FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Hunt, LR Meyer, G AF Hunt, LR Meyer, G TI Stable inversion for nonlinear systems SO AUTOMATICA LA English DT Article DE nonlinear control systems; tracking systems; stable inversion; aircraft control; guidance systems ID OUTPUT TRACKING AB There have been two recent major developments in output tracking for nonlinear systems, and our first main contribution is to relate these. Under appropriate assumptions, we show that the bounded solution of the partial differential equation of Isidori and Byrnes for each trajectory of an exosystem must be given by an integral representation formula of Devasia, Chen and Paden. Under restrictive Chen and Paden develop a Picard process that converges to the solution of the integral equation. This solution to the integral equation is also a bounded solution a dynamical equation driven by the desired outputs. In aircraft applications our nonlinear are perturbations of 'pure-feedback systems' with outputs, and we find a solution to the stable inversion problem, i.e. finding bounded controls and bounded state trajectories in response to bounded output signals, in two steps. The first step ignores the perturbation error and computes the major part of the desired control and corresponding state trajectory. The second step computes the remaining control and states by finding a noncausal and stable solution to an 'error-driven dynamical equation'. In other words, the method of Devasia, Chen and Paden is applied to an 'error system' and not to the full system. This two-step procedure is the second main contribution of this paper. Throughout this paper it is assumed that our nonlinear systems have vector relative degree. (C) 1997 Elsevier Science Ltd. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Hunt, LR (reprint author), UNIV TEXAS, CTR ENGN MATH, POB 830688, RICHARDSON, TX 75083 USA. NR 16 TC 111 Z9 121 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0005-1098 J9 AUTOMATICA JI Automatica PD AUG PY 1997 VL 33 IS 8 BP 1549 EP 1554 DI 10.1016/S0005-1098(97)00064-2 PG 6 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA XU556 UT WOS:A1997XU55600010 ER PT J AU Nimmagudda, RR Ramanathan, R Putcha, L AF Nimmagudda, RR Ramanathan, R Putcha, L TI A method for preserving saliva samples at ambient temperatures SO BIOCHEMICAL ARCHIVES LA English DT Article ID URINE; BACTERIAL; CORTISOL; SYSTEM; PLASMA AB To facilitate biochemical and biopharmaceutical studies when cold storage is unavailable, we assessed the stability of saliva samples containing preservatives stored at room temperature over a 1-year period. Two preservative mixtures were evaluated: sodium benzoate and citric acid (P1), and ethyl and propyl paraben (P2). Saliva samples were spiked with acetaminophen (APAP) or antipyrine (AP) and stored in preservative-coated vials and examined for concentrations of APAP, AP, melatonin, and cortisol at regular intervals as a function of preservative type and storage duration. Samples were stored at room temperature or at -20 degrees C (positive control) and analyzed periodically for APAP and AP by high-performance liquid chromatography and for melatonin and cortisol by radioimmunoassay. The effectiveness of the preservatives was determined by calculating the value of samples stored at room temperature in terms of percent of control (-20 degrees C) values. P1 effectively maintained the stability of APAP (100%) and AP (100%) for 360 days at room temperature; concentrations in samples at room temperature on day 360 were comparable to those on day 01. P1 also effectively maintained melatonin (100%) and cortisol (95%) concentrations for 180 days at room temperature. P2 preserved AP and cortisol in saliva for 60 days, but APAP for only 14 days. C1 NASA,LYNDON B JOHNSON SPACE CTR,LIFE SCI RES LABS,HOUSTON,TX 77058. KRUG LIFE SCI,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Nimmagudda, RR (reprint author), UNIV SPACE RES ASSOC,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058, USA. NR 19 TC 7 Z9 8 U1 0 U2 3 PU MBR PRESS INC PI KENYON PA PO BOX P, KENYON, MN 55946-000P SN 0749-5331 J9 BIOCHEM ARCH JI Biochem. Arch. PD AUG PY 1997 VL 13 IS 3 BP 171 EP 178 PG 8 WC Biochemistry & Molecular Biology SC Biochemistry & Molecular Biology GA XT508 UT WOS:A1997XT50800004 PM 11541121 ER PT J AU Abdullah, WS AlZoubi, MS Alshibli, KA AF Abdullah, WS AlZoubi, MS Alshibli, KA TI On the physicochemical aspects of compacted clay compressibility SO CANADIAN GEOTECHNICAL JOURNAL LA English DT Article DE consolidation; temperature; permeability; expansive; compacted clays; cation exchange AB The effects of the clay-water-electrolyte system and the temperature on soil compressibility due to primary consolidation and secondary compression are investigated. The method used for the alteration of the exchange complex yielded a single species of cation (Na+, Ca++, or K+) to dominate the exchange complex, representing more than 87% of the total exchangeable cations present. The potassium (K+) dominated exchange complex caused fundamental changes in the behavior of the tested soil: from the untreated soil to the K-soil, there was a decrease in the plasticity index (PI) from 66 to 13%, a decrease in free swell from 10.5 to 1.74%, and about a 10-fold increase in the coefficient of permeability. The virgin compression index (C-c) is found to be strongly related to the soil dry density and can be accurately modeled accordingly. Temperature significantly affects the behavior of the untreated soil: the measured coefficient of permeability was increased by about 100% for a temperature change from 26 to 40 degrees C; whereas temperature has almost no influence on the K-treated soil. C1 UNIV ILLINOIS,DEPT CIVIL ENGN,URBANA,IL 61801. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. RP Abdullah, WS (reprint author), JORDAN UNIV SCI & TECHNOL,DEPT CIVIL ENGN,IRBID,JORDAN. NR 16 TC 13 Z9 15 U1 3 U2 13 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA ON K1A 0R6, CANADA SN 0008-3674 J9 CAN GEOTECH J JI Can. Geotech. J. PD AUG PY 1997 VL 34 IS 4 BP 551 EP 559 DI 10.1139/cgj-34-4-551 PG 9 WC Engineering, Geological; Geosciences, Multidisciplinary SC Engineering; Geology GA YC105 UT WOS:A1997YC10500007 ER PT J AU Chiu, HY AF Chiu, HY TI Modern cosmology SO CHINESE JOURNAL OF PHYSICS LA English DT Article; Proceedings Paper CT Symposium on Contemporary Physics CY DEC 28-30, 1996 CL NATL TAIWAN UNIV, DEPT PHYS, TAIPEI, TAIWAN HO NATL TAIWAN UNIV, DEPT PHYS AB In this paper we review the current status of cosmological theory. First a brief discussion of Friedmann model and classical observations is presented. Next the events of the early Universe from a fraction of a second to the present are discussed from the point of view of high temperature thermodynamics. The most important phenomena in this phase are pair creation of particles and nuclear equilibrium at temperatures 10(9) K and above. When the temperature drops, nuclear equilibrium will freeze out, resulting in the synthesis of helium and some light elements. Likewise pairs of particles will annihilate at lower temperatures but some relic particles may remain intact today. So far the theory seems to be on solid ground. However, there are many unanswered questions which force one to make certain drastic assumptions, such as the existence of dark (invisible) matter. One is also forced to retrace the evolution of the Universe back in time to 10(-36) second, during which quantum effects of gravity become important. This then leads to the Inflationary Theory. This theory is still under development. Scanty data exist to support or to refute the theory. The origin of our Universe - the ultimate frontier in astrophysics and a Pandora Box - is now open for exploration. RP Chiu, HY (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU PHYSICAL SOC REPUBLIC CHINA PI TAIPEI PA CHINESE JOURNAL PHYSICS PO BOX 23-30, TAIPEI 10764, TAIWAN SN 0577-9073 J9 CHINESE J PHYS JI Chin. J. Phys. PD AUG PY 1997 VL 35 IS 4 BP 305 EP 313 PG 9 WC Physics, Multidisciplinary SC Physics GA XR077 UT WOS:A1997XR07700002 ER PT J AU Yeh, NC AF Yeh, NC TI The science and technology of condensed matter physics - From atomic imaging to space research SO CHINESE JOURNAL OF PHYSICS LA English DT Article; Proceedings Paper CT Symposium on Contemporary Physics CY DEC 28-30, 1996 CL NATL TAIWAN UNIV, DEPT PHYS, TAIPEI, TAIWAN HO NATL TAIWAN UNIV, DEPT PHYS ID YBA2CU3O7 SINGLE-CRYSTALS; CA-MN-O; HIGH-TEMPERATURE SUPERCONDUCTORS; BOSON LOCALIZATION; GLASS TRANSITION; MAGNETORESISTANCE; FILMS; RESISTIVITY; DISORDER AB Various areas of our ongoing condensed matter physics research which involve both fundamental physics and advanced technology are described. The research topics include studies of the vortex dynamics and pairing symmetry of high-temperature superconductors; development of precision clocks using high-Q superconducting microwave cavities; state-of-the-art measurements of the density and critical phenomena of liquid helium near phase transitions and under microgravity; as well as the physics and device applications of various magnetoresistive perovskites. The experimental scope encompasses techniques from atomic imaging to space research, and the important interplay of fundamental science and frontier technology in our research is also addressed. C1 CALTECH,JET PROP LAB,PASADENA,CA. ECOLE POLYTECH,F-91128 PALAISEAU,FRANCE. IBM CORP,THOMAS J WATSON RES CTR,YORKTOWN HTS,NY 10598. BOEING CO,DEF & SPACE GRP,SEATTLE,WA 98124. RP Yeh, NC (reprint author), CALTECH,DEPT PHYS,PASADENA,CA 91125, USA. NR 40 TC 0 Z9 0 U1 0 U2 2 PU PHYSICAL SOC REPUBLIC CHINA PI TAIPEI PA CHINESE JOURNAL PHYSICS PO BOX 23-30, TAIPEI 10764, TAIWAN SN 0577-9073 J9 CHINESE J PHYS JI Chin. J. Phys. PD AUG PY 1997 VL 35 IS 4 BP 373 EP 386 PG 14 WC Physics, Multidisciplinary SC Physics GA XR077 UT WOS:A1997XR07700008 ER PT J AU VanSelst, M Jolicoeur, P AF VanSelst, M Jolicoeur, P TI Decision and response in dual-task interference SO COGNITIVE PSYCHOLOGY LA English DT Article ID MULTIPROCESSOR MODELS; OVERLAPPING TASKS; DIVIDED ATTENTION; SAMPLE-SIZE; PERFORMANCE; BOTTLENECK; STRATEGIES; SELECTION; CAPACITY; SUPPORT AB Experiments with two stimuli (S-1 and S-2) and two responses suggest the existence of a stage of processing that cannot be shared between two concurrent tasks. Widespread support has been found for the hypothesis that response selection for Task(2) is postponed when the S-1 to S-2 stimulus onset asynchrony (SOA) is short (Pashler, 1994a). At short SOAs, manipulations which impact Task(2) processing prior to response selection (e.g., degradation of stimulus quality) have little effect on Task(2) response times (RTs). On the other hand, manipulations which art: thought to impact response selection or execution (e.g., Stroop interference) always impact Task(2) RTs. There is, however, one particularly compelling demonstration that appears to be inconsistent with the response selection bottleneck hypothesis: Karlin and Kestenbaum (1968) report that the RT difference between detection (i.e., 1-choice) and 2-choice discrimination dramatically decreases with decreasing SOA. Given that the primary difference between detection and discrimination is believed to be at response selection, their result may indicate a processing bottleneck at response execution (Keele, 1973). We fail to replicate the Karlin and Kestenbaum result in two substantive replications of Karlin and Kestenbaum's tasks and procedures. In the single experiment in which Karlin and Kestenbaum's result is replicated, a simple response execution bottleneck account is ruled out by the stability of the difference between 2-choice and 3-choice discrimination times across SOA. Two additional experiments demonstrate that response preparation and task strategy do not substantially contribute to the attenuation of response selection-level effects with decreasing SOA. (C) 1997 Academic Press. C1 UNIV WATERLOO,DEPT PSYCHOL,WATERLOO,ON N2L 3G1,CANADA. RP VanSelst, M (reprint author), NASA,AMES RES CTR,MS 262 2,MOFFETT FIELD,CA 94035, USA. NR 56 TC 71 Z9 71 U1 0 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0010-0285 J9 COGNITIVE PSYCHOL JI Cogn. Psychol. PD AUG PY 1997 VL 33 IS 3 BP 266 EP 307 DI 10.1006/cogp.1997.0662 PG 42 WC Psychology; Psychology, Experimental SC Psychology GA XP283 UT WOS:A1997XP28300002 ER PT J AU Patnaik, SN Lavelle, TM Hopkins, DA AF Patnaik, SN Lavelle, TM Hopkins, DA TI Optimization of air-breathing propulsion engine concept SO COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING LA English DT Article DE design optimization; air-breathing engine; wave rotor; multiflow turbofan engine AB The design optimization of air-breathing propulsion engine concepts has been accomplished by soft-coupling the NASA Engine Performance Program (NEPP) analyser with the NASA Lewis multidisciplinary optimization tool COMETBOARDS. Engine problems, with their associated design Variables and constraints, were cast as non-linear optimization problems with thrust as the merit function. Because of the large number of mission points in the flight envelope, the diversity of constraint types, and the overall distortion of the design space, the most reliable optimization algorithm available in COMETBOARDS, when used by itself, could not produce satisfactory, feasible, optimum solutions. However, COMETBOARDS' unique features-which include a cascade strategy, variable and constraint formulations, and scaling devised especially for difficult multidisciplinary applications-successfully optimized the performance of subsonic and supersonic engine concepts. Even when started from different design points, the combined COMETBOARDS and NEPP results converged to the same global optimum solution. This reliable and robust design tool eliminates manual intervention in the design of air-breathing propulsion engines and eases the cycle analysis procedures. It is also much easier to use than other codes, which is an added benefit. This paper describes COMETBOARDS and its cascade strategy and illustrates the capabilities of the combined design tool through the optimization of a high-bypass-turbofan wave-rotor-topped subsonic engine and a mixed-flow-turbofan supersonic engine. (C) 1997 John Wiley & Sons, Ltd. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Patnaik, SN (reprint author), OHIO AEROSP INST,22800 CEDAR POINT RD,CLEVELAND,OH 44142, USA. NR 6 TC 3 Z9 3 U1 1 U2 2 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1069-8299 J9 COMMUN NUMER METH EN JI Commun. Numer. Methods Eng. PD AUG PY 1997 VL 13 IS 8 BP 635 EP 641 DI 10.1002/(SICI)1099-0887(199708)13:8<635::AID-CNM89>3.0.CO;2-X PG 7 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA XT723 UT WOS:A1997XT72300004 ER PT J AU Mine, MR AF Mine, MR TI ISAAC: A meta-CAD system for virtual environments SO COMPUTER-AIDED DESIGN LA English DT Article DE immersive design; object manipulation; virtual environment; interaction techniques AB This paper presents a description of ISAAC; the Immersive Simulation Animation And Construction program designed and built at the University of North Carolina at Chapel Hill (UNC-CH). ISAAC is a scene composition application used for the interactive construction of virtual worlds. In ISAAC you work directly in a virtual environment; you position, orient and scale objects using direct and indirect manipulation techniques. ISAAC stores object configurations in ASCII files that it uses to recreate scenes at a later date for further manipulation and interactive exploration. ISAAC is not a modeling program; you create worlds by manipulating pre-generated three-dimensional models (which can come from sources such as computer-aided design programs or three-dimensional scanning devices). ISAAC was designed to overcome some of the limitations of working in a virtual environment and to take advantage of the natural and intuitive forms of interaction available in a virtual world. (C) 1997 Elsevier Science Ltd. C1 NASA,JET PROP LAB,WASHINGTON,DC. UNIV N CAROLINA,DEPT COMP SCI,CHAPEL HILL,NC 27599. NR 11 TC 27 Z9 29 U1 0 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0010-4485 J9 COMPUT AIDED DESIGN JI Comput.-Aided Des. PD AUG PY 1997 VL 29 IS 8 BP 547 EP 553 DI 10.1016/S0010-4485(96)00095-4 PG 7 WC Computer Science, Software Engineering SC Computer Science GA XW829 UT WOS:A1997XW82900002 ER PT J AU Sun, XH Moitra, S AF Sun, XH Moitra, S TI Performance comparison of a set of periodic and non-periodic tridiagonal solvers on SP2 and Paragon parallel computers SO CONCURRENCY-PRACTICE AND EXPERIENCE LA English DT Article AB Various tridiagonal solvers have been proposed in recent years for different parallel platforms, In this paper, the performance of three tridiagonal solvers, namely, the parallel partition LU algorithm, the parallel diagonal dominant algorithm, and the reduced diagonal dominant algorithm, is studied, These algorithms are designed for distributed-memory machines and are tested on an Intel Paragon and an IBM SP2 machine, Measured results are reported in terms of execution time and speedup, Analytical studies are conducted for different communication topologies and for different tridiagonal systems, The measured results match the analytical results closely, In addition to addressing implementation issues, performance considerations such as problem sizes and models of speedup are also discussed. (C) 1997 by John Wiley & Sons, Ltd. C1 LOUISIANA STATE UNIV,DEPT COMP SCI,BATON ROUGE,LA 70803. NASA,LANGLEY RES CTR,SCI APPLICAT BRANCH,HAMPTON,VA 23681. NR 19 TC 1 Z9 1 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1040-3108 J9 CONCURRENCY-PRACT EX JI Concurrency-Pract. Exp. PD AUG PY 1997 VL 9 IS 8 BP 781 EP 801 DI 10.1002/(SICI)1096-9128(199708)9:8<781::AID-CPE264>3.0.CO;2-X PG 21 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA XR671 UT WOS:A1997XR67100002 ER PT J AU Short, JW Heintz, RA AF Short, JW Heintz, RA TI Identification of Exxon Valdez oil in sediments and tissues from Prince William Sound and the northwestern Gulf of Alaska based on a PAH weathering model SO ENVIRONMENTAL SCIENCE & TECHNOLOGY LA English DT Article AB We used a first-order loss-rate kinetic model of polynuclear aromatic hydrocarbon (PAH) weathering to evaluate 7767 environmental samples collected for the Exxon Valdez oil spill (EVOS) for the presence of spilled oil. The model was developed from experiments with gravel coated with crude oil and washed for 6 months. The modeled PAH included the 14 most persistent compounds of 31 analyzed by GC/MS. Parameters include loss-rate constants related to the energy required for PAH to escape from petroleum and a quantitative index of weathering. The model accounts for 91% of the temporal variability of modeled PAH concentrations. We compared the discrepancies between measured and model-predicted PAH concentrations of EVOS samples with a probability distribution of these discrepancies derived from the experimental weathering results, Only 1541 field samples contained sufficient PAH for valid application of the model; three-fourths fit the model at alpha greater than or equal to 0.01 type I error, 9% fit an alternate model characterized by the absence of weathering, 17% fit neither model, and a few fit both models. The 1164 total samples that fit the weathering model account for 86% of the summed PAH concentrations detected in all 7767 samples. We conclude that first-order loss-rate kinetics account for the dominant PAH weathering processes in the EVOS and that the rate of weathering is determined mainly by the ratio of surface area to volume of petroleum in the environment. RP Short, JW (reprint author), NOAA,ALASKA FISHERIES SCI CTR,NATL MARINE FISHERIES SERV,11305 GLACIER HIGHWAY,JUNEAU,AK 99801, USA. NR 33 TC 96 Z9 96 U1 0 U2 13 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0013-936X J9 ENVIRON SCI TECHNOL JI Environ. Sci. Technol. PD AUG PY 1997 VL 31 IS 8 BP 2375 EP 2384 DI 10.1021/es960985d PG 10 WC Engineering, Environmental; Environmental Sciences SC Engineering; Environmental Sciences & Ecology GA XN758 UT WOS:A1997XN75800059 ER PT J AU VanderWal, RL AF VanderWal, RL TI LIF-LII measurements in a turbulent gas-jet flame SO EXPERIMENTS IN FLUIDS LA English DT Article ID LASER-INDUCED INCANDESCENCE; SOOT-VOLUME FRACTION; DIFFUSION FLAMES; INDUCED FLUORESCENCE; VISUALIZATION; TEMPERATURE; DIAGNOSTICS; COMBUSTION AB Detection of soot by laser-induced incandescence (LIT) and fuel-rich (PAH containing) regions by laser-induced fluorescence (LIF) is demonstrated in a turbulent, Re=2500, ethylene gas-jet diffusion flame. Simultaneous combined LIF-LII images allow identification of regions containing PAT-I or soot and their relative spatial relationship. Separate LII images confirm the identity of the soot containing regions shown in the LIF-LII images. Variations in the size, structure, spatial location and intensity of the PAH and soot containing regions are shown qualitatively in the images and quantified through histograms of image intensities and spatial extents. RP VanderWal, RL (reprint author), NASA,LEWIS RES CTR,NYMA,MS 1103,21,000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 38 TC 8 Z9 8 U1 0 U2 4 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD AUG PY 1997 VL 23 IS 4 BP 281 EP 287 DI 10.1007/s003480050112 PG 7 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA XV295 UT WOS:A1997XV29500003 ER PT J AU Liebowitz, J Krishnamurthy, V Rodens, I Houston, C Baek, S Liebowitz, A Zeide, J Potter, WJ AF Liebowitz, J Krishnamurthy, V Rodens, I Houston, C Baek, S Liebowitz, A Zeide, J Potter, WJ TI Intelligent scheduling with GUESS (Generically Used Expert Scheduling System): Development and testing results SO EXPERT SYSTEMS LA English DT Article DE intelligent scheduling; expert systems; genetic algorithm; constraint-based satisfaction; intelligent systems AB Scheduling is a prevalent function that is omnipresent throughout many industries and applications (Pinedo, 1995; Morton & Pentico, 1993; Zweben & Fox, 1994; Brown & Scherer, 1995). A great need exists for developing scheduling toolkits that carl be generically applied to a number of different scheduling problems. To meet this need, more research is warranted for developing a state-of-the-art generic constraint problem-solver as related to scheduling. This paper discusses the development and resting of the Generically Used Expert Scheduling System (GUESS). C1 George Washington Univ, Dept Management Sci, Washington, DC 20052 USA. Amer Minor Engn Corp, Kensington, MD 20895 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Liebowitz, J (reprint author), George Washington Univ, Dept Management Sci, Washington, DC 20052 USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU BLACKWELL PUBL LTD PI OXFORD PA 108 COWLEY RD, OXFORD OX4 1JF, OXON, ENGLAND SN 0266-4720 J9 EXPERT SYST JI Expert Syst. PD AUG PY 1997 VL 14 IS 3 BP 119 EP 128 DI 10.1111/1468-0394.00048 PG 10 WC Computer Science, Artificial Intelligence; Computer Science, Theory & Methods SC Computer Science GA ZH502 UT WOS:000073117500001 ER PT J AU Dong, D Dickey, JO Chao, Y Cheng, MK AF Dong, D Dickey, JO Chao, Y Cheng, MK TI Geocenter variations caused by atmosphere, ocean and surface ground water SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GRAVITATIONAL-FIELD; EARTHS ROTATION AB The geocenter variations reflect the global scale mass redistribution and the interaction between the solid Earth and the mass load. Determination of the geocenter variations due to surface mass load from various geophysical sources places constraints on the variations of the origin of terrestrial reference frame, and provides the expected range of variations for space-geodesy. Our results suggest that on the time scale from 30 days to 10 years the primary variability of geocenter variations from atmosphere, ocean and surface ground water occurs on the annual and semiannual scales. The lumped sum of these surface mass load induced geocenter variations is within 1 cm level. C1 UNIV TEXAS,SPACE RES CTR,AUSTIN,TX 78759. RP Dong, D (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 17 TC 72 Z9 83 U1 1 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 AUG 1 PY 1997 VL 24 IS 15 BP 1867 EP 1870 DI 10.1029/97GL01849 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XP337 UT WOS:A1997XP33700007 ER PT J AU Larson, DE Lin, RP McTiernan, JM McFadden, JP Ergun, RE McCarthy, M Reme, H Sanderson, TR Kaiser, M Lepping, RP Mazur, J AF Larson, DE Lin, RP McTiernan, JM McFadden, JP Ergun, RE McCarthy, M Reme, H Sanderson, TR Kaiser, M Lepping, RP Mazur, J TI Tracing the topology of the October 18-20, 1995, magnetic cloud with similar to 0.1-10(2) keV electrons SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HEAT-FLUX DROPOUTS; SOLAR-WIND; SPACECRAFT; RECONNECTION; PLASMA; FIELDS; RADIO; AU AB Five solar impulsive similar to 1-10(2) keV electron events were detected while the WIND spacecraft was inside the magnetic cloud observed upstream of the Earth on October 18 - 20, 1995. The solar type III radio bursts produced by these electrons can be directly traced from similar to 1 AU back to X-ray flares in solar active region AR 7912, implying that at least one leg of the cloud was magnetically connected to that region. Analysis of the electron arrival times shows that the lengths of magnetic field lines in that leg vary from similar to 3 AU near the cloud exterior to similar to 1.2 AU near the cloud center, consistent with a model force-free helical flux rope. Although the cloud magnetic field exhibits the smooth, continuous rotation signature of a helical flux rope, the similar to 0.1-1 keV heat flux electrons and similar to 1-10(2) keV energetic electrons show numerous simultaneous abrupt changes from bidirectional streaming to unidirectional streaming to complete flux dropouts. We interpret these as evidence for patchy disconnection of one end or both ends of cloud magnetic field lines from the Sun. C1 UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. UNIV WASHINGTON, GEOPHYS PROGRAM, SEATTLE, WA 98195 USA. UNIV TOULOUSE 3, CTR ETUD SPATIALE RAYONNEMENTS, F-31062 TOULOUSE, FRANCE. ESA, EUROPEAN SPACE RES & TECHNOL CTR, DEPT SPACE SCI, F-75738 PARIS 15, FRANCE. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV MARYLAND, COLLEGE PK, MD 20742 USA. RP Larson, DE (reprint author), UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. NR 22 TC 135 Z9 139 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1997 VL 24 IS 15 BP 1911 EP 1914 DI 10.1029/97GL01878 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XP337 UT WOS:A1997XP33700018 ER PT J AU Tabazadeh, A Toon, OB Clegg, SL Hamill, P AF Tabazadeh, A Toon, OB Clegg, SL Hamill, P TI A new parameterization of H2SO4/H2O aerosol composition: Atmospheric implications SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SULFURIC-ACID; TEMPERATURE AB Recent results from a thermodynamic model of aqueous sulfuric acid are used to derive a new parameterization for the variation of sulfuric acid aerosol composition with temperature and relative humidity. This formulation is valid for relative humidities above 1 % in the temperature range of 185 to 260 K. An expression for calculating the vapor pressure of supercooled liquid water, consistent with the sulfuric acid model, is also presented. We show that the Steele and Hamill [1981] formulation underestimates the water partial pressure over aqueous H2SO4 solutions by up to 12% at low temperatures. This difference results in a corresponding underestimate of the H2SO4 concentration in the aerosol by about 6 % of the weight percent at approximately 190 K. In addition, the relation commonly used for estimating the vapor pressure of H2O over supercooled liquid water differs by up to 10 % from our derived expression. The combined error can result in a 20 % underestimation of water activity over a H2SO4 solution droplet in the stratosphere, which has implications for the parameterization of heterogeneous reaction rates in stratospheric sulfuric acid aerosols. The influence of aerosol composition on the rate of homogeneous ice nucleation from a H2SO4 solution droplet is also discussed. This parameterization can also be used for homogeneous gas phase nucleation calculations of H2SO4 solution droplets under various conditions such as in aircraft exhaust or in volcanic plumes. C1 UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. UNIV E ANGLIA,SCH ENVIRONM SCI,NORWICH NR4 7TJ,NORFOLK,ENGLAND. SAN JOSE STATE UNIV,DEPT PHYS,SAN JOSE,CA 95192. RP Tabazadeh, A (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 13 TC 70 Z9 70 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1997 VL 24 IS 15 BP 1931 EP 1934 DI 10.1029/97GL01879 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XP337 UT WOS:A1997XP33700023 ER PT J AU Carlson, RW Drossart, P Encrenaz, T Weissman, PR Hui, J Segura, M AF Carlson, RW Drossart, P Encrenaz, T Weissman, PR Hui, J Segura, M TI Temperature, size, and energy of the Shoemaker-Levy 9 G-impact fireball SO ICARUS LA English DT Article ID COMET SHOEMAKER-LEVY-9; JUPITER ATMOSPHERE; FRAGMENT-G; COLLISION; GALILEO; SPECTROPHOTOMETRY; METHANE; SPECTRA; CM(-1) AB The fortunate position of the Galileo spacecraft provided us with a unique opportunity to directly observe the Shoemaker-Levy 9 impacts as they occurred on the far side of Jupiter, and we present observations of the G fireball obtained by the Near Infrared Mapping Spectrometer (NIMS). These measurements were performed using 10 spectral bands, 4 representing continua and spanning the wavelength range 1.84 to 4.38 mu. Fireball signals were evident for up to 80 sec, with the time of intensity maxima and duration being greater for longer wavelengths. Color temperatures and effective emitting areas were estimated by fitting blackbody functions at the four continuum wavelengths. Good blackbody fits were found, and their intensities at shorter wavelengths show excellent agreement with the Galileo Photopolarimeter/Radiometer measurements. Temperatures near the beginning are above 3000 K, decreasing to similar to 1000 K after 1 min. The corresponding areas range from 400 to 20,000 km(2). The effective diameter of the luminous fireball shows approximately linear time variation, at least for the first 45 sec. From the temperature-effective diameter relation we find an adiabatic coefficient of gamma = 1.2 +/- 0.1, much as expected from theoretical considerations. The luminosity, when integrated over the period of observations and assuming a Stephan-Boltzmann radiator, gives an above-cloud radiative energy loss of 0.48 +/- 0.13 x 10(25) erg. As a conceptual aid, we developed a simple, heuristic theory of the fireball phenomenon, considering the penetrating fragment's wake (termed debris channel) to consist of high-temperature jovian and cometary material, which undergoes radial expansion and acceleration back along the wake axis. The outer layer of the material in this debris channel is presumed optically thick, radiating as a blackbody to produce the observed emissions (we speculate that the opacity is produced by condensed refractories such as MgO and SiO2, probably containing impurities). One-dimensional, variable-area axial flow of a radiating, compressible, inviscid gas is concurrently solved with the radial shock motion occurring in the non-axisymmetric atmosphere. We calculate debris surface radii and velocities using Sedov's theory for line explosions. The assumed initial debris surface temperature is consistent with entry shock heating. Our simple model shows good agreement with the observations, for both the temperature and luminous area, and suggests that the diameter of the G fragment (assumed spherical and of unit density) was 300 +/- 100 m, with a nominal energy of 2.5 x 10(26) erg. The measured luminous energy is within a factor of 2 of that predicted for the nominal impactor size, whereas the amount of water in the splashback, as measured by G. L. Bjoraker et al. (1996, Icarus 121, 411-421) and Th. Encrenaz et al., (1997, Planet. Space Sci.) agrees to a factor of 3 with the model results; however, the large CO abundance obtained by E. Lellouch et al. (1995, Nature 373, 592-595) is inconsistent with the suggested size. This diameter estimate must be considered provisional and probably a lower limit; precise estimates require comparison of the measurements with comprehensive numerical simulations, which we encourage. (C) 1997 Academic Press. C1 OBSERV PARIS,DEPT RECH SPATIALE,F-92195 MEUDON,FRANCE. RP Carlson, RW (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 59 TC 18 Z9 18 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1997 VL 128 IS 2 BP 251 EP 274 DI 10.1006/icar.1997.5756 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT893 UT WOS:A1997XT89300001 ER PT J AU SanchezLavega, A Rojas, JF Acarreta, JR Lecacheux, J Colas, F Sada, PV AF SanchezLavega, A Rojas, JF Acarreta, JR Lecacheux, J Colas, F Sada, PV TI New observations and studies of Saturn's long-lived north polar spot SO ICARUS LA English DT Article ID HUBBLE-SPACE-TELESCOPE; ROTATION PERIOD; ATMOSPHERE; HEXAGON; IMAGES; PHOTOMETRY; DYNAMICS; JUPITER AB We report on a new series of ground-based CCD observations at visual wavelengths, covering a period of 1255 days between May 1992 and November 1995, of the longest-lived asymmetric feature known in Saturn's atmosphere: the north polar spot (NPS). This completes our previous analysis of this feature during the period 1990-1991 (A. Sanchez-Lavega, J. Lecacheux, F. Colas, and P. Lagues, 1993, Science 260, 329-332). Longitude measurements of the NPS indicate an averaged longitudinal drift of -0.030 deg/day for the whole period 1990-1995 corresponding to a zonal velocity of 0.11 msec(-1). These data, when combined with previous and new measurements of the NPS position on Voyager 1 and 2 images obtained in 1980 and 1981, indicate a long-term drift in longitude of the NPS with a constant angular acceleration of 1.1 x 10(-5) deg/(day)(2). High-resolution Voyager 2 violet, blue, green, and orange images were used to measure the size and reflectivity of the NPS. Its structure is characterized by a bright elliptical core surrounded by a dark ring and a large uniform area. The contrast between all these features changes appreciably from violet to orange: the spot is dark in violet but bright in orange relative to its surroundings. The spot is embedded within a region seeded by a ''field of bright clouds'' with characteristic size 1000 km reminiscent of a cellular convection pattern. The NPS's east-west apparent size is shorter at violet-blue (about 7000 km as limited by a dark ring at these wavelengths) than al green-orange (about 11,000 km corresponding to the large uniform area). Green processed images show apparent spiral patterns within the NPS consistent with anticyclonic vorticity, The results of ground-based photometry of the north polar region (NPR) and the NPS in the red methane absorption bands and their adjacent continuum are consistent with a radiative transfer model of the cloud vertical structure consisting of a clear gas layer, a haze layer, and a semi-infinite cloud. In the context of this model the NPS cloud tops are slightly higher than neighboring clouds reaching a pressure level of 45 mbar. Calculations of the seasonal insolation at the north pole, together with a simple linear radiative response of the atmosphere to this heating at different altitudes, suggest temperature changes at the level of the NPS cloud tops which should influence the NPS dynamics. Because of the long lifetime of the NPS, and because its motions did not vary appreciably during the long observing period, we suggest that the main properties and dynamics of the NPS are insensitive to the external solar forcing. (C) 1997 Academic Press. C1 INTA, LAEFF, LAB ASTROFIS & FIS FUNDAMENTALE, MADRID, SPAIN. OBSERV PARIS, DEPT RECH SPATIALES, MEUDON, FRANCE. BUR LONGITUDES, PARIS, FRANCE. NASA, GODDARD SPACE FLIGHT CTR, PLANETARY SYST BRANCH, GREENBELT, MD 20771 USA. RP SanchezLavega, A (reprint author), UNIV BASQUE COUNTRY, ETS INGN, DEPT FIS APLICADA 1, ALDA URQUIJO S-N, BILBAO, SPAIN. RI Rojas Palenzuela, Jose Felix/H-2782-2015; OI Rojas Palenzuela, Jose Felix/0000-0002-1102-5612; Sanchez-Lavega, Agustin/0000-0001-7355-1522 NR 37 TC 13 Z9 13 U1 2 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 AUG PY 1997 VL 128 IS 2 BP 322 EP 334 DI 10.1006/icar.1997.5761 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT893 UT WOS:A1997XT89300005 ER PT J AU Liou, JC Zook, HA AF Liou, JC Zook, HA TI Evolution of interplanetary dust particles in mean motion resonances with planets SO ICARUS LA English DT Article ID POYNTING-ROBERTSON DRAG; RESTRICTED 3-BODY PROBLEM; ASTEROIDAL DUST; BETA-PICTORIS; SOLAR-SYSTEM; RING; SATELLITE; EARTH; PERTURBATIONS; STABILITY AB The three-dimensional orbital evolution of interplanetary dust particles in mean motion resonances (MMRs) with planets is investigated in a restricted three-body system. Using the time variation of the jacobi ''constant'' due to drag forces, we develop simple analytical expressions that describe the orbital evolution of a dust grain in MMRs with a planet. Together with the time rate of change of the Tisserand criterion, the variations in eccentricity and inclination of a dust grain in any MMR are related to each other in one single equation. When expanded to the second order in eccentricity and inclination, the equation can be split into two parts and be used to describe separately the time variation of both orbital elements of a dust grain in a MMR. Dust grains in retrograde orbits in MMRs are also discussed, Numerical simulations of various Sun-planet-dust three-body systems are performed to verify the new analytical expressions, Simulations of different types of dust grains (asteroidal, cometary) in MMRs with planets in the real Solar System are also discussed and compared with our analytical predictions. (C) 1997 Academic Press. RP Liou, JC (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SN3,HOUSTON,TX 77058, USA. NR 36 TC 48 Z9 48 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1997 VL 128 IS 2 BP 354 EP 367 DI 10.1006/icar.1997.5755 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT893 UT WOS:A1997XT89300007 ER PT J AU Krasnopolsky, V AF Krasnopolsky, V TI On the nature of soft X-ray radiation in comets SO ICARUS LA English DT Article ID VEGA-2 3-CHANNEL SPECTROMETER; ELECTRON-ENERGY DEPOSITION; C/1996 B2 HYAKUTAKE; DUST PARTICLES; CROSS-SECTIONS; FLUX MODEL; P/HALLEY; IONS; COLLISIONS; IONIZATION AB EUVE and ROSAT observations of Comet Hyakutake revealed emission of 7 x 10(24) photons per second in the soft Xray, We discuss and develop methods to calculate production of soft X-ray photons in cometary dust and gas by the following processes: (1) scattering and (2) fluorescence of solar X-rays; (3) K- and L-shell ionization by solar-wind protons and (4) electrons, and (5) by high-energy cometary ions; (6) bremsstrahlung of solar-wind electrons; (7) cometary magnetospheric substorms; (8) collisions between cometary and interplanetary dust particles; (9) scattering, fluorescence, and bremsstrahlung by very small particles with mass on the order of 10(-19) g; and (10) charge transfer of the solar-wind heavy ions with cometary molecules suggested by T. E. Cravens (1997, Geophys. Res. Lett. 24, 105-108). Very small attogram particles were detected in Comet Halley by N. G. Utterback and J. Kissel (1990, Astron. J. 100, 1315-1322) using the PUMA and PIA dust analyzers from the Vega and Giotto spacecraft. Of all these processes, only scattering by very small particles and charge transfer of the solar-wind heavy ions are capable of producing the measured soft X-ray emission. Ln the case of very small particles, the mean particle mass of 4.6 x 10(-19) g suggested by Utterback and Kissel implies that the total production of these particles, which exceeds that of gas by a factor 3.6 (in mass), is inconsistent with the polarization and color of Comet Halley, Both polarization and color require a reduction of the mean mass to (1-2) x 10(-19) g. This reduction strongly affects the visible brightness of the par-tides, which is proportional to m(2), with a relatively weak effect on the soft X-ray emission. We calculate the charge transfer process using the solar-wind ion densities and velocities in comet from both the model of T. I. Gombosi et al. (1994, J. Geophys. Res. 99, 21,525-21,539) and the Giotto measurements of Lu-particles and. Hei ions in Comet Halley. The calculated emission constitutes 20-35% of the measured value. X-ray spectroscopy of the observed emission, spectroscopy of the He+ 304 Angstrom and He 522 Angstrom lines, and UV spectroscopy of cometary dust down to 1800 Angstrom may help in determining the contributions of the above processes. (C) 1997 Academic Press. RP Krasnopolsky, V (reprint author), NASA, NRC, GODDARD SPACE FLIGHT CTR, CODE 693, GREENBELT, MD 20771 USA. RI Krasnopolsky, Vladimir/L-5085-2013 NR 77 TC 67 Z9 67 U1 0 U2 3 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1997 VL 128 IS 2 BP 368 EP 385 DI 10.1006/icar.1997.5722 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT893 UT WOS:A1997XT89300008 ER PT J AU Haldemann, AFC Muhleman, DO Butler, BJ Slade, MA AF Haldemann, AFC Muhleman, DO Butler, BJ Slade, MA TI The western hemisphere of Venus: 3.5 cm dual circular-polarization radar images SO ICARUS LA English DT Article ID BETA-REGIO; MAGELLAN OBSERVATIONS; EISTLA REGIO; ALPHA-REGIO; SURFACE; GEOLOGY; REFLECTIVITY; ARECIBO; EMISSIVITY; TECTONICS AB We present new dual circular-polarization radar maps of the western hemisphere of Venus. The results are from a 1993 experiment imaging Venus with 3.5 cm radar. Continuous-wave right circularly polarized flux was transmitted toward Venus from the 70 m Deep Space Network antenna in Goldstone, California, The echo was received in both the same sense (SS) and the opposite sense (OS) of circular polarization at the Very Large Array in New Mexico, By spatially reconstructing the echo with the interferometer er, maps of Venusian radar albedo were made for each of two days of observation in both OS (echo principally due to specular reflection) and SS (diffuse echo) channels, On both days, the sub-earth longitude was near 300 E. The SS maps are dominated by a significant component of diffuse backscatter from the 285 E longitude highlands: Beta, Phoebe, and Themis Regiones. Beta Regio includes radar-anomalous regions with high reflectivity and low emissivity, The nature of these altitude-related electrical properties on Venus is one of the outstanding surface process questions that remain after Magellan. Our experiment adds the first full-disk polarization ratio (mu(c)) maps to the discussion, The data show that different geology determines different radar scattering properties within Beta. Diffuse scattering is very important in Beta, and may be due to either surface or volume scattering. We find a strong correlation of the SS albedo sigma(ss) with altitude R-p (km) in Beta, sigma(ss) proportional to 0.3R(p). Also, sigma(os) proportional to 0.7R(p). The onset of this relationship is at the R-p similar to 6054 km planetary radius contour, The nature and morphology of the highland radar anomalies in Beta is consistent with a diffuse scattering mechanism. In Beta Regio we find mu(c) > 0.5 in general, with mu(c) as high as 0.8 between Rhea and Theia Montes, to the west of Devana Chasma, These values are compatible with measurements of blocky terrestrial lava flows if surface scattering dominates, If volume scattering Is important, the high RCP cross-sections may indicate an important decrease in embedded scatterer size with altitude, which could be related to enhanced weathering. (C) 1997 Academic Press. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Haldemann, AFC (reprint author), CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA 91125 USA. NR 48 TC 6 Z9 6 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1997 VL 128 IS 2 BP 398 EP 414 DI 10.1006/icar.1997.5729 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT893 UT WOS:A1997XT89300010 ER PT J AU Northrop, TG AF Northrop, TG TI The spectrum of X-rays from Comet Hyakutake SO ICARUS LA English DT Article ID B2 AB A previous paper (1997. T. G. Northrop, C. M. Lisse, M. J. Mumma, and M. D. Desch. Icarus 127, 246-250.) established that the total X-ray radiation intensity from Comet Hyakutake can be attributed to electron-neutral bremsstrahlung by using an electron energy spectrum of the shape seen by Vega 2 at Halley, but otherwise using solar wind and cometary parameters characteristic of Hyakutake. In this paper we find that the predicted photon spectrum also agrees with Hyakutake observations, insofar as they are known, in both shape and intensity. (C) 1997 Academic Press. RP Northrop, TG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 13 TC 11 Z9 11 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1997 VL 128 IS 2 BP 480 EP 482 DI 10.1006/icar.1997.5762 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT893 UT WOS:A1997XT89300018 ER PT J AU Rao, G Vaidyanathan, H Nakhleh, W AF Rao, G Vaidyanathan, H Nakhleh, W TI Behavior of a cycled Ni-Cd battery during pulse discharge SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article AB The pulse discharge behavior of a 9-Ah, 6-V nickel-cadmium (Ni-Cd) battery fabricated for the FAST program was studied. The response of the battery voltage to a pulse with a current of 60 A and duration of 10 to 200 ms was measured, along with the capacity remaining at the end of pulse discharge. The maximum drop in voltage at the beginning of the pulse was 505 to 1,049 mV, and battery capacity remained stable. C1 COMSAT LABS,CLARKSBURG,MD 20871. RP Rao, G (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 2 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 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD AUG PY 1997 VL 12 IS 8 BP 41 EP 44 DI 10.1109/62.609532 PG 4 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA XN833 UT WOS:A1997XN83300013 ER PT J AU Garg, S AF Garg, S TI A simplified scheme for scheduling multivariable controllers SO IEEE CONTROL SYSTEMS MAGAZINE LA English DT Article ID OPTIMIZATION; DESIGN RP Garg, S (reprint author), NASA,LEWIS RES CTR,CONTROLS & DYNAM TECHNOL BRANCH,MSS 77-1,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 16 TC 3 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0272-1708 J9 IEEE CONTR SYST MAG JI IEEE Control Syst. Mag. PD AUG PY 1997 VL 17 IS 4 BP 24 EP 30 DI 10.1109/37.608529 PG 7 WC Automation & Control Systems SC Automation & Control Systems GA XL689 UT WOS:A1997XL68900004 ER PT J AU Haley, P Soloway, D AF Haley, P Soloway, D TI Generalized predictive control for active flutter suppression SO IEEE CONTROL SYSTEMS MAGAZINE LA English DT Article; Proceedings Paper CT 5th IEEE International Conference on Control Applications CY SEP 15-18, 1996 CL DEARBORN, MI SP IEEE, Control Syst Soc C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Haley, P (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 8 TC 12 Z9 12 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 0272-1708 J9 IEEE CONTR SYST MAG JI IEEE Control Syst. Mag. PD AUG PY 1997 VL 17 IS 4 BP 64 EP 70 DI 10.1109/37.608553 PG 7 WC Automation & Control Systems SC Automation & Control Systems GA XL689 UT WOS:A1997XL68900008 ER PT J AU Gau, JRJ Burnside, WD Gilreath, M AF Gau, JRJ Burnside, WD Gilreath, M TI Chebyshev multilevel absorber design concept SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article DE anechoic chambers ID MOMENT METHOD SOLUTION; DIELECTRIC BODIES; WEDGE AB Pyramidal- and wedge-absorber materials are used extensively in anechoic measurement chambers to attenuate stray signals. Typical absorber layouts result in large absorber walls in which the absorber tips and bases are roughly aligned in the same plane. Such a quasi-periodic configuration produces a strong coherent specular reflection which dominates the absorber scattered field. Based on the multisection impedance transformer concept, one can divide absorber elements into different levels (layers) set that this coherence can be destroyed to reduce the specular-absorber scattering level. The synthesis of this desired behavior can be implemented by the Chebyshev transformer technique, which provides the largest bandwidth given a passband ripple threshold. The resulting reflected field is then the product of the original absorber response times the Chebyshev reduction factor, which is independent of polarization and absorber properties. Various measured results are used to show that more than a 10-dB improvement can be achieved at the critical low end of the frequency band using this approach. This improvement cannot be achieved using conventional design concepts unless the absorber size is doubled. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP Gau, JRJ (reprint author), OHIO STATE UNIV,ELECTROSCI LAB,COLUMBUS,OH 43212, USA. NR 11 TC 21 Z9 22 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 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD AUG PY 1997 VL 45 IS 8 BP 1286 EP 1293 DI 10.1109/8.611249 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA XP189 UT WOS:A1997XP18900013 ER PT J AU Chen, M Houshmand, B Itoh, T AF Chen, M Houshmand, B Itoh, T TI FDTD analysis of a metal-strip-loaded dielectric leaky-wave antenna SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article DE FDTD methods; leaky-wave antennas ID ABSORBING BOUNDARY-CONDITIONS; WAVEGUIDE; CIRCUITS AB The finite-difference time-domain (FDTD) method is used to analyze a dielectric leaky-wave antenna comprising metal strips etched on a rectangular dielectric rod. The radiation patterns of the leaky-wave antenna with and without the transition are determined by using FDTD. The effects of the launching discontinuity on the performance of the antenna are discussed in this paper. In addition, the application of the perfectly matched layer (PML) technique to the three-dimensional (3-D) dielectric waveguide and its performance, compared to those of the Mur's first-order and super-absorbing Mur's first-order absorbing boundary conditions (ABC's) are described. In addition, the effects caused by perturbation on the wave propagation characteristics of dielectric waveguide are also discussed. The FDTD results are verified by a W-band experiment and found to be in good agreement. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Chen, M (reprint author), UNIV CALIF LOS ANGELES,DEPT ELECT ENGN,LOS ANGELES,CA 90095, USA. NR 21 TC 16 Z9 16 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD AUG PY 1997 VL 45 IS 8 BP 1294 EP 1301 DI 10.1109/8.611250 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA XP189 UT WOS:A1997XP18900014 ER PT J AU Lee, RQ Simons, RN AF Lee, RQ Simons, RN TI Measured mutual coupling between linearly tapered slot antennas SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Letter DE antenna proximity factors; slot antennas AB Mutual coupling between two linearly tapered slot antennas arranged in coplanar as well as stacked configurations has been measured. Results indicate that mutual coupling level generally decreases with antenna separations and varies with dielectric constant, flared angles, and antenna lengths. RP Lee, RQ (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 3 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 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD AUG PY 1997 VL 45 IS 8 BP 1320 EP 1322 DI 10.1109/8.611256 PG 3 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA XP189 UT WOS:A1997XP18900020 ER PT J AU Kemeny, SE Panicacci, R Pain, B Matthies, L Fossum, ER AF Kemeny, SE Panicacci, R Pain, B Matthies, L Fossum, ER TI Multiresolution image sensor SO IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY LA English DT Article DE focal plane array; image processing; imager; multimedia; sensor AB The recent development of the CMOS active pixel sensor (APS) has, for the first time, permitted large scale integration of supporting circuitry and smart camera functions on the same chip as a high-performance image sensor, This paper reports on the demonstration of a new 128 x 128 CMOS APS with programmable multiresolution readout capability, By placing signal processing circuitry on the imaging focal plane, the image sensor can output data at varying resolutions which can decrease the computational load of downstream image processing, For instance, software intensive image pyramid reconstruction can be eliminated, The circuit uses a passive switched capacitor network to average arbitrarily large neighborhoods of pixels which can then be read out at any user-defined resolution by configuring a set of digital shift registers, The full resolution frame rate is 30 Hz with higher rates for all other image resolutions, The sensor achieved 80 dB of dynamic range while dissipating only 5 mW of power, Circuit error was less than -34 dB and introduced no objectionable fixed pattern noise or other artifacts into the image. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Kemeny, SE (reprint author), PHOTOBIT,LA CRESCENTA,CA 91214, USA. NR 13 TC 40 Z9 40 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 1051-8215 J9 IEEE T CIRC SYST VID JI IEEE Trans. Circuits Syst. Video Technol. PD AUG PY 1997 VL 7 IS 4 BP 575 EP 583 DI 10.1109/76.611169 PG 9 WC Engineering, Electrical & Electronic SC Engineering GA XP520 UT WOS:A1997XP52000004 ER PT J AU Watson, AB Yang, GY Solomon, JA Villasenor, J AF Watson, AB Yang, GY Solomon, JA Villasenor, J TI Visibility of wavelet quantization noise SO IEEE TRANSACTIONS ON IMAGE PROCESSING LA English DT Article DE discrete wavelet transform; image compression; quantization; wavelet ID PROBABILITY SUMMATION; IMAGE COMPRESSION; MODEL; CONTRAST; CORTEX AB The discrete wavelet transform (DWT) decomposes an image into bands that vary in spatial frequency and orientation., it is widely used for image compression, Measures of the visibility of DWT quantization errors are required to achieve optimal compression, Uniform quantization of a single band of coefficients results in an artifact that we call DWT uniform quantization noise; it is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter. We measured visual detection thresholds for samples of DWT uniform quantization noise in Y, Cb, and Cr color channels, The spatial frequency of a wavelet is r2(-lambda), where r is display visual resolution in pixels/degree, and lambda is the wavelet level, Thresholds increase rapidly with wavelet spatial frequency. Thresholds also increase from Y to Cr to Ch, and with orientation from lowpass to horizontal/vertical to diagonal, We construct a mathematical model for DWT noise detection thresholds that is a function of level, orientation, and display visual resolution, This allows calculation of a ''perceptually lossless'' quantization matrix for which ail errors are in theory below the visual threshold, The model may also be used as the basis for adaptive quantization schemes. C1 UNIV CALIF LOS ANGELES,DEPT ELECT ENGN,LOS ANGELES,CA 90095. RP Watson, AB (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 41 TC 354 Z9 406 U1 1 U2 11 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1057-7149 J9 IEEE T IMAGE PROCESS JI IEEE Trans. Image Process. PD AUG PY 1997 VL 6 IS 8 BP 1164 EP 1175 DI 10.1109/83.605413 PG 12 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA XL870 UT WOS:A1997XL87000010 PM 11541660 ER PT J AU Lin, LY Wu, MC Itoh, T Vang, TA Muller, RE Sivco, DL Cho, AY AF Lin, LY Wu, MC Itoh, T Vang, TA Muller, RE Sivco, DL Cho, AY TI High-power high-speed photodetectors - Design, analysis, and experimental demonstration SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE coplanar transmission lines; millimeter-wave generation; MSM photodiodes; nonlinearities; photodetectors; optical pulse measurements; traveling-wave devices ID TRAVELING-WAVE PHOTODETECTORS; ANALOG FIBEROPTIC LINKS; I-N PHOTODETECTORS; DYNAMIC-RANGE; PHOTODIODE; WAVELENGTH; BANDWIDTH; 110-GHZ AB A novel velocity-matched distributed photodetector (VMDP) is proposed to simultaneously achieve high saturation photocurrent and broach bandwidth. Theoretical analysis on the tradeoff between saturation power and bandwidth shows that the VMDP offers fundamental advantages over conventional photodetectors. A comprehensive theoretical model has been developed for the design and simulation of the VMDP. Experimentally, the VMDP with very high saturation (56-mA) photocurrent and instrument-limited 3-dB bandwidth (49 GHz) has been demonstrated, The theoretical analysis and experimental results shaw that the VMDP is very attractive for high-performance microwave photonic links and high-power optical microwave applications. C1 UNIV CALIF LOS ANGELES,DEPT ELECT ENGN,LOS ANGELES,CA 90095. CALTECH,JET PROP LAB,PASADENA,CA 91109. AT&T BELL LABS,LUCENT TECHNOL,MURRAY HILL,NJ 07974. NR 32 TC 93 Z9 96 U1 0 U2 11 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 AUG PY 1997 VL 45 IS 8 BP 1320 EP 1331 DI 10.1109/22.618430 PN 2 PG 12 WC Engineering, Electrical & Electronic SC Engineering GA XT119 UT WOS:A1997XT11900007 ER PT J AU Ziock, KP Bixler, J Cline, T Stilwell, D Sheppard, D Hurley, K Berg, P Primbsch, JH SlassiSenou, S Madden, N Anfimov, DS Chernenko, AM Isupov, OM Litvak, ML Litvin, DA Loznikov, VM Mitrofanov, IG Pozanenko, AS Tonshev, AK Ushakov, DA AF Ziock, KP Bixler, J Cline, T Stilwell, D Sheppard, D Hurley, K Berg, P Primbsch, JH SlassiSenou, S Madden, N Anfimov, DS Chernenko, AM Isupov, OM Litvak, ML Litvin, DA Loznikov, VM Mitrofanov, IG Pozanenko, AS Tonshev, AK Ushakov, DA TI The gamma-ray burst monitor for the Russian Mars 1996 mission SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1996 Medical Imaging Conference CY NOV 07-09, 1996 CL ANAHEIM, CA DE bursts; gamma-ray AB We describe an innovative detector designed primarily for the study of cosmic gamma-ray bursts aboard interplanetary. spacecraft. The experiment is a fully functional, low cost, low mass, low-power instrument, which, when combined with other similar instruments, has the capability of localizing bursts to arcminute precision, The burst monitor is based on a photomultiplier tube and a plastic/CsI(Tl) phoswich detector and records photons in the 20-150-keV energy range with time resolutions up to several milliseconds, In addition, it records photon energy spectra, Events in the plastic scintillator are distinguished by a pulse shape discrimination circuit and are used to count electrons and protons, In a planetary orbiter or fly-by mission, this capability can be used to detect the presence of a magnetosphere. We describe in detail a version of this instrument which was built for the Russian Mars 1996 mission. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. SPACE RES INST,MOSCOW,RUSSIA. RP Ziock, KP (reprint author), LAWRENCE LIVERMORE NATL LAB,LIVERMORE,CA 94550, USA. NR 14 TC 4 Z9 4 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD AUG PY 1997 VL 44 IS 4 BP 1692 EP 1701 DI 10.1109/23.604134 PN 2 PG 10 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA XP921 UT WOS:A1997XP92100010 ER PT J AU Ashokkumar, CR Yedavalli, RK AF Ashokkumar, CR Yedavalli, RK TI Eigenstructure perturbation analysis in disjointed domains for linear uncertain systems SO INTERNATIONAL JOURNAL OF CONTROL LA English DT Article ID OUTPUT-FEEDBACK; EIGENVALUE ASSIGNMENT; PARAMETER SPACE; POLE ASSIGNMENT; STATE FEEDBACK; ROBUSTNESS; DESIGN AB Sufficient bounds are presented on the norm bounded uncertainties for the perturbed eigenvalues to remain in a set of disjointed neighbourhoods of the nominal eigenvalues. For such perturbed eigenvalues, bounds on the corresponding eigenvector perturbations are also presented. The study is used to analyse design methodologies based on eigenstructure assignment with parameter variations in a conrollable pair. The left and right eigenvector perturbation analysis carried out in this paper is useful in the time response analysis of linear uncertain systems. C1 OHIO STATE UNIV,DEPT AERSP ENGN APPL MECH & AVIAT,COLUMBUS,OH 43210. RP Ashokkumar, CR (reprint author), N CAROLINA AGR & TECH STATE UNIV,NASA,CTR RES EXCELLENCE,GREENSBORO,NC 27411, USA. NR 25 TC 15 Z9 15 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0020-7179 J9 INT J CONTROL JI Int. J. Control PD AUG PY 1997 VL 67 IS 6 BP 887 EP 899 DI 10.1080/002071797223848 PG 13 WC Automation & Control Systems SC Automation & Control Systems GA XT731 UT WOS:A1997XT73100004 ER PT J AU Huang, J Xu, F Vallieres, M Feng, DH Qian, YH Fryxell, B Strayer, MR AF Huang, J Xu, F Vallieres, M Feng, DH Qian, YH Fryxell, B Strayer, MR TI A thermal LBGK model for large density and temperature differences SO INTERNATIONAL JOURNAL OF MODERN PHYSICS C LA English DT Article; Proceedings Paper CT 6th International Conference on Discrete Models for Fluid Mechanics CY AUG 26-28, 1996 CL BOSTON UNIV, CTR COMPUTAT SCI, BOSTON, MA HO BOSTON UNIV, CTR COMPUTAT SCI DE hydrodynamics; Boltzmann equation; BGK model ID EQUATIONS AB We present a new lattice-Boltzmann method for hydrodynamic simulations, which is capable of handling very large density and temperature gradients. Unlike other LBGK models, the discrete velocities we used center at the local mean Bow velocity, and their values vary according to the local temperature. The adiabatic index of the gas can be easily controlled by a parameter. C1 COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY 10027. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. OAK RIDGE NATL LAB,DIV PHYS,OAK RIDGE,TN 37831. RP Huang, J (reprint author), DREXEL UNIV,DEPT PHYS,PHILADELPHIA,PA 19104, USA. NR 10 TC 17 Z9 17 U1 0 U2 2 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 9128, SINGAPORE SN 0129-1831 J9 INT J MOD PHYS C JI Int. J. Mod. Phys. C PD AUG PY 1997 VL 8 IS 4 BP 827 EP 841 DI 10.1142/S0129183197000710 PG 15 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA YE900 UT WOS:A1997YE90000018 ER PT J AU Luo, LS AF Luo, LS TI Symmetry breaking of flow in 2D symmetric channels: Simulations by lattice-Boltzmann method SO INTERNATIONAL JOURNAL OF MODERN PHYSICS C LA English DT Article; Proceedings Paper CT 6th International Conference on Discrete Models for Fluid Mechanics CY AUG 26-28, 1996 CL BOSTON UNIV, CTR COMPUTAT SCI, BOSTON, MA HO BOSTON UNIV, CTR COMPUTAT SCI DE lattice-Boltzmann and lattice-BGK methods; symmetry breaking; flow in 2D symmetric channel with expansion ID NAVIER-STOKES EQUATION; SUDDEN-EXPANSION; GAS AUTOMATA AB In this paper, a numerical study of nonlinear flow phenomena in two-dimensional symmetric channels using the lattice-Boltzmann equation method is presented. The results are compared with both experimental results and other numerical results using some traditional methods. Comparisons are found to be quantitatively accurate. C1 LOS ALAMOS NATL LAB,COMPLEX SYST GRP T13,THEORET T DIV,LOS ALAMOS,NM 87545. RP Luo, LS (reprint author), NASA,LANGLEY RES CTR,ICASE,MAIL STOP 403,6 N DRYDEN ST,BLDG 1298,HAMPTON,VA 23681, USA. RI Luo, Li-Shi/A-4561-2011 OI Luo, Li-Shi/0000-0003-1215-7892 NR 22 TC 20 Z9 22 U1 0 U2 2 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 9128, SINGAPORE SN 0129-1831 J9 INT J MOD PHYS C JI Int. J. Mod. Phys. C PD AUG PY 1997 VL 8 IS 4 BP 859 EP 867 DI 10.1142/S0129183197000734 PG 9 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA YE900 UT WOS:A1997YE90000020 ER PT J AU Weissman, DE Li, FK Lou, SH Nghiem, SV Neumann, G McIntosh, RE Carson, SC Carswell, JR Jensen, RE AF Weissman, DE Li, FK Lou, SH Nghiem, SV Neumann, G McIntosh, RE Carson, SC Carswell, JR Jensen, RE TI Measurements of ocean surface stress using aircraft scatterometers SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID INTERACTION EXPERIMENT FASINEX; SEA-SURFACE; WIND STRESS; RADAR BACKSCATTER; MODEL FUNCTION; HEAT-FLUX; WAVES; COEFFICIENTS; ROUGHNESS; SPEED AB Scatterometer model functions that directly estimate friction velocity have been developed and are being tested with radar and in situ data acquired during the Surface Wave Dynamics Experiment (SWADE) of 1991. K-u-band and C-band scatterometers were operated simultaneously for extensive intervals for each of 10 days during SWADE. The model function developed previously from the FASINEX experiment converts the K-u-band normalized radar cross-section (NRCS) measurements into friction velocity estimates. These are compared to in situ estimates of surface wind stress and direction across a wide area both on and off the Gulf Stream (for hourly intervals), which were determined from buoy and meteorological measurements during February and March 1991. This involved the combination of a local, specially derived wind field, with an ocean wave model coupled through a sea-state-dependent drag coefficient. The K-u-band estimates u* magnitude are in excellent agreement with the in situ values. The C-band scatterometer measurements were coincident with the K-u-band NRCSs, whose u* estimates are then used to calibrate the C band. The results show the C-band NRCS dependence at 20 degrees, 30 degrees, 40 degrees, and 50 degrees to be less sensitive to friction velocity than the corresponding cases for K-u band. The goal is to develop the capability of making friction velocity estimates (and surface stress) from radar cross-sectional data acquired by satellite scatterometers. C1 CALTECH,JET PROP LAB,PASADENA,CA. UNIV MASSACHUSETTS,DEPT ELECT ENGN,AMHERST,MA 01003. UNIV MIAMI,ROSENSTIEL SCH MARINE & ATMOSPHER SCI,MIAMI,FL 33149. USA CORP ENGINEERS,COASTAL ENGN RES CTR,VICKSBURG,MS. RP Weissman, DE (reprint author), HOFSTRA UNIV,DEPT ENGN,HEMPSTEAD,NY 11550, USA. NR 40 TC 10 Z9 10 U1 0 U2 0 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 AUG PY 1997 VL 14 IS 4 BP 835 EP 848 DI 10.1175/1520-0426(1997)014<0835:MOOSSU>2.0.CO;2 PG 14 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA XN532 UT WOS:A1997XN53200007 ER PT J AU Pinto, O Mendes, O Pinto, IRCA Gonzalez, WD Holzworth, RH Hu, H AF Pinto, O Mendes, O Pinto, IRCA Gonzalez, WD Holzworth, RH Hu, H TI Atmospheric X-rays in the Southern hemisphere SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article AB Atmospheric X-rays in the energy range from 30 to 150 keV were measured in the Southern hemisphere extending from 53 to 81 degrees magnetic latitude during two long-duration balloon flights. The measurements were obtained during the Extended Life Balloon Borne Observatories (ELBBO) experiment. The experiment consisted of five superpressure balloon flights launched from Dunedin, New Zealand, in November and December 1992. The ELBBO X-ray data can be considered the longest continuous data set ever obtained in the Southern hemisphere, and extend over 30 degrees of magnetic latitude previously unmeasured. The X-ray measurements are compared to similar data obtained in the past by several groups in the Southern and Northern hemispheres, as well as with available model results. Most ELBBO results confirm earlier findings about the flux and spectra of atmospheric X-rays and are in general agreement with model results for higher energies. However, they indicate that the X-ray flux in the Southern hemisphere is almost constant from high latitudes up to 30 magnetic degrees, in contrast to the model results that indicate a drop off around 50 magnetic degrees. Whether such discrepancy should be attributed to the different energies involved or to the presence of the South Atlantic magnetic anomaly is a point that remains to be investigated. (C) 1997 Elsevier Science Ltd. C1 UNIV WASHINGTON,SEATTLE,WA 98195. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Pinto, O (reprint author), INPE,BR-12227010 S JOSE CAMPOS,SP,BRAZIL. RI Mendes, Odim/K-2241-2012 NR 16 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD AUG PY 1997 VL 59 IS 12 BP 1381 EP 1390 DI 10.1016/S1364-6826(96)00180-0 PG 10 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA XH940 UT WOS:A1997XH94000003 ER PT J AU Globus, RK Doty, SB Damsky, CH AF Globus, RK Doty, SB Damsky, CH TI Disruption of fibronectin interactions causes differentiation-dependent apoptosis of cultured osteoblasts. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 UNIV CALIF SAN FRANCISCO,SAN FRANCISCO,CA 94143. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. HOSP SPECIAL SURG,NEW YORK,NY 10021. NR 0 TC 0 Z9 0 U1 0 U2 0 PU BLACKWELL SCIENCE INC PI MALDEN PA 350 MAIN ST, MALDEN, MA 02148 SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD AUG PY 1997 VL 12 SU 1 BP 176 EP 176 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA XP627 UT WOS:A1997XP62700176 ER PT J AU Kostenuik, P Halloran, B MoreyHolton, E Harris, J Bikle, D AF Kostenuik, P Halloran, B MoreyHolton, E Harris, J Bikle, D TI Skeletal unloading alters the osteoblast phenotype in vitro and in vivo. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 UNIV CALIF SAN FRANCISCO,SAN FRANCISCO,CA 94143. VET ADM MED CTR,NASA,AMES RES CTR,MOFFETT FIELD,CA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU BLACKWELL SCIENCE INC PI MALDEN PA 350 MAIN ST, MALDEN, MA 02148 SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD AUG PY 1997 VL 12 SU 1 BP F228 EP F228 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA XP627 UT WOS:A1997XP62700718 ER PT J AU Arnaud, SB Navidi, M Wren, J AF Arnaud, SB Navidi, M Wren, J TI Deoxypyridinoline in the urine of rats with unloaded hindlimbs. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU BLACKWELL SCIENCE INC PI MALDEN PA 350 MAIN ST, MALDEN, MA 02148 SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD AUG PY 1997 VL 12 SU 1 BP S604 EP S604 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA XP627 UT WOS:A1997XP62701598 ER PT J AU Dehority, W Halloran, B Bikle, D Harris, J Curren, T Kostenuik, P MoreyHolton, E AF Dehority, W Halloran, B Bikle, D Harris, J Curren, T Kostenuik, P MoreyHolton, E TI Bone, muscle, and hormonal changes induced by hindlimb elevation in the mature rat. SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Meeting Abstract C1 UNIV CALIF SAN FRANCISCO,SAN FRANCISCO,CA 94143. VET AFFAIRS MED CTR,SAN FRANCISCO,CA 94121. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 1 PU BLACKWELL SCIENCE INC PI MALDEN PA 350 MAIN ST, MALDEN, MA 02148 SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD AUG PY 1997 VL 12 SU 1 BP S452 EP S452 PG 1 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA XP627 UT WOS:A1997XP62701447 ER PT J AU Rosenzweig, C Abramopoulos, F AF Rosenzweig, C Abramopoulos, F TI Land-surface model development for the GISS GCM SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODELS; CLIMATE MODELS; SPATIAL VARIABILITY; RIVER-RUNOFF; FLUXES; PARAMETERIZATION; TEMPERATURE; VEGETATION; VALIDATION AB A land-surface model is linked to the Goddard Institute for Space Studies (GISS) GCM Model II to form Model LI-LS. The land-surface model primarily influences the simulation of surface air temperature over land, both in monthly means and diurnal range, and affects the major components of the hydrologic cycle over land-evapotranspiration, runoff, and, more indirectly, precipitation. Comparisons of January and July results of Model II-LS to results generated from the GISS GCM Model II and to observations show that the new land surface primarily provides improvements in the simulation of global evaporation and diurnal surface temperature range. The interannual variability of June-August surface air temperature in the Northern Hemisphere is also improved. When the land-surface model is combined with new parameterizations for moist convection and the planetary boundary layer, the combined version of the GCM yields improvements in evaporation. Simulations of a grassland site from an off-line version of the land-surface model compared to observations provided by the Project for Intercomparison of Land-Surface Parameterization Schemes of the Global Energy and Water Cycle Experiment show that the land-surface model simulates the ground temperature lag with depth in a reasonable way. Thus, the land-surface parameterization provides a more realistic simulation of climate variables over land in conjunction with other improvements to the GISS GCM. C1 SCI SYST & APPLICAT INC, NEW YORK, NY USA. RP Rosenzweig, C (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 39 TC 68 Z9 69 U1 1 U2 1 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 AUG PY 1997 VL 10 IS 8 BP 2040 EP 2054 DI 10.1175/1520-0442(1997)010<2040:LSMDFT>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XU085 UT WOS:A1997XU08500015 ER PT J AU Bony, S Lau, KM Sud, YC AF Bony, S Lau, KM Sud, YC TI Sea surface temperature and large-scale circulation influences on tropical greenhouse effect and cloud radiative forcing SO JOURNAL OF CLIMATE LA English DT Article ID OUTGOING LONGWAVE RADIATION; DEEP CONVECTION; ATMOSPHERIC HYDROLOGY; WATER-VAPOR; OBSERVED DEPENDENCE; CLIMATE FEEDBACK; NORTHERN WINTER; OCEANS; BUDGET; THERMOSTAT AB Two independent sets of meteorological reanalyses are used to investigate relationships between the tropical sea surface temperature (SST) and the large-scale vertical motion of the atmosphere for spatial and seasonal variations, as well as for El Nino/La Nina episodes of 1987-88. Supergreenhouse effect (SGE) situations are found to be linked to the occurrence of enhanced large-scale rising motion associated with increasing SST. In regions where the large-scale atmospheric motion is largely decoupled from the local SST due to internal or remote forcings, the SGE occurrence is weak. On seasonal and interannual timescales, such regions are found mainly over equatorial regions of the Indian Ocean and western Pacific, especially for SSTs exceeding 29.5 degrees C. In these regions, the activation of feedback processes that regulate the ocean temperature is thus likely to be more related to the large-scale remote processes, such as those that govern the monsoon circulations and the low-frequency variability of the atmosphere, than to the local SST change. The relationships among SST, clouds, and cloud radiative forcing inferred from satellite observations are also investigated. In large-scale subsidence regimes, regardless of the SST range, the cloudiness, the cloud optical thickness, and the shortwave cloud forcing decrease with increasing SST. In convective regions maintained by the large-scale circulation, the strong dependence of both the longwave (LW) and shortwave (SW) cloud forcing on SST mainly results from changes in the large-scale vertical motion accompanying the SST changes. Indeed, for a given large-scale rising motion, the cloud optical thickness decreases with SST, and the SW cloud forcing remains essentially unaffected by SST changes. However, the LW cloud forcing still increases with SST because the detrainment height of deep convection, and thus the cloud-top altitude, tend to increase with SST. The dependence of the net cloud radiative forcing on SST may thus provide a larger positive climate feedback when the ocean warming is associated with weak large-scale circulation changes than during seasonal or El Nino variations. C1 NASA,GODDARD LAB ATMOSPHERES,GREENBELT,MD. 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 57 TC 119 Z9 122 U1 0 U2 11 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD AUG PY 1997 VL 10 IS 8 BP 2055 EP 2077 DI 10.1175/1520-0442(1997)010<2055:SSTALS>2.0.CO;2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XU085 UT WOS:A1997XU08500016 ER PT J AU Jorgensen, JH Skweres, JA Mishra, SK McElmeel, ML Maher, LA Mulder, R Lancaster, MV Pierson, DL AF Jorgensen, JH Skweres, JA Mishra, SK McElmeel, ML Maher, LA Mulder, R Lancaster, MV Pierson, DL TI Development of an antimicrobial susceptibility testing method suitable for performance during space flight SO JOURNAL OF CLINICAL MICROBIOLOGY LA English DT Article ID DURATION MISSIONS; IMMUNE CHANGES AB Very little is known regarding the effects of the microgravity environment of space flight upon the action of antimicrobial agents on bacterial pathogens, This study was undertaken to develop a simple method for conducting antibacterial susceptibility tests during a space shuttle mission, Specially prepared susceptibility test research cards (bioMerieux Vitek, Hazelwood, Mo.) were designed to include 6 to 11 serial twofold dilutions of 14 antimicrobial agents, including penicillins, cephalosporins, a beta-lactamase inhibitor, vancomycin, erythromycin, tetracycline, gentamicin, ciprofloxacin, and trimethoprim-sulfamethoxazole. MICs of the drugs were determined by visual reading of color end points in the Vitek research cards made possible by incorporation of a colorimetric growth indicator (alamarBlue; Accumed International, Westlake, Ohio), This study has demonstrated reproducible susceptibility results in the testing of isolates of Staphylococcus aureus, group A Streptococcus species, Enterococcus faecalis, Escherichia coli (beta-lactamase-positive and -negative strains), Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa, In some instances, the MICs were comparable to those determined by a standard broth microdilution method, while in some cases the unique test media and format yielded slightly different values that were themselves reproducible, The proposed in-flight experiment will include inoculation of the Vitek cards on the ground prior to launch of the space shuttle, storage of inoculated cards at refrigeration temperature aboard the space shuttle until experiment initiation, and then incubation of the cards for 18 to 48 h prior to visual interpretation of MICs by the mission's astronauts, Ground-based studies have shown reproducible MICs following storage of inoculated cards for 7 days at 4 to 8 degrees C to accommodate the mission's time schedule and the astronaut's activities, For comparison, ground-based control (normal gravity) MIC values will be generated by simultaneous inoculation and incubation of a second set of test cards in a laboratory at the launch site, This procedure can provide for a safe and compact experiment that should yield new information on the effects of microgravity on the biological activities of various classes of antibiotics. C1 NASA,KRUG LIFE SCI,HOUSTON,TX. NASA,JOHNSON SPACE CTR,HOUSTON,TX. BIOMERIEUX VITEK,HAZELWOOD,MO. ACCUMED INT,WESTLAKE,OH. RP Jorgensen, JH (reprint author), UNIV TEXAS,HLTH SCI CTR,DEPT PATHOL,7703 FLOYD CURL DR,SAN ANTONIO,TX 78284, USA. NR 15 TC 12 Z9 12 U1 0 U2 0 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1325 MASSACHUSETTS AVENUE, NW, WASHINGTON, DC 20005-4171 SN 0095-1137 J9 J CLIN MICROBIOL JI J. Clin. Microbiol. PD AUG PY 1997 VL 35 IS 8 BP 2093 EP 2097 PG 5 WC Microbiology SC Microbiology GA XL745 UT WOS:A1997XL74500033 PM 9230388 ER PT J AU Zalesak, ST AF Zalesak, ST TI Flux-corrected transport .1. SHASTA, a fluid transport algorithm that works - Introduction SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Editorial Material ID HYPERBOLIC CONSERVATION-LAWS RP NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NR 14 TC 5 Z9 5 U1 0 U2 5 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 EI 1090-2716 J9 J COMPUT PHYS JI J. Comput. Phys. PD AUG PY 1997 VL 135 IS 2 BP 170 EP 171 DI 10.1006/jcph.1997.5756 PG 2 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA XQ327 UT WOS:A1997XQ32700013 ER PT J AU Cane, HV Richardson, IG AF Cane, HV Richardson, IG TI What caused the large geomagnetic storm of November 1978? SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID COROTATING INTERACTION REGIONS; SOLAR-WIND; INTERPLANETARY SHOCKS; FILAMENT DISAPPEARANCES; EVENTS; DISTURBANCES; STREAMS AB We discuss energetic particle and solar wind plasma data for the period around the large geomagnetic storm of November 24-25, 1978. The storm was clearly caused by an ejecta interacting with a corotating high-speed stream, We conclude that there are no data to support the attribution of this storm to specific solar activity as previously suggested. This case study illustrates the important role of energetic particles in making correct associations between solar and interplanetary phenomena. Even if there had been an identifiable source region for the ejecta, the intensity of the geomagnetic storm resulted from the interplanetary interaction. Thus predictions of the strengths of such storms cannot be based on solar observations alone but also require knowledge of stream interactions. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. RP Cane, HV (reprint author), UNIV TASMANIA,DEPT PHYS,GPO BOX 252-21,HOBART,TAS 7001,AUSTRALIA. OI Richardson, Ian/0000-0002-3855-3634 NR 35 TC 13 Z9 13 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 AUG 1 PY 1997 VL 102 IS A8 BP 17445 EP 17449 DI 10.1029/97JA01420 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP071 UT WOS:A1997XP07100020 ER PT J AU Marklund, G Karlsson, T Clemmons, J AF Marklund, G Karlsson, T Clemmons, J TI On low-altitude particle acceleration and intense electric fields and their relationship to black aurora SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FREJA AB Recent findings by the Freja satellite have shown the existence of extremely intense (1-2 V/m) and small-scale (1 km) diverging electric fields which are interpreted to be associated with east-west aligned dark striations or black auroral curls. Precipitating or transversely energized ions, downward field-aligned currents carried by upward fluxes of ionospheric electrons and dropouts of energetic electron precipitation, are found to be characteristic features of such events. A comparison of these characteristics to those of the aurora point at a symmetry between the aurora and the black aurora, the aurora being associated with negative divergence of the electric field and the black aurora with positive divergence. The diverging field events typically occur during winter conditions within the midnight to early morning sector of the auroral oval. Estimates of the ambient conductivity due to solar EUV radiation for each of these events show a clear anticorrelation with the electric field magnitude. The black auroral structures are likely to be associated with localized ionospheric density depletions below that of the ambient density and caused by the upward flow of ionospheric electrons. The efficiency by which such density holes are created in regions of downward field-aligned current flow have recently been demonstrated in model studies. The electric field magnitudes are found to decrease with the scale size, not inversely as suggested in recent theoretical work but with a power law exponent of 0.6-0.8. At lower altitudes (around 800 km) the maximum intensities for a majority of the events are in the range of values that have been reported from rocket and radar measurements in the ionosphere, i.e., around 150-200 mV/m. However, close to magnetic midnight and during winter conditions small-scale diverging electric fields of 1 V/m are occasionally found to exist down to at least 800 km. We suggest that the diverging electric fields observed by Freja are associated with low-altitude and narrow ( approximate to 1-2 km) potential structures similar to the auroral potential structures at higher altitude but associated with a positive space charge and a downward parallel electric field. This is supported by Freja observations of narrow upward beams of 2 keV electrons in good agreement with a 2 kV positive peak in the electrostatic potential for a black aurora event. The existence of a downward parallel electric field at low altitudes is also supported by low-altitude observations by the S3-3 and Viking satellites. If such low-altitude potential structures do exist as our results suggest, an outstanding problem for future investigation is how they may be formed and maintained. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Marklund, G (reprint author), ALFVEN LAB,DIV PLASMA PHYS,S-10044 STOCKHOLM,SWEDEN. OI Clemmons, James/0000-0002-5298-5222 NR 20 TC 108 Z9 107 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1997 VL 102 IS A8 BP 17509 EP 17522 DI 10.1029/97JA00334 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP071 UT WOS:A1997XP07100027 ER PT J AU Nakabe, S Iyemori, T Sugiura, M Slavin, JA AF Nakabe, S Iyemori, T Sugiura, M Slavin, JA TI A statistical study of the magnetic field structure in the inner magnetosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID BIRKELAND CURRENTS; GEOMAGNETIC-FIELD; RING CURRENT; MODEL; IONOSPHERE; PARAMETERS; SYSTEM AB Three-dimensional magnetic field structure in the inner magnetosphere is statistically analyzed using data obtained by the DE-1 magnetometer. The main results are as follows: (1) The magnetic field. structure of the rotational pattern associated with an eastward current is clearly seen in the dayside equatorial region at geocentric distances around 2.5R(e) but not on the nightside, The current density is approximately 0.05 mu A/m(2), and does not show any clear dependence on geomagnetic disturbance, but shows a solar activity dependence which possibly suggests that a substantial part of the closure of the eastward current is through the dayside mid-latitude ionosphere, (2) The azimuthal component of the magnetic field associated with field-aligned currents is seen in the low-latitude magnetosphere, The intensity of this component is about 5 to 10 nT, and has a dependence on geomagnetic activity, (3) Compared with the currently available magnetospheric models, the observed inner magnetospheric magnetic fields have much more complex structures than the models indicate, The necessity of including the field-aligned current system and an eastward current in the models is evident, (4) A noon-midnight asymmetry of the magnetic structure is clearly seen, particularly in the southward component associated with the ring current, The asymmetry is much larger in this meridian than that in the dawn-dusk meridian, This is in contrast with the asymmetry observed on the ground or by low-altitude satellites over the ionosphere. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. TOKAI UNIV, INST RES & DEV, TOKYO 151, JAPAN. RP Nakabe, S (reprint author), KYOTO UNIV, FAC SCI, INST GEOPHYS, KYOTO 60601, JAPAN. RI Slavin, James/H-3170-2012 OI Slavin, James/0000-0002-9206-724X NR 27 TC 13 Z9 13 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 AUG 1 PY 1997 VL 102 IS A8 BP 17571 EP 17582 DI 10.1029/97JA01181 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP071 UT WOS:A1997XP07100031 ER PT J AU Eldridge, JI Wheeler, DR Bowman, RR KorenyiBoth, A AF Eldridge, JI Wheeler, DR Bowman, RR KorenyiBoth, A TI The influence of binders on interfacial failure in sapphire fiber-reinforced NiAl composites SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID METAL AB The influence of organic binders on fiber/matrix bonding during the powder metallurgy fabrication of sapphire fiber-reinforced NiAl matrix composites (sapphire/NiAl) was investigated. One composite panel was fabricated using a poly(methyl methacrylate) (PMMA) fiber binder and a teflon matrix powder binder; another panel was fabricated by binderless powder metallurgy consolidation. The effect of the binders on fiber/matrix bonding was evaluated by fiber push-out testing from room temperature to 900 degrees C. Examination of mating fiber and matrix-trough fracture surfaces by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) revealed differences in interfacial morphology and chemistry, depending on the use of binders in fabrication. The primary difference between the two composites was the much higher concentration of carbon at the fiber/matrix interface in sapphire/NiAl fabricated with binders. This carbon residue from binder burnout prevented clean contact between the sapphire fiber and NiAl matrix surfaces, resulting in a weak, thermomechanically clamped fiber/matrix interface, in contrast to the stronger, less temperature dependent, interfacial bonding observed without binders. C1 GILCREST,CLEVELAND,OH 44135. RP Eldridge, JI (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 10 TC 5 Z9 6 U1 0 U2 1 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD AUG PY 1997 VL 12 IS 8 BP 2191 EP 2197 DI 10.1557/JMR.1997.0293 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA XQ278 UT WOS:A1997XQ27800031 ER PT J AU Rabot, S Viso, M Martin, F Blanquie, JP Popot, F Bensaada, M Vaissade, P Searby, N Szylit, O AF Rabot, S Viso, M Martin, F Blanquie, JP Popot, F Bensaada, M Vaissade, P Searby, N Szylit, O TI Effects of chair-restraint on gastrointestinal transit time and colonic fermentation in male rhesus monkey (Macaca mulatta) SO JOURNAL OF MEDICAL PRIMATOLOGY LA English DT Article DE primate; chronic restraint; space flight; digestive physiology; colonic microflora; feces; fecal pH; short chain fatty acids; ammonia; breath methane ID DIETARY FIBER; METABOLISM; DIGESTION; EXERCISE; STRESS AB The incidence of an 18 day chair-restraint on the digestive physiology of male rhesus monkey was investigated for space research purposes, comparing four trained restraint subjects with two vivarium controls. Chair-restraint induced a 2.5-fold acceleration of the gastrointestinal transit time, which persisted throughout the 7 day postrestraint period, and an increase of the fecal dry matter content, which mean value rose from 40.7% to 69.6%. Fecal pH remained unaltered throughout the experiment. Modifications of fermentative metabolites produced by the colonic microflora and excreted through the breath (hydrogen and methane) or in the feces (short chain fatty acids and ammonia) could not be reliably related to chair-restraint and probably involved side-stress factors. On the whole, alterations due to chair-restraint are shown to be different from those reported in the literature, following a modification of the dietary composition. These data may help to predict the alterations of digestive physiology likely to occur in immobilized human patients. C1 CTR NATL ETUD SPATIALES,F-75039 PARIS 01,FRANCE. CTR ETUD MOUSSEAU,F-41150 MESLAND,FRANCE. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Rabot, S (reprint author), INRA,UNITE ECOL & PHYSIOL SYST DIGEST,BATIMENT 440,F-78352 JOUY EN JOSAS,FRANCE. NR 28 TC 5 Z9 5 U1 0 U2 3 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0047-2565 J9 J MED PRIMATOL JI J. Med. Primatol. PD AUG PY 1997 VL 26 IS 4 BP 190 EP 195 PG 6 WC Veterinary Sciences; Zoology SC Veterinary Sciences; Zoology GA YG918 UT WOS:A1997YG91800002 PM 9416569 ER PT J AU Miller, CE Sander, SP AF Miller, CE Sander, SP TI The nu(1) and nu(2) bands of FNO2 SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID ROTATION AB High-resolution infrared spectra of the strong a-type absorptions corresponding to the nu(1) (nu(0) similar to -1310.75 cm(-1)) and nu(2) (nu(0) = 821.9387 cm(-1)) bands of FNO2 have been analyzed. The nu(1) line positions exhibited extensive perturbations as a result of three nearly degenerate vibrational states-nu(1), nu(3) + nu(6), and nu(5) + nu(6)-which interact through strong Coriolis coupling. The weak Coriolis interaction between nu(2) and nu(6) reported by Tanaka and Morino (1969, J. Mol. Spectrosc. 32, 436-448) manifested itself through changes in the b-axis constants of the nu(2) = 1 state; nevertheless, over 1400 nu(2) transitions were fit with an rms error of 0.00066 cm(-1) using the standard A-reduced Hamiltonian. Line positions, assignments, and relative intensities for the dominant transitions in both bands have been established, although a comprehensive analysis of the perturbations requires a detailed understanding of the lower frequency vibrational states. (C) 1997 Academic Press. RP Miller, CE (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183-901,PASADENA,CA 91109, USA. NR 16 TC 2 Z9 2 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD AUG PY 1997 VL 184 IS 2 BP 442 EP 447 DI 10.1006/jmsp.1997.7347 PG 6 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA XY001 UT WOS:A1997XY00100022 ER PT J AU Schneegurt, MA Sherman, DM Sherman, LA AF Schneegurt, MA Sherman, DM Sherman, LA TI Growth, physiology, and ultrastructure of a diazotrophic cyanobacterium, Cyanothece sp. strain ATCC 51142, in mixotrophic and chemoheterotrophic cultures SO JOURNAL OF PHYCOLOGY LA English DT Article DE chemoheterotrophy; chlorophyll; circadian rhythm; cyanobacteria; diazotrophy; glycogen; mixotrophy; N-2-fixation; photosynthesis ID BLUE-GREEN-ALGAE; ANABAENA-VARIABILIS; HETEROTROPHIC GROWTH; NITROGEN-FIXATION; DARK; METABOLISM; LIGHT AB The growth, physiology, and ultrastructure of the marine, unicellular, diazotrophic cyanobacterium, Cyanothece sp. strain ATCC 51142 was examined under mixotrophic and chemoheterotrophic conditions. Several organic substrates were tested for the capacity to support heterotrophic growth. Glycerol was the only substrate capable of enhancing mixotrophic growth in the light and supporting chemoheterotrophic growth in the dark. Dextrose enhanced mixotrophic growth bat could not support chemoheterotrophic growth. Chemoheterotrophic cultures in continuous darkness grew faster and to higher densities than photoautotrophic cultures, thus demonstrating the great respiratory capacity of this cyanobacterial strain. Only small differences in the pigment content and ultrastructure of the heterotrophic strains were observed in comparison to photoautotrophic control strains. The chemoheterotrophic strain grown in continuous darkness and the mixotrophic strain grown in light/dark cycles exhibited daily metabolic oscillations in N-2 fixation and glycogen accumulation similar to those manifested in photoautotrophic cultures grown in light/dark cycles or continuous light. This ''temporal separation'' helps protect O-2-sensitive N-2 fixation from photosynthetic O-2 evolution. The rationale for cyclic glycogen accumulation in cultures with an ample source of organic carbon substrate is unclear, but the observation of similar daily rhythmicities in cultures grown in light/dark cycles, continuous light, and continuous dark suggests an underlying circadian mechanism. C1 PURDUE UNIV,NASA,SPECIALIZED CTR RES & TRAINING,W LAFAYETTE,IN 47907. PURDUE UNIV,DEPT BOT & PLANT PATHOL,W LAFAYETTE,IN 47907. RP Schneegurt, MA (reprint author), PURDUE UNIV,DEPT BIOL SCI,W LAFAYETTE,IN 47907, USA. NR 48 TC 29 Z9 30 U1 2 U2 12 PU PHYCOLOGICAL SOC AMER INC PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044 SN 0022-3646 J9 J PHYCOL JI J. Phycol. PD AUG PY 1997 VL 33 IS 4 BP 632 EP 642 DI 10.1111/j.0022-3646.1997.00632.x PG 11 WC Plant Sciences; Marine & Freshwater Biology SC Plant Sciences; Marine & Freshwater Biology GA XR355 UT WOS:A1997XR35500010 ER PT J AU Sirota, JM Reuter, DC Frye, J AF Sirota, JM Reuter, DC Frye, J TI Absolute line intensities and broadening coefficients for the nu(11) band of allene SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID ATMOSPHERE AB Line strengths for the nu(11) band of allene (352.636 cm(-1)) have been measured using tunable diode laser spectroscopy. The dipole moment and band strengths have been derived, and pressure broadening coefficients for self and N-2, broadening were determined at temperatures representative of Titan's atmosphere (160-190 K). The absolute value for the dipole moment is 0.1093 debye giving a band intensity of 26.29 cm(-2) atm(-1) (300 K). This band strength is about 6% lower than that inferred from the low resolution measurements performed by Koga et al,(14) which is the only previous strength measurement for this band. (C) 1997 Elsevier Science Ltd. C1 NASA,GODDARD SPACE FLIGHT CTR,PLANETARY SYST BRANCH,GREENBELT,MD 20771. HOWARD UNIV,DEPT CHEM,WASHINGTON,DC 20059. RP Sirota, JM (reprint author), UNIV MARYLAND BALTIMORE CTY,DEPT PHYS,1000 HILLTOP CIRCLE,BALTIMORE,MD 21250, USA. NR 14 TC 4 Z9 4 U1 0 U2 0 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 AUG PY 1997 VL 58 IS 2 BP 145 EP 149 DI 10.1016/S0022-4073(97)00043-5 PG 5 WC Optics; Spectroscopy SC Optics; Spectroscopy GA XY946 UT WOS:A1997XY94600001 ER PT J AU Kastner, SO Bhatia, AK AF Kastner, SO Bhatia, AK TI Half-widths, escape probabilities and intensity factors of opacity-broadened Doppler- and Voigt-profile lines SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article AB Half-widths at half-maximum, photon escape probabilities and line-center intensity factors are calculated for lines formed by scattering in the Doppler and Voigt spectral profiles, in homogeneous plane-parallel media. Tables of values, and illustrative figures, are provided for optical thicknesses 0 less than or equal to tau(0) less than or equal to 100 and Voigt parameters 0 less than or equal to (a) under bar less than or equal to 10. The applicability of the results is discussed and relationships needed for their application are summarized. (C) 1997 Elsevier Science Ltd. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. NR 17 TC 29 Z9 30 U1 1 U2 2 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 AUG PY 1997 VL 58 IS 2 BP 217 EP 231 DI 10.1016/S0022-4073(97)00019-8 PG 15 WC Optics; Spectroscopy SC Optics; Spectroscopy GA XY946 UT WOS:A1997XY94600005 ER PT J AU Ozanne, L Ma, Q NguyenVanThanh Brodbeck, C Bouanich, JP Hartmann, JM Boulet, C Tipping, RH AF Ozanne, L Ma, Q NguyenVanThanh Brodbeck, C Bouanich, JP Hartmann, JM Boulet, C Tipping, RH TI Line-mixing, finite duration of collision, vibrational shift, and non-linear density effects in the nu(3) and 3 nu(3) bands of CO2 perturbed by Ar up to 1000 bar SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID INFRARED-ABSORPTION SPECTRA; DETAILED BALANCE; CROSS-SECTIONS; LINEWIDTHS; PROFILE; SHAPES AB We present high-density experimental and theoretical results on CO2-Ar gas-phase absorption in the nu(3) and 3 nu(3) infrared bands. Measurements have been made at room temperature for pressures up to 1000 bar in both the central and wing regions of the bands. A non-linear perturber density dependence of the absorption, clearly shown in the far wing, is attributed to the finite volume of the molecules. Furthermore, experiments show vibrational dephasing and narrowing effects. We have performed line-mixing computations based on the Energy Corrected Sudden approximation (ECS impact model). Significant discrepancies between experimental and calculated spectra appear when pressure increases. We then tested the influence of the finite duration of collision by using interpolations between ECS and quasi-static calculations, and we have evaluated the sensitivity of the band profiles to the interbranch mixing effects. Finally, an effective width is used in order to take other effects into account. (C) 1997 Elsevier Science Ltd. C1 UNIV PARIS 06,LAB PHYS MOL & APPLICAT,CNRS UPR 136,F-91405 ORSAY,FRANCE. UNIV PARIS 11,CNRS UPR 136,LAB PHYS MOL & APPLICAT,F-91405 ORSAY,FRANCE. COLUMBIA UNIV,DEPT APPL PHYS,NEW YORK,NY 10027. NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,NEW YORK,NY 10025. UNIV ALABAMA,DEPT PHYS & ASTRON,TUSCALOOSA,AL 35487. NR 33 TC 12 Z9 12 U1 1 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 AUG PY 1997 VL 58 IS 2 BP 261 EP 277 DI 10.1016/S0022-4073(97)00007-1 PG 17 WC Optics; Spectroscopy SC Optics; Spectroscopy GA XY946 UT WOS:A1997XY94600007 ER PT J AU Luo, LS AF Luo, LS TI Analytic solutions of linearized lattice Boltzmann equation for simple flows SO JOURNAL OF STATISTICAL PHYSICS LA English DT Article DE Lattice Boltzmann equation; lattice-gas automata; linearized lattice Boltzmann equation; analytic solutions for the plane Couette and the Poiseuille flows; slip at wall ID GAS AUTOMATA; GENERALIZED HYDRODYNAMICS; TRANSPORT; FLUIDS AB A general procedure to obtain analytic solutions of the linearized lattice Boltzmann equation for simple flows is developed. As examples, the solutions for the Poiseuille and the plane Couette flows in two-dimensional space are obtained and studied in detail. The solutions not only have a component which is the solution of the Navier-Stokes equation, they also include a kinetic component which cannot be obtained by the Navier-Stokes equation. The kinetic component of the solutions is due to the finite-mean-free-path effect. Comparison between the analytic results and the numerical results of lattice-gas simulations is made, and they are found to be in accurate agreement. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Luo, LS (reprint author), LOS ALAMOS NATL LAB,COMPLEX SYST GRP T13,DIV THEORET,MS-B213,LOS ALAMOS,NM 87545, USA. RI Luo, Li-Shi/A-4561-2011 OI Luo, Li-Shi/0000-0003-1215-7892 NR 21 TC 31 Z9 32 U1 1 U2 2 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 SN 0022-4715 J9 J STAT PHYS JI J. Stat. Phys. PD AUG PY 1997 VL 88 IS 3-4 BP 913 EP 926 DI 10.1023/B:JOSS.0000015178.19008.78 PG 14 WC Physics, Mathematical SC Physics GA XV186 UT WOS:A1997XV18600016 ER PT J AU He, XY Luo, LS AF He, XY Luo, LS TI Lattice Boltzmann model for the incompressible Navier-Stokes equation SO JOURNAL OF STATISTICAL PHYSICS LA English DT Article DE lattice Boltzmann method; incompressible Navier-Stokes equation; Poiseuille flow; Womersley flow AB In this paper a lattice Boltzmann (LB) model to simulate incompressible flow is developed. The main idea is to explicitly eliminate the terms of o(M-2), where M is the Mach number, due to the density fluctuation in the existing LB models. In the proposed incompressible LB model, the pressure p instead of the mass density p is the independent dynamic variable. The incompressible Navier-Stokes equations are derived from the incompressible LB model via Chapman-Enskog procedure. Numerical results of simulations of the plane Poiseuille now driven either by pressure gradient or a Fixed velocity profile at entrance as well as of the 2D Womersley flow are presented. The numerical results are found to be in excellent agreement with theory. C1 LOS ALAMOS NATL LAB,CTR NONLINEAR STUDIES,LOS ALAMOS,NM 87545. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP He, XY (reprint author), UNIV CALIF LOS ALAMOS NATL LAB,COMPLEX SYST GRP T13,DIV THEORET,MS B213,LOS ALAMOS,NM 87545, USA. RI Luo, Li-Shi/A-4561-2011 OI Luo, Li-Shi/0000-0003-1215-7892 NR 14 TC 514 Z9 538 U1 10 U2 65 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 SN 0022-4715 J9 J STAT PHYS JI J. Stat. Phys. PD AUG PY 1997 VL 88 IS 3-4 BP 927 EP 944 DI 10.1023/B:JOSS.0000015179.12689.e4 PG 18 WC Physics, Mathematical SC Physics GA XV186 UT WOS:A1997XV18600017 ER PT J AU Haddad, ZS Smith, EA Kummerow, CD Iguchi, T Farrar, MR Durden, SL Alves, M Olson, WS AF Haddad, ZS Smith, EA Kummerow, CD Iguchi, T Farrar, MR Durden, SL Alves, M Olson, WS TI The TRMM 'day-1' radar/radiometer combined rain-profiling algorithm SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID RADAR AB The Tropical Rainfall Measuring Mission (TRMM)'s 'day-1' combined radar/radiometer algorithm uses a rain-profiling approach which gives as much importance to the measurements of the TRMM satellite's precipitation radar (PR) and the TRMM microwave imager (TMI) as their respective intrinsic ambiguities warrant, which avoids any ad hoc shortcuts that might introduce large biases in the rain estimates, yet which is simple enough to be operational when TRMM is launched in 1997. The algorithm is based on the idea of estimating the rain profile using the radar reflectivities, while constraining this inversion to be consistent with the radiometer-derived estimate of the total attenuation. To perform the data fusion, the problem is expressed in terms of drop-size-distribution variables. Starting with an a priori probability density function (pdf) for these variables, a Bayesian approach is used to condition the pdf successively on the radar and the radiometer measurements. The resulting algorithm is mathematically consistent and physically reasonable. The conditional variances which it calculates serve to quantify the accuracy of its estimates: small variances indicate that the TRMM observations can indeed be explained by the models used; large variances imply that the models are not sufficiently consistent with the measurements. C1 FLORIDA STATE UNIV, TALLAHASSEE, FL 32306 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. COMMUN RES LABS, TOKYO, JAPAN. RP Haddad, ZS (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91125 USA. RI PMM, JAXA/K-8537-2016 NR 11 TC 139 Z9 141 U1 2 U2 7 PU METEOROLOGICAL SOC JAPAN PI TOKYO PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO, 100-0004, JAPAN SN 0026-1165 EI 2186-9057 J9 J METEOROL SOC JPN JI J. Meteorol. Soc. Jpn. PD AUG PY 1997 VL 75 IS 4 BP 799 EP 809 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XY694 UT WOS:A1997XY69400003 ER PT J AU Walker, JL Russell, SS Workman, GL Hill, EV AF Walker, JL Russell, SS Workman, GL Hill, EV TI Neural network/acoustic emission burst pressure prediction for impact damaged composite pressure vessels SO MATERIALS EVALUATION LA English DT Article DE acoustic emission; composite materials; neural network; nondestructive testing; pressure vessel; proof testing; quantitative analysis; signal analysis AB Acoustic emission signal analysis has been used to measure the effect impact damage has on the burst pressure of 146 mm (5.75 in.) diameter graphite/epoxy and the organic polymer, Kevlar/epoxy filament wound pressure vessels. Burst pressure prediction models were developed by correlating the differential acoustic emission amplitude distribution collected during low level hydroproof tests to known burst pressures using backpropagation artificial neural networks. Impact damage conditions ranging from barely visible to obvious fiber breakage, matrix cracking, and delamination were included in this work. A simulated (inert) propellant was also cast into a series of the vessels from each material class, before impact loading, to provide boundary conditions during impact that would simulate those found on solid rocket motors. The results of this research effort demonstrate that a quantitative assessment of the effects that impact damage has on burst pressure can be made for both organic polymer/epoxy and graphite/epoxy pressure vessels. Here, an artificial neural network analysis of the acoustic emission parametric data recorded during low pressure hydroproof testing is used to relate burst pressure to the vessel's acoustic signature. Burst pressure predictions within 6.0 percent of the actual failure pressure are demonstrated for a series of vessels. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. EMBRY RIDDLE AERONAUT UNIV,DAYTONA BEACH,FL 32114. RP Walker, JL (reprint author), UNIV ALABAMA,HUNTSVILLE,AL 35899, USA. NR 9 TC 6 Z9 7 U1 0 U2 3 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD AUG PY 1997 VL 55 IS 8 BP 903 EP 907 PG 5 WC Materials Science, Characterization & Testing SC Materials Science GA XQ056 UT WOS:A1997XQ05600012 ER PT J AU Hart, RC Balla, RJ Herring, GC AF Hart, RC Balla, RJ Herring, GC TI Observation of H2O in a flame by two-colour laser-induced-grating spectroscopy SO MEASUREMENT SCIENCE AND TECHNOLOGY LA English DT Article AB By using two-colour laser-induced-grating spectroscopy (TC-LIGS), we observed the third-overtone spectrum of the O-H stretch of water vapour at a point in a stoichiometric CH4-air flame. We also demonstrated the extension of these point measurements to a line image in a flame. Only thermal gratings could be observed. The reasons for this and the difficulties in making a practical combustion diagnostic are discussed. RP NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. NR 11 TC 8 Z9 8 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0957-0233 EI 1361-6501 J9 MEAS SCI TECHNOL JI Meas. Sci. Technol. PD AUG PY 1997 VL 8 IS 8 BP 917 EP 920 DI 10.1088/0957-0233/8/8/013 PG 4 WC Engineering, Multidisciplinary; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA XQ216 UT WOS:A1997XQ21600013 ER PT J AU Kaukler, WF Rosenberger, F Curreri, PA AF Kaukler, WF Rosenberger, F Curreri, PA TI In situ studies of precipitate formation in Al-Pb monotectic solidification by X-ray transmission microscopy SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID SYSTEMS; ALLOYS; GROWTH AB Al-1.5 wt pct Pb monotectic alloys were unidirectionally solidified. X-ray transmission microscope (XTM) observations, both during and after solidification, revealed various new morphological/compositional features in the melt and solid. In the melt, nonuniform lead-rich interfacial segregation layers and droplets were observed to form well ahead of the interface. In the solid, periodic striae formed at translation/solidification velocities as low as 6 X 10(-6) m/s. The striae shape does not replicate that of the interface. The striae spacing decreases from 4 to 2 X 10(-4) m with an increasing solidification rate between 6 and 16 X 10(-6) m/s. High resolution post-solidification XTM examination reveals that these striae consist of Pb-rich particles of 2 to 3 X 10(-6) m diameter. At translation/solidification velocities below 6 X 10(-6) m/s, Pb incorporation into the solid occurs in the form of continuous fibers and strings of particles of about 5 X 10(-6) m diameter. Bands, parallel to the interface, in which these fibers were aligned in the solidification direction, alternated with bands of poor fiber alignment. The width of these bands is comparable to the striae spacings obtained at the high solidification rates. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,MET & ALLOYS GRP,HUNTSVILLE,AL 35812. RP Kaukler, WF (reprint author), UNIV ALABAMA,CTR MICROGRAV & MAT RES,HUNTSVILLE,AL 35899, USA. OI Kaukler, William/0000-0002-7758-269X NR 27 TC 18 Z9 21 U1 1 U2 8 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD AUG PY 1997 VL 28 IS 8 BP 1705 EP 1710 DI 10.1007/s11661-997-0262-8 PG 6 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA XR033 UT WOS:A1997XR03300012 ER PT J AU Evans, JW Evans, JY AF Evans, JW Evans, JY TI Reliability assessment for development of microtechnologies SO MICROSYSTEM TECHNOLOGIES LA English DT Article AB In recent years, developments in the micro electronics industry have focused on semiconductors and semiconductor processes. However, microcircuit assembly technologies have lagged chip development. This has spurred research in interconnection and packaging creating many new technologies and enhancing integration. These new microelectronic technologies are enabling micro systems, and resulting in products, from portable work stations to advanced automotive electronics. This evolution of technology has also created the need to reexamine how we achieve a reliable system. Clearly, in highly competitive marketplaces, reliability is a key element in achieving successful products. To achieve a reliable product in a cost effective manner, ''upstream problem solving'' must be employed which focuses on root cause of failure. This paper provides an overview of the reliability assessment process needed to achieve effective microsystem development. A case study of reliability in a complex multi-chip module is presented which includes an assessment of the stochastic nature of via fatigue by applying Monte Carlo simulations. C1 NASA,GODDARD SPACE FLIGHT CTR,OFF FLIGHT ASSURANCE,GREENBELT,MD 20771. RP Evans, JW (reprint author), AJOU UNIV,INST ADV ENGN,SEOUL,SOUTH KOREA. NR 13 TC 4 Z9 4 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0946-7076 J9 MICROSYST TECHNOL JI Microsyst. Technol. PD AUG PY 1997 VL 3 IS 4 BP 145 EP 154 DI 10.1007/s005420050072 PG 10 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Science & Technology - Other Topics; Materials Science; Physics GA YD298 UT WOS:A1997YD29800001 ER PT J AU Ogbuji, LUJT AF Ogbuji, LUJT TI Scientific communication and the role of editors SO MRS BULLETIN LA English DT Letter RP Ogbuji, LUJT (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 SN 0883-7694 J9 MRS BULL JI MRS Bull. PD AUG PY 1997 VL 22 IS 8 BP 6 EP 7 PG 2 WC Materials Science, Multidisciplinary; Physics, Applied SC Materials Science; Physics GA XR891 UT WOS:A1997XR89100003 ER PT J AU McGill, MJ Marzouk, M Scott, VS Spinhirne, JD AF McGill, MJ Marzouk, M Scott, VS Spinhirne, JD TI Holographic circle-to-point converter with particular applications for lidar work SO OPTICAL ENGINEERING LA English DT Article DE holography; holographic lenses; Fabry-Perot interferometer; lidar; Doppler lidar ID IMAGE PLANE DETECTOR; INTERFEROMETER AB A holographic optical element is developed that functions as a circle-to-point converter. The holographic plate looks like a zone plate but functions like a collection of field lenses, Each annulus of the holographic plate acts as a separate lens, Imaging incident light to a point focus. The plate was developed for use with Fabry-Perot interferometers, but other applications are also possible. The plate has high throughput, and when coupled with high quantum efficiency solid state detectors provides an efficient photon-collecting detection system. Development of the plate was driven by need for an efficient Doppler lidar detection system, and specific lidar applications are discussed. (C) 1997 Society of Photo-Optical Instrumentation Engineers. C1 UNIV MICHIGAN,SPACE PHYS RES LAB,ANN ARBOR,MI 48109. ORBITAL SCI CORP,GREENBELT,MD 20770. RP McGill, MJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 912,GREENBELT,MD 20771, USA. RI McGill, Matthew/D-8176-2012; Scott, Vibart/B-5086-2013 NR 16 TC 15 Z9 15 U1 0 U2 1 PU SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS PI BELLINGHAM PA PO BOX 10, BELLINGHAM, WA 98227-0010 SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD AUG PY 1997 VL 36 IS 8 BP 2171 EP 2175 DI 10.1117/1.601437 PG 5 WC Optics SC Optics GA XQ115 UT WOS:A1997XQ11500009 ER PT J AU Seasholtz, RG Buggele, AE Reeder, MF AF Seasholtz, RG Buggele, AE Reeder, MF TI Flow measurements based on Rayleigh scattering and Fabry-Perot interferometer SO OPTICS AND LASERS IN ENGINEERING LA English DT Article ID LIGHT-SCATTERING; BRILLOUIN SCATTERING; TEMPERATURE; DENSITY; GASES; PROFILES AB Flow diagnostics based on molecular Rayleigh scattering are discussed along with the results of a feasibility study to non-intrusively measure flow properties in a small supersonic wind tunnel. The technique uses an injection seeded, frequency doubled Nd:YAG laser tuned to an absorption band of iodine. The molecular Rayleigh scattered light is filtered with an iodine cell to block light at the laser frequency. The Doppler-shifted Rayleigh scattered light that passes through the iodine cell is analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode. An intensified CCD camera is used to record the images. The images are analyzed at several subregions, where the flow properties are determined. Each image is obtained with a single laser pulse, giving instantaneous measurements. Published by Elsevier Science Ltd. RP Seasholtz, RG (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 36 TC 16 Z9 17 U1 0 U2 2 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0143-8166 J9 OPT LASER ENG JI Opt. Lasers Eng. PD AUG PY 1997 VL 27 IS 6 BP 543 EP 570 DI 10.1016/S0143-8166(96)00063-2 PG 28 WC Optics SC Optics GA XK035 UT WOS:A1997XK03500003 ER PT J AU Hardin, RW AF Hardin, RW TI Can business learn from baboons? You bet SO PHOTONICS SPECTRA LA English DT Editorial Material RP Hardin, RW (reprint author), NASA,GREENBELT,MD 20771, USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU LAURIN PUBL CO INC PI PITTSFIELD PA BERKSHIRE COMMON PO BOX 1146, PITTSFIELD, MA 01202 SN 0731-1230 J9 PHOTON SPECTRA JI Photon. Spect. PD AUG PY 1997 VL 31 IS 8 BP 71 EP 72 PG 2 WC Optics SC Optics GA XP706 UT WOS:A1997XP70600034 ER PT J AU Li, N Noever, D Robertson, T Koczor, R Brantley, W AF Li, N Noever, D Robertson, T Koczor, R Brantley, W TI Static test for a gravitational force coupled to type II YBCO superconductors SO PHYSICA C LA English DT Article DE bulk YBCO; gravitational anomalies; bose condensate ID GRAVITY AB As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (similar to 10(-6) g cm(3)). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating type II, YBCO superconductor, with the percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10(4) was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field. Changes in acceleration were measured to be less than 2 parts in 10(8) of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between static superconductors and gravity. (C) 1997 Elsevier Science B.V. C1 UNIV ALABAMA,HUNTSVILLE,AL 35804. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NR 20 TC 14 Z9 14 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-4534 J9 PHYSICA C JI Physica C PD AUG 1 PY 1997 VL 281 IS 2-3 BP 260 EP 267 DI 10.1016/S0921-4534(97)01462-7 PG 8 WC Physics, Applied SC Physics GA YD495 UT WOS:A1997YD49500019 ER PT J AU Tuve, C Albergo, S Boemi, D Caccia, Z Chen, CX Costa, S Crawford, HJ Cronqvist, M Engelage, J Greiner, L Guzik, TG Insolia, A Knott, CN Lindstrom, PJ Mitchell, JW Potenza, R Reito, S Romanski, J Russo, GV Soutoul, A Testard, O Tull, CE Waddington, CJ Webber, WR Wefel, JP AF Tuve, C Albergo, S Boemi, D Caccia, Z Chen, CX Costa, S Crawford, HJ Cronqvist, M Engelage, J Greiner, L Guzik, TG Insolia, A Knott, CN Lindstrom, PJ Mitchell, JW Potenza, R Reito, S Romanski, J Russo, GV Soutoul, A Testard, O Tull, CE Waddington, CJ Webber, WR Wefel, JP TI Neutron production at 0 degrees from the Ca-40+H reaction at E-lab=357A and 565A MeV SO PHYSICAL REVIEW C LA English DT Article ID HEAVY-ION COLLISIONS; CROSS-SECTIONS; ENERGY; DISTRIBUTIONS; INTERMEDIATE; NUCLEON AB Neutrons produced in the Ca-40+H reaction at E-lab=357A and 565A MeV have been detected using a three-module version of the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range around the beam in the forward direction (0 degrees-3.2 degrees). Semi-inclusive neutron production cross sections, at the two energies, are reported together with neutron energy spectra, angular, rapidity, and transverse momentum distributions. Comparison with a Boltzmann-Nordheim-Vlasov approach + phase space coalescence model is discussed. C1 INFN I, I-95129 CATANIA, ITALY. UNIV CALIF BERKELEY, LAWRENCE BERKELEY LAB, BERKELEY, CA 94720 USA. LOUISIANA STATE UNIV, BATON ROUGE, LA 70803 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. UNIV MINNESOTA, MINNEAPOLIS, MN 55455 USA. UNIV NEW MEXICO, LAS CRUCES, NM 88003 USA. CEN, SERV ASTROPHYS, SACLAY, FRANCE. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Tuve, C (reprint author), UNIV CATANIA, I-95129 CATANIA, ITALY. RI Insolia, Antonio/M-3447-2015; TUVE', Cristina/P-3933-2015 OI Insolia, Antonio/0000-0002-9040-1566; TUVE', Cristina/0000-0003-0739-3153 NR 27 TC 10 Z9 10 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD AUG PY 1997 VL 56 IS 2 BP 1057 EP 1063 DI 10.1103/PhysRevC.56.1057 PG 7 WC Physics, Nuclear SC Physics GA XR162 UT WOS:A1997XR16200054 ER PT J AU Nollett, KM Lemoine, M Schramm, DN AF Nollett, KM Lemoine, M Schramm, DN TI Nuclear reaction rates and primordial Li-6 SO PHYSICAL REVIEW C LA English DT Article ID THERMONUCLEAR REACTION-RATES; LOW METAL ABUNDANCE; CROSS-SECTIONS; LI-6(P,HE-3)HE-4 REACTION; BIG-BANG; ASTROPHYSICAL INTEREST; COULOMB DISSOCIATION; CAPTURE REACTION; HALO-STARS; NUCLEOSYNTHESIS AB We examine the possibility that big-bang nucleosynthesis (BBN) may produce nontrivial amounts of Li-6. If a primordial component of this isotope could be observed, it would provide a new fundamental test of big-bang cosmology, as well as new constraints on the baryon density of the universe. At present, however, theoretical predictions of the primordial Li-6 abundance are extremely uncertain due to difficulties in both theoretical estimates and experimental determinations of the H-2(alpha, gamma)Li-6 radiative capture reaction cross section. We also argue that present observational capabilities do not yet allow the detection of primeval Li-6 in very metal-poor stars of the galactic halo. However, if the critical cross section is very high in its plausible range and the baryon density is relatively low, then improvements in Li-6 detection capabilities may anew the establishment of Li-6 as another product of BBN. It is also doted that a primordial Li-6 detection could help resolve current concerns about the extragalactic D/H determination. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RP Nollett, KM (reprint author), UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637, USA. OI Nollett, Kenneth/0000-0002-0671-320X; Lemoine, Martin/0000-0002-2395-7812 NR 48 TC 53 Z9 53 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD AUG PY 1997 VL 56 IS 2 BP 1144 EP 1151 DI 10.1103/PhysRevC.56.1144 PG 8 WC Physics, Nuclear SC Physics GA XR162 UT WOS:A1997XR16200063 ER PT J AU Yeung, PK Zhou, Y AF Yeung, PK Zhou, Y TI Universality of the Kolmogorov constant in numerical simulations of turbulence SO PHYSICAL REVIEW E LA English DT Article ID PASSIVE SCALAR DIFFUSION; HIGH REYNOLDS-NUMBER; ISOTROPIC TURBULENCE; HOMOGENEOUS TURBULENCE; DEVELOPED TURBULENCE; LOCAL ISOTROPY; DISSIPATION; INTERMITTENCY; VELOCITY; DYNAMICS AB Motivated by a recent survey of experimental data [K. R, Sreenivasan, Phys. Fluids 7, 2778 (1995)], we examine data on the Kolmogorov spectrum constant in numerical simulations of isotropic turbulence, using results both from previous studies and from new direct numerical simulations over a range of Reynolds numbers (up to 240 on the Taylor scale) at grid resolutions up to 512 degrees. It is noted that in addition to k(-5/3) scaling, identification of a true inertial range requires spectral isotropy in the same wave-number range. The new simulations indicate approximate inertial range behavior at lower wave numbers than previously thought, with proportionality constants C-1, and C in the one-and three-dimensional energy spectra, retrospectively, about 0,60 and 1.62. The latter suggests C-1 approximate to 0.53, in excellent agreement with experiments. However, the one-and three-dimensional estimates are not fully consistent, because of departures (due to numerical and statistical limitations) from isotropy of the computed spectra at low wave numbers, The inertial scaling of structure functions in physical space is briefly addressed. C1 NASA,LANGLEY RES CTR,INST COMP APPL SCI & ENGN,HAMPTON,VA 23681. IBM CORP,DIV RES,TJ WATSON RES CTR,YORKTOWN HTS,NY 10598. RP Yeung, PK (reprint author), GEORGIA INST TECHNOL,SCH AEROSP ENGN,ATLANTA,GA 30332, USA. NR 35 TC 127 Z9 127 U1 0 U2 9 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 AUG PY 1997 VL 56 IS 2 BP 1746 EP 1752 DI 10.1103/PhysRevE.56.1746 PG 7 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA XR160 UT WOS:A1997XR16000063 ER PT J AU Anicich, VG McEwan, MJ AF Anicich, VG McEwan, MJ TI Ion-molecule chemistry in Titan's ionosphere SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ASSOCIATION REACTIONS; CH3+/CH3CN SYSTEM; LOW-PRESSURE; ATMOSPHERE; PHOTOCHEMISTRY; MODEL AB A summary is presented of the information available from laboratory studies of ion-molecule reactions that is relevant to the chemistry occurring in Titan's ionosphere. Reaction information from the literature has been collated and many new reactions have been measured, including some ion-atom reactions. The sequences of ion-neutral reactions can lead to a rapid increase in ion size. How this increase may lead to aerosol production at the base of the ionosphere is briefly discussed. Laboratory observations of extremely rapid termolecular ion-neutral association reactions indicate that these association reactions are viable contributors to the ion chemistry at the base of Titan's ionosphere. (C) 1997 Elsevier Science Ltd. C1 UNIV CANTERBURY,DEPT CHEM,CHRISTCHURCH 1,NEW ZEALAND. RP Anicich, VG (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 18 TC 83 Z9 83 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1997 VL 45 IS 8 BP 897 EP 921 DI 10.1016/S0032-0633(97)00053-6 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA305 UT WOS:A1997YA30500003 ER PT J AU Kostiuk, T Fast, K Livengood, TA Goldstein, J Hewagama, T Buhl, D Espenak, F Ro, KH AF Kostiuk, T Fast, K Livengood, TA Goldstein, J Hewagama, T Buhl, D Espenak, F Ro, KH TI Ethane abundance on Titan SO PLANETARY AND SPACE SCIENCE LA English DT Article ID VOYAGER INFRARED OBSERVATIONS; JOVIAN AURORAL STRATOSPHERE; ATMOSPHERE; TEMPERATURE; REGION; JUPITER; HYDROCARBONS; SURFACE; PROBE; BAND AB Ethane (C2H6) abundance in Titan's stratosphere is determined from recent ground based high spectral resolution measurements of individual ethane emission line spectra. Lines near 12 mu m in the v(9) band of C2H6, were measured at a resolving power of lambda/Delta lambda similar to 10(6) with infrared heterodyne spectroscopy at the NASA Infrared Telescope Facility (IRTF). Globally averaged constant-with-height C2H6 mole fractions are retrieved for various possible thermal profiles on Titan. A range of possible stratospheric temperatures is investigated with respect to the data and a corresponding range of acceptable globally averaged ethane mole fractions is retrieved, The data and physical constraints imposed by the observations limit the temperatures in Titan's upper stratosphere to 160-180K. Corresponding acceptable mole fractions can range from 4 x 10(-6) to 1.6 x 10(-5) depending on the thermal profile used. For a currently ''recommended'' thermal profile a mole fraction of 9.4(-4.7, +9.4) x 10(-6) is retrieved, somewhat lower than previous results, but centrally placed in the acceptable temperature-abundance parameter space. Published by Elsevier Science Ltd. C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. SMITHSONIAN INST,NATL AIR & SPACE MUSEUM,ASTROPHYS LAB,WASHINGTON,DC 20560. RP Kostiuk, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,PLANETARY SYST BRANCH,CODE 693,GREENBELT,MD 20771, USA. RI Hewagama, T/C-8488-2012; Livengood, Timothy/C-8512-2012; Kostiuk, Theodor/A-3077-2014 NR 32 TC 19 Z9 19 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1997 VL 45 IS 8 BP 931 EP 939 DI 10.1016/S0032-0633(97)00086-X PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA305 UT WOS:A1997YA30500005 ER PT J AU Samuelson, RE Mayo, LA Knuckles, MA Khanna, RJ AF Samuelson, RE Mayo, LA Knuckles, MA Khanna, RJ TI C4N2 ice in Titan's north polar stratosphere SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ATMOSPHERE; TEMPERATURE; PHOTOCHEMISTRY AB The 478 cm(-1) v(8), band of condensed dicyanoacetylene (C4N2) associated with Titan's north polar hood has been modeled using a radiative transfer program developed for tangent viewing in spherical atmospheres. Absence of the associated 471 cm(-1) band of gaseous C4N2 leads to an upper limit of 4 x 10(-10) for the vapour mole fraction, and a corresponding upper limit of 90 km for the cloud top. The condensate/vapor abundance ratio ranges between 50 and 200 at the loud top, depending on the cloud scale height. Corresponding cloud optical thicknesses are similar to 0.1 and 0.006, respectively, while the majority of particles appear to have radii between 5 and 10 mu m. Because of ed response to the changing seasons, Titan's polar stratosphere appears to be cooling down as it becomes more illuminated by sunlight during the progression of winter into spring. As a result, photolytic decomposition of C4N2 vapor occurs above the advancing sunlight/shadow boundary at the same time that condensation increases below the boundary. This time-dependant cyclic process appears to give rise to a C4N2 condensate/vapor ratio approximately two orders of magnitude greater than that expected under steady-state conditions. Published by Elsevier Science Ltd. C1 HUGHES STX,GREENBELT,MD 20770. FED BUR INVEST,WASHINGTON,DC 20535. UNIV MARYLAND,DEPT CHEM & BIOCHEM,COLLEGE PK,MD 20742. RP Samuelson, RE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 15 TC 71 Z9 71 U1 1 U2 11 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1997 VL 45 IS 8 BP 941 EP 948 DI 10.1016/S0032-0633(97)00088-3 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA305 UT WOS:A1997YA30500006 ER PT J AU Samuelson, RE Mayo, LA AF Samuelson, RE Mayo, LA TI Steady-state model for methane condensation in Titan's troposphere SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ATMOSPHERE; EQUILIBRIUM; PHOTOCHEMISTRY AB In an attempt to better understand the physical-basis for the large degrees of methane super-saturation inferred to be in Titan's troposphere from recent analyses of Voyager 1 IRIS data, a steady-state model has been developed in which the loss of methane at every level due to condensation and precipitation is exactly balanced by the replacement of methane vapor through eddy diffusion. Ethane ice crystals precipitating from the lower stratosphere serve as nucleation sites for methane condensation in the troposphere. Free parameters include a normalized methane abundance, eddy diffusion coefficient, ana particle nux (equivalently an initial ethane particle radius); the downward ethane molecular flux is fixed from photochemical theory. Solutions are obtained for the altitude-dependences of methane particle size: degree of methane supersaturation, and methane mole fraction. It is found that the large degrees of methane super-saturation inferred from IRIS data require rather low initial ethane particle fluxes, corresponding to ethane particle radii similar to 100 mu m or so. A logical corollary to the theory suggests Titan's troposphere is stable against moist convection. From other analyses it is inferred that condensation and precipitation may occur cyclically with the season, and preferentially at the spring poles. It follows that there should be latitudinal gradients for both the degree of methane supersaturation in the upper troposphere, and methane mole fraction near the surface, with both quantities decreasing from equator to pole. This is consistent with the latitude-dependance for these quantities inferred from Voyager IRIS data. Published by Elsevier Science Ltd. C1 HUGHES STX,GREENBELT,MD 20770. RP Samuelson, RE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 39 TC 34 Z9 34 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1997 VL 45 IS 8 BP 949 EP 958 DI 10.1016/S0032-0633(97)00089-5 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA305 UT WOS:A1997YA30500007 ER PT J AU Samuelson, RE Nath, NR Borysow, A AF Samuelson, RE Nath, NR Borysow, A TI Gaseous abundances and methane supersaturation in Titan's troposphere SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ROTOTRANSLATIONAL ABSORPTION-SPECTRA; FAR-INFRARED-ABSORPTION; COLLISION-INDUCED ABSORPTION; VOYAGER-1 RADIO-OCCULTATION; OPTICAL-CONSTANTS; OUTER PLANETS; H2-CH4 PAIRS; H2-N2 PAIRS; ATMOSPHERE; TEMPERATURES AB Various properties of Titan's troposphere are inferred from an analysis of Voyager 1 infrared spectrometer (IRIS) data between 200 and 600 cm(-1). Two homogeneous spectral averages acquired at widely separated emission angles are chosen for the analysis. Both data sets are associated with northern low latitudes very close to that of the radio science ingress occultation point. Solutions require simultaneous nonlinear least-squares fits to the two IRIS data sets, coupled with iteration of the radio occultation refractivity dart. Values and associated 1-sigma uncertainties of several parameters are inferred from our analysis. These include mole fractions for molecular hydrogen (similar to 0.0011), argon (small), and methane near the surface (similar to 0.057). Solutions are also obtained for the hydrogen para-fraction (close to equilibrium, with considerable uncertainty), air temperature near the surface (similar to 93 K), surface temperature discontinuity (similar to 1 K), and maximum degree of methane supersaturation in the upper troposphere (similar to 1.5). Actual values for the above-mentioned parameters depend on the amount of ethane cloud near the tropopause. There is no evidence for methane clouds in the upper troposphere, nor is their presence compatible with large degrees of supersaturation. A wave number dependence for the stratospheric haze opacity is inferred similar to that found for a polymeric residue created in laboratory discharge experiments. This haze appears to be uniformly distributed with latitude between altitudes of 40 and 160 km, provided those nighttime data at southern high latitudes that are subject to possible systematic calibration errors are discounted. Assuming uniform haze distribution, both the air temperature and methane vapor mole fraction near the surface are symmetrically distributed about the equator, with-lower values at higher latitudes. Either the tropopause temperature or the maximum degree of methane supersaturation is asymmetrically distributed about the equator. In either case, the data are consistent with a decrease of methane supersaturation toward the poles, which suggests an increase in mean annual precipitation at high latitudes compared with the equatorial region. If methane vapor is in saturation equilibrium with Titan's surface, the deprived latitudinal gradient of the near surface methane vapor mole fraction implies that the liquid content of the surface is ethane-enriched near the poles. Published by Elsevier Science Ltd. C1 HUGHES STX CORP,GREENBELT,MD 20770. MICHIGAN TECHNOL UNIV,DEPT PHYS,HOUGHTON,MI 49931. COPENHAGEN UNIV OBSERV,NIELS BOHR INST,DK-2100 COPENHAGEN,DENMARK. RP Samuelson, RE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 57 TC 131 Z9 131 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1997 VL 45 IS 8 BP 959 EP 980 DI 10.1016/S0032-0633(97)00090-1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA305 UT WOS:A1997YA30500008 ER PT J AU Ellis, SR Menges, BM AF Ellis, SR Menges, BM TI Judgments of the distance to nearby virtual objects: Interaction of viewing conditions and accommodative demand SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article ID DEPTH AB Ten subjects adjusted a real-object probe to match the distance of nearby virtual objects optically presented via a see-through, helmet-mounted display, Monocular, biocular, and stereoscopic viewing conditions were used with two levels of required locus. Observed errors may be related to changes in the subjects' binocular convergence. The results suggest ways in which virtual objects may be presented with improved spatial fidelity. RP Ellis, SR (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 12 TC 25 Z9 25 U1 1 U2 2 PU M I T PRESS PI CAMBRIDGE PA FIVE CAMBRIDGE CENTER, CAMBRIDGE, MA 02142 SN 1054-7460 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD AUG PY 1997 VL 6 IS 4 BP 452 EP 460 PG 9 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA XQ356 UT WOS:A1997XQ35600007 PM 11540610 ER PT J AU Huemmrich, KF Goward, SN AF Huemmrich, KF Goward, SN TI Vegetation canopy PAR absorptance and NDVI: An assessment for ten tree species with the SAIL model SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID PHOTOSYNTHETICALLY ACTIVE RADIATION; SPECTRAL REFLECTANCE; LEAF-AREA; INDEXES; FOREST; LIMITS; OREGON; FIFE AB The relation between the normalized difference vegetation index (NDVI) and the fraction of absorbed photo-synthetically active radiation (f(APAR)) was examined for ten different forest types by using the scattering-from-arbitrarily-inclined-leaves (SAIL) radiative transfer model. Leaf reflectance and transmittance, twig reflectance, and background reflectance data were collected as part of field experiments whose sites contain species whose ranges cover a significant part of western and northern North America. This provides a sense of variations that occur at continental scales. Actual backgrounds of forests include litter and mosses; these materials did not fall along a soil line in red-near infrared reflectance space. The simulations indicated that, at low values of the leaf area index (LAI), the background reflectance had a significant effect on the canopy reflectance, although little effect on photosynthetically active radiation (PAR) absorption. At higher values of LAI, leaf optical properties were the factors that dominated canopy reflectance and NDVI. Variations in canopy reflectance due to leaf optical properties were large, but most species had similar reflectance patterns. Green leaf optical properties, among the species studied, had little effect on f(APAR). The presence of twigs in the canopy had a noticeable effect on canopy reflectance and absorption of PAR, but these effects were secondary to the effects of background and leaf optical properties. (C) Elsevier Science Inc. C1 UNIV MARYLAND,LAB GLOBAL REMOTE SENSING STUDIES,DEPT GEOG,COLLEGE PK,MD. RP Huemmrich, KF (reprint author), NASA,HUGHES STX,GODDARD SPACE FLIGHT CTR,CODE 923,GREENBELT,MD 20771, USA. NR 28 TC 58 Z9 69 U1 0 U2 17 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 AUG PY 1997 VL 61 IS 2 BP 254 EP 269 DI 10.1016/S0034-4257(97)00042-4 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XG793 UT WOS:A1997XG79300007 ER PT J AU Goldsby, JC Yun, HM DiCarlo, JA AF Goldsby, JC Yun, HM DiCarlo, JA TI Creep and rupture of an advanced CVD SIC fiber SO SCRIPTA MATERIALIA LA English DT Article AB In the as-produced condition the room temperature strength (similar to 6 Gpa) of Textron Specialty Materials' 50 mu m CVD SiC fiber represents the highest value thus far obtained for commercially produced polycrystalline SiC fibers. To understand whether this strength can be maintained after composite processing conditions, high temperature studies were performed on the effects of time, stress, and environment on 1400 degrees C tensile creep strain and stress rupture on as-produced, chemically vapor deposited SiC fibers. Creep strain results were consistent, allowing an evaluation of time and stress effects. Test environment had no influence on creep strain but 1 hour annealing at 1600 degrees C in argon gas significantly reduced the total creep strain and increased the stress dependence. This is attributed to changes in the free carbon morphology and its distribution within the CVD SiC fiber. For the as-produced and annealed fibers, strength at 1400 degrees C was found to decrease from a fast fracture value of 2 GPa to a 100-hour rupture strength value of 0.8 GPa. In addition a loss of fast fracture strength from 6 GPa is attributed to thermally induced changes in the outer carbon coating and microstructure. Scatter in rupture times made a definitive analysis of environmental and annealing effects on creep strength difficult. Published by Elsevier Science Ltd. C1 CLEVELAND STATE UNIV,CLEVELAND,OH 44115. RP Goldsby, JC (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 5 TC 5 Z9 6 U1 2 U2 7 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD AUG 1 PY 1997 VL 37 IS 3 BP 299 EP 303 DI 10.1016/S1359-6462(97)00115-2 PG 5 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA XL697 UT WOS:A1997XL69700009 ER PT J AU Feng, D Pulliam, TH AF Feng, D Pulliam, TH TI Tensor-GMRES method for large systems of nonlinear equations SO SIAM JOURNAL ON OPTIMIZATION LA English DT Article DE nonlinear systems; Krylov subspaces; inexact Newton methods; tensor methods; generalized minimal residual methods; singularity ID HYPERBOLIC CONSERVATION-LAWS; HIGH-RESOLUTION SCHEMES; INEXACT NEWTON METHODS; SINGULAR POINTS; OPTIMIZATION AB This paper introduces a tensor-Krylov method, the tensor-GMRES method, for large systems of nonlinear equations. Krylov subspace projection techniques for asymmetric systems of linear equations are coupled with a tensor model formation and solution technique for nonlinear equations. Similar to traditional tensor methods, the new tensor method is shown to have significant computational advantages over the analogous Newton counterpart on a set of nonsingular end singular problems. For example, an application to the Euler equations for the how through a nozzle with a given area ratio shows that the tensor-GMRES method can be much more efficient than the analogous Newton-GMRES method. The new tensor method is also consistent with preconditioning and matrix-free implementation. C1 Cadence Design Syst Inc, San Jose, CA 95134 USA. NASA, Ames Res Ctr, Fluid Dynam Div, Moffett Field, CA 94035 USA. RP Feng, D (reprint author), Cadence Design Syst Inc, 555 River Oaks Pkwy,Bldg 3,MS 3B1, San Jose, CA 95134 USA. NR 33 TC 10 Z9 10 U1 0 U2 0 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 USA SN 1052-6234 J9 SIAM J OPTIMIZ JI SIAM J. Optim. PD AUG PY 1997 VL 7 IS 3 BP 757 EP 779 DI 10.1137/S105262349527646X PG 23 WC Mathematics, Applied SC Mathematics GA YM026 UT WOS:000071020000010 ER PT J AU Poletto, G Romoli, M Suess, ST Wang, AH Wu, ST AF Poletto, G Romoli, M Suess, ST Wang, AH Wu, ST TI Inferences on coronal magnetic fields from SOHO UVCS observations SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT Workshop on Measurements and Analyses of the 3-D Solar Magnetic Fields CY APR 09-11, 1996 CL HUNTSVILLE, AL SP SCOSTEP, STEP, WG-1, Univ Alabama, Ctr Space Plasma Aeronom Res ID SOLAR ACTIVE REGIONS; HELMET STREAMERS; VLA STEREOSCOPY; MASS EJECTIONS; RECONNECTION; MODEL; HOLE AB The characteristics of the magnetic field ubiquitously permeating the coronal plasma are still largely unknown. In this paper we analyze some aspects of coronal physics, related to the magnetic field behavior, which forthcoming SOHO UVCS observations can help better understand. To this end, three coronal structures will be examined: streamers, coronal mass ejections (CMEs), and coronal holes. As to streamers and CMEs, we show, via simulations of the Ly-alpha and white-light emission from these objects, calculated on the basis of recent theoretical models (Wang ct al., 1995), how new data from SOHO can help in advancing our knowledge of the streamer/CME magnetic configuration. Our discussion highlights also those observational signatures which might offer clues on reconnection processes in streamers' current sheets. Coronal holes (CHs) are discussed in the last section of the paper. Little is known about CH flux tube geometry, which is closely related to the behavior of the solar wind at small heliocentric distances. Indirect evidence for the flux tube spreading factors, within a few solar radii, is here examined. C1 UNIV FLORENCE,DIPARTIMENTO ASTRON & SCI SPAZIO,I-50125 FLORENCE,ITALY. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NASA,CTR SPACE PLASMA & AERON RES,HUNTSVILLE,AL 35812. RP Poletto, G (reprint author), OSSERV ASTROFIS ARCETRI,LARGO E FERMI 5,I-50125 FLORENCE,ITALY. RI Romoli, Marco/H-6859-2012 NR 30 TC 0 Z9 0 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD AUG PY 1997 VL 174 IS 1-2 BP 53 EP 63 DI 10.1023/A:1004939308866 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB565 UT WOS:A1997YB56500005 ER PT J AU Gary, GA AF Gary, GA TI Rendering three-dimensional solar coronal structures SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT Workshop on Measurements and Analyses of the 3-D Solar Magnetic Fields CY APR 09-11, 1996 CL HUNTSVILLE, AL SP SCOSTEP, STEP, WG-1, Univ Alabama, Ctr Space Plasma Aeronom Res ID X-RAY TELESCOPE; MAGNETIC-FIELDS; VECTOR MAGNETOGRAPH; THICKNESS VARIATIONS; ACTIVE REGIONS; FLARE; YOHKOH; LOOPS; DIAGNOSTICS; EVOLUTION AB An X-ray or EW image of the corona or chromosphere is a 2D representation of an extended 3D complex for which a general inversion process is impossible. A specific model must be incorporated in order to understand the full 3D structure. We approach this problem by modeling a set of optically-thin 3D plasma flux tubes which we render these as synthetic images. The resulting images allow the interpretation of the X-ray/EUV observations to obtain information on (1) the 3D structure of X-ray images, i.e., the geometric structure of the flux tubes, and on (2) the internal structure using specific plasma characteristics, i.e., the physical structure of the flux tubes. The data-analysis technique uses magnetograms to characterize photospheric magnetic fields and extrapolation techniques to form the held lines. Using a new set of software tools, we have generated 3D flux tube structures around these field lines and integrated the plasma emission along the line of sight to obtain a rendered image. A set of individual flux-tube images is selected by a non-negative least-squares technique to provide a match with an observed X-ray image. The scheme minimizes the squares of the differences between the synthesized image and the observed image with a non-negative constraint on the coefficients of the brightness of the individual flux-tube loops. The derived images are used to determine the specific photospheric foot points and physical data, i.e., scaling laws for densities and loop lengths. The development has led to computer efficient integration and display software that is compatible for comparison with observations (e.g., Yohkoh SXT data, NIXT, or EIT). This analysis is important in determining directly the magnetic field configuration, which provides the structure of coronal loops, and indirectly the electric currents or waves, which provide the energy for the heating of the plasma. We have used very simple assumptions (i.e., potential magnetic fields and isothermal corona) to provide an initial test of the techniques before complex models are introduced. We have separated the physical and geometric contributions of the emission for a set of flux tubes and concentrated, in this initial study, on the geometric contributions by making approximations to the physical contributions. The initial results are consistent with the scaling laws derived from the Yohkoh SXT data. RP NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB ES82, HUNTSVILLE, AL 35812 USA. NR 73 TC 16 Z9 16 U1 0 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD AUG PY 1997 VL 174 IS 1-2 BP 241 EP 263 DI 10.1023/A:1004978630098 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB565 UT WOS:A1997YB56500018 ER PT J AU Stark, B Adams, M Hathaway, DH Hagyard, MJ AF Stark, B Adams, M Hathaway, DH Hagyard, MJ TI Evaluation of two fractal methods for magnetogram image analysis SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT Workshop on Measurements and Analyses of the 3-D Solar Magnetic Fields CY APR 09-11, 1996 CL HUNTSVILLE, AL SP SCOSTEP, STEP, WG-1, Univ Alabama, Ctr Space Plasma Aeronom Res ID SOLAR MAGNETIC-FIELDS; DIMENSION; FLARES; SHEAR AB Fractal and multifractal techniques have been applied to various types of solar data to study the fractal properties of sunspots as well as the distribution of photospheric magnetic fields and the role of random motions on the solar surface in this distribution. Other research includes the investigation of changes in the fractal dimension as an indicator for solar flares. Here we evaluate the efficacy of two methods for determining the fractal dimension of an image data set: the Differential Box Counting scheme and a new method, the Jaenisch scheme. To determine the sensitivity of the techniques to changes in image complexity, Various types of constructed images are analyzed. In addition, we apply this method to solar magnetogram data from Marshall Space Flight Center's vector magnetograph. RP Stark, B (reprint author), NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. NR 32 TC 8 Z9 8 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD AUG PY 1997 VL 174 IS 1-2 BP 297 EP 309 DI 10.1023/A:1004908523578 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB565 UT WOS:A1997YB56500022 ER PT J AU Parenti, S Velli, M Poletto, G Suess, ST McComas, DJ AF Parenti, S Velli, M Poletto, G Suess, ST McComas, DJ TI Magnetic flux tubes at 3 AU? SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT Workshop on Measurements and Analyses of the 3-D Solar Magnetic Fields CY APR 09-11, 1996 CL HUNTSVILLE, AL SP SCOSTEP, STEP, WG-1, Univ Alabama, Ctr Space Plasma Aeronom Res ID SOLAR-WIND FLUCTUATIONS; ULYSSES; EVOLUTION; STREAMS; PLASMA; WAVES AB We present an analysis of plasma and magnetic field data acquired by the Ulysses spacecraft on May 1994. Our study is motivated by the result of Poletto ei al. (1996) who found some evidence for a peak in the power spectrum of magnetic pressure at a frequency nu approximate to 2 x 10(-5) Hz, during that period. A re-evaluation of the plasma pressure power spectrum, on the basis of better data than used in the previous work, gives only marginal evidence for a peak at that frequency. If both spectra had excess power in the same spectral range, one might hypothesize that the Pressure Balanced Structures (PBS) detected in the data trace periodically distributed coronal structures which maintain their identity up to large distances. A careful data analysis, however, shows that this interpretation is hardly tenable. Hence, we consider the alternative hypotheses that the observed PBS are either a bundle of magnetic Bur tubes, with no characteristic periodicity, in pressure equilibrium with the ambient, or the manifestation, at large distances, of waves generated close to the Sun. To prove the latter case, we made a test simulation of the evolution with heliocentric distance of an ensemble of Alfven and slow mode waves, generated close to the Sun, and show that structures similar to those we analyzed may form in the interplanetary medium. Our simulations also seem to show that together with PBS, magnetic holes, frequently observed in the Ulysses data, could also originate from the nonlinear evolution of large amplitude slow waves in quasi-perpendicular propagation We conclude-that the observed PBS most likely arise via an irt situ generation mechanism, rather than being remnants of solar structures. C1 OSSERV ASTROFIS ARCETRI,I-50125 FLORENCE,ITALY. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES82,HUNTSVILLE,AL 35812. LOS ALAMOS NATL LAB,LOS ALAMOS,NM. RP Parenti, S (reprint author), UNIV FLORENCE,DEPT ASTRON & SPACE SCI,LARGO ENRICO FERMI 5,I-50125 FLORENCE,ITALY. NR 20 TC 5 Z9 6 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD AUG PY 1997 VL 174 IS 1-2 BP 329 EP 340 DI 10.1023/A:1004912821117 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB565 UT WOS:A1997YB56500024 ER PT J AU Adams, M Hathaway, DH Stark, BA Musielak, ZE AF Adams, M Hathaway, DH Stark, BA Musielak, ZE TI A study of magnetic complexity using Hurst's rescaled range analysis SO SOLAR PHYSICS LA English DT Article; Proceedings Paper CT Workshop on Measurements and Analyses of the 3-D Solar Magnetic Fields CY APR 09-11, 1996 CL HUNTSVILLE, AL SP SCOSTEP, STEP, WG-1, Univ Alabama, Ctr Space Plasma Aeronom Res AB A fractal analysis using the classical Hurst method has been applied to artificial data, simulated sunspot magnetic field data, and to data acquired with NASA/Marshall Space Flight Center's vector magnetograph. The main goals of this study are to quantify the complexity of an active region and to determine if significant changes in complexity are associated with flare activity. We tested the analysis using three basic types of two-dimensional synthetic data: (1) data composed of gaussians with various types of superimposed features, (2) random data, and (3) synthetic sunspots created from a basic, simple configuration on which are placed increasingly smaller structures. Our results confirm that the Hurst method of analysis is sensitive to the presence of large-scale structures within a two-dimensional image. When the large-scale structure has been removed, the value of the Hurst exponent is inversely proportional to increasing complexity in the image. The Hurst exponent of magnetograph data with the large-scale structure of the sunspot removed, shows a tantalizing variation in the shear parameter five minutes prior to a flare. C1 NASA,MSFC,SPACE SCI LAB,HUNTSVILLE,AL 35812. UNIV ALABAMA,HUNTSVILLE,AL 35803. RP Adams, M (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 23 TC 5 Z9 5 U1 1 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD AUG PY 1997 VL 174 IS 1-2 BP 341 EP 355 DI 10.1023/A:1004972624527 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB565 UT WOS:A1997YB56500025 ER PT J AU Allen, MJ Oluseyi, HM Walker, ABC Hoover, RB Barbee, TW AF Allen, MJ Oluseyi, HM Walker, ABC Hoover, RB Barbee, TW TI Chromospheric and coronal structure of polar plumes .1. Magnetic structure and radiative energy balance SO SOLAR PHYSICS LA English DT Article ID SOLAR TELESCOPE ARRAY; SOFT-X-RAY; MULTILAYER TELESCOPE; STELLAR CORONAE; WIND; MODELS; DYNAMICS; REGION; POINTS; HOLE AB The Multi-Spectral Solar Telescope Array (MSSTA), a rocket-borne solar observatory, was successfully launched from White Sands Missile Range, New Mexico, on May 13, 1991 at 19:05 UT. The telescope systems onboard the MSSTA obtained several full disk solar images in narrow bandpasses centered around strong soft X-ray, EUV, and FUV emission lines. Each telescope was designed to be sensitive to the coronal plasmas at a particular temperature, for seven temperatures ranging from 20 000 K to 4 000 000 K. We report here on the images obtained during the initial flight of the MSSTA, and on the chromospheric and coronal structure of polar plumes observed over both poles of the Sun. We have also co-aligned the MSSTA images with Kitt Peak magnetograms taken on the same day. We are able to positively identify the magnetic structures underlying the polar plumes we analyze as unipolar. We discuss the plume observations and present a radiative energy balance model derived from them. C1 STANFORD UNIV, PHYS LAB, STANFORD, CA 94305 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94550 USA. NR 57 TC 15 Z9 16 U1 0 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD AUG PY 1997 VL 174 IS 1-2 BP 367 EP 401 DI 10.1023/A:1004955129119 PG 35 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB565 UT WOS:A1997YB56500027 ER PT J AU Pappa, RS Woodard, SE Juang, JN AF Pappa, RS Woodard, SE Juang, JN TI The development of autonomous structural modal identification SO SOUND AND VIBRATION LA English DT Article; Proceedings Paper CT 15th International Modal Analysis Conference CY FEB, 1997 CL ORLANDO, FL ID EIGENSYSTEM REALIZATION-ALGORITHM AB This article summarizes modal identification results obtained using an autonomous version of the Eigensystem Realization Algorithm on a dynamically complex laboratory structure, The benchmark problem uses 48 of 768 free-decay responses measured in a complete modal survey test, The true modal parameters of the structure are well-known from two previous independent investigations, Without user involvement, the autonomous data analysis procedure identified 24 of 33 structural modes with good to excellent accuracy in 62 sec of CPU time (on a DEC Alpha 4000 computer), The modal identification technique described is the baseline algorithm for NASA's Autonomous Dynamics Determination (ADD) experiment developed for use on International Space Station assembly flights in 1998-2000. RP Pappa, RS (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA. NR 15 TC 2 Z9 2 U1 0 U2 0 PU ACOUSTICAL PUBL INC PI BAY VILLAGE PA 27101 E OVIATT RD PO BOX 40416, BAY VILLAGE, OH 44140 SN 0038-1810 J9 SOUND VIB JI Sound Vib. PD AUG PY 1997 VL 31 IS 8 BP 18 EP 23 PG 6 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA XX595 UT WOS:A1997XX59500003 ER PT J AU Lassiter, JO AF Lassiter, JO TI A poor man's approach for testing surface damping treatments SO SOUND AND VIBRATION LA English DT Article; Proceedings Paper CT 15th International Modal Analysis Conference CY FEB, 1997 CL ORLANDO, FL AB This article describes how experimental modal testing can be used for designing and determining the effectiveness of add-on damping systems for small structures or substructures, Two examples will show how impact modal tests verified the effectiveness of add-on damping systems for small payloads developed by the Marshall Space Flight Center, The dynamic response of each payload was significantly reduced by the treatment. RP Lassiter, JO (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU ACOUSTICAL PUBL INC PI BAY VILLAGE PA 27101 E OVIATT RD PO BOX 40416, BAY VILLAGE, OH 44140 SN 0038-1810 J9 SOUND VIB JI Sound Vib. PD AUG PY 1997 VL 31 IS 8 BP 24 EP 29 PG 6 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA XX595 UT WOS:A1997XX59500004 ER PT J AU Wessen, RR Porter, D AF Wessen, RR Porter, D TI A management approach for allocating instrument development resources SO SPACE POLICY LA English DT Article AB The Cassini Science Management Plan was developed for NASA's Cassini mission to Saturn to assist the Science Instrument Manager in guiding the development of the spacecraft's science payload, This plan, unlike previous development approaches, allocated the entire mass, power, data rate and budget resources for the science instruments to the Principal Investigators, The result removed the Cassini Project from adjudicating and reallocating resources for instrument development problems. Instrument development problems that did occur were resolved by the Principal Investigators themselves through the use of a 'resource exchange', The exchange allowed Principal Investigators to submit 'bids' (i.e. a request for resources) to a database. Principal Investigators were allowed to barter their own resources with other investigators, The resulting exchange or multilateral trade allowed the investigators to reallocate their resource to 'better' their current position. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wessen, RR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 5 Z9 5 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0265-9646 J9 SPACE POLICY JI Space Policy PD AUG PY 1997 VL 13 IS 3 BP 191 EP 201 DI 10.1016/S0265-9646(97)00014-3 PG 11 WC International Relations; Social Sciences, Interdisciplinary SC International Relations; Social Sciences - Other Topics GA YP496 UT WOS:000071283300003 ER PT J AU SobieszczanskiSobieski, J Haftka, RT AF SobieszczanskiSobieski, J Haftka, RT TI Multidisciplinary aerospace design optimization: survey of recent developments SO STRUCTURAL OPTIMIZATION LA English DT Review ID NONHIERARCHIC SYSTEM OPTIMIZATION; AERODYNAMIC-STRUCTURAL DESIGN; HELICOPTER ROTOR BLADES; APPROXIMATION CONCEPTS; COMPOSITE WINGS; MULTILEVEL OPTIMIZATION; EFFICIENT OPTIMIZATION; DYNAMIC OPTIMIZATION; SENSITIVITY ANALYSIS; AIRCRAFT STRUCTURES AB The increasing complexity of engineering systems has sparked rising interest in multidisciplinary optimization (MDO). This paper surveys recent publications in the field of aerospace, in which the interest in MDO has been particularly intense. The primary c hallenges in MDO are computational expense and organizational complexity. Accordingly, this survey focuses on various methods used by different researchers to address these challenges. The survey is organized by a breakdown of MDO into its conceptual components, reflected in sections on mathematical modelling, approximation concepts, optimization procedures, system sensitivity, and human interface. Because the authors' primary area of expertise is in the structures discipline, the majority of the references focus on the interaction of this discipline with others. In particular, two sections at the end of this review focus on two interactions that have recently been pursued with vigour: the simultaneous optimization of structures and aerodynamics and the simultaneous optimization of structures with active control. RP SobieszczanskiSobieski, J (reprint author), NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. RI UF, MDO/G-8720-2012 NR 360 TC 346 Z9 384 U1 10 U2 87 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0934-4373 J9 STRUCT OPTIMIZATION JI Struct. Optim. PD AUG PY 1997 VL 14 IS 1 BP 1 EP 23 DI 10.1007/BF01197554 PG 23 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary; Mechanics SC Computer Science; Engineering; Mechanics GA XT265 UT WOS:A1997XT26500001 ER PT J AU Bauschlicher, CW Rosi, M AF Bauschlicher, CW Rosi, M TI Differentiating between hydrogen and fluorine on a diamond surface SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Letter DE interaction energies; pyridine; hydrogen; fluorine; diamond(111); nanotechnology; chemical storage of data AB We have computed the interaction energies for pyridine (C5H5N) and (CH3)(3)PO with H and F atoms on the surface of diamond(111) as a function of the type of neighboring surface atom. The pyridine-H and -F interaction energies differ by about 5 kcal/mol, which is only about one-third of that found for a one-dimensional model for the surface. The difference in the interaction energies for (CH3)(3)PO is larger. However, the (CH3)(3)PO-neighbor interaction energy is larger than for pyridine, so that the (CH3)(3)PO-H interaction becomes repulsive for six neighboring F atoms. Substituting CN for F dramatically increases the repulsion between the surface atoms and molecules. The repulsion is sufficiently large that H/CN does not appear to be better than H/F as a possible way to store data on a surface. While pyridine shows some potential as a possible probe to differentiate between H and F on a diamond surface, it is not ideal. C1 UNIV PERUGIA, DEPT CHEM, I-06100 PERUGIA, ITALY. RP Bauschlicher, CW (reprint author), NASA, AMES RES CTR STC 2303, MOFFETT FIELD, CA 94035 USA. RI Rosi, Marzio/L-5748-2015 OI Rosi, Marzio/0000-0002-1264-3877 NR 7 TC 7 Z9 7 U1 0 U2 2 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD AUG PY 1997 VL 96 IS 4 BP 213 EP 216 DI 10.1007/s002140050223 PG 4 WC Chemistry, Physical SC Chemistry GA YA682 UT WOS:A1997YA68200001 ER PT J AU Margolis, HA Ryan, MG AF Margolis, HA Ryan, MG TI A physiological basis for biosphere-atmosphere interactions in the boreal forest: an overview SO TREE PHYSIOLOGY LA English DT Article DE carbon flux; climate change; ecosystem productivity; energy flux; flux of trace gases; scaling; transpiration; water flux ID FIELD EXPERIMENT FIFE; CARBON-DIOXIDE; EASTERN SIBERIA; CLIMATIC-CHANGE; CO2; ECOSYSTEM; REFLECTANCE; EXCHANGE; MODELS; RADIATION AB Interdisciplinary field experiments for global change research are large, intensive efforts that study the controls on fluxes of carbon, water, trace gases, and energy between terrestrial ecosystems and the atmosphere at a range of spatial scales. Forest ecophysiology can make significant contributions to such efforts by measuring, interpreting, and modeling these fluxes for the individual components of forest ecosystems and then integrating the results into holistic ecosystem process models. The Boreal Ecosystem-Atmosphere Study (BOREAS) was undertaken because of the importance of the boreal forest biome to various global change issues. The study was conducted from 1993 to 1996 at sites in Saskatchewan and Manitoba, Canada. Results have shown that physiological processes of plants in the boreal forest can have large-scale consequences. For example, the composition of tree species strongly influences flux rates, with deciduous species having much higher carbon and water fluxes than coniferous species. Additionally, physiological limitations to transpiration in boreal conifers, even when soil water is abundant, reduces latent heat flux and increases sensible heat flux over large regions. This physiological control of transpiration can increase the depth of the atmospheric boundary layer on warm spring days to a level similar to that found in desert biomes. This special issue features 10 articles that address various aspects of the physiological basis of biosphere-atmosphere interactions in the boreal forest. The articles emphasize the environmental controls on water flux, carbon flux, and ecosystem productivity. C1 NASA,BIOSPHER SCI BRANCH,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. US FOREST SERV,USDA,ROCKY MT RES STN,FT COLLINS,CO 80526. RP Margolis, HA (reprint author), UNIV LAVAL,FAC FORESTERIE & GEOMAT,CTR RECH BIOL FORESTIERE,ST FOY,PQ G1K 7P4,CANADA. RI Ryan, Michael/A-9805-2008 OI Ryan, Michael/0000-0002-2500-6738 NR 60 TC 35 Z9 35 U1 0 U2 6 PU HERON PUBLISHING PI VICTORIA PA 202, 3994 SHELBOURNE ST, VICTORIA BC V8N 3E2, CANADA SN 0829-318X J9 TREE PHYSIOL JI Tree Physiol. PD AUG-SEP PY 1997 VL 17 IS 8-9 BP 491 EP 499 PG 9 WC Forestry SC Forestry GA YK381 UT WOS:A1997YK38100001 ER PT J AU Dang, QL Margolis, HA Coyea, MR Sy, M Collatz, GJ AF Dang, QL Margolis, HA Coyea, MR Sy, M Collatz, GJ TI Regulation of branch-level gas exchange of boreal trees: roles of shoot water potential and vapor pressure difference SO TREE PHYSIOLOGY LA English DT Article DE aspen; black spruce; jack pine; photosynthesis; stomatal conductance ID GENERAL-CIRCULATION MODEL; CORYLUS-AVELLANA L; ATMOSPHERIC CO2; STOMATAL CONDUCTANCE; ENVIRONMENTAL-FACTORS; STAND DEVELOPMENT; LEAF CONDUCTANCE; BOUNDARY-LAYER; CARBON-DIOXIDE; BLACK SPRUCE AB Effects of shoot water potential (Psi) and leaf-to-atmosphere vapor pressure difference (VPD) on gas exchange of jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) B.S.P.), and aspen (Populus tremuloides Michx.) were investigated at the northern edge of the boreal forest in Manitoba, Canada, Laboratory measurements on cut branches showed that net photosynthesis (A(n)) and mesophyll conductance (g(m)) of jack pine and g(m) of black spruce did not respond to Psi until a threshold Psi was reached below which they decreased linearly. Photosynthesis of black spruce decreased slowly with decreasing Psi above the threshold and declined more rapidly thereafter. The threshold Psi was lower in black spruce than in jack pine. However, stomatal conductance (g(s)) of black spruce decreased continuously with decreasing Psi, whereas g(s) of jack pine showed a threshold response. Mesophyll limitations were primarily responsible for the decline in A(n) at low Psi for jack pine and black spruce in the middle of the growing season, but stomatal limitations became more important later in the season. Field measurements on in situ branches on warm sunny days showed that both conifer species maintained Psi above the corresponding threshold and there was no evidence of Psi limitation on A(n) of jack pine, black spruce or aspen. Vapor pressure difference was important in regulating gas exchange in all three species, An empirical model was used to quantify the g(s) response to VPD. When parameterized with laboratory data for the conifers, the model also fit the corresponding field data. When parameterized with field data, the model showed that stomata of aspen were the most sensitive of the three species to VPD, and stomata of black spruce were the least sensitive. For jack pine and aspen, stomata of foliage in the upper canopy were significantly more sensitive than stomata of foliage in the lower canopy. Vapor pressure difference had a greater impact on A(n) of aspen than on A(n) of the conifers as a result of aspen's greater stomatal sensitivity to VPD and greater slope of the relationship between A(n) and intercellular CO2 concentration (C-i). During the 1994 growing season, VPD averaged 1.0 kPa, corresponding to ratios of C-i to ambient CO2 of 0.77, 0.71 and 0.81 for jack pine, black spruce and aspen, respectively. We conclude that increases in VPD at the leaf surface in response to climate change should affect the absolute CO2 and H2O fluxes per unit leaf area of the aspen component of a boreal forest landscape more than those of the conifer component. C1 NASA,BIOSPHER SCI BRANCH,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV LAVAL,CTR RECH BIOL FORESTIERE,ST FOY,PQ G1K 7P4,CANADA. RI collatz, george/D-5381-2012 NR 81 TC 116 Z9 117 U1 0 U2 16 PU HERON PUBLISHING PI VICTORIA PA 202, 3994 SHELBOURNE ST, VICTORIA BC V8N 3E2, CANADA SN 0829-318X J9 TREE PHYSIOL JI Tree Physiol. PD AUG-SEP PY 1997 VL 17 IS 8-9 BP 521 EP 535 PG 15 WC Forestry SC Forestry GA YK381 UT WOS:A1997YK38100004 ER PT J AU Sullivan, JH Bovard, BD Middleton, EM AF Sullivan, JH Bovard, BD Middleton, EM TI Variability in leaf-level CO2 and water fluxes in Pinus banksiana and Picea mariana in Saskatchewan SO TREE PHYSIOLOGY LA English DT Article DE black spruce; boreal forest; BOREAS; canopy position; jack pine; photosynthesis; shade acclimation ID LAMB SEEDLINGS; LOBLOLLY-PINE; PHOTOSYNTHESIS; LEAVES; CAROTENOIDS; LIMITATIONS; SPRUCE; GROWTH; MODEL; TREES AB We measured seasonal and canopy-level gas exchange in two stands of jack pine (Pinus banksiana Lamb.) and one stand of black spruce (Picea mariana (Mill.) B.S.P.) on relatively clear days from late May until mid-September 1994. Field measurements were made with a portable infrared gas analyzer, and laboratory measurements included photosynthetic oxygen evolution and needle chemical composition. Seasonally averaged light-saturated assimilation rates in the field were 4.0 mu mol m(-2) s(-1) in jack pine and 2.7 mu mol m(-2) s(-1) in black spruce. Rates of assimilation and transpiration were highest in midsummer. The seasonal pattern was especially pronounced for black spruce, probably because cold soil temperatures limited early season gas exchange rates in this species. Among stands, instantaneous water-use efficiency was highest in a young jack pine stand early in the season and higher in the upper canopy foliage than in the lower canopy foliage at all sites at the end of the season. Needles of young jack pine exhibited higher photosynthetic capacity, dark respiration and needle N concentrations than needles of trees at the old site. In both species, slight acclimation to shading was manifested by reductions in photosynthetic capacity in the lower canopy foliage. In both species, first-year needles had greater photosynthetic capacity than older needles but in situ rates of CO2 assimilation in the field showed little difference among needle age classes. In both species, there was a strong correlation between assimilation and stomatal conductance, indicating that assimilation was highly stomatal limited and that environmental factors that alter conductance (e.g., VPD) have a strong influence on CO2 and water fluxes, especially after early season thawing concludes. C1 DUKE UNIV,DEPT BOT,DURHAM,NC 27708. NASA,TERR PHYS LAB,GREENBELT,MD 20771. RP Sullivan, JH (reprint author), UNIV MARYLAND,DEPT NAT RESOURCE SCI & LANDSCAPE ARCHITECTURE,COLLEGE PK,MD 20742, USA. NR 29 TC 27 Z9 26 U1 2 U2 5 PU HERON PUBLISHING PI VICTORIA PA 202, 3994 SHELBOURNE ST, VICTORIA BC V8N 3E2, CANADA SN 0829-318X J9 TREE PHYSIOL JI Tree Physiol. PD AUG-SEP PY 1997 VL 17 IS 8-9 BP 553 EP 561 PG 9 WC Forestry SC Forestry GA YK381 UT WOS:A1997YK38100007 ER PT J AU Xu, K Noor, AK AF Xu, K Noor, AK TI Predictor-corrector finite element approach for electroelastic analysis of hybrid composite plates SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID ACTUATORS AB A predictor-corrector finite element approach is presented for the steady-state (static) electroelastic analysis of multilayered hybrid composite plates. The plates consist of a combination of fiber-reinforced and piezoelectric layers (or patches). The problem is formulated in terms of the displacement components and the electric potential. A two-dimensional finite element model is used in the predictor phase. Linear displacement variation and quadratic electric potential variation are assumed in the thickness direction (five displacement parameters and three electric potential parameters). The functional dependence of the displacement components and the electric potential are then calculated using three-dimensional equations. The corrected quantities are used to obtain better estimates for the different response quantities. The effectiveness of the predictor-corrector approach is demonstrated by numerical examples of five-layer plates consisting of four graphite-epoxy layers and one piezoelectric layer, subjected to transverse mechanical loading and electric potential. C1 UNIV VIRGINIA,CTR ADV COMPUTAT TECHNOL,NASA,LANGLEY RES CTR,HAMPTON,VA 23681. NR 16 TC 5 Z9 5 U1 1 U2 2 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD JUL 30 PY 1997 VL 147 IS 1-2 BP 139 EP 145 DI 10.1016/S0045-7825(97)00009-1 PG 7 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA XH489 UT WOS:A1997XH48900009 ER PT J AU Wasfy, TM Noor, AK AF Wasfy, TM Noor, AK TI Computational procedure for simulating the contact/impact response in flexible multibody systems SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID MECHANICAL SYSTEMS; LARGE DISPLACEMENT; TRANSIENT ANALYSIS; DYNAMIC ANALYSIS; IMPACT ANALYSIS; ELEMENT; ALGORITHM; PENALTY; FRAMES; BEAMS AB A computational procedure for simulating the contact/impact response in flexible multibody systems is presented. The multibody system is discretized by using beam and shell finite element models. The conservation of momentum and restitution equations are used as local velocity constraints to determine the 'post-impact' velocities of the impacting nodes. In case a node impacts an element edge, the impact effect is distributed to the element nodes by using the element shape functions. Two restitution parameters-one in the normal impact direction and the other in the tangential impact directions-can be used to model friction. Two numerical examples are presented to demonstrate the effectiveness of the procedure. C1 UNIV VIRGINIA, NASA, LANGLEY RES CTR, CTR ADV COMPUTAT TECHNOL, HAMPTON, VA 23681 USA. NR 30 TC 12 Z9 15 U1 0 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 EI 1879-2138 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD JUL 30 PY 1997 VL 147 IS 1-2 BP 153 EP 166 DI 10.1016/S0045-7825(97)00005-4 PG 14 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA XH489 UT WOS:A1997XH48900011 ER PT J AU Dateo, CE Lee, TJ AF Dateo, CE Lee, TJ TI An accurate ab initio quartic force field and vibrational frequencies for cyclopropenylidene SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE coupled-cluster method; Fermi resonances; vibrational frequencies; anharmonic progression ID MOLECULAR CALCULATIONS; DIPOLE-MOMENT; DARK CLOUDS; BASIS SETS; C3H2; ISOTOPOMERS; SPECTRA; IDENTIFICATION; CATION; ATOMS AB The singles and doubles coupled-cluster method that includes a perturbative correction for connected triple excitations, denoted CCSD(T), is used in conjunction with an spdf quality one-particle basis set to determine an accurate quartic force field for cyclopropenylidene. A second-order perturbation theory treatment of vibrational anharmonicities, together with proper treatment of Fermi resonances, is used to predict fundamental vibrational frequencies of cyclopropenylidene and its C-13 and deuterium isotopomers. Agreement between theory and the available experimental data is excellent. It is demonstrated that four vibrational bands assigned to cyclopropenylidene in 1984 matrix isolation experiments are correct, contrary to a recent suggestion. The anharmonic progression in the C-H stretches is examined and found to be similar for both the symmetric and antisymmetric C-H stretches, contrary to the findings from another recent study. (C) 1997 Elsevier Science B.V. C1 NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035. RI Lee, Timothy/K-2838-2012 NR 34 TC 21 Z9 21 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD JUL 30 PY 1997 VL 53 IS 8 BP 1065 EP 1077 DI 10.1016/S1386-1425(96)01871-9 PG 13 WC Spectroscopy SC Spectroscopy GA XL198 UT WOS:A1997XL19800004 ER PT J AU Bauschlicher, CW Langhoff, SR AF Bauschlicher, CW Langhoff, SR TI The calculation of accurate harmonic frequencies of large molecules: The polycyclic aromatic hydrocarbons, a case study SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE charge delocalization; harmonic frequencies; infrared intensities ID MATRIX-ISOLATED NAPHTHALENE; GAUSSIAN-BASIS SETS; INFRARED-SPECTROSCOPY; EMISSION FEATURES; SPECTRA; CATIONS; DUST; APPROXIMATION; IONIZATION; EXCHANGE AB The vibrational frequencies and infrared intensities of naphthalene neutral and cation are studied at the self-consistent-field (SCF), second-order Moller-Plesset (MP2), and density functional theory (DFT) levels using a variety of one-particle basis sets. Very accurate frequencies can be obtained at the DFT level in conjunction with large basis sets if they are scaled with two factors, one for the C-H stretches and a second for all other modes. We also find remarkably good agreement at the B3LYP/4-31G lever using only one scale factor. Unlike the neutral polycyclic aromatic hydrocarbons (PAHs) where all methods do reasonably well for the intensities, only the DFT results are accurate for the PAH cations. The failure of the SCF and MP2 methods is caused by symmetry breaking and an inability to describe charge delocalization. We present several interesting cases of symmetry breaking in this study. An assessment is made as to whether an ensemble of PAH neutrals or cations could account for the unidentified infrared bands observed in many astronomical sources. (C) 1997 Elsevier Science B.V. RP NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NR 47 TC 135 Z9 135 U1 0 U2 18 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD JUL 30 PY 1997 VL 53 IS 8 BP 1225 EP 1240 DI 10.1016/S1386-1425(97)00022-X PG 16 WC Spectroscopy SC Spectroscopy GA XL198 UT WOS:A1997XL19800018 ER PT J AU Smith, GD Borodin, O Pekny, M Annis, B Londono, D Jaffe, RL AF Smith, GD Borodin, O Pekny, M Annis, B Londono, D Jaffe, RL TI Polymer force fields from ab initio studies of small model molecules: Can we achieve chemical accuracy? SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE molecular modeling techniques; polymer force fields; small model molecules ID ELECTRONIC-STRUCTURE CALCULATIONS; 1,2-DIMETHOXYETHANE; CONFORMATIONS; SIMULATIONS; GAS AB We endeavor to demonstrate, using poly(ethylene oxide) (PEG) as a model system, that atomistic force fields based upon high-level quantum chemistry calculations on small model molecules can accurately reproduce static and dynamic properties of polymer melts and solutions. The validity of the force field is demonstrated through (1) comparison of predicted properties of the small molecules obtained from quantum chemistry with experiment, (2) comparison of properties predicted by the force field for larger molecules with those determined from quantum chemistry and (3) comparison of static and dynamic properties obtained from molecular dynamics simulations of PEO melts and PEO/LiI solutions using the quantum chemistry based force field with experimental neutron scattering and NMR measurements on these systems. (C) 1997 Published by Elsevier Science B.V. C1 UNIV MISSOURI, DEPT CHEM ENGN, COLUMBIA, MO 65211 USA. OAK RIDGE NATL LAB, DIV CHEM & ANALYT SCI, OAK RIDGE, TN 37831 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RI Borodin, Oleg/B-6855-2012 OI Borodin, Oleg/0000-0002-9428-5291 NR 19 TC 27 Z9 27 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD JUL 30 PY 1997 VL 53 IS 8 BP 1273 EP 1283 DI 10.1016/S1386-1425(97)00012-7 PG 11 WC Spectroscopy SC Spectroscopy GA XL198 UT WOS:A1997XL19800021 ER PT J AU Lee, TJ AF Lee, TJ TI Special issue - Ab initio and ab initio derived force fields: State of the science - Preface SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Editorial Material RP Lee, TJ (reprint author), NASA,AMES RES CTR,MS230-3,MOFFETT FIELD,CA 94035, USA. RI Lee, Timothy/K-2838-2012 NR 0 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD JUL 30 PY 1997 VL 53 IS 8 BP R7 EP R9 DI 10.1016/S1386-1425(97)00033-4 PG 3 WC Spectroscopy SC Spectroscopy GA XL198 UT WOS:A1997XL19800001 ER PT J AU Joshi, RP McAdoo, JA AF Joshi, RP McAdoo, JA TI Picosecond dynamic response of nanoscale low-temperature grown GaAs metal-semiconductor-metal photodetectors (vol 68, pg 1972, 1996) SO APPLIED PHYSICS LETTERS LA English DT Correction, Addition C1 NASA,LANGLEY RES CTR,ELECTROOPT BRANCH,AEROSP ELECT SYST DIV,HAMPTON,VA 23681. USN,RES LAB,NANOELECT PROC FACIL,SACHS FREEMAN ASSOCIATES,WASHINGTON,DC 20375. USN,RES LAB,DIV OPT SCI,WASHINGTON,DC 20375. RP Joshi, RP (reprint author), OLD DOMINION UNIV,DEPT ELECT & COMP ENGN,NORFOLK,VA 23529, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD JUL 28 PY 1997 VL 71 IS 4 BP 557 EP 557 DI 10.1063/1.120558 PG 1 WC Physics, Applied SC Physics GA XM733 UT WOS:A1997XM73300045 ER PT J AU Hartke, GJ Rind, D AF Hartke, GJ Rind, D TI Improved surface and boundary layer models for the Goddard Institute for Space Studies general circulation model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CLIMATE AB Improved surface and boundary layer models have been developed and implemented in the Goddard Institute for Space Studies (GISS) general circulation model (GCM). The new boundary layer model retains the methodology of the Model 2 version in which the surface winds are interpolated using a model profile but amends the approximations that were previously used to keep the model analytical for ease of computation. The new surface layer model is entirely different than that previously used in the GISS GCM and uses similarity theory to compute the transport coefficients, drag coefficient, Dalton number, and Stanton number. The combination yields distinct improvements in the general circulation characteristics of the GISS GCM. The new boundary layer and surface models were chosen to allow surface properties to be precomputed, resulting in minimal impact to the overall execution time. This is particularly important in a GCM used for climate experiments with timescales spanning centuries. C1 NASA, GODDARD SPACE FLIGHT CTR, INST SPACE STUDIES, NEW YORK, NY 10025 USA. RP COLUMBIA UNIV, CTR CLIMATE SYST RES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 23 TC 25 Z9 25 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16407 EP 16422 DI 10.1029/97JD00698 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400002 ER PT J AU Hide, R Dickey, JO Marcus, SL Rosen, RD Salstein, DA AF Hide, R Dickey, JO Marcus, SL Rosen, RD Salstein, DA TI Atmospheric angular momentum fluctuations during 1979-1988 simulated by global circulation models SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OF-DAY VARIATION; EL-NINO; SOUTHERN OSCILLATION; EARTH ROTATION; SOLID EARTH; LENGTH; EXCHANGE; OCEANS; SCALES AB Changes in major global dynamical phenomena in the Earth's atmosphere are manifested in the time series of atmospheric angular momentum (AAM), as determined directly from meteorological observations and indirectly from geodetic observations of small fluctuations in the rotation of the solid Earth which are proportional to length of day. AAM fluctuations are intimately linked with energetic processes throughout the whole atmosphere and also with the stresses at the Earth's surface produced largely by turbulent momentum transport in the oceanic and continental boundary layers and by the action of normal pressure forces on orographic features. A stringent test of any numerical global circulation model (GCM) is therefore provided by a quantitative assessment of its ability to represent AAM fluctuations on all relevant timescales, ranging from months to several years. From monthly data provided by the Atmospheric Model Intercomparison Project (AMIP) of the World Climate Research Programme, we have investigated seasonal and interannual fluctuations and the decadal mean in the axial component of AAM in 23 AMIP GCMs over the period 1979-1988. The decadal means are generally well simulated, with the model median value (1.58 x 10(26) kg m(2) s(-1)) being only 3.5% larger than the observed mean and with 10 of the models being within 5% of the observed. The seasonal cycle is well reproduced, with the median amplitude of the models' seasonal standard deviations being only 2.4% larger than observed. Half the seasonal amplitudes lie within 15% of the observed, and the median correlation found between the observed and model seasonal cycles is 0.95. The dominant seasonal error is an underestimation of AAM during northern hemisphere winter associated with errors in the position of subtropical jets. Less robust are the modeled interannual variations, although the median correlation of 0.61 between model simulations and observed AAM is statistically significant. The two El Nino-Southern Oscillation events that occurred during the AMIP decade 1979-1988 have the expected positive AAM anomalies, although the AAM signature of the 1982-1983 event tends to be underestimated and that of the 1986-1987 event overestimated. C1 CALTECH, JET PROP LAB, SPACE GEODET SCI & APPLICAT GRP, PASADENA, CA 91109 USA. ATMOSPHER & ENVIRONM RES INC, CAMBRIDGE, MA 02139 USA. RP UNIV OXFORD, DEPT PHYS, CLARENDON LAB, PARKS RD, OXFORD OX1 3PU, ENGLAND. OI Marcus, Steven/0000-0002-5763-6961 NR 45 TC 30 Z9 33 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16423 EP 16438 DI 10.1029/97JD00699 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400003 ER PT J AU Cordero, EC Kawa, SR Schoeberl, MR AF Cordero, EC Kawa, SR Schoeberl, MR TI An analysis of tropical transport: Influence of the quasi-biennial oscillation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DIABATIC CIRCULATION; DIMENSIONAL MODEL; ZONAL WIND; OZONE; STRATOSPHERE; TEMPERATURE; HALOE; WAVE; QBO AB An analysis of over 4 years of Upper Atmosphere Research Satellite (UARS) measurements of CH4 HF, O-3, and zonal wind are used to study the influence of the quasi-biennial oscillation (QBO) on constituent transport in the tropics. At the equator, spectral analysis of the Halogen Occultation Experiment (HALOE) and Microwave Limb Sounder (MLS) observations reveals QBO signals in constituent and temperature fields at altitudes between 20 and 45 km Between these altitudes, the location of the maximum QBO amplitude roughly corresponds with the location of the largest vertical gradient in the constituent field. Thus, at 40 km where CH4 and HF have strong vertical gradients, QBO signals are correspondingly large, while at lower altitudes where the vertical gradients are weak, so are the QBO variations, Similarly, ozone, which is largely under dynamical control below 30 km in the tropics, has a strong QBO signal in the region of sharp vertical gradients (similar to 28 km) below the ozone peak. Above 35 km, annual and semi-annual variations are also found to be important components of the variability of long-lived tracers. Therefore, above 30 km, the variability in CH4 and HF at the equator is represented by a combination of semiannual, annual, and QBO timescales. A one-dimensional vertical transport model is used to further investigate the influence of annual and QBO variations on tropical constituent fields. QBO-induced vertical motions are calculated from observed high resolution Doppler imager (HRDI) zonal winds at the equator, while the mean annually varying tropical ascent rate is obtained from the Goddard two-dimensional model. Model simulations of tropical CH4 confirm the importance of both the annual cycle and the QBO in describing the HALOE CH4 observations above 30 km. Estimates of the tropical ascent late and the variation due to the annual cycle and QBO are also discussed. RP NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. RI Kawa, Stephan/E-9040-2012 NR 48 TC 14 Z9 14 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16453 EP 16461 DI 10.1029/97JD01053 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400005 ER PT J AU Haskins, RD Goody, RM Chen, L AF Haskins, RD Goody, RM Chen, L TI A statistical method for testing a general circulation model with spectrally resolved satellite data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GREENHOUSE GASES AB The motivation for this paper is to understand better the means available for testing climate models. Statistics of observed, outgoing, thermal spectra are compared with those predicted from a climate model, on the basis of data collected over a period of approximately 1 year. This is a powerful approach to testing a model with respect to processes internal to the atmosphere. These processes, which have characteristic timescales of less than a year, define the atmosphere's response to external forcing. Second-moment statistics are particularly important fur testing model variability, which is key to predicting the results of forcing the atmosphere, for example, by ocean surface temperature changes, increase of greenhouse gases, etc. Comparisons are presented between statistical data from the infrared interferometer spectrometer (IRIS), an orbiting fourier transform spectrometer, and spectra calculated using the medium-resolution spectral code, MODTRAN, applied to the temperature and humidity profiles from a well-known climate model. Ten months of IRIS data are available, and we have compared means, standard deviations, skew, and kurtosis of its spectrally resolved brightness temperature in three tropical regions for individual months and for a range of timescales. Also presented are comparisons of covariances using Empirical Orthogonal Functions (EOFs) calculated in frequency space. All data that are presented are based on radiance differences from two like spectra, which eliminates many of the errors generated by the use of MODTRAN and most of the errors due to calibration uncertainties in IRIS. Important differences (i.e., residuals) between the IRIS and the GCM statistics are found in comparisons, demonstrating that the spectral data can provide a severe test of many aspects of the variability of a general circulation model. Vile discuss some of the residuals and how they may be used to improve model performance in the context of an adjoint formalism. In the long run the only way to have confidence in the performance of a model is to subject it to as many discriminating comparisons with data as are practicable, and we present a good candidate. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 30 TC 30 Z9 30 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16563 EP 16581 DI 10.1029/97JD00897 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400012 ER PT J AU Cess, RD Zhang, MH Potter, GL Alekseev, V Barker, HW Bony, S Colman, RA Dazlich, DA DelGenio, AD Deque, M Dix, MR Dymnikov, V Esch, M Fowler, LD Fraser, JR Galin, V Gates, WL Hack, JJ Ingram, WJ Kiehl, JT Kim, Y LeTreut, H Liang, XZ McAvaney, BJ Meleshko, VP Morcrette, JJ Randall, DA Roeckner, E Schlesinger, ME Sporyshev, PV Taylor, KE Timbal, B Volodin, EM Wang, W Wang, WC Wetherald, RT AF Cess, RD Zhang, MH Potter, GL Alekseev, V Barker, HW Bony, S Colman, RA Dazlich, DA DelGenio, AD Deque, M Dix, MR Dymnikov, V Esch, M Fowler, LD Fraser, JR Galin, V Gates, WL Hack, JJ Ingram, WJ Kiehl, JT Kim, Y LeTreut, H Liang, XZ McAvaney, BJ Meleshko, VP Morcrette, JJ Randall, DA Roeckner, E Schlesinger, ME Sporyshev, PV Taylor, KE Timbal, B Volodin, EM Wang, W Wang, WC Wetherald, RT TI Comparison of the seasonal change in cloud-radiative forcing from atmospheric general circulation models and satellite observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BUDGET EXPERIMENT DATA; CLIMATE; EARTH; ABSORPTION AB We compare seasonal changes in cloud-radiative forcing (CRF) at the top of the atmosphere from 18 atmospheric general circulation models, and observations from the Earth Radiation Budget Experiment (ERBE). To enhance the CRF signal and suppress interannual variability, we consider only zonal mean quantities for which the extreme months (January and July), as well as the northern and southern hemispheres, have been differenced. Since seasonal variations of the shortwave component of CRF are caused by seasonal changes in both cloudiness and solar irradiance, the latter was removed. In the ERBE data, seasonal changes in CRF are driven primarily by changes in cloud amount. The same conclusion applies to the models. The shortwave component of seasonal CRF is a measure of changes in cloud amount at all altitudes, while the longwave component is more a measure of upper level clouds. Thus important insights into seasonal cloud amount variations of the models have been obtained by comparing both components, as generated by the models, with the satellite data. For example, in 10 of the 18 models the seasonal oscillations of zonal cloud patterns extend too far poleward by one latitudinal grid. C1 RUSSIAN ACAD SCI, OTDELENIE CHISLITELNOI MATEMATIKI, MOSCOW 117334, RUSSIA. CANADIAN CLIMATE CTR, DOWNSVIEW, ON M3H 5T4, CANADA. METEOROL DYNAM LAB, F-75231 PARIS 05, FRANCE. BUR METEOROL RES CTR, MELBOURNE, VIC 3001, AUSTRALIA. COLORADO STATE UNIV, DEPT ATMOSPHER SCI, FT COLLINS, CO 80523 USA. NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. NATL CTR RECH METEOROL, F-31057 TOULOUSE, FRANCE. CSIRO, DIV ATMOSPHER RES, ASPENDALE, VIC 3195, AUSTRALIA. MAX PLANCK INST METEOROL, D-21046 HAMBURG, GERMANY. LAWRENCE LIVERMORE NATL LAB, PROGRAM CLIMATE MODEL DIAG & INTERCOMPARISON, LIVERMORE, CA 94550 USA. NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. UK METEOROL OFF, HADLEY CTR CLIMATE PREDICT & RES, BRACKNELL RG12 2SY, BERKS, ENGLAND. SUNY ALBANY, ATMOSPHER SCI RES CTR, ALBANY, NY 12205 USA. GLAVNAYA GEOFIZICHESKAYA OBSERV IMENI AI VOEIKOVA, ST PETERSBURG 194018, RUSSIA. EUROPEAN CTR MEDIUM RANGE WEATHER FORECASTS, READING RG2 9AX, BERKS, ENGLAND. UNIV ILLINOIS, DEPT ATMOSPHER SCI, URBANA, IL 61801 USA. PRINCETON UNIV, NOAA, GEOPHYS FLUID DYNAM LAB, PRINCETON, NJ 08540 USA. RP SUNY STONY BROOK, MARINE SCI RES CTR, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RI alexeev, vladimir/B-2234-2010; Taylor, Karl/F-7290-2011; Del Genio, Anthony/D-4663-2012; Dix, Martin/A-2334-2012; Randall, David/E-6113-2011; Meleshko, Valentin/D-2157-2016; Sporyshev, Petr/P-7323-2015; OI alexeev, vladimir/0000-0003-3519-2797; Taylor, Karl/0000-0002-6491-2135; Del Genio, Anthony/0000-0001-7450-1359; Dix, Martin/0000-0002-7534-0654; Randall, David/0000-0001-6935-4112; Sporyshev, Petr/0000-0002-4047-8178; Bony, Sandrine/0000-0002-4791-4438 NR 19 TC 38 Z9 39 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16593 EP 16603 DI 10.1029/97JD00927 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400014 ER PT J AU Srivastava, V Clarke, AD Jarzembski, MA Rothermel, J AF Srivastava, V Clarke, AD Jarzembski, MA Rothermel, J TI Comparison of modeled backscatter using measured aerosol microphysics with focused CW lidar data over Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC AEROSOL; OPTICAL-CONSTANTS; WAVELENGTHS; SULFATE AB During NASA's GLObal Backscatter Experiment (GLOBE) II flight mission over the Pacific Ocean in May-June 1990, extensive aerosol backscatter data sets from two continuous wave, focused CO2 Doppler lidars and an aerosol microphysics data set from a laser optical particle counter (LOPC) were obtained. Changes in aerosol loading in various air masses with associated changes in chemical composition, from sulfuric acid and sulfates to dustlike crustal material, significantly affected aerosol backscatter, causing variation of about 3 to 4 orders of magnitude. Some of the significant backscatter features encountered in different air masses were the low backscatter in subtropical air with even lower values in the tropics ?ear the Intertropical Convergence Zone (ITCZ), highly variable backscatter in the ITCZ, mid-tropospheric aerosol backscatter background mode, and high backscatter in an Asian dust plume off the Japanese coast. Differences in aerosol composition and backscatter for northern and southern hemisphere also were observed. Using the LOPC measurements of physical and chemical aerosol properties, we determined the complex refractive index from three different aerosol mixture models to calculate backscatter. These values provided a well-defined envelope of modeled backscatter for various atmospheric conditions, giving good agreement with the lidar data over a horizontal sampling of similar to 18,000 km in the mid-troposphere. C1 UNIV HAWAII, DEPT OCEANOG, HONOLULU, HI 96822 USA. UNIV SPACE RES ASSOC, GLOBAL HYDROL & CLIMATE CTR, HUNTSVILLE, AL USA. RP NASA, GLOBAL HYDROL & CLIMATE CTR, 977 EXPLORER BLVD, HUNTSVILLE, AL 35805 USA. NR 35 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16605 EP 16617 DI 10.1029/97JD00604 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400015 ER PT J AU Marshak, A Davis, A Wiscombe, W Cahalan, R AF Marshak, A Davis, A Wiscombe, W Cahalan, R TI Inhomogeneity effects on cloud shortwave absorption measurements: Two-aircraft simulations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR-RADIATION; STRATOCUMULUS CLOUDS; ALBEDO; MODELS AB We set up an Observation System Simulation in order to quantify the idiosyncratic uncertainties caused by cloud inhomogeneity in two-aircraft measurements. An independently validated fractal model is used to simulate the horizontal variability of optical depth for boundary layer stratus, with and without gaps. A spectral band between 0.9 and 1.0 mu m, with a combination of strong and weak water vapor absorption and negligible weak liquid water absorption, is selected for a detailed study of column absorption. Measurements of upwelling and downwelling radiative fluxes are simulated by the Monte Carlo method at two altitudes in a realistic cloudy atmosphere. We consider three methods of estimating column absorption: cloud forcing ratio, reflectance (R) versus transmittance (T) regression, and Ackerman-Cox correction. Emphasis is on the second method, R versus T, which is shown to be biased in the direction of enhanced absorption as long as the R and T data points are affected by horizontal fluxes. In other words, to reduce the bias to an acceptable level, (R, T) measurements must be at a scale well within the regime where the independent pixel approximation is accurate. Under completely cloudy skies, radiative smoothing processes dominate the bias in the absorption estimate at small scales; hence spatial averages over at least 30 times the radiative smoothing scale, which is commensurate with cloud thickness, are required. If there are substantial gaps in the cloud cover, geometrical shadowing and cloud side-illumination effects overwhelm the radiative smoothing. As a result, the bias in R versus T methodology is worsened, and aircraft positioning becomes more critical. We also examine the effect of Sun angle and instrumental parameters such as vertical separation and horizontal offset between aircraft. The Ackerman-Cox correction offers an alternative to spatial averaging; a modification of this intrinsically small-scare approach that can virtually eliminate horizontal flux contributions in the data is presented. C1 SCI SYST & APPLICAT INC, LANHAM, MD USA. RP NASA, GODDARD SPACE FLIGHT CTR, CLIMATE & RADIAT BRANCH, MC 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 34 TC 31 Z9 31 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16619 EP 16637 DI 10.1029/97JD01153 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400016 ER PT J AU Nedoluha, GE Bevilacqua, RM Gomez, RM Waltman, WB Hicks, BC Thacker, DL Russell, JM Abrams, M Pumphrey, HC Connor, BJ AF Nedoluha, GE Bevilacqua, RM Gomez, RM Waltman, WB Hicks, BC Thacker, DL Russell, JM Abrams, M Pumphrey, HC Connor, BJ TI A comparative study of mesospheric water vapor measurements from the ground-based water vapor millimeter-wave spectrometer and space-based instruments SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE; STRATOSPHERE; OZONE AB We compare water vapor measurements from the Naval Research Laboratory groundbased Water Vapor Millimeter-wave Spectrometer (WVMS) instruments with measurements taken by five space-based instruments. For coincident measurements the retrievals from all of the instruments show qualitatively similar altitude profiles. The retrieved mixing ratios from most instruments generally differ from an average calculated using retrievals from all of the instruments by <1 ppmv at most altitudes from 40 km to 80 km. Comparisons with the Microwave Limb Sounder (MLS) and the Halogen Occultation Experiment (HALOE) allow for the validation of observed temporal variations. The observed variations show similar annual and semiannual cycles. A comparison of several years of data from HALOE and WVMS also shows that the instruments are detecting similar interannual variations. A regression analysis of the WVMS and HALOE data sets shows that the observed variability is consistent within the estimated errors in the mesosphere and that in the upper stratosphere, where the natural variability is small, there is a positive correlation between the WVMS and the HALOE data. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. UNIV EDINBURGH, DEPT METEOROL, EDINBURGH EH9 3JZ, MIDLOTHIAN, SCOTLAND. INTERFEROMETR INC, VIENNA, VA USA. NATL INST WATER & ATMOSPHER RES, LAUDER, NEW ZEALAND. RP USN, RES LAB, REMOTE SENSING DIV, CODE 7227, WASHINGTON, DC 20375 USA. NR 15 TC 23 Z9 23 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16647 EP 16661 DI 10.1029/97JD01095 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400018 ER PT J AU Seftor, CJ Hsu, NC Herman, JR Bhartia, PK Torres, O Rose, WI Schneider, DJ Krotkov, N AF Seftor, CJ Hsu, NC Herman, JR Bhartia, PK Torres, O Rose, WI Schneider, DJ Krotkov, N TI Detection of volcanic ash clouds from Nimbus 7/total ozone mapping spectrometer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID EL-CHICHON VOLCANO; ERUPTIONS; TRANSPORT AB Measured radiances from the Version 7 reprocessing of the Nimbus 7/total ozone mapping spectrometer (TOMS) 340- and 380-nm channels are used to detect absorbing particulates injected into the atmosphere after the El Chichon eruption on April 4, 1982. It is shown that while the single-channel reflectivity determined from the 380-nm channel is able to detect clouds and haze composed of nonabsorbing aerosols, the spectral contrast between the 340- and 380-nm channels is sensitive to absorbing particulates such as volcanic ash, desert dust, or smoke from biomass burning. In this paper the spectral contrast between these two channels is used to detect the volcanic ash injection into the atmosphere and to track its evolution for several days. The movement of the ash clouds is shown to be consistent with the motions expected from the National Centers for Environmental Prediction (NCEP)-derived balanced wind fields in the troposphere and lower stratosphere. The movement of the volcanic SO2 cloud detected from TOMS data was also in agreement with the NCEP wind at higher altitudes of up to 100-10 mbar. The vertical wind shear in the neighborhood of the eruption site resulted in a clear separation of the ash and SO2 clouds. The location and movement of the ash cloud are consistent with information obtained by the advanced very high resolution radiometer (AVHRR) instrument on board the NOAA 7 satellite and to ground reports of ash fall. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. MICHIGAN TECHNOL UNIV, DEPT GEOL ENGN & SCI, HOUGHTON, MI 49931 USA. RP HUGHES STX CORP, 7701 GREENBELT RD, GREENBELT, MD 20770 USA. RI Rose, William/A-7923-2009; Hsu, N. Christina/H-3420-2013; Krotkov, Nickolay/E-1541-2012; Torres, Omar/G-4929-2013; Bhartia, Pawan/A-4209-2016; OI Krotkov, Nickolay/0000-0001-6170-6750; Bhartia, Pawan/0000-0001-8307-9137; Herman, Jay/0000-0002-9146-1632 NR 25 TC 49 Z9 52 U1 0 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16749 EP 16759 DI 10.1029/97JD00925 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400024 ER PT J AU Kaufman, YJ Tanre, D Gordon, HR Nakajima, T Lenoble, J Frouin, R Grassl, H Herman, BM King, MD Teillet, PM AF Kaufman, YJ Tanre, D Gordon, HR Nakajima, T Lenoble, J Frouin, R Grassl, H Herman, BM King, MD Teillet, PM TI Passive remote sensing of tropospheric aerosol and atmospheric correction for the aerosol effect SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SURFACE REFLECTANCE; OPTICAL-THICKNESS; OCEANIC WATERS; PHASE FUNCTION; SATELLITE; RETRIEVAL; RADIANCE; ABSORPTION; TURBIDITY; IMAGERY AB The launch of ADEOS in August 1996 with POLDER, TOMS, and OCTS instruments on board and the future launch of EOS-AM 1 in mid-1998 with MODIS and MISR instruments on board start a new era in remote sensing of aerosol as part of a new remote sensing of the whole Earth system (see a list of the acronyms in the Notation section of the paper). These platforms will be followed by other international platforms with unique aerosol sensing capability, some still in this century (e.g., ENVISAT in 1999). These international spaceborne multispectral, multiangular, and polarization measurements, combined for the first time with international automatic, routine monitoring of aerosol from the ground, are expected to form a quantum leap in our ability to observe the highly variable global aerosol. This new capability is contrasted with present single-channel techniques for AVHRR, Meteosat, and GOES that although poorly calibrated and poorly characterized already generated important aerosol global maps and regional transport assessments. The new data will improve significantly atmospheric corrections for the aerosol effect on remote sensing of the oceans and be used to generate first real-time atmospheric corrections over the land. This special issue summarizes the science behind this change in remote sensing, and the sensitivity studies and applications of the new algorithms to data from present satellite and aircraft instruments. Background information and a summary of a critical discussion that took place in a workshop devoted to this topic is given in this introductory paper. In the discussion it was concluded that the anticipated remote sensing of aerosol simultaneously from several space platforms with different observation strategies, together with continuous validations around the world, is expected to be of significant importance to test remote sensing approaches to characterize the complex and highly variable aerosol field. So far, we have only partial understanding of the information content and accuracy of the radiative transfer inversion of aerosol information from the satellite data, due to lack of sufficient theoretical analysis and applications to proper field data. This limitation will make the anticipated new data even more interesting and challenging. A main concern is the present inadequate ability to sense aerosol absorption, from space or from the ground. Absorption is a critical parameter for climate studies and atmospheric corrections. Over oceans, main concerns are the effects of white caps and dust on the correction scheme. Future improvement in aerosol retrieval and atmospheric corrections will require better climatology of the aerosol properties and understanding of the effects of mixed composition and shape of the particles. The main ingredient missing in the planned remote sensing of aerosol are spaceborne and ground-based lidar observations of the aerosol profiles. C1 UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA. UNIV MIAMI, DEPT PHYS, CORAL GABLES, FL 33124 USA. WORLD CLIMATE RES PROGRAMME, CH-1211 GENEVA, SWITZERLAND. UNIV ARIZONA, INST ATMOSPHER PHYS, TUCSON, AZ 85721 USA. NASA, GODDARD SPACE FLIGHT CTR, EARTH SCI DIRECTORATE, GREENBELT, MD 20771 USA. UNIV SCI & TECH LILLE FLANDRES ARTOIS, OPT ATMOSPHER LAB, F-59655 VILLENEUVE DASCQ, FRANCE. UNIV TOKYO, CTR CLIMATE SYST RES, TOKYO 113, JAPAN. CANADA CTR REMOTE SENSING, OTTAWA, ON K1A 0Y7, CANADA. RP NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CODE 913, GREENBELT, MD 20771 USA. RI King, Michael/C-7153-2011; Nakajima, Teruyuki/H-2370-2013 OI King, Michael/0000-0003-2645-7298; Nakajima, Teruyuki/0000-0002-9042-504X NR 67 TC 291 Z9 325 U1 8 U2 74 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16815 EP 16830 DI 10.1029/97JD01496 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400030 ER PT J AU Mishchenko, MI Travis, LD Kahn, RA West, RA AF Mishchenko, MI Travis, LD Kahn, RA West, RA TI Modeling phase functions for dustlike tropospheric aerosols using a shape mixture of randomly oriented polydisperse spheroids SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NONSPHERICAL TSCHEBYSCHEFF PARTICLES; DISCRETE-DIPOLE APPROXIMATION; AXIALLY-SYMMETRICAL PARTICLES; LIGHT-SCATTERING; SINGLE-SCATTERING; ICE CRYSTALS; BACKSCATTERED FRACTION; ATMOSPHERIC AEROSOLS; RADIATIVE-TRANSFER; OPTICAL-PROPERTIES AB Laboratory and in situ measurements show that scattering properties of natural nonspherical particles can be significantly different from those of volume- or surface-equivalent spheres, thus suggesting that Mie theory may not be suitable for interpreting satellite reflectance measurements for dustlike tropospheric aerosols. In this paper we use the rigorous T-matrix method to extensively compute light scattering by shape distributions of polydisperse, randomly oriented spheroids with refractive indices and size distributions representative of naturally occurring dust aerosols. Our calculations show that even after size and orientation averaging, a single spheroidal shape always produces a unique, shape-specific phase function distinctly different from those produced by other spheroidal shapes. However, phase functions averaged over a wide aspect-ratio distribution of prolate and oblate spheroids are smooth, featureless, and nearly flat at side-scattering angles and closely resemble those measured for natural soil and dust particles. Thus, although natural dust particles are, of course, not perfect spheroids, they are always mixtures of highly variable shapes, and their phase function can be adequately modeled using a wide aspect-ratio distribution of prolate and oblate spheroidal grains. Our comparisons of nonspherical versus projected-area-equivalent spherical particles show that spherical-nonspherical differences in the scattering phase function can be large and therefore can cause significant errors in the retrieved aerosol optical thickness if Mie theory is used to analyze reflectance measurements of nonspherical aerosols. On the other hand, the differences in the total optical cross sections, single-scattering albedo, asymmetry parameter of the phase function, and backscattered fraction are much smaller and in most cases do not exceed 10%. This may suggest that for a given aerosol optical thickness the influence of particle shape on the aerosol radiative forcing is negligibly small. Spherical-nonspherical differences in the extinction-to-backscatter ratio are very large and should be explicitly taken into account in inverting lidar measurements of dustlike aerosols. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. SUNY STONY BROOK, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Kahn, Ralph/D-5371-2012; Mishchenko, Michael/D-4426-2012 OI Kahn, Ralph/0000-0002-5234-6359; NR 67 TC 387 Z9 392 U1 3 U2 32 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16831 EP 16847 DI 10.1029/96JD02110 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400031 ER PT J AU Remer, LA Gasso, S Hegg, DA Kaufman, YJ Holben, BN AF Remer, LA Gasso, S Hegg, DA Kaufman, YJ Holben, BN TI Urban/industrial aerosol: Ground-based Sun/sky radiometer and airborne in situ measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SIZE DISTRIBUTIONS; ATLANTIC-OCEAN; UNITED-STATES; OPTICAL-PROPERTIES; SULFATE AEROSOLS; GREENHOUSE GASES; BOUNDARY-LAYER; AIR-POLLUTION; EAST-COAST; PARTICLE AB Both airborne in situ and ground-based remote sensing methods are used to measure the properties of urban/industrial aerosols during the Sulfate Clouds and Radiation-Atlantic (SCAR-A) experiment in 1993. Airborne in situ methods directly measure aerosol characteristics such as size distribution and scattering coefficient at a particular altitude and infer the total column optical properties, such as optical thickness. Ground-based remote sensing is sensitive to the aerosol optical properties of the entire column and infers the physical properties from inversion of sky radiance. Comparison of optical thickness measurements are encouraging but inconclusive because of measured profiles which extend no higher than 2 km. By comparing aerosol volume size distributions we find that the two systems are in agreement in the radius size range 0.05-2 mu m, after the stratospheric aerosol mode is removed from the remote sensing data. At larger aerosol sizes both systems suffer from greater uncertainty, and the larger aerosols themselves are less spatially uniform because of their short lifetimes. The combination of factors makes the comparison at larger radii impossible. The disadvantages of the in situ systems are that there is a measuring efficiency for each device which is dependent on aerosol size and that airborne in situ measurements are rare events in time and space. Also, in situ instruments dry the aerosol before measurement. Automatic remote sensing procedures measure the total column ambient aerosol unaffected by drying or sampling issues, and these instruments can be installed globally to make observations many times per day. However, the disadvantages to remote sensing are that the inferred physical properties are dependent on the assumptions and numerical limitations of the inversion procedures. The favorable comparison between the two types of measurement systems suggests that these drawbacks are manageable in both cases. C1 UNIV WASHINGTON, DEPT ATMOSPHER SCI, SEATTLE, WA 98195 USA. NASA, GODDARD SPACE FLIGHT CTR, TERR PHYS LAB, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP NASA, GODDARD SPACE FLIGHT CTR, SCI & SYST & APPLICAT INC, CODE 913, GREENBELT, MD 20771 USA. RI Gasso, Santiago/H-9571-2014 OI Gasso, Santiago/0000-0002-6872-0018 NR 45 TC 58 Z9 60 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16849 EP 16859 DI 10.1029/96JD01932 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400032 ER PT J AU Kahn, R West, R McDonald, D Rheingans, B Mishchenko, MI AF Kahn, R West, R McDonald, D Rheingans, B Mishchenko, MI TI Sensitivity of multiangle remote sensing observations to aerosol sphericity SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ANTHROPOGENIC AEROSOLS; GREENHOUSE GASES; LIGHT-SCATTERING; RELATIVE ROLES; DUST AB Multiangle, multispectral remote sensing observations, such as those anticipated from the Earth Observing System (EOS) multiangle imaging spectroradiometer (MISR), can distinguish spherical from nonspherical particles over calm ocean for mineral-dust-like particles with the range of sizes and column amounts expected under natural conditions. The ability to make such distinctions is critical if remote sensing of atmospheric aerosol properties is to provide significant new contributions to our understanding of the global-scale, clear-sky solar radiation balance. According to theoretical simulations the measurements can retrieve column optical depth for nonspherical particles to an accuracy of at least 0.05 or 10%, whichever is larger. In addition, three to four distinct size groups between 0.1 and 2.0 microns effective radius can be identified at most latitudes. C1 NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. RI Kahn, Ralph/D-5371-2012; Mishchenko, Michael/D-4426-2012 OI Kahn, Ralph/0000-0002-5234-6359; NR 14 TC 72 Z9 72 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16861 EP 16870 DI 10.1029/96JD01934 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400033 ER PT J AU West, RA Doose, LR Eibl, AM Tomasko, MG Mishchenko, MI AF West, RA Doose, LR Eibl, AM Tomasko, MG Mishchenko, MI TI Laboratory measurements of mineral dust scattering phase function and linear polarization SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DISCRETE-DIPOLE APPROXIMATION; AXIALLY-SYMMETRICAL PARTICLES; SIZE SHAPE DISTRIBUTIONS; LIGHT-SCATTERING; NONSPHERICAL PARTICLES; TROPOSPHERIC AEROSOLS; WAVELENGTH; MATRICES AB With the goal of improving our understanding of how small mineral dust particles scatter light at visible and near-infrared wavelengths, we measured the scattering phase function and linear polarization of small mineral dust particles over the scattering angle range 15 degrees-170 degrees at three wavelengths (0.47, 0.652, and 0.937 mu m). Particle samples were obtained from Duke Scientific Corp., and include aluminum oxide, silicon carbide, aluminum silicate, antimony oxide, calcium carbonate, and cerium oxide. Particle equivalent-sphere radii range from a few tenths of a micron to about 10 mu m. The particles were injected into a laboratory chamber, where they scattered light as they fell through the air. They were collected on a scanning electron micrograph (SEM) substrate. Particle shapes and sizes were then measured from the SEM images. We compare measured phase functions with those calculated for spheroids with a distribution of axial ratios and sizes, random orientation, and refractive index 1.53 + 0.008i [Mishchenko et al., this issue]. Two of the samples (one of which has a refractive index close to that used in theoretical computations) produced scattering phase functions that were quite similar to those for spheroids. Two samples produced phase functions whose variation between 15 degrees and 170 degrees was much less than that for the spheroids or for the other samples. We suspect this difference may be due to the very high refractive index of those particles, although differences in particle microstructure may also be important. Two samples produced positive linear polarization which had a single broad maximum near 100 degrees scattering angle, and a magnitude greater than 40% at some wavelengths. Two samples had generally positive linear polarization but a more complicated structure, and two samples produced mostly negative polarization whose amplitude was small. We do not have numerical results for the appropriate refractive index and size parameter with which to compare the polarization measurements. We hope the questions raised by this work will stimulate additional effort to develop and test numerical codes for scattering by nonspherical particles. C1 UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA. NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. SUNY STONY BROOK, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 169-237, PASADENA, CA 91109 USA. RI Mishchenko, Michael/D-4426-2012 NR 28 TC 60 Z9 61 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16871 EP 16881 DI 10.1029/96JD02584 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400034 ER PT J AU Abdou, WA Martonchik, JV Kahn, RA West, RA Diner, DJ AF Abdou, WA Martonchik, JV Kahn, RA West, RA Diner, DJ TI A modified linear-mixing method for calculating atmospheric path radiances of aerosol mixtures SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SIZE DISTRIBUTION AB The top-of-atmosphere (TOA) path radiance generated by an aerosol mixture can be synthesized by linearly adding the contributions of the individual aerosol components, weighted by their fractional optical depths. The method, known as linear mixing, is exact in the single-scattering limit. When multiple scattering is significant, the method reproduces the atmospheric path radiance of the mixture with <3% errors for weakly absorbing aerosols up to optical thickness of 0.5. However, when strongly absorbing aerosols are included in the mixture, the errors are much larger. This is due to neglecting the effect of multiple interactions between the aerosol components, especially when the values of the single-scattering albedos of these components are so different that the parameter epsilon = Sigma f(i)\pi(i) - pi(mix)\/pi(i) is larger than similar to 0.1, where pi(i) and f(i) are the single-scattering albedo and the fractional abundance of the ith component, and pi(mix) is the effective single-scattering albedo of the mixture. We describe an empirical, modified linear-mixing method which effectively accounts for the multiple interactions between aerosol components. The modified and standard methods are identical when epsilon = 0.0 and give similar results when epsilon less than or equal to 0.05. For optical depths larger than similar to 0.5, or when epsilon > 0.05, only the modified method can reproduce the radiances within 5% error for common aerosol types up to optical thickness of 2.0. Because this method facilitates efficient and accurate atmospheric path radiance calculations for mixtures of a wide variety of aerosol types, it will be used as part of the aerosol retrieval methodology for the Earth Observing System (EOS) multiangle imaging spectroradiometer (MISR), scheduled for launch into polar orbit in 1998. RP CALTECH, JET PROP LAB, MS 169-237, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. RI Kahn, Ralph/D-5371-2012 OI Kahn, Ralph/0000-0002-5234-6359 NR 6 TC 19 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16883 EP 16888 DI 10.1029/96JD03434 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400035 ER PT J AU Herman, JR Bhartia, PK Torres, O Hsu, C Seftor, C Celarier, E AF Herman, JR Bhartia, PK Torres, O Hsu, C Seftor, C Celarier, E TI Global distribution of UV-absorbing aerosols from Nimbus 7/TOMS data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MOUNT-PINATUBO AEROSOLS; BACKSCATTER ULTRAVIOLET; SATELLITE DETECTION; RADIATION BUDGET; VARIABILITY; SURFACE; INDEX; ASH AB wGlobal distributions of UV-absorbing aerosols are obtained using measured differences between the 340 and the 380 nm radiances from the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) for the years 1979-1993. Time series are shown for major sources of biomass burning and desert dust giving the frequency of occurrence and areal coverage over land and oceans. Minor sources of UV-absorbing aerosols in the atmosphere are also discussed (volcanic ash and oil fires). Relative values of year-to-year variability of UV-absorbing aerosol amounts are shown for major aerosol source regions: (1) central South America (Brazil) near 10 degrees S latitude; (2) Africa near 0 degrees-20 degrees S and 0 degrees to 10 degrees N latitude; (3) Saharan Desert and sub-Saharan region (Sahel), Arabian Peninsula, and the northern border region of India; (4) agricultural burning in Indonesia, Eastern China, and Indochina, and near the mouth of the Amazon River; and (5) coal burning and dust in northeastern China. The first three of these regions dominate the injection of UV-absorbing aerosols into the atmosphere each year and cover areas far outside of their source regions from advection of UV-absorbing particulates by atmospheric wind systems. During the peak months, smoke and dust from these sources are transported at altitudes above 1 km with an optical depth of at least 0.1 and can cover about 10% of the Earth's surface. Boundary layer absorbing aerosols are not readily seen by TOMS because the small amount of underlying Rayleigh scattering leads to a small signal. Significant portions of the observed dust originate from agricultural regions frequently within arid areas, such as in the Sahel region of Africa, especially from the dry lake-bed near Lake Chad (13.5 degrees N, 14 degrees E), and intermittently dry drainage areas and streams. In addition to drought cycle effects, this suggests there may be an anthropogenic component to the amount of dust injected into the atmosphere each year. Detection of absorbing aerosols and calculation of optical depths are affected by the presence of large-scale and subpixel clouds in the TOMS field of view. C1 SOFTWARE CORP AMER, LANHAM, MD 20706 USA. HUGHES STX CORP, GREENBELT, MD 20770 USA. RP NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CODE 916, GREENBELT, MD 20771 USA. RI Hsu, N. Christina/H-3420-2013; Torres, Omar/G-4929-2013; Bhartia, Pawan/A-4209-2016; OI Bhartia, Pawan/0000-0001-8307-9137; Herman, Jay/0000-0002-9146-1632 NR 36 TC 734 Z9 755 U1 3 U2 57 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16911 EP 16922 DI 10.1029/96JD03680 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400037 ER PT J AU Tanre, D Kaufman, YJ Herman, M Mattoo, S AF Tanre, D Kaufman, YJ Herman, M Mattoo, S TI Remote sensing of aerosol properties over oceans using the MODIS/EOS spectral radiances SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SAHARAN DUST OUTBREAKS; OPTICAL-PROPERTIES; TROPOSPHERIC AEROSOLS; SIZE DISTRIBUTIONS; II MEASUREMENTS; SATELLITE; ATMOSPHERE; INSTRUMENT; SCATTERING; PARTICLES AB Spectral radiances measured at the top of the atmosphere in a wide spectral range (0.55-2.13 mu m) are used to monitor the aerosol optical thickness and the aerosol size distribution (integrated on the vertical column) of the ambient (undisturbed) aerosol over the oceans. Even for the moderate resolution imaging spectrometer (MODIS) wide spectral range, only three parameters that describe the aerosol loading and size distribution can be retrieved. These three parameters are not always unique. For instance, the spectral radiance of an aerosol with a bilognormal size distribution can be simulated very well with a single lognormal aerosol with an appropriate mean radius and width of distribution. Preassumptions on the general structure of the size distribution are therefore required in the inversion of MODIS data. The retrieval of the aerosol properties is performed using lookup table computations. The volume size distribution in the lookup table is described with two lognormal modes: a single mode to describe the accumulation mode particles (radius <0.5 mu m) and a single coarse mode to describe dust and/or salt particles (radius >1.0 mu m). Note that two accumulation modes may be present, one dominated by gas phase processes and a second dominated by cloud phase processes. The coarse mode can also be split into several partially overlapping modes describing maritime salt particles and dust. The aerosol parameters we expect to retrieve are eta, the fractional contribution of the accumulation mode to scattering; tau, the spectral optical thickness; and r(m), the mean particle size of the dominant mode. Additional radiative quantities such as asymmetry parameter and effective radius are derived subsequently. The impact of the surface conditions, wind speed and chlorophyll content on the retrieval is estimated, the impact of potential sources of error like the calibration of the instrument is also tested. The algorithm has been applied successfully to actual data sets provided by the Thematic Mapper on Landsat 5 and by the MODIS airborne simulator on the ER-2 and tested against ground and airborne measurements. A first estimate of the general accuracy is Delta tau = +/-0.05 +/- 0.05 tau (at 550 nm), Delta r(m) = 0.3r(m), Delta eta = 10.25. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. APPL RES CORP, LANDOVER, MD 20785 USA. RP UNIV SCI & TECH LILLE FLANDRES ARTOIS, OPT ATMOSPHER LAB, CNRS, UA 713, BAT P5, F-59655 VILLENEUVE DASCQ, FRANCE. NR 63 TC 540 Z9 560 U1 7 U2 47 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16971 EP 16988 DI 10.1029/96JD03437 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400042 ER PT J AU Mishchenko, MI Travis, LD AF Mishchenko, MI Travis, LD TI Satellite retrieval of aerosol properties over the ocean using polarization as well as intensity of reflected sunlight SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MULTIPLE-SCATTERING CALCULATIONS; INVARIANT IMBEDDING METHOD; ANTHROPOGENIC AEROSOLS; PLANETARY ATMOSPHERES; RADIATIVE-TRANSFER; LIGHT-SCATTERING; PARTICLES; EXPANSION; SYSTEM; VENUS AB Most current and proposed satellite remote sensing of tropospheric aerosols relies upon radiance measurements that are interpreted using algorithms that determine best fits to precalculated scattered sunlight for one or more ''standard'' aerosol models. However, the number of different types of aerosol and the substantial space and time variations typically encountered can pose a severe uniqueness problem even for the multiple constraints provided by multispectral radiances of a scene at a number of observation zenith angles. Experience with polarimetry remote sensing on planetary missions has demonstrated that the measurement of polarization as well as the radiance can resolve such uniqueness problems. We use numerically accurate solutions of the vector radiative transfer equation for a realistic atmosphere-ocean model to theoretically simulate; several types of satellite aerosol retrievals over the ocean utilizing radiance measurements alone, polarization measurements alone, and radiance and polarization measurements combined. We have restricted all simulations to a single near-infrared wavelength of 0.865 mu m and assumed that aerosols are spherical, monomodal, and nonabsorbing. These simplifications permit a study of practical scope that tests the retrieval algorithms under exactly the same conditions, thus clearly demonstrating their relative capabilities. in agreement with previous analyses, we have found that radiance-only algorithms using multiple-viewing-angle observations perform far better than those based on single-viewing-angle measurements. However, even multiple-viewing-angle radiance measurements taken at a single wavelength are not always sufficient to determine the aerosol optical thickness, effective radius, and refractive index with high enough accuracy. In contrast, high-accuracy, single-wavelength, multiple-viewing-angle polarimetry alone is capable of uniquely retrieving all three aerosol characteristics with extremely high accuracy (+/-0.015 in aerosol optical thickness, +/-0.03 mu m in effective radius, and +/-0.01 in refractive index). Furthermore, the accuracy of the optical thickness retrieval can be slightly improved by simultaneously using radiance measurements. Our analysis demonstrates that algorithms utilizing high-accuracy polarization as well as radiance measurements are much less dependent on the availability and use of a priori information and can be expected to provide a physically based retrieval of aerosol characteristics (optical thickness, refractive index, and size) with accuracy needed for long-term monitoring of global climate forcings and feedbacks. C1 SUNY STONY BROOK, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012 NR 52 TC 224 Z9 234 U1 2 U2 22 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 16989 EP 17013 DI 10.1029/96JD02425 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400043 ER PT J AU Martonchik, JV AF Martonchik, JV TI Determination of aerosol optical depth and land surface directional reflectances using multiangle imagery SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SPECTRORADIOMETER; CANOPIES; ALBEDO AB Spectral aerosol optical depths, surface hemispherical-directional reflectance factors, and bihemispherical reflectances (albedos) are retrieved for an area of Glacier National Park using spectral, multiangle imagery obtained with the airborne advanced solid state array spectroradiometer (ASAS). The retrieval algorithms are described and are identical in principle to those being devised for use by the multiangle imaging spectroradiometer (MISR) which will fly on the EOS-AMI spacecraft in 1998. As part of its science mission, MISR will produce global coverage of both aerosol amounts and land surface reflection properties. The results in this paper represent the initial effort in applying the MISR algorithms to rear data. These algorithms will undergo additional testing and validation as more multiangle data become available. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 169-237, PASADENA, CA 91109 USA. NR 18 TC 19 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 17015 EP 17022 DI 10.1029/96JD02444 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400044 ER PT J AU Kaufman, YJ Tanre, D Remer, LA Vermote, EF Chu, A Holben, BN AF Kaufman, YJ Tanre, D Remer, LA Vermote, EF Chu, A Holben, BN TI Operational remote sensing of tropospheric aerosol over land from EOS moderate resolution imaging spectroradiometer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID SAHARAN DUST OUTBREAKS; SATELLITE IMAGERY; SIZE DISTRIBUTIONS; OPTICAL-PROPERTIES; ATMOSPHERIC CORRECTIONS; GREENHOUSE GASES; SULFATE AEROSOLS; RELATIVE ROLES; PHASE FUNCTION; CLIMATE MODEL AB Daily distribution of the aerosol optical thickness and columnar mass concentration will be derived over the continents, from the EOS moderate resolution imaging spectroradiometer (MODIS) using dark land targets. Dark land covers are mainly vegetated areas and dark soils observed in the red and blue channels; therefore the method will be limited to the moist parts of the continents (excluding water and ice cover). After the launch of MODIS the distribution of elevated aerosol concentrations, for example, biomass burning in the tropics or urban industrial aerosol in the midlatitudes, will be continuously monitored. The algorithm takes advantage of the MODIS wide spectral range and high spatial resolution and the strong spectral dependence of the aerosol opacity for most aerosol types that result in low optical thickness in the mid-IR (2.1 and 3.8 mu m). The main steps of the algorithm are (1) identification of dark pixels in the mid-IR; (2) estimation of their reflectance at 0.47 and 0.66 mu m; and (3) derivation of the optical thickness and mass concentration of the accumulation mode from the detected radiance. To differentiate between dust and aerosol dominated by accumulation mode particles, for example, smoke or sulfates, ratios of the aerosol path radiance at 0.47 and 0.66 mu m are used. New dynamic aerosol models for biomass burning aerosol, dust and aerosol from industrial/urban origin, are used to determine the aerosol optical properties used in the algorithm. The error in the retrieved aerosol optical thicknesses, tau(a), is expected to be Delta tau(a) = 0.05 +/- 0.2 tau(a). Daily values are stored on a resolution of 10 x 10 pixels (1 km nadir resolution). Weighted and gridded 8-day and monthly composites of the optical thickness, the aerosol mass concentration and spectral radiative forcing are generated for selected scattering angles to increase the accuracy. The daily aerosol information over land and oceans [Tanre et al., this issue], combined with continuous aerosol remote sensing from the ground, will be used to study aerosol climatology, to monitor the sources and sinks of specific aerosol types, and to study the interaction of aerosol with water vapor and clouds and their radiative forcing of climate. The aerosol information will also be used for atmospheric corrections of remotely sensed surface reflectance. In this paper, examples of applications and validations are provided. C1 UNIV SCI & TECH LILLE FLANDRES ARTOIS, OPT ATMOSPHER LAB, VILLENEUVE DASCQ, FRANCE. UNIV MARYLAND, DEPT GEOG, GREENBELT, MD 20771 USA. RP NASA, GODDARD SPACE FLIGHT CTR, SCI SYST & APPLICAT INC, CODE 913, GREENBELT, MD 20771 USA. RI Vermote, Eric/K-3733-2012 NR 102 TC 824 Z9 912 U1 11 U2 101 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 17051 EP 17067 DI 10.1029/96JD03988 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400047 ER PT J AU Fraser, RS Mattoo, S Yeh, EN McClain, CR AF Fraser, RS Mattoo, S Yeh, EN McClain, CR TI Algorithm for atmospheric and glint corrections of satellite measurements of ocean pigment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ZONE COLOR SCANNER; ATLANTIC BIGHT; IMAGERY AB An algorithm is developed to correct satellite measurements of ocean color for atmospheric and surface reflection effects. The algorithm depends on taking the difference between measured and tabulated radiances for deriving water-leaving radiances. The tabulated radiances are related to the measured radiance when the water-leaving radiance is negligible (670 nm). The tabulated radiances are calculated for rough surface reflection, polarization of the scattered light, and multiple scattering. The accuracy of the tables is discussed. The method is validated by simulating the effect of different wind speeds than that for which the lookup table is calculated, and aerosol models different from the maritime model for which the table is computed. The derived water-leaving radiances are accurate enough to compute the pigment concentration with an error of less than +/-15% for wind speeds of 6 and 10 m/s and an urban atmosphere with aerosol optical thickness of 0.20 at lambda 443 nm and decreasing to 0.10 at lambda 670 nm. The pigment accuracy is less for wind speeds less than 6 mis and is about 30% for a model with aeolian dust. On the other hand, in a preliminary comparison with coastal zone color scanner (CZCS) measurements this algorithm and the CZCS operational algorithm produced values of pigment concentration in one image that agreed closely. C1 APPL RES CORP, LANDOVER, MD 20785 USA. GEN SCI CORP, LAUREL, MD 20707 USA. RP NASA, GODDARD SPACE FLIGHT CTR, CODE 913, GREENBELT, MD 20771 USA. NR 30 TC 34 Z9 34 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 17107 EP 17118 DI 10.1029/97JD00357 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400050 ER PT J AU Vermote, EF ElSaleous, N Justice, CO Kaufman, YJ Privette, JL Remer, L Roger, JC Tanre, D AF Vermote, EF ElSaleous, N Justice, CO Kaufman, YJ Privette, JL Remer, L Roger, JC Tanre, D TI Atmospheric correction of visible to middle-infrared EOS-MODIS data over land surfaces: Background, operational algorithm and validation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID REFLECTANCE AB The NASA moderate resolution imaging spectroradiometer (MODIS) instrument will provide a global and improved source of information for the study of land surfaces with a spatial resolution of up to 250 m. Prior to the derivation of various biophysical parameters based on surface reflectances, the top of the atmosphere signals need to be radiometrically calibrated and corrected for atmospheric effects. The present paper describes in detail the state of the art techniques that will be used for atmospheric correction of MODIS bands 1 through 7, centered at 648, 858, 470, 555, 1240, 1640, and 2130 nm, respectively. Previous operational correction schemes have assumed a standard atmosphere with zero or constant aerosol loading and a uniform, Lambertian surface. The MODIS operational atmospheric correction algorithm, reported here, uses aerosol and water vapor information derived from the MODIS data, corrects for adjacency effects and takes into account the directional properties of the observed surface. This paper also describes the operational implementation of these techniques and its optimization. The techniques are applied to remote sensing data from the Landsat Thematic Mapper (TM), the NOAA advanced very high resolution radiometer (AVHRR), and the MODIS airborne simulator (MAS) and Validated against ground-based measurements from the Aerosol Robotic Network (AERONET). C1 UNIV SCI & TECH LILLE FLANDRES ARTOIS, OPT ATMOSPHER LAB, VILLENEUVE DASCQ, FRANCE. UNIV MARYLAND, DEPT GEOG, GREENBELT, MD USA. RP NASA, GODDARD SPACE FLIGHT CTR, SCI SYST & APPLICAT INC, CODE 923, GREENBELT, MD 20771 USA. RI Privette, Jeffrey/G-7807-2011; Vermote, Eric/K-3733-2012 OI Privette, Jeffrey/0000-0001-8267-9894; NR 16 TC 326 Z9 336 U1 9 U2 44 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 17131 EP 17141 DI 10.1029/97JD00201 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400052 ER PT J AU Liang, SL FallahAdl, H Kalluri, S JaJa, J Kaufman, YJ Townshend, JRG AF Liang, SL FallahAdl, H Kalluri, S JaJa, J Kaufman, YJ Townshend, JRG TI An operational atmospheric correction algorithm for Landsat Thematic Mapper imagery over the land SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RADIATIVE-TRANSFER; SATELLITE IMAGERY; SURFACE AB An operational atmospheric correction algorithm for Thematic Mapper (TM) imagery has been developed for both sequential and parallel computer environments considering both aerosol and molecular scattering and absorption. The aerosol optical depth is estimated from the image itself using the dark object approach on a moving-window basis, and the surface reflectance is then retrieved by searching lookup tables that are created using a numerical radiative transfer code. The dark object pixels are identified and their surface reflectance estimated using TM channel 7 (2.1 mu m). A variety of techniques are employed to improve computational efficiency. This method is validated by measured aerosol optical depth and extensive visual evaluations accompanied by statistical analysis. Results indicate that the approach is highly stable and useful for both qualitative imagery interpretation (haze removal) and quantitative analysis. Future research activities are also highlighted. The computer codes are available to the general scientific community. C1 UNIV MARYLAND, INST ADV COMP STUDIES, COLLEGE PK, MD 20742 USA. UNIV MARYLAND, DEPT ELECT ENGN, COLLEGE PK, MD 20742 USA. NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP UNIV MARYLAND, DEPT GEOG, LAB GLOBAL REMOTE SENSING STUDIES, 2181 LEFRAK HALL, COLLEGE PK, MD 20742 USA. RI liang, shunlin/C-2809-2015 NR 22 TC 69 Z9 82 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1997 VL 102 IS D14 BP 17173 EP 17186 DI 10.1029/97JD00336 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XN384 UT WOS:A1997XN38400055 ER PT J AU Lemoine, FGR Smith, DE Zuber, MT Neumann, GA Rowlands, DD AF Lemoine, FGR Smith, DE Zuber, MT Neumann, GA Rowlands, DD TI A 70th degree lunar gravity model (GLGM-2) from Clementine and other tracking data SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GRAVITATIONAL MODEL; EARTH; MOON; MISSION; SYSTEM; VENUS AB A spherical harmonic model of the lunar gravity field complete to degree and order 70 has been developed from S band Doppler tracking data from the Clementine mission, as well as historical tracking data from Lunar Orbiters 1-5 and the Apollo 15 and 16 subsatellites. The model combines 361,000 Doppler observations from Clementine with 347,000 historical observations. The historical data consist of mostly 60-s Doppler with a noise of 0.25 to several mm/s. The Clementine data consist of mostly 10-s Doppler data, with a data noise of 0.25 mm/s for the observations from the Deep Space Network, and 2.5 mm/s for the data from a naval tracking station at Pomonkey, Maryland. Observations provided Clementine, provide the strongest satellite constraint on the Moon's low-degree field. In contrast the historical data, collected by spacecraft that had lower periapsis altitudes, provide distributed regions of high-resolution coverage within +/-29 degrees of the nearside lunar equator. To obtain the solution for a high-degree field in the absence of a uniform distribution of observations, we applied an a priori power law constraint of the form 15 x 10(-5)/l(2) which had the effect of limiting the gravitational power and noise at short wavelengths. Coefficients through degree and order 18 are not significantly affected by the constraint, and so the model permits geophysical analysis of effects of the major basins at degrees 10-12. The GLGM-2 model confirms major features of the lunar gravity field shown in previous gravitational field models but also reveals significantly more detail, particularly at intermediate wavelengths (10(3) km). Free-air gravity anomaly maps derived from the new model show the nearside and farside highlands to be gravitationally smooth, reflecting a state of isostatic compensation. Mascon basins (including Imbrium, Serenitatis, Crisium, Smythii, and Humorum) are denoted by gravity highs first recognized from Lunar Orbiter tracking. All of the major mascons are bounded by annuli of negative anomalies representing significant subsurface mass deficiencies. Mare Orientale appears as a minor mascon surrounded by a horseshoe-shaped gravity low centered on the Inner and Outer Rook rings that is evidence of significant subsurface structural heterogeneity. Although direct tracking is not available over a significant part of the lunar farside, GLGM-2 resolves negative anomalies that correlate with many farside basins, including South Pole-Aitken, Hertzsprung, Korolev, Moscoviense, Tsiolkovsky, and Freundlich-Sharonov. C1 MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA. RP Lemoine, FGR (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771, USA. RI Rowlands, David/D-2751-2012; Lemoine, Frank/D-1215-2013; Neumann, Gregory/I-5591-2013 OI Neumann, Gregory/0000-0003-0644-9944 NR 60 TC 98 Z9 114 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUL 25 PY 1997 VL 102 IS E7 BP 16339 EP 16359 DI 10.1029/97JE01418 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XN540 UT WOS:A1997XN54000005 ER PT J AU Clark, PE Trombka, JI AF Clark, PE Trombka, JI TI Remote X-ray spectrometry for NEAR and future missions: Modeling and analyzing X-ray production from source to surface SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SOLAR; RADIATION; MOON AB Remote X-ray spectrometry will play a key role in the geochemical exploration of solar system bodies, provided the methodology for data analysis efficiently detects and removes solar source and flight trajectory-induced geometric variations. In this paper, we discuss the nature of such variations expected for missions to an asteroid, the Moon, and Mercury. An effective means of removing the effects of solar variability from surface measurements, as indicated by the agreement between theoretical models presented here and Apollo X-ray observations, is also discussed. We calculate X-ray spectra anticipated for these targets using probable surface compositions, solar outputs, and flight trajectories. Generally, the spectra show three distinctive regions where line intensities are clearly correlated with surface abundances: a high-energy Fe region, a moderate-energy Ca region, and a low-energy region which contains Mg, Al, and Si lines. In addition, we calculate anticipated integration times required for acceptable levels of certainty and estimate spatial resolutions achievable for those integration times for elements Mg, Al, Si, S, Ca, Ti, and Fe. Required integration times are lower (on the order of minutes or even seconds) and achievable spatial resolutions improved (on the order of kilometers) for the lower energy lines and for periods of higher solar activity. Using the Near Earth Asteroid Rendezvous (NEAR) mission to asteroid 433 Eros as an example, we describe a recommended approach for analysis of X-ray measurements based on our findings. Most importantly, we clearly demonstrate that major scientific goals for future exploration of asteroids, Mercury, and the Moon can be met by obtaining remote orbital X-ray measurements of these bodies. C1 CATHOLIC UNIV AMER, DEPT PHYS, WASHINGTON, DC 20064 USA. RP Clark, PE (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 691, GREENBELT, MD 20771 USA. NR 59 TC 39 Z9 40 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUL 25 PY 1997 VL 102 IS E7 BP 16361 EP 16384 DI 10.1029/97JE01086 PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XN540 UT WOS:A1997XN54000006 ER PT J AU Delitsky, ML Lane, AL AF Delitsky, ML Lane, AL TI Chemical schemes for surface modification of icy satellites: A road map SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GALILEAN SATELLITES; PLASMA TORUS; ICES; MOLECULES; MAGNETOSPHERE; FORMALDEHYDE; SPECTRUM; OXYGEN; EUROPA; IONS AB The icy Galilean satellites of Jupiter are subject to magnetospheric plasma ion bombardment, which induces chemical changes within the ice. The possible detection of CO2 on the surface of Ganymede by the Galileo spacecraft makes for a more complicated chemistry and increases the number of chemical compounds that may then be present. We outline chemical schemes for the irradiation of pure and mixed ices H2O/CO2 and suggest species which observers may detect on Europa, Ganymede, and Callisto, such as C3O2, H2CO3, H2O2, CO3, HO2, CO, H2CO, CH2CO, as well as K2O, KOH, and SO3, from plasma implantation. Column abundances of compounds in the ice are calculated using a specified energy input and G values (yield per 100 eV). RP Delitsky, ML (reprint author), CALTECH,JET PROP LAB,MS 183-601,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 38 TC 31 Z9 31 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUL 25 PY 1997 VL 102 IS E7 BP 16385 EP 16390 DI 10.1029/97JE01250 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XN540 UT WOS:A1997XN54000007 ER PT J AU Meier, DL Edgington, S Godon, P Payne, DG Lind, KR AF Meier, DL Edgington, S Godon, P Payne, DG Lind, KR TI A magnetic switch that determines the speed of astrophysical jets SO NATURE LA English DT Article ID EXTRAGALACTIC RADIO-SOURCES; ACCRETION DISKS; NUMERICAL SIMULATIONS; FLOWS AB The mechanism by which astrophysical jets form is an important factor in understanding the nature and evolution of phenomena such as active galactic nuclei and quasars, Galactic superluminal X-ray sources and young stellar objects. Of the many schemes proposed for jet production, only the magnetized accretion disk model of Blandford and Payne(1) seems to be applicable to all of these systems, and also offers the potential for generating the highly relativistic flows observed in some quasars(2). But the source of variation in jet morphology observed for different sources remains unclear. Here we report time-dependent numerical simulations of jet formation which show that the character and speed of the jets produced depend dramatically on whether magnetic forces dominate over gravity in the accretion disk corona. This 'magnetic switch' is not predicted by steady-state, self-similar disk models, or by relativistic wind theory (which generally ignores the gravitational field). The effect provides a natural explanation for the existence of two known classes of extragalactic radio source and for the variation of their properties with radio luminosity. It also provides insight into protostellar and galactic microquasar systems. C1 PRINCETON UNIV, PRINCETON, NJ 08544 USA. INTEL CORP, HILLSBORO, OR 97124 USA. DIGITAL EQUIPMENT CORP, LLNL, LIVERMORE, CA 94550 USA. RP Meier, DL (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 25 TC 84 Z9 84 U1 0 U2 5 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 24 PY 1997 VL 388 IS 6640 BP 350 EP 352 DI 10.1038/41034 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XM528 UT WOS:A1997XM52800041 ER PT J AU Jenniskens, P Banham, SF Blake, DF McCoustra, MRS AF Jenniskens, P Banham, SF Blake, DF McCoustra, MRS TI Liquid water in the domain of cubic crystalline ice I-c SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID AMORPHOUS SOLID WATER; OH STRETCHING REGION; INTERSTELLAR GRAINS; INFRARED-SPECTRA; SURFACES; FILMS AB Vapor-deposited amorphous water ice, when warmed above the glass transition temperature (120-140 K), is a viscous liquid which exhibits a viscosity vs temperature relationship different from that of liquid water at room temperature. New studies of thin water ice films now demonstrate that viscous liquid water persists in the temperature range 140-210 K, where it coexists with cubic crystalline ice. The liquid character of amorphous water above the glass transition is demonstrated by (1) changes in the morphology of water ice films on a nonwetting surface observed in transmission electron microscopy (TEM) at around 175 K during slow warming, (2) changes in the binding energy of water molecules measured in temperature programmed desorption (TPD) studies, and (3) changes in the shape of the 3.07 mu m absorption band observed in,orating angle reflection-absorption infrared spectroscopy (RAIRS) during annealing at high temperature, whereby the decreased roughness of the water surface is thought to cause changes in the selectin rules for the excitation of O-H stretch vibrations, Because it is present over such a wide range of temperatures, we propose that this form of liquid water is a common material in nature, where it is expected to exist in the subsurface layers of comets and on the surfaces of some planets and satellites, (C) 1997 American Institute of Physics. C1 UNIV E ANGLIA,SCH CHEM SCI,NORWICH NR4 7TJ,NORFOLK,ENGLAND. NASA,AMES RES CTR,PLANETARY BIOL BRANCH,MOFFETT FIELD,CA 94035. UNIV NOTTINGHAM,DEPT CHEM,NOTTINGHAM NG7 2RD,ENGLAND. RP Jenniskens, P (reprint author), SETI INST,2035 LANDINGS DR,MT VIEW,CA 94043, USA. OI McCoustra, Martin/0000-0002-5716-110X NR 45 TC 142 Z9 143 U1 3 U2 23 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 JUL 22 PY 1997 VL 107 IS 4 BP 1232 EP 1241 DI 10.1063/1.474468 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XL402 UT WOS:A1997XL40200023 PM 11542399 ER PT J AU Giampieri, G AF Giampieri, G TI On the antenna pattern of an orbiting interferometer SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE gravitation; instrumentation, detectors; instrumentation, interferometers ID GRAVITATIONAL-RADIATION; DETECTORS; WAVES AB The response of an interferometer changing its orientation with respect to a fixed reference frame is analysed in terms of the beam-pattern factors and the polarization-averaged antenna power pattern. Given the motion of the antenna, the latter quantity describes the directionality of the antenna as a function of time. An interesting case is represented by the class of motions where the plane of the detector is constrained to move on the surface of a cone of constant aperture; at the same time, the two arms are rotating around a vertical axis. This picture describes, in particular, the motion of LISA, a proposed space-based laser interferometer, as well as of other planned missions. The overall sky coverage, and that of the Galactic plane in particular, is provided as a function of the aperture of the cone. Similarly, one can consider the case of an Earth-based interferometer. Using the same formalism, one can derive a simple expression for the antenna pattern, averaged over the time of arrival of the signal, as a function of the position and orientation on the Earth's surface. In particular, there turn out to be particular values for the terrestrial latitude and the inclination angle with respect to the local parallel which render the time-averaged antenna response perfectly isotropic. In the frequency domain, the general result is that the motion of the detector introduces in the instrumental response to a long-duration continuous signal a few harmonics of the orbital frequency, whose magnitude depends on the position of the source in the sky. In particular, we describe the response of LISA to sinusoidal waves coming from a few known binary systems in our Galaxy. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 13 TC 9 Z9 9 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD JUL 21 PY 1997 VL 289 IS 1 BP 185 EP 195 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM317 UT WOS:A1997XM31700019 ER PT J AU Sikora, M Madejski, G Moderski, R Poutanen, J AF Sikora, M Madejski, G Moderski, R Poutanen, J TI Learning about active galactic nucleus jets from properties of blazars SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, jets; gamma rays, theory; radiation mechanisms, nonthermal ID EXTRAGALACTIC RADIO-SOURCES; GAMMA-RAY EMISSION; X-RAY; RELATIVISTIC JETS; MULTIFREQUENCY OBSERVATIONS; OPTICAL POLARIZATION; AMBIENT RADIATION; PAIR CASCADES; ENERGY; CONTINUUM AB We use multiwavelength spectra of core-dominated hat spectrum radio-loud quasars (FSRQs) to study properties of jets in active galactic nuclei. From a comparison of the predicted bulk Compton radiation with the observed soft X-ray fluxes, we find that these jets must be optically very thin. This eliminates the importance of such processes as Coulomb interactions, pair annihilation, and bremsstrahlung and determines the minimum distance from the black hole where a powerful jet can be fully developed (accelerated, collimated, and mass loaded). In the case of pair dominated jets, this distance is much greater than 100GM(BH)/c(2). Further constraints on the parameters of a jet can be derived from luminosities and positions of spectral peaks of low-energy (IR/optical) and high-energy (gamma-ray) radiation components, provided that both are produced by the same population of electrons. Whereas there appears to be a consensus about the synchrotron origin of the low-energy component, there is still debate about the mechanism of production of gamma-rays. Most likely, they result from Comptonization of a soft radiation field by the same electrons that produce synchrotron radiation. Such a soft radiation field can be provided by the synchrotron process in a jet, by the accretion disk, and by a fraction of the disk radiation that is reprocessed/ rescattered by emission line clouds, dust, and intercloud medium. We show that for FSRQs, the production of the high-energy radiation can be dominated by Comptonization of synchrotron radiation only for jets with moderate bulk Lorentz factors Gamma(j) (less than or similar to 3) or if external radiation fields are much weaker than those observed in typical quasars. Furthermore, in synchrotron self-Compton (SSC) models, the relativistic plasma producing nonthermal radiation is constrained to be very weakly magnetized (B' < 0.01 gauss) and located at very large distances (r similar to 10(19) cm). These can impose problems with jet confinement and with short observed timescale of variability. In the external radiation Compton (ERC) models, the magnetic fields are predicted to be much stronger (B' similar to 100 gauss), and nonthermal radiation can be produced very closely to the black hole (r similar to 10(16) cm), which alleviates the problems with plasma confinement and short timescale variability. However, because of the close proximity to the black hale, the constraints imposed by the bulk Compton radiation imply that the plasma must be free of e(+)e(-) pairs. Finally, we discuss the difficulties that existing models have in explaining the sharp spectral breaks at MeV energies and postulate a ''hot electron'' version of the ERC scenario for the production of MeV peaks. We show that appropriate electron ''temperatures'' (kT similar to 100 MeV) to produce the luminosity peak at MeV energies by Comptonization of external UV radiation are achievable at subparsec distances only for proton-electron plasmas. C1 NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. STOCKHOLM OBSERV, S-13336 SALTSJOBADEN, SWEDEN. UPPSALA OBSERV, S-75120 UPPSALA, SWEDEN. RP Sikora, M (reprint author), NICOLAUS COPERNICUS ASTRON CTR, BARTYCKA 18, PL-00716 WARSAW, POLAND. RI Poutanen, Juri/H-6651-2016 OI Poutanen, Juri/0000-0002-0983-0049 NR 48 TC 118 Z9 118 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1997 VL 484 IS 1 BP 108 EP 117 DI 10.1086/304305 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000011 ER PT J AU Jones, DL Wehrle, AE AF Jones, DL Wehrle, AE TI VLBA imaging of NGC 4261: Symmetric parsec-scale jets and the inner accretion region SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies, active; galaxies, individual (NGC 4261, 3C 270); galaxies, ISM; galaxies, jets; galaxies, nuclei ID ELLIPTICAL GALAXIES; RADIO GALAXIES; COUNTERJET; NGC-4261; NGC-1275; NGC4261; PROBE; DISK AB We observed the nuclear region of NGC 4261 (3C 270) with VLBI to determine the morphology of the central radio source on parsec scales and in particular to see whether the inner radio axis remained in the same direction as the kiloparsec-scale jets or whether it was aligned with the apparent rotation axis of the nuclear disk imaged by HST. The position angle of the radio axis in our Very Long Baseline Array (VLBA) images agrees, within the errors, with the position angle of the VLA-scale jet. Thus, there is no evidence for precession of the jets on timescales shorter than the material propagation time from the nucleus to the diffuse radio lobes. Our dual frequency observations also reveal basically symmetric radio structures at both 1.6 and 8.4 GHz. Analysis of these images shows that most of the central 10 pc of this source is not significantly affected by free-free absorption, even though NST images of the nucleus of the galaxy show it to contain a nearly edge-on disk of gas and dust on larger scales. The lack of detectable absorption over most of the central 10 pc implies that the density of ionized gas in this region is less than similar to 10(3) cm(-3), assuming a temperature of similar to 10(4) K. Our highest angular resolution images show a very narrow absorption feature just east of the radio core, suggesting that there may be a small, dense inner accretion disk with a width of less than 0.1 pc. If the inclination of this inner disk is close to that of the larger scale HST disk, it becomes optically thin to 8.4 GHz radiation at a deprojected radius of about 0.8 pc. The brightness of the parsec-scale jets falls off very rapidly on both sides of the core, suggesting that the jets are rapidly expanding during the first several parsecs of their travel. The rate of jet expansion must slow when the internal pressure falls below that of the external medium. We suggest that this occurs between about 10 and 200 pc from the core because the rate of decrease in radio brightness is far slower at more than 200 pc from the core than it is within 10 pc of the core. It appears that there is a small, dense inner disk centered on the radio core (the base of the jets; less than 1 pc), a low-density, presumably hot ''bubble'' filling most of the inner several parsecs of the nucleus (within which the radio jets expand rapidly; similar to 10 pc), and a surrounding cool, higher density region (of which the HST absorption disk is part: >10 pc) within which the transverse expansion of the radio jets, as implied by the rate of decrease in jet brightness, is nearly halted. C1 CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,PASADENA,CA 91125. RP Jones, DL (reprint author), CALTECH,JET PROP LAB,MAIL CODE 238-332,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 23 TC 39 Z9 39 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1997 VL 484 IS 1 BP 186 EP 192 DI 10.1086/304320 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000019 ER PT J AU Kuntz, KD Snowden, SL Verter, F AF Kuntz, KD Snowden, SL Verter, F TI X-ray shadows by high-latitude molecular clouds .1. Cartography SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, clouds; ISM, molecules; X-rays, ISM ID LOCAL INTERSTELLAR-MEDIUM; SPECTROSCOPIC ANALYSIS; OPTICAL EXTINCTION; SCORPIO-CENTAURUS; OB ASSOCIATION; DARK NEBULAE; ROSAT PSPC; LOOP-I; DIFFUSE; DISTANCES AB We have observed X-ray shadowing by nine nearby high-latitude molecular clouds with the ROSAT PSPC. The 1/4 keV emission from the Local Bubble is used to calculate an average electron density, n(e), toward all of our sample clouds. Given the uniformity of emission within the Local Bubble, and previously determined cloud distances, one can determine whether the clouds are within or without the Local Bubble. We confirm that three of the sample clouds, MBM 12, MBM 16, and possibly MBM 20, which have been thought to be within the Local Bubble, are actually within. A combination of 1/4 keV and n(e) measures suggest that MBM 6 and LDN 1563 may also lie within the Local Bubble or its boundary layer. The shadows cast by the clouds at 3/4 keV and 1.5 keV imply little if any foreground emission in those bands, and produce lower limits for the distance to the hotter emission component responsible for the observed flux. The results are in agreement with previous estimates for the distances to the Loop I Bubble and the Eridion Bubble. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Kuntz, KD (reprint author), UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742, USA. RI Snowden, Steven/D-5292-2012 NR 53 TC 26 Z9 26 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 JUL 20 PY 1997 VL 484 IS 1 BP 245 EP & DI 10.1086/304303 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000025 ER PT J AU Soker, N Dgani, R AF Soker, N Dgani, R TI Interaction of planetary nebulae with a magnetized ISM SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; ISM, magnetic fields; MHD; planetary nebulae, general ID INTERSTELLAR-MEDIUM; CENTRAL STAR; SHOCK; EVOLUTION; CLOUDS AB We study the interaction of planetary nebulae with a magnetized interstellar medium (ISM) and show that the ISM magnetic field cannot be ignored in analysis of the interaction of planetary nebulae with (PNs) with the ISM. We show that stretching and bending of magnetic field Lines can increase the effective pressure of the ISM. In particular, near the stagnation point of the flow of the ISM around the nebula, the ISM magnetic pressure can overcome the thermal pressure, leading to strong MHD instabilities even in isothermal flows. At early stages, when the planetary nebula outer regions are still neutral, the ISM magnetic field can penetrate the nebula via ambipolar diffusion. As a result, when pulled downstream by the flow, the magnetic field will strip the outer layers of the nebula. The Rayleigh-Taylor and Kelvin-Helmholtz instabilities with wavenumbers along the magnetic field lines are suppressed. Therefore, the ISM magnetic field can break the cylindrical symmetrical nature of the interaction. C1 UNIV TEXAS, DEPT ASTRON, AUSTIN, TX 78712 USA. CALTECH, JET PROP LAB, CTR INFRARED PROC & ANAL, PASADENA, CA 91109 USA. RP Soker, N (reprint author), UNIV HAIFA, DEPT PHYS, IL-36006 TIVON, ISRAEL. NR 42 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1997 VL 484 IS 1 BP 277 EP 285 DI 10.1086/304317 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000027 ER PT J AU Kozlovsky, B Ramaty, R Lingenfelter, RE AF Kozlovsky, B Ramaty, R Lingenfelter, RE TI Anisotropic broad nuclear gamma-ray lines: Application to the COMPTEL observations of Orion SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; ISM, individual (Orion OMC) ID CROSS-SECTIONS; SOLAR-FLARES; COMPLEX; ACCELERATION; ABUNDANCES; PARTICLES; ELEMENTS; WINDS AB We investigated in detail the shape of the broad nuclear gamma-ray line emission resulting from accelerated C, N, and O interacting with ambient H and He in an attempt to fit the recent COMPTEL observations of Orion. The fact that the observed gamma-ray emission shows a strong enhancement in the 3-7 MeV region with significant structure within this energy band is the main motivation for assuming that the emission is due to nuclear de-excitations in C, N, and O. We found that the strong emission peak observed at similar to 4 MeV, with a red wing extending down to almost 3 MeV, can be understood as broad line emission produced by accelerated C, N, and O with a relatively hard spectrum but with the blue wing of the C-12 line suppressed by the anisotropy of the interactions. The fact that the observed spectrum does not show narrow emission peaks at 4.44 and 6.13 MeV indicates that the bulk of the observed emission is produced by accelerated C, N, and O, rather than by accelerated protons and a-particles. The anisotropic interaction scenario removes the constraint placed by the line widths on the hardness of the accelerated ion spectrum, a useful feature because harder ion energy spectra are energetically more efficient than softer spectra. We have incorporated in our calculations the anisotropic angular distribution of the gamma-ray line emission in the rest frame of the heavy ions leading to line-splitting effects. The only feature in the COMPTEL data that would indicate the presence of splitting is a structure in the 5-7.5 MeV region. However, for calculations that account for the similar to 4 MeV peak, the characteristic maxima due to line splitting in this region are apparent only in models employing multiple sources. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. RP Kozlovsky, B (reprint author), TEL AVIV UNIV,SACKLER FAC EXACT SCI,RAMAT AVIV,TEL AVIV,ISRAEL. NR 33 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1997 VL 484 IS 1 BP 286 EP 295 DI 10.1086/304340 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000028 ER PT J AU Levenson, NA Graham, JR Aschenbach, B Blair, WP Brinkmann, W Busser, JU Egger, R Fesen, RA Hester, JJ Kahn, SM Klein, RI McKee, CF Petre, R Pisarski, R Raymond, JC Snowden, SL AF Levenson, NA Graham, JR Aschenbach, B Blair, WP Brinkmann, W Busser, JU Egger, R Fesen, RA Hester, JJ Kahn, SM Klein, RI McKee, CF Petre, R Pisarski, R Raymond, JC Snowden, SL TI The ROSAT HRI X-ray survey of the Cygnus Loop SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (Cygnus Loop); supernova remnants; X-rays, ISM ID SUPER-NOVA REMNANTS; FAST SHOCK-WAVE; INTERSTELLAR CLOUDS; EINSTEIN OBSERVATIONS; OPTICAL-EMISSION; PHOTOEVAPORATION; EVOLUTION AB We describe and report progress on the joint U.S. and German campaign to map the X-ray emission from the entire Cygnus Loop with the ROSAT High Resolution Imager. The Cygnus Loop is the prototype for a supernova remnant that is dominated by interactions with the interstellar medium and supplies fundamental physical information on this basic mechanism for shaping the interstellar medium. The global view that these high-resolution (FWHM similar to 10 '') observations provide emphasizes the inhomogeneity of the interstellar medium and the pivotal nature of cloud-blast-wave interactions in determining the X-ray morphology of the supernova remnant. While investigating the details of the evolution of the blast wave, we also describe the interstellar medium in the vicinity of the Cygnus Loop, which the progenitor star has processed. Although we do not expect the X-ray observations to be complete until 1997 September, the incomplete data combined with deep H alpha images provide definitive evidence that the Cygnus Loop was formed by an explosion within a preexisting cavity. C1 MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. JOHNS HOPKINS UNIV, DEPT PHYS & ASTRON, BALTIMORE, MD 21218 USA. DARTMOUTH COLL, DEPT PHYS & ASTRON, HANOVER, NH 03755 USA. ARIZONA STATE UNIV, DEPT PHYS & ASTRON, TEMPE, AZ 85287 USA. COLUMBIA UNIV, DEPT ASTRON, NEW YORK, NY 10027 USA. COLUMBIA UNIV, DEPT PHYS, NEW YORK, NY 10027 USA. LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94550 USA. UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. RP Levenson, NA (reprint author), UNIV CALIF BERKELEY, DEPT ASTRON, 601 CAMPBELL HALL, BERKELEY, CA 94720 USA. RI Snowden, Steven/D-5292-2012 NR 41 TC 64 Z9 64 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1997 VL 484 IS 1 BP 304 EP + DI 10.1086/304334 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000030 ER PT J AU Keohane, JW Petre, R Gotthelf, EV Ozaki, M Koyama, K AF Keohane, JW Petre, R Gotthelf, EV Ozaki, M Koyama, K TI A possible site of cosmic ray acceleration in the supernova remnant IC 443 SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; radiation mechanisms, nonthermal; shock waves; supernova remnants; supernovae, individual (IC 443) ID X-RAY; IC-443; EMISSION; DISCOVERY; SHOCKS; ASCA AB We present evidence for shock acceleration of cosmic rays to high energies (similar to 10 TeV) in the supernova remnant IC 443. X-ray imaging spectroscopy with ASCA reveals two regions of particularly hard emission: an unresolved source embedded in an extended emission region, and a ridge of emission coincident with the southeastern rim. Both features are located on part of the radio shell where the shock wave is interacting with molecular gas, and together they account for a majority of the emission at 7 keV. Though we would not have noticed it a priori, the unresolved feature is coincident with one resolved by the ROSAT HRI. Because this feature overlaps a unique region of hat radio spectral index (alpha < 0.24), has about equal light-crossing and synchrotron loss times, and a power-law spectrum with a spectral index of alpha = 1.3 +/- 0.2, we conclude that the hard X-ray feature is synchrotron radiation from a site of enhanced particle acceleration. Evidence against a plerion includes a lack of observed periodicity (the pulsed fraction upper limit is 33%), the spectral similarity with the more extended hard region, the location of the source outside the 95% error circle of the nearby EGRET source, the fact that it is nestled in a bend in the molecular cloud ring with which IC 443 is interacting, and the requirement of an extremely high transverse velocity (greater than or equal to 5000 km s(-1)). We conclude that the anomalous feature is most likely tracing enhanced particle acceleration by shocks that are formed as the supernova blast wave impacts the ring of molecular clouds. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. KYOTO UNIV,FAC SCI,DEPT PHYS,SAKYO KU,KYOTO 60601,JAPAN. RI Ozaki, Masanobu/K-1165-2013 NR 30 TC 79 Z9 79 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1997 VL 484 IS 1 BP 350 EP 359 DI 10.1086/304329 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000035 ER PT J AU Simon, T Landsman, WB AF Simon, T Landsman, WB TI Convection, thermal bifurcation, and the colors of a stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, abundances; stars, atmospheres; stars, fundamental parameters; stars, rotation; ultraviolet, stars ID A-TYPE STARS; DELTA-SCUTI STARS; F-TYPE STARS; MAIN-SEQUENCE; EMPIRICAL CALIBRATIONS; ATMOSPHERIC PARAMETERS; CHROMOSPHERIC ACTIVITY; EFFECTIVE TEMPERATURE; STELLAR GRANULATION; BETA-SYSTEMS AB Broadband ultraviolet photometry from the TD-1 satellite and low-dispersion spectra from the short wavelength camera of IUE have been used to investigate a long-standing proposal of Bohm-Vitense that the normal main-sequence A and early-F stars may divide into two different temperature sequences: (1) a high-temperature branch (and plateau) comprised of slowly rotating convective stars, and (2) a low-temperature branch populated by rapidly rotating radiative stars. We find no evidence from either data set to support such a claim, or to confirm the existence of an ''A-star gap'' in the B-V color range 0.22 less than or equal to B-V less than or equal to 0.28 due to the sudden onset of convection. We do observe, nonetheless, a large scatter in the 1800-2000 Angstrom colors of the A-F stars, which amounts to similar to 0.65 mag at a given B-V color index. The scatter is not caused by interstellar or circumstellar reddening. A convincing case can also be made against binarity and intrinsic variability due to pulsations of delta Sct origin. We find no correlation with established chromospheric and coronal proxies of convection, and thus no demonstrable link to the possible onset of convection among the A-F stars. The scatter is not instrumental. Approximately 0.4 mag of the scatter is shown to arise from individual differences in surface gravity as well as a moderate spread (factor of similar to 3) in heavy metal abundance and UV line blanketing. A dispersion of similar to 0.25 mag remains, which has no clear and obvious explanation. The most likely cause, we believe, is a residual imprecision in our correction for the spread in metal abundances. However, the existing data do not rule out possible contributions from intrinsic stellar variability or from differential UV line blanketing effects owing to a dispersion in microturbulent velocity. C1 NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. RP Simon, T (reprint author), UNIV HAWAII,INST ASTRON,2680 WOODLAWN DR,HONOLULU,HI 96822, USA. NR 67 TC 8 Z9 8 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 JUL 20 PY 1997 VL 484 IS 1 BP 360 EP 374 DI 10.1086/304321 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000036 ER PT J AU Ling, JC Wheaton, WA Wallyn, P Mahoney, WA Paciesas, WS Harmon, BA Fishman, GJ Zhang, SN Hua, XM AF Ling, JC Wheaton, WA Wallyn, P Mahoney, WA Paciesas, WS Harmon, BA Fishman, GJ Zhang, SN Hua, XM TI Gamma-ray spectra and variability of Cygnus X-1 observed by BATSE SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; radiation mechanisms, nonthermal; stars, individual (Cygnus X-1) ID COMPTONIZATION; TELESCOPE; ACCRETION; EMISSION; SEARCH; STATES AB We present new BATSE Earth occultation observations of the 25 keV-1.8 MeV spectrum and variability of Cyg X-1 made between 1993 August and 1994 May. We observed that the normal soft gamma-ray spectrum (gamma(2)) of Cyg X-1 has two components: a Comptonized part seen below 300 keV and a high-energy tail in the 0.3-2 MeV range that was only hinted at in previous gamma(2) spectrum observed by HEAO 3. The source went through an extended sequence of changes between 1993 August and 1994 May; the 45-140 keV flux first decreased steadily from similar to gamma(2) to below the gamma(1) flux level seen previously by HEAO 3 in 1979 to a new level, gamma(0), roughly one-quarter of its intensity over a period of similar to 140 days. The flux remained at this low level for about 40 days before returning swiftly (similar to 20 days) to approximately the initial gamma(2) level. The gamma(2) spectrum may be interpreted in terms of an interacting two-region model, consisting of a high-temperature (similar to 210-250 keV) core embedded in an similar to 50 keV corona. In this scenario, the observed 25-300 keV photons were produced by Compton scattering of soft photons (similar to 0.5 keV) by the hot electrons in the outer corona. These same hard X-rays were further upscattered by a population of energetic electrons in the inner core, producing the spectral tail above 300 keV. During the excursion of the 45-140 keV flux from the gamma(2) to the gamma(0) level, the spectrum evolved to a form consistent with either a power law with a photon index of similar to 2.6 or a single-temperature Compton model with an electron temperature, kT, of 108 +/- 11 keV and an optical depth, tau, of 0.40 +/- 0.06 and then returned essentially to the original gamma(2) spectrum at the end of the active period. The overall cooling of the system during the low-flux period may be due to an increase in the soft photon population that effectively quenched the hot electrons in these regions through Compton scattering. C1 UNIV ALABAMA, HUNTSVILLE, AL 35899 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35812 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Ling, JC (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 33 TC 41 Z9 41 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1997 VL 484 IS 1 BP 375 EP 382 DI 10.1086/304323 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000037 ER PT J AU Cui, W Zhang, SN Focke, W Swank, JH AF Cui, W Zhang, SN Focke, W Swank, JH TI Temporal properties of Cygnus X-1 during the spectral transitions SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; stars, individual (Cygnus X-1); X-rays, stars ID X-RAYS; VARIABILITY; ACCRETION AB We report the results from our timing analysis of 15 Rossi X-Ray Timing Explorer observations of Cygnus X-1 throughout its 1996 spectral transitions. The entire period can be divided into three distinct phases: (1) transition from the hard state to the soft state, (2) soft state, and (3) transition from the soft state back to the hard state. The observed X-ray properties (both temporal and spectral) in Phases 1 and 3 are remarkably similar, suggesting that the same physical processes are likely involved in triggering such transitions. The power density spectrum (PDS) during the transition can be characterized by a low-frequency red-noise (power-law) component, followed by a white-noise (flat) component that extends to roughly 1-3 Hz, where it is cut off, and a steeper power law (similar to 1/f(2)) at higher frequencies. The X-ray flux also exhibits apparent quasi-periodic oscillations (QPOs), with the centroid frequency varying in the range of 4-12 Hz. The QPO shows no correlation with the source flux, but it becomes more prominent at higher energies. This type of PDS bears resemblance to that of other black hole candidates often observed in a so-called very high state, although the origin of the observed QPO may be very different. The low-frequency red noise has not been observed in the hard state, and thus seems to be correlated positively with the disk mass accretion rate, which is presumably low in the hard state and high in the soft state; in fact, it completely dominates the PDS in the soft state. In the framework of thermal Comptonization models, Cui et al. recently speculated that the difference in the observed spectral and timing properties between the hard and soft states is due to the presence of a ''fluctuating'' Comptonizing corona during the transition. Here we present the measured hard X-ray time lags and coherence functions between various energy bands, and we show that the results strongly support such a scenario. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20741. RP Cui, W (reprint author), MIT,CTR SPACE RES,ROOM 37-571,CAMBRIDGE,MA 02139, USA. RI Swank, Jean/F-2693-2012 NR 46 TC 137 Z9 141 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 JUL 20 PY 1997 VL 484 IS 1 BP 383 EP 393 DI 10.1086/304341 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM780 UT WOS:A1997XM78000038 ER PT J AU Hubeny, I Hubeny, V AF Hubeny, I Hubeny, V TI Non-LTE models and theoretical spectra of accretion disks in active galactic nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies, active; galaxies, nuclei; radiative transfer ID KERR BLACK-HOLE; LYMAN EDGE; QUASARS; ORIGIN AB We present self-consistent models of the vertical structure and emergent spectrum of active galactic nucleus (AGN) accretion disks. The central object is assumed to be a supermassive Kerr black hole. We demonstrate that non-LTE (NLTE) effects and the effects of a self-consistent vertical structure of a disk play a very important role in determining the emergent radiation and therefore should be taken into account. In particular, NLTE models exhibit a largely diminished H I Lyman discontinuity when compared to LTE models, and the He II discontinuity appears strongly in emission for NLTE models. Consequently, the number of ionizing photons in the He rr Lyman continuum predicted by NLTE disk models is 1-2 orders of magnitude higher than that following from the blackbody approximation. This prediction has important implications for ionization models of AGN broad-line regions and for models of the intergalactic radiation field and the ionization of helium in the intergalactic medium. RP Hubeny, I (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 30 TC 42 Z9 42 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 JUL 20 PY 1997 VL 484 IS 1 BP L37 EP L40 DI 10.1086/310774 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM782 UT WOS:A1997XM78200009 ER PT J AU Rich, RM Sosin, C Djorgovski, SG Piotto, G King, IR Renzini, A Phinney, ES Dorman, B Liebert, J Meylan, G AF Rich, RM Sosin, C Djorgovski, SG Piotto, G King, IR Renzini, A Phinney, ES Dorman, B Liebert, J Meylan, G TI Discovery of extended blue horizontal branches in two metal-rich globular clusters SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy, kinematics and dynamics; globular clusters, individual (NGC 104, 47 Tucanae, NGC 5927, NGC 6388, NGC 6441); stars, horizontal-branch ID PHOTOMETRY; STARS; HOT; GALAXIES; BULGE; COLOR; CORE AB We have used WFPC2 to construct B, V color-magnitude diagrams of four metal-rich globular clusters, NGC 104 (47 Tuc), NGC 5927, NGC 6388, and NGC 6441. All four clusters have well populated red horizontal branches (RHB), as expected for their metallicity. However, NGC 6388 and 6441 also exhibit a prominent blue horizontal-branch (BHB) extension, including stars reaching as faint in V as the turnoff luminosity. This discovery demonstrates directly for the first time that a major population of hot horizontal-branch (HB) stars can exist in old, metal-rich systems. This may have important implications for the interpretation of the integrated spectra of elliptical galaxies. The cause of the phenomenon remains uncertain. We examine the possibility that NGC 6388 and 6441 are older than the other clusters, but a simple difference in age may not be sufficient to produce the observed distributions along the HB. The high central densities in NGC 6388 and 6441 suggest that the existence of the BHB tails might be caused by stellar interactions in the dense cores of these clusters, which we calculate to have two of the highest collision rates among globular clusters in the Galaxy. Tidal collisions might act in various ways to enhance loss of envelope mass and therefore populate the blue side of the HB. However, the relative frequency of tidal collisions does not seem large enough (compared to that of the clusters with pure RHBs) to account for such a drastic difference in HB morphology. While a combination of an age difference and dynamical interactions may help, prima facie the lack of a radial gradient in the BHB/RHB star ratio seems to argue against dynamical effects playing a role. C1 UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. CALTECH,DEPT ASTRON,PASADENA,CA 91125. UNIV PADUA,DIPARTIMENTO ASTRON,I-35122 PADUA,ITALY. EUROPEAN SO OBSERV,D-8046 GARCHING,GERMANY. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903. UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. RP Rich, RM (reprint author), COLUMBIA UNIV,DEPT ASTRON,MAIL CODE 5242,NEW YORK,NY 10027, USA. NR 35 TC 120 Z9 120 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 JUL 20 PY 1997 VL 484 IS 1 BP L25 EP L28 DI 10.1086/310758 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM782 UT WOS:A1997XM78200006 ER PT J AU Wang, YM Sheeley, NR Dere, KP Duffin, RT Howard, RA Michels, DJ Moses, JD Harvey, JW Branston, DD Delaboudiniere, JP Artzner, GE Hochedez, JF Defise, JM Catura, RC Lemen, JR Gurman, JB Neupert, WM Newmark, J Thompson, B Maucherat, A Clette, F AF Wang, YM Sheeley, NR Dere, KP Duffin, RT Howard, RA Michels, DJ Moses, JD Harvey, JW Branston, DD Delaboudiniere, JP Artzner, GE Hochedez, JF Defise, JM Catura, RC Lemen, JR Gurman, JB Neupert, WM Newmark, J Thompson, B Maucherat, A Clette, F TI Association of extreme-ultraviolet imaging telescope (EIT) polar plumes with mixed-polarity magnetic network SO ASTROPHYSICAL JOURNAL LA English DT Article DE solar wind; Sun, chromosphere; Sun, corona; Sun, magnetic fields; Sun, UV radiation; Sun, X-rays, gamma rays ID SOLAR-WIND; FIELDS AB SOHO EIT spectroheliograms showing the polar coronal holes during the present sunspot minimum are compared with National Solar Observatory (Kitt Peak) magnetograms taken in Fe I lambda 8688 and Ca II lambda 8542. The chromospheric lambda 8542 magnetograms, obtained on a routine, near-daily basis since 1996 June, reveal the Sun's strong polar fields with remarkable clarity. We find that the Fe Ix lambda 171 polar plumes occur where minority-polarity flux is in contact with flux of the dominant polarity inside each polar hole. Moreover, the locations of ''plume haze'' coincide approximately with the patterns of brightened He II lambda 304 network within the coronal hole. The observations appear to be consistent with mechanisms of plume formation involving magnetic reconnection between unipolar flux concentrations and nearby bipoles. The fact that minority-polarity fields constitute only a small fraction of the total magnetic flux within the polar holes suggests that plumes are not the main source of the high-speed polar wind. C1 NATL OPT ASTRON OBSERV,NATL SOLAR OBSERV,TUCSON,AZ 85726. INST ASTROPHYS SPATIALE,F-91405 ORSAY,FRANCE. CTR SPATIAL LIEGE,B-4031 ANGLEUR,BELGIUM. LOCKHEED PALO ALTO RES LABS,PALO ALTO,CA 94304. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. ASTRON SPATIALE LAB,F-13376 MARSEILLE 12,FRANCE. OBSERV ROYAL BELGIQUE,B-1180 BRUSSELS,BELGIUM. RP Wang, YM (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375, USA. RI Thompson, Barbara/C-9429-2012 NR 25 TC 36 Z9 37 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 JUL 20 PY 1997 VL 484 IS 1 BP L75 EP & DI 10.1086/310773 PN 2 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM782 UT WOS:A1997XM78200018 ER PT J AU Canuto, VM Dubovikov, MS AF Canuto, VM Dubovikov, MS TI A new approach to turbulence SO INTERNATIONAL JOURNAL OF MODERN PHYSICS A LA English DT Review ID DEVELOPED HYDRODYNAMIC TURBULENCE; SCALE-INVARIANT-THEORY; TEMPERATURE-FLUCTUATIONS; RENORMALIZATION-GROUP; ISOTROPIC TURBULENCE; THERMAL TURBULENCE; CONVECTION; CONSTANT; SPECTRA; NUMBER AB We propose a closed set of dynamic equations to describe turbulence. The equations are the result of systematic and heuristic elements. Specifically, the UV part of the nonlinear interactions, represented by a dynamical viscosity, is computed for a stirring force of a particular nature. However, since the results exhibit a general structure, we suggest heuristically to extend them to arbitrary flows. Because of nonrenormalizable divergences, the IR part of the nonlinear interactions has constituted a serious problem. We suggest a heuristic model, the basic ingredient of which is that the transfer of energy among eddies is mostly a local process. We show that possible adjustable parameters are actually fixed by the model itself. Because of the heuristic nature of one part of the model, its overall validity rests largely on the accumulated evidence gathered from checking its predictions against data from a wide variety of flows. The model has been tested against more than seventy turbulence statistics for homogeneous isotropic and anisotropic flows (the Kolmogorov constant is predicted to be Ko = 5/3). The overall performance is good. Here, we first extend the model to inhomogeneous flows and test the predictions using the newest laboratory and DNS data on turbulent convection at large Ra (Rayleigh number). The model reproduces both types of data quite accurately. Second, we study the problem of the so-called ''sweeping effect'' and derive the relation between the omega and k-spectra. Third, we show that for shear driven flows the present model reproduces well the data at large strain rates while the widely used K - epsilon model does not. RP Canuto, VM (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 50 TC 7 Z9 7 U1 0 U2 1 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA 5 TOH TUCK LINK, SINGAPORE 596224, SINGAPORE SN 0217-751X EI 1793-656X J9 INT J MOD PHYS A JI Int. J. Mod. Phys. A PD JUL 20 PY 1997 VL 12 IS 18 BP 3121 EP 3152 DI 10.1142/S0217751X9700164X PG 32 WC Physics, Nuclear; Physics, Particles & Fields SC Physics GA XH345 UT WOS:A1997XH34500001 ER PT J AU Vukovich, FM Brackett, V Fishman, J Sickles, JE AF Vukovich, FM Brackett, V Fishman, J Sickles, JE TI A 5-year evaluation of the representativeness of the tropospheric ozone residual at nonclimatological periods SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB Daily values, monthly averages, and seasonal averages of the tropospheric ozone residual (TOR) were estimated using the Total Ozone Mapping Spectrometer (TOMS) and the Solar Backscattered Ultraviolet (SEW) data for the five-year period 1985-1989. Comparisons were made at these various timescales between TOR and tropospheric ozone using data from eight ozonesonde stations within the region 50 degrees N to 50 degrees S and between normalized departures of the TOR and surface ozone data averaged over four 5 degrees latitude by 5 degrees longitude squares within the eastern United States. These comparisons were accomplished to determine the usefulness of the TOR to represent tropospheric ozone at nonclimatological periods. The results indicated that the annual cycle of the TOR determined using monthly and seasonally averaged values provides a realistic depiction of the annual cycle of tropospheric ozone in the northern hemisphere; that is, approximately a 2% mean error and an 81% correlation. However, in a limited number of comparisons (Hilo and Natal), the annual cycle of the TOR represented the annual cycle of tropospheric ozone at tropical latitudes poorly; that is, approximately a 38% mean error and a 59% correlation. C1 SCI APPLICAT INT CORP, HAMPTON, VA 23665 USA. NASA, LANGLEY RES CTR, CHEM & DYNAM BRANCH, HAMPTON, VA 23665 USA. US EPA, NATL EXPOSURE RES LAB, RES TRIANGLE PK, NC 27511 USA. RP Vukovich, FM (reprint author), SCI APPLICAT INT CORP, 615 OBERLIN RD, SUITE 300, RALEIGH, NC 27605 USA. NR 9 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1997 VL 102 IS D13 BP 15927 EP 15932 DI 10.1029/97JD00455 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XM347 UT WOS:A1997XM34700007 ER PT J AU Lu, JJ Mohnen, VA Yue, GK Jager, H AF Lu, JJ Mohnen, VA Yue, GK Jager, H TI Intercomparison of multiplatform stratospheric aerosol and ozone observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; SAGE-II DATA; CORRELATIVE MEASUREMENTS; PINATUBO ERUPTION; REFRACTIVE-INDEX; SAM-II; LIDAR; SATELLITE; VALIDATION; DUSTSONDES AB Stratospheric aerosol extinction profiles from the satellite-borne Stratospheric Aerosol and Gas Experiment (SAGE II, data version 5.93) and Halogen Occultation Experiment (HALOE, data version 17) instruments are intercompared with the aerosol lidar data at Garmisch-Partenkirchen, Germany (47.5 degrees N, 11.1 degrees E) during January and April 1993. Both the HALOE 5.26 mu m aerosol extinction and aerosol lidar 0.532 mu m backscattering profiles are converted to extinction profiles at the SAGE II 0.525 mu m wavelength channel using aerosol size distributions measured by ER-2 in northern midlatitudes. Within the altitude range of 18-22 km, where most of the stratospheric aerosol resides, the differences between the SAGE II and the HALOE extinction coefficients with respect to HALOE are in general within 30%. The SAGE II-lidar and HALOE-lidar differences (with respect to lidar) are generally within 50% in 15-25 km altitudes. The HALOE extinction values are systematically larger than the SAGE II and aerosol lidar values above 25 km altitude. Stratospheric ozone mixing ratio profiles measured by the SAGE II and HALOE sensors are also intercompared during the same period. The percent differences between the SAGE II and HALOE ozone mixing ratios with respect to HALOE are within 20% in 20-60 km altitudes, in general, within the separation between the compared profiles. C1 FRAUNHOFER INST ATMOSPHAR UMWELTFORSCH, GARMISCH PARTENKIRCHEN, GERMANY. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. RP Lu, JJ (reprint author), SUNY ALBANY, ATMOSPHER SCI RES CTR, 100 FULLER RD, ALBANY, NY 12205 USA. RI Garmisch-Pa, Ifu/H-9902-2014 NR 26 TC 10 Z9 10 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 JUL 20 PY 1997 VL 102 IS D13 BP 16127 EP 16136 DI 10.1029/97JD01016 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XM347 UT WOS:A1997XM34700023 ER PT J AU Lu, JJ Mohnen, VA Yue, GK Atkinson, RJ Matthews, WA AF Lu, JJ Mohnen, VA Yue, GK Atkinson, RJ Matthews, WA TI Intercomparison of stratospheric ozone profiles obtained by stratospheric aerosol and gas experiment II, halogen occultation experiment, and ozonesondes in 1994-1995 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STATISTICAL TREND ANALYSIS; NORTHERN-HEMISPHERE; CLIMATE AB Stratospheric ozone mixing ratio profiles measured by satellite-borne Stratospheric Aerosol and Gas Experiment (SAGE II data version 5.93) and Halogen Occultation Experiment (HALOE data versions 17 and 18) are compared with each other and with balloon-borne ozonesonde profiles at Payerne, Lauder, and Macquarie Island stations during 1994-1995. The SAGE II-HALOE ozone mixing ratio profiles are compared at 13-55 km altitudes, and the satellite-ozonesonde profiles are compared at 13-33 km altitudes. It is found that HALOE data version 18 ozone values are systematically larger than HALOE data version 17, particularly in the lower stratosphere. HALOE data version 18 ozone profiles are about 2%, 5-8%, and 10-20% larger than the corresponding HALOE data version 17 at 40-55, 25-40, and 15-25 km altitudes, respectively. The new version of HALOE ozone agrees better with SAGE II and Payerne ozonesonde profiles than HALOE data version 17 does. In general, the agreements between satellite-borne sensors and ozonesondes are all within their stated level of uncertainties, Intercomparison results between SAGE II-Payerne ozonesonde and SAGE II-Lauder ozonesonde are compared with earlier comparative studies between SAGE I-Payerne ozonesonde and SAGE II-Lauder ozonesonde by Veiga et al. [1995], Better agreement is achieved at Payerne station, but no improvement is discernible at Lauder ozonesonde station. At altitudes above 20 km the intercomparisons between SAGE II and HALOE data version 18 and between SAGE II and ozonesondes seem to indicate that aerosol has no statistically significant impact on SAGE II ozone retrieval during the period of 1994-1995. C1 NATL INST WATER & ATMOSPHER RES, OMAKAU, CENTRAL OTAGO, NEW ZEALAND. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. COOPERAT RES CTR SO HEMISPHERE METEOROL, MELBOURNE, VIC, AUSTRALIA. RP Lu, JJ (reprint author), SUNY ALBANY, ATMOSPHER SCI RES CTR, 100 FULLER RD, ALBANY, NY 12205 USA. NR 27 TC 15 Z9 15 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 JUL 20 PY 1997 VL 102 IS D13 BP 16137 EP 16144 DI 10.1029/97JD00846 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XM347 UT WOS:A1997XM34700024 ER PT J AU Luo, M Park, JH Lee, KM Russell, JM Bruehl, C AF Luo, M Park, JH Lee, KM Russell, JM Bruehl, C TI An analysis of HALOE observations in summer high latitudes using airmass trajectory and photochemical model calculations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TEMPORAL VARIANCE; STRATOSPHERE; CONSTITUENTS; CHEMISTRY; EVOLUTION; VORTEX AB Stratospheric ozone, HCl, NO, and NO2 observed by the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite (UARS) in late summer at high latitudes show nonuniform distributions in their volume mixing ratios along a latitude circle, while the mixing ratios of the long-lived tracers; such as CH4 and HF, are observed to be quite uniform. These anomalous distributions of the reactive gases are confined in approximately 20-35 km, It is found that in the summer high latitudes, the isosurfaces of long-lived tracers nearly coincide with isentropes. On the basis of meridional distributions of these species, it appears that the HALOE-observed features are the results of quasi-isentropic transport across latitude lines with a timescale shorter than the chemical relaxation times of those HALOE observed ozone and other gases, A spectral analysis of the United Kingdom Meteorological Office meridional wind data indicates the existence of episodically amplified wave 1 that is quasi-stationary in July and then slowly westward moving after mid-August 1992. A quasi-stationary wave 2 is also found to be important in late August, The isentropic trajectory calculations show that these planetary scale waves seem to pull air masses out of the polar region as far as 10 degrees-15 degrees latitude equatorward in a week, Midlatitude sir is also pushed into the high summer latitude region, A photochemical box model is used to simulate the chemical evolution of HALOE-observed species along air parcel trajectories which are initialized at HALOE positions. Reasonable agreement is found in comparisons between coincident HALOE measurements and the model results in later days. The characteristic structures in HALOE-observed ozone and other gases in the low and middle stratosphere indicate that the chemical relaxation times taken for these species to relax to their new local mixing ratios under new sunlit conditions are comparable with or longer than the timescale of the meridional transport induced by waves in late summer. C1 UNIV CALIF IRVINE, DEPT EARTH SYST SCI, IRVINE, CA 92717 USA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. MAX PLANCK INST CHEM, DIV ATMOSPHER CHEM, D-55128 MAINZ, GERMANY. NR 22 TC 9 Z9 10 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1997 VL 102 IS D13 BP 16145 EP 16156 DI 10.1029/97JD00694 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XM347 UT WOS:A1997XM34700025 ER PT J AU Ruth, S Kennaugh, R Gray, LJ Russell, JM AF Ruth, S Kennaugh, R Gray, LJ Russell, JM TI Seasonal, semiannual, and interannual variability seen in measurements of methane made by the UARS halogen occultation experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; GENERAL-CIRCULATION MODEL; TWO-DIMENSIONAL MODEL; MIDDLE ATMOSPHERE; ZONAL WIND; TRACER DISTRIBUTIONS; KELVIN WAVE; STRATOSPHERE; TRANSPORT; NIMBUS-7 AB Variability in atmospheric methane on semiannual, seasonal, and interannual timescales is investigated using measurements of CH4 made by the Upper Atmosphere Research Satellite Halogen Occultation Experiment (HALOE). It is shown that there is a strong correlation between the appearance of the stratopause double peak in methane mixing ratio (which is thought to be associated with the semiannual oscillation (SAO)) and the phase of the quasi-biennial oscillation (QBO) in the equatorial lower stratosphere. In a descending westerly QBO phase the double peak is seen clearly in the HALOE methane data, but during the onset of the easterly phase the double peak is not observed. This is the opposite of that which might be expected if the cause was a straightforward modulation of the strength of the SAO due to wave filtering by the QBO. The intra-annual variability in HALOE methane is shown to be broadly consistent with previous observations. One interesting feature is the apparent occurrence of descent in the summer high latitudes near the stratopause. It is shown that this feature is, in fact, due to enhanced photochemical destruction in this region in the presence of weak transport. C1 RUTHERFORD APPLETON LAB, DIDCOT OX11 0QX, OXON, ENGLAND. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. RI Gray, Lesley/D-3610-2009 NR 39 TC 22 Z9 23 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1997 VL 102 IS D13 BP 16189 EP 16199 DI 10.1029/97JD00868 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XM347 UT WOS:A1997XM34700028 ER PT J AU Chen, L Rabitz, H Considine, DB Jackman, CH Shorter, JA AF Chen, L Rabitz, H Considine, DB Jackman, CH Shorter, JA TI Chemical reaction rate sensitivity and uncertainty in a two-dimensional middle atmospheric ozone model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LIMB INFRARED MONITOR; 2-DIMENSIONAL MODEL; CHLORINE PERTURBATIONS; PHOTOCHEMISTRY MODEL; RADIATIVE-TRANSFER; STRATOSPHERE DATA; PROPAGATION; DEPLETION; ACID; HO2 AB The NASA Goddard Space Flight Center two-dimensional (2-D) model has been used to study the sensitivity of model ozone concentrations to input chemical reaction rates, and the uncertainty of the model-calculated concentrations. Ozone sensitivity coefficients to changes in chemical reaction rates are defined as logarithmic partial derivatives of the ozone concentration with respect to the chemical reaction rates. These logarithmic derivatives are estimated using a finite difference technique. The ozone sensitivity coefficients to 96 gas phase chemical reactions in the 2-D model show that the ozone concentration is sensitive to the rates of about 25 reactions, The magnitude of the ozone sensitivity coefficients varies from 0.05 to 0.9. The latitude-altitude distributions of the ozone sensitivity coefficients to several reactions are presented. The uncertainty of the model-calculated ozone concentration is evaluated using a guided Monte Carlo (GMC) method from a probability distribution function. The GMC method judiciously combines uncertainty estimates derived from the sensitivity information with Monte Carlo runs of the model. The uncertainty of the model ozone concentration due to uncertainties in gas phase reaction rates is calculated from published chemical rate uncertainties and varies from 10-20% in the lower stratosphere to 30-40% in the mesosphere. Details concerning the GMC method are discussed, and the latitude-altitude distribution of The uncertainty of the model-calculated ozone is presented. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHER CHEM & DYNAM BRANCH, GREENBELT, MD 20771 USA. MISSION RES CORP, ATMOSPHER & SPACE SCI DIV, NASHUA, NH 03062 USA. RI Jackman, Charles/D-4699-2012 NR 31 TC 14 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1997 VL 102 IS D13 BP 16201 EP 16214 DI 10.1029/97JD00702 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XM347 UT WOS:A1997XM34700029 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI Displacement energies for nanorods SO CHEMICAL PHYSICS LETTERS LA English DT Article AB The geometries have been optimized and harmonic frequencies computed fcr three small hydrocarbon rods. The two lowest unique frequencies correspond to a torsion and a bend of the rods. The energy to bend or twist the rods has been computed by adding a fraction of the normal coordinate corresponding to these two modes to the equilibrium geometry. The density functional theory (using B3LYP) and Hartree-Fock (HF) results are very similar for all properties considered. (C) 1997 Elsevier Science B.V. RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,STC 230-3,MOFFETT FIELD,CA 94035, USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD JUL 18 PY 1997 VL 273 IS 3-4 BP 195 EP 198 DI 10.1016/S0009-2614(97)00584-8 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XM262 UT WOS:A1997XM26200014 ER PT J AU Moore, TE Chappell, CR Chandler, MO Craven, PD Giles, BL Pollock, CJ Burch, JL Young, DT Waite, JH Nordholt, JE Thomsen, MF McComas, DJ Berthelier, JJ Williamson, WS Robson, R Mozer, FS AF Moore, TE Chappell, CR Chandler, MO Craven, PD Giles, BL Pollock, CJ Burch, JL Young, DT Waite, JH Nordholt, JE Thomsen, MF McComas, DJ Berthelier, JJ Williamson, WS Robson, R Mozer, FS TI High-altitude observations of the polar wind SO SCIENCE LA English DT Article ID PLASMA; IONOSPHERE; MAGNETOSPHERE; INSTRUMENT; LOBE AB Plasma outflows, escaping from Earth through the high-altitude polar caps into the tail of the magnetosphere, have been observed with a xenon plasma source instrument to reduce the floating potential of the POLAR spacecraft. The largest component of H+ flow, along the local magnetic field (30 to 60 kilometers per second), is faster than predicted by theory. The flows contain more O+ than predicted by theories of thermal polar wind but also have elevated ion temperatures. These plasma outflows contribute to the plasmas energized in the elongated nightside tail of the magnetosphere, creating auroras, substorms, and storms. They also constitute an appreciable loss of terrestrial water dissociation products into space. C1 SW RES INST,SAN ANTONIO,TX. LOS ALAMOS NATL LAB,LOS ALAMOS,NM. CTR ETUD TERR & PLANETAIRE,ST MAUR FOSSES,FRANCE. HUGHES RES LABS,MALIBU,CA 90265. UNIV CALIF BERKELEY,BERKELEY,CA 94720. RP Moore, TE (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 18 TC 55 Z9 55 U1 0 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD JUL 18 PY 1997 VL 277 IS 5324 BP 349 EP 351 DI 10.1126/science.277.5324.349 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XL358 UT WOS:A1997XL35800039 ER PT J AU Kliore, AJ Hinson, DP Flasar, FM Nagy, AF Cravens, TE AF Kliore, AJ Hinson, DP Flasar, FM Nagy, AF Cravens, TE TI The ionosphere of Europa from Galileo radio occultations SO SCIENCE LA English DT Article ID ATMOSPHERE; JUPITER AB The Galileo spacecraft performed six radio occultation observations of Jupiter's Galilean satellite Europa during its tour of the jovian system, In five of the six instances, these occultations revealed the presence of a tenuous ionosphere on Europa, with an average maximum electron density of nearly 10(4) per cubic centimeter near the surface and a plasma scale height of about 240 +/- 40 kilometers from the surface to 300 kilometers and of 440 +/- 60 kilometers above 300 kilometers. Such an ionosphere could be produced by solar photoionization and jovian magnetospheric particle impact in an atmosphere having a surface density of about 10(8) electrons per cubic centimeter. If this atmosphere is composed primarily of O-2, then the principal ion is O-2(+) and the neutral atmosphere temperature implied by the 240-kilometer scale height is about 600 kelvin. If it is composed of H2O, the principal ion is H3O+ and the neutral temperature is about 340 kelvin. In either case, these temperatures are much higher than those observed on Europa's surface, and an external heating source from the jovian magnetosphere is required. C1 STANFORD UNIV,CTR RADAR ASTRON,STANFORD,CA 94305. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. UNIV MICHIGAN,SPACE PHYS RES LAB,ANN ARBOR,MI 48109. UNIV KANSAS,DEPT PHYS & ASTRON,LAWRENCE,KS 66045. RP Kliore, AJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Flasar, F Michael/C-8509-2012 NR 16 TC 76 Z9 77 U1 2 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 JUL 18 PY 1997 VL 277 IS 5324 BP 355 EP 358 DI 10.1126/science.277.5324.355 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XL358 UT WOS:A1997XL35800041 PM 9219689 ER PT J AU Gleiser, M Heckler, AF Kolb, EW AF Gleiser, M Heckler, AF Kolb, EW TI Modeling thermal fluctuations: phase mixing and percolation SO PHYSICS LETTERS B LA English DT Article DE nonequilibrium dynamics; symmetry restoration; percolation; scalar field dynamics ID SUBCRITICAL BUBBLES; TRANSITIONS AB We consider the nonequilibrium dynamics of a real scalar held in a double-well potential. The system is initially prepared in one well and coupled to a thermal bath. Using a simple analytical model, we compute the equilibrium fraction of the total volume in each phase as a function of the parameters of the potential. We also show how complete phase mixing, i.e. symmetry restoration, is related to percolation, which is dynamically driven by domain instability. Our method describes quantitatively recent numerical results, and is applicable to systems in the Ising universality class. (C) 1997 Published by Elsevier Science B.V. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Gleiser, M (reprint author), DARTMOUTH COLL,DEPT PHYS & ASTRON,HANOVER,NH 03755, USA. RI Heckler, Andrew/A-7291-2010 OI Heckler, Andrew/0000-0001-5494-7855 NR 13 TC 17 Z9 18 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-2693 J9 PHYS LETT B JI Phys. Lett. B PD JUL 17 PY 1997 VL 405 IS 1-2 BP 121 EP 125 DI 10.1016/S0370-2693(97)00621-7 PG 5 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XM606 UT WOS:A1997XM60600019 ER PT J AU Fok, MC Moore, TE AF Fok, MC Moore, TE TI Ring current modeling in a realistic magnetic field configuration SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STORM AB A 3-dimensional kinetic model has been developed to study the dynamics of the storm time ring current in a dipole magnetic field. In this paper, the ring current model is extended to include a realistic, time-varying magnetic field model. The magnetic field is expressed as the cross product of the gradients of two Euler potentials and the bounce-averaged particle drifts are calculated in the Euler potential coordinates. A dipolarization event is modeled by collapsing a tail-like magnetosphere to a dipole-like configuration. Our model is able to simulate the sudden enhancements in the ring current ion fluxes and the corresponding ionospheric precipitation during the substorm expansion. RP Fok, MC (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,UNIV SPACE RES ASSOC,ES83,HUNTSVILLE,AL 35812, USA. RI Moore, Thomas/D-4675-2012; Fok, Mei-Ching/D-1626-2012 OI Moore, Thomas/0000-0002-3150-1137; NR 15 TC 59 Z9 58 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 JUL 15 PY 1997 VL 24 IS 14 BP 1775 EP 1778 DI 10.1029/97GL01255 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XL837 UT WOS:A1997XL83700015 ER PT J AU Fu, LL Chao, Y AF Fu, LL Chao, Y TI The sensitivity of a global ocean model to wind forcing: A test using sea level and wind observations from satellites and operational wind analysis SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Investigated in this study is the response of a global ocean general circulation model to forcing provided by two wind products: operational analysis at 1000 mb from the National Center for Environmental Prediction (NCEP); observations made by the ERS-1 radar scatterometer. The sea level simulated by the model using the two wind fields is compared to the observations made by the TOPEX/POSEIDON radar altimeter for a period of two years. The focus of the analysis is placed on the large-scale ocean variabilities at mid and high latitudes. The sea level simulations resulting from the ERS-1 wind are found to be closer to the TOPEX/POSEIDON observations over most of the global oceans. However, after being scaled down in wind stress by 50 %, the NCEP wind becomes consistent with the ERS-1 wind in driving the ocean model to simulate the seasonal and intraseasonal sea level variabilities. The sensitivity of the model to wind forcing at the investigated scales is particularly pronounced in the Southern Ocean, where the sea level variabilities are primarily caused by large-scale barotropic motions driven by wind. Other areas of appreciable sensitivity to wind forcing include the western and central North Pacific, the western subtropical South Pacific and the South Indian Ocean. The result of the study has demonstrated the sensitivity of a widely-used ocean model to the quality of wind forcing, as well as the synergistic use of two satellite sensors in the study of ocean dynamics. RP Fu, LL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 21 TC 10 Z9 11 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 JUL 15 PY 1997 VL 24 IS 14 BP 1783 EP 1786 DI 10.1029/97GL01532 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XL837 UT WOS:A1997XL83700017 ER PT J AU Arian, E AF Arian, E TI On the coupling of aerodynamic and structural design SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article AB The symbol of the Hessian for a static aeroelastic optimization model problem is analyzed for the optimization of a plate's shape and rigidity distribution with respect to a given cost function. The flow is modeled by the small-disturbance full-potential equation and the structure is modeled by an isotropic (von Karman) plate equation. The cost function consists of both aerodynamic and structural terms. In the new analysis the symbol of the cost function Hessian near the minimum is approximated for the nonsmooth error components in the shape and rigidity. The result indicates that the system can be decoupled to two single discipline subminimization problems which will effectively converge to the multidisciplinary optimal solution. The result also indicates that the structure part in the Hessian is well conditioned while the aerodynamic part is ill conditioned. Applications of the result to optimization strategies are discussed and demonstrated numerically. (C) 1997 Academic Press. RP Arian, E (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681, USA. NR 22 TC 5 Z9 6 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD JUL 15 PY 1997 VL 135 IS 1 BP 83 EP 96 DI 10.1006/jcph.1997.5741 PG 14 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA XL997 UT WOS:A1997XL99700007 ER PT J AU Hagan, D Rogers, D Friehe, C Weller, R Walsh, E AF Hagan, D Rogers, D Friehe, C Weller, R Walsh, E TI Aircraft observations of sea surface temperature variability in the tropical Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID PLANETARY BOUNDARY-LAYER; OCEAN; CONVECTION AB During the southern summer of 1992-1993, a series of aircraft observations of sea surface temperature (SST) were obtained over the tropical western Pacific ocean as part of the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Down-looking thermal infrared (10-11 mu m) observations of the sea surface, coincident with uplooking infrared observations (9-11 mu m) and meteorological measurements from the same aircraft platform are described. The data are compared with buoy and ship-based measurements of SST, and show good agreement. The radiometric measurements, corrected for surface emissivity effects, show diurnal warming which precedes warming measured by sub-surface buoy sensors. Mesoscale surface features are also seen which have spatial dimensions similar to those of tropical cloud clusters in the wavelength range of 1-100 km. Significant horizontal temperature gradients of 1 degrees C occur in less than 10 km. On some days, the gradients can be directly related to precipitation. Clouds appear to create 'imprints' of their structure on the ocean surface by shielding incoming solar radiation, consistent with calculations of such a process using a one-dimensional ocean mixed layer model. Measurements of the height of the well-mixed region of the boundary layer and air potential temperature show a positive relation with increasing SST. An increase in buoyancy flux with increasing SST is identified with mesoscale sub-cloud processes in fair weather conditions, and suggests that SST maxima on scales of 10-50 km enhance the transfer of moisture in the boundary layer by natural convection processes. C1 UNIV CALIF IRVINE,IRVINE,CA 92717. UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA 92093. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. WOODS HOLE OCEANOG INST,WOODS HOLE,MA 02543. RP Hagan, D (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 18 TC 13 Z9 13 U1 0 U2 0 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 JUL 15 PY 1997 VL 102 IS C7 BP 15733 EP 15747 DI 10.1029/97JC00469 PG 15 WC Oceanography SC Oceanography GA XL452 UT WOS:A1997XL45200014 ER PT J AU Elfouhaily, T Chapron, B Katsaros, K Vandemark, D AF Elfouhaily, T Chapron, B Katsaros, K Vandemark, D TI A unified directional spectrum for long and short wind-driven waves SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID GENERATED GRAVITY-WAVES; SEA-SURFACE SLOPE; DRAG COEFFICIENTS; CAPILLARY-GRAVITY; EQUILIBRIUM RANGE; WATER-SURFACE; OCEAN WAVES; AIR-FLOW; STRESS; MODEL AB Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jahne and Riemer [1990] and Hara et al. [1994] data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips [1985] and Kitaigorodskii [1973] at the high wavenumbers. The;omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results. C1 NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,WALLOPS ISL,VA 23337. RP Elfouhaily, T (reprint author), IFREMER,CTR BREST,BP 70,F-29280 PLOUZANE,FRANCE. RI Chapron, Bertrand/O-6527-2015 NR 65 TC 464 Z9 490 U1 6 U2 39 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 JUL 15 PY 1997 VL 102 IS C7 BP 15781 EP 15796 DI 10.1029/97JC00467 PG 16 WC Oceanography SC Oceanography GA XL452 UT WOS:A1997XL45200018 ER PT J AU Su, CH Sha, YG Lehoczky, SL Szofran, FR Gillies, DC Cobb, SD AF Su, CH Sha, YG Lehoczky, SL Szofran, FR Gillies, DC Cobb, SD TI Crystal growth of selected II-VI semiconducting alloys by directional solidification .1. Ground-based experiments SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID HGCDTE ALLOYS; THERMAL-CONDUCTIVITY; PHASE-DIAGRAM; HEAT-TRANSFER; BRIDGMAN; MELTS AB A series of Hg0.84Zn0.16Te crystal ingots have been grown from pseudobinary melts by the Bridgman-Stockbarger type directional solidification using a Marshall Space Flight Center/Space Science Laboratory heat-pipe furnace and the ground control experiment laboratory furnace of the crystal growth furnace which was flown on the first United States Microgravity Mission. A number of translation rates and a series of hot- and cold-zone temperatures were employed to assess the influence of growth parameters on the crystal properties for the purpose of optimizing the in-flight growth conditions. C1 UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. UNIV ALABAMA,BIRMINGHAM,AL 35294. RP Su, CH (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. NR 24 TC 2 Z9 2 U1 2 U2 2 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 JUL 15 PY 1997 VL 32 IS 14 BP 3765 EP 3768 DI 10.1023/A:1018619522208 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA XM074 UT WOS:A1997XM07400020 ER PT J AU Singh, J Jerman, G Poorman, R Bhat, BN Kuruvilla, AK AF Singh, J Jerman, G Poorman, R Bhat, BN Kuruvilla, AK TI Mechanical properties and microstructural stability of wrought, laser, and electron beam glazed NARloy-Z alloy at elevated temperatures SO JOURNAL OF MATERIALS SCIENCE LA English DT Article AB Microstructure of wrought, laser and electron beam processed NARloy-Z (Cu-3wt% Ag-0.5 wt% Zr) was investigated for thermal stability at elevated temperatures 539-760 degrees C (1100 to 1400 degrees F) up to 94 h. Optical and scanning electron microscopy and electron probe microanalysis were employed for studying microstructural evolution and kinetics of precipitation. Grain boundary precipitation and precipitate free zones (PFZs) were observed in the wrought alloy after exposing to temperatures above 605 degrees C (1120 degrees F). Fine-grained microstructure observed in the laser and electron beam (EB) processed NARloy-Z was much more stable at elevated temperatures. Tensile properties of laser and EB glazed NARloy-Z can be tailored by giving suitable heat treatments and maintaining the same strength with increased ductility. Microstructural changes correlated well with hardness measurements and mechanical properties. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,IIT RES INST,HUNTSVILLE,AL 35812. RP Singh, J (reprint author), PENN STATE UNIV,APPL RES LAB,UNIVERSITY PK,PA 16804, USA. NR 7 TC 10 Z9 10 U1 1 U2 2 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 JUL 15 PY 1997 VL 32 IS 14 BP 3891 EP 3903 DI 10.1023/A:1018604513547 PG 13 WC Materials Science, Multidisciplinary SC Materials Science GA XM074 UT WOS:A1997XM07400037 ER PT J AU Bansal, NP AF Bansal, NP TI Mechanical behavior of silicon carbide fiber-reinforced strontium aluminosilicate glass-ceramic composites SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE celsian; ceramic composite; ceramic fiber; interface; mechanical properties ID MATRIX COMPOSITES; STRENGTH; FRACTURE AB Unidirectional CVD SiC fiber-reinforced SrO . Al2O3 . 2SiO(2) (SAS) glass-ceramic matrix composites have been fabricated by hot pressing. Both carbon-rich surface coated SCS-6 and uncoated SCS-0 fibers were used as reinforcements. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase observed in the matrix from X-ray diffraction. During three point flexure testing of composites, a test span to thickness ratio of greater than or equal to 25 was necessary to avoid delamination. Strong and tough SCS-6/SAS composites having a first matrix cracking stress of similar to 300 MPa and an ultimate strength of similar to 825 MPa were fabricated. No chemical reaction between the SCS-6 fibers and the matrix was observed after high temperature processing. The SCS-0/SAS composite, having a fiber volume fraction of 0.24, exhibited a first matrix cracking stress of similar to 231 +/- 20 MPa and ultimate strength of 265 +/- 17 MPa indicating a somewhat limited improvement over the monolithic material. From fiber push-out tests, the fiber/matrix debonding stress (tau(debond)) and frictional sliding stress (tau(friction)) in the SCS-6/SAS system were evaluated to be similar to 6.7 +/- 2.3 and 4.3 +/- 0.6 MPa, respectively, indicating a weak interface. However, for the SCS-0/SAS composite, somewhat higher values of similar to 17.5 +/- 2.7 MPa for tau(debond) and 11.3 +/- 1.6 MPa for tau(friction) respectively, were observed; some of the fibers were strongly bonded to the matrix and could not be pushed out. Examination of fracture surfaces revealed limited short pull-out lengths of SCS-0 fibers. The applicability of theoretical models in predicting the values of first matrix cracking stress and ultimate strength of these composites has been investigated. (C) 1997 Elsevier Science S.A. RP Bansal, NP (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 33 TC 16 Z9 16 U1 2 U2 11 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD JUL 15 PY 1997 VL 231 IS 1-2 BP 117 EP 127 DI 10.1016/S0921-5093(97)00082-8 PG 11 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA XN044 UT WOS:A1997XN04400016 ER PT J AU Wang, Y Turner, EL AF Wang, Y Turner, EL TI Cosmological constant and advanced gravitational wave detectors SO PHYSICAL REVIEW D LA English DT Article ID COMPACT BINARIES; NEUTRON-STAR; PARAMETERS; RADIATION AB Interferometric gravitational wave detectors could measure the frequency sweep of a binary inspiral (characterized by its chirp mass) to high accuracy. The observed chirp mass is the intrinsic chirp mass of the binary source multiplied by (1+z), where z is the redshift of the source. Assuming a nonzero cosmological constant, we compute the expected redshift distribution of observed events for an advanced LIGO detector. We find that the redshift distribution has a robust and sizable dependence on the cosmological constant; the data from advanced LIGO detectors could provide an independent measurement of the cosmological constant. C1 PRINCETON UNIV OBSERV,PRINCETON,NJ 08544. RP Wang, Y (reprint author), NASA,FERMILAB ASTROPHYS CTR,FNAL,BATAVIA,IL 60510, USA. RI Wang, Yun/B-5724-2011; Turner, Edwin/A-4295-2011 OI Wang, Yun/0000-0002-4749-2984; NR 10 TC 8 Z9 8 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD JUL 15 PY 1997 VL 56 IS 2 BP 724 EP 729 DI 10.1103/PhysRevD.56.724 PG 6 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XM240 UT WOS:A1997XM24000017 ER PT J AU Detweiler, S Brown, LH AF Detweiler, S Brown, LH TI Post-Minkowski expansion of general relativity SO PHYSICAL REVIEW D LA English DT Article ID GRAVITATIONAL-RADIATION; NEWTONIAN GENERATION; WAVES; ORDER AB A post-Minkowski approximation of general relativity is. described as a power series expansion in G, Newton's gravitational constant. Material sources are hidden behind boundaries, and only the vacuum Einstein equations are considered. An iterative procedure is outlined which, in one complete step, takes any approximate solution of the Einstein equations and produces a new approximation which has the error decreased by a factor of G. Each step in the procedure consists of three parts: first the equations of motion are used to update the trajectories of the boundaries; then the field equations are solved using a retarded Green function for Minkowski space; finally, a gauge transformation is performed which makes the geometry well behaved at future null infinity. Differences between this approach to the Einstein equations and similar ones are that we use a general (nonharmonic) gauge and formulate the procedure in a constructive manner which emphasizes its suitability for implementation on a computer. C1 JET PROP LAB, PASADENA, CA USA. RP UNIV FLORIDA, DEPT PHYS, GAINESVILLE, FL 32605 USA. RI Detweiler, Steven/H-3015-2012 NR 17 TC 3 Z9 3 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2470-0010 EI 2470-0029 J9 PHYS REV D JI Phys. Rev. D PD JUL 15 PY 1997 VL 56 IS 2 BP 826 EP 841 DI 10.1103/PhysRevD.56.826 PG 16 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XM240 UT WOS:A1997XM24000026 ER PT J AU Lewis, MS AF Lewis, MS TI Safety program underway SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter RP Lewis, MS (reprint author), NASA,LANGLEY RES CTR,AVIAT SAFETY PROGRAM OFF,HAMPTON,VA 23665, 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 JUL 14 PY 1997 VL 147 IS 2 BP 6 EP 6 PG 1 WC Engineering, Aerospace SC Engineering GA XK490 UT WOS:A1997XK49000002 ER PT J AU Gierlinski, M Zdziarski, AA Done, C Johnson, WN Ebisawa, K Ueda, Y Haardt, F Philips, BF AF Gierlinski, M Zdziarski, AA Done, C Johnson, WN Ebisawa, K Ueda, Y Haardt, F Philips, BF TI Simultaneous X-ray and gamma-ray observations of Cyg X-1 in the hard state by Ginga and OSSE SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; stars, individual, Cygnus X-1; gamma-rays, observations; gamma-rays, theory; X-rays, stars ID RELATIVISTIC THERMAL PLASMAS; ACTIVE GALACTIC NUCLEI; PAIR PRODUCTION; ORBITAL INCLINATION; ACCRETION DISKS; COMPACT SOURCES; EMISSION; SPECTRUM AB We present four X-ray/gamma-ray spectra of Cyg X-1 observed in the hard ('low') state simultaneously by Ginga and GRO OSSE on 1991 June 6. The four spectra have almost identical spectral form but vary in normalization within a factor of 2. The 3-30 keV Ginga spectra are well represented by power laws with an energy spectral index of alpha similar to 0.6 and a Compton reflection component including a fluorescent Fe K alpha corresponding to the solid angle of the reflector of similar to 0.3 x 2 pi. These spectra join smoothly on to the OSSE range (greater than or equal to 50 keV) and are then cut off above similar to 150 keV. The overall spectra can be modelled by repeated Compton scattering in a mildly relativistic, thermal plasma with an optical depth of tau similar to 1. However, the high-energy cut-off is steeper than that due to single-temperature thermal Comptonization, It can be described by a superposition of dominant tau similar to 1-2, thermal emission at kT similar to 100 keV and a Wien-like component from an optically thick plasma at kT similar to 50 keV. The X-ray spectra do not show the presence of the anisotropy break required if thermal Compton scattering takes place in a corona above a cold disc, Also, the flat spectral index shows that the plasma is soft-photon starved, i.e., the luminosity in incident soft X-ray seed photons is very much less than that in the hard X-rays. Furthermore, the observed solid angle of the reflector is significantly less than 2 pi. These facts taken together strongly rule out a disc-corona geometry, Rather, the observed spectra are consistent with a geometry in which the cold accretion disc (which both supplies the seed soft X-rays and reflects hard X-rays) only exists at large radii, while the Comptonizing hot plasma is located in an inner region with no cold disc, This hot plasma consists of pure e(+/-) pairs if the source size is similar to 5 Schwarzschild radii or it also contains protons if the size is larger. C1 NICHOLAS COPERNICUS ASTRON CTR,PL-00716 WARSAW,POLAND. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV DURHAM,DEPT PHYS,DURHAM DH1 3LE,ENGLAND. USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. GOTHENBURG UNIV,DEPT ASTRON & ASTROPHYS,S-41296 GOTHENBURG,SWEDEN. UNIV SPACE RES ASSOC,WASHINGTON,DC 20024. RP Gierlinski, M (reprint author), JAGIELLONIAN UNIV,ASTRON OBSERV,ORLA 171,PL-30244 KRAKOW,POLAND. RI Johnson, Neil/G-3309-2014; done, chris/D-4605-2016; OI done, chris/0000-0002-1065-7239; Gierlinski, Marek/0000-0001-9149-3514 NR 42 TC 228 Z9 229 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 JUL 11 PY 1997 VL 288 IS 4 BP 958 EP 964 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL795 UT WOS:A1997XL79500011 ER PT J AU Fields, BD Mathews, GJ Schramm, DN AF Fields, BD Mathews, GJ Schramm, DN TI Halo white dwarfs and the hot intergalactic medium SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, evolution; galaxies, halos; galaxies, interactions; galaxies, stellar content; intergalactic medium; white dwarfs ID DARK-MATTER; GALACTIC-HALO; LUMINOSITY FUNCTION; GALAXY; MASS; CONSTRAINTS; OBJECTS; STARS; SUPERNOVAE; EVOLUTION AB We present a schematic model for the formation of baryonic galactic halos and hot gas in the Local Group and the intergalactic medium. We follow the dynamics, chemical evolution, heat flow, and gas flows of a hierarchy of scales, including protogalactic clouds, galactic halos, and the Local Group itself. Within this hierarchy the Galaxy is built up via mergers of protogalactic fragments. Hot and cold gas components are distinguished, with star formation occurring in cold molecular cloud cores, while stellar winds, supernovae, and mergers convert cold gas into a hot intercloud medium. We find that early bursts of star formation lead to a large population of remnants (mostly white dwarfs) that would presently reside in the halo and contribute to the dark component observed in the microlensing experiments. The starbursts and mergers heat the gas and lead to powerful evaporation-driven winds. This outflow is crucial, as it drives gas out of the clouds and eventually into the intergalactic medium. The model thus suggests that most microlensing objects could be white dwarfs (m similar to 0.5 M-circle dot), which comprise a significant fraction of the halo mass. Furthermore, the Local Group could have a component of metal-rich hot gas similar to, although less than, that observed in larger clusters. We discuss the known constraints on such a scenario and show that all local observations can be satisfied with present data in this model. The most stringent constraint comes from the metallicity distribution in the halo. The best-fit model has a halo that is 40% baryonic, with an upper limit of 77%. Our model predicts that the hot intragroup gas has a total luminosity 1.5 x 10(40) ergs(-1) and a temperature of 0.26 keV, just at the margin of detectability. Improved X-ray data could provide a key constraint on any remnant component in the halo. C1 UNIV CHICAGO,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Fields, BD (reprint author), UNIV NOTRE DAME,DEPT PHYS,NOTRE DAME,IN 46635, USA. NR 60 TC 39 Z9 39 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1997 VL 483 IS 2 BP 625 EP 637 DI 10.1086/304291 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL759 UT WOS:A1997XL75900009 ER PT J AU Howard, AM Kulsrud, RM AF Howard, AM Kulsrud, RM TI The evolution of a primordial galactic magnetic field SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, evolution; galaxies, kinematics and dynamics; galaxies, magnetic fields; MHD ID INFLATION AB We consider the hypothesis that galactic magnetic fields are primordial. We also discuss the various objections to this hypothesis. To test this hypothesis properly we assume that there was a magnetic field present in the galactic plasma before the galaxy formed and explore how such a field would evolve assuming a specific model for the interstellar medium in the galactic disk. After the galactic disk formed, the lines of force thread through it and remain connected to the external cosmic medium. They enter through one side of the disk, proceed horizontally a distance l in the disk, and then leave through the other side. We find that the lines of force are stretched by the differential rotation of the galactic disk, amplifying the toroidal component of the field and increasing l. When the magnetic field is strong enough, it produces ambipolar velocities that try to lift the line out of the galactic disk but in opposite directions on different parts of the line. The result is that, instead of the line being expelled from the disk, its horizontal length I is shortened, both in the radial and in the toroidal direction. This leads to a reduction of the rate of horizontal stretching and finally a reduction in the magnetic field strength. After a sufficient time, the magnetic field at all points goes through this reduction and the field strength approaches a universal function of time. This function is slowly decreasing and only depends on the ambipolar properties of the interstellar medium. At any given time the magnetic field is toroidal and has the same strength everywhere. On the other hand, it turns out that its direction varies rapidly with radius, changing sign every 100 parsecs or so. However, if the initial cosmic magnetic field is not uniform, the areas of one sign of the toroidal field dominate over the other. The resulting field has a net Faraday rotation. If such a field were observed with low resolution in an external galaxy, then the field would appear toroidal in between the spiral arms. The spiral density wave would turn it so that the lines appear to trace out the spiral arm, although the apparent lines really are the sum of pieces of magnetic lines as they cross the disk. They do not necessarily extend very far along the arms. We contend that this model of the magnetic field, which arises naturally from a primordial origin, can fit the observations as well as other models for the magnetic field, such as those arising from the mean field dynamo theory. Finally, because the field lines are topologically threaded through the disk, they cannot be expelled from the disk. This counters the objection against the primordial origin, namely that such a field could not survive very long in the galaxy. C1 PRINCETON UNIV OBSERV, PRINCETON, NJ 08544 USA. RP Howard, AM (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 29 TC 31 Z9 31 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1997 VL 483 IS 2 BP 648 EP 665 DI 10.1086/304262 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL759 UT WOS:A1997XL75900011 ER PT J AU Leighly, KM OBrien, PT Edelson, R George, IM Malkan, MA Matsuoka, M Mushotzky, RF Peterson, BM AF Leighly, KM OBrien, PT Edelson, R George, IM Malkan, MA Matsuoka, M Mushotzky, RF Peterson, BM TI X-ray observations of the broad-line radio galaxy 3C 390.3 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (3C 390.3); X-rays, galaxies ID VARIABILITY; SPECTRUM; 3C-390.3 AB We present the data and preliminary analysis for a series of 90 ROSAT HRI and two ASCA observations of the broad-line radio galaxy 3C 390.3. These data were obtained during the period 1995 January 2 to October 6 as part of an intensive multiwavelength monitoring campaign. The soft X-ray flux in the ROSAT band varied by nearly a factor of 4 during the campaign, and the well-resolved Light curve shows several distinct features. Several large-amplitude flares were observed, including one in which the flux increased by a factor of about 3 in 12 days. Periods of reduced variability were also seen, including one nearly 30 days long. While the HRI hardness ratio decreased significantly, it is apparently consistent with that expected from the detector during the monitoring period. The two ASCA observations were made on 1995 January 15 and May 5. The 0.5-10.0 keV spectra can be described adequately by an absorbed power law. There is no evidence for a soft excess in the ASCA spectra, indicating that the ROSAT HRI is sampling variability of the X-ray power law. A broad iron line was observed in a longer 1993 ASCA observation, and while there is statistical evidence that the line is present in the 1995 spectra, it could not be resolved clearly. There is evidence, significant at greater than 90% confidence, that the photon index changed from 1.7 to 1.82 while the flux increased by 63%. The spectral change can be detected in the spectra below 5 keV, indicating that the origin cannot be a change in the ratio of reflected to power-law flux. A compilation of results from ASCA and Ginga observations show that on long timescales, the intrinsic photon index is correlated with the flux. C1 RIKEN,COSM RADIAT LAB,WAKO,SAITAMA 351,JAPAN. UNIV LEICESTER,DEPT PHYS & ASTRON,LEICESTER LE1 7RH,LEICS,ENGLAND. UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90024. OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210. NR 26 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1997 VL 483 IS 2 BP 767 EP 773 DI 10.1086/304276 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL759 UT WOS:A1997XL75900020 ER PT J AU Sambruna, RM George, IM Madejski, G Urry, CM Turner, TJ Weaver, KA Maraschi, L Treves, A AF Sambruna, RM George, IM Madejski, G Urry, CM Turner, TJ Weaver, KA Maraschi, L Treves, A TI An X-ray absorption feature in the BL Lacertae object H1426+428 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, individual (H1426+428); line, identification; radiation mechanisms, nonthermal; X-rays, galaxies ID EXTRAGALACTIC RADIO-SOURCES; PKS 2155-304; SPECTRAL PROPERTIES; BLAZARS; EXOSAT; HOT AB We report the presence of an absorption feature in the X-ray spectrum of the BL Lacertae object H1426+428 (z = 0.129). H1426+428 was observed at three separate epochs with BBXRT, ROSAT, and ASCA. In the BBXRT spectrum an absorption feature is clearly present at similar to 0.66 keV, consistent with absorption by highly ionized oxygen. The phenomenological model that best describes the absorption feature is an inverted Gaussian with width FWHM less than or similar to 43,000 km s(-1). This feature is not present in the ROSAT and ASCA data, both taken when the source flux was fainter by a factor approximate to 2. Instead, these data show some evidence for absorption edge(s) at lower energies. These results are consistent with partially ionized, low-density gas surrounding the central engine of H1426+428. As a first approximation the X-ray continuum can be described with a power law with photon index Gamma approximate to 2. The BBXRT and ASCA data are better fitted with a convex (downward-curved) broken power law. The exact shape of the continuum depends on the assumed profile for the absorption feature. We show that, using a specific warm absorber to fit the data, there is no need for a continuum model more complex than a single power law. C1 NASA,GODDARD SPACE FLIGHT CTR,USRA,GREENBELT,MD 20771. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. JOHNS HOPKINS UNIV,BALTIMORE,MD 21218. OSSERV ASTRON BRERA,MILAN,ITALY. UNIV MILAN,MILAN,ITALY. RP Sambruna, RM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,NRC,CODE 662,GREENBELT,MD 20771, USA. RI Urry, Claudia/G-7381-2011 OI Urry, Claudia/0000-0002-0745-9792 NR 41 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 JUL 10 PY 1997 VL 483 IS 2 BP 774 EP 782 DI 10.1086/304270 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL759 UT WOS:A1997XL75900021 ER PT J AU Chan, KW Moseley, SH Casey, S Harrington, JP Dwek, E Loewenstein, R Varosi, F Glaccum, W AF Chan, KW Moseley, SH Casey, S Harrington, JP Dwek, E Loewenstein, R Varosi, F Glaccum, W TI Dust composition, energetics, and morphology of the galactic center SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; Galaxy, center; infrared, ISM, lines and bands ID CARBON-RICH STARS; IONIZED-GAS; OPTICAL-PROPERTIES; PLANETARY-NEBULAE; SILICATE GRAINS; CENTRAL PARSEC; SAGITTARIUS-A; NEUTRAL GAS; BLACK-HOLE; GALAXY AB Spectra at 16-45 mu m of several regions within the central 80 '' of the Galaxy have been obtained at 20 '' resolution using the Goddard Cryogenic Grating Spectrometer No. 2 on the Kuiper Airborne Observatory. A broad band of excess emission extending from 24 to 45 mu m is present in the spectra at positions covering the ''tongue'' and the inner edge of the circumnuclear disk. A similar dust emission feature has been observed in some carbon-rich evolved stars and in a nitrogen-rich evolved massive star. The observations reported here are the first detection of this dust emission feature in the interstellar medium. We find that the dust properties in the ''tongue'' and the inner edge of the circumnuclear disk are different from the dust in the cavity, which shows no evidence for the similar to 30 mu m feature in its spectrum. The relation between the tongue feature and the inner disk has been a subject of considerable debate, with suggestions that the tongue material is either falling in or has been expelled from the Galactic center. Our observations suggest that if there is a physical connection between the two regions, then the tongue material is more likely falling in toward the Galactic center. Two kinds of dust components and corresponding heating sources are argued to be responsible for the dust emission in the Galactic center: (1) the hot dust component (140-300 K) heated by IRS sources that are distributed throughout the cavity; and (2) the warm dust component (60-90 K) heated by a He I emission-line star cluster that give rise to a local interstellar radiation field that heats the dust in the central several parsecs. We find a lower limit of similar to 1 x 10(6) L. for the He I emission-line star cluster. Finally, we find that the line-of-sight extinction across the cavity is not uniform. It is diminished and roughly constant in the northeastern side of the cavity but increases to the southwestern side. Based on this result, together with the 1995 study by Zylka et al. who found that there is a cold dust component along the line of sight to the central 30 '' of the Galaxy, we propose that there is a cool dust envelope with nonuniform distribution covering the cavity of the Galactic center. C1 NASA, GODDARD SPACE FLIGHT CTR, STX, GREENBELT, MD 20771 USA. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. UNIV CHICAGO, YERKES OBSERV, WILLIAMS BAY, WI 53191 USA. APPL RES CORP, LANDOVER, MD 20785 USA. RP Chan, KW (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, CODE 685, GREENBELT, MD 20771 USA. RI Moseley, Harvey/D-5069-2012 NR 66 TC 23 Z9 23 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1997 VL 483 IS 2 BP 798 EP 810 DI 10.1086/304252 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL759 UT WOS:A1997XL75900024 ER PT J AU Godon, P AF Godon, P TI Advection in accretion disk boundary layers SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, symbiotic; methods, numerical; stars, pre-main-sequence ID MAGNETOCENTRIFUGALLY DRIVEN FLOWS; YOUNG STARS; EMISSION; CYGNI; JETS AB Recent numerical simulations of accretion disk boundary layers have shown qualitatively the importance of advected energy in the inner region of the disk. In this short paper we present quantitative results of advective boundary layers in the optically thick regime. Numerical results are obtained for various systems, by means of a one-dimensional time-dependent numerical code. At high accretion mass rates, (M) over dot approximate to 10(-4) M. yr(-1), or low values of the viscosity parameter, alpha approximate to 0.001-0.01 (characteristic of FU Orionis systems and some symbiotic stars), the optical thickness in the inner part of the disk becomes very large (tau much greater than 1). The disk, unable to cool efficiently, becomes geometrically thick (H/r approximate to 0.5). The energy dissipated in the dynamical boundary layer is radiated outward to larger radii and advected into the star. The boundary-layer luminosity is only a fraction of its expected value; the rest of the energy is advected into the star. The fraction of the advected energy is zeta = L-adv/L-acc approximate to 0.1 in symbiotic stars (accretion onto a low-mass main-sequence star) and zeta approximate to 0.2 in FU Ori systems (accretion onto a pre-main sequence star). RP Godon, P (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STN,PASADENA,CA 91109, USA. NR 38 TC 9 Z9 9 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 JUL 10 PY 1997 VL 483 IS 2 BP 882 EP 886 DI 10.1086/304266 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL759 UT WOS:A1997XL75900032 ER PT J AU Sion, EM Cheng, FH Szkody, P Huang, M Provencal, J Sparks, W Abbott, B Hubeny, I Mattei, J Shipman, H AF Sion, EM Cheng, FH Szkody, P Huang, M Provencal, J Sparks, W Abbott, B Hubeny, I Mattei, J Shipman, H TI Hubble Space Telescope GHRS spectroscopy of U Geminorum during two outbursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; novae, cataclysmic variables; stars, emission-line, Be; stars, individual (U Germinorum); ultraviolet, stars ID SS-CYGNI; CATACLYSMIC VARIABLES; MULTIWAVELENGTH CAMPAIGN; DWARF NOVAE; IUE; SPECTRA; MODEL; DISK AB We obtained Hubble Space Telescope Goddard High-Resolution Spectrograph medium-resolution (G160M grating) phase-resolved spectroscopic observations of the prototype dwarf nova U Geminorum during different stages of two different outbursts. The spectral wavelength ranges were centered on three different line regions: N V (1238 Angstrom), 1242 Angstrom, Si III (1300 Angstrom), and He II (1640 Angstrom). The spectrum corresponding to the early decline phase of outburst 1 is essentially featureless except for weak N V absorption and narrow interstellar lines, while the spectrum at the peak of outburst 2 reveals broad emission peaks separated by narrow central absorption. The double-peaked emission-line profile structure with low-velocity central absorption seen in the second outburst suggests a disk origin, but the emission velocity widths appear narrower than the widths of the optical disk emission features. We interpret the high-excitation emission lines, with central absorption below the continuum, to be due to photoionized material (coronal?) above the disk plane with the thickened outer disk absorbing the boundary layer or inner disk radiation. The possibility of a wind origin for the profiles is also discussed, as well as the possibility of an ejected optically thin shell. The N V absorption velocity versus orbital phase traces the motion of the white dwarf, but the He II absorption velocity appears to deviate from the white dwarf motion. We present the results of synthetic accretion disk spectral fitting to the data of both outbursts and derive accretion rates for the two outbursts of 6 x 10(-10) M. yr(-1) and 2 x 10(-9) M. yr(-1). Implications are discussed. C1 UNIV WASHINGTON,DEPT ASTRON,SEATTLE,WA 98195. UNIV DELAWARE,DEPT PHYS & ASTRON,NEWARK,DE 19716. LOS ALAMOS NATL LAB,NUCL HYDRODYNAM APPLICAT GRP,LOS ALAMOS,NM 87545. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. AMER ASSOC VARIABLE STAR OBSERVERS,CAMBRIDGE,MA 02138. RP Sion, EM (reprint author), VILLANOVA UNIV,DEPT ASTRON & ASTROPHYS,VILLANOVA,PA 19085, USA. NR 30 TC 8 Z9 8 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 JUL 10 PY 1997 VL 483 IS 2 BP 907 EP 912 DI 10.1086/304269 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL759 UT WOS:A1997XL75900035 ER PT J AU Charpinet, S Fontaine, G Brassard, P Chayer, P Rogers, FJ Iglesias, CA Dorman, B AF Charpinet, S Fontaine, G Brassard, P Chayer, P Rogers, FJ Iglesias, CA Dorman, B TI A driving mechanism for the newly discovered class of pulsating subdwarf B stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, interiors; stars, oscillations; subdwarfs ID DA WHITE-DWARFS; OPACITIES AB We present new calculations that strongly reinforce the idea-originally proposed by Charpinet et al.-that pulsation modes are driven through an opacity bump due to a local enhancement of the iron abundance in the envelopes of sdB stars. Our improved models incorporate nonuniform iron abundance distributions obtained through the condition of diffusive equilibrium between gravitational settling and radiative levitation. They also include special Rosseland opacity tables that take into account the large variations of the iron abundance about the cosmic value that are predicted by equilibrium radiative levitation theory. For representative models with M = 0.48 M. and log g = 5.8, we find strong instabilities for low-order radial and nonradial (p and f) pulsation modes in the range 36,500 K greater than or similar to T-eff greater than or similar to 29,000 K. The four pulsating sdB stars currently known all have effective temperatures in that range. In addition, one of our models with T-eff = 34,000 K has a band of unstable modes with periods in the range 116-195 s, in excellent agreement with those of the known pulsators. We therefore claim that our proposed iron bump mechanism provides a natural explanation for the instabilities found in the newly discovered class of pulsating sdB stars. C1 UNIV CALIF BERKELEY,CTR EUV ASTROPHYS,BERKELEY,CA 94720. LAWRENCE LIVERMORE NATL LAB,LIVERMORE,CA 94550. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903. RP Charpinet, S (reprint author), UNIV MONTREAL,DEPT PHYS,CP 6128,MONTREAL,PQ H3C 3J7,CANADA. OI Charpinet, Stephane/0000-0002-6018-6180 NR 22 TC 197 Z9 197 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1997 VL 483 IS 2 BP L123 EP L126 DI 10.1086/310741 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL756 UT WOS:A1997XL75600013 ER PT J AU Skibo, JG Johnson, WN Kurfess, JD Kinzer, RL Jung, G Grove, JE Purcell, WR Ulmer, MP Gehrels, N Tueller, J AF Skibo, JG Johnson, WN Kurfess, JD Kinzer, RL Jung, G Grove, JE Purcell, WR Ulmer, MP Gehrels, N Tueller, J TI OSSE observations of the soft gamma-ray continuum from the galactic plane at longitude 95 degrees SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; gamma rays, observations; ISM, general; supernova remnants ID SUPERNOVA REMNANT; EMISSION; RADIATION; GALAXY; 4U-2129+47; POWER AB We present the results of OSSE observations of the soft gamma-ray continuum emission from the Galactic plane at longitude 95 degrees. Emission is detected between 50 and 600 keV where the spectrum is fitted well by a power law with photon index -2.6 +/- 0.3 and flux (4.0 +/- 0.5) x 10(-2) photons s(-1) cm(-2) rad(-1) MeV-1 at 100 keV. This spectral shape in this range is similar to that found for the continuum emission from the inner Galaxy, but the amplitude is lower by a factor of 4. This emission is due to either unresolved and previously unknown point sources, or diffuse electron bremsstrahlung, or a combination of the two. Simultaneous observations with OSSE and smaller field-of-view instruments operating in the soft gamma-ray energy band, such as X-ray Timing Explorer or Beppo-SAX, would help resolve this issue. If it is primarily diffuse emission due to nonthermal electron bremsstrahlung, as is the >1 MeV Galactic ridge continuum, then the power in low-energy cosmic-ray electrons exceeds that of the nuclear component of the cosmic rays by an order of magnitude. This would have profound implications for the origin of cosmic rays and the energetics of the interstellar medium. Alternatively, if the emission is diffuse and thermal, then there must be a component of the interstellar medium at temperatures similar to 10(9) K. C1 NORTHWESTERN UNIV,EVANSTON,IL 60208. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Skibo, JG (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7653,WASHINGTON,DC 20375, USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012; Johnson, Neil/G-3309-2014 NR 44 TC 25 Z9 25 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1997 VL 483 IS 2 BP L95 EP L98 DI 10.1086/310755 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL756 UT WOS:A1997XL75600006 ER PT J AU Smale, AP Zhang, W White, NE AF Smale, AP Zhang, W White, NE TI Discovery of kilohertz quasi-periodic oscillations from 4U 1820-303 with Rossi x-ray timing explorer SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars, individual (4U 1820-303); stars, neutron; X-rays, stars ID RADIUS EXPANSION; NGC 6624; BINARIES; 4U-1820-30; BURSTS; GINGA; FLUX AB We have detected high-frequency (HF) quasi-periodic oscillations (QPOs) from the low-mass X-ray binary 4U 1820-303 during observations performed in 1996 October using the Rossi X-ray Timing Explorer. The QPOs are visible when the source occupies the low-state luminosity range L-x = 2.4-3.1 x 10(37) ergs s(-1) (2-20 keV, at 6.4 kpc); the centroid frequency of the main QPO peak varies between 546 +/- 2 Hz and 796 +/- 6 Hz and is tightly correlated with the source count rate. The measured QPO widths are typically similar to 20 Hz, with mean rms amplitude 4.1% +/- 0.3%. At the upper end of this luminosity range a second significant QPO peak appears with frequency 1065 +/- 7 Hz, width 40 +/- 20 Hz, and rms amplitude 3.2% +/- 0.8%. When both QPOs are visible simultaneously, the difference between their frequencies is 275 +/- 8 Hz. When the source brightens beyond L-x = 3.1 x 10(37) ergs s(-1) (similar to 10% of the Eddington limit for a helium-rich envelope), neither QPO is detected. Neither the magnetospheric beat frequency model nor the sonic point model of HF QPOs provides a perfect explanation of the phenomenology we observe. These results represent the first detection of kilohertz QPO activity in a globular cluster X-ray binary, and provide a new method of directly comparing the properties of cluster and noncluster neutron star binaries. If the highest QPO frequency we observe is identified with the marginally stable orbit in the accretion disk, the neutron star mass may be similar to 2 M., 35%-50% more massive than usually assumed. This may have consequences for the current evolutionary scenarios for this source and also for the debate about the evolution of millisecond pulsars in globular clusters. C1 NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. RP Smale, AP (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 30 TC 50 Z9 50 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 JUL 10 PY 1997 VL 483 IS 2 BP L119 EP L122 DI 10.1086/310749 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL756 UT WOS:A1997XL75600012 ER PT J AU Kimes, DS Ranson, KJ Sun, G AF Kimes, DS Ranson, KJ Sun, G TI Inversion of a forest backscatter model using neural networks SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID RADAR BACKSCATTER; SCATTERING MODEL; BOREAL FOREST; BIOMASS; CLASSIFICATION; AREAS; SAR AB A neural network approach was used to develop acccurate algorithms for inverting a complex forest backscatter model. The model combines a forest growth model with a radar backscatter model. The forest growth model captures natural variations of forest stands (e.g., growth, regeneration, death, multiple species and competition for light). This model was used to produce vegetation structure data typical of transitional/northern boreal hardwood forests in Maine. These data supplied inputs to the radar backscatter model which simulated the polarimetric radar backscatter (C, L, P, X bands) above the forests. Using these simulated data, various neural networks were trained with inputs of different backscatter bands and output parameters of above ground biomass, total number of trees, mean tree height and mean tree age. These trained neural networks act as efficient algorithms for inverting the complex forest backscatter model. The accuracies (r.m.s. and R-2 values) for inferring various parameters from radar backscatter were above ground biomass (1.6 kg m(-2), 0.94), number of trees (48 ha(-1), 0.94), tree height (0.47 m, 0.88) and tree age (24.0 years, 0.83). The networks that used only AIRSAR bands (C, L, P) had a high degree of accuracy. The inclusion of the X band with the AIRSAR bands did not seem to increase significantly the accuracy of the networks. The networks that used only the C and L bands still had a relatively high degree of accuracy for all forest parameter (R-2 values from 0.75 to 0.91). Modest accuracies (R-2 values from 0.65 to 0.84) were obtained with networks that used only the L band and poor accuracies (R-2 values from 0.36 to 0.46) were obtained with networks that used only the C band. Several networks were shown to be relatively insensitive to the addition of random noise to radar backscatter. The results demonstrate that complex, forest backscatter models can be efficiently inverted using neural networks that use only radar backscatter data. C1 UNIV MARYLAND,DEPT GEOG,COLLEGE PK,MD 20742. RP Kimes, DS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. RI Ranson, Kenneth/G-2446-2012 OI Ranson, Kenneth/0000-0003-3806-7270 NR 39 TC 19 Z9 22 U1 0 U2 3 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 JUL 10 PY 1997 VL 18 IS 10 BP 2181 EP 2199 DI 10.1080/014311697217828 PG 19 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA XH143 UT WOS:A1997XH14300008 ER PT J AU Craeye, C Sobieski, PW Bliven, LF AF Craeye, C Sobieski, PW Bliven, LF TI Scattering by artificial wind and rain roughened water surfaces at oblique incidences SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID DROP IMPACT AB Rain affects wind retrievals from scatterometric measurements of the sea surface. To depict the additional roughness caused by rain on a wind driven surface, we use a ring-wave spectral model. This enables us to analyse the rain effect on K-u band scatterometric observations from two laboratory experiments. Calculations based on the small perturbation method provide good simulation of scattering measurements for the rain-only case, whereas for combined wind and rain cases, the boundary perturbation method is appropriate. C1 NASA,GODDARD SPACE FLIGHT CTR,WFF,LAB HYDROSPHER PROC,WALLOPS ISL,VA 23337. RP Craeye, C (reprint author), UNIV CATHOLIQUE LOUVAIN,B-1348 LOUVAIN,BELGIUM. RI bliven, francis/E-1450-2012 NR 11 TC 23 Z9 24 U1 1 U2 4 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 JUL 10 PY 1997 VL 18 IS 10 BP 2241 EP 2246 DI 10.1080/014311697217864 PG 6 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA XH143 UT WOS:A1997XH14300012 ER PT J AU Hlavka, CA Livingston, GP AF Hlavka, CA Livingston, GP TI Statistical models of fragmented land cover and the effect of coarse spatial resolution on the estimation of area with satellite sensor imagery SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID AVHRR DATA; ERRORS; SCALE AB The feasibility of correcting for errors in apparent extent of land cover types on coarse spatial resolution satellite imagery was analysed using a modelling approach. The size distributions for small burn scars mapped with two Landsat Multi-spectral Scanner (MSS) images and ponds mapped with an ERS-1 synthetic aperture radar (SAR) image were measured using geographical information system (GIS) software. Regression analysis showed that these size distributions could be modelled with two types of statistical distributions-a power distribution and an exponential distribution. A comparison of the size distributions of small burn scars as observed with the Landsat MSS imagery to the distribution observed with National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) imagery indicated that distortions due to the coarse spatial resolution of AVHRR caused overestimation of the burn area. This bias was primarily caused by detection in two or three AVHRR pixels of burns whose actual size was on the order of a single AVHRR pixel. Knowledge of the type of the actual size distribution of small fragments in a scene and the causes of distortion may lead to methods for correcting area estimates involving models of the size distribution observed with coarse imagery and requiring little or no recourse to fine scale data. C1 UNIV VERMONT,SCH NAT RESOURCES,BURLINGTON,VT 05405. RP Hlavka, CA (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 16 TC 18 Z9 18 U1 0 U2 3 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 JUL 10 PY 1997 VL 18 IS 10 BP 2253 EP 2259 DI 10.1080/014311697217882 PG 7 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA XH143 UT WOS:A1997XH14300014 ER PT J AU Realmuto, VJ Sutton, AJ Elias, T AF Realmuto, VJ Sutton, AJ Elias, T TI Multispectral thermal infrared mapping of sulfur dioxide plumes: A case study from the East Rift Zone of Kilauea Volcano, Hawaii SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID MOUNT ST-HELENS; SO2 EMISSION; FLOW-FIELD; ERUPTIONS; ETNA; SPECTROMETER; ANTARCTICA; ATMOSPHERE; CLOUDS; EREBUS AB The synoptic perspective and rapid mode of data acquisition provided by remote sensing are well suited for the study of volcanic SO2 plumes. In this paper we describe a plume-mapping procedure that is based on image data acquired with NASA's airborne thermal infrared multispectral scanner (TIMS) and apply the procedure to TIMS data collected over the East Rift Zone of Kilauea Volcano, Hawaii, on September 30, 1988. These image data covered the Pu'u 'O'o and Kupaianaha vents and a skylight in the lava tube that was draining the Kupaianaha lava pond. Our estimate of the SO2 emission rate from Pu'u 'O'o (17 - 20 kg s) is roughly twice the average of estimates derived from correlation spectrometer (COSPEC) measurements collected 10 days prior to the TIMS overflight (10 kg s(-1)). The agreement between the TIMS and COSPEC results improves when we compare SO2 burden estimates, which are relatively independent of wind speed. We demonstrate the feasibility of mapping Pu'u 'O'o - scale SO2 plumes from space in anticipation of the 1998 launch of the advanced spaceborne thermal emission and reflectance radiometer (ASTER). RP Realmuto, VJ (reprint author), CALTECH, JET PROP LAB, MS 168-514, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 58 TC 61 Z9 61 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD JUL 10 PY 1997 VL 102 IS B7 BP 15057 EP 15072 DI 10.1029/96JB03916 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XJ831 UT WOS:A1997XJ83100019 ER PT J AU Mushotzky, R AF Mushotzky, R TI X-ray astronomy - How one galaxy can be a cluster SO NATURE LA English DT Editorial Material ID LENS SYSTEM 2016+112 RP Mushotzky, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 13 TC 3 Z9 3 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JUL 10 PY 1997 VL 388 IS 6638 BP 126 EP 127 DI 10.1038/40521 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XK109 UT WOS:A1997XK10900024 ER PT J AU Hattori, M Ikebe, Y Asaoka, I Takeshima, T Bohringer, H Mihara, T Neumann, DM Schindler, S Tsuru, T Tamura, T AF Hattori, M Ikebe, Y Asaoka, I Takeshima, T Bohringer, H Mihara, T Neumann, DM Schindler, S Tsuru, T Tamura, T TI A dark cluster of galaxies at redshift z=1 SO NATURE LA English DT Article ID GRAVITATIONAL LENS SYSTEM; RAY; CONSTRAINTS AB The abundance of metals in the hot, gaseous X-ray haloes of galaxy clusters depends crucially on the evolution of the constituent galaxies and their associated stellar populations. The metal abundances in X-ray clusters at high redshifts should therefore provide important insights into the nature and epoch of galaxy formation. Here we report the detection of an extended X-ray source in the direction of the lensed quasi-stellar object MG2016 + 112 (refs 1, 2). Although deep optical searches have failed to reveal a galaxy duster at the lens position(3,4), the X-ray emission is consistent with thermal bremsstrahlung radiation from a hot metal-rich, diffuse gaseous halo, as observed in nearby galaxy dusters. This is the most distant galaxy duster discovered in X-rays so far. Furthermore, the mass of the duster derived from this emission is consistent with that implied by lensing models of the system(5). Given that the duster apparently comprises few galaxies, yet contains a large amount of iron, a new type of astronomical object is implied by our results. A revision of theoretical models of the metal enrichment process in galaxy dusters may therefore be required. C1 RIKEN,INST PHYS & CHEM RES,WAKO,SAITAMA 35101,JAPAN. TOHOKU UNIV,INST ASTRON,SENDAI,MIYAGI 980,JAPAN. NASA,GODDARD SPACE FLIGHT CTR USRA,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. MAX PLANCK INST ASTROPHYS,D-85740 GARCHING,GERMANY. KYOTO UNIV,DEPT PHYS,SAKYO KU,KYOTO,JAPAN. UNIV TOKYO,DEPT PHYS,BUNKYO KU,TOKYO 113,JAPAN. RP Hattori, M (reprint author), MAX PLANCK INST EXTRATERR PHYS,GIESSENBACHSTR,D-85740 GARCHING,GERMANY. RI Tamura, Takayuki/K-8236-2012; Mihara, Tatehiro/C-5536-2017 OI Mihara, Tatehiro/0000-0002-6337-7943 NR 24 TC 58 Z9 58 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 JUL 10 PY 1997 VL 388 IS 6638 BP 146 EP 148 DI 10.1038/40572 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XK109 UT WOS:A1997XK10900041 ER PT J AU Russel, WB Chaikin, PM Zhu, J Meyer, WV Rogers, R AF Russel, WB Chaikin, PM Zhu, J Meyer, WV Rogers, R TI Dendritic growth of hard sphere crystals SO LANGMUIR LA English DT Article ID DENSITY-FLUCTUATIONS; COLLOIDAL CRYSTALS; CRYSTALLIZATION; TRANSITION AB Recent observations of the disorder-order transition for colloidal hard spheres under microgravity revealed dendritic crystallites roughly 1-2 mm in size for samples in the coexistence region of the phase diagram. Order of magnitude estimates rationalize the absence of large or dendritic crystals under normal gravity and their stability to annealing in microgravity. A linear stability analysis of the Ackerson and Schatzel model for crystallization of hard spheres establishes the domain of instability for diffusion-limited growth at small supersaturations. The relationship between hard sphere and molecular crystal growth is established and exploited to relate the predicted linear instability to the well-developed dendrites observed. C1 PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08544. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Russel, WB (reprint author), PRINCETON UNIV,DEPT CHEM ENGN,PRINCETON,NJ 08544, USA. NR 26 TC 44 Z9 44 U1 1 U2 11 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0743-7463 J9 LANGMUIR JI Langmuir PD JUL 9 PY 1997 VL 13 IS 14 BP 3871 EP 3881 DI 10.1021/la970062b PG 11 WC Chemistry, Multidisciplinary; Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA XJ925 UT WOS:A1997XJ92500041 ER PT J AU Sengupta, DK Fang, W Malin, JI Li, J Horton, T Curtis, AP Hsieh, KC Chuang, SL Chen, H Feng, M Stillman, GE Li, L Liu, HC Bandara, KMSV Gunapala, SD Wang, WI AF Sengupta, DK Fang, W Malin, JI Li, J Horton, T Curtis, AP Hsieh, KC Chuang, SL Chen, H Feng, M Stillman, GE Li, L Liu, HC Bandara, KMSV Gunapala, SD Wang, WI TI GaAs/AlGaAs quantum-well infrared photodetectors on GaAs-on-Si substrates SO APPLIED PHYSICS LETTERS LA English DT Article ID INTERSUBBAND ABSORPTION; MULTIQUANTUM WELL; IMAGING CAMERA; MU-M; DETECTOR; ARRAY AB In this letter, we describe the characteristics of molecular beam epitaxy GaAs/AlGaAs quantum-well infrared photodetectors (QWIP's) grown on a GaAs substrate, and on a GaAs-on-Si substrate produced by metalorganic chemical-vapor deposition. Important issues for QWIP applications such as dark current, spectral response, and absolute responsivity are studied. We find that compared to a similar detector structure grown on a GaAs substrate, the detector grown on a GaAs-on-Si substrate exhibits similar dark current and absolute responsivity while displaying a small blueshift in the spectral response. (C) 1997 American Institute of Physics. C1 UNIV ILLINOIS,CTR CPDS SEMICOND MICROELECT,DEPT MAT SCI & ENGN,URBANA,IL 61801. NATL RES COUNCIL CANADA,INST MICROSTRUCT SCI,OTTAWA,ON K1A 0R6,CANADA. CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. COLUMBIA UNIV,DEPT ELECT ENGN,NEW YORK,NY 11007. RP Sengupta, DK (reprint author), UNIV ILLINOIS,CTR CPDS SEMICOND MICROELECT,DEPT ELECT & COMP ENGN,URBANA,IL 61801, USA. RI Li, Jian/B-1627-2016 NR 22 TC 10 Z9 10 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD JUL 7 PY 1997 VL 71 IS 1 BP 78 EP 80 DI 10.1063/1.119473 PG 3 WC Physics, Applied SC Physics GA XJ139 UT WOS:A1997XJ13900027 ER PT J AU Arrault, J Arneodo, A Davis, A Marshak, A AF Arrault, J Arneodo, A Davis, A Marshak, A TI Wavelet based multifractal analysis of rough surfaces: Application to cloud models and satellite data SO PHYSICAL REVIEW LETTERS LA English DT Article ID FORMALISM; SIGNALS; TURBULENCE; TRANSFORM; RAIN AB The wavelet transform modulus maxima (WTMM) method is generalized to multifractal image analysis, providing a statistical characterization of the fluctuating roughness of fractal surfaces. This isotropic 2D version of WTMM methodology is calibrated on deterministic self-similar interfaces and random self-affine surfaces (fractional Brownian surfaces and multifractal counterparts). Applications to high-resolution satellite data and simulated radiance fields for stratocumulus clouds are presented. C1 NASA,GODDARD SPACE FLIGHT CTR,CLIMATE & RADIAT BRANCH,GREENBELT,MD 20771. CTR RECH PAUL PASCAL,F-33600 PESSAC,FRANCE. RI Marshak, Alexander/D-5671-2012 NR 29 TC 64 Z9 65 U1 1 U2 4 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD JUL 7 PY 1997 VL 79 IS 1 BP 75 EP 78 DI 10.1103/PhysRevLett.79.75 PG 4 WC Physics, Multidisciplinary SC Physics GA XH870 UT WOS:A1997XH87000019 ER PT J AU Noll, KS Roush, TL Cruikshank, DP Johnson, RE Pendleton, YJ AF Noll, KS Roush, TL Cruikshank, DP Johnson, RE Pendleton, YJ TI Detection of ozone on Saturn's satellites Rhea and Dione SO NATURE LA English DT Article ID CHARGED-PARTICLE IRRADIATION; EUROPA; GANYMEDE; OXYGEN; CALLISTO; SPECTRA; ALBEDO; SEARCH; ICES; LIFE AB The satellites Rhea and Dione orbit within the magnetosphere of Saturn, where they are exposed to particle irradiation from trapped ions. A similar situation applies to the galilean moons Europa, Ganymede and Callisto, which reside within Jupiter's radiation belts. All of these satellites have surfaces rich in water ice(1,2). Laboratory studies of the interaction of charged-particle radiation with water ice predicted(3) the tenuous oxygen atmospheres recently found on Europa(4) and Ganymede(5). However, theoretical investigations did not anticipate the trapping of significantly larger quantities of O-2 within the surface ice(6). The accumulation of detectable abundances of O-3, produced by the action of ultraviolet or charged-particle radiation on O-2, was also not predicted before being observed on Ganymede(7). Here we report the identification of O-3 in spectra of the saturnian satellites Rhea and Dione. The presence of trapped O-3 is thus no longer unique to Ganymede, suggesting that special circumstances may not be required for its production. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. SAN FRANCISCO STATE UNIV, DEPT GEOSCI, SAN FRANCISCO, CA 94132 USA. UNIV VIRGINIA, CHARLOTTESVILLE, VA 22901 USA. RP Noll, KS (reprint author), SPACE TELESCOPE SCI INST, 3700 SAN MARTIN DR, BALTIMORE, MD 21218 USA. RI Noll, Keith/C-8447-2012 NR 29 TC 107 Z9 107 U1 1 U2 10 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 3 PY 1997 VL 388 IS 6637 BP 45 EP 47 DI 10.1038/40348 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XJ143 UT WOS:A1997XJ14300043 PM 9214500 ER PT J AU Stansberry, G Matney, M Settecerri, T Bade, A AF Stansberry, G Matney, M Settecerri, T Bade, A TI Debris families observed by the haystack orbital debris radar SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 46th International Astronautical Congress CY OCT 01-06, 1995 CL OSLO, NORWAY AB The Haystack radar provides a unique capability to observe and monitor the orbital debris environment in low-Earth orbit for debris sizes down to less than 1 cm in diameter. Recent changes in the observation geometry of the Haystack radar have greatly enhanced the capability of the radar in separating debris objects into orbit families. Using this capability, it is possible to identify Specific families of debris based on inclination and altitude regimes. The radar measurements can then be used to obtain size distributions and polarization characteristics of the debris in the families. Using this method, one previously unrecognized debris family in 65 degrees inclination circular orbits between 850 and 1000 km altitude has been tentatively identified as the leaking sodium-potassium coolant from Russian RORSAT reactors. Debris from specific breakups have also been identified, such as from the breakups of Cosmos 1275 and Cosmos 1484. This ability to assign some debris objects to specific sources opens up new possibilities in studying the nature and causes of breakup events. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Stansberry, G (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 3 TC 8 Z9 9 U1 3 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD JUL PY 1997 VL 41 IS 1 BP 53 EP 56 DI 10.1016/S0094-5765(97)00193-8 PG 4 WC Engineering, Aerospace SC Engineering GA ZN393 UT WOS:000073641400008 ER PT J AU Whitson, PA Chen, YM AF Whitson, PA Chen, YM TI Salivary endothelin and its response to postural changes in humans SO ACTA PHYSIOLOGICA SCANDINAVICA LA English DT Article DE endothelin; HPLC; plasma; posture; radio-immunoassay; saliva C1 KRUG LIFE SCI INC,HOUSTON,TX. RP Whitson, PA (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,ASTRONAUT OFF,DIV MED SCI,MAIL CODE CB,HOUSTON,TX 77058, USA. NR 8 TC 4 Z9 4 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE SN 0001-6772 J9 ACTA PHYSIOL SCAND JI Acta Physiol. Scand. PD JUL PY 1997 VL 160 IS 3 BP 291 EP 293 PG 3 WC Physiology SC Physiology GA XK113 UT WOS:A1997XK11300012 PM 9246393 ER PT J AU Benson, J Ladwig, A AF Benson, J Ladwig, A TI Untitled SO AEROSPACE AMERICA LA English DT Editorial Material RP Benson, J (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD JUL PY 1997 VL 35 IS 7 BP 16 EP 18 PG 3 WC Engineering, Aerospace SC Engineering GA XK685 UT WOS:A1997XK68500005 ER PT J AU Ko, SH McCroskey, WJ AF Ko, SH McCroskey, WJ TI Computations of unsteady separating flows over an oscillating airfoil SO AIAA JOURNAL LA English DT Article ID STOKES C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 10 TC 12 Z9 13 U1 1 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 JUL PY 1997 VL 35 IS 7 BP 1235 EP 1238 PG 4 WC Engineering, Aerospace SC Engineering GA XG886 UT WOS:A1997XG88600024 ER PT J AU Convertino, VA Polet, JL Engelke, KA Hoffler, GW Lane, LD Blomqvist, CG AF Convertino, VA Polet, JL Engelke, KA Hoffler, GW Lane, LD Blomqvist, CG TI Evidence for increased beta-adrenoreceptor responsiveness induced by 14 days of simulated microgravity in humans SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Article DE autonomic function; sympathetic activity; heart rate; blood pressure; baroreflex; vascular resistance ID DOWN BED REST; ORTHOSTATIC HYPOTENSION; VASCULAR-RESISTANCE; BAROREFLEX CONTROL; SPACE-FLIGHT; HEART-RATE; SPACEFLIGHT; RESPONSES; SALINE AB We studied hemodynamic responses to alpha- and beta-receptor agonists in eight healthy men before and after 14 days of 6 degrees head-down tilt (HDT) to test the hypothesis that increased adrenoreceptor responsiveness is induced by prolonged exposure to simulated microgravity. Steady-state infusions of isoproterenol (Iso) at rates of 0.005, 0.01, and 0.02 mu g . kg(-1). min(-1) were used to assess beta(1)- and beta(2)-adrenoreceptor responsiveness. Infusions of phenylephrine (PE) at rates of 0.25, 0.50, and 1.00 mu g . kg(-1)min(-1) were used to assess responsiveness of alpha(1)-vascular adrenoreceptors. Slopes calculated from linear regressions between Iso and PE doses and changes in beat-to-beat heart rate, blood pressure, and leg vascular resistance (occlusion plethysmography) for each subject were used as an index of alpha- and beta-adrenoreceptor responsiveness. HDT increased the slopes of heart rate (1,056 +/- 107 to 1,553 +/- 83 beats mu g(-1). kg(-1). min(-1); P = 0.014) and vasodilation (-469 +/- 111 to -1,446 +/- 309 peripheral resistance units .mu g(-1). kg(-1). min(-1); P = 0.0224) to Iso infusion. There was no alteration in blood pressure or vascular resistance responses to PE infusion after HDT. Our results provide evidence that simulated microgravity causes selective increases in beta(1)- and beta(2)-adrenoreceptor responsiveness without affecting alpha(1)-vascular adrenoreceptor responses. C1 NASA, BIOMED OPERAT & RES OFF, KENNEDY SPACE CTR, FL 32899 USA. UNIV FLORIDA, DEPT PHYSIOL, GAINESVILLE, FL 32611 USA. UNIV TEXAS, SW MED CTR, DALLAS, TX 75235 USA. RP Convertino, VA (reprint author), AL AOCY, DIV CLIN SCI, PHYSIOL RES BRANCH, 2507 KENNEDY CIRCLE, BROOKS AFB, TX 78232 USA. NR 31 TC 61 Z9 63 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0363-6119 J9 AM J PHYSIOL-REG I JI Am. J. Physiol.-Regul. Integr. Comp. Physiol. PD JUL PY 1997 VL 273 IS 1 BP R93 EP R99 PG 7 WC Physiology SC Physiology GA XK680 UT WOS:A1997XK68000012 PM 9249537 ER PT J AU Kouveliotou, C vanParadijs, J AF Kouveliotou, C vanParadijs, J TI Bursts of cosmic x rays SO AMERICAN SCIENTIST LA English DT Article C1 UNIV ALABAMA,HUNTSVILLE,AL 35899. UNIV AMSTERDAM,NL-1012 WX AMSTERDAM,NETHERLANDS. RP Kouveliotou, C (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,ES84,HUNTSVILLE,AL 35812, USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU SIGMA XI-SCI RES SOC PI RES TRIANGLE PK PA PO BOX 13975, RES TRIANGLE PK, NC 27709 SN 0003-0996 J9 AM SCI JI Am. Scientist PD JUL-AUG PY 1997 VL 85 IS 4 BP 347 EP 355 PG 9 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XH450 UT WOS:A1997XH45000019 ER PT J AU Graczyk, TK Balazs, GH Work, T Aguirre, AA Ellis, DM Murakawa, SKK Morris, R AF Graczyk, TK Balazs, GH Work, T Aguirre, AA Ellis, DM Murakawa, SKK Morris, R TI Cryptosporidium sp. infections in green turtles, Chelonia mydas, as a potential source of marine waterborne oocysts in the Hawaiian Islands SO APPLIED AND ENVIRONMENTAL MICROBIOLOGY LA English DT Article ID PARVUM OOCYSTS; WILD AB For the first time, Cryptosporidium sp. oocysts were identified in fecal and intestinal samples from free-ranging marine turtles, Chelonia mydas, from the Hawaiian Islands. The oocysts produced positive reactions with commercial test kits recommended for the detection of human-infectious waterborne oocysts of Cryptosporidium parvum. C1 NATL MARINE FISHERIES SERV,HONOLULU LAB,SW FISHERIES SCI CTR,HONOLULU,HI 96822. JOINT INST MARINE & ATMOSPHER RES,HONOLULU,HI 96822. NATL WILDLIFE HLTH RES CTR,HONOLULU FIELD STN,HONOLULU,HI 96850. MAKAI ANIM CLIN,KAILUA,HI 96734. RP Graczyk, TK (reprint author), JOHNS HOPKINS UNIV,SCH HYG & PUBL HLTH,DEPT MOL MICROBIOL & IMMUNOL,615 N WOLFE ST,BALTIMORE,MD 21205, USA. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 NR 21 TC 12 Z9 15 U1 0 U2 7 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1325 MASSACHUSETTS AVENUE, NW, WASHINGTON, DC 20005-4171 SN 0099-2240 J9 APPL ENVIRON MICROB JI Appl. Environ. Microbiol. PD JUL PY 1997 VL 63 IS 7 BP 2925 EP 2927 PG 3 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA XJ182 UT WOS:A1997XJ18200065 PM 16535658 ER PT J AU Matheson, LJ Jahnke, LL Oremland, RS AF Matheson, LJ Jahnke, LL Oremland, RS TI Inhibition of methane oxidation by Methylococcus capsulatus with hydrochlorofluorocarbons and fluorinated methanes SO APPLIED AND ENVIRONMENTAL MICROBIOLOGY LA English DT Article ID METHANOTROPHIC BACTERIA; ESTUARINE SEDIMENTS; ANAEROBIC SEDIMENTS; OXIDIZING BACTERIA; CELL-SUSPENSIONS; METHYL-FLUORIDE; MIXED CULTURE; TRICHLOROETHYLENE; DEGRADATION; ACETYLENE AB The inhibition of methane oxidation by cell suspensions of Methylococcus capsulatus (Bath) exposed to hydrochlorofluorocarbon 21 (HCFC-21; difluorochloromethane [CHF2CI]), HCFC-22 (fluorodichloromethane [CHFCI2]), and various fluorinated methanes was investigated. HCFC-21 inhibited methane oxidation to a greater extent than HCFC-22, for both the particulate and soluble methane monooxygenases. Among the fluorinated methanes, both methyl fluoride (CH3F) and difluoromethane (CH2F2) were inhibitory while fluoroform (CHF3) and carbon tetrafluoride (CF4) were not. The inhibition of methane oxidation by HCFC-21 and HCFC-22 was irreversible, while that by methyl fluoride was reversible. The HCFCs also proved inhibitory to methanol dehydrogenase, which suggests that they disrupt other aspects of C-1 catabolism in addition to methane monooxygenase activity. C1 US GEOL SURVEY,MENLO PK,CA 94025. NASA,AMES RES CTR,EXOBIOL DIV,MOFFETT FIELD,CA 94035. NR 35 TC 17 Z9 17 U1 1 U2 6 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1325 MASSACHUSETTS AVENUE, NW, WASHINGTON, DC 20005-4171 SN 0099-2240 J9 APPL ENVIRON MICROB JI Appl. Environ. Microbiol. PD JUL PY 1997 VL 63 IS 7 BP 2952 EP 2956 PG 5 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA XJ182 UT WOS:A1997XJ18200072 PM 16535662 ER PT J AU KeskiKuha, RAM Fleetwood, CM Robichaud, J AF KeskiKuha, RAM Fleetwood, CM Robichaud, J TI Performance of high-density cast silicon carbide in the extreme ultraviolet SO APPLIED OPTICS LA English DT Article DE silicon carbide; extreme ultraviolet; optical materials; reflectivity AB The normal-incidence reflectance of high-density cast silicon carbide (SiC) is evaluated in the extreme ultraviolet (EUV) spectral region. High reflectivity in the EUV is achieved. High reflectivity and the relatively low-cost manufacturing process make high-density cast SiC a promising mirror material for EUV applications. C1 SSG INC,WALTHAM,MA 02154. RP KeskiKuha, RAM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 9 TC 5 Z9 6 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD JUL 1 PY 1997 VL 36 IS 19 BP 4409 EP 4410 DI 10.1364/AO.36.004409 PG 2 WC Optics SC Optics GA XJ185 UT WOS:A1997XJ18500011 PM 18259229 ER PT J AU Wehrle, AE Keel, WC Jones, DL AF Wehrle, AE Keel, WC Jones, DL TI The nature of the optical ''jets'' in the spiral galaxy NGC 1097 SO ASTRONOMICAL JOURNAL LA English DT Article ID POWERFUL RADIO GALAXIES; LINE EMITTING GAS; NGC-1097; EMISSION; NUCLEUS AB We present new observations of the jet features in the barred spiral galaxy NGC 1097, including optical spectroscopy of the brightest jet features, two-color optical imagery, new VLA mapping at 327 MHz, and archival 1.4 GHz VLA data reprocessed for improved sensitivity. No optical emission lines appear to an equivalent width limit of 15-30 Angstrom (depending on the Line wavelength). The jets are uniformly blue, with B - V = 0.45 for the two well-observed jets R1 and R2. No radio emission from the jets is detected at either frequency; the 327-MHz data set particularly stringent limits on ''fossil'' emission from aging synchrotron electrons. The morphology of the jets is shown to be inconsistent with any conical distribution of emission enhanced by edge-brightening; their combination of transverse profile and relative narrowness cannot be reproduced with cone models. The optical colors, lack of radio emission, and morphology of the features lead us to conclude that they are tidal manifestations, perhaps produced by multiple encounters of the small elliptical companion NGC 1097A with the disk of NGC 1097. We present photometric and morphological comparisons to the tail of NGC 4651, which is similar in scale and morphology to the northeast ''dogleg'' feature R1 in NGC 1097. (C) 1997 American Astronomical Society. C1 UNIV ALABAMA,DEPT PHYS & ASTRON,TUSCALOOSA,AL 35487. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Wehrle, AE (reprint author), CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,4800 OAK GROVE DR,PASADENA,CA 91125, USA. OI Keel, William/0000-0002-6131-9539 NR 28 TC 8 Z9 9 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 JUL PY 1997 VL 114 IS 1 BP 115 EP & DI 10.1086/118458 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XH226 UT WOS:A1997XH22600013 ER PT J AU Smith, BJ Madden, SC AF Smith, BJ Madden, SC TI Interstellar gas in low mass Virgo Cluster spiral galaxies SO ASTRONOMICAL JOURNAL LA English DT Article ID CO-TO-H2 CONVERSION FACTOR; DWARF IRREGULAR GALAXIES; H-II REGIONS; 158 MICRON; MOLECULAR GAS; MAGELLANIC CLOUD; STAR FORMATION; LINE EMISSION; IONIZED-GAS; ABUNDANCES AB We have measured the strengths of the [C II] 158 mu m, [N II] 122 mu m, and CO (1-O) lines from five low blue luminosity spiral galaxies in the Virgo Cluster, using the Infrared Space Observatory and the NRAO 12 m millimeter telescope. Two of the five galaxies have high L([C II])/L(CO) and L(FIR)/L(CO) ratios compared to higher mass spirals. These two galaxies, NGC 4294 and NGC 4299, have L([C II])/L(CO) ratios of greater than or equal to 14,300 and 15,600, respectively, which are similar to values found in dwarf irregular galaxies. This is the first time that such enhanced L([C II])/L(CO) ratios have been found in spiral galaxies. This result may be due to low abundances of dust and heavy elements, which can cause the CO (1-0) measurements to underestimate the molecular gas content. Another possibility is that radiation from diffuse H I clouds may dominate the [C II] emission from these galaxies. Less than a third of the observed [C II] emission arises from H II regions. (C) 1997 American Astronomical Society. C1 CTR ETUD SACLAY, SERV ASTROPHYS, F-91191 GIF SUR YVETTE, FRANCE. RP Smith, BJ (reprint author), CALTECH, JET PROP LAB, IPAC, EXTRAGALACT DATABASE NED, MS 100-22, PASADENA, CA 91125 USA. NR 65 TC 35 Z9 35 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 1997 VL 114 IS 1 BP 138 EP 146 DI 10.1086/118460 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XH226 UT WOS:A1997XH22600015 ER PT J AU Aringer, B Jorgensen, UG Langhoff, SR AF Aringer, B Jorgensen, UG Langhoff, SR TI SiO rotation-vibration bands in cool giants .1. A grid of model spectra for different stellar parameters SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars, atmospheres; stars, fundamental parameters; stars, late-type; stars, AGB and post-AGB; infrared, stars ID PARTITION-FUNCTIONS; ANGULAR DIAMETERS; STAR ATMOSPHERES; SILICON MONOXIDE; EMISSION; TEMPERATURES; INSTABILITY; ABUNDANCES; VARIABLES; ENVELOPES AB In order to study the behavior of the SiO bands of cool oxygen-rich stars we have computed a grid of 138 hydrostatic model atmospheres using an improved version of the MARCS code and new SiO line data. We found that the corresponding opacity never produces large changes of the atmospheric structure, especially if one compares it with the enormous effects from TiO or water. Based on the atmospheres, synthetic SiO spectra have been calculated with a high resolution for the photometric L-band and with a low resolution (opacity sampling) for the large wavelength range between 2.0 and 12.5 mu m, which includes the fundamental as well as the first and second overtone transitions. Thus, we could study the behavior of the SiO bands as a function of different stellar parameters. It turned out that the intensity of the absorption features monotonously increases with lower temperature and gravitational acceleration as well as with higher metallicity. We expect the strongest bands in the coolest and most extended objects. When we compared our results to observations of K and M giants, we found a good agreement showing the correctness of the line data and atmospheres. On the other hand the calculations can not reproduce the relatively weak and variable bands of AGE stars indicating that our classical model atmospheres may not always work for this kind of objects. This will be discussed in a second paper, where we will focus on our observations of AGE stars. C1 COPENHAGEN UNIV OBSERV, DK-2100 COPENHAGEN, DENMARK. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Aringer, B (reprint author), UNIV VIENNA, INST ASTRON, TURKENSCHANZSTR 17, A-1180 VIENNA, AUSTRIA. NR 36 TC 27 Z9 27 U1 1 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1997 VL 323 IS 1 BP 202 EP 210 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ141 UT WOS:A1997XJ14100038 ER PT J AU Walker, HJ Tsikoudi, V Clayton, CA Geballe, T Wooden, DH Butner, HM AF Walker, HