & PLANETARY PHYS,PARKS RD,OXFORD OX1 3PU,ENGLAND. OI Calcutt, Simon/0000-0002-0102-3170; Irwin, Patrick/0000-0002-6772-384X NR 16 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1347 EP 1360 DI 10.1016/S0032-0633(96)00036-0 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000012 ER PT J AU Haberle, RM Catling, DC AF Haberle, RM Catling, DC TI A Micro-Meteorological mission for global network science on Mars: Rationale and measurement requirements SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy ID GENERAL-CIRCULATION MODEL; MARTIAN ATMOSPHERE; DUST STORMS; NUMERICAL SIMULATIONS; CHAOTIC OBLIQUITY; SURFACE PRESSURE; WATER-VAPOR; CYCLE; CLIMATE; CO2 AB The general circulation of the Martian atmosphere and how it relates to the planet's climate system are the main goals of post-Viking atmospheric science investigations. An unambiguous determination of the wind systems associated with the general circulation requires simultaneous measurements from at least 15-20 globally-distributed surface stations and a single, high inclination, short period orbiter. The required number of stations would be too costly using conventional multi-instrumented lander designs. However, truly global network science for meteorology can be accomplished using landers instrumented for a single measurement, namely pressure. Pressure is the most important meteorological parameter and pressure sensors do not require deployment or orientation. This facilitates the design of relatively simple landers that are sufficiently small and light that the required number can be launched on a single Med-Lite launch vehicle (see the accompanying paper by Merrihew et al. (Planet. Space Sci. 44, 1385-1393, 1996)). Of equal importance, the low power demand of the stations would allow them to last for a Martian year and provide the necessary seasonal coverage. The rationale and measurement requirements are given for such a network, and it is shown how it would contribute to the understanding of the Martian general circulation and climate system. In particular, the number and siting of stations is discussed, and the basic science specifications for barometric pressure sensors and an atmospheric sounder. The proposed mission would, for the first time, observationally define the seasonally-varying global wind held on another planet. C1 SAN JOSE STATE UNIV FDN,SAN JOSE,CA. RP Haberle, RM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245-3,MOFFETT FIELD,CA 94035, USA. RI Catling, David/D-2082-2009; OI Catling, David/0000-0001-5646-120X NR 96 TC 17 Z9 17 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1361 EP & DI 10.1016/S0032-0633(96)00056-6 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000013 ER PT J AU Merrihew, SC Haberle, RM Lemke, LG AF Merrihew, SC Haberle, RM Lemke, LG TI A Micro-Meteorological mission for global network science on Mars: A conceptual design SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy AB The Mars Micro-Meteorological Station (''mu-Met'') mission is designed to provide the global surface pressure measurements required to help characterize the Martian general circulation and climate system. Measurements of surface pressure distributed both spatially and temporally, coupled with simultaneous measurements from orbit, will enable the determination of the general circulation, structure and driving factors of the Martian atmosphere as well as the seasonal CO2 cycle. The influence of these atmospheric factors will in turn provide insight into the overall Martian climate system. With the science objective defined as the long-term (at least 1 Mars year) globally distributed: measurement of surface atmospheric pressure, a readily achievable and low-cost network mission has been designed. The mu-Met mission utilizes microsensors coupled with a robust and lightweight surface station to deliver 16 mu-Met stations to Mars via a Med-Lite launch vehicle. The battery powered mu-Met surface stations are designed to autonomously measure, record and transmit the science data via a UHF relay satellite. Entry, descent and landing is provided by an aeroshell with a new lightweight ceramic thermal protection system, a parachute and an impact absorbing structure. The robust lander is capable of surviving the landing loads imposed by the high altitude landing sites required in a global network. By trading the ability to make many measurements at a single site for the ability to make a single measurement at many sites, the mu-Met mission can provide truly global meteorological science. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,ADV PROJECTS BRANCH,MOFFETT FIELD,CA 94035. RP Merrihew, SC (reprint author), STANFORD UNIV,DEPT AERONAUT & ASTRONAUT,DURAND BLDG,STANFORD,CA 94305, USA. NR 8 TC 5 Z9 5 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1385 EP 1393 DI 10.1016/S0032-0633(96)00055-4 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000014 ER PT J AU Landis, GA Jenkins, P Flatico, J Oberle, L Krasowski, M Stevenson, S AF Landis, GA Jenkins, P Flatico, J Oberle, L Krasowski, M Stevenson, S TI Development of a Mars dust characterization instrument SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy ID ATMOSPHERIC DUST; SOLAR-RADIATION; VIKING AB The atmosphere of Mars has a considerable load of suspended dust. Over time, this dust deposits out of the atmosphere. The mechanism and the temporal and geographical variation of this deposition are not well characterized. Measurements of settling rates and dust properties are of considerable scientific interest. Suspended dust affects the atmospheric solar absorption and thus the heat balance of Mars, as well as serving as nucleation sites for water and CO2 frost, while settled dust causes albedo changes across the surface; knowledge of dust properties is also of engineering interest to the design of mechanisms, solar arrays, and radiators. Two instruments have been designed and fabricated to measure the dust accumulation during the course of the Mars Pathfinder rover mission: a solar-cell coverglass transmission experiment to measure the change in optical opacity of a transparent coverglass as dust settles on the surface, and a quartz crystal monitor to measure the mass of dust deposited on an oscillating quartz crystal as dust settles on the surface. An additional instrument, a CCD microscope to image individual dust particles is under development for flight on a future mission. Copyright (C) 1996 Elsevier Science Ltd RP Landis, GA (reprint author), NASA,LEWIS RES CTR,MAILSTOP 302-1,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 23 TC 10 Z9 10 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1425 EP & DI 10.1016/S0032-0633(96)00042-6 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000017 ER PT J AU MacDermott, AJ Barron, LD Brack, A Buhse, T Drake, AF Emery, R Gottarelli, G Greenberg, JM Haberle, R Hegstrom, RA Hobbs, K Kondepudi, DK McKay, C Moorbath, S Raulin, F Sandford, M Schwartzman, DW Thiemann, WHP Tranter, GE Zarnecki, JC AF MacDermott, AJ Barron, LD Brack, A Buhse, T Drake, AF Emery, R Gottarelli, G Greenberg, JM Haberle, R Hegstrom, RA Hobbs, K Kondepudi, DK McKay, C Moorbath, S Raulin, F Sandford, M Schwartzman, DW Thiemann, WHP Tranter, GE Zarnecki, JC TI Homochirality as the signature of life: The SETH Cigar SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on INTERMARSNET CY SEP 28-30, 1995 CL CAPRI, ITALY SP European Space Agcy ID MOLECULAR CHIRALITY; ENERGY DIFFERENCE; BETA-STRUCTURES; L-RESIDUES; ORIGIN; POLYPEPTIDES; SELECTION; SYMMETRY; SEARCH AB A characteristic hallmark of life is its homochirality: all biomolecules are usually of one hand, e.g. on Earth life uses only L-amino acids for protein synthesis and not their D mirror images. It is therefore suggested that a search for extra-terrestrial life can be approached as a Search for Extra-Terrestrial Homochirality (SETH). A novel miniaturized space polarimeter, called the SETH Cigar, is described which could be used to detect optical rotation as the homochiral signature of life on other planets. Moving parts are avoided by replacing the normal rotating polarizer by multiple fixed polarizers at different angles as in the eye of the bee. It is believed that homochirality will be found in the subsurface layers on Mars as a relic of extinct life. Copyright (C) 1996 Elsevier Science Ltd C1 UNIV GLASGOW,DEPT CHEM,GLASGOW G12 8QQ,LANARK,SCOTLAND. CNRS,F-45071 ORLEANS 2,FRANCE. UNIV BREMEN,D-28334 BREMEN,GERMANY. UNIV LONDON BIRKBECK COLL,DEPT CHEM,LONDON WC1H 0AJ,ENGLAND. RUTHERFORD APPLETON LAB,DIDCOT OX11 0QX,OXON,ENGLAND. UNIV BOLOGNA,BOLOGNA,ITALY. LEIDEN UNIV,HUYGENS LAB,NL-2300 RA LEIDEN,NETHERLANDS. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. WAKE FOREST UNIV,DEPT CHEM,WINSTON SALEM,NC 27109. GLAXO WELLCOME RES LABS,WARE,HERTS,ENGLAND. UNIV OXFORD,DEPT EARTH SCI,OXFORD OX1 3PR,ENGLAND. UNIV PARIS 12,LISA,F-94010 CRETEIL,FRANCE. HOWARD UNIV,DEPT BIOL,WASHINGTON,DC 20011. GLAXO WELLCOME RES LABS,STEVENAGE,HERTS,ENGLAND. UNIV KENT,PHYS LAB,CANTERBURY CT2 7NR,KENT,ENGLAND. RP MacDermott, AJ (reprint author), UNIV CAMBRIDGE,DEPT CHEM,LENSFIELD RD,CAMBRIDGE CB2 1EW,ENGLAND. NR 32 TC 27 Z9 28 U1 2 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD NOV PY 1996 VL 44 IS 11 BP 1441 EP 1446 DI 10.1016/S0032-0633(96)00057-8 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC340 UT WOS:A1996WC34000019 PM 11541123 ER PT J AU Leitherer, C Alloin, D FritzVonAlvensleben, U Gallagher, JS Huchra, JP Matteucci, F OConnell, RW Beckman, JE Bertelli, GP Bica, E Boisson, C Bonatto, C Bothun, GD Bressan, A Brodie, JP Bruzual, G Burstein, D Buser, R Caldwell, N Casuso, E Cervino, M Charlot, S Chavez, M Chiosi, C Christian, CA Cuisinier, F Dallier, R deKoter, A Delisle, S Diaz, AI Dopita, MA Dorman, B Fagotto, F Fanelli, MN Fioc, M GarciaVargas, ML Girardi, L Goldader, JD Hardy, E Heckman, TM Iglesias, J Jablonka, P Joly, M Jones, L Kurth, O Lancon, A Lejeune, T Loxen, J Maeder, A Malagnini, ML Marigo, P MasHesse, JM Meynet, G Moller, CS Molla, ML Morossi, C Nasi, E Nichols, JS Odegaard, KJR Parker, JWM Pastoriza, MG Peletier, R Robert, C RoccaVolmerange, B Schaerer, D Schmidt, A Schmitt, HR Schommer, RA Schmutz, W Roos, MS Silva, L Stasinska, G Sutherland, RS Tantalo, R Traat, P Vallenari, A Vazdekis, A Walborn, NR Worthey, G Wu, CC AF Leitherer, C Alloin, D FritzVonAlvensleben, U Gallagher, JS Huchra, JP Matteucci, F OConnell, RW Beckman, JE Bertelli, GP Bica, E Boisson, C Bonatto, C Bothun, GD Bressan, A Brodie, JP Bruzual, G Burstein, D Buser, R Caldwell, N Casuso, E Cervino, M Charlot, S Chavez, M Chiosi, C Christian, CA Cuisinier, F Dallier, R deKoter, A Delisle, S Diaz, AI Dopita, MA Dorman, B Fagotto, F Fanelli, MN Fioc, M GarciaVargas, ML Girardi, L Goldader, JD Hardy, E Heckman, TM Iglesias, J Jablonka, P Joly, M Jones, L Kurth, O Lancon, A Lejeune, T Loxen, J Maeder, A Malagnini, ML Marigo, P MasHesse, JM Meynet, G Moller, CS Molla, ML Morossi, C Nasi, E Nichols, JS Odegaard, KJR Parker, JWM Pastoriza, MG Peletier, R Robert, C RoccaVolmerange, B Schaerer, D Schmidt, A Schmitt, HR Schommer, RA Schmutz, W Roos, MS Silva, L Stasinska, G Sutherland, RS Tantalo, R Traat, P Vallenari, A Vazdekis, A Walborn, NR Worthey, G Wu, CC TI A data base for galaxy evolution modeling SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Review ID INTERMEDIATE-MASS STARS; ASYMPTOTIC GIANT BRANCH; STELLAR POPULATION SYNTHESIS; RADIATION-DRIVEN WINDS; THEORETICAL ISOCHRONES; GALACTIC NUCLEI; HII-REGIONS; LOSS RATES; SPECTRAL PROPERTIES; GLOBULAR-CLUSTERS AB This paper represents a collective effort to provide an extensive electronic data base useful for the interpretation of the spectra and evolution of galaxies. A broad variety of empirical and theoretical data is discussed here, and the data are made fully available in the AAS CD-ROM Series, Vol. 7. Several empirical stellar libraries are part of this data base. They cover the ultraviolet spectral range observed with IUE, optical data from different ground-based telescopes, and ground-based infrared data. Spectral type coverage depends on the wavelength, but is mostly complete for types O to M and luminosity classes V to I. A large metallicity range is covered as well. Theoretical libraries of selected spectral indices of cool stars and of stellar continuum fluxes in the temperature range 2000-50,000 K as well as Wolf-Rayet energy distributions are presented. Several libraries of star clusters and early-type galaxies have been selected for this data base. We discuss an extensive set of empirical spectral templates covering the wavelength region from 1200 to 9800 Angstrom, as well as narrow-band line indices in a large number of passbands. Bench-mark spectra of nearby galaxies for model tests are included as well. We compiled numerous evolutionary models and isochrones for stars of all mass ranges of interest, wide metallicity range, and for all evolutionary phases, including the pre-main-sequence phase. The majority of the models have been computed by the Geneva and Padova groups. Evolutionary synthesis models computed by several independent groups are made available. They can be applied to old and young systems, and are optimized with respect to different aspects of input physics. The model predictions include stellar (colors, magnitudes, absorption features) and nebular (emission-line fluxes) properties. Finally, we present models of ionized gas to be used for the interpretation of active galactic nuclei and young star-forming galaxies. The community is encouraged to make use of this electronic data base and to perform a critical comparison between the individual datasets. C1 CEA SACLAY, SERV ASTROPHYS, F-91191 GIF SUR YVETTE, FRANCE. UNIV STERNWARTE GOTTINGEN, D-37083 GOTTINGEN, GERMANY. UNIV WISCONSIN, DEPT ASTRON, MADISON, WI 53706 USA. HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. SISSA, I-34013 TRIESTE, ITALY. IAC, E-38200 SANTA CRUZ PALMA, TENERIFE, SPAIN. CNR, I-00185 ROME, ITALY. UNIV FED RIO GRANDE SUL, IF, BR-91501970 PORTO ALEGRE, RS, BRAZIL. UNIV OREGON, DEPT PHYS, F-92195 MEUDON, FRANCE. ASTRON OBSERV PADOVA, I-35122 PADUA, ITALY. UNIV CALIF SANTA CRUZ, LICK OBSERV, SANTA CRUZ, CA 95064 USA. CIDA, MERIDA 5101A, VENEZUELA. ARIZONA STATE UNIV, DEPT PHYS & ASTRON, TEMPE, AZ 85287 USA. UNIV ARIZONA, STEWARD OBSERV, TUCSON, AZ 85721 USA. LAEFE, E-28080 MADRID, SPAIN. INST ASTROPHYS, F-75014 PARIS, FRANCE. INST NACL ASTROFIS OPT & ELECTR, PUEBLA 72000, MEXICO. UNIV PADUA, DEPT ASTRON, I-35122 PADUA, ITALY. UNIV VIRGINIA, DEPT ASTRON, UNIV STN, CHARLOTTESVILLE, VA 22903 USA. UNIV PARIS 07, URA 173, OBSERV PARIS MEUDON, DAEC, F-92195 MEUDON, FRANCE. UNIV BASEL, INST ASTRON, CH-4102 BINNINGEN, SWITZERLAND. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. UNIV LAVAL, DEPT PHYS, ST FOY, PQ G1K 7P4, CANADA. UNIV AUTONOMA MADRID, DEPT FIS TEOR, FAC CIENCIAS, E-28049 MADRID, SPAIN. MT STROMLO & SIDING SPRING OBSERV, WESTON, ACT 2611, AUSTRALIA. IUE OBSERV VILLAFRANCA CASTILLO, E-28080 MADRID, SPAIN. JOHNS HOPKINS UNIV, BLOOMBERG CTR PHYS & ASTRON, BALTIMORE, MD 21218 USA. UNIV N CAROLINA, DEPT PHYS & ASTRON, CHAPEL HILL, NC 27599 USA. OBSERV STRASBOURG, F-67000 STRASBOURG, FRANCE. OBSERV GENEVA, CH-1290 SAUVERNY, SWITZERLAND. UNIV TRIESTE, DEPT ASTRON, I-34131 TRIESTE, ITALY. OSSERV ASTRON TRIESTE, I-34131 TRIESTE, ITALY. NASA, GODDARD SPACE FLIGHT CTR, IUE OBSERV CSC, GREENBELT, MD 20771 USA. UNIV OSLO, INST THEORET ASTROPHYS, N-0315 OSLO, NORWAY. SW RES INST, BOULDER, CO 80302 USA. KAPTEYN INST, NL-9700 AV GRONINGEN, NETHERLANDS. UNIV FED SANTA MARIA, DEPT MATEMAT NEPAE, BR-97100 SANTA MARIA, RS, BRAZIL. CTIO, LA SERENA, CHILE. ETH ZENTRUM, INST ASTRON, CH-8092 ZURICH, SWITZERLAND. TARTU OBSERV, EE-2400 TORAVERE, TARTUMAA, ESTONIA. UNIV MICHIGAN, DEPT ASTRON, ANN ARBOR, MI 48109 USA. RP Leitherer, C (reprint author), SPACE TELESCOPE SCI INST, 3700 SAN MARTIN DR, BALTIMORE, MD 21218 USA. RI Peletier, Reynier/B-9633-2012; Cervino, Miguel/L-7024-2014; Dopita, Michael/P-5413-2014; Schmidt, Alex/G-1886-2012; Molla, Mercedes/I-3189-2015; Schmutz, Werner/B-4153-2014; Mas-Hesse, J. Miguel /K-6805-2014; OI Cervino, Miguel/0000-0001-8009-231X; Dopita, Michael/0000-0003-0922-4986; Schmidt, Alex/0000-0001-8609-4375; Molla, Mercedes/0000-0003-0817-581X; Schmutz, Werner/0000-0003-1159-5639; Mas-Hesse, J. Miguel /0000-0002-8823-9723; Vallenari, Antonella/0000-0003-0014-519X NR 172 TC 173 Z9 173 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD NOV PY 1996 VL 108 IS 729 BP 996 EP 1017 DI 10.1086/133825 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VT192 UT WOS:A1996VT19200007 ER PT J AU Armstrong, TW Colborn, BL Harmon, BA Laird, CE AF Armstrong, TW Colborn, BL Harmon, BA Laird, CE TI Predictions of the nuclear activation of materials on LDEF produced by the space radiation environment and comparison with flight measurements SO RADIATION MEASUREMENTS LA English DT Article AB Model calculations have been made to compare with the induced radioactivity measured for materials on the LDEF satellite. Predictions and data comparisons are made for aluminum spacecraft components and for vanadium and nickel samples placed at multiple locations on the spacecraft. The calculated vs observed activations provide an indication of present model uncertainties in predicting nuclear activation as well as the magnitude and directionality of the trapped proton environment for low-Earth orbit missions. Environment model uncertainties based on the activation measurements are consistent with the uncertainties evaluated using other LDEF radiation dosimetry data. Copyright (C) 1996 Elsevier Science Ltd C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. EASTERN KENTUCKY UNIV,RICHMOND,KY 40475. RP Armstrong, TW (reprint author), SCI APPLICAT INT CORP,ROUTE 2,PROSPECT,TN 38477, USA. NR 22 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP 765 EP 777 DI 10.1016/S1350-4487(96)00081-9 PG 13 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800005 PM 11540508 ER PT J AU Harmon, BA Laird, CE Fishman, GJ Parnell, TA Camp, DC Frederick, CE Hurley, DL Lindstrom, DJ Moss, CE Reedy, RC Reeves, JH Smith, AR Winn, WG Benton, EV AF Harmon, BA Laird, CE Fishman, GJ Parnell, TA Camp, DC Frederick, CE Hurley, DL Lindstrom, DJ Moss, CE Reedy, RC Reeves, JH Smith, AR Winn, WG Benton, EV TI Induced radioactivity of LDEF materials and structural components SO RADIATION MEASUREMENTS LA English DT Article ID SPACECRAFT; BE-7 AB We present an overview of the Long Duration Exposure Facility (LDEF) induced activation measurements. The LDEF, which was gravity-gradient stabilized, was exposed to the low Earth orbit (LEG) radiation environment over a 5.8 year period. Retrieved activation samples and structural components from the spacecraft were analyzed with low and ultra-low background HPGe gamma spectrometry at several national facilities. This allowed a very sensitive measurement of long-lived radionuclides produced by proton- and neutron-induced reactions in the time-dependent, non-isotropic LEO environment. A summary of major findings from this study is given that consists of directionally dependent activation, depth profiles, thermal neutron activation, and surface beryllium-7 deposition from the upper atmosphere. We also describe a database of these measurements that has been prepared for use in testing radiation environmental models and spacecraft design. Published by Elsevier Science Ltd C1 EASTERN KENTUCKY UNIV, DEPT PHYS, RICHMOND, KY 40475 USA. LAWRENCE LIVERMORE NATL LAB, DIV NUCL CHEM, LIVERMORE, CA 94550 USA. TENNESSEE VALLEY AUTHOR, WESTERN AREA RADIOL LAB, MUSCLE SHOALS, AL 35660 USA. UNIV CALIF BERKELEY, LAWRENCE BERKELEY LAB, DIV NUCL SCI, BERKELEY, CA 94720 USA. NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. LOS ALAMOS NATL LAB, LOS ALAMOS, NM 87545 USA. PACIFIC NW LAB, RICHLAND, WA 99352 USA. WESTINGHOUSE SAVANNAH RIVER CO, AIKEN, SC 29808 USA. UNIV SAN FRANCISCO, PHYS RES LAB, SAN FRANCISCO, CA 94117 USA. RP Harmon, BA (reprint author), NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. OI Reedy, Robert/0000-0002-2189-1303 NR 48 TC 4 Z9 4 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP 863 EP 880 DI 10.1016/S1350-4487(96)00094-7 PG 18 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800016 PM 11540519 ER PT J AU Watts, JW Armstrong, TW Colborn, BL AF Watts, JW Armstrong, TW Colborn, BL TI Prediction of LDEF exposure to the ionizing radiation environment SO RADIATION MEASUREMENTS LA English DT Article AB Predictions of the LDEF mission's trapped proton and electron and galactic cosmic ray proton exposures have been made using the currently accepted models with improved resolution near mission end and better modeling of solar cycle effects. An extension of previous calculations, to provide a more definitive description of the LDEF exposure to ionizing radiation, is represented by trapped proton and electron flux as a function of mission time, presented considering altitude and solar activity variation during the mission and the change in galactic cosmic ray proton flux over the mission. Modifications of the AP8MAX and AP8MM fluence led to a reduction of fluence by 20%. A modified interpolation model developed by Daly and Evans resulted in 30% higher dose and activation levels, which better agreed with measured values than results predicted using the Vette model. Published by Elsevier Science Ltd C1 SCI APPLICAT INT CORP,PROSPECT,TN 38477. RP Watts, JW (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES84,HUNTSVILLE,AL 35812, USA. NR 17 TC 5 Z9 5 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP 893 EP 899 DI 10.1016/S1350-4487(96)00103-5 PG 7 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800019 PM 11540522 ER PT J AU Badhwar, GD Atwell, W Cash, B Weyland, M Petrov, VM Tchernykh, IV Akatov, WA Shurshakov, VA Arkhangelsky, VV Kushin, VV Klyachin, NA Benton, EV Frank, AL Benton, ER Frigo, LA Dudkin, VE Potapov, YV Vana, N Schoner, W Fugger, M AF Badhwar, GD Atwell, W Cash, B Weyland, M Petrov, VM Tchernykh, IV Akatov, WA Shurshakov, VA Arkhangelsky, VV Kushin, VV Klyachin, NA Benton, EV Frank, AL Benton, ER Frigo, LA Dudkin, VE Potapov, YV Vana, N Schoner, W Fugger, M TI Intercomparison of radiation measurements on STS-63 SO RADIATION MEASUREMENTS LA English DT Article ID SPECTRA; ORBIT AB A joint NASA Russia study of the radiation environment inside the Space Shuttle was performed on STS-63. This was the second flight under the Shuttle-Mir Science Program (Phase 1). The Shuttle was launched on 2 February 1995, in a 51.65 degrees inclination orbit and landed at Remedy Space Center on 11 February 1995, for a total flight duration of 8.27 days. The Shuttle carried a complement of both passive and active detectors distributed throughout the Shuttle volume. The crew exposure varied from 1962 to 2790 mu Gy with an average of 2265.8 mu Gy or 273.98 mu Gy/day. Crew exposures varied by a factor of 1.4, which is higher than usual for STS mission. The flight altitude varied from 314 to 395 km and provided a unique opportunity to obtain dose variation with altitude. Measurements of the average east-west dose variation were made using two active solid state detectors. The dose rate in the Spacehab locker, measured using a tissue equivalent proportional counter (TEPC), was 413.3 mu Gy/day, consistent with measurements made using thermoluminescent detectors (TLDs) in the same locker. The average quality factor was 2.33, and although it was higher than model calculations, it was consistent with values derived from high temperature peaks in TLDs. The dose rate due to galactic cosmic radiation was 110.6 mu Gy/day and agreed with model calculations. The dose rate from trapped particles was 302.7 mu Gy/day, nearly a factor of 2 lower than the prediction of the AP8 model. The neutrons in the intermediate energy range of 1-20 MeV contributed 13 mu Gy/day and 156 mu Sv/day, respectively. Analysis of data from the charged particle spectrometer has not yet been completed. Copyright (C) 1996 Elsevier Science Ltd C1 LOCKHEED MARTIN CO,HOUSTON,TX 77058. MOSCOW BIOMED PROBLEMS INST,SPACE RADIAT SAFETY DEPT,MOSCOW 123007,RUSSIA. MOSCOW ENGN PHYS INST,MOSCOW 115409,RUSSIA. UNIV SAN FRANCISCO,SAN FRANCISCO,CA 94117. RES CTR SPACECRAFT SAFETY,MOSCOW 123182,RUSSIA. UNIV VIENNA,ATOMINST,A-1020 VIENNA,AUSTRIA. RP Badhwar, GD (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058, USA. NR 32 TC 10 Z9 10 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP 901 EP 916 DI 10.1016/S1350-4487(96)00082-0 PG 16 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800020 PM 11540523 ER PT J AU Cucinotta, FA Wilson, JW Shinn, JL Badavi, FF Badhwar, GD AF Cucinotta, FA Wilson, JW Shinn, JL Badavi, FF Badhwar, GD TI Effects of target fragmentation on evaluation of LET spectra from space radiations: Implications for space radiation protection studies SO RADIATION MEASUREMENTS LA English DT Article ID MUTATION-INDUCTION; HZE PROPAGATION; TRANSPORT; SHUTTLE; MODEL; CELLS AB We present calculations of linear energy transfer (LET) spectra in low earth orbit from galactic cosmic rays and trapped protons using the HZETRN/BRYNTRN computer code. The emphasis of our calculations is on the analysis of the effects of secondary nuclei produced through target fragmentation in the spacecraft shield or detectors. Recent improvements in the HZETRN/BRYNTRN radiation transport computer code are described. Calculations show that at large values of LET (> 100 keV/mu m) the LET spectra seen in free space and low earth orbit (LEG) are dominated by target fragments and not the primary nuclei. Although the evaluation of microdosimetric spectra is not considered here, calculations of LET spectra support that the large lineal energy (y) events are dominated by the target fragments. Finally, we discuss the situation for interplanetary exposures to galactic cosmic rays and show that current radiation transport codes predict that in the region of high LET values the LET spectra at significant shield depths ( > 10 g/cm(2) of Al) is greatly modified by target fragments. These results suggest that studies of track structure and biological response of space radiation should place emphasis on short tracks of medium charge fragments produced in the human body by high energy protons and neutrons. Published by Elsevier Science Ltd C1 CHRISTOPHER NEWPORT UNIV,NEWPORT NEWS,VA 23602. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Cucinotta, FA (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 30 TC 28 Z9 30 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP 923 EP 934 DI 10.1016/S1350-4487(96)00070-4 PG 12 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800022 PM 11540525 ER PT J AU Hayashi, T Doke, T Kikuchi, J Takeuchi, R Hasebe, N Ogura, K Nagaoka, S Kato, M Badhwar, GD AF Hayashi, T Doke, T Kikuchi, J Takeuchi, R Hasebe, N Ogura, K Nagaoka, S Kato, M Badhwar, GD TI Measurement of LET distribution and dose equivalent on board the space shuttle STS-65 SO RADIATION MEASUREMENTS LA English DT Article ID CR-39; RADIATION AB Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called ''Real-time Radiation Monitoring Device (RRMD)'' utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 mu Sv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit fdr space radiation with a small inclination (28.5 degrees) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15-200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks. Copyright (C) 1996 Elsevier Science Ltd C1 EHIME UNIV,FAC GEN EDUC,MATSUYAMA,EHIME 790,JAPAN. NIHON UNIV,COLL IND TECHNOL,NARASHINO,CHIBA 275,JAPAN. NASDA,TSUKUBA SPACE CTR,SPACE EXPT GRP,TSUKUBA,IBARAKI 305,JAPAN. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Hayashi, T (reprint author), WASEDA UNIV,ADV RES CTR SCI & ENGN,SHINJUKU KU,OKUBO 3-4-1,TOKYO 169,JAPAN. NR 14 TC 15 Z9 15 U1 1 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP 935 EP 945 DI 10.1016/S1350-4487(96)00095-9 PG 11 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800023 PM 11540526 ER PT J AU Stassinopoulos, EG Brucker, GJ Stauffer, CA AF Stassinopoulos, EG Brucker, GJ Stauffer, CA TI Analysis of space radiation data of semiconductor memories SO RADIATION MEASUREMENTS LA English DT Article ID CRRES AB This article presents an analysis of radiation effects for several select device types and technologies aboard the Combined Release and Radiation Effects Satellite (CRRES) satellite. These space-flight measurements covered a period of about 14 months of mission lifetime. Single Event Upset (SEU) data of the investigated devices from the Microelectronics Package (MEP) were processed and analyzed. Valid upset measurements were determined by correcting for invalid readings, hard failures, missing data tapes (thus voids in data), and periods over which devices were disabled from interrogation. The basic resolution time of the measurement system was confirmed to be 2 s. Lessons learned, important findings, and recommendations are presented. Published by Elsevier Science Ltd C1 SYST ENGN & SECUR,GREENBELT,MD 20770. RP Stassinopoulos, EG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 900,GREENBELT,MD 20771, USA. NR 16 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP 987 EP 994 DI 10.1016/S1350-4487(96)00102-3 PG 8 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800029 PM 11540532 ER PT J AU Kinard, B AF Kinard, B TI Space radiation - Results of the long duration exposure facility (LDEF) SO RADIATION MEASUREMENTS LA English DT Editorial Material RP Kinard, B (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA. NR 0 TC 0 Z9 0 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP R7 EP R7 DI 10.1016/S1350-4487(97)88178-4 PG 1 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800002 ER PT J AU Parnell, TA Benton, EV AF Parnell, TA Benton, EV TI Space radiation - Results of the long duration exposure facility (LDEF) - Preface SO RADIATION MEASUREMENTS LA English DT Editorial Material C1 UNIV SAN FRANCISCO,SAN FRANCISCO,CA 94117. RP Parnell, TA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD NOV PY 1996 VL 26 IS 6 BP R5 EP R6 DI 10.1016/S1350-4487(97)88177-2 PG 2 WC Nuclear Science & Technology SC Nuclear Science & Technology GA WD818 UT WOS:A1996WD81800001 ER PT J AU Treuhaft, RN Madsen, SN Moghaddam, M vanZyl, JJ AF Treuhaft, RN Madsen, SN Moghaddam, M vanZyl, JJ TI Vegetation characteristics and underlying topography from interferometric radar SO RADIO SCIENCE LA English DT Article ID SYNTHETIC APERTURE RADARS; FORESTS; MODEL AB This paper formulates and demonstrates methods for extracting vegetation characteristics and underlying ground surface topography from interferometric synthetic aperture radar (INSAR) data. The electromagnetic scattering and radar processing, which produce the INSAR observations, are modeled, vegetation and topographic parameters are identified for estimation, the parameter errors are assessed in terms of INSAR instrumental performance, and the parameter estimation is demonstrated on INSAR data and compared to ground truth. The fundamental observations from which vegetation and surface topographic parameters are estimated are (1) the cross-correlation amplitude, (2) the cross-correlation phase, and (3) the synthetic aperture radar (SAR) backscattered power. A calculation based on scattering from vegetation treated as a random medium, including the effects of refractivity and absorption in the vegetation, yields expressions for the complex cross correlation and backscattered power in terms of vegetation characteristics. These expressions lead to the identification of a minimal set of four parameters describing the vegetation and surface topography: (1) the vegetation layer depth, (2) the vegetation extinction coefficient (power loss per unit length), (3) a parameter involving the product of the average backscattering amplitude and scatterer number density, and (4) the height of the underlying ground surface. The accuracy of vegetation and ground surface parameters, as a function of INSAR observation accuracy, is evaluated for aircraft INSAR, which is characterized by a 2.5-m baseline, an altitude of about 8 km, and a wavelength of 5.6 cm. It is found that for approximate to 0.5% accuracy in the INSAR normalized cross-correlation amplitude and approximate to 5 degrees accuracy in the interferometric phase, few-meter vegetation layer depths and ground surface heights can be determined from INSAR for many types of vegetation layers. With the same observational accuracies, extinction coefficients can be estimated at the 0.1-dB/m level. Because the number of parameters exceeds the number of observations for current INSAR data sets, external extinction coefficient data are used to demonstrate the estimation of the vegetation layer depth and ground surface height from INSAR data taken at the Bonanza Creek Experimental Forest in Alaska. This demonstration shows approximately 5-m average ground truth agreement for vegetation layer depths and ground-surface heights, with a clear dependence of error on stand height. These errors suggest refinements in INSAR data acquisition and analysis techniques which will potentially yield few-meter accuracies. The information in the INSAR parameters is applicable to a variety of ecological modeling issues including the successional modeling of forested ecosystems. RP Treuhaft, RN (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 30 TC 184 Z9 199 U1 3 U2 18 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD NOV-DEC PY 1996 VL 31 IS 6 BP 1449 EP 1485 DI 10.1029/96RS01763 PG 37 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA VW106 UT WOS:A1996VW10600014 ER PT J AU Fogarty, MJ Mayo, RK OBrien, L Serchuk, FM Rosenberg, AA AF Fogarty, MJ Mayo, RK OBrien, L Serchuk, FM Rosenberg, AA TI Assessing uncertainty and risk in exploited marine populations SO RELIABILITY ENGINEERING & SYSTEM SAFETY LA English DT Article ID STOCK ASSESSMENT; RECRUITMENT; FISHERIES; MANAGEMENT; TRENDS AB The assessment and management of exploited fish and invertebrate populations is subject to several types of uncertainty. This uncertainty translates into risk to the population in the development and implementation of fishery management advice. Here, we define risk as the probability that exploitation rates will exceed a threshold level where long term sustainability of the stock is threatened. We distinguish among several sources of error or uncertainty due to (a) stochasticity in demographic rates and processes, particularly in survival rates during the early life stages; (b) measurement error resulting from sampling variation in the determination of population parameters or in model estimation; and (c) the lack of complete information on population and ecosystem dynamics. The first represents a form of aleatory uncertainty while the latter two factors represent forms of epistemic uncertainty. To illustrate these points, we evaluate the recent status of the Georges Bank cod stock in a risk assessment framework. Short term stochastic projections are made accounting for uncertainty in population size and for random variability in the number of young surviving to enter the fishery. We show that recent declines in this cod stock can be attributed to exploitation rates that have substantially exceeded sustainable levels. Published by Elsevier Science Limited. C1 NATL MARINE FISHERIES SERV,NATL OCEAN & ATMOSPHER ADM,GLOUCESTER,MA 01930. RP Fogarty, MJ (reprint author), NOAA,NATL MARINE FISHERIES SERV,NE FISHERIES SCI CTR,WOODS HOLE,MA 02543, USA. NR 37 TC 13 Z9 13 U1 1 U2 8 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0951-8320 J9 RELIAB ENG SYST SAFE JI Reliab. Eng. Syst. Saf. PD NOV-DEC PY 1996 VL 54 IS 2-3 BP 183 EP 195 DI 10.1016/S0951-8320(96)00074-9 PG 13 WC Engineering, Industrial; Operations Research & Management Science SC Engineering; Operations Research & Management Science GA WB789 UT WOS:A1996WB78900009 ER PT J AU Chehbouni, A LoSeen, D Njoku, EG Monteny, BM AF Chehbouni, A LoSeen, D Njoku, EG Monteny, BM TI Examination of the difference between radiative and aerodynamic surface temperatures over sparsely vegetated surfaces SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID ENERGY BALANCE; MODEL; REFLECTANCE; EVAPORATION; RESISTANCE; SCATTERING; FLUXES; INDEX; CROPS; FIFE AB A four-layer hydrologic model, coupled to a vegetation growth model, has been used to investigate the differences between aerodynamic surface temperature and radiative surface temperature over sparsely vegetated surface. The rationale for the coupling of the two models was to assess the dependency of these differences on changing surface conditions (i.e., growing vegetation). A simulation was carried out for a 3-month period corresponding to a typical growth seasonal cycle of an herbaceous canopy in the Sahel region of West Africa (Goutorbe et al., 1993). The results showed that the ratio of radiative-aerodynamic temperature difference to radiative-air temperature difference was constant for a given day. However, the seasonal trend of this ratio was changing with respect to the leaf area index (LAI). A parameterization involving radiative surface temperature, air temperature, and LAI was then developed to estimate aerodynamic-air temperature gradient, and thus sensible heat flux. This parameterization was validated using data collected over herbaceous site during the Hapex-Sahel experiment. This approach was further advanced by using a radiative transfer model in conjunction with the above models to simulate the temporal behavior of surface reflectances in the visible and the near-infrared spectral bands. The result showed that sensible heat flux can be fairly accurately estimated by combining remotely sensed surface temperature, air temperature, and spectral vegetation index. The result of this study may represent a great opportunity of using remotely sensed data to estimate spatiotemporal variabilities of surface fluxes in arid and semiarid regions. (C) Elsevier Science Inc., 1996. C1 CALTECH,JET PROP LAB,PASADENA,CA. RP Chehbouni, A (reprint author), ORSTOM,HYDROL LAB,DEPT TERRE OCEAN ATMOSPHERE,911 AVE AGROPOLIS,BP 5045,F-30042 MONTPELLIER,FRANCE. RI Lo Seen, Danny/C-2679-2008 OI Lo Seen, Danny/0000-0002-7773-2109 NR 35 TC 56 Z9 66 U1 1 U2 13 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD NOV PY 1996 VL 58 IS 2 BP 177 EP 186 DI 10.1016/S0034-4257(96)00037-5 PG 10 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA VT371 UT WOS:A1996VT37100004 ER PT J AU Verstraete, MM Pinty, B Myneni, RB AF Verstraete, MM Pinty, B Myneni, RB TI Potential and limitations of information extraction on the terrestrial biosphere from satellite remote sensing SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID BIDIRECTIONAL REFLECTANCE; VEGETATION CANOPIES; MODEL; INVERSION; SURFACE; INDEX; RADIOMETER; VALIDATION AB The extraction of information on terrestrial environments from satellite observations requires the use of quantitative models to interpret the radiation data collected in space. Several approaches are feasible, ranging from the development of models capable of explaining the nature of the measured physical signal or of characterizing the state of the system under observation, to the establishment of empirical correlations between the variables of interest and the remote measurements. The premises and implications of these approaches are discussed with special emphasis on the mathematical and numerical requirements. Findings are condensed in 10 formal propositions, in the hope of clarifying the nature and domain of applicability of remote sensing. (C) Elsevier Science Inc., 1996. C1 UNIV MARYLAND, NASA, GODDARD SPACE FLIGHT CTR, BIOSPHER SCI BRANCH, GREENBELT, MD USA. RP Verstraete, MM (reprint author), SPACE APPLICAT INST, JOINT RES CTR, TP 440, I-21020 ISPRA, ITALY. RI Myneni, Ranga/F-5129-2012; OI Verstraete, Michel/0000-0003-0968-8721 NR 42 TC 146 Z9 158 U1 0 U2 36 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD NOV PY 1996 VL 58 IS 2 BP 201 EP 214 DI 10.1016/S0034-4257(96)00069-7 PG 14 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA VT371 UT WOS:A1996VT37100006 ER PT J AU Cheng, ES Meyer, SS Page, LA AF Cheng, ES Meyer, SS Page, LA TI A high capacity 0.23 K He-3 refrigerator for balloon-borne payloads SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID ANISOTROPY; MILLIMETER; RADIATION AB We describe the design, operation, and performance of a high capacity, single stage, He-3 refrigerator optimized for balloon-borne payloads. A temperature of similar to 0.2 K is routinely maintained for more than seven days at similar to 100 mu W total heat load. Recycling can be completed in less than 12 h. A simple design avoids valves and explicit heat switches, resulting in simplified construction and improved performance. A numerical model characterizes the operating temperature of the system over a large range of conditions. (C) 1996 American Institute of Physics. C1 UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08540. RP Cheng, ES (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 21 TC 6 Z9 6 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD NOV PY 1996 VL 67 IS 11 BP 4008 EP 4016 DI 10.1063/1.1147275 PG 9 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA VT188 UT WOS:A1996VT18800036 ER PT J AU Tejwani, GD Bircher, FE VanDyke, DB McVay, GP Stewart, CD Langford, LA Thurman, CC AF Tejwani, GD Bircher, FE VanDyke, DB McVay, GP Stewart, CD Langford, LA Thurman, CC TI Space shuttle main engine exhaust-plume spectroscopy SO SPECTROSCOPY LA English DT Article AB Exhaust-plume spectroscopic methods provide ideal non-intrusive technologies for the development of rocket-engine-health monitoring and failure detection systems. The John C. Stennis Space Center (SSC), as NASA's designated Center of Excellence for large-space-propulsion-system testing, is in the forefront of advancing experimental and analytical techniques in the field of plume spectroscopy. This article gives an overview of our instrumentation and computational systems for plume diagnostics at SSC and presents some recent applications. C1 LOCKHEED MARTIN STENNIS OPERAT,BAY ST LOUIS,MS 39529. NASA,BAY ST LOUIS,MS 39529. NR 21 TC 4 Z9 4 U1 0 U2 2 PU ADVANSTAR COMMUNICATIONS PI DULUTH PA 131 W FIRST ST, DULUTH, MN 55802 SN 0887-6703 J9 SPECTROSCOPY JI Spectroscopy PD NOV-DEC PY 1996 VL 11 IS 9 BP 31 EP 43 PG 13 WC Spectroscopy SC Spectroscopy GA VT417 UT WOS:A1996VT41700005 ER PT J AU Mital, SK Murthy, PLN Chamis, CC AF Mital, SK Murthy, PLN Chamis, CC TI Computational simulation of microfracture in high temperature composites SO THEORETICAL AND APPLIED FRACTURE MECHANICS LA English DT Article AB This paper presents a summary and typical results of the research activities pertaining to composite microfracture in high temperature metal matrix composites carried out by the authors, The various failure modes and their effect on macro behavior as well as the hierarchy of their occurrences are examined by computationally simulating these events using three-dimensional finite element analyses, The procedure is based on the macro strain energy release rate which predicts the direction of crack growth and establishes the hierarchy and sequence of respective failure modes, Step-by-step procedures are outlined for evaluating composite microfracture. Microfracture results for various loading cases for a unidirectional metal matrix composite are presented and discussed. A key result is that interfacial debonding is a consequence of either fiber or matrix fracture. C1 UNIV TOLEDO,TOLEDO,OH 43606. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. NR 6 TC 0 Z9 0 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8442 J9 THEOR APPL FRACT MEC JI Theor. Appl. Fract. Mech. PD NOV-DEC PY 1996 VL 25 IS 3 BP 203 EP 209 DI 10.1016/S0167-8442(96)00022-5 PG 7 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA VY293 UT WOS:A1996VY29300003 ER PT J AU Gotsis, PK Chamis, CC Minnetyan, L AF Gotsis, PK Chamis, CC Minnetyan, L TI Computational simulation of damage progression of composite thin shells subjected to mechanical loads SO THEORETICAL AND APPLIED FRACTURE MECHANICS LA English DT Article AB Defect-free and defected composite thin shells with ply orientation (90/0/+/-75) made of graphite/epoxy are simulated for damage progression and fracture due to internal pressure and axial loading, The thin shells have a cylindrical geometry with one end fixed and the other free, The applied load consists of an internal pressure in conjunction with an axial load at the free end, the cure temperature was 177 degrees C (350 degrees F) and the operational temperature was 21 degrees C (70 degrees F), The residual stresses due to the processing are taken into account. Shells with defect and without defects were examined by using CODSTRAN an integrated computer code that couples composite mechanics, finite element and account for all possible failure modes inherent in composites. CODSTRAN traces damage initiation, growth, accumulation, damage propagation and the final fracture of the structure. The results show that damage initiation started with matrix failure while damage/fracture progression occurred due to additional matrix failure and fiber fracture, The burst pressure of the (90/0/+/-75) defected shell was 0.092% of that of the free defect. Finally the results of the damage progression of the (90/0/+/-75), defective composite shell was compared with the (90/0/+/-theta), where theta=45 and 60, layup configurations, It was shown that the examined laminate (90/0/+/-75) has the least damage tolerant of the two compared defective shells with the (90/0/+/-theta), theta=45 and 60 laminates. C1 CLARKSON UNIV,DEPT CIVIL & ENVIRONM ENGN,POTSDAM,NY 13699. RP Gotsis, PK (reprint author), NASA,LEWIS RES CTR,DIV STRUCT,CLEVELAND,OH 44135, USA. NR 13 TC 3 Z9 3 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8442 J9 THEOR APPL FRACT MEC JI Theor. Appl. Fract. Mech. PD NOV-DEC PY 1996 VL 25 IS 3 BP 211 EP 224 DI 10.1016/S0167-8442(96)00023-7 PG 14 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA VY293 UT WOS:A1996VY29300004 ER PT J AU Girimaji, SS AF Girimaji, SS TI Fully explicit and self-consistent algebraic Reynolds stress model SO THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS LA English DT Article ID TURBULENCE AB A fully explicit, self-consistent algebraic expression (for Reynolds stress) which is the exact solution to the Reynolds stress transport equation in the ''weak-equilibrium'' limit for two-dimensional mean flows for all linear and some quasi-linear pressure-strain models, is derived. Current explicit algebraic Reynolds stress models derived by employing the ''weak-equilibrium'' assumption treat the production-to-dissipation (PIE) ratio as a constant, resulting in an effective viscosity that can be singular away from the equilibrium limit. In this paper the set of simultaneous algebraic Reynolds stress equations in the weak-equilibrium limit are solved in the full nonlinear form and the eddy viscosity is found to be nonsingular. Preliminary tests indicate that the model performs adequately, even for three-dimensional mean-flow cases. Due to the explicit and nonsingular nature of the effective viscosity, this model should mitigate many of the difficulties encountered in computing complex turbulent flows with the algebraic Reynolds stress models. RP Girimaji, SS (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681, USA. NR 11 TC 74 Z9 76 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0935-4964 J9 THEOR COMP FLUID DYN JI Theor. Comput. Fluid Dyn. PD NOV PY 1996 VL 8 IS 6 BP 387 EP 402 DI 10.1007/BF00455991 PG 16 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA VX001 UT WOS:A1996VX00100001 ER PT J AU Iga, I Rao, MVVS Srivastava, SK Nogueira, JC AF Iga, I Rao, MVVS Srivastava, SK Nogueira, JC TI Cross-sections for the formation of S- ions by electron impact on OCS SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY AND ION PROCESSES LA English DT Article DE cross-sections; electron attachment; negative ions ID ATTACHMENT; IONIZATION; SCATTERING; CO2; CS2 AB Cross-sections, appearance energies and peak energies at which S- ion intensities are maximal have been measured for electron attachment to OCS as a function of electron impact energy in the energy range 0-20 eV using a time-of-flight mass spectrometer in a crossed-beams collision geometry. Maximum intensities of formation of S - were observed at four electron impact energies of 1.4, 4.7, 7.0, and 10.2 eV with an accuracy to +/-0.25 eV. The cross-sections measured at these energies were 2.6 x 10(-17), 1.5 x 10(-19), 1.8 x 10(-19), and 0.4 x 10(-19) cm(2) respectively, with an uncertainty of about +/-15%. From appearance energies of various resonance processes for S- formation and by using thermochemical data we have been able to identify various dissociative electron attachment channels of OCS. Cross-section values for three additional dissociative channels for the formation of S- and time-of-flight spectra representing the kinetic energies of these ions are reported for the first time. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV FED SAO CARLOS,DEPT QUIM,BR-13565905 SAO CARLOS,SP,BRAZIL. RI Iga, Ione/C-1273-2015 NR 17 TC 5 Z9 5 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-1176 J9 INT J MASS SPECTROM JI Int. J. Mass Spectrom. Ion Process. PD OCT 31 PY 1996 VL 155 IS 1-2 BP 99 EP 105 DI 10.1016/0168-1176(96)04385-6 PG 7 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA VR999 UT WOS:A1996VR99900005 ER PT J AU McKay, CP AF McKay, CP TI The case for Mars: The plan to settle the red planet and why we must - Zubrin,R, Wagner,R SO NATURE LA English DT Book Review RP McKay, CP (reprint author), NASA,AMES RES CTR,SPACE SCI DIV 2453,MOFFETT FIELD,CA 94035, USA. NR 1 TC 1 Z9 1 U1 1 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD OCT 31 PY 1996 VL 383 IS 6603 BP 780 EP 780 DI 10.1038/383780a0 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VQ144 UT WOS:A1996VQ14400046 ER PT J AU Andreae, MO Fishman, J Lindesay, J AF Andreae, MO Fishman, J Lindesay, J TI The Southern Tropical Atlantic Region Experiment (STARE): Transport and Atmospheric Chemistry near the Equator-Atlantic (TRACE A) and Southern African Fire-Atmosphere Research Initiative (SAFARI): An introduction SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. UNIV WITWATERSRAND, CLIMATOL RES GRP, JOHANNESBURG, SOUTH AFRICA. RP Andreae, MO (reprint author), MAX PLANCK INST CHEM, BIOGEOCHEM DEPT, POSTFACH 3060, D-55020 MAINZ, GERMANY. RI Andreae, Meinrat/B-1068-2008 OI Andreae, Meinrat/0000-0003-1968-7925 NR 0 TC 52 Z9 52 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23519 EP 23520 DI 10.1029/96JD01786 PG 2 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300001 ER PT J AU Cofer, WR Levine, JS Winstead, EL Cahoon, DR Sebacher, DI Pinto, JP Stocks, BJ AF Cofer, WR Levine, JS Winstead, EL Cahoon, DR Sebacher, DI Pinto, JP Stocks, BJ TI Source compositions of trace gases released during African savanna fires SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC CHEMISTRY; BIOMASS FIRES; EMISSIONS; WETLANDS; AEROSOL; METHANE; FLUXES; CARBON; OXIDE; CO2 AB Measurements of biomass burn-produced trace gases were made using low-altitude helicopter penetrations of smoke plumes above burning African savanna during the Southern African Fire-Atmosphere Research Initiative (SAFARI-92). Smoke from two large prescribed fires conducted in the Kruger National Park, South Africa, on September 18 and 24, 1992, was sampled at altitudes ranging from 20 to 100 m above ground level during flaming and smoldering phases of combustion. Carbon dioxide (CO2) normalized emission ratios (dX/dCO(2) (vol/vol), where X denotes a trace gas) for carbon monoxide (CO), hydrogen (H-2), methane (CH4), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N2O) were determined. The emission ratios were used in conjunction with fuel consumption estimates to calculate emission factors (grams df product per gram of fuel) for these gases. Emission factors for CO2, CO, CH4, and N2O of 1.61, 0.055, 0.003, and 1.6 x 10(-4) g/g fuel, respectively, were determined. The fires advanced rapidly through the savanna (primarily grass) fuels with minimal amounts of smoldering combustion. The relatively low emission ratios determined for these fires indicated excellent combustion efficiency. About 93% of the carbon released into the atmosphere as a result of these fires was in the form of CO2. C1 US EPA, ATMOSPHER RES & EXPOSURE ASSESSMENT LABS, RES TRIANGLE PK, NC 27711 USA. SCI APPLICAT INT CORP, HAMPTON, VA 23666 USA. FORESTRY CANADA, GREAT LAKES FORESTRY CTR, SAULT ST MARIE, ON P6A 5M7, CANADA. RP Cofer, WR (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. NR 36 TC 41 Z9 41 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23597 EP 23602 DI 10.1029/95JD02048 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300009 ER PT J AU Scholes, RJ Kendall, J Justice, CO AF Scholes, RJ Kendall, J Justice, CO TI The quantity of biomass burned in southern Africa SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE; RAINFALL; CARBON AB A new method is described fur calculating the amount of biomass burned, its type and location, and the time of burning. Active fires in 1989 were detected using daily advanced very high resolution radiometer (AVHRR) satellite imagery. The fire count was calibrated to area burned using a stratified sample of multitemporal multispectral scanner (MSS) imagery. The calibration factor is strongly dependent on mean individual fire area, which is in turn strongly related to cumulative normalized difference vegetation index (NDVI). The best available vegetation maps for southern hemisphere Africa were combined and reclassified into functional vegetation types with a similar fire ecology. The fuel load was calculated in each 0.5 degrees x 0.5 degrees grid square using a production model specific for each vegetation type, driven by monthly rainfall data. Multiyear fuel accumulation, herbivory, and decay were accounted for. Combustion completeness was modeled as a function of fuel mass and fuel type, established from field-collected data. The method was compared to the conventional procedure for calculating biomass burned, based on classification. The estimated amount of biomass burned in vegetation fires in southern hemisphere Africa annually is 90-264 Tg dry matter (DM) by the new modeling method and 247-2719 Tg DM by the conventional classification method. The modeling method is conservative since it does not include burning due to forest clearing or the burning of agricultural waste or domestic biomass fuels, but it is believed to be more realistic than the classification method and provides space-and-time-resolved output. The bulk of the burning occurs between June and September, with a peak in August. Half of the burning takes place in the broad-leaved, low-nutrient-status savannas which dominate the zone between 5 degrees and 18 degrees S. C1 NASA, GIMMS GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV MARYLAND, DEPT GEOG, COLLEGE PK, MD 20742 USA. RP Scholes, RJ (reprint author), CSIR, DIV WATER ENVIRONM & FOREST TECHNOL, POB 395, ZA-0001 PRETORIA, SOUTH AFRICA. OI Scholes, Robert/0000-0001-5537-6935 NR 36 TC 109 Z9 110 U1 0 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23667 EP 23676 DI 10.1029/96JD01623 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300014 ER PT J AU Parsons, DAB Scholes, MC Scholes, RJ Levine, JS AF Parsons, DAB Scholes, MC Scholes, RJ Levine, JS TI Biogenic NO emissions from savanna soils as a function of fire regime, soil type, soil nitrogen, and water status SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NITRIC-OXIDE; TROPICAL SAVANNA; FOREST; SEASON; N2O AB A study of NOx emissions from soils representative of nutrient-poor and nutrient-rich savannas and their response to burning and soil water content was carried out in the southern Kruger National Park, South Africa. The study spanned the end of the dry season and the beginning of the wet season (September-December 1992). Nitrogen mineralization rates were measured using an in situ technique simultaneously with measurements of NOx emissions. NOx emissions were almost entirely as NO. The relationship between NO emission rate and soil moisture was parabolic regardless of soil type and management practice, with the lowest NO emission rates being measured at low (<0.087) and high (>0.542) water-filled pore space values. The initial increase in NO emission rates with increasing soil moisture are paralleled by increases in the nitrate concentration in the soil. The highest NO emission rates (20 ng N-NO m(-2) s(-1)-excluding the brief initial peak) were measured on plots from which fire had been excluded for 35 years. The next highest rates (8 ng N-NO m(-2) s(-1)) were measured on the more fertile soils. Infertile soils, burned every second year, had rates of 3.5 ng N-NO m(-2) s(-1). The NO emission rates show a positive correlation with soil total N content and N nitrification rate. The effect of excluding fire from a savanna is to increase the soil nitrogen content through increased litter inputs, which in turn increases nitrification rates and soil NO emissions. C1 UNIV WITWATERSRAND, DEPT BOT, ZA-2050 JOHANNESBURG, SOUTH AFRICA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RP Parsons, DAB (reprint author), CSIR, DIV WATER FORESTRY & ENVIRONM, PRIVATE BAG 395, ZA-0001 PRETORIA, SOUTH AFRICA. OI Scholes, Robert/0000-0001-5537-6935 NR 28 TC 50 Z9 50 U1 2 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23683 EP 23688 DI 10.1029/95JD02140 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300016 ER PT J AU Thompson, AM Diab, RD Bodeker, GE Zunckel, M Coetzee, GJR Archer, CB McNamara, DP Pickering, KE Combrink, J Fishman, J Nganga, D AF Thompson, AM Diab, RD Bodeker, GE Zunckel, M Coetzee, GJR Archer, CB McNamara, DP Pickering, KE Combrink, J Fishman, J Nganga, D TI Ozone over southern Africa during SAFARI-92 TRACE A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; TROPOSPHERIC OZONE; SATELLITE DATA; TROPICS; EMISSIONS; PRETORIA AB Characteristics of total O-3 in southern Africa and over the adjacent Atlantic during the IGAC/STARE/SAFARI-92/TRACE A (International Global Atmospheric Chemistry/South Tropical Atlantic Regional Experiment/Southern African Fire Atmospheric Research Initiative/Transport and Atmospheric Chemistry near the Equator-Atlantic) field experiments are described, Most of the analysis is based on data from the Nimbus 7/total ozone mapping spectrometer (TOMS) gridded O-3 data archive (version 6.0), which is used to examine O-3 in terms of seasonal and interannual variability. Total O-3 column variability is compared to the tropospheric O-3 column derived from balloon-borne ozonesondes at four fixed SAFARI-92/TRACE A sites (Ascension Island, Brazzaville, Okaukuejo, and Irene) from September 1 to October 23, 1992. All of these sites except Okaukuejo had regular ozonesonde launches from 1990 to 1992. Total O-3 and integrated tropospheric O-3 at the sounding sites showed the expected September-October maxima over southern Africa and the adjacent Atlantic Ocean. Statistical analysis of the TOMS record for 1979-1992 allows disaggregation of components contributing to total O-3 variability: Signals due to semiannual and annual cycles and the quasi-biennial oscillation are identified at the sounding sites. The tropospheric O-3 column estimated from integrated sondes (to similar to 16 km) at the four sites ranged from 24 to 62 Dobson units (DU) (mean, 45 DU) and averaged 15% of total O-3 at Irene (14 launches) and 19% of total O-3 at Ascension (20 launches). Tropospheric O-3 was higher at Ascension and Brazzaville than at the sites south of 15 degrees S because transport from biomass burning regions was more direct at these sites. This transport is seen in Hovmoller (time-longitude) plots of total O-3. A comparison of 1990-1992 integrated tropospheric O-3 amounts with the annual total ozone cycle shows that tropospheric ozone variations may account for all of the annual signal at Ascension (8 degrees S) and Brazzaville (4 degrees S) but only 30-40% of the seasonal total O-3 variation at Irene (26 degrees S). Hovmoller plots of daily TOMS O-3 over Southern Africa and the Atlantic show easterly flow of local O-3 maxima at 0 degrees-10 degrees S and westerly movement from 30 degrees-40 degrees S. At 0 degrees-10 degrees S the continent-ocean total O-3 gradient and Ascension and Brazzaville O-3 soundings are used to estimate a photochemical O-3 formation rate of 1-2 ppbv O-3/d over the Atlantic. This agrees with model calculations of moderately aged biomass burning emissions from SAFARI-92/TRACE A. C1 APPL RES CORP, LANDOVER, MD 20785 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. MARIEN NGOUABI UNIV, DEPT ATMOSPHER PHYS, BRAZZAVILLE, CONGO. WEATHER BUR, ZA-0001 PRETORIA, SOUTH AFRICA. CSIC, ZA-0001 PRETORIA, SOUTH AFRICA. UNIV NATAL, DEPT GEOG & ENVIRONM SCI, ZA-4001 DURBAN, SOUTH AFRICA. UNIV MARYLAND, JCESS, DEPT METEOROL, COLLEGE PK, MD 20742 USA. UNIV NATAL, SPACE PHYS RES INST, DURBAN, SOUTH AFRICA. RP Thompson, AM (reprint author), NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RI Pickering, Kenneth/E-6274-2012; Bodeker, Greg/A-8870-2008; Thompson, Anne /C-3649-2014; OI Bodeker, Greg/0000-0003-1094-5852; Thompson, Anne /0000-0002-7829-0920; Diab, Roseanne/0000-0002-3564-8320 NR 36 TC 45 Z9 46 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23793 EP 23807 DI 10.1029/95JD02459 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300027 ER PT J AU Diab, RD Thompson, AM Zunckel, M Coetzee, GJR Combrink, J Bodeker, GE Fishman, J Sokolic, F McNamara, DP Archer, CB Nganga, D AF Diab, RD Thompson, AM Zunckel, M Coetzee, GJR Combrink, J Bodeker, GE Fishman, J Sokolic, F McNamara, DP Archer, CB Nganga, D TI Vertical ozone distribution over southern Africa and adjacent oceans during SAFARI-92 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; SATELLITE; POLLUTION; TROPICS; FOREST AB A set of four ozonesonde stations located at Ascension Island, Brazzaville, Okaukuejo, and Irene, operational during the TRACE A and SAFARI-92 experiments has provided an opportunity to investigate the vertical distribution of ozone over southern Africa and adjacent oceans. All stations display a springtime maximum in tropospheric ozone. Enhanced tropospheric ozone, which occurs between June and September at Brazzaville and between July and October at Ascension Island, is linked to dry season biomass burning. The influence of tropical biomass burning is delayed until September at Okaukuejo when a sharp increase in tropospheric ozone is experienced. The biomass burning influence at Irene is less because of its more southerly location. A general tropospheric enhancement is observed at all stations. It is manifest as an enriched layer in the upper troposphere at Okaukuejo (9-12 km) and Brazzaville (11-14 km) and in the lower troposphere (2-8 km) at Ascension Island. At Ascension Island lower tropospheric ozone values are about 20 parts per billion by volume greater than elsewhere and the tropospheric component here accounts for about 18% of the total column ozone. A series of tethersonde soundings conducted at hourly intervals at Okaukuejo revealed ozone to be well mixed in the lower boundary layer during the day, but to display marked vertical stratification at night. C1 CSIC, ZA-0001 PRETORIA, SOUTH AFRICA. S AFRICAN WEATHER BUR, ZA-0001 PRETORIA, SOUTH AFRICA. UNIV NATAL, SPACE PHYS RES INST, DURBAN, SOUTH AFRICA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP, GREENBELT, MD 20771 USA. MARIEN NGOUABI UNIV, DEPT ATMOSPHER PHYS, BRAZZAVILLE, CONGO. RP Diab, RD (reprint author), UNIV NATAL, DEPT GEOG & ENVIRONM SCI, DURBAN, SOUTH AFRICA. RI Bodeker, Greg/A-8870-2008; Thompson, Anne /C-3649-2014; OI Bodeker, Greg/0000-0003-1094-5852; Thompson, Anne /0000-0002-7829-0920; Diab, Roseanne/0000-0002-3564-8320 NR 24 TC 42 Z9 42 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23823 EP 23833 DI 10.1029/96JD01267 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300029 ER PT J AU Fishman, J Hoell, JM Bendura, RD McNeil, RJ Kirchhoff, VWJH AF Fishman, J Hoell, JM Bendura, RD McNeil, RJ Kirchhoff, VWJH TI NASA GTE TRACE A experiment (September October 1992): Overview SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; SATELLITE AB An overview of the Transport and Atmospheric Chemistry near the Equator-Atlantic (TRACE A) field mission is presented. TRACE A was conducted to provide a comprehensive investigation of the chemical composition, transport, and chemistry of the atmosphere over the tropical South Atlantic Ocean and the adjacent South American and African continents. Measurements for TRACE A consisted of a remote sensing component to derive tropospheric ozone and biomass burning patterns, an airborne atmospheric chemistry component to determine the composition of the air in the most pristine areas of our research domain as well as to characterize the photochemistry and transport of trace gas emissions from both fire and biogenic sources, a series of ozonesonde observations, and an enhanced radiosonde network and airborne meteorological measurements that provided information about the transport of trace gases and the physical processes that were responsible for their observed distributions. The data were interpreted through the use of both photochemical and meteorological numerical models. The picture that emerges from TRACE A is that widespread biomass burning in both South America and southern Africa is the dominant source of the precursor gases necessary for the formation of the huge amounts of ozone over the South Atlantic Ocean. In addition, however, the meteorology in this region of the world is favorable for the accumulation of these pollutants over the tropical Atlantic basin so that photochemical processes produce large quantities of ozone in situ. The generation of ozone occurs over scales of thousands of kilometers and is unusually enhanced in the upper troposphere where relatively high concentrations of nitrogen oxides (NOx) prevail. This latter finding suggests that convective processes (or other lifting mechanisms) may play an important role in the generation of tropospheric ozone or that there may be an additional significant upper tropospheric source of NOx, such as from lightning. C1 NASA HEADQUARTERS, WASHINGTON, DC 20456 USA. INST NACL PESQUISAS ESPACIAIS, SAO JOSE DOS CAMPOS, SP, BRAZIL. RP Fishman, J (reprint author), NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. NR 25 TC 143 Z9 143 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23865 EP 23879 DI 10.1029/96JD00123 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300032 ER PT J AU Krishnamurti, TN Sinha, MC Kanamitsu, M Oosterhof, D Fuelberg, H Chatfield, R Jacob, DJ Logan, J AF Krishnamurti, TN Sinha, MC Kanamitsu, M Oosterhof, D Fuelberg, H Chatfield, R Jacob, DJ Logan, J TI Passive tracer transport relevant to the TRACE a experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE; MODEL; ABSORPTION; ATMOSPHERE AB This paper explores some of the mechanisms governing the accumulation of passive tracers over the tropical southern Atlantic Ocean during the northern hemisphere fall season. There has been a pioneering observation regarding ozone maxima over the South Atlantic during austral spring. The understanding of the formation of this maxima has been the prime motivation for this study. Using a global model as a frame of reference, we have carried out three kinds of experiments during the period of the Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) project of 1992. The first of these is a simple advection of total ozone (a passive tracer) in time using the Florida State University global spectral model. Integration over the period of roughly 1 week showed that the model quite closely replicates the behavior of the observed total ozone from the total ozone mapping spectrometer (TOMS). This includes many of the changes in the features of total ozone over the tropical and subtropical region of the southern Atlantic Ocean. These studies suggest a correlation of 0.8 between the observed ozone over this region and ozone modeled from ''dynamics alone,'' i.e., without recourse to any photochemistry. The second series of experiments invoke sustained sources of a tracer over the biomass burn region of Africa and Brazil. Furthermore, sustained sources were also introduced in the active frontal ''descending air'' region of the southern hemisphere and over the Asian monsoon's east-west circulation. These experiments strongly suggest that air motions help to accumulate tracer elements over the tropical southern Atlantic Ocean. A third series of experiments address what may be required to improve the deficiencies of the vertical stratification of ozone predicted by the model over the flight region of the tropical southern Atlantic during TRACE A. Here we use the global model to optimally derive plausible accumulation of burn elements over the fire count regions of Brazil and Africa to provide passive tracer advections to closely match what was observed from reconnaissance aircraft-based measurements of ozone over the tropical southern Atlantic Ocean. C1 NATL METEOROL CTR, WASHINGTON, DC 20233 USA. NASA, AMES RES CTR, DIV EARTH SYST SCI, MOFFETT FIELD, CA 94035 USA. HARVARD UNIV, DEPT EARTH & PLANETARY SCI, CAMBRIDGE, MA 02138 USA. RP Krishnamurti, TN (reprint author), FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. NR 22 TC 42 Z9 42 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23889 EP 23907 DI 10.1029/95JD02419 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300034 ER PT J AU Pickering, KE Thompson, AM McNamara, DP Schoeberl, MR Fuelberg, HE Loring, RO Watson, MV Fakhruzzaman, K Bachmeier, AS AF Pickering, KE Thompson, AM McNamara, DP Schoeberl, MR Fuelberg, HE Loring, RO Watson, MV Fakhruzzaman, K Bachmeier, AS TI TRACE a trajectory intercomparison .1. Effects of different input analyses SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NATIONAL-METEOROLOGICAL-CENTER AB We address the problem of air mass trajectory uncertainty through an intercomparison of trajectories computed from operational meteorological analyses from the region and time period of the NASA/GTE/TRACE A experiment. This paper examines the trajectory uncertainty that results from the input meteorological analyses, We first compare the National Meteorological Center (NMC) and European Centre for Medium-Range Forecasts (ECMWF) meteorological analyses to an independent set of observations, the dropsondes released from the NASA DC-8 over the South Atlantic during TRACE A, We also compare the gridded wind and temperature fields with selected rawinsonde data that entered the analyses. These comparisons show that the ECMWF fields are marginally better than the ones from NMC, particularly in the tropical regions of the southern hemisphere. The NMC analyses are marginally better in the midlatitude westerlies in some cases. In general, slightly more confidence can be placed in trajectories computed with ECMWF data over the TRACE A region, based on our comparisons of the analyses with observations. Second, we compute 5-day back trajectories with three different models from a grid of points over the South Atlantic and adjacent portions of South America and Africa as well as on the track of TRACE A flight 15 over the South Atlantic. When using the Goddard Space Flight Center isentropic model, horizontal separations of greater than 1000 km occur for about 50% of the points when trajectories run with the ECMWF and NMC analyses are compared. Greater sensitivity to the input analysis differences is noted when trajectories are computed with the FSU kinematic model (separations exceed 1000 km for 75% of the points). The problem of meteorological uncertainty should be addressed with two approaches. There are large differences between both sets of analyses and the TRACE A soundings; this is also likely to be the case in other remote regions. Therefore we recommend that a test set of trajectories be computed with both sets of input data to quantify the uncertainty due to analysis differences. In addition, clusters of trajectories about the points of interest should be run to assess the uncertainty due to wind shear. These recommendations are applicable to any region of the globe with sparse observations. The companion paper [Fuelberg et al., this issue, part 2] addresses uncertainties due to trajectory technique. C1 NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP, GREENBELT, MD 20771 USA. FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. NASA, LANGLEY RES CTR, LOCKHEED ENGN & SCI CO, HAMPTON, VA 23681 USA. RP Pickering, KE (reprint author), UNIV MARYLAND, JOINT CTR EARTH SYST SCI, DEPT METEOROL, COLLEGE PK, MD 20742 USA. RI Pickering, Kenneth/E-6274-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 11 TC 26 Z9 26 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23909 EP 23925 DI 10.1029/95JD03297 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300035 ER PT J AU Fuelberg, HE Loring, RO Watson, MV Sinha, MC Pickering, KE Thompson, AM Sachse, GW Blake, DR Schoeberl, MR AF Fuelberg, HE Loring, RO Watson, MV Sinha, MC Pickering, KE Thompson, AM Sachse, GW Blake, DR Schoeberl, MR TI TRACE a trajectory intercomparison .2. Isentropic and kinematic methods SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MOISTURE BUDGETS; SOUTH-ATLANTIC; ACCURACY; SYSTEM; MODELS; HEAT AB Kinematic and isentropic trajectories are compared quantitatively during a single 5-day period (October 13-18, 1992) when several flights for the Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) experiment were conducted off the west coast of Africa. European Centre for Medium-Range Weather Forecasts (ECMWF) data are used to compute the 5-day backward trajectories arriving at locations over the South Atlantic Ocean and nearby parts of South America and southern Africa. Two versions of kinematic trajectories are examined. One version employs vertical motions supplied with the ECMWF data. These trajectories often differ greatly from those based on the isentropic assumption. The kinematic trajectories usually undergo considerably greater vertical displacements than their isentropic counterparts; however, most diabatic rates are consistent with those of synoptic-scale systems. Ratios of acetylene to carbon monoxide are related to backward trajectories at various locations along a TRACE A flight. A second version of kinematic trajectories employs vertical motions diagnosed from ECMWF horizontal wind components using the continuity equation, These vertical motions are stronger than those supplied with the ECMWF data, causing many of the trajectories to have larger vertical displacements and considerably different paths than the original kinematic versions. Many of these kinematic trajectories undergo diabatic rates that exceed generally accepted values on the synoptic scale. This occurs, in part, because the diagnosed vertical motions are inconsistent with the ECMWF data. The research indicates that the kinematic procedure yields realistic 5-day backward trajectories when the three-dimensional wind data are available from a numerical model or other dynamically consistent data set such as provided by ECMWF. C1 UNIV MARYLAND, NASA, GODDARD SPACE FLIGHT CTR, JOINT CTR EARTH SYST SCI, GREENBELT, MD 20771 USA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. RP Fuelberg, HE (reprint author), FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. RI Pickering, Kenneth/E-6274-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 24 TC 56 Z9 56 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23927 EP 23939 DI 10.1029/95JD02122 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300036 ER PT J AU Loring, RO Fuelberg, HE Fishman, J Watson, MV Browell, EV AF Loring, RO Fuelberg, HE Fishman, J Watson, MV Browell, EV TI Influence of a middle-latitude cyclone on tropospheric ozone distributions during a period of TRACE A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FRONTAL ZONE SYSTEMS; TROPOPAUSE FOLDS; CARBON-MONOXIDE; SATELLITE DATA; EXCHANGE; TRANSPORT; TROPICS; STRATOSPHERE; BRAZIL; AUGUST AB A middle-latitude cyclone occurring during the Transport and Atmospheric Chemistry near the Equator-Atlantic (TRACE A) experiment is examined to determine its influence on distributions of tropospheric ozone over the South Atlantic Ocean. A maximum of tropospheric ozone is located in the vicinity of this cyclone on October 3, 1992. Flight level data and meteorological analyses indicate a downward protrusion of dry, ozone-rich stratospheric air near the cyclone, i.e., a tropopause fold. Backward trajectories show that air parcels arriving in the upper troposphere of the cyclone originate in the stratosphere. Forward trajectories are calculated from these locations having stratospheric histories. They indicate that some air is transported as far north as 22 degrees S, subsiding into the middle troposphere along the southern fringes of a region of enhanced tropospheric ozone that is located west of Africa on October 6. Backward trajectories then are computed along the Greenwich meridian over much of the South Atlantic Ocean. This axis passes through the tropospheric ozone maximum west of Africa and the region of strong horizontal ozone gradients along its southern border. Results indicate that most air parcels arriving north of 20 degrees S (in the ozone-rich region) originate over Africa. Conversely, most parcels arriving south of 20 degrees S (where there is less ozone) originate from the west, passing over the southern half of South America. Thus the tropospheric ozone maximum west of Africa on October 6 appears to be attributable to outflow from Africa, with stratospheric transport being much less important. Formerly stratospheric air near the cyclone on October 3 also is transported forward into the middle troposphere near Madagascar where there is a second maximum of tropospheric ozone on October 6. Backward trajectories from this region indicate that middle-latitude systems exert a much greater influence here than over the South Atlantic. This area experiences relatively little outflow from Africa during our period of study. C1 FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. NR 48 TC 14 Z9 14 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23941 EP 23956 DI 10.1029/95JD03573 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300037 ER PT J AU Gregory, GL Fuelberg, HE Longmore, SP Anderson, BE Collins, JE Blake, DR AF Gregory, GL Fuelberg, HE Longmore, SP Anderson, BE Collins, JE Blake, DR TI Chemical characteristics of tropospheric air over the tropical South Atlantic ocean: Relationship to trajectory history SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC CHEMISTRY; CARBON-MONOXIDE; OZONE; EMISSIONS; FOREST; FIRES AB The TRACE A (Transport and Atmospheric Chemistry Near the Equator-Atlantic) experiment was designed to explore the atmospheric chemistry and meteorology over the tropical South Atlantic Ocean with a focus on the impact of South American and African biomass burning and continental outflow on the region. TRACE A was conducted in September/October 1992. Companion papers in this special issue show that the chemical composition of tropospheric air throughout the region is strongly impacted by biomass burning and outflow from both continents. This paper shows similar results and examines the chemical composition of air measured during NASA DC-8 aircraft ascents/descents at locations along the coast of both continents as well as at mid-Atlantic Ocean locations. Chemical composition of the air and backward trajectory calculations are used to illustrate the influences of continental outflow and how influences change with location throughout the region. Included in the examples are data which show that air along the Atlantic coast of Africa is impacted by outflow from both South America and Africa as air at the higher altitudes (e.g., 8 to 10 km) originates from South America, while lower-altitude air is from African sources. Of additional interest are data measured over the Indian Ocean near the tip of Africa which show aged air from South America being impacted by biomass burning emissions as the air passes over Africa 1 to 2 days prior to sampling. C1 FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. LOCKHEED ENGN & SCI CO, HAMPTON, VA 23681 USA. RP Gregory, GL (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, MS 483, HAMPTON, VA 23665 USA. NR 20 TC 24 Z9 24 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23957 EP 23972 DI 10.1029/96JD01160 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300038 ER PT J AU Pickering, KE Thompson, AM Wang, YS Tao, WK McNamara, DP Kirchhoff, VWJH Heikes, BG Sachse, GW Bradshaw, JD Gregory, GL Blake, DR AF Pickering, KE Thompson, AM Wang, YS Tao, WK McNamara, DP Kirchhoff, VWJH Heikes, BG Sachse, GW Bradshaw, JD Gregory, GL Blake, DR TI Convective transport of biomass burning emissions over Brazil during TRACE A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; AIR AB A series of large mesoscale convective systems that occurred during the Brazilian phase of GTE/TRACE A (Transport and Atmospheric Chemistry near the Equator-Atlantic) provided an opportunity to observe deep convective transport of trace gases from biomass burning. This paper reports a detailed analysis uf flight 6, on September 27, 1992, which sampled cloud- and biomass-burning-perturbed regions north of Brasilia. High-frequency sampling of cloud outflow at 9-12 km from the NASA DC-8 showed enhancement of CO mixing ratios typically a factor of 3 above background (200-300 parts per billion by volume (ppbv) versus 90 ppbv) and significant increases in NO, and hydrocarbons, Clear signals of lightning-generated NO were detected; we estimate that at least 40% of NOx at the 9.5-km level and 32% at 11.3 km originated from lightning, Four types of model studies have been performed to analyze the dynamical and photochemical characteristics of the series of convective events. (1) Regional simulations for the period have been performed with the NCAR/Penn State mesoscale model (MM5), including tracer transport of carbon monoxide, initialized with observations. Middle-upper tropospheric enhancements of a factor of 3 above background are reproduced. (2) A cloud-resolving model (the Goddard cumulus ensemble (GCE) model) has been run for one representative convective cell during the September 26-27 episode. (3) Photochemical calculations (the Goddard tropospheric chemical model), initialized with trace gas observations (e.g., CO, NOx, hydrocarbons, O-3) observed in cloud outflow, show appreciable O-3 formation postconvection, initially up to 7-8 ppbv O-3/d. (4) Forward trajectories from cloud outflow levels (postconvective conditions) put the ozone-producing air masses in eastern Brazil and the tropical Atlantic within 2-4 days and over the Atlantic, Africa, and the Indian Ocean in 6-8 days, Indeed, 3-4 days after the convective episode (September 30, 1992), upper tropospheric levels in the Natal ozone sounding show an average increase of similar to 30 ppbv (3 Dobson units (DU) integrated) compared to the September 28 sounding. Our simulated net O-3 production rates in cloud outflow are a factor of 3 or more greater than those in air undisturbed by the storms, Integrated over the 8- to 16-km cloud outflow layer, the postconvection net O-3 production (similar to 5-6 DU over 8 days) accounts for similar to 25% of the excess O-3 (15-25 DU) over the South Atlantic. Comparison of TRACE A Brazilian ozonesondes and the frequency of deep convection with climatology [Kirchhoff et al., this issue] suggests that the late September 1992 conditions represented an unusually active period for both convection and upper tropospheric ozone formation. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. SCI SYST & APPLICAT INC, LANHAM, MD 20706 USA. UNIV CALIF IRVINE, IRVINE, CA 92717 USA. GEORGIA INST TECHNOL, ATLANTA, GA 30332 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. UNIV RHODE ISL, GRAD SCH OCEANOG, NARRAGANSETT, RI 02882 USA. APPL RES CORP, LANDOVER, MD 20785 USA. INST NACL PESQUISAS ESPACIAIS, SAO JOSE DOS CAMPOS, BRAZIL. RP Pickering, KE (reprint author), UNIV MARYLAND, JOINT CTR EARTH SYST SCI, DEPT METEOROL, CODE 916, COLLEGE PK, MD 20742 USA. RI Pickering, Kenneth/E-6274-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 17 TC 173 Z9 175 U1 1 U2 14 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 23993 EP 24012 DI 10.1029/96JD00346 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300041 ER PT J AU Wang, Y Tao, WK Pickering, KE Thompson, AM Kain, JS Adler, RF Simpson, J Keehn, PR Lai, GS AF Wang, Y Tao, WK Pickering, KE Thompson, AM Kain, JS Adler, RF Simpson, J Keehn, PR Lai, GS TI Mesoscale model simulations of TRACE A and Preliminary Regional Experiment for Storm-Scale Operational and Research Meteorology convective systems and associated tracer transport SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SQUALL LINE; OZONE PRODUCTION; NUMERICAL-SIMULATION; BOUNDARY-LAYER; PARAMETERIZATION; SCHEME; PRECIPITATION; RESOLUTION; ALGORITHM; CLOUDS AB A tropical mesoscale convective system (MCS) during the Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) experiment and a midlatitude squall line during Preliminary Regional Experiment for Storm-scale Operational and Research Meteorology (PRESTORM) were simulated with the National Center for Atmospheric Research/Pennsylvania Slate University (NCAR/PSU) MM5 model. For the TRACE A case the model simulation predicted locations of convection systems fairly accurately compared with satellite images and the rainfall pattern from rain gauge data, For the PRESTORM case the model simulation captured many observed features such as the rainfall field and wind circulation pattern. Model simulated wind fields were used to transport an inert tracer (GO) in the mesoscale systems, Tracer transport in the two convective systems (TRACE A-tropical MCS versus PRESTORM midlatitude squall line) are substantially different over 24-hour simulation periods and over the regional scale (about 2000 x 2000 km domains). The time-evolving tracer fields in the upper troposphere are different in the tropical MCS and midlatitude squall line regimes as a consequence of different propagation speeds of the two convective systems. The nearly ''stationary'' tropical MCS produced regions of large upper tropospheric CO mixing ratios that had moved very little in the horizontal by the end of the 24-hour simulation. The enhanced upper tropospheric CO region propagates with the ''fast-moving'' line in the midlatitude case. Model transport and redistribution of CO agrees well with aircraft measurements in the TRACE A case, Significant subgrid-scale (parameterized) upward transport (48% with Grell scheme, 41% with Kain-Fritsch scheme) occurred in the TRACE A case. The subgrid upward transport in the PRESTORM event was even greater, accounting for 64% of total upward transport. Downward transport in both events was dominated by grid-scale motions. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. PENN STATE UNIV, DEPT METEOROL, UNIVERSITY PK, PA 16802 USA. UNIV MARYLAND, JCESS, DEPT METEOROL, COLLEGE PK, MD 20742 USA. RP SCI SYST & APPLICAT INC, LANHAM, MD 20706 USA. RI Pickering, Kenneth/E-6274-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 34 TC 15 Z9 15 U1 1 U2 1 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 OCT 30 PY 1996 VL 101 IS D19 BP 24013 EP 24027 DI 10.1029/96JD00933 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300042 ER PT J AU Kirchhoff, VWJH Alves, JR daSilva, FR Fishman, J AF Kirchhoff, VWJH Alves, JR daSilva, FR Fishman, J TI Observations of ozone concentrations in the Brazilian cerrado during the TRACE A field expedition SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPICAL SOUTH-ATLANTIC; TROPOSPHERIC OZONE; SURFACE OZONE; AMAZON BASIN; DRY SEASON; CITE-3; DISTRIBUTIONS; TRAJECTORIES; CLIMATOLOGY; ENVIRONMENT AB The Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) experiment, sponsored by the NASA GTE program, was a multinational field mission that took place simultaneously in Brazil, Africa, and the South Atlantic region, between the African and the Brazilian coasts. The general objective of the field mission was to investigate the tropospheric minor constituent composition, known to be disturbed by biomass burning practices. This report describes ozone measurements that were made by the Brazilian component. Two field missions in central Brazil were made with the objective of investigating ozone concentrations in the biomass burning source region: one smaller mission in the wet season period, April, and a major mission in the dry season, September/October 1992. The main field expedition during the dry season obtained data over a period of about 20 days in September and a few days in October 1992, in a savanna environment of central Brazil. Simultaneous surface ozone and ozone soundings were made. In the wet season the observation site was Goiania (16 degrees S, 49 degrees W); and in the dry season, two other sites were added: Cuiaba (16 degrees S, 56 degrees W) and Porto Nacional (11 degrees S, 48 degrees W). In addition, measurements were also made at an Atlantic coast site, Natal (6 degrees S, 35 degrees W), outside of the savanna region, and not affected directly by the biomass burning source areas, used as a control site. The average behavior of the ozone concentrations at the different sites suggests that surface ozone concentrations tend to be rather uniform, despite different precipitation rates, but slightly larger at the drier sites. However, other factors, such as burning fuel, for example, or cloudiness, may be also important to determine ozone concentrations. This is reflected by large day-to-day variabilities that are common in the source region. The diurnal variation of the surface ozone concentrations maximize around 1600 LT. Hourly averages in September, at this time, amount to 47 parts per billion by volume (ppbv) at Porto Nacional and 40 ppbv at Cuiaba. For this station the values are lower than those of previous years (55 ppbv in 1991 and 48 ppbv in 1990). Only small differences, of the order of 5 ppbv, are observed between the source (burning) sites and Natal (the control site) in the wet season. In April, only 16 ppbv are observed at Natal. Much larger concentrations may be observed occasionally in the source areas, in the dry season. For example, at Porto Nacional, SO ppbv have been measured at the surface and in the lower troposphere. In comparison with the coastal site, near the surface, large scatter in concentration values at Porto Nacional (20-80 ppbv) contrast with the smaller concentration range seen at Natal (20-40 ppbv). In addition, at Natal the ozone mixing ratios below about 600 hPa are distributed around a vertical gradient in which the mixing ratios increase with height, whereas at Porto Nacional in the same height region, larger concentrations and a large scatter of the data are apparent. In the upper troposphere, perhaps surprisingly, the ozone concentrations at Natal and Porto Nacional are about equal, 70 ppbv at 10 km (with larger scatter at Natal than at Porto Nacional), probably reflecting a net production of ozone along the pathways from the source regions, coupled with its longer lifetime at the higher altitudes. This data set is consistent with the hypothesis that tropical ozone in the troposphere is produced photochemically from biomass burning products in the dry season. These products are exported from the source regions to the upper atmospheric levels by dry and wet convection and once in the upper atmospheric levels are taken eastward to the South Atlantic by the prevailing winds, where they contribute to local ozone formation. The air masses at Natal, Brazil, in the lower atmospheric levels, i.e., below about 500 hPa, originate from the South Atlantic. This allows one to classify Natal air masses as pristine over most of the year and justifies the stations use as a control station. However, the data now presented, combined with the detailed analyses of the other TRACE A studies, allows on to conclude that in the dry season, Natal ozone concentrations below about 500 hPa are perturbed by combustion products consistent with long-range transport from Africa. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RP Kirchhoff, VWJH (reprint author), INST PESQUISAS ESPACIAIS, AV ASTRONAUTAS 1758, CAIXA POSTAL 515, BR-12201970 SAO JOSE DOS CAMPOS, SP, BRAZIL. NR 43 TC 37 Z9 37 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24029 EP 24042 DI 10.1029/95JD03030 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300043 ER PT J AU Browell, EV Fenn, MA Butler, CF Grant, WB Clayton, MB Fishman, J Bachmeier, AS Anderson, BE Gregory, GL Fuelberg, HE Bradshaw, JD Sandholm, ST Blake, DR Heikes, BG Sachse, GW Singh, HB Talbot, RW AF Browell, EV Fenn, MA Butler, CF Grant, WB Clayton, MB Fishman, J Bachmeier, AS Anderson, BE Gregory, GL Fuelberg, HE Bradshaw, JD Sandholm, ST Blake, DR Heikes, BG Sachse, GW Singh, HB Talbot, RW TI Ozone and aerosol distributions and air mass characteristics over the South Atlantic Basin during the burning season SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; SATELLITE; PROFILES; EMISSIONS; GASES AB In situ and laser remote measurements of gases and aerosols were made with airborne instrumentation to investigate the sources and sinks of tropospheric gases;md aerosols over the tropical South Atlantic during the NASA Global Tropospheric Experiment (GTE)/Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) field experiment conducted in September-October 1992. Gases from extensive fires in Brazil were transported by convective storms into the upper troposphere where tropospheric ozone (O-3) was photochemically produced and advected eastward over the South Atlantic. In central Africa, the fires were widespread, and in the absence of deep convection, the fire plumes were advected at low altitudes (below similar to 6 lan) over the Atlantic, There was a positive correlation between O-3 and aerosols found in the plumes that were not involved in convection. High O-3 (>75 parts per billion by volume (ppbv)) was observed in the low-altitude plumes, and also in the upper troposphere where O-3 often exceeded 100 ppbv with low aerosol loading. The average tropospheric O-3 distributions were determined for the following: Brazil and western South Atlantic, eastern and central South Atlantic, central and east coast of Africa, and the entire South Atlantic Basin. The tropopause heights and O-3 columns across the troposphere were calculated for individual flights and for the average O-3 distributions in the above regions. A maximum tropospheric O-3 column of 56 Dobson units (DU) was found over the biomass burning region in Zambia and in the subsidence region over the central South Atlantic. The high O-3 region over the South Atlantic from 4 degrees to 18 degrees S corresponded with the latitudinal extent of the fires in Africa. In situ and laser remote measurements were used to determine the frequency of observation and chemical composition of nine major air mass types. Biomass burning emissions contributed to most of the air masses observed over the South Atlantic Basin, and biomass burning was found to contribute up to half (28 DU) of the O-3 column across this region. C1 FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. GEORGIA INST TECHNOL, ATLANTA, GA 30332 USA. UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. UNIV RHODE ISL, GRAD SCH OCEANOG, NARRAGANSETT, RI 02882 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV NEW HAMPSHIRE, INST STUDY EARTH OCEANS & SPACE, COMPLEX SYST RES CTR, DURHAM, NH 03820 USA. SCI APPLICAT INT CORP, HAMPTON, VA USA. RP Browell, EV (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, MAIL STOP 483, HAMPTON, VA 23681 USA. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 36 TC 74 Z9 75 U1 2 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24043 EP 24068 DI 10.1029/95JD02536 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300044 ER PT J AU Fishman, J Brackett, VG Browell, EV Grant, WB AF Fishman, J Brackett, VG Browell, EV Grant, WB TI Tropospheric ozone derived from TOMS/SBUV measurements during TRACE A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SATELLITE; BRAZIL AB The use of data from Total Ozone Mapping Spectrometer (TOMS) and Solar Backscatter Ultraviolet (SEW) measurements to develop daily maps of the amount of ozone in the troposphere during Transport and Atmospheric chemistry Near the Equator-Atlantic (TRACE A) is presented. By comparing these maps with available ozone measurements from sensors aboard the NASA DC-8, we show that the agreement between the satellite-derived measurements and the other data is generally very good. The TOMS/SBUV technique successfully captures large-scale gradients and the derived integrated tropospheric ozone amount is generally within 10-15% of the observed amounts. The largest discrepancy between the two data sets occurs when copious amounts of lower-tropospheric (1-6 km) aerosols (from intense widespread biomass burning) are present. The amount of ozone found over the TRACE A region for the September-October 1992 period agrees well with the climatological values published previously using TOMS and Stratospheric Aerosol and Gas Experiment (SAGE) measurements and with ozonesonde measurements from several tropical sites established as part of TRACE A. The satellite-derived ozone maximum observed during TRACE A is similar to 1000 km north of the previously published climatological data and it is not obvious whether or not this northward shift is due to normal interannual variability, or if it is a result of systematic data processing differences between the SAGE and the SBUV data sets. C1 SCI APPLICAT INT CORP, HAMPTON, VA USA. RP Fishman, J (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 17 TC 67 Z9 70 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24069 EP 24082 DI 10.1029/95JD03576 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300045 ER PT J AU Olson, JR Fishman, J Kirchhoff, VWJH Nganga, D Cros, B AF Olson, JR Fishman, J Kirchhoff, VWJH Nganga, D Cros, B TI Analysis of the distribution of ozone over the southern Atlantic region SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OBSERVATORY PHOTOCHEMISTRY EXPERIMENT; BIOMASS-BURNING EMISSIONS; TROPOSPHERIC OZONE; SURFACE OZONE; SEASONAL-VARIATIONS; CARBON-MONOXIDE; SATELLITE; O3; CONVECTION; AMAZONIA AB Tropospheric ozone data measured by ozonesondes during the Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) field mission and the multiyear pre-TRACE A program are analyzed jointly with tropospheric ozone amounts derived from remote satellite data (''residuals''), We present here the first detailed analysis of the entire Ascension Island pre-TRACE A data set, Data from the three pre-TRACE A ozonesonde sites are used to establish a coherent spatial and temporal climatology of ozone in the southern tropical Atlantic region. This analysis shows a significant ozone seasonality over the Atlantic region, with a period of maximum values that extends from the austral winter through at least October at Natal, Brazil, and Ascension Island. Concentrations begin to decline somewhat earlier at Brazzaville, Congo, especially at lower altitudes. Although Natal exhibits a significantly lower annual average than Ascension Island or Brazzaville by about 4 Dobson Units (DU), the magnitude of the seasonal amplitude at Natal is the largest of the three stations. Additionally, more of the seasonal amplitude at Natal is due to a contribution from ozone in the middle and upper troposphere than at either Ascension Island or Brazzaville, Amplitudes as large as 15 DU are measured at individual sites, and the residuals show an average amplitude over the southern tropical Atlantic region of 10-12 DU. Statistical comparison of the residuals to the ozonesonde climatology show that while the residuals tend to underpredict both the means and the seasonal amplitudes compared to the in situ data, they provide a good representation of the variance of ozone in this region and predict the local annual and seasonal means to within better than 10% and seasonal amplitudes to within 15%. C1 UNIV MAIEN NGOUABI, FAC SCI, LAT PHYS ATMOSPHERE, DEPT PHYS, BRAZZAVILLE, CONGO. SECRETARIA ESPECIAL CIENCIA & TECNOL PRESIDENCIA, INST PESQUISAS ESPACIAIS, BR-12201 SAO JOSE DOS CAMPOS, BRAZIL. RP Olson, JR (reprint author), NASA, LANGLEY RES CTR, MAIL STOP 401 A, HAMPTON, VA 23681 USA. NR 57 TC 31 Z9 31 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24083 EP 24093 DI 10.1029/95JD03273 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300046 ER PT J AU Nganga, D Minga, A Cros, B Biona, CB Fishman, J Grant, WB AF Nganga, D Minga, A Cros, B Biona, CB Fishman, J Grant, WB TI The vertical distribution of ozone measured at Brazzaville, Congo during TRACE A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; CHEMISTRY; TROPICS; STRATOSPHERE; REGION; SEASON; BRAZIL AB The distribution of ozone in the African tropical region is examined for measurements made between late June 1990 and early October 1992 in support of the NASA Global Tropospheric Experiment/Transport and Atmospheric Chemistry Near the Equator-Atlantic (GTE/TRACE A) experiment conducted at Brazzaville (4 degrees 17'S, 15 degrees 15'E) in September and October 1992. A set of ozone data has been obtained in the troposphere,and the stratosphere to above 30 km using balloon-borne electrochemical concentration cell ozonesondes. The analysis of the tropospheric data confirms the seasonal trends of ozone in these latitudes, which shows in particular, the presence of an ozone-enriched layer located between 1- and 4-km altitude during the dry season of each hemisphere. A more detailed analysis of the data set for September-October 1992 shows a behavior of ozone which suggests the presence of two periods of biomass burning in the dry season of the southern hemisphere. In addition, this study shows that the dry season of the northern hemisphere has a limited influence on tropospheric ozone at large distances. C1 ORSTOM, DGRST, LAB BIOCLIMATOL, BRAZZAVILLE, CONGO. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. RP Nganga, D (reprint author), UNIV MARIEN NGOUABI, LAB PHYS ATMOSPHERE, DEPT PHYS, FAC SCI, BRAZZAVILLE, CONGO. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 38 TC 19 Z9 19 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24095 EP 24103 DI 10.1029/95JD02535 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300047 ER PT J AU Fuelberg, HE VanAusdall, JD Browell, EV Longmore, SP AF Fuelberg, HE VanAusdall, JD Browell, EV Longmore, SP TI Meteorological conditions associated with vertical distributions of aerosols off the west coast of Africa SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE AB Vertical distributions of aerosol backscattering were obtained on Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) flights parallel to the west coast of Africa using the airborne differential absorption lidar (DIAL) instrument. Aerosol distributions on the flight of October 15, 1992 (from 22 degrees S to 5.5 degrees S), exhibit strong horizontal and vertical gradients. The top of the aerosol layer ranges from 3.5 to 5.7 km above sea level, while its thickness ranges from 1.4 to 4.5 km. The greatest aerosol loading generally occurs near 4.0- to 4.5-km altitude between 8 degrees and 12 degrees S. Meteorological conditions are found to exert a major influence on the aerosol distributions. Dropsonde data along the flight track indicate numerous temperature inversions and stable layers in each sounding. The top of the aerosol region is associated with strong inversions due to subsidence. Five-day backward trajectories are calculated along the flight track at vertical intervals of 1 km using global meteorological analyses, Trajectories arriving at most locations of large aerosol loading originate over southern Africa, where biomass burning is occurring and deep surface-based mixed layers are common. Conversely, the air with less aerosol loading originates over the Atlantic Ocean. The exception is the northernmost segment of the flight above 3.5 km. Although this segment receives flow off Africa at these altitudes, lower level stable layers inhibit transport to higher levels. In addition, trajectories arriving at this part of the flight pass over a portion of Africa with reduced biomass burning and extensive deep convection that penetrates the stable layers. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. RP Fuelberg, HE (reprint author), FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. NR 18 TC 17 Z9 17 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24105 EP 24115 DI 10.1029/95JD02889 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300048 ER PT J AU Anderson, BE Grant, WB Gregory, GL Browell, EV Collins, JE Sachse, GW Bagwell, DR Hudgins, CH Blake, BR Blake, NJ AF Anderson, BE Grant, WB Gregory, GL Browell, EV Collins, JE Sachse, GW Bagwell, DR Hudgins, CH Blake, BR Blake, NJ TI Aerosols from biomass burning over the tropical South Atlantic region: Distributions and impacts SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ANTHROPOGENIC AEROSOLS; ATMOSPHERIC CHEMISTRY; CLOUD REFLECTIVITY; RADIATION BUDGET; SMOKE PARTICLES; CLIMATE; OZONE; SIZE; FOREST; GASES AB The NASA Global Tropospheric Experiment (GTE) Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) expedition was conducted September 21 through October 26, 1992 to investigate factors responsible for creating the seasonal South Atlantic tropospheric ozone maximum. During these flights, fine aerosol(0.1-3.0 mu m) number densities were observed to be enhanced roughly tenfold over remote regions of the tropical South Atlantic and greater over adjacent continental areas, relative to northern hemisphere observations and to measurements recorded in the same area during the wet season. Chemical and meteorological analyses as well as visual observations indicate that the primary source of these enhancements was biomass burning occurring within grassland regions of north central Brazil and southeastern Africa. These fires exhibited fine aerosol (N) emission ratios relative to CO (dN/dCO) of 22.5 +/- 9.7 and 23.6 +/- 15.1 cm(-3) parts per billion by volume (ppbv)(-1) over Brazil and Africa, respectively. Convection coupled with counterclockwise now around the South Atlantic subtropical anticyclone subsequently distributed these aerosols throughout the remote South Atlantic troposphere. We calculate that dilute smoke from biomass burning produced an average tenfold enhancement in optical depth over the continental regions as well as a 50% increase in this parameter over the middle South Atlantic Ocean; these changes correspond to an estimated net cooling of up to 25 W m(-2) and 2.4 W m(-2) during clear-sky conditions over savannas and ocean respectively. Over the ocean our analyses suggest that modification of CCN concentrations within the persistent eastern Atlantic marine stratocumulus clouds by entrainment of subsiding haze layers could significantly increase cloud albedo resulting in an additional surface radiative cooling potentially greater in magnitude than that caused by direct extinction of solar radiation by the aerosol particles themselves. C1 NASA, LANGLEY RES CTR, OPERAT SUPPORT DIV, HAMPTON, VA 23681 USA. UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. SCI & TECHNOL CORP, HAMPTON, VA 23665 USA. NASA, LANGLEY RES CTR, DIV AEROSP ELECT SYST, HAMPTON, VA 23681 USA. RP Anderson, BE (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, MS 483, HAMPTON, VA 23681 USA. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 55 TC 115 Z9 115 U1 3 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24117 EP 24137 DI 10.1029/96JD00717 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300049 ER PT J AU Bartlett, KB Sachse, GW Collins, JE Harriss, RC AF Bartlett, KB Sachse, GW Collins, JE Harriss, RC TI Methane in the tropical South Atlantic: Sources and distribution during the late dry season SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TRACE GAS EMISSIONS; ATMOSPHERIC METHANE; CARBON-MONOXIDE; BIOMASS; HEMISPHERE; WETLANDS AB Methane (CH4) mixing ratios in the South Atlantic basin were sampled from a DC-8 aircraft during the TRACE A expedition over the months of September and October 1992. This high-precision (+/- 0.1%), high-resolution data set (independent measurements every 5 s) includes a total of 67,335 observations and ranges from 1586.6 to 2152.8 parts per billion by volume(ppbv). The observed values were influenced by emissions from biomass burning and local urban/industrial areas, stratosphere-troposphere exchange, active convective mixing, and possible long-range transport of pollution. Average mixing ratios increased from the atmospheric mixed layer (0-2 km) to the free troposphere (2-6 km) and were greatest at altitudes above 6 km. A longitudinal trend observed between 5 degrees N and 40 degrees S latitude suggests that CH4 inputs were greater on the South American side of the basin. A latitudinal trend in values between the near-surface and 11 km exhibits the expected gradient from north to south, but differs from the latitudinal gradient observed in surface level clean air at this time. Higher concentrations at altitude, at least at this time of year, indicate that ground-based atmospheric monitoring sites may underestimate pollution inputs to the region. C1 SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. NASA, LANGLEY RES CTR, AEROSP ELECT SYST DIV, HAMPTON, VA 23665 USA. RP Bartlett, KB (reprint author), UNIV NEW HAMPSHIRE, COMPLEX SYST RES CTR, INST STUDY EARTH OCEANS & SPACE, MORSE HALL, DURHAM, NH 03824 USA. NR 35 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24139 EP 24150 DI 10.1029/95JD03572 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300050 ER PT J AU Blake, NJ Blake, DR Sive, BC Chen, TY Rowland, FS Collins, JE Sachse, GW Anderson, BE AF Blake, NJ Blake, DR Sive, BC Chen, TY Rowland, FS Collins, JE Sachse, GW Anderson, BE TI Biomass burning emissions and vertical distribution of atmospheric methyl halides and other reduced carbon gases in the South Atlantic region SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SEASONAL-VARIATIONS; TROPOSPHERIC OZONE; TRACE GASES; DRY SEASON; BRAZIL; FIRES; HYDROCARBON; CHEMISTRY; MONOXIDE; CHLORIDE AB The NASA TRACE A experiment (September - October 1992) investigated effects of dry season biomass burning emissions from both South America and southern Africa on the tropical South Atlantic troposphere. Whole air canister samples were collected aboard the NASA DC-8 aircraft and analyzed for a wide range of nonmethane hydrocarbons (NMHCs) and halocarbons. Fast response in situ quantification of CH4, CO, and CO2 were also performed on the DC-8. Sampling took place over Brazilian agricultural areas and southern African savanna where there was active biomass burning. The vertical distribution of the measured gases revealed that the concentrations of most hydrocarbons, methyl halides, CH4, CO, and CO2, were enhanced in the boundary layer of these regions principally as a result of biomass fires. Brazilian and African biomass burning emission ratios were calculated for CH3Br, CH3Cl, CH3I, and NMHCs relative to CO and CO2. Although both fire regions were dominated by efficient (flaming) combustion (CO/CO2 ratios <0.1), the Brazilian samples exhibited the lower (more flaming) CO/CO2 ratio of 0.037 compared with the African savanna value of 0.062. This difference in combustion efficiency was reflected in lower ratios versus CO2 for all correlated gases. However, the gases more closely associated with smoldering combustion (e.g., C3H8 and CH3Cl) exhibited significantly higher ratios relative to CO for the Brazilian fires, while the African samples exhibited higher values versus CO for compounds associated more closely with flaming combustion (e.g., C2H2). This variation in the trace gas ratios versus CO is most likely caused by different fuel characteristics. On the basis of the emission ratios obtained, the total biomass burning emission rates for savannas and worldwide were calculated for the hydrocarbons and methyl halides. From these it was estimated that roughly 25% and 20% of global CH3Cl and CH3Br emissions, respectively, derive from biomass burning but that the contribution of biomass burning to total CH3I emissions was not significant. