FN Thomson Reuters Web of Science™ VR 1.0 PT S AU Stecher, FW AF Stecher, FW BE Krizmanic, JF Ormes, JF Streitmatter, RE TI Intergalactic propagation of heavy nuclei - Are they the trans-Greisen events SO WORKSHOP ON OBSERVING GIANT COSMIC RAY AIR SHOWERS FROM >10(20) EV PARTICLES FROM SPACE SE AIP CONFERENCE PROCEEDINGS LA English DT Proceedings Paper CT Workshop on Observing Giant Cosmic Ray Air Showers from >10(20)eV Particles from Space CY NOV 13-15, 1997 CL COLLEGE PK, MD AB The critical interactions for energy loss and photodisintegration of ultrahigh energy cosmic-ray (UHCR) nuclei occur with photons of the infrared background radiation (IBR). I present here the results of a new estimation of the photodisintegration and propagation of (UHCR) nuclei in intergalactic space. I have reexamined this problem making use of a new determination of the IBR based on empirical data, primarily from IRAS galaxies, and also collateral information from TeV gamma-ray observations of two nearby BL Lac objects. The results of this new calculation indicate that a 200 EeV nucleus which started out as Fe can have propagated similar to 100 Mpc though the IBR. I argue that it is possible that the highest energy cosmic rays observed may be nuclei rather than protons. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Stecher, FW (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. RI Stecker, Floyd/D-3169-2012 NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0094-243X BN 1-56396-788-X J9 AIP CONF PROC PY 1998 IS 433 BP 212 EP 216 DI 10.1063/1.56111 PG 5 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA BL30A UT WOS:000075033900017 ER PT S AU Mitchell, JW AF Mitchell, JW CA OWL Study Collaboration BE Krizmanic, JF Ormes, JF Streitmatter, RE TI Photodetectors for OWL SO WORKSHOP ON OBSERVING GIANT COSMIC RAY AIR SHOWERS FROM >10(20) EV PARTICLES FROM SPACE SE AIP CONFERENCE PROCEEDINGS LA English DT Proceedings Paper CT Workshop on Observing Giant Cosmic Ray Air Showers from >10(20)eV Particles from Space CY NOV 13-15, 1997 CL COLLEGE PK, MD AB At its focal plane, an Orbiting Wide-Angle Light Collector (OWL) will require a highly segmented large area photon detector, able to detect ultraviolet light at the single photoelectron (few photon)level. Depending on the OWL field-of-view and collecting optics, the focal plane detector must have 6 to 20 square meters of contiguous active area segmented into. between 0.4 and 1.7 million individual pixels. Each pixel must have a time response of ten nanoseconds to one microsecond, depending on the readout technique, and be able to resolve and record single photoelectrons. The technical requirements of the OWL focal plane detector and possible approaches to its realization will be presented and discussed. A baseline photodetector system is identified. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Mitchell, JW (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA SN 0094-243X BN 1-56396-788-X J9 AIP CONF PROC PY 1998 IS 433 BP 500 EP 510 DI 10.1063/1.56137 PG 11 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA BL30A UT WOS:000075033900046 ER PT B AU Patterson, FG AF Patterson, FG BE Callaos, N Omolayole, O Wang, L TI Three reasons why reengineering legacy software is difficult SO WORLD MULTICONFERENCE ON SYSTEMICS, CYBERNETICS AND INFORMATICS, VOL 1, PROCEEDINGS: ISAS '98 LA English DT Proceedings Paper CT World Multi-Conference on Systemics Cybernetics, and Informatics (SCI 98)/4th International Conference on Information Systems, Analysis and Synthesis (ISAS 98) CY JUL 12-16, 1998 CL ORLANDO, FL SP Int Inst Informat & System, World Org System & Cybernet, Int Federat Syst Res, Int Soc Syst Sci, Int Syst Inst, CUST, Int Inst Adv Studies Syst Res & Cybernet, Soc Appl Syst Res DE reengineering; reuse; metrics; measurement; reverse engineering; software engineering; software maintenance ID METRICS; COMPLEXITY; REQUIREMENTS AB It is our belief that reverse engineering is the principal contributor to the difficulty of software reengineering. This difficulty is manifest as cost, measured in engineering resources. In this paper we look at three dimensions of reverse engineering based on three metrics believed to be classes of contributing factors and based on previous research. There are various types of reengineering that may be differentiated by their principal product and ordered according to the amount of reverse engineering required. The three "reasons" in the title refer to metrics: we will examine reengineering in each of these types in terms of understandability, effort, and coupling, three metrics that have been shown both theoretically and empirically to correlate strongly with reengineerability. C1 NASA, Washington, DC 20546 USA. RP Patterson, FG (reprint author), NASA, Washington, DC 20546 USA. NR 36 TC 0 Z9 0 U1 0 U2 0 PU INT INST INFORMATICS & SYSTEMICS PI ORLANDO PA 14269 LORD BARCLAY DR, ORLANDO, FL 32837 USA BN 980-07-5078-9 PY 1998 BP 424 EP 431 PG 8 WC Computer Science, Artificial Intelligence; Computer Science, Information Systems; Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA BU33F UT WOS:000175705800067 ER PT S AU Leviton, DB Saha, TT Gardner, LD AF Leviton, DB Saha, TT Gardner, LD BE Fineschi, S TI Far ultraviolet and visible light scatter measurements for CVD SiC mirrors for SOHO SO X-RAY AND ULTRAVIOLET SPECTROSCOPY AND POLARIMETRY II SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on X-Ray and Ultraviolet Spectroscopy and Polarimetry II CY JUL 23-24, 1998 CL SAN DIEGO, CA SP SPIE Int Soc Opt Engn DE CVD silicon carbide; ultraviolet; scatter; solar telescope mirrors; SOHO; SUMER; UVCS AB Chemically-vapor-deposited (CVD) silicon carbide (SiC) has become a popular mirror material for spaceborne solar instrumentation for the vacuum ultraviolet wavelength range due to its appreciable broadband reflectance and favorable thermal and opto-mechanical properties. Scatter from surfaces of mirrors operating in this wavelength range can destroy otherwise good image contrast especially for extended targets such as the sun. While valid far ultraviolet (FUV) scatter measurements are entirely non-trivial to conduct and so are rarely performed, visible light scatter measurements are comparatively easy. Unfortunately, it is not straightforward to predict FUV scatter performance based on visible light scatter measurements for mirrors made of CVD SiC. It is hoped that by carrying out scatter measurements in both wavelength regimes for the same CVD SiC mirror, that the ability to make such predictions may be enhanced. Visible light (633 nm) scatter measurements were performed at Goddard Space Flight Center (GSFC) by two different means on CVD SIC telescope mirrors (from the same process and same vendor) for two instruments on the Solar and Heliospheric Observatory (SOHO) -- the Ultraviolet Coronagraph Spectrometer (UVCS) and Solar Ultraviolet Measurement of Emitted Radiation (SUMER). Additionally, extensive FUV scatter measurements were made for SUMER telescope mirrors. In this paper, we correlate the results for those FUV and visible light scatter measurements for this important material. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Leviton, DB (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 7 TC 3 Z9 3 U1 0 U2 1 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2898-1 J9 P SOC PHOTO-OPT INS PY 1998 VL 3443 BP 19 EP 30 DI 10.1117/12.333616 PG 12 WC Optics; Physics, Applied; Spectroscopy SC Optics; Physics; Spectroscopy GA BM32Q UT WOS:000078392000003 ER PT S AU Leviton, DB Gardner, LD Fineschi, S Jhabvala, MD Kohl, JL Romoli, M Noci, G AF Leviton, DB Gardner, LD Fineschi, S Jhabvala, MD Kohl, JL Romoli, M Noci, G BE Fineschi, S TI White light stray light test of the SOHO UVCS SO X-RAY AND ULTRAVIOLET SPECTROSCOPY AND POLARIMETRY II SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on X-Ray and Ultraviolet Spectroscopy and Polarimetry II CY JUL 23-24, 1998 CL SAN DIEGO, CA SP SPIE Int Soc Opt Engn DE stray light testing; stray light rejection; stray light suppression; solar disk; solar corona; coronagraph ID CORONAGRAPH AB During the late stages of integration at MATRA-Marconi in Toulouse, France of the Ultraviolet Coronagraph Spectrometer (UVCS) for the joint NASA/ESA (European Space Agency) Solar and Heliospheric Observatory (SOI-IO), project management for the International Solar and Terrestrial Physics Project (ISTP) at Goddard Space Flight Center (GSFC) became concerned that the instrument's elaborate stray light rejection system had not been tested and might possibly be misaligned such that the instrument could not deliver promised scientific returns. A white light stray light test, which would place an upper bound on UVCS's stray light rejection capability, was commissioned, conceived, and carried out. This upper bound value would be indicative of the weakest coronal features the spectrometer would be capable of discerning. The test was rapidly developed at GSFC, in parallel with spacecraft integration, in coordination with science team members from Harvard-Smithsonian Center far Astrophysics (CFA) and was carried out at MATRA in late February 1995. The outcome of this test helped justify later impact to integration schedule to conduct similar much needed testing with visible and far ultraviolet light at CFA in a facility specifically designed to perform such tests. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Leviton, DB (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Romoli, Marco/H-6859-2012 NR 4 TC 0 Z9 0 U1 0 U2 0 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2898-1 J9 P SOC PHOTO-OPT INS PY 1998 VL 3443 BP 50 EP 60 DI 10.1117/12.333613 PG 11 WC Optics; Physics, Applied; Spectroscopy SC Optics; Physics; Spectroscopy GA BM32Q UT WOS:000078392000006 ER PT S AU O'Dell, SL Weisskopf, MC AF O'Dell, SL Weisskopf, MC BE Hoover, RB Walker, ABC TI Advanced X-ray Astrophysics Facility (AXAF): Calibration overview SO X-RAY OPTICS, INSTRUMENTS, AND MISSIONS SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on X-Ray Optics, Instruments, and Missions CY JUL 19-22, 1998 CL SAN DIEGO, CA SP SPIE Int Soc Opt Engn DE AXAF; space missions; x rays; calibration; grazing-incidence optics; gratings; detectors; x-ray imaging; x-ray spectroscopy ID HIGH-RESOLUTION CAMERA; TRANSMISSION GRATING SPECTROMETER; QUANTUM EFFICIENCY CALIBRATION; EFFECTIVE AREA; DIFFRACTION EFFICIENCIES; PERFORMANCE; 2-12-KEV; DETECTOR; OPTICS; CCD AB The Advanced X-ray Astrophysics Facility (AXAF), the x-ray component of NASA's Great Observatories, will launch in 1999. As integration and testing of the flight system are concluding, analysis of the ground calibration data continues. This analysis verifies AXAF's unique capabilities for high-resolution imaging and for high-resolution dispersive spectroscopy. However, it finds unexpectedly high (approximate to 10%) residuals between the data and the model for effective area of the AXAF optics. Reconciling the physical model with the data, to an accuracy of a few percent, remains a goal of the analysis and interpretation of the calibration data. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP O'Dell, SL (reprint author), NASA, George C Marshall Space Flight Ctr, ES84, Huntsville, AL 35812 USA. OI O'Dell, Stephen/0000-0002-1868-8056 NR 43 TC 20 Z9 20 U1 0 U2 0 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2899-X J9 P SOC PHOTO-OPT INS PY 1998 VL 3444 BP 2 EP 18 DI 10.1117/12.331231 PG 17 WC Astronomy & Astrophysics; Instruments & Instrumentation; Optics SC Astronomy & Astrophysics; Instruments & Instrumentation; Optics GA BM32R UT WOS:000078392400001 ER PT S AU Elsner, RF O'Dell, SL Ramsey, BD Tennant, AF Weisskopf, MC Kolodziejczak, JJ Swartz, DA Engelhaupt, DE Garmire, GP Nousek, JA Bautz, MW Gaetz, TJ Zhao, P AF Elsner, RF O'Dell, SL Ramsey, BD Tennant, AF Weisskopf, MC Kolodziejczak, JJ Swartz, DA Engelhaupt, DE Garmire, GP Nousek, JA Bautz, MW Gaetz, TJ Zhao, P BE Hoover, RB Walker, ABC TI Calibration results for the AXAF flight contamination monitor SO X-RAY OPTICS, INSTRUMENTS, AND MISSIONS SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on X-Ray Optics, Instruments, and Missions CY JUL 19-22, 1998 CL SAN DIEGO, CA SP SPIE Int Soc Opt Engn DE X-ray optics; calibration AB The Advanced X-ray Astrophysics Facility (AXAF) ground calibration program, easily the most extensive in the history of high energy astrophysics, requires careful attention to the verification of its validity for on-orbit operations of the observatory. The purpose of the Flight Contamination Monitor (FCM) is to verify the transfer of the AXAF absolute flux scale calibration from ground to on-orbit operations and to measure or bound any changes in molecular contamination on the AXAF mirrors. This paper reports the current status of the analysis of FCM measurements taken during ground calibration. The FCM measurements during the AXAF activation phase will be the first look at the on-orbit AXAF performance. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Elsner, RF (reprint author), NASA, George C Marshall Space Flight Ctr, ES84, Huntsville, AL 35812 USA. OI O'Dell, Stephen/0000-0002-1868-8056 NR 9 TC 11 Z9 11 U1 0 U2 0 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2899-X J9 P SOC PHOTO-OPT INS PY 1998 VL 3444 BP 177 EP 188 DI 10.1117/12.331235 PG 12 WC Astronomy & Astrophysics; Instruments & Instrumentation; Optics SC Astronomy & Astrophysics; Instruments & Instrumentation; Optics GA BM32R UT WOS:000078392400013 ER PT S AU Swartz, DA Elsner, RF Kolodziejczak, JJ O'Dell, SL Tennant, AF Sulkanen, ME Weisskopf, MC Edgar, RJ AF Swartz, DA Elsner, RF Kolodziejczak, JJ O'Dell, SL Tennant, AF Sulkanen, ME Weisskopf, MC Edgar, RJ BE Hoover, RB Walker, ABC TI On the use of monochromators during AXAF calibration SO X-RAY OPTICS, INSTRUMENTS, AND MISSIONS SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on X-Ray Optics, Instruments, and Missions CY JUL 19-22, 1998 CL SAN DIEGO, CA SP SPIE Int Soc Opt Engn DE X-rays; Calibration; X-ray sources; detectors ID PROPORTIONAL-COUNTERS; DETECTORS AB Two monochromator sources were used during the Advanced X-ray Astrophysics Facility calibration at Marshall Space Flight Center's X-Ray Calibration Facility. Data aquired using these sources require special analysis owing to large spatial variations in the monochromators' beams and to higher-order contributions to the spectral content. A description of the two monochromators is given, followed by a discussion of the spectral and spatial content as monitored by beam-normalization detector flow proportional counters. Emphasis is given to the methodology employed in determining the spatial content through fits to Beam uniformity measurements. A model is described which adequately represents the beam spatial properties over the range of source conditions encountered during calibration. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Swartz, DA (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, ES84, Huntsville, AL 35812 USA. OI O'Dell, Stephen/0000-0002-1868-8056 NR 9 TC 3 Z9 3 U1 0 U2 0 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2899-X J9 P SOC PHOTO-OPT INS PY 1998 VL 3444 BP 189 EP 197 DI 10.1117/12.331236 PG 9 WC Astronomy & Astrophysics; Instruments & Instrumentation; Optics SC Astronomy & Astrophysics; Instruments & Instrumentation; Optics GA BM32R UT WOS:000078392400014 ER PT S AU Peele, A Fraser, G Brunton, A Martin, A Rideout, R White, N Petre, R Feller, B AF Peele, A Fraser, G Brunton, A Martin, A Rideout, R White, N Petre, R Feller, B BE Hoover, RB Walker, ABC TI Recent studies of lobster-eye optics. SO X-RAY OPTICS, INSTRUMENTS, AND MISSIONS SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on X-Ray Optics, Instruments, and Missions CY JUL 19-22, 1998 CL SAN DIEGO, CA SP SPIE Int Soc Opt Engn DE lobster-eye optics; x-ray reflectivity; x-ray optics ID CHANNEL-CAPILLARY ARRAYS; MICROCHANNEL PLATES; RAY AB Lobster-eye optics have been proposed as an exciting development in the field of x-ray all-sky monitors. However, to date their potential has mainly been analyzed in the context of an all-sky monitor for a small satellite mission. We examine the wide range of parameters available for lobster-eye optics with different configurations. The sensitivity of the various schemes is calculated. We have also examined the current state of the art in actual lobster-eye optics. We present our experimental results and discuss realistic targets for manufacture. The impact of these targets on the calculated sensitivities is also described. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Peele, A (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 20 TC 15 Z9 15 U1 1 U2 4 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2899-X J9 P SOC PHOTO-OPT INS PY 1998 VL 3444 BP 404 EP 415 DI 10.1117/12.331255 PG 12 WC Astronomy & Astrophysics; Instruments & Instrumentation; Optics SC Astronomy & Astrophysics; Instruments & Instrumentation; Optics GA BM32R UT WOS:000078392400033 ER PT S AU Zhang, W Peele, AG Petre, R Soong, Y White, NE AF Zhang, W Peele, AG Petre, R Soong, Y White, NE BE Hoover, RB Walker, ABC TI A practical implementation of the lobster eye optics SO X-RAY OPTICS, INSTRUMENTS, AND MISSIONS SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on X-Ray Optics, Instruments, and Missions CY JUL 19-22, 1998 CL SAN DIEGO, CA SP SPIE Int Soc Opt Engn DE lobster-eye optics; X-ray all sky monitors ID RAY AB The concept of the lobster eye optics was proposed in the nineteen seventies. It has gained widespread interest in X-ray astronomy for its potential for constructing compact and focusing X-ray all sky monitors with unprecedented sensitivities. The majority of the efforts of developing a practical implementation of this optics has been devoted toward slumping square-pore micro-channel plates. While the advantages of the slumped micro-channel plates are obvious in that they can achieve potentially are-second angular resolutions, the smoothness requirements for reflecting X-rays are hard to meet by micro-channel plates. It is not clear how the interior of the micro-channel plate pores can be polished to the desire smoothness. In this paper we propose the feasibility of a more straightforward approach of implementing the lobster eye optics with flat glass mirrors assembled in a standard Kirkpatrick-Baez configuration. We demonstrate with both simulations and laboratory test results that this implementation is both practical and meets all the requirements of an X-ray all sky monitor. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 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 5 TC 1 Z9 1 U1 0 U2 2 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2899-X J9 P SOC PHOTO-OPT INS PY 1998 VL 3444 BP 416 EP 422 DI 10.1117/12.331256 PG 7 WC Astronomy & Astrophysics; Instruments & Instrumentation; Optics SC Astronomy & Astrophysics; Instruments & Instrumentation; Optics GA BM32R UT WOS:000078392400034 ER PT S AU Giles, AB Jahoda, K Strohmayer, T AF Giles, AB Jahoda, K Strohmayer, T BE Swank, JH Kouvelitou, C Hurley, K TI PCA observations of Cyg X-1 from RXTE using fast timing and high telemetry rates SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH-SERIES LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union AB The Rossi X-ray Timing Explorer (RXTE) spacecraft contains a very large area, high resolution timing experiment provided by the NASA's Goddard Space Flight Center. This Proportional Counter Array (PCA) has an area of 7000 cm(2) and a time resolution down to one micro second. A 450 Mbit memory on board the spacecraft allows science data acquisition at rates up to 512 kbps but a more typical high rate of -256 kbps can be continuously supported for up to 30 minutes. This performance far surpasses previous rocket and satellite timing experiments. Since the launch of RXTE several observations have been made of Cyg X-1 in this special high telemetry rate mode to specifically search for, and attempt to confirm, the existence of millisecond bursts. Such features were reported in several observations of Cyg X-1 in the mid 1970's. This paper briefly summarizes the PCA performance compared to earlier large timing experiments and then presents early results from the analysis of these data sets. Individual millisecond bursts do not seem to exist in the data examined so far. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. RI Jahoda, Keith/D-5616-2012 NR 19 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES-SERIES PY 1998 VL 22 IS 7 BP 965 EP 968 DI 10.1016/S0273-1177(98)00138-0 PG 4 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700007 ER PT S AU Peterson, LE Marsden, D Blanco, P Gruber, DE Heindl, WA Pelling, MR Rothschild, RE Hink, PL Swank, J Jahoda, K Rots, A AF Peterson, LE Marsden, D Blanco, P Gruber, DE Heindl, WA Pelling, MR Rothschild, RE Hink, PL Swank, J Jahoda, K Rots, A BE Swank, JH Kouvelitou, C Hurley, K TI Radio pulsars observed at X-ray energies by the X-ray timing explorer SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID RAPIDLY SPINNING PULSARS; ENERGETIC RADIATION; REMNANT MSH-15-52; PSR 1509-58; CRAB PULSAR; GUEST STAR; NEBULA; IDENTIFICATION; SUPERNOVA; SPECTRUM AB The Rossi X-Ray Timing Explorer observed a number of X-ray emitting radio pulsars soon after launch on 30 Dec. 1995. These included two plerionic systems formed in recent supernova events, the Crab Nebula with its 33 ms pulsar PSR 0531+21 and MSH 15-52 with its 151 ms pulsar PSR 1509-58. Observations of these sources for 20-30 ksec with both the PCA and HEXTE allowed precision phase resolved spectroscopy for the Crab Nebula, confirmation of the light curve and pulsed spectrum for PSR 1509-58, and separation of the Nebular emissions from the pulsed X-rays over the 18-250 keV range for both sources. Within statistical uncertainties, a power law spectrum fits all the observations over this limited energy range. The nebular region for both sources has a photon index of about -2.1, while the pulsed spectra are considerably harder. Significant differences in spectral index are observed for the first pulse, the second pulse, and the interpulse of PSR 0531+21. Published by Elsevier Science Ltd on behalf of COSPAR. C1 Univ Calif San Diego, CASS 0424, La Jolla, CA 92093 USA. Washington Univ, Dept Phys, St Louis, MO 63130 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Peterson, LE (reprint author), Univ Calif San Diego, CASS 0424, 9500 Gilman Dr, La Jolla, CA 92093 USA. RI Jahoda, Keith/D-5616-2012; Swank, Jean/F-2693-2012; OI Rots, Arnold/0000-0003-2377-2356 NR 19 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 981 EP 986 DI 10.1016/S0273-1177(98)00130-6 PG 6 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700010 ER PT S AU Finger, MH AF Finger, MH BE Swank, JH Kouvelitou, C Hurley, K TI QPO in transient pulsars SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH-SERIES LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID QUASI-PERIODIC OSCILLATIONS; X-RAY SOURCES; DISCOVERY; ACCRETION; V0332+53; OUTBURST AB QPOs have now been observed from five transient X-ray pulsars. Four of these are in Be/X-ray systems, and one is the newly discovered LMXB transient GRO J1744-28. I review the observations, and discuss their interpretation in terms of the beat or Keplerian frequency models. These models are successful in explaining the observations for two of the Be/X-ray transients. For one of these, A0535+262, the observations constrain the ratio of the radius of the accretion disk inner edge to the Alfven radius, providing new information on the accretion disk-magnetosphere boundary region. Neither model can explain the QPO in the remaining two Be/X-ray systems, nor that in GRO J1744-28. It is likely therefore that two or more QPO mechanisms are at work. I discuss the potential for gaining new insight into QPOs from analysis tools unique to pulsed systems, and discuss what we can learn from new observations. (C)1998 COSPAR. Published by Elsevier Science Ltd. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 24 TC 11 Z9 11 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES-SERIES PY 1998 VL 22 IS 7 BP 1007 EP 1016 DI 10.1016/S0273-1177(98)00136-7 PG 10 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700014 ER PT S AU Ghosh, P AF Ghosh, P BE Swank, JH Kouvelitou, C Hurley, K TI Lessons from QPOs in X-ray pulsars SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH-SERIES LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID QUASI-PERIODIC OSCILLATIONS; ACCRETION DISK; A0535+262; STARS AB We discuss the diagnostic potential of the studies of quasiperiodic oscillations (QPO) in X-ray pulsars. We show that probing the conditions in the inner accretion disks in these systems, and mapping out the accretion torques on the pulsars are possible by these diagnostics. We suggest that the magnetospheric beat frequency model may not be applicable to all QPOs observed in X-ray pulsars. We suggest possible future lines of investigation with these diagnostics. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ghosh, P (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 21 TC 3 Z9 3 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES-SERIES PY 1998 VL 22 IS 7 BP 1017 EP 1024 DI 10.1016/S0273-1177(98)00137-9 PG 8 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700015 ER PT S AU Israel, GL Stella, L Angelini, L White, NE Kallman, TR Giommi, P Treves, A AF Israel, GL Stella, L Angelini, L White, NE Kallman, TR Giommi, P Treves, A BE Swank, JH Kouvelitou, C Hurley, K TI The discovery of 13 s X-ray pulsations from the hydrogen depleted subdwarf O6 star binary HD49798 SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID CYGNI AB We discovered strong 13 s pulsations in the X-ray Aux of HD49798 (Israel et al. 1995), a 1.55 d single-component spectroscopic binary containing a hydrogen depleted subdwarf O6 star. The source X-ray spectrum is extremely soft, corresponding to an unabsorbed 0.1-2 keV luminosity of a few x 10(32) erg s(-1) (distance of 650 pc). A higher luminosity might be hidden in the EUV. Our results imply that the unseen companion is an accreting degenerate star, either a white dwarf or a neutron star. In either case HD49798 corresponds to a previously unobserved evolutionary stage of a massive binary system, after common envelope and spiral-in. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 Scuola Int Super Studi Avanzati, Int Sch Adv Studies, ISAS, I-34014 Trieste, Italy. Osservatorio Astron Roma, I-00040 Monte Porzio Catone, Italy. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. ASI, SAX, Sci Data Ctr, I-00198 Rome, Italy. RP Israel, GL (reprint author), Scuola Int Super Studi Avanzati, Int Sch Adv Studies, ISAS, Via Beirut 2-4, I-34014 Trieste, Italy. RI White, Nicholas/B-6428-2012; OI White, Nicholas/0000-0003-3853-3462; giommi, paolo/0000-0002-2265-5003; Israel, GianLuca/0000-0001-5480-6438 NR 15 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1035 EP 1038 DI 10.1016/S0273-1177(98)00139-2 PG 4 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700017 ER PT S AU Rho, JH Petre, R Ballet, J AF Rho, JH Petre, R Ballet, J BE Swank, JH Kouvelitou, C Hurley, K TI Thermal X-ray emission of the extended lobe near 1E 2259+586 with CTB 109 SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID REMNANTS; PULSAR AB A "jet-like" lobe runs northeastward from the pulsar 1E2259+586 to the shell within the supernova remnant CTB 109, and it was previously suspected to be an "X-ray jet" in a binary system analogous to SS433/W50 (Gregory & Fahlman, 1983). We report X-ray spectra of the lobe relative to elsewhere in the remnant using ASCA and ROSAT, and comparison with other X-ray jets. X-ray emission from the "jet-like" lobe is thermal with dominant lines of Ne IX, Ne X, Mg XI, and Si XIII, and has softer emission than elsewhere in the remnant. The spectral fit for the lobe indicates that the plasma is in ionization non-equilibrium and its best fit is T(s)similar to 10(6.5) K and n(o)t similar to 48,000 cm(-3)yr. This lobe contrasts with the double lobes in W50 where non-thermal X-ray emission is found (Yamauchi et al., 1994). If the lobe in CTB109 is a jet, it would be similar to the Vela jet because it was recently discovered to have thermal X-rays (Markwardt & Ogelman, 1995). The Vela jet is connected with the pulsar, providing the loss mechanism for most of the pulsar's rotational energy, and it has high pressure of the "cocoon" of shocked jet material. On the contrary, the "jet-like" lobe in CTB 109 is not connected with 1E 2259+586 in the ROSAT image (Rho & Petre, 1997) and does not have higher pressure than elsewhere in the remnant. Therefore, this lobe may not be a supersonic beam; it is neither powered by nor related to the central pulsar. We suggest this lobe was produced by Rayleigh-Taylor instability due to a reflected shock arising from the blast wave-molecular cloud interaction. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 CENS, Serv Astrophys, F-91191 Gif Sur Yvette, France. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Rho, JH (reprint author), CENS, Serv Astrophys, F-91191 Gif Sur Yvette, France. NR 16 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1039 EP 1042 DI 10.1016/S0273-1177(98)00145-8 PG 4 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700018 ER PT S AU Giles, AB AF Giles, AB BE Swank, JH Kouvelitou, C Hurley, K TI Real time science displays for the PCA experiment on the Rossi X-ray Timing Explorer SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union AB The Rossi X-ray Timing Explorer (RXTE) spacecraft was launched on 30th December 1995 and contains a large Proportional Counter Array (PCA) experiment developed at GSFC. Telemetry from RXTE is returned via the NASA Tracking and Data Relay Satellite System (TDRSS) which, apart from specific gaps in coverage, provides a steady stream of nearly continuous real time data packets. The PCA has an area of 7000 cm(2) and produces high count rates for many x-ray sources. This provides the opportunity for some serious interpretation and decision making in real time. The display programs developed by the PCA team fall into 4 classes: Housekeeping, General performance (Instrumental and calibration bias), Spectral (Science bias) and Temporal (Science bias). These displays are used by the duty scientist and experiment controllers to monitor the observation in progress to try and ensure that the observation is proceeding as planned and that modifications to the observing modes are not required. Guest Observers (GO's) can be present in the Science Operations Facility (SOF) for their observations. The PCA team can also monitor their experiment using these programs. The SOF are planning to make some or all of these display tools available to GO's at their home institutions for the specific duration of their observations. This paper briefly describes the available display options. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Giles, AB (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1049 EP 1052 DI 10.1016/S0273-1177(98)00140-9 PG 4 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700020 ER PT S AU Meegan, CA AF Meegan, CA BE Swank, JH Kouvelitou, C Hurley, K TI Gamma-ray burst overview SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID COSMOLOGICAL TIME DILATION; HIGH-VELOCITY PULSARS; OPTICAL COUNTERPART; SPECTRAL EVOLUTION; BATSE OBSERVATIONS; GALACTIC HALO; LINE SEARCH; HIGH-ENERGY; RADIATION; FIREBALLS AB Over 25 years since their discovery, gamma-ray bursts (GRBs) remain an unsolved mystery. They occur about once a day, last from about 0.1 to 1000 seconds, and emit detectable radiation only at X-ray and gamma-ray energies. The spatial distribution of the sources is isotropic but inhomogeneous, inconsistent with any known galactic component. Two very different hypotheses are currently debated: either the bums arise from an extended galactic halo, possibly populated by high velocity neutron stars, or they lie at cosmological distances and redshift effects are responsible for the apparant inhomogeneity. The current observational and theoretical status of the GRB problem will be discussed with emphasis on the central question of the distance to the sources. Published by Elsevier Science Ltd on behalf of COSPAR. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Meegan, CA (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 53 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1065 EP 1075 DI 10.1016/S0273-1177(98)00197-5 PG 11 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700023 ER PT S AU Teegarden, BJ AF Teegarden, BJ BE Swank, JH Kouvelitou, C Hurley, K TI Spectroscopy of gamma-ray bursts: An overview SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID HIGH-ENERGY; BATSE OBSERVATIONS; LINE SEARCH; ABSORPTION; EVOLUTION; CYCLOTRON; FEATURES; SPECTRA AB More than two decades of accumulated data on the spectra of gamma-ray bursts (GRB's) are now in hand. In general, burst spectra display a wide variety of both spectral and temporal behavior. In essentially all bursts where spectral measurements are possible, the spectrum evolves during the burst, This spectral complexity and variability has presented researchers with a challenging task. Early spectral measurements contained evidence for cyclotron-line-like absorption and emission features. These results were the main anchor for the galactic neutron star paradigm for the origin of gamma-ray bursts. Ginga provided striking confirmation with evidence in three bursts for cyclotron absorption with both first and second harmonics present in two of them. The absorption line energies were consistent with the teragauss magnetic fields expected for neutron stars, However, the BATSE experiment on CGRO has dealt a severe blow to this paradigm. BATSE has found no evidence for the expected galactic anisotropy and also no evidence for cyclotron lines. This paper will: 1) provide an historical overview of GRB spectroscopic measurements 2) a discussion of the BATSE/Ginga controversy and 3) a sampling of the most recent results and analyses of GRB spectral data, (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Teegarden, BJ (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. NR 23 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1083 EP 1092 DI 10.1016/S0273-1177(98)00199-9 PG 10 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700025 ER PT S AU Baring, MG Harding, AK AF Baring, MG Harding, AK BE Swank, JH Kouvelitou, C Hurley, K TI Pair production opacities for gamma-ray burst spectra in the 10 GeV-1 TeV range SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID HIGH-ENERGY; BREAKS AB Recent calculations of pair production opacities for gamma-ray bursts detected by EGRET have suggested that relativistic bulk motion with large Lorentz factors must exist in these sources, whether of galactic or cosmological origin, to permit the emergence of a high energy continuum. The extant calculations usually assume an infinite power-law source spectrum for simplicity, an approximation that is quite adequate for most bursts detected by EGRET. However, for a given bulk Lorentz factor, photons above the EGRET range can potentially interact with sub-MeV photons in pair production opacity calculations, so it is important to accurately include the spectral curvature in bursts seen by BATSE. In this paper we modify our previous work to include such spectral forms, well-represented by broken power-laws, determining opacity as a function of energy for different source Lorentz factors Gamma. The comparative depletion of low energy photons below 1 MeV turns out to be immaterial to considerations of bulk motion in cosmological bursts, but is crucial to estimates of source transparency in the 1 GeV - 1 TeV range for sources located in the galactic halo. We find that broad absorption dips can arise at these energies for suitable expansion parameters. Whipple, MILAGRO and GLAST will play an important role in the observation of the presence or absence of such distinctive structure in GRB spectra. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Baring, MG (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. RI Harding, Alice/D-3160-2012 NR 16 TC 0 Z9 0 U1 0 U2 2 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1115 EP 1119 DI 10.1016/S0273-1177(98)00205-1 PG 5 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700031 ER PT S AU Baring, MG Harding, AK AF Baring, MG Harding, AK BE Swank, JH Kouvelitou, C Hurley, K TI Numerical evaluation of magnetic photon splitting rates via a proper-time technique SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID SOFT GAMMA-REPEATERS; QUANTUM ELECTRODYNAMICS; FIELDS AB The results of our numerical computation of magnetic photon splitting rates according to the proper-time formulation developed by Stoneham are presented in this paper. Calculations were performed for both the total rate of splitting and the differential distributions for the polarization mode perpendicular to --> parallel to parallel to Of splitting. Analytic asymptotic limits obtainable from the triple integral expressions of Stoneham's formalism are also presented, and these are reproduced by the full computation of the integrals. The rates produced here agree with numerous previous analyses of photon splitting but fall somewhat below the S-matrix calculation of Wilke and Wunner. The numerical determination of these rates is of great use to current topical models of gamma-ray pulsars and magnetar scenarios for soft gamma repeaters. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Baring, MG (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. RI Harding, Alice/D-3160-2012 NR 16 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1121 EP 1124 DI 10.1016/S0273-1177(98)00206-3 PG 4 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700032 ER PT S AU Hurley, K Kouveliotou, C Harmon, A Fishman, G Briggs, M van Paradijs, J Kommers, J Lewin, W Cline, T Boer, M Niel, M AF Hurley, K Kouveliotou, C Harmon, A Fishman, G Briggs, M van Paradijs, J Kommers, J Lewin, W Cline, T Boer, M Niel, M BE Swank, JH Kouvelitou, C Hurley, K TI Verifying the accuracy of the third interplanetary network: Localization of the bursting pulsar GRO J1744-28 by triangulation SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union AB The bursting pulsar GRO J1744-28 is the first repeating source of intense bursts whose position is accurately known, which has become active since the establishment of the third interplanetary network. We show how observations of this object with Ulysses and BATSE can be used to verify many aspects of the triangulation method. Analysis of the preliminary data indicates that there are no unknown sources of error in this method. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35889 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France. RP Hurley, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. OI Boer, Michel/0000-0001-9157-4349 NR 5 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES PY 1998 VL 22 IS 7 BP 1125 EP 1128 DI 10.1016/S0273-1177(98)00207-5 PG 4 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700033 ER PT S AU Smith, IA Hurley, K van Paradijs, J Waters, LBFM Schultz, ASB Durouchoux, P Joyce, R Vrba, FJ Hartmann, D Kouveliotou, C Wallyn, P Corbel, S AF Smith, IA Hurley, K van Paradijs, J Waters, LBFM Schultz, ASB Durouchoux, P Joyce, R Vrba, FJ Hartmann, D Kouveliotou, C Wallyn, P Corbel, S BE Swank, JH Kouvelitou, C Hurley, K TI Infrared, submillimeter, and millimeter observations of the Soft Gamma-Ray Repeaters SO X-RAY TIMING AND COSMIC GAMMA RAY BURSTS SE ADVANCES IN SPACE RESEARCH-SERIES LA English DT Article; Proceedings Paper CT Symposium of the COSPAR Scientific-Commission-E on X-Ray Timing and Cosmic Gamma Ray Bursts at the 31st COSPAR Assembly CY JUL 14-21, 1996 CL BIRMINGHAM, ENGLAND SP Comm Space Res, Sci Commiss E, European Space Agcy, Intl Astron Union ID CRAB-NEBULA; SGR-1806-20; COUNTERPART; SGR-1900+14 AB The Soft Gamma-Ray Repeaters appear to be a completely new manifestation of neutron stars. SGR 1806-20 and SGR 1900+14 may have highly unusual stellar counterparts, whose spectra peak in the far infrared. They have not been detected at submillimeter or millimeter wavelengths. Their infrared spectra appear to contain several components: the photospheric emission from star(s) dominates at shorter wavelengths, a bright point source dominates at 25 mu m, while an extended source dominates at 60 mu m. Their spectra are inconsistent with monoenergetic synchrotron and black body radiation models, but are consistent with simple dust models. We briefly review here our latest millimeter, submillimeter, and infrared observations. We include new upper limits at 235 GHz (1.3 mm) for SGR 1806-20 and SGR 0525-66. The extended IRAS emission detected for SGR 0525-66 is consistent with that expected from heated dust in the supernova remnant N49. Here we show a preliminary analysis of our recent 9.862 mu m imaging of the region around SGR 0525-66. We do not detect any point sources, at flux limits lower than would be expected if the other two SGR were placed at the distance of the LMC. (C) 1998 COSPAR. Published by Elsevier Science Ltd. C1 Rice Univ, Houston, TX 77005 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Ctr Etud Saclay, DAPNIA, Serv Astrophys, F-91191 Gif Sur Yvette, France. Kitt Peak Natl Observ, Tucson, AZ 85726 USA. USN Observ, Flagstaff Stn, Flagstaff, AZ 86002 USA. Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Smith, IA (reprint author), Rice Univ, 6100 South Main, Houston, TX 77005 USA. NR 26 TC 2 Z9 2 U1 0 U2 1 PU PERGAMON PRESS LTD PI OXFORD PA THE BOULEVARD LANGFORD LANE KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0273-1177 BN 0-08-043471-1 J9 ADV SPACE RES-SERIES PY 1998 VL 22 IS 7 BP 1133 EP 1138 DI 10.1016/S0273-1177(98)00209-9 PG 6 WC Engineering, Aerospace; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Engineering; Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA BL94S UT WOS:000077255700035 ER PT B AU Caillat, T Chung, S Fleurial, JP Snyder, GJ Borshchevsky, A AF Caillat, T Chung, S Fleurial, JP Snyder, GJ Borshchevsky, A GP IEEE IEEE TI Some properties of Re2Te5-based materials SO XVII INTERNATIONAL CONFERENCE ON THERMOELECTRICS, PROCEEDINGS ICT 98 LA English DT Proceedings Paper CT 17th International Conference on Thermoelectrics (ICT98) CY MAY 24-28, 1998 CL NAGOYA, JAPAN SP Int Thermoelect Soc, IEEE, Components, Packaging, & Mfg Technol Soc, IEEE AB Re2Te5 is a semiconducting compound with an energy band gap of about 0.8 eV. It has a relatively complex crystal structure with 84 atoms per unit cell. Initial results obtained at the Jet Propulsion Laboratory on p-type polycrystalline samples showed that they possess large Seebeck coefficient values but also large electrical resistivity values. They also exhibit very low thermal conductivity with a room temperature value of 13 mW/cmK. Another attractive feature of Re2Te5 is the possibility of inserting a variety of atoms in the large voids (2.8 Angstrom in diameter) of the crystal structure to form Re6Mn2Te15 filled compositions. The void fillers could act as phonon scattering centers, further reducing the thermal conductivity in these materials. As part of an effort to evaluate the potential of Re2Te5-based materials for thermoelectric applications, we are currently exploring the synthesis and properties of filled compositions as well as n-type Re2Te5 samples. We present and discuss in this paper initial results obtained on Fe and Ag doped Re2Te5 samples. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Caillat, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 277-207, Pasadena, CA 91109 USA. RI Snyder, G. Jeffrey/E-4453-2011; Snyder, G/I-2263-2015 OI Snyder, G. Jeffrey/0000-0003-1414-8682; NR 0 TC 0 Z9 0 U1 0 U2 3 PU IEEE PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA BN 0-7803-4907-5 PY 1998 BP 298 EP 301 DI 10.1109/ICT.1998.740377 PG 4 WC Thermodynamics; Engineering, Electrical & Electronic; Physics, Applied SC Thermodynamics; Engineering; Physics GA BM13Z UT WOS:000077768700071 ER PT B AU Gardner, JP Collins, NR Hill, RS Malumuth, EM Lindler, DJ Sandoval, JL Gull, TR Heap, SR Woodgate, BE Baum, SA Ferguson, HC Gilliland, RL Fosbury, RAE Micol, A Pirzkal, N Tolstoy, E Walsh, JR Green, RF AF Gardner, JP Collins, NR Hill, RS Malumuth, EM Lindler, DJ Sandoval, JL Gull, TR Heap, SR Woodgate, BE Baum, SA Ferguson, HC Gilliland, RL Fosbury, RAE Micol, A Pirzkal, N Tolstoy, E Walsh, JR Green, RF BE DOdorico, S Fontana, A Giallongo, E TI The STIS Parallel Survey: Introduction and first results SO YOUNG UNIVERSE: GALAXY FORMATION AND EVOLUTION AT INTERMEDIATE AND HIGH REDSHIFT SE ASTRONOMICAL SOCIETY OF THE PACIFIC CONFERENCE SERIES LA English DT Proceedings Paper CT Meeting on the Young Universe - Galaxy Formation and Evolution at Intermediate and High Redshift CY SEP 29-OCT 03, 1997 CL ROME ASTRON OBSERV, MONTE PORZIO CATO, ITALY HO ROME ASTRON OBSERV AB The installation of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) allows for the first time two-dimensional optical and ultraviolet slitless spectroscopy of faint objects from space. The STIS Parallel Survey (SPS) routinely obtains broad band images and slitless spectra of random fields in parallel with HST observations using other instruments. The SPS is designed to study a wide variety of astrophysical phenomena, including the rate of star formation in galaxies at intermediate to high redshift through the detection of emission-line galaxies. We present the first results of the SPS: which demonstrate the capability of STIS slitless spectroscopy to detect and identify high-redshift galaxies. C1 NASA, GSFC, Washington, DC 20546 USA. RP Gardner, JP (reprint author), NASA, GSFC, Washington, DC 20546 USA. RI Gull, Theodore/D-2753-2012; Woodgate, Bruce/D-2970-2012; heap, sara/E-2237-2012 OI Gull, Theodore/0000-0002-6851-5380; NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA BN 1-886733-66-X J9 ASTR SOC P PY 1998 VL 146 BP 367 EP 370 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA BL75D UT WOS:000076564500063 ER PT J AU Friedrich, S Segall, K Gaidis, MC Wilson, CM Prober, DE Szymkowiak, AE Moseley, SH AF Friedrich, S Segall, K Gaidis, MC Wilson, CM Prober, DE Szymkowiak, AE Moseley, SH TI Experimental quasiparticle dynamics in a superconducting, imaging x-ray spectrometer SO APPLIED PHYSICS LETTERS LA English DT Article ID TUNNEL-JUNCTIONS; DETECTORS; RESOLUTION AB We present an experimental study of the time scales for various quasiparticle processes in a superconducting single photon spectrometer. Processes studied include quasiparticle recombination, diffusion, trapping, tunneling, and energy redistribution. Experiments were performed with a double junction, imaging x-ray detector whose charge output provides a measure of the photon energy. Time scales are extracted with a simple model and the values of several parameters, including the diffusion constant and recombination time, are found to differ from theoretical predictions. These results provide guidelines for performance analysis, device scaling, and future designs. (C) 1997 American Institute of Physics. C1 Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Friedrich, S (reprint author), Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. RI Wilson, Christopher/A-9676-2008; Moseley, Harvey/D-5069-2012; Gaidis, Michael/D-3327-2013 NR 11 TC 43 Z9 43 U1 2 U2 6 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD DEC 29 PY 1997 VL 71 IS 26 BP 3901 EP 3903 DI 10.1063/1.120538 PG 3 WC Physics, Applied SC Physics GA YN588 UT WOS:000071184700052 ER PT J AU Ahn, MK Eaton, SS Eaton, GR Meador, MAB AF Ahn, MK Eaton, SS Eaton, GR Meador, MAB TI Electron paramagnetic resonance imaging of the spatial distribution of free radicals in PMR-15 polyimide resins SO MACROMOLECULES LA English DT Article AB Prior studies have shown that free radicals generated by heating polyimides above 300 degrees C are stable at room temperature and are involved in thermo-oxidative degradation in the presence of oxygen gas. Electron paramagnetic resonance imaging (EPRI) is a technique to determine the spatial distribution of free radicals. X-band (9.5 GHz) EPR images of PMR-15 polyimide were obtained with a spatial resolution of similar to 0.18 mm along a 2-mm dimension of the sample. In a polyimide sample that was not thermocycled, the radical distribution was uniform along the 2-mm dimension of the sample. For a polyimide sample that was exposed to thermocycling in air for 300 1-h cycles at 335 degrees C, one-dimensional EPRI showed a higher concentration of free radicals in the surface layers than in the bulk sample. A spectral-spatial tffa-dimensional image showed that the EPR lineshape of the surface layer remained the same as that of the bulk. These EPRI results suggest that the thermo-oxidative degradation of PMR-15 in involves free radicals present in the oxygen-rich surface layer. C1 Indiana State Univ, Dept Chem, Terre Haute, IN 47809 USA. Univ Denver, Dept Chem & Biochem, Denver, CO 80208 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Ahn, MK (reprint author), Indiana State Univ, Dept Chem, Terre Haute, IN 47809 USA. OI Meador, Mary Ann/0000-0003-2513-7372; Eaton, Gareth R/0000-0001-7429-8469; Eaton, Sandra S/0000-0002-2731-7986 NR 22 TC 7 Z9 7 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD DEC 29 PY 1997 VL 30 IS 26 BP 8318 EP 8321 DI 10.1021/ma970580t PG 4 WC Polymer Science SC Polymer Science GA YR259 UT WOS:000071476900030 ER PT J AU Valero, FPJ Bucholtz, A Bush, BC Pope, SK Collins, WD Flatau, P Strawa, A Gore, WJY AF Valero, FPJ Bucholtz, A Bush, BC Pope, SK Collins, WD Flatau, P Strawa, A Gore, WJY TI Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE): Experimental and data details SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MARINE STRATOCUMULUS CLOUDS; SOLAR-RADIATION; ABSORPTION; AIRCRAFT AB Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE) was conducted to study the magnitude and spectral characteristics of the absorption Of solar radiation by the clear and cloudy atmosphere. Three aircraft platforms, a Grob Egrett, a NASA ER-2, and a Twin Otter, were used during ARESE in conjunction with the Atmospheric Radiation Measurements (ARM) central and extended facilities in north central Oklahoma. The aircraft were coordinated to simultaneously measure solar irradiances in the total spectral broadband (0.224-3.91 mu m), near infrared broadband (0.678-3.3 mu m), and in seven narrow band-pass (similar to 10 nm width) channels centered at 0.500, 0.862, 1.064, 1.249, 1.501, 1.651, and 1.750 mu m. Instrumental calibration issues are discussed in some detail, in particular radiometric power, angular, and spectral responses. The data discussed in this paper are available at the ARM ARESE data archive via anonymous FTP to ftp.arm.gov. C1 Univ Calif San Diego, Scripps Inst Oceanog, Ctr Atmospher Sci, Atmospher Res Lab, La Jolla, CA 92093 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Valero, FPJ (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, Ctr Atmospher Sci, Atmospher Res Lab, La Jolla, CA 92093 USA. EM fvalero@ucsd.edu; abucholtz@ucsd.edu; brbush@ucsd.edu; spope@ucsd.edu; wcollins@kavieng.cgd.ucar.edu; pflatau@ucsd.edu; strawa@ra.arc.nasa.gov RI Collins, William/J-3147-2014; Flatau, Piotr/E-2219-2011 OI Collins, William/0000-0002-4463-9848; NR 23 TC 34 Z9 34 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1997 VL 102 IS D25 BP 29929 EP 29937 DI 10.1029/97JD02434 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YP443 UT WOS:000071277300015 ER PT J AU Lean, JL Rottman, GJ Kyle, HL Woods, TN Hickey, JR Puga, LC AF Lean, JL Rottman, GJ Kyle, HL Woods, TN Hickey, JR Puga, LC TI Detection and parameterization of variations in solar mid- and near-ultraviolet radiation (200-400 nm) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IRRADIANCE COMPARISON EXPERIMENT-1; TROPOSPHERE-STRATOSPHERE SYSTEM; PHOTOMETRIC SUNSPOT INDEX; LONG-TERM; FLUX VARIATIONS; SPECTRAL IRRADIANCE; EMPIRICAL-MODEL; UV VARIABILITY; CYCLE; OZONE AB Nimbus 7 and Solar Stellar Irradiance Comparison Experiment (SOLSTICE) spacecraft measurements of solar irradiance both exhibit variability at mid (200-300 nm) and near (309-400 nm) ultraviolet (UV) wavelengths that are attributable to the Sun's 27-day solar rotation, even though instrument sensitivity drifts obscure longer-term, 11-year cycle variations, Competing influences of dark sunspots and bright faculae are the dominant causes of this rotational modulation, Parameterizations of these influences using a newly developed UV sunspot darkening index and the Mg index facular proxy replicate the rotational modulation detected in both the broadband Nimbus 7 filter data (275-360 nm and 300-410 nm) and in SOLSTICE l-nm spectra from 200 to 400 nm. Assuming that these rotational modulation influences scale linearly over the solar cycle, long-term databases of sunspot and global facular proxies permit estimation of Ii-year cycle amplitudes of the mid-and near-UV solar spectrum, unmeasured at wavelengths longward of 300 nm because of insufficient long-term repeatability (relative accuracy) of state-of-the-art solar radiometers at these wavelengths. Reconstructions of UV irradiances throughout the Ii-year solar cycle indicate variabilities of 0.173 W/m(2) (1.1%) in the integrated radiation from 200 to 300 nm and 0.24 W/m(2) (0.25%) in radiation from 300 to 400 nm, These two UV bands thus contribute about 13% and 18%, respectively, to the 1.54 W/m(2) (0.1%) total (spectrally integrated) radiative output solar cycle. The parameterizations allow customization of UV irradiance time series for specific wavelength bands required as inputs to general circulation model simulations of solar cycle forcing of global climate change, and have practical implications regarding the long-term repeatability required for future solar monitoring. C1 USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Eppley Lab Inc, Newport, RI 02840 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Space Environm Lab, Boulder, CO 80303 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. RP Lean, JL (reprint author), USN, Res Lab, EO Hulburt Ctr Space Res, Code 7673L,4555 Overlook Ave SW, Washington, DC 20375 USA. EM lean@demeter.nrl.navy.mil OI Lean, Judith/0000-0002-0087-9639 NR 79 TC 197 Z9 200 U1 2 U2 12 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1997 VL 102 IS D25 BP 29939 EP 29956 DI 10.1029/97JD02092 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YP443 UT WOS:000071277300016 ER PT J AU Halthore, RN Schwartz, SE Michalsky, JJ Anderson, GP Ferrare, RA Holben, BN Ten Brink, HM AF Halthore, RN Schwartz, SE Michalsky, JJ Anderson, GP Ferrare, RA Holben, BN Ten Brink, HM TI Comparison of model estimated and measured direct-normal solar irradiance SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC RADIATION; OPTICAL DEPTH; ABSORPTION; CLOUD; PHYSICS; OZONE; BAND AB Direct-normal solar irradiance (DNSI), the energy in the solar spectrum incident in unit time at the Earth's surface on a unit area perpendicular to the direction to the Sun, depends only on atmospheric extinction of solar energy without regard to the details of the extinction, whether absorption or scattering. Here we report a set of closure experiments performed in north central Oklahoma in April 1996 under cloud-free conditions, wherein measured atmospheric composition and aerosol optical thickness are input to a radiative transfer model, MODTRAN 3, to estimate DNSI, which is then compared with measured values obtained with normal incidence pyrheliometers and absolute cavity radiometers. Uncertainty in aerosol optical thickness (AOT) dominates the uncertainty in DNSI calculation. AOT measured by an independently calibrated Sun photometer and a rotating shadow-band radiometer agree to within the uncertainties of each measurement. For 36 independent comparisons the agreement between measured and model-estimated values of DNSI falls within the combined uncertainties in the measurement (0.3-0.7%) and model calculation (1.8%), albeit with a slight average model underestimate (-0.18 +/- 0.94)%; for a DNSI of 839 W m(-2) this corresponds to -1.5 +/- 7.9 W m(-2). The agreement is nearly independent of air mass and water-vapor path abundance. These results thus establish the accuracy of the current knowledge of the solar spectrum, its integrated power, and the atmospheric extinction as a function of wavelength as represented in MODTRAN 3. An important consequence is that atmospheric absorption of short-wave energy is accurately parametrized in the model to within the above uncertainties. C1 Brookhaven Natl Lab, Dept Appl Sci, Upton, NY 11973 USA. SUNY Albany, Atmospher Sci Res Ctr, Albany, NY 12222 USA. Phillips Lab, Geophys Directorate, Hanscom AFB, MA USA. Hughes STX Corp, Lanham, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Netherlands Energy Res Fdn, ECN, NL-1755 ZG Petten, Netherlands. RP Halthore, RN (reprint author), Brookhaven Natl Lab, Dept Appl Sci, Upton, NY 11973 USA. EM halthore@bnl.gov; ses@bnl.gov; joe@asrc.cestm.albany.edu; ganderson@PLH.AF.MIL; rferrare@larc.nasa.gov; brent@spawer.gsfc.nasa.gov RI Schwartz, Stephen/C-2729-2008 OI Schwartz, Stephen/0000-0001-6288-310X NR 31 TC 40 Z9 41 U1 0 U2 11 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 DEC 27 PY 1997 VL 102 IS D25 BP 29991 EP 30002 DI 10.1029/97JD02628 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YP443 UT WOS:000071277300019 ER PT J AU Polyak, I AF Polyak, I TI Comment on "Evaluation of the GFDL GCM climate variability, 2, stochastic modeling and latitude-temporal fields" by I. Polyak and G. R. North - Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Polyak, I (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Mail Code 970, Greenbelt, MD 20771 USA. EM polyak@neptune.gsfc.nasa.gov NR 2 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 27 PY 1997 VL 102 IS D25 BP 30163 EP 30163 DI 10.1029/97JD02251 PG 1 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YP443 UT WOS:000071277300034 ER PT J AU Sellers, PJ Hall, FG Kelly, RD Black, A Baldocchi, D Berry, J Ryan, M Ranson, KJ Crill, PM Lettenmaier, DP Margolis, H Cihlar, J Newcomer, J Fitzjarrald, D Jarvis, PG Gower, ST Halliwell, D Williams, D Goodison, B Wickland, DE Guertin, FE AF Sellers, PJ Hall, FG Kelly, RD Black, A Baldocchi, D Berry, J Ryan, M Ranson, KJ Crill, PM Lettenmaier, DP Margolis, H Cihlar, J Newcomer, J Fitzjarrald, D Jarvis, PG Gower, ST Halliwell, D Williams, D Goodison, B Wickland, DE Guertin, FE TI BOREAS in 1997: Experiment overview, scientific results, and future directions SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; FIELD EXPERIMENT FIFE; LAND-SURFACE; ATMOSPHERIC CO2; CARBON-DIOXIDE; AMAZONIAN FOREST; WATER-VAPOR; EXCHANGE; ENERGY; CANOPY AB The goal of the Boreal Ecosystem-Atmosphere Study (BOREAS) is to improve our understanding of the interactions between the boreal forest biome and the atmosphere in order to clarify their roles in global change. This overview paper describes the science background and motivations for BOREAS and the experimental design and operations of the BOREAS 1994 and BOREAS 1996 field years. The findings of the 83 papers in this journal special issue are reviewed, In section 7, important scientific results of the project to date are summarized and future research directions are identified. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Oceanog & Atmospher Adm, Oak Ridge, TN 37831 USA. Univ British Columbia, Vancouver, BC V5Z 1M9, Canada. Carnegie Inst, Stanford, CA USA. Canada Ctr Remote Sensing, Ottawa, ON K1A OY7, Canada. Univ New Hampshire, Durham, NH 03824 USA. Atmospher Sci Resource Ctr, Albany, NY 12205 USA. Atmospher Environm Serv, Downsview, ON, Canada. Univ Wisconsin, Madison, WI 53706 USA. Forestry Canada, Edmonton, AB, Canada. Univ Edinburgh, Edinburgh, Midlothian, Scotland. Univ Wyoming, Laramie, WY 82070 USA. Univ Washington, Seattle, WA 98195 USA. Ctr Rech Biol Forestiere, Ste Foy, PQ, Canada. USDA, Ft Collins, CO 80526 USA. NASA Headquarters, Washington, DC 20546 USA. RP NASA, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. EM fghall@tpmail.gsfc.nasa.gov RI Ryan, Michael/A-9805-2008; Baldocchi, Dennis/A-1625-2009; Ranson, Kenneth/G-2446-2012; lettenmaier, dennis/F-8780-2011; OI Ryan, Michael/0000-0002-2500-6738; Baldocchi, Dennis/0000-0003-3496-4919; Ranson, Kenneth/0000-0003-3806-7270; lettenmaier, dennis/0000-0003-3317-1327; Crill, Patrick/0000-0003-1110-3059 NR 61 TC 358 Z9 369 U1 2 U2 33 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 DEC 26 PY 1997 VL 102 IS D24 BP 28731 EP 28769 DI 10.1029/97JD03300 PG 39 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900001 ER PT J AU Middleton, EM Sullivan, JH Bovard, BD Deluca, AJ Chan, SS Cannon, TA AF Middleton, EM Sullivan, JH Bovard, BD Deluca, AJ Chan, SS Cannon, TA TI Seasonal variability in foliar characteristics and physiology for boreal forest species at the five Saskatchewan tower sites during the 1994 Boreal Ecosystem-Atmosphere Study SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CARBON-DIOXIDE; PHOTOSYNTHESIS; CAROTENOIDS; CLIMATE AB Leaf-level measurements of gas exchange, chemistry, morphology, and spectral optical properties were acquired at the five instrumented tower sites during the three 1994 growing season intensive field campaigns (IFCs) conducted near Prince Albert, Saskatchewan, as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). Stands included old and young aspen (OA, YA) associated with the hazelnut shrub, old and young jack pine (OJP, YJP) stands, and an old black spruce (OBS) stand; white spruce (at YA) and an understory herb (dogbane, at OJP) were also examined. Midsummer peak photosynthesis for aspen leaves in the field (A, light saturated) and laboratory (A(max) light and CO2 saturated) was similar to 12.6 and 33-41 mu mol CO2 m(-2) s(-1). Black spruce exhibited the lowest A, 3 mu mol CO2 m(-2) s(-1). Jack pine and black spruce attained their highest A(max) (17-20 mu mol CO2 m(-2) s(-1)) in late summer/early fall. Gas exchange by white spruce was significantly higher and stomatal limitation lower than for other conifers, at levels comparable to broadleaf responses. White spruce foliage had the highest chlorophyll content in fall (similar to 41 mu g cm(-2)), followed by aspen (OA) and hazelnut (YA) in midsummer (similar to 31 mu g cm(-2)). Specific leaf mass of aspen, hazelnut, and conifer foliage was 86, similar to 47, and similar to 174 g m(-2), respectively. Leaf nitrogen content of broadleaves (18-40 g N g(-1) dry wt) was 2-3 times greater than conifer needles (8-12 g N g(-1)). Significantly larger needles were produced at OJP versus YJP, but needle number per age class was greater at YJP. The absorbed photosynthetically active radiation fraction (fAPAR) in June/July averaged similar to 80% for broadleaves and similar to 83% in conifer needles. The simple ratio (SR, near-infrared/red ratio) calculated from foliar transmittances was more strongly related to fAPAR than SR calculated from reflectances, with stronger correlation for broadleaves (r = 0.92) than for conifers (r = 0.78). C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20770 USA. Duke Univ, Dept Bot, Durham, NC 27708 USA. Univ Virginia, Dept Biol, Charlottesville, VA 22903 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. Univ Maryland, Dept Hort & Landscape Architecture, College Pk, MD 20744 USA. RP NASA, Goddard Space Flight Ctr, Terr Phys Lab, Code 923, Greenbelt, MD 20770 USA. EM betsym@ltpmail.gsfc.nasa.gov NR 22 TC 55 Z9 55 U1 1 U2 10 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 DEC 26 PY 1997 VL 102 IS D24 BP 28831 EP 28844 DI 10.1029/97JD02560 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900008 ER PT J AU Dang, QL Margolis, HA Sy, M Coyea, MR Collatz, GJ Walthall, CL AF Dang, QL Margolis, HA Sy, M Coyea, MR Collatz, GJ Walthall, CL TI Profiles of photosynthetically active radiation, nitrogen and photosynthetic capacity in the boreal forest: Implications for scaling from leaf to canopy SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID WATER-USE EFFICIENCY; GAS-EXCHANGE; AREA INDEX; STOMATAL CONDUCTANCE; LEAVES; LIGHT; TRANSPIRATION; PLANTS; STAND; FOLIAGE AB Profiles of photosynthetically active radiation (PAR), leaf nitrogen per unit leaf area (N-area), and photosynthetic capacity (A(max)) were measured in an aspen, two jack pine, and two black spruce stands in the BOREAS northern study area. N-area decreased with decreasing %PAR in each stand, in all conifer stands combined (r = 0.52) and in all stands combined (r = 0.46). Understory alder had higher N-area for similar %PAR than did aspen early in the growing season. A(max) decreased with decreasing N-area except for the negative correlation between N-area and A(max) during shoot flush for jack pine. For the middle and late growing season data, N-area and A(max) had r values of 0.51 for all stands combined and 0.60 for all conifer stands combined. For similar N-area the aspen stand had higher A(max) than did the conifer stands. Photosynthetic capacity expressed as a percentage of A(max) at the top of the canopy (%A(max0)) decreased with %PAR similarly in all stands, but %A(max0) decreased at a much slower rate than did %PAR. To demonstrate the implications of the vertical distribution of A(max), three different assumptions were used to scale leaf A(max) to the canopy (A(can-max)): (1) constant A(max) with canopy depth, (2) A(max) scaled proportionally to %PAR, and (3) a linear relationship between A(max) and cumulative leaf area index derived from our data. The first and third methods resulted in similar A(can-max); the second was much lower. All methods resulted in linear correlations between normalized difference vegetation indices measured from a helicopter and A(can-max) (r = 0.97, 0.93, and 0.97, respectively), but the slope was strongly influenced by the scaling method. C1 Lakehead Univ, Fac Forestry, Thunder Bay, ON P7B 5E1, Canada. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Univ Laval, Ctr Rech Biol Forestiere, Ste Foy, PQ G1K 7P4, Canada. Carleton Univ, Dept Biol, Inst Biol, Ottawa, ON K1S 5B6, Canada. USDA ARS, Remote Sensing Res Lab, BARC W, Beltsville, MD 20705 USA. RP Lakehead Univ, Fac Forestry, 955 Oliver Rd, Thunder Bay, ON P7B 5E1, Canada. EM qdang@skylakeheadU.ca RI collatz, george/D-5381-2012 NR 60 TC 66 Z9 68 U1 0 U2 12 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 26 PY 1997 VL 102 IS D24 BP 28845 EP 28859 DI 10.1029/97JD00194 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900009 ER PT J AU Hogg, EH Black, TA den Hartog, G Neumann, HH Zimmermann, R Hurdle, PA Blanken, PD Nesic, Z Yang, PC Staebler, RM McDonald, KC Oren, R AF Hogg, EH Black, TA den Hartog, G Neumann, HH Zimmermann, R Hurdle, PA Blanken, PD Nesic, Z Yang, PC Staebler, RM McDonald, KC Oren, R TI A comparison of sap flow and eddy fluxes of water vapor from a boreal deciduous forest SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HEAT PULSE VELOCITY; PINUS-PINASTER AIT; STOMATAL CONDUCTANCE; BOUNDARY-LAYER; RAIN-FOREST; DOUGLAS-FIR; TRANSPIRATION; TREES; STAND; XYLEM AB Water flux to the atmosphere was measured from a mature stand of aspen (Populus tremuloides Michx.) in Saskatchewan, Canada, as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). Diurnal and seasonal changes in transpiration were monitored using two sap flow techniques and were compared against the difference between eddy correlation measurements of water vapor flux made above and below the aspen canopy. The three methods showed similar diurnal and seasonal trends in water flux, although sap flow lagged the eddy correlation measurements by about 1 hour diurnally due to changes in water storage within the trees. During the growing season, all methods showed a linear increase in midday transpiration with above-canopy vapor pressure deficit (VPD) up to similar to 1 kPa, beyond which transpiration was relatively constant (VPD 1-2.5 kPa). A similar relationship was obtained when total daily transpiration was plotted against mean daytime VPD. The results are consistent with other observations that stomatal conductance of the aspen canopy decreases at high VPD. The complementary benefits of simultaneous monitoring of canopy transpiration by both eddy correlation and sap flow measurements are discussed. C1 Canadian Forest Serv, Edmonton, AB T6H 3S5, Canada. Univ British Columbia, Vancouver, BC V6T 1Z4, Canada. Atmospher Environm Serv, Downsview, ON M3H 5T4, Canada. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Duke Univ, Durham, NC 27728 USA. RP Canadian Forest Serv, 5320-122 St, Edmonton, AB T6H 3S5, Canada. RI Nesic, Zoran/C-9655-2015; OI Hogg, Ted/0000-0002-6198-0124; BLANKEN, PETER/0000-0002-7405-2220 NR 40 TC 48 Z9 49 U1 1 U2 19 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 DEC 26 PY 1997 VL 102 IS D24 BP 28929 EP 28937 DI 10.1029/96JD03881 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900016 ER PT J AU Vidale, PL Pielke, RA Steyaert, LT Barr, A AF Vidale, PL Pielke, RA Steyaert, LT Barr, A TI Case study modeling of turbulent and mesoscale fluxes over the BOREAS region SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID INDUCED ATMOSPHERIC FLOW; AVERAGED SURFACE FLUXES; LEAF-AREA INDEX; THERMAL INHOMOGENEITIES; SPATIAL VARIABILITY; ROUGHNESS LENGTHS; NUMERICAL-MODELS; LAND SURFACES; SOIL-MOISTURE; HAPEX-MOBILHY AB Results from aircraft and surface observations provided evidence for the existence of mesoscale circulations over the Boreal Ecosystem-Atmosphere Study (BOREAS) domain. Using an integrated approach that included the use of analytical modeling, numerical modeling, and data analysis, we have found that there are substantial contributions to the total budgets of heat over the BOREAS domain generated by mesoscale circulations. This effect is largest when the synoptic flow is relatively weak, yet it is present under less favorable conditions, as shown by the case study presented here. While further analysis is warranted to document this effect, the existence of mesoscale flow is not surprising, since it is related to the presence of landscape patches, including lakes, which are of a size on the order of the local Rossby radius and which have spatial differences in maximum sensible heat flux of about 300 W m(-2). We have also analyzed the vertical temperature profile simulated in our case study as well as high-resolution soundings and we have found vertical profiles of temperature change above the boundary layer height, which we attribute in part to mesoscale contributions. Our conclusion is that in regions with organized landscapes, such as BOREAS, even with relatively strong synoptic winds, dynamical scaling criteria should be used to assess whether mesoscale effects should be parameterized or explicitly resolved in numerical models of the atmosphere. C1 Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. Natl Hydrol Res Ctr, Atmospher Environm Serv, Saskatoon, SK S7N 3H5, Canada. NASA, Goddard Space Flight Ctr, US Geol Survey, EROS Data Ctr, Greenbelt, MD 20771 USA. RP Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. EM vidale@homebrew.atmos.colostate.edu RI Pielke, Roger/A-5015-2009; Barr, Alan/H-9939-2014; OI Vidale, Pier Luigi/0000-0002-1800-8460 NR 79 TC 31 Z9 33 U1 0 U2 3 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 DEC 26 PY 1997 VL 102 IS D24 BP 29167 EP 29188 DI 10.1029/97JD02561 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900037 ER PT J AU Levine, ER Knox, RG AF Levine, ER Knox, RG TI Modeling soil temperature and snow dynamics in northern forests SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ECOSYSTEM AB A simulation model of soil moisture and heat flux, FroST (frozen soil temperatures) was developed and applied to field data for the BOREAS northern and southern study areas (NSA, SSA). FroST is a modification of another soil physics model ("Residue") [Bidlake et al., 1982] to which simple representations of snow dynamics and transpiration, canopy, and litter properties were added. Simulations were run for the old jack pine and black spruce sites at the SSA and NSA. Predicted results showed good fit to measured data for snow depth and soil temperature at various depths at the old jack pine sites for which measured data were available for 1994. The presence of ice through the soil profile was also predicted, indicating a longer and deeper frozen period in the NSA and the development of permafrost at the NSA black spruce site. The model was sensitive to initial conditions of soil moisture and temperature and soil profile characteristics. With the availability of these data, estimates of temperature and moisture flux in soils over time can be predicted. Because the model relies on soil characterization data and yet represents fundamental physical processes, it can be readily extended to new conditions or a wider range of sites. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Biospher Sci Branch, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Terr Phys Lab, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. EM elissa@lichen.gsfc.nasa.gov RI Knox, Robert/E-9657-2011 NR 15 TC 14 Z9 17 U1 2 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 26 PY 1997 VL 102 IS D24 BP 29407 EP 29416 DI 10.1029/97JD01328 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900058 ER PT J AU Loechel, SE Walthall, CL de Colstoun, EB Chen, J Markham, BL AF Loechel, SE Walthall, CL de Colstoun, EB Chen, J Markham, BL TI Variability of boreal forest reflectances as measured from a helicopter platform SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LEAF-AREA INDEX; CANOPY; VEGETATION AB Helicopter and surface-based radiometric measurements of forested sites acquired during the Boreal Ecosystem-Atmosphere Study (BOREAS) were analyzed to assess reflectance variability and to address the relationships of reflectances and vegetation indices (VIs) with overstory leaf area index (LAI). Statistical measures of central tendency and linear regression analysis, including a multivariate regression which introduced the effects of understory reflectance, were used. The sensors were deployed during all three intensive field campaigns (IFCs) of 1994 and consisted of (1) a helicopter-based eight-channel Barnes modular multiband radiometer (MMR) and a ground-based Spectron Engineering SE-590 field spectroradiometer to measure spectral reflectance factors, (2) a ground-based Sun photometer used for atmospheric correction, and (3) a LI-COR LAI-2000 plant canopy analyzer and the tracing radiation and architecture of canopies (TRAC) sensor for retrieval of canopy LAI, Of the eight MMR bands, those most strongly correlated to variations in surface LAI were the second and third middle infrared (IR) (1.57-1.80 mu m and 2.08-2.37 mu m, respectively) with r(2) = 0.45 in both cases, and the red (0.63-0.68 mu m) with r(2) = 0.34. In general, linear regression analyses between the canopy LAI measurements and both the helicopter reflectances and VIs resulted in low r(2) values commonly less than 0.3, When stratified by season and species, only among sites that were vegetated by aspen (Populus tremuloides) was a stronger relationship observed. In the aspen stands, LAI displayed a traditional trend that maximizes the utility of the VIs: a negative relationship with red reflectance (r(2) = 0.62) and a positive relationship with the near IR (NIR) of r(2) = 0.21, The absence of a positive LAI-NIR reflectance trend degraded the information content of the VIs for the conifers. A multivariate regression confirmed the influence of the understory vegetation on the sparse canopies of the boreal forest and suggested that a more complex model-based approach is necessary to better characterize variations in canopy reflectance. Atmospheric contamination of the radiometric signal by smoke from forest fires may also have contributed to the initial unsatisfactory results. C1 USDA ARS, Beltsville Agr Res Ctr, Remote Sensing & Modeling Lab, Beltsville, MD 20705 USA. Univ Maryland, Dept Geog, Lab Global Remote Sensing Studies, College Pk, MD 20742 USA. Canada Ctr Remote Sensing, Ottawa, ON K1A OY7, Canada. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. York Univ, Dept Phys & Astron, N York, ON M3J 1P3, Canada. RP USDA ARS, Beltsville Agr Res Ctr, Remote Sensing & Modeling Lab, W Bldg 007,Room 008,10300 Baltimore Ave, Beltsville, MD 20705 USA. RI Markham, Brian/M-4842-2013 OI Markham, Brian/0000-0002-9612-8169 NR 23 TC 14 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 26 PY 1997 VL 102 IS D24 BP 29495 EP 29503 DI 10.1029/97JD02232 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900065 ER PT J AU Russell, CA Irons, JR Dabney, PW AF Russell, CA Irons, JR Dabney, PW TI Bidirectional reflectance of selected BOREAS sites from multiangle airborne data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HEMISPHERICAL REFLECTANCE; ALBEDO; SURFACES; NADIR; SPECTRORADIOMETER; ECOSYSTEM; CANOPIES AB Hyperspectral, multiangle reflected radiances were obtained using the airborne advanced solid-state array spectroradiometer (ASAS) over Boreal Ecosystem-Atmosphere Study (BOREAS) sites in Canada during four field campaigns in 1994. Atmospherically corrected bidirectional reflectance factors and estimates of spectral hemispherical reflectance for three canopies in the BOREAS southern study area (old aspen, old black spruce, and old jack pine) are presented. The multiangle spectral reflectance factors derived from data acquired July 21, 1994 (for a limited solar zenith angle range of 34 degrees-37 degrees) for the forested sites showed distributions of high backscatter and consistently low forward scatter due to shadowing. Position and shape of the retrosolar maximums for the three sites varied. Spectral distinction among the sites was evident in the red, where reflectance factors for the jack pine exceeded those for spruce and aspen. and in the near infrared (NIR), where the aspen reflectance factors were twice those for the conifers. Data presented here suggest that spectral reflectances acquired at 26 degrees backscatter in the principal plane would provide better discrimination among the major cover types than those obtained from a nadir view. Red reflectance was strongly dependent on view geometry for the spruce and jack pine sites due to the varying amounts of deep shadow and red-reflecting materials observed as a function of view azimuth and zenith. At the aspen site the red reflectance displayed much less variation with changing view zenith and azimuth. Accordingly, angular effects on the normalized difference vegetation index were large for the spruce and jack pine canopies but small for the aspen site. Estimated spectral hemispherical reflectances for photosynthetically active radiation (PAR) (0.4-0.7 mu m), red (0.63-0.69 mu m), and NIR (0.83-0.87 mu m) calculated using various combinations of azimuthal data sets as input to the Walthall et al. [1985] model showed the following trends: maximum estimates were generated using data from the solar principal plane (spp) only; minimum values were derived from perpendicular plane data and amounted to 50-83% (relative) of the corresponding spp value; and inclusion of data from three view azimuths together (spp + perpendicular + oblique) produced intermediate values totaling 73-91% (relative) of the spp result. A preliminary review of ASAS-derived and independent ground-based measures of PAR hemispherical reflectance revealed a sizable range in this parameter. C1 Univ Maryland, Dept Geog, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RI Irons, James/D-8535-2012; Dabney, Philip/C-9976-2013 NR 16 TC 17 Z9 18 U1 0 U2 2 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 DEC 26 PY 1997 VL 102 IS D24 BP 29505 EP 29516 DI 10.1029/96JD03880 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900066 ER PT J AU Privette, JL Eck, TF Deering, DW AF Privette, JL Eck, TF Deering, DW TI Estimating spectral albedo and nadir reflectance through inversion of simple BRDF models with AVHRR/MODIS-like data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SPRUCE-HEMLOCK FOREST; REMOTE-SENSING DATA; BIDIRECTIONAL REFLECTANCE; CANOPY REFLECTANCE; PLANT CANOPY; ANISOTROPY; SURFACE; RADIOMETER AB In recent years, many computationally efficient bidirectional reflectance models have been developed to account for angular effects in land remote sensing data, particularly those from the NOAA advanced very high resolution radiometer (AVHRR), polarization and directionality of the Earth's reflectances (POLDER), and the planned EOS moderate-resolution imaging spectrometer (MODIS) and multi-angle imaging spectroradiometer (MISR) sensors. In this study, we assessed the relative ability of 10 such models to predict commonly used remote sensing products (nadir reflectance and albedo). Specifically, we inverted each model with ground-based data from the portable apparatus for rapid acquisition of bidirectional observations of the land and atmosphere (PARABOLA) arranged in subsets representative of satellite sampling geometries. We used data from nine land cover types, ranging from soil to grassland (First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE)) to forest (Boreal Ecosystem-Atmosphere Study (BOREAS)). Retrieved parameters were used in forward model runs to estimate nadir reflectance and spectral albedo over a wide range of solar angles. We rank the models by the accuracy of the estimated products and find results to be strongly dependent on the view azimuth angle range of the inversion data, and less dependent on the spectral band and land cover type. Overall, the nonlinear model of Rahman et al. [1993] and the linear kernel-driven RossThickLiSparse model [Wanner et al., 1995] were most accurate. The latter was at least 25 times faster to invert than the former. Interestingly, we found these two models were not able to match the various bidirectional reflectance distribution function (BRDF) shapes as well as other models, suggesting their superior performance lies in their ability to be more reliably inverted with sparse data sets. These results should be useful to those interested in the computationally fast normalization of bidirectional reflectance data and the estimation of radiation flux parameters (albedo, absorbed radiation) over diverse land covers. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Hughes STX Corp, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. EM jeff.privette@gsfc.nasa.gov; teck@gsfc.nasa.gov; ddeering@gsfc.nasa.gov RI Privette, Jeffrey/G-7807-2011; ECK, THOMAS/D-7407-2012 OI Privette, Jeffrey/0000-0001-8267-9894; NR 40 TC 106 Z9 109 U1 1 U2 11 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 DEC 26 PY 1997 VL 102 IS D24 BP 29529 EP 29542 DI 10.1029/97JD01215 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900068 ER PT J AU Hall, FG Knapp, DE Huemmrich, KF AF Hall, FG Knapp, DE Huemmrich, KF TI Physically based classification and satellite mapping of biophysical characteristics in the southern boreal forest SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID REFLECTANCE MODELS; VEGETATION; CANOPY; EXTRACTION; PARAMETERS; VARIABLES; IMAGES; INDEX AB Fundamental problems inherent to the existing land cover and biophysical characteristic algorithms are fourfold: (1) their failure to deal physically with global and interannual variations in surface reflectance arising from Sun and view angle variations, (2) decoupling of the land cover classification algorithm from the biophysical characteristic inference algorithm with no ability to control biophysical parameter estimation error arising from misclassification, (3) invalid statistical assumptions within classification algorithms used to model reflectance distribution functions, and (4) sole reliance on vegetation indices that can limit performance for several major land cover classes. To address these problems, we develop an integrated, physically based classification and biophysical characteristics estimation algorithm that utilizes canopy reflectance models to account directly for signature variations from Sun angle, topographic, and other variations. Our approach fuses into a single algorithm both land cover classification and biophysical characteristics estimation, permitting one set of physically based canopy reflectance models to be used for both. The use of canopy reflectance models eliminates the need for unrealistic assumptions, such as multivariate-normal distributions, underlying many classification algorithms. Using the algorithm, we have classified a 10,000 km(2) area of the BOREAS southern study area. Our classification shows that low-productivity wetland conifer is the dominant land cover and that nearly 7% of the area is occupied by boreal fens, a major source of methane. In addition, nearly 23% of the area has been disturbed by either fire or logging in the last 20 years, suggesting an important role for disturbance to the regional carbon budget. A thorough evaluation of the physically based classifier within the southern study area shows accuracies superior to those obtained with conventional statistically based algorithms, implying even better performance when extended over multiple Landsat frames since the physically based approach can account directly for regional variations in reflectance resulting from varying illumination and viewing conditions (topography, Sun angle). The conifer biomass density estimation algorithm is based on our discovery of a convenient natural relationship between crown height and volumetric density that renders the biomass density for black spruce stands independent of tree height, and a function only of sunlit canopy fraction. This permits us to calculate directly the relationship between reflectance and biomass density. An evaluation of the algorithm using ground sites shows our algorithm can estimate black spruce biomass density with a root-mean-square error of 2.73 kg/m(2) for correctly classified sites. Our evaluation also demonstrates the importance of correct classification. Root-mean-square errors for misclassified sites were 3.96 kg/m(2). Using this approach we have estimated the biomass density in the BOREAS southern study area for the dominant land. cover type in the circumpolar boreal ecosystem, wetland black spruce. These results show a bimodality to the biomass density regional distribution, controlled perhaps by underlying topographic and edaphic factors. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Hughes STX, Goddard Space Flight Ctr, Greenbelt, MD 20770 USA. RP NASA, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. EM fghall@ltpmail.gsfc.nasa.gov NR 33 TC 65 Z9 67 U1 1 U2 13 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 DEC 26 PY 1997 VL 102 IS D24 BP 29567 EP 29580 DI 10.1029/97JD02578 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900071 ER PT J AU Steyaert, LT Hall, FG Loveland, TR AF Steyaert, LT Hall, FG Loveland, TR TI Land cover mapping, fire regeneration, and scaling studies in the Canadian boreal forest with 1 km AVHRR and Landsat TM data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CONTERMINOUS UNITED-STATES; SATELLITE DATA; DATA SET; SURFACE; CLASSIFICATION; MODELS; ATMOSPHERE; ALGORITHMS; WILDFIRES; CLIMATE AB A multitemporal 1 km advanced very high resolution radiometer (AVHRR) land cover analysis approach was used as the basis for regional land cover mapping, fire disturbance-regeneration, and multiresolution land cover scaling studies in the boreal forest ecosystem of central Canada. The land cover classification was developed by using regional field observations from ground and low-level aircraft transits to analyze spectral-temporal clusters that were derived from an unsupervised cluster analysis of monthly normalized difference vegetation index (NDVI) image composites (April-September 1992). Quantitative areal proportions of the major boreal forest components were determined for a 821 km x 619 km region, ranging from the southern grasslands-boreal forest ecotone to the northern boreal transitional forest. The boreal wetlands (mostly lowland black spruce, tamarack, mosses, fens, and bogs) occupied approximately 33% of the region, while lakes accounted for another 13%. Upland mixed coniferous-deciduous forests represented 23% of the ecosystem. A SW-NE productivity gradient across the region is manifested by three levels of tree stand density for both the boreal wetland conifer and the mixed forest classes, which are generally aligned with isopleths of regional growing degree days. Approximately 30% of the region was directly affected by fire disturbance within the preceding 30-35 years, especially in the Canadian Shield Zone where large fire-regeneration patterns contribute to the heterogeneous boreal landscape. Intercomparisons with land cover classifications derived from 30-m Landsat Thematic Mapper (TM) data provided important insights into the relative accuracy of the 1 km AVHRR land cover classification. Primarily due to the multitemporal NDVI image compositing process, the 1 km AVHRR land cover classes have an effective spatial resolution in the 3-4 km range therefore fens, bogs, small water bodies, and small patches of dry jack pine cannot be resolved within the wet conifer mosaic. Major differences in the l-km AVHRR and 30-m Landsat TM-derived land cover classes are most likely due to differences in the spatial resolution of the data sets. In general, the 1 km AVHRR land cover classes are vegetation mosaics consisting of mixed combinations of the Landsat classes. Detailed mapping of the global boreal forest with this approach will benefit from algorithms for cloud screening and to atmospherically correct reflectance data for both aerosol and water vapor effects. We believe that this 1 km AVHRR land cover analysis provides new and useful information for regional water, energy, carbon, and trace gases studies in BOREAS, especially given the significant spatial variability in land cover type and associated biophysical land cover parameters (e.g., albedo, leaf area index, FPAR, and surface roughness). Multiresolution land cover comparisons (30 m, 1 km, and 100 km grid cells) also illustrated how heterogeneous landscape patterns are represented in land cover maps with differing spatial scales and provided insights on the requirements and challenges for parameterizing landscape heterogeneity as part of land surface process research. C1 NASA, Goddard Space Flight Ctr, US Geol Survey, EROS,Data Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. US Geol Survey, EROS, Ctr Data, Sioux Falls, SD 57198 USA. RP NASA, Goddard Space Flight Ctr, US Geol Survey, EROS,Data Ctr, Code 923, Greenbelt, MD 20771 USA. NR 44 TC 55 Z9 55 U1 1 U2 15 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 DEC 26 PY 1997 VL 102 IS D24 BP 29581 EP 29598 DI 10.1029/97JD01220 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900072 ER PT J AU Ranson, KJ Sun, GQ Lang, RH Chauhan, NS Cacciola, RJ Kilic, O AF Ranson, KJ Sun, GQ Lang, RH Chauhan, NS Cacciola, RJ Kilic, O TI Mapping of boreal forest biomass from spaceborne synthetic aperture radar SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DATA QUALITY; SAR DATA; BACKSCATTER; CALIBRATION; ERS-1 AB As part of the Boreal-Ecosystem Atmosphere Study (BOREAS), an investigation is being made of the use of satellite data including shuttle imaging radar-C (SIR-C), X-band synthetic aperture radar (XSAR), and Landsat-Thematic Mapper data for estimating total and component aboveground woody biomass in boreal forest study sites in Canada. The goal of this paper is to present progress in mapping above ground woody biomass over portions of the BOREAS southern study area using spaceborne sensor data. Relationships of backscatter to total biomass and total biomass to foliage, branch, and bale biomass are used to estimate biomass across the landscape. The procedure involves image classification with SAR and Landsat data and development of simple mapping techniques using combinations of SAR channels. The analysis uses measurements from forest stands representing a range of biomass and structures. Field measurements included plot level mensuration (species, stem diameter, height, density, and basal area) and tree geometry measurements (leaf, branch, bole size, and angle distributions). The results indicate that aboveground biomass can be estimated to within about 1.6 kg/m(2) and up to about 15 kg/m(2) across the SIR-C image evaluated. A general method produced equivalent results with those obtained by treating forest type (pine, spruce, and aspen) separately. The biomass mapping was extended to bole, branch, and foliage components from relationships with total aboveground biomass developed from detailed tree measurements. Average biomass within the imaged area was estimated to be about 7.3 kg/m(2) with biomass components of bole, branch, and foliage comprising 83, 12, and 5% of the total. Examination of the scaling of biomass estimates from remote sensing images of varying resolution shows that information at scales useful for ecosystem models can be obtained. In addition, the biomass estimation technique provides similar information at different image resolutions. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. George Washington Univ, Dept Elect Engn & Comp Sci, Washington, DC 20052 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. RI Ranson, Kenneth/G-2446-2012 OI Ranson, Kenneth/0000-0003-3806-7270 NR 30 TC 55 Z9 58 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 26 PY 1997 VL 102 IS D24 BP 29599 EP 29610 DI 10.1029/96JD03708 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900073 ER PT J AU Chang, ATC Foster, JL Hall, DK Goodison, BE Walker, AE Metcalfe, JR Harby, A AF Chang, ATC Foster, JL Hall, DK Goodison, BE Walker, AE Metcalfe, JR Harby, A TI Snow parameters derived from microwave measurements during the BOREAS winter field campaign SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID WATER EQUIVALENT; MOUNTAIN BASIN; SATELLITE DATA; SMMR DATA; ALASKA; REMOTE AB Passive microwave data have been used to infer the snow-covered area and snow water equivalent (SWE) over forested areas, but the accuracy of these retrieved snow parameters cannot be easily validated for heterogeneous vegetated regions. The Boreal Ecosystem-Atmosphere Study Winter Field Campaign provided the opportunity to study the effect of boreal forests on snow parameter retrieval in detail. Microwave radiometers (18, 37, and 92 GHz) were flown on board the Canadian National Aeronautical Establishment's Twin Otter. Flight lines covered both the southern study area near Prince Albert and the northern study area near Thompson, Canada. During the 1994 winter campaign, extensive ground-based snow cover information, including depth, density, and grain size, was collected along most of the flight lines, jointly by U.S. and Canadian investigators. Satellite data collected by the special sensor microwave imager are also used for comparison. Preliminary results reconfirmed the relationship between microwave brightness temperature and SWE. However, the effect of forest cover observed by the aircraft sensors is different from that of the satellite observations. This is probably due to the difference in footprint averaging. There were also several flight lines flown over Candle Lake and Waskesiu Lake to assess lake ice signatures. Preliminary results show the thickness of the lake ice may be inferred from the airborne microwave observations. The microwave signature relationship between lake ice and snow matches the results from radiative transfer calculations. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Canadian Climate Ctr, Atmospher Environm Serv, Downsview, ON M3H 5T4, Canada. Norwegian Hydrotech Lab, N-7034 Trondheim, Norway. RP NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. EM achang@rainfall.gsfc.nasa.gov RI Hall, Dorothy/D-5562-2012 NR 46 TC 53 Z9 60 U1 1 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 DEC 26 PY 1997 VL 102 IS D24 BP 29663 EP 29671 DI 10.1029/96JD03327 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900078 ER PT J AU Way, J Zimmermann, R Rignot, E McDonald, K Oren, R AF Way, J Zimmermann, R Rignot, E McDonald, K Oren, R TI Winter and spring thaw as observed with imaging radar at BOREAS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE-BIOSPHERE EXCHANGE; CARBON-DIOXIDE; ENVIRONMENTAL-CONDITIONS; MICROWAVE SIGNATURES; TAIGA FORESTS; ERS-1 SAR; CO2; VARIABILITY; ECOSYSTEM; PHENOLOGY AB Measurements of the length of the growing season in the boreal regions, during which significant carbon exchange due to metabolic activity occurs, may improve current estimates of annual CO2 fluxes at high northern latitudes. For coniferous, evergreen forest species, the summer frost free period bounds the growing season length and period of net carbon uptake. Spring soil thaw bounds the period of soil respiration and decomposition and thus carbon release. The balance of these to exchanges determines whether the boreal region is a net carbon source or sink. Imaging radar data can potentially be used to monitor these periods of soil and canopy thaw due to the sensitivity of radar to surface freeze/thaw state. In considering the use of imaging radar, two issues must be addressed. First, the temporal relationship between the time of freezing and thawing of the forest canopy and soil and the periods of photosynthetic and respiration activity must be ascertained. Second, the sensitivity of imaging radar to freeze/thaw processes in each of the forest components must be assessed. Of particular interest is the extent to which radar is selectively sensitive to tree and soil thawing. In 1994, in situ soil, stem and root temperatures, and stem xylem flux were measured over a complete annual cycle at the Boreal Ecosystem-Atmosphere Study (BOREAS) test sites in Canada. Imaging radar data from the European Space Agency Remote Sensing (ERS-1) satellite were also acquired throughout 1994. The in situ temperature data show clear transitions in soil and stem thawing related to the start of soil respiration and canopy photosynthesis, respectively. The imaging radar data show clear shifts in backscatter related directly to soil thaw, and possibly to canopy thaw, as two independent transitions. These results are compared to seasonal ecosystem model results for carbon exchange. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Duke Univ, Sch Environm, Durham, NC 27708 USA. Univ Bayreuth, BIOTEK, Bayreuth Inst Terr Ecosyst Res, D-95448 Bayreuth, Germany. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 300-233, Pasadena, CA 91109 USA. EM way@lor.jpl.nasa.gov RI Rignot, Eric/A-4560-2014 OI Rignot, Eric/0000-0002-3366-0481 NR 37 TC 35 Z9 36 U1 1 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 DEC 26 PY 1997 VL 102 IS D24 BP 29673 EP 29684 DI 10.1029/96JD03878 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900079 ER PT J AU Kaminsky, KZ Dubayah, R AF Kaminsky, KZ Dubayah, R TI Estimation of surface net radiation in the boreal forest and northern prairie from shortwave flux measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR-RADIATION; BASIN AB The relationships between net radiation and surface shortwave fluxes were explored by using one year of 15 min surface flux data for nine sites in central Canada. The sites were located throughout a 50,000 km(2) area, in conjunction with the BOREAS project, across a gradient in surface cover from prairie grassland to boreal forest. When insolation alone was used to estimate instantaneous net radiation, the r(2) values at the nine sites ranged from 0.93 to 0.98. The use of the net shortwave flux as a predictor improved the range in r(2) values to between 0.96 and 0.99. The root-mean-square error across sites varied from 26 to 41 W m(-2) without albedo to a range of 18-36 W m(-2) when albedo was included. The data for all sites were combined to produce a single linear relationship with an r(2) value of 0.97 and a root-mean-square error (RMSE) of 29 W m(-2) when the surface albedo is included. Cross validations were performed where the data for eight sites were used to predict net radiation at a ninth (excluded) site, revealing little site-specific bias. Classifications of the data by season and by transmittance provided little improvement in estimated net radiation at any site. Our study suggests that a single equation using net shortwave flux alone can be used to estimate net radiation for large portions of the boreal forest and northern prairie, regardless of spatial and temporal variation in surface cover and atmospheric conditions. C1 Hughes STX, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. Univ Maryland, Lab Global Remote Sensing Studies, College Pk, MD 20742 USA. RP Hughes STX, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. EM kaminsky@ltpmailgsfc.nasa.gov NR 22 TC 29 Z9 30 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 26 PY 1997 VL 102 IS D24 BP 29707 EP 29716 DI 10.1029/97JD02314 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900081 ER PT J AU Markham, BL Schafer, JS Holben, BN Halthore, RN AF Markham, BL Schafer, JS Holben, BN Halthore, RN TI Atmospheric aerosol and water vapor characteristics over north central Canada during BOREAS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OPTICAL-PROPERTIES; UNITED-STATES; RETRIEVALS; DEPTH AB A network of five automated and two handheld solar radiometers was operated during the 1993-1996 Boreal Ecosystem-Atmosphere Study (BOREAS) in northern Saskatchewan and Manitoba, Canada, in order to characterize the atmospheric aerosol properties. Direct solar measurements were used to measure atmospheric transmission and infer aerosol optical thickness and water vapor column abundance. Near-Sun sky radiance measurements (solar aureole) were used to estimate the aerosol size distribution. Aerosol conditions were heavily influenced by the presence or absence of forest fires. In 1996, when few fires occurred, conditions were uniform across the region with median aerosol optical thickness (AOT) at 500 nm of 0.12 and 90th percentile values of 0.27 for the May-October period. During the 1994 and 1995 seasons, numerous fires occurred in the vicinity of the sites. The median AOT values were comparable with the 1996 values, though the 90th percentile values were larger, in general measuring 0.85 (southern 1994 season was 0.43). Median column water vapor measurements for the same 7 month period were in the range from 1.32 to 1.58 cm at both sites, with 1995 being the driest year of observation. Winter median values of AOT and water vapor were typically 0.09 and 0.34 cm, respectively. Size distributions derived from solar almucantar measurements show the predominance of small particles during smoke episodes when compared to that for background conditions. Spectral dependence of the AOT as characterized by the wavelength exponent, alpha, asymptotes at 1.8 for high optical depths for a 7 month season of cloud-screened data at the northern young jack pine site. This observed wavelength exponent for boreal biomass burning conditions is within the range of values found during the burning season in a study in Brazil. C1 Brookhaven Natl Lab, DAS, ECD, Upton, NY 11973 USA. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Hughes STX Corp, Code 923, Greenbelt, MD 20771 USA. EM Brian_Markham@gsfc.nasa.gov; schafer@ltpmail.gsfc.nasa.gov; brent@kratmos.gsfc.nasa.gov; halthore@aerosol.das.bnl.gov RI Schafer, Joel/A-3978-2010; Markham, Brian/M-4842-2013 OI Markham, Brian/0000-0002-9612-8169 NR 24 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 26 PY 1997 VL 102 IS D24 BP 29737 EP 29745 DI 10.1029/97JD00241 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YQ418 UT WOS:000071384900084 ER PT J AU Veynante, D Poinsot, T AF Veynante, D Poinsot, T TI Effects of pressure gradients on turbulent premixed flames SO JOURNAL OF FLUID MECHANICS LA English DT Article ID SIMULATIONS; REACTANTS; VELOCITY; FLOWS AB In most practical situations, turbulent premixed flames are ducted and, accordingly, subjected to externally imposed pressure gradients. These pressure gradients may induce strong modifications of the turbulent flame structure because of buoyancy effects between heavy cold fresh and light hot burnt gases, In the present work, the influence of a constant acceleration, inducing large pressure gradients; on a premixed turbulent flame is studied using direct numerical simulations, A favourable pressure gradient, i.e. a pressure decrease from unburnt to burnt gases, is found to decrease the flame wrinkling, the flame brush thickness, and the turbulent flame speed, It also promotes counter-gradient turbulent transport, On the other hand: adverse pressure gradients tend to increase the flame brush thickness and turbulent flame speed, and promote classical gradient turbulent transport, As proposed by Libby (1989), the turbulent flame speed is modified by a buoyancy term linearly dependent on both the imposed pressure gradient and the integral length scale l(t). A simple model for the turbulent flux <(u" c")over tilde> is also proposed, validated from simulation data and compared to existing models, It is shown that turbulent premixed flames can exhibit both gradient and counter-gradient transport and a criterion integrating the effects of pressure gradients is derived to differentiate between these regimes. In fact, counter-gradient diffusion may occur in most practical ducted flames. C1 Stanford Univ, Ctr Turbulent Res, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Stanford, CA 94305 USA. Ecole Cent Paris, CNRS, Lab EM2C, Paris, France. Inst Mecan Fluides Toulouse, Toulouse, France. CERFACS, Toulouse, France. RP Veynante, D (reprint author), Stanford Univ, Ctr Turbulent Res, Stanford, CA 94305 USA. NR 19 TC 58 Z9 60 U1 0 U2 7 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD DEC 25 PY 1997 VL 353 BP 83 EP 114 DI 10.1017/S0022112097007556 PG 32 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA YQ376 UT WOS:000071380700005 ER PT J AU Zuber, MT Smith, DE AF Zuber, MT Smith, DE TI Mars without Tharsis SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID TERRESTRIAL PLANETS; LITHOSPHERIC STRESS; GRAVITY; INERTIA; MOMENT; MODEL; CONSTRAINTS; THICKNESS; TECTONICS; ANOMALIES AB The significant power in the Martian gravitational field due to the Tharsis rise may mask or modify gravitational signatures that contain important information on Martian geophysical processes. in order to isolate gravity signals in regions where the field is significantly affected by Tharsis as well to investigate characteristics of the global field, we present a numerical technique to "remove" Tharsis from the Martian gravitational field. Our analysis will show that to first order Tharsis can be represented as a sixth-degree spherical harmonic zonal gravitational feature in a reference frame in which the axis of symmetry runs through the center of the province. We produced the "Mars without Tharsis" (MWT) field by subtracting the gravitational signature of Tharsis from the full field and rotating the spherical harmonics back to the original coordinate system, in which the z-axis is coincident with the planetary rotation axis. Our study yields limits on the moment of inertia factor of 0.361 e(+)e(-) considerations for GRBs were limited to cases of a beam with opening half-angle Theta(B) similar to 1/Gamma, or expansions of infinitely thin spherical shells. This paper presents our extension of pair production optical depth calculations in relativistically expanding sources to more general geometries, including shells of finite thickness and arbitrary opening angle. The problem is reduced analytically to a single integral in the special, but quite broadly applicable, case of observing photons only along the axis of the expansion. We find that the minimum bulk Lorentz factor for the EGRET sources to be optically thin, i.e., display no spectral attenuation, is only moderately dependent on the shell thickness and virtually independent of its opening solid angle if Theta(B) greater than or similar to 1/Gamma. This insensitivity to Theta(B) relieves the commonly perceived number problem for nonrepeating sources at cosmological distances, i.e., it is not necessary to invoke small Theta(B) to effect photon escape. The values of Gamma obtained, typically of the order of 10 for halo bursts and greater than or similar to 100 for sources of cosmological origin, depend somewhat on the choice of GRB timescale used to determine the expansion size. Our new limits on required velocity for given source geometries will aid in placing realistic constraints on GRB source models. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. RP Baring, MG (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. EM baring@lheavx.gsfc.nasa.gov; harding@twinkie.gsfc.nasa.gov RI Harding, Alice/D-3160-2012 NR 69 TC 109 Z9 110 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP 663 EP 686 DI 10.1086/304982 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600020 ER PT J AU Seifert, H Teegarden, BJ Cline, TL Gehrels, N Zand, JJMI Palmer, DM Ramaty, R Hurley, K Madden, NW Pehl, R AF Seifert, H Teegarden, BJ Cline, TL Gehrels, N Zand, JJMI Palmer, DM Ramaty, R Hurley, K Madden, NW Pehl, R TI Transient gamma-ray spectrometer observation of the bright gamma-ray burst GRB 950822 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; gamma rays, observations ID LINE SEARCH; BATSE OBSERVATIONS; TIME DILATION; EVOLUTION; CYCLOTRON; SPECTRA AB The Transient Gamma-Ray Spectrometer (TGRS) on the Wind satellite is designed to perform spectroscopy of bright gamma-ray bursts in the similar to 20-8000 keV energy range, having a resolution 5-30 times better than that of earlier generation detectors. GRB 950822 was the brightest burst observed by TGRS in its first year of operation, with a peak flux (1024 ms) of similar to 78.3 photons cm(-2) s(-1) and a fluence (50-300 keV) of similar to 1.4 x 10(-4) ergs cm(-2); therefore, the GRB data in this paper represent the first high-resolution spectroscopy ever performed on a burst of this brightness. The continuum spectrum of GRB 950822 has the classical gamma-ray burst shape and exhibits typical evolution from hard to soft over the course of the burst. We found no evidence of line features or any other spectral fine structure with significance greater than 3.5 sigma in our data. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. RP Seifert, H (reprint author), Univ Space Res Assoc, Washington, DC 20036 USA. RI Gehrels, Neil/D-2971-2012 NR 29 TC 2 Z9 2 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP 697 EP 703 DI 10.1086/304991 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600022 ER PT J AU Kommers, JM Lewin, WHG Kouveliotou, C van Paradijs, J Pendleton, GN Meegan, CA Fishman, GJ AF Kommers, JM Lewin, WHG Kouveliotou, C van Paradijs, J Pendleton, GN Meegan, CA Fishman, GJ TI A search for nontriggered gamma-ray bursts in the BATSE database SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; X-rays, bursts AB We describe a search of archival data from the Burst and Transient Source Experiment (BATSE). The purpose of the search is to find astronomically interesting transients that did not activate the burst-detection (or "trigger") system on board the spacecraft. Our search is sensitive to events with peak fluxes (on the 1.024 s timescale) that are lower by a factor of similar to 2 than can be detected with the on-board burst trigger. In a search of 345 days of archival data, we detected 91 events in the 50-300 keV range that resemble classical gamma-ray bursts but that did not activate the on-board burst trigger. We also detected 110 low-energy (25-50 keV) events of unknown origin that may include activity from soft gamma repeater (SGR) 1805-20 and bursts and flares from X-ray binaries. This paper gives the occurrence times, estimated source directions, durations, peak fluxes, and fluences for the 91 gamma-ray burst candidates. The direction and intensity distributions of these bursts imply that the biases, inherent in the on-board trigger mechanism have not significantly affected the completeness of the published BATSE gamma-ray burst catalogs. C1 MIT, Dept Phys, Cambridge, MA 02139 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Space Res Assoc, Huntsville, AL 35800 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35812 USA. Univ Amsterdam, Amsterdam, Netherlands. RP Kommers, JM (reprint author), MIT, Dept Phys, Cambridge, MA 02139 USA. NR 26 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP 704 EP 719 DI 10.1086/304992 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600023 ER PT J AU Purcell, WR Cheng, LX Dixon, DD Kinzer, RL Kurfess, JD Leventhal, M Saunders, MA Skibo, JG Smith, DM Tueller, J AF Purcell, WR Cheng, LX Dixon, DD Kinzer, RL Kurfess, JD Leventhal, M Saunders, MA Skibo, JG Smith, DM Tueller, J TI OSSE mapping of galactic 511 keV positron annihilation line emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy, center; gamma-rays, observations; ISM, general; line, formation nuclear; reactions, nucleosynthesis, abundances ID GAMMA-RAY LINE; CENTER REGION; CENTER DIRECTION; RADIATION; GALAXY; CONTINUUM; 511-KEV; ORIGIN AB The Oriented Scintillation Spectrometer Experiment (OSSE) observations of the Galactic plane and Galactic center region have been combined with scanning observations by the Transient Gamma-Ray Spectrometer (TGRS) and Solar Maximum Mission (SMM) instruments to produce maps of the Galactic narrow 511 keV positron annihilation line radiation. Two different mapping methods, singular value decomposition and maximum entropy, have been applied to the data. In both cases, the resulting maps show evidence for three distinct features: (1) a central bulge, (2) emission in the Galactic plane, and (3) an enhancement or extension of emission at positive latitudes above the Galactic center. Modeling of the data confirmed the existence of these features. The derived distribution is found to be in good qualitative agreement with nearly all of the historical observations of narrow 511 keV line emission from the Galactic center region. No evidence of time variability is found. Various possible production mechanisms for the observed positrons, including the positive-latitude enhancement, are presented. It is found that supernovae are capable of producing positrons at the required rate to account for the intensity and morphology of the observed 511 keV line emission. C1 Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Calif Riverside, Dept Geophys & Planetary Phys, Riverside, CA 92521 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Code 7650, Washington, DC 20375 USA. Stanford Univ, Syst Optimizat Lab, Stanford, CA 94305 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Purcell, WR (reprint author), Ball Aerosp & Technol Corp, Boulder, CO 80301 USA. RI Tueller, Jack/D-5334-2012 NR 66 TC 117 Z9 117 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 DEC 20 PY 1997 VL 491 IS 2 BP 725 EP 748 DI 10.1086/304994 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600025 ER PT J AU Pravdo, SH Angelini, L Harding, AK AF Pravdo, SH Angelini, L Harding, AK TI X-ray spectral evolution of the Crab pulse SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, individual (Crab); X-rays, stars ID OUTER MAGNETOSPHERE; NEBULA PULSAR; RADIATION; EMISSION AB The Crab pulsar was observed with the X-ray detectors on the Rossi X-Ray Timing Explorer (RXTE) on 1996 May 2. The large area, high time resolution, extended energy range, and moderate energy resolution of the RXTE instruments provided an unprecedented measurement of the Crab pulsar spectrum as it evolved in phase across the 33 ms pulse. The X-rays are pulsed over the detected range 5-200 keV, and the pulse shape changes with energy in concert with the spectral evolution. The X-ray pulse as seen with RXTE has a well-known double-peak shape with significant emission in the smaller phase region between the peaks (the "interpeak") and no detectable pulsed emission in the "nebular" phase region. The new RXTE results show an evolution of the spectral index across the pulse in a reverse S shape: (1) the spectrum softens (i.e., the power-law index increases) starting at the leading edge of the first peak until the intensity maximum of the first peak; (2) the spectrum hardens in the interpeak region; and (3) the spectrum softens throughout the second peak. The temporal resolution and statistical quality of prior data did not allow behavior 1 or behavior 3 to be seen, while behavior 2 confirms previous results, but with higher temporal and spectral resolution. Thus there is a significant difference in the spectral evolution across each of the two intensity peaks. While existing models can, in principle, explain spectral behaviors 2 and 3, the hardening toward the leading edge of the first peak (behavior 1) is unexpected. This hardening occurs in the same phase region where there is enhanced emission in a "precursor" to the first radio peak at much lower energies and there is a possible broadening of the first gamma-ray peak at much higher energies. The discovery that the first X-ray peak is symmetric with respect to spectral evolution is a new clue toward understanding the interaction between emerging photons and the magnetic field that creates the pulse and defines its phases. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Pravdo, SH (reprint author), CALTECH, Jet Prop Lab, Mail Stop 306-431, Pasadena, CA 91109 USA. RI Harding, Alice/D-3160-2012 NR 26 TC 38 Z9 38 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP 808 EP 815 DI 10.1086/304996 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600030 ER PT J AU Burrows, A Marley, M Hubbard, WB Lunine, JI Guillot, T Saumon, D Freedman, R Sudarsky, D Sharp, C AF Burrows, A Marley, M Hubbard, WB Lunine, JI Guillot, T Saumon, D Freedman, R Sudarsky, D Sharp, C TI A nongray theory of extrasolar giant planets and brown dwarfs SO ASTROPHYSICAL JOURNAL LA English DT Article DE planetary systems; stars, atmospheres; stars, interiors; stars, low-mass, brown dwarfs ID LOW-MASS STARS; GLIESE 229B; INFRARED-ABSORPTION; MULTIPLE-SCATTERING; THEORETICAL-MODELS; CORRELATED-KAPPA; MAIN-SEQUENCE; NU(4) BAND; ATMOSPHERES; JUPITER AB We present the results of a new series of nongray calculations of the atmospheres, spectra, colors, and evolution of extrasolar giant planets (EGPs) and brown dwarfs for effective temperatures below 1300 K. This theory encompasses most of the mass/age parameter space occupied by substellar objects and is the first spectral study down to 100 K. These calculations are in aid of the multitude of searches being conducted or planned around the world for giant planets and brown dwarfs and reveal the exotic nature of the class. Generically, absorption by H-2 at longer wavelengths and H2O opacity windows at shorter wavelengths conspire to redistribute flux blueward. Below 1200 K, methane is the dominant carbon bearing molecule and is a universal diagnostic feature of EGP and brown dwarf spectra. We find that the primary bands in which to search are Z (similar to 1.05 mu m), J (similar to 1.2 mu m), H (similar to 1.6 mu m), K (similar to 2.2 mu m), M (similar to 5 mu m), and N (similar to 10 mu m), that enhancements of the emergent flux over blackbody values, in particular in the near infrared, can be by many orders of magnitude, and that the infrared colors of EGPs and brown dwarfs are much bluer than previously believed. In particular, relative to J and H, the K band flux is reduced by CH4 and H-2 absorption. Furthermore, we conclude that for T-eff's below 1200 K most or all true metals may be sequestered below the photosphere, that an interior radiative zone is a generic feature of substellar objects, and that clouds of H2O and NH3 are formed for T-eff's below similar to 400 and similar to 200 K, respectively. This study is done for solar-metallicity objects in isolation and does not include the effects of stellar insulation. Nevertheless, it is a comprehensive attempt to bridge the gap between the planetary and stellar realms and to develop a nongray theory of objects from 0.3M(J) ("Saturn") to 70M(J) (similar to 0.07 M-.). We find that the detection ranges for brown dwarf/EGP discovery of both ground-and space-based telescopes are larger than previously estimated. C1 Univ Arizona, Dept Astron, Tucson, AZ 85721 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Reading, Dept Meteorol, Reading RG6 6AU, Berks, England. Vanderbilt Univ, Dept Phys & Astron, Nashville, TN 37235 USA. NASA, Ames Res Ctr, Space Phys Res Inst, Moffett Field, CA 94035 USA. RP Univ Arizona, Dept Astron, Tucson, AZ 85721 USA. RI Marley, Mark/I-4704-2013 NR 97 TC 948 Z9 949 U1 2 U2 28 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP 856 EP 875 DI 10.1086/305002 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600035 ER PT J AU Ayres, TR Brown, A Harper, GM Bennett, PD Linsky, JL Carpenter, KG Robinson, RD AF Ayres, TR Brown, A Harper, GM Bennett, PD Linsky, JL Carpenter, KG Robinson, RD TI Digging deeper in the coronal graveyard SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, coronae; stars, late-type; ultraviolet, stars; X-rays, stars ID RED GIANT ARCTURUS; FAR-ULTRAVIOLET FLUORESCENCE; SOLAR-TYPE STARS; X-RAY; COOL STARS; OUTER ATMOSPHERES; DIVIDING LINE; STELLAR ACTIVITY; CARBON-MONOXIDE; MAGNETIC-FIELDS AB Soft X-ray detections of stellar coronae (T similar to 10(6) K) are rare in the giant branch redward of similar to K1 III. We have conducted a less direct-but more sensitive-search using the Hubble Space Telescope Goddard High-Resolution Spectrograph to probe for far-ultraviolet proxies of the hot coronal gas in representative "noncoronal" red giants. In every target so far examined, we find weak but statistically significant Si IV emission, as well as, commonly, C IV and, in some cases, N v. Si IV is not affected by the CNO anomalies produced by the first dredge-up, which can deplete the carbon abundance and weaken C IV. In the low-activity giants, the lambda 1393 component of the Si IV doublet must be corrected for sharp absorptions, which we believe are caused by carbon monoxide in overlying cool material. The normalized flux ratios (R = f/f(bol)) of Si IV and X-rays among the "coronal" yellow giants (lying just blueward of the "noncoronal" zone) fall on a uniform track, R-X similar to R-SiIV(2). In the noncoronal zone, however, the Si IV index is nearly constant (R-SiIV similar to 10(-8)), independent of R-X, (which ranges from similar to 10(-8) to less than or similar to 10(-10)). The mechanism that diminishes X-ray activity in the red giants is highly sensitive to an as yet unidentified stellar property. Photoelectric absorption by cool gas might play a more important role than previously suspected, particularly if hot magnetic loops are partly or completely buried in the chromosphere. C1 Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Comp Sci Corp, Astron Programs,Code 681 CSC, Greenbelt, MD 20771 USA. RP Ayres, TR (reprint author), Univ Colorado, Ctr Astrophys & Space Astron, Campus Box 389 CASA, Boulder, CO 80309 USA. RI Carpenter, Kenneth/D-4740-2012 NR 43 TC 22 Z9 22 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP 876 EP 884 DI 10.1086/304989 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600036 ER PT J AU Fontenla, J Rovira, M Tandberg-Hanssen, E AF Fontenla, J Rovira, M Tandberg-Hanssen, E TI Ultraviolet events observed in active regions. II. An interpretation of flaring arches and associated small flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, activity; Sun, flares; Sun, UV radiation; Sun, X-rays, gamma rays ID ENERGY-BALANCE; H-ALPHA; SOLAR; SPECTROMETER; NOVEMBER AB We analyze H alpha, UV, and X-ray emissions in and around the spectacular arch system seen in the corona on 1980 March 27 during the Solar Maximum Mission. The flaring of the arch plasma is studied, and its dependence on triggering mechanisms related to the observed small limb flare in the arch foot-point is analyzed. To drive these events, we propose a mechanism in which small electric current circuits and the localized magnetic free energy are continuously generated at a magnetic null by a pressure gradient, which then compress or expand the plasma. This free energy dissipates by Joule effect and upward transport. C1 Inst Astron & Fis Espacio, RA-1428 Buenos Aires, DF, Argentina. