FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Spencer, RW Braswell, WD AF Spencer, RW Braswell, WD TI How dry is the tropical free troposphere? Implications for global warming theory SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID RELATIVE-HUMIDITY; WATER-VAPOR; RADIOSONDE; CLIMATE; SENSITIVITY; GREENHOUSE; COOLNESS; MODEL AB The humidity of the free troposphere is being increasingly scrutinized in climate research due to its central role in global warming theory through positive water vapor feedback. This feedback is the primary source of global warming in general circulation models (GCMs). Because the loss of infrared energy to space increases nonlinearly with decreases in relative humidity, the vast dry zones in the Tropics are of particular interest. These dry zones are nearly devoid of radiosonde stations, and most of those stations have, until recently, ignored the low humidity information from the sondes. This results in substantial uncertainty in GCM tuning and validation based on sonde data. While satellite infrared radiometers are now beginning to reveal some information about the aridity of the tropical free troposphere, the authors show that the latest microwave humidity sounder data suggests even drier conditions than have been previously reported. This underscores the importance of understanding how these low humidity levels are controlled in order to tune and validate GCMs, and to predict the magnitude of water vapor feedback and thus the magnitude of global warming. C1 NICHOLS RES CORP,GLOBAL HYDROL & CLIM CTR,HUNTSVILLE,AL. RP Spencer, RW (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,EARTH SYST SCI DIV,GLOBAL HYDROL & CLIMATE CTR,ES41,HUNTSVILLE,AL 35806, USA. NR 28 TC 119 Z9 121 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD JUN PY 1997 VL 78 IS 6 BP 1097 EP 1106 DI 10.1175/1520-0477(1997)078<1097:HDITTF>2.0.CO;2 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XH868 UT WOS:A1997XH86800005 ER PT J AU Marty, GD Heintz, RA Hinton, DE AF Marty, GD Heintz, RA Hinton, DE TI Histology and teratology of pink salmon larvae near the time of emergence from gravel substrate in the laboratory SO CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE LA English DT Article ID SEX-DIFFERENTIATION; FRY AB During salmonid larval development, emergence from gravel substrate is a major event marked by final yolk absorption and transition to exogenous feeding. The gross and histological changes associated with this fundamental biological process were investigated in pink salmon (Oncorhynchus gorbuscha) 4 weeks before emergence (alevins), at emergence (swim-up fry), and 2 weeks after emergence with or without exogenous feeding. Larvae were derived from artificially spawned eggs reared in gravel-filled incubators in the laboratory. Less than 1% of emergent larvae had gross lesions. These included opercular hypoplasia or dysplasia (semioperculum), spinal anomalies (lordosis and kyphosis), conjoined twins, and ophthalmic dysplasia. Apoptosis, or programmed cell death, was a common cellular change, and several cell types were involved: (i) intragonadal supporting cells, (ii) gastric submucosal gland epithelial cells, and (iii) midventral skin cells. Semiquantitative scores for apoptosis were usually highest in pre-emergent larvae and lowest in postemergent larvae. Larvae that were not fed during the first 2 weeks after emergence had slightly higher scores for apoptosis and hepatocellular megalocytosis than did fed controls. C1 NATL MARINE FISHERIES SERV,AUKE BAY LAB,JUNEAU,AK 99801. RP Marty, GD (reprint author), UNIV CALIF DAVIS,SCH VET MED,DEPT ANAT PHYSIOL & CELL BIOL,DAVIS,CA 95616, USA. NR 23 TC 14 Z9 14 U1 3 U2 14 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA ON K1A 0R6, CANADA SN 0008-4301 J9 CAN J ZOOL JI Can. J. Zool.-Rev. Can. Zool. PD JUN PY 1997 VL 75 IS 6 BP 978 EP 988 DI 10.1139/z97-119 PG 11 WC Zoology SC Zoology GA XC870 UT WOS:A1997XC87000014 ER PT J AU Marty, GD Short, JW Dambach, DM Willits, NH Heintz, RA Rice, SD Stegeman, JJ Hinton, DE AF Marty, GD Short, JW Dambach, DM Willits, NH Heintz, RA Rice, SD Stegeman, JJ Hinton, DE TI Ascites, premature emergence, increased gonadal cell apoptosis, and cytochrome P4501A induction in pink salmon larvae continuously exposed to oil-contaminated gravel during development SO CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE LA English DT Article ID STENOTOMUS-CHRYSOPS SCUP; MEDAKA ORYZIAS-LATIPES; LAKE TROUT; TISSUES; LIVER; EGGS AB Development of pink salmon (Oncorhynchus gorbuscha) incubating in gravel contaminated with weathered Prudhoe Bay crude oil was retarded at concentrations as low as 55.2 mu g oil/g gravel. Larvae exposed to various levels of oil contamination were sampled 4 weeks before emergence, at emergence, and 13 days after emergence for histopathology (quantitative and semiquantitative) and cytochrome P4501A (CYP1A) induction (using immunohistochemical staining). A subset of postemergent fish was not fed. Hydrocarbon analysis by gas chromatography and mass spectroscopy revealed that tissue uptake of polynuclear aromatic hydrocarbons (PAH) was mediated by oil's dissolution in water, with significant biological effects when the peak total PAH concentration in water was as low as 4.4 mu g/L. Oil-related effects included induction of CYP1A, development of ascites, and increased mortality. Several oil-related changes were indicative of premature emergence. Compared with control fish, for example, exposed fish of the same age and emerging on the same day had greater amounts of yolk and hepatocellular glycogen, increased apoptosis of gonadal cells and midventral skin cells, and less food in the gastrointestinal tract. Histological features were similar within groups of larvae sampled 4 weeks before and 13 days after emergence, and oil-induced changes were not affected by feeding during the first 13 days after emergence. Increased gonadal cell apoptosis may be related to later reproductive impairment documented in field studies of pink salmon up to 4 years after the Exxon Valdez oil spill. C1 NATL MARINE FISHERIES SERV,AUKE BAY LAB,JUNEAU,AK 99801. UNIV PENN,SCH VET MED,DEPT PATHOBIOL,PHILADELPHIA,PA 19104. UNIV CALIF DAVIS,STAT LAB,DAVIS,CA 95616. WOODS HOLE OCEANOG INST,DEPT BIOL,WOODS HOLE,MA 02543. RP Marty, GD (reprint author), UNIV CALIF DAVIS,SCH VET MED,DEPT ANAT PHYSIOL & CELL BIOL,DAVIS,CA 95616, USA. NR 42 TC 117 Z9 121 U1 6 U2 33 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA ON K1A 0R6, CANADA SN 0008-4301 J9 CAN J ZOOL JI Can. J. Zool.-Rev. Can. Zool. PD JUN PY 1997 VL 75 IS 6 BP 989 EP 1007 DI 10.1139/z97-120 PG 19 WC Zoology SC Zoology GA XC870 UT WOS:A1997XC87000015 ER PT J AU Folkner, WM Hechler, F Sweetser, TH Vincent, MA Bender, PL AF Folkner, WM Hechler, F Sweetser, TH Vincent, MA Bender, PL TI LISA orbit selection and stability SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article AB The Laser Interferometer Space Antenna (LISA) is a space mission designed to detect gravitational waves in the frequency range from below 0.0001 Hz to 1 Hz by measuring changes in the distance between spacecraft separated by several million kilometres. The spacecraft orbit in a triangular formation forming three (not independent) interferometers with arm lengths determined by the distances between the vertices. The nominal orbit configuration is described and contrasted with an alternative configuration. Changes in the distances between the vertices cause a Doppler shift in the laser signals between spacecraft. The size of the measurement error introduced by this Doppler shift is dependent on the stability of the spacecraft formation. C1 ESOC,D-64293 DARMSTADT,GERMANY. UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309. RP Folkner, WM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 8 TC 39 Z9 42 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD JUN PY 1997 VL 14 IS 6 BP 1405 EP 1410 DI 10.1088/0264-9381/14/6/003 PG 6 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XF507 UT WOS:A1997XF50700003 ER PT J AU Stebbins, RT Bender, PL Folkner, WM AF Stebbins, RT Bender, PL Folkner, WM TI Getting astrophysical information from LISA data SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article AB Gravitational wave signals from a large number of astrophysical sources will be present in the LISA data. Information about as many sources as possible must be estimated from time series of strain measurements. Several types of signals are expected to be present: simple periodic signals from relatively stable binary systems, chirped signals from coalescing binary systems, complex waveforms from highly relativistic binary systems, stochastic backgrounds from galactic and extragalactic binary systems and possibly stochastic backgrounds from the early Universe. The orbital motion of the LISA antenna will modulate the phase and amplitude of all these signals, except the isotropic backgrounds and thereby give information on the directions of sources. Here we describe a candidate process for disentangling the gravitational wave signals and estimating the relevant astrophysical parameters from one year of LISA data. Nearly all of the sources will be identified by searching with templates based on source parameters and directions. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Stebbins, RT (reprint author), UNIV COLORADO,JOINT INST LAB ASTROPHYS,CB 440,BOULDER,CO 80309, USA. RI Stebbins, Robin/G-5009-2013 NR 17 TC 1 Z9 1 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD JUN PY 1997 VL 14 IS 6 BP 1499 EP 1505 DI 10.1088/0264-9381/14/6/018 PG 7 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XF507 UT WOS:A1997XF50700018 ER PT J AU Smith, SM DaviesStreet, JE Fontenot, TB Lane, HW AF Smith, SM DaviesStreet, JE Fontenot, TB Lane, HW TI Assessment of a portable clinical blood analyzer during space flight SO CLINICAL CHEMISTRY LA English DT Article DE point-of-care testing; electrolytes; ionized calcium; pH biosensors AB This study was designed to validate the utility of a commercial portable clinical blood analyzer (PCBA) in ground-based studies and on the space shuttle. Ionized calcium, pH, electrolytes, glucose, and hematocrit were determined. Results agreed well with those from traditional laboratory methods, and the PCBA demonstrated good between-day precision fur all analytes. In-flight analysis of control samples revealed differences in one analyte (sodium). There were few changes in crew members' results during flight, and these were expected, Potassium increased in flight compared with before flight, and potassium, pH, and hematocrit decreased after flight. Ionized calcium was decreased in flight and on landing day. Changes during flight were likely related to sample collection technique. Postflight changes likely reflected the fluid redistribution that occurs after exposure to weightlessness. These data confirm that the PCBA is a reliable instrument for mast analytes, and can provide important medical data in remote locations, such as orbiting spacecraft. C1 NASA,LYNDON B JOHNSON SPACE CTR,DIV MED SCI,HOUSTON,TX 77058. KRUG LIFE SCI,HOUSTON,TX 77058. RP Smith, SM (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,LIFE SCI RES LABS,NUTR BIOCHEM LAB,MAIL CODE SD3,HOUSTON,TX 77058, USA. NR 17 TC 31 Z9 31 U1 1 U2 2 PU AMER ASSOC CLINICAL CHEMISTRY PI WASHINGTON PA 2101 L STREET NW, SUITE 202, WASHINGTON, DC 20037-1526 SN 0009-9147 J9 CLIN CHEM JI Clin. Chem. PD JUN PY 1997 VL 43 IS 6 BP 1056 EP 1065 PN 1 PG 10 WC Medical Laboratory Technology SC Medical Laboratory Technology GA XC898 UT WOS:A1997XC89800024 PM 9191561 ER PT J AU Bailey, DH AF Bailey, DH TI Onward to Petaflops computing SO COMMUNICATIONS OF THE ACM LA English DT Editorial Material RP Bailey, DH (reprint author), NASA,AMES RES CTR,NUMER AERODYNAM SIMULAT PROGRAM,MOFFETT FIELD,CA 94035, USA. NR 6 TC 2 Z9 2 U1 0 U2 0 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 1515 BROADWAY, NEW YORK, NY 10036 SN 0001-0782 J9 COMMUN ACM JI Commun. ACM PD JUN PY 1997 VL 40 IS 6 BP 90 EP 92 DI 10.1145/255656.255710 PG 3 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA XB052 UT WOS:A1997XB05200018 ER PT J AU Strayer, RF Atkinson, CF AF Strayer, RF Atkinson, CF TI An overview: Recycling nutrients from crop residues for space applications SO COMPOST SCIENCE & UTILIZATION LA English DT Article AB Without some form of regenerative life support system, long duration space habitation or travel will be limited severely by the prohibitive costs of resupplying air, water, and food from Earth. Components under consideration for inclusion in a regenerative life support system are based on either physicochemical or biological processes. Physicochemical systems would use filtration and elemental phase changes to convert waste materials into usable products, while biological systems would use higher plants and bioreactors to supply crew needs. Neither a purely biological nor strictly a physicochemical approach can supply all crew needs, thus, the best each approach can offer will be combined into a hybrid regenerative life support system. Researchers at Kennedy Space Center (KSC) Advanced Life Support Breadboard Project have taken the lead on bioregenerative aspects of space life support. The major focus has been on utilization of higher plants for production of food, oxygen, and clean water. However, a key to any regenerative Life support system is recycling and recovery of resources (wastes). In keeping with the emphasis at KSC on bioregenerative systems and with the focus on plants, this paper focuses on research with biologically-based options for resource recovery from inedible crop residues. C1 NASA,NRC,KENNEDY SPACE CTR,FL. RP Strayer, RF (reprint author), GEN DYNAM CORP,KENNEDY SPACE CTR,FL 32815, USA. NR 19 TC 4 Z9 4 U1 0 U2 1 PU JG PRESS, INC PI EMMAUS PA 419 STATE AVE, EMMAUS, PA 18049 SN 1065-657X J9 COMPOST SCI UTIL JI Compost Sci. Util. PD SUM PY 1997 VL 5 IS 3 BP 25 EP 31 PG 7 WC Ecology; Soil Science SC Environmental Sciences & Ecology; Agriculture GA XV318 UT WOS:A1997XV31800004 PM 11541065 ER PT J AU Matijevic, J Shirley, D AF Matijevic, J Shirley, D TI The mission and operation of the Mars Pathfinder Microrover SO CONTROL ENGINEERING PRACTICE LA English DT Article DE autonomous mobile robots; navigation; mobility; hazard avoidance; Mars exploration AB The Microrover Flight Experiment (MFEX) is a NASA OACT (Office of Advanced Concepts and Technology) flight experiment which is planned to be delivered and integrated with the Mars Pathfinder (MPF) lander and spacecraft system for landing on Mars on July 4, 1997. After landing, the MFEX rover will be deployed from the lander and begin a nominal 7 sol (1 sol = 1 Martian day approximate to 24 hours, 40 min.) mission to conduct a series of technology experiments, deploy an alpha proton x-ray spectrometer (APXS) on rocks and soil, and image the lander. This mission will be conducted under the constraints of a once-per-sol opportunity for command and telemetry transmissions between the lander and earth operators. As such, the MFEX rover must be capable of carrying out its mission under supervised autonomous control, in which, for example, goal locations are commanded and the rover navigates and safely traverses to these locations. In this paper, the mission of the MFEX is described, along with the on-board and ground-based systems which provide the capability for operating the vehicle. RP Matijevic, J (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 6 TC 8 Z9 11 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0967-0661 J9 CONTROL ENG PRACT JI Control Eng. Practice PD JUN PY 1997 VL 5 IS 6 BP 827 EP 835 DI 10.1016/S0967-0661(97)00067-1 PG 9 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA XG617 UT WOS:A1997XG61700010 ER PT J AU Slivinsky, GG Hymer, WC Bauer, J Morrison, DR AF Slivinsky, GG Hymer, WC Bauer, J Morrison, DR TI Cellular electrophoretic mobility data: A first approach to a database SO ELECTROPHORESIS LA English DT Article; Proceedings Paper CT Australian-Electrophoresis-Society Annual Conference, at Chromatography 96 - Separation Sciences CY JUL 09-11, 1996 CL ROSEHILL, AUSTRALIA SP Austr Electrophoresis Soc DE cell electrophoresis; electrophoretic mobility; ionic strength; electric field; standard cell ID SURFACE-CHARGE; FLOW ELECTROPHORESIS; SECRETING CELLS; TUMOR-CELLS; LYMPHOCYTES; MATURATION; LINES; SEPARATION; TISSUES; SYSTEM AB Cellular electrophoretic mobility values of 288 types of eucaryotic cells were collected from literature published worldwide by a series of authors during the past forty years and arranged in a list. This list contains well-known recent electrophoretic results and also data that cannot be found anymore with modern literature retrieval systems. It will be a valuable help for scientists trying to purify cell populations. In addition, it confirms the observation that most eucaryotic cells have very similar electrophoretic mobilities, ranging from 40% above to 50% below the electrophoretic mobility of human erythrocytes, and thus reinforces the suggestion that electrophoretic mobilities of eucaryotic cells are subjected to strong biological controls. C1 MAX PLANCK INST BIOCHEM,D-82152 MARTINSRIED,GERMANY. KAZAKH ACAD SCI,INST ZOOL,ALMA ATA 480021,KAZAKHSTAN. PENN STATE UNIV,CTR CELL RES,UNIVERSITY PK,PA 16802. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 127 TC 30 Z9 30 U1 1 U2 8 PU VCH PUBLISHERS INC PI DEERFIELD BEACH PA 303 NW 12TH AVE, DEERFIELD BEACH, FL 33442-1788 SN 0173-0835 J9 ELECTROPHORESIS JI Electrophoresis PD JUN PY 1997 VL 18 IS 7 BP 1109 EP 1119 DI 10.1002/elps.1150180715 PG 11 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA XK713 UT WOS:A1997XK71300014 PM 9237565 ER PT J AU Keller, LP McKay, DS AF Keller, LP McKay, DS TI The nature and origin of rims on lunar soil grains SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID INTERPLANETARY DUST PARTICLES; VAPOR DEPOSITS; REGOLITH; FRACTIONATION; SURFACE AB Space weathering processes that operate in the lunar regolith modify the surfaces of lunar soil gains. Transmission electron microscope analysis of the lunar soil grains from the fine size fraction of several lunar soils show that most grains are surrounded by thin (60-200 nm thick) rims. The microstructure and chemical compositions of the rims can be used to classify rims into four broad categories: amorphous, inclusion-rich, multiple, and vesicular. Amorphous rims are noncrystalline, generally lack crystalline inclusions, show evidence for preferential sputtering of cations, and are produced largely by solar-wind irradiation damage. Inclusion-rich rims contain abundant nanometer-sized grains of Fe metal as randomly dispersed inclusions or as distinct layers embedded in an amorphous silica-rich matrix. Inclusion-rich rims are compositionally distinct from their host grains and typically contain accumulations of elements that are not indigenous to the host. Inclusion-rich rims are formed largely by the deposition of impact-generated vapors with a contribution from the deposition of sputtered ions. A continuum in the chemical and microstructural properties exists between typical amorphous rims and typical inclusion-rich rims. Multiple-rims consist of a distinct radiation-damaged layer up to 50 nm thick, that is overlain by vapor-deposited material of comparable thickness. Vesicular rims are compositionally similar to their hosts and are characterized by an abundance of small (<50 nm in diameter) vesicles concentrated in the outer 100 nm of the rims. The formation of vesicular rims is apparently due to the evolution of solar-wind implanted gases in response to a pulse-heating event. The formation of rims on lunar soils is complex and involves several processes whose effects may be superimposed. From this study, it is shown that one process does not dominate and that the relative importance of vapor-deposition is comparable to radiation-damage in the formation of rims on lunar silicate grains. The presence of rims on lunar soil grains, particularly those with nanometer-sized Fe metal inclusions, may have a major influence on the optical and magnetic properties of lunar soils. Copyright (C) 1997 Elsevier Science Ltd C1 NASA,LYNDON B JOHNSON SPACE CTR,SOLAR SYST EXPLORAT DIV,HOUSTON,TX 77058. RP Keller, LP (reprint author), MVA INC,5500 OAKBROOK PKWY,SUITE 200,NORCROSS,GA 30093, USA. NR 49 TC 166 Z9 173 U1 3 U2 28 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD JUN PY 1997 VL 61 IS 11 BP 2331 EP 2341 DI 10.1016/S0016-7037(97)00085-9 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XE654 UT WOS:A1997XE65400016 ER PT J AU vanDam, TM Wahr, J Chao, Y Leuliette, E AF vanDam, TM Wahr, J Chao, Y Leuliette, E TI Predictions of crustal deformation and of geoid and sea-level variability caused by oceanic and atmospheric loading SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Article DE geoid; global positioning system; gravity; oceans ID SATELLITE ALTIMETRY; TEMPORAL VARIATIONS AB In this paper we consider several small effects related to oceanic loading of the Earth and atmospheric loading of the oceans. Non-tidal ocean loading induces changes in oceanic bottom pressure, which in turn deform the geoid and the nearby crust. Changes in bottom pressure are derived from estimates of sea-surface height variability and density changes output from an oceanic general circulation model. Sea-surface heights measured by the TOPEX/POSEIDON altimeter are also used to infer changes in bottom pressure. We estimate that non-tidal ocean loading can typically cause approximate to 5 mm of peak-to-peak (2 mm root-mean-square, rms) vertical motion at sites near the shore, with displacements of up to 10 mm possible. Amplitudes of horizontal displacements are about one-third those of vertical ones. Deformation-associated gravity changes are usually of the order of 2-3 mu Gal; however, peak-to-peak changes of 5 mu Gal are also predicted. Loading-induced geoid perturbations in mid-ocean regions are typically 5-10 mm peak-to-peak (3 mm rms) and can extend over a region of 20 degrees. In the case of atmospheric loading of the oceans, we estimate the difference between the inverted barometer correction, usually used to describe the ocean's response to atmospheric pressure, and the complete equilibrium response. There are two sources of this difference. One is that the inverted barometer correction does not conserve oceanic mass. We use National Meteorological Center (NMC) global pressure data to estimate the time-dependent, average change in pressure over the oceans. A time-series of the net pressure over the oceans contains an annual signal with a peak-to-peak amplitude of 1.2 mbar superimposed on a linear trend of 0.09 mbar yr(-1). The secular signal is caused by a redistribution of atmospheric mass from over continental land masses to the oceans. We conclude that this effect introduces additional variability into the ocean's response to pressure at annual, secular, and multi-year timescales, with a total peak-to-peak amplitude of a few tens of millimetres. The second difference between the inverted barometer response and the complete equilibrium response is due to gravitational forcing by the atmosphere and by the displaced mass in the solid Earth and oceans caused by the atmospheric loading. This effect is largest within about 1000 km of the coast and at high latitudes. We use NMC pressure data to estimate the effect, and rind that it causes differences from the inverted barometer solution in those regions of up to 10-30 mm peak-to-peak, with values as large as 50-60 mm possible at certain locations. The time dependence of this effect is negatively correlated with the inverted barometer response. The effect causes an apparent reduction of the inverted barometer response by a few per cent within a few hundred kilometres of the coast, with reductions of more than 6-7 per cent at a few places. C1 UNIV COLORADO,DEPT PHYS,BOULDER,CO 80309. CALTECH,JET PROP LAB,PASADENA,CA 91006. RP vanDam, TM (reprint author), UNIV COLORADO,NOAA,COOPERAT INST RES ENVIRONM SCI,CAMPUS BOX 216,BOULDER,CO 80309, USA. RI Leuliette, Eric/D-1527-2010 OI Leuliette, Eric/0000-0002-3425-4039 NR 24 TC 36 Z9 37 U1 3 U2 5 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 JUN PY 1997 VL 129 IS 3 BP 507 EP 517 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XC862 UT WOS:A1997XC86200004 ER PT J AU Nerem, RS Haines, BJ Hendricks, J Minster, JF Mitchum, GT White, WB AF Nerem, RS Haines, BJ Hendricks, J Minster, JF Mitchum, GT White, WB TI Improved determination of global mean sea level variations using TOPEX/POSEIDON altimeter data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CALIBRATION; HARVEST AB The TOPEX/POSEIDON satellite altimeter mission has measured sea level on a global basis over the last 4 years at 10 day intervals. After correcting for a recently discovered error in the measurements, the estimated rate of global mean sea level change over this time period is -0.2 mm/year. Comparisons to tide gauge sea levels measured in spatial and temporal proximity to the satellite measurements suggest there is a residual drift in the satellite measurement system of -2.3 +/- 1.2 mm/year, the origin of which is presently unknown. Application of this rate correction yields a ''calibrated'' estimate of +2.1 +/- 1.3 mm/year for the rate of sea level rise, which agrees statistically with tide gauge observations of sea level change over the last 50 years. Since the contribution of interannual and decadal mean sea level variations cannot presently be isolated, a longer time series is required before long-term climate change signals can be detected. in addition, an improved understanding of the T/P measurement system performance with time is needed. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV COLORADO, COLORADO CTR ASTRODYNAM RES, BOULDER, CO 80309 USA. UPS, CNES, LAB CNRS, UMR 5566, F-31055 TOULOUSE, FRANCE. UNIV S FLORIDA, DEPT MARINE SCI, ST PETERSBURG, FL 33701 USA. UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA. UNIV TEXAS, DEPT AEROSP ENGN & ENGN MECH, AUSTIN, TX 78712 USA. RP UNIV TEXAS, CTR SPACE RES, R1000, AUSTIN, TX 78712 USA. NR 22 TC 62 Z9 69 U1 1 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 EI 1944-8007 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUN 1 PY 1997 VL 24 IS 11 BP 1331 EP 1334 DI 10.1029/97GL01288 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XD217 UT WOS:A1997XD21700013 ER PT J AU Bale, SD Owen, CJ Bougeret, JL Goetz, K Kellogg, PJ Lepping, RP Manning, R Monson, SJ AF Bale, SD Owen, CJ Bougeret, JL Goetz, K Kellogg, PJ Lepping, RP Manning, R Monson, SJ TI Evidence of currents and unstable particle distributions in an extended region around the lunar plasma wake SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FREQUENCY AB We report observations of electrostatic ion acoustic waves and Langmuir waves during a recent lunar encounter by the Wind spacecraft. These waves are observed when Wind is magnetically connected to the nominal wake and at distances greater than 8 lunar radii from the wake. When interpreted in the context of a simple time-of-flight model, these observations imply the existence of a system of currents and disturbed particle distributions that extends far into solar wind. C1 OBSERV PARIS,DESPA,F-92125 MEUDON,FRANCE. UNIV MINNESOTA,SCH PHYS & ASTRON,MINNEAPOLIS,MN 55455. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RP Bale, SD (reprint author), UNIV LONDON QUEEN MARY & WESTFIELD COLL,ASTRON UNIT,MILE END RD,LONDON E1 4NS,ENGLAND. RI Owen, Christopher/C-2999-2008; Bale, Stuart/E-7533-2011 OI Owen, Christopher/0000-0002-5982-4667; Bale, Stuart/0000-0002-1989-3596 NR 14 TC 24 Z9 24 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 JUN 1 PY 1997 VL 24 IS 11 BP 1427 EP 1430 DI 10.1029/97GL01193 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XD217 UT WOS:A1997XD21700037 ER PT J AU Delvigs, P Klopotek, DL Cavano, PJ AF Delvigs, P Klopotek, DL Cavano, PJ TI Structure-property relationships in addition polyimides .2. Resins from three-ring aromatic diamines containing carbonyl and methylene groups SO HIGH PERFORMANCE POLYMERS LA English DT Article AB The use of flexibilized three-ring aromatic diamine moieties was investigated in an effort to improve the processing characteristics of addition-type polyimide resins. A series of 10 diamines containing carbonyl and methylene bridging groups was synthesized. The diamines were polymerized with the dimethylester of 3,3',4,4'-benzophenonetetracarboxylic acid (BTDE), using the monomethyl ester of nadic acid (NE) as an endcap. The effect of diamine structure on the solubility and rheological properties during cure was determined. The effect of diamine structure and formulated molecular weight on the thermo-oxidative stability and glass transition temperature of the polyimides was also investigated. Unidirectional laminates were fabricated from selected resins, using carbon fibre as the reinforcement. Interlaminar shear strength and flexural properties of the laminates were determined. The results indicate that polyimides from some of the diamines containing methylene bridging groups have potential as matrix resins for long-term applications at temperatures up to 300 degrees C. C1 ST NORBERT COLL,DE PERE,WI 54115. CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44106. RP Delvigs, P (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 14 TC 11 Z9 12 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD JUN PY 1997 VL 9 IS 2 BP 161 EP 176 DI 10.1088/0954-0083/9/2/008 PG 16 WC Polymer Science SC Polymer Science GA XL177 UT WOS:A1997XL17700008 ER PT J AU Reach, WT Franz, BA Weiland, JL AF Reach, WT Franz, BA Weiland, JL TI The three-dimensional structure of the zodiacal dust bands SO ICARUS LA English DT Article ID ASTEROID FAMILIES; SOLAR-SYSTEM; IRAS; EMISSION; SEARCH; RING; COMPLEX; ORIGIN; TRAILS; EARTH AB Using observations of the infrared sky brightness by the Cosmic Background Explorer (COBE)(1) Diffuse Infrared Background Experiment (DIRBE) and Infrared Astronomical Satellite (IRAS), we have created maps of the surface brightness Fourier-filtered to suppress the smallest (< 1 degrees) structures and the large-scale background (>15 degrees). Dust bands associated with the Themis, Koronis, and Eos families are readily evident. A dust band associated with the Maria family is also present, The parallactic distances to the emitting regions of the Koronis, Eos, and Maria dust bands were found to be 1.4 to 2.5 AU, A weak dust band associated with the Eunomia/Io family is evident, together with another weak and previously unattributed dust band, which may split further into two band pairs, potentially associated with the Hygiea or Vesta family, The brightnesses of the blended Themis/Koronis bands and the Eos dust band vary with ecliptic longitude, such that the northern or southern component of the band pair becomes brighter when its tilt brings it into the ecliptic plane. We attribute the brightness variations to the motion of the Earth within the emitting region, and conclude that at least some dust-band particles are on Earth-crossing orbits. For the Themis and Koronis families, the tilt is sufficient that the Earth may pass to the edges of the emitting region, where the density is highest, leading to ''glints'' two or four times a year, We compared the observed distributions to theoretically motivated, empirical models for the three-dimensional distribution of asteroid family dust. In the torus model, the dust is distributed among the asteroid family members with the same distributions of proper orbital inclination and semimajor axis but a random ascending node. In the migrating model, particles are presumed to be under the influence of Poynting-Robertson drag, so that they are distributed throughout the inner Solar System. The migrating model is better able to match the parallactic variation of dust-band latitude as well as the 12- to 60-mu m spectrum of the dust bands. The annual brightness variations can be explained only by the migrating model. Upper limits are placed on the dust density associated with the Nysa and Flora families-both of the large, inner-belt families with wide inclination dispersions, The association of five (and potentially seven) dust bands with the largest asteroid families suggests that dust bands are an integral part of asteroid families, If nonfamily asteroids produce dust at a rate similar to that of the families with the lowest dust density, then they can account for the brightness of the zodiacal light in the ecliptic. (C) 1997 Academic Press. C1 NASA, GODDARD SPACE FLIGHT CTR, GEN SCI CORP, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, HUGHES STX, GREENBELT, MD 20771 USA. RP Reach, WT (reprint author), UNIV SPACE RES ASSOC, CODE 685, GREENBELT, MD 20771 USA. RI Reach, William/C-4710-2008; Franz, Bryan/D-6284-2012; OI Franz, Bryan/0000-0003-0293-2082; Reach, William/0000-0001-8362-4094 NR 51 TC 45 Z9 45 U1 1 U2 1 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1997 VL 127 IS 2 BP 461 EP 484 DI 10.1006/icar.1997.5704 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XH365 UT WOS:A1997XH36500013 ER PT J AU Pryor, WR West, RA Simmons, KE AF Pryor, WR West, RA Simmons, KE TI High-phase-angle observations of Uranus at 2650 angstrom: Haze structure and particle properties SO ICARUS LA English DT Article ID STRATOSPHERIC HAZE; NEPTUNE; ATMOSPHERE; VOYAGER-2; JUPITER; SATURN; PHOTOCHEMISTRY; SCATTERING; PHOTOMETRY; METHANE AB Spatially resolved photometric observations of Uranus at 2650 Angstrom obtained with the Voyager 2 Photopolarimeter Subsystem (PPS) are presented and analyzed with model atmospheres, A vertically homogenous atmospheric model with Rayleigh scattering and absorption fits Uranus well at 2650 Angstrom at phase angles from 16 degrees to 157 degrees; no strong forward scattering typical of abundant large particles is observed, A microphysical model developed for Uranus to fit Voyager imaging system data CK, Rages, J, B, Pollack, M, G, Tomasko, and L, R, Doose, 1991, Icarus 89, 359-376) predicts the vertical distribution and properties of stratospheric haze aerosols at 22.5 degrees and 65 degrees S, This microphysical model also fits the 2650-Angstrom PPS data at low latitudes, Increasing the aerosol sizes in the Rages et al, size distribution by a factor of 1.2 creates an unobserved forward scattering peak and can be excluded. The low-latitude upper stratospheric aerosols on Uranus are smaller (<0,1 mu m radius) and/or much less abundant than the 0.2 to 0.25-mu m stratospheric aerosol population found by PPS on Neptune; however, to fit the Uranus 2650-Angstrom data at all latitudes requires darker and/or more abundant (1.5-3 times more) aerosols near the sunlit pole. (C) 1997 Academic Press. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Pryor, WR (reprint author), UNIV COLORADO, ATMOSPHER & SPACE PHYS LAB, 1234 INNOVAT DR, BOULDER, CO 80303 USA. NR 36 TC 6 Z9 6 U1 0 U2 2 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1997 VL 127 IS 2 BP 508 EP 522 DI 10.1006/icar.1997.5706 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XH365 UT WOS:A1997XH36500016 ER PT J AU Chetty, PRK Richardson, R Sherwood, R AF Chetty, PRK Richardson, R Sherwood, R TI TOPEX/Poseidon electrical power system - Lessons learned SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article AB The main objective of the TOPEX/Poseidon Spacecraft is to monitor the world's oceans for scientific study of weather and climate prediction, coastal storm warning and maritime safety. The operational conditions of this satellite imposed challenging requirements for the on-board Electrical Power System (EPS). Going through various phases of its development and on-orbit performance verifications, there were certain events and/or circumstances we would have liked to avoid. Some circumstances were avoided with preventative measures, other potentially detrimental events were not. Thus, a number of valuable lessons were learned which are presented in this paper. C1 ORBITAL SCI CORP,GERMANTOWN,MD 20874. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Chetty, PRK (reprint author), KRIS ENGN INC,14120 STONECUTTER DR,N POTOMAC,MD 20878, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD JUN PY 1997 VL 12 IS 6 BP 18 EP 24 DI 10.1109/62.587053 PG 7 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA XA689 UT WOS:A1997XA68900004 ER PT J AU Chiu, DK Lee, S AF Chiu, DK Lee, S TI Design and experimentation of a jump impact controller SO IEEE CONTROL SYSTEMS MAGAZINE LA English DT Article; Proceedings Paper CT IEEE International Conference on Robotics and Automation CY APR 22-28, 1996 CL MINNEAPOLIS, MN SP IEEE, Robot & Automat Soc ID ROBOTIC MANIPULATORS C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP UNIV SO CALIF, DEPT EE SYST & COMP SCI, LOS ANGELES, CA 90089 USA. NR 21 TC 1 Z9 1 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1066-033X EI 1941-000X J9 IEEE CONTR SYST MAG JI IEEE Control Syst. Mag. PD JUN PY 1997 VL 17 IS 3 BP 99 EP 106 DI 10.1109/37.588216 PG 8 WC Automation & Control Systems SC Automation & Control Systems GA XB621 UT WOS:A1997XB62100010 ER PT J AU Jackson, AW Pinsukanjana, PR Gossard, AC Coldren, LA AF Jackson, AW Pinsukanjana, PR Gossard, AC Coldren, LA TI In situ monitoring and control for MBE growth of optoelectronic devices SO IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS LA English DT Article DE diffuse reflectance spectroscopy; film thickness measurement; growth control; in situ monitoring; molecular beam epitaxy; optical flux monitoring; reflection spectrometry; substrate temperature measurement ID MOLECULAR-BEAM EPITAXY; SUBSTRATE-TEMPERATURE MEASUREMENT; ATOMIC-ABSORPTION SPECTROSCOPY; V LAYERED STRUCTURES; PYROMETRIC INTERFEROMETRY; ACCURATE MEASUREMENT; VAPOR-DEPOSITION; FLUX; REFLECTANCE; THICKNESS AB In situ monitoring and control techniques for MBE growth of optoelectronic devices am presented. Improved control over layer thickness has been realized using optical interference techniques such as reflectance spectroscopy. It is now common to observe spectra of distributed-Bragg-reflector (DBR) mirrors during growth to make corrections for growth rate drifts. Real-time optical faux monitoring (OFM) by atomic absorption allows precise layer control by measuring group III fluxes continuously during growth. The flux information can be used to operate growth shutters and to control effusion cell heaters in a feedback loop. Improved substrate temperature measurement by diffuse reflectance spectroscopy (DRS) allows precise measurement of substrate temperature. DRS is not subject to the same errors encountered in pyrometer or thermocouple measurements of substrate temperature. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV CALIF SANTA BARBARA,DEPT ELECT & COMP ENGN,SANTA BARBARA,CA 93106. RP Jackson, AW (reprint author), UNIV CALIF SANTA BARBARA,DEPT MAT,SANTA BARBARA,CA 93106, USA. NR 34 TC 13 Z9 13 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 1077-260X J9 IEEE J SEL TOP QUANT JI IEEE J. Sel. Top. Quantum Electron. PD JUN PY 1997 VL 3 IS 3 BP 836 EP 844 DI 10.1109/2944.640637 PG 9 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA YE078 UT WOS:A1997YE07800013 ER PT J AU Lubell, MS Lue, JW Palaszewski, B AF Lubell, MS Lue, JW Palaszewski, B TI Large-bore, superconducting magnets for high-energy density propellant storage SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA ID FIELD AB A study has been conducted on the design of large-bore, superconducting solenoid magnets in an effort to determine how weight and cost scales with field and size. The fields considered ranged from 0.5 to 20 T and bore sizes from 3 to 10 m, the designs are based on light-weight, high-performance superconducting magnet designs using cable-in-conduit niobium-titanium and niobium-tin conductors. All methods to reduce the weight of the magnets are used, and both aluminum and stainless steel are considered for the structure. With the length of the magnets fixed at 10 m, the amount and cost of the conductor is determined for each field and bore size, The largest magnets are determined for each field value that have weights under 10(4), 10(5), and 10(6) kg. The cost scales as the square root of stored energy and in millions of dollars is twice the product of field (T) and bore (m). C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Lubell, MS (reprint author), OAK RIDGE NATL LAB,POB 2009,OAK RIDGE,TN 37831, USA. NR 22 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 412 EP 418 DI 10.1109/77.614517 PN 1 PG 7 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH864 UT WOS:A1997XH86400073 ER PT J AU Barner, JB Kleinsasser, AW Hunt, BD AF Barner, JB Kleinsasser, AW Hunt, BD TI High-T-c superconductor-normal-superconductor junctions with polyimide-passivated ambient-temperature edge formation SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA ID WEAK LINKS AB Superconductor-Normal-Superconductor (SNS) edge Josephson Junctions (JJ's) continue to be a focus of frigh-T-c superconductor (HTS) electronics development, The ability to form clean edges in HTS materials is essential for successful SMS edge JJ's as well as crossovers and via contacts, We report a novel SNS JJ fabrication process in which a YBa2Cu3O7-delta/SrTiO3 base electrode/insulator bilayer coated with a polyimide passivation layer is rotated during Ar ion milling through a reflowed photoresist mask to form omnidirectional edges, No sample cooling is used during milling, YBa2Cu2.8Co0.2O7-delta normal layers and YLa0.95Ba2Cu3O7-delta counter-electrodes completed the SNS JJ's. Devices fabricated using this polyimide passivation layer have significantly smaller spreads in critical current and resistance than those processed without it. C1 NORTHROP GRUMMAN STC,PITTSBURGH,PA 15235. RP Barner, JB (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. NR 9 TC 0 Z9 0 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 2502 EP 2505 DI 10.1109/77.621747 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700057 ER PT J AU Kleinsasser, AW Delin, KA AF Kleinsasser, AW Delin, KA TI High-T-c SNS Josephson junctions: Moving beyond adolescence? SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA ID EDGE JUNCTIONS; BARRIER LAYERS; YBA2CU3O7-X AB Attempts to develop high temperature superconductor (HTS) microelectronics have been limited by the immature nature of HTS circuit technology. Much of the present effort worldwide is based on superconductor-normal-superconductor (SNS) Josephson junctions (JJ's). Only within the past three years have SNS junctions been fabricated which can be interpreted with conventional proximity effect theory. We discuss the history and present status of HTS SNS devices and the prospects for producing a mature technology for practical applications. RP CALTECH, JET PROP LAB, CTR SPACE MICROELECT TECHNOL, PASADENA, CA 91109 USA. NR 34 TC 5 Z9 5 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1051-8223 EI 1558-2515 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 2964 EP 2967 DI 10.1109/77.621937 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700168 ER PT J AU Friedrich, S Segall, K Gaidis, MC Wilson, CM Prober, DE Kindlmann, PJ Szymkowiak, AE Moseley, SH AF Friedrich, S Segall, K Gaidis, MC Wilson, CM Prober, DE Kindlmann, PJ Szymkowiak, AE Moseley, SH TI Single photon imaging x-ray spectrometers using low noise current preamplifiers with dc voltage bias SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA AB We have developed superconducting single-photon imaging x-ray detectors with an energy resolution of 54 eV at 6 keV and a spatial resolution of 1 mu m over an effective length of 40 mu m. They utilize a current-sensitive low-noise preamplifier with a de voltage bias. It has a signal bandwidth of 300 kHz, current noise of i(n) = 0.26 pA/root Hz and voltage noise of e(n) = 0.5 nV/root Hz with an input capacitance of 200 pF under operating conditions. Injected pulses with a charge Q = 3.7.10(6) electrons have been measured with a standard deviation sigma(Q) = 3400 electrons, corresponding to an electronic noise of 13 eV at 6 keV. C1 YALE UNIV,DEPT ELECT ENGN,NEW HAVEN,CT 06520. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Friedrich, S (reprint author), YALE UNIV,DEPT APPL PHYS,NEW HAVEN,CT 06520, USA. RI Wilson, Christopher/A-9676-2008; Gaidis, Michael/D-3327-2013 NR 7 TC 29 Z9 29 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3383 EP 3386 DI 10.1109/77.622100 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700270 ER PT J AU Mueller, CH Treece, RE Rivkin, TV Miranda, FA Moutinho, HR SwartzlanderFranz, A Dalberth, M Rogers, CT AF Mueller, CH Treece, RE Rivkin, TV Miranda, FA Moutinho, HR SwartzlanderFranz, A Dalberth, M Rogers, CT TI Tunable SrTiO3 varactors using parallel plate and interdigital structures SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA ID HETEROSTRUCTURES AB The dielectric properties of SrTiO3 (STO)/YBCO and STO films deposited on LaAlO3 substrates were evaluated, for potential varactor applications wherein the capacitance is altered via a de voltage applied across the STO film. The optimal growth temperature for the STO films in the STO/YBCO structures was 800 degrees C; higher temperatures resulted in interfacial degradation and poor film quality, and lower temperatures resulted in films with lower dielectric constants (epsilon(r)) and tunabilities. Interdigital varactors comprised of STO films deposited directly on LaAlO3 displayed higher tunabilities and significantly lower losses. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. NATL RENEWABLE ENERGY LAB,GOLDEN,CO 80401. UNIV COLORADO,BOULDER,CO 80309. RP Mueller, CH (reprint author), SCT,GOLDEN,CO 80401, USA. NR 14 TC 15 Z9 15 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3512 EP 3515 DI 10.1109/77.622151 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700303 ER PT J AU Bumble, B LeDuc, HG AF Bumble, B LeDuc, HG TI Fabrication of a diffusion cooled superconducting hot electron bolometer for THz mixing applications SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA AB Recent interest in bolometers for heterodyne mixing applications has prompted development of microbridges which are small enough to allow electron diffusion to dominate over electron-phonon interaction as a cooling mechanism. Prior results at 533 GHz have demonstrated several GHz intermediate frequency (IF) bandwidth. Here we describe our processing method in which the bolometer element is a 10 nm thin film of niobium defined by electron beam lithography down to dimensions of 80 nm. This microbridge is embedded in a normal metal (Au) antenna structure for 1.2 and 2.5 THz applications. RP Bumble, B (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. NR 5 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 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3560 EP 3563 DI 10.1109/77.622167 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700315 ER PT J AU Burns, MJ Kleinsasser, AW Delin, KA Vasquez, RP Karasik, BS McGrath, WR Gaidis, MC AF Burns, MJ Kleinsasser, AW Delin, KA Vasquez, RP Karasik, BS McGrath, WR Gaidis, MC TI Fabrication of high-T-c hot-electron bolometric mixers for terahertz applications SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA ID THIN-FILMS; NONEQUILIBRIUM; RADIATION AB Superconducting hot-electron bolometers (HEB) represent a promising candidate for heterodyne mixing at frequencies exceeding 1 THz. Nb HEB mixers offer performance competitive with tunnel junctions without the frequency limit imposed by the superconducting energy gap. Although the performance of YB2Cu3O7-delta HEB mixers is not projected to be superior to that of Nb devices, which operate at low temperatures, they introduce the possibility of sensitive, low power heterodyne detectors operating at temperatures approaching 90 K for applications requiring portability and closed-cycle refrigeration. We report on the fabrication and characterization, both DC and RF, of high-T-c mixers based on ultra-thin (less than or equal to 20 nm) YBa2Cu3O7-delta films patterned to micrometer dimensions and incorporated into 2.5 THz planar mixer circuits. RP Burns, MJ (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. RI Gaidis, Michael/D-3327-2013; Burns, Michael/D-2939-2011 OI Burns, Michael/0000-0001-9804-405X NR 12 TC 8 Z9 8 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3564 EP 3567 DI 10.1109/77.622168 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700316 ER PT J AU Skalare, A McGrath, WR Bumble, B LeDuc, HG AF Skalare, A McGrath, WR Bumble, B LeDuc, HG TI Receiver measurements at 1267 GHz using a diffusion-cooled superconducting transition-edge bolometer SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA AB We report receiver noise temperature measurements using a quasioptically coupled diffusion-cooled hot-electron bolometer mixer at a local oscillator frequency of 1267 GHz, and an intermediate frequency of 1.4 GHz. A best double-sideband (DSB) receiver noise temperature of 1880 K was measured, with an estimated mixer noise of 945 K (DSB), and a conversion efficiency including coupling losses of -19 dB (DSB). The coupled local oscillator power requirement for this device is estimated at roughly 6 nW. The mixer noise temperature is less than twice that measured earlier in a waveguide receiver at 530 GHz, which shows that the sensitivity of this type of mixer does not degrade sharply with increasing frequency in this regime. RP Skalare, A (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. NR 11 TC 15 Z9 15 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3568 EP 3571 DI 10.1109/77.622170 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700317 ER PT J AU Schoelkopf, RJ Burke, PJ Prober, DE Karasik, B Skalare, A McGrath, WR Gaidis, MC Bumble, B LeDuc, HG AF Schoelkopf, RJ Burke, PJ Prober, DE Karasik, B Skalare, A McGrath, WR Gaidis, MC Bumble, B LeDuc, HG TI Noise bandwidth of diffusion-cooled hot-electron bolometers SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA ID SUPERCONDUCTING MIXERS AB We present studies of the input and output noise of diffusion cooled hot-electron bolometer mixers. By simultaneously measuring the gain and noise (with a 14 GHz LO) as a function of intermediate frequency for a 0.16 mu m diffusion cooled Nb device, we shaw that the noise bandwidth (4 GHz) is larger than the gain bandwidth (2.4 GHz). The output noise is 55 K, and the mixer noise is very low, 340 It DSB. This shows that diffusion cooled devices have low noise over a broad enough intermediate frequency band for practical applications in THz receivers. C1 YALE UNIV,DEPT PHYS,NEW HAVEN,CT 06520. CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. RP Schoelkopf, RJ (reprint author), YALE UNIV,DEPT APPL PHYS,15 PROSPECT ST,NEW HAVEN,CT 06520, USA. RI Schoelkopf, Robert/J-8178-2012; Gaidis, Michael/D-3327-2013; Burke, Peter/F-3308-2010; Karasik, Boris/C-5918-2011 NR 13 TC 5 Z9 5 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 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3576 EP 3579 DI 10.1109/77.622173 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700319 ER PT J AU Karasik, BS Gaidis, MC McGrath, WR Bumble, B LeDuc, HG AF Karasik, BS Gaidis, MC McGrath, WR Bumble, B LeDuc, HG TI A low-noise 2.5 THz superconductive Nb hot-electron mixer SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA AB We report on the development of a quasioptical Nb hot-electron bolometer mixer for a 2.5 THz heterodyne receiver, The devices are fabricated from a 12 nm thick Nb film, and have a 0.3 mu mx0.15 mu m in-plane size, thus exploiting diffusion as the electron cooling mechanism, The rf coupling was provided by a twin-slot planar antenna on an elliptical Si lens. A specially designed 2.5 THz system, using a CO2-pumped FIR laser as local oscillator (LO), with rf hot/cold loads enclosed in vacuum to avoid atmospheric absorption, was used in the experiment The experimentally measured double sideband (DSE) noise temperature of the receiver was as low as less than or equal to 3000 K, with an estimated mixer noise temperature of approximate to 750 K. These results demonstrate the operation of the diffusion-cooled bolometer mixer above 2 THz. RP Karasik, BS (reprint author), CALTECH, JET PROP LAB, CTR SPACE MICROELECT TECHNOL, PASADENA, CA 91109 USA. RI Gaidis, Michael/D-3327-2013; Karasik, Boris/C-5918-2011 NR 9 TC 21 Z9 21 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3580 EP 3583 DI 10.1109/77.622174 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700320 ER PT J AU Bin, M Gaidis, MC Zmuidzinas, J Phillips, TG AF Bin, M Gaidis, MC Zmuidzinas, J Phillips, TG TI Quasi-optical SIS mixers with normal metal tuning structures SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA DE SIS mixers; submillimeter receivers ID NOISE; FREQUENCY AB We recently reported [8] a quasi-optical SIS mixer which used Nb/Al-oxide/Nb tunnel junctions nad a normal-metal (Al) tuning circuit to achieve and uncorrected receiver noise temperature of 840 K (DSB) at 1042 GHz. Here we present results on several different device designs, which together cover the 300 - 1200 GHz frequency range. The mixers utilize an antireflection-coated silicon hyper-hemispherical lens, a twin-slot antenna, and a two-junction tuning circuit. The broad-band frequency response was measured using Fourier transform spectrometry (FTS), and is in good agreement with model calculations. Heterodyne tests were carried out from 400 GHz up to 1040 GHz, and these measurements agree well with the FTS results and with calculations based on Tucker's theory. C1 JET PROP LAB 320 231,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. RP Bin, M (reprint author), CALTECH,DOWNS LAB PHYS 320 47,PASADENA,CA 91125, USA. RI Gaidis, Michael/D-3327-2013 NR 15 TC 22 Z9 22 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3584 EP 3588 DI 10.1109/77.622176 PN 3 PG 5 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700321 ER PT J AU Tong, CYE Blundell, R Bumble, B Stern, JA LeDuc, HG AF Tong, CYE Blundell, R Bumble, B Stern, JA LeDuc, HG TI Distributed quasiparticle mixing in a non-linear transmission line at sub-millimeter wavelengths SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA ID SIS; DESIGN; MIXER AB A new class of distributed mixer based on the non-linear quasiparticle tunnel current in a superconductor-insulator-superconductor transmission line has been proposed and tested. The Nb /Al/AlOx/Nb junctions used in our mixers are typically 200 nm wide and are between 1 and 2 guided wavelengths long. Compared with the traditional submillimeter lumped element quasiparticle mixer, the distributed mixer requires lower critical current densties, lower magnetic field as well as simpler tuning circuitry. Experiments have been performed in various sub-millimeter frequency bands. Receiver noise temperatures of 66 K at 460 GHz, 210 K at 630 GHz and 600 K at 780 GHz have been measured. These noise temperatures are comparable to or slightly better than the noise temperatures of the corresponding lumped element mixers. C1 CALTECH,JET PROP LAB,CTR SPACE MICROELECT,PASADENA,CA 91109. RP Tong, CYE (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. OI Tong, Edward/0000-0002-7736-4203 NR 13 TC 6 Z9 6 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3597 EP 3600 DI 10.1109/77.622181 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700324 ER PT J AU Kwok, RS Fiedziuszko, SJ Miranda, FA Leon, GV Demo, MS Bohman, HY AF Kwok, RS Fiedziuszko, SJ Miranda, FA Leon, GV Demo, MS Bohman, HY TI Miniaturized HTS/dielectric multilayer filters for satellite communications SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1996 Applied Superconductivity Conference CY AUG 25-30, 1996 CL PITTSBURGH, PA AB Presently, most communication satellites contain well over a hundred of filters in their payload, Typical satellite multiplexers use dual mode cavity or dielectric resonator filters which are large and heavy, As future advanced electronic systems for satellite communication become more complex, they will need even more filters requiring filter miniaturization without performance degradation, Therefore, any improvement in filter technology consistent with this requirement could enhance satellite's performance, To reduce the size, weight, and cost of the multiplexers without compromising performance, ne introduce a new class oh dual mode multilayer filters consisting of YBa2Cu3O7-delta and LaAlO3 thin films, The multilayer configuration in C-band, for example, occupies only 1% of the volume of its dielectric resonator counterpart, Details of the design, fabrication, and testing of these filters will be presented. C1 SPACE SYST LORAL,PALO ALTO,CA 94303. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RENSSELAER POLYTECH INST,DEPT ELECT ENGN,TROY,NY 12180. RICE UNIV,DEPT ELECT ENGN,HOUSTON,TX 77005. NR 7 TC 7 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1997 VL 7 IS 2 BP 3706 EP 3709 DI 10.1109/77.622223 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XH867 UT WOS:A1997XH86700351 ER PT J AU Greenhall, CA AF Greenhall, CA TI The third-difference approach to modified Allan variance SO IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT LA English DT Article DE Allan variance; clock noise; finite differences; frequency stability; power-law noise; time and frequency ID FREQUENCY STABILITY AB This study gives strategies for estimating the modified Allan variance (MVAR), and formulas for computing the equivalent degrees of freedom (edf) of the estimators, A third-difference formulation of MVAR leads to a tractable formula for edf in the presence of power-law phase noise. The effect of estimation stride on edf is shown, First-degree rational-function approximations for edf are derived, and their errors tabulated, A theorem allowing conservative estimates of edf in the presence of compound noise processes is given. RP Greenhall, CA (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 19 TC 10 Z9 10 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9456 J9 IEEE T INSTRUM MEAS JI IEEE Trans. Instrum. Meas. PD JUN PY 1997 VL 46 IS 3 BP 696 EP 703 DI 10.1109/19.585434 PG 8 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA WY935 UT WOS:A1997WY93500010 ER PT J AU Ponchak, GE Katehi, LPB AF Ponchak, GE Katehi, LPB TI Open- and short-circuit terminated series stubs in finite-width coplanar waveguide on silicon SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE bandpass filters; bandstop filters; coplanar transmission lines; coplanar waveguides ID WAVE-GUIDE AB Open- and short-circuit terminated series stubs in finite-width coplanar waveguide (FCPW) fabricated are high-resistivity Si are experimentally characterized over the frequency range of 2-40 GHz, In coplanar waveguide (CPW), these stubs ape typically placed in the center conductor, but in FCPW, the stubs may also be placed in the ground planes resulting in novel circuit elements with characteristics that make the stubs useful for matching circuits and filters, Equivalent circuit models for the stubs are presented, and it Is shown that when the stub is in the ground plane the resonant frequency is equal, the inductance and resistance is halved, and the capacitance is double the values of the same stub in the center conductor, Furthermore, it is shown that by varying the stub position in the ground plane, higher Q stubs can be obtained. C1 UNIV MICHIGAN,DEPT COMP SCI & ELECT ENGN,ANN ARBOR,MI 48109. RP Ponchak, GE (reprint author), NASA,LEWIS RES CTR,ELECTRON DEVICE TECHNOL BRANCH,CLEVELAND,OH 44135, USA. NR 14 TC 26 Z9 26 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD JUN PY 1997 VL 45 IS 6 BP 970 EP 976 DI 10.1109/22.588611 PG 7 WC Engineering, Electrical & Electronic SC Engineering GA XD039 UT WOS:A1997XD03900014 ER PT J AU Gunji, S Austin, RA Elsner, RF Ramsey, BD Weisskopf, MC AF Gunji, S Austin, RA Elsner, RF Ramsey, BD Weisskopf, MC TI Development of a high energy X-ray polarimeter for small satellites SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Nuclear Science Symposium and Medical Imaging Conference CY NOV 03-09, 1996 CL ANAHEIM, CA ID ABSORPTION FEATURE; CONTAMINATION; GINGA AB We are developing a Thomson-scattering-type polarimeter sensitive in the energy range from 10keV to 20keV for a small satellite. The polarimeter consists of three beryllium disks as scatterers and a cylindrical position-sensitive proportional counter as a detector of the scattered X rays. Its performance has been investigated through computer simulations. From these, it was concluded that the polarimeter can obtain a modulation factor of 34%, a detection efficiency of similar to 10%, and a minimum detectable polarization of about 3.0% for Her X-1 in 2keV bands and a 2x10(5)sec observation. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. RP Gunji, S (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,NATL RES COUNCIL,HUNTSVILLE,AL 35812, USA. NR 17 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 577 EP 580 DI 10.1109/23.603714 PN 1 PG 4 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF302 UT WOS:A1997XF30200059 ER PT J AU Ramsey, BD Peskov, V Kolodziejczak, JJ AF Ramsey, BD Peskov, V Kolodziejczak, JJ TI A study of factors limiting the maximum gain in microstrip gas counters SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Nuclear Science Symposium and Medical Imaging Conference CY NOV 03-09, 1996 CL ANAHEIM, CA AB It was shown in our previous paper [1] that the maximum achievable gain in microstrip Gas Counters (MSGC's) is limited by surface streamers, which are self-quenched over a very limited voltage region and quickly transit to breakdown sparks. In this work we have tried to identify the main factors governing the maximum gain at which the streamers appear, and towards this end have made simulations and tested MSGC's of different geometries and on different substrates in both Ar- and Xe-based gas mixtures at pressures from 0.1 to 3 atm. From these studies we conclude that in order to reduce surface breakdowns in MSGC's, the multiplication should be concentrated to the narrowest region around the anode strips and the gas gain elsewhere, especially near the cathodes, should be maximally suppressed. For this purpose, narrow anodes and gas mixtures with proper Townsend coefficients should be used. Control experiments we performed confirm these hypotheses. RP Ramsey, BD (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 15 TC 6 Z9 6 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 640 EP 645 DI 10.1109/23.603725 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF302 UT WOS:A1997XF30200070 ER PT J AU Yamashita, A Dotani, T Bautz, M Crew, G Ezuka, H Gendreau, K Kotani, T Mitsuda, K Otani, C Rasmussen, A Ricker, G Tsunemi, H AF Yamashita, A Dotani, T Bautz, M Crew, G Ezuka, H Gendreau, K Kotani, T Mitsuda, K Otani, C Rasmussen, A Ricker, G Tsunemi, H TI Radiation damage to charge coupled devices in the space environment SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Nuclear Science Symposium and Medical Imaging Conference CY NOV 03-09, 1996 CL ANAHEIM, CA ID ASCA; SATELLITE; CCDS AB We have investigated the characteristics of radiation damage to charge coupled devices (CCDs) in the space environment. The X-ray astronomy satellite ASCA launched on February 20, 1993 in low Earth orbit carries CCDs specially developed for soft X-ray detection. We have traced the performance of the CCDs for 3 years. We have observed both the gradual decrease of charge transfer efficiency (CTE) and the increase of dark current. These are phenomenologically explained by the increase of charge traps due to irradiation by high energy charged particles. However, some of the effects of the radiation damage in the CCD are quite non-uniform over the chip on various scales. We discuss characteristics of the charge traps and possible origins of the non-uniformity. C1 MIT,CAMBRIDGE,MA 02139. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. INST PHYS & CHEM RES,WAKO,SAITAMA 35101,JAPAN. COLUMBIA UNIV,NEW YORK,NY 10027. OSAKA UNIV,TOYONAKA,OSAKA 560,JAPAN. RP Yamashita, A (reprint author), INST SPACE & ASTRONAUT SCI,3-1-1 YOSHINODAI,SAGAMIHARA,KANAGAWA 229,JAPAN. RI Mitsuda, Kazuhisa/C-2649-2008; Otani, Chiko/A-6510-2016 NR 13 TC 91 Z9 93 U1 1 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 847 EP 853 DI 10.1109/23.603763 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF302 UT WOS:A1997XF30200108 ER PT J AU Hull, EL Pehl, RH Varnell, LS AF Hull, EL Pehl, RH Varnell, LS TI The effects of 199 MeV proton radiation damage on CdZnTe photon detectors SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Nuclear Science Symposium and Medical Imaging Conference CY NOV 03-09, 1996 CL ANAHEIM, CA ID GERMANIUM AB Four CdZnTe detectors were irradiated with 199 MeV protons to simulate the damaging radiation in space. The gamma-ray spectra of Am-241 and Co-57 as well as the detector leakage currents were monitored at room temperature to assess the effects of radiation damage. Surprisingly, after a fluence of a few x 10(8) p/cm(2) gamma-ray peak shifts and resolution degradation became visible. After a fluence of 5x10(9) p/cm(2) the degradation was quite dramatic. An analysis of these effects dearly demonstrates that radiation damage causes electron trapping in CdZnTe detectors. No increase in leakage current or electronic noise was observed. Radiation damage effects in CdZnTe and germanium detectors are compared. CdZnTe detectors are similar to 250 times more sensitive to radiation damage than germanium detectors per unit charge-drift distance. C1 UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,BERKELEY,CA 94720. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Hull, EL (reprint author), INDIANA UNIV,CYCLOTRON FACIL,BLOOMINGTON,IN 47408, USA. NR 11 TC 8 Z9 8 U1 0 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 870 EP 873 DI 10.1109/23.603768 PN 1 PG 4 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF302 UT WOS:A1997XF30200113 ER PT J AU Burger, A Chen, H Tong, J Shi, D George, MA Chen, KT Collins, WE James, RB Stahle, CM Bartlett, LM AF Burger, A Chen, H Tong, J Shi, D George, MA Chen, KT Collins, WE James, RB Stahle, CM Bartlett, LM TI Investigation of electrical contacts for Cd1-xZnxTe nuclear radiation detectors SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Nuclear Science Symposium and Medical Imaging Conference CY NOV 03-09, 1996 CL ANAHEIM, CA AB A comparative study of four different metal deposition methods on detector grade Cd1-xZnxTe crystal has been done using current-voltage (I-V) characterization and Ba-133 gamma spectroscopy. Electroless Au contact and thermal evaporated Au contact have been found to yield a smaller leakage current and a more linear/symmetric I-V curve than that of sputtered Pt and Au contact. An optimum detector performance can be achieved by combining the thermal evaporated Au deposition method with a chemical surface treatment consisting of 5%Br-MeOH followed by 2% Br-20% lactic acid in ethylene glycol. Low temperature photoluminescence spectra of Cd1-xZnxTe samples corresponding to these different metallization schemes are also presented and discussed. C1 SANDIA NATL LABS,ADV ELECT MFG TECHNOL DEPT,LIVERMORE,CA 94550. NASA,GODDARD SPACE FLIGHT CTR,OSC,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,NRC,GREENBELT,MD 20771. RP Burger, A (reprint author), FISK UNIV,DEPT PHYS,CTR PHOTON MAT & DEVICES,NASHVILLE,TN 37208, USA. NR 5 TC 40 Z9 43 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 934 EP 938 DI 10.1109/23.603780 PN 1 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF302 UT WOS:A1997XF30200125 ER PT J AU Bolotnikov, A Ramsey, B AF Bolotnikov, A Ramsey, B TI Improving the energy resolution of high-pressure Xe cylindrical ionization chambers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Nuclear Science Symposium and Medical Imaging Conference CY NOV 03-09, 1996 CL ANAHEIM, CA AB Results are presented on the development of high-pressure (>50 atm) Xe cylindrical ionization chambers for hard X-ray and low energy gamma-ray astronomy. Two methods to improve the energy resolution of these devices have been tested. One uses a shielding mesh and the other employs no mesh but substitutes a rise-time correction. Both techniques can give similar resolutions, with 2.2% FWHM being measured at 662 keV and 2.4% at 511 keV. RP Bolotnikov, A (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 10 TC 31 Z9 31 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 1006 EP 1010 DI 10.1109/23.603794 PN 1 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF302 UT WOS:A1997XF30200139 ER PT J AU Kurczynski, P Krizmanic, JF Stahle, CM Parsons, A Palmer, DM Barbier, LM Bartlett, LM Barthelmy, SD Birsa, F Gehrels, N Odom, J Hanchak, C Shu, P Teegarden, BJ Tueller, J AF Kurczynski, P Krizmanic, JF Stahle, CM Parsons, A Palmer, DM Barbier, LM Bartlett, LM Barthelmy, SD Birsa, F Gehrels, N Odom, J Hanchak, C Shu, P Teegarden, BJ Tueller, J TI CZT strip detectors for imaging and spectroscopy: Collimated beam and ASIC readout experiments SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Nuclear Science Symposium and Medical Imaging Conference CY NOV 03-09, 1996 CL ANAHEIM, CA AB We report the status of ongoing investigations into Cadmium Zinc Telluride (CZT) strip detectors for application in hard x-ray astronomy. We have instrumented a nine strip by nine strip region of a two sided strip detector made in our detector fabrication facility. In order to measure the position resolution of our detectors, we have implemented a collimated beam that concentrates radiation to a spot size less than 50 mu m We have placed a 30 mu m upper limit on the width of the point spread function for this system. We have also performed charge collection studies as a function of incident photon energy and bias voltage with a single sided, 100 mu m pitch CZT strip detector wire bonded to an SVX ASIC charge amplifier. The detectors exhibited excellent strip uniformity in terms of photon count rate and spectroscopic information. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Kurczynski, P (reprint author), UNIV MARYLAND,DEPT PHYS,BOX 100,COLLEGE PK,MD 20742, USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012; Barthelmy, Scott/D-2943-2012; Parsons, Ann/I-6604-2012 NR 9 TC 5 Z9 5 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 1011 EP 1016 DI 10.1109/23.603795 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF302 UT WOS:A1997XF30200140 ER PT J AU Edmonds, LD AF Edmonds, LD TI Charge collection from ion tracks in simple EPI diodes SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article DE charge collection; funneling; ion track; single event ID N-TYPE; DEVICES; SILICON AB Charge collection from ion tracks in epi diodes is investigated, As previously noted by others, the collected charge san exceed the charge liberated in the epi layer, Fundamental concepts are discussed rad illustrated bg computer simulation results, lit is found that the u(+)-p-p(+) diode displays a funneling regime and a diffusion regime (as previously noted by others), but the p(+)-n-n(+) diode does not display separate regimes, Simple quantitative models are provided which agree fairly well with computer simulation results. Experimental data were compared to one of the models, and good agreement was found. RP Edmonds, LD (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 16 TC 49 Z9 50 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1997 VL 44 IS 3 BP 1448 EP 1463 DI 10.1109/23.589631 PN 3 PG 16 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XF303 UT WOS:A1997XF30300004 ER PT J AU Tingate, TR Lugg, DJ Muller, HK Stowe, RP Pierson, DL AF Tingate, TR Lugg, DJ Muller, HK Stowe, RP Pierson, DL TI Antarctic isolation: Immune and viral studies SO IMMUNOLOGY AND CELL BIOLOGY LA English DT Article DE Antarctica; cell-mediated immunity; CMI Multitest; cytokines; herpesvirus; isolation; monocytes; phytohaemagglutinin; stress ID HUMAN MONONUCLEAR LEUKOCYTES; CELL-MEDIATED-IMMUNITY; DURATION MISSIONS; STRESS; CONFINEMENT; IMMUNOCOMPETENCE; LYMPHOCYTE; ENDOCRINE; RESPONSES AB Stressful environmental conditions ape a major determinant of immune reactivity. This effect is pronounced in Australian National Antarctic Research Expedition populations exposed to prolonged periods of isolation in the Antarctic. Alterations of T cell function, including depression of cutaneous delayed-type hypersensitivity responses and a peak 48.9% reduction of T cell proliferation to the mitogen phytohaemagglutinin, were documented during a 9-month period of isolation. T cell dysfunction was mediated by changes within the peripheral blood mononuclear cell compartment, including a paradoxical atypical monocytosis associated with altered production of inflammatory cytokines. There was a striking reduction in the production by peripheral blood mononuclear cells of the predominant pro-inflammatory monokine TNF-alpha and changes were also detected in the production of IL-1, IL-2, IL-6, IL-1ra and IL-10. Prolonged Antarctic isolation is also associated with altered latent herpesvirus homeostasis, including increased herpesvirus shedding and expansion of the polyclonal latent Epstein-Barr virus-infected B cell population. These findings have important long-term health implications. C1 POLAR MED,AUSTRALIAN ANTARCTIC DIV,KINGSTON,TAS,AUSTRALIA. KRUG LIFE SCI INC,HOUSTON,TX. NASA,LYNDON B JOHNSON SPACE CTR,LIFE SCI RES LABS,HOUSTON,TX 77058. RP Tingate, TR (reprint author), UNIV TASMANIA,DIV PATHOL,43 COLLINS ST,HOBART,TAS 7000,AUSTRALIA. NR 33 TC 43 Z9 45 U1 0 U2 6 PU BLACKWELL SCIENCE PI CARLTON PA 54 UNIVERSITY ST, P O BOX 378, CARLTON VICTORIA 3053, AUSTRALIA SN 0818-9641 J9 IMMUNOL CELL BIOL JI Immunol. Cell Biol. PD JUN PY 1997 VL 75 IS 3 BP 275 EP 283 DI 10.1038/icb.1997.42 PG 9 WC Cell Biology; Immunology SC Cell Biology; Immunology GA XK382 UT WOS:A1997XK38200008 PM 9243293 ER PT J AU Ingram, M Techy, GB Saroufeem, R Yazan, O Narayan, KS Goodwin, TJ Spaulding, GF AF Ingram, M Techy, GB Saroufeem, R Yazan, O Narayan, KS Goodwin, TJ Spaulding, GF TI Three-dimensional growth patterns of various human tumor cell lines in simulated microgravity of a NASA bioreactor SO IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL LA English DT Article DE spheroid architecture; suspension culture; low-shear culture ID ROTATING-WALL VESSEL; MULTICELLULAR SPHEROIDS; TISSUE-CULTURE; CANCER; CD44; DIFFERENTIATION; CARCINOMA; ADHESION; MODEL AB Growth patterns of a number of human tumor cell lines that form three-dimensional structures of various architectures when cultured without carrier beads in a NASA rotary cell culture system are described and illustrated. The culture system, which was designed to mimic microgravity, maintained cells in suspension under very low-shear stress throughout culture. Spheroid (particulate) production occurred within a few hours after culture was started, and spheroids increased in size by cell division and fusion of small spheroids, usually stabilizing at a spheroid diameter of about 0.5 mm. Architecture of spheroids varied with cell type. Cellular interactions that occurred in spheroids resulted in conformation and shape changes of cells, and some cell lines produced complex, epithelial-like architectures. Expression of the cell adhesion molecules, CD44 and E cadherin, was upregulated in the three-dimensional constructs. Coculture of fibroblast spheroids with PC3 prostate cancer cells induced tenascin expression by the fibroblasts underlying the adherent prostate epithelial cells. Invasion of the fibroblast spheroids by the malignant epithelium was also demonstrated. C1 CLEAR LAKE MED FDN,HOUSTON,TX. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Ingram, M (reprint author), HUNTINGTON MED RES INST,99 N EL MOLINO AVE,PASADENA,CA 91101, USA. RI Narayan, K/I-5490-2012 NR 25 TC 106 Z9 110 U1 1 U2 23 PU SOC IN VITRO BIOLOGY PI LARGO PA 9315 LARGO DR WEST, STE 25, LARGO, MD 20774 SN 1071-2690 J9 IN VITRO CELL DEV-AN JI In Vitro Cell. Dev. Biol.-Anim. PD JUN PY 1997 VL 33 IS 6 BP 459 EP 466 PG 8 WC Cell Biology; Developmental Biology SC Cell Biology; Developmental Biology GA XF925 UT WOS:A1997XF92500011 PM 9201514 ER PT J AU Anagnostou, EN Kummerow, C AF Anagnostou, EN Kummerow, C TI Stratiform and convective classification of rainfall using SSM/I 85-GHz brightness temperature observations SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article; Proceedings Paper CT 7th International Symposium on Acoustic Remote Sensing and Associated Techniques of the Atmosphere and Oceans CY OCT 03-07, 1994 CL NOAA ENVIRONM TECHNOL LAB, BOULDER, CO SP Int Soc Acoust Remote Sensing HO NOAA ENVIRONM TECHNOL LAB ID CLOUD LIQUID WATER; TROPICAL RAINFALL; STOCHASTIC-MODEL; SAMPLING ERRORS; SATELLITE; RETRIEVAL; TRMM AB A better understanding of global climate calls for more accurate estimates of liquid and ice water content profiles of precipitating clouds and their associated latent heating profiles. Convective and stratiform precipitation regimes have different latent heating and therefore impact the earth's climate differently. Classification of clouds over oceans has traditionally been part of more general rainfall retrieval schemes. These schemes are based on individual or combined visible and infrared, and microwave satellite observations. However, none of these schemes report validations of their cloud classification with independent ground observations. The objective of this study is to develop a scheme to classify convective and stratiform precipitating clouds using satellite brightness temperature observations. The proposed scheme probabilistically relates a quantity called variability index (VI) to the stratiform fractional precipitation coverage over the satellite field of view (FOV). The VI for a satellite pixel is the mean absolute 85-GHz brightness temperature difference between the pixel and the eight surrounding neighbor pixels. The classification scheme has been applied to four different rainfall regimes. All four regimes show that the frequency of stratiform rainfall in the satellite FOV increases as the satellite-based VI decreases. The results of this study demonstrate that the satellite-based VI is consistently related to the probability of occurrence of three classes (0%-40%, 40%-70%, and 70%-100%) of FOV stratiform coverage. C1 UNIV IOWA,DEPT CIVIL & ENVIRONM ENGN,IOWA CITY,IA 52242. NASA,GODDARD SPACE FLIGHT CTR,MESOSCALE ATMOSPHER PROC BRANCH,GREENBELT,MD 20771. RP Anagnostou, EN (reprint author), UNIV IOWA,INST HYDRAUL RES,HYDRAUL LAB 404,IOWA CITY,IA 52242, USA. NR 23 TC 39 Z9 40 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 JUN PY 1997 VL 14 IS 3 BP 570 EP 575 DI 10.1175/1520-0426(1997)014<0570:SACCOR>2.0.CO;2 PN 1 PG 6 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA XC594 UT WOS:A1997XC59400023 ER PT J AU Vandemark, D Edson, JB Chapron, B AF Vandemark, D Edson, JB Chapron, B TI Altimeter estimation of sea surface wind stress for light to moderate winds SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID TOWER-BASED MEASUREMENTS; RADAR CROSS-SECTION; ATMOSPHERIC STABILITY; SPEED; BACKSCATTERING; DEPENDENCE; MODEL; SLOPE AB Aircraft altimeter and in situ measurements are used to examine relationships between altimeter backscatter and the magnitude of near-surface wind and friction velocities. Comparison of altimeter radar cross section with wind speed is made through the modified Chelton-Wentz algorithm. Improved agreement is found after correcting 10-m winds for both surface current and atmospheric stability. An altimeter friction velocity algorithm is derived based on the wind speed model and an open-ocean drag coefficient. Close agreement between altimeter- and in situ-derived friction velocities is found. For this dataset, quality of the altimeter inversion to surface friction velocity is comparable to that for adjusted winds and clearly better than the inversion to true 10-m wind speed. C1 WOODS HOLE OCEANOG INST, WOODS HOLE, MA 02543 USA. IFREMER, PLOUZANE, FRANCE. RP NASA, GODDARD SPACE FLIGHT CTR, BLDG N-159, WALLOPS ISLAND, VA 23337 USA. RI Chapron, Bertrand/O-6527-2015 NR 26 TC 17 Z9 17 U1 0 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 EI 1520-0426 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD JUN PY 1997 VL 14 IS 3 BP 716 EP 722 DI 10.1175/1520-0426(1997)014<0716:AEOSSW>2.0.CO;2 PN 2 PG 7 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA XC595 UT WOS:A1997XC59500012 ER PT J AU Engel, A Schmidt, U Stachnik, RA AF Engel, A Schmidt, U Stachnik, RA TI Partitioning between chlorine reservoir species deduced from observations in the arctic winter stratosphere SO JOURNAL OF ATMOSPHERIC CHEMISTRY LA English DT Article DE stratosphere; polar processes; chlorine partitioning ID OZONE DEPLETION; PROFILE OBSERVATIONS; POLAR VORTEX; EASOE; HCL; SUBMILLIMETER; RADICALS; AIRCRAFT; CAMPAIGN; CLONO2 AB Simultaneous observations of several chlorine source gases, as well as HCl and ClO, have been performed in the Arctic stratosphere on 1 and 9 February 1994, using ballooon-borne instrumentation as a contribution to SESAME (Second European Stratospheric Arctic and Mid latitude Experiment). The observed mixing ratios of HCl and N2O show a clear anticorrelation. No severe loss of HCl was observed inside the vortex during our measurement. These measurements showed that during this period at 20 km and above, HCl was either in excess, or at least as abundant, as ClONO2 and comprised between 50 and 70% of the available chlorine, Cl-y. On I February, measurements were made inside the polar vortex, The air mass sampled on this day showed a clear signature of diabatic descent, and also enhanced levels of ClO with a maximum of 230 pptv at 22.5 km. A 10 day backward trajectory analysis showed that these air masses had passed a large region of low temperatures a few hours prior to the measurement. Temperatures along the back trajectory at the 475 K and 550 K levels (20.1 and 23.7 km respectively) were cold enough for heterogeneous chlorine activation to occur, in agreement with the observed elevated CIO mixing ratios. C1 FORSCHUNGSZENTRUM JULICH, FORSCHUNGSZENTRUM, INST STRATOSPHAR CHEM, JULICH, GERMANY. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RI Engel, Andreas/E-3100-2014 OI Engel, Andreas/0000-0003-0557-3935 NR 41 TC 29 Z9 29 U1 0 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0167-7764 J9 J ATMOS CHEM JI J. Atmos. Chem. PD JUN PY 1997 VL 27 IS 2 BP 107 EP 126 DI 10.1023/A:1005781919448 PG 20 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA YD259 UT WOS:A1997YD25900001 ER PT J AU Breit, GA Gross, JH Watenpaugh, DE Chance, B Hargens, AR AF Breit, GA Gross, JH Watenpaugh, DE Chance, B Hargens, AR TI Near-infrared spectroscopy for monitoring of tissue oxygenation of exercising skeletal muscle in a chronic compartment syndrome model SO JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME LA English DT Article ID LOCAL COMPRESSION; LOWER LEG; DIAGNOSIS; HUMANS; PRESSURE AB Variations in the levels of muscle hemoglobin and of myoglobin oxygen saturation can be detected non-invasively with near-infrared spectroscopy, This technique could be applied to the diagnosis of chronic compartment syndrome, in which invasive testing has shown increased intramuscular pressure associated with ischemia and pain during exercise, We simulated chronic compartment syndrome in ten healthy subjects (seven men and three women) by applying external compression, through a wide inflatable cuff, to increase the intramuscular pressure in the anterior compartment of the leg, The tissue oxygenation of the tibialis anterior muscle was measured with near-infrared spectroscopy during gradual inflation of the cuff to a pressure of forty millimeters of mercury (5.33 kilopascals) during fourteen minutes of cyclic isokinetic dorsiflexion and plantar flexion of the ankle, The subjects exercised with and without external compression, The data on tissue oxygenation for each subject then were normalized to a scale of 100 per cent (the baseline value, or the value at rest) to 0 per cent (the physiological minimum, or the level of oxygenation achieved by exercise to exhaustion during arterial occlusion of the lower extremity), With external compression, tissue oxygenation declined at a rate of 1.4 +/- 0.3 per cent per minute (mean and standard error) during exercise, After an initial decrease at the onset, tissue oxygenation did not decline during exercise without compression, The recovery of tissue oxygenation after exercise was twice as slow with compression (2.5 +/- 0.6 minutes) than it was without the use of compression (1.3 +/- 0.2 minutes), CLINICAL RELEVANCE: The results of this study demonstrate that near-infrared spectroscopy ran detect deoxygenation of skeletal muscle caused by elevated intramuscular pressure during exercise. Thus, this technique may prove to be a useful diagnostic tool for the non-invasive detection of chronic compartment syndrome. RP Breit, GA (reprint author), NASA,AMES RES CTR,LIFE SCI DIV 23911,MOFFETT FIELD,CA 94035, USA. FU NHLBI NIH HHS [HL44125-05] NR 20 TC 50 Z9 50 U1 0 U2 2 PU JOURNAL BONE JOINT SURGERY INC PI NEEDHAM PA 20 PICKERING ST, NEEDHAM, MA 02192 SN 0021-9355 J9 J BONE JOINT SURG AM JI J. Bone Joint Surg.-Am. Vol. PD JUN PY 1997 VL 79A IS 6 BP 838 EP 843 PG 6 WC Orthopedics; Surgery SC Orthopedics; Surgery GA XF138 UT WOS:A1997XF13800006 PM 9199380 ER PT J AU Topaler, MS Hack, MD Allison, TC Liu, YP Mielke, SL Schwenke, DW Truhlar, DG AF Topaler, MS Hack, MD Allison, TC Liu, YP Mielke, SL Schwenke, DW Truhlar, DG TI Validation of trajectory surface hopping methods against accurate quantum mechanical dynamics and semiclassical analysis of electronic-to-vibrational energy transfer SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID NONADIABATIC MOLECULAR COLLISIONS; PREDISSOCIATION RATE CONSTANTS; CONICAL INTERSECTION; EXTRAPOLATION METHODS; INELASTIC-COLLISIONS; CHEMICAL-REACTION; CHARGE-EXCHANGE; SYSTEM; TRANSITIONS; STATES AB The validity of the quasiclassical trajectory surface hopping method is tested by comparison against accurate quantum dynamics calculations. Two versions of the method, one including electronic coherence between hops and one neglecting this effect, are applied to the electronically nonadiabatic quenching processes Na(3p) + H-2(nu = 0, j= 0 or 2) --> Na(3s) + H-2(nu',j'). They are found to agree well, not only for quenching probabilities and final-state distributions, but also for collision lifetimes and hopping statistics, demonstrating that electronic coherence is not important for this system. In general the accurate quantum dynamical calculations and both semiclassical surface hopping models agree well on the average, which lends credence to applications of semiclassical methods to provide insight into the mechanistic details of photochemical processes proceeding on coupled potential surfaces. In the second part of the paper the intimate details of the trajectories are analyzed to provide such insight for the present electronic-to-vibrational energy transfer process. (C) 1997 American Institute of Physics. C1 UNIV MINNESOTA,INST SUPERCOMP,MINNEAPOLIS,MN 55455. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Topaler, MS (reprint author), UNIV MINNESOTA,DEPT CHEM,207 PLEASANT ST SE,MINNEAPOLIS,MN 55455, USA. RI Mielke, Steven/B-7533-2008; schwenke, david/I-3564-2013; Truhlar, Donald/G-7076-2015 OI Mielke, Steven/0000-0002-1938-7503; Truhlar, Donald/0000-0002-7742-7294 NR 78 TC 65 Z9 65 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 JUN 1 PY 1997 VL 106 IS 21 BP 8699 EP 8709 DI 10.1063/1.473931 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XA478 UT WOS:A1997XA47800008 ER PT J AU Chen, TH Henderson-Sellers, A Milly, PCD Pitman, AJ Beljaars, ACM Polcher, J Abramopoulos, F Boone, A Chang, S Chen, F Dai, Y Desborough, CE Dickinson, RE Dumenil, L Ek, M Garratt, JR Gedney, N Gusev, YM Kim, J Koster, R Kowalczyk, EA Laval, K Lean, J Lettenmaier, D Liang, X Mahfouf, JF Mengelkamp, HT Mitchell, K Nasonova, ON Noilhan, J Robock, A Rosenzweig, C Schaake, J Schlosser, CA Schulz, JP Shao, Y Shmakin, AB Verseghy, DL Wetzel, P Wood, EF Xue, Y Yang, ZL Zeng, Q AF Chen, TH Henderson-Sellers, A Milly, PCD Pitman, AJ Beljaars, ACM Polcher, J Abramopoulos, F Boone, A Chang, S Chen, F Dai, Y Desborough, CE Dickinson, RE Dumenil, L Ek, M Garratt, JR Gedney, N Gusev, YM Kim, J Koster, R Kowalczyk, EA Laval, K Lean, J Lettenmaier, D Liang, X Mahfouf, JF Mengelkamp, HT Mitchell, K Nasonova, ON Noilhan, J Robock, A Rosenzweig, C Schaake, J Schlosser, CA Schulz, JP Shao, Y Shmakin, AB Verseghy, DL Wetzel, P Wood, EF Xue, Y Yang, ZL Zeng, Q TI Cabauw experimental results from the project for intercomparison of land-surface parameterization schemes SO JOURNAL OF CLIMATE LA English DT Article ID ANNUAL WATER-BALANCE; SOIL-MOISTURE; BIOSPHERE MODEL; BOUNDARY-LAYER; ECMWF MODEL; CLIMATE; HYDROLOGY; STORAGE; FLUXES; GCMS AB In the Project for Intercomparison of Land-Surface Parameterization Schemes phase 2a experiment, meteorological data for the year 1987 from Cabauw, the Netherlands, were used as inputs to 23 land-surface flux schemes designed for use in climate and weather models. Schemes were evaluated by comparing their outputs with long-term measurements of surface sensible heat fluxes into the atmosphere and the ground, and of upward longwave radiation and total net radiative fluxes, and also comparing them with latent heat fluxes derived from a surface energy balance. Tuning of schemes by use of the observed flux data was not permitted. On an annual basis, the predicted surface radiative temperature exhibits a range of 2 K across schemes, consistent with the range of about 10 W m(-2) in predicted surface net radiation. Most modeled values of monthly net radiation differ from the observations by less than the estimated maximum monthly observational error (+/-10 W m(-2)). However, modeled radiative surface temperature appears to have a systematic positive bias in most schemes; this might be explained by an error in assumed emissivity and by models' neglect of canopy thermal heterogeneity. Annual means of sensible and latent heat fluxes, into which net radiation is partitioned, have ranges across schemes of 30 W m(-2) and 25 W m(-2), respectively. Annual totals of evapotranspiration and runoff, into which the precipitation is partitioned, both have ranges of 315 mm. These ranges in annual heat and water fluxes were approximately halved upon exclusion of the three schemes that have no stomatal resistance under non-water-stressed conditions. Many schemes tend to underestimate latent heat flux and overestimate sensible heat flux in summer, with a reverse tendency in winter. For six schemes, root-mean-square deviations of predictions from monthly observations are less than the estimated upper bounds on observation errors (5 W m(-2) for sensible heat flux and 10 W m(-2) for latent heat flux). Actual runoff at the site is believed to be dominated by vertical drainage to groundwater, but several schemes produced significant amounts of runoff as overland flow or interflow. There is a range across schemes of 184 mm (40% of total pore volume) in the simulated annual mean root-zone soil moisture. Unfortunately, no measurements of soil moisture were available for model evaluation. A theoretical analysis suggested that differences in boundary conditions used in various schemes are not sufficient to explain the large variance in soil moisture. However, many of the extreme values of soil moisture could be explained in terms of the particulars of experimental setup or excessive evapotranspiration. C1 MACQUARIE UNIV, CLIMAT IMPACTS CTR, SYDNEY, NSW 2109, AUSTRALIA. US GEOL SURVEY, PRINCETON, NJ USA. NOAA, GEOPHYS FLUID DYNAM LAB, PRINCETON, NJ USA. ROYAL NETHERLANDS METEOROL INST, NL-3730 AE DE BILT, NETHERLANDS. CNRS, METEOROL DYNAM LAB, PARIS, FRANCE. SCI SYST & APPLICAT INC, NEW YORK, NY USA. NASA, GODDARD SPACE FLIGHT CTR, MESOSCALE DYNAM & PRECIPITAT BRANCH, GREENBELT, MD 20771 USA. PHILLIPS LAB, GPAB, HANSCOM AFB, MA USA. NOAA, DEV DIV, NATL CTR ENVIRONM PREDICT, CAMP SPRINGS, MD USA. CHINESE ACAD SCI, INST ATMOSPHER PHYS, BEIJING, PEOPLES R CHINA. UNIV ARIZONA, INST ATMOSPHER PHYS, TUCSON, AZ 85721 USA. MAX PLANCK INST METEOROL, HAMBURG, GERMANY. CSIRO, DIV ATMOSPHER RES, ASPENDALE, VIC 3195, AUSTRALIA. UNIV READING, DEPT METEOROL, READING, BERKS, ENGLAND. RUSSIAN ACAD SCI, INST WATER PROBLEMS, MOSCOW 103064, RUSSIA. LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA USA. NASA, GODDARD SPACE FLIGHT CTR, HYDROL SCI BRANCH, GREENBELT, MD 20771 USA. METEOROL OFF, HADLEY CTR CLIMATE PREDICT & RES, BRACKNELL, BERKS, ENGLAND. UNIV WASHINGTON, DEPT CIVIL ENGN, SEATTLE, WA 98195 USA. PRINCETON UNIV, DEPT CIVIL ENGN & OPERAT RES, PRINCETON, NJ 08544 USA. ECMWF, READING, BERKS, ENGLAND. GKSS FORSCHUNGSZENTRUM GEESTHACHT GMBH, INST ATMOSPHER PHYS, GEESTHACHT, GERMANY. METEO FRANCE, CNRM, TOULOUSE, FRANCE. UNIV MARYLAND, DEPT METEOROL, COLLEGE PK, MD 20742 USA. NATL WEATHER SERV, NOAA, OFF HYDROL, SILVER SPRING, MD USA. UNIV NEW S WALES, CTR ADV NUMER COMPUTAT ENGN & SCI, SYDNEY, NSW, AUSTRALIA. INST GEOG, MOSCOW, RUSSIA. ATMOSPHER ENVIRONM SERV, CLIMATE RES BRANCH, DOWNSVIEW, ON, CANADA. CTR OCEAN LAND ATMOSPHERE STUDIES, CALVERTON, MD USA. RI Shao, Yaping/G-3606-2013; Dai, Yongjiu/D-6261-2014; Yang, Zong-Liang/B-4916-2011; Pitman, Andrew/A-7353-2011; Henderson-Sellers, Ann/H-5323-2011; Koster, Randal/F-5881-2012; Chen, Fei/B-1747-2009; lettenmaier, dennis/F-8780-2011; Nasonova, Olga/B-6093-2014; gusev, yugeniy/G-4711-2014; Robock, Alan/B-6385-2016; OI Shao, Yaping/0000-0002-2041-5479; Dai, Yongjiu/0000-0002-3588-6644; Pitman, Andrew/0000-0003-0604-3274; Koster, Randal/0000-0001-6418-6383; lettenmaier, dennis/0000-0003-3317-1327; gusev, yugeniy/0000-0003-3886-2143; Wood, Eric/0000-0001-7037-9675 NR 49 TC 229 Z9 245 U1 3 U2 28 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 EI 1520-0442 J9 J CLIMATE JI J. Clim. PD JUN PY 1997 VL 10 IS 6 BP 1194 EP 1215 DI 10.1175/1520-0442(1997)010<1194:CERFTP>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XJ208 UT WOS:A1997XJ20800004 ER PT J AU Bony, S Sud, Y Lau, KM Susskind, J Saha, S AF Bony, S Sud, Y Lau, KM Susskind, J Saha, S TI Comparison and satellite assessment of NASA/DAO and NCEP-NCAR reanalyses over tropical ocean: Atmospheric hydrology and radiation SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; SEASONAL-VARIATION; BUDGET EXPERIMENT; WATER-VAPOR; PARAMETERIZATION; CLOUDS; MODEL; ERBE; FLUX; INTERPOLATION AB This study compares the atmospheric reanalyses that have been produced independently at the Data Assimilation Office (DAO) of Goddard Laboratory for Atmospheres and at the National Centers for Environmental Prediction (NCEP). These reanalyses were produced by using a frozen state-of-the-art version of the global data assimilation system developed at these two centers. For the period 1987-88 and for the tropical oceanic regions of 30 degrees S-30 degrees N, surface and atmospheric fields related to atmospheric hydrology and radiation are compared and assessed, wherever possible, with satellite data. Some common biases as well as discrepancies between the two independent reassimilation products are highlighted. Considering both annual averages and interannual variability (1987-88), discrepancies between DAO and NCEP reanalysis in water vapor, precipitation, and clear-sky longwave radiation at the top of the atmosphere are generally smaller than discrepancies that exist between corresponding satellite estimates. Among common biases identified in the reanalyses, the authors note an underestimation of the total precipitable water and an overestimation of the shortwave cloud radiative forcing in warm convective regions. Both lead to an underestimation of the surface radiation budget. The authors also note an overestimaton of the clear-sky outgoing longwave radiation in most tropical ocean regions, as well as an overestimation of the longwave radiative cooling at the ocean surface. Surface latent and sensible heat fluxes differ by about 20 and 3 W m(-2), respectively, in the two reanalyses, Differences in the surface radiation budget are larger than the uncertainties of satellite-based estimates. Biases in the surface radiation fluxes derived from the reanalyses are primarily due to incorrect shortwave cloud radiative forcing and, to a lesser degree, due to a deficit in the total precipitable water and a cold bias at lower-tropospheric. temperatures. This study suggests that individual features and biases of each set of reanalyses should be carefully studied, especially when using analyzed surface fluxes to force other physical or geophysical models such as ocean circulation models. Over large regions of the tropical oceans, DAO and NCEP reanalyses produce surface net heat fluxes that can differ by up to 50 W m(-2) in the average and by a factor of 2 when considering interannual anomalies. This may lead to vastly different thermal forcings for driving ocean circulations. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NATL CTR ENVIRONM PREDICT, WASHINGTON, DC USA. RP Bony, S (reprint author), ECOLE NORMALE SUPER, CNRS, METEOROL DYNAM LAB, 24 RUE LHOMOND, F-75231 PARIS 05, FRANCE. RI Lau, William /E-1510-2012; OI Lau, William /0000-0002-3587-3691; Bony, Sandrine/0000-0002-4791-4438 NR 65 TC 48 Z9 49 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD JUN PY 1997 VL 10 IS 6 BP 1441 EP 1462 DI 10.1175/1520-0442(1997)010<1441:CASAON>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XJ208 UT WOS:A1997XJ20800018 ER PT J AU Chuang, CH Courouge, O Juang, JN AF Chuang, CH Courouge, O Juang, JN TI A robust controller for second-order systems using acceleration measurements SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME LA English DT Article AB This paper presents a robust control design using strictly positive realness for second-order dynamic systems. A robust strictly positive real controller stabilizes second-order systems with only acceleration measurements. An important property of this design is that the stabilization is independent of the system plant parameters. The control design connects a virtual system to a given plant such that any strictly positive real controller can be used to achieve robust stability. A spring-mass system is used as an example to demonstrate the robust stability and robust performance of this design. C1 NASA,LANGLEY RES CTR,SPACECRAFT DYNAM BRANCH,HAMPTON,VA 23665. RP Chuang, CH (reprint author), GEORGIA INST TECHNOL,ATLANTA,GA 30332, USA. NR 12 TC 1 Z9 1 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0022-0434 J9 J DYN SYST-T ASME JI J. Dyn. Syst. Meas. Control-Trans. ASME PD JUN PY 1997 VL 119 IS 2 BP 350 EP 355 DI 10.1115/1.2801264 PG 6 WC Automation & Control Systems; Instruments & Instrumentation SC Automation & Control Systems; Instruments & Instrumentation GA XE290 UT WOS:A1997XE29000040 ER PT J AU Olla, BL Davis, MW Schreck, CB AF Olla, BL Davis, MW Schreck, CB TI Effects of simulated trawling on sablefish and walleye pollock: The role of light intensity, net velocity and towing duration SO JOURNAL OF FISH BIOLOGY LA English DT Article DE behaviour; bycatch; cortisol; mortality; stress; towing speed ID PLASMA-CORTISOL CONCENTRATIONS; SCOMBER-SCOMBRUS L; STRESS RESPONSES; CHINOOK SALMON; ONCORHYNCHUS-TSHAWYTSCHA; HANDLING STRESS; COHO SALMON; NORTH-SEA; SURVIVAL; FISH AB Laboratory apparatus which simulated capture of fish in the cod-end of a towed trawl was used to induce post-capture stress as measured by alterations in behavioural, physiological and mortality indices in juvenile walleye pollock Theragra chalcogramma and juvenile and adult sablefish Anoplopoma fimbria. Differences in resistance to net entrainment varied between species with the severity of stress and the potential for recovery depending on light intensity, net velocity and towing duration. At a light intensity which simulated daylight at depth in clear ocean water (0.5 mu mol photons m(-2) s(-1)), walleye pollock juveniles were able to maintain swimming in nets towed at 0.65 m s(-1) for 3 h with no discernible effects on behaviour or mortality. However, when net velocity was increased to >0.75 m s(-1) or light intensity was decreased to <0.002 mu mol photons m(-2) s(-1), fish became entrained in the meshes of the net and exhibited significant alterations in feeding behaviour, predator evasion and increases in plasma cortisol concentrations. Marked increases in stress-induced mortality also occurred, in some cases after a delay of 6 days and eventually reaching 100%. In comparison with walleye pollock, sablefish juveniles became entrained in the meshes of the net at higher velocities (>0.92 m s(-1)) or lower light intensities (<0.0004 mu mol photons m(-2) s(-1)) and were much more resistant to post-capture stress. Towing of net-entrained fish for 15 min caused no detectable changes in feeding and cortisol and for 2 h, no changes in feeding although mortality increased from 0% for 15-min tows to 19% for 2-h tows. Towing for 4 h caused significant alterations in feeding and cortisol with feeding recovering to control levels by 6 days and cortisol by 3 days; mortality was 25%. When adult sablefish were towed for 4 h followed by 15-min exposure to air, feeding was inhibited 6 days after towing, but recovered within 30 days with no mortality observed after 30 days. The results demonstrate the value of using laboratory-based behavioural and biochemical indices to identify factors that may potentially affect post-capture survival among different species of fish. (C) 1997 The Fisheries Society of the British Isles. C1 OREGON STATE UNIV,DEPT FISHERIES & WILDLIFE,OREGON COOPERAT FISHERY RES UNIT,US NATL BIOL SERV,CORVALLIS,OR 97331. RP Olla, BL (reprint author), OREGON STATE UNIV,HATFIELD MARINE SCI CTR,NATL MARINE FISHERIES SERV,ALASKA FISHERIES SCI CTR,NEWPORT,OR 97365, USA. NR 35 TC 58 Z9 60 U1 4 U2 14 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0022-1112 J9 J FISH BIOL JI J. Fish Biol. PD JUN PY 1997 VL 50 IS 6 BP 1181 EP 1194 DI 10.1111/j.1095-8649.1997.tb01646.x PG 14 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA XF362 UT WOS:A1997XF36200004 ER PT J AU Chen, SH Boardsen, SA Fung, SF Green, JL Kessel, RL Tan, LC Eastman, TE Craven, JD AF Chen, SH Boardsen, SA Fung, SF Green, JL Kessel, RL Tan, LC Eastman, TE Craven, JD TI Exterior and interior polar cusps: Observations from Hawkeye SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLANETARY MAGNETIC-FIELD; MAGNETOSPHERIC CUSP; PLASMA INJECTION; MAGNETOPAUSE; MAGNETOSHEATH; PENETRATION; CONVECTION; CURRENTS; DYNAMICS; MOTION AB Hawkeye plasma, magnetic field, and plasma wave instruments directly sampled the throat of the northern polar cusp as the orientation of the interplanetary magnetic field (IMF) changed from southward to northward on July 3, 1974. Two distinct regions in the polar cusp were identified based on magnetic field, plasma flow and magnetic and electric noise: the interior and exterior cusps. The observations show highly variable flows in the exterior portion of the cusp and constantly strong dawn-dusk flows in the interior portion during periods of strong IMF By component. Results of a minimum variance analysis of the magnetic field at each cusp interface crossing provides evidence that the magnetopause surface normal deviated highly from empirical models. During intervals of relatively steady solar wind dynamic pressure, the motion of the cusp relative to the slow moving spacecraft was modulated by the varying IMF clock angle as observed by IMP 8 in the upstream solar wind. The motion did not show a correlation with internal processes monitored by the AE index. We propose that observed plasma flow patterns and cusp motion are results of reconnection between the IMF and the magnetospheric magnetic field. Flow velocity observed in the interior cusp is consistent with stress balance for a reconnection process. This unique interval provides an opportunity for detailed studies of the plasma, magnetic field, and plasma wave properties in both the exterior and interior cusp. C1 UNIV ALASKA,INST GEOPHYS,FAIRBANKS,AK 99775. UNIV ALASKA,DEPT PHYS,FAIRBANKS,AK 99775. UNIV MARYLAND,INST PHYS SCI & TECHNOL,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,SPACE SCI DATA OPERAT OFF,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,SPACE PHYS DATA FACIL,GREENBELT,MD 20771. NATL ACAD SCI,NATL RES COUNCIL,WASHINGTON,DC 20418. RI Fung, Shing/F-5647-2012 NR 48 TC 29 Z9 29 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 JUN 1 PY 1997 VL 102 IS A6 BP 11335 EP 11347 DI 10.1029/97JA00743 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD974 UT WOS:A1997XD97400010 ER PT J AU Zong, QG Wilken, B Reeves, GD Daglis, IA Doke, T Iyemori, T Livi, S Maezawa, K Mukai, T Kokubun, S Pu, ZY Ullaland, S Woch, J Lepping, R Yamamoto, T AF Zong, QG Wilken, B Reeves, GD Daglis, IA Doke, T Iyemori, T Livi, S Maezawa, K Mukai, T Kokubun, S Pu, ZY Ullaland, S Woch, J Lepping, R Yamamoto, T TI Geotail observations of energetic ion species and magnetic field in plasmoid-like structures in the course of an isolated substorm event SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TRAVELING COMPRESSION REGIONS; NEAR-EARTH MAGNETOTAIL; DEEP GEOMAGNETIC TAIL; FLUX ROPES; DISTANT MAGNETOTAIL; RECONNECTION PROCESSES; ISEE-3 OBSERVATIONS; BOUNDARY-LAYER; MAGNETOSPHERE; CDAW-8 AB On January 15, 1994, the ion spectrometer high energy particle - low energy particle detector (HEP-LD) on the Japanese spacecraft Geotail observed five quasi-periodic energetic ion bursts in the deep tail (X=-96 RE) These bursts were associated with plasmoid-like structures in the magnetic field components. In addition, three multiple TCR groups were identified in the interval. The observations in the distant tail occurred during a time interval of substorm activity which also produced multiple injections in the geosynchronous orbit region. The HEP-LD observations show that B-z bipolar plasmoid-like structures are associated with tailward flowing particle bursts. However, earthward flowing particle bursts are predominantly associated with bipolar signatures in B-y. In addition, an oxygen burst was seen in the back of a plasmoid (postplasmoid) which showed both B-y and B-z bipolar magnetic field signatures. The oxygen burst lasted for 23 min, and the density ratio (O/H) reached 15% for the HEP-LD energy range (in the same plasmoid, this ratio was approximately 1% before the oxygen burst). The oxygen burst exhibited a strong beam-like structure which occupied only 6 similar to 7% of the full solid angle (4 pi). We suggest that energized oxygen ions of ionospheric origin travel downtail in the narrow postplasmoid-plasma sheet which trails the plasmoid. Furthermore, we suggest that the magnetosphere dissipated larger quantities of energy during this very intense substorm event by ejecting multiple relatively small plasmoids rather than through the formation and ejection of a single large plasmoid. C1 WASEDA UNIV,ADV RES CTR SCI & ENGN,TOKYO,JAPAN. KYOTO UNIV,FAC SCI,KYOTO 60601,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NAGOYA UNIV,DEPT PHYS,NAGOYA,AICHI 46401,JAPAN. INST SPACE & ASTRONAUT SCI,KANAGAWA 229,JAPAN. NAGOYA UNIV,SOLAR TERR ENVIRONM LAB,TOYOKAWA,AICHI 442,JAPAN. BEIJING UNIV,DEPT GEOPHYS,BEIJING 100871,PEOPLES R CHINA. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. UNIV BERGEN,BERGEN,NORWAY. RP Zong, QG (reprint author), MAX PLANCK INST AERON,D-37191 KATLENBURG DUHM,GERMANY. RI Daglis, Ioannis/L-6100-2013; Reeves, Geoffrey/E-8101-2011 OI Daglis, Ioannis/0000-0002-0764-3442; Reeves, Geoffrey/0000-0002-7985-8098 NR 77 TC 50 Z9 55 U1 1 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 JUN 1 PY 1997 VL 102 IS A6 BP 11409 EP 11428 DI 10.1029/97JA00076 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD974 UT WOS:A1997XD97400016 ER PT J AU Liemohn, MW Khazanov, GV Kozyra, JU AF Liemohn, MW Khazanov, GV Kozyra, JU TI Guided plasmaspheric hiss interactions with superthermal electrons .1. Resonance curves and timescales SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PITCH-ANGLE DIFFUSION; RADIATION BELT PROTONS; RING CURRENT; DIRECTION; EMISSIONS; ENERGY; WAVES AB Under the proper conditions, guided plasmaspheric hiss is shown to be more efficient than Coulomb collisions at scattering electrons in the superthermal energy range of 50 to 500 eV. Broadband, whistler mode hiss becomes guided by plasma density gradients, intensifying the wave energy densities and focusing the wave normal angles. These waves are shown to interact through Cherenkov (Landau) resonance with electrons below 500 eV, and the presented equatorial plane timescales for pitch angle, energy, acid mixed diffusion are shown to be faster than Coulomb collision timescales for typical values at the inner edge of the plasmapause and in detached plasma regions. In the latter case, energy diffusion timescales of less than 100 s for small pitch angle electrons between 250 and 500 eV indicate that these waves have the potential to dramatically change the distribution function. C1 UNIV MICHIGAN,SPACE PHYS RES LAB,ANN ARBOR,MI 48109. RP Liemohn, MW (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES-83,HUNTSVILLE,AL 35812, USA. RI Liemohn, Michael/H-8703-2012 OI Liemohn, Michael/0000-0002-7039-2631 NR 29 TC 14 Z9 14 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 JUN 1 PY 1997 VL 102 IS A6 BP 11619 EP 11623 DI 10.1029/97JA00825 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD974 UT WOS:A1997XD97400033 ER PT J AU Cole, KD Hoegy, WR AF Cole, KD Hoegy, WR TI Joule heating by ac electric fields in the ionosphere of Venus - Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Editorial Material RP Cole, KD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. NR 5 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 JUN 1 PY 1997 VL 102 IS A6 BP 11669 EP 11671 DI 10.1029/97JA00745 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD974 UT WOS:A1997XD97400037 ER PT J AU Singh, M Farmer, SC AF Singh, M Farmer, SC TI Morphological characterization of microporous carbon materials SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article ID REACTIVE MELT INFILTRATION; FORMED SILICON-CARBIDE; ALLOYS C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Singh, M (reprint author), NYMA INC,LEWIS RES CTR GRP,CLEVELAND,OH 44135, USA. NR 13 TC 8 Z9 8 U1 0 U2 1 PU CHAPMAN HALL LTD PI LONDON PA 2-6 BOUNDARY ROW, LONDON, ENGLAND SE1 8HN SN 0261-8028 J9 J MATER SCI LETT JI J. Mater. Sci. Lett. PD JUN 1 PY 1997 VL 16 IS 11 BP 946 EP 949 DI 10.1023/A:1018512910724 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA XD824 UT WOS:A1997XD82400024 ER PT J AU Roth, DJ AF Roth, DJ TI Using a single transducer ultrasonic imaging method to eliminate the effect of thickness variation in the images of ceramic and composite plates SO JOURNAL OF NONDESTRUCTIVE EVALUATION LA English DT Article DE ultrasonic imaging; thickness independent; velocity images; microstructural characterization ID VELOCITY AB This article describes a single transducer ultrasonic imaging method based on ultrasonic velocity measurement that eliminates the effect of thickness variation in the images of ceramic and composite plate samples. The method is based on using a reflector located behind the sample and acquiring echoes off the sample and reflector surfaces in two scans. As a result of being thickness-independent, the method isolates ultrasonic variations due to material microstructure. Its use can result in significant cost savings because the ultrasonic image can be interpreted correctly without the need for precision thickness machining during nondestructive evaluation stages of material development. Velocity images obtained using the thickness-independent methodology are compared with apparent velocity maps and c-scan echo peak amplitude images for monolithic ceramic (silicon nitride), metal matrix composite and polymer matrix composite materials having thickness and microstructural variations. It was found that the thickness-independent ultrasonic images reveal and quantify correctly areas of global microstructural (pore and fiber volume fraction) variation due to the elimination of thickness effects. A major goal achieved in this study was to move the thickness-independent imaging technology out of the lab prototype environment and into the commercial arena so that it would be available to users worldwide. RP Roth, DJ (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 14 TC 8 Z9 8 U1 0 U2 2 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 SN 0195-9298 J9 J NONDESTRUCT EVAL JI J. Nondestruct. Eval. PD JUN PY 1997 VL 16 IS 2 BP 101 EP 120 PG 20 WC Materials Science, Characterization & Testing SC Materials Science GA XP554 UT WOS:A1997XP55400005 ER PT J AU Herring, GC Hillard, ME AF Herring, GC Hillard, ME TI Stark broadening using crossed Gaussian beams in stimulated Raman spectroscopy of N-2 SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID TRANSITIONS AB We have studied the effect of crossing two Gaussian laser beams on Stark-broadened line shapes in stimulated Raman gain spectroscopy of N-2 Q-branch transitions. At about 350 GW/cm(2) of pump laser peak intensity in a 0.11 atm, 298 K gas sample, the Stark-broadened crossed-beam linewidth is about twice the linewidth of collinear beams. For the crossed condition, the two focussed (f/93) beams are crossed at 0.9 deg. The line shape measurements are in qualitative agreement with a numerical model for Stark-broadened line shapes that spatially resolves the laser intensity variations over the sample volume. Published by Elsevier Science Ltd. RP Herring, GC (reprint author), NASA,LANGLEY RES CTR,FLUID MECH & ACOUST DIV,HAMPTON,VA 23681, USA. NR 13 TC 3 Z9 3 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUN PY 1997 VL 57 IS 6 BP 739 EP 744 DI 10.1016/S0022-4073(97)00030-7 PG 6 WC Optics; Spectroscopy SC Optics; Spectroscopy GA XH975 UT WOS:A1997XH97500002 ER PT J AU Mishchenko, MI Macke, A AF Mishchenko, MI Macke, A TI Asymmetry parameters of the phase function for isolated and densely packed spherical particles with multiple internal inclusions in the geometric optics limit SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; RADIATIVE HEAT-TRANSFER; LIGHT-SCATTERING; NONSPHERICAL PARTICLES; INTERPLANETARY DUST; POLARIZED-LIGHT; RANDOM-MEDIA; SPHERES; TRANSPORT; CLOUDS AB Since large, homogeneous dielectric particles have positive asymmetry parameters even when they are densely packed, it has been hypothesized that negative asymmetry parameters retrieved with Hapke's phenomenological model of bidirectional reflectance result from a complicated internal structure of planetary regolith particles. This paper tests that hypothesis by theoretically computing asymmetry parameters for isolated and densely packed composite spherical particles with size typical of regolith grains. It is assumed that the wavelength of the scattered light is much smaller than the particle size, and that particles are filled with large numbers of small inclusions. The computations show that it is essentially impossible to make asymmetry parameters of planetary regolith particles even slightly negative by filling the particles with large numbers of internal inclusions in the form of voids and/or grains with a refractive index substantially different from that of the host medium. Asymmetry parameters are positive even for densely packed composite particles with no internal absorption and extreme values of the internal scattering coefficient. Furthermore, they are sharply increased by even modest absorption inside composite particles, by reducing the refractive index contrast between the inclusions and the host particles, and/or by decreasing the packing density. Thus, the negative asymmetry parameters retrieved with Hapke's model need another explanation rather than assuming that they are real and are the result of a complicated internal structure of regolith particles. Besides the opposition-effect term, Hapke's model is nothing more than an approximate solution of the radiative transfer equation which inherently violates the energy conservation law. Therefore, the negative asymmetry parameters are likely to be numerical artefacts resulting from the approximations made in the model. (C) 1997 Elsevier Science Ltd. RP Mishchenko, MI (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012 NR 87 TC 65 Z9 65 U1 2 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 EI 1879-1352 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUN PY 1997 VL 57 IS 6 BP 767 EP 794 DI 10.1016/S0022-4073(97)00012-5 PG 28 WC Optics; Spectroscopy SC Optics; Spectroscopy GA XH975 UT WOS:A1997XH97500005 ER PT J AU Jiang, YB Yung, YL Sander, SP AF Jiang, YB Yung, YL Sander, SP TI Detection of tropospheric ozone by remote sensing from the ground SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID RADIATION; ULTRAVIOLET AB Due to larger multiple scattering effects in the troposphere compared to that in the stratosphere, the optical path of tropospheric ozone is markedly enhanced (as compared with that of stratospheric ozone) in the Huggins bands from 310 to 345 nm. Model study of the direct and diffuse solar fluxes on the ground shows differences between tropospheric and stratospheric ozone. The characteristic signature of tropospheric ozone enables us to distinguish a change in troposheric ozone from that of stratospheric ozone. A simple retrieval algorithm is used to recover the tropospheric column ozone from simulated data. (C) 1997 Elsevier Science Ltd. C1 CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109. NR 13 TC 8 Z9 8 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUN PY 1997 VL 57 IS 6 BP 811 EP 818 DI 10.1016/S0022-4073(96)00145-8 PG 8 WC Optics; Spectroscopy SC Optics; Spectroscopy GA XH975 UT WOS:A1997XH97500007 ER PT J AU Ogbuji, LUJT AF Ogbuji, LUJT TI Effect of oxide devitrification on oxidation kinetics of SiC SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID DEPOSITED SILICON-CARBIDE; HIGH-TEMPERATURE OXIDATION; OXYGEN; DIFFUSION; BEHAVIOR; CRYSTALS; SI3N4 AB The effect of oxide crystallinity on the oxidation rate of silicon carbide was investigated, CVD SiC coupons were oxidized in a clean TGA reactor system at 1300 degrees C initially in flowing oxygen, immediately annealed in argon, and then reoxidized, all in situ and without cooling iso as to preserve oxide integrity), The parabolic rate constants determined for the preoxidation regime (of mainly amorphous oxide film) and reoxidation regime (of devitrified oxide) were compared, The oxidation rate decreased by a factor of similar to 30 following full oxide crystallization induced by the anneal. RP Ogbuji, LUJT (reprint author), NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NR 24 TC 36 Z9 38 U1 1 U2 7 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD JUN PY 1997 VL 80 IS 6 BP 1544 EP 1550 PG 7 WC Materials Science, Ceramics SC Materials Science GA XF130 UT WOS:A1997XF13000027 ER PT J AU Marshak, A Davis, A Wiscombe, W Cahalan, R AF Marshak, A Davis, A Wiscombe, W Cahalan, R TI Scale invariance in liquid water distributions in marine stratocumulus .2. Multifractal properties and intermittency issues SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID FULLY-DEVELOPED TURBULENCE; ANGLE RADIATIVE-TRANSFER; GENERALIZED DIMENSIONS; STRANGE ATTRACTORS; FLUID TURBULENCE; CLOUDS; EXPONENTS; FRACTALS; CASCADE; NUMBER AB This is the second of two papers analyzing the internal liquid water content (LWC) structure of marine stratocumulus (Sc) based on observations taken during the First ICCP (International Commission on Cloud Physics) Regional Experiment (FIRE) 1987 and Atlantic Stratocumulus Transition Experiment (ASTEX) 1992 held programs. Part I examined wavenumber spectra and the three-decade scale range (tens of meters to tens of kilometers) over which scale invariance holds; the inability of spectral analysis to distinguish between different random processes was also underscored. This indetermination is removed in this part by applying multifractal analysis techniques to the LWC fields, leading to a characterization of the role of intermittency in marine Sc. Two multiscaling statistics are computed and associated nonincreasing hierarchies of exponents are obtained: structure functions and H(q), singular measures and D(q). The real variable q is the order of a statistical moment (e.g., q = 1.0 yields a mean); D(q) quantifies intermittency, H(q) nonstationarity. Being derived from the slopes of lines on log(statistic) versus log(scale) plots, these exponents are only defined when those lines are reasonably straight and where this happens defines the scare-invariant range. Being nonconstant, the derived H(q) and D(q) indicate multifractality rather than monofractality of LWC fields. Two exponents can serve as first-order measures of nonstationarity and intermittency: H-1 = H(1) and C-1 = 1 - D(1). For the ensemble average of all FIRE and all ASTEX data, the authors find the two corresponding points fn the (H-1, C-1) plane to be close: (0.28, 0.10) for FIRE and (0.29, 0.08) for ASTEX. This indicates that the dynamics determining the internal structure of marine Sc depend little on the local climatology. In contrast, the scatter of spatial averages for the individual flight around the ensemble average illustrates ergodicity violation. Finally, neither multiplicative cascades (with H-1 = 0) nor additive Gaussian models such as fractional Brownian motions (with C-1 = 0) adequately reproduce the LWC fluctuations in marine Sc. RP Marshak, A (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CLIMATE & RADIAT BRANCH,CODE 913,GREENBELT,MD 20771, USA. RI Cahalan, Robert/E-3462-2012; Wiscombe, Warren/D-4665-2012; Marshak, Alexander/D-5671-2012 OI Cahalan, Robert/0000-0001-9724-1270; Wiscombe, Warren/0000-0001-6844-9849; NR 66 TC 70 Z9 78 U1 0 U2 3 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 JUN 1 PY 1997 VL 54 IS 11 BP 1423 EP 1444 DI 10.1175/1520-0469(1997)054<1423:SIILWD>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XC335 UT WOS:A1997XC33500003 ER PT J AU Chambers, LH Wielicki, BA Evans, KF AF Chambers, LH Wielicki, BA Evans, KF TI Independent pixel and two-dimensional estimates of Landsat-derived cloud field albedo SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID STRATOCUMULUS AB A theoretical study has been conducted on the effects of cloud horizontal inhomogeneity on cloud albedo bias. A two-dimensional (2D) version of the Spherical Harmonic Discrete Ordinate Method (SHDOM) is used to estimate the albedo bias of the plane-parallel (PP-IPA) and independent pixel (IPA-2D) approximations for a wide range of 2D cloud fields obtained from Landsat. They include single-layer trade cumulus, open and closed cell broken stratocumulus, and solid stratocumulus boundary layer cloud fields over ocean. Findings are presented on a variety of averaging scales and are summarized as a function of cloud fraction, mean cloud optical depth, cloud aspect ratio, standard deviation of optical depth, and the gamma function parameter v (a measure of the width of the optical depth distribution). Biases are found to be small for small cloud fraction or mean optical depth, where the cloud fields under study behave linearly. They are large (up to 0.20 for PP-IPA bias, -0.12 for IPA-2D bias) for large v. On a scene-average basis, PP-IPA bias can reach 0.30, while IPA-2D bias reaches its largest magnitude at -0.07. Biases due to horizontal transport (IPA-2D) are much smaller than PP-IPA biases but account for 20% rms of the bias overall. Limitations of this work include the particular cloud field set used, assumptions of conservative scattering, constant cloud droplet size, no gas absorption or surface reflectance, and restriction to 2D radiative transport. The Landsat data used may also be affected by radiative smoothing. C1 UNIV COLORADO,BOULDER,CO 80309. RP Chambers, LH (reprint author), NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681, USA. NR 11 TC 24 Z9 25 U1 0 U2 6 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 JUN 1 PY 1997 VL 54 IS 11 BP 1525 EP 1532 DI 10.1175/1520-0469(1997)054<1525:IPATDE>2.0.CO;2 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XC335 UT WOS:A1997XC33500009 ER PT J AU Eckert, J Varma, R Diebolt, L Reid, M AF Eckert, J Varma, R Diebolt, L Reid, M TI Effects of cycling conditions of active material from discharged Ni positive plates studied by inelastic neutron scattering spectroscopy SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID PROTON DYNAMICS; NICKEL ELECTRODES; MANGANESE OXIDES; DIFFRACTION; INSERTION; WATER; SPECTROMETER; HYDROXIDES; GAMMA-MNO2; BRUCITE AB A series of cycled Ni battery plate materials has been examined by means of inelastic neutron scattering spectroscopy in order to determine the nature of the protons in the discharged and cycled material. Our results clearly demonstrate that some amount of the NiOOH phases which form on oxidation does not convert back to p-Ni(OH), upon discharging the battery and that this amount increases with the number of cycles the battery undergoes. Moreover, we have identified vibrational signatures of lattice water and found that its amount increases with KOH concentration used in the cell. Since cells operated at higher KOH concentrations are known to fail after fewer cycles, our inelastic neutron scattering studies clearly implicate the irreversible formation of lattice water as one of the main reasons for this failure. C1 ARIZONA STATE UNIV,DEPT CHEM & BIOCHEM,TEMPE,AZ 85281. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Eckert, J (reprint author), LOS ALAMOS NATL LAB,POB 1663,LOS ALAMOS,NM 87545, USA. NR 37 TC 0 Z9 0 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 JUN PY 1997 VL 144 IS 6 BP 1895 EP 1899 DI 10.1149/1.1837717 PG 5 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA XH828 UT WOS:A1997XH82800019 ER PT J AU Zhou, L Audurier, V Pirouz, P Powell, JA AF Zhou, L Audurier, V Pirouz, P Powell, JA TI Chemomechanical polishing of silicon carbide SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Letter ID SURFACE AB In an effort to improve silicon carbide (SIG) substrates surfaces prior to epitaxial growth, two chemomechanical polishing (CMP) techniques were investigated and the results were compared with a mechanical polishing procedure involving various grades of diamond paste. This work focused on silicon-terminated (0001) SiC surfaces. The two CMP techniques utilized (i) chromium oxide(lll) abrasives and (ii) colloidal silica polishing slurry. The best surfaces were obtained after colloidal silica polishing under conditions that combined elevated temperatures (similar to 55 degrees C) with a high slurry alkalinity (pH > 10) and a high solute content. Cross-sectional transmission electron microscopy showed no observable subsurface damage, and atomic force microscopy showed a significant reduction in roughness compared to commercial diamond-polished wafers. Growth experiments following colloidal silica polishing yielded a much improved film surface morphology. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Zhou, L (reprint author), CASE WESTERN RESERVE UNIV,DEPT MAT SCI & ENGN,CLEVELAND,OH 44106, USA. NR 12 TC 95 Z9 96 U1 3 U2 19 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 JUN PY 1997 VL 144 IS 6 BP L161 EP L163 DI 10.1149/1.1837711 PG 3 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA XH828 UT WOS:A1997XH82800013 ER PT J AU Baer, LA Corbin, BJ Vasques, MF Grindeland, RE AF Baer, LA Corbin, BJ Vasques, MF Grindeland, RE TI Effects of the use of filtered microisolator tops on cage microenvironment and growth rate of mice SO LABORATORY ANIMAL SCIENCE LA English DT Article RP Baer, LA (reprint author), NASA,AMES RES CTR,DIV LIFE SCI,MS 239-11,MOFFETT FIELD,CA 94035, USA. NR 6 TC 4 Z9 4 U1 0 U2 0 PU AMER ASSOC LABORATORY ANIMAL SCIENCE PI CORDOVA PA 70 TIMBERCREEK DR, SUITE 5, CORDOVA, TN 38018 SN 0023-6764 J9 LAB ANIM SCI JI Lab. Anim. Sci. PD JUN PY 1997 VL 47 IS 3 BP 327 EP 329 PG 3 WC Veterinary Sciences; Zoology SC Veterinary Sciences; Zoology GA XH887 UT WOS:A1997XH88700017 PM 9241640 ER PT J AU Coughlan, JC Running, SW AF Coughlan, JC Running, SW TI Regional ecosystem simulation: A general model for simulating snow accumulation and melt in mountainous terrain SO LANDSCAPE ECOLOGY LA English DT Article DE snow; model; regional simulation; forest; remote sensing ID ENERGY EXCHANGE; WATERSHED SCALE; ALPINE REGION; SIERRA-NEVADA; FOREST; BALANCE; SURFACE; CLIMATE; TEMPERATURE AB A general snow accumulation and melt model was developed to (1) determine how accurately snow accumulation and ablation can be modeled over heterogeneous landscapes with routinely available climatologic, topographic. and vegetation data, and (2) improve estimates of annual forest snow hydrology for point and regional calculations of annual forest productivity. The snow model was designed to operate within the Regional Hydroecological Simulation System (RHESSys), a GIS based modeling system to manage spatial data for distributed computer simulations on watershed scales. One feature of the RHESSys Snow Model (RSM) is it can use satellite derived forest leaf area index (LAI) to represent catchment forest cover; difficult to obtain in adequate cover and resolution by any other means. The model was tested over 3 water years (October to September) with data recorded by 10 snow telemetry stations (SNOTEL) in 5 slates ranging in meso-climate and elevations from a coastal Oregon site (1067 m) to a continental Colorado site (3261 m). Predictions for the 10 sites were made with identical parameter values and only site climate varied for all sites, The average difference between observed and predicted snow depletion dates for all sites and water years was 6.2 days and 8 of the 30 simulations were within +/-2 days (R-2 = 0.91). Radiation melt was the dominate snow ablation component at the Colorado site where sublimation was 10% (LAI = 0) to 20% (LAI = 6) of snow loss while air temperature was the dominate component at the Oregon site with sublimation reduced to 1% (LAI = 0) to 6% (LAI = 6) of snow loss. LAI had a greater effect determining snow depletion than site aspect, Aspect increased in importance if the snow depletion occurred during early spring when solar insolation differences between hillslopes is greater than in the late spring. An accurate prediction of daily snowpack water equivalent (SWE) was not a strong determinant for making an accurate prediction of snowpack depletion date. Predicted snowpack depletion dates were more sensitive to timing when the snowpack reached an isothermal condition. Daily estimates of SWE were most sensitive to correctly estimating snowfall from SNOTEL data. This means that for purposes of determining the snow depletion dates which are useful for forest ecosystem modeling, tracking SWE is less important then triggering snowmelt. Comparisons of simulations to published snow depletion dates show that RSM predicted the relative ranking and magnitude of depletion for different combinations of forest cover, elevation, and aspect. RP Coughlan, JC (reprint author), NASA,AMES RES CTR,JOHNSON CONTROLS WORLD SERV,NASA AMES OPERAT,MS 242-4,MOFFETT FIELD,CA 94035, USA. NR 49 TC 47 Z9 49 U1 1 U2 22 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0921-2973 J9 LANDSCAPE ECOL JI Landsc. Ecol. PD JUN PY 1997 VL 12 IS 3 BP 119 EP 136 DI 10.1023/A:1007933813251 PG 18 WC Ecology; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA XV634 UT WOS:A1997XV63400002 ER PT J AU Jones, WR Ajayi, OO Wedeven, LD AF Jones, WR Ajayi, OO Wedeven, LD TI Enhancement of perfluoropolyether boundary lubrication performance SO LUBRICATION ENGINEERING LA English DT Article; Proceedings Paper CT ASME/STLE 1996 Tribology Conference CY OCT 13-17, 1996 CL SAN FRANCISCO, CA SP Amer Soc Mech Engineers, Soc Tribologists & Lubricat Engineers DE boundary lubrication; perfluoropolyethers ID OXIDATIVE-DEGRADATION REACTIONS; PERFLUOROALKYL ETHERS; SOLUBLE ADDITIVES; HIGH-VACUUM AB A ball bearing simulator operating under starved conditions was used to perform screening tests to evaluate the boundary lubrication performance of a branched perfluoropolyether (PFPE), K-143 AB. Several approaches to enhance boundary lubrication were studied. These included soluble boundary additives, bearing surface modifications, ''run-in'' surface films and ceramic bearing components. In addition, results were compared with two nonperfluorinated liquid lubricant formulations. Based on these tests, the following tentative conclusions can be made: 1. Substantial improvements in boundary lubrication performance were observed with a beta-diketone boundary additive and a tricresyl phosphate (TCP) liquid surface pretreatment. 2. The use of rough Si3N4 balls (R-a = 40 mu in) also provided increases in test duration, but with concomitant abrasive wear. 3. Moderate improvements were seen with two boundary additives (a phosphine and a phosphatriazine) and a neat (100%) fluid (a carboxylic acid terminated PFPE). Small improvements occurred with surface pretreatments with synthetic hydrocarbons, a polytetrafluoroethylene (PTFE) coating, and TiC-coated 440C and smooth Si3N4 balls (R-a = 1 mu in). 4. Two non-PFPE lubricant formulations (a polyalphaolefin (PAO) and a synthetic hydrocarbon) yielded substantial improvements. C1 WEDEVEN ASSOCIATES INC,EDGEMONT,PA 19028. RP Jones, WR (reprint author), NASA,LEWIS RES CTR,LUBRICANT BRANCH,CLEVELAND,OH 44135, USA. NR 40 TC 1 Z9 1 U1 1 U2 5 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD JUN PY 1997 VL 53 IS 6 BP 24 EP 31 PG 8 WC Engineering, Mechanical SC Engineering GA XD611 UT WOS:A1997XD61100009 ER PT J AU Morales, W AF Morales, W TI Elijah McCoy: The father of modern lubrication SO LUBRICATION ENGINEERING LA English DT Item About an Individual RP Morales, W (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 1 TC 0 Z9 0 U1 1 U2 1 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD JUN PY 1997 VL 53 IS 6 BP 39 EP 39 PG 1 WC Engineering, Mechanical SC Engineering GA XD611 UT WOS:A1997XD61100010 ER PT J AU Chen, C Bishop, CR Lai, GS Tao, WK AF Chen, C Bishop, CR Lai, GS Tao, WK TI Numerical simulations of an observed narrow cold-frontal rainband SO MONTHLY WEATHER REVIEW LA English DT Article ID PLANETARY BOUNDARY-LAYER; CONDITIONAL SYMMETRIC INSTABILITY; 4-DIMENSIONAL DATA ASSIMILATION; AREA MESOSCALE MODEL; SHEAR FLOWS; DYNAMICS; FRONTOGENESIS; CURRENTS; CYCLONE; TESTS AB A cold-frontal rainband, which occurred during the afternoon of 28 December 1988, is numerically simulated using the Penn State-NCAR three-dimensional MM5 modeling system. This case is characterized by a line of severe convection that has a gravity current-like structure along the leading edge of a strong surface cold front. The authors test whether this gravity current-like structure is associated with the cold-air outflow boundary generated by the evaporation of hydrometeors from the postfrontal precipitation system. It is found that the neglect of moist processes in the model did not significantly affect the gravity current-like structure of the front. PBL (planetary boundary layer) frictional processes, which produce cross-frontal low-level wind shear (u(z)), play an important role. The role of this cross-frontal low-level wind shear is to generate low-level convergence and to steepen the frontal slope. Thus, the observed intense NCFR (narrow cold-frontal rainband) is closely related to frictionally induced PBL processes. C1 SCI SYST & APPLICAT INC, LANHAM, MD USA. PENN STATE UNIV, DEPT METEOROL, UNIVERSITY PK, PA 16802 USA. RP NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, MESOSCALE ATMOSPHER PROC BRANCH, CODE 912, GREENBELT, MD 20771 USA. NR 30 TC 12 Z9 12 U1 1 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 EI 1520-0493 J9 MON WEATHER REV JI Mon. Weather Rev. PD JUN PY 1997 VL 125 IS 6 BP 1027 EP 1045 DI 10.1175/1520-0493(1997)125<1027:NSOAON>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XD651 UT WOS:A1997XD65100002 ER PT J AU Tripathi, RK Wilson, JW Cucinotta, FA AF Tripathi, RK Wilson, JW Cucinotta, FA TI Accurate universal parameterization of absorption cross sections .2. Neutron absorption cross sections SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article AB A recent parameterization (here after referred as paper I, Ref. [4]) of absorption cross sections for any system of charged ions collisions including proton -nucleus collisions, is extended for neutron-nucleus collisions valid from similar to 1 MeV to a few GeV, thus providing a comprehensive picture of absorption cross sections for any system of collision pair (charged and/or uncharged). The parameters are associated with the physics of the problem. Al lower energies, the optical potential at the surface is important and the Pauli operator plays an increasingly important role at intermediate energies. The agreement between the calculated and experimental data is better than earlier published results. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Tripathi, RK (reprint author), HAMPTON UNIV,HAMPTON,VA 23669, USA. NR 12 TC 39 Z9 39 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD JUN PY 1997 VL 129 IS 1 BP 11 EP 15 DI 10.1016/S0168-583X(97)00121-3 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA XJ089 UT WOS:A1997XJ08900003 PM 11541233 ER PT J AU Liu, J Shang, HM Chen, YS Wang, TS AF Liu, J Shang, HM Chen, YS Wang, TS TI Prediction of radiative transfer in general body-fitted coordinates SO NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS LA English DT Article ID FINITE-VOLUME METHOD; DISCRETE-ORDINATES METHOD; HEAT-TRANSFER PROCEDURE; CYLINDRICAL ENCLOSURES; MULTIDIMENSIONAL GEOMETRIES; RECTANGULAR ENCLOSURES; IRREGULAR GEOMETRIES; SCATTERING MEDIA; EQUATION AB The discrete ordinates method (DOM) and the finite-volume method (FVM) are employed to simulate two-dimensional and three-dimensional radiation problems in general body-fitted coordinates. Numerical analyses of these two methods indicate that the discretized equations for the DOM and the FVM are very similar. However, the FVM uses the averaged direction and scattering phase function over a control angle rather than the discrete direction and scattering phase function as in the DOM. To examine the accuracy and computational efficiency of the DOM and FVM in general body-fitted coordinates, five two-dimensional and three-dimensional benchmark problems with transparent, absorbing, emitting and scattering media are considered. The solutions from both methods are found to be in good agreement with other available solutions. In some cases, the results from the FVM seem slightly better than those from the DOM. The required CPU time and iterations for the DOM and FVM are essentially the same for each problem. This finding is slightly different from other studies that claim that the FVM requires more CPU time to converge than the DOM for scattering-medium computation. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP Liu, J (reprint author), ENGN SCI INC,1900 GOLF RD,SUITE D,HUNTSVILLE,AL 35802, USA. NR 23 TC 59 Z9 62 U1 0 U2 2 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 SN 1040-7790 J9 NUMER HEAT TR B-FUND JI Numer Heat Tranf. B-Fundam. PD JUN PY 1997 VL 31 IS 4 BP 423 EP 439 DI 10.1080/10407799708915118 PG 17 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA XH315 UT WOS:A1997XH31500003 ER PT J AU MontesUsategui, M Monroe, SE Juday, RD AF MontesUsategui, M Monroe, SE Juday, RD TI Automated self-alignment procedure for optical correlators SO OPTICAL ENGINEERING LA English DT Article; Proceedings Paper CT Optical Pattern Recognition VII Conference CY APR 09-10, 1996 CL ORLANDO, FL SP Soc Photo Opt Instrumentat Engineers DE optical pattern recognition; optical correlators; alignment procedures; self-calibration ID LIQUID-CRYSTAL TELEVISION; FILTERS; MODULATORS AB We propose a general and fully automated procedure that enables the self-correction of the errors and performance losses produced by the misalignment of the components of an optical correlator. This method is simple, is carried out entirely by software, and has minimal operating constraints. There are no moving parts and no extra hardware is required. (C) 1997 Society of Photo-Optical Instrumentation Engineers. C1 LOCKHEED ENGN & SCI CO,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,AUTOMAT ROBOT & SIMULAT DIV,HOUSTON,TX 77058. RP MontesUsategui, M (reprint author), UNIV BARCELONA,LAB OPT,DIAGONAL 647,E-08028 BARCELONA,SPAIN. OI Montes-Usategui, Mario/0000-0003-2811-1485 NR 20 TC 13 Z9 13 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 JUN PY 1997 VL 36 IS 6 BP 1782 EP 1791 DI 10.1117/1.601323 PG 10 WC Optics SC Optics GA XD388 UT WOS:A1997XD38800032 ER PT J AU Tielens, AGGM Charnley, SB AF Tielens, AGGM Charnley, SB TI Circumstellar and interstellar synthesis of organic molecules SO ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES LA English DT Review ID CARBON-CHAIN MOLECULES; POLYCYCLIC AROMATIC-HYDROCARBONS; TIME-DEPENDENT CHEMISTRY; GRAIN SURFACE-CHEMISTRY; COMETARY ICE ANALOGS; INTER-STELLAR CLOUDS; IRC + 10216; INFRARED-SPECTROSCOPY; DENSE CLOUDS; CHEMICAL DIFFERENTIATION AB We review the formation and evolution of complex circumstellar and interstellar molecules. A number of promising chemical routes are discussed which may lead to the formation of polycyclic aromatic hydrocarbon molecules, fullerenes, and unsaturated hydrocarbon chains in the outflows from stars. Some of the problems with these chemical schemes are pointed out as well. We also review the role of grains in the formation of complex molecules in interstellar molecular clouds. This starts with the formation of simple molecules in an ice grain mantle. UV photolysis and/or thermal polymerization can convert some of these simple molecules into more complex polymeric structures. Some of these species may be released to the gas phase, particularly in the warm regions around newly formed stars. Methanol and formaldehyde seem to play an important role in this drive towards molecular complexity and their chemistry is traced in some detail. C1 UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. RP NASA, AMES RES CTR, MS 245-3, MOFFETT FIELD, CA 94035 USA. RI Charnley, Steven/C-9538-2012 NR 148 TC 96 Z9 97 U1 3 U2 13 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0169-6149 EI 1573-0875 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD JUN PY 1997 VL 27 IS 1-3 BP 23 EP 51 DI 10.1023/A:1006513928588 PG 29 WC Biology SC Life Sciences & Biomedicine - Other Topics GA WV694 UT WOS:A1997WV69400003 PM 9150566 ER PT J AU Pendleton, YJ AF Pendleton, YJ TI Detection of organic matter in interstellar grains SO ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES LA English DT Review ID EXTENDED RED EMISSION; HYDROGENATED AMORPHOUS-CARBON; UNIDENTIFIED INFRARED BANDS; GALACTIC-CENTER; REFLECTION NEBULAE; ABSORPTION FEATURE; ALIPHATIC-HYDROCARBONS; MURCHISON METEORITE; MOLECULAR CLOUDS; ICE ANALOGS AB Star formation and the subsequent evolution of planetary systems occurs in dense molecular clouds, which are comprised, in part, of interstellar dust grains gathered from the diffuse interstellar medium (DISM). Radio observations of the interstellar medium reveal the presence of organic molecules in the gas phase and infrared observational studies provide details concerning the solid-state features in dust grains. In particular, a series of absorption bands have been observed near 3.4 mu m (similar to 2940 cm(-1)) towards bright infrared objects which are seen through large column densities of interstellar dust. Comparisons of organic residues, produced under a variety of laboratory conditions, to the diffuse interstellar medium observations have shown that aliphatic hydrocarbon grains are responsible for the spectral absorption features observed near 3.4 mu m (similar to 2940 cm(-1)). These hydrocarbons appear to carry the -CH2- and -CH3 functional groups in the abundance ratio CH2/CH3 similar to 2.5, and the amount of carbon tied up in this component is greater than 4% of the cosmic carbon available. On a galactic scale, the strength of the 3.4 mu m band does not scale linearly with visual extinction, but instead increases more rapidly for objects near the Galactic Center. A similar trend is noted in the strength of the Si-O absorption band near 9.7 mu m. The similar behavior of the C-H and Si-O stretching bands suggests that these two components may be coupled, perhaps in the form of grains with silicate cores and refractory organic mantles. The ubiquity of the hydrocarbon features seen in the near infrared near 3.4 mu m throughout our Galaxy and in other galaxies demonstrates the widespread availability of such material for incorporation into the many newly forming planetary systems. The similarity of the 3.4 mu m features in any organic material with aliphatic hydrocarbons underscores the need for complete astronomical observational coverage in the 2-30 mu m region, of lines of sight which sample dust in both dense and diffuse interstellar clouds, in order to uniquely specify the composition of interstellar organics. This paper reviews the information available from ground-based observations, although currently the Infrared Satellite Observatory is adding to our body of knowledge on this subject by providing more extensive wavelength coverage. The Murchison carbonaceous meteorite has also been used as an analog to the interstellar observations and has revealed a striking similarity between the light hydrocarbons in the meteorite and the ISM; therefore this review includes comparisons with the meteoritic analog as well as with relevant laboratory residues. Fundamental to the evolution of the biogenic molecules, to the process of planetary system formation, and perhaps to the origin of life, is the connection between the organic material found in the interstellar medium and that incorporated in the most primitive solar system bodies. RP NASA, AMES RES CTR, MS 245-3, MOFFETT FIELD, CA 94035 USA. NR 104 TC 27 Z9 27 U1 1 U2 2 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0169-6149 EI 1573-0875 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD JUN PY 1997 VL 27 IS 1-3 BP 53 EP 78 DI 10.1023/A:1006565912658 PG 26 WC Biology SC Life Sciences & Biomedicine - Other Topics GA WV694 UT WOS:A1997WV69400004 PM 9150567 ER PT J AU Koerner, DW AF Koerner, DW TI Analogs of the early solar system SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Review ID T-TAURI STARS; YOUNG STELLAR OBJECTS; PICTORIS CIRCUMSTELLAR DISK; MAIN-SEQUENCE STARS; BETA-PICTORIS; ORION-NEBULA; HL-TAURI; ACCRETION DISKS; PROTOPLANETARY DISKS; PROTOSTELLAR DISKS AB Within the last few decades, the existence of protoplanetary disks has been inferred on the basis of emission from T Tauri stars that does not arise from a stellar photosphere. More recently, high-resolution interferometric techniques have resolved the dust continuum emission, and millimeter arrays have imaged circumstellar molecular gas. These measurements corroborate the disk interpretation; many T Tauri stars are surrounded by centrifugally supported circumstellar disks with radial sizes of order 100 AU. Further proof issues from Hubble Space Telescope images of disks that are illuminated externally. The morphology of circumstellar dust is revealed in striking detail and affirms the prevalence and dimensions of disks imaged at longer wavelengths. The fate of circumstellar material around young stars must be understood in order to discern the degree to which these disks are proto-planetary. Observational studies of circumstellar disks which are in the beginning of a dispersal phase are challenging and place great demands on astronomical techniques. Nevertheless, the connection between disks and the formation of extra-solar planets is supported by increasing circumstantial evidence. Optically thin dust continuum emission persists in T Tauri stars and is detected around some young main sequence stars. Since the dust is subject to rapid dispersal by radiation pressure and Poynting-Robertson drag, some mechanism of replenishment is required. Disks around nearby young main sequence stars show evidence for inner voids and disk asymmetries that should also disappear on short timescales. The presence of large orbiting bodies which collide and interact with the resulting debris can explain both the persistence of optically thin dust and the maintenance of otherwise-ephemeral dynamical features. Together with recent detections of extra-solar planets, these observations lend some support to the hypothesis that circumstellar disks commonly give birth to planetary systems. RP Koerner, DW (reprint author), CALTECH,JET PROP LAB,MS 183-501,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 178 TC 21 Z9 21 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD JUN PY 1997 VL 27 IS 1-3 BP 157 EP 184 DI 10.1023/A:1006526331314 PG 28 WC Biology SC Life Sciences & Biomedicine - Other Topics GA WV694 UT WOS:A1997WV69400009 PM 9150572 ER PT J AU McKay, CP AF McKay, CP TI The search for life on Mars SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Review ID CRYPTOENDOLITHIC MICROBIAL ENVIRONMENT; SNC METEORITES; VALLES MARINERIS; EARLY ATMOSPHERE; ANTARCTIC LAKE; MARTIAN SOIL; ROSS DESERT; GROUND ICE; EVOLUTION; MODEL AB Mars appears to have no life on its surface today. However, the presence of fluvial features provides evidence that liquid water was once present on the martian surface. By analogy with Earth, life may have originated on Mars early in its history, possibly during the end of the late heavy bombardment. Analysis of the one meteorite from Mars which dates to this early time appears to contain evidence of this early environment and possibly life. As the climate cooled and liquid water became unavailable, life would have eventually died out. The cold deserts of Antarctica provide a glimpse of what martian ecosystems might have been like as conditions worsened. The search for fossil evidence of past life on Mars may provide the first direct indication of life beyond Earth. RP McKay, CP (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035, USA. NR 123 TC 88 Z9 91 U1 11 U2 28 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD JUN PY 1997 VL 27 IS 1-3 BP 263 EP 289 DI 10.1023/A:1006500116990 PG 27 WC Biology SC Life Sciences & Biomedicine - Other Topics GA WV694 UT WOS:A1997WV69400014 PM 9150577 ER PT J AU Vasquez, RP Novikov, DL Freeman, AJ Siegal, MP AF Vasquez, RP Novikov, DL Freeman, AJ Siegal, MP TI Electronic structure of TlBa2CaCu2O7-delta SO PHYSICAL REVIEW B LA English DT Article ID RAY PHOTOELECTRON-SPECTROSCOPY; HIGH-TEMPERATURE SUPERCONDUCTORS; T-C SUPERCONDUCTORS; CORE-LEVEL; DOPING DEPENDENCE; SINGLE-CRYSTALS; STATE PROPERTIES; PHOTOEMISSION; SPECTRA; BA AB The core levels of TlBa2CaCu2O7-delta (Tl-1212) epitaxial films have been measured with x-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level (E-F) for the stoichiometric compound (delta = 0), while for 50% oxygen vacancies in the Tl-O layer (delta = 0.5) E-F is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher T-c, consistent with a shift of E-F closer to the VHS. Comparisons are made to the core levels and valence bands of Tl2Ba2CaCu2O8+delta (Tl-2212) and HgBa2CaCu2O6+delta (Hg-1212). The similarity of the Cu 2p(3/2) spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu 2p(3/2) signals exhibit differences which suggest that the replacement of Tl3+ with Hg2+ results in a decrease in the O 2p --> Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl,Hg) 6s/5d partial densities of states. C1 NORTHWESTERN UNIV,DEPT PHYS & ASTRON,SCI & TECHNOL CTR SUPERCONDUCT,EVANSTON,IL 60208. SANDIA NATL LABS,ALBUQUERQUE,NM 87185. RP Vasquez, RP (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. NR 48 TC 16 Z9 16 U1 0 U2 4 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0163-1829 J9 PHYS REV B JI Phys. Rev. B PD JUN 1 PY 1997 VL 55 IS 21 BP 14623 EP 14631 DI 10.1103/PhysRevB.55.14623 PG 9 WC Physics, Condensed Matter SC Physics GA XE371 UT WOS:A1997XE37100088 ER PT J AU He, XY Luo, LS AF He, XY Luo, LS TI A priori derivation of the lattice Boltzmann equation SO PHYSICAL REVIEW E LA English DT Article ID NAVIER-STOKES EQUATION; GAS AUTOMATA; HYDRODYNAMICS; MODELS AB The lattice Boltzmann equation (LBE) is directly derived from the Boltzmann equation by discretization in both time and phase space. A procedure to systematically derive discrete velocity models is presented. A LBE algorithm with arbitrary mesh grids is proposed and a numerical simulation of the backward-facing step is conducted. The numerical result agrees well with experimental and previous numerical results. Various improvements on the LBE models are discussed, and an explanation of the instability of the existing LBE thermal models is also provided. C1 LOS ALAMOS NATL LAB,COMPLEX SYST GRP T13,THEORET T DIV,LOS ALAMOS,NM 87545. NASA,LANGLEY RES CTR,ICASE,HAMPTON,VA 23681. RP He, XY (reprint author), 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 26 TC 435 Z9 439 U1 7 U2 34 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 JUN PY 1997 VL 55 IS 6 BP R6333 EP R6336 PN A PG 4 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA XG965 UT WOS:A1997XG96500006 ER PT J AU Ghosal, S Rogers, MM AF Ghosal, S Rogers, MM TI A numerical study of self-similarity in a turbulent plane wake using large-eddy simulation SO PHYSICS OF FLUIDS LA English DT Article ID NAVIER-STOKES EQUATIONS; INFINITE AB Turbulent wakes are known to develop self-similarly sufficiently far downstream from obstacles that generate them. It has long been assumed that the spreading rate of the wake in the self-similar regime is independent of the details of the body generating the wake, being dependent only on the total drag (or momentum deficit). This assumption seems to be in contradiction with some recent experiments. In this study we attempt to complement these experimental investigations through a numerical study of a time-developing wake. A numerical study has the advantage of eliminating many of the uncontrolled factors present in experiments and allowing precise control of initial conditions. Large-eddy simulations employing the recently developed dynamic localization model are used to extend previous results from direct numerical simulations. The large-eddy simulation results are compared to the direct numerical simulation database, wherever such comparisons are feasible, as a check of the method. Like the experiments, the large-eddy simulations suggest that non-unique self-similar states, characterized by different spreading rates and turbulent statistics, are possible and that they can be maintained for significant time periods. The study also demonstrates the predictive capability of the dynamic localization subgrid model. (C) 1997 American Institute of Physics. C1 STANFORD UNIV,CTR TURBULENCE RES,STANFORD,CA 94305. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RI Ghosal, Sandip/A-3534-2009; Ghosal, Sandip/B-7595-2009 OI Ghosal, Sandip/0000-0001-6587-3716; NR 15 TC 34 Z9 34 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD JUN PY 1997 VL 9 IS 6 BP 1729 EP 1739 DI 10.1063/1.869289 PG 11 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XB197 UT WOS:A1997XB19700018 ER PT J AU Cole, KD AF Cole, KD TI Diamagnetism in a plasma SO PHYSICS OF PLASMAS LA English DT Article AB This is an extension of a study of electric currents and force balance orthogonal to a unidirectional magnetic field of induction (B) in a collisionless plasma [K. D. Cole, Phys. Plasmas 3, 2717 (1996)]. All quantities are assumed to vary only in one direction orthogonal to B. Two new concepts are introduced, which are not in conventional plasma physics. First a magnetic polarization effect corresponding to electric polarization is found. This defines a contribution to the magnetic moment per unit volume of -rho(m)c(2)E(2)/B-3. Second the conduction current is defined in terms of the curl of the magnetic field intensity H, in accordance with Maxwell. In this scheme, when there is no electric field, (1/4 pi)(partial derivative H/partial derivative z)B + (partial derivative p(perpendicular to)/partial derivative z) = 0, instead of the conventional equation with B/mu(0) in place of H. In both schemes, j x B-del p(perpendicular to) = 0. Though this makes no difference to the electric current intensity calculated in the two schemes, and no difference to the force balance equation, it makes a significant difference to the relationship between B and p(perpendicular to) in many plasma conditions of interest. When the electric field is nonzero, the situation is more complex. It is shown that the new diamagnetism of this paper and the dielectric current of the earlier one are consistent with special relativity. Some applications of the theory are discussed. (C) 1997 American Institute of Physics. RP Cole, KD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 9104,GREENBELT,MD 20771, USA. NR 13 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 JUN PY 1997 VL 4 IS 6 BP 2072 EP 2080 DI 10.1063/1.872373 PG 9 WC Physics, Fluids & Plasmas SC Physics GA XB803 UT WOS:A1997XB80300006 ER PT J AU Davarian, F Rogers, DV Bauer, R AF Davarian, F Rogers, DV Bauer, R TI Special issue on Ka-band propagation effects on earth-satellite links SO PROCEEDINGS OF THE IEEE LA English DT Editorial Material C1 COMMUN RES CTR,OTTAWA,ON K2H 8S2,CANADA. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Davarian, F (reprint author), HUGHES SPACE & COMMUN,EL SEGUNDO,CA 90245, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9219 J9 P IEEE JI Proc. IEEE PD JUN PY 1997 VL 85 IS 6 BP 807 EP 809 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA XK296 UT WOS:A1997XK29600001 ER PT J AU Bauer, R AF Bauer, R TI Ka-band propagation measurements: An opportunity with the advanced communications technology satellite (ACTS) SO PROCEEDINGS OF THE IEEE LA English DT Article DE ACTS; beacons; Ka-band; propagation measurements; 30/20 GHz program AB The Advanced Communications Technology Satellite (ACTS) was conceived at the National Aeronautics and Space Administration (NASA) as a follow-on program to its long history in satellite communications projects that have reduced the risk of developing new technologies that fall outside the sponsorship capability of the private sector. To counter the foreign challenge that developed in the late 1970's to the once insuperable U.S. lead in this field, ACTS was developed to maintain the U.S. preeminence. Launched in September 1993 from the space shuttle, key technologies on ACTS include a multibeam antenna, a baseband processor, a 900-MHz wideband microwave switch matrix, adaptive rain fade compensation techniques, and the rise of Ka-band frequencies. Since this is the United States' first effort in using Ka-band for satellite communications, beacons are incorporated on the satellite, which provide all opportunity for propagation measurements. NASA is sponsoring a network of propagation experimenters rising these beacons and receive-only terminals identical in design. This paper provides some history that leads to the eventual development of ACTS. Also, a system overview of the spacecraft is provided for those less familiar with it. RP Bauer, R (reprint author), NASA,LEWIS RES CTR,COLUMBUS,OH 44135, USA. NR 26 TC 19 Z9 19 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 0018-9219 J9 P IEEE JI Proc. IEEE PD JUN PY 1997 VL 85 IS 6 BP 853 EP 862 DI 10.1109/5.598409 PG 10 WC Engineering, Electrical & Electronic SC Engineering GA XK296 UT WOS:A1997XK29600005 ER PT J AU Feibelman, WA AF Feibelman, WA TI The IUE spectrum of the binary nucleus of the planetary nebula NGC 1514 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID CENTRAL STARS; EVOLUTION; WINDS AB Archival IUE low-dispersion spectra and the first ultraviolet high-dispersion spectrum of the binary nucleus of NGC 1514 have been analyzed. Both SWP and LWR low-dispersion spectra show variability by as much as a factor of two in the continuum level between the years 1978 and 1989. Weak P Cygni features for O V lambda 1371 and C IV lambda 1549 yield terminal wind velocities of - 105 +/- 25 and - 960 +/- 150 km s(-1), respectively. No nebular emission lines were detected, but several photospheric and interstellar absorption features were observed. Absorption lines of Fe VII are suspected. The He II lambda 1640 absorption line has a radial velocity of + 49 +/- 3 km s(-1) and is in good agreement with optical data. The peculiar energy distribution of the SWP continuum for NGC 1514 can be synthesized by the coaddition of spectral-type A0-A3 III plus hot subdwarf lUE spectra. RP Feibelman, WA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 681,GREENBELT,MD 20771, USA. NR 32 TC 2 Z9 2 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD JUN PY 1997 VL 109 IS 736 BP 659 EP 666 DI 10.1086/133928 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XE154 UT WOS:A1997XE15400005 ER PT J AU Carroll, BC Cotter, GA AF Carroll, BC Cotter, GA TI A new generation of grey literature: The impact of advanced information technologies SO PUBLISHING RESEARCH QUARTERLY LA English DT Article AB A basic challenge of the Weinberg Report addressed the question of information overload. The Weinberg Panel was extremely concerned with the proliferation of scientific literature and the specific issue of how to sift through reams of data to find the ''gems'' of wisdom, or that which is truly new and useful. In the early 1960s when the report was being written, computers were not part of the information access and retrieval infrastructure. Writing twenty-five years later, in 1988, Dr. Weinberg recognized that the panel had not adequately taken into account the impact of the computer and the growth of the information industry. Today we have a new world of microcomputers and networked information which is fundamentally shifting the paradigm of scientific communication. We have new capabilities, including electronic publishing, visualization techniques, even virtual reality. Without getting into a great debate about the definition of ''grey literature,'' the main characteristics have traditionally been described as: rapid publication, variable formats, no public peer review, and no commercial source of general availability. With networked information and multi-media technology, the new world of grey literature is emerging with an interesting set of new and revived challenges. This article looks at the most interesting characteristics, and based on them, presents the thesis that in the 1990s we are facing a new generation of ''grey literature.'' C1 INFORMAT INT ASSOCIATES INC,OAK RIDGE,TN 37831. RP Carroll, BC (reprint author), NASA,SCI & TECH INFORMAT PROGRAM,CODE JTT,WASHINGTON,DC 20546, USA. NR 19 TC 2 Z9 2 U1 1 U2 4 PU TRANSACTION PERIOD CONSORTIUM PI NEW BRUNSWICK PA DEPT 3091 RUTGERS-THE STATE UNIV OF NJ, NEW BRUNSWICK, NJ 08903 SN 1053-8801 J9 PUBLISH RES Q JI Publ. Res. Q. PD SUM PY 1997 VL 13 IS 2 BP 5 EP 14 DI 10.1007/s12109-997-0014-z PG 10 WC Communication; Information Science & Library Science SC Communication; Information Science & Library Science GA YB838 UT WOS:A1997YB83800002 ER PT J AU Pinelli, TE Barclay, RO Kennedy, JM AF Pinelli, TE Barclay, RO Kennedy, JM TI Survey of reader preferences concerning the format of NASA Langley-authored technical reports SO PUBLISHING RESEARCH QUARTERLY LA English DT Article AB The U.S. government technical report is a primary means by which the results of federally funded research and development (R&D) are transferred to the U.S. aerospace industry. However, little is known about this information product in terms of its actual use, importance, and value in the transfer of federally funded R&D. Little is also known about the intermediary-based system that is used to transfer the results of federally funded R&D to the U.S. aerospace industry. To help establish a body of knowledge, the U.S. government technical report is being investigated as part of the NASA/DoD Aerospace Knowledge Diffusion Research Project. In this article, we summarize the literature on the U.S. government technical report and present the results of a survey of U.S. aerospace engineers and scientists that solicited their opinions concerning the format of NASA Langley Research Center (LaRC)-authored technical reports. To learn more about the preferences of U.S. aerospace engineers and scientists concerning the format of NASA LaRC-authored technical reports, we surveyed 133 report producers (i.e., authors) and 137 report users in March-April 1996. Questions covered such topics as: (a) the order in which report components are read; (b) components used to determine if a report would be read; (c) those components that could be deleted; (d) the placement of such components as the symbols list; (e) the desirability of a table of contents; (f) the format of reference citations; (g) column layout and right margin treatment; and (h) writing style in terms of person and voice. Mail (self-reported) surveys were used to collect the data. The response rates for report producers (i.e., authors) was 68% and for users was 62%. RP Pinelli, TE (reprint author), NASA,LANGLEY RES CTR,VISUAL IMAGING BRANCH,HAMPTON,VA 23665, USA. NR 19 TC 0 Z9 0 U1 0 U2 1 PU TRANSACTION PERIOD CONSORTIUM PI NEW BRUNSWICK PA DEPT 3091 RUTGERS-THE STATE UNIV OF NJ, NEW BRUNSWICK, NJ 08903 SN 1053-8801 J9 PUBLISH RES Q JI Publ. Res. Q. PD SUM PY 1997 VL 13 IS 2 BP 48 EP 68 DI 10.1007/s12109-997-0018-8 PG 21 WC Communication; Information Science & Library Science SC Communication; Information Science & Library Science GA YB838 UT WOS:A1997YB83800006 ER PT J AU Wetherhold, RC Thomas, DJ AF Wetherhold, RC Thomas, DJ TI Regularity of the transverse crack spacing in a damaged laminate SO RELIABILITY ENGINEERING & SYSTEM SAFETY LA English DT Article ID COMPOSITE; LOCATION; FRACTURE AB In evaluating elastic constants for a damaged laminate, the assumption is often made that transverse matrix cracks are equally spaced. To investigate the plausibility of this assumption, an analytical expression for the probability density function of the next failure location in a region of the cross-ply laminate bounded by two existing transverse matrix cracks is derived. The derivation employs the method developed by Oh and Finney for modeling the characteristics of the location of failure in conjunction with a shear-lag solution for the stress state in a transversely cracked layer of a multi-ply laminate. In exercising this model, it is found that the assumption of regularly spaced transverse matrix cracks becomes more plausible as the crack density increases (crack spacing decreases). (C) 1997 Elsevier Science Limited. C1 CLEVELAND STATE UNIV,DEPT CIVIL ENGN,CLEVELAND,OH 44115. NASA,WASHINGTON,DC. RP Wetherhold, RC (reprint author), SUNY BUFFALO,DEPT MECH & AEROSP ENGN,BUFFALO,NY 14260, USA. NR 6 TC 0 Z9 0 U1 0 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0951-8320 J9 RELIAB ENG SYST SAFE JI Reliab. Eng. Syst. Saf. PD JUN PY 1997 VL 56 IS 3 BP 221 EP 224 DI 10.1016/S0951-8320(95)00083-6 PG 4 WC Engineering, Industrial; Operations Research & Management Science SC Engineering; Operations Research & Management Science GA XK051 UT WOS:A1997XK05100005 ER PT J AU Imhoff, ML Sisk, TD Milne, A Morgan, G Orr, T AF Imhoff, ML Sisk, TD Milne, A Morgan, G Orr, T TI Remotely sensed indicators of habitat heterogeneity: Use of synthetic aperture radar in mapping vegetation structure and bird habitat SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID NORTHERN-TERRITORY; FOREST ECOSYSTEM; AUSTRALIA; SAR; BACKSCATTER; BIOMASS; CONSERVATION; TROPICS AB All integrated remote sensing/field ecology project linked the use of synthetic aperture radar (SAR) and aerial photography to studies of landscape spatial heterogeneity and bird community ecology. P-, L-, and C-band SAR data, collected over a section of Kakadu National Park in Australia's Northern Territory during the Joint NASA/Australia DC-8 data acquisition campaign, were analyzed in light of field data integrating vegetation structure and floristics with bird abundances across a heterogeneous study site. Results indicate that SAR data are able to discern structural differences relevant to bird habitat quality within floristically homogeneous stands, while multispectral sensors successfully identified floristic differences among habitat types. Simplifying indices of bird diversity showed ambiguous changes across the site; however, the abundances of individual species were observed to change significantly across both floristic and structural gradients. These results suggest that efforts to map bird diversity should focus on species-specific habitat relationships and that some measure of vegetation structure is needed to understand bird habitat. The approach employed here advances the use of SAR data in the three-dimensional mapping of animal habitats from remotely sensed data, and extends current capabilities for mapping and modeling large-scale patterns in the distribution of biological diversity. (C) Elsevier Science Inc., 1997. C1 US DEPT INTERIOR,NATL BIOL SERV,WASHINGTON,DC. STANFORD UNIV,CTR CONSERVAT BIOL,STANFORD,CA 94305. UNIV NEW S WALES,SYDNEY,NSW,AUSTRALIA. DEF SCI & TECHNOL ORG,ADELAIDE,SA,AUSTRALIA. RP Imhoff, ML (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 923,GREENBELT,MD 20771, USA. NR 33 TC 48 Z9 48 U1 0 U2 11 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 JUN PY 1997 VL 60 IS 3 BP 217 EP 227 DI 10.1016/S0034-4257(96)00116-2 PG 11 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XA305 UT WOS:A1997XA30500001 ER PT J AU Saatchi, SS Rignot, E AF Saatchi, SS Rignot, E TI Classification of boreal forest cover types using SAR images SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID APERTURE RADAR DATA; MULTIFREQUENCY; PARAMETERS AB Mapping forest cover types in the boreal ecosystem is important for understanding the processes governing the interaction of the surface with the atmosphere. In this paper we report the results of the land-cover classification of the SAR (synthetic aperture radar) data acquired during the Boreal Ecosystem Atmospheric Study's intensive field campaigns over the southern study area near Prince Albert, Canada. A Bayesian maximum a posteriori classifier was applied on the National Aeronautics and Space Administration/Jet Propulsion Laboratory airborne SAR images covering the region during the peak of the growing season in July 1994. The approach is supervised in the sense that a combination of field data and existing land-cover maps are used to develop training areas for the desired classes. The images acquired were first radiometrically and absolutely calibrated the incidence angle effect in airborne images was corrected to art acceptable accuracy, and the images were used in a mosaic form and geocoded and georeferenced with an existing land-cover map for validation purposes. The results shore that SAR images can be classified into dominant forest types such as jack pine, black spruce, trembling aspen, clearing, open. water and three categories of mired strands with better than 90% accuracy. The unispecies stands such as jack pine and black spruce are separated with 98% accuracy, but the accuracy of mixed coniferous and deciduous stands suffers from confusing factors such as varying species composition, surface moisture, and understory effects. To satisfy the requirements of process models, the number of cover types was reduced from eight to five general classes of conifer wet, conifer dry, mixed deciduous, disturbed, and open water. Reduction of classes improved the overall accuracy of the classification over the entire region from 77% to 92%. (C) Elsevier Science Inc., 1997. RP Saatchi, SS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Rignot, Eric/A-4560-2014 OI Rignot, Eric/0000-0002-3366-0481 NR 21 TC 24 Z9 26 U1 0 U2 7 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD JUN PY 1997 VL 60 IS 3 BP 270 EP 281 DI 10.1016/S0034-4257(96)00181-2 PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XA305 UT WOS:A1997XA30500005 ER PT J AU Nelson, R Oderwald, R Gregoire, TG AF Nelson, R Oderwald, R Gregoire, TG TI Separating the ground and airborne laser sampling phases to estimate tropical forest basal area, volume, and biomass SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID SYSTEM; CANOPY AB Airborne laser profiling data were used to estimate the basal area, volume, and biomass of primary tropical forests. A procedure was developed and tested to divorce the laser and ground data collection efforts using three distinct data sets acquired in and over the tropical forests of Costa Rica. Fixed-area ground plot data were used to simulate the height characteristics of the tropical forest canopy and to simulate laser measurements of that canopy. On two of the three study sites, the airborne laser estimates of basal area, volume, and biomass grossly misrepresented ground estimates of same. On the third study site, where the widest ground plots were utilized, airborne and ground estimates agreed within 24%. Basal area, volume, and biomass prediction inaccuracies in the first two study areas were tied directly to disagreements between simulated laser estimates and the corresponding airborne measurements of average canopy height, height variability, and canopy density. A number of sampling issues were investigated; the following results were noted in the analyses of the three study areas. 1) Of the four ground segment lengths considered (25 m, 50 m, 75 m, and 100 m), the 25 m segment length introduced a level of variability which may severely degrade prediction accuracy in these Costa Rican primary tropical forests. This effect was more pronounced as plot width decreased. A minimum segment length was on the order of 50 m. 2) The decision to transform or not to transform the dependent variable (e.g., biomass) was by far the most important factor of those considered in this experiment. The natural log transformation of the dependent variable increased prediction error, and error increased dramatically at the shorter segment lengths. The most accurate models were multiple linear models with forced zero intercept and an untransformed dependent variable. 3) General linear models were developed to predict basal area, volume, and biomass using airborne laser height measurements. Useful laser measurements include average canopy height, all pulses ((h) over bar(a)), average canopy height, canopy hits ((h) over bar(c)) and the coefficients of variation of these terms (c(a) and c(c)). Coefficients of determination range from 0.4 to 0.6. Based on this research, airborne laser and ground sampling procedures are proposed for use for reconnaissance level surveys of inaccessible forested regions. (C) Elsevier Science Inc., 1997. RP Nelson, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. RI Nelson, Ross/H-8266-2014 NR 27 TC 72 Z9 86 U1 1 U2 9 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 JUN PY 1997 VL 60 IS 3 BP 311 EP 326 DI 10.1016/S0034-4257(96)00213-1 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XA305 UT WOS:A1997XA30500008 ER PT J AU Nelson, R AF Nelson, R TI Modeling forest canopy heights: The effects of canopy shape SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID AIRBORNE LASER DATA AB Three-dimensional models that represent the top-of-canopy forest height structure were developed to simulate airborne laser profiling responses along forested transects. The simulator which produced these 3-D models constructed individual tree crowns according to a tree's total height, height to first branch, crown diameter, and crown shape (cone, parabola, ellipse, sphere, or a random assortment of these shapes), and then inserted these crowns into a fixed-area plot using mapped stand (x,y) coordinates. This two-dimensional array of forest canopy heights was randomly transected to simulate measurements made by an airborne ranging laser. These simulated laser measurements were regressed with ground reference measures to develop predictive linear relationships. The assumed crown shape had a significant impact on 1) simulated laser measurements of height and 2) estimates of basal area, woody volume, and above-ground dry biomass derived via simulation. As canopy shape progressed from a conic form to a more spheric structure, average canopy height, canopy profile area, and canopy volume increased, canopy height variation decreased, and coefficients of variability were stable or decreased. In Costa Rican tropical forests, simulated laser measurements of average height, canopy profile area, and canopy volume increased 8-10% when a parabolic rather than a conic shape was assumed. An elliptic canopy was 16-18% taller, on average, than a conic canopy, and a spheric canopy was 23-25% taller. The effect of these height increases and height variability changes can profoundly affect basal area, volume, and biomass estimates, but the degree to which these estimates are affected is study-area-dependent. Since canopy shape may significantly affect such estimates, canopy shapes should be noted when field data are collected for purposes of height simulation. If canopy shapes are not noted and are unknown, an assumption of an elliptical shape is suggested in order to mitigate potentially large errors which may be incurred using a generic assumption of a cone or sphere. (C) Elsevier Science Inc., 1997. RP Nelson, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. RI Nelson, Ross/H-8266-2014 NR 10 TC 76 Z9 80 U1 2 U2 12 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 JUN PY 1997 VL 60 IS 3 BP 327 EP 334 DI 10.1016/S0034-4257(96)00214-3 PG 8 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XA305 UT WOS:A1997XA30500009 ER PT J AU Comiso, JC Cavalieri, DJ Parkinson, CL Gloersen, P AF Comiso, JC Cavalieri, DJ Parkinson, CL Gloersen, P TI Passive microwave algorithms for sea ice concentration: A comparison of two techniques SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID WEDDELL SEA; INSITU OBSERVATIONS; SATELLITE DATA; SIGNATURES; RADIOMETER; WINTER; REDUCTION; IMAGER; COVER; OCEAN AB The most comprehensive large-scale characterization of the global sea ice cover so far has been provided by satellite passive microwave data. Accurate retrieval of ice concentrations from these data is important because of the sensitivity of surface flux (e.g., heat, salt, and water) calculations to small changes in the amount of open water (leads and polynyas) within the polar ice packs. Two algorithms that have been used for deriving ice concentrations from multichannel data are compared. One is the NASA Team algorithm and the other is the Bootstrap algorithm, both of which were developed at NASA's Goddard Space Flight Center. The two algorithms use different channel combinations, reference brightness temperatures, weather filters, and techniques. Analyses are made to evaluate the sensitivity of algorithm results to variations of emissivity and temperature with space and time. To assess the difference in the performance of the two algorithms, analyses were performed with data from both hemispheres and for all seasons. The results show only small differences in the central Arctic in winter but larger disagreements in the seasonal regions and in summer. In some areas in the Antarctic, the Bootstrap technique shows ice concentrations higher than those of the Team algorithm by as much as 25%; whereas, in other areas, it shows ice concentrations lower by as much as 30%. The differences in the results are caused by temperature effects, emissivity effects, and tie point differences. The Team and the Bootstrap results were compared with available Landsat, advanced very high resolution radiometer (AVHRR) and synthetic aperture radar (SAR) data. AVHRR, Landsat, and SAR data sets all yield higher concentrations than the passive microwave algorithms. Inconsistencies among results suggest the need for further validation studies. (C) Elsevier Science Inc., 1997. RP Comiso, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,OCEANS & ICE BRANCH,LAB HYDRSPHER PROCESSES,GREENBELT,MD 20771, USA. RI Parkinson, Claire/E-1747-2012 OI Parkinson, Claire/0000-0001-6730-4197 NR 36 TC 211 Z9 220 U1 2 U2 22 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 JUN PY 1997 VL 60 IS 3 BP 357 EP 384 DI 10.1016/S0034-4257(96)00220-9 PG 28 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XA305 UT WOS:A1997XA30500012 ER PT J AU Chung, SK Thiessen, DB Rhim, WK AF Chung, SK Thiessen, DB Rhim, WK TI A noncontact measurement technique for the density and thermal expansion coefficient of solid and liquid materials (vol 67, pg 3175, 1996) SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Correction, Addition RP Chung, SK (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Thiessen, David/A-2731-2011 NR 1 TC 1 Z9 1 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUN PY 1997 VL 68 IS 6 BP 2597 EP 2597 DI 10.1063/1.1148454 PG 1 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA XF624 UT WOS:A1997XF62400063 ER PT J AU Rai, AK Bhattacharya, RS Zabinski, JS Miyoshi, K AF Rai, AK Bhattacharya, RS Zabinski, JS Miyoshi, K TI A comparison of the wear life of as-deposited and ion-irradiated WS2 coatings SO SURFACE & COATINGS TECHNOLOGY LA English DT Article DE ion-irradiation; sputtering; tungstendisulphide; wear life ID SPUTTERED MOS2 COATINGS; BEAM MODIFICATIONS; SLIDING LIFE; FILMS; ENHANCEMENT AB The effects of high energy (MeV) ion-irradiation on the wear life of amorphous sputter-deposited WS2 coatings were studied. The coatings were deposited by DC magnetron sputtering on M50 steel and Si3N4 substrates. The coatings were characterized by transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) for microstructure and composition, respectively. Nano-hardness indentation was used to determine the hardness of as-deposited and ion-irradiated WS2 coatings. Scratch tests were performed to determine the coating adhesion with the substrate. The wear life was measured in vacuum as well as in 50% relative humidity using a pin on disc tribotester. The results indicated the amorphous nature of the coatings both before and after irradiations. Compared to the as-deposited coating, the ion-irradiated WS, coating exhibited higher hardness and increased adhesion. The wear life of ion-irradiated WS2 coating was significantly improved in both vacuum and humid environments due to enhanced adhesion and higher hardness. (C) 1997 Elsevier Science S.A. C1 USAF,WRIGHT LAB,MLBT,WRIGHT PATTERSON AFB,OH 45433. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Rai, AK (reprint author), UNIVERSAL ENERGY SYST INC,DAYTON,OH 45432, USA. NR 12 TC 16 Z9 24 U1 0 U2 8 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD JUN PY 1997 VL 92 IS 1-2 BP 120 EP 128 DI 10.1016/S0257-8972(97)00081-9 PG 9 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA XJ316 UT WOS:A1997XJ31600018 ER PT J AU Atwater, HA Ahn, CC Wong, SS He, G Yoshino, H Nikzad, S AF Atwater, HA Ahn, CC Wong, SS He, G Yoshino, H Nikzad, S TI Energy-filtered rheed and reels for in situ real time analysis during film growth SO SURFACE REVIEW AND LETTERS LA English DT Article; Proceedings Paper CT Winter Workshop on Electron Diffraction and Imaging at Surfaces CY JAN 03-06, 1996 CL SCOTTSDALE, AZ SP Int Union Crystallog, US DOE, Arizona State Univ, Eiko Engn Ltd, JEOL Inc, Matsushita Res Inst, Tokyo, Inc, Nagoya Ind Sci Res Inst, NEC Corp, Japan, Toshiba Corp, Toyota Motor Corp, Lawrence Berkeley Natl Lab ID MOLECULAR-BEAM EPITAXY; LOSS SPECTROSCOPY; ELECTRON-DIFFRACTION AB Energy-filtered reflection high energy electron diffraction and reflection electron energy loss spectroscopy expand the usefulness of reflection high energy electron diffraction for quantitative structure determination and surface spectroscopy during film growth. Several implementations of energy-filtered reflection high energy electron diffraction are discussed, along with the progress and prospects for structure determination. New developments in parallel detection reflection electron energy loss spectroscopy (PREELS) enable the use of this method to obtain surface-spectroscopic information in real time during thin film growth, greatly expanding the range of surface information available during growth. C1 CALTECH,JET PROP LAB,PASADENA,CA. RP Atwater, HA (reprint author), CALTECH,THOMAS J WATSON LAB APPL PHYS,PASADENA,CA 91125, USA. NR 12 TC 1 Z9 1 U1 3 U2 4 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 9128, SINGAPORE SN 0218-625X J9 SURF REV LETT JI Surf. Rev. Lett. PD JUN PY 1997 VL 4 IS 3 BP 525 EP 534 DI 10.1142/S0218625X9700050X PG 10 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA XV337 UT WOS:A1997XV33700010 ER PT J AU Miyoshi, K Wu, RLC Lanter, WC AF Miyoshi, Kazuhisa Wu, Richard L. C. Lanter, William C. TI Friction and wear of diamond like carbon on fine-grain diamond SO TRIBOLOGY LETTERS LA English DT Article DE diamond like carboncoatings; CVD diamond coatings; tribology AB Friction and wear behavior of ion-beam-deposited diamondlike carbon (DLC) films coated on chemical-vapor-deposited (CVD), fine-grain diamond coatings were examined in ultrahigh vacuum,dry nitrogen, and humid air environments. The DLC films were produced by the direct impact of an ion beam (composed of a 3 :17 mixture of Ar and CH(4)) at ion energies of 1500 and 700 eV. Sliding friction experiments were conducted with hemispherical CVD diamond pins sliding on four different carbon-base coating systems: DLC films on CVD diamond; DLC films on silicon; as-deposited, fine-grain CVD diamond; and carbon-ion-implanted, fine-grain CVD diamond on silicon. Results indicate that in ultrahigh vacuum the ion-beam-deposited DLC films on fine-grain CVD diamond (similar to the ion-implanted CVD diamond) greatly decrease both the friction and wear of fine-grain CVD diamond films and provide solid lubrication. In dry nitrogen and in humid air, ion-beam-deposited DLC films on fine-grain CVD diamond films also had a low steady-state coefficient of friction and a low wear rate. These tribological performance benefits, coupled with a wider range of coating thicknesses, led to longer endurance life and improved wear resistance for the DLC deposited on fine-grain CVD diamond in comparison to the ion-implanted diamond films. Thus, DLC deposited on fine-grain CVD diamond films can be an effective wear-resistant, lubricating coating regardless of environment. C1 [Miyoshi, Kazuhisa] NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. [Wu, Richard L. C.; Lanter, William C.] K Syst Corp, Dayton, OH 45432 USA. RP Miyoshi, K (reprint author), NASA, Lewis Res Ctr, 21000 Brookpk Rd,Mail Stop 23-2, Cleveland, OH 44135 USA. EM miyoshi@lerc.nasa-gov FU US Air Force Scientific Research through Wright Laboratory [F33615-95-2551]; K Systems Corporation FX This study was supported by US Air Force Scientific Research through Wright Laboratory under Contract F33615-95-2551 with K Systems Corporation. The authors thank Drs. M. Murakawa, S. Miyake, S. Watanabe, and S. Takeuchi of the Nippon Institute of Technology for producing the CVD diamond pin specimens; Dr. Susan L. Heidger for the Raman analysis; Ronald E. Miller for the experimental setups; and Duane J. Dixon for the scanning electron microscopy. NR 10 TC 9 Z9 9 U1 0 U2 7 PU SPRINGER/PLENUM PUBLISHERS PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1023-8883 J9 TRIBOL LETT JI Tribol. Lett. PD JUN PY 1997 VL 3 IS 2 BP 141 EP 145 DI 10.1023/A:1019160501019 PG 5 WC Engineering, Chemical; Engineering, Mechanical SC Engineering GA V17SF UT WOS:000207956200001 ER PT J AU Koch, SE OHandley, C AF Koch, SE OHandley, C TI Operational forecasting and detection of mesoscale gravity waves SO WEATHER AND FORECASTING LA English DT Article ID OBJECTIVE ANALYSIS SCHEME; SEVERE WEATHER OUTBREAK; SQUALL-LINE; NUMERICAL-SIMULATION; CONVECTIVE STORMS; EVENT; DISTURBANCES; CCOPE; ATMOSPHERE; EVOLUTION AB Mesoscale gravity waves display periods of 1-4 h, have wavelengths of 50-500 km, and can have important effects upon the sensible weather. Real-time prediction, detection, and nowcasting of these mesoscale phenomena is shown to be feasible, due to recent major advances in operational observing and modelling systems. The ability to predict the likelihood of a gravity wave event rests upon recognizing the synoptic flow pattern in which such waves are consistently found to occur The delineation of the most likely region for wave activity can be further refined by computing simple indicators of unbalanced flow and conducting a cursory search for a suitable wave ''duct'' with meso-Eta Model data. particular emphasis should be placed on propagating unbalanced fields. Whenever and wherever a suitable gravity wave environment is found, the Automated Surface Observing System pressure data should be carefully monitored for evidence of gravity wave activity. An automated gravity wave detection system is developed. It is shown that application of a time-to-space conversion adaptation of the Barnes objective analysis scheme to bandpass-filtered 5-min surface observations enables the detection of gravity waves with scales as small as 150 km and their separation from smaller-scale convective phenomena. This scheme requires accurate knowledge of the wave propagation velocity. A method is presented and successfully tested for this purpose, which is based on an adaptation of wave-ducting theory to the mesoscale model forecast fields. The proposed procedure is demonstrated with a gravity wave event that occurred during STORM-FEST. A solitary wave of depression formed as an upper-level jet streak approached an inflection axis in the diffluent height field downstream of the Rocky Mountains. This wave generation region was diagnosed from mesoscale model forecasts as being unbalanced. A wave duct was diagnosed north of a warm front in both the model forecasts and the STORM-FEST soundings over the region traversed by the observed waves. The analysed pressure and wind perturbation fields successfully portray the evolution of the gravity wave into a wave train as strong thunderstorms developed with the wave. The mesoscale model produced a gravity wave similar in most respects to that analysed prior to the development of convection. These results suggest that mesoscale gravity waves can be predicted and analysed with operationally available data and numerical model guidance. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. RP Koch, SE (reprint author), N CAROLINA STATE UNIV,DEPT MARINE EARTH & ATMOSPHER SCI,BOX 8208,RALEIGH,NC 27695, USA. NR 56 TC 49 Z9 53 U1 0 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0882-8156 J9 WEATHER FORECAST JI Weather Forecast. PD JUN PY 1997 VL 12 IS 2 BP 253 EP 281 DI 10.1175/1520-0434(1997)012<0253:OFADOM>2.0.CO;2 PG 29 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XF203 UT WOS:A1997XF20300004 ER PT J AU Hirschberg, PA Parke, MC Wash, CH Mickelinc, M Spencer, RW Thaler, E AF Hirschberg, PA Parke, MC Wash, CH Mickelinc, M Spencer, RW Thaler, E TI The usefulness of MSU3 analyses as a forecasting aid: A statistical study SO WEATHER AND FORECASTING LA English DT Article ID EXTRATROPICAL CYCLONES; TROPOPAUSE UNDULATIONS; HEIGHT TENDENCY; ANALYTIC MODEL; UNITED-STATES; CYCLOGENESIS; CIRCULATION; DIAGNOSIS; VORTICITY; ANOMALIES AB A statistical analysis is performed on a 6-month global dataset consisting of satellite-derived channel 3 Microwave Sounding Unit (MSU3) brightness temperature and various conventionally derived fields to quantify the potential usefulness of MSU3 analyses in the nowcasting and forecasting of baroclinic waves. High positive spatial and temporal correlations are obtained between the MSU3 brightness temperature and 400-100-mb thickness fields over all wavelengths in the data. Slightly lesser positive correlations are found between the MSU3 and the 200-mb temperature. The MSU3-500-mb and MSU3-50-mb height correlation results indicate a scale dependence in the hydrostatic spreading of thickness anomalies in the vertical, Most significantly, relatively high negative MSU3-500-mb height correlations for the short (less than or equal to synoptic scale) wavelength portion of the data suggest that upper-level thermal anomalies are reflected downward and that MSU3 analyses can be used to track midlevel synoptic-scale baroclinic waves. This conclusion is also supported by relatively high negative MSU3-500-mb vorticity and MSU3-dynamic tropopause correlations along the climatological storm tracks. C1 USN,POSTGRAD SCH,DEPT METEOROL,MONTEREY,CA 93943. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,EARTH SYST SCI DIV,HUNTSVILLE,AL 35812. NATL WEATHER SERV,DENVER,CO. NR 34 TC 3 Z9 3 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0882-8156 J9 WEATHER FORECAST JI Weather Forecast. PD JUN PY 1997 VL 12 IS 2 BP 324 EP 346 DI 10.1175/1520-0434(1997)012<0324:TUOMAA>2.0.CO;2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XF203 UT WOS:A1997XF20300008 ER PT J AU Chertihin, GV Andrews, L Bauschlicher, CW AF Chertihin, GV Andrews, L Bauschlicher, CW TI Reactions of laser-ablated copper atoms with dioxygen. Infrared spectra of the copper oxides CuO, OCuO, CuOCuO, and OCuOCuO and superoxide CuOO in solid argon SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID ELECTRON-SPIN-RESONANCE; TRANSITION-METAL ATOMS; GAUSSIAN-BASIS SETS; RARE-GAS MATRICES; MOLECULAR-OXYGEN; COMPLEXES; PHASE; SPECTROSCOPY; STATES; CUNO AB Laser-ablated copper atoms react directly with O-2 to make CuO (627.7 cm(-1)), and linear OCuO (823.0 cm(-1)) which are identified by copper and oxygen isotopic shifts, comparison to earlier work, and DFT frequency calculations. The highest frequency Cu-O vibration (995.3 cm(-1)) exhibits a resolved copper isotopic triplet appropriate for the vibration of two equivalent copper atoms and oxygen isotopic components consistent with DFT-calculated frequencies for the nearly linear OCuOCuO molecule. Absorptions at 970.0 and 955.1 cm(-1) are assigned to CuOCuO isomers. The simple addition product CuOO is characterized by O-O and Cu-O stretching frequencies at 1089.6 and 550.4 cm(-1), isotopic shifts, and DFT calculations. The CuOO molecule forms higher complexes (O-2)(x)CuOO readily on annealing the matrix sample. C1 UNIV VIRGINIA,DEPT CHEM,CHARLOTTESVILLE,VA 22901. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 40 TC 64 Z9 64 U1 2 U2 25 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 MAY 29 PY 1997 VL 101 IS 22 BP 4026 EP 4034 DI 10.1021/jp9701653 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XB799 UT WOS:A1997XB79900006 ER PT J AU Kuo, SC Zhang, ZY Ross, SK Klemm, RB Johnson, RD Monks, PS Thorn, RP Stief, LJ AF Kuo, SC Zhang, ZY Ross, SK Klemm, RB Johnson, RD Monks, PS Thorn, RP Stief, LJ TI Discharge flow-photoionization mass spectrometric study of HNO: Photoionization efficiency spectrum and ionization energy and proton affinity of NO SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID KINETIC DATA-BASE; AB-INITIO; HIGH-RESOLUTION; PHOTOELECTRON-SPECTROSCOPY; ELECTRONIC STATES; COUPLED-CLUSTER; SURFACES; RADICALS; THERMOCHEMISTRY; ISOMERIZATION AB Photoionization efficiency (PIE) spectra of HNO were measured over the wavelength range lambda = 110-125 nm and in the ionization threshold region, lambda = 118-124 nm, using a discharge flow-photoionization mass spectometer (DF-PIMS) apparatus coupled to a synchrotron radiation source. HNO was generated in situ by the following reaction sequence: N + NO --> N-2 + O; O + C2H4 --> CH3 + HCO; HCO + NO --> HNO + CO. The PIE spectrum displays steplike behavior near threshold and an HN-O stretching frequency in the cation of 1972 +/- 67 cm(-1). A value of 10.18(4) +/- 0.01(2) eV for the adiabatic ionization energy (IE) of HNO was obtained from photoionization thresholds, which correspond to the HNO+(X(2)A') <-- HNO(X(1)A') transition. This result is the first PIMS determination of IE(HNO). Also, an ab initio molecular orbital calculation (QCISD(T)/aug-cc-pVQZ) was performed that yields a value for IE(HNO) of 10.186 +/- 0.050 eV, There is good agreement between the experimental and the theoretical values for IE(HNO) reported here and that from a recent photoelectron spectroscopy study. The present experimental value for IE(HNO) was employed along with other, known thermodynamic quantities to obtain values for the heat of formation of the HNO cation and the absolute proton affinity of NO: Delta(f)H degrees(298)(HNO+) = 1089.73 +/- 1.18 kJ mol(-1) (Delta(f)H degrees(0)(HNO+) = 1092.65 +/- 1.18 kJ mol(-1)); PA(298)(NO) = 531.55 +/- 1.26 kJ mol(-1) (PA(0)(NO) = 526.12 +/- 1.26 kJ mol(-1)). C1 BROOKHAVEN NATL LAB,UPTON,NY 11973. NATL INST STAND & TECHNOL,DIV PHYS & CHEM PROPERTIES,GAITHERSBURG,MD 20899. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RI Monks, Paul/H-6468-2016 OI Monks, Paul/0000-0001-9984-4390 NR 77 TC 16 Z9 16 U1 1 U2 3 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 MAY 29 PY 1997 VL 101 IS 22 BP 4035 EP 4041 DI 10.1021/jp9705941 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XB799 UT WOS:A1997XB79900007 ER PT J AU Brentner, KS AF Brentner, KS TI An efficient and robust method for predicting helicopter high-speed impulsive noise SO JOURNAL OF SOUND AND VIBRATION LA English DT Article; Proceedings Paper CT AIAA 34th Aerospace Sciences Meeting and Exhibit CY JAN 15-19, 1996 CL RENO, NV SP Amer Inst Aeronaut & Astronaut ID ROTOR AB A new formulation for the Ffowcs Williams-Hawkings quadrupole source is presented for helicopter-rotor noise prediction. The formulation is a far-field approximation which is exact for a far-field in-plane observer. The approximation is new and unique in that no further approximation of the quadrupole source strength is made and integrands with 1/r(2) and 1/r(3) dependence are retained. This paper focuses on the development of a retarded-time formulation in which time derivatives are analytically taken inside the integrals to avoid unnecessary computational work when the observer is in motion (e.g., the wind tunnel case). The new quadrupole formulation is similar to Farassat's thickness and loading formulation 1A. Because it is a retarded-time formulation, the current implementation is intentionally limited to subsonic source motion to avoid singular integrals. Quadrupole noise prediction is carried out in two parts: a preprocessing stage in which the previously computed flow field is integrated in the direction normal to the rotor disk, and a noise computation stage in which quadrupole surface integrals are evaluated for a particular observer position. Preliminary predictions for hover and forward flight agree well with experimental data. The method is robust and requires computer resources comparable to thickness and loading noise prediction. (C) 1997 Academic Press Limited. RP Brentner, KS (reprint author), NASA,LANGLEY RES CTR,FLUID MECH & ACOUST DIV,HAMPTON,VA 23681, USA. NR 26 TC 28 Z9 29 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 MAY 29 PY 1997 VL 203 IS 1 BP 87 EP 100 DI 10.1006/jsvi.1996.0834 PG 14 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA XB646 UT WOS:A1997XB64600006 ER PT J AU Sahu, KC Livio, M Petro, L Macchetto, FD vanParadijs, J Kouveliotou, C Fishman, GJ Meegan, CA Groot, PJ Galama, T AF Sahu, KC Livio, M Petro, L Macchetto, FD vanParadijs, J Kouveliotou, C Fishman, GJ Meegan, CA Groot, PJ Galama, T TI The optical counterpart to gamma-ray burst GRB970228 observed using the Hubble Space Telescope SO NATURE LA English DT Article ID NEUTRON-STAR AB Although more than 2,000 astronomical gamma-ray bursts (GRBs) have been detected, and numerous models proposed to explain their occurrence(1), they have remained enigmatic owing to the lack of an obvious counterpart at other wavelengths(2-5). The recent groundbased detection(6,7) of a transient optical source in the vicinity of GRB970228 (refs 8-11) may therefore have provided a breakthrough. The optical counterpart appears to be embedded in an extended source which, if a galaxy as has been suggested(7,12), would lend weight to those models that place GRBs at cosmological distances. Here we report observations using the Hubble Space Telescope of the transient counterpart and extended source 26 and 39 days after the initial gamma-ray outburst. We find that the counterpart has faded since the initial detection (and continues to fade), but the extended source exhibits no significant change in brightness between the two dates of the observations reported here, The size and apparent constancy of the extended source imply that it is extragalactic, but its faintness makes a definitive statement about its nature difficult. Nevertheless, the decay profile of the transient source is consistent with a popular impulsive-fireball model(13), which assumes a merger between two neutron stars in a distant galaxy. C1 UNIV AMSTERDAM, ASTRON INST ANTON PANNEKOEK, NL-1098 SJ AMSTERDAM, NETHERLANDS. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35812 USA. CTR HIGH ENERGY ASTROPHYS, NL-1098 SJ AMSTERDAM, NETHERLANDS. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. 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 NR 43 TC 153 Z9 156 U1 0 U2 1 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD MAY 29 PY 1997 VL 387 IS 6632 BP 476 EP 478 DI 10.1038/387476a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XB479 UT WOS:A1997XB47900040 ER PT J AU Galama, T Groot, PJ vanParadijs, J Kouveliotou, C Robinson, CR Fishman, GJ Meegan, CA Sahu, KC Livio, M Petro, L Macchetto, FD Heise, J Zand, JI Strom, RG Telting, J Rutten, RGM Pettini, M Tanvir, N Bloom, J AF Galama, T Groot, PJ vanParadijs, J Kouveliotou, C Robinson, CR Fishman, GJ Meegan, CA Sahu, KC Livio, M Petro, L Macchetto, FD Heise, J Zand, JI Strom, RG Telting, J Rutten, RGM Pettini, M Tanvir, N Bloom, J TI The decay of optical emission from the gamma-ray burst GRB970228 SO NATURE LA English DT Article ID UBVRI PHOTOMETRY; CALIBRATION; SYSTEM AB The origin of gamma-ray bursts has been one of the great unsolved mysteries in high-energy astrophysics for almost 30 years. The recent discovery of fading sources at X-ray(1) and optical(2,3) wavelengths coincident with the location of the gamma-ray burst GRB970228 therefore provides an unprecedented opportunity to probe the nature of these high-energy events. The optical counterpart appears to be a transient point source embedded in a region of extended nebulosity(3-6), the latter having been tentatively identified as a high-redshift galaxy(3). This would seem to favour models that place gamma-ray bursts at cosmological distances, although a range of mechanisms for producing the bursts is still allowed. A crucial piece of information for distinguishing between such models is how the brightness of the optical counterpart evolves with time. Here we re-evaluate the existing photometry of the optical counterpart of GRB970228 to construct an optical light curve for the transient event. We find that between 21 hours and six days after the burst, the R-band brightness decreased by a factor of similar to 40, with any subsequent decrease in brightness occurring at a much slower rate. As the point source faded, it also became redder. The initial behaviour of the source appears to be consistent with the 'fireball' model(7), but the subsequent decrease in the rate of fading may prove harder to explain. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. 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. SRON,SPACE RES LAB,NL-3584 CA UTRECHT,NETHERLANDS. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. NETHERLANDS FDN RES ASTRON,NL-7990 AA DWINGELOO,NETHERLANDS. ISSAC NEWTON GROUP,SANTA CRUZ PALMA 38780,TENERIFE,SPAIN. ROYAL GREENWICH OBSERV,CAMBRIDGE CB3 0EZ,ENGLAND. UNIV CAMBRIDGE,INST ASTRON,CAMBRIDGE CB3 0HA,ENGLAND. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016 OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X NR 23 TC 74 Z9 77 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD MAY 29 PY 1997 VL 387 IS 6632 BP 479 EP 481 DI 10.1038/387479a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XB479 UT WOS:A1997XB47900041 ER PT J AU Mazur, V Williams, E Boldi, R Maier, L Proctor, DE AF Mazur, V Williams, E Boldi, R Maier, L Proctor, DE TI Initial comparison of lightning mapping with operational time-of-arrival and interferometric systems SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VHF RADIO PICTURES; FLASHES; THUNDERSTORMS AB The mapping of lightning radiation sources produced by the operational Time-of-Arrival National Aeronautics and Space Administration/Lightning Detection and Ranging (NASA/LDAR) system is compared with that of the Interferometric French Office National D'Etudes et de Recherches Aerospatiales (ONERA-3D) system. The comparison comprises lightning activity in three Florida storms and also individual flashes in one of these storms. Although limited in scope, the comparison and analysis show a significant difference in the representation of lighting radiation by each mapping system. During the duration of a flash, the LDAR data show a continuity in time and a three-dimensional structure of radiation sources. The ONERA-3D radiation source data are more intermittent in time and have a more two-dimensional structure. The distinction between the radiation sources mapped by the two systems is also reflected in the difference between their propagation speeds, 10(4)-10(5) m s(-1), estimated by the LDAR system, and 10(7)-10(8) m s(-1), estimated by the ONERA-3D system. We infer that this difference occurs because most of the radiation sources mapped with LDAR are associated with virgin breakdown processes typical of slowly propagating negative leaders. On the other hand, most of the radiation sources mapped with ONERA-3D are produced by fast intermittent negative breakdown processes typical of dart leaders and K changes as they traverse the previously ionized channels. Thus each operational system may emphasize different stages of the lightning flash, but neither appears to map the entire flash. C1 MIT, LINCOLN LAB, LEXINGTON, MA 02173 USA. NASA, KENNEDY SPACE CTR, KENNEDY SPACE CTR, FL 32899 USA. MIT, RALPH M PARSONS LAB, CAMBRIDGE, MA 02139 USA. RP Mazur, V (reprint author), NOAA, NATL SEVERE STORMS LAB, NORMAN, OK 73069 USA. NR 20 TC 41 Z9 46 U1 3 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 MAY 27 PY 1997 VL 102 IS D10 BP 11071 EP 11085 DI 10.1029/97JD00174 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XB488 UT WOS:A1997XB48800005 ER PT J AU Polyak, I North, GR Kucera, PA Smith, NR AF Polyak, I North, GR Kucera, PA Smith, NR TI Variability of the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment rain rate observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID COARE AB This paper presents the description of the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) rain rate database and its different spatial and temporal variability characteristics. Accuracy and reliability of this database are evaluated with the position of the appropriateness of its use for the practical (ground truth, beam filling error for the Tropical Rainfall Measuring Mission) and theoretical (spectral estimation) problems, The following is shown in this paper: the concentration of a significant power in the origin of the frequency axis in the temporal spectra; the existence of a diurnal cycle (which has a range of variation of about 1.43 to 2.03 mm/h); the distinction between the north-south and east-west transport of rain, reflected in the two-dimensional spectrum and correlation function of the spatial field, and character of its anisotropy; the scales of the differences between the corresponding estimates of the TOGA and Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE) data. The documentation of the TOGA COARE database is given, Methodology and software (in IDL and Fortran languages) for management of the TOGA COARE database system and for estimating of different variability statistics were developed. The results obtained can be used for choosing any subset appropriate for the particular rain analysis study, for rain modeling, for comparison with corresponding estimates of other sources of data (satellite or simulated by physical models), and for solving some other scientific and engineering problems connected with rain measurements and modeling. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. TEXAS A&M UNIV, COLL GEOSCI & MARITIME STUDIES, CLIMATE SYST RES PROGRAM, COLLEGE STN, TX 77843 USA. RI North, Gerald/G-1019-2011 NR 10 TC 2 Z9 2 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 MAY 27 PY 1997 VL 102 IS D10 BP 11103 EP 11111 DI 10.1029/97JD00610 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XB488 UT WOS:A1997XB48800007 ER PT J AU Pinker, RT Ferrare, RA Karnieli, A Aro, TO Kaufman, YJ Zangvil, A AF Pinker, RT Ferrare, RA Karnieli, A Aro, TO Kaufman, YJ Zangvil, A TI Aerosol optical depths in a semiarid region SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RADIATION BUDGET; DUST; VARIABILITY; SCATTERING; CLIMATE; CLOUD; SUN AB To monitor changes in surface conditions from space requires information on the state of the atmosphere to correct for atmospheric effects in the remotely sensed signal. The least observed and most variable atmospheric parameters are aerosols. Of particular interest are changes of surface conditions in areas where desert encroachment is of concern An effort was initiated at one of such locations to monitor atmospheric conditions from the ground and surface conditions from space. In this paper we present results only on the ground observations of the aerosol optical depths, in particular their annual and diurnal variations, in the context of prevailing synoptic conditions. C1 UNIV ILORIN, DEPT PHYS, ILORIN, NIGERIA. NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. BEN GURION UNIV NEGEV, JACOB BLAUSTEIN INST DESERT RES, IL-84993 SEDE BOQER, ISRAEL. RP Pinker, RT (reprint author), UNIV MARYLAND, DEPT METEOROL, COLLEGE PK, MD 20742 USA. RI Pinker, Rachel/F-6565-2010 NR 31 TC 18 Z9 22 U1 2 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1997 VL 102 IS D10 BP 11123 EP 11137 DI 10.1029/96JD03589 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XB488 UT WOS:A1997XB48800009 ER PT J AU Criminale, WO Jackson, TL Lasseigne, DG Joslin, RD AF Criminale, WO Jackson, TL Lasseigne, DG Joslin, RD TI Perturbation dynamics in viscous channel flows SO JOURNAL OF FLUID MECHANICS LA English DT Article ID BOUNDARY-LAYER; ENERGY GROWTH; SHEAR-FLOW; DISTURBANCES; INSTABILITY; SIMULATION; STABILITY; SPECTRUM; EQUATION AB Plane viscous channel flows are perturbed and the ensuing initial-value problems are investigated in detail. Unlike traditional methods where travelling wave normal modes are assumed as solutions, this work offers a means whereby arbitrary initial input can be specified without having to resort to eigenfunction expansions. The full temporal behaviour, including both early-time transients and the long-time asymptotics, can be determined for any initial small-amplitude three-dimensional disturbance. The bases for the theoretical analysis are: (a) linearization of the governing equations; (b) Fourier decomposition in the spanwise and streamwise directions of the flow; and (c) direct numerical integration of the resulting partial differential equations. All of the stability criteria that are known for such flows can be reproduced. Also, optimal initial conditions measured in terms of the normalized energy growth can be determined in a straightforward manner and such optimal conditions clearly reflect transient growth data that are easily determined by a rational choice of a basis for the initial conditions. Although there can be significant transient growth for subcritical values of the Reynolds number, it does not appear possible that arbitrary initial conditions will lead to the exceptionally large transient amplitudes that have been determined by optimization of normal modes when used without regard to a particular initial-value problem. The approach is general and can be applied to other classes of problems where only a finite discrete spectrum exists (e.g. the Blasius boundary layer). Finally, results from the temporal theory are compared with the equivalent transient test case in the spatially evolving problem with the spatial results having been obtained using both a temporally and spatially accurate direct numerical simulation code. C1 NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681. OLD DOMINION UNIV,DEPT MATH & STAT,NORFOLK,VA 23529. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Criminale, WO (reprint author), UNIV WASHINGTON,DEPT APPL MATH,SEATTLE,WA 98195, USA. NR 35 TC 25 Z9 25 U1 0 U2 1 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD MAY 25 PY 1997 VL 339 BP 55 EP 75 DI 10.1017/S0022112097005235 PG 21 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XC837 UT WOS:A1997XC83700003 ER PT J AU Short, M Quirk, JJ AF Short, M Quirk, JJ TI On the nonlinear stability and detonability limit of a detonation wave for a model three-step chain-branching reaction SO JOURNAL OF FLUID MECHANICS LA English DT Article AB The nonlinear stability of a pulsating detonation wave driven by a three-step chain-branching reaction is studied. The reaction model consists sequentially of a chain-initiation step and a chain-branching step, both governed by Arrhenius kinetics, followed by a temperature-independent chain-termination step. The model mimics the essential dynamics of a real chain-branching chemical system, but is sufficiently idealized that a theoretical analysis of the instability is possible. We introduce as a bifurcation parameter the chain-branching cross-over temperature (T-B), which is the temperature at which the chain-branching and chain-termination rates are equal. In the steady detonation structure, this parameter controls the ratio of the chain-branching induction length to the length of the recombination zone. When T-B is at the lower end of the range studied, the steady detonation structure, which is dominated by the temperature-independent recombination zone, is found to be stable. Increasing T-B increases the length of the chain-branching induction region relative to the length of the recombination zone, and a critical value of T-B is reached where the detonation becomes unstable, with the detonation shock pressure evolving as a single-mode low-frequency pulsating oscillation. This single-mode nonlinear oscillation becomes progressively less stable as T-B is increased further, persisting as the longterm dynamical behaviour for a significant range of T-B before eventually undergoing a period-doubling bifurcation to a two-mode oscillation. Further increases in T-B lead to a chaotic behaviour, where the detonation shock pressure history consists of a sequence of substantive discontinuous jumps, followed by lower-amplitude continuous oscillations. Finally, for further increases in T-B a detonability limit is reached, where during the early onset of the detonation instability, the detonation shock temperature drops below the chain-branching cross-over temperature causing the wave to quench. C1 UNIV BRISTOL, SCH MATH, BRISTOL BS8 1TW, AVON, ENGLAND. NASA, LANGLEY RES CTR, INST COMP APPLICAT SCI & ENGN, HAMPTON, VA 23681 USA. NR 31 TC 79 Z9 84 U1 0 U2 8 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 EI 1469-7645 J9 J FLUID MECH JI J. Fluid Mech. PD MAY 25 PY 1997 VL 339 BP 89 EP 119 DI 10.1017/S002211209700503X PG 31 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XC837 UT WOS:A1997XC83700005 ER PT J AU Christensen, PR Pearl, JC AF Christensen, PR Pearl, JC TI Initial data from the Mars Global Surveyor thermal emission spectrometer experiment: Observations of the Earth SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID INFRARED INTERFEROMETER AB The thermal emission spectrometer (TES) on the Mars Global Surveyor spacecraft acquired observations of the Earth from a distance of 4.7 million km for instrument performance characterization on November 24, 1996. The data were calibrated using an internal reference surface and deep space in a manner identical to that which will be used in;Mars orbit, and scaled to account for the fact the Earth filled only 9.3% of the field of view. These first, calibrated, in-flight spectra from the TES confirm the expected instrument performance and radiometric accuracy and precision. The data provide the first known whole-disk thermal infrared spectral observations of the Earth. These spectra represent how an Earth-like planet would appear during a search for ''extrasolar'' planets. Spectral features in the Earth's atmosphere are readily apparent; CO2 (centered at 668 cm(-1)), ozone (1000-1075 cm(-1)), and water vapor (200-550 and 1260-1650 cm(-1)) absorptions are evident. Radiation at the center of the CO2 band arises mainly from the lower stratosphere; near 650 and 700 cm(-1) from near the tropopause; and further into the band wings from the troposphere and surface. Thus, in the disk-averaged sense, the spectrum indicates a warm stratosphere above a tropopause somewhat colder than 215 K, in good agreement with results from similar instruments previously flown in low Earth orbit. The atmospheric window between approximately 800 and 1200 cm(-1) is relatively featureless, as expected, given the observing geometry centered over the Pacific Ocean and the partial obscuration by clouds. The derived window brightness temperature, assuming an emissivity of unity, is 270 K, a reasonable average temperature of the ocean surface, the polar regions, and the cloud tops, especially given the uncertainties in the exact scaling to account for the fact that the Earth did not fill the field of view. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP ARIZONA STATE UNIV, DEPT GEOL, TEMPE, AZ 85287 USA. NR 9 TC 35 Z9 35 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9097 EI 2169-9100 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAY 25 PY 1997 VL 102 IS E5 BP 10875 EP 10880 DI 10.1029/97JE00637 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XB640 UT WOS:A1997XB64000001 ER PT J AU Stoker, CR Bullock, MA AF Stoker, CR Bullock, MA TI Organic degradation under simulated Martian conditions SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID VIKING BIOLOGY EXPERIMENTS; LIFE DETECTION EXPERIMENT; MARS; SOIL; ATMOSPHERE; MODEL; REGOLITH; SURFACE; SEARCH; GLASS AB We report on laboratory experiments which simulate the breakdown of organic compounds under Martian surface conditions. Chambers containing Mars-analog soil mixed with the amino acid glycine were evacuated and filled to 100 mbar pressure with a Martian atmosphere gas mixture and then irradiated with a broad spectrum Xe lamp. Headspace gases were periodically withdrawn and analyzed via gas chromatography for the presence of organic gases expected to be decomposition products of the glycine. The quantum efficiency for the decomposition of glycine by light at wavelengths from 2000 to 2400 Angstrom was measured to be 1.46 +/- 1.0 x 10(-6) molecules/photon. Scaled to Mars, this represents an organic destruction rate of 2.24 +/- 1.2 x 10(-4) g of C m(-2) yr(-1). We compare this degradation rate with the rate that organic compounds are brought to Mars as a result of meteoritic infall to show that organic compounds are destroyed on Mars at rates far exceeding the rate that they are deposited by meteorites. Thus the fact that no organic compounds were found on Mars by the Viking Lander Gas Chromatograph Mass Spectrometer experiment can be explained without invoking the presence of strong oxidants in the surface soils. The organic destruction rate may be considered as an upper bound for the globally averaged biomass production rate of extant organisms at the surface of Mars. This upper bound is comparable to the slow growing cryptoendolithic microbial communities found in dry Antarctica deserts. Finally, comparing these organic destruction rates to recently reported experiments on the stability of carbonate on the surface of Mars, we find that organic compounds may currently be more stable than calcite. C1 UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. UNIV COLORADO,DEPT ASTROPHYS PLANETARY & ATMOSPHER SCI,BOULDER,CO 80309. RP Stoker, CR (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,M-S 245-3,MOFFETT FIELD,CA 94035, USA. NR 46 TC 80 Z9 81 U1 4 U2 18 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 MAY 25 PY 1997 VL 102 IS E5 BP 10881 EP 10888 DI 10.1029/97JE00667 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XB640 UT WOS:A1997XB64000002 PM 11541744 ER PT J AU Knibbe, WJJ deHaan, JF Hovenier, JW Travis, LD AF Knibbe, WJJ deHaan, JF Hovenier, JW Travis, LD TI A biwavelength analysis of Pioneer Venus polarization observations SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SCATTERING; LIGHT AB A new method for analyzing Pioneer Venus polarimetry data on a pixel-wise basis is presented. Quasi-simultaneous observations at two wavelengths (550 and 935 nm) are combined and compared with results of multiple scattering calculations. In this manner, hypotheses about particle size distributions in the upper part of the Venus atmosphere are tested. Particles composed of a sulfuric acid solution are considered, and a distinction is made between large and small particles, called cloud and haze particles, respectively. Three model atmospheres have been investigated: (1) a single layer containing cloud particles, (2) a single layer containing a mixture of cloud and haze particles, and (3) a two layer model with an upper layer composed of haze particles and a lower layer containing cloud particles. It is found that all three models agree with the observations at phase angles near 20 degrees, but that the first model cannot be made to agree with the observations for phase angles near 90 degrees. This confirms the presence of haze particles in the Venus atmosphere found earlier by Kawabata et al. [1980]. We find that the haze particles may be situated either above or mixed within the main cloud deck of Venus. We derived effective radii between 0.85 and 1.15 mu m for the cloud particles, and effective radii of 0.2 or 0.3 mu m for the haze particles. When the haze particles are situated above the cloud layer, the haze optical thickness can take values of up to 0.6 at 550 nm. When the haze particles are mixed with the cloud particles, their contribution to the total atmospheric scattering coefficient at 550 nm can become as large as 70%. C1 NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. RP FREE UNIV AMSTERDAM, DEPT PHYS & ASTRON, DE BOELELAAN 1081, NL-1081 HV AMSTERDAM, NETHERLANDS. NR 32 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9097 EI 2169-9100 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAY 25 PY 1997 VL 102 IS E5 BP 10945 EP 10957 DI 10.1029/97JE00312 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XB640 UT WOS:A1997XB64000007 ER PT J AU Greeley, R Blumberg, DG McHone, JF Dobrovolskis, A Iversen, JD Lancaster, N Rasmussen, KR Wall, SD White, BR AF Greeley, R Blumberg, DG McHone, JF Dobrovolskis, A Iversen, JD Lancaster, N Rasmussen, KR Wall, SD White, BR TI Applications of spaceborne radar laboratory data to the study of aeolian processes SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GENERAL-CIRCULATION MODELS; NAMIB SAND SEA; SURFACE-ROUGHNESS; JULY CIRCULATION; CLIMATE; CALIBRATION; TRANSPORT; BIOSPHERE; SAR AB Aerodynamic roughness (z(0)) is an important parameter in studies of sand and dust transport, as well as atmospheric circulation models. Aerodynamic roughness is a function of the size and spacing of surface roughness elements and is typically determined at point locations in the field from wind velocity profiles. Because field measurements require complex logistics, z(0) values have been obtained for very few localities. If radar can be used to map z(0), estimates can be obtained for large areas. In addition, because aerodynamic roughness can change in response to surface processes (e.g., flooding of alluvial surfaces), radar remote sensing could obtain new measurements on short timescales. Both z(0) and the radar backscatter coefficient sigma(0) are dependent on topographic roughness at the submeter scale, and correlation between these two parameters was developed based on radar data obtained from aircraft (AIRSAR). The Spaceborne Radar Laboratory (SRL) afforded the opportunity to test the correlation for data obtained from orbit. SRL data for sites in Death Valley, California; Lunar Lake, Nevada; and Gobabeb, Namibia, were correlated with wind data and compared with previous radar z(0) relations. Correlations between sigma(0) and z(0) for L band (lambda = 24 cm) HV (H, vertically and V, vertically polarized modes) L band HH, and C band (lambda = 5.6 cm) HV compare favorably with previous studies. Based on these results, maps of z(0), values were derived from SRL data for each site, demonstrating the potential to map z(0) for large vegetation-free areas from orbit using radar systems. C1 ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. IOWA STATE UNIV,DEPT AEROSP ENGN,AMES,IA 50011. UNIV NEVADA,DESERT RES INST,QUATERNARY SCI CTR,RENO,NV 89506. AARHUS UNIV,INST GEOL,DK-8000 AARHUS C,DENMARK. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV CALIF DAVIS,DEPT MECH & AERONAUT ENGN,DAVIS,CA 95616. RI BLUMBERG, DAN/F-1285-2012 OI BLUMBERG, DAN/0000-0001-9337-1617 NR 39 TC 40 Z9 41 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAY 25 PY 1997 VL 102 IS E5 BP 10971 EP 10983 DI 10.1029/97JE00518 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XB640 UT WOS:A1997XB64000009 ER PT J AU Marder, SR Torruellas, WE BlanchardDesce, M Ricci, V Stegeman, GI Gilmour, S Bredas, JL Li, J Bublitz, GU Boxer, SG AF Marder, SR Torruellas, WE BlanchardDesce, M Ricci, V Stegeman, GI Gilmour, S Bredas, JL Li, J Bublitz, GU Boxer, SG TI Large molecular third-order optical nonlinearities in polarized carotenoids SO SCIENCE LA English DT Article ID POLARIZABILITIES; SUSCEPTIBILITY; GENERATION; POLYENES; LENGTH; BETA AB Garito and cc-workers have suggested a mechanism to dramatically increase the second hyperpolarizability, gamma, in linear pi-electron-conjugated molecules. Polarization is introduced that leads to a difference between the dipole moments of the molecule's ground state and excited state. Here a series of carotenoids was examined that had increasing intramolecular charge transfer (ICT) from the polyenic chain to the acceptor moiety in the ground state, and gamma was measured for these compounds as a function of wavelength by third-harmonic generation. The compound with the greatest ICT exhibited a 35-fold enhancement of gamma(max) (the gamma measured at the peak of the three-photon resonance) relative to the symmetric molecule beta-carotene, which itself has one of the largest third-order nonlinearities known. Stark spectroscopic measurements revealed the existence of a large difference dipole moment, Delta mu, between the ground and excited state. Quantum-chemical calculations underline the importance of interactions involving states with large Delta mu. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV CENT FLORIDA,CTR RES EDUC OPT & LASERS,ORLANDO,FL 32816. ECOLE NORMALE SUPER,DEPT CHIM,URA 1679,CNRS,F-75231 PARIS 05,FRANCE. UNIV MONS,CTR RES MOL ELECT & PHOTON,B-7000 MONS,BELGIUM. STANFORD UNIV,DEPT CHEM,STANFORD,CA 94305. RP Marder, SR (reprint author), CALTECH,BECKMAN INST,PASADENA,CA 91125, USA. RI Bredas, Jean-Luc/A-3431-2008 OI Bredas, Jean-Luc/0000-0001-7278-4471 NR 22 TC 285 Z9 292 U1 3 U2 31 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 23 PY 1997 VL 276 IS 5316 BP 1233 EP 1236 DI 10.1126/science.276.5316.1233 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XA497 UT WOS:A1997XA49700035 PM 9157876 ER PT J AU Anderson, JD Lau, EL Sjogren, WL Schubert, G Moore, WB AF Anderson, JD Lau, EL Sjogren, WL Schubert, G Moore, WB TI Europa's differentiated internal structure: Inferences from two Galileo encounters SO SCIENCE LA English DT Article ID GRAVITY-FIELD; TRACKING DATA; SATELLITES; JUPITER AB Doppler data generated with the Galileo spacecraft's radio carrier wave during two Europa encounters on 19 December 1996 (E4) and 20 February 1997 (E6) were used to measure Europa's external gravitational field. The measurements indicate that Europa has a predominantly water ice-liquid outer shell about 100 to 200 kilometers thick and a deep interior with a density in excess of about 4000 kilograms per cubic meter. The deep interior could be a mixture of metal and rock or it could consist of a metal core with a radius about 40 percent of Europa's radius surrounded by a rock mantle with a density of 3000 to 3500 kilograms per cubic meter. The metallic core is favored if Europa has a magnetic field. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095. RP Anderson, JD (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 17 TC 92 Z9 96 U1 0 U2 10 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 23 PY 1997 VL 276 IS 5316 BP 1236 EP 1239 DI 10.1126/science.276.5316.1236 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XA497 UT WOS:A1997XA49700036 PM 9157877 ER PT J AU Kivelson, MG Khurana, KK Joy, S Russell, CT Southwood, DJ Walker, RJ Polanskey, C AF Kivelson, MG Khurana, KK Joy, S Russell, CT Southwood, DJ Walker, RJ Polanskey, C TI Europa's magnetic signature: Report from Galileo's pass on 19 December 1996 SO SCIENCE LA English DT Article ID FIELD AB On 19 December 1996 as Galileo passed close to Jupiter's moon, Europa, the magnetometer measured substantial departures from the slowly Varying background field of Jupiter's magnetosphere. Currents coupling Europa to Jupiter's magnetospheric plasma could produce perturbations of the observed size. However, the trend of the field perturbations is here modeled as the signature of a Europa-centered dipole moment whose maximum surface magnitude is similar to 240 nanotesla, giving a rough upper limit to the internal field. The dipole orientation is oblique to Europa's spin axis. This orientation may not be probable for a field generated by a core dynamo, but higher order multipoles may be important as they are at Uranus and Neptune. Although the data can be modeled as contributions of an internal field of Europa, they do not confirm its existence. The dipole orientation is also oblique to the imposed field of Jupiter and thus not directly produced as a response to that field. Close to Europa, plasma currents appear to produce perturbations with scale sizes that are smalt compared with a Europa radius. C1 UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT PHYS,LONDON SW7 2BZ,ENGLAND. JET PROPULS LAB,PASADENA,CA 91109. RP Kivelson, MG (reprint author), UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095, USA. RI Kivelson, Margaret/I-9019-2012; OI Kivelson, Margaret/0000-0003-3859-8581; Russell, Christopher/0000-0003-1639-8298 NR 14 TC 62 Z9 63 U1 1 U2 7 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 23 PY 1997 VL 276 IS 5316 BP 1239 EP 1241 DI 10.1126/science.276.5316.1239 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XA497 UT WOS:A1997XA49700037 PM 9157878 ER PT J AU Muller, HSP Cohen, EA AF Muller, HSP Cohen, EA TI Dibromine monoxide, Br2O: The rotational spectrum and molecular properties SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID MILLIMETER-WAVE SPECTRUM; HYPERFINE CONSTANTS; BROMINE; MOMENT; HOBR AB The rotational spectra of (Br2O)-Br-79, (BrOBr)-Br-79-Br-81, and (Br2O)-Br-81 in their ground vibrational states as well as (BrOBr)-Br-79-Br-81 in its v(2)=1 state have been studied in selected regions between 90 and 523 Transitions involving a large range of quantum numbers, 6 less than or equal to J less than or equal to 123 and 0 less than or equal to K-a less than or equal to 12, have been observed permitting precise rotational and a large set of centrifugal distortion constants to be determined. All isotopic species as well as the excited state data were fit simultaneously. Ground-state effective and average structural parameters as well as an estimate of the equilibrium structure have been derived. The quartic distortion constants were used for a calculation of the harmonic force field. The complete quadrupole tensor has been determined. Its diagonalization reveals a largely covalent BrO bond with little pi-bonding. The derived properties of Br2O an compared with those of related compounds such as Cl2O, HOBr, and HOCl. (C) 1997 American Institute of Physics. RP Muller, HSP (reprint author), CALTECH,JET PROP LAB,MAIL STOP 183-301,PASADENA,CA 91109, USA. OI Mueller, Holger/0000-0002-0183-8927 NR 50 TC 20 Z9 20 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD MAY 22 PY 1997 VL 106 IS 20 BP 8344 EP 8354 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XA041 UT WOS:A1997XA04100006 ER PT J AU Gawronski, W AF Gawronski, W TI Almost-balanced structural dynamics SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID MODEL-REDUCTION; MULTIVARIABLE SYSTEMS; SENSOR PLACEMENT; SPACE STRUCTURES; LINEAR-SYSTEMS; CONTROLLABILITY; ACTUATOR; OBSERVABILITY; SELECTION AB Analytical models and experimentally derived models are often represented in the modal co-ordinates. The modal models include natural modes and their displacements; The scaling of the modes is arbitrary, and thus the scaling factor can be freely chosen. By the proper choice of the scaling factor one obtains controllability and observability grammians of a structure that are almost equal, and the system model is almost balanced. This new model is given either in the form of a second order differential equation or in state space representation. The properties of the almost-balanced modes and structures are derived, including its H-2, H-infinity, and Hankel norms. The norms of the modes and of the system are expressed in terms of the modal parameters, such as natural frequencies, modal damping, and input and output gains. The properties of the almost balanced structure are used to reduce the model. In particular, the H-2 H-infinity and Hankel system norms are used to evaluate and to minimize the reduction error. Next, the method of placement of actuators or sensors in the almost-balanced co-ordinates is presented. The norm of the almost-balanced mode with a set of actuators (or sensors) is the root-mean-square sum of the norms of this mode for each single actuator (or sensor). Using this property one finds a specified number of actuator or sensor locations such that the system performance evaluated at these locations is close to that of the system with a larger set of candidate locations. (C) 1997 Academic Press Limited. RP Gawronski, W (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 27 TC 6 Z9 6 U1 0 U2 2 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 MAY 22 PY 1997 VL 202 IS 5 BP 669 EP 687 DI 10.1006/jsvi.1996.0847 PG 19 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA XB328 UT WOS:A1997XB32800005 ER PT J AU Charnley, SB Latter, WB AF Charnley, SB Latter, WB TI Methane in oxygen-rich circumstellar envelopes: A search for CH3OH and CCH SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE molecular processes; circumstellar matter; stars, late-type ID CARBON-BEARING MOLECULES; 1ST DETECTION; O-RICH; MILLIMETER; FORMALDEHYDE; CHEMISTRY; SHELLS; GIANTS; STARS AB We have searched for rotational emission from CH3OH and CCH molecules in several oxygen-rich circumstellar envelopes known to display HCN emission. We find no evidence for emission from either molecule. When compared with theoretical models, our upper limits on CH3OH and CCH in IRC+10011, TX Cam and IK Tau appear to rule out the hypothesis that the unexpected presence of HCN and other carbon-bearing molecules in these outflows is due to a substantial abundance of methane. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. RP Charnley, SB (reprint author), UNIV CALIF BERKELEY,DEPT ASTRON,601 CAMPBELL HALL,BERKELEY,CA 94720, USA. RI Charnley, Steven/C-9538-2012 NR 24 TC 13 Z9 13 U1 0 U2 0 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 MAY 21 PY 1997 VL 287 IS 3 BP 538 EP 542 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB175 UT WOS:A1997XB17500008 ER PT J AU Ishida, M Matsuzaki, K Fujimoto, R Mukai, K Osborne, JP AF Ishida, M Matsuzaki, K Fujimoto, R Mukai, K Osborne, JP TI Detailed x-ray spectroscopy of AM Herculis with ASCA SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; binaries, close; stars, individual, AM Her; novae, cataclysmic variables; X-rays, stars ID EMISSION; EXCESS; ACCRETION; POLE AB We present the results of high-energy resolution X-ray spectroscopy of AM Herculis (Her) carried out with ASCA on 1993 September. Owing to the high sensitivity of the solid-state imaging spectrometer (SIS) down to similar to 0.4 keV, we have detected the Wien tail of the soft blackbody component during the rotational maximum phase. The rotational intensity modulation of the soft blackbody and the hard bremsstrahlung are in phase, indicating that they originate from the same accretion pole. Using Extreme Ultraviolet Explorer (EUVE) data taken simultaneously with ASCA, we find the soft excess to be as great as 17 +/- 7 if we approximate the soft component observed by EUVE and A,TCA with a single-temperature blackbody. From the blackbody luminosity, the fractional area is determined to be of order 10(-5). The spectrum during the rotational minimum phase is characterized by a strong fluorescent iron K alpha emission with an equivalent width of similar to 1 keV. This indicates that the hard X-ray emission during the rotational minimum phase consists entirely of scattered emission, and geometrical consideration suggests the pre-shock accretion column as a possible scattering site. The observed spectrum is softer than would be expected from optically thick scattering matter, and suggests that the column density of the scattering matter is not more than similar to 10(23) cm(-2). The high-energy resolution of the SIS has enabled us to resolve the emission lines from hydrogenic and He-like K alpha emission lines from iron. However, the emission lines from the other light elements are generally weaker than those seen in EX Hya, in which a significant post-shock cooling flow is found from the ASCA observation. The spectrum of AM Her in the bright phase is, on the other hand, consistent with a single-temperature optically thin thermal plasma spectrum with the abundance of 0.4(-0.1)(+0.2).. These facts indicate that most of the cooling part of the post-shock plasma is hidden from the observer in AM Her. A possible interpretation is that the post-shock plasma is highly inhomogeneous, and it penetrates the photosphere before it has cooled significantly. C1 UNIV TOKYO, FAC SCI, BUNKYO KU, TOKYO 113, JAPAN. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV LEICESTER, DEPT PHYS & ASTRON, LEICESTER LE1 7RH, LEICS, ENGLAND. RP INST SPACE & ASTRONAUT SCI, 3-1-1 YOSHINODAI, SAGAMIHARA, KANAGAWA 229, JAPAN. NR 35 TC 34 Z9 34 U1 0 U2 0 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0035-8711 EI 1365-2966 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAY 21 PY 1997 VL 287 IS 3 BP 651 EP 662 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB175 UT WOS:A1997XB17500021 ER PT J AU Jani, MG Barnes, NP Murray, KE AF Jani, MG Barnes, NP Murray, KE TI Flash-lamp-pumped Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF lasers: Experimental results of a single, long pulse length comparison SO APPLIED OPTICS LA English DT Article ID OPERATION AB Flash-lamp-pumped, room-temperature Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF are compared for single but long pulse operation, with pulse lengths of approximately 1.0 mu s Under similar operating conditions in normal-mode operation, a slope efficiency of 0.0331 was observed for Ho:Tm:Er:YLF compared with 0.0047 for Ho:Tm:Cr:YAG. For Q-switched operation, Ho:Tm:Er:YLF yielded a slope efficiency of 0.0075. In comparison, a slope efficiency of 0.0012 was obtained for Ho:Tm:Cr:YAG. Two methods of producing long pulse lengths are compared: pulse selection of normal-mode relaxation oscillations and Q-switcking in a long resonator. Theoretical models developed in a companion paper for normal-mode relaxation oscillations and Q-switching in quasi-four-level solid-state lasers are in agreement with the experimental results. (C) 1997 Optical Society of America. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Jani, MG (reprint author), SCI & TECHNOL CORP,HAMPTON,VA 23665, USA. NR 14 TC 10 Z9 13 U1 2 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 MAY 20 PY 1997 VL 36 IS 15 BP 3357 EP 3362 DI 10.1364/AO.36.003357 PG 6 WC Optics SC Optics GA WZ080 UT WOS:A1997WZ08000026 PM 18253349 ER PT J AU Barnes, NP Murray, KE Jani, MG AF Barnes, NP Murray, KE Jani, MG TI Flash-lamp-pumped Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF lasers: Modeling of a single, long pulse length comparison SO APPLIED OPTICS LA English DT Article ID ENERGY-TRANSFER; OPERATION AB Two methods of producing the long pulse lengths that promote efficient extraction of energy from low-gain, quasi-four-level lasers are analyzed. A long pulse length output can mitigate laser-induced damage effects and can be generated in quasi-four-level lasers by two disparate methods. One method utilizes Q-switching techniques in resonators designed to extend the pulse length and another utilizes the first pulse in a relaxation oscillation pulse train. Models for quasi-four-level lasers are derived here taking into account the nonnegligible thermal population of the lower laser level. Closed-form expressions are derived for both modes of operation of quasi-four-level laser systems so the parametric dependencies of both forms of operation become obvious, allowing facile comparison. In addition, a combined absorption and quantum efficiency, germane for flash-lamp pumping, is calculated for both Cr and Er sensitizers. Although the former has the advantage of broad absorption bands, the latter has the advantage of a quantum efficiency approaching 3. (C) 1997 Optical Society of America. C1 SCI & TECHNOL CORP,HAMPTON,VA 23665. RP Barnes, NP (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 27 TC 19 Z9 20 U1 2 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 MAY 20 PY 1997 VL 36 IS 15 BP 3363 EP 3374 DI 10.1364/AO.36.003363 PG 12 WC Optics SC Optics GA WZ080 UT WOS:A1997WZ08000027 PM 18253350 ER PT J AU Spinhirne, JD Chudamani, S Cavanaugh, JF Bufton, JL AF Spinhirne, JD Chudamani, S Cavanaugh, JF Bufton, JL TI Aerosol and cloud backscatter at 1.06, 1.54, and 0.53 mu m by airborne hard-target-calibrated Nd:YAG/methane Raman lidar SO APPLIED OPTICS LA English DT Article DE lidar; aerosol backscatter; near infrared; Raman cell ID TROPOSPHERE AB A lidar instrument was developed to make simultaneous measurements at three distinct wavelengths in the visible and near infrared at 0.532, 1.064, and 1.54 mu m with high cross-sectional calibration accuracy. Aerosol and cloud backscatter cross sections were acquired during November and December 1989 and May and June 1990 by the NASA DC-8 aircraft as part of the Global Backscatter Experiment. The instrument, methodology, and measurement results are described. A Nd:YAG laser produced 1.064- and 0.532-mu m energy. The 1.54-mu m transmitted pulse was generated by Raman-shifted downconversion of the 1.064-mu m pulse through a Raman cell pressured with methane gas. The lidar could be pointed in the nadir or zenith direction from the aircraft. A hard-target-based calibration procedure was used to obtain the ratio of the system calibration between the three wavelengths, and the absolute calibration was referenced to the 0.532-mu m lidar molecular backscatter cross section for the dearest scattering regions. From the relative wavelength calibration, the aerosol backscatter cross sections at the longer wavelengths are resolved for values as small as 1% of the molecular cross section. Backscatter measurement accuracies are better than 10(-9) (m sr)(-1) at 1.064 and 1.54 mu m. Results from the Pacific Ocean region of the multiwavelength backscatter dependence are presented. Results show extensive structure and variation for the aerosol cross sections.; The range of observed aerosol cross section is over 4 orders of magnitude, from less than 10(-9) (m sr)(-1) to greater than 10(-5) (m sr)(-1). (C) 1997 Optical Society of America. C1 SCI SYST APPLICAT INC,LANHAM,MD 20706. RP Spinhirne, JD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 19 TC 33 Z9 36 U1 1 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1997 VL 36 IS 15 BP 3475 EP 3490 DI 10.1364/AO.36.003475 PG 16 WC Optics SC Optics GA WZ080 UT WOS:A1997WZ08000043 PM 18253366 ER PT J AU Melfi, SH Evans, KD Li, J Whiteman, D Ferrare, R Schwemmer, G AF Melfi, SH Evans, KD Li, J Whiteman, D Ferrare, R Schwemmer, G TI Observation of Raman scattering by cloud droplets in the atmosphere SO APPLIED OPTICS LA English DT Article ID WATER-VAPOR; LIDAR SYSTEM; AEROSOLS; SENSITIVITY; MOISTURE; AIRBORNE; SPECTRA; LASER AB In a recent field campaign, the NASA Goddard Space Flight Center scanning Raman lidar measured, in the water vapor channel, Raman scattering from low-level clouds well in excess of 100% relative humidity. The excess scattering has been interpreted to be spontaneous Raman scattering by liquid water in the cloud droplets. A review of research on Raman scattering by microspheres indicates that the technique may provide a remote method to observe cloud liquid water. The clouds studied appear, from Mie scattering, to have two distinct layers with only the upper layer showing significant Raman scattering from liquid water in the droplets. (C) 1997 Optical Society of America. C1 UNIV MARYLAND BALTIMORE CTY,DEPT PHYS,BALTIMORE,MD 21250. HUGHES STX,LANHAM,MD 20706. RP Melfi, SH (reprint author), NASA,GODDARD SPACE FLIGHT CTR,RAMAN LIDAR TEAM,GREENBELT,MD 21250, USA. NR 33 TC 27 Z9 27 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 MAY 20 PY 1997 VL 36 IS 15 BP 3551 EP 3559 DI 10.1364/AO.36.003551 PG 9 WC Optics SC Optics GA WZ080 UT WOS:A1997WZ08000052 PM 18253375 ER PT J AU Ratra, B Sugiyama, N Banday, AJ Gorski, KM AF Ratra, B Sugiyama, N Banday, AJ Gorski, KM TI Cosmic microwave background anisotropy in COBE DMR-normalized open and flat-Lambda cold dark matter cosmogonies SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology, observations; galaxies, formation; large-scale structure of universe ID OPEN UNIVERSE; SCALE ANISOTROPY; COSMOLOGICAL CONSTANT; MASS FLUCTUATIONS; OPEN INFLATION; RADIATION; AMPLITUDE; OMEGA AB We compute the cosmic microwave background (CMB) anisotropy in open and flat-Lambda cold dark matter (CDM) cosmogonies which are normalized to the two-year DMR sky maps. Presently available CMB data are consistent with Omega(0) similar to 0.3-0.4 open models but do not strongly disfavor open models with either Omega(0) similar to 0.1 or Omega(0) similar to 1. There are indications that old (t(0) greater than or similar to 15-16 Gyr), high baryon density (Omega(B) greater than or similar to 0.0175 h(-2)), low-density (Omega(0) similar to 0.2-0.4), spatially flat Lambda models have more intermediate-scale power than is suggested by presently available CMB anisotropy observations. Accumulating CMB data should strengthen the observational discriminative power; however, a better understanding of systematic effects will be needed before it will be possible to draw robust conclusions about model viability. C1 PRINCETON UNIV,JOSEPH HENRY LABS,PRINCETON,NJ 08544. UNIV TOKYO,DEPT PHYS,TOKYO 113,JAPAN. UNIV TOKYO,RES CTR EARLY UNIVERSE,TOKYO 113,JAPAN. HUGHES STX CORP,LANHAM,MD 20706. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,GREENBELT,MD 20771. UNIV WARSAW OBSERV,PL-00478 WARSAW,POLAND. RI Ratra, Bharat/I-4979-2012 NR 57 TC 41 Z9 41 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 MAY 20 PY 1997 VL 481 IS 1 BP 22 EP 34 DI 10.1086/304051 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400002 ER PT J AU Mattox, JR Schachter, J Molnar, L Hartman, RC Patnaik, AR AF Mattox, JR Schachter, J Molnar, L Hartman, RC Patnaik, AR TI The identification of EGRET sources with flat-spectrum radio sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; gamma rays, observations; quasars, general ID ENERGY GAMMA-RAYS; EMISSION; RADIATION; CATALOG; GHZ; MHZ AB We present a method to assess the reliability of the identification of EGRET sources with extragalactic radio sources. We verify that EGRET is detecting the blazar class of active galactic nuclei (AGNs). However, many published identifications are found to be questionable. We provide a table of 42 blazars that we expect to be robust identifications of EGRET sources. This includes one previously unidentified EGRET source, the lensed AGN PKS 1830-210, near the direction of the Galactic center. We provide the best available positions for 16 more radio sources that are also potential identifications for previously unidentified EGRET sources. All high Galactic latitude EGRET sources (\ b \ > 3 degrees) that demonstrate significant variability can be identified with flat-spectrum radio sources. This suggests that EGRET is not detecting any type of AGN other than blazars. This identification method has been used to establish with 99.998% confidence that the peak gamma-ray flux of a blazar is correlated with its average 5 GHz radio flux. An even better correlation is seen between gamma-ray flux and the 2.29 GHz flux density measured with VLBI at the base of the radio jet. Also, using high-confidence identifications, we find that the radio sources identified with EGRET sources have greater correlated VLBI flux densities than the parent population of flat radio spectrum sources. C1 HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. UNIV IOWA, DEPT PHYS & ASTRON, IOWA CITY, IA 52242 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. MAX PLANCK INST RADIOASTRON, D-53121 BONN, GERMANY. RP Mattox, JR (reprint author), BOSTON UNIV, DEPT ASTRON, 725 COMMONWEALTH AVE, BOSTON, MA 02215 USA. NR 69 TC 158 Z9 160 U1 1 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 MAY 20 PY 1997 VL 481 IS 1 BP 95 EP 115 DI 10.1086/304039 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400006 ER PT J AU Waller, WH Bohlin, RC Cornett, RH Fanelli, MN Freedman, WL Hill, JK Madore, BF Neff, SG Offenberg, JD OConnell, RW Roberts, MS Smith, AM Stecher, TP AF Waller, WH Bohlin, RC Cornett, RH Fanelli, MN Freedman, WL Hill, JK Madore, BF Neff, SG Offenberg, JD OConnell, RW Roberts, MS Smith, AM Stecher, TP TI Ultraviolet signatures of tidal interaction in the giant spiral galaxy M101 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, evolution; galaxies, individual (M101); galaxies, interactions; galaxies, spiral; ultraviolet, galaxies ID H-II-REGIONS; IMAGING TELESCOPE; M-101; DISTANCE; NEBULA; IMAGES; SCALE; DISKS; ATLAS AB We present new evidence for the occurrence of tidal interactions in the disk of M101 during the last 10(8)-10(9) yr. Recent imaging of the far-ultraviolet emission from M101 by the shuttle-borne Ultraviolet Imaging Telescope (UIT) reveals with unprecedented clarity a disk-wide pattern of multiple linear arm segments (''crooked arms''). The deep far-ultraviolet (FUV) image also shows a faint outer spiral arm with a (''curly tail'') feature that appears to loop around the supergiant H II region NGC 5471, linking this outlying starburst with the rest of the galaxy. These FUV-bright features most likely trace hot O-and B-type stars along with scattered light from associated nebular dust. Counterparts of the outermost ''crooked arms'' are evident in maps at visible wavelengths and in the 21 cm line of H I. The inner-disk FUV arms are most closely associated with Ha knots and the outer (downstream) sides of CO arms. Comparisons of the ''crooked arm'' and ''curly tail'' morphologies with dynamical simulations yield the greatest similitude, when the nonaxisymmetric forcing comes from a combination of external interactions with one or more companion galaxies and internal perturbations from massive objects orbiting within the disk. We speculate that NGC 5471 represents one of these ''massive disturbers'' within the disk, whose formation followed from a tidal interaction between M101 and a smaller galaxy. C1 SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. OBSERV CARNEGIE INST WASHINGTON, PASADENA, CA 91101 USA. CALTECH, CTR INFRARED PROC & ANAL, PASADENA, CA 91125 USA. NATL RADIO ASTRON OBSERV, CHARLOTTESVILLE, VA 22903 USA. RP Waller, WH (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, HUGHES STX CORP, CODE 681, GREENBELT, MD 20771 USA. NR 43 TC 29 Z9 29 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 MAY 20 PY 1997 VL 481 IS 1 BP 169 EP + DI 10.1086/304057 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400011 ER PT J AU Hunter, SD Bertsch, DL Catelli, JR Dame, TM Digel, SW Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Schneid, E Sreekumar, P Thaddeus, P Thompson, DJ AF Hunter, SD Bertsch, DL Catelli, JR Dame, TM Digel, SW Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Schneid, E Sreekumar, P Thaddeus, P Thompson, DJ TI EGRET observations of the diffuse gamma-ray emission from the Galactic plane SO ASTROPHYSICAL JOURNAL LA English DT Review DE cosmic rays; diffuse radiation; Galaxy, structure; gamma rays, observations ID NEUTRAL HYDROGEN SURVEY; LARGE MAGELLANIC CLOUD; SOUTHERN MILKY-WAY; RADIAL-DISTRIBUTION; COSMIC-RAY; OUTER GALAXY; MOLECULAR CLOUDS; SOLAR CIRCLE; CO SURVEY; INTERSTELLAR GAS AB The high-energy diffuse gamma-ray emission from the Galactic plane, \ b \ less than or equal to 10 degrees, is studied using observations from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton GammaRay Observatory. The spatial distribution of the diffuse emission has been determined for four broad energy ranges after removing the contribution from point sources detected with greater than 5 sigma significance. The longitude and latitude distributions of the intensity, averaged over 4 degrees latitude ranges and 10 degrees longitude ranges, respectively, are shown for the four energy ranges. Spectra of the diffuse emission in 11 energy bands, covering the energy range 30 MeV to 30 GeV, were determined for 10 degrees x 4 degrees (l x b) bins after correcting for the finite EGRET angular resolution. The average spectrum from the direction of the inner Galaxy is shown for 29 energy bands, covering the energy range 30 MeV to 50 GeV. At latitudes \ b \ > 2 degrees, corresponding to gamma rays emitted within about 3 kpc of the Sun, there is no significant variation in the spectra with Galactic longitude. Comparison of the spectra from the Galactic plane (\ b \ < 2 degrees) reveals no significant variation with Galactic longitude below about 4 GeV, which suggests that the cosmic-ray electron to proton ratio does not vary significantly throughout the Galaxy. Above 4 GeV, however, there is weak (about 3 sigma) evidence for variation of the Galactic plane (\ b \ < 2 degrees) spectrum with longitude. The spectrum is softer in the direction of the outer Galaxy by about E-gamma(-0.4+/-0.1) compared to the spectrum from the inner Galaxy. This variation of the diffuse gamma-ray emission hints at a variation of the cosmic-ray proton spectrum with Galactic radius, which might be expected if cosmic rays are accelerated primarily in the inner Galaxy and then propagate to the outer Galaxy or if the high-energy cosmic rays are confined less well in the outer Galaxy. The spatial and spectral distributions of the diffuse emission are compared with a model calculation of this emission based on dynamic balance and realistic interstellar matter and photon distributions. The spatial comparison is used to establish the value of the molecular mass calibrating ratio N(H-2)/W-CO and the cosmic-ray/matter coupling scale r(0), which are the only adjustable parameters of the model. Comparisons with the observations indicates N(H-2)/W-CO = (1.56 +/- 0.05) x 10(20) mol cm(-2) (K km s(-1))(-1) and r(0) = (1.76 +/- 0.2) kpc. The spatial agreement between this model is about 60% less than the observed intensity. Although the explanation of this excess is unclear, uncertainties in the neutral pion production function or variations in the cosmic-ray spectrum with Galactic radius may partially account for the underprediction. A small medium-latitude (2 degrees < \ b \ < 10 degrees) excess in the direction of the inner Galaxy exists and may indicate that the low-energy photon density used in the model is too low. C1 UNIV MARYLAND, COLLEGE PK, MD 20742 USA. HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. NASA, GODDARD SPACE FLIGHT CTR, HUGHES STX, GREENBELT, MD 20771 USA. HAMPDEN SYDNEY COLL, HAMPDEN SYDNEY, VA 23943 USA. STANFORD UNIV, HANSEN EXPT PHYS LAB, STANFORD, CA 94305 USA. NASA, NRC RES ASSOC, WASHINGTON, DC 20546 USA. NORTHROP GRUMMAN CORP, BETHPAGE, NY 11714 USA. MAX PLANCK INST EXTRATERR PHYS, D-85748 GARCHING, GERMANY. RP Hunter, SD (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 661, GREENBELT, MD 20771 USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; OI Thompson, David/0000-0001-5217-9135; Dingus, Brenda/0000-0001-8451-7450 NR 109 TC 617 Z9 625 U1 0 U2 6 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 MAY 20 PY 1997 VL 481 IS 1 BP 205 EP 240 DI 10.1086/304012 PN 1 PG 36 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400016 ER PT J AU Charnley, SB AF Charnley, SB TI Sulfuretted molecules in hot cores SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; molecular processes; stars, formation ID DENSE INTERSTELLAR CLOUDS; TIME-DEPENDENT CHEMISTRY; APERTURE SYNTHESIS MAPS; SAGITTARIUS B2; LINE SURVEY; ORION-KL; SHOCKS; GAS; ABUNDANCES; EMISSION AB The chemistry of sulfur-bearing molecules that result from grain-mantle evaporation into warm gas is described. Evaporation of ices, in which all the available sulfur is contained in H2S, drives a hot-phase chemistry that produces SO, SO2, CS, OCS, and H2CS. It is predicted that S-2 can attain significant abundances in hot cores. Large variations in abundances occur as a core evolves, and eventually almost all the original H2S is converted to SO and SO2. The SO/H2S and SO/SO2 abundance ratios could be useful as a crude molecular clock to measure the time since mantles were disrupted. Model calculations can reasonably explain the observed distribution of S-bearing molecules in the Orion Hot Core, the Orion Compact Ridge, and in Sgr B2N. In these sources, the theory requires that OCS be formed on grain surfaces. Hot core chemistry alone cannot explain the sulfur chemistry in the Sgr B2M source. 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 67 TC 193 Z9 193 U1 0 U2 5 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 MAY 20 PY 1997 VL 481 IS 1 BP 396 EP 405 DI 10.1086/304011 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400033 ER PT J AU Krist, JE Burrows, CJ Stapelfeldt, KR Ballester, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Holtzman, JA Hoessel, JG Mould, JR Scowen, PA Trauger, JT Watson, AM Westphal, JA AF Krist, JE Burrows, CJ Stapelfeldt, KR Ballester, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Holtzman, JA Hoessel, JG Mould, JR Scowen, PA Trauger, JT Watson, AM Westphal, JA TI Hubble Space Telescope WFPC2 images of emission nebulosity near XZ Tauri SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, jets and outflows; stars, individual (XZ Tauri); stars, pre-main-sequence ID HL TAURI; STARS AB XZ Tauri is a M3 V T Tauri star with a pre-main-sequence binary companion detected by infrared speckle interferometry at a projected separation of 0''.3 (about 40 AU). Previous ground-based observations of the system have shown bipolar emission nebulosity, including a possible jet knot. Images obtained with the Wide Field and Planetary Camera 2 on the Hubble Space Telescope show an elongated, filled bubble of emission nebulosity extending over 4'' to the north of the system which contains two or three compact knots. The source of the nebulosity is undetermined. For the first time, the components are separated in visible light, and the southern component (XZ Tau S) dominates the integrated light of the system. The reverse has been found to be true in the near-infrared. Thus we confirm that XZ Tauri belongs to the small class of young binaries with cool infrared companions. C1 EUROPEAN SPACE AGCY,DEPT SPACE SCI,DIV ASTROPHYS,F-75738 PARIS 15,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,ANN ARBOR,MI 48109. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. CARNEGIE MELLON UNIV,DEPT PHYS,PITTSBURGH,PA 15213. ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. RP Krist, JE (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 19 TC 22 Z9 22 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 MAY 20 PY 1997 VL 481 IS 1 BP 447 EP & DI 10.1086/304056 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400037 ER PT J AU Smith, MA Cohen, DH Hubeny, I Plett, K Basri, G JohnsKrull, CM MacFarlane, JJ Hirata, R AF Smith, MA Cohen, DH Hubeny, I Plett, K Basri, G JohnsKrull, CM MacFarlane, JJ Hirata, R TI Dynamic processes in Be star atmospheres .5. Helium line emissions from the outer atmosphere of lambda Eridani SO ASTROPHYSICAL JOURNAL LA English DT Article DE line, formation; line, profiles; stars, atmospheres; stars, emission-line, Be; stars, individual (lambda Eridani); ultraviolet, stars ID HE-I LINES; STELLAR ATMOSPHERES; SYMBIOTIC STARS; B-STARS; EQUILIBRIUM MODELS; O-STAR; ABUNDANCES; IONIZATION; RADIATION; SPECTRA AB The He I lines of the mild B2e star lambda Eri often exhibit rapid, small-amplitude emissions that can occur at random places in their photospheric lines, even when the star is in a ''nonemission state.'' New simultaneous observations of the triplet lambda 5876 and singlet lambda 6678 lines show that the emission ratio for these lines is near unity, contrary to the predictions of either non-LTE model atmospheres or nebular recombination theory. Several He I emission events point to the formation of short-lived structures near the star's surface. On 1995 September 12 the line lambda 6678 exhibited a strong (0.13I(cont)) emission lasting some 20 minutes. The rapid decay of this feature implies a density of greater than or equal to 10(11.5) cm(-3) for an emitting plasma structure near the cm star. This value is consistent with density estimates for slabs which may be responsible for ephemeral ''dimples'' in this star's He I lines on other occasions. We argue that photospheric helium emissions during Ha-quiescent phases are caused by foreground material and ask what mechanism might produce these features against the stellar background. To answer this question we have simulated He I line emission from model slabs having various properties and suspended over the star. We find that illumination by a source of extreme-ultraviolet (EUV) or X-ray flux depletes the He I column density so that it is difficult to form observable He I lines. A more interesting set of conditions occur for slabs with high densities (similar to 10(12) cm(-3)) and moderately large optical thicknesses in optical He I lines. Under these modified assumptions modest amounts of emission can be reproduced in singlet and triplet lines, and in the observed ratio. The key to producing this emission is for the slab to feel its own Lyman continuum radiation. This condition causes lambda 584 and other resonance lines to partially depopulate the ground state and to overpopulate the first few excited levels, ensuring that the departure coefficients of relevant atomic levels approach common values. The second necessary ingredient is a high density, which tends to equalize the departure coefficients of excited levels through recombinations and through redistribution of electrons among the l-sublevels. The combination is a kind of ''Lyman-pumped recombination'' because it relies on the Lyman continuum being marginally optically thick. Our results are consistent with studies of He I emission from planetary nebulae, symbiotic variables, and active galactic nuclei (AGNs), and may have a bearing on other ''detached atmospheres'' problems as well. This study appears to be the first application of such a recombination mechanism to a quasi-photospheric setting. C1 UNIV WISCONSIN, DEPT ASTRON, MADISON, WI 53706 USA. NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. UNIV WISCONSIN, FUS TECHNOL INST, MADISON, WI 53706 USA. KYOTO UNIV, DEPT ASTRON, KYOTO 606, JAPAN. RP Smith, MA (reprint author), IUE OBSERV, CSC, SCI PROGRAMS, COMP SCI CORP, 10000A AEROSP RD, LANHAM, MD 20706 USA. NR 40 TC 13 Z9 13 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1997 VL 481 IS 1 BP 467 EP 478 DI 10.1086/304028 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400039 ER PT J AU Smith, MA Murakami, T Ezuka, H Anandarao, BG Chakraborty, A Corcoran, MF Hirata, R AF Smith, MA Murakami, T Ezuka, H Anandarao, BG Chakraborty, A Corcoran, MF Hirata, R TI Dynamic processes in Be star atmospheres .6. Simultaneous X-ray, ultraviolet, and optical variations in lambda Eridani SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, emission-line, Be; stars, individual (gamma Eridani); stars, mass loss; stars, oscillations; ultraviolet, stars; X-rays, stars ID GAMMA-CASSIOPEIAE; VARIABILITY; LINE; B2E; EMISSION; MODEL; FLARE AB We document the results of simultaneous wavelength monitoring of the B2e star lambda Eri. This campaign was carried out from ground stations and with the ROSAT, ASCA, IUE, and voyager 2 space platforms during a week in 1995 February-March; a smaller follow-up was conducted in 1995 September. During the first of these intervals lambda Eri exhibited extraordinary wind and disk-ejection activity. The ROSAT/ HRI X-ray light curves showed no large flares such as the one the ROSAT/PSPC observed in 1991. However, possible low-level fluctuations in the February-March ROSAT data occurred at the same time as unusual activity in H alpha, He I lambda 6678, He II lambda 1640, and the C IV doublet. For example, the hydrogen and helium lines exhibited an emission in the blue half of their profiles, probably lasting several hours. The C IV lines showed a strong high-velocity discrete absorption component (DAC) accompanied by unusually strong absorption at lower velocities. The helium line activity suggests that a mass ejection occurred at the base of the wind, while the strong C III (Voyager) and C IV (IUE) lines imply that shock interactions occurred in the wind flow. It is not clear that the X-ray elevations are directly related to the strong C rv absorptions because the former changed on a much more rapid timescale than absorptions in the C IV lines. Within hours of the mild X-ray flux variations found by ROSAT on February 28, the Voyager UV spectrometer (UVS) observed a ''ringing'' that decayed over three 3 hr cycles. The amplitude of these fluctuations was strong (50%) at 950-1100 Angstrom decreased rapidly with wavelength, and faded to nondetection longward of 1300 Angstrom. Various considerations indicate that these continuum variations were not due to an instrumental poathology in the UVS. Rather, they appear to be due to a time-dependent flux deficit in the 950-1250 A region. We outline a scenario in which a dense plasma structure over the star's surface is heated and cooled quasi-periodically to produce such flux changes. Observations of new examples of this phenomenon are badly needed. Amateur astronomers can make a significant contribution to its understanding by searching for ringing in light curves of Be stars during their outburst phases. Finally, we draw attention to an increase in the emission of the H alpha line that occurred at about the time the far-ultraviolet ringing started. This increased emission hints that similar to 50,000 K plasma near the star's surface can influence the circumstellar disk at similar to 12 R-* by its increased Lyman continuum flux. C1 INST SPACE & ASTRONAUT SCI, KANAGAWA 229, JAPAN. PHYS RES LAB, AHMEDABAD 380009, GUJARAT, INDIA. NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. KYOTO UNIV, DEPT ASTRON, KYOTO 606, JAPAN. RP Smith, MA (reprint author), IUE OBSERV, CSC, SCI PROGRAMS, COMP SCI CORP, 10000A AEROSP RD, LANHAM, MD 20706 USA. NR 37 TC 14 Z9 14 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1997 VL 481 IS 1 BP 479 EP 488 DI 10.1086/304045 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400040 ER PT J AU Abgrall, H Roueff, E Liu, XM Shemansky, DE AF Abgrall, H Roueff, E Liu, XM Shemansky, DE TI The emission continuum of electron-excited molecular hydrogen SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, molecules; methods, laboratory; molecular processes ID HUBBLE-SPACE-TELESCOPE; WERNER BAND SYSTEMS; VACUUM-ULTRAVIOLET; H-2 MOLECULE; INTERSTELLAR-MOLECULES; TRANSITION MOMENTS; RYDBERG SERIES; LYMAN; SPECTRUM; IMPACT AB The emission continua of the dissociative transitions B (1) Sigma(u)(+)-X (1) Sigma(g)(+), B' (1) Sigma(u)(+)-X (1) Sigma(g)(+), C (1) Pi(u)-X (1) Sigma(g)(+), and D (1) Pi(u)-X (1) Sigma(g)(+) of molecular hydrogen have been calculated. Synthetic spectra of H-2 are in excellent agreement with high-resolution electron-impact-induced emission spectra obtained at 100 eV. An improved calibration standard is obtained, and the dissociation yields of the Lyman and Werner continua produced by electron-impact excitation are presented. C1 CNRS URA 173,F-92195 MEUDON,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV SO CALIF,DEPT AEROSP ENGN,LOS ANGELES,CA 90089. RP Abgrall, H (reprint author), OBSERV PARIS,DAEC,SECT MEUDON,F-92195 MEUDON,FRANCE. NR 51 TC 54 Z9 54 U1 1 U2 7 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1997 VL 481 IS 1 BP 557 EP 566 DI 10.1086/304017 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA544 UT WOS:A1997XA54400048 ER PT J AU Cheng, LX Leventhal, M Smith, DM Purcell, WR Tueller, J Connors, A Dixon, D Kinzer, RL Skibo, JG AF Cheng, LX Leventhal, M Smith, DM Purcell, WR Tueller, J Connors, A Dixon, D Kinzer, RL Skibo, JG TI A maximum entropy map of the 511 keV positron annihilation line emission distribution near the galactic center SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy, general; gamma rays, observations ID CENTER REGION; RAY; RADIATION AB We have applied the maximum entropy method to a large data set based on Compton Gamma Ray Observatory (CGRO)/OSSE, Solar Maximum Mission, Transient Gamma-Ray Spectrometer, Gamma-Ray Imaging Spectrometer, HEXAGONE, and FIGARO observational results of the Galactic center 511 keV radiation in order to produce a map of the 511 keV line emission. This map suggests two components: a central bulge with a flux of 5.7 +/- 0.29 x 10(-4) photons cm(-2)s(-1) and a Galactic plane (GP) component with a flux of 2.2 +/- 0.4 x 10(-4) photons cm(-2) s(-1). The central bulge is located at l = -0.degrees 47 +/- 0.degrees 24, b = 0.degrees 1 +/- 0.degrees 18, and FWHM = 5.degrees 28 +/- 0.degrees 48. We note that the position of the GP component coincides with a strong hot spot in the COMPTEL map of 1.8 MeV Al-26 line emission. A comparison between CGRO/OSSE and other instruments with larger field of view suggests an extended diffuse 511 keV emission. An interesting hot spot at l = -4 degrees, b = 7 degrees with a flux of similar to 2 x 10(-4)photons cm(-2)s(-1) is shown on our map. A bootstrap test indicates that the significance level of this feature is 3.5 sigma. C1 NORTHWESTERN UNIV,DEPT PHYS & ASTRON,EVANSTON,IL 60208. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV NEW HAMPSHIRE,DURHAM,NH 03824. UNIV CALIF RIVERSIDE,INST GEOPHYS & PLANETARY PHYS,RIVERSIDE,CA 92521. USN,RES LAB,WASHINGTON,DC 20375. RP Cheng, LX (reprint author), UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742, USA. RI Tueller, Jack/D-5334-2012 NR 26 TC 27 Z9 27 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 MAY 20 PY 1997 VL 481 IS 1 BP L43 EP L46 DI 10.1086/310638 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA546 UT WOS:A1997XA54600011 ER PT J AU Szapudi, I Szalay, AS AF Szapudi, I Szalay, AS TI Cumulant correlators from the APM SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, statistics; large-scale structure of universe methods, data analysis; methods, statistical ID GALAXY CORRELATION-FUNCTIONS; HIERARCHY; STATISTICS; SKEWNESS AB This work presents a set of new statistics, the cumulant correlators (CCs), aimed at high-precision analysis of the galaxy distribution. They form a symmetric matrix, Q(NM), related to moment correlators in the same way cumulants are related to the moments of the distribution. They encode more information than the usual cumulants S-N, and their extraction from data is similar to the calculation of the two-point correlation function. Perturbation theory (PT), its generalization in the extended perturbation theory (EPT), and the hierarchical assumption (HA) have simple predictions for these statistics. As an example, the factorial moment correlators measured by Szapudi and coworkers in the APM catalog are reanalyzed using this technique. While the previous analysis assumed hierarchical structure constants, this method can directly investigate the validity of the HA, along with PT and EPT. The results in agreement with previous findings indicate that, at the small scales used for this analysis, the APM data support the HA. When all nonlinear corrections are taken into account, it is a good approximation at the 20% level. It appears that PT, and a natural generalization of EPT for CCs, does not provide such a good fit for the APM at small scales. Once the validity of the HA is approximately established, CCs can separate the amplitudes of different tree types in the hierarchy up to fifth order. As an example, the weights for the fourth-order tree topologies are calculated including all nonlinear corrections. C1 JOHNS HOPKINS UNIV,BALTIMORE,MD 21218. RP Szapudi, I (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,POB 500,BATAVIA,IL 60510, USA. NR 25 TC 34 Z9 34 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 MAY 20 PY 1997 VL 481 IS 1 BP L1 EP L4 DI 10.1086/310641 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XA546 UT WOS:A1997XA54600001 ER PT J AU Bowman, RC Witham, C Fultz, B Ratnakumar, BV Ellis, TW Anderson, IE AF Bowman, RC Witham, C Fultz, B Ratnakumar, BV Ellis, TW Anderson, IE TI Hydriding behavior of gas-atomized AB(5) alloys SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article; Proceedings Paper CT International Symposium on Metal Hydrogen Systems: Fundamentals and Applications CY AUG 25-30, 1996 CL LES DIABLERETS, SWITZERLAND DE metal hydrides; gas atomization; electrochemical hydride properties; hydrogen storage alloys; Ni-MH battery alloys; LaNi5 ID HYDROGEN STORAGE ALLOYS; DEGRADATION; LANI5 AB The hydriding characteristics of some AB(5) alloys produced by high pressure gas atomization (HPGA) have been examined during reactions with hydrogen gas, and in electrochemical cells. The hydrogen storage capacities and the equilibrium pressures for HPGA processed LaNi5, LaNi4.75Sn0.25, and MmNi(3.5)Co(0.8)Al(0.4)Mn(0.3) alloys (where Mm denotes Mischmetal) are found to be nearly identical to annealed alloys produced as ingots. The large discontinuous volume change across the alpha-beta plateau region for gas-atomized LaNi5Hx was seen to produce extensive fracturing in all but the smallest alloy spheres. However, only the largest spheres of the gas-atomized MmNi(3.5)Co(0.8)Al(0.4)Mn(0.3) and LaNi4.75Sn0.25Hx alloys exhibited any discernible fracturing. The maximum electrochemical storage capacities of the gas-atomized LaNi4.75Sn0.25 and MmNi(3.5)Co(0.8)Al(0.4)Mn(0.3) alloys were found to be smaller than the capacities of annealed alloys prepared from ingots. C1 CALTECH,JET PROP LAB,ELECTROCHEM TECHNOL PROGRAM,PASADENA,CA 91109. IOWA STATE UNIV,AMES LAB,AMES,IA 50011. RP Bowman, RC (reprint author), CALTECH,DIV ENGN & APPL SCI,PASADENA,CA 91125, USA. OI Bowman, Robert/0000-0002-2114-1713 NR 10 TC 28 Z9 30 U1 0 U2 1 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-8388 J9 J ALLOY COMPD JI J. Alloy. Compd. PD MAY 20 PY 1997 VL 253 BP 613 EP 616 DI 10.1016/S0925-8388(96)02929-5 PG 4 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA XJ169 UT WOS:A1997XJ16900145 ER PT J AU McMillan, WW Strow, LL Smith, WL Revercomb, HE Huang, HL Thompson, AM McNamara, DP Ryan, WF AF McMillan, WW Strow, LL Smith, WL Revercomb, HE Huang, HL Thompson, AM McNamara, DP Ryan, WF TI Remote sensing of carbon monoxide over the continental United States on September 12-13, 1993 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID EARTHS ATMOSPHERE; TROPOSPHERIC CHEMISTRY; AIRCRAFT MEASUREMENTS; OZONE PRODUCTION; EASTERN PACIFIC; CO; PROFILES; DISTRIBUTIONS; TEMPERATURE; TRANSPORT AB Tropospheric carbon monoxide (CO) column densities were retrieved from 491 nadir infrared spectra obtained by the University of Wisconsin's High-Resolution Interferometer Sounder (HIS) during a cross-country flight of a NASA ER-2 on September 12-13, 1993 (UT). A classical, Fourier-based signal-processing technique was utilized to retrieve the CO column density from the 2135-2200 cm(-1) portion of the CO 1-0 vibration-rotation band. Error analysis indicates column CO retrieval uncertainties of approximately +/-10%. Retrieved CO column densities over the western United States from this flight, similar to 1.2 x 10(18) cm(-2), agree well with previous ground-based CO column measurements over the western United States at the same season. Derived CO sensitivity functions for these measurements possess a broad peak centered in the 500-600 mbar region, thus implying the retrieved tropospheric CO mixing ratios are indicative of the mean free troposphere (mft). Across the United States, three spatial groupings of CO were observed: west, mft CO similar to 76 parts per billion by volume (ppbv); midwest, mft CO similar to 56 ppbv; and east, mft CO similar to 71 ppbv. Weather map and back trajectory analyses indicate different source regions for the air parcels in each of these regions. The low CO amounts over the midwest most likely result from the mixing of rapidly subsiding air naturally low in CO with a low-altitude inflow of similarly clean subtropical air off the Gulf of Mexico. These results demonstrate the utility of satellite infrared spectrometer observations to globally map tropospheric CO abundances and further reveal the impact of synoptic scale atmospheric circulations on CO abundances. C1 UNIV WISCONSIN, COOPERAT INST METEOROL SATELLITE STUDIES, MADISON, WI 53706 USA. UNIV MARYLAND, DEPT METEOROL, COLLEGE PK, MD 20742 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. APPL RES CORP, LANDOVER, MD 20785 USA. RP McMillan, WW (reprint author), UNIV MARYLAND, DEPT PHYS, 1000 HILLTOP CIRCLE, BALTIMORE, MD 21250 USA. RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 53 TC 12 Z9 12 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 MAY 20 PY 1997 VL 102 IS D9 BP 10695 EP 10709 DI 10.1029/97JD00074 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XA717 UT WOS:A1997XA71700009 ER PT J AU Bird, JC Pal, SR Carswell, AI Donovan, DP Manney, GL Harris, JM Uchino, O AF Bird, JC Pal, SR Carswell, AI Donovan, DP Manney, GL Harris, JM Uchino, O TI Observations of ozone structures in the Arctic polar vortex SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID POTENTIAL VORTICITY; LOWER STRATOSPHERE; ANTARCTIC VORTEX; WINTER; EVOLUTION; TRANSPORT; FEBRUARY; LAMINAE; MOTION; TRACER AB Lidar and balloon measurements at the new observatory, AStrO (80.05 degrees N, 86.42 degrees W), near Eureka, in the Canadian Arctic, have revealed laminations inside the ozone layer both inside and outside the polar vortex. These observations have been conducted by the lidar group of the Institute for Space and Terrestrial Science during February-March 1993 and the winters of 1993-1994 and 1994-1995. Observations of the vortex edge region were obtained as it passed over Eureka, revealing ozone profiles rich in structure. This paper discusses the observed ozone structures and their relationship to vortex filaments, the vortex edge structure, low-ozone pockets, motion of the vortex edge region in the ozone profiles, and observed temperatures. Complementing the observations are back trajectories, potential vorticity maps, and Lagrangian domain-filling potential vorticity trajectories. The relations of magnitude and thickness of the laminations to their positions relative to the vortex are revealed by presenting data as a function of potential vorticity. Mechanisms for the formation and transport of the laminae are discussed, as well as their role as a possible exchange mechanism of air masses across the polar vortex boundary. From observations of the laminations and their relation to potential vorticity, it is suggested that motion of the vortex, sometimes associated with warmings, is involved in the formation of laminations, which are subsequently advected as filamentary structures. C1 NOAA, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA. JET PROP LAB, PASADENA, CA 91109 USA. JAPAN METEOROL AGCY, CHIYODA KU, TOKYO 100, JAPAN. YORK UNIV, DEPT PHYS & ASTRON, N YORK, ON M3J 3K1, CANADA. RP Bird, JC (reprint author), YORK UNIV, INST SPACE & TERR SCI, 4850 KEELE ST, N YORK, ON M3J 3K1, CANADA. NR 41 TC 22 Z9 22 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 20 PY 1997 VL 102 IS D9 BP 10785 EP 10800 DI 10.1029/96JD03787 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XA717 UT WOS:A1997XA71700016 ER PT J AU Yung, YL Lee, AYT Irion, FW DeMore, WB Wen, J AF Yung, YL Lee, AYT Irion, FW DeMore, WB Wen, J TI Carbon dioxide in the atmosphere: Isotopic exchange with ozone and its use as a tracer in the middle atmosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC CO2; HEAVY OZONE; OXYGEN; FRACTIONATION; ENHANCEMENT; CHEMISTRY AB Atmospheric heavy ozone is enriched in the isotopes O-18 and O-17. The magnitude of this enhancement, of the order of 100 parts per thousand, is very large compared with that commonly known in atmospheric chemistry and geochemistry. The heavy oxygen atom in heavy ozone is therefore useful as a tracer of chemical species and pathways that involve ozone or its derived products. As a test of the isotopic exchange reactions, we successfully carry out a series of numerical experiments to simulate the results of the laboratory experiments performed by Wen and Thiemens [1993] on ozone and CO2. A small discrepancy between the experimental and the model values for O-17 exchange is also revealed. The results are used to compute the magnitude of isotopic exchange between ozone and carbon dioxide via the excited atom O(D-1) in the middle atmosphere. The model for O-18 is in good agreement with the observed values. C1 CALTECH, JET PROP LAB, DIV EARTH & SPACE SCI, PASADENA, CA 91109 USA. DEPT HLTH SERV, DRINKING WATER FIELD OPERAT BRANCH, LOS ANGELES, CA 90026 USA. RP Yung, YL (reprint author), CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA 91125 USA. NR 27 TC 74 Z9 75 U1 2 U2 22 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 MAY 20 PY 1997 VL 102 IS D9 BP 10857 EP 10866 DI 10.1029/97JD00528 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XA717 UT WOS:A1997XA71700021 PM 11541125 ER PT J AU Cikanek, HA AF Cikanek, HA TI You forgot Lewis SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter C1 NASA,LEWIS RES CTR,TRANSPORTAT PROJECT OFF,CLEVELAND,OH 44135. RP Cikanek, HA (reprint author), NASA,LEWIS RES CTR,LAUNCH SERV 3,CLEVELAND,OH 44135, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD MAY 19 PY 1997 VL 146 IS 21 BP 6 EP 6 PG 1 WC Engineering, Aerospace SC Engineering GA WZ285 UT WOS:A1997WZ28500005 ER PT J AU Boggess, RK Taylor, LT Stoakley, DM StClair, AK AF Boggess, RK Taylor, LT Stoakley, DM StClair, AK TI Highly reflective polyimide films created by supercritical fluid infusion of a silver additive SO JOURNAL OF APPLIED POLYMER SCIENCE LA English DT Article ID CARBON-DIOXIDE; POLYMERS; STRATEGIES AB Supercritical fluid infusion of a silver-containing additive [1,5-cyclooctadiene silver(I)-1,1,1,5,5,5-hexafluoroacetylacetonate] into a fully cured polyimide was achieved with moderately high-density carbon dioxide at 110 degrees C for the first time. The polyimide was derived from 4,4'-oxydianiline and 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride. After infusion for approximately 60 min, the resulting film was then recured at 300 degrees C in air. During this time, a silver mirror formed on both film surfaces. The nature of the silver and its distribution within the film and on the film surface were established via microscopy and surface analysis techniques. (C) 1997 John Wiley & Sons, Inc. C1 VIRGINIA TECH,DEPT CHEM,BLACKSBURG,VA 24061. RADFORD UNIV,DEPT CHEM & PHYS,RADFORD,VA 24142. NASA,LANGLEY RES CTR,DIV MAT,HAMPTON,VA 23665. NR 26 TC 31 Z9 32 U1 0 U2 2 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0021-8995 J9 J APPL POLYM SCI JI J. Appl. Polym. Sci. PD MAY 16 PY 1997 VL 64 IS 7 BP 1309 EP 1317 DI 10.1002/(SICI)1097-4628(19970516)64:7<1309::AID-APP10>3.3.CO;2-7 PG 9 WC Polymer Science SC Polymer Science GA WU622 UT WOS:A1997WU62200010 ER PT J AU Woo, R Habbal, SR AF Woo, R Habbal, SR TI Extension of coronal structure into interplanetary space SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR; FLOW; HOLE AB We investigate the extension and evolution of the solar corona into interplanetary space by comparing 1995 Ulysses radio occultation measurements of path-integrated electron density and density fluctuations measured between 21 and 32 R-0, with simultaneous white-light measurements made by the HAO Mauna Loa K-coronameter below 2.5 R-0. The surprising picture of the extended corona to emerge from this comparison is one in which stalks of streamers, occupying a small fraction of volume in interplanetary space, are superimposed on a background corona distinguished by a plethora of raylike structures, often referred to as plumes in polar coronal holes. The radial preservation of the boundary between polar coronal holes and the base of streamers implies that the solar wind from polar coronal holes expands radially rather than undergoing any significant divergence as previously thought. Combining this picture of the extended corona with in situ velocity measurements made by Ulysses throughout its two polar passages, we conclude that the raylike structures, except for the stalks of streamers, seem to be the source of the fast wind. The existence of the fast wind at low latitudes can be attributed to these raylike structures, rather than the expansion of the boundaries of polar coronal holes to low latitudes. C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02178. RP Woo, R (reprint author), CALTECH,JET PROP LAB,MS 238-725,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 18 TC 48 Z9 48 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 MAY 15 PY 1997 VL 24 IS 10 BP 1159 EP 1162 DI 10.1029/97GL01156 PG 4 WC Geosciences, Multidisciplinary SC Geology GA WZ425 UT WOS:A1997WZ42500001 ER PT J AU Grunwaldt, H Neugebauer, M Hilchenbach, M Bochsler, P Hovestadt, D Burgi, A Ipavich, FM Reiche, KU Axford, WL Balsiger, H Galvin, AB Geiss, J Gliem, F Gloeckler, G Hsieh, KC Kallenbach, R Klecker, B Livi, S Lee, MA Managadze, GG Marsch, E Mobius, E Scholer, M Verigin, MI Wilken, B Wurz, P AF Grunwaldt, H Neugebauer, M Hilchenbach, M Bochsler, P Hovestadt, D Burgi, A Ipavich, FM Reiche, KU Axford, WL Balsiger, H Galvin, AB Geiss, J Gliem, F Gloeckler, G Hsieh, KC Kallenbach, R Klecker, B Livi, S Lee, MA Managadze, GG Marsch, E Mobius, E Scholer, M Verigin, MI Wilken, B Wurz, P TI Venus tail ray observation near Earth SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PIONEER VENUS; PLASMA OBSERVATIONS; IONS AB In June, 1996, Venus passed through a very close inferior conjunction with the Sun, At that time the CTOF detector of the CELIAS mass spectrometer experiment on the SOHO spacecraft near Earth's L1 Lagrangian point was measuring heavy ions in the solar wind similar to 4.5x10(7) km downstream of Venus. Close to the time predicted by simple geometric arguments for passage of SOHO through the Venus wake, CTOF made three encounters with unusual fluxes of O+ and C+ ions. Their energy distributions resembled those of tail rays originating in the Venus ionosphere or ionopause region rather than of ions produced in the corona of neutral atoms that surrounds the planet. The C+ abundance was approximate to 10% of O+. The observed O+ speed was very close to the simultaneous solar wind speed and the O+ temperature was a cool 5600 K/amu. The flux densities for the three events were (2.4-4.4)x10(3) cm(-2)s(-1). C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV BERN,INST PHYS,CH-3012 BERN,SWITZERLAND. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. UNIV MARYLAND,COLLEGE PK,MD 20742. TECH UNIV CAROLO WILHELMINA BRAUNSCHWEIG,INST DV ANLAGEN,D-38023 BRAUNSCHWEIG,GERMANY. UNIV ARIZONA,TUCSON,AZ 85721. UNIV NEW HAMPSHIRE,DURHAM,NH 03824. INST SPACE PHYS,MOSCOW,RUSSIA. RP Grunwaldt, H (reprint author), MAX PLANCK INST AERON,D-37189 KATLENBURG DUHM,GERMANY. RI Galvin, Antoinette/A-6114-2013; OI Moebius, Eberhard/0000-0002-2745-6978 NR 15 TC 19 Z9 19 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 15 PY 1997 VL 24 IS 10 BP 1163 EP 1166 DI 10.1029/97GL01159 PG 4 WC Geosciences, Multidisciplinary SC Geology GA WZ425 UT WOS:A1997WZ42500002 ER PT J AU Kurth, WS Bolton, SJ Gurnett, DA Levin, S AF Kurth, WS Bolton, SJ Gurnett, DA Levin, S TI A determination of the source of Jovian hectometric radiation via occultation by Ganymede SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIO EMISSIONS; VOYAGER AB During the first Galileo flyby of Ganymede, Jovian radio emissions in the frequency range of 700 kHz to 5.6 MHz were completely occulted by the satellite. We take advantage of this serendipitous observation to determine the lo cation of the radio emission source relative to Jupiter. The evidence suggests that the apparent source is along an L greater than or similar to 7 magnetic field line near the central meridian longitude (similar to 160 degrees) of the spacecraft and at 1 to 3 Jovian radii above the northern hemisphere of Jupiter. These results are consistent with a source located along either the Ganymede or Europa flux tube. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Kurth, WS (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242, USA. OI Kurth, William/0000-0002-5471-6202 NR 14 TC 15 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 MAY 15 PY 1997 VL 24 IS 10 BP 1171 EP 1174 DI 10.1029/97GL00988 PG 4 WC Geosciences, Multidisciplinary SC Geology GA WZ425 UT WOS:A1997WZ42500004 ER PT J AU Wilson, GR Khazanov, G Horwitz, JL AF Wilson, GR Khazanov, G Horwitz, JL TI Achieving zero current for polar wind outflow on open flux tubes subjected to large photoelectron fluxes SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA AB In this study we investigate how the condition of zero current on open flux tubes with polar wind outflow, subjected to large photoelectron fluxes, can be achieved. We employ a steady state collisionless semikinetic model to determine the density profiles of O+, H+, thermal electrons and photoelectrons coming from the ionosphere along with H+, ions and electrons coming from the magnetosphere. The model solution attains a potential distribution which both satisfies the condition of charge neutrality and zero current. For the range of parameters considered in this study we find that a 45-60 volt discontinuous potential drop may develop to reflect most of the photoelectrons back toward the ionosphere. This develops because the downward flux of electrons from the magnetosphere to the ionosphere on typical open flux tubes (e.g. the polar rain) appears to be insufficient to balance the photoelectron flux from the ionosphere. C1 UNIV ALABAMA,CTR SPACE PLASMA AERON & ASTROPHYS RES,HUNTSVILLE,AL 35899. RP Wilson, GR (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES83,HUNTSVILLE,AL 35816, USA. NR 18 TC 27 Z9 27 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 MAY 15 PY 1997 VL 24 IS 10 BP 1183 EP 1186 DI 10.1029/97GL00923 PG 4 WC Geosciences, Multidisciplinary SC Geology GA WZ425 UT WOS:A1997WZ42500007 ER PT J AU Natarajan, M Callis, LB AF Natarajan, M Callis, LB TI Ozone variability in the high latitude summer stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Observations made by the HALOE instrument aboard UARS show very low stratospheric ozone in the Arctic and Antarctic summers of 1992 and 1993 [Park and Russell,1994]. Large longitudinal variability is seen in ozone between 8 and 45 mb, poleward of 60 degrees during late summer. This paper examines the cause of this variability using isentropic trajectory analysis and photochemical calculations. According to trajectory analysis using UKMO wind fields, air parcels with higher ozone mixing ratios move to 73 degrees N from lower latitudes in the longitude sector 180 degrees E - 225 degrees E over a 9 day period beginning on 10 August, 1993. Low ozone values seen in the HALOE data around 100 degrees E at 73 degrees N correspond to air parcels that remain mostly in higher latitudes. We present results from photochemical calculations conducted in conjunction with UARS data, and conclude that the longitudinal asymmetry in ozone can be be explained by transport along isentropic trajectories with standard chemistry. C1 NASA,LANGLEY RES CTR,ASD,HAMPTON,VA 23681. RP Natarajan, M (reprint author), SCI APPLICAT INT CORP,HAMPTON,VA 23666, USA. NR 6 TC 13 Z9 13 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 MAY 15 PY 1997 VL 24 IS 10 BP 1191 EP 1194 DI 10.1029/97GL01155 PG 4 WC Geosciences, Multidisciplinary SC Geology GA WZ425 UT WOS:A1997WZ42500009 ER PT J AU Self, S Rampino, MR Zhao, J Katz, MG AF Self, S Rampino, MR Zhao, J Katz, MG TI Volcanic aerosol perturbations and strong El Nino events: No general correlation SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOUTHERN OSCILLATION; STRATOSPHERIC AEROSOLS; POSSIBLE ASSOCIATION; PINATUBO ERUPTION; ICE CORE; CLIMATE; OCEAN; TEMPERATURE; MODEL; INDEX AB We test the hypothesis that El Nino/Southern Oscillation (ENSO) events are caused or enhanced by volcanic aerosol perturbations using two methods: 1) A case-by-case comparison of the 16 strongest El Nino events of the last 150 years with the characteristics of the largest concurrent volcanic events, and 2) Comparison of the timing of strong El Nino events and the independently determined record of stratospheric optical depth (2) perturbations. Many eruptions that occurred near times of strong El Nino years produced small amounts of stratospheric aerosols, in many cases the relative timing of the two events argues against triggering. The correlation of 4 of 11 peaks in global stratospheric optical depth (tau greater than or equal to 0.025) within 3 years of strong El Nino events over the last 150 years is what would be expected by chance. Moreover, five strong El Ninos occurred between 1915 and 1960, when the stratosphere was largely free of volcanic aerosols. Of the three strongest tropical volcanic aerosol perturbations that coincided with or were followed by strong El Ninos in the period studied (Krakatau in 1883, El Chichon in 1982, and Pinatubo in 1991), the two modern ones occurred after the earliest SST warming of the El Nino events. The coincidence of these two phenomena indicates no causative relationship. C1 UNIV OREGON,DEPT GEOL SCI,EUGENE,OR 97403. NYU,EARTH & ENVIRONM SCI PROGRAM,NEW YORK,NY 10003. UNIV HAWAII MANOA,DEPT METEOROL,HONOLULU,HI 96822. NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RP Self, S (reprint author), UNIV HAWAII MANOA,DEPT GEOL & GEOPHYS,HAWAII CTR VOLCANOL,HONOLULU,HI 96822, USA. NR 41 TC 27 Z9 27 U1 3 U2 9 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 MAY 15 PY 1997 VL 24 IS 10 BP 1247 EP 1250 DI 10.1029/97GL01127 PG 4 WC Geosciences, Multidisciplinary SC Geology GA WZ425 UT WOS:A1997WZ42500023 ER PT J AU Chen, G Chapron, B Tournadre, J Katsaros, K Vandemark, D AF Chen, G Chapron, B Tournadre, J Katsaros, K Vandemark, D TI Global oceanic precipitation: A joint view by TOPEX and the TOPEX microwave radiometer SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID RADAR ALTIMETER; RAIN; SEA; SATELLITE; ATLANTIC; ERS-1 AB The TOPEX/POSEIDON mission offers the first opportunity to observe rain cells over the ocean by a dual-frequency radar altimeter (TOPEX) and simultaneously observe their natural radiative properties by a three-frequency radiometer (TOPEX microwave radiometer (TMR)). This work is a feasibility study aimed at understanding the capability and potential of the active/passive TOPEX/TMR system for oceanic rainfall detection. On the basis of past experiences in rain flagging, a joint TOPEX/TMR rain probability index is proposed. This index integrates several advantages of the two sensors and provides a more reliable rain estimate than the radiometer alone. One year's TOPEX/TMR TMR data are used to test the performance of the index. The resulting rain frequency statistics show quantitative agreement with those obtained from the Comprehensive Ocean-Atmosphere Data Set (COADS) in the Intertropical Convergence Zone (ITCZ), while qualitative agreement is found for other regions of the world ocean. A recent finding that the latitudinal frequency of precipitation over the Southern Ocean increases steadily toward the Antarctic continent is confirmed by our result. Annual and seasonal precipitation maps are derived from the index. Notable features revealed include an overall similarity in rainfall pattern from the Pacific, the Atlantic, and the Indian Oceans and a general phase reversal between the two hemispheres, as well as a number of regional anomalies in terms of rain intensity. Comparisons with simultaneous Global Precipitation Climatology Project (GPCP) multisatellite precipitation rate and COADS rain climatology suggest that systematic differences also exist. One example is that the maximum rainfall in the ITCZ of the Indian Ocean appears to be more intensive and concentrated in our result compared to that of the GPCP. Another example is that the annual precipitation produced by TOPEX/TMR is constantly higher than those from GPCP and COADS in the extratropical regions of the northern hemisphere, especially in the northwest Pacific Ocean. Analyses of the seasonal variations of prominent rainy and dry zones in the tropics and subtropics show various behaviors such as systematic migration, expansion and contraction, merging and breakup, and pure intensity variations, The seasonality of regional features is largely influenced by local atmospheric events such as monsoon, storm, or snow activities. The results of this study suggest that TOPEX and its follow-on may serve as a complementary sensor to the special sensor microwave/imager in observing global oceanic precipitation. C1 IFREMER,CTR BREST,DEPT OCEANOG SPATIALE,F-29280 PLOUZANE,FRANCE. NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,WALLOPS FLIGHT FACIL,WALLOPS ISL,VA 23337. RP Chen, G (reprint author), OCEAN UNIV QINGDAO,OCEAN REMOTE SENSING INST,5 YUSHAN RD,QINGDAO 266003,PEOPLES R CHINA. RI Chapron, Bertrand/O-6527-2015; tournadre, jean/F-8402-2010 OI tournadre, jean/0000-0003-1159-4388 NR 33 TC 31 Z9 34 U1 1 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 MAY 15 PY 1997 VL 102 IS C5 BP 10457 EP 10471 DI 10.1029/97JC00047 PG 15 WC Oceanography SC Oceanography GA XA569 UT WOS:A1997XA56900007 ER PT J AU Lee, T Marotzke, J AF Lee, T Marotzke, J TI Inferring meridional mass and heat transports of the Indian Ocean by fitting a general circulation model to climatological data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NORTH-ATLANTIC; DATA ASSIMILATION; STEADY-STATE; DYNAMICS AB The meridional overturning and heat transport of the Indian Ocean are studied by fitting the steady state dynamics of a general circulation model (GCM) to climatological annual mean temperatures, salinities, and surface forcings using the GCM and its adjoint. By estimating target temperatures and salinities near the artificially closed side boundaries as part of the optimization procedure, a steady solution that is consistent with climatological data within limits of observational errors is found. The resultant meridional overturning is vigorous (14 Sv; 1 Sv = 10(6) m(3)/s) only in the upper 1000 m. The estimated deep inflow entering the Indian Ocean from the south is weak. Requiring a large net northward inflow at depth does not result in strong inferior upwelling but leads to unrealistically large baroclinic mass exchange and implied vertical mixing near the Indonesian throughflow region. The shallow overturning is the main carrier of the southward heat transport, which has a maximum of 0.8 PW (1 PW = 10(15) W) near 15 degrees S. Wind forcing plays a key role in driving the estimated overturning of the Indian Ocean. This result is in disagreement with previous interpretations about the central role of surface heat flux in driving a vigorous deep overturning of the Indian Ocean. C1 MIT,CTR GLOBAL CHANGE SCI,CAMBRIDGE,MA 02139. RP Lee, T (reprint author), CALTECH,JET PROP LAB,MS 300-323,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 33 TC 47 Z9 48 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 MAY 15 PY 1997 VL 102 IS C5 BP 10585 EP 10602 DI 10.1029/97JC00464 PG 18 WC Oceanography SC Oceanography GA XA569 UT WOS:A1997XA56900017 ER PT J AU Ferreyra, E Murr, LE Garcia, EP Horz, F AF Ferreyra, E Murr, LE Garcia, EP Horz, F TI Effect of initial microstructure on high velocity and hypervelocity impact cratering and crater-related microstructures in thick copper targets .1. Soda-lime glass projectiles SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID DEFORMATION AB Three uniquely different initial microstructure regimes were created in 2.5 cm thick copper targets: an as-received 98 mu m grain size containing similar to 10(10) disiocations/cm(2). (Vickers hardness of 0.89 GPa); an annealed 124 mu m grain size containing similar to 10(9) dislocations/cm(2) (Vickers hardness of 0.69 GPa); and a 763 mu m grain size containing similar to 10(9) dislocations/cm(2) (Vickers hardness of 0.67 GPa). Each of these target plates was impacted by 3.18 mm diameter soda-lime glass spheres at nominal impact velocities of 2, 4 and 6 km s(-1). Grain size was observed to have only a very small or negligible contribution to cratering, while the dislocation density had a controlling influence on both the target hardness and the cratering process. Residual crater hardness profiles were correlated with specific microstructure zones extending from the crater wall into the target, and both hardness profiles a nd residual microstructures differed for each specific target, and for each different impact velocity. Microbands coincident with traces of {111} planes were associated with a zone of residual target hardening and increased with increasing grain size and impact velocity. No significant melt-related phenomena were observed, and crater-related target flow occurs by solid-state plastic flow through dynamic recrystallization, forming a narrow, softened zone at the crater wall. C1 NASA,LYNDON B JOHNSON SPACE CTR,SOLAR SYST EXPLORAT DIV,HOUSTON,TX 77058. RP Ferreyra, E (reprint author), UNIV TEXAS,DEPT MET & MAT ENGN,EL PASO,TX 79968, USA. NR 22 TC 14 Z9 15 U1 0 U2 1 PU CHAPMAN HALL LTD PI LONDON PA 2-6 BOUNDARY ROW, LONDON, ENGLAND SE1 8HN SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD MAY 15 PY 1997 VL 32 IS 10 BP 2573 EP 2585 DI 10.1023/A:1018646916872 PG 13 WC Materials Science, Multidisciplinary SC Materials Science GA XB297 UT WOS:A1997XB29700008 ER PT J AU Costanza, R dArge, R deGroot, R Farber, S Grasso, M Hannon, B Limburg, K Naeem, S ONeill, RV Paruelo, J Raskin, RG Sutton, P vandenBelt, M AF Costanza, R dArge, R deGroot, R Farber, S Grasso, M Hannon, B Limburg, K Naeem, S ONeill, RV Paruelo, J Raskin, RG Sutton, P vandenBelt, M TI The value of the world's ecosystem services and natural capital SO NATURE LA English DT Article ID ENVIRONMENTAL FUNCTIONS; VALUATION; MANAGEMENT; ECONOMICS; FISHERIES AB The services of ecological systems and the natural capital stocks that produce them are critical to the functioning of the Earth's life-support system. They contribute to human welfare, both directly and indirectly, and therefore represent part of the total economic value of the planet. We have estimated the current economic value of 17 ecosystem services for 16 biomes, based on published studies and a few original calculations. For the entire biosphere, the value (most of which is outside the market) is estimated to be in the range of US$16-54 trillion (10(12)) per year, with an average of US$33 trillion per year. Because of the nature of the uncertainties, this must be considered a minimum estimate. Global gross national product total is around US$18 trillion per year. C1 UNIV MARYLAND,INST ECOL ECON,SOLOMONS,MD 20688. UNIV WYOMING,DEPT ECON,LARAMIE,WY 82070. AGR UNIV WAGENINGEN,CTR ENVIRONM & CLIMATE STUDIES,NL-6700 HB WAGENINGEN,NETHERLANDS. UNIV PITTSBURGH,GRAD SCH PUBL & INT AFFAIRS,PITTSBURGH,PA 15260. UNIV ILLINOIS,DEPT GEOG,URBANA,IL 61801. UNIV ILLINOIS,NCSA,URBANA,IL 61801. INST ECOSYST STUDIES,MILLBROOK,NY 12545. UNIV MINNESOTA,DEPT ECOL EVOLUT & BEHAV,ST PAUL,MN 55108. OAK RIDGE NATL LAB,DIV ENVIRONM SCI,OAK RIDGE,TN 37831. UNIV BUENOS AIRES,FAC AGRON,DEPT ECOL,RA-1417 BUENOS AIRES,DF,ARGENTINA. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV CALIF SANTA BARBARA,NATL CTR GEOG INFORMAT & ANAL,DEPT GEOG,SANTA BARBARA,CA 93106. ECOL ECON RES & APPLICAT INC,SOLOMONS,MD 20688. RP Costanza, R (reprint author), UNIV MARYLAND,CTR ENVIRONM & ESTUARINE STUDIES,DEPT ZOOL,BOX 38,SOLOMONS,MD 20688, USA. RI Costanza, Robert/A-4912-2008; Sutton, Paul/A-6764-2013; Limburg, Karin/M-8380-2013 OI Costanza, Robert/0000-0001-6348-8734; Sutton, Paul/0000-0001-6972-3256; NR 33 TC 5197 Z9 7038 U1 449 U2 3477 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD MAY 15 PY 1997 VL 387 IS 6630 BP 253 EP 260 DI 10.1038/387253a0 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA WZ167 UT WOS:A1997WZ16700043 ER PT J AU Gurnett, DA Kurth, WS Roux, A Bolton, SJ AF Gurnett, DA Kurth, WS Roux, A Bolton, SJ TI Absence of a magnetic-field signature in plasma-wave observations at Callisto SO NATURE LA English DT Article ID MAGNETOSPHERE; JUPITER AB The galilean moons of Jupiter are substantial bodies-three of them are larger than the Earth's Moon, and one is larger than Mercury-yet little has been known about them until very recently. The discovery of a magnetosphere(1) and magnetic field(2) associated with Ganymede was surprising, and raised the possibility that other galilean satellites,. particularly Callisto (which is the second largest after Ganymede), also might have an internally generated magnetic field. Here we report observations of plasma waves around Callisto, detected during the recent fly-by of the Galileo spacecraft. The nature of the plasma waves indicates that Callisto, unlike Ganymede, does not have a magnetosphere or an internal magnetic field The electron density near Callisto, however, is substantially higher than that in Jupiter's magnetosphere at this orbital radius, indicating that Callisto is a significant source of locally generated plasma, This plasma most probably comes from a tenuous atmosphere around Callisto, which may be similar to the hydrogen cloud around Ganymede, as the electron densities are somewhat comparable. C1 UNIV VERSAILLES, CTR ETUD ENVIRONM TERR & PLANETAIRES, F-78140 VELIZY VILLACOUBLAY, FRANCE. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Gurnett, DA (reprint author), UNIV IOWA, DEPT PHYS & ASTRON, IOWA CITY, IA 52242 USA. OI Kurth, William/0000-0002-5471-6202 NR 16 TC 15 Z9 15 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD MAY 15 PY 1997 VL 387 IS 6630 BP 261 EP 262 DI 10.1038/387261a0 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA WZ167 UT WOS:A1997WZ16700044 ER PT J AU Anderson, JD Lau, EL Sjogren, WL Schubert, G Moore, WB AF Anderson, JD Lau, EL Sjogren, WL Schubert, G Moore, WB TI Gravitational evidence for an undifferentiated Callisto SO NATURE LA English DT Article ID GALILEAN SATELLITES; GRAVITY-FIELD; TRACKING DATA; JUPITER AB Before the arrival of the Galileo spacecraft at Jupiter, models for the interior structure of the four galilean satellites-Io, Europa, Ganymede and Callisto-ranged from uniform mixtures of rock and ice (that is, undifferentiated objects) or rocky cores surrounded by a mantle of water ice(1). Now it appears that Io has a large metallic core(2) and that Ganymede is strongly differentiated, most probably into a three-layer structure consisting of a metallic core, a silicate mantle and a deep outer layer of ice(3). Direct information on the interior structure of Callisto determined from previous spacecraft fly-bys(4-6) was essentially limited to an estimate of the mean density being intermediate between pure ice and pure rock, Here we report measurements of Callisto's gravitational field which reveal that, in contrast to Io and Ganymede, this galilean satellite is most probably a homogeneous object consisting of a solar mixture of 40% compressed ice and 60% rock (including iron and iron sulphide), Callisto's undifferentiated state is consistent with the apparent lack of an intrinsic magnetic field(7), and indicates that the outermost galilean satellite has not experienced a heating phase sufficiently high to separate its rock and metal components from the lighter ices. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095. RP Anderson, JD (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 19 TC 44 Z9 47 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD MAY 15 PY 1997 VL 387 IS 6630 BP 264 EP 266 DI 10.1038/387264a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA WZ167 UT WOS:A1997WZ16700046 PM 9153389 ER PT J AU Kippelen, B Meyers, F Peyghambarian, N Marder, SR AF Kippelen, B Meyers, F Peyghambarian, N Marder, SR TI Chromophore design for photorefractive applications SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Article ID BOND-LENGTH ALTERNATION; CONJUGATED ORGANIC-MOLECULES; DONOR-ACCEPTOR POLYENES; HYPERPOLARIZABILITY; POLARIZABILITIES; POLYMER C1 CALTECH,BECKMAN INST,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Kippelen, B (reprint author), UNIV ARIZONA,CTR OPT SCI,TUCSON,AZ 85721, USA. RI Kippelen, Bernard/I-4058-2013 OI Kippelen, Bernard/0000-0002-8417-7051 NR 14 TC 75 Z9 76 U1 0 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0002-7863 J9 J AM CHEM SOC JI J. Am. Chem. Soc. PD MAY 14 PY 1997 VL 119 IS 19 BP 4559 EP 4560 DI 10.1021/ja9643477 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA WZ081 UT WOS:A1997WZ08100037 ER PT J AU Catanese, M Akerlof, CW Biller, SD Boyle, P Buckley, JH CarterLewis, DA Cawley, MF Connaughton, V Dingus, BL Fegan, DJ Fichtel, CE Finley, JP Gaidos, JA Gear, WK Hartman, RC Hillas, AM Krennrich, F Lamb, RC Lessard, RW Lin, YC McEnery, JE Marscher, AP Mohanty, G Mukherjee, R Quinn, J Robson, EI Rodgers, AJ Rose, HJ Samuelson, FW Sembroski, G Schubnell, MS Stevens, JA Terasranta, H Thompson, DJ Weekes, TC Wilson, C Zweerink, J AF Catanese, M Akerlof, CW Biller, SD Boyle, P Buckley, JH CarterLewis, DA Cawley, MF Connaughton, V Dingus, BL Fegan, DJ Fichtel, CE Finley, JP Gaidos, JA Gear, WK Hartman, RC Hillas, AM Krennrich, F Lamb, RC Lessard, RW Lin, YC McEnery, JE Marscher, AP Mohanty, G Mukherjee, R Quinn, J Robson, EI Rodgers, AJ Rose, HJ Samuelson, FW Sembroski, G Schubnell, MS Stevens, JA Terasranta, H Thompson, DJ Weekes, TC Wilson, C Zweerink, J TI Detection of gamma rays with E>100 MeV from BL Lacertae SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects; individual (BL Lacertae); gamma rays, observations ID EXTRAGALACTIC RADIO-SOURCES; ACTIVE GALACTIC NUCLEI; X-RAY; MULTIFREQUENCY OBSERVATIONS; RELATIVISTIC JETS; COMPLETE SAMPLE; TEV ENERGIES; UPPER LIMITS; LAC OBJECTS; BLAZARS AB We present evidence for the first detection of gamma rays from the extragalactic object BL Lacertae. Observations taken with EGRET on the Compton Gamma Ray Observatory between 1995 January 24 and 1995 February 14 indicate a 4.4 sigma excess from the direction of BL Lacertae. The corresponding flux is (40 +/- 12) x 10(-8) photons cm(-2) s(-1) above 100 MeV. The combination of all previous observations where BL Lacertae was in EGRET's field of view result in a 2.4 sigma excess and a corresponding 95% confidence upper limit of 14 x 10(-8) photons cm(-2) s(-1), indicating that its gamma-ray emission is variable, at least on timescales of several months. Observations of BL Lacertae between 22 and 375 GHz were also taken between 1995 January 24 and 1995 February 14, and the flux levels for those measurements are similar to the historical average values for this object. A deep exposure on BL Lacertae with the Whipple Observatory 10 m gamma-ray telescope shows no evidence of emission above 350 GeV during a period 9 months after the EGRET observations. The 99.9% confidence flux upper limit derived from these observations is 0.53 x 10(-11) photons cm-2 s(-1) which implies a large reduction in the gamma-ray emission of BL Lacertae between EGRET and Whipple Observatory energies. This reduction should result from processes intrinsic to BL Lacertae because it is near enough to Earth that intergalactic background IR fields should not significantly reduce the flux of gamma rays to which the Whipple Observatory telescope is sensitive. C1 UNIV MICHIGAN,RANDALL LAB PHYS,ANN ARBOR,MI 48109. UNIV LEEDS,DEPT PHYS,LEEDS LS2 9JT,W YORKSHIRE,ENGLAND. NATL UNIV IRELAND UNIV COLL DUBLIN,DEPT PHYS,DUBLIN 4,IRELAND. HARVARD SMITHSONIAN CTR ASTROPHYS,FRED LAWRENCE WHIPPLE OBSERV,AMADO,AZ 85645. ST PATRICKS COLL,DEPT PHYS,MAYNOOTH,KILDARE,IRELAND. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,WASHINGTON,DC. PURDUE UNIV,DEPT PHYS,W LAFAYETTE,IN 47907. ROYAL OBSERV,EDINBURGH EH9 3HJ,MIDLOTHIAN,SCOTLAND. STANFORD UNIV,HANSEN EXPT PHYS LAB,STANFORD,CA 94305. BOSTON UNIV,DEPT ASTRON,BOSTON,MA 02215. JOINT ASTRON CTR,HILO,HI 96720. HELSINKI UNIV TECHNOL,METSAHOVI RADIO RES STN,SF-02150 ESPOO,FINLAND. RP Catanese, M (reprint author), IOWA STATE UNIV SCI & TECHNOL,DEPT PHYS & ASTRON,AMES,IA 50011, USA. RI Thompson, David/D-2939-2012; OI Thompson, David/0000-0001-5217-9135; Dingus, Brenda/0000-0001-8451-7450 NR 56 TC 44 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1997 VL 480 IS 2 BP 562 EP 567 DI 10.1086/303998 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500010 ER PT J AU Sakai, S Madore, BF Freedman, WL AF Sakai, S Madore, BF Freedman, WL TI Tip of the red giant branch distances to galaxies .4. Sextans B SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies, distances and redshifts; galaxies, individual (Sextans B) ID DWARF IRREGULAR GALAXIES; RR LYRAE VARIABLES; STELLAR POPULATIONS; GLOBULAR-CLUSTERS; LOCAL GROUP; STARS; CEPHEID; LUMINOSITY; MAGNITUDES; PHOTOMETRY AB We present color-magnitude diagrams and luminosity functions of stellar populations in the nearby dwarf galaxy Sextans B, based on VI photometry acquired with the Carnegie Observatories spectroscopic multislit and imaging camera CCD prime-focus camera on the Palomar 5 m telescope. Combining previously published Cepheid observations with our new data, we obtain a distance to Sextans B based on the multiwavelength period-luminosity (PL) relations; BVRI data for eight Cepheids having periods ranging from 4 to 30 days were used. This Population I true distance modulus for Sextans B is found to be (m - M)(0) = 25.69 +/- 0.27 mag (1.37 +/- 0.18 Mpc) with an extinction value of A(V) = 0.05 mag. The Cepheid distance is then compared with the Population II distance, determined by applying the tip of the red giant branch (TRGB) method. A discontinuity in the I-band luminosity function is detected at I = 21.60 +/- 0.10 mag. Adopting M-I = -4.04 +/- 0.02 mag as the absolute magnitude of the TRGB, and taking into account the Galactic extinction value of A(I) = 0.02 mag, we obtain a Population II distance modulus of (m-M)(0) = 25.56 +/- 0.10 mag (1.29 +/- 0.07 Mpc). Additional systematic uncertainties in the TRGB distance scale probably exist at the 5%-10% level. The agreement between the two distances and their uncertainties derived from distinctly independent methods further demonstrates that the accuracy and precision of the TRGB method as an extragalactic distance indicator are comparable to those of the Cepheid PL relation. C1 CALTECH,NASA,IPAC EXTRAGALACT DATABASE,PASADENA,CA 91125. CARNEGIE INST WASHINGTON OBSERV,PASADENA,CA 91101. RP Sakai, S (reprint author), CALTECH,JET PROP LAB,MS 100-22,PASADENA,CA 91125, USA. NR 27 TC 27 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 MAY 10 PY 1997 VL 480 IS 2 BP 589 EP 595 DI 10.1086/304000 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500012 ER PT J AU Unwin, SC Wehrle, AE Lobanov, AP Zensus, JA Aller, MF Aller, HD AF Unwin, SC Wehrle, AE Lobanov, AP Zensus, JA Aller, MF Aller, HD TI Variability in the inverse-Compton X-ray flux from the jet in quasar 3C 345 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, jets; quasars, individual, (3C 345); radiation mechanisms, nonthermal; radio continuum, galaxies; X-rays, galaxies ID POLARIZATION STRUCTURE; VLBI-OBSERVATIONS; VLA OBSERVATIONS; RADIO-SOURCES; EVOLUTION; OBJECTS; SAMPLE; 3C-345; QUASAR-3C-345; EMISSION AB We present the results of the first systematic study of correlated variability in the X-ray emission and the parsec-scale radio structure of the ''superluminal'' quasar 3C 345. This quasar is one of a class af core-dominated flat-spectrum radio sources that are believed to emit X-rays via the synchrotron self-Compton process. By studying its variability in X-rays, we can test this hypothesis for 3C 345 by modeling the expected inverse-Comptom flux from the parsec-scale jet, using parameters derived from multifrequency VLBI imaging. Since the predicted X-ray flux is very sensitive to the physical parameters of the compact radio-emitting regions, a study of variability, with quasi-simultaneous X-ray and VLBI data, is of particular interest because it is less sensitive to assumptions in the adopted model. The soft X-ray flux density of 3C 345 was observed by the ROSAT PSPC instrument at seven epochs during 1990-1993, during which time its flux density varied by a factor of 2, but with no change in spectral index; The X-ray points closely track the high-frequency radio Bur light curve. Using a series of VLBI images, we followed the time evolution of spectral shapes and angular sizes of the nucleus and the strongest jet component ''C7,'' at a distance of similar or equal to 0.5 mas (2 pc) from the nucleus, and derived physical parameters for the components. We find that component C7, not the nucleus, is the dominant generator of the observed X-rays during 1992-1993. For the nucleus, we applied the inhomogeneous-jet model of Konigl and found find that it underpredicts the X-ray flux for any plausible combination of physical parameters derived from observation. A homogeneous sphere, with flux density peaking at a few GHz, is adequate for modeling the evolution of C7. This sphere model requires that C7 dominated the X-ray emission, unless its Doppler factor is much greater than 10. This contrasts with the situation at epoch 1990.55, for which comparable data (Unwin et al. 1994) showed that the nucleus and C5 (the dominant jet feature at that time) both contributed to the X-ray emission. We discuss the lack of detectable gamma-rays from 3C 345 in relation to other gamma-ray loud blazars with which it shares many observational properties, Combining the superluminal speed (from VLBI) and Doppler factor deduced from the synchrotron self-Compton calculation, we solve for the jet kinematics at the position of C7, and we nd that the jet bends away from the line of sight (from theta similar or equal to 2 degrees to similar or equal to 10 degrees) and accelerates from gamma similar or equal to 5 to greater than or similar to 10 over the range of (deprojected) distance from the nucleus of similar or equal to 3 to similar or equal to 20 pc. C1 CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,PASADENA,CA 91125. NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109. RP Unwin, SC (reprint author), CALTECH,DEPT MATH PHYS & ASTRON,PASADENA,CA 91125, USA. RI Lobanov, Andrei/G-5891-2014 NR 46 TC 42 Z9 43 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1997 VL 480 IS 2 BP 596 EP 606 DI 10.1086/303988 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500013 ER PT J AU Williams, RM Chu, YH Dickel, JR Beyer, R Petre, R Smith, RC Milne, DK AF Williams, RM Chu, YH Dickel, JR Beyer, R Petre, R Smith, RC Milne, DK TI Supernova remnants in the magellanic clouds .1. The colliding remnants DEM L316 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, ISM; ISM, individual (DEM L316); ISM, structure; Magellanic Clouds; supernova remnants ID SCANNING INTERFEROMETER OBSERVATIONS; NOVA REMNANTS; HOT; PLASMA AB The Large Magellanic Cloud (LMC) supernova remnant (SNR) DEM L316 is of considerable interest, as it shows two overlapping shells at radio and optical wavelengths. This morphology suggests that DEM L316 is in fact two SNRs, which may or may not be spatially connected. We have observed the DEM L316 remnants at optical, radio, and X-ray wavelengths in order to address the question of whether the SNRs are interacting, and if so, whether a tunnel might have formed between the remnants, allowing them to equilibrate. Besides the connecting shell morphologies at optical and radio wavelengths, our observations show enhanced [O III] emission at the juncture between the shells, enhanced X-ray emission from one shell at that juncture, and a change in the structure of the magnetic fieId near the interaction region. These factors strongly imply that the two remnants are indeed colliding. In addition, we have done a detailed study on the physical properties of the remnants, including an examination of thermal and kinetic energies and of the balance of thermal and magnetic pressures. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109. CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA. RP Williams, RM (reprint author), UNIV ILLINOIS,DEPT ASTRON,1002 W GREEN ST,URBANA,IL 61801, USA. NR 38 TC 45 Z9 45 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 MAY 10 PY 1997 VL 480 IS 2 BP 618 EP 632 DI 10.1086/303990 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500015 ER PT J AU Dominik, C Tielens, AGGM AF Dominik, C Tielens, AGGM TI The physics of dust coagulation and the structure of dust aggregates in space SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; dust, extinction; interplanetary medium; ISM, clouds; solar system, formation ID INTERSTELLAR GRAINS; SURFACE-ENERGY; CONTACT; SOLIDS; CLOUDS AB Even though dust coagulation is a very important dust-processing mechanism in interstellar space and protoplanetary disks, there are still important parts of the physics involved that are poorly understood. This imposes a serious problem for model calculations of any kind. In this paper, we attempt to improve the situation by including the effects of tangential forces on the contact in some detail. These have been studied in recent papers. We summarize the main results from these papers and apply them to detailed simulations of the coagulation process and of collisions between dust aggregates. Our results show the following: (1) the growth of aggregates by monomers will normally not involve major restructuring of the aggregates, (2) the classical hit-ann-stick assumption is reasonably valid for this case, (3) collisions of aggregates with each other or with large grains can lead to significant compaction, and (4) the results can be easily understood in terms of critical energies for different restructuring processes. We also derive a short summary that may be used as a recipe for determining the outcome of collisions in coagulation calculations. It is shown that turbulent velocity fields in interstellar clouds are capable of producing considerably compressed aggregates, while the small aggregates forming early on in the solar nebula will not be compacted by collisions. However, compaction provides an important energy sink in collisions of larger aggregates in the solar nebula. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Dominik, C (reprint author), LEIDEN OBSERV,POB 9513,NL-2300 RA LEIDEN,NETHERLANDS. NR 48 TC 309 Z9 311 U1 0 U2 14 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1997 VL 480 IS 2 BP 647 EP 673 DI 10.1086/303996 PN 1 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500017 ER PT J AU Kazanas, D Hua, XM Titarchuk, L AF Kazanas, D Hua, XM Titarchuk, L TI Temporal and spectral properties of comptonized radiation and its applications SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms, nonthermal; stars, neutron ID BLACK-HOLES; ACCRETION AB We have found relations between the temporal and spectral properties of radiation Comptonized in an extended atmosphere associated with compact accreting sources. We demonstrate that the fluctuation power spectrum density (PSD) imposes constraints on the atmosphere scale and profile. Furthermore, we indicate that the slope and low-frequency break of the PSD are related to the Thomson depth, tau(0), of the atmosphere and the radius of its physical size, respectively. Since the energy spectrum of the escaping radiation also depends on tau(0) (and the electron temperature kT(e)), the relation between spectral and temporal properties follows. This relation allows, for the first time, an estimate of the accreting matter Thomson depth, tau(0), independent of arguments involving Comptonization. We present figures for the light curves and PSDs of different energy bands, the photon energy spectra, and the phase lags as functions of the variability frequency. The temporal properties of the high (soft) and low (hard) state of black hole sources are discussed in this context. RP Kazanas, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. NR 18 TC 110 Z9 112 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 MAY 10 PY 1997 VL 480 IS 2 BP 735 EP 740 DI 10.1086/303991 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500024 ER PT J AU Turner, NJJ Bodenheimer, P Bell, KR AF Turner, NJJ Bodenheimer, P Bell, KR TI Models of the spectral energy distributions of FU Orionis stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; radiative transfer; stars, pre-main-sequence; stars, variables, other (FU Orionis) ID T-TAURI STARS; ACCRETION DISKS; INFRARED-SPECTRA; YOUNG STARS; MASS-LOSS; EVOLUTION; ENVELOPES; OBJECTS; OPACITY; EXTINCTION AB Observed spectral energy distributions (SEDs) of FU Orionis, V1057 Cygni, and V1515 Cygni are fitted by theoretical spectra, which are calculated from models consisting of outbursting accretion disks together with flattened envelopes. Temperature in the envelopes is determined by approximate radiative equilibrium with a central source. The disk models are two-dimensional and include reprocessing of disk radiation by the disk. The theoretical spectra are calculated using a radiative transfer code and frequency-dependent opacities, at a spectral resolution of lambda/Delta lambda = 14. Excellent matches to the data are obtained for all three objects with reasonable model parameters. Radiative transfer is also used to calculate a time series of images showing the progress of an outburst as imaged through a B-band filter. C1 UNIV CALIF SANTA CRUZ,BOARD STUDIES ASTRON & ASTROPHYS,SANTA CRUZ,CA 95064. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Turner, NJJ (reprint author), UNIV CALIF SANTA CRUZ,LICK OBSERV,SANTA CRUZ,CA 95064, USA. NR 57 TC 21 Z9 21 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 MAY 10 PY 1997 VL 480 IS 2 BP 754 EP 766 DI 10.1086/303983 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500026 ER PT J AU Chae, J Yun, HS Poland, AI AF Chae, J Yun, HS Poland, AI TI Effects of non-LTE radiative loss and partial ionization on the structure of the transition region SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; radiative transfer; Sun, magnetic fields; Sun, transition region ID ENERGY-BALANCE; CORONAL LOOPS; SOLAR CHROMOSPHERE; OBSERVED REDSHIFTS; MAGNETIC-FIELD; FAST DOWNFLOWS; QUIET-SUN; MODELS; FLOWS; EXPLANATION AB In this paper we address the question of how non-LTE radiative losses with partial ionization of hydrogen and helium affects the energetics and structure of the solar transition region. To accomplish this we have constructed theoretical models of a thin rigid magnetic flux tube with a steady material flow, which is embedded vertically in the solar atmosphere. These models include the effects of material flow, conduction, non-LTE radiative transfer in H and He, and partial ionization. We find from this study that the effect of non-LTE radiative transfer with partial ionization is significant near the base of the transition region at temperatures less than 2.5 x 10(4) K. This leads to a 1 order of magnitude increase in the differential emission measure in comparison with the optically thin approximation with complete ionization in the low (less than 2.5 x 10(4) K) temperature regime. Above this region the non-LTE and opacity effects are small. In the upflow case the conductive and convective energy processes dominate to such a large extent that non-LTE radiative process and partial ionization are not important. In this work we also confirm the previous work of other authors who provided the explanation for why downflowing transition region material is much more visible than upflowing material. We present the results in a manner that gives a good physical understanding as to why this occurs. C1 SEOUL NATL UNIV,DEPT ASTRON,SEOUL 151742,SOUTH KOREA. RP Chae, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,SOLAR PHYS BRANCH,GREENBELT,MD 20771, USA. NR 29 TC 14 Z9 14 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1997 VL 480 IS 2 BP 817 EP 824 DI 10.1086/303999 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WW855 UT WOS:A1997WW85500032 ER PT J AU Ritter, N Bryant, N AF Ritter, N Bryant, N TI An optimal vertical reference plane correction algorithm for multiple source digital elevation models SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB The JPL Cartographic Group is currently constructing a worldwide database of digital elevation at nominal 100 m postings, using multiple sources of elevation data available from the U.S. Defense Mapping Agency, including DTED Level-1, and DCW hypsography. In the process of constructing the database, vertical shear anomalies were observed on 1 degrees cell boundaries. The source was attributed primarily to uncontrolled variations in the vertical reference surface used from cell to cell, varying by as much as 80 m. This paper describes algorithms developed to merge these problematic cells into a morphologically consistent database, while preserving the local accuracy estimates. RP Ritter, N (reprint author), CALTECH,JET PROP LAB,CARTOG APPLICAT GRP,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 6 TC 1 Z9 1 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 MAY 10 PY 1997 VL 18 IS 7 BP 1617 EP 1626 DI 10.1080/014311697218322 PG 10 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA WV632 UT WOS:A1997WV63200014 ER PT J AU Ritter, N Ruth, M AF Ritter, N Ruth, M TI The GeoTiff data interchange standard for raster geographic images SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB The GeoTIFF interchange standard is an extension of the popular TIFF format, to support a geodetically sound raster data georeferencing capability. The geographic content supported in the GeoTIFF tag structure includes its cartographic projection, datum, ground pixel dimension, and other geographic variables, based upon the non-profit Petrotechnical Open Software Company (POSC)'s Epicentre 2.0 geodetic model. This paper is a review of the progress and status of the GeoTIFF initiative, as well as an overview of the main technical characteristics and principles of the GeoTIFF format. C1 SPOT IMAGE CORP,PROD DEV TEAM,RESTON,VA 22091. RP Ritter, N (reprint author), CALTECH,JET PROP LAB,CARTOG APPLICAT GRP,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 6 TC 9 Z9 9 U1 0 U2 5 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 MAY 10 PY 1997 VL 18 IS 7 BP 1637 EP 1647 DI 10.1080/014311697218340 PG 11 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA WV632 UT WOS:A1997WV63200016 ER PT J AU Rignot, EJ Gogineni, SP Krabill, WB Ekholm, S AF Rignot, EJ Gogineni, SP Krabill, WB Ekholm, S TI North and northeast Greenland ice discharge from satellite radar interferometry SO SCIENCE LA English DT Article ID GROUNDING LINES; MASS-BALANCE; ANTARCTICA; SHELF; SHEET; ABLATION; FLEXURE; STREAM AB Ice discharge from north and northeast Greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3.5 times that estimated from iceberg production. The satellite estimates, obtained at the grounding line of the outlet glaciers, differ from those obtained at the glacier front, because basal melting is extensive at the underside of the floating glacier sections. The results suggest that the north and northeast parts of the Greenland ice sheet may be thinning and contributing positively to sea-level rise. C1 UNIV KANSAS,RADAR SYST & REMOTE SENSING LAB,LAWRENCE,KS 66045. NASA,GODDARD SPACE FLIGHT CTR,WALLOPS FLIGHT FACIL,LAB HYDROSPHER PROC,WALLOPS ISL,VA 23337. KORT & MATRIKELSTYRELSEN,GEODET DIV,DK-2400 COPENHAGEN NV,DENMARK. RP Rignot, EJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Rignot, Eric/A-4560-2014 OI Rignot, Eric/0000-0002-3366-0481 NR 41 TC 73 Z9 78 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 MAY 9 PY 1997 VL 276 IS 5314 BP 934 EP 937 DI 10.1126/science.276.5314.934 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA WY792 UT WOS:A1997WY79200043 ER PT J AU Brown, RH Cruikshank, DP Pendleton, Y Veeder, GJ AF Brown, RH Cruikshank, DP Pendleton, Y Veeder, GJ TI Surface composition of Kuiper belt object 1993SC SO SCIENCE LA English DT Article ID TRITON; PLUTO; ICES AB The 1.42- to 2.40-micrometer spectrum of Kuiper belt object 1993SC was measured at the Keck Observatory in October 1996. It shows a strongly red continuum reflectance and several prominent infrared absorption features. The strongest absorptions in 1993SC's spectrum occur near 1.62, 1.79, 1.95, 2.20, and 2.32 micrometers in wavelength, Features near the same wavelengths in the spectra of Pluto and Neptune's satellite Triton are due to CH4 on their surfaces, suggesting the presence of a simple hydrocarbon ice such as CH4, C2H6, C2H4, or C2H2 on 1993SC. In addition, the red continuum reflectance of 1993SC suggests the presence of more complex hydrocarbons. C1 UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Brown, RH (reprint author), UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721, USA. NR 20 TC 49 Z9 49 U1 1 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 9 PY 1997 VL 276 IS 5314 BP 937 EP 939 DI 10.1126/science.276.5314.937 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA WY792 UT WOS:A1997WY79200044 PM 9163038 ER PT J AU Hudgins, DM Allamandola, LJ AF Hudgins, DM Allamandola, LJ TI Infrared spectroscopy of matrix-isolated polycyclic aromatic hydrocarbon cations .4. The tetracyclic PAH isomers chrysene and 1,2-benzanthracene SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID ISOLATED NAPHTHALENE; VIBRATIONAL-SPECTRA; ELECTRONIC-SPECTRA; RADICAL CATIONS; ANTHRACENE; TETRACENE; PENTACENE AB The mid-infrared spectra of the polycyclic aromatic hydrocarbon (PAH) cations of the tetracyclic isomers chrysene (C18H12+) and 1,2-benzanthracene (C18H12+) are presented. As with previous PAH cations studied to date, the CC stretching and CH in-plane bending mode absorptions are about an order of magnitude stronger than the aromatic CH out-of-plane bending absorptions and nearly 2 orders of magnitude more intense than the corresponding bands in the neutral molecule. The CH bands arising from the out-of-plane bends in the cation are slightly weaker than the corresponding bands in the neutral species. The strongest cation bands of these species fall between 1300 and 1330 cm(-1), close to the peak of the most intense interstellar emission feature in HII regions and reflection nebulae. A strong PAH cation band at slightly higher frequency than 1300 cm(-1) may be associated with an asymmetric CC stretching vibration involving rings adjacent to the kink in the chain of aromatic rings. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. ADRIAN COLL,DEPT CHEM,ADRIAN,MI. NR 25 TC 50 Z9 50 U1 0 U2 7 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 MAY 8 PY 1997 VL 101 IS 19 BP 3472 EP 3477 DI 10.1021/jp9609794 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA WY394 UT WOS:A1997WY39400009 PM 11541094 ER PT J AU Caillat, T Fleurial, JP Borshchevsky, A AF Caillat, T Fleurial, JP Borshchevsky, A TI Growth and some properties of Cr11Ge19 SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article DE chromium germanide; intermetallic compounds; crystals; transport properties ID CHROMIUM AB Cr11Ge19 belongs to a large family of materials known as the Nowotny chimney-ladder compounds, some of which were recently proposed as advanced thermoelectric materials, particularly because of their low thermal conductivity related to their relatively complex crystal structure. In order to assess the potential of the compound Cr11Ge19 for thermoelectric applications, we grew large single crystals of this peritectic compound by a vertical gradient freeze technique and measured the thermoelectric properties of the crystals. Cr11Ge19 forms peritectically at 1201K and crystals were grown from Ge-rich solutions. The conditions and the results of the crystal growth experiments are presented. The crystals were characterized by X-ray diffractometry, Laue technique, and electron probe microanalysis. The results of the thermoelectric property measurements suggest that Cr11Ge19 has a metallic behavior and therefore presents little interest for thermoelectric applications. RP Caillat, T (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 277-207, PASADENA, CA 91109 USA. NR 18 TC 11 Z9 11 U1 3 U2 18 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-8388 J9 J ALLOY COMPD JI J. Alloy. Compd. PD MAY 5 PY 1997 VL 252 IS 1-2 BP 12 EP 15 DI 10.1016/S0925-8388(96)02614-X PG 4 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA XE340 UT WOS:A1997XE34000013 ER PT J AU Kaneko, H Noren, RD Padilla, PA AF Kaneko, H Noren, RD Padilla, PA TI Superconvergence of the iterated collocation methods for Hammerstein equations SO JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS LA English DT Article DE the iterated collocation method; the discrete collocation method; Hammerstein equations with weakly singular kernels; superconvergence ID FREDHOLM INTEGRAL-EQUATIONS; 2ND KIND; GALERKIN; KERNEL AB In this paper, we analyse the iterated collocation method for Hammerstein equations with smooth and weakly singular kernels. The paper expands the study which began in [16] concerning the superconvergence of the iterated Galerkin method for Hammerstein equations. We obtain in this paper a similar superconvergence result for the iterated collocation method for Hammerstein equations. We also discuss the discrete collocation method for weakly singular Hammerstein equations. Some discrete collocation methods for Hammerstein equations with smooth kernels were given previously in [3, 18]. C1 OLD DOMINION UNIV,DEPT MATH & STAT,NORFOLK,VA 23529. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. NR 24 TC 27 Z9 27 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0377-0427 J9 J COMPUT APPL MATH JI J. Comput. Appl. Math. PD MAY 5 PY 1997 VL 80 IS 2 BP 335 EP 349 DI 10.1016/S0377-0427(97)00040-X PG 15 WC Mathematics, Applied SC Mathematics GA XE525 UT WOS:A1997XE52500011 ER PT J AU Yeh, NC Vasquez, RP Beam, DA Fu, CC Huynh, J Beach, G AF Yeh, NC Vasquez, RP Beam, DA Fu, CC Huynh, J Beach, G TI Effects of lattice distortion and Jahn-Teller coupling on the magnetoresistance of La0.7Ca0.3MnO3 and La0.5Ca0.5CoO3 epitaxial films SO JOURNAL OF PHYSICS-CONDENSED MATTER LA English DT Article ID CA-MN-O; LA1-XSRXCOO3; RESISTIVITY; PEROVSKITE; CRYSTALS AB Studies of La0.7Ca0.3MnO3 epitaxial films on substrates with a range of lattice constants reveal two dominant contributions to the occurrence of colossal negative magnetoresistance (CMR) in these manganites: at high temperatures (T --> T-C, T-C being the Curie temperature), the magnetotransport properties are predominantly determined by the conduction of lattice polarons, while at low temperatures (T much less than T-C), the residual negative magnetoresistance is correlated with the substrate-induced lattice distortion which incurs excess magnetic domain wall scattering. The importance of lattice polaron conduction associated with the presence of Jahn-Teller coupling in the manganites is further verified by comparing the manganites with epitaxial films of another ferromagnetic perovskite, La0.5Ca0.5CoO3. Regardless of the differences in the substrate-induced lattice distortion, the cobaltite films exhibit much smaller negative magnetoresistance, which may be attributed to the absence of Jahn-Teller coupling and the high electron mobility that prevents the formation of lattice polarons. We therefore suggest that lattice polaron conduction associated with the Jahn-Teller coupling is essential for the occurrence of CMR, and that lattice distortion further enhances the CMR effects in the manganites. C1 CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. RP Yeh, NC (reprint author), CALTECH,DEPT PHYS,PASADENA,CA 91125, USA. OI Beach, Geoffrey/0000-0001-9158-7430 NR 28 TC 68 Z9 68 U1 0 U2 11 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0953-8984 J9 J PHYS-CONDENS MAT JI J. Phys.-Condes. Matter PD MAY 5 PY 1997 VL 9 IS 18 BP 3713 EP 3721 DI 10.1088/0953-8984/9/18/010 PG 9 WC Physics, Condensed Matter SC Physics GA WY534 UT WOS:A1997WY53400010 ER PT J AU Bindschadler, R AF Bindschadler, R TI West Antarctic ice sheet collapse? SO SCIENCE LA English DT Letter ID GLACIAL HISTORY; STREAM-B; QUATERNARY RP Bindschadler, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,OCEANS & ICE BRANCH,LAB HYDROSPHER PROC,WAIS WORKING GRP,GREENBELT,MD 20771, USA. NR 14 TC 12 Z9 12 U1 1 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAY 2 PY 1997 VL 276 IS 5313 BP 662 EP 663 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA WW900 UT WOS:A1997WW90000007 ER PT J AU Kufeld, RM Bousman, WG AF Kufeld, RM Bousman, WG TI UH-60A helicopter rotor airloads measured in flight SO AERONAUTICAL JOURNAL LA English DT Article; Proceedings Paper CT 22nd European Rotorcraft Forum CY SEP, 1996 CL BRIGHTON, ENGLAND SP Royal Aeronaut Soc AB The flight test phase of the Nasa-Army UH-60A Airloads Program was completed in February 1994. The objective of the project was to measure the airloads in flight on an UH-60A Black Hawk using 221 blade pressure transducers installed in nine radial arrays. In addition, 21 transducers were installed along the blade leading edge to better identify blade-vortex interaction phenomena. This paper briefly describes the program's background and history, instrumentation, and data acquisition. Airloads data are presented for two test conditions with different levels of complexity: steady, level flight and a diving turn. These flight data provide useful information of relatively simple and complex nonlinear flow for the validation of theoretical analyses. Evidence of shock waves, reverse flow, dynamic stall and blade vortex interactions are presented. RP Kufeld, RM (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 37 TC 5 Z9 5 U1 0 U2 1 PU ROYAL AERONAUTICAL SOC PI LONDON PA 4 HAMILTON PL, LONDON, ENGLAND W1V OBQ SN 0001-9240 J9 AERONAUT J JI Aeronaut. J. PD MAY PY 1997 VL 101 IS 1005 BP 217 EP 227 PG 11 WC Engineering, Aerospace SC Engineering GA XA377 UT WOS:A1997XA37700005 ER PT J AU Mankins, JC AF Mankins, JC TI The space solar power option SO AEROSPACE AMERICA LA English DT Article RP Mankins, JC (reprint author), NASA,OFF SPACE FLIGHT,ADV PROJECTS OFF,WASHINGTON,DC 20546, USA. NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD MAY PY 1997 VL 35 IS 5 BP 30 EP & PG 5 WC Engineering, Aerospace SC Engineering GA WX855 UT WOS:A1997WX85500009 ER PT J AU Maestrello, L AF Maestrello, L TI Active control of panel oscillation induced by accelerating boundary layer and sound SO AIAA JOURNAL LA English DT Article ID CHAOS; SYSTEMS; JET AB Measurements are made of the response and acoustic radiation of a panel structure forced by a constantly accelerating subsonic turbulent boundary layer with superimposed pure-tone sound in a wind tunnel, Both panel loading and response exhibit convective instability and high-dimensional complex behaviors because of nonlinear coupling between the convective short-scale instability wave in the boundary layer and the localized intense long scales of the pure-tone sound and its harmonics. In each run, the panel response exhibits unique dynamics, indicating a dependency on the initial conditions characteristic of a temporal chaotic system,Pure-tone and harmonic response over the broadband are stabilized and suppressed by a local external fixed temporal oscillator system. The controller almost suppresses the nonstationary multiharmonics in the panel. The response reduces to that of an accelerated turbulent boundary layer loading in the absence of sound. The experiments are motivated by considerations of aircraft interior noise and structural response during initial acceleration. RP Maestrello, L (reprint author), NASA,LANGLEY RES CTR,STRUCT ACOUST BRANCH,FLUID MECH & ACOUST DIV,MAIL STOP 463,HAMPTON,VA 23681, USA. NR 18 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 0001-1452 J9 AIAA J JI AIAA J. PD MAY PY 1997 VL 35 IS 5 BP 796 EP 801 PG 6 WC Engineering, Aerospace SC Engineering GA WY030 UT WOS:A1997WY03000005 ER PT J AU Hardin, JC Martin, JE AF Hardin, JC Martin, JE TI Flap side-edge noise: Acoustic analysis of Sen's model SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/CEAS 2nd Joint Aeroacoustics Conference CY MAY 06-08, 1996 CL STATE COLL, PA SP AIAA, CEAS AB The two-dimensional flap side-edge flow model developed by Sen (Sen, R., ''Local Dynamics and Acoustics in a Simple Model of Airfoil Lateral-Edge-Noise,'' AIAA paper 96-1673, May 1996) is analyzed to reveal the noise-production potential of the proposed mechanism, The model assumes that a Fortes will form at the equilibrium position off the side edge of the flap. The vortex is then perturbed away from the equilibrium position bg incoming turbulence, causing it to oscillate and thus radiate sound, The noise field is calculated three-dimensionally by taking the flap to have a finite chord. Spectra and directivity of the far-field sound are presented, In addition, the effect of retarded time differences is evaluated. The parameters in the model are related to typical aircraft parameters and noise reduction possibilities are proposed. C1 CHRISTOPHER NEWPORT UNIV, DEPT MATH, NEWPORT NEWS, VA 23606 USA. RP Hardin, JC (reprint author), NASA, LANGLEY RES CTR, FLUID MECH & ACOUST DIV, MS 462, HAMPTON, VA 23681 USA. NR 18 TC 3 Z9 4 U1 0 U2 1 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 MAY PY 1997 VL 35 IS 5 BP 810 EP 815 DI 10.2514/2.7451 PG 6 WC Engineering, Aerospace SC Engineering GA WY030 UT WOS:A1997WY03000007 ER PT J AU Joslin, RD Gunzburger, MD Nicolaides, RA Erlebacher, G Hussaini, MY AF Joslin, RD Gunzburger, MD Nicolaides, RA Erlebacher, G Hussaini, MY TI Self-contained automated methodology for optimal flow control SO AIAA JOURNAL LA English DT Article ID LAMINAR-INSTABILITY WAVES; BOUNDARY-LAYER-TRANSITION; ACTIVE CONTROL; NUMERICAL-SIMULATION; EQUATION AB A self-contained, automated methodology for active flow control is described, which couples the time-dependent Navier-Stokes system with an adjoint Navier-Stokes system and optimality conditions from which optimal states, i.e., unsteady flowfields and controls (e.g.,actuators), may be determined. The problem of boundary-layer instability suppression through wave cancellation is used as the initial validation case to test the methodology. Here, the objective of control is to match the stress vector along a portion of the boundary to a given vector; instability suppression is achieved by choosing the given vector to be that of a steady baseflow. Control effected through the injection or suction of fluid through a single orifice on the boundary. The results demonstrate that instability suppression can be achieved without any a priori knowledge of the disturbance, which is significant because other control techniques have required some knowledge of the flea unsteadiness such as frequencies, instability type, etc, The present methodology has been extended to three dimensions and may potentially be applied to separation control, relaminarization, and turbulence control applications using one to many sensors and actuators. C1 FLORIDA STATE UNIV,INST COMP APPLICAT SCI & ENGN,TALLAHASSEE,FL 32306. RP Joslin, RD (reprint author), NASA,LANGLEY RES CTR,LAMINAR FLOW CONTROL PROJECT TEAM,MAIL STOP 170,HAMPTON,VA 23681, USA. NR 32 TC 61 Z9 64 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD MAY PY 1997 VL 35 IS 5 BP 816 EP 824 DI 10.2514/2.7452 PG 9 WC Engineering, Aerospace SC Engineering GA WY030 UT WOS:A1997WY03000008 ER PT J AU Venkatesh, PK Chang, AY Dean, AM Cohen, MH Carr, RW AF Venkatesh, PK Chang, AY Dean, AM Cohen, MH Carr, RW TI Parameterization of pressure- and temperature-dependent kinetics in multiple well reactions SO AICHE JOURNAL LA English DT Article ID SCATTERED DATA; INTERPOLATION AB It is now well confirmed that the influence of temperature on the fall-off behavior of dissociation recombination and chemically-activated reactions can be dramatic. For single-well, single-product dissociation reactions, it is customary to approximate these fall-off surfaces using extensions of Lindemann's empirical expression. We consider here chemical-activation and dissociation reactions possessing multiple wells and multiple products. We show that direct approximation of the rate coefficients via Chebyshev expansions yields reliable and accurate representations of their pressure and temperature dependences, which are superior to those from a Lindemann approach to fit the form factor representing the fall-off surface. The superiority of the method is demonstrated in a study of seven channels corresponding to four different reactions important in combustion chemistry over the ranges 300-3,000 K and 0.02-200 atm. C1 EXXON RES & ENGN CO,CORP RES SCI LAB,ANNANDALE,NJ 08801. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Venkatesh, PK (reprint author), UNIV MINNESOTA,DEPT CHEM ENGN & MAT SCI,421 WASHINGTON AVE SE,MINNEAPOLIS,MN 55455, USA. RI Dean, Anthony/A-8590-2009 NR 26 TC 25 Z9 25 U1 0 U2 3 PU AMER INST CHEMICAL ENGINEERS PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0001-1541 J9 AICHE J JI AICHE J. PD MAY PY 1997 VL 43 IS 5 BP 1331 EP 1340 DI 10.1002/aic.690430522 PG 10 WC Engineering, Chemical SC Engineering GA WX759 UT WOS:A1997WX75900022 ER PT J AU Wheeler, RM Tibbitts, TW AF Wheeler, RM Tibbitts, TW TI Influence of changes in daylength and carbon dioxide on the growth of potato SO ANNALS OF BOTANY LA English DT Article DE Solanum tuberosum; potato; photoperiod; carbon dioxide; CO2; photosynthetic photon flux; PPF; controlled ecological life support systems; CELSS ID SOLANUM-TUBEROSUM-L; TEMPERATURE; PHOTOPERIODS; TUBERIZATION; LIGHT; CUTTINGS; SYSTEMS; YIELDS AB Potatoes (Solanum tuberosum L.) are highly productive in mid- to high-latitude areas where photoperiods change significantly throughout the growing season. To study the effects of changes in photoperiod on growth and tuber development of potato cv. Denali, plants were grown for 112 d with 400 mu mol m(-2) s(-1) photosynthetic photon flux (PPF) under a 12-h photoperiod (short days, SD), a 24-h photoperiod (long days, LD), and combinations where plants were moved between the two photoperiods 28, 56, or 84 d after planting. Plants given LD throughout growth received the greatest total daily PPF and produced the greatest tuber yields. At similar levels of total PPF, plants given SD followed by LD yielded greater tuber dry mass (DM) than plants given IID followed by SD. Stem DM per plant, leaf DM, and total plant DM all increased with an increasing proportion of LD and increasing daily PPF, regardless of the daylength sequence. When studies were repeated, but at an enriched (1000 mu mol mol(-1)) CO2 concentration, overall growth trends were similar, with high CO2 resulting in greater stem length, stem DM, leaf DM, and total plant DM; but high CO2 did not increase tuber DM. (C) 1997 Annals of Botany Company. C1 UNIV WISCONSIN,DEPT HORT,MADISON,WI 53706. RP Wheeler, RM (reprint author), NASA,BIOMED OPERAT & RES OFF,KENNEDY SPACE CTR,FL 32899, USA. NR 29 TC 18 Z9 19 U1 2 U2 9 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0305-7364 J9 ANN BOT-LONDON JI Ann. Bot. PD MAY PY 1997 VL 79 IS 5 BP 529 EP 533 DI 10.1006/anbo.1996.9999 PG 5 WC Plant Sciences SC Plant Sciences GA WY422 UT WOS:A1997WY42200008 PM 11540428 ER PT J AU Brasunas, JC Cushman, GM Lakew, B AF Brasunas, JC Cushman, GM Lakew, B TI Crystalline quartz as a far-infrared beam splitter for Fourier transform spectroscopy SO APPLIED OPTICS LA English DT Article DE Fourier transform spectroscopy; beam splitter; quartz AB We show that room-temperature, crystalline quartz is a useful material for a beam splitter for spectroscopy in the far infrared, similar to 60-mu m wavelength and longer. We compare such a beam splitter with the traditional far-infrared candidates: Mylar, polarizing, and lamellar beam splitters. C1 HUGHES STX CORP,LANHAM,MD 20706. RP Brasunas, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI brasunas, john/I-2798-2013 NR 6 TC 1 Z9 1 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 MAY 1 PY 1997 VL 36 IS 13 BP 2893 EP 2896 DI 10.1364/AO.36.002893 PG 4 WC Optics SC Optics GA WX242 UT WOS:A1997WX24200024 PM 18253288 ER PT J AU Newell, MP KeskiKuha, RAM AF Newell, MP KeskiKuha, RAM TI Extreme ultraviolet scatterometer: Design and capability SO APPLIED OPTICS LA English DT Article DE BRDF; scatter; extreme ultraviolet; far ultraviolet; ultraviolet; scatterometer; grating ID HIGH-RESOLUTION; ROUGH SURFACES; HIGH-SPEED; SCATTERING; REFLECTION; MIRRORS; REGION; LIGHT AB A scatterometer capable of plane-of-incidence bidirectional reflectance distribution function (BRDF) measurements at extreme ultraviolet wavelengths between 58.4 and 121.6 nm has been developed. This instrument has a lower measurement limit of approximately 10(-5) sr(-1), and it is able to accommodate angles of incidence between 10 degrees and 75 degrees. The scatterometer can measure scatter to within 1.5 degrees of the specular beam, and the scatter angle can be measured to within 0.1 degrees. The design, analysis, and performance of this instrument are discussed here. Scatter data, in the form of BRDF measurements, are presented for a 3000-line/mm grating and a flat chemical vapor deposited diamond sample. (C) 1997 Optical Society of America. C1 GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 38 TC 3 Z9 3 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 MAY 1 PY 1997 VL 36 IS 13 BP 2897 EP 2904 DI 10.1364/AO.36.002897 PG 8 WC Optics SC Optics GA WX242 UT WOS:A1997WX24200025 PM 18253289 ER PT J AU Cuomo, V DiGirolamo, P Esposito, F Pappalardo, G Serio, C Spinelli, N Armenante, M Bartoli, B Berardi, V Bruzzese, R Bellecci, C Caputi, GE DeDonato, F Gaudio, P Valentini, M Melfi, H McCormick, MP AF Cuomo, V DiGirolamo, P Esposito, F Pappalardo, G Serio, C Spinelli, N Armenante, M Bartoli, B Berardi, V Bruzzese, R Bellecci, C Caputi, GE DeDonato, F Gaudio, P Valentini, M Melfi, H McCormick, MP TI The LITE correlative measurements campaign in southern Italy: Preliminary results SO APPLIED PHYSICS B-LASERS AND OPTICS LA English DT Article ID STRATOSPHERIC AEROSOLS; LIDAR MEASUREMENTS; SIZE DISTRIBUTION AB In conjunction with the LITE mission an intensive LIDAR measurement campaign was carried out in Napoli (40 degrees 50'N-14 degrees 10'E, at sea level) and Potenza (40 degrees 36'N-15 degrees 44'E, 820 m a.s.l.). The LITE experiment, flying on board the Space Shuttle in the period September 10-19, 1994, represents the first attempt to perform global coverage LIDAR measurements from space. The LITE experiment was planned to provide measurements of clouds, tropospheric and stratospheric aerosols, stratospheric temperature and density, characteristics of the planetary boundary level as well as surface albedo. Because of the relative distance between LITE ground tracks and the two southern Italy validation stations for all passes, measurements carried out in Napoli and Potenza were primarily aimed at validation of LITE stratospheric measurements. In the present preliminary analysis Potenza LIDAR measurements in coincidence with the orbit 128 LITE overpass, are reported and discussed. Potenza LIDAR data show a good agreement with LITE data in terms of aerosol scattering ratio both at 355 nm and 532 nm (R-A,R-355 and R-A,R-532); the two data sets appearing to be highly correlated, LITE vs, Potenza LIDAR measurements of R-A,R-355 and R-A,R-532 display a correlation coefficient of 0.72 and 0.86, respectively. Stratospheric aerosol dimensional characteristics are determined starting from the measured values of the Angstrom coefficient. C1 CNR,IST METODOL AVANZATE ANAL AMBIENTALE,AREA IND,I-85100 TITO,PZ,ITALY. IST NAZL FIS NUCL,I-80125 NAPLES,ITALY. UNIV NAPLES FEDERICO II,DIPARTIMENTO SCI FISICHE,I-80125 NAPLES,ITALY. UNIV CALABRIA,DIPARTIMENTO FIS,I-87036 ARCAVACATA,COSENZA,ITALY. UNIV MARYLAND BALTIMORE CTY,BALTIMORE,MD 21228. NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681. RP Cuomo, V (reprint author), UNIV BASILICATA,DIPARTIMENTO INGN & FIS AMBIENTE,VIA TECN 3,I-85100 POTENZA,ITALY. RI Berardi, Vincenzo/H-4550-2011; Gaudio, Pasqualino /B-3009-2014; OI Gaudio, Pasqualino /0000-0003-0861-558X; Serio, Carmine/0000-0002-5931-7681 NR 11 TC 6 Z9 6 U1 1 U2 4 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0946-2171 J9 APPL PHYS B-LASERS O JI Appl. Phys. B-Lasers Opt. PD MAY PY 1997 VL 64 IS 5 BP 553 EP 559 DI 10.1007/s003400050214 PG 7 WC Optics; Physics, Applied SC Optics; Physics GA XB494 UT WOS:A1997XB49400008 ER PT J AU Baum, WA Hammergren, M Thomsen, B Groth, EJ Faber, SM Grillmair, CJ Ajhar, EA AF Baum, WA Hammergren, M Thomsen, B Groth, EJ Faber, SM Grillmair, CJ Ajhar, EA TI Distance to the coma cluster and a value for H-0 inferred from globular clusters in IC 4051 SO ASTRONOMICAL JOURNAL LA English DT Article ID SPACE-TELESCOPE OBSERVATIONS; HUBBLE CONSTANT; VIRGO CLUSTER; SPATIAL-DISTRIBUTION; ELLIPTICAL GALAXIES; LUMINOSITY FUNCTION; CEPHEID VARIABLES; PHOTOMETRY; M87; SPECTROSCOPY AB We report HST-WFPC2 observations of the giant E2 galaxy IC 4051 located 14' east of the center of the Coma Cluster. Eight full-orbit exposures were obtained with the F606W filter, and two with the F814W filter. Counts of globular clusters (GCs) in 0.2-mag wide bins were made within the PC1 (f/28) frame, where faint GCs can be distinguished from noise spikes and background objects by PSF fitting. The detection probability was above 86% for F606W<27.6 mag, and it was 40% at F606W=28.1 mag (bin center), which we chose as a working threshold. The latter is equivalent to V approximate to 28.4 mag, which is beyond the peak (turnover) of the globular cluster luminosity function (GCLF). After very small k and reddening corrections, we found the mean rest-frame color index of the IC 4051 GCs to be (V-I)(0)=1.06 mag, which implies [Fe/H]=-0.74 and is about average for the GC systems of giant elliptical galaxies. The intrinsic dispersion of color indices is sigma(V-I)=0.16 mag. The specific frequency of the GC system in IC 4051 is similar to 10, which is an order of magnitude larger than we found in the Coma EO galaxy NGC 4881. Using a maximum likelihood method, we have compared the observed GCLF of IC 4051 with model GCLFs transported to various strawman Coma Cluster distances, with photometric errors and incompleteness taken into account. For a model based on the CC systems of the Milky Way and M31, the inferred bolometric modulus of IC 4051 is 35.15+/-0.16 mag. For a model based on the GC system of M87, the apparent V modulus difference (IC 4051 minus M87) is 4.15+/-0.07 mag, and the inferred bolometric modulus of IC 4051 is 35.07+/-0.17 mag. These moduli rest on RR Lyrae and Cepheid zero points that may be subject to future adjustments. The difference between the IC 4051 modulus based on the spiral-galaxy GCLF model (Milky Way and M31) and that based on the elliptical-galaxy GCLF model (M87) is only 0.08+/-0.23 mag, which is not statistically significant. Adopting the mean IC 4051 bolometric modulus, 35.11+/-0.12 mag, and assuming q(0)=0.5, we obtain a luminosity distance of 105+/-6 Mpc (random error). For a cosmological redshift of 7186+/-428 km/s, the implied Hubble Constant H-0=68+/-6 km/s per Mpc. (C) 1997 American Astronomical Society. C1 AARHUS UNIV,INST PHYS & ASTRON,DK-8000 AARHUS C,DENMARK. PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08544. UNIV CALIF SANTA CRUZ,LICK OBSERV,SANTA CRUZ,CA 95064. CALTECH,JET PROP LAB,PASADENA,CA 91109. NATL OPT ASTRON OBSERV,TUCSON,AZ 85726. RP Baum, WA (reprint author), UNIV WASHINGTON,DEPT ASTRON,BOX 351580,SEATTLE,WA 98195, USA. NR 76 TC 25 Z9 25 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 MAY PY 1997 VL 113 IS 5 BP 1483 EP 1494 DI 10.1086/118365 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WX752 UT WOS:A1997WX75200002 ER PT J AU Hutchings, JB Neff, SG AF Hutchings, JB Neff, SG TI A QSO in a cluster at z=2.4 SO ASTRONOMICAL JOURNAL LA English DT Article ID QUASI-STELLAR OBJECTS; GALAXIES; CATALOG AB Photometry is presented in R, J, H, K of the z = 2.37 QSO 0820+296 and its environment. Colors and magnitudes of most of the objects within 50 arcsec of the QSO suggest they are a group of galaxies at the QSO redshift with a young stellar population. (C) 1997 American Astronomical Society. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTROPHYS LAB,GREENBELT,MD 20771. RP Hutchings, JB (reprint author), NATL RES COUNCIL CANADA,DOMINION ASTROPHYS OBSERV,5071 W SAANICH RD,VICTORIA,BC V8X 4M6,CANADA. NR 14 TC 3 Z9 3 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAY PY 1997 VL 113 IS 5 BP 1514 EP 1516 DI 10.1086/118368 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WX752 UT WOS:A1997WX75200005 ER PT J AU Forbes, DA Grillmair, CJ Smith, RC AF Forbes, DA Grillmair, CJ Smith, RC TI Globular clusters in the Sombrero galaxy (NGC 4594) SO ASTRONOMICAL JOURNAL LA English DT Article ID LUMINOSITY FUNCTION; GALACTIC STRUCTURE; SYSTEM; DISK; HALO; METALLICITY; NGC-4594; M31; M81 AB The Sombrero galaxy, NGC 4594, contains the roost numerous globular cluster system of any nearby spiral. It is an ideal candidate in which to study the globular clusters and contrast them with those in Local Group spirals. Here we present B and I imaging from the CTIO Schmidt telescope which gives a field of view of 31'x31'. Using DAOPHOT we have detected over 400 globular clusters and derived their magnitudes, B - I colors and photometric metallicities. We have attempted to separate our sample into disk and bulge/ halo globular cluster populations, based on location in the galaxy, There is some evidence that the disk population is more metal rich than the bulge/halo globular clusters, however contamination, dust reddening and small number statistics makes this result very tentative. We find that the median metallicity of the bulge/halo globular clusters is [Fe/H] = -0.8. This metallicity is consistent with previous estimates based on smaller samples. It is also similar to the metallicity predicted by the globular cluster metallicity-galaxy luminosity relation. As with our Galaxy, there is no radial metallicity gradient in the halo globular clusters. This suggests that the spheriodal component of NGC 4594 did not form by a dissipational process. (C) 1997 American Astronomical Society. C1 UNIV BIRMINGHAM, SCH PHYS & SPACE RES, BIRMINGHAM B15 2TT, W MIDLANDS, ENGLAND. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV MICHIGAN, DEPT ASTRON, ANN ARBOR, MI 48109 USA. RP Forbes, DA (reprint author), UNIV CALIF SANTA CRUZ, LICK OBSERV, SANTA CRUZ, CA 95064 USA. NR 24 TC 9 Z9 9 U1 0 U2 0 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 MAY PY 1997 VL 113 IS 5 BP 1648 EP 1651 DI 10.1086/118381 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WX752 UT WOS:A1997WX75200018 ER PT J AU Forbes, DA Brodie, JP Grillmair, CJ AF Forbes, DA Brodie, JP Grillmair, CJ TI On the origin of globular clusters in elliptical and cD galaxies SO ASTRONOMICAL JOURNAL LA English DT Article ID SURFACE-BRIGHTNESS; METAL ABUNDANCES; LOCAL GROUP; M87; SYSTEM; PHOTOMETRY; HALO; SPECTROSCOPY; EVOLUTION; NGC-5128 AB Perhaps the most noteworthy of recent findings in extragalactic globular cluster (GC) research are the multimodal GC metallicity distributions seen in massive early-type galaxies. We explore the origin of these distinct GC populations, the implications for galaxy formation and evolution, and identify several new properties of GC systems. First, when we separate the metal-rich and metal-poor subpopulations, in galaxies with bimodal GC metallicity distributions, we find that the mean metallicity of the metal-rich GCs correlates well with parent galaxy luminosity but the mean metallicity of the metal-poor ones does not. This indicates that the metal-rich GCs are closely coupled to the galaxy and share a common chemical enrichment history with the galaxy field stars. The mean metallicity of the metal-poor population is largely independent of the galaxy luminosity. Second, the slope of the GC system radial surface density varies considerably in early-type galaxies. However, the galaxies with relatively populous GC systems for their luminosity (called high specific frequency, S-N) only have shallow, extended radial distributions. A characteristic of high S-N galaxies is that their GCs are preferentially located in the outer galaxy regions relative to the underlying starlight. Third, we find that the ratio of metal-rich to metal-poor GCs correlates with S-N. In other words, high S-N galaxies have proportionately more metal-poor GCs, per unit galaxy light, than low S-N galaxies. Fourth, Mwe find steeper metallicity gradients in high S-N galaxies. This is due to the greater number of metal-poor GCs at large galactocentric radii. We critically review current ideas for the origin of GCs in giant elliptical (gE) and cD galaxies and conclude that the gaseous merger model of Ashman & Zepf (1992, ApJ, 384, 50) is unlikely to account for the GC systems in these galaxies. Tidal stripping of the GCs from nearby galaxies appears to contribute to the GC population in the outer parts of cD galaxies, but we suggest that the vast majority of GCs in gE and cD galaxies have probably formed in situ. We speculate that these indigenous GCs formed in two distinct phases of star formation from gas of differing metallicity, giving rise to the bimodal GC metallicity distributions. The metal-poor GCs are formed at an early stage in the collapse of the protogalactic cloud. The metal-rich GCs formed out of more enriched gas, roughly contemporaneously with the galaxy stars. In this sense the metal-rich GCs in elliptical galaxies are the analog of the metal-poor halo GCs in spirals. The disk GCs in spirals may represent a third phase of this formation process. (C) 1997 American Astronomical Society. C1 UNIV BIRMINGHAM, SCH PHYS & SPACE RES, BIRMINGHAM B15 2TT, W MIDLANDS, ENGLAND. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Forbes, DA (reprint author), UNIV CALIF SANTA CRUZ, LICK OBSERV, SANTA CRUZ, CA 95064 USA. NR 91 TC 297 Z9 298 U1 0 U2 2 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 MAY PY 1997 VL 113 IS 5 BP 1652 EP 1665 DI 10.1086/118382 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WX752 UT WOS:A1997WX75200019 ER PT J AU Galama, TJ deBruyn, AG vanParadijs, J Hanlon, L Groot, PJ vanderKlis, M Strom, R Spoelstra, T Bennett, K Fishman, G Hurley, K AF Galama, TJ deBruyn, AG vanParadijs, J Hanlon, L Groot, PJ vanderKlis, M Strom, R Spoelstra, T Bennett, K Fishman, G Hurley, K TI Two variable radio sources near the position of GRB 940301 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE gamma rays: bursts; techniques: interferometric ID RAPID RESPONSE NETWORK; GAMMA-RAY BURSTERS; GALACTIC HALO; COUNTERPART; SEARCH; MHZ; VARIABILITY; GRB-940301 AB We report on the results of a search for a radio counterpart to the strong gamma-ray burst GRB 940301. Observations with the Westerbork Synthesis Radio Telescope of the Compton Telescope error box region of GRB 940301 began on March 4, 1994, at 21 cm and April 2, 1994, at 92 cm. No flux density variations were detected at 92 cm above S = 10 mJy (5 sigma) within a period of 1 to 4 months after the burst. However, when we compared the field with Westerbork Northern Sky Survey data, taken two years prior to GRB 940301, we found two radio sources with significantly increased flux densities. These sources, only 17' apart, are located at the 2.3 and 2.6 sigma Compton Telescope confidence contours. Their separation from the Inter Planetary Network annulus virtually excludes association with GRB 940301. Further observations in January 1996 reveal that the sources continued to change in flux density. The relatively large flux density variations at 92 cm, compared to those at higher frequencies, and the inverted spectra in the frequency range from 325-380 MHz make the sources somewhat unusual. Because the sources were already detected at 5 GHz in 1986 most, if not all, of the radio emission is probably associated with activity in Active Galactic Nuclei in distant galaxies. C1 NFRA, RADIO OBSERV, NL-7990 AA DWINGELOO, NETHERLANDS. KAPTEYN ASTRON INST, NL-9700 AV GRONINGEN, NETHERLANDS. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. NATL UNIV IRELAND UNIV COLL DUBLIN, DEPT PHYS, DUBLIN 4, IRELAND. ESTEC, DIV ASTROPHYS, NOORDWIJK, NETHERLANDS. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. RP UNIV AMSTERDAM, ASTRON INST ANTON PANNEKOEK, CHEAF, KRUISLAAN 403, NL-1098 SJ AMSTERDAM, NETHERLANDS. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016 OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X NR 25 TC 5 Z9 5 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 MAY PY 1997 VL 321 IS 1 BP 229 EP 235 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB420 UT WOS:A1997XB42000030 ER PT J AU Dubath, P Grillmair, CJ AF Dubath, P Grillmair, CJ TI Velocity dispersions and mass-to-light ratios for 9 globular clusters in M31 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE galaxies, individual, M 31; galaxies, star clusters; galaxies, halos; stars, kinematics; techniques, radial velocities ID HST OBSERVATIONS; SYSTEM; CORE; SEARCH; PHOTOMETRY; GALAXY; PLANE; RADII AB We present internal velocity dispersion determinations from high-resolution spectroscopic observations of a sample of nine globular clusters in M 31. Comprehensive numerical simulations are used to show that the typical uncertainty of our velocity dispersion measurements is similar to 5%, Using these new velocity dispersions together with structural parameters derived from HST observations, we estimate the M/L-V ratios of these clusters and find that they are typical of those measured for Galactic clusters. We show relations between velocity dispersion, luminosity and physical scales for globular clusters belonging to the Galaxy, the Magellanic clouds, Fornax, M 31, and Centaurus A. The mean relations and the degree of scatter are similar in all galaxies. This reveals remarkable similarities, in term of structure and M/L-V ratio, between the globular clusters belonging to these different galaxies. We briefly discuss the possible use of individual globular clusters as extragalactic distance indicators. C1 INTEGRAL, SCI DATA CTR, CH-1290 VERSOIX, SWITZERLAND. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Dubath, P (reprint author), OBSERV GENEVA, CH MAILLETTES 51, CH-1290 SAUVERNY, SWITZERLAND. NR 35 TC 50 Z9 50 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 MAY PY 1997 VL 321 IS 2 BP 379 EP 388 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB498 UT WOS:A1997XB49800011 ER PT J AU DeKeyser, J Roth, M Tsurutani, BT Ho, CM Phillips, JL AF DeKeyser, J Roth, M Tsurutani, BT Ho, CM Phillips, JL TI Solar wind velocity jumps across tangential discontinuities: Ulysses observations and kinetic interpretation SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE magnetic fields; plasmas; solar wind; interplanetary medium ID MAGNETOPAUSE CURRENT LAYER; AU AB Some tangential discontinuities (TDs) observed by the ULYSSES spacecraft interface solar wind regions that differ only in their bulk velocity and magnetic field orientation; composition, density, temperature and magnetic field intensity are essentially the same in both regions. The relation between the plasma velocity jump across the TD and the magnetic field is investigated through the analysis and simulation of equilibrium plane TD configurations. These theoretical results are compared with ULYSSES observations. It is concluded that (a) the theoretically predicted magnetic field profile agrees with the morphology of the observed profile, (b) solar wind transitions are essentially of mixed type, i.e. both ion and electron velocity distribution functions are non-Maxwellian inside the transition layer, (c) there are constraints on the orientation and magnitude of the velocity jump that can be supported across a single transition, (d) large magnetic field rotations correspond io wide transition layers, and (e) in addition to density and temperature inhomogeneities, variations in the bulk velocity are a major reason for the solar wind plasma to set up current-carrying boundary layers. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. LOS ALAMOS NATL LAB, LOS ALAMOS, NM 87545 USA. RP DeKeyser, J (reprint author), BELGIAN INST SPACE AERON, RINGLAAN 3, B-1180 BRUSSELS, BELGIUM. NR 26 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 MAY PY 1997 VL 321 IS 3 BP 945 EP 959 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB660 UT WOS:A1997XB66000032 ER PT J AU desEtangs, AL VidalMadjar, A Backman, DE Deleuil, M Lagrange, AM Lissauer, JJ Ferlet, R Beust, H Mouillet, D AF desEtangs, AL VidalMadjar, A Backman, DE Deleuil, M Lagrange, AM Lissauer, JJ Ferlet, R Beust, H Mouillet, D TI Discovery of CI around 51 ophiuchi SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE stars: 51 Oph; circumstellar matter; planetary systems; line: profiles ID PICTORIS CIRCUMSTELLAR DISK; BETA-PICTORIS; 51-OPHIUCHI; SYSTEM; STARS AB We present the discovery of cold CI in the 51 Oph environment, with a column density of N=5 x 10(13) cm(-2) and temperature T approximate to 20K. This is the first beta Pic-like star other than beta Pic with simultaneous detection of cold dust and gas. The CI/infrared continuum ratio and consequently the gas/dust ratio are similar to the beta Pic ones. Since CI has a very short life-time, it must be continuously replenished, probably by molecular gas dissociation. This provides evidence for the presence of evaporating bodies. A new upper limit on CO content is also given. C1 CNRS, ASTRON SPATIALE LAB, F-13376 MARSEILLE 12, FRANCE. CERMO, GRP ASTROPHYS GRENOBLE, F-38041 GRENOBLE, FRANCE. SUNY STONY BROOK, DEPT EARTH & SPACE SCI, ASTRON PROGRAM, STONY BROOK, NY 11794 USA. NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. RP desEtangs, AL (reprint author), INST ASTROPHYS, CNRS, 98 BIS BLVD ARAGO, F-75014 PARIS, FRANCE. NR 21 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 MAY PY 1997 VL 321 IS 3 BP L39 EP L42 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB660 UT WOS:A1997XB66000001 ER PT J AU Sodroski, TJ Odegard, N Arendt, RG Dwek, E Weiland, JL Hauser, MG Kelsall, T AF Sodroski, TJ Odegard, N Arendt, RG Dwek, E Weiland, JL Hauser, MG Kelsall, T TI A three-dimensional decomposition of the infrared emission from dust in the Milky Way SO ASTROPHYSICAL JOURNAL LA English DT Review DE diffuse radiation; dust, extinction; galaxy, structure; infrared, ISM, continuum; ISM, abundances; ISM, molecules ID HIGH GALACTIC LATITUDES; GIANT MOLECULAR CLOUDS; RADIATIVE-TRANSFER; INTERSTELLAR DUST; STAR FORMATION; OUTER GALAXY; SOLAR CIRCLE; SPECTRAL OBSERVATIONS; ABUNDANCE GRADIENTS; (CO)-C-12 INTENSITY AB We have constructed a three-dimensional model of the Galactic large-scale infrared emission from dust associated with the molecular (H-2), neutral atomic (H I), and extended low-density (n(e) similar to 1-100 cm(-3)) ionized (H II) gas phases of the interstellar medium. The model incorporates a three-dimensional map of the molecular and neutral atomic hydrogen gas distributions, derived from available (CO)-C-12 and H I surveys by using the radial velocity information in the spectral lines as a distance indicator, and available 5 and 19 GHz radio continuum surveys to trace the column density of ionized gas. We use the model to decompose the COBE5 Diffuse Infrared Background Experiment (DIRBE) 12-240 mu m observations of the Galactic plane region (/b/less than or equal to 5 degrees), from which the zodiacal light and stellar emission have been subtracted, into distinct emission components associated with each gas phase within selected ranges of Galactocentric distance. An interstellar dust model is fitted to the resulting infrared spectra to derive the following quantities within each Galactocentric distance interval: (1) the abundance and equilibrium temperature of the large dust grain component within each gas phase; (2) estimates of the abundance of very small (<200 Angstrom) transiently heated dust grains and polycyclic aromatic hydrocarbon (PAH) molecules; and (3) constraints on various model parameters, such as the energy density of the ambient interstellar radiation held, which heats the dust within the H I gas phase. Our results show steep negative Galactocentric gradients in the equilibrium temperature of the large dust grain component within the H I, H-2, and H II gas phases, the Galaxy's ambient interstellar radiation held, and the dust-to-gas mass ratio for each gas phase. The intensity of the ambient interstellar radiation held increases by a factor of similar to 3 between the solar circle (8.5 kpc) and the molecular ring at a Galactocentric distance of similar to 5 kpc. The dust abundance gradient of (-0.05+/-0.03) dex kpc(-1) is equivalent, within the uncertainties, to the metallicity gradient in the Galactic disk. The derived emission spectra are consistent with a model in which very small transiently heated dust grains and PAHs are abundant and the dominant contributors to the mid-infrared (5 mu m