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. RP Blake, NJ (reprint author), UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. NR 36 TC 144 Z9 145 U1 1 U2 14 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24151 EP 24164 DI 10.1029/96JD00561 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300051 ER PT J AU Smyth, SB Sandholm, ST Bradshaw, JD Talbot, RW Blake, DR Blake, NJ Rowland, FS Singh, HB Gregory, GL Anderson, BE Sachse, GW Collins, JE Bachmeier, AS AF Smyth, SB Sandholm, ST Bradshaw, JD Talbot, RW Blake, DR Blake, NJ Rowland, FS Singh, HB Gregory, GL Anderson, BE Sachse, GW Collins, JE Bachmeier, AS TI Factors influencing the upper free tropospheric distribution of reactive nitrogen over the South Atlantic during the TRACE A experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC CHEMISTRY; CARBON-MONOXIDE; DRY SEASON; OZONE; BRAZIL; FIRES AB This paper evaluates the potential sources of the enhanced levels of NO that were observed throughout the upper troposphere over the equatorial and tropical South Atlantic. During September/October 1992 NOx (NO + NO2) mixing ratios in the 8-to 13-km region averaged 150 parts per trillion by volume (pptv) and were greatly affected by what appeared as spatially large ''plumes'' (100 to 1000 km) with NO enhancements of over 800 parts per trillion by volume. Other trace gases were also enhanced within these plumes (e.g., CO, CO2, CH4, CH3Cl, C2H2, C2H6, C3H8, and PAN). However, for these tracers of surface emissions, inconsistent patterns of enhancement were found with respect to one another and to NO. We analyzed these plumes for indications of coherent relationships between the enhanced levels of NO and the enhanced levels of biogenic and combustion-related tracers. This analysis indicated that the tracer relationships were primarily produced by their common injection via deep convection into the upper troposphere. A corollary analysis using a combustion tracer reference frame in combination with meteorological analysis indicates a longer than expected lifetime of NO, in the upper troposphere. This analysis also suggests that an efficient mechanism may exist in the upper troposphere for recycling HNO3 back into NOx with a rate comparable to that predicted for the HNO3 formation. During the Transport and Atmospheric Chemistry Near the Equator Atlantic study period this in-situ formation of NOx is estimated to provide the equivalent of approximately 0.7 TgN/yr of NOx within the South Atlantic basin's upper troposphere. This magnitude of local in situ source is estimated to be comparable to the combined inputs from lightning and biomass burning, which are both injected via deep convection. Our analysis also suggests that lightning can contribute as much as half of the external input of NOx into this region of the upper troposphere with biomass burning possibly representing the remainder. C1 GEORGIA INST TECHNOL, SCH EARTH & ATMOSPHER SCI, ATLANTA, GA 30332 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. LOCKHEED ENGN & SCI CO, HAMPTON, VA 23668 USA. UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV NEW HAMPSHIRE, INST STUDY EARTH OCEANS & SPACE, DURHAM, NH 03824 USA. NR 49 TC 44 Z9 44 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24165 EP 24186 DI 10.1029/96JD00224 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300052 ER PT J AU Talbot, RW Bradshaw, JD Sandholm, ST Smyth, S Blake, DR Blake, NR Sachse, GW Collins, JE Heikes, BG Anderson, BE Gregory, GL Singh, HB Lefer, BL Bachmeier, AS AF Talbot, RW Bradshaw, JD Sandholm, ST Smyth, S Blake, DR Blake, NR Sachse, GW Collins, JE Heikes, BG Anderson, BE Gregory, GL Singh, HB Lefer, BL Bachmeier, AS TI Chemical characteristics of continental outflow over the tropical South Atlantic Ocean from Brazil and Africa SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BIOMASS-BURNING EMISSIONS; TROPOSPHERIC OZONE; EQUATORIAL AFRICA; METHANE FLUX; NITROGEN; PRECIPITATION; AEROSOL; CARBON; FOREST; HYDROCARBON AB The chemical characteristics of air parcels over the tropical South Atlantic during September - October 1992 are summarized by analysis of aged marine and continental outflow classifications. Positive correlations between CO and CH3Cl and minimal enhancements of C2Cl4 and various chlorofluorocarbon (CFC) species in air parcels recently advected over the South Atlantic basin strongly suggest an impact on tropospheric chemistry from biomass burning on adjacent continental areas of Brazil and Africa. Comparison of the composition of aged Pacific air with aged marine air over the South Atlantic basin from 0.3 to 12.5 km altitude indicates potential accumulation of long-lived species during the local dry season. This may amount to enhancements of up to two-fold for C2H6, 30% for CO, and 10% for CH3Cl. Nitric oxide and NOx were significantly enhanced (up to similar to 1 part per billion by volume (ppbv)) above 10 km altitude and poorly correlated with CO and CH3Cl. In addition, median mixing ratios of NO and NOx were essentially identical in aged marine and continental outflow air masses. It appears that in addition to biomass burning, lightning or recycled reactive nitrogen may be an important source of NOx to the upper troposphere. Methane exhibited a monotonic increase with altitude from similar to 1690 to 1720 ppbv in both aged marine and continental outflow air masses. The largest mixing ratios in the upper troposphere were often anticorrelated with CO, CH3Cl, and CO2, suggesting CH4 contributions from natural sources. We also argue, based on CH4/CO ratios and relationships with various hydrocarbon and CFC species, that inputs from biomass burning and the northern hemisphere are unlikely to be the dominant sources of CO, CH4, and C2H6 in aged marine air. Emissions from urban areas would seem to be necessary to account for the distribution of at least CH4 and C2H6. Over the African and South American continents an efficient mechanism of convective vertical transport coupled with large-scale circulations conveys biomass burning, urban, and natural emissions to the upper troposphere over the South Atlantic basin. Slow subsidence over the eastern South Atlantic basin may play an important role in establishing and maintaining the rather uniform vertical distribution of long-lived species over this region. The common occurrence of values greater than 1 for the ratio CH3OOH/H2O2 in the upper troposphere suggests that precipitation scavenging effectively removed highly water soluble gases (H2O2, HNO3, HCOOH, and CH3COOH) and aerosols during vertical convective transport over the continents. However, horizontal injection of biomass burning products over the South Atlantic, particularly water soluble species and aerosol particles, was frequent below 6 km altitude. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. GEORGIA INST TECHNOL, SCH EARTH & ATMOSPHER SCI, ATLANTA, GA 30332 USA. LOCKHEED ENGN & SCI CO, HAMPTON, VA 23681 USA. UNIV RHODE ISL, CTR ATMOSPHER CHEM STUDIES, NARRAGANSETT, RI 02882 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Talbot, RW (reprint author), UNIV NEW HAMPSHIRE, INST STUDY EARTH OCEANS & SPACE, MORSE HALL, DURHAM, NH 03824 USA. RI Lefer, Barry/B-5417-2012 OI Lefer, Barry/0000-0001-9520-5495 NR 43 TC 56 Z9 56 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24187 EP 24202 DI 10.1029/95JD03630 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300053 ER PT J AU Singh, HB Herlth, D Kolyer, R Chatfield, R Viezee, W Salas, LJ Chen, Y Bradshaw, JD Sandholm, ST Talbot, R Gregory, GL Anderson, B Sachse, GW Browell, E Bachmeier, AS Blake, DR Heikes, B Jacob, D Fuelberg, HE AF Singh, HB Herlth, D Kolyer, R Chatfield, R Viezee, W Salas, LJ Chen, Y Bradshaw, JD Sandholm, ST Talbot, R Gregory, GL Anderson, B Sachse, GW Browell, E Bachmeier, AS Blake, DR Heikes, B Jacob, D Fuelberg, HE TI Impact of biomass burning emissions on the composition of the South Atlantic troposphere: Reactive nitrogen and ozone SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MARINE STRATOCUMULUS; CHEMISTRY; OCEAN; POLLUTION; LAYER AB In September/October 1992 an instrumented DC-8 aircraft was employed to study the composition and chemistry of the atmosphere over the southern tropical Atlantic Ocean. Analysis of measurements, which included tracers of biomass combustion and industrial emissions, showed that this atmosphere was highly influenced by biomass burning emissions from the South American and African continents. Marine boundary layer was generally capped off by a subsidence inversion and its composition to a large degree was determined by slow entrainment from aloft. Insoluble species (such as PAN, NO, hydrocarbons, CO) were enhanced throughout the troposphere. Soluble species (such as HNO3, HCOOH, H2O2) were minimally elevated in the upper troposphere in part due to scavenging during cloud (wet) convection. Ozone mixing ratios throughout the South Atlantic basin were enhanced by approximate to 20 ppb. These enhancements were larger in the eastern South Atlantic (African emissions) compared to the western South Atlantic (South American emissions). In much of the troposphere, total reactive nitrogen (NOy) correlated well with tracers of biomass combustion (e.g., CH3Cl, CO). Although NOx (NO + NO2) correlated reasonably with these tracers in the lower (0-3 km) and middle troposphere (3-7 km), these relationships deteriorated in the upper troposphere (7-12 km). Stratospheric intrusions were found to be a minor source of upper tropospheric NOx or HNO3. Sizable nonsurface sources of NOx (e.g., lightning) as well as secondary formation from the NOy reservoir species (such as HNO3, PAN, and organic nitrates) must be invoked to explain the NOx abundance present in the upper troposphere. It is found that HNO3, PAN, and NOx were able to account for most of the NOy in the middle troposphere (3-7 km); but a significant shortfall was present in the upper troposphere (7-12). This shortfall was also most pronounced in air masses with low HNOy. The reasons for the upper tropospheric reactive nitrogen shortfall is probably due to instrumental uncertainties and the presence of unidentified organic and inorganic nitrogen species. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. UNIV CALIF IRVINE, IRVINE, CA 92717 USA. GEORGIA INST TECHNOL, ATLANTA, GA 30332 USA. SYMTECH CORP, MOFFETT FIELD, CA 94035 USA. FLORIDA STATE UNIV, TALLAHASSEE, FL 32306 USA. UNIV RHODE ISL, NARRAGANSETT, RI 02882 USA. HARVARD UNIV, CAMBRIDGE, MA 02138 USA. SAN JOSE STATE UNIV FDN, MOFFETT FIELD, CA 94035 USA. UNIV NEW HAMPSHIRE, DURHAM, NH 03824 USA. RP Singh, HB (reprint author), NASA, AMES RES CTR, MS 245-5, MOFFETT FIELD, CA 94035 USA. NR 28 TC 41 Z9 41 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24203 EP 24219 DI 10.1029/96JD01018 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300054 ER PT J AU Heikes, B Lee, MH Jacob, D Talbot, R Bradshaw, J Singh, H Blake, D Anderson, B Fuelberg, H Thompson, AM AF Heikes, B Lee, MH Jacob, D Talbot, R Bradshaw, J Singh, H Blake, D Anderson, B Fuelberg, H Thompson, AM TI Ozone, hydroperoxides, oxides of nitrogen, and hydrocarbon budgets in the marine boundary layer over the South Atlantic SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PHOTOCHEMISTRY EXPERIMENT; EQUATORIAL PACIFIC; NITRIC-OXIDE; FORMIC-ACID; ATMOSPHERE; CHEMISTRY; CLOUDS; AIR; FORMALDEHYDE; FLUXES AB The NASA GTE TRACE A mission sampled air over the South Atlantic and western Indian Oceans. Thirteen flight legs were flown within the marine boundary layer (MBL). The MBL was typically the cleanest air sampled (e.g., CH4 < 1680 ppb, CO < 70 ppb, C2H6 < 400 ppt, C3H8 < 40 ppt, NOx < 15 ppt, and midday NO < 5 ppt) but was overlain by polluted air. The photochemistry of the MBL was influenced by oceanic emissions, surface deposition, and entrainment of pollutants from aloft. Chemical budgets were constructed for several species in the MBL in order to investigate these effects and are presented for ethane, ethylene, propane, propylene, n-butane, formic acid (HFo), methylhydroperoxide (CH3OOH), oxides of nitrogen (i.e., NO, NO2, PAN, HNO3), hydrogen peroxide (H2O2), and ozone (O-3). A photochemical point model was used to evaluate local chemical production and loss. An entrainment model was used to assess material exchange between the lower free troposphere (FT) and the MBL and a resistance deposition model was used to evaluate material exchange across the air-sea interface. The results suggested the ocean to be the source of measured alkenes in the MBL and to be the most likely source of the shorter-lived alkanes: propane and n-butane. Ethane was the only hydrocarbon for which input from aloft may have exceeded its photochemical destruction. The estimated hydrocarbon sources from the ocean were in agreement with prior analyses. Transport from the lower FT together with surface loss could not account for measured concentrations of CH2O, HFo, and HNO3. The transport of peroxyacetylnitrate (PAN) from the FT to the MBL exceeded the rate or HNO3 production and was more than sufficient to maintain observed NOx levels without having to invoke an oceanic source for NO. The flux of NOx, PAN, and HNO3 was in balance with the surface deposition flux of HNO3. However, the predicted rates of HNO3 formation from the oxidation of NO2 and HNO3 entrainment from aloft were inadequate to maintain observed levels of HNO3 unless HNO3 was partitioned between the gas phase and a more slowly depositing aerosol phase. The estimated dry deposition flux of HNO3 to the South Atlantic during TRACE A, 2-4 x 10(9) molecules cm(-2) s(-1) was about 10 times the annual average estimate for this region. The destruction of O-3 within the MBL was found to be exceeded by transport into the MBL from aloft, 6 +/- 2 X 10(10) compared to 11 +/- 10 X 10(10) molecules cm(-2) s(-1). The principal O-3 destruction process was mediated by the formation and surface deposition of H2O2 and CH3OOH, 4 +/- 4 X 10(10) and 1.1 +/- 0.5 x 10(10) molecules cm(-2) s(-1). The direct loss of O-3 to the sea surface was estimated to be 1.7 +/- 0.2 x 10(10) molecules cm(-2) s(-1). CH3OOH was lost to the sea and transported into the FT from the MBL. Its first-order loss rate was estimated to be 7 x 10(-6) s(-1) for a mean MBL height of 700 m. H2O2 and CH2O losses from the MBL were estimated at rates of 1.3 x 10(-5) s(-1) for both species. The inclusion of surface deposition improved the agreement between predicted and measured concentrations of HNO3, CH3OOH, H2O2, and CH2O. However, model CH2O remained significantly greater than that measured in the MBL. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. UNIV CALIF IRVINE, IRVINE, CA 92717 USA. GEORGIA INST TECHNOL, ATLANTA, GA 30332 USA. FLORIDA STATE UNIV, TALLAHASSEE, FL 32306 USA. HARVARD UNIV, CAMBRIDGE, MA 02138 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV NEW HAMPSHIRE, DURHAM, NH 03824 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Heikes, B (reprint author), UNIV RHODE ISL, GRAD SCH OCEANOG, CTR ATMOSPHER CHEM STUDIES, NARRAGANSETT, RI 02882 USA. RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 52 TC 74 Z9 75 U1 6 U2 25 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24221 EP 24234 DI 10.1029/95JD03631 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300055 ER PT J AU Jacob, DJ Heikes, BG Fan, SM Logan, JA Mauzerall, DL Bradshaw, JD Singh, HB Gregory, GL Talbot, RW Blake, DR Sachse, GW AF Jacob, DJ Heikes, BG Fan, SM Logan, JA Mauzerall, DL Bradshaw, JD Singh, HB Gregory, GL Talbot, RW Blake, DR Sachse, GW TI Origin of ozone and NOx in the tropical troposphere: A photochemical analysis of aircraft observations over the South Atlantic basin SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OXYGENATED HYDROCARBONS; PHOTOLYSIS FREQUENCIES; LATITUDINAL VARIATION; PEROXYACETYL NITRATE; EQUATORIAL PACIFIC; POLARSTERN CRUISE; NITRIC-OXIDE; OCEAN; MODEL; FORMALDEHYDE AB The photochemistry of the troposphere over the South Atlantic basin is examined by modeling of aircraft observations up to 12-km altitude taken during the TRACE A expedition in September-October 1992. A close balance is found in the 0 to 12-km column between photochemical production and loss of O-3, With net production at high altitudes compensating for weak net loss at low altitudes. This balance implies that O-3 concentrations in the 0-12 km column can be explained solely by in situ photochemistry; influx from the stratosphere is negligible. Simulation of H2O2, CH3OOH, and CH2O concentrations measured aboard the aircraft lends confidence in the computations of O-3 production and loss rates, although there appeals to be a major gap in current understanding of CH2O chemistry in the marine boundary layer. The primary sources of NOx over the South Atlantic Basin appear to be continental (biomass burning, lightning, soils). There is evidence that NOx throughout the 0 to 12-km column is recycled from its oxidation products rather than directly transported fi om its primary sources. There is also evidence for rapid conversion of HNO3 to NOx in the upper troposphere by a mechanism not included in current models. A general representation of the O-3 budget in the tropical troposphere is proposed that couples the large-scale Walker circulation and in situ photochemistry. Deep convection in the rising branches of the Walker circulation injects NOx from combustion, soils, and lightning to the upper troposphere, leading to O-3 production; eventually, the air subsides and net O-3 loss takes place in the lower troposphere, closing the O-3 cycle. This scheme implies a great sensitivity of the oxidizing power of the atmosphere to NOx emissions in the tropics. C1 HARVARD UNIV, DEPT EARTH & PLANETARY SCI, CAMBRIDGE, MA 02138 USA. UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. GEORGIA INST TECHNOL, SCH EARTH & ATMOSPHER SCI, ATLANTA, GA 30332 USA. PRINCETON UNIV, DEPT GEOL & GEOPHYS SCI, PRINCETON, NJ 08542 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. UNIV RHODE ISL, GRAD SCH OCEANOG, NARRAGANSETT, RI 02882 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV NEW HAMPSHIRE, INST STUDY EARTH OCEANS & SPACE, DURHAM, NH 03824 USA. RP Jacob, DJ (reprint author), HARVARD UNIV, DEPT EARTH & PLANETARY SCI, PIERCE HALL, 29 OXFORD ST, CAMBRIDGE, MA 02138 USA. RI Mauzerall, Denise/I-5977-2013 OI Mauzerall, Denise/0000-0003-3479-1798 NR 78 TC 247 Z9 250 U1 6 U2 38 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24235 EP 24250 DI 10.1029/96JD00336 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300056 ER PT J AU Thompson, AM Pickering, KE McNamara, DP Schoeberl, MR Hudson, RD Kim, JH Browell, EV Kirchhoff, VWJH Nganga, D AF Thompson, AM Pickering, KE McNamara, DP Schoeberl, MR Hudson, RD Kim, JH Browell, EV Kirchhoff, VWJH Nganga, D TI Where did tropospheric ozone over southern Africa and the tropical Atlantic come from in October 1992? Insights from TOMS, GTE TRACE A, and SAFARI 1992 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SEASONAL-VARIATIONS; SATELLITE DATA; BRAZIL; CO AB The seasonal tropospheric ozone maximum in the tropical South Atlantic, first recognized from satellite observations [Fishman et al., 1986, 1991], Save rise to the IGAC/ STARE/SAFARI 1992/TRACE A campaigns (International Global Atmospheric Chemistry/South Tropical Atlantic Regional Experiment/Southern African Fire Atmospheric Research Initiative/Transport and Atmospheric Chemistry Near the Equator-Atlantic) in September and October 1992. Along with a new TOMS-based method for deriving tropospheric column ozone, we used the TRACE A/SAFARI 1992 data set to put together a regional picture of the O-3 distribution during this period, Sondes and aircraft profiling showed a troposphere with layers of high O-3 (greater than or equal to 90 ppbv) all the way to the tropopause. These features extend in a band from 0 degrees to 25 degrees S, over the SE Indian Ocean, Africa, the Atlantic, and eastern South America. A combination of trajectory and photochemical modeling (the Goddard (GSFC) isentropic trajectory and tropospheric point model, respectively) shows a strong connection between regions of high ozone and concentrated biomass burning, the latter identified using satellite-derived fire counts [Justice et al., this issue]. Back trajectories from a high-O-3 tropical Atlantic region (column ozone at Ascension averaged 50 Dobson units (DU)) and forward trajectories from fire-rich and convectively active areas show that the Atlantic and southern Africa are supplied with O-3 and O-3-forming trace gases by midlevel easterlies and/or recirculating air from Africa, with lesser contributions from South American burning and urban pollution. Limited sampling in the mixed layer over Namibia shows possible biogenic sources of NO, High-level westerlies from Brazil (following deep convective transport of ozone precursors to the upper troposphere) dominate the upper tropospheric O-3 budget over Natal, Ascension, and Okaukuejo (Namibia), although most enhanced O-3 (75% or more) equatorward of 10 degrees S was from Africa. Deep convection may be responsible for the timing of the seasonal tropospheric O-3 maximum: Natal and Ascension show a 1- to 2-month lag relative to the period of maximum burning [cf. Baldy et al., this issue; Olson ct al., this issue]. Photochemical model calculations constrained with TRACE A and SAFARI airborne observations of O-3 and O-3 precursors (NOx, CO, hydrocarbons) show robust ozone formation (up to 15 ppbv O-3/d or several DU/d) in a widespread, persistent, and well-mixed layer to 4 km. Slower but still positive net O-3 formation took place throughout the tropical upper troposphere [cf. Pickering et al., this issue (a); Jacob et al., this issue]. Thus whether it is faster rates of O-3 formation in source regions with higher turnover rates or slower O-3 production in long-lived stable layers ubiquitous in the TRACE A region, 10-30 DU tropospheric O-3 above a similar to 25-DU background can be accounted for, In summary, the O-3 maximum studied in October 1992 was caused by a coincidence of abundant O-3 precursors from biomass fires, a long residence time of stable air parcels over the eastern Atlantic and southern Africa, and deep convective transport of biomass burning products, with additional NO from lightning and occasionally biogenic sources. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. UNIV MARYLAND, JCESS, DEPT METEOROL, COLLEGE PK, MD 20742 USA. UNIV ALABAMA, EARTH SYST SCI LAB, HUNTSVILLE, AL 35899 USA. INPE, BR-12201970 SAO PAULO, BRAZIL. APPL RES CORP, LANDOVER, MD 20785 USA. MARIEN NGOUABI UNIV, DEPT ATMOSPHER PHYS, BRAZZAVILLE, CONGO. RP Thompson, AM (reprint author), NASA, CODE 916, BLDG 21, ROOM 264, GREENBELT, MD 20771 USA. RI Hudson, Robert/F-4506-2010; Pickering, Kenneth/E-6274-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 32 TC 148 Z9 148 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24251 EP 24278 DI 10.1029/96JD01463 PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300057 ER PT J AU Chatfield, RB Vastano, JA Singh, HB Sachse, G AF Chatfield, RB Vastano, JA Singh, HB Sachse, G TI A general model of how fire emissions and chemistry produce African/oceanic plumes (O-3, CO, PAN, smoke) in TRACE A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; BOUNDARY-LAYER; SAVANNA FIRES; BIOMASS; DISTRIBUTIONS; AEROSOLS; BRAZIL; CYCLES; AIR; NOX AB A full-chemistry simulation of the Great African Plume gives one example of a broad conceptual model of the intercontinental pollution of the tropical middle troposphere by lofted biomass burning plumes. This two-dimensional idealization ''calibrated'' by carbon monoxide distributions links conventional estimates of burning emissions to oceanic concentrations of pollutants, This paper makes use of GRACES, a modular photochemical simulation system, in two forms. The results of the chemically intensive two-dimensional form, using idealized winds, mixing, deposition, and rainout, match the general concentration patterns of a three-dimensional GRACES model study of CO during the TRACE A/SAFARI period of October 1992 (reported separately), The study highlights the importance of simulating the vertical and diurnal variation of the planetary boundary layer and cloud activity. These correlate temporally with the intensity of tropical agricultural burning. We emphasize one situation, the drift northward and eastward of pollution into the interocean convergence region, where it rises by small-scale motions and rides out westward in the lower midtroposphere (<5 km). These effects help set in place large strata of enhanced CO, ozone, and other pollution over the equatorial Atlantic Ocean. Overall, our comparisons of simulations with the TRACE A data on the cycling of CO, NOx, and O-3 in the tropical atmosphere suggest substantial agreement of current emission estimates and atmospheric concentrations. In certain regions, ozone is simulated slightly below observed levels. The striking major disagreements are in NOy (total reactive nitrogen) and HNO3, which are intimately related to CO and O-3; this suggests that current theory omits at least one fundamental process. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. SAN JOSE STATE UNIV, RES FDN, SAN JOSE, CA 95192 USA. RP Chatfield, RB (reprint author), NASA, AMES RES CTR, MS 245-5, MOFFETT FIELD, CA 94035 USA. NR 45 TC 50 Z9 51 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24279 EP 24306 DI 10.1029/96JD01871 PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300058 ER PT J AU Collins, JE Anderson, BE Sachse, GW Barrick, JDW Wade, LO Burney, LG Hill, GF AF Collins, JE Anderson, BE Sachse, GW Barrick, JDW Wade, LO Burney, LG Hill, GF TI Atmospheric fine structure during GTE TRACE A: Relationships among ozone, carbon monoxide, and water vapor SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPICAL SOUTH-ATLANTIC; TROPOSPHERIC OZONE; SATELLITE DATA; AMAZON BASIN; DRY SEASON AB A major focus of the Global Tropospheric Experiment/Transport and Chemistry Near the Equator-Atlantic (GTE TRACE A) experiment was to determine whether the seasonal tropospheric ozone (O-3) buildup over the tropical South Atlantic, observed by both satellites and sondes, is due to photochemical production of O-3 from biomass burning effluents or from transport of O-3 from the stratosphere. During this expedition, fast response in situ measurements were made of O-3, carbon monoxide (CO), and dew point (DP) from aboard the NASA DC-8 aircraft. Numerous vertical profiles were obtained over Brazil, Africa, and the South Atlantic to determine the origin of the observed O-3 enhancement. Fine structure in these data was examined by (1) investigating differences in the species concentration (5-s averages) and its 2 km vertical running mean during altitude profiles, (2) calculating Fishman-Seiler coefficients for all vertical profiles with altitude range greater than 3 km, and (3) calculating linear regressions between species across short time intervals (2.5 min) using time series data. The fine structure holds information about the recent history of an air mass and therefore can indicate the ''source'' of tropospheric O-3 enhancement: either transport from the stratosphere (negative correlation with CO and DP) or from photochemistry in the troposphere (positive correlation with CO). All three methods indicate that within the tropical South Atlantic during the TRACE A experiment, net in situ photochemical production is significantly more important than transport from the stratosphere. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. NASA, LANGLEY RES CTR, AEROSP ELECT SYST DIV, HAMPTON, VA 23681 USA. LOCKHEED ENGN & SCI CORP, HAMPTON, VA 23666 USA. RP Collins, JE (reprint author), SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. NR 17 TC 8 Z9 8 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24307 EP 24316 DI 10.1029/96JD02180 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300059 ER PT J AU Kim, JH Hudson, RD Thompson, AM AF Kim, JH Hudson, RD Thompson, AM TI A new method of deriving time-averaged tropospheric column ozone over the tropics using total ozone mapping spectrometer (TOMS) radiances: Intercomparison and analysis using TRACE A data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC OZONE; SATELLITE; WAVES; POLLUTION AB Error analysis of archived total O-3 from total ozone mapping spectrometer (TOMS) (version 6) presented in earlier studies [Hudson and Kim, 1994; Hudson et al., 1995] is extended to include scan angle effects. Daily total O-3 maps for the tropics, from the period October 6-21, 1992, are derived from TOMS radiances following correction for these errors, These daily maps, averaged together, show a wavelike feature, which is observed in all latitude bands (10 degrees N to 14 degrees S), underlying sharp peaks which occur at different longitudes depending on the latitude. The wave pattern is used to derive both time-averaged stratospheric and tropospheric O-3 fields, The nature of the wave pattern (stratospheric or tropospheric) cannot be determined with certainty due to missing data (no Pacific sondes, no lower stratospheric Stratospheric Aerosol and Gas Experiment (SAGE) ozone for 18 months after the Mt. Pinatubo eruption) and significant uncertainties in the corroborative satellite record in the lower stratosphere (solar backscattered ultraviolet (SBUV), microwave limb sounder (MLS)). However, the time-averaged tropospheric ozone field, based on the assumption that the wave feature is stratospheric, agrees within 10% with ultraviolet differential absorption laser Transport and Atmospheric Chemistry near the Equator-Atlantic) (TRACE A) O-3 measurements from the DC-8 [Browell et al., this issue] and with ozonesonde measurements over Brazzaville, Congo (4 degrees S, 15 degrees E), Ascension Island (8 degrees S, 15 degrees W), and Natal, Brazil (5.5 degrees S, 35 degrees W), for the period October 6-21, 1992, The derived background (nonpolluted) Indian Ocean tropospheric ozone amount, 26 Dobson units (DU), agrees with the cleanest African ozonesonde profiles for September-October 1992. The assumption of a totally tropospheric wave (flat stratosphere) gives 38 DU above the western Indian Ocean and 15-40% disagreements with the sondes. Tropospheric column O-3 is high from South America to Africa, owing to interaction of dynamics with biomass burning emissions [Thompson et al., this issue (a, b)]. Comparison with fire distributions from advanced very high resolution radiometer (AVHHR) during October 1992 suggests that tropospheric O-3 produced from biomass burning in South America and Africa dominates the O-3 budget in the tropical southern hemisphere during the study period. C1 UNIV MARYLAND, DEPT METEOROL, COLLEGE PK, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Kim, JH (reprint author), UNIV ALABAMA, EARTH SYST SCI LAB, HUNTSVILLE, AL 35899 USA. RI Hudson, Robert/F-4506-2010; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 35 TC 42 Z9 42 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 30 PY 1996 VL 101 IS D19 BP 24317 EP 24330 DI 10.1029/96JD01223 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ493 UT WOS:A1996VQ49300060 ER PT J AU Holt, RG Gaitan, DF AF Holt, RG Gaitan, DF TI Observation of stability boundaries in the parameter space of single bubble sonoluminescence SO PHYSICAL REVIEW LETTERS LA English DT Article ID SPHERICAL OSCILLATING BUBBLES; RECTIFIED DIFFUSION; SHAPE OSCILLATIONS; AIR BUBBLES; DYNAMICS; GROWTH; DISSOLUTION AB The region of parameter space (acoustic pressure P-a, bubble radius R(0)) in which stable single bubble sonoluminescence (SBSL) occurs in an air-water system is a small fraction of that which is accessible. This is due to the existence of an island of dissolution at high P-a and small R(0). For dissolved gas concentrations above 50% of saturation, the region lies above the threshold for shape oscillations and is unobservable. Below 50%, an oscillating bubble is stabilized on the boundary of the island which lies below the shape threshold. SBSL is shown to exist exclusively along this boundary. RP Holt, RG (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. RI Holt, Ray/G-5677-2010; GAITAN, DARIO/N-2727-2016 OI GAITAN, DARIO/0000-0002-2139-8535 NR 43 TC 114 Z9 115 U1 2 U2 9 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 OCT 28 PY 1996 VL 77 IS 18 BP 3791 EP 3794 DI 10.1103/PhysRevLett.77.3791 PG 4 WC Physics, Multidisciplinary SC Physics GA VP225 UT WOS:A1996VP22500025 ER PT J AU Bell, LD AF Bell, LD TI Evidence of momentum conservation at a nonepitaxial metal/semiconductor interface using ballistic electron emission microscopy SO PHYSICAL REVIEW LETTERS LA English DT Article ID SCATTERING AB Ballistic-electron-emission microscopy (BEEM) spectroscopy has been performed on Au/Si(111) structures as a function of Au thickness and temperature. At 77 K a direct signature of parallel momentum conservation at the Au/Si interface is observed in the BEEM spectra. The variation in spectral shape with both Au thickness and temperature places restrictions on allowable values of inelastic and elastic mean-free paths in the metal, and also requires the presence of multiple electron passes within the Au layer. An independent indication of multiple reflections is directly observed in the attenuation of BEEM current with Au thickness. RP Bell, LD (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. NR 20 TC 70 Z9 70 U1 0 U2 4 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 OCT 28 PY 1996 VL 77 IS 18 BP 3893 EP 3896 DI 10.1103/PhysRevLett.77.3893 PG 4 WC Physics, Multidisciplinary SC Physics GA VP225 UT WOS:A1996VP22500051 ER PT J AU Macke, A Mishchenko, MI Cairns, B AF Macke, A Mishchenko, MI Cairns, B TI The influence of inclusions on light scattering by large ice particles SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OPTICAL-CONSTANTS; CIRRUS CLOUDS; WAVELENGTH; EXTINCTION; CRYSTALS AB The scattering of visible light by ice crystals containing scattering and absorbing inclusions is calculated by a combination of ray-tracing and Monte Carlo techniques. Results are shown for a randomly oriented hexagonal ice column containing ammonium sulfate particles, soot particles, and air bubbles. It is shown that a noticeable change in the ice crystal scattering properties compared to a pure crystal requires about 10(3) to 10(4) internal scatterers of a size comparable to the wavelength. While the nonabsorbing ammonium and air bubble inclusions generally decrease the asymmetry parameter g, soot provides a strong increase in g caused by the additional absorption. An independent superposition of the scattering properties of ice crystal and inclusions does not give satisfactory results because of the strong influence of internal scatterers on the characteristic ray paths inside the crystal. Multiple-scattering calculations show that the strongest changes in the radiative fluxes are associated with the soot contaminated ice crystals. C1 COLUMBIA UNIV, DEPT APPL PHYS, NEW YORK, NY 10027 USA. SUNY STONY BROOK, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012; OI Cairns, Brian/0000-0002-1980-1022 NR 16 TC 73 Z9 75 U1 0 U2 9 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 OCT 27 PY 1996 VL 101 IS D18 BP 23311 EP 23316 DI 10.1029/96JD02364 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VP976 UT WOS:A1996VP97600004 ER PT J AU Plaut, JJ AF Plaut, JJ TI Special section: SIR-C/X-SAR - Foreword SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Editorial Material RP Plaut, JJ (reprint author), CALTECH,NASA,JET PROP LAB,PASADENA,CA 91125, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1996 VL 101 IS E10 BP 23061 EP 23061 DI 10.1029/96JE01825 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VP977 UT WOS:A1996VP97700001 ER PT J AU Farr, TG Chadwick, OA AF Farr, TG Chadwick, OA TI Geomorphic processes and remote sensing signatures of alluvial fans in the Kun Lun mountains, China SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID CIMA VOLCANIC FIELD; MOJAVE-DESERT; LANDSCAPE EVOLUTION; SOIL DEVELOPMENT; THEMATIC MAPPER; LAVA FLOWS; CALIFORNIA; DEGRADATION; VALLEY AB The timing of alluvial deposition in arid and semiarid areas is tied to land-surface instability caused by regional climate changes; The distribution pattern of dated deposits provides maps of regional land-surface response to past climate change. Sensitivity to differences in surface roughness and composition makes remote sensing techniques useful for regional mapping of alluvial deposits. Radar images from the Spaceborne Radar Laboratory and visible wavelength images from the French SPOT satellite were used to determine remote sensing signatures of alluvial fan units for an area in the Kun Lun Mountains of northwestern China, These data were combined with field observations to compare surface processes and their effects on remote sensing signatures in northwestern China and the southwestern United States, Geomorphic processes affecting alluvial fans in the two areas include aeolian deposition, desert varnish, and fluvial dissection. However, salt weathering is a much more important process in the Kun Lun than in the southwestern United States. This slows the formation of desert varnish and prevents desert pavement from forming. Thus the Kun Lun signatures are indicative of the dominance of salt weathering, while signatures from the southwestern United States are characteristic of the dominance of desert varnish and pavement processes. Remote sensing signatures are consistent enough in these two regions to be used for mapping fan units over large areas. C1 UNIV CALIF SANTA BARBARA,DEPT GEOG,SANTA BARBARA,CA 93106. RP Farr, TG (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 300-233,PASADENA,CA 91109, USA. OI Farr, Thomas/0000-0001-5406-2096 NR 32 TC 27 Z9 30 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1996 VL 101 IS E10 BP 23091 EP 23100 DI 10.1029/96JE01603 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VP977 UT WOS:A1996VP97700004 ER PT J AU Rosen, PA Hensley, S Zebker, HA Webb, FH Fielding, EJ AF Rosen, PA Hensley, S Zebker, HA Webb, FH Fielding, EJ TI Surface deformation and coherence measurements of Kilauea volcano, Hawaii, from SIR-C radar interferometry SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID LANDERS EARTHQUAKE; EUREKA VALLEY; SATELLITE; CALIFORNIA; FIELD AB The shuttle imaging radar C/X synthetic aperture radar (SIR-C/X-SAR) radar on board the space shuttle Endeavor imaged Kilauea Volcano, Hawaii, in April and October 1994 for the purpose of measuring active surface deformation by the methods of repeat-pass differential radar interferometry. Observations at 24 cm (L band) and 5.6 cm (C band) wavelengths were reduced to interferograms showing apparent surface deformation over the 6-month interval and over a succession of 1-day intervals in October. A statistically significant local phase signature in the 6-month interferogram is coincident with the Pu'u O'o lava vent. Interpreted as deformation, the signal implies centimeter-scale deflation in an area several kilometers wide surrounding the vent. Peak deflation is roughly 14 cm if the deformation is purely vertical, centered southward of the Pu'u O'o caldera. Delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures, at the level of 12 cm peak-to-peak in the radar line-of-sight direction. Though the phase observations are suggestive of the wide-area deformation measured by Global Positioning System (GPS) methods, the atmospheric effects are large enough to limit the interpretation of the result. It is difficult to characterize centimeter-scale deformations spatially distribute over tens of kilometers using differential interferometry without supporting simultaneous, spatially distributed measurements of refractivity along the radar line of sight. Studies of the interferometric correlation of images acquired at different times show that L band is far superior to C band in the vegetated areas, even when the observations are separated by only 1 day. These results imply longer wavelength instruments are more appropriate for studying surfaces by repeat-pass observations. C1 STANFORD UNIV,DEPT ELECT ENGN & GEOPHYS,STANFORD,CA 94305. RP Rosen, PA (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 300-235,PASADENA,CA 91109, USA. RI Fielding, Eric/A-1288-2007 OI Fielding, Eric/0000-0002-6648-8067 NR 20 TC 130 Z9 138 U1 2 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1996 VL 101 IS E10 BP 23109 EP 23125 DI 10.1029/96JE01459 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VP977 UT WOS:A1996VP97700006 ER PT J AU Izenberg, NR Arvidson, RE Brackett, RA Saatchi, SS Osburn, GR Dohrenwend, J AF Izenberg, NR Arvidson, RE Brackett, RA Saatchi, SS Osburn, GR Dohrenwend, J TI Erosional and depositional patterns associated with the 1993 Missouri river floods inferred from SIR-C and TOPSAR radar data SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article AB The Missouri River floods of 1993 caused significant and widespread damage to the floodplains between Kansas City and St. Louis. Immediately downstream of levee breaks, flood waters scoured the bottoms. As the floodwaters continued, they spread laterally and deposited massive amounts of sand as crevasse splays on top of agricultural fields. We explore the use of radar interferometry and backscatter data for quantitative estimation of scour and deposition for Jameson Island/Arrow Rock Bottoms and Lisbon Bottoms, two bottoms that were heavily damaged during the floods and subsequently abandoned. Shuttle imaging radar C (SIR-C) L band (24 cm) HH (horizontally transmitted and horizontally received) radar backscatter data acquired in October 1994 were used together with a distorted Born approximation canopy scattering model to determine that the abundance of natural leafy forbs controlled the magnitude of backscatter for former agricultural fields. Forb areal density was found to be inversely correlated with thickness of sand deposited during the floods, presumably because thick sands prevented roots from reaching nutrient rich, moist bottoms soils. Using the inverse relationship, a lower bound for the mass of sand added was found to be 6.3 million metric tons over the 17 km(2) study area. Digital elevation data from topographic synthetic aperture radar (TOPSAR) C band (5.6 cm) interferometric observations acquired in August 1994 were compared to a series of elevation profiles collected on the ground. Vertical errors in TOPSAR were estimated to range from 1 to 2 m, providing enough accuracy to generate an estimate of total mass (4.7 million metric tons) removed during erosion of levees and scour of the bottoms terrains. Net accretion of material to the study areas is consistent with the geologic record of major floods where sediment-laden floodwaters crested over natural levees, initially scoured into the bottoms, and then deposited sands as crevasse splays as the flows spread out and slowed by frictional dissipation. The addition of artificial levees to the Missouri River system has undoubtedly enhanced flood damage, although quantitative estimation of the degree of enhancement will require additional work. C1 US GEOL SURVEY,CIMRI,TUCSON,AZ 85705. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Izenberg, NR (reprint author), WASHINGTON UNIV,DEPT EARTH & PLANETARY SCI,CAMPUS BOX 1169,1 BROOKINGS DR,ST LOUIS,MO 63130, USA. RI Izenberg, Noam/F-3952-2015 OI Izenberg, Noam/0000-0003-1629-6478 NR 38 TC 9 Z9 9 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1996 VL 101 IS E10 BP 23149 EP 23167 DI 10.1029/96JE01975 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VP977 UT WOS:A1996VP97700008 ER PT J AU Tamura, T Day, CS Fukazawa, Y Hatsukade, I Ikebe, Y Makishima, K Mushotzky, RF Ohashi, T Takenaka, K Yamashita, K AF Tamura, T Day, CS Fukazawa, Y Hatsukade, I Ikebe, Y Makishima, K Mushotzky, RF Ohashi, T Takenaka, K Yamashita, K TI Uniformity in the temperature and metallicity of the X-ray emitting gas in the Abell 1060 cluster of galaxies SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE galaxies, abundances; galaxies, clustering; galaxies, clusters, individual, (Abell 1060); X-rays, galaxies ID COOLING FLOWS; INTRACLUSTER GAS; PERSEUS CLUSTER; EXOSAT OBSERVATIONS; IRON; ABUNDANCE; ASCA; NGC-4472; EINSTEIN; NGC-1399 AB The results from ASCA observations of the Abell 1060 cluster of galaxies are presented. Spatially sorted X-ray spectra were used to derive the distributions of the temperature and metallicity in the X-ray emitting gas of the cluster. Within similar to 20' (or 400 kpc assuming H-0 = 50 km s(-1) Mpc(-1)) of the cluster center, the gas temperature has been found to be radially constant at 3.1(-0.5)(+0.3) keV (or 3.1 +/- 0.2 keV within similar to 10'), and the 2-10 keV luminosity was estimated to be 2 x 10(43) erg s(-1). An upper limit on the cool emission component at the cluster center was derived to be 6 x 10(41) erg s(-1) in 0.5-3 keV, assuming that it has a temperature of 1 keV. Although the metallicity is consistent with being radially constant at 0.3 relative to solar value, the present observations do not constrain the abundance well beyond 10', allowing values in the range from 0.2 to 0.4 solar value. There is some indication that O, Ne, and Si are more abundant than Fe and Ni, when compared to the solar-abundance ratios. These results suggest the importance of galactic winds driven by type-II supernovae during the early phase of galaxy formation. In comparison with the Centaurus and Virgo clusters, discussions are made concerning the possible role of the cD galaxy in generating a metal concentration and a cool X-ray component at the cluster center. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. MIYAZAKI UNIV, FAC ENGN, MIYAZAKI 88921, JAPAN. INST PHYS & CHEM RES, COSM RADIAT LAB, WAKO, SAITAMA 35101, JAPAN. TOKYO METROPOLITAN UNIV, DEPT PHYS, HACHIOJI, TOKYO 19203, JAPAN. NAGOYA UNIV, DEPT ASTROPHYS, SCH SCI, CHIKUSA KU, NAGOYA, AICHI 46401, JAPAN. RP UNIV TOKYO, DEPT PHYS, SCH SCI, BUNKYO KU, 7-3-1 HONGO, TOKYO 113, JAPAN. RI Tamura, Takayuki/K-8236-2012 NR 49 TC 42 Z9 42 U1 0 U2 1 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 OCT 25 PY 1996 VL 48 IS 5 BP 671 EP 677 DI 10.1093/pasj/48.5.671 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP793 UT WOS:A1996VP79300014 ER PT J AU Hirao, T Matsumoto, T Sato, S Ganga, K Lange, AE Smith, BJ Freund, MM AF Hirao, T Matsumoto, T Sato, S Ganga, K Lange, AE Smith, BJ Freund, MM TI Submillimeter observations of the galactic plane by IRTS SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE galaxies, Milky Way; infrared, general; interstellar, dust ID TELESCOPE IN-SPACE; SPECTRAL OBSERVATIONS; COBE; MISSION; GRAINS; GALAXY AB We report on observations of interstellar dust emission at \b\ less than or equal to 3.degrees 5 and l similar to 46 degrees with the Far Infrared Photometer (FIRP) on board the Infrared Telescope in Space (IRTS). The FIRP is a four-channel photometer with bands centered at 150, 250, 400, and 700 mu m and with a spatial resolution of 0.degrees 5 (FWHM). The 150-250 mu m and the 250-400 mu m brightness ratios of the interstellar dust emission show a slight decrease with increasing galactic latitude at \b\ less than or equal to 3.degrees 5, consistent with the 140-240 mu m brightness ratio observed by COBE/DIRBE. The 250-700 mu m brightness ratio shows a much stronger dependence on the galactic latitude. The effect may be due to a single component of warm (T similar to 20 K) dust with an emissivity index of n < 2, that decreases with galactic latitude. Alternatively, the effect may be due to the existence of two components of dust, a warm (T similar to 20 K) component and a cold (T similar to 4-7 K) component, each with an emissivity index of n = 2. In the latter case, either the temperature or the optical depth of the cold component increases as a function of the galactic latitude. In either case, the physical properties of the interstellar dust must be assumed to vary significantly over the range \b\ less than or equal to 3.degrees 5. C1 INST SPACE & ASTRONAUT SCI, SAGAMIHARA, KANAGAWA 229, JAPAN. NAGOYA UNIV, DEPT PHYS, SCH SCI, CHIKUSA KU, NAGOYA, AICHI 46401, JAPAN. CALTECH, PASADENA, CA 91125 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP COMMUN RES LABS, 4-2-1 NUKUI KITAMACHI, KOGANEI, TOKYO 184, JAPAN. NR 13 TC 7 Z9 7 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 OCT 25 PY 1996 VL 48 IS 5 BP L77 EP + DI 10.1093/pasj/48.5.L77 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP793 UT WOS:A1996VP79300007 ER PT J AU Murakami, H Freund, MM Ganga, K Guo, HF Hirao, T Hiromoto, N Kawada, M Lange, AE Makiuti, S Matsuhara, H Matsumoto, T Matsuura, S Murakami, M Nakagawa, T Narita, M Noda, M Okuda, H Okumura, K Onaka, T Roellig, TL Sato, S Shibai, H Smith, BJ Tanabe, T Tanaka, M Watabe, T Yamamura, I Yuen, LM AF Murakami, H Freund, MM Ganga, K Guo, HF Hirao, T Hiromoto, N Kawada, M Lange, AE Makiuti, S Matsuhara, H Matsumoto, T Matsuura, S Murakami, M Nakagawa, T Narita, M Noda, M Okuda, H Okumura, K Onaka, T Roellig, TL Sato, S Shibai, H Smith, BJ Tanabe, T Tanaka, M Watabe, T Yamamura, I Yuen, LM TI The IRTS (Infrared Telescope in Space) mission SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE infrared, general; instruments; spacecraft ID IN-SPACE; SYSTEM; DESIGN AB The Japanese satellite-borne infrared telescope, the Infrared Telescope in Space (IRTS), has completed a successful survey of a portion of the infrared sky. The IRTS consists of a 15 cm telescope cooled with superfluid liquid helium, and is installed on board the Space Flyer Unit (SFU) spacecraft. The SFU was launched on 1995 March 18 UT. The sky survey by the IRTS started on March 29 UT, and was completed on April 25 UT after exhausting its liquid helium. The cryogenic system operated as designed, and maintained the telescope and the focal-plane instruments at a stable temperature of 1.9 K for 38 days. The four focal-plane instruments, which together covered almost the entire infrared wavelength range, observed a sky area of about 2700 deg(2) and returned a wealth of new data on a variety of objects, including the zodiacal light, interstellar gas and dust, near-infrared cosmic background light and point sources. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. CALTECH, OBSERVAT COSMOL, PASADENA, CA 91125 USA. BEIJING OBSERV, BEIJING 100080, PEOPLES R CHINA. COMMUN RES LABS, KOGANEI, TOKYO 184, JAPAN. NAGOYA UNIV, SCH SCI, DEPT ASTROPHYS, CHIKUSA KU, NAGOYA, AICHI 464, JAPAN. COMMUN RES LABS, KANSAI ADV RES CTR, NISHI KU, KOBE 65124, JAPAN. UNIV TSUKUBA, INST ENGN MECH, TSUKUBA, IBARAKI 305, JAPAN. NAGOYA MUNICIPAL IND RES INST, ATSUTA KU, NAGOYA, AICHI 456, JAPAN. UNIV TOKYO, SCH SCI, DEPT ASTRON, BUNKYO KU, TOKYO 113, JAPAN. CALTECH, CTR INFRARED PROC & ANAL, PASADENA, CA 91125 USA. UNIV TOKYO, FAC SCI, INST ASTRON, BUNKYO KU, TOKYO 181, JAPAN. RP INST SPACE & ASTRONAUT SCI, 3-1-1 YOSHINODAI, SAGAMIHARA, KANAGAWA 229, JAPAN. RI Matsuura, Shuji/B-5658-2016 OI Matsuura, Shuji/0000-0002-5698-9634 NR 19 TC 92 Z9 93 U1 0 U2 1 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 OCT 25 PY 1996 VL 48 IS 5 BP L41 EP L46 DI 10.1093/pasj/48.5.L41 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP793 UT WOS:A1996VP79300001 ER PT J AU Onaka, T Yamamura, I Tanabe, T Roellig, TL Yuen, LM AF Onaka, T Yamamura, I Tanabe, T Roellig, TL Yuen, LM TI Detection of the mid-infrared unidentified bands in the diffuse galactic emission by IRTS SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE infrared, diffuse emission; infrared, spectra; interstellar, dust; spacecraft ID CARBONACEOUS COMPOSITE QCC; IN-SPACE IRTS; INTERSTELLAR-MEDIUM; IRAS SOURCES; MU-M; SPECTRUM; DUST; IDENTIFICATION; FEATURES; MICRONS AB This letter presents the first results of the mid-infrared spectrum (4.5-11.7 mu m) of the diffuse emission near to the galactic plane (l similar to 50 degrees; \b\ less than or equal to 5 degrees) obtained by the mid-infrared spectrometer on board the Infrared Telescope in Space mission. The results clearly demonstrate the presence of unidentified infrared emission (UIR) bands at 6.2, 7.7, 8.6, and 11.3 mu m in the diffuse galactic emission. The distribution of the UIR bands correlates well with the IRAS 100 mu m map, suggesting that the UIR-band emitting material is well mixed with the classical dust grains in general interstellar space. The present results indicate that more than 70% of the IRAS 12 mu m flux diffuse emission is emitted in the spectral range 8-11.7 mu m, and that most of the 12 mu m excess comes from the features associated with the UIR bands. C1 UNIV TOKYO, INST ASTRON, FAC SCI, MITAKA, TOKYO 181, JAPAN. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP UNIV TOKYO, SCH SCI, DEPT ASTRON, BUNKYO KU, TOKYO 113, JAPAN. NR 29 TC 110 Z9 111 U1 0 U2 1 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 OCT 25 PY 1996 VL 48 IS 5 BP L59 EP + DI 10.1093/pasj/48.5.L59 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP793 UT WOS:A1996VP79300004 ER PT J AU Yamamura, I Onaka, T Tanabe, T Roellig, TL Yuen, LM AF Yamamura, I Onaka, T Tanabe, T Roellig, TL Yuen, LM TI Mid-infrared spectral observations of point sources by IRTS SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE infrared, sources; infrared, spectra; interstellar, dust; spacecraft; stars, late-type; stars, mass loss ID TELESCOPE IN-SPACE; IRRADIANCE CALIBRATION; STARS; SPECTROMETER; BAND AB The mid-infrared spectrometer on board Infrared Telescope in Space has detected thousands of pointlike sources in the spectral range of 4.5-11.7 mu m. Extraction of point sources from the survey data has been carried out for the observing period after the spin-flip, where accurate pointing information is presently available, and 129 point sources have been extracted with signal-to-noise ratios greater than 3 throughout the MIRS spectral range. A two-color diagram of these objects, derived from bands of 5 mu m, 8 mu m, and 10 mu m of the sources, is presented. The sources can be classified into five groups on the diagram: visible late-type stars, stars with dust envelopes, stars with silicate emission, objects with the unidentified infrared (UIR) emission bands, and very peculiar red objects. With the help of the 5 mu m and 8 Irm colors, objects with the UIR bands can clearly be distinguished from objects without those features. The characteristics of the sources in each group are discussed based on the spectra. C1 UNIV TOKYO, INST ASTRON, FAC SCI, MITAKA, TOKYO 181, JAPAN. UNIV TOKYO, SCH SCI, DEPT ASTRON, BUNKYO KU, TOKYO 113, JAPAN. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NR 17 TC 8 Z9 8 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 OCT 25 PY 1996 VL 48 IS 5 BP L65 EP L69 DI 10.1093/pasj/48.5.L65 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP793 UT WOS:A1996VP79300005 ER PT J AU Zahnle, K AF Zahnle, K TI Tunguska - Leaving no stone unburned SO NATURE LA English DT Editorial Material ID IMPACT RP Zahnle, K (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 10 TC 9 Z9 9 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD OCT 24 PY 1996 VL 383 IS 6602 BP 674 EP 675 DI 10.1038/383674a0 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN918 UT WOS:A1996VN91800032 ER PT J AU Kogut, A Banday, AJ Bennett, CL Gorski, KM Hinshaw, G Jackson, PD Keegstra, P Lineweaver, C Smoot, GF Tenorio, L Wright, EL AF Kogut, A Banday, AJ Bennett, CL Gorski, KM Hinshaw, G Jackson, PD Keegstra, P Lineweaver, C Smoot, GF Tenorio, L Wright, EL TI Calibration and systematic error analysis for the COBE(1) DMR 4 year sky maps SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; instrumentation, detectors; radio continuum, general; space vehicles ID DIFFERENTIAL MICROWAVE RADIOMETERS; DESIGN AB The Differential Microwave Radiometers (DMR) instrument aboard the Cosmic Background Explorer (COBE) has mapped the full microwave sky to mean sensitivity 26 mu K per 7 degrees held of view. The absolute calibration is determined to 0.7% with drifts smaller than 0.2% per year. We have analyzed both the raw differential data and the pixelized sky maps for evidence of contaminating sources such as solar system foregrounds, instrumental susceptibilities, and artifacts from data recovery and processing. Most systematic effects couple only weakly to the sky maps. The largest uncertainties in the maps result from the instrument susceptibility to Earth's magnetic field, microwave emission from Earth, and upper limits to potential effects at the spacecraft spin period. Systematic effects in the maps are small compared to either the noise or the celestial signal: the 95% confidence upper limit for the pixel-pixel rms from all identified systematics is less than 6 mu K in the worst channel. A power spectrum analysis of the (A-B)/2 difference maps shows no evidence for additional undetected systematic effects. C1 UNIV CALIF BERKELEY, LAWRENCE BERKELEY LAB, BERKELEY, CA 94720 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. UNIV CALIF BERKELEY, CFPA, BERKELEY, CA 94720 USA. UNIV CALIF LOS ANGELES, LOS ANGELES, CA 90095 USA. RP Kogut, A (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HUGHES STX CORP, ASTRON & SOLAR PHYS LAB, CODE 685, GREENBELT, MD 20771 USA. RI Kogut, Alan/D-6293-2012 NR 23 TC 38 Z9 38 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP 653 EP 673 DI 10.1086/177898 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM998 UT WOS:A1996VM99800001 ER PT J AU Kashlinsky, A Mather, JC Odenwald, S Hauser, MG AF Kashlinsky, A Mather, JC Odenwald, S Hauser, MG TI Clustering of the diffuse infrared light from the COBE DIRBE maps .1. C(0) and limits on the near-infrared background SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, observations; cosmology, theory; diffuse radiation; galaxies, clusters, general; infrared, general ID COSMOLOGICAL DECELERATION PARAMETER; MINIMAL ISOCURVATURE MODEL; LARGE-SCALE STRUCTURE; FAINT GALAXIES; LUMINOSITY FUNCTION; GALACTIC EVOLUTION; NUMBER COUNTS; DUST; FIELD; CONSTRAINTS AB The cosmic infrared background (CIB) and its anisotropy have not yet been measured but are important signatures of the early evolution and clustering of galaxies. The near-IR is particularly interesting because redshift effects bring the peak luminosity of distant galaxies into the near-IR, allowing high-redshift objects to dominate the theoretical predictions of the CIB and its fluctuations. This paper is devoted to studying the CIB through its correlation properties. We studied the limits on CIB anisotropy in the near-IR (1.25, 2.2, and 3.5 mu m, or J, K, L) bands at a scale of 0.degrees 7 using the COBE(5) Diffuse Infrared Background Experiment (DIRBE) data. In single bands, we obtain the upper limits on the zero-lag correlation signal C(0)= [(v delta I-v)(2)] < 3.6 x 10(-16), 5.1 x 10(-17), and 5.7 x 10(-18) W-2 m(-4) sr(-2) for the J, K, and L bands, respectively. The DIRBE data exhibit a clear color between the various bands with a small dispersion. On the other hand, most of the CIB is expected to come from redshifted galaxies, and thus it should have different color properties. We use this observation to develop a ''color subtraction'' method of linear combinations of maps at two different bands. This method is expected to suppress the dominant fluctuations from foreground stars and nearby galaxies, while not reducing (or perhaps even amplifying) the extragalactic contribution to C(0). Applying this technique gives significantly lower and more isotropic limits. For the J-K, J-L, and K-L combinations, these limits are C(0)< 6.3 x 10(-17) 1.4 x 10(-16), and 1.2 x 10(-17) W-2 m(-4) sr(-2), respectively. We also use simple no-evolution models to interpret these numbers in terms of the total CIB levels, postponing a more detailed interpretation to a forthcoming paper. From the single-band fluctuations, we estimate upper limits on the CIB from clustered matter of (vI(v))(z,rms) =[integral(dvI(v)/dz)(2) dz](1/2) < 200, 78, and 26 nW m(-2) sr(-1) in the J, K, and L bands independently of the evolution history or spectral energy distribution. The color-subtracted signals constrain strongly the color evolution of galaxy populations and, if their degree of isotropy is indicative of a cosmological origin, they could allow determination of the total diffuse fluxes due to clustered material. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Kashlinsky, A (reprint author), NORDITA, BLEGDAMSVEJ 17, DK-2100 COPENHAGEN, DENMARK. NR 85 TC 36 Z9 36 U1 1 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 OCT 20 PY 1996 VL 470 IS 2 BP 681 EP 705 DI 10.1086/177900 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM998 UT WOS:A1996VM99800003 ER PT J AU Mukherjee, R Dingus, BL Gear, WK Hartman, RC Hunter, SD Marscher, AP Moore, EM Pohl, M Robson, EI Sreekumar, P Stevens, JA Terasranta, H Tornikoski, M Travis, JP Wagner, SJ Zhang, YF AF Mukherjee, R Dingus, BL Gear, WK Hartman, RC Hunter, SD Marscher, AP Moore, EM Pohl, M Robson, EI Sreekumar, P Stevens, JA Terasranta, H Tornikoski, M Travis, JP Wagner, SJ Zhang, YF TI EGRET observations of the 1993 March gamma-ray flare from PKS 0528+134 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; quasars, individual, (PKS 0528 + 134) ID EXTRAGALACTIC RADIO-SOURCES; X-RAY; MILLIMETER-SUBMILLIMETER; RELATIVISTIC JETS; EMISSION; RADIATION; BLAZARS; 3C-279; TELESCOPE; MODELS AB EGRET observation of PKS 0528 + 134 during the 1993 March flare in gamma-rays is presented here. During the flare gamma-rays were detected at a level approximately three times greater than the observed intensity in earlier observations. Spectra of the source during the flare, as well as during the nonflaring state are presented. The flux history of PKS 0528 + 134 as observed from the start of the Compton Gamma Ray Observatory (CGRO) mission up to the end of Phase 3 (1993 October) is given. Multiwavelength observations of PKS 0528+134 during the flare are also presented. A detailed relativistic SSC jet model agrees well with the 1993 March Multiwavelength spectrum; the data, however, are insufficient to discriminate between this and other emission models. C1 UNIV SPACE RES ASSOC, COLUMBIA, MD USA. ROYAL OBSERV, EDINBURGH EH9 3HJ, MIDLOTHIAN, SCOTLAND. BOSTON UNIV, DEPT ASTRON, BOSTON, MA 02215 USA. MAX PLANCK INST EXTRATERR PHYS, D-37075 GARCHING, GERMANY. JOINT ASTRON CTR, HILO, HI 96720 USA. METSAHOVI RADIO RES STN, SF-02540 KYLMALA, FINLAND. LANDESSTERNWARTE KONIGSTUHL, D-69117 HEIDELBERG, GERMANY. RP Mukherjee, R (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 661, GREENBELT, MD 20771 USA. RI Hunter, Stanley/D-2942-2012; OI Dingus, Brenda/0000-0001-8451-7450 NR 66 TC 43 Z9 43 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP 831 EP 838 DI 10.1086/177914 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM998 UT WOS:A1996VM99800017 ER PT J AU Colgan, SWJ Erickson, EF Simpson, JP Haas, MR Morris, M AF Colgan, SWJ Erickson, EF Simpson, JP Haas, MR Morris, M TI Excitation of the ''arched'' filaments near the Galactic center SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy, center; infrared, ISM, lines and bands; ISM, structure ID RADIO ARC; MAGNETIC-FIELD; PHOTODISSOCIATION REGIONS; CONTINUUM OBSERVATIONS; INTERSTELLAR-MEDIUM; NEBULAR PROPERTIES; MODEL; SUBMILLIMETER; MICRON; SPECTROSCOPY AB We present measurements of the far-infrared (FIR) fine structure lines [S III] (33 mu m), [Si II] (35 mu m), [O III] (52, 88 mu m), [O I] (63 mu m), and [C II] (158 mu m) and the adjacent continua at these wavelengths in a strip crossing the E2 and W1 thermal radio filaments in the Galactic center ''are.'' The properties of the two filaments are similar: the line and continuum fluxes peak in the vicinity of the radio ridges, and the contrast of the ridge fluxes relative to the off-ridge fluxes is greatest for the FIR continuum and doubly ionized lines, lower for the single-dish radio measurements (Sofue et al. 1986) and smallest for the low-excitation lines. The near spatial coincidence of the line and continuum emission maxima with the radio filaments demonstrates that the same excitation source must be responsible for both the line and the continuum emission. The peak FIR luminosity of similar to 2.5 x 10(5) L(.) per 30'' beam and the association of [O III] intensity with the filaments pose difficulties for shock and MHD models. Excitation by a string of stars is also unlikely, but photoionization of molecular cloud edges by a quasi-uniform distribution of stars is the most plausible excitation source proposed. The peak ionized line intensity is shifted slightly eastward relative to the FIR continuum emission. The deduced excitation, as measured by the [O III] to [S III] line flux ratios, also peaks slightly east of the radio ridges. Together, these two measurements suggest a substantial contribution from an ionizing source to the east. The strengths of the [O I] and [C II] lines are consistent with their production in photodissociated molecular material adjacent to the photoionized gas, but the FIR luminosity and the [S II] emission appear to originate predominantly in or very near to the ionized gas. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90024. RP Colgan, SWJ (reprint author), SETI INST,MT VIEW,CA, USA. RI Colgan, Sean/M-4742-2014 NR 58 TC 13 Z9 13 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP 882 EP 892 DI 10.1086/177918 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM998 UT WOS:A1996VM99800021 ER PT J AU Hubeny, I Heap, SR AF Hubeny, I Heap, SR TI HST/GHRS observations of the beta Pictoris system .2. Exploring the potential for tracking comet-like objects orbiting the star SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; line, profiles; stars, individual (B Pictoris) ID CIRCUMSTELLAR DISK; CA-II; ABSORPTION FEATURES; K-LINE; PARAMETERS AB We present a systematic study of the transient absorption features observed in the spectra of beta Pictoris. We calculate detailed synthetic spectra of a star, which is partially obscured by a permanent circumstellar disk and by an absorbing body of a given size, position, radial velocity with respect to the star, and total column density. We show that because of the nonuniform surface brightness of the star, the strength of an absorption feature is an intricate function of both position and size. Consequently, one cannot determine the projected area of the body or its position from a single measurement only. However, by studying several closely spaced lines simultaneously, like those in the region of the Fe II UV1 multiplet at lambda approximate to 2600 Angstrom, one can determine both the position and size of the body. We present a preliminary analysis of Goddard High Resolution Spectrograph observations of beta Pic in this region and show that while existing spectra do not have sufficient time coverage to allow us to track a single body during its transit across the stellar disk, our approach provides a robust means of tracking cometlike objects transiting the star and should be used to interpret future monitoring of beta Pic and other stars showing similar variable absorption features. Conversely, the effect of body position is so great that it must be taken into account; absorption-line analyses based on techniques developed for interstellar lines should not be used. RP Hubeny, I (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 21 TC 22 Z9 22 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP 1144 EP 1156 DI 10.1086/177938 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM998 UT WOS:A1996VM99800041 ER PT J AU Aschwanden, MJ Kosugi, T Hudson, HS Wills, MJ Schwartz, RA AF Aschwanden, MJ Kosugi, T Hudson, HS Wills, MJ Schwartz, RA TI The scaling law between electron time-of-flight distances and loop lengths in solar flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; radiation mechanisms, nonthermal; Sun, corona; Sun, flares; Sun, X-rays, gamma rays ID HARD X-RAY; 1991 NOVEMBER 15; WHITE-LIGHT FLARES; YOHKOH OBSERVATIONS; A MISSION; BURSTS; TARGET; SPECTROMETER; RECONNECTION; PARTICLES AB From the complete data set of solar flares simultaneously observed with the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO) in the high-time resolution mode (64 ms) and the Hard X-ray Telescope (HXT) on board Yohkoh, we were able to determine the electron time-of-flight (TOF) distance l' and the flare loop geometry in 42 events. The electron TOF distances were determined from time delays (of approximate to 10-100 ms) of hard X-ray (HXR) pulses (measured in 16 channel spectra over approximate to 20-200 keV), produced by the velocity difference of the HXR-producing electrons. The hare loops were mostly identified from double footpoint sources in greater than or similar to 30 keV HXT images, with radii in the range r = 3000-25,000 km. We find a scaling law between the electron TOF distance l' and the flare loop half-length s = r(pi/2), having a mean ratio (and standard deviation) of l'/s = 1.4 +/- 0.3. In five flares, we observe coronal greater than or similar to 30 keV HXR sources of the Masuda type in the cusp region above the flare loop and find that their heights are consistent with the electron TOF distance to the footpoints. These results provide strong evidence that particle acceleration in solar flares occurs in the cusp region above the flare loop and that the coronal HXR sources discovered by Masuda et al. are a signature of the acceleration site, probably controlled by a magnetic reconnection process. C1 NATL ASTRON OBSERV, MITAKA, TOKYO 181, JAPAN. UNIV HAWAII, INST ASTRON, HONOLULU, HI 96822 USA. HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. NASA, GODDARD SPACE FLIGHT CTR, HUGES STX, GREENBELT, MD 20771 USA. RP Aschwanden, MJ (reprint author), UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. NR 63 TC 83 Z9 83 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP 1198 EP 1217 DI 10.1086/177943 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM998 UT WOS:A1996VM99800046 ER PT J AU Ellis, J Fields, BD Schramm, DN AF Ellis, J Fields, BD Schramm, DN TI Geological isotope anomalies as signatures of nearby supernovae SO ASTROPHYSICAL JOURNAL LA English DT Article DE Earth; nuclear reactions, nucleosynthesis, abundances; supernovae, general ID ENHANCED BE-10 DEPOSITION; EARLY SOLAR-SYSTEM; ANTARCTIC ICE; GEMINGA; NUCLEOSYNTHESIS; EXTINCTION; PERIOD; BUBBLE; 1987A AB Nearby supernova explosions may cause geological isotope anomalies via the direct deposition of debris or by cosmic-ray spallation in the Earth's atmosphere. We estimate the mass of material deposited terrestrially by these two mechanisms, showing the dependence on the supernova distance. A number of radioactive isotopes are identified as possible diagnostic tools, such as Be-10, Al-26, Cl-36, Mn-53, Fe-60, and Ni-59, as well as the longer-lived I-129, Sm-146, and Pu-244. We discuss whether the 35 and 60 kyr old Be-10 anomalies observed in the Vostok Antarctic ice cores could be due to supernova explosions. Combining our estimates for matter deposition with results of recent nucleosynthesis yields, we calculate the expected signal from nearby supernovae using ice cores back to O(300) kyr ago, and we discuss using deep-ocean sediments back to several hundred Myr. In particular, we examine the prospects for identifying isotope anomalies due to the Geminga supernova explosion, and signatures of the possibility that supernovae might have caused one or more biological mass extinctions. C1 UNIV NOTRE DAME,DEPT PHYS,NOTRE DAME,IN 46556. UNIV CHICAGO,CHICAGO,IL 60637. INST ASTROPHYS PARIS,F-75014 PARIS,FRANCE. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Ellis, J (reprint author), CERN,DIV THEORET PHYS,CH-1211 GENEVA,SWITZERLAND. NR 45 TC 65 Z9 65 U1 1 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP 1227 EP 1236 DI 10.1086/177945 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM998 UT WOS:A1996VM99800048 ER PT J AU Focke, WB AF Focke, WB TI Horizontal-branch quasi-periodic oscillation from Cygnus X-2 with a second harmonic SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, general; stars, magnetic fields; stars, neutron; stars, rotation; X-rays, stars ID X-RAY BINARIES; SPECTRAL BEHAVIOR; FREQUENCY; GX5-1 AB Cyg X-2 was observed by the Rossi X-Ray Timing Explorer during in-orbit checkout in 1996 January and was found in the horizontal, normal, and flaring branches. Horizontal-branch quasi-periodic oscillations were seen with an rms variability of approximately 6% in the fundamental. The second harmonic was also seen with an rms variability about three-fourths that of the fundamental. In the course of 2 hr, the centroid frequency of the fundamental ranged from 17 to 22 Hz, with significant variations on timescales of tens of seconds, and it was positively correlated with source intensity in the 0-20 keV band. The ratio of the width of the fundamental to its centroid frequency was 0.15-0.2. The centroid and width of the second harmonic were 2 times those of the fundamental. The relative positions of the fundamental and harmonic, as well as their correlation with intensity, are consistent with the beat-frequency-modulated accretion model of the quasi-periodic oscillation, which predicts a magnetic field of 2.2 x 10(9) G and a spin frequency of 165 Hz for the neutron star. The relative widths of the two peaks and the time history of the fundamental frequency suggest that the observed width of the peaks is due to more than temporal variation of the frequency. C1 UNIV MARYLAND, DEPT PHYS, COLLEGE PK, MD 20741 USA. RP Focke, WB (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. NR 14 TC 13 Z9 13 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP L127 EP L130 DI 10.1086/310314 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM999 UT WOS:A1996VM99900013 ER PT J AU Hjellming, RM Rupen, MP Shrader, CR CampbellWilson, D Hunstead, RW McKay, DJ AF Hjellming, RM Rupen, MP Shrader, CR CampbellWilson, D Hunstead, RW McKay, DJ TI Radio and X-ray flaring events in X-ray Nova Ophiuchi 1993 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; radio continuum, stars; stars, individual (Nova Ophiuchi 1993, GRS 1716-249); X-rays, stars ID TRANSIENT GRO J1655-40 AB The X-ray ''Nova'' Ophiuchi 1993, GRS 1716-249 (=GRO J1719-24), discovered in 1993 September, was redetected as an X-ray source by the Mir/Kvant team on 1995 February 16, and later by BATSE. Radio observations by the Molonglo Observatory Synthesis Telescope and the Very Large Array show a rapidly decaying radio flare followed by recurrent radio flaring activity. Although the X-ray flares, as seen at 20-200 keV by BATSE, are unusual in having sawtooth-like, slow-rise, fast-decay time profiles, the relation between X-ray and radio events is similar to that in the superluminal radio jet X-ray transient GRO J1655-40. This strengthens the apparent empirical link between changes in accretion disk X-ray emission and radio activity in galactic black hole binaries. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV SYDNEY,SCH PHYS,SYDNEY,NSW 2006,AUSTRALIA. CSIRO,AUSTRALIA TELESCOPE,PAUL WILD OBSERV,NARRABRI,NSW 2390,AUSTRALIA. RP Hjellming, RM (reprint author), NATL RADIO ASTRON OBSERV,POB O,SOCORRO,NM 87801, USA. NR 18 TC 15 Z9 15 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP L105 EP L107 DI 10.1086/310312 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM999 UT WOS:A1996VM99900008 ER PT J AU Stark, MJ Baykal, A Strohmayer, T Swank, JH AF Stark, MJ Baykal, A Strohmayer, T Swank, JH TI Pulse arrival time glitches in GRO 51744-28 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; pulsars, individual (GRO J1744-28); X-rays, bursts ID NEUTRON STARS AB We observe glitches in the arrival times of X-ray pulses from GRO J1744-28 associated with the large X-ray bursts observed from this source. In early observations, the pulse arrival time becomes delayed by 28 ms (6% of the 467 ms pulsar period) following bursts while the shape of the nearly sinusoidal light curve is essentially unchanged. This arrival-time lag decays exponentially over the next similar to 1000 s. In later observations, the observed phase lags are smaller, and eventually, some bursts appear to be accompanied by a small phase advance. While explanations of these observations that rely upon changes in the postburst accretion flow are natural, our observations present some problems for these explanations. It may be that this behavior can be understood by analogy with glitches in spinning-down radio pulsars, though this explanation has its own problems. Explained as a glitch, the phase shift is the result of coupling of the neutron star's crust to the crustal superfluid, which is spun up more slowly than the rest of the star, and the recovery is due to coupling between the crust and the core of the neutron star. C1 MIDDLE E TECH UNIV,DEPT PHYS,TR-06531 ANKARA,TURKEY. RP Stark, MJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 662,GREENBELT,MD 20771, USA. RI Swank, Jean/F-2693-2012 NR 18 TC 14 Z9 14 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP L109 EP L112 DI 10.1086/310311 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM999 UT WOS:A1996VM99900009 ER PT J AU Takahashi, T Tashiro, M Madejski, G Kubo, H Kamae, T Kataoka, J Kii, T Makino, F Makishima, K Yamasaki, N AF Takahashi, T Tashiro, M Madejski, G Kubo, H Kamae, T Kataoka, J Kii, T Makino, F Makishima, K Yamasaki, N TI ASCA observation of an X-ray/TeV flare from the BL Lacertae object Markarian 421 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, general; BL Lacertae objects, individual (Markarian 421); X-rays, general ID RAY; VARIABILITY; SPECTRUM AB We observed the BL Lac object Mrk 421 with the X-ray satellite ASCA in 1994 as part of a multifrequency observation. The 24 hr observation was conducted 1 day after the onset of a TeV flare detected by the Whipple Observatory and detected an X-ray flare, with no apparent variability in the optical, UV, and EGRET GeV flux. The ASCA 2-10 keV flux peaked at 3.7 x 10(-10) ergs cm(-2) s(-1) and then decreased to 1.8 x 10(-10) ergs cm(-2) s(-1) with a doubling timescale of similar to 12 hr. The shape of the X-ray spectrum varied during the observation, such that the hard X-rays always led the soft X-rays, both in brightening and dimming of the source, with a lag of the 0.5-1 keV photons versus those in the 2-7.5 keV band of similar to 1 hr. The rapid TeV variability indicates a compact TeV-producing region, suggesting relativistic beaming with a Doppler factor delta greater than or equal to 5. The correlation of the flux in the X-ray and the TeV bands indicates that a high-energy tail of a single electron population is responsible for both X-rays and TeV gamma-rays, with radio, IR, UV and X-rays produced via the synchrotron process and GeV and TeV gamma-rays produced via Comptonization. Under the assumption that the ''soft lag'' observed in the X-ray band is due to the synchrotron-lifetime effects, with delta = 5, we calculate the magnetic field for the X-ray-producing region to be similar to 0.2 G. The Lorentz factors gamma(el) of the electrons responsible for the emission in the keV and TeV bands are similar to 10(6), consistent with the values implied by the Klein-Nishina limit. C1 UNIV TOKYO,DEPT PHYS,BUNKYO KU,TOKYO 113,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. TOKYO METROPOLITAN UNIV,DEPT PHYS,HACHIOJI,TOKYO 19203,JAPAN. RP Takahashi, T (reprint author), INST SPACE & ASTRONAUT SCI,3-1-1 YOSHINODAI,SAGAMIHARA,KANAGAWA 229,JAPAN. RI Yamasaki, Noriko/C-2252-2008; Tashiro, Makoto/J-4562-2012 NR 23 TC 116 Z9 116 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1996 VL 470 IS 2 BP L89 EP L92 DI 10.1086/310302 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM999 UT WOS:A1996VM99900004 ER PT J AU Konzelmann, T Cahoon, DR Whitlock, CH AF Konzelmann, T Cahoon, DR Whitlock, CH TI Impact of biomass burning in equatorial Africa on the downward surface shortwave irradiance: Observations versus calculations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC CHEMISTRY; SOLAR IRRADIANCE; RADIATION; EMISSIONS; TRANSPORT; AIRBORNE; AEROSOLS; TROPICS; PROJECT; FOREST AB Long-term ground-based measurements of downward surface shortwave irradiance are compared with the satellite-derived downward surface shortwave irradiance for equatorial Africa. Good agreement between satellite-derived and measured values are shown in the spring and fall (seasons relative to the northern hemisphere). Large differences between satellite-derived and measured values are found in regions where extensive savanna fires take place during the dry season. Discrepancies are found in regions north of the equator during the winter months, and the differences shift to the southern hemisphere during summer. Significant differences of 40-80 W m(-2) are found for extended areas, corresponding to 25-40% of the measured monthly mean downward surface shortwave irradiance. Savanna fires release large amounts of particles into the atmosphere, increasing the aerosol optical depth. The increased optical depth leads to an overestimation of the downward surface shortwave irradiance by the satellite reduction algorithms which do not account for the fire-produced aerosol. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. RP Konzelmann, T (reprint author), SWISS FED INST TECHNOL, DEPT GEOG, WINTERTHURERSTR 190, CH-8057 ZURICH, SWITZERLAND. NR 47 TC 26 Z9 27 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1996 VL 101 IS D17 BP 22833 EP 22844 DI 10.1029/96JD01556 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VN184 UT WOS:A1996VN18400009 ER PT J AU Jouzel, J Koster, RD AF Jouzel, J Koster, RD TI A reconsideration of the initial conditions used for stable water isotope models SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; LAST GLACIAL MAXIMUM; DEUTERIUM EXCESS; ICE; PRECIPITATION; TEMPERATURE; SIMULATIONS; CLIMATE; SURFACE; RECORD AB Many of the ''simple models'' used to study and explain the global distributions of stable water isotopes assume that the initial isotope content of an air mass can be estimated from local conditions at the oceanic source through the application of a global-scale closure equation. Using a general circulation model fitted with isotope tracer diagnostics, we show that the closure equation is generally invalid at the local scale, leading to a systematic bias in the modeled isotope contents. The quantitative results obtained in earlier simple model studies may need some adjustment in light of this bias, particularly if deuterium excess was used to characterize conditions prevailing at the evaporative source. C1 NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, HYDROL SCI BRANCH, GREENBELT, MD 20771 USA. RP Jouzel, J (reprint author), CTR ETUD SACLAY, CEA, DSM, LAB MODELISAT CLIMAT & ENVIRONNEMENT, F-91191 GIF SUR YVETTE, FRANCE. RI Koster, Randal/F-5881-2012 OI Koster, Randal/0000-0001-6418-6383 NR 25 TC 47 Z9 48 U1 0 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1996 VL 101 IS D17 BP 22933 EP 22938 DI 10.1029/96JD02362 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VN184 UT WOS:A1996VN18400016 ER PT J AU Eckman, RS Grose, WL Turner, RE Blackshear, WT AF Eckman, RS Grose, WL Turner, RE Blackshear, WT TI Polar ozone depletion: A three-dimensional chemical modeling study of its long-term global impact SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; HETEROGENEOUS CHEMISTRY; LOWER STRATOSPHERE; UNITED-STATES; LATE WINTER; HOLE; TRANSPORT; TRENDS; DESTRUCTION; VARIABILITY AB The export of ozone-poor air from the polar region following the breakup of the southern hemisphere polar vortex is examined with a three-dimensional chemistry transport model. This volume of depleted ozone, the result of-chemical processing during the southern wintertime and springtime, is long-lived in the lower stratosphere and can affect ozone concentrations at southern middle latitudes following its transport out of the polar region. Two 5-year simulations were performed utilizing the NASA Langley Research Center three-dimensional chemistry transport model. One simulation included only gas phase and sulfate aerosol chemistry, while the second simulation also included reactions occurring on polar stratospheric clouds (PSCs). The model-calculated seasonal variation of southern hemispheric O-3, HNO3, and active chlorine as a result of PSC chemistry is in reasonable accord with satellite observations. The model reveals that ozone is transported equatorward following the breakup of the polar vortex to approximately 20 degrees S latitude by the first southern summer following the activation of PSC chemistry. A residual column-integrated ozone depletion of 9% remained by the springtime of the second year, In subsequent years, the southern ozone hole itself increased in depth from a column-integrated depletion of 37% in the first year to 43% in the fifth year with respect to the baseline simulation with no PSC chemistry. The isopleths of column-integrated ozone loss showed a slow equatorward movement during the 5-year run. These model results, in general agreement with earlier model studies using parameterized chemistry, show that a potential exists for a long-term accumulation of ozone loss in the southern polar region and a gradual increase in the global impact of polar ozone depletion. Comparison with satellite and ground-based observations of ozone trends at midlatitudes suggests that ozone dilution may be a contributing factor. Experiments were performed to examine the sensitivity of the rate of local ozone recovery following the breakup of the vortex to the depth and spatial extent of the denitrification of polar air, These simulations revealed that deeper denitrification led to a more persistent column-integrated ozone loss and a slight increase in its equatorward progression. RP Eckman, RS (reprint author), NASA, LANGLEY RES CTR, MAIL STOP 401B, HAMPTON, VA 23681 USA. NR 41 TC 21 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1996 VL 101 IS D17 BP 22977 EP 22989 DI 10.1029/96JD02130 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VN184 UT WOS:A1996VN18400020 ER PT J AU Portmann, RW Solomon, S Garcia, RR Thomason, LW Poole, LR McCormick, MP AF Portmann, RW Solomon, S Garcia, RR Thomason, LW Poole, LR McCormick, MP TI Role of aerosol variations in anthropogenic ozone depletion in the polar regions SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SULFURIC-ACID AEROSOL; ANTARCTIC OZONE; CLOUD FORMATION; NITRIC-ACID; HETEROGENEOUS CHEMISTRY; BALLOON OBSERVATIONS; ARCTIC STRATOSPHERE; MIDDLE ATMOSPHERE; VORTEX; WINTER AB A climatology of aerosol surface area inferred from satellite measurements is used as input in a two-dimensional model to study the long-term evolution of polar ozone depletion, especially the Antarctic ozone hole. It is found that volcanic aerosol inputs very likely modulate the severity of the ozone hole. In particular, the rapid deepening of the ozone hole in the early 1980s, as seen, for example, in the Halley Bay total ozone measurements, was probably caused by accelerated heterogeneous chemistry associated with an increase in aerosol surface area due to volcanic injection combined with the anthropogenic perturbation of stratospheric chlorine. This is further substantiated by the large Antarctic ozone decline observed and modeled after the eruption of Mount Pinatubo. A number of factors that influence the ozone hole are also investigated, including the effect of liquid versus frozen aerosol, the effects of denitrification and dehydration, the role of HOx in HCl and ClONO2 recovery, and the effect of chlorine partitioning at the start of winter. Denitrification tends to slightly increase modeled ozone loss, primarily between about 17 and 25 km late in the season, while dehydration tends to decrease the amount of ozone depletion. However, temperature and aerosol amount have the strongest control on the model ozone loss for a given chlorine loading. These findings suggest that future Arctic ozone depletion could be severe in unusually cold winters or years with large volcanic aerosol surface area. C1 NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. NASA, LANGLEY RES CTR, AEROSOL RES BRANCH, HAMPTON, VA 23665 USA. UNIV COLORADO, CIRES, BOULDER, CO 80309 USA. RP Portmann, RW (reprint author), NOAA, AERON LAB, 325 S BROADWAY, BOULDER, CO 80303 USA. RI Portmann, Robert/C-4903-2009; OI Portmann, Robert/0000-0002-0279-6087; Thomason, Larry/0000-0002-1902-0840 NR 60 TC 76 Z9 77 U1 1 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1996 VL 101 IS D17 BP 22991 EP 23006 DI 10.1029/96JD02608 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VN184 UT WOS:A1996VN18400021 ER PT J AU Massie, ST Deshler, T Thomas, GE Mergenthaler, JL Russell, JM AF Massie, ST Deshler, T Thomas, GE Mergenthaler, JL Russell, JM TI Evolution of the infrared properties of the Mount Pinatubo aerosol cloud over Laramie, Wyoming SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID EXPLORER SATELLITE MEASUREMENTS; CHICHON STRATOSPHERIC AEROSOLS; EL-CHICHON; SULFURIC-ACID; OPTICAL-PROPERTIES; SIZE DISTRIBUTION; VALIDATION; ISAMS; UARS; VOLATILITY AB Particle size distributions measured from May 1991 to April 1994 over Laramie, Wyoming, are used in Mie calculations to model the wavelength dependence and the time evolution of the extinction, single-scattering albedo, and asymmetry parameters of stratospheric sulfate particles. The calculations cover the time period from 45 days before to 1080 days after the eruption of Mt. Pinatubo. The time evolution of the particle size distribution parameters and the evolution of the infrared extinction are examined concurrently and interrelated in terms of the variables present in the Mie equation for the extinction coefficient. The calculations are validated by comparing the theoretical model values to extinction measurements obtained by the Cryogenic Limb Array Etalon Spectrometer (CLAES), Improved Stratospheric and Mesospheric Sounder (ISAMS), Halogen Occultation Experiment (HALOE), and Stratospheric Aerosol and Gas Experiment (SAGE II) experiments. The Wyoming size distributions are also used to derive simple mathematical expressions from which area and volume densities can be estimated using CLAES extinction measurements. C1 UNIV WYOMING, LARAMIE, WY 82071 USA. LOCKHEED MARTIN PALO ALTO RES LAB, PALO ALTO, CA USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. UNIV COLORADO, ATMOSPHER & SPACE PHYS LAB, BOULDER, CO 80309 USA. RP Massie, ST (reprint author), NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. NR 42 TC 25 Z9 25 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1996 VL 101 IS D17 BP 23007 EP 23019 DI 10.1029/96JD01991 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VN184 UT WOS:A1996VN18400022 ER PT J AU Belton, MJS Head, JW Ingersoll, AP Greeley, R McEwen, AS Klaasen, KP Senske, D Pappalardo, R Collins, G Vasavada, AR Sullivan, R Simonelli, D Geissler, P Carr, MH Davies, ME Veverka, J Gierasch, PJ Banfield, D Bell, M Chapman, CR Anger, C Greenberg, R Neukum, G Pilcher, CB Beebe, RF Burns, JA Fanale, F Ip, W Johnson, TV Morrison, D Moore, J Orton, GS Thomas, P West, RA AF Belton, MJS Head, JW Ingersoll, AP Greeley, R McEwen, AS Klaasen, KP Senske, D Pappalardo, R Collins, G Vasavada, AR Sullivan, R Simonelli, D Geissler, P Carr, MH Davies, ME Veverka, J Gierasch, PJ Banfield, D Bell, M Chapman, CR Anger, C Greenberg, R Neukum, G Pilcher, CB Beebe, RF Burns, JA Fanale, F Ip, W Johnson, TV Morrison, D Moore, J Orton, GS Thomas, P West, RA TI Galileo's first images of Jupiter and the Galilean satellites SO SCIENCE LA English DT Article ID ICE SHELL; IO; GANYMEDE; EUROPA; EVOLUTION; SURFACE; PLUMES; STATE AB The first images of Jupiter, Io, Europa, and Ganymede from the Galileo spacecraft reveal new information about Jupiter's Great Red Spot (GRS) and the surfaces of the Galilean satellites. Features similar to clusters of thunderstorms were found in the GRS. Nearby wave structures suggest that the GRS may be a shallow atmospheric feature. Changes in surface color and plume distribution indicate differences in resurfacing processes near hot spots on to. Patchy emissions were seen while lo was in eclipse by Jupiter. The outer margins of prominent linear markings (triple bands) on Europa are diffuse, suggesting that material has been vented from fractures. Numerous small circular craters indicate localized areas of relatively old surface. Pervasive brittle deformation of an ice layer appears to have formed grooves on Ganymede. Dark terrain unexpectedly shows distinctive albedo variations to the limit of resolution. C1 BROWN UNIV,DEPT GEOL SCI,PROVIDENCE,RI 02912. CALTECH,DEPT GEOL & PLANETARY SCI,PASADENA,CA 91125. ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. CALTECH,JET PROP LAB,PASADENA,CA 91109. CORNELL UNIV,DEPT ASTRON,ITHACA,NY 14853. US GEOL SURVEY,MENLO PK,CA 94025. SW RES INST,BOULDER,CO 80302. ITTRES LTD,CALGARY,AB T1Y 5Z6,CANADA. DEUTSCH FORSCH ANSTALT LUFT & RAUMFAHRT,INST PLANETARY EXPLORAT,BERLIN,GERMANY. NASA,WASHINGTON,DC 20546. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. MAX PLANCK INST AERON,LINDAU,GERMANY. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Belton, MJS (reprint author), NATL OPT ASTRON OBSERV,950 N CHERRY AVE,TUCSON,AZ 85719, USA. OI Banfield, Don/0000-0003-2664-0164 NR 67 TC 105 Z9 105 U1 3 U2 8 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 377 EP 385 PG 9 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300040 ER PT J AU Carlson, R Smythe, W Baines, K Barbinis, E Becker, K Burns, R Calcutt, S Calvin, W Clark, R Danielson, G Davies, A Drossart, P Encrenaz, T Fanale, F Granahan, J Hansen, G Herrera, P Hibbitts, C Hui, J Irwin, P Johnson, T Kamp, L Kieffer, H Leader, F Lellouch, E LopesGautier, R Matson, D McCord, T Mehlman, R Ocampo, A Orton, G RoosSerote, M Segura, M Shirley, J Soderblom, L Stevenson, A Taylor, F Torson, J Weir, A Weissman, P AF Carlson, R Smythe, W Baines, K Barbinis, E Becker, K Burns, R Calcutt, S Calvin, W Clark, R Danielson, G Davies, A Drossart, P Encrenaz, T Fanale, F Granahan, J Hansen, G Herrera, P Hibbitts, C Hui, J Irwin, P Johnson, T Kamp, L Kieffer, H Leader, F Lellouch, E LopesGautier, R Matson, D McCord, T Mehlman, R Ocampo, A Orton, G RoosSerote, M Segura, M Shirley, J Soderblom, L Stevenson, A Taylor, F Torson, J Weir, A Weissman, P TI Near-infrared spectroscopy and spectral mapping of Jupiter and the Galilean satellites: Results from Galileo's initial orbit SO SCIENCE LA English DT Article ID MU-M; 5-MU-M; WATER; BELT AB The Near Infrared Mapping Spectrometer performed spectral studies of Jupiter and the Galilean satellites during the June 1996 perijove pass of the Galileo spacecraft. Spectra for a 5-micrometer hot spot on Jupiter are consistent with the absence of a significant water cloud above 8 bars and with a depletion of water compared lo that predicted for solar composition, corroborating results from the Galileo probe. Great Red Spot (GRS) spectral images show that parts of this feature extend upward to 240 millibars, although considerable altitude-dependent structure is found within it. A ring of dense clouds surrounds the GRS and is lower than it by 3 to 7 kilometers. Spectra of Callisto and Ganymede reveal a feature at 4.25 micrometers, attributed to the presence of hydrated minerals or possibly carbon dioxide on their surfaces. Spectra of Europa's high latitudes imply that fine-grained water frost overlies larger grains. Several active volcanic regions were found on lo, with temperatures of 420 to 620 kelvin and projected areas of 5 to 70 square kilometers. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095. UNIV OXFORD,DEPT ATMOSPHER OCEAN & PLANETARY SCI,OXFORD OX1 3PU,ENGLAND. US GEOL SURVEY,FLAGSTAFF,AZ 86001. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. US GEOL SURVEY,DENVER,CO 80225. OBSERV PARIS,F-92150 MEUDON,FRANCE. UNIV HAWAII,HAWAII INST GEOPHYS & PLANETOL,HONOLULU,HI 96822. RP Carlson, R (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Lopes, Rosaly/D-1608-2016; Hibbitts, Charles/B-7787-2016; OI Lopes, Rosaly/0000-0002-7928-3167; Hibbitts, Charles/0000-0001-9089-4391; Calcutt, Simon/0000-0002-0102-3170; Irwin, Patrick/0000-0002-6772-384X NR 25 TC 106 Z9 106 U1 1 U2 7 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 385 EP 388 DI 10.1126/science.274.5286.385 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300041 PM 8832878 ER PT J AU Orton, GS Spencer, JR Travis, LD Martin, TZ Tamppari, LK AF Orton, GS Spencer, JR Travis, LD Martin, TZ Tamppari, LK TI Galileo photopolarimeter-radiometer observations of Jupiter and the Galilean satellites SO SCIENCE LA English DT Article AB Photopolarimeter-Radiometer (PPR) maps of daytime temperatures on Ganymede at a resolution of 220 kilometers show the expected anticorrelation with albedo, but morning temperatures were about 10 kelvin warmer than expected. Europa had a subsolar temperature of 128 kelvin and a lower effective thermal inertia than either Ganymede or Callisto, and Io's night side was cooler than predicted by recent models, perhaps requiring revision of heat-flow estimates. The lowest 250-millibar temperatures in the Great Red Spot (GRS) generally corresponded to the visually darkest regions, Temperatures remained cold north of the GRS, but they rose by as much as 6 kelvin to the south over the 2800-kilometer PPR resolution. A visually bright region northwest of the GRS was also relatively cold. It is likely that NH3 clouds affected the determination of the 500-millibar temperature field, which appears qualitatively different. C1 LOWELL OBSERV,FLAGSTAFF,AZ 86001. NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,NEW YORK,NY 10025. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Orton, GS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 12 TC 34 Z9 34 U1 0 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 389 EP 391 DI 10.1126/science.274.5286.389 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300042 ER PT J AU Gurnett, DA Kurth, WS Roux, A Bolton, SJ Kennel, CF AF Gurnett, DA Kurth, WS Roux, A Bolton, SJ Kennel, CF TI Galileo plasma wave observations in the Io plasma torus and near Io SO SCIENCE LA English DT Article ID RADIO ASTRONOMY OBSERVATIONS; VOYAGER-1; JUPITER AB The Galileo plasma wave instrument detected jovian radio emissions, narrowband upper hybrid waves, and whistler-mode emissions during the inbound pass through the to torus. The upper hybrid waves provided an accurate profile of electron density through the Io torus and in the vicinity of Io. These measurements show that the torus density has increased by about a factor of 2 since the Voyager 1 flyby in 1979. A well-defined peak in the electron density was observed in the wake of to, with densities as high as about 4 x 10(4) per cubic centimeter. C1 UNIV VERSAILLES ST QUENTIN,CTR ETUD ENVIRONM TERR & PLANETAIRES,VELIZY VILLACOUBL,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV CALIF LOS ANGELES,OFF CHANCELLOR,LOS ANGELES,CA 90025. RP Gurnett, DA (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242, USA. OI Kurth, William/0000-0002-5471-6202 NR 25 TC 109 Z9 110 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 391 EP 392 DI 10.1126/science.274.5286.391 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300043 ER PT J AU Garrard, TL Stone, EC Murphy, N AF Garrard, TL Stone, EC Murphy, N TI Effects of absorption by Io on composition of energetic heavy ions SO SCIENCE LA English DT Article AB The Galileo heavy ion counter is sensitive to ions with atomic numbers Z greater than or equal to 6 and energies greater than similar to 6 MeV per nucleon, During Galileo's passage through Jupiter's inner magnetosphere, the observed composition of these heavy ions was consistent with the presence of singly ionized iogenic. O, Na, and S and highly ionized solar C, O, and Ne. The solar component is absorbed more strongly by Io because its gyroradius is smaller than Io's diameter. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Garrard, TL (reprint author), CALTECH,SPACE RADIAT LAB,PASADENA,CA 91125, USA. NR 10 TC 9 Z9 9 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 393 EP 394 DI 10.1126/science.274.5286.393 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300044 PM 8832881 ER PT J AU Frank, LA Paterson, WR Ackerson, KL Vasyliunas, VM Coroniti, FV Bolton, SJ AF Frank, LA Paterson, WR Ackerson, KL Vasyliunas, VM Coroniti, FV Bolton, SJ TI Plasma observations at Io with the Galileo spacecraft SO SCIENCE LA English DT Article ID ATMOSPHERE AB Plasma measurements made during the flyby of Io on 7 December 1995 with the Galileo spacecraft plasma analyzers reveal that the spacecraft unexpectedly passed directly through the ionosphere of Io. The ionosphere is identified by a dense plasma that is at rest with respect to Io. This plasma is cool relative to those encountered outside the ionosphere. The composition of the ionospheric plasmas includes O++, O+ and S++, S+, and SO2+ ions. The plasma conditions at Io appear to account for the decrease in the magnetic field, without the need to assume that Io has a magnetized interior. C1 MAX PLANCK INST AERON,D-3411 KATLENBURG DUHM,GERMANY. UNIV CALIF LOS ANGELES,DEPT PHYS & ASTRON,LOS ANGELES,CA 90095. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Frank, LA (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242, USA. RI Paterson, William/F-5684-2012 NR 18 TC 164 Z9 166 U1 1 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 394 EP 395 DI 10.1126/science.274.5286.394 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300045 PM 8832882 ER PT J AU Kivelson, MG Khurana, KK Walker, RJ Warnecke, J Russell, CT Linker, JA Southwood, DJ Polanskey, C AF Kivelson, MG Khurana, KK Walker, RJ Warnecke, J Russell, CT Linker, JA Southwood, DJ Polanskey, C TI Io's interaction with the plasma torus: Galileo magnetometer report SO SCIENCE LA English DT Article ID FLOW PAST IO; MHD SIMULATION; ALFVEN; SODIUM; PICKUP; ENERGY AB Galileo magnetometer data at 0.22-second resolution reveal a complex interaction between Io and the flowing plasma of the Io torus. The highly structured magnetic field depression across the downstream wake, although consistent with a magnetized Io, is modified by sources of currents within the plasma that introduce ambiguity into the interpretation of the signature. Highly monochromatic ion cyclotron waves appear to be correlated with the local neutral particle density. The power peaks in the range of molecular ion gyrofrequencies, suggesting that molecules from Io can remain undissociated over a region of more than 15 Io radii around Io. C1 SCI APPLICAT INT CORP,SAN DIEGO,CA 92171. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT PHYS,LONDON SW7 2BZ,ENGLAND. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Kivelson, MG (reprint author), UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90025, USA. RI Kivelson, Margaret/I-9019-2012; OI Kivelson, Margaret/0000-0003-3859-8581; Russell, Christopher/0000-0003-1639-8298 NR 26 TC 140 Z9 141 U1 1 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 396 EP 398 DI 10.1126/science.274.5286.396 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300046 ER PT J AU Grun, E Hamilton, DP Riemann, R Dermott, S Fechtig, H Gustafson, BA Hanner, MS Heck, A Horanyi, M Kissel, J Kruger, H Lindblad, BA Linkert, D Linkert, G Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R Zook, HA AF Grun, E Hamilton, DP Riemann, R Dermott, S Fechtig, H Gustafson, BA Hanner, MS Heck, A Horanyi, M Kissel, J Kruger, H Lindblad, BA Linkert, D Linkert, G Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R Zook, HA TI Dust measurements during Galileo's approach to Jupiter and Io encounter SO SCIENCE LA English DT Article ID ULYSSES; EJECTION; GRAINS AB About a hundred dust impacts per day were detected during the first week in December 1995 by Galileo during its approach to Jupiter, These impacts were caused by submicrometer-sized particles that were just above the detection limit. After the closest approach to Io on 7 December, impacts of these small particles ceased, This effect is expected for dust grains emitted from Io that exit the field of view of the instrument after the flyby. The impact rate of bigger micrometer-sized dust grains continued to increase toward Jupiter. These dust particles are in orbit about Jupiter or are interplanetary grains that are gravitationally concentrated near Jupiter. C1 UNIV MARYLAND,COLLEGE PK,MD 20742. UNIV FLORIDA,GAINESVILLE,FL 32611. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. LUND OBSERV,S-22100 LUND,SWEDEN. UNIV KENT,CANTERBURY CT2 7NR,KENT,ENGLAND. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. EUROPEAN SPACE AGCY,EUROPEAN SPACE RES & TECHNOL CTR,NL-2200 AG NOORDWIJK,NETHERLANDS. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Grun, E (reprint author), MAX PLANCK INST KERNPHYS,SAUPFERCHECKWEG 1,D-69117 HEIDELBERG,GERMANY. RI Gustafson, Bo/B-9526-2011; OI Horanyi, Mihaly/0000-0002-5920-9226 NR 14 TC 23 Z9 23 U1 0 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 399 EP 401 DI 10.1126/science.274.5286.399 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300047 ER PT J AU Clarke, JT Ballester, GE Trauger, J Evans, R Connerney, JEP Stapelfeldt, K Crisp, D Feldman, PD Burrows, CJ Casertano, S Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Meadows, V Mould, JR Scowen, PA Watson, AM Westphal, JA AF Clarke, JT Ballester, GE Trauger, J Evans, R Connerney, JEP Stapelfeldt, K Crisp, D Feldman, PD Burrows, CJ Casertano, S Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Meadows, V Mould, JR Scowen, PA Watson, AM Westphal, JA TI Far-ultraviolet imaging of Jupiter's aurora and the Io ''footprint'' SO SCIENCE LA English DT Article ID HUBBLE-SPACE-TELESCOPE; WAVE CURRENT SYSTEM; H-3+ EMISSIONS; JOVIAN AURORA; POLAR AURORA; MU-M; MORPHOLOGY; IMAGES; UV; ENCOUNTER AB Far-ultraviolet images of Jupiter from the Hubble Space Telescope Wide Field Planetary camera 2 reveal polar auroral emissions at 300 kilometer resolution and three times higher sensitivity than previously achieved. Persistent features include a main oval containing most of the emission and magnetically connected to the middle magnetosphere, diffuse and variable emissions poleward of the main oval, and discrete emission from Io's magnetic footprint equatorward of the oval. The auroral emissions are variable, exhibit magnetic conjugacy, and are visible above the planet limb. All emissions approximately co-rotate with Jupiter except the Io ''footprint,'' which is fixed along Io's magnetic flux tube. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. ARIZONA STATE UNIV,DEPT ASTRON,TEMPE,AZ 85287. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA. RP Clarke, JT (reprint author), UNIV MICHIGAN,SPACE PHYS RES LAB,ANN ARBOR,MI 48109, USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013; connerney, john/I-5127-2013 NR 51 TC 148 Z9 148 U1 1 U2 11 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 404 EP 409 DI 10.1126/science.274.5286.404 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300049 ER PT J AU Ballester, GE Clarke, JT Trauger, JT Harris, WM Stapelfeldt, KR Crisp, D Evans, RW Burgh, EB Burrows, CJ Casertano, S Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Meadows, V Mould, JR Sahai, R Scowen, PA Watson, AM Westphal, JA AF Ballester, GE Clarke, JT Trauger, JT Harris, WM Stapelfeldt, KR Crisp, D Evans, RW Burgh, EB Burrows, CJ Casertano, S Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Meadows, V Mould, JR Sahai, R Scowen, PA Watson, AM Westphal, JA TI Time-resolved observations of Jupiter's far-ultraviolet aurora SO SCIENCE LA English DT Article ID HUBBLE-SPACE-TELESCOPE; COMET SHOEMAKER-LEVY-9; JOVIAN AURORA; MU-M; ENCOUNTER; EMISSIONS; NORTH; IUE; UV; PRECIPITATION AB Simultaneous imaging and spectroscopic observations of Jupiter's far-ultraviolet aurora covering half a jovian rotation were made on 31 May 1994, The Hubble Space Telescope Wide Field Planetary Camera 2 images revealed dramatic and rapidly changing auroral features, including discrete longitudinal structures along the auroral ovals, with variable contrast; a poleward offset in a north oval sector, showing equatorward motion near dusk; emissions polewards of the ovals, apparently co-rotating; and a bright event developing near the dawn limb. Viewing geometry effects explain the rotational intensity modulation observed by the International Ultraviolet Explorer, without intrinsic longitudinal asymmetries. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. ARIZONA STATE UNIV,DEPT ASTRON,TEMPE,AZ 85287. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. RP Ballester, GE (reprint author), UNIV MICHIGAN,SPACE PHYS RES LAB,ANN ARBOR,MI 48109, USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 38 TC 61 Z9 61 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 18 PY 1996 VL 274 IS 5286 BP 409 EP 413 DI 10.1126/science.274.5286.409 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN173 UT WOS:A1996VN17300050 ER PT J AU Mumma, MJ AF Mumma, MJ TI Comets - Hyakutake's interstellar ices SO NATURE LA English DT Editorial Material ID DELIVERY RP Mumma, MJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI mumma, michael/I-2764-2013 NR 16 TC 16 Z9 16 U1 0 U2 3 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD OCT 17 PY 1996 VL 383 IS 6601 BP 581 EP 582 DI 10.1038/383581a0 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VM755 UT WOS:A1996VM75500032 PM 8857530 ER PT J AU Brooke, TY Tokunaga, AT Weaver, HA Crovisier, J BockeleeMorvan, D Crisp, D AF Brooke, TY Tokunaga, AT Weaver, HA Crovisier, J BockeleeMorvan, D Crisp, D TI Detection of acetylene in the infrared spectrum of comet Hyakutake SO NATURE LA English DT Article ID CHEMICAL-MODELS; MOLECULES; FLUORESCENCE; ATMOSPHERES; RESOLUTION; HALLEY; GAS AB COMETS are rich in volatile materials, of which roughly 80% (by number) are mater molecules(1). Considerable progress(2-4) being made in identifying the other volatile species, the abundances of which should enable us to determine whether comets formed primarily from ice-covered interstellar grains(5), or from material that was chemically processed in the early solar nebula(6,7). Here we report the detection of acetylene (C2H2,) in the infrared spectrum of comet C/1996 B2 (Hyakutake). The estimated abundance is 0.3-0.9%, relative to water, which is comparable to the predicted solid-phase abundance in cold interstellar clouds. This suggests that the volatiles in comet Hyakotake may have come from ice-covered interstellar grains, rather than material processed in the accretion disk out of which the Solar System formed. C1 UNIV HAWAII, INST ASTRON, HONOLULU, HI 96822 USA. JOHNS HOPKINS UNIV, DEPT PHYS & ASTRON, BALTIMORE, MD 21218 USA. OBSERV PARIS, F-92195 MEUDON, FRANCE. RP Brooke, TY (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, M-S 169-237, PASADENA, CA 91109 USA. RI Weaver, Harold/D-9188-2016 NR 29 TC 106 Z9 106 U1 1 U2 7 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD OCT 17 PY 1996 VL 383 IS 6601 BP 606 EP 608 DI 10.1038/383606a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VM755 UT WOS:A1996VM75500047 PM 8857534 ER PT J AU Mack, WJ Hodis, HN LaBree, L Liu, CR Liu, CH Selzer, RH AF Mack, WJ Hodis, HN LaBree, L Liu, CR Liu, CH Selzer, RH TI Progression of carotid intima-media thickness correlates with angiographic progression of coronary SO CIRCULATION LA English DT Meeting Abstract C1 UNIV SO CALIF,LOS ANGELES,CA 90089. CALTECH,JET PROP LAB,PASADENA,CA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER HEART ASSOC PI DALLAS PA 7272 GREENVILLE AVENUE, DALLAS, TX 75231-4596 SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 15 PY 1996 VL 94 IS 8 SU S BP 709 EP 709 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA VN119 UT WOS:A1996VN11900707 ER PT J AU Hodis, HN Mack, WJ LaBree, L Liu, CR Liu, CH Selzer, RH AF Hodis, HN Mack, WJ LaBree, L Liu, CR Liu, CH Selzer, RH TI Progression of carotid artery intima-media thickness and coronary artery disease comparably predict clinical coronary events SO CIRCULATION LA English DT Meeting Abstract C1 UNIV SO CALIF,SCH MED,LOS ANGELES,CA 90089. CALTECH,JET PROP LAB,PASADENA,CA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER HEART ASSOC PI DALLAS PA 7272 GREENVILLE AVENUE, DALLAS, TX 75231-4596 SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 15 PY 1996 VL 94 IS 8 SU S BP 710 EP 710 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA VN119 UT WOS:A1996VN11900708 ER PT J AU David, M Hathorn, B McAllister, HAH Bearman, G Krabach, T Casscells, WS Willerson, JT AF David, M Hathorn, B McAllister, HAH Bearman, G Krabach, T Casscells, WS Willerson, JT TI Atherosclerotic plaque thermography - A new approach to the diagnosis of unstable plaques SO CIRCULATION LA English DT Meeting Abstract C1 UNIV TEXAS,SCH MED,HOUSTON,TX. TEXAS HEART INST,HOUSTON,TX 77025. NASA,JET PROP LAB,PASADENA,CA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER HEART ASSOC PI DALLAS PA 7272 GREENVILLE AVENUE, DALLAS, TX 75231-4596 SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 15 PY 1996 VL 94 IS 8 SU S BP 4154 EP 4154 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA VN119 UT WOS:A1996VN11904145 ER PT J AU Joshi, MM Lawrence, BN Lewis, SR AF Joshi, MM Lawrence, BN Lewis, SR TI The effect of spatial variations in unresolved topography on gravity wave drag in the Martian atmosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ZONAL-MEAN CIRCULATION; MIDDLE ATMOSPHERE; MARS; MODEL AB Recent three dimensional simulations of the Martian atmosphere have shown that gravity wave drag is a large, and possibly dominant, term in the momentum balance above 50 km. In previous simulations, a constant value was used for the topographic variance on scales smaller than the model grid. Spatial variations in this quantity are now taken into account, and the results described. The topographic variance has its highest amplitude in the Tharsis and Hellas regions. Correspondingly, relatively low breaking levels are found here. Longitudinal variations in breaking levels and hence accelerations are very large, as are zonal asymmetries in zonal wind u. These asymmetries are expected to play a role in planetary wave propagation in the Martian middle atmosphere. Momentum balances are found to be dependent on nonlinear coupling terms in the momentum equations due to the high zonal winds and small planetary radius. At the equinoxes two regimes exist. One is where breaking levels are very low: here accelerations and eddy diffusion coefficients resulting from the parameterization of gravity wave breaking in the model are also very low. The other regime is where breaking levels are higher, and winds are stronger. In this region, vertical mixing is also very weak. These results give further credence to the idea that breaking thermal tides cause the intense vertical diffusion that has been inferred from observations at the Martian equinox. C1 UNIV OXFORD,DEPT PHYS,CLARENDON LAB,OXFORD OX1 3PU,ENGLAND. RP Joshi, MM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245-3,MOFFETT FIELD,CA 94035, USA. RI Joshi, Manoj/C-1795-2008; OI Joshi, Manoj/0000-0002-2948-2811; Lawrence, Bryan/0000-0001-9262-7860; Lewis, Stephen/0000-0001-7237-6494 NR 15 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1996 VL 23 IS 21 BP 2927 EP 2930 DI 10.1029/96GL02758 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VM610 UT WOS:A1996VM61000016 ER PT J AU Chandra, S Froidevaux, L Waters, JW White, OR Rottman, GJ Prinz, DK Brueckner, GE AF Chandra, S Froidevaux, L Waters, JW White, OR Rottman, GJ Prinz, DK Brueckner, GE TI Ozone variability in the upper stratosphere during the declining phase of the solar cycle 22 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MIDDLE ATMOSPHERE; RECENT TRENDS; NIMBUS-7; INSTRUMENT; MODEL; SBUV AB Recent studies of the solar cycle variation of ozone have shown that the response of ozone in the upper stratosphere to solar UV variation, as inferred from the SBUV (Solar Backscatter Ultraviolet) type measurements, is about a factor of two greater than estimated from 2-D photochemical models. Because of potential errors in accounting for the long term instrument drift in the SBUV type of measurements, the significance of this discrepancy is difficult to quantify. In this paper, ozone measurements from the Microwave Limb Sounder (MLS) and the solar irradiance measurements from the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) and the Solar Ultraviolet Irradiance Monitor (SUSIM) onboard the Upper Atmosphere Research Satellite (UARS) are analyzed to estimate the upper stratosphere ozone response to changes in the solar UV irradiance. During the three year period of UARS measurements, analyzed here for the declining phase of the solar cycle 22, the solar irradiance in the 200-205 nm range decreased by about 5 % from a near solar maximum to a near solar minimum level. During the same period, ozone mixing ratio measured from the MLS instrument decreased by about 2-4 % in the 0.7-3 hPa region. In the upper stratosphere, the general characateristics of the MLS time series are similar to those inferred from the NOAA-11 SBUV/2 measurements. The SBUV/2 trends above 1.5 hPa, however, are significantly greater than those derived from the MLS data. The UARS data suggest that the long term solar UV response of ozone in the upper stratosphere is underestimated by 2-D photochemical models as in previous studies based on the SBUV type measurements. C1 CALTECH,JET PROP LAB,PASADENA,CA. NCAR,HIGH ALTITUDE OBSERV,BOULDER,CO. USN,RES LAB,WASHINGTON,DC 20375. RP Chandra, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA. NR 21 TC 13 Z9 13 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1996 VL 23 IS 21 BP 2935 EP 2938 DI 10.1029/96GL02760 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VM610 UT WOS:A1996VM61000018 ER PT J AU Stone, EM Randel, WJ Stanford, JL Read, WG Waters, JW AF Stone, EM Randel, WJ Stanford, JL Read, WG Waters, JW TI Baroclinic wave variations observed in MLS upper tropospheric water vapor SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOUTHERN-HEMISPHERE SUMMER; LIFE-CYCLES; TOTAL OZONE AB Upper tropospheric water vapor measurements from the UARS Microwave Limb Sounder are used to investigate the structure and evolution of eastward traveling medium-scale wave features in Southern Hemisphere summertime. The extratropical Southern Hemisphere summer circulation pattern is frequently dominated by medium scale waves which exhibit life cycles of baroclinic growth and barotropic decay. The water vapor field during such life cycles is examined here and found to be well correlated with meteorological fields derived from European Centre for Medium Range Weather Forecasts global analyses. From mid January to mid February 1992 several episodes of growth and decay in the amplitude of eastward traveling waves are found in the water vapor and meteorological data at levels of the upper troposphere, with zonal waves four, five and six being predominant modes. The water vapor data are compared with derived potential vorticity (PV) fields, with strong anticorrelation observed in middle and high latitudes. The results are consistent with model paradigms for the structure and evolution of baroclinic disturbances, coupled with the known characteristics of high PV and low water vapor mixing ratios in lower stratospheric air. parcels and the reverse for upper tropospheric air. C1 IOWA STATE UNIV,DEPT PHYS & ASTRON,AMES,IA 50011. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Stone, EM (reprint author), NAT CTR ATMOSPHER RES,BOULDER,CO 80307, USA. RI Randel, William/K-3267-2016 OI Randel, William/0000-0002-5999-7162 NR 19 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1996 VL 23 IS 21 BP 2967 EP 2970 DI 10.1029/96GL02576 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VM610 UT WOS:A1996VM61000026 ER PT J AU Lau, KM Ho, CH Chou, MD AF Lau, KM Ho, CH Chou, MD TI Water vapor and cloud feedback over the tropical oceans: Can we use ENSO as a surrogate for climate change? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SEA-SURFACE TEMPERATURE; OBSERVED DEPENDENCE; RADIATION AB Based on experiments with the Goddard Earth Observing System (GEOS) global climate model, we find that the basic patterns of anomalous water vapor greenhouse effect and cloud radiative forcing during ENSO are primarily determined by the basin-wide dynamical response to large scale sea surface temperature (SST) forcing, There is no supergreenhouse effect in the sense of unstable interaction due to local thermodynamics and water vapor radiative feedback on interannual time scales. About 80% of the clear sky water vapor greenhouse sensitivity to SST deduced from ENSO anomalies are due to the transport of water vapor by the large scale circulation, The sensitivity of water vapor greenhouse effect to SST due to radiative feedback is found to be about 1.8 Wm(-2)/degrees C, much smaller than the values of 6-9 Wm(-2)/degrees C previously estimated from satellite observations from ENSO conditions, Our results show that regionally based interannual variability should not be used to infer radiative feedback sensitivity for climate change unless propel corrections are made for the effect of the large scale circulation. RP Lau, KM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CLIMATE & RADIAT BRANCH,GREENBELT,MD 20771, USA. RI Ho, Chang-Hoi/H-8354-2015 NR 9 TC 29 Z9 29 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1996 VL 23 IS 21 BP 2971 EP 2974 DI 10.1029/96GL02414 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VM610 UT WOS:A1996VM61000027 ER PT J AU Bills, BG James, TS AF Bills, BG James, TS TI Late quaternary variations in relative sea level due to glacial cycle polar wander SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EARTHS ROTATION; MANTLE VISCOSITY; HUDSON-BAY; TIDE; FLUCTUATIONS; CONSTRAINTS; PLEISTOCENE; REGION AB Growth and decay of continental ice sheets can excite significant motion of the Earth's rotation pole and cause a complex spatio-temporal pattern of changes in relative sea level. These two effects have generally been considered separately, but may interact in important ways. In particular, a simple model of the melting of the Laurentide ice sheet causes a uniform eustatic sea level rise of 55 m, and also induces a motion of the rotation pole by 0.1 to 1 degree, depending on viscosity structure in the mantle. This motion produces a secular pole tide, which is a spherical harmonic degree 2, order 1 component of the relative sea level pattern, with peak-to-peak amplitude of 20 to 40 m. The maximum effect is along the great circle passing through the path of the pole and at latitudes of +/-45 degrees. This secular pole tide has been ignored in most previous attempts to estimate from global patterns of relative sea level change. It has a large influence along the East coast of North America and the West coast of South America, and significantly contributes to present day rates of relative sea level change. C1 GEOL SURVEY CANADA, OTTAWA, ON K1A 0Y3, CANADA. RP Bills, BG (reprint author), NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RI Bills, Bruce/C-1156-2008; James, Thomas/D-9301-2013 OI James, Thomas/0000-0001-7321-047X NR 27 TC 21 Z9 21 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 OCT 15 PY 1996 VL 23 IS 21 BP 3023 EP 3026 DI 10.1029/96GL02886 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VM610 UT WOS:A1996VM61000040 ER PT J AU Caillat, T Borshchevsky, A Fleurial, JP AF Caillat, T Borshchevsky, A Fleurial, JP TI Properties of single crystalline semiconducting CoSb3 SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID TRANSPORT AB A study of the thermoelectric properties of the skutterudite compound CoSb3 was carried out on single crystals grown by the Bridgman gradient freeze technique. p- and n-type samples were obtained over a wide range of carrier concentration, Undoped As-grown crystals show p-type conductivity while n-type samples were obtained by addition of Te or Pd. Samples were characterized by x-ray diffractometry, electron microprobe analysis, and density measurements. The physical properties of CoSb, such as Linear thermal expansion coefficient, sound velocity, and Debye temperature were also determined and are presented. Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect measurements were performed between room temperature and about 900 K, Exceptionally high Hall mobilities were obtained on p-type samples with a maximum room-temperature Hall mobility of 3300 cm(2) V-1 s(-1) at a carrier concentration of 1 x 10(17) cm(-3). The results of the transport property measurements are discussed and an in agreement with some recent predictions based on band structure calculations, The potential of CoSb3 for thermoelectric applications is evaluated. (C) 1996 American Institute of Physics. RP Caillat, T (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 277-207, PASADENA, CA 91109 USA. NR 22 TC 403 Z9 417 U1 18 U2 136 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD OCT 15 PY 1996 VL 80 IS 8 BP 4442 EP 4449 DI 10.1063/1.363405 PG 8 WC Physics, Applied SC Physics GA VM272 UT WOS:A1996VM27200031 ER PT J AU Anderson, WK Rausch, RD Bonhaus, DL AF Anderson, WK Rausch, RD Bonhaus, DL TI Implicit/multigrid algorithms for incompressible turbulent flows on unstructured grids SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID COMPUTATIONS; EQUATIONS; SOLVERS; MESHES AB An implicit code for computing inviscid and viscous incompressible flows on unstructured grids is described. The foundation of the code is a backward Euler time discretization for which the linear system is approximately solved at each time step with either a point implicit method or a preconditioned generalized minimal residual (GMRES) technique. For the GMRES calculations, several techniques are investigated for forming the matrix-vector product. Convergence acceleration is achieved through a multigrid scheme that uses nonnested coarse grids that are generated using a technique described in the present paper. Convergence characteristics are investigated and results are compared with an exact solution for the inviscid flow over a four-element airfoil. Viscous results, which are compared with experimental data, include the turbulent flow over a NACA 4412 airfoil, a three-element airfoil for which Mach number effects are investigated, and three-dimensional flow over a wing with a partial-span flap. (C) 1996 Academic Press, Inc. C1 LOCKHEED ENGN & SCI CO,HOUSTON,TX 77058. RP Anderson, WK (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 56 TC 80 Z9 80 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD OCT 15 PY 1996 VL 128 IS 2 BP 391 EP 408 DI 10.1006/jcph.1996.0219 PG 18 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA VN964 UT WOS:A1996VN96400011 ER PT J AU Cane, MA Kaplan, A Miller, RN Tang, BY Hackert, EC Busalacchi, AJ AF Cane, MA Kaplan, A Miller, RN Tang, BY Hackert, EC Busalacchi, AJ TI Mapping tropical Pacific sea level: Data assimilation via a reduced state space Kalman filter SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID METEOROLOGICAL DATA ASSIMILATION; EQUATORIAL OCEAN MODEL; EL-NINO; VARIATIONAL ASSIMILATION; SURFACE TOPOGRAPHY; GULF-STREAM; WIND STRESS; XBT DATA; VARIABILITY; COVARIANCES AB The well-known fact that tropical sea level can be usefully simulated by linear wind driven models recommends it as a realistic test problem for data assimilation schemes. Here we report on an assimilation of monthly data for the period 1975-1992 from 34 tropical Pacific tide gauges into such a model using a Kalman filter. We present an approach to the Kalman filter that uses a reduced state space representation for the required error covariance matrices. This reduction makes the calculation highly feasible. We argue that a more complete representation will be of no value in typical oceanographic practice, that in principle it is unlikely to be helpful, and that it may even be harmful if the data coverage is sparse, the usual case in oceanography. This is in part a consequence of ignorance of the correct error statistics for the data and model, but only in part. The reduced state space is obtained from a truncated set of multivariate empirical orthogonal functions (EOFs) derived from a long model run without assimilation. The reduced state space filter is compared with a full grid point Kalman filter using the same dynamical model for the period 1979-1985, assimilating eight tide guage stations and using an additional seven for verification [Miller et al., 1995]. Results are not inferior to the full grid point filter, even when the reduced filter retains only nine EOFs. Five sets of reduced space filter assimilations are run with all tide gauge data for the period 1975-1992. In each set a different number of EOFs is retained: 5, 9, 17, 32, and 93, accounting for 60, 70, 80, 90, and 99% of the model variance, respectively. Each set consists of 34 runs, in each of which one station is withheld for verification. Comparing each set to the nonassimilation run, the average rms error at the withheld stations decreases by more than 1 cm. The improvement is generally larger for the stations at lowest latitudes. Increasing the number of EOFs increases agreement with data at locations where data are assimilated; the added structures allow better fits locally. In contrast, results at withheld stations are almost insensitive to the number of EOFs retained. We also compare the Kalman filter theoretical error estimates with the actual errors of the assimilations. Features agree on average, but not in detail, a reminder of the fact that the quality of theoretical estimates is limited by the quality of error models they assume. We briefly discuss the implications of our work for future studies, including the application of the method to full ocean general circulation models and coupled models. C1 NASA,GODDARD SPACE FLIGHT CTR,HYDROSPHER PROC LAB,GREENBELT,MD 20771. HUGHES STX CORP,LANHAM,MD 20706. OREGON STATE UNIV,COLL OCEAN & ATMOSPHER SCI,CORVALLIS,OR 97331. UNIV VICTORIA,CTR EARTH & OCEAN SCI,VICTORIA,BC V8W 262,CANADA. RP Cane, MA (reprint author), COLUMBIA UNIV,LAMONT DOHERTY GEOL OBSERV,PALISADES,NY 10964, USA. RI Hackert, Eric/A-9915-2011; Cane, Mark/I-8086-2012 NR 45 TC 125 Z9 126 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD OCT 15 PY 1996 VL 101 IS C10 BP 22599 EP 22617 DI 10.1029/96JC01684 PG 19 WC Oceanography SC Oceanography GA VM834 UT WOS:A1996VM83400008 ER PT J AU Mitchell, DL Macke, A Liu, YG AF Mitchell, DL Macke, A Liu, YG TI Modeling cirrus clouds .2. Treatment of radiative properties SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID PARTICLE-SIZE SPECTRA; ICE CRYSTALS; PARAMETERIZATION; SCATTERING; EVOLUTION; MICROPHYSICS; EXTINCTION; AIRCRAFT; GROWTH; LIGHT AB A new radiation scheme, suitable for two-stream radiation transfer models, was developed for cirrus clouds. Analytical expressions were derived for the extinction and absorption coefficients and the asymmetry parameter. These are functions of the ice particle size distribution parameters, ice particle shapes, and wavelength. The ice particle shapes considered were hexagonal plates and columns, bullet rosettes, and planar polycrystals. These appear to be the principal crystal types found in cirrus clouds. The formulation of radiative properties accounts for the size distribution projected area and the distance radiation travels through ice particles. For absorption, refraction and internal reflection of radiation were parameterized. By assuming an idealized cirrus cloud, the dependence of the single scatter albedo, reflectance, and emissivity on wavelength, ice particle shape, and size distribution was demonstrated. Reflectance and emissivity exhibited a strong dependence on ice particle shape, with planar polycrystals and bullet rosettes often being twice or more reflective than hexagonal columns and plates. The radiation scheme was tested with microphysical and radiation measurements from two cirrus cloud field studies. It was shown for both case studies that, by matching observed and predicted albedo-emissivity curves, the radiation scheme could predict the observed mean ice particle size and ice water path (IWP), provided the dominant ice particle shape was known or inferred. Retrieved IWP values differed from measurement-derived values by less than or equal to 15% for the first case study and 18% on average for the second case study. Hence, it may be feasible to retrieve realistic IWP estimates from satellite data for a given ice particle shape. Other radiation schemes have not been able to explain the second case study, which was characterized by relatively high albedos. These high albedos appeared to result from unusually small hexagonal plate crystals having asymmetry parameter values similar to those of cloud droplets. An improved treatment of the asymmetry parameter was not the primary reason for the good agreement between theory and observations. Rather, key factors appeared to be improved treatments of ice particle photon path, projected area and mass, and the omission of certain physical processes included in Mie theory that may not be appropriate for ice particles. The radiative properties were predicted from analytical expressions, making this scheme useful for predicting radiative properties in large-scale models without excessive increases in computation time. C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RP Mitchell, DL (reprint author), UNIV & COMMUNITY COLL SYST NEVADA,DESERT RES INST,POB 60220,RENO,NV 89506, USA. RI Liu, Yangang/H-6154-2011 NR 43 TC 122 Z9 124 U1 1 U2 8 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD OCT 15 PY 1996 VL 53 IS 20 BP 2967 EP 2988 DI 10.1175/1520-0469(1996)053<2967:MCCPIT>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VP767 UT WOS:A1996VP76700007 ER PT J AU Godon, P AF Godon, P TI Non-reflective boundary conditions and the viscous instability in accretion discs SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; instabilities; waves; methods, numerical; binaries, close; stars, oscillations ID BINARY-SYSTEMS; DISKS; OSCILLATIONS; OVERSTABILITY AB A numerical investigation is carried out to analyse the effects of the outer boundary conditions on the viscous instability of accretion discs. A one-dimensional time-dependent calculation of geometrically thin accretion discs is used. When the outer boundary is reflective, oscillations are trapped between the outer boundary and the outer edge of the inner evanescent region. When the outer boundary is nonreflective, the oscillations decay on a viscous time-scale. An analytical treatment of numerically non-reflective boundary conditions is carried out for a polytropic flow and for a gas including radiation. RP Godon, P (reprint author), CALTECH,NASA,JET PROP LAB,MS 238-332,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 23 TC 22 Z9 22 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD OCT 15 PY 1996 VL 282 IS 4 BP 1107 EP 1113 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN513 UT WOS:A1996VN51300004 ER PT J AU GrahamSmith, F Dolan, JF Boyd, PT Biggs, JD Lyne, AG Percival, JW AF GrahamSmith, F Dolan, JF Boyd, PT Biggs, JD Lyne, AG Percival, JW TI The ultraviolet polarization of the Crab pulsar SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE polarization; pulsars, individual, Crab; ultraviolet, stars ID LINEAR-POLARIZATION AB The linear polarization of the Crab pulsar has been observed in the ultraviolet using the High Speed Photometer on the Hubble Space Telescope. The polarization as a function of pulse phase is strikingly similar to that observed in the visible, with the same values of fractional polarization and the same swing of position angle occurring through the main and secondary pulses, The polarization pulse profile must be essentially wavelength-independent at wave-lengths shorter than the infrared, as predicted by the geometric model of the emission region proposed by Smith et al. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,GREENBELT,MD 20771. PERTH OBSERV,BICKLEY,WA 6076,AUSTRALIA. UNIV WISCONSIN,SPACE ASTRON LAB,MADISON,WI 53707. RP GrahamSmith, F (reprint author), UNIV MANCHESTER,NUFFIELD RADIO ASTRON LABS,JODRELL BANK,MACCLESFIELD SK11 9DL,CHESHIRE,ENGLAND. RI Boyd, Patricia/D-3274-2012 NR 10 TC 15 Z9 15 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD OCT 15 PY 1996 VL 282 IS 4 BP 1354 EP 1358 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN513 UT WOS:A1996VN51300026 ER PT J AU Shahbaz, T Smale, AP Naylor, T Charles, PA vanParadijs, J Hassall, BJM Callanan, P AF Shahbaz, T Smale, AP Naylor, T Charles, PA vanParadijs, J Hassall, BJM Callanan, P TI An atlas of optical continuum and line emission from low-mass X-ray binaries SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Review DE accretion, accretion discs; atlases; binaries, close; stars, neutron; X-rays, stars ID CENTAURUS X-4; CYGNUS X-2; ACCRETION DISKS; ORBITAL PERIOD; SCORPIUS X-1; BLACK-HOLE; AQUILA X-1; 4U 2129+47; OPTIMAL EXTRACTION; LIGHT-CURVE AB We have obtained broad-band optical spectra of a sample of 15 low-mass X-ray binaries (LMXBs) in the range 4000-9000 Angstrom and fitted them with combinations of standard accretion disc models plus secondary star templates. For the sample of LMXBs in which we determined the power-law indices of the accretion disc flux distribution, we can explain the steepness of the slopes in terms of an optically thick accretion disc and X-ray heating of the outer parts of the disc. We present for the first time optical spectra of X 1705 - 250, XB 1905 + 00 and XB 1916 - 053. Optical line emission was detected in most of the sample. The Balmer lines H alpha and H beta were generally the strongest lines with mean equivalent widths of 3.7 and 1.9 Angstrom, respectively. The He II lambda 4686 and the Bowen C III/N III blend at lambda 4640 were also observed, with equivalent widths of 3.0 and 4.1 Angstrom, respectively, The Paschen lines were: also present in Cen X - 4, GS 2000 + 25, and for the first time detected in Aql X - 1. The only systems in which stellar features were detected were those in which the companions were evolved e.g. GX 1 + 4, Cyg X - 2 and the source in which the mass accretion rate is low i.e. Cen X - 4. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV KEELE,DEPT PHYS,KEELE ST5 5BG,STAFFS,ENGLAND. UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,NIKHEF H,NL-1098 SJ AMSTERDAM,NETHERLANDS. UNIV CENT LANCASHIRE,DEPT PHYS & ASTRON,PRESTON PR1 2HE,LANCS,ENGLAND. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. RP Shahbaz, T (reprint author), UNIV OXFORD,DEPT ASTROPHYS,NUCL PHYS BLDG,OXFORD OX1 3RH,ENGLAND. RI Naylor, Tim /A-9465-2015 NR 103 TC 36 Z9 36 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD OCT 15 PY 1996 VL 282 IS 4 BP 1437 EP 1453 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN513 UT WOS:A1996VN51300034 ER PT J AU Huck, FO Fales, CL Rahman, Z AF Huck, FO Fales, CL Rahman, Z TI An information theory of visual communication SO PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES LA English DT Article ID SYSTEM-DESIGN; IMAGE; FIDELITY AB The fundamental problem of visual communication is that of producing the best possible picture at the lowest data rate. We address this problem by extending information theory to the assessment of the visual communication channel as a whole, from image gathering to display. The extension unites two disciplines, the electrooptical design of image gathering and display devices and the digital processing for image coding and restoration. The mathematical development leads to several intuitively attractive figures of merit for assessing the visual communication channel as a function of the critical limiting factors that constrain its performance. Multiresolution decomposition is included in the mathematical development to optimally combine the economical encoding of the transmitted signal with image gathering and restoration. Quantitative and qualitative assessments demonstrate that a visual communication channel ordinarily can be expected to produce the best possible picture at the lowest data rate only if the image-gathering device produces the maximum-realizable information rate and the image-restoration algorithm properly accounts for the critical limiting factors that constrain the visual communication. These assessments encompass (a) the electro-optical design of the image-gathering device in terms of the trade-off between blurring and aliasing in the presence of photodetector and quantization noises, (b) the compression of data transmission by redundancy reduction, (c) the robustness of the image restoration to uncertainties in the statistical properties of the captured radiance field, and (d) the enhancement of particular features or, more generally, of the visual quality of the observed image. The 'best visual quality' in this context normally implies a compromise among maximum-realizable fidelity, sharpness, and clarity which depends on the characteristics of the scene and the purpose of the visual communication (e.g. diagnosis versus entertainment). C1 SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. RP Huck, FO (reprint author), NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. NR 54 TC 31 Z9 32 U1 0 U2 1 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 1364-503X J9 PHILOS T R SOC A JI Philos. Trans. R. Soc. A-Math. Phys. Eng. Sci. PD OCT 15 PY 1996 VL 354 IS 1716 BP 2193 EP 2248 DI 10.1098/rsta.1996.0098 PG 56 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN523 UT WOS:A1996VN52300001 ER PT J AU Fales, CL Huck, FO AlterGartenberg, R Rahman, Z AF Fales, CL Huck, FO AlterGartenberg, R Rahman, Z TI Image gathering and digital restoration SO PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES LA English DT Article ID VISUAL QUALITY; FIDELITY; INFORMATION; CONVOLUTION; DESIGN AB This paper seeks to unite two disciplines: the electro-optical design of image gathering and display devices and the digital processing for image restoration. So far, these two disciplines have remained independent, following distinctly separate traditions. However, the best possible performance can be attained only when the digital processing algorithm accounts for the critical limiting factors of image gathering and display and the image-gathering device is designed to enhance the performance of the digital-processing algorithm. The following salient advantages accrue: 1. Spatial detail as fine as the sampling interval of the image-gathering device ordinarily can be restored sharply and clearly. 2. Even finer spatial detail than the sampling interval can be restored by combining a multiresponse image-gathering sequence with a restoration filter that properly reassembles the within-passband and aliased signal components. 3. The visual quality produced by traditional image gathering (e.g. television camera) and reconstruction (e.g. cubic convolution) can be improved with a small-kernel restoration operator without an increase in digital processing. 4. The enhancement of radiance-field transitions can be improved for dynamic-range compression (to suppress shadow obscurations) and for edge detection (for computer vision). C1 COLL WILLIAM & MARY, WILLIAMSBURG, VA 23187 USA. SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. RP Fales, CL (reprint author), NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. NR 34 TC 19 Z9 19 U1 0 U2 1 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 1364-503X J9 PHILOS T R SOC A JI Philos. Trans. R. Soc. A-Math. Phys. Eng. Sci. PD OCT 15 PY 1996 VL 354 IS 1716 BP 2249 EP 2287 DI 10.1098/rsta.1996.0099 PG 39 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VN523 UT WOS:A1996VN52300002 ER PT J AU Lisse, CM Dennerl, K Englhauser, J Harden, M Marshall, FE Mumma, MJ Petre, R Pye, JP Ricketts, MJ Schmitt, J Trumper, J West, RG AF Lisse, CM Dennerl, K Englhauser, J Harden, M Marshall, FE Mumma, MJ Petre, R Pye, JP Ricketts, MJ Schmitt, J Trumper, J West, RG TI Discovery of x-ray and extreme ultraviolet emission from comet C/Hyakutake 1996 B2 SO SCIENCE LA English DT Article ID SOLAR-WIND AB `During its close approach to Earth, comet C/Hyakutake 1996 B2 was observed at extreme ultraviolet and x-ray wavelengths with the Rontgen X-ray Satellite and Rossi X-ray Timing Explorer. The emission morphology was symmetric with respect to a vector from the comet's nucleus toward the sun, but not symmetric around the direction of motion of the comet with respect to interplanetary dust. A slowly varying emission and a large impulsive event that varied on time scales of 1 to 2 hours were observed. An interaction between the comet and the solar wind/solar magnetic field seems to be the most likely mechanism for the observed emission. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. RUTHERFORD APPLETON LAB,SPACE & ASTROPHYS DIV,DIDCOT OX11 0QX,OXON,ENGLAND. UNIV LEICESTER,DEPT PHYS & ASTRON,LEICESTER LE1 7RH,LEICS,ENGLAND. RP Lisse, CM (reprint author), UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742, USA. RI mumma, michael/I-2764-2013; Lisse, Carey/B-7772-2016 OI Lisse, Carey/0000-0002-9548-1526 NR 26 TC 313 Z9 314 U1 1 U2 5 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 11 PY 1996 VL 274 IS 5285 BP 205 EP 209 DI 10.1126/science.274.5285.205 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VM671 UT WOS:A1996VM67100031 ER PT J AU Joughin, I Tulaczyk, S Fahnestock, M Kwok, R AF Joughin, I Tulaczyk, S Fahnestock, M Kwok, R TI A mini-surge on the Ryder Glacier, Greenland, observed by satellite radar interferometry SO SCIENCE LA English DT Article ID LARGE TIDEWATER GLACIER; VARIEGATED GLACIER; ICE-SHEET; HYDROLOGIC BASIS; RAPID MOTION; ALASKA; DYNAMICS; USA AB Satellite radar interferometry reveals that the speed oi the Ryder Glacier increased roughly threefold and then returned to normal (100 to 500 meters/year) over a 7-week period near the end of the 1995 melt season. The accelerated flow represents a substantial, through short-lived, change in ice discharge. During the period of rapid motion, meltwater-filled supraglacial lakes may have drained, which could have increased basal water pressure and caused the mini-surge. There are too few velocity measurements on other large outlet glaciers to determine whether this type of event is a widespread phenomenon in Greenland, but because most other outlet glaciers are at lower latitudes, they should experience more extensive melting, making them more susceptible to meltwater-induced surges. C1 CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. UNIV MARYLAND,DEPT METEOROL,JOINT CTR EARTH SYST SCI,COLLEGE PK,MD 20742. RP Joughin, I (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 300-235,PASADENA,CA 91109, USA. RI Kwok, Ron/A-9762-2008; Joughin, Ian/A-2998-2008; Fahnestock, Mark/N-2678-2013 OI Kwok, Ron/0000-0003-4051-5896; Joughin, Ian/0000-0001-6229-679X; NR 18 TC 59 Z9 66 U1 0 U2 7 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 11 PY 1996 VL 274 IS 5285 BP 228 EP 230 DI 10.1126/science.274.5285.228 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VM671 UT WOS:A1996VM67100037 ER PT J AU Downie, JD Smithey, DT AF Downie, JD Smithey, DT TI Measurements of holographic properties of bacteriorhodopsin films SO APPLIED OPTICS LA English DT Article ID THIN-FILMS; ANISOTROPY; VARIANTS AB Several different bacteriorhodopsin (BR) films are characterized with respect to general holographic properties. Experimental measurements include diffraction efficiency and sensitivity as functions of the writing intensity and grating frequency, hologram thermal-decay behavior, diffraction efficiency as a function of the grating tilt within the film and the modulation depth, and estimates of the refractive-index change from the diffraction-efficiency data. The films studied include those made from wildtype BR and the genetic variants D96N and D96N/T46V. The film holographic properties were found to be relatively insensitive to the grating frequency and the grating-tilt angle. The diffraction efficiency dropped off more sharply as a function of the modulation depth than did a purely linear medium, and only the hydrated wildtype film exhibited significant behavior variation with different writing intensities because of its short M-state lifetime. The maximum diffraction efficiency measured was approximately 7.5% for a hydrated D96N BR film. We also find that the hydrated BR films exhibit significantly higher refractive-index modulation than do dry films. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. BEND RES INC,BEND,OR 97701. NR 17 TC 39 Z9 39 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD OCT 10 PY 1996 VL 35 IS 29 BP 5780 EP 5789 DI 10.1364/AO.35.005780 PG 10 WC Optics SC Optics GA VL749 UT WOS:A1996VL74900006 PM 21127589 ER PT J AU Silbermann, NA Harding, P Madore, BF Kennicutt, RC Saha, A Stetson, PB Freedman, WL Mould, JR Graham, JA Hill, RJ Turner, A Bresolin, F Ferrarese, L Ford, H Hoessel, JG Han, MS Huchra, J Hughes, SMG Illingworth, GD Phelps, R Sakai, S AF Silbermann, NA Harding, P Madore, BF Kennicutt, RC Saha, A Stetson, PB Freedman, WL Mould, JR Graham, JA Hill, RJ Turner, A Bresolin, F Ferrarese, L Ford, H Hoessel, JG Han, MS Huchra, J Hughes, SMG Illingworth, GD Phelps, R Sakai, S TI The Hubble Space Telescope Key Project on the Extragalactic Distance Scale .6. The Cepheids in NGC 925 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; distance scale; galaxies, individual (NGC 925) ID LINE-WIDTH RELATIONS; STELLAR PHOTOMETRY; SPIRAL GALAXIES; CCD PHOTOMETRY; NGC-1023 GROUP; II SUPERNOVAE; NEARBY GROUPS; FIELD; EXTINCTION; REDSHIFT AB We report the detection of Cepheid variable stars in the barred spiral galaxy NGC 925, using the Hubble Space Telescope (HST) Wide-Field and Planetary Camera 2 (WFPC2). Twelve V (F555W) and four I (F814W) epochs of cosmic-ray split observations were obtained. Eighty Cepheids were discovered, with periods from 6 to similar to 80 days. Light curves of the Cepheids are presented, and their corresponding period-luminosity diagrams are discussed. Using a distance modulus for the Large Magellanic Cloud Cepheids of 18.50 mag and an extinction of E(V-I)=0.13 mag, the measured distance modulus to NGC 925 is 29.84+/-0.16 mag, corresponding to a distance of 9.29+/-0.69 Mpc. A mean reddening of E(V-I)=0.17 mag is found for the Cepheids in this region of NGC 925. C1 UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. CALTECH,NASA,EXTRAGALACT DATABASE,INFRARED PROC & ANAL CTR,PASADENA,CA 91125. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA. CARNEGIE INST WASHINGTON OBSERV,PASADENA,CA 91101. AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,INST ADV STUDIES,WESTON,ACT 2611,AUSTRALIA. CARNEGIE INST WASHINGTON,DEPT TERR MAGNETISM,WASHINGTON,DC 20015. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. JOHNS HOPKINS UNIV,BALTIMORE,MD 21218. UNIV WISCONSIN,MADISON,WI 53706. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. ROYAL GREENWICH OBSERV,CAMBRIDGE CB3 0EZ,ENGLAND. UNIV CALIF SANTA CRUZ,LICK OBSERV,SANTA CRUZ,CA 95064. RP Silbermann, NA (reprint author), CALTECH,JET PROP LAB,INFRARED PROC & ANAL CTR,MS 100-22,PASADENA,CA 91125, USA. NR 46 TC 91 Z9 91 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 1 EP & DI 10.1086/177845 PN 1 PG 38 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300001 ER PT J AU Lineweaver, CH Tenorio, L Smoot, GF Keegstra, P Banday, AJ Lubin, P AF Lineweaver, CH Tenorio, L Smoot, GF Keegstra, P Banday, AJ Lubin, P TI The dipole observed in the COBE DMR 4 year data SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology, observations ID DIFFERENTIAL MICROWAVE RADIOMETERS; MAPS AB The largest anisotropy in the cosmic microwave background (CMB) is the approximate to 3 mK dipole assumed to be due to our velocity with respect to the CMB. Using the 4 year data set from all six channels of the COBE Differential Microwave Radiometers (DMR), we obtain a best-fit dipole amplitude 3.358+/-0.001+/-0.023 mK in the direction (l, b)=(264.degrees 31+/-0.degrees 04+/-0.degrees 16, +48.degrees 05+/-0.degrees 02+/-0.degrees 09), where the first uncertainties are statistical. and the second include calibration and combined systematic uncertainties. This measurement is consistent with previous DMR and FIRAS results. C1 UNIV CARLOS III MADRID,MADRID,SPAIN. UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,SPACE SCI LAB,BERKELEY,CA 94720. UNIV CALIF BERKELEY,CTR PARTICLE ASTROPHYS,BERKELEY,CA 94720. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. MAX PLANCK INST ASTROPHYS,D-85740 GARCHING,GERMANY. UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106. RP Lineweaver, CH (reprint author), OBSERV STRASBOURG,F-67000 STRASBOURG,FRANCE. NR 12 TC 120 Z9 120 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 38 EP 42 DI 10.1086/177846 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300002 ER PT J AU Fixsen, DJ Cheng, ES Cottingham, DA Folz, WC Inman, CA Kowitt, MS Meyer, SS Page, LA Puchalla, JL Ruhl, JE Silverberg, RF AF Fixsen, DJ Cheng, ES Cottingham, DA Folz, WC Inman, CA Kowitt, MS Meyer, SS Page, LA Puchalla, JL Ruhl, JE Silverberg, RF TI A balloon-borne millimeter-wave telescope for cosmic microwave background anisotropy measurements SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic microwave background; instrumentation, miscellaneous; telescopes ID WAVELENGTH AB We report on the characteristics and design details of the Medium Scale Anisotropy Measurement telescope, a millimeter-wave, balloon-borne experiment that measures anisotropy in the cosmic microwave background radiation on 0.degrees 5 angular scales. The gondola is capable of maintaining orientation to 2' rms and determining absolute pointing to 2.'5 accuracy during a one-night flight. Emphasis is placed on the optical and pointing performance as well as the weight and power budgets. We also discuss the total balloon/gondola mechanical system. The pendulation from this system is a ubiquitous perturbation on the pointing system. A detailed understanding in these areas is needed for developing the next generation of balloon-borne instruments. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GLOBAL SCI & TECHNOL INC,GREENBELT,MD 20771. UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637. PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08540. RP Fixsen, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,APPL RES CORP,CODE 6853,GREENBELT,MD 20771, USA. NR 22 TC 29 Z9 29 U1 2 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 63 EP 77 DI 10.1086/177850 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300006 ER PT J AU Szapudi, I Colombi, S AF Szapudi, I Colombi, S TI Cosmic error and statistics of large-scale structure SO ASTROPHYSICAL JOURNAL LA English DT Article DE large-scale structure of the universe; methods, numerical; methods, statistical ID 3-POINT CORRELATION-FUNCTION; GALAXY CORRELATION-FUNCTION; HIGHER-ORDER STATISTICS; COLD DARK MATTER; CLUSTER CORRELATIONS; REDSHIFT SURVEY; EXTRAGALACTIC OBJECTS; CORRELATION HIERARCHY; ZWICKY CATALOG; IRAS GALAXIES AB We use a generating function approach to examine the errors on quantities related to counts in cells extracted from galaxy surveys. The measurement error, related to the finite number of sampling cells, is distinguished from the ''cosmic error,'' due to the finiteness of the survey. While the measurement error can be circumvented through the application of a proper algorithm, the cosmic error is an irrecoverable property of any survey. Using the hierarchical model and assuming locally Poisson behavior, we identify three contributions to the cosmic error: 1. The finite volume effect is proportional to the average of the two-point correlation function over the whole survey. It accounts for possible fluctuations of the density field at scales larger than the sample size. 2. The edge effect is related to the geometry of the survey. It accounts for the fact that objects near the boundary carry less statistical weight than those further away from it. 3. The discreteness effect is due to the fact that the underlying smooth random held is sampled with finite number of objects. This is the ''shot noise'' error. To check the validity of our results, we measured the factorial moments of order N less than or equal to 4 in a large number of small subsamples randomly extracted from a hierarchical sample realized by Raighley-Levy random walks. The measured statistical errors are in excellent agreement with our predictions. The probability distribution of errors is increasingly skewed when the order N and/or the cell size increases. This suggests that ''cosmic errors'' tend to be systematic: it is likely to underestimate the true value of the factorial moments. Our study of the various regimes showed that the errors strongly depend on the clustering of the system, i.e., on the hierarchy of underlying correlations. The Gaussian approximation is valid only in the weakly nonlinear regime, otherwise it severely underestimates the true errors. We study the concept of ''number of statistically independent cells '' (re)defined as the number of sampling cells required to have the measurement error of same order as the cosmic error. This number is found to depend highly on the statistical object under study and is generally quite different from the number of cells needed to cover the survey volume. In light of these findings we advocate high oversampling for measurements of counts in cells. As a preliminary application to realistic situations, we study contour plots of the cosmic error expected in typical three-dimensional galaxy catalogs. C1 CANADIAN INST THEORET ASTROPHYS,TORONTO,ON M5S 3H8,CANADA. RP Szapudi, I (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. NR 53 TC 79 Z9 79 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 131 EP 148 DI 10.1086/177855 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300011 ER PT J AU Taylor, JA AF Taylor, JA TI Line emission in active galactic nuclei: Effects of local delays upon line variability SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, nuclei; line, formation ID REGIONS; CLOUDS; QUASARS AB Previous works concerning active galactic nuclei (AGNs) variability (e.g., Blandford & McKee 1982) have assumed that the emission characteristics of illuminated clouds are purely a function of the instant continuum flux to which they are exposed. This paper shows that this assumption is not necessarily justified and that the history of exposure accounting for ''local delays'' due to finite cloud equilibrium times can also be relevant. For this reason, a new formalism is developed in this paper for computing the observational properties of models that have local delays. The nature of the nonlinear behavior that results is calculated for some very simple nonlinear cloud line emission models. It is found that the mean response time is a function of the recent average value of the continuum. Linear models fitted to these nonlinear systems respond too slowly when there are low-energy (and generally rapid) changes in the continuum, yet respond too rapidly when there are high-energy (and generally slow) changes in the continuum. As with systems without local delays, the expression for the time-dependent line flux contains an integration over history of the ''spatial'' response function, which has structure at lags of the light travel times of the emission region. However, the kernel of this integral itself is a function of additional integrations over individual ''cloud'' response functions that have structure at lags of the equilibrium times of the cloud properties relevant to line emission. In the linear regime, the response can be approximated using a single response function. The integral of this function over lag is not generally equal to the mean flux in the line. Rather, it differs by a factor that is the strength of response for low-frequency continuum excitations or simply the ''asymptotic gain,'' which is unity only in fully Linear models. If instantaneous or linear response is incorrectly assumed, local delays and nonlinear response can make a system appear larger than it actually is. These effects are similar to those that beaming can cause. Local delays can also be a source of asymmetry about the peak of the cross-correlation function. C1 UNIV MARYLAND, DEPT PHYS, COLLEGE PK, MD 20742 USA. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. NR 21 TC 2 Z9 2 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 269 EP 279 DI 10.1086/177866 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300022 ER PT J AU Crenshaw, DM RodriguezPascual, PM Penton, SV Edelson, RA Alloin, D Ayres, TR Clavel, J Horne, K Johnson, WN Kaspi, S Korista, KT Kriss, GA Krolik, JH Malkan, MA Maoz, D Netzer, H OBrien, PT Peterson, BM Reichert, GA Shull, JM Ulrich, MH Wamsteker, W Warwick, RS Yaqoob, T Balonek, TJ Barr, P Bromage, GE Carini, M Carone, TE Cheng, FZ Chuvaev, KK Dietrich, M Doroshenko, VT DultzinHacyan, D Filippenko, AV Gaskell, CM Glass, IS Goad, MR Hutchings, J Kazanas, D Kollatschny, W Koratkar, AP Laor, A Leighly, K Lyutyi, VM MacAlpine, GM Malkov, YF Martin, PG McCollum, B Merkulova, NI Metik, L Metlov, VG Miller, HR Morris, SL Oknyanskij, VL Penfold, J Perez, E Perola, GC Pike, G Pogge, RW Pronik, I Pronik, VI Ptak, RL RecondoGonzalez, MC RodriguezEspinoza, JM Rokaki, EL Roland, J Sadun, AC Salamanca, I SantosLleo, M Sergeev, SG Smith, SM Snijders, MAJ Sparke, LS Stirpe, GM Stoner, RE Sun, WH vanGroningen, E Wagner, RM Wagner, S Wanders, I Welsh, WF Weymann, RJ Wilkes, BJ Zheng, W AF Crenshaw, DM RodriguezPascual, PM Penton, SV Edelson, RA Alloin, D Ayres, TR Clavel, J Horne, K Johnson, WN Kaspi, S Korista, KT Kriss, GA Krolik, JH Malkan, MA Maoz, D Netzer, H OBrien, PT Peterson, BM Reichert, GA Shull, JM Ulrich, MH Wamsteker, W Warwick, RS Yaqoob, T Balonek, TJ Barr, P Bromage, GE Carini, M Carone, TE Cheng, FZ Chuvaev, KK Dietrich, M Doroshenko, VT DultzinHacyan, D Filippenko, AV Gaskell, CM Glass, IS Goad, MR Hutchings, J Kazanas, D Kollatschny, W Koratkar, AP Laor, A Leighly, K Lyutyi, VM MacAlpine, GM Malkov, YF Martin, PG McCollum, B Merkulova, NI Metik, L Metlov, VG Miller, HR Morris, SL Oknyanskij, VL Penfold, J Perez, E Perola, GC Pike, G Pogge, RW Pronik, I Pronik, VI Ptak, RL RecondoGonzalez, MC RodriguezEspinoza, JM Rokaki, EL Roland, J Sadun, AC Salamanca, I SantosLleo, M Sergeev, SG Smith, SM Snijders, MAJ Sparke, LS Stirpe, GM Stoner, RE Sun, WH vanGroningen, E Wagner, RM Wagner, S Wanders, I Welsh, WF Weymann, RJ Wilkes, BJ Zheng, W TI Multiwavelength observations of short-timescale variability in NGC 4151 .1. Ultraviolet observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (NGC 4151); galaxies, Seyfert; ultraviolet, galaxies ID BROAD-LINE REGION; ACTIVE GALACTIC NUCLEI; X-RAY; DETAILED OBSERVATIONS; SEYFERT-GALAXIES; OPTICAL WAVELENGTHS; NGC-4151; IUE; NGC-5548; SIZE AB We present the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every similar to 70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Angstrom went through four significant and well-defined ''events'' of duration 2-3 days during the continuous-monitoring period. We find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of similar to 0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines. C1 EUROPEAN SPACE AGCY, IUE OBSERV, E-28080 MADRID, SPAIN. UNIV COLORADO, CTR ASTROPHYS & SPACE ASTRON, BOULDER, CO 80309 USA. UNIV IOWA, DEPT PHYS & ASTRON, IOWA CITY, IA 52242 USA. OBSERV PARIS, CNRS, URA 173, F-92195 MEUDON, FRANCE. ESTEC, EUROPEAN SPACE AGCY, DIV ASTROPHYS, ISO OBSERV, NL-2200 AG NOORDWIJK, NETHERLANDS. UNIV ST ANDREWS, SCH PHYS & ASTRON, ST ANDREWS KY16 9SS, FIFE, SCOTLAND. USN, RES LAB, WASHINGTON, DC 20375 USA. TEL AVIV UNIV, RAYMOND & BEVERLY SACKLER FAC EXACT SCI, SCH PHYS & ASTRON, IL-69978 TEL AVIV, ISRAEL. TEL AVIV UNIV, RAYMOND & BEVERLY SACKLER FAC EXACT SCI, WISE OBSERV, IL-69978 TEL AVIV, ISRAEL. UNIV KENTUCKY, DEPT PHYS & ASTRON, LEXINGTON, KY 40506 USA. JOHNS HOPKINS UNIV, DEPT PHYS & ASTRON, BLOOMBERG CTR, BALTIMORE, MD 21218 USA. UNIV CALIF LOS ANGELES, DEPT ASTRON, LOS ANGELES, CA 90024 USA. UNIV OXFORD, DEPT ASTRON, OXFORD OX1 3RH, ENGLAND. OHIO STATE UNIV, DEPT ASTRON, COLUMBUS, OH 43210 USA. NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. UNIV COLORADO, JOINT INST LAB ASTROPHYS, BOULDER, CO 80309 USA. UNIV COLORADO, NATL INST STAND & TECHNOL, BOULDER, CO 80309 USA. European So Observ, D-85748 Garching, GERMANY. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, ENGLAND. NASA, Goddard Space Flight Ctr, Lab High Energy Astrophys, Greenbelt, MD 20771 USA. Colgate Univ, Dept Phys & Astron, Hamilton, NY 13346 USA. Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, ENGLAND. Western Kentucky Univ, Dept Phys & Astron, Ctr Automated Space Studies, Bowling Green, KY 42101 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Sci & Technol China, Ctr Astrophys, Hefei 230026, Anhui, PEOPLES R CHINA. Landessternwarte Konigstuhl, D-69117 Heidelberg, GERMANY. Sternberg State Astron Inst, UA-334413 Crimea, UKRAINE. Univ Nacl Autonoma Mexico, Inst Astron, Mexico City 04510, DF, MEXICO. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Univ Nebraska, Dept Phys & Astron, Lincoln, NE 68588 USA. S African Astron Observ, ZA-7935 Observ, SOUTH AFRICA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, CANADA. Univ Sternwarte Gottingen, D-37083 Gottingen, GERMANY. CALTECH, Dept Astron, Pasadena, CA 91125 USA. RIKEN, Cosm Radiat Lab, Wako, Saitama 35101, JAPAN. Univ Moscow, Sternberg Astron Inst, Moscow 119899, RUSSIA. Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. Crimean Astrophys Observ, UA-334413 Crimea, UKRAINE. Univ Toronto, Canadian Inst Theoret Astrophys, Toronto, ON M5S 1A1, CANADA. NASA, Goddard Space Flight Ctr, Comp Sci Corp, Greenbelt, MD 20771 USA. Georgia State Univ, Dept Phys & Astron, Atlanta, GA 30303 USA. Astron Observ, S-75120 Uppsala, SWEDEN. Univ Calgary, Dept Phys & Astron, Calgary, AB T2N 1N4, CANADA. Mt Royal Coll, Dept Math Phys & Engn, Calgary, AB T3E 6K6, CANADA. Inst Astrofis Andalucia, E-18080 Granada, SPAIN. Univ Rome, Inst Astron, I-00161 Rome, ITALY. Bowling Green State Univ, Dept Phys & Astron, Bowling Green, OH 43403 USA. Inst Astrofis Canarias, E-38200 La Laguna, Tenerife, SPAIN. Univ Edinburgh, Royal Observ Edinburgh, Edinburgh EH9 3HJ, Midlothian, SCOTLAND. Inst Astrophys, F-75014 Paris, FRANCE. Agnes Scott Coll, Dept Phys & Astron, Decatur, GA 30030 USA. Agnes Scott Coll, Bradley Observ, Decatur, GA 30030 USA. Inst Radio Astron Millimetr, F-38046 St Martin Dheres, FRANCE. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Osservatorio Astron Bologna, I-40126 Bologna, ITALY. Natl Cent Univ, Inst Astron, Chungli 32054, TAIWAN. Lowell Observ, Flagstaff, AZ 86001 USA. Keele Univ, Dept Phys, Keele ST5 5BG, Staffs, ENGLAND. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Harvard Univ, Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Crenshaw, DM (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, COMP SCI CORP, CODE 681, GREENBELT, MD 20771 USA. RI Morris, Simon/G-7981-2011; Oknyanskij, Victor/I-9267-2012; Johnson, Neil/G-3309-2014; Recondo, Carmen/B-1215-2012; Stirpe, Giovanna/O-9393-2015; OI Perez, Enrique/0000-0001-9737-4559; Morris, Simon/0000-0003-4866-110X; Recondo, Carmen/0000-0001-9813-6798; Stirpe, Giovanna/0000-0002-3702-8731; Gaskell, C/0000-0003-4888-2009; Wilkes, Belinda/0000-0003-1809-2364 NR 53 TC 66 Z9 66 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 322 EP 335 DI 10.1086/177869 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300025 ER PT J AU Warwick, RS Smith, DA Yaqoob, T Edelson, R Johnson, WN Reichert, GA Clavel, J Magdziarz, P Peterson, BM Zdziarski, AA AF Warwick, RS Smith, DA Yaqoob, T Edelson, R Johnson, WN Reichert, GA Clavel, J Magdziarz, P Peterson, BM Zdziarski, AA TI Multiwavelength observations of short-timescale variability in NGC 4151 .3. X-ray and gammma-ray observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 4151); galaxies, Seyfert; gamma rays, observations; X-rays, galaxies ID SEYFERT-GALAXIES; NGC-4151; EMISSION; CONSTRAINTS; ABSORPTION; ASTRONOMY; GEOMETRY; FEATURES; SPECTRUM; ASCA AB A series of ROSAT, ASCA and Compton Gamma Ray Observatory (CGRO) observations of the Seyfert galaxy NGC 4151 were carried out during the period 1993 November 30-December 13 as part of an intensive campaign to study the multiwavelength spectral characteristics of its short-timescale variability. In the softest X-ray bands monitored by ROSAT (0.1-0.4 keV, 0.5-1.0 keV), the source flux remained constant throughout the observing period. However, in an adjacent band (1.0-2.0 keV) significant variability was evident, the most obvious feature being a marked increase (a factor of 1.45) in the count rate over a timescale of similar to 2 days commencing roughly 3 days into the monitoring period. In contrast, only a low amplitude of variability (less than or similar to 10%) was measured in the four ASCA observations in the 2-10 keV band (but note that the first ASCA observation was performed somewhat after the onset of the flux increase seen by ROSAT). The count rates recorded by the Oriented Scintillation Spectrometer Experiment (OSSE) on CGRO are consistent with +/-15% variations in the 50-150 keV gamma-ray band, but there is no direct correspondence between the gamma-ray and soft X-ray light curves. The 0.1 to similar to 300 keV spectrum of NGC 4151 is dominated by a hard power-law continuum which is cutoff at both high (similar to 90 keV) and low (similar to 4 keV) energy. A high-energy cutoff is characteristic of a continuum generated by the process of thermal Comptonization, whereas that at low energy arises from absorption in line-of-sight gas. In NGC 4151 this gas may be partially photoionized by the continuum source, but still retains significant opacity below 1 keV. The observed soft X-ray variability may be the result of changes in the level of the underlying soft-hard X-ray continuum or changes in the line-of-sight absorption. The data marginally favor the former, in which case the difference between the soft X-ray and gamma-ray light curves implies a steepening of the continuum as the source brightens, consistent with earlier observations. As noted in earlier studies, there is a soft excess below 1 keV which probably arises from more than one scattered and/or thermal component. The 1-2 keV soft X-ray and the ultraviolet continuum light curves (e.g., near 1440 Angstrom) show reasonably good correspondence, although the relative amplitude of the variations is much higher in the X-ray data. The observed ultraviolet to X-ray correlation has a slope similar to that established in earlier studies, although a significant residual ultraviolet flux is evident in the recent observations. A possible interpretation is that the X-ray to gamma-ray continuum is produced in a patchy dissipative corona above the surface of an accretion disk and that the correlated ultraviolet flux results from the reprocessing of part of this continuum by the disk. The residual ultraviolet flux may then arise from the reprocessing and/or the viscous heating of the disk. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY PHYS LAB,GREENBELT,MD 20771. UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242. USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. ESTEC,ISO OBSERV,NL-2200 AG NOORDWIJK,NETHERLANDS. JAGIELLONIAN UNIV,ASTRON OBSERV,PL-30244 KRAKOW,POLAND. OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210. NICHOLAS COPERNICUS ASTRON CTR,PL-00716 WARSAW,POLAND. RP Warwick, RS (reprint author), UNIV LEICESTER,DEPT PHYS & ASTRON,LEICESTER LE1 7RH,LEICS,ENGLAND. RI Johnson, Neil/G-3309-2014 NR 35 TC 42 Z9 43 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 349 EP 363 DI 10.1086/177871 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300027 ER PT J AU Edelson, RA Alexander, T Crenshaw, DM Kaspi, S Malkan, MA Peterson, BM Warwick, RS Clavel, J Filippenko, AV Horne, K Korista, KT Kriss, GA Krolik, JH Maoz, D Nandra, K OBrien, PT Penton, SV Yaqoob, T Albrecht, P Alloin, D Ayres, TR Balonek, TJ Barr, P Barth, AJ Bertram, R Bromage, GE Carini, M Carone, TE Cheng, FZ Chuvaev, KK Dietrich, M DultzinHacyan, D Gaskell, CM Glass, IS Goad, MR Hemar, S Ho, LC Huchra, JP Hutchings, J Johnson, WN Kazanas, D Kollatschny, W Koratkar, AP Kovo, O Laor, A MacAlpine, GM Magdziarz, P Martin, PG Matheson, T McCollum, B Miller, HR Morris, SL Oknyanskij, VL Penfold, J Perez, E Perola, GC Pike, G Pogge, RW Ptak, RL Qian, BC RecondoGonzalez, MC Reichert, GA RodriguezEspinoza, JM RodriguezPascual, PM Rokaki, EL Roland, J Sadun, AC Salamanca, I SantosLleo, M Shields, JC Shull, JM Smith, DA Smith, SM Snijders, MAJ Stirpe, GM Stoner, RE Sun, WH Ulrich, MH vanGroningen, E Wagner, RM Wagner, S Wanders, I Welsh, WF Weymann, RJ Wilkes, BJ Wu, H Wurster, J Xue, SJ Zdziarski, AA Zheng, W Zou, ZL AF Edelson, RA Alexander, T Crenshaw, DM Kaspi, S Malkan, MA Peterson, BM Warwick, RS Clavel, J Filippenko, AV Horne, K Korista, KT Kriss, GA Krolik, JH Maoz, D Nandra, K OBrien, PT Penton, SV Yaqoob, T Albrecht, P Alloin, D Ayres, TR Balonek, TJ Barr, P Barth, AJ Bertram, R Bromage, GE Carini, M Carone, TE Cheng, FZ Chuvaev, KK Dietrich, M DultzinHacyan, D Gaskell, CM Glass, IS Goad, MR Hemar, S Ho, LC Huchra, JP Hutchings, J Johnson, WN Kazanas, D Kollatschny, W Koratkar, AP Kovo, O Laor, A MacAlpine, GM Magdziarz, P Martin, PG Matheson, T McCollum, B Miller, HR Morris, SL Oknyanskij, VL Penfold, J Perez, E Perola, GC Pike, G Pogge, RW Ptak, RL Qian, BC RecondoGonzalez, MC Reichert, GA RodriguezEspinoza, JM RodriguezPascual, PM Rokaki, EL Roland, J Sadun, AC Salamanca, I SantosLleo, M Shields, JC Shull, JM Smith, DA Smith, SM Snijders, MAJ Stirpe, GM Stoner, RE Sun, WH Ulrich, MH vanGroningen, E Wagner, RM Wagner, S Wanders, I Welsh, WF Weymann, RJ Wilkes, BJ Wu, H Wurster, J Xue, SJ Zdziarski, AA Zheng, W Zou, ZL TI Multiwavelength observations of short-timescale variability in NGC 4151 .4. Analysis of multiwavelength continuum variability SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (NGC 4151); galaxies, Seyfert; ultraviolet, galaxies; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; OBJECT PKS 2155-304; BROAD-LINE REGION; X-RAY-EMISSION; CFA SEYFERT-GALAXIES; ULTRAVIOLET VARIABILITY; ACCRETION DISKS; COMPTON REFLECTION; BAND PROPERTIES; UV CONTINUUM AB This paper combines data from the three preceding papers in order to analyze the multi-wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (similar to 1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA = 6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of similar to 100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Angstrom These data do not probe extreme ultraviolet (1200 Angstrom to 0.1 keV) or hard X-ray (2-50 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of less than or similar to 0.15 day between 1275 Angstrom and the other ultraviolet bands, less than or similar to 0,3 day between 1275 Angstrom and 1.5 keV, and less than or similar to 1 day between 1275 and 5125 Angstrom These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (a less than or equal to -2.5). If photons emitted at a ''primary'' wave band are absorbed by nearby material and ''reprocessed'' to produce emission at a secondary wave band, causality arguments require that variations in the secondary band follow those in the primary band. The tight interband correlation and limits on the ultraviolet and medium-energy X-ray lags indicate that the reprocessing region is smaller than similar to 0.15 it-day in size. After correcting for strong (a factor of greater than or similar to 15) line-of-sight absorption, the medium-energy X-ray luminosity variations appear adequate to drive the ultraviolet/optical variations. However, the medium-energy X-ray NVA is 2-4 times that in the ultraviolet, and the single-epoch, absorption-corrected X-ray/gamma-ray luminosity is only about one-third of that of the ultraviolet/optical/infrared, suggesting that at most about a third of the total low-energy flux could be reprocessed high-energy emission. The strong wavelength dependence of the ultraviolet NVAs is consistent with an origin in an accretion disk, with the variable emission coming from the hotter inner regions and nonvariable emission from the cooler outer regions. These data, when combined with the results of disk fits, indicate a boundary between these regions near a radius of order R approximate to 0.07 1t-day. No interband lag would be expected, as reprocessing (and thus propagation between regions) need not occur, and the orbital timescale of similar to 1 day is consistent with the observed variability timescale. However, such a model does not immediately explain the good correlation between ultraviolet and X-ray variations. C1 TEL AVIV UNIV,SACKLER FAC EXACT SCI,SCH PHYS & ASTRON,IL-69978 TEL AVIV,ISRAEL. TEL AVIV UNIV,SACKLER FAC EXACT SCI,WISE OBSERV,IL-69978 TEL AVIV,ISRAEL. NASA,GODDARD SPACE FLIGHT CTR,ASTRON PROGRAM,COMP SCI CORP,GREENBELT,MD 20771. UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90024. OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210. UNIV LEICESTER,DEPT ASTRON,LEICESTER LE1 7RH,LEICS,ENGLAND. EUROPEAN SPACE AGCY,ISO PROJECT,MADRID 28080,SPAIN. UNIV ST ANDREWS,SCH PHYS & ASTRON,ST ANDREWS KY16 9SS,FIFE,SCOTLAND. UNIV KENTUCKY,DEPT PHYS & ASTRON,LEXINGTON,KY 40506. JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY PHYS LAB,GREENBELT,MD 20771. UNIV COLORADO,CTR ASTROPHYS & SPACE ASTRON,BOULDER,CO 80309. UNIV STERNWARTE GOTTINGEN,D-37083 GOTTINGEN,GERMANY. CTR ETUD SACLAY,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. COLGATE UNIV,DEPT PHYS & ASTRON,HAMILTON,NY 13346. LOWELL OBSERV,FLAGSTAFF,AZ 86001. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. EUREKA SCI INC,OAKLAND,CA. UNIV SCI & TECHNOL,CTR ASTROPHYS,HEFEI,ANHUI,PEOPLES R CHINA. CRIMEAN ASTROPHYS OBSERV,UA-334413 NAUCHNYI,CRIMEA,UKRAINE. LANDESSTERNWARTE KONIGSTUHL,D-69117 HEIDELBERG,GERMANY. UNIV NACL AUTONOMA MEXICO,INST ASTRON,MEXICO CITY 04510,DF,MEXICO. UNIV NEBRASKA,DEPT PHYS & ASTRON,LINCOLN,NE 68588. S AFRICAN ASTRON OBSERV,ZA-7935 CAPE TOWN,SOUTH AFRICA. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA. USN,RES LAB,WASHINGTON,DC 20375. TECHNION ISRAEL INST TECHNOL,DEPT PHYS,IL-32000 HAIFA,ISRAEL. UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109. JAGIELLONIAN UNIV,ASTRON OBSERV,PL-30244 KRAKOW,POLAND. UNIV TORONTO,CANADIAN INST THEORET ASTROPHYS,TORONTO,ON M5S 1A1,CANADA. GEORGIA STATE UNIV,DEPT PHYS & ASTRON,ATLANTA,GA 30303. MOSCOW MV LOMONOSOV STATE UNIV,STERNBERG ASTRON INST,MOSCOW 119899,RUSSIA. UNIV CALGARY,DEPT PHYS & ASTRON,CALGARY,AB T2N 1N4,CANADA. MT ROYAL COLL,DEPT ENGN MATH & PHYS,CALGARY,AB T3E 6K6,CANADA. UNIV ROMA LA SAPIENZA,IST ASTRON,I-00161 ROME,ITALY. BOWLING GREEN STATE UNIV,DEPT PHYS & ASTRON,BOWLING GREEN,OH 43403. CHINESE ACAD SCI,SHANGHAI OBSERV,SHANGHAI,PEOPLES R CHINA. UNIV OVIEDO,FAC CIENCIAS,DEPT FIS,OVIEDO,ASTURIAS,SPAIN. INST ASTROFIS CANARIAS,E-38200 LA LAGUNA,TENERIFE,SPAIN. ESA,IUE OBSERV,MADRID 28080,SPAIN. UNIV EDINBURGH,ROYAL OBSERV EDINBURGH,EDINBURGH EH9 3HJ,MIDLOTHIAN,SCOTLAND. INST ASTROPHYS,F-75014 PARIS,FRANCE. AGNES SCOTT COLL,DEPT PHYS & ASTRON,DECATUR,GA 30030. AGNES SCOTT COLL,BRADLEY OBSERV,DECATUR,GA 30030. ROYAL GREENWICH OBSERV,CAMBRIDGE CB3 0EZ,ENGLAND. LAEFF,E-28080 MADRID,SPAIN. UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85726. UNIV COLORADO,JILA,BOULDER,CO 80309. NATL INST STAND & TECHNOL,BOULDER,CO 80309. IRAM,F-38046 ST MARTIN DHERES,FRANCE. OSSERVATORIO ASTRON BOLOGNA,I-40126 BOLOGNA,ITALY. NATL CENT UNIV,INST ASTRON,CHUNGLI 32054,TAIWAN. EUROPEAN SO OBSERV,D-85748 GARCHING,GERMANY. ASTRON OBSERV,S-75120 UPPSALA,SWEDEN. UNIV KEELE,DEPT PHYS,KEELE ST5 5BG,STAFFS,ENGLAND. CARNEGIE INST WASHINGTON OBSERV,PASADENA,CA 91101. CHINESE ACAD SCI,BEIJING ASTRON OBSERV,BEIJING 100080,PEOPLES R CHINA. NICHOLAS COPERNICUS ASTRON CTR,PL-00716 WARSAW,POLAND. RP Edelson, RA (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,203 VAN ALLEN,IOWA CITY,IA 52242, USA. RI Morris, Simon/G-7981-2011; Oknyanskij, Victor/I-9267-2012; Johnson, Neil/G-3309-2014; Recondo, Carmen/B-1215-2012; Stirpe, Giovanna/O-9393-2015; OI Morris, Simon/0000-0003-4866-110X; Recondo, Carmen/0000-0001-9813-6798; Stirpe, Giovanna/0000-0002-3702-8731; Gaskell, C/0000-0003-4888-2009; Wilkes, Belinda/0000-0003-1809-2364; Perez, Enrique/0000-0001-9737-4559 NR 64 TC 141 Z9 144 U1 0 U2 7 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP 364 EP 377 DI 10.1086/177872 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300028 ER PT J AU Koratkar, A Goad, MR OBrien, PT Salamanca, I Wanders, I Axon, D Crenshaw, D Robinson, A Korista, K RodriguezPascual, P Horne, K Blackwell, J Carini, M England, M Perez, M Pitts, R Rawley, L Reichert, G Shrader, C Wamsteker, W AF Koratkar, A Goad, MR OBrien, PT Salamanca, I Wanders, I Axon, D Crenshaw, D Robinson, A Korista, K RodriguezPascual, P Horne, K Blackwell, J Carini, M England, M Perez, M Pitts, R Rawley, L Reichert, G Shrader, C Wamsteker, W TI The disappearing broad absorption lines and variable emission lines in NGC 3516 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (NGC 3516); galaxies, Seyfert; ultraviolet, galaxies ID ACTIVE GALACTIC NUCLEI; SEYFERT-GALAXY NGC-3516; HUBBLE-SPACE-TELESCOPE; IONIZING CONTINUUM VARIATIONS; ULTRAVIOLET EXPLORER IUE; QUASI-STELLAR OBJECTS; RESPONSE FUNCTIONS; LOW-DISPERSION; REGION; NGC-4151 AB The Seyfert 1 galaxy NGC 3516 was monitored during 1993 February 16-May 13 by IUE every 4 days for the first month, and then every 2 days for 2 months giving a total of 40 observations. This paper gives the initial results from this campaign, (1) The broad C IV lambda 1549 emission line variations are delayed relative to those of the ionizing continuum by similar to 4.5 days, consistent with that of other similar luminosity active galactic nuclei. (2) The mean 1993 UV continuum level was about a factor of 3 higher than the mean archive spectrum and was at a record level throughout the campaign. (3) There was dramatic variability in the C IV lambda 1549 line profile when compared to the IUE archival data. A narrow absorption line is present in all of the 1993 spectra. In contrast, the broad variable trough was undetectable, whereas it is a very strong feature in all of the IUE archival spectra. The N V lambda 1240 and Si N lambda 1400 lines showed a similar behavior. A variable broad absorption line (VAL) model is required to explain the archival data, but it is unclear if a VAL model. alone can explain the 1993 IUE data. Photoionization models suggest that the lack of line troughs in 1993 cannot be caused simply by increased ionization of the VAL gas. We propose two distinct models to explain the 1993 spectra: either the VAL gas has been dissipated, leaving a narrow absorption line presumably due to a more distant absorber, or an emission component, possibly a bicone, has greatly increased its contribution to the blue wing. Dissipation of the VAL gas implies a dynamic absorber, possibly the ionized surface layer of a molecular torus. An extra emission component implies that the broad line region properties in NGC 3516 may be radically different than has hitherto been proposed. C1 RUTHERFORD APPLETON LAB, DIDCOT OX11 0QX, OXON, ENGLAND. UCL, DEPT PHYS & ASTRON, LONDON WC1E 6BT, ENGLAND. UNIV OXFORD, DEPT PHYS, OXFORD OX1 3RH, ENGLAND. UNIV LEICESTER, DEPT PHYS & ASTRON, LEICESTER LE1 7RH, LEICS, ENGLAND. OBSERV PARIS, URA 173, F-92195 MEUDON, FRANCE. UPPSALA ASTRON OBSERV, S-75120 UPPSALA, SWEDEN. OHIO STATE UNIV, DEPT ASTRON, COLUMBUS, OH 43210 USA. UNIV MANCHESTER, NUFFIELD RADIO ASTRON LABS, JODRELL BANK, MACCLESFIELD SK11 9DL, CHESHIRE, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, COMP SCI CORP, GREENBELT, MD 20771 USA. UNIV HERTFORDSHIRE, DEPT PHYS SCI, HATFIELD AL10 9AB, HERTS, ENGLAND. UNIV CAMBRIDGE, INST ASTRON, CAMBRIDGE CB3 0HA, ENGLAND. UNIV KENTUCKY, DEPT PHYS & ASTRON, LEXINGTON, KY 40506 USA. ESA, IUE OBSERV, MADRID 28080, SPAIN. UNIV ST ANDREWS, ST ANDREWS KY16 922, FIFE, SCOTLAND. NASA, GODDARD SPACE FLIGHT CTR, IUE OBSERV, COMP SCI CORP, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, GRO SCI SUPPORT CTR, GREENBELT, MD 20771 USA. RP Koratkar, A (reprint author), SPACE TELESCOPE SCI INST, 3700 SAN MARTIN DR, BALTIMORE, MD 21218 USA. NR 59 TC 31 Z9 31 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 OCT 10 PY 1996 VL 470 IS 1 BP 378 EP 393 DI 10.1086/177873 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL723 UT WOS:A1996VL72300029 ER PT J AU Jones, DL Preston, RA Murphy, DW Jauncey, DL Reynolds, JE Tzioumis, AK King, EA McCulloch, PM Lovell, JEJ Costa, ME vanOmmen, TD AF Jones, DL Preston, RA Murphy, DW Jauncey, DL Reynolds, JE Tzioumis, AK King, EA McCulloch, PM Lovell, JEJ Costa, ME vanOmmen, TD TI Interstellar broadening of images in the gravitational lens PKS 1830-211 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (PKS 1830-211); gravitational lensing; scattering ID EINSTEIN RING; RADIO-SOURCE; PKS-1830-211 AB The remarkably strong radio gravitational lens PKS 1830-211 consists of a 1 '' diameter Einstein ring with two bright compact (milliarcsecond) components located on opposite sides of the ring, We have obtained 22 GHz Very Long Baseline Array (VLBA) data on this source in order to determine the intrinsic angular sizes of the compact components. Previous VLBI observations at lower frequencies indicate that the brightness temperatures of these components are significantly lower than 10(10) K (Jauncey et al.), less than is typical for compact synchrotron radio sources and less than is implied by the short timescales of flux density variations. A possible explanation is that interstellar scattering is broadening the apparent angular size of the source and thereby reducing the observed brightness temperature, Our VLBA data support this hypothesis, At 22 GHz, the measured brightness temperature is at least 10(11) K, and the deconvolved size of the core in the southwest compact component is proportional to v(-2) between 1.7 and 22 GHz. VLBI observations at still higher frequencies should be unaffected by interstellar scattering. C1 CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA. UNIV TASMANIA,DEPT PHYS,HOBART,TAS 7001,AUSTRALIA. UNIV TASMANIA,ANTARCTIC CRC,HOBART,TAS,AUSTRALIA. RP Jones, DL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI van Ommen, Tas/B-5020-2012; King, Edward/A-1473-2012 OI van Ommen, Tas/0000-0002-2463-1718; King, Edward/0000-0002-6898-2130 NR 25 TC 15 Z9 15 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP L23 EP L25 DI 10.1086/310292 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL724 UT WOS:A1996VL72400006 ER PT J AU Yaqoob, T Serlemitsos, PJ Turner, TJ George, IM Nandra, K AF Yaqoob, T Serlemitsos, PJ Turner, TJ George, IM Nandra, K TI Discovery of rapid variability of the iron K-line profile in the Seyfert galaxy NGC 7314 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; galaxies, active; galaxies, individual (NGC 7314); line, profiles; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY-SPECTRUM; COLD MATTER; EMISSION; DISK AB We present evidence of rapid variability of the shape of the Fe K line in the narrow-line Seyfert galaxy NGC 7314. The time-averaged line profile is strongly peaked near 6.4 keV and extends to similar to 5 and similar to 7 keV on the red and blue sides, respectively. The X-ray continuum varies by a factor of 2 on a timescale of hundreds of seconds, and it appears that emission in the red wing of the Fe K line below similar to 6 keV responds to these variations on timescales of less than similar to 3 x 10(4) s. The response becomes slower and slower toward the line peak near similar to 6.4 keV. The line broadening is unlikely to be due to scattering in material that fully encloses both continuum- and line-emitting regions, as it would not then be possible for the continuum to vary faster than any part of the Fe K line. Doppler and gravitational broadening (corresponding to a FWHM of similar to 8 x 10(4) km s(-1)) are likely to dominate. We show that the line-emitting region cannot lie completely outside r = 4.1 x 10(15) cm from the continuum source. This implies a strong upper limit on the putative black hole mass of 4.7 x 10(9) M(.) for a Schwarzschild metric and 2.3 x 10(10) M(.) for a maximally rotating Kerr metric. If the Fe K line originates entirely in an accretion disk, the disk cannot be highly ionized and has an inclination greater than 33 degrees. The equivalent width of the line is model dependent, most likely to be in the range similar to 300-460 eV, but could formally be as small as similar to 130 eV. An obvious interpretation of the less variable narrow core of the iron line is that it originates in distant, cold matter such as a molecular torus. In this case, low and high disk inclinations are preferred for ionized and neutral disks, respectively. RP Yaqoob, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. NR 26 TC 20 Z9 20 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1996 VL 470 IS 1 BP L27 EP L30 DI 10.1086/310297 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VL724 UT WOS:A1996VL72400007 ER PT J AU VanderWijngaart, RF Sarukkai, SR Mehra, P AF VanderWijngaart, RF Sarukkai, SR Mehra, P TI Analysis and optimization of software pipeline performance on MIMD parallel computers SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Article AB Observations show that fine-grain software pipelines on MIMD parallel computers with asynchronous communication suffer from dynamic load imbalances which cause delays in addition to the expected pipeline fill time. An analytical model that explains these load imbalances is presented. Optimization derived from the analysis leads to significant improvements in program performance. The results of applying this optimization to general pipeline algorithms on the Intel iPSC/860, Intel Paragon, and IBM SP/2, as well as to pipelined tri-diagonal equation solvers on the Intel Paragon and the IBM SP/2, are presented. (C) 1996 Academic Press, Inc. RP VanderWijngaart, RF (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 11 TC 0 Z9 0 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0743-7315 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD OCT 10 PY 1996 VL 38 IS 1 BP 37 EP 50 DI 10.1006/jpdc.1996.0127 PG 14 WC Computer Science, Theory & Methods SC Computer Science GA VV400 UT WOS:A1996VV40000004 ER PT J AU Murphy, KD Virgin, LN Rizzi, SA AF Murphy, KD Virgin, LN Rizzi, SA TI Characterizing the dynamic response of a thermally loaded, acoustically excited plate SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID LYAPUNOV EXPONENTS; TIME-SERIES; DIMENSION; ATTRACTORS; SYSTEMS AB In this work the dynamic response is considered of a homogeneous, fully clamped rectangular plate subject to spatially uniform thermal loads and narrow-band acoustic excitation. In both the pre and post-buckled regimes, the small amplitude, linear response is confirmed. However, the primary focus is on the large amplitude, non-linear, snap-through response, because of the obvious implications for fatigue in aircraft components. A theoretical model is developed which uses nine spatial modes and incorporates initial imperfections and non-ideal boundary conditions. Because of the higher order nature of this model, it is inherently more complicated than a one-mode buckled beam equation (Duffing's equation). An experimental system was developed to complement the theoretical results, and also to measure certain system parameters for the model which are not available theoretically. Several analysis techniques are used to characterize the response. These include time series, power spectra and autocorrelation functions. In addition, the fractal dimension and Lyapunov exponents for the response are computed to address the issue of spatial dimension and temporal complexity (chaos), respectively. Comparisons between theory and experiment are made and show considerable agreement. However, these comparisons also serve to point out difficulties in computing the fractal dimension and Lyapunov exponents from experimental data. (C) 1996 Academic Press Limited C1 DUKE UNIV,DEPT MECH ENGN,DURHAM,NC 27708. NASA,LANGLEY RES CTR,STRUCT ACOUST BRANCH,HAMPTON,VA 23681. RP Murphy, KD (reprint author), UNIV NEBRASKA,DEPT MECH ENGN,LINCOLN,NE 68588, USA. NR 39 TC 28 Z9 30 U1 0 U2 7 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD OCT 10 PY 1996 VL 196 IS 5 BP 635 EP 658 DI 10.1006/jsvi.1996.0506 PG 24 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA VL955 UT WOS:A1996VL95500006 ER PT J AU Muller, HSP Miller, CE Cohen, EA AF Muller, HSP Miller, CE Cohen, EA TI Dibromine monoxide, Br2O, and bromine dioxide, OBrO: Spectroscopic properties, molecular structures, and harmonic force fields SO ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH LA English DT Article DE bromine oxides; halogen compounds; radicals spectroscopy; structure elucidation ID EXCITED VIBRATIONAL-STATES; ROTATIONAL SPECTRUM; HYPERFINE CONSTANTS; CHLORINE DIOXIDE; SUPEROXIDE; MOMENT; HOBR RP Muller, HSP (reprint author), CALTECH,JET PROP LAB,MAIL STOP 183-301,4800 OAK GROVE DR,PASADENA,CA 91109, USA. OI Mueller, Holger/0000-0002-0183-8927 NR 35 TC 42 Z9 42 U1 1 U2 5 PU VCH PUBLISHERS INC PI DEERFIELD BEACH PA 303 NW 12TH AVE, DEERFIELD BEACH, FL 33442-1788 SN 0570-0833 J9 ANGEW CHEM INT EDIT JI Angew. Chem.-Int. Edit. Engl. PD OCT 7 PY 1996 VL 35 IS 18 BP 2129 EP 2131 DI 10.1002/anie.199621291 PG 3 WC Chemistry, Multidisciplinary SC Chemistry GA VN917 UT WOS:A1996VN91700020 ER PT J AU Allen, B Caldwell, RR Shellard, EPS Stebbins, A Veeraraghavan, S AF Allen, B Caldwell, RR Shellard, EPS Stebbins, A Veeraraghavan, S TI Large angular scale anisotropy in cosmic microwave background induced by cosmic strings SO PHYSICAL REVIEW LETTERS LA English DT Article ID COBE; RADIATION AB We simulate the anisotropy in the cosmic microwave background (CMB) induced by cosmic strings. By numerically evolving a network of cosmic strings we generate full-sky CMB temperature anisotropy maps. Based on 192 maps, we compute the anisotropy power spectrum for multipole moments l less than or equal to 20. By comparing with the observed temperature anisotropy, we set the normalization for the cosmic string mass per unit length mu, obtaining G mu/c(2) = 1.05(-0.20)(0.35) x 10(-6), which is consistent with all other observational constraints on Cosmic strings. We demonstrate that the anisotropy pattern is consistent with a Gaussian random field on large angular scales. C1 UNIV CAMBRIDGE,DEPT APPL MATH & THEORET PHYS,CAMBRIDGE CB3 9EW,ENGLAND. NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. UNIV MANCHESTER,NUFFIELD RADIO ASTRON LABS,JODRELL BANK,MACCLESFIELD SK11 9DL,CHESHIRE,ENGLAND. RP Allen, B (reprint author), UNIV WISCONSIN,DEPT PHYS,POB 413,MILWAUKEE,WI 53201, USA. RI Allen, Bruce/K-2327-2012; OI Allen, Bruce/0000-0003-4285-6256; Caldwell, Robert/0000-0001-7490-7463 NR 22 TC 53 Z9 53 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 OCT 7 PY 1996 VL 77 IS 15 BP 3061 EP 3065 DI 10.1103/PhysRevLett.77.3061 PG 5 WC Physics, Multidisciplinary SC Physics GA VL096 UT WOS:A1996VL09600001 ER PT J AU Kolb, EW Mohapatra, RN Teplitz, VL AF Kolb, EW Mohapatra, RN Teplitz, VL TI New supernova constraints on sterile-neutrino production SO PHYSICAL REVIEW LETTERS LA English DT Article ID DARK-MATTER; OSCILLATIONS; SN1987A; BURST AB We consider the possibility that a light, sterile-neutrino species nu(S) can be produced by nu(e) scattering during the cooling of a proto-neutron star. If we parametrize the sterile-neutrino production cross section by a parameter A as sigma(nu(e)X --> nu(S)X) = A sigma(nu(e) --> nu(e)X), where X is an electron, neutron, or proton, we show that A Is constrained by limits to the conversion of nu(e) to nu(S) in the region between the sterile-neutrino trapping region and the electron-neutrino, trapping region. This consideration excludes values of A in the range 10(-4) less than or similar to A less than or similar to 10(-1). C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742. SO METHODIST UNIV,DEPT PHYS,DALLAS,TX 75275. RP Kolb, EW (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. NR 31 TC 14 Z9 14 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 OCT 7 PY 1996 VL 77 IS 15 BP 3066 EP 3069 DI 10.1103/PhysRevLett.77.3066 PG 4 WC Physics, Multidisciplinary SC Physics GA VL096 UT WOS:A1996VL09600002 ER PT J AU Nguyen, H Ponchak, GE Kunath, R Bohman, D Varaljay, N AF Nguyen, H Ponchak, GE Kunath, R Bohman, D Varaljay, N TI Optimization of the rf circuit for wide-bandwidth cross-linked polymer electro-optic modulators SO MICROWAVE AND OPTICAL TECHNOLOGY LETTERS LA English DT Article DE optical modulation; losses; optical polymers; tapered waveguides ID WAVE AB A transmission-line theory approach that includes the complex propagation constant of the microwave electrodes and the impedance match between the electrode and the rf source and load is used to analyze the bandwidth of polyamide optical modulators. The analysis is then applied to an electro-optic modulator that has microstrip transmission lines placed directly over an optical waveguide buried in the polyamide substrate. The modulator is designed with coplanar waveguide (CPW) input and output contacts for rf characterization. The transition between the microstrip electrode and the CPW lines is presented. In addition, the processing techniques that yield polyamide side-wall profiles that are highly suited for transitioning from the CPW and the microstrip are presented. Finally, rf measurements of the complete microwave electrode are presented. (C) 1996 John Wiley & Sons, Inc. C1 CASE WESTERN RESERVE UNIV,DEPT ELECT ENGN & APPL PHYS,CLEVELAND,OH 44106. RP Nguyen, H (reprint author), NASA,LEWIS RES CTR,SPACE COMMUN DIV,MAIL STOP 54-8,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 12 TC 1 Z9 1 U1 0 U2 1 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0895-2477 J9 MICROW OPT TECHN LET JI Microw. Opt. Technol. Lett. PD OCT 5 PY 1996 VL 13 IS 2 BP 90 EP 94 DI 10.1002/(SICI)1098-2760(19961005)13:2<90::AID-MOP10>3.0.CO;2-D PG 5 WC Engineering, Electrical & Electronic; Optics SC Engineering; Optics GA VG746 UT WOS:A1996VG74600010 ER PT J AU Dodelson, S Gates, EI Turner, MS AF Dodelson, S Gates, EI Turner, MS TI Cold dark matter SO SCIENCE LA English DT Review ID LARGE-SCALE STRUCTURE; BIG-BANG NUCLEOSYNTHESIS; MICROWAVE BACKGROUND ANISOTROPIES; MINIMAL ISOCURVATURE MODEL; DAMPED LYMAN-ALPHA; COSMOLOGICAL CONSTANT; MASS FLUCTUATIONS; CMB ANISOTROPIES; HUBBLE CONSTANT; COBE SATELLITE AB Motivated by inflation, the theory of big-bang nucleosynthesis, and the quest for a deeper understanding of fundamental forces and particles, a paradigm for the development of structure in the universe has evolved. It holds that most of the matter exists in the form of slowly moving elementary particles left over from the earliest moments-cold dark matter-and that the small density inhomogeneities that seed structure formation arose from quantum fluctuations around 10(-34) seconds after the big bang. A flood of observations, from determinations of the Hubble constant to measurements of the anisotropy of cosmic background radiation, are now testing the cold dark matter paradigm. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637. RP Dodelson, S (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. NR 131 TC 56 Z9 56 U1 1 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 4 PY 1996 VL 274 IS 5284 BP 69 EP 75 DI 10.1126/science.274.5284.69 PG 7 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VK748 UT WOS:A1996VK74800047 ER PT J AU Cooper, JB Vess, TM Campbell, LA Jensen, BJ AF Cooper, JB Vess, TM Campbell, LA Jensen, BJ TI Real-time in situ monitoring of the thermal cure of a bisphenol cyanate: A view toward intelligent processing SO JOURNAL OF APPLIED POLYMER SCIENCE LA English DT Article ID SQUARES REGRESSION-ANALYSIS; INFRARED-SPECTROSCOPY; RAMAN-SPECTROSCOPY; FT-IR; INSITU; FIBER; SENSOR AB A dispersive fiber-optic Raman spectrometer was used to remotely monitor, in real-time, the local temperature and the extent of reaction of a commercial cyanate ester polymer (AroCy L-10). The local temperature was determined by solving the Boltzmann relation governing the intensity ratio of the Raman Stokes and anti-Stokes scattering of a reference eo mode which does not vary with the reaction chemistry. The extent of the reaction can be monitored using either individual peaks associated with the reactant or product or by using the entire spectrum and principal component multivariate calibration. The use of principal component analysis has distinct advantages over the single-peak method. (C) 1996 John Wiley & Sons, Inc. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Cooper, JB (reprint author), OLD DOMINION UNIV,DEPT CHEM & BIOCHEM,NORFOLK,VA 23529, USA. NR 32 TC 15 Z9 15 U1 0 U2 3 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0021-8995 J9 J APPL POLYM SCI JI J. Appl. Polym. Sci. PD OCT 3 PY 1996 VL 62 IS 1 BP 135 EP 144 DI 10.1002/(SICI)1097-4628(19961003)62:1<135::AID-APP17>3.3.CO;2-N PG 10 WC Polymer Science SC Polymer Science GA VG685 UT WOS:A1996VG68500017 ER PT J AU Leonard, PJT AF Leonard, PJT TI Gamma-ray astronomy - A keener eye than EGRET SO NATURE LA English DT Editorial Material RP Leonard, PJT (reprint author), GODDARD SPACE FLIGHT CTR,COMPTON GAMMA RAY OBSERV,SCI SUPPORT CTR,GREENBELT,MD 20771, USA. NR 0 TC 3 Z9 3 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD OCT 3 PY 1996 VL 383 IS 6599 BP 394 EP 395 DI 10.1038/383394a0 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VL463 UT WOS:A1996VL46300041 ER PT J AU Bekey, I AF Bekey, I TI Access to space SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 45th International Astronautical Congress CY OCT 09-14, 1994 CL JERUSALEM, ISRAEL AB This paper reviews a NASA study on Access to Space, as well as a U.S. Department of Defense report, ''The Space Launch Modernization Study'', both from 1994. Space transportation policy is discussed, while the nation's current and future options are examined and compared. RP Bekey, I (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 0 TC 0 Z9 0 U1 1 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD OCT PY 1996 VL 39 IS 7 BP 537 EP 552 DI 10.1016/S0094-5765(97)85434-3 PG 16 WC Engineering, Aerospace SC Engineering GA XA622 UT WOS:A1996XA62200007 ER PT J AU Davis, DO Willis, BP Hingst, WR AF Davis, DO Willis, BP Hingst, WR TI Flowfield measurements inside a boundary-layer bleed slot SO AIAA JOURNAL LA English DT Article AB An experimental investigation was conducted to determine the flowfield inside a bleed slot used to control an oblique shock-wave and turbulent boundary-layer interaction, The slot was oriented normal to the primary how direction and had a width of 1.0 cm (primary how direction) and a length of 2.54 cm and spanned 16.5 cm, The approach boundary layer upstream of the interaction was nominally 3.0 cm thick. Two operating conditions were studied: M = 1.98 with a shock generator deflection angle of 6 deg and M = 2.46 with a shock generator deflection angle of 8 deg. Measurements include surface and flowfield static pressure, pitot pressure, and total mass flow through the slot, The results show that despite an initially two-dimensional interaction for the zero-bleed-how case, the slot does not remove mass uniformly in the spanwise direction, Inside the slot, the flow is characterized by two separation regions, which significantly reduce the effective how area, The upper separation region acts as an aerodynamic throat, resulting in supersonic flow through much of the slot. RP Davis, DO (reprint author), NASA,LEWIS RES CTR,INLET DUCT & NOZZLE FLOW PHYS BRANCH,INTERNAL FLUID MECH DIV,CLEVELAND,OH 44135, USA. NR 20 TC 1 Z9 1 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1996 VL 34 IS 10 BP 1977 EP 1983 DI 10.2514/3.13342 PG 7 WC Engineering, Aerospace SC Engineering GA VK555 UT WOS:A1996VK55500001 ER PT J AU Stremel, PM AF Stremel, PM TI Effect of fences on airfoil aerodynamics at -90 degree incidence SO AIAA JOURNAL LA English DT Article AB A two-dimensional computational method is applied to accurately calculate the viscous flow about airfoils normal to the freestream flow, In particular, the flow about an XV-15 wing airfoil with an upper or lower surface fence at -90 deg incidence is evaluated, A parametric study is conducted to investigate and understand the effect of fences on the flow about an airfoil normal to the freestream flow. This investigation includes the effect of fence location for both upper and lower surfaces and of fence height on airfoil aerodynamic characteristics. Comparisons of the time-averaged lift, drag, pitching moment, and surface pressure distributions are made to evaluate the effectiveness of each airfoil/fence configuration, The results indicate that 1) the airfoil drag is highly dependent on the fence chordwise location, ranging from a 15% increase in drag for an upper surface fence to a 35% decrease in drag for a lower surface fence with respect to the basic airfoil value; 2) the airfoil drag is also dependent on the fence height, with a drag reduction of 25% for a lower surface fence of 35% chord height located at 15%; chord; and 3) the reduction in drag is the direct result of decreased pressure on the airfoil upper surface near the leading edge and an increase in the lower surface pressure over the entire airfoil chord. RP Stremel, PM (reprint author), NASA,AMES RES CTR,APPL AERODYNAM DIV,APPL COMPUTAT AERODYNAM BRANCH,MOFFETT FIELD,CA 94035, USA. NR 9 TC 1 Z9 1 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1996 VL 34 IS 10 BP 1984 EP 1989 DI 10.2514/3.13343 PG 6 WC Engineering, Aerospace SC Engineering GA VK555 UT WOS:A1996VK55500002 ER PT J AU Fung, KY Man, RSO Davis, S AF Fung, KY Man, RSO Davis, S TI Implicit high-order compact algorithm for computational acoustics SO AIAA JOURNAL LA English DT Article ID FINITE-DIFFERENCE SCHEMES; HYPERBOLIC SYSTEMS AB Accurate solution of the linearized, multidimensional Euler equations for aeroacoustics as a system of simple wave equations is demonstrated, If organized, this system has unambiguous, easily implemented boundary conditions allowing waves of same group speeds to pass through numerical boundaries or comply with wall conditions, Thus, the task of designing a complex multidimensional scheme with approximate boundary conditions reduces to the design of accurate schemes for the simple wave equation, In particular, an implicit compact finite difference scheme and a characteristically exact but numerically nth-order-accurate boundary condition are used, This low-dispersion scheme has a third-order spatial accuracy for various types of nonuniform meshes, fourth-order accuracy on uniform meshes, and by choice a temporal accuracy of second order for algorithmic simplicity as the Crank-Nicolson scheme, The robustness and accuracy of the scheme and the validity of the system decoupling are demonstrated through a series of numerical experiments and comparisons with published results, including the recent Institute for Computer Applications in Science and Engineering, NASA Langley Research Center, benchmark problems of acoustic and convective wave propagation in Cartesian and cylindrical domains and reflection at stationary and/or moving boundaries. C1 NASA,AMES RES CTR,FLUID MECH LAB BRANCH,MOFFETT FIELD,CA 94035. UNIV ARIZONA,TUCSON,AZ 85721. RP Fung, KY (reprint author), UNIV MIAMI,DEPT MECH ENGN,CORAL GABLES,FL 33124, USA. NR 13 TC 15 Z9 16 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1996 VL 34 IS 10 BP 2029 EP 2037 DI 10.2514/3.13349 PG 9 WC Engineering, Aerospace SC Engineering GA VK555 UT WOS:A1996VK55500008 ER PT J AU Nikolaidis, E Stroud, WJ AF Nikolaidis, E Stroud, WJ TI Reliability-based optimization: A proposed analytical-experimental study SO AIAA JOURNAL LA English DT Article ID DESIGN AB An analytical and experimental study for assessing the potential of reliability-based structural optimization is proposed and described. Competing designs obtained by deterministic and reliability-based optimization are compared. The experimental portion of the study is practical because the structure selected is a modular, actively and passively controlled truss that consists of many identical members, and because the competing designs are compared in terms of their dynamic performance and are not destroyed if failure occurs. The analytical portion of tills study is illustrated on a 10-bar truss example. In the illustrative example, it is shown that reliability-based optimization can yield a design that is superior to an alternate design obtained by deterministic optimization. These analytical results provide motivation for the proposed analytical-experimental study, which is described elsewhere. C1 NASA, LANGLEY RES CTR, COMPUTAT STRUCT BRANCH, HAMPTON, VA 23681 USA. RP Nikolaidis, E (reprint author), VIRGINIA POLYTECH INST & STATE UNIV, BLACKSBURG, VA 24061 USA. NR 16 TC 3 Z9 6 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1996 VL 34 IS 10 BP 2154 EP 2161 DI 10.2514/3.13365 PG 8 WC Engineering, Aerospace SC Engineering GA VK555 UT WOS:A1996VK55500024 ER PT J AU Harvey, AD Rogers, SE AF Harvey, AD Rogers, SE TI Steady and unsteady computation of impeller-stirred reactors SO AICHE JOURNAL LA English DT Article AB A general computational approach is presented for numerical modeling of viscous flow in baffled, impeller-stirred-tank reactors. A multiblock, body-fitted grid structure facilitates modeling of various impeller and baffle designs, and a new procedure offers averaged velocity data from a complex 3-D CFD dataset. Impellers are modeled precisely, eliminating the need for inputting experimental velocity data for boundary conditions. The method can be used quickly to obtain extremely detailed flow computations at a fraction of the cost of computing unsteady moving grid solutions. A steady-state computational approach that neglects the relative motion between impeller and baffles yields numerical results comparably accurate to full unsteady computations for laminar flow at a fraction of the time and expense. The approximate steady-state method is used to predict power requirements of a Rushton turbine in laminar flow. An unsteady, moving grid technique provides time-accurate solutions for the pow inside an impeller-stirred reactor with side-wall baffles. These computed results are compared with those using the approximate steady-state method and with experimental measurements. The unsteady, moving gild method uses two different initial conditions: one starting from rest and the other starting from an approximate steady-state solution obtained at the starting position of the impeller relative to rite baffles. For unsteady simulations of laminar flow in stirred vessels, the final operating condition call be achieved much more efficiently if the solution obtained from the steady-state procedure is used as an approximate initial condition. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Harvey, AD (reprint author), DOW CHEM CO USA,PLAQUEMINE,LA 70765, USA. NR 15 TC 66 Z9 68 U1 0 U2 4 PU AMER INST CHEMICAL ENGINEERS PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0001-1541 J9 AICHE J JI AICHE J. PD OCT PY 1996 VL 42 IS 10 BP 2701 EP 2712 DI 10.1002/aic.690421002 PG 12 WC Engineering, Chemical SC Engineering GA VL162 UT WOS:A1996VL16200001 ER PT J AU Chang, DS Breit, GA Styf, JR Hargens, AR AF Chang, DS Breit, GA Styf, JR Hargens, AR TI Cutaneous microvascular flow in the foot during simulated variable gravities SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Article DE capillary blood flow; weight bearing; microgravity; tissue ischemia; posture; skin ID PRESSURE DISTRIBUTION; DIABETES-MELLITUS; BLOOD-FLOW; COMPRESSION; RESPONSES; POSITION; HUMANS; SKIN; BODY AB Our objective was to understand how weight bearing with varying gravitational fields affects blood perfusion in the sole of the foot. Human subjects underwent whole body tilting at four angles: upright [1 gravitational vector from head to foot (G(z))], 22 degrees (0.38 G(z)), 10 degrees (0.17 G(z)), and supine (0 G(z)), simulating the gravitational fields of Earth, Mars, Moon, and microgravity, respectively. Cutaneous capillary blood flow was monitored on the plantar surface of the heel by laser Doppler flowmetry while weight-bearing load was measured. At each tilt angle, subjects increased weight bearing on one foot in graded load increments of 1 kg beginning with zero. The weight bearing at which null flow first occurred was determined as the closing load. Subsequently, the weight bearing was reduced in reverse steps until blood flow returned (opening load). Mean closing loads for simulated Earth gravity, Mars gravity, Moon gravity, and microgravity were 9.1, 4.6, 4.4, and 3.6 kg, respectively. Mean opening loads were 7.9, 4.1, 3.5, and 3.1 kg, respectively. Mean arterial pressures in the foot (MAP(foot)) calculated for each simulated gravitational field were 192, 127, 106, and 87 mmHg, respectively. Closing load and opening load were significantly correlated with MAP(foot) (r = 0.70, 0.72, respectively) and were significantly different (P < 0.001) from each other. The data suggest that decreased local arterial pressure in the foot lowers tolerance to external compression. Consequently, the human foot sole may be more prone to cutaneous ischemia during load bearing in microgravity than on Earth. C1 NASA, AMES RES CTR, GRAVITAT RES BRANCH 239-11, DIV LIFE SCI, MOFFETT FIELD, CA 94035 USA. NR 24 TC 1 Z9 1 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0363-6119 J9 AM J PHYSIOL-REG I JI Am. J. Physiol.-Regul. Integr. Comp. Physiol. PD OCT PY 1996 VL 271 IS 4 BP R961 EP R966 PG 6 WC Physiology SC Physiology GA VL794 UT WOS:A1996VL79400019 PM 8897988 ER PT J AU Engelke, KA Doerr, DF Convertino, VA AF Engelke, KA Doerr, DF Convertino, VA TI Application of acute maximal exercise to protect orthostatic tolerance after simulated microgravity SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Article DE bed rest; baroreflex; blood pressure; orthostasis; orthostatic hypotension; vasoconstriction ID VAGAL BAROREFLEX; INTENSE EXERCISE; BLOOD-VOLUME; BED REST; 24 H; RESPONSES; PRESSURE; REFLEX; INTOLERANCE; HYPOTENSION AB We tested the hypothesis that one bout of maximal exercise performed at the conclusion of prolonged simulated microgravity would improve blood pressure stability during an orthostatic challenge. Heart rate (HR), mean arterial blood pressure (MAP), norepinephrine (NE), epinephrine (E), arginine vasopressin (AVP), plasma renin activity (PRA), atrial natriuretic peptide (ANP), cardiac output (Q over dot), forearm vascular resistance (FVR), and changes in leg volume were measured during lower body negative pressure (LBNP) to presyncope in seven subjects immediately prior to reambulation from 16 days of 6 degrees head-down tilt (HDT) under two experimental conditions: 1) after maximal supine cycle ergometry performed 24 h before returning to the upright posture (exercise) and 2) without exercise (control). After HDT, the reduction of LBNP tolerance time from pre-HDT levels was greater (P = 0.041) in the control condition (-2.0 +/- 0.2 min) compared with the exercise condition (-0.4 +/- 0.2 min). At presyncope after HDT, FVR and NE were higher (P < 0.05) after exercise compared with control, whereas MAP, HR, E, AVP, PRA, ANP, and leg volume were similar in both conditions. Plasma volume (PV) and carotid-cardiac baroreflex sensitivity were reduced after control HDT, but were restored by the exercise treatment. Maintenance of orthostatic tolerance by application of acute intense exercise after 16 days of simulated microgravity was associated with greater circulating levels of NE, vasoconstriction, Q over dot, baroreflex sensitivity, and PV. C1 ARMSTRONG LAB, AOCY, PHYSIOL RES BRANCH, DIV CLIN SCI, BROOKS AFB, TX 78235 USA. UNIV FLORIDA, DEPT PHYSIOL, GAINESVILLE, FL 32610 USA. NASA, KENNEDY SPACE CTR, CAPE CANAVERAL, FL 32899 USA. NR 32 TC 60 Z9 60 U1 1 U2 4 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0363-6119 J9 AM J PHYSIOL-REG I JI Am. J. Physiol.-Regul. Integr. Comp. Physiol. PD OCT PY 1996 VL 271 IS 4 BP R837 EP R847 PG 11 WC Physiology SC Physiology GA VL794 UT WOS:A1996VL79400003 PM 8897972 ER PT J AU Kowitt, MS Fixsen, DJ Goldin, A Meyer, SS AF Kowitt, MS Fixsen, DJ Goldin, A Meyer, SS TI Frequency selective bolometers SO APPLIED OPTICS LA English DT Article DE bolometer; resonance filter; frequency selective bolometer; resonant mesh; cryogenic ID MICROWAVE BACKGROUND-RADIATION; MILLIMETER; ANISOTROPY; FILTERS; SYSTEM AB We propose a concept for radiometry in the millimeter, the submillimeter, and the far-IR spectral regions, the frequency selective bolometer (FSB). This system uses a bolometer as a coupled element of a tuned quasi-optical interference filter in which the absorption, the transmission, and the reflection characteristics of the filter depend on the frequency in a controlled manner. Several FSB's can be cascaded within a straight light pipe to produce a high-efficiency, compact, multiband radiometer. A prototype design is presented together with its anticipated performance based on a one-dimensional transmission-line model. Instruments based on FSB technology should have several advantages over current multiband bolometric radiometers including smaller and more compact cryogenic optics; reduced demands on cryostat size and weight, high coupling efficiency, minimum constraints on the geometry in the focal plane. An FSB system can be configured as a multiband, close-packed focal-plane array, permitting efficient use of the throughput of a telescope. (C) 1996 Optical Society of America C1 NASA,GODDARD SPACE FLIGHT CTR,APPL RES CORP,GREENBELT,MD 20771. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. DANISH SPACE RES INST,COPENHAGEN,DENMARK. RP Kowitt, MS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 685-0,GREENBELT,MD 20771, USA. NR 23 TC 18 Z9 18 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD OCT 1 PY 1996 VL 35 IS 28 BP 5630 EP 5635 DI 10.1364/AO.35.005630 PG 6 WC Optics SC Optics GA VJ501 UT WOS:A1996VJ50100023 PM 21127568 ER PT J AU vanParadijs, J Waters, LBFM Groot, PJ Kouveliotou, C Smith, IA Hurley, KC Schultz, ASB Wallyn, P Telesco, C vanderHooft, F Bontekoe, TJR Kester, DJM AF vanParadijs, J Waters, LBFM Groot, PJ Kouveliotou, C Smith, IA Hurley, KC Schultz, ASB Wallyn, P Telesco, C vanderHooft, F Bontekoe, TJR Kester, DJM TI Infrared observations of soft gamma repeaters SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE gamma rays, bursts; circumstellar matter; supernova remnants; infrared, ISM, continuum ID LARGE MAGELLANIC CLOUD; SUPERNOVA-REMNANTS; IRAS SURVEY; RAY BURSTS; IDENTIFICATION; SGR1806-20; COINCIDENT; NEBULA AB We have made IRAS (12, 25, and 60 mu m) maximum entropy images of the three known soft gamma repeaters SGR 0526-66, SGR 1806-20, and SGR 1900+14. In addition we have obtained a high-resolution 10 mu m image of SGR 1900+14 using TIMMI at the ESO 3.6 m telescope. All three SGRs have associated with them an infrared source. The infrared emission associated with SGR 0526-66 likely originates from heated dust in the supernova remnant N49. The infrared properties of the two galactic SGRs ate similar; both are unresolved at 12 and 25 mu m, and extended at 60 mu m. The relation of these infrared sources (if any) to the SGRs is as yet unclear. C1 CTR HIGH ENERGY ASTROPHYS, NL-1098 SJ AMSTERDAM, NETHERLANDS. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, USRA, HUNTSVILLE, AL 35812 USA. RICE UNIV, HOUSTON, TX 77251 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV FLORIDA, DEPT ASTRON, GAINESVILLE, FL 32611 USA. SRON, LAB SPACE RES, NL-9700 AV GRONINGEN, NETHERLANDS. RP vanParadijs, J (reprint author), UNIV AMSTERDAM, ASTRON INST ANTON PANNEKOEK, KRUISLAAN 403, NL-1098 SJ AMSTERDAM, NETHERLANDS. RI Groot, Paul/K-4391-2016 OI Groot, Paul/0000-0002-4488-726X NR 42 TC 9 Z9 9 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 OCT PY 1996 VL 314 IS 1 BP 146 EP 152 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM335 UT WOS:A1996VM33500020 ER PT J AU Sekanina, Z AF Sekanina, Z TI Collision of comet Shoemaker-Levy 9 with Jupiter: Impact study of two fragments from the timing of precursor events SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE impact of Shoemaker-Levy 9 on Jupiter; precursors; fragmentation as dominant ablation of brittle impacters; penetration depth; terminal explosion ID FIREBALL AB The impacts of fragments K and R of comet Shoemaker-Levy 9 are examined with the aims to interpret the timing of the observed precursors to the main thermal emission event and to correlate the results of ground-based infrared observations with a variety of observations made onboard the Galilee spacecraft. Analysis of the phenomena associated with the impact and explosion of fragment K shows that there is no discrepancy in the timing of the Earth- and Galileo-based observations and that the time of 53 +/- 3 seconds between the emission peak of Precursor I and the onset of Precursor 2, as recorded by terrestrial observers, can be interpreted as the interval between the impactor's disappearance behind the Jovian limb and the first appearance of the ejecta's plume over the limb following the explosion of the fragment's residual mass. It is concluded that the impactor exploded at an altitude of 45 to 50 km above the pressure level of 1 bar and that the residual mass involved in the explosion, approximately 6 to 7 million tons and about 400 meters across, represented only a fraction of 1 percent of the fragment's preatmospheric mass. The explosion is calculated to have taken place under a dynamic pressure of several hundred bars and the explosion energy is found to have been on the order of 10(26) erg. The results for fragment R show it to be smaller and less massive than fragment K, exploding slightly higher in the Jovian stratosphere, 50-60 km above 1 bar. Most of the entry kinetic energy of either impactor was rapidly dissipated during atmospheric flight by prolific mass ablation - dominated by the object's fragmentation - before the point of explosion was reached. The rate of ablation of these massive fragments was comparable with that observed in the Earth's atmosphere for category IIIb fireballs, which belong to the population of "soft" cometary material and whose bulk density was determined to be typically 0.2 g/cm(3). Vigorous fragmentation - both continuous and occurring in discrete events of extremely short duration is known for such impactors to be independent of their mass and to surpass vastly (especially for massive objects) ablation effects due to evaporation and spraying. Evidence from several other observations of comet Shoemaker-Levy 9 appears to corroborate the present conclusions on the bulk properties and the penetration depths of the major fragments of comet Shoemaker-Levy 9. RP Sekanina, Z (reprint author), CALTECH, JET PROPULS LAB, PASADENA, CA 91109 USA. NR 37 TC 0 Z9 0 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 OCT PY 1996 VL 314 IS 1 BP 315 EP 327 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VM335 UT WOS:A1996VM33500039 ER PT J AU Kaastra, JS Mewe, R Liedahl, DA Singh, KP White, NE Drake, SA AF Kaastra, JS Mewe, R Liedahl, DA Singh, KP White, NE Drake, SA TI Emission measure analysis methods: The corona of AR lacertae revisited SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE methods, data analysis; stars, abundances; stars, coronae; stars, individual, AR Lac; X-rays, stars ID EUV SPECTROSCOPY; COOL STARS; SOLAR AB A simultaneous ROSAT/ASCA observation of the RS CVn binary AR Lac has been re-analysed using updated calculations for the plasma emission. Several analysis methods are applied that serve to reconstruct the emission measure distribution of AR Lac. In particular we describe the regularisation method, a Chebyshev polynomial method, a clean algorithm, a genetic algorithm and a method based upon broadened discrete temperature components. We confirm earlier results that the abundance are non-solar; for most elements (O, Mg, Si, S, Ar, Ca and Fe), we find abundances that are consistent with 1/3 of the solar photospheric abundances. The abundances of Ne (0.7) and Ni (1.1) are somewhat larger. The emission measure analysis shows that there are at least two and probably three temperature components: a cool, intermediate and hot component at temperatures of 0.6, 1 and 2.4 keV, respectively. The cool component is rather narrow (less than 50 % relative width) and there is no significant emission below 0.3 keV down to our detection limit at about 0.03 keV. The intermediate and hot component may be separate structures, but could also be the dominant features of a more continuous emission measure distribution between 1-4 keV. High-temperature emission above 5 keV is limited to at most 5 % of the total. C1 LAWRENCE LIVERMORE NATL LAB, DIV 5, LIVERMORE, CA 94550 USA. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RP Kaastra, JS (reprint author), SRON, SPACE RES LAB, SORBONNELAAN 2, NL-3584 CA UTRECHT, NETHERLANDS. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 30 TC 72 Z9 72 U1 1 U2 2 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 OCT PY 1996 VL 314 IS 2 BP 547 EP 557 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN758 UT WOS:A1996VN75800020 ER PT J AU Lara, L Marcaide, JM Alberdi, A Guirado, JC AF Lara, L Marcaide, JM Alberdi, A Guirado, JC TI VLBI differential astrometry at large angular separation: 3C 395-3C 382 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE astrometry techniques, interferometric; quasars, individual (3C 395); galaxies, individual (3C 382) ID BASELINE RADIO INTERFEROMETRY; PROPER MOTION; GEODESY; SYSTEM AB We have observed the pair of radio sources 3C 395 and 3C 382 using Very Long Baseline Interferometry in November 1990, simultaneously at 8.4 and 2.3 GHz. Through the use of differential astrometry techniques we have determined with sub-milliarcsecond precision the angular separation between these two sources. We have demonstrated the feasibility of differential astrometry for pairs of radio sources separated 6 degrees on the sky, being the reference source a low luminosity radio galaxy. Successive differential astrometry observations would allow to clarify unambiguously the internal kinematics of the quasar 3C 395. C1 CSIC, INST ASTROFIS ANDALUCIA, E-18080 GRANADA, SPAIN. UNIV VALENCIA, DEPT ASTRON & ASTROFIS, E-46100 BURJASSOT, VALENCIA, SPAIN. LAEFF, E-28080 MADRID, SPAIN. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Lara, L (reprint author), CNR, IST RADIOASTRON, VIA GOBETTI 101, I-40129 BOLOGNA, ITALY. NR 26 TC 9 Z9 9 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 OCT PY 1996 VL 314 IS 2 BP 672 EP 678 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN758 UT WOS:A1996VN75800034 ER PT J AU Hesse, A Acharya, BS Heinbach, U Heinrich, W Henkel, M Luzietti, B Simon, M Christian, ER Esposito, JA Balasubrahmanyan, VK Barbier, LM Ormes, JF Streitmatter, RE AF Hesse, A Acharya, BS Heinbach, U Heinrich, W Henkel, M Luzietti, B Simon, M Christian, ER Esposito, JA Balasubrahmanyan, VK Barbier, LM Ormes, JF Streitmatter, RE TI Isotopic composition of silicon and iron in the galactic cosmic radiation SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE cosmic rays ID FRAGMENTATION CROSS-SECTIONS; RELATIVISTIC NUCLEI; CARBON TARGETS; RAY PROPAGATION; HYDROGEN; HELIUM; ABUNDANCES; NICKEL; CHARGE; MN-54 AB In this paper, we report on the isotopic abundances of galactic cosmic ray silicon and iron as measured on our 1987 balloon flight from Prince Albert, Saskatchewan, Canada. The ALICE (A Large Isotopic Composition Experiment) instrument is a balloon-borne spectrometer designed to measure the isotopic composition of cosmic rays in the elemental range silicon through iron. The instrument uses the Cherenkov-range technique and resolves masses for particles with kinetic energies from similar to 350 MeV/nucleon to similar to 800 MeV/nucleon incident upon the Cherenkov detector. We observe no measurable excess of Si-29, Si-30, Fe-54, Fe-57 or Fe-58 and therefore are consistent with a solar-system-like cosmic ray source abundance. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV SIEGEN, DEPT PHYS, D-57068 SIEGEN, GERMANY. RI Christian, Eric/D-4974-2012 OI Christian, Eric/0000-0003-2134-3937 NR 41 TC 7 Z9 7 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 OCT PY 1996 VL 314 IS 3 BP 785 EP 794 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN759 UT WOS:A1996VN75900014 ER PT J AU Sekanina, Z AF Sekanina, Z TI Activity of comet Hale-Bopp (1995 O1) beyond 6 AU from the Sun SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE comet Hale-Bopp ID HALLEY; GAS AB The physical evolution of comet Hale-Bopp is investigated along the preperihelic are of its orbit at heliocentric distances larger than 6 AU. The comet's considerable intrinsic brightness and activity are explained by the existence of a relatively large area on its nucleus surface that is a reservoir of both carbon monoxide and dust particulates. Three recurring dust emission events observed in August-October 1995 are studied in some detail. The characteristic shape of the features produced in the course of these episodes is interpreted as a product of a sharply peaked temporal profile of the dust emission and suggests a probable common source to all the three events. The timing of these events is shown to exhibit a periodicity that may indicate the state of rotation of the comet, which apparently is not pure spin. The total mass of dust ejected during one of the episodes is calculated from reports of the comet's ''nuclear magnitudes'' at pertinent times to be on the order of 10(11) grams. Estimates of the dust production rate are compared with the published production rates of carbon monoxide and it is concluded that the mass loading of the CO gas flow by dust was enormous, certainly much greater than a factor of 15. Finally, comet Hale-Bopp is compared with other comets known to have experienced activity at large heliocentric distances. Most similarities are found with the dust emission pattern of comet 29P/Schwassmann-Wachmann 1. RP Sekanina, Z (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 47 TC 28 Z9 28 U1 1 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT PY 1996 VL 314 IS 3 BP 957 EP 965 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN759 UT WOS:A1996VN75900032 ER PT J AU Evrard, AE Metzler, CA Navarro, JF AF Evrard, AE Metzler, CA Navarro, JF TI Mass estimates of X-ray clusters SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; galaxies, clusters, general; hydrodynamics; X-rays, galaxies ID DISSIPATIVE GALAXY FORMATION; DARK-MATTER; HUBBLE CONSTANT; COMA CLUSTER; SIMULATIONS; DYNAMICS; EVOLUTION; GAS; NUCLEOSYNTHESIS; SUBSTRUCTURE AB We use cosmological gasdynamic simulations to investigate the accuracy of galaxy cluster mass estimates based on X-ray observations. The experiments follow the formation of clusters in different cosmological models and include the effects of gravity, pressure gradients, and hydrodynamical shocks. A subset of our ensemble also allows for feedback of mass and energy from galactic winds into the intracluster medium. We find that mass estimates based on the hydrostatic, isothermal beta-model are remarkably accurate when evaluated at radii where the cluster mean density is between 500 and 2500 times the critical density. At lower densities, radial temperature information becomes important. In the quoted radial regime, the distribution of the estimated-to-true mass ratio, derived from 174 artificial images constructed from the simulations, is nearly unbiased and has a standard deviation of 14%-29%. The scatter can be considerably reduced (to 8%-15%) by using an alternative mass estimator that exploits the tightness of the mass-temperature relation found in the simulations. The improvement over beta-model estimates is due to the elimination of the variance contributed by the gas outer slope parameter. We discuss these findings and their implications for recent measurements of cluster baryon fractions. C1 NASA, FERMILAB ASTROPHYS CTR, BATAVIA, IL 60510 USA. UNIV ARIZONA, STEWARD OBSERV, TUCSON, AZ 85721 USA. UNIV CALIF SANTA BARBARA, INST THEORET PHYS, SANTA BARBARA, CA 93106 USA. RP UNIV MICHIGAN, DEPT PHYS, ANN ARBOR, MI 48109 USA. OI Evrard, August/0000-0002-4876-956X NR 62 TC 559 Z9 559 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1996 VL 469 IS 2 BP 494 EP 507 DI 10.1086/177798 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ788 UT WOS:A1996VJ78800006 ER PT J AU Massey, P Bianchi, L Hutchings, JB Stecher, TP AF Massey, P Bianchi, L Hutchings, JB Stecher, TP TI The UV-brightest stars of M33 and its nucleus: Discovery, photometry, and optical spectroscopy SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (M33); galaxies, stellar content; stars, early-type; stars, Wolf-Rayet; supergiants; ultraviolet, stars ID WOLF-RAYET STARS; LARGE MAGELLANIC CLOUD; LOCAL GROUP GALAXIES; H-II REGIONS; OB ASSOCIATIONS; SPECTRAL CLASSIFICATION; ABSOLUTE MAGNITUDES; INTRINSIC COLORS; GALACTIC-CENTER; STELLAR WINDS AB We investigate the UV-brightest sources in the nearby galaxy M33. Our catalog of 356 sources is constructed from far-ultraviolet (FUV; 1500 Angstrom) and near-ultraviolet (NUV; 2400 Angstrom) images obtained with the Ultraviolet Imaging Telescope (UIT) matched with ground-based UBV data. We find that our survey is limited by the FUV flux and is complete to F-lambda 1500 = 2.5 x 10(-15) ergs cm(-2) s(-1) Angstrom(-1), other than in the most crowded regions; this corresponds roughly to M(bol) = -9.2 to -10.0 (or masses of 40-60 M.), for T-eff = 50,000 degrees to 10,000 degrees. We use Hubble Space Telescope (HST) WFPC2 images of several M33 fields to conclude that at least one-half of our sample is uncontaminated by unresolved neighbors, at least at the 0 degrees.1 (0.4 pc) level, a resolution similar to that achieved in the LMC from the ground. Spectral types have been obtained for 131 of our objects. We discuss the spatial distribution of the UIT sources, finding that they provide an excellent tracer of the spiral arm pattern and confirm that star formation continues in the nuclear region to the present day. Our survey has found a large number of and early B-type supergiants, including stars as early as O6, but the optical spectroscopic sample is dominated by later type B supergiants, as these are the visually brighter. Among the brightest stars (both at 1500 A and at V) are the ''superluminous'' Wolf-Rayet stars first discovered by Conti & Massey in the largest H II regions of M33; these objects are now known to be small groups of stars in modest analog to R136 in 30 Dor. In general, our survey has failed to detect the known W-R stars, as they are too faint, but we did find several new late-type WN stars and composite systems, which are brighter. Two stars of high absolute visual magnitude (M(v) approximate to -9.0) are found to be B I+WN binaries, similar to HDE 269546 in the LMC; one of these is multiple at HST resolution. Most interesting, perhaps, is our finding six Ofpe/ WN9 ''slash'' stars, five of them newly discovered. These stars show properties intermediate between those of Of and WN stars and are believed to be a quiescent form of luminous blue variables (LBVs). Our spectroscopy found five additional stars that are spectroscopically similar to the known LBVs of M33. One of these stars has recently been shown to be spectroscopically variable, and we suggest that all of these stars deserve continued scrutiny. The nucleus of M33 is the visually brightest object in our survey, and its UV colors are indicative of a hotter component than its optical photometry or spectral type would suggest. We discuss the possibility that the pointlike nucleus may contain a few interesting hot stars that dominate the light in the UV, and we make the comparison to the cluster of He I emission-line stars found near the center of the Milky Way. We comment on which color-magnitude and color-color plots make the best diagnostic tools for studying the hot, massive star population of a galaxy like M33. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Massey, P (reprint author), KITT PEAK NATL OBSERV,NATL OPT ASTRON OBSERV,POB 26732,TUCSON,AZ 85726, USA. OI Massey, Philip/0000-0001-6563-7828 NR 82 TC 74 Z9 75 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1996 VL 469 IS 2 BP 629 EP & DI 10.1086/177811 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ788 UT WOS:A1996VJ78800019 ER PT J AU Jones, AP Tielens, AGGM Hollenbach, DJ AF Jones, AP Tielens, AGGM Hollenbach, DJ TI Grain shattering in shocks: The interstellar grain size distribution SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; methods, numerical; shock waves; supernovae, general ID INTER-STELLAR SPACE; DUST GRAINS; DESTRUCTION; COLLISIONS; EXTINCTION; EVOLUTION; VELOCITY; PHYSICS; GROWTH; GAS AB We have studied the effects of shattering in grain-grain collisions. Based upon extensive numerical simulation of surface explosions and impacts, an analytical model has been developed which relates the final crater mass and fragment size distribution to the relative collision velocity, grain sizes, and material properties of projectile and target. Our model contains one free parameter, the critical shock pressure for shattering. We have compared the calculated crater masses to laboratory experiments on (sub)micron-sized particle impacts on a wide variety of materials and find good agreement assuming that the critical pressure for shattering is equal to the shear strength of the material. This critical pressure corresponds to minimum collision velocities of similar to 1 km s(-1) for shattering to occur. The shattering threshold is much smaller than the vaporization threshold, and we therefore conclude that shattering dominates over vaporization in grain-grain collisions. The calculated size distribution of the shattered fragments scales with a(-3.3); slightly less steep than the Mathis, Rumpl, & Nordsieck (MRN) size distribution. Essentially, any shattering model where the size of the fragments is related to the pressure experienced will lead to fragment power-law size distributions with indices slightly steeper than similar to 3. The maximum fragment size increases with increasing crater size (i.e., increasing collision velocity) until the target grain is completely disrupted by the collision. For higher velocity collisions, our theory predicts that the maximum shattered fragment size will decrease again. Dust destruction (return of grain mass to the gas) in the interstellar medium occurs predominantly in shock waves in the warm neutral/ionized medium (density similar or equal to 0.25 cm(-3), temperature similar or equal to 10(4) K). The new theory for grain shattering in grain-grain collisions has been incorporated into a grain destruction code and used to reevaluate the grain destruction rate in interstellar shocks in the warm medium, We find that, for all the grain materials we consider (graphite, silicate, silicon carbide, diamond, iron, and ice) nonthermal and thermal sputtering dominate the grain destruction. We also find that grain disruption (shattering) in grain-grain collisions dominates the grain mass redistribution. We present detailed results for grain destruction as a function of the grain size and composition. In particular, we consider MRN size distributions of silicate and carbonaceous (amorphous carbon/graphite) grains. We also present results for silicon carbide, diamond, iron, and ice test particles. For both carbonaceous and silicate grains we find that the fractional destruction (i.e., return of solid material to the gas phase) is less than or equal to 0.5, for upsilon(s) less than or equal to 200 km s(-1). The grain lifetimes against destruction, assuming the three-phase model of the interstellar medium, are 6 x 10(8) yr, and 4 x 10(8) yr, for carbonaceous and silicate grains, respectively, only slightly longer than previous studies that ignored shattering. Grain shattering in grain-grain collisions in shock waves leads to the redistribution of the dust mass from large grains(a greater than or equal to 1000 Angstrom) into small grains (a<500 Angstrom). After processing by a single shock, a major fraction of the grains larger than 300 Angstrom have experienced shattering grain-grain collisions. The slope of the fragment size distribution produced in single collisions has little influence on the size distribution produced by shocks. Essentially, the resulting grain size distribution is slightly steeper than MRN, because the largest grains move at the highest postshock velocities and hence are preferentially shattered into the smallest fragments. Large grains are lost from the interstellar grain size distribution on time scales less than 10(8) yr in the warm medium. For 50 km s(-1) less than or equal to upsilon(s) less than or equal to 200 km s(-1) as much as 5%-15% of the initial grain mass (all grain radii greater than or equal to 50 Angstrom) may end up in sub-14 Angstrom fragments. Thus, interstellar shocks may be a prodigious source of PAH molecules, PAH clusters, and small grains. Given that the typical stardust injection time scale is 2.5 x 10(9) yr, we conclude that efficient mechanisms for grain growth, and in particular, the reformation of grains with radii greater than or equal to 1000 Angstrom must exist in interstellar medium in order that the refractory elements be incorporated in dust and that most of the dust mass is in sizes greater than or equal to 1000 Angstrom as observed. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. OI Jones, Anthony/0000-0003-0577-6425 NR 62 TC 406 Z9 406 U1 3 U2 25 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1996 VL 469 IS 2 BP 740 EP 764 DI 10.1086/177823 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ788 UT WOS:A1996VJ78800031 ER PT J AU Robinson, RD Airapetian, VS Maran, SP Carpenter, KG AF Robinson, RD Airapetian, VS Maran, SP Carpenter, KG TI Observing stellar coronae with the Goddard High Resolution Spectrograph .2. The RS CVn binary system HR 1099 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, chromospheres; stars, coronae; stars, individual (HR 1099); ultraviolet, stars ID SOLAR TRANSITION ZONE; RESONANT ABSORPTION; ALFVEN WAVES; EXPLOSIVE EVENTS; AU-MICROSCOPII; SURFACE-WAVES; RADIO FLARES; X-RAY; REGION; MODEL AB We report time series observations of the RS CVn star HR 1099 taken with the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope. The data cover a wavelength range from 1342 to 1375 Angstrom and show a measurable continuum, as well as emission lines of O I, C I, Cl I, Fe II, O V, and Fe XXI. The chromospheric and transition region features are seen only in the active K1 IV component of the binary system, while the Fe XXI (10(7) K) flux may come from both components, with the active component having the stronger flux, There is no indication of Fe XII emission, formed at 1.3 x 10(6) K. The width of the Fe XXI profile indicates that the corona of the primary is unlikely to extend to heights greater than 2.3R(star), while other indicators suggest that the average loops are really much smaller, having a length of similar to 3 x 10(10) cm with an electron density on the order of 10(10) cm(-3). Some evidence for atmospheric turbulence is detected in all of the observed emission lines. This turbulence initially increases with height, going from less than 30 km s(-1) in the chromosphere to as much as 150 km s(-1) in the transition region. The turbulence then decreases in the corona, where velocities of less than 65 km s(-1) are indicated. Theoretical fits to the O V profile also suggest that this turbulence is anisotropically distributed, with motions directed primarily along or perpendicular to the radial direction. While admitting the possibility that the atmosphere is heated by microflare events, we examine an alternative heating process that involves the damping of MHD turbulence, which might be generated by nonlinear Alfven waves or by shocks. Simple calculations indicate that the observed turbulence is sufficient to account for the transition region and coronal heating. C1 NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. RP COMP SCI CORP, GODDARD SPACE FLIGHT CTR, ASTRON PROGRAM, CODE 681, GREENBELT, MD 20771 USA. RI Carpenter, Kenneth/D-4740-2012 NR 65 TC 22 Z9 22 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1996 VL 469 IS 2 BP 872 EP 883 DI 10.1086/177834 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ788 UT WOS:A1996VJ78800042 ER PT J AU Guo, WP Wu, ST TandbergHanssen, E AF Guo, WP Wu, ST TandbergHanssen, E TI Disruption of helmet streamers by current emergence SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; sun, corona; sun, prominences ID CORONAL MASS EJECTIONS; MAGNETIC-FIELD; SOLAR CORONA; EVOLUTION; MODEL AB We have investigated the dynamic response of a coronal helmet streamer to the emergence from below of a current with its magnetic field in a direction opposite to the overlying streamer field. Once the emerging current moves into the closed region of the streamer, a current sheet forms between the emerging field and the streamer field, because the preexisting held and the newly emerging field have opposite polarities, Thus magnetic reconnection will occur at the flanks of the emerged structure where the current density is maximum. If the emerging current is large enough, the energy contained in the current and the reconnection will promptly disrupt the streamer. If the emerging current is small, the streamer will experience a stage of slow evolution. In this stage, slow magnetic reconnection occurring at the hanks of the emerged structure leads to the degeneration of the emerged current to a neutral point. Above this point, a new magnetic bubble will form. The resulting configuration resembles an inverse-polarity prominence. Depending on the initial input energy of the current, the resulting structure will either remain in situ, forming a quasi-static structure, or move upward, forming a coronal transient similar to coronal jets. The numerical method used in this paper can be used to construct helmet streamers containing a detached magnetic structure in their closed field region. The quasi-static solution may serve as a preevent corona for studying coronal mass ejection initiation. C1 NASA,MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. RP Guo, WP (reprint author), UNIV ALABAMA,DEPT MECH & AEROSP ENGN,CTR SPACE PLASMA & AERONOM RES,HUNTSVILLE,AL 35899, USA. NR 24 TC 20 Z9 25 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1996 VL 469 IS 2 BP 944 EP 953 DI 10.1086/177841 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ788 UT WOS:A1996VJ78800049 ER PT J AU Hurley, K Li, P Murakami, T Shibata, R Ogasaka, Y Pedersen, H Vrba, F Luginbuhl, C Cline, T Palmer, D Ricker, G Kouveliotou, C Kawai, N Matsuoka, M Yoshida, A Yamauchi, M AF Hurley, K Li, P Murakami, T Shibata, R Ogasaka, Y Pedersen, H Vrba, F Luginbuhl, C Cline, T Palmer, D Ricker, G Kouveliotou, C Kawai, N Matsuoka, M Yoshida, A Yamauchi, M TI ASCA rediscovery of the X-ray source in the 1978 November 19 gamma-ray burst error box SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; stars, neutron ID NEUTRON STAR MODELS; CONSTRAINTS AB We present an analysis of the X-ray content of the 1978 November 19 gamma-ray burst error box using ASCA. We confirm the presence of a source that was detected by Einstein, but not confirmed by EXOSAT, and measure its spectrum between 0.5 and 8 keV. Using a power-law fit with an index of 1.77, the source flux is 1.6 x 10(-13) erg cm(-2) s(-1). This source was also observed by ROSAT. Using both old and new optical and radio data, we examine a possible counterpart for the X-ray source. We find that the probability of a chance association between the X-ray source and the gamma-ray burst error box is small enough to warrant its consideration as a possible counterpart to the burst source. C1 INST SPACE & ASTRONAUT SCI, KANAGAWA 229, JAPAN. COPENHAGEN UNIV OBSERV, NBIFAFG, DK-2100 COPENHAGEN O, DENMARK. USN OBSERV, FLAGSTAFF STN, FLAGSTAFF, AZ 86002 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. MIT, CTR SPACE RES, CAMBRIDGE, MA 02139 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. RIKEN, WAKO, SAITAMA 35101, JAPAN. MIYAZAKI UNIV, MIYAZAKI 88921, JAPAN. KANAGAWA UNIV, KANAGAWA KU, YOKOHAMA, KANAGAWA 221, JAPAN. RP Hurley, K (reprint author), UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. NR 15 TC 6 Z9 6 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1996 VL 469 IS 2 BP L105 EP + DI 10.1086/310272 PN 2 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ790 UT WOS:A1996VJ79000010 ER PT J AU Klein, RI Jernigan, JG Arons, J Morgan, EH Zhang, W AF Klein, RI Jernigan, JG Arons, J Morgan, EH Zhang, W TI GRO J1744-28 and Scorpius X-1: First evidence for photon bubble oscillations and turbulence SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion; hydrodynamics; instabilities; stars, neutron AB We discuss our recent Rossi X-Ray Timing Explorer (RXTE) observations of GRO J1744-28, which discovered quasi-periodic oscillations (QPOs) of the intensities in the energy band 3-12 keV during observations starting on 1996 January 18.77 UT. We have found that the power spectrum in the frequency band 5-1000 Hz consists of two red-noise components that can be characterized by two power laws, each with an index of -5/3 and a QPO peak centered at 40 Hz. We suggest that the power peak is due to a newly discovered form of turbulence in the accretion column of super-Eddington accretion-powered pulsars driven by photon bubble instabilities. These instabilities give rise to strong power peaks at frequencies characteristic of photon diffusion and bubble coalescence in the highly nonlaminar accretion column resulting in photon bubble oscillations (PBOs). The relationship between the rms amplitude of the PBOs and the intensity is in qualitative agreement with observations. Our calculations also suggest that the observed high-frequency red-noise component with a -5/3 power-law index from 40 to 600 Hz is the first evidence of photon bubble turbulence in the accretion column of an X-ray pulsar. Recent RXTE observations of Sco X-l have found high-frequency QPOs at 1100 and 830 Hz. We show that PBOs at these frequencies are a natural consequence of photon bubble instabilities. We also show that the rms amplitudes of the calculated PBOs at these frequencies are consistent with the observations. We predict that further RXTE observations of Sco X-l should reveal additional PBOs at 2000 and 2600 Hz as well as a broadband continuum spectrum with a -5/3 power law, extending from 3000 to several times 10(4) Hz. C1 LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94550 USA. LAWRENCE LIVERMORE NATL LAB, INST GEOPHYS & PLANETARY PHYS, LIVERMORE, CA 94550 USA. UNIV CALIF BERKELEY, THEORET ASTROPHYS CTR, BERKELEY, CA 94720 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. MIT, CTR SPACE RES, CAMBRIDGE, MA 02139 USA. GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RP Klein, RI (reprint author), UNIV CALIF BERKELEY, DEPT ASTRON, 601 CAMPBELL HALL, BERKELEY, CA 94720 USA. NR 11 TC 33 Z9 33 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 OCT 1 PY 1996 VL 469 IS 2 BP L119 EP L123 DI 10.1086/310277 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ790 UT WOS:A1996VJ79000013 ER PT J AU Silva, AVR White, SM Lin, RP DePater, I Gary, DE McTiernan, JM Hudson, HS Doyle, JG Hagyard, MJ Kundu, MR AF Silva, AVR White, SM Lin, RP DePater, I Gary, DE McTiernan, JM Hudson, HS Doyle, JG Hagyard, MJ Kundu, MR TI Comprehensive multiwavelength observations of the 1992 January 7 solar flare SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE sun, flares; sun, magnetic fields; sun, radio radiation; sun, X-rays, gamma rays ID HARD X-RAY; DIELECTRONIC SATELLITE SPECTRA; HELIUM-LIKE IONS; ELECTRON POPULATIONS; MULTIFREQUENCY OBSERVATIONS; SPATIAL-RESOLUTION; A MISSION; MICROWAVE; MILLIMETER; TELESCOPE AB Observations of a solar flare that occurred at 2022 UT on 1992 January 7, during the 1991 December/ 1992 January Max '91 campaign, are presented. This flare was observed simultaneously in H alpha, radio (at microwave and millimeter wavelengths), and soft and hard X-rays (by the Yohkoh spacecraft) with high spatial and moderate spectral resolution. A comparison of magnetograms before and after the flare shows evidence of the emergence of new magnetic flux of opposite polarity at the flare site. Although this flare was only of moderate size (GOES classification C8.9 and H alpha importance SF), it exhibited several distinct bursts and at least 10 spatially distinct hard/soft X-ray sources. Cospatial H alpha brightenings suggest that most of the X-ray sources are located at footpoints of magnetic loops. Two of the hard X-ray sources have no H alpha counterparts and are therefore believed to be located at loop tops. The flare consisted of three bursts of particle acceleration followed by a purely thermal phase. High spectral resolution Ca XIX line profiles indicate upflows shortly after the second acceleration phase. Analysis of the microwave/hard X-ray/soft X-ray emission from individual sources provides information on the radio emission mechanisms, the energetic electron population, the magnetic field strength, and the plasma density. These parameters were estimated for the two microwave sources observed during the third acceleration burst; these sources were simultaneously detected in soft X-rays, and one of the sources is also seen in hard X-ray maps. Although the microwave emission is consistent with the gyrosynchrotron mechanism, the millimeter emission, which peaks during the thermal phase when all nonthermal activity has ceased, is likely due to thermal bremsstrahlung from the soft X-ray-emitting hot plasma. The energy lost to collisions by the energetic (>15 keV) electrons and the energy contained in the thermal plasma are calculated for each source. The energy injected by the nonthermal electrons from all sources is estimated to be similar to 10(30) ergs. Only the soft X-ray sources with gradual time profiles seem to show the Neupert effect. C1 UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. CALTECH, PASADENA, CA 91103 USA. UNIV HAWAII, INST ASTRON, HONOLULU, HI 96822 USA. ARMAGH OBSERV, ARMAGH BT61 9DG, NORTH IRELAND. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. RP Silva, AVR (reprint author), UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. RI Valio, Adriana/I-2531-2012; OI Valio, Adriana/0000-0002-1671-8370; Gary, Dale/0000-0003-2520-8396 NR 49 TC 9 Z9 9 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD OCT PY 1996 VL 106 IS 2 BP 621 EP 646 DI 10.1086/192351 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE459 UT WOS:A1996WE45900015 ER PT J AU Dobrovolski, SG Choudhury, BJ AF Dobrovolski, SG Choudhury, BJ TI Temporal climatic variabilities of global atmospheric, oceanic, and land surface parameters SO ATMOSFERA LA English DT Article ID TEMPERATURE; MODELS AB Changes in the states of two groups of major earth climatic subsystems are investigated: (a) ''thick'' subsystems (atmosphere, and ocean), and (b), ''thin'' subsystems (vegetation, snow, and sea ice). These two groups are distinguished with respect to temporal variations of their spatial extent which is dynamic for the ''thin'' subsystems and stable for ''thick'' subsystems. Stochastic models governing monthly and longer-term anomalies of remotely sensed and in situ, globally averaged parameters of these layers (tropospheric temperature, sea surface temperature, vegetation, snow and sea ice cover areas) are evaluated according to a new modification of the maximum entropy method with frequency truncation of normalized spectra. The analysis shows that global temporal variations of global ''thick'' subsystems are governed by the Bernoulli-Wiener type stochastic processes, while variabilities of the global ''thin'' subsystems are described by the first order Markov processes with intermediate values of coefficients. It is hypothesized that stochastic variations in global sea ice, snow, and vegetation covers depend on only a small number of independent regional variations and therefore still show the Markov characteristics of the latter. On the basis of the analysis of observational data and stochastic modeling, the authors propose a concept of mechanisms of climatic variations which takes into consideration different climatic subsystems as well as different temporal and spatial scales. The proposed hypothesis explains the stationarity of changes in the are-a of global ''thin'' covers, and the non-stationary, random walk (i.e. without deterministic trends) character of global temperature changes. RP Dobrovolski, SG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,LAB HYDROSPHER PROC,GREENBELT,MD 20771, USA. NR 35 TC 0 Z9 0 U1 0 U2 2 PU CENTRO CIENCIAS ATMOSFERA UNAM PI MEXICO CITY PA CIRCUITO EXTERIOR, MEXICO CITY CU 04510, MEXICO SN 0187-6236 J9 ATMOSFERA JI Atmosfera PD OCT 1 PY 1996 VL 9 IS 4 BP 273 EP 289 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VK125 UT WOS:A1996VK12500004 ER PT J AU Thompson, AM AF Thompson, AM TI Biomass burning and the atmosphere - Accomplishments and research opportunities SO ATMOSPHERIC ENVIRONMENT LA English DT Article RP Thompson, AM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA. RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 0 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1352-2310 J9 ATMOS ENVIRON JI Atmos. Environ. PD OCT PY 1996 VL 30 IS 19 BP R1 EP R2 DI 10.1016/S1352-2310(96)90021-7 PG 2 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA VB161 UT WOS:A1996VB16100015 ER PT J AU Wickman, LA Luna, B AF Wickman, LA Luna, B TI Locomotion while load-carrying in reduced gravities SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article AB Supporting the mass of a protective suit and portable life support system (PLSS) will impose an energy requirement on planetary astronauts. To design extravehicular protective equipment for planetary missions, scientists must learn more about human physical capabilities while load-carrying in reduced gravities. In this study, an underwater treadmill and weighting system were used to simulate reduced-gravity locomotion while load-carrying. The test matrix included 3 gravity levels, 6 subjects, 2 locomotion speeds, and a range of load sizes. Energy expenditure, calculated from measured oxygen consumption, is positively correlated with gravity level, speed, and load size. The data are used to project that individuals in average physical condition will be able to walk for 8 h on the Moon while carrying up to 170% of their body mass without undue fatigue, and on Mars with up to 50% of their body mass. These approximate limits, especially for Martian gravity, may prove quite a challenge for designers of advanced protective systems. Requirements for regenerable and non-venting PLSS components have been driving the total projected masses of advanced PLSSs increasingly higher, perhaps beyond what is reasonable to carry. However, the larger mass can be beneficial in maintaining bone mass. Using Whalen's model (1988), the daily planetary walking times required to maintain bone mass were calculated for a range of carried load sizes. The calculated times were unattainably high, suggesting that some combination of load-carrying and supplemental bone maintenance measures will likely be required to maintain bone mass in reduced gravity environments. C1 LOCKHEED MARTIN MISSILES & SPACE CO,SUNNYVALE,CA. NASA,AMES RES CTR,EXTRAVEHICULAR & PROTECT SYST BRANCH,MOFFETT FIELD,CA 94035. NR 9 TC 4 Z9 5 U1 0 U2 1 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD OCT PY 1996 VL 67 IS 10 BP 940 EP 946 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA VL585 UT WOS:A1996VL58500004 PM 9025816 ER PT J AU Wilson, LJ AdcockDowney, L Pusey, ML AF Wilson, LJ AdcockDowney, L Pusey, ML TI Monomer concentrations and dimerization constants in crystallizing lysozyme solutions by dialysis kinetics SO BIOPHYSICAL JOURNAL LA English DT Article ID LIGHT-SCATTERING; GROWTH AB Dialysis kinetics measurements have been made to study the effect of ionic strength on the dimerization of lysozyme in acidic solutions that lead to the growth of tetragonal lysozyme crystals, Using glutaraldehyde cross-linked dimers of lysozyme, we have determined that both monomers and dimers can escape from 25,000 molecular weight cutoff dialysis membranes with velocity constants of 5.1 x 10(-7) and 1.9 x 10(-7) s(-1) for the monomer and dimer species, respectively. The flux from 25K MWCO membranes has been measured for lysozyme in pH 4.0 buffered solutions of 1, 3, 4, 5, and 7% NaCl over a wide range of protein concentrations. Assuming that dimerization is the first step in crystallization, a simple monomer to dimer equilibrium was used to model the flux rates, Dimerization constants calculated at low protein concentrations were 265, 750, 1212, and 7879 M(-1) for 3, 4, 5, and 7% NaCl, respectively, These values indicate that dimerization increases with the ionic strength of the solution suggesting that aggregation is moderated by electrostatic interactions, At high protein concentrations and high supersaturation, the dimerization model does not describe the data well, However, the Li model that uses a pathway of monomer <-> dimer <-> tetramer <-> octamer <-> 16-mer fits the measured flux data remarkably well suggesting the presence of higher order aggregates in crystallizing solutions. C1 MEVATECH CORP,HUNTSVILLE,AL 35806. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,BIOPHYS BRANCH,HUNTSVILLE,AL 35812. RP Wilson, LJ (reprint author), E TENNESSEE STATE UNIV,DEPT CHEM,BOX 70695,JOHNSON CITY,TN 37614, USA. NR 17 TC 28 Z9 28 U1 0 U2 4 PU BIOPHYSICAL SOCIETY PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0006-3495 J9 BIOPHYS J JI Biophys. J. PD OCT PY 1996 VL 71 IS 4 BP 2123 EP 2129 PG 7 WC Biophysics SC Biophysics GA VK295 UT WOS:A1996VK29500044 PM 8889187 ER PT J AU Lau, KM Kim, JH Sud, Y AF Lau, KM Kim, JH Sud, Y TI Intercomparison of hydrologic processes in AMIP GCMs SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SURFACE AIR-TEMPERATURE; PRECIPITATION AB Results of an intercomparison study under the Atmospheric Model Intercomparison Project (AMIP) to assess the abilities of 29 global climate models (GCMs) in simulating various aspects of regional and hydrologic processes in response to observed sea surface temperature and sea ice boundary forcings are presented. The authors find that the models generally portray an earthlike climate to approximately 10%-20% of the global land surface temperature (= 14.8 degrees C) and global precipitation (= 2.3 mm day(-1)). While a majority of the models have a reasonable global water budget, about a quarter of the models show significant errors in the total global water balance. While the model frequency distributions of heavy precipitation associated with deep convection are in reasonable agreement with observations, a systematic underestimate of the frequency of occurrence of light precipitation events (< 1 mm day(-1)) is present in almost all the AMIP models, especially over continental desert regions and over tropical and subtropical oceanic regions contiguous to the west coasts of continents where low-level stratocumulus clouds tend to occur. This discrepancy is presumably related to the crude treatment of moist processes, especially those related to low clouds and nonconvective precipitation in the models. Another common problem in the global rainfall distribution is the presence of spectral rain or spurious gridpoint-scale heavy rain. The artificial anchoring of rainfall to topographic features in the Maritime Continent appears to be a generic problem in many GCMs. Models differ substantially in the magnitude of the rainfall amount over the eastern Pacific ITCZ for all seasons. The simulated boreal summer rainfall distributions have large variability over the Indian subcontinent and the Bay of Bengal. The northward migration of the monsoon convective zones are not well simulated. In particular, the East Asian monsoon rainband over the subtropical western Pacific is ill-defined or absent in all models. On the interannual timescale, the models show reasonable skills in simulating the fluctuations of the Southern Oscillation and the eastward migration of the major equatorial precipitation zone during ENSO. Most models show useful rainfall prediction skill in the Tropics associated with ENSO-related SST forcing. However, the models do not show any useful skill for extratropical rainfall prediction from specified anomalous global SST forcing. Overall, the models depict a reasonably realistic annual cycle of water balance over regions where long-term local moisture balance is maintained-that is, (P-E) approximate to 0-over large interior land regions in the extratropics. In regions of strong dynamic control-that is, (P-E) much greater than 0-such as the tropical western Pacific, monsoon regions, and the ITCZ, the intermodel variability is very large. The simulated water balance over large river basins has been validated against hydrographic river discharge data using a river-routing model. Results show that while the model ensemble mean runoffs are consistent with the climatological observed river discharge for the Amazon and Mississippi, the intermodel variability is substantial. The models yield even more divergent results over other world river basins. These results suggest that while some GCMs may have moderate capability in capturing some aspects of the climatological variation of runoff, it is premature to use them for climate studies related to continental-scale water balance. A ranking of the AMIP models and some possible implications based on the above performance are also presented. RP Lau, KM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CLIMATE & RADIAT BRANCH,CODE 913,GREENBELT,MD 20771, USA. RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 23 TC 91 Z9 95 U1 1 U2 6 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD OCT PY 1996 VL 77 IS 10 BP 2209 EP 2227 DI 10.1175/1520-0477(1996)077<2209:IOHPIA>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VP991 UT WOS:A1996VP99100001 ER PT J AU Cohen, SC AF Cohen, SC TI Convenient formulas for determining dip-slip fault parameters from geophysical observables SO BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA LA English DT Article ID KENAI PENINSULA; SUBDUCTION ZONE; HALF-SPACE; DEFORMATION; EARTHQUAKE; ALASKA AB Simple equations are presented for estimating slip magnitude, fault dip angle, width of the zone of compression, and other co-seismic parameters from geologic, seismic, and geodetic observations made in subduction zone and continental dip-slip environments. These equations are easy to memorize and use without computational aids. RP Cohen, SC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,GREENBELT,MD 20771, USA. NR 11 TC 13 Z9 14 U1 0 U2 0 PU SEISMOLOGICAL SOC AMER PI EL CERRITO PA PLAZA PROFESSIONAL BLDG, SUITE 201, EL CERRITO, CA 94530 SN 0037-1106 J9 B SEISMOL SOC AM JI Bull. Seismol. Soc. Amer. PD OCT PY 1996 VL 86 IS 5 BP 1642 EP 1644 PG 3 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VP989 UT WOS:A1996VP98900034 ER PT J AU Yu, ST Jiang, BN Wu, J Liu, NS AF Yu, ST Jiang, BN Wu, J Liu, NS TI A div-curl-grad formulation for compressible buoyant flows solved by the least-squares finite element method SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID NONSYMMETRIC LINEAR-SYSTEMS; FLUID-DYNAMICS; VISCOUS FLOWS; EQUATIONS; COMPUTATION; CONVECTION AB The present paper reports the development of the least-squares finite-element method for simulating compressible buoyant flows at low Mach numbers. We propose a div-curl-grad formulation with unknowns including vorticity, velocity, heat fluxes, temperature and pressure variation. The formulation is proved to be elliptic such that permissible boundary conditions become self-evident for a well posed flow problem. In contrast to conventional approaches. the present method evades the predicament of the 'singularity' problem of low-speed flows and no special treatment or artificial boundary condition is needed. Moreover, the assembled coefficient matrix is symmetric and positive-definite: its inversion is implemented by an element-by-element jacobi conjugate gradient method. As a numerical example, we calculate two-dimensional compressible buoyant flows inside a square enclosure at various Rayleigh numbers. For Rayleigh number one million, four secondary vortices were found embedded in the primary vortex. Due to significant temperature variations, the fluid flows are highly compressible in the interior. Along the walls, however, the flows are incompressible. The Nusselt number-Rayleigh number correlation deduced from the numerical result compared favorably with previously reported data. C1 NASA,LEWIS RES CTR,OHIO AEROSP INST,INST COMPUTAT MECH & PROPULS,CLEVELAND,OH 44135. RP Yu, ST (reprint author), NASA,LEWIS RES CTR,NYMA TECHNOL INC,BROOKPARK,OH, USA. NR 38 TC 13 Z9 13 U1 1 U2 2 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD OCT 1 PY 1996 VL 137 IS 1 BP 59 EP 88 DI 10.1016/0045-7825(95)00989-2 PG 30 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA VP560 UT WOS:A1996VP56000002 ER PT J AU Mathews, GJ Towheed, SS AF Mathews, GJ Towheed, SS TI WWW-based data systems for interactive manipulation of science data SO COMPUTER NETWORKS AND ISDN SYSTEMS LA English DT Article DE research; analysis; visualization; distribution; CGI; HTML; VRML AB The World Wide Web (WWW), which was originally conceived for document delivery, has now evolved into a vehicle supporting interactive data visualization and distribution. Two WWW-based data systems, OMNIWeb and COHOWeb, for providing enhanced access to scientific data have been developed at the National Space Science Data Center (NSSDC) at NASA's Goddard Space Flight Center. This paper discusses these systems and how the underlying model can be extended to support large amounts of data. Research in using VRML for scientific visualization is discussed with its potential in an interactive data system. C1 HUGHES STX,GREENBELT,MD 20771. RP Mathews, GJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,MAIL CODE 633,GREENBELT RD,GREENBELT,MD 20771, USA. NR 6 TC 0 Z9 0 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0169-7552 J9 COMPUT NETWORKS ISDN JI Comput. Netw. ISDN Syst. PD OCT PY 1996 VL 28 IS 13 BP 1857 EP 1864 DI 10.1016/0169-7552(96)00004-9 PG 8 WC Computer Science, Information Systems; Engineering, Electrical & Electronic; Telecommunications SC Computer Science; Engineering; Telecommunications GA VP077 UT WOS:A1996VP07700010 ER PT J AU Pollock, GD Noor, AK AF Pollock, GD Noor, AK TI Sensitivity analysis of the contact/impact response of composite structures SO COMPUTERS & STRUCTURES LA English DT Article ID FINITE-ELEMENT FORMULATION; IMPACT PROBLEMS; FRICTION; CONSTRAINTS; PENALTY RP Pollock, GD (reprint author), UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23681, USA. NR 35 TC 11 Z9 13 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD OCT PY 1996 VL 61 IS 2 BP 251 EP 269 DI 10.1016/0045-7949(95)00455-6 PG 19 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA VC579 UT WOS:A1996VC57900004 ER PT J AU DiPirro, M AF DiPirro, M TI Summary of the 1995 Space Cryogenics Workshop - Foreword SO CRYOGENICS LA English DT Editorial Material RP DiPirro, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 719 EP 720 DI 10.1016/0011-2275(96)00033-1 PG 2 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800001 ER PT J AU Russo, SC Sugimura, RS AF Russo, SC Sugimura, RS TI NASA IN-STEP Cryo System Experiment flight test SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE cryocooler; diode heat pipe; Stirling cycle AB The Cryo System Experiment (CSE), a NASA In-Space Technology Experiments Program (IN-STEP) flight experiment, was flown on Space Shuttle Discovery (STS 63) in February 1995. The experiment was developed by Hughes Aircraft Company to validate in zero-g space a 65 K cryogenic system for focal planes, optics, instruments or other equipment (gamma ray spectrometers and infrared and submillimetre imaging instruments) that requires continuous cryogenic cooling. The CSE is funded by the NASA Office of Advanced Concepts and Technology's IN-STEP and managed by the Jet Propulsion Laboratory (JPL). The overall goal of the CSE was to validate and characterize the on-orbit performance of the two thermal management technologies that comprise a hybrid cryogenic system. These thermal management technologies consist of (1) a second-generation long-life, low-vibration, Stirling-cycle 65 K cryocooler that was used to cool a simulated thermal energy storage device (TRP) and (2) a diode oxygen heat pipe thermal switch that enables physical separation between a cryogenic refrigerator and a TRP. All CSE experiment objectives and 100% of the experiment success criteria were achieved. The level of confidence provided by this flight experiment is an important NASA and Department of Defense (DoD) milestone prior to multi-year mission commitment. Presented are generic lessons learned from the system integration of cryocoolers for a flight experiment and the recorded zero-g performance of the Stirling cryocooler and the diode oxygen heat pipe. (C) 1996 Published by Elsevier Science Limited C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Russo, SC (reprint author), HUGHES AIRCRAFT CO,ELECTRO OPT SYST,EL SEGUNDO,CA 90245, USA. NR 1 TC 0 Z9 0 U1 0 U2 1 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 721 EP 730 DI 10.1016/0011-2275(96)00034-3 PG 10 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800002 ER PT J AU Volz, SM Mitsuda, K Inoue, H Ogawara, Y Hirabayashi, M Kyoya, M AF Volz, SM Mitsuda, K Inoue, H Ogawara, Y Hirabayashi, M Kyoya, M TI The X-ray spectrometer (XRS): A multi-stage cryogenic instrument for the Astro-E X-ray astrophysics mission SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE ADR; space cryogenics; XRS AB The XRS cryogenic system has undergone numerous system configuration changes since its inception in the early 1980s. The Astro-E XRS is a high precision X-ray spectrometer with better than 20 eV resolution between 0.3 and 10 keV. It is a single photon counting solid-state calorimeter with pixel elements cooled to similar to 0.065 K by a unique three-stage cooling system. The low temperature is produced by an adiabatic demagnetization refrigerator (ADR) operating between 0.065 K and 1.3 K. The 1.3 K temperature is maintained by a 33 litre helium tank. Graphite/epoxy straps suspend the helium tank from an outer cryogen tank containing 120 litres of solid neon at similar to 17 K. The neon tank is in turn suspended from the dewar mainshell by low-conductivity straps. The system has a minimum design lifetime of 2 years, with a 2.5-year goal. The instrument design is severely constrained by mass limitations (less than or equal to 400 kg) and high launch loads. The Astro-E will fly in 2000 on an ISAS M-V solid rocket. The M-V is a new launch vehicle, with the first launch scheduled for 1996. C1 INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA,JAPAN. RP Volz, SM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Mitsuda, Kazuhisa/C-2649-2008 NR 8 TC 9 Z9 10 U1 0 U2 2 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 763 EP 771 DI 10.1016/0011-2275(96)00038-0 PG 9 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800006 ER PT J AU Breon, SR Gibbon, JA Boyle, RF DiPirro, MJ Warner, BA Tuttle, JG AF Breon, SR Gibbon, JA Boyle, RF DiPirro, MJ Warner, BA Tuttle, JG TI Thermal design of the XRS helium cryostat SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE space cryogenics; X-Ray Spectrometer (XRS); space-flight helium dewars ID FLIGHT DEMONSTRATION; SUPERFLUID AB The required lifetime for the Astro-E X-Ray Spectrometer (XRS) is 2 years, with a goal of 2.5 years. To meet this requirement, significant advances in state-of-the-art long-life cryogenic systems are required. The XRS system is a hybrid neon/helium system with a final stage of cooling provided by an adiabatic demagnetization refrigerator. The thermal design of the helium cryostat is described in this paper. To achieve a lifetime of 2.5 years with a helium volume of approximately 20 litres, the heat load on the helium must be of the order of 800 mu W or less. The expected lifetime and sensitivity of the lifetime to changes in the design or external heat loads is modelled. Results of preliminary thermal conductivity measurements are presented and future tests are identified. A study of heat loads that were small enough to be neglected in previous designs of long-life cryogenic systems was undertaken. A summary of the findings is presented. (C) 1996 Elsevier Science Limited C1 HUGHES STX,LANHAM,MD 20706. RP Breon, SR (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 16 TC 8 Z9 8 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 773 EP 780 DI 10.1016/0011-2275(96)00039-2 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800007 ER PT J AU Qin, X Nissen, JA Swanson, DR Williamson, PR Stricker, DA Lipa, JA Chui, TCP Israelsson, UE AF Qin, X Nissen, JA Swanson, DR Williamson, PR Stricker, DA Lipa, JA Chui, TCP Israelsson, UE TI Heat capacity experiment for very high resolution tests of the theory of confined materials SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE helium; finite size effect; heat capacity ID LAMBDA-POINT AB We report the current status of an experiment to measure the heat capacity of helium confined within a stack of evenly spaced silicon plates at temperatures very close to the superfluid transition. Newly developed high-resolution thermometry has substantially improved our ability to look into regions where three-dimensional crosses over to two-dimensional behaviour and where two-dimensional behaviour dominates. These regions have been of interest to theorists and experimentalists for decades. The main part of the apparatus consists of a high-purity copper calorimeter containing a stack of 408 silicon plates spaced 57 mu m apart and a pair of high-resolution, fast response, paramagnetic salt thermometers. The thermometers have been shown to have a noise level of 10(-10) K with 1 Hz bandwidth. The expected resolution of the heat capacity measurements is 10(-9) K. To avoid the smearing effects of gravity in the 4.5-cm high helium sample, the measurements will be performed on the Space Shuttle. The results from the experiment can be combined with supplementary ground measurements on smaller length scales to perform additional tests of the renormalization group predictions for crossover to lower-dimensional behaviour. (C) 1996 Elsevier Science Limited C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Qin, X (reprint author), STANFORD UNIV,DEPT PHYS,STANFORD,CA 94305, USA. NR 13 TC 7 Z9 7 U1 0 U2 0 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 781 EP 786 DI 10.1016/0011-2275(96)00040-9 PG 6 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800008 ER PT J AU Adriaans, MJ Moeur, WA Boyd, STP Strayer, DM Duncan, RV AF Adriaans, MJ Moeur, WA Boyd, STP Strayer, DM Duncan, RV TI Cryogenic design of the liquid helium experiment 'Critical Dynamics in Microgravity' SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE superfluid helium; lambda transition; microgravity; critical phenomena ID NONLINEAR HEAT-TRANSPORT; RENORMALIZATION-GROUP THEORY; THERMAL-BOUNDARY RESISTANCE; SUPERFLUID TRANSITION; T-LAMBDA; KAPITZA RESISTANCE; HE-4; POINT; PHASE; DEPRESSION AB Although many well-controlled experiments have been conducted to measure the static properties of systems near criticality, few experiments have explored the transport properties in systems driven far away from equilibrium as a phase transition occurs. The cryogenic design of an experiment to study the dynamic aspect of critical phenomena is reported here. Measurements of the thermal gradient across the super-fluid (He Il)-normal fluid (He I) interface in helium under microgravity conditions will be performed as a heat flux holds the system away from equilibrium. New technologies are under development for this experiment, which is in the definition phase for a space shuttle flight. (C) 1996 Elsevier Science Limited C1 UNIV NEW MEXICO,ALBUQUERQUE,NM 87131. CALTECH,JET PROP LAB,PASADENA,CA 91125. RP Adriaans, MJ (reprint author), SANDIA NATL LABS,ALBUQUERQUE,NM 87185, USA. NR 35 TC 5 Z9 5 U1 0 U2 2 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 787 EP 794 DI 10.1016/0011-2275(96)00041-0 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800009 ER PT J AU Canavan, ER Moody, MV Paik, HJ Shirron, PJ DiPirro, MJ AF Canavan, ER Moody, MV Paik, HJ Shirron, PJ DiPirro, MJ TI Predicted performance of the superconducting gravity gradiometer on the Space Shuttle SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE space cryogenics; gravity gradiometer; Space Shuttle; acceleration AB A high-resolution global gravity map would provide tremendous benefits to the Earth sciences. Mapping the lateral fluctuations of a planers gravity field is one of the few means of probing its interior. For the Earth, a high-resolution gravity map would also reveal dynamic ocean current information presently hidden in existing sea surface height data. The use of gradiometers for gravity mapping has inherent advantages over other techniques and has the potential of providing the highest spatial resolution for global surveys from orbit. Extremely sensitive superconducting gravity gradiometers (SGGs) have been developed for space applications under NASA support. The present laboratory model has demonstrated a sensitivity almost two orders of magnitude better than any other gradiometer (<20 mE Hz(-1/2), where 1 mE = 10(-12) m s(-2) m(-1) approximate to 10(-13) g(E) m(-1)). In preparation for a dedicated gravity mapping mission, we have proposed a flight test of a spaceworthy version of the instrument in the SHOOT (Superfluid Helium On Orbit Transfer) dewars, which flew on the Shuttle in 1993. We have examined potential error sources for the instrument operating in the Shuttle environment. Of the largest error sources, most are motion-related. We obtained the motion of the Orbiter in six degrees of freedom (d.o.f.) by examining the SAMS (shuttle acceleration measurement system) and the CAS (calibrated ancillary system) data sets. Using this information and the measured error coupling coefficients of the laboratory SGG, we can predict the resolution with which the Earth's gravity gradient signal can be recovered on this Shuttle test flight. Although the Orbiter provides a much worse environment-for the SGG than a dedicated satellite, our analysis shows that during quiet periods on the Orbiter, the ability to recover gravity data will approach the limit imposed by the instrument thermal noise. (C) 1996 Elsevier Science Limited C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20711. RP Canavan, ER (reprint author), UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742, USA. NR 5 TC 1 Z9 2 U1 1 U2 1 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 795 EP 804 DI 10.1016/0011-2275(96)00042-2 PG 10 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800010 ER PT J AU Shirron, PJ DiPirro, MJ Castles, SH Bills, B Paik, HJ Canavan, ER Moody, MV AF Shirron, PJ DiPirro, MJ Castles, SH Bills, B Paik, HJ Canavan, ER Moody, MV TI Mission concepts for the Superconducting Gravity Gradiometer SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE gravity; gradiometers; geodesy; superconductivity ID LIQUID-HELIUM; SHOOT AB The Superconducting Gravity Gradiometer (SGG), which can measure gravitational field fluctuations to unprecedented precisions, is currently being evaluated for use in an Earth-orbiting platform. Two missions are planned: a Shuttle-based demonstration flight and a dedicated gravity surveying mission. The Shuttle mission will feature a fully functional, self-contained instrument with an intrinsic noise level of 10(-3) E Hz(-1/2) where E is defined at 10(-9) m s(-2) m(-1). Calibration hardware, residual error correction techniques, and surface tension devices which control liquid helium motion in the dewar will be tested. For a dedicated free-flier gravity mission, two concepts have been studied. Both have been formulated to achieve low cost while maintaining an instrument sensitivity of 10(-3) E Hz(-1/2). One concept uses the spacecraft developed for the Sub-mi Iii meter Wave Astronomical Satellite (SWAS), and would be in a polar orbit, decaying from an initial altitude of 380 km. A mission lifetime of 6-9 months is planned. The other concept is based on a re-usable SPARTAN 400 carrier which would be deployed from, and retrieved by, the Shuttle. The carrier can be periodically reboosted and would maintain an altitude between 275 and 350 km. The mission lifetime is restricted to about 3 months, and the orbit inclination is limited to 57 degrees, the maximum the Shuttle can reach. Since the carrier is retrieved, the instrument could be periodially reflown. The free-flier missions, including experiment and spacecraft design, are described. C1 UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742. RP Shirron, PJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 713,GREENBELT,MD 20771, USA. NR 11 TC 2 Z9 2 U1 1 U2 1 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 805 EP 813 DI 10.1016/0011-2275(96)00043-4 PG 9 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800011 ER PT J AU Nakano, A Petrac, D Paine, C AF Nakano, A Petrac, D Paine, C TI He II liquid/vapour phase separator for large dynamic range operation SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE space cryogenics; He II liquid/vapour separators; SIRTF; helium AB A phase separator, which separates helium vapour from liquid superfluid helium (He II), is an indispensable device for space cryogenics. The most recent approach to the Space Infrared Telescope Facility (SIRTF) uses a new design concept in which only the detector package is cold at launch, the remainder of the telescope being subsequently cooled to operating temperature on orbit. Therefore, a large dynamic operational range is required of the cryogen system. This is a report of initial laboratory test results with candidate porous plugs as phase separators. Mass flow rates and pressure and temperature differences across a porous plug were measured in this experiment. Relatively large mass flow rates were observed even at small pressure differences. In the high mass flow rate region, hysteresis was observed with increases and decreases in the pressure difference. A linear theory is proposed and compared with experimental data to explain several phenomena observed in this system. (C) 1996 Elsevier Science Limited RP Nakano, A (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 8 TC 6 Z9 12 U1 0 U2 2 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 823 EP 828 DI 10.1016/0011-2275(96)00045-8 PG 6 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800013 ER PT J AU Kittel, P Kashani, A Lee, JM Roach, PR AF Kittel, P Kashani, A Lee, JM Roach, PR TI General pulse tube theory SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE pulse tube refrigerators; cryocoolers; regenerative cycles AB A brief review of pulse tube thermodynamics is given. The underlying phenomena are described starting with a very simplified model. The concept of phasor analysis is used to show the fundamental behaviour. The concept of enthalpy flow is expanded to include entropy and Gibbs free energy flows and to apply these for the first time to regenerative refrigerators. A simplified model based on enthalpy, entropy and Gibbs free energy flows is presented to illustrate the effects of temperature gradients, thermal conduction and viscosity. As models become more sophisticated, more features are included. Furthermore, it is shown that, contrary to common usage, the concepts of work, flow and heat flow are not useful when applied to regenerative refrigerators. Rather, the Gibbs free energy flow fulfils the role usually assigned to work and heat flows. Recent advances in thermoacoustic and 2-D flow models are also reviewed. C1 AMES RES CTR,MOFFETT FIELD,CA 94035. RP Kittel, P (reprint author), NASA,AMES RES CTR,SPACE PROJECTS DIV,SENSORS & INSTRUMENTAT BRANCH,MOFFETT FIELD,CA 94035, USA. NR 14 TC 23 Z9 23 U1 1 U2 3 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 849 EP 857 DI 10.1016/0011-2275(96)00048-3 PG 9 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800016 ER PT J AU Tuttle, JG DiPirro, MJ Shirron, PJ Welty, RP Radparvar, M AF Tuttle, JG DiPirro, MJ Shirron, PJ Welty, RP Radparvar, M TI Two-stage series array SQUID amplifier for space applications SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1995 Space Cryogenics Workshop CY JUL 25-26, 1995 CL CALVERTON, MD SP NASA, Goddard Space Flight Ctr DE SQUID; series array; amplifier AB We present test results for a two-stage integrated SQUID amplifier which uses a series array of d.c. SQUIDS to amplify the signal from a single input SQUID. The device was developed by Welty and Martinis at NIST and recent versions have been manufactured by HYPRES, Inc. Shielding and filtering techniques were employed during the testing to minimize the external noise. Energy resolution of 300 h was demonstrated using a d.c. excitation at frequencies above 1 kHz, and better than 500 h resolution was typical down to 300 Hz. (C) 1996 Elsevier Science Limited C1 PHIZERO CONSULTING,BOULDER,CO 80303. HYPRES INC,ELMSFORD,NY 10523. RP Tuttle, JG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 713,GREENBELT,MD 20771, USA. NR 1 TC 2 Z9 3 U1 0 U2 3 PU BUTTERWORTH-HEINEMANN LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1996 VL 36 IS 10 BP 879 EP 883 DI 10.1016/0011-2275(96)00052-5 PG 5 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA VJ538 UT WOS:A1996VJ53800020 ER PT J AU Zeller, M AF Zeller, M TI A technology transfer center in action SO DATABASE LA English DT Article RP Zeller, M (reprint author), NASA,FAR W RTTC,INFORMAT SERV,3716 S HOPE ST,ROOM 200,LOS ANGELES,CA 90007, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ONLINE INC PI WILTON PA 462 DANBURY RD, WILTON, CT 06897-2126 SN 0162-4105 J9 DATABASE JI Database PD OCT-NOV PY 1996 VL 19 IS 5 BP 36 EP 36 PG 1 WC Computer Science, Information Systems; Information Science & Library Science SC Computer Science; Information Science & Library Science GA VK639 UT WOS:A1996VK63900017 ER PT J AU Baroth, E McGregor, J Razo, F Rubio, P AF Baroth, E McGregor, J Razo, F Rubio, P TI More on visual programming data acquisition software tools SO EE-EVALUATION ENGINEERING LA English DT Article RP Baroth, E (reprint author), CALTECH,JET PROP LAB,MEASUREMENT TEST & ENGN SUPPORT SECT,MEASUREMENT TECHNOL CTR,PASADENA,CA 91109, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU NELSON PUBLISHING PI NOKOMIS PA 2504 NORTH TAMIAMI TRAIL, NOKOMIS, FL 34275-3482 SN 0149-0370 J9 EE-EVAL ENG JI EE-Eval. Eng. PD OCT PY 1996 VL 35 IS 10 BP 16 EP & PG 5 WC Engineering, Electrical & Electronic SC Engineering GA VL452 UT WOS:A1996VL45200003 ER PT J AU Tan, PW Newman, JC Bigelow, CA AF Tan, PW Newman, JC Bigelow, CA TI Three-dimensional finite-element analyses of corner cracks at stress concentrations SO ENGINEERING FRACTURE MECHANICS LA English DT Article ID ELLIPTICAL SURFACE CRACKS; INTENSITY FACTORS; SEMICIRCULAR NOTCH; ALTERNATING METHOD AB Stress-intensity factors for corner cracks at a semicircular edge notch in a plate subjected to tensile load were obtained by using three-dimensional finite-element analyses. Stress-intensity factor solutions were obtained for a wide range of crack shapes, crack sizes and notch-radius-to-plate-thickness ratios. The range of crack-depth-to-plate-thickness (a/t) ratios considered was 0.2-0.8 and the crack-depth-to-crack-length (a/c) ratios were 0.4 and 1. Two notch-radii-to-plate-thickness (r/t) ratios were studied: 1.5 and 3. The stress-intensity factor solutions are compared with equations that were developed from these results and others from the literature. Copyright (C) 1996 Published by Elsevier Science Ltd. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP Tan, PW (reprint author), FAA,CTR TECH,ATLANTIC CITY,NJ, USA. NR 27 TC 8 Z9 8 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0013-7944 J9 ENG FRACT MECH JI Eng. Fract. Mech. PD OCT PY 1996 VL 55 IS 3 BP 505 EP 512 DI 10.1016/0013-7944(94)00231-2 PG 8 WC Mechanics SC Mechanics GA VJ922 UT WOS:A1996VJ92200016 ER PT J AU Evans, BR Lane, LM Margalit, R Hathaway, GM Ragauskas, A Woodward, J AF Evans, BR Lane, LM Margalit, R Hathaway, GM Ragauskas, A Woodward, J TI Comparison of the properties of native and pentaamminenruthenium(III)-modified xylanase SO ENZYME AND MICROBIAL TECHNOLOGY LA English DT Article DE chemical modification; xylanase; ruthenium; oxidase ID BACILLUS-PUMILUS; NUCLEOTIDE-SEQUENCE; CATALYTIC ACTIVITY; PULP; SITE; PENTAAMMINERUTHENIUM(III); IDENTIFICATION; PRETREATMENT; REDUCTION; MYOGLOBIN AB Two xylanases, xynA of Bacillus pumilus and xyn II of Trichoderma reesei, were purified and then modified by the attachment of pentaammineruthenium, thereby resulting in the generation of a xylanase with veratryl alcohol oxidase activity. Hydrolytic activity of T. reesei xyn II on soluble xylans was unchanged by modification with pentaammineruthenium; however modification of B. pumilus xynA greatly reduced xylan hydrolysis unless the active site of the xylanase was protected with xylose during the modification. The presence of histidine, cysteine, or reduced glutathione during xylan hydrolysis greatly increased the xylanase activity of the pentaammineruthenium-modified B. pumilus xylanase. Glycine, glutamic acid, methionine, or oxidized glutathione had no effect on xylanase activity. C1 CALTECH,JET PROP LAB,PASADENA,CA. CALTECH,BECKMAN INST,PASADENA,CA 91125. INST PAPER SCI & TECHNOL,ATLANTA,GA 30318. RP Evans, BR (reprint author), OAK RIDGE NATL LAB,MS6194,RM A-5,4500 N BETHEL VALLEY RD,OAK RIDGE,TN 37831, USA. NR 29 TC 0 Z9 0 U1 0 U2 3 PU BUTTERWORTH-HEINEMANN PI WOBURN PA 225 WILDWOOD AVE #UNITB PO BOX 4500, WOBURN, MA 01801-2084 SN 0141-0229 J9 ENZYME MICROB TECH JI Enzyme Microb. Technol. PD OCT PY 1996 VL 19 IS 5 BP 367 EP 373 DI 10.1016/S0141-0229(96)00014-2 PG 7 WC Biotechnology & Applied Microbiology SC Biotechnology & Applied Microbiology GA VE716 UT WOS:A1996VE71600009 PM 8987538 ER PT J AU Plesniak, MW Mehta, RD Johnston, JP AF Plesniak, MW Mehta, RD Johnston, JP TI Curved two-stream turbulent mixing layers revisited SO EXPERIMENTAL THERMAL AND FLUID SCIENCE LA English DT Article; Proceedings Paper CT Meeting to Celebrate Peter Bradshaws 60th Birthday CY JAN 12, 1996 CL STANFORD UNIV, STANFORD, CA HO STANFORD UNIV DE mixing layer; curvature; two-stream; turbulence; experimental ID FREE SHEAR LAYERS; VORTICAL STRUCTURES; INITIAL CONDITIONS; PLANE; EVOLUTION AB Two experimental studies of mildly curved (delta(omega)/(R) over bar approximate to 5%) two-stream mixing layers, using different fluids and covering a wide range of Reynolds numbers, are analyzed. One study was performed in a low-speed water channel at Stanford University, utilizing flow visualization and laser Doppler velocimetry. In this case, the Reynolds number was low (Re-delta omega approximate to 7400), the initial boundary layers were laminar, and the velocity ratio was 0.5. The other investigation was performed in the NASA Ames Mixing Layer Wind Tunnel, in which the three-dimensional structure and streamwise evolution of curved mixing layers at high Reynolds numbers (Re-delta omega approximate to 5.7 x 10(4)) were studied, using hot-wire anemometry. Mixing layers with velocity ratios of 0.5 and 0.6, and both laminar and turbulent initial boundary layers,were subjected to stabilizing and destabilizing longitudinal curvature (in the Taylor-Gortler sense). In stable and unstable mixing layers originating from laminar boundary layers, well-organized spatially stationary streamwise vorticity was generated, which produced significant spanwise variations in the mean velocity and Reynolds stress distributions. With the initial boundary layers on the splitter plate turbulent, spatially stationary, streamwise vorticity was not generated in either the stable or the unstable mixing layer. Linear growth was achieved for both initial conditions, but the rate of growth for the unstable case was higher than that of the stable case. Correspondingly, the far-field, spanwise-averaged peak Reynolds stresses were significantly higher for the destabilized cases compared with the stabilized cases, which exhibited levels comparable to, or slightly lower than, those for the straight case. Universal scaling of the streamwise evolution of the vorticity thickness and Reynolds stresses, using the velocity difference parameter, lambda, and the momentum thickness of the high-speed boundary layer, theta(1), was reasonably successful in grouping the straight, stable, and unstable mixing-layer results over the diverse range of conditions. (C) Elsevier Science Inc., 1996 C1 NASA, AMES RES CTR, FLUID MECH LAB, MOFFETT FIELD, CA 94035 USA. STANFORD UNIV, JIAA, DEPT AERONAUT & ASTRONAUT, STANFORD, CA 94305 USA. STANFORD UNIV, DEPT MECH ENGN, STANFORD, CA 94305 USA. RP Plesniak, MW (reprint author), PURDUE UNIV, SCH MECH ENGN, 1288 MECH ENGN, W LAFAYETTE, IN 47907 USA. OI Plesniak, Michael/0000-0001-6575-5074 NR 46 TC 9 Z9 9 U1 0 U2 7 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0894-1777 EI 1879-2286 J9 EXP THERM FLUID SCI JI Exp. Therm. Fluid Sci. PD OCT PY 1996 VL 13 IS 3 BP 190 EP 205 DI 10.1016/S0894-1777(96)00080-5 PG 16 WC Thermodynamics; Engineering, Mechanical; Physics, Fluids & Plasmas SC Thermodynamics; Engineering; Physics GA VN804 UT WOS:A1996VN80400003 ER PT J AU LeBoeuf, RL Mehta, RD AF LeBoeuf, RL Mehta, RD TI Topology of the near-field vortical structures in a three-dimensional wake SO EXPERIMENTAL THERMAL AND FLUID SCIENCE LA English DT Article; Proceedings Paper CT Meeting to Celebrate Peter Bradshaws 60th Birthday CY JAN 12, 1996 CL STANFORD UNIV, STANFORD, CA HO STANFORD UNIV DE three-dimensional wake; vortical structures; phase-locked measurements ID SHEAR FLOWS; PLANE WAKES; TRANSITION; LAYERS; NUMBER AB Detailed three-dimensional phase-averaged measurements have been obtained of the spanwise and streamwise vorticity formation and near-field development in a forced plane wake. The plane wake with nominally two-dimensional laminar initial boundary layers was generated in a shear layer wind tunnel. Acoustic forcing at the fundamental roll-up frequency was used to phase-lock the initial formation and subsequent development of the spanwise vortical structures. Phase-averaged measurements of all three velocity components permitted the study of three-dimensional vorticity distributions without involving Taylor's hypothesis. The phase-averaged measurements show that the streamwise vorticity first appears just upstream of the spanwise vortex roll-up, in a region experiencing streamwise stretching as rollers are formed. As spanwise rollers of opposite sign are shed alternately, a row of streamwise vortices is generated in an alternating sequence on either side of the wake. The streamwise vortices go on to form vortex-loop structures, the ''legs'' (ribs) of which connect adjacent spanwise rollers of opposite sign while the ''heads'' ride over the rollers. In addition, relatively strong contributions to the streamwise vorticity are obtained from the rollers as a result of their kinking in the streamwise direction. The contribution from the rollers is of opposite sign to that of the surrounding rib. In terms of phase-averaged quantities, the maximum streamwise vorticity in the initial ribs is equivalent to about 40% of the peak spanwise vorticity and the rib circulation is equivalent to about 20% of the spanwise roller circulation. (C) Elsevier Science Inc., 1996 C1 STANFORD UNIV,CTR TURBULENCE RES,STANFORD,CA 94305. STANFORD UNIV,JIAA,DEPT AERONAUT & ASTRONAUT,STANFORD,CA. NASA,AMES RES CTR,FLUID MECH LAB BRANCH,MOFFETT FIELD,CA 94035. NR 20 TC 3 Z9 3 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0894-1777 J9 EXP THERM FLUID SCI JI Exp. Therm. Fluid Sci. PD OCT PY 1996 VL 13 IS 3 BP 223 EP 238 DI 10.1016/S0894-1777(96)00083-0 PG 16 WC Thermodynamics; Engineering, Mechanical; Physics, Fluids & Plasmas SC Thermodynamics; Engineering; Physics GA VN804 UT WOS:A1996VN80400006 ER PT J AU Schwarz, WR Flack, KA Driver, DM Jovic, S AF Schwarz, WR Flack, KA Driver, DM Jovic, S TI A combined experimental and computational study of pressure-driven three-dimensional separation in a turbulent boundary layer SO EXPERIMENTAL THERMAL AND FLUID SCIENCE LA English DT Article; Proceedings Paper CT Meeting to Celebrate Peter Bradshaws 60th Birthday CY JAN 12, 1996 CL STANFORD UNIV, STANFORD, CA HO STANFORD UNIV DE three-dimensional separation; turbulent boundary layer; adverse pressure gradient ID NAVIER-STOKES EQUATIONS; 3-DIMENSIONAL SEPARATION; TOPOLOGY AB Experimental data and computational results are compared for a pressure-driven three-dimensional separation in a two-dimensional turbulent boundary layer. The comparisons include surface-flow visualizations, wall static pressures, and skin-friction coefficients. With the use of an open-circuit low-speed wind tunnel, the separation pattern was generated by a streamwise adverse pressure gradient combined with localized overhead suction that represented 6% of the test section entrance flow. This separation pattern was characterized by its topological critical points: a saddle point of separation, a nodal point of attachment, two additional saddle points, and two foci. Calculations of the experiment were made by using the INS3D computer code with the Spalart-Allmaras one-equation turbulence model. The topology of the computed near-wall particle traces was similar to the experimental separation pattern having the same geometric aspect ratio and the same number and types of critical points seen in the experiment. Comparisons between experimental data and computed results for static-pressure coefficient and skin-friction coefficient also showed good agreement. Results from the use of another turbulence model, Baldwin-Barth, had a much larger separated region. This experiment provides new data that isolate a three-dimensional separation pattern driven by pressure gradient and the amount of turbulent mixing. (C) Elsevier Science Inc., 1996 C1 STEVENS INST TECHNOL,DEPT MECH ENGN,HOBOKEN,NJ 07030. USN ACAD,DEPT ENGN MECH,ANNAPOLIS,MD 21402. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. ELORET INST,PALO ALTO,CA 94035. NR 25 TC 0 Z9 0 U1 1 U2 5 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0894-1777 J9 EXP THERM FLUID SCI JI Exp. Therm. Fluid Sci. PD OCT PY 1996 VL 13 IS 3 BP 252 EP 265 DI 10.1016/S0894-1777(96)00085-4 PG 14 WC Thermodynamics; Engineering, Mechanical; Physics, Fluids & Plasmas SC Thermodynamics; Engineering; Physics GA VN804 UT WOS:A1996VN80400008 ER PT J AU Sheridan, P AF Sheridan, P TI Forecasting the fishery for pink shrimp, Penaeus duorarum, on the Tortugas Grounds, Florida SO FISHERY BULLETIN LA English DT Article ID PRAWN METAPENAEUS-MACLEAYI; WINTER TEMPERATURE; NORTH-CAROLINA; RIVER-REGION; BAY; LANDINGS; RECRUITMENT; ABUNDANCE; AUSTRALIA AB In this report I review the biology of and fishery for pink shrimp, Penaeus duorarum, harvested from the Tortugas Grounds off southwest Florida, and present models used to forecast annual pink shrimp landings in this area. Pink shrimp spawn all year, and larvae recruit to nurseries in the seagrass-mangrove ecosystem surrounding Everglades National Park and Florida Bay. Juveniles move out of the nurseries all year, but catch per unit of effort for smallest size classes generally exhibits March and September peaks. Total landings usually rise sharply in November and taper off after April. The fishery was relatively stable during 1960-85, averaging 4,350 metric tons annually, but it has shown a singular decline and potential recovery since 1985. In 1987, I began forecasting annual landings by using multiple regression analyses of fishery catch statistics and environmental factors that could affect survival, growth, and recruitment. Potential predictor variables from May through October were investigated in order to release a timely annual forecast by November. Each year, the updated data set from 1966 onwards was examined to derive the ''best'' forecast models. Important predictor variables included indices of fishing activity during the waning months of the fishery (May-July) and surface and ground water levels within Everglades National Park during June-September. Forecasts were within +/-20% of actual landings for five of eight years, whereas forecast direction (increase or decrease over the prior year) was usually correct. Cause-effect relationships between predictor variables and pink shrimp recruitment to the fishery remain to be determined. RP Sheridan, P (reprint author), NOAA,NATL MARINE FISHERIES SERV,SE FISHERIES SCI CTR,4700 AVE U,GALVESTON,TX 77551, USA. NR 58 TC 25 Z9 26 U1 0 U2 5 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD OCT PY 1996 VL 94 IS 4 BP 743 EP 755 PG 13 WC Fisheries SC Fisheries GA VM745 UT WOS:A1996VM74500013 ER PT J AU Vassiliadis, D Angelopoulos, V Baker, DN Klimas, AJ AF Vassiliadis, D Angelopoulos, V Baker, DN Klimas, AJ TI The relation between the northern polar cap and auroral electrojet geomagnetic indices in the wintertime SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INDEXES; AE AB The polar cap (PC) index is a measure of the high-latitude geomagnetic disturbances due to Hall and field-aligned currents. The index is well correlated with the auroral electrojet AL and AU indices (correlation with the PC index is 76% and 66%, resp.). Here we obtain several types of data-based models that relate the PC to the AL and AU indices in the wintertime, when the ionospheric conductivity is mostly due to the precipitating particles of the field-aligned currents. The new models predict AL and AU from PC with correlations much higher than those found by earlier studies. Thus linear moving-average filters reproduce the observed ill with a correlation of 88% (AU: 75%) while linear autoregressive moving-average (ARMA) models based on the PC index produce in-sample single-step predictions with 98% and 97% correlations with AL and AU respectively. For long-term, out-of-sample prediction, the linear ARMA prediction from the PC index has an asymptotic prediction error which is at least 25% more accurate than the prediction from solar wind input. Nonlinear models are slightly more accurate than their linear counterparts, indicating a weak nonlinearity in the relation between the polar cap and auroral zone indices. The prediction-observation correlations are sufficiently high that models based on the PC index can be used for specification of the auroral geomagnetic activity. C1 UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. UNIV SPACE RES ASSOC,GREENBELT,MD. RP Vassiliadis, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 692,GREENBELT,MD 20771, USA. NR 12 TC 40 Z9 40 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 1 PY 1996 VL 23 IS 20 BP 2781 EP 2784 DI 10.1029/96GL02575 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VL370 UT WOS:A1996VL37000017 ER PT J AU Cabrol, NA Grin, EA Dawidowicz, G AF Cabrol, NA Grin, EA Dawidowicz, G TI Ma'adim Vallis revisited through new topographic data: Evidence for an ancient intravalley lake SO ICARUS LA English DT Article ID MARS; CHANNELS; VALLEYS; WATER AB Based on a comprehensive study of the recent topographic map USGS MC-23 SE I-2119 (USGS, 1991, Topographical Map of Aeolis) plus geomorphic and digital elevation, we have constructed a geometric model of Ma'adim Vallis, The sedimentary history of the valley was determined by the damming of the valley by two impact craters, one by the southern crater over Gusev rim and the second located 120 km upstream. The presence of an intravalley lake system is inferred from independent sedimentary analysis and from geomorphic evidence for valley benches. Peripheral and parallel topographic contour intervals of the putative intravalley lake shores suggest that the lake was covered by a thick ice sheet. The longitudinal profile of the valley floor shows a peculiar reverse slope located 300 km upstream from the southern Gusev crater rim. We conclude that this is an accumulation of sedimentary deposits adjacent to the crater rampart which defined the northern boundary of the lake. When the water level reached the lowest point of the west bank, which is 0.4 km below the top of the rim of Gusev crater, it began to floor the surrounding plateau, As the intravalley lake level raised, its ice cover formed a wide lateral bench. Later, this ponded water was funneled into Gusev crater through the breaching of the southern Gusev rampart by an impact crater. The paleolacustrine sediments transported by the lake water that channeled through the rampart debris slope mantled the floor of Gusev crater. The sublacustrine sediments are promising targets for future missions and of high priority in the search for past life. (C) 1996 Academic Press,Inc. C1 UNIV PARIS 01,F-75005 PARIS,FRANCE. RP Cabrol, NA (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 31 TC 54 Z9 54 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1996 VL 123 IS 2 BP 269 EP 283 DI 10.1006/icar.1996.0157 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700003 ER PT J AU Smith, MD Gierasch, PJ AF Smith, MD Gierasch, PJ TI Global-scale winds at the Venus cloud-top inferred from cloud streak orientations SO ICARUS LA English DT Article ID PHOTOPOLARIMETER IMAGES; LEVEL CIRCULATION; THERMAL TIDES; ATMOSPHERE; WAVES; GALILEO AB The orientations of the small cloud streaks that are always found at mid-latitudes in ultraviolet images of the Venus cloud-top provide a means for characterizing the global-scale circulation, including the wind field on the night side of Venus. Assuming that small clouds act as passive tracers of the cloud-top wind field, the orientation of cloud streaks is determined by the wind shear that the cloud has recently experienced. The typical deformation time for small clouds is about 50 hr, or one-half of a cloud-top rotation, so clouds viewed on the sunlit half of Venus show the influence of daytime and nighttime winds. By recording the orientations of cloud streaks and their variation with local solar time, we for the first time use cloud orientation information to place a constraint on the amplitudes of the Hadley circulation and solar thermal tides at the cloud-top level. A large solar thermal tide with a cloud-top meridional wind amplitude at 45 degrees latitude of between 5.5-10.5 m sec(-1) is found to be necessary to account for the observed variation with local solar time of cloud streak orientations. Maximum poleward tidal winds occur in the early afternoon. The cloud-top Hadley circulation is estimated to have an amplitude at 45 degrees latitude of between 3.5 and 8.5 m s(-1). This means the Hadley circulation may not be the dominant contributor to cloud-top meridional velocities, and that equatorward meridional velocities may exist over a portion of the night side at the Venus cloud-top. (C) 1996 Academic Press, Inc. C1 CORNELL UNIV,DEPT ASTRON,ITHACA,NY 14853. RP Smith, MD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 693,GREENBELT,MD 20771, USA. RI Smith, Michael/C-8875-2012 NR 18 TC 14 Z9 14 U1 0 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1996 VL 123 IS 2 BP 313 EP 323 DI 10.1006/icar.1996.0160 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700006 ER PT J AU Borucki, WJ McKay, CP Jebens, D Lakkaraju, HS Vanajakshi, CT AF Borucki, WJ McKay, CP Jebens, D Lakkaraju, HS Vanajakshi, CT TI Spectral irradiance measurements of simulated lightning in planetary atmospheres SO ICARUS LA English DT Article ID ELECTROSTATIC DISCHARGES; TITANS ATMOSPHERE; VENUS; JUPITER; VOYAGER-1; WHISTLERS; AEROSOLS; CLOUD AB Measurements of the spectral irradiance from approximately 380 to 820 nm are reported for laboratory simulations of lightning in the atmospheres of Venus, Jupiter, and Titan. The observations were made at 1 and 5 bars of pressure for Venus and Jupiter and at 1 bar for the Titan mixture, The spectra were obtained by observing laser-induced plasmas with a scanning spectrometer and an optical multichannel analyzer. Simulations of lightning show that atomic line and continuum radiation dominate the spectra. Weak molecular band radiation from CN was also observed for Venus and Titan. As the ambient pressure was increased from 1 to 5 bars, the prominence of the line radiation diminishes compared to the continuum radiation, some lines disappear, and the intensity of the molecular band radiation increases. Laboratory results for the venusian lightning spectrum are consistent with those found by the Venera 9 spectrometer when it viewed a storm on the nightside bf Venus. For both Jupiter and Venus, narrow spectral features are present that are ideal for detecting lightning from Earth-based telescopes. (C) 1996 Academic Press,Inc. C1 SOANE TECHNOL INC,HAYWARD,CA 94545. SAN JOSE STATE UNIV,DEPT PHYS,SAN JOSE,CA 95172. STERLING SOFTWARE,REDWOOD CITY,CA 94065. RP Borucki, WJ (reprint author), NASA,AMES RES CTR,PLANETARY SCI BRANCH,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 44 TC 22 Z9 23 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1996 VL 123 IS 2 BP 336 EP 344 DI 10.1006/icar.1996.0162 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700008 ER PT J AU Michalowski, T AF Michalowski, T TI Pole and shape determination for 12 asteroids SO ICARUS LA English DT Article ID MAIN-BELT ASTEROIDS; PHOTOMETRIC GEODESY; SPIN AXES; PERIODS; LIGHTCURVES; ROTATION; SENSES AB The results of pole and shape determination for 12 asteroids are presented. They have been obtained by using the method described in Michalowski (1993; Icarus 106, 563-572). These parameters have been determined for the first time for 4 objects and they have been improved or confirmed for the rest. Because of the small number of lightcurves available in the present study, future observations, taking into account the results from this paper, are proposed. (C) 1996 Academic Press, Inc. C1 ADAM MICKIEWICZ UNIV POZNAN,ASTRON OBSERV,PL-60286 POZNAN,POLAND. RP Michalowski, T (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 29 TC 9 Z9 10 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1996 VL 123 IS 2 BP 456 EP 462 DI 10.1006/icar.1996.0171 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700017 ER PT J AU Bus, SJ Buie, MW Schleicher, DG Hubbard, WB Marcialis, RL Hill, R Wasserman, LH Spencer, JR Millis, RL Franz, OG Bosh, AS Dunham, EW Ford, CH Young, JW Elliot, JL Meserole, R Olkin, CB McDonald, SW Foust, JA Sopata, LM Bandyopadhyay, RM AF Bus, SJ Buie, MW Schleicher, DG Hubbard, WB Marcialis, RL Hill, R Wasserman, LH Spencer, JR Millis, RL Franz, OG Bosh, AS Dunham, EW Ford, CH Young, JW Elliot, JL Meserole, R Olkin, CB McDonald, SW Foust, JA Sopata, LM Bandyopadhyay, RM TI Stellar occultation by 2060 Chiron SO ICARUS LA English DT Article ID 2060-CHIRON; CCD; (2060)CHIRON; PHOTOMETRY; NUCLEUS; COMA AB A 14th magnitude double star was occulted by 2060 Chiron on 1993 November 7. Observations of this event were obtained from five locations in California, An occultation by Chiron's nucleus was recorded at one of these sites, while a possible graze by the nucleus was seen at the next closest location. If this possible graze represents a true detection of the nucleus, Chiron's radius is determined to be 89.6 +/- 6.8 km, assuming a circular outline for the shape, If the nucleus was not seen at the second location, Chiron's radius is only constrained as being greater than 90.2 +/- 6.5 km, The presence of dust in Chiron's inner coma was also detected in four of the five occultation datasets, Lightcurve features were identified that may be explained by narrow, collimated jets of material, and by a much larger region of dust distributed asymmetrically about Chiron's nucleus, Periodic fluctuations in the dust may have been detected in one of the lightcurves, If this periodicity is real, and is induced as a result of Chiron's rotation, then a minimum expansion velocity for the dust is found to be similar to 40 m sec(-1). (C) 1996 Academic Press, Inc. C1 LOWELL OBSERV,FLAGSTAFF,AZ 86001. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. CALTECH,JET PROP LAB,TABLE MT OBSERV,WRIGHTWOOD,CA 92397. RP Bus, SJ (reprint author), MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139, USA. NR 31 TC 28 Z9 28 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1996 VL 123 IS 2 BP 478 EP 490 DI 10.1006/icar.1996.0173 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700019 ER PT J AU Liou, JC Zook, HA AF Liou, JC Zook, HA TI Comets as a source of low eccentricity and low inclination interplanetary dust particles SO ICARUS LA English DT Article ID POYNTING-ROBERTSON DRAG; SHORT-PERIOD COMETS; ZODIACAL DUST; SOLAR-SYSTEM; STRATOSPHERE; RESONANCES; COLLECTION; PLANETARY; EVOLUTION; ORIGIN AB In the all sky survey by the Infrared Astronomical Satellite in 1983, eight comets were discovered to have dust trails (Sykes, M. V., and R. G. Walker 1992. Icarus 95, 180-210). Among those eight comets, the most prominent trail belonged to Tempel 2, suggesting that this comet recently has been the most prolific producer of interplanetary dust. A numerical simulation of the orbital evolution of 4- and 9-mu m diameter dust particles from Tempel 2 shows that radiation pressure causes a significant fraction of dust particles in this size range to be directly injected into a 1:2 interior mean motion resonance with Jupiter. There, they remain trapped for thousands of years. When they escape the resonance, their orbital eccentricities are quite small. These, and dust grains from other similar Tempel-type comets, approach the Earth with the low velocities typical of asteroidal dust grains. Many dust particles collected from the stratosphere have been shown to have undergone little heating upon entry into the Earth's atmosphere and were assigned an asteroidal origin on this basis. This includes a sub-group, the chondritic porous aggregates. Our new analysis shows, however, that it is quite possible that this sub-group of grains derive from Tempel-type comets, and not from asteroids. (C) 1996 Academic Press,Inc. RP Liou, JC (reprint author), NASA, LYNDON B JOHNSON SPACE CTR, SN3, HOUSTON, TX 77058 USA. NR 40 TC 26 Z9 26 U1 0 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 OCT PY 1996 VL 123 IS 2 BP 491 EP 502 DI 10.1006/icar.1996.0174 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700020 ER PT J AU Nelson, RM Wallis, BD Barker, ES Horn, LJ Smythe, WD Lane, AL AF Nelson, RM Wallis, BD Barker, ES Horn, LJ Smythe, WD Lane, AL TI Compositional mapping of Jupiter's satellite lo utilizing high speed multifilter photometry during mutual satellite occultations, 1990-1991 SO ICARUS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; GALILEAN SATELLITES; HOT SPOTS; IO; SULFUR; MICROMETERS; FROST AB We observed selected mutual occultations of Jupiter's satellites in 1990-1991 at four wavelengths and we used the occultation profiles to constrain the areal distribution of selected spectrally active compounds on Io's surface. We performed high speed photometry of Io at four wavelengths while it was being occulted by another Galilean satellite. The wavelengths of the filters that we used for this work were 0.305, 0.345, 0.45, and 0.56 mu m. These wavelengths were selected to constrain the areal distribution of sulfur and/or sulfur-bearing compounds and sulfur dioxide (SO2) frost, believed to be the two major surface constituents on Io. During a typical occultation, a Galilean satellite whose spectral properties are well defined passed in front of Io, gradually blocking the sunlight reflected by Io from reaching an Earth-based observer. In the observations reported here the occulting satellite was always Europa. Europa's contribution to the combined signal was removed and the remaining Io occultation brightness variations were compared to curves produced by synthesized occultations that would be expected assuming a two component surface, where one component is an unknown mixture of sulfur bearing materials and the other is SO2 frost. We utilized the results of previous IUE derived ultraviolet longitudinal phase angle variation studies (Nelson, R. M., A. L. Lane, D. L. Matson, F. P. Fanale, D. B. Nash, and T. V. Johnson 1980. Science 210, 784-786) which localized the distribution of SO2 on Io in longitude. Thus, we were able to vary the distribution of SO2 in latitude and produce a synthetic lightcurve based on the reflectance properties of solid SO2 and elemental sulfur. This was done by simulating different distributions of sulfur bearing materials and SO2 frost on Io's surface and minimizing the difference between the synthetic lightcurve and the observed lightcurve. On Io's trailing hemisphere, we find that the region north of the equator between latitudes 0 degrees and 60 degrees and between 180 degrees and 270 degrees longitude to be highest in concentration of SO2 frost. It also coincides with the highly reflective ''white areas'' seen in the Voyager spacecraft television images. All of the observations reported are of Io's trailing hemisphere. (C) 1996 Academic Press, Inc. C1 UNIV TEXAS,MCDONALD OBSERV,AUSTIN,TX 78712. UNIV PITTSBURGH,DEPT GEOL & PLANETARY SCI,PITTSBURGH,PA 15260. RP Nelson, RM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 0 Z9 0 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1996 VL 123 IS 2 BP 568 EP 577 DI 10.1006/icar.1996.0179 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700025 ER PT J AU Zwier, TS Allen, M AF Zwier, TS Allen, M TI Metastable diacetylene reactions as routes to large hydrocarbons in Titan's atmosphere SO ICARUS LA English DT Article ID ULTRAVIOLET PHOTOCHEMISTRY; METHANE PHOTOCHEMISTRY; HAZE PRODUCTION; ACETYLENE; NEPTUNE; AEROSOLS; ETHANE; URANUS; C4H2 AB Recent experimental data on the relative rates of metastable diacetylene (C4H2*) reactions are used to estimate the potential effects of their inclusion into the photochemical model of the atmosphere of Titan. It is demonstrated that the reactions of C4H2* have the potential for successfully competing with free radical routes to formation of larger hydrocarbon species in Titan's atmosphere, especially at altitudes below about 200 km. At an altitude of 105 km, the net production rate of larger hydrocarbons from C4H2*, C4H, and C2H is estimated to be in the ratio 90:30:1. (C) 1996 Academic Press,Inc. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. RP Zwier, TS (reprint author), PURDUE UNIV,DEPT CHEM,W LAFAYETTE,IN 47907, USA. NR 35 TC 37 Z9 37 U1 0 U2 3 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD OCT PY 1996 VL 123 IS 2 BP 578 EP 583 DI 10.1006/icar.1996.0180 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP447 UT WOS:A1996VP44700026 ER PT J AU Elbuluk, ME Kankam, MD AF Elbuluk, ME Kankam, MD TI Potential starter/generator technologies for future aerospace application SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article ID EXCITED INDUCTION GENERATORS; REACTIVE POWER-CONTROL; RELUCTANCE MOTOR; VARIABLE-SPEED; SYSTEM; CONVERTER; PERFORMANCE; MACHINES; TORQUE; MODEL AB This paper presents a search and comparative review of the literature available on variable speed constant frequency (VSCF) technologies. In particular, most of the progress made in the past ten years, using power electronics and electric machines for VSCF systems is reported. Two VSCF systems, based on induction and switched reluctance machine technologies, are presented, The research on the singly- and doubly-fed induction machines has focused on VSCF for wind power generation; whereas, that on switched reluctance machines has been directly studied as a VSCF technology in aircraft system. Results obtained so far favor the switched reluctance machine over the induction machine. Based on the foregoing comparative review, it is recommended that the induction machine be fully investigated as a VSCF drive in aircraft system. The findings should then be compared with the counterpart SRM system. Issues of comparison may include fault tolerance and redundancy, power density, torque requirements, overload ratings, temperature range and cooling, efficiency and stability over expected operating speed range. C1 NASA,LEWIS RES CTR,POWER TECHNOL DIV,CLEVELAND,OH 44135. RP Elbuluk, ME (reprint author), UNIV AKRON,DEPT ELECT ENGN,AKRON,OH 44325, USA. NR 44 TC 22 Z9 30 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD OCT PY 1996 VL 11 IS 10 BP 17 EP 24 DI 10.1109/62.538797 PG 8 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA VM208 UT WOS:A1996VM20800008 ER PT J AU Krainak, MA Yu, AW AF Krainak, MA Yu, AW TI Evidence of electron compensation in a LiNbO3:Fe holographic optical filter SO IEEE PHOTONICS TECHNOLOGY LETTERS LA English DT Article ID PHOTOREFRACTIVE CENTERS; GRATINGS AB We present experimental evidence of electron compensation of a fixed ionic hologram in a photorefractive iron doped lithium niobate crystal. When the hologram is stored in the dark, the fixed hologram diffraction efficiency decreased from 20% to 6% in a 15 day period. 30 J/cm(2) of 488 nm wavelength uniform illumination was required to mitigate the electron compensation and restore the diffraction efficiency to 20% (reveal the fixed ionic grating). C1 HUGHES STX CORP,GREENBELT,MD 20770. RP Krainak, MA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,MAIL CODE 7175,GREENBELT,MD 20771, USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1041-1135 J9 IEEE PHOTONIC TECH L JI IEEE Photonics Technol. Lett. PD OCT PY 1996 VL 8 IS 10 BP 1343 EP 1345 DI 10.1109/68.536649 PG 3 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA VH227 UT WOS:A1996VH22700021 ER PT J AU Lin, LY Wu, MC Itoh, T Vang, TA Muller, RE Sivco, DL Cho, AY AF Lin, LY Wu, MC Itoh, T Vang, TA Muller, RE Sivco, DL Cho, AY TI Velocity-matched distributed photodetectors with high-saturation power and large bandwidth SO IEEE PHOTONICS TECHNOLOGY LETTERS LA English DT Article ID TRAVELING-WAVE PHOTODETECTORS; PHOTODIODE; 110-GHZ AB A high-power, high-bandwidth photodetector is experimentally demonstrated using a novel velocity-matched distributed photodetector (VMDP), The distributed photodetector structure can achieve large absorption volume and high-saturation power while maintaining the high-speed performance of the fast photodiodes, The VMDP with 56 mA saturation photocurrent and an instrument-limited 3-dB bandwidth of 49 GHz is achieved, The results show that VMDP is ideal for high-performance microwave fiber-optic links and high-power optical-microwave applications. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. LUCENT TECHNOL,BELL LABS INNOVAT,MURRAY HILL,NJ 07974. RP Lin, LY (reprint author), UNIV CALIF LOS ANGELES,DEPT ELECT ENGN,405 HILGARD AVE,LOS ANGELES,CA 90095, USA. NR 13 TC 68 Z9 69 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1041-1135 J9 IEEE PHOTONIC TECH L JI IEEE Photonics Technol. Lett. PD OCT PY 1996 VL 8 IS 10 BP 1376 EP 1378 DI 10.1109/68.536660 PG 3 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA VH227 UT WOS:A1996VH22700032 ER PT J AU Gambhir, BL Wallace, RG Affens, DW Bellantoni, JF AF Gambhir, BL Wallace, RG Affens, DW Bellantoni, JF TI Improved COSPAS-SARSAT locating with geostationary satellite data SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Article AB The COSPAS-SARSAT system locates distress beacons via Doppler analysis of beacon transmissions as observed by low Earth orbiting (LEO) satellites. By contrast, the 406 MHz search and rescue transponder on the geostationary satellites can measure only the transmitted frequency of the beacon, which is not currently being used in location determination. This report shows that a combined data approach can significantly improve the locating success rate, the time delay to the rust solution, and the accuracy of location estimates. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CAMBRIDGE ANALYT,BOSTON,MA 02116. RP Gambhir, BL (reprint author), SCI SYST & APPLICAT INC,5900 PRINCESS GARDEN PKWY,LANHAM,MD 20706, USA. NR 5 TC 0 Z9 0 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9251 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD OCT PY 1996 VL 32 IS 4 BP 1405 EP 1411 DI 10.1109/7.543861 PG 7 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA VP816 UT WOS:A1996VP81600019 ER PT J AU Reddy, CJ Deshpande, MD Cockrell, CR Beck, FB AF Reddy, CJ Deshpande, MD Cockrell, CR Beck, FB TI Radiation characteristics of cavity backed aperture antennas in finite ground plane using the hybrid FEM/MoM technique and geometrical theory of diffraction SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article ID ELECTROMAGNETIC SCATTERING; ELEMENT METHOD AB A technique using hybrid finite element method (FEM)/method of moments (MoM) and geometrical theory of diffraction (GTD) is presented to analyze the radiation characteristics of cavity fed aperture antennas in a finite ground plane, The cavity which excites the aperture is assumed to be fed by a cylindrical transmission line, The electromagnetic (EM) fields inside the cavity are obtained using finite element method (FEM). The EM fields and their normal derivatives required for FEM solution are obtained using: 1) the modal expansion in the feed region and 2) the MoM for the radiating aperture region (assuming an infinite ground plane). The finiteness of the ground plane is taken into account using GTD. The input admittance of open-ended circular, rectangular, and coaxial line radiating into free space through an infinite ground plane are computed and compared with earlier published results, Radiation characteristics of a coaxial cavity-fed circular aperture in a finite rectangular ground plane are verified with experimental results. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. VIGYAN INC,HAMPTON,VA 23681. NR 14 TC 23 Z9 25 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD OCT PY 1996 VL 44 IS 10 BP 1327 EP 1333 DI 10.1109/8.537326 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA VK650 UT WOS:A1996VK65000003 ER PT J AU Dickens, PM Heidelberger, P Nicol, DM AF Dickens, PM Heidelberger, P Nicol, DM TI Parallelized direct execution simulation of message-passing parallel programs SO IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS LA English DT Article DE direct execution simulation; parallel simulation; architectural simulation; message-passing programs; MIMD; synchronization; contention ID DISTRIBUTED SIMULATION AB As massively parallel computers proliferate, there is growing interest in finding ways by which performance of massively parallel codes can be efficiently predicted. This problem arises in diverse contexts such as parallelizing compilers, parallel performance monitoring, and parallel algorithm development. In this paper, we describe one solution where one directly executes the application code, but uses a discrete-event simulator to model details of the presumed parallel machine, such as operating system and communication network behavior, Because this approach is computationally expensive, we are interested in Its own parallelization, specifically the parallelization of the discrete-event simulator. We describe methods suitable for parallelized direct execution simulation of message-passing parallel programs, and report on the performance of such a system, LAPSE (Large Application Parallel Simulation Environment), we have built on the Intel Paragon. On all codes measured to date, LAPSE predicts performance well, typically within 10% relative error. Depending on the nature of the application code, we have observed low slowdowns (relative to natively executing code) and high relative speedups using up to 64 processors. C1 ICASE,NASA,LANGLEY RES CTR,HAMPTON,VA 23681. IBM CORP,THOMAS J WATSON RES CTR,YORKTOWN HTS,NY 10598. COLL WILLIAM & MARY,DEPT COMP SCI,WILLIAMSBURG,VA 23185. NR 38 TC 24 Z9 25 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1045-9219 J9 IEEE T PARALL DISTR JI IEEE Trans. Parallel Distrib. Syst. PD OCT PY 1996 VL 7 IS 10 BP 1090 EP 1105 DI 10.1109/71.539740 PG 16 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA VN737 UT WOS:A1996VN73700009 ER PT J AU Farry, KA Walker, ID Baraniuk, RG AF Farry, KA Walker, ID Baraniuk, RG TI Myoelectric teleoperation of a complex robotic hand SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article ID SIGNAL ANALYSIS AB Teleoperation continues to be a primary control mode in robotics applications, particularly for robots with complex hands, This paper details a novel method of teleoperation of complex anthropomorphic robotic hands: converting the myoelectric signal (generated by the operator's muscles during movement) into robot commands replicating the motion, Myoelectric prosthetic hands have used this user interface for over two decades; however, the feasibility of using this approach for commanding more than one degree-of-freedom, as in the pincher type grip in current myoelectric hands, has been in question, The research described in this paper addresses myoelectric control of NASA/Johnson Space Center's sixteen degree-of-freedom Utah/MIT Dextrous Hand for two grasping (key and chuck) options and three thumb motions (abduction, extension, and flexion), We discuss myoelectric signal processing approaches, data collection apparatus, and a realtime teleoperation implementation, We also present results in realtime discrimination of key and chuck grasps and offline discrimination of thumb motions, Our results include a 90% correct grasp selection rate and an 87% correct thumb motion selection, both using the myoelectric spectrum. C1 RICE UNIV,DEPT ELECT & COMP ENGN,HOUSTON,TX 77251. RP Farry, KA (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,ENGN DIRECTORATE,AUTOMAT ROBOT & SIMULAT DIV,HOUSTON,TX 77058, USA. NR 68 TC 123 Z9 134 U1 2 U2 14 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD OCT PY 1996 VL 12 IS 5 BP 775 EP 788 DI 10.1109/70.538982 PG 14 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA VL563 UT WOS:A1996VL56300012 ER PT J AU Hall, FG Peddle, DR Ledrew, EF AF Hall, FG Peddle, DR Ledrew, EF TI Remote sensing of biophysical variables in boreal forest stands of Picea mariana SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID CANOPY; REFLECTANCE; ATMOSPHERE; BIOSPHERE; EXCHANGE; RED; CO2 AB Using two hybrid radiative transfer models to represent conifer canopies and stands, algorithms to infer several important structural parameters of stands of black spruce (Picea mariana), the most common boreal forest dominant, were developed and evaluated. Spectral mixture analysis and multi-spectral reflectance data for 31 black spruce stands of varying density and structure were used to infer the values for the areal proportions of sunlit canopy, sunlit background and shadow fraction, which we call radiometric elements, and the areal proportions of these radiometric elements were strongly related to leaf area index, biomass density, and annual above ground net primary productivity. The best overall correspondence between the radiometric elements and biophysical variables was found from the shadow fraction obtained with the cone-based canopy reflectance model corrected for variations in solar zenith angle. C1 UNIV WATERLOO,DEPT GEOG,WATERLOO,ON N2L 3G1,CANADA. RP Hall, FG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,CODE 923,GREENBELT,MD 20771, USA. NR 17 TC 28 Z9 29 U1 1 U2 3 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD OCT PY 1996 VL 17 IS 15 BP 3077 EP 3081 PG 5 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA VJ564 UT WOS:A1996VJ56400014 ER PT J AU Jangchud, I Eby, RK Serrano, AM Meador, MA AF Jangchud, I Eby, RK Serrano, AM Meador, MA TI Studies of PAN-based carbon fiber surfaces: Their influence on interfacial bonding with PMR-15 polyimide and composite thermo-oxidative stability SO JOURNAL OF ADVANCED MATERIALS LA English DT Article ID SCANNING TUNNELING MICROSCOPY; GOLD AB Atomic force microscopy has been used to study the surfaces of PAN-based carbon fibers to gain a better understanding of their interactions with PMR-15 polyimide. Topographic images, average roughness, excess area, and fractal dimension were obtained. The polar nature of the surfaces was characterized as percent weighted dipole moment (% WDM) and interlaminar shear strength (ILSS) was measured for the composites. The loss of ILSS and mass under aging at 316 degrees C wets measured. There is a linear correlation between the inverse of % WDM and initial ILSS indicating a limiting value of the latter of about 170 Mpa for this system. Further increases of the ILSS by dipolar bonding require an increase of polar components in the matrix. Fiber/matrix dipolar interactions govern the thermooxidative stability. By inhibiting the development of cracks along the fiber matrix interface, they slow the loss of ILSS and mass. Previous(1) correlations of roughness with % WDM and ILSS do not extend to additional types of fibers. Other surface parameters also correlate for some types of fibers, but not for others. Correlations of surface morphology with ILSS might be obtained at dimensional scales below 25 nm. However correlations might not exist because of differences among fiber manufacturing and surface treatment. C1 UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325. NASA,LEWIS RES CTR,POLYMER BRANCH,CLEVELAND,OH 44135. RP Jangchud, I (reprint author), UNIV AKRON,DEPT POLYMER SCI,AKRON,OH 44325, USA. NR 34 TC 5 Z9 5 U1 0 U2 1 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD OCT PY 1996 VL 28 IS 1 BP 19 EP 25 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA VY573 UT WOS:A1996VY57300003 ER PT J AU Bansal, NP AF Bansal, NP TI Influence of fiber volume fraction on mechanical behavior of CVD SiC fiber/SrAl2Si2O8 glass-ceramic matrix composites SO JOURNAL OF ADVANCED MATERIALS LA English DT Article ID REINFORCED CERAMICS; STRENGTH; FRACTURE AB Unidirectional CVD SiCf(SCS-6) fiber-reinforced strontium aluminosilicate (SAS) glass-ceramic matrix composites containing various volume fractions, similar to 16 to 40%, of fibers were fabricated by hot pressing. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase formed, with complete absence of the undesired hexacelsian phase in the matrix. Room temperature mechanical properties were measured in three-point flexure. The matrix microcracking stress and the ultimate strength increased with increase in fiber volume fraction, reached maximum values for V-f 0.35, and degraded at higher fiber contents. This degradation in mechanical properties is related to the change in failure mode, form tensile at lower V-f to interlaminar shear at higher fiber contents. The extent of fiber loading did not have a noticeable effect on either fiber-matrix debonding stress or frictional sliding stress at the interface. The applicability of currently available micromechanical models in predicting the mechanical properties of the composites was also examined. RP Bansal, NP (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 26 TC 3 Z9 3 U1 0 U2 1 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD OCT PY 1996 VL 28 IS 1 BP 48 EP 58 PG 11 WC Materials Science, Multidisciplinary SC Materials Science GA VY573 UT WOS:A1996VY57300007 ER PT J AU Meneghini, R Liao, L AF Meneghini, R Liao, L TI Comparisons of cross sections for melting hydrometeors as derived from dielectric mixing formulas and a numerical method SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID CONJUGATE-GRADIENT METHOD; RADAR BACKSCATTERING; ELECTROMAGNETIC SCATTERING; PRECIPITATION; PARTICLES; LAYER; PREDICTIONS; HAILSTONES; SPHERES; WAVES AB One of the impediments to the interpretation of radar signatures from the melting layer is the uncertainty over the dielectric mixing formula for ice-water mixtures. In the commonly used Maxwell Garnett mixing formula, the dielectric constant for ice inclusions in a water matrix differs from that for water inclusions in an ice matrix for the same fraction of meltwater. While the choice of materials for the matrix and inclusion is clear for either small or large fractions of meltwater, it is not obvious how these are to he chosen in the intermediate ranges of melting. In this paper, cross sections derived from the various mixing formulas are compared to a conjugate gradient-fast Fourier transform numerical method. In the numerical method the particle is divided into equivolume subcells in which the composition of the particle is controlled by assigning a probability of water to each subcell. For a uniform distribution of water and ice, where the probability of water in a subcell is independent of its location within the particle, the numerical results for fractional water contents of less than about 0.7 indicate that the scattering coefficients are closest to those predicted by the Maxwell Garnett mixing formula if an ice matrix with water inclusions is assumed. However, if the meltwater is highly concentrated near the boundary of the particle or if the fractional volume of water is greater than about 0.8, the Maxwell Garnett formula is in fair agreement with the numerical results, if the roles of ice and water are interchanged. A discussion of the relevance of these results to the modeling of melting snow aggregates and the interpretation of radar signatures of the bright band is given in the final section of the paper. C1 CAELUM RES CORP,SILVER SPRING,MD. RP Meneghini, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 975,GREENBELT,MD 20771, USA. NR 33 TC 31 Z9 32 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD OCT PY 1996 VL 35 IS 10 BP 1658 EP 1670 DI 10.1175/1520-0450(1996)035<1658:COCSFM>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VP281 UT WOS:A1996VP28100006 ER PT J AU Heymsfield, GM Caylor, IJ Shepherd, JM Olson, WS Bidwell, SW Boncyk, WC Ameen, S AF Heymsfield, GM Caylor, IJ Shepherd, JM Olson, WS Bidwell, SW Boncyk, WC Ameen, S TI Structure of Florida thunderstorms using high-altitude aircraft radiometer and radar observations SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID MICROWAVE PRECIPITATION RADIOMETER; MULTIPARAMETER RADAR; RAINFALL RATES; 183 GHZ; CLOUDS; ICE; RADIANCES; SATELLITE; SYSTEMS; HYDROMETEORS AB This paper presents an analysis of a unique radar and radiometer dataset from the National Aeronautics and Space Administration (NASA) ER-2 high-altitude aircraft overflying Florida thunderstorms on 5 October 1993 during the Convection and Moisture Experiment (CAMEX). The observations represent the first ER-2 Doppler radar (EDOP) measurements and perhaps the most comprehensive multispectral precipitation measurements collected from a single aircraft. The objectives of this paper are to 1) examine the relation of the vertical radar reflectivity structure to the radiometric responses over a wide range of remote sensing frequencies, 2) examine the limitations of rain estimation schemes over land and ocean backgrounds based on the observed vertical reflectivity structures and brightness temperatures, and 3) assess the usefulness of scattering-based microwave frequencies (86 GHz and above) to provide information on vertical structure in the ice region. Analysis focused on two types of convection: a small group of thunderstorms over the Florida Straits and sea-breeze-initiated convection along the Florida Atlantic coast. Various radiometric datasets are synthesized including visible, infrared (IR), and microwave (10-220 GHz). The rain cores observed over an ocean background by EDOP, compared quite well with elevated brightness temperatures from the Advanced Microwave Precipitation Radiometer (AMPR) 10.7-GHz channel. However, at higher microwave frequencies, which are ice-scattering based, storm evolution and vertical wind shear were found to be important in interpretation of the radiometric observations. As found in previous studies, the ice-scattering region was displaced significantly downshear of the convective and surface rainfall regions due to upper-level wind advection. The ice region above the rain layer was more opaque in the IR, although the 150- and 220-GHz brightness temperatures T-b approached the IR measurements and both corresponded well with the radar-detected ice regions. It was found that ice layer reflectivities and thicknesses were approximately 15 dBZ and a few kilometers, respectively, for detectable ice scattering to be present at these higher microwave frequencies. The EDOP-derived rainfall rates and the simultaneous microwave T-b's were compared with single-frequency forward radiative transfer calculations using a family of vertical cloud and precipitation water profiles derived from a three-dimensional cloud model. Over water backgrounds, the lower-frequency emission-based theoretical curves agreed in a rough sense with the observed radar rainfall rate-T-b data points, in view of the uncertainties in the measurements and the scatter of the cloud model profiles. The characteristics of the ice regions of the thunderstorms were examined using brightness temperature differences Delta T-b such as T-b (37 GHZ) - T-b (220 GHz). The Delta T-b's (150-220, 89-220, and 37-86 GHz) suggested a possible classification of the clouds and precipitation according to convective cores, elevated ice layers, and rain without significant ice above the melting layer. Although some qualitative classification of the ice is possible, the quantitative connection with ice path was difficult to obtain from the present observations. C1 SCI SYST & APPLICAT INC,LANHAM,MD. CAELUM RES CORP,SILVER SPRING,MD. RP Heymsfield, GM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 912,GREENBELT,MD 20771, USA. NR 50 TC 26 Z9 26 U1 3 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD OCT PY 1996 VL 35 IS 10 BP 1736 EP 1762 DI 10.1175/1520-0450(1996)035<1736:SOFTUH>2.0.CO;2 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VP281 UT WOS:A1996VP28100011 ER PT J AU Olson, WS Kummerow, CD Heymsfield, GM Giglio, L AF Olson, WS Kummerow, CD Heymsfield, GM Giglio, L TI A method for combined passive-active microwave retrievals of cloud and precipitation profiles SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID ADVECTION TRANSPORT ALGORITHM; SMALL IMPLICIT DIFFUSION; RAIN-RATE; TROPICAL ATMOSPHERE; RADAR MEASUREMENTS; MESOSCALE SYSTEMS; SPACEBORNE RADAR; CONVECTIVE CELLS; MODEL; RADIOMETER AB Three-dimensional tropical squall-line simulations from the Goddard cumulus ensemble (GCE) model are used as input to radiative computations of upwelling microwave brightness temperatures and radar reflectivities at selected microwave sensor frequencies. These cloud/radiative calculations form the basis of a physical cloud/precipitation profile retrieval method that yields estimates of the expected values of the hydrometeor water contents. Application of the retrieval method to simulated nadir-view observations of the aircraft-borne Advanced Microwave Precipitation Radiometer (AMPR) and NASA ER-2 Doppler radar (EDOP) produce random errors of 23%, 19%, and 53% in instantaneous estimates of integrated precipitating liquid, integrated precipitating ice, and surface rain rate, respectively. On 5 October 1993, during the Convection and Atmospheric Moisture Experiment (CAMEX), the AMPR and EDOP were used to observe convective systems in the vicinity of the Florida peninsula. Although the AMPR data alone could be used to retrieve cloud and precipitation vertical profiles over the ocean, retrievals of high-resolution vertical precipitation structure and profile information over land required the combination of AMPR and EDOP observations. No validation data are available for this study; however, the retrieved precipitation distributions from the convective systems are compatible with limited radar climatologies of such systems, as well as being radiometrically consistent with both the AMPR and EDOP observations. In the future, the retrieval method will be adapted to the passive and active microwave measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite sensors. C1 CAELUM RES CORP,SILVER SPRING,MD. SCI SYST & APPLICAT INC,LANHAM,MD. RP Olson, WS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 912,GREENBELT,MD 20771, USA. NR 62 TC 104 Z9 111 U1 0 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD OCT PY 1996 VL 35 IS 10 BP 1763 EP 1789 DI 10.1175/1520-0450(1996)035<1763:AMFCPM>2.0.CO;2 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VP281 UT WOS:A1996VP28100012 ER PT J AU Valero, FPJ Pope, SK Ellingson, RG Strawa, AW Vitko, J AF Valero, FPJ Pope, SK Ellingson, RG Strawa, AW Vitko, J TI Determination of clear-sky radiative flux profiles, heating Rates and optical depths using unmanned aerospace vehicles as a platform SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID PARTICLE SIZES; CLOUD; MODELS AB In this paper the authors report results obtained using an unmanned aerospace vehicle (UAV) as an experimental platform for atmospheric radiative transfer research. These are the first ever climate measurements made from a UAV and represent a major step forward in realizing the unique potential of long-endurance, high-altitude UAVs to contribute to climate and environmental studies. Furthermore, the radiative flux divergences determined during these experiments are some of the highest quality measurements of this kind obtained from any type of aircraft and constitute an important test of radiative transfer models. C1 UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,ATMOSPHER RES LAB,DEPT 0242,LA JOLLA,CA 92093. UNIV MARYLAND,DEPT METEOROL,COLLEGE PK,MD 20742. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. SANDIA NATL LABS,LIVERMORE,CA. NR 11 TC 7 Z9 7 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD OCT PY 1996 VL 13 IS 5 BP 1024 EP 1030 DI 10.1175/1520-0426(1996)013<1024:DOCSRF>2.0.CO;2 PG 7 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA VN010 UT WOS:A1996VN01000007 ER PT J AU Durden, SL Werner, CL AF Durden, SL Werner, CL TI Application of an interferometric phase unwrapping technique to dealiasing of weather radar velocity fields SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID DOPPLER VELOCITIES; ALGORITHM; EQUATION AB Dealiasing of Doppler weather radar velocity measurements is analogous to the problem of phase unwrapping encountered in radar and optical interferometry. A technique developed for phase unwrapping in interferometric synthetic aperture radar is described and successfully applied to weather radar velocity dealiasing. RP Durden, SL (reprint author), CALTECH,JET PROP LAB,MAIL STOP 300-325,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 11 TC 3 Z9 4 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD OCT PY 1996 VL 13 IS 5 BP 1107 EP 1109 DI 10.1175/1520-0426(1996)013<1107:AOAIPU>2.0.CO;2 PG 3 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA VN010 UT WOS:A1996VN01000013 ER PT J AU Green, S Keller, HM Schinke, R Werner, HJ AF Green, S Keller, HM Schinke, R Werner, HJ TI Vibration-rotation excitation of CO by hot hydrogen atoms: Comparison of two potential energy surfaces SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID ELECTRONICALLY INELASTIC-COLLISIONS; QUANTUM SCATTERING; UNIMOLECULAR DISSOCIATION; RESONANCE ENERGIES; FLUORINE ATOMS; HCO; WIDTHS; PREDISSOCIATION; SPECTROSCOPY; DYNAMICS AB Collision doss sections for rotational and vibrational excitation of CO by fast H atoms are calculated for two potential energy surfaces, the older Bowman-Bitman-Harding potential and the recently constructed surface of Werner, Keller, and Schinke. Both quantum mechanical and classical calculations are performed. The results obtained with the new potential energy surface are very similar to those obtained with the older potential; in particular, they do not rectify the discrepancies between the experimental and theoretical cross sections for vibrationally elastic transitions into small rotational states of CO. (C) 1996 American Institute of Physics. C1 MAX PLANCK INST STROMUNGSFORSCH,D-37073 GOTTINGEN,GERMANY. UNIV STUTTGART,INST THEORET CHEM,D-70569 STUTTGART,GERMANY. RP Green, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,NEW YORK,NY 10025, USA. RI Werner, Hans-Joachim/G-9509-2011 OI Werner, Hans-Joachim/0000-0002-0435-539X NR 32 TC 11 Z9 11 U1 0 U2 4 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD OCT 1 PY 1996 VL 105 IS 13 BP 5416 EP 5422 DI 10.1063/1.472382 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VL469 UT WOS:A1996VL46900015 ER PT J AU Koster, RD Suarez, MJ AF Koster, RD Suarez, MJ TI The influence of land surface moisture retention on precipitation statistics SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; NORTHEAST BRAZIL; SOIL-MOISTURE; RAINFALL; DROUGHT; VARIABILITY; TEMPERATURE; ANOMALIES; DYNAMICS AB The retention of precipitation water in land surface reservoirs damps higher frequencies of evaporation variability and can thereby influence the feedback of evaporation on precipitation. The extent of this influence is examined in a series of general circulation model simulations in which the timescale of surface moisture retention is very carefully controlled. Shorter timescales lead to increased daily precipitation variance and one-day-lagged precipitation autocorrelations but to decreased autocorrelations at longer lags. An explanation for the simulated precipitation statistics is offered in the form of a heuristic model of evaporation feedback that describes precipitation variance and autocorrelation in terms of three parameters: (i) the timescale of precipitation persistence in the absence of feedback; (ii) the surface retention timescale; and (iii) a parameter describing the atmosphere's responsiveness to variations in evaporation. The heuristic model reproduces the statistical trends seen in the GCM diagnostics, and it can be used to explain geographical variations in precipitation statistics generated by a GCM coupled to a full biosphere model. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CLIMATE & RADIAT BRANCH, GREENBELT, MD 20771 USA. RP Koster, RD (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HYDROL SCI BRANCH, LAB HYDROSPHER PROC, CODE 974, GREENBELT, MD 20771 USA. RI Koster, Randal/F-5881-2012 OI Koster, Randal/0000-0001-6418-6383 NR 31 TC 43 Z9 44 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD OCT PY 1996 VL 9 IS 10 BP 2551 EP 2567 DI 10.1175/1520-0442(1996)009<2551:TIOLSM>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VQ571 UT WOS:A1996VQ57100017 ER PT J AU Forsythe, EL Pusey, ML AF Forsythe, EL Pusey, ML TI The effects of acetate buffer concentration on lysozyme solubility SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 6th International Conference on Crystallization of Biological Macromolecules CY NOV 12-17, 1995 CL HIROSHIMA, JAPAN SP Japanese Assoc Crystal Growth, Crystallog Soc Japan, Hiroshima Prefecture, Hiroshima City, Minist Educ Sci Sports & Culture, Japan, Int Union Crystallog, Japanese Soc Biosci Biotechnol & Agrochem, Pharm Soc Japan, Chem Soc Japan, Japan Soc Appl Phys, Japan Soc Micrograv Appl, Japanese Biochem Soc, Japanese Soc Synchrotron Radiat Res, Molec Biol Soc Japan, Phys Soc Japan, Soc Fermentat & Bioengn, Japan, Soc Polym Sci, Japan ID FACE GROWTH-RATES; PROTEIN SOLUBILITIES; CRYSTAL-GROWTH; TEMPERATURE AB The micro-solubility column technique was employed to systematically investigate the effects of buffer concentration on tetragonal lysozyme solubility. While keeping the NaCl concentrations constant at 2%, 3%, 4%, 5% and 7%, and the pH at 4.0, we have studied the solubility of tetragonal lysozyme over an acetate buffer concentration range of 0.01M to 0.5M as a function of temperature. The lysozyme solubility decreased with increasing acetate concentration from 0.01M to 0.1M. This decrease may simply be due to the net increase in solvent ionic strength. Increasing the acetate concentration beyond 0.1M resulted in an increase in the lysozyme solubility, which reached a peak at similar to 0.3M acetate concentration. This increase was believed to be due to the increased binding of acetate to the anionic binding sites of lysozyme, preventing their occupation by chloride. In keeping with the previously observed reversal of the Hoffmeister series for effectiveness of anions in crystallizing lysozyme, acetate would be a less effective precipitant than chloride. Further increasing the acetate concentration beyond 0.3M resulted in a subsequent gradual decrease in the lysozyme solubility at all NaCl concentrations. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV SPACE RES ADM,HUNTSVILLE,AL 35806. NR 21 TC 23 Z9 23 U1 0 U2 4 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 OCT PY 1996 VL 168 IS 1-4 BP 112 EP 117 DI 10.1016/0022-0248(96)00368-5 PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VQ249 UT WOS:A1996VQ24900012 ER PT J AU Ansari, RR Suh, KI Arabshahi, A Wilson, WW Bray, TL DeLucas, LJ AF Ansari, RR Suh, KI Arabshahi, A Wilson, WW Bray, TL DeLucas, LJ TI A fiber optic probe for monitoring protein aggregation, nucleation and crystallization SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 6th International Conference on Crystallization of Biological Macromolecules CY NOV 12-17, 1995 CL HIROSHIMA, JAPAN SP Japanese Assoc Crystal Growth, Crystallog Soc Japan, Hiroshima Prefecture, Hiroshima City, Minist Educ Sci Sports & Culture, Japan, Int Union Crystallog, Japanese Soc Biosci Biotechnol & Agrochem, Pharm Soc Japan, Chem Soc Japan, Japan Soc Appl Phys, Japan Soc Micrograv Appl, Japanese Biochem Soc, Japanese Soc Synchrotron Radiat Res, Molec Biol Soc Japan, Phys Soc Japan, Soc Fermentat & Bioengn, Japan, Soc Polym Sci, Japan DE dynamic light scattering; protein crystallization; on-line diagnostics ID CRYSTAL-GROWTH; SCATTERING; MICROGRAVITY AB Protein crystals are often experimentally grown in hanging drops in microgravity experiments on-board the Space Shuttle orbiter. The technique of dynamic light scattering (DLS) can be used to monitor crystal growth processes in hanging droplets (similar to 30 mu L) in microgravity experiments, but elaborate instrumentation and optical alignment problems have made in-situ applications difficult. In this paper we demonstrate that such experiments are now feasible. We apply a newly developed fiber optic probe to various earth and space (microgravity) protein crystallization system configurations to test its capabilities. These include conventional batch (cuvette or capillary) systems, a hanging drop method in a six-pack hanging drop vapor diffusion apparatus (HDVDA), a modified HDVDA for temperature induced nucleation and aggregation studies, and a newly envisioned dynamically controlled vapor diffusion system (DCVDS) configuration. Our compact system exploits the principles of DLS and offers a fast (within a few seconds) means of quantitatively and non-invasively monitoring the various growth stages of protein crystallization. In addition to DLS capability, the probe can also be used for performing single-angle static light scattering measurements. It utilizes extremely low levels of laser power (a few mu W) and essentially eliminates the usual problems associated with optical alignment and vibration isolation. The compact probe is also equipped with a miniaturized microscope for visualization of macroscopic protein crystals. This new optical diagnostic system makes possible the exploration of new ways to grow good quality crystals suitable for X-ray crystallographic analysis and may contribute to a concrete scientific basis for understanding the process of crystallization. C1 MISSISSIPPI STATE UNIV,DEPT CHEM,MISSISSIPPI STATE,MS 39762. UNIV ALABAMA,CTR MACROMOL CRYSTALLOG,BIRMINGHAM,AL 35294. RP Ansari, RR (reprint author), NASA,LEWIS RES CTR,MICROGRAV FLUIDS BRANCH,SPACE EXPT DIV,MAIL STOP 333-1,21000 BROOKPARK RD,CLEVELAND,OH 44135, USA. NR 14 TC 31 Z9 31 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD OCT PY 1996 VL 168 IS 1-4 BP 216 EP 226 DI 10.1016/0022-0248(96)00357-0 PG 11 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VQ249 UT WOS:A1996VQ24900027 ER PT J AU Watring, DA Lehoczky, SL AF Watring, DA Lehoczky, SL TI Magneto-hydrodynamic damping of convection during vertical Bridgman-Stockbarger growth of HgCdTe SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID DIRECTIONALLY SOLIDIFIED HGCDTE; SEGREGATION; ALLOYS; FIELD; INTERFERENCE AB In order to quantify the effects of convection on segregation, Hg0.8Cd0.2Te crystals were grown by the vertical Bridgman-Stockbarger method in the presence of an applied axial magnetic field of 50 kG. The influence of convection, by magneto-hydrodynamic damping, on mass transfer in the melt and segregation at the solid-liquid interface was investigated by measuring the axial and radial compositional variations in the grown samples. The reduction of convective mixing in the melt through the application of the magnetic field is found to decrease radial segregation to the diffusion-limited regime. It was also found that the suppression of the convective cell near the solid-liquid interface results in an increase in the slope of the diffusion-controlled solute boundary layer, which can lead to constitutional supercooling. RP Watring, DA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. NR 34 TC 26 Z9 28 U1 1 U2 5 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 OCT PY 1996 VL 167 IS 3-4 BP 478 EP 487 DI 10.1016/0022-0248(96)00279-5 PG 10 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VN986 UT WOS:A1996VN98600013 ER PT J AU Zhou, H Zebib, A Trivedi, S Duval, WMB AF Zhou, H Zebib, A Trivedi, S Duval, WMB TI Physical vapor transport of zinc-telluride by dissociative sublimation SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID CONVECTION AB We investigate the effects of convection on physical vapor transport of zinc-telluride by dissociative sublimation computationally and experimentally. We show by solving the coupled set of conservation equations for the corresponding experimental conditions that the flow field is advective-diffusive, This result proves that the traditional approach of calculating the mass flux assuming one-dimensional (1D) flow for low vapor pressure systems is indeed correct. The limit of low Grashof numbers Gr --> 0 yields identical results to the 1D case. This implies that for the model considered, a microgravity condition would not affect the transport. C1 RUTGERS STATE UNIV,DEPT AEROSP & MECH ENGN,PISCATAWAY,NJ 08855. BRIMROSE CORP AMER,BALTIMORE,MD 21236. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. NR 17 TC 12 Z9 12 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD OCT PY 1996 VL 167 IS 3-4 BP 534 EP 542 DI 10.1016/0022-0248(96)00305-3 PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VN986 UT WOS:A1996VN98600020 ER PT J AU Pines, V Chait, A Zlatkowski, M AF Pines, V Chait, A Zlatkowski, M TI Dynamic scaling in dendritic growth SO JOURNAL OF CRYSTAL GROWTH LA English DT Article AB We use simple scaling analysis to examine the fundamental relations in dendritic growth between dynamic parameters such as dendrite tip radius and growth velocity, and the dimensionless net heat flux through the dendrite surface (Peclet number). The resulting relations are then expanded in powers of the Peclet number. It is demonstrated that for a small Peclet number, a two term expansion is sufficient to fit the entire range of data in supercooling of Glicksman's recent microgravity experiment [M.E. Glicksman, M.B. Koss and E.A. Winsa, Phys. Rev. Lett. 73 (1994) 573; M.E. Glicksman, M.B. Koss, L.T. Bushnell, J.C. LaCombe and E.A. Winsa, ISIJ Int. 35 (1995) 1216; MRS Fall Meeting, Symp. P, Boston, MA, 1995, in press]. We also show that conventional theories using a single parameter are not supported from basic scaling arguments, nor do they correspond to experimental observations. C1 NASA,LEWIS RES CTR,COMPUTAT MAT LAB,CLEVELAND,OH 44135. CASE WESTERN RESERVE UNIV,DEPT PHYS,CLEVELAND,OH 44106. NR 8 TC 8 Z9 8 U1 0 U2 0 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 OCT PY 1996 VL 167 IS 3-4 BP 777 EP 781 DI 10.1016/0022-0248(96)00303-X PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VN986 UT WOS:A1996VN98600056 ER PT J AU Salem, JA Nemeth, NN Powers, LM Choi, SR AF Salem, JA Nemeth, NN Powers, LM Choi, SR TI Reliability analysis of uniaxially ground brittle materials SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 40th International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 05-08, 1995 CL HOUSTON, TX ID FRACTURE AB The fast fracture strength distribution of uniaxially ground, alpha silicon carbide was investigated as a function of grinding angle relative to the principal stress direction in flexure. Both as-ground and ground/annealed surfaces were investigated. The resulting flexural strength distributions were used to verify reliability models and predict the strength distribution of larger plate specimens tested in biaxial flexure. Complete fractography was done,on the specimens. Failures occurred from agglomerates, machining cracks, or hybrid flaws that consisted of a machining crack located at a processing agglomerate. Annealing eliminated failures due to machining damage. Reliability analyses were performed using two and three-parameter Weibull and Batdorf methodologies. The Weibull size effect was demonstrated for machining flaws. Mixed mode reliability models reasonably predicted the strength distributions of uniaxial flexure and biaxial plate specimens. C1 CLEVELAND STATE UNIV,DEPT CIVIL ENGN,CLEVELAND,OH 44135. RP Salem, JA (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 10 TC 11 Z9 11 U1 1 U2 3 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD OCT PY 1996 VL 118 IS 4 BP 863 EP 871 DI 10.1115/1.2817007 PG 9 WC Engineering, Mechanical SC Engineering GA VT092 UT WOS:A1996VT09200026 ER PT J AU Stasiewicz, K Holback, B Krasnoselskikh, V Boehm, M Bostrom, R Kintner, PM AF Stasiewicz, K Holback, B Krasnoselskikh, V Boehm, M Bostrom, R Kintner, PM TI Parametric instabilities of Langmuir waves observed by Freja SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ELECTRON EVENT; PLASMA-WAVES; TURBULENCE; IONOSPHERE; COLLAPSE; PACKETS AB We have analyzed complete spectrum of waves (0-4 MHz) and electron distributions during events of modulated Langmuir waves observed by Freja in the topside polar ionosphere. Modulated Langmuir waves are observed with amplitudes 1-1000 mV/m in association with beams of electrons with energies 50-5000 eV streaming through cold ionospheric plasma. We find overwhelming evidence for interactions of Langmuir (L) waves with lower hybrid (LH) waves. The interactions are consistent with parametric decay of beam induced L waves (L --> L' + LH) as well as with scattering of L waves on preexisting LH waves (L + LH --> L'). These interactions are observed at all wave amplitudes similar to 1 - 1000 mV/m but are sensitive to the k vectors of the primary waves (i.e., electron beam energy). In association with modulated Langmuir waves we also observe ion acoustic-like signals which appear to be produced by rectification of the high-frequency waves in the probe sheath through nonlinearities in the current-voltage characteristic. The Langmuir wave events occur frequently in localized regions which are usually related to the phase of magnetic perturbation of an Alfven wave. The observations show that Langmuir waves with amplitudes > 50 mV/m are very common in the auroral zone, and they represent the strongest electrostatic wave mode at altitudes of similar to 1500 km. Langmuir waves appear to be an important element in the energy exchange chain in which part of the energy carried by Alfven waves is transferred to energetic electrons and finally deposited to thermal plasma in a sequence: Alfven wave --> electron beam --> Langmuir wave --> LH decays --> heating of thermal plasma. C1 JET PROPULS LAB,PASADENA,CA 91109. CORNELL UNIV,DEPT ELECT ENGN,ITHACA,NY 14853. LAB PHYS & CHEM ENVIRONM,ORLEANS,FRANCE. RP Stasiewicz, K (reprint author), SWEDISH INST SPACE PHYS,S-75591 UPPSALA,SWEDEN. NR 27 TC 41 Z9 41 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1996 VL 101 IS A10 BP 21515 EP 21525 DI 10.1029/96JA01747 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VK704 UT WOS:A1996VK70400007 ER PT J AU Cane, HV Richardson, IG vonRosenvinge, TT AF Cane, HV Richardson, IG vonRosenvinge, TT TI Cosmic ray decreases: 1964-1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; SOLAR-WIND; INTERPLANETARY SHOCKS; FORBUSH DECREASES; MAGNETIC CLOUDS; MODULATION; RADIATION AB We have studied 30 years (1964-1994) of neutron monitor data in order to understand the principle mechanisms causing short-term (< 20-day duration) cosmic ray decreases seen at Earth. By examining the characteristics of associated low energy (<200 MeV) particle enhancements in combination with the neutron monitor data, we have determined the responsible solar wind disturbances for 153 of the 180 greater than or equal to 4% decreases. The vast majority (86% of the 153 events) are caused by coronal mass ejections and the shocks that they generate. The ejecta is intercepted only when the solar event originates within 50 degrees of the Sun's central meridian. For more distant events, only the shock is intercepted at Earth. We present a fist of all 180 events seen in the years 1964-1994 together with the associated solar event, when this can be determined, and some details about the solar wind structures based on in situ solar wind data, if available. This list represents a compendium of major solar wind disturbances affecting a large section of the inner heliosphere over this time period. We also discuss enhanced daily variations in some events which are related to radial gradients caused by strong disturbances inside the Earth's orbit. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Cane, HV (reprint author), UNIV TASMANIA,DEPT PHYS,GPO BOX 252C,HOBART,TAS 7001,AUSTRALIA. OI Richardson, Ian/0000-0002-3855-3634 NR 38 TC 104 Z9 105 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1996 VL 101 IS A10 BP 21561 EP 21572 DI 10.1029/96JA01964 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VK704 UT WOS:A1996VK70400011 ER PT J AU Verma, MK Roberts, DA Goldstein, ML Ghosh, S Stribling, WT AF Verma, MK Roberts, DA Goldstein, ML Ghosh, S Stribling, WT TI A numerical study of the nonlinear cascade of energy in magnetohydrodynamic turbulence SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY ALFVENIC FLUCTUATIONS; SOLAR-WIND TURBULENCE; MEAN MAGNETIC-FIELD; MHD TURBULENCE; STREAM STRUCTURE; EVOLUTION; SPECTRA; PHENOMENOLOGY; DEPENDENCE AB Power spectra of solar wind magnetic field and velocity fluctuations more closely resemble those of turbulent fluids (spectral index of -5/3) than they do predictions for magnetofluid turbulence (a -3/2 index). Furthermore, the amount the solar wind is heated by turbulence is uncertain. To aid in the study of both of these issues, we report numerically derived energy cascade rates in magnetohydrodynamic (MHD) turbulence and compare them with predictions of MHD turbulence phenomenologies. Either of the commonly predicted spectral indices of 5/3 and 3/2 are consistent with the simulations. Explicit calculation of inertial range energy cascade rates in the simulations show that for unequal levels of fluctuations propagating parallel and antiparallel to the magnetic field, the majority species always cascades faster than does the minority species, and the cascade rates are in better agreement with a Kolmogoroff-like MHD turbulence phenomenology than with a generalized Kraichnan phenomenology even in situations where the fluctuations are much smaller than the mean magnetic field. The ''Kolmogoroff constant'' for MHD turbulence for small normalized cross helicity is roughly. 6.7 in two dimensions and 3.6 for one calculation in three dimensions. For large normalized cross helicity, however; none of the existing models can account for the numerical results, although the Kolmogoroff-like case still works somewhat better than the Kraichnan-like. fn particular, the applied magnetic field has much less influence than expected, and Alfvenicity is more important than predicted. These results imply the need for better phenomenological models to make dear predictions about the solar wind. C1 INDIAN INST TECHNOL,DEPT PHYS,KANPUR 208016,UTTAR PRADESH,INDIA. RP Verma, MK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008; verma, mahendra/G-4041-2013 OI verma, mahendra/0000-0002-3380-4561 NR 36 TC 58 Z9 58 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1996 VL 101 IS A10 BP 21619 EP 21625 DI 10.1029/96JA01773 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VK704 UT WOS:A1996VK70400016 ER PT J AU Wilson, TL Chlouber, D Jost, RJ AF Wilson, TL Chlouber, D Jost, RJ TI Electrodynamic tether currents in the day/night ionosphere: Correlations during the Plasma Motor Generator mission SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID LOW EARTH ORBIT; CURRENT COLLECTION; LABORATORY PLASMA; SATELLITE SYSTEM; WAVES; CONTACTORS; RADIATION; SOLITONS; MAGNETOPLASMA; TSS-1 AB Ground-based radar observations during NASA's Plasma Motor Generator (PMG) electrodynamic tether mission are reported, which indicate the existence of ion-acoustic or soliton wave packets produced as ionospheric excitations by the orbiting PMG tether system. These appear to be the first such radar measurements of traveling ionospheric disturbances propagating along geomagnetic field lines during an active orbiting ionospheric tether-plasma experiment. The presence of such excitations gives added importance to earlier studies of the plasma radiation modes involved in tether electrodynamics and the part they play in the ionospheric energy balance mechanisms. In addition, tether-current measurements studied during postflight data analysis show a pronounced current decrease when the spacecraft passed from daylight to darkness, which may be related to current limiting. The significance of this observed day/night correlation in conjunction with the soliton-like wave packet radiation modes calls for a detailed investigation of the PMG tether-current measurements in terms of local and global interactions of the PMG with Earth's ionosphere, the initial work for which we show here. This includes an analysis of the radiation impedance due to Alfven and lower hybrid bands, ion-acoustic (soliton) modes, and whistler waves. A decomposition of the measured tether currents into Hall, Pedersen, Cowling, and Birkeland conductivities is presented. C1 SYST PLANNING CORP, CTR SPACE PHYS, HOUSTON, TX 77058 USA. RP NASA, LYNDON B JOHNSON SPACE CTR, EARTH SCI & SOLAR SYST EXPLORAT DIV, CODE SN3, HOUSTON, TX 77058 USA. OI Chlouber, Clyde/0000-0001-8884-6294 NR 64 TC 5 Z9 5 U1 0 U2 3 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 OCT 1 PY 1996 VL 101 IS A10 BP 21657 EP 21688 DI 10.1029/96JA01900 PG 32 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VK704 UT WOS:A1996VK70400019 ER PT J AU Cole, KD Hoegy, WR AF Cole, KD Hoegy, WR TI The 100 Hz electric fields observed on Pioneer Venus Orbiter and a case against the whistler hypothesis for them SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID NIGHTSIDE IONOSPHERE; LOW ALTITUDES AB Without invoking the whistler hypothesis, but assuming they are nor man-made it is shown (1) that the 100 Hz electric fields observed on the Pioneer Venus orbiter in the lower ionosphere (below 160 km, at night) can be so intense that they would produce unrealistic heating and depletion of the ionosphere, if they existed on a planetary scale; and (2) assuming the signal is not electrostatic, their accompanying magnetic field b at high intensity would be greater than the ambient field Similar conclusions follow from invoking linear theory at whistler frequencies to explain the signal. Nonlinear theory would be needed to describe the propagation, if whistlers are the cause of the high-intensity signals, but this would not overcome the heating problem. Previous conclusions based on linear theory would be invalid for these high-intensity signals. In addition, for the most intense electric fields at 129 km altitude the ionization produced by the intensely heated electrons would be excessive. It is concluded that the 100 Hz signals can not be due to whistlers, or electromagnetic waves of planetary scale, and therefore these signals could not be used to support the case for lightning on Venus, These arguments favor the hypothesis that the 100 Hz electric fields are highly localized to the spacecraft. RP Cole, KD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 9104,GREENBELT,MD 20771, USA. NR 19 TC 6 Z9 6 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1996 VL 101 IS A10 BP 21785 EP 21793 DI 10.1029/96JA01822 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VK704 UT WOS:A1996VK70400027 ER PT J AU Ulaby, FT Dubois, PC vanZyl, J AF Ulaby, FT Dubois, PC vanZyl, J TI Radar mapping of surface soil moisture SO JOURNAL OF HYDROLOGY LA English DT Article ID SYNTHETIC-APERTURE RADAR; POLARIMETRIC SAR IMAGES; CLASSIFICATION; SCATTERING; COVER; MODEL AB Intended as an overview aimed at potential users of remotely sensed spatial distributions and temporal variations of soil moisture, this paper begins with an introductory section on the fundamentals of radar imaging and associated attributes. To place the soil moisture sensing task in proper perspective, the prerequisite step of classifying terrain into four basic types-bare surfaces, short vegetation, tall vegetation, and urban-is addressed by demonstrating how a dual-frequency polarimetric radar can correctly classify terrain with an accuracy greater than 90%. Over 5000 image pixels with known terrain identity were involved in the evaluation of the radar image classifier. For bare soil (with vegetation cover shorter than 15 cm), radar can estimate the volumetric moisture content (expressed in per cent) of the top 5 cm soil layer with an r.m.s. error of 3.5%. Based on theoretical model predictions as well as experimental observations, strong evidence exists in support of radar's potential for sensing soil moisture under vegetation cover, but no operational algorithm exists at present. C1 CALTECH,JET PROP LAB,PASADENA,CA 91101. RP Ulaby, FT (reprint author), UNIV MICHIGAN,ANN ARBOR,MI 48109, USA. RI Dubois-Fernandez, Pascale/A-6743-2012 NR 23 TC 149 Z9 152 U1 0 U2 24 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD OCT 1 PY 1996 VL 184 IS 1-2 BP 57 EP 84 DI 10.1016/0022-1694(95)02968-0 PG 28 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA VK068 UT WOS:A1996VK06800005 ER PT J AU Jackson, TJ LeVine, DE AF Jackson, TJ LeVine, DE TI Mapping surface soil moisture using an aircraft-based passive microwave instrument: Algorithm and example SO JOURNAL OF HYDROLOGY LA English DT Article ID RADIOMETER AB Microwave remote sensing at L-band (21 cm wavelength) can provide a direct measurement of the surface soil moisture for a range of cover conditions and within reasonable error bounds. Surface soil moisture observations are rare and, therefore, the use of these data in hydrology and other disciplines has not been fully explored or developed. Without satellite-based observing systems, the only way to collect these data in large-scale studies is with an aircraft platform. Recently, aircraft systems such as the push broom microwave radiometer (PBMR) and the electronically scanned thinned array radiometer (ESTAR) have been developed to facilitate such investigations. In addition, field experiments have attempted to collect the passive microwave data as part of an integrated set of hydrologic data. One of the most ambitious of these investigations was the Washita'92 experiment. Preliminary analysis of these data has shown that the microwave observations are indicative of deterministic spatial and temporal variations in the surface soil moisture. Users of these data should be aware of a number of issues related to using aircraft-based systems and practical approaches to applying soil moisture estimation algorithms to large data sets. This paper outlines the process of mapping surface soil moisture from an aircraft-based passive microwave radiometer system for the Washita'92 experiment. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Jackson, TJ (reprint author), USDA ARS,BELTSVILLE AGR RES CTR,HYDROL LAB,104 BLDG 007 BARC W,BELTSVILLE,MD 20705, USA. NR 13 TC 98 Z9 102 U1 0 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD OCT 1 PY 1996 VL 184 IS 1-2 BP 85 EP 99 DI 10.1016/0022-1694(95)02969-9 PG 15 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA VK068 UT WOS:A1996VK06800006 ER PT J AU Njoku, EG Entekhabi, D AF Njoku, EG Entekhabi, D TI Passive microwave remote sensing of soil moisture SO JOURNAL OF HYDROLOGY LA English DT Article ID WATER-CONTENT; SURFACE-ROUGHNESS; RADIOMETER DATA; EMISSION; VEGETATION; TEMPERATURE; MODEL; TEXTURE; FIELDS; LAYER AB Microwave remote sensing provides a unique capability for direct observation of soil moisture. Remote measurements from space afford the possibility of obtaining frequent, global sampling of soil moisture over a large fraction of the Earth's land surface. Microwave measurements have the benefit of being largely unaffected by cloud cover and variable surface solar illumination, but accurate soil moisture estimates are limited to regions that have either bare soil or low to moderate amounts of vegetation cover. A particular advantage of passive microwave sensors is that in the absence of significant vegetation cover soil moisture is the dominant effect on the received signal. The spatial resolutions of passive microwave soil moisture sensors currently considered for space operation are in the range 10-20 km. The most useful frequency range for soil moisture sensing is 1-5 GHz. System design considerations include optimum choice of frequencies, polarizations, and scanning configurations, based on trade-offs between requirements for high vegetation penetration capability, freedom from electromagnetic interference, manageable antenna size and complexity, and the requirement that a sufficient number of information channels be available to correct for perturbing geophysical effects. This paper outlines the basic principles of the passive microwave technique for soil moisture sensing, and reviews briefly the status of current retrieval methods. Particularly promising are methods for optimally assimilating passive microwave data into hydrologic models. Further studies are needed to investigate the effects on microwave observations of within-footprint spatial heterogeneity of vegetation cover and subsurface soil characteristics, and to assess the limitations imposed by heterogeneity on the retrievability of large-scale soil moisture information from remote observations. C1 MIT,DEPT CIVIL & ENVIRONM ENGN,CAMBRIDGE,MA 02139. RP Njoku, EG (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 58 TC 307 Z9 311 U1 6 U2 51 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD OCT 1 PY 1996 VL 184 IS 1-2 BP 101 EP 129 DI 10.1016/0022-1694(95)02970-2 PG 29 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA VK068 UT WOS:A1996VK06800007 ER PT J AU Ahlers, G Liu, FC AF Ahlers, G Liu, FC TI He-4 very near T-lambda heated from above SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article ID SELF-ORGANIZED CRITICALITY; SUPERFLUID TRANSITION; THERMAL-CONDUCTIVITY; VAPOR-PRESSURE; TRANSPORT; TEMPERATURE; DEPRESSION; BARS AB We discuss the feasibility and likely results of measurements of the thermal conductivity lambda(Q, t) of He-4 very near T-lambda = T-lambda(Q = 0) as a function of the heat current Q and the reduced temperature t = [T - T-lambda]/T-lambda by heating a sample from above and cooling it from below. Although the expansion coefficient is negative, the experiment should be possible without inducing convection in the Hel layer provided the sample length does not significantly exceed one cm. For t less than or similar to 10(-7)(Q greater than or similar to 0.2 erg/s cm(2)), a state of self-organized criticality can be attained. For these conditions, ther thermal gradient cancels the gradient in T-lambda induced by gravity, thus permitting measurements extremely close to the transition even in a Earthbound laboratory. However, the data will be only for a unique path in the Q - t plane. For 0.2 less than or similar to Q less than or similar to 0.5 erg/s cm(2) (10(-7) greater than or similar to t greater than or similar to(-8)) they will be in the range of linear response and give lambda(0, t); for Q between about 0.5 and 10 erg/s cm(2) can over a temperature range of about 20 nK, the experimental path samples the regime where the conductivity is expected to be influenced by nonlinear finite-current effects. The small currents and narrow temperature range of the experiment imply that ultra-high resolution thermometry as well as very careful control of stray heat currents will be required. For Q greater than or similar to 10 erg/s cm(2) and up to very large Q, the method can be used to determine the onset temperature T-c(Q) of thermal resistance. C1 UNIV CALIF SANTA BARBARA,CTR NONLINEAR SCI,SANTA BARBARA,CA 93106. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Ahlers, G (reprint author), UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106, USA. NR 24 TC 13 Z9 13 U1 0 U2 2 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD OCT PY 1996 VL 105 IS 1-2 BP 255 EP 266 DI 10.1007/BF00754636 PG 12 WC Physics, Applied; Physics, Condensed Matter SC Physics GA VU214 UT WOS:A1996VU21400012 ER PT J AU Wickramasekera, I Pope, AT Kolm, P AF Wickramasekera, I Pope, AT Kolm, P TI On the interaction of hypnotizability and negative affect in chronic pain - Implications for the somatization of trauma SO JOURNAL OF NERVOUS AND MENTAL DISEASE LA English DT Article ID POSTTRAUMATIC STRESS DISORDER; THREAT PERCEPTION; HYPNOTIC ABILITY; PHOBIC BEHAVIOR; DISSOCIATION; AUTOMATICITY; ABSORPTION; EXPERIENCE; AMYGDALA; IMAGERY AB The high risk model of threat perception predicts that high hypnotizability is a risk factor for trauma-related somatization. It is hypothesized that high hypnotizability can increase experimentally induced threat or negative affect, as measured by skin conductance level, in a linear or dose-response manner. This hypothesized interaction of hypnotic ability and negative affect was found in a consecutive series of 118 adult patients with chronic pain symptoms. Larger increases in skin conductance levels during cognitive threat were significantly related to higher levels of hypnotizability. In addition, individuals with high hypnotizability retained higher skin conductance levels than individuals with low hypnotizability after stress. The clinical implications of the interaction of hypnotizability and negative affect during threat perception and delayed recovery from threat perception are discussed in terms of cognitive mechanisms in the etiology and therapy of trauma-related dissociative disorders. C1 STANFORD UNIV,SCH MED,STANFORD,CA 94305. SAYBROOK INST,SAN FRANCISCO,CA. NASA,HAMPTON,VA. EASTERN VIRGINIA MED SCH,NORFOLK,VA 23501. NR 64 TC 29 Z9 29 U1 0 U2 5 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0022-3018 J9 J NERV MENT DIS JI J. Nerv. Ment. Dis. PD OCT PY 1996 VL 184 IS 10 BP 628 EP 635 DI 10.1097/00005053-199610000-00008 PG 8 WC Clinical Neurology; Psychiatry SC Neurosciences & Neurology; Psychiatry GA VN957 UT WOS:A1996VN95700008 PM 8917161 ER PT J AU Gamache, RR Lynch, R Brown, LR AF Gamache, RR Lynch, R Brown, LR TI Theoretical calculations of pressure broadening coefficients for H2O perturbed by hydrogen or helium gas SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID ROTATION-VIBRATION LINES; ASYMMETRIC-TOP MOLECULES; WATER-VAPOR LINES; TEMPERATURE-DEPENDENCE; OZONE; SPECTROSCOPY; PARAMETERS; TRANSITION; HALFWIDTHS; MOMENT AB To aid in the reduction of remote-sensing data from the outer planets, collision-broadened halfwidths are calculated for water vapor broadened by H-2 and are estimated for He-broadening. The model used is a fully complex implementation of the Robert and Bonamy formalism with parabolic trajectories and all relevant terms in the interaction potential. Calculations are performed for 386 pure rotational transitions of H2O with J '' = 0 to 14 and Ka '' = 0 to 8. In addition, the temperature dependence of the halfwidth is computed for a temperature range from 200 to 750 K for 33 transitions with J '' = 1 to 10 and Ka '' = 0 to 8. The calculations are compared with known measurements of pure rotational and v(2) lines and good agreement is observed (-2 and -4% difference respectively). Finally, methods for estimating halfwidths for H-2- and He-broadening are presented. Copyright (C) 1996 Elsevier Science Ltd C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Gamache, RR (reprint author), UNIV LOWELL,CTR ATMOSPHER RES,450 AIKEN ST,LOWELL,MA 01854, USA. NR 46 TC 40 Z9 42 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD OCT PY 1996 VL 56 IS 4 BP 471 EP 487 DI 10.1016/0022-4073(96)00098-2 PG 17 WC Optics; Spectroscopy SC Optics; Spectroscopy GA VQ853 UT WOS:A1996VQ85300001 ER PT J AU Yamauchi, GK Signor, DB Watts, ME Hernandez, FJ LeMasurier, P AF Yamauchi, GK Signor, DB Watts, ME Hernandez, FJ LeMasurier, P TI Flight measurements of blade-vortex interaction noise including comparisons with full-scale wind tunnel data SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article AB Acoustic measurements of a Sikorsky S-76C helicopter in flight were compared with acoustic measurements of a full-scale S-76 rotor tested in the 80- by 120-Foot Wind Tunnel at NASA Ames Research Center. The flight measurements were acquired using the NASA Ames YO-3A research aircraft fitted with acoustic instrumentation. Flight and wind tunnel data were compared for three conditions, For the low and moderate advance ratio conditions, the BVI pulse widths of the flight and wind tunnel data were very similar, indicating the conditions were well-matched, Comparisons between the flight and wind tunnel data waveforms for the high advance ratio case (mu approximate to 0.25) were poor, For this condition, the wind tunnel data showed greater blade-to-blade and revolution-to-revolution variability than the flight data. Effects of tip-path-plane angle and advance ratio on the BVI flight data were also analyzed, The flight data showed the BVI peaks increased with increasing tip-path-plane angle until reaching a maximum at an angle which varied with flight condition, Further increases in the tip-path plane angle resulted in BVI peak reduction. Increasing advance ratio increased the magnitude of the BVI noise for the flight conditions tested. C1 SIKORSKY AIRCRAFT,TRUMBULL,CT. RP Yamauchi, GK (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 15 TC 2 Z9 2 U1 0 U2 0 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD OCT PY 1996 VL 41 IS 4 BP 291 EP 301 PG 11 WC Engineering, Aerospace SC Engineering GA VN424 UT WOS:A1996VN42400002 ER PT J AU Lepicovsky, J Bruckner, RJ Smith, FA AF Lepicovsky, J Bruckner, RJ Smith, FA TI Thin-film thermocouples for localized heat transfer measurements SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB This paper describes a proof-of-concept experiment on thin-film thermocouples used for localized heat transfer measurements applicable to experiments in warm turbine testing, Using thin-film thermocouples to measure turbine blade temperatures and heat transfer will noticeably improve the accuracy of the acquired data because the current method of embedded conventional thermocouples introduces large experimental uncertainty, First, we introduce the thin-film sensors and manufacturing procedures. Attention is paid to connections between thin-film thermocouples and lead wires, which have been a source of problems in the past, Then, we discuss the test arrangement and facility used for the heat transfer measurements, Finally, we present the results of bulk and local heat flux measurements, as well as overall heat transfer coefficients obtained from measurements in a narrow passage with an AR of 11.8. Experimental data acquired from thin-film thermocouples and their trends agree very well with data acquired using conventional thermocouples. The results we obtained establish confidence about using thin-film thermocouples for heat transfer measurements in warm turbine testing. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Lepicovsky, J (reprint author), NYMA INC,EXPT FLUID MECH SECT,BROOKPARK,OH 44142, USA. NR 9 TC 1 Z9 1 U1 1 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1996 VL 10 IS 4 BP 607 EP 612 DI 10.2514/3.836 PG 6 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA VN988 UT WOS:A1996VN98800009 ER PT J AU Fore, LB Witte, LC McQuillen, JB AF Fore, LB Witte, LC McQuillen, JB TI Heat transfer to annular gas-liquid mixtures at reduced gravity SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID FLOW AB A series of fluid flow and heat transfer experiments was conducted for annular gas-liquid mixtures at reduced gravity aboard NASA's KC-135 aircraft, Air and two liquids, water and 50% aqueous glycerine, were used to produce a range of liquid Reynolds numbers from 1.4 x 10(2) to 1.4 x 10(4) in a 25.4-mm-i.d. tube. Pressure drop measurements compare reasonably well with the Lockhart and Martinelli and Wallis correlations, Film thickness measurements compare reasonably well with correlations derived from ground-based vertical annular flow data, The asymptotic Nusselt numbers for 50% glycerine compare well with a turbulent flat-film model, whereas the model overpredicts the water data, For both fluids at higher Reynolds numbers, the asymptotic Nusselt numbers follow a common dependence on Reynolds and Prandtl numbers, Nu = ARe(n)Pr(1/3). C1 UNIV HOUSTON,DEPT MECH ENGN,HOUSTON,TX 77204. UNIV HOUSTON,DEPT CHEM ENGN,HOUSTON,TX 77204. NASA,LEWIS RES CTR,SPACE EXPT DIV,CLEVELAND,OH 44135. NR 25 TC 5 Z9 5 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1996 VL 10 IS 4 BP 633 EP 639 DI 10.2514/3.840 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA VN988 UT WOS:A1996VN98800013 ER PT J AU Lee, S Salamon, NJ Sullivan, RM AF Lee, S Salamon, NJ Sullivan, RM TI Finite element analysis of poroelastic composites undergoing thermal and gas diffusion SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID THERMOCHEMICAL DECOMPOSITION; POLYMERIC MATERIALS AB A theory for time-dependent thermal and gas diffusion in mechanically time-rate-independent anisotropic poroelastic composites has been developed. This theory advances previous work by fits latter two authors by providing for critical transverse shear through a three-dimensional axisymmetric formulation and using it in a new hypothesis for determining the Biot fluid pressure-solid stress coupling factor. The derived governing equations couple material deformation with temperature and internal pore pressure and more strongly couple gas diffusion and heat transfer than the previous theory. Hence, the theory accounts for the interactions between conductive heat transfer in the porous body and convective heat carried by the mass flux through the pores. The Bubnov Galerkin finite element method is applied to the governing equations to transform them into a semidiscrete finite element system. A numerical procedure is developed to solve the coupled equations in the space and time domains. The method is used to simulate two high-temperature tests involving thermal-chemical :decomposition of carbon-phenolic composites. Compared to measured data, the results are accurate. Moreover, unlike previous work, for a single set of poroelastic parameters they are consistent with two measurements in a restrained thermal growth test. C1 PENN STATE UNIV, DEPT ENGN SCI & MECH, UNIVERSITY PK, PA 16802 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, STRUCT & DYNAM LAB, HUNTSVILLE, AL 35812 USA. RP Lee, S (reprint author), KYONGGI UNIV, DEPT MECH ENGN, SUWON 440760, SOUTH KOREA. NR 16 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1996 VL 10 IS 4 BP 672 EP 680 DI 10.2514/3.844 PG 9 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA VN988 UT WOS:A1996VN98800017 ER PT J AU Siegel, R AF Siegel, R TI Two-blur Green's function analysis for transient spectral radiation in a composite SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID CONDUCTION AB An analysis is developed for obtaining transient temperatures in a two-layer semitransparent composite with spectrally dependent properties. Each external boundary of the composite is subjected to radiation and convection. The two-flux radiative transfer equations are solved by deriving a Green's function. This yields the local radiative heat source needed to numerically solve the transient energy equation. An advantage of the two-flux method is that isotropic scattering Is included without added complexity. The layer refractive indices are larger than one. This produces internal reflections at the boundaries and the internal interface; the reflections are assumed diffuse. Spectral results using the Green's function method are verified by comparing with numerical solutions using the exact radiative transfer equations. Transient temperature distributions are given to illustrate the effect of radiative heating on one side of a composite with external convective cooling. The protection of a material from incident radiation is illustrated by adding scattering to the layer adjacent to the radiative source. RP Siegel, R (reprint author), NASA,LEWIS RES CTR,RES ACAD,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 17 TC 16 Z9 16 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1996 VL 10 IS 4 BP 681 EP 688 DI 10.2514/3.845 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA VN988 UT WOS:A1996VN98800018 ER PT J AU Stallcop, JR Partridge, H Levin, E AF Stallcop, JR Partridge, H Levin, E TI Analytical fits for the determination of the transport properties of air SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID COLLISION INTEGRALS; CROSS-SECTIONS C1 NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035. RP Stallcop, JR (reprint author), NASA,AMES RES CTR,COMPUTAT CHEM BRANCH,SPACE TECHNOL DIV,MOFFETT FIELD,CA 94035, USA. NR 11 TC 7 Z9 7 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1996 VL 10 IS 4 BP 697 EP 699 DI 10.2514/3.847 PG 3 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA VN988 UT WOS:A1996VN98800020 ER PT J AU Siegel, R AF Siegel, R TI Internal radiation effects in zirconia thermal barrier coatings SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article RP Siegel, R (reprint author), NASA,LEWIS RES CTR,RES ACAD,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 5 TC 16 Z9 19 U1 1 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1996 VL 10 IS 4 BP 707 EP 709 DI 10.2514/3.851 PG 3 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA VN988 UT WOS:A1996VN98800024 ER PT J AU Huber, FW Johnson, PD Sharma, OP Staubach, JB Gaddis, SW AF Huber, FW Johnson, PD Sharma, OP Staubach, JB Gaddis, SW TI Performance improvement through indexing of turbine airfoils .1. Experimental investigation SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 40th International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 05-08, 1995 CL HOUSTON, TX AB This paper describes the results of a study to determine the performance improvements achievable by circumferentially indexing successive rows of turbine stator airfoils. An experimental/analytical investigation has been completed that indicates significant stage efficiency increases can be attained through application of this airfoil clocking concept. A series of tests was conducted at the National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) to experimentally investigate stator wake clocking effects on the performance of the Space Shuttle Main Engine Alternate Fuel Turbopump Turbine Test Article. Extensive time-accurate Computational Fluid Dynamics (CFD) simulations have been completed for the test configurations. The CFD results provide insight into the performance improvement mechanism. Part one of this paper describes details of the test facility, rig geometry, instrumentation, and aerodynamic operating parameters. Results of turbine testing at the aerodynamic design point are presented for six circumferential positions of the first stage stator, along with a description of the initial CFD analyses performed for the test article. It should be noted that first vane positions 1 and 6 produced identical first to second vane indexing. Results obtained from off-design testing of the ''best'' and ''worst'' stator clocking positions, and testing over a range of Reynolds numbers are also presented. Part two of this paper describes the numerical simulations performed in support of the experimental test program described in part one. Time-accurate Navier-Stokes flow analyses have been completed for the five different turbine stator positions tested. Details of the computational procedure and results are presented. Analysis results include predictions of instantaneous and time-average midspan airfoil and turbine performance, as well as gas conditions throughout the flow field. An initial understanding of the turbine performance improvement mechanism is described. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. PRATT & WHITNEY,TECH,E HARTFORD,CT 06108. RP Huber, FW (reprint author), PRATT & WHITNEY AIRCRAFT,TECH,W PALM BEACH,FL 33410, USA. NR 7 TC 41 Z9 41 U1 0 U2 3 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1996 VL 118 IS 4 BP 630 EP 635 PG 6 WC Engineering, Mechanical SC Engineering GA VP982 UT WOS:A1996VP98200003 ER PT J AU Griffin, LW Huber, FW Sharma, OP AF Griffin, LW Huber, FW Sharma, OP TI Performance improvement through indexing of turbine airfoils .2. Numerical simulation SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 40th International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 05-08, 1995 CL HOUSTON, TX AB An experimental/analytical study has been conducted to determine the performance improvements achievable by circumferentially indexing succeeding rows of turbine stator airfoils. A series of tests was conducted to experimentally investigate stator wake clocking effects on the performance of the space shuttle main engine (SSME) alternate turbopump development (ATD) fuel turbine test article (TTA). The results from this study indicate that significant increases in stage efficiency can be attained through application of this airfoil clocking concept. Details of the experiment and its results are documented in part 1 of this paper. In order to gain insight into the mechanisms of the performance improvement, extensive computational fluid dynamics (CFD) simulations were executed. The subject of the present paper is the initial results from the CFD investigation of the configurations nad conditions detailed in part 1 of the paper. To characterize the aerodynamic environments in the experimental test series, two-dimensional, time-accurate, multistage, viscous analyses wee performed at the TTA midspan. Computational analyses for five different circumferential positions of the first stage stator have been completed. Details of the computational procedure and the results are presented. The analytical results verify the experimentally demonstrated performance improvement and are compared with data whenever possible. Predictions of time-average turbine efficiencies as well as gas conditions throughout the flow field are presented. An initial understanding of the turbine performance improvement mechanism based on the results from this investigation is described. C1 PRATT & WHITNEY,E HARTFORD,CT 06108. PRATT & WHITNEY AIRCRAFT,TECH,W PALM BEACH,FL. RP Griffin, LW (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,MARSHALL SPACE FLIGHT CTR,AL 35812, USA. NR 12 TC 25 Z9 25 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1996 VL 118 IS 4 BP 636 EP 642 PG 7 WC Engineering, Mechanical SC Engineering GA VP982 UT WOS:A1996VP98200004 ER PT J AU vandeWall, AG Kadambi, JR Boyle, RJ Adamczyk, JJ AF vandeWall, AG Kadambi, JR Boyle, RJ Adamczyk, JJ TI The transport of vortices through a turbine cascade SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 40th International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 05-08, 1995 CL HOUSTON, TX ID VORTEX BREAKDOWN; SECONDARY FLOWS AB An experiment was conducted to determine how incident vortices created by upstream blade rows interacted with a downstream turbine cascade. Specifically, the kinematics of the vortex transport through turbine blade passages was investigated. A stationary water table and a flow visualization system using the pH indicator Bromothymol Blue was used to visualize the vortices generated by vortex generators placed upstream of a turbine blade cascade. Two test series were conducted. In the first test series, stationary vortex generators were positioned at various locations along the turbine blade pitch to observe how a steady incident streamwise vortex was transported through the turbine cascade. Observations showed an unsteady vortex response of the streamwise vortex when the incident vortex was located at the stagnation area of the blade. In the second test series, the vortex generators were moved to simulate the relative motion of an upstream blade row. In these tests, the unsteady vortex response was no longer seen at the stagnation region but was instead located a the suction side of the blade. In addition, the breakdown of the vortex varied greatly with the reduced frequency of the incident vorticity and showed an ''explosive'' type vortex breakdown that occurred at reduced frequencies greater than 8. The dissimilar behavior between the stationary and moving incident vortices indicates that losses and leading edge heat transfer could differ to some degree when determined from a stationary test as opposed to a full-stage simulation. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP vandeWall, AG (reprint author), CASE WESTERN RESERVE UNIV,DEPT MECH & AEROSP ENGN,CLEVELAND,OH 44106, USA. NR 17 TC 2 Z9 2 U1 0 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1996 VL 118 IS 4 BP 654 EP 662 PG 9 WC Engineering, Mechanical SC Engineering GA VP982 UT WOS:A1996VP98200006 ER PT J AU Dorney, DJ Schwab, JR AF Dorney, DJ Schwab, JR TI Unsteady numerical simulations of radial temperature profile redistribution in a single-stage turbine SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 40th International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 05-08, 1995 CL HOUSTON, TX AB Experimental data taken front gas turbine combustors indicate that the flow exiting the combustor can contain both circumferential and radial temperature gradients. A significant amount of research recently has been devoted to studying turbine flows with inlet temperature gradients, but no total pressure gradients. Less attention has been given to flows containing both temperature and total pressure gradients at the inlet. The significance of the total pressure gradients is that the secondary flows and the temperature redistribution process in the vane blade row can be significantly altered Experimental data previously obtained in a single-stage turbine with inlet total temperature and total pressure gradients indicated a redistribution of the warmer fluid to the pressure surface of the airfoils, and a severe underturning of the flow at the exit of the stage. In a concurrent numerical simulation, a steady, inviscid three-dimensional flow analysis was able to capture the redistribution process, but not the exit flow angle distribution. In the current research program, a series of unsteady two- and three-dimensional Navier-Stokes simulations have been performed to study the redistribution of the radial temperature profile in the turbine stage. The three-dimensional analysis predicts both the temperature redistribution and the flow underturning observed in the experiments. C1 NASA,LEWIS RES CTR,TURBOMACHINERY FLOW PHYS BRANCH,CLEVELAND,OH 44135. RP Dorney, DJ (reprint author), WESTERN MICHIGAN UNIV,DEPT MECH & AERONAUT ENGN,KALAMAZOO,MI 49008, USA. NR 22 TC 14 Z9 14 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1996 VL 118 IS 4 BP 783 EP 791 PG 9 WC Engineering, Mechanical SC Engineering GA VP982 UT WOS:A1996VP98200019 ER PT J AU Baumeister, KJ Kreider, KL AF Baumeister, KJ Kreider, KL TI Finite difference time marching in the frequency domain: A parabolic formulation for the convective wave equation SO JOURNAL OF VIBRATION AND ACOUSTICS-TRANSACTIONS OF THE ASME LA English DT Article AB An explicit finite difference iteration scheme is developed to study harmonic sound propagation in ducts. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow. RP Baumeister, KJ (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 17 TC 2 Z9 2 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 1048-9002 J9 J VIB ACOUST JI J. Vib. Acoust.-Trans. ASME PD OCT PY 1996 VL 118 IS 4 BP 622 EP 629 DI 10.1115/1.2888344 PG 8 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA VU989 UT WOS:A1996VU98900013 ER PT J AU Saddoughi, SG Veeravalli, SV AF Saddoughi, SG Veeravalli, SV TI Hot-wire anemometry behaviour at very high frequencies SO MEASUREMENT SCIENCE AND TECHNOLOGY LA English DT Article AB It is shown that most of the present-day hot-wire anemometers have a limitation at high frequencies: namely that the tail of the power spectrum of the anemometer output signal has a spurious rise with frequency. This rise, which is proportional to the square of frequency (f(2)), is of great concern when one deals with small-scale measurements in high-Reynolds-number flows. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP STANFORD UNIV, CTR TURBULENCE RES, BLDG 500, STANFORD, CA 94305 USA. NR 2 TC 22 Z9 22 U1 1 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0957-0233 EI 1361-6501 J9 MEAS SCI TECHNOL JI Meas. Sci. Technol. PD OCT PY 1996 VL 7 IS 10 BP 1297 EP 1300 DI 10.1088/0957-0233/7/10/002 PG 4 WC Engineering, Multidisciplinary; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VM780 UT WOS:A1996VM78000002 ER PT J AU Baldwin, KM White, TP Arnaud, SB Edgerton, VR Kraemer, WJ Kram, R RaabCullen, D Snow, CM AF Baldwin, KM White, TP Arnaud, SB Edgerton, VR Kraemer, WJ Kram, R RaabCullen, D Snow, CM TI Musculoskeletal adaptations to weightlessness and development of effective countermeasures SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article DE skeletal muscle atrophy; localized bone loss; human; rat; resistance training; exercise; muscle ID EXERCISE; SPACEFLIGHT; DENSITY; GROWTH; MASS; MEN AB A Research Roundtable, organized by the American College of Sports Medicine with sponsorship from the National Aeronautics and Space Administration, met in November 1995 to define research strategies for effective exercise countermeasures to weightlessness. Exercise was considered both independently of and in conjunction with, other therapeutic modalities (e.g., pharmacological, nutritional, hormonal, and growth-related factors) that could prevent or minimize the structural and functional deficits involving skeletal muscle and bone in response to chronic exposure to weightlessness, as well as return to Earth baseline function if a degree of loss is inevitable. Musculoskeletal deficits and countermeasures are described with respect to: 1) muscle and connective tissue atrophy and localized bone loss, 2) reductions in motor performance, 3) potential proneness to injury of hard and soft tissues, and 4) probable interaction between muscle atrophy and cardiovascular alterations that contribute to the postural hypotension observed immediately upon return from space flight. In spite of a variety of countermeasure protocols utilized previously involving largely endurance types of exercise, there is presently no activity-specific countermeasure(s) that adequately prevent or reduce musculoskeletal deficiencies. It seems apparent that countermeasure exercises that have a greater resistance element, as compared to endurance activities, may prove beneficial to the musculoskeletal system. Many questions remain for scientific investigation to identify efficacious countermeasure protocols, which will be imperative with the emerging era of long-term space flight. C1 OREGON STATE UNIV,COLL HLTH & HUMAN PERFORMANCE,OFF DEAN,CORVALLIS,OR 97331. UNIV CALIF IRVINE,DEPT PHYSIOL & BIOPHYS,IRVINE,CA 92717. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV CALIF LOS ANGELES,DEPT PHYSIOL SCI,LOS ANGELES,CA 90024. PENN STATE UNIV,CTR SPORTS MED,UNIVERSITY PK,PA 16802. UNIV CALIF BERKELEY,DEPT HUMAN BIODYNAM,BERKELEY,CA 94720. CREIGHTON UNIV,DEPT MED,OMAHA,NE 68178. OREGON STATE UNIV,DEPT EXERCISE & SPORT SCI,CORVALLIS,OR 97331. NR 26 TC 74 Z9 74 U1 1 U2 5 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD OCT PY 1996 VL 28 IS 10 BP 1247 EP 1253 DI 10.1097/00005768-199610000-00007 PG 7 WC Sport Sciences SC Sport Sciences GA VM734 UT WOS:A1996VM73400007 PM 8897381 ER PT J AU Alfrey, CP Udden, MM Huntoon, CL Driscoll, T AF Alfrey, CP Udden, MM Huntoon, CL Driscoll, T TI Destruction of newly released red blood cells in space flight SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article; Proceedings Paper CT International Workshop on Cardiovascular Research in Space CY SEP 12-14, 1995 CL DALLAS, TX SP Int Space Life Sci Strateg Planning Working Grp, NASA, Univ Texas SW Med Ctr, Univ Space Res Assoc, Div Space Life Sci ID ERYTHROPOIETIN AB Space flight results in a rapid change in total blood volume, plasma volume, and red blood cell mass because the space to contain blood is decreased. The plasma volume and total blood volume de creases during the first hours in space and remain at a decreased level for the remainder of the flight. During the first several hours following return to earth, plasma volume and total blood volume increase to preflight levels. During the first few days in space recently produced red blood cells disappear from the blood resulting in a decrease in red blood cell mass of 10-15%. Red cells 12 d old or older survive normally and production of new cells continues at near preflight levels. After the first few days in space, the red cell mass is stable at the decreased level. Following return to earth the hemoglobin and red blood cell mass concentrations decrease reflecting the increase in plasma volume. The erythropoietin levels increase responding to ''postflight anemia''; red cell production increases, and the red cell mass is restored to preflight levels after several weeks. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Alfrey, CP (reprint author), BAYLOR COLL MED,1 BAYLOR PLAZA,HOUSTON,TX 77030, USA. NR 12 TC 32 Z9 33 U1 0 U2 1 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD OCT PY 1996 VL 28 IS 10 SU S BP S42 EP S44 PG 3 WC Sport Sciences SC Sport Sciences GA VN545 UT WOS:A1996VN54500010 PM 8897403 ER PT J AU Frey, MAB AF Frey, MAB TI Space research activities during missions of the past SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article; Proceedings Paper CT International Workshop on Cardiovascular Research in Space CY SEP 12-14, 1995 CL DALLAS, TX SP Int Space Life Sci Strateg Planning Working Grp, NASA, Univ Texas SW Med Ctr, Univ Space Res Assoc, Div Space Life Sci DE weightless environment; spacelab missions; responses to exercise ID SPACEFLIGHT AB For over 30 yr, men and women have lived for various periods of time in a weightless (or free-fall) environment while orbiting the Earth. During these years, we have learned that humans function quite well for short periods of weightlessness, that is, for up to a little more than a year. Some space flight missions have provided physiologic data, including cardiovascular data, from the spacefarers. In fact, some missions have provided laboratories for systematic study of cardiovascular responses and adaptation to space flight. However, the opportunity to obtain physiologic data from people in space is a rarity. It is important to remember that the population sample sizes are small, other stresses may confound the effects of weightlessness, and in some situations the crewmembers are subjects for several experiments at the same time. Furthermore, comparison of cardiovascular data from space flight to data obtained on the ground is sometimes difficult because the subject's posture on the ground is not always reported; in a gravity environment, posture influences the hydrostatic gradient. This overview describes what we have learned about cardiovascular functions during flight and after return to Earth. RP Frey, MAB (reprint author), NASA,DIV LIFE SCI,CODE UL,300 E ST SW,WASHINGTON,DC 20546, USA. NR 28 TC 9 Z9 10 U1 0 U2 0 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD OCT PY 1996 VL 28 IS 10 SU S BP S3 EP S8 PG 6 WC Sport Sciences SC Sport Sciences GA VN545 UT WOS:A1996VN54500002 PM 8897395 ER PT J AU Hargens, AR Alfrey Edgerton Green Stegemann Norsk Blomqvist Gerzer Rutishauser Baldwin AF Hargens, AR Alfrey Edgerton Green Stegemann Norsk Blomqvist Gerzer Rutishauser Baldwin TI Critical discussion of research issues in body fluid metabolism and control of intravascular volume SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Editorial Material RP Hargens, AR (reprint author), NASA,AMES RES CTR,DIV LIFE SCI,MOFFETT FIELD,CA 94035, USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD OCT PY 1996 VL 28 IS 10 SU S BP S56 EP S59 PG 4 WC Sport Sciences SC Sport Sciences GA VN545 UT WOS:A1996VN54500013 PM 8897406 ER PT J AU White, RJ AF White, RJ TI International Workshop on Cardiovascular Research in Space - Dallas, Texas, September 12-14, 1995 - Workshop purpose and structure - September 12, 1995 - Introduction SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Editorial Material C1 NASA,BIOMED SCI & APPL DIV,WASHINGTON,DC 20546. RP White, RJ (reprint author), NASA,UL LIFE,WASHINGTON,DC 20546, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD OCT PY 1996 VL 28 IS 10 SU S BP S1 EP S2 PG 2 WC Sport Sciences SC Sport Sciences GA VN545 UT WOS:A1996VN54500001 PM 11536776 ER PT J AU Whittenberger, JD Noebe, RD Garg, A AF Whittenberger, JD Noebe, RD Garg, A TI Elevated temperature compressive properties of N-doped NiAl SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID PLASTIC-FLOW PROPERTIES; GRAIN-SIZE; CREEP AB The elevated temperature properties of NiAl slightly enriched with similar to 900 appm nitrogen by atomizing the aluminide to powder under a nitrogen atmosphere have been determined. Compression samples were machined from hot extruded material and tested in air between 1100 and 1400 K under both constant velocity and constant load conditions. It appears that N in solid solution contributes little to the creep strength of B2 nickel aluminide. Excess nitrogen leading to the formation of AlN and Al(O,N) particles, however, can have a pronounced effect on creep behavior. These fine second-phase particles stabilize a small grain structure which, in turn, can improve or reduce the mechanical strength, depending on the deformation conditions. Under certain test conditions, high-angle grain boundaries can break away from the particles and overall grain growth occurs, leaving behind a network of AlN and Al(O,N) particles. This network of particles is very effective in anchoring a small, stable subgrain structure that provides elevated temperature strength without being subject to undesirable, weakening grain-boundary deformation mechanisms. Overall, the results provide further evidence that creep in NiAl is dislocation-climb controlled which involves subgrain formation and that stabilization of subgrains will improve mechanical strength in the manner proposed by Sherby et al. RP Whittenberger, JD (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 24 TC 5 Z9 6 U1 1 U2 2 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD OCT PY 1996 VL 27 IS 10 BP 3170 EP 3180 DI 10.1007/BF02663867 PG 11 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA VM042 UT WOS:A1996VM04200033 ER PT J AU Lee, KN Arya, VK Halford, GR Barrett, CA AF Lee, KN Arya, VK Halford, GR Barrett, CA TI Kinetics of cyclic oxidation and cracking and finite element analysis of MA956 and Sapphire/MA956 composite system SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID CERAMIC-MATRIX COMPOSITES; ALLOYS; INTERFACE; FAILURE AB Sapphire fiber-reinforced MA956 composites hold promise for significant weight savings and increased high-temperature structural capability, as compared to unreinforced MA956. As part of an overall assessment of the high-temperature characteristics of this material system, cyclic oxidation behavior was studied at 1093 degrees C and 1204 degrees C. Initially, both sets of coupons exhibited parabolic oxidation kinetics. Later, monolithic MA956 exhibited spallation and a linear weight loss, whereas the composite showed a linear weight gain without spallation. Weight loss of the monolithic MA956 resulted from the linking of a multiplicity of randomly oriented and closely spaced surface cracks that facilitated ready spallation. By contrast, cracking of the composite's oxide layer was nonintersecting and aligned nominally parallel with the orientation of the subsurface reinforcing fibers. Oxidative lifetime of monolithic MA956 was projected from the observed oxidation kinetics. Linear elastic, finite element continuum, and micromechanics analyses were performed on coupons of the monolithic and composite materials. Results of the analyses qualitatively agreed well with the observed oxide cracking and spallation behavior of both the MA956 and the Sapphire/MA956 composite coupons. C1 UNIV AKRON,NASA,LEWIS RES CTR,AKRON,OH 44325. RP Lee, KN (reprint author), CLEVELAND STATE UNIV,NASA,LEWIS RES CTR,CLEVELAND,OH 44115, USA. NR 21 TC 3 Z9 3 U1 0 U2 2 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD OCT PY 1996 VL 27 IS 10 BP 3279 EP 3291 DI 10.1007/BF02663878 PG 13 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA VM042 UT WOS:A1996VM04200044 ER PT J AU Javadi, HHS AF Javadi, HHS TI Composite material behavior under applied electric field: Material switches to a high-resistive state SO MICROELECTRONICS AND RELIABILITY LA English DT Article AB Current-voltage characteristics of the electrically conductive silver-filled epoxy Ablefilm ECF-563 preform switches to a high-resistive state under low bias voltage. The observed phenomena is argued to be an intrinsic property of electrically conducting composite materials caused by strong localized centers that introduce space charge. Copyright (C) 1996 Elsevier Science Ltd RP Javadi, HHS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 17 TC 0 Z9 0 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0026-2714 J9 MICROELECTRON RELIAB JI Microelectron. Reliab. PD OCT PY 1996 VL 36 IS 10 BP 1499 EP 1513 DI 10.1016/0026-2714(95)00208-1 PG 15 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA VD934 UT WOS:A1996VD93400018 ER PT J AU Iwasawa, K Fabian, AC Reynolds, CS Nandra, K Otani, C Inoue, H Hayashida, G Brandt, WN Dotani, T Kunieda, H Matsuoka, M Tanaka, Y AF Iwasawa, K Fabian, AC Reynolds, CS Nandra, K Otani, C Inoue, H Hayashida, G Brandt, WN Dotani, T Kunieda, H Matsuoka, M Tanaka, Y TI The variable iron K emission line in MCG-6-30-15 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; line, profiles; galaxies, individual, MCG-6-30-15; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY REFLECTION; GALAXY MCG-6-30-15; COLD MATTER; BLACK-HOLE; SEYFERT-1 GALAXIES; VARIABILITY; DISK; PROFILES; NGC-4151 AB We report on the variability of the iron K emission line in the Seyfert 1 galaxy MCG-6-30-15 during a four-day ASCA observation. The line consists of a narrow core at an energy of about 6.4 keV, and a broad red wing extending to below 5 keV, which are interpreted as line emission arising from the inner parts of an accretion disc. The narrow core correlates well with the continuum flux whereas the broad wing weakly anticorrelates. When the source is brightest, the line is dominated by the narrow core, whilst, during a deep minimum, the narrow core is very weak and a huge red tail appears. However, at other times when the continuum shows rather rapid changes, the broad wing is more variable than the narrow core, and shows evidence for correlated changes contrary to its long-time-scale behaviour. The peculiar line profile during the deep minimum spectrum suggests that the line-emitting region is very close to a central spinning (Kerr) black hole where enormous gravitational effects operate. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RIKEN,INST PHYS & CHEM RES,WAKO,SAITAMA 35101,JAPAN. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. OSAKA UNIV,DEPT EARTH & SPACE SCI,TOYONAKA,OSAKA 560,JAPAN. NAGOYA UNIV,DEPT ASTROPHYS,NAGOYA,AICHI 46401,JAPAN. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. RP Iwasawa, K (reprint author), INST ASTRON,MADINGLEY RD,CAMBRIDGE CB3 0HA,ENGLAND. RI Brandt, William/N-2844-2015; Otani, Chiko/A-6510-2016 OI Brandt, William/0000-0002-0167-2453; NR 30 TC 257 Z9 259 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD OCT 1 PY 1996 VL 282 IS 3 BP 1038 EP 1048 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VK875 UT WOS:A1996VK87500039 ER PT J AU Srinivasan, J Smith, GL AF Srinivasan, J Smith, GL TI The role of heat fluxes and moist static energy in tropical convergence zones SO MONTHLY WEATHER REVIEW LA English DT Article ID RADIATION BUDGET EXPERIMENT; SEA-SURFACE TEMPERATURE; SEASONAL-VARIATION; CIRCULATION; MODEL; CONVECTION; CLIMATOLOGY; VARIABILITY; OCEANS AB The relationship between monthly mean outgoing longwave radiation (OLR) and the mean moist static energy of the lower troposphere is shown to be similar to the relationship between monthly mean OLR and sea surface temperature over the oceanic regions. The relationship between monthly mean OLR and surface moist static energy shows that the threshold value for the onset of convection is different in continental and oceanic regions. However, the threshold of moist static stability for the troposphere (surface to 400 mb) is the same for oceans and continents. This relationship is consistent with the simple model of the tropical convergence zones proposed by Neelin and Held. The net energy convergence in the troposphere was found to be positive in regions with OLR below 210 W m(-2). This result is consistent with the Neelin and Held hypothesis that the necessary but not sufficient condition for the existence of tropical convergence zone is a positive energy convergence in the troposphere. C1 NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681. INDIAN INST SCI,CTR ATMOSPHER SCI,BANGALORE 560012,KARNATAKA,INDIA. NR 21 TC 12 Z9 12 U1 1 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD OCT PY 1996 VL 124 IS 10 BP 2089 EP 2099 DI 10.1175/1520-0493(1996)124<2089:TROHFA>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VL888 UT WOS:A1996VL88800001 ER PT J AU Ferrier, BS Simpson, J Tao, WK AF Ferrier, BS Simpson, J Tao, WK TI Factors responsible for precipitation efficiencies in midlatitude and tropical squall simulations SO MONTHLY WEATHER REVIEW LA English DT Article ID CUMULUS ENSEMBLE MODEL; VERTICAL WIND SHEAR; BULK ICE SCHEME; NUMERICAL-SIMULATION; CONVECTIVE SYSTEM; BOUNDARY-LAYER; STRATIFORM REGIONS; MOISTURE BUDGETS; DEEP CONVECTION; MOMENTUM FLUX AB Different definitions of storm precipitation efficiency were investigated from numerical simulations of convective systems in widely varying ambient conditions using a two-dimensional cloud model with sophisticated ice microphysics. The model results indicate that the vertical orientation of the updrafts, which is controlled by the vertical wind shear, and the ambient moisture content are important in determining storm efficiency. In terms of rainfall divided by condensation, simulated efficiencies ranged from 20%-35% for convective systems that tilted strongly against the low-level shear (upshear), to 30%-50% for erect storms. Changes in environmental moisture produced smaller Variations in efficiency that were less than 10%. Upright convection allows for effective collection of cloud condensate by precipitation, whereas lower efficiencies in upshear storms are due to greater evaporation of cloud at middle levels and evaporation of rain at lower levels. Development of trailing stratiform precipitation is promoted by the rearward transport of moisture and condensate in upshear-tilted updrafts with evaporation moistening the ambient air as it passes through the convection. The fraction of rainfall from stratiform processes increases with upshear tilt of the convection and is inefficient. Rainfall from convection tilting downshear is efficient in terms of the total condensation, but is inefficient in terms of the flux of vapor into the storm because the gust fronts are too weak to completely block the low-level inflow. Different closure assumptions in cumulus parameterization schemes that use functional relationships for precipitation efficiency were evaluated. None of them showed consistent agreement with the efficiency parameters diagnosed from the simulations. Detailed diagnostics over various temporal and spatial scales indicate that storm efficiency determined by total condensation varied much less than that obtained from moisture convergence. The former definition should be more useful in cumulus parameterizations. Spatial variations in moisture convergence were dominated by changes in net condensation within the area of the storm, while variability at larger scales resulted from the advection of dry air in downdraft wakes. C1 SCI SYST & APPLICAT INC, LANHAM, MD USA. RP NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, MESOSCALE DYNAM & PRECIPITAT BRANCH, CODE 912, GREENBELT, MD 20771 USA. NR 65 TC 82 Z9 86 U1 1 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 EI 1520-0493 J9 MON WEATHER REV JI Mon. Weather Rev. PD OCT PY 1996 VL 124 IS 10 BP 2100 EP 2125 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VL888 UT WOS:A1996VL88800002 ER PT J AU Baram, Y AF Baram, Y TI Classification by balanced binary representation SO NEUROCOMPUTING LA English DT Article DE classification; pattern recognition; balancing; learning capacity ID FLOW AB Classifiers for binary and for real-valued data, consisting of a single internal layer of spherical threshold cells are defined by two fundamental requirements: asymptotic linear separability of the internal representations, which defines the cells' activation threshold, and input-space covering, which defines the minimal number of cells required. Both parameters depend solely on the input dimension. Class assignments are learnt by applying Rosenblatt's learning rule to the internal representations which, by choice of the activation threshold, are balanced, having equally probable bit values, Balancing guarantees that the asymptotic separation capacity of the proposed classifiers is equal to the size of the internal layer. Generalization is achieved when the data points are clustered. The advantage of balancing is demonstrated by application to two 'real-world' problems, one involving binary data and the other real-valued data. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Baram, Y (reprint author), TECHNION ISRAEL INST TECHNOL,DEPT COMP SCI,IL-32000 HAIFA,ISRAEL. NR 21 TC 2 Z9 2 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-2312 J9 NEUROCOMPUTING JI Neurocomputing PD OCT PY 1996 VL 13 IS 2-4 BP 347 EP 357 DI 10.1016/0925-2312(96)00047-1 PG 11 WC Computer Science, Artificial Intelligence SC Computer Science GA VN056 UT WOS:A1996VN05600017 ER PT J AU Stahle, CM Palmer, D Bartlett, LM Parsons, A Shi, ZQ Lisse, CM Sappington, C Cao, N Shu, P Gehrels, N Teegarden, B Birsa, F Singh, S Odom, J Hanchak, C Tueller, J Barthelmy, S Krizmanic, J Barbier, L AF Stahle, CM Palmer, D Bartlett, LM Parsons, A Shi, ZQ Lisse, CM Sappington, C Cao, N Shu, P Gehrels, N Teegarden, B Birsa, F Singh, S Odom, J Hanchak, C Tueller, J Barthelmy, S Krizmanic, J Barbier, L TI CdZnTe detectors for gamma-ray Burst ArcSecond Imaging and Spectroscopy (BASIS) SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray Detectors, Associated Electronics and Applications CY SEP 18-22, 1995 CL GRENOBLE, FRANCE SP CNRS, CEA, European Mat Res Soc, European Synchrotron Radiat Facil, Mairie Grenoble, Sandia Natl Lab, Soc Electriciens & Electroniciens Dauphine Savoie, Conseil Gen Isere, Sci Applicat Int Corp AB A CdZnTe detector array is being developed for the proposed gamma-ray Burst ArcSecond Imaging and Spectroscopy (BASIS) spaceflight mission to accurately locate gamma-ray bursts, determine their distance scale, and measure the physical characteristics of the emission region. Two-dimensional strip detectors with 100 mu m pitch have been fabricated and wire bonded to readout electronics to demonstrate the ability to localize 60 and 122 keV gamma-rays to less than 100 mu m. Radiation damage studies on a CdZnTe detector exposed to MeV neutrons showed a small amount of activation but no detector performance degradation for fluences up to 10(10) neutrons/cm(2). A 1 x 1 in. CdZnTe detector has also been flown on a balloon payload at 115 000 ft in order to measure the CdZnTe background rates. C1 ORBITAL SCI CORP,GREENBELT,MD 20771. UNIV SPACE RES ASSOCIATES,GREENBELT,MD 20771. NAS,NRC,RESIDENT RES ASSOCIATE,GREENBELT,MD 20771. HUGHES STX,GREENBELT,MD 20771. RP Stahle, CM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 7181,GREENBELT,MD 20771, USA. RI Barthelmy, Scott/D-2943-2012; Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012; Parsons, Ann/I-6604-2012; Lisse, Carey/B-7772-2016 OI Lisse, Carey/0000-0002-9548-1526 NR 4 TC 4 Z9 4 U1 2 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 OCT 1 PY 1996 VL 380 IS 1-2 BP 486 EP 489 DI 10.1016/S0168-9002(96)00367-1 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA VW527 UT WOS:A1996VW52700105 ER PT J AU Murphy, CT Carrigan, R Chen, D Jackson, G Mokhov, N Shih, HJ Cox, B Golovatyuk, V McManus, A Bogacz, A Cline, D Ramachandran, S Rhoades, J Rosenzweig, J Newberger, B Ellison, JA Baker, S Sun, CR Gabella, W Tsyganov, E Taratin, A Asseev, A Biryukov, V Khanzadeev, A Prokofieva, T Samsonov, V Solodov, G AF Murphy, CT Carrigan, R Chen, D Jackson, G Mokhov, N Shih, HJ Cox, B Golovatyuk, V McManus, A Bogacz, A Cline, D Ramachandran, S Rhoades, J Rosenzweig, J Newberger, B Ellison, JA Baker, S Sun, CR Gabella, W Tsyganov, E Taratin, A Asseev, A Biryukov, V Khanzadeev, A Prokofieva, T Samsonov, V Solodov, G TI First results from bent crystal extraction at the Fermilab Tevatron SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article AB First results from Fermilab Experiment 853 are presented. E853 is an experiment to test the feasibility and efficiency of extracting a low-intensity beam from the halo of the Tevatron using channeling in a bent silicon crystal. The motivation of the experiment is to apply crystal extraction to trans-TeV accelerators like the LHC. Extensive simulation work has been carried out. Two accelerator operating modes have been developed for crystal studies, ''kick'' mode and diffusion mode. Results from the first successful extraction in kick mode are presented. C1 SUPERCONDUCTING SUPER COLLIDER LAB,DALLAS,TX 75237. UNIV VIRGINIA,CHARLOTTESVILLE,VA. UNIV CALIF LOS ANGELES,LOS ANGELES,CA. UNIV TEXAS,AUSTIN,TX 78712. UNIV NEW MEXICO,ALBUQUERQUE,NM 87131. ARGONNE NATL LAB,ARGONNE,IL 60439. SUNY ALBANY,ALBANY,NY 12222. VANDERBILT UNIV,NASHVILLE,TN. UNIV TEXAS,SW MED CTR,DALLAS,TX 75235. JOINT INST NUCL RES,DUBNA,RUSSIA. SERPUKHOV HIGH ENERGY PHYS INST,SERPUKHOV 142284,RUSSIA. PETERSBURG NUCL PHYS INST,GATCHINA,RUSSIA. RP Murphy, CT (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. RI Biryukov, Valery/C-8432-2017 OI Biryukov, Valery/0000-0002-3591-7762 NR 10 TC 26 Z9 30 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD OCT PY 1996 VL 119 IS 1-2 BP 231 EP 238 DI 10.1016/0168-583X(96)00356-4 PG 8 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA VN993 UT WOS:A1996VN99300031 ER PT J AU Tripathi, RK Cucinotta, FA Wilson, JW AF Tripathi, RK Cucinotta, FA Wilson, JW TI Accurate universal parameterization of absorption cross sections SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article ID HEAVY-ION COLLISIONS; SCATTERING; NUCLEI; DENSITY; TARGETS; MODEL AB We present a simple universal parameterization of total reaction cross sections for any system of colliding nuclei valid for the entire energy range from a few A MeV to a few A GeV. The universal picture presented here treats the proton-nucleus collision as a special case of the nucleus-nucleus collision, where the projectile has charge and mass number one. The parameters are associated with the physics of the collision system. In general terms Coulomb interaction modifies cross sections at lower energies and the effects of Pauli blocking are important at higher energies, The agreement between the calculated and experimental data is better than all earlier published results. C1 HAMPTON UNIV,HAMPTON,VA 23668. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Tripathi, RK (reprint author), SO ILLINOIS UNIV,CARBONDALE,IL 62901, USA. NR 26 TC 79 Z9 79 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD OCT PY 1996 VL 117 IS 4 BP 347 EP 349 DI 10.1016/0168-583X(96)00331-X PG 3 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA VL218 UT WOS:A1996VL21800002 PM 11542649 ER PT J AU Hecht, H Kaiser, MK Banks, MS AF Hecht, H Kaiser, MK Banks, MS TI Gravitational acceleration as a cue for absolute size and distance? SO PERCEPTION & PSYCHOPHYSICS LA English DT Article; Proceedings Paper CT 35th Annual Meeting of the Psychonomic-Society CY NOV, 1994 CL ST LOUIS, MO SP Psychon Soc ID FREE-FALL TRAJECTORIES; VERTICAL DISPARITIES; MONOCULAR CUE; PERCEPTION; GRAVITY; MOTION AB When an object's motion is influenced by gravity, as in the rise and fall of a thrown ball, the vertical component of acceleration is roughly constant at 9.8 m/sec(2). In principle, an observer could use this information to estimate the absolute size and distance of the object (Saxberg, 1987a; Watson, Banks, von Hofsten, & Royden, 1992). In five experiments, we examined people's ability to utilize the size and distance information provided by gravitational acceleration. Observers viewed computer simulations of an object rising and falling on a trajectory aligned with the gravitational vector The simulated objects were balls of different diameters presented across a wide range of simulated distances, Observers were asked to identify the ball that was presented and to estimate its distance, The results showed that observers were much more sensitive to average velocity than to the gravitational acceleration pattern. Likewise, verticality of the motion and visibility of the trajectory's apex had negligible effects on the accuracy of size and distance judgements. C1 UNIV BIELEFELD,D-4800 BIELEFELD,GERMANY. UNIV CALIF BERKELEY,BERKELEY,CA. RP Hecht, H (reprint author), NASA,AMES RES CTR,MAIL STOP 262-2,MOFFETT FIELD,CA 94035, USA. RI Hecht, Heiko/H-3106-2011 NR 21 TC 24 Z9 24 U1 1 U2 1 PU PSYCHONOMIC SOC INC PI AUSTIN PA 1710 FORTVIEW RD, AUSTIN, TX 78704 SN 0031-5117 J9 PERCEPT PSYCHOPHYS JI Percept. Psychophys. PD OCT PY 1996 VL 58 IS 7 BP 1066 EP 1075 DI 10.3758/BF03206833 PG 10 WC Psychology; Psychology, Experimental SC Psychology GA VM323 UT WOS:A1996VM32300009 PM 8920842 ER PT J AU Blaisdell, GA Coleman, GN Mansour, NN AF Blaisdell, GA Coleman, GN Mansour, NN TI Rapid distortion theory for compressible homogeneous turbulence under isotropic mean strain SO PHYSICS OF FLUIDS LA English DT Article AB Isotropic compressible turbulence subjected to rapid isotropic compression is studied using inviscid rapid distortion theory (RDT) and direct numerical simulation. An exact solution to the rapid distortion problem is given. Comparisons are made between the simulation results and the RDT solution, as well as previously studied limiting cases of the RDT solution. The comparisons illustrate the range of applicability of the RDT solutions. Implications for the use of RDT results in modeling compressible turbulent flows are briefly discussed. (C) 1996 American Institute of Physics. C1 UNIV CALIF LOS ANGELES, DEPT AEROSP & MECH ENGN, LOS ANGELES, CA 90024 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP PURDUE UNIV, SCH AERONAUT & ASTRONAUT, W LAFAYETTE, IN 47907 USA. NR 19 TC 13 Z9 13 U1 1 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 1070-6631 EI 1089-7666 J9 PHYS FLUIDS JI Phys. Fluids PD OCT PY 1996 VL 8 IS 10 BP 2692 EP 2705 DI 10.1063/1.869055 PG 14 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA VL144 UT WOS:A1996VL14400014 ER PT J AU Ristorcelli, JR Morrison, JH AF Ristorcelli, JR Morrison, JH TI The Favre-Reynolds average distinction and a consistent gradient transport expression for the dissipation SO PHYSICS OF FLUIDS LA English DT Article ID TURBULENCE AB Two equation and higher order closures for compressible turbulence fail to capture the compressible wall layers' log scaling. Accounting for the distinction between Favre and Reynolds averaged variables in the compressible moment equations indicate that turbulent transport expressions obtained using the ''variable density approximation'' are in error. The error is related to the enstrophy, a Reynolds averaged variable appearing in the equation for the Favre averaged k; recognizing this fact an expression for the transport of dissipation consistent with simple mixing length arguments is obtained. Within the (Limited) context of a gradient transport hypothesis a rational form for the turbulent transport of the dissipation is found. Modestly better agreement with the well established compressible Van Driest log scaling is found in a k-epsilon calculation. C1 ANALYT SERV & MAT INC,HAMPTON,VA 23681. RP Ristorcelli, JR (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681, USA. NR 5 TC 2 Z9 2 U1 1 U2 5 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD OCT PY 1996 VL 8 IS 10 BP 2783 EP 2785 DI 10.1063/1.869063 PG 3 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA VL144 UT WOS:A1996VL14400024 ER PT J AU Barton, CE Baldwin, RT Barraclough, DR Bushati, S Chiappini, M Cohen, Y Coleman, R Hulot, G Kotze, P Golovkov, VP Jackson, A Langel, RA Lowes, FJ McKnight, DJ Macmillan, S Newitt, LR Peddie, NW Quinn, JM Sabaka, TJ AF Barton, CE Baldwin, RT Barraclough, DR Bushati, S Chiappini, M Cohen, Y Coleman, R Hulot, G Kotze, P Golovkov, VP Jackson, A Langel, RA Lowes, FJ McKnight, DJ Macmillan, S Newitt, LR Peddie, NW Quinn, JM Sabaka, TJ TI International Geomagnetic Reference Field, 1995 revision - Presented by IAGA Division V, Working Group 8 SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Letter C1 RUSSIAN ACAD SCI,RUSSIAN GEOPHYS COMM,MOSCOW 117296,RUSSIA. BRITISH GEOL SURVEY,WORLD DATA CTR C1 GEOMAGNETISM,EDINBURGH EH9 3LA,MIDLOTHIAN,SCOTLAND. KYOTO INST TECHNOL,FAC SCI,WORLD DATA CTR C2 GEOMAGNETISM,KYOTO 606,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,WORLD DATA CTR A ROCKETS & SATELLITES,GREENBELT,MD 20771. RP Barton, CE (reprint author), NOAA,NATL GEOPHYS DATA CTR,WORLD DATA CTR A SOLID EARTH GEOPHYS,CODE E-GCI,325 BROADWAY,BOULDER,CO 80303, USA. RI Hulot, Gauthier/A-5627-2011; Sabaka, Terence/D-5618-2012; Cohen, Yves/A-4521-2013 NR 9 TC 12 Z9 12 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-9201 J9 PHYS EARTH PLANET IN JI Phys. Earth Planet. Inter. PD OCT PY 1996 VL 97 IS 1-4 BP 23 EP 26 DI 10.1016/0031-9201(96)03139-1 PG 4 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VP185 UT WOS:A1996VP18500004 ER PT J AU Butler, JN Quarrie, DR AF Butler, JN Quarrie, DR TI Data acquisition and analysis in extremely high data rate experiments SO PHYSICS TODAY LA English DT Article C1 LAWRENCE BERKELEY LAB,BERKELEY,CA. RP Butler, JN (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,COMP DIV,RES STAFF,BATAVIA,IL 60510, USA. NR 7 TC 2 Z9 2 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD OCT PY 1996 VL 49 IS 10 BP 50 EP 56 DI 10.1063/1.881524 PG 7 WC Physics, Multidisciplinary SC Physics GA VK080 UT WOS:A1996VK08000013 ER PT J AU Mather, JC AF Mather, JC TI The John Scott Award: What really happened SO PHYSICS TODAY LA English DT Letter RP Mather, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD OCT PY 1996 VL 49 IS 10 BP 97 EP 97 DI 10.1063/1.2807823 PG 1 WC Physics, Multidisciplinary SC Physics GA VK080 UT WOS:A1996VK08000021 ER PT J AU Williams, JG Newhall, XX Dickey, JO AF Williams, JG Newhall, XX Dickey, JO TI Lunar moments, tides, orientation, and coordinate frames SO PLANETARY AND SPACE SCIENCE LA English DT Article ID MOON AB To determine the lunar moments of inertia (A < B < C) it is necessary to determine three quantities. (C - A)/B and (B - A)/C come from Lunar Laser Ranging (LLR) measurements of the lunar orientation. Spacecraft or lunar orbit perturbations provide J(2). Combining five reported J(2) results gives a normalized polar moment of inertia C/MR(2) = 0.3929 +/- 0.0009. Solid-body tides displace the surface about 0.1 m, but can perturb the orbit of a Moon-orbiting spacecraft. The selenocentric coordinates of four lunar retro-reflectors are accurately known and can serve as reference points. The orientation and orbit of the Moon are very well known for the time span of the LLR data. Copyright (C) 1996 Published by Elsevier Science Ltd RP Williams, JG (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 11 TC 25 Z9 32 U1 1 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD OCT PY 1996 VL 44 IS 10 BP 1077 EP 1080 DI 10.1016/0032-0633(95)00154-9 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VY599 UT WOS:A1996VY59900002 ER PT J AU Oberst, J Roatsch, T Zhang, W Cook, AC Jaumann, R Duxbury, T Wewel, F Uebbing, R Scholten, F Albertz, J AF Oberst, J Roatsch, T Zhang, W Cook, AC Jaumann, R Duxbury, T Wewel, F Uebbing, R Scholten, F Albertz, J TI Photogrammetric analysis of Clementine multi-look angle images obtained near Mare Orientale SO PLANETARY AND SPACE SCIENCE LA English DT Article AB A local control point network and a DTM (Digital Terrain Model) are derived from Clementine UVVIS multi-look angle images that were obtained on April 30, 1994, covering a small region of the Lunar Orientale Basin (19.5 degrees S to 15 degrees S adn 84.5 degrees W to 86.0 degrees W). The nominal camera pointing and spacecraft trajectory data were photogrammetrically adjusted, a procedure which was found to improve estimates of the coordinates of 41 control points significantly to an internally consistent accuracy of 30 m in the horizontal and 50 m in the height direction. The terrain model correlates well with features identified in the image data, two craters, volcanic constructs, and the dark lava-filled Lacus Veris, located in a topographic depression. The terrain model indicates a steep 2000 m drop in elevation within a range of only 6-8 km towards the center of Orientale. Further studies of the lunar topography in this particular region using Clementine stereo data seem well warranted and feasible. Copyright (C) 1996 Elsevier Science Ltd C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. TECH UNIV BERLIN, DEPT PHOTOGRAMMETRY & CARTOG, D-10623 BERLIN, GERMANY. RP DLR, INST PLANETARY EXPLORAT, RUDOWER CHAUSSEE 5, D-12489 BERLIN, GERMANY. NR 25 TC 12 Z9 13 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 OCT PY 1996 VL 44 IS 10 BP 1123 EP 1133 DI 10.1016/S0032-0633(96)00060-8 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VY599 UT WOS:A1996VY59900005 ER PT J AU Cook, AC Oberst, J Roatsch, T Jaumann, R Acton, C AF Cook, AC Oberst, J Roatsch, T Jaumann, R Acton, C TI Clementine imagery: Selenographic coverage for cartographic and scientific use SO PLANETARY AND SPACE SCIENCE LA English DT Article ID MOON; MISSION AB An investigation is made into the potential use of Clementine imagery for cartographic and scientific studies. A computer search was performed using almost 2 million Clementine image records held on a database at DLR. From this it has been possible to construct maps that illustrate the lunar coverage and height precision of Clementine stereo imagery for stereo mapping. In addition it has been possible to investigate the minimum ground pixel size of multispectral imagery as a function of latitude, and to identify regions where multiple phase angle, and near zero phase angle imagery were obtained. Copyright (C) 1996 Elsevier Science Ltd C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Cook, AC (reprint author), GERMAN AEROSP RES ESTAB,DLR,INST PLANETARY EXPLORAT,RUDOWER CHAUSSEE 5,D-12489 BERLIN,GERMANY. NR 14 TC 14 Z9 15 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD OCT PY 1996 VL 44 IS 10 BP 1135 EP 1148 DI 10.1016/S0032-0633(96)00061-X PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VY599 UT WOS:A1996VY59900006 ER PT J AU Crenshaw, DM Bruegman, OW Johnson, R Fitzurka, M AF Crenshaw, DM Bruegman, OW Johnson, R Fitzurka, M TI Camera artifacts in IUE high-dispersion spectra SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB Sky-background images obtained with the International Ultraviolet Explorer (IUE) have been analyzed to identify camera artifacts in high-dispersion point-source spectra observed through the large aperture. The camera artifacts are artificial emission features that are apparent in all IUE spectra with exposure times longer than about 1 hr. The positions of the strong artifacts in each order are given, and plots of the sky-background spectra are made available to aid scientists in the identification of artifacts in their spectra. C1 OMITRON INC,GREENBELT,MD 20770. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,GREENBELT,MD 20771. CATHOLIC UNIV AMER,DEPT PHYS,WASHINGTON,DC 20064. RP Crenshaw, DM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,COMP SCI CORP,CODE 681,GREENBELT,MD 20771, USA. NR 8 TC 2 Z9 2 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD OCT PY 1996 VL 108 IS 728 BP 925 EP 928 DI 10.1086/133814 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN251 UT WOS:A1996VN25100011 ER PT J AU Li, Y Bates, JR AF Li, Y Bates, JR TI A study of the behaviour of semi-Lagrangian models in the presence of orography SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE numerical modelling; orography; semi-Lagrangian models ID SPURIOUS RESONANT RESPONSE; FINITE-DIFFERENCE SCHEME; SHALLOW-WATER EQUATIONS; SPECTRAL MODELS; INTEGRATION; VERSION; SPHERE AB Orography is incorporated into two global shallow-water numerical models, the first (which is termed the (u, v) model) based on a semi-Lagrangian vector discretization of the momentum equation, the second (which is termed the PV-D model) based on the semi-Lagrangian advection of potential vorticity. Both models are two-time-level and use the finite-difference approach. Linear analyses of both models are performed for the idealized situation of stationary flow over orography on an f-plane. In extension of the analysis of Rivest et al. the effects of spatial discretization are included. Spurious orographic resonance in the sense of infinite amplitude is eliminated by the damping effects of spatial interpolation, but spurious enhanced responses in the neighbourhood of the points at which resonance previously occurred still remain. The linear analyses indicate similar spurious enhanced responses for both models, which is confirmed by the numerical experiments. The spurious orographic noise in both models can be eliminated by a sufficient amount of uncentring, though it is shown that uncentring of either first order or second order can have negative impacts on the large-scale Rossby waves. The PV-D model formulation, however, allows the use of a scheme in which only the divergence and continuity equations are uncentred, which minimizes such negative impacts. RP Li, Y (reprint author), NASA,GODDARD SPACE FLIGHT CTR,DATA ASSIMILAT OFF,ATMOSPHERES LAB,CODE 9103,GREENBELT,MD 20771, USA. NR 26 TC 8 Z9 8 U1 1 U2 1 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD OCT PY 1996 VL 122 IS 535 BP 1675 EP 1700 PN A PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VN471 UT WOS:A1996VN47100009 ER PT J AU Hapke, B DiMucci, D Nelson, R Smythe, W AF Hapke, B DiMucci, D Nelson, R Smythe, W TI The cause of the hot spot in vegetation canopies and soils: Shadow-hiding versus coherent backscatter SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; WEAK LOCALIZATION; LIGHT; POLARIZATION; SATELLITES; MODEL AB Two different mechanisms, shadow-hiding and coherent backscatter, can cause a hot spot, or opposition effect, in the bidirectional reflectance of vegetation and soils. Because the two mechanisms sample different properties, it is important to know which one is primarily responsible in a given medium. This question can be answered by measuring the bidirectional reflectance in circularly polarized light. If the results of the limited experiments reported here can be extrapolated to a wider range of materials, it appears that the primary cause of the hot spot in most vegetation canopies and in moist, clumpy soils is shadow-hiding. However, in vegetation with large numbers of wavelength-sized structures, such as mosses, and in dry, fine-grained soils, the hot spot is dominated by coherent backscatter. C1 CALTECH,JET PROP LAB,PASADENA,CA. RP Hapke, B (reprint author), UNIV PITTSBURGH,DEPT GEOL & PLANETARY SCI,321 OLD ENGN HALL,PITTSBURGH,PA 15260, USA. NR 21 TC 71 Z9 74 U1 1 U2 7 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD OCT PY 1996 VL 58 IS 1 BP 63 EP 68 DI 10.1016/0034-4257(95)00257-X PG 6 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA VJ819 UT WOS:A1996VJ81900006 ER PT J AU Veroustraete, F Patyn, J Myneni, RB AF Veroustraete, F Patyn, J Myneni, RB TI Estimating net ecosystem exchange of carbon using the normalized difference vegetation index and an ecosystem model SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID STOMATAL CONDUCTANCE; DECIDUOUS FOREST; PHOTOSYNTHESIS; TRANSPIRATION; RADIATION; DYNAMICS; IMAGERY; CO2 AB The evaluation and prediction of changes in carbon dynamics at the ecosystem level is a key issue in studies of global change. An operational concept for the determination of carbon fluxes for the Belgian territory is the goal of the presented study. The approach is based on the integration of remotely sensed data into ecosystem models in order to evaluate photosynthetic assimilation and net ecosystem exchange (NEE). Remote sensing can be developed as an operational tool to determine the fraction of absorbed photosynthetically active radiation (fPAR). A review of the methodological approach of mapping fPAR dynamics at the regional scale by means of NOAA11-AVHRR/2 data for the year 1990 is given. The processing sequence from raw radiance values to fPAR is presented. An interesting aspect of incorporating remote sensing derived fPAR in ecosystem models is the potential for modeling actual as opposed to potential vegetation. Further work should prove whether the concepts presented and the assumptions made in this study are valid. C1 NASA, GODDARD SPACE FLIGHT CTR, BIOSPHER SCI BRANCH, GREENBELT, MD 20771 USA. RP Veroustraete, F (reprint author), VLAAMSE INSTELLING TECHNOL ONDERZOEK, DEPT ENERGY, CTR TELEDETECT, BOERETANG 200, B-2400 MOL, BELGIUM. RI Myneni, Ranga/F-5129-2012 NR 32 TC 54 Z9 75 U1 4 U2 15 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD OCT PY 1996 VL 58 IS 1 BP 115 EP 130 DI 10.1016/0034-4257(95)00258-8 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA VJ819 UT WOS:A1996VJ81900010 ER PT J AU Raz, E AF Raz, E TI A multiple white light interferometer SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB A multiple interferometer using the short coherence length of white light has been constructed and its operation demonstrated. With this apparatus, it is possible to count the number of light reflections between two parallel mirrors. The shift in fringe position resulting from differences in the optical thickness is proportional to the number of reflections between the two mirrors, enabling the resolution and measurement of a step difference of the order of 20 Angstrom. This technique inherently has higher resolution than Michelson interferometers. As compared with Fabry-Perot interferometers, it offers an independent determination of the density of fringes, and has lower sensitivity to errors in minor parallelism. Further, the method does not require the extreme closeness in mirror spacing as compared to the Tolansky interferometer. (C) 1996 American Institute of Physics. C1 TECHNION ISRAEL INST TECHNOL,IL-32000 HAIFA,ISRAEL. RP Raz, E (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 4 TC 3 Z9 3 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD OCT PY 1996 VL 67 IS 10 BP 3416 EP 3419 DI 10.1063/1.1147152 PG 4 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA VN037 UT WOS:A1996VN03700004 ER PT J AU Gottlieb, D Gustafsson, B Olsson, P Strand, B AF Gottlieb, D Gustafsson, B Olsson, P Strand, B TI On the superconvergence of Galerkin methods for hyperbolic IBVP SO SIAM JOURNAL ON NUMERICAL ANALYSIS LA English DT Article DE superconvergence; Galerkin methods; partial differential equations; boundary accuracy; initial-boundary value problems AB Finite-element Galerkin methods using B-splines of order r for periodic first-order hyperbolic equations exhibit superconvergence on uniform grids (mesh size h) at the nodes; i.e., there is an error estimate O(h(2r)) instead of the expected convergence rate O(h(r)). In this paper it will be shown that no matter how the approximating subspace S-h is modified in a boundary layer [0, (s - 1)h], s arbitrary but fixed, the superconvergence property is lost for the hyperbolic model problem u(t) = u(x), 0 less than or equal to x < infinity, t greater than or equal to 0. We shall also discuss the implications of this result when constructing compact implicit difference schemes. C1 UNIV UPPSALA,DEPT COMP SCI,S-75104 UPPSALA,SWEDEN. NASA,AMES RES CTR,ADV COMP SCI RES INST,MOFFETT FIELD,CA 94035. RP Gottlieb, D (reprint author), BROWN UNIV,DEPT APPL MATH,PROVIDENCE,RI 02912, USA. NR 19 TC 4 Z9 4 U1 0 U2 0 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER PH#382-9800, PHILADELPHIA, PA 19104-2688 SN 0036-1429 J9 SIAM J NUMER ANAL JI SIAM J. Numer. Anal. PD OCT PY 1996 VL 33 IS 5 BP 1778 EP 1796 DI 10.1137/S0036142993257689 PG 19 WC Mathematics, Applied SC Mathematics GA VJ275 UT WOS:A1996VJ27500005 ER PT J AU Burlaga, LF Ness, NF Belcher, JW Lazarus, AJ Richardson, JD AF Burlaga, LF Ness, NF Belcher, JW Lazarus, AJ Richardson, JD TI Voyager observations of the magnetic field, interstellar pickup ions and solar wind in the distant heliosphere SO SPACE SCIENCE REVIEWS LA English DT Review AB Voyagers 1 and 2 are now observing the latitudinal structure of the heliospheric magnetic field in the distant heliosphere (the region between similar or equal to 30 AU and the termination shock). Voyager 2 is observing the influence of the interstellar medium on the solar wind. The pressure of the interstellar pickup protons, measured by their contribution to pressure balanced structures, is greater than or equal to the magnetic pressure and much greater than the thermal pressures of the solar wind protons and electrons in the distant heliosphere. The solar wind speed is observed to decrease and the proton temperature increase with increasing distance from the sun. This mag result from the production of pickup ions by the charge exchange process with the interstellar neutrals. The introduction of the pickup ions into the dynamics of the magnetised solar wind plasma appears to be an important new process which must be considered in future theoretical studies of the termination shock and boundary with the local interstellar medium. C1 NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA. MIT, DEPT PHYS, CAMBRIDGE, MA 02139 USA. MIT, CTR SPACE RES, CAMBRIDGE, MA 02139 USA. RP UNIV DELAWARE, BARTOL RES INST, NEWARK, DE 19716 USA. NR 11 TC 9 Z9 9 U1 0 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-6308 EI 1572-9672 J9 SPACE SCI REV JI Space Sci. Rev. PD OCT PY 1996 VL 78 IS 1-2 BP 33 EP 42 DI 10.1007/BF00170790 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW650 UT WOS:A1996VW65000007 ER PT J AU Leske, RA Mewaldt, RA Cummings, AC Cummings, JR Stone, EC VonRosenvinge, TT AF Leske, RA Mewaldt, RA Cummings, AC Cummings, JR Stone, EC VonRosenvinge, TT TI The isotopic composition of anomalous cosmic rays from SAMPEX SO SPACE SCIENCE REVIEWS LA English DT Review DE abundances; isotopes; anomalous cosmic rays; SAMPEX; neon; interstellar medium; heliosphere; trapped heavy ions ID SOLAR ENERGETIC PARTICLES; ABUNDANCES; COMPONENT; NUCLEI AB Measurements of the anomalous cosmic ray (ACR) isotopic composition have been made in three regions of the magnetosphere accessible from the polar Earth orbit of SAMPEX, including the interplanetary medium at high latitudes and geomagnetically trapped ACRs. At those latitudes where ACRs can penetrate the Earth's magnetic field while fully stripped galactic cosmic rays (GCRs) of similar energies are excluded, a pure ACR sample is observed to have the following composition: N-15/N < 0.023, O-18/O-16 < 0.0034, and Ne-22/Ne-20 = 0.077(+0.085, -0.023). We compare our values with those found by previous investigators and with those measured in other samples of solar and galactic material. In particular, a comparison of Ne-22/Ne-20 measurements from various sources implies that GCRs are not simply an accelerated sample of the local interstellar medium. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP CALTECH, MAIL CODE 220-47, PASADENA, CA 91125 USA. NR 28 TC 20 Z9 20 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-6308 EI 1572-9672 J9 SPACE SCI REV JI Space Sci. Rev. PD OCT PY 1996 VL 78 IS 1-2 BP 149 EP 154 DI 10.1007/BF00170801 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW650 UT WOS:A1996VW65000018 ER PT J AU Frisch, PC Slavin, JD AF Frisch, PC Slavin, JD TI Relative ionizations in the nearest interstellar gas SO SPACE SCIENCE REVIEWS LA English DT Review DE local interstellar medium; EUV emission; soft X-ray background; local bubble models ID VELA SUPERNOVA; DISCOVERY; BOUNDARY; HYDROGEN; OXYGEN; PLASMA AB We compare CLOUDY predictions for the equilibrium ionization in the interstellar cloud surrounding the solar system with pick-up ion data. The incident radiation held includes contributions from hot stars, the emission from the conductive cloud boundary and the diffuse EUV background. To within the observational uncertainties, CLOUDY predictions for the ratios n(He degrees)/n(O degrees), n(N degrees)/n(O degrees), n(Ne degrees)/n(O degrees), and n(He degrees)/n(Ne degrees) are consistent with pick-up ion data, provided that O degrees and N degrees are filtered by similar to 50% in the heliopause region and the outer heliosphere as predicted by others. Thus, the steady-state ionization model and assumed radiation held appear approximately valid. However, the youth and low intervening column density towards the Vela pulsar leave open the possibility that the parent supernova explosion similar to 10,500 years ago, and 200 pc distant, may also have affected LISM ionization, although the mechanism is uncertain. Support for this last possibility is provided by the apparent signature of the Vela explosion in the terrestrial geological record. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP UNIV CHICAGO, DEPT ASTRON ASTROPHYS, 5640 S ELLIS AVE, CHICAGO, IL 60637 USA. NR 29 TC 18 Z9 18 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-6308 EI 1572-9672 J9 SPACE SCI REV JI Space Sci. Rev. PD OCT PY 1996 VL 78 IS 1-2 BP 223 EP 228 DI 10.1007/BF00170808 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW650 UT WOS:A1996VW65000025 ER PT J AU Whang, YC Burlaga, LF Ness, NF AF Whang, YC Burlaga, LF Ness, NF TI Pickup protons in the heliosphere SO SPACE SCIENCE REVIEWS LA English DT Review ID LOCAL INTERSTELLAR-MEDIUM; SOLAR-WIND INTERACTION; HYDROGEN; MODEL; GAS AB We calculate the conditions of pickup protons inside the termination shock. Outside 50 AU the partial pressure of pickup protons is greater than the magnetic pressure by a factor of > 10, and greater than the partial pressure of solar wind protons by a factor of > 100. Thus, pickup protons have a significant dynamical influence on the structures of the solar wind in the outer heliosphere. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV DELAWARE, BARTOL RES INST, NEWARK, DE 19716 USA. RP CATHOLIC UNIV AMER, WASHINGTON, DC 20064 USA. NR 15 TC 17 Z9 17 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-6308 EI 1572-9672 J9 SPACE SCI REV JI Space Sci. Rev. PD OCT PY 1996 VL 78 IS 1-2 BP 393 EP 398 DI 10.1007/BF00170825 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW650 UT WOS:A1996VW65000042 ER PT J AU Shanabarger, MR Moorhead, RD AF Shanabarger, MR Moorhead, RD TI H2S adsorption onto clean and oxygen covered iron films SO SURFACE SCIENCE LA English DT Article DE adsorption kinetics; auger electron spectroscopy; chemisorption; electrical transport measurements; hydrogen sulphide; ion etching; iron; iron oxide; oxidation; polycrystalline surfaces; polycrystalline thin films ID SULFUR; SURFACE; OXIDATION; AES; CHEMISORPTION; POTASSIUM; HYDROGEN; KINETICS; SULFIDE; NI(110) AB Auger electron spectroscopy (AES) and the chemisorption-induced resistance change (CIRC) have been employed to compare the kinetics of low pressure H2S adsorption on clean and oxygen-covered Fe films. Although the oxygen overlayer does not appear to affect the saturation coverage of adsorbed H2S, it does significantly enhance the adsorption rate when compared with the clean Fe surface. Differences are also observed in the sulfur Auger spectrum obtained from the two surfaces. It is suggested that the differences observed in the adsorption rates and the shapes of the uptake curves result from a change in the rate-limiting adsorption step; from island growth for the clean Fe surface to molecular-precursor mediated adsorption on the oxygen-covered Fe surface. The adsorption of H2S did not lead to any obvious corrosion of the oxygen overlayer at the temperature of these measurements, about 295 K. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Shanabarger, MR (reprint author), UNIV CALIF SANTA BARBARA,SANTA BARBARA,CA 93106, USA. NR 39 TC 8 Z9 8 U1 1 U2 10 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD OCT 1 PY 1996 VL 365 IS 3 BP 614 EP 624 DI 10.1016/0039-6028(96)00764-9 PG 11 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA VH120 UT WOS:A1996VH12000008 ER PT J AU Beutter, BR Mulligan, JB Stone, LS AF Beutter, BR Mulligan, JB Stone, LS TI The barberplaid illusion: Plaid motion is biased by elongated apertures SO VISION RESEARCH LA English DT Article DE plaids; motion models; direction discrimination; aperture; intersection-of-constraints rule ID MACAQUE VISUAL-CORTEX; SPATIAL-FREQUENCY SELECTIVITY; AREA MT; 2-DIMENSIONAL PATTERNS; PERCEIVED DIRECTION; RESPONSE PROPERTIES; APPARENT MOTION; AFFERENT BASIS; HUMAN VISION; PERCEPTION AB The perceived direction of motion of plaids windowed by elongated spatial Gaussians is biased toward the window's long axis. The bias increases as the relative angle between the plaid motion and the long axis of the window increases, peaks at a relative angle of similar to 45 deg, and then decreases. The bias increases as the window is made narrower (at fixed height) and decreases as the component spatial frequency increases (at fixed aperture size). We examine several models of human motion processing (cross-correlation, motion-energy, intersection-of-constraints, and vector-sum), and show that none of these standard models can predict our data. We conclude that spatial integration of motion signals plays a crucial role in plaid motion perception and that current models must be explicitly expanded to include such spatial interactions. C1 NASA,AMES RES CTR,FLIGHT MANAGEMENT & HUMAN FACTORS DIV,HUMAN & SYST TECHNOL BRANCH,MOFFETT FIELD,CA 94035. NR 73 TC 14 Z9 14 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0042-6989 J9 VISION RES JI Vision Res. PD OCT PY 1996 VL 36 IS 19 BP 3061 EP 3075 DI 10.1016/0042-6989(96)00064-8 PG 15 WC Neurosciences; Ophthalmology SC Neurosciences & Neurology; Ophthalmology GA VL160 UT WOS:A1996VL16000005 PM 8917769 ER PT J AU Vorosmarty, CJ Willmott, CJ Choudhury, BJ Schloss, AL Stearns, TK Robeson, SM Dorman, TJ AF Vorosmarty, CJ Willmott, CJ Choudhury, BJ Schloss, AL Stearns, TK Robeson, SM Dorman, TJ TI Analyzing the discharge regime of a large tropical river through remote sensing, ground-based climatic data, and modeling SO WATER RESOURCES RESEARCH LA English DT Article ID GHZ POLARIZATION DIFFERENCE; SURFACE AIR-TEMPERATURE; AMAZON DEFORESTATION; SPATIAL VARIABILITY; HYDROLOGICAL CYCLE; INUNDATION AREA; PRECIPITATION; BASIN; INTERPOLATION; FLOODPLAIN AB This study demonstrates the potential for applying passive microwave satellite sensor data to infer the discharge dynamics of large river systems using the main stem Amazon as a test case. The methodology combines (1) interpolated ground-based meteorological station data, (2) horizontally and vertically polarized temperature differences (HVPTD) from the 37-GHz scanning multichannel microwave radiometer (SMMR) aboard the Nimbus 7 satellite, and (3) a calibrated water balance/water transport model (WBM/WTM). Monthly HVPTD values at 0.25 degrees (latitude by longitude) resolution were resampled spatially and temporally to produce an enhanced HVPTD; time series at 0.5 degrees resolution for the period May 1979 through February 1985. Enhanced HVPTD values were regressed against monthly discharge derived from the WBM/WTM for each of 40 grid cells along the main stem over a calibration period from May 1979 to February 1983 to provide a spatially contiguous estimate of time-varying discharge. HVPTD-estimated flows generated for a validation period from March 1983 to February 1985 were found to be in good agreement with both observed and modeled discharges over a 1400-km section of the main stem Amazon. This span of river is bounded downstream by a region of tidal influence and upstream by low sensor response associated with dense forest canopy. Both the WBM/WTM and HVPTD-derived flow rates reflect the significant impact of the 1982-1983 El Nino-Southern Oscillation (ENSO) event on water balances within the drainage basin. C1 NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,GREENBELT,MD 20771. SCI SYST & APPLICAT INC,LANHAM,MD 20703. INDIANA UNIV,DEPT GEOG,BLOOMINGTON,IN 47401. UNIV DELAWARE,DEPT GEOG,CTR CLIMAT RES,NEWARK,DE 19716. RP Vorosmarty, CJ (reprint author), UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,DURHAM,NH 03824, USA. RI Robeson, Scott/A-9895-2008 OI Robeson, Scott/0000-0002-1558-6951 NR 62 TC 82 Z9 85 U1 2 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0043-1397 J9 WATER RESOUR RES JI Water Resour. Res. PD OCT PY 1996 VL 32 IS 10 BP 3137 EP 3150 DI 10.1029/96WR01333 PG 14 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA VL614 UT WOS:A1996VL61400016 ER PT J AU Hou, R Evans, DM McClure, JC Nunes, AC Garcia, G AF Hou, R Evans, DM McClure, JC Nunes, AC Garcia, G TI Shielding gas and heat transfer efficiency in plasma are welding SO WELDING JOURNAL LA English DT Article DE plasma arc welding; shielding gas; heat transfer; melt efficiency; undercutting; HAZ; Al 6016; VPPA AB Variable polarity plasma are welding is widely used in the aerospace industry for producing high-quality welds on aluminum. In plasma welding the are is produced in a narrow stream of plasma gas while workpiece shielding is accomplished by a lower velocity but higher flow rate stream of shielding gas that surrounds the are. This paper will show that on aluminum welds both the melt zone and the heat-affected zone are appreciably decreased by this flow of shielding gas. Moreover, the amount of cooling is changed by the detailed shape of this flow as well as the flow rate. On the other hand, it will be shown that excessively high shielding flow rates can cause undercutting from contamination in the shielding gas. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV SAN LUIS POTOSI,INST MET,SAN LUIS POTOSI,MEXICO. RP Hou, R (reprint author), UNIV TEXAS,DEPT MET & MAT ENGN,EL PASO,TX 79968, USA. NR 13 TC 5 Z9 5 U1 1 U2 1 PU AMER WELDING SOC PI MIAMI PA PO BOX 351040, MIAMI, FL 33135 SN 0043-2296 J9 WELD J JI Weld. J. PD OCT PY 1996 VL 75 IS 10 BP S305 EP S310 PG 6 WC Metallurgy & Metallurgical Engineering SC Metallurgy & Metallurgical Engineering GA VK586 UT WOS:A1996VK58600014 ER PT J AU Mavriplis, DJ Venkatakrishnan, V AF Mavriplis, DJ Venkatakrishnan, V TI A 3D agglomeration multigrid solver for the Reynolds-averaged-Navier-Stokes equations on unstructured meshes SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS LA English DT Article DE multigrid; unstructured; Navier-Stokes ID FLOWS; GRIDS AB An agglomeration multigrid strategy is developed and implemented for the solution of three-dimensional steady viscous flows. The method enables convergence acceleration with minimal additional memory overhead and is completely automated in that it can deal with grids of arbitrary construction. The multigrid technique is validated by comparing the delivered convergence rates with those obtained by a previously developed overset-mesh multigrid approach and by demonstrating grid-independent convergence rates for aerodynamic problems on very large grids. Prospects for further increases in multigrid efficiency for high-Reynolds-number viscous flows on highly stretched meshes are discussed. RP Mavriplis, DJ (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23665, USA. NR 28 TC 38 Z9 38 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0271-2091 J9 INT J NUMER METH FL JI Int. J. Numer. Methods Fluids PD SEP 30 PY 1996 VL 23 IS 6 BP 527 EP 544 DI 10.1002/(SICI)1097-0363(19960930)23:6<527::AID-FLD429>3.0.CO;2-Z PG 18 WC Computer Science, Interdisciplinary Applications; Mathematics, Interdisciplinary Applications; Mechanics; Physics, Fluids & Plasmas SC Computer Science; Mathematics; Mechanics; Physics GA VJ309 UT WOS:A1996VJ30900001 ER PT J AU Wang, Y Stebbins, A Turner, EL AF Wang, Y Stebbins, A Turner, EL TI Gravitational lensing of gravitational waves from merging neutron star binaries SO PHYSICAL REVIEW LETTERS LA English DT Article ID COSMOLOGICAL CONSTANT; COMPACT BINARIES; PARAMETERS; RADIATION; UNIVERSE; GALAXY AB We discuss the gravitational lensing of gravitational waves from merging neutron star binaries, in the context of advanced LIGO type gravitational wave detectors. An advanced LIGO should see unlensed inspiral events with a redshift distribution with cutoff at a redshift z(max) < 1 for h less than or equal to 0.8. Any inspiral events detected at z > z(max) should be lensed. We compute the expected total number of events which are present due to gravitational lensing and their redshift distribution for an advanced LIGO in a flat universe. if the matter fraction in compact lenses is close to 10%, an advanced LIGO should see a few strongly lensed events per year with a signal-to-noise ratio rho > 5. C1 PRINCETON UNIV OBSERV,PRINCETON,NJ 08544. RP Wang, Y (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. RI Wang, Yun/B-5724-2011; Turner, Edwin/A-4295-2011 OI Wang, Yun/0000-0002-4749-2984; NR 17 TC 22 Z9 23 U1 0 U2 1 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 SEP 30 PY 1996 VL 77 IS 14 BP 2875 EP 2878 DI 10.1103/PhysRevLett.77.2875 PG 4 WC Physics, Multidisciplinary SC Physics GA VJ723 UT WOS:A1996VJ72300008 ER PT J AU Halicioglu, T AF Halicioglu, T TI Multilayer relaxation features on (100) and (111) surface of beta-SiC SO THIN SOLID FILMS LA English DT Article DE multilayers ID BETA-SIC(100); ENERGETICS AB Multilayer relaxation features were investigated for beta-SiC surfaces. Calculations include (1 x 1), (2 x 1) and c(2 x 2) phases of the (100) surface, and the (1 x 1) structure of the (111) surface. For both C-terminated and Si-terminated surfaces, variations in the top 3 interlayer spacings were calculated. The largest vertical displacement was calculated for the top interlayer spacing of the (111) surface. In general, it was found that too interlayer spacings contact, while the second interlayer spacings expand moderately. The third interlayer spacings, on the other hand, were found to exhibit very small amounts of contraction. Dimerization energies and bond distances were also calculated for reconstructed phases of the (100) surface. Calculated results were compared with data from the literature. C1 NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035. NR 10 TC 6 Z9 6 U1 1 U2 4 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD SEP 30 PY 1996 VL 286 IS 1-2 BP 184 EP 187 DI 10.1016/S0040-6090(96)08539-2 PG 4 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA VY061 UT WOS:A1996VY06100029 ER PT J AU Begue, A Myneni, R AF Begue, A Myneni, R TI Operational relationships between NOAA-advanced very high resolution radiometer vegetation indices and daily fraction of absorbed photosynthetically active radiation, established for Sahelian vegetation canopies SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SENSITIVITY ANALYSIS; PLANT CANOPIES; REFLECTANCE; NDVI; EFFICIENCY; SCATTERING; EQUATION; INDEX AB To improve the estimation of primary production ata-regional scale, an assessment of the utility of fraction of absorbed photosynthetically active radiation (fAPAR) estimated from spectral vegetation indices (VI) for the case of the Sahelian vegetation was studied. Simulations using a three-dimensional radiative transfer model were conducted for two types of structurally distinct vegetation canopies: millet crop (regularly distributed clumps of vegetation over bare soil) and savanna (mixture of a grass layer and a sparse woody layer). A realistic range of values is extracted for each vegetation input variable (leaf area index, ground cover, height and spatial distribution) from published literature. Bidirectional reflectance factors were calculated in the NOAA-advanced very high resolution radiometer (AVHRR) spectral bands for a geometric configuration representative of the NOAA satellite series. Two vegetation indices were tested : normalized difference vegetation index (NDVI) and modified soil adjusted vegetation index (MSAVI). The simulations indicate that the fAPAR-VI relationship is sensitive to the geometry of measurement and soil optical properties, especially in the case of a millet crop. Simple linear models that include this variability and are directly applicable to atmospherically corrected AVHRR data-are proposed, and the error of estimation of fAPAR is evaluated. MSAVI gives better results, especially when the brightness of soil is known. For natural vegetation the relationship between fAPAR and MSAVI is then reduced to a coefficient that is a constant (similar to 2.2). For millet canopies this coefficient is a function of Sun and view angles. Finally, the utility of our approach is illustrated with two examples of fAPAR-VI relationships applied to a NOAA time series. C1 NASA, GODDARD SPACE FLIGHT CTR, BIOSPHER SCI BRANCH, GREENBELT, MD 20771 USA. RP Begue, A (reprint author), MAISON TELEDETECT, CIRAD CA, DEPT CULTURES ANNUELLES, 500 RUE JF BRETON, F-34093 MONTPELLIER 5, FRANCE. RI begue, agnes/A-5718-2011; Myneni, Ranga/F-5129-2012 OI begue, agnes/0000-0002-9289-1052; NR 45 TC 8 Z9 8 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 27 PY 1996 VL 101 IS D16 BP 21275 EP 21289 DI 10.1029/96JD01621 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VK041 UT WOS:A1996VK04100009 ER PT J AU Jensen, EJ Toon, OB Selkirk, HB Spinhirne, JD Schoeberl, MR AF Jensen, EJ Toon, OB Selkirk, HB Spinhirne, JD Schoeberl, MR TI On the formation and persistence of subvisible cirrus clouds near the tropical tropopause SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID POLAR STRATOSPHERIC CLOUDS; ICE; TROPOSPHERE; MODEL AB We have used a detailed cirrus cloud model to evaluate the physical processes responsible for the formation and persistence of subvisible cirrus near the tropical tropopause and the apparent absence of these clouds at midlatitudes. We find that two distinct formation mechanisms are viable. Energetic tropical cumulonimbus clouds transport large amounts of ice water to the upper troposphere and generate extensive cirrus outflow anvils. Ice crystals with radii larger than 10 - 20 mu m should precipitate out of these anvils within a few hours, leaving behind an optically thin layer of small ice crystals (tau(vis) similar or equal to 0.01 - 0.2, depending upon the initial ice crystal size distribution). Given the long lifetimes of the clouds, wind shear is probably responsible for the observed cloud thickness less than or equal to 1 km. Ice crystals can also be generated in situ by slow, synoptic scale uplift of a humid layer. Given the very low temperatures at the tropical tropopause (similar or equal to -85 degrees C), synoptic-scale uplift can generate the moderate ice supersaturations (less than 10%) required for homogeneous freezing of sulfuric acid aerosols. In addition, simulations suggest that relatively large ice crystal number densities should be generated (more than 0.5 cm(-3)). The numerous crystals cannot grow larger than about 10 - 20 mu m given the available vapor, and their low fall velocities will allow them to remain in the narrow supersaturated region for at least a day. The absorption of infrared radiation in the thin cirrus results in heating rates on the order of a few K per day. If this energy drives local parcel temperature change, the cirrus will dissipate within several hours. However, if the absorbed radiative energy drives lifting of the cloud layer, the vertical wind speed will be about 0.2 cm-s(-1), and the cloud may persist for days with very little change in optical or microphysical properties. The fact that these clouds form most-frequently over the tropical western Pacific is probably related (through the nucleation physics) to the very low tropopause temperatures in this region. Simulations using midlatitude tropopause temperatures near -65 degrees C suggest that at the higher temperatures, fewer ice crystals nucleate, resulting in more rapid crystal growth and cloud dissipation by precipitation. Hence, the lifetime of thin cirrus formed near the midlatitude tropopause should be limited to a few hours after the synoptic-scale system that initiated cloud formation has passed. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. SAN JOSE STATE UNIV FDN, SAN JOSE, COSTA RICA. SPACE PHYS RES INST, SUNNYVALE, CA USA. RP Jensen, EJ (reprint author), NASA, AMES RES CTR, MS 245-4, MOFFETT FIELD, CA 94035 USA. RI Selkirk, Henry/H-2021-2012 NR 31 TC 167 Z9 169 U1 0 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 27 PY 1996 VL 101 IS D16 BP 21361 EP 21375 DI 10.1029/95JD03575 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VK041 UT WOS:A1996VK04100017 ER PT J AU Riotto, A Tkachev, II AF Riotto, A Tkachev, II TI Non-equilibrium symmetry restoration beyond one loop SO PHYSICS LETTERS B LA English DT Article ID FINITE-TEMPERATURE; FIELD-THEORIES; INFLATION; UNIVERSE AB We calculate the strength of symmetry restoration effects in highly non-equilibrium states which can arise, for example, during preheating after inflation. We show that in certain parameter range the one-loop results are unstable, requiring summation of multiloop diagrams. We solve this problem for the O(N) model in the large N-limit and show that the symmetry restoration may be less effective than what predicted by the one-loop estimate. C1 OHIO STATE UNIV,DEPT PHYS,COLUMBUS,OH 43210. RUSSIAN ACAD SCI,INST NUCL RES,MOSCOW 117312,RUSSIA. RP Riotto, A (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. NR 26 TC 18 Z9 18 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-2693 J9 PHYS LETT B JI Phys. Lett. B PD SEP 26 PY 1996 VL 385 IS 1-4 BP 57 EP 62 DI 10.1016/0370-2693(96)00882-9 PG 6 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA VL389 UT WOS:A1996VL38900010 ER PT J AU Gabrion, J Maurel, D Clavel, B Davet, J Fareh, J Herbute, S OMara, K Gharib, C Hinds, W Krasnov, I Guell, A AF Gabrion, J Maurel, D Clavel, B Davet, J Fareh, J Herbute, S OMara, K Gharib, C Hinds, W Krasnov, I Guell, A TI Changes in apical organization of choroidal cells in rats adapted to spaceflight or head-down tilt SO BRAIN RESEARCH LA English DT Article DE choroid plexus; microvillus; ezrin; cell polarity; spaceflight; gravity; electron microscopy; immunocytochemistry ID ATRIAL-NATRIURETIC-PEPTIDE; CEREBROSPINAL-FLUID PRESSURE; MORPHOLOGICAL-CHANGES; HYPERTENSIVE RATS; BINDING-SITES; PLEXUS; BRAIN; EZRIN; WEIGHTLESSNESS; HYDROCEPHALUS AB Structural changes observed in choroid plexuses from rats dissected aboard a space shuttle, on day 13 of an orbital flight (NASA STS-58 mission, SLS-2 Experiments) demonstrated that choroidal epithelial cells display a modified organization in a microgravitational environment. Results were compared with ultrastructural observations of choroid plexus from rats maintained under anti-orthostatic restraint (head-down tilt) for 14 days. In both experiment types, the main alterations observed by transmission electron microscopy, at the level of choroidal epithelial cells from the third and fourth ventricles, concerned the formation and the organization of apical microvilli, whereas pseudopod-like structures appeared. Immunocytochemical distribution of ezrin, a cytoskeletal protein involved in apical cell differentiation in choroid plexus, confirmed the structural alteration of microvilli in head-down tilted rats. Kinocilia tended to disappear from the apical surface, suggesting a partial loss of cell polarization. In addition, large amounts of clear vesicles were gathered in the apical cytoplasm of choroidal epithelial cells. Disorganization of apical microvilli, accumulations of apical vesicles and partial loss of cell polarity showed that long-stays in weightlessness induced alterations in the fine structure of choroid plexus! consistent with a marked reduction of cerebrospinal fluid production. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. LOCKHEED MARTIN ENGN & SCI SERV,MOFFETT FIELD,CA. MINIST PUBL HLTH RUSSIA,INST BIOMED PROBLEMS,MOSCOW,RUSSIA. CTR NATL ETUD SPATIALES,F-31055 TOULOUSE,FRANCE. RP Gabrion, J (reprint author), UNIV MONTPELLIER 2,URA CNRS 1856,MONTPELLIER,FRANCE. NR 60 TC 17 Z9 17 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0006-8993 J9 BRAIN RES JI Brain Res. PD SEP 23 PY 1996 VL 734 IS 1-2 BP 301 EP 315 DI 10.1016/S0006-8993(96)00659-2 PG 15 WC Neurosciences SC Neurosciences & Neurology GA VL410 UT WOS:A1996VL41000037 PM 8896838 ER PT J AU Leighly, KM Mushotzky, RF Yaqoob, T Kunieda, H Edelson, R AF Leighly, KM Mushotzky, RF Yaqoob, T Kunieda, H Edelson, R TI The X-ray spectral variability of Markarian 766 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (Markarian 766); galaxies, Seyfert; radiation mechanisms, nonthermal; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; LINE SEYFERT-1 GALAXIES; AGN; REFLECTION; NGC-4151; PLASMAS; MKN-766; ROSAT AB Analysis results from ASCA and ROSAT observations of the narrow-line Seyfert 1 galaxy Mrk 766 are reported. In the ASCA observation, we observed rapid variability with a doubling timescale of 1000 s. A spectral variability event was observed in which the spectrum softened and hardened above and below similar to 1 keV, respectively, as the flux increased. The spectra could be modeled with five components: an absorbed power law, warm absorber, iron Kcl line, and soft excess component flux. The spectral variability resulted from a highly significant change in the intrinsic photon index from Gamma similar to 1.6 to similar to 2.0, an increase in the warm absorber ionization, and a marginally significant decrease in the soft component normalization. A similar to 100 eV equivalent width narrow iron K alpha line was detected in the high-state spectrum. Spectral hardening during flux increases was observed in three ROSAT observations. The change in intrinsic photon index and disappearance of the soft excess component in the ASCA spectra can be explained as a transition from a first-order pair-reprocessed spectrum to a pair cascade brought about by a sudden increase in the injected electron Lorentz factor. The change in the ionization of the warm absorber, though model dependent, could correspond to the increase in flux at the oxygen edges resulting from the spectral index change. The ROSAT spectral variability can be interpreted by variable intensity hard power law and a relatively nonvarying soft component, possibly primary disk emission. These results are compared with those reported from other narrow-line Seyfert 1 galaxies. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NAGOYA UNIV, DEPT PHYS, CHIKUSA KU, NAGOYA, AICHI 464, JAPAN. UNIV IOWA, DEPT PHYS & ASTRON, IOWA CITY, IA 52242 USA. RP Leighly, KM (reprint author), INST PHYS & CHEM RES, COSM RADIAT LAB, HIROSAWA 2-1, WAKO, SAITAMA 351, JAPAN. NR 42 TC 45 Z9 45 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP 147 EP 165 DI 10.1086/177767 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG436 UT WOS:A1996VG43600017 ER PT J AU Stothers, RB Chin, CW AF Stothers, RB Chin, CW TI Metal dependences of two convection theories for cool stellar envelopes SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; open clusters and associations, general; stars, interiors; stars, late-type; supergiants; turbulence ID SMALL-MAGELLANIC-CLOUD; ROSSELAND MEAN OPACITIES; CCD STROMGREN PHOTOMETRY; YOUNG CLUSTER NGC-330; SMC GLOBULAR-CLUSTER; STANDARD SOLAR MODEL; MIXING-LENGTH THEORY; TURBULENT CONVECTION; EFFECTIVE TEMPERATURES; MOLECULAR OPACITIES AB Most theories of turbulent convection in stellar envelopes assume incompressible how, and so require the assignment of a characteristic length scale from external evidence. In mixing-length theory, this length I is usually assigned to be a constant, alpha, times the local pressure scale height, H-P, or, alternatively, times the distance from the top of the convection zone, z. The new full-spectrum-of-turbulence theory of Canuto & Mazzitelli uses l = z, and therefore is formally parameter-free, Chieffi, Straniero, & Salaris have recently suggested that alpha in mixing-length theory depends on metallicity, Z, but they considered only low-mass stars. We do a similar analysis for stars of higher mass. Specifically, we compare predicted and observed effective temperatures of red giants and red supergiants of widely differing metallicities, but identical luminosities, within the mass range 5-10 M(circle dot). The stars utilized belong to several open clusters in the Galaxy with Z approximate to 0.02 and to the clusters NGC 330 and NGC 458 in the Small Magellanic Cloud with Z = 0.002-0.004. It appears that either alpha in mixing-length theory is independent of metallicity or, since the empirical effective temperatures of the SMC stars may have been underestimated, alpha increases slightly with decreasing metallicity. On the other hand, Canuto & Mazzitelli's theory with l = z is found to perform quite well in all cases, within the possible errors of the observations and of the low temperature opacities. RP Stothers, RB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 64 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP 166 EP 170 DI 10.1086/177768 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG436 UT WOS:A1996VG43600018 ER PT J AU Hua, XM Titarchuk, L AF Hua, XM Titarchuk, L TI Time variation of emissions from comptonization sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; plasmas; radiation mechanisms, thermal; radiative transfer; scattering; X-rays, general ID X-RAYS; CYGNUS X-1; HARD; RADIATION; SPECTRA; STATE AB Previous analytical results on the temporal behavior of emissions from Comptonization plasma are obtained for nonrelativistic diffusion approximation and are therefore applicable only to plasma clouds with low temperatures and large optical radii. By introducing the concept of varied mean free path and corresponding parameter, we are able to extend the analytical results to Comptonization clouds with small optical radii. We also compare the results of Monte Carlo calculations with the analytical formulae for light curves in given energy ranges and show that these formulae cannot be used to analyze the temporal behavior of the emission observed from black hole candidates or other sources if the energy spectra of these sources indicate the existence of clouds with temperature greater than or similar to 25 keV and radius similar to 1 Thomson mean free path. We performed Monte Carlo calculations based on a more realistic model and obtain the light curves in various energy ranges used in previous analyses. We performed Fourier analysis on these light curves and obtained the phase lags of harder X-rays with respect to softer ones as well as power spectrum density. Sire investigate the effects of various conditions of plasma clouds and source photons upon the phase lag and power spectrum density as functions of Fourier frequency. We discuss the implication of these results when compared to observations by instruments with high time resolution. RP Hua, XM (reprint author), GODDARD SPACE FLIGHT CTR, LHEA, CODE 661, GREENBELT, MD 20771 USA. NR 16 TC 14 Z9 14 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP 280 EP 304 DI 10.1086/177778 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG436 UT WOS:A1996VG43600028 ER PT J AU Lundberg, H Johansson, SG Larsson, J Leckrone, DS Litzen, U Svanberg, S Wahlgren, GM Zerne, R AF Lundberg, H Johansson, SG Larsson, J Leckrone, DS Litzen, U Svanberg, S Wahlgren, GM Zerne, R TI Experimental Pd II oscillator strengths and the palladium abundance in the HgMn-type star chi Lupi SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; line, identification; stars, abundances; stars, individual (Chi Lupi); ultraviolet, stars ID SPECTRA; REGION; HST AB Experimental oscillator strengths for 19 ultraviolet lines of Pd II have been derived from measurements of line intensities in calibrated Fourier transform spectra, combined with picosecond-pulse laser measurements of radiative lifetimes. Five of these 19 lines, in addition to other Pd nr lines, are present in Hubble Space Telescope/Goddard High-Resolution Spectrograph echelle spectra of the chemically peculiar HgMn star chi Lupi, yielding a palladium abundance of log (N-Pd) = +5.0, which is 3.3 dex above the solar abundance. Theoretical oscillator strengths have been calculated for all strong ultraviolet transitions associated with the lowest odd-parity configuration of Pd II. C1 LUND UNIV, DEPT PHYS, S-22362 LUND, SWEDEN. LUND UNIV, LUND OBSERV, S-22100 LUND, SWEDEN. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. COMP SCI CORP, ASTRON PROGRAM, CINCINNATI, OH 45202 USA. NASA, GODDARD SPACE FLIGHT CTR, ASTRON PROGRAM, GHRS SCI TEAM, GREENBELT, MD 20771 USA. RP Lundberg, H (reprint author), LUND INST TECHNOL, DEPT PHYS, POB 118, S-22100 LUND, SWEDEN. NR 22 TC 16 Z9 16 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP 388 EP 392 DI 10.1086/177788 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG436 UT WOS:A1996VG43600038 ER PT J AU Marconi, ML Dagum, L Smyth, WH AF Marconi, ML Dagum, L Smyth, WH TI Hybrid fluid/kinetic approach to planetary atmospheres: An example of an intermediate mass body SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; planets and satellites, general ID MODEL AB The atmosphere of an intermediate mass planetary body is calculated in a self-consistent fashion by the use of a hybrid fluid/kinetic theory approach on massively parallel computers. Assuming a spherical atmosphere and a heating layer, this technique is used to obtain the atmosphere from the collisional hydrodynamic regime, through the quasi-collisional nonlinear kinetic regime, and into the self-collisionless linear kinetic regime. The results display significant nonequilibrium phenomena in both macroscopic variables such as temperature and microscopic variables such as the velocity distribution. Comparison with a standard hydrodynamic model demonstrates substantial differences. This method which is valid for all Knudsen numbers can be easily generalized to more complex problems and should be a powerful tool to study the structure, dynamics, and evolution of planetary atmospheres. C1 SILICON GRAPH INC,SUPERCOMP APPLICAT,MT VIEW,CA 94043. NASA,AMES RES CTR,COMP SCI CORP,MOFFETT FIELD,CA 94035. RP Marconi, ML (reprint author), ATMOSPHER & ENVIRONM RES INC,840 MEM DR,CAMBRIDGE,MA 02139, USA. NR 11 TC 16 Z9 16 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP 393 EP 401 DI 10.1086/177789 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG436 UT WOS:A1996VG43600039 ER PT J AU Berger, M vanderKlis, M vanParadijs, J Lewin, WHG Lamb, F Vaughan, B Kuulkers, E Augusteijn, T Zhang, W Marshall, FE Swank, JH Lapidus, I Lochner, JC Strohmayer, TE AF Berger, M vanderKlis, M vanParadijs, J Lewin, WHG Lamb, F Vaughan, B Kuulkers, E Augusteijn, T Zhang, W Marshall, FE Swank, JH Lapidus, I Lochner, JC Strohmayer, TE TI Discovery of 800 Hz quasi-periodic oscillations in 4U 1608-52 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars, individual (4U 1608-52); stars, neutron ID GX5-1; BEHAVIOR AB We present results of Rossi X-Ray Timing Explorer observations of the low-mass X-ray binary and atoll source 4U 1608-52 made over 9 days during the decline of an X-ray intensity outburst in 1996 March. A fast-timing analysis shows a strong and narrow quasi-periodic oscillation (QPO) peak at frequencies between 850 and 890 Hz on March 3 and 6, as well as a broad peak around 690 Hz on March 9. Observations on March 12 show no significant signal. On March 3, the X-ray spectrum of the QPO is quite hard; its strength increases steadily from 5% at similar to 2 keV to similar to 20% at similar to 12 keV. The QPO frequency varies between 850 and 890 Hz on that day, and the peak widens and its rms decreases with centroid frequency in a way very similar to the well-known horizontal branch oscillations (HBO) in Z sources. We apply the HBO beat frequency model to atoll sources and suggest that, whereas the model could produce QPOs at the observed frequencies, the lack of correlation we observe between QPO properties and X-ray count rate is hard to reconcile with this model. C1 UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. MIT,DEPT PHYS,CAMBRIDGE,MA 02139. UNIV ILLINOIS,DEPT PHYS,URBANA,IL 61801. CALTECH,RADIAT LAB,PASADENA,CA 91125. EUROPEAN SPACE AGCY,ESTEC,DIV ASTROPHYS,NL-2200 AG NOORDWIJK,NETHERLANDS. EUROPEAN SO OBSERV,LA SILLA OBSERV,SANTIAGO 19,CHILE. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,WASHINGTON,DC. UNIV CAMBRIDGE,INST ASTRON,CAMBRIDGE CB2 0HA,ENGLAND. RP Berger, M (reprint author), UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,CTR HIGH ENERGY ASTROPHYS,KRUISLAAN 403,NL-1098 SJ AMSTERDAM,NETHERLANDS. RI Swank, Jean/F-2693-2012 NR 20 TC 81 Z9 81 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L13 EP & DI 10.1086/310256 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800004 ER PT J AU Ford, E Kaaret, P Tavani, M Harmon, BA Zhang, SN Barret, D Grindlay, J Bloser, P Remillard, RA AF Ford, E Kaaret, P Tavani, M Harmon, BA Zhang, SN Barret, D Grindlay, J Bloser, P Remillard, RA TI Anticorrelated hard/soft X-ray emission from the X-ray burster 4U 0614+091 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars, individual (4U 0614+091); stars, neutron; X-Rays, Stars ID EXOSAT OBSERVATIONS; COMPTONIZATION AB We have detected transient X-ray activity from the X-ray burster 4U 0614+091 simultaneously with BATSE on board the Compton Gamma Ray Observatory (20-100 keV) and the all-sky monitor (ASM) on board the Rossi X-Ray Timing Explorer (1-12 keV). The peak fluxes reach approximately 40 mcrab in both instruments over a period of about 20 days. The variable emission shows a clear anticorrelation of the hard X-ray flux with the soft X-ray count rate. The observed anticorrelation is another clear counterexample to the notion that only black hole binaries exhibit such correlations. The individual spectra during this period can be fitted by power laws with photon indices 2.2 +/- 0.3 (ASM) and 2.7 +/- 0.4 (BATSE), while the combined spectra can be described by a single power law with index 2.09 +/- 0.08. BATSE and the Rossi X-Ray Timing Explorer ASM are a good combination for monitoring X-ray sources over a wide energy band. C1 COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,NEW YORK,NY 10027. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. RP Ford, E (reprint author), COLUMBIA UNIV,DEPT PHYS,538 W 120TH ST,NEW YORK,NY 10027, USA. NR 28 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L37 EP L40 DI 10.1086/310265 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800010 ER PT J AU Giles, AB Swank, JH Jahoda, K Zhang, W Strohmayer, T Stark, MJ Morgan, EH AF Giles, AB Swank, JH Jahoda, K Zhang, W Strohmayer, T Stark, MJ Morgan, EH TI The main characteristics of GRO J1744-28 observed by the proportional counter array experiment on the Rossi X-ray timing explorer SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, neutron; X-rays, bursts ID PROSPECTS AB In this Letter, we provide an introduction to the main features seen in a series of observations of the bursting pulsar GRO J1744-28. The observations were made from 1996 January through May with the proportional counter array on the Rossi X-Ray Timing Explorer spacecraft. In the 2-10 keV band, GRO J1744-28 emitted large bursts of similar to 10 s duration at a rate of about 2 per hour. The peak flux during these bursts was similar to 6-40 times greater than that in the quiescent, or nonbursting, periods. For the earliest bursts, the inferred peak luminosity approaches 100 times the Eddington limit, which is suggestive of some kind of beaming mechanism. A range of smaller bursts and quasi-periodic oscillation features were also seen. All this activity was superposed on an almost perfect sinusoidal modulation at a frequency of 2.14 Hz with an amplitude of similar to 10% of the nonbursting flux. The source's persistent flux declined in a roughly linear trend from late January until mid-May, by which time its intensity was confused with several other sources. C1 UNIV SPACE RES ASSOC,WASHINGTON,DC. UNIV MARYLAND,COLLEGE PK,MD 20742. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. RP Giles, AB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Jahoda, Keith/D-5616-2012; Swank, Jean/F-2693-2012 NR 30 TC 44 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L25 EP L28 DI 10.1086/310262 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800007 ER PT J AU Phillips, KJH Greer, CJ Bhatia, AK Keenan, FP AF Phillips, KJH Greer, CJ Bhatia, AK Keenan, FP TI Active region electron density and dimensions from Fe XVII X-ray lines SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; atomic processes; line, formation; Sun, activity; Sun, flares; Sun, X-rays, gamma rays ID CORONA; RATIOS AB The Fe XVII 2p(6) S-1(0)-2p(5)3d P-1(1), X-ray line at 15.015 Angstrom is resonance-scattered in solar active region and Rare spectra, as has been deduced by comparing theoretical intensities of lines in the Fe XVII 2p(6)-2p(5)3l (l = s, d) arrays with intensities observed by the flat crystal spectrometer (FCS) on the Solar Maximum Mission. We show that the amount of resonance scattering is strongly dependent on the heliocentric distance of the emitting plasma, disk regions showing much larger scattering than limb regions. Average values for electron density N-e and path length l can be derived for various heliocentric distances using the X-ray line intensities. We find N-e approximate to 10(9) cm(-3) and l approximate to 100,000 km (region on the disk) to N-e approximate to 10(11) cm(-3) and l approximate to 1000 km (region on the limb) for active region AR 4787, as it rotated across the solar disk to the limb. These lengths appear to be consistent with FCS images. We note, from our findings, that the approximate extent of stellar X-ray active regions could be determined, if high-resolution Fe XVII or equivalent observations were available. C1 QUEENS UNIV BELFAST,DEPT PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Phillips, KJH (reprint author), RUTHERFORD APPLETON LAB,DEPT SPACE SCI,DIDCOT OX11 0QX,OXON,ENGLAND. NR 10 TC 25 Z9 25 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L57 EP L59 DI 10.1086/310258 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800015 ER PT J AU Strohmayer, TE Zhang, W Swank, JH Smale, A Titarchuk, L Day, C AF Strohmayer, TE Zhang, W Swank, JH Smale, A Titarchuk, L Day, C TI Millisecond X-ray variability from an accreting neutron star system SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, neutron; stars, rotation; X-rays, stars ID QUASI-PERIODIC OSCILLATIONS; POWER SPECTRA; MXB 1728-34; BURST; PULSAR; GINGA AB We report the detection with the Proportional Counter Array (PCA) on board the Rossi X-Ray Timing Explorer (RXTE) of millisecond variability in the X-ray emission from the low-mass X-ray binary 4U 1728-34. Pulsations at 363 Hz with amplitudes (rms) of 2.5%-10% are present in six of the eight bursts analyzed to date. The strongest were seen in two successive bursts recorded on 1996 February 16 when the quiescent count rate was near the highest seen by PCA. The pulsations during these bursts show frequency changes of 1.5 fit during the first few seconds but become effectively coherent as the burst decays. We interpret the 363 Hz pulsations as rotationally induced modulations of inhomogeneous burst emission. This represents the first compelling evidence for a millisecond spin period in a low-mass X-ray binary. Complex, intensity-dependent, millisecond X-ray variability is also present in all the quiescent flux intervals we examined. Most interesting was the behavior as the count rate approached its highest observed level. Two quasi-periodic oscillations (QPOs) were simultaneously observed in the 650-1100 Hz range. Both QPOs increased in frequency together, maintaining a nearly constant frequency separation of about 363 Hz, the spin period inferred from the burst oscillations. This phenomenology is strongly suggestive of the magnetospheric beat frequency model proposed for the horizontal-branch oscillations (HBOs) seen in Z sources. We discuss this and several other possible physical interpretations for the observed X-ray variability. C1 TOHOKU UNIV,INST ASTRON,SENDAI,MIYAGI 980,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,USRA,GREENBELT,MD 20771. GEORGE MASON UNIV,FAIRFAX,VA 22030. RP Strohmayer, TE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Swank, Jean/F-2693-2012 NR 27 TC 320 Z9 320 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L9 EP & DI 10.1086/310261 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800003 ER PT J AU vanderKlis, M Swank, JH Zhang, W Jahoda, K Morgan, EH Lewin, WHG Vaughan, B vanParadus, J AF vanderKlis, M Swank, JH Zhang, W Jahoda, K Morgan, EH Lewin, WHG Vaughan, B vanParadus, J TI Discovery of submillisecond quasi-periodic oscillations in the X-ray flux of Scorpius X-1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, general; stars, individual (Scorpius X-1); stars, neutron ID SPECTRAL BEHAVIOR; GX5-1 AB We report the discovery, with NASA's Rossi X-Ray Timing Explorer (RXTE), of the first submillisecond oscillations found in a celestial X-ray source. The quasi-periodic oscillations (QPOs) come from Sco X-1 and have a frequency of similar to 1100 Hz and amplitudes of 0.6%-1.2% (rms) and are relatively coherent, with Q up to similar to 10(2). The frequency of the QPOs increases with accretion rate, rising from 1050 to 1130 Hz when the source moves from top to bottom along the normal branch in the X-ray color-color diagram, and shows a strong, approximately linear correlation with the frequency of the well-known 6-20 Hz normal/flaring-branch QPOs. We also report the discovery of QPOs with a frequency near 800 Hz that occur, simultaneously with the 1100 Hz QPOs, in the upper normal branch. We discuss several possible interpretations, one involving a millisecond X-ray pulsar whose pulses we see reflected off accretion flow inhomogeneities. Finally, we report the discovery of similar to 45 Hz QPOs, most prominent in the middle of the normal branch, which might be magnetospheric beat-frequency QPOs. C1 NATL INST NUCL & HIGH ENERGY PHYS,CTR HIGH ENERGY ASTROPHYS,NL-1098 SJ AMSTERDAM,NETHERLANDS. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. MIT,CAMBRIDGE,MA 02139. CALTECH,PASADENA,CA 91125. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. RP vanderKlis, M (reprint author), UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,KRUISLAAN 403,NL-1098 SJ AMSTERDAM,NETHERLANDS. RI Jahoda, Keith/D-5616-2012; Swank, Jean/F-2693-2012 NR 23 TC 161 Z9 161 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L1 EP L4 DI 10.1086/310251 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800001 ER PT J AU Zhang, W Lapidus, I White, NE Titarchuk, L AF Zhang, W Lapidus, I White, NE Titarchuk, L TI Kilohertz quasi-periodic intensity oscillations from 4U 1636-536 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; stars, individual (4U 1636-536); stars, neutron; X-rays, stars ID X-RAY BINARIES; GX5-1; FLUX AB We report the discovery of 870 Hz quasi-periodic intensity oscillations with the Rossi X-Ray Timing Explorer from the X-ray burster 4U 1636-536. This is the fourth Galactic low-mass X-ray binary (LMXB) that has shown this type of oscillations. We present the fractional rms amplitude as a function of energy and compare the characteristics of these oscillations with those discovered in other sources. C1 UNIV SPACE RES ASSOC, WASHINGTON, DC USA. UNIV CAMBRIDGE, INST ASTRON, CAMBRIDGE CB3 0HA, ENGLAND. GEORGE MASON UNIV, COMPUTAT SCI & INFORMAT INS, FAIRFAX, VA 22030 USA. RP Zhang, W (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 16 TC 48 Z9 48 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L17 EP L19 DI 10.1086/310255 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800005 ER PT J AU Zhang, W Morgan, EH Jahoda, K Swank, JH Strohmayer, TE Jernigan, G Klein, RI AF Zhang, W Morgan, EH Jahoda, K Swank, JH Strohmayer, TE Jernigan, G Klein, RI TI Quasi-periodic X-ray brightness oscillations of GRO J1744-28 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; pulsars, general; stars, individual (GRO J1744-28); stars, neutron; X-rays, bursts; X-rays, stars AB The newly discovered source GRO J1744-28 is remarkable in many respects. It is a low-mass X-ray binary system that shows 2.1 Hz coherent pulsations. It also produces type II X-ray bursts similar to those seen in the Rapid Burster. In this Letter we report results from a series of observations with the Rossi X-Ray Timing Explorer (RXTE) during which GRO J1744-28 showed quasi-periodic X-ray brightness oscillations (QPOs) at 20, 40, and 60 Hz. Their fractional rms amplitudes are 0.19%, 5.9%, and 0.42%, respectively. The QPO centroid frequency and its rms amplitude as a function of source brightness in the band of 2-60 keV indicate that these QPOs are of a different kind from the beat-frequency QPOs that have been observed among Z sources as well as X-ray pulsars, We discuss possible interpretations of these QPOs in the context of neutron star g-mode oscillations and photon bubble oscillations. C1 UNIV SPACE RES ASSOC,WASHINGTON,DC. MIT,SPACE RES CTR,CAMBRIDGE,MA 02139. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. LAWRENCE LIVERMORE NATL LAB,LIVERMORE,CA 94550. RP Zhang, W (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Jahoda, Keith/D-5616-2012; Swank, Jean/F-2693-2012 NR 21 TC 43 Z9 43 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1996 VL 469 IS 1 BP L29 EP L32 DI 10.1086/310259 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG438 UT WOS:A1996VG43800008 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI On the photoelectron spectrum of Li-4(-) SO CHEMICAL PHYSICS LETTERS LA English DT Article ID ELECTRON CORRELATION; CLUSTERS; SPECTROSCOPY; ANIONS AB The most stable structure for Li-4(-) is found to be the rhombus. Electron detachment from this structure does not seem able to fully explain the experimental photoelectron spectrum. The computed results are consistent with those of Rao, Jena, and Ray, who have proposed that the experimental spectrum consists of a superposition of detachment from the Li-4(-) rhombus(B-2(2n)) and tetrahedron ((4)A(1)), forming the singlet and tripler states of Li-4, respectively. RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,STC-230-3,MOFFETT FIELD,CA 94035, USA. NR 18 TC 2 Z9 2 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 SEP 20 PY 1996 VL 260 IS 1-2 BP 309 EP 313 DI 10.1016/0009-2614(96)00867-6 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VH100 UT WOS:A1996VH10000050 ER PT J AU Schoeberl, MR Douglass, AR Kawa, SR Dessler, AE Newman, PA Stolarski, RS Roche, AE Waters, JW Russell, JM AF Schoeberl, MR Douglass, AR Kawa, SR Dessler, AE Newman, PA Stolarski, RS Roche, AE Waters, JW Russell, JM TI Development of the Antarctic ozone hole SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC POLAR VORTEX; REACTIVE NITROGEN; CLOUD PARTICLES; LATE WINTER; UARS DATA; CHLORINE; EVOLUTION; CLONO2; HCL; MLS AB A Lagrangian chemical model is used to simulate the formation of the Antarctic ''ozone hole'': the decrease in high-latitude southern hemisphere ozone between mid-August and mid-September of each year. The model benchmark simulation of HNO3, ClONO2, ClO, and ozone for September 17, 1992, is in good agreement with UARS observations. Simulations of the ozone column over the years 1979-1994 show quantitative agreement with the secular decline in Antarctic ozone and change in the area of the ozone hole as observed by the total ozone mapping spectrometer (TOMS). The model calculates that the Antarctic ozone loss and ozone hole area both increased linearly with time after the early 1970s until the early 1990s. After the early 1990s the growth of the area of the ozone hole slows as a result of the slowing of the growth rate of total inorganic chlorine. A hypothetical doubling of the 1992 atmospheric chlorine amount would expand the ozone hole to the very edge of the polar vortex. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. LOCKHEED PALO ALTO RES LABS, PALO ALTO, CA USA. RP Schoeberl, MR (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 916, GREENBELT, MD 20771 USA. RI Newman, Paul/D-6208-2012; Douglass, Anne/D-4655-2012; Kawa, Stephan/E-9040-2012; Stolarski, Richard/B-8499-2013; Dessler, Andrew/G-8852-2012 OI Newman, Paul/0000-0003-1139-2508; Stolarski, Richard/0000-0001-8722-4012; Dessler, Andrew/0000-0003-3939-4820 NR 55 TC 14 Z9 14 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1996 VL 101 IS D15 BP 20909 EP 20924 DI 10.1029/96JD01707 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VJ677 UT WOS:A1996VJ67700001 ER PT J AU Stewart, RW Thompson, AM AF Stewart, RW Thompson, AM TI Kinetic data imprecisions in photochemical rate calculations: Means, medians, and temperature dependence SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MODEL; SENSITIVITY; TROPOSPHERE; CLOUDS AB The uncertainty in computed species concentrations resulting from measurement imprecision in reaction rate components is investigated in two tropospheric photochemical models. In this study, which extends Thompson nod Stewart [1991], we perform statistical analysis on reaction rate coefficients to focus on two aspects of model uncertainty: (1) the change in the magnitude of concentration;uncertainty as temperature varies throughout a model grid and (2) the difference resulting from selection of mean, as opposed to median, rates for model calculations. Reaction rates are treated as realizations of random variables having statistical properties given by component terms and their imprecisions. These assumptions lead to expressions for probability distributions of bimolecular rates and for the high- and low-pressure limits for termolecular and thermolytic processes. They also imply that bimolecular rates and high- and low-pressure limits used in photochemical models correspond to median values taken from a lognormal distribution. We derive analytic expressions for mean values, which are always larger than the medians, an intrinsic property of lognormal variables. We suggest that comparison of species concentrations computed using median and mean rates tan provide some measure of the effect of rate imprecision in multidimensional models. We also find that the temperature dependence derived for the imprecision in bimolecular rates differs from that given in standard references, with our expression giving a smaller increase in imprecision as temperatures deviate from 298 K. Results are illustrated using a box and a one-dimensional (1-D) model. RP Stewart, RW (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 916, GREENBELT, MD 20771 USA. RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 20 TC 19 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1996 VL 101 IS D15 BP 20953 EP 20964 DI 10.1029/96JD01708 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VJ677 UT WOS:A1996VJ67700005 ER PT J AU Weaver, CJ Douglass, AR Considine, DB AF Weaver, CJ Douglass, AR Considine, DB TI A 5-year simulation of supersonic aircraft emission transport using a three-dimensional model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TRACER AB A 5-year simulation of supersonic aircraft exhaust using a three-dimensional transport model has been completed using winds from the NASA/Goddard data assimilation system. A tracer based on emission rates of reactive nitrogen species (NOy) for all forecasted night routes is continuously injected into the model. A parameterized upper stratospheric loss mechanism and a tropospheric sink due to rainout approximately balance the nitrogen emissions after several years of integration. Maximum values for exhaust NOy occur during the northern hemisphere (NH) summer months, and minimum values occur during winter. The pollutant is most zonally asymmetric during the NH summer. The peak values are never more than twice the zonal mean. This supports the use of zonally averaged two-dimensional models to evaluate the impact of the exhaust on the lower stratospheric composition. Budget calculations from the transport model show that most exhaust released in the NH is transported downward into the troposphere, where it is destroyed. In the model, about 15-20% of exhaust released poleward of 30 degrees N is transported into the tropics, where it is lofted. The stratospheric residence time for the exhaust is estimated to be 13 months. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP Weaver, CJ (reprint author), APPL RES CORP, 8201 CORP DR, LANDOVER, MD 20785 USA. RI Douglass, Anne/D-4655-2012 NR 21 TC 10 Z9 10 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1996 VL 101 IS D15 BP 20975 EP 20984 DI 10.1029/96JD01700 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VJ677 UT WOS:A1996VJ67700007 ER PT J AU McKay, DS Gibson, EK ThomasKeprta, KL AF McKay, DS Gibson, EK ThomasKeprta, KL TI Past life on Mars? Response SO SCIENCE LA English DT Letter C1 LOCKHEED MARTIN,HOUSTON,TX 77058. RP McKay, DS (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,MAIL CODE SN,HOUSTON,TX 77058, USA. NR 3 TC 1 Z9 1 U1 0 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD SEP 20 PY 1996 VL 273 IS 5282 BP 1640 EP 1640 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VH408 UT WOS:A1996VH40800005 ER PT J AU Gonzalez, WD Tsurutani, BT McIntosh, PS deGonzalez, AL AF Gonzalez, WD Tsurutani, BT McIntosh, PS deGonzalez, AL TI Coronal Hole Active Region Current Sheet (CHARCS) association with intense interplanetary and geomagnetic activity SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAJOR MAGNETIC STORMS; MASS EJECTIONS; DISTURBANCES AB Intense geomagnetic storms (Dst less than or equal to -100 nT) have been associated with interplanetary structures involving large-intensity (B-s greater than or equal to 10 nT) and long-duration (T greater than or equal to 3 hours) values of the southward cam component of the IMF. We show that near solar maximum, the solar origin of such structures seems to be associated with active regions* (involving flares and/ or filament eruptions) occurring close to the streamer belt and to growing low-latitude coronal holes. It is also shown that low-latitude coronal holes had a dual-peak solar cycle distribution during solar cycle 21, similar to that previously reported for the above mentioned interplanetary and geomagnetic phenomena. C1 NOAA, SPACE ENVIRONM LAB, BOULDER, CO 80303 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Gonzalez, WD (reprint author), INPE, CP 515, BR-12201970 SAO JOSE DOS CAMPOS, SP, BRAZIL. NR 16 TC 40 Z9 40 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 SEP 15 PY 1996 VL 23 IS 19 BP 2577 EP 2580 DI 10.1029/96GL02393 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VH169 UT WOS:A1996VH16900001 ER PT J AU Lienesch, JH Planet, WG DeLand, MT Laamann, K Cebula, RP Hilsenrath, E Horvath, K AF Lienesch, JH Planet, WG DeLand, MT Laamann, K Cebula, RP Hilsenrath, E Horvath, K TI Validation of NOAA-9 SBUV/2 total ozone measurements during the 1994 Antarctic ozone hole SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR BACKSCATTER ULTRAVIOLET; INSTRUMENT AB The Solar Backscatter Ultraviolet (SBUV/2) instrument on the NOAA-9 spacecraft made total ozone measurements over Antarctica during the 1994 Austral Spring depletion. These measurements continue those made by the SBUV/2 on NOAA-11. In recent years NOAA-9 drifted from a poor orbit to one where earth observations and calibration capabilities are not restricted. An interim calibration of the NOAA-9 SBUV/2 instrument was established with data from June 1994 and applied to observations during September, October, and November 1994. To validate the NOAA-9 ozone measurements, daily zonal ozone averages from NOAA-9 and NOAA-11 measurements in the Northern Hemisphere have been compared. Comparisons have also been made with ground-based measurements from five Dobson stations dispersed on the Antarctic continent. The results show that, on average, the NOAA-9 data agree to within 1-2 percent with the Dobson stations with standard deviations of the difference ranging from 5.3 to 7.7% and to within several percent with NOAA-11 Northern Hemisphere data when restricted to solar zenith angles less than 80 degrees. This agreement makes possible not only a continuation of the Antarctic measurements without a large instrument-related bias, but also establishes the NOAA-9 data as a suitable transition data set during the replacement of NOAA-11 by NOAA-14. C1 HUGHES STX CORP,GREENBELT,MD 20770. GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. RES & DATA SYST CORP,RDC,GREENBELT,MD 20770. NOAA,NATL ENVIRONM SATELLITE DATA & INFORMAT SERV,CAMP SPRINGS,MD. NR 13 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 15 PY 1996 VL 23 IS 19 BP 2593 EP 2596 DI 10.1029/96GL02417 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VH169 UT WOS:A1996VH16900005 ER PT J AU Ruzmaikin, AA AF Ruzmaikin, AA TI Redistribution of magnetic helicity at the sun SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FIELDS; RECONNECTION; EJECTION AB Evolution of magnetic loops associated with filaments and coronal mass ejections involves a redistribution of solar magnetic helicity. Two mechanisms of the helicity redistribution are discussed. The first one involves magnetic reconnections among magnetic loops and can introduce helicity into an erupting magnetic field accompanied with an encapture of helicity by the Sun. The second one involves the MHD helicity redistribution in the Sun and indicates that the magnetic helicity of each hemisphere of the Sun oscillates about a mean with the half-period of the solar cycle (11 years), but does not change sign from one 11 year period to the next. RP Ruzmaikin, AA (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 18 TC 14 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 15 PY 1996 VL 23 IS 19 BP 2649 EP 2652 DI 10.1029/96GL02391 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VH169 UT WOS:A1996VH16900019 ER PT J AU Song, NH Starr, DO Wuebbles, DJ Williams, A Larson, SM AF Song, NH Starr, DO Wuebbles, DJ Williams, A Larson, SM TI Volcanic aerosols and interannual variation of high clouds SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MOUNT-PINATUBO ERUPTION; STRATOSPHERIC AEROSOL; OPTICAL-PROPERTIES; II MEASUREMENTS; SAGE-II; CIRRUS AB Interannual variability of high-level cloudiness (HC) is examined using global outgoing longwave radiation (OLR). Variations of HC are analyzed versus a measure of global stratospheric aerosol amount and an El Nine index. Volcanic aerosols are apparently associated with widespread increases of up to 10% in an OLR-based HC index. The most significant effects occurred in middle latitudes and persisted for several years after major eruptions. El Nine is found to be associated with decreased cloud activity in the subtropics. This study suggests that volcanic aerosols can significantly modify global cloudiness, and that stratospheric aerosol loading can be an important variable controlling the interannual variations of high level clouds and climate. C1 UNIV ILLINOIS,DEPT ATMOSPHER SCI,URBANA,IL 61801. ILLINOIS STATE WATER SURVEY,CHAMPAIGN,IL 61820. UNIV ILLINOIS,DEPT CIVIL ENGN,URBANA,IL 61801. UNIV SEABROOK,SPACE RES ASSOC,SEABROOK,MD. RP Song, NH (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CLIMATE & RADIAT BRANCH,CODE 913,GREENBELT,MD 20771, USA. NR 24 TC 19 Z9 19 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 15 PY 1996 VL 23 IS 19 BP 2657 EP 2660 DI 10.1029/96GL02372 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VH169 UT WOS:A1996VH16900021 ER PT J AU Yeh, C Bergman, L AF Yeh, C Bergman, L TI Pulse shepherding in nonlinear fiber optics SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID SOLITONS; TRANSMISSION; DISPERSION; WAVEGUIDES; STABILITY AB In a wavelength division multiplexed fiber system, where pulses on different wavelength beams may copropagate in a single mode fiber, the cross-phase-modulation (CPM) effects caused by the nonlinearity of the optical fiber are unavoidable. In other words, pulses on different wavelength beams can interact with and affect each other through the intensity dependence of the refractive index of the fiber. Although CPM will not cause energy to be exchanged among the beams, the pulse shapes and locations on these beams can be altered significantly. This phenomenon makes possible the manipulation and control of pulses copropagating on different wavelength beams through the introduction of a shepherd pulse at a separate wavelength. How this can be accomplished is demonstrated in this paper. (C) 1996 American Institute of Physics. RP Yeh, C (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 525-3660,PASADENA,CA 91109, USA. NR 27 TC 15 Z9 15 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD SEP 15 PY 1996 VL 80 IS 6 BP 3174 EP 3178 DI 10.1063/1.363256 PG 5 WC Physics, Applied SC Physics GA VG681 UT WOS:A1996VG68100006 ER PT J AU Chen, H Tong, J Hu, Z Shi, DT Wu, GH Chen, KT George, MA Collins, WE Burger, A James, RB Stahle, CM Bartlett, LM AF Chen, H Tong, J Hu, Z Shi, DT Wu, GH Chen, KT George, MA Collins, WE Burger, A James, RB Stahle, CM Bartlett, LM TI Low-temperature photoluminescence of detector grade Cd1-xZnxTe crystal treated by different chemical etchants SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID BULK AB Low-temperature photoluminescence (PL) spectra of detector grade Cd1-xZnxTe (x=0.1) have been measured to obtain information about shallow level defect concentration introduced during mechanical polishing and chemical etching processes. We present here a comparative PL study of Cd0.9Zn0.1Te crystals treated by different chemical solutions used for nuclear detector surface treatment. The results show that the 5% Br-MeOH+2%Br-20% lactic acid in ethylene glycol treatment combines the advantages of bromine and lactic acid for chemical etching and results in the best surface condition, as evidenced by the largest I(D-0,X)/I-def intensity ratio and the narrowest full width at half-maximum of the main peak (D-0,X). Changes in the surface morphology were also analyzed by atomic force microscopy and correlated with the PL results. Current-voltage (I-V) curves and the room-temperature Fe-55 spectral response of the sample etched by the best treatment are also presented and discussed. (C) 1996 American Institute of Physics. C1 SANDIA NATL LABS,ADV ELECT MFG TECHNOL DEPT,LIVERMORE,CA 94550. NASA,GODDARD SPACE FLIGHT CTR,OSC,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,NRC,GREENBELT,MD 20771. RP Chen, H (reprint author), FISK UNIV,CTR PHOTON MAT & DEVICES,DEPT PHYS,NASHVILLE,TN 37208, USA. RI Hu, Zhiyu/J-7742-2013 NR 18 TC 60 Z9 69 U1 2 U2 6 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD SEP 15 PY 1996 VL 80 IS 6 BP 3509 EP 3512 DI 10.1063/1.363222 PG 4 WC Physics, Applied SC Physics GA VG681 UT WOS:A1996VG68100058 ER PT J AU Tao, WK Lang, S Simpson, J Sui, CH Ferrier, B Chou, MD AF Tao, WK Lang, S Simpson, J Sui, CH Ferrier, B Chou, MD TI Mechanisms of cloud-radiation interaction in the tropics and midlatitudes SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MESOSCALE CONVECTIVE SYSTEM; BULK ICE SCHEME; SOLAR-RADIATION; SQUALL-LINE; CIRRUS CLOUDS; PARAMETERIZATION SCHEMES; ATMOSPHERIC ABSORPTION; NUMERICAL SIMULATIONS; STRATOCUMULUS CLOUDS; MACROSCOPIC BEHAVIOR AB Radiative forcing and latent heat associated with precipitation are the two most important diabatic processes that drive the circulation of the atmosphere. Clouds can affect radiation and vice versa. It is known that longwave radiative processes can enhance precipitation in cloud systems. This paper concentrates on determining the relative importance of three specific longwave radiative mechanisms by comparing cloud-resolving models with and without one or more of these processes. Three of the ways that longwave radiation is thought to interact with clouds are as follows: 1) cloud-top cooling and cloud-base warming may alter the thermal stratification of cloud layers, 2) differential cooling between clear and cloudy regions might enhance convergence into the cloud system, and 3) large-scale cooling could change the environment. A two-dimensional version of the Goddard Cumulus Ensemble model has been used to perform a series of sensitivity tests to identify which is the dominant cloud-radiative forcing mechanism with respect to the organization, structure, and precipitation processes for both a tropical (EMEX) and a midlatitude (PRE-STORM) mesoscale convective system. The model results indicate that the dominant process for enhancing the surface precipitation in both the PRE-STORM and EMEX squall cases is the large-scale radiative cooling. However, the overall effect is really to increase the relative humidity and not the convective available potential energy (CAFE). Because of the high moisture in the Tropics, the increase in relative humidity by radiative cooling can have more of an impact on precipitation in the tropical case than in the midlatitude case. The large-scale cooling led to a 36% increase in rainfall for the tropical case. The midlatitude model squall with a higher CAFE and lower humidity environment was only slightly affected (8%) by any of the longwave mechanisms. Our results also indicated that the squall systems' overall (convective and stratiform) precipitation is increased by turning off the cloud-top cooling and cloud-base warming. Therefore, the cloud-rep cooling-cloud-base warming mechanism was not the responsible cloud-radiative mechanism for enhancing the surface precipitation. However, the circulation as well as the microphysical processes were indeed (slightly) enhanced in the stratiform region by the cloud-top cooling and cloud-base warming mechanism for the midlatitude squall case. For both cases, the model results show that the mechanism associated with differential cooling between the clear and cloudy regions may or may not enhance precipitation processes. However, this mechanism is definitely less important than the large-scale longwave radiative cooling. Solar heating was run from 0900 to 1300 LST in both environments and was found to decrease the precipitation by 7% in each case compared to the runs with longwave radiation only. This result suggests that solar heating may play a significant role in the daytime minimum/nighttime maximum precipitation cycle found over most oceans. C1 SCI SYST & APPLICAT INC,LANHAM,MD. RP Tao, WK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,MESOSCALE ATMOSPHER PROC BRANCH,LAB ATMOSPHERES,CODE 912,GREENBELT,MD 20771, USA. OI SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 74 TC 133 Z9 142 U1 2 U2 10 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD SEP 15 PY 1996 VL 53 IS 18 BP 2624 EP 2651 DI 10.1175/1520-0469(1996)053<2624:MOCRII>2.0.CO;2 PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VK779 UT WOS:A1996VK77900006 ER PT J AU Lopez, R Riera, A Raga, AC Anglada, G Lopez, JA NoriegaCrespo, A Estalella, R AF Lopez, R Riera, A Raga, AC Anglada, G Lopez, JA NoriegaCrespo, A Estalella, R TI The complex kinematical properties of the HH objects aligned with the HL Tauri and HH 30 outflows SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE ISM, individual, HL Tauri; ISM, individual, HH 30; ISM, individual, HH 266; ISM, jets and outflows; ISM, kinematics and dynamics ID HERBIG-HARO OBJECTS; YOUNG STARS; JET; REGION; MOTIONS AB In a previous paper we reported the detection of emission regions which might correspond to the heads of the HL Tauri and HH 30 jets. We now present preliminary proper motion measurements which appear to confirm these identifications. However, we also find that the possible head of the HH 30 jet has a radial velocity of similar or equal to -80 km s(-1), which is in clear disagreement with the low (similar or equal to + 18 km s(-1)) radial velocity which has been measured for the jet. This result might imply that the jet not only has a change of direction of 14 in the plane of the sky (which is implied by the proper motion measurements), but is also curving towards us by an angle of similar or equal to 22 degrees. C1 UNIV POLITECN CATALUNYA,DEPT FIS & ENGN NUCL,E-08000 VILANOVA I GELTRU,BARCELONA,SPAIN. UNIV NACL AUTONOMA MEXICO,INST ASTRON,MEXICO CITY 04510,DF,MEXICO. UNIV NACL AUTONOMA MEXICO,INST ASTRON,ENSENADA 22800,BAJA CALIFORNIA,MEXICO. CALTECH,JET PROP LAB,IPAC,PASADENA,CA 91125. RP Lopez, R (reprint author), DEPT ASTRON & METEOROL,AV DIAGONAL 647,E-08028 BARCELONA,SPAIN. NR 14 TC 16 Z9 16 U1 1 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 15 PY 1996 VL 282 IS 2 BP 470 EP & PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ094 UT WOS:A1996VJ09400014 ER PT J AU Vanlandingham, KM Starrfield, S Wagner, RM Shore, SN Sonneborn, G AF Vanlandingham, KM Starrfield, S Wagner, RM Shore, SN Sonneborn, G TI Optical and ultraviolet spectrophotometry of the ONeMg nova V838 Herculis 1991 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars, individual, nova Herculis 1991; novae, cataclysmic variables; ultraviolet, stars ID INFRARED PHOTOMETRY; SPECTRAL EVOLUTION; DISTANCE SCALE; WHITE-DWARF; NOVA-HERCULIS-1991; SPECTROSCOPY; ABUNDANCES; ACCRETION; OUTBURST; EJECTA AB We present an analysis of-optical and UV spectra of the fast nova V838 Herculis 1991. IUE observations began on 1991 March 25 and continued through 1991 August 20, while optical observations began on 1991 March 29 and continued through 1991 August 20. We determine a value for the reddening of E(B-V)similar to 0.5+/-0.1 and a distance of similar to 3+/-1 kpc based both on our own observations and on those of other groups. This nova was remarkable in being both fast and optically thick in the UV at maximum light. Our spectra show strong lines of helium, neon, sulphur and nitrogen. In contrast, oxygen lines were never present in our UV spectra and very weak in our optical spectra. We use a new optimization method to perform an abundance analysis of the spectra, and find that carbon, nitrogen, neon, silicon and sulphur are overabundant with respect to solar material by factors ranging from 5 to 37, while helium and oxygen are both underabundant by a factor of 0.3. Our best model is obtained with a luminosity for the central source of 5.1 x 10(36) erg s(-1), indicating that this nova may have turned off by two months after outburst. We also find an ejected mass for this nova of M(ej) similar to 1.8 x 10(-4) M(.). Based on both the characteristics of the outburst and our observed abundances, we suggest that this outburst occurred on a very massive ONeMg white dwarf. C1 OHIO STATE UNIV, DEPT ASTRON, COLUMBUS, OH 43210 USA. INDIANA UNIV, DEPT PHYS & ASTRON, S BEND, IN 46634 USA. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. RP Vanlandingham, KM (reprint author), ARIZONA STATE UNIV, DEPT PHYS & ASTRON, TEMPE, AZ 85287 USA. NR 47 TC 39 Z9 39 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 15 PY 1996 VL 282 IS 2 BP 563 EP 579 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ094 UT WOS:A1996VJ09400021 ER PT J AU Larwood, JD Nelson, RP Papaloizou, JCB Terquem, C AF Larwood, JD Nelson, RP Papaloizou, JCB Terquem, C TI The tidally induced warping, precession and truncation of accretion discs in binary systems: Three-dimensional simulations SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; binaries, close; binaries, general; stars, pre-main-sequence ID SMOOTHED PARTICLE HYDRODYNAMICS; DISKS; STARS; DYNAMICS; ORIGIN; SHOCKS AB We present the results of non-linear, hydrodynamic simulations, in three dimensions, of the tidal perturbation of accretion discs in binary systems where the orbit is circular and not necessarily coplanar with the disc mid-plane. The accretion discs are assumed to be geometrically thin, and of low mass relative to the stellar mass so that they are governed by thermal pressure and viscosity, but not self-gravity. The parameters that we consider in our models are the ratio of the orbital distance to the disc radius, D/R, the binary mass ratio, M(s)/M(p), the initial inclination angle between the orbit and disc planes, delta, and the Mach number in the outer parts of the unperturbed disc, M. Since we consider non-self-gravitating discs, these calculations are relevant to protostellar binaries with separations below a few hundred au. For binary mass ratios of around unity and D/R in the range 3 to 4, we find that the global evolution of the discs is governed primarily by the value of M. For relatively low Mach numbers (i.e. M = 10 to 20) we find that the discs develop a mildly warped structure, are tidally truncated, and undergo a near rigid body precession at a rate which is in close agreement with analytical arguments. For higher Mach numbers (M approximate to 30), the evolution is towards a considerably more warped structure, but the disc none the less maintains itself as a long-lived, coherent entity. A further increase in Mach number to M = 50 leads to a dramatic disruption of the disc as a result of differential precession, since the sound speed is too low to allow efficient communication between constituent parts of the disc. Additionally, it is found that the inclination angle between the disc and the orbital angular momentum vectors evolves on a longer time-scale, which is probably the viscous evolution time-scale of the disc. The calculations are relevant to a number of observed astrophysical phenomena, including the precession of-jets associated with young stars, the high spectral index of some T Tauri stars, and the light curves of X-ray binaries such as Hercules X-1 which suggest the presence of precessing accretion discs. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV GRENOBLE 1,CNRS,OBSERV GRENOBLE,ASTROPHYS LAB,F-38041 GRENOBLE,FRANCE. RP Larwood, JD (reprint author), UNIV LONDON QUEEN MARY & WESTFIELD COLL,ASTRON UNIT,SCH MATH SCI,MILE END RD,LONDON E1 4NS,ENGLAND. NR 33 TC 126 Z9 126 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 15 PY 1996 VL 282 IS 2 BP 597 EP 613 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ094 UT WOS:A1996VJ09400024 ER PT J AU Gondek, D Zdziarski, AA Johnson, WN George, IM McNaronBrown, K Magdziarz, P Smith, D Gruber, DE AF Gondek, D Zdziarski, AA Johnson, WN George, IM McNaronBrown, K Magdziarz, P Smith, D Gruber, DE TI The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; galaxies, active; galaxies, Seyfert; gamma-rays, observations; gamma-rays, theory; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; PAIR PRODUCTION; COLD MATTER; BLACK-HOLE; COMPTON-SCATTERING; PHYSICAL PROCESSES; ACCRETION DISKS; COMPACT SOURCES; EMISSION; GALAXIES AB We have obtained the average 1-500 keV spectrum of radio-quiet Seyfert Is using data from EXOSAT, Ginga, HEAO-1 and GRO OSSE. The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample. The average spectrum is well fitted by a power-law X-ray continuum with an energy spectral index of alpha similar or equal to 0.9 moderately absorbed by an ionized medium and with a Compton reflection component. A high-energy cut-off (or a break) in the power-law component at a few hundred keV or more is required by the data. We also show that the corresponding average spectrum from HEAO-1 A1 and A4 is fully compatible with that obtained from EXOSAT, Ginga and OSSE. These results confirm that the apparent discrepancy between the results of Ginga (with alpha similar or equal to 0.9) and the previous results of EXOSAT and HEAO-1 (with alpha similar or equal to 0.7) is indeed due to ionized absorption and Compton reflection first taken into account for Ginga but not for the previous missions. Also, our results confirm that the Seyfert 1 spectra are on average cut off in gamma-rays at energies of at least a few hundred keV, not at similar to 40 keV (as suggested earlier by OSSE data alone). The average spectrum is compatible either with emission from an optically thin relativistic thermal plasma in a disc corona, or with a non-thermal plasma with a power-law injection of relativistic electrons. C1 UNIV CALIF SANTA BARBARA, INST THEORET PHYS, SANTA BARBARA, CA 93106 USA. USN, RES LAB, EO HULBURT CTR SPACE RES, WASHINGTON, DC 20375 USA. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY PHYS LAB, GREENBELT, MD 20771 USA. UNIV SPACE RES ASSOC, TUCSON, AZ USA. GEORGE MASON UNIV, FAIRFAX, VA 22030 USA. JAGIELLONIAN UNIV, ASTRON OBSERV, PL-30244 KRAKOW, POLAND. UNIV LEICESTER, DEPT PHYS, LEICESTER LE1 7RH, LEICS, ENGLAND. UNIV CALIF SAN DIEGO, CTR ASTROPHYS & SPACE SCI, LA JOLLA, CA 92093 USA. RP Gondek, D (reprint author), NICHOLAS COPERNICUS ASTRON CTR, BARTYCKA 18, PL-00716 WARSAW, POLAND. RI Johnson, Neil/G-3309-2014 NR 49 TC 76 Z9 76 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 15 PY 1996 VL 282 IS 2 BP 646 EP 652 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VJ094 UT WOS:A1996VJ09400029 ER PT J AU Zypman, F Ferrante, J AF Zypman, F Ferrante, J TI Impurity induced correction to the embedded atom method embedding function SO PHYSICA A LA English DT Article; Proceedings Paper CT Workshop on Colloid and Interface Science - Trends and Applications, on the Occasion of the Celebration of the 60th Birthday of Sow-Hsin Chen CY MAY 02-05, 1995 CL GUANICA, PR SP ES, PSCoR NSF, USN, Off Naval Res ID TRANSITION-METALS; SURFACE ENERGIES; FCC METALS; HYDROGEN; ALLOYS; MODEL; NI; CU AB In this paper, an atomic impurity embedding function, F-imp, for the embedded atom method (EAM) is proposed. The existence of an F for impurity atoms different from the one for bulk atoms stems from the fact that the presence of defects modifies the energy band structure of the solid. In order to study this change, we used the tight binding method, which provides the ingredients to obtain an explicit expression for the relevant quantities. By comparing the energies of EAM and tight binding for a bulk with an impurity, we obtain a correction to the EAM embedding function and the EAM energy for the system. C1 PEDECIBA,MONTEVIDEO,URUGUAY. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Zypman, F (reprint author), UNIV PUERTO RICO,DEPT PHYS,HUMACAO,PR 00791, USA. NR 16 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0378-4371 J9 PHYSICA A JI Physica A PD SEP 15 PY 1996 VL 231 IS 1-3 BP 337 EP 345 DI 10.1016/0378-4371(95)00459-9 PG 9 WC Physics, Multidisciplinary SC Physics GA VH367 UT WOS:A1996VH36700030 ER PT J AU Kolb, EW Riotto, A AF Kolb, EW Riotto, A TI Eternal annihilations of light photinos SO PHYSICAL REVIEW D LA English DT Article ID BIG-BANG NUCLEOSYNTHESIS; DARK-MATTER; PARTICLES; CONSTRAINTS; ABUNDANCE; DEUTERIUM; ELEMENTS; UNIVERSE AB In a class of low-energy supersymmetry models the photino is a natural dark-matter candidate. We investigate the effects of post-freeze-out photino annihilations that generate electromagnetic cascades and lead to photodestruction of He-4 and subsequent overproduction of D and He-3. We also generalize our analysis of electromagnetic showers to include those from a generic dark-matter component whose relic abundance is not determined by the self-annihilation cross section. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RP Kolb, EW (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510, USA. NR 31 TC 4 Z9 4 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 SEP 15 PY 1996 VL 54 IS 6 BP 3722 EP 3726 DI 10.1103/PhysRevD.54.3722 PG 5 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA VK631 UT WOS:A1996VK63100007 ER PT J AU Ahmed, SM Kanik, I Link, R AF Ahmed, SM Kanik, I Link, R TI Temperature-dependent photoabsorption cross section measurements of O-2 at the OI-1304 angstrom triplet emission lines SO CHEMICAL PHYSICS LETTERS LA English DT Article ID DAYGLOW; MOLECULES; OXYGEN AB We report the first temperature-dependent measurements (at 295, 373, 473, and 573 K) of the O-2 photoabsorption cross sections at the aeronomically-important OI-1304 Angstrom triplet emission lines. A high current, low voltage argon mini-are source was used as the light source. The measurements were carried out at a spectral resolution of 0.5 Angstrom at full-width-at-half-maximum (FWHM). Direct application of the Beer-Lambert absorption equation yielded the absolute photoabsorption cross sections for O-2 at each line of the OI triplet. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. SW RES INST,SAN ANTONIO,TX 78228. NR 21 TC 3 Z9 3 U1 1 U2 3 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 SEP 13 PY 1996 VL 259 IS 5-6 BP 545 EP 553 DI 10.1016/0009-2614(96)00783-X PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VG765 UT WOS:A1996VG76500012 ER PT J AU Alagia, M Balucani, N Cartechini, L Casavecchia, P vanKleef, EH Volpi, GG Aoiz, FJ Banares, L Schwenke, DW Allison, TC Mielke, SL Truhlar, DG AF Alagia, M Balucani, N Cartechini, L Casavecchia, P vanKleef, EH Volpi, GG Aoiz, FJ Banares, L Schwenke, DW Allison, TC Mielke, SL Truhlar, DG TI Dynamics of the simplest chlorine atom reaction: An experimental and theoretical study SO SCIENCE LA English DT Article ID POTENTIAL-ENERGY SURFACES; DIFFERENTIAL CROSS-SECTIONS; H+D-2->HD+D REACTION; TRANSITION-STATE; RATE COEFFICIENT; 4-ATOM REACTIONS; HYDROGEN SYSTEM; MOLECULAR-BEAM; RATE CONSTANTS; H+D2 REACTION AB Angular distributions and time-of-flight spectra for the reaction Cl + H-2 --> HCl + H obtained from a high-resolution, crossed-molecular beam experiment were compared to differential cross sections calculated by both converged quantum mechanical scattering and quasi-classical trajectory methods. Good agreement was found between the experimental results and each theoretical prediction. The results demonstrate that excellent agreement can be obtained between state-of-the-art simulations and experiments for the detailed dynamical properties of this prototype chlorine atom reaction. C1 UNIV PERUGIA,DIPARTIMENTO CHIM,I-06100 PERUGIA,ITALY. UNIV COMPLUTENSE,FAC QUIM,DEPT QUIM FIS,E-28040 MADRID,SPAIN. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV MINNESOTA,DEPT CHEM,CHEM PHYS PROGRAM,MINNEAPOLIS,MN 55455. UNIV MINNESOTA,INST SUPERCOMP,MINNEAPOLIS,MN 55455. RI Cartechini, Laura/C-6067-2009; Alagia, Michele/C-9405-2012; Balucani, Nadia/B-8211-2011; Mielke, Steven/B-7533-2008; Banares, Luis/B-7922-2014; Casavecchia, Piergiorgio/F-4175-2014; schwenke, david/I-3564-2013; Aoiz, F. Javier/G-8240-2015; Truhlar, Donald/G-7076-2015 OI Cartechini, Laura/0000-0001-9834-0801; Alagia, Michele/0000-0002-8467-1842; Balucani, Nadia/0000-0001-5121-5683; Mielke, Steven/0000-0002-1938-7503; Banares, Luis/0000-0002-0777-2375; Casavecchia, Piergiorgio/0000-0003-1934-7891; Aoiz, F. Javier/0000-0001-5718-5905; Truhlar, Donald/0000-0002-7742-7294 NR 65 TC 95 Z9 95 U1 2 U2 23 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD SEP 13 PY 1996 VL 273 IS 5281 BP 1519 EP 1522 DI 10.1126/science.273.5281.1519 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VG597 UT WOS:A1996VG59700030 ER PT J AU Perry, JW Mansour, K Lee, IYS Wu, XL Bedworth, PV Chen, CT Ng, D Marder, SR Miles, P Wada, T Tian, M Sasabe, H AF Perry, JW Mansour, K Lee, IYS Wu, XL Bedworth, PV Chen, CT Ng, D Marder, SR Miles, P Wada, T Tian, M Sasabe, H TI Organic optical limiter with a strong nonlinear absorptive response SO SCIENCE LA English DT Article ID PHTHALOCYANINES; SEMICONDUCTORS; SILICON; C-60 AB Molecules with weak ground-state absorption that form strongly absorbing excited states can be used in optical limiters, which can protect sensors or human eyes from optical damage. Phthalocyanine complexes bearing heavy atoms or paramagnetic groups or in solvents containing heavy atoms show optical limiting enhanced by excited tripler-state absorption. A nonhomogeneous distribution of indium tetra(tert-butyl)phthalocyanine chloride along the beam path substantially enhances the excited-state absorption, yielding an optical limiter with a linear transmittance of 0.70 that can attenuate 8-nanosecond, 532-nanometer laser pulses by factors of up to 540. C1 CALTECH,BECKMAN INST,PASADENA,CA 91125. INST PHYS & CHEM RES,FRONTIER RES PROGRAM,LAB NANOPHOTON MAT,WAKO,SAITAMA 35101,JAPAN. RP Perry, JW (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Perry, Joseph/B-7191-2011; Chen, Chin-Ti/E-5341-2015 OI Perry, Joseph/0000-0003-1101-7337; NR 23 TC 642 Z9 675 U1 7 U2 59 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD SEP 13 PY 1996 VL 273 IS 5281 BP 1533 EP 1536 DI 10.1126/science.273.5281.1533 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VG597 UT WOS:A1996VG59700035 ER PT J AU Young, K Scargle, JD AF Young, K Scargle, JD TI The dripping handrail model: Transient chaos in accretion systems SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretions, accretion disks; binaries, close; galaxies, active; pulsars, general; X-rays, stars ID QUASI-PERIODIC OSCILLATIONS; RAY PULSAR EXO-2030+375; LUMINOSITY DEPENDENCE; INTERMITTENCY; TURBULENCE; NOISE AB We define and study a simple dynamical model for accretion systems, the ''dripping handrail'' (DHR). The time evolution of this spatially extended system is a mixture of periodic and apparently random (but actually deterministic) behavior. The nature of this mixture depends on the values of its physical parameters-the accretion rate, diffusion coefficient, and density threshold. The aperiodic component is a special kind of deterministic chaos called transient chaos. The model can simultaneously exhibit both the quasi-periodic oscillations and very low frequency noise that characterize the power spectra of fluctuations of several classes of accretion systems in astronomy. For this reason, our model may be relevant to many such astrophysical systems, including binary stars with accretion onto a compact object-white dwarf, neutron star, or black hole-as well as active galactic nuclei. We describe the systematics of the DHR's temporal behavior by exploring its physical parameter space using several diagnostics: power spectra, wavelet ''scalegrams,'' and Lyapunov exponents (which characterize the degree of chaos inherent in the time evolution of a system). In addition, we note that for large accretion rates, the DHR has periodic modes; the effective pulse shapes for these modes-evaluated by folding the time series at the known period-bear a resemblance to the similarly determined shapes for some X-ray pulsars. The pulsing observed in some of these systems may be such periodic-mode accretion and not be due to pure rotation as in the standard pulsar model. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. NR 30 TC 10 Z9 10 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP 617 EP & DI 10.1086/177720 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE596 UT WOS:A1996VE59600015 ER PT J AU Freudenreich, HT AF Freudenreich, HT TI The shape and color of the galactic disk SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; Galaxy, structure; infrared, ISM, continuum; ISM, structure ID ON SPIRAL GALAXIES; SURFACE PHOTOMETRY; 3-DIMENSIONAL DISTRIBUTION; INTERSTELLAR DUST; STELLAR DISK; MILKY-WAY; MODEL; LIGHT; MAGNITUDES; PARAMETERS AB A model of the old Galactic disk has been derived from the survey of the Diffuse Infrared Background Experiment (DIRBE) of the Cosmic Background Explorer at wavelengths of 1.25, 2.2, 3.5, and 4.9 pm. The model includes an exponential radial dependence and a sech(2) vertical dependence of the Galactic luminosity density and allows for a radial truncation of the disk and a global warping characterized by five parameters. A dust layer is also modeled to account for emission by dust as well as extinction. The fit of model to DIRBE surface brightness data is good. According to the model, if we are 8.5 kpc from the Galactic center, the Sun is 15.6 pc above the midplane of the disk, which has radial and vertical scale lengths of 2.64 and 0.333 kpc, respectively, and is warped in a way consistent with the H I layer. The disk is truncated at a radius of 12 kpc, but this may be only a lower limit if the vertical scale length increases outside the solar circle. There are no indications of a thick disk. RP Freudenreich, HT (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,CODE 6859,GREENBELT,MD 20771, USA. NR 48 TC 25 Z9 25 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP 663 EP & DI 10.1086/177724 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE596 UT WOS:A1996VE59600019 ER PT J AU Lizano, S Canto, J Garay, G Hollenbach, D AF Lizano, S Canto, J Garay, G Hollenbach, D TI Photoevaporated flows from H II regions SO ASTROPHYSICAL JOURNAL LA English DT Article DE H II regions; ISM, globules; ISM, jets and outflows; radio lines, ISM ID ORION-NEBULA; RECOMBINATION LINE; INTERSTELLAR CLOUDS; PHYSICAL-PROPERTIES; VLA OBSERVATIONS; MASSIVE STARS; AMMONIA; RESOLUTION; EVOLUTION; GLOBULES AB We model the dynamics of a fast, isothermal ionized stellar wind loaded with mass injected from photoevaporated globules surrounding the massive star. The effect of the mass injection is to produce a density profile such that the ionization front can be trapped for 10(5) yr, depending on the physical characteristics of the neutral globules inside the H II region. We find that for neutral globules with sizes R(g) similar to 0.01 pc, masses of M(g) similar to 1 M., and number densities N-g similar to 2 x 10(4) pc(-3), thought to be representative of globules in regions of massive star formation, the implied mean density and size of the mass-loaded regions of ionized gas are about 10(3)-10(4) cm(-3) and about 0.1 pc, respectively, similar to those of compact H II regions. Dust absorption of ionizing photons is important and decreases the densities of the mass-loaded winds with respect to their dust-free counterparts. Also, mass-loaded winds with dust evolve more slowly, since the dusty globules survive for longer times than the dust-free ones. Our models predict ionized hows with mass flow rates of M similar to 10(-5) to 10(-4) M. yr(-1). These ionized flows could be studied in radio recombination lines. Assuming N-g does not decline sharply with distance to the central star, the ionized flow will recombine after the characteristic ''Stromgren'' radius r(S) at which the ionizing photon rate goes to zero. Therefore, after this radius a neutral flow will accelerate adiabatically to a terminal velocity of v(HI) similar to 40 km s(-1). Neutral flows of this type could be searched for in the neutral hydrogen line at 21 cm in absorption against the continuum of the compact H II regions. C1 UNIV CHILE,DEPT ASTRON,SANTIAGO,CHILE. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Lizano, S (reprint author), UNIV NACL AUTONOMA MEXICO,INST ASTRON,APDO POSTAL 70-264,MEXICO CITY 04510,DF,MEXICO. RI Garay, Guido/H-8840-2013 OI Garay, Guido/0000-0003-1649-7958 NR 57 TC 42 Z9 42 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP 739 EP 748 DI 10.1086/177729 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE596 UT WOS:A1996VE59600024 ER PT J AU Kuiper, TBH Langer, WD Velusamy, T AF Kuiper, TBH Langer, WD Velusamy, T TI Evolutionary status of the pre-protostellar core L1498 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, clouds; ISM, individual (L1498); ISM, molecules; radio lines, ISM; stars, formation ID DENSE CORES; DARK CLOUDS; MOLECULAR CLOUD; NH3 OBSERVATIONS; PROTOSTARS; CHEMISTRY; COMPLEX; TMC-1; C3H2; CCS AB L1498 is a classic example of a dense cold pre-protostellar core. To study the evolutionary status, the structure, dynamics, and chemical properties of this core we have obtained high spatial and high spectral resolution observations of molecules tracing densities of 10(3)-10(5) cm. We observed CCS, NH3, C3H2, and HC7N with NASA's DSN 70 m antennas. We also present large-scale maps of (CO)-O-18 and (CO)-C-13 observed with the AT&T 7 m antenna. For the high spatial resolution maps of selected regions within the core we used the VLA for CCS at 22 GHz, and the Owens Valley Radio Observatory (OVRO) MMA for CCS at 94 GHz and CS (2-1). The 22 GHz CCS emission marks a high-density [n(H-2)>10(4) cm(-3)] core, which is elongated with a major axis along the SE-NW direction. NH, and C,H, emissions are located inside the boundary of the CCS emission. (CO)-O-18 emission traces a lower density gas extending beyond the CCS boundary. Along the major axis of the dense core, CCS, NH3 and C3H2 emission show evidence of limb brightening. The observations are consistent with a chemically differentiated onion-shell structure for the L1498 core, with NH3 in the inner and CCS in the outer parts of the core. The high angular resolution (9 ''-12 '') spectral line maps obtained by combining NASA Goldstone 70 m and VLA data resolve the CCS 22 GHz emission in the southeast and northwest boundaries into arclike enhancements, supporting the picture that CCS emission originates in a shell outside the NH3 emitting legion. Interferometric maps of CCS at 94 GHz and CS at 98 GHz show that their emitting regions contain several small-scale dense condensations. We suggest that the differences between the CCS, CS, C3H2, and NH3 emission are caused by a time-dependent effect as the core evolves slowly. We interpret the chemical and physical properties of L1498 in terms of a quasi-static (or slowly contracting) dense core in which the outer envelope is still growing. The growth rate of the core is determined by the density increase in the CCS shell resulting from the accretion of the outer low-density gas traced by (CO)-O-18. We conclude that L1498 could become unstable to rapid collapse to form a protostar in less than 5 x 10(6) yr. RP Kuiper, TBH (reprint author), CALTECH,JET PROP LAB,MS 169-506,PASADENA,CA 91109, USA. NR 37 TC 89 Z9 89 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP 761 EP 773 DI 10.1086/177732 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE596 UT WOS:A1996VE59600027 PM 11541465 ER PT J AU Stothers, RB Chin, CW AF Stothers, RB Chin, CW TI Evolution of massive stars into luminous blue variables and Wolf-Rayet stars for a range of metallicities: Theory versus observation SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, evolution; stars, oscillation; stars, variables (luminous blue variables); stars, Wolf-Rayet; supergiants ID LARGE MAGELLANIC CLOUD; H-II REGIONS; P-CYGNI; CHEMICAL-COMPOSITION; STELLAR MODELS; HEAVY-ELEMENTS; AG-CARINAE; LOSS RATES; O-STARS; SUPERGIANTS AB Evolutionary tracks for 30-90 M. stars, computed along the Lines described in our recent series of papers, suggest that luminous blue variables (LBVs) are the blue remnants of a prior phase of heavy mass loss. They are now intermittently experiencing ionization-induced dynamical instability within their hydrogen-poor envelopes, while their massive helium cores are in an advanced stage of central helium burning. In the H-R diagram, our new evolutionary models successfully explain the high- and low-temperature limits, the low-luminosity limit, and the relative luminosity function of the observed LBVs at quiescence which have log (L/L.)<6.3. Metal-poor LBVs are predicted (correctly, in the only case known) to be significantly cooler than LBVs with normal metallicities. In the (mass, luminosity) plane, the models and observed stars agree closely, and show no discernible metals dependence. Predicted values of the surface hydrogen abundance and of the expelled mass during the LBV phase match reasonably well the available observational data, which, however, are still very crude. The observed cycles of mass loss are predicted correctly. Pre-LBV and post-LBV stars can be identified with the hydrogen-poor and hydrogen-free WN stars, respectively. Post-red-supergiant lifetimes, derived from published star counts and kinematical ages of nebulae around the WN stars and LBVs, are used to infer an approximate mean value of the rate of stellar wind mass loss from luminous red supergiants. This parameter is crucial for understanding stellar evolution at log (L/L.)<5.8. Stars more luminous may never become red, and may spend all, or nearly all, of their post-main-sequence lives as blue supergiants. Our theory of LBVs makes a number of other predictions that have not yet been tested. A critical comparison with the very different theory of Langer et al. is presented. RP Stothers, RB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,2800 BROADWAY,NEW YORK,NY 10025, USA. NR 62 TC 75 Z9 75 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP 842 EP 850 DI 10.1086/177740 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE596 UT WOS:A1996VE59600035 ER PT J AU Schrijver, CJ Shine, RA Hagenaar, HJ Hurlburt, NE Title, AM Strous, LH Harvey, JW Duvall, TL AF Schrijver, CJ Shine, RA Hagenaar, HJ Hurlburt, NE Title, AM Strous, LH Harvey, JW Duvall, TL TI Dynamics of the chromospheric network: Mobility, dispersal, and diffusion coefficients SO ASTROPHYSICAL JOURNAL LA English DT Article DE sun, activity; sun, chromosphere; sun, magnetic fields ID MAGNETIC-FIELD; SOLAR SURFACE; COOL STARS; QUIET SUN; FLUX; ATMOSPHERES; TRANSPORT; PATTERNS; ELEMENTS; ROTATION AB Understanding the physics behind the dispersal of photospheric magnetic flux is crucial to studies of magnetoconvection, dynamos, and stellar atmospheric activity. The rate of flux dispersal is often quantified by a diffusion coefficient, D. Published values of D differ by more than a factor of 2, which is more than the uncertainties anew. We propose that the discrepancies between the published values for D are the result of a correlation between the mobility and flux content of concentrations of magnetic flux. This conclusion is based on measurements of displacement velocities of Ca II K mottles using an uninterrupted 2 day sequence of filtergrams obtained at the South Pole near cycle minimum. We transform the Ca II K intensity to an equivalent magnetic flux density through a power-law relationship defined by a comparison with a nearly simultaneously observed magnetogram. One result is that, wherever the network is clearly defined in the filtergrams, the displacement vectors of the mottles are preferentially aligned with the network, suggesting that network-aligned motions are more important to held dispersal than deformation of the network pattern by cell evolution. The rms value of the inferred velocities, R = [\upsilon\(2)](1/2), decreases with increasing flux, phi, contained in the mottles, from R approximate to 240 m s(-1) down to 140 -1 m s(-1). The value of R(phi) appears to be independent of the flux surrounding the concentration, to the extreme that it does not matter whether the concentration is in a plage or in the network. The determination of a proper effective diffusion coefficient requires that the function R(phi) be weighted by the number density n(phi) of mottles that contain a total flux phi. We find that n(phi) decreases exponentially with phi and propose a model of continual random splitting and merging of concentrations of flux to explain this dependence. Traditional methods used to measure D tend to be biased toward the larger, more sluggish flux concentrations. Such methods neglect or underestimate the significant effects of the relatively large number of the more mobile, smaller concentrations. We argue that the effective diffusion coefficient for the dispersal of photospheric magnetic flux is similar to 600 km(2) s(-1). C1 UNIV UTRECHT,ASTRON INST,NL-3512 TA UTRECHT,NETHERLANDS. NEW JERSEY INST TECHNOL,NEWARK,NJ 07102. UNIV DELAWARE,BARTOL RES INST,NEWARK,DE 19716. NATL OPT ASTRON OBSERV,NATL SOLAR OBSERV,TUCSON,AZ 85726. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Schrijver, CJ (reprint author), LOCKHEED MARTIN PALO ALTO ADV TECHNOL CTR,DEPT 9130,BLDG 252,3251 HANOVER ST,PALO ALTO,CA 94304, USA. RI Duvall, Thomas/C-9998-2012 NR 30 TC 44 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP 921 EP 932 DI 10.1086/177747 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE596 UT WOS:A1996VE59600042 ER PT J AU Baldwin, JA Crotts, A Dufour, RJ Ferland, GJ Heathcote, S Hester, JJ Korista, KT Martin, PG ODell, CR Rubin, RH Tielens, AGGM Verner, DA Verner, EM Walter, DK Wen, Z AF Baldwin, JA Crotts, A Dufour, RJ Ferland, GJ Heathcote, S Hester, JJ Korista, KT Martin, PG ODell, CR Rubin, RH Tielens, AGGM Verner, DA Verner, EM Walter, DK Wen, Z TI Physical conditions in low-ionization regions of the Orion Nebula SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, abundances; ISM, atoms; ISM, H II regions; ISM, individual (Orion Nebula) ID FE-II; EMISSION; MODEL; ABUNDANCES; LINES; IRON AB We reexamine the spectroscopic underpinnings of recent suggestions that [O I] and [Fe II] lines from the Orion H II region are produced in gas where the iron-carrying grains have been destroyed and the electron density is surprisingly high. Our new observations show that previous detections of [O I] 5577 were dominated by telluric emission. Our limits are consistent with a moderate density (approximate to 10(4) cm(-3)) photoionized gas. We show that a previously proposed model of the Orion H II region reproduces the observed [O I] and [Fe II] spectrum. These lines are fully consistent with formation in a dusty region of moderate density. C1 COLUMBIA UNIV,DEPT ASTRON,NEW YORK,NY 10027. RICE UNIV,HOUSTON,TX 77251. UNIV KENTUCKY,LEXINGTON,KY 40503. ARIZONA STATE UNIV,TEMPE,AZ 85287. UNIV TORONTO,CANADIAN INST THEORET ASTROPHYS,TORONTO,ON M5S 3H8,CANADA. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. S CAROLINA STATE UNIV,DEPT PHYS SCI,ORANGEBURG,SC 29117. RP Baldwin, JA (reprint author), CERRO TOLOLO INTERAMER OBSERV,CASILLA 603,LA SERENA,CHILE. OI Ferland, Gary/0000-0003-4503-6333 NR 27 TC 40 Z9 40 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP L115 EP L118 DI 10.1086/310245 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE597 UT WOS:A1996VE59700010 ER PT J AU Banday, AJ Gorski, KM Bennett, CL Hinshaw, G Kogut, A Smoot, GF AF Banday, AJ Gorski, KM Bennett, CL Hinshaw, G Kogut, A Smoot, GF TI Noncosmological signal contributions to the COBE DMR 4 year sky maps SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; diffuse radiation; intergalactic medium ID NRAO PMN SURVEYS; COSMIC MICROWAVE; SOURCE CATALOG; GALAXIES; ANISOTROPY; SEARCH; GAS AB We limit the possible contributions from noncosmological sources to the COBE Differential Microwave Radiometer (DMR) 4 year sky maps. The DMR data are cross-correlated with maps of rich clusters, extragalactic IRAS sources, HEAO I A-2 X-ray emission, and 5 GHz radio sources using a Fourier space technique. There is no evidence of significant contamination by such sources at an rms level of similar to 8 mu K [95% confidence level (c.l.) at 70 resolution] in the most sensitive 53 GHz sky map. This level is consistent with previous limits set by analysis of earlier DMR data and by simple extrapolations from existing source models. We place a limit on the rms Comptonization parameter averaged over the high-latitude sky of delta gamma < 1 x 10(-6) (95% c.l.). Extragalactic sources have an insignificant effect on the cosmic microwave background power spectrum parameterizations determined from the DMR data. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,GREENBELT,MD 20771. UNIV CALIF BERKELEY,LBL,SSL,BERKELEY,CA 94720. UNIV CALIF BERKELEY,CIPA,BERKELEY,CA 94720. RI Kogut, Alan/D-6293-2012 NR 30 TC 44 Z9 43 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP L85 EP L89 DI 10.1086/310235 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE597 UT WOS:A1996VE59700003 ER PT J AU Ferrarese, L Livio, M Freedman, W Saha, A Stetson, PB Ford, HC Hill, RJ Madore, BF AF Ferrarese, L Livio, M Freedman, W Saha, A Stetson, PB Ford, HC Hill, RJ Madore, BF TI Discovery of a nova in the Virgo galaxy M100 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (M100, NGC 4321); novae, cataclysmic variables; stars, distances ID HUBBLE-SPACE-TELESCOPE; EXTRAGALACTIC DISTANCE SCALE; CONSTANT AB We present the V and I light curves of a nova discovered in the disk of the spiral galaxy M100, located in the Virgo Cluster. In spite of the fact that the light curve is not well sampled around maximum light and the reddening to the nova is not accurately known, by adopting the maximum magnitude versus rate of decline relation by Della Valle & Livio we derive a distance modulus to M100 of mu(0) similar to 31.0 +/- 0.3 mag, fully consistent with the Cepheid distance modulus of 31.04 +/- 0.17 mag found by Ferrarese et al. from the same set of HST/WFPC2 data. C1 OBSERV CARNEGIE INST WASHINGTON,PASADENA,CA 91101. NATL RES COUNCIL CANADA,HERZBERG INST ASTROPHYS,DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA. JOHNS HOPKINS UNIV,BALTIMORE,MD 21218. GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CALTECH,PASADENA,CA 91125. NASA,IPAC EXTRAGALACT DATABASE,PASADENA,CA 91125. RP Ferrarese, L (reprint author), SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218, USA. NR 21 TC 12 Z9 12 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1996 VL 468 IS 2 BP L95 EP & DI 10.1086/310246 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE597 UT WOS:A1996VE59700005 ER PT J AU Gawronski, W Lim, KB AF Gawronski, W Lim, KB TI Balanced actuator and sensor placement for flexible structures SO INTERNATIONAL JOURNAL OF CONTROL LA English DT Article ID MODEL-REDUCTION; SPACE STRUCTURES; LINEAR-SYSTEMS; CONTROLLABILITY; OBSERVABILITY; SELECTION; LOCATION AB Properties of flexible structures in modal and balanced coordinates are derived. From these properties the root-mean-square law of the Hankel singular values is obtained. It says that the squares of the Hankel singular values of a set of sensors and actuators is approximately a root-mean-square sum of the squares of the Hankel singular values for each individual sensor and actuator. This property allows us to evaluate each actuator and sensor in terms of the joint controllability and observability, and to serve as a tool of the actuator and/or sensor placement methodology. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Gawronski, W (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 35 TC 50 Z9 52 U1 0 U2 8 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0020-7179 J9 INT J CONTROL JI Int. J. Control PD SEP 10 PY 1996 VL 65 IS 1 BP 131 EP 145 DI 10.1080/00207179608921690 PG 15 WC Automation & Control Systems SC Automation & Control Systems GA VG308 UT WOS:A1996VG30800008 ER PT J AU Pettersson, MI Askne, J Cavalieri, DJ AF Pettersson, MI Askne, J Cavalieri, DJ TI SAR observations of arctic freeze-up compared to SSM/I during ARCTIC '91 SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID SEA ICE CONCENTRATION; BACKSCATTER AB Ice concentration in the Arctic derived from ERS-1 Synthetic Aperture Radar (SAR) and Special Scanning Microwave/Imager (SSM/I) images are compared. The satellite data are compared to video images and in situ measurements. The data were acquired during the freeze-up period of the ARCTIC'91 expedition. The studied areas were characterized by melting conditions and new ice formation with frost flowers. The ERS-1 SAR images are classified by a local averaging method and a segmentation method. Parameters for the methods are derived from the backscattering distributions. Temporal sequences and meteorological information are used for consistent results. Ice concentration derived from SAR are compared with the SSM/I ice concentration (NASA team algorithm) and ship observations. SSM/I may underestimate the ice concentration by 20 per cent due to thin ice formation and melting conditions while SAR may overestimate. However, by using the SAR estimate of the different ice classes we believe it is possible to increase the accuracy of the NASA team algorithm. We conclude that it is important to compare results from different sensors and methods. C1 NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,GREENBELT,MD 20771. RP Pettersson, MI (reprint author), CHALMERS UNIV TECHNOL,DEPT RADIO & SPACE SCI,S-41296 GOTHENBURG,SWEDEN. RI Pettersson, Mats/N-1063-2016; OI Pettersson, Mats/0000-0002-6643-312X; Askne, Jan/0000-0002-7860-5419 NR 33 TC 3 Z9 3 U1 0 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD SEP 10 PY 1996 VL 17 IS 13 BP 2603 EP 2624 PG 22 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA VC476 UT WOS:A1996VC47600009 ER PT J AU Glazman, RE Fabrikant, A Greysukh, A AF Glazman, RE Fabrikant, A Greysukh, A TI Statistics of spatial-temporal variations of sea surface height based on Topex altimeter measurements SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID OCEANIC MESOSCALE VARIABILITY; NORTH-ATLANTIC; PACIFIC-OCEAN; ROSSBY WAVES; LEVEL AB A data analysis technique is developed to estimate 3-D spatial-temporal autocorrelation functions and 2-D power spectra of sea surface height (SSH) variations, based on non-gridded Topex/Poseidon altimeter data. The resulting wavenumber spectra are rather anisotropic and characterized by a rapid, nearly power-law-type roll-off at wavenumbers above 0.02 rad km(-1) (wavelengths under 300 km) in mid-latitude regions-consistent with the kinetic energy spectra of geostrophic turbulence. The autocorrelation functions contain information on long-wave processes, such as baroclinic Rossby waves. The present statistical approach provides quantitative description of the SSH field variations in a broad range of scales, and it yields an experimental confirmation of baroclinic inertia-gravity wave turbulence. C1 PENN STATE UNIV,DEPT METEOROL,COLL EARTH & MINERAL SCI,UNIVERSITY PK,PA 16802. RP Glazman, RE (reprint author), JET PROPULS LAB,M-S 300-323,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 25 TC 10 Z9 10 U1 0 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD SEP 10 PY 1996 VL 17 IS 13 BP 2647 EP 2666 PG 20 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA VC476 UT WOS:A1996VC47600011 ER PT J AU Chao, BF Ray, RD Gipson, JM Egbert, GD Ma, C AF Chao, BF Ray, RD Gipson, JM Egbert, GD Ma, C TI Diurnal/semidiurnal polar motion excited by oceanic tidal angular momentum SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID EARTHS ROTATION RATE; SEMIDIURNAL VARIATIONS; PERIODIC CHANGES; TIDES; TOPEX/POSEIDON; ORIENTATION; ALTIMETRY; MODEL; INTERFEROMETRY AB The axial component of the oceanic tidal angular momentum (OTAM) has been demonstrated to be responsible for most of the diurnal and semidiurnal variations in Earth's rotational rate. In this paper we study the equatorial components of OTAM and their corresponding effects on the orientation of Earth's rotational axis, or polar motion. Three ocean tide models derived from TOPEX/Poseidon satellite altimetry are employed to predict the polar motion excited by eight major diurnal/semidiurnal tides (Q(1), O-1, P-1, K-1, N-2, M(2), S-2, K-2). The predictions are compared with geodetic measurements of polar motion from both long-term observations and during the intensive campaign Cont94. The prograde diurnal and prograde and retrograde semidiurnal periods are treated, whereas the retrograde diurnal polar motion is not treated (because it cannot be observed directly and uniquely.) The comparison shows generally good agreement, with discrepancies typically within 10-30 micro-arc-seconds for the largest tides. The eight tides collectively explain nearly 60% of the total variance in subdaily polar motion during Cont94. This establishes the dominant role of OTAM in exciting the diurnal/semidiurnal polar motion and paves the way for detailed studies of short-period nontidal polar motion. The present accuracy, however, is inadequate to shed light on the prograde diurnal polar libration. C1 NASA, GODDARD SPACE FLIGHT CTR, HUGHES STX, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, NVI INC, GREENBELT, MD 20771 USA. OREGON STATE UNIV, COLL FORESTRY, COLL OCEAN & ATMOSPHER SCI, CORVALLIS, OR 97331 USA. RP NASA, GODDARD SPACE FLIGHT CTR, TERR PHYS LAB, GREENBELT, MD 20771 USA. RI Ray, Richard/D-1034-2012; Ma, Chopo/D-4751-2012; Chao, Benjamin Fong/N-6156-2013; OI Egbert, Gary/0000-0003-1276-8538 NR 53 TC 52 Z9 55 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD SEP 10 PY 1996 VL 101 IS B9 BP 20151 EP 20163 DI 10.1029/96JB01649 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VG396 UT WOS:A1996VG39600011 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI A modification of the Gaussian-2 approach using density functional theory (vol 103, pg 1788, 1995) SO JOURNAL OF CHEMICAL PHYSICS LA English DT Correction, Addition RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 1 TC 5 Z9 5 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD SEP 8 PY 1996 VL 105 IS 10 BP 4398 EP 4398 DI 10.1063/1.473016 PG 1 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VF657 UT WOS:A1996VF65700055 ER PT J AU Gregory, FD AF Gregory, FD TI Safety and mission assurance in a better, faster, cheaper environment SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 46th International Astronautical Congress CY OCT 01-06, 1995 CL OSLO, NORWAY AB To provide the American people with an exciting aeronautics and space program that provides more tangible value in products and services and more relevance to the public, NASA has developed a philosophy that emphasizes better, faster, and cheaper ways of conducting business. The integration of safety, reliability and quality assurance (SR&QA) products and services into all NASA's programs and projects, from beginning to end, and the implementation of progressive quality management and contracting practices are direct applications of this philosophy. NASA's new test effectiveness program integrates the oribital performance and reliability experience of prior spacecraft with new design processes and improved telemetry to achieve higher performance and reliability, faster, and at reduced cost. As United States government leaders for ISO 9000 implementation, NASA is promoting single quality systems for contractors, the use of advanced quality practices, and methods for the implementation of baseline quality systems with the appropriate oversight to further low cost, high performance programs in the future. To remain vital in today's era of fiscal constraint, NASA must be efficient, effective, and relevant. The innovative integration and application of SR&QA tools, techniques, and management approaches in all NASA's programs and projects will play an integral role in achieving this end. (C) 1997 Elsevier Science Ltd (except USA). RP Gregory, FD (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 0 TC 0 Z9 0 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD SEP PY 1996 VL 39 IS 6 BP 465 EP 469 DI 10.1016/S0094-5765(96)00154-3 PG 5 WC Engineering, Aerospace SC Engineering GA WR453 UT WOS:A1996WR45300008 ER PT J AU Nadarajah, A Pusey, ML AF Nadarajah, A Pusey, ML TI Growth mechanism and morphology of tetragonal lysozyme crystals SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID ATOMIC-FORCE MICROSCOPY; RATES; ASSOCIATION; TEMPERATURE; SIMULATIONS; RESOLUTION AB The tetragonal form of hen egg-white lysozyme is the most investigated protein crystal for growth studies, but the relationship between its surface morphology and internal structure is still not well understood. One method of determining this relationship for inorganic crystals is by employing the periodic bond chain (PBC) theory of Hartman & Perdok [Hartman & Perdok (1955). Acta Cryst. 8, 49-52, 521-524, 525-529]. However, complexities resulting from the packing arrangements and the number of intermolecular bonds in protein crystals have resulted in the use of only simplified versions of this theory so far. In this study a more complete PBC analysis of tetragonal lysozyme crystals was carried out, coupled with an approach incorporating the molecular orientations of the crystal structure. The analysis revealed the existence of a helical tetramer building block of the entire crystal structure, centered around the 4(3) crystallographic axes, resulting in double-layered slices and PBC's throughout. The analysis also indicated that the crystallizing units for the faces are at least as large as this tetramer, with the experimental evidence suggesting that it is a tetramer unit for the {101} faces and an octamer unit for the {110} faces. The {110} faces were shown to be molecularly smooth F faces, while the {101} to be essentially rough S faces. The predicted morphology and growth mechanisms were found to explain numerous experimental observations from electron and atomic force microscopy, etching studies, lysozyme aggregation studies and measurements of growth kinetics. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,BIOPHYS BRANCH ES76,HUNTSVILLE,AL 35812. RP Nadarajah, A (reprint author), UNIV ALABAMA,DEPT CHEM & MAT ENGN,HUNTSVILLE,AL 35899, USA. NR 47 TC 55 Z9 55 U1 0 U2 12 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD SEP 1 PY 1996 VL 52 BP 983 EP 996 DI 10.1107/S0907444996004532 PN 5 PG 14 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA VM251 UT WOS:A1996VM25100013 PM 15299608 ER PT J AU Williams, BC Nayak, PP AF Williams, BC Nayak, PP TI Immobile robots - AI in the new millennium SO AI MAGAZINE LA English DT Article AB A new generation of sensor-rich, massively distributed, autonomous systems are being developed that have the potential for profound social, environmental, and economic change. These systems include networked building energy systems, autonomous space probes, chemical plant control systems, satellite constellations for remote ecosystem monitoring, power grids, biospherelike life-support systems, and reconfigurable traffic systems, to highlight but a few. To achieve high performance, these immobile robots (or immobots) will need to develop sophisticated regulatory and immune systems that accurately and robustly control their complex internal functions. Thus, immobots will exploit a vast nervous system of sensors to model themselves and their environment on a grand scale. They will use these models to dramatically reconfigure themselves to survive decades of autonomous operation. Achieving these large-scale modeling and configuration tasks will require a tight coupling between the higher-level coordination function provided by symbolic reasoning and the lower-level autonomic processes of adaptive estimation and control. To be economically viable, they will need to be programmable purely through high-level compositional models. Self-modeling and self-configuration, autonomic functions coordinated through symbolic reasoning, and compositional, model-based programming are the three key elements of a model-based autonomous system architecture that is taking us into the new millennium. RP Williams, BC (reprint author), NASA,AMES RES CTR,COMPUTAT SCI DIV,MOFFETT FIELD,CA 94035, USA. NR 28 TC 16 Z9 16 U1 0 U2 0 PU AMER ASSOC ARTIFICIAL INTELL PI MENLO PK PA 445 BURGESS DRIVE, MENLO PK, CA 94025-3496 SN 0738-4602 J9 AI MAG JI AI Mag. PD FAL PY 1996 VL 17 IS 3 BP 16 EP 35 PG 20 WC Computer Science, Artificial Intelligence SC Computer Science GA VJ671 UT WOS:A1996VJ67100005 ER PT J AU Hudson, ST Bordelon, WJ Coleman, HW AF Hudson, ST Bordelon, WJ Coleman, HW TI Effect of correlated precision errors on uncertainty of a subsonic venturi calibration SO AIAA JOURNAL LA English DT Article AB An uncertainty analysis performed in conjunction with the calibration of a subsonic venturi for use in a turbine test facility produced some unanticipated results that may have a significant impact in a variety of test situations, Precision uncertainty estimates using the preferred propagation techniques in the applicable American National Standards Institute/American Society of Mechanical Engineers standards were an order of magnitude larger than precision uncertainty estimates calculated directly from a sample of results (discharge coefficient) obtained at the same experimental set point. The differences were attributable to the effect of correlated precision errors, which previously have been considered negligible. An analysis explaining this phenomenon is presented, The article is not meant to document the venturi calibration, but rather to give a real example of results where correlated precision terms are important, The significance of the correlated precision terms could apply to many test situations. C1 UNIV ALABAMA,PROP RES CTR,DEPT MECH & AEROSP ENGN,HUNTSVILLE,AL 35899. RP Hudson, ST (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,STUCT & DYNAM LAB,HUNTSVILLE,AL 35812, USA. NR 13 TC 3 Z9 3 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1996 VL 34 IS 9 BP 1862 EP 1867 DI 10.2514/3.13319 PG 6 WC Engineering, Aerospace SC Engineering GA VD950 UT WOS:A1996VD95000015 ER PT J AU Birman, V Saravanos, DA Hopkins, DA AF Birman, V Saravanos, DA Hopkins, DA TI Micromechanics of composites with shape memory alloy fibers in uniform thermal fields SO AIAA JOURNAL LA English DT Article ID BEHAVIOR AB Analytical procedures are developed for a composite system consisting of shape memory alloy fibers within an elastic matrix subject to uniform temperature. A three-phase concentric cylinder model is developed for the analysis of local stresses, which includes the fiber, the matrix, and the surrounding homogenized composite, The solution addresses the complexities induced by the nonlinear dependence of the in situ martensite fraction of the fibers on the local stresses and temperature and the local stresses developed from interactions between the fibers and matrix during the martensitic and reverse phase transformations. Results are presented for a Ni-44.8wt% Ti/epoxy composite. The applications illustrate the response of the composite in isothermal longitudinal loading and unloading. The local stresses developed in the composite under various stages of the martensitic and reverse phase transformations are also shown. C1 OHIO AEROSP INST,CLEVELAND,OH 44142. NASA,LEWIS RES CTR,STRUCT MECH BRANCH,CLEVELAND,OH 44135. RP Birman, V (reprint author), UNIV MISSOURI,ENGN EDUC CTR,8001 NAT BRIDGE RD,ST LOUIS,MO 63121, USA. NR 27 TC 32 Z9 33 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1996 VL 34 IS 9 BP 1905 EP 1912 DI 10.2514/3.13324 PG 8 WC Engineering, Aerospace SC Engineering GA VD950 UT WOS:A1996VD95000020 ER PT J AU DeChant, LJ Seidel, JA Andrews, MJ AF DeChant, LJ Seidel, JA Andrews, MJ TI Interface wavelength between supersonic jets and subsonic flowfields SO AIAA JOURNAL LA English DT Article C1 NASA,LEWIS RES CTR,HSR PROP SYST STUDIES PROJECT OFF,CLEVELAND,OH 44135. RP DeChant, LJ (reprint author), TEXAS A&M UNIV,DEPT MECH ENGN,MS 3123,BOX 172,COLLEGE STN,TX 77843, USA. NR 8 TC 2 Z9 2 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1996 VL 34 IS 9 BP 1946 EP 1948 DI 10.2514/3.13331 PG 3 WC Engineering, Aerospace SC Engineering GA VD950 UT WOS:A1996VD95000027 ER PT J AU Schwandt, CS Papike, JJ Shearer, CK AF Schwandt, CS Papike, JJ Shearer, CK TI Trace element zoning in pelitic garnet of the Black Hills, South Dakota SO AMERICAN MINERALOGIST LA English DT Article ID PARTITION-COEFFICIENTS; METAMORPHIC GARNET; ZONED PEGMATITES; REE; TEMPERATURE; CONSTRAINTS; PRESSURE; ROCKS; EVOLUTION; CHEMISTRY AB Trace element (REE, Cr, Ti, V, Y, and Zr) analysis of garnet from the garnet, staurolite, and lower sillimanite zones of an aluminous schist of the Black Hills, South Dakota, indicates that REE zoning varies as a function of grade. Garnet-zone garnet has high concentrations of REEs, Cr, Ti, V, Y, and Zr in the cores and low concentrations in the rims. Profiles of heavy REEs contain inflections between the cores and rims, which are approximately symmetric about the cores. Staurolite-zone garnet contains cores enriched with Y and heavy REEs, which decrease toward the rim and increase again at the rim edges but to lower concentrations than in the cores. Cr, V, Ti, Zr, and light REE zoning is less pronounced than heavy REE zoning and is less symmetric about the garnet cores. Almandine-rich garnet of the lower sillimanite zone displays no major element zonation. Trace element (Ti, Cr, V, and Zr) concentrations are minimal, and the zoning is irregular and not symmetric about the garnet cores. Garnet from all three zones has core-to-rim Fe/(Fe + Mg) profiles that suggest garnet growth was uninterrupted with respect to major element components and that Mn zoning formed by a fractionation process. Analysis of trace element zoning in this garnet reveals that the major element zoning was relatively unaffected by volume-diffusion reequilibration. Trace element zonation of all samples of garnet is best explained by a fractionation mechanism in conjunction with limited intergranular diffusion and changing partition coefficients during garnet growth. Heavy REE partitioning is especially dependent on the major element composition of garnet. This research complements previous research by others on the use of trace elements as metamorphic petrogenetic indicators, which demonstrated the importance of bulk-rock composition and phase assemblage on trace element partitioning. C1 UNIV NEW MEXICO, DEPT EARTH & PLANETARY SCI, INST METEORIT, ALBUQUERQUE, NM 87131 USA. RP Schwandt, CS (reprint author), NASA, LYNDON B JOHNSON SPACE CTR, SN4, HOUSTON, TX 77058 USA. NR 62 TC 52 Z9 52 U1 2 U2 11 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 SEP-OCT PY 1996 VL 81 IS 9-10 BP 1195 EP 1207 PG 13 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA VN940 UT WOS:A1996VN94000018 ER PT J AU Hanson, B Delano, JW Lindstrom, DJ AF Hanson, B Delano, JW Lindstrom, DJ TI High-precision analysis of hydrous rhyolitic glass inclusions in quartz phenocrysts using the electron microprobe and INAA SO AMERICAN MINERALOGIST LA English DT Article ID ORDOVICIAN K-BENTONITES; MELT INCLUSIONS; TRACE-ELEMENT; UNITED-STATES; BISHOP TUFF; NEW-MEXICO; ASH BEDS; AIR-FALL; WATER; MAGMA AB A high-precision electron microprobe (EMP) technique has been developed that is capable of analyzing major, minor, and trace element abundances (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, Cl) in hydrous rhyolitic glasses. The technique was developed to characterize the chemical compositions of rhyolitic glass inclusions in phenocrysts that occur in layers of Paleozoic altered volcanic ash. The compositions of these inclusions serve as excellent chemical ''fingerprints'' of the altered volcanic ash layers for use in stratigraphic correlation. The precision and reproducibility of the analyses is sufficient not only to distinguish one altered volcanic ash layer from another on the basis of inclusion compositions, but also to discern differences in the compositions of different inclusions from the same layer. A high-precision instrumental neutron activation analytical (INAA) technique was also developed that is capable of measuring an additional suite of trace elements (e.g., Sc, Co, Rb, Cs, Sr, Ba, La, Ce, Sm, Eu, Tb, Yb, Lu, Zr, Hf, Ta) in rhyolitic glass inclusions in quartz phenocrysts with excellent accuracy and precision after correcting for the presence of the host quartz. The abundances of elements measured by the EMP technique and the corrected abundances determined using the INAA technique are identical within analytical uncertainty, thus demonstrating the internal consistency of the results. C1 SUNY ALBANY,DEPT GEOL SCI,ALBANY,NY 12222. RP Hanson, B (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY MAT BRANCH,HOUSTON,TX 77058, USA. NR 44 TC 19 Z9 19 U1 0 U2 1 PU MINERALOGICAL SOC AMER PI WASHINGTON PA 1130 17TH ST NW SUITE 330, WASHINGTON, DC 20036 SN 0003-004X J9 AM MINERAL JI Am. Miner. PD SEP-OCT PY 1996 VL 81 IS 9-10 BP 1249 EP 1262 PG 14 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA VN940 UT WOS:A1996VN94000023 ER PT J AU Zent, AP AF Zent, AP TI The evolution of the Martian climate SO AMERICAN SCIENTIST LA English DT Article C1 NASA,SETI INST,MT VIEW,CA. NASA,DIV SPACE SCI,MT VIEW,CA. NR 2 TC 4 Z9 4 U1 0 U2 0 PU SIGMA XI-SCI RES SOC PI RES TRIANGLE PK PA PO BOX 13975, RES TRIANGLE PK, NC 27709 SN 0003-0996 J9 AM SCI JI Am. Scientist PD SEP-OCT PY 1996 VL 84 IS 5 BP 442 EP 451 PG 10 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VC027 UT WOS:A1996VC02700010 ER PT J AU Akapo, SO AF Akapo, SO TI Retention behaviour of C-1-C-4 hydrocarbons on copper(II) complexes of cyano- and mercaptopropyl bonded phases SO ANALYTICAL COMMUNICATIONS LA English DT Article ID TRANSITION-METAL COMPLEXES; GAS-CHROMATOGRAPHY; SOLID ADSORBENTS; PERMANENT GASES; SEPARATION; GC; OLEFINS AB The retention behaviour of light (C-1-C-4) hydrocarbons on micropacked cyano- and mercaptopropyl bonded silica columns and their copper(II) complexes was examined by GC under isothermal conditions (25 degrees C), All the phases gave excellent separation of a mixture of methane, ethane, propane and butane with high reproducibility of retention times, Presumably due to specific metal-olefin interactions, the metal-containing packings gave a better separation of a ten-component mixture of C-1-C-4 saturated and unsaturated hydrocarbons, However, this effect appears to be weaker than the dispersive interactions between the solutes and the hydrocarbon chains of the bonded ligands as their chromatograms are similar to those obtained on micropacked n-alkyl and bidentate alkylsilane silica columns, Among the phases examined, a 3 m column of cyanopropyl-copper(II) complex offered a better resolution of a ten-component mixture of C-1-C-4 hydrocarbons. RP Akapo, SO (reprint author), NASA,AMES RES CTR,SETI INST,MAIL STOP 239-12,MOFFETT FIELD,CA 94035, USA. NR 22 TC 6 Z9 6 U1 0 U2 0 PU ROYAL SOC CHEMISTRY PI CAMBRIDGE PA THOMAS GRAHAM HOUSE, SCIENCE PARK MILTON ROAD, CAMBRIDGE, CAMBS, ENGLAND CB4 4WF SN 1359-7337 J9 ANAL COMMUN JI Anal. Commun. PD SEP PY 1996 VL 33 IS 9 BP 311 EP 313 DI 10.1039/ac9963300311 PG 3 WC Chemistry, Analytical SC Chemistry GA VG499 UT WOS:A1996VG49900007 ER PT J AU Doran, PT McKay, CP Meyer, MA Andersen, DT Wharton, RA Hastings, JT AF Doran, PT McKay, CP Meyer, MA Andersen, DT Wharton, RA Hastings, JT TI Climatology and implications for perennial lake ice occurrence at Bunger Hills oasis, east Antarctica SO ANTARCTIC SCIENCE LA English DT Article DE Bunger Hills; climate; lake ice ID THICKNESS AB The Bunger Hills Oasis (66 degrees 15'S; 100 degrees 45'E), a large ice-free expanse on the coast of East Antarctica, contains many lakes, only a few of which maintain an ice cover all year. To understand the environmental conditions that allow for persistent ice cover we established an automatic meteorological station on White Smoke Lake, a perennially ice-covered lake in contact with the Apfel Glacier. The data were collected from January 1992-July 1993. The mean annual solar flux during this period was 115 W m(-2), the mean wind speed 4.6 m s(-1), and the mean air temperature -11.2 degrees C. Summer degree-days above freezing (71 degrees C-days) are similar to regions of the Antarctic (the McMurdo Dry Valleys -78 degrees 45'S; 163 degrees 00'E) with thick perennial lake ice but the winter freezing degree days (3987 degrees C-Days) are much smaller and are closer to regions with seasonal ice covers (e.g. the high Arctic). The Bunger Hills Oasis seems to be in a marginal climatic region for the persistence of thick lake ice. Therefore, the extent of glacier ice contact becomes the controlling factor in maintaining an ice cover all year. We propose that this is either through the heat sink the glacier offers, and/or the positive feedback for ice growth provided by the high albedo of the adjacent glacier. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Doran, PT (reprint author), UNIV NEVADA,DESERT RES INST,CTR BIOL SCI,BOX 60220,RENO,NV 89506, USA. NR 13 TC 12 Z9 12 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0954-1020 J9 ANTARCT SCI JI Antarct. Sci. PD SEP PY 1996 VL 8 IS 3 BP 289 EP 296 PG 8 WC Environmental Sciences; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA VF018 UT WOS:A1996VF01800012 ER PT J AU Froggatt, M AF Froggatt, M TI Distributed measurement of the complex modulation of a photoinduced Bragg grating in an optical fiber SO APPLIED OPTICS LA English DT Article ID FABRICATION; WAVEGUIDES AB A method of measuring the complex modulation of a Bragg grating is derived from a one-dimensional model of light propagating in an optical fiber. Interference fringes between the Bragg grating and a reference air-gap reflector are measured, and a Fourier transform of the interference fringes generated as a laser is swept through the wavelength is used to compute the complex modulation function of the Bragg grating over a restricted domain. Supporting data, taken by temperature tuning a distributed feedback diode laser, are shown. RP Froggatt, M (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 8 TC 55 Z9 57 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD SEP 1 PY 1996 VL 35 IS 25 BP 5162 EP 5164 DI 10.1364/AO.35.005162 PG 3 WC Optics SC Optics GA VE604 UT WOS:A1996VE60400031 PM 21102951 ER PT J AU Kawahito, K Benkowski, R Otsubo, S Rosenbaum, B Moreland, R Noon, GP Nose, Y DeBakey, ME AF Kawahito, K Benkowski, R Otsubo, S Rosenbaum, B Moreland, R Noon, GP Nose, Y DeBakey, ME TI Ex vivo evaluation of the NASA/DeBakey axial flow ventricular assist device - Results of a 2 week screening test SO ASAIO JOURNAL LA English DT Article ID BLOOD PUMP; SYSTEM AB The authors investigated the antithombogenicity of the NASA/DeBakey axial flow ventricular assist device in an ex vivo calf model. The device is 3 inches in length and 1 inch in largest diameter. The pump weighs 53 g and displaces 15 ml. The unit consists of three major components: a flow straightener, a spinning inducer/impeller, and a diffuser. The impeller has rod shaped permanent magnets embedded within the six blades and is activated magnetically by a motor stator that is positioned outside the flow tube. Previous 2 day screening tests demonstrated an antithrombogenic configuration in short-term implantation. Based on the results of these 2 day screening tests, five pumps with the best configuration were implanted into a calf for 2 weeks for anti thrombogenicity confirmation. Pumps were implanted paracorporeally, and heparin was used to maintain activated clotting time to approximate to 250 sec. Each pump was changed every 2 weeks as planned. During the experiment, all pumps demonstrated stable pumping. The required electric power was 7 to 8 watts and pump flow was maintained at 4 L/min. The calf was in excellent condition. Liver and renal function were maintained, plasma free hemoglobin was kept at less than 4 mg/dl (3.3 +/- 0.3 mg/dl), and lactate dehydrogenase was 1043 +/- 36 units/L. In this experimental series, all five pumps passed the 2 week implantation. Two week ex vivo test results indicated very slight thrombus in the hub areas of some pumps. For the next phase of the implantation study, minor design optimization is necessary to completely eliminate thrombus formation. According to our step by step approach, the in vivo test aiming for long-term implantation is ongoing. C1 BAYLOR COLL MED,DEPT SURG,HOUSTON,TX 77030. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 13 TC 11 Z9 11 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 1058-2916 J9 ASAIO J JI Asaio J. PD SEP-OCT PY 1996 VL 42 IS 5 BP M754 EP M757 PG 4 WC Engineering, Biomedical; Transplantation SC Engineering; Transplantation GA VP508 UT WOS:A1996VP50800089 PM 8944983 ER PT J AU Malumuth, EM Sandoval, JL AF Malumuth, EM Sandoval, JL TI The discovery of a small group of galaxies in ursa major by the Hubble Space Telescope SO ASTRONOMICAL JOURNAL LA English DT Article ID FAINT GALAXIES; COMPACT-GROUPS; LUMINOSITY; EVOLUTION AB We present HST/WFPC2 images of a previously unknown loose group of galaxies in Ursa Major. These images were obtained as part of the GTO parallel program in which WFPC2 images are taken using the F606W (wide V) and F814W (I band) filters in parallel with GTO observations using other HST instruments. These WFPC2 images, obtained in parallel with FGS observations of ED + 67 degrees 552 on 1994 April 22 contain a number of galaxies between 4'' and 11'' in diameter as well as a multitude of other, smaller galaxies, The group is dominated by eight spiral galaxies and one elliptical galaxy in an area smaller than one Wide Field Camera chip (80''X80''). We present V and I band photometry, V-I colors, and V-I color gradients of each galaxy in the group. The luminosity function provides evidence that the smaller, fainter galaxies are background to the group. We estimate the redshift of the cluster to be z similar to 0.2(H-0 = 75 and q(0) = 0). (C) 1996 American Astronomical Society. C1 GODDARD SPACE FLIGHT CTR, LAB ASTRON & SOLAR PHYS, ADV COMP CONCEPTS, GREENBELT, MD 20771 USA. RP Malumuth, EM (reprint author), GODDARD SPACE FLIGHT CTR, LAB ASTRON & SOLAR PHYS, COMP SCI CORP, ASTRON PROGRAMS, GREENBELT, MD 20771 USA. NR 16 TC 0 Z9 0 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD SEP PY 1996 VL 112 IS 3 BP 887 EP 896 DI 10.1086/118061 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VG154 UT WOS:A1996VG15400004 ER PT J AU Worthey, G Dorman, B Jones, LA AF Worthey, G Dorman, B Jones, LA TI The G dwarf problem exists in other galaxies SO ASTRONOMICAL JOURNAL LA English DT Article ID OLD STELLAR POPULATIONS; CHEMICAL EVOLUTION; ELLIPTICAL GALAXIES; STARS; ABUNDANCES; REMNANTS; SPECTRA; SEARCH; MODELS AB Stellar population models with abundance distributions determined from the analytic Simple model of chemical evolution fail to match observations of the nuclei of bulge-dominated galaxies in three respects. First, the spectral energy distribution in the mid-ultraviolet range 20002.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VL660 UT WOS:A1996VL66000002 ER PT J AU Sellers, PJ Meeson, BW Closs, J Collatz, J Corprew, F Dazlich, D Hall, FG Kerr, Y Koster, R Los, S Mitchell, K McManus, J Myers, D Sun, KJ Try, P AF Sellers, PJ Meeson, BW Closs, J Collatz, J Corprew, F Dazlich, D Hall, FG Kerr, Y Koster, R Los, S Mitchell, K McManus, J Myers, D Sun, KJ Try, P TI The ISLSCP initiative I global datasets: Surface boundary conditions and atmospheric forcings for land-atmosphere studies SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SIMPLE BIOSPHERE MODEL; DATA SET; CLIMATE; ALGORITHMS; BUDGET AB A comprehensive series of global datasets for land-atmosphere models has been collected, formatted to a common grid, and released on a set of CD-ROMs. This paper describes the motivation for and the contents of the dataset. In June of 1992, an interdisciplinary earth science workshop was convened in Columbia, Maryland, to assess progress in land-atmosphere research, specifically in the areas of models, satellite data algorithms, and field experiments. At the workshop, representatives of the land-atmosphere modeling community defined a need for global datasets to prescribe boundary conditions, initialize state variables, and provide near-surface meteorological and radiative forcings for their models. The International Satellite Land Surface Climatology Project (ISLSCP), a part of the Global Energy and Water Cycle Experiment, worked with the Distributed Active Archive Center of the National Aeronautics and Space Administration Goddard Space Flight Center to bring the required datasets together in a usable format. The data have since been released on a collection of CD-ROMs. The datasets on the CD-ROMs are grouped under the following headings: vegetation; hydrology and soils; snow, ice, and oceans; radiation and clouds; and near-surface meteorology. All datasets cover the period 1987-88, and all but a few are spatially continuous over the earth's land surface. All have been mapped to a common 1 degrees x 1 degrees equal-angle grid. The temporal frequency for most of the datasets is monthly. A few of the near-surface meteorological parameters are available both as six-hourly values and as monthly means. C1 NASA,GODDARD SPACE FLIGHT CTR,DAAC,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,HSTX,GREENBELT,MD 20771. COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523. LERTS,BPI,TOULOUSE,FRANCE. NASA,GSFC,SSAI,GREENBELT,MD. NOAA,NMC,CAMP SPRINGS,MD. INT GEWEX PROJECT OFF,WASHINGTON,DC. RI collatz, george/D-5381-2012; Koster, Randal/F-5881-2012; Los, Sietse/G-8985-2012; zhong, honglin/C-2633-2012; OI Koster, Randal/0000-0001-6418-6383; Los, Sietse/0000-0002-1325-3555 NR 26 TC 81 Z9 81 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD SEP PY 1996 VL 77 IS 9 BP 1987 EP 2005 DI 10.1175/1520-0477(1996)077<1987:TIIIGD>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VL660 UT WOS:A1996VL66000003 ER PT J AU Bechtold, P Krueger, SK Lewellen, WS vanMeijgaard, E Moeng, CH Randall, DA vanUlden, A Wang, S AF Bechtold, P Krueger, SK Lewellen, WS vanMeijgaard, E Moeng, CH Randall, DA vanUlden, A Wang, S TI Modeling a stratocumulus-topped PBL: Intercomparison among different one-dimensional codes and with large eddy simulation SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID ASTEX LAGRANGIAN EXPERIMENTS; BOUNDARY-LAYER DYNAMICS; CLOUDINESS; ENTRAINMENT; CLOUDS AB Several one-dimensional (1D) cloud/turbulence ensemble modeling results of an idealized nighttime marine stratocumulus case are compared to large eddy simulation (LES). This type of model intercomparison was one of the objects of the first Global Energy and Water Cycle Experiment Cloud System Study boundary layer modeling workshop held at the National Center for Atmospheric Research on 16-18 August 1994. Presented are results obtained with different 1D models, ranging from bulk models (including only one or two vertical layers) to various types (first order to third order) of multilayer turbulence closure models. The 1D results fall within the scatter of the LES results. It is shown that 1D models can reasonably represent the main features (cloud water content, cloud fraction, and some turbulence statistics) of a well-mixed stratocumulus-topped boundary layer. Also addressed is the question of what model complexity is necessary and can be afforded for a reasonable representation of stratocumulus clouds in mesoscale or global-scale operational models. Bulk models seem to be more appropriate for climate studies, whereas a multilayer turbulence scheme is best suited in mesoscale models having at least 100- to 200-m vertical resolution inside the boundary layer. C1 UNIV UTAH,DEPT METEOROL,SALT LAKE CITY,UT 84112. W VIRGINIA UNIV,DEPT METEOROL,MORGANTOWN,WV 26506. KNMI,DE BILT,NETHERLANDS. NCAR,BOULDER,CO. COLORADO STATE UNIV,DEPT METEOROL,FT COLLINS,CO 80523. NASA,MSFC,HUNTSVILLE,AL 35812. RP Bechtold, P (reprint author), OBSERV MIDI PYRENEES,LAB AEROL,CNRS 5560,UMR,UPS,F-31400 TOULOUSE,FRANCE. RI Randall, David/E-6113-2011 OI Randall, David/0000-0001-6935-4112 NR 19 TC 38 Z9 38 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD SEP PY 1996 VL 77 IS 9 BP 2033 EP 2042 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VL660 UT WOS:A1996VL66000005 ER PT J AU Potter, CS Klooster, SA Chatfield, RB AF Potter, CS Klooster, SA Chatfield, RB TI Consumption and production of carbon monoxide in soils: A global model analysis of spatial and seasonal variation SO CHEMOSPHERE LA English DT Article ID GAS DIFFUSIVITY; POROUS-MEDIA; FLUXES; CO; ATMOSPHERE; MATTER; H-2 AB We have developed a simulation model to estimate net seasonal emission of carbon monoxide (CO) from soils world-wide which implies a smaller biogenic sink for CO than previously surmised. Field measurements have suggested that soils can play an important regional role in the net terrestrial exchange of carbon monoxide with the atmosphere. Previous global estimates of the net soil sink for atmospheric CO have been made by multiplying averages of small chamber measurements for various soil or vegetation classes by estimates of the area covered by each class. Simulation models driven by gridded databases can also contribute to global flux estimates. Such models are useful for evaluation of potential effects of changes in climate and land use, and for identification of weaknesses in both data and mechanistic understanding. We applied a modified version of Fick's first law based on computations for diffusivity in aggregated media, together with a soil water balance model run on a 1 degrees global grid, to make independent estimates of CO uptake by soils worldwide. Unlike previous global assessments, we assume that gross uptake rates are negligible in very dry desert soils (that are mostly devoid of microbial activity), in frozen soils, and in wetlands. The model results support a reference case estimate of 16 Tg CO yr(-1) for gross consumption of atmospheric CO in soils worldwide. However, owing to uncertainties in the seasonal boundary conditions and the actual soil depth for CO consumption activity, we estimate that this reference case for gross CO consumption in soils could go as high as 50 Tg CO yr(-1) globally. We also estimated production of CO from decaying soil organic matter as a process of chemical oxidation. Our model for gross production of CO from surface soils supports a global reference case flux of 9.4+/-2.5 Tg CO yr(-1). Combination of gross consumption and production fluxes implies a global net CO uptake flux of about 7-40 Tg CO yr(-1) in soils. Model results also support the hypothesis that temperate dry zones are the primary global sinks for soil CO, whereas tropical wet zones are the primary global sources for soil CO production. Notably, there is an order-of-magnitude difference between our model estimates and previous sink calculations based on extrapolations of measured fluxes, which suggests the need for more extensive soil CO flux studies, especially in remote regions where biogenic emissions could potentially exceed industrial sources of CO. Copyright (C) 1996 Elsevier Science Ltd. C1 NASA, AMES RES CTR, EARTH SYST SCI DIV, ATMOSPHER CHEM BRANCH, MOFFETT FIELD, CA 94035 USA. RP Potter, CS (reprint author), NASA, AMES RES CTR, EARTH SYST SCI DIV, ATMOSPHER CHEM BRANCH, MOFFETT FIELD, CA 94035 USA. NR 54 TC 21 Z9 21 U1 0 U2 12 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-6535 J9 CHEMOSPHERE JI Chemosphere PD SEP PY 1996 VL 33 IS 6 BP 1175 EP 1193 DI 10.1016/0045-6535(96)00254-8 PG 19 WC Environmental Sciences SC Environmental Sciences & Ecology GA VE440 UT WOS:A1996VE44000015 ER PT J AU McGrattan, KB Kashiwagi, T Baum, HR Olson, SL AF McGrattan, KB Kashiwagi, T Baum, HR Olson, SL TI Effects of ignition and wind on the transition to flame spread in a microgravity environment SO COMBUSTION AND FLAME LA English DT Article ID FUEL; MODEL; FEEDBACK; SURFACE; FLOW AB A two-dimensional time-dependent model is developed describing ignition and the subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. The effects of a slow external wind (0-5 cm/s), and of the flux distribution of the external radiation on the transition are studied mainly in an atmosphere of 30% oxygen concentration. The ignition is initiated along the width of a sample strip, giving rise initially to two flame fronts spreading in opposite directions. The calculated results are compared with data obtained in the 2.2-s drop tower. Both experimental and calculated results show that with a slow, imposed wind, the upstream flame front (opposed mode) is stronger and slightly faster than the quiescent counterpart due to a greater supply of oxygen. However, the downstream flame front (concurrent mode) tends to die during the transition period. For all calculated cases studied in this work using the selected kinetic constants for the global one-step gas phase reaction, the downstream flame front dies out in oxygen concentrations up to 50% and wind velocity up to 5 cm/s. This is caused by the ''oxygen shadow'' cast by the upstream flame. The ignition delay time depends mainly on the peak flux of external radiation, whereas the transition time to steady state flame spread depends mainly on the broadness of the flux distribution. The broader the radiative flux distribution, the greater the transient flame spread rate due to the preheating of the sample ahead of the flame front by the external radiation and thus the greater the delay to steady state flame spread. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP McGrattan, KB (reprint author), NATL INST STAND & TECHNOL,BLDG & FIRE RES LAB,ROOM A-345,BLDG 224,GAITHERSBURG,MD 20899, USA. NR 20 TC 30 Z9 34 U1 1 U2 4 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD SEP PY 1996 VL 106 IS 4 BP 377 EP & DI 10.1016/0010-2180(96)00184-8 PG 16 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA VE509 UT WOS:A1996VE50900002 ER PT J AU Atkinson, CF Jones, DD Gauthier, JJ AF Atkinson, CF Jones, DD Gauthier, JJ TI Biodegradabilities and microbial activities during composting of municipal solid waste in bench-scale reactors SO COMPOST SCIENCE & UTILIZATION LA English DT Article ID EVALUATING GARBAGE COMPOST; ORGANIC-MATTER; DEGRADATION; SLUDGE; ATP AB Ln the design of large scale, in-vessel systems, the biodegradability of the waste, the optimal nutritional conditions, and the length of time required to complete the high-rate phase are important. Because composting is a microbial process, the overall levels and activities of microorganisms influence the rate and extent of degradation. In this study, bench-scale reactors were used to determine the biodegradability of municipal solid waste, primarily office trash, and the effects of nutrient supplementation on biodegradability during six weeks of composting. Supplementation with nitrogen, phosphorus, vitamins, and trace minerals did not increase the biodegradability of the waste. Although the levels of specific microbial subpopulations varied, total numbers of microorganisms did not change significantly. C1 UNIV ALABAMA,DEPT BIOL,BIRMINGHAM,AL. RP Atkinson, CF (reprint author), NASA,KENNEDY SPACE CTR,FL 32899, USA. NR 28 TC 29 Z9 32 U1 1 U2 3 PU JG PRESS, INC PI EMMAUS PA 419 STATE AVE, EMMAUS, PA 18049 SN 1065-657X J9 COMPOST SCI UTIL JI Compost Sci. Util. PD FAL PY 1996 VL 4 IS 4 BP 14 EP 23 PG 10 WC Ecology; Soil Science SC Environmental Sciences & Ecology; Agriculture GA VX385 UT WOS:A1996VX38500003 ER PT J AU MacKinnon, DJ Chavez, PS Fraser, RS Niemeyer, TC Gillette, DA AF MacKinnon, DJ Chavez, PS Fraser, RS Niemeyer, TC Gillette, DA TI Calibration of GOES-VISSR, visible-band satellite data and its application to the analysis of a dust storm at Owens lake, California SO GEOMORPHOLOGY LA English DT Article ID ATMOSPHERIC DUST; SCATTERING; AEROSOLS; IMAGES; INDEX AB As part of a joint Russian/American dust-storm experiment, GOES-VISSR (Geostationary Operational Environmental Satellite, Visible-Infrared Spin-Scan Radiometer), data from a visible-band satellite image of a large dust storm emanating from Owens Lake, California were acquired on March 10 and 11, 1993. The satellite data were calibrated to targets of known ground reflectance factors and processed with radiative transfer techniques to yield aerosol (dust) optical depth at those stages of the dust storm when concurrent ground-based measurements of optical depth were made. Calibration of the satellite data is crucial for comparing surficial changes in remotely sensed data acquired over a period of time from the same area and for determining accurate concentrations of atmospheric aerosols using radiative transfer techniques. The calibration procedure forces the distribution of visible-band, DN (digital number) values, acquired on July 1, 1992, at 1731 GMT from the GOES-VISSR sensor over a large test area, to match the distribution of visible-band, DN values concurrently acquired from a Landsat MSS (Multispectral Scanner) sensor over the same test area; the Landsat MSS DN values were directly associated with reflectance factors measured from ground targets. The calibrated GOES-VISSR data for July 1, 1992, were then used to calibrate other GOES-VISSR data acquired on March 10 and 11, 1993, during the dust storm, Uncertainties in location of ground targets, bi-directional reflectance and atmospheric attenuation contribute an error of approximately +/-0.02 in the satellite-inferred ground reflectance factors. On March 11 at 1031 PST the satellite-received radiances during the peak of the storm were 3 times larger than predicted by our radiative transfer model for a pure clay dust plume of infinite optical depth. This result supported ground-based measurements that the plume at that time was composed primarily of large salt grains, probably sodium sulfate, which could not be properly characterized in our radiative transfer model. Further, the satellite data showed that the salt fell out of the plume within 35 km from the source. Finer-grained, clay dust was observed to extend beyond the salt-laden plume and was the major component of the dust plume after 1131 PST, when erosion of the salt crust on Owens Lake ceased. By 1331 and 1401 PST satellite-inferred, optical depths compared favorably with measurements concurrently acquired at the ground. Uncertainties in bi-directional reflectance, atmospheric attenuation, and locating ground points in the satellite data manifest errors between the inferred and measured optical depths in the range of 20 to 50%; these errors would be much greater without the calibration of the GOES-VISSR data. Changes in satellite-inferred reflectance factors over the lake bed during the course of the storm showed that 76 km(2) of the surface was disrupted during the March 11 storm, suggesting as much as 76 x 10(3) m(3) of crustal material were displaced for each millimeter of several estimated to have been moved during the storm; an unknown fraction of the displaced material was suspended. The satellite data also showed dust fallout on mountain snowfields. Whereas fallout may have removed most of the salt, satellite data acquired at 1631 PST, when the plume had a large brightness contrast with the ground, showed that it covered over 2500 km(2) and contained at least 1.6 x 10(9) g of sediment. For such a small source area, the dust represents a substantial contribution to the regional and global load of aerosols. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. ENVIRONM CONSULTING, SWANSEA, CA USA. NOAA, RES TRIANGLE PK, NC USA. RP US GEOL SURVEY, FLAGSTAFF, AZ 86001 USA. NR 25 TC 7 Z9 7 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0169-555X EI 1872-695X J9 GEOMORPHOLOGY JI Geomorphology PD SEP PY 1996 VL 17 IS 1-3 BP 229 EP 248 DI 10.1016/0169-555X(95)00105-E PG 20 WC Geography, Physical; Geosciences, Multidisciplinary SC Physical Geography; Geology GA VE330 UT WOS:A1996VE33000017 ER PT J AU Andres, RJ Marland, G Fung, I Matthews, E AF Andres, RJ Marland, G Fung, I Matthews, E TI A 1 degrees x1 degrees distribution of carbon dioxide emissions from fossil fuel consumption and cement manufacture, 1950-1990 SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID CO2 AB One degree latitude by one degree longitude (1 degrees x 1 degrees) data sets of carbon dioxide emissions from fossil fuel consumption and cement manufacture were produced for 1950, 1960, 1970, 1980, and 1990. National estimates of carbon emissions were combined with 1 degrees x 1 degrees data sets of political units and human population density to create the new 1 degrees x 1 degrees carbon emissions data sets. The human population density data set has an effective resolution of the country/state level. This resolution translates to the 1 degrees x 1 degrees carbon emissions data set. Latitudinal distribution of emissions have also been calculated. The data show continual growth with time over most of the world, with increased growth rates in major urban areas. A slow southerly shift in the bulk of the emissions is apparent as Asian countries increase their energy consumption to support their growing economies and populations. The digital data sets are available by anonymous ftp. C1 OAK RIDGE NATL LAB,DIV ENVIRONM SCI,OAK RIDGE,TN 37831. NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,NEW YORK,NY 10025. RI ANDRES, ROBERT/B-9786-2012; OI ANDRES, ROBERT/0000-0001-8781-4979 NR 22 TC 190 Z9 199 U1 3 U2 17 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0886-6236 J9 GLOBAL BIOGEOCHEM CY JI Glob. Biogeochem. Cycle PD SEP PY 1996 VL 10 IS 3 BP 419 EP 429 DI 10.1029/96GB01523 PG 11 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA VD604 UT WOS:A1996VD60400005 ER PT J AU Meador, MAB Lowell, CE Cavano, PJ HerreraFierro, P AF Meador, MAB Lowell, CE Cavano, PJ HerreraFierro, P TI On the oxidative degradation of nadic endcapped polyimides .1. Effect of thermocycling on weight loss and crack formation SO HIGH PERFORMANCE POLYMERS LA English DT Article ID PMR-15; CROSSLINKING AB The effects of thermocycle frequency, aging temperature and post-cure conditions on weight loss, microhardness and crack formation of PMR-15 neat resins were investigated. Crack formation was monitored by metallography. The molecular level changes, occurring under the same conditions, were monitored by microscopic FT-IR in reflectance mode on the same samples. FT-IR analysis was carried out in zones 100 mu m in diameter, allowing examination of different regions of the aged samples. It was found that weight loss, crack formation and microhardness were highly dependent on aging rime and temperature, but not thermocycling frequency. Molecular level changes were also highly correlated to time and temperature of aging. Both the physical effects of aging and the chemical effects were isolated to a thin surface layer. No changes whatsoever to the interiors of the samples were evident by FT-IR, microhardness or microscopy. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44106. OHIO AEROSP INST,CLEVELAND,OH. NR 15 TC 47 Z9 49 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD SEP PY 1996 VL 8 IS 3 BP 363 EP 379 DI 10.1088/0954-0083/8/3/003 PG 17 WC Polymer Science SC Polymer Science GA VL499 UT WOS:A1996VL49900003 ER PT J AU Hinkley, JA AF Hinkley, JA TI Average dipole moments of aromatic polymer chains SO HIGH PERFORMANCE POLYMERS LA English DT Article ID PHENYL; PYROELECTRICITY; RELAXATION AB Recently, certain aromatic polyimides with polar substituents were shown to exhibit piezoelectricity after poling. To help interpret these results, mean square chain dipole moments for model chains were calculated using a rotational isomeric state scheme. Average moments ranged from 1.7 to 3.6 debye(2) per backbone link, and correlated well with the magnitudes of the piezoelectric coefficients within the series. C1 NASA,LANGLEY RES CTR,COMPOSITES & POLYMERS BRANCH,HAMPTON,VA 23681. NR 14 TC 2 Z9 2 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD SEP PY 1996 VL 8 IS 3 BP 427 EP 431 DI 10.1088/0954-0083/8/3/007 PG 5 WC Polymer Science SC Polymer Science GA VL499 UT WOS:A1996VL49900007 ER PT J AU Birnbaum, G Borysow, A Orton, GS AF Birnbaum, G Borysow, A Orton, GS TI Collision-induced absorption of H-2-H-2 and H-2-He in the rotational and fundamental bands for planetary applications SO ICARUS LA English DT Article ID INDUCED ROTOTRANSLATIONAL SPECTRA; PRESSURE-INDUCED ABSORPTION; INDUCED INFRARED-ABSORPTION; MOLECULAR-HYDROGEN; HELIUM ABUNDANCE; VOYAGER MEASUREMENTS; THERMAL STRUCTURE; OUTER PLANETS; H2-H2 PAIRS; TEMPERATURES AB In recent years there has been significant progress in the ab initio computation and modeling of the collision-induced absorption in H-2-H-2 and H-2-He pairs in the rotovibrational and purely rototranslational bands covering 0-6000 cm(-1) at temperatures from 40 to 300 K. Extensive experimental and theoretical results have been obtained in a number of laboratories regarding this absorption as a function of frequency and temperature. This report summarizes the most advanced literature on this subject and presents a number of new results. Moreover, this report is designed to facilitate the utilization of this knowledge for the study of planetary atmospheres, and for future research of the H-2-H-2 and H-2-He infrared spectra. The theoretical absorption coefficients arising from free-free transitions in collisional pairs are available in the form of FORTRAN programs which permit rapid and reliable evaluation of spectral intensities even for frequencies and temperatures at which laboratory measurements do not exist. The various approximations affecting the accuracy of the theory applied here are discussed in some detail. The theoretical spectra closely duplicate the existing laboratory measurements of collision-induced absorption, whose accuracy is discussed; only for the case of the fundamental band of H-2-He are there small discrepancies from recent measurements which exceed somewhat the combined uncertainties of theory and measurement. The simple analytical functions on which these computer programs are based have also been compared with the quantum mechanical computations of the spectra and very close agreement has been observed. Notes regarding the use of the computer programs and sample outputs are given to serve as a test for their applications. (C) 1996 Academic Press, Inc. C1 MICHIGAN TECHNOL UNIV, DEPT PHYS, HOUGHTON, MI 49931 USA. CALTECH, JET PROP LAB, DIV EARTH & SPACE SCI, PASADENA, CA 91109 USA. RP Birnbaum, G (reprint author), NATL INST STAND & TECHNOL, GAITHERSBURG, MD 20899 USA. NR 64 TC 56 Z9 56 U1 0 U2 5 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 SEP PY 1996 VL 123 IS 1 BP 4 EP 22 DI 10.1006/icar.1996.0138 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN300 UT WOS:A1996VN30000002 ER PT J AU Magnusson, P Dahlgren, M Barucci, MA Jorda, L Binzel, RP Slivan, SM Blanco, C Riccioli, D Buratti, BJ Colas, F Berthier, J DeAngelis, G DiMartino, M Dotto, E Drummond, JD Fink, U Hicks, M Grundy, W Wisniewski, W Gaftonyuk, NM Geyer, EH Bauer, T Hoffmann, M Ivanova, V Komitov, B Donchev, Z Denchev, P Krugly, YN Velichko, FP Chiorny, VG Lupishko, DF Shevchenko, VG Kwiatkowski, T Kryszczynska, A Lahulla, JF Licandro, J Mendez, O Mottola, S Erikson, A Ostro, SJ Pravec, P Pych, W Tholen, DJ Whiteley, R Wild, WJ Wolf, M Sarounova, L AF Magnusson, P Dahlgren, M Barucci, MA Jorda, L Binzel, RP Slivan, SM Blanco, C Riccioli, D Buratti, BJ Colas, F Berthier, J DeAngelis, G DiMartino, M Dotto, E Drummond, JD Fink, U Hicks, M Grundy, W Wisniewski, W Gaftonyuk, NM Geyer, EH Bauer, T Hoffmann, M Ivanova, V Komitov, B Donchev, Z Denchev, P Krugly, YN Velichko, FP Chiorny, VG Lupishko, DF Shevchenko, VG Kwiatkowski, T Kryszczynska, A Lahulla, JF Licandro, J Mendez, O Mottola, S Erikson, A Ostro, SJ Pravec, P Pych, W Tholen, DJ Whiteley, R Wild, WJ Wolf, M Sarounova, L TI Photometric observations and modeling of asteroid 1620 Geographos SO ICARUS LA English DT Article ID GALILEO PHYSICAL MODEL; MAIN-BELT ASTEROIDS; POLE DETERMINATIONS; S-TYPE; LIGHTCURVES; 1620-GEOGRAPHOS; GEODESY; SHAPES; IMAGE; IDA AB Photometric observations of 1620 Geographos in 1993 and 1993 are presented and, in combination with previously published data, are used to derive models of Geographos, We estimate that the sidereal period of rotation is 0.21763860 +/- 0.00000003 days (5(h)13(m)23.975(s) +/- 0.0033(s)). The sense of rotation is retrograde, The ecliptic coordinates of the spin angular velocity vector are estimated to lambda(p) = 56 degrees +/- 6 degrees and beta(p) = -47 degrees +/- 4 degrees (equinox J2000.0), The lightcurve amplitudes are well-explained by an ellipsoidal model with axis ratios a/b 2.58 +/- 0.16 and b/c = 1.00 +/- 0.15. Models that have one or both ends more sharply pointed than the ellipsoid improve the fit to the observations. There are no significant indications of albedo variegation, but non-geometric scattering effects are tentatively suggested based on significant rotational color variation. (C) 1996 Academic Press, Inc. C1 OBSERV PARIS,F-92195 MEUDON,FRANCE. MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139. UNIV CATANIA,IST ASTRON,I-95125 CATANIA,ITALY. CALTECH,JET PROP LAB,PASADENA,CA 91109. BUR LONGITUDES,PARIS,FRANCE. UNIV ROMA LA SAPIENZA,IST ASTRON,I-00161 ROME,ITALY. ESA,ESRIN,INFORMAT SYST DIV,I-00044 FRASCATI,ITALY. OSSERV ASTRON TORINO,I-10025 PINO TORINESE,ITALY. USAF,PHILLIPS LAB,LIG,KIRTLAND AFB,NM 87117. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. ASTRON OBSERV,UA-334242 SIMEIZ,CRIMEA,UKRAINE. UNIV BONN,OBSERV HOHER LIST,D-54550 DAUN,GERMANY. BULGARIAN ACAD SCI,DEPT ASTRON,BU-1784 SOFIA,BULGARIA. ASTRON OBSERV,UA-310022 KHARKOV,UKRAINE. ADAM MICKIEWICZ UNIV POZNAN,ASTRON OBSERV,PL-60286 POZNAN,POLAND. ASTRON OBSERV,E-28014 MADRID,SPAIN. FAC CIENCIAS,INST FIS,DEPT ASTRON,MONTEVIDEO 11200,URUGUAY. GERMAN AEROSP RES ESTAB,DLR,D-12489 BERLIN,GERMANY. ACAD SCI CZECH REPUBL,INST ASTRON,CZ-25165 ONDREJOV,CZECH REPUBLIC. WARSAW UNIV,ASTRON OBSERV,PL-00478 WARSAW,POLAND. UNIV HAWAII,INST ASTRON,HONOLULU,HI 96822. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. CHARLES UNIV,INST ASTRON,CZ-15000 PRAGUE,CZECH REPUBLIC. RP Magnusson, P (reprint author), ASTRON OBSERV,BOX 515,S-75120 UPPSALA,SWEDEN. RI Pravec, Petr/G-9037-2014; Shevchenko, Vasilij/H-1366-2011; OI Shevchenko, Vasilij/0000-0003-1000-223X; Dotto, Elisabetta/0000-0002-9335-1656 NR 40 TC 19 Z9 19 U1 0 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1996 VL 123 IS 1 BP 227 EP 244 DI 10.1006/icar.1996.0151 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VN300 UT WOS:A1996VN30000015 ER PT J AU Bokhari, SH AF Bokhari, SH TI Multiphase complete exchange on paragon, SP2, and CS-2 SO IEEE PARALLEL & DISTRIBUTED TECHNOLOGY LA English DT Article ID NETWORKS AB The complete exchange is the severest communication pattern in that it requires each processor to send a distinct message to every other processor, This pattern is at the heart of many important parallel applications. There are three main algorithms for complete exchange, all designed for hypercubes: the direct exchange, the standard exchange, and the multiphase exchange. Most contemporary commercial multicomputer systems are not hypercubes. However, through special-purpose hardware and dedicated communication processors, these systems can achieve very high performance communication and can emulate hypercubes quite well. Multiphase complete exchange, which is actually a family of algorithms with standard and direct exchange as extreme cases, performs optimally for varying message sizes. The author has implemented multiphase complete exchange on three contemporary parallel architectures: the Intel Paragon, the IBM SP2, and the Meiko CS-2, He describes the essential features of these machines and discusses their basic interprocessor communication overheads. Then he evaluates the performance of multi phase complete exchange on each machine. He discovered that the Paragon executes the multiphase well and yields smooth performance plots, with the cyclic variations in these plots stemming from memory access patterns; the SP2 exhibits enormous fluctuations in its plots because of interference from other jobs; and the CS-2 exhibits small fluctuations, and the largest differences between predicted and observed timings, The author concludes that the theoretical ideas developed for hypercubes also apply to these machines and that multiphase complete exchange can lead to major savings in execution time over traditional solutions. C1 NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23665. RP Bokhari, SH (reprint author), UNIV ENGN & TECHNOL,DEPT ELECT ENGN,LAHORE 54890,PAKISTAN. RI Bokhari, Shahid/H-1330-2011 NR 15 TC 8 Z9 8 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 1063-6552 J9 IEEE PARALL DISTRIB JI IEEE Parallel Distrib. Technol. PD FAL PY 1996 VL 4 IS 3 BP 45 EP & DI 10.1109/88.532139 PG 17 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA VC083 UT WOS:A1996VC08300007 ER PT J AU Rosenberg, L AF Rosenberg, L TI More self-help for practitioners SO IEEE SOFTWARE LA English DT Letter RP Rosenberg, L (reprint author), GSFC,UNISYS,GREENBELT,MD, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 0740-7459 J9 IEEE SOFTWARE JI IEEE Softw. PD SEP PY 1996 VL 13 IS 5 BP 6 EP 6 PG 1 WC Computer Science, Software Engineering SC Computer Science GA VE581 UT WOS:A1996VE58100002 ER PT J AU Ekroot, L Dolinar, S AF Ekroot, L Dolinar, S TI A* decoding of block codes SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article DE maximum likelihood decoding; soft-decision decoding; binary linear block codes; algorithm A* AB The A* algorithm is applied to maximum-likelihood soft-decision decoding of binary linear block codes, This paper gives a tutorial on the A* algorithm, compares the decoding complexity with that of exhaustive search and Viterbi decoding algorithms, and presents performance curves obtained for several codes. RP Ekroot, L (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 13 TC 24 Z9 24 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD SEP PY 1996 VL 44 IS 9 BP 1052 EP 1056 DI 10.1109/26.536908 PG 5 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA VH230 UT WOS:A1996VH23000002 ER PT J AU Casady, JB Dillard, WC Johnson, RW Rao, U AF Casady, JB Dillard, WC Johnson, RW Rao, U TI A hybrid GH-SiC temperature sensor operational from 25 degrees C to 500 degrees C SO IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY PART A LA English DT Article DE temperature sensor; silicon carbide; SiC; transistor; diode; hybrid; electronics ID MESFETS; JFETS AB 6H-SiC buried-gate n-channel depletion-mode junction field-effect transistors (JFET's) were characterized from 25 degrees C to 350 degrees C in terms of transconductance (g(m)), pinchoff voltage (V-p), output resistance (r(o)), input resistance (R(in)), drain-to-source current at zero gate-to-source voltage (I-DSS), gate-to-source reverse biased leakage current (I-GSS), off-state drain-to-source current (I-DSS(off)), and noise power spectral density (S-V) The 6H-SiC JFET's were used in a hybrid temperature monitoring circuit (tested from -196 degrees C to 500 degrees C) fabricated at Auburn University for use in numerous industrial applications. Simulation program with integrated circuit emphasis (SPICE) simulations of the temperature monitoring circuit's output voltage corresponded well with measured data as a function of temperature. Linear regression (LR) analysis of measured data revealed a notably sensitive (similar to 2.3 mV/degrees), and an eminently linear (correlation coefficient = -0.9996G... over 25 degrees C to 500 degrees C range) relationship between the measured output voltage and temperature. Below -50 degrees C, the output became nonlinear, presumably from carrier freeze-out effects. To the best of our knowledge, this represents the first successful implementation of SiC active devices into a temperature sensor which demonstrated stable operation up to 500 degrees C. RP Casady, JB (reprint author), AUBURN UNIV,NASA,CTR COMMERCIAL DEV & ADV ELECT,AUBURN,AL 36849, USA. NR 26 TC 32 Z9 32 U1 2 U2 10 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1070-9886 J9 IEEE T COMPON PACK A JI IEEE Trans Compon. Packag. Manuf. Technol. Part A PD SEP PY 1996 VL 19 IS 3 BP 416 EP 422 DI 10.1109/95.536843 PG 7 WC Engineering, Manufacturing; Engineering, Electrical & Electronic; Materials Science, Multidisciplinary SC Engineering; Materials Science GA VJ590 UT WOS:A1996VJ59000016 ER PT J AU LeVine, DM Karam, MA AF LeVine, DM Karam, MA TI Dependence of attenuation in a vegetation canopy on frequency and plant water content SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 5th IEEE International Geoscience and Remote Sensing Symposium (IGARSS 95) - Quantitative Remote Sensing for Science and Applications CY JUL 10-14, 1995 CL FLORENCE, ITALY SP IEEE, Geosci & Remote Sensing Soc, Int Union Radio Sci ID MICROWAVE EMISSION; DIELECTRIC DISKS; SCATTERING; MODEL; LAYER; BACKSCATTERING; CORN AB Theory is presented to provide insight into the observation that attenuation through vegetation is proportional to vegetation water content, In this analysis, the canopy is modeled as a sparse layer of randomly oriented particles (leaves, stalks, etc.) over a flat, homogeneous ground plane (soil) and an expression is obtained for the ''optical depth.'' The formulas developed by Ulaby and El-Rayes are used to relate this expression to the water content of the canopy, In the low frequency extreme (Rayleigh scatterers), the attenuation varies almost linearly with water content and inversely with wavelength, in contrast, in the high frequency limit, the attenuation is independent of both water content and frequency, In between, geometry dependent ''resonances'' occur even at the low frequency end of the microwave spectrum (e.g., L-band) making the dependence of attenuation on frequency and water content specific to canopy architecture. C1 GENCROP AEROJET,AZUSA,CA 91702. RP LeVine, DM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 31 TC 47 Z9 50 U1 1 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1996 VL 34 IS 5 BP 1090 EP 1096 DI 10.1109/36.536525 PG 7 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA VJ871 UT WOS:A1996VJ87100006 ER PT J AU Beaven, SG Gogineni, S Carsey, FD AF Beaven, SG Gogineni, S Carsey, FD TI Fusion of satellite active and passive microwave data for sea ice type concentration estimates SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 5th IEEE International Geoscience and Remote Sensing Symposium (IGARSS 95) - Quantitative Remote Sensing for Science and Applications CY JUL 10-14, 1995 CL FLORENCE, ITALY SP IEEE, Geosci & Remote Sensing Soc, Int Union Radio Sci ID APERTURE RADAR DATA; SUMMER; SIGNATURES; IMAGERY; BAY AB Young first-year sea ice is nearly as important as open water in modulating heat flux between the ocean and atmosphere in the Arctic, Just after the onset of freeze-up, first-year ice is in the early stages of growth and will consist of young first-year and thin ice. The distribution of sea ice in this thickness range impacts heat transfer in the Arctic. Therefore, improving the estimates of ice concentrations in this thickness range is significant, NASA Team Algorithm (NTA) for passive microwave data inaccurately classifies sea ice during the melt and freeze-up seasons because it misclassifies multiyear ice as first-year ice. We developed a hybrid fusion technique for incorporating multiyear ice information derived from synthetic aperture radar (SAR) images into a passive microwave algorithm to improve ice type concentration estimates, First, we classified SAW images using a dynamic thresholding technique and estimated the multiyear ice concentration. Then we used the SAR-derived multiyear ice concentration to constrain the NTA and obtained an improved first-year ice concentration estimate, We computed multiyear and first-year Ice concentration estimates over a region in the eastern-central Arctic in which field observations of ice and in situ radar backscatter measurements were performed. with the NTA alone, the first-year ice concentration in our study area varied between 0.11 and 0.40, while the multiyear Ice concentration varied from 0.63 to 0.39, with the hybrid fusion technique, the first-year Ice concentration varied between 0.08 and 0.23 and the multiyear ice concentration was between 0.62 and 0.66. The fused estimates of first-year and multiyear ice concentration appear to be more accurate than NTA, based on ice observations that were logged aboard the U.S. Coast Guard icebreaker Polar Star in the study area during 1991. C1 UNIV KANSAS, DEPT ELECT & COMP ENGN, RADAR SYST & REMOTE SENSING LAB, LAWRENCE, KS 66045 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Beaven, SG (reprint author), USN, CONTROL & OCEAN SURVEILLANCE CTR, RES DEV TEST & EVALUAT DIV, NAVAL COMMAND, SAN DIEGO, CA 92152 USA. NR 35 TC 5 Z9 5 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1996 VL 34 IS 5 BP 1172 EP 1183 DI 10.1109/36.536534 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 VJ871 UT WOS:A1996VJ87100015 ER PT J AU Kummerow, C Olson, WS Giglio, L AF Kummerow, C Olson, WS Giglio, L TI A simplified scheme for obtaining precipitation and vertical hydrometeor profiles from passive microwave sensors SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 5th IEEE International Geoscience and Remote Sensing Symposium (IGARSS 95) - Quantitative Remote Sensing for Science and Applications CY JUL 10-14, 1995 CL FLORENCE, ITALY SP IEEE, Geosci & Remote Sensing Soc, Int Union Radio Sci ID RADIATIVE-TRANSFER; CLOUD MODEL; STRUCTURE INFORMATION; ESTIMATING RAINFALL; SOLAR-RADIATION; WATER-VAPOR; RETRIEVAL; SCATTERING; ALGORITHM; PARAMETERIZATION AB This paper presents a computationally simple technique for retrieving the precipitation and vertical hydrometeor profiles from downward viewing radiometers. The technique is computationally much less expensive than previous profiling schemes and has been designed specifically to allow for tractability of assumptions. In this paper, the emphasis is placed upon passive microwave applications, but the combination of passive with active microwave sensors, infrared sensors, or other a priori information can be adapted easily to the framework described here, The technique is based upon a Bayesian approach, Here, we use many realizations of the Goddard Cumulus Ensemble model to establish a prior probpability density function of rainfall profiles. Detailed three-dimensional radiative transfer calculations are used to determine the upwelling brightness temperatures from the cloud model to establish the similarity of radiative signatures and thus the probability that a given profile is actually observed. In this study, we show that good results may be obtained by weighting profiles from the prior probability density function according to their deviation from the observed brightness temperatures, Examples of the retrieval results are shown for oceanic as well as land situations, Microwave data from the Advanced Microwave Precipitation Radiometer (AMPR) instrument are used to illustrate the retrieval structure results for high-resolution data while SSM/I is used to illustrate satellite applications. Simulations are performed to compare the expected retrieval performance of the SSM/I instrument with that of the upcoming TMI instrument aboard the Tropical Rainfall Measuring Mission (TRMM) to be launched in August 1997. These simulations show that correlations of similar to 0.77 may be obtained for 10-km retrievals of the integrated liquid water content based upon SSM/I channels. This correlation increases to similar to 0.90 for the same retrievals using the TMI channels and resolution. Due to the lack of quantitative validation data, hydrometeor profiles cannot be compared directly but are instead converted to an equivalent reflectivity structure and compared to existing radar observations where possible. C1 CAELUM RES CORP,SILVER SPRING,MD. SCI SYST & APPLICAT INC,LANHAM,MD 20706. RP Kummerow, C (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 47 TC 348 Z9 359 U1 0 U2 9 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1996 VL 34 IS 5 BP 1213 EP 1232 DI 10.1109/36.536538 PG 20 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA VJ871 UT WOS:A1996VJ87100019 ER PT J AU Chang, CY Jin, MY Lou, YL Holt, B AF Chang, CY Jin, MY Lou, YL Holt, B TI First SIR-C scansar results SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 5th IEEE International Geoscience and Remote Sensing Symposium (IGARSS 95) - Quantitative Remote Sensing for Science and Applications CY JUL 10-14, 1995 CL FLORENCE, ITALY SP IEEE, Geosci & Remote Sensing Soc, Int Union Radio Sci ID SYNTHETIC-APERTURE RADAR; SYSTEM AB During the two space shuttle missions in 1994, the Spaceborne Imaging Radar-C (SIR-C) acquired several experimental datatakes using the ScanSAR mode, Some of these ScanSAR data have been processed into images of swath wider than 200 km. Example images are shown in this paper. These early results demonstrate that ScanSAR operation is not only feasible, but also represents a potentially useful tool for regional and global scale imaging by the future SAR missions. RP Chang, CY (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 12 TC 6 Z9 8 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1996 VL 34 IS 5 BP 1278 EP 1281 DI 10.1109/36.536543 PG 4 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA VJ871 UT WOS:A1996VJ87100024 ER PT J AU Zhuang, XH Huang, Y Palaniappan, K Zhao, YX AF Zhuang, XH Huang, Y Palaniappan, K Zhao, YX TI Gaussian mixture density modeling, decomposition, and applications SO IEEE TRANSACTIONS ON IMAGE PROCESSING LA English DT Article ID COMPUTER VISION; LIKELIHOOD AB Gaussian mixture density modeling and decomposition is a classic yet challenging research topic. We present a new approach to the modeling and decomposition of Gaussian mixtures by using robust statistical methods. The mixture distribution is viewed as a (severely) contaminated Gaussian density. Using this model and the model-fitting (MF) estimator, we propose a recursive algorithm called the Gaussian mixture density decomposition (GMDD) algorithm for successively identifying each Gaussian component in the mixture. The proposed decomposition scheme has several distinct advantages that are desirable but lacking in most existing techniques. In the GMDD algorithm the number of components does not need to be specified a priori, the proportion of noisy data in the mixture can be large, the parameter estimation of each component is virtually initial independent, and the variability in the shape and size of the component densities in the mixture is taken into account. Gaussian mixture density modeling and decomposition has been widely applied in a variety of disciplines that require signal or waveform characterization for classification and recognition, including remote sensing, target identification, spectroscopy, electrocardiography, speech recognition, or scene segmentation. We apply the proposed GMDD algorithm to the identification and extraction of clusters, and the estimation of unknown probability densities. Probability density estimation by identifying a decomposition using the GMDD algorithm, that is, a superposition of normal distributions, is successfully applied to the difficult biomedical problem of automated cell classification. Computer experiments using both real data and simulated data demonstrate the validity and power of the GMDD algorithm for various models and different noise assumptions. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. UNIV ILLINOIS,BECKMAN INST,URBANA,IL 61801. RP Zhuang, XH (reprint author), UNIV MISSOURI,DEPT ELECT & COMP ENGN,COLUMBIA,MO 65211, USA. RI Palaniappan, Kannappan/A-3231-2008 NR 21 TC 76 Z9 88 U1 0 U2 7 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1057-7149 J9 IEEE T IMAGE PROCESS JI IEEE Trans. Image Process. PD SEP PY 1996 VL 5 IS 9 BP 1293 EP 1302 DI 10.1109/83.535841 PG 10 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA VH478 UT WOS:A1996VH47800001 PM 18285218 ER PT J AU Namkung, M Bryant, RG Fox, RL Buchman, A AF Namkung, M Bryant, RG Fox, RL Buchman, A TI Magnetic and mechanical properties of molded iron particle cores SO IEEE TRANSACTIONS ON MAGNETICS LA English DT Article; Proceedings Paper CT 1996 IEEE International Magnetics Conference (INTERMAG 96) CY APR 09-12, 1996 CL SEATTLE, WA SP IEEE AB Using high performance soluble imide polymer as a binder, it was possible to accomplish a substantial mechanical strength in iron particle cores molded under uniaxial compacting pressure which was much lower than that was commonly applied by others in the past. The directional ordering of oblate spheroidal iron particles occurred despite the low compacting pressure resulting in strong anisotropy in the magnetic properties and mechanical strength in the fabricated cores. The low molding pressure, however, resulted in a low density of core which, in turn, caused the low permeability. C1 OLD DOMINION UNIV,NORFOLK,VA 23527. RP Namkung, M (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. RI Namkung, Min/E-1533-2012 NR 8 TC 1 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 SN 0018-9464 J9 IEEE T MAGN JI IEEE Trans. Magn. PD SEP PY 1996 VL 32 IS 5 BP 4890 EP 4892 DI 10.1109/20.539279 PN 2 PG 3 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA VM259 UT WOS:A1996VM25900195 ER PT J AU Tong, CYE Blundell, R Paine, S Papa, DC Kawamura, J Zhang, XL Stern, JA LeDuc, HG AF Tong, CYE Blundell, R Paine, S Papa, DC Kawamura, J Zhang, XL Stern, JA LeDuc, HG TI Design and characterization of a 250-350-GHz fixed-tuned superconductor-insulator-superconductor receiver SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article ID SIS RECEIVERS; MIXER; NOISE; JUNCTIONS AB A fixed-tuned superconductor-insulator-superconductor (SIS) receiver has been designed to operate in the 250-350-GHz frequency band, This receiver has a double-side-band noise temperature of between 35 and 45 K, or about 3hv/k(B), over its entire operating band, Extensive characterization of the receiver has been carried out using techniques developed for submillimeter waves. The input noise, side-band ratio, 1 dB compression point, optimum LO drive level, and vector near-field beam profile have all been measured experimentally, The measurement techniques and results are presented and discussed. C1 CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. RP Tong, CYE (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. OI Tong, Edward/0000-0002-7736-4203; Paine, Scott/0000-0003-4622-5857 NR 27 TC 32 Z9 32 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD SEP PY 1996 VL 44 IS 9 BP 1548 EP 1556 DI 10.1109/22.536603 PG 9 WC Engineering, Electrical & Electronic SC Engineering GA VH032 UT WOS:A1996VH03200005 ER PT J AU Weller, TM Katehi, LPB Herman, MI Wamhof, PD Lee, K Kolawa, EA Tai, BH AF Weller, TM Katehi, LPB Herman, MI Wamhof, PD Lee, K Kolawa, EA Tai, BH TI New results using membrane-supported circuits: A Ka-band power amplifier and survivability testing SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article AB This paper describes recent results which pertain to the integration and reliability testing of micromachined, membrane-supported transmission line circuits. These circuits employ a 1.4- mu m-thick dielectric membrane to support thin-film conducting Lines above an air substrate. With regard to integration, the development of a Ka-band solid state power amplifier (SSPA) is presented. The design includes a membrane-supported Wilkinson power divider/combiner with 0.2 dB loss, along with a commercially available monolithic microwave/millimeter wave integrated circuit (MMIC) amplifier stage. Also reported are tests which investigated the survivability of membrane lines under space qualification conditions. No failures occurred as a result of thermal cycling and vibration testing at levels which reached 39.6 grms. C1 UNIV MICHIGAN,RADIAT LAB,ANN ARBOR,MI 48109. CALTECH,JET PROP LAB,PASADENA,CA 91109. CORE DYNAM CORP,IRVINE,CA 91109. UNIV CALIF DAVIS,DEPT MAT SCI & CHEM ENGN,DAVIS,CA 95616. RP Weller, TM (reprint author), UNIV S FLORIDA,MICROWAVE & WIRELESS LAB,TAMPA,FL 33620, USA. NR 9 TC 9 Z9 9 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD SEP PY 1996 VL 44 IS 9 BP 1603 EP 1606 DI 10.1109/22.536614 PG 4 WC Engineering, Electrical & Electronic SC Engineering GA VH032 UT WOS:A1996VH03200016 ER PT J AU Roth, Z Baram, Y AF Roth, Z Baram, Y TI Multidimensional density shaping by sigmoids SO IEEE TRANSACTIONS ON NEURAL NETWORKS LA English DT Article ID INFORMATION; NETWORK AB An estimate of the probability density function of a random vector is obtained by maximizing the output entropy of a feedforward network of sigmoidal units with respect to the input weights, Classification problems can be solved by selecting the class associated with the maximal estimated density, Newton's optimization method, applied to the estimated density, yields a recursive estimator for a random variable or a random sequence, A constrained connectivity structure yields a linear estimator, which is particularly suitable for ''real time'' prediction, A Gaussian nonlinearity yields a closed-form solution for the network's parameters, which may also be used for initializing the optimization algorithm when other nonlinearities are employed. A triangular connectivity between the neurons and the input, which is naturally suggested by the statistical setting, reduces the number of parameters, Applications to classification and forecasting problems are demonstrated. C1 TECHNION ISRAEL INST TECHNOL,DEPT CHEM ENGN,IL-32000 HAIFA,ISRAEL. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Roth, Z (reprint author), QUALCOMM,CTR ADV TECHNOL,IL-31000 HAIFA,ISRAEL. NR 21 TC 42 Z9 42 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1045-9227 J9 IEEE T NEURAL NETWOR JI IEEE Trans. Neural Netw. PD SEP PY 1996 VL 7 IS 5 BP 1291 EP 1298 DI 10.1109/72.536322 PG 8 WC Computer Science, Artificial Intelligence; Computer Science, Hardware & Architecture; Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA VG695 UT WOS:A1996VG69500020 PM 18263522 ER PT J AU Li, PP Duquette, WH Curkendall, DW AF Li, PP Duquette, WH Curkendall, DW TI RIVA: A versatile parallel rendering system for interactive scientific visualization SO IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS LA English DT Article DE parallel terrain rendering; feed forward rendering; scientific visualization; massively parallel processor (MPP) AB JPL's Remote Interactive Visualization and Analysis System (RIVA) is described in detail. The RIVA system integrates workstation graphics, massively parallel computing technology, and gigabit communication networks to provide a flexible interactive environment for scientific data perusal, analysis, and visualization. RIVA's kernel is a highly scalable parallel perspective renderer tailored especially for the demands of large datasets beyond the sensible reach of workstations. Early experience with using RIVA to interactively explore and process multivariate, multiresolution datasets is reported; several examples using data from a variety of remote sensing instruments are discussed in detail and the results shown. Particular attention is placed on describing the algorithmic details of RIVA's parallel renderer kernel, with emphasis on the key aspects of achieving the algorithm's overall scalability. The paper summarizes the performance achieved for machine sizes up to more than 500 nodes and for initial input image/terrain bases in the 2 Gbyte range. RP CALTECH, JET PROP LAB, AUTOMAT & SCHEDULING TECHNOL GRP, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 14 TC 10 Z9 10 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 1077-2626 EI 1941-0506 J9 IEEE T VIS COMPUT GR JI IEEE Trans. Vis. Comput. Graph. PD SEP PY 1996 VL 2 IS 3 BP 186 EP 201 DI 10.1109/2945.537303 PG 16 WC Computer Science, Software Engineering SC Computer Science GA VL564 UT WOS:A1996VL56400002 ER PT J AU Ferguson, FT Lilleleht, LU AF Ferguson, FT Lilleleht, LU TI Thermovibrational convection in a vertical cylinder SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID MODULATION; ENCLOSURE; GRAVITY AB We have completed a study of thermovibrational convection in a vertical, cylindrical cavity for Rayleigh numbers, Ra, of 0, 10(4) and 10(5), and vibrational Grashof numbers, Gr(v), of 10(5) and 10(6). Results indicate that vibrational convection greatly increases heat transfer rates over the unmodulated case-by 7-15% at Gr(v) = 10(5) and by 50-65% at Gr(v) = 10(6). The observed resonant frequencies seem to agree reasonably well with the predictions given by the resonance frequency expression derived by Fu and Shieh [Int. J. Heat Mass Transfer 35, 1695-1710 (1992)]. However, this equation has been modified to include the effect of a static gravitational component and this modified equation appears to give better results when Ra and Gr(v) are roughly comparable in magnitude. Copyright (C) 1996 Elsevier Science Ltd. C1 UNIV VIRGINIA,DEPT CHEM ENGN,CHARLOTTESVILLE,VA 22903. RP Ferguson, FT (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Ferguson, Frank/C-9493-2012 NR 15 TC 4 Z9 4 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD SEP PY 1996 VL 39 IS 14 BP 2895 EP 2906 DI 10.1016/0017-9310(95)00384-3 PG 12 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA UT279 UT WOS:A1996UT27900005 ER PT J AU Hassouni, K Farhat, S Scott, CD Gicquel, A AF Hassouni, K Farhat, S Scott, CD Gicquel, A TI Modeling species and energy transport in moderate pressure diamond deposition H-2 plasmas SO JOURNAL DE PHYSIQUE III LA English DT Article; Proceedings Paper CT COST-PISE (Plasma Ion Surface Engineering) Meeting CY OCT 19-20, 1995 CL ORSAY, FRANCE ID VIBRATIONAL KINETICS; ELECTRON; HYDROGEN; REACTOR; STATES AB A one-dimensional diffusion model for H-2 plasma obtained under moderate pressure discharge conditions is presented. The transport equations resulting from this model are solved and enable the estimation of the axial profiles of the plasma species densities and of plasma temperatures on the axis of a diamond deposition microwave plasma reactor. The comparison between the calculated results and experimental measurements shows that the temperatures are well predicted by the model, while some discrepancy was observed for H-atom mole fraction. The analysis of the energy dissipation channels shows that, at low pressure, most of the power lost by the electron is dissipated in activating electron-impact H-2 dissociation reaction. The model is also used to investigate the effect of the microwave power density on the plasma composition and temperatures. It shows that the increase of the power density leads to a strong and non-linear increase of gas temperature and H-atom mole fraction. This result is also in a good agreement with measurements and is consistent with the high quality of the diamond films obtained at high power density discharge conditions. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Hassouni, K (reprint author), UNIV PARIS 13,LAB INGN MAT & HAUTES PRESS,CNRS,AVE JB CLEMENT,F-93430 VILLETANEUSE,FRANCE. NR 15 TC 29 Z9 29 U1 0 U2 3 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 1155-4320 J9 J PHYS III JI J. Phys. III PD SEP PY 1996 VL 6 IS 9 BP 1229 EP 1243 PG 15 WC Materials Science, Multidisciplinary; Physics, Applied; Physics, Fluids & Plasmas SC Materials Science; Physics GA VF356 UT WOS:A1996VF35600010 ER PT J AU Shen, J Parks, EK Bach, RE AF Shen, J Parks, EK Bach, RE TI Comprehensive analysis of two downburst-related aircraft accidents SO JOURNAL OF AIRCRAFT LA English DT Article ID IDENTIFICATION AB Although downbursts have been identified as the major cause of a number of aircraft takeoff and landing accidents, only the 1985 Dallas/Fort Worth (DFW) and the more recent (July 1994) Charlotte, North Carolina, landing accidents provided sufficient onboard recorded data to perform a comprehensive analysis of the downburst phenomenon, The first step in the present analysis was the determination of the downburst wind components, Once the wind components and their gradients were determined, the degrading effect of the wind environment on the airplane's performance was calculated, This wind-shear-induced aircraft performance degradation, sometimes called the F-factor, was broken down into two components F-1 and F-2, representing the effect of the horizontal wind gradient and the vertical wind velocity, respectively, In both the DFW and Charlotte cases, F-1 was found to be the dominant causal factor of the accident. Next, the aircraft in the two cases were mathematically modeled using the longitudinal equations of motion and the appropriate aerodynamic parameters. Based on the aircraft model and the determined winds, the aircraft response to the recorded pilot inputs showed good agreement with the onboard recordings, Finally, various landing abort strategies were studied, It was concluded that the most acceptable landing abort strategy from both an analytical and pilot's standpoint was to hold constant nose-up pitch attitude while operating at maximum engine thrust. C1 UNIV ARIZONA,DEPT AEROSP & MECH ENGN,TUCSON,AZ 85721. NASA,AMES RES CTR,GUIDANCE & NAVIGAT BRANCH,MOFFETT FIELD,CA 94035. RP Shen, J (reprint author), UNIV TEXAS,AUSTIN,TX 78723, USA. NR 12 TC 6 Z9 6 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1996 VL 33 IS 5 BP 924 EP 930 DI 10.2514/3.47037 PG 7 WC Engineering, Aerospace SC Engineering GA VL276 UT WOS:A1996VL27600011 ER PT J AU Whitmore, SA Davis, RJ Fife, JM AF Whitmore, SA Davis, RJ Fife, JM TI In-flight demonstration of a real-time flush airdata sensing system SO JOURNAL OF AIRCRAFT LA English DT Article AB A prototype real-time flush airdata sensing system has been developed and night tested at the NASA Dryden Flight Research Center, This system uses a matrix of pressure orifices on the vehicle nose to estimate airdata parameters in real time using nonlinear regression. The algorithm is robust to sensor failures and noise in the measured pressures, The real-time flush airdata sensing (FADS) system has been calibrated using inertial trajectory measurements that were bootstrapped for atmospheric conditions using meteorological data, Mach numbers as high as 1.6 and angles of attack greater than 45 deg have been tested. The system performance has been evaluated by comparing the real-time FADS to the ship system airdata computer measurements to give a quantitative evaluation relative to an accepted measurement standard, Nominal agreements of approximately 0.003 in Mach number and 0.20 deg in angle of attack and angle of sideslip have been achieved. RP Whitmore, SA (reprint author), NASA,DRYDEN FLIGHT RES CTR,AERODYNAM BRANCH,VEHICLE DYNAM GRP,M-S D-2033,POB 273,EDWARDS AFB,CA 93523, USA. NR 15 TC 3 Z9 4 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1996 VL 33 IS 5 BP 970 EP 977 DI 10.2514/3.47043 PG 8 WC Engineering, Aerospace SC Engineering GA VL276 UT WOS:A1996VL27600017 ER PT J AU Gupta, KK AF Gupta, KK TI Development of a finite element aeroelastic analysis capability SO JOURNAL OF AIRCRAFT LA English DT Article ID LANCZOS-ALGORITHM; MESH; COMPUTATIONS AB Extensions of the general-purpose finite element (FE) structural analysis program STARS for computational fluid dynamics (CFD) based aeroelastic analysis are described, Previous capabilities include structural as well as aeroelastic and aeroservoelastic analyses using linear aerodynamic theories, The current extension involves FE-based CFD solution techniques for aeroelastic analysis, and this article describes the development and application of this integrated, multidisciplinary FE analysis tool for effective modeling and simulation of aerospace vehicles, Numerical examples of flutter solution of two representative problems, namely a panel and a 45-deg swept-back wing are presented in this article, along with comparisons of computed and experimental results that testify to the efficacy of the presently developed numerical techniques. RP Gupta, KK (reprint author), NASA,DRYDEN FLIGHT RES CTR,EDWARDS AFB,CA 93523, USA. NR 26 TC 45 Z9 47 U1 1 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1996 VL 33 IS 5 BP 995 EP 1002 DI 10.2514/3.47046 PG 8 WC Engineering, Aerospace SC Engineering GA VL276 UT WOS:A1996VL27600020 ER PT J AU Stith, J Scala, J Reinking, R Martner, B AF Stith, J Scala, J Reinking, R Martner, B TI Combined use of three techniques for studying transport and dispersion in cumuli SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article; Proceedings Paper CT 6th World-Meteorological-Organization Scientific Conference on Weather Modification CY MAY-JUN -, 1994 CL PAESTUM, ITALY SP World Meteorol Org ID TRACIR; CLOUDS AB The results from three methods for studying transport and dispersion in cumuli are compared. These three methods include two tracer techniques and a numerical simulation. The tracers, SF6 and radar chaff, were simultaneously released below the base of a convective storm. The SF6 was measured in situ by two research. aircraft and the chaff was followed using TRACIR (tracking air with circular-polarized radar), a method that measures the circular depolarization ratio (CDR) of the chaff, which is much stronger than that of most hydrometeors. TRACIR allows the CDR signal from the chaff to be measured and traced even when the reflectivity from the chaff is much less than that from the cloud. The behavior of the two-tracer release was compared with the trajectories of air from a two-dimensional simulation of the storm, using a nonhydrostatic cloud model, the National Aeronautics and Space Administration/Goddard Cumulus Ensemble Model. By combining information hom the three techniques, their individual shortcomings are alleviated, and a more complete documentation of transport and dispersion is provided. The tracers were followed during a 32-min period as they were transported 6 km vertically by the storm at an average rate of 2.6 m s(-1). This was within the ranges of the vertical transport rate of trajectories in the model simulation. The maximum updraft speed measured by the aircraft was 18 m s(-1), which agreed well with the maximum updraft in the simulations of 20 m s(-1). Both the simulation and the chaff observations show that portions of the released material were incorporated into the cloud and other portions were not. The main area of downward transport was located in the lower third of the simulated cloud where the rainfall was the heaviest. Major downdrafts were not found in the upper regions of the storm where the aircraft were sampling. The simulation suggests that the precipitation;induced downdraft played the major role in determining the trajectories of air from the cloud base, at least at the mature stage of the storm. Interactions between cloud-base air and downdrafts took place in the lower third of the storm where the bulk of the precipitation was located. C1 UNIV N DAKOTA,GRAND FORKS,ND 58201. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NOAA,ENVIRONM TECHNOL LAB,BOULDER,CO. NR 11 TC 3 Z9 3 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD SEP PY 1996 VL 35 IS 9 BP 1387 EP 1401 DI 10.1175/1520-0450(1996)035<1387:CUOTTF>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VJ476 UT WOS:A1996VJ47600002 ER PT J AU Hedin, AE Fleming, EL Manson, AH Schmidlin, FJ Avery, SK Clark, RR Franke, SJ Fraser, GJ Tsuda, T Vial, F Vincent, RA AF Hedin, AE Fleming, EL Manson, AH Schmidlin, FJ Avery, SK Clark, RR Franke, SJ Fraser, GJ Tsuda, T Vial, F Vincent, RA TI Empirical wind model for the upper, middle and lower atmosphere SO JOURNAL OF ATMOSPHERIC AND TERRESTRIAL PHYSICS LA English DT Article ID LOWER-THERMOSPHERIC WINDS; INCOHERENT-SCATTER; METEOR RADAR; SASKATOON 52-DEGREES-N; HIGH-LATITUDE; GLOBAL-MODEL; MEAN WINDS; TIDES; MESOSPHERE; REGION AB The HWM90 thermospheric wind model has been revised in the lower thermosphere and extended into the mesosphere, stratosphere and lower atmosphere to provide a single analytic model for calculating zonal and meridional wind profiles representative of the climatological average for various geophysical conditions. Gradient winds from CIRA-86 plus rocket soundings, incoherent scatter radar, MF radar, and meteor radar provide the data base and are supplemented by previous data driven model summaries. Low-order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, local time (tides), and longitude (stationary wave 1), with a cubic spline interpolation in altitude. The model represents a smoothed compromise between the original data sources. Although agreement between various data sources is generally good, some systematic differences are noted, particularly near the mesopause. Overall root mean square differences between data and model values are on the order of 15 m/s in the mesosphere and 10 m/s in the stratosphere for zonal winds, and 10 m/s and 5 m/s respectively for meridional winds. (C) 1996 Published by Elsevier Science Ltd. C1 APPL RES CORP,LANDOVER,MD 20771. UNIV SASKATCHEWAN,SASKATOON,SK S7N 0W0,CANADA. NASA,GODDARD SPACE FLIGHT CTR,WALLOPS FLIGHT FACIL,WALLOPS ISL,VA 23337. UNIV COLORADO,BOULDER,CO 80309. UNIV NEW HAMPSHIRE,DURHAM,NH 03824. UNIV ILLINOIS,URBANA,IL 62801. UNIV CANTERBURY,CHRISTCHURCH 1,NEW ZEALAND. KYOTO UNIV,KYOTO,JAPAN. ECOLE POLYTECH,F-91128 PALAISEAU,FRANCE. UNIV ADELAIDE,ADELAIDE,SA 5001,AUSTRALIA. RP Hedin, AE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI tsuda, toshitaka/A-3035-2015 NR 55 TC 471 Z9 486 U1 2 U2 25 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0021-9169 J9 J ATMOS TERR PHYS JI J. Atmos. Terr. Phys. PD SEP PY 1996 VL 58 IS 13 BP 1421 EP 1447 DI 10.1016/0021-9169(95)00122-0 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UQ457 UT WOS:A1996UQ45700005 ER PT J AU Strawn, RC Biswas, R Lyrintzis, AS AF Strawn, RC Biswas, R Lyrintzis, AS TI Helicopter noise predictions using Kirchhoff methods SO JOURNAL OF COMPUTATIONAL ACOUSTICS LA English DT Article ID BLADE-VORTEX INTERACTIONS; SPEED IMPULSIVE NOISE; ROTOR; HOVER AB This paper presents two methods for predicting the noise from helicopter rotors in forward flight. Aerodynamic and acoustic solutions in the near held are computed with a finite-difference solver for the Euler equations. Two different Kirchhoff acoustics methods are then used to propagate the acoustic signals to the far field in a computationally-efficient manner. One of the methods uses a Kirchhoff surface that rotates with the rotor blades. The other uses a nonrotating Kirchhoff surface. Results from both methods are compared to experimental data for both highspeed impulsive noise and blade-vortex interaction noise. Agreement between experimental data and computational results is excellent for both cases. The rotating and nonrotating Kirchhoff methods are also compared for accuracy and efficiency. Both offer high accuracy with reasonable computer resource requirements. The Kirchhoff integrations efficiently extend the near-field finite-difference results to predict the far field helicopter noise. C1 NASA,AMES RES CTR,RIACS,MOFFETT FIELD,CA 94035. PURDUE UNIV,SCH AERONAUT & ASTRONAUT,W LAFAYETTE,IN 47907. RP Strawn, RC (reprint author), USA,NASA,AMES RES CTR,AFDD,MOFFETT FIELD,CA 94035, USA. NR 27 TC 9 Z9 9 U1 0 U2 1 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 9128, SINGAPORE SN 0218-396X J9 J COMPUT ACOUST JI J. Comput. Acoust. PD SEP PY 1996 VL 4 IS 3 BP 321 EP 339 DI 10.1142/S0218396X96000106 PG 19 WC Acoustics; Mathematics, Interdisciplinary Applications SC Acoustics; Mathematics GA VP303 UT WOS:A1996VP30300004 ER PT J AU Venkatakrishnan, V Mavriplis, DJ AF Venkatakrishnan, V Mavriplis, DJ TI Implicit method for the computation of unsteady flows on unstructured grids SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID NAVIER-STOKES EQUATIONS; MOVING FINITE-ELEMENTS; EULER EQUATIONS; DYNAMIC MESHES; ALGORITHM; AGGLOMERATION; SCHEMES AB An implicit method for the computation of unsteady Rows on unstructured grids is presented. Following a finite difference approximation for the time derivative, the resulting nonlinear system of equations is solved at each time step by using an agglomeration multigrid procedure. The method allows for arbitrarily large time steps and is efficient in terms of computational effort and storage. Inviscid and viscous unsteady flows are computed to validate the procedure. The issue of the mass matrix which arises with vertex-centered finite volume schemes is addressed. The present formulation allows the mass matrix to be inverted indirectly. A mesh point movement and reconnection procedure is described that allows the grids to evolve with the motion of bodies. As an example of flow over bodies in relative motion, flow over a multi-element airfoil system undergoing deployment is computed. (C) 1996 Academic Press, Inc. RP NASA, LANGLEY RES CTR, INST COMP APPL SCI & ENGN, MS 132C, HAMPTON, VA 23681 USA. NR 48 TC 57 Z9 63 U1 1 U2 3 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 EI 1090-2716 J9 J COMPUT PHYS JI J. Comput. Phys. PD SEP PY 1996 VL 127 IS 2 BP 380 EP 397 DI 10.1006/jcph.1996.0182 PG 18 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA VF912 UT WOS:A1996VF91200011 ER PT J AU Singh, NB Glicksman, ME Coriell, SR Duval, WMB Santoro, GJ DeWitt, R AF Singh, NB Glicksman, ME Coriell, SR Duval, WMB Santoro, GJ DeWitt, R TI Measurement of diffusion coefficient using a diaphragm cell: PbBr2-AgBr system SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID LEAD BROMIDE CRYSTALS; QUALITY; GROWTH AB The diffusion coefficient of molten lead bromide-silver bromide was determined using a two chamber diaphragm cell separated by the porous membrane of a sintered glass disk. Only dilute mixtures of PbBr2-AgBr were studied. The interdiffusion coefficient was determined to be 1.71 x 10(-5) cm(2)/s. C1 RENSSELAER POLYTECH INST,DEPT MAT SCI & ENGN,TROY,NY 12180. NIST,DIV MET,GAITHERSBURG,MD 20899. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Singh, NB (reprint author), NORTHROP GRUMMAN SCI & TECHNOL CTR,PITTSBURGH,PA 15235, USA. OI Glicksman, Martin/0000-0002-2675-2759 NR 4 TC 7 Z9 8 U1 0 U2 2 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 SEP PY 1996 VL 167 IS 1-2 BP 107 EP 110 DI 10.1016/0022-0248(96)00245-X PG 4 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VN615 UT WOS:A1996VN61500013 ER PT J AU Noever, D Pusey, ML Forsythe, EL Baskaran, S AF Noever, D Pusey, ML Forsythe, EL Baskaran, S TI Artificial neural network prediction of tetragonal lysozyme face growth rates SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID CRYSTAL-GROWTH; CRYSTALLIZATION AB To predict unknown growth rates for the tetragonal lysozyme (110) crystal face, an artificial neural network (ANN) is designed and tested using five input variables (including protein and salt concentration, temperature, initial crystal size and angle of the (110) crystal face to the vertical). The ANN shows ninety percent prediction success for the entire data set of face growth rates, compared to a multidimensional linear regression which shows a maximum correlation coefficient, R = 0.768. In this case, using the number of categories criterion (NCC) for the standard multiple regression, traditional statistical methods can distinguish fewer than 2 categories (high and low growth rates) and cannot group or cluster the data to give more refined partitions. A non-linear surface requires at least 3 categories (high, low, and medium growth rates) to define its curvature. The outcome of the neural net, on the other hand, shows that a complex, multimodal surface (> 2000 measurements) can be reduced to a smaller, more manageable subset (< 150 significant training points) of best and worst growth conditions. The isocontours for best temperature and protein concentration values for lysozyme growth have a complex saddle, the geometrical structure of which would elude a simple experimental design based on usual gradient descent methods for finding optimum. These results suggest that a more complete optimization plan, comparable in sophistication to the protein folding optimization itself, may be required to define a global summit on the crystallization surface. Criteria for producing a general optimization strategy for protein crystallization are critically discussed and recommendations for building such an experimental design program based on neural networks are briefly put forward. C1 UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. INST MOL BIOTECHNOL EV,D-7745 JENA,GERMANY. RP Noever, D (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,BIOPHYS BRANCH,MAIL CODE ES-76,HUNTSVILLE,AL 35812, USA. NR 17 TC 6 Z9 6 U1 0 U2 2 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 SEP PY 1996 VL 167 IS 1-2 BP 221 EP 236 DI 10.1016/0022-0248(96)00173-X PG 16 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VN615 UT WOS:A1996VN61500029 ER PT J AU Pines, V Chait, A Zlatkowski, M AF Pines, V Chait, A Zlatkowski, M TI Thermal diffusion dominated dendritic growth - An analysis of the wall proximity effect SO JOURNAL OF CRYSTAL GROWTH LA English DT Letter ID STATE AB It is demonstrated that using a simple correction to the original Ivantsov solution to account for wall proximity effects is sufficient to describe the Peclet number microgravity data of Glicksman et al. [M.E. Glicksman, M.B. Koss and E.A. Winsa, Phys. Rev. Lett. 73 (1994) 573; M.E. Glicksman, M.B. Koss, L.T. Bushnell, J.C. LaCombe and E.A. Winsa, ISLJ International 35 (1995) 1216; MRS Fall Meeting, Symp. P, Boston MA, 1995, in press] at low supercooling. The analytical correction provides for the enhanced diffusive heat transfer when the thermal diffusion length becomes comparable to the physical chamber dimension. The wall proximity effect is also responsible for the existence of a lower supercooling limit below which the dendrite cannot grow in a steady-state manner. It is concluded that Glicksman's USMP-2 microgravity data is thermal diffusion dominated and thus entirely appropriate for comparison with dendritic growth theories. C1 NASA,LEWIS RES CTR,COMPUTAT MAT LAB,CLEVELAND,OH 44135. CASE WESTERN RESERVE UNIV,DEPT PHYS,CLEVELAND,OH 44106. NR 13 TC 34 Z9 34 U1 0 U2 0 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 SEP PY 1996 VL 167 IS 1-2 BP 383 EP 386 DI 10.1016/0022-0248(96)00252-7 PG 4 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VN615 UT WOS:A1996VN61500048 ER PT J AU Singh, NB Mani, SS Adam, JD Coriell, SR Glicksman, ME Duval, WMB Santoro, GJ DeWitt, R AF Singh, NB Mani, SS Adam, JD Coriell, SR Glicksman, ME Duval, WMB Santoro, GJ DeWitt, R TI Direct observations of interface instabilities SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th International Conference on Crystal Growth CY JUN 18-23, 1995 CL THE HAGUE, NETHERLANDS SP Int Org Crystal Growth, Dutch Assoc Crystal Growth ID LEAD BROMIDE CRYSTALS; BINARY ALLOY; SOLIDIFICATION; GROWTH AB Single crystals of lead bromide doped with silver bromide were grown by the vertical Bridgman method. Direct observations were made in order to understand the interfacial instabilities. Numerical studies were carried out to provide a framework for interpreting the observed convective and morphological instabilities. Observations on interfacial instabilities in lead bromide with 500 and 5000 ppm silver bromide impurities supported the numerical results predicted for 1-g conditions. X-ray rocking curves, X-ray contour scans, and etch-pit studies showed that increasing solutal convection deteriorated the crystal quality of the crystals. C1 NIST,GAITHERSBURG,MD 20899. RENSSELAER POLYTECH INST,DEPT MAT SCI & ENGN,TROY,NY 12180. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Singh, NB (reprint author), WESTINGHOUSE SCI & TECHNOL CTR,1310 BEULAH RD,PITTSBURGH,PA 15235, USA. OI Glicksman, Martin/0000-0002-2675-2759 NR 7 TC 13 Z9 13 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD SEP PY 1996 VL 166 IS 1-4 BP 364 EP 369 DI 10.1016/0022-0248(95)00529-3 PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VM089 UT WOS:A1996VM08900063 ER PT J AU Aggarwal, MD Wang, WS Choi, J Myers, T Clark, RD Penn, BG Frazier, DO Sanghadasa, M AF Aggarwal, MD Wang, WS Choi, J Myers, T Clark, RD Penn, BG Frazier, DO Sanghadasa, M TI Modified Bridgman-Stockbarger growth of a novel NLO organic crystal (2-methoxyphenyl)-methylene-propanedinitrile SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th International Conference on Crystal Growth CY JUN 18-23, 1995 CL THE HAGUE, NETHERLANDS SP Int Org Crystal Growth, Dutch Assoc Crystal Growth AB The Bridgman-Stockbarger method offers a unique opportunity for positioning the solid-liquid interface in the hot zone by a suitable adjustment of the two zone temperatures. The method, however, yields inhomogeneous organic crystals in relation to the progressive degradation of the material during growth. To solve this problem, a modified Bridgman-Stockbar barger method (MBS) has been developed and is used to keep the smallest possible quantity of product in the melt for a short time period. In this method, the gradient is chosen to be 5 to 10 degrees C/cm and the ampoules downward rate is chosen to be 0.1 to 0.3 mm/h. For the given conditions, several (2-methoxyphenyl)-methylene-propanedinitrile or 2-dicyanavinylanisole (DIVA) single crystals of good optical quality and a size of 10 x 10 x 50 mm(3) have been successfully grown. Preliminary results on the characterization of these crystals are presented. C1 NEW MEXICO HIGHLANDS UNIV,LAS VEGAS,NM 87701. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. RP Aggarwal, MD (reprint author), ALABAMA A&M UNIV,DEPT PHYS,NORMAL,AL 35762, USA. NR 7 TC 3 Z9 3 U1 1 U2 2 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 SEP PY 1996 VL 166 IS 1-4 BP 542 EP 544 DI 10.1016/0022-0248(95)00500-5 PG 3 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VM089 UT WOS:A1996VM08900093 ER PT J AU Caillat, T Fleurial, JP Borshchevsky, A AF Caillat, T Fleurial, JP Borshchevsky, A TI Bridgman-solution crystal growth and characterization of the skutterudite compounds CoSb3 and RhSb3 SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th International Conference on Crystal Growth CY JUN 18-23, 1995 CL THE HAGUE, NETHERLANDS SP Int Org Crystal Growth, Dutch Assoc Crystal Growth ID TRANSPORT AB Compounds with the skutterudite structure have recently been identified as advanced thermoelectric materials. We report on the crystal growth and characterization of the skutterudite compounds CoSb3 and RhSb3 which form peritectically at 873 and 900 degrees C, respectively. Large single crystals were obtained by the vertical gradient freeze technique from solutions rich in antimony. The samples were characterized by high-temperature Hall-effect and electrical resistivity measurements. Bandgaps of 0.56 and 0.80 eV were estimated from these measurements for CoSb3 and RhSb3, respectively. N-type CoSb3 samples were obtained by doping with Te. Exceptionally high p-type Hall-mobility values have been measured and a room-temperature value of 3445 cm(2) V-1 s(-1) was obtained for CoSb3 at a carrier concentration of 4 x 10(17) cm(-3) and 8000 cm(2) V-1 s(-1) was obtained for RhSb3 at a carrier concentration of 3.5 x 10(18) cm(-3). RP Caillat, T (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 10 TC 71 Z9 76 U1 4 U2 37 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 SEP PY 1996 VL 166 IS 1-4 BP 722 EP 726 DI 10.1016/0022-0248(95)00478-5 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VM089 UT WOS:A1996VM08900126 ER PT J AU Chen, KT Zhang, Y Egarievwe, SU George, MA Burger, A Su, CH Sha, YG Lehoczky, SL AF Chen, KT Zhang, Y Egarievwe, SU George, MA Burger, A Su, CH Sha, YG Lehoczky, SL TI Post-growth annealing of CdS crystals grown by physical vapor transport SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th International Conference on Crystal Growth CY JUN 18-23, 1995 CL THE HAGUE, NETHERLANDS SP Int Org Crystal Growth, Dutch Assoc Crystal Growth ID LUMINESCENCE; PRESSURE; SPECTRA; RAMAN AB In this study, the photoluminescent and electric properties of as-grown CdS crystals and the effects observed after post-growth annealing in a cadmium, sulphur, and selenium overpressure were investigated. Bulk CdS crystals were grown by physical vapor transport (PVT) from high-purity starting materials, and two types of as-grown crystals, one ''dark'' and the other ''clear'' were obtained both having a medium resistivity of 10(6)-10(8) Omega . cm. The ''dark''-type crystals are cadmium rich, as evidenced by an emission peak centered around 2.07 eV, which may be attributed to sulphur vacancies, while in the ''clear'' crystals, this emission is less pronounced. Heal treatment under a cadmium-vapor atmosphere has the effect of decreasing the resistivity by approximately 5 orders of magnitude, while sulphur annealing at 500 degrees C, increases the resistivity of the as-grown crystals by 4 orders of magnitude and creates a new emission peak centered around 620 nm (2 ev). C1 FISK UNIV,DEPT PHYS,CTR PHOTON MAT & DEVICES,NASHVILLE,TN 37208. GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. NR 26 TC 12 Z9 13 U1 1 U2 4 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 SEP PY 1996 VL 166 IS 1-4 BP 731 EP 735 DI 10.1016/0022-0248(95)00513-7 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VM089 UT WOS:A1996VM08900128 ER PT J AU Su, CH Sha, YG Mazuruk, K Lehoczky, SL Liu, HC Fang, R Brebrick, RF AF Su, CH Sha, YG Mazuruk, K Lehoczky, SL Liu, HC Fang, R Brebrick, RF TI Mass flux and partial pressures of ZnSe by physical vapor transport SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 11th International Conference on Crystal Growth CY JUN 18-23, 1995 CL THE HAGUE, NETHERLANDS SP Int Org Crystal Growth, Dutch Assoc Crystal Growth ID SILICA GLASS AMPOULES; CDTE SOLID-SOLUTIONS; MOLE PERCENT CDTE; THERMODYNAMIC PROPERTIES; CLOSED AMPOULES; SINGLE-CRYSTALS; RESIDUAL-GAS; GROWTH; ABSORPTION; TELLURIDE AB Mass fluxes of ZnSe by physical vapor transport (PVT) were measured in the temperature range of 1050-1140 degrees C using an in situ dynamic technique. The starting materials were heat treated by a hydrogen reduction process followed by the dynamic bake-out method. The amount and composition of the residual gas inside the experimental ampoules were measured after the transport experiments using a total-pressure gauge. The total residual gas pressures measured were about one order of magnitude lower than the values reported on similar processed ZnSe ampoules which were not treated with a hydrogen reduction process. As a result of the reduction in the residual gas pressure, the measured fluxes were 3-7 times higher than previously reported and correspond to a growth rate higher than 10 mm/day at 1120 degrees C. The simultaneous measurements of partial pressures of transport species and the mass fluxes were also performed on a ZnSe optical ampoule. The partial pressures of Zn and Se-2 were obtained by measuring the optical densities of the vapor at the wavelengths of 2138, 3405, 3508, 3613, and 3792 Angstrom. For the first time, the experimentally obtained mass fluxes were compared with those calculated, without any adjustable parameters, from a one-dimensional diffusion model which uses all the measured parameters (thermal field, partial pressures of transport species, and residual gas) as inputs, and good agreement was observed. C1 MARQUETTE UNIV,MAT SCI & MET PROGRAM,MILWAUKEE,WI 53233. RP Su, CH (reprint author), NASA,MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. NR 43 TC 6 Z9 6 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD SEP PY 1996 VL 166 IS 1-4 BP 736 EP 744 DI 10.1016/0022-0248(95)00509-9 PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VM089 UT WOS:A1996VM08900129 ER PT J AU Joslin, RD Eriebacher, G Hussaini, MV AF Joslin, RD Eriebacher, G Hussaini, MV TI Active control of instabilities in laminar boundary layers - Overview and concept validation SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID TRANSITION; SIMULATION; WAVES AB This paper (the first in a series) focuses on using active-control methods to maintain laminar flow in a region of the flow in which the natural instabilities, if left unattended, lead to turbulent flow. The authors review previous studies that examine wave cancellation (currently the most prominent method) and solve the unsteady, nonlinear Navier-Stokes equations to evaluate this method of controlling instabilities. It is definitively shown that instabilities are controlled by the linear summation of waves (i.e., wave cancellation). Although a mathematically complete method for controlling arbitrary instabilities has been developed, the review, duplication, and physical explanation of previous studies are important steps for providing an independent verification of those studies, for establishing a framework for the work which will involve automated transition control, and for detailing the phenomena by-which the automated studies can be used to expand knowledge of flow control. C1 FLORIDA STATE UNIV,INST COMP APPLICAT SCI & ENGN,TALLAHASSEE,FL 32306. RP Joslin, RD (reprint author), NASA,LANGLEY RES CTR,FLUID MECH & ACOUST DIV,LFC PROJECT TEAM,HAMPTON,VA 23681, USA. NR 19 TC 10 Z9 11 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0098-2202 J9 J FLUID ENG-T ASME JI J. Fluids Eng.-Trans. ASME PD SEP PY 1996 VL 118 IS 3 BP 494 EP 497 DI 10.1115/1.2817785 PG 4 WC Engineering, Mechanical SC Engineering GA VN191 UT WOS:A1996VN19100010 ER PT J AU Menter, FR AF Menter, FR TI A comparison of some recent eddy-viscosity turbulence models SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID FLOWS AB The performance of recently developed eddy-viscosity turbulence models, including the author's SST model, is evaluated against a number of attached and separated adverse pressure gradient flows. The results are compared in detail against experimental data, as well as against the standard k-epsilon model. Grid convergence was established for all computations. The study involves four different, state-of-the-art finite difference (finite volume) codes. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Menter, FR (reprint author), ASC GMBH,SOFTWARE DEV,D-83607 HOLZKIRCHEN,GERMANY. NR 20 TC 40 Z9 41 U1 2 U2 12 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0098-2202 J9 J FLUID ENG-T ASME JI J. Fluids Eng.-Trans. ASME PD SEP PY 1996 VL 118 IS 3 BP 514 EP 519 DI 10.1115/1.2817788 PG 6 WC Engineering, Mechanical SC Engineering GA VN191 UT WOS:A1996VN19100013 ER PT J AU French, JRP Bur, MT AF French, JRP Bur, MT TI The effect of zebra mussel consumption on growth of freshwater drum in Lake Erie SO JOURNAL OF FRESHWATER ECOLOGY LA English DT Article ID DREISSENA-POLYMORPHA; GREAT-LAKES AB We examined food habits and scale annuli of freshwater drum (Aplodinotus grunniens) from western Lake Erie to determine whether increasing predation on zebra mussels (Dreissena polymorpha) had affected growth of freshwater drum. The volume of zebra mussels in drum guts was greater in older fish. Growth of age classes 3-4, which consumed few zebra mussels, was greater in the most productive year for zebra mussels, July 1990 - August 1991, than in three prior years. The total lengths of 5-year-old drum changed little. The mean total length of 6-year-old females has declined since the zebra mussel invaded Lake Erie, even through mussels comprised more than two-thirds of gut samples in these fish. These studies suggest that zebra mussels may not benefit freshwater drum when serving as a staple in the diet. C1 NASA,PLUM BROOK STN,SANDUSKY BIOL STN,SANDUSKY,OH 44870. RP French, JRP (reprint author), GREAT LAKES SCI CTR,NATL BIOL SERV,1451 GREEN RD,ANN ARBOR,MI 48105, USA. NR 24 TC 34 Z9 34 U1 1 U2 8 PU OIKOS PUBL INC PI LA CROSSE PA PO BOX 2558, LA CROSSE, WI 54601 SN 0270-5060 J9 J FRESHWATER ECOL JI J. Freshw. Ecol. PD SEP PY 1996 VL 11 IS 3 BP 283 EP 289 DI 10.1080/02705060.1996.9664450 PG 7 WC Ecology; Limnology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA VM970 UT WOS:A1996VM97000004 ER PT J AU BarSever, YE AF BarSever, YE TI A new model for GPS yaw attitude SO JOURNAL OF GEODESY LA English DT Article AB modeling of the GPS satellite yaw attitude is a key element in high-precision geophysical applications. This fact is illustrated here as a new model for the GPS satellite yaw attitude is introduced. The model constitutes a significant improvement over the previously available model in terms of efficiency, flexibility and portability. The model is described in detail and implementation issues, including the proper estimation strategy, are addressed. The performance of the new model is analyzed and an error budget is presented. Finally, the implementation of the yaw bias on the GPS satellites is reviewed from its inception until it reached a steady state in November, 1995. RP BarSever, YE (reprint author), CALTECH,JET PROP LAB,MS 238-600,PASADENA,CA 91109, USA. NR 9 TC 49 Z9 58 U1 1 U2 7 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0949-7714 J9 J GEODESY JI J. Geodesy PD SEP PY 1996 VL 70 IS 11 BP 714 EP 723 DI 10.1007/s001900050060 PG 10 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA VK824 UT WOS:A1996VK82400006 ER PT J AU Vassiliadis, D Klimas, AJ Baker, DN Roberts, DA AF Vassiliadis, D Klimas, AJ Baker, DN Roberts, DA TI The nonlinearity of models of the vB(south)-AL coupling SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HIGH TIME RESOLUTION; GEOMAGNETIC-ACTIVITY; PARAMETER CORRELATIONS; MAGNETOSPHERE; SPACE AB We study the solar wind-geomagnetic activity coupling by analyzing time series of upsilon B-South and AL data in the period of December 29-31, 1974. We construct state-space models whose parameters are adjusted so that when their input is upsilon B-South their output is as close to AL as possible and find that nonlinear models are significantly more accurate than linear models in short-term predictions. Because the real dynamics is unknown, we measure the degree of nonlinearity indirectly as the number of geomagnetic/solar wind events required to make the best prediction. Linear models are related to large event numbers, comparable to the size of the database (>40 k of samples, or 2 months of data). Small numbers of events (values between 10 and 100 are typical) correspond to nonlinear models. Model performance is measured by the short-term time-averaged prediction error. Nonlinear models have consistently lower prediction error than linear ones, often by as much as an order of magnitude. In testing the above result (1) we show that conclusions regarding model nonlinearity are biased if the prediction error is averaged over many prediction runs with different levels of activity. When we average over activity level, nonlinear and linear models appear to be equally accurate. (2) There is a range of prediction times over which linear and nonlinear models are adequately separated in accuracy. However, the models are similarly accurate if the prediction time is too short (such as 1-2 min, when the models fit high-frequency effects and noise) or for long prediction times (>1 hour, when the prediction error stops increasing). (3) The model nonlinearity is an indication for nonlinearity in the physical coupling. We show that two alternative explanations, namely nonstationarity and non-Gaussian nature of the data, are not sufficient: nonlinear models predict better even after we suppress these properties in the data. (4) The prediction error depends on the location in the state-input space, or roughly, on the activity level. In conclusion, this study further confirms the nonlinear character of the upsilon B-South-AL coupling. C1 UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RP Vassiliadis, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771, USA. RI Roberts, Dana/D-4625-2012 NR 34 TC 26 Z9 27 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1996 VL 101 IS A9 BP 19779 EP 19787 DI 10.1029/96JA01408 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VF257 UT WOS:A1996VF25700014 ER PT J AU Delcourt, DC Belmont, G Sauvaud, JA Moore, TE Martin, RF AF Delcourt, DC Belmont, G Sauvaud, JA Moore, TE Martin, RF TI Centrifugally driven phase bunching and related current sheet structure in the near-Earth magnetotail SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INNER PLASMA SHEET; TAIL CURRENT SHEET; MAGNETIC-FIELD; GROWTH-PHASE; NONLINEAR DYNAMICS; CHARGED-PARTICLES; SUBSTORM; MODEL; PRECIPITATION; MOTION AB We examine the role of centrifugal effects during nonadiabatic interactions of charged particles with the magnetotail current sheet. It is shown that when the parameter kappa (defined as the square root of the minimum curvature radius- to- maximum Larmor radius) is of the order of unity, as is the case for ions traveling in the near-Earth plasma sheet, enhanced centrifugal effects lead to prominent bunching of the particles in gyration phase. As a result of this bunching effect we demonstrate that a thin current sheet develops in the vicinity of the tail midplane. When average values of the plasma density (a few tenths of ions per cubic centimeter) and temperature (several keV) in the near-Earth tail are used, the current sheet obtained has a characteristic thickness of the order of a few tenths of an Earth radius and leads to significant stretching of the local magnetic field lines. A further consequence of phase bunching is the buildup of a substantial current in the Earth-tail direction at law latitudes, which leads to field line inclination in the dawn-dusk direction. This phase bunching mechanism, which maximizes when the bulk of the ion distribution nears kappa = 1, is of potential importance for the dynamics of the inner plasma sheet during the growth phase of substorms. C1 CNRS,CTR ETUD ENVIRONM TERR & PLANETAIRES,F-78140 VELIZY VILLACOUBL,FRANCE. ILLINOIS STATE UNIV,DEPT PHYS,NORMAL,IL 61740. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. CNRS,CTR ETUD SPATIALE RAYONNEMENTS,F-31029 TOULOUSE,FRANCE. RP Delcourt, DC (reprint author), CNRS,CTR ETUD ENVIRONM TERR & PLANETAIRES,4 AVE NEPTUNE,F-94107 ST MAUR FOSSES,FRANCE. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 21 TC 18 Z9 18 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1996 VL 101 IS A9 BP 19839 EP 19847 DI 10.1029/96JA01772 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VF257 UT WOS:A1996VF25700017 ER PT J AU Suess, ST Wang, AH Wu, ST AF Suess, ST Wang, AH Wu, ST TI Volumetric heating in coronal streamers SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WHITE-LIGHT BRIGHTNESS; SOLAR-WIND; MASS EJECTIONS; MAGNETIC-FIELD; MODEL; DENSITY; FLOWS; SUN AB The addition of a volumetric heat source to a coronal streamer model produces distinct, important changes in the model. Originally, such beating was added to meet the observational requirement for a thin current sheet above streamers. Here we report additional consequences of a volumetric heat source, together with the effects of redistribution of heat through thermal conduction. Specifically, we address the question of whether a heat source will allow a truly steady state to be achieved in the presence of thermal conduction, something known to be impossible for an adiabatic gas. The heat source causes a slow, continuing expansion and stripping of magnetic flux from the top of a streamer until the streamer essentially evaporates and the field is fully open to the interplanetary medium after an interval which depends on the magnitude of the source but typically varies from weeks to months. We find that thermal conduction does not quench the evaporation. We also find that the heat source, in the absence of other processes, must depend on the magnetic field geometry to simulate both the thinness of current sheets above streamers and the low density/high flow speed in coronal holes. Finally, we find that the expansion is not necessarily continuous. C1 UNIV ALABAMA,CTR SPACE PLASMA & AERON RES,HUNTSVILLE,AL 35899. RP Suess, ST (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SOLAR PHYS BRANCH,MAIL CODE ES82,HUNTSVILLE,AL 35812, USA. NR 24 TC 66 Z9 67 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1996 VL 101 IS A9 BP 19957 EP 19966 DI 10.1029/96JA01458 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VF257 UT WOS:A1996VF25700028 ER PT J AU Wilson, RM Hathaway, DH Reichmann, EJ AF Wilson, RM Hathaway, DH Reichmann, EJ TI On the behavior of the sunspot cycle near minimum SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-CYCLE; MAXIMUM AB The decline of cycle 22 is shown to be consistent with the notion that it will have a period <11 years. On the basis of the modern era of sunspot cycles, the average length of short-period cycles has been 123 +/- 3 months, suggesting that onset for cycle 23 will be about December 1996 (+/- 3 months). As yet, no high-latitude (25 degrees or more) new cycle spots have been reported. Because the occurrence of a high-latitude new cycle spot group has always preceded conventional cycle onset by at least 3 months, one infers that its occurrence is most imminent. RP Wilson, RM (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,SOLAR PHYS BRANCH,ES82 96-025,HUNTSVILLE,AL 35812, USA. NR 11 TC 27 Z9 30 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1996 VL 101 IS A9 BP 19967 EP 19972 DI 10.1029/96JA01820 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VF257 UT WOS:A1996VF25700029 ER PT J AU Riley, P Sonett, CP Tsurutani, BT Balogh, A Forsyth, RJ Hoogeveen, GW AF Riley, P Sonett, CP Tsurutani, BT Balogh, A Forsyth, RJ Hoogeveen, GW TI Properties of arc-polarized Alfven waves in the ecliptic plane: Ulysses observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; INTERPLANETARY DISCONTINUITIES; TURBULENCE AB Ulysses observations of the interplanetary magnetic field reveal well-ordered rotations on the timescale of several hours. These have been previously identified as ''arc-polarized'' Alfven waves. Rotational discontinuities (RDs) are often an integral part of the wave. This study focuses on a statistical description of these rotations (ARCs) in the ecliptic plane. It is found that (1) most ARCs are limited to 180 degrees or less in rotation; (2) these ARCs account for between 5 and 10% of the total data set; (3) there appears to be no preferred helicity; (4) the minimum-variance direction typically makes a large oblique angle with the average magnetic field (< B >), while the intermediate-variance direction is loosely aligned with < B >; (5) most of the events display a small but significant nonzero magnetic field component in the direction of minimum variance; (6) the cross helicity of the ARCs tends to be higher than during non-ARC intervals; (7) there are 2.4 times more discontinuities during ARC intervals than during non-ARC intervals; (8) essentially all ARCs are propagating outward in the rest frame of the solar wind plasma; and (9) there is no simple relationship between the rate of occurrence of the ARCs and heliocentric distance. Comparing these results with the predicted signatures of a number of models, it is found that arc-polarized Alfven waves with embedded RDs propagating along the minimum-variance direction best fit the majority of events. C1 UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA. JET PROP LAB, PASADENA, CA 91109 USA. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND. UNIV ARIZONA, DEPT PLANETARY SCI, TUCSON, AZ 85721 USA. RP Riley, P (reprint author), LOS ALAMOS NATL LAB, POB 1663, LOS ALAMOS, NM 87545 USA. NR 22 TC 27 Z9 28 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1996 VL 101 IS A9 BP 19987 EP 19993 DI 10.1029/96JA01743 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VF257 UT WOS:A1996VF25700031 ER PT J AU Thurman, SW Flashner, H AF Thurman, SW Flashner, H TI New pulse-modulation technique for guidance and control of automated spacecraft SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID UNCERTAIN SYSTEMS AB A comprehensive approach to problems such as automated on-orbit rendezvous and soft landing on a planetary surface is presented for spacecraft employing pulse-operated (on-off) propulsion systems. Using a technique derived from robust control theory, a new class of guidance algorithms that modulate the duration and frequency of thruster firings Is developed. These algorithms allow analytical characterization of transient errors, limit cycle deadband, and the set of possible terminal conditions in the design process, without the use of dynamic al approximations such as linearization. with this approach, the desired performance is ensured in the presence of dynamical modeling errors with known bounds; the effects of navigational errors can be minimized to the extent that they can be bounded, A realistic application is illustrated via computer simulation of a hypothetical mission scenario, in which a robotic spacecraft equipped with an aided-inertial guidance system soft lands on the planet Mars. C1 UNIV SO CALIF,LOS ANGELES,CA 90089. RP Thurman, SW (reprint author), CALTECH,JET PROP LAB,SYST DIV,FLIGHT SYST ENGN SECT,TECH STAFF,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 27 TC 4 Z9 4 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1996 VL 19 IS 5 BP 1007 EP 1016 DI 10.2514/3.21739 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VE513 UT WOS:A1996VE51300004 ER PT J AU BarItzhack, IY AF BarItzhack, IY TI REQUEST: A recursive QUEST algorithm for sequential attitude determination SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB QUEST is a well-known algorithm for least squares fitting of the attitude quaternion of a spacecraft to vector measurements. QUEST, however, is a single time point (single frame) batch algorithm; thus, measurements that were taken at previous time points are discarded, The algorithm presented provides a recursive routine, which considers all past measurements. The algorithm is based on the fact that the so-called K matrix, one of whose eigenvectors is the sought quaternion, is linearly related to the measured vector pairs and on the ability to propagate K, The extraction of the appropriate eigenvector is done according to the classical QUEST algorithm, This stage, however, can be eliminated, and the computation simplified, if a standard eigenvalue-eigenvector solver algorithm is used. C1 NASA,GODDARD SPACE FLIGHT CTR,FLIGHT MECH BRANCH,GREENBELT,MD 20771. NR 9 TC 51 Z9 58 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1996 VL 19 IS 5 BP 1034 EP 1038 DI 10.2514/3.21742 PG 5 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VE513 UT WOS:A1996VE51300007 ER PT J AU THurman, SW Flashner, H AF THurman, SW Flashner, H TI Robust digital autopilot design for spacecraft equipped with pulse-operated thrusters SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID QUATERNION FEEDBACK; UNCERTAIN SYSTEMS; ATTITUDE-CONTROL; MANEUVERS AB The analysis and design of attitude control systems for spacecraft employing pulse-operated (on-off) thrusters is usually accomplished through a combination of modeling approximations and empirical techniques. A new thruster pulse-modulation theory for pointing and tracking applications is developed from nonlinear control theory. This theory provides the framework for an autopilot suitable for use in digital computers whose performance and robustness properties are characterized analytically, in the design process. Given bounds on the anticipated dynamical modeling errors and sensor errors, it is shown that design specifications can be established and acceptable performance ensured in the presence of these error sources. Spacecraft with time-varying inertia properties can be accommodated, as well as clustered thruster configurations that provide multiple discrete torque levels about one or more spacecraft axes. A realistic application of the theory is illustrated via detailed computer simulation of a digital autopilot designed for midcourse guidance of a hypothetical interplanetary spacecraft. C1 UNIV SO CALIF,DEPT MECH,LOS ANGELES,CA 90089. UNIV SO CALIF,DEPT AEROSP ENGN,LOS ANGELES,CA 90089. RP THurman, SW (reprint author), CALTECH,JET PROP LAB,SYST DIV,FLIGHT SYST ENGN SECT,TECH STAFF,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 30 TC 12 Z9 13 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1996 VL 19 IS 5 BP 1047 EP 1055 DI 10.2514/3.21744 PG 9 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VE513 UT WOS:A1996VE51300009 ER PT J AU LeeGlauser, GJ Juang, JN Longman, RW AF LeeGlauser, GJ Juang, JN Longman, RW TI Comparison and combination of learning controllers: Computational enhancement and experiments SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID DYNAMIC CONTROL; IMPLEMENTATION; MANIPULATORS AB Five discrete-frequency linear learning-control laws are compared and experimentally tested, These include simple integral-control-based learning using a single learning gain, phase-cancellation learning control, a contraction-mapping learning-control law with monotonic decay of the error norm, and leaning controllers that invert the system model and the observer model. The inversion designs converge the fastest initially, but phase cancellation with identification updates and the contraction-mapping method with model updates have better stability robustness properties. The learning control approaches are combined to obtain the advantages of each, by using inversion methods for the first few repetitions, followed by a more robust method, It is demonstrated that the computation of the learning action can be made in the frequency domain using fast Fourier transform methods, with as much as 94% reduction in computation time, In experiments on a Robotics Research Corporation robot, the learning-control laws result in a reduced rms tracking errors for all joints, by a factor of close to 3 orders of magnitude. C1 NASA, LANGLEY RES CTR, STRUCT DYNAM BRANCH, HAMPTON, VA 23681 USA. COLUMBIA UNIV, DEPT MECH ENGN, NEW YORK, NY 10027 USA. RP CLARKSON UNIV, DEPT MECH & AERONAUT ENGN, POTSDAM, NY 13699 USA. NR 32 TC 30 Z9 30 U1 0 U2 0 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0731-5090 EI 1533-3884 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1996 VL 19 IS 5 BP 1116 EP 1123 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VE513 UT WOS:A1996VE51300018 ER PT J AU Lorenzini, EC Bortolami, SB Rupp, CC Angrilli, E AF Lorenzini, EC Bortolami, SB Rupp, CC Angrilli, E TI Control and flight performance of tethered satellite small expendable deployment system-II SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID SUBSATELLITE AB The second mission of the small expendable deployment system (SEDS-II) followed the successful mission of SEDS-I, which deployed freely a small instrumented probe on a 20-km tether. Unlike SEDS-I, the deployment of SEDS-II was controlled to provide a small libration amplitude and tether velocity at the end of deployment, The preflight goal for SEDS-II was a maximum libration of less than 10 deg and a final velocity of less than 1 m/s. The control problem was made difficult by the limited capabilities of the SEDS sensors and onboard computer and the large uncertainties inherent in the response of the actuator (brake) and the plant (deployer). The nonlinear, nonautonomous control problem is divided in two parts by using a numerically formulated feedback linearization, i.e., by devising 1) a nonlinear control (reference) trajectory and 2) a linear control about the reference trajectory. An ad hoc feedback law that forces the perturbed system to follow the reference trajectory is derived by using a linearized variational model. The controller is then tested, through computer simulations, for large deviations of the model parameters on the nonlinear model. The relevant flight data are also presented and compared to the reference values to demonstrate the validity and robustness of the control law, which provided a maximum libration amplitude of less than 4 deg and a final tether velocity of less than 0.02 m/s. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI & APPLICAT SYST OFF,HUNTSVILLE,AL 35812. UNIV PADUA,DEPT ENGN MECH,I-35100 PADUA,ITALY. RP Lorenzini, EC (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,RADIO & GEOASTRON DIV,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 19 TC 37 Z9 43 U1 0 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1996 VL 19 IS 5 BP 1148 EP 1156 DI 10.2514/3.21757 PG 9 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VE513 UT WOS:A1996VE51300022 ER PT J AU Ardema, MD Chou, HC Bowles, JV AF Ardema, MD Chou, HC Bowles, JV TI Near-optimal operation of dual-fuel launch vehicles SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID OPTIMIZATION; PROPULSION; SYSTEMS; DESIGN C1 NASA,AMES RES CTR,SYST ANAL BRANCH,MOFFETT FIELD,CA 94035. RP Ardema, MD (reprint author), SANTA CLARA UNIV,DEPT MECH ENGN,SANTA CLARA,CA 95053, USA. NR 9 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1996 VL 19 IS 5 BP 1180 EP 1182 DI 10.2514/3.21771 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VE513 UT WOS:A1996VE51300027 ER PT J AU Kelkar, AG Joshi, SM AF Kelkar, AG Joshi, SM TI Global stabilization of flexible multibody spacecraft using quaternion-based nonlinear control law SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Kelkar, AG (reprint author), KANSAS STATE UNIV,DEPT MECH ENGN,MANHATTAN,KS 66506, USA. NR 4 TC 8 Z9 9 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1996 VL 19 IS 5 BP 1186 EP 1188 DI 10.2514/3.21764 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VE513 UT WOS:A1996VE51300030 ER PT J AU McGinnis, MR Molina, TC Pierson, DL Mishra, SK AF McGinnis, MR Molina, TC Pierson, DL Mishra, SK TI Evaluation of the Biolog MicroStation System for yeast identification SO JOURNAL OF MEDICAL AND VETERINARY MYCOLOGY LA English DT Article DE automation; Biolog; yeast identification; yeast taxonomy AB One hundred and fifty-nine isolates representing 16 genera and 53 species of yeasts were processed with the Biolog MicroStation System for yeast identification, Thirteen genera and 38 species were included in the Biolog database. For these 129 isolates, correct identifications to the species level were 13.2, 39.5 and 48.8 % after 24, 48 and 72 hours incubation at 30 degrees C, respectively. Three genera and 15 species which were not included in the Biolog database were also tested. Of the 30 isolates studied, 16.7, 53.3 and 56.7% of the isolates were given incorrect names from the system's database after 24, 48 and 72 h incubation at 30 degrees C, respectively. The remaining isolates of this group were not identified. C1 UNIV TEXAS,MED BRANCH,DEPT PATHOL,GALVESTON,TX 77555. KRUG LIFE SCI,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,BIOMED OPERAT & RES BRANCH,HOUSTON,TX 77058. RP McGinnis, MR (reprint author), UNIV TEXAS,MED BRANCH,MED MYCOL RES CTR,WHO,COLLABORATING CTR TROP DIS,301 UNIV BLVD,GALVESTON,TX 77555, USA. NR 5 TC 12 Z9 13 U1 0 U2 5 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0268-1218 J9 J MED VET MYCOL JI J. Med. Vet. Mycol. PD SEP-OCT PY 1996 VL 34 IS 5 BP 349 EP 352 PG 4 WC Mycology SC Mycology GA VN877 UT WOS:A1996VN87700008 PM 8912169 ER PT J AU Wang, PKC Hadaegh, FY AF Wang, PKC Hadaegh, FY TI Computation of static shapes and voltages for micromachined deformable mirrors with nonlinear electrostatic actuators SO JOURNAL OF MICROELECTROMECHANICAL SYSTEMS LA English DT Article AB In modeling micromachined deformable mirrors with electrostatic actuators whose gap spacings are of the same order of magnitude as those of the surface deformations, it is necessary to use nonlinear models for the actuators. In this paper, we consider micromachined deformable mirrors modeled by a membrane or plate equation with nonlinear electrostatic actuator characteristics. Numerical methods for computing the mirror deformation due to given actuator voltages and the actuator voltages required for producing the desired deformations at the actuator locations are presented. The application of the proposed methods to circular deformable mirrors whose surfaces are modeled by elastic membranes is discussed in detail. Numerical results are obtained for a typical circular micromachined mirror with electrostatic actuators. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP UNIV CALIF LOS ANGELES, DEPT ELECT ENGN, LOS ANGELES, CA 90024 USA. NR 25 TC 27 Z9 31 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1057-7157 EI 1941-0158 J9 J MICROELECTROMECH S JI J. Microelectromech. Syst. PD SEP PY 1996 VL 5 IS 3 BP 205 EP 220 DI 10.1109/84.536627 PG 16 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Instruments & Instrumentation; Physics, Applied SC Engineering; Science & Technology - Other Topics; Instruments & Instrumentation; Physics GA VH439 UT WOS:A1996VH43900008 ER PT J AU Zavracky, PM McClelland, B Warner, K Wang, JC Hartley, F Dolgin, B AF Zavracky, PM McClelland, B Warner, K Wang, JC Hartley, F Dolgin, B TI Design and process considerations for a tunneling tip accelerometer SO JOURNAL OF MICROMECHANICS AND MICROENGINEERING LA English DT Article ID SENSOR AB In this paper, we discuss the fabrication and initial testing of a bulk micromachined single axis accelerometer, The accelerometer is designed to have a full scale range of 10(-2)g and a sensitivity of 10(-8)g. Three distinctly different dice are fabricated during the process and are subsequently assembled using an alloy bonding technique. Electrical contacts are made between layers during the bonding operation. The accelerometer is controlled by electrostatic force plates above and below the proof mass. The lower electrode has a dual role. in operation, it provides a necessary control electrode. When not in operation, it is used to immobilize the proof mass. C1 JET PROP LAB,PASADENA,CA 91190. RP Zavracky, PM (reprint author), NORTHEASTERN UNIV,360 HUNTINGTON AVE,BOSTON,MA 02115, USA. NR 10 TC 7 Z9 7 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0960-1317 J9 J MICROMECH MICROENG JI J. Micromech. Microeng. PD SEP PY 1996 VL 6 IS 3 BP 352 EP 358 DI 10.1088/0960-1317/6/3/008 PG 7 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Instruments & Instrumentation; Physics, Applied SC Engineering; Science & Technology - Other Topics; Instruments & Instrumentation; Physics GA VM112 UT WOS:A1996VM11200008 ER PT J AU Greiner, E Perigaud, C AF Greiner, E Perigaud, C TI Assimilation of geosat altimetric data in a nonlinear shallow-water model of the Indian Ocean by adjoint approach .2. Some validation and interpretation of the assimilated results SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID BOUNDARY CURRENTS EAST; TROPICAL PACIFIC; SURFACE CURRENT; TEMPERATURE; VARIABILITY; MADAGASCAR; NORTH AB This paper examines the results of assimilating Geosat sea level variations relative to the November 1986-November 1988 mean reference, in a nonlinear reduced-gravity model of the Indian Ocean. Data have been assimilated during one year starting in November 1986 with the objective of optimizing the initial conditions and the yearly averaged reference surface. The thermocline slope simulated by the model with or without assimilation is validated by comparison with the signal, which can be derived from expandable bathythermograph measurements performed in the Indian Ocean at that time. The topography simulated with assimilation on November 1986 is in very good agreement with the hydrographic data. The slopes corresponding to the South Equatorial Current and to the South Equatorial Countercurrent are better reproduced with assimilation than without during the first nine months. The whole circulation of the cyclonic gyre south of the equator is then strongly intensified by assimilation. Another assimilation experiment is run over the following year starting in November 1987. The difference between the two yearly mean surfaces simulated with assimilation is in excellent agreement with Geosat. In the southeastern Indian Ocean, the correction to the yearly mean dynamic topography due to assimilation over the second year is negatively correlated to the one the year before. This correction is also in agreement with hydrographic data. It is likely that the signal corrected by assimilation is not only due to wind error, because simulations driven by various wind forcings present the same features over the two years. Model simulations run with a prescribed throughflow transport anomaly indicate that assimilation is rather correcting in the interior of the model domain for inadequate boundary conditions with the Pacific. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. GRGS,TOULOUSE,FRANCE. NR 26 TC 6 Z9 6 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD SEP PY 1996 VL 26 IS 9 BP 1735 EP 1746 DI 10.1175/1520-0485(1996)026<1735:AOGADI>2.0.CO;2 PG 12 WC Oceanography SC Oceanography GA VM284 UT WOS:A1996VM28400005 ER PT J AU Caillat, T AF Caillat, T TI Preparation and thermoelectric properties of IrxCo1-xSb2 alloys SO JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS LA English DT Article DE intermetallic compounds; semiconductors; crystal growth; transport properties ID HIGH-TEMPERATURE; SB AB The preparation and characterization of the binary arsenopyrite compounds CoSb2 and IrSb2 and IrxCo1-xSb2 alloys is reported. Single crystals of CoSb2 were grown by the vertical gradient-freeze technique from solutions rich in antimony. Polycrystalline samples of IrSb2 and IrxCo1-xSb2 alloys were prepared by hot-pressing of prereacted elemental powders. Samples were investigated by X-ray diffractometry, microprobe analysis and density measurements. It was found that a range of solid solutions exists in the system IrxCo1-xSb2. Samples were also characterized by high temperature electrical resistivity, Seebeck coefficient and thermal conductivity measurements. All materials have p-type conductivity and are semiconductors. A band gap of about 0.98 eV was calculated for IrSb2. Preliminary measurements of the thermoelectric properties of these materials showed that their potential for thermoelectric applications is limited. RP Caillat, T (reprint author), CALTECH,JET PROP LAB,MS 277-207,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 14 TC 13 Z9 13 U1 0 U2 16 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0022-3697 J9 J PHYS CHEM SOLIDS JI J. Phys. Chem. Solids PD SEP PY 1996 VL 57 IS 9 BP 1351 EP 1358 DI 10.1016/0022-3697(96)00026-1 PG 8 WC Chemistry, Multidisciplinary; Physics, Condensed Matter SC Chemistry; Physics GA VC879 UT WOS:A1996VC87900023 ER PT J AU Detwiler, R Surampudi, S Stella, P Clark, K Bankston, P AF Detwiler, R Surampudi, S Stella, P Clark, K Bankston, P TI Designs and technologies for future planetary power systems SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID LOW-INTENSITY; SOLAR-CELLS; TEMPERATURE AB Planetary missions place unique demands on spacecraft systems and operations in terms of lifetime and autonomous operation. at the same time, the new faster better, cheaper environment requires more technological innovation than ever before to enable us to continue to explore the planets with the same successes that we have enjoyed in the past. This article discusses new electric power system design and component technologies that provide the basis for planetary exploration in the late 1990s and far beyond, especially for small spacecraft, Power technologies for the New Millennium spacecraft series are presented, me discuss new concepts in power management and distribution technology, followed by an assessment of the status of photovoltaic and nuclear power source technologies, and we conclude with a discussion of advanced battery technologies for small spacecraft. C1 CALTECH, JET PROP LAB,ELECT POWER SECT, AV SYST & TECHNOL DIV,TECH STAFF, PASADENA, CA 91109 USA. RP Detwiler, R (reprint author), CALTECH, JET PROP LAB, AV EQUIPMENT SECT, AV SYST & TECHNOL DIV, PASADENA, CA 91109 USA. NR 18 TC 5 Z9 5 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 828 EP 834 DI 10.2514/3.24110 PG 7 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000004 ER PT J AU Landis, GA Bailey, SG Piszczor, MF AF Landis, GA Bailey, SG Piszczor, MF TI Recent advances in solar cell technology SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID THIN; POWER; MODULES; SPACE; RADIATION AB The advances in solar cell efficiency, radiation tolerance, and cost over the last decade are reviewed, Potential performance of thin-film solar cells in space are discussed, and the cost and the historical trends in production capability of the photovoltaics industry are considered with respect to the requirements of space power systems, Concentrator cells with conversion efficiency over 30%, and nonconcentrating solar cells with efficiency over 25% are now available, and advanced radiation-tolerant cells and lightweight, thin-film arrays are both being developed, Nonsolar applications of solar cells, including thermophotovoltaics, alpha- and betavoltaics, and laser power receivers, are also discussed. C1 NASA, LEWIS RES CTR, PHOTOVOLTA BRANCH, CLEVELAND, OH 44135 USA. NR 54 TC 5 Z9 5 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 835 EP 841 DI 10.2514/3.24111 PG 7 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000005 ER PT J AU Shaltens, RK Mason, LS AF Shaltens, RK Mason, LS TI Early results from solar dynamic space power system testing SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB A government/industry team designed, built, and tested a 2-kWe solar dynamic space power system in a large thermal/vacuum facility with a simulated son at the NASA Lewis Research Center, The Lewis facility provides an accurate simulation of temperatures, high vacuum, and solar flux as encountered in low-Earth orbit. The solar dynamic system includes a Brayton power conversion unit integrated with a solar receiver that is designed to store energy for continuous power operation during the eclipse phase of the orbit. This article reviews the goals and status: of the Solar Dynamic Ground Test Demonstration project and describes the initial testing, including both operational and performance data, System testing to date has accumulated over 365 h of power operation (ranging from 400 W to 2.0 kWe), including 187 simulated orbits, 16 ambient starts, and two hot restarts. Data are shown for an orbital startup, transient and steady-state orbital operation, and shutdown. System testing with varying insolation Levels and operating speeds is discussed. The solar dynamic ground test demonstration is providing the experience and confidence toward a successful flight demonstration of the solar dynamic technologies on the Space Station Mir in 1997. RP Shaltens, RK (reprint author), NASA,LEWIS RES CTR,SOLAR DYNAM GROUND TEST DEMONSTRAT PROJECT,CLEVELAND,OH 44135, USA. NR 22 TC 15 Z9 15 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 852 EP 858 DI 10.2514/3.24113 PG 7 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000008 ER PT J AU Smithrick, JJ ODonnell, PM AF Smithrick, JJ ODonnell, PM TI Nickel-hydrogen batteries - An overview SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID CYCLE LIFE; CELLS AB This article on nickel-hydrogen batteries is an overview of the various nickel-hydrogen battery design options, technical accomplishments, validation test results, and trends, There is more than one nickel-hydrogen battery design, each having its advantage for specific applications, The major battery designs are individual pressure vessel (IPV), common pressure vessel (CPV), bipolar, and low-pressure metal hydride, State-of-the-art nickel-hydrogen batteries are replacing nickel-cadmium batteries in almost all geosynchronous Earth orbit applications requiring power above 1 kW, However, for the more severe low-Earth orbit (LEG) applications (>30,000 cycles), the current cycle life of 4000-10,000 cycles at 60-80% DOD should be improved. A NASA Lewis Research Center innovative advanced design IPV nickel-hydrogen cell led to a breakthrough in cycle life enabling LEO applications at deep depths of discharge (DOD). A trend for some future satellites is to increase the power level to greater than 6 kW. Another trend is to decrease the power to less than 1 kW for small low-cost satellites. Hence, the challenge is to reduce battery mass, volume, and cost, A key is to develop a lightweight nickel electrode and alternate battery designs, A CPV nickel-hydrogen battery is emerging as a viable alternative to the IPV design, It has the advantage of reduced mass, volume, and manufacturing costs, A 10-A-h CPV battery has successfully provided power on the relatively short-lived Clementine spacecraft, A bipolar nickel-hydrogen battery design has been demonstrated (15,000 LEO cycles, 40% DOD). The advantage is also a significant reduction in volume, a modest reduction in mass, and like most bipolar designs, features a high-pulse power capability, A low-pressure aerospace nickel-metal-hydride battery cell has been developed and is on the market, It is a prismatic design that has the advantage of a significant reduction in volume and a reduction in manufacturing cost. RP Smithrick, JJ (reprint author), NASA,LEWIS RES CTR,M-S 5420,CLEVELAND,OH 44135, USA. NR 33 TC 4 Z9 4 U1 1 U2 7 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 873 EP 878 DI 10.2514/3.24116 PG 6 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000011 ER PT J AU Cohen, F Dalton, PJ AF Cohen, F Dalton, PJ TI Space-station nickel-hydrogen battery orbital replacement unit test SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB The International Space Station electrical power system utilizes nickel-hydrogen (Ni-H-2) batteries as part of its power system to store electrical energy. The batteries are charged during insolation and discharged during eclipse, The batteries are designed to operate at a 35% depth of discharge maximum during normal operation, Thirty-eight individual pressure vessel Ni-H-2 battery cells are series-connected and packaged in an orbit replacement unit (ORU). Two ORUs are series connected, a total of 76 cells, to form one battery, The International Space Station will be the first application for low Earth orbit cycling of this quantity of series connected cells, The Space Station Photovoltaic Electronics Team, consisting of NASA and Rocketdyne personnel, began a unique test program at the Power Systems Facility at the NASA Lewis Research Center. The test plan was created to evaluate near- and long-term performance as a battery as,yell as charge management characteristics. The testing would also validate the ORU configuration including the ORU box and thermal interface design, This article describes the test program and the results of the 3000 LEO cycles on a Space Station engineering model battery. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44136. RP Cohen, F (reprint author), ROCKWELL INT CORP,DIV ROCKETDYNE,6633 CANOGA AVE,POB 7922,CANOGA PK,CA 91306, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 886 EP 892 DI 10.2514/3.24118 PG 7 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000013 ER PT J AU Ewell, R Zoltan, A AF Ewell, R Zoltan, A TI SP-100 thermoelectric cell testing SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB Five prototypic SP-100 thermoelectric cells were put on test in vacuum at prototypic temperatures. Their thermal and electrical performances were characterized with 200, 300, 400, and 500 degrees C temperature gradients across the cell, The latter was representative of prototypic operating conditions with a 1050 degrees C hot-side temperature and a 550 degrees C cold-side temperature, The initial thermal and electrical performance of all five cells closely matched predictions. Following the characterization testing the cells were put on an extended life test at the prototypic temperatures to determine any significant degradation modes of the cell, Throughout this test, the thermal performance of the cells was nearly identical to predictions, The tests with the initial three cells also confirmed earlier suspicions that the hot-side silicon-germanium-to-electrode interface would degrade without some significant protective coating at the bond line, Because of resource limitations and early development problems with this coating, the necessary protective layers had not yet been fully developed at the time the first three cells were manufactured, Subsequent to these tests, new cells were fabricated with this technology, two of which are currently on test, These two tells have not shown any significant degradation in performance beyond predictions. These tests along with accelerated experiments with coupons, have now validated the type-approval cell technology. RP Ewell, R (reprint author), CALTECH, JET PROP LAB, TECH STAFF, M-S 303-308, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 9 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 911 EP 917 DI 10.2514/3.24122 PG 7 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000017 ER PT J AU Mehta, UB AF Mehta, UB TI Guide to credible computer simulations of fluid flows SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID DYNAMICS AB The significance of computer simulations depends solely on their credibility, A user of computer products, simulations and software, expects that these products are credible for the intended use, Because no standards exist for fluid-flow simulations by which to establish this credibility, a guide is presented here. The credibility is established by conducting verification and validation of simulation models and certification of simulations and of simulation software. Verification assesses whether the problem is solved correctly and estimates the level of computational accuracy of simulations; validation determines whether the right problem is solved and assesses the level of the validity of the simulation model by estimating the degree to which simulations accurately represent reality. These processes are achieved by identifying the intended uses of the simulations and the sources of uncertainties in them and by conducting sensitivity-uncertainty analyses. Certification determines 1) whether a software in terms of its logic, conceptual and computational models, procedures, rules, and documentation and 2) whether the simulations derived from the software are in compliance with specified requirements. RP Mehta, UB (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 53 TC 20 Z9 20 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 940 EP 948 DI 10.2514/3.24126 PG 9 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000021 ER PT J AU Paxson, DE AF Paxson, DE TI Numerical simulation of dynamic wave rotor performance SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB A numerical model has been developed that can simulate the dynamic (and steady-state) performance of a wave rotor, given the geometry and time-dependent boundary conditions, The one-dimensional, perfect-gas, computational fluid dynamics-based code tracks the gasdynamics in each of the wave rotor passages as they rotate past the various ducts. The model can operate both on and off-design, allowing dynamic behavior to be studied throughout the operating range of the wave rotor, The model accounts for several major loss mechanisms including finite passage opening time, fluid friction, heat transfer to and from the passage walls, and leakage to and from the passage ends, In addition it can calculate the amount of work transferred to or from the fluid when the now in the ducts is not aligned with the passages such as occurs in off-design operation, Since it is one-dimensional, the model runs reasonably fast on a typical workstation, This article will describe the model and present the results of some transient calculations for a conceptual four-port wave rotor designed as a topping cycle for a small gas-turbine engine. RP Paxson, DE (reprint author), NASA,LEWIS RES CTR,CONTROLS & DYNAM TECHNOL BRANCH,M-S 77-1,CLEVELAND,OH 44135, USA. NR 14 TC 13 Z9 13 U1 1 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 949 EP 957 DI 10.2514/3.24127 PG 9 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000022 ER PT J AU Taghavi, R Raman, G AF Taghavi, R Raman, G TI Flow characteristics of a rectangular multielement supersonic mixer-ejector SO JOURNAL OF PROPULSION AND POWER LA English DT Article C1 NYMA INC,NASA,LEWIS RES CTR GRP,EXPT FLUID DYNAM SECT,BROOKPARK,OH 44142. RP Taghavi, R (reprint author), UNIV KANSAS,DEPT AEROSP ENGN,LAWRENCE,KS 66045, USA. NR 9 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1996 VL 12 IS 5 BP 1004 EP 1007 DI 10.2514/3.51464 PG 4 WC Engineering, Aerospace SC Engineering GA VG130 UT WOS:A1996VG13000031 ER PT J AU Seraji, H Steele, R Ivlev, R AF Seraji, H Steele, R Ivlev, R TI Sensor-based collision avoidance: Theory and experiments SO JOURNAL OF ROBOTIC SYSTEMS LA English DT Article AB A new on-line control strategy for sensor-based collision avoidance of manipulators and supporting experimental results are presented in this article. This control strategy is based on nullification of virtual forces applied to the end-effector by a hypothetical spring-plus-damper attached to the object's surface. In the proposed approach, the real-time arm control software continuously monitors the object distance measured by the arm-mounted proximity sensors. When this distance is less than a preset threshold, the collision avoidance control action is initiated to inhibit motion toward the object and thus prevent collision. This is accomplished by employing an outer feedback loop to perturb the end-effector nominal motion trajectory in real-time based on the sensory data. The perturbation is generated by a proportional-plus-integral (PI) collision avoidance controller acting on the difference between the sensed distance and the preset threshold. This approach is computationally very fast, requires minimal modification to the existing manipulator positioning system, and provides the manipulator with an on-line collision avoidance capability to react autonomously and intelligently. A dexterous RRC robotic arm is instrumented with infrared proximity sensors and is operated under the proposed collision avoidance strategy. Experimental results are presented to demonstrate end-effector collision avoidance both with an approaching object and while reaching inside a constricted opening. (C) 1996 John Wiley & Sons, Inc. RP Seraji, H (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 13 TC 8 Z9 9 U1 0 U2 0 PU JOHN WILEY & SONS INC PI HOBOKEN PA 111 RIVER ST, HOBOKEN, NJ 07030 USA SN 0741-2223 J9 J ROBOTIC SYST JI J. Robot. Syst. PD SEP PY 1996 VL 13 IS 9 BP 571 EP 586 DI 10.1002/(SICI)1097-4563(199609)13:9<571::AID-ROB2>3.3.CO;2-9 PG 16 WC Robotics SC Robotics GA VC606 UT WOS:A1996VC60600002 ER PT J AU Wedeward, K Colbaugh, R Engelmann, A AF Wedeward, K Colbaugh, R Engelmann, A TI Adaptive explicit force control of position-controlled manipulators SO JOURNAL OF ROBOTIC SYSTEMS LA English DT Article ID ROBOT MANIPULATORS; IMPEDANCE CONTROL; STABILITY AB This article presents a new adaptive outer-loop approach for explicit force regulation of position-controlled robot manipulators. The strategy is computationally simple and does not require knowledge of the manipulator dynamic model, the inner-loop position controller parameters, or the environment. It is shown that the control strategy guarantees global uniform boundedness of all signals and convergence of the position/force regulation errors to zero when applied to the full nonlinear robot dynamic model. If bounded external disturbances are present, a slight modification to the control scheme ensures that global uniform boundedness of all signals is retained and that arbitrarily accurate stabilization of the regulation errors can be achieved. Additionally, it is shown that the adaptive controller is also applicable to robotic systems with PID inner-loop position controllers. Computer simulation results are given for a Robotics Research Corporation (RRC) Model K-1207 redundant arm and demonstrate that accurate and robust force control is achievable with the proposed controller. Experimental results are presented for the RRC Model K-1207 robot and confirm that the control scheme provides a simple and effective means of obtaining high-performance force control. (C) 1996 John Wiley & Sons, Inc. C1 NEW MEXICO STATE UNIV,DEPT MECH ENGN,LAS CRUCES,NM 88003. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Wedeward, K (reprint author), USN ACAD,DEPT SYST ENGN,ANNAPOLIS,MD 21402, USA. NR 29 TC 0 Z9 1 U1 0 U2 2 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0741-2223 J9 J ROBOTIC SYST JI J. Robot. Syst. PD SEP PY 1996 VL 13 IS 9 BP 603 EP 618 DI 10.1002/(SICI)1097-4563(199609)13:9<603::AID-ROB4>3.0.CO;2-Q PG 16 WC Robotics SC Robotics GA VC606 UT WOS:A1996VC60600004 ER PT J AU Swaminathan, PK Taylor, JC Rault, DFG Erlandson, RE Meng, CI AF Swaminathan, PK Taylor, JC Rault, DFG Erlandson, RE Meng, CI TI Transition regime aerodynamic heating of missiles SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID MONTE-CARLO SIMULATION AB The three-dimensional hows over the ARIES missile at approximately 138-, 110-, and 91-km altitudes are simulated at zero angle of attack using the direct simulation Monte Carlo method, At these altitudes, the aerodynamics near the missile range from the transition to near free-molecule flow regimes. The aerodynamic heating predictions along the missile surface from the simulations are used to benchmark three empirical bridging relations. Furthermore, the effect of using an approximate free-molecular expression in the bridging relations is investigated. The values predicted using the approximate free-molecular expressions fail to predict any heat transfer along the cylindrical portions of the missile, and differ by as much as 90% along other sections. The bridging relations are found to predict heating rates within a factor of 2 of the simulated results, provided the full free-molecular expression from kinetic theory is used. It is found that no one bridging relation outperformed the others. Each has regions along the length of the missile, where it is in good agreement with the simulations, and other regions, where significant differences are observed. C1 NASA,LANGLEY RES CTR,DIV GAS DYNAM,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681. RP Swaminathan, PK (reprint author), JOHNS HOPKINS UNIV,APPL PHYS LAB,DEPT SPACE,SPACE SCI BRANCH,LAUREL,MD 20723, USA. RI Swaminathan, Pazhayannur/I-3609-2012; Erlandson, Robert/G-2767-2015 OI Swaminathan, Pazhayannur/0000-0003-1272-9694; NR 24 TC 2 Z9 3 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1996 VL 33 IS 5 BP 607 EP 613 DI 10.2514/3.26809 PG 7 WC Engineering, Aerospace SC Engineering GA VM676 UT WOS:A1996VM67600002 ER PT J AU Wood, WA Gnoffo, PA Rault, DFG AF Wood, WA Gnoffo, PA Rault, DFG TI Aerodynamic analysis of Commercial Experiment Transporter re-entry capsule SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB An aerodynamic analysis of the Commercial Experiment Transporter re-entry capsule has been performed using the laminar thin-layer Navier-Stokes solver LAURA. Flowfield solutions were obtained at Mach numbers 1.5, 2, 5, 10, 15, 20, 25, and 27.5. Axisymmetric and 5-, 10-, and 20-deg angles of attack were considered across the Mach-number range, with the Mach 25 conditions taken to 90-deg angle of attack and the Mach 27.5 cases taken to 60-deg angle of attack. Finite-rate chemistry solutions were performed above Mach 10; otherwise, perfect-gas computations were made. Drag, lift, and pitching-moment coefficients were computed, and details of a wake flow are presented. The effect of including the wake in the solution domain was investigated, and base-pressure corrections to forebody drag coefficients were numerically determined for the lower Mach numbers. Pitching-moment comparisons were made with direct simulation Monte Carlo results in the more rarefied flow at the highest Mach numbers, showing agreement within 2%. Thin-layer Navier-Stokes computations of the axial force were found to be 15% higher than the empirical/Newtonian-based results used during the initial trajectory analyses. RP Wood, WA (reprint author), NASA,LANGLEY RES CTR,DIV GAS DYNAM,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681, USA. NR 15 TC 7 Z9 7 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1996 VL 33 IS 5 BP 643 EP 646 DI 10.2514/3.26814 PG 4 WC Engineering, Aerospace SC Engineering GA VM676 UT WOS:A1996VM67600007 ER PT J AU Spencer, DA Braun, RD AF Spencer, DA Braun, RD TI Mars Pathfinder atmospheric entry: Trajectory design and dispersion analysis SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID VIKING AB The Mars Pathfinder spacecraft will enter the Martian atmosphere directly from the interplanetary trajectory, with a velocity of up to 7.35 km/s. The definition of the nominal entry trajectory and the accurate determination of potential trajectory dispersions are necessary for the design of the Pathfinder entry, descent, and landing system. Monte Carlo numerical simulations have been developed to quantify the range of possible entry trajectories and attitude profiles. The entry trajectory requirements and constraints are discussed, and the design approach and uncertainties used in the Monte Carlo analysis are described. Three-degree-of-freedom and six-degree-of-freedom trajectory results are compared. The Monte Carlo analysis shows that the Mars Pathfinder parachute will be deployed within the required ranges of dynamic pressure, Mach number, and altitude, over a 3 sigma range of trajectories. The Pathfinder 3 sigma landing ellipse is shown to he roughly 50 x 300 km. C1 NASA,LANGLEY RES CTR,DIV SPACE SYST & CONCEPTS,HAMPTON,VA 23665. RP Spencer, DA (reprint author), CALTECH,JET PROP LAB,TECH STAFF,NAVIGAT & FLIGHT MECH SECT,PASADENA,CA 91109, USA. NR 12 TC 29 Z9 32 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1996 VL 33 IS 5 BP 670 EP 676 DI 10.2514/3.26819 PG 7 WC Engineering, Aerospace SC Engineering GA VM676 UT WOS:A1996VM67600012 ER PT J AU Spagnuolo, J Cheng, C Schwuttke, UM Hervias, F AF Spagnuolo, J Cheng, C Schwuttke, UM Hervias, F TI Visual utility for the localization of corona-accelerated nuclei SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The proton prediction system developed by Smart and Shea (Smart, D.F., and Shea, M.A., ''PPS76-A Computerized 'Event Mode' Solar Proton Forecasting Technique,'' Solar Terrestrial Prediction Proceedings, edited by R.F. Donnelly, Vol. 1, National Oceanic and Atmospheric Administration/Environmental Research Lab., U.S. Dept. of Commerce, 1979, pp. 406-423) provides the approximate magnitude of the fluxes of solar-flare-ejected protons in the vicinity of the Earth. A system is described that extends Smart and Shea's work in that it predicts fluxes of such protons at arbitrary points of the inner heliosphere near the plane of the solar equator. It has interactive graphical components that enhance the user's overall perception of a flare's effects upon the solar system while also providing precise user-requested data. The flux predictions of the system agree well with proton fluxes as measured by various spacecraft. Results are given. A database of flare events is maintained and can be used for a retroactive analysis when it is desired to know the magnitudes of potential proton fluxes due to a previous flare. RP Spagnuolo, J (reprint author), CALTECH, JET PROP LAB, INFORMAT SYST DEV & OPERAT DIV, ADV MULTIMISS SOFTWARE TECHNOL GRP, PASADENA, CA 91109 USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1996 VL 33 IS 5 BP 722 EP 728 DI 10.2514/3.26826 PG 7 WC Engineering, Aerospace SC Engineering GA VM676 UT WOS:A1996VM67600019 ER PT J AU Lutz, RR AF Lutz, RR TI Targeting safety-related errors during software requirements analysis SO JOURNAL OF SYSTEMS AND SOFTWARE LA English DT Article ID SYSTEMS AB This article provides a safety checklist for use during the analysis of software requirements for spacecraft and other safety-critical, embedded systems. The checklist specifically targets the two most common causes of safety-related software errors: 1) inadequate interface requirements and 2) discrepancies between the documented requirements and the requirements actually needed for correct functioning of the system. The analysis criteria represented in the checklist are evaluated by application to two spacecraft projects. Use of the checklist to enhance the software requirements analysis is shown to reduce the number of safety-related software errors. C1 CALTECH,JET PROP LAB,PASADENA,CA. NR 21 TC 17 Z9 17 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0164-1212 J9 J SYST SOFTWARE JI J. Syst. Softw. PD SEP PY 1996 VL 34 IS 3 BP 223 EP 230 DI 10.1016/0164-1212(95)00077-1 PG 8 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA VC501 UT WOS:A1996VC50100005 ER PT J AU Witham, C Ratnakumar, BV Bowman, RC Hightower, A Fultz, B AF Witham, C Ratnakumar, BV Bowman, RC Hightower, A Fultz, B TI Electrochemical evaluation of LaNi5-xGex metal hydride alloys SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID ELECTRODES AB We report a detailed evaluation of Ge-substituted LaNi5 for electrochemical application as a negative electrode in alkaline rechargeable cells. Alloys with small substitutions of Ge for Ni show operating pressures, chargeability, cyclic lifetime, and kinetics for hydrogen absorption and desorption all superior to those found in many other substituted LaNi, alloys. These improved properties were achieved with a minimal reduction in hydrogen storage capacity. C1 JET PROP LAB,ELECTROCHEM TECHNOL GRP,PASADENA,CA 91109. RP Witham, C (reprint author), CALTECH,DIV ENGN & APPL SCI,PASADENA,CA 91125, USA. NR 13 TC 9 Z9 9 U1 0 U2 0 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 10 SOUTH MAIN STREET, PENNINGTON, NJ 08534 SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD SEP PY 1996 VL 143 IS 9 BP L205 EP L208 DI 10.1149/1.1837088 PG 4 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA VH209 UT WOS:A1996VH20900011 ER PT J AU Hine, MJ AF Hine, MJ TI Transient synthesis using a Fourier transform envelope - An alternative to swept-sine vibration testing SO JOURNAL OF THE INSTITUTE OF ENVIRONMENTAL SCIENCES LA English DT Article DE conservatism; envelope; Fourier transform; test; transient; vibration AB Transient vibration tests offer an alternative to the conventional swept-sine vibration test, with controllable conservatism. A method of deriving a single vibration test transient from several spacecraft flight transients is described. These transients were from different physical locations on the spacecraft. The test transient was derived by taking the inverse Fourier transform of an envelope of the Fourier transforms of the flight transients. The inverse transformation was performed using the real and imaginary parts of that Fourier transform forming the envelope amplitude at each frequency. The test transient therefore has the same frequency content and maximum amplitudes as the flight transients. A generic test transient was therefore produced that duplicates many operating conditions at separate physical locations. It could be applied to many different structural components of a spacecraft, simplifying a vibration test program. The transient vibration test produces significantly less overtest than a conventional swept-sine vibration test. RP Hine, MJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 6 TC 0 Z9 0 U1 1 U2 1 PU INST ENVIRONMENTAL SCI PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 SN 1052-2883 J9 J INST ENVIRON SCI JI J. Inst. Environ. Sci. PD SEP-OCT PY 1996 VL 39 IS 5 BP 17 EP 22 PG 6 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA VQ197 UT WOS:A1996VQ19700005 ER PT J AU Kennedy, RS Hettinger, LJ Harm, DL Ordy, JM Dunlap, WP AF Kennedy, RS Hettinger, LJ Harm, DL Ordy, JM Dunlap, WP TI Psychophysical scaling of circular vection (CV) produced by optokinetic (OKN) motion: Individual differences and effects of practice SO JOURNAL OF VESTIBULAR RESEARCH-EQUILIBRIUM & ORIENTATION LA English DT Article DE vection; self-motion; disorientation; neural ID LABYRINTHINE-DEFECTIVE SUBJECTS; SELF-MOTION; SICKNESS AB Vection (V) refers to the compelling visual illusion of self-motion experienced by stationary individuals when viewing moving visual surrounds, The phenomenon is of theoretical interest because of its relevance for understanding the neural basis of ordinary self-motion perception, and of practical importance because it is the experience that makes simulation, virtual reality displays, and entertainment devices more vicarious, This experiment was performed to address whether an optokinetically induced vection illusion exhibits monotonic and stable psychometric properties and whether individuals differ reliably in these (V) perceptions, Subjects were exposed to varying velocities of the circular vection (CV) display in an optokinetic (OKN) drum 2 meters in diameter in 5 one-hour daily sessions extending over al week period. For grouped data, psychophysical scalings of velocity estimates showed that exponents in a Stevens' type power function were essentially linear (slope = 0.95) and largely stable over sessions, Latencies were slightly longer for the slowest and fastest induction stimuli, and the trend over sessions for average latency was longer as a function of practice implying time course adaptation effects, Test-retest reliabilities for individual slope and intercept measures were moderately strong (r = 0.45) and showed no evidence of superdiagonal form, This implies stability of the individual circularvection (CV) sensitivities, Because the individual CV scores were stable, reliabilities were improved by averaging 4 sessions in order to provide a stronger retest reliability (r = 0.80), Individual latency responses were highly reliable (r = 0.80), Mean CV latency and motion sickness symptoms were greater in males than in females, These individual differences in CV could be predictive of other outcomes, such as susceptibility to disorientation or motion sickness, and for CNS localization of visual-vestibular interactions in the experience of self-motion. C1 LOGICON TECH SERV INC,DAYTON,OH. NASA,JOHNSON SPACE CTR,HOUSTON,TX. MEMORY RES ASSOCIATES,PITTSFORD,NY. TULANE UNIV,NEW ORLEANS,LA 70118. RP Kennedy, RS (reprint author), ESSEX CORP,1040 WOODCOCK RD,SUITE 227,ORLANDO,FL 32803, USA. NR 30 TC 58 Z9 58 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0957-4271 J9 J VESTIBUL RES-EQUIL JI J. Vestib. Res.-Equilib. Orientat. PD SEP-OCT PY 1996 VL 6 IS 5 BP 331 EP 341 PG 11 WC Neurosciences; Otorhinolaryngology SC Neurosciences & Neurology; Otorhinolaryngology GA VK426 UT WOS:A1996VK42600002 PM 8887891 ER PT J AU Shogrin, B Jones, WR HerreraFierro, P AF Shogrin, B Jones, WR HerreraFierro, P TI Spontaneous dewetting of a perfluoropolyether(c) SO LUBRICATION ENGINEERING LA English DT Article DE adverse environments tribology; synthetic lubricants ID SOLID-SURFACES; LUBRICANTS; TEMPERATURE; FLUIDS AB Eight different production lots of a commercial perfluoropolyether (PFPE) based on hexafluoropropene oxide (HFPO) were applied to polished metal surfaces by spinning. One of the lots repeatedly dewetted from a clean 440C steel surface, forming droplets on the surface, whereas the other seven did not dewet. This dewetting phenomenon also repeatedly occurred on 2024 aluminum and 1018 steel, but not on copper or gold. Fourier transform infrared microspectroscopy (mu-FTIR) was used to determine the thickness and uniformity of the PFPE films. The dewetting lot was found to dewet from 440C steel at a film thickness greater than 520 Angstrom. A portion of the dewetting lot was heated at 316 degrees C for 12 days in the presence of oxygen and M-50 steel. This fluid did not dewet. Sequentially, samples of the dewetting lot were filtered either with an alumina or a silica cartridge which can remove polar impurities. Neither of the filtered samples dewetted from 440C steel. It was concluded that an unknown impurity, both thermally labile and polar, present at very low concentration and undetected by the authors' analytical techniques (FTIR, proto NMR, or F-19 NMR), was responsible for the dewetting phenomenon. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. OHIO AEROSP INST,CLEVELAND,OH 44142. RP Shogrin, B (reprint author), CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44106, USA. NR 28 TC 4 Z9 4 U1 1 U2 3 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 838 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD SEP PY 1996 VL 52 IS 9 BP 712 EP 717 PG 6 WC Engineering, Mechanical SC Engineering GA VH249 UT WOS:A1996VH24900031 ER PT J AU Arrigo, KR Brown, CW AF Arrigo, KR Brown, CW TI Impact of chromophoric dissolved organic matter on UV inhibition of primary productivity in the sea SO MARINE ECOLOGY PROGRESS SERIES LA English DT Article DE CDOM; UV; photosynthesis; primary production ID INHERENT OPTICAL-PROPERTIES; ULTRAVIOLET-RADIATION; FLUORESCENCE MEASUREMENTS; OZONE DEPLETION; ABSORPTION-COEFFICIENT; PHYTOPLANKTON; WATERS; OCEAN; PHOTOSYNTHESIS; RETRIEVAL AB A model was developed to assess the impact of chromophoric dissolved organic matter (CDOM) on phytoplankton production within the euphotic zone. The rate of depth-integrated daily gross primary productivity within the euphotic zone (integral(z)GPP(ez)) was evaluated as a function of dale, latitude, CDOM absorption (a(CDOM)) characteristics, chlorophyll a (chl a) concentration, vertical stratification, and phytoplankton sensitivity to UV radiation (UVR). Results demonstrated that primary production was enhanced in the upper similar to 30 m of the water column by the presence of CDOM, where predicted increases in production due to the removal of damaging UVR more than offset its reduction resulting from the absorption of photosynthetically usable radiation. At greater depths, where Little UVR remained, primary production was always reduced due to removal by CDOM of photosynthetically usable radiation. When CDOM was distributed homogeneously within the euphotic zone, integral(z)GPP(ez) was reduced under most bio-optical (i.e. solar zenith angle, chi a and CDOM absorption, and ozone concentration) and photophysiological (i.e. sensitivity to UVR) conditions because the predicted reduction in primary production at depth was greater than the enhancement of production at the surface. A reduction in integral(z)GPP(ez) was also predicted when CDOM or phyloplankton was restricted to near-surface waters (similar to 30 m) and CDOM absorption was moderate [a(CDOM)(450) > 0.015 m(-1)]. integral(z)GPP(ez), however, was enhanced when CDOM or phytoplankton was restricted to a very shallow surface layer (similar to 10 m), even ii CDOM absorption was high [a(CDOM)(lambda) at 450 nm similar to 0.07 m(-1)]. Changes in integral(z)GPP(ez) resulting from the presence of CDOM were only slightly sensitive to ozone concentrations. In well-mixed waters where the flux of UVB is relatively high, such as in the Southern Ocean when the ozone hole is present, the presence of CDOM should result in little or no enhancement of integral(z)GPP(ez), although phytoplankton production would be expected to increase somewhat in surface waters. RP Arrigo, KR (reprint author), NASA, GODDARD SPACE FLIGHT CTR, OCEANS & ICE BRANCH, CODE 971, GREENBELT, MD 20771 USA. RI Brown, Christopher/B-8213-2008 OI Brown, Christopher/0000-0002-9905-6391 NR 21 TC 65 Z9 69 U1 1 U2 9 PU INTER-RESEARCH PI OLDENDORF LUHE PA NORDBUNTE 23, D-21385 OLDENDORF LUHE, GERMANY SN 0171-8630 J9 MAR ECOL PROG SER JI Mar. Ecol.-Prog. Ser. PD SEP PY 1996 VL 140 IS 1-3 BP 207 EP 216 DI 10.3354/meps140207 PG 10 WC Ecology; Marine & Freshwater Biology; Oceanography SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Oceanography GA VJ377 UT WOS:A1996VJ37700019 ER PT J AU Lee, S Ro, S AF Lee, S Ro, S TI A self-calibration model for hand-eye systems with motion estimation SO MATHEMATICAL AND COMPUTER MODELLING LA English DT Article DE self-calibration; hand-eye systems; motion estimations; 3-D reconstruction; stereo vision AB A self-calibration model of a hand-eye system having a stereo camera mounted on the manipulator end-effector is presented. The proposed self-calibration method is based on estimating the motion parameters of an object observed by the stereo camera under varying manipulator configurations. The object is assumed fixed in space or moving with a known form of trajectory but with unknown parameters. First, we derive theoretically a general form of self-calibration model for an overview of the proposed method. Then, a detailed set of self-calibration equations is formulated by relating the noise and biases involved in the hand-eye system to the variations of an object pose estimation error in time. The noise and biases include the uncertainty and nonlinearity involved in imaging and 3-D reconstruction, as well as the uncalibrated optical and kinematic parameters of the camera and manipulator. Simulations are conducted to verify the validity of the proposed self-calibration model. C1 UNIV SO CALIF, DEPT EE SYST & COMP SCI, LOS ANGELES, CA 90089 USA. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 29 TC 5 Z9 6 U1 2 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0895-7177 EI 1872-9479 J9 MATH COMPUT MODEL JI Math. Comput. Model. PD SEP PY 1996 VL 24 IS 5-6 BP 49 EP 77 DI 10.1016/0895-7177(96)00115-X PG 29 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA VK766 UT WOS:A1996VK76600005 ER PT J AU Nalim, R AF Nalim, R TI Radical combustion SO MECHANICAL ENGINEERING LA English DT Letter RP Nalim, R (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0025-6501 J9 MECH ENG JI Mech. Eng. PD SEP PY 1996 VL 118 IS 9 BP 8 EP 8 PG 1 WC Engineering, Mechanical SC Engineering GA VE288 UT WOS:A1996VE28800006 ER PT J AU Whittenberger, JD Noebe, RD AF Whittenberger, JD Noebe, RD TI Elevated temperature compressive properties of Zr-modified NiAl SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID PLASTIC-FLOW PROPERTIES; GRAIN-SIZE; MECHANICAL-PROPERTIES; INTERMETALLIC ALLOYS; BEHAVIOR; ALUMINIDES; ZIRCONIUM; BRITTLE; TENSILE; NICKEL AB Small Zr additions are known to substantially affect the deformation behavior and strength of polycrystalline NiAl, yet little information is currently available regarding the high-temperature properties of such alloys. Utilizing prealloyed powder technology, a series of four NiAl alloys have been produced containing from 0.05 to 0.7 at. pct Zr. The creep behavior of these alloys was characterized in compression between 1000 and 1400 K at strain rates ranging from similar to 0.1 to 10(-9) s(-1). All the Zr-modified alloys were significantly stronger than binary NiAl under fewer temperature and faster strain-rate conditions; however, the single-phase materials (Zr less than or equal to 0.1 at. pct) and binary NiAl had similar strengths at high temperatures and slow strain rates. The two-phase NiAl-Ni2AlZr alloys containing 0.3 and 0.7 at. pct Zr had nearly identical strengths. While the two-phase alloys were stronger than the single-phase materials at all test conditions, the degree of microstructural damage in the two-phase alloys due to internal oxidation during testing appeared to increase with Zr level. Balancing the poor oxidation behavior with the consistent strength advantage of the two-phase alloys, it is concluded that optimum elevated-temperature properties could be obtained in Heusler-strengthened NiAl containing between 0.1 and 0.3 at. pct Zr. RP Whittenberger, JD (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 33 TC 27 Z9 30 U1 0 U2 3 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD SEP PY 1996 VL 27 IS 9 BP 2628 EP 2641 DI 10.1007/BF02652356 PG 14 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA VH386 UT WOS:A1996VH38600023 ER PT J AU Ivanov, AV MacPherson, GJ Zolensky, ME Kononkova, NN Migdisova, LF AF Ivanov, AV MacPherson, GJ Zolensky, ME Kononkova, NN Migdisova, LF TI The Kaidun meteorite: Composition and origin of inclusions in the metal of an enstatite chondrite clast SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID CHEMISTRY; BEARING AB Metal nodules are one of the major textural components of Kaidun sample #01.3.06 EH3-4. In terms of structure, the nodules are of three types: (1) globular, (2) zoned with a massive core and globular mantle, and (3) nodules with no internal structure. The size and composition of the globules in the nodules and grains of metal of the matrix are almost identical: no greater than 20 mu m and Ni, 5.95; Si, 3.33 wt%. The nodules contain small (usually <5 mu m) inclusions of SiO2; albitic glass; enstatite; roedderite; and a mixture of SiO2 and Na2S2. This is the first reported occurrence of a simple sulfide of an alkaline metal in nature. The formation of the inclusions appears to be related to condensation of material onto the surfaces of metal grains. The nodules appear to have formed by aggregation of separate grains (globules) of metal, with conservation of condensates on the grain surfaces as inclusions. The inclusions probably condensed over a significant temperature range from 1400 to 600 K. The aggregation of metal grains and formation of the nodules probably occurred simultaneously with condensation. C1 SMITHSONIAN INST,DEPT MINERAL SCI,WASHINGTON,DC 20560. NASA,LYNDON B JOHNSON SPACE CTR,DIV EARTH SCI & SOLAR SYST EXPLORAT,HOUSTON,TX 77058. RP Ivanov, AV (reprint author), RUSSIAN ACAD SCI,VI VERNADSKII INST GEOCHEM & ANALYT CHEM,MOSCOW 117975,RUSSIA. NR 23 TC 19 Z9 20 U1 2 U2 4 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METORIT PLANET SCI JI Meteorit. Planet. Sci. PD SEP PY 1996 VL 31 IS 5 BP 621 EP 626 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VJ141 UT WOS:A1996VJ14100006 ER PT J AU RomeroColmenero, E BranduardiRaymont, G Carrera, FJ Jones, LR Mason, KO McHardy, IM Mittaz, JPD AF RomeroColmenero, E BranduardiRaymont, G Carrera, FJ Jones, LR Mason, KO McHardy, IM Mittaz, JPD TI ROSAT PSPC spectra of X-ray-selected narrow-emission-line galaxies SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, active; X-rays, galaxies ID N-LOG-S; DEEP AB We analyse the ROSAT PSPC spectra of 19 X-ray-selected narrow-emission-line galaxies (NELGs) discovered during the optical identification of sources in the ROSAT UK Deep Survey. Their properties are compared with those of broad-line active galactic nuclei (AGN) in the same sample. Counts in three spectral bands have been extracted for all the sources, and have been fitted with a power-law model assuming the Galactic value for N-H. The average slope of the NELGs is alpha = 0.45 +/- 0.09, whilst for the AGN it is alpha = 0.96 +/- 0.03. The power-law model is a good fit for similar to 90 per cent of NELGs and similar to 75 per cent of AGN. Recent work shows that the fractional surface density of NELGs increases with respect to AGN at faint fluxes. Thus they are expected to be an important component of the residual soft (< 2 keV) X-ray background. The slope of the X-ray background (alpha similar to 0.4, 1-10 keV) is harder than that of AGN (alpha similar to 1) but our results show that it is consistent with the summed spectrum of the NELGs in the deep survey (alpha similar to 0.4). This may finally reconcile the spectrum of the background with the properties of the sources that constitute it. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV SOUTHAMPTON, DEPT PHYS, SOUTHAMPTON SO9 5NH, HANTS, ENGLAND. RP RomeroColmenero, E (reprint author), UCL, MULLARD SPACE SCI LAB, HOLMBURY ST MARY, DORKING RH5 6NT, SURREY, ENGLAND. NR 16 TC 37 Z9 37 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 1 PY 1996 VL 282 IS 1 BP 94 EP 98 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VE636 UT WOS:A1996VE63600012 ER PT J AU Takayabu, YN Lau, KM Sui, CH AF Takayabu, YN Lau, KM Sui, CH TI Observation of a quasi-2-day wave during TOGA COARE SO MONTHLY WEATHER REVIEW LA English DT Article ID EQUATORIAL LOWER STRATOSPHERE; 40-50 DAY OSCILLATION; WESTERN PACIFIC; PERIOD DISTURBANCES; CLOUD DISTURBANCES; TROPICAL PACIFIC; GRAVITY WAVES; ATMOSPHERE; CONVECTION; CLUSTERS AB Detailed structure of the quasi-2-day oscillation observed in the active phase of the Madden-Julian oscillations during the intensive observation period of Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE IOP) was described. A variety of observational platforms is used including high-resolution GMS infrared histogram, rain-rate estimate from TOGA and MIT radar measurements, upper-air soundings, and boundary layer profiler winds from the integrated Sounding System and surface data from the IMET buoy. The quasi-2-day mode had a westward propagation speed of 12 degrees-15 degrees day(-1), a horizontal wavelength of 25 degrees-30 degrees longitude. A coupling with the westward-propagating n = 1 inertio-gravity waves was hypothesized from the space-time power spectral distribution of the cloud field. The wind disturbance structure was consistent with the hypothesis. The vertical wave structure had an eastward phase tilt with height below 175 hPa and vice versa above, indicating the wave energy emanating from the upper troposphere. Four stages in the life cycle of the oscillating cloud-circulation system were identified: 1) the shallow convection stage with a duration time of 12 h, 2) the initial tower Stage (9 h), 3) the mature stage (12 h), and 4) the decaying stage (15 h). Surface and boundary layer observations also showed substantial variation associated with the different stages in the Life cycle. Results suggest that the timescale of quasi-2-day oscillation is determined by the time required by the lower-tropospheric moisture field to recover from the drying caused by deep convection. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Takayabu, YN (reprint author), NATL INST ENVIRONM STUDIES,DIV ATMOSPHER ENVIRONM,16-2 ONOGAWA,TSUKUBA,IBARAKI 305,JAPAN. RI Lau, William /E-1510-2012; OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 26 TC 96 Z9 96 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD SEP PY 1996 VL 124 IS 9 BP 1892 EP 1913 DI 10.1175/1520-0493(1996)124<1892:OOAQDW>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VE282 UT WOS:A1996VE28200002 ER PT J AU Chen, MH Bates, JR AF Chen, MH Bates, JR TI Forecast experiments with a global finite-difference semi-Lagrangian model SO MONTHLY WEATHER REVIEW LA English DT Article ID SHALLOW-WATER EQUATIONS; SCHEMES; INTEGRATION; PREDICTION; VERSION AB A series of 10-day forecast experiments has been carried out to investigate the sensitivity of a global semi-Lagrangian model to the value of the uncentering parameter epsilon, the magnitude of the time step for the dynamics, and the numerical treatment of the physical parameterizations (semi-Lagrangian versus Eulerian). The model has been run at a resolution of 2 degrees latitude by 2.5 degrees longitude with 20 vertical levels. Results from the experiments with Values of epsilon ranging from 0 to 0.4 show that epsilon = 0.2 gives the best overall forecasts. The experiments with the time step for the dynamics varying from 15 to 60 min indicate that the forecasts are sensitive to the time step for the dynamics, even when the time steps for the physical parameterizations are held constant. The forecasts with the 60-min time step for the dynamics show the best overall objective skill scores. The two versions of the semi-Lagrangian model, one with Eulerian physics and the other with semi-Lagrangian physics, give similar forecast skill scores. The semi-Lagrangian model is also compared with a corresponding Eulerian model. It is found that the forecasts from the two models have similar quality, even though the time step for the dynamics in the semi-Lagrangian model is 16 times as long as that in the Eulerian model and the physical parameterizations have been developed and tuned for the Eulerian model. C1 NASA, GODDARD SPACE FLIGHT CTR, DATA ASSIMILAT OFF, GREENBELT, MD 20771 USA. APPL RES CORP, LANDOVER, MD 20785 USA. NR 24 TC 11 Z9 11 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD SEP PY 1996 VL 124 IS 9 BP 1992 EP 2007 DI 10.1175/1520-0493(1996)124<1992:FEWAGF>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VE282 UT WOS:A1996VE28200010 ER PT J AU Lin, SJ Rood, RB AF Lin, SJ Rood, RB TI Multidimensional flux-form semi-Lagrangian transport schemes SO MONTHLY WEATHER REVIEW LA English DT Article ID CONSERVATIVE DIFFERENCE SCHEME; SMALL IMPLICIT DIFFUSION; PARABOLIC METHOD PPM; ADVECTION SCHEME; CORRECTED TRANSPORT; NUMERICAL ADVECTION; GODUNOV METHOD; MIXING RATIOS; ALGORITHMS; LAWS AB An algorithm for extending one-dimensional, forward-in-time, upstream-biased, flux-form transport schemes (e.g., the van Leer scheme and the piecewise parabolic method) to multidimensions is proposed. ri method is also proposed to extend the resulting Eulerian multidimensional flux-form scheme to arbitrarily long time steps. Because of similarities to the semi-Lagrangian approach of extending rime steps, the scheme is called flux-form semi-Lagrangian (FFSL). The FFSL scheme can be easily and efficiently implemented on the sphere. Idealized rests as well as realistic three-dimensional global transport simulations using winds from data assimilation systems are demonstrated. Stability is analyzed with a von Neuman approach as well as empirically on the 2D Cartesian plane. The resulting algorithm is conservative and upstream biased. In addition, it contains monotonicity constraints and conserves tracer correlations, therefore representing the physical characteristics of constituent transport. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, DATA ASSIMILAT OFF, GREENBELT, MD 20771 USA. RI Rood, Richard/C-5611-2008 OI Rood, Richard/0000-0002-2310-4262 NR 56 TC 614 Z9 623 U1 3 U2 38 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 EI 1520-0493 J9 MON WEATHER REV JI Mon. Weather Rev. PD SEP PY 1996 VL 124 IS 9 BP 2046 EP 2070 DI 10.1175/1520-0493(1996)124<2046:MFFSLT>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VE282 UT WOS:A1996VE28200013 ER PT J AU Saini, S AF Saini, S TI Petaflops computing and computational nanotechnology SO NANOTECHNOLOGY LA English DT Article ID SEMICLASSICAL QUANTIZATION; MOLECULAR MECHANICS; FIELD; PERTURBATION; SIMULATIONS; RESONANCE; SYSTEMS AB One of the biggest challenges in nanotechnology is the need to simulate entire molecular assemblies of up to 100 million atoms or more. This requires about one million to one billion fold more computing power than is available today. For nanotechnology to be successful, it will be essential to develop Petaflops computing systems and associated software. We will survey the various enabling technologies, such as semiconductors, superconducting, photonic, and exotic (quantum integrated circuits, molecular computers, DNA computers) that are expected to be available in the next 20 to 25 years for making Petaflops computing and nanotechnology feasible. It will be shown that progress in nanotechnology and progress in future high-performance computer systems are mutually interdependent. RP Saini, S (reprint author), NASA,AMES RES CTR,MS T27A-1,MOFFETT FIELD,CA 94035, USA. NR 50 TC 1 Z9 1 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1996 VL 7 IS 3 BP 224 EP 235 DI 10.1088/0957-4484/7/3/010 PG 12 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA VL331 UT WOS:A1996VL33100011 ER PT J AU Humenik, K Matthews, P Stephens, AB Yesha, Y AF Humenik, K Matthews, P Stephens, AB Yesha, Y TI Minimizing message complexity of partially replicated data on hypercubes SO NETWORKS LA English DT Article ID COMPUTER-NETWORKS AB Within the framework of distributed and parallel computing, we consider partially replicated data on a hypercube. We address the problem of placing copies on the hypercube in order to minimize message complexity. With realistic restrictions on the read/write ratio and the number of copies, we find the unique optimal configuration of copies. We compute the communication cost of this configuration. The optimal configuration is a linear array satisfying certain properties. (C) 1996 John Wiley & Sons, Inc. C1 UNIV MARYLAND,DEPT MATH & STAT,BALTIMORE,MD 21228. UNIV MARYLAND,DEPT COMP SCI,BALTIMORE,MD 21228. GODDARD SPACE FLIGHT CTR,CTR EXCELLENCE SPACE DATA & INFORMAT SCI,GREENBELT,MD. RP Humenik, K (reprint author), INDIANA UNIV,DEPT MATH & COMP SCI,S BEND,IN 46634, USA. NR 18 TC 1 Z9 1 U1 0 U2 0 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0028-3045 J9 NETWORKS JI Networks PD SEP PY 1996 VL 28 IS 2 BP 87 EP 95 PG 9 WC Computer Science, Hardware & Architecture; Operations Research & Management Science SC Computer Science; Operations Research & Management Science GA VD043 UT WOS:A1996VD04300002 ER PT J AU Artoni, M Marani, R AF Artoni, M Marani, R TI Squeezed states in multiple atomic fluorescence SO PHYSICAL REVIEW A LA English DT Article ID POISSONIAN PHOTON STATISTICS; RESONANCE FLUORESCENCE; LIGHT; SPECTRUM; FREQUENCY; NOISE AB We study the propagation of squeezing in the resonance fluorescence from a two-atom system within the weak-field approximation. We show that squeezing occurs in the fluorescence from both atoms, although with different falloff in time. C1 NYU,DEPT PHYS,NEW YORK,NY 10003. RP Artoni, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,PHOTON DIV,GREENBELT,MD 20771, USA. NR 28 TC 1 Z9 1 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 SEP PY 1996 VL 54 IS 3 BP 2280 EP 2291 DI 10.1103/PhysRevA.54.2280 PG 12 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA VH090 UT WOS:A1996VH09000069 ER PT J AU Vasquez, RP Ren, ZF Wang, JH AF Vasquez, RP Ren, ZF Wang, JH TI Electronic structure of Tl2Ba2CuO6+delta epitaxial films measured by x-ray photoemission SO PHYSICAL REVIEW B LA English DT Article ID HIGH-TEMPERATURE SUPERCONDUCTORS; T-C SUPERCONDUCTORS; PHOTOELECTRON-SPECTROSCOPY; DOPING DEPENDENCE; SPECTRA; BI2SR2CA1-XYXCU2O8+DELTA; BI2SR2CACU2O8+DELTA; TL2BA2CA2CU3O10; STATES AB The valence electronic structure and core levels of Tl2Ba2CuO6+delta (Tl-2201) epitaxial films have been measured with x-ray photoelectron spectroscopy and are compared to those of Tl2Ba2CaCu2O8+delta (Tl-2212). Changes in the Tl-2201 core-level binding energies with oxygen doping are consistent with a change in the chemical potential. Differences between the Tl-2201 and Tl-2212 measured densities of states are consistent with the calculated Cu 3d and Tl 6s partial densities of states. C1 SUNY BUFFALO,DEPT CHEM,SUPERCONDUCT MAT LAB,BUFFALO,NY 14260. SUNY BUFFALO,NEW YORK STATE INST SUPERCONDUCT,BUFFALO,NY 14260. RP Vasquez, RP (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. RI Ren, Zhifeng/B-4275-2014 NR 29 TC 8 Z9 8 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0163-1829 J9 PHYS REV B JI Phys. Rev. B PD SEP 1 PY 1996 VL 54 IS 9 BP 6115 EP 6118 DI 10.1103/PhysRevB.54.6115 PG 4 WC Physics, Condensed Matter SC Physics GA VG949 UT WOS:A1996VG94900029 ER PT J AU Young, JB Presgrave, BW Aichele, H Wiens, DA Flinn, EA AF Young, JB Presgrave, BW Aichele, H Wiens, DA Flinn, EA TI The Flinn-Engdahl regionalisation scheme: The 1995 revision SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Article ID REGIONALIZATION SCHEME AB The Flinn-Engdahl Regionalisation Scheme, also known as the F-E Code, has been used by seismologists for many years to identify and specify regions of the Earth. The Working Group on Regionalisation of the International Association of Seismology and Physics of the Earth's Interior (IASPEI) Commission on Practice has the task of defining a new standard for the regionalisation of the Earth. In the meantime, it was agreed that a revision of the F-E Code would be appropriate. This paper presents the 1995 revision and supersedes the F-E Code standard published in 1974. C1 US GEOL SURVEY,NATL EARTHQUAKE INFORMAT CTR,DENVER,CO 80225. SEISMOL ZENT OBSERV,D-91054 ERLANGEN,GERMANY. WASHINGTON UNIV,DEPT EARTH & PLANETARY SCI,ST LOUIS,MO 63130. NASA,WASHINGTON,DC 20546. RP Young, JB (reprint author), AWE BLACKNEST,READING RG7 4RS,BERKS,ENGLAND. NR 12 TC 24 Z9 24 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-9201 J9 PHYS EARTH PLANET IN JI Phys. Earth Planet. Inter. PD SEP PY 1996 VL 96 IS 4 BP 223 EP 297 DI 10.1016/0031-9201(96)03141-X PG 75 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VG530 UT WOS:A1996VG53000002 ER PT J AU Brown, AH Johnsson, A Chapman, DK Heathcote, D AF Brown, AH Johnsson, A Chapman, DK Heathcote, D TI Gravitropic responses of the Avena coleoptile in space and on clinostats .4. The clinostat as a substitute for space experiments SO PHYSIOLOGIA PLANTARUM LA English DT Article DE Avena; clinostat; gravitropism; microgravity; space ID IN-SPACE AB Gravitropic responses of dark grown oat coleoptiles were measured in weightlessness and under clinorotation on earth. The tests in microgravity were conducted in Spacelab during the IML-1 mission and those on clinostats were conducted in laboratories on earth. The same apparatus was used for both kinds of tests. In both cases autotropism and gravitropic responsiveness were determined. This allowed a quantitative comparison between the plants' responses after receiving the same tropistic stimulations either in weightlessness or on clinostats. Autotropism was observed with oat coleoptiles responding in weightlessness but it did not occur on clinostats. Gravitropic responsiveness was measured as the ratio between the incremental bending response (degrees curvature) and the corresponding incremental g-dose (stimulus intensity times duration for which it was applied). Plants were tested at either of two stages of coleoptile development (i.e. different coleoptile lengths). From a total of six different kinds of critical comparisons that could be made from our rests that provided data for clinorotated vs weightless plants, three showed no significant difference between responses in simulated vs authentic weightlessness. Three other comparisons showed highly significant differences. Therefore, the validity of clinorotation as a general substitute for space flight was not supported by these results. C1 NORWEGIAN UNIV SCI & TECHNOL,DEPT PHYS,N-7055 DRAGVOLL,NORWAY. UNIV PENN,GODDARD LABS,PHILADELPHIA,PA 19104. AMES RES CTR,MOFFETT FIELD,CA 94035. BIONET CORP,KENNEDY SPACE CTR,FL 32899. NR 14 TC 10 Z9 10 U1 1 U2 1 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0031-9317 J9 PHYSIOL PLANTARUM JI Physiol. Plant. PD SEP PY 1996 VL 98 IS 1 BP 210 EP 214 PG 5 WC Plant Sciences SC Plant Sciences GA VJ373 UT WOS:A1996VJ37300026 ER PT J AU Moore, MH Ferrante, RF Nuth, JA AF Moore, MH Ferrante, RF Nuth, JA TI Infrared spectra of proton irradiated ices containing methanol SO PLANETARY AND SPACE SCIENCE LA English DT Article ID EXPERIMENTS RELEVANT; ASTROPHYSICAL ICES; SILICATE SMOKES; COMET HALLEY; WATER ICE; PHYSICS AB A set of experimental results on the spectral identification of new species synthesized in irradiated CH3OH and H2O+CH3OH ices is reported. Mass spectroscopy of volatile species released during slow warming gives supporting information on identifications. H2CO is the dominant volatile species identified in the irradiated ices; CH4, CO and CO2 are also formed. During warming the ice evolves into a residual film near 200 K whose features are similar to those of ethylene glycol along with a C=O bonded molecular group. Irradiation simulates expected cosmic ray processing of ices in comets stored in the Oort cloud region for 4.6 billion years. Results support the idea that a comet originally containing an H2O+CH3OH ice component has a decreasing concentration of CH3OH towards its outer, most heavily irradiated layers (if independent of all other sources and sinks). The CH4/CO and CO/CO2 ratios are calculated as a function of irradiation; after 22 eV per molecule, CH4/CO = 1.96 and CO/CO2 = 1.45 in an H2O+CH3OH ice mixture. Infrared spectra of CH3OH at T < 20 K on amorphous silicate smokes show a predominantly crystalline phase ice. Irradiation of the ice/silicate composite is compared with irradiated CH3OH on aluminum substrates. Implication for cometary type ices are discussed. Published by Elsevier Science Ltd C1 USN ACAD, DEPT CHEM, ANNAPOLIS, MD 21402 USA. RP Moore, MH (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTROCHEM BRANCH, GREENBELT, MD 20771 USA. RI Nuth, Joseph/E-7085-2012 NR 35 TC 61 Z9 61 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP PY 1996 VL 44 IS 9 BP 927 EP 935 DI 10.1016/0032-0633(95)00120-4 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VU306 UT WOS:A1996VU30600005 ER PT J AU Flynn, B Stern, A Buratti, B Schenk, P Trafton, L Mosher, J AF Flynn, B Stern, A Buratti, B Schenk, P Trafton, L Mosher, J TI The spatial distribution of UV-absorbing regions on Triton SO PLANETARY AND SPACE SCIENCE LA English DT Article ID OUTER SOLAR-SYSTEM; REFLECTANCE SPECTRA; SURFACE; IRRADIATION; NEPTUNE; ALBEDO; PLUTO; COLOR C1 SW RES INST, BOULDER, CO 80302 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. LUNAR & PLANETARY INST, HOUSTON, TX 77058 USA. UNIV TEXAS, DEPT ASTRON, AUSTIN, TX 78712 USA. NR 20 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP PY 1996 VL 44 IS 9 BP 1039 EP 1046 DI 10.1016/0032-0633(96)00077-3 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VU306 UT WOS:A1996VU30600017 ER PT J AU Reddy, VS Weikel, WJ Arbaugh, J Fitch, JW Cassidy, PE Clair, AKS AF Reddy, VS Weikel, WJ Arbaugh, J Fitch, JW Cassidy, PE Clair, AKS TI Synthesis and characterization of new fluorinated polyacrylates .2. SO POLYMER LA English DT Article DE polyacrylates; fluoro polymers; polymethacrylates AB A series of new fluorinated acrylate polymers and copolymers (with methyl acrylate and methyl methacrylate) has been prepared starting from 1,3-bis(hexafluoro-2-hydroxy-2-propyl)benzene HFAB). 1,3-HFAB was first reacted with dimethylsulfate in the presence of aqueous sodium hydroxide to yield 1-(hexafluoro-2-hydroxy-2-propyl)-3-(hexafluoro-2-methoxy-2- propyl)benzene which was reacted with acryloyl or methacryloyl chloride to give the corresponding fluorinated acrylate or methacrylate monomers. The polymers were obtained by bulk or solution free radical polymerization techniques with alpha,alpha'-azobisisobutyronitrile as initiator. The polymers had viscosities ranging from 0.21-0.41 dl g(-1), and the polyacrylates formed brittle films by solution casting. Thermogravimetric analysis showed that they had thermal stability up to 391 degrees C in nitrogen and glass transition temperatures from 50 to 104 degrees C. Copyright (C) 1996 Elsevier Science Ltd. C1 SW TEXAS STATE UNIV,DEPT CHEM,POLYMER RES GRP,SAN MARCOS,TX 78666. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. NR 14 TC 8 Z9 9 U1 0 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0032-3861 J9 POLYMER JI Polymer PD SEP PY 1996 VL 37 IS 20 BP 4653 EP 4656 PG 4 WC Polymer Science SC Polymer Science GA VK902 UT WOS:A1996VK90200027 ER PT J AU Wood, JC Barry, DT AF Wood, JC Barry, DT TI Time-frequency analysis of skeletal muscle and cardiac vibrations SO PROCEEDINGS OF THE IEEE LA English DT Article ID FIRST HEART-SOUND; ACOUSTIC MYOGRAPHY; SPECTRAL-ANALYSIS; MULTICOMPONENT SIGNALS; NONSTATIONARY SIGNALS; WIGNER DISTRIBUTION; PROSTHETIC VALVES; MUSCULAR SOUND; REPRESENTATION; CONTRACTION AB Skeletal muscle and the heart vibrate during contraction producing nonstationary signals whose time-varying frequency reflects dynamic changes in physiological properties. Consequently, pathological changes in the mechanical integrity or lending of skeletal muscle or the heart can be expected to alter their vibrations.' Classic frequency analysis techniques have been inadequate to characterize these subtle changes because of rapidly varying frequency components. A poor understanding of heart and muscle sound generation has also limited investigations. This paper demonstrates how time-frequency (TF) techniques have illuminated the relationships between muscle/heart material properties and loading, and frequency dynamics of heart and muscle vibrations. Studies of evoked twitches from frog skeletal muscle reveal that muscle vibrations occur as transverse oscillations at the muscle's resonant frequency. Using a classic Rayleigh-Ritz model and crude estimates of the muscle geometry muscle force can be accurately predicted from the muscle sound TF profile. First heart sound vibrations, in contrast, are shown to be a nonresonant phenomena consisting of propagating transients superimposed upon bulk acceleration of myocardial contraction. Consequently, first heart sound frequency dynamics depend upon cardiac electrical excitation and hemodynamic loading in addition to intrinsic material properties and geometry, necessitating further work to characterize pathophysiologic correlations. C1 NASA,LYNDON B JOHNSON SPACE CTR,ASTRONAUT OFF,HOUSTON,TX 77058. RP Wood, JC (reprint author), YALE UNIV,NEW HAVEN HOSP,PEDIAT CARDIOL SECT,NEW HAVEN,CT 06520, USA. NR 64 TC 32 Z9 32 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9219 J9 P IEEE JI Proc. IEEE PD SEP PY 1996 VL 84 IS 9 BP 1281 EP 1294 DI 10.1109/5.535246 PG 14 WC Engineering, Electrical & Electronic SC Engineering GA VF276 UT WOS:A1996VF27600008 ER PT J AU Cesare, SJ AF Cesare, SJ TI Subjective judgment and the selection interview: A methodological review SO PUBLIC PERSONNEL MANAGEMENT LA English DT Article ID EMPLOYMENT INTERVIEW; META-ANALYSIS; PHYSICAL ATTRACTIVENESS; SITUATIONAL INTERVIEW; APPLICANT QUALIFICATIONS; DISCRIMINATION RESEARCH; PERFORMANCE-APPRAISAL; HIRING DECISIONS; SEX; RACE AB Research on the employment interview frequently involves various studies containing disparate methodological factors that mitigate definitive conclusions regarding interview effectiveness. Two characteristics frequently cited as pertinent to the employment interview are the applicant's gender and race. From that position, the purpose of this research was to review the empirical literature identifying those methodological factors relevant to gender/race effects in the interview. It is hoped that this summary will represent a meaningful compilation of the methodological considerations that often confuse interpretation concerning the effects of applicant gender and race on interview judgments. C1 CITICORP,NEW YORK,NY. NASA,WASHINGTON,DC 20546. UNIV CALIF SAN DIEGO,SCH BUSINESS,LA JOLLA,CA 92093. UNIV CALIF SAN DIEGO,DEPT PSYCHOL,LA JOLLA,CA 92093. RP Cesare, SJ (reprint author), CTY SAN DIEGOS DEPT INFORMAT SERV,SAN DIEGO,CA, USA. NR 57 TC 11 Z9 11 U1 4 U2 17 PU INT PERSONNEL MANAGEMENT ASSN PI ALEXANDRIA PA 1617 DUKE ST, ALEXANDRIA, VA 22314 SN 0091-0260 J9 PUBLIC PERS MANAGE JI Public Personnel Manage. PD FAL PY 1996 VL 25 IS 3 BP 291 EP 306 PG 16 WC Industrial Relations & Labor; Public Administration SC Business & Economics; Public Administration GA VM138 UT WOS:A1996VM13800003 ER PT J AU Reddy, CJ Deshpande, MD Fralick, DT Cockrell, CR Beck, FB AF Reddy, CJ Deshpande, MD Fralick, DT Cockrell, CR Beck, FB TI Calculation of radiation characteristics of cavity-backed aperture antennas using a combined finite element method, method of moments, and geometrical theory of diffraction technique SO RADIO SCIENCE LA English DT Article ID ELECTROMAGNETIC SCATTERING; ARBITRARY SHAPE; PATCH ANTENNAS; ARRAYS AB Radiation pattern prediction analysis of elliptically polarized cavity-backed aperture antennas in a finite ground plane is carried out using a combination of the finite element method (FEM), method of moments (MoM), and geometrical theory of diffraction (GTD). The magnetic current on the cavity-backed aperture in an infinite ground plane is calculated using the combined FEM-MoM analysis. GTD is used to calculate the diffracted fields due to both soft and hard polarizations at the edges of the finite ground plane. The slope of the incident magnetic field at the diffraction points is derived and analytical expressions are presented. Numerical results for the radiation patterns of a cavity-backed coaxial cavity and also a cavity-backed circular spiral microstrip patch antenna excited by a coaxial probe in a finite rectangular ground plane are computed and compared with measured results. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. VIGYAN INC,HAMPTON,VA 23681. LOCKHEED MARTIN ENGN & SCI CO,HAMPTON,VA 23681. RP Reddy, CJ (reprint author), HAMPTON UNIV,SCH ENGN & TECHNOL,DEPT ELECT ENGN,E QUEEN ST,HAMPTON,VA 23668, USA. NR 19 TC 0 Z9 0 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD SEP-OCT PY 1996 VL 31 IS 5 BP 1181 EP 1189 DI 10.1029/96RS01363 PG 9 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA VK772 UT WOS:A1996VK77200018 ER EF