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Fontenla, J (reprint author), 771 W Dahlia St, Louisville, CO 80027 USA. NR 19 TC 0 Z9 0 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP 925 EP + DI 10.1086/304970 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600041 ER PT J AU Kankelborg, CC Walker, ABC Hoover, RB AF Kankelborg, CC Walker, ABC Hoover, RB TI Observation and modeling of soft X-ray bright points. II. Determination of temperature and energy balance SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, corona; Sun, magnetic fields; Sun, transition region; Sun, UV radiation; Sun, X-rays ID SOLAR CORONAL LOOPS; PHOTOGRAPHIC FILMS; QUIET-SUN; TELESCOPE; REGION; YOHKOH AB The Multispectral Solar Telescope Array was launched on 1991 May 13, in order to obtain narrowband images of the solar corona and transition region. Calibrated EUV and H Lyman-alpha images are used to constrain a simple loop model of the energy balance in 23 X-ray bright points (XBPs). The results are consistent with substantial back heating of the lower transition region by thermal conduction from the corona. Statistical analysis shows that length and temperature are uncorrelated for XBP loops; implications of this finding for coronal heating are discussed. Some evidence is found for a systematic imbalance between radiative and conductive losses. Inferences of effective loop cross section by modeling suggest that the coronal filling factor is nearly unity. C1 Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. EM kankel@physics.montana.edu; walker@banneker.stanford.edu; Richard.Hoover@msfc.nasa.gov NR 27 TC 28 Z9 28 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 DEC 20 PY 1997 VL 491 IS 2 BP 952 EP 966 DI 10.1086/304976 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN295 UT WOS:000071152600044 ER PT J AU Andersson, BG Wannier, PG AF Andersson, BG Wannier, PG TI Multicolor polarimetry of the dust disk candidate BD +31 degrees 643 SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; polarization; stars, individual (BD +31 degrees 643) ID OPTICAL POLARIZATION; STARS; CLOUDS; PERSEUS AB The tentative detection of a dust disk around the main-sequence star BD+31 degrees 643 was recently announced by Kalas & Jewitt and represents only the second such object ever to be imaged. Here, we present multiband visual polarimetry of this object. Our single-aperture polarimetry also strongly suggests the presence of a disk. We find that the poles of the disk are oriented parallel to the polarization of the majority of background sources in the region and, hence, probably to the magnetic field in the cloud, as would be expected from star formation theory. The polarization observed toward BD+31 degrees 643 can be modeled as a combination of Rayleigh scattering from material in the polar regions of the disk and a term due to the disk itself. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Andersson, BG (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 29 TC 9 Z9 9 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP L103 EP L106 DI 10.1086/311061 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN296 UT WOS:000071152700010 ER PT J AU Mumma, MJ Krasnopolsky, VA Abbott, MJ AF Mumma, MJ Krasnopolsky, VA Abbott, MJ TI Soft X-rays from four comets observed with EUVE SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets, general; comets, individual (Hyakutake, Hale-Bopp); scattering; solar wind; X-rays, general ID C/1996 B2 HYAKUTAKE AB EUVE observations of X-ray production rates, brightness distributions, and brightness maximum offsets from nuclei in four comets are compared with gas and dust production rates in those comets. This comparison favors charge transfer of solar wind heavy ions to cometary neutrals as a dominant process for X-ray excitation. C1 NASA, Goddard Space Flight Ctr, Catholic Univ Amer, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Ctr Euv Astrophys, Berkeley, CA 94720 USA. RP Mumma, MJ (reprint author), NASA, Goddard Space Flight Ctr, Catholic Univ Amer, Greenbelt, MD 20771 USA. RI mumma, michael/I-2764-2013; Krasnopolsky, Vladimir/L-5085-2013 NR 34 TC 60 Z9 60 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP L125 EP + DI 10.1086/311071 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN296 UT WOS:000071152700015 ER PT J AU Ofman, L Romoli, M Poletto, G Noci, G Kohl, JL AF Ofman, L Romoli, M Poletto, G Noci, G Kohl, JL TI Ultraviolet coronagraph spectrometer observations of density fluctuations in the solar wind SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; solar wind; sun, corona; sun, magnetic fields; waves ID HOLES AB Recent Ultraviolet Coronagraph Spectrometer (UVCS) white-light channel (WLC) observations on board the Solar and Heliospheric Observatory (SOHO) indicate quasi-periodic variations in the polarized brightness (pB) in the polar coronal holes, This is the first observation of possible signatures of compressional waves high above the limb (at heliocentric distances in the range 1.9-2.45 R.). The Fourier power spectrum of the pB time series at 1.9 R. shows significant peak at about 6 minutes and possible fluctuations on longer timescales (20-50 minutes), The observation at 1.9 R. is the only currently available WLC data set with sufficient cadence to resolve the 6 minute period. These preliminary observations may result from density fluctuations caused by compressional waves propagating in polar coronal holes. We stress that our results are preliminary, and we plan future high-cadence observations in both plume and interplume regions of coronal holes, Recently, Ofman & Davila used a 2.5 D MHD model and found that Alfven waves with an amplitude of 20-70 km s(-1) at the base of the coronal hole can generate nonlinear, high-amplitude compressional waves that can contribute significantly to the acceleration of the fast solar wind, The nonlinear solitary-like waves appear as fluctuations in the density and the radial outflow velocity and contribute significantly to solar wind acceleration in open magnetic field structures, The motivation for the reported observations is the MHD model prediction. C1 Hughes STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Florence, Dept Astron & Space Sci, I-50125 Florence, Italy. Osserv Astrofis Arcetri, I-50125 Florence, Italy. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Ofman, L (reprint author), Hughes STX, Code 682, Greenbelt, MD 20771 USA. RI Romoli, Marco/H-6859-2012 NR 17 TC 147 Z9 147 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1997 VL 491 IS 2 BP L111 EP L114 DI 10.1086/311067 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN296 UT WOS:000071152700012 ER PT J AU Herman, JR Celarier, EA AF Herman, JR Celarier, EA TI Earth surface reflectivity climatology at 340-380 nm from TOMS data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TOTAL OZONE; BACKSCATTER ULTRAVIOLET; INSTRUMENT AB The 340-380 nm (UV) Lambertian equivalent reflectivities (LER) of the Earth's surface, between the latitudes +/-70 degrees, are constructed from 14.5 years of radiances measured by Nimbus-7/total ozone mapping spectrometer (November 1978 to May 1993). The surface LER values are obtained from the minimum reflectivity values for each 1 degrees x 1.25 degrees (latitude x longitude) pixel with statistically improbable outlier values removed. The resulting LER climatology shows low surface reflectivity values over the entire globe at 340 and 380 nm that are nearly independent of wavelength (the difference is less than 0.2%). In general, the LER is lower over the land (2-4%) than over the oceans (5-8%), though both land and water have features outside of these ranges. Monthly maps of LER are derived that include seasonally persistent cloud features, as well as showing seasonal surface variations. There are low reflectivity regions in the ocean coastal waters that appear to be indicative of chlorophyll or silt from wave action or from rivers. There also an mid-ocean areas of comparatively high reflectivity with a seasonal variation that is not solar zenith angle dependent. These areas of high ocean reflectivity correlate with coastal zone color scanner observations that were associated with the absence of phytoplankton (clear water). C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Software Corp Amer, Lanham, MD 20706 USA. RP Herman, JR (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916, Greenbelt, MD 20771 USA. EM herman@tparty.gsfc.nasa.gov; edward.a.celarier.1@gsfc.nasa.gov OI Herman, Jay/0000-0002-9146-1632 NR 32 TC 228 Z9 237 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 DEC 20 PY 1997 VL 102 IS D23 BP 28003 EP 28011 DI 10.1029/97JD02074 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700002 ER PT J AU Hoell, JM Davis, DD Liu, SC Newell, RE Akimoto, H McNeal, RJ Bendura, RJ AF Hoell, JM Davis, DD Liu, SC Newell, RE Akimoto, H McNeal, RJ Bendura, RJ TI The Pacific Exploratory Mission West phase B: February-March, 1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HYDROXYL INSTRUMENTATION; ATMOSPHERIC NUCLEI; CARBON-MONOXIDE; NORTH PACIFIC; NITRIC-OXIDE; TRANSPORT AB The NASA Pacific Exploratory Mission in the Western Pacific Ocean (PEM-West) is a major component of the East Asia/North Pacific Regional Study (APARE), a project within the International Global Atmospheric Chemistry (IGAC) Program. The broad objectives of the PEM-West/APARE initiative are to study chemical processes and long-range transport of atmospheric trace species over the northwest Pacific Ocean and to estimate the magnitude of the human impact on these species over this region. The first phase of PEM-West (PEM-West A) was conducted in September-October 1991, a period characterized by minimum outflow from the Asian continent. The second phase of this mission, PEM-West B, was conducted during February-March 1994, a period characterized by enhanced outflow from the Asian continent. Both field campaigns of PEM-West included intensive airborne measurements of trace gases and aerosols from the NASA DC-8 aircraft coordinated with measurements at surface sites. This paper reports the experimental design for PEM-West B and provides a brief summary of the salient results of the PEM-West B campaign with particular emphases on the difference/similarities between phases A and B. Results from the two campaigns clearly quantify, from a trace gas perspective, the seasonal differences in the continental outflow that were qualitatively anticipated based upon meteorological considerations, and show the impact of major meteorological features within the region on the quality of tropospheric air over the North Pacific Ocean regions. The PEM-West database provides a "baseline" tool by which future assessments of a continuing impact of Asian emissions on remote Pacific regions can be judged. [These data are currently available through the Global Troposhperic Experiment Data Archive at NASPL's Langley Research Center (http://www-gte.larc.nasa.gov) and the Langley Distributed Archive Center (http://eosdis.larc.nasa.gov)]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Tokyo, Adv Sci & Technol Res Ctr, Meguro Ku, Tokyo 153, Japan. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Washington, DC 20546 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Hoell, JM (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 27 TC 167 Z9 171 U1 1 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 DEC 20 PY 1997 VL 102 IS D23 BP 28223 EP 28239 DI 10.1029/97JD02581 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700021 ER PT J AU Talbot, RW Dibb, JE Lefer, BL Bradshaw, JD Sandholm, ST Blake, DR Blake, NJ Sachse, GW Collins, JE Heikes, BG Merrill, JT Gregory, GL Anderson, BE Singh, HB Thornton, DC Bandy, AR Pueschel, RF AF Talbot, RW Dibb, JE Lefer, BL Bradshaw, JD Sandholm, ST Blake, DR Blake, NJ Sachse, GW Collins, JE Heikes, BG Merrill, JT Gregory, GL Anderson, BE Singh, HB Thornton, DC Bandy, AR Pueschel, RF TI Chemical characteristics of continental outflow from Asia to the troposphere over the western Pacific Ocean during February-March 1994: Results from PEM-West B SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NORTH PACIFIC; UNITED-STATES; TRANSPORT; AEROSOLS; NITRATE; RATIOS; ACID; DUST AB We present here the chemical composition of outflow from the Asian continent to the atmosphere over the western Pacific basin during the Pacific Exploratory Mission - West (PEM-West B) in February-March 1994. Comprehensive measurements of important tropospheric trace gases and aerosol particulate matter were performed from the NASA DC-8 airborne laboratory. Backward 5 day isentropic trajectories were used to partition the outflow from two major source regions: continental north (>20 degrees N) and continental south (<20 degrees N). Air parcels that had not passed over continental areas for the previous 5 days were classified as originating from an aged marine source. The trajectories and the chemistry together indicated that there was extensive rapid outflow of air parcels at altitudes below 5 km, while aged marine air was rarely encountered and only at <20 degrees N latitude. The outflow at low altitudes had enhancements in common industrial solvent vapors such as C2Cl4, CH3CCl3, and C6H6, intermixed with the combustion emission products C2H2, C2H6, CO, and NO. The mixing ratios of all species were up to tenfold greater in outflow from the continental north compared to the continental south source region, with Pb-210 concentrations reaching 38 fCi (10(-15) curies) per standard cubic meter. In the upper troposphere we again observed significant enhancements in combustion-derived species in the 8-10 km altitude range, but water-soluble trace gases and aerosol species were depleted. These observations suggest that ground level emissions were lofted to the upper troposphere by wet convective systems which stripped water-soluble components from these air parcels. There were good correlations between C2H2 and CO and C2H6 (r(2) = 0.70 - 0.97) in these air parcels and much weaker ones between C2H2 and H2O2 or CH3OOH (r(2) approximate to 0.50). These correlations were the strongest in the continental north outflow where combustion inputs appeared to be recent (I - 2 days old). Ozone and PAN showed general correlation in these same air parcels but not with the combustion products. It thus appears that several source inputs were intermixed in these upper tropospheric air masses, with possible contributions from European or Middle Eastern source regions. In aged marine air mixing ratios of O-3 (approximate to 20 parts per billion by volume) and PAN (less than or equal to 10 parts per trillion by volume) were nearly identical at <2 km and 10 - 12 km altitudes due to extensive convective uplifting of marine boundary layer air over the equatorial Pacific even in wintertime. Comparison of the Pacific Exploratory Mission-West A and PEM-West B data sets shows significantly larger mixing ratios of SO2 and H2O2 during PEM-West A. Emissions from eruption of Mount Pinatubo are a likely cause for the former, while suppressed photochemical activity in winter was probably responsible for the latter. This comparison also highlighted the twofold enhancement in C2H2, C2H6, and C3H8 in the continental north outflow during PEM-West B. Although this could be due to reduced OH oxidation rates of these species in wintertime, we argue that increased source emissions are primarily responsible. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92716 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Univ Rhode Isl, Ctr Atmospher Chem, 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, Durham, NH 03824 USA. RI Lefer, Barry/B-5417-2012 OI Lefer, Barry/0000-0001-9520-5495 NR 31 TC 97 Z9 98 U1 3 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28255 EP 28274 DI 10.1029/96JD02340 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700023 ER PT J AU Gregory, GL Merrill, JT Shipham, MC Blake, DR Sachse, GW Singh, HB AF Gregory, GL Merrill, JT Shipham, MC Blake, DR Sachse, GW Singh, HB TI Chemical characteristics of tropospheric air over the Pacific Ocean as measured during PEM-West B: Relationship to Asian outflow and trajectory history SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NORTH PACIFIC; EMISSIONS; TRANSPORT; GAS AB The Pacific Exploratory Missions (PEM) were designed to study the chemistry of tropospheric air within the Pacific Rim region extending from the equator to about 50 degrees N. Missions emphasized the importance of Asian outflow to the chemistry of tropospheric air. PEM-West A was conducted in September and October 1991, and PEM-West B was conducted in February and March 1994. The PEM-West B winter mission coincides with the time of maximum impact of Asian outflow on the Pacific Rim region. This paper examines the chemical composition of air measured during PEM-West B aircraft ascents/descents. Chemical composition of tropospheric air is related to its history as determined from 5- to 10-day back trajectory calculations at multiple altitudes of the vertical profiles. Locations and the altitudes for trajectory calculations are selected to elucidate relationships between Asian source regions, transport within the region, and the chemical characteristics of tropospheric air. Data are over-ocean measurements at locations ranging from hundreds of kilometers from the Asian coast to remote ocean sites thousands of kilometers east of Asia. Seasonal differences are illustrated by comparing PEM-West A and B results. In general, the chemical composition of tropospheric air throughout the Pacific Rim region is influenced by Asian outflow, and transported continental emissions are an important source of pollution to the region during both seasons. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aerosp Elect Syst Div, Hampton, VA 23681 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. RP Gregory, GL (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. EM g.l.gregory@larc.nasa.gov; jmerrill@boreas.gso.uri.edu; m.c.shipham@larc.nasa.gov; d.blake@orion.oac.uci.edu; g.w.sachse@larc.nasa.gov; hanwant_singh@gmgate.arc.nasa.gov NR 23 TC 33 Z9 33 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28275 EP 28285 DI 10.1029/97JD02292 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700024 ER PT J AU Dibb, JE Talbot, RW Lefer, BL Scheuer, E Gregory, GL Browell, EV Bradshaw, JD Sandholm, ST Singh, HB AF Dibb, JE Talbot, RW Lefer, BL Scheuer, E Gregory, GL Browell, EV Bradshaw, JD Sandholm, ST Singh, HB TI Distributions of beryllium 7 and lead 210, and soluble aerosol-associated ionic species over the western Pacific: PEM West B, February-March 1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BOUNDARY-LAYER; SURFACE AIR; OZONE; TRANSPORT; NITRATE; PB-210; BE-7 AB Aerosol sampling for the determination of the concentrations of soluble ionic species and the natural radionuclides Be-7 and Pb-210 was conducted from the NASA DC-8 over the western Pacific as part of GTE/PEM-West B during February - March 1994. Concentrations of most soluble ionic species in the free troposphere were higher in samples collected on flights originating from Hong Kong and Japan than those collected further east over the open ocean. In both regions the measured concentrations were higher than those found during PEM-West A (fall 1991). Activities of Pb-210, a tracer of air masses influenced by sources on the Asian continent, showed the same patterns. These data indicate the effect of stronger continental outflow from Asia over the western Pacific during the spring compared to fall season. For readily scavenged aerosol-associated species and soluble acidic gases the strongest indications of Asian outflow were restricted to altitudes below 6 km. The distribution of the continental tracer Pb-210 was also compared to those of a large number of gas phase species measured on the DC-8. Relatively strong correlations were found with O-3 and peroxyacetylnitrate (PAN), but only during the flights over the remote Pacific. During PEM-West A, similar correlations were seen, but they were stronger near Asia. We believe that these correlations are a signature of continental air that has been processed by deep wet convection over land before being advected over the ocean. One flight over the Sea of Japan provided the opportunity to sample upper troposphere/lower stratosphere air in and around a tropopause fold. Concentrations of Be-7 reached 7 pCi m(-3) STP, and peak O-3 mixing ratios of 480 ppb were encountered at 10.7 km. The Be-7 data are used to estimate the fraction of stratospheric air mixed down into the troposphere by circulation in the fold. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ New Hampshire, Dept Earth Sci, Durham, NH 03824 USA. RP Dibb, JE (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. EM jack.dibb@unh.edu RI Lefer, Barry/B-5417-2012 OI Lefer, Barry/0000-0001-9520-5495 NR 20 TC 44 Z9 44 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28287 EP 28302 DI 10.1029/96JD02981 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700025 ER PT J AU Talbot, RW Dibb, JE Lefer, BL Scheuer, EM Bradshaw, JD Sandholm, ST Smyth, S Blake, DR Blake, NJ Sachse, GW Collins, JE Gregory, GL AF Talbot, RW Dibb, JE Lefer, BL Scheuer, EM Bradshaw, JD Sandholm, ST Smyth, S Blake, DR Blake, NJ Sachse, GW Collins, JE Gregory, GL TI Large-scale distributions of tropospheric nitric, formic, and acetic acids over the western Pacific basin during wintertime SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MAUNA-LOA; PHOTOCHEMISTRY EXPERIMENT; NITRATE MEASUREMENTS; AEROSOL NITRATE; NORTH PACIFIC; STRATOSPHERE; VARIABILITY; HAWAII; HNO3 AB We report here measurements of the acidic gases nitric (HNO3), formic (HCOOH), and acetic (CH3COOH) over the western Pacific basin during the February-March 1994 Pacific Exploratory Mission-West (PEM-West B). These data were obtained aboard the NASA DC-8 research aircraft as it flew missions in the altitude range of 0.3 - 12.5 km over equatorial regions near Guam and then further westward encompassing the entire Pacific Rim are. Aged marine air over the equatorial Pacific generally exhibited mixing ratios of acidic gases <100 parts per trillion by volume (pptv). Near the Asian continent, discrete plumes encountered below 6 km altitude contained up to 8 parts per billion by volume (ppbv) HNO3 and 10 ppbv HCOOH and CH3COOH. Overall there was a general correlation between mixing ratios of acidic gases with those of CO, C2H2, and C2Cl4, indicative of emissions from combustion and industrial sources. The latitudinal distributions of HNO3 and CO showed that the largest mixing ratios were centered around 15 degrees N, while HCOOH, CH3COOH, and C2Cl4 peaked at 25 degrees N. The mixing ratios of HCOOH and CH3COOH were highly correlated (r(2)=0.87) below 6 km altitude, with a slope (0.89) characteristic of the nongrowing season at midlatitudes in the northern hemisphere. Above 6 km altitude, HCOOH and CH3COOH were marginally correlated (r(2)=0.50), and plumes well defined by CO, C2H2, and C2Cl4 were depleted in acidic gases, most likely due to scavenging during vertical transport of air masses through convective cloud systems over the Asian continent. Zn stratospheric air masses, HNO3 mixing ratios were several parts per billion by volume (ppbv), yielding relationships with O-3 and N2O consistent with those previously reported for NOy. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Talbot, RW (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. EM rwt@christa.unh.edu RI Lefer, Barry/B-5417-2012 OI Lefer, Barry/0000-0001-9520-5495 NR 31 TC 51 Z9 51 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28303 EP 28313 DI 10.1029/96JD02975 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700026 ER PT J AU Blake, NJ Blake, DR Chen, TY Collins, JE Sachse, GW Anderson, BE Rowland, FS AF Blake, NJ Blake, DR Chen, TY Collins, JE Sachse, GW Anderson, BE Rowland, FS TI Distribution and seasonality of selected hydrocarbons and halocarbons over the western Pacific basin during PEM-West A and PEM-West B SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NONMETHANE HYDROCARBON; REACTIVE CHLORINE; METHYL HALIDES; TROPOSPHERE; EMISSIONS; MIDLATITUDES; ATMOSPHERE; ETHANE; IODINE; BUDGET AB Nonmethane hydrocarbons (NMHCs) and halocarbons were measured in the troposphere over the northwestern Pacific as part of the airborne component of NASA's Pacific Exploratory Mission-West Phase B (PEM-West B). This study took place in late winter of 1994, a period characterized by maximum outflow from the Asian continent. The results are compared to those from Pacific Exploratory Mission-West Phase A (PEM-West A), which was flown in the same region during late summer of 1991, when flow from the subtropical western Pacific dominated the lower troposphere. Mixing ratios of NMHCs, tetrachloroethene (C2Cl4), and methyl bromide (CH3Br) were significantly higher during PEM-West B than during PEM-West A, particularly at latitudes north of 25 degrees N and altitudes lower than 6 lan. The primary reasons for these higher ambient concentrations were the seasonal increase in the atmospheric lifetimes of trace gases controlled by HO radical reactions, and the more frequent input of continental air masses. During PEM-West B, air masses of continental origin observed north of 25 degrees N latitude were augmented with urban signature gases such as C2Cl4. By contrast, more southerly continental outflow had characteristics associated with combustion sources such as biomass burning, including wood fuel burning. During the summer PEM-West A period, the spatial distribution of methyl iodide (CH3I) was consistent with effective oceanic sources at all latitudes, being especially strong in tropical and subtropical regions. At low latitudes, PEM-West B CH3I mixing ratios in the lower troposphere were similar to PEM-West A, but at latitudes greater than about 25 degrees N PEM-West B concentrations were significantly reduced. Equatorial regions exhibited enhanced CH3I mixing ratios extending into the upper tropical troposphere, consistent with fast vertical transport of air from the tropical marine boundary layer. C1 Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Sci & Technol Corp, Hampton, VA 23666 USA. RP Blake, NJ (reprint author), Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. EM nblake@uci.edu; drblake@uci.edu; tchen@orion.oac.uci.edu; j.e.collins@larc.nasa.gov; g.w.sachse@larc.nasa.gov; b.e.anderson@larc.nasa.gov; rowland@uci.edu NR 52 TC 100 Z9 100 U1 4 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 DEC 20 PY 1997 VL 102 IS D23 BP 28315 EP 28331 DI 10.1029/97JD02538 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700027 ER PT J AU Wu, ZX Newell, RE Zhu, Y Anderson, BE Browell, EV Gregory, GL Sachse, GW Collins, JE AF Wu, ZX Newell, RE Zhu, Y Anderson, BE Browell, EV Gregory, GL Sachse, GW Collins, JE TI Atmospheric layers measured from the NASA DC-8 during PEM-West B and comparison with PEM-West A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB The Pacific Exploratory Mission-West B (PEM-West B) explored atmospheric layer structure using measurements of O-3, H2O, CO, and CH4 from the NASA DC-8 fast-response instruments. The mission took place in February-March 1994 over the western Pacific, mainly in the northern hemisphere. Results were compared with similar measurements made during the Pacific Exploratory Mission-West A (PEM-West A) in September-October 1991. PEM-West B sampled 94 vertical profiles, with an average atmospheric depth per profile of 6.4 km, and this sampling yielded 254 discrete layers. PEM-West A sampled 105 profiles, also with a 6.4 km average depth, yielding 538 layers. Both missions revealed that layers containing high ozone and low water vapor were the most abundant, and low ozone and high water vapor layers were the next most abundant. Lidar images and potential vorticity cross sections showed the former associated with subsidence from the stratosphere in middle latitudes, spreading into the tropics. The latter was associated with convection from the boundary layer. The partition among different types of layers only changed slightly in the two missions, although PEM-West B had half as many layers. Compared to PEM-West A, PEM-West B showed only one-third the number of layers associated with polluted continental air. However, PEM-West B revealed significantly more layers showing characteristics of descended clean marine air. In some cases these layers originated from the southern hemisphere. For ozone-and water-vapor-rich layers, the ozone deviation amplitude was higher in low latitudes and lower in high latitudes in PEM-West B. The mean thickness of layers increased from about 450 m in PEM-West A to 680 m in PEM-West B. Layers also existed in the Intertropical Convergence Zone. CO2 measurements had sufficient vertical resolution to show layer structure as well. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Sci & Technol Corp, Hampton, VA 23665 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. RP Wu, ZX (reprint author), Earth Tech, 196 Baker Ave, W Concord, MA 01742 USA. EM zhong@src.com; newell@newell1.mit.edu; zhu@newell1.mit.edu; b.e.anderson@larc.nasagov; e.v.browell@larc.nasa.gov; g.l.gregory@larc.nasa.gov; g.w.sachse@larc.nasa.gov; j.e.collins@larc.nasa.gov NR 4 TC 30 Z9 30 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28353 EP 28365 DI 10.1029/97JD01097 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700029 ER PT J AU Kawakami, S Kondo, Y Koike, M Nakajima, H Gregory, GL Sachse, GW Newell, RE Browell, EV Blake, DR Rodriguez, JM Merrill, JT AF Kawakami, S Kondo, Y Koike, M Nakajima, H Gregory, GL Sachse, GW Newell, RE Browell, EV Blake, DR Rodriguez, JM Merrill, JT TI Impact of lightning and convection on reactive nitrogen in the tropical free troposphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NITRIC-OXIDE; GLOBAL DISTRIBUTION; PACIFIC-OCEAN; CARBON-MONOXIDE; BOUNDARY-LAYER; NORTH PACIFIC; OZONE; CIRCULATION; WESTERN; NOY AB Latitudinal distributions of NO, NOy, O-3, CO, CH3I, and H2O mixing ratios at 8.9-12 km were obtained between 30 degrees N and 10 degrees S by DC-8 aircraft measurements made in February 1994 during Pacific Exploratory Mission-West B (PEM-West B). Very low NO mixing ratios with a median value of 51 parts per trillion by volume (pptv) were observed at 9.5-12 km at 1 degrees N-14 degrees N during two flights made within 3 days. A very low median O-3 mixing ratio of 19 parts per billion by volume (ppbv) and high mixing ratios of H,O and CH,I were simultaneously observed, suggesting that the low NO, values were probably due to the convective transport of air from the tropical marine Boundary layer to this altitude. The median NOy/O-3 ratio being a factor of 2 smaller than in the air masses in the tropical marine boundary layer might suggest the possibility that the heterogeneous removal of HNO3 during convective transport further reduced NOy levels. In addition to the measurements between 9.5 and 12 km, low values of NOy and O-3 were observed between 4 and 12 km at 1 degrees N. Divergent wind fields at 200 and 1000 hPa and infrared (IR) cloud images show that there was large scale convection (>1000 km x 1000 km) in the northeast of New Guinea Island centered around 0 degrees S and 150 degrees E as part of systematic convective activity of the Intertropical Convergence Zone (ITCZ) and the South Pacific Convergence Zone (SPCZ). This type of large scale convection could have transported air with low levels of NOy and O-3 to the middle and upper troposphere over a wide area in the tropics. On the other hand, NO mixing ratios of 50-200 pptv and high NOx/NOy ratios of 0.4-0.6 were observed at 9.5 km between 4 degrees S and 10 degrees S. High H2O mixing ratios of 600-1200 parts per million by volume (ppmv) and low CO mixing ratios of 65 ppbv observed in the air mass indicated that the high NO values were probably due to NO production by lightning. Satellite observations showed relatively frequent lightning flashes over the New Guinea Island for 3 days prior to the aircraft measurements. These results are considered to be consistent with the idea that, in general, marine convection is not accompanied by lightning activity, whereas convection over land is. Because of the large areal extent of the influences from these processes, the convective transport of low NO air and NO production by lightning should play critical roles in controlling the abundance of reactive nitrogen in the equatorial region. C1 Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. AER Inc, Cambridge, MA 02139 USA. Univ Rhode Isl, Grad Sch Oceanog, Ctr Atmospher Chem Studies, Narragansett, RI 02882 USA. RP Kawakami, S (reprint author), Natl Space Dev Agcy Japan, Earth Observat Res Ctr, Minato Ku, 1-9-9 Roppongi, Tokyo 106, Japan. EM kawakami@eorc.nasda.go.jp; kondo@stelab.nagoya-u.ac.jp; koike@stelab.nagoya-u.ac.jp; nakajima@stelab.nagoya-u.ac.jp; g.l.gregory@larc.nasa.gov; g.w.sachse@larc.nasa.gov; newell@newell1.mit.edu; e.v.browell@larc.nasa.gov; dblake@orion.oac.uci.edu; jose_rodriguez@mailgate.aer.com; jmerrill@boreas.gso.uri.edu RI Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012; Rodriguez, Jose/G-3751-2013 OI Rodriguez, Jose/0000-0002-1902-4649 NR 41 TC 15 Z9 15 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28367 EP 28384 DI 10.1029/97JD02073 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700030 ER PT J AU Koike, M Kondo, Y Kawakami, S Nakajima, H Gregory, GL Sachse, GW Singh, HB Browell, EV Merrill, JT Newell, RE AF Koike, M Kondo, Y Kawakami, S Nakajima, H Gregory, GL Sachse, GW Singh, HB Browell, EV Merrill, JT Newell, RE TI Reactive nitrogen and its correlation with O-3 and CO over the Pacific in winter and early spring SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID WESTERN; RATIOS; NOY AB Measurements of NO, NOy, O-3, and CO were made during NASA's Global Tropospheric Experiment/Pacific Exploratory Mission-West B (GTE/PEM-West B) carried out over the western Pacific in February and March 1994. NOx was calculated from NO using a photostationary state model ((NOx)(mc)). Correlations between these species are presented, and some insights into the sources of NO, and NO, are described. The boundaries between the lower, middle, and upper troposphere have been defined at potential temperatures of 311 K and 328 K, which correspond to the geometric altitudes of about 5 and 9 km at 30 degrees N. Enhancements in the mixing ratios of NOy and CO were observed in the lower and middle troposphere. A positive correlation was found between these two species suggesting that the high NOy values were due to anthropogenic emissions over the continental surface. On the other hand, O-3 increased little with increase in CO. As a result, NOy/O-3 ratios were higher in air more influenced by pollution. NOy values in 55 and 28% of the air masses sampled in the lower and middle troposphere, respectively, were higher than the clean free tropospheric NOy-O-3 range when O-3 values simultaneously observed were used. High (NOx)(mc)/NOy ratios between 0.15 and 0.3 were found in the boundary layer with relatively low mixing ratios of CO and NO. during the three flights. These air masses were transported from a higher altitude (similar to 5 km) and a higher latitude (similar to-50 degrees N) within a few days. The peroxyacetyl nitrate (PAN)/NOy ratios were generally high (similar to 0.4) in these air masses, and the thermal decomposition of PAN was a probable source of NO,. In the middle troposphere the (NO,),, mixing ratio did not generally increase with NOy or CO, suggesting that the transport of air masses affected by anthropogenic emissions did not increase the NO, level significantly. In the upper troposphere, very minor effects from the continental surface sources were seen in the CO mixing ratio. By contrast, NOy values in 33% of the air masses were higher than those expected when stratospheric air intrusion is assumed to be a single source of NO based on NOy-O-3 correlation analyses. This result suggests significant free tropospheric NOy sources, namely exhaust from the aircraft and NO production by lightning activity. In fact, spikes in the (NOx)(mc) mixing ratios were observed near the aircraft corridor south of Tokyo at an altitude of 10 km. These two free tropospheric NOx sources were considered to be important in determining the levels of the upper tropospheric NOx and NOy during PEM-West B. C1 Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Koike, M (reprint author), Nagoya Univ, Solar Terr Environm Lab, 3-13 Honohara, Aichi 442, Japan. EM koike@stelab.nagoya-u.ac.jp; kondo@stelab.nagoya-u.ac.jp; kawakami@eorc.nasda.go.jp; nakajima@stelab.nagoya-u.ac.jp; g.l.gregory@larc.nasa.gov; g.w.sachse@larc.nasa.gov; hb_singh@arc.nasa.gov; e.v.browell@larc.nasa.gov; jmerrill@borras.gso.uri.edu; newell@newell1.mit.edu RI Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012 NR 28 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28385 EP 28404 DI 10.1029/97JD02085 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700031 ER PT J AU Kondo, Y Koike, M Kawakami, S Singh, HB Nakajima, H Gregory, GL Blake, DR Sachse, GW Merrill, JT Newell, RE AF Kondo, Y Koike, M Kawakami, S Singh, HB Nakajima, H Gregory, GL Blake, DR Sachse, GW Merrill, JT Newell, RE TI Profiles and partitioning of reactive nitrogen over the Pacific Ocean in winter and early spring SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID UNITED-STATES; ORGANIC NITRATES; EASTERN PACIFIC; CARBON-MONOXIDE; BOUNDARY-LAYER; NORTH PACIFIC; NIWOT RIDGE; TROPOSPHERE; NOY; HYDROCARBONS AB Measurements of NO, NOy, PAN, HNO3, O-3, CO, CH4, nonmethane hydrocarbons (NMHCs), and H2O were made over the Pacific Ocean in February and March during the Pacific Exploratory Mission West B (PEM-West B). NOx was calculated from NO using a photochemical model. These data were classified according to six air mass categories: western Pacific maritime, tropical, tropical convective, western Pacific continental, high latitude, and stratospheric. It has been found that the mixing ratios of many of the observed species and partitioning of NOy varied significantly depending on altitude, air mass, and season. These variations have been interpreted in terms of chemical and transport processes. In the maritime air below 7 km, the mixing ratios of calculated NOx ((NOx)(mc)), PAN, and NOy were lower than those in the continental air masses. The lowest values of PAN, HNO3, NOy, and O-3 were observed in the tropical region below 5 km. In the continental air, NOy, PAN, CO, and NMHC levels below 4 km were much higher than those obtained in September and October during PEM-West A, due to rapid transport of these species from anthropogenic sources on the continent to the Pacific Ocean by the westerly winds which dominated in early winter and spring. Reduced photochemistry during winter also contributed to the higher values of CO and NMHCs. Above 7 km the values of these species were lower during PEM-West B, possibly due to much weaker convective activity in early spring. In spite of the weaker vertical transport, the median values of (NOx)(mc) and the (NOx)(mc)/C3H8 ratio at 10 km were 110-140 parts per trillion by volume (pptv) and 2.9-3.4 pptv/pptv, respectively, in the continental and maritime air masses, indicating the importance of in situ NOx production in the upper troposphere. In the continental air the PAN/NOy and HNO3/NOy ratios ranged between 0.2 and 0.5, showing clear anticorrelation. The PAN/NOy ratio was also anticorrelated with the temperature. In the high-latitude air between 1 and 7 km the PAN/NOy ratio was 0.5-0.8, and the (NOx)(mc)/NOy ratio was less than 0.05. Temperature and the concentrations of OH and NMHCs are considered to have strongly influenced the partitioning of NOy at middle and high latitudes. Generally, the sum of (NOx)(mc), PAN, and HNO3 constituted 90 +/- 10% of the observed NOy from the boundary layer up to 7 km in all types of air masses. This finding improves our basic understanding on the chemistry and budget of the reactive nitrogen. C1 Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Rhode Isl, Grad Sch Oceanog, Ctr Atmospher Chem Studies, Narragansett, RI 02882 USA. MIT, Cambridge, MA 02139 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Kondo, Y (reprint author), Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. EM kondo@stelab.nagoya-u.ac.jp; dblake@orion.oac.uci.edu RI Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012 NR 41 TC 51 Z9 51 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28405 EP 28424 DI 10.1029/96JD03818 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700032 ER PT J AU Kotamarthi, VR Rodriguez, JM Sze, ND Kondo, Y Pueschel, R Ferry, G Bradshaw, J Sandholm, S Gregory, G Davis, D Liu, S AF Kotamarthi, VR Rodriguez, JM Sze, ND Kondo, Y Pueschel, R Ferry, G Bradshaw, J Sandholm, S Gregory, G Davis, D Liu, S TI Evidence of heterogeneous chemistry on sulfate aerosols in stratospherically influenced air masses sampled during PEM-West B SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC AIR; OZONE BUDGET; AASE-II; MODEL; NOX; N2O5; PHOTOCHEMISTRY; CONVERSION; PACIFIC; RATIO AB Signatures of the N2O5 hydrolysis by sulfate aerosols have been previously documented, primarily from balloon and remote-sensing platforms, by measurements of nitrogen species aboard the NASA ER-2 flying at an altitude of approximately 20 km and some ER-2 and DC-8 measurements near the tropopause during stratospheric campaigns. This study documents such signatures in the NOX/NOY ratios derived from DC-8 measurements during Pacific Exploratory Measurements in the Western Pacific Ocean (PEM-West B) in stratospherically influenced air masses sampled during a level leg at an altitude of 10.7 km in flight 17 out of Japan. Despite the very low abundance of total bromine, we also show that heterogeneous hydrolysis of BrNO3 on sulphate aerosols can catalytically convert NOX and liquid H2O into HNO3 and OH and thereby lower the calculated equilibrium NOx/NOy by about 20 to 35% in these air masses, bringing closer agreement with the nitrogen partitioning deduced from measurements. However, the NOx/NO ratios calculated from a model including heterogeneous chemistry were a factor of 3 smaller than ratios derived from data for a segment of this flight leg when DC-8 measurements indicated a stronger tropospheric influence. We also modeled the equilibrium partitioning of nitrogen species for all upper tropospheric air masses encountered by the DC-8; since NOy in the troposphere may contain nonnegligible contributions from long-lived nitrates (such as peroxyacetylnitrate), we have compared instead modeled and measured NOx/HNO3. The calculated equilibrium NOx/HNO3 ratios using only gas-phase chemistry are on the average smaller than those deduced from measurements in upper tropospheric air masses; inclusion of N2O5 hydrolysis reduces these ratios by an additional 20%, thus worsening the discrepancy. These results suggest a rapid transition from "denoxified" conditions in the lower stratosphere to "renoxified" conditions in the upper troposphere. This transition could be due to intrinsically different chemistry in the troposphere. Alternatively, rapid transport in the troposphere could keep the NOx and HNO3 away from chemical equilibrium. Detailed analysis of current and future tropospheric data could shed light on this issue. C1 Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. RP Kotamarthi, VR (reprint author), Argonne Natl Lab, 9700 S Cass Ave, Argonne, IL 60439 USA. EM rao@maria.er.anl.gov; jose_rodriguez@aer.com; dsze@aer.com; kondo@steldb.nagoya.u.ac.jp; rpueschel@mail.arc.nasa.gov; guy@aerosol.arc.nasa.gov; ss27@prism.gatech.edu; g.l.gregory@larc.nasa.gov; dpiyard@aol.com; shaw.liu@eas.gatech.edu RI Kondo, Yutaka/D-1459-2012; Rodriguez, Jose/G-3751-2013; OI Rodriguez, Jose/0000-0002-1902-4649; Kotamarthi, Veerabhadra Rao/0000-0002-2612-7590 NR 38 TC 10 Z9 10 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28425 EP 28436 DI 10.1029/97JD02511 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700033 ER PT J AU Thompson, AM Singh, HB Stewart, RW Kucsera, TL Kondo, Y AF Thompson, AM Singh, HB Stewart, RW Kucsera, TL Kondo, Y TI A Monte Carlo study of upper tropospheric reactive nitrogen during the Pacific Exploratory Mission in the Western Pacific Ocean (PEM-West B) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE AB A subset of Pacific Exploratory Mission in the Western Pacific Ocean (PEM-West B) data (northwestern Pacific, March 1994), selected to represent upper troposphere (UT) midlatitude conditions, is analyzed to answer the following questions: (1) Is there a shortfall in total reactive nitrogen (NOy) as measured during PEM-West B in this region? (2) If so, what are the likely contributions of interfering constituents like HCN or of other reactive nitrogen species? For question 1 our analyses show that 87% of total reactive nitrogen measured in the UT is accounted for by NOx + HNO3 + PAN (similar to Kondo et al. [this issue (a, b)], Talbot et al. [this issue], and Singh et al. [1997a, bl). For question 2 we find that less than 20 pptv (<5% of mean NOy) is possibly HCN. A one-dimensional model that simulates mean mixing ratios of this PEM-West B data is used with a Monte Carlo approach to explore other candidates for unmeasured nitrogen species and NO, partitioning. Using standard gas-phase reactions with varying rate coefficients [Thompson and Stewart, 1991; Stewart and Thompson, 1996], it is found, on average, that NOx + HNO3 + PAN = 399 pptv (observed mean equal to 432 +/- 97 pptv). A more complete inventory for total reactive nitrogen (Sigma NOi = NOx + HNO3 + PAN + HNO4 + CH3O2NO2 + allyl nitrates + C2H5O2NO2) is 494 +/- 91 pptv, with 19% consisting of HNO4 + CH3O2NO2 + alkyl nitrates. Thus, whether unmeasured forms of reactive nitrogen are present or not, total reactive nitrogen as measured at midlatitude UT during PEM-West B is accounted for within the measurement uncertainty. The greatest kinetics uncertainties are in thermolytic losses for HNO4, PAN, and CH3O2NO2 (120-150% by the method of Stewart and Thompson [1996]). Nonetheless, comparison with PEM-West B data shows that panel-recommended kinetics expressions [Demore et al., 1994] can explain reactive nitrogen observations without invoking extreme rates or heterogeneous processes. In summary, large concentrations of unmeasured reactive nitrogen species were not prevalent during midlatitude UT PEM-West B sampling although the observed shortfall (13%) can be explained by HNO4 + alkyl nitrates + CH3O2NO2. Agreement between theory and observations may also reflect improved instrument capabilities for measuring reactive nitrogen. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Nagoya Univ, Solar Terr Environm Lab, Tokoyawa, Japan. NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Thompson, AM (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916, Greenbelt, MD 20771 USA. EM thompson@gatorl.gsfc.nasa.gov; hsingh@mail.arc.nasa.gov; stewart@oasis.gsfc.nasa.gov; tlk@croc.gsfc.nasa.gov; kondo@stelab.nagoya-u.ac.jp RI Kondo, Yutaka/D-1459-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 17 TC 6 Z9 6 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 DEC 20 PY 1997 VL 102 IS D23 BP 28437 EP 28446 DI 10.1029/97JD02555 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700034 ER PT J AU Crawford, JH Davis, DD Chen, G Bradshaw, J Sandholm, S Kondo, Y Merrill, J Liu, S Browell, E Gregory, G Anderson, B Sachse, G Barrick, J Blake, D Talbot, R Pueschel, R AF Crawford, JH Davis, DD Chen, G Bradshaw, J Sandholm, S Kondo, Y Merrill, J Liu, S Browell, E Gregory, G Anderson, B Sachse, G Barrick, J Blake, D Talbot, R Pueschel, R TI Implications of large scale shifts in tropospheric NOx levels in the remote tropical Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NITRIC-OXIDE MEASUREMENTS; CENTRAL NORTH PACIFIC; PHOTOCHEMICAL PRODUCTION; PHOTOSTATIONARY STATE; GLOBAL DISTRIBUTION; EQUATORIAL PACIFIC; OZONE PRODUCTION; VERTICAL FLUX; MODEL; EMISSIONS AB A major observation recorded during NASA's western Pacific Exploratory Mission (PEM-West B) was the large shift in tropical NO levels as a function of geographical location. High-altitude NO levels exceeding 100 pptv were observed during portions of tropical flights 5-8, while values almost never exceeded 20 pptv during tropical flights 9 and 10. The geographical regions encompassing these two flight groupings are here labeled "high" and "low" NOx regimes. A comparison of these two regimes, based on back trajectories and chemical tracers, suggests that air parcels in both were strongly influenced by deep convection. The low NOx regime appears to have been predominantly impacted by marine convection, whereas the high NOx regime shows evidence of having been more influenced by deep convection over a continental land mass. DMSP satellite observations point strongly toward lightning as the major source of NO, in the latter regime. Photochemical ozone formation in the high NOx regime exceeded that for low NOx by factors of 2 to 6, whereas O-3 destruction in the low NOx regime exceeded that for high NOx by factors of up to 3. Taking the tropopause height to be 17 km, estimates of the net photochemical effect on the O-3 column revealed that the high NO, regime led to a small net production. By contrast, the low NO, regime was shown to destroy O-3 at the rate of 3.4% per day. One proposed mechanism for off-setting this projected large deficit would involve the transport of O-3 rich midlatitude air into the tropics. Alternatively, it is suggested that O-3 within the tropics may be overall near self-sustaining with respect to photochemical activity. This scenario would require that some tropical regions, unsampled at the time of PEM-B, display significant net column O-3 production, leading to an overall balanced budget for the "greater" tropical Pacific basin. Details concerning the chemical nature of such regimes are discussed. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Univ Calif Irvine, Dept Chem, CMOO Gen Dept, Irvine, CA 92717 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. 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 Crawford, JH (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. EM crawford@asdsun.larc.nasa.gov; douglas.davis@eas.gatech.edu; gc37@prism.gatech.edu; scott.sandholm@eas.gatech.edu; kondo@stelab.nagoya.u.ac.jp; jmerrill@boreas.gso.uri.edu; shaw.liu@eas.gatech.edu; e.v.browell@larc.nasa.gov; g.l.gregory@larc.nasa.gov; b.e.anderson@larc.nasa.gov; g.w.sachse@larc.nasa.gov; j.d.barrick@larc.nasa.gov; dblake@orion.oac.uci.edu; rwt@christa.unh.edu; rudolf_pueschel@qmgate.arc.nasa.gov RI Kondo, Yutaka/D-1459-2012; Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 69 TC 44 Z9 44 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28447 EP 28468 DI 10.1029/97JD00011 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700035 ER PT J AU Crawford, J Davis, D Chen, G Bradshaw, J Sandholm, S Kondo, Y Liu, S Browell, E Gregory, G Anderson, B Sachse, G Collins, J Barrick, J Blake, D Talbot, R Singh, H AF Crawford, J Davis, D Chen, G Bradshaw, J Sandholm, S Kondo, Y Liu, S Browell, E Gregory, G Anderson, B Sachse, G Collins, J Barrick, J Blake, D Talbot, R Singh, H TI An assessment of ozone photochemistry in the extratropical western North Pacific: Impact of continental outflow during the late winter early spring SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; VERTICAL FLUX; CHEMISTRY; MODEL; CONSTITUENTS; STRATOSPHERE; OH AB This study examines the influence of photochemical processes on tropospheric ozone distributions over the extratropical western North Pacific. The analysis presented here is based on data collected during the Pacific Exploratory Mission-West Phase B (PEM-West B) field study conducted in February-March 1994. Sampling in the study region involved altitudes of 0-12 km and latitudes of 10 degrees S to 50 degrees N. The extratropical component of the data set (i.e., 20-50 degrees N) was defined by markedly different photochemical environments north and south of 30 degrees N. This separation was clearly defined by an abrupt decrease in the tropopause height near 30 degrees N and a concomitant increase in total O-3 Column density. This shift in overhead O-3 led to highly reduced rates of O-3 formation and destruction for the 30-50 degrees N latitude regime. Both latitude ranges, however, still exhibited net O-3 production at all altitudes. Of special significance was the finding that net O-3 production prevailed even at boundary layer and lower free tropospheric altitudes (e.g., less than or equal to 4 km), a condition uncommon to Pacific marine environments. These results reflect the strong impact of continental outflow of O-3 precursors (e.g., NO and NMHCs) into the northwestern Pacific Basin. Comparisons with PEM-West A, which sampled the same region in a different season (September-October), revealed major differences at altitudes below 4 km, the altitude range most influenced by continental outflow. The resulting net rate of increase in the tropospheric O-3 column for PEM-West B was 1-3% per day, while for PEM-West A it was approximately zero. Unique to the PEM-West B study is the finding that even under wintertime conditions substantial column production of tropospheric O-3 can occur at subtropical and mid-latitudes. While such impacts may not be totally unexpected at near coast locations, the present study suggests that the impact from continental outflow on the marine BL could extend out to distances of more than 2000 km from the Asian Pacific Rim. C1 Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Calif Irvine, Chem CMOO Gen Dept, Irvine, CA 92717 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Crawford, J (reprint author), Georgia Inst Technol, Sch Earth & Atmospher Sci, 221 Bobby Dodd Way, Atlanta, GA 30332 USA. EM douglas.davis@eas.gatech.edu; gc37@prism.gatech.edu; scott.sandholm@eas.gatech.edu; kondo@stelab.nagoya.u.ac.jp; shaw.liu@eas.gatech.edu; e.v.browell@larc.nasa.gov; g.l.gregory@larc.nasa.gov; b.e.anderson@larc.nasa.gov; g.w.sachse@larc.nasa.gov; j.d.barrick@larc.nasa.gov; dblake@orion.oac.uci.edu; rwt@christa.unh.edu; hanwant_singh@qmgate.arc.nasa.gov RI Kondo, Yutaka/D-1459-2012; Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 30 TC 74 Z9 74 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1997 VL 102 IS D23 BP 28469 EP 28487 DI 10.1029/97JD02600 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN380 UT WOS:000071162700036 ER PT J AU Andronache, C Chameides, WL Davis, DD Anderson, BE Pueschel, RF Bandy, AR Thornton, DC Talbot, RW Kasibhatla, P Kiang, CS AF Andronache, C Chameides, WL Davis, DD Anderson, BE Pueschel, RF Bandy, AR Thornton, DC Talbot, RW Kasibhatla, P Kiang, CS TI Gas-to-particle conversion of tropospheric sulfur as estimated from observations in the western North Pacific during PEM-West B SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MARINE BOUNDARY-LAYER; CLOUD CONDENSATION NUCLEI; ATMOSPHERIC NUCLEI; SULFATE AEROSOLS; VAPOR-PRESSURES; ACID; NUCLEATION; WATER; DISTRIBUTIONS; TEMPERATURE AB Aircraft observations during the Pacific Exploratory Mission in the western Pacific Ocean, phase B (PEM-West B), taken in February-March 1994, have been used to constrain a numerical model that calculates local concentrations of gaseous H2SO4, rates of homogeneous nucleation, and concentrations of newly formed, nanometer-sized particles. The data was selected from 13 flights over the western Pacific Ocean that covered an altitude range from the boundary layer (BL) to the upper troposphere (UT) and latitudes from 10 degrees S to 60 degrees N. The largest nucleation rates were calculated for the data from the flights over the temperate latitudes (lambda>30 degrees N). Within these latitudes, homogeneous nucleation rates averaged about 1-100 particles cm(-3) s(-1). Significantly smaller nucleation rates were calculated for the tropical (lambda<20 degrees N and subtropical (20 degrees N CH2D + H, k(1a)(infinity) = (2.3 +/- 0.6) x 10(-10) cm(3) molecule(-1) s(-1); (Ib) CH2D + D --> CHD2 + H, k(1b)(infinity) = 2.1 +/- 0.5) x 10(-10) cm(3) molecule(-1) s(-1); (Ic) CHD2 + D --> CD3 + H, k(1c)(infinity) = (1.9 +/- 0.5) x 10(-10) cm(3) molecule(-1) s(-1). These, in turn, can be corrected for isotopic substitution and averaged to give a value of (2.9 +/- 0.7) x 10(-10) cm(3) molecule(-1) s(-1) for the limiting high-pressure recombination rate coefficient of CH3 and H. The errors of similar to 25% are estimates of both the statistical and systematic errors in the measurements and calculations. The results are in agreement with an earlier direct determination of reaction la and recent theoretical calculations. The previous direct studies of CH3 + H in the fall off region have been reanalyzed using master equation techniques and are now shown to be in good agreement with current experimental and theoretical calculations. Reaction Ic was also studied at 200 K, with k(1c) failing by approximately 35% from its room-temperature value, confirming theoretical predictions of a positive temperature dependence for the high-pressure Limiting rate coefficient for the reaction CH3 + H + M --> CH4 + M. C1 Univ Leeds, Sch Chem, Leeds LS2 9JT, W Yorkshire, England. Queens Univ, Dept Chem, Kingston, ON K7L 3N6, Canada. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Seakins, PW (reprint author), Mol Simulat Inc, 240-250 Quorum,Barnwell Rd, Cambridge CB5 8RE, England. NR 56 TC 27 Z9 27 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD DEC 18 PY 1997 VL 101 IS 51 BP 9974 EP 9987 DI 10.1021/jp9720348 PG 14 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YP423 UT WOS:000071275300020 ER PT J AU Parks, G Brittnacher, M Chen, LJ Elsen, R McCarthy, M Germany, G Spann, J AF Parks, G Brittnacher, M Chen, LJ Elsen, R McCarthy, M Germany, G Spann, J TI Does the UVI on polar detect cosmic snowballs? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EARTHS UPPER-ATMOSPHERE; SMALL COMETS; INFLUX AB If 20 to 40 ton cosmic snowballs pelt Earth as claimed by Frank and Sigwarth [1997a], dark pixels will be produced in the 130.4 nm images of dayglow obtained by the Ultraviolet Imager (UVI) on the Polar spacecraft. Examination of the UVI images has revealed that dayglow images are indeed spotted with single and multiple dark pixels. But is a snowball the only explanation for these dark pixels? To learn more about the dark pixels, we have examined the calibration images obtained from the same camera just before the instrument was launched. We find that dark pixels similar to those in dayglow images also exist in calibration images. This strongly indicates that the source of the dark pixels is instrumental. For further verification, a statistical analysis found the dark pixels from dayglow and calibration images have nearly identically shaped occurrence patterns. We have also looked for evidence of spacecraft "wobble" which demonstrates that the source of a bright or dark feature in the images is external to the camera, but found none for dark pixels. Finally, we studied the bright streaks that frequently appear in UVI images, sometimes comet-like in appearance. These trails are ionization tracks produced by cosmic rays or other penetrating energetic particles interacting with our camera. We conclude that the source of the dark pixels in dayglow images is internal to the camera system and there is no scientific evidence from UVI that snowballs pelt Earth. C1 Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Alabama, CSPAR, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Parks, G (reprint author), Univ Washington, Geophys Program, Box 351650, Seattle, WA 98195 USA. RI Chen, Li-Jen/C-2106-2012 NR 6 TC 14 Z9 14 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3109 EP 3112 DI 10.1029/97GL03005 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700002 ER PT J AU Tsurutani, BT Lakhina, GS Neubauer, FM Glassmeier, KH AF Tsurutani, BT Lakhina, GS Neubauer, FM Glassmeier, KH TI A new look at the nature of comet Halley's LF electromagnetic waves: Giotto observations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETIC-FIELD FLUCTUATIONS; ALFVEN WAVES; INTERPLANETARY DISCONTINUITIES; PLASMA TURBULENCE; GIACOBINI-ZINNER; BOW SHOCK; FREQUENCY; P/HALLEY; ULYSSES; INSTABILITIES AB All of the comet Halley high-time resolution magnetic field data have been examined to determine the nature of the "turbulence" and its difference from that of comets Giacobini-Zinner and Grigg-Skjellerup. Although much of the wave appears unpolarized, occasionally there are intervals of clear order. We find several interesting new wave polarizations: arc-, left-hand/arc- (sunglass) and left-hand circular polarized waves (in the spacecraft frame). The former two types have separations of similar to 120 s between individual pulses, indicating that the waves are generated from pickup of the H2O group cometary ions. The third type of waves occurs in a wave-train and may be a detached whistler packet. The unusual polarizations could be caused by wave refraction in the highly turbulent (and high beta) Halley environment or by nonlinear evolution due to strong growth rates. It is noted that some of the large amplitude waves are non-planar. These results are further details of the "linear polarization" of Halley waves determined by previous coherency analyses, and may explain some of the evolution leading to its plasma turbulence. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Tech Univ Braunschweig, Inst Geophys, D-3300 Braunschweig, Germany. Univ Cologne, Inst Geophys & Meteorol, Cologne 41, Germany. Indian Inst Geomagnetism, Bombay 400005, Maharashtra, India. RP Tsurutani, BT (reprint author), CALTECH, Jet Prop Lab, MS 169-506,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 25 TC 10 Z9 10 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3129 EP 3132 DI 10.1029/97GL03222 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700007 ER PT J AU Sibeck, DG Takahashi, K Kokubun, S Mukai, T Ogilvie, KW Szabo, A AF Sibeck, DG Takahashi, K Kokubun, S Mukai, T Ogilvie, KW Szabo, A TI A case study of oppositely propagating Alfvenic fluctuations in the solar wind and magnetosheath SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID BOW SHOCK; DYNAMIC PRESSURE; MAGNETOPAUSE; WAVES AB MHD solutions indicate that solar wind Alfvenic fluctuations striking the bow shock should launch a variety of disturbances into the magnetosheath, including both forward (antisunward) and reverse (sunward) propagating Alfvenic fluctuations. We present the first observational evidence of this prediction. This case study presents observations of the Wind spacecraft of Alfvenic fluctuations propagating antisunward along the away sector Parker spiral interplanetary magnetic field (IMF) on April 26 to 27, 1995. Simultaneous Geotail solar wind observations confirm the presence of Alfvenic fluctuations propagating along the spiral IMF, but Geotail magnetosheath observations indicate Alfvenic fluctuations propagating in the opposite direction relative to the draped, prenoon, magnetic field. The reversal in wave propagation direction at the bow shock provides striking evidence for the MHD model of wave-shock interaction. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Nagoya Univ, Solar Terr Environm Lab, Toyokawa, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Sibeck, DG (reprint author), Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RI Sibeck, David/D-4424-2012 NR 14 TC 18 Z9 18 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3133 EP 3136 DI 10.1029/97GL03263 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700008 ER PT J AU Whang, YC Fairfield, D Smith, EJ Lepping, RP Kokubun, S Saito, Y AF Whang, YC Fairfield, D Smith, EJ Lepping, RP Kokubun, S Saito, Y TI Observations of double discontinuities in the magnetotail SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SLOW-MODE SHOCKS; GEOMAGNETIC TAIL; SOLAR-WIND AB Observations of slow shocks in the Earth's magnetotail at the plasma sheet-lobe boundaries have been well documented. We restudy the magnetic field data of two slow shocks: one was observed from Geotail on January 17, 1994 at X-GSE = -92 RE and another was observed from ISEE-3 on February 2, 1983 at X-GSE = -220 R-E. In both cases, the slow shock layer was followed by an adjoining rotational discontinuity layer on the postshock side. Compound structures each composed of a slow shock layer and an adjoining rotational discontinuity layer have been recently observed in interplanetary space from Wind, Geotail and Imp-g. Because the two successive discontinuities are very close to each other, the compound structure looks like a new kind of MHD discontinuity. It may be called a double discontinuity. Since double discontinuities exist not only in interplanetary space but also in the magnetotail region, they could be a general MHD structure in space plasma. C1 Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Inst Space & Astronaut Sci, Kanagawa 229, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Whang, YC (reprint author), Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NR 15 TC 15 Z9 15 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3153 EP 3156 DI 10.1029/97GL03164 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700013 ER PT J AU Valdivia, JA Milikh, G Papadopoulos, K AF Valdivia, JA Milikh, G Papadopoulos, K TI Red sprites: Lightning as a fractal antenna SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OPTICAL FLASHES; IONIZATION; PULSES; EMP AB A new and improved model of red sprites is presented. Emphasis is placed in accounting for the puzzling observation of the spatial structure in the red sprite's optical emissions. The model relies upon a horizontal fractal lightning discharge, which generates the EMPs that excites the optical emissions in the lower ionosphere. It is shown that the fractal model may account for the observed sprite's spatially structured optical pattern, while reducing the typical charge threshold to approximately 100 C. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. RP Valdivia, JA (reprint author), NASA, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 18 TC 51 Z9 54 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3169 EP 3172 DI 10.1029/97GL03188 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700017 ER PT J AU Jaegle, L Jacob, DJ Wennberg, PO Spivakovsky, CM Hanisco, TF Lanzendorf, EJ Hintsa, EJ Fahey, DW Keim, ER Proffitt, MH Atlas, EL Flocke, F Schauffler, S McElroy, CT Midwinter, C Pfister, L Wilson, JC AF Jaegle, L Jacob, DJ Wennberg, PO Spivakovsky, CM Hanisco, TF Lanzendorf, EJ Hintsa, EJ Fahey, DW Keim, ER Proffitt, MH Atlas, EL Flocke, F Schauffler, S McElroy, CT Midwinter, C Pfister, L Wilson, JC TI Observed OH and HO2 in the upper troposphere suggest a major source from convective injection of peroxides SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID IN-SITU MEASUREMENTS; OXYGENATED HYDROCARBONS; OZONE; STRATOSPHERE; CONSTRAINTS; ATMOSPHERE; TRANSPORT; CHEMISTRY; AIRCRAFT; AIR AB ER-2 aircraft observations of OH and HO2 concentrations in the upper troposphere during the NASA/STRAT campaign are interpreted using a photochemical model constrained by local observations of O-3, H2O, NO, CO, hydrocarbons, albedo and overhead ozone column. We find that the reaction O(D-1) + H2O is minor compared to acetone photolysis as a primary source of HOx (= OH + peroxy radicals) in the upper troposphere. Calculations using a diel steady state model agree with observed HOx concentrations in the lower stratosphere and, for some flights, in the upper troposphere. However, for other flights in the upper troposphere, the steady state model underestimates observations by a factor of 2 or more. These model underestimates are found to be related to a recent (< 1 week) convective origin of the air. By conducting time-dependent model calculations along air trajectories determined for the STRAT flights, we show that convective injection of CH3OOH and H2O2 from the boundary layer to the upper troposphere could resolve the discrepancy. These injections of HOx reservoirs cause large HOx increases in the tropical upper troposphere for over a week downwind of the convective activity. We propose that this mechanism provides a major source of HOx in the upper troposphere. Simultaneous measurements of peroxides, formaldehyde and acetone along with OH and HO2 are needed to test our hypothesis. C1 Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. Atmospher Environm Serv, Downsview, ON M3H 5TA, Canada. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Denver, Denver, CO 80208 USA. RP Jaegle, L (reprint author), Harvard Univ, Dept Earth & Planetary Sci, 29 Oxford St,Pierce Hall, Cambridge, MA 02138 USA. RI Wennberg, Paul/A-5460-2012; Atlas, Elliot/J-8171-2015; Fahey, David/G-4499-2013 OI Fahey, David/0000-0003-1720-0634 NR 22 TC 124 Z9 125 U1 1 U2 22 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3181 EP 3184 DI 10.1029/97GL03004 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700020 ER PT J AU Folkins, I Wennberg, PO Hanisco, TF Anderson, JG Salawitch, RJ AF Folkins, I Wennberg, PO Hanisco, TF Anderson, JG Salawitch, RJ TI OH, HO2, and NO in two biomass burning plumes: Sources of HOx and implications for ozone production SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CLOUD AB The ER-2 made two descents through upper tropospheric biomass burning plumes during ASHOE/MAESA. HOx (= OH + HO2) concentrations are largely self-limited outside the plumes, but become progressively more limited by reactions with NOx (= NO + NO2) at the higher NOx concentrations inside the plumes. Sources of HOx in addition to H2O and CH4 oxidation are required to balance the known HOx sinks both in the plumes and in the background upper troposphere. HOx concentrations were consistently underestimated by a model constrained by observed NOx concentrations. The size of the model underestimate is reduced when acetone photolysis is included. Models which do not include the additional HOx sources required to balance the HOx budget are likely to underestimate ozone production rates. C1 Dalhousie Univ, Dept Oceanog, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Dalhousie Univ, Dept Phys, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. Harvard Univ, Dept Chem & Biol Chem, Cambridge, MA 02138 USA. RP Folkins, I (reprint author), Dalhousie Univ, Dept Oceanog, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. RI Salawitch, Ross/B-4605-2009; Wennberg, Paul/A-5460-2012 OI Salawitch, Ross/0000-0001-8597-5832; NR 9 TC 30 Z9 30 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3185 EP 3188 DI 10.1029/97GL03047 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700021 ER PT J AU Considine, GD Deaver, L Remsberg, EE Russell, JM AF Considine, GD Deaver, L Remsberg, EE Russell, JM TI HALOE observations of a slowdown in the rate of increase of HF in the lower mesosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB A statistical analysis of monthly averaged HF measurements from HALOE shows definite signs of a slowdown of the increase in HF at 55 km. The data used in this study are monthly averaged HF data from a latitude band from 50N to 50S at an altitude of 55 km. We find that the combination of a third-order polynomial, an annual and semi-annual cycle, and a 900-day cycle provides a good model of the data. The changes in the HF trend are consistent with the trends of CFC-11 and CFC-12 in the troposphere in the early 1990's, adjusted by an estimated lag time to account for transport from the troposphere up to 55 km. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. RP Considine, GD (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NR 6 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3217 EP 3220 DI 10.1029/97GL03301 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700029 ER PT J AU Callis, LB AF Callis, LB TI Odd nitrogen formed by energetic electron precipitation as calculated from TIROS data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MIDDLE ATMOSPHERE AB Daily odd nitrogen formation due to energetic electron precipitation has been calculated for 840101 through 841231. Electron energy spectra between 4.25 and 1050 keV were used as derived from TED and MEPED observations made aboard NOAA spacecraft. Results indicate the importance of electron precipitation to the middle atmospheric NOy budget between 70 and 111 km. The column NOy source for 42 less than or equal to Z less than or equal to 111 km and for invariant latitudes between 63 degrees and 76 degrees in both hemispheres is calculated to be approximate to 13 times that of the global source of NOy derived from N2O. This source is. larger in the southern hemisphere and is dominated by electrons which deposit their energy above 80 km. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Callis, LB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 401B, Hampton, VA 23681 USA. NR 14 TC 19 Z9 19 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3237 EP 3240 DI 10.1029/97GL03276 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700034 ER PT J AU Mauritzen, C Hakkinen, S AF Mauritzen, C Hakkinen, S TI Influence of sea ice on the thermohaline circulation in the Arctic-North Atlantic Ocean SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERANNUAL VARIABILITY; SIMULATION; TRANSPORT; SYSTEM; WATER; MODEL AB A fully prognostic coupled ocean-ice model is used to study the sensitivity of the overturning cell of the Arctic-North-Atlantic system to sea ice forcing. The strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the Arctic to the Greenland Sea and further to the subpolar gyre. The model produces a 2-3 Sv increase of the meridional circulation cell at 25N (at the simulation year 15) corresponding to a decrease of 800 km(3) in the sea ice export from the Arctic. Previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic, implying that sea ice induced variability in the overturning cell can reach 5-6 Sv from peak to peak. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Natl Res Council, Greenbelt, MD 20771 USA. RP Mauritzen, C (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Natl Res Council, MC 971, Greenbelt, MD 20771 USA. RI Hakkinen, Sirpa/E-1461-2012 NR 17 TC 62 Z9 64 U1 1 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1997 VL 24 IS 24 BP 3257 EP 3260 DI 10.1029/97GL03192 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YN927 UT WOS:000071222700039 ER PT J AU Crawford, TD Lee, TJ Handy, NC Schaefer, HF AF Crawford, TD Lee, TJ Handy, NC Schaefer, HF TI Spin-restricted Brueckner orbitals for coupled-cluster wavefunctions SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID SYMMETRY-BREAKING; PERTURBATION-THEORY; HARTREE-FOCK; MOLECULAR-ORBITALS; WAVE-FUNCTIONS; DOUBLES METHOD; STATE; NO2; ENERGY; CONVERGENCE AB The theory of spin-restricted Brueckner orbitals for high-spin open-shell coupled-cluster wavefunctions is presented. The orbitals are based on single-excitation amplitudes constructed using the symmetric spin-orbital basis coupled-cluster method of Jayatilaka and Lee. It is shown how this approach may be easily implemented within existing open-shell coupled-cluster programs. The method's performance is compared to conventional spin-unrestricted Brueckner orbitals for (C) over tilde(2)A(2)NO(2) and (X) over tilde(2)A(2)'NO3, for which instabilities in the Hartree-Fock reference determinant cause serious difficulties for highly correlated wavefunctions. (C) 1997 American Institute of Physics. [S0021-9606(97)03747-1]. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV CAMBRIDGE,DEPT CHEM,CAMBRIDGE CB2 1EW,ENGLAND. RP Crawford, TD (reprint author), UNIV GEORGIA,CTR COMPUTAT QUANTUM CHEM,ATHENS,GA 30602, USA. RI Lee, Timothy/K-2838-2012; Crawford, Thomas/A-9271-2017 OI Crawford, Thomas/0000-0002-7961-7016 NR 46 TC 26 Z9 26 U1 0 U2 1 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 DEC 15 PY 1997 VL 107 IS 23 BP 9980 EP 9984 DI 10.1063/1.475302 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YK982 UT WOS:A1997YK98200032 ER PT J AU Sohn, A Biswas, R AF Sohn, A Biswas, R TI Special issue on dynamic load balancing - Introduction SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Editorial Material C1 New Jersey Inst Technol, Dept Comp & Informat Sci, Newark, NJ 07102 USA. NASA, MRJ Technol Solut, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Sohn, A (reprint author), New Jersey Inst Technol, Dept Comp & Informat Sci, Newark, NJ 07102 USA. NR 9 TC 1 Z9 1 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0743-7315 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD DEC 15 PY 1997 VL 47 IS 2 BP 99 EP 101 DI 10.1006/jpdc.1997.1406 PG 3 WC Computer Science, Theory & Methods SC Computer Science GA ZD820 UT WOS:000072727700001 ER PT J AU Barker, HW Wielicki, BA AF Barker, HW Wielicki, BA TI Parameterizing grid-averaged longwave fluxes for inhomogeneous marine boundary layer clouds SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID RADIATIVE-TRANSFER; SATELLITE DATA; SOLAR FLUXES; WATER CLOUDS; STRATOCUMULUS; ALBEDO; RESOLUTION; FIELDS; COVER AB This paper examines the relative impacts on grid-averaged longwave flux transmittance (emittance) for marine boundary layer (MEL) cloud fields arising from horizontal variability of optical depth tau and cloud sides. First, using fields of Landsat-inferred tau and a Monte Carlo photon transport algorithm, it is demonstrated that mean all-sky transmittances for 3D variable MBL clouds can be computed accurately by the conventional method of linearly weighting clear and cloudy transmittances by their respective sky fractions. Then, the approximations of decoupling cloud and radiative properties and assuming independent columns are shown to be adequate for computation of mean flux transmittance. Since real clouds have nonzero geometric thicknesses, cloud fractions (A) over cap(c) presented to isotropic beams usually exceed the more familiar vertically projected cloud fractions A(c). It is shown, however, that when A(c) less than or similar to 0.9, biases for all-sky transmittance stemming from use of A(c) as opposed to (A) over cap(c) are roughly 2-5 times smaller than, and opposite in sign to, biases due to neglect of horizontal variability of tau. By neglecting variable tau, all-sky transmittances are underestimated often by more than 0.1 for A(c) near 0.75 and this translates into relative errors that can exceed 40% (corresponding errors for all-sky emittance are about 20% for most values of A(c)). Thus, priority should be given to development of general circulation model (GCM) parameterizations that account for the effects of horizontal variations in unresolved tau, effects of cloud sides are of secondary importance. On this note, an efficient stochastic model for computing grid-averaged cloudy-sky flux transmittances is furnished that assumes that distributions of tau, for regions comparable in size to GCM grid cells, can be described adequately by gamma distribution functions. While the plane-parallel, homogeneous model underestimates cloud transmittance by about an order of magnitude when 3D variable cloud transmittances are less than or similar to 0.2 and by similar to 20% to 100% otherwise, the stochastic model reduces these biases often by more than 80%. C1 Atmospher Environm Serv, Cloud Phys Res Div, ARMP, Downsview, ON M3H 5T4, Canada. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. RP Barker, HW (reprint author), Atmospher Environm Serv, Cloud Phys Res Div, ARMP, 4905 Dufferin St, Downsview, ON M3H 5T4, Canada. EM howard.barker@ec.gc.ca NR 41 TC 20 Z9 20 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD DEC 15 PY 1997 VL 54 IS 24 BP 2785 EP 2798 DI 10.1175/1520-0469(1997)054<2785:PGALFF>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN821 UT WOS:000071211200001 ER PT J AU Fu, Q Liou, KN Cribb, MC Charlock, TP Grossman, A AF Fu, Q Liou, KN Cribb, MC Charlock, TP Grossman, A TI Multiple scattering parameterization in thermal infrared radiative transfer SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID NUMERICAL WEATHER PREDICTION; TO-CUMULUS TRANSITION; MARINE BOUNDARY-LAYER; CIRRUS CLOUDS; CLIMATE; APPROXIMATION; ATMOSPHERES; ACCURACY; PERSPECTIVE; SIMULATION AB A systematic formulation of various radiative transfer parameterizations is presented, including the absorption approximation (AA), delta-two-stream approximation (D2S), delta-four-stream approximation (D4S), and delta-two- and four-stream combination approximation (D2/4S), in a consistent manner for thermal infrared flux calculations. The D2/4S scheme uses a source function from the delta-two-stream approximation and evaluates intensities in the four-stream directions. A wide range of accuracy checks for monochromatic emissivity of a homogeneous layer and broadband heating rates and fluxes in nonhomogeneous atmospheres is performed with respect to the "exact" results computed from the delta-128-stream scheme for radiative transfer. The computer time required for the calculations using different radiative transfer parameterizations is compared. The results pertaining to the accuracy and efficiency of various radiative transfer approximations can be utilized to decide which approximate method is most appropriate for a particular application. In view of its overall high accuracy and computational economy, it is recommended that the D2/4S scheme is well suited for GCM and climate modeling applications. C1 Dalhousie Univ, Dept Oceanog, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. Univ Utah, Dept Meteorol, CARSS, Salt Lake City, UT 84112 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Univ Calif Lawrence Livermore Natl Lab, Div Atmospher Sci, Livermore, CA USA. RP Fu, Q (reprint author), Dalhousie Univ, Dept Oceanog, Atmospher Sci Program, Halifax, NS B3H 4J1, Canada. RI Cribb, Maureen/K-1341-2013 OI Cribb, Maureen/0000-0002-9745-3676 NR 35 TC 126 Z9 133 U1 1 U2 9 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD DEC 15 PY 1997 VL 54 IS 24 BP 2799 EP 2812 DI 10.1175/1520-0469(1997)054<2799:MSPITI>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YN821 UT WOS:000071211200002 ER PT J AU Ehrlich, JE Wu, XL Lee, IYS Hu, ZY Rockel, H Marder, SR Perry, JW AF Ehrlich, JE Wu, XL Lee, IYS Hu, ZY Rockel, H Marder, SR Perry, JW TI Two-photon absorption and broadband optical limiting with bis-donor stilbenes SO OPTICS LETTERS LA English DT Article ID 2-PHOTON ABSORPTION AB Large two-photon absorptivities are reported for symmetrical bis-donor stilbene derivatives with dialkylamino or diphenylamino groups. These molecules exhibit strong optical limiting of nanosecond pulses over a broad spectral range in the visible. Relative to bis(di-n-butylamino)stilbene, bis(diphenylamino)stilbene exhibits a 90-nm red shift of its optical limiting band but only a minimal shift of similar to 13 nm of its lowest one-photon electronic absorption band. Mixtures of these compounds offer an unprecedented combination of broad optical limiting bandwidth and high linear transparency. (C) 1997 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Beckman Inst, Pasadena, CA 91109 USA. RP Ehrlich, JE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Perry, Joseph/B-7191-2011 OI Perry, Joseph/0000-0003-1101-7337 NR 14 TC 618 Z9 651 U1 11 U2 70 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD DEC 15 PY 1997 VL 22 IS 24 BP 1843 EP 1845 DI 10.1364/OL.22.001843 PG 3 WC Optics SC Optics GA YM121 UT WOS:000071030800005 PM 18188382 ER PT J AU Yao, XS Maleki, L AF Yao, XS Maleki, L TI Dual microwave and optical oscillator SO OPTICS LETTERS LA English DT Article ID PULSE GENERATION; LASER; PICOSECOND AB We describe and demonstrate a novel device in which a microwave oscillation and an optical oscillation are generated and directly coupled with each other. With the mutual influence between the microwave and the optical oscillations, we project that this device is capable of simultaneously generating stable optical pulses down to the subpicosecond level and spectrally pure microwave signals at frequencies greater than 70 GHz. (C) 1997 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yao, XS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 73 Z9 75 U1 2 U2 5 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD DEC 15 PY 1997 VL 22 IS 24 BP 1867 EP 1869 DI 10.1364/OL.22.001867 PG 3 WC Optics SC Optics GA YM121 UT WOS:000071030800013 PM 18188390 ER PT J AU Green, AM Liddle, AR Riotto, A AF Green, AM Liddle, AR Riotto, A TI Primordial black hole constraints in cosmologies with early matter domination SO PHYSICAL REVIEW D LA English DT Article ID SUPERSYMMETRY BREAKING; SPECTRAL DISTORTIONS; ENTROPY CRISIS; MODULI PROBLEM; PARTICLES; MODEL; SUPERGRAVITY; INFLATION; PHYSICS; RELICS AB Moduli fields. a natural prediction of any supergravity and superstring-inspired supersymmetry theory. may lead to a prolonged period of matter domination in the early universe. This can be observationally viable provided the moduli decay early enough to avoid harming nucleosynthesis. If primordial black holes form, they would be expected to do so before or during this matter-dominated era. We examine the extent to which the standard primordial black hole constraints are weakened in such a cosmology. Permitted mass fractions of black holes at formation are of order 10(-8), rather than the usual 10(-20) or so. If the black holes form from density perturbations with a power-law spectrum, its spectral index is limited to n less than or similar to 1.3, rather than the n less than or similar to 1.25 obtained in the standard cosmology. [S0556-2821(97)03424-3]. C1 Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Green, AM (reprint author), Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. OI Green, Anne/0000-0002-7135-1671 NR 41 TC 17 Z9 17 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD DEC 15 PY 1997 VL 56 IS 12 BP 7559 EP 7565 DI 10.1103/PhysRevD.56.7559 PG 7 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YM238 UT WOS:000071043600008 ER PT J AU Rawers, JC Krabbe, RA Wittenberger, JD AF Rawers, JC Krabbe, RA Wittenberger, JD TI Hot-extrusion of attrition milled, iron alloy powders SO SCRIPTA MATERIALIA LA English DT Article C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Rawers, JC (reprint author), US DOE,ALBANY RES CTR,ALBANY,OR 97321, USA. NR 13 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 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD DEC 15 PY 1997 VL 37 IS 12 BP 2053 EP 2059 DI 10.1016/S1359-6462(97)00397-7 PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA YJ070 UT WOS:A1997YJ07000033 ER PT J AU Zhang, YD Hokari, H Wada, T Shang, YM Marder, SR Sasabe, H AF Zhang, YD Hokari, H Wada, T Shang, YM Marder, SR Sasabe, H TI Synthesis of N-vinylcarbazole derivatives with acceptor groups SO TETRAHEDRON LETTERS LA English DT Article ID POLYMERS AB A new series of N-vinylcarbazole with various acceptor groups has been synthesized starting from 3-formyl-N-vinylcarbazole by the Knoevenagel condensation. The key starting compound, 3-formyl-N-vinylcarbazole, was prepared from 3-formyl-N-(2-chloroethyl)carbazole by 1,2-elimination reaction. (C) 1997 Elsevier Science Ltd. C1 RIKEN,INST PHYS & CHEM RES,JST,CREST,WAKO,SAITAMA 35101,JAPAN. RIKEN,INST PHYS & CHEM RES,FRONTIER RES PROGRAM,WAKO,SAITAMA 35101,JAPAN. CALTECH,BECKMAN INST,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 9 TC 14 Z9 14 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0040-4039 J9 TETRAHEDRON LETT JI Tetrahedron Lett. PD DEC 15 PY 1997 VL 38 IS 50 BP 8721 EP 8722 DI 10.1016/S0040-4039(97)10318-5 PG 2 WC Chemistry, Organic SC Chemistry GA YJ413 UT WOS:A1997YJ41300031 ER PT J AU Scherer, K Fichtner, H Anderson, JD Lau, EL AF Scherer, K Fichtner, H Anderson, JD Lau, EL TI A pulsar, the Heliosphere, and Pioneer 10: Probable mimicking of a planet of PSR B1257+12 by solar rotation SO SCIENCE LA English DT Article ID WIND; ULYSSES; PERIOD AB Doppler data generated with the Pioneer 10 spacecraft's radio carrier wave between 1987 and 1995 show a 25.3-day periodicity which is related to the solar rotation. The timing data of the pulsar PSR B1257+12 also show a periodicity of 25.34 days, which has been explained as a signature of the pulsar's barycentric motion in response to the existence of a small moon-like object. However, because PSR B1257+12 is located close to the ecliptic and because the timing variations are in the range of microseconds, it is likely that the pulsar signal is affected by the same mechanism acting on the Pioneer 10 Doppler data. Hence, the hypothesized inner planet around PSR B1257+12 is probably an artifact of the heliosphere. C1 JET PROP LAB,PASADENA,CA 91119. UNIV BONN,INST ASTROPHYS & EXTRATERR FORSCH,D-53121 BONN,GERMANY. NR 18 TC 14 Z9 14 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 DEC 12 PY 1997 VL 278 IS 5345 BP 1919 EP 1921 DI 10.1126/science.278.5345.1919 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YL002 UT WOS:A1997YL00200026 ER PT J AU Harmon, JK Ostro, SJ Benner, LAM Rosema, KD Jurgens, RF Winkler, R Yeomans, DK Choate, D Cormier, R Giorgini, JD Mitchell, DL Chodas, PW Rose, R Kelley, D Slade, MA Thomas, ML AF Harmon, JK Ostro, SJ Benner, LAM Rosema, KD Jurgens, RF Winkler, R Yeomans, DK Choate, D Cormier, R Giorgini, JD Mitchell, DL Chodas, PW Rose, R Kelley, D Slade, MA Thomas, ML TI Radar detection of the nucleus and Coma of Comet Hyakutake (C/1996 B2) SO SCIENCE LA English DT Article ID GRAINS AB Radar observations of comet Hyakutake (C/1996 B2) made at the Goldstone Deep Space Communications Complex in California have detected echoes from the nucleus and from large grains in the inner coma. The nucleus of this bright comet was estimated to be only 2 to 3 kilometers in diameter. Models of the coma echo indicate backscatter from porous, centimeter-size grains ejected anisotropically at velocities of tens of meters per second. The radar observations suggest that a comet's activity may be a poor indicator of its size and provide evidence that large grains constitute an important component of the mass loss from a typical active comet. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Harmon, JK (reprint author), NATL ASTRON & IONOSPHERE CTR,ARECIBO OBSERV,POB 995,ARECIBO,PR 00614, USA. NR 32 TC 38 Z9 39 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 DEC 12 PY 1997 VL 278 IS 5345 BP 1921 EP 1924 DI 10.1126/science.278.5345.1921 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YL002 UT WOS:A1997YL00200027 ER PT J AU Lyubarskii, YE AF Lyubarskii, YE TI Flicker noise in accretion discs SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; X-rays : general ID ADVECTION-DOMINATED ACCRETION; X-RAY BINARIES; BLACK-HOLES; VISCOUS DISKS; VARIABILITY; EVOLUTION; OBJECTS AB An accretion disc with an alpha parameter fluctuating at different radii is considered. The relation between the alpha fluctuations and the resulting fluctuations of the accretion rate near the accreting body is obtained. Fluctuations of the accretion rate and, consequently, of the luminosity proved to be of the flicker-noise type provided that the characteristic time-scale of the alpha fluctuations is of the order of the local viscous time-scale, and that the fluctuations at different radial scales are uncorrelated. C1 Inst Radio Astron, UA-310002 Kharkov, Ukraine. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lyubarskii, YE (reprint author), Inst Radio Astron, 4 Krasncznamyonnaya, UA-310002 Kharkov, Ukraine. RI LYUBARSKY, YURY/F-2362-2012 NR 26 TC 248 Z9 249 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD DEC 11 PY 1997 VL 292 IS 3 BP 679 EP 685 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YN899 UT WOS:000071219900015 ER PT J AU Corcoran, MF Ishibashi, K Swank, JH Davidson, K Petre, R Schmitt, JHMM AF Corcoran, MF Ishibashi, K Swank, JH Davidson, K Petre, R Schmitt, JHMM TI Increasing X-ray emissions and periodic outbursts from the massive star eta Carinae SO NATURE LA English DT Article ID SPECTRA AB Eta Carinae is one of the most massive, luminous and unstable stars known. The basic nature of this star is poorly understood, despite much study(1,2). It is a fluctuating source of hard X-rays(3-5), indicative of gas at an unusually high temperature (60 million kelvin): the mechanism for producing this gas has yet to be established, but may be related to strong shocks in a dense stellar wind. We have monitored the hard X-ray emission (2-10 keV) from eta Car over the past 1.5 years, in order to better understand the nature of these emissions and their variations. We shaw here that there has been an overall increase in the mean X-ray flux which has accelerated since January 1997, and that there are also small-scale periodic outbursts that occur every 85 days. It has recently been argued(6,7) that eta Car is in fact a binary stellar system whose components are approaching periastron near 1 January 1998. If this is indeed the case, then it is plausible that the hard Xray emission is produced by shocks associated with the collision of the winds from the two stars, in which case the X-ray flux should increase through periastron, and rapidly decline thereafter. Continued monitoring will test this prediction. C1 UNIV SPACE RES ASSOC,COLUMBIA,MD 21044. UNIV MINNESOTA,DEPT ASTRON,MINNEAPOLIS,MN 55455. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. RP Corcoran, MF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Swank, Jean/F-2693-2012 NR 23 TC 46 Z9 46 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD DEC 11 PY 1997 VL 390 IS 6660 BP 587 EP 589 DI 10.1038/37558 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YK853 UT WOS:A1997YK85300041 ER PT J AU Pohl, M Kanbach, G Hunter, SD Jones, BB AF Pohl, M Kanbach, G Hunter, SD Jones, BB TI The pulsar contribution to the diffuse Galactic gamma-ray emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; gamma rays, observations; pulsars, general ID POWERED PULSARS; RADIO PULSARS AB There is active interest in the extent to which unresolved gamma-ray pulsars contribute to the Galactic diffuse emission, and in whether unresolved gamma-ray pulsars could be responsible for the excess of diffuse Galactic emission above 1 GeV that has been observed by EGRET. The diffuse gamma-ray intensity due to unresolved pulsars is directly linked to the number of objects that should be observed in the EGRET data. We can therefore use our knowledge of the unidentified EGRET sources to constrain model parameters like the pulsar birthrate and their beaming angle. This analysis is based only on the properties of the six pulsars that have been identified in the EGRET data and is independent of choice of a pulsar emission model. We find that pulsars contribute very little to the diffuse emission at lower energies, whereas above 1 GeV they can account for 18% of the observed intensity in selected regions for a reasonable number of directly observable gamma-ray pulsars (similar to 14). The latitude distribution of the diffuse emission caused by unresolved pulsars is narrower than that of the observed diffuse emission. While the excess above 1 GeV gamma-ray energy is observed up to at least 6 degrees-8 degrees off the plane, the pulsar contribution would be small there. Thus, pulsars do significantly contribute to the diffuse Galactic gamma-ray emission above 1 GeV, but they cannot be made responsible for all the discrepancies between observed intensity and model predictions in this energy range. C1 MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. STANFORD UNIV,DEPT PHYS,WW HANSEN LAB,STANFORD,CA 94305. RI Hunter, Stanley/D-2942-2012 NR 23 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 DEC 10 PY 1997 VL 491 IS 1 BP 159 EP 164 DI 10.1086/304959 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL507 UT WOS:A1997YL50700016 ER PT J AU Park, S Finley, JP Snowden, SL AF Park, S Finley, JP Snowden, SL TI Small-scale variations in the 1/4 keV X-ray background along the Galactic plane SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; ISM, bubbles; ISM, structure; X-rays, ISM ID INTERSTELLAR MATTER; EVOLUTION; DENSITY; BUBBLES; MODELS; MAPS; GAS AB Forty-two ROSAT Position Sensitive Proportional Counter pointed observations in the first quadrant (l similar to 4 degrees-26 degrees) of the Galactic plane are mosaicked in order to study the spatial structure of the X-ray-emitting gas in the Local Hot Bubble (LHB). X-ray intensity variations at various angular scales are examined in the 1/4 keV band, and degree-scale variations are detected. In the context of the LHB and the displacement model for the origin of the 1/4 keV band background, the hardness ratio, angular size, and magnitude of the intensity variations suggest that at the +/- 10% level there is an influence of a clumpy boundary structure superposed upon the emission from the uniformly distributed similar to 10(6) K plasma of the LHB interior. The possible origins of such a clumpy boundary structure of the LHB are discussed with Rayleigh-Taylor instabilities and clumping of the cooler interstellar medium at the boundary region being likely candidates. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,COLUMBIA,MD. RP Park, S (reprint author), PURDUE UNIV,DEPT PHYS,1396 PHYS BLDG,W LAFAYETTE,IN 47907, USA. NR 28 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 DEC 10 PY 1997 VL 491 IS 1 BP 165 EP 171 DI 10.1086/304951 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL507 UT WOS:A1997YL50700017 ER PT J AU Chen, W Shrader, CR Livio, M AF Chen, W Shrader, CR Livio, M TI The properties of X-ray and optical light curves of R-ray novae SO ASTROPHYSICAL JOURNAL LA English DT Review DE accretion, accretion disks; binaries, close; novae, cataclysmic variables; X-rays, stars ID TRANSIENT GRO J1655-40; DISK-INSTABILITY MODEL; HOLE BINARY A0620-00; LONG-TERM BEHAVIOR; BLACK-HOLE; ACCRETION DISKS; AQUILA X-1; MUSCAE 1991; CENTAURUS X-4; V404 CYGNI AB We have collected the available data from the literature and from public data archives covering the past two decades for the long-term X-ray and optical light curves of X-ray nova (XN) outbursts. XN outbursts are due to episodic accretion events, primarily in low-mass X-ray binaries normally characterized by low mass transfer rates. Dynamical studies indicate that most XNs contain a black hole. The soft X-ray emission during outburst traces the accretion rate through the inner edge of the accretion disk, while the optical light curve traces the physical conditions at the outer disk-thus, collectively, they contain information on the time-dependent behavior of accretion processes through the disks. In this paper, we carry out for the first time a systematic, statistical study of XN light curves that are classified into five morphological types. Basic light-curve parameters, such as the outburst peak flux, amplitude, luminosity, rise and decay timescales, the observed and expected outburst durations, and the total energy radiated, are tabulated and discussed. We find that the rise timescales have a flat distribution while the decay timescales have a much narrower and near-Gaussian distribution, centered around 30 days and dominated by the strongest outbursts. The peak luminosity is also distributed like a Gaussian, centered around 0.2 in Eddington units, while the total energy released has a much broader distribution around 10(44) ergs. We find no intrinsic difference between black hole and neutron star systems in their distribution of peak amplitudes. We identify and discuss additional light-curve features, such as precursors, plateaus, and secondary maxima. The plateaus exhibited in the light curves of black hole sources are found to have, on average, longer durations, and they are followed by longer decays. The identified secondary maxima seem to occur mostly in black hole systems. For the frequency of outbursts, we find that the average XN outburst rate is about 2.6 yr(-1) for events greater than 0.3 crab and that the mean recurrence time between outbursts from a single source is 6 yr. The spatial and log N-log S distribution of the XN sources, with limited statistics, agrees with a source population in the Galactic disk, as observed from a point at a distance of 8.5 kpc from the Galactic center. Finally, we point out that the observed XN light-curve properties can be explained in general by a disk thermal instability model, although some important problems still remain. C1 UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. UNIV SPACE RES ASSOC, COLUMBIA, MD 21044 USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. RP Chen, W (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. NR 161 TC 374 Z9 376 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1997 VL 491 IS 1 BP 312 EP 338 DI 10.1086/304921 PN 1 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL507 UT WOS:A1997YL50700032 ER PT J AU Reames, DV Kahler, SW Ng, CK AF Reames, DV Kahler, SW Ng, CK TI Spatial and temporal invariance in the spectra of energetic particles in gradual solar events SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; shock waves; Sun, corona; Sun, particle emission ID CORONAL MASS EJECTIONS; MEAN IONIC CHARGE; INTERPLANETARY SHOCKS; FLARES; ACCELERATION; ABUNDANCES; STATE AB We show evidence of spatial and temporal invariance in the energy spectra of similar to 1-100 MeV protons from large gradual solar energetic particle (SEP) events. Nearly identical spectra are seen over longitude intervals of up to 160 degrees, and the intensities at all energies decline with e-folding time constants of 6-18 hr for periods of similar to 3 days. The region of the invariant spectra is associated with acceleration on the eastern flank of the shock wave driven out from the Sun by a coronal-mass ejection (CME). The quasi-parallel shock in this region changes only slowly with time, and a quasi equilibrium is established for particles stored on field lines in the expanding volume between the shock and the Sun. On the western flank of the shock, the SEP event is more dynamic. Here, the nearly quasi-perpendicular shock produces harder spectra that change more rapidly with time as regions of the shock with varying speed and angle sweep across the observer's field line. Gradual SEP events arise from large CMEs with sufficient speeds to generate shocks that are fast enough to accelerate particles. In our study, shocks with transit speed >750 km s(-1) always accelerate particles, while those with speeds of 500-750 km s(-1) sometimes do. However, invariant spectra seem to occur in all gradual SEP events as a consequence of the structure and topology of the CME and shock. C1 PHILLIPS LAB,GPSG,HANSCOM AFB,MA 01731. ROYAL MELBOURNE INST TECHNOL,DEPT MATH,MELBOURNE,VIC 3001,AUSTRALIA. RP Reames, DV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 23 TC 103 Z9 105 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 DEC 10 PY 1997 VL 491 IS 1 BP 414 EP 420 DI 10.1086/304939 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL507 UT WOS:A1997YL50700042 ER PT J AU Malhotra, S Helou, G Stacey, G Hollenbach, D Lord, S Beichman, CA Dinerstein, H Hunter, DA Lo, KY Lu, NY Rubin, RH Silbermann, N Thronson, HA Werner, MW AF Malhotra, S Helou, G Stacey, G Hollenbach, D Lord, S Beichman, CA Dinerstein, H Hunter, DA Lo, KY Lu, NY Rubin, RH Silbermann, N Thronson, HA Werner, MW TI Infrared space observatory measurements of [C II] line variations in galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, ISM; infrared, ISM, lines and bands; ISM, atoms; radiation mechanisms, thermal ID PHOTODISSOCIATION REGIONS; EMISSION; SPECTROSCOPY; NGC-4418; CLOUDS; COBE; GAS AB We report measurements of the [C II] fine-structure line at 157.714 mu m in 30 normal star-forming galaxies with the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory, (ISO). The ratio of the line to total far-infrared (FIR) luminosity, L-[CII]/L-FIR, measures the ratio of the cooling of gas to that of dust, and thus the efficiency of the grain photoelectric heating process. This ratio varies by more than a factor of 40 in the current sample. About two-thirds of the galaxies have L-[CII]/L-FIR ratios in the narrow range of (2-7) x 10(-3). The other one-third show trends of decreasing L-[CII]/L-FIR with increasing dust temperature, as measured by the flux ratio of infrared emission at 60 and 100 mu m, F-v(60 mu m)/F-v(100 mu m), and with increasing star formation activity, measured by the ratio of FIR and blue-band luminosity, L-FIR/L-B. We also find three FIR-bright galaxies that are deficient in the [C II] line, which is undetected with 3 sigma upper limits of L-[CII]/L-FIR < (0.5-2) x 10(-4). The trend in the L-[CII]/L-FIR ratio with the temperature of dust and with star formation activity may be due to decreased efficiency of photoelectric heating of gas at high UV radiation intensity as dust grains become positively charged, decreasing the yield and the energy of the photoelectrons. The three galaxies with no observed photodissociation region lines have among the highest L-FIR/L-B and F-v(60 mu m)/F-v(100 mu m) ratios. Their lack of [C II] lines may be due to a continuing trend of decreasing L-[CII]/L-FIR with increasing star formation activity and dust temperature seen in one-third of the sample with warm IRAS colors. In that case, the upper limits on L-[CII]/L-FIR imply a ratio of UV flux to gas density of G(0)/(n) > 10 cm(3) (where G(0) is in units of the local average interstellar field). The low L-[CII]/L-FIR ratio could also be due to either weak [CII], owing to self-absorption, or a strong FIR continuum from regions weak in [C II], such as dense H II regions or plasma ionized by hard radiation of active galactic nuclei. The mid-infrared and radio images of these galaxies show that most of the emission comes from a compact nucleus. CO and H I are detected in these galaxies, with H I seen in absorption toward the nucleus. C1 CORNELL UNIV,DEPT ASTRON,ITHACA,NY 14853. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV TEXAS,DEPT ASTRON,AUSTIN,TX 78712. LOWELL OBSERV,FLAGSTAFF,AZ 86001. UNIV ILLINOIS,DEPT ASTRON,URBANA,IL 61801. UNIV WYOMING,WYOMING INFRARED OBSERV,LARAMIE,WY 82071. RP Malhotra, S (reprint author), CALTECH,IPAC,JET PROP LAB,PASADENA,CA 91125, USA. NR 35 TC 115 Z9 115 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 DEC 10 PY 1997 VL 491 IS 1 BP L27 EP L30 DI 10.1086/311044 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL509 UT WOS:A1997YL50900007 ER PT J AU Marsden, D Blanco, PR Gruber, DE Heindl, WA Pelling, MR Peterson, LE Rothschild, RE Rots, AH Jahoda, K Macomb, DJ AF Marsden, D Blanco, PR Gruber, DE Heindl, WA Pelling, MR Peterson, LE Rothschild, RE Rots, AH Jahoda, K Macomb, DJ TI The x-ray spectrum of the plerionic system PSR B1509-58 MSH 15-52 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (MSH 15-52); pulsar, individual (PSR B1509-58); stars, neutron ID CRAB-NEBULA; SUPERNOVA REMNANT; PULSAR; RADIATION; MSH-15-52; GAPS AB We present the results of observations of the PSR B1509-58/MSH 15-52 system in X-rays (2-250 keV) by the Rossi X-Ray Timing Explorer. The spectra of the peak of the pulsed component (radio phase 0.17-0.53) is fitted by a power law of photon index 1.36 +/- 0.01, with no evidence of a high-energy spectral break seen up to similar to 200 keV. For the off-pulse spectral component, the spectrum from 2-250 keV is fitted by a power law of photon index 2.215 +/- 0.005. An iron emission line at 6.7 keV with an equivalent width of 129 eV improves the fit, but only at a marginal significance, Thermal bremsstrahlung and Raymond-Smith models produce much worse fits to the unpulsed data. The lack of a high-energy spectral break in the pulsed emission implies an efficiency of greater than or equal to 3% in the conversion of pulsar spin-down energy to pulsed X-rays in the system. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Marsden, D (reprint author), UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093, USA. RI Jahoda, Keith/D-5616-2012; OI Rots, Arnold/0000-0003-2377-2356 NR 27 TC 28 Z9 28 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 DEC 10 PY 1997 VL 491 IS 1 BP L39 EP L42 DI 10.1086/311054 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL509 UT WOS:A1997YL50900010 ER PT J AU Matsubara, T Suto, Y Szapudi, I AF Matsubara, T Suto, Y Szapudi, I TI Light-cone effect on higher order clustering in redshift surveys SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, theory; dark matter; galaxies, distances and redshifts; large-scale structure of universe ID N-BODY SIMULATIONS; FLUCTUATIONS; EVOLUTION; SPECTRUM AB We have evaluated a systematic effect on counts-in-cells analysis of deep, wide-field galaxy catalogs induced by the evolution of clustering within the survey volume. A multiplicative correction factor is explicitly presented, which can be applied after the higher order correlation functions have been extracted in the usual way, without taking into account the evolution. The general theory of this effect combined with the Ansatz describing the nonlinear evolution of clustering in simulations enables us to estimate the magnitude of the correction factor in different cosmologies. In a series of numerical calculations assuming an array of cold dark matter models, it is found that, as long as galaxies are unbiased tracers of underlying density field, the effect is relatively small (similar or equal to 10%) for the shallow surveys (z < 0.2), while it becomes significant (of order unity) in deep surveys (z similar or equal to 1). Depending on the scales of interest, the required correction is comparable to or smaller than the expected errors of ongoing wide-field galaxy surveys such as the Sloan Digital Sky Survey and the 2 Degree Field Survey. Therefore, at present, the effect has to be taken into account for high-precision measurements at very small scales only, while in future deep surveys it amounts to a significant correction. C1 UNIV TOKYO, SCH SCI, RES CTR EARLY UNIV, RESCEU, TOKYO 113, JAPAN. FERMILAB NATL ACCELERATOR LAB, NASA, CTR ASTROPHYS, BATAVIA, IL 60510 USA. RP UNIV TOKYO, DEPT PHYS, 7-3-1 HONGO, TOKYO 113, JAPAN. NR 23 TC 24 Z9 24 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 DEC 10 PY 1997 VL 491 IS 1 BP L1 EP L5 DI 10.1086/311051 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL509 UT WOS:A1997YL50900001 ER PT J AU Child, MS Naumenko, OV Smirnov, MA Brown, LR AF Child, MS Naumenko, OV Smirnov, MA Brown, LR TI Local mode axis tilting in H2S SO MOLECULAR PHYSICS LA English DT Article ID OVERTONE BAND SYSTEM; ENERGY-LEVEL STRUCTURE; SYMMETRICAL HYDRIDES; ROTATIONAL STRUCTURE; MU-M; LIMIT; MOLECULES; SPECTROSCOPY; SPECTRUM; CM-1 AB A physically intuitive non-resonant local mode axis tilting model for the interpretation of higher overtone bands of XH2 species is outlined and illustrated by reference to the near-infrared of spectrum H2S. Quantitative connections with the conventional normal mode resonance coupled picture are derived and local mode based expressions for the vibrational-rotational wavefunctions are given. Constants are reported for the (311)-(212) and (302)-(203) bands at 11 008 cm(-1) and 12 149 cm(-1), respectively. C1 Phys & Theoret Chem Lab, Oxford OX1 3QZ, England. Russian Acad Sci, Inst Atmospher Opt, Tomsk, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Child, MS (reprint author), Phys & Theoret Chem Lab, S Parks Rd, Oxford OX1 3QZ, England. NR 28 TC 18 Z9 19 U1 2 U2 5 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0026-8976 J9 MOL PHYS JI Mol. Phys. PD DEC 10 PY 1997 VL 92 IS 5 BP 885 EP 893 DI 10.1080/002689797169826 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YL944 UT WOS:000071011100009 ER PT J AU Freed, LE Langer, R Martin, I Pellis, NR VunjakNovakovic, G AF Freed, LE Langer, R Martin, I Pellis, NR VunjakNovakovic, G TI Tissue engineering of cartilage in space SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article DE spaceflight; microgravity; chondrocyte; polymer; bioreactor ID ARTICULAR-CARTILAGE; CHONDROCYTES; EXPLANTS; CULTURE; BONE AB Tissue engineering of cartilage, i.e., the in vitro cultivation of cartilage cells on synthetic polymer scaffolds, was studied on the Mir Space Station and on Earth. Specifically, three-dimensional cell-polymer constructs consisting of bovine articular chondrocytes and polyglycolic acid scaffolds were grown in rotating bioreactors, first for 3 months on Earth and then for an additional 4 months on either Mir (10(-4) - 10(-6) g) or Earth (1 g). This mission provided a unique opportunity to study the feasibility of long-term cell culture flight experiments and to assess the effects of spaceflight on the growth and function of a model musculoskeletal tissue. Both environments yielded cartilaginous constructs, each weighing between 0.3 and 0.4 g and consisting of viable, differentiated cells that synthesized proteoglycan and type II collagen. Compared with the Earth group, Mir-grown constructs were more spherical, smaller, and mechanically inferior. The same bioreactor system can be used for a variety of controlled microgravity studies of cartilage and other tissues. These results may have implications for human spaceflight, e.g., a Mars mission, and clinical medicine, e.g., improved understanding of the effects of pseudo-weightlessness in prolonged immobilization, hydrotherapy, and intrauterine development. C1 MIT, DEPT CHEM ENGN, CAMBRIDGE, MA 02139 USA. NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. RP Freed, LE (reprint author), MIT, DIV HLTH SCI, E25-342, 45 CARLETON ST, CAMBRIDGE, MA 02139 USA. OI Vunjak-Novakovic, Gordana/0000-0002-9382-1574 NR 32 TC 252 Z9 272 U1 3 U2 31 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD DEC 9 PY 1997 VL 94 IS 25 BP 13885 EP 13890 DI 10.1073/pnas.94.25.13885 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YK825 UT WOS:A1997YK82500095 PM 9391122 ER PT J AU Nguyen, H AF Nguyen, H TI Optimized transition between coplanar waveguide and the microstrip electrode of polymer electrode-optic modulators SO MICROWAVE AND OPTICAL TECHNOLOGY LETTERS LA English DT Article DE coplanar waveguides; cross-linked polymers; microstrip; optical modulations ID BANDWIDTH AB The characterization of transitions between the coplanar waveguide (CPW) input/output terminals and the microstrip traveling-wave electrode of wide-bandwidth, cross-linked polymer electrode-optic modulators is presented. The transitions employ linear, exponential, cosine-squared, parabolic, power, and Guassian tapered coplanar waveguides (TCPW) fabricated on a vertical stacked polymer structure of organic nonlinear optical (NLO) U9020D cladding layer, thermally NLO chromophores, and U9020D. Results of RF loss measurements of the microstrip electrode of each candidate taper are reported. It is shown that the cosine-squared taper yields an lower insertion loss of 1.8 dB per transition. The fabrication procedure used to fabricate the transition and optical waveguide is also presented, along with a comparison of the insertion loss before and after the application of a poling field of 30 V/mu m. (C) 1997 Wiley & Sons, Inc. RP Nguyen, H (reprint author), NASA,LEWIS RES CTR,SPACE COMMUN DIV,CLEVELAND,OH 44135, USA. NR 9 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 DEC 5 PY 1997 VL 16 IS 5 BP 283 EP 287 PG 5 WC Engineering, Electrical & Electronic; Optics SC Engineering; Optics GA YG436 UT WOS:A1997YG43600005 ER PT J AU Golombek, MP Cook, RA Economou, T Folkner, WM Haldemann, AFC Kallemeyn, PH Knudsen, JM Manning, RM Moore, HJ Parker, TJ Rieder, R Schofield, JT Smith, PH Vaughan, RM AF Golombek, MP Cook, RA Economou, T Folkner, WM Haldemann, AFC Kallemeyn, PH Knudsen, JM Manning, RM Moore, HJ Parker, TJ Rieder, R Schofield, JT Smith, PH Vaughan, RM TI Overview of the Mars Pathfinder Mission and assessment of landing site predictions SO SCIENCE LA English DT Article ID THERMAL INERTIA; PHYSICAL-PROPERTIES; ALBEDO AB Chemical analyses returned by Mars Pathfinder indicate that some rocks may be high in silica, implying differentiated parent materials. Rounded pebbles and cobbles and a possible conglomerate suggest fluvial processes that imply liquid water in equilibrium with the atmosphere and thus a warmer and wetter past. The moment of inertia indicates a central metallic core of 1300 to 2000 kilometers in radius. Composite airborne dust particles appear magnetized by freeze-dried maghemite stain or cement that may have been leached from crustal materials by an active hydrologic cycle. Remote-sensing data at a scale of generally greater than similar to 1 kilometer and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catastrophic floods that are relatively dust-free. C1 UNIV CHICAGO, ENRICO FERMI INST, CHICAGO, IL 60637 USA. UNIV COPENHAGEN, NIELS BOHR INST, DK-1168 COPENHAGEN, DENMARK. US GEOL SURVEY, ASTROGEOL TEAM, MENLO PK, CA 94025 USA. MAX PLANCK INST CHEM, D-55128 MAINZ, GERMANY. UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA. RP Golombek, MP (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 42 TC 148 Z9 152 U1 1 U2 18 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD DEC 5 PY 1997 VL 278 IS 5344 BP 1743 EP 1748 DI 10.1126/science.278.5344.1743 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ901 UT WOS:A1997YJ90100033 PM 9388167 ER PT J AU Folkner, WM Yoder, CF Yuan, DN Standish, EM Preston, RA AF Folkner, WM Yoder, CF Yuan, DN Standish, EM Preston, RA TI Interior structure and seasonal mass redistribution of Mars from radio tracking of Mars Pathfinder SO SCIENCE LA English DT Article ID INERTIA; OBLIQUITY; MOMENT; CYCLE AB Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 +/- 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps. RP Folkner, WM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 191 Z9 199 U1 0 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 DEC 5 PY 1997 VL 278 IS 5344 BP 1749 EP 1752 DI 10.1126/science.278.5344.1749 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ901 UT WOS:A1997YJ90100034 PM 9388168 ER PT J AU Schofield, JT Barnes, JR Crisp, D Haberle, RM Larsen, S Magalhaes, JA Murphy, JR Seiff, A Wilson, G AF Schofield, JT Barnes, JR Crisp, D Haberle, RM Larsen, S Magalhaes, JA Murphy, JR Seiff, A Wilson, G TI The Mars Pathfinder atmospheric structure investigation meteorology (ASI/MET) experiment SO SCIENCE LA English DT Article ID MARTIAN ATMOSPHERE; BOUNDARY-LAYER; THERMAL TIDES; DUST STORMS; DEVILS; MODEL AB The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET) experiment measured the vertical density, pressure, and temperature structure of the martian atmosphere from the surface to 160 km, and monitored surface meteorology and climate for 83 sols (1 sol = 1 martian day = 24.7 hours). The atmospheric structure and the weather record are similar to those observed by the Viking 1 lander (VL-1) at the same latitude, altitude, and season 21 years ago, but there are differences related to diurnal effects and the surface properties of the landing site. These include a cold nighttime upper atmosphere; atmospheric temperatures that are 10 to 12 degrees kelvin warmer near the surface; light slope-controlled winds; and dust devils, identified by their pressure, wind, and temperature signatures. The results are consistent with the warm, moderately dusty atmosphere seen by VL-1. C1 OREGON STATE UNIV,COLL OCEAN & ATMOSPHER SCI,CORVALLIS,OR 97331. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RISO NATL LAB,DK-4000 ROSKILDE,DENMARK. SAN JOSE STATE UNIV FDN,SAN JOSE,CA. ARIZONA STATE UNIV,TEMPE,AZ. RP Schofield, JT (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 29 TC 249 Z9 251 U1 2 U2 19 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 5 PY 1997 VL 278 IS 5344 BP 1752 EP 1758 DI 10.1126/science.278.5344.1752 PG 7 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ901 UT WOS:A1997YJ90100035 PM 9388169 ER PT J AU Smith, PH Bell, JF Bridges, NT Britt, DT Gaddis, L Greeley, R Keller, HU Herkenhoff, KE Jaumann, R Johnson, JR Kirk, RL Lemmon, M Maki, JN Malin, MC Murchie, SL Oberst, J Parker, TJ Reid, RJ Sablotny, R Soderblom, LA Stoker, C Sullivan, R Thomas, N Tomasko, MG Ward, W Wegryn, E AF Smith, PH Bell, JF Bridges, NT Britt, DT Gaddis, L Greeley, R Keller, HU Herkenhoff, KE Jaumann, R Johnson, JR Kirk, RL Lemmon, M Maki, JN Malin, MC Murchie, SL Oberst, J Parker, TJ Reid, RJ Sablotny, R Soderblom, LA Stoker, C Sullivan, R Thomas, N Tomasko, MG Ward, W Wegryn, E TI Results from the Mars Pathfinder camera SO SCIENCE LA English DT Article ID SPECTRAL REFLECTANCE; VIKING LANDERS; IRON-OXIDES; DUST; SPECTROSCOPY; MINERALOGY; HEMATITE; PYROXENE; SURFACE AB Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity similar to 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers. C1 CORNELL UNIV,ITHACA,NY 14853. CALTECH,JET PROP LAB,PASADENA,CA 91109. US GEOL SURVEY,FLAGSTAFF,AZ 86001. ARIZONA STATE UNIV,TEMPE,AZ 85287. MAX PLANCK INST AERON,KATHENBURG LINDAU,GERMANY. DLR,BERLIN,GERMANY. MALIN SPACE SCI SYST,SAN DIEGO,CA. JOHNS HOPKINS UNIV,APPL PHYS LAB,BALTIMORE,MD 21218. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Smith, PH (reprint author), UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721, USA. RI Lemmon, Mark/E-9983-2010; Murchie, Scott/E-8030-2015; Johnson, Jeffrey/F-3972-2015; Bridges, Nathan/D-6341-2016 OI Lemmon, Mark/0000-0002-4504-5136; Murchie, Scott/0000-0002-1616-8751; NR 48 TC 184 Z9 185 U1 1 U2 18 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 5 PY 1997 VL 278 IS 5344 BP 1758 EP 1765 DI 10.1126/science.278.5344.1758 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ901 UT WOS:A1997YJ90100036 PM 9388170 ER PT J AU Matijevic, JR Crisp, J Bickler, DB Banes, RS Cooper, BK Eisen, HJ Gensler, J Haldemann, A Hartman, F Jewett, KA Matthies, LH Laubach, SL Mishkin, AH Morrison, JC Nguyen, TT Sirota, AR Stone, HW Stride, S Sword, LF Tarsala, JA Thompson, AD Wallace, MT Welch, R Wellman, E Wilcox, BH Ferguson, D Jenkins, P Kolecki, J Landis, GA Wilt, D AF Matijevic, JR Crisp, J Bickler, DB Banes, RS Cooper, BK Eisen, HJ Gensler, J Haldemann, A Hartman, F Jewett, KA Matthies, LH Laubach, SL Mishkin, AH Morrison, JC Nguyen, TT Sirota, AR Stone, HW Stride, S Sword, LF Tarsala, JA Thompson, AD Wallace, MT Welch, R Wellman, E Wilcox, BH Ferguson, D Jenkins, P Kolecki, J Landis, GA Wilt, D TI Characterization of the Martian surface deposits by the Mars Pathfinder rover, Sojourner SO SCIENCE LA English DT Article AB Sojourner, the Mars Pathfinder rover, discovered pebbles on the surface and in rocks that may be sedimentary-not volcanic-in origin. Surface pebbles may have been rounded by Ares flood waters or liberated by weathering of sedimentary rocks called conglomerates. Conglomerates imply that water existed elsewhere and earlier than the Ares flood. Most soil-like deposits are similar to moderately dense soils on Earth. Small amounts of dust are currently settling from the atmosphere. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Matijevic, JR (reprint author), US GEOL SURVEY,345 MIDDLEFIELD RD,MENLO PK,CA 94025, USA. RI Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 14 TC 97 Z9 97 U1 2 U2 14 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 5 PY 1997 VL 278 IS 5344 BP 1765 EP 1768 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ901 UT WOS:A1997YJ90100037 ER PT J AU Rieder, R Economou, T Wanke, H Turkevich, A Crisp, J Bruckner, J Dreibus, G McSween, HY AF Rieder, R Economou, T Wanke, H Turkevich, A Crisp, J Bruckner, J Dreibus, G McSween, HY TI The chemical composition of Martian soil and rocks returned by the mobile alpha proton x-ray spectrometer: Preliminary results from the x-ray mode SO SCIENCE LA English DT Article AB The alpha proton x-ray spectrometer (APXS) on board the rover of the Mars Pathfinder mission measured the chemical composition of six soils and five rocks at the Ares Vallis landing site, The soil analyses show similarity to those determined by the Viking missions. The analyzed rocks were partially covered by dust but otherwise compositionally similar to each other. They are unexpectedly high in silica and potassium, but low in magnesium compared to martian soils and martian meteorites, The analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of Earth's crust. Addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition. C1 MAX PLANCK INST CHEM,D-55020 MAINZ,GERMANY. UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV TENNESSEE,DEPT GEOL SCI,KNOXVILLE,TN 37996. RI Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 14 TC 299 Z9 303 U1 9 U2 54 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 5 PY 1997 VL 278 IS 5344 BP 1771 EP 1774 DI 10.1126/science.278.5344.1771 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ901 UT WOS:A1997YJ90100039 PM 9388173 ER PT J AU Yung, YL Miller, CE AF Yung, YL Miller, CE TI Isotopic fractionation of stratospheric nitrous oxide SO SCIENCE LA English DT Article ID ULTRAVIOLET-ABSORPTION; N2O; PHOTODISSOCIATION; TEMPERATURE; SPECTRA; CF2CL2; REGION; CFCL3; SINK; O2 AB We propose an isotopic fractionation mechanism, based on photolytic destruction, to explain the N-15/N-14 and O-18/O-16 fractionation of stratospheric nitrous oxide (N2O) and reconcile laboratory experiments with atmospheric observations. The theory predicts that (i) the isotopomers (NNO)-N-15-N-14-O-16 and (NNO)-N-14-N-15-O-16 have very different isotopic fractionations in the stratosphere, and (ii) laboratory photolysis experiments conducted at 205 nanometers should better simulate the observed isotopic fractionation of stratospheric N2O. Modeling results indicate that there is no compelling reason to invoke a significant chemical source of N2O in the middle atmosphere and that individual N2O isotopomers might be useful tracers of stratospheric air parcel motion. C1 CALTECH,JET PROP LAB,ATMOSPHER KINET & PHOTOCHEM GRP,PASADENA,CA 91109. RP Yung, YL (reprint author), CALTECH,DIV GEOL & PLANETARY SCI,MAIL STOP 150-21,PASADENA,CA 91125, USA. NR 32 TC 122 Z9 122 U1 1 U2 83 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 5 PY 1997 VL 278 IS 5344 BP 1778 EP 1780 DI 10.1126/science.278.5344.1778 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ901 UT WOS:A1997YJ90100042 ER PT J AU Lester, MI Loomis, RA Schwartz, RL Walch, SP AF Lester, MI Loomis, RA Schwartz, RL Walch, SP TI Electronic quenching of OH A (2)Sigma(+) (v' = 0, 1) in complexes with hydrogen and nitrogen SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID POTENTIAL-ENERGY SURFACE; RESOLVED CROSS-SECTIONS; ELEVATED-TEMPERATURES; OH-H2 COLLISIONS; A2SIGMA+ STATE; A2-SIGMA+ OH; SHOCK-TUBE; DYNAMICS; LASER; OD AB The quenching of electronically excited PH A (2) Sigma(+) radicals has been investigated in complexes of OH with molecular hydrogen, deuterium, and nitrogen and through complementary theoretical calculations. Many of the intermolecular vibrational levels supported by the OH A (2) Sigma(+) (v' = 0, 1) + H-2, D-2, and N-2 potentials have been characterized by laser-induced fluorescence and fluorescence depletion measurements of the complexes in the OH A (2) Sigma(+)-X (2) Pi 1-0 and 0-0 spectral regions. Homogeneous line broadening of the spectral features yields picosecond lifetimes for complexes prepared in levels derived from OH A (2) Sigma(+) (v' = 0) as a result of electronic quenching and/or chemical reaction. More extensive line broadening is observed for complexes excited to levels correlating with OH A (2) Sigma(+) (v' = 1). The corresponding decay rates are 10-75 times faster than obtained for upsilon' = 0 due to the opening of the vibrational predissociation channel and/or enhancement of the quenching/reaction processes upon OH vibrational excitation. Ab initio calculations of the OH (A (2) Sigma(+), X (2) Pi) + H-2 and N-2 potential energy surfaces reveal the minimum energy configurations, T-shaped O-H-H-2 and linear O-H-N=N, and the large increases in interaction energy upon electronic excitation of OH. The theoretical calculations also identify specific orientations, T-shaped H-O-H-2 and linear H-O-N=N, that lead to conical intersections between the ground-and excited-state surfaces and give rise to quenching of OH A (2) Sigma(+) by hydrogen and nitrogen. C1 NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035. RP Lester, MI (reprint author), UNIV PENN,DEPT CHEM,PHILADELPHIA,PA 19104, USA. NR 53 TC 55 Z9 55 U1 1 U2 14 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD DEC 4 PY 1997 VL 101 IS 49 BP 9195 EP 9206 DI 10.1021/jp9727557 PG 12 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YL174 UT WOS:A1997YL17400003 ER PT J AU McKay, DS Gibson, E ThomasKeprta, K Vali, H AF McKay, DS Gibson, E ThomasKeprta, K Vali, H TI No 'nanofossils' in Martian meteorite - Reply SO NATURE LA English DT Letter ID ALH84001 C1 LOCKHEED MARTIN,HOUSTON,TX 77058. MCGILL UNIV,MONTREAL,PQ H3A 2A7,CANADA. RP McKay, DS (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058, USA. RI Vali, Hojatollah/F-3511-2012 OI Vali, Hojatollah/0000-0003-3464-9943 NR 12 TC 22 Z9 24 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD DEC 4 PY 1997 VL 390 IS 6659 BP 455 EP 456 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YJ865 UT WOS:A1997YJ86500032 ER PT J AU Caines, PE Gupta, V Shen, G AF Caines, PE Gupta, V Shen, G TI The hierarchical control of ST-finite-state machines SO SYSTEMS & CONTROL LETTERS LA English DT Article DE controllability; discrete event systems; hierarchical control; dynamical consistency; source-target systems; state-space partitions ID DISCRETE-EVENT SYSTEMS AB This paper follows (Caines and Wei, 1995) where a new notion of state aggregation for finite machines was introduced via the concept of the dynamical consistency (DC) relation between the blocks of states in any given state-space partition pi. This formulation results in a definition of high-level dynamics on the finite (partition) machine M(pi) whose states correspond to the given partition elements. This paper heats the more general case of ST-systems where there is a preferred sense of flow from a set of source states (S) to a set of target states (T) which is to be achieved by hierarchical control. A generalisation of the theory of Caines and Wei to ST-systems is given which includes the generalisation of the notions of dynamical consistency, in block controllability and hierarchical feedback control on the associated hierarchical lattices. (C) 1997 Elsevier Science B.V. C1 McGill Univ, Dept Elect Engn, Montreal, PQ H3A 2A7, Canada. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Caines, PE (reprint author), McGill Univ, Dept Elect Engn, 3480 Univ St, Montreal, PQ H3A 2A7, Canada. EM peterc@cim.mcgill; shg@cim.mcgill NR 14 TC 8 Z9 8 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-6911 J9 SYST CONTROL LETT JI Syst. Control Lett. PD DEC 3 PY 1997 VL 32 IS 4 BP 185 EP 192 DI 10.1016/S0167-6911(97)00072-8 PG 8 WC Automation & Control Systems; Operations Research & Management Science SC Automation & Control Systems; Operations Research & Management Science GA YR101 UT WOS:000071458400001 ER PT J AU Freeman, DC Talay, TA Austin, RE AF Freeman, DC Talay, TA Austin, RE TI Reusable launch vehicle technology program SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 47th International Astronautical Congress CY OCT 07-11, 1996 CL BEIJING, PEOPLES R CHINA AB Industry/NASA reusable launch vehicle (RLV) technology program efforts are underway to design, test, and develop technologies and concepts for viable commercial launch systems that also satisfy national needs at acceptable recurring costs. Significant progress has been made in understanding the technical challenges of fully reusable launch systems and the accompanying management and operational approaches for achieving a low-cost program. This paper reviews the current status of the RLV technology program including the DC-XA, X-33 and X-34 flight systems and associated technology programs. It addresses the specific technologies being tested that address the technical and operability challenges of reusable launch systems including reusable cryogenic propellant tanks, composite structures, thermal protection systems, improved propulsion. and subsystem operability enhancements. The recently concluded DC-XA lest program demonstrated some of these technologies in ground and flight tests. Contracts were awarded recently for both the X-33 and X-34 flight demonstrator systems. The Orbital Sciences Corporation X-33 flight test vehicle will demonstrate an air-launched reusable vehicle capable of flight to speeds of Mach 8. The Lockheed-Martin X-33 flight test vehicle will expand the test envelope for critical technologies to flight speeds of Mach 15. A propulsion program to lest the X-33 linear aerospike rocket engine using a NASA SR-71 high speed aircraft as a test bed is also discussed. The paper also describes the management and operational approaches that address the challenge of new cost-effective, reusable launch vehicle systems. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Freeman, DC (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 2 TC 17 Z9 18 U1 1 U2 12 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD DEC PY 1997 VL 41 IS 11 BP 777 EP 790 DI 10.1016/S0094-5765(97)00197-5 PG 14 WC Engineering, Aerospace SC Engineering GA ZX596 UT WOS:000074534100007 ER PT J AU Hornstein, RS Miller, RE Hei, DJ Kaufmann, DE Lopinto, FJ Todd, JE AF Hornstein, RS Miller, RE Hei, DJ Kaufmann, DE Lopinto, FJ Todd, JE TI A multi-disciplinary plan for easier access, management, and analysts of science data SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 47th International Astronautical Congress CY OCT 07-11, 1996 CL BEIJING, PEOPLES R CHINA AB NASA's COST LESS Team is pursuing strategies to reduce the cost and complexity of planning and executing space missions. The team's technical goal is to reverse the trend of constructing unique solutions for similar problems. To this end, the team is exploring-ways to represent mission functionality in terms of building blocks and is discovering approaches that could accommodate the same building blocks for seemingly disparate activities, such as organizing processed telemetry data, controlling onboard experiments, searching science archives, reducing and presenting information to science users, and supporting educational outreach. Reusable object technology (UOT), a research undertaking by the authors, is showing promise in recognizing similarities in functions which were previously viewed as unique because they appeared in different programs or mission phases. Since UOT is aimed at being implementation independent (i.e. the function performed could be accomplished manually, by an automated process, by a specialized instrument, etc.), no premature judgment for automation or autonomy need be made. In this paper, the authors attempt to strike a balance between theory and reality as they describe UOT, including its beginnings, its underpinning, its utility, and its potential for achieving substantive reductions in cost and complexity for the Agency's space programs. The authors discuss their collaboration with the Center for EUV Astrophysics, University of California, Berkeley to reduce the cost and complexity of science investigations. Their multi-disciplinary plan incorporates both UOT and a complementary technology introduced in this paper, called interactive archives. (C) 1998 Published by Elsevier Science Ltd. All rights reserved C1 NASA, Washington, DC 20546 USA. RP Hornstein, RS (reprint author), NASA, Washington, DC 20546 USA. NR 18 TC 0 Z9 0 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD DEC PY 1997 VL 41 IS 12 BP 833 EP 840 DI 10.1016/S0094-5765(98)00004-6 PG 8 WC Engineering, Aerospace SC Engineering GA 101XT UT WOS:000074894000004 ER PT J AU Hayes, P Ford, K AF Hayes, P Ford, K TI Drawing the line SO AI MAGAZINE LA English DT Editorial Material C1 Univ W Florida, Inst Human & Machine Cognit, Pensacola, FL 32514 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hayes, P (reprint author), Univ W Florida, Inst Human & Machine Cognit, Pensacola, FL 32514 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER ASSOC ARTIFICIAL INTELL PI MENLO PK PA 445 BURGESS DRIVE, MENLO PK, CA 94025-3496 USA SN 0738-4602 J9 AI MAG JI AI Mag. PD WIN PY 1997 VL 18 IS 4 BP 168 EP 168 PG 1 WC Computer Science, Artificial Intelligence SC Computer Science GA YN301 UT WOS:000071153200013 ER PT J AU Mukasyan, A Pelekh, A Varma, A Rogachev, A Jenkins, A AF Mukasyan, A Pelekh, A Varma, A Rogachev, A Jenkins, A TI Effects of gravity on combustion synthesis in heterogeneous gasless systems SO AIAA JOURNAL LA English DT Article AB The first systematic experimental investigation of combustion synthesis from elements conducted under low (10(-4) m/s(2)) gravity conditions is reported. Several classes of gasless heterogeneous reaction systems were studied, e.g., Ni-Al, Ti-C, and Ni-Al-Ti-B. A variety of gravity-related effects were observed. It was shown that the convection of inert gas, occurring in the reaction chamber during the combustion process in terrestrial conditions, leads to instability of combustion front propagation along the sample. Also, composite materials (Ni3Al-TiB2) produced in microgravity have finer size of refractory phase (TiB2) that is more uniformly distributed in the Ni3Al intermetallic matrix. The grains formed in terrestrial conditions were approximately 50% larger. The results obtained with quenched samples showed that this difference is related to the buoyancy enhanced coalescence process. For the Ti-C system, dynamics of sample expansion have been determined, and materials with final porosity up to 90% have been synthesized in microgravity conditions without the use of any gasifying additives. Finally, it was observed that the combustion velocity for loose Ni-Al mixtures in microgravity is about three times larger than in terrestrial conditions. This effect may be explained by a change in the primary mechanism of heat transfer through the reaction medium. C1 NASA, LEWIS RES CTR, SPACE EXPT DIV, GROUND BASED FACIL BRANCH, CLEVELAND, OH 44135 USA. RP UNIV NOTRE DAME, DEPT CHEM ENGN, NOTRE DAME, IN 46656 USA. RI Mukasyan, Alexander/K-1784-2013 OI Mukasyan, Alexander/0000-0001-8866-0043 NR 27 TC 23 Z9 23 U1 0 U2 3 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0001-1452 EI 1533-385X J9 AIAA J JI AIAA J. PD DEC PY 1997 VL 35 IS 12 BP 1821 EP 1828 DI 10.2514/2.57 PG 8 WC Engineering, Aerospace SC Engineering GA YJ078 UT WOS:A1997YJ07800004 ER PT J AU Kostenuik, PJ Halloran, BP Morey-Holton, ER Bikle, DD AF Kostenuik, PJ Halloran, BP Morey-Holton, ER Bikle, DD TI Skeletal unloading inhibits the in vitro proliferation and differentiation of rat osteoprogenitor cells SO AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM LA English DT Article DE bone; alkaline phosphatase; c-fos; osteocalcin; mineralization ID MESSENGER-RNA; BONE MATURATION; MARROW; WEIGHTLESSNESS; SPACEFLIGHT; EXPRESSION; DECREASES; CULTURES; GROWTH AB Loss of weight bearing in the growing rat decreases bone formation, osteoblast numbers, and bone maturation in unloaded bones. These responses suggest an impairment of osteoblast proliferation and differentiation. To test this assumption, we assessed the effects of skeletal unloading using an in vitro model of osteoprogenitor cell differentiation. Rats were hindlimb elevated for 0 (control), 2, or 5 days, after which their tibial bone marrow stromal cells (BMSCs) were harvested and cultured. Five days of hindlimb elevation led to significant decreases in proliferation, alkaline phosphatase (AP) enzyme activity, and mineralization of BMSC cultures. Differentiation of BMSCs was analyzed by quantitative competitive polymerase chain reaction of cDNA after 10, 15, 20, and 28 days of culture. cDNA pools were analyzed for the expression of c-fos (an index of proliferation), AP (an index of early osteoblast differentiation), and osteocalcin (a marker of late differentiation). BMSCs from 5-day unloaded rats expressed 50% less c-fos, 61% more AP, and 35% less osteocalcin mRNA compared with controls. These data demonstrate that cultured osteoprogenitor cells retain a memory of their in vivo loading history and indicate that skeletal unloading inhibits proliferation and differentiation of osteoprogenitor cells in vitro. C1 Univ Calif San Francisco, Vet Adm Med Ctr, Dept Med, San Francisco, CA 94121 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bikle, DD (reprint author), Univ Calif San Francisco, Vet Adm Med Ctr, Dept Med, 4150 Clement St, San Francisco, CA 94121 USA. NR 27 TC 89 Z9 95 U1 0 U2 2 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 0193-1849 J9 AM J PHYSIOL-ENDOC M JI Am. J. Physiol.-Endocrinol. Metab. PD DEC PY 1997 VL 273 IS 6 BP E1133 EP E1139 PG 7 WC Endocrinology & Metabolism; Physiology SC Endocrinology & Metabolism; Physiology GA YM202 UT WOS:000071040000013 ER PT J AU Dister, SW Fish, D Bros, SM Frank, DH Wood, BL AF Dister, SW Fish, D Bros, SM Frank, DH Wood, BL TI Landscape characterization of peridomestic risk for Lyme disease using satellite imagery SO AMERICAN JOURNAL OF TROPICAL MEDICINE AND HYGIENE LA English DT Article ID IXODES-DAMMINI ACARI; WHITE-TAILED DEER; NEW-YORK; SCAPULARIS ACARI; TASSELED CAP; LANDSAT-TM; IXODIDAE; ABUNDANCE; HABITATS; ISLAND AB Remotely sensed characterizations of landscape composition were evaluated for Lyme disease exposure risk on 337 residential properties in two communities of suburban Westchester County, New York. Properties were categorized as no, low, or high risk based on seasonally adjusted densities of Ixodes scapularis nymphs, determined by drag sampling during June and July 1990. Spectral indices based on Landsat Thematic Mapper data provided relative measures of vegetation structure and moisture (wetness), as well as vegetation abundance (greenness). A geographic information system (GIS) was used to spatially quantify and relate the remotely sensed landscape variables to risk category. A comparison of the two communities showed that Chappaqua, which had more high-risk properties (P < 0.001), was significantly greener and wetter than Armonk (P < 0.001). Furthermore, within Chappaqua, highrisk properties were significantly greener and wetter than lower-risk properties in this community (P < 0.01). The high-risk properties appeared to contain a greater proportion of broadleaf trees, while lower-risk properties were interpreted as having a greater proportion of nonvegetative cover and/or open lawn. The ability to distinguish these fine scale differences among communities and individual properties illustrates the efficiency of a remote sensing/GIS-based approach for identifying peridomestic risk of Lyme disease over large geographic areas. C1 NASA, Johnson Controls World Serv Inc, Ames Res Ctr, Moffett Field, CA 94035 USA. Yale Univ, Sch Med, Dept Epidemiol & Publ Hlth, New Haven, CT 06520 USA. San Jose State Univ, Dept Sci Biol, San Jose, CA 95192 USA. New York Med Coll, Dept Community & Prevent Med, Valhalla, NY 10595 USA. NASA, Ecosyst Sci & Technol Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dister, SW (reprint author), NASA, Johnson Controls World Serv Inc, Ames Res Ctr, MS 242-4, Moffett Field, CA 94035 USA. FU NIAID NIH HHS [AI-28956] NR 43 TC 100 Z9 108 U1 1 U2 17 PU AMER SOC TROP MED & HYGIENE PI MCLEAN PA 8000 WESTPARK DRIVE SUITE 130, MCLEAN, VA 22101 USA SN 0002-9637 J9 AM J TROP MED HYG JI Am. J. Trop. Med. Hyg. PD DEC PY 1997 VL 57 IS 6 BP 687 EP 692 PG 6 WC Public, Environmental & Occupational Health; Tropical Medicine SC Public, Environmental & Occupational Health; Tropical Medicine GA YQ731 UT WOS:000071417600012 PM 9430528 ER PT J AU Leviton, DB Hagopian, JG Geithner, PH Boucarut, RA Madison, TJ KeskiKuha, RAM Hartig, G Gardner, LD French, TA AF Leviton, DB Hagopian, JG Geithner, PH Boucarut, RA Madison, TJ KeskiKuha, RAM Hartig, G Gardner, LD French, TA TI Measuring efficiency of far ultraviolet optical systems in gaseous nitrogen SO APPLIED OPTICS LA English DT Editorial Material AB Goddard Space Flight Center has developed the practice of measuring far ultraviolet (FUV) transmission of optical systems, and components, in a gaseous nitrogen environment, and applied the technique to tests of several flight optical systems. This practice is a flexible, cheap, safe, and reliable alternative to equivalent testing in vacuum chambers. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. HARVARD SMITHSONIAN ASTROPHYS OBSERV,CAMBRIDGE,MA. NSI TECH SERV CORP,GREENBELT,MD. RP Leviton, DB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 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 DEC 1 PY 1997 VL 36 IS 34 BP 9099 EP 9100 DI 10.1364/AO.36.009099 PG 2 WC Optics SC Optics GA YJ899 UT WOS:A1997YJ89900041 ER PT J AU Stanford, SA Elston, R Eisenhardt, PR Spinrad, H Stern, D Dey, A AF Stanford, SA Elston, R Eisenhardt, PR Spinrad, H Stern, D Dey, A TI An IR-selected galaxy cluster at z=1.27 SO ASTRONOMICAL JOURNAL LA English DT Article ID DARK MATTER THEORY; RICH CLUSTERS; X-RAY; SCALE AB We report the discovery of a galaxy cluster at z=1.27. CIG J0848+4453 was found in a near-IR field survey as a high density region of objects with very red J-K colors. Optical spectroscopy of a limited number of 24 less than or similar to R less than or similar to 25 objects in the area shows that 6 galaxies within a 90 arcsec (0.49h(100)(-1), Mpc, q(0) = 0.1) diameter region lie at z = 1.273+/-0.002. Most of these 6 member galaxies have broad-band colors consistent with the expected spectral energy distribution of a passively-evolving elliptical galaxy formed at high redshift, An additional 2 galaxies located similar to 2 arcmin from the cluster center are also at z = 1.27. Using all 8 of these spectroscopic members, we estimate the velocity dispersion sigma=700+/-180 km s(-1), which in similar to that of Abell richness class R = 1 clusters in the present epoch. A deep ROSAT/PSPC observation detects X-ray emission at the 4.5 sigma level coincident with the nominal cluster center. Assuming that the X-ray flux is emitted by hot gas trapped in rbe potential well of a collapsed system (no AGN are known to exist in the area), the resulting X-ray luminosity in the rest frame 0.1-2.4 keV band of L-x = 1.5 X 10(44) ergs s(-1) suggests the presence of a moderately massive system, CIG J0848+4453 is the highest redshift cluster found in a held survey. (C) 1997 American Astronomical Society. [S0004-6256(97)02112-2]. C1 UNIV FLORIDA, DEPT ASTRON, GAINESVILLE, FL 32611 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. NATL OPT ASTRON OBSERV, TUCSON, AZ 85726 USA. RP Stanford, SA (reprint author), LAWRENCE LIVERMORE NATL LAB, INST GEOPHYS & PLANETARY PHYS, LIVERMORE, CA 94550 USA. NR 43 TC 143 Z9 143 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 DEC PY 1997 VL 114 IS 6 BP 2232 EP + DI 10.1086/118643 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL191 UT WOS:A1997YL19100004 ER PT J AU Barth, AJ Reichert, GA Ho, LC Shields, JC Filippenko, AV Puchnarewicz, EM AF Barth, AJ Reichert, GA Ho, LC Shields, JC Filippenko, AV Puchnarewicz, EM TI Ultraviolet emission from the liner nucleus of NGC 6500 SO ASTRONOMICAL JOURNAL LA English DT Article ID PHOTOIONIZATION MODELS; GALACTIC NUCLEI; GALAXIES; EXTINCTION; TELESCOPE; SPECTRUM; NGC-4579; NGC-6500; STARS; DUST AB As a step towards clarifying the ionization mechanism of LINERs, we have used the Hubble Space Telescope Faint Object Spectrograph to obtain an ultraviolet spectrum of the nucleus of NGC 6500. This is the first time that such a spectrum has been taken of a ''LINER 2'' nucleus-that is, a LINER lacking broad permitted emission lines like those in Type 1 Seyfert nuclei. Compared with more luminous Seyfert nuclei, the ultraviolet emission-line spectrum of. NGC 6500 is remarkable for its low-excitation character: C III] lambda 1909, C II] lambda 2326, and Mg II lambda 2800 are the strongest collisionally-excited lines in the spectrum, and C IV lambda 1549 is not detected. We use the emission-line fluxes to test the hypothesis, advanced by Dopita & Sutherland (1995, ApJ, 455, 468), that the narrow-line regions of LINERs are primarily excited by fast (150-500 km s(-1)) shocks, rather than photoionized by a central continuum source. The fast shock models are a poor match to the observed spectrum, as they predict much stronger emission than is observed for high-excitation lines such as C IV lambda 1549. Photoionization by an obscured nonstellar continuum source, or possibly ionization by slower (similar to 100 km s(-1)) shocks, are more likely explanations for the emission-line ratios. The origin of the ultraviolet continuum is unclear; its overall spectral shape is reasonably well matched by spectral evolution models for single-burst populations with ages in the range 70-100 Myr, but no definite stellar absorption features due to young stars are present. Alternately, the ultraviolet continuum (or some fraction of it) may be scattered radiation from a hidden active nucleus. We tentatively detect a broad He II lambda 4686 emission feature, which may be due to Wolf-Rayet stars, although the ultraviolet spectrum does not show any clear Wolf-Rayet signatures. We also find that NGC 6500 is weakly detected in an archival ROSAT HRI image with a luminosity of similar to 5 X 10(40) erg s(-1) in the 0.1-2.4 keV band, within the normal range for LINERs. (C) 1997 American Astronomical Society. [S0004-6256(97)00812-1]. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. OHIO UNIV, DEPT PHYS & ASTRON, ATHENS, OH 45701 USA. UCL, MULLARD SPACE SCI LAB, DORKING RH5 6NT, SURREY, ENGLAND. RP Barth, AJ (reprint author), UNIV CALIF BERKELEY, DEPT ASTRON, 601 CAMPBELL HALL, BERKELEY, CA 94720 USA. OI Barth, Aaron/0000-0002-3026-0562 NR 53 TC 23 Z9 23 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 DEC PY 1997 VL 114 IS 6 BP 2313 EP 2322 DI 10.1086/118650 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL191 UT WOS:A1997YL19100011 ER PT J AU Curiel, S Raga, A Raymond, J NoriegaCrespo, A Canto, J AF Curiel, S Raga, A Raymond, J NoriegaCrespo, A Canto, J TI HST images of the high-excitation Herbig-Haro object HH 32 SO ASTRONOMICAL JOURNAL LA English DT Article ID BOW-SHOCK; STELLAR JET; EMISSION; MODELS; AS-353A/HH-32; PERFORMANCE; COMPLEX; TAURI; HH-32; WFPC2 AB We present high angular resolution emission-line and continuum images of the remarkable Herbig-Haro jet HH 32 obtained with the Wide Field and Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope. We have obtained narrow band [S II] lambda lambda 6716,6731, [N II] lambda 6583 and H alpha images, as well as an R continuum image, of this HH jet. The 0.'' 1 spatial resolution (corresponding to 30 AU at the distance of HH 32) and the high signal-to-noise ratio of these WFPC2 images allow us to study this highly collimated outflow in unprecedented detail. The images show differences between the stratification of the different emission lines. The knots are clearly resolved into complex structures that resemble working surfaces. The western side of the jet starts in a funnel-shaped structure that points toward the bright condensations HH 32D, 32B, and 32A, while on the other side of the jet the dominant structure is an arc-like feature that points almost directly away from the young star AS 353A. The HH 32A condensation exhibits a region strong in [S II] that we identify as the Mach Disk at the tip of the jet. Finally, the HST images are used in combination with previous, high resolution ground based observations (obtained with the Canada-France-Hawaii telescope) to obtain proper motion determinations. We find that the kinematical properties deduced from these proper motions are consistent with those of a jet moving at about 300 km/s, penetrating into the maternal cloud at an angle of 70 degrees between the outflow axis and the plane of the sky. This is also consistent with the properties deduced from previously obtained high resolution spectra of HH 32. We find that the kinematical properties deduced from these proper motions are completely consistent with previous proper motion measurements, as well as with the properties deduced from previously obtained, high resolution spectra of HH 32. (C) 1997 American Astronomical Society. [S0004-6256(97)01012-1]. C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,PASADENA,CA 91125. RP Curiel, S (reprint author), UNIV NACL AUTONOMA MEXICO,INST ASTRON,AP 70-264,MEXICO CITY 04510,DF,MEXICO. NR 35 TC 20 Z9 20 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD DEC PY 1997 VL 114 IS 6 BP 2736 EP & DI 10.1086/118682 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL191 UT WOS:A1997YL19100043 ER PT J AU Hemenway, PD Duncombe, RL Bozyan, EP Lalich, AM Argue, AN Franz, OG McArthur, B Nelan, E Taylor, D White, G Benedict, GF Crifo, F Fredrick, LW Jefferys, WH Johnston, K Kovalevsky, J Kristian, J Perryman, MAC Preston, R Shelus, PJ Turon, C vanAltena, W AF Hemenway, PD Duncombe, RL Bozyan, EP Lalich, AM Argue, AN Franz, OG McArthur, B Nelan, E Taylor, D White, G Benedict, GF Crifo, F Fredrick, LW Jefferys, WH Johnston, K Kovalevsky, J Kristian, J Perryman, MAC Preston, R Shelus, PJ Turon, C vanAltena, W TI The program to link the HIPPARCOS reference frame to an extragalactic reference system using the fine guidance sensors of the Hubble Space Telescope SO ASTRONOMICAL JOURNAL LA English DT Article ID SPECKLE INTERFEROMETRY; STARS AB The Hipparcos Satellite Mission has produced positions, proper motions, and parallaxes of unprecedented accuracy for 118,000 stars. For the positions and proper motions to represent true directions and physical motions in space, they must refer to an accurate realization of a nonrotating (inertial) reference frame. One of the major problems confronting the Hipparcos Project was the determination of the relationship of the satellite coordinate system to the best available celestial coordinate system, hopefully at an accuracy approaching the systematic accuracy of the Hipparcos satellite itself. In 1978 we recognized the possibility of using the Fine Guidance Sensors of the Hubble Space Telescope (HST) to measure the Hipparcos coordinate offset and its time variation with respect to extragalactic objects, and we undertook that project. The first HST observation for the project was made in 1993 April, and the last observation used in the solution was made in 1995 October. The HST data consist of accurate angular separations of Extragalactic Objects from Hipparcos stars. Ultimately the HST solution was incorporated with other techniques to form the final link between Hipparcos and the International Celestial Reference System. This link determined the final catalogue system for the published Hipparcos data. We describe the problem, the instrumentation of the two space missions, the limitations imposed by the missions on the observations, the reduction and analysis procedures, and the final results with respect to the final Hipparcos solution. We determine the relation of the Hipparcos coordinate axes with respect to the ICRS coordinate axes from the HST, Hipparcos, and VLBI data alone. The rms uncertainties are about 2 milliarcseconds for the angular offsets and about 2.5 milliarcseconds/yr for the angular rotations. (C) 1997 American Astronomical Society. [S0004-6256(97)03612-1]. C1 UNIV TEXAS, DEPT AEROSP ENGN, CTR SPACE RES, AUSTIN, TX 78712 USA. UNIV RHODE ISL, DEPT PHYS, KINGSTON, RI 02881 USA. UNIV CAMBRIDGE, CAMBRIDGE, ENGLAND. LOWELL OBSERV, FLAGSTAFF, AZ 86001 USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. UNIV WESTERN SYDNEY NEPEAN, NEPEAN, ON, CANADA. OBSERV PARIS, MEUDON, FRANCE. UNIV VIRGINIA, DEPT ASTRON, CHARLOTTESVILLE, VA 22903 USA. UNIV TEXAS, DEPT ASTRON, AUSTIN, TX 78712 USA. USN OBSERV, WASHINGTON, DC 20392 USA. CERGA, OBSERV COTE AZUR, GRASSE, FRANCE. CARNEGIE INST WASHINGTON OBSERV, PASADENA, CA 91101 USA. ESA, NOORDWIJK, NETHERLANDS. CALTECH, JET PROP LAB, PASADENA, CA USA. YALE UNIV, DEPT ASTRON, NEW HAVEN, CT 06511 USA. RP Hemenway, PD (reprint author), UNIV TEXAS, MCDONALD OBSERV, AUSTIN, TX 78712 USA. OI Perryman, Michael/0000-0002-3953-4750 NR 15 TC 7 Z9 8 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 EI 1538-3881 J9 ASTRON J JI Astron. J. PD DEC PY 1997 VL 114 IS 6 BP 2796 EP 2810 DI 10.1086/118688 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL191 UT WOS:A1997YL19100049 ER PT J AU Skinner, CJ Meixner, M Barlow, MJ Collison, AJ Justtanont, K Blanco, P Pina, R Ball, JR Keto, E Arens, JF Jernigan, JG AF Skinner, CJ Meixner, M Barlow, MJ Collison, AJ Justtanont, K Blanco, P Pina, R Ball, JR Keto, E Arens, JF Jernigan, JG TI The remarkable asymmetric outflow from the Cygnus Egg Nebula SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE circumstellar matter; stars: evolution; stars: individual (AFGL2688); stars: AGB and post-AGB; stars: mass-loss; infrared: stars ID PROTO-PLANETARY-NEBULAE; PROTOPLANETARY NEBULA; EVOLVED STARS; INFRARED SPECTROSCOPY; CIRCUMSTELLAR DUST; REFLECTION NEBULAE; IRAS 21282+5050; MASS-LOSS; CRL-2688; EMISSION AB We present ground based continuum images in the infrared, from 1.2 to 19 mu m, and an H-2 2.122 mu m line emission image of the post-AGE star AFGL2688, the Cygnus Egg Nebula. We show that the standard model of this source, comprising a fast wind focussed by a dense, equatorial, dusty torus into a bipolar flow at position angle 15 degrees and close to the plane of the sky, cannot explain the combination of kinematic information from previous studies and morphological information in our own observations. Nor are the images consistent with a classical bipolar flow, since the apex of the two lobes observed in scattered light in the visible and near-IR are offset in R.A. with respect to one another. We suggest a model which is physically similar, but substantially different geometrically, in which there is a bipolar flow at a position angle closer to 60 degrees, rather than 15 degrees, still collimated by a dense, equatorial, dusty torus, but the opening angle of the cones out of which the Fast bipolar flow is directed is closer to 90 degrees, rather than 20 degrees or so as previously suggested. The bipolar flow axis is inclined by about 20-30 degrees, rather than in the plane of the sky as in previous models. The dust distribution in the nebula has to be extremely clumpy, and there is evidence that large scale mass loss from the progenitor AGE star occurred in discrete phases, recurring on a timescale of similar to 750 years. This model implies a much lower velocity for the 'fast' bipolar outflow than does the standard model, which is consistent with very recent Nobeyama Millimetre Array images in (CO)-C-13 emission. In support of our new model, we present a full radiative transfer model for the source, in axial symmetry, which reveals that the final phase of heavy mass loss included a superwind phase which lasted about two hundred years and removed about 0.7 M. from the envelope of the progenitor AGE star. Our results imply that the progenitor star must have been a relatively high mass AGB star. Our radiative transfer model also demonstrates convincingly that, in contrast with previous models, the core of the nebula has to be exceptionally optically thick, with an optical depth greater than unity even at 10 mu m. C1 LAWRENCE LIVERMORE NATL LAB, EXPT ASTROPHYS LAB, LIVERMORE, CA 94550 USA. LAWRENCE LIVERMORE NATL LAB, INST GEOPHYS & PLANETARY PHYS, LIVERMORE, CA 94550 USA. UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. UNIV ILLINOIS, DEPT ASTRON, URBANA, IL 61801 USA. UNIV LONDON UNIV COLL, DEPT PHYS & ASTRON, LONDON WC1E 6BT, ENGLAND. UNIV ILLINOIS, DEPT PHYS, LOOMIS LAB, URBANA, IL 61801 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV CALIF SAN DIEGO, CTR ASTROPHYS & SPACE SCI, LA JOLLA, CA 92093 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94551 USA. RP Skinner, CJ (reprint author), SPACE TELESCOPE SCI INST, 3700 SAN MARTIN DR, BALTIMORE, MD 21218 USA. RI Barlow, Michael/A-5638-2009; OI Barlow, Michael/0000-0002-3875-1171; /0000-0003-1689-9201 NR 67 TC 43 Z9 43 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1997 VL 328 IS 1 BP 290 EP 310 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ082 UT WOS:A1997YJ08200033 ER PT J AU Kraus, GF Nuth, JA Nelson, RN AF Kraus, GF Nuth, JA Nelson, RN TI Is SiS2 the carrier of the unidentified 21 micron emission feature? SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE line: identifications; stars: circumstellar matter; ISM: dust; infrared: lines and bands; methods: laboratory ID INTERSTELLAR-MEDIUM; OPTICAL-PROPERTIES; SPECTRA; OXIDE; DUST AB Spectra are presented of SiS2 samples in a variety of crystal forms taken at both room temperature and at 600 K over the wavelength range from 5-25 microns. All spectra show strong features at 22.5 and 9.5 microns as well as less intense bands at 7.5, 8.5, and 12.5 microns. All room temperature spectra also show a feature at 10.7 microns that disappears on heating. One form of SiS2 shows strong correlated absorption features at 20 and 17 microns that are rapidly quenched by exposure to humid air with no significant change to the 7-13 and 22 micron features also present in the sample. These SiS2 spectra are consistent with previous spectra obtained by Nuth et al. (1985), are marginally consistent with the identification of SiS2 as the source of the observed 21 micron peak in several carbon-rich stellar sources, and suggest additional observations of these stellar sources that might confirm or refute the presence of SiS2. Specifically, if no feature at 17 microns is detected in objects that display the strong 21 micron emission feature then SiS2 should be ruled out as a candidate for this band. C1 NASA, GODDARD SPACE FLIGHT CTR, ASTROCHEM BRANCH, GREENBELT, MD 20771 USA. CHARLES CTY COMMUNITY COLL, DEPT PHYS SCI, LA PLATA, MD 20646 USA. GEORGIA SO UNIV, DEPT CHEM, STATESBORO, GA 30460 USA. RI Nuth, Joseph/E-7085-2012 NR 21 TC 8 Z9 9 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1997 VL 328 IS 1 BP 419 EP 425 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ082 UT WOS:A1997YJ08200046 ER PT J AU Ehrenfreund, P Boogert, ACA Gerakines, PA Tielens, AGGM van Dishoeck, EF AF Ehrenfreund, P Boogert, ACA Gerakines, PA Tielens, AGGM van Dishoeck, EF TI Infrared spectroscopy of interstellar apolar ice analogs SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : molecules, dust; infrared : interstellar : lines; methods : laboratory ID TIME-DEPENDENT CHEMISTRY; DENSE MOLECULAR CLOUDS; GRAIN MANTLES; SOLID CO; SPECTRAL PROPERTIES; CARBON-MONOXIDE; DARK CLOUD; DUST; PROTOSTARS; METHANOL AB Apolar ices have been observed in several regions in dense clouds and are likely dominated by molecules such as CO, CO(2) and the infrared inactive molecules O(2) and N(2). Interstellar solid CO has been well characterized by ground-based high resolution measurements. Recent ISO results showed the ubiquitous presence of abundant CO(2) ice and the presence of CO(2)-rich ice mantles towards several molecular clouds. CO and CO(2) have sharp bands in the infrared and their band shape depends strongly on the ice composition. The profiles of the strong CO and CO(2) bands can therefore provide important information on the composition, temperature and thermal history of interstellar and precometary ices. We address, in this paper, the infrared spectra of 70 apolar ice mixtures of pure, binary, and multicomponent type. We studied their spectral properties at 10 K, during warm up and UV photolysis, and derived the optical constants. We discuss the importance of particle shape calculations for strong transitions such as CO and CO(2). In the laboratory context, we investigate the formation of CO(2) in the interstellar medium by UV photolysis of interstellar ices. Together with astronomical spectra taken by the ISO satellite these laboratory data will be extremely valuable for the determination of the grain mantle composition in dense clouds. C1 Leiden Observ, NL-2300 RA Leiden, Netherlands. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ehrenfreund, P (reprint author), Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands. RI Gerakines, Perry/B-9705-2009; Gerakines, Perry/D-2226-2012 OI Gerakines, Perry/0000-0002-9667-5904 NR 52 TC 142 Z9 143 U1 1 U2 9 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1997 VL 328 IS 2 BP 649 EP 669 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL875 UT WOS:000071002700032 ER PT J AU Frick, P Galyagin, D Hoyt, DV Nesme-Ribes, E Schatten, KH Sokoloff, D Zakharov, V AF Frick, P Galyagin, D Hoyt, DV Nesme-Ribes, E Schatten, KH Sokoloff, D Zakharov, V TI Wavelet analysis of solar activity recorded by sunspot groups SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE sun : activity; sunspots; methods : data analysis ID MAUNDER MINIMUM; DIAMETER; CYCLE AB The wavelet transform of monthly sunspot group data from 1610 to 1994 is investigated. Only two pronounced peaks corresponding to the Schwabe and the Gleissberg cycles, are present in this transform. The wavelet analysis of the time-series also shows the Maunder and Dalton minima as well as a deviation in the cycle length around 1900. The variations in the periodicity of the main 11 year cycle are studied. We show that all the minima of this cycle occur when the derivative of cycle length as a function of time is negative. Cycles of greater duration are connected with periods of weak solar activity. While the sunspot group number was periodic at the end of the Maunder minimum, it did not seem to follow any periodic behavior during the main part of this minimum. The abrupt transition between normal and Maunder minimum cycles is present in the sunspot group data. C1 Moscow State Univ, Dept Phys, Moscow 119899, Russia. Inst Continuous Media Mech, Perm 614061, Russia. Res & Data Syst Corp, Greenbelt, MD 20770 USA. Observ Paris, CNRS, URA 326, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sokoloff, D (reprint author), Moscow State Univ, Dept Phys, Moscow 119899, Russia. RI Frick, Peter/D-2345-2013; OI Frick, Peter/0000-0001-7156-1583 NR 24 TC 98 Z9 101 U1 0 U2 3 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1997 VL 328 IS 2 BP 670 EP 681 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL875 UT WOS:000071002700033 ER PT J AU Fixsen, DJ Weiland, JL Brodd, S Hauser, MG Kelsall, T Leisawitz, DT Mather, JC Jensen, KA Shafer, RA Silverberg, RF AF Fixsen, DJ Weiland, JL Brodd, S Hauser, MG Kelsall, T Leisawitz, DT Mather, JC Jensen, KA Shafer, RA Silverberg, RF TI Comparison of the COBE FIRAS and DIRBE calibrations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; infrared, general; instrumentation, photometers ID DESIGN; INSTRUMENT AB We compare the independent FIRAS and DIRBE observations from COBE in the wavelength range of 100-300 mu m. This cross calibration provides checks of both data sets. The results show that the data sets are consistent within the estimated gain and offset uncertainties of the two instruments. They show the possibility of improving the gain and offset determination of DIRBE at 140 and 240 mu m. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. RP Fixsen, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,CODE 6859,GREENBELT,MD 20771, USA. NR 12 TC 30 Z9 30 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 DEC 1 PY 1997 VL 490 IS 2 BP 482 EP 487 DI 10.1086/304906 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400002 ER PT J AU Rawson, DM Macri, LM Mould, JR Huchra, JP Freedman, WL Kennicutt, RC Ferrarese, L Ford, HC Graham, JA Harding, P Han, MS Hill, RJ Hoessel, JG Hughes, SMG Illingworth, GD Madore, BF Phelps, RL Saha, A Sakai, S Silbermann, NA Stetson, PB AF Rawson, DM Macri, LM Mould, JR Huchra, JP Freedman, WL Kennicutt, RC Ferrarese, L Ford, HC Graham, JA Harding, P Han, MS Hill, RJ Hoessel, JG Hughes, SMG Illingworth, GD Madore, BF Phelps, RL Saha, A Sakai, S Silbermann, NA Stetson, PB TI The extragalactic distance scale key project .8. The discovery of cepheids and a new distance to NGC 3621 using the Hubble Space Telescope SO ASTROPHYSICAL JOURNAL LA English DT Article DE cepheids; distance scale; galaxies, distances and redshifts; galaxies, individual (NGC 3621); galaxies, photometry ID CCD PHOTOMETRY; CALIBRATION; GALAXIES; PERFORMANCE; CONSTANT; WFPC2; M100 AB We report on the discovery of Cepheids in the field spiral galaxy NGC 3621, based on observations made with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). NGC 3621 is one of 18 galaxies observed as a part of the HST Key Project on the Extragalactic Distance Scale, which aims to measure the Hubble constant to 10% accuracy. Sixty-nine Cepheids with periods in the range 9-60 days were observed over 12 epochs using the F555W filter, and over four epochs using the F814W filter. The HST F555W and F814W data were transformed to the Johnson V and Kron-Cousins I magnitude systems, respectively. Photometry was performed using two-independent packages, DAOPHOT II/ALLFRAME and DoPHOT. Period-luminosity relations in the V and I bands were constructed using 36 fairly isolated Cepheids present in our set of 69 variables. Extinction-corrected distance moduli relative to the LMC of 10.63 +/- 0.09 and 10.56 +/- 0.10 mag were obtained using the ALLFRAME and DoPHOT data, respectively. True distance moduli of 29.13 +/- 0.18 and 29.06 +/- 0.18 mag, corresponding to distances of 6.3 +/- 0.7 and 6.1 +/- 0.7 Mpc, were obtained by assuming values of mu(0) = 18.50 +/- 0.10 mag and E(V-I) = 0.13 mag for the distance modulus and reddening of the LMC, respectively. C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. CARNEGIE INST WASHINGTON OBSERV,PASADENA,CA 91101. UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. CALTECH,CTR INFRARED PROC & ANAL,PASADENA,CA 91125. JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. CARNEGIE INST WASHINGTON,DEPT TERR MAGNETISM,WASHINGTON,DC 20015. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. ROYAL GREENWICH OBSERV,CAMBRIDGE CB3 0EZ,ENGLAND. UNIV CALIF SANTA CRUZ,LICK OBSERV,UCO,SANTA CRUZ,CA 95064. NATL RES COUNCIL CANADA,HERZBERG INST ASTROPHYS,DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA. RP Rawson, DM (reprint author), AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,INST ADV STUDIES,WESTON,ACT 2611,AUSTRALIA. OI Macri, Lucas/0000-0002-1775-4859 NR 32 TC 41 Z9 41 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 DEC 1 PY 1997 VL 490 IS 2 BP 517 EP & DI 10.1086/304882 PN 1 PG 398 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400006 ER PT J AU Sturner, SJ Skibo, JG Dermer, CD Mattox, JR AF Sturner, SJ Skibo, JG Dermer, CD Mattox, JR TI Temporal evolution of nonthermal spectra from supernova remnants SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; gamma rays, theory; shock waves; supernova remnants ID HIGH-ENERGY ELECTRONS; COSMIC-RAY ORIGIN; SHOCK ACCELERATION; PARTICLE-ACCELERATION; SYNCHROTRON RADIATION; EGRET SOURCES; SOLAR-FLARES; EMISSION; BREMSSTRAHLUNG; IC-443 AB Assuming that supernova shocks accelerate nonthermal particles, we model the temporally evolving nonthermal particle and photon spectra at different stages in the lifetime of a standard shell-type supernova remnant (SNR). A characteristic vF(v) spectrum of an SNR consists of a peak at radio through optical energies from nonthermal electron synchrotron emission and another high-energy gamma-ray peak due primarily to secondary pion production, nonthermal electron bremsstrahlung, and Compton scattering. We find that supernova remnants are capable of producing maximum gamma-ray luminosities greater than or similar to 10(35) ergs s(-1) if the density of the local interstellar medium is greater than or similar to 10 cm(-3). This emission will persist for greater than or similar to 10(5) yr after the supernova explosion because of the long energy loss timescales for electrons with kinetic energy similar to 1 GeV. This long gamma-ray lifetime implies that SNRs with a wide range of ages could be gamma-ray sources and could constitute some of the unidentified EGRET sources. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. BOSTON UNIV,DEPT ASTRON,BOSTON,MA 02215. RP Sturner, SJ (reprint author), UNIV SPACE RES ASSOC,7501 FORBES BLVD,SUITE 206,SEABROOK,MD 20706, USA. NR 62 TC 93 Z9 94 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 DEC 1 PY 1997 VL 490 IS 2 BP 619 EP 632 DI 10.1086/304894 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400013 ER PT J AU Whittet, DCB Boogert, ACA Gerakines, PA Schutte, W Tielens, AGGM deGraauw, T Prusti, T vanDishoeck, EF Wesselius, PR Wright, CM AF Whittet, DCB Boogert, ACA Gerakines, PA Schutte, W Tielens, AGGM deGraauw, T Prusti, T vanDishoeck, EF Wesselius, PR Wright, CM TI Infrared spectroscopy of dust in the diffuse interstellar medium toward Cygnus OB2 No. 12 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; Galaxy, center; infrared, ISM, lines and bands; ISM, abundances; ISM, molecules; stars, individual (Cyg OB2 No. 12) ID SHORT-WAVELENGTH SPECTROMETER; GALACTIC-CENTER; HYDRATED SILICATES; SWS OBSERVATIONS; CARBON-MONOXIDE; GRAINS; STARS; BAND; CO; CALIBRATION AB Observations made with the short-wavelength spectrometer of the Infrared Space Observatory are used to investigate the composition of interstellar dust in the line of sight to Cygnus OB2 No. 12, commonly taken as representative of the diffuse (low-density) interstellar medium. Results are compared with data for the Galactic center source Sgr A*. Nondetections of the 3.0 and 4.27 mu m features of H2O and CO2 ices in Cyg OB2 No. 12 confirm the absence of dense molecular material in this line of sight, whereas the presence of these features in Sgr A* indicates that molecular clouds may contribute as much as 10 mag of visual extinction toward the Galactic center. The spectrum of Cyg OB2 No. 12 is dominated by the well-known 9.7 mu m silicate feature; detection of a shallow feature near 2.75 mu m indicates that the silicates are at least partially hydrated, with composition possibly similar to that of terrestrial phyllosilicates such as serpentine or chlorite. However, the 2.75 mu m feature is not seen in the Galactic center spectrum, suggesting that silicates in this line of sight are less hydrated or of different composition. The primary spectral signatures of C-rich dust in the diffuse ISM are weak absorptions at 3.4 mu m (the aliphatic C-H stretch) and 6.2 mu m (the aromatic C=C stretch). We conclude, based on infrared spectroscopy, that the most probable composition of the dust toward Cyg OB2 No. 12 is a mixture of silicates and carbonaceous solids in a volume ratio of approximately 3:2, with the carbonaceous component primarily in an aromatic form such as amorphous carbon. C1 KAPTEYN ASTRON INST,NL-9700 AV GRONINGEN,NETHERLANDS. LEIDEN OBSERV,NL-2300 RA LEIDEN,NETHERLANDS. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. SRON,NL-9700 AV GRONINGEN,NETHERLANDS. ESA,DIV ASTROPHYS,ISO SCI OPERAT CTR,MADRID 28080,SPAIN. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. RP Whittet, DCB (reprint author), RENSSELAER POLYTECH INST,DEPT PHYS APPL PHYS & ASTRON,TROY,NY 12180, USA. RI Gerakines, Perry/B-9705-2009; Gerakines, Perry/D-2226-2012 OI Gerakines, Perry/0000-0002-9667-5904 NR 44 TC 124 Z9 124 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 DEC 1 PY 1997 VL 490 IS 2 BP 729 EP 734 DI 10.1086/304914 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400022 ER PT J AU Garnavich, PM NoriegaCrespo, A Raga, AC Bohm, KH AF Garnavich, PM NoriegaCrespo, A Raga, AC Bohm, KH TI Highly collimated molecular hydrogen jets near iras 05487+0255: Near-infrared imaging and spectroscopy SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared, ISM, lines and bands; ISM, individual (IRAS 05487 + 0255); ISM, jets and outflows; stars, formation ID HERBIG-HARO OBJECTS; PROPER MOTIONS; ORION; VELOCITY; LINE; H-2; OUTFLOWS; EMISSION; SHOCKS; HH-110 AB We present new narrowband near-infrared images together with K-band spectra of highly collimated bipolar jets close to the IRAS 05487+0255 source. The jets are located similar to 50 '' west of the Herbig-Haro 110 outflow. The jets are not visible at optical wavelengths and therefore do not fall into the ''standard'' Herbig-Haro object classification scheme. Nevertheless, they belong to an ever growing group of molecular hydrogen jets associated with young stellar objects that are optically undetected. The jets are very well collimated, with length-to-width ratios of similar to 10-20. The spectra of the jet and its counterjet in the K band show a limited number of H-2 emission lines that make it difficult to obtain an accurate excitation temperature. We estimate T-ex = 1104+/-67 K and T-ex = 920+/-156 K for the red and blue jet components, respectively. The radial velocities of the jet and counterjet, based on the shift of the (1,0) S(1) 2.121 mu m line, are similar to-275+/-50 km s(-1) and similar to 180+/-50 km s(-1), respectively, suggesting an angle of similar to 30 degrees-45 degrees between the jet and the line of sight. The H-2 emission di the entire jet extends for ar least 40 '', similar to 0.1 pc at the distance of Orion. If the flow velocity is comparable to that of the radial velocities, then the dynamical age of the system is quite short (similar to 500 yr), consistent with a young jet arising from an embedded source. Entrainment in a turbulent mixing layer may explain this morphology and spectral character. C1 CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,PASADENA,CA 91125. NATL AUTONOMOUS UNIV MEXICO,INST ASTRON,MEXICO CITY 04510,DF,MEXICO. UNIV WASHINGTON,DEPT ASTRON FM20,SEATTLE,WA 98195. RP Garnavich, PM (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 31 TC 10 Z9 10 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 DEC 1 PY 1997 VL 490 IS 2 BP 752 EP 757 DI 10.1086/304887 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400025 ER PT J AU Li, P Hurley, K Vrba, F Kouveliotou, C Meegan, C Fishman, G Kulkarni, S Frail, D AF Li, P Hurley, K Vrba, F Kouveliotou, C Meegan, C Fishman, G Kulkarni, S Frail, D TI ROSAT X-ray observation of the second error box for SGR 1900+14 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; methods, statistical; stars, individual (SGR 1900 + 14); supernova remnants ID REPEATER 1806-20; GAMMA; IDENTIFICATION; COUNTERPART; SGR-1900+14; COINCIDENT AB The positions of the two error boxes for the soft gamma repeater (SGR) 1900 + 14 were determined by the ''network synthesis'' method, which employs observations by the Ulysses gamma-ray burst and CGRO BATSE instruments. The location of the first error box has been observed at optical, infrared, and X-ray wavelengths, resulting in the discovery of a ROSAT X-ray point source and a curious double infrared source. We have recently used the ROSAT HRI to observe the second error box to complete the counterpart search. A total of six X-ray sources were identified within the field of view. None of them fails within the network synthesis error box, and a 3 sigma upper limit to any X-ray counterpart was estimated to be 6.35 x 10(-14) ergs cm(-2) s(-1). The closest source is similar to 3' away, and has an estimated unabsorbed flux of 1.5 x 10(-12) ergs cm(-2) s(-1). Unlike the first error box, there is no supernova remnant near the second error box. The closest one, G43.9+1.6, lies similar to 2.degrees 6 away. For these reasons, we believe that the first error box is more likely to be the correct one. C1 USN OBSERV,FLAGSTAFF STN,FLAGSTAFF,AZ 86002. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. CALTECH,DEPT ASTRON,PASADENA,CA 91125. NATL RADIO ASTRON OBSERV,VLA,SOCORRO,NM 87801. RP Li, P (reprint author), UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720, USA. NR 13 TC 2 Z9 2 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 DEC 1 PY 1997 VL 490 IS 2 BP 823 EP 825 DI 10.1086/304910 PN 1 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400034 ER PT J AU Glinski, RJ Lauroesch, JT Reese, MD Sitko, ML AF Glinski, RJ Lauroesch, JT Reese, MD Sitko, ML TI Temperature and velocity diagnostics of the red rectangle from UV spectra of CO and C I SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (Red Rectangle); ISM, molecules; stars, individual (HD 44179); ultraviolet, ISM ID YOUNG STARS; ULTRAVIOLET-SPECTRUM; MOLECULAR-EMISSION; GHRS OBSERVATIONS; HD-44179; BANDS; SPECTROSCOPY; ALPHA; DISKS; STATE AB The UV spectrum of the Red Rectangle and its central source, HD 44179, was examined using the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST). Spectra have been obtained of the 0-0, 0-1, and 0-2 vibronic bands of the CO fourth positive system, the 1657 Angstrom C I multiplet, and the 1931 Angstrom C I line. All of the lines and bands display both absorption and emission components. The components do not display P Cygni profiles, but are nearly symmetrically reversed and show different spreads of radial velocity. The widths and Doppler shifts of each component provide information about the environment of its origin, as do the rotational and vibrational distributions in CO. The 1657 Angstrom multiplet is too complex for analysis, but the 1931 Angstrom line can be deconvolved into two components: emission with narrow velocity dispersion, 25 km s(-1), and absorption with a broad velocity dispersion, 230 km s(-1). The radial velocity of these atomic features is consistent with the velocity of the center of mass of this known spectroscopic binary. For the CO bands, we obtained a best fit from a four-component model, consistent for all three bands. There are three emission components and one absorption component. Two emission components display narrow velocity spreads (29 km s(-1)), and one shows a rotational temperature of 50 K, the other, of about 3000 K. The third emission component has a very wide velocity spread (600 km s(-1)) and a rotational temperature of about 100 K. The absorption component shows a wide velocity spread (230 km s(-1)) and a rotational temperature of about 100 K. The high-temperature emission displayed partially-resolved rotational line structure corresponding to levels of J = 50. The Doppler shifts of these features place the narrow, cold emission with one of the binary components and the narrow, hot emission with the center of mass. We discuss these observations with respect to the accretion disk model of this object. We also compare our UV CO observations with the work of others on the IR CO overtone spectra in young stellar objects. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV CINCINNATI, DEPT PHYS, CINCINNATI, OH 45221 USA. RP Glinski, RJ (reprint author), TENNESSEE TECHNOL UNIV, DEPT CHEM, BOX 5055, COOKEVILLE, TN 38505 USA. NR 42 TC 11 Z9 11 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1997 VL 490 IS 2 BP 826 EP 834 DI 10.1086/304903 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400035 ER PT J AU Guirado, JC Reynolds, JE Lestrade, JF Preston, RA Jauncey, DL Jones, DL Tzioumis, AK Ferris, RH King, EA Lovell, JEJ McCulloch, PM Johnston, KJ Kingham, KA Martin, JO White, GL Jones, PA Arenou, F Froeschle, M Kovalevsky, J Martin, C Lindegren, L Soderhjelm, S AF Guirado, JC Reynolds, JE Lestrade, JF Preston, RA Jauncey, DL Jones, DL Tzioumis, AK Ferris, RH King, EA Lovell, JEJ McCulloch, PM Johnston, KJ Kingham, KA Martin, JO White, GL Jones, PA Arenou, F Froeschle, M Kovalevsky, J Martin, C Lindegren, L Soderhjelm, S TI Astrometric detection of a low-mass companion orbiting the star AB Doradus SO ASTROPHYSICAL JOURNAL LA English DT Article DE astrometry; stars, individual (AB Doradus); stars, kinematics; stars, low-mass, brown dwarfs; techniques, interferometric ID HD 36705; SYSTEM; INTERFEROMETRY; SPECTROSCOPY; LUMINOSITY; HIPPARCOS AB We report submilliarcsecond-precise astrometric measurements for the late-type star AB Doradus via a combination of VLBI (very long baseline interferometry) and HIPPARCOS data. Our astrometric analysis results in the precise determination of the kinematics of this star, which reveals an orbital motion readily explained as caused by gravitational interaction with a low-mass companion. From the portion of the reflex orbit covered by our data and using a revised mass of the primary star (0.76 M-circle dot) derived from our new value of the parallax (66.3 mas < pi < 67.2 mas), we find the dynamical mass of the newly discovered companion to be between 0.08 and 0.11 M-circle dot. If accurate photometric information can be obtained for the low-mass companion, our precise mass estimate could serve as an accurate calibration point for different theoretical evolutionary models of low-mass objects. This represents the first detection of a low-mass stellar companion using VLBI, a technique that will become an important tool in future searches for planets and brown dwarfs orbiting other stars. C1 UNIV VALENCIA, DEPT ASTRON & ASTROFIS, E-46100 BURJASSOT, VALENCIA, SPAIN. AUSTRALIA TELESCOPE NATL FACIL, EPPING, NSW 2121, AUSTRALIA. OBSERV PARIS, SECT MEUDON, F-92195 MEUDON, FRANCE. UNIV TASMANIA, DEPT PHYS, HOBART, TAS 7001, AUSTRALIA. USN OBSERV, WASHINGTON, DC 20392 USA. UNIV WESTERN SYDNEY NEPEAN, KINGSWOOD, NSW 2747, AUSTRALIA. OBSERV COTE AZUR, F-06130 GRASSE, FRANCE. LUND OBSERV, S-22100 LUND, SWEDEN. RP Guirado, JC (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. RI King, Edward/A-1473-2012; Arenou, Frederic/B-1846-2014 OI King, Edward/0000-0002-6898-2130; Arenou, Frederic/0000-0003-2837-3899 NR 27 TC 55 Z9 56 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 DEC 1 PY 1997 VL 490 IS 2 BP 835 EP 839 DI 10.1086/304920 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ454 UT WOS:A1997YJ45400036 ER PT J AU Bloom, SD Bertsch, DL Hartman, RC Sreekumar, P Thompson, DJ Balonek, TJ Beckerman, E Davis, SM Whitman, K Miller, HR Nair, AD Roberts, LC Tosti, G Massaro, E Nesci, R Maesano, M Montagni, F Jang, M Bock, HA Dietrich, M Herter, M Otterbein, K Pfeiffer, M Seitz, T Wagner, S AF Bloom, SD Bertsch, DL Hartman, RC Sreekumar, P Thompson, DJ Balonek, TJ Beckerman, E Davis, SM Whitman, K Miller, HR Nair, AD Roberts, LC Tosti, G Massaro, E Nesci, R Maesano, M Montagni, F Jang, M Bock, HA Dietrich, M Herter, M Otterbein, K Pfeiffer, M Seitz, T Wagner, S TI Observations of a correlated gamma-ray and optical flare for BL lacertae SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, individual (BL Lacertae); galaxies, active; gamma rays, observations ID EMISSION AB BL Lacertae was detected by the EGRET instrument on the Compton Gamma Ray Observatory at the 10.2 sigma level with an average flux of (171 +/- 42) x 10(-8) photons cm(-2) s(-1), at energies greater than 100 MeV, during the optical outburst of 1997 July. This flux is more than 4 times the previously highest level. Within the July 15-22 observation there was a dramatic factor of 2.5 increase in the gamma-ray Aux on July 18.75-19.08, apparently preceding, by several hours, a brief optical flare, The gamma-ray flux decreased to its previous level within 8 hr, and the optical flux decreased to its prior level in less than 2 hr. The gamma-ray photon spectral index of 1.68 +/- 0.12 indicates that the spectrum during the 7 day observation was harder than the previous detection. C1 COLGATE UNIV,DEPT PHYS & ASTRON,HAMILTON,NY 13346. GEORGIA STATE UNIV,DEPT PHYS & ASTRON,ATLANTA,GA 30303. UNIV PERUGIA,CATTEDRA ASTROFIS,I-06100 PERUGIA,ITALY. UNIV ROMA LA SAPIENZA,IST ASTRON,I-00161 ROME,ITALY. LANDESSTERNWARTE HEIDELBERG,D-69117 HEIDELBERG,GERMANY. RP Bloom, SD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. RI Thompson, David/D-2939-2012; Tosti, Gino/E-9976-2013 OI Thompson, David/0000-0001-5217-9135; NR 24 TC 87 Z9 87 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 DEC 1 PY 1997 VL 490 IS 2 BP L145 EP L148 DI 10.1086/311035 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ477 UT WOS:A1997YJ47700006 ER PT J AU Gotthelf, EV Kulkarni, SR AF Gotthelf, EV Kulkarni, SR TI An unusual X-ray burst from the globular cluster M28 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (M28, PSR B1821-24); stars, neutron; X-rays, bursts; X-rays, stars ID ACCRETING NEUTRON-STARS; FLASHES; DISCOVERY AB We report the discovery of an unusual X-ray burst from the direction of the globular cluster M28 using data acquired with ASCA. The burst was recorded by all four ASCA telescopes and displays a fast (less than or similar to 70 ms) rise followed by an exponential decay (tau = 7.5 s) and a steady afterglow that lasts between 800 and 3250 a. The image of the burst is consistent with an ASCA point source and is centered on quiescent X-ray emission from the core of M28. The burst temporal profile is similar to type I bursts emitted by accreting neutron stars of low-mass X-ray binaries (LMXBs). We argue that the burst arises from a LMXB that is located in the core of M28. The burst is unique in two ways: it is intrinsically subluminous, similar to 0.02L(E), and more importantly it originates from a source whose quiescent luminosity is fainter than that of the known cluster bursters by 3 orders of magnitude. We suggest that this burst is from a highly magnetized neutron star accreting at a low rate. These accreting systems may account for the mysterious low-luminosity X-ray sources in globular clusters. C1 CALTECH,DEPT PHYS MATH & ASTRON,PASADENA,CA 91125. RP Gotthelf, EV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. NR 22 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 DEC 1 PY 1997 VL 490 IS 2 BP L161 EP & DI 10.1086/311038 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ477 UT WOS:A1997YJ47700010 ER PT J AU Yu, W Zhang, SN Harmon, BA Paciesas, WS Robinson, CR Grindlay, JE Bloser, P Barret, D Ford, EC Tavani, M Kaaret, P AF Yu, W Zhang, SN Harmon, BA Paciesas, WS Robinson, CR Grindlay, JE Bloser, P Barret, D Ford, EC Tavani, M Kaaret, P TI kHz quasi-periodic oscillation in island state of 4U 1608-52 as observed with RXTE/PCA SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (4U 1608-52); stars, neutron; X-rays, stars ID RAY; 4U-1608-52 AB We report RXTE/PCA observations of 4U 1608-52 on March 15, 18, and 22 immediately after the outburst in early 1996. The persistent count rates ranged from 190 to 450 counts s(-1) (1-60 keV). During this period of time, 4U 1608-52 was in the island state. We detected quasi-periodic oscillation (QPO) features in the power density spectra (PDS) at 567-800 Hz on March 15 and 22, with source fractional root mean square (rms) amplitude of 13%-17% and widths of 78-180 Hz. The average rms amplitude of these QPO features is positively correlated with the energy. Our results imply that the neutron star spin frequency is possibly between 300 and 365 Hz. C1 UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. UPS,CNRS,CTR ETUD SPATIALE RAYONNEMENTS,F-31028 TOULOUSE 04,FRANCE. COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,NEW YORK,NY 10027. RP Yu, W (reprint author), INST HIGH ENERGY PHYS,LCRHEA,BEIJING 100039,PEOPLES R CHINA. NR 23 TC 35 Z9 36 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 DEC 1 PY 1997 VL 490 IS 2 BP L153 EP L156 DI 10.1086/311033 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ477 UT WOS:A1997YJ47700008 ER PT J AU Bildsten, L Chakrabarty, D Chiu, J Finger, MH Koh, DT Nelson, RW Prince, TA Rubin, BC Scott, DM Stollberg, M Vaughan, BA Wilson, CA Wilson, RB AF Bildsten, L Chakrabarty, D Chiu, J Finger, MH Koh, DT Nelson, RW Prince, TA Rubin, BC Scott, DM Stollberg, M Vaughan, BA Wilson, CA Wilson, RB TI Observations of accreting pulsars SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Review DE accretion, accretion disks; binaries, close; pulsars, general stars, magnetic fields; stars, neutron; X-rays, stars ID X-RAY PULSAR; QUASI-PERIODIC OSCILLATIONS; MAGNETIZED NEUTRON STARS; SMALL MAGELLANIC CLOUD; OPTICAL COUNTERPART; BINARY-SYSTEMS; GINGA OBSERVATIONS; ORBITAL ELEMENTS; RADIO PULSARS; CENTAURUS X-3 AB We summarize 5 years of continuous monitoring of accretion-powered pulsars with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory. Our 20-70 keV observations have determined or refined the orbital parameters of 13 binaries, discovered five new transient accreting pulsars, measured the pulsed flux history during outbursts of 12 transients (GRO J1744-28, 4U 0115+634, GRO J1750-27, GS 0834-430, 2S 1417-624, GRO J1948+32, EXO 2030+375, GRO J1008-57, A0535+26, GRO J2058+42, 4U 1145-619, and A1118-616), and also measured the accretion torque history during outbursts of six of those transients whose orbital parameters were also known. We have also continuously measured the pulsed flux and spin frequency for eight persistently accreting pulsars (Her X-1, Cen X-3, Vela X-1, OAO 1657-415, GX 301-2, 4U 1626-67, 4U 1538-52, and GX 1+4). Because of their continuity and uniformity over a long baseline, BATSE observations have provided new insights into the long-term behavior of accreting magnetic neutron stars. We have found that all accreting pulsars show stochastic variations in their spin frequencies and luminosities, including those displaying secular spin-up or spin-down on long timescales, which blurs the conventional distinction between disk-fed and wind-fed binaries. Pulsed flux and accretion torque are strongly correlated in outbursts of transient accreting pulsars but are uncorrelated, or even anti-correlated, in persistent sources. We describe daily folded pulse profiles, frequency, and flux measurements that are available through the Compton Observatory Science Support Center at NASA/Goddard Space Flight Center. C1 UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. MIT, CTR SPACE RES, CAMBRIDGE, MA 02139 USA. CALTECH, SPACE RADIAT LAB, PASADENA, CA 91125 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, ES84, HUNTSVILLE, AL 35812 USA. UNIV SPACE RES ASSOC, COLUMBIA, MD USA. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. RP Bildsten, L (reprint author), UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. NR 234 TC 458 Z9 461 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 EI 1538-4365 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD DEC PY 1997 VL 113 IS 2 BP 367 EP 408 DI 10.1086/313060 PG 42 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YH578 UT WOS:A1997YH57800007 ER PT J AU Ying, R Canuto, VM AF Ying, R Canuto, VM TI Numerical simulation of flow over two-dimensional hills using a second-order turbulence closure model SO BOUNDARY-LAYER METEOROLOGY LA English DT Article DE numerical simulation; turbulence closure model; complex terrain ID BOUNDARY-LAYER FLOW; FINITE-DIFFERENCE MODEL; REYNOLDS-STRESS; REAL TERRAIN; TOPOGRAPHY; EQUATIONS AB We study turbulent flow over two-dimensional hills. The Reynolds stresses are represented by a second-order closure model, where advection, diffusion, production and dissipation processes are all accounted for. We solve a full set of primitive non-hydrostatic dynamic equations for mean flow quantities using a finite-difference numerical method. The model predictions for the mean velocity and Reynolds stresses are compared with the measured data from a wind-tunnel experiment that simulates the atmospheric boundary layer. The agreement is good. The performance of the second-order closure model is also compared with that of lower level turbulence models, including the eddy-viscosity model and algebraic Reynolds stress models. It is concluded that the present closure is a considerable improvement over the other models in representing various physical effects in flow over hills. The feasibility of running a finite-difference numerical simulation incorporating a full second-order closure model on an IBM workstation is also demonstrated. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Ying, R (reprint author), NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NR 36 TC 14 Z9 14 U1 1 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0006-8314 J9 BOUND-LAY METEOROL JI Bound.-Layer Meteor. PD DEC PY 1997 VL 85 IS 3 BP 447 EP 474 DI 10.1023/A:1000534921008 PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YU847 UT WOS:000071762000006 ER PT J AU Short, DA Kucera, PA Ferrier, BS Gerlach, JC Rutledge, SA Thiele, OW AF Short, DA Kucera, PA Ferrier, BS Gerlach, JC Rutledge, SA Thiele, OW TI Shipboard radar rainfall patterns within the TOGA COARE IFA SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID ATMOSPHERE RESPONSE EXPERIMENT; TROPICAL WESTERN PACIFIC; SEA-SURFACE TEMPERATURE; 40-50 DAY OSCILLATION; MESOSCALE SYSTEMS; SENSIBLE HEAT; DIURNAL CYCLE; WARM POOL; OCEAN; PRECIPITATION AB Radar rainfall measurements over the equatorial western Pacific warm pool were collected by two shipboard Doppler radars as part of the Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment during the intensive observing period (November 1992-February 1993). A comprehensive dataset of gridded rainfall fields, convective/stratiform identification maps, and vertical structure products has been produced, covering an area approximately 400 km (E-W) by 300 km (N-S) within the Intensive Flux Array (IFA), centered near 2 degrees S, 156 degrees E. The radar rainfall product, which was used as validation for the Third Algorithm Intercomparison Project of the Global Precipitation Climatology Project, indicates an overall average of 4.8 mm day(-1); however, correction for range dependence increases the total to 5.4 mm day(-1). Rainfall patterns varied considerably during the experiment with isolated convection dominating periods of light winds, while squall Lines and organized mesoscale systems were abundant during two westerly wind bursts. An area-average rainfall of 9.9 mm day(-1) was observed during the active 2-week period at the end of December, while 0.4 mm day(-1) was observed during the quiescent week of 2-8 February. The eastern portion of the IFA received the most rainfall with localized maxima exceeding 16 mm day(-1) for the most active 3-week period. Comparison of daily radar rainfall totals with those observed by an optical rain gauge (ORG) on the 2 degrees S, 156 degrees E buoy shows ORG totals to be systematically higher, by a factor of 2.5. The discrepancy results from a higher average rainfall rate, when raining, as reported by the buoy ORG. However, rainfall rate statistics from the ORGs on the research vessel Xiang Yang Hong #5 and from its radar are in excellent agreement under the following conditions: 1) the ship is drifting, and 2) the radar data are in the near vicinity of the ship (3-7 km). C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Appl Res Corp, Landover, MD 20785 USA. Sci Syst & Applicat Inc, Lanham, MD USA. NASA, SPANDAR Radar Facil, Wallops Island, VA USA. Colorado State Univ, Ft Collins, CO 80523 USA. RP Short, DA (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 910, Greenbelt, MD 20771 USA. EM short@trmm.gsfc.nasa.gov NR 82 TC 119 Z9 121 U1 1 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD DEC PY 1997 VL 78 IS 12 BP 2817 EP 2836 DI 10.1175/1520-0477(1997)078<2817:SRRPWT>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ885 UT WOS:000072304100006 ER PT J AU Murphy, ML Koski, KV Lorenz, JM Thedinga, JF AF Murphy, ML Koski, KV Lorenz, JM Thedinga, JF TI Downstream migrations of juvenile Pacific salmon (Oncorhynchus spp.) in a glacial transboundary river SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID SOCKEYE-SALMON; TAKU RIVER; BRITISH-COLUMBIA; COHO SALMON; ALASKA; HABITAT; SALAR; KISUTCH; PARR AB Migrations of juvenile Pacific salmon (Oncorhynchus spp.) in the glacial Taku River (seventh order) were studied to assess movement from upriver spawning areas (in British Columbia) into lower-river rearing areas (in Alaska). Differences between fyke-net catches in the river and seine catches in the river's estuary indicated that many downstream migrants remained in the lower river instead of migrating to sea. In particular, age-0 coho salmon (O. kisutch) and chinook salmon (O. tshawytscha) moved downriver from May to November but were not caught in the estuary. Age-0 sockeye salmon (O. nerka), coho presmolts, and other groups delayed entry into the estuary after moving downriver. We tagged groups of juvenile coho (ages 0-2) from the fyke net with coded-wire to determine when they left the river. One-third of all tags recovered from sport and commercial fisheries occurred 2-3 years later, showing that many coho remained in fresh water for 1-2 years after moving to the lower river. Lower-river areas of large glacial rivers like the Taku River can provide essential rearing habitat for juvenile salmon spawned upriver and are important to consider in integrated whole-river management of transboundary rivers. C1 NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Cr, Auke Bay Lab, Juneau, AK 99801 USA. RP Murphy, ML (reprint author), NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Cr, Auke Bay Lab, 11 305 Glacier Highway, Juneau, AK 99801 USA. NR 41 TC 20 Z9 21 U1 1 U2 2 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD DEC PY 1997 VL 54 IS 12 BP 2837 EP 2846 DI 10.1139/cjfas-54-12-2837 PG 10 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA ZC037 UT WOS:000072533200013 ER PT J AU Thayumanavan, S Barlow, S Marder, SR AF Thayumanavan, S Barlow, S Marder, SR TI Synthesis of unsymmetrical triarylamines for photonic applications via one-pot palladium-catalyzed aminations SO CHEMISTRY OF MATERIALS LA English DT Article ID LIGHT-EMITTING DIODE; THERMAL STABILITIES; HOLE TRANSPORT; CHROMOPHORES; DEVICES AB Syntheses of unsymmetrically substituted triarylamines have been achieved by a one-pot procedure using C-N bond-forming reactions, where two aryl bromides are sequentially added to an arylamine in the presence of a palladium catalyst. This methodology has been utilized to synthesize a number of substituted analogs of 4,4'-bis(m-tolylphenylamino)-biphenyl, which may be useful as the hole transport component of vapor-deposited organic light-emitting diodes. The variations in the substitution are anticipated to lead to a variety of band gaps, band offsets, and glass transition temperatures in this class of materials. C1 CALTECH, Beckman Inst, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Marder, SR (reprint author), CALTECH, Beckman Inst, 139-74, Pasadena, CA 91125 USA. RI Barlow, Stephen/E-9754-2010; OI Thayumanavan, S/0000-0002-6475-6726 NR 20 TC 88 Z9 89 U1 1 U2 9 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0897-4756 J9 CHEM MATER JI Chem. Mat. PD DEC PY 1997 VL 9 IS 12 BP 3231 EP 3235 DI 10.1021/cm970567n PG 5 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA YQ434 UT WOS:000071386900085 ER PT J AU Chang, CY Huang, NE Shen, Z AF Chang, CY Huang, NE Shen, Z TI A statistically significant periodicity in the homestake solar neutrino data. SO CHINESE JOURNAL OF PHYSICS LA English DT Article; Proceedings Paper CT Meeting in Honour of Dr Ta-You Wus Birthday CY AUG 11-15, 1997 CL TAIPEI, TAIWAN SP Academia Sin, Inst Phys, Natl Sci Council R O C, Nat Sci Div, Phys Res Promot Ctr, Phys Soc Republic China ID DIFFUSION; MODELS; HELIUM; TIME AB Using the Empirical Mode Decomposition method developed by Huang, et al., we have examined the time dependence of the solar neutrino fluxes measured by the Homestake Cl-37 experiment. Our analysis shows that a prominent feature in the Homestake data is the statistically significant peak found at a frequency of approximately 0.1 y(-1). A similar analysis has been applied to the Wolf Index on sunspot numbers. Possible correlation among the Intrinsic Mode Functions of the two analysed data sets can be achieved with a 3.5 year shift in phase. C1 Univ Maryland, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Baltimore, MD 21218 USA. CALTECH, Pasadena, CA 91125 USA. RP Univ Maryland, College Pk, MD 20742 USA. NR 21 TC 4 Z9 4 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0577-9073 J9 CHINESE J PHYS JI Chin. J. Phys. PD DEC PY 1997 VL 35 IS 6 BP 818 EP 831 PN 2 PG 14 WC Physics, Multidisciplinary SC Physics GA YN966 UT WOS:000071227600014 ER PT J AU Romanovsky, VE Osterkamp, TE Duxbury, NS AF Romanovsky, VE Osterkamp, TE Duxbury, NS TI An evaluation of three numerical models used in simulations of the active layer and permafrost temperature regimes SO COLD REGIONS SCIENCE AND TECHNOLOGY LA English DT Article DE active layer; permafrost; modelling; unfrozen water ID THERMAL REGIME; ALASKA; SOILS; HEAT AB Three numerical models (designated the Goodrich, Guymon/Hromadka, and Seregina models) used for calculations of the ground thermal regime which are based on different numerical methods and employ different treatments of freezing and thawing were compared with each other, with analytical solutions, and with measured temperature data. Comparisons of the models with the Neumann solution show differences generally less than 0.2 degrees C between calculated temperatures using a wide range of time and depth steps. The Goodrich and Guymon/Hromadka models have been shown to predict temperature field dynamics reliably in the active layer and permafrost using small time and depth steps. However, comparisons of the models with each other using large time and depth steps and field data for the surface boundary condition showed significant differences between them (RMS deviations exceeding 1 degrees C) and, in addition, the development of a non-physical feature (thaw bulb after freeze-up). Therefore, with large time and depth steps, the models cannot reproduce the temperature field dynamics in the active layer and permafrost. Consequently, agreement with the Neumann solution is necessary but not sufficient to qualify the models for calculations of real temperature fields. The Goodrich model requires a time step not longer than 1 h and depth step in the upper 1 m not larger than 0.02 m to reproduce the temperature regime with reasonable accuracy. However, the choice of optimum time and depth steps appears to be specific to the application. Using the Guymon/Hromadka model, similar accuracy can be obtained with a 1 h time step and 0.1 m space step within the upper 1 m depth or a 1 day time step and 0.01 m space step. However, the use of larger steps does not necessarily decrease the calculational time compared to the Goodrich model. For the case with unfrozen water present in the frozen soil, the results of calculations using the numerical models were compared with an analytical solution and were found to agree within 0.02 degrees C. (C) 1997 Elsevier Science B.V. C1 Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Romanovsky, VE (reprint author), Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. NR 26 TC 30 Z9 31 U1 0 U2 9 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0165-232X J9 COLD REG SCI TECHNOL JI Cold Reg. Sci. Tech. PD DEC PY 1997 VL 26 IS 3 BP 195 EP 203 DI 10.1016/S0165-232X(97)00016-5 PG 9 WC Engineering, Environmental; Engineering, Civil; Geosciences, Multidisciplinary SC Engineering; Geology GA ZF596 UT WOS:000072912900003 ER PT J AU Bedir, H T'ien, JS Lee, HS AF Bedir, H T'ien, JS Lee, HS TI Comparison of different radiation treatments for a one-dimensional diffusion flame SO COMBUSTION THEORY AND MODELLING LA English DT Article ID BLACKBODY DISTRIBUTION FUNCTION; GRAY-GASES MODEL; EXTINCTION; COMBUSTION; CO2 AB A comparison of several radiative heat transfer models is made for a stagnation-point diffusion flame at low stretch rate, with CO2 and H2O as the participating media. Computed results of the radiative source distribution for wideband, narrowband and SLWSGG show reasonable agreement with each other. Results from the optically thin and grey gas models with Planck mean absorption coefficient are shown to underestimate the self-absorption and overestimate the emission substantially for the low stretch flame. The relative computation times of using the various radiation models are also given. C1 Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bedir, H (reprint author), Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NR 28 TC 40 Z9 41 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 1364-7830 J9 COMBUST THEOR MODEL JI Combust. Theory Model. PD DEC PY 1997 VL 1 IS 4 BP 395 EP 404 DI 10.1088/1364-7830/1/4/003 PG 10 WC Thermodynamics; Energy & Fuels; Engineering, Chemical; Mathematics, Interdisciplinary Applications SC Thermodynamics; Energy & Fuels; Engineering; Mathematics GA YT389 UT WOS:000071597900003 ER PT J AU Werner, RA AF Werner, RA TI Spherical harmonic coefficients for the potential of a constant-density polyhedron SO COMPUTERS & GEOSCIENCES LA English DT Article DE gravitational potential; polyhedron; solid spherical harmonics ID GRAVITATIONAL-FIELD; SHAPE; PHOBOS AB Recurrent relationships for the definitions of fully normalized spheric:il harmonic coefficients (C) over bar(n,m) and (S) over bar(n,m) are derived and integrated analytically to yield the gravitational potential of a constant density polyhedron. The algorithm is expressed in a C language computer program. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Werner, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 301-150, Pasadena, CA 91109 USA. NR 12 TC 33 Z9 35 U1 0 U2 8 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0098-3004 J9 COMPUT GEOSCI JI Comput. Geosci. PD DEC PY 1997 VL 23 IS 10 BP 1071 EP 1077 DI 10.1016/S0098-3004(97)00110-6 PG 7 WC Computer Science, Interdisciplinary Applications; Geosciences, Multidisciplinary SC Computer Science; Geology GA ZM933 UT WOS:000073590900006 ER PT J AU Szewczyk, ZP Noor, AK AF Szewczyk, ZP Noor, AK TI A hybrid numerical/neurocomputing strategy for sensitivity analysis of nonlinear structures SO COMPUTERS & STRUCTURES LA English DT Article ID NEURAL NETWORKS AB A hybrid numerical/neurocomputing (HN/N) strategy is presented for the evaluation of selective sensitivity coefficients of nonlinear structures. In the hybrid strategy, multilayer feedforward neural networks are used to extend a range of the validity of predictions of sensitivity coefficients made by Pade approximants. To further increase the accuracy and the range of network predictions, a data expansion strategy is used in which additional training data are generated by using extrapolated values of the coefficients in a Taylor series. Within this strategy a number of techniques are examined for evaluating derivatives of response functions. The effectiveness of the HN/N strategy is assessed by performing numerical experiments for composite panels subjected to combined thermal and mechanical loads. It is shown that the HN/N strategy reduces the number of full-system analyses and allows obtaining selective information about the structural response and the sensitivity coefficients. (C) 1997 Published by Elsevier Science Ltd. C1 Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. RP Szewczyk, ZP (reprint author), Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. NR 28 TC 5 Z9 5 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD DEC PY 1997 VL 65 IS 6 BP 869 EP 880 DI 10.1016/S0045-7949(97)00059-X PG 12 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA YU232 UT WOS:000071695500008 ER PT J AU Watson, BC Noor, AK AF Watson, BC Noor, AK TI Sensitivity analysis of frictional contact/impact response on distributed-memory computers SO COMPUTERS & STRUCTURES LA English DT Article ID AXISYMMETRICAL COMPOSITE STRUCTURES; FINITE-ELEMENT ANALYSIS; PARALLEL COMPUTERS AB Multilevel parallel computational strategies are presented for predicting the frictional contact/impact response and evaluating the sensitivity coefficients of axisymmetric composite structures. Both implicit and explicit temporal integration techniques are considered. For implicit techniques, parallelism is exploited in both the spatial and temporal domains. Spatial parallelism is achieved by using a parallel sparse equation solver based on a nested dissection node-ordering scheme. The explicit techniques exploit parallelism using both an element-based domain decomposition strategy, as well as concurrent evaluation of sensitivity coefficients. Implementations of the strategies on distributed-memory computers are described. The strategies are applied to the problem of an axisymmetric composite spherical cap impacting a rigid surface, and the performance characteristics are assessed on the IBM SP2 and the Gray T3D parallel computer systems. (C) 1997 Published by Elsevier Science Ltd. C1 Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA USA. RP Watson, BC (reprint author), Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA USA. NR 21 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 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD DEC PY 1997 VL 65 IS 6 BP 881 EP 891 DI 10.1016/S0045-7949(97)00060-6 PG 11 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA YU232 UT WOS:000071695500009 ER PT J AU Stolorz, P Musick, R AF Stolorz, P Musick, R TI Special issue: Scalable high performance computing for KDD SO DATA MINING AND KNOWLEDGE DISCOVERY LA English DT Editorial Material C1 Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA USA. RP Stolorz, P (reprint author), Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 1384-5810 J9 DATA MIN KNOWL DISC JI Data Min. Knowl. Discov. PD DEC PY 1997 VL 1 IS 4 BP 339 EP 341 DI 10.1023/A:1009799201038 PG 3 WC Computer Science, Artificial Intelligence; Computer Science, Information Systems SC Computer Science GA ZA833 UT WOS:000072406600001 ER PT J AU Sogard, SM Olla, BL AF Sogard, SM Olla, BL TI The influence of hunger and predation risk on group cohesion in a pelagic fish, walleye pollock Theragra chalcogramma SO ENVIRONMENTAL BIOLOGY OF FISHES LA English DT Article DE fish behavior; schooling; food deprivation; predator avoidance ID SHOAL SIZE; GASTEROSTEUS-ACULEATUS; FOOD DISTRIBUTION; MARINE FISH; BEHAVIOR; MINNOWS; STICKLEBACKS; MECHANISMS; PATTERNS; ECOLOGY AB Variation in the intensity of schooling behavior in fishes suggests that the benefits of aggregation are balanced by certain costs. We examined the proximity of group members to each other in juvenile walleye pollock, Theragra chalcogramma, under different environmental conditions. Food availability, simulated by a gradient of six ration treatments, had a major influence on group cohesion, with increasing dispersion as food level decreased. Group cohesion also decreased at night relative to daytime levels. Small juveniles ((x) over bar = 53 mm TL) maintained on high rations were highly responsive to the potential threat of a predator, with groups becoming more cohesive and remaining so for up to an hour after the initial threat. A chronic threat (continual presence of predators) resulted in tighter group cohesion than an acute threat (single simulated attack). Small juveniles maintained on low rations were less responsive to predation threats and recovered quickly, supporting the hypothesis that hunger induces risk-taking behavior. Large juveniles ((x) over bar = 149 mm TL) did not change their degree of aggregation in response to either type of predation threat. An overall plasticity in the degree of cohesiveness among group members indicates that walleye pollock are capable of gradually modifying their schooling behavior according to the environmental context. C1 Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Hatfield Marine Sci Ctr, Newport, OR 97365 USA. RP Sogard, SM (reprint author), Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Hatfield Marine Sci Ctr, Newport, OR 97365 USA. NR 38 TC 40 Z9 42 U1 0 U2 12 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0378-1909 J9 ENVIRON BIOL FISH JI Environ. Biol. Fishes PD DEC PY 1997 VL 50 IS 4 BP 405 EP 413 DI 10.1023/A:1007393307007 PG 9 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA YL654 UT WOS:000070978100007 ER PT J AU Shook, TD Gorla, RSR AF Shook, TD Gorla, RSR TI Finite element analysis and redesign of a compressor hub spinner SO FINITE ELEMENTS IN ANALYSIS AND DESIGN LA English DT Article DE finite elements; compressor design; compressor hub AB The current performance of a transonic axial compressor can be improved by modifying the design of the compressor hub spinner. The shape of the hub spinner will be changed to provide better inlet how conditions to the compressor. A two-dimensional finite element analysis is used first to determine the baseline rotor system characteristics, and then to analyze these characteristics for the proposed redesign. Results from this analysis are used to verify that the compressor hub spinner redesign has positive margins of safety, and therefore, satisfies good engineering design practices. (C) 1997 Elsevier Science B.V. C1 Cleveland State Univ, Dept Mech Engn, Cleveland, OH 44115 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Gorla, RSR (reprint author), Cleveland State Univ, Dept Mech Engn, Cleveland, OH 44115 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-874X J9 FINITE ELEM ANAL DES JI Finite Elem. Anal. Des. PD DEC 1 PY 1997 VL 28 IS 1 BP 19 EP 31 DI 10.1016/S0168-874X(97)81960-9 PG 13 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA YM067 UT WOS:000071024600002 ER PT J AU Chargin, ML Dunne, LW Herting, DN AF Chargin, ML Dunne, LW Herting, DN TI Nonlinear dynamics of brake squeal SO FINITE ELEMENTS IN ANALYSIS AND DESIGN LA English DT Article AB An efficient procedure for the analysis of brake squeal using MSC/NASTRAN models is described. A unique nonlinear method accounts for both superelement modes and surface friction data. The motions at the pad/rotor interface are described by small velocities and pressures relative to the steady-state condition. Both transient analysis and complex eigenvalues are provided for the analysis of brake systems. (C) 1997 Elsevier Science B.V. C1 CDH, Los Angeles, CA 90036 USA. NASA, Ames Res Ctr, Moffett Field, CA 90036 USA. CDH GMBH, D-85051 Ingolstadt, Germany. RP Herting, DN (reprint author), CDH, 107 So Highland Ave, Los Angeles, CA 90036 USA. NR 24 TC 25 Z9 29 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-874X J9 FINITE ELEM ANAL DES JI Finite Elem. Anal. Des. PD DEC 1 PY 1997 VL 28 IS 1 BP 69 EP 82 DI 10.1016/S0168-874X(97)81963-4 PG 14 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA YM067 UT WOS:000071024600005 ER PT J AU Zolensky, ME Mittlefehldt, DW Lipschutz, ME Wang, MS Clayton, RN Mayeda, TK Grady, MM Pillinger, C Barber, D AF Zolensky, ME Mittlefehldt, DW Lipschutz, ME Wang, MS Clayton, RN Mayeda, TK Grady, MM Pillinger, C Barber, D TI CM chondrites exhibit the complete petrologic range from type 2 to 1 SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID LABILE TRACE-ELEMENTS; CARBONACEOUS CHONDRITES; AQUEOUS ALTERATION; COMPUTER-SIMULATIONS; OXYGEN ISOTOPES; NANOMOLE LEVEL; CI CHONDRITES; PARENT BODY; MINERALOGY; ABUNDANCES AB We have characterized the most phyllosilicate-rich members of the CM chondrite group. Based upon petrographic and compositional factors, we conclude that these particular meteorites have experienced pervasive aqueous alteration far beyond that witnessed by typical CMs. The lack of anhydrous silicates, CAI and (except as relicts) chondrules merits the classification of type CM1 for three meteorites (EET 83334, ALH 88045, and one Kaidun lithology). Still other CMs, notably ALH 83100, EET 90047, and Yamato 82042, are clearly intermediate between types 1 and 2. Brecciated CM chondrites like Cold Bokkeveld contain all of these varied lithologies. The CM chondrites thus exhibit the complete petrologic range from 2 through 1. Our results show that progressive aqueous alteration on the parent CM asteroid(s) was, locally, accompanied by significant increases in temperature (to a peak of similar to 450 degrees C for the Kaidun lithology), f(O2), and (locally) degree of chemical leaching, all well beyond the conditions recorded by typical CM2s. The most altered CMs also are commonly deformed, displaying a distinct lineation probably due to static rather than dynamic forces. Copyright (C) 1997 Elsevier Science Ltd. C1 NASA, Earth Sci & Solar Syst Explorat Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin ESS, C23, Houston, TX 77058 USA. Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Open Univ, Planetary Sci Res Inst, Milton Keynes MK7 6AA, Bucks, England. Univ Essex, Dept Phys, Colchester CO4 3SQ, Essex, England. RP Zolensky, ME (reprint author), NASA, Earth Sci & Solar Syst Explorat Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. OI Grady, Monica/0000-0002-4055-533X NR 67 TC 108 Z9 108 U1 0 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 EI 1872-9533 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD DEC PY 1997 VL 61 IS 23 BP 5099 EP 5115 DI 10.1016/S0016-7037(97)00357-8 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YM713 UT WOS:000071093400015 ER PT J AU Choi, WY Leu, MT AF Choi, WY Leu, MT TI Kinetics of the heterogeneous reaction CO+O->CO2 on inorganic oxide and water ice surfaces: Implications for the Martian atmosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MARS; STABILITY; ADSORPTION; DIFFUSION; FILMS AB The heterogeneous reaction CO + O --> CO2 on water ice and various inorganic oxide (SiO2, Al2O3, Fe2O3, Fe3O4, CaO, MgO, and TiO2) surfaces has been investigated in order to evaluate the proposition that this heterogeneous reaction may contribute to the CO, stability in the Martian atmosphere. The reaction probabilities were measured at bath 196 K and 294 K by using a fast flow-tube reactor coupled to an electron-impact ionization mass spectrometer. The atomic oxygen was generated by passing a mixture of O-2 and He through a microwave discharge at a side-arm inlet and then allowed to react with CO over these substrates in the reactor. The reaction product, CO,, was monitored as a function of time at the downstream end of the flow-tube reactor. The measured reaction probabilities were determined from the growth rates of CO2 signal and were found to range from 1.6 x 10(-7) to 1.0 x 10(-5) on the basis of the geometric area of the reactor. If we adopt a typical reaction probability of 5 x 10(-7) for the heterogeneous CO + O reaction on Martian aerosols at 196 K, a simple calculation suggests that this mechanism plays a negligible role in CO2 recycling as compared to that of the homogeneous CO + OH reaction. RP Choi, WY (reprint author), CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Choi, Wonyong/F-8206-2010 OI Choi, Wonyong/0000-0003-1801-9386 NR 24 TC 6 Z9 6 U1 0 U2 3 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 DEC 1 PY 1997 VL 24 IS 23 BP 2957 EP 2960 DI 10.1029/97GL03103 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YJ981 UT WOS:A1997YJ98100003 ER PT J AU Joughin, I Fahnestock, M Ekholm, S Kwok, R AF Joughin, I Fahnestock, M Ekholm, S Kwok, R TI Balance velocities of the Greenland ice sheet SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetery data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail the location of an ice stream in northeastern Greenland, which was only recently discovered using satellite imagery. Enhanced how associated with all of the major outlets is clearly visible, although small errors in the source data result in less accurate estimates of the absolute flow speeds. Nevertheless, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning. C1 UNIV MARYLAND,DEPT METEOROL,JCESS,COLLEGE PK,MD 20742. KORT & MATRIKELSTYRELSEN,DK-2400 COPENHAGEN NV,DENMARK. 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 14 TC 27 Z9 27 U1 0 U2 3 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 DEC 1 PY 1997 VL 24 IS 23 BP 3045 EP 3048 DI 10.1029/97GL53151 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YJ981 UT WOS:A1997YJ98100026 ER PT J AU Forsyth, RJ Balogh, A Smith, EJ Gosling, JT AF Forsyth, RJ Balogh, A Smith, EJ Gosling, JT TI Ulysses observations of the northward extension of the heliospheric current sheet SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERPLANETARY SECTOR STRUCTURE; MAGNETIC-FIELD; VOYAGER-2 OBSERVATIONS AB After passing through the northern polar regions of the heliosphere during the summer of 1995, the Ulysses spacecraft has been gradually returning towards lower equatorial latitudes, reaching 30 degrees N in August 1996 at about which time low speed solar wind from the streamer belt was once again observed. This paper reports on the Ulysses magnetic field observations, beginning from this time, concentrating on encounters with the heliospheric current sheet. These encounters restarted at a latitude of 25.5 degrees N, a higher latitude than might be expected at solar activity minimum. We show that this early reappearance was due to a northward deflection of the current sheet caused by a long-lived active region at the corresponding heliographic longitude in the photosphere. C1 LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Forsyth, RJ (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,BLACKETT LAB,LONDON SW7 2BZ,ENGLAND. NR 18 TC 25 Z9 25 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 DEC 1 PY 1997 VL 24 IS 23 BP 3101 EP 3104 DI 10.1029/97GL03099 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YJ981 UT WOS:A1997YJ98100040 ER PT J AU Potter, CS AF Potter, CS TI An ecosystem simulation model for methane production and emission from wetlands SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID MONTHLY AIR-TEMPERATURE; NORTHERN WETLANDS; SOLAR-RADIATION; ARCTIC TUNDRA; CARBON; WATER; FLUX; DECOMPOSITION; OXIDATION; PEATLAND AB Previous experimental studies suggest that methane emission from wetlands is influenced by multiple interactive pathways of gas production and transport through soil and sediment layers to the atmosphere. The objective of this study is to evaluate a new simulation model of methane production and emission in wetland soils that was developed initially to help identify key processes that regulate methanogenesis and net flux of CH4 to the air but which is designed ultimately for regional simulation using remotely sensed inputs for land cover characteristics. The foundation for these computer simulations is based on a well-documented model (Carnegie-Ames-Stanford Approach, CASA) of ecosystem production and carbon cycling in the terrestrial biosphere. Modifications to represent flooded wetland soils and anaerobic decomposition include three new submodels for (1) layered soil temperature and water table depth (WTD) as a function of daily climate drivers, (2) CH4 production within the anoxic soil layer as a function of WTD and CO2 production under poorly drained conditions, and (3) CH4 gaseous transport pathways (molecular diffusion, ebullition, and plant vascular transport) as a function of WTD and ecosystem type. The model was applied and tested using climate and ecological data to characterize tundra wetland sites near Fairbanks, Alaska, studied previously by Whaler, and Reeburgh [1992]. Comparison of model predictions to measurements of soil temperature and thaw depth, water table depth, and CH4 emissions over a 2-year period suggest that intersite differences in soil physical conditions and methane fluxes could be reproduced accurately for selected periods. Day-to-day comparison of predicted emissions to measured CH4 flux rates reveals good agreement during the early part of the thaw season, but the model tends to underestimate production of CH4 during the months of July and August in both test years. Important seasonal effects, including that of falling WTD during these periods, are apparently overlooked in the model formulation. Nevertheless, reasonably close agreement was achieved between the model's mean daily and seasonal estimates of CH4 flux and observed emission rates for northern wetland ecosystems. Several features of the model are identified as crucial to more accurate prediction of wetland methane emission, including the capacity to incorporate influences of localized topographic and hydrologic features on site-specific soil temperature and WTD dynamics and mechanistic simulation of methane emission transport pathways from within the soil profile. RP Potter, CS (reprint author), NASA, AMES RES CTR, ECOSYST SCI & TECHNOL BRANCH, MS 242-4, MOFFETT FIELD, CA 94035 USA. NR 78 TC 68 Z9 72 U1 2 U2 24 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0886-6236 J9 GLOBAL BIOGEOCHEM CY JI Glob. Biogeochem. Cycle PD DEC PY 1997 VL 11 IS 4 BP 495 EP 506 DI 10.1029/97GB02302 PG 12 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA YK118 UT WOS:A1997YK11800003 ER PT J AU Fung, I Field, CB Berry, JA Thompson, MV Randerson, JT Malmstrom, CM Vitousek, PM Collatz, GJ Sellers, PJ Randall, DA Denning, AS Badeck, F John, J AF Fung, I Field, CB Berry, JA Thompson, MV Randerson, JT Malmstrom, CM Vitousek, PM Collatz, GJ Sellers, PJ Randall, DA Denning, AS Badeck, F John, J TI Carbon 13 exchanges between the atmosphere and biosphere SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID SURFACE PARAMETERIZATION SIB2; ISOTOPE DISCRIMINATION; STOMATAL CONDUCTANCE; CO2 ASSIMILATION; C-13/C-12 RATIO; ICE CORE; MODEL; PHOTOSYNTHESIS; LEAVES; PLANTS AB We present a detailed investigation of the gross C-12 and C-13 exchanges between the atmosphere and biosphere and their influence on the delta(13)C variations in the atmosphere. The photosynthetic discrimination Delta against C-13 is derived from a biophysical model coupled to a general circulation model [Sellers et al., 1996a], where stomatal conductance and carbon assimilation are determined simultaneously with the ambient climate, The delta(13)C of the respired carbon is calculated by a biogeochemical model [Potter et al., 1993; Randerson et al., 1996] as the sum of the contributions from compartments with varying ages, The global flux-weighted mean photosynthetic discrimination is 12-16 parts per thousand, which is lower than previous estimates. Factors that lower the discrimination are reduced stomatal conductance and C-4 photosynthesis. The decreasing atmospheric delta(13)C causes an isotopic disequilibrium between the outgoing and incoming fluxes; the disequilibrium is similar to 0.33 parts per thousand for 1988. The disequilibrium is higher than previous estimates because it accounts for the lifetime of trees and for the ages rather than turnover times of the biospheric pools. The atmospheric delta(13)C signature resulting from the biospheric fluxes is investigated using a three-dimensional atmospheric tracer model. The isotopic disequilibrium alone produces a hemispheric difference of similar to 0.02 parts per thousand, in atmospheric delta(13)C, comparable to the signal from a hypothetical carbon sink of 0.5 Gt C yr(-1) into the midlatitude northern hemisphere biosphere, However, the rectifier effect, due to the seasonal covariation of CO2 fluxes and height of the atmospheric boundary layer, yields a background delta(13)C gradient of the opposite sign. These effects nearly cancel thus favoring a stronger net biospheric uptake than without the background CO2 gradient. Our analysis of the globally averaged carbon budget for the decade of the 1980s indicates that the biospheric uptake of fossil fuel CO2 is likely to be greater than the oceanic uptake; the relative proportions of the sinks cannot be uniquely determined using C-12 and C-13 alone. The land-ocean sink partitioning requires in addition, information about the land use source, isotopic disequilibrium associated with gross oceanic exchanges, as well as the fractions of C-3 and C-4 vegetation involved in the biospheric uptake. C1 NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. CARNEGIE INST WASHINGTON, DEPT PLANT BIOL, STANFORD, CA 94305 USA. STANFORD UNIV, DEPT BIOL SCI, STANFORD, CA 94305 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NASA, JOHNSON SPACE FLIGHT CTR, HOUSTON, TX USA. COLORADO STATE UNIV, DEPT ATMOSPHER SCI, FT COLLINS, CO 80523 USA. UNIV PARIS 11, ECOL VEGETALE LAB, F-91405 ORSAY, FRANCE. COLUMBIA UNIV, DEPT APPL PHYS, NEW YORK, NY USA. RP Fung, I (reprint author), UNIV VICTORIA, SCH EARTH & OCEAN SCI, POB 3055, VICTORIA, BC V8W 3P6, CANADA. RI Badeck, Franz/C-6722-2008; collatz, george/D-5381-2012; John, Jasmin/F-8194-2012; Denning, Scott/F-4974-2011; Randall, David/E-6113-2011 OI Badeck, Franz/0000-0001-7821-8825; John, Jasmin/0000-0003-2696-277X; Denning, Scott/0000-0003-3032-7875; Randall, David/0000-0001-6935-4112 NR 64 TC 175 Z9 180 U1 2 U2 32 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0886-6236 EI 1944-9224 J9 GLOBAL BIOGEOCHEM CY JI Glob. Biogeochem. Cycle PD DEC PY 1997 VL 11 IS 4 BP 507 EP 533 DI 10.1029/97GB01751 PG 27 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA YK118 UT WOS:A1997YK11800004 ER PT J AU Randerson, JT Thompson, MV Conway, TJ Fung, IY Field, CB AF Randerson, JT Thompson, MV Conway, TJ Fung, IY Field, CB TI The contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric carbon dioxide SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID NET PRIMARY PRODUCTION; GENERAL-CIRCULATION MODEL; SOIL ORGANIC-MATTER; NDVI DATA SET; CO2 CONCENTRATIONS; NORTHERN-HEMISPHERE; BIOSPHERE EXCHANGE; VEGETATION INDEX; AIR-TEMPERATURE; TRANSPORT MODEL AB We characterized decadal changes in the amplitude and shape of the seasonal cycle of atmospheric CO2 with three kinds of analysis. First, we calculated the trends in the seasonal cycle of measured atmospheric CO2 at observation stations in the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostic Laboratory network. Second, we assessed the impact of terrestrial ecosystems in various localities on the mean seasonal cycle of CO2 at observation stations using the Carnegie-Ames-Stanford Approach terrestrial biosphere model and the Goddard Institute for Space Studies (GISS) atmospheric tracer transport model, Third, we used the GISS tracer model to quantify the contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric CO2 for the period 1961-1990, specifically examining the effects of biomass burning, emissions from fossil fuel combustion, and regional increases in net primary production (NPP). Our analysis supports results from previous studies that indicate a significant positive increase in the amplitude of the seasonal cycle of CO2 at Arctic and subarctic observation stations. For stations north of 55 degrees N the amplitude increased at a mean rate of 0.66% yr(-1) from 1981 to 1995. From the analysis of ecosystem impacts on the mean seasonal cycle we find that tundra, boreal forest, and other northern ecosystems are responsible for most of the seasonal variation in CO2 at stations north of 55 degrees N. The effects of tropical biomass burning on trends in the seasonal cycle are minimal at these stations, probably because of strong vertical convection in equatorial regions. From 1981 to 1990, fossil fuel emissions contributed a trend of 0.20% yr(-1) to the seasonal cycle amplitude at Mauna Loa and less than 0.10% yr(-1) at stations north of 55 degrees N. To match the observed amplitude increases at Arctic and subarctic stations with NPP increases, we find that north of 30 degrees N a 1.7 Pg C yr(-1) terrestrial sink would be required. In contrast, over regions south of 30 degrees N, even large NPP increases and accompanying terrestrial sinks would be insufficient to account for the increase in high-latitude amplitudes. C1 STANFORD UNIV, DEPT BIOL SCI, STANFORD, CA 94305 USA. NATL OCEAN & ATMOSPHER ADMIN, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO USA. NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. UNIV VICTORIA, SCH EARTH & OCEAN SCI, VICTORIA, BC, CANADA. RP Randerson, JT (reprint author), CARNEGIE INST WASHINGTON, DEPT PLANT BIOL, STANFORD, CA 94305 USA. NR 81 TC 284 Z9 284 U1 6 U2 58 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0886-6236 J9 GLOBAL BIOGEOCHEM CY JI Glob. Biogeochem. Cycle PD DEC PY 1997 VL 11 IS 4 BP 535 EP 560 DI 10.1029/97GB02268 PG 26 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA YK118 UT WOS:A1997YK11800005 ER PT J AU Hou, TH Bryant, RG AF Hou, TH Bryant, RG TI Processing and properties of IM7/LARC((TM))-SI polyimide composites SO HIGH PERFORMANCE POLYMERS LA English DT Article AB LARC(TM)-SI (NASA Langley Research Center-Soluble Imide) is an aromatic thermoplastic polyimide. LARC(TM)-SI is synthesized from equimolar amounts of oxydiphthalic anhydride (ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and the equivalent amount of 3,4'-oxydianiline (3,4'-ODA). Phthalic anhydride (PA) was used as an endcapper to control molecular weight. A 30% solid LARC(TM)-SI solution (in NMP/Xylene: 9/1 v/v) with 3% stoichiometric imbalance was made into unidirectional long-fibre-reinforced prepregs. Thermal properties, volatile depletion behaviour and resin rheology were thoroughly characterized. Using this information, two composite moulding cycles were developed that consistently yielded well consolidated, void-free laminates. Composite mechanical properties such as short-beam shear strength, longitudinal and transverse flexural strength and flexural modulus, longitudinal tensile strength and notched and un-notched compression strengths, fracture toughness, open-hole compression strength and compression after impact (CAI) strength were measured at room temperature (RT) and elevated temperatures. LARC(TM)-SI composite exhibited very good toughness and damage tolerance. The interlaminar fracture toughness and the CAI strength were measured at 1.72 kJ m(-2) at 35.2 GPa respectively. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Hou, TH (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 13 TC 19 Z9 19 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD DEC PY 1997 VL 9 IS 4 BP 437 EP 448 DI 10.1088/0954-0083/9/4/007 PG 12 WC Polymer Science SC Polymer Science GA YR431 UT WOS:000071494600007 ER PT J AU Pravec, P Wolf, M Sarounova, L Mottola, S Erikson, A Hahn, G Harris, AW Harris, AW Young, JW AF Pravec, P Wolf, M Sarounova, L Mottola, S Erikson, A Hahn, G Harris, AW Harris, AW Young, JW TI The near-earth objects follow-up program - II. Results for 8 asteroids from 1982 to 1995 SO ICARUS LA English DT Article DE asteroids; rotation; photometry; near-Earth objects; lightcurves AB We present the results of photometric observations of the near-Earth asteroids (1943) Anteros, (2102) Tantalus, (2212) Hephaistos, (3199) Nefertiti, (5751) Zao = 1992 AC, (6322) 1991 CQ, (7474) 1992 TC, and 1989 VA made between 1982 and 1995, Synodic rotation periods in the range from 2.39 to 5.54 hr were derived for five of them, and we were able to place lower limits on periods of (2212) and (5751)-both > 20 hr, Only the period of the low amplitude case of (1943) was not constrained, The most interesting results were obtained for the following objects: (2102), a fast rotator (period 2.39 hr) in an extremely inclined orbit (i approximate to 64 degrees); (2212), a low amplitude slow rotator considered as an inactive cometary nucleus candidate; (3199), which showed similar lightcurves at quite different positions of the phase angle bisector, constraining its rotational pole; and 1989 VA, an unusual Aten asteroid with a rotation period of 2.51 hr and a relatively large amplitude, Overall, these results continue the pattern that NEO spins exhibit a bimodal distribution of spin rates. (C) 1997 Academic Press. C1 Acad Sci Czech Republ, Inst Astron, CZ-25165 Ondrejov, Czech Republic. Charles Univ, Inst Astron, CZ-15000 Prague 5, Czech Republic. DLR, Inst Planetary Explorat, D-12489 Berlin, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Pravec, P (reprint author), Acad Sci Czech Republ, Inst Astron, CZ-25165 Ondrejov, Czech Republic. RI Pravec, Petr/G-9037-2014 NR 21 TC 12 Z9 12 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1997 VL 130 IS 2 BP 275 EP 286 DI 10.1006/icar.1997.5816 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX415 UT WOS:000072037700004 ER PT J AU Rabinowitz, DL AF Rabinowitz, DL TI Are main-belt asteroids a sufficient source for the earth-approaching asteroids? Part II. Predicted vs observed size distributions SO ICARUS LA English DT Article DE asteroids; meteoroids; meteorites; orbits AB This paper predicts the size distribution of the Earth-approaching asteroids with diameter d = 10 m to 10 km, assuming they originate as the fragments of main-belt asteroids with a cumulative size distribution proportional to d(-25) and that they have self-similar fragmentation properties. The resulting distribution is dominated by "fast-track" bodies originating from parent asteroids with orbits close to the 3:1 mean-motion resonance with Jupiter. Because the dynamical lifetimes of these Earth approachers are shorter than their collisional lifetimes, their size distribution is nearly proportional to d(-3.0), the production distribution in the main belt. This prediction, however, is at odds with the Spacewatch observations. The observed distribution is relatively flat for d > similar to 100 m, and relatively steep for d < similar to 100 m, so that the number of Earth approachers with d similar to 10 m to 0.3 km is overestimated. If these populations are predominantly of main-belt origin, then the size distribution in the main belt is not a simple power law. A nonuniform size distribution with wave-like oscillations, possibly caused by a cutoff at small sizes, would lead to Earth approachers with a size distribution in better agreement with the observations. If such wave-like oscillations are realistic, then the main belt is sufficient to supply the observed number of Earth approachers throughout the observed size range. (C) 1997 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rabinowitz, DL (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-501, Pasadena, CA 91109 USA. NR 15 TC 14 Z9 14 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1997 VL 130 IS 2 BP 287 EP 295 DI 10.1006/icar.1997.5823 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX415 UT WOS:000072037700005 ER PT J AU Benner, LAM Ostro, SJ Giorgini, JD Jurgens, RF Mitchell, DL Rose, R Rosema, KD Slade, MA Winkler, R Yeomans, DK Campbell, DB Chandler, JF Shapiro, II AF Benner, LAM Ostro, SJ Giorgini, JD Jurgens, RF Mitchell, DL Rose, R Rosema, KD Slade, MA Winkler, R Yeomans, DK Campbell, DB Chandler, JF Shapiro, II TI Radar detection of near-earth asteroids 2062 Aten, 2101 Adonis, 3103 Eger, 4544 Xanthus, and 1992 QN SO ICARUS LA English DT Article DE asteroids; radar; Aten; Adonis; Eger; Xanthus ID GREENLAND ICE-SHEET; DYNAMICS; OBJECTS; APOLLO; VENUS AB We describe Doppler-only radar observations of near-Earth asteroids 2062 Aten, 2101 Adonis, 3103 Eger, 4544 Xanthus, and 1992 QN that were obtained at Arecibo and Goldstone between 1984 and 1996. Estimates of the echo spectral bandwidths, radar cross sections, and circular polarization ratios of these objects constrain their pole-on breadths, radar albedos, surface roughnesses, taxonomic classes, rotation periods, and pole directions. Aten's bandwidth is consistent with its radiometrically determined diameter of 0.9 km. Adonis has a rotation period P less than or equal to 11 h and an effective diameter (the diameter of a sphere with the same projected area as the asteroid) between 0.3 and 0.8 km. The radar properties of Adonis suggest it is not a member of taxonomic classes C or M. The effective diameter of Xanthus is between 0.4 and 2.2 km with a rotation period P less than or equal to 20 h. Echoes from 1992 QN constrain the asteroid's pole-on breadth to be greater than or equal to 0.6 km and probably exclude it from the C and M taxonomic classes. The strongest Eger echoes are asymmetric with bandwidths that set lower bounds of 1.5 and 2.3 km on the minimum and maximum breadths of the asteroid's pole-on silhouette. If Eger is modeled as a 1.5 x 2.3 km biaxial ellipsoid, then its effective diameter for an equatorial view is 1.5 km end-on and 1.9 km broadside or pole-on, implying a geometric albedo smaller than published values but still consistent with a classification as an E-type object, The near-unity circular polarization ratios of Adonis, Eger, and 1992 QN are among the highest values measured for any asteroid extreme near-surface roughness at centimeter to meter scales. (C) 1997 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Cornell Univ, Natl Astron & Ionosphere Ctr, Ithaca, NY 14853 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Benner, LAM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM lance@think.jpl.nasa.gov NR 47 TC 26 Z9 26 U1 1 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1997 VL 130 IS 2 BP 296 EP 312 DI 10.1006/icar.1997.5834 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX415 UT WOS:000072037700006 ER PT J AU Hillier, JK AF Hillier, JK TI Scattering of light by composite particles in a planetary surface SO ICARUS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; OPTICAL-PROPERTIES; SATELLITES; PARAMETERS; PHOTOMETRY; TERRAINS; GRAINS; DUST AB It has been proposed that composite particles containing internal scatterers may provide the explanation for the fact that most photometric studies of planetary surfaces based on Hapke's model of bidirectional reflectance have found the planetary particles to exhibit moderately backscattering phase functions, However, an implicit assumption made in this explanation is that the scattering by composite particles containing multiple internal inclusions in a planetary surface can still be adequately computed using standard radiative transfer theory assuming the composite particles to be the fundamental individual scatterers even though such particles are necessarily in close proximity to each other, In this paper, this assumption is explored by examining the effects of close packing on the light scattering by spherical particles containing isotropic internal scatterers using a Monte Carlo routine, ils expected, classical radiative transfer (assuming a random distribution of scattering particles) coupled with the assumption that the composite particle is the fundamental scatterer provides a good approximation in the high porosity limit, However, even for porosities as high as 90% the effects of close packing are clearly seen with the radiative transfer calculation underestimating the scattering by similar to 10% at high incidence, emission, and phase angles, As the porosity is lowered further, the discrepancy becomes more severe and can reach 50% or more, In contrast, assuming the individual scatterer properties in the radiative transfer calculation leads to a substantial overestimate of the scattering even for porosities as low as 27.5%. This suggests that parameters derived using the classical radiative transfer theory will yield results intermediate between those of the composite as a whole and those of the internal scatterers, Thus, one should exercise caution in interpreting the results of models based on classical radiative transfer theory in terms of the physical properties of the surface particles and, where possible, the bidirectional reflectance of densely packed composite particles should be computed using more accurate methods such as the stochastic radiative transfer theory. (C) 1997 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hillier, JK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 23 TC 11 Z9 11 U1 1 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1997 VL 130 IS 2 BP 328 EP 335 DI 10.1006/icar.1997.5829 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX415 UT WOS:000072037700009 ER PT J AU Bird, MK Dutta-Roy, R Asmar, SW Rebold, TA AF Bird, MK Dutta-Roy, R Asmar, SW Rebold, TA TI Detection of Titan's ionosphere from Voyager 1 radio occultation observations SO ICARUS LA English DT Article DE Titan; radio observations; planetary ionospheres ID PLANETARY-ATMOSPHERES; MODELS; TRITON; SATURN; SYSTEM AB Evidence for a marginal detection of the Titan ionosphere has been obtained from a new analysis of the dual-frequency Doppler data recorded during the Voyager 1 occultation in 1980. The original report by Lindal et al. (1983, Icarus 53, 348-363) gave only upper bounds on the peak electron density of 3000 cm(-3) during ingress, (evening terminator) and 5000 cm(-3) during egress (morning terminator). The dual-frequency ingress data imply a maximum electron density of 2400 +/-: 1100 cm(-3) for Titan's upper ionosphere at an altitude of 1180 +/- 150 km, The egress data were determined to be of limited use for this analysis because the X-band signal was received for only a few seconds. Nevertheless, a distinct ionospheric peak is revealed in the S-band data for both ingress and ,egress. The height and peak density of this ionized layer are in good agreement with expectations from numerical models that invoke photoionization and energetic electron impacts, (C) 1997 Academic Press. C1 Univ Bonn, Inst Radioastron, D-53121 Bonn, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bird, MK (reprint author), Univ Bonn, Inst Radioastron, Auf Hugel 71, D-53121 Bonn, Germany. EM mbird@astro.uni-bonn.de NR 28 TC 79 Z9 79 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1997 VL 130 IS 2 BP 426 EP 436 DI 10.1006/icar.1997.5831 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX415 UT WOS:000072037700015 ER PT J AU Grin, EA Cabrol, NA AF Grin, EA Cabrol, NA TI Limnologic analysis of Gusev crater paleolake, Mars SO ICARUS LA English DT Article DE Mars; surface; geological processes; planets ID MAADIM-VALLIS; ICE; LAKE; WATER; SEDIMENTATION; ANTARCTICA; ENVIRONMENT; TOPOGRAPHY; THICKNESS; EVOLUTION AB The survey of the hydrogeologic system formed by Gusev crater and Ma'adim Vallis (Aeolis subquadrangle of Mars) points out evidence for the existence of an ice-covered lake in Gusev crater. A first lake was formed by the drainage of the aquifer in the region surrounding Gusev before the entry of Ma'adim Vallis in the crater. The existence of a former lake in Gusev is deduced from the morphology of the Ma'adim delta. Its comparison with terrestrial Antarctic analogs argues for the presence of an ice-covered lake in Gusev at the time that the southern part of the crater's rampart was breached by Ma'adim first release, and for a subice-lacustrine construction of the valley's delta. Our survey shows that Ma'adim Vallis may have entered Gusev crater as late as Late Hesperian/Early Amazonian as part of a second lake episode. The relationship between the variation of the Gusev lake water-level, the volume of the lake, and the surface of the lake bed is established by our bathymetric model. The elevation of the former lake is deduced from the elevation of the mesa-like structures in the delta of Ma'adim Vallis. Furthermore, the correlation of the crater frequency of Gusev rampart with Mars' stratigraphic age shows that lakes may have occupied Gusev crater over a period of time covering 2 Gyrs., from the formation of the crater to the last episode of water release from Ma'adim Vallis. Though it is most likely that the lake was episodical, the recurrence of abundant water in Gusev crater makes this site a high priority for missions, either for martian resource exploration, or for the search of life. (C) 1997 Academic Press. C1 NASA, Ames Res Ctr, Div Space Sci, Ctr Mars Explorat, Moffett Field, CA 94035 USA. RP Grin, EA (reprint author), NASA, Ames Res Ctr, Div Space Sci, Ctr Mars Explorat, MS 239-20, Moffett Field, CA 94035 USA. NR 43 TC 63 Z9 64 U1 1 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1997 VL 130 IS 2 BP 461 EP 474 DI 10.1006/icar.1997.5817 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX415 UT WOS:000072037700018 ER PT J AU Koljonen, ML Pella, JJ AF Koljonen, ML Pella, JJ TI The advantage of using smolt age with allozymes for assessing wild stock contributions to Atlantic salmon catches in the Baltic Sea SO ICES JOURNAL OF MARINE SCIENCE LA English DT Article; Proceedings Paper CT ICES/NASCO Symposium on Interactions Between Salmon Culture and Wild Stocks of Atlantic Salmon - THe Scientific and Management Issues CY APR 18-22, 1997 CL BATH, ENGLAND SP Int Council Explorat Sea, NASCO DE allozyme variation; stock mixtures; Salmo salar; smolt age ID IDENTIFICATION; FISHERIES AB Information about the occurrence and proportions of endangered wild Atlantic salmon stocks in Baltic Sea catches is invaluable to the fishery managers responsible for sustaining these populations. The usefulness of stock mixture analysis (SMA) from characters of sampled fish was evaluated by applying the method in an estimation of actual and simulated catch compositions. Samples for seven Variable genetic loci, expressed by allozymes, and smelt age from 17 stocks from Finland and Sweden which are potential contributors to the fishery were used with similar samples collected in 1993 from catches in a Finnish trapnet fishery along the east coast of the Bothnian Sea. Identified by their character similarities, three stock management units and their estimated catch contributions were: resident Neva stock (29%), wild baseline stocks (28%), and migratory hatchery stocks (43%). The contributions of the units varied during the fishing season. With allozyme data alone, the management units were not so distinctive. Nevertheless, three major wild stocks (Tornionjoki, Kalixalven, and Simojoki), which accounted for 68% of the total wild smelt production of the area, were similar in their allozymes and distinctive from the other stocks. The increase in reliability of wild stock composition estimates when smelt age was added to the allozyme loci was evaluated by simulation. Smelt age improved the precision of composition estimates for both the combined wild baseline stocks and their aforementioned subset comprising three major stocks; it controlled bias better for the combined wild baseline stocks than their subset. (C) 1997 International Council for the Exploration or the Sea. C1 Finnish Game & Fisheries Res Inst, FIN-00721 Helsinki, Finland. Natl Marine Fisheries Serv, Natl Ocean & Atmospher Adm, US Dept Commerce, Juneau, AK 99801 USA. RP Koljonen, ML (reprint author), Finnish Game & Fisheries Res Inst, POB 6, FIN-00721 Helsinki, Finland. NR 30 TC 14 Z9 15 U1 1 U2 5 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1054-3139 J9 ICES J MAR SCI JI ICES J. Mar. Sci. PD DEC PY 1997 VL 54 IS 6 BP 1015 EP 1030 DI 10.1006/jmsc.1997.0310 PG 16 WC Fisheries; Marine & Freshwater Biology; Oceanography SC Fisheries; Marine & Freshwater Biology; Oceanography GA YT714 UT WOS:000071635600007 ER PT J AU Berejikian, BA Tezak, EP Schroder, SL Knudsen, CM Hard, JJ AF Berejikian, BA Tezak, EP Schroder, SL Knudsen, CM Hard, JJ TI Reproductive behavioral interactions between wild and captively reared coho salmon (Oncorhynchus kisutch) SO ICES JOURNAL OF MARINE SCIENCE LA English DT Article; Proceedings Paper CT ICES/NASCO Symposium on Interactions Between Salmon Culture and Wild Stocks of Atlantic Salmon - THe Scientific and Management Issues CY APR 18-22, 1997 CL BATH, ENGLAND SP Int Council Explorat Sea, NASCO DE captive rearing; Pacific salmon; reproductive interactions; spawning ID MALE ATLANTIC SALMON; SOCKEYE-SALMON; PACIFIC SALMON; BREEDING COMPETITION; MATING SUCCESS; SALAR; SELECTION; HATCHERY; CHOICE; NERKA AB Captive rearing is an evolving strategy for restoring depleted salmon populations; it involves capturing wild juvenile salmon from natural streams; rearing them in captivity to adulthood, and then releasing them as adults back into their natal streams to spawn naturally. The conservation benefit of captive rearing is that it bypasses the typically high smolt-to-adult mortality experienced by wild populations, but its success as a restoration strategy depends upon the ability of captively reared salmon to spawn and reproduce in natural streams. In an experimental channel, wild males dominated captively reared males of similar size in 86% of spawning events. Both wild and captively reared females attacked captively reared males more frequently than wild males, indicating a preference for wild over captively reared males, although the interplay between male dominance and Female mate choice was unclear. Wild females established nesting territories earlier and constructed more nests per individual than captively reared females of similar size, suggesting a competitive advantage for wild females. Nevertheless, captively reared coho salmon demonstrated the full range of behaviors shown by wild coho salmon of both sexes and the ability to spawn naturally. (C) 1997 International Council for the Exploration of the Sea. C1 Natl Marine Fisheries Serv, Manchester Marine Expt Serv, Manchester, WA 98353 USA. NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Seattle, WA 98112 USA. Washington Dept Fish & Wildlife, Olympia, WA 98501 USA. RP Berejikian, BA (reprint author), Natl Marine Fisheries Serv, Manchester Marine Expt Serv, POB 130, Manchester, WA 98353 USA. RI Hard, Jeffrey/C-7229-2009 NR 36 TC 50 Z9 50 U1 1 U2 12 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1054-3139 J9 ICES J MAR SCI JI ICES J. Mar. Sci. PD DEC PY 1997 VL 54 IS 6 BP 1040 EP 1050 DI 10.1006/jmsc.1997.0293 PG 11 WC Fisheries; Marine & Freshwater Biology; Oceanography SC Fisheries; Marine & Freshwater Biology; Oceanography GA YT714 UT WOS:000071635600009 ER PT J AU Beamish, RJ Mahnken, C Neville, CM AF Beamish, RJ Mahnken, C Neville, CM TI Hatchery and wild production of Pacific salmon in relation to large-scale, natural shifts in the productivity of the marine environment SO ICES JOURNAL OF MARINE SCIENCE LA English DT Article; Proceedings Paper CT ICES/NASCO Symposium on Interactions Between Salmon Culture and Wild Stocks of Atlantic Salmon - THe Scientific and Management Issues CY APR 18-22, 1997 CL BATH, ENGLAND SP Int Council Explorat Sea, NASCO DE climate change; hatcheries; Pacific salmon ID NORTH PACIFIC; BRITISH-COLUMBIA; SOCKEYE-SALMON; CLIMATE; ONCORHYNCHUS; TRENDS; RIVER; OCEAN; SIZE; CALIFORNIA AB Pacific salmon have been fished extensively for at least a century and artificial production of Pacific salmon has been a management strategy to improve production for almost as long. Hatchery production is considered important because it is commonly believed that the carrying capacity for salmon in the ocean has remained more or less constant and is underutilized as a consequence of limited production of smelts in fresh water. Since the mid-1960s, there has been an increase in hatchery production, partly as a response to a desire to increase catch and partly because of improved hatchery techniques. Since the late 1970s there has been a dramatic increase in the total Pacific salmon catch. The increases in catch are now known to result from a large-scale shift in the productivity of the sub-arctic Pacific and management and enhancement actions. Environmental indices changed about 1989-1990 and may indicate that the productive regime of the 1980s has ended. This would imply that under natural conditions Pacific salmon abundance would decline. There are no clear indications of what to expect in the new regime, but it is apparent that the massive production of artificially reared Pacific salmon would not be necessary in a less productive regime. OF concern is the impact that the large numbers of artificially reared salmon will have on wild salmon stock levels. (C) 1997 International Council for the Exploration of the Sea. C1 Fisheries & Oceans Canada, Pacific Biol Stn, Nanaimo, BC V9R 5K6, Canada. Natl Marine Fisheries Serv, Manchester Marine Expt Stn, Manchester, WA 98353 USA. RP Beamish, RJ (reprint author), Fisheries & Oceans Canada, Pacific Biol Stn, Hammond Bay Rd, Nanaimo, BC V9R 5K6, Canada. NR 59 TC 55 Z9 56 U1 2 U2 9 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1054-3139 J9 ICES J MAR SCI JI ICES J. Mar. Sci. PD DEC PY 1997 VL 54 IS 6 BP 1200 EP 1215 DI 10.1006/jmsc.1997.0305 PG 16 WC Fisheries; Marine & Freshwater Biology; Oceanography SC Fisheries; Marine & Freshwater Biology; Oceanography GA YT714 UT WOS:000071635600028 ER PT J AU Butrica, AJ AF Butrica, AJ TI In conjunction with Venus SO IEEE SPECTRUM LA English DT Article ID ORIGINS RP Butrica, AJ (reprint author), NASA,PROGRAM X33,WASHINGTON,DC 20546, USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9235 J9 IEEE SPECTRUM JI IEEE Spectr. PD DEC PY 1997 VL 34 IS 12 BP 31 EP 38 DI 10.1109/6.642966 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA YL247 UT WOS:A1997YL24700009 ER PT J AU Sun, XL Reusser, D Dautet, H Abshire, JB AF Sun, XL Reusser, D Dautet, H Abshire, JB TI Measurement of proton radiation damage to Si avalanche photodiodes SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article ID PHOTO-DIODES; SILICON AB The effects of proton radiation damage on EG&G C30902S Si avalanche photodiodes (APD's) were measured, The APD bulk leakage current increased at 0.29 fA/rad, or about 1800 dark photoelectrons per rad(Si) at -10 degrees C under 16.2 MeV protons. There were little changes in the breakdown voltage, with the radiation doses up to 30 krad(Si). The increase in the total dark currents below the breakdown voltage was insignificant until 3 krad(Si). C1 NASA,GODDARD SPACE FLIGHT CTR,LASER REMOTE SENSING BRANCH,GREENBELT,MD 20771. EG&G OPTOELECT CANADA,VAUDREUIL,PQ J7V 8P7,CANADA. SWISS NATL SCI FDN,CH-2014 BOLE,SWITZERLAND. RP Sun, XL (reprint author), JOHNS HOPKINS UNIV,DEPT ELECT & COMP ENGN,BALTIMORE,MD 21218, USA. RI Sun, Xiaoli/B-5120-2013; Abshire, James/I-2800-2013 NR 19 TC 13 Z9 13 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 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD DEC PY 1997 VL 44 IS 12 BP 2160 EP 2166 DI 10.1109/16.644630 PG 7 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA YH432 UT WOS:A1997YH43200007 ER PT J AU Wilson, JD AF Wilson, JD TI A simulated annealing algorithm for optimizing RF power efficiency in coupled-cavity traveling-wave tubes SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article ID TAPER AB Decreasing the radio frequency (RF) phase velocity in the output section of a traveling-wave tube (TWT) is a technique commonly used to increase RF power efficiency. In order to optimize the profile of the phase velocity, a simulated annealing algorithm has been developed and implemented into the NASA multidimensional large-signal coupled cavity TWT computer model, This algorithm allows the determination of the lengths of the individual cavities at the end of the output section necessary to provide the optimized phase velocity profile, The resulting nonlinear computer-generated phase velocity profile provides a design with optimized RF efficiency, In this paper, the optimization algorithm will be described and computational results will be shown, These results indicate an increase in center-frequency RF efficiency from 7.1 to 13.5% for a V-band coupled-cavity TWT. RP Wilson, JD (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 15 TC 11 Z9 12 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 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD DEC PY 1997 VL 44 IS 12 BP 2295 EP 2299 DI 10.1109/16.644656 PG 5 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA YH432 UT WOS:A1997YH43200026 ER PT J AU Carts, MA Marshall, PW Marshall, CJ Label, KA Flanegan, M Bretthauer, J AF Carts, MA Marshall, PW Marshall, CJ Label, KA Flanegan, M Bretthauer, J TI Single event test methodology and test results of commercial gigabit per second fiber channel hardware SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID OPTIC DATA BUS AB This article presents a detailed description of the single event test methods used to evaluate two different component sets conforming to the Fiber Channel (FC) commercial high-speed serial bus standard. The devices tested perform the hierarchically low-level functions such as transmission coding and actual electrical or optical linking. Pertinent portions of the FC specification, and details of the test setup and methods are presented prior to description of the observed error types, correlation of error types to source circuitry, and radiation test results. The authors conclude that one of these COTS device sets may be suitable for space use with the use of additional circuit hardening, and that the other (also a COTS device set) is not suitable for space use. The test methods and descriptions of error types should prove useful in preparation for future FC component SEE testing. C1 USN, Res Lab, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Carts, MA (reprint author), USN, Res Lab, 4555 Overlook Ave, Washington, DC 20375 USA. NR 6 TC 3 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 1878 EP 1884 DI 10.1109/23.658956 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800017 ER PT J AU LaBel, KA Marshall, PW Marshall, CJ D'Ordine, M Carts, M Lum, G Kim, HS Seidleck, CM Powell, T Abbott, R Barth, J Stassinopoulos, EG AF LaBel, KA Marshall, PW Marshall, CJ D'Ordine, M Carts, M Lum, G Kim, HS Seidleck, CM Powell, T Abbott, R Barth, J Stassinopoulos, EG TI Proton-induced transients in optocouplers: In-flight anomalies, ground irradiation test, mitigation and implications SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID SATELLITE DATA MANAGEMENT; OPTIC DATA LINKS; DATA BUS; FIBER AB We present data on recent optocoupler in-flight anomalies and the subsequent ground test irradiation performed. Discussions of the single event mechanisms involved, transient filtering analysis, and design implications are included. Proton-induced transients were observed on higher speed optocouplers with a unique dependence on the incidence particle angle. The results indicate that both direct ionization and nuclear reaction-related mechanisms are responsible for the single events observed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SFA Inc, NRL, Landover, MD 20785 USA. Ball Aerosp & Technol Corp, Broomfield, CO USA. Lockheed Missile & Space Corp, Sunnyvale, CA USA. Hewlett Packard, Palo Alto, CA USA. RP LaBel, KA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 21 TC 29 Z9 32 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 1885 EP 1892 DI 10.1109/23.658957 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800018 ER PT J AU Rax, BG Lee, CI Johnston, AH AF Rax, BG Lee, CI Johnston, AH TI Degradation of precision reference devices in space environments SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID BIPOLAR-JUNCTION TRANSISTORS; DOSE-RATE; DEPENDENCE; DAMAGE AB The degradation of precision reference devices is investigated to determine the relative importance of ionization and displacement damage. The results are compared with theoretical calculations of a basic bandgap reference circuit. Several of the device types were degraded severely at 20 krad(Si), with about the same degradation as that predicted for the basic bandgap reference circuit. One very high precision device with an internal heater performed far better than any of the other devices in the study. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rax, BG (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 25 Z9 25 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 1939 EP 1944 DI 10.1109/23.658965 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800025 ER PT J AU Katz, R LaBel, K Wang, JJ Cronquist, B Koga, R Penzin, S Swift, G AF Katz, R LaBel, K Wang, JJ Cronquist, B Koga, R Penzin, S Swift, G TI Radiation effects on current field programmable technologies SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Manufacturers of field programmable gate arrays (FPGAs) take different technological and architectural approaches that directly affect radiation performance. Similar technological and architectural features are used in related technologies such as programmable substrates and quick-turn application specific integrated circuits (ASICs). After analyzing current technologies and architectures and their radiation-effects implications, this paper includes extensive test data quantifying various devices' total dose and single event susceptibilities, including performance degradation effects and temporary or permanent re-configuration faults. Test results will concentrate on recent technologies being used in space flight electronic systems and those being developed for use in the near term. This paper will provide the first extensive study of various configuration memories used in programmable devices. Radiation performance limits and their impacts will be discussed for each design. In addition, the interplay between device scaling, process, bias voltage, design, and architecture will be explored. Lastly, areas of ongoing research will be discussed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Actel Corp, Sunnyvale, CA 94086 USA. Aerospace Corp, Los Angeles, CA 90009 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Katz, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 8 TC 48 Z9 52 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 1945 EP 1956 DI 10.1109/23.658966 PN 1 PG 12 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800026 ER PT J AU Hancock, BR Soli, GA AF Hancock, BR Soli, GA TI Total dose testing of a CMOS charged particle spectrometer SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID DEVICES; NOISE; CHIP AB A first-generation CMOS Charged Particle Spectrometer chip [1] was designed at JPL for flight on the STRV-2 spacecraft. These devices will collect electron and proton spectra in low Earth orbit as part of an experiment to demonstrate Active Pixel Sensor (APS) technology in space. This paper presents the results of total dose testing on these chips and, where possible, attempts to extend the results to other Active Pixel Sensors. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hancock, BR (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 11 TC 16 Z9 16 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 1957 EP 1964 DI 10.1109/23.658968 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800027 ER PT J AU Pease, RL Cohn, LM Fleetwood, DM Gehlhausen, MA Turflinger, TL Brown, DB Johnston, AH AF Pease, RL Cohn, LM Fleetwood, DM Gehlhausen, MA Turflinger, TL Brown, DB Johnston, AH TI A proposed hardness assurance test methodology for bipolar linear circuits and devices in a space ionizing radiation environment SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID TOTAL-DOSE RESPONSE; ISSUES AB A hardness assurance test approach has been developed for bipolar linear circuits and devices in space. It consists of an initial test for dose rate sensitivity and a characterization test method to develop the conditions for a lot acceptance test at high dose rate. For parts with adequate design margin and/or well behaved parts a generic elevated temperature irradiation test is proposed. C1 RLP Res, Albuquerque, NM 87122 USA. Def Special Weap Agcy, Alexandria, VA 22310 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. Naval Surface Warfare Ctr, Crane, IN 47522 USA. USN, Res Lab, Washington, DC 20375 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Pease, RL (reprint author), RLP Res, Albuquerque, NM 87122 USA. NR 18 TC 57 Z9 62 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 1981 EP 1988 DI 10.1109/23.658976 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800030 ER PT J AU Reed, RA Carts, MA Marshall, PW Marshall, CJ Musseau, O McNulty, PJ Roth, DR Buchner, S Melinger, J Corbiere, T AF Reed, RA Carts, MA Marshall, PW Marshall, CJ Musseau, O McNulty, PJ Roth, DR Buchner, S Melinger, J Corbiere, T TI Heavy ion and proton-induced single event multiple upset SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID HIGH-DENSITY SRAMS; BIT UPSETS; FLIGHT DATA; DEVICES; TRACKS; ORBIT; RAMS AB Individual ionizing heavy ion events are shown to cause two or more adjacent memory cells to change logic states in a high density CMOS SRAM. A majority of the upsets produced by normally incident heavy ions are due to single particle events that causes a single cell to upset. However, for grazing angles a majority of the upsets produced by heavy-ion irradiation are due to single-particle events that cause two or more cells to change logic states. Experimental evidence of a single proton-induced spallation reaction that causes two adjacent memory cells to change logic states is presented. Results from a dual volume Monte-Carlo simulation code for proton-induced single-event multiple upsets are within a factor of three of experimental data for protons at normal incidence and 70 degrees. C1 SFA Inc, Landover, MD 20785 USA. CEA, Bruyeres Le Chatel, France. Clemson Univ, Clemson, SC USA. Matra MHS, Nantes, France. USN, Res Lab, Washington, DC 20375 USA. RP Reed, RA (reprint author), NASA, Goddard Space Flight Ctr, Code 735, Greenbelt, MD 20771 USA. NR 28 TC 41 Z9 43 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 2224 EP 2229 DI 10.1109/23.659039 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800062 ER PT J AU O'Neill, PM Badhwar, GD Culpepper, WX AF O'Neill, PM Badhwar, GD Culpepper, WX TI Risk assessment for heavy ions of parts tested with protons SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID ENERGY DEPOSITION; MODEL AB An internuclear cascade - evaporation code is used to model energy deposition in thin slabs of silicon. This model shows that protons produce a significant number of events with effective Linear Energy Transfer (LET) greater than 8 MeV cm(2)/mg and demonstrates that proton testing of microelectronic components can be an effective way to screen devices for low earth orbit susceptibility to heavy ions. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP O'Neill, PM (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 10 TC 30 Z9 30 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 2311 EP 2314 DI 10.1109/23.659052 PN 1 PG 4 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800074 PM 11542769 ER PT J AU Schwartz, HR Nichols, DK Johnston, AH AF Schwartz, HR Nichols, DK Johnston, AH TI Single-event upset in flash memories SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Single-event upset was investigated in high-density flash memories from two different manufacturers. Many types of functional abnormalities can be introduced in these devices by heavy-ions because of their complex internal architecture. Changes in the stored memory contents sometimes occurred, even when devices were irradiated in a read mode with the internal charge pump inactive. For one device technology, unusually high currents were observed during post-irradiation cycling that were high enough to cause catastrophic failure. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Schwartz, HR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 18 TC 62 Z9 71 U1 1 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 2315 EP 2324 DI 10.1109/23.659053 PN 1 PG 10 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800075 ER PT J AU Johnston, AH Swift, GM Edmonds, LD AF Johnston, AH Swift, GM Edmonds, LD TI Latchup in integrated circuits from energetic protons SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard ID CHARGE COLLECTION; UPSET; SIMULATION; PARTICLES; MODEL; SPACE; CMOS AB Proton latchup was investigated for several CMOS integrated circuits, including a modem microprocessor. The proton latchup cross sections of these devices differed by more than two orders of magnitude. A modeling approach that takes differences in charge collection processes for long- and short-range particles into account was effective in comparing latchup cross sections in heavy-ion and proton environments, as well as explaining why the proton cross sections were so different among the device types. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Johnston, AH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 23 TC 41 Z9 42 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 2367 EP 2377 DI 10.1109/23.659064 PN 1 PG 11 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM431 UT WOS:000071062800082 ER PT J AU Badhwar, GD Shurshakov, VA Tsetlin, VV AF Badhwar, GD Shurshakov, VA Tsetlin, VV TI Solar modulation of dose rate onboard the Mir station SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article DE atmospheric density; dose; radiation belt ID RADIATION; MODELS AB Models of the radiation belts that are currently used to estimate exposure for astronauts describe the environment at times of either solar minimum or solar maximum, Static models, constructed using data acquired prior to 1970 during a solar cycle with relatively low solar radio flux, have flux uncertainties of a factor of two to five and dose-rate uncertainties of a factor of about two, The inability of these static models to provide a dynamic description of the radiation belt environment limits our ability to predict radiation exposures for long-duration missions in low earth orbits, In an attempt to add some predictive capability of these models, we studied the measured daily absorbed dose rate on the Mir orbital station over roughly the complete 22nd solar cycle that saw some of the highest solar flux values in the last 40 y, We show that the daily trapped particle dose rate is an approximate power law function of daily atmospheric density, Atmospheric density values are in turn obtained from standard correlation with observed solar radio noise flux, This correlation improves, particularly during periods of high solar activity, if the density at roughly 400 days earlier time is used, This study suggests the possibility of a dose-and flux-predictive trapped-belt model based on atmospheric density. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Inst Biomed Problems, Moscow 10051, Russia. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 30 TC 14 Z9 14 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1997 VL 44 IS 6 BP 2529 EP 2541 DI 10.1109/23.650860 PN 3 PG 13 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YM435 UT WOS:000071063200001 PM 11542263 ER PT J AU Stewart, DB Volpe, RA Khosla, PK AF Stewart, DB Volpe, RA Khosla, PK TI Design of dynamically reconfigurable real-time software using port-based objects SO IEEE TRANSACTIONS ON SOFTWARE ENGINEERING LA English DT Article DE dynamic reconfiguration; real-time operating system; software architecture; object-based design; port-automaton theory; reusable software; component-based design; evolutionary design; digital control systems; robotics ID SYSTEMS; MODEL AB The port-based object is a new software abstraction for designing and implementing dynamically reconfigurable real-time software. it forms the basis of a programming model that uses domain-specific elemental units to provide specific, yet flexible, guidelines to control engineers for creating and integrating software components. We use a port-based object abstraction, based on combining the notion of an object with the port-automaton algebraic model of concurrent processes. It is supported by an implementation using domain-specific communication mechanisms and templates that have been incorporated into the Chimera Real-Time Operating System and applied to several robotic applications. This paper describes the port-based object abstraction, provides a detailed analysis of communication and synchronization based on distributed shared memory, and describes a programming paradigm based on a framework process and code templates for quickly implementing applications. C1 Univ Maryland, Dept Elect Engn, College Pk, MD 20742 USA. Univ Maryland, Inst Adv Comp Studies, College Pk, MD 20742 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carnegie Mellon Univ, Dept Elect & Comp Engn, Pittsburgh, PA 15213 USA. Carnegie Mellon Univ, Inst Complex Engn Syst, Pittsburgh, PA 15213 USA. RP Stewart, DB (reprint author), Univ Maryland, Dept Elect Engn, College Pk, MD 20742 USA. NR 43 TC 108 Z9 112 U1 0 U2 4 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0098-5589 J9 IEEE T SOFTWARE ENG JI IEEE Trans. Softw. Eng. PD DEC PY 1997 VL 23 IS 12 BP 759 EP 776 DI 10.1109/32.637390 PG 18 WC Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA YN663 UT WOS:000071193000002 ER PT J AU Toll, DL Shirey, D Kimes, DS AF Toll, DL Shirey, D Kimes, DS TI NOAA AVHRR land surface albedo algorithm development SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID HEMISPHERICAL REFLECTANCE ALBEDO; NEAR-INFRARED CHANNELS; DIGITAL ELEVATION DATA; BIDIRECTIONAL REFLECTANCE; ATMOSPHERIC CORRECTION; VEGETATION CANOPIES; SOLAR-RADIATION; SATELLITE DATA; CALIBRATION; SCATTERING AB The primary objective of this research is to develop a surface albedo model for the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR). The primary test site is the Konza prairie, Kansas (U.S.A.), used by the International Satellite Land Surface Climatology Project (ISLSCP) in the First ISLSCP Field Experiment (FIFE). In this research, high spectral resolution held spectrometer data was analyzed to simulate AVHRR wavebands and to derive surface albedos. Development of a surface albedo algorithm was completed by analysing a combination of satellite, field spectrometer, and ancillary data. Estimated albedos from the field spectrometer data were compared to reference albedos derived using pyranometer data. Variations from surface anisotropy of reflected solar radiation were found to be the most significant albedo-related error. Additional error or sensitivity came from estimation of a shortwave mid-IR reflectance (1.3-4.0 mu m) using the AVHRR red and near-IR bands. Errors caused by the use of AVHRR spectral reflectance to estimate both a total visible (0.4-0.7 mu m) and near-IR (0.7-1.3 mu m) reflectance were small. The solar spectral integration, using the derived ultraviolet, visible, near-IR and SW mid-IR reflectivities, was not sensitive to many clear-sky changes in atmospheric properties and illumination conditions. C1 NASA, Goddard Space Flight Ctr, Hydrol Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Biospher Branch, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Toll, DL (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Branch, Lab Hydrospher Proc, Code 974, Greenbelt, MD 20771 USA. NR 58 TC 9 Z9 9 U1 1 U2 1 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD DEC PY 1997 VL 18 IS 18 BP 3761 EP 3796 DI 10.1080/014311697216612 PG 36 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA YL454 UT WOS:000070957300007 ER PT J AU Sakaguchi, T Doke, T Hayashi, T Kikuchi, J Hasebe, N Kashiwagi, T Takashima, T Takahashi, K Nakano, T Nagaoka, SJ Takahashi, SP Yamanaka, H Yamaguchi, K Badhwar, GD AF Sakaguchi, T Doke, T Hayashi, T Kikuchi, J Hasebe, N Kashiwagi, T Takashima, T Takahashi, K Nakano, T Nagaoka, SJ Takahashi, SP Yamanaka, H Yamaguchi, K Badhwar, GD TI Radiation dosimetry measurements with real time radiation monitoring device (RRMD)-II in space shuttle STS-79 SO JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS LA English DT Article DE space radiation; dose equivalent; Space Shuttle; real-time monitor; radiation environment AB The real-time measurement of radiation environment was made with an improved real-time radiation monitoring device (RRMD)-II onboard Space Shuttle STS-79 (S/MM#4: 4th Shuttle MIR Mission, at an inclination angle of 51.6 degrees and an altitude of 250-400km) for 199 h during 17-25 September, 1996. The observation of the detector covered the linear energy transfer (LET) range of 3.5-6000 keV/mu m. The Shuttle orbital profile in this mission was equivalent to that of the currently planned Space Station, and provided an opportunity to investigate variations in count rate and dose equivalent rate depending on altitude, longitude: and latitude in detail. Particle count rate and dose equivalent rate were mapped geographically during the mission. Based on the map of count rate, an analysis was made by dividing whole region into three regions: South Atlantic Anomaly (SAA) region, high latitude region and other regions. The averaged absorbed dose rate during the mission was 39.3 mu Gy/day for a LET range of 3.5-6000 keV/mu m. The corresponding average dose equivalent rates during the mission are estimated to be 293 mu Sv/day with quality actors from International Commission on Radiological Protection (ICRP)-Pub. 60 and 270 mu Sv/day with quality factors from ICRP-Pub. 26. The effective quality factors for ICRP-Pub. 60 and 26 are 7.45 and 6.88, respectively. From the present data for particles of LET > 3.5keV/mu m, we conclude that the average dose equivalent rate is dominated by the contribution of galactic cosmic ray (GCR) particles. The dose-detector depth dependence was also investigated. C1 Waseda Univ, Adv Res Inst Sci & Engn, Shinjuku Ku, Tokyo 169, Japan. Ehime Univ, Dept Comp Sci, Matsuyama, Ehime 790, Japan. Kanagawa Univ, Dept Business & Engn, Kanagawa 221, Japan. NASDA, Space Environm Res Ctr, Ibaraki, Osaka, Japan. NASDA, Space Expt Grp, Ibaraki, Osaka, Japan. Japan Space Utilizat Promot, Shinjuku Ku, Tokyo, Japan. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Sakaguchi, T (reprint author), Waseda Univ, Adv Res Inst Sci & Engn, Shinjuku Ku, 3-4-1 Okubo, Tokyo 169, Japan. NR 11 TC 5 Z9 5 U1 1 U2 3 PU JAPAN J APPLIED PHYSICS PI MINATO-KU TOKYO PA DAINI TOYOKAIJI BLDG 24-8 SHINBASHI 4-CHOME, MINATO-KU TOKYO, 105, JAPAN SN 0021-4922 J9 JPN J APPL PHYS 1 JI Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. PD DEC PY 1997 VL 36 IS 12A BP 7453 EP 7459 DI 10.1143/JJAP.36.7453 PG 7 WC Physics, Applied SC Physics GA YR906 UT WOS:000071543500074 PM 11542403 ER PT J AU Allen, DL Linderman, JK Roy, RR Grindeland, RE Mukku, V Edgerton, VR AF Allen, DL Linderman, JK Roy, RR Grindeland, RE Mukku, V Edgerton, VR TI Growth hormone IGF-I and/or resistive exercise maintains myonuclear number in hindlimb unweighted muscles SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE atrophy; unloading; remodeling; plasticity; countermeasures ID PERIODIC WEIGHT SUPPORT; HEAVY-CHAIN EXPRESSION; PROGRAMMED CELL-DEATH; SKELETAL-MUSCLE; SUSPENDED RATS; BEARING SOLEUS; FIBERS; ATROPHY; SPACEFLIGHT; HYPERTROPHY AB In the present study of rats, we examined the role, during 2 wk of hindlimb suspension, of growth hormone/insulin-like growth factor I (GH/IGF-I) administration and/or brief bouts of resistance exercise in ameliorating the loss of myonuclei in fibers of the soleus muscle that express type I myosin heavy chain. Hindlimb suspension resulted in a significant decrease in mean soleus wet weight that was attenuated either by exercise alone or by exercise plus GH/IGF-I treatment but was not attenuated by hormonal treatment alone. Both mean myonuclear number and mean fiber cross-sectional area (CSA) of fibers expressing type I myosin heavy chain decreased after 2 wk of suspension compared with control (134 vs. 162 myonuclei/mm and 917 vs. 2,076 mu m(2), respectively). Neither GH/IGF-I treatment nor exercise alone affected myonuclear number or fiber CSA, but the combination of exercise and growth-factor treatment attenuated the decrease in both variables. A significant correlation was found between mean myonuclear number and mean CSA across all groups. Thus GH/IGF-I administration and brief bouts of muscle loading had an interactive effect in attenuating the loss of myonuclei induced by chronic unloading. C1 UNIV CALIF LOS ANGELES,SCH MED,BRAIN RES INST,HLTH SCI CTR,LOS ANGELES,CA 90095. UNIV CALIF LOS ANGELES,DEPT PHYSIOL SCI,LOS ANGELES,CA 90095. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. GENENTECH INC,S SAN FRANCISCO,CA 94080. FU NINDS NIH HHS [NS-16333] NR 26 TC 77 Z9 78 U1 1 U2 2 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD DEC PY 1997 VL 83 IS 6 BP 1857 EP 1861 PG 5 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA YK807 UT WOS:A1997YK80700010 PM 9390955 ER PT J AU McCall, GE Goulet, C Grindeland, RE Hodgson, JA Bigbee, AJ Edgerton, VR AF McCall, GE Goulet, C Grindeland, RE Hodgson, JA Bigbee, AJ Edgerton, VR TI Bed rest suppresses bioassayable growth hormone release in response tcs muscle activity SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE humans; isometric exercise; endocrine regulation; plantar flexion ID ADAPTATIONS; EXERCISE AB Hormonal responses to muscle activity were studied in eight men before (-13 or -12 and -8 or -7 days), during (2 or 3, 8 or 9, and 13 or 14 days) and after (+2 or +3 and +10 or +11 days) 17 days of bed rest. Muscle activity consisted of a series of unilateral isometric plantar flexions, including 4 maximal voluntary contractions (MVCs), 48 contractions at 30% MVC, and 12 contractions at 80% MVC, all performed at a 4:1-s work-to-rest ratio. Blood was collected before and immediately after muscle activity to measure plasma growth hormone by radioimmunoassay (IGH) and by bioassay (BGH) of tibia epiphyseal cartilage growth in hypophysectomized rats. Plasma IGH was unchanged by muscle activity before, during, or after bed rest. Before bed rest, muscle activity increased (P < 0.05) BGH by 66% at -13 or -12 days (2,146 +/- 192 to 3,565 +/- 197 mu g/l) and by 92% at -8 or -7 days (2,162 +/- 159 to 4,161 +/- 204 mu g/l). After 2 or 3 days of bed rest, there was no response of BGH to the muscle activity, a pattern that persisted through 8 or 9 days of bed rest. However, after 13 or 14 days of bed rest, plasma concentration of BGH was significantly lower after than before muscle activity (2,594 +/- 211 to 2,085 +/- 109 mu g/l). After completion of bed rest, muscle activity increased BGH by 31% at 2 or 3 days (1,807 +/- 117 to 2,379 +/- 473 mu g/l; P < 0.05), and by 10 or 11 days the BGH response was similar to that before bed rest (1,881 +/- 75 to 4,160 +/- 315 mu g/l; P < 0.05). These data demonstrate that the ambulatory state of an individual can have a major impact on the release of BGH, but not IGH, in response to a single bout of muscle activity. C1 UNIV CALIF LOS ANGELES,BRAIN RES INST,LOS ANGELES,CA 90095. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP McCall, GE (reprint author), UNIV CALIF LOS ANGELES,DEPT PHYSIOL SCI,2301 LIFE SCI,621 CIRCLE DR S,LOS ANGELES,CA 90095, USA. NR 25 TC 28 Z9 28 U1 0 U2 1 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD DEC PY 1997 VL 83 IS 6 BP 2086 EP 2090 PG 5 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA YK807 UT WOS:A1997YK80700040 PM 9390985 ER PT J AU Huffman, PA Arkoosh, MR Casillas, E AF Huffman, PA Arkoosh, MR Casillas, E TI Characteristics of peripheral blood cells from rainbow trout evaluated by particle counter, image analysis, and hemocytometric techniques SO JOURNAL OF AQUATIC ANIMAL HEALTH LA English DT Article ID HEMATOLOGICAL ASSESSMENT; FRESHWATER-FISH; SALMO-GAIRDNERI; SYSTEM AB Hematological assessments of peripheral blood cells from rainbow trout Oncorhynchus mykiss were compared by using a hemocytometer, image analysis, and an electronic particle counter. Although statistical differences were noted, the diameters of white blood cells (WBCs) were comparable among the methods used, but lengths and widths of red blood cells (RBCs) were remarkably different among the three methods. Red blood cells were significantly smaller when the particle counter was used compared with sizes obtained by using the hemocytometer or image analysis. Counts of whole blood and isolated RBC concentrations were similar between the hemocytometer and the particle counter in the automatic calculation mode; yet they were significantly different with the manual calculation method, which used the raw data from the particle counter. White blood cell counts from peripheral whole blood could not be obtained with the particle counter; it converted all particle volumes into spherical equivalents and, thus, interpreted rainbow trout RBCs and WBCs to be similar in size, resulting in an inability to accurately count the number of WBCs in mixed-cell populations. In addition, a lysing agent, which is commonly used to count WBCs in mammalian peripheral blood, did not completely remove all RBCs from samples of trout peripheral whole blood because of the presence of nuclei within the fish RBCs. These results indicate that assessing fish hematological characteristics with the particle counter may have limitations. C1 NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Environm Conservat Div, Newport, OR 97365 USA. NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Environm Conservat Div, Seattle, WA 98112 USA. RP Arkoosh, MR (reprint author), NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Environm Conservat Div, 2030 S Marine Sci Dr, Newport, OR 97365 USA. NR 23 TC 11 Z9 11 U1 1 U2 5 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 0899-7659 J9 J AQUAT ANIM HEALTH JI J. Aquat. Anim. Health PD DEC PY 1997 VL 9 IS 4 BP 239 EP 248 DI 10.1577/1548-8667(1997)009<0239:COPBCF>2.3.CO;2 PG 10 WC Fisheries; Veterinary Sciences SC Fisheries; Veterinary Sciences GA ZE328 UT WOS:000072781600001 ER PT J AU Bhattacharjee, P AF Bhattacharjee, P TI Cosmic thermal neutrino background: Can it be detected? SO JOURNAL OF ASTROPHYSICS AND ASTRONOMY LA English DT Article; Proceedings Paper CT Meeting on Big Bang and Alternative Cosmologies - a Critical Appraisal CY JAN, 1997 CL JAWAHARLAL NEHRU CTR ADV SCI RES, BANGALORE, INDIA SP Inter Univ Ctr Astron & Astrophys, Pune, Mehtra Res Inst, Allahabad HO JAWAHARLAL NEHRU CTR ADV SCI RES DE cosmic neutrino background; cosmic rays; massive neutrino; topological defects ID DARK-MATTER; ABSORPTION; LIMIT; RAYS AB The detection of the Cosmic Thermal Neutrino Background (CTNB) would provide the "cleanest" evidence for the hot big bang model of the early Universe. I discuss some recent thoughts on the possibility of detecting the CTNB (especially if neutrinos have a small mass of similar to few eV) by looking for certain CTNB-induced features in the extremely high energy (E greater than or similar to 10(20) eV) cosmic neutrino spectrum that may become measurable in the future by some of the large-area extensive air-shower detectors being built for detecting extremely high energy cosmic rays. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Bhattacharjee, P (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 17 TC 1 Z9 1 U1 0 U2 0 PU INDIAN ACADEMY SCIENCES PI BANGALORE PA P B 8005 C V RAMAN AVENUE, BANGALORE 560 080, INDIA SN 0250-6335 J9 J ASTROPHYS ASTRON JI J. Astrophys. Astron. PD DEC PY 1997 VL 18 IS 4 BP 263 EP 269 DI 10.1007/BF02709316 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 122RG UT WOS:000076084800006 ER PT J AU Gangopadhyay, A Robinson, AR AF Gangopadhyay, A Robinson, AR TI Circulation and dynamics of the western North Atlantic .3. Forecasting the meanders and rings SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID GULF-STREAM MODEL; PRIMITIVE EQUATION; ALTIMETER DATA; ASSIMILATION; OCEAN AB The multiscale feature models (MSFMs) developed for the circulation of the western North Atlantic (Part I) have been used for initialization in this study to forecast the Gulf Stream meanders and rings. The Harvard primitive equation model, which was calibrated and verified for the statistics of the synoptical dynamics in this region (Part II), provides the basis for these simulations. Three 2-week-long synoptical dynamical hindcasts are presented. These hindcasts are carried out in a forecast mode without assimilating any future information. In general, when compared against SST-derived frontal location and ring-stream interactions, 2-week-long forecasts are found to be statistically superior than persistence and dynamically consistent. These forecasts are also compared against similar forecasts based on the U.S. Navy's Optimum Thermal Interpolation System (OTIS) initializations. It is found that the MSFM-initialized simulations provide a better predictive capability than OTIS-initialized simulations over 2 weeks. Quantitatively, in terms of a statistical measure called the average offset of the axis of the stream, the former did better than persistence in all three cases over the 2-week periods. However. OTIS has two inherent characteristics, namely, a longitudinal distribution of temperature-salinity from climatology, and a warm pool at the core of the stream, which should be incorporated in the MSFM scheme to further enhance its predictive capability. The usefulness of multiscale kinematic synthesis in the initialization of the calibrated primitive equation dynamical model for forecasting the region over a 2-week period brings a closure to this three-part study of circulation and dynamics of the western North Atlantic. C1 JPL,PASADENA,CA. HARVARD UNIV,DEPT EARTH & PLANETARY SCI,DIV APPL SCI,CAMBRIDGE,MA 02138. NR 23 TC 14 Z9 15 U1 0 U2 2 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 DEC PY 1997 VL 14 IS 6 BP 1352 EP 1365 DI 10.1175/1520-0426(1997)014<1352:CADOTW>2.0.CO;2 PG 14 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA YH198 UT WOS:A1997YH19800008 ER PT J AU Benson, RF AF Benson, RF TI Evidence for the stimulation of field-aligned electron density irregularities on a short time scale by ionospheric topside sounders SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article; Proceedings Paper CT IV Suzdal URSI Symposium on Artificial Modification of the Ionosphere CY AUG 15-20, 1994 CL UPPSALA, SWEDEN ID DIFFUSE PLASMA RESONANCES; WAVE; INSTABILITY; GENERATION; SATELLITES; PARTICLES; SEQUENCE; PULSES; HF AB Ionospheric topside sounders can be considered to act as mobile ionospheric heating facilities. They stimulate a wide variety of plasma phenomena that suggests that significant plasma heating can be produced in the vicinity of the spacecraft following the short duration (0.1 ms) high-power (hundreds of watts) sounder pulse. Most of these phenomena are sensitive to the ambient plasma conditions, particularly to the ratio of the plasma frequency f(N) to the gyro frequency f(H). Certain stimulated phenomena only occur, or are greatly enhanced, when f(N)/f(H) congruent to n where n is an integer. One example is a diffuse signal return that appears at a frequency just above the Z mode wave cutoff frequency f(Z) (the L = 0 condition in the notation of Stir). This signal, which is the subject of the present paper, is present only for moderately large near-integer values for f(N)/f(H) (e.g., n > 3). It is a relatively short-duration echo- usually less than about 10 ms. These characteristics are quite different from the Z mode echoes often observed between f(H) or f(N) (whichever is greater) and the upper hybrid frequency f(T). These latter echoes occur for smaller values (not necessarily near-integer values) of f(N)/f(H) and are received during the entire 30 ms listening time period following the sounder pulse. They have been attributed to the scattering of sounder Z mode signals from naturally occurring electron density field-aligned irregularities (FAI). The short-duration echoes observed just above f(Z), on the other hand, are here attributed to the ducting of sounder-generated Z mode waves in sounder-stimulated (or sounder-enhanced) FAI. These FAI are believed to be generated (or enhanced) on a very short time scale(much less than 1 s) by the efficient absorption of sounder energy when the plasma/gyro frequency ratio is nearly an integer value significantly greater than one. The most likely generation process is the filamentation instability driven by the ponderomotive force due to the high-power sounder pulse. (C) 1997 Elsevier Science Ltd. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Benson, RF (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 38 TC 10 Z9 11 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD DEC PY 1997 VL 59 IS 18 BP 2281 EP 2293 DI 10.1016/S1364-6826(96)00122-8 PG 13 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA YU322 UT WOS:000071705700005 ER PT J AU Osherovich, VA Fainberg, J Benson, RF Stone, RG AF Osherovich, VA Fainberg, J Benson, RF Stone, RG TI Theoretical analysis of resonance conditions in magnetized plasmas when the plasma/gyro frequency ratio is close to an integer SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article; Proceedings Paper CT IV Suzdal URSI Symposium on Artificial Modification of the Ionosphere CY AUG 15-20, 1994 CL UPPSALA, SWEDEN ID TURBULENCE; SEQUENCE; JUPITER; WAVES; TORUS AB We study cylindrical oscillations of electrons in a plasma where the background magnetic field is parallel to the axis of a cylinder and the ion background is taken to have a constant positive density. Assuming self-similarity, we reduce the problem to two second order nonlinear differential equations, relating fluctuations of electron density and fluctuations of magnetic field. The system studied is shown to have two fundamental frequencies. In the linear domain, these frequencies correspond to the Z and X cold plasma wave cutoff frequencies (R = 0 and L = 0 conditions in the notation of Stix (1992), respectively). Thus they differ by the gyrofrequency. In the nonlinear domain, these frequencies change and resonances at harmonics and at the sum and difference frequencies appear. When the plasma/gyro frequency ratio is close to an integer, our results indicate special resonance conditions which are characterized by an increase of the amplitude and a narrowing of the fundamental resonances. (C) 1997 Elsevier Science Ltd. C1 NASA, Hughes STX, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Osherovich, VA (reprint author), NASA, Hughes STX, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. NR 16 TC 5 Z9 5 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD DEC PY 1997 VL 59 IS 18 BP 2361 EP 2366 DI 10.1016/S1364-6826(96)00129-0 PG 6 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA YU322 UT WOS:000071705700012 ER PT J AU Nicholson, SE Kim, J Ba, MB Lare, AR AF Nicholson, SE Kim, J Ba, MB Lare, AR TI The mean surface water balance over Africa and its interannual variability SO JOURNAL OF CLIMATE LA English DT Article ID SOIL-MOISTURE; CLIMATONOMIC DESCRIPTION; SEMIARID BOTSWANA; AIR-TEMPERATURE; ENERGY BALANCE; NDVI RESPONSE; CENTRAL SAHEL; RAINFALL; EVAPOCLIMATONOMY; PRECIPITATION AB This article presents calculations of surface water balance for the African continent using a revised version of the Lettau climatonomy. Calculations are based on approximately 1400 rainfall stations, with records generally covering 60 yr or longer. Continental maps of evapotranspiration, runoff, and soil moisture are derived for January, July, and the annual mean. The model is also used to provide a gross estimate of the interannual variability of these parameters over most of the continent and local water balance calculations for a variety of locations in Africa. The results are compared with four other comprehensive global water balance studies. The results of this study are being used to produce a 1 degrees X 1 degrees gridded dataset for the continent, with potential applications for numerical modeling studies. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. NASA, Appl Res Corp, GSFC, Greenbelt, MD USA. RP Nicholson, SE (reprint author), Florida State Univ, Dept Meteorol, B-161, Tallahassee, FL 32306 USA. NR 46 TC 22 Z9 22 U1 1 U2 7 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD DEC PY 1997 VL 10 IS 12 BP 2981 EP 3002 DI 10.1175/1520-0442(1997)010<2981:TMSWBO>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YR813 UT WOS:000071532800001 ER PT J AU Fairbridge, RW AF Fairbridge, RW TI Seal level: To hyphenate or not? SO JOURNAL OF COASTAL RESEARCH LA English DT Editorial Material RP Fairbridge, RW (reprint author), COLUMBIA UNIV,NASA,GISS,NEW YORK,NY 10027, USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU COASTAL EDUCATION & RESEARCH FOUNDATION PI LAWRENCE PA 810 EAST 10TH STREET, LAWRENCE, KS 66044 SN 0749-0208 J9 J COASTAL RES JI J. Coast. Res. PD WIN PY 1997 VL 13 IS 1 BP R3 EP R4 PG 2 WC Environmental Sciences; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA WL799 UT WOS:A1997WL79900001 ER PT J AU Koumoutsakos, P AF Koumoutsakos, P TI Inviscid axisymmetrization of an elliptical vortex SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE vortex methods; inviscid vortical flows; vorticity axisymmetrization ID CONTOUR DYNAMICS; PARTICLE METHODS; VORTICES; FLOWS; HYDRODYNAMICS; SIMULATIONS; EQUATIONS; SURGERY AB The inviscid evolution of elliptical, nonuniform vorticity distributions is studied computationally using a high resolution Lagrangian (vortex) method with minimal numerical dissipation. The simulations reveal that the vortices evolve, through a process of filamentation, to a configuration consisting of a vortex surrounded by weak filamentary structures. The shape of the final configuration depends on the profile of the initial vorticity distribution. For the same ellipticity, relatively smooth profiles evolve to axisymmetric vortical structures, whereas sharper initial vorticity distributions result in robust nonaxisymmetric configurations. A systematic convergence study is conducted to establish the accuracy of the method for long time inviscid simulations. To further assess the issue of axisymmetrization we compare our results with related numerical and experimental studies. (C) 1997 Academic Press. C1 NASA, Ames Res Ctr, Ctr Turbulence Res, Moffett Field, CA 94035 USA. ETH Zurich, Inst Fluid Dynam, CH-8092 Zurich, Switzerland. RP Koumoutsakos, P (reprint author), NASA, Ames Res Ctr, Ctr Turbulence Res, Ames 202A-1, Moffett Field, CA 94035 USA. EM petros@nas.nasa.gov RI Koumoutsakos, Petros/A-2846-2008 OI Koumoutsakos, Petros/0000-0001-8337-2122 NR 30 TC 79 Z9 79 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD DEC PY 1997 VL 138 IS 2 BP 821 EP 857 DI 10.1006/jcph.1997.5749 PG 37 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA YZ054 UT WOS:000072215600024 ER PT J AU Palosz, W Gillies, D Grasza, K Chung, H Raghothamachar, B Dudley, M AF Palosz, W Gillies, D Grasza, K Chung, H Raghothamachar, B Dudley, M TI Characterization of cadmium-zinc telluride crystals grown by 'contactless' PVT using synchrotron white beam topography SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE PVT; cadmium-zinc telluride; defects ID PHYSICAL VAPOR TRANSPORT; SINGLE-CRYSTALS; CDTE AB Crystals of Cd1-xZnxTe grown by PVT using self-seeding 'contactless' technique were characterized using synchrotron radiation (reflection, transmission, and Laue back-reflection X-ray topography). Crystals of low (x = 0.04) and high (up to x approximate to 0.4) ZnTe content were investigated. Twins and defects such as dislocations, precipitates, and slip bands were identified. Extensive inhomogeneous strains present in some samples were found to be generated by interaction (sticking) with the pedestal and by composition gradients in the crystals. Large (up to about 5 mm) oval strain fields were observed around some Te precipitates. Low angle grain boundaries were found only in higher ZnTe content (x greater than or equal to 0.2) samples. C1 IPPAS,WARSAW,POLAND. SUNY STONY BROOK,STONY BROOK,NY 11794. RP Palosz, W (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. RI Raghothamachar, Balaji/B-1094-2008 NR 16 TC 6 Z9 6 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD DEC PY 1997 VL 182 IS 1-2 BP 37 EP 44 DI 10.1016/S0022-0248(97)00337-0 PG 8 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA YJ718 UT WOS:A1997YJ71800007 ER PT J AU Pines, V Chait, A Zlatkowski, M AF Pines, V Chait, A Zlatkowski, M TI Dynamic scaling in dendritic growth: significance of the initial nucleus size SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID PERTURBED-SPHERICAL NUCLEUS; PURE SUPERCOOLED LIQUID; TIME DEVELOPMENT; INSTABILITIES AB This paper is concerned with the physical origin of one of the recently introduced dendrite tip scaling parameters [V. Pines, A. Chait, M. Zlatkowski, J. Crystal Growth 167 (1996) 777]. Using at least two parameters, sigma(1) and sigma(2), the above quoted scaling analysis permits a consistent determination of the dendrite tip curvature radius and solidification velocity. In this work, the parameter sigma(1) is shown to account for the divergence of the conventional dendrite tip scaling parameter, sigma, at low supercooling. The parameter sigma(1) is traced to the linear stage of development of the morphological instability of a small spherical nucleus placed in a supercooled melt. We demonstrate that sigma(1) is proportional to the characteristic initial mean curvature of an unstable nucleus. The initial curvature may take different values depending on the origin of the unstable nucleus, and could be specified in a careful experimental setup. C1 NASA,LEWIS RES CTR,COMPUTAT MICROGRAV LAB,CLEVELAND,OH 44135. CASE WESTERN RESERVE UNIV,DEPT PHYS,CLEVELAND,OH 44106. NR 18 TC 10 Z9 10 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 DEC PY 1997 VL 182 IS 1-2 BP 219 EP 226 DI 10.1016/S0022-0248(97)00315-1 PG 8 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA YJ718 UT WOS:A1997YJ71800028 ER PT J AU Croxdale, J Cook, M Tibbitts, TW Brown, CS Wheeler, RM AF Croxdale, J Cook, M Tibbitts, TW Brown, CS Wheeler, RM TI Structure of potato tubers formed during spaceflight SO JOURNAL OF EXPERIMENTAL BOTANY LA English DT Article DE spaceflight; development; potato tuber; microgravity ID GRAVITY; CELLS AB Potato (Solanum tuberosum L. cv. Norland) explants, consisting of a leaf, axillary bud, and small stem segment, were used as a model system to study the influence of spaceflight on the formation of sessile tubers from axillary buds, The explants were flown on the space shuttle Columbia (STS-73, 20 October to 5 November 1995) in the ASTROCULTURE (TM) flight package, which provided a controlled environment for plant growth. Light and scanning electron microscopy were used to compare the precisely ordered tissues of tubers formed on Earth with those formed during spaceflight, The structure of tubers produced during spaceflight was similar to that of tubers produced in a control experiment. The size and shape of tubers, the geometry of tuber tissues, and the distribution of starch grains and proteinaceous crystals were comparable in tubers formed in both environments, The shape, surface texture, and size range of starch grains from both environments were similar, but a greater percentage of smaller starch grains formed in spaceflight than on Earth, Since explant leaves must be of given developmental age before tubers form, instructions regarding the regular shape and ordered tissue geometry of tubers may have been provided in the presence of gravity. Regardless of when the signalling occurred, gravity was not required to produce a tuber of typical structure. C1 Univ Wisconsin, Dept Bot, Madison, WI 53706 USA. Univ Wisconsin, Dept Hort, Madison, WI 53706 USA. Dynamac Corp, Durham, NC 27713 USA. NASA, Kennedy Space Ctr, FL 32899 USA. RP Croxdale, J (reprint author), Univ Wisconsin, Dept Bot, Madison, WI 53706 USA. EM croxdale@facstaff.wisc.edu NR 22 TC 18 Z9 20 U1 0 U2 3 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0022-0957 EI 1460-2431 J9 J EXP BOT JI J. Exp. Bot. PD DEC PY 1997 VL 48 IS 317 BP 2037 EP 2043 DI 10.1093/jexbot/48.317.2037 PG 7 WC Plant Sciences SC Plant Sciences GA YQ739 UT WOS:000071418400006 PM 11541084 ER PT J AU Johnston, JC Ruthruff, E Monheit, M AF Johnston, JC Ruthruff, E Monheit, M TI Dependence by any other name smells just as sweet: Reply to van der Velde and van der Heijden (1997) SO JOURNAL OF EXPERIMENTAL PSYCHOLOGY-HUMAN PERCEPTION AND PERFORMANCE LA English DT Article ID VISUAL INFORMATION; ATTENTION AB The hypothesis that people selectively attend to entire objects predicts that all attributes of an object will be reported either very accurately (if the object was attended) or very inaccurately (if it was unattended). Hence, reports of object attributes should show positive dependence. M. Monheit and J. Johnston (1994) have confirmed this prediction. F. van der Velde and A. H. C. van der Heijden (1997), however, have argued that dependence in the overall data is spurious. They advocate a model that partitions the data into 2 subsets, 1 for perception trials and 1 for guessing trials, each of which separately exhibits independence. Here, the authors argue that this treatment of guessing is misguided because, in effect, guesses are discarded rather than treated as failures of perception. The Monheit and Johnston analysis, on the other hand, is fundamentally sound and demonstrates precisely the kind of dependence predicted by the spatial attention hypothesis. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Lexicus Corp, Mt View, CA USA. RP Johnston, JC (reprint author), NASA, Ames Res Ctr, Mailstop 262-4, Moffett Field, CA 94035 USA. NR 6 TC 4 Z9 4 U1 2 U2 2 PU AMER PSYCHOLOGICAL ASSOC PI WASHINGTON PA 750 FIRST ST NE, WASHINGTON, DC 20002-4242 USA SN 0096-1523 J9 J EXP PSYCHOL HUMAN JI J. Exp. Psychol.-Hum. Percept. Perform. PD DEC PY 1997 VL 23 IS 6 BP 1813 EP 1818 PG 6 WC Psychology; Psychology, Experimental SC Psychology GA YM225 UT WOS:000071042300014 PM 9425683 ER PT J AU Menter, FR AF Menter, FR TI Eddy viscosity transport equations and their relation to the k-epsilon model SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID ADVERSE PRESSURE-GRADIENT; TURBULENCE MODELS; FLOWS AB A formalism will be presented which allows transforming two-equation eddy viscosity turbulence models into one-equation models. The transformation is based on Bradshaw's assumption that the turbulent shear stress is proportional to the turbulent kinetic energy. This assumption is supported by experimental evidence for a large number of boundary layer flows and has led to improved predictions when incorporated into two-equation models of turbulence. Based on it, a new one-equation turbulence model will be derived from the k-epsilon model. The model will be tested against the one-equation model of Baldwin and Earth, which is also derived from the k-epsilon model (plus additional assumptions) and against its parent two-equation model. It will be shown that the assumptions involved in the derivation of the Baldwin-Barth model cause significant problems at the edge of a turbulent layer. C1 AEA Technol GmbH, Dept Dev, D-83624 Otterfing, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Menter, FR (reprint author), AEA Technol GmbH, Dept Dev, Staudenfeldweg, D-83624 Otterfing, Germany. NR 29 TC 107 Z9 110 U1 2 U2 10 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0098-2202 J9 J FLUID ENG-T ASME JI J. Fluids Eng.-Trans. ASME PD DEC PY 1997 VL 119 IS 4 BP 876 EP 884 DI 10.1115/1.2819511 PG 9 WC Engineering, Mechanical SC Engineering GA YM562 UT WOS:000071077200022 ER PT J AU Sader, SA Reining, C Sever, T Soza, C AF Sader, SA Reining, C Sever, T Soza, C TI Human migration and agricultural expansion - A threat to the Maya tropical forests SO JOURNAL OF FORESTRY LA English DT Article ID DEFORESTATION; VEGETATION; GUATEMALA; AMAZON C1 CONSERVAT INT, WASHINGTON, DC USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. CONSERVAT INT, PROPETEN PROGRAM, FLORES, GUATEMALA. RP Sader, SA (reprint author), UNIV MAINE, DEPT FOREST MANAGEMENT, ORONO, ME 04469 USA. NR 17 TC 14 Z9 16 U1 0 U2 3 PU SOC AMER FORESTERS PI BETHESDA PA 5400 GROSVENOR LANE, BETHESDA, MD 20814 USA SN 0022-1201 J9 J FOREST JI J. For. PD DEC PY 1997 VL 95 IS 12 BP 27 EP 32 PG 6 WC Forestry SC Forestry GA YJ875 UT WOS:A1997YJ87500009 ER PT J AU Neugebauer, M AF Neugebauer, M TI Pioneers of space physics: A career in the solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TANGENTIAL DISCONTINUITIES; BOW SHOCK AB This paper is a personal history of the author's experiences, starting with the earliest direct measurements of the solar wind and continuing through later experiments to investigate the physics of the solar wind and its interaction with comets. RP Neugebauer, M (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 169-506,PASADENA,CA 91109, USA. NR 43 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1997 VL 102 IS A12 BP 26887 EP 26894 DI 10.1029/97JA02444 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ888 UT WOS:A1997YJ88800001 ER PT J AU Kallenbach, R Ipavich, FM Bochsler, P Hefti, S Hovestadt, D Grunwaldt, H Hilchenbach, M Axford, WI Balsiger, H Burgi, A Coplan, MA Galvin, AB Geiss, J Gliem, F Gloeckler, G Hsieh, KC Klecker, B Lee, MA Livi, S Managadze, GG Marsch, E Mobius, E Neugebauer, M Reiche, KU Scholer, M Verigin, MI Wilken, B Wurz, P AF Kallenbach, R Ipavich, FM Bochsler, P Hefti, S Hovestadt, D Grunwaldt, H Hilchenbach, M Axford, WI Balsiger, H Burgi, A Coplan, MA Galvin, AB Geiss, J Gliem, F Gloeckler, G Hsieh, KC Klecker, B Lee, MA Livi, S Managadze, GG Marsch, E Mobius, E Neugebauer, M Reiche, KU Scholer, M Verigin, MI Wilken, B Wurz, P TI Isotopic composition of solar wind neon measured by CELIAS/MTOF on board SOHO SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ENERGETIC PARTICLES; CHARGE-EXCHANGE; HIGH-RESOLUTION; CARBON FOILS; SYSTEM; NUCLEI; MG AB We present first results taken from the high-resolution mass time-of-flight spectrometer (MTOF) of the charge, element, and isotope analysis system (CELIAS) experiment on board the Solar and Heliospheric Observatory (SOHO) spacecraft launched in December 1995, concerning the abundance ratios of neon isotopes in the solar wind. We obtain the isotopic ratios Ne-20/Ne-22 = (13.8 +/- 0.7) and Ne-20/Ne-21 = (440 +/- 110), which agree with the values obtained from the Apollo foil solar wind experiments and which have been derived from measurements of solar particles implanted in lunar and meteoritic samples. C1 MAX PLANCK INST AERON,D-37189 KATLENBURG DUHM,GERMANY. UNIV BERN,INST PHYS,CH-3012 BERN,SWITZERLAND. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. UNIV MARYLAND,DEPT PHYS & ASTRON,COLLEGE PK,MD 20742. TECH UNIV CAROLO WILHELMINA BRAUNSCHWEIG,INST DATENVERARBEITUNGSANLAGEN,D-38106 BRAUNSCHWEIG,GERMANY. UNIV ARIZONA,DEPT PHYS,TUCSON,AZ 85721. UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,DURHAM,NH 03824. RUSSIAN ACAD SCI,IKI,INST SPACE RES,MOSCOW 117810,RUSSIA. CALTECH,JET PROP LAB,PASADENA,CA 91103. RP Kallenbach, R (reprint author), INT SPACE SCI INST,HALLERSTR 6,CH-3012 BERN,SWITZERLAND. RI Galvin, Antoinette/A-6114-2013 NR 23 TC 49 Z9 49 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1997 VL 102 IS A12 BP 26895 EP 26904 DI 10.1029/97JA02325 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ888 UT WOS:A1997YJ88800002 ER PT J AU Klimas, AJ Vassiliadis, D Baker, DN AF Klimas, AJ Vassiliadis, D Baker, DN TI Data-derived analogues of the magnetospheric dynamics SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GEOMAGNETIC-ACTIVITY; PREDICTION; MODELS AB A method is presented for transforming a local-linear prediction model into dynamical analogues of the coupling between the input and output data that enters and forms the prediction model, Two types of analogues are produced: (1) local-linear analogues composed of readily recognized physical components and (2) nonlinear analogues suitable for prediction purposes; both are data derived. Second-order analogues of the magnetospheric dynamics are examined in detail using the composite ISEE 3 solar wind parameter VBs for input and simultaneous Dst index data for output, An optimized local-linear analogue is constructed which minimizes the rms difference between analogue output and measured Dst. It is shown that the optimized local-linear analogue reduces, in behavior, to that of the first-order Burton er nl. [1975] Dst model during periods of Dst recoveries, both large and small. During those periods, however, the analogue effectively decouples from the solar wind VBs driver. At other times the coupling strength is found in general agreement with the value deduced by Burton et al., but, at those times, the analogue behavior is beyond the scope of their first-order equation. Nonlinear analogues are also constructed and studied. These are driven, damped, harmonic oscillators in which the dissipation rate, restoring force, and coupling strength to the VBs driver are expressed as functions of the Dst and VBs variables; these expressions are data derived. It is found that these analogues couple to the solar wind through the expression (VBs/Dst)VBs, rather than through the usual linear dependence on VBs. The suitability of these nonlinear analogues for prediction purposes is discussed. C1 UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80302. UNIV SPACE RES ASSOC,SEABROOK,MD 20706. RP Klimas, AJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 18 TC 38 Z9 38 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1997 VL 102 IS A12 BP 26993 EP 27009 DI 10.1029/97JA02414 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ888 UT WOS:A1997YJ88800009 ER PT J AU Lyons, LR Blanchard, GT Samson, JC Lepping, RP Yamamoto, T Moretto, T AF Lyons, LR Blanchard, GT Samson, JC Lepping, RP Yamamoto, T Moretto, T TI Coordinated observations demonstrating external substorm triggering SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; MAGNETOSPHERIC SUBSTORMS; GEOMAGNETIC TAIL; DYNAMICS; INTENSIFICATIONS; RECONNECTION; SIGNATURES; GROWTH; ONSET; PHASE AB To understand the magnetospheric substorm, it is necessary to determine whether its onset is externally triggered by the interplanetary magnetic field (IMF). We analyze the relationship between the IMF and the onset of classical substorms with well-defined onset times. A classical substorm is one that has auroral brightening and electrojet formation at onset, followed by poleward expansion of the region of bright aurora. Substorms meeting these criteria are identified using Canadian Auroral Network for the OPEN Program United Study ground photometer data. We find that a clear IMF trigger (a northward turning or a reduction in the magnitude of the y component) can be identified for 14 of the 20 substorms used in our study, All but one of the identified triggers are northward turnings. We develop a rigorous set of criteria that represents these triggers, By applying the criteria to a large set of IMF data, we find that it is essentially impossible for the observed association between triggers and substorms to happen by chance. This demonstrates that substorm triggering is a real phenomenon and not the result of the requirement that the IMF be southward before but not after a substorm. We also find that spatial structure in the plane perpendicular to the Earth-Sun line critically affects whether or not a trigger is observed from a particular IMF monitor; the probability of seeing a trigger for the substorms in our study is 89% for monitors that are < 30 R-E from the Earth-Sun line but only 50% for monitors 30 R-E to 56.7 R-E from the Earth-Sun line. Thus a well-defined IMF trigger is associated with most of substorms considered here, and the probability of trigger identification is a strong function of IMF monitor distance from the Earth-Sun line. Given this limitation of trigger identification due to spatial structure, our observations imply that a large majority of classical substorms are triggered by the IMF, We also obtain estimates of similar to 9 min for the mean time delay between magnetopause contact of an IMF trigger and substorm onset and similar to 64-72 min for the median growth-phase period of southward IMF that precedes triggered classical substorms. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. DANISH METEOROL INST,DK-2100 COPENHAGEN,DENMARK. UNIV ALBERTA,DEPT PHYS,EDMONTON,AB T6G 2E9,CANADA. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. AEROSP CORP,SPACE & ENVIRONM TECHNOL CTR,LOS ANGELES,CA 90009. RP Lyons, LR (reprint author), UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90095, USA. RI Moretto, Therese/B-6846-2013 OI Moretto, Therese/0000-0002-2403-5561 NR 32 TC 125 Z9 129 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1997 VL 102 IS A12 BP 27039 EP 27051 DI 10.1029/97JA02639 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ888 UT WOS:A1997YJ88800012 ER PT J AU Gary, SP Wang, J Winske, D Fuselier, SA AF Gary, SP Wang, J Winske, D Fuselier, SA TI Proton temperature anisotropy upper bound SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLASMA DEPLETION LAYER; ION-CYCLOTRON WAVES; MIRROR INSTABILITY; EARTHS MAGNETOSHEATH; MAGNETIC-FIELD; SUBSOLAR MAGNETOSHEATH; COLLISIONLESS SHOCKS; INVERSE CORRELATION; FLUID MODEL; MACH NUMBER AB The electromagnetic proton cyclotron instability and the mirror instability are driven by the proton temperature anisotropy T-perpendicular to p/T-parallel to p > 1, where perpendicular to and parallel to denote directions relative to the background magnetic field. Linear theory and one-dimensional hybrid simulations imply that the former mode grows more rapidly over 0.05 less than or equal to beta(parallel to p) less than or equal to 5 and that wave-particle scattering by its enhanced fluctuations imposes an upper bound on the temperature anisotropy of the form T-perpendicular to p/T-parallel to p - 1 = S-p/beta(parallel to p)alpha(p) where beta(parallel to p) = 8 pi n(p)T(parallel to p)/B-o(2) and B-o is the background magnetic field. Here S-p and alpha(p) are fitting parameters, and 0.4 less than or similar to alpha(p) less than or similar to 0.5. This paper describes results from more general two-dimensional hybrid simulations, which permit both instabilities to grow simultaneously. These simulations confirm the one-dimensional results on the initial domain 0.05 less than or equal to beta(parallel to p) similar or equal to 5; enhanced fluctuations display the properties of the proton cyclotron instability and alpha(p) similar or equal to 0.4. On this domain the two-dimensional simulations also yield an upper bound for the fluctuating field energy density of the form \delta B\(2)/B-o(2) = Sigma k\delta B-k\(2)/B-o(2) = S-B beta(parallel to p)(alpha B) with fitting parameter 0.5 less than or similar to alpha(B) less than or similar to 1. The simulations on the initial domain 10 less than or equal to beta(parallel to p) less than or equal to 100 show spectral characteristics of both instabilities and exhibit a more stringent bound on the proton anisotropy, in agreement with observations in the terrestrial magnetosheath. C1 LOCKHEED MARTIN PALO ALTO,RES LAB,PALO ALTO,CA 94304. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Gary, SP (reprint author), LOS ALAMOS NATL LAB,MS D466,LOS ALAMOS,NM 87545, USA. NR 48 TC 72 Z9 73 U1 2 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1997 VL 102 IS A12 BP 27159 EP 27169 DI 10.1029/97JA01726 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ888 UT WOS:A1997YJ88800022 ER PT J AU Dausch, DE Hooker, MW AF Dausch, DE Hooker, MW TI Low-field and high-field fatigue in PZT-based RAINBOW actuators SO JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES LA English DT Article ID FERROELECTRIC CERAMICS; BEHAVIOR; PLZT AB The fatigue characteristics of the electromechanical and ferroelectric properties of high-displacement RAINBOW (Reduced And INternally Biased Oxide Wafer) actuators were investigated. Rainbows were fabricated from three types of lead-zirconate-titanate-based ferroelectric materials: soft ferroelectrics (PZT-5A and PZT-5H), hard ferroelectrics (PZT-4) and slim-loop ferroelectrics (PLZT 9/65/35). The PZT-4, -5A and -5H compositions were piezoelectric, and PLZT 9/65/35 was electrostrictive. Before fatigue testing, the flexural strength and electromechanical displacement versus load properties were measured for these compositions. Fatigue in the electromechanical displacement properties of Rainbows with increasing number of electric field cycles was observed at low field levels (below the coercive field) under various static loading conditions. For all of the compositions evaluated, actuator free displacement (no load) decreased <10% over 10(7) electric field cycles. Under 300 g of static load, displacements decreased 20-50% over 10(7) cycles with PZT-5A and PLZT 9/65/35 exhibiting the least fatigue. The decrease in displacement at high electric field levels (above the coercive field) was measured simultaneously with the degradation of ferroelectric polarization with increasing number of cycles for all compositions except PZT-4. High-field displacements decreased only 7% over 10(8) cycles for electrostrictive PLZT 9/65/35 Rainbows, whereas the displacements of the piezoelectric PZT-5A and PZT-5H compositions decreased 66% and 43%, respectively. The ferroelectric polarization in PZT-5A and PZT-5H Rainbows fatigued more rapidly than in bulk ceramics of these compositions. PLZT 9/65/35 Rainbows and bulk ceramics exhibited similar fatigue behavior and were more fatigue resistant than PZT-5A and PZT-5H at high fields. The effects of post-fatigue heat-treatment and electrical repoling were also observed. C1 Lockheed Martin Engn & Sci, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Natl Res Council, Hampton, VA 23681 USA. RP Dausch, DE (reprint author), MCNC, Elect Technol Div, POB 12889,3021 Cornwallis Rd, Res Triangle Pk, NC 27709 USA. NR 16 TC 12 Z9 15 U1 0 U2 5 PU TECHNOMIC PUBL CO INC PI LANCASTER PA 851 NEW HOLLAND AVE, BOX 3535, LANCASTER, PA 17604 USA SN 1045-389X J9 J INTEL MAT SYST STR JI J. Intell. Mater. Syst. Struct. PD DEC PY 1997 VL 8 IS 12 BP 1044 EP 1051 DI 10.1177/1045389X9700801205 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA 121KQ UT WOS:000076013300005 ER PT J AU Sadler, DJ Garter, MJ Ahn, CH Koh, S Cook, AL AF Sadler, DJ Garter, MJ Ahn, CH Koh, S Cook, AL TI Optical reflectivity of micromachined {111}-oriented silicon mirrors for optical input-output couplers SO JOURNAL OF MICROMECHANICS AND MICROENGINEERING LA English DT Article AB In this work, bulk-micromachined {111}-oriented silicon mirrors at 54.7 degrees have been fabricated in 20 wt% KOH solution at various temperatures and characterized with single-mode fibers (10/125 and 5/125). In fabricating the mirrors, the etch rate of the (100) silicon surface was widely varied from 5.3 to 73 mu m hr(-1) as the-processing temperatures were varied from 40 to 80 degrees C. In spite of the tremendous variation of etch rate, the measured reflectivities of the mirrors showed fairly stable values of 63.7-58% at 1330 nm and 55.4-57.7% at 1550 nm. This paper describes the silicon mirror processing conditions, measured reflectivities, reflected beam profiles, and a prototype integrated optical I-O coupler with the realized mirrors. The results obtained from this work show that optical I-O couplers with 54.7 degrees mirrors on conventional (100)-oriented silicon wafers are feasible, enabling us to envisage a synchronized optical clock distribution system as well as a distributed remote optical sensing system with low manufacturing cost. C1 Univ Cincinnati, Ctr Microelect Sensors, Cincinnati, OH 45221 USA. Univ Cincinnati, MEMS, Dept Elect & Comp Engn & Comp Sci, Cincinnati, OH 45221 USA. Univ Dayton, Dept Elect & Comp Engn, Dayton, OH 45469 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Sadler, DJ (reprint author), Univ Cincinnati, Ctr Microelect Sensors, POB 210030, Cincinnati, OH 45221 USA. NR 12 TC 22 Z9 22 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0960-1317 J9 J MICROMECH MICROENG JI J. Micromech. Microeng. PD DEC PY 1997 VL 7 IS 4 BP 263 EP 269 DI 10.1088/0960-1317/7/4/001 PG 7 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Instruments & Instrumentation; Physics, Applied SC Engineering; Science & Technology - Other Topics; Instruments & Instrumentation; Physics GA YQ038 UT WOS:000071341200001 ER PT J AU Toth, RA AF Toth, RA TI Measurements of HDO between 4719 and 5843 cm(-1) SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID LINE POSITIONS; STRENGTHS; BANDS AB Fourier transform spectrometer data of heavy water vapor were obtained at resolutions of 0.01 and 0.02 cm(-1). The spectra were analyzed to obtain line center frequencies and line strengths of (HDO)-O-16 from 4719 to 5843 cm(-1). The analysis included 1700 assigned lines of the (011)-(000), (200)-(000), (120)-(000), and (021)-(010) bands. This is the first report of assignments in the weak (120)-(000) band which borrows much of its strength from the (200)-(000) band. The measurements provided in this work are a marked improvement over the HDO listing presently available on the HITRAN database in the spectral region. (C) 1997 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 17 Z9 18 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 EI 1096-083X J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD DEC PY 1997 VL 186 IS 2 BP 276 EP 292 DI 10.1006/jmsp.1997.7451 PG 17 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA YV239 UT WOS:000071803300010 ER PT J AU Ray-Culp, M Davis, M Stoner, AW AF Ray-Culp, M Davis, M Stoner, AW TI The micropredators of settling and newly settled queen conch (Strombus gigas Linnaeus) SO JOURNAL OF SHELLFISH RESEARCH LA English DT Article DE benthos; crustacean; fish; gastropod; polychaete; predation ID PREDATION; GASTROPOD; COMMUNITY; RECRUITMENT; ABUNDANCE; BEHAVIOR; PATTERNS; CRABS AB Minute settlers to soft-bottom marine communities are potentially vulnerable to a variety of micropredators. Although these micropredators shape the postsettlement community structure of their benthic prey, they are not often well identified. In the laboratory, we tested species from 10 families of polychaetes, 8 families of crustaeans, 4 families of mollusks, and 2 families of fishes for their ability to kill newly settled queen conch (Strombus gigas Linnaeus). This species is a commercially important Caribbean gastropod that produces pelagic larvae that settle onto the benthos at similar to 1 mm shell length. All micropredators were collected from conch nursery areas. Conch kills were made by calappid, portunid, majid, and hermit crabs; alpheid and palaemonid shrimps; panulirid lobsters; file fish; and five families of polychaete worms (glycerids, nereids, sigalionids, spionids, and syllids). Species from five families of polychaete worms (dorvilleids, glycerids, lumbrinerids, nereids, and phyllodocids) also killed competent conch veligers. All of the species that killed conch veligers, and most of those that killed newly settled conch, had not been documented as conch micropredators before this study, and they probably have a significant effect on recruitment. Given the relatively high densities known for some micropredator species living in queen conch nursery areas, the effects of predation-induced mortality on the very earliest life stages are an important consideration in studies of queen conch population dynamics. C1 Caribbean Marine Res Ctr, Vero Beach, FL 32963 USA. Harbor Branch Oceanog Inst Inc, Ft Pierce, FL 34946 USA. Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Highlands, NJ 07732 USA. RP Ray-Culp, M (reprint author), Caribbean Marine Res Ctr, 805 E 46th Pl, Vero Beach, FL 32963 USA. NR 30 TC 6 Z9 6 U1 0 U2 4 PU NATL SHELLFISHERIES ASSOC PI SOUTHAMPTON PA C/O DR. SANDRA E. SHUMWAY, NATURAL SCIENCE DIVISION, SOUTHAMPTON COLLEGE, SOUTHAMPTON, NY 11968 USA SN 0730-8000 J9 J SHELLFISH RES JI J. Shellfish Res. PD DEC PY 1997 VL 16 IS 2 BP 423 EP 428 PG 6 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA YV647 UT WOS:000071848700009 ER PT J AU De Oliveira, V Kedem, B Short, DA AF De Oliveira, V Kedem, B Short, DA TI Bayesian prediction of transformed Gaussian random fields SO JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION LA English DT Article DE Box-Cox family; cross-validation; family of transformations; kriging; Monte Carlo integration; rainfall; spatial prediction AB A model for prediction in some types of non-Gaussian random fields is presented. It extends the work of Handcock and Stein to prediction in transformed Gaussian random fields, where the transformation is known to belong to a parametric family of monotone transformations. The Bayesian transformed Gaussian model (BTG) provides an alternative to trans-Gaussian kriging taking into account the major sources of uncertainty, including uncertainty about the "normalizing transformation" itself, in the computation of the predictive density function. Unlike trans-Gaussian kriging, this approach mitigates the consequences of a misspecified transformation, giving in this sense a more robust predictive inference. Because the mean of the predictive distribution does not exist for some commonly used families of transformations, the median is used as the optimal predictor. The BTG model is applied in the spatial prediction of weekly rainfall amounts. Cross-validation shows the predicting performance of the BTG model compares favorably with several kriging variants. C1 Natl Inst Stat Sci, Res Triangle Pk, NC 27709 USA. Univ Maryland, Syst Res Inst, College Pk, MD 20742 USA. NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Math, College Pk, MD 20742 USA. RP De Oliveira, V (reprint author), Natl Inst Stat Sci, Res Triangle Pk, NC 27709 USA. NR 25 TC 73 Z9 73 U1 2 U2 8 PU AMER STATISTICAL ASSOC PI ALEXANDRIA PA 1429 DUKE ST, ALEXANDRIA, VA 22314 USA SN 0162-1459 J9 J AM STAT ASSOC JI J. Am. Stat. Assoc. PD DEC PY 1997 VL 92 IS 440 BP 1422 EP 1433 PG 12 WC Statistics & Probability SC Mathematics GA YN091 UT WOS:000071132200023 ER PT J AU Narayanan, SR Vamos, E Surampudi, S Frank, H Halpert, G Prakash, GKS Smart, MC Knieler, R Olah, GA Kosek, J Cropley, C AF Narayanan, SR Vamos, E Surampudi, S Frank, H Halpert, G Prakash, GKS Smart, MC Knieler, R Olah, GA Kosek, J Cropley, C TI Direct electro-oxidation of dimethoxymethane, trimethoxymethane, and trioxane and their application in fuel cells SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID METHANOL AB Significant advantages in weight, volume, and overall system performance of fuel cells would result if high-energy organic substances such as methane and its derivatives can be made to undergo direct electro-oxidation at the electrodes of the fuel cell without having to be converted by some catalytic process to hydrogen. This study demonstrates three novel fuels for direct-oxidation-type fuel cells. These new fuels are dimethoxymethane (DMM, dimethyl orthoformate), trimethoxymethane (TMM, trimethyl orthoformate), and trioxane (1,3,5-trioxane). The electro-oxidation and electrosorption characteristics of these new fuels at Pt, Pt-Sn, and Pt-Ru electrodes and the performance of these fuels in direct-oxidation fuel cells is described. Sustained direct electrochemical oxidation of aqueous solutions of DMM, TMM, and trioxane at high current densities has been demonstrated for the first time in half-cells and liquid-feed polymer electrolyte fuel cells. The oxidation of these fuels leads to the formation of methanol and ultimately carbon dioxide. Cyclic voltammetry and steady-state studies suggest that the electro-oxidation processes occur by chemisorption steps followed by surface reactions of adsorbed intermediates. The electro-oxidation of trioxane is preceded by an acid-catalyzed hydrolysis step on Nafion and in sulfuric acid solutions. These new fuels are best used without further processing in direct liquid-feed polymer electrolyte fuel cells. C1 UNIV SO CALIF,LOKER HYDROCARBON RES INST,LOS ANGELES,CA 90089. GINER INC,WALTHAM,MA 02154. RP Narayanan, SR (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 38 Z9 42 U1 1 U2 9 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 DEC PY 1997 VL 144 IS 12 BP 4195 EP 4201 DI 10.1149/1.1838165 PG 7 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA YL468 UT WOS:A1997YL46800025 ER PT J AU Timucin, DA Downie, JD AF Timucin, DA Downie, JD TI Phenomenological theory of photochromic media: optical data storage and processing with bacteriorhodopsin films SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID CHEMICALLY ENHANCED BACTERIORHODOPSIN; SPATIAL LIGHT-MODULATION; BORN-RYTOV CONTROVERSY; REFRACTIVE-INDEX; CYTOPLASMIC SURFACE; GENETIC VARIANT; THIN-FILM; PHOTOCYCLE; DYNAMICS; NONLINEARITY AB A phenomenological model for photochromic films incorporating bacteriorhodopsin (BR) molecules is developed. Equations for the propagation of electromagnetic waves inside a BR film and the temporal evolution of the volume population densities of the molecular states of BR are derived and subsequently coupled in a self-consistent fashion by means of an expression for the overall susceptibility of the film. Solutions for the scattered fields in a slab geometry are given in terms of the appropriate dyadic Green's functions, and perturbative approximations through the Born and the Rytov methods are discussed. The theory provides an analytical framework within which various optical data storage and processing applications for BR films may be studied. (C) 1997 Optical Society of America. RP Timucin, DA (reprint author), NASA,AMES RES CTR,MS 269-3,MOFFETT FIELD,CA 94035, USA. NR 62 TC 7 Z9 7 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD DEC PY 1997 VL 14 IS 12 BP 3285 EP 3299 DI 10.1364/JOSAA.14.003285 PG 15 WC Optics SC Optics GA YH550 UT WOS:A1997YH55000014 ER PT J AU Whitson, PA Pietrzyk, RA Pak, CYC AF Whitson, PA Pietrzyk, RA Pak, CYC TI Renal stone risk assessment during space shuttle flights SO JOURNAL OF UROLOGY LA English DT Article DE renal stone; risk assessment; space flight ID CALCIUM; THERAPY; DIET; NEPHROLITHIASIS; PATHOGENESIS; METABOLISM; ABSORPTION; CALCULI; FORMERS; OXALATE AB Purpose: The metabolic and environmental factors influencing renal stone formation before, during, and after Space Shuttle flights were assessed. We established the contributing roles of dietary factors in relationship to the urinary risk factors associated with renal stone formation. Materials and Methods: 24-hr, urine samples were collected prior to, during space flight, and following landing. Urinary and dietary factors associated with renal stone formation were analyzed and the relative urinary supersaturation of calcium oxalate, calcium phosphate (brushite), sodium urate, struvite and uric acid were calculated. Results: Urinary composition changed during flight to favor the crystallization of calcium-forming salts. Factors that contributed to increased potential for stone formation during space flight were significant reductions in urinary pH and increases in urinary calcium. Urinary output and citrate, a potent inhibitor of calcium-containing stones, were slightly reduced during space flight. Dietary intakes were significantly reduced for a number of variables, including fluid, energy, protein, potassium, phosphorus and magnesium. Conclusions: This is the first in-flight characterization of the renal stone forming potential in astronauts. With the examination of urinary components and nutritional factors, it was possible to determine the factors that contributed to increased risk or protected from risk. In spite of the protective components, the negative contributions to renal stone risk predominated and resulted in a urinary environment that favored the supersaturation of stone-forming salts. Dietary and pharmacologic therapies need to be assessed to minimize the potential for renal stone formation in astronauts during/after space flight. C1 UNIV TEXAS,HLTH SCI CTR,SW MED SCH,SECT MINERAL METAB,DALLAS,TX 75235. RP Whitson, PA (reprint author), KRUG LIFE SCI INC,NASA,LYNDON B JOHNSON SPACE CTR,MED SCI DIV,ASTRONAUT OFF,HOUSTON,TX 77058, USA. NR 32 TC 42 Z9 44 U1 0 U2 0 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0022-5347 J9 J UROLOGY JI J. Urol. PD DEC PY 1997 VL 158 IS 6 BP 2305 EP 2310 DI 10.1016/S0022-5347(01)68240-5 PG 6 WC Urology & Nephrology SC Urology & Nephrology GA YE617 UT WOS:A1997YE61700096 PM 9366381 ER PT J AU Bozzolo, G Noebe, RD Ferrante, J Garg, A AF Bozzolo, G Noebe, RD Ferrante, J Garg, A TI Atomistic simulations of alloying additions to NiAl SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA DE atomistic simulation; NiAl-Ti alloys; Cr additions AB Alloying additions of Ti to NiAl are of technological interest since NiAl + Ti alloys are extremely creep resistant. Also, Cr additions are of interest due to its low solubility and the potential for precipitating alpha-Cr, which at higher volume fractions acts as a ductile phase toughening component. However, very little is known about the structure of the corresponding ternary alloys besides the formation of Ni-Al-Ti Heusler precipitates or the phase separation of Cr in the NiAl + Cr alloys. Consequently, an atomistic analysis of NiAl + X (X = Ti, Cr) alloys using the method of Bozzolo, Ferrante and Smith (BFS) for alloys, along with complementary TEM analysis, was performed. The results include the determination of the corresponding solubility limits for each alloying addition, site preference and the formation of ordered structures within the B2 NiAl matrix. Analytical results as well as temperature dependent Monte Carlo numerical simulations are presented, highlighting the formation of Ni2AlTi Heusler precipitates and the alpha-Cr phase separation, in excellent agreement with experiment. (C) 1997 Elsevier Science S.A. C1 Ohio Aerosp Inst, Brook Pk, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bozzolo, G (reprint author), Ohio Aerosp Inst, Brook Pk, OH 44142 USA. NR 9 TC 12 Z9 12 U1 0 U2 0 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD DEC PY 1997 VL 240 BP 769 EP 776 DI 10.1016/S0921-5093(97)00665-5 PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA YV834 UT WOS:000071868000108 ER PT J AU Shieh, LS Wang, WM Sunkel, JW AF Shieh, LS Wang, WM Sunkel, JW TI Model conversions of uncertain linear system using the improved block-pulse function approach SO MATHEMATICAL AND COMPUTER MODELLING LA English DT Article DE analog uncertain model; block-pulse function; digital uncertain model; model conversions; structured uncertain systems ID EQUATIONS AB This paper presents an improved block-pulse function approach to convert a continuous-time (respectively, discrete-time) structured uncertain linear system into an equivalent discrete time (respectively, continuous-time) structured uncertain linear model. The concept of the principle of equivalent areas is utilized for the uncertain model conversions. This allows the use of well-established theorems and algorithms in the discrete-time (respectively, continuous-time) domain to indirectly solve the continuous-time (respectively, discrete-time) domain problems. A numerical example is given to demonstrate the effectiveness of the proposed method. C1 Univ Houston, Dept Elect & Comp Engn, Houston, TX 77204 USA. NASA, Lyndon B Johnson Space Ctr, Aerosci & Flight Mech Div, Houston, TX 77058 USA. RP Shieh, LS (reprint author), Univ Houston, Dept Elect & Comp Engn, Houston, TX 77204 USA. NR 11 TC 0 Z9 0 U1 1 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0895-7177 J9 MATH COMPUT MODEL JI Math. Comput. Model. PD DEC PY 1997 VL 26 IS 12 BP 115 EP 124 DI 10.1016/S0895-7177(97)00244-6 PG 10 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA YQ242 UT WOS:000071365700009 ER PT J AU Bailey, DH Borwein, JM Borwein, PB Plouffe, S AF Bailey, DH Borwein, JM Borwein, PB Plouffe, S TI The quest for Pi SO MATHEMATICAL INTELLIGENCER LA English DT Article C1 SIMON FRASER UNIV,CTR EXPT & CONSTRUCT MATH,BURNABY,BC V5A 1S6,CANADA. RP Bailey, DH (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. RI Borwein, Jonathan/A-6082-2009; OI Borwein, Jonathan/0000-0002-1263-0646 NR 19 TC 30 Z9 31 U1 0 U2 8 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0343-6993 J9 MATH INTELL JI Math. Intell. PD WIN PY 1997 VL 19 IS 1 BP 50 EP 57 PG 8 WC Mathematics SC Mathematics GA WE105 UT WOS:A1997WE10500014 ER PT J AU Wang, L Xu, K Bowman, RR Arsenault, RJ AF Wang, L Xu, K Bowman, RR Arsenault, RJ TI Dislocations in continuous filament reinforced W/NiAl and Al2O3/NiAl composites SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID DEFORMATION; INTERFACES; STRESSES; MATRIX; AL AB Continuous filament reinforced W/NiAl and Al2O3/NiAl composites (as-processed, annealed, and thermally cycled) have much higher dislocation densities than that of monolithic NiAl. These higher dislocation densities resulted from the relaxation of thermal residual stress, which developed during the cooling of the sample from elevated temperatures and was caused by the difference in the coefficients of thermal expansion between the matrix and the reinforcement. The dislocation density in the region adjacent to the matrix-filament interface was high and decreased only slightly with distance from the interface in the 30 vol pct composites. The as-processed and annealed composites exhibited a rather homogeneous dislocation density in the matrix. After thermal cycling, these composites showed no large difference in the dislocation density and morphology. However, there were local regions of lower dislocation densities. This difference was examined in relationship to filament fracture, surface matrix cracking, and degree of bonding. C1 NASA, Goddard Space Flight Ctr, Mat Engn Branch, Greenbelt, MD 20771 USA. NIST, Div Ceram, Gaithersburg, MD 20899 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Maryland, Dept Mat & Nucl Engn, College Pk, MD 20742 USA. RP Wang, L (reprint author), NASA, Goddard Space Flight Ctr, Mat Engn Branch, Greenbelt, MD 20771 USA. NR 24 TC 4 Z9 4 U1 1 U2 1 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD DEC PY 1997 VL 28 IS 12 BP 2755 EP 2761 DI 10.1007/s11661-997-0032-7 PG 7 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA YR348 UT WOS:000071486400032 ER PT J AU Lamaster, H Meylor, J Meylor, F AF Lamaster, H Meylor, J Meylor, F TI Internet technologies and requirements for telemedicine SO MINIMALLY INVASIVE THERAPY & ALLIED TECHNOLOGIES LA English DT Article DE Internet; IP; multicast; privacy; quality of service; Russia; Spacebridge; telemedicine AB Internet technologies are briefly introduced and those applicable for telemedicine are reviewed. Multicast internet technologies are described. The National Aeronautics and Space Administration (NASA) 'Telemedicine Spacebridge to Russia' project is described and used to derive requirements for internet telemedicine. Telemedicine privacy and Quality of Service (QoS) requirements are described. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Lamaster, H (reprint author), 260 Matadero Ave, Palo Alto, CA 94306 USA. NR 13 TC 0 Z9 0 U1 0 U2 0 PU ISIS MEDICAL MEDIA LTD PI OXFORD PA 59 ST ALDATES, OXFORD OX1 1ST, ENGLAND SN 1364-5706 J9 MINIM INVASIV THER JI Minim. Invasive Ther. Allied Technol. PD DEC PY 1997 VL 6 IS 5-6 BP 436 EP 443 DI 10.3109/13645709709153347 PG 8 WC Surgery SC Surgery GA YT935 UT WOS:000071661300013 PM 11541057 ER PT J AU Newsam, AM McHardy, IM Jones, LR Mason, KO AF Newsam, AM McHardy, IM Jones, LR Mason, KO TI The discovery of very red counterparts to faint X-ray sources SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, active; galaxies, clusters, general; cosmology, observations; diffuse radiation; infrared, galaxies ID DEEP ROSAT SURVEY; CATACLYSMIC VARIABLES; ORIGIN AB We present deep K-band imaging at the positions of four very faint X-ray sources found in the UK ROSAT Deep Survey to have no optical counterpart brighter than R similar to 23. Likely identifications are found within the ROSAT error circle in all four fields with R - K colours of between 3.2+/-0.4 and 6.4+/-0.6, From a consideration of the R - K colours and X-ray to optical luminosity ratios of the candidate identifications, we tentatively classify two of the X-ray sources as very distant (z similar to 1) clusters of galaxies, one as a narrow emission line galaxy and one as an obscured QSO. C1 Univ Southampton, Dept Phys & Astron, Southampton SO17 1BJ, Hants, England. Univ Birmingham, Sch Phys & Space Res, Birmingham B15 2TT, W Midlands, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. RP Newsam, AM (reprint author), Univ Southampton, Dept Phys & Astron, Southampton SO17 1BJ, Hants, England. NR 26 TC 14 Z9 14 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 DEC 1 PY 1997 VL 292 IS 2 BP 378 EP 384 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL833 UT WOS:000070998400017 ER PT J AU Hellier, C Mukai, K Beardmore, AP AF Hellier, C Mukai, K Beardmore, AP TI An outburst of the magnetic cataclysmic variable XY Arietis observed with RXTE SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; binaries, close; binaries, eclipsing; stars, individual, XY Ari; novae, cataclysmic variables; X-rays, stars ID DWARF NOVA OUTBURSTS; GK-PERSEI; INTERMEDIATE POLARS; HERCULIS SYSTEMS; ACCRETION DISKS; MASS-TRANSFER; LIGHT-CURVES; WHITE-DWARF; TV-COLUMBAE; RAY PULSAR AB We report the first observed outburst of the magnetic cataclysmic variable XY Ari. X-ray observations show a flux increase by an order of magnitude the day after the first signs of outburst. For the 5-d duration the X-ray spin pulse is greatly enhanced and the X-ray spectrum far more absorbed. We suggest that the inner disc pushes inwards during outburst, blocking the view to the lower accreting pole, breaking the symmetry present in quiescence, and so producing a large pulsation. The observations are consistent with a disc instability as the cause of the outburst, although we cannot rule out alternatives. We draw parallels between our data and the UV delay and dwarf nova oscillations seen in non-magnetic dwarf novae. C1 Univ Keele, Dept Phys, Keele ST5 5BG, Staffs, England. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hellier, C (reprint author), Univ Keele, Dept Phys, Keele ST5 5BG, Staffs, England. NR 50 TC 33 Z9 33 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD DEC 1 PY 1997 VL 292 IS 2 BP 397 EP 406 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL833 UT WOS:000070998400019 ER PT J AU Ferraro, FR Paltrinieri, B Pecci, FF Rood, RT Dorman, B AF Ferraro, FR Paltrinieri, B Pecci, FF Rood, RT Dorman, B TI Faint ultraviolet objects in the core of M13: optical counterparts of the low-luminosity X-ray source? SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE stars, evolution; novae, cataclysmic variables; globular clusters, individual, M13; ultraviolet, stars ID GLOBULAR-CLUSTERS; CATACLYSMIC VARIABLES; DISCOVERY; BINARIES; 47-TUCANAE; NGC-6397; STARS; ROSAT AB The core of the Galactic globular cluster M13 (NGC 6205) has been observed with WFPC2 on the Hubble Space Telescope through visual, blue, and mid-and Ear-UV filters in a programme devoted to studying the UV population in a sample of Galactic globular clusters. In the UV colour-magnitude diagrams derived from the HST images we have discovered three faint objects with a strong UV excess, which lie significantly outside the main loci defined by more than 12 000 normal cluster stars. The positions of two of the UV stars are nearly coincident (7 and 1 arcsec) with those of a low-luminosity X-ray source recently found in the core of M13 and with a 3.5-sigma peak in the X-ray contour map. We suggest that the UV stars are physically connected to the X-ray emission. The UV stars are very similar to the quiescent nova in the globular cluster M80, and they might be a, perhaps new, subclass of cataclysmic variable. C1 Osservatorio Astron Bologna, I-40126 Bologna, Italy. Stn Astron Cagliari, I-09012 Capoterra, Italy. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ferraro, FR (reprint author), Osservatorio Astron Bologna, Via Zamboni 33, I-40126 Bologna, Italy. NR 29 TC 16 Z9 16 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 DEC 1 PY 1997 VL 292 IS 2 BP L45 EP L49 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YL833 UT WOS:000070998400001 ER PT J AU Duffy, DG AF Duffy, DG TI Hydrostatic adjustment in nonhydrostatic, compressible mesoscale models SO MONTHLY WEATHER REVIEW LA English DT Article ID FORECAST MODEL; SIMULATION; INVERSION AB The ability of various numerical techniques used in compressible, nonhydrostatic models to handle hydrostatic adjustment is intercompared. The exact solution of a linearized model of an isothermal, compressible, nonrotating atmosphere is compared against those from finite-differenced versions of the same model. For the semi-implicit scheme, the scheme traps acoustic waves near the point of excitation but has little effect on gravity waves. The time-splitting scheme captures hydrostatic adjustment well. RP Duffy, DG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 912,GREENBELT,MD 20771, USA. NR 18 TC 1 Z9 1 U1 0 U2 0 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 DEC PY 1997 VL 125 IS 12 BP 3357 EP 3367 DI 10.1175/1520-0493(1997)125<3357:HAINCM>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YJ555 UT WOS:A1997YJ55500018 ER PT J AU Barry, DT AF Barry, DT TI Acoustic myography SO MUSCLE & NERVE LA English DT Letter ID SKELETAL-MUSCLE; SOUND PRODUCTION; FREQUENCIES; FROG RP Barry, DT (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,ASTRONAUT OFF,CODE CB,2101 NASA RD 1,HOUSTON,TX 77058, USA. NR 8 TC 0 Z9 0 U1 0 U2 1 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0148-639X J9 MUSCLE NERVE JI Muscle Nerve PD DEC PY 1997 VL 20 IS 12 BP 1601 EP 1601 PG 1 WC Clinical Neurology; Neurosciences SC Neurosciences & Neurology GA YH665 UT WOS:A1997YH66500020 PM 9390677 ER PT J AU Feibelman, TP Doudrick, RL Cibula, WG Bennett, JW AF Feibelman, TP Doudrick, RL Cibula, WG Bennett, JW TI Phylogenetic relationships within the Cantharellaceae inferred from sequence analysis of the nuclear large subunit rDNA SO MYCOLOGICAL RESEARCH LA English DT Article ID RIBOSOMAL DNA-SEQUENCES; IDENTIFICATION; AMPLIFICATION; SPACERS; RNA AB DNA was extracted from dried specimens of nine taxa of the Cantharellaceae. Approximately 325 bases near the 5' end of the nuclear 28S ribosomal gene were sequenced, and the sequences were compared. Sequence analyses demonstrated that Cantharellus and Craterellus should be treated as distinct genera. The phylogeny generated using parsimony suggests that Cantharellus tubaeformis and Pseudocraterellus sinuosus should be considered species of Craterellus. As a result of this study, we recognize the first placement of these two species in Craterellus by Fries and Qui let. A reassessment of the morphological characters used to separate Cantharellus and Craterellus is indicated. C1 USDA Forest Serv, So Inst Forest Genet, Saucier, MS 39575 USA. Tulane Univ, Dept Ecol Evolut & Organismal Biol, New Orleans, LA 70118 USA. NASA, John C Stennis Space Ctr, Stennis Space Ctr, MS 39529 USA. Tulane Univ, Dept Cell & Mol Biol, New Orleans, LA 70118 USA. RP Doudrick, RL (reprint author), USDA Forest Serv, So Inst Forest Genet, Saucier, MS 39575 USA. NR 50 TC 22 Z9 24 U1 2 U2 9 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0953-7562 J9 MYCOL RES JI Mycol. Res. PD DEC PY 1997 VL 101 BP 1423 EP 1430 DI 10.1017/S0953756297004115 PN 12 PG 8 WC Mycology SC Mycology GA YP072 UT WOS:000071238400002 ER PT J AU Srivastava, D AF Srivastava, D TI A phenomenological model of the rotation dynamics of carbon nanotube gears with laser electric fields SO NANOTECHNOLOGY LA English DT Article AB A phenomenological model for the rotational dynamics of a single laser-powered molecular motor is discussed and tested through molecular dynamics simulations. The motor is used to power carbon nanotube-based gears. For a given laser power density and arrangement of free charges in the body of the gear we have defined an intrinsic frequency of the gear oscillatory rotations. The nanotube rotations are not of an oscillatory nature if the laser field frequency is of the same order of magnitude as the intrinsic frequency of the tube and there is an additional phase match between the two. For the laser-powered gear motor dynamics, the rotational angular momentum of the driven gear tend to stabilize the rotational dynamics of the system, and unidirectional rotations for the entire duration of the simulations are observed. C1 NASA, Computat Nanotechnol NAS Syst Div, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Srivastava, D (reprint author), NASA, Computat Nanotechnol NAS Syst Div, Ames Res Ctr, Mail Stop T27A-1, Moffett Field, CA 94035 USA. NR 13 TC 80 Z9 86 U1 0 U2 7 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD DEC PY 1997 VL 8 IS 4 BP 186 EP 192 DI 10.1088/0957-4484/8/4/005 PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA YP835 UT WOS:000071320300005 ER PT J AU Cole, T AF Cole, T TI Solar system exploration, technology development, and neurosurgery SO NEUROSURGERY LA English DT Editorial Material RP Cole, T (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0148-396X J9 NEUROSURGERY JI Neurosurgery PD DEC PY 1997 VL 41 IS 6 BP 1440 EP 1441 DI 10.1097/00006123-199712000-00048 PG 2 WC Clinical Neurology; Surgery SC Neurosciences & Neurology; Surgery GA YH863 UT WOS:A1997YH86300121 PM 9402601 ER PT J AU Gupta, SK Barbier, LM Christian, ER Geier, S Krizmanic, JF MItchell, JW Streitmatter, RE Wasilewski, PJ AF Gupta, SK Barbier, LM Christian, ER Geier, S Krizmanic, JF MItchell, JW Streitmatter, RE Wasilewski, PJ TI Performance of CAMAC TDC and ADC in magnetic field SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article DE magnetic spectrometer; TDC; ADC; magnetic field; inductor AB The performance of a LeCroy CAMAC 2228A TDC and a 2249A ADC have been studied in presence of magnetic fields up to 5000 G. The conversion gains of the TDC and ADC increased with magnetic field in a non-linear fashion which can be adequately parameterized by a fourth-order polynomial. The behavior of both the TDC and ADC can be completely understood in terms of a change in the inductance of a ferromagnetic core inductor in the 20 MHz clock circuit of these units. RP Gupta, SK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. RI Christian, Eric/D-4974-2012 OI Christian, Eric/0000-0003-2134-3937 NR 7 TC 2 Z9 2 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD DEC 1 PY 1997 VL 400 IS 2-3 BP 428 EP 434 DI 10.1016/S0168-9002(97)01019-X PG 7 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA YK079 UT WOS:A1997YK07900021 ER PT J AU Garg, VK AF Garg, VK TI Adiabatic effectiveness and heat transfer coefficient on a film-cooled rotating blade SO NUMERICAL HEAT TRANSFER PART A-APPLICATIONS LA English DT Article ID TURBULENCE MODEL; TURBINE; PREDICTIONS; SIMULATION; TRANSITION; FLOW; JET AB A three dimensional Navier-Stokes code has been used to compute the adiabatic effectiveness and heat transfer coefficient on a rotatingfilm-cooled turbine blade. The blade chosen is the United Technologies Research Center (UTRC) rotor with five film-cooling rows containing 83 holes, including three rows on the shower head with 49 holes, covering about 86% of the blade span. The mainstream is akin to that under real engine conditions with stagnation temperature 1900 K and stagnation pressure 3 MPa. The blade speed is taken to be 5200 rpm. The adiabatic effectiveness is higher for a rotating blade as compared to that for a stationary blade. Also, the direction of coolant injection from the shower-head holes considerably affects the effectiveness and heat transfer coefficient values on both the pressure and suction surfaces. In all cases the heat transfer coefficient and adiabatic effectiveness me highly three-dimensional in the vicinity of holes but tend to become two-dimensional far downstream. C1 AYT Corp, NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Garg, VK (reprint author), AYT Corp, NASA, Lewis Res Ctr, Mail Stop 5-11, Cleveland, OH 44135 USA. NR 34 TC 13 Z9 22 U1 0 U2 0 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 USA SN 1040-7782 J9 NUMER HEAT TR A-APPL JI Numer. Heat Tranf. A-Appl. PD DEC PY 1997 VL 32 IS 8 BP 811 EP 830 DI 10.1080/10407789708913919 PG 20 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA YP261 UT WOS:000071259200003 ER PT J AU Gilbert, JA Shepherd, RL Cole, HJ Ashley, PR AF Gilbert, JA Shepherd, RL Cole, HJ Ashley, PR TI Three-dimensional displacement measurement using diffractive optic interferometry SO OPTICAL ENGINEERING LA English DT Article DE diffractive optic interferometry; 3-D displacement measurement ID MOIRE INTERFEROMETRY AB A powerful new optical method that utilizes diffractive optic interferometry (DOI) to measure both in-plane and out-of-plane displacement with variable sensitivity using the same optical system is introduced. Sensitivity is varied utilizing various combinations of the different wavefronts produced by a conjugate pair of binary optical elements; a transmission grating is used to produce several illumination beams, while a reflective grating, replicated an the surface of a specimen, provides the reference for the undeformed state. A derivation of the equations that govern the method is included along with a discussion of the experimental tests conducted to verify the theory. Overall, the results are excellent, with experimental data agreeing to within a few percent of the theoretical predictions. (C) 1997 Society of Photo-Optical Instrumentation Engineers. C1 COLORADO SCH MINES,DIV ENGN,GOLDEN,CO 80401. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ASTRION LAB,HUNTSVILLE,AL 35812. USA,MISSILE COMMAND,WEAP SCI DIRECTORATE RES,CTR DEV & ENGN,REDSTONE ARSENAL,AL 35898. RP Gilbert, JA (reprint author), UNIV ALABAMA,CONSORTIUM HOLOG APPL MECH & PHOTON,HUNTSVILLE,AL 35899, USA. NR 12 TC 7 Z9 7 U1 0 U2 2 PU SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS PI BELLINGHAM PA PO BOX 10, BELLINGHAM, WA 98227-0010 SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD DEC PY 1997 VL 36 IS 12 BP 3336 EP 3342 DI 10.1117/1.601571 PG 7 WC Optics SC Optics GA YK902 UT WOS:A1997YK90200015 ER PT J AU Bethea, MD Lock, JA Merat, F AF Bethea, MD Lock, JA Merat, F TI Three-dimensional camera calibration technique for stereo imaging velocimetry experiments SO OPTICAL ENGINEERING LA English DT Article DE stereo imaging velocimetry; three-dimensional camera calibration technique; stereo imaging geometry; computer vision; machine vision; particle imaging velocimetry ID MODELS AB A three-dimensional camera calibration technique is developed by combining two, 2-D camera calibrations for an orthogonal stereo viewing geometry. The left camera view (YZ view) and the right camera view (XZ view) are calibrated separately and then combined to produce an XYZ (3-D) calibration routine, Our technique employs three parallel calibration planes. One is placed along the main diagonal of the cubic experimental chamber, and the other two planes are placed known distances in front of it and behind it within the chamber. Both cameras view the calibration points on the planes simultaneously. Given the coordinates of a number of points, we use a physical model to determine the exact pixel locations of the calibration points. After inverting the model equations, we input the absolute coordinates and measured pixel locations into a least-squares fitting algorithm to obtain the experimental camera parameters for each camera individually, We then combine the two camera views via a ray-tracing method. We calibrated 3-in.(3) (7.62-mm(3)), 4-in.(3) (10.16-mm(3)), 5-in.(3) (12.70-mm(3)), and 6-in.(3) (15.24-mm(3)) chambers with accuracies between 1.66 and 2.01 pixels (0.60 and 0.77% of full field), 1.26 and 1.86 pixels (0.43 and 0.63% of full field), 1.16 and 1.34 pixels (0.33 and 0.39% of full field), and 1.91 and 2.49 pixels (0.59 and 0.77% of full field), respectively, using our 3-D camera calibration routine. (C) 1997 Society of Photo-Optical Instrumentation Engineers. C1 CLEVELAND STATE UNIV,DEPT PHYS,CLEVELAND,OH 44115. CASE WESTERN RESERVE UNIV,DEPT ELECT ENGN & APPL PHYS,CLEVELAND,OH 44106. CASE WESTERN RESERVE UNIV,DEPT COMP ENGN & SCI,CLEVELAND,OH 44106. RP Bethea, MD (reprint author), NASA,LEWIS RES CTR,PROC SCI & TECHNOL BRANCH,CLEVELAND,OH 44135, USA. NR 12 TC 6 Z9 7 U1 0 U2 0 PU SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS PI BELLINGHAM PA PO BOX 10, BELLINGHAM, WA 98227-0010 SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD DEC PY 1997 VL 36 IS 12 BP 3445 EP 3454 DI 10.1117/1.601584 PG 10 WC Optics SC Optics GA YK902 UT WOS:A1997YK90200031 ER PT J AU Roach, S Magee, M AF Roach, S Magee, M TI Relative spatial pose estimation for autonomous grasping SO OPTICAL ENGINEERING LA English DT Article DE robot vision; image processing; spatial reasoning; pose estimation; sensor repositioning; iterative refinement AB A technique for finding the relative spatial pose between a robotic end effector and a target object to be grasped without a priori knowledge of the spatial relationship between the camera and the robot is presented, The transformation between the coordinate system of the camera and the coordinate system of the robot is computed dynamically using knowledge about the location of the end effector relative to both the camera and the robot. A previously developed computer vision technique is used to determine the pose of the end effector relative to the camera. The robot geometry and data from the robot controller is used to determine the pose of the end effector relative to the robot. The spatial transformation between the robot end effector and the target object is computed with respect to the robot's coordinate system. The algorithm was demonstrated using a five-degree-of-freedom robot and an RGB camera system. The camera can be dynamically positioned without concern for an assumed spatial relationship between the camera and robot, enabling optimization of the view of the object and the end effector. Further, the iterative nature of the grasping algorithm reduces the effects of camera calibration errors. (C) 1997 Society of Photo-Optical Instrumentation Engineers. C1 SW RES INST,AUTOMAT & DATA SYST DIV,SAN ANTONIO,TX 78228. RP Roach, S (reprint author), NASA,AMES RES CTR,RECOM TECHNOL,MS 296-2,MOFFETT FIELD,CA 94035, USA. NR 11 TC 0 Z9 0 U1 0 U2 0 PU SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS PI BELLINGHAM PA PO BOX 10, BELLINGHAM, WA 98227-0010 SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD DEC PY 1997 VL 36 IS 12 BP 3462 EP 3470 DI 10.1117/1.601586 PG 9 WC Optics SC Optics GA YK902 UT WOS:A1997YK90200033 ER PT J AU Chen, ZG Shih, MF Segev, M Wilson, DW Muller, RE Maker, PD AF Chen, ZG Shih, MF Segev, M Wilson, DW Muller, RE Maker, PD TI Steady-state vortex-screening solitons formed in biased photorefractive media SO OPTICS LETTERS LA English DT Article ID PHOTOVOLTAIC SPATIAL SOLITONS; OPTICAL VORTEX; DARK; BRIGHT AB We report the observation of steady-state photorefractive vortex-screening solitons. As a singly charged circular vortex nested on a broad beam propagates through a biased strontium barium niobate crystal, it self-traps in both transverse dimensions despite the inherent anisotropy of the photorefractive nonlinearity. When the vortex beam is a doughnut-shaped narrow beam, it breaks up into two elongated slices (with a self-defocusing nonlinearity) or into two focused filaments (with a self-focusing nonlinearity). We demonstrate the optical guidance of a probe beam in a circular waveguide induced by the self-trapped vortex. (C) 1997 Optical Society of America. C1 PRINCETON UNIV, CTR PHOTON & OPTOELECT MAT, PRINCETON, NJ 08544 USA. CALTECH, JET PROP LAB, CTR SPACE MICROELECT TECHNOL, PASADENA, CA 91109 USA. RP Chen, ZG (reprint author), PRINCETON UNIV, DEPT ELECT ENGN, PRINCETON, NJ 08544 USA. RI Shih, Ming-Feng/A-3818-2010; Chen, Zhigang/B-2112-2010 OI Shih, Ming-Feng/0000-0003-4984-9702; NR 21 TC 59 Z9 64 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 EI 1539-4794 J9 OPT LETT JI Opt. Lett. PD DEC 1 PY 1997 VL 22 IS 23 BP 1751 EP 1753 DI 10.1364/OL.22.001751 PG 3 WC Optics SC Optics GA YJ147 UT WOS:A1997YJ14700005 PM 18188354 ER PT J AU Imhoff, ML AF Imhoff, ML TI Letter to the editor SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Letter RP Imhoff, ML (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD DEC PY 1997 VL 63 IS 12 BP 1344 EP 1344 PG 1 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA YL252 UT WOS:A1997YL25200003 ER PT J AU He, XY Luo, LS AF He, XY Luo, LS TI Theory of the lattice Boltzmann method: From the Boltzmann equation to the lattice Boltzmann equation SO PHYSICAL REVIEW E LA English DT Article ID NAVIER-STOKES EQUATION; PARTICULATE SUSPENSIONS; NUMERICAL SIMULATIONS; GAS AUTOMATA; MODEL; FLUID; HYDRODYNAMICS AB In this paper, the lattice Boltzmann equation is directly derived from the Boltzmann equation. It is shown that the lattice Boltzmann equation is a special discretized form of the Boltzmann equation. Various approximations for the discretization of the Boltzmann equation in both time and phase space are discussed in detail. A general procedure to derive the lattice Boltzmann model from the continuous Boltzmann equation is demonstrated explicitly. The lattice Boltzmann models derived include the two-dimensional 6-bit, 7-bit, and 9-bit, and three-dimensional 27-bit models. C1 Univ Calif Los Alamos Natl Lab, Ctr Nonlinear Studies, Los Alamos, NM 87545 USA. Univ Calif Los Alamos Natl Lab, Complex Syst Grp T13, Los Alamos, NM 87545 USA. NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. RP He, XY (reprint author), Univ Calif Los Alamos Natl Lab, Ctr Nonlinear Studies, MS-B258, Los Alamos, NM 87545 USA. RI Luo, Li-Shi/A-4561-2011 OI Luo, Li-Shi/0000-0003-1215-7892 NR 46 TC 746 Z9 767 U1 18 U2 114 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1063-651X J9 PHYS REV E JI Phys. Rev. E PD DEC PY 1997 VL 56 IS 6 BP 6811 EP 6817 DI 10.1103/PhysRevE.56.6811 PG 7 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA YM237 UT WOS:000071043500077 ER PT J AU Menon, M Srivastava, D AF Menon, M Srivastava, D TI Carbon nanotube ''T junctions'': Nanoscale metal-semiconductor-metal contact devices SO PHYSICAL REVIEW LETTERS LA English DT Article ID ELECTRONIC-PROPERTIES; MICROTUBULES; CLUSTERS AB Stable ''T junctions'' of single-walled carbon nanotubes forming one of the smallest prototypes of microscopic metal-semiconductor-metal contacts are proposed; The structures have been found to be local minima of the total energy on relaxation with a generalized tight-binding molecular dynamics; scheme. These quasi-2D junctions could be the building blocks of nanoscale tunnel junctions in a 2D network of nanoelectronic devices. C1 UNIV KENTUCKY,CTR COMPUTAT SCI,LEXINGTON,KY 40506. NASA,AMES RES CTR,NAS SYST DIV,MRJ,MOFFETT FIELD,CA 94035. RP Menon, M (reprint author), UNIV KENTUCKY,DEPT PHYS & ASTRON,LEXINGTON,KY 40506, USA. NR 17 TC 261 Z9 269 U1 3 U2 26 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD DEC 1 PY 1997 VL 79 IS 22 BP 4453 EP 4456 DI 10.1103/PhysRevLett.79.4453 PG 4 WC Physics, Multidisciplinary SC Physics GA YJ388 UT WOS:A1997YJ38800039 ER PT J AU Zaman, KBMQ Raman, G AF Zaman, KBMQ Raman, G TI Reversal in spreading of a tabbed circular jet under controlled excitation SO PHYSICS OF FLUIDS LA English DT Article ID AXISYMMETRICAL JET; MIXING LAYERS; STREAMWISE; ENTRAINMENT AB Detailed flow field measurements have been carried out for a turbulent circular jet perturbed by tabs and artificial excitation. Two ''delta tabs'' were placed at the nozzle exit at diametrically opposite locations. The excitation condition involved subharmonic resonance that manifested in a periodic vortex pairing in the near flow field. While the excitation and the tabs independently increased jet spreading, a combination of the two diminished the effect. The jet spreading was most pronounced with the tabs but was reduced when excitation was applied to the tabbed jet. The tabs generated streamwise vortex pairs that caused a lateral spreading of the jet in a direction perpendicular to the plane containing the tabs. The excitation, on the other hand, organized the azimuthal vorticity into coherent ring structures whose evolution and pairing also increased entrainment by the jet. In the tabbed case, the excitation produced coherent azimuthal structures that were distorted and asymmetric in shape. The self-induction of these structures produced an effect that opposed the tendency for the lateral spreading of the streamwise vortex pairs. The passage of the distorted vortices, and their pairing, also had a cancellation effect on the time-averaged streamwise vorticity field. These led to the reduction in jet spreading. [S1070-6631(97)03012-2]. RP Zaman, KBMQ (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 22 TC 15 Z9 15 U1 0 U2 2 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 DEC PY 1997 VL 9 IS 12 BP 3733 EP 3741 DI 10.1063/1.869511 PG 9 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA YH897 UT WOS:A1997YH89700017 ER PT J AU Koumoutsakos, P AF Koumoutsakos, P TI Active control of vortex-wall interactions SO PHYSICS OF FLUIDS LA English DT Article ID VORTICITY FLUX; BOUNDARY-LAYER; FLOW AB A new simple and efficient methodology is presented for the active control of vortical wall bounded flows. The method is based on sensing of the wall pressure and the calculation of the wall vorticity flux. This information is used to determine explicitly the amount of unsteady, spatially varying mass transpiration, used as an actuating mechanism, necessary to achieve a desired wall vorticity flux. The present scheme is based on the physical mechanism of vorticity generation at solid boundaries. It has the advantage of implementing quantities that can be measured and manipulated at the wall, in computations as well as in experiments. It is shown to reproduce efficiently phenomena previously attained using off-wall information. An active control methodology is outlined and the practical implementation of the present scheme is discussed. (C) 1997 American Institute of Physics. [S1070-6631(97)03712-4]. C1 ETH ZURICH,IFD,CH-8092 ZURICH,SWITZERLAND. RP Koumoutsakos, P (reprint author), NASA,AMES 202A1,CTR,MOFFETT FIELD,CA 94035, USA. RI Koumoutsakos, Petros/A-2846-2008 OI Koumoutsakos, Petros/0000-0001-8337-2122 NR 18 TC 28 Z9 28 U1 0 U2 2 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 DEC PY 1997 VL 9 IS 12 BP 3808 EP 3816 DI 10.1063/1.869515 PG 9 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA YH897 UT WOS:A1997YH89700022 ER PT J AU Huebner, WF AF Huebner, WF TI Obituary Jurgen H. Rahe SO PHYSICS TODAY LA English DT Item About an Individual RP Huebner, WF (reprint author), NASA,WASHINGTON,DC 20546, 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 DEC PY 1997 VL 50 IS 12 BP 92 EP 92 DI 10.1063/1.882038 PG 1 WC Physics, Multidisciplinary SC Physics GA YJ169 UT WOS:A1997YJ16900027 ER PT J AU Jenniskens, P van Leeuwen, GD AF Jenniskens, P van Leeuwen, GD TI The alpha-Monocerotids meteor outburst: the cross section of a comet dust trail SO PLANETARY AND SPACE SCIENCE LA English DT Article ID STREAM AB One minute counts obtained during the meteor outburst of alpha-Monocerotids on November 22, 1995, are analyzed in order to examine the possibility of filamentary structure in the stream profile. None is found. It is argued that far-comet type outbursts are due to the Earth's passage through the dust trail of a long period comet, thus offering a direct means of studying such comet dust trails. Hence, the meteor stream activity curve is the first accurate cross section of dust densities through a comet dust trail. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Dutch Meteor Soc, NL-2318 NB Leiden, Netherlands. RP Jenniskens, P (reprint author), NASA, Ames Res Ctr, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 21 TC 5 Z9 5 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD DEC PY 1997 VL 45 IS 12 BP 1649 EP 1652 DI 10.1016/S0032-0633(97)00092-5 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD412 UT WOS:000072682600017 ER PT J AU Steinberg, SL Henninger, DL AF Steinberg, SL Henninger, DL TI Response of the water status of soybean to changes in soil water potentials controlled by the water pressure in microporous tubes SO PLANT CELL AND ENVIRONMENT LA English DT Article DE conductance; microporous tubes; sap flow; soil desorption relation; transpiration; water potential ID GROWING PLANTS; GAS-EXCHANGE; POROUS TUBE; RESISTANCE; CONDUCTANCE; TRANSPORT; CONSTANT; DEFICITS; GROWTH; SYSTEM AB Water transport through a microporous tube-soil-plant system was investigated by measuring the response of soil and plant water status to step change reductions in the water pressure within the tubes, Soybeans were germinated and grown in a porous ceramic 'soil' at a porous tube water pressure of -0.5 kPa for 28 d. During this time, the soil matric potential was nearly in equilibrium with tube water pressure, Water pressure in the porous tubes was then reduced to either -1.0, -1.5 or -2.0 kPa. Sap flow rates, leaf conductance and soil, root and leaf water potentials were measured before and after this change, a reduction in porous tube water pressure from -0.5 to -1.0 or -1.5 kPa did not result in any significant change in soil or plant water status, A reduction in porous tube water pressure to -2.0 kPa resulted in significant reductions in sap flow, leaf conductance, and soil, root and leaf mater potentials, Hydraulic conductance, calculated as the transpiration rate/Delta psi between two points in the water transport pathway, was used to analyse water transport through the tube-soil-plant continuum. At porous tube water pressures of -0.5 to -1.5 kPa soil moisture was readily available and hydraulic conductance of the plant limited water transport. At -2.0 kPa, hydraulic conductance of the bulk soil was the dominant factor in water movement. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Steinberg, SL (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 37 TC 15 Z9 15 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0140-7791 J9 PLANT CELL ENVIRON JI Plant Cell Environ. PD DEC PY 1997 VL 20 IS 12 BP 1506 EP 1516 DI 10.1046/j.1365-3040.1997.d01-46.x PG 11 WC Plant Sciences SC Plant Sciences GA YT083 UT WOS:000071562300007 PM 11541524 ER PT J AU Roberts, DA Green, RO Adams, JB AF Roberts, DA Green, RO Adams, JB TI Temporal and spatial patterns in vegetation and atmospheric properties from AVIRIS SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID AVHRR DATA; MULTISPECTRAL IMAGES; REFLECTANCE SPECTRA; GREEN VEGETATION; BRAZILIAN AMAZON; SATELLITE DATA; CANOPY; MODEL; DEFORESTATION; INFORMATION AB Little research has focused on the use of imaging spectrometry for change detection. In this paper, we apply Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data to the monitoring of seasonal changes in atmospheric water vapor, liquid water, and surface cover in the vicinity of the Jasper Ridge, CA, for three dates in 1992. Apparent surface reflectance was retrieved and water vapor and liquid water mapped by using a radiative-transfer-based inversion that accounts for spatially variable atmospheres. Spectral mixture analysis (SMA) was used to model reflectance data as mixtures of green vegetation (GV), nonphotosynthetic vegetation (NPV), soil, and shade. Temporal and spatial patterns in endmember fractions and liquid water were compared to the normalized difference vegetation index (NDVI). The reflectance retrieval algorithm was tested by using a temporally invariant target. Atmospheric analysis showed a strongly negative linear between water vapor and elevation with significant seasonal variation in water vapor. Comparison of AVIRIS estimates of specific humidity to ground-based measures showed good correspondence for all three dates. Analysis of surface properties showed that GV, NDVI, and liquid water varied in response to green vegetation and were highly correlated. However, whereas the NDVI peaked between 0.7 and 0.85 in forests, liquid water continued to vary by as much as a factor of two. Seasonal patterns included senescence in herbaceous and nonconiferous vegetation, potential leaf growth in coniferous forests, and a general increase in shadows. This resulted in seasonal declines in NDVI, GV, and liquid water for nonforested vegetation and increases in NPV. Nonconiferous forests showed similar declines in liquid water and GV and increases in shade and NPV, but they showed an increase in NDVI. In coniferous forests, liquid water and NDVI increased seasonally, matching an interpretation of continued growth, but GV decreased owing to increased shade. The combination of retrieved surface reflectance, atmospheric modeling, and mapping of liquid water demonstrates the utility of imaging spectrometry for change detection. SMA with the use of reference end-members is an effective method for monitoring surficial changes. Temporal patterns in NDVI that contradict trends of GV and liquid water in nonconiferous forests raise additional questions about the NDVI. Liquid water may be more appropriate for analysis of high-leaf-area, shadowed forests because it overcomes the problem of saturation with NDVI. (C) Elsevier Science Inc., 1997. C1 CALTECH,JET PROP LAB,PASADENA,CA. UNIV WASHINGTON,DEPT GEOL SCI,SEATTLE,WA 98195. RP Roberts, DA (reprint author), UNIV CALIF SANTA BARBARA,DEPT GEOG,ELLISON HALL 3611,SANTA BARBARA,CA 93106, USA. NR 63 TC 153 Z9 166 U1 1 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 DEC PY 1997 VL 62 IS 3 BP 223 EP 240 DI 10.1016/S0034-4257(97)00092-8 PG 18 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA YD929 UT WOS:A1997YD92900003 ER PT J AU Cushman, GM Mather, JC Fixsen, DJ AF Cushman, GM Mather, JC Fixsen, DJ TI Demonstration of low temperature radiative cooler for future space missions SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID TELESCOPES AB Low temperature radiative coolers permit more sensitive, lower temperature detectors for science instruments in space, and can extend the length of missions at low cost and mass. A miniature radiative cooler was designed, constructed, and tested and achieved a stabilized temperature of 34 K with no load and an outer shell temperature of 91 K. This is an improvement upon previous lower limits of radiative coolers of 50 K. Thermal modeling and experiment agree within 2 K. (C) 1997 American Institute of Physics. C1 NASA, Goddard Space Flight Ctr, Hughes STX, Greenbelt, MD 20771 USA. RP Cushman, GM (reprint author), NASA, Goddard Space Flight Ctr, Hughes STX, Code 685, Greenbelt, MD 20771 USA. NR 13 TC 3 Z9 3 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD DEC PY 1997 VL 68 IS 12 BP 4596 EP 4599 DI 10.1063/1.1148438 PG 4 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA YM344 UT WOS:000071054200049 ER PT J AU Garcia-Gorriz, E Font, J Candela, J AF Garcia-Gorriz, E Font, J Candela, J TI Data quality control for vessel mounted acoustic Doppler current profiler. Application for the Western Mediterranean Sea SO SCIENTIA MARINA LA English DT Article DE ADCP; GPS; horizontal currents determination; data reliability; western Mediterranean ID SUBTIDAL CURRENTS; PERFORMANCE; BIAS AB A systematic Data Quality Checking Protocol for Vessel Mounted Acoustic Doppler Current Profiler observations is proposed. Previous-to-acquisition conditions are considered along with simultaneous ones. Independently of internal systems, location and misalignment, the auxiliary systems to acquisition determine the accuracy range of the current velocity profiles. Simultaneous to-acquisition navigation conditions provide the physically descriptive weight (or reliability) of significance for each individual current profile. The formulation of the Data Quality Checking Protocol is followed by actual applications and examples from cruises aboard RN "Garcia del Cid" in the Western Mediterranean Sea. C1 Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA. CSIC, Inst Ciencies Mar, Barcelona, Spain. RP Garcia-Gorriz, E (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 300-323, Pasadena, CA 91109 USA. RI Font, Jordi/E-5355-2013 OI Font, Jordi/0000-0003-2590-1457 NR 26 TC 9 Z9 9 U1 0 U2 3 PU INST CIENCIAS MAR BARCELONA PI BARCELONA PA PASSEIG JOAN DE BORBO, 08039 BARCELONA, SPAIN SN 0214-8358 J9 SCI MAR JI Sci. Mar. PD DEC PY 1997 VL 61 IS 4 BP 417 EP 430 PG 14 WC Marine & Freshwater Biology SC Marine & Freshwater Biology GA ZB573 UT WOS:000072486100001 ER PT J AU Gibson, EK McKay, DS ThomasKeprta, K Romanek, CS AF Gibson, EK McKay, DS ThomasKeprta, K Romanek, CS TI The case for relic life on Mars SO SCIENTIFIC AMERICAN LA English DT Article C1 UNIV CHICAGO,DEPT GEOL,CHICAGO,IL 60637. UNIV CHICAGO,SAVANNAH RIVER ECOL LAB,CHICAGO,IL 60637. RP Gibson, EK (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,EARTH SCI & SOLAR SYST EXPLORAT DIV,HOUSTON,TX 77058, USA. NR 6 TC 9 Z9 9 U1 0 U2 2 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 SN 0036-8733 J9 SCI AM JI Sci.Am. PD DEC PY 1997 VL 277 IS 6 BP 58 EP 65 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YG852 UT WOS:A1997YG85200025 PM 11536819 ER PT J AU Yungster, S Radhakrishnan, K AF Yungster, S Radhakrishnan, K TI Computational study of reacting flow establishment in expansion tube facilities SO SHOCK WAVES LA English DT Article DE hypersonic flow; shock induced combustion; unsteady combustion; detailed chemistry; ram accelerator ID NUMERICAL-SIMULATION; RAM ACCELERATOR; PROJECTILES; COMBUSTION; GASES AB We study the temporal evolution of the combustion flowfield established by the interaction of ram accelerator-type projectiles with an explosive gas mixture accelerated to hypersonic speeds in an expansion tube. The Navier-Stokes equations for a chemically reacting gas mixture are solved in a fully coupled manner using an implicit, time accurate algorithm. The solution procedure is based on a spatially second order, total variation diminishing scheme and a temporally second order, variable-step, backward differentiation formula method. The hydrogen-oxygen-argon chemistry is modeled with a 9-species, 19-step mechanism. The accuracy of the solution method is first demonstrated by several benchmark calculations. Numerical simulations of expansion tube flowfields are then presented for two different geometries: an axisymmetric projectile and a ram accelerator configuration. The development of the shock-induced combustion process is followed. The temporal variations of the calculated thrust and drag forces on the ram accelerator projectile are also presented. In the axisymmetric projectile case, which was designed to ensure combustion only in the boundary layer, the radial extent of the flame front during the initial transient phase was surprisingly large. In the ram accelerator configuration the flame propagated upstream along both the projectile and tube wall boundary layers, resulting in unstart. C1 NASA, Inst Computat Mech Prop, Lewis Res Ctr, Cleveland, OH 44135 USA. NASA, NYMA Inc, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Yungster, S (reprint author), NASA, Inst Computat Mech Prop, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 21 TC 2 Z9 2 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0938-1287 J9 SHOCK WAVES JI Shock Waves PD DEC PY 1997 VL 7 IS 6 BP 335 EP 342 DI 10.1007/s001930050088 PG 8 WC Mechanics SC Mechanics GA YL951 UT WOS:000071011800003 ER PT J AU Rohaly, AM Ahumada, AJ Watson, AB AF Rohaly, AM Ahumada, AJ Watson, AB TI Object detection in natural backgrounds predicted by discrimination performance and models SO VISION RESEARCH LA English DT Article DE object detection; discrimination; modeling; natural images ID MASKING; VISION AB Many models of visual performance predict image discriminability, the visibility of the difference between a pair of images, We compared the ability of three image discrimination models to predict the detectability of objects embedded in natural backgrounds, The three models were: a multiple channel Cortex transform model with within-channel masking; a single channel contrast sensitivity filter model; and a digital image difference metric, Each model used a Minkowski distance metric (generalized vector magnitude) to summate absolute differences between the background and object plus background images, For each model, this summation was implemented with three different exponents: 2, 4 and infinity. In addition, each combination of model and summation exponent was implemented with and without a simple contrast gain factor, The model outputs were compared to measures of object detectability obtained from 19 observers, Among the models without the contrast gain factor, the multiple channel model with a summation exponent of 4 performed best, predicting the pattern of observer d's with an RMS error of 2.3 dB, The contrast gain factor improved the predictions of all three models for all three exponents, With the factor, the best exponent was 4 for all three models, and their prediction errors were near 1 dB. These results demonstrate that image discrimination models can predict the relative detectability of objects in natural scenes. Published by Elsevier Science Ltd. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Rohaly, AM (reprint author), USA,RES LAB,ABERDEEN PROVING GROUND,MD 21005, USA. NR 26 TC 50 Z9 50 U1 0 U2 3 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 DEC PY 1997 VL 37 IS 23 BP 3225 EP 3235 DI 10.1016/S0042-6989(97)00156-9 PG 11 WC Neurosciences; Ophthalmology SC Neurosciences & Neurology; Ophthalmology GA YG155 UT WOS:A1997YG15500004 PM 9425540 ER PT J AU Alley, RB Shuman, CA Meese, DA Gow, AJ Taylor, KC Cuffey, KM Fitzpatrick, JJ Grootes, PM Zielinski, GA Ram, M Spinelli, G Elder, B AF Alley, RB Shuman, CA Meese, DA Gow, AJ Taylor, KC Cuffey, KM Fitzpatrick, JJ Grootes, PM Zielinski, GA Ram, M Spinelli, G Elder, B TI Visual-stratigraphic dating of the GISP2 ice core: Basis, reproducibility, and application SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID LASER-LIGHT SCATTERING; AIR-HYDRATE CRYSTALS; GREENLAND ICE; POLAR ICE; YOUNGER DRYAS; ELECTRICAL-CONDUCTIVITY; NORTH-ATLANTIC; GRAIN-GROWTH; CLIMATE; RECORD AB Annual layers are visible in the Greenland Ice Sheet Project 2 ice core from central Greenland, allowing rapid dating of the core. Changes in bubble and grain structure caused by near-surface, primarily summertime formation of hear complexes provide the main visible annual marker in the Holocene, and changes in ''cloudiness'' of the ice correlated with dustiness mark Wisconsinan annual cycles; both markers are evident and have been intercalibrated in early Holocene ice. Layer counts are reproducible between different workers and for one worker at different times, with 1% error over century-length times in the Holocene. Reproducibility is typically 5% in Wisconsinan ice-age ice and decreases with increasing age and depth. Cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50,000 years. Visible observations are not greatly degraded by ''brittle ice'' or many other core-quality problems, allowing construction of long, consistently sampled time series. High accuracy requires careful study of the core by dedicated observers. C1 PENN STATE UNIV,DEPT GEOSCI,UNIVERSITY PK,PA 16802. UNIV WASHINGTON,DEPT GEOL SCI,SEATTLE,WA 98195. USA,COLD REG RES & ENGN LAB,HANOVER,NH 03755. US GEOL SURVEY,OFF CENT REG GEOLOGIST,DENVER,CO 80225. CHRISTIAN ALBRECHTS UNIV KIEL,LAB C14,KIEL,GERMANY. SUNY BUFFALO,DEPT PHYS,BUFFALO,NY 14620. NASA,GODDARD SPACE FLIGHT CTR,OCEANS & ICE BRANCH,GREENBELT,MD 20771. UNIV NEVADA,DESERT RES INST,UNIV & COMMUNITY COLL SYST NEVADA,RENO,NV 89506. UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,DURHAM,NH 03824. RP Alley, RB (reprint author), PENN STATE UNIV,CTR EARTH SYST SCI,UNIVERSITY PK,PA 16802, USA. RI Spinelli, Glenn/B-1346-2009; Grootes, Pieter/F-4952-2011; Taylor, Kendrick/A-3469-2016 OI Taylor, Kendrick/0000-0001-8535-1261 NR 65 TC 130 Z9 136 U1 0 U2 18 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 30 PY 1997 VL 102 IS C12 BP 26367 EP 26381 DI 10.1029/96JC03837 PG 15 WC Oceanography SC Oceanography GA YJ671 UT WOS:A1997YJ67100006 ER PT J AU Jouzel, J Alley, RB Cuffey, KM Dansgaard, W Grootes, P Hoffmann, G Johnsen, SJ Koster, RD Peel, D Shuman, CA Stievenard, M Stuiver, M White, J AF Jouzel, J Alley, RB Cuffey, KM Dansgaard, W Grootes, P Hoffmann, G Johnsen, SJ Koster, RD Peel, D Shuman, CA Stievenard, M Stuiver, M White, J TI Validity of the temperature reconstruction from water isotopes in ice cores SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID GENERAL-CIRCULATION MODEL; ANTARCTIC PENINSULA CLIMATE; LAST GLACIAL MAXIMUM; DEUTERIUM EXCESS; CENTRAL GREENLAND; OXYGEN-ISOTOPE; RECORD; PRECIPITATION; SHEET; SNOW AB Well-documented present-day distributions of stable water isotopes (HDO and (H2O)-O-18) show the existence, in middle and high latitudes, of a linear relationship between the mean annual isotope content of precipitation (delta D and delta(18)O) and the mean annual temperature at the precipitation site. Paleoclimatologists have used this relationship, which is particularly well obeyed over Greenland and Antarctica, to infer paleotemperatures from ice core data. There is, however, growing evidence that spatial and temporal isotope/ surface temperature slopes differ, thus complicating the use of stable water isotopes as paleothermometers. In this paper we review empirical estimates of temporal slopes in polar regions and relevant information that can be inferred from isotope models: simple, Rayleigh-type distillation models and (particularly over Greenland) general circulation models (GCMs) fitted with isotope tracer diagnostics. Empirical estimates of temporal slopes appear consistently lower than present-day spatial slopes and are dependent on the timescale considered. This difference is most probably due to changes in the evaporative origins of moisture, changes in the seasonality of the precipitation, changes in the strength of the inversion layer, or some combination of these changes. Isotope models have not yet been used to evaluate the relative influences of these different factors. The apparent disagreement in the temporal and spatial slopes clearly makes calibrating the isotope paleothermometer difficult. Nevertheless, the use of a (calibrated) isotope paleothermometer appears justified; empirical estimates and most (though not all) GCM results support the practice of interpreting ice core isotope records in terms of local temperature changes. C1 PENN STATE UNIV,DEPT GEOSCI,UNIVERSITY PK,PA 16802. PENN STATE UNIV,CTR EARTH SYST SCI,UNIVERSITY PK,PA 16802. UNIV WASHINGTON,DEPT GEOL SCI,SEATTLE,WA 98195. UNIV WASHINGTON,QUATERNARY RES CTR,SEATTLE,WA 98195. UNIV COPENHAGEN,DEPT GEOPHYS,DK-2100 COPENHAGEN,DENMARK. MAX PLANCK INST METEOROL,D-20146 HAMBURG,GERMANY. NASA,HYDROL SCI BRANCH,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. BRITISH ANTARCTIC SURVEY,CAMBRIDGE CB3 0ET,ENGLAND. NASA,OCEANS & ICE BRANCH,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV COLORADO,INST ARCTIC & ALPINE RES,BOULDER,CO 80309. UNIV COLORADO,DEPT GEOL SCI,BOULDER,CO 80309. UNIV REYKJAVIK,INST SCI,REYKJAVIK,ICELAND. RP Jouzel, J (reprint author), CTR ETUD SACLAY,LAB MODELISAT CLIMAT ENVIRONM,F-91191 GIF SUR YVETTE,FRANCE. RI Grootes, Pieter/F-4952-2011; White, James/A-7845-2009; Koster, Randal/F-5881-2012 OI White, James/0000-0001-6041-4684; Koster, Randal/0000-0001-6418-6383 NR 95 TC 307 Z9 319 U1 8 U2 83 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 30 PY 1997 VL 102 IS C12 BP 26471 EP 26487 DI 10.1029/97JC01283 PG 17 WC Oceanography SC Oceanography GA YJ671 UT WOS:A1997YJ67100013 ER PT J AU Shuman, CA Alley, RB Fahnestock, MA Fawcett, PJ Bindschadler, RA White, JWC Grootes, PM Anandakrishnan, S Stearns, CR AF Shuman, CA Alley, RB Fahnestock, MA Fawcett, PJ Bindschadler, RA White, JWC Grootes, PM Anandakrishnan, S Stearns, CR TI Detection and monitoring of stratigraphic markers and temperature trends at the Greenland Ice Sheet Project 2 using passive-microwave remote-sensing data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SSM/I BRIGHTNESS TEMPERATURES; DEPTH HOAR; ACCUMULATION; SUMMIT; SNOW AB Satellite passive-microwave sensors provide a sensitive means of studying ice-sheet surface processes that assists ice-core interpretation and can extend local observations across regional scales. Analysis of special sensor microwave/imager (SSM/I) brightness temperature (T-B) data supports ice-core research in two specific ways. First, the summer hear complex layers used to date the Holocene portion of the Greenland Ice Sheet Project 2 ice core can be defined temporally and spatially by SSM/I 37-GHz vertically (V) and horizontally (H) polarized (B) ratio (V/H) trends. Second, comparison of automatic weather station temperatures to SSM/I 37-GHz V T-B data shows that they are an effective proxy temperature record in this region. Also, the T-B data can be correlated with proxy temperature trends from stable-isotope-ratio (delta(18)O and delta D) profiles from snow pits and this allows the assignment of dates to specific snow depths. C1 PENN STATE UNIV,CTR EARTH SYST SCI,UNIVERSITY PK,PA 16802. PENN STATE UNIV,DEPT GEOSCI,UNIVERSITY PK,PA 16802. UNIV MARYLAND,JOINT CTR EARTH SCI,COLLEGE PK,MD 20742. UNIV NEW MEXICO,DEPT EARTH & PLANETARY SCI,ALBUQUERQUE,NM 87131. CHRISTIAN ALBRECHTS UNIV KIEL,LEBNIZ LABOR,INST REINE & ANGEW KERNPHYS,D-24118 KIEL,GERMANY. UNIV WISCONSIN,CTR SPACE SCI & ENGN,MADISON,WI 53706. UNIV COLORADO,INST ARCTIC & ALPINE RES,BOULDER,CO 80309. RP Shuman, CA (reprint author), NASA,OCEANS & ICE BRANCH,GODDARD SPACE FLIGHT CTR,MAIL CODE 971,GREENBELT,MD 20771, USA. RI Grootes, Pieter/F-4952-2011; White, James/A-7845-2009; Fahnestock, Mark/N-2678-2013 OI White, James/0000-0001-6041-4684; NR 31 TC 12 Z9 12 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 30 PY 1997 VL 102 IS C12 BP 26877 EP 26886 DI 10.1029/96JC02323 PG 10 WC Oceanography SC Oceanography GA YJ671 UT WOS:A1997YJ67100048 ER PT J AU Zetner, PW Trajmar, S Wang, S Kanik, I Csanak, G Clark, REH Abdallah, J Nickel, JC AF Zetner, PW Trajmar, S Wang, S Kanik, I Csanak, G Clark, REH Abdallah, J Nickel, JC TI Inelastic electron scattering by laser-excited Ba-138( ... 6s6p P-1(1)) atoms SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID IMPACT COHERENCE PARAMETERS; CROSS-SECTIONS; SUPERELASTIC SCATTERING; NEUTRAL BARIUM; EXCITATION; ORIENTATION; TRANSITION; ALIGNMENT; SODIUM; LEVEL AB We present experimental and theoretical results of an investigation into low-energy electron scattering from Ba-138 atoms coherently prepared in the (...6s6p)P-l(1) state by laser excitation. We measured the differential cross section from the coherently prepared (...6s6p)P-1(1) state (referred to as partial differential cross section) for excitations of the (...5d(2))P-3(2), (...6p5d)F-1(3), (...6s6d)D-1(2), (...6s7p)P-1(1), (...6s8s)S-3(1), and (...6s8d)D-1(2) levels at E-o = 20 eV and 36.7 eV incident electron energies and compared them with theoretical results obtained from unitarized distorted wave approximation calculations. In some cases (e.g, the excitation of D-1(2) and P-1(1) levels) there is reasonable or good agreement between theory and experiment, in other cases (e.g, the excitation of the P-3(2) and S-3, levels) there are order of magnitude (or more) differences. C1 CALTECH,JET PROP LAB,PASADENA,CA. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. UNIV CALIF RIVERSIDE,DEPT PHYS,RIVERSIDE,CA 92521. RP Zetner, PW (reprint author), UNIV MANITOBA,DEPT PHYS,WINNIPEG,MB R3T 2N2,CANADA. NR 61 TC 22 Z9 22 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD NOV 28 PY 1997 VL 30 IS 22 BP 5317 EP 5339 DI 10.1088/0953-4075/30/22/026 PG 23 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA YK156 UT WOS:A1997YK15600026 ER PT J AU Hansen, J Harris, C Borenstein, S Curran, B Fox, M AF Hansen, J Harris, C Borenstein, S Curran, B Fox, M TI Research education SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article RP Hansen, J (reprint author), NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. NR 3 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 25677 EP 25678 DI 10.1029/97JD02172 PG 2 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300001 ER PT J AU Hansen, J Sato, M Ruedy, R Lacis, A Asamoah, K Beckford, K Borenstein, S Brown, E Cairns, B Carlson, B Curran, B deCastro, S Druyan, L Etwarrow, P Ferede, T Fox, M Gaffen, D Glascoe, J Gordon, H Hollandsworth, S Jiang, X Johnson, C Lawrence, N Lean, J Lerner, J Lo, K Logan, J Luckett, A McCormick, MP McPeters, R Miller, R Minnis, P Ramberran, I Russell, G Russell, P Stone, P Tegen, I Thomas, S Thomason, L Thompson, A Wilder, J Willson, R Zawodny, J AF Hansen, J Sato, M Ruedy, R Lacis, A Asamoah, K Beckford, K Borenstein, S Brown, E Cairns, B Carlson, B Curran, B deCastro, S Druyan, L Etwarrow, P Ferede, T Fox, M Gaffen, D Glascoe, J Gordon, H Hollandsworth, S Jiang, X Johnson, C Lawrence, N Lean, J Lerner, J Lo, K Logan, J Luckett, A McCormick, MP McPeters, R Miller, R Minnis, P Ramberran, I Russell, G Russell, P Stone, P Tegen, I Thomas, S Thomason, L Thompson, A Wilder, J Willson, R Zawodny, J TI Forcings and chaos in interannual to decadal climate change SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID GENERAL-CIRCULATION MODEL; SEA-SURFACE TEMPERATURES; TROPICAL PACIFIC-OCEAN; STRATOSPHERIC AEROSOLS; ATMOSPHERIC MODEL; LAND-SURFACE; INTERCOMPARISON PROJECT; 3-DIMENSIONAL MODEL; GLOBAL TEMPERATURE; GREENHOUSE GASES AB We investigate the roles of climate forcings and chaos (unforced variability) in climate change via ensembles of climate simulations in which we add forcings one by one. The experiments suggest that most interannual climate variability in the period 1979-1996 at middle and high latitudes is chaotic. But observed SST anomalies, which themselves are partly forced and partly chaotic, account for much of the climate variability at low latitudes and a small portion of the variability at high latitudes. Both a natural radiative forcing (volcanic aerosols) and an anthropogenic forcing (ozone depletion) leave clear signatures in the simulated climate change that are identified in observations. Pinatubo aerosols warm the stratosphere and cool the surface glc:,ally, causing a tendency for regional surface cooling. Ozone depletion cools the lower stratosphere, troposphere and surface, steepening the temperature lapse rate in the troposphere. Solar irradiance effects are small, but our model is inadequate to fully explore this forcing. Well-mixed anthropogenic greenhouse gases cause a large surface warming that, over the 17 years, approximately offsets cooling by the other three mechanisms. Thus the net calculated effect of all measured radiative forcings is approximately zero surface temperature trend and zero heat storage in the ocean for the period 1979-1996. Finally, in addition to the four measured radiative forcings, we add an initial (1979) disequilibrium forcing of +0.65 W/m(2). This forcing yields a global surface warming of about 0.2 degrees C over 1979-1996, close to observations, and measurable heat storage in the ocean. We argue that the results represent evidence of a planetary radiative imbalance of at least 0.5 W/m(2); this disequilibrium presumably represents unrealized warming due to changes of atmospheric composition prior to 1979. One implication of the disequilibrium forcing is an expectation of new record global temperatures in the next few years. The best opportunity for observational confirmation of the disequilibrium is measurement of ocean temperatures adequate to define heat storage. C1 MAST HIGH SCH, QUEENS, NY 11411 USA. CUNY YORK COLL, DEPT NAT SCI, JAMAICA, NY 11451 USA. UNIV MIAMI, DEPT PHYS, CORAL GABLES, FL 33124 USA. BRONX HIGH SCH SCI, BRONX, NY 10468 USA. FAR ROCKAWAY HIGH SCH, BROOKLYN, NY 11691 USA. NOAA, AIR RESOURCES LAB, SILVER SPRING, MD 20910 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. USN, RES LAB, EO HULBURT CTR SPACE RES, WASHINGTON, DC 20375 USA. HARVARD UNIV, DEPT EARTH & PLANETARY SCI, CAMBRIDGE, MA 02137 USA. HAMPTON UNIV, DEPT PHYS, HAMPTON, VA 23668 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. MIT, CTR METEOROL, CAMBRIDGE, MA 02139 USA. POLYTECH UNIV, DIV ENGN, BROOKLYN, NY 11201 USA. COLUMBIA UNIV, DEPT APPL PHYS, NEW YORK, NY 10027 USA. COLUMBIA UNIV, CTR CLIMATE SYST RES, NEW YORK, NY 10027 USA. RP Hansen, J (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Lacis, Andrew/D-4658-2012; Carlson, Barbara/D-8319-2012; Miller, Ron/E-1902-2012; McPeters, Richard/G-4955-2013; Minnis, Patrick/G-1902-2010; Thompson, Anne /C-3649-2014; OI McPeters, Richard/0000-0002-8926-8462; Minnis, Patrick/0000-0002-4733-6148; Thompson, Anne /0000-0002-7829-0920; Thomason, Larry/0000-0002-1902-0840 NR 146 TC 144 Z9 147 U1 2 U2 23 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 25679 EP 25720 DI 10.1029/97JD01495 PG 42 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300002 ER PT J AU Sparling, LC Kettleborough, JA Haynes, PH McIntyre, ME Rosenfield, JE Schoeberl, MR Newman, PA AF Sparling, LC Kettleborough, JA Haynes, PH McIntyre, ME Rosenfield, JE Schoeberl, MR Newman, PA TI Diabatic cross-isentropic dispersion in the lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID POLAR VORTEX; GENERAL-CIRCULATION; MIDDLE ATMOSPHERE; TRANSPORT CHARACTERISTICS; FLUID-DYNAMICS; MODEL; CONSTITUENTS; TURBULENCE; EXCHANGE; DESCENT AB A significant contribution to vertical dispersion of tracers in the stratosphere arises from the variability in the diabatic heating of air parcels. Air parcels starting on a given isentropic surface experience different time histories of diabatic heating, which causes vertical dispersion across isentropic surfaces. We refer to this process as ''diabatic cross-isentropic dispersion,'' or ''diabatic dispersion'' for brevity. The present study investigates diabatic dispersion in the lower stratosphere by computing parcel trajectories initialized uniformly over the 500 K surface on January 1, 1993. Parcels are followed for 2 months using analyzed winds and diabatic heating rates computed from analyzed temperatures. Diabatic dispersion depends on the statistics of the large-scale horizontal eddy motion as well as on the spatial structure of the diabatic heating field. The trajectory statistics suggest that the polar vortex, surf zone, tropics, and extratropical summer hemisphere are, to varying extents, isolated from each other and that the diabatic dispersion within each of these regions is different. In both the surf zone and southern hemisphere extratropics the dispersion is initially advective, with potential temperature variance increasing as t(2) as time t increases. After about 1 month, the dispersion becomes diffusive in the sense that [delta theta(t)(2)]similar to 2K(theta theta)t and with a diffusivity K-theta theta in the range 2-6 K-2 d(-1), roughly equivalent to K-zz similar to 0.1-0.2 m(2) s(-1). The emergence of a diffusive regime is discussed in terms of loss of memory of diabatic heating along parcel paths, as measured by the decay of the Lagrangian autocorrelation function. Diabatic dispersion within the tropics and polar vortex over the 2-month period is more than an order of magnitude smaller and is less clearly diffusive. The diabatic dispersion of parcels moving poleward out of the tropics into either hemisphere is faster than either differential advection or diffusion, and in this case, [delta theta(t)(2)] increases as t(3) For the total ensemble of all parcels, the potential temperature variance increases as t(2), consistent with global-scale differential advection by the mean diabatic circulation. This is inconsistent, at least on the 2-month timescale considered here, with a one-dimensional diffusive model of vertical dispersion. C1 UNIV CAMBRIDGE, DEPT APPL MATH & THEORET PHYS, CTR ATMOSPHER SCI, CAMBRIDGE CB3 9EW, ENGLAND. HUGHES STX, LANHAM, MD USA. GEN SCI CORP, LAUREL, MD USA. RP Sparling, LC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, MC 916, GREENBELT, MD 20771 USA. RI Newman, Paul/D-6208-2012 OI Newman, Paul/0000-0003-1139-2508 NR 50 TC 37 Z9 36 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 25817 EP 25829 DI 10.1029/97JD01968 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300010 ER PT J AU Wang, MH King, MD AF Wang, MH King, MD TI Correction of Rayleigh scattering effects in cloud optical thickness retrievals SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR-RADIATION MEASUREMENTS AB We present results that demonstrate the effects of Rayleigh scattering on the retrieval of cloud optical thickness at a visible wavelength (0.66 mu m). The sensor-measured radiance at a visible wavelength (0.66 mu m) is usually used to infer remotely the cloud optical thickness from aircraft or satellite instruments. For example, we find that without removing Rayleigh scattering effects, errors in the retrieved cloud optical thickness for a thin water cloud layer (tau(c)= 2.0) range from 15 to 60%, depending on solar zenith angle and viewing geometry. For an optically thick cloud (tau(c) greater than or similar to 10), on the other hand, errors can range from 10 to 60% for large solar zenith angles (theta(O) greater than or similar to 60 degrees) because of enhanced Rayleigh scattering. It is therefore particularly important to correct for Rayleigh scattering contributions to the reflected signal from a cloud layer both (1) for the case of thin clouds and (2) for large solar zenith angles and all clouds. On the basis of the single scattering approximation, we propose an iterative method for effectively removing Rayleigh scattering contributions from the measured radiance signal in cloud optical thickness retrievals. The proposed correction algorithm works very well and can easily be incorporated into any cloud retrieval algorithm. The Rayleigh correction method is applicable to cloud at any pressure, providing that the cloud top pressure is known to within +/-100 hPa. With the Rayleigh correction the errors in retrieved cloud optical thickness are usually reduced to within 3%. In cases of both thin cloud layers and thick clouds with large solar zenith angles, the errors are usually reduced by a factor of about 2 to over 10. The Rayleigh correction algorithm has been tested with simulations for realistic cloud optical and microphysical properties with different solar and viewing geometries. We apply the Rayleigh correction algorithm to the cloud optical thickness retrievals from experimental data obtained during the Atlantic Stratocumulus Transition Experiment (ASTEX) conducted near the Azores in June 1992 and compare these results to corresponding retrievals obtained using 0.88 mu m. These results provide an example of the Rayleigh scattering effects on thin clouds and further test the Rayleigh correction scheme. Using a nonabsorbing near-infrared wavelength (0.88 mu m) in retrieving cloud optical thickness is only applicable over oceans, however, since most land surfaces are highly reflective at 0.88 mu m. Hence successful global retrievals of cloud optical thickness should remove Rayleigh scattering effects when using reflectance measurements at 0.66 mu m. C1 NASA, GODDARD SPACE FLIGHT CTR, EARTH SCI DIRECTORATE, GREENBELT, MD 20771 USA. RP Wang, MH (reprint author), UNIV MARYLAND BALTIMORE CTY, NASA, GODDARD SPACE FLIGHT CTR, CODE 970-2, GREENBELT, MD 20771 USA. RI King, Michael/C-7153-2011; Wang, Menghua/F-5631-2010 OI King, Michael/0000-0003-2645-7298; Wang, Menghua/0000-0001-7019-3125 NR 15 TC 22 Z9 22 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 25915 EP 25926 DI 10.1029/97JD02225 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300016 ER PT J AU Mayr, HG Mengel, JG Hines, CO Chan, KL Arnold, NF Reddy, CA Porter, HS AF Mayr, HG Mengel, JG Hines, CO Chan, KL Arnold, NF Reddy, CA Porter, HS TI The gravity wave Doppler spread theory applied in numerical spectral model of the middle atmosphere .1. Model and global scale seasonal variations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SEMIANNUAL OSCILLATION; SATURATION; PARAMETERIZATION; MESOSPHERE; DIFFUSION; BREAKDOWN; DYNAMICS; THERMOSPHERE; VARIABILITY; TURBULENCE AB Hines [1997a, b] has developed a Doppler spread parameterization (DSP) for the deposition of small-scale gravity wave (GW) momentum and energy in the middle atmosphere. We have incorporated this DSP into the two-dimensional (2-D) version of the numerical spectral model (NSM) of Chart et al. [1994a, b] which is applied to the Earth's middle atmosphere. With a globally uniform flux of(quasi) isotropically propagating GW emanating from the troposphere, the NSM has been integrated for several model years to describe seasonal variations and equatorial oscillations. Here, after a review of the NSM and DSP, we discuss numerical results that describe the temperature and wind fields during solstice and equinox conditions, emphasizing the role played by the GW spectrum. That spectrum is filtered as it ascends through the stratosphere and provides, at the solstices, a highly anisotropic wave and momentum flux at mesospheric heights. Upon further filtering there, with attendant momentum deposition, the waves decelerate and then reverse the zonal circulation. In quasi-geostrophic balance latitudinally, this reversal is accompanied by a reversal of the latitudinal temperature gradient, one that leads to a temperature minimum in the summer polar mesopause region, as is observed. Corresponding results for equinox are obtained, and all are discussed. Our results differ only in detail from those of similar analyses that employ other GW parameterizations. They are presented here in part to exhibit the success of the DSP at this elementary level and in part to provide a point of departure against which future refinements may be judged. Our first extension of the modeling concerns the semiannual and quasi-biennial oscillations that are produced by the DSP in the NSM at equatorial latitudes with the same, constant and uniform, incident GW flux. Initial results are presented in the companion paper and are compared there with observations. C1 UNIV SPACE RES ASSOC, SEABROOK, MD 20706 USA. HINES CONSULTANCY, TORONTO, ON M5T 1W9, CANADA. APPL RES CORP, LANDOVER, MD 20785 USA. FURMAN UNIV, DEPT COMP SCI, GREENVILLE, SC 29613 USA. VICRAM SARABHAI SPACE CTR, SPACE PHYS LAB, TRIVANDRUM, KERALA, INDIA. HONG KONG UNIV SCI & TECHNOL, KOWLOON, HONG KONG. RP Mayr, HG (reprint author), NASA, GODDARD SPACE FLIGHT CTR, MAIL CODE 910-4, GREENBELT, MD 20771 USA. NR 61 TC 18 Z9 18 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 26077 EP 26091 DI 10.1029/96JD03213 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300029 ER PT J AU Mayr, HG Mengel, JG Hines, CO Chan, KL Arnold, NF Reddy, CA Porter, HS AF Mayr, HG Mengel, JG Hines, CO Chan, KL Arnold, NF Reddy, CA Porter, HS TI The gravity wave Doppler spread theory applied in a numerical spectral model of the middle atmosphere .2. Equatorial oscillations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; SEMIANNUAL OSCILLATION; ZONAL WIND; TROPICAL STRATOSPHERE; KELVIN WAVE; SATURATION; MESOSPHERE; PARAMETERIZATION; CIRCULATION AB Mayr et al. [this issue] discussed a two-dimensional version of the numerical spectral model (NSM) of Chan et al. [1994a, b] that incorporates the Doppler spread parameterization (DSP) for momentum deposition by small-scale gravity waves (GW) developed by Hines [1997a, b] and presented numerical results describing the global scale seasonal variations in the temperature and wind fields of the middle atmosphere. Even with the simplest assumptions for the GW flux emanating from the troposphere, to be isotropic and independent of latitude and season, this model also produces significant oscillations in the equatorial zonal circulation which are discussed here. Our model results lead to the following conclusions: (1) At altitudes above 40 km, a periodicity of 6 month dominates, resembling the observed semiannual oscillation (SAO). The peak amplitude of this oscillation is close to 18 m/s near 50 km (20-30 m/s observed). A secondary maximum is excited near 80 km with an amplitude of about 11 m/s (15-25 m/s observed), whose phase is opposite to that at 50 km. In this altitude range, the downward phase progression is about 9 km/month, in agreement with observations. The computed SAO is confined to equatorial latitudes, as observed. (2) At altitudes below 40 km, the period of the computed oscillation is almost 21 months, approaching that of the observed quasi-biennial oscillation (QBO). The maximum wind amplitudes are close to 8 m/s (20 m/s observed), and the downward phase progression is about 1.6 km/month (1.3 km/month observed). The model also produces a QBO in the upper mesosphere, in qualitative agreement with recent UARS measurements [Burrage et al., 1996]. (3) When the eddy diffusivity is reduced by a factor of two, the QBO period increases to 30 months and the maximum wind amplitude approaches 13 m/s. Computer experiments are discussed for constant, equinoctial solar heating to elucidate the GW excitation mechanism for the equatorial oscillations in the zonal circulation. C1 UNIV SPACE RES ASSOC, SEABROOK, MD 20706 USA. HONG KONG UNIV SCI & TECHNOL, KOWLOON, HONG KONG. HINES CONSULTANCY, TORONTO, ON M5T 1W9, CANADA. APPL RES CORP, LANDOVER, MD 20785 USA. FURMAN UNIV, DEPT COMP SCI, GREENVILLE, SC 29613 USA. VICRAM SARABHAI SPACE CTR, SPACE PHYS LAB, TRIVANDRUM, KERALA, INDIA. RP Mayr, HG (reprint author), NASA, GODDARD SPACE FLIGHT CTR, MAIL CODE 910-4, GREENBELT, MD 20771 USA. NR 42 TC 54 Z9 54 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 26093 EP 26105 DI 10.1029/96JD03214 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300030 ER PT J AU Goldberg, RA Lehmacher, GA Schmidlin, FJ Fritts, DC Mitchell, JD Croskey, CL Friedrich, M Swartz, WE AF Goldberg, RA Lehmacher, GA Schmidlin, FJ Fritts, DC Mitchell, JD Croskey, CL Friedrich, M Swartz, WE TI Equatorial dynamics observed by rocket, radar, and satellite during the CADRE/MALTED campaign .1. Programmatics and small-scale fluctuations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LATITUDE MESOSPHERIC TURBULENCE; LOWER THERMOSPHERE; SEMIANNUAL OSCILLATION; VARIABILITY; ATMOSPHERE; ENERGY; MODEL; PARAMETERS; IONOSPHERE; WAVES AB In August 1994, the Mesospheric and Lower Thermospheric Equatorial Dynamics (MALTED) Program was conducted from the Alcantara rocket site in northeastern Brazil as part of the International Guara Rocket Campaign to study equatorial dynamics, irregularities, and instabilities in the ionosphere. This site was selected because of its proximity to the geographic (2.3 degrees S) and magnetic (similar to 0.5 degrees S) equators. MALTED was concerned with planetary wave modulation of the diurnal tidal amplitude, which exhibits considerable amplitude variability at equatorial and subtropical latitudes. Our goals were to study this global modulation of the tidal motions where tidal influences on the thermal structure are maximum, to study the interaction of these tidal structures with gravity waves and turbulence at mesopause altitudes, and to gain a better understanding of dynamic influences and variability on the equatorial middle atmosphere. Four (two daytime and two nighttime) identical Nike-Orion payloads designed to investigate small-scale turbulence and irregularities were coordinated with 20 meteorological falling-sphere rockets designed to measure temperature and wind fields during a 10-day period. These in situ measurements were coordinated with observations of global-scale mesospheric motions that were provided by various ground based radars and the Upper Atmosphere Research Satellite (UARS) through the Coupling and Dynamics of Regions Equatorial (CADRE) campaign. The ground-based observatories included the Jicamarca radar observatory near Lima, Peru, and medium frequency (MF) radars in Hawaii Christmas Island, and Adelaide. Since all four Nike-Orion flights penetrated and overflew the electrojet with apogees near 125 km, these flights provided additional information about the electrodynamics and irregularities in the equatorial ionospheric E region and may provide information on wave coupling between the mesosphere and the electrojet. Simultaneous with these flights, the CUPRI 50-MHz radar (Cornell University) provided local sounding of the electrojet region. A description of the campaign logistics and the measurements performed with the Nike-Orion instrumentation and their implications for turbulence due to gravity waves and tidal instability in the mesosphere and lower thermosphere (MLT) are presented here. From a study of electron density fluctuations measured by rocket probes, we have found evidence for equatorial mesospheric neutral-atmospheric turbulence between 85 and 90 km. Furthermore, falling-sphere data imply that gravity wave breaking was a source for this turbulence. Mean motions and the various planetary, tidal, and gravity wave structures and their coherence and variability are the subjects of a companion paper. C1 PENN STATE UNIV, COMMUN & SPACE SCI LAB, UNIVERSITY PK, PA 16802 USA. GRAZ TECH UNIV, INST NACHRICHTENTECH & WELLENAUSBREITUNG, A-8010 GRAZ, AUSTRIA. NASA, GODDARD SPACE FLIGHT CTR, WALLOPS FLIGHT FACIL, WALLOPS ISL, VA 23337 USA. CORNELL UNIV, SCH ELECT ENGN, ITHACA, NY 14853 USA. UNIV COLORADO, ATMOSPHER & SPACE PHYS LAB, BOULDER, CO 80309 USA. RP Goldberg, RA (reprint author), NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, CODE 690, GREENBELT, MD 20771 USA. RI Goldberg, Richard /E-1881-2012; Lehmacher, Gerald/F-2653-2013 NR 22 TC 12 Z9 12 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 26179 EP 26190 DI 10.1029/96JD03653 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300037 ER PT J AU Fritts, DC Garten, JF Riggin, DM Goldberg, RA Lehmacher, GA Schmidlin, FJ McCarthy, S Kudeki, E Fawcett, CD Hitchman, MH Lieberman, RS Reid, IM Vincent, RA AF Fritts, DC Garten, JF Riggin, DM Goldberg, RA Lehmacher, GA Schmidlin, FJ McCarthy, S Kudeki, E Fawcett, CD Hitchman, MH Lieberman, RS Reid, IM Vincent, RA TI Equatorial dynamics observed by rocket, radar, and satellite during the CADRE/MALTED campaign .2. Mean and wave structures, coherence, and variability SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; ATMOSPHERE RESEARCH SATELLITE; GRAVITY-WAVE; MIDDLE ATMOSPHERE; SEMIANNUAL OSCILLATION; LOWER THERMOSPHERE; MOMENTUM FLUXES; LOWER STRATOSPHERE; AUGUST 1987; MST RADAR AB We present an analysis of the wind and temperature measurements made by rocket, radar, and satellite instrumentation in the equatorial and subtropical middle atmosphere accompanying the MALTED/CADRE campaign conducted at Alcantara, Brazil during August 1994. Measured mean winds and temperatures extended from similar to 10 to 110 km, exhibited general consistency between instruments, and revealed an oscillatory nature of the mean zonal wind with altitude at equatorial latitudes. MF radar measurements of tidal structures showed these to exhibit variability on similar to 8- and 16-day periods, but to be largely uncorrelated in time. Two-day wave structures displayed the same periodicities, but were well correlated among sites at northern and equatorial latitudes. Rocket and radar measurements at smaller scales of motion revealed inertia-gravity waves having significant temporal coherence, quadrature correlations between components indicating clear directions of propagation, and momentum flux and mean wind correlations indicative of gravity wave filtering processes. Rochet estimates of diurnal tidal amplitudes suggest that the diurnal tide achieves convectively unstable amplitudes in the upper equatorial mesosphere. C1 UNIV ILLINOIS, DEPT ELECT & COMP ENGN, CSRL, URBANA, IL 61801 USA. NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA. UNIV WISCONSIN, DEPT ATMOSPHER & OCEAN SCI, MADISON, WI 53706 USA. UNIV MICHIGAN, SPACE PHYS RES LAB, ANN ARBOR, MI 48109 USA. NASA, GODDARD SPACE FLIGHT CTR, WALLOPS FLIGHT FACIL, WALLOPS ISL, VA 23337 USA. UNIV ADELAIDE, DEPT PHYS & MATH PHYS, ADELAIDE, SA 5001, AUSTRALIA. UNIV COLORADO, PROGRAM ATMOSPHER & OCEAN SCI, BOULDER, CO 80309 USA. RP COLORADO RES ASSOCIATES NWRA, 3380 MITCHELL LANE, BOULDER, CO 80301 USA. RI Goldberg, Richard /E-1881-2012; Reid, Iain/B-5681-2012; Lehmacher, Gerald/F-2653-2013; OI Reid, Iain/0000-0003-2340-9047; Riggin, Dennis/0000-0001-5094-7620 NR 52 TC 13 Z9 13 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 26191 EP 26216 DI 10.1029/96JD03966 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300038 ER PT J AU Taylor, MJ Pendleton, WR Clark, S Takahashi, H Gobbi, D Goldberg, RA AF Taylor, MJ Pendleton, WR Clark, S Takahashi, H Gobbi, D Goldberg, RA TI Image measurements of short-period gravity waves at equatorial latitudes SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID UPPER MIDDLE ATMOSPHERE; OH NIGHTGLOW EMISSIONS; NEAR-INFRARED OH; LIDAR OBSERVATIONS; HORIZONTAL SCALES; PHASE VELOCITIES; OI(557.7 NM); AIRGLOW; PROPAGATION; SKY AB A high-performance, all-sky imaging system has been used to obtain novel data on the morphology and dynamics of short-period (<1 hour) gravity waves at equatorial latitudes. Gravity waves imaged in the upper mesosphere and lower thermosphere were recorded in three nightglow emissions, the near-infrared OH emission, and the visible wavelength OI (557.7 nm) and Na (589.2 nm) emissions spanning the altitude range similar to 80-100 km. The measurements were made from, Alcantara, Brazil (2.3 degrees S, 44.5 degrees W), during the period August-October 1994 as part of the NASA/Instituto Nacional de Pesquisas Espaciais ''Guara campaign''. Over 50 wave events were imaged from which a statistical study of the characteristics of equatorial gravity waves has been performed. The data were found to divide naturally into two groups. The first group corresponded to extensive, freely propagating (or ducted) gravity waves with observed periods ranging from 3.7 to 36.6 min, while the second group consisted of waves of a much smaller scale and transient nature. The later group exhibited a bimodal distribution for the observed periods at 5.18 +/- 0.26 min and 4.32 +/- 0.15 min, close to the local Brunt-Vaisala period and the acoustic cutoff period, respectively. In comparison, the larger-scale waves exhibited a clear tendency for their horizontal wavelengths to increase almost linearly with observed period. This trend was particularly well defined around the equinox and can be represented by a power-law relationship of the form lambda(h) = (3.1 +/- 0.5)tau(ob)(1.06+/-0.10), where lambda(h) is measured in kilometers and tau(ob) in minutes. This result is in very good agreement with previous radar and passive optical measurements but differs significantly from the relationship lambda(h) proportional to tau(ob)(1.5) inferred from recent lidar studies. The larger-scale waves were also found to exhibit strong anisotropy in their propagation headings with the dominant direction of motion toward the similar to NE-ENE suggesting a preponderance for wave generation over the South American continent. C1 UTAH STATE UNIV, DEPT PHYS, LOGAN, UT 84322 USA. INST NACL PESQUISAS ESPACIAIS, BR-12201970 S JOSE CAMPOS, SP, BRAZIL. NASA, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA. RP Taylor, MJ (reprint author), UTAH STATE UNIV, SPACE DYNAM LAB, ROOM 241, LOGAN, UT 84322 USA. RI Goldberg, Richard /E-1881-2012 NR 53 TC 88 Z9 88 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1997 VL 102 IS D22 BP 26283 EP 26299 DI 10.1029/96JD03515 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH593 UT WOS:A1997YH59300044 ER PT J AU Chertihin, GV Andrews, L Rosi, M Bauschlicher, CW AF Chertihin, GV Andrews, L Rosi, M Bauschlicher, CW TI Reactions of laser-ablated scandium atoms with dioxygen. Infrared spectra of ScO, OScO, (O-2)ScO, (ScO)(2), and Sc(O-2)(2) in solid argon SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID DENSITY-FUNCTIONAL CALCULATIONS; TRANSITION-METAL ATOMS; GAUSSIAN-BASIS SETS; OXYGEN MOLECULES; CONDENSING ARGON; IRON ATOMS; REACTION-PRODUCTS; MATRIX REACTIONS; GAS-PHASE; OXIDES AB Laser-ablated Sc atoms react with Oz during condensation in excess argon to give ScO, OScO, and (O-2)ScO as major products, which are identified from oxygen isotopic substitution on their matrix infrared spectra. The linear suboxide molecule ScOSc is a minor product. Annealing allows further association to form ScO3, (ScO)(2) and Sc(O-2)(2). The OScO molecule is bent: based on the oxygen-18 shift in the nu(3) mode, the valence angle is 128 +/- 4 degrees. The nu(3) fundamental of OScO at 722 cm(-1) is substantially lower than the ScO fundamental at 976 cm(-1), which is in accord with weaker bonds in the dioxide. Similar reactions in excess nitrogen give evidence of extensive ligation. C1 UNIV CHEM,DEPT CHEM,CHARLOTTESVILLE,VA 22901. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RI Rosi, Marzio/L-5748-2015 OI Rosi, Marzio/0000-0002-1264-3877 NR 55 TC 65 Z9 65 U1 0 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD NOV 27 PY 1997 VL 101 IS 48 BP 9085 EP 9091 DI 10.1021/jp972482f PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YK289 UT WOS:A1997YK28900014 ER PT J AU Feldman, WC Barraclough, BL Hansen, CJ Sprague, AL AF Feldman, WC Barraclough, BL Hansen, CJ Sprague, AL TI The neutron signature of Mercury's volatile polar deposits SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID HYDROGEN CONTENT; ICE; STABILITY; ANOMALIES; IMAGES; POLES AB Neutron leakage flux spectra are simulated to explore whether the nature of volatile deposits residing within the permanently shaded craters near the poles of Mercury can be identified using state-of-the-art space neutron detection techniques deployed aboard a flyby mission to Mercury. The most sensitive method for discriminating between H2O (ice)-rich and S-rich deposits involves measurement of the flux of epithermal neutrons. We conclude that a single flyby over crater Chao Meng-Fu at an altitude of 200 km is sufficient to detect a circular deposit rich in elemental sulfur at the 2.6 sigma statistical significance level, and that a similar deposit rich in H2O can be identified at the 7.8 sigma level. Whereas identification of a S-rich deposit is not unique but compelling because of auxiliary physical arguments, that of an H2O deposit is unique. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. RP Feldman, WC (reprint author), LOS ALAMOS NATL LAB,MS-D466,LOS ALAMOS,NM 87545, USA. NR 23 TC 19 Z9 19 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-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1997 VL 102 IS E11 BP 25565 EP 25574 DI 10.1029/97JE02353 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YK014 UT WOS:A1997YK01400001 ER PT J AU Mellon, MT AF Mellon, MT TI Small-scale polygonal features on Mars: Seasonal thermal contraction cracks in permafrost SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID POLYCRYSTALLINE ICE; GROUND ICE; WATER; TEMPERATURES; CREEP; SOIL AB A time-dependent viscoelastic model of thermal stress in Martian ice-rich permafrost is developed to test the hypothesis that small-scale polygonal features observed from orbit and by the Viking Lander 2 are the result of thermal contraction cracking, as commonly occurs in terrestrial permafrost. Results indicate that significant tensile stress occurs in Martian ice-rich permafrost as a result of seasonal cycles in the ground temperature. Using conservative rheological parameters appropriate for ice at low temperatures, tensile stresses poleward of about 20 degrees to 30 degrees latitude easily exceed the tensile strength (assumed to be 2 to 3 MPa) and fractures should readily form. In the equatorial regions, special conditions may allow tensile stresses to approach the tensile strength. These results support a thermal contraction origin of observed small-scale polygonal features and emphasize the utility of these features as valuable morphological indicators of ground ice. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RI Mellon, Michael/C-3456-2016 NR 55 TC 108 Z9 108 U1 0 U2 6 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 NOV 25 PY 1997 VL 102 IS E11 BP 25617 EP 25628 DI 10.1029/97JE02582 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YK014 UT WOS:A1997YK01400006 ER PT J AU Parker, TJ Rice, JW AF Parker, TJ Rice, JW TI Sedimentary geomorphology of the Mars Pathfinder landing site SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article AB The first landing on Mars in over 20 years will take place July 4, 1997, near the mouth of the Ares Vallis outflow channel located in southeastern Chryse Planitia. Mars Pathfinder, unlike Viking 1, is expected to land on a surface that has a distinct and unambiguous fluvial signature. For safety reasons, the landing site was selected within a broad plains region beyond the mouth of Ares Vallis so as to avoid large topographic obstacles that could pose hazards to the landing. However, this plain is not without its interesting, and in some cases rather problematic, landforms. The 100 km by 200 km landing ellipse contains the following features: (1) primary impact craters, (2) clusters of small secondary craters, (3) streamlined islands, (4) longitudinal grooves, (5) ''scabland'' or ''etched'' terrain, (6) pancake-like shields and dike-like structures, (7) knobs or buttes, and (8) a previously undetected, subtle undulating or hummocky texture to the plains surface. The nature of these landforms has important bearing on how we will interpret what we see at the scale of the Pathfinder lander once the first images are transmitted to Earth. With the exception of the craters, all of the remaining features described within the Mars Pathfinder landing ellipse can be interpreted as forming as a result of catastrophic flooding from Ares and Tiu Valles into Chryse Planitia, either during the flood itself, or through secondary modification of thick flood deposits after the event. C1 ARIZONA STATE UNIV,DEPT GEOG,TEMPE,AZ 85287. RP Parker, TJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183-501,PASADENA,CA 91109, USA. NR 28 TC 13 Z9 13 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-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1997 VL 102 IS E11 BP 25641 EP 25656 DI 10.1029/97JE02276 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YK014 UT WOS:A1997YK01400008 ER PT J AU VanKeuls, FW Romanofsky, RR Bohman, DY Winters, MD Miranda, FA Mueller, CH Treece, RE Rivkin, TV Galt, D AF VanKeuls, FW Romanofsky, RR Bohman, DY Winters, MD Miranda, FA Mueller, CH Treece, RE Rivkin, TV Galt, D TI (YBa2Cu3O7-delta,Au)/SrTiO3/LaAlO3 thin film conductor ferroelectric coupled microstripline phase shifters for phased array applications SO APPLIED PHYSICS LETTERS LA English DT Article ID MICROWAVE AB We report on the design, fabrication, and testing of novel YBa2Cu3O7-delta/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3/LaAlO3 (Au/STO/LAO) coupled microstrip line phase shifters (CMPS). These CMPS were tested at frequencies within the Ku and K bands (12-20 GHz), at temperatures from 24 to 77 K, and at de voltages (V-dc) from zero to 350 V. A relative insertion phase shift (Delta phi) of 390 degrees was measured for an eight-element YBCO/STO/LAO CMPS at V-dc=350 V, 16 GHz, and 40 K. At 77 K, a Delta phi similar to 260 degrees was obtained for the CMPS at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. At both temperatures, the phase shifter exhibits a figure of merit of similar to 30 degrees/dB. To our knowledge, these are the best results published so far at these frequencies where miniaturization, insertion loss, and phase delay are key considerations. (C) 1997 American Institute of Physics. C1 SCT,GOLDEN,CO 80401. CORNELL UNIV,DEPT ELECT ENGN,ITHACA,NY 14853. RP VanKeuls, FW (reprint author), NASA,LEWIS RES CTR,NATL RES COUNCIL,CLEVELAND,OH 44135, USA. NR 12 TC 118 Z9 118 U1 0 U2 5 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD NOV 24 PY 1997 VL 71 IS 21 BP 3075 EP 3077 DI 10.1063/1.120251 PG 3 WC Physics, Applied SC Physics GA YG834 UT WOS:A1997YG83400015 ER PT J AU Muller, HSP Miller, CE Cohen, EA AF Muller, HSP Miller, CE Cohen, EA TI The rotational spectrum and molecular properties of bromine dioxide, OBrO SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID EXCITED VIBRATIONAL-STATES; SPIN-ROTATION; RESONANCE SPECTRUM; CHLORINE DIOXIDE; SPECTROSCOPY; CONSTANTS; PHOTOISOMERIZATION; SUPEROXIDE; PARAMETERS; MILLIMETER AB The rotational spectrum of the OBrO radical has been observed in the gas phase over the solid products of the O+Br-2 reaction. Spectra have been measured for both (OBrO)-Br-79 and (OBrO)-Br-81 in their (000), (010), and (020) vibrational states in selected regions between 88 and 627 GHz spanning the quantum numbers 1 less than or equal to N less than or equal to 61 and 0 less than or equal to K-a less than or equal to 14. The spectra are well described by a Hamiltonian which includes centrifugal distortion effects for fine and hyperfine terms. The molecular structure, the dipole moment, and the harmonic force field have been derived, and they, as well as fine and hyperfine structure constants, are compared with data of related molecules and electron spin resonance data from OBrO isolated in cryogenic salt matrices. (C) 1997 American Institute of Physics. [S0021-9606(97)01544-4]. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. OI Mueller, Holger/0000-0002-0183-8927 NR 69 TC 45 Z9 45 U1 0 U2 1 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 NOV 22 PY 1997 VL 107 IS 20 BP 8292 EP 8302 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YG958 UT WOS:A1997YG95800007 ER PT J AU Kanik, I Beegle, L Noren, C Ahmed, SM Link, R AF Kanik, I Beegle, L Noren, C Ahmed, SM Link, R TI Temperature-dependent photoabsorption cross section measurements of O-2 at the NI airglow and auroral emission Lines SO CHEMICAL PHYSICS LETTERS LA English DT Article ID OXYGEN AB In this Letter, 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 NI airglow and auroral emission lines (at 1200, 1492 and 1742 Angstrom) in the far ultraviolet spectral region. A high-current low-voltage argon mini-are source was used as the light source in the present measurements. The measurements were carried out at a spectral resolution of 0.30 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 NI emission lines of interest. (C) 1997 Published by Elsevier Science B.V. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SW Res Inst, San Antonio, TX 78228 USA. RP Kanik, I (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Beegle, Luther/A-6354-2010 NR 9 TC 14 Z9 14 U1 2 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 NOV 21 PY 1997 VL 279 IS 5-6 BP 297 EP 302 DI 10.1016/S0009-2614(97)01077-4 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YL759 UT WOS:000070990000007 ER PT J AU Hui, L Gnedin, NY AF Hui, L Gnedin, NY TI Equation of state of the photoionized intergalactic medium SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE equation of state; intergalactic medium; quasars, absorption lines; cosmology, theory ID LYMAN-ALPHA FOREST; GRAVITATIONAL-INSTABILITY; COSMOLOGICAL CONSTANT; SCALE STRUCTURE; DARK MATTER; EVOLUTION; CLOUDS; MODEL; ABSORPTION; REDSHIFT AB We develop an efficient method of studying the effects of reionization history on the temperature-density relation of the intergalactic medium in the low-density limit (overdensity delta less than or similar to 5). It is applied to the study of photo-reionization models in which the amplitude, spectrum and onset epoch of the ionizing flux, as well as the cosmology: are systematically varied. We find that the mean temperature-density relation at z = 2-4 is well approximated by a power-law equation of state for uniform reionization models. We derive analytical expressions for its evolution and exhibit its asymptotic behaviour: it is found that for sufficiently early reionization, imprints of reionization history prior to z similar to 10 on the temperature-density relation are washed out. In this limit the temperature at the cosmic mean density is proportional to [Omega(b)h/root Omega(0)](1/1.7). While the amplitude of the radiation flux at the ionizing frequency of H I is found to have a negligible effect on the temperature-density relation as long as the universe reionizes before z similar to 5, the spectrum can change the overall temperature by about 20 per cent, through variations in the abundances of helium species. However, the slope of the mean equation of state is found to lie within a narrow range for all reionization models we study, where reionization takes place before z similar to 5, We discuss the implications of these findings for the observational properties of the Ly alpha forest. In particular, uncertainties in the temperature of the intergalactic medium, arising from the uncertain reionization history of our Universe, introduce a 30 per cent scaling in the amplitude of the column density distribution while the slope of the distribution is only affected by about 7 per cent. Finally, we discuss how a fluctuating ionizing field affects the above results. We argue that under certain conditions, the loss of memory of reionization history implies that at late times, the temperature-density relation of a gas in a fluctuating ionizing background can be approximated by one that results from a uniform radiation field, provided the universe reionizes sufficiently early. C1 UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. RP Hui, L (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,POB 500,BATAVIA,IL 60510, USA. NR 49 TC 395 Z9 395 U1 1 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 21 PY 1997 VL 292 IS 1 BP 27 EP 42 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YK356 UT WOS:A1997YK35600013 ER PT J AU DeNatale, P Lorini, L Inguscio, M Nolt, IG Park, JH DiLonardo, G Fusina, L Ade, PAR Murray, AG AF DeNatale, P Lorini, L Inguscio, M Nolt, IG Park, JH DiLonardo, G Fusina, L Ade, PAR Murray, AG TI Accurate frequency measurements for H2O and O-16(3) in the 119-cm(-1) OH atmospheric window SO APPLIED OPTICS LA English DT Article DE far-infrared spectroscopy; atmospheric molecules ID FAR-INFRARED-SPECTROSCOPY; MICROWAVE-SPECTRA; STRATOSPHERIC OH; OZONE; SPECTROMETER; SUBMILLIMETER; MILLIMETER; STATES; CM-1; THZ AB We report frequency measurements for relatively weak H2O and O-16(3) rotational transitions in the ground state and in the v(2) = 1 vibrationally excited state. We obtained the frequency measurements by using the laboratory technique of tunable far-infrared spectroscopy with the objective of improving H2O and O-3 line parameters required for modeling the important atmospheric spectral window near 119 cm(-1). New sets of molecular constants are calculated from the O-16(3) data, and improved values are reported for the frequencies of the H2O lines. The improvement in atmospheric simulations obtained with the new results is illustrated by comparison with recent high-resolution balloon-based atmospheric measurements. These new data significantly improve simulations of high-resolution atmospheric emission spectra. (C) 1997 Optical Society of America. C1 UNIV FLORENCE,DIPARTIMENTO FIS,EUROPEAN LAB NONLINEAR SPECT,I-50125 FLORENCE,ITALY. INFM,I-50125 FLORENCE,ITALY. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. UNIV BOLOGNA,DIPARTIMENTO CHIM FIS & INORGAN,I-40136 BOLOGNA,ITALY. UNIV LONDON QUEEN MARY & WESTFIELD COLL,DEPT PHYS,LONDON E1 4NS,ENGLAND. RP DeNatale, P (reprint author), IST NAZL OTTICA,DIPARTIMENTO SCI FIS,MOSTRA OLTREMARE PAD 19,I-80125 NAPLES,ITALY. OI De Natale, Paolo/0000-0002-3308-8569 NR 32 TC 10 Z9 11 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 NOV 20 PY 1997 VL 36 IS 33 BP 8526 EP 8532 DI 10.1364/AO.36.008526 PG 7 WC Optics SC Optics GA YF886 UT WOS:A1997YF88600002 PM 18264397 ER PT J AU Kokhanovsky, AA Macke, A AF Kokhanovsky, AA Macke, A TI Integral light-scattering and absorption characteristics of large, nonspherical particles SO APPLIED OPTICS LA English DT Article ID T-MATRIX COMPUTATIONS; ICE CRYSTALS; CIRRUS CLOUDS; RADIATIVE PROPERTIES; SINGLE-SCATTERING; SHAPES; SIZE AB We obtain and analyze simple analytical formulas for asymmetry parameters and absorption cross sections of large, nonspherical particles. The formulas are based on the asymptotic properties of these characteristics at strong and weak absorption of radiation inside particles. The absorption cross section depends on parameter phi, which determines the value of the light-absorption cross section for weakly absorbing particles. It is larger for nonspherical scatterers. The asymmetry parameter depends on two parameters. The first is the asymmetry parameter g(0) of a nonspherical, transparent particle with the same shape as an absorbing one. The second parameter, beta, determines the strength of the influence of light absorption on the value of the asymmetry parameter. Parameter beta is larger for nonspherical particles. One can find these three parameters (phi, g(0), and beta) using a ray-tracing code (RTC) for nonabsorbing and weakly absorbing particles. The RTC can then be used to check the accuracy of the equations at any absorption for hexagonal cylinders and spheroids. It is found that the error of computing the absorption cross section and 1 - g (g is the asymmetry parameter) is less than 20% at the refractive index of particles n = 1.333. Values for asymmetry parameters of large, nonabsorbing, spheroidal particles with different aspect ratios are tabulated for the first time to our knowledge. They do not depend on the size of particles and can serve as an independent check of the accuracy of T-matrix codes for large parameters. (C) 1997 Optical Society of America. C1 NATL SPACE DEV AGCY JAPAN,EARTH OBSERVAT RES CTR,MINATO KU,TOKYO 106,JAPAN. NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RI Kokhanovsky, Alexander/C-6234-2016 OI Kokhanovsky, Alexander/0000-0001-7370-1164 NR 21 TC 16 Z9 16 U1 0 U2 7 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD NOV 20 PY 1997 VL 36 IS 33 BP 8785 EP 8790 DI 10.1364/AO.36.008785 PG 6 WC Optics SC Optics GA YF886 UT WOS:A1997YF88600033 PM 18264428 ER PT J AU Bonnell, JT Norris, JP Nemiroff, RJ Scargle, JD AF Bonnell, JT Norris, JP Nemiroff, RJ Scargle, JD TI Brightness-independent measurements of gamma-ray burst durations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, observations; gamma rays, bursts; gamma rays, observations ID COSMOLOGICAL TIME DILATION; BATSE; DISTRIBUTIONS; EVOLUTION AB We demonstrate that a brightness bias exists in the third BATSE catalog duration measurements of cosmic gamma-ray bursts. This bias, caused by the fact that the outlying emission from bright bursts is easier to detect than from dim bursts, is sufficient to obscure a time-dilation factor of order 2. To avoid this problem, we construct brightness-independent measures of duration and apply them to a sample of long bursts containing no known brightness biases. We render all bursts to the same signal-to-noise ratio level, and thereby miss comparable amounts of temporal structure in both dim and bright bursts. We show that of two popular duration measures, T-50 and T-90, the former is to be preferred when the primary requirement is a comparison between bright and dim bursts. Our background subtraction approach involves the simultaneous examination of time profiles from all eight of the BATSE's large area detectors and all four energy channels, enabling us to identify appropriate background regions and to discriminate effectively between burst and nonburst emission. We report the first brightness-independent duration measurements over a continuous range of peak flux. These results indicate an increasing time-dilation factor with decreasing flux. We estimate that the energy dependence of the derived durations is relatively small. Under the cosmological hypothesis, a self-consistent treatment, including the corresponding energy correction implied by redshift, indicates that (1 + z(dim))/(1 + z(brt)) is similar to 2. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 28 TC 31 Z9 31 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 NOV 20 PY 1997 VL 490 IS 1 BP 79 EP 91 DI 10.1086/304841 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG999 UT WOS:A1997YG99900010 ER PT J AU Park, HS Ables, E Band, DL Barthelmy, SD Bionta, RM Butterworth, PS Cline, TL Ferguson, DH Fishman, GJ Gehrels, N Hurley, K Kouveliotou, C Lee, BC Meegan, CA Ott, LL Parker, EL AF Park, HS Ables, E Band, DL Barthelmy, SD Bionta, RM Butterworth, PS Cline, TL Ferguson, DH Fishman, GJ Gehrels, N Hurley, K Kouveliotou, C Lee, BC Meegan, CA Ott, LL Parker, EL TI Real-time optical flux limits from gamma-ray bursts measured by the gamma-ray optical counterpart search experiment SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts ID RELATIVISTIC FIREBALLS; X-RAY; SPECTRA; MODELS; RADIATION; EMISSION; ENERGY; GRB AB The Gamma-Ray Optical Counterpart Search Experiment presents new experimental upper limits on the optical flux from gamma-ray bursts (GRBs). Our experiment consisted of a fully automated very wide-held opto-electronic detection system that imaged locations of GRBs within a few seconds of receiving trigger signals provided by BATSE's real-time burst coordinate distribution network. The experiment acquired 3800 observing hours, recording 22 gamma-ray burst triggers within similar to 30 s of the start of the burst event. Some of these bursts were imaged while gamma-ray radiation was being detected by BATSE. We identified no optical counterparts associated with gamma-ray bursts among these events at the m(V) similar to 7.0-8.3 sensitivity level. We find the ratio of the upper limit to the V-band optical flux, F-nu, to the gamma-ray fluence, Phi(gamma), from these data to be 1 x 10(-18) < F-nu/Phi(gamma) < 2 x 10(-16). C1 UNIV CALIF SAN DIEGO,CASS 0424,LA JOLLA,CA 92093. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,COLUMBIA,MD. CALIF STATE UNIV HAYWARD,DEPT PHYS,HAYWARD,CA 94542. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV MICHIGAN,DEPT PHYS,ANN ARBOR,MI 48109. RP Park, HS (reprint author), LAWRENCE LIVERMORE NATL LAB,LIVERMORE,CA 94550, USA. RI Gehrels, Neil/D-2971-2012; Barthelmy, Scott/D-2943-2012 NR 56 TC 13 Z9 13 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 NOV 20 PY 1997 VL 490 IS 1 BP 99 EP 108 DI 10.1086/304860 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG999 UT WOS:A1997YG99900012 ER PT J AU Mukherjee, R Bertsch, DL Bloom, SD Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA McDonald, LM Michelson, PF vonMontigny, C Mucke, A Nolan, PL Pohl, M Reimer, O Schneid, E Sreekumar, P Thompson, DJ AF Mukherjee, R Bertsch, DL Bloom, SD Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA McDonald, LM Michelson, PF vonMontigny, C Mucke, A Nolan, PL Pohl, M Reimer, O Schneid, E Sreekumar, P Thompson, DJ TI EGRET observations of high-energy gamma-ray emission from blazars: An update SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; gamma rays, observations; quasars, general ID ACTIVE GALACTIC NUCLEI; TELESCOPE; RADIATION; 3C-279; JETS AB The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) has so far detected 51 blazars during phases 1, 2, and 3, and cycle 4 of the CGRO mission. We present here a summary of these observations, including flux variations and spectra of the blazars. The high luminosities and time variations seen in the gamma-ray data indicate that gamma rays are an important component of the relativistic jet thought to characterize blazars. C1 UNIV SPACE RES ASSOC,COLUMBIA,MD. MCGILL UNIV,DEPT PHYS,MONTREAL,PQ H3A 2T8,CANADA. UNIV UTAH,DEPT PHYS,SALT LAKE CITY,UT 84112. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. STANFORD UNIV,WW HANSEN EXPT PHYS LAB,STANFORD,CA 94305. HUGHES STX,LANHAM,MD. LANDESSTERNWARTE KONIGSTUHL,D-69117 HEIDELBERG,GERMANY. NORTHROP GRUMMAN CORP,BETHPAGE,NY 11714. RP Mukherjee, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 660,GREENBELT,MD 20771, USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; Reimer, Olaf/A-3117-2013 OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385 NR 57 TC 245 Z9 250 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 NOV 20 PY 1997 VL 490 IS 1 BP 116 EP 135 DI 10.1086/304851 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG999 UT WOS:A1997YG99900014 ER PT J AU Hollis, JM Pedelty, JA Kafatos, M AF Hollis, JM Pedelty, JA Kafatos, M TI Lateral shock of the R Aquarii jet SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (R Aquarii); ISM, jets and outflows; radio continuum, ISM; shock waves; ultraviolet, ISM ID SYSTEM; EMISSION; NEBULA AB The R Aqr jet was observed with the VLA B-configuration at two epochs separated by similar to 13.2 yr. Comparison of the resulting 6 cm continuum images show that the radio jet has undergone a lateral counterclockwise rotation of -6 degrees-12 degrees on the plane of the sky. The model of jet parcels on independent trajectories is difficult to reconcile with these observations and leads us to consider a path-oriented jet (i.e., younger parcels follow the same path as older parcels). Comparison of the most recent radio image with a nearly contemporaneous HST/FOC ultraviolet image at similar to 2330 Angstrom suggests that the ultraviolet emission lies along the leading side of the rotating radio jet. In conjunction with a proper motion analysis of the jet material that yields empirical space-velocity and resulting acceleration-magnitude relationships as a function of distance from the central source, we evaluate the observational results in terms of a schematic model in which the jet emission consists of plane-parallel isothermal shocks along the leading edge of rotation. In such a radiating shock, the ultraviolet-emitting region is consistent with the adiabatic region in the form of a high-temperature, low-density sheath that surrounds the cooled postshock radio-emitting region. Within the context of the schematic model, we obtain the temperatures, densities, and pressures within the preshock, adiabatic, and postshock regions as a function of distance from the central source; the physical parameters so derived compare favorably to previously published estimates. We obtain a total jet mass of 3.1 x 10(-5) M-. and an age of similar to 115 yr. We evaluate the model in the context of its density-boundary condition, its applicability to an episodic or quasi-continuous jet, and angular momentum considerations. C1 NASA, GODDARD SPACE FLIGHT CTR, BIOSPHER SCI BRANCH, GREENBELT, MD 20771 USA. GEORGE MASON UNIV, INST COMPUTAT SCI & INFORMAT, CTR EARTH OBSERVING & SPACE RES, FAIRFAX, VA 22030 USA. GEORGE MASON UNIV, DEPT PHYS, FAIRFAX, VA 22030 USA. RP Hollis, JM (reprint author), NASA, GODDARD SPACE FLIGHT CTR, DIV SPACE DATA & COMP, CODE 930, GREENBELT, MD 20771 USA. NR 37 TC 9 Z9 9 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 NOV 20 PY 1997 VL 490 IS 1 BP 302 EP + DI 10.1086/304844 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG999 UT WOS:A1997YG99900032 ER PT J AU Shore, SN Starrfield, S Ake, TB Hauschildt, PH AF Shore, SN Starrfield, S Ake, TB Hauschildt, PH TI Spatially resolved spectra of V1974 Cygni (nova Cygni 1992) with the Goddard high resolution spectrograph SO ASTROPHYSICAL JOURNAL LA English DT Article DE novae, cataclysmic variables; stars, individual (V1974 Cygni); ultraviolet, stars ID EVOLUTION; ULTRAVIOLET AB We report the observation of spatially resolved low-resolution GHRS spectra of the shell of the bright Galactic ONeMg nova Cygni 1992. The spectra were obtained in 1995 September, after the X-ray turnoff of the nova. We have determined the dynamical structure of the ejecta and show the evolution of the ionization within the ejecta. Abundance limits have been found to agree with the published analyses based on earlier IUE data for key species in the ejecta, especially neon. The knot spectrum, obtained with the 0.'' 25 aperture, shows an enhanced Ne/He ratio compared with the 2 '' aperture observation. These data provide a detailed picture of physical conditions and abundances of the knots and larger scale ejecta that have not previously been available from UV spectra, including those taken before the COSTAR installation and IUE data. The knots were created during the initial stages of the explosion, and the differential mixing that may have resulted can be studied using the spatially resolved spectra. The 1995 spectra were compared with archival Faint Object Spectrograph data from 1994 and previous GHRS spectra from 1992 and 1993. We also obtained high signal-to-noise ratio (S/N) observations of the UV continuum of the hot central star in order to study the physical conditions in the post-thermonuclear runaway envelope. These show that the white dwarf had relaxed to a very low effective temperature, about 20,000 K, and a luminosity of about 30 L., within 2 years after the X-ray turnoff. We also used reprocessed archival IUE spectra to determine the decay time for the ultraviolet continuum flux for this nova, which we find to be about 1.7 years. The current temperature and luminosity do not fall on the white dwarf cooling tracks for any reasonable stellar mass. C1 ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287. NASA,GODDARD SPACE FLIGHT CTR,COMP SCI CORP,GHRS SCI TEAM,GREENBELT,MD 20771. UNIV GEORGIA,DEPT PHYS & ASTRON,ATHENS,GA 30602. RP Shore, SN (reprint author), INDIANA UNIV,DEPT PHYS & ASTRON,S BEND,IN 46634, USA. NR 26 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 NOV 20 PY 1997 VL 490 IS 1 BP 393 EP 400 DI 10.1086/304850 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG999 UT WOS:A1997YG99900040 ER PT J AU Milano, LJ Gomez, DO Martens, PCH AF Milano, LJ Gomez, DO Martens, PCH TI Solar coronal heating: AC versus DC SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun, corona; turbulence ID MAGNETOHYDRODYNAMIC TURBULENCE; MAGNETIC LOOPS; ENERGY AB The heating of the plasma confined in active regions of the solar corona is caused by the dissipation of magnetic stresses induced by the photospheric motions of the loop footpoints. The aim of the present paper is to analyze whether solar coronal heating is dominated by slow (DC) or rapid (AC) photospheric driving motions. We describe the dynamics of a coronal loop through the reduced magnetohydrodynamic equations and assume a fully turbulent state in the coronal plasma. The boundary condition for these equations is the subphotospheric velocity field that stresses the magnetic field lines, thus replenishing the magnetic energy that is continuously being dissipated inside the corona. In a turbulent scenario, energy is efficiently transferred by a direct cascade to the microscale, where viscous and Joule dissipation take place. Therefore, for the macroscopic dynamics of the fields, the net effect of turbulence is to produce a dramatic enhancement of the dissipation rate. This effect of the microscale on the macroscale is modeled through effective dissipation coefficients much larger than the molecular ones. We consistently integrate the large-scale evolution of a coronal loop and compute the effective dissipation coefficients by applying a closure model (the eddy-damped, quasi-normal Markovian approximation). For broadband power-law photospheric power spectra, the heating of coronal loops is DC dominated. Nonetheless, a better knowledge of the photospheric power spectrum as a function of both frequency and wavenumber will allow for more accurate predictions of the heating rate from this simple model. C1 NASA,GODDARD SPACE FLIGHT CTR,SOHO EXPT OPERAT FACIL,ESA SPACE SCI DEPT,GREENBELT,MD 20771. UNIV BUENOS AIRES,DEPT PHYS,RA-1053 BUENOS AIRES,DF,ARGENTINA. RP Milano, LJ (reprint author), INST ASTRON & FIS ESPACIO,CC 67 SUC 28,RA-1428 BUENOS AIRES,DF,ARGENTINA. OI Gomez, Daniel/0000-0002-4935-4358 NR 24 TC 35 Z9 36 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 NOV 20 PY 1997 VL 490 IS 1 BP 442 EP 451 DI 10.1086/304845 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG999 UT WOS:A1997YG99900046 ER PT J AU Dwyer, JR Mason, GM Mazur, JE Jokipii, JR vonRosenvinge, TT Lepping, RP AF Dwyer, JR Mason, GM Mazur, JE Jokipii, JR vonRosenvinge, TT Lepping, RP TI Perpendicular transport of low-energy corotating interaction region-associated nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; diffusion; interplanetary medium; magnetic fields; solar wind ID SOLAR-WIND; COSMIC-RAYS; ACCELERATION; INSTRUMENT; TURBULENCE; SPACECRAFT; PARTICLES AB We present compelling observational evidence for substantial transport of energetic charged particles across the local average magnetic field. Using data from the STEP/EPACT instrument on board the Wind spacecraft, we find that during three intense corotating interaction region (CIR) events, for periods greater than 12 hr, the observed anisotropy of the particle intensity at 1 AU is often directed at a significant angle to the measured magnetic field direction, which implies significant transport across the local magnetic field. A simple diffusion model is found to fit the three events very well with a large inferred kappa(perpendicular to)/kappa(parallel to). For example, for 80-154 keV nucleon(-1) helium, we find that kappa(perpendicular to)/kappa(parallel to) = 1.47 +/- 0.07, kappa(perpendicular to)/kappa(parallel to) = 0.13 +/- 0.02, and kappa(perpendicular to)/kappa(parallel to) = 0.45 +/- 0.05 for the most intense periods of the three events. We believe that this is the first direct, quantitative measurement in space of large cross-field particle transport, utilizing simultaneous measurements of the streaming particle flux, the solar wind velocity and the magnetic field direction. C1 UNIV ARIZONA,DEPT PLANETARY SCI,TUCSON,AZ 85721. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MARYLAND,INST PHYS SCI & TECHNOL,COLLEGE PK,MD 20742. RP Dwyer, JR (reprint author), UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742, USA. NR 30 TC 68 Z9 69 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 NOV 20 PY 1997 VL 490 IS 1 BP L115 EP L118 DI 10.1086/311003 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YH001 UT WOS:A1997YH00100028 ER PT J AU Park, HS Williams, GG Ables, E Band, DL Barthelmy, SD Bionta, R Butterworth, PS Cline, TL Ferguson, DH Fishman, GJ Gehrels, N Hartmann, D Hurley, K Kouveliotou, C Meegan, CA Ott, L Parker, E Wurtz, R AF Park, HS Williams, GG Ables, E Band, DL Barthelmy, SD Bionta, R Butterworth, PS Cline, TL Ferguson, DH Fishman, GJ Gehrels, N Hartmann, D Hurley, K Kouveliotou, C Meegan, CA Ott, L Parker, E Wurtz, R TI New constraints on simultaneous optical emission from gamma-ray bursts measured by the Livermore Optical Transient Imaging System experiment SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts ID BATSE AB LOTIS is a gamma-ray burst optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. Since operations began in 1996 October, LOTIS has responded to five triggers as of 1997 July 30, which occurred during good weather conditions. GRB 970223 (BATSE trigger 6100) was an exceptionally strong burst, lasting similar to 30 s with a peak at similar to 8 s. LOTIS began imaging the error box similar to 11 s after the burst began and achieved simultaneous optical coverage of 100% of the region enclosed by the BATSE 3 sigma error circle and the interplanetary network annulus. No optical transients were observed brighter than the m(V) similar to 11 completeness limit of the resulting images, providing a new upper limit on the ratio of simultaneous optical to gamma-ray fluence of R-L < 1.1 x 10(-4) and on the ratio of simultaneous optical (at 700 nm) to gamma-ray (at 100 keV) flux density of R-F < 305 for a B-type spectrum and R-F < 475 for an M-type spectrum. C1 CLEMSON UNIV,DEPT PHYS & ASTRON,CLEMSON,SC 29634. UNIV CALIF SAN DIEGO,CASS 0424,LA JOLLA,CA 92093. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,COLUMBIA,MD. CALIF STATE UNIV HAYWARD,DEPT PHYS,HAYWARD,CA 94542. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. RP Park, HS (reprint author), LAWRENCE LIVERMORE NATL LAB,LIVERMORE,CA 94550, USA. RI Gehrels, Neil/D-2971-2012; Barthelmy, Scott/D-2943-2012 NR 18 TC 18 Z9 18 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 NOV 20 PY 1997 VL 490 IS 1 BP L21 EP L24 DI 10.1086/311020 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YH001 UT WOS:A1997YH00100006 ER PT J AU Serabyn, E Carlstrom, J Lay, O Lis, DC Hunter, TR Lacy, JH Hills, RE AF Serabyn, E Carlstrom, J Lay, O Lis, DC Hunter, TR Lacy, JH Hills, RE TI High-frequency measurements of the spectrum of Sagittarius A* SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, nuclei; galaxy, center ID GALACTIC-CENTER; BLACK-HOLE; ANATOMY; COMPLEX; CAVITY; VLBI; FLUX AB We report near-simultaneous interferometric measurements of the spectrum of Sagittarius A* over the 5-354 GHz range and single-dish observations that have yielded the first detection of Sgr A* at 850 GHz. We confirm that Sgr A*'s spectrum rises more steeply at short millimeter wavelengths than at centimeter wavelengths, leading to a near-millimeter/submillimeter excess that dominates its luminosity. Below 900 GHz, Sgr A*'s observed luminosity is 70 +/- 30 L.. A new upper limit to Sgr A*'s 24.3 mu m flux, together with a compilation of other extant IR data, imply a far-infrared spectral turnover, which can result from either an intrinsic synchrotron cutoff or excess extinction near Sgr A*. If the former applies, Sgr A*'s total synchrotron luminosity is <10(3) L., while in the latter case it is <3 x 10(4) L. if spherical symmetry also applies. C1 UNIV CHICAGO, DEPT ASTRON & ASTROPHYS, CHICAGO, IL 60637 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. SMITHSONIAN ASTROPHYS OBSERV, CAMBRIDGE, MA 02138 USA. UNIV TEXAS, AUSTIN, TX 78712 USA. MULLARD RADIO ASTRON OBSERV, CAMBRIDGE CB3 OHE, ENGLAND. CALTECH, PASADENA, CA 91125 USA. OI Hunter, Todd/0000-0001-6492-0090 NR 29 TC 73 Z9 73 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1997 VL 490 IS 1 BP L77 EP + DI 10.1086/311010 PN 2 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YH001 UT WOS:A1997YH00100019 ER PT J AU White, NE Zhang, W AF White, NE Zhang, W TI Millisecond X-ray pulsars in low-mass X-ray binaries SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, neutron; stars, rotation; X-rays, stars ID MAGNETIC-FIELD; NEUTRON-STARS; SCORPIUS X-1; ACCRETION; EVOLUTION AB The discovery of millisecond X-ray pulsars in low-mass X-ray binaries (LMXRBs) with the Rossi X-Ray Timing Explorer (RXTE) has resulted in the determination of the neutron star spin periods to be in a very narrow period range. Based on evolutionary models for LMXRBs, it is likely that these pulsars have accreted sufficient material to be at or close to their equilibrium spin periods. If this is the case, then the similar neutron star rotation periods over 2 orders of magnitudes in observed luminosity require a comparable magnetospheric radius in all these systems to give a similar spin period. This means that either there is a correlation between surface magnetic field strength and X-ray luminosity (B proportional to L-X(1/2) for the commonly used magnetospheric scaling for a gas pressure dominated accretion disk) or, if the neutron star surface magnetic field is comparable in all cases, the magnetospheric radius is very weakly dependent on the accretion rate in the inner radiation-dominated disk relevant to this regime. We suggest that the anomalous case of Sco X-1, where there is an apparent change in the inferred neutron star spin period, may be understood in terms of the radiation-driven expansion of the neutron star photosphere by up to 30%. RP White, NE (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 32 TC 77 Z9 77 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 NOV 20 PY 1997 VL 490 IS 1 BP L87 EP L90 DI 10.1086/311018 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YH001 UT WOS:A1997YH00100021 ER PT J AU Yaqoob, T McKernan, B Ptak, A Nandra, K Serlemitsos, PJ AF Yaqoob, T McKernan, B Ptak, A Nandra, K Serlemitsos, PJ TI A simple new method for analyzing gapped time series: Search for a high-frequency cutoff in the x-ray power spectrum of the Seyfert galaxy MCG-6-30-15 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (MCG -6-30-15); methods, data analysis; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; VARIABILITY; EMISSION; AMPLITUDE; NGC-4151 AB We present a new, simple method for analyzing gapped time series that is particularly suited to probe the Xray power spectra of active galactic nuclei (AGNs). The method is applied to a 4 day observation of the Seyfert 1 galaxy MCG -6-30-15 with ASCA (Advanced Satellite for Cosmology and Astrophysics). MCG -6-30-15 is well known for rapid, large-amplitude X-ray variability and was one of the first AGNs to show evidence of relativistic effects in its Fe-K line profile. In this source, our method probes the power spectrum in the range 10(-3)-5 x 10(-2) Hz, thus extending the high-frequency coverage by a factor of over 50 compared to previous studies. The ASCA data rule out a cessation of variability up to 1.6 x 10(-2) Hz at greater than 90% confidence. The power-law index of the power spectrum in this range is consistent with similar to-1.4. At 2.1 x 10(-2) Hz we can place an upper limit of 7% on the intrinsic fluctuations of the source luminosity at greater than 99% confidence. Above this frequency Poisson noise becomes dominant, but we can place an upper limit of 10% on intrinsic fluctuations up to 5 x 10(-2) Hz at 98.9% confidence. The data argue against orbital modulation as the origin of the variability since it would imply upper limits on the mass of the putative black hole of less than 5 x 10(5) M., and therefore super-Eddington luminosities. C1 UNIV LEEDS,DEPT PHYS,LEEDS LS2 9JT,W YORKSHIRE,ENGLAND. UNIV SPACE RES ASSOC,COLUMBIA,MD. UNIV MARYLAND,COLLEGE PK,MD 20742. RP Yaqoob, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 662,GREENBELT,MD 20771, USA. NR 15 TC 26 Z9 26 U1 1 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 NOV 20 PY 1997 VL 490 IS 1 BP L25 EP L28 DI 10.1086/311014 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YH001 UT WOS:A1997YH00100007 ER PT J AU Eck, TF Deering, DW Vierling, LA AF Eck, TF Deering, DW Vierling, LA TI Arctic tundra albedo and its estimation from spectral hemispheric reflectance SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID PHOTOSYNTHETICALLY ACTIVE RADIATION; BIDIRECTIONAL REFLECTANCE; SOLAR-RADIATION; SURFACE; MODEL; IRRADIANCE; COMPONENTS; RADIANCE; DIFFUSE; CLIMATE AB We present the results of a held experiment in which the nearly complete bidirectional reflectance distribution function of Alaskan arctic tundra sites early in the growing season is measured by the PARABOLA instrument. The spectral hemispheric reflectances were computed by angular integration of these measurements for three wavebands: red (650-670 nm), near-infrared (810-840 nm) and shortwave infrared (1620-1690 nm). Total albedo was then estimated by weighting the spectral hemispheric reflectances by the fraction of total solar inadiance in three broadband spectral regions (300-700, 700-1300 and 1300-4000 nm) and representing each spectral region by the narrowband PARABOLA measurements. These calculations resulted in albedo estimates with a mean relative error of 15.7 per cent as compared to pyranometer measured albedo. Since vegetation reflectance varies signifrcantly over each of the three broadband regions, additional reflectance weighting factors were computed from a combination of high spectral resolution canopy reflectance data and corresponding computed spectral solar irradiance. This additional reflectance weighting resulted in a reduction in the mean relative error to 7.5 per cent relative to pyranometer measured albedo. It is noted that the three spectral bands of the PARABOLA instrument data reported here are similar to those of the spectral wavebands planned for future Advanced Very High Resolution Radiometer (AVHRR) sensors on National Oceanic and Atmospheric Administration (NOAA) satellites. Therefore the results and techniques presented here may be useful for future global albedo estimation utilizing AVHRR sensors. The analysis presented here may also be applied to albedo estimation from satellite sensors with higher spectral resolution and more complete spectral coverage, such as the future orbiting MODIS sensor, in which the errors of spectral reflectance weighting will be reduced considerably due to a more complete sampling of the reflected spectrum. C1 UNIV COLORADO,DEPT ENVIRONM POPULAT & ORGANISM BIOL,CSES,CIRES,BOULDER,CO 80309. RP Eck, TF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,CODE 923,GREENBELT,MD 20771, USA. RI ECK, THOMAS/D-7407-2012; Vierling, Lee/E-6428-2010 OI Vierling, Lee/0000-0001-5344-1983 NR 30 TC 7 Z9 7 U1 0 U2 2 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD NOV 20 PY 1997 VL 18 IS 17 BP 3535 EP 3549 DI 10.1080/014311697216784 PG 15 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA YG764 UT WOS:A1997YG76400002 ER PT J AU Beratan, KK Peer, B Dunbar, NW Blom, R AF Beratan, KK Peer, B Dunbar, NW Blom, R TI A remote sensing approach to alteration mapping: AVIRIS data and extension-related potassium metasomatism, socorro, New Mexico SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID VOLCANIC-ROCKS; UNITED-STATES; ARIZONA; CALIFORNIA AB Miocene crustal extension in the south-western United States was accompanied by potassium metasomatism, a type of alteration marked by addition of large amounts of potassium at the expense of other constituents, notably sodium. The fluids responsible for the potassic alteration may have played a role in triggering extensional fault motion; one way to determine this is to compare the geographic distribution of the alteration to fault and sedimentary facies maps. Despite the large impact on rock composition, however, the alteration is visually subtle and difficult to map in the field. In this paper we present a preliminary alteration map of the Lemitar Mountains near Socorro, New Mexico, within the Rio Grande rift. This map was created from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data. The potential to discriminate potassium metasomatism in Landsat Thematic Mapper satellite data is part of the motivation for this study, since such data are widely available. Although the potassic minerals do not exhibit spectral features in the visible and near-infrared, iron was mobilized during potassium metasomatism, and the distribution of haematite thus serves as a proxy for the potassium. Evidence supporting the proxy relationship between haematite and metasomatism include (a) published reports by previous workers stating that haematite is added to rocks during K-metasomatism; (b) limited chemical evidence that samples collected from areas displaying a distinctive spectral response are strongly metasomatized; (c) the presence of large amounts of haematite in metasomatized rocks, observed petrographically and with an EDAX microprobe; and (d) the coincidence of the southern edge of the K-anomaly in the Lemitar Mountains as defined by chemical analysis and the southernmost occurrence of the anomalous spectral response. No other significant source of haematite has been reported from this area. Manganese oxide, occurring as localized veins or as rock varnish, is black in colour and highly absorptive, resulting in a distinctly different spectral response than the metasomatism-related haematite. This work shows that K-metasomatism can be mapped using AVIRIS data. The spectral response is not subtle, and can be observed in Landsat Thematic Mapper data; it is likely that K-metasomatism can be mapped, at least to some significant degree, from the Landsat data. Ongoing work is focusing on calibrating the strength of the spectral response to the intensity of alteration. C1 NEW MEXICO BUR MINES & MINERAL RESOURCES,SOCORRO,NM 87801. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Beratan, KK (reprint author), UNIV PITTSBURGH,EH 321,PITTSBURGH,PA 15260, USA. NR 22 TC 7 Z9 8 U1 0 U2 2 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD NOV 20 PY 1997 VL 18 IS 17 BP 3595 EP 3609 DI 10.1080/014311697216829 PG 15 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA YG764 UT WOS:A1997YG76400006 ER PT J AU Hegg, DA Livingston, J Hobbs, PV Novakov, T Russell, P AF Hegg, DA Livingston, J Hobbs, PV Novakov, T Russell, P TI Chemical apportionment of aerosol column optical depth off the mid-Atlantic coast of the United States SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DIFFUSION DENUDER SAMPLER; ATMOSPHERIC AEROSOLS; VERTICAL PROFILES; GREENHOUSE GASES; EXTINCTION; PARTICLE; CLIMATE; RELEVANT; SULFATE; SYSTEM AB Aerosol column optical depths derived from airborne Sun photometer and in situ measurements of aerosol properties in 14 vertical profiles off the mid-Atlantic coast of the United States in June show excellent agreement. Simultaneous measurements of the chemical compositions of the aerosol allows an assessment of the chemical apportionment of the aerosol column optical depths. The optical depths had essentially three chemical components, which, in order of descending average contributions, were condensed water, carbonaceous species, and sulfate. These results do not support the common assumption that sulfate dominates aerosol optical depths in polluted regions. C1 SRI INT, MENLO PK, CA 94025 USA. UNIV CALIF BERKELEY, LAWRENCE BERKELEY LAB, BERKELEY, CA 94720 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Hegg, DA (reprint author), UNIV WASHINGTON, DEPT ATMOSPHER SCI, BOX 351640, SEATTLE, WA 98195 USA. NR 41 TC 203 Z9 204 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1997 VL 102 IS D21 BP 25293 EP 25303 DI 10.1029/97JD02293 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH548 UT WOS:A1997YH54800003 ER PT J AU Volk, CM Elkins, JW Fahey, DW Dutton, GS Gilligan, JM Loewenstein, M Podolske, JR Chan, KR Gunson, MR AF Volk, CM Elkins, JW Fahey, DW Dutton, GS Gilligan, JM Loewenstein, M Podolske, JR Chan, KR Gunson, MR TI Evaluation of source gas lifetimes from stratospheric observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CARBON-DIOXIDE; NITROUS-OXIDE; 3-DIMENSIONAL SIMULATIONS; ATMOSPHERIC LIFETIMES; OZONE DEPLETION; GROWTH-RATES; TRANSPORT; N2O; AGE; AIR AB Simultaneous in situ measurements of the long-lived trace species N2O, CH4, CFC-12, CFC-113, CFC-11, CCl4, CH3CCl3, H-1211, and SF6 were made in the lower stratosphere and upper troposphere on board the NASA ER-2 high-altitude aircraft during the 1994 campaign Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft. The observed extratropical tracer abundances exhibit compact mutual correlations that show little interhemispheric difference or seasonal variability except at higher altitudes in southern hemisphere spring. The environmental impact of the measured source gases depends, among other factors, on the rate at which they release ozone-depleting chemicals in the stratosphere, that is, on their stratospheric lifetimes. We calculate the mean age of the air from the SF6 measurements and show how stratospheric lifetimes of the other species may be derived semiempirically from their observed gradients with respect to mean age at the extratropical tropopause. We also derive independent stratospheric lifetimes using the CFC-11 lifetime and the slopes of the tracer's correlations with CFC-11. In both cases, we correct for the influence of tropospheric growth on stratospheric tracer gradients using the observed mean age of the air, time series of observed tropospheric abundances, and model-derived estimates of the width of the stratospheric age spectrum. Lifetime results from the two methods are consistent with each other. Our best estimates for stratospheric lifetimes are 122 +/- 24 years for N2O, 93 +/- 18 years for CH4, 87 +/- 17 years for CFC-12, 100 +/- 32 years for CFC-113, 32 +/- 6 years for CCl4, 34 +/- 7 years for CH3CCl3, and 24 +/- 6 years for H-1211. Most of these estimates are significantly smaller than currently recommended lifetimes, which are based largely on photochemical model calculations. Because the derived stratospheric lifetimes are identical to atmospheric lifetimes for most of the species considered, the shorter lifetimes would imply a faster recovery of the ozone layer following the phaseout of industrial halocarbons than currently predicted. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NOAA, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV COLORADO, COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80309 USA. RI Gilligan, Jonathan/I-8938-2014; Fahey, David/G-4499-2013 OI Gilligan, Jonathan/0000-0003-1375-6686; Fahey, David/0000-0003-1720-0634 NR 82 TC 140 Z9 140 U1 1 U2 13 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1997 VL 102 IS D21 BP 25543 EP 25564 DI 10.1029/97JD02215 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH548 UT WOS:A1997YH54800022 ER PT J AU Chertihin, GV Citra, A Andrews, L Bauschlicher, CW AF Chertihin, GV Citra, A Andrews, L Bauschlicher, CW TI Reactions of laser-ablated cobalt atoms with O-2. Infrared spectra of cobalt oxides in solid argon SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; DENSITY-FUNCTIONAL CALCULATIONS; OXYGEN MOLECULES; GROUND-STATE; IRON ATOMS; CONDENSING ARGON; MATRIX; COO; SPECTROSCOPY; PRODUCTS AB Laser-ablated Co atoms react with Oz to give the linear dioxide, the monoxide, and the rhombic (CoO)(2) dimer molecules. The linear OCoO molecule is characterized by oxygen-18 substitution in strong nu(3) (945.4 cm-(1)) fundamental and weak nu(1)+nu(3) (1717.6 cm(-1)) combination bands. Annealing to 20-30 K to allow diffusion and reaction of cold cobalt atoms and dioxygen markedly increases weak bands due to the Co(Oz) and CoOO complexes and higher species including OOCoO, OOCoO2, (O-2)CoO2, and the dimer (CoO2)(2) DFT and CASSCF calculations performed on the three CoO2 isomers and rhombic (CoO)(2) support these assignments; DFT calculations are also presented for the rhombic (FeO)(2) molecule. C1 UNIV VIRGINIA,DEPT CHEM,CHARLOTTESVILLE,VA 22901. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 48 TC 67 Z9 67 U1 1 U2 15 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD NOV 20 PY 1997 VL 101 IS 47 BP 8793 EP 8802 DI 10.1021/jp972022m PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YH530 UT WOS:A1997YH53000007 ER PT J AU Ricca, A Bauschlicher, CW AF Ricca, A Bauschlicher, CW TI Successive OH binding energies of M(OH)(n)(+) for n=1-3 and M=Sc, Ti, V, Co, Ni, and Cu SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; ORBITAL BASIS-SETS; MOLECULAR CALCULATIONS; ROW ATOMS; ELECTRON CORRELATION; TRANSITION-METALS; WAVE-FUNCTIONS; BOND-ENERGIES; CONTRACTION AB The M(OH)(n)(+) geometries, for n = 1-3, have been optimized and the zero-point energies computed using the B3LYP approach. The calculations show that strong bonds are formed for the early metals, and much weaker bonds are formed for the late metal atoms. The successive OH bond energies have been computed at the CCSD(T) level for n = 1 and 2. The M+-OH bond energies are in good agreement with the guided ion beam results. This implies that the CID values for TiOH+, VOH+, and CoOH+, and the photodissociation value for CoOH+ are accurate, but that the CID values for ScOH+ and NiOH+ are too small. The B3LYP binding energies are found to be in qualitative agreement with the CCSD(T) results. The relative size of the first and second OH binding energies at the B3LYP level disagrees with the CCSD(T) for Sc+, Ti+, and V+ The B3LYP results show that the third OH binding energy for Ti+ and V+ will be large (85 kcal/mol, or more), while for the remaining systems the third OH is electrostatically bound, with a binding energy of only about 30 kcal/mol. RP Ricca, A (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 33 TC 56 Z9 56 U1 1 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD NOV 20 PY 1997 VL 101 IS 47 BP 8949 EP 8955 DI 10.1021/jp972531o PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YH530 UT WOS:A1997YH53000028 ER PT J AU Gawronski, W AF Gawronski, W TI Actuator and sensor placement for structural testing and control SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID FLEXIBLE STRUCTURES; SELECTION; SYSTEMS AB In this paper, the actuator and sensor locations of a structural test item are selected as a replacement of the disturbance inputs and the performance outputs of areal structure. The most straightforward approach is to place sensors in the areas of performance evaluation, and actuators in the areas of disturbance action. However, this solution is rarely possible due to technical and economical reasons. Therefore, the actuators and sensors need to be placed in preselected regions, and should duplicate as close as possible the disturbance action and the performance measurements. In this paper a placement problem with non-collocated actuators and disturbances, as well as non-collocated performance and sensor outputs, is solved. The solution is determined by locating sensors (actuators) such that the Hankel singular value vector of a structure from actuator inputs to sensor outputs is closely correlated with the Hankel singular value vector of the structure from the disturbance inputs to performance outputs. It is shown that this approach improves additionally the cross-coupling between actuators and performance, and between disturbances and the sensors, thus improving overall closed loop performance. The method is illustrated with the determination of sensors of a truss structure, where two selected sensors replaced an original set of 36 sensors. (C) 1997 Academic-Press Limited. RP Gawronski, W (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 14 TC 43 Z9 46 U1 0 U2 3 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 NOV 20 PY 1997 VL 208 IS 1 BP 101 EP 109 DI 10.1006/jsvi.1997.1190 PG 9 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA YK827 UT WOS:A1997YK82700007 ER PT J AU Chuang, KC Kinder, JD Hull, DL McConville, DB Youngs, WJ AF Chuang, KC Kinder, JD Hull, DL McConville, DB Youngs, WJ TI Rigid-rod polyimides based on noncoplanar 4,4'-biphenyldiamines: A review of polymer properties vs configuration of diamines SO MACROMOLECULES LA English DT Article ID POLYESTERS; CRYSTALLINE; DIANHYDRIDE; POLYAMIDES; FIBERS; UNITS AB X-ray crystal structures of three substituted 4,4'-biphenyldiamines, namely, 2,2',6,6'-tetramethylbenzidine (TMBZ), 2,2'-dimethylbenzidine (DMBZ) and 2,2'-bis(trifluoromethyl)benzidine (BFBZ), were determined. The torsional angles between the two phenyl rings for TMBZ, DMBZ, and BFBZ are phi = 83 degrees, 75 degrees, and 59 degrees, respectively. A structure-property relationship between the three-dimensional configuration of diamine monomers End the corresponding polyimides is discussed. C1 UNIV AKRON,DEPT CHEM,AKRON,OH 44325. RP Chuang, KC (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 24 TC 25 Z9 25 U1 2 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD NOV 17 PY 1997 VL 30 IS 23 BP 7183 EP 7190 DI 10.1021/ma970309b PG 8 WC Polymer Science SC Polymer Science GA YH247 UT WOS:A1997YH24700022 ER PT J AU Han, J Jaffe, RL Yoon, DY AF Han, J Jaffe, RL Yoon, DY TI Conformational characteristics of polymethylene chains in melts and in various phantom chains from explicit atom molecular dynamics simulations SO MACROMOLECULES LA English DT Article ID ANGLE NEUTRON-SCATTERING; MONTE-CARLO SIMULATION; TEMPERATURE-DEPENDENCE; BROWNIAN DYNAMICS; THETA-CONDITIONS; N-ALKANES; POLYMER; POLYETHYLENE; 1,2-DIMETHOXYETHANE; CONFIGURATIONS AB Conformer populations, man-square chain dimensions, and end-to-end distance distributions for polymethylene (PM) chains, H(CH2)(n)H with n = 13, 44, and 100, in melts and in various phantom chains have been studied using a parallel computational method of molecular (and Brownian) dynamics simulations with a well-calibrated explicit atom force field. The specific volume-temperature properties of the simulated melt systems are in excellent agreement with experiments. Conformational characteristics of PM chains in melts are identical to those of 1,5 phantom chains, characterized by short-range intramolecular interactions between the atoms separated by up to four skeletal bonds, which correspond to unperturbed chains in Theta solvents according to recent implicit solvent model results of Sariban et al. and Destree et al. Moreover, a Gaussian approximation of end-to-end distance distributions is found to be valid only for long PM chains with n greater than 100. According to our simulation results, the characteristic ratio C-infinity for unperturbed polyethylene chains is found to be ca. 7.9 at 413 K. This value is larger than the generally accepted value? 6.8 (derived from intrinsic viscosity data for relatively polydisperse polyethylene samples), but is corroborated by recent small angle neutron scattering results (7.8 +/- 0.4) for melt chains of nearly monodisperse samples. The fact that; PM chains exhibit identical conformational characteristics in melts, 1,5 phantom chains, and Theta solvents is attributed to the lack of any correlation between local chain conformations and (polymer-polymer or polymer-solvent) intermolecular attractions. Departures from such an ideal behavior seen for other polymers are also discussed. C1 IBM CORP,ALMADEN RES CTR,SAN JOSE,CA 95120. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 44 TC 28 Z9 28 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD NOV 17 PY 1997 VL 30 IS 23 BP 7245 EP 7252 DI 10.1021/ma961772b PG 8 WC Polymer Science SC Polymer Science GA YH247 UT WOS:A1997YH24700031 ER PT J AU Newman, PA Gleason, JF McPeters, RD Stolarski, RS AF Newman, PA Gleason, JF McPeters, RD Stolarski, RS TI Anomalously low ozone over the Arctic SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WINTER; STRATOSPHERE AB Total ozone observations from the Total Ozone Mapping Spectrometer (TOMS) instruments during March 1997 reveal an extensive region of low column densities in the Arctic region centered near the north pole. Values were below 250 Dobson units for nearly a two week period during this period, and were correlated with the position of the northern lower stratospheric polar vortex. The March 1997 average total ozone column densities were more than 30% lower than the average of column densities observed during the 1979-1982 March period. RP Newman, PA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA. RI Newman, Paul/D-6208-2012; Gleason, James/E-1421-2012; Stolarski, Richard/B-8499-2013; McPeters, Richard/G-4955-2013 OI Newman, Paul/0000-0003-1139-2508; Stolarski, Richard/0000-0001-8722-4012; McPeters, Richard/0000-0002-8926-8462 NR 15 TC 147 Z9 153 U1 0 U2 4 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 NOV 15 PY 1997 VL 24 IS 22 BP 2689 EP 2692 DI 10.1029/97GL52831 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900001 ER PT J AU Coy, L Nash, ER Newman, PA AF Coy, L Nash, ER Newman, PA TI Meteorology of the polar vortex: Spring 1997 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERE; OZONE; WINTER AB The 1996-1997 northern hemisphere spring polar vortex was very strong, cold, and symmetric, somewhat similar to those found in the Antarctic spring vortex. The vortex did not form until late in December and was very symmetric from February into late April. The spring vortex was characterized by record low temperatures, record low ozone amounts as measured from the Total Ozone Mapping Spectrometer (TOMS) instruments, and a wide band of strong winds in the lower stratosphere. Spring wave activity was greatly reduced, with 100 hPa February-March eddy heat fluxes that were lower by a factor of 2 from any previously observed values over the last 18 years. C1 GEN SCI CORP,LAUREL,MD. SCI APPLICAT CORP,VIENNA,VA. RP Coy, L (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA. RI Newman, Paul/D-6208-2012 OI Newman, Paul/0000-0003-1139-2508 NR 16 TC 129 Z9 130 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 NOV 15 PY 1997 VL 24 IS 22 BP 2693 EP 2696 DI 10.1029/97GL52832 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900002 ER PT J AU Manney, GL Froidevaux, L Santee, ML Zurek, RW Waters, JW AF Manney, GL Froidevaux, L Santee, ML Zurek, RW Waters, JW TI MLS observations of Arctic ozone loss in 1996-97 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID POLAR VORTEX AB The Microwave Limb Sounder (MLS) observed ozone (O-3) loss in the Arctic vortex beginning in January 1997 at 585 K (similar to 25 hPa) and in February 1997 at 465 K (similar to 50 hPa). Minimum vortex-averaged O-3 mixing ratios observed in 1997 were higher than those in 1996, which were the lowest ever recorded by MLS. The vertical extent of O-3 loss and maximum local O-3 decreases were larger, but the decrease filled the vortex less completely, in 1997 than in 1996. Unusually low high-latitude column O-3 above 100 hPa in April 1997 resulted mainly from dynamical effects of the unusually persistent lower stratospheric vortex and winter-like temperature patterns. Column O-3 above 100 hPa averaged in comparable regions of the vortex showed a stronger decreasing trend in 1996-97 than in 1995-96, consistent with the larger vertical extent and maximum local values of lower stratospheric O-3 loss. Chemical O-3 loss resulted in an similar to 10% observed decrease in column O-3 between late January and early April 1997. RP Manney, GL (reprint author), CALTECH,JET PROP LAB,MAIL STOP 183-701,PASADENA,CA 91109, USA. NR 7 TC 63 Z9 63 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 NOV 15 PY 1997 VL 24 IS 22 BP 2697 EP 2700 DI 10.1029/97GL52827 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900003 ER PT J AU Pierce, RB Fairlie, TD Remsberg, EE Russell, JM Grose, WL AF Pierce, RB Fairlie, TD Remsberg, EE Russell, JM Grose, WL TI HALOE observations of the Arctic vortex during the 1997 spring: Horizontal structure in the lower stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ANTARCTIC STRATOSPHERE; OZONE LOSS; WINTER; DEPLETION AB In late March, 1997, HALOE observed very low ozone (less than 1 ppmv at 480K), low HCl, generally high NOx, and normal levels of H2O within the Arctic vortex. Trajectory mapping techniques show that the lower stratospheric Arctic vortex was locally chemically perturbed during this period. Regions of low HCl and low NOx mixing ratios found within the Arctic vortex indicate that partitioning within the odd chlorine family had been shifted from reservoir species to active species. Low O-3 mixing ratios within these regions strongly suggest that chlorine-catalyzed photochemical destruction of O-3 had recently taken place. Regions of low HCl and higher NOx mixing ratios are also observed within the Arctic vortex. Correlations of O-3, H2O, NOx, and HCl with HF are used to quantify the changes in these constituents during March and early April, 1997. Temporal changes in the correlation of HCl and NOx with HF indicate increases in these species. No trend in the correlations of H2O or O-3 with HF was found in the lower stratosphere. C1 SCI & TECHNOL CORP,HAMPTON,VA 23666. HAMPTON UNIV,DEPT PHYS,HAMPTON,VA 23666. RP Pierce, RB (reprint author), NASA,LANGLEY RES CTR,MS 401B,HAMPTON,VA 23681, USA. RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 17 TC 16 Z9 16 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 NOV 15 PY 1997 VL 24 IS 22 BP 2701 EP 2704 DI 10.1029/97GL52833 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900004 ER PT J AU Santee, ML Manney, GL Froidevaux, L Zurek, RW Waters, JW AF Santee, ML Manney, GL Froidevaux, L Zurek, RW Waters, JW TI MLS observations of ClO and HNO3 in the 1996-97 Arctic polar vortex SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NITRIC-ACID; STRATOSPHERE; WINTER; OZONE AB Microwave Limb Sounder (MLS) measurements of lower stratospheric ClO and gas-phase HNO3 are presented for the 1996-97 Arctic winter. The horizontal and vertical extent of enhanced ClO were smaller in 1997 than in 1996, as was the degree of enhancement. This is consistent with differences in the evolution and vertical structure of temperatures in the two years. Gas-phase HNO3 abundances, which increased in early winter due to diabatic descent, exhibited a decreasing trend from mid to late winter in all six Arctic winters observed by MLS, probably due to increasing HNO3 photolysis throughout this period. RP Santee, ML (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183-701,PASADENA,CA 91109, USA. NR 11 TC 44 Z9 44 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 NOV 15 PY 1997 VL 24 IS 22 BP 2713 EP 2716 DI 10.1029/97GL52830 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900007 ER PT J AU McCormack, JP Hood, LL Nagatani, R Miller, AJ Planet, WG McPeters, RD AF McCormack, JP Hood, LL Nagatani, R Miller, AJ Planet, WG McPeters, RD TI Approximate separation of volcanic and 11-year signals in the SBUV-SBUV/2 total ozone record over the 1979-1995 period SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR VARIABILITY; TOMS DATA; NIMBUS-7 AB The combined Nimbus 7 SBUV, NOAA 11, and preliminary NOAA 9 SBUV/2 monthly zonal mean total ozone data set, extending from January 1979 to December 1995, is analyzed with a multiple regression statistical model that includes a term to describe the direct effect of volcanic aerosols on total ozone. Outside of polar regions, which are not included in this analysis, the volcanic regression coefficients in the northern hemisphere are negative (consistent with heterogeneous chemical losses of ozone on volcanic sulfate aerosols) and reach their maximum values between 40 degrees N-60 degrees N latitude. Although inclusion of the aerosol term in the statistical model introduces some additional uncertainty to the derived solar response, statistically significant values of the solar coefficients are found in northern and southern subtropical regions throughout the year, with maximum amplitudes of similar to 2.5% at 30 degrees latitude in both hemispheres during winter. We conclude that the 11-year signal in the SBUV-SBUV/2 total ozone record is approximately separable from volcanic aerosol effects. C1 UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NOAA,CLIMATE RES & APPLICAT DIV,WASHINGTON,DC 20233. RP McCormack, JP (reprint author), NOAA,NATL WEATHER SERV,CLIMATE PREDICT CTR,WASHINGTON,DC 20233, USA. RI McPeters, Richard/G-4955-2013; OI McPeters, Richard/0000-0002-8926-8462; McCormack, John/0000-0002-3674-0508 NR 18 TC 24 Z9 24 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 NOV 15 PY 1997 VL 24 IS 22 BP 2729 EP 2732 DI 10.1029/97GL02900 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900011 ER PT J AU Newell, RE Browell, EV Davis, DD Liu, SC AF Newell, RE Browell, EV Davis, DD Liu, SC TI Western Pacific tropospheric ozone and potential vorticity: Implications for Asian pollution SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Tropospheric ozone (O-3) Cross sections measured with lidar from a DC-8 aircraft over the western Pacific correspond closely with potential vorticity (PV). Both are transported from the middle latitude stratosphere, although this is not the only source of O-3, and both have sinks in the tropical boundary layer. O-3 and PV are good indicators of photochemical and transport process interactions. In summer, some Asian pollution, raised by convection to the upper troposphere, passes southward into the tropics and to the Southern Hemisphere. In winter, subsidence keeps the pollution at low altitudes where it moves over the ocean towards the ITCZ, with photochemical destruction and secondary pollutant generation occurring en route. Convection raises this modified air to the upper troposphere, where some may enter the stratosphere. Thus winter Asian pollution may have a smaller direct influence on the global atmosphere than it would if injected at other longitudes and seasons. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. GEORGIA INST TECHNOL,SCH EARTH & ATMOSPHER SCI,ATLANTA,GA 30332. RP Newell, RE (reprint author), MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139, USA. NR 25 TC 29 Z9 29 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 NOV 15 PY 1997 VL 24 IS 22 BP 2733 EP 2736 DI 10.1029/97GL02799 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900012 ER PT J AU Sauber, J McClusky, S King, R AF Sauber, J McClusky, S King, R TI Relation of ongoing deformation rates to the subduction zone process in southern Alaska SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GEODETIC MEASUREMENT; SEISMIC GAP; EARTHQUAKES; MOTIONS; STRAIN; PLATE; GULF AB The rate and orientation of ongoing strain associated with subduction of the Pacific plate and the accretion of the Yakutat terrane to southern Alaska has been estimated at 13 sites from Global Positioning System measurements made in June 1993 and 1995. Along the Gulf of Alaska coast near Cape Yakataga, the average rate of deformation, relative to Fairbanks, was approximate to 38 mm/yr at N32 degrees W. Further inland, above the region where the dip of the downgoing Pacific plate changes from about 10 degrees to > 30 degrees, the deformation rate was approximate to 12 mm/yr at N26 degrees W. In the Sourdough/Paxson area, the deformation rate drops to 2-5 mm/yr and suggests a low short-term deformation rate across the Denali fault. Elastic straining of the overriding plate due to back-slip on a main thrust zone with an average dip of about 10 degrees can account for the overall rate and distribution of short-term compressional strain across south central Alaska. Above the transitional region between unstable and stable sliding we suggest that strain associated with approximate to 15 mm/yr of right-lateral strike-slip occurs also. If the strain accumulated since the two 1899 earthquakes (both M-W = 8.1) from the offshore Pamplona fault zone to south of the Border Ranges fault (down-dip width approximate to 100 km) was seismically released on a single fault it would correspond to a M = 8.1 earthquake. C1 MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139. RP Sauber, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,CODE 921,GREENBELT,MD 20771, USA. RI Sauber, Jeanne/D-7684-2012; OI McClusky, Simon/0000-0003-4040-925X NR 19 TC 36 Z9 36 U1 0 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 NOV 15 PY 1997 VL 24 IS 22 BP 2853 EP 2856 DI 10.1029/97GL52979 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900042 ER PT J AU Edgett, KS Parker, TJ AF Edgett, KS Parker, TJ TI Water on early Mars: Possible subaqueous sedimentary deposits covering ancient cratered terrain in western Arabia and Sinus Meridiani SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MORPHOLOGY AB Western Arabia and northern Sinus Meridiani (30 degrees N-10 degrees S; 40 degrees W-40 degrees E) are almost entirely covered by wind-eroded, horizontally-bedded, sedimentary layers that lap against local topographic features. This portion of Mars' ancient cratered terrain is relatively low (< 1 km elevation) and flat (sloping westward 0.7 m/km over 3,000 km). The region lacks valley network channels. We propose that at some time in early Martian history, this region was under water. The water hypothesis is strengthened by the presence of (1) a shore-like contact between smooth-surfaced deposits and ancient cratered terrain in central Sinus Meridiani, (2) polygonal structures in northern Sinus Meridiani, and (3) sand (which cannot be from airfall), possibly reworked by wind from the underlying sedimentary units. The September 1997 arrival of Mars Global Surveyor's thermal emission spectrometer offers an opportunity to begin to test this hypothesis by searching for carbonate and evaporite minerals among the sediment covering the region. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Edgett, KS (reprint author), ARIZONA STATE UNIV,DEPT GEOL,BOX 871404,TEMPE,AZ 85287, USA. OI Edgett, Kenneth/0000-0001-7197-5751 NR 15 TC 77 Z9 77 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 NOV 15 PY 1997 VL 24 IS 22 BP 2897 EP 2900 DI 10.1029/97GL02840 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900053 ER PT J AU Lorenz, RD Lunine, JI McKay, CP AF Lorenz, RD Lunine, JI McKay, CP TI Titan under a red giant sun: A new kind of ''habitable'' moon SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLANETOLOGICAL APPLICATIONS; SURFACE TEMPERATURES; ATMOSPHERE; EARTH; GREENHOUSE; LIQUID; MARS AB We explore the response of Titan's surface and massive atmosphere to the change in solar spectrum and intensity as the sun evolves into a red giant. Titan's surface temperature is insensitive to insolation increases as the haze-laden atmosphere ''puffs up'' and blocks more sunlight. However, we find a window of several hundred Myr exists, roughly 6 Gyr from now, when liquid water-ammonia can form oceans on the surface and react with the abundant organic compounds there. The window opens due to a drop in haze production as the ultraviolet flux from the reddening sun plummets. The duration of such a window exceeds the time necessary for life to have begun on Earth. Similar environments, with similar to 200 K water-ammonia oceans warmed by methane greenhouses under red stars, are an alternative to the similar to 300 K water-CO2 environments considered the classic ''habitable'' planet. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Lorenz, RD (reprint author), UNIV ARIZONA,DEPT PLANETARY SCI,LUNAR & PLANETARY LAB,TUCSON,AZ 85721, USA. RI Lorenz, Ralph/B-8759-2016 OI Lorenz, Ralph/0000-0001-8528-4644 NR 19 TC 22 Z9 22 U1 0 U2 6 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 NOV 15 PY 1997 VL 24 IS 22 BP 2905 EP 2908 DI 10.1029/97GL52843 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900055 PM 11542268 ER PT J AU Purucker, ME Sabaka, TJ Langel, RA Olsen, N AF Purucker, ME Sabaka, TJ Langel, RA Olsen, N TI The missing dimension in Magsat and POGO anomaly studies SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AUSTRALIA AB The development of a comprehensive model of the near-Earth magnetic field in terms of sources in the core, ionosphere, and magnetosphere has allowed the isolation of heretofore unknown north-south trending anomalies of lithospheric origin. Previously, along-track filtering of satellite magnetic field data had been necessary in order to remove unmodeled magnetospheric and ionospheric magnetic fields. These fields change between adjacent passes by tens of nanoTeslas and have wavelengths which overlap the crustal spectrum. An example from Australia illustrates the additional information that can be extracted from the Magsat data set when this 'missing dimension' is included. A north-south trending low covers most of eastern Australia, in agreement with the aeromagnetic map of Australia. This feature is seen in both the dawn and dusk subsets collected from Magsat. The center of this low is roughly coincident with the Eromanga Basin but extends for almost 2000 km in a N-S direction. The low corresponds to a region of almost featureless magnetic field on the aeromagnetic map. It is also consistent with an elevated geotherm previously proposed from studies of xenoliths in southeastern Australia. Filtering the new map in a north-south direction reproduces the previous best estimate of the Australian satellite anomaly field. We expect that this comprehensive model will provide a new window into the magnetic field of the earth's lithosphere. The model continues to be enhanced. C1 UNIV COPENHAGEN,DEPT GEOPHYS,DK-2100 COPENHAGEN,DENMARK. RP Purucker, ME (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,CODE 921,GREENBELT,MD 20771, USA. RI Olsen, Nils/H-1822-2011; Sabaka, Terence/D-5618-2012 OI Olsen, Nils/0000-0003-1132-6113; NR 13 TC 10 Z9 15 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 NOV 15 PY 1997 VL 24 IS 22 BP 2909 EP 2912 DI 10.1029/97GL52978 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900056 ER PT J AU Reames, DV Ng, CK Mason, GM Dwyer, JR Mazur, JE vonRosenvinge, TT AF Reames, DV Ng, CK Mason, GM Dwyer, JR Mazur, JE vonRosenvinge, TT TI Late-phase acceleration of energetic ions in corotating interaction regions SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-WIND; PARTICLES; PIONEER-10; ABUNDANCES AB We report on new high-sensitivity measurements from the WIND spacecraft of the spatial distributions of 30 keV\amu to 10 MeV/amu ions from corotating interaction regions (CIRs) that extend far beyond the confines of the parent high-speed solar-wind stream. Not only do late-phase MeV ions persist far into the declining solar wind, but they also show a continual gain in energy, even after sector boundary passage, until the next small increase in solar wind speed occurs. These ions are accelerated in the distant heliosphere as the reverse shock from the CIR propagates completely across the rarefaction region produced by the declining solar wind, growing in acceleration efficiency as it propagates. Energetic ions from a single CIR event are seen for a period of 17 days and similar to 225 degrees in solar longitude. The observed energy spectra can be fit to the theory of Fisk and Lee [1980] only if shock compression increases with time so that the spectra harden significantly. C1 ROYAL MELBOURNE INST TECHNOL,DEPT MATH,MELBOURNE,VIC 3001,AUSTRALIA. UNIV MARYLAND,COLLEGE PK,MD 20742. RP Reames, DV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. NR 14 TC 18 Z9 18 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 NOV 15 PY 1997 VL 24 IS 22 BP 2917 EP 2920 DI 10.1029/97GL02841 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900058 ER PT J AU Myong, RS AF Myong, RS TI Analytical results on MHD intermediate shocks SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WAVES AB The admissibility of MHD intermediate shocks has been a matter of much debate over the years. Though the legitimacy of such shocks was shown in a recent series of investigations by Wu, rigorous analytical proof of the results was considered being unsettled. In this paper, as a step towards developing such proof, we present a theory of MHD shocks. On the basis of global analysis, we develop a shock admissibility condition. Using this theory, we explain how intermediate shocks and compound waves are generated. RP Myong, RS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,MAIL STOP 930,GREENBELT,MD 20771, USA. NR 15 TC 3 Z9 3 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 NOV 15 PY 1997 VL 24 IS 22 BP 2929 EP 2932 DI 10.1029/97GL53006 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YG509 UT WOS:A1997YG50900061 ER PT J AU Crawford, TD Lee, TJ Schaefer, HF AF Crawford, TD Lee, TJ Schaefer, HF TI A new spin-restricted triple excitation correction for coupled cluster theory SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID OPEN-SHELL SYSTEMS; HARTREE-FOCK REFERENCE; BODY PERTURBATION-THEORY; ELECTRON CORRELATION; WAVE-FUNCTIONS; ORBITALS; SINGLES; ENERGY; INVARIANCE; GRADIENTS AB A new approach to the noniterative inclusion of the effects of connected triple excitations in the coupled cluster singles and doubles (CCSD) model is presented. The method is based on the recently developed Z-averaged perturbation theory, and reduces to the usual Moller-Plesset-based triples correction in the absence of open shells. This new correction maintains the same invariance properties as those of the CCSD energy, and requires storage of only one-third the number of two-electron integrals as more conventional corrections. The derivation and implementation of the equations are described, and the method's performance relative to more conventional triples corrections is assessed via benchmark calculations for a series of diatomic molecules. (C) 1997 American Institute of Physics. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV GEORGIA,DEPT CHEM,CTR COMPUTAT QUANTUM CHEM,ATHENS,GA 30602. RP Crawford, TD (reprint author), UNIV GEORGIA,DEPT CHEM,CTR COMPUTAT QUANTUM CHEM,ATHENS,GA 30602, USA. RI Lee, Timothy/K-2838-2012; Crawford, Thomas/A-9271-2017 OI Crawford, Thomas/0000-0002-7961-7016 NR 52 TC 15 Z9 15 U1 0 U2 2 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 NOV 15 PY 1997 VL 107 IS 19 BP 7943 EP 7950 DI 10.1063/1.475081 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YG655 UT WOS:A1997YG65500038 ER PT J AU Alikhani, ME Dateo, CE Lee, TJ AF Alikhani, ME Dateo, CE Lee, TJ TI Density functional and coupled-cluster study an the HNO->HON transition state SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID MOLECULAR-ORBITAL METHODS; GAUSSIAN-BASIS SETS; HNO; DNO C1 NASA, AMES RES CTR, THERMOSCI INST, MOFFETT FIELD, CA 94035 USA. RP UNIV PARIS 06, LAB SPECTROCHIM MOL,URA 508,BOITE 49,BATIMENT F74, 4 PL JUSSIEU, PARIS 05, FRANCE. RI Lee, Timothy/K-2838-2012 NR 19 TC 9 Z9 9 U1 0 U2 1 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0021-9606 EI 1089-7690 J9 J CHEM PHYS JI J. Chem. Phys. PD NOV 15 PY 1997 VL 107 IS 19 BP 8208 EP 8209 DI 10.1063/1.475123 PG 2 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YG655 UT WOS:A1997YG65500073 ER PT J AU Desai, SD Wahr, JM Chao, Y AF Desai, SD Wahr, JM Chao, Y TI Error analysis of empirical ocean tide models estimated from TOPEX/POSEIDON altimetry SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-STATE BIAS; ERS 1; TOPEX; CIRCULATION; DEFORMATION; EARTH AB An error budget is proposed for the TOFEX/POSEIDON (T/P) empirical ocean tide models estimated during the primary mission. The error budget evaluates the individual contribution of errors in each of the altimetric range corrections, orbit errors caused by errors in the background ocean tide potential, and errors caused by the general circulation of the oceans, to errors in the ocean tide models of the eight principal diurnal and semidiurnal tidal components, and the two principal long-period tidal components. The effect of continually updating the T/P empirical ocean tide models during the primary T/P mission is illustrated through tide gauge comparisons and then used to predict the impact of further updates during the extended mission. Both the tide gauge comparisons and the error analysis predict errors in the tide models for the eight principal diurnal and semidiurnal constituents to be of the order of 2-3 cm root-sum-square. The dominant source of errors in the T/P ocean tide models appears to be caused by the general circulation of the oceans observed by the T/P altimeter. Further updates of the T/P empirical ocean tide models during the extended mission should not provide significant improvements in the diurnal and semidiurnal ocean tide models but should provide significant improvements in the long-period ocean tide models, particularly in the monthly (Mm) tidal component. C1 UNIV COLORADO,DEPT PHYS,COOPERAT INST RES ENVIRONM SCI,BOULDER,CO 80309. RP Desai, SD (reprint author), CALTECH,JET PROP LAB,MAIL STOP 301-150,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 38 TC 8 Z9 8 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1997 VL 102 IS C11 BP 25157 EP 25172 DI 10.1029/97JC01916 PG 16 WC Oceanography SC Oceanography GA YG654 UT WOS:A1997YG65400015 ER PT J AU Shum, CK Woodworth, PL Andersen, OB Egbert, GD Francis, O King, C Klosko, SM LeProvost, C Li, X Molines, JM Parke, ME Ray, RD Schlax, MG Stammer, D Tierney, CC Vincent, P Wunsch, CI AF Shum, CK Woodworth, PL Andersen, OB Egbert, GD Francis, O King, C Klosko, SM LeProvost, C Li, X Molines, JM Parke, ME Ray, RD Schlax, MG Stammer, D Tierney, CC Vincent, P Wunsch, CI TI Accuracy assessment of recent ocean tide models SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID EARTHS ROTATION RATE; TOPEX/POSEIDON ALTIMETRY; CONSTITUENTS; VARIABILITY AB Over 20 global ocean tide models have been developed since 1994, primarily as a consequence of analysis of the precise altimetric measurements from TOPEX/POSEIDON and as a result of parallel developments in numerical tidal modeling and data assimilation, This paper provides an accuracy assessment of 10 such tide models and discusses their benefits in many fields including geodesy, oceanography, and geophysics. A variety of tests indicate that all these tide models agree within 2-3 cm in the deep ocean, and they represent a significant improvement over the classical Schwiderski 1980 model by approximately 5 cm rms. As a result, two tide models were selected for the reprocessing of TOPEX/POSEIDON Geophysical Data Records in late 1995. Current ocean tide models allow an improved observation of deep ocean surface dynamic topography using satellite altimetry. Other significant contributions include their applications in an improved orbit computation for TOPEX/POSEIDON and other geodetic satellites, to yield accurate predictions of Earth rotation excitations and improved estimates of ocean loading corrections for geodetic observatories, and to allow better separation of astronomical tides from phenomena with meteorological and geophysical origins. The largest differences between these tide models occur in shallow waters, indicating that the current models are still problematic in these areas. Future improvement of global tide models is anticipated with additional high-quality altimeter data and with advances in numerical techniques to assimilate data into high-resolution hydrodynamic models. C1 KORT OG MATRIKELSTYRELSEN,GEODET DIV,DK-2400 COPENHAGEN NV,DENMARK. OREGON STATE UNIV,COLL OCEAN & ATMOSPHER SCI,CORVALLIS,OR 97331. OBSERV ROYAL BELGIQUE,B-1180 BRUSSELS,BELGIUM. MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. INST MECAN GRENOBLE,LAB ECOULEMENTS GEOPHYS & IND,F-38041 GRENOBLE,FRANCE. UNIV COLORADO,DEPT AEROSP ENGN SCI,COLORADO CTR ASTRODYNAM RES,BOULDER,CO 80309. CTR NATL ETUD SPATIALES,GRP RECH GEODESIE SPATIALE,F-31055 TOULOUSE,FRANCE. BIDSTON OBSERV,PROUDMAN OCEANOG LAB,BIRKENHEAD L43 7RE,MERSEYSIDE,ENGLAND. RP Shum, CK (reprint author), UNIV TEXAS,CTR SPACE RES R1000,AUSTIN,TX 78712, USA. RI Ray, Richard/D-1034-2012; Andersen, Ole /H-7481-2016 OI Andersen, Ole /0000-0002-6685-3415 NR 45 TC 181 Z9 197 U1 1 U2 17 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1997 VL 102 IS C11 BP 25173 EP 25194 DI 10.1029/97JC00445 PG 22 WC Oceanography SC Oceanography GA YG654 UT WOS:A1997YG65400016 ER PT J AU McClean, JL Semtner, AJ Zlotnicki, V AF McClean, JL Semtner, AJ Zlotnicki, V TI Comparisons of mesoscale variability in the Semtner-Chervin 1/4 degrees model, the Los Alamos Parallel Ocean Program 1/6 degrees model, and TOPEX/POSEIDON data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID GENERAL-CIRCULATION MODEL; NORTH-ATLANTIC OCEAN; BRAZIL CURRENT RETROFLECTION; EDDY KINETIC-ENERGY; GEOSAT ALTIMETRY; HORIZONTAL RESOLUTION; 50-DAY OSCILLATIONS; TROPICAL PACIFIC; SOUTHERN-OCEAN; MOMENTUM FLUX AB Measures of mesoscale variability in the Semtner-Chervin 1/4 degrees and the Los Alamos Parallel Ocean Program (POP) 1/6 degrees models were compared with those obtained from TOPEX/POSEIDON (T/P) data. The objectives of these comparisons were two-fold: the first was to validate the models using altimetry as a measure of the variability of the real ocean, and the second was to evaluate the effect of increased model resolution/decreased horizontal friction. Mesoscale root-mean-square (rms) sea surface height (SSH), eddy kinetic energies, and length scales were used to quantify the mesoscale variability. Results showed that the models reproduced the distribution and much of the magnitude of this variability associated with the major current systems; however, in the oceans' interiors the magnitude was underrepresented. The 1/6 degrees and 1/4 degrees models were found to explain about 60% and 50% of the global T/P variability, respectively. Estimates of eddy kinetic energy (and rms velocities) from T/P and the models were compared, demonstrating that the models were less energetic than the T/P fields, Independent comparisons were made with lagrangian drifters in the Pacific basin. Excellent agreement was found between the total POP velocity fields and the drifter data in the tropics, where the T/P geostrophic values were too high due to error amplification by the 1/f factor. In the midlatitudes, the drifter values exceeded those derived from the total model velocities; the T/P results lay between the two. Differences are attributed to the drifter analysis choices and possible residual noise in the altimetry data. The effect of increased resolution/decreased friction was best seen in the length scales where the POP scales agreed more closely with the T/P values than with the 1/4 degrees model. The distribution and magnitude of the POP length scales were generally in agreement with the T/P values between 10 degrees and 40 degrees. Near the equator, discrepancies were due to the long equatorial and instability waves, whose long wavelengths were too great to be resolved by the the combination of noise in the altimeter slopes, and the particular definition of length scale chosen. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP McClean, JL (reprint author), USN,POSTGRAD SCH,DEPT OCEANOG,MONTEREY,CA 93943, USA. NR 71 TC 42 Z9 42 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1997 VL 102 IS C11 BP 25203 EP 25226 DI 10.1029/97JC01222 PG 24 WC Oceanography SC Oceanography GA YG654 UT WOS:A1997YG65400018 ER PT J AU Krainsky, IL Asnin, VM AF Krainsky, IL Asnin, VM TI Auger spectroscopy of hydrogenated diamond surfaces SO PHYSICAL REVIEW B LA English DT Article ID VAPOR-DEPOSITED DIAMOND; VALENCE-VALENCE PROCESSES; ELECTRON-SPECTROSCOPY; SIMPLE METALS; LINE-SHAPES; FILMS; EMISSION AB An energy shift and a change of the line shape of the carbon core-valence-valence Auger spectra are observed for diamond surfaces after their exposure to an electron beam, or annealing at temperatures higher then 950 degrees C. The effect is studied for both natural diamond crystals and chemical-vapor-deposited diamond films. A theoretical model is proposed for Auger spectra of hydrogenated diamond surfaces. The observed changes of the carbon Auger line shape are shown to be related to the redistribution of the valence-band local density of states caused by the hydrogen desorption from the surface. One-electron calculation of Auger spectra of diamond surfaces with various hydrogen coverages are presented. They are based on self-consistent wave functions and matrix elements calculated in the framework of the local-density approximation and the self-consistent linear muffin-tin orbital method with static core-hole effects taken into account. The major features of experimental spectra are explained. C1 S DAKOTA SCH MINES & TECHNOL,DEPT PHYS,RAPID CITY,SD 57701. RP Krainsky, IL (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 27 TC 7 Z9 7 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 J9 PHYS REV B JI Phys. Rev. B PD NOV 15 PY 1997 VL 56 IS 20 BP 13529 EP 13534 DI 10.1103/PhysRevB.56.13529 PG 6 WC Physics, Condensed Matter SC Physics GA YH588 UT WOS:A1997YH58800114 ER PT J AU Chung, DJH Farrar, GR Kolb, EW AF Chung, DJH Farrar, GR Kolb, EW TI Relic abundance of light photinos SO PHYSICAL REVIEW D LA English DT Article ID NEUTRALINO DARK MATTER; CROSS-SECTIONS; PARTICLES; GLUINO; MASSES; CANDIDATES; GAUGINO AB We solve the coupled Boltzmann equation for the system of light photinos interacting with pions and R-0's (the gluon-gluino bound state) to determine the relic abundance of light photinos in the light gaugino scenario. Cosmology bounds the ratio r of the R-0 mass to the <(gamma)over tilde> mass to be less than about 1.8. We also use a model Lagrangian embodying crossing symmetry between the R-0<-><(gamma)over tilde>pi pi and R-0 pi<-><(gamma)over tilde>pi reactions to identify cosmologically favored regions of R-0 lifetime as a function of R-0 and <(gamma)over tilde> masses. [S0556-2821(97)07322-0]. C1 UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RUTGERS STATE UNIV,DEPT PHYS & ASTRON,PISCATAWAY,NJ 08855. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RP Chung, DJH (reprint author), UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637, USA. NR 30 TC 10 Z9 10 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 NOV 15 PY 1997 VL 56 IS 10 BP 6096 EP 6106 DI 10.1103/PhysRevD.56.6096 PG 11 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YH166 UT WOS:A1997YH16600008 ER PT J AU Kolb, EW Riotto, A Tkachev, II AF Kolb, EW Riotto, A Tkachev, II TI Evolution of the order parameter after bubble collisions SO PHYSICAL REVIEW D LA English DT Article ID PHASE-TRANSITIONS; PARTICLE-PRODUCTION; INFLATION; BARYOGENESIS; UNIVERSE AB If a first-order phase transition is terminated by percolation and collisions of new-phase bubbles, there will exist a period of nonequilibrium between the time bubbles collide and the time thermal equilibrium is established. We study the behavior of the order parameter during this phase. We find that large nonthermal fluctuations at this stage reduce the order parameter below its eventual thermal equilibrium value. We comment on possible consequences for electroweak baryogenesis. [S0556-2821(97)04422-6]. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. OHIO STATE UNIV,DEPT PHYS,COLUMBUS,OH 43210. RUSSIAN ACAD SCI,INST NUCL RES,MOSCOW 117312,RUSSIA. RP Kolb, EW (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,POB 500,BATAVIA,IL 60510, USA. NR 22 TC 11 Z9 11 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 NOV 15 PY 1997 VL 56 IS 10 BP 6133 EP 6138 DI 10.1103/PhysRevD.56.6133 PG 6 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YH166 UT WOS:A1997YH16600013 ER PT J AU Oumi, M Maurice, D Lee, TJ HeadGordon, M AF Oumi, M Maurice, D Lee, TJ HeadGordon, M TI A diagnostic for the applicability of the CIS and CIS(D) excitation energy methods SO CHEMICAL PHYSICS LETTERS LA English DT Article ID COUPLED-CLUSTER SINGLES; MOLECULAR-ORBITAL THEORY; EXCITED-STATES; CONFIGURATION-INTERACTION; AB-INITIO; EQUATION; TRANSITION; MODEL AB A 'theta diagnostic' is introduced that measures the reliability of the single excitation configuration interaction (CIS) approach to excitation energies, and a second order perturbation correction, CIS(D). This diagnostic characterizes the extent of mixing between CIS excited states due to electron correlation effects through second order in a Moller-Plesset expansion. Its evaluation requires negligible additional computation in a CIS(D) calculation. Calculations on ethylene, formaldehyde, nitric acid, chlorine nitrate, styrene and benzaldehyde are presented to show its utility. Small diagnostic values indicate the CIS states are stable to near-degeneracy effects. (C) 1997 Elsevier Science B.V. C1 UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,DIV CHEM SCI,BERKELEY,CA 94720. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Oumi, M (reprint author), UNIV CALIF BERKELEY,DEPT CHEM,BERKELEY,CA 94720, USA. RI Lee, Timothy/K-2838-2012 NR 28 TC 25 Z9 25 U1 0 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 NOV 14 PY 1997 VL 279 IS 3-4 BP 151 EP 157 DI 10.1016/S0009-2614(97)01028-2 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YL310 UT WOS:A1997YL31000005 ER PT J AU Gatski, TB AF Gatski, TB TI Prediction of complex flow fields using higher-order turbulent closures SO MATHEMATICS AND COMPUTERS IN SIMULATION LA English DT Article; Proceedings Paper CT IMACS-COST Conference on Computational Fluid Dynamics, 3-Dimensional Complex Flows CY SEP, 1995 CL LAUSANNE, SWITZERLAND ID ALGEBRAIC STRESS MODELS; LAYERS AB The tool of choice in computing turbulent flows of engineering interest is the Reynolds averaged Navier-Stokes equations for the mean motion, coupled with a closure scheme for the unknown higher-order turbulent correlations. The focus of this paper is to discuss some recent advances in turbulent closure schemes and their application to a weakly compressible flow. Specifically highlighted are the development and utilization of formulations for obtaining explicit algebraic stress and dissipation rate models. Results are presented for the flow over a two-dimensional single element airfoil as well as the downstream wake flow using the explicit algebraic stress model with a comparison to both experiment and a standard isotropic eddy viscosity model. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Gatski, TB (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 20 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0378-4754 J9 MATH COMPUT SIMULAT JI Math. Comput. Simul. PD NOV 14 PY 1997 VL 44 IS 4 BP 331 EP 345 DI 10.1016/S0378-4754(97)00063-3 PG 15 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA YM939 UT WOS:000071117000003 ER PT J AU Yeomans, D AF Yeomans, D TI Comets, popular culture, and the birth of modern cosmology - Genuth,SS SO NATURE LA English DT Book Review RP Yeomans, D (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 1 TC 0 Z9 0 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD NOV 13 PY 1997 VL 390 IS 6656 BP 135 EP 136 DI 10.1038/36498 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YF494 UT WOS:A1997YF49400039 ER PT J AU Ozernoy, LM AF Ozernoy, LM TI Precision measuring of velocities via the relativistic Doppler effect SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE relativity; techniques, radial velocities; celestial mechanics, stellar dynamics; binaries, general; stars, kinematics; globular clusters, general ID RADIAL-VELOCITIES AB Just as the ordinary Doppler;effect serves as a tool to measure radial velocities of celestial objects, so can the relativistic Doppler effect be implemented to measure a combination of radial and transverse velocities by using recent improvements in observing techniques. A key element that makes a further use of this combination feasible is the periodicity in changes of the orbital velocity direction for the source. Two cases are considered: (i) a binary star; and (ii) a solitary star with a planetary companion. It is shown that, in case (i), precision Doppler measurements employing the gas absorption cell technique would determine both the total orbital velocity and the inclination angle of the binary orbit disentangled from the peculiar velocity of the system. The necessary condition for that is the measurable, at least with a modest precision, proper motion and distance to the system. C1 GEORGE MASON UNIV,DEPT PHYS & ASTRON,FAIRFAX,VA 22030. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Ozernoy, LM (reprint author), GEORGE MASON UNIV,COMPUTAT SCI INST,5C3,FAIRFAX,VA 22030, USA. NR 13 TC 2 Z9 2 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 11 PY 1997 VL 291 IS 4 BP L63 EP L66 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YH485 UT WOS:A1997YH48500002 ER PT J AU Welty, DE Lauroesch, JT Blades, JC Hobbs, LM York, DG AF Welty, DE Lauroesch, JT Blades, JC Hobbs, LM York, DG TI Interstellar abundances in the Magellanic Clouds .1. GHRS observations of the Small Magellanic Cloud star Sk 108 SO ASTROPHYSICAL JOURNAL LA English DT Review DE galaxies, abundances; galaxies, ISM; ISM, abundances; Magellanic Clouds; quasars, absorption lines; stars, individual (Sk 108) ID H-II REGIONS; ABSORPTION-LINE SYSTEMS; CCD STROMGREN PHOTOMETRY; LYMAN-ALPHA ABSORBER; HIGHLY IONIZED-GAS; WOLF-RAYET STARS; CHEMICAL EVOLUTION; CARBON ABUNDANCES; HEAVY-ELEMENTS; METAL ABUNDANCES AB We present HST GHRS echelle-B and G160M spectra of the Wolf-Rayet binary Sk 108, located in the northeastern part of the main ''bar'' of the Small Magellanic Cloud. The spectra show interstellar absorption from C I, O I, Si II, Si II*, S II, P II, Cr II, Mn II, Fe II, Ni II, and Zn II. We find at least 25 interstellar components, which may be grouped via similar kinematics and/or similar relative heavy element abundances into two sets arising in the Galactic disk and halo, plus three sets located in the SMC. The SMC component groups may correspond to large-scale SMC gas complexes identified in H I 21 cm emission surveys. The relative gas phase abundances for Si II, Cr II, Mn II, Fe II, Ni II, and Zn II found for the SMC interstellar components are similar to those found for interstellar clouds in the Galactic halo. Since the relative total abundances for those elements found for F-G supergiants and gaseous nebulae in the SMC are similar to those present in comparable Galactic objects, we conclude that the interstellar depletion patterns are also similar in the SMC and in the Galactic halo clouds, despite the significantly lower metallicity and dust-to-gas ratio in the SMC. We do not see the distinctive depletion patterns commonly found for cold and warm clouds in the Galactic disk for any of the SMC components along the line of sight to Sk 108. We discuss some implications of these results for understanding the abundances found for QSO absorption-line systems and conclude that both nucleosynthetic and depletion effects contribute to the observed abundances-to different degrees for different systems. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. UNIV CHICAGO, YERKES OBSERV, WILLIAMS BAY, WI 53191 USA. UNIV CHICAGO, ENRICO FERMI INST, CHICAGO, IL 60637 USA. RP Welty, DE (reprint author), UNIV CHICAGO, DEPT ASTRON & ASTROPHYS, 5640 S ELLIS AVE, CHICAGO, IL 60637 USA. NR 130 TC 86 Z9 86 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1997 VL 489 IS 2 BP 672 EP 692 DI 10.1086/304811 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF300 UT WOS:A1997YF30000018 ER PT J AU Schaefer, BE Cline, TL Hurley, KC Laros, JG AF Schaefer, BE Cline, TL Hurley, KC Laros, JG TI Gamma-ray burster counterparts: Hubble Space Telescope blue and ultraviolet data SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts ID OPTICAL TRANSIENT; ERROR BOX; SEARCH AB The surest solution of the gamma-ray burst (GRB) mystery is to find an unambiguous low-energy quiescent counterpart. However, to date no reasonable candidates have been identified in the X-ray, optical, infrared, or radio ranges. The Hubble Space Telescope (HST) has now allowed for the first deep ultraviolet searches for quiescent counterparts. This paper reports on multiepoch ultraviolet searches of five GRB positions with HST. We found no sources with significant ultraviolet excesses, variability, parallax, or proper motion in any of the burst error regions. In particular, we see no sources similar to that proposed as a counterpart to the GRB 970228. While this negative result is disappointing, it still has good utility for its strict limits on the no-host-galaxy problem in cosmological models of GRBs. For most cosmological models (with peak luminosity 6 x 10(50) ergs s(-1)), the absolute B magnitude of any possible host galaxy must be fainter than -15.5 to -17.4. These smallest boxes for some of the brightest bursts provide the most critical test, and our limits are a severe problem for all published cosmological burst models. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. RP Schaefer, BE (reprint author), YALE UNIV,DEPT PHYS,POB 208121,NEW HAVEN,CT 06520, USA. NR 26 TC 17 Z9 17 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 NOV 10 PY 1997 VL 489 IS 2 BP 693 EP 697 DI 10.1086/304809 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF300 UT WOS:A1997YF30000019 ER PT J AU Federman, SR Knauth, DC Lambert, DL Andersson, BG AF Federman, SR Knauth, DC Lambert, DL Andersson, BG TI Probing the photodissociation region toward HD 200775 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, abundances; ISM, individual (NGC 7023); ISM, molecules; reflection nebulae; stars, individual (HD 200775) ID DIFFUSE INTERSTELLAR CLOUDS; HOPKINS ULTRAVIOLET TELESCOPE; REFLECTION NEBULA NGC-7023; HERBIG AE/BE STARS; MOLECULAR-HYDROGEN; PHYSICAL CONDITIONS; CARBON-MONOXIDE; PHILLIPS SYSTEM; I ABSORPTION; HIGH-DENSITY AB The illuminating source of the photodissociation region associated with the reflection nebula NGC 7023 is HD 200775. We probed the foreground atomic and molecular material through diagnostics observed in absorption against the background star. Ground-based measurements of Na I, K I, and Ca II and of the molecules CH, CH+, C-2, and CN were analyzed in order to extract the physical conditions for this material. In particular, estimates for gas density, gas temperature, and the flux of ultraviolet radiation were derived and compared with information obtained from maps of radio emission. The foreground material has lower density than the other portions of the photodissociation region; the observed excitation of C-2, the observed column of C-2, and the columns of neutral sodium and potassium are reproduced when the extinction curve derived for this line of sight is adopted. Future models of the NGC 7023 nebula should include the effects associated with this extinction curve. The observed CN column density is larger than our predicted amount; an additional contribution from the background molecular cloud is inferred. C1 UNIV TEXAS,DEPT ASTRON,AUSTIN,TX 78712. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Federman, SR (reprint author), UNIV TOLEDO,DEPT PHYS & ASTRON,TOLEDO,OH 43606, USA. NR 64 TC 17 Z9 17 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 NOV 10 PY 1997 VL 489 IS 2 BP 758 EP 765 DI 10.1086/304804 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF300 UT WOS:A1997YF30000025 ER PT J AU Middleditch, J Imamura, JN SteimanCameron, TY AF Middleditch, J Imamura, JN SteimanCameron, TY TI Discovery of quasi-periodic oscillations in the AM Herculis object BL Hydri SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; novae, cataclysmic variables; stars, individual (BL Hydri, H0139-68); stars, oscillations ID DRIVEN RADIATIVE SHOCKS; WHITE-DWARFS; VARIABILITY AB We obtained high-speed optical photometry of the AM Her object BL Hyi at the Las Campanas Observatory and the Cerro Tololo Inter-American Observatory during 1989-1996. BL Hyi was in its faint-luminosity state in 1989; it subsequently brightened and was in its high-luminosity state for our 1994-1996 observations. We discovered broad, 0.2-0.8 Hz quasi-periodic oscillations (QPOs) and narrower QPOs superposed on the broad QPOs when BL Hyi was in its high-luminosity state. The broad QPOs had widths of Delta f/f(p) similar to 0.5-1 and rms pulsed amplitudes of similar to 1%-4%, wheref(p) is the frequency of the QPO peak. The narrow QPOs had widths of Delta f/f(p) < 0.1 and rms pulsed amplitudes of less than 1%. BL Hyi showed stronger QPOs and was slightly brighter in 1994 than in 1995-1996. The amplitudes of the broad and narrow QPOs were modulated on the orbital period of the system; they were strongest during the bright orbital phase. BL Hyi is the fifth AM Her system to show the short-period QPOs discovered by Middleditch. C1 UNIV OREGON, DEPT PHYS, EUGENE, OR 97403 USA. UNIV OREGON, INST THEORET SCI, EUGENE, OR 97403 USA. NASA, AMES RES CTR, MS 245 3, MOFFETT FIELD, CA 94035 USA. RP Middleditch, J (reprint author), LOS ALAMOS NATL LAB, COMP INFORMAT & COMMUN DIV, MS B256, CIC 19, POB 1663, LOS ALAMOS, NM 87545 USA. NR 18 TC 11 Z9 11 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1997 VL 489 IS 2 BP 912 EP 916 DI 10.1086/304834 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF300 UT WOS:A1997YF30000036 ER PT J AU Lay, OP Carlstrom, JE Hills, RE AF Lay, OP Carlstrom, JE Hills, RE TI Constraints on the HL Tauri protostellar disk from millimeter- and submillimeter-wave interferometry SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; infrared, stars; stars, individual (HL Tauri); stars, pre-main-sequence; techniques, interferometric ID YOUNG STELLAR OBJECTS; CIRCUMSTELLAR DISK; ACCRETION DISKS; STARS; EVOLUTION; ENVELOPE; MODELS AB Millimeter and submillimeter interferometry is used to probe the dusty accretion disks around young protostars. New 460 GHz (lambda = 650 mu m) data from the Caltech Submillimeter Observatory and the James Clerk Maxwell Telescope CSO-JCMT Interferometer are combined with previous 345 GHz (lambda = 870 pm) data from CSO-JCMT, 220 GHz (lambda = 1.4 mm) data from the Owens Valley Radio Observatory (OVRO) Millimeter Array, 110 GHz (lambda = 2.7 mm) data from the Berkeley-Illinois-Maryland Association Array (BIMA), and 43 GHz (lambda = 7 mm) data from the VLA, in order to constrain the nature of the protostellar disk around HL Tau on size scales of 50 AU and above. A power-law disk model is fitted directly to the measured visibility data, and probability distributions are derived for the parameters. The effects of instrumental uncertainties are included in a consistent way. The position angle of the major axis of the emission is determined to be 127 degrees +/- 5 degrees and the inclination 42 degrees +/- 5 degrees (where 0 degrees is face-on), assuming the disk is thin, flat, and circular. A strongly flared disk that is close to edge-on cannot be ruled out, however. The CSO-JCMT and OVRO data favor centrally concentrated distributions of the surface density Sigma, where Sigma chi r(-p), and p > 1. This is not compatible with the relatively large sizes measured at lower frequency by BIMA and the VLA. No simple power-law disk model can be found that reproduces all of the millimeter and submillimeter data well. Such a model, with radial power laws in the surface density and temperature, and a single dust component, is therefore unlikely to be a good representation of the actual disk structure. One possibility that would help to reconcile the model with the data is the existence of more than one dust component, i.e., a range of grain sizes or structures in the disk and no unique value of the emissivity index beta. Future models should allow for this as well as for disk geometries that are not thin and flat. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. UNIV CAMBRIDGE,CAVENDISH LAB,MULLARD RADIO ASTRON OBSERV,CAMBRIDGE CB3 0HE,ENGLAND. NR 43 TC 79 Z9 79 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 NOV 10 PY 1997 VL 489 IS 2 BP 917 EP 927 DI 10.1086/304815 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF300 UT WOS:A1997YF30000037 ER PT J AU Charpinet, S Fontaine, G Brassard, P Dorman, B AF Charpinet, S Fontaine, G Brassard, P Dorman, B TI Gravity-mode instabilities in models of post-extreme horizontal branch stars: Another class of pulsating stars? SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, interiors; stars, oscillations; subdwarfs; white dwarfs ID SUBDWARF B-STARS; DA WHITE-DWARFS; THERMAL-CONDUCTIVITIES; DENSE MATTER; OPACITIES; PHASE; HOT AB We present new results of a stability analysis of realistic models of post-extreme horizontal branch stars. We find that g-mode instabilities develop in some of these models as a result of a potent epsilon-mechanism associated with the presence of an active H-burning shell. The epsilon-process drives low-order and low-degree g modes with typical periods in the range 40-125 s. The unstable models populate a broad instability strip covering the interval 76,000 greater than or similar to T(eef)greater than or similar to 44,000 K and are identified with low-mass DAO white dwarfs. They descend from stars that reach the zero-age ''extended'' horizontal branch with H-rich envelope masses M(env)greater than or similar to 0.0010 M.. Our computations indicate that some DAO stars should show luminosity variations resulting from pulsational instabilities. We suggest looking for brightness variations in six particularly promising candidates. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903. RP Charpinet, S (reprint author), UNIV MONTREAL,DEPT PHYS,CP 6128,SUCC CTR VILLE,MONTREAL,PQ H3C 3J7,CANADA. OI Charpinet, Stephane/0000-0002-6018-6180 NR 28 TC 24 Z9 24 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 NOV 10 PY 1997 VL 489 IS 2 BP L149 EP L152 DI 10.1086/316792 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF301 UT WOS:A1997YF30100008 ER PT J AU Sahu, KC Livio, M Petro, L Bond, HE Macchetto, FD Galama, TJ Groot, PJ vanParadijs, J Kouveliotou, C AF Sahu, KC Livio, M Petro, L Bond, HE Macchetto, FD Galama, TJ Groot, PJ vanParadijs, J Kouveliotou, C TI Observations of GRB 970228 and GRB 970508 and the neutron star merger model SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, observations; gamma rays, bursts ID GAMMA-RAY BURSTS; GALAXIES; COUNTS AB We present the discovery observations for the optical counterpart of the gamma-ray burster GRB 970508 and discuss its light curve in the context of the fireball model. We analyze the HST data for this object and conclude that any underlying galaxy must be fainter than R = 25.5. We also present a detailed analysis of the HST images of GRB 970228, from which a proper motion of the optical counterpart was claimed by Caraveo et al., and conclude that, within the uncertainties, there is no proper motion. We examine several aspects of the neutron star merger model for gamma-ray bursts. In particular, we use this model to predict the redshift distribution of gamma-ray bursters, and, adopting a recent determination of the cosmic star formation history, we show that the predicted log N-log P distribution is consistent with that observed for GRBs. C1 UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,NL-1098 SJ AMSTERDAM,NETHERLANDS. UNIV AMSTERDAM,CTR HIGH ENERGY ASTROPHYS,NL-1098 SJ AMSTERDAM,NETHERLANDS. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. RP Sahu, KC (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X; Petro, Larry/0000-0001-8879-528X NR 60 TC 32 Z9 32 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 NOV 10 PY 1997 VL 489 IS 2 BP L127 EP & DI 10.1086/316786 PN 2 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF301 UT WOS:A1997YF30100003 ER PT J AU Patt, FS Woodward, RH Gregg, WW AF Patt, FS Woodward, RH Gregg, WW TI An automated method for navigation assessment for Earth survey sensors using island targets SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID AVHRR IMAGE NAVIGATION AB An automated method has been developed for performing navigation assessment on satellite-based Earth sensor data. The method utilizes islands as targets which can be readily located in the sensor data and identified with reference locations. The essential elements are an algorithm for classifying the sensor data according to source, a reference catalogue of island locations, and a robust pattern-matching algorithm for island identification. The algorithms were developed and tested for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), an ocean colour sensor. This method will allow navigation error statistics to be automatically generated for large numbers of points, supporting analysis over large spatial and temporal ranges. C1 NASA,GODDARD SPACE FLIGHT CTR,GLOBAL CHANGE DATA CTR,GREENBELT,MD 20771. RP Patt, FS (reprint author), GEN SCI CORP,LAUREL,MD 20702, USA. NR 7 TC 14 Z9 14 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD NOV 10 PY 1997 VL 18 IS 16 BP 3311 EP 3336 DI 10.1080/014311697216900 PG 26 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA YD746 UT WOS:A1997YD74600002 ER PT J AU Cavalieri, DJ Gloersen, P Parkinson, CL Comiso, JC Zwally, HJ AF Cavalieri, DJ Gloersen, P Parkinson, CL Comiso, JC Zwally, HJ TI Observed hemispheric asymmetry in global sea ice changes SO SCIENCE LA English DT Article ID OCEAN-ATMOSPHERE MODEL; CARBON-DIOXIDE; TEMPERATURE; VARIABILITY; CO2 AB From November 1978 through December 1996, the areal extent of sea ice decreased by 2.9 +/- 0.4 percent per decade in the Arctic and increased by 1.3 +/- 0.2 percent per decade in the Antarctic, The observed hemispheric asymmetry in these trends is consistent with a modeled response to a carbon dioxide-induced climate warming. The interannual variations, which are 2.3 percent of the annual mean in the Arctic, with a predominant period of about 5 years, and 3.4 percent of the annual mean in the Antarctic, with a predominant period of about 3 years, are uncorrelated. RP Cavalieri, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,CODE 971,GREENBELT,MD 20771, USA. RI Parkinson, Claire/E-1747-2012 OI Parkinson, Claire/0000-0001-6730-4197 NR 23 TC 244 Z9 260 U1 0 U2 9 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD NOV 7 PY 1997 VL 278 IS 5340 BP 1104 EP 1106 DI 10.1126/science.278.5340.1104 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YE652 UT WOS:A1997YE65200045 ER PT J AU Thomas, JLC Bauschlicher, CW Hall, MB AF Thomas, JLC Bauschlicher, CW Hall, MB TI Binding of nitric oxide to first-transition-row metal cations: An ab initio study SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; MOLECULAR-ORBITAL METHODS; QUADRATIC CONFIGURATION-INTERACTION; ELECTRON CORRELATION THEORIES; COUPLED-CLUSTER SINGLES; BOND-ENERGIES; ORGANIC-MOLECULES; INTERACTION QCISD; CHARGE-TRANSFER; HARTREE-FOCK AB Equilibrium geometries and binding energies have been determined for several states of the transition metal nitrosyl cations, M(NO)(+), for the first-transition-row metals, scandium through copper, (M = Sc-Cu). The geometries were optimized using density functional theory (DFT) with a hybrid functional (B3LYP). Our calculations predict that the ground states for Sc(NO)(+), Ti(NO)(+), and V(NO)(+) have side-on geometries with the N and O approximately equidistant from the metal center. In these structures, N and O both form covalent bonds with the metal center. The ground states of M(NO)(+) for chromium through nickel are linearly bound at the nitrogen and Cr+-Co+ form bonds that are primarily electrostatic and dative in nature. Ground-state Ni(NO)(+) is more strongly bound than the other linear M(NO)(+) complexes, due to a larger contribution from NO to metal charge transfer in the bonding. Ground-state Cu(NO)+ has a bent structure with a one-electron bond between the Cu and N. All the ground-state electronic configurations are dominated by d(n+1) occupations of the metals. Binding energies were calculated with both DFT and the coupled cluster approximation with single and double excitations and perturbational estimate of the triple excitations (CCSD(T)) and corrected for zero-point energy. The binding energies for the ground-state complexes calculated with respect to the ground states of the metal ions at the CCSD(T) level increase from Sc to Ti, decrease to Mn, then increase again to nickel, decreasing again to copper. We found that the DFT binding energies for the ground-state complexes in this system were larger than the CCSD(T) values by as little as 3 kcal/mol for Sc(NO)(+) and Co(NO)(+) and as much as 17 kcal/mol for Mn(NO)(+), except for Ti(NO)(+) and Ni(NO)(+), where the DFT binding energies are 6.3 and 7.4 kcal/mol smaller than the CCSD(T) value, respectively. The weaker bond strengths in the middle of the transition row can be attributed to the dominance of electrostatic contributions in the bonding of these M(NO)(+) complexes. Excluding Cu, the M-NO bonds are stronger at either end of the row where the contribution from covalent bonding is larger. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. TEXAS A&M UNIV,DEPT CHEM,COLLEGE STN,TX 77843. RI Hall, Michael/B-9118-2013 OI Hall, Michael/0000-0003-3263-3219 NR 64 TC 68 Z9 68 U1 0 U2 19 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD NOV 6 PY 1997 VL 101 IS 45 BP 8530 EP 8539 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YF251 UT WOS:A1997YF25100023 ER PT J AU Lee, S Kim, J Yu, YH Isom, MP AF Lee, S Kim, J Yu, YH Isom, MP TI Prediction of rotor high-speed impulsive noise with a combined CFD-Kirchhoff method SO JOURNAL OF SOUND AND VIBRATION LA English DT Article AB A combined Computational Fluid Dynamics(CFD)-Kirchhoff method is presented for predicting high-speed impulsive noise generated by a rotor in hover. Two types of Kirchhoff integral formulas are used: one of them is a classical linear Kirchhoff formulation and the other a non-linear Kirchhoff formulation. An Euler finite-difference solver is executed first, from which a flow field is obtained to be used as an input to the KirchhofF formulation to predict the acoustic far-field. The calculations are performed at Mach numbers of 0.90 and 0.95 to investigate the effectiveness of the linear and non-linear Kirchhoff formulas for delocalized flow. During these calculations, the retarded time equation is also carefully examined, in particular, for the cases where a control surface is located outside the sonic cylinder, for which multiple roots are obtained. Predicted results of acoustic far-field with the linear Kirchhoff formulation agree well with the experimental data when the control surface is at a particular location (R-cs/R = 1.46), but the correlation weakens as it moves away from this specific location of the control surface due to the delocalized non-linear aerodynamic flow field. Calculations based on the non-linear Kirchhoff equation using the sonic cylinders as the control surfaces show reasonable agreements with the experimental data in the negative amplitudes for both tip Mach numbers of 0.90 and 0.95, except for some computational integration problems over a shock. It can be concluded that a non-linear formulation is necessary if the control surface is close to the blade and the flow is delocalized. (C) 1997 Academic Press Limited. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Lee, S (reprint author), SEOUL NATL UNIV,DEPT AEROSP ENGN,SEOUL,SOUTH KOREA. NR 19 TC 2 Z9 2 U1 0 U2 1 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 NOV 6 PY 1997 VL 207 IS 4 BP 453 EP 464 DI 10.1006/jsvi.1997.1069 PG 12 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA YH108 UT WOS:A1997YH10800002 ER PT J AU Giles, PM Duvall, TL Scherrer, PH Bogart, RS AF Giles, PM Duvall, TL Scherrer, PH Bogart, RS TI A subsurface flow of material from the Sun's equator to its poles SO NATURE LA English DT Article ID TIME-DISTANCE HELIOSEISMOLOGY; VELOCITY-FIELDS; MERIDIONAL FLOW; MOUNT-WILSON; SOLAR; CONVECTION; ROTATION AB Gas an the Sun's surface has been observed(1-4) to flow away from the equator towards both poles. If the same flow persists to great depths, it could plap an important dynamical role in the the eleven-year sunspot cycle, by carrying the magnetic remnants of the sunspots to high latitudes(5). An even deeper counterflow, which would be required to maintain mass balance, could explain why new sunspots form at lower latitudes as the cycle progresses(6). These deep flows would also redistribute angular momentum within the Sun, and therefore help to maintain the faster rotation of the equator relative to the poles(7). Here pie report the detection, using helioseismic tomography, of the longitude-averaged subsurface now in the outer 4% of the Sun. We find that the subsurface now is approximately constant in this depth range, and that the speed is similar to that seen on the surface. This demonstrates that the surface flow penetrates deeply, sep that it is likely to be an important factor In solar dynamics. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. STANFORD UNIV,WW HANSEN EXPT PHYS LAB,STANFORD,CA 94305. RP Giles, PM (reprint author), STANFORD UNIV,DEPT APPL PHYS,STANFORD,CA 94305, USA. RI Duvall, Thomas/C-9998-2012 NR 22 TC 213 Z9 215 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD NOV 6 PY 1997 VL 390 IS 6655 BP 52 EP 54 DI 10.1038/36294 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YE477 UT WOS:A1997YE47700046 ER PT J AU Riotto, A AF Riotto, A TI Cosmological implications of low energy supersymmetry breaking models SO PHYSICS LETTERS B LA English DT Article ID COSMIC STRINGS; SUPERCONDUCTING STRINGS; STANDARD MODEL; ANOMALOUS U(1); PHYSICS; SUPERGRAVITY; TECHNICOLOR; SYMMETRIES; DYNAMICS; SPRINGS AB We show that stable local cosmic strings are a generic prediction of supersymmetric models where supersymmetry is broken at scales within a few orders of magnitude of the weak scale and is fed down to the observable sector by gauge interactions. The typical energy scale of these strings is about 10(2) TeV. Since in the most general and natural scenario there are two different sources of contributions to ordinary superpartner masses, gauge mediation from the messanger sector and anomalous U(1) D-terms, novel features are that the cosmic strings may be superconducting with the role of bosonic charge carriers played by squarks and sleptons and that some baryonic or leptonic charge may be stored in the core of the string. Possible cosmological and astrophysical implications of these superconducting strings are discussed. (C) 1997 Published by Elsevier Science B.V. RP Riotto, A (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,POB 500,BATAVIA,IL 60510, USA. NR 51 TC 7 Z9 7 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 NOV 6 PY 1997 VL 413 IS 1-2 BP 22 EP 29 DI 10.1016/S0370-2693(97)01100-3 PG 8 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YH890 UT WOS:A1997YH89000004 ER PT J AU Snell, EH Boggon, TJ Helliwell, JR Moskowitz, ME Nadarajah, A AF Snell, EH Boggon, TJ Helliwell, JR Moskowitz, ME Nadarajah, A TI CCD video observation of microgravity crystallization of lysozyme and correlation with accelerometer data SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID PROTEIN CRYSTAL-GROWTH; KINETICS; FACILITIES; SOLUBILITY; TRANSPORT AB Lysozyme has been crystallized using the ESA Advanced Protein Crystallization Facility onboard the NASA Space Shuttle Orbiter during the IML-2 mission. CCD video monitoring was used to follow the crystallization process and evaluate the growth rate. During the mission some tetragonal crystals were observed moving over distances of up to 200 mu m. This was correlated with microgravity disturbances caused by firings of vernier jets on the Orbiter. Growth-rate measurement of a stationary crystal (which had nucleated on the growth reactor wall) showed spurts and lulls correlated with an onboard activity: astronaut exercise. The stepped growth rates may be responsible for the residual mosaic block structure seen in crystal mosaicity and topography measurements. C1 UNIV MANCHESTER,DEPT CHEM,MANCHESTER M13 9PL,LANCS,ENGLAND. NASA,LEWIS RES CTR,TAL CUT CO,PIMS GRP,CLEVELAND,OH 44135. UNIV TOLEDO,DEPT CHEM ENGN,MACROMOL ENGN LAB,TOLEDO,OH 43606. RI Helliwell, John /C-4587-2014 OI Helliwell, John /0000-0002-0520-7540 NR 28 TC 23 Z9 23 U1 0 U2 2 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 NOV 1 PY 1997 VL 53 BP 747 EP 755 DI 10.1107/S0907444997007968 PN 6 PG 9 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA YJ649 UT WOS:A1997YJ64900015 PM 11540584 ER PT J AU Forsythe, EL Snell, EH Pusey, ML AF Forsythe, EL Snell, EH Pusey, ML TI Crystallization of chicken egg-white lysozyme from ammonium sulfate SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID DYNAMIC LIGHT-SCATTERING; PROTEIN CRYSTALLIZATION; PHASE-TRANSITION; CRYSTAL-GROWTH; RESOLUTION; SOLUBILITY; TEMPERATURE; APPARATUS; EXAMPLE; SALTS AB Chicken egg-white lysozyme was crystallized from ammonium sulfate over the pH range 4.0-7.8, with protein concentrations from 100 to 150 mg ml(-1). Crystals were obtained by vapor-diffusion or batch-crystallization methods. The protein crystallized in two morphologies with an apparent morphology dependence on temperature and protein concentration. In general, tetragonal crystals could be grown by lowering the protein concentration or temperature. Increasing the temperature or protein concentration resulted in the growth of orthorhombic crystals. Representative crystals of each morphology were selected for X-ray analysis. The tetragonal crystals belonged to the P4(3)2(1)2 space group with crystals grown at pH 4.4 having unit-cell dimensions of a = b = 78.71, c = 38.6 Angstrom and diffracting to beyond 2.0 Angstrom. The orthorhombic crystals, grown at pH 4.8, were of space group P2(1)2(1)2 and had unit-cell dimensions of a = 30.51, b = 56.51 and c = 73.62 Angstrom. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP Forsythe, EL (reprint author), USRA,4950 COR DR,SUITE 100,HUNTSVILLE,AL 35806, USA. NR 30 TC 14 Z9 14 U1 0 U2 8 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 NOV 1 PY 1997 VL 53 BP 795 EP 797 DI 10.1107/S0907444997006896 PN 6 PG 3 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA YJ649 UT WOS:A1997YJ64900025 PM 15299874 ER PT J AU Anderson, JL AF Anderson, JL TI Untitled SO AEROSPACE AMERICA LA English DT Letter RP Anderson, JL (reprint author), NASA,ADV CONCEPTS OFF,WASHINGTON,DC 20546, USA. NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD NOV PY 1997 VL 35 IS 11 BP 8 EP 8 PG 1 WC Engineering, Aerospace SC Engineering GA YE113 UT WOS:A1997YE11300004 ER PT J AU Zapata, E Dankhoff, WF AF Zapata, E Dankhoff, WF TI Defining the parameters for affordable space transportation SO AEROSPACE AMERICA LA English DT Article RP Zapata, E (reprint author), NASA KENNEDY,KENNEDY SPACE CTR,FL, USA. NR 0 TC 0 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD NOV PY 1997 VL 35 IS 11 BP 38 EP 41 PG 4 WC Engineering, Aerospace SC Engineering GA YE113 UT WOS:A1997YE11300012 ER PT J AU Hurst, CJ Roman, MC Garland, JL Obenhuber, DC Brittain, AM AF Hurst, CJ Roman, MC Garland, JL Obenhuber, DC Brittain, AM TI Microbiological aspects of space exploration SO ASM NEWS LA English DT Article C1 US EPA,NATL RISK MANAGEMENT RES LAB,MICROBIAL CONTAMINANTS CONTROL BRANCH,CINCINNATI,OH 45268. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ENVIRONM CONTROL & LIFE SUPPORT BRANCH,HUNTSVILLE,AL 35812. ADV LIFE SUPPORT & SPACE BIOL GRP,KENNEDY SPACE CTR,FL. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ENVIRONM CHEM LAB,HUNTSVILLE,AL 35812. HAWAII PACIFIC COLL,HONOLULU,HI. NR 0 TC 3 Z9 3 U1 0 U2 3 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1325 MASSACHUSETTS AVENUE, NW, WASHINGTON, DC 20005-4171 SN 0044-7897 J9 ASM NEWS JI ASM News PD NOV PY 1997 VL 63 IS 11 BP 611 EP 615 PG 21 WC Microbiology SC Microbiology GA YF693 UT WOS:A1997YF69300015 ER PT J AU Cole, AA Mould, JR Gallagher, JS Clarke, JT Trauger, JT Ballester, GE Burrows, CJ Casertano, S Crisp, D Griffiths, R Hester, JJ Hoessel, JG Holtzman, JA Scowen, PA Stapelfeldt, KR Westphal, JA AF Cole, AA Mould, JR Gallagher, JS Clarke, JT Trauger, JT Ballester, GE Burrows, CJ Casertano, S Crisp, D Griffiths, R Hester, JJ Hoessel, JG Holtzman, JA Scowen, PA Stapelfeldt, KR Westphal, JA TI Far-ultraviolet imaging of the Large Magellanic Cloud populous cluster NGC 1978 with WFPC2 SO ASTRONOMICAL JOURNAL LA English DT Article ID ASYMPTOTIC GIANT BRANCH; INTERMEDIATE-MASS STARS; GLOBULAR-CLUSTERS; BLUE STRAGGLERS; AGE CALIBRATION; PERFORMANCE; EVOLUTION; FIELD; LMC; EXTINCTION AB We have imaged the similar to 2.2 billion-year-old Large Magellanic Cloud populous cluster NGC 1978 in the far-ultraviolet and visible with the second Wide Field/Planetary Camera (WFPC2) on the Hubble Space Telescope. The far-ultraviolet images show a sparse stellar held with little apparent density enhancement in the cluster core. The visible images are dominated by the cluster's first-ascent and second-ascent red giants, which are completely invisible to the far-ultraviolet filter. No evidence for a hot horizontal branch population of core-helium-burning stars is seen; nor is there any apparent indication of a significant blue straggler population. These results suggest that the presence of a rich, young population of field stars in the NGC 1978 region is responsible for the unusual location of the cluster in the integrated light color-color plots produced by IUE. (C) 1997 American Astronomical Society. C1 AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA. UNIV MICHIGAN,DEPT ATMOSPHER & OCEAN SCI,ANN ARBOR,MI 48109. CALTECH,JET PROP LAB,PASADENA,CA 91109. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. JOHNS HOPKINS UNIV,DEPT ASTRON,BALTIMORE,MD 21218. ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. RP Cole, AA (reprint author), UNIV WISCONSIN,DEPT ASTRON,475 N CHARTER ST,MADISON,WI 53706, USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013; OI Cole, Andrew/0000-0003-0303-3855 NR 35 TC 6 Z9 6 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1997 VL 114 IS 5 BP 1945 EP 1950 DI 10.1086/118616 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD884 UT WOS:A1997YD88400018 ER PT J AU OConnell, RW Dorman, B Shah, RY Rood, RT Landsman, WB Witt, AN Bohlin, RC Neff, SG Roberts, MS Smith, AM Stecher, TP AF OConnell, RW Dorman, B Shah, RY Rood, RT Landsman, WB Witt, AN Bohlin, RC Neff, SG Roberts, MS Smith, AM Stecher, TP TI Ultraviolet imaging of the globular cluster 47 Tucanae SO ASTRONOMICAL JOURNAL LA English DT Article ID HORIZONTAL-BRANCH; STELLAR PHOTOMETRY; BLUE STRAGGLERS; COLOR-MAGNITUDE; 47-TUCANAE; GALAXIES; STARS; POPULATIONS; TELESCOPE; NGC-1851 AB We have used the Ultraviolet Imaging Telescope to obtain far-UV (1620 Angstrom), wide field (40' diameter) images of the prototypical metal-rich globular cluster 47 Tucanae. We find a population of about 20 hot (T-eff>9000 K) objects near or above the predicted UV luminosity of the hot horizontal branch (HE) and lying within two half-light radii of the cluster center. We believe these are normal hot HE and post-HE objects. IUE spectra of two of the post-HE candidates, lying similar to 1.5 mag above the theoretical ZAHB, imply temperatures of 14 000 and greater than or similar to 30 000 K. The radial distribution of the detected stars parallels the distribution of the V-band light. These observations, and recent HST photometry of two other metal-rich clusters, demonstrate that systems with populous, cool HBs can nonetheless produce hot HE and post-HE stars, probably through normal single-star evolutionary processes rather than from binary or other dynamical interactions. The cluster center also contains an unusual diffuse far-UV source which is more extended than its V-band light. It is possible that this is associated with an intracluster medium, for which there was earlier infrared and x-ray evidence. (C) 1997 American Astronomical Society. C1 NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, HUGHES STX CORP, GREENBELT, MD 20771 USA. UNIV TOLEDO, RITTER OBSERV, TOLEDO, OH 43606 USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. NATL RADIO ASTRON OBSERV, CHARLOTTESVILLE, VA 22903 USA. RP OConnell, RW (reprint author), UNIV VIRGINIA, DEPT ASTRON, POB 3818, CHARLOTTESVILLE, VA 22903 USA. OI Shah, Ronak/0000-0002-2801-6317; Witt, Adolf/0000-0003-0760-4483 NR 49 TC 19 Z9 19 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 EI 1538-3881 J9 ASTRON J JI Astron. J. PD NOV PY 1997 VL 114 IS 5 BP 1982 EP 1991 DI 10.1086/118619 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD884 UT WOS:A1997YD88400021 ER PT J AU Shen, ZQ Wan, TS Moran, JM Jauncey, DL Reynolds, JE Tzioumis, AK Gough, RG Ferris, RH Sinclair, MW Jiang, DR Hong, XY Liang, SG Costa, ME Tingay, SJ McCulloch, PM Lovell, JEJ King, EA Nicolson, GD Murphy, DW Meier, DL vanOmmen, TD Edwards, PG White, GL AF Shen, ZQ Wan, TS Moran, JM Jauncey, DL Reynolds, JE Tzioumis, AK Gough, RG Ferris, RH Sinclair, MW Jiang, DR Hong, XY Liang, SG Costa, ME Tingay, SJ McCulloch, PM Lovell, JEJ King, EA Nicolson, GD Murphy, DW Meier, DL vanOmmen, TD Edwards, PG White, GL TI A 5-GHz southern hemisphere VLBI survey of compact radio sources .1. SO ASTRONOMICAL JOURNAL LA English DT Review ID BL-LACERTAE OBJECTS; FREQUENCY VARIABLE SOURCES; ACTIVE GALACTIC NUCLEI; MILLIMETER CONTINUUM MEASUREMENTS; CORE-DOMINATED QUASARS; COMPLETE SAMPLE; AO 0235+164; SPECTROSCOPIC OBSERVATIONS; MILLIARCSECOND STRUCTURE; OPTICAL POLARIZATION AB We report the results of a 5-GHz southern hemisphere VLBI survey of compact extragalactic radio sources. These observations were undertaken with the SHEVE array plus Shanghai station in 1992 November. A sample of 22 sources was observed and images of 20 of them were obtained. Of the 20 sources imaged, 15 showed core-jet structure, I had a two-sided jet, and 4 had only single compact cores. Eleven of the 16 core-jet (including one two-sided jet) sources showed some evidence of bent jets. No compact doubles were found. A comparison with previous images and the temporal variability of the radio flux density showed evidence for superluminal motion in four of the sources. Five sources were high-energy (> 100 MeV) gamma-ray sources. Statistical analysis showed the dominance of highly polarized quasars among the detected gamma-ray sources, which emphasizes the importance of beaming effect in the gamma-ray emission. (C) 1997 American Astronomical Society. C1 SHANGHAI ASTRON OBSERV,SHANGHAI 200030,PEOPLES R CHINA. CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA. UNIV WESTERN AUSTRALIA,DEPT PHYS,NEDLANDS,WA 6009,AUSTRALIA. AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA. UNIV TASMANIA,DEPT PHYS,HOBART,TAS 7001,AUSTRALIA. HARTEBEESTHOEK RADIO ASTRON OBSERV,ZA-1740 KRUGERSDORP,SOUTH AFRICA. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV ADELAIDE,DEPT PHYS,ADELAIDE,SA 5005,AUSTRALIA. UNIV WESTERN SYDNEY NEPEAN,DEPT PHYS,NEPEAN,NSW 2747,AUSTRALIA. RP Shen, ZQ (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. RI Tingay, Steven/B-5271-2013; 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 114 TC 44 Z9 45 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1997 VL 114 IS 5 BP 1999 EP 2015 DI 10.1086/118621 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD884 UT WOS:A1997YD88400023 ER PT J AU vanBelle, GT Dyck, HM Thompson, RR Benson, JA Kannappan, SJ AF vanBelle, GT Dyck, HM Thompson, RR Benson, JA Kannappan, SJ TI Angular size measurements of carbon Miras and S-type stars SO ASTRONOMICAL JOURNAL LA English DT Article ID CIRCUMSTELLAR DUST SHELLS; ASYMPTOTIC GIANT BRANCH; FLUX-LIMITED SAMPLE; MASS-LOSS; OXYGEN-RICH; IOTA INTERFEROMETER; RADIATIVE-TRANSFER; INTERSTELLAR DUST; EVOLVED STARS; EVOLUTION AB In our continuing investigation of highly evolved stars, we report new interferometric angular diameter observations of 5 carbon and 4 S-type Mira variable stars, and 4 non-Mira S stars. From the data, effective temperatures and linear radii are calculated. We compare the values of these parameters obtained for stars discussed in this paper with the same parameters for oxygen-rich giants/supergiants, oxygen-rich Mira variables, and non-Mira carbon stars presented in Dyck et al. (1996a, AJ, 111, 1705), van Belie et al. (1996, AJ, 112, 2147), and Dyck et al. (1996b, AJ, 112, 294), respectively. There are two principal findings from a synthesis of these studies. First, the non-Mira variables of each chemical class are consistently hotter and smaller than their Mira-variable counterparts. Second, the S stars lie between the oxygen-rich and the carbon-rich stars in both effective temperature and linear radius, for both the Mim-type and non-Mira stars. (C) 1997 American Astronomical Society. C1 UNIV WYOMING,DEPT PHYS & ASTRON,LARAMIE,WY 82071. USN OBSERV,FLAGSTAFF STN,FLAGSTAFF,AZ 86002. HARVARD UNIV,JEFFERSON LAB,DEPT PHYS,CAMBRIDGE,MA 02138. RP vanBelle, GT (reprint author), CALTECH,JET PROP LAB,MS 306-388,PASADENA,CA 91109, USA. NR 45 TC 39 Z9 39 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1997 VL 114 IS 5 BP 2150 EP 2156 DI 10.1086/118635 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD884 UT WOS:A1997YD88400037 ER PT J AU Burton, MG Haas, MR AF Burton, MG Haas, MR TI 17 mu m molecular hydrogen line emission from OMC-1 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM: molecules; ISM: individual objects (OMC-1); shock waves; molecular processes; techniques: spectroscopic; infrared: ISM: lines and bands ID PURE-ROTATIONAL EMISSION; SHOCK-WAVES; ORION NEBULA; BOW SHOCKS; REGION; H-2; CLOUDS; EXCITATION AB The v=0-0 S(1) line of molecular hydrogen at 17.03 mu m has been measured in the source OMC-1 along a 90 '' cut passing through the near-IR H-2 emission Peaks 1 and 2 using the Kuiper Airborne Observatory. The line flux is typically 50% of the 2.12 mu m v=1-0 S(1) line, but its distribution is somewhat more extended and it is relatively brighter at Peak 2. We interpret this as shocked emission coming from two regions of roughly equal brightness and lying close to the plane of the sky, plus a more extended contribution from slower shocks (similar to 5 km s(-1)) which do not contribute significantly to the near-IR vibrational-rotational lines. The 17 mu m line flux is an order of magnitude too strong to be explained by planar J- and C-shock models. However our data cannot distinguish between the merits of a cooling flow dominated by H-2 line emission and the integrated emission from a C-type bow-shock. Both models predict column density ratios close to those observed from a variety of lines covering a range from 1 000 to 25 000 K in upper state energy. We predict a flux for the ground state 28.2 mu m 0-0 S(0) line of similar to 2% that of the 1-0 S(1) line at Peak 1, and suggest that a consistent set of observations of the lowest pure rotational lines of Hz would allow us to distinguish between these shock models. C1 NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. RP Burton, MG (reprint author), UNIV NEW S WALES, SCH PHYS, SYDNEY, NSW 2052, AUSTRALIA. OI Burton, Michael/0000-0001-7289-1998 NR 39 TC 19 Z9 19 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1997 VL 327 IS 1 BP 309 EP 316 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YC422 UT WOS:A1997YC42200037 ER PT J AU Jenniskens, P Mulas, G Porceddu, I Benvenuti, P AF Jenniskens, P Mulas, G Porceddu, I Benvenuti, P TI Diffuse interstellar bands near 9600 angstrom: not due to C60(+) yet SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM: molecules; line: identification ID HYDROCARBONS; C-60(+); SEARCH AB High spectral resolution studies of the two Diffuse Interstellar Bands (DIB) previously assigned to C60(+) (lambda 9577 and lambda 9632) confirm that these DIBs have the same full-width-at-half-maximum and behave similarly in dense cloud environments where the DIBs are weakened relative to the diffuse interstellar medium. Their relative strength, however, is less than previously reported and differs from the relative intensities measured from matrix isolation spectroscopy. A simultaneous search for the two laboratory derived vibronic tranistions of C60(+) at about 9366 and 9419 Angstrom has not lead to the detection of the two weak counterparts stronger than 15% of lambda 9577. We conclude that for the diffuse band spectrum to be consistent with C60(+), not only the measured band positions have to be slightly different in the gas-phase, but also the relative intensity of the two main lines has to differ significantly from that of the known laboratory data. C1 UNIV CAGLIARI, DIPARTIMENTO SCI FIS, I-09124 CAGLIARI, ITALY. OSSERVATORIO ASTRON CAGLIARI, I-09012 CAPOTERRA, CA, ITALY. EUROPEAN SO OBSERV, SPACE TELESCOPE EUROPEAN COORDINATING FACIL, D-8046 GARCHING, GERMANY. ESA, SSD, DIV ASTROPHYS, F-75738 PARIS 15, FRANCE. RP NASA, AMES RES CTR, SETI INST, MAIL STOP 239-4, MOFFETT FIELD, CA 94035 USA. RI Mulas, Giacomo/B-7480-2013 OI Mulas, Giacomo/0000-0003-0602-6669 NR 15 TC 29 Z9 31 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1997 VL 327 IS 1 BP 337 EP 341 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YC422 UT WOS:A1997YC42200041 ER PT J AU Tingay, SJ AF Tingay, SJ TI Jet deflections in radio galaxies SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE shock waves; galaxies: individual: PKS 1308-441, 3C 277.3; galaxies: active; galaxies: jets; radio continuum: galaxies ID GAS AB Convincing evidence for the interaction between jets and their environments has been found in many extragalactic radio sources. In some radio galaxies these interactions appear to cause the jet to be deflected, not completely stopped or disrupted. This paper presents a simple model which accounts for jet deflections with oblique shocks in a relativistic flow. Using the model in conjunction with measurements of jet deflection angles, it is possible to derive estimates of pre and post-shock jet speeds as well as the strength and obliquity of the shocks. The model is applied to two radio galaxies, PKS 1308-441 and 3C 277.3. A range in shock strength of 2 - 30 and jet Lorentz factors of 2 - 5 are required to explain the data for these two sources. RP Tingay, SJ (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS238-332, PASADENA, CA 91109 USA. RI Tingay, Steven/B-5271-2013 NR 9 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 NOV PY 1997 VL 327 IS 2 BP 550 EP 554 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF731 UT WOS:A1997YF73100016 ER PT J AU Dolan, JF Boyd, PT Fabrika, S Tapia, S Bychkov, V Panferov, AA Nelson, MJ Percival, JW vanCitters, GW Taylor, DC Taylor, MJ AF Dolan, JF Boyd, PT Fabrika, S Tapia, S Bychkov, V Panferov, AA Nelson, MJ Percival, JW vanCitters, GW Taylor, DC Taylor, MJ TI SS433 in the ultraviolet SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE polarization; stars, individual, SS433; ultraviolet, stars ID LINEAR-POLARIZATION; X-RAY; SS-433; EMISSION; RADIO; SPECTROPOLARIMETRY; EXTINCTION; SPECTRUM; BINARY; STARS AB The High Speed Photometer (HSP) on the Hubble Space Telescope observed SS433 at 15 different epochs between 1993 May and November. Polarimetric observations were obtained in a 340 Angstrom FWHM bandpass centered at 2770 Angstrom; photometric observations were made in a bandpass extending between 1400 and 3000 Angstrom. The polarization in the UV is both large (< p > = 13 +/- 4%) and variable. Observations at the 6-m telescope of the Special Astrophysical Observatory find the polarization in the U band to be intermediate in magnitude between that in the V band and that we detect in the UV. These results are best explained by the existence of a Rayleigh scattering component in the polarized radiation. Less than 1.2% of the flux from SS433 between 1400 and 3000 Angstrom is modulated with a period between 200 mu s and 100 s at 164-d phase psi, = 0.131, when the two sets of emission lines in the SS433 spectrum have a local maximum in the separation of their redshifts. C1 NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. SPECIAL ASTROPHYS OBSERV, NIZHNII ARKHYZ 357147, RUSSIA. UNIV WISCONSIN, DEPT ASTRON, MADISON, WI 53706 USA. UNIV WISCONSIN, SPACE ASTRON LAB, MADISON, WI 53706 USA. NATL SCI FDN, DIV ASTRON SCI, ARLINGTON, VA 22230 USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. LORAS COLL, DEPT PHYS & ENGN, DUBUQUE, IA 52004 USA. RP Dolan, JF (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. RI Boyd, Patricia/D-3274-2012 NR 44 TC 30 Z9 32 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1997 VL 327 IS 2 BP 648 EP 655 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF731 UT WOS:A1997YF73100028 ER PT J AU Jenniskens, P Betlem, H deLignie, M Langbroek, M vanVliet, M AF Jenniskens, P Betlem, H deLignie, M Langbroek, M vanVliet, M TI Meteor stream activity .5. The Quadrantids, a very young stream SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE comets; meteors, meteoroids ID DUST TRAILS; ORBITS; COMETS AB This paper presents the first large set of precisely reduced orbits of Quadrantid meteoroids. These orbits were ob-l rained from photographic observations during the 1995 return of the Quadrantid stream. The orbits refer to the main peak of the activity curve, with an unidentified few being part of a broad background component. The measured dispersion of orbits is less than from previous data obtained by less accurate techniques.-In combination with existing stream models, we conclude that the main component is only about 500 years young, much less than the 5000-7500 year age that was widely assumed before. This main peak is now interpreted as an ''outburst'', with an evolution history similar to other near-comet type outbursts, while the background is thought to be the classical ''annual'' dust component. The stream does not originate from comet 96P/Machholz !. Rather? the parent object may be hiding as an asteroid-like object in a high-inclination orbit. An estimate of that orbit is given. C1 DUTCH METEOR SOC, NL-2318 NB LEIDEN, NETHERLANDS. RP Jenniskens, P (reprint author), NASA, AMES RES CTR, MAIL STOP 239-4, MOFFETT FIELD, CA 94035 USA. NR 68 TC 30 Z9 30 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1997 VL 327 IS 3 BP 1242 EP 1252 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YJ223 UT WOS:A1997YJ22300040 ER PT J AU Rudolph, AL Simpson, JP Haas, MR Erickson, EF Fich, M AF Rudolph, AL Simpson, JP Haas, MR Erickson, EF Fich, M TI Far-infrared abundance measurements in the outer galaxy SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy, abundances; H II regions; infrared, ISM lines and bands; ISM, abundances; ISM, individual (S127) ID H-II-REGIONS; CHEMICAL-COMPOSITION; INTERSTELLAR EXTINCTION; IONIZED-GAS; VLA SURVEY; GRADIENT; NITROGEN; MODELS; LINES; RATIO AB Five H II regions at large distances from the center of the Galaxy (R = 13-17 kpc) have been observed in the far-IR emission lines of [O III] (52 and 88 mu m), [N III] (57 mu m), and [S III] (19 mu m) using the Kuiper Airborne Observatory. These observations have been combined with Very Large Array radio continuum observations of these sources to determine the abundances of O++, N++, and S++ relative to hydrogen. A simple ionization correction scheme has been used to determine the total abundances of nitrogen and sulfur relative to hydrogen as well as the relative abundance N/O. For the two sources in common with previous optical studies (S127 and S128), we find good agreement between the far-infrared and optical determinations of N/H, S/H, and N/O. Our results from the outer Galaxy have been combined with previous far-infrared results to determine the abundance gradient of these elements in the Milky Way over a range of Galactocentric radii from R = 0 to R = 17 kpc. Our results are consistent with a gradient of log N/H = -0.111 +/- 0.012 dex kpc(-1) and a gradient of log SH = -0.079 +/- 0.009 dex kpc(-1). Our method is not able to determine: independently the abundances of both S and 0, although other evidence suggests that the O/S ratio is approximately constant. While these results differ from recent optical studies, which suggest that these abundance gradients flatten in the outer Galaxy, we do not vet have sufficient data to rule out such a change in the gradient. The log N/O data are better fitted by a two-step function with a value of -0.50 +/- 0.02 for R < 6.2 kpc and -0.83 +/- 0.04 for R > 6.2 kpc. Both of these values are consistent with secondary production of nitrogen, However, the outer Galaxy oxygen abundances are in the low abundance regime where nitrogen is expected to be produced by primary processes. C1 SETI INST, MT VIEW, CA USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV WATERLOO, GUELPH WATERLOO PROGRAM GRAD WORK PHYS, DEPT PHYS, WATERLOO, ON N2L 3G1, CANADA. UNIV TORONTO, CANADIAN INST THEORET ASTROPHYS, TORONTO, ON M5S 1A1, CANADA. RP Rudolph, AL (reprint author), HARVEY MUDD COLL, DEPT PHYS, CLAREMONT, CA 91711 USA. NR 44 TC 54 Z9 54 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1997 VL 489 IS 1 BP 94 EP 101 DI 10.1086/304758 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE139 UT WOS:A1997YE13900009 ER PT J AU Pendleton, GN Paciesas, WS Briggs, MS Preece, RD Mallozzi, RS Meegan, CA Horack, JM Fishman, CJ Band, DL Matteson, JL Skelton, RT Hakkila, J Ford, LA Kouveliotou, C Koshut, TM AF Pendleton, GN Paciesas, WS Briggs, MS Preece, RD Mallozzi, RS Meegan, CA Horack, JM Fishman, CJ Band, DL Matteson, JL Skelton, RT Hakkila, J Ford, LA Kouveliotou, C Koshut, TM TI The identification of two different spectral types of pulses in gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; radiation mechanisms, nonthermal ID INTENSITY DISTRIBUTION; BATSE; CONTINUUM AB It is shown in this study that two different types of spectral emission are generally produced in gamma-ray bursts. A subset of bursts is identified that exhibits a marked lack of fluence above 300 keV, and these bursts are shown to have luminosities about an order of magnitude lower than bursts with significant fluence above 300 keV. The bursts lacking emission above 300 keV exhibit an effectively homogeneous intensity distribution. In addition, it is shown that both types of emission are common in many bursts, demonstrating that a single source object is capable of generating both of them. These results strongly favor a gamma-ray burst source object that produces two different types of emission with varying degrees of superposition The impact of this behavior is strong enough that it affects the properties of the burst intensity distribution, as well as the burst spectral characteristics. C1 UNIV CALIF SAN DIEGO,CASS0111,LA JOLLA,CA 92093. MANKATO STATE UNIV,DEPT PHYS & ASTRON,MANKATO,MN 56002. UNIV WISCONSIN,DEPT PHYS & ASTRON,EAU CLAIRE,WI 54702. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. RP Pendleton, GN (reprint author), UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899, USA. RI Horack, John/J-6670-2016; OI Preece, Robert/0000-0003-1626-7335 NR 17 TC 70 Z9 71 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 NOV 1 PY 1997 VL 489 IS 1 BP 175 EP 198 DI 10.1086/304763 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE139 UT WOS:A1997YE13900017 ER PT J AU Takizawa, M Dotani, T Mitsuda, K Matsuba, E Ogawa, M Aoki, T Asai, K Ebisawa, K Makishima, K Miyamoto, S Iga, S Vaughan, B Rutledge, RE Lewin, WHG AF Takizawa, M Dotani, T Mitsuda, K Matsuba, E Ogawa, M Aoki, T Asai, K Ebisawa, K Makishima, K Miyamoto, S Iga, S Vaughan, B Rutledge, RE Lewin, WHG TI Spectral and temporal variability in the X-ray flux of GS 1124-683, Nova Muscae 1991 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; novae, cataclysmic variables; stars, individual (Novae Muscae 1991); stars, oscillations; X-rays, stars ID BLACK-HOLE CANDIDATES; DISCOVERY; EVOLUTION; GINGA; GRS-1124-68; GS-1124-683; SATELLITE; STATE; LINE AB Correlated variations in timing and spectral properties were observed near the peak of the outburst of Nova Muscae 1991 (GS 1124-683). Two regions with different spectral and timing characteristics can be distinguished in color-color and hardness-intensity diagrams. Two types of quasi-periodic oscillations (QPOs), each associated with regions in these diagrams, have been observed. Rapid flip-flop transitions sometimes occur between the regions. In one region the QPOs' centroid frequency is a strong, increasing function of X-ray intensity. Regions with similar characteristics and similar forms of QPOs were earlier found in GX 339-4 in its very high state. These two regions may turn out to be common and unique to black hole candidates in their very high state, even though they bear some similarities to the spectral branches in neutron star Z sources. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV TOKYO,DEPT PHYS,BUNKYO KU,TOKYO 113,JAPAN. OSAKA UNIV,FAC SCI,DEPT PHYS,TOYONAKA,OSAKA 560,JAPAN. CALTECH,DIV PHYS MATH & ASTRON,SPACE RADIAT LAB,PASADENA,CA 91125. MIT,DEPT PHYS,CAMBRIDGE,MA 02139. RP Takizawa, M (reprint author), INST SPACE & ASTRONAUT SCI,YOSHINODAI 3 CHOME,SAGAMIHARA,KANAGAWA 229,JAPAN. RI Mitsuda, Kazuhisa/C-2649-2008 NR 32 TC 47 Z9 49 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 NOV 1 PY 1997 VL 489 IS 1 BP 272 EP 283 DI 10.1086/304759 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE139 UT WOS:A1997YE13900025 ER PT J AU Stothers, RB Chin, CW AF Stothers, RB Chin, CW TI On two theories of the cyclical outbursts of eta Carinae SO ASTROPHYSICAL JOURNAL LA English DT Review DE stars, evolution; stars, individual (eta Carinae); stars, interiors; stars, oscillations; stars, variables, other (luminous blue variables) ID LUMINOUS BLUE VARIABLES; WOLF-RAYET STARS; HERTZSPRUNG-RUSSELL DIAGRAM; SMALL MAGELLANIC CLOUD; S-DORADUS VARIABLES; MASSIVE STARS; NEARBY GALAXIES; FLUCTUATION THEORY; HOMUNCULUS NEBULA; STELLAR EVOLUTION AB The star eta Carinae is an exceptionally luminous, blue variable that is at least partially evolved and undergoes major outbursts once every 3-6 yr on the average. On the basis of a new grid of stellar evolutionary tracks, we estimate that eta Car possessed an initial mass of 150-300 M. and is still burning hydrogen in its core. We test a hypothesis that eta Car is repeatedly encountering ionization-induced dynamical instability within its outer envelope. In that case, the star has probably already lost a third of its initial mass, while its surface hydrogen abundance has fallen to about half its original value. Its effective temperature, defined from quasi-static models in the conventional way, is predicted to be 8000 +/- 2000 K, but theoretically it might be as high as 200,000 K and so is not accurately known from the models. Although our assumption of hydrostatic equilibrium in the envelope of such an extremely luminous star is crude, the predicted cycles of mass loss agree well with these actually observed. Nevertheless, the models impose requirements before instability first breaks out that seem to be at variance with observations of extremely massive stars: stellar wind mass-loss rates falling too far on the low side and a significant amount of time spent as a B-type supergiant. Our models for eta Car itself may be too cool. An alternative destabilizing mechanism, based on an assumed supercritical radiative acceleration of material outward from the photosphere, applies potentially to very luminous, hot stars like eta Car, but produces no sustained cycles in our models. However, our models are only quasi-static, not hydrodynamic. For luminous blue variables generally, we confirm that the mean cycle time is, to a rough approximation, inversely proportional to luminosity. Our results, therefore, justify the use of luminous blue variables as extragalactic distance indicators. Analysis of a simple one-zone model supports our adopted criterion for dynamical instability and hence at least our theoretical results for ordinary luminous blue variables with low and moderate luminosities. RP Stothers, RB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 156 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 NOV 1 PY 1997 VL 489 IS 1 BP 319 EP 330 DI 10.1086/304771 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE139 UT WOS:A1997YE13900029 ER PT J AU Park, BT Petrosian, V Schwartz, RA AF Park, BT Petrosian, V Schwartz, RA TI Stochastic acceleration and photon emission in electron-dominated solar flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; plasmas; Sun, flares; Sun, X-rays, gamma rays waves ID FOKKER-PLANCK EQUATIONS; PARTICLES; COLLISIONS; DERIVATION; TRANSPORT; RAYS AB We examine four electron-dominated flares, two from the GRS instrument on 1989 March 6, and two from the EGRET and BATSE instruments on 1991 June 30 and 1991 July 2. Their photon spectra, which are almost all caused by electron bremsstrahlung radiation, show significant deviations from a simple power-law form. These are attributed to the deviations in the spectra of the accelerated electrons. We develop three stochastic acceleration models to explain the shape of the photon spectra: the hard sphere model, the whistler wave model, and a more general, but still simplified, stochastic acceleration model. For photon emissions, Ne use a simple sum of the thin target emission from the trapped electrons at the acceleration site near the loop top and the thick target emission from the escaping electrons which travel along the magnetic field lines and radiate in the denser chromosphere at the footpoints. Pie find that the hard sphere model does not fit any of the flares and can be ruled out. The other two models show that the high-energy cutoff in the two GRS flares can be attributed to synchrotron radiation losses in the presence of a 500 G magnetic field at the acceleration site. The observed break in the photon spectra of all four flares around 1 MeV is attributed to a combination of the energy dependence of the escape time of particles out of the acceleration region and the change in the energy dependence of the bremsstrahlung cross section between the nonrelativistic and relativistic regimes. Further steepening of the spectrum at even lower energies is caused by Coulomb losses at the acceleration site. We find that acceleration timescales as low as similar to 1 s are possible with a ratio of turbulent to the magnetic field energy densities of similar to 10(-4). We also set limits on the plasma density, the size of the acceleration region, and the spectrum of the plasma turbulence. C1 STANFORD UNIV,CTR SPACE SCI & ASTROPHYS,DEPT PHYS,STANFORD,CA 94305. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. HUGHES STX,GREENBELT,MD 20771. RP Park, BT (reprint author), STANFORD UNIV,CTR SPACE SCI & ASTROPHYS,DEPT APPL PHYS,STANFORD,CA 94305, USA. NR 36 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 NOV 1 PY 1997 VL 489 IS 1 BP 358 EP 366 DI 10.1086/304753 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE139 UT WOS:A1997YE13900032 ER PT J AU Andretta, V Jones, HP AF Andretta, V Jones, HP TI On the role of the solar corona and transition region in the excitation of the spectrum of neutral helium SO ASTROPHYSICAL JOURNAL LA English DT Article DE line, formation; radiative transfer; Sun, chromosphere; Sun, corona; Sun, transition region ID ENERGY-BALANCE; OPACITY CALCULATIONS; ACTIVE REGIONS; CROSS-SECTIONS; ATOMIC DATA; QUIET SUN; MODELS; CHROMOSPHERE; LINE; STARS AB We investigate the formation of the spectrum of neutral helium in the solar atmosphere by solving the corresponding non-LTE problem in an extended grid of model atmospheres. From the results we infer several general properties and scaling laws that can be used to discriminate the different proposed formation mechanisms. Some of the scaling laws have also been tested in a comparison with previous calculations made with different assumptions. In our models, the excitation of the spectrum by direct photoionization by EUV radiation shortward of 504 Angstrom followed by recombinations (PR mechanism), seems to be capable of influencing significantly the resonance continuum and the subordinate lines, even in the presence of other (collisional) excitation mechanisms. While this influence is almost unavoidable in most atmospheric features, it is hardly justifiable as the only possible contribution. Moreover, the resonance lines seem inclined to respond much more effectively to the conditions of the lower transition region, even in the presence of a significant coronal EUV illumination. With the help of the detailed non-LTE calculations and of the derived scaling laws, we explore the interplay of the possible formation mechanisms and their effect on the individual spectral features. C1 NATL SOLAR OBSERV, NASA,GODDARD SPACE FLIGHT CTR, LAB ASTRON & SOLAR PHYS,SW SOLAR STN, TUCSON, AZ 85726 USA. RP NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, CODE 682, GREENBELT, MD 20771 USA. NR 59 TC 111 Z9 111 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1997 VL 489 IS 1 BP 375 EP 394 DI 10.1086/304760 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE139 UT WOS:A1997YE13900034 ER PT J AU Canuto, VM AF Canuto, VM TI Overshooting in stars: Five old fallacies and a new model SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; stars, kinematics; turbulence ID CONVECTION; SIMULATION AB First, I discuss five fallacies of previous theoretical attempts to quantify overshooting in stars. I then suggest that the only reliable procedure is to solve the five dynamic equations for convective flux, kinetic and potential energy, turbulent pressure and dissipation rate of kinetic energy, plus the mean temperature equation. Finally, I discuss a recent solution of the new model that agrees with the latest helioseismological OV data and suggest that the same data be used to check the validity of the Schwarzschild criterion. RP Canuto, VM (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 22 TC 23 Z9 23 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 NOV 1 PY 1997 VL 489 IS 1 BP L71 EP L74 DI 10.1086/310955 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE140 UT WOS:A1997YE14000017 ER PT J AU Corbet, RHD Peele, AG AF Corbet, RHD Peele, AG TI RXTE observations of the Be star X-ray transient X0726-260 (4U 0728-25): Orbital and pulse periods SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (X0726-260); stars, neutron; X-rays, stars ID SPACED DATA; BINARIES; CATALOG AB Rossi X-Ray Timing Explorer (RXTE) All-Sky Monitor observations of the transient Be star X-ray source X0726-260 suggest a 34.5 day period. This is apparently confirmed by a serendipitous RXTE Proportional Counter Array (PCA) slew detection of the source on 1997 May 5, near the time of a predicted flux maximum. A subsequent 5 ks pointed observation of X0726-260 with the RXTE PCA detector was carried out on 1997 June 7, when X0726-260 was predicted to be bright again, and this revealed pulsations at a period of 103.2 s. If the 34.5 day period is orbital, then the pulse period is surprisingly long compared with that predicted by the correlation between orbital period and spin period observed for other Be/neutron star systems. A possible similarity with GRO J2058+42 is briefly discussed. C1 NASA,GODDARD SPACE FLIGHT CTR,NATL RES COUNCIL,GREENBELT,MD 20771. RP Corbet, RHD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,CODE 662,GREENBELT,MD 20771, USA. NR 24 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 NOV 1 PY 1997 VL 489 IS 1 BP L83 EP L86 DI 10.1086/310972 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE140 UT WOS:A1997YE14000020 ER PT J AU Habbal, SR Woo, R Fineschi, S ONeal, R Kohl, J Noci, G Korendyke, C AF Habbal, SR Woo, R Fineschi, S ONeal, R Kohl, J Noci, G Korendyke, C TI Origins of the slow and the ubiquitous fast solar wind SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, corona; Sun, solar wind ID POLAR CORONAL HOLE AB We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5R(s), obtained during the Galileo solar conjunction in 1997 January, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scattered component of the oxygen 1032 and 1037.6 Angstrom lines as measured with the ultraviolet coronagraph spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO). White light images of the corona from the large-angle spectroscopic coronagraph (LASCO) on SOHO taken simultaneously are used to place the Doppler radio scintillation and ultraviolet measurements in the context of coronal structures. These combined observations provide the first direct confirmation of the view recently proposed by Woo & Martin that the slow solar wind is associated with the axes, also known as stalks, of streamers. Furthermore, the ultraviolet observations also show how the fast solar wind is ubiquitous in the inner corona and that a velocity shear between the fast and slow solar wind develops along the streamer stalks. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV FLORENCE,I-50125 FLORENCE,ITALY. USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. RP Habbal, SR (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 30 TC 102 Z9 104 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 NOV 1 PY 1997 VL 489 IS 1 BP L103 EP & DI 10.1086/310970 PN 2 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE140 UT WOS:A1997YE14000025 ER PT J AU Leighly, KM Mushotzky, RF Nandra, K Forster, K AF Leighly, KM Mushotzky, RF Nandra, K Forster, K TI Evidence for relativistic outflows in narrow-line Seyfert 1 galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (IRAS 13224-3809, 1H 0707-495, PG 1404+226); X-rays, galaxies ID X-RAY; RADIO PROPERTIES; HIGH-STATE; QUASARS; QSOS AB We report the observation of features near 1 keV in the ASCA spectra from three narrow-line Seyfert 1 (NLS 1) galaxies. We interpret these as oxygen absorption in a highly relativistic outflow. If interpreted as absorption edges, the implied velocities are 0.2-0.3 c, near the limit predicted by ''line-locking'' radiative acceleration. If instead interpreted as broad absorption lines, the implied velocities are similar to 0.57 c, interestingly near the velocity of particles in the last stable orbit around a Kerr black hole, although a physical interpretation of this is not obvious. The features are reminiscent of the UV absorption lines seen in broad absorption Line quasars (BALQSOs), but with larger velocities, and we note the remarkable similarities in the optical emission line and broadband properties of NLS1s and low-ionization BALQSOs. C1 GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20770 USA. COLUMBIA UNIV, DEPT ASTRON, NEW YORK, NY 10027 USA. RP Leighly, KM (reprint author), COLUMBIA UNIV, COLUMBIA ASTROPHYS LAB, 538 W 120TH ST, NEW YORK, NY 10027 USA. NR 35 TC 41 Z9 43 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1997 VL 489 IS 1 BP L25 EP L28 DI 10.1086/310950 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE140 UT WOS:A1997YE14000006 ER PT J AU Mandzhavidze, N Ramaty, R Kozlovsky, B AF Mandzhavidze, N Ramaty, R Kozlovsky, B TI Solar atmospheric and solar flare accelerated helium abundances from gamma-ray spectroscopy SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; solar wind; Sun, abundances; Sun, atmosphere; Sun, flares; Sun, X-rays, gamma rays ID PROTON; OXYGEN; WIND AB From the measured fluences of alpha alpha and narrow gamma-ray lines we derive He abundances (He/O) in the gamma-ray production region of solar flares, most likely subcoronal regions located above the photosphere. The alpha alpha line is a spectral feature due to de-excitations in Li-7 and Be-7 produced by the interactions of alpha-particles with He. We find that the derived values of He/O are consistent with the photospheric He/O only if the accelerated particle alpha/p greater than or similar to 0.5. More conventional values (alpha/p similar or equal to 0.1) imply a higher He abundance in the subcoronal regions than in the photosphere. Indications for the existence of such He-enriched regions in the solar atmosphere are obtained from solar wind observations. We show how future high-resolution observations with Ge detectors could distinguish between the two possibilities of high alpha/p or high He/O (and hence high He/H) values by resolving an already observed spectral feature at similar to 1.02 MeV. This feature is dominated by lines produced exclusively in alpha-particle interactions with Fe-56 and He-3 interactions with O-16. In addition to the determination of alpha/p and the ambient He abundance, this will also determine the accelerated He-3/He-4 and its time development as the acceleration progresses. The relative intensities of the alpha alpha and narrow de-excitation lines confirm our previous finding that in the gamma-ray production region the abundance of Ne exceeds its measured coronal and generally accepted photospheric value. Thus, the subcoronal abundances of the two elements with the highest first ionization potential, He and Ne, are higher than their corresponding coronal abundances. C1 UNIV SPACE RES ASSOC,GREENBELT,MD 20771. TEL AVIV UNIV,SCH PHYS & ASTRON,RAMAT AVIV,ISRAEL. RP Mandzhavidze, N (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. NR 22 TC 38 Z9 39 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 NOV 1 PY 1997 VL 489 IS 1 BP L99 EP L102 DI 10.1086/310965 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE140 UT WOS:A1997YE14000024 ER PT J AU Smith, DM Heindl, WA Swank, J Leventhal, M Mirabel, IF Rodriguez, LF AF Smith, DM Heindl, WA Swank, J Leventhal, M Mirabel, IF Rodriguez, LF TI X-ray timing in 1E 1740.7-2942 and GRS 1758-258 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; X-rays, stars ID BLACK-HOLE CANDIDATES; GALACTIC-CENTER; GRANAT SIGMA; CYGNUS X-1; LOW STATE; 1E-1740.7-2942; GRS-1758-258; 1E1740.7-2942; VARIABILITY; SEARCH AB We report on deep observations of the Galactic bulge sources 1E 1740.7-2942 and GRS 1758-258 with the Rossi X-Ray Timing Explorer. These objects form a class of two, showing radio jets, very hard spectra, and persistent emission. Here we show that their power spectra are also similar: flat-topped noise, breaking to a power law, with a pair of weak, harmonically spaced quasi-periodic oscillations above the break and an integrated rms variability of similar to 20%. We discuss to what extent these results can be considered support for the identification of both as black hole candidates. C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. CEA SACLAY,CEN,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. NATL AUTONOMOUS UNIV MEXICO,INST ASTRON,MEXICO CITY 04510,DF,MEXICO. RP Smith, DM (reprint author), UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720, USA. RI Swank, Jean/F-2693-2012 NR 39 TC 29 Z9 30 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 NOV 1 PY 1997 VL 489 IS 1 BP L51 EP L54 DI 10.1086/310963 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE140 UT WOS:A1997YE14000012 ER PT J AU Williams, DM Mason, CG Gehrz, RD Jones, TJ Woodward, CE Harker, DE Hanner, MS Wooden, DH Witteborn, FC Butner, HM AF Williams, DM Mason, CG Gehrz, RD Jones, TJ Woodward, CE Harker, DE Hanner, MS Wooden, DH Witteborn, FC Butner, HM TI Measurement of submicron grains in the coma of comet Hale-Bopp C/1995 O1 during 1997 February 15-20 UT SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets, individual (Hale-Bopp C/1995 O1); interplanetary medium ID DUST COMA; EMISSION AB We present 1.20-18.5 mu m infrared (IR) spectrophotometric measurements of comet C/1995 O1 (Hale-Bopp) during 1997 February 15 and 20 UT. The spectral energy distribution (SED) was dominated by scattering and thermal emission from submicron sized dust grains that were unusually small, Hale-Bopp's surprising brightness may have been largely a result of the properties of its coma grains rather than the size of its nucleus. The thermal emission continuum from the grains had a superheat of S = T-color/T-BB approximate to 1.84, the peak of the 10 mu m silicate emission feature was 1.81 mag above the carbon grain continuum, and the albedo (reflectivity) of the grains was approximate to 0.41 at a scattering angle of theta = 144 degrees. These are the highest values for these empirical parameters ever observed in 20 years of optical/IR measurements of bright comets. The observations indicate that the optically important grains dominating the visual scattering and near-IR emission from the coma had an average radius of a less than or equal to 0.4 mu m. The strong silicate feature is produced by grains with a similar size range. These dust radii are comparable to the radii of the grains that condense in the outflows of some novae (''stardust'') but still about 10 times larger than the average radius of the grains that produce the general interstellar extinction. C1 WYOMING INFRARED OBSERV,DEPT PHYS & ASTRON,LARAMIE,WY 82071. CALTECH,JET PROP LAB,PASADENA,CA 91109. NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. UNIV ARIZONA,CARNEGIE INST WASHINGTON,DEPT TERR MAGNETISM,TUCSON,AZ 85721. UNIV ARIZONA,SUBMILLIMETER TELESCOPE OBSERV,TUCSON,AZ 85721. RP Williams, DM (reprint author), UNIV MINNESOTA,SCH PHYS & ASTRON,DEPT ASTRON,116 CHURCH ST SE,MINNEAPOLIS,MN 55455, USA. NR 20 TC 54 Z9 54 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 NOV 1 PY 1997 VL 489 IS 1 BP L91 EP L94 DI 10.1086/310973 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE140 UT WOS:A1997YE14000022 ER PT J AU Turner, TJ George, IM Nandra, K Mushotzky, RF AF Turner, TJ George, IM Nandra, K Mushotzky, RF TI ASCA observations of type 2 Seyfert galaxies .1. Data analysis results SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Review DE galaxies, active; galaxies, nuclei; galaxies, Seyfert; X-rays, galaxies ID X-RAY-SPECTRUM; ACTIVE GALACTIC NUCLEI; BROAD-LINE REGIONS; IONIZING-RADIATION; INFRARED GALAXIES; NEARBY GALAXIES; H-I; EMISSION; STARBURST; NGC-1068 AB We present ASCA spatial, temporal, and spectral data for a sample of 26 observations of 25 type 2 active galactic nuclei (AGNs), composed of 17 Seyfert 2 galaxies and eight narrow emission line galaxies (NELGs). Twenty-four of the 25 sources were detected. The ASCA images are generally consistent with emission from point sources at energies above similar to 3 keV. We use archival ROSAT data to examine each field at high spatial resolution and to check for the presence of sources that would contaminate the ASCA data. Of the five sources bright enough for 128 s temporal analysis, three are variable at >99% confidence, with characteristics consistent with those observed in Seyfert 1 galaxies. Analysis on a timescale of 5760 s reveals six sources variable at >99% confidence, and comparison with previous X-ray results shows most of the sample to be variable in hard X-ray flux on timescales of years. Simple continuum models are fitted to the sample spectra to characterize the variety of spectral forms and hence to determine the fundamental nature of the X-ray spectrum of each source. No single spectral model provides an adequate fit to all the sample sources. Thirty-six percent of the sample cannot be adequately fitted by any of our test models (all rejected at >95% confidence). Approximately half of the sample have an iron K alpha line with an equivalent width consistent with an origin in the line-of-sight absorber; the remaining lines must be produced in material out of the line of sight. Absorbing columns up to 10(24) atoms cm(-2) are detected, and even larger columns are inferred for some sources. The mean underlying hard X-ray power-law index is Gamma similar to 2. Many X-ray emission lines were detected at high levels of confidence. The iron K-shell regime is dominated by emission from ''neutral'' material. Many data sets also show evidence for complexity in the iron K alpha profile, which may be interpreted as evidence for broad-line profiles, including flux both redward and blueward of the line peak, and/or for the existence of hydrogen-like and helium-like iron K lines. Hydrogen-like and helium-like lines are detected from Fe, Ne, Si, S, and Ar in addition to Mg Lines. While almost half of the sample have an estimated starburst contribution of >30% in the 0.5-4.5 keV bandpass, the soft X-ray emission lines are not solely associated with a strong starburst component. C1 UNIV SPACE RES ASSOC,WASHINGTON,DC. NRC,NAS,WASHINGTON,DC. RP Turner, TJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 660,GREENBELT,MD 20771, USA. NR 123 TC 283 Z9 283 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 NOV PY 1997 VL 113 IS 1 BP 23 EP 67 DI 10.1086/313053 PG 45 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD367 UT WOS:A1997YD36700002 ER PT J AU Wanders, I Peterson, BM Alloin, D Ayres, TR Clavel, J Crenshaw, DM Horne, K Kriss, GA Krolik, JH Malkan, MA Netzer, H OBrien, PT Reichert, GA RodriguezPascual, PM Wamsteker, W Alexander, T Anderson, KSJ Benitez, E Bochkarev, NG Burenkov, AN Cheng, FZ Collier, SJ Comastri, A Dietrich, M DultzinHacyan, D Espey, BR Filippenko, AV Gaskell, CM George, IM Goad, MR Ho, LC Kaspi, S Kollatschny, W Korista, KT Laor, A MacAlpine, GM Mignoli, M Morris, SL Nandra, K Penton, S Pogge, RW Ptak, RL RodriguezEspinoza, JM SantosLleo, M Shapovalova, AI Shull, JM Snedden, SA Sparke, LS Stirpe, GM Sun, WH Turner, TJ Ulrich, MH Wang, TG Wei, C Welsh, WF Xue, SJ Zou, ZL AF Wanders, I Peterson, BM Alloin, D Ayres, TR Clavel, J Crenshaw, DM Horne, K Kriss, GA Krolik, JH Malkan, MA Netzer, H OBrien, PT Reichert, GA RodriguezPascual, PM Wamsteker, W Alexander, T Anderson, KSJ Benitez, E Bochkarev, NG Burenkov, AN Cheng, FZ Collier, SJ Comastri, A Dietrich, M DultzinHacyan, D Espey, BR Filippenko, AV Gaskell, CM George, IM Goad, MR Ho, LC Kaspi, S Kollatschny, W Korista, KT Laor, A MacAlpine, GM Mignoli, M Morris, SL Nandra, K Penton, S Pogge, RW Ptak, RL RodriguezEspinoza, JM SantosLleo, M Shapovalova, AI Shull, JM Snedden, SA Sparke, LS Stirpe, GM Sun, WH Turner, TJ Ulrich, MH Wang, TG Wei, C Welsh, WF Xue, SJ Zou, ZL TI Steps toward determination of the size and structure of the broad-line region in active galactic nuclei .11. Intensive monitoring of the ultraviolet spectrum of NGC 7469 SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE galaxies, active; galaxies, individual (NGC 7469); galaxies, Seyfert; ultraviolet, galaxies ID SHORT-TIMESCALE VARIABILITY; MULTIWAVELENGTH OBSERVATIONS; SEYFERT-GALAXIES; EMISSION-LINES; NGC-5548; CONTINUUM; NGC-4151; QUASARS; IUE; GEOMETRY AB From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line fluxes. From the time delays, one can estimate the size of the region dominating the production of the UV emission lines in this source. We find the strong UV emission lines to respond to continuum variations with time delays of about 2.(d)3-3.(d)1 for Ly alpha, 2.(d)7 for C IV lambda 1549, 1.(d)9-2.(d)4 for N V lambda 1240, 1.(d)7-1.(d)8 for Si IV lambda 1400, and 0.(d)7-1.(d)0 for He II lambda 1640. The most remarkable result, however, is the detection of apparent time delays between the different UV continuum bands. With respect to the UV continuum flux at 1315 Angstrom, the flux at 1485 Angstrom, 1740 Angstrom, and 1825 Angstrom lags with time delays of 0.(d)21, 0.(d)35, and 0.(d)28, respectively. Determination of the significance of this detection is somewhat problematic since it depends on accurate estimation of the uncertainties in the lag measurements, which are difficult to assess. We attempt to estimate the uncertainties in the time delays through Monte Carlo simulations, and these yield estimates of similar to 0.(d)07 for the 1 sigma uncertainties in the interband continuum time delays. Possible explanations for the delays include the existence of a continuum-flux reprocessing region close to the central source and/or a contamination of the continuum flux with a very broad time-delayed emission feature such as the Balmer continuum or merged Fe II multiplets. C1 UNIV ST ANDREWS, SCH PHYS & ASTRON, ST ANDREWS KY16 9SS, FIFE, SCOTLAND. CTR ETUD SACLAY, SERV ASTROPHYS, F-91191 GIF SUR YVETTE, FRANCE. UNIV COLORADO, CTR ASTROPHYS & SPACE ASTRON, BOULDER, CO 80309 USA. EUROPEAN SPACE AGCY, ISO PROJECT, MADRID 28080, SPAIN. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, COMP SCI CORP, GREENBELT, MD 20771 USA. JOHNS HOPKINS UNIV, DEPT PHYS & ASTRON, BALTIMORE, MD 21218 USA. UNIV CALIF LOS ANGELES, DEPT ASTRON, LOS ANGELES, CA 90024 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 LEICESTER, DEPT PHYS & ASTRON, LEICESTER LE1 7RH, LEICS, ENGLAND. EUROPEAN SPACE AGCY, IUE OBSERV, MADRID 28080, SPAIN. MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. NEW MEXICO STATE UNIV, DEPT ASTRON, DEPT 4500, LAS CRUCES, NM 88003 USA. UNIV NACL AUTONOMA MEXICO, INST ASTRON, MEXICO CITY 04510, DF, MEXICO. MOSCOW MV LOMONOSOV STATE UNIV, STERNBERG ASTRON INST, MOSCOW 119899, RUSSIA. RUSSIAN ACAD SCI, SPECIAL ASTROPHYS OBSERV, NIZHNII ARKHYZ 357147, KARACHAJ CHERKE, RUSSIA. UNIV SCI & TECHNOL, CTR ASTROPHYS, HEFEI, PEOPLES R CHINA. OSSERVATORIO ASTRON BOLOGNA, I-40126 BOLOGNA, ITALY. LANDESSTERNWARTE HEIDELBERG, KONIGSTUHL, D-69117 HEIDELBERG, GERMANY. UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. UNIV NEBRASKA, DEPT PHYS & ASTRON, LINCOLN, NE 68588 USA. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. UNIV SPACE RES ASSOC, WASHINGTON, DC USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. UNIV STERNWARTE GOTTINGEN, D-37083 GOTTINGEN, GERMANY. UNIV KENTUCKY, DEPT PHYS & ASTRON, LEXINGTON, KY 40506 USA. TECHNION ISRAEL INST TECHNOL, DEPT PHYS, IL-32000 HAIFA, ISRAEL. UNIV MICHIGAN, DEPT ASTRON, ANN ARBOR, MI 48109 USA. DOMINION ASTROPHYS OBSERV, VICTORIA, BC V8X 4M6, CANADA. BOWLING GREEN STATE UNIV, DEPT PHYS & ASTRON, BOWLING GREEN, OH 43403 USA. INST ASTROFIS CANARIAS, E-38200 LA LAGUNA, TENERIFE, SPAIN. LAEFF, E-28080 MADRID, SPAIN. UNIV COLORADO, JOINT INST LAB ASTROPHYS, BOULDER, CO 80309 USA. NATL INST STAND & TECHNOL, BOULDER, CO 80309 USA. UNIV WISCONSIN, DEPT ASTRON, MADISON, WI 53706 USA. NATL CENT UNIV, INST ASTRON, CHUNGLI 32054, TAIWAN. EUROPEAN SO OBSERV, D-85748 GARCHING, GERMANY. UNIV TEXAS, MCDONALD OBSERV, AUSTIN, TX 78712 USA. UNIV TEXAS, DEPT ASTRON, RLM 15308, AUSTIN, TX 78712 USA. CHINESE ACAD SCI, BEIJING ASTRON OBSERV, BEIJING 100080, PEOPLES R CHINA. RP Wanders, I (reprint author), OHIO STATE UNIV, DEPT ASTRON, 174 W 18TH AVE, COLUMBUS, OH 43210 USA. RI Morris, Simon/G-7981-2011; 王, 挺贵/B-8293-2013; Stirpe, Giovanna/O-9393-2015; Mignoli, Marco/O-9426-2015; Comastri, Andrea/O-9543-2015; OI Morris, Simon/0000-0003-4866-110X; Stirpe, Giovanna/0000-0002-3702-8731; Mignoli, Marco/0000-0002-9087-2835; Comastri, Andrea/0000-0003-3451-9970; Espey, Brian/0000-0002-2457-1380; Gaskell, C/0000-0003-4888-2009; SUN, WEI-HSIN/0000-0002-7474-8658 NR 39 TC 121 Z9 121 U1 1 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD NOV PY 1997 VL 113 IS 1 BP 69 EP 88 DI 10.1086/313054 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD367 UT WOS:A1997YD36700003 ER PT J AU Feldman, U Behring, WE Curdt, W Schuhle, U Wilhelm, K Lemaire, P Moran, TM AF Feldman, U Behring, WE Curdt, W Schuhle, U Wilhelm, K Lemaire, P Moran, TM TI A coronal spectrum in the 500-1610 angstrom wavelength range recorded at a height of 21,000 kilometers above the west solar limb by the SUMER instrument on Solar and Heliospheric Observatory SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE line, identification; Sun, corona; Sun, UV radiation ID EXPERIMENTAL LEVEL VALUES; ISOELECTRONIC SEQUENCE; N=2 CONFIGURATIONS; LINES; CLASSIFICATIONS; IONS AB We present a solar coronal spectrum recorded by the extreme UV spectrometer SUMER on the Solar and Heliospheric Observatory. The spectrum was taken between 21:28 UT on 1996 June 25 and 02:47 UT on 1996 June 26, at a height of 21,000 km above the west equatorial limb with the slit oriented in the north-south direction. At the time of the observations the Sun was rather quiet, and the west limb appeared ''devoid of any activity.'' The spectrum, which covers the 500-1610 Angstrom wavelength range, originates from plasmas with temperatures ranging between 1.5 x 10(4) and 1.5 x 10(6) K. Identification of lines originating from different temperature regimes is facilitated by the appearance of their intensity along the 300'' long slit. Well over 800 lines have been found, many of which were not previously observed. We present the entire spectrum and discuss line identifications. A table of the wavelengths of lines observed, with their identifications and peak intensities, is provided. Although we have identified fines previously detected in laboratory plasmas and a number of new lines not previously observed, over 40% of the SUMER lines remain unidentified. Among the newly detected lines, some have a potential as plasma density diagnostics. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. MAX PLANCK INST AERON,D-37189 KATLENBURG DUHM,GERMANY. UNIV PARIS 11,INST ASTROPHYS SPATIALE,UNITE MIXTE CNRS,F-91405 ORSAY,FRANCE. APPL RES CORP,LANDOVER,MD 20785. RP Feldman, U (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375, USA. NR 34 TC 142 Z9 143 U1 0 U2 2 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 NOV PY 1997 VL 113 IS 1 BP 195 EP 219 DI 10.1086/313048 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD367 UT WOS:A1997YD36700008 ER PT J AU Visscher, L Dyall, KG AF Visscher, L Dyall, KG TI Dirac-Fock atomic electronic structure calculations using different nuclear charge distributions SO ATOMIC DATA AND NUCLEAR DATA TABLES LA English DT Article ID CONSISTENT FIELD METHOD; CLOSED-SHELL MOLECULES; KINETIC BALANCE; SIZE AB Numerical Hartree-Fock calculations based on the Dirac-Coulomb Hamiltonian for the first 109 elements of the periodic table are presented. The results give the total electronic energy, as a function of the nuclear model that is used, for four different models of the nuclear charge distribution. The main purpose of the calculations is to provide a set of benchmark results for basis set calculations that use a finite size nuclear model. (C) 1997 Academic Press. C1 Univ Groningen, Chem Phys Lab, NL-9747 AG Groningen, Netherlands. Univ Groningen, Ctr Mat Sci, NL-9747 AG Groningen, Netherlands. NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Visscher, L (reprint author), Odense Univ, Dept Chem, Campusvej 55, DK-5230 Odense M, Denmark. RI Visscher, Lucas/A-3523-2010 OI Visscher, Lucas/0000-0002-7748-6243 NR 9 TC 324 Z9 326 U1 7 U2 36 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0092-640X J9 ATOM DATA NUCL DATA JI Atom. Data Nucl. Data Tables PD NOV PY 1997 VL 67 IS 2 BP 207 EP 224 DI 10.1006/adnd.1997.0751 PG 18 WC Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Physics GA YR497 UT WOS:000071501200001 ER PT J AU Robinson, R Swaby, G Sutton, T Fife, C Powell, M Butler, BD AF Robinson, R Swaby, G Sutton, T Fife, C Powell, M Butler, BD TI Venturi vacuum systems for hypobaric chamber operations SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article AB Physiological studies of the effects of high altitude on man often require the use of a hypobaric chamber to simulate the reduced ambient pressures. Typical ''altitude'' chambers in use today require complex mechanical vacuum systems to evacuate the chamber air, either directly or via reservoir system. Use of these pumps adds to the cost of both chamber procurement and maintenance, and service of these pumps requires trained support personnel and regular upkeep. In this report we describe use of venturi vacuum pumps to perform the function of mechanical vacuum pumps for human and experimental altitude chamber operations. Advantages of the venturi pumps include their relatively low procurement cost, small size and light weight, ease of installation and plumbing, lack of moving parts, and independence from electrical power sources, fossil fuels and lubricants. Conversion of three hyperbaric chambers to combined hyper/hypobaric use is described. C1 UNIV TEXAS, SCH MED, DEPT ANESTHESIOL, BAROMED LAB, HOUSTON, TX 77030 USA. UNIV TEXAS, SCH MED, HERMANN CTR ENVIERONM AEROSP & IND MED, HOUSTON, TX 77030 USA. NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 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 NOV PY 1997 VL 68 IS 11 BP 1046 EP 1049 PG 4 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA YE737 UT WOS:A1997YE73700011 PM 9383507 ER PT J AU Stoner, AW AF Stoner, AW TI Shell middens as indicators of long-term distributional pattern in Strombus gigas, a heavily exploited marine gastropod SO BULLETIN OF MARINE SCIENCE LA English DT Article ID JUVENILE QUEEN CONCH; BAHAMAS AB Shell middens of the economically important gastropod Strombus gigas in the Exuma Sound system of the central Bahamas were located on the shores of islands near tidal inlets between the Exuma Sound and the Great Bahama Bank. The volume of shell middens was directly correlated (r = 0.944) with the abundance of juvenile conch in the shallow surrounding waters (log-log relationship). Radiocarbon dates for shells collected from the bottoms of large middens indicated that these shell accumulations reflect a history of fishing in the region dating back more than 400 yrs. The middens probably originated with the indigenous Lucayan population, then continued to accumulate through the European invasion of the Bahamas, the British Loyalist period, and up to the present date. The distribution of shell middens indicates that the eastern Sound never had an important conch fishery corroborating the present day low abundance of conch in the area, and advection of queen conch larvae from east to west. High shell volumes in the northern Sound reflect large conch populations and larval retention in that region. Shell middens can yield important insights into human history, and useful information on the biogeography, ecology, and long-term fisheries of heavily exploited molluscan species such as S. gigas. C1 Caribbean Marine Res Ctr, Vero Beach, FL 32963 USA. RP Stoner, AW (reprint author), Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 39 TC 9 Z9 9 U1 0 U2 5 PU ROSENSTIEL SCH MAR ATMOS SCI PI MIAMI PA 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA SN 0007-4977 J9 B MAR SCI JI Bull. Mar. Sci. PD NOV PY 1997 VL 61 IS 3 BP 559 EP 570 PG 12 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA ZP875 UT WOS:000073797400004 ER PT J AU Parrish, FA Goto, RS AF Parrish, FA Goto, RS TI Patterns of insular shark dynamics based on fishery bycatch and lifeguard surveillance at Oahu, Hawaii, 1983-1992 SO BULLETIN OF MARINE SCIENCE LA English DT Article AB Incidental shark sightings recorded by beach lifeguards and records of shark bycatch from fishery catch reports were evaluated as possible long-term indices (1983-1992) of insular shark dynamics. The daily lifeguarding of the 17 Oahu beaches provided a documentation of effort not available from fishery data. Identified seasonal and spatial trends in shark sightings were found to persist through successive years of surveillance and were roughly consistent with distributions of fishery bycatch. However, it was possible to attribute shark bycatch to changes in accessibility of fishing grounds and size of the fishing fleet. An evaluation of the potential biases in lifeguard data indicated that variables such as wind/surf conditions and beach attendance did not govern the frequency with which sharks were reported. Summer increases in sightings coincided with shark pupping activities, and winter pulses were roughly associated with periods of increased rainfall. Relationships with coast and season were evident, with significantly more sightings on the island's leeward coast. A survey of shark-related news stories compared with reports of shark sightings suggested that shark sightings increased on a limited scale with high media exposure. No consistent trend in abundance of sharks was detected over the full 10-yr period. The interannual pattern of shark sightings (scaled for effort) remains unexplained, despite comparison with fishery data, island runoff, sea-surface temperature, and known El Nino events. C1 NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. Dept Parks & Recreat City & Cty Honolulu, Div Water Safety, Honolulu, HI 96815 USA. RP Parrish, FA (reprint author), NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, 2570 Dole St, Honolulu, HI 96822 USA. NR 31 TC 1 Z9 1 U1 0 U2 1 PU ROSENSTIEL SCH MAR ATMOS SCI PI MIAMI PA 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA SN 0007-4977 J9 B MAR SCI JI Bull. Mar. Sci. PD NOV PY 1997 VL 61 IS 3 BP 763 EP 777 PG 15 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA ZP875 UT WOS:000073797400012 ER PT J AU Sheridan, P McMahan, G Conley, G Williams, A Thayer, G AF Sheridan, P McMahan, G Conley, G Williams, A Thayer, G TI Nekton use of macrophyte patches following mortality of turtlegrass, Thalassia testudinum, in shallow waters of Florida Bay (Florida, USA) SO BULLETIN OF MARINE SCIENCE LA English DT Article ID COVERED MUD BANKS; SNAPPER LUTJANUS-GRISEUS; CYNOSCION-NEBULOSUS; ADJACENT WATERS; GRAY SNAPPER; POPULATION-DYNAMICS; CALLINECTES-SAPIDUS; AUSTRALIAN ESTUARY; SPOTTED SEATROUT; FISHERY HARVEST AB Widespread seagrass mortality in western Florida Bay has led to increased habitat heterogeneity: once-dominant Thalassia testudinum beds have become punctuated by mud algae, and Halodule wrightii patches. We tested the hypothesis that increased habitat heterogeneity leads to increased secondary production and diversity. Nekton densities in shallow (depths <1 m) Thalassia meadows and in mud algae, and Halodule patches were compared 12 times over 3 yrs using a quantitative 2.6 m(2) drop trap. Mean densities of fishes and decapods were usually significantly higher in Thalassia beds than in Halodule, algae, and mud patches. The reverse was true for species diversity and richness, which were usually significantly lower in Thalassia beds than in one or more patch types. Macrofaunal densities and species richness and diversity were usually not affected by site (two areas 15 km apart) or time (day vs, night). Six species comprised 84-99% of all organisms in each floral type. Mean densities of Lucania parva Opsanus beta, and Thor floridanus were almost always significantly higher in Thalassia beds than in Halodule, algae or mud patches. The opposite was true for mean densities of Floridichthys carpio, which were usually significantly lower in Thalassia than elsewhere. Mean densities of Penaeus duorarum were irregularly related to plant type, and those of Gobiosoma robustum were never related to plant type. Time of collection did not affect densities of any dominant species, but mean densities of Thor and Floridichthys were significantly higher on Ninemile Bank than on Sandy Key Bank. Lower nekton standing crops and increased species richness and diversity at the local scale may lead to system-wide faunal changes. However, fisheries seem not to have been affected by seagrass mortality and associated changes in habitat heterogeneity and the forage base. C1 Natl Marine Fisheries Serv, US Dept Commerce, NOAA, SE Fisheries Sci Ctr, Galveston, TX 77551 USA. Natl Marine Fisheries Serv, US Dept Commerce, NOAA, SE Fisheries Sci Ctr, Beaufort, NC 28516 USA. RP Natl Marine Fisheries Serv, US Dept Commerce, NOAA, SE Fisheries Sci Ctr, 4700 Ave U, Galveston, TX 77551 USA. NR 53 TC 11 Z9 12 U1 1 U2 1 PU ROSENSTIEL SCH MAR ATMOS SCI PI MIAMI PA 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA SN 0007-4977 EI 1553-6955 J9 B MAR SCI JI Bull. Mar. Sci. PD NOV PY 1997 VL 61 IS 3 BP 801 EP 820 PG 20 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA ZP875 UT WOS:000073797400015 ER PT J AU Hansen, MJ Madenjian, CP Selgeby, JH Helser, TE AF Hansen, MJ Madenjian, CP Selgeby, JH Helser, TE TI Gillnet selectivity for lake trout (Salvelinus namaycush) in Lake Superior SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID SPOTTED SEA-TROUT; SIZE-SELECTIVITY; FISHING GEAR; POPULATION; NEBULOSUS; EXAMPLE AB Gillnet selectivity for lake trout (Salvelinus namaycush) was estimated indirectly from catches in nets of 102-, 114-, 127-, 140-, and 152-mm stretch measure. Mesh selectivity was modeled as a nonlinear response surface that describes changes in the mean, standard deviation, and skewness of fish lengths across mesh sizes. Gillnet selectivity for lake trout was described by five parameters that explained 88% of the variation in wedged and entangled catches, 81% of the variation in wedged catches, and 82% of the variation in entangled catches. Combined catches of wedged and entangled lake trout were therefore described more parsimoniously than separate catches of wedged and entangled lake trout. Peak selectivity of wedged and entangled fish increased from 588 to 663 mm total length as mesh size increased from 102 to 152 mm, and relative selectivity peaked at a total length of 638 mm. The estimated lake trout population size-frequency indicated that gillnet catches were negatively biased toward both small and large lake trout. As a consequence of this bias, survival of Lake Superior lake trout across ages 9-11 was underestimated by about 20% when the catch curve was not adjusted for gillnet selectivity. C1 Univ Wisconsin, Coll Nat Resources, Stevens Point, WI 54481 USA. US Geol Survey, Great Lakes Sci Ctr, Ann Arbor, MI 48105 USA. US Geol Survey, Great Lakes Sci Ctr, Lake Super Biol Stn, Ashland, WI 54806 USA. Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. RP Hansen, MJ (reprint author), Univ Wisconsin, Coll Nat Resources, Stevens Point, WI 54481 USA. OI Hansen, Michael/0000-0001-8522-3876 NR 21 TC 38 Z9 43 U1 0 U2 7 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD NOV PY 1997 VL 54 IS 11 BP 2483 EP 2490 DI 10.1139/cjfas-54-11-2483 PG 8 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA YX539 UT WOS:000072050700002 ER PT J AU Sperber, KR Slingo, JM Inness, PM Lau, WKM AF Sperber, KR Slingo, JM Inness, PM Lau, WKM TI On the maintenance and initiation of the intraseasonal oscillation in the NCEP/NCAR reanalysis and in the GLA and UKMO AMIP simulations SO CLIMATE DYNAMICS LA English DT Article ID GENERAL-CIRCULATION MODEL; OUTGOING LONGWAVE RADIATION; MADDEN-JULIAN OSCILLATION; TROPICAL-EXTRATROPICAL INTERACTION; 30-60 DAY OSCILLATION; 40-50 DAY OSCILLATION; AIR-SEA INTERACTION; NORTHERN WINTER; SCALE CIRCULATION; PHASE PROPAGATION AB In this study, satellite-derived outgoing longwave radiation (OLR) and the reanalysis from the National Centers for Environmental Prediction/National Center for Atmospheric Research are used as verification data in a study of intraseasonal variability in the Goddard Laboratory for Atmospheres (GLA) and the United Kingdom Meteorological Office (UKMO) atmospheric general circulation models. These models simulated the most realistic intraseasonal oscillations (IO) of the 15 Atmospheric Model Intercomparison Project models previously analysed. During the active phase of the intraseasonal oscillation, convection is observed to migrate from the Indian Ocean to the western/central Pacific Ocean, and into the South Pacific Convergence Zone (SPCZ). The simulated convection, particularly in the GLA model, is most realistic over the western/central Pacific Ocean and the SPCZ. In the reanalysis, the baroclinic structure of the IO is evident in the eddy-stream function, and eastward migration of the anticyclone/cyclone pairs occurs in conjunction with the eastward development of convection. Both the GLA and UKMO models exhibit a baroclinic structure on intraseasonal time scales. The GLA model is more realistic than the UKMO model at simulating the eastward migration of the anticyclone/cyclone pairs when the convection is active over the western/central Pacific. In the UKMO model, the main heating is located off the equator, which contributes to the irregular structures seen in this model on intraseasonal time scales. The maintenance and initiation of the intraseasonal oscillation has also been investigated. Analysis of the latent heat flux indicates that evaporative wind feedback is not the dominant mechanism for promoting the eastward propagation of the intraseasonal oscillation since evaporation to the west of the convection dominants. The data suggest a wave-CISK (conditional instability of the second-kind) type mechanism, although the contribution by frictional convergence is not apparent. In the GLA model, enhanced evaporation tends to develop in-place over the west Pacific warm pool, while in the UKMO simulation westward propagation of enhanced evaporation is evident. It is suggested that lack of an interactive ocean may be associated with the models systematic failure to simulate the eastward transition of convection from the Indian Ocean into the western Pacific Ocean. This hypothesis is based upon the examination of observed sea surface temperature (SST) and its relationship to the active phase of the intraseasonal oscillation, which indicates that the IO may evolve as a coupled ocean-atmosphere mode. The eastward propagation of convection appears to be related to the gradient of SST, with above normal SST to the east of the convection maintaining the eastward evolution, and decreasing SST near the western portion of the convective envelope being associated with the cessation of convection. C1 UNIV READING,DEPT METEOROL,READING RG6 6AU,BERKS,ENGLAND. UNITED KINGDOM METEOROL OFF,HADLEY CTR CLIMATE PREDICT & RES,BRACKNELL RG12 2SY,BERKS,ENGLAND. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Sperber, KR (reprint author), LAWRENCE LIVERMORE NATL LAB,PROGRAM CLIMATE MODEL DIAG & INTERCOMPARISON,POB 808,LIVERMORE,CA 94551, USA. RI Sperber, Kenneth/H-2333-2012; Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 66 TC 115 Z9 122 U1 0 U2 8 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD NOV PY 1997 VL 13 IS 11 BP 769 EP 795 DI 10.1007/s003820050197 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YK951 UT WOS:A1997YK95100002 ER PT J AU Zhang, Y Sperber, KR Boyle, JS Dix, M Ferranti, L Kitoh, A Lau, KM Miyakoda, K Randall, D Takacs, L Wetherald, R AF Zhang, Y Sperber, KR Boyle, JS Dix, M Ferranti, L Kitoh, A Lau, KM Miyakoda, K Randall, D Takacs, L Wetherald, R TI East Asian winter monsoon: results from eight AMIP models SO CLIMATE DYNAMICS LA English DT Article ID SUMMER MONSOON; COLD SURGES; INTERCOMPARISON PROJECT; DECEMBER 1974; FIELDS; ENSO AB This study evaluates simulations of the East Asian winter monsoon in eight GCMs that participated in the Atmospheric Model Intercomparison Project (AMIP). In addition to validating the mean state of the winter monsoon, the cold surge and its transient properties, which includes the frequency, intensity, preferred propagation tracks, and the evolution patterns of the surges, are examined. GCM simulated temporal distribution of the Siberian high and cold surges is also discussed.:Finally, the forcing of the cold surges on the tropical surface wind and convection, along with their interannual variation is analysed. The mean state of the winter monsoon is generally portrayed well in most of the models. These include the climatological position of the Siberian high, the 200 hPa divergent center, and the large-scale wind patterns at the surface and the 200 hPa. Models display a wide range of skill in simulating the cold surge and its transient properties. In some of the models, the simulated cold surge trajectory, intensity, frequency, propagation patterns and source regions are in general agreement with those from the observed. While in others, the models cannot adequately capture these observed characteristics. The temporal distribution of the Siberian high and cold surges were realistically reproduced in most GCMs. Most models were able to simulate the effect of the cold surges on the tropical surface wind, although a few models unrealistically generated subtropical southerly wine! in the mid-winter. The relationship between cold surges and the tropical convection was not satisfactorily simulated in most models. The common discrepancies in the winter monsoon simulation can be attributed to many factors. In some models: the reason is directly related to the improper location of the large-scale convective center near the western Pacific. The satisfactory simulations of the monsoon circulation and the cold surges are partly due to the topographical characteristics of the East Asian continent, i.e., the Tibetan Plateau to the west and the oceans to the east. The correct simulation of the interannual variation of the surface wind near the South China Sea (SCS) and the maritime continent is a demanding task for most of the models. This will require adequate simulations of many aspects, including tropical convection, the Siberian cold dome, the extratropical-tropical linkage, and the air-sea interaction. The discrepancies noted here furnish a guide for the continuing improvement of the winter monsoon simulations. Improved simulations will lead to an adequate delineation of the surface wind and convection near the maritime continent, which is essential for portraying the winter monsoon forcing in a coupled model. C1 CSIRO,MORDIALLOC,VIC 3195,AUSTRALIA. EUROPEAN CTR MEDIUM RANGE WEATHER FORECASTS,READING RG2 9AX,BERKS,ENGLAND. METEOROL RES INST,TSUKUBA,IBARAKI 305,JAPAN. CNR,IMGA,I-41100 MODENA,ITALY. COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523. NASA,GODDARD SPACE FLIGHT CTR,GODDARD LAB ATMOSPHERES,GREENBELT,MD 20771. PRINCETON UNIV,NOAA,GEOPHYS FLUID DYNAM LAB,PRINCETON,NJ 08540. RP Zhang, Y (reprint author), LAWRENCE LIVERMORE NATL LAB,PROGRAM CLIMATE MODEL DIAG & INTERCOMPARISON,LIVERMORE,CA 94550, USA. RI Dix, Martin/A-2334-2012; Sperber, Kenneth/H-2333-2012; Lau, William /E-1510-2012; Randall, David/E-6113-2011 OI Dix, Martin/0000-0002-7534-0654; Lau, William /0000-0002-3587-3691; Randall, David/0000-0001-6935-4112 NR 39 TC 28 Z9 32 U1 2 U2 10 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD NOV PY 1997 VL 13 IS 11 BP 797 EP 820 DI 10.1007/s003820050198 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YK951 UT WOS:A1997YK95100003 ER PT J AU Alpert, P Shafir, H Issahary, D AF Alpert, P Shafir, H Issahary, D TI Recent changes in the climate at the dead sea - A preliminary study SO CLIMATIC CHANGE LA English DT Article ID PLANETARY BOUNDARY-LAYER; LEVEL CHANGES; TEMPERATURE; EVAPORATION; MODEL AB In the last decade pan evaporation measured at the Southern Dead Sea has significantly increased. Wind, temperature and humidity measurements at the Dead Sea starting in the 1930s as well as 3-D model simulations all seem to indicate a statistically significant change in the local climate of the Dead Sea region. The potential contribution to this climatic change through the weakening of the local land-sea breeze circulation caused by the reduction in the Dead Sea surface area in 1979-1981, is examined. It is suggested that since the breeze tempers the Dead Sea climate, its weakening has caused the air temperature to increase, the relative humidity to decrease and thus increased the pan evaporation. The climatic changes as implied by the MM4 Mesoscale PSU/NCAR model simulations, seem to fit the observed changes and to suggest a local tendency to the more arid climate that now prevails to the south of the study region. C1 DEAD SEA WORKS,RES DEPT,S DEAD SEA,ISRAEL. NASA,GODDARD SPACE FLIGHT CTR,DATA ASSIMILAT OFF,GREENBELT,MD 20771. RP Alpert, P (reprint author), TEL AVIV UNIV,DEPT GEOPHYS & PLANETARY SCI,IL-69978 TEL AVIV,ISRAEL. NR 27 TC 15 Z9 15 U1 0 U2 5 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0165-0009 J9 CLIMATIC CHANGE JI Clim. Change PD NOV PY 1997 VL 37 IS 3 BP 513 EP 537 DI 10.1023/A:1005330908974 PG 25 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA YE335 UT WOS:A1997YE33500006 ER PT J AU Messina, P AF Messina, P TI High-performance computers: The next generation (part II) SO COMPUTERS IN PHYSICS LA English DT Article C1 CALTECH, Ctr Adv Comp Res, Pasadena, CA 91125 USA. Jet Propuls Lab, Pasadena, CA USA. RP Messina, P (reprint author), CALTECH, Ctr Adv Comp Res, Pasadena, CA 91125 USA. NR 15 TC 1 Z9 1 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0894-1866 J9 COMPUT PHYS JI Comput. Phys. PD NOV-DEC PY 1997 VL 11 IS 6 BP 598 EP 610 PG 13 WC Computer Science, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Computer Science; Physics GA YM133 UT WOS:000071032200016 ER PT J AU Hua, XM AF Hua, XM TI Monte Carlo simulation of comptonization in inhomogeneous media SO COMPUTERS IN PHYSICS LA English DT Article ID RADIATION; MODELS AB Comptonization is the process in which the photon spectrum changes due to multiple Compton scatterings in the electronic plasma. It plays an important role in the spectral formation of astrophysical x-ray and gamma-ray sources. There are several intrinsic limitations to the analytical method in dealing with the Comptonization problem and Monte Carlo simulation provides one of the few alternatives. We describe an efficient Monte Carlo method that can solve the Comptonization problem in a fully relativistic way. We expanded the method so that it is capable of simulating Comptonization in the media where electron density and temperature vary discontinuously from one region to the other and in the isothermal media where density varies continuously along photon paths. The algorithms are presented in detail to facilitate computer code implementation. We also present a few examples of its application to astrophysical research. (C) 1997 American Institute of Physics. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Hua, XM (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 25 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 USA SN 0894-1866 J9 COMPUT PHYS JI Comput. Phys. PD NOV-DEC PY 1997 VL 11 IS 6 BP 660 EP 668 DI 10.1063/1.168615 PG 9 WC Computer Science, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Computer Science; Physics GA YM133 UT WOS:000071032200024 ER PT J AU Chen, ZK Maly, K Mehrotra, P Vangala, PK Zubair, M AF Chen, ZK Maly, K Mehrotra, P Vangala, PK Zubair, M TI Web-based framework for distributed computing SO CONCURRENCY-PRACTICE AND EXPERIENCE LA English DT Article; Proceedings Paper CT Simulation and Modelling Workshop II - Java for Computational Science and Engineering CY JUN 21, 1997 CL LAS VEGAS, NV SP ACM AB Parallel and distributed computing on a cluster of workstations is being increasingly applied to a variety of large size computational Problems. Several software systems have been developed that make distributed computing available to an application programmer, However, these systems either are not Web-based or lack a collaborative environment, The increasing use of Web technology for Internet and Intranet applications is making the Web an attractive framework for solving distributed applications, in particular, because the interface can be made platform-independent. In this paper we describe JAVADC, a Web-Java-based framework for the execution of parallel SPMD applications which use PVM, pPVM and MPI, We also discuss the design of a collaborative, distributed computing environment, Arcade, focused on more general programming paradigms for multidisciplinary applications. Arcade is a Web-based integrated environment which provides support in all phases of the development of general multidisciplinary applications including the design, execution, monitoring and control of such applications. (C) 1997 John Wiley & Sons, Ltd. C1 NASA,LANGLEY RES CTR,ICASE,MS 403,HAMPTON,VA 23681. OLD DOMINION UNIV,DEPT COMP SCI,NORFOLK,VA 23529. NR 6 TC 2 Z9 2 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1040-3108 J9 CONCURRENCY-PRACT EX JI Concurrency-Pract. Exp. PD NOV PY 1997 VL 9 IS 11 BP 1175 EP 1180 PG 6 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA YJ185 UT WOS:A1997YJ18500015 ER PT J AU Ahearn, DG Crow, SA Simmons, RB Price, DL Mishra, SK Pierson, DL AF Ahearn, DG Crow, SA Simmons, RB Price, DL Mishra, SK Pierson, DL TI Fungal colonization of air filters and insulation in a multi-story office building: Production of volatile organics SO CURRENT MICROBIOLOGY LA English DT Article ID FIBERGLASS AB Secondary air filters in the air-handling units on four floors of a multi-story office building with a history of fungal colonization of insulation within the air distribution system were examined for the presence of growing fungi and production of volatile organic compounds. Fungal mycelium and conidia of Cladosporium and Penicillium spp. were observed on insulation from all floors and both sides of the air filters from one floor. Lower concentrations of volatile organics were released from air filter medium colonized with fungi as compared with noncolonized filter medium. However, the volatiles from the colonized filter medium included fungal metabolites such as acetone and a carbonyl sulfide-like compound that were not released from noncolonized filter medium. The growth of fungi in air distribution systems may affect the content of volatile organics in indoor air. C1 INTERFACE RES CORP,KENNESAW,GA 30144. NASA,LYNDON B JOHNSON SPACE CTR,BIOMED OPERAT & RES BRANCH,HOUSTON,TX 77058. RP Ahearn, DG (reprint author), GEORGIA STATE UNIV,DEPT BIOL,ENVIRONM RES CTR,POB 4010,ATLANTA,GA 30302, USA. NR 7 TC 35 Z9 36 U1 0 U2 8 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0343-8651 J9 CURR MICROBIOL JI Curr. Microbiol. PD NOV PY 1997 VL 35 IS 5 BP 305 EP 308 DI 10.1007/s002849900259 PG 4 WC Microbiology SC Microbiology GA YC102 UT WOS:A1997YC10200011 PM 9462961 ER PT J AU Riddell, WT Ingraffea, AR Wawrzynek, PA AF Riddell, WT Ingraffea, AR Wawrzynek, PA TI Experimental observations and numerical predictions of three-dimensional fatigue crack propagation SO ENGINEERING FRACTURE MECHANICS LA English DT Article DE experimental; fatigue life; fracture mechanics; numerical; three-dimensional ID SHAPE DEVELOPMENT; FINITE AB Experimental observations of three-dimensional fatigue crack growth are compared to numerical predictions from three computer codes. For simple geometries contained in standard libraries of some codes, restricting numerically predicted crack shapes to elliptical quadrants does not adversely affect crack growth rate predictions. However, this approach is limited by the availability of pre-existing solutions. Furthermore, elliptical quadrants are not always representative of true crack shape. More general modeling capabilities allow accurate geometric representation of both the base specimen and the crack front shape for a wide range of configurations. This capability allows reasonable and/or conservative Fatigue crack growth predictions for many cases not handled by geometric libraries. However, the more general modeling capability does not lead to improved fatigue life predictions for simple geometries. Further research is necessary to improve fatigue life prediction capabilities for complex geometries. (C) 1997 Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Natl Res Council, Hampton, VA 23681 USA. Cornell Univ, Cornell Fracture Grp, Ithaca, NY 14853 USA. Cornell Univ, Dept Civil Engn, Ithaca, NY 14853 USA. RP Riddell, WT (reprint author), NASA, Langley Res Ctr, Natl Res Council, Mail Stop 188E, Hampton, VA 23681 USA. NR 40 TC 25 Z9 26 U1 0 U2 6 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0013-7944 J9 ENG FRACT MECH JI Eng. Fract. Mech. PD NOV PY 1997 VL 58 IS 4 BP 293 EP + DI 10.1016/S0013-7944(97)00122-7 PG 17 WC Mechanics SC Mechanics GA YR783 UT WOS:000071529800003 ER PT J AU Kohlhase, C Peterson, CE AF Kohlhase, C Peterson, CE TI The Cassini mission to Saturn and Titan SO ESA BULLETIN-EUROPEAN SPACE AGENCY LA English DT Article AB When Cassini/Huygens was launched from Cape Canaveral on 15 October 1997, the 5.5 t, 6.8 m-high spacecraft carried a suite of scientific sensors to support 27 investigations probing the mysteries of Saturn's system. In addition to a fascinating atmosphere and interior, the vast system contains the most spectacular of the four planetary ring systems, numerous icy satellites with a variety of unique surface features, a huge magnetosphere teeming with particles interacting with the rings and moons, and the intriguing moon Titan - slightly larger than the planet Mercury and with a hazy atmosphere denser than Earth's. C1 CALTECH, Jet Prop Lab, Cassini Project, Pasadena, CA 91109 USA. RP Kohlhase, C (reprint author), CALTECH, Jet Prop Lab, Cassini Project, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 1 U2 2 PU EUROPEAN SPACE AGENCY PI NOORDWIJK PA ESTEC, PO BOX 299, 2200 AG NOORDWIJK, NETHERLANDS SN 0376-4265 J9 ESA BULL-EUR SPACE JI ESA Bull.-Eur. Space Agency PD NOV PY 1997 IS 92 BP 55 EP 68 PG 14 WC Engineering, Aerospace SC Engineering GA YP806 UT WOS:000071317000007 ER PT J AU McGarry, A Angold, N AF McGarry, A Angold, N TI Ulysses 7 years on - Operational challenges and lessons learned SO ESA BULLETIN-EUROPEAN SPACE AGENCY LA English DT Article AB Although the Ulysses mission is currently only one third of its way through its second orbit of the Sun, it is worth remembering that this very successful mission was launched 7 years ago, Many current and future missions with ESA participation (e.g. Hubble Space Telescope, ISO, SOHO, Cassini/Huygens, Rosetta) have one or more of the following in common with Ulysses: interplanetary-type trajectories; missions of long duration; multidisciplinary science; cooperation with other international space agencies, it would therefore seem prudent to pass on some of the lessons learned in these areas from the first 7 years of Ulysses operations. C1 Jet Prop Lab, ESA Ulysses Mission Operat Team, Pasadena, CA USA. RP McGarry, A (reprint author), Vega Grp PLC, Harpenden, Herts, England. NR 0 TC 0 Z9 0 U1 0 U2 0 PU EUROPEAN SPACE AGENCY PI NOORDWIJK PA ESTEC, PO BOX 299, 2200 AG NOORDWIJK, NETHERLANDS SN 0376-4265 J9 ESA BULL-EUR SPACE JI ESA Bull.-Eur. Space Agency PD NOV PY 1997 IS 92 BP 69 EP 74 PG 6 WC Engineering, Aerospace SC Engineering GA YP806 UT WOS:000071317000008 ER PT J AU Danielson, KT Noor, AK AF Danielson, KT Noor, AK TI Three-dimensional finite element analysis in cylindrical coordinates for nonlinear solid mechanics problems SO FINITE ELEMENTS IN ANALYSIS AND DESIGN LA English DT Article ID DEFORMATION; STRATEGIES AB A formulation for three-dimensional nonlinear finite element analysis in cylindrical coordinates in presented. The elements are isoparametric with the same interpolation functions used to represent the geometry and the physical displacement components. The elements can be used for general three-dimensional analysis, but they are most effective for cases when the geometry and the response are best described in cylindrical coordinates. In contrast to formulations in Cartesian coordinates, the foregoing formulation allows the exact representation of a circular shape. For structures with circular geometries, the improved accuracy of the elements can provide better finite element predictions and reduce the number of elements needed in the circumferential direction. The reduction in the number of elements can result in a significant reduction in computer resources needed for large three-dimensional analyses, particularly in the presence of nonlinearities. Whereas the elements may, for some problems, be less efficient than semianalytic elements, the generality of the interpolation provides greater flexibility in modeling different shapes and responses. The mathematical formulation of the three-dimensional finite element equations in cylindrical coordinates is first described for finite strain and deformation. The advantages and additional complexities associated with the cylindrical coordinate formulation are discussed, and the implementation into finite element codes is described. Numerical studies are then presented for two static nonlinear three-dimensional problems: a pneumatic tire in contact with a rigid pavement and the skew bending of a stiffened annular plate. The finite element predictions of the cylindrical coordinate formulation are compared to experimental data and to the predictions from a commercial code using isoparametric finite elements developed in Cartesian coordinates. (C) 1997 Elsevier Science B.V. C1 UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23681. UNIV MINNESOTA,USA,CORPS ENGINEERS,WATERWAYS EXPT STN,DEPT AEROSP ENGN & MECH,VICKSBURG,MS 39180. UNIV MINNESOTA,USA,CORPS ENGINEERS,WATERWAYS EXPT STN,ARMY HIGH PERFORMANCE COMP RES CTR,VICKSBURG,MS 39180. NR 44 TC 12 Z9 12 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-874X J9 FINITE ELEM ANAL DES JI Finite Elem. Anal. Des. PD NOV 1 PY 1997 VL 27 IS 3 BP 225 EP 249 DI 10.1016/S0168-874X(97)00013-9 PG 25 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA YF983 UT WOS:A1997YF98300001 ER PT J AU Fayyad, U Stolorz, P AF Fayyad, U Stolorz, P TI Data mining and KDD: Promise and challenges SO FUTURE GENERATION COMPUTER SYSTEMS LA English DT Article DE data mining; data analysis; science data analysis; overview article; knowledge discovery in databases; databases; parallel data mining ID DIGITIZED POSS-II AB Databases are growing in size to a stage where traditional techniques for analysis and visualization of the data are breaking down. Data mining and knowledge discovery in databases (KDD) are concerned with extracting models and patterns of interest from large databases. Data mining techniques have their origins in methods from statistics, pattern recognition, databases, artificial intelligence, high performance and parallel computing, and visualization. In this article, we provide an overview of this growing multi-disciplinary research area, outline the basic techniques, and provide brief coverage of how they are used in some applications. We discuss the role of high performance and parallel computing in data mining problems, and we provide a brief overview of a few applications in science data analysis. We conclude by listing challenges and opportunites for future research. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Fayyad, U (reprint author), MICROSOFT CORP,RES,1 MICROSOFT WAY,REDMOND,WA 98052, USA. NR 26 TC 75 Z9 87 U1 1 U2 14 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-739X J9 FUTURE GENER COMP SY JI Futur. Gener. Comp. Syst. PD NOV PY 1997 VL 13 IS 2-3 BP 99 EP 115 DI 10.1016/S0167-739X(97)00015-0 PG 17 WC Computer Science, Theory & Methods SC Computer Science GA YJ828 UT WOS:A1997YJ82800002 ER PT J AU Lerner, NR AF Lerner, NR TI Influence of Allende minerals on deuterium retention of products of the Strecker synthesis SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID MURCHISON METEORITE; AMINO-ACIDS; CARBONACEOUS CHONDRITES; ISOTOPIC ANALYSES; HYDROGEN AB The alpha-amino and alpha-hydroxy acids found in the Murchison carbonaceous chondrite are deuterium enriched. These compounds are thought to have originated from common deuterium enriched carbonyl precursors, by way of a Strecker synthesis which took place in an aqueous solution of HCN, NH3, and carbonyl compounds during the period of aqueous alteration of the meteorite parent body. However, the hydroxy acids found in Murchison are less deuterium enriched than the amino acids. With the objective of determining if the discrepancy in deuterium enrichment between the amino acids and the hydroxy acids found in Murchison is consistent with their formation in a Strecker synthesis, we have measured the deuterium content of alpha-amino and alpha-hydroxy acids produced in solutions of deuterated carbonyl compounds, KCN and NH4Cl, and also in mixtures of such solutions and Allende dust at 263 degrees K and 295 degrees K. Retention of the isotopic signature of the starting carbonyl by both alpha-amino acids and alpha-hydroxy acids is more dependent upon temperature, concentration, and pH than upon the presence of meteorite dust in the solution. In order to determine if hydroxy acids retain their carbon-bonded hydrons better than amino acids, deuterium exchange of alpha-hydroxy acids in D2O was investigated at temperatures in excess of 393 degrees K. No measurable exchange of hydrogen was observed. While these results do not rule out the Strecker synthesis as a source of meteoritic amino acids, they do indicate that other reaction schemes may have been more important. Copyright (C) 1997 Elsevier Science Ltd. C1 NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. RP Lerner, NR (reprint author), NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. NR 16 TC 15 Z9 15 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD NOV PY 1997 VL 61 IS 22 BP 4885 EP 4893 DI 10.1016/S0016-7037(97)00275-5 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YM712 UT WOS:000071093300012 ER PT J AU Borg, LE Nyquist, LE Taylor, LA Wiesmann, H Shih, CY AF Borg, LE Nyquist, LE Taylor, LA Wiesmann, H Shih, CY TI Constraints on Martian differentiation processes from Rb-Sr and Sm-Nd isotopic analyses of the basaltic shergottite QUE 94201 SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID SNC METEORITES; MARE BASALTS; PARENT BODY; SYSTEMATICS; LUNAR; AGE; MELT; REE; CRYSTALLIZATION; PETROGENESIS AB Isotopic analyses of mineral, leachate, and whole rock fractions from the Martian shergottite meteorite QUE 94201 yield Rb-Sr and Sm-Nd crystallization ages of 327 +/- 12 and 327 +/- 19 Ma, respectively. These ages are concordant, although the isochrons are defined by different fractions within the meteorite. Comparison of isotope dilution Sm and Nd data for the various QUE 94201 fractions with in situ ion microprobe data for QUE 94201 minerals from the literature demonstrate the presence of a leachable crustal component in the meteorite. This component is likely to have been added to QUE 94201 by secondary alteration processes on Mars and can affect the isochrons by selectively altering the isotopic systematics of the leachates and some of the mineral fractions. Initial Sr-87/Sr-86 Of 0.701298 +/- 14, epsilon(Nd)(143) Of +47.6 +/- 1.7, and whole rock epsilon(Nd)(142) Of +0.92 +/- 0.11 indicate that QUE 94201 was derived from a source that was strongly depleted in Rb-87/Sr-86 and enriched in Sm-147/Nd-144 early in its history. Modeling demonstrates that the Sm-Nd isotopic compositions of QUE 94201 can be produced by either four episodes of melting at 327 Ma of cumulates crystallized from a magma ocean at 4.525 Ga or five episodes of melting of an initially solid Mars at 4.525 Ga and 327 Ma. The neodymium isotopic systematics of QUE 94201 are not consistent with significant melting between 4.525 Ga and 327 Ma. The estimated timing of these events is based on initial neodymium isotopic ratios and is independent of differentiation of the QUE 94201 parental magma, Rb-Sr-based partial melting models are unable to reproduce the composition of QUE 94201 using the same model parameters employed in the Sm-Nd-based models, implying a decoupling of Rb-Sr and Sm-Nd isotopic systems. The initial decoupling of the two isotopic systems can be attributed to either cumulate or crust formation processes which are able to more efficiently fractionate Rb from Sr compared to Sm from Nd. The fact that all Martian meteorites analyzed so far define a Rb-Sr whole rock isochron age of 4.5 Ga suggests that virtually all Rb was partitioned out of their mantle source regions and into either fractionated residual liquids trapped in the cumulate pile or into the crust at that time. Thus, the Martian mantle cumulates and restites are not expected to evolve past Sr-87/Sr-86 Of 0.700 and could not have been significantly enriched in incompatible elements by crustal recycling processes. All Martian meteorites have initial Sr-87/Sr-86 values that are higher than similar to 0.700 and are, therefore, likely to be produced by mixing between evolved crustal-like and depleted mantle reservoirs. The absence of crustal recycling processes on Mars may preserve the geochemical evidence for decoupling of the Rb-Sr and Sm-Nd isotopic systems, underscoring one of the fundamental differences between geologic processes on Mars and the Earth. Copyright (C) 1997 Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. Lockheed Martin, Houston, TX 77258 USA. RP Borg, LE (reprint author), NASA, Lyndon B Johnson Space Ctr, SN4, Houston, TX 77058 USA. NR 53 TC 178 Z9 178 U1 2 U2 17 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD NOV PY 1997 VL 61 IS 22 BP 4915 EP 4931 DI 10.1016/S0016-7037(97)00276-7 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YM712 UT WOS:000071093300014 ER PT J AU Ridgway, JR Minster, JB Williams, N Bufton, JL Krabill, WB AF Ridgway, JR Minster, JB Williams, N Bufton, JL Krabill, WB TI Airborne laser altimeter survey of Long Valley, California SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Article DE caldera; California; geodesy; topography; uplift ID GREENLAND ICE-SHEET; EASTERN CALIFORNIA; CALDERA; DEFORMATION; INFLATION AB Airborne laser altimetry has proved useful in recent years in examining volcanic landforms and glacial ice sheets. With the advent of accurate differential GPS aircraft tracking, we believe that airborne lasers will also prove useful in monitoring time-varying topographic uplift, with rates as low as several centimetres of vertical motion per year. The Long Valley, California, caldera provides an excellent testing ground for this new technology. The region has a history of extensive volcanism, and its central dome has recently been undergoing resurgent uplift of up to 4 cm per year. In September 1993 we conducted three aircraft topographic surveys over the caldera and resurgent dome, utilizing a NASA T39 jet aircraft outfitted with a nadir-profiling altimetric laser (ATLAS), two P-code GPS receivers, a Litton LTN92 inertial unit for attitude, and aerial cameras. In addition, we operated two base-station GPS receivers for post-flight differential navigation and conducted a kinematic automobile survey of roads crossing the dome. The aircraft flew at a mean altitude of 500m above ground, and at speeds of 80-100 m s(-1). The laser had a divergence of 1.7 mrad, and output 50 pulses per second, yielding footprints of 0.9 m diameter separated by about 2 m along track. Precision flying yielded multiple profiles along nearly identical paths, including crossing profiles over the resurgent dome, off the dome, and along a nearby highway. The surveys included daily flights over Mono Lake for roll and pitch bias calibrations, and over the well-surveyed Lake Crowley to provide an independent check of estimated elevations. Much progress has been made in developing analysis procedures for the laser timing and attitude corrections. Crossover points from repeated profiles over the dome and the lake indicate that although some profiles contain relative bias errors of up to 10 cm, most are substantially more accurate. The accuracy of the measurements will increase as the various sources of error are better defined and dealt with. Even with the present analysis level, the distribution of crossovers near the centre of the dome is roughly Gaussian, with a mean of 2.6 cm and a standard deviation of 11 cm. The standard error of the mean is low (1 cm), due to the high number of crossover points, which holds promise for measuring systematic changes in the dome height from year to year. Also, comparison of laser heights of Lake Crowley to tidal gauge heights yields only a 1-4 cm difference in absolute height. These encouraging results serve to confirm further the concept of using aircraft laser surveys for geodetic tectonic monitoring. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NASA,WALLOPS FLIGHT FACIL,HAMPTON,VA. RP Ridgway, JR (reprint author), UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,IGPP,LA JOLLA,CA 92093, USA. OI Minster, Jean Bernard/0000-0003-1268-5177 NR 31 TC 23 Z9 23 U1 0 U2 4 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE SN 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD NOV PY 1997 VL 131 IS 2 BP 267 EP 280 DI 10.1111/j.1365-246X.1997.tb01221.x PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YG198 UT WOS:A1997YG19800007 ER PT J AU Papadopoulos, K Valdivia, JA AF Papadopoulos, K Valdivia, JA TI High altitude discharges and gamma-ray flashes: A manifestation of runaway breakdown - Comment SO GEOPHYSICAL RESEARCH LETTERS LA English DT Editorial Material ID AIR-BREAKDOWN; ELECTRICAL ENVIRONMENT; THUNDERSTORMS; RADIATION C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Papadopoulos, K (reprint author), UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742, USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 14 TC 3 Z9 3 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 NOV 1 PY 1997 VL 24 IS 21 BP 2643 EP 2644 DI 10.1029/97GL02687 PG 2 WC Geosciences, Multidisciplinary SC Geology GA YE985 UT WOS:A1997YE98500028 ER PT J AU Mishchenko, MI Travis, LD Rossow, WB Cairns, B Carlson, BE Han, Q AF Mishchenko, MI Travis, LD Rossow, WB Cairns, B Carlson, BE Han, Q TI Retrieving CCN column density from single-channel measurements of reflected sunlight over the ocean: A sensitivity study SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLANETARY AB The Twomey effect is an increase of the cloud albedo with increasing concentration of tropospheric aerosols serving as cloud condensation nuclei (CCN). Confirmation and quantification of this effect on a global basis requires accurate satellite retrievals of CCN concentrations. We present a theoretical study of the ability of passive satellite remote sensing techniques to provide reliable estimates of tropospheric aerosol column densities over the ocean. We show that a retrieval algorithm based on single-channel single-viewing-angle radiance measurements is incapable of accurately determining CCN column densities and that an algorithm based on multiangle radiance measurements provides much better retrievals. However, even for the latter algorithm the errors in the retrieved CCN column densities can exceed a factor of 5. The poor performance of single-channel radiance-only algorithms is explained by the strong dependence of the extinction cross section and weak dependence of the phase function on aerosol effective radius. In contrast, high-precision multiangle polarization measurements, which are much more sensitive to aerosol microphysics, are capable of constraining CCN column densities to within a few tens of percent. C1 S DAKOTA SCH MINES & TECHNOL,INST ATMOSPHER SCI,RAPID CITY,SD 57701. COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY 10027. SUNY STONY BROOK,ITPA,MSRC,STONY BROOK,NY 11794. RP Mishchenko, MI (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Carlson, Barbara/D-8319-2012; Rossow, William/F-3138-2015; Mishchenko, Michael/D-4426-2012; OI Cairns, Brian/0000-0002-1980-1022 NR 17 TC 14 Z9 15 U1 0 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 NOV 1 PY 1997 VL 24 IS 21 BP 2655 EP 2658 DI 10.1029/97GL02783 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YE985 UT WOS:A1997YE98500032 ER PT J AU Sada, PV Jennings, DE McCabe, GH Bjoraker, GL Deming, D AF Sada, PV Jennings, DE McCabe, GH Bjoraker, GL Deming, D TI Upper limit for NH3 in the stratosphere of Jupiter 16 and 21 weeks after the SL9 collision SO ICARUS LA English DT Article ID COMET SHOEMAKER-LEVY-9; INFRARED OBSERVATIONS; AMMONIA; IMPACT; ABUNDANCES; PHOTOCHEMISTRY; PH3 AB Spectroscopic observations of Jupiter at thermal-infrared wavelengths were performed on November 8-9 and December 14, 1994, 16 and 21 weeks after the fragments of comet Shoemaker-levy 9 collided with Jupiter, Residual stratospheric ammonia was searched for in emission at 930.76 cm(-1) over the longitudes corresponding to the remnants of the D/G/R/S impact sites. We believe a small amount of ammonia may have been detected in November, but report an upper limit for both dates. The constant volume mixing ratio for pressure levels less than 10 mbar that best fits the observation on November 8 is no more than 3.6 +/- 2.4 x 10(-10). This upper limit decreased to less than or equal to 2.3 +/- 3.0 x 10(-10) on December 14. These values are equivalent to upper limits of 1.9 +/- 1.2 x 10(-10) on November 8 and less than or equal to 1.2 +/- 1.5 x 10(-10) on December 14 if we adopt a constant volume mixing ratio above a base at 100 mbar, We also searched, without success, for stratospheric ammonia on November 9 over the K/W and L impact site remnants. Our upper limits place stronger constraints on the stratospheric ammonia lifetimes and photochemical depletion models. (C) 1997 Academic Press. C1 NASA,PLANETARY SYST BRANCH,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RI Bjoraker, Gordon/D-5032-2012; Jennings, Donald/D-7978-2012 NR 32 TC 1 Z9 1 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 NOV PY 1997 VL 130 IS 1 BP 49 EP 56 DI 10.1006/icar.1997.5790 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YK784 UT WOS:A1997YK78400004 ER PT J AU Gulick, VC Tyler, D McKay, CP AF Gulick, VC Tyler, D McKay, CP TI Episodic ocean-induced CO2 greenhouse on Mars: Implications for fluvial valley formation SO ICARUS LA English DT Article ID MARTIAN NORTHERN PLAINS; EVOLUTION; GLACIATION; CLIMATE; ORIGIN; CYCLE; WATER; MODEL AB Pulses of CO2 injected into the martian atmosphere more recently than 4 Ga can place the atmosphere into a stable, higher pressure, warmer greenhouse state, One to two bar pulses of CO2 added to the atmosphere during the past several billion years are sufficient to raise global mean temperatures above 240 or 250 K for tens to hundreds of millions of years, even when accounting for CO2 condensation. Over time, the added CO2 is lost to carbonates, the atmosphere collapses and returns to its buffered state. A substantial amount of water could be transported during the greenhouse periods from the surface of a frozen body of water created by outflow channel discharges to higher elevations, despite global temperatures well below freezing, This water, precipitated as snow, could ultimately form fluvial valleys if deposition sites are associated with localized heat sources, such as magmatic intrusions or volcanoes, Thus, if outflow channel discharges were accompanied by the release of sufficient quantities of CO2, a limited hydrological cycle could have resulted that would have been capable of producing geomorphic change sufficient for fluvial erosion and valley formation, Glacial or periglacial landforms would also be a consequence of such a mechanism. (C) 1997 Academic Press. C1 NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. RP Gulick, VC (reprint author), NASA,DIV SPACE SCI,AMES RES CTR,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 31 TC 59 Z9 59 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 NOV PY 1997 VL 130 IS 1 BP 68 EP 86 DI 10.1006/icar.1997.5802 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YK784 UT WOS:A1997YK78400006 PM 11541758 ER PT J AU Jakosky, BM Zent, AP Zurek, RW AF Jakosky, BM Zent, AP Zurek, RW TI The Mars water cycle: Determining the role of exchange with the regolith SO ICARUS LA English DT Article ID BOUNDARY-LAYER MODEL; SEASONAL RESERVOIRS; VIKING LANDER; ATMOSPHERE; CLIMATE; SURFACE; TRANSPORT; VAPOR; SITES; H2O AB The near-surface nighttime atmospheric water vapor concentrations inferred by Ryan et al. (J. A. Ryan, R. D. Sharman, and R. D. Lucich 1982, J. Geophys. Res. 87, 7279-7284) from Viking Lander air temperature measurements are a factor of 2-3 lower than the same quantities estimated from daytime atmospheric column water vapor abundances observed from the Viking Orbiters. We show that a physical model of the atmospheric boundary layer and regolith can produce a nighttime depletion of this magnitude by diffusion of water into the regolith and adsorption onto regolith grains, Quantitative validation of the model is not possible at present due to the lack of direct measurements of the near-surface atmospheric water vapor concentration and by uncertainties regarding surface regolith and atmospheric boundary layer properties. However, if the diurnal exchange of water vapor with the surface is as large as is suggested by the Viking Lander and Orbiter measurements, then the exchange of water between the atmosphere and regolith also is important in the seasonal cycle of water vapor. Further characterization of these processes can be made using measurements from the various landing site and atmospheric profiling experiments to be conducted by the Mars Pathfinder and Mars Surveyor Lander and Orbiter missions. (C) 1997 Academic Press. C1 UNIV COLORADO,DEPT GEOL SCI,BOULDER,CO 80309. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. CALTECH,JET PROP LAB,PASADENA,CA 91125. RP Jakosky, BM (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,CAMPUS BOX 392,BOULDER,CO 80309, USA. NR 26 TC 46 Z9 46 U1 1 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 NOV PY 1997 VL 130 IS 1 BP 87 EP 95 DI 10.1006/icar.1997.5799 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YK784 UT WOS:A1997YK78400007 ER PT J AU Fenton, LK Pearl, JC Martin, TZ AF Fenton, LK Pearl, JC Martin, TZ TI Mapping Mariner 9 dust opacities SO ICARUS LA English DT Article DE atmosphere structure; clouds; dust; infrared observations; Mars atmosphere ID INFRARED THERMAL MAPPER; MARTIAN ATMOSPHERE AB We present the results from a study of the spatial and temporal 9-mu m opacity variation of the Martian 1971 global dust storm. T. Z. Martin (1986, Icarus 66, 2-21) designed a procedure to calculate 9-mu m opacities from the Viking IR Thermal Mapper data set. We have convolved the Mariner 9 IRIS data with Viking IRTM filter functions in order to use Martin's approach. We find a mean opacity of 0.32 and a modal opacity of 0.21. The resulting opacities are mapped and binned by solar longitude in order to investigate the structure of the 1971 dust storm. There is a diminishing spatial variation in opacity as the storm decays. The highest opacities occur in the southern tropics while the lowest opacities consistently appear in the southern polar region and near the equator. Hellas is relatively clear at the peak of the storm but becomes dustier than the rest of the planet as the storm dissipates. This behavior may be typical of Hellas and Argyre during global dust storms. In contrast, the Tharsis plateau is relatively dusty early in the mission but clears quickly, We have also calculated storm decay constants for different regions. The storm has a decay constant of 67 days in the 20 degrees-30 degrees S zone, 42 days in the 55 degrees-65 degrees S zone, and 46 days on the Tharsis plateau. (C) 1997 Academic Press. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,ENGN & SCI DIRECTORATE,PASADENA,CA 91109. RP Fenton, LK (reprint author), CALTECH,DIV GEOL & PLANETARY SCI,MAIL CODE 150-21,PASADENA,CA 91125, USA. NR 19 TC 23 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 NOV PY 1997 VL 130 IS 1 BP 115 EP 124 DI 10.1006/icar.1997.5810 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YK784 UT WOS:A1997YK78400009 ER PT J AU Hudson, RS Ostro, SJ Harris, AW AF Hudson, RS Ostro, SJ Harris, AW TI Constraints on spin state and Hapke parameters of asteroid 4769 Castalia using lightcurves and a radar-derived shape model SO ICARUS LA English DT Article DE asteroids; photometry; radar; surfaces ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; GALILEO PHOTOMETRY; GASPRA; IDA AB A 167-parameter, 3-D shape model of the Earth-crossing asteroid Castalia, obtained from inversion of delay-Doppler images (Hudson and Ostro, 1994, Science 263, 940-943) constrained the object's pole to lie on a cone of half angle 55 +/- 10 degrees centered on the radar line of sight (right ascension 0.3 hr, declination 25.4 degrees) at the time of observations (Aug. 22, 1989) but could not constrain the pole's azimuthal orientation or the sense of rotation. Here we fit lightcurves obtained at Table Mountain Observatory on Aug. 23-25 with lightcurves calculated from Castalia's shape and Hapke's photometric model (Hapke 1981, J. Geophys. Res. 86, 3039-3054; 1984, Icarus 59, 41-59; 1986, Icarus 67, 264-280). The fits strongly constrain Castalia's spin state to one of two possibilities, One has a north pole within similar to 13 degrees of lambda = 253 degrees, beta = 56 degrees and a sidereal spin period P = 4.089 +/- 0.001 hr. The other has a south pole within similar to 13 degrees of lambda = 242 degrees, beta = 7 degrees and a sidereal spin period P = 4.094 +/- 0.001 hr, The north-pole solution has global-average Hapke photometric parameters w = 0.38 +/- 0.07, g = -0.11 +/- 0.09, <(theta)over bar> = 46 degrees +/- 10 degrees while the south-pole solution has w = 0.24 +/- 0.07, g = -0.30 +/- 0.09, <(theta)over bar> = 25 degrees +/- 10 degrees. Due to the large solar phase angles (60 degrees-90 degrees) the fits are not sensitive to the opposition surge parameters h and B-0. At a more subtle level, the least-bifurcated shape (''lower-bound model'') allowed by the radar data (Hudson and Ostro, 1994, Science 263, 940-943) consistently gives statistically better fits than the more bifurcated possibilities, However, the differences are small enough that the possibility that they are due to unmodeled photometric effects cannot be discounted. The fits are improved by allowing the macroscopic roughness parameter <(theta)over bar> to be a function of surface position. Statistically, this process improves the north-pole solution more than the south-pole solution suggesting that the radar observations viewed a northern latitude, thereby indicating a resolution of the ''mirror ambiguity'' inherent in the single-date radar data set. (C) 1997 Academic Press. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Hudson, RS (reprint author), WASHINGTON STATE UNIV,SCH ELECT ENGN & COMP SCI,PULLMAN,WA 99164, USA. NR 21 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 NOV PY 1997 VL 130 IS 1 BP 165 EP 176 DI 10.1006/icar.1997.5804 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YK784 UT WOS:A1997YK78400012 ER PT J AU Sandford, SP Antill, CW AF Sandford, SP Antill, CW TI Laser frequency control using an optical resonator locked to an electronic oscillator SO IEEE JOURNAL OF QUANTUM ELECTRONICS LA English DT Article DE Fabry-Perot resonators; frequency control; frequency stability; lasers; phase-locked loops ID STABILIZATION; CAVITY AB A new method for controlling a laser's center frequency is reported. This method extends the Pound-Drever-Hall technique, which delivers exceptional laser linewidth. The new technique, applicable over a broad range of wavelengths, produces a laser beam with both narrow linewidth and stable center frequency. A diode-pumped ring laser is locked to an ultrahigh-finesse, tunable optical. resonator which, in turn, is locked to an electronic (5 MHz) oscillator using a difference frequency developed by locking a second laser to the resonator. A 1064-nm beam is reported with linewidth less than 0.004 Hz and center-frequency stability given by the electronic reference. For the case of an oven-controlled quartz crystal, the laser center-frequency stability is less than 1 part in 10(11) per day with root Allan variance of 10(-12) for a 1000-s time delay. The entire system is compact, and all elements are solid-state, making it useful both in the laboratory and in a number of space-based applications. RP Sandford, SP (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 17 TC 3 Z9 3 U1 2 U2 9 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9197 J9 IEEE J QUANTUM ELECT JI IEEE J. Quantum Electron. PD NOV PY 1997 VL 33 IS 11 BP 1991 EP 1996 DI 10.1109/3.641314 PG 6 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA YC838 UT WOS:A1997YC83800011 ER PT J AU Janaswamy, R AF Janaswamy, R TI An unstaggered colocated finite-difference scheme for solving time-domain Maxwell's equations in curvilinear coordinates SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article DE FDTD methods ID ABSORBING BOUNDARY-CONDITIONS; WAVES AB In this paper, we present a new unstaggered colocated finite-difference scheme for solving time-domain Maxwell's equations in a curvilinear coordinate system. All components of the electric and. magnetic fields are defined al the same spatial point, A combination of one-sided forward-and backward-difference (FD/BD) operators for the spatial derivatives is used to produce the same order of accuracy as a staggered, central differencing scheme. In the temporal variable, the usual leapfrog integration is used. The computational domain is bounded at the far end by a curvilinear perfectly matched layer (PML). The PML region is terminated with a first-order Engquist-Majda-type absorbing boundary condition (ABC). Comparison is shown with results available in the literature for TEz scattering by conducting cylinders. Equations are also presented for the three-dimensional (3-D) case. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Janaswamy, R (reprint author), USN,POSTGRAD SCH,DEPT ELECT & COMP ENGN,CODE EC JS,MONTEREY,CA 93943, USA. NR 16 TC 11 Z9 11 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 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD NOV PY 1997 VL 45 IS 11 BP 1584 EP 1591 DI 10.1109/8.650069 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA YE079 UT WOS:A1997YE07900003 ER PT J AU Hooker, SB Mied, RP Brown, JW Kirwan, AD AF Hooker, SB Mied, RP Brown, JW Kirwan, AD TI Remote sensing of dipole rings SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID WARM-CORE RING; GULF-STREAM RINGS; BETA-PLANE; EDDY; EVOLUTION; VORTICES; MODONS; MODEL; JET AB Historical satellite-derived sea surface temperature (SST) data are reanalyzed with a zebra color palette and a thermal separatrix method. The new results from this reanalysis are as follows: a) Thirteen observational sequences of six rings from the Gulf Stream and the Brazil Current, which have historically been interpreted as solitary vortices or monopoles are shown to have a dipolar character; b) some of these dipole rings have been observed in the open ocean, thereby eliminating the possibility that they are sustained by topographic interactions with the continental slope; c) whether interacting with other features or evolving as isolated circulations, dipoles are seen to rotate within a relatively narrow range of approximately 4-8 degrees day(-1) (interacting) and 10-15 degrees day(-1) (isolated); and d) feature tracking delineates energetic fluid in both vortices and eliminates the possibility of interpreting dipole rings as transient features produced by active monopoles and patches of entrained fluid. C1 USN, RES LAB, REMOTE SENSING DIV, WASHINGTON, DC 20375 USA. UNIV MIAMI, ROSENSTIEL SCH MARINE & ATMOSPHER SCI, MPO, MIAMI, FL 33149 USA. OLD DOMINION UNIV, CCPO, NORFOLK, VA 23508 USA. RP NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, CODE 971, GREENBELT, MD 20771 USA. RI Hooker, Stanford/E-2162-2012 NR 27 TC 4 Z9 4 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 EI 1558-0644 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD NOV PY 1997 VL 35 IS 6 BP 1394 EP 1399 DI 10.1109/36.649791 PG 6 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA YF976 UT WOS:A1997YF97600002 ER PT J AU Yueh, SH AF Yueh, SH TI Modeling of wind direction signals in polarimetric sea surface brightness temperatures SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID OCEAN SURFACE; MICROWAVE EMISSION; THERMAL EMISSION; SCATTERING; WATER; BAND; BACKSCATTERING; POLARIZATION; SPECTRUM; WAVES AB There has been an increasing interest in the applications of polarimetric microwave radiometers for ocean wind remote sensing, Aircraft and spaceborne radiometers have found a few Kelvins wind direction signals in sea surface brightness temperatures, in addition to their sensitivities to wind speeds. However, it was not clear what physical scattering mechanisms produced the observed brightness dependence on wind direction, To this end, polarimetric microwave emissions from wind-generated sea surfaces are investigated with a polarimetric two-scale scattering model, which relates the directional wind-wave spectrum to passive microwave signatures of sea surfaces. Theoretical azimuthal modulations are found to agree well with experimental observations for all Stokes parameters from near nadir to 65 degrees incidence angles. The upwind and downwind asymmetries of brightness temperatures were interpreted using the hydrodynamic modulation, The contributions of Bragg scattering by short craves, geometric optics scattering by long waves and sea foam are examined, The geometric optics scattering mechanism underestimates the directional signals in the first three Stokes parameters, and predicts no signals in the fourth Stokes parameter (V). in contrast, the Bragg scattering was found to dominate the wind direction signals from the two-scale model and correctly predicted the phase changes of the upwind and crosswind asymmetries in T-v and U from middle to high incidence angles. The phase changes predicted by the Bragg scattering theory for radiometric emission from mater ripples is corroborated by the numerical Monte Carlo simulation of rough surface scattering, This theoretical interpretation indicates the potential use of polarimetric brightness temperatures for retrieving the directional wave spectrum of short gravity and capillary waves. RP Yueh, SH (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 44 TC 163 Z9 179 U1 0 U2 13 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 NOV PY 1997 VL 35 IS 6 BP 1400 EP 1418 DI 10.1109/36.649793 PG 19 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA YF976 UT WOS:A1997YF97600003 ER PT J AU Durden, SL Kitiyakara, A Im, E Tanner, AB Haddad, ZS Li, FK Wilson, WJ AF Durden, SL Kitiyakara, A Im, E Tanner, AB Haddad, ZS Li, FK Wilson, WJ TI ARMAR observations of the melting layer during TOGA COARE SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID RADAR OBSERVATIONS; PRECIPITATION; OCEAN; RAIN AB The NASA/JPL Airborne Rain MApping Radar (ARMAR) was operated on the NASA DC-8 aircraft during TOGA COARE in early 1993, On 12 flights ARMAR observed stratiform precipitation associated with mesoscale convective systems. The statistics of 16 melting layer parameters, including maximum reflectivity, cooling rate, Doppler velocity, LDR, and the HH-VV correlation coefficient are presented and discussed. RP Durden, SL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 12 TC 4 Z9 4 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD NOV PY 1997 VL 35 IS 6 BP 1453 EP 1456 DI 10.1109/36.649800 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 YF976 UT WOS:A1997YF97600008 ER PT J AU Hamkins, J Zeger, K AF Hamkins, J Zeger, K TI Asymptotically dense spherical codes .1. Wrapped spherical codes SO IEEE TRANSACTIONS ON INFORMATION THEORY LA English DT Article; Proceedings Paper CT 30th Annual Conference on Information Sciences and Systems CY MAR, 1996 CL PRINCETON, NJ DE asymptotic density; laminated lattices; packing; source and channel coding; spherical codes ID PACKING AB A new class of spherical codes called wrapped spherical codes is constructed by ''wrapping'' any sphere packing Lambda in Euclidean space onto a finite subset of the unit sphere in one higher dimension. The mapping preserves much of the structure of Lambda, and unlike previously proposed maps, the density of wrapped spherical codes approaches the density of Lambda as the minimum distance approaches zero. We show that this implies that the asymptotically maximum spherical coding density is achieved by wrapped spherical codes whenever Lambda is the densest possible sphere packing. C1 UNIV CALIF SAN DIEGO, DEPT ELECT & COMP ENGN, LA JOLLA, CA 92093 USA. RP Hamkins, J (reprint author), CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. NR 49 TC 29 Z9 29 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9448 J9 IEEE T INFORM THEORY JI IEEE Trans. Inf. Theory PD NOV PY 1997 VL 43 IS 6 BP 1774 EP 1785 DI 10.1109/18.641544 PG 12 WC Computer Science, Information Systems; Engineering, Electrical & Electronic SC Computer Science; Engineering GA YG269 UT WOS:A1997YG26900003 ER PT J AU Hamkins, J Zeger, K AF Hamkins, J Zeger, K TI Asymptotically dense spherical codes .2. Laminated spherical codes SO IEEE TRANSACTIONS ON INFORMATION THEORY LA English DT Article; Proceedings Paper CT 1995 IEEE International Symposium on Information Theory CY SEP 17-22, 1995 CL WHISTLER, CANADA SP IEEE, Informat Theory Soc DE asymptotic density; laminated lattices; packing; source and channel coding; spherical codes AB New spherical codes called laminated spherical codes are constructed in dimensions 2-49 using a technique similar to the construction of laminated lattices. Each spherical code is recursively constructed from existing spherical codes in one lower dimension. Laminated spherical codes outperform the best known spherical codes in the minimum distance sense for many code sizes. The density of a laminated spherical code approaches the density of the laminated lattice in one lower dimension, as the minimum distance approaches zero. In particular, the three-dimensional laminated spherical code is asymptotically optimal, in the sense that its density approaches the Fejes Toth upper bound as the minimum distance approaches zero. Laminated spherical codes perform asymptotically as well as wrapped spherical codes in those dimensions where laminated lattices are optimal sphere packings. C1 UNIV CALIF SAN DIEGO,DEPT ELECT & COMP ENGN,LA JOLLA,CA 92093. RP Hamkins, J (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 7 TC 13 Z9 13 U1 1 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9448 J9 IEEE T INFORM THEORY JI IEEE Trans. Inf. Theory PD NOV PY 1997 VL 43 IS 6 BP 1786 EP 1798 DI 10.1109/18.641545 PG 13 WC Computer Science, Information Systems; Engineering, Electrical & Electronic SC Computer Science; Engineering GA YG269 UT WOS:A1997YG26900004 ER PT J AU Hubona, GS Shirah, GW Fout, DG AF Hubona, GS Shirah, GW Fout, DG TI The effects of motion and stereopsis on three-dimensional visualization SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Article ID GRAPHICS AB Previous studies have demonstrated that motion cues combined with stereoscopic viewing can enhance the perception of three-dimensional objects displayed on a two-dimensional computer screen. Using a variant of the mental rotation paradigm, subjects view pairs of object images presented on a computer terminal and judge whether the objects are the same or different. The effects of four variables on the accuracy and speed of decision performances are assessed: stereo vs. mono viewing, controlled vs. uncontrolled object motion, cube vs. sphere construction and wire frame vs. solid surface characteristic. Viewing the objects as three-dimensional images results in more accurate and faster decision performances. Furthermore, accuracy improves although response time increases when subjects control the object motion. Subjects are equally accurate comparing wire frame and solid images, although they take longer comparing wire frame images. The cube-based or sphere-based object construction has no impact on decision accuracy nor response time. (C) 1997 Academic Press Limited. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CENTURY COMP INC,LAUREL,MD 20707. RP Hubona, GS (reprint author), VIRGINIA COMMONWEALTH UNIV,DEPT INFORMAT SCI,POB 844000,RICHMOND,VA 23284, USA. NR 29 TC 14 Z9 14 U1 0 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 1071-5819 J9 INT J HUM-COMPUT ST JI Int. J. Hum.-Comput. Stud. PD NOV PY 1997 VL 47 IS 5 BP 609 EP 627 DI 10.1006/ijhc.1997.0154 PG 19 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA YG325 UT WOS:A1997YG32500001 PM 11541533 ER PT J AU Staender, S Davies, J Helmreich, B Sexton, B Kaufmann, M AF Staender, S Davies, J Helmreich, B Sexton, B Kaufmann, M TI The anaesthesia critical incident reporting system: an experience based database SO INTERNATIONAL JOURNAL OF MEDICAL INFORMATICS LA English DT Article DE critical incident; anaesthesia; death ID ERRORS AB To date there have been fewer than a dozen studies on the nature of, and contributory factors in, critical incidents (CI) in anaesthesia. The first of these, by Cooper and colleagues, showed that the vast majority of their CI involved human error [1]. Most recently, the on-going Australian Incident Monitoring Study (AIMS), with now more than 2000 reports, has shows that aspects of 'system failure' may constitute the bulk of the contributory factors, even though some human error may be detected in about 80% of the analysed cases [2]. We set up a Critical Incident Reporting System (CIRS) to collect anonymous CI in anaesthesia using a reporting form on the Internet. CIRS analysis of the first 60 cases corroborates the findings of previous CI studies. In addition, our preliminary results have shown certain important trends, especially those concerning the contributory factor of communication in the Operating Theatre. Although to date we are unable to assess the educational importance of these CI reports, we believe that there is great potential for this aspect of CIRS. (C) 1997 Elsevier Science B.V. C1 Univ Basel, Kantonsspital, Dept Anaesthesia, CH-4031 Basel, Switzerland. Univ Calgary, Dept Anaesthesia, Calgary, AB T2N 1N4, Canada. Univ Texas, NASA, Austin, TX 78712 USA. RP Staender, S (reprint author), Univ Basel, Kantonsspital, Dept Anaesthesia, CH-4031 Basel, Switzerland. EM staender@ubaclu.unibas.ch NR 5 TC 51 Z9 52 U1 0 U2 0 PU ELSEVIER SCI IRELAND LTD PI CLARE PA CUSTOMER RELATIONS MANAGER, BAY 15, SHANNON INDUSTRIAL ESTATE CO, CLARE, IRELAND SN 1386-5056 J9 INT J MED INFORM JI Int. J. Med. Inform. PD NOV PY 1997 VL 47 IS 1-2 BP 87 EP 90 DI 10.1016/S1386-5056(97)00087-7 PG 4 WC Computer Science, Information Systems; Health Care Sciences & Services; Medical Informatics SC Computer Science; Health Care Sciences & Services; Medical Informatics GA YV178 UT WOS:000071797200016 PM 9506400 ER PT J AU Green, BE Whitesides, JL Campbell, RL Mineck, RE AF Green, BE Whitesides, JL Campbell, RL Mineck, RE TI Method for the constrained design of natural laminar flow airfoils SO JOURNAL OF AIRCRAFT LA English DT Article ID EULER AB An automated iterative design method has been developed by which an airfoil with a substantial amount of natural laminar now can be designed while maintaining other aerodynamic and geometric constraints, Drag reductions have been realized using the design method over a range of Mach numbers, Reynolds numbers, and airfoil thicknesses, The key features of the method are the compressible linear stability analysis code used to calculate N-factors; the ability to calculate a target N-factor distribution that forces the flow to undergo transition at the desired location; the target pressure/N-factor relationship that is used to modify target pressures to produce the desired N-factor distribution; and its ability to design airfoils to meet lift, pitching moment, thickness, and leading-edge radius constraints while also being able to meet the natural laminar flow constraint. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Green, BE (reprint author), GEORGE WASHINGTON UNIV,JOINT INST ADV FLIGHT SCI,HAMPTON,VA 23681, USA. NR 15 TC 2 Z9 3 U1 1 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 NOV-DEC PY 1997 VL 34 IS 6 BP 706 EP 712 DI 10.2514/2.2248 PG 7 WC Engineering, Aerospace SC Engineering GA YK024 UT WOS:A1997YK02400002 ER PT J AU vanDam, CP Los, SM Miley, SJ Roback, VE Yip, LP Bertelrud, A Vijgen, PMHW AF vanDam, CP Los, SM Miley, SJ Roback, VE Yip, LP Bertelrud, A Vijgen, PMHW TI In-flight boundary-layer state measurements on a high-lift system: Slat SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 1st Aircraft Engineering Technology and Operations Congress CY SEP 19-21, 1995 CL LOS ANGELES, CA SP Amer Inst Aeronaut & Astronaut Inc ID STABILITY AB Flight experiments on NASA Langley Research Center's B737-100 airplane were conducted to document flow characteristics for further understanding of high-lift now physics. The measurements included surface pressure distributions measured using flush pressure taps and pressure belts on the slats, main element, and flap elements, and boundary-layer state changes measured using hot-film anemometry and infrared thermography. In this paper, results obtained in the final phase of flight experiments are presented and analyzed. The analysis primarily focuses on changes in the boundary-layer state measured on the slat as a result of changes in nap setting and/or flight condition. The measurements show that extended runs of laminar now exist on the slat at relevant angles of attack. Flow mechanisms that affect the extent of laminar flow include attachment-line contamination, crossflow instability, and relaminarization. C1 OLD DOMINION UNIV,NORFOLK,VA 23508. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. ANALYT SERV & MAT INC,HAMPTON,VA 23666. HIGH TECHNOL CORP,R&D,HAMPTON,VA 23666. RP vanDam, CP (reprint author), UNIV CALIF DAVIS,DEPT MECH & AERONAUT ENGN,DAVIS,CA 95616, USA. NR 31 TC 10 Z9 10 U1 0 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 NOV-DEC PY 1997 VL 34 IS 6 BP 748 EP 756 PG 9 WC Engineering, Aerospace SC Engineering GA YK024 UT WOS:A1997YK02400007 ER PT J AU vanDam, CP Los, SM Miley, SJ Roback, VE Yip, LP Bertelrud, A Vijgen, PMHW AF vanDam, CP Los, SM Miley, SJ Roback, VE Yip, LP Bertelrud, A Vijgen, PMHW TI In-flight boundary-layer state measurements on a high-lift system: Main element and flap SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 1st Aircraft Engineering Technology and Operations Congress CY SEP 19-21, 1995 CL LOS ANGELES, CA SP Amer Inst Aeronaut & Astronaut Inc AB Flight experiments on NASA Langley Research Center's B737-100 airplane were conducted to document flow characteristics for further understanding of the flow physics on multielement high-lift systems, The measurements presented in this paper show that significant regions of laminar flow exist on the main element and the foreflap of the airplane. Flow mechanisms that affect the extent of laminar now include relaminarization of the flow in the leading-edge region of the main element and contamination of the laminar now on the nap by turbulent shear layers emanating from upstream elements. This information should be valuable in the development and assessment of high-Reynolds-number wind-tunnel experiments and numerical models for predicting the flows around multielement wings at full-scale high-lift conditions. C1 OLD DOMINION UNIV,NORFOLK,VA 23508. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. ANALYT SERV & MAT INC,HAMPTON,VA 23666. HIGH TECHNOL CORP,R&D,HAMPTON,VA 23666. RP vanDam, CP (reprint author), UNIV CALIF DAVIS,DEPT MECH & AERONAUT ENGN,DAVIS,CA 95616, USA. NR 13 TC 7 Z9 7 U1 0 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 NOV-DEC PY 1997 VL 34 IS 6 BP 757 EP 763 PG 7 WC Engineering, Aerospace SC Engineering GA YK024 UT WOS:A1997YK02400008 ER PT J AU Ribner, HS AF Ribner, HS TI Neglect of wake roll-up in Theodorsen's theory of propellers SO JOURNAL OF AIRCRAFT LA English DT Article ID IDEAL C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Ribner, HS (reprint author), UNIV TORONTO,INST AEROSP STUDIES,4925 DUFFERIN ST,DOWNSVIEW,ON M3H 5T6,CANADA. NR 13 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 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1997 VL 34 IS 6 BP 814 EP 816 DI 10.2514/2.7577 PG 3 WC Engineering, Aerospace SC Engineering GA YK024 UT WOS:A1997YK02400017 ER PT J AU Dobson, JEF McClure, FD Rainosek, AP AF Dobson, JEF McClure, FD Rainosek, AP TI Determination of fish flesh content in frozen coated fish products (modification of AOAC Official Method 971.13): Collaborative study SO JOURNAL OF AOAC INTERNATIONAL LA English DT Article AB An intralaboratory(1) collaborative study evaluated a modified version of AOAC Official Method 971.13 for determining the fish flesh content (FFC) in frozen coated fish products by comparing it with the on-line method, Eleven collaborators analyzed 36 products (a total of 6336 test samples), Each product targeted one of 4 percent fish flesh (PFF) levels (35, 50, 65, and 80), Products were manufactured from one of 3 raw materials (fillet blocks, minced blocks, and natural fillets) and processed in one of 4 forms (sticks, portions, formed portions, and fillets) and one of 4 styles (raw breaded, batter-dipped, precooked, and fully cooked). Each ''official'' test sample was tracked through the processing system and weighed (1) before battering and/or breading and, depending on product style, before frying; and (2) after battering and/or breading and, depending on product style, after frying; so that it served as its own control, These weights were used to calculate actual percent fish flesh (APFF) and considered to be generated by the on-line method. Collaborators weighed official test samples (1) before scraping; and (2) after scraping, These weights were used to calculate determined percent fish flesh (DPFF) and considered to be generated by the modified AOAC method, APFF and DPFF were the primary data for statistical analysis, Recoveries ranged from 71.75 to 106.40%, Repeatability (method precision indicator for a single collaborator) relative standard deviation (RSDr) values ranged from 1.04 to 8.37%, Corresponding reproducibility (method precision indicator among collaborators) relative standard deviation (RSDR) values ranged from 1.41 to 11.95%, The DPFF mean was lower than the APFF mean for 30 (83.33%) of 36 products, For 29 of these 30 products, the differences between method means (APFF minus DPFF) ranged from 0.38 to 6.51%, For the remaining product within this group (C/06, fillet blocks, fully cooked portions), the difference between method means was 21.73%. For the remaining 6 (16.67%) of 36 products, the DPFF mean was greater than the APFF mean, The differences between method means ranged from -0.03 to -2.76%. RSD values were considered acceptable (i.e., RSDr < 9% and RSDR < 12%) for all products studied, The modified method for determining FFC in frozen coated fish products has been adopted first action to replace AOAC Official Method 971.13. C1 US FDA,CTR FOOD SAFETY & APPL NUTR,US DEPT HLTH & HUMAN SERV,OFF SCI ANAL & SUPPORT,DIV MATH,WASHINGTON,DC 20204. UNIV S ALABAMA,DEPT MATH & STAT,MOBILE,AL 36688. NATL MARINE FISHERIES SERV,US DEPT COMMERCE,NATL OCEAN & ATMOSPHER ADM,NATL SEAFOOD INSPECT LAB,PASCAGOULA,MS 39568. RP Dobson, JEF (reprint author), NATL MARINE FISHERIES SERV,US DEPT COMMERCE,NATL OCEAN & ATMOSPHER ADM,TECH SERV BRANCH,GLOUCESTER,MA 01930, USA. NR 21 TC 0 Z9 0 U1 0 U2 0 PU AOAC INTERNATIONAL PI GAITHERSBURG PA 481 NORTH FREDRICK AVE, STE 500, GAITHERSBURG, MD 20877-2504 SN 1060-3271 J9 J AOAC INT JI J. AOAC Int. PD NOV-DEC PY 1997 VL 80 IS 6 BP 1235 EP 1271 PG 37 WC Chemistry, Analytical; Food Science & Technology SC Chemistry; Food Science & Technology GA YL259 UT WOS:A1997YL25900014 PM 9419864 ER PT J AU Oki, R Sumi, A Short, DA AF Oki, R Sumi, A Short, DA TI TRMM sampling of radar-AMeDAS rainfall using the threshold method SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID TIME STOCHASTIC-MODEL; MEAN AREAL RAINFALL; CONVECTIVE RAINFALL; TROPICAL RAINFALL; RATE MOMENTS; SATELLITE; SIMULATION; INTEGRALS AB It is known that spatially averaged rainfall rate [R] is highly correlated with the fractional area (F) of rain rate exceeding a preset threshold (tau), when the area is large enough to include numerous convective systems in various stages of their life cycles. Using this fact, a method to estimate area-averaged rain rate from F(tau), which is obtained from satellite observations, is proposed For Tropical Rainfall Measuring Mission (TRMM). There have been numerous studies investigating F-[R] relationships and optimal thresholds at several radar observation sites around the world but no studies to confirm the performance of the method within Japan. In this study an analysis of radar-AMeDAS (Automatic Meteorological Data Acquisition System) precipitation data is presented. The F-[R] relationships of radar-AMeDAS rain data have been examined systematically, with the result that the optimum threshold that maximizes the correlation between [R] and F(tau) is neat 3.5 mm h(-1) in every year and season of available data. Using the threshold method with the average coefficients obtained when the threshold is set to 3.5 mm h(-1), TRMM sampling of radar-AMeDAS rainfall is simulated. Fixing 5 degrees x 5 degrees areas, monthly mean area-averaged rain rate is estimated from the observational coverage that would he obtained by TRMM during a month. The errors from the threshold method are only 3%-4% larger than the sampling errors (14%-19% on average) obtained by using the full dynamic range of observed rain rates. Considering the dynamic range of TRMM sensors, the threshold method would be an effective method to estimate area-average rain rate. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. UNIV TOKYO,CTR CLIMATE SYST RES,MEGURO KU,TOKYO,JAPAN. RI PMM, JAXA/K-8537-2016 NR 35 TC 9 Z9 9 U1 1 U2 2 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 NOV PY 1997 VL 36 IS 11 BP 1480 EP 1492 DI 10.1175/1520-0450(1997)036<1480:TSORAR>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YE059 UT WOS:A1997YE05900004 ER PT J AU Baum, BA Tovinkere, V Titlow, J Welch, RM AF Baum, BA Tovinkere, V Titlow, J Welch, RM TI Automated cloud classification of global AVHRR data using a fuzzy logic approach SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID POLAR-REGIONS; SURFACE CLASSIFICATION; PATTERN-RECOGNITION; SPATIAL-RESOLUTION; TEXTURAL FEATURES; SATELLITE IMAGERY; NEURAL-NETWORK; EXPERT-SYSTEM; IDENTIFICATION; MISSION AB A fuzzy logic classification (FLC) methodology is proposed to achieve the two goals of this paper: 1) to discriminate between clear sky and clouds in a 32 x 32 pixel array, or sample, of 1.1-km Advanced Very High Resolution Radiometer (AVHRR) data, and 2) if clouds are present, to discriminate between single-layered and multilayered clouds within the sample. To achieve these goals, eight FLC modules are derived that are based broadly on airmass type and surface type (land or water): equatorial over land, marine tropical over land, marine tropical/equatorial over water, continental tropical over land, marine polar over land, marine polar over water, continental polar over land, and continental polar/arctic over water. Derivation of airmass type is performed using gridded analyses provided by the National Centers for Environmental Prediction. The training and testing data used by the FLC are collected from more than 150 daytime AVHRR local area coverage scenes recorded between 1991 and 1994 over all seasons and over all continents and oceans. A total of 190 textural and spectral features are computed from the AVHRR data. A forward feature selection method is implemented to reduce the number of features used to discriminate between classes in each FLC module. The number of features selected ranges from 13 (marine tropical over land) to 24 (marine tropical/equatorial over water). An estimate of the classifier accuracy is determined using the hold-one-out method in which the classifier is trained with all but one of the data samples; the classifier is applied subsequently to the remaining sample. The overall accuracies of the eight classification modules are calculated by dividing the number of correctly classified samples by the total number of manually labeled samples of clear-sky and single-layer clouds. Individual module classification accuracies are as follows: equatorial over land (86.2%), marine tropical over land (85.6%), marine tropical/equatorial over water (88.6%), continental tropical over land (87.4%), marine polar over land (86.8%), marine polar over water (84.8%), continental polar over land (91.1%), and continental polar/arctic over water (89.8%). Single-level cloud samples misclassified as multilayered clouds range between 0.5% (continental polar over land) and 3.4% (marine polar over land) for the eight airmass modules. Classification accuracies for a set of labeled multilayered cloud samples range between 64% and 81% for six of the eight airmass modules (excluded are the continental polar over land and continental polar/arctic over water modules, for which multilayered cloud samples are difficult to find). The results indicate that the FLC has an encouraging ability to distinguish between single-level and multilayered clouds. C1 SCI APPLICAT INT CORP,HAMPTON,VA. S DAKOTA SCH MINES & TECHNOL,INST ATMOSPHER SCI,RAPID CITY,SD. RP Baum, BA (reprint author), NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,MS 420,HAMPTON,VA 23681, USA. RI Baum, Bryan/B-7670-2011 OI Baum, Bryan/0000-0002-7193-2767 NR 38 TC 48 Z9 57 U1 1 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 NOV PY 1997 VL 36 IS 11 BP 1519 EP 1540 DI 10.1175/1520-0450(1997)036<1519:ACCOGA>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YE059 UT WOS:A1997YE05900007 ER PT J AU Merceret, FJ AF Merceret, FJ TI Rapid temporal changes of midtropospheric winds SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID PROFILER; RADAR; AIR AB The statistical distribution of the magnitude of the vector wind change over 0.25-, 1-, 2-, and 4-h periods based on data from October 1995 through March 1996 over central Florida is presented. The wind changes at altitudes from 6 to 17 km were measured using the Kennedy Space Center 50-MHz Doppler radar wind profiler. Quality controlled profiles were produced every 5 min for 112 gates, each representing 150 m in altitude. Gates 28 through 100 were selected for analysis because of their significance to ascending space launch vehicles. The distribution was found to be lognormal. The parameters of the lognormal distribution depend systematically on the time interval. This dependence is consistent with the behavior of structure functions in the f(5/3) spectral regime. There is a small difference between the 1995 data and the 1996 data, which may represent a weak seasonal effect. RP Merceret, FJ (reprint author), NASA,APPL METEOROL UNIT,MAIL CODE PH-B3,KENNEDY SPACE CTR,FL 32899, USA. NR 14 TC 9 Z9 9 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 NOV PY 1997 VL 36 IS 11 BP 1567 EP 1575 DI 10.1175/1520-0450(1997)036<1567:RTCOMW>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YE059 UT WOS:A1997YE05900010 ER PT J AU Grossman, EJ Grindeland, RE Roy, RR Talmadge, RJ Evans, J Edgerton, VR AF Grossman, EJ Grindeland, RE Roy, RR Talmadge, RJ Evans, J Edgerton, VR TI Growth hormone, IGF-I, and exercise effects on non-weight-bearing fast muscles of hypophysectomized rats SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE growth factors; hindlimb suspension; medial gastrocnemius; myosin heavy chain; fiber cross-sectional area; insulin-like growth factor I ID SKELETAL-MUSCLE; MESSENGER-RNA; STIMULATES GROWTH; SUSPENDED RATS; SUSPENSION; EXPRESSION; NUTRITION; RESPONSES; SOLEUS; FIBERS AB The effects of growth hormone (GH) or insulin-like growth factor I (ICE-I) with or without exercise (ladder climbing) in countering the effects of unweighting on fast muscles of hypophysectomized rats during 10 days of hindlimb suspension were determined. Compared with untreated suspended rats, muscle weights were 16-29% larger in GH-treated and 5-15% larger in IGF-I-treated suspended rats. Exercise alone had no effect on muscle weights. Compared with ambulatory control, the medial gastrocnemius weight in suspended, exercised rats was larger after GH treatment and maintained with IGF-I treatment. The combination of GH or IGF-I plus exercise in suspended rats resulted in an increase in the size of each predominant fiber type, i.e., types I, I+IIa and IIa+IIx, in the medial gastrocnemius compared with untreated suspended rats. Normal ambulation or exercise during suspension increased the proportion of fibers expressing embryonic myosin heavy chain in hypophysectomized rats. The phenotype of the medial gastrocnemius was minimally affected by GH, IGF-I, and/or exercise. These results show that there is an IGF-I, as well as a GH, and exercise interactive effect in maintaining medial gastrocnemius fiber size in suspended hypophysectomized rats. C1 UNIV CALIF LOS ANGELES,SCH MED,HLTH SCI CTR,BRAIN RES INST,LOS ANGELES,CA 90095. UNIV CALIF LOS ANGELES,DEPT PHYSIOL SCI,LOS ANGELES,CA 90095. NASA,AMES RES CTR,DIV LIFE SCI,MOFFETT FIELD,CA 94035. FU NINDS NIH HHS [NS-16333] NR 30 TC 20 Z9 21 U1 2 U2 3 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD NOV PY 1997 VL 83 IS 5 BP 1522 EP 1530 PG 9 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA YE867 UT WOS:A1997YE86700017 PM 9375315 ER PT J AU Zabotin, NA Bratsun, DS Pulinets, SA Benson, RF AF Zabotin, NA Bratsun, DS Pulinets, SA Benson, RF TI Response of topside radio sounding signals to small-scale field-aligned ionospheric irregularities SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article AB Small-scale ionospheric irregularities produce numerous observed effects during high-frequency radio wave sounding from a satellite. Scattering of z-mode waves radiated by an ionosonde, which results in the occurrence of characteristic traces on ionograms, are among the most complex of them. In the present paper the factors determining the power characteristics of such signals are considered. These are the size and shape of the surface of orthogonality for a family of z-mode waves radiated from a satellite, features of the radiating and propagating radio waves in a non-uniform magnetized plasma, and the details of the scattering process. Simple but adequate physical models for each of these factors are presented and a numerical calculation algorithm of the power of the z-mode scattered signals received by the satellite sounder receiver has been constructed. Values for this calculated quantity are presented as a function of time delay, sounding frequency, and magnetic latitude. A synthesis of topside ionograms showing z-mode scattered traces has been performed. The results support new diagnostic methods of detecting small-scale ionospheric irregularities using topside-sounder z-mode signal returns and the concept that the sounder radiation can, under certain conditions, stimulate artificial plasma turbulence. In addition, it was shown that z-mode scattering may contribute to the resonance observed at the plasma frequency on topside ionograms. (C) 1997 Elsevier Science Ltd. All rights reserved. C1 Rostov Don State Univ, Phys Res Inst, Rostov On Don 344090, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. IZMIRAN, Troitsk 142092, Moscow Region, Russia. RP Zabotin, NA (reprint author), Rostov Don State Univ, Phys Res Inst, Rostov On Don 344090, Russia. RI Zabotin, Nikolay/A-9639-2015; Pulinets, Sergey/F-7462-2011 OI Zabotin, Nikolay/0000-0003-0715-1082; Pulinets, Sergey/0000-0003-3944-6686 NR 34 TC 8 Z9 8 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD NOV PY 1997 VL 59 IS 17 BP 2231 EP 2246 DI 10.1016/S1364-6826(97)00028-X PG 16 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA YN459 UT WOS:000071170700008 ER PT J AU Kiris, C Kwak, D Rogers, S Chang, ID AF Kiris, C Kwak, D Rogers, S Chang, ID TI Computational approach for probing the flow through artificial heart devices SO JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID NAVIER-STOKES EQUATIONS; BLOOD-FLOW; VELOCITY-MEASUREMENTS; INVITRO MEASUREMENTS; VALVES; INDENTATION; SYSTEMS; CHANNEL; STEADY AB Computational fluid dynamics (CFD) has become an indispensable part of aerospace research and design. The solution procedure for incompressible Navier-Stokes equations can be used for biofluid mechanics research. The computational approach provides detailed knowledge of the flowfield complementary to that obtained by experimental measurements. This paper illustrates the extension of CFD techniques to artificial heart flow simulation. Unsteady incompressible Navier-Stokes equations written in three-dimensional generalized curvilinear coordinates are solved iteratively at each physical time step until the incompressibility condition is satisfied The solution method is based on the pseudocompressibility approach. It uses an implicit upwind-differencing scheme together with the Gauss-Seidel line-relaxation method. The efficiency and robustness of the time-accurate formulation of the numerical algorithm are tested by computing the flow through model geometries. A channel flow with a moving indentation is computed and validated by experimental measurements and other numerical solutions. In order to handle the geometric complexity and the moving boundary problems, a zonal method and an overlapped grid embedding scheme are employed respectively. Steady-state solutions for the flow through a tilting-disk heart valve are compared with experimental measurements. Good agreement is obtained. Aided by experimental data, the flow through an entire Penn State artificial heart model is computed. C1 NASA,ADV COMPUTAT METHODS BRANCH,AMES RES CTR,MOFFETT FIELD,CA 94035. STANFORD UNIV,STANFORD,CA 94305. RP Kiris, C (reprint author), MCAT INC,MT VIEW,CA 94039, USA. NR 23 TC 45 Z9 45 U1 2 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0148-0731 J9 J BIOMECH ENG-T ASME JI J. Biomech. Eng.-Trans. ASME PD NOV PY 1997 VL 119 IS 4 BP 452 EP 460 DI 10.1115/1.2798293 PG 9 WC Biophysics; Engineering, Biomedical SC Biophysics; Engineering GA YH791 UT WOS:A1997YH79100013 PM 9407285 ER PT J AU Pickett, HM AF Pickett, HM TI Theoretical studies of internal rotation for an asymmetric top SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID MOLECULES AB For internal rotation in three-fold tops, the internal axis system (IAS) has been a great convenience because the vibrational angular momentum is constant and is directed along a single axis. A procedure for finding an IAS for the general asymmetric top-asymmetric frame case is given. This procedure is an existence proof that such an axis system can be found. However, such an IAS will have an orientation which is a function of the internal rotation coordinate. Once the IAS is found, details will be given on how the Matthieu equation can be solved and how the results can be described as a Fourier series. A useful alternative to the IAS is an axis system obtained by rotating away from the IAS by a constant amount (independent of the torsional angle) so as to position the frame in a more convenient orientation. For this rotated internal axis system (RIAS), a Matthieu equation can also be used as a basis except that the kinetic energy for the Matthieu solution only contains contributions from the a component of the vibrational angular momentum. Expectation values for other operators including contributions from the b component of the vibrational angular momentum are deferred to the full diagonalization of the rotation-vibration Hamiltonian. (C) 1997 American Institute of Physics. [S0021-9606(97)03541-1]. RP Pickett, HM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 8 TC 23 Z9 23 U1 0 U2 5 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 NOV 1 PY 1997 VL 107 IS 17 BP 6732 EP 6735 DI 10.1063/1.474916 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YC706 UT WOS:A1997YC70600026 ER PT J AU Dai, A Fung, IY DelGenio, AD AF Dai, A Fung, IY DelGenio, AD TI Surface observed global land precipitation variations during 1900-88 SO JOURNAL OF CLIMATE LA English DT Article ID UNITED-STATES; SOUTHERN OSCILLATION; GEOPOTENTIAL HEIGHT; CLIMATE VARIATIONS; GAUGE OBSERVATIONS; AIR-TEMPERATURE; NORTH-AMERICA; 1988 DROUGHT; EL-NINO; TRENDS AB The authors have analyzed global station data and created a gridded dataset of monthly precipitation for the period of 1900-88. Statistical analyses suggest that discontinuities associated with instrumental errors are large for many high-latitude station records, although they are unlikely to be significant for the majority of the stations. The first leading EGF in global precipitation fields is an ENSO-related pattern, concentrating mostly in the low latitudes. The second leading EOF depicts a linear increasing trend (similar to 2.4 mm decade(-1)) in global precipitation fields during the period of 1900-88. Consistent with the zonal precipitation trends identified in previous analyses, the EOF trend is seen as a long-term increase mostly in North America, mid-to high-latitude Eurasia, Argentina, and Australia. The spatial patterns of the trend EOF and the rate of increase are generally consistent with those of the precipitation changes in increasing CO2 GCM experiments. The North Atlantic oscillation (NAO) accounts for similar to 10% of December-February precipitation variance over North Atlantic surrounding regions. The mode suggests that during high-NAG-index winters: precipitation is above normal in northern (> 50 degrees N) Europe, the eastern United States, northern Africa, and the Mediterranean, while below-normal precipitation occurs in southern Europe, eastern Canada, and western Greenland. Wet and dry months of one standard deviation occur at probabilities close to those of a normal distribution in midlatitudes. Ln the subtropics, the mean interval between two extreme events is longer. The monthly wet and dry events seldom (probability < 5%) last longer than 2 months. ENSO is the single largest cause of global extreme precipitation events; Consistent with the upward trend in global precipitation, globally, the averaged mean interval between two dry months increased by similar to 28% from 1900-44 to 1945-88. The percentage of wet areas over the United States has more than doubled (from similar to 12% to > 24%) since the 1970s, while the percentage of dry areas has decreased by a similar amount since the 1940s. Severe droughts and floods comparable to the 1988 drought and 1993 flood in the Midwest have occurred 2-9 times in each of several other regions of the world during this century. C1 COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY 10027. UNIV VICTORIA,SCH EARTH & OCEAN SCI,VICTORIA,BC,CANADA. NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RI Del Genio, Anthony/D-4663-2012; Dai, Aiguo/D-3487-2009 OI Del Genio, Anthony/0000-0001-7450-1359; NR 79 TC 408 Z9 429 U1 5 U2 68 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD NOV PY 1997 VL 10 IS 11 BP 2943 EP 2962 DI 10.1175/1520-0442(1997)010<2943:SOGLPV>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YH745 UT WOS:A1997YH74500017 ER PT J AU Garrett, ES Jahncke, ML Tennyson, JM AF Garrett, ES Jahncke, ML Tennyson, JM TI Microbiological hazards and emerging food-safety issues associated with seafoods SO JOURNAL OF FOOD PROTECTION LA English DT Article; Proceedings Paper CT ILSI Symposium on Ensuring a Safe Global Food Supply at the 83rd IAMFES Annual Meeting CY JUN 30-JUL 03, 1996 CL SEATTLE, WA SP ILSI N Amer, Tech Comm Food Microbiol, Int Assoc Milk Food & Environm Sanitorians DE seafood safety; seafood microbial hazards; coastal health AB The United States is entering into a new era in which dwindling natural fisheries resources are forcing regulatory agencies to develop a more holistic approach to seafood safety and natural marine resource issues. Public health issues associated with seafoods can be grouped as (i) environmentally induced (i.e., natural or anthropogenic), (ii) process-induced, (iii) distribution-induced, or (iv) consumer-induced hazards. Similarly, loss of habitat and ecosystem degradation threaten the future viability of fisheries and have important ramifications for seafood safety. In the United States, large-scale legistlative efforts are underway to reexamine regulatory food control systems. The driving forces behind these efforts are the discovery of new emerging pathogens for which little information is available and dramatic improvements in analytic technology that allow for detection of low levels of microbial and chemical contaminants in foods. The global nature of seafood trading issues and the worldwide implementation of new preventative food safety programs such as hazard analysis for critical control points are driving some of the efforts to build new scientific bridges that will reevaluate current risk analysis strategies. New scientific bridges are needed to close the gaps between the scientific community and society concerning the effects of anthropogenic impacts on seafood safety and the heatlh of coastal habitats and associated fishery resources. The driving force behind this latter issue is the realization that the United States has lost over half of its original coastal wetlands areas. Protecting, conserving, and restoring the health and safety of our fisheries resources will require an integrated approach of food science and fishery science. RP Garrett, ES (reprint author), NATL MARINE FISHERIES SERV, NATL SEAFOOD INSPECT LAB, 3209 FREDERIC ST, PASCAGOULA, MS 39567 USA. NR 44 TC 12 Z9 12 U1 0 U2 4 PU INT ASSOC FOOD PROTECTION PI DES MOINES PA 6200 AURORA AVE SUITE 200W, DES MOINES, IA 50322-2863 USA SN 0362-028X J9 J FOOD PROTECT JI J. Food Prot. PD NOV PY 1997 VL 60 IS 11 BP 1409 EP 1415 PG 7 WC Biotechnology & Applied Microbiology; Food Science & Technology SC Biotechnology & Applied Microbiology; Food Science & Technology GA YH532 UT WOS:A1997YH53200022 ER PT J AU Sorensen, JE Stone, NH Wright, KH AF Sorensen, JE Stone, NH Wright, KH TI Change in ion distribution function while crossing the space shuttle wake SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLASMA DIAGNOSTICS PACKAGE; ORBITER; PERTURBATIONS; TEMPERATURE; TURBULENCE; EXPANSION AB During the space shuttle/Spacelab 2 mission (STS-51F) the Plasma Diagnostic Package (PDP) was placed in free flight in the vicinity of the Orbiter and provided the first opportunity to measure the midwake and far-wake regions of an orbiting spacecraft. During this period the PDP crossed the wake 4 times at downstream distances ranging from 40 m to 240 m. During each crossing a definite change in the ion-retarding potential curves was measured when the PDP was in the shuttle wake compared to the ambient ionosphere. These measurements were obtained by both the differential ion flux probe and the retarding potential analyzer instruments on the PDP. The temperature of the ions, derived from fitting the data to a Maxwellian distribution, are consistent with an enhancement during each wake crossing of as much as a factor of 2.5 (from about 0.08 eV to 0.2 eV). Such studies of plasma wakes were never before performed. C1 UNIV ALABAMA,CTR SPACE PLASMA & AERON RES,HUNTSVILLE,AL 35899. RP Sorensen, JE (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES83,HUNTSVILLE,AL 35812, USA. NR 29 TC 3 Z9 3 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1997 VL 102 IS A11 BP 24117 EP 24126 DI 10.1029/97JA01869 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE924 UT WOS:A1997YE92400010 ER PT J AU Patzold, M Tsurutani, BT Bird, MK AF Patzold, M Tsurutani, BT Bird, MK TI An estimate of large-scale solar wind density and velocity profiles in a coronal hole and the coronal streamer belt SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID RANGING MEASUREMENTS; PHYSICAL-PROPERTIES; ULYSSES SPACECRAFT; ELECTRON-DENSITIES; CONJUNCTION AB With the use of the total electron content data obtained by the Ulysses Solar Corona Experiment (SCE) during the first solar conjunction in summer 1991, two data sets were selected, one associated with a coronal hole and the other associated with coronal streamer belt crossings. To determine a large-scale coronal streamer belt density profile, the electron content of the tracking passes embedded in the coronal streamer belt were corrected for the contributions from coronal hole densities. The inferred large-scale streamer belt electron density profile has a radial falloff exponent of -2.4 for distances greater than 7 R-s implying the acceleration of the slow solar wind according to v(r) similar to r(0.4), in qualitative agreement with SOHO results. The acceleration terminates beyond 60 R-s in agreement with Hellos in situ observations. All radial electron density profiles inferred from coronal radio sounding observations, particularly during times of high solar activity, are dominated by coronal streamer contributions. They are applicable to coronal streamers, confined to a limited latitude range about the heliospheric current sheet, and they are not representative of a large-scale mean coronal electron density profile. Because of a lack of data, similar analysis of the coronal hole electron content data was not unequivocally feasible. The coronal hole tracking passes corrected for contributions from coronal streamer areas display large electron content and density fluctuations inconsisting with the plume interpretation by Woo [1996]. Assuming that the lowest densities represent typical hole densities and comparing these with streamer densities at the same distance, we found the streamer-to-hole density ratio to be a factor of 10, which agrees with white light coronagraph results. C1 UNIV BONN, INST RADIOASTRON, D-53121 BONN, GERMANY. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Patzold, M (reprint author), UNIV COLOGNE, INST METEOROL & GEOPHYS, ALBERTUS MAGNUS PL, D-50923 COLOGNE, GERMANY. NR 29 TC 11 Z9 11 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1997 VL 102 IS A11 BP 24151 EP 24160 DI 10.1029/97JA01868 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE924 UT WOS:A1997YE92400013 ER PT J AU Gazis, PR AF Gazis, PR TI Limits on the asymmetry of solar wind temperature in the outer heliosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PRESSURE-BALANCED STRUCTURES; VOYAGER-2 OBSERVATIONS; PLASMA OBSERVATIONS; PICKUP PROTONS; HYDROGEN; PIONEER-10; EVOLUTION; MINIMUM; IMP-8; SPEED AB Interstellar pickup ions, if they are thermalized, could produce a longitudinal asymmetry in solar wind temperature in the outer heliosphere. Between 1978 and mid-1992, the Pioneer 10 and Voyager 2 spacecraft were well situated to search for such an asymmetry. Pioneer 10 was headed downstream with respect to the local interstellar medium while Voyager 2 was headed upstream. Both spacecraft were at large heliocentric distances; by mid-1992, Pioneer 10 was at 55 AU, while Voyager 2 was at 37 AU. Measurements from these spacecraft and the Pioneer Venus Orbiter are complicated by solar cycle effects but suggest an upper Limit of 5000 K for any asymmetry that might be present. These measurements are also consistent with no asymmetry. There is also some suggestion that the radial profile of solar wind temperature in the vicinity of the solar equator was steeper during the declining phase of the last solar cycle. The solar wind temperature has increased at Voyager 2 after mid-1992, but Voyager 2 has also been moving to higher heliographic latitudes, where such an increase should be expected from the well-known latitudinal gradient in solar wind temperature that has been observed by Pioneer 11 and Ulysses. RP Gazis, PR (reprint author), NASA,AMES RES CTR,SAN JOSE STATE UNIV FDN,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 31 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1997 VL 102 IS A11 BP 24195 EP 24200 DI 10.1029/97JA01460 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE924 UT WOS:A1997YE92400017 ER PT J AU Huddleston, DE Russell, CT Le, G Szabo, A AF Huddleston, DE Russell, CT Le, G Szabo, A TI Magnetopause structure and the role of reconnection at the outer planets SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FLUX-TRANSFER EVENTS; PLASMA OBSERVATIONS; DAYSIDE MAGNETOPAUSE; MAGNETIC-FIELD; HOT PLASMA; JOVIAN MAGNETOPAUSE; SURFACE-WAVES; MIRROR WAVES; JUPITER; MAGNETOSPHERE AB In situ measurements have been obtained at the magnetopause boundary of all the giant outer planets. The Jovian magnetopause was probed by Pioneers 10 and 11, Voyagers 1 and 2, Ulysses, and most recently by Galileo. Saturn was visited by Pioneer Il and Voyagers 1 and 2, and Uranus and Neptune were visited by Voyager 2. The observations at Jupiter show evidence for flux transfer event (FTE) structures and rotational discontinuities associated with magnetic reconnection with the interplanetary magnetic field (IMF), but in accord with previous studies we find no FTE signatures beyond Jupiter in the data sets we studied. At Saturn, one magnetopause encounter shows evidence for reconnection in the form of a rotational discontinuity with a finite magnetic field component through the boundary and significant plasma acceleration. At Uranus and Neptune the flank magnetopause boundary observed by Voyager 2 exhibits a complex structure (similar to that seen at Earth during high-P conditions) for which unsteady reconnection appears to occur. Closely spaced multiple magnetopause crossings at Jupiter and Saturn are consistent with a boundary surface disturbance or wave, occurring with unsteady reconnection, and coincident with a jump in upstream solar wind dynamic pressure in the Jupiter case. Because of the transient, bursty nature of the reconnection signatures and their low (similar to 0.1 to 0.4 mV/m) convective electric fields compared to those of corotation at Jupiter and Saturn, the role of reconnection in driving the dynamics of these magnetospheres is thought to be minimal in the general case. Nevertheless, the unsteady reconnection observed is important to the properties of the boundary layers. At Uranus and Neptune, observations are limited (Voyager 2 only) but suggest that bursty reconnection at the flank magnetopause can only remove plasma (in the antisunward direction), and infrequent reconnection on the dayside would provide little opportunity for solar wind entry to energize the ionospheric plasma and supply the magnetosphere; these factors may contribute to producing the relatively empty magnetospheres that were seen. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095. RP Huddleston, DE (reprint author), UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,405 HILGARD AVE,LOS ANGELES,CA 90095, USA. RI Le, Guan/C-9524-2012 OI Le, Guan/0000-0002-9504-5214 NR 67 TC 45 Z9 45 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1997 VL 102 IS A11 BP 24289 EP 24302 DI 10.1029/97JA02416 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE924 UT WOS:A1997YE92400026 ER PT J AU Delcourt, DC Sauvaud, JA Moore, TE AF Delcourt, DC Sauvaud, JA Moore, TE TI Phase bunching during substorm dipolarization SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOSPHERIC SUBSTORMS; CHARGED-PARTICLES; ION ENERGIZATION; ELECTRIC-FIELD; CURRENT SHEET; MAGNETOTAIL; PLASMA; MODEL; ACCELERATION; EXPANSION AB We investigate the dynamics of near-Earth plasma sheet ions during storm time dipolarization of the magnetospheric field lines. We more specifically examine the behavior of O+ ions that are trapped in the equatorial vicinity. We show that during field line dipolarization, these particles may be transported in a nonadiabatic manner and experience: large magnetic moment enhancement together with prominent bunching in gyration phase. An analytical estimate is obtained that is in good agreement with numerical trajectory calculations and allows detailed analysis of the adiabatic-nonadiabatic transition. We focus on the gyrophase bunching effect and demonstrate that it occurs below some threshold energy at the dipolarization onset, this threshold energy being controlled by the amplitude of the magnetic transition and by the injection depth in the magnetotail. In the near-Earth tail, the phase-bunched particles possibly experience intense (up to the hundred of keV range) nonadiabatic energization and are radially distributed in a well-structured manner. As a result of this, systematic trajectory computations reveal that phase bunching during storm time dipolarization can lead to significant though localized variations of the cross-tail current and may thus be responsible for large fluctuations of the magnetic field. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. CTR ETUD SPATIALE RAYONNEMENTS,CNRS,F-31029 TOULOUSE,FRANCE. RP Delcourt, DC (reprint author), CTR ETUD ENVIRONM TERRESTRE & PLANETAIRES,CNRS,4 AVE NEPTUNE,F-94107 ST MAUR FOSSES,FRANCE. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 28 TC 21 Z9 22 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1997 VL 102 IS A11 BP 24313 EP 24324 DI 10.1029/97JA02039 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YE924 UT WOS:A1997YE92400028 ER PT J AU Crassidis, JL Markley, FL Anthony, TC Andrews, SF AF Crassidis, JL Markley, FL Anthony, TC Andrews, SF TI Nonlinear predictive control of spacecraft SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA 35th Aerospace Science Meeting / Nonlinear Dynamical Systems Symposium CY JAN 06-09, 1997 CL RENO, NV SP Amer Inst Aeronaut & Astronaut, USAF, Off Sci Res, Sandia Natl Labs ID LARGE-ANGLE MANEUVERS; ATTITUDE MANEUVERS; RIGID SPACECRAFT; FEEDBACK; SYSTEMS AB A new approach for the control of a spacecraft with large-angle maneuvers is presented. This new approach is based on a nonlinear predictive control scheme that determines the required torque input so that the predicted responses match the desired trajectories. This is accomplished by minimizing the norm-squared local errors between the predicted and desired quantities. Formulations that use either attitude and rate tracking or attitude tracking alone are presented. The robustness of the new controller with respect to large system uncertainties is also demonstrated. Finally, simulation results that use the new control strategy to stabilize the motion of the Microwave Anisotropy Probe spacecraft are shown. C1 NASA,GODDARD SPACE FLIGHT CTR,GUIDANCE NAVIGAT & CONTROL BRANCH,GREENBELT,MD 20771. RP Crassidis, JL (reprint author), CATHOLIC UNIV AMER,DEPT MECH ENGN,WASHINGTON,DC 20064, USA. NR 24 TC 21 Z9 21 U1 0 U2 4 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 NOV-DEC PY 1997 VL 20 IS 6 BP 1096 EP 1103 DI 10.2514/2.4191 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA YF147 UT WOS:A1997YF14700007 ER PT J AU Crassidis, JL Markley, FL AF Crassidis, JL Markley, FL TI Minimum model error approach for attitude estimation SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID VECTOR OBSERVATIONS; ALGORITHM AB An optimal batch estimator and smoother based on the minimum model error (MME) approach is developed for three-axis stabilized spacecraft. The formulation is shown using only attitude sensors, e.g., three-axis magnetometers, sun sensors, star trackers, This algorithm accurately estimates the attitude of a spacecraft and substantially smoothes noise associated with attitude sensor measurements. The general functional form of the optimal estimation approach involves the solution of a nonlinear two-point-boundary-value problem that can be solved only by using computationally intense methods. A linearized solution also is shown that is computationally more efficient than methods that solve the general form. The linearized solution is useful when an a priori estimate of the angular velocity is already known, which can be obtained from a finite difference of a determined attitude, or from propagation of a dynamics model. Results using this new algorithm indicate that an MME-based approach accurately estimates the attitude of an actual spacecraft with the sole use of magnetometer sensor measurements. C1 NASA,GODDARD SPACE FLIGHT CTR,GUIDANCE NAVIGAT & CONTROL BRANCH,GREENBELT,MD 20771. RP Crassidis, JL (reprint author), CATHOLIC UNIV AMER,DEPT MECH ENGN,WASHINGTON,DC 20064, USA. NR 26 TC 36 Z9 37 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 NOV-DEC PY 1997 VL 20 IS 6 BP 1241 EP 1247 DI 10.2514/2.4183 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA YF147 UT WOS:A1997YF14700026 ER PT J AU Rosolovsky, J Boggess, RK Rubira, AF Taylor, LT Stoakley, DM StClair, AK AF Rosolovsky, J Boggess, RK Rubira, AF Taylor, LT Stoakley, DM StClair, AK TI Supercritical fluid infusion of silver into polyimide films of varying chemical composition SO JOURNAL OF MATERIALS RESEARCH LA English DT Article AB Polyimides can be infused with silver complexes by the use of supercritical fluids. Highly reflective polyimide films were formed by infusing (1,5-cyclooctadiene-1,1,1,5,5,5-hexafluoroacetylacetonato)silver(I) [Ag(COD)(HFA)] into a number of polyimides and then thermally curing those films at 300 degrees C for time intervals between 30 min and 3 h. Reflectivities of the films exhibited strong dependence on the infusion and cure conditions as well as on the type of polyimide used, The highest reflectivity of 67.1% was achieved with a silvered film prepared from 3.3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA) and oxydianiline (ODA) infused at 5000 psi, 100 degrees C, for 30 min and cured for 1 h at 300 degrees C. Reflectivities of silvered surfaces of other polyimides investigated varied from 39% to 61%. A strong correlation between the presence of a ketonic group in the polyimide structure and the formation of mirror surfaces was detected. C1 RADFORD UNIV,DEPT CHEM & PHYS,RADFORD,VA 24142. UNIV ESTADUAL MARINGA,DEPT QUIM,BR-87020900 MARINGA,PARANA,BRAZIL. VIRGINIA POLYTECH INST & STATE UNIV,DEPT CHEM,BLACKSBURG,VA 24061. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP Rosolovsky, J (reprint author), MIT,DEPT CHEM ENGN,CAMBRIDGE,MA 02139, USA. NR 16 TC 28 Z9 29 U1 1 U2 3 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD NOV PY 1997 VL 12 IS 11 BP 3127 EP 3133 DI 10.1557/JMR.1997.0408 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA YG457 UT WOS:A1997YG45700032 ER PT J AU Toth, RA AF Toth, RA TI Line positions and strengths of HDO between 6000 and 7700 cm(-1) SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID TRANSITION FREQUENCIES AB High-resolution spectra of gas sample mixtures of HDO, D2O, and H2O were obtained with a Fourier-transform spectrometer at resolutions of 0.01 and 0.02 cm(-1). The spectra were analyzed to obtain line positions and strengths of HDO transitions covering the region from 6000 to 7700 cm(-1). The analysis included 2445 lines involving the (101)-(000), (021)-(000), (210)-(000), and (002)-(000) bands; this is the first report of assignments in the (210)-(000) and (002)-(000) bands as well as line strength measurements of any HDO transitions in this spectral interval. (C) 1997 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 28 Z9 29 U1 0 U2 1 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 EI 1096-083X J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD NOV PY 1997 VL 186 IS 1 BP 66 EP 89 DI 10.1006/jmsp.1997.7398 PG 24 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA YM564 UT WOS:000071077400008 ER PT J AU Muller, HSP Sorensen, GO Birk, M Friedl, RR AF Muller, HSP Sorensen, GO Birk, M Friedl, RR TI The rotational spectrum and anharmonic force field of chlorine dioxide, OClO SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID INFRARED-SPECTRUM; NU-1 BAND; OCIO; CONSTANTS; PHOTOCHEMISTRY; SPECTROSCOPY; (CLO2)-CL-35; BROMINE; ICE; NM AB The rotational spectra of (OClO)-Cl-35 and (OClO)-Cl-37 in their (000), (100), (010), (001), and (020) states have been reinvestigated in selected regions between 130 and 526 GHz. About 800 newly measured lines spanning the quantum numbers 2 less than or equal to N less than or equal to 65 and 0 less than or equal to K-a less than or equal to 17 have been analyzed together with data from two previous microwave and millimeter wave studies. In particular, the spectroscopic constants in the ground vibrational states have been improved enabeling precise predictions of line positions into the submillimeter region. The newly derived ground state rotational and quartic centrifugal distortion constants, their vibrational changes, and the sextic centrifugal distortion constants were used together with data from infrared studies in a calculation of the quartic force field. (C) 1997 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Copenhagen, HC Orsted Inst, Chem Lab, DK-2100 Copenhagen 0, Denmark. RP Muller, HSP (reprint author), Univ Cologne, Inst Phys 1, Zulpicher Str 77, D-50937 Cologne, Germany. NR 40 TC 36 Z9 36 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD NOV PY 1997 VL 186 IS 1 BP 177 EP 188 DI 10.1006/jmsp.1997.7435 PG 12 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA YM564 UT WOS:000071077400018 ER PT J AU Angel, PW Cooper, AR AF Angel, PW Cooper, AR TI Effect of melting time and temperature on properties of a sodium borate glass SO JOURNAL OF NON-CRYSTALLINE SOLIDS LA English DT Article ID ELECTRICAL RELAXATION; THERMAL HISTORY; GEO2 GLASSES; CONDUCTIVITY AB Two melts, each nominally 30Na(2)O-70B(2)O(3) mol%, were prepared from batches melted at 825 degrees C after which one melt was held for an additional 15 min at 1200 degrees C. The two melts were then held at 850 degrees C for up to 3 h during which glass samples were cast at specified time intervals. All samples were then annealed together and the temperature at which the glass volume curve intersected the supercooled liquid curve was determined by dilatometry for one bar to he 454 degrees C. The density at room temperature and de conductivity, sigma(dc), from 100 to 250 degrees C were each measured for all the samples. The measurements of the glass density and sigma(dc) were not statistically different within the precision of the measurements for the various heat treatments. Thus. the glass properties were found to be only a function of glass composition and not thermal history at these elevated temperatures. (C) 1997 Elsevier Science B.V. C1 CASE WESTERN RESERVE UNIV,DEPT MAT SCI & ENGN,CLEVELAND,OH 44106. RP Angel, PW (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 34 TC 3 Z9 3 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-3093 J9 J NON-CRYST SOLIDS JI J. Non-Cryst. Solids PD NOV PY 1997 VL 221 IS 1 BP 70 EP 77 DI 10.1016/S0022-3093(97)00303-7 PG 8 WC Materials Science, Ceramics; Materials Science, Multidisciplinary SC Materials Science GA YH784 UT WOS:A1997YH78400008 ER PT J AU He, Y Yan, XH Liu, WT AF He, Y Yan, XH Liu, WT TI Surface heat fluxes in the western equatorial Pacific Ocean estimated by bulk parameterization and by an inverse mixed layer model SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID TROPICAL PACIFIC; SATELLITE DATA; VAPOR-PRESSURE; SOLAR IRRADIANCE; WIND STRESS; WARM POOL; TEMPERATURE; LATENT; VARIABILITIES; COMPUTATION AB Sea surface heat fluxes in the western equatorial Pacific Ocean estimated by bulk parameterization are compared with fluxes computed with a one-dimensional, level 2.5 turbulence closure inverse mixed layer model. The bulk parameterization method requires the inputs of sea surface temperature, cloud amount, wind speed, air temperature, and specific humidity. With the inverse mixed layer model: the authors estimate the surface net heat flux using surface wind stresses and sea surface temperature (SST)as input, assuming a linear variation of surface heat fluxes between two time intervals of known SST in a secant root-finding algorithm. The meteorological data time series from the Woods Hole Oceanography Institution buoy at 1 degrees 45'S, 156 degrees E during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment intensive observation period is used as the test dataset. The inverse method generates large variations in daily mean heat flux estimation while the derived longer time-averaged net heat flux is more consistent with the bulk formula result. This can be explained by an experiment that shows that the heat flux is highly sensitive to relatively small SST errors in the input. The use of satellite data is also discussed by testing the model with a blended SST input composed of satellite-observed and mooring-measured SST. C1 UNIV DELAWARE,GRAD COLL MARINE STUDIES,CTR REMOTE SENSING,NEWARK,DE 19716. CALTECH,JET PROP LAB,PASADENA,CA 91125. NR 47 TC 2 Z9 2 U1 1 U2 1 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 NOV PY 1997 VL 27 IS 11 BP 2477 EP 2487 DI 10.1175/1520-0485(1997)027<2477:SHFITW>2.0.CO;2 PG 11 WC Oceanography SC Oceanography GA YF289 UT WOS:A1997YF28900012 ER PT J AU Codino, A Brunetti, MT Federico, C Grimani, C Lanfranchi, M Menichelli, M Miozza, M Golden, RL Stochaj, SJ Stephens, SA Mitchell, JW Ormes, JF Streitmatter, RE Hof, M Pfeifer, C Menn, W Simon, M Basini, G Ricci, M Brancaccio, FM Papini, P Piccardi, S Spillantini, P DePascale, MP Morselli, A Picozza, P AF Codino, A Brunetti, MT Federico, C Grimani, C Lanfranchi, M Menichelli, M Miozza, M Golden, RL Stochaj, SJ Stephens, SA Mitchell, JW Ormes, JF Streitmatter, RE Hof, M Pfeifer, C Menn, W Simon, M Basini, G Ricci, M Brancaccio, FM Papini, P Piccardi, S Spillantini, P DePascale, MP Morselli, A Picozza, P TI Momentum spectra of atmospheric pions, muons, electrons and positrons at balloon altitudes SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS LA English DT Article ID COSMIC-RAY; NEUTRINO; FLUX; SPECTROMETER; PERFORMANCE AB Momentum spectra of pions, muons, electrons and secondary positrons have been measured at an atmospheric depth of 5.8 g cm(-2) with the same instrument. Data was collected by the Matter Antimatter Space Spectrometer of the New Mexico State University in a balloon flight in September 1991 at the rigidity cut-off of 4.5 GV c(-1) in Fort Sumner, New Mexico. The first measurement of the positive muon spectrum in the range 0.15 GeV c(-1) to 2 GeV c(-1) is reported in this paper. The spectral index above 3 GeV c(-1) of the negative muon momentum spectrum of this measurement is -2.39 +/- 0.05 in agreement with analytical cascade calculations which assume a primary proton kinetic energy spectrum with a slope of -2.74 +/- 0.02 in the corresponding kinetic energy range. In the momentum interval 300-700 MeV c(-1), both negative and positive muon fluxes turn out to be larger than calculated fluxes by a factor of about 1.4. The measurement of the secondary electron and positron energy spectra allows a reliable subtraction of the atmospheric background from the primary electron and positron fluxes which are affected by large uncertainties in most of the experiments. The energy spectra of the secondary particles reported here have the same systematic errors implying a higher relative accuracy with respect to those measurements made in different flights. C1 IST NAZL FIS NUCL, I-06100 PERUGIA, ITALY. NEW MEXICO STATE UNIV, PARTICLE ASTROPHYS LAB, LAS CRUCES, NM 88003 USA. TATA INST FUNDAMENTAL RES, BOMBAY 400005, MAHARASHTRA, INDIA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV SIEGEN, D-5900 SIEGEN, GERMANY. IST NAZL FIS NUCL, LAB NAZL FRASCATI, I-00044 FRASCATI, ITALY. UNIV FLORENCE, DIPARTIMENTO FIS, FLORENCE, ITALY. IST NAZL FIS NUCL, I-50125 FLORENCE, ITALY. UNIV ROMA TOR VERGATA, DIPARTIMENTO FIS, I-00173 ROME, ITALY. IST NAZL FIS NUCL, SEZ ROMA 2, ROME, ITALY. RP Codino, A (reprint author), UNIV PERUGIA, DIPARTIMENTO FIS, I-06100 PERUGIA, ITALY. RI Morselli, Aldo/G-6769-2011; OI Morselli, Aldo/0000-0002-7704-9553; Picozza, Piergiorgio/0000-0002-7986-3321; Papini, Paolo/0000-0003-4718-2895 NR 32 TC 10 Z9 10 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0954-3899 J9 J PHYS G NUCL PARTIC JI J. Phys. G-Nucl. Part. Phys. PD NOV PY 1997 VL 23 IS 11 BP 1751 EP 1763 PG 13 WC Physics, Nuclear; Physics, Particles & Fields SC Physics GA YG224 UT WOS:A1997YG22400021 ER PT J AU Sullivan, RM Hoffman, CG Rao, GM AF Sullivan, RM Hoffman, CG Rao, GM TI Orbital performance of AMPTE/CCE nickel-cadmium batteries with a large number of charger-induced, very small, charge/discharge cycles SO JOURNAL OF POWER SOURCES LA English DT Article DE orbital performance; nickel-cadmium batteries AB The AMPTE/CCE spacecraft used switching regulators to short-circuit the excess solar array current and control the charge to each of its two 28 V, 4 Ah nickel-cadmium batteries. This digital regulation of the battery overcharge current caused approximately 10 x 10(6), very small battery charge/discharge cycles during the long sunlight periods of the highly elliptical, 24 h orbit; a unique system influence that did not significantly degrade battery performance during the mission life. The occurrence of three Very long eclipses at the beginning, middle and end of the mission, provided a rare opportunity to analyze the performance of the batteries for the mission Life. This paper presents the power system design, and the battery performance for about five years of mission life. (C) 1997 Elsevier Science S.A. C1 Swales & Associates, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sullivan, RM (reprint author), Swales & Associates, 5050 Powder Mill Rd, Beltsville, MD 20705 USA. NR 7 TC 0 Z9 0 U1 0 U2 1 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0378-7753 J9 J POWER SOURCES JI J. Power Sources PD NOV-DEC PY 1997 VL 69 IS 1-2 BP 27 EP 36 DI 10.1016/S0378-7753(97)02543-3 PG 10 WC Chemistry, Physical; Electrochemistry; Energy & Fuels; Materials Science, Multidisciplinary SC Chemistry; Electrochemistry; Energy & Fuels; Materials Science GA YN822 UT WOS:000071211300003 ER PT J AU Eklund, DR Stouffer, SD Northam, GB AF Eklund, DR Stouffer, SD Northam, GB TI Study of a supersonic combustor employing swept ramp fuel injectors SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID MACH-2 AB A computational study of a scramjet combustor with swept ramp fuel injectors was conducted with the SPARK Navier-Stokes computer code, Turbulence was modeled with a two-zone algebraic turbulence model, while combustion was modeled with two finite rate H-2-air chemistry models, The calculated reacting flowfield was mixing-limited. However, the extent of mixing was affected by the chemical reactions, Heat release from the chemical reactions significantly reduced the mixing between the fuel and airstreams. Comparisons between the calculations and experimental measurements of the wall pressure, surface heat flux, in-stream pitot pressure, as well as Mie scattering now visualization were made and good overall agreement was observed. C1 VIRGINIA POLYTECH INST & STATE UNIV,DEPT MECH ENGN,BLACKSBURG,VA 24061. NASA,LANGLEY RES CTR,HYPERSON PROP BRANCH,HAMPTON,VA 23681. RP Eklund, DR (reprint author), ROYAL INST TECHNOL,S-10044 STOCKHOLM,SWEDEN. NR 23 TC 8 Z9 9 U1 3 U2 5 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 NOV-DEC PY 1997 VL 13 IS 6 BP 697 EP 704 DI 10.2514/2.5230 PG 8 WC Engineering, Aerospace SC Engineering GA YG296 UT WOS:A1997YG29600001 ER PT J AU Shih, SH Hixon, DR Mankbadi, RR AF Shih, SH Hixon, DR Mankbadi, RR TI Zonal approach for prediction of jet noise SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/CEAS 1st Joint Aeroacoustics Conference CY JUN 12-15, 1995 CL MUNICH, GERMANY SP AIAA, CEAS ID BOUNDARY-CONDITIONS; SHEAR LAYERS; SOUND; FIELD; FLOW AB A zonal approach for direct computation of sound generation and propagation from a supersonic jet is investigated. The present work splits the computational domain into a nonlinear, acoustic-source regime and a linear acoustic wave propagation regime, In the nonlinear regime, the unsteady now is governed by the large-scale equations, which are the filtered compressible Navier-Stokes equations. In the linear acoustic regime, the sound wave propagation is described by the linearized Euler equations. Computational results are presented for a supersonic jet at M = 2.1. It is demonstrated that no spurious modes are generated in the matching region and the computational expense is reduced as opposed to fully large-scale simulation. RP Shih, SH (reprint author), NASA,LEWIS RES CTR,OHIO AEROSP INST,INST COMPUTAT MECH PROP,M-S 5-11,CLEVELAND,OH 44135, USA. NR 35 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 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD NOV-DEC PY 1997 VL 13 IS 6 BP 745 EP 752 DI 10.2514/2.5247 PG 8 WC Engineering, Aerospace SC Engineering GA YG296 UT WOS:A1997YG29600007 ER PT J AU VanDresar, NT AF VanDresar, NT TI Prediction of pressurant mass requirements for axisymmetric liquid hydrogen tanks SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 31st Joint Propulsion Conference and Exhibit CY JUL 10-12, 1995 CL SAN DIEGO, CA SP AIAA, ASME, SAE, ASEE AB Experimental data from several lest series are compared to an existing correlation that predicts the amount of pressurant gas mass required to expel liquid hydrogen from axisymmetric tanks, It was necessary to use an alternative definition of the tank equivalent diameter to accommodate thermal mass in the tank wall that is initially warm, and to accommodate liquid residuals in the tank after expulsion is stopped, With this modification, the existing correlation predicted mass requirements to within 14% of experimental results. Revision of the correlation constants using a nonlinear Least-squares fit of the current experimental data has a minor effect, thus supporting the validity of the original correlation's form, its fitted constants, and the alternative definition of the tank equivalent diameter. RP VanDresar, NT (reprint author), NASA,LEWIS RES CTR,PROPELLANT SYST TECHNOL BRANCH,M-S 60-4,CLEVELAND,OH 44135, USA. NR 9 TC 3 Z9 3 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 NOV-DEC PY 1997 VL 13 IS 6 BP 796 EP 799 PG 4 WC Engineering, Aerospace SC Engineering GA YG296 UT WOS:A1997YG29600014 ER PT J AU King, MK AF King, MK TI Further examination of enthalpy rocket performance SO JOURNAL OF PROPULSION AND POWER LA English DT Article RP King, MK (reprint author), NASA HEADQUARTERS,CODE UG,300 E ST SW,WASHINGTON,DC 20546, USA. NR 2 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 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD NOV-DEC PY 1997 VL 13 IS 6 BP 804 EP 806 DI 10.2514/2.5238 PG 3 WC Engineering, Aerospace SC Engineering GA YG296 UT WOS:A1997YG29600017 ER PT J AU Johnson, BC Sakuma, F Butler, JJ Biggar, SF Cooper, JW Ishida, J Suzuki, K AF Johnson, BC Sakuma, F Butler, JJ Biggar, SF Cooper, JW Ishida, J Suzuki, K TI Radiometric measurement comparison using the Ocean Color Temperature Scanner (OCTS) visible and near infrared integrating sphere SO JOURNAL OF RESEARCH OF THE NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY LA English DT Article DE calibration; EOS; integrating sphere; measurement comparison; OCTS; ocean color; SeaWiFS; spectral radiometry; remote sensing; transfer radiometers ID CALIBRATION; INSTRUMENT AB As a part of the pre-flight calibration and validation activities for the Ocean Color and Temperature Scanner (OCTS) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color satellite instruments, a radiometric measurement comparison was held in February 1995 at the NEC Corporation in Yokohama, Japan. Researchers from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration/Goddard Space Right Center (NASA/GSFC), the University of Arizona Optical Sciences Center (UA), and the National Research Laboratory of Metrology (NRLM) in Tsukuba, Japan used their portable radiometers to measure the spec tral radiance of the OCTS visible and near-infrared integrating sphere at four radiance levels. These four levels corresponded to the configuration of the OCTS integrating sphere when the calibration coefficients for five of the eight spectral channels, or bands, of the OCTS instrument were determined. The measurements of the four radiometers differed by -2.7 % to 3.9 % when compared to the NEC calibration of the sphere and the overall agreement was within the combined measurement uncertainties. A comparison of the measurements from the participating radiometers also resulted in agreement within the combined measurement uncertainties. These results are encouraging and demonstrate the utility of comparisons using laboratory calibration integrating sphere sources. Other comparisons will focus on instruments that are scheduled for spacecraft in the NASA study of climate change, the Earth Observing System (EOS). C1 Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. Natl Res Lab Metrol, Tsukuba, Ibaraki 305, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. Hughes STX Corp, Greenbelt, MD 20771 USA. NEC Corp Ltd, Div Space Syst, Tsuzuki Ku, Yokohama, Kanagawa 224, Japan. RP Johnson, BC (reprint author), Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. RI Butler, James/D-4188-2013 NR 16 TC 16 Z9 16 U1 1 U2 3 PU US GOVERNMENT PRINTING OFFICE PI WASHINGTON PA SUPERINTENDENT DOCUMENTS,, WASHINGTON, DC 20402-9325 USA SN 1044-677X J9 J RES NATL INST STAN JI J. Res. Natl. Inst. Stand. Technol. PD NOV-DEC PY 1997 VL 102 IS 6 BP 627 EP 646 DI 10.6028/jres.102.043 PG 20 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA YW259 UT WOS:000071914400001 PM 27805113 ER PT J AU Choi, SH Lee, JH Meador, WE Conway, EJ AF Choi, SH Lee, JH Meador, WE Conway, EJ TI A 50-kW module power station of directly solar-pumped iodine laser SO JOURNAL OF SOLAR ENERGY ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article AB The conceptual design of a 50 kW directly solar-pumped iodine laser (DSPIL) module was developed for a space-based power station which transmits its coherent-beam power to-users such as the moon, Martian revers, or other satellites with large (>25 kW) electric power requirements. Integration of multiple modules would provide an amount of power that exceeds the power of a single module by combining and directing the coherent beams to the user's receiver. The model developed for the DSPIL system conservatively predicts the laser output power (50 kW) that appears much less than the laser output (93 kW) obtained from the gain volume ratio extrapolation of experimental data. The difference in laser outputs may be attributed to reflector configurations adopted in both design and experiment. Even though the photon absorption by multiple reflections in experimental cavity setup was more efficient, the maximum secondary absorption amounts to be only 24.7 percent of the primary. However, the gain volume ratio shows 86 percent more power output than theoretical estimation that is roughly 60 percent more than the contribution by the secondary absorption. Such a difference indicates that the theoretical model adopted in the study underestimates the overall performance of the DSPIL. This fact may tolerate more flexible and radical selection of design parameters than used in this design study. The design achieves an overall specific power of approximately 5 W/kg and total mass of 10 metric tons. RP Choi, SH (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 20 TC 7 Z9 7 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0199-6231 J9 J SOL ENERG-T ASME JI J. Sol. Energy Eng. Trans.-ASME PD NOV PY 1997 VL 119 IS 4 BP 304 EP 311 DI 10.1115/1.2888037 PG 8 WC Energy & Fuels; Engineering, Mechanical SC Energy & Fuels; Engineering GA YG911 UT WOS:A1997YG91100007 ER PT J AU Weilmuenster, KJ Gnoffo, PA Greene, FA Riley, CJ Hamilton, HH AF Weilmuenster, KJ Gnoffo, PA Greene, FA Riley, CJ Hamilton, HH TI Hypersonic thermal environment of a proposed single-stage-to-orbit vehicle SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID SCHEMES AB The thermal environment of a representative single-stage-to-orbit winged body vehicle has been investigated at a Mach number of 21.89 and an altitude of 233,000 ft, which corresponds to the peak heating condition on a nominal re-entry trajectory. Both surface heating and temperatures are mapped for the baseline configuration and for control surfaces both fixed (tip fins) and deflected (body flap and elevens). The thermal environment is predicted for angles of attack of 28, 32, and 36 deg; for body flap deflections of 10 and 20 deg; and for a matrix of tip fin parameters based on leading-edge radius and leading-edge sweep angle. The analysis is based on laminar flow in chemical equilibrium and chemical nonequilibrium including catalytic surface effects. The analysis shows that, in the vicinity of the wing fuselage juncture and tip fin leading edge, the localized heating can be as much as three times and temperatures as much as one-third greater than those found at the stagnation point. These extremes are the result of shock interactions that are influenced by vehicle aerolines and attitude, as well as the chemical state of the gas in the flowfield. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Res Technol Grp, Hampton, VA 23681 USA. RP Weilmuenster, KJ (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Res Technol Grp, Hampton, VA 23681 USA. NR 16 TC 5 Z9 5 U1 1 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 697 EP 704 DI 10.2514/2.3282 PG 8 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200001 ER PT J AU Milos, FS AF Milos, FS TI Galileo probe heat shield ablation experiment SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID JUPITER ATMOSPHERE AB The Galileo Probe deceleration module contained an experiment that measured the surface recession of the forebody heat shield during the hypersonic entry into the Jovian atmosphere. A detailed description of the experiment, reduction of the recession data, reconstruction of the heat-shield shape history, and comparisons with preflight predictions are presented. Sensor performance was compromised by an extraneous signal during the first half of the hypersonic entry, but data quality was reasonably good for the second half of the entry. To within measurement accuracy the ablation was axisymmetric, and the final shape was well defined. Stagnation point recession was significantly less than predicted. Frustum recession exceeded predictions and was comparable to stagnation point recession. C1 NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. RP Milos, FS (reprint author), NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, MS 234-1, Moffett Field, CA 94035 USA. NR 35 TC 25 Z9 26 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 705 EP 713 DI 10.2514/2.3293 PG 9 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200002 ER PT J AU Weinacht, P Sturek, WB Schiff, LB AF Weinacht, P Sturek, WB Schiff, LB TI Navier-Stokes predictions of pitch damping for axisymmetric projectiles SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB An approach for predicting the pitch-damping coefficient sum for axisymmetric flight bodies is presented. The approach utilizes a specific combination of spinning and coning motions that allows the pitch-damping force and moment coefficient to be directly related to the aerodynamic side force and moment. The use of combined spinning and coning motion represents an improvement over existing techniques that utilize lunar coning motion for predicting the pitch-damping coefficients. A parabolized Navier-Stokes approach that utilizes a missile fixed, noninertial rotating coordinate frame is applied to predict the flowfields about axisymmetric projectiles undergoing steady coning motion. The governing equations are modified to include the centrifugal and Coriolis force terms due to the rotating coordinate frame. From the computed flowfield, the side force and moment due to coning motion, spinning motion, and combined spinning and coning motion are used to determine the pitch-damping coefficients. Computations are performed for a generic shell configuration (with and without boattail), and the predictions show good agreement with an existing inviscid code. The comparisons of computational results for a family of ogive-cylinder configurations with aerodynamics range data show excellent agreement and further validate the approach. C1 USA, Res Lab, Aerodynam Branch, Prop & Flight Div,Weap & Mat Res Directorate, Aberdeen Proving Ground, MD 21005 USA. NASA, Ames Res Ctr, Fluid Dynam Div, Moffett Field, CA 94035 USA. USA, Res Lab, High Performance Comp Div, Corp Informat & Comp Ctr, Aberdeen Proving Ground, MD 21005 USA. RP Weinacht, P (reprint author), USA, Res Lab, Aerodynam Branch, Prop & Flight Div,Weap & Mat Res Directorate, Aberdeen Proving Ground, MD 21005 USA. NR 17 TC 17 Z9 18 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 753 EP 761 DI 10.2514/2.3306 PG 9 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200009 ER PT J AU Cho, CS Fralick, GC Bhatt, HD AF Cho, CS Fralick, GC Bhatt, HD TI Steady-state and frequency response of a thin-film heat flux gauge SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID TEMPERATURE AB A new and simpler design of thin-film heat flux gauge has been developed for use in high-heat flux environments. Heat flux gauges of the same design were fabricated on three different substrates and tested. The heat flux gauge comprises a thermopile and a thermocouple junction, which measures the surface temperature. The thermopile has 40 pairs of S-type thermocouples and is covered by two thermal resistance layers. Calibration and testing of these gauges were first carried out in an are-lamp calibration facility, Sensitivity of the gauge was discussed in terms of the relative conductivity and surface temperature. The heat flux calculated from the gauge output was in good agreement with the precalibrated standard sensor. The steady-state and the transient response characteristics of the heat flux gauge were also investigated using a carbon dioxide pulse laser as a heat source. The dynamic frequency response was evaluated in terms of the nondimensional amplitude ratio with respect to the frequency spectrum of a chopped laser beam. The frequency response of the gauge was determined to be about 3 kHz. The temperature profiles in the thin-film heat flux gauge mere obtained numerically in steady state conditions using FLUENT and compared with the experimental results. C1 Western Michigan Univ, Dept Aeronaut & Mech Engn, Kalamazoo, MI 49008 USA. NASA, Lewis Res Ctr, Res Sensors Technol Branch, Cleveland, OH 44135 USA. RP Cho, CS (reprint author), Western Michigan Univ, Dept Aeronaut & Mech Engn, Kalamazoo, MI 49008 USA. NR 17 TC 5 Z9 5 U1 1 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 792 EP 798 DI 10.2514/2.3288 PG 7 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200015 ER PT J AU Katz, I Gardner, BM Mandell, MJ Jongeward, GA Patterson, M Myers, RM AF Katz, I Gardner, BM Mandell, MJ Jongeward, GA Patterson, M Myers, RM TI Model of plasma contactor performance SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID ELECTRON AB A hollow cathode based plasma contactor will be flown on the international space station to control the station's potential to within +/-40 V of the local ionosphere. Extensive testing of the plasma contactor has been conducted in vacuum facilities at the NASA Lewis Research Center. Significant performance differences were observed between tests of the same plasma contactor in different facilities. Why measured plasma contactor performance differs in the laboratory in different tank environments and how the plasma contactor performance measured in the laboratory relates to expected performance in space is addressed. Presented are models of plasma contactor plasma generation and interaction in a laboratory environment, including anode area limiting. These models were integrated using the Space Station Environment Work Bench to predict plasma contactor operation, and the results are compared with the laboratory measurements. C1 Maxwell Technol, Maxwell Fed Div, San Diego, CA 92123 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Olin Aerosp Co, PRIMEX Aerosp, Elect Prop, Redmond, WA 98073 USA. RP Katz, I (reprint author), Maxwell Technol, Maxwell Fed Div, 8888 Balboa Ave, San Diego, CA 92123 USA. NR 11 TC 12 Z9 13 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 824 EP 828 DI 10.2514/2.3294 PG 5 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200020 ER PT J AU Wang, JS Lai, ST AF Wang, JS Lai, ST TI Virtual anode in ion beam emissions in space: Numerical simulations SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID PARTICLE AB The plasma interactions associated with the emission of an unneutralized ion beam in space are discussed. Three-dimensional particle simulations, which follow the beam ions as well as the ambient electrons and ions in the self-consistent electric field, are performed for various emission conditions. Classical theories and laboratory experiments for one-dimensional beam flow in diodes have shown that a potential hump will form when the beam current density exceeds a critical value. When the potential hump becomes so high that the beam kinetic energy is near zero there, it becomes a virtual electrode. We show that similar characteristics are also exhibited in high-density ion beams emitted from spacecraft to space plasma, although three-dimensional effects and the ambient plasma make the interaction more complex. Once a virtual anode has formed, it will partly block the beam transmission and discharge the spacecraft potential. C1 CALTECH, Jet Prop Lab, Adv Prop Technol Grp, Pasadena, CA 91109 USA. USA, Phillips Lab, GPSS, PL, Hanscom AFB, MA 01731 USA. RP Wang, JS (reprint author), CALTECH, Jet Prop Lab, Adv Prop Technol Grp, MS125-224,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 15 TC 10 Z9 10 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 829 EP 836 DI 10.2514/2.3295 PG 8 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200021 ER PT J AU Hwu, SU Panneton, RJ AF Hwu, SU Panneton, RJ TI International space station electromagnetic environment SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 Lockheed Martin Space Mission Syst & Serv, Commun Tracking Anal & Test Sect, Houston, TX 77258 USA. NASA, Johnson Space Ctr, Avion Test & Anal Branch, Houston, TX 77258 USA. RP Hwu, SU (reprint author), Lockheed Martin Space Mission Syst & Serv, Commun Tracking Anal & Test Sect, MC-C02,2400 NASA Rd 1, Houston, TX 77258 USA. NR 5 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 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 847 EP 848 DI 10.2514/2.3297 PG 2 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200023 ER PT J AU Hwu, SU Panneton, RJ Gomez, SF AF Hwu, SU Panneton, RJ Gomez, SF TI Efficient approach for international space station global positioning system multipath analysis SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 Lockheed Martin Space Mission Syst & Serv, Commun Tracking Anal & Test Sect, Houston, TX 77258 USA. NASA, Johnson Space Ctr, Avion Test & Anal Branch, Houston, TX 77258 USA. NASA, Johnson Space Ctr, Guidance & Navigat Branch, Houston, TX 77258 USA. RP Hwu, SU (reprint author), Lockheed Martin Space Mission Syst & Serv, Commun Tracking Anal & Test Sect, MC-C02,2400 NASA Rd 1, Houston, TX 77258 USA. NR 3 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1997 VL 34 IS 6 BP 848 EP 850 DI 10.2514/2.3298 PG 3 WC Engineering, Aerospace SC Engineering GA YQ067 UT WOS:000071344200024 ER PT J AU Clark, RL Cox, DE AF Clark, RL Cox, DE TI Multi-variable structural acoustic control with static compensation SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID SOUND RADIATION AB Structural acoustic control of stochastic disturbance sources based on static compensation of multiple input, multiple-output colocated transducer arrays is addressed in this work. Prior feedback controller designs for structural acoustic systems have been based on linear quadratic regulator theory or linear quadratic Gaussian theory, however, the need for a state estimator limits the practical implementation of such control systems on plants characterized by model uncertainty and high modal density. Results presented in this work serve to demonstrate that direct output-feedback control can be successfully employed to attenuate the structural acoustic response of a panel subjected to exogenous input disturbances. Colocated transducer pairs were implemented with a fully populated constant feedback gain matrix from sensor outputs to control inputs. The colocated transducer array serves to enhance robust stability, while the constant feedback gain matrix provides a practical means of implementation. The effects of instrumentation density, control effort penalty, and model order on predicted performance are considered. (C) 1997 Acoustical Society of America. C1 NASA,LANGLEY RES CTR,GUIDANCE & CONTROL BRANCH,HAMPTON,VA 23681. RP Clark, RL (reprint author), DUKE UNIV,DEPT MECH ENGN & MAT SCI,DURHAM,NC 27708, USA. NR 19 TC 15 Z9 15 U1 4 U2 4 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD NOV PY 1997 VL 102 IS 5 BP 2747 EP 2756 DI 10.1121/1.420329 PN 1 PG 10 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA YG922 UT WOS:A1997YG92200028 ER PT J AU Fox, DS Cuy, MD Strangman, TE AF Fox, DS Cuy, MD Strangman, TE TI Sea salt hot corrosion and strength of an yttria-containing silicon nitride SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID DEGRADATION; CERAMICS AB A commercially available, hot isostatically pressed Si3N4 containing 4 wt% yttria was exposed to 982 degrees C for up to 75 h in a burner rig pressurized to 500 kPa. Synthetic sea salt added to the flame (5 ppm) resulted in formation of a sodium magnesium silicate corrosion product. A 33% reduction in room-temperature strength occurred after 5 h exposure. This is thought to be due to modification of the near-surface grain boundary phase and relief of surface compressive stresses. Exposures to longer times resulted in continued strength reduction, up to 46% at 75 h. Strength also decreased when salt concentration was increased, as shown by exposures using 2 and 10 ppm sea salt. In tests at 100 and 300 kPa with other variables held constant, post-corrosion strengths were similar to those after 500 kPa exposure. C1 NYMA INC,BROOKPARK,OH 44142. ALLIEDSIGNAL ENGINES,PHOENIX,AZ 85702. RP Fox, DS (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 18 TC 7 Z9 7 U1 0 U2 0 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD NOV PY 1997 VL 80 IS 11 BP 2798 EP 2804 DI 10.1111/j.1151-2916.1997.tb03196.x PG 7 WC Materials Science, Ceramics SC Materials Science GA YG203 UT WOS:A1997YG20300005 ER PT J AU Bubenheim, D Wignarajah, K Berry, W Wydeven, T AF Bubenheim, D Wignarajah, K Berry, W Wydeven, T TI Phytotoxic effects of gray water due to surfactants SO JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE LA English DT Article DE lettuce; surfactants; phytotoxicity; hydroponics; rhizosphere; microorganisms; toxic level; dose response ID BIODEGRADATION AB Recycling wastewater containing soaps and detergents for plant growth is highly desirable when fresh water is limited, This is especially true during times of drought and is imperative in some specialized situations such as a regenerative space habitat. To regenerate food, water, and air, the National Aeronautics and Space Administration's Controlled Ecological Life Support System (CELSS) must recycle wastewater commonly known as gray water, The anionic surfactant Igepon is the principal ingredient of many detergent formulations and soaps and is a prime candidate for use in a space habitat, To determine if gray water would have phytotoxic effects on crops grown in a CELSS, 'Waldmann's Green' lettuce (Lactuca sativa L.) was grown in nutrient solutions containing varying concentrations of Igepon TC-42, Igepon concentrations of 250 mg.L-1 or higher in nutrient solutions resulted in phytotoxic effects in lettuce, Thus, the toxic threshold of Igepon is <250 mg.L-1. Toxicity symptoms include browning of the roots within 4 hours of exposure to Igepon followed by suppression of root dry mass within 24 hours, Plant death never resulted from exposure to Igepon used in these experiments, although roots were killed, The phytotoxic effect of Igepon was not persistent; plants initially displaying acute toxicity show clear signs of recovery within 3 days of initial exposure, Further, when fresh plants were exposed to these same nutrient solutions 3 days or more following initial Igepon addition, no phytotoxic effect was observed, The elimination of the phytotoxicity was associated with a decrease in fatty acid components in the nutrient solution associated with Igepon, The degradation of phytotoxicity appears to be associated with microbes present on the surface of the roots and not directly due to any plant process or instability of the surfactant. RP Bubenheim, D (reprint author), NASA,AMES RES CTR,ADV LIFE SUPPORT DIV,REGENERAT SYST BRANCH,MOFFETT FIELD,CA 94035, USA. NR 18 TC 12 Z9 12 U1 2 U2 14 PU AMER SOC HORTICULTURAL SCIENCE PI ALEXANDRIA PA 701 NORTH SAINT ASAPH STREET, ALEXANDRIA, VA 22314-1998 SN 0003-1062 J9 J AM SOC HORTIC SCI JI J. Am. Soc. Hortic. Sci. PD NOV PY 1997 VL 122 IS 6 BP 792 EP 796 PG 5 WC Horticulture SC Agriculture GA YF080 UT WOS:A1997YF08000010 ER PT J AU DelSole, T AF DelSole, T TI Absolute instability induced by dissipation SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID EXTERNAL ROSSBY WAVES; BAROCLINIC INSTABILITY; PULSE ASYMPTOTICS; FLOW AB A two-layer quasigeostrophic model is used to investigate whether dissipation can induce absolute instability in otherwise convectively unstable or stable background states. It is shown that dissipation of either temperature or lower-layer potential vorticity can cause absolute instabilities over a wide range of parameter values and over a wide range of positive lower-layer velocities (for positive vertical shear). It is further shown that these induced absolute instabilities can be manifested as local instabilities with similar properties. Compared to the previously known absolute instabilities, the induced absolute instabilities are characterized by larger scales, weaker absolute growth rates, and substantially weaker vertical phase tilt (typical values for subtropical states are zonal wave-number 1-3, absolute growth rate 80-100 days, and period 7-10 days). The analysis of absolute instabilities, including the case of multiple absolute instabilities, is reviewed in an appendix. Because the dispersion relation of the two-layer model can be written as a polynomial in both wavenumber and frequency, all possible saddle points and poles of the dispersion relation can be determined directly. An unusual feature of induced absolute instabilities is that the absolute growth rate can change discontinuously for small changes in the basic-state parameters. The occurrence of a discontinuity in the secondary instability is not limited to the two-layer model but is a general possibility in ang system involving multiple absolute instabilities. Depending on th; location of the discontinuity relative to the packet peak, a purely local analysis, as used in many numerical techniques, would extrapolate the secondary absolute instability lo incorrect regions of parameter space or fail to detect the secondary absolute instability altogether. An efficient procedure for identifying absolute instabilities that accounts for these issues is developed and applied to the two-layer model. RP DelSole, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,DATA ASSIMILAT OFF,CODE 910-3,GREENBELT,MD 20771, USA. NR 18 TC 2 Z9 2 U1 0 U2 2 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 NOV 1 PY 1997 VL 54 IS 21 BP 2586 EP 2595 DI 10.1175/1520-0469(1997)054<2586:AIIBD>2.0.CO;2 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YE046 UT WOS:A1997YE04600006 ER PT J AU Witham, C Hightower, A Fultz, B Ratnakumar, BV Bowman, RC AF Witham, C Hightower, A Fultz, B Ratnakumar, BV Bowman, RC TI Electrochemical properties of LaNi5-xGex alloys in Ni-MH batteries SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID HYDRIDE ELECTRODES; METAL; SURFACE AB Electrochemical studies were performed on LaNi5-xGex metal hydride alloys with 0 less than or equal to x less than or equal to 0.5. We carried out single-electrode studies to understand the effects of the Ge substituent on the hydrogen absorption characteristics, the electrochemical capacity, and the electrochemical kinetics of hydrogen absorption and desorption. The electrochemical characteristics of the Ge-substituted alloys are compared to those of the Sn-substituted alloys reported earlier. LaNi5-xGex alloys show compositional trends similar to LaNi5-xSnx alloys, but unlike the Sn-substituted alloys, Ge-substituted alloys continue to exhibit facile kinetics for hydrogen absorption/desorption at high solute concentrations. Cycle lives of LaNi5-xGex electrodes were measured in 300 mAh laboratory test cells and were found to be superior to the Sn-substituted LaNi5 and comparable to a Mm(Ni, Co, Mn, Al)(5) alloy. The optimum Ge content for LaNi5-xGex metal hydride alloys in alkaline rechargeable cells is in the range 0.4 less than or equal to x less than or equal to 0.5. C1 CALTECH,JET PROP LAB,ELECTROCHEM TECHNOL GRP,PASADENA,CA 91109. CALTECH,JET PROP LAB,ADV THERMAL & STRUCT TECHNOL GRP,PASADENA,CA 91109. RP Witham, C (reprint author), CALTECH,DIV ENGN & APPL SCI,PASADENA,CA 91125, USA. NR 22 TC 21 Z9 21 U1 0 U2 2 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 NOV PY 1997 VL 144 IS 11 BP 3758 EP 3764 DI 10.1149/1.1838087 PG 7 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA YF272 UT WOS:A1997YF27200017 ER PT J AU Hash, D Meyyappan, M AF Hash, D Meyyappan, M TI A direct simulation Monte Carlo study of flow considerations in plasma reactor development for 300 mm processing SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID CHEMICAL-VAPOR-DEPOSITION; NEUTRAL TRANSPORT; GAS-FLOW; MODEL; DSMC AB Fluid flow related issues in plasma process equipment design for 300 mm wafer processing are considered. A direct simulation Monte Carlo technique is used to simulate molecular chlorine flow and chlorine atom etching of polysilicon. The effects of process chamber diameter, wafer location, and exit design on processing uniformity are investigated, and guidelines are provided regarding the choices for these parameters. RP Hash, D (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 22 TC 9 Z9 9 U1 0 U2 1 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 NOV PY 1997 VL 144 IS 11 BP 3999 EP 4004 DI 10.1149/1.1838126 PG 6 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA YF272 UT WOS:A1997YF27200056 ER PT J AU Goorjian, PM Silberberg, Y AF Goorjian, PM Silberberg, Y TI Numerical simulations of light bullets using the full-vector time-dependent nonlinear Maxwell equations SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID FEMTOSECOND OPTICAL SOLITONS; NORMALLY DISPERSIVE MEDIA; SAPPHIRE LASER; MODE-LOCKING; PULSES; PROPAGATION; COLLAPSE AB The vector Maxwell's equations are solved to simulate propagating and colliding optical pulses in planar waveguides. The slowly varying envelope approximation is not made, and therefore the dynamics of the optical carrier are retained in the calculations. Some short optical pulses are found to be essentially unchanged over rather long propagation distances and stable over some energy variation in a manner characteristic of light bullets. With greater energy increase the pulses do not collapse, as predicted by the nonlinear Schrodinger equation; rather, after initially compressing, they undergo unlimited expansion. Because the optical pulses that are employed in these simulations are extremely short, they are beyond the limitations of the slowly varying envelope approximation that is used in the derivation of the nonlinear Schrodinger equation. The dispersive effects are modeled by a single Lorentzian resonance, and the nonlinear refraction is modeled by a Kerr-like instantaneous nonlinearity. The procedure for obtaining numerical solutions to the nonlinear Maxwell equations is described, and solutions are obtained by a finite-difference algorithm. (C) 1997 Optical Society of America. C1 WEIZMANN INST SCI, IL-76100 REHOVOT, ISRAEL. RP NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RI SILBERBERG, YARON/K-1564-2012 NR 39 TC 31 Z9 31 U1 1 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 EI 1520-8540 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD NOV PY 1997 VL 14 IS 11 BP 3253 EP 3260 DI 10.1364/JOSAB.14.003253 PG 8 WC Optics SC Optics GA YF411 UT WOS:A1997YF41100062 ER PT J AU Wong, J Scherer, A George, T AF Wong, J Scherer, A George, T TI Surface micromachined membranes for tunnel transducers SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B LA English DT Article; Proceedings Paper CT 41st International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication (EIBPN) CY MAY 27-30, 1997 CL DANA POINT, CALIFORNIA SP Amer Vacuum Soc, IEEE, Electron Device Soc, Optical Soc Amer ID DISPLACEMENT AB We have developed low-temperature surface micromachining procedures for the fabrication of suspended SiO2/Si3N4 membranes. This fabrication method was integrated with electron beam lithography, anisotropic ion etching, and electroplating to construct electrostatically deflectable tunnel transducers. We show the structures and some preliminary measurements on the performance of these monolithic devices. (C) 1997 American Vacuum Society. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wong, J (reprint author), CALTECH, Pasadena, CA 91125 USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1071-1023 J9 J VAC SCI TECHNOL B JI J. Vac. Sci. Technol. B PD NOV-DEC PY 1997 VL 15 IS 6 BP 2768 EP 2772 DI 10.1116/1.589724 PG 5 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA YM807 UT WOS:000071103100171 ER PT J AU Benson, AJ Guedry, FE Parker, DE Reschke, MF AF Benson, AJ Guedry, FE Parker, DE Reschke, MF TI Microgravity vestibular investigations: Perception of self-orientation and self-motion SO JOURNAL OF VESTIBULAR RESEARCH-EQUILIBRIUM & ORIENTATION LA English DT Article DE perception; weightlessness; self-motion; self-orientation ID GRAVITY AB Four astronauts experienced passive whole-body rotation in a number of test sessions during a 7-day orbital mission, Pitch (Y-axis) and roll (X-axis) rotation required subject orientations on the rotator in which the otolith system was at radius of 0.5 m, Thus subjects experienced a constant -0.22 G(z) stimulus to the otoliths during the 60 s constant-velocity segments of "pitch" and "roll" ramp profiles, The G(z) stimulus, a radius-dependent vector ranging from -0.22 G(z) at the otoliths to +0.36 G(z) at the feet, generated sensory information that was not interpreted as inversion in any of the 16 tests carried out in flight (12 in pitch and 4 in roll orientation), None of the subjects was rotated with head off-center during the first 33 h of the mission, In the state of orbital adaptation of these subjects, a -0.22 G(z) otolith stimulus did not provide a vertical reference in the presence of a gradient of +G(z) stimuli to the trunk and legs. (C) 1997 Elsevier Science Inc. C1 Univ Washington, Dept Otolaryngol Head & Neck Surg, Seattle, WA 98195 USA. RAF Sch Aviat Med, Farnborough, Hants, England. Univ W Florida, Pensacola, FL 32514 USA. USN, Aerosp Med Res Lab, Pensacola, FL USA. NASA, Lyndon B Johnson Space Ctr, Space Biomed Res Inst, Houston, TX 77058 USA. RP Parker, DE (reprint author), Univ Washington, Dept Otolaryngol Head & Neck Surg, Box 357923, Seattle, WA 98195 USA. NR 10 TC 11 Z9 11 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0957-4271 J9 J VESTIBUL RES-EQUIL JI J. Vestib. Res.-Equilib. Orientat. PD NOV-DEC PY 1997 VL 7 IS 6 BP 453 EP 457 PG 5 WC Neurosciences; Otorhinolaryngology SC Neurosciences & Neurology; Otorhinolaryngology GA YT404 UT WOS:000071599500004 PM 9397395 ER PT J AU VanderWal, RL AF VanderWal, RL TI Laser-induced incandescence measures soot and smoke SO LASER FOCUS WORLD LA English DT Article ID FLICKERING METHANE; VOLUME FRACTION; DIFFUSION FLAME RP VanderWal, RL (reprint author), NASA,LEWIS RES CTR,NYMA INC,MS 110-3,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 23 TC 0 Z9 0 U1 0 U2 0 PU PENNWELL PUBL CO PI NASHUA PA 5TH FLOOR TEN TARA BOULEVARD, NASHUA, NH 03062-2801 SN 0740-2511 J9 LASER FOCUS WORLD JI Laser Focus World PD NOV PY 1997 VL 33 IS 11 BP 99 EP 107 PG 9 WC Optics SC Optics GA YF034 UT WOS:A1997YF03400034 ER PT J AU Bamman, MM Hunter, GR Stevens, BR Guilliams, ME Greenisen, MC AF Bamman, MM Hunter, GR Stevens, BR Guilliams, ME Greenisen, MC TI Resistance exercise prevents plantar flexor deconditioning during bed rest SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article DE unloading; space flight; neural activation; strength; torque-velocity-power relationships ID SKELETAL-MUSCLE ADAPTATIONS; SIMULATED WEIGHTLESSNESS; FORCE-VELOCITY; STRENGTH; ENDURANCE; MASS; COMPATIBILITY; SPECIFICITY; HUMANS; TORQUE AB Because resistance exercise (REX) and unloading induce opposing neuromuscular adaptations, we tested the efficacy of REX against the effects of 14 d of bed rest unloading (BRU) on the plantar flexor muscle group. Sixteen men were randomly assigned to no exercise (NOE, N = 8) or REX (N = 8). REX performed 5 sets x 6-10 repetitions to failure of constant resistance concentric/eccentric plantar flexion every other day during BRU. One-repetition maximum (1RM) strength was tested on the training device. The angle-specific torque-velocity relationship across 5 velocities (0, 0.52, 1.05, 1.75, and 2.97 rad.s(-1)) and the full range-of-motion power-velocity relationship were assessed on a dynamometer. Torque-position analyses identified strength changes at shortened, neutral, and stretched muscle lengths. Concentric and eccentric contractile work were measured across ten repetitions at 1.05 rad.s(-1). Maximal neural activation was measured by surface electromyography (EMG). 1RM decreased 9% in NOE and improved 11% in REX (P < 0.05). Concentric (0.52 and 1.05 rad.s(-1)), eccentric (0.52 and 2.97 rad.s(-1)), and isometric angle-specific torques decreased (P < 0.05) in NOE, averaging 18%, 17%, and 13%, respectively. Power dropped (P < 0.05) in NOE at three eccentric (21%) and two concentric (14%) velocities. REX protected angle-specific torque and average power at all velocities. Concentric and eccentric strength decreased at stretched (16%) and neutral (17%) muscle lengths (P < 0.05) in NOE while REX maintained or improved strength at all joint positions. Concentric (15%) and eccentric (11%) contractile work fell in NOE (P < 0.05) but not in REX. Maximal plantar flexor EMG did not change in either group. In summary, constant resistance concentric/eccentric REX completely prevented plantar flexor performance deconditioning induced by BRU. The reported benefits of REX should prove useful in prescribing exercise for astronauts in microgravity and for patients susceptible to functional decline during bed- or chair-bound hospital stays. C1 UNIV FLORIDA,DEPT PHYSIOL,GAINESVILLE,FL 32611. KRUG LIFE SCI,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,LIFE SCI RES LABS,HOUSTON,TX 77058. RP Bamman, MM (reprint author), UNIV ALABAMA,DEPT HUMAN STUDIES,801 S 13TH ST,BIRMINGHAM,AL 35294, USA. FU NCRR NIH HHS [M01 RR00073] NR 35 TC 52 Z9 52 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 NOV PY 1997 VL 29 IS 11 BP 1462 EP 1468 DI 10.1097/00005768-199711000-00012 PG 7 WC Sport Sciences SC Sport Sciences GA YF165 UT WOS:A1997YF16500012 PM 9372483 ER PT J AU Cassen, P AF Cassen, P TI Workshop on parent-body and nebular modifications of chondritic materials SO METEORITICS & PLANETARY SCIENCE LA English DT Editorial Material ID SOLAR NEBULA C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Cassen, P (reprint author), CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125, USA. NR 7 TC 1 Z9 1 U1 0 U2 0 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 1997 VL 32 IS 6 BP 740 EP 741 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YG981 UT WOS:A1997YG98100002 ER PT J AU Weisberg, MK Zolensky, ME Prinz, M AF Weisberg, MK Zolensky, ME Prinz, M TI Fayalitic olivine in matrix of the Krymka LL3.1 chondrite: Vapor-solid growth in the solar nebula SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID UNEQUILIBRATED ORDINARY CHONDRITES; HIGH-TEMPERATURE CONDENSATION; TYPE-3 ORDINARY CHONDRITES; IRON-RICH OLIVINE; AQUEOUS ALTERATION; MINERALOGICAL EVIDENCE; METEORITE MATRIX; ORIGIN; ALLENDE; CHEMISTRY AB Fayalitic olivine (Fa(54-94)) is a ubiquitous component in the matrix of Krymka (LL3.1) as well as in other highly unequilibrated chondrites (ordinary and carbonaceous). In Krymka, the fayalitic olivine has an unusual anisotropic platy morphology that occurs in at least five types of textural settings that can be characterized as: (1) isolated platelets, (2) clusters of platelets, (3) euhedral to subhedral crystals, (4) overgrowths of platelets on forsteritic olivine, and (5) fluffy (porous) aggregates. From transmission electron microscope (TEM) investigation, the direction of elongation of the platy olivine overgrowths on forsteritic olivine substrates is along the c axis and in most cases it corresponds with the c axis of the substrate olivine, which suggests that the fayalitic olivine grew in this unusual morphology and is not a replacement product of pre-existing material. The fayalitic olivine in the matrix of Krymka is compositionally similar to olivine with platy morphology in the matrix of some CV3 chondrites and both have similar Fe/Mn ratios, but important morphological differences indicate that their relationship needs to be explored further. Textural and compositional data indicate that the fayalitic olivine in the matrix of Krymka, as well as in some other unequilibrated ordinary chondrites, formed prior to final lithification of the meteorite and probably prior to parent body accretion. We find that formation of the fayalitic olivine by vapor-solid growth provides the best explanation for our observations and data and is the only feasible mechanism for the formation of fayalitic olivine in the matrix of Krymka. We propose that the fayalitic olivine formed by vaporization and recondensation of olivine rich-dust, during a period of enhanced dust/gas ratio in the nebula. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Weisberg, MK (reprint author), AMER MUSEUM NAT HIST,DEPT EARTH & PLANETARY SCI,NEW YORK,NY 10024, USA. NR 50 TC 22 Z9 23 U1 0 U2 1 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 1997 VL 32 IS 6 BP 791 EP 801 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YG981 UT WOS:A1997YG98100010 ER PT J AU Asphaug, E AF Asphaug, E TI Impact origin of the Vesta family SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID LARGE EJECTA FRAGMENTS; COLLISIONAL DISRUPTION; VELOCITY DISTRIBUTION; PARENT BODY; MAIN-BELT; 4 VESTA; ASTEROIDS; METEORITES; EVOLUTION; SIMULATIONS AB The compelling petrographic link (Consolmagno and Drake, 1977; Gaffey, 1983) between basaltic achondrite meteorites and the similar to 530 km diameter asteroid 4 Vesta has been tempered by a perceived difficulty in launching rocks from this asteroid's surface at speeds sufficient to bring them to Earth (Wasson and Wetherill, 1979) without obliterating Vesta's signature crust. I address this impasse in response to recent imaging (Zellner et al., 1996; Dumas and Hainaut, 1996) of a similar to 450 km impact basin across Vesta's southern hemisphere (Thomas et al., 1997) and model the basin-forming collision using a detailed two-dimensional hydrocode with brittle fracture including self-gravitational compression (cf., Asphaug and Melosh, 1993). A similar to 42 km diameter asteroid striking Vesta's basaltic crust (atop a denser mantle and iron core) at 5.4 km/s launches multikilometer fragments up to similar to 600 m/s without inverting distal stratigraphy, according to the code. This modeling, together with collisional, dynamical, rheological and exposure-age timescales (Marzari et al., 1996; Welten et al., 1996), and observations of V-type asteroids (Binzel and Xu, 1993) suggests a recent (cl Ga) impact origin for the Vesta family and a possible Vesta origin for Earth-approaching V-type asteroids (Cruikshank et al., 1991). RP Asphaug, E (reprint author), NASA,AMES RES CTR,SETI INST,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 78 TC 79 Z9 81 U1 0 U2 3 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 1997 VL 32 IS 6 BP 965 EP 980 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YG981 UT WOS:A1997YG98100024 ER PT J AU Harris, AL Fitzgerald, W Baibakov, B Margolis, LB Zimmerberg, J AF Harris, AL Fitzgerald, W Baibakov, B Margolis, LB Zimmerberg, J TI Inhibition of specific antibody production by gap junction inhibitors SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NICHHD,NASA,NIH,CTR 3 DIMENS CULTURE,LCMB,BETHESDA,MD 20892. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1997 VL 8 SU S BP 556 EP 556 PG 1 WC Cell Biology SC Cell Biology GA YF096 UT WOS:A1997YF09600554 ER PT J AU Williams, SD Rothschild, LJ AF Williams, SD Rothschild, LJ TI The effect of natural levels of solar ultraviolet radiation on RNA synthesis SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 ST LOUIS UNIV,SCH MED,DEPT BIOCHEM & MOL BIOL,ST LOUIS,MO 63104. NASA,AMES RES CTR,ECOSYST SCI & TECHNOL BRANCH,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1997 VL 8 SU S BP 846 EP 846 PG 1 WC Cell Biology SC Cell Biology GA YF096 UT WOS:A1997YF09600845 ER PT J AU Gonda, SR Yang, TC Pingerelli, PL Wyborski, DL Lee, W Haddad, RS Fritz, PH AF Gonda, SR Yang, TC Pingerelli, PL Wyborski, DL Lee, W Haddad, RS Fritz, PH TI A multicellular spheroid model for studying genotoxic effects from environmental insults SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. STRATAGENE,LA JOLLA,CA. KRUG LIFE SCI,HOUSTON,TX. UNIV SPACE RES ASSOC,HOUSTON,TX. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1997 VL 8 SU S BP 1180 EP 1180 PG 1 WC Cell Biology SC Cell Biology GA YF096 UT WOS:A1997YF09601177 ER PT J AU Hashemi, BB Vens, C Huls, H Penkala, JE Sams, CF AF Hashemi, BB Vens, C Huls, H Penkala, JE Sams, CF TI Differential regulation of T-cell activation responses in microgravity culture. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,LIFE SCI RES LABS,HOUSTON,TX 77058. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1997 VL 8 SU S BP 2091 EP 2091 PG 1 WC Cell Biology SC Cell Biology GA YF096 UT WOS:A1997YF09602083 ER PT J AU Hammond, TG Goodwin, TJ Navar, GL Goda, FO Campbell, WC Ostberg, JR Verroust, PJ Kaysen, JH AF Hammond, TG Goodwin, TJ Navar, GL Goda, FO Campbell, WC Ostberg, JR Verroust, PJ Kaysen, JH TI Epithelial cell gene expression is shear stress responsive. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 TULANE UNIV,SCH MED,VA MED CTR,NEW ORLEANS,LA 70112. INSERM,PARIS,FRANCE. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1997 VL 8 SU S BP 2517 EP 2517 PG 1 WC Cell Biology SC Cell Biology GA YF096 UT WOS:A1997YF09602511 ER PT J AU Charnley, SB AF Charnley, SB TI Chemical models of interstellar gas-grain processes .3. Molecular depletion in NGC 2024 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE molecular processes; ISM, clouds; ISM, individual, NGC 2024; ISM, molecules ID MAGNETIC-FLUX LOSS; PROTOSTELLAR CONDENSATIONS; SURFACE-CHEMISTRY; DUST EMISSION; CLOUDS; NGC-2024; CORES; IONS; ASTROCHEMISTRY; ABUNDANCES AB The chemistry arising from the exchange of molecules between dust and gas in ultradense (n(H) greater than or equal to 10(7) cm(-3)) cool cores is described, Under certain assumptions concerning molecule-grain binding energies and dust temperature, slight warming of cold dust grains can induce selective desorption of mantle volatiles. It is theoretically possible for ultradense cores to become depleted in CO but to remain abundant in N-2 and so be relatively rich in nitrogen-bearing molecules. This effect may explain the apparent depletion of CO and the presence of ammonia in several cores within the NGC 2024 cloud, The theory implies that heavy metal atoms should be almost entirely absent from the gas phase of high-density cores, and that a mantle of CO, O-2, N-2 and other weakly bound molecules should cover water ice mantles, forming a 'volatile crust'. Molecular observations are suggested which will allow a test of this model. C1 NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. RP Charnley, SB (reprint author), UNIV CALIF BERKELEY, DEPT ASTRON, 601 CAMPBELL HALL, BERKELEY, CA 94720 USA. RI Charnley, Steven/C-9538-2012 NR 44 TC 44 Z9 44 U1 0 U2 1 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 NOV 1 PY 1997 VL 291 IS 3 BP 455 EP 460 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YF570 UT WOS:A1997YF57000015 ER PT J AU FoxRabinovitz, MS Stenchikov, GL Suarez, MJ Takacs, LL AF FoxRabinovitz, MS Stenchikov, GL Suarez, MJ Takacs, LL TI A finite-difference GCM dynamical core with a variable-resolution stretched grid SO MONTHLY WEATHER REVIEW LA English DT Article ID SHALLOW-WATER EQUATIONS; NUMERICAL WEATHER PREDICTION; PRIMITIVE EQUATIONS; MESH REFINEMENT; FLUID-DYNAMICS; FORECAST MODEL; GLOBAL-MODEL; BOUNDARY; FORMULATION; SIMULATION AB A finite-difference atmospheric model dynamics, or dynamical core using variable resolution, or stretched grids, is developed and used for regional-global medium-term and long-term integrations. The goal of the study is to verify whether using a variable-resolution dynamical core allows us to represent adequately the regional scales over the area of interest (and its vicinity). In other words, it is shown that a significant downscaling is taking place over the area of interest, due to better-resolved regional fields and boundary forcings. It is true not only for short-term integrations, but also for medium-term and, most importantly, long-term integrations. Numerical experiments are performed with a stretched grid version of the dynamical core of the Goddard Earth Observing System (GEOS) general circulation model (GCM). The dynamical core includes the discrete (finite-difference) model dynamics and a Newtonian-type rhs zonal forcing, which is symmetric for both hemispheres about the equator. A flexible, portable global stretched grid design allows one to allocate the area of interest with uniform fine-horizontal (latitude by longitude) resolution over any part of the globe, such as the U.S. territory used in these experiments. Outside the region, grid intervals increase, or stretch, with latitude and longitude. The grids with moderate to large total (global) stretching factors or ratios of maximum to minimum grid intervals on the sphere are considered. Dynamical core versions with the total stretching factors ranging from 4 to 32 are used. The model numerical scheme, with all its desirable conservation and other properties, is kept unchanged when using stretched grids. Two model basic horizontal filtering techniques, the polar or high-latitude Fourier filter and the Shapiro filter, are applied to stretched grid fields. Two filtering approaches based on the projection of a stretched grid onto a uniform one are tested. One of them does not provide the necessary computational noise control globally. Another approach provides a workable monotonic global solution. The latter is used within the developed stretched grid version of the GEOS GCM dynamical core that can be run in both the middle-range and long-term modes. This filtering approach allows one to use even large stretching factors. The successful experiments were performed with the dynamical core for several stretched, grid versions with moderate to large total stretching factors ranging from 4 to 32. For these versions, the fine resolutions (in degrees) used over the area of interest are 2 x 2.5, 1 x 1.25, 0.5 x 0.625, and 0.25 x 0.3125. Outside the area of interest, grid intervals are stretching to 4 x 5 or 8 x 10. The medium-range 10-day integrations with summer climate initial conditions show a pronounced similarity of synoptic patterns over the area of interest and its vicinity when using a stretched grid or a control global uniform fine-resolution grid. For a long-term benchmark integration performed with the first aforementioned grid, the annual mean circulation characteristics obtained with the stretched grid dynamical core appeared to be profoundly similar to those of the control run with the global uniform fine-resolution grid over the area of interest, or the United States. The similarity is also evident over the best resolved within the used stretched grid northwestern quadrant, whereas it does not take place over the least-resolved southeastern quadrant. In the better-resolved Northern Hemisphere, the jet and Hadley cell are close to those of the control run, which does not take place for the Southern Hemisphere with coarser variable resolution. The stretched grid dynamical core integrations have shown no negative computational effects accumulating in time. The major result of the study is that a stretched grid approach allows one to take advantage of enhanced resolution over the region of interest. It provides a better representation of regional fields for both medium-term and long-term integrations. C1 UNIV MARYLAND,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. GEN SCI CORP,LAUREL,MD. RI Georgiy, Stenchikov/J-8569-2013 NR 59 TC 60 Z9 60 U1 0 U2 4 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 NOV PY 1997 VL 125 IS 11 BP 2943 EP 2968 DI 10.1175/1520-0493(1997)125<2943:AFDGDC>2.0.CO;2 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YE253 UT WOS:A1997YE25300011 ER PT J AU Ishihara, A Ohira, Y Roy, RR Nagaoka, S Sekiguchi, C Hinds, WE Edgerton, VR AF Ishihara, A Ohira, Y Roy, RR Nagaoka, S Sekiguchi, C Hinds, WE Edgerton, VR TI Effects of 14 days of spaceflight and nine days of recovery on cell body size and succinate dehydrogenase activity of rat dorsal root ganglion neurons SO NEUROSCIENCE LA English DT Article DE microgravity; oxidative potential; quantitative histochemistry; sensory neurons; spaceflight ID CYTOCHROME-OXIDASE ACTIVITY; SOMA SIZE; SKELETAL-MUSCLES; IMPULSE BLOCKAGE; VISUAL-SYSTEM; MOTONEURONS; CATS AB The cross-sectional areas and succinate dehydrogenase activities of L-5 dorsal root ganglion neurons in rats were determined after 14 days of spaceflight and after nine days of recovery. The mean and distribution of the cross-sectional areas were similar to age-matched, ground-based controls for both the spaceflight and for the spaceflight plus recovery groups. The mean succinate dehydrogenase activity was significantly lower in spaceflight compared to aged-matched control rats, whereas the mean succinate dehydrogenase activity was similar in age-matched control and spaceflight plus recovery rats. The mean succinate dehydrogenase activity of neurons with cross-sectional areas between 1000 and 2000 mu m(2) was lower (between 7 and 10%) in both the spaceflight and the spaceflight plus recovery groups compared to the appropriate control groups. The reduction in the oxidative capacity of a subpopulation of sensory neurons having relatively large cross-sectional areas immediately following spaceflight and the sustained depression for nine days after returning to 1 g suggest that the 0 g environment induced significant alterations in proprioceptive function. (C) 1997 IBRO. Published by Elsevier Science Ltd. C1 UNIV CALIF LOS ANGELES,INST BRAIN RES,LOS ANGELES,CA 90095. KYOTO UNIV,FAC INTEGRATED HUMAN STUDIES,NEUROCHEM LAB,KYOTO 60601,JAPAN. NATL INST FITNESS & SPORTS,DEPT PHYSIOL & BIOMECH,KANOYA 89123,JAPAN. NATL SPACE DEV AGCY JAPAN,SPACE EXPT GRP,TSUKUBA,IBARAKI 305,JAPAN. NASA,AMES RES CTR,PAYLOADS OFF,MOFFETT FIELD,CA 94035. UNIV CALIF LOS ANGELES,DEPT PHYSIOL SCI,LOS ANGELES,CA 90095. NR 22 TC 31 Z9 31 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0306-4522 J9 NEUROSCIENCE JI Neuroscience PD NOV PY 1997 VL 81 IS 1 BP 275 EP 279 DI 10.1016/S0306-4522(97)00097-3 PG 5 WC Neurosciences SC Neurosciences & Neurology GA XU143 UT WOS:A1997XU14300026 PM 9300420 ER PT J AU Turner, MS AF Turner, MS TI Cosmology 1996 SO NUCLEAR PHYSICS B LA English DT Article; Proceedings Paper CT 4th KEK Topical Conference on Flavor Physics CY OCT 29-31, 1996 CL NATL LAB HIGH ENERGY PHYS, TSUKUBA, JAPAN SP Inst Particle & Nucl Studies, High Energy Accelator Res Org, Minist Educ Sci Sports & Culture, Japan, Fdn High Energy Accelerator Sci HO NATL LAB HIGH ENERGY PHYS ID COLD DARK-MATTER; BIG-BANG NUCLEOSYNTHESIS; LARGE-SCALE STRUCTURE; GRAND-UNIFIED THEORIES; INFLATIONARY UNIVERSE; DEUTERIUM ABUNDANCE; TENSOR PERTURBATIONS; BACKGROUND-RADIATION; BARYON DENSITY; CONSTANT AB The current state of cosmology is easy to summarize: a very successful standard model - the hot big-bang cosmology - that accounts for the evolution of the Universe from 10(-2) sec until the present; bold ideas based upon early-Universe physics - foremost among them inflation and cold dark matter - that can extend the standard cosmology to times as early as 10(-32) sec and address the most pressing questions; and a flood of observations from determinations of the Hubble constant to measurements of CBR anisotropy - that are testing inflation and cold dark matter. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Turner, MS (reprint author), UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637, USA. NR 79 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 1997 SU 59 BP 239 EP 248 DI 10.1016/S0920-5632(97)00448-9 PG 10 WC Physics, Particles & Fields SC Physics GA YG180 UT WOS:A1997YG18000027 ER PT J AU Klaasen, KP Belton, MJS Breneman, HH McEwen, AS Davies, ME Sullivan, RJ Chapman, CR Neukum, G Heffernan, CM AF Klaasen, KP Belton, MJS Breneman, HH McEwen, AS Davies, ME Sullivan, RJ Chapman, CR Neukum, G Heffernan, CM TI Inflight performance characteristics, calibration, and utilization of the Galileo solid-state imaging camera SO OPTICAL ENGINEERING LA English DT Article DE charge-coupled-device camera; calibration; digital imaging; remote sensing; space instrumentation; astronomy ID SPECTROPHOTOMETRIC ATLAS; ASTEROID 951-GASPRA; IMAGES; MOON; JUPITER; LIMB AB The solid-state imaging subsystem (SSI) on NASA's Galileo Jupiter orbiter spacecraft has already demonstrated its superior performance as a scientific imager by returning stunning pictures of several planetary bodies as well as detailed inflight calibration data during its cruise to Jupiter. The SSI inflight performance remains excellent; the instrument calibration is stable and accurate. Improved determinations of the SSI's absolute spectral radiometric response and scattered-light properties have been made. Evaluation of the camera's point spread function suggests that the focus setting may be slightly nonoptimum, but the spatial resolution in returned images is still very good. The shielding of the SSI's CCD detector against energetic particle radiation appears to be adequate for operation in Jupiter's intense radiation field. New camera modes, onboard editing and data compression capabilities, and an adaptive mission operations plan have been implemented for the Jupiter orbital mission phase in order to mitigate the effects of a spacecraft anomaly that limits the allowable data return rate from Jupiter. These new capabilities are expected to allow the accomplishment of a historic scientific investigation of the Jupiter system using the SSI. (C) 1997 Society of Photo-Optical instrumentation Engineers. C1 NATL OPT ASTRON OBSERV,TUCSON,AZ 85756. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. RAND CORP,SANTA MONICA,CA 90406. ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287. SW RES INST,BOULDER,CO 80302. DEUTSCH FORSCH ANSTALT LUFT & RAUMFAHRT,BERLIN ADLERSHOF,INST PLANETARY EXPLORAT,D-12489 BERLIN,GERMANY. RP Klaasen, KP (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 44 TC 47 Z9 47 U1 4 U2 9 PU SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS PI BELLINGHAM PA PO BOX 10, BELLINGHAM, WA 98227-0010 SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD NOV PY 1997 VL 36 IS 11 BP 3001 EP 3027 DI 10.1117/1.601525 PG 27 WC Optics SC Optics GA YF405 UT WOS:A1997YF40500011 ER PT J AU Smith, JA Ballard, JR Pedelty, JA AF Smith, JA Ballard, JR Pedelty, JA TI Effect of three-dimensional canopy architecture on thermal infrared exitance SO OPTICAL ENGINEERING LA English DT Article DE thermal infrared; canopy model; brightness temperature; directional exitance; surface flux ID MODEL; SURFACE; TEMPERATURE; EMISSIVITY AB We present a theoretical study of the effects of three-dimensional canopy structure on directional thermal infrared exitance. A physics-based model employing steady-state energy budget formulations is used to compute scene element temperatures. Two approaches are then used to combine soil and vegetation contributions to the composite scene response. One method uses a plane-parallel abstraction of canopy architecture to estimate canopy view factors for weighting of soil and vegetation emission terms. The second approach employs computer graphics and rendering techniques to estimate 3-D canopy view factors and scene shadows. Both approaches are applied to a test agricultural scene and compared with available measurements. The models correctly estimate hemispherically averaged thermal infrared exitance to within experimental error with root-mean-square errors of 15.3 W m(-2) for the I-D model and 12.5 W m(-2) for the 3-D model. However, the I-D model systematically underestimates exitance at high sun angles. Explicit modeling of canopy 3-D row structure indicates potential directional anisotropy in brightness temperature of up to 14 degrees C. (C) 1997 Society of Photo-Optical Instrumentation Engineers. C1 USA,ENGINEER WATERWAYS EXPT STN,ENVIRONM LAB,VICKSBURG,MS 39180. NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771. RP Smith, JA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771, USA. NR 19 TC 15 Z9 15 U1 0 U2 1 PU SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS PI BELLINGHAM PA PO BOX 10, BELLINGHAM, WA 98227-0010 SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD NOV PY 1997 VL 36 IS 11 BP 3093 EP 3100 DI 10.1117/1.601527 PG 8 WC Optics SC Optics GA YF405 UT WOS:A1997YF40500019 ER PT J AU Parikh, JA DaPonte, JS Vitale, JN Tselioudis, G AF Parikh, JA DaPonte, JS Vitale, JN Tselioudis, G TI Comparison of genetic algorithm systems with neural network and statistical techniques for analysis of cloud structures in midlatitude storm systems SO PATTERN RECOGNITION LETTERS LA English DT Article; Proceedings Paper CT Pattern Recognition in Practice V Conference CY JUN 04-06, 1997 CL VLIELAND, NETHERLANDS DE cloud tracking; neural network; generic algorithm AB Cloud analyses provide information which is vital to the detection, understanding and prediction of meteorological trends and environmental changes. This paper compares statistical, neural network and genetic algorithm methods for recognition and tracking of midlatitude storm clouds in sequences of low-resolution cloud-top pressure data sets. Regions of interest are identified and tracked from one image frame to the next consecutive frame in an eight-frame sequence. Classification techniques are used to determine the relationships between regions of interest in consecutive time frames. A genetic algorithm procedure is then used to revise classifier outputs to ensure that consistency constraints are not violated. (C) 1997 Elsevier Science B.V. C1 So Connecticut State Univ, Dept Comp Sci, New Haven, CT 06515 USA. Columbia Univ, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Parikh, JA (reprint author), So Connecticut State Univ, Dept Comp Sci, New Haven, CT 06515 USA. EM parikh@scsu.ctstateu.edu; ccgxt@giss.nasa.gov NR 13 TC 8 Z9 8 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8655 J9 PATTERN RECOGN LETT JI Pattern Recognit. Lett. PD NOV PY 1997 VL 18 IS 11-13 BP 1347 EP 1351 DI 10.1016/S0167-8655(97)00115-3 PG 5 WC Computer Science, Artificial Intelligence SC Computer Science GA ZM233 UT WOS:000073518000036 ER PT J AU Han, D Kim, YS Noz, ME AF Han, D Kim, YS Noz, ME TI Stokes parameters as a Minkowskian four-vector SO PHYSICAL REVIEW E LA English DT Article ID 2-PHOTON QUANTUM OPTICS; GROUP BERRY PHASES; POLARIZATION OPTICS; SQUEEZED STATES; TRANSFORMATIONS; FORMALISM; COHERENT; WIGNER; LIGHT AB It is noted that the Jones-matrix formalism for polarization optics is a six-parameter two-by-two representation of the Lorentz group. It is shown that the four independent Stokes parameters form a Minkowskian four-vector, just like the energy-momentum four-vector in special relativity. The optical filters are represented by four-by-four Lorentz-transformation matrices. This four-by-four formalism can deal with partial coherence described by the Stokes parameters. A four-by-four matrix formulation is given for decoherence effects on the Stokes parameters, and a possible experiment is proposed. It is shown also that this Lorentz-group formalism leads to optical filters with a symmetry property corresponding to-that of two-dimensional Euclidean transformations. C1 UNIV MARYLAND, DEPT PHYS, COLLEGE PK, MD 20742 USA. NYU, DEPT RADIOL, NEW YORK, NY 10016 USA. RP NASA, GODDARD SPACE FLIGHT CTR, CODE 910-1, GREENBELT, MD 20771 USA. NR 33 TC 44 Z9 47 U1 0 U2 4 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2470-0045 EI 2470-0053 J9 PHYS REV E JI Phys. Rev. E PD NOV PY 1997 VL 56 IS 5 BP 6065 EP 6076 DI 10.1103/PhysRevE.56.6065 PN B PG 12 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA YH168 UT WOS:A1997YH16800054 ER PT J AU Vahala, G Vahala, L Morrison, J AF Vahala, G Vahala, L Morrison, J TI Turbulence modeling of the toroidal wall heat load due to shear flows over cavities in the neutral gas blanket divertor regime SO PHYSICS OF PLASMAS LA English DT Article ID UEDGE CODE; DIII-D; SIMULATION; PLASMAS AB Heat loads to the target plate in reactor tokamaks are estimated to be orders of magnitude higher than those that can be withstood by known materials. In regimes of plasma detachment, there is strong evidence that plasma recombination occurs near the divertor plate, leading to a cold neutral gas blanket. Because of the strong coupling between the plasma and the neutrals within the divertor region, there is significant neutral flows along field lines up to Mach 1.2 and Reynolds numbers over 1000. Here the effects of three dimensional (3D) neutral turbulence within the gas blanket on heat deposition to the toroidal wall are examined. Both two dimensional (2D) mean shear flows over toroidal cavities as well as a fully 3D initial value problem of heat pulse propagation are considered. The results for algebraic stress model, K-epsilon and laminar flows are compared. It is found that 3D velocity shear turbulence has profound effects on the heat loads, indicating that simple (linear) Reynolds stress closure schemes are inadequate. (C) 1997 American Institute of Physics. C1 NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23666. WILLIAM & MARY,DEPT PHYS,WILLIAMSBURG,VA 23187. OLD DOMINION UNIV,DEPT ELECT & COMP ENGN,NORFOLK,VA 23529. ANALYT SERV & MAT INC,HAMPTON,VA 23666. NR 29 TC 1 Z9 1 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD NOV PY 1997 VL 4 IS 11 BP 3992 EP 4000 DI 10.1063/1.872540 PG 9 WC Physics, Fluids & Plasmas SC Physics GA YF076 UT WOS:A1997YF07600024 ER PT J AU Bennett, CL Turner, MS White, M AF Bennett, CL Turner, MS White, M TI The cosmic Rosetta stone SO PHYSICS TODAY LA English DT Article ID COLD DARK-MATTER; INFLATIONARY UNIVERSE; BACKGROUND-RADIATION; PERTURBATIONS; FLUCTUATIONS C1 UNIV CHICAGO,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,BATAVIA,IL. RP Bennett, CL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,INFRARED ASTROPHYS BRANCH,GREENBELT,MD 20771, USA. RI White, Martin/I-3880-2015 OI White, Martin/0000-0001-9912-5070 NR 37 TC 22 Z9 22 U1 0 U2 1 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 NOV PY 1997 VL 50 IS 11 BP 32 EP 38 DI 10.1063/1.881995 PG 7 WC Physics, Multidisciplinary SC Physics GA YF769 UT WOS:A1997YF76900011 ER PT J AU Maurice, S Blanc, M Prange, R Sittler, EC AF Maurice, S Blanc, M Prange, R Sittler, EC TI The magnetic-field-aligned polarization electric field and its effects on particle distribution in the magnetospheres of Jupiter and Saturn SO PLANETARY AND SPACE SCIENCE LA English DT Article ID IO PLASMA TORUS; INNER MAGNETOSPHERE; JOVIAN MAGNETOSPHERE; VOYAGER SPACECRAFT; HOT PLASMA; MODEL; REGION; SHEET AB In the magnetospheres of Saturn and Jupiter, it is well known that, even in the absence of electric currents, a polarization electric field appears along field lines to tie together ions and electrons. The present study focuses on this parallel electric field (E-parallel to), the potential drop it implies across these magnetospheres, and its consequences on the mapping of the particle densities. We start from a general expression of this field, in terms of centrifugal, gravitational and mirror forces. We conduct simple numerical simulations for n-component plasmae, where we analyze the influence of different parameters on the plasma equilibrium: the plasma anisotropy, the mass and temperatures of all species and the field line geometry. We apply the equilibrium model to existing plasma distributions at Saturn and Jupiter. Typical potential drops between the ionosphere and the equator are similar to 30 Volts at Saturn and similar to 300 Volts at Jupiter. Effects of E-parallel to on the mapping of particle densities along field lines of Saturn's and Jupiter's magnetospheres are discussed in detail. (C) 1997 Published by Elsevier Science Ltd. All rights reserved. C1 Univ Calif Los Alamos Natl Lab, Space & Atmospher Sci Grp, Los Alamos, NM 87544 USA. Observ Midi Pyrenees, Astrophys Lab, F-31400 Toulouse, France. Univ Paris 11, CNRS, IAS, F-91405 Orsay, France. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. European Space Agcy, Estec, Dept Space Sci, NL-2200 AG Noordwijk, Netherlands. Inst Astrophys, F-75014 Paris, France. RP Maurice, S (reprint author), Univ Calif Los Alamos Natl Lab, Space & Atmospher Sci Grp, POB 1663, Los Alamos, NM 87544 USA. NR 33 TC 21 Z9 21 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 NOV PY 1997 VL 45 IS 11 BP 1449 EP 1465 DI 10.1016/S0032-0633(97)00084-6 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YU251 UT WOS:000071697400010 ER PT J AU McDaniel, PR Orwoll, RA Connell, JW AF McDaniel, PR Orwoll, RA Connell, JW TI Modification of a high performance epoxy matrix with poly(arylene ether-co-imidazole)s SO POLYMER LA English DT Article DE epoxy; poly(arylene ether); poly(arylene ether imidazole); toughening ID COMPOSITES AB In an effort to improve toughness N,N,N',N'-tetraglycidyl-4,4'diaminodiphenyl methane (TGMDA) was modified with poly(arylene ether-co-imidazole)s (PAE-co-Is). The PAE-co-Is contain imidazole units distributed randomly along the backbone which react with the epoxies upon curing. A system modified with 10% w/w high molecular weight polymer exhibited increases in fracture toughness of 1.7 times that of the unmodified system; however, controlled molecular weight PAE-co-Is were required to retain processablility. Modification also resulted in significant decreases in the tetrahydrofuran sensitivity. Scanning electron photomicrographs of the fractured surface showed stress whitening with no clear phase separation whereas poly(arylene ether)s without imidazole groups exhibited gross phase separation. (C) 1997 Published by Elsevier Science Ltd. C1 COLL WILLIAM & MARY,DEPT APPL SCI,WILLIAMSBURG,VA 23187. RP McDaniel, PR (reprint author), NASA,LANGLEY RES CTR,6 W TAYLOR RD,HAMPTON,VA 23681, USA. NR 17 TC 1 Z9 1 U1 0 U2 3 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 NOV PY 1997 VL 38 IS 24 BP 6023 EP 6030 DI 10.1016/S0032-3861(97)00144-4 PG 8 WC Polymer Science SC Polymer Science GA YC404 UT WOS:A1997YC40400014 ER PT J AU Flood, DJ Clark, EB AF Flood, DJ Clark, EB TI Introduction to a selection of papers from the fifteenth space photovoltaic research and technology (SPRAT XV) conference held in June 1997 at the Lewis Research Center, Cleveland, OH, USA SO PROGRESS IN PHOTOVOLTAICS LA English DT Editorial Material C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Flood, DJ (reprint author), NASA, Lewis Res Ctr, MS 302-1,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD NOV-DEC PY 1997 VL 5 IS 6 BP 381 EP 384 DI 10.1002/(SICI)1099-159X(199711/12)5:6<381::AID-PIP198>3.0.CO;2-K PG 4 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA YX081 UT WOS:000072004500001 ER PT J AU Gaddy, EM Kichak, R Niemeyer, L Stegeman, R AF Gaddy, EM Kichak, R Niemeyer, L Stegeman, R TI The Rossi x-ray timing explorer (XTE) solar array anomaly SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 15th Space Photovoltaic Research and Technology (SPRAT XV) CY JUN, 1997 CL CLEVELAND, OHIO SP NASA, Lewis Res Ctr AB The Rossi X-ray timing explorer (XTE) was launched on 30 December 1995. Shortly after launch, it became apparent that the solar array was not performing as expected, On leaving shadow, the array exhibited many discontinuous drops in current output. The size of each of these drops teas consistent with the loss of part of a cell. The current decreases could not be caused by the loss of an entire cell or an entire circuit, This meant that the array had numerous cracked solar cells that opened as the array got war mer. Studies performed on the array's qualification panel suggest that the cell cracks may have been caused by extensive tap testing performed on the array and that these cracks were undetectable at room temperature using usual inspection methods. (C) 1997 John Wiley & Sons, Ltd. This paper was produced under the auspices of the US Government and it is therefore not subject to copyright in the USA. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Jackson & Tull, Seabrook, MD 20706 USA. RP Gaddy, EM (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD NOV-DEC PY 1997 VL 5 IS 6 BP 385 EP 392 DI 10.1002/(SICI)1099-159X(199711/12)5:6<385::AID-PIP196>3.0.CO;2-E PG 8 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA YX081 UT WOS:000072004500002 ER PT J AU Eskenazi, MI Murphy, DM Anspaugh, BE Brinker, D O'Neill, MJ AF Eskenazi, MI Murphy, DM Anspaugh, BE Brinker, D O'Neill, MJ TI Balloon and Lear jet testing of SCARLET modules and cells SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 15th Space Photovoltaic Research and Technology (SPRAT XV) CY JUN, 1997 CL CLEVELAND, OHIO SP NASA, Lewis Res Ctr AB This paper presents test results from SCARLET (solar concentrator array with refractive linear element technology) experiments performed on several Lewis Research Center Lear jet flights and two JPL balloon flights, The tests rt,ere performed in support of the BMDO-sponsored SCARLET II program, which is building a 2-6-kW SCARLET to supply the primary power for the JPL New Millennium Deep Space I Mission, The experiments involve TECSTAR dual-junction GalnP(2)/GaAs/Ge cells flown bare and under two different types of SCARLET lenses, The two types of lenses tested were a developmental design consisting of a monolithic fluoroplastic and the current baseline flight design consisting of cel ia-doped microsheet and silicone, Measured lens and total module efficiencies are presented and the flight data ave compared to various solar simulator test results, (C) 1997 John Wiley & Sons, Ltd. C1 AEC Able Engn Co Inc, Goleta, CA 93117 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. ENTECH Inc, Keller, TX 76248 USA. RP Eskenazi, MI (reprint author), AEC Able Engn Co Inc, Goleta, CA 93117 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD NOV-DEC PY 1997 VL 5 IS 6 BP 393 EP 405 PG 13 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA YX081 UT WOS:000072004500003 ER PT J AU Hoffman, RW Fatemi, NS Weizer, VG Jenkins, PP Stan, MA Ringel, SA Scheiman, DA Wilt, DM Brinker, DJ AF Hoffman, RW Fatemi, NS Weizer, VG Jenkins, PP Stan, MA Ringel, SA Scheiman, DA Wilt, DM Brinker, DJ TI High beginning-of-life efficiency p/n InP solar cells SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 15th Space Photovoltaic Research and Technology (SPRAT XV) CY JUN, 1997 CL CLEVELAND, OHIO SP NASA, Lewis Res Ctr AB The high electrical conversion performance and radiation resistance of InP solar cells was discovered during the last decade, The combination of these two characteristics makes InP a very attractive material for space solar cells, To dare, the best performance results for both homo-epitaxial and hetero-epitaxial InP solar cells were achieved using an n/p configuration, The pin configuration is desirable for hetero-epitaxial growth on inexpensive, strong, lightweight group IV substrates such as Si and Ge, Furthermore , diffused-junction pin cells demonstrated a higher radiation resistance than the n/p configuration cells; however, the testing of the pin configuration was limited to lower quality cells as judged by their beginning-of-life (BOL) efficiencies. We have succeeded in developing pin configuration homo-epitaxy InP solar. cells with BOL efficiency values exceeding 17.6% tested under air mass zero (AMO) conditions, The high efficiency values obtained from our cells resulted from improved emitter performance, which was due to better control of the growth of Zn-doped p-type InP. (C) 1997 John Wiley & Sons, Ltd. C1 Essential Res Inc, Cleveland, OH 44135 USA. Ohio State Univ, Columbus, OH 43210 USA. NYMA Setar, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hoffman, RW (reprint author), Essential Res Inc, Cleveland, OH 44135 USA. NR 14 TC 0 Z9 0 U1 1 U2 4 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD NOV-DEC PY 1997 VL 5 IS 6 BP 415 EP 422 DI 10.1002/(SICI)1099-159X(199711/12)5:6<415::AID-PIP193>3.0.CO;2-R PG 8 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA YX081 UT WOS:000072004500005 ER PT J AU Badhwar, GD AF Badhwar, GD TI The radiation environment in low-earth orbit SO RADIATION RESEARCH LA English DT Article; Proceedings Paper CT Workshop on Space Radiation Damage and Biodosimetry CY SEP 09-10, 1996 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID MODEL AB The radiation environment in low-Earth orbit is a complex mixture of galactic cosmic radiation, particles of trapped belts and secondary particles generated in both the spacecraft and Earth's atmosphere. Infrequently, solar energetic particles are injected into the Earth's magnetosphere and can penetrate into low-Earth orbiting spacecraft. In this paper, the sources of charged-particle radiation that contribute significantly to radiation exposure on manned spacecraft are reviewed briefly, and estimates of expected dose rate for the upcoming International Space Station that are based on measurements made on the Russian Mir orbital station are provided. (C) 1997 by Radiation Research Society. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 14 TC 39 Z9 42 U1 0 U2 4 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD NOV PY 1997 VL 148 IS 5 SU S BP S3 EP S10 DI 10.2307/3579710 PG 8 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA YU196 UT WOS:000071691900002 PM 9355850 ER PT J AU Durante, M George, K Yang, TC AF Durante, M George, K Yang, TC TI Biodosimetry of ionizing radiation by selective painting of prematurely condensed chromosomes in human lymphocytes SO RADIATION RESEARCH LA English DT Article; Proceedings Paper CT Workshop on Space Radiation Damage and Biodosimetry CY SEP 09-10, 1996 CL CTR ADV SPACE STUDIES, HOUSTON, TX HO CTR ADV SPACE STUDIES ID BIOLOGICAL DOSIMETRY; MAMMALIAN-CELLS; IRRADIATION; ABERRATIONS; INDUCTION; DAMAGE; BEAMS AB Painting of interphase chromosomes can be useful for biodosimetric purposes in particular cases such as radiation therapy, accidental exposure to very high radiation doses and exposure to densely ionizing radiation, for example during space missions. Biodosimetry of charged-particle radiation is analyzed in the present paper. Target cells were human peripheral blood lymphocytes irradiated in vitro with gamma rays, protons and iron ions. After exposure, lymphocytes were incubated for different times to allow repair of radiation-induced damage and then fused to mitotic hamster cells to promote premature condensation in the interphase chromosomes. Chromosome spreads were then hybridized with whole-chromosome DNA probes labeled with fluorescent stains. Dose-response curves for the induction of chromatin fragments shortly after exposure, as well as the kinetics of rejoining and misrejoining, were not markedly dependent on linear energy transfer. However, after exposure to heavy ions, more aberrations were scored in the interphase cells after incubation for repair than in metaphase samples harvested at the first postirradiation mitosis. On the other hand, no significant differences were observed in the two samples after exposure to sparsely ionizing radiation. These results suggest that interphase chromosome painting can be a useful tool for biodosimetry of particle radiation. (C) 1997 by Radiation Research Society. C1 NASA, Radiat Biol Lab, Houston, TX 77058 USA. KRUG Life Sci, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Durante, M (reprint author), Univ Naples Federico 2, Dipartimento Sci Fis, Mostra dOltremare Pad 20, I-80125 Naples, Italy. RI Durante, Marco/K-1315-2014; OI Durante, Marco/0000-0002-4615-553X NR 16 TC 15 Z9 15 U1 0 U2 1 PU RADIATION RESEARCH SOC PI LAWRENCE PA 810 E TENTH STREET, LAWRENCE, KS 66044 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD NOV PY 1997 VL 148 IS 5 SU S BP S45 EP S50 DI 10.2307/3579716 PG 6 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA YU196 UT WOS:000071691900008 PM 9355856 ER PT J AU James, JT AF James, JT TI Carcinogens in spacecraft air SO RADIATION RESEARCH LA English DT Article; Proceedings Paper CT Workshop on Space Radiation Damage and Biodosimetry CY SEP 09-10, 1996 CL CTR ADV SPACE STUDIES, HOUSTON, TX HO CTR ADV SPACE STUDIES ID MUTAGENICITY; ISOPRENE; FORMALDEHYDE; LYMPHOCYTES; METABOLISM; INHALATION; INDUCTION; EXPOSURE; INVITRO; DAMAGE AB The health effects of long-term exposure to ionizing radiation during spaceflight are a major concern to NASA, especially for missions beyond low-Earth orbit. Experiments involving astronauts will be conducted during the next few years to improve the risk assessment for exposures to ionizing radiation during flights; however, concomitant exposure to certain airborne chemical carcinogens during these experiments could confound the results of radiation experiments. Carcinogens can reach the spacecraft atmosphere from leaking thrusters, from off-gassing materials, from chemical experiments and from human metabolism. The Johnson Space Center Toxicology Group routinely analyzes atmospheric samples collected aboard spacecraft. The exposure limits for radiomimetic compounds such as benzene are reduced because of the potential interaction between radiation and chemical exposures. Analysis of recent spacecraft air samples indicates that the following carcinogens are often present in measurable concentrations: acetaldehyde, dichloromethane, formaldehyde and isoprene. Occasionally, the carcinogens 1,2-dichloroethane, acrolein, benzene and furan are found in atmospheric samples. During normal operating conditions, the low concentrations of and limited periods of exposure to airborne carcinogens are thought to pose minimal health risks to crew members, and should not confound experiments involving sensitive methods to detect biological effects of ionizing radiation. (C) 1997 by Radiation Research Society. C1 NASA, Lyndon B Johnson Space Ctr, Div Med Sci, Houston, TX 77058 USA. RP NASA, Lyndon B Johnson Space Ctr, Div Med Sci, Houston, TX 77058 USA. NR 36 TC 3 Z9 4 U1 0 U2 0 PU RADIATION RESEARCH SOC PI LAWRENCE PA 810 E TENTH STREET, LAWRENCE, KS 66044 USA SN 0033-7587 EI 1938-5404 J9 RADIAT RES JI Radiat. Res. PD NOV PY 1997 VL 148 IS 5 SU S BP S11 EP S16 DI 10.2307/3579711 PG 6 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA YU196 UT WOS:000071691900003 PM 9355851 ER PT J AU Wu, HL Durante, M George, K Yang, TC AF Wu, HL Durante, M George, K Yang, TC TI Induction of chromosome aberrations in human cells by charged particles SO RADIATION RESEARCH LA English DT Article; Proceedings Paper CT Workshop on Space Radiation Damage and Biodosimetry CY SEP 09-10, 1996 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID IN-SITU HYBRIDIZATION; INDUCED CHROMATIN BREAKS; HUMAN-LYMPHOCYTES; ALPHA-PARTICLES; MEV PROTONS; RADIATION; FREQUENCIES; EXCHANGES; IONS AB Chromosome aberrations induced by high-energy charged particles in normal human lymphocytes and human fibroblasts have been investigated, The charged particles included 250 MeV/nucleon protons, 290 MeV/nucleon carbon ions and 1 GeV/nucleon iron ions. The energies of the charged particles were higher than in most of the studies reported in the literature, Lymphocytes were stimulated to grow immediately after irradiation, while fibroblasts were incubated at 37 degrees C for 24 h for repair, Chromosomes were collected at the first mitosis after irradiation and chromosome aberrations were scored using the fluorescence in situ hybridization (FISH) technique with a whole-chromosome 4 probe. Chromosome aberrations were classified as reciprocal exchanges, incomplete exchanges, deletions and complex exchanges, The relative biological effectiveness (RBE) for each type of aberration was calculated by dividing a dose of 4 Gy by the dose of the charged particles producing the same effect as 4 Gy of gamma rays. Results of this study showed that complex aberrations have the highest RBE for radiation of high linear energy transfer (LET) for human lymphocytes, but for fibroblasts, the greatest effect was for incomplete exchanges. For both lymphocytes and fibroblasts, iron ions induced a similar fraction of aberrant cells. (C) 1997 by Radiation Research Society. C1 NASA, Lyndon B Johnson Space Ctr, Radiat Biol Lab, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Kelsey Seybold Clin, Houston, TX 77058 USA. KRUG Life Sci, Houston, TX 77058 USA. Univ Naples Federico II, Dept Phys, Naples, Italy. RP Yang, TC (reprint author), NASA, Lyndon B Johnson Space Ctr, Radiat Biol Lab, Mail Code SD2, Houston, TX 77058 USA. RI Durante, Marco/K-1315-2014 NR 22 TC 45 Z9 46 U1 0 U2 1 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD NOV PY 1997 VL 148 IS 5 SU S BP S102 EP S107 DI 10.2307/3579723 PG 6 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA YU196 UT WOS:000071691900015 PM 9355863 ER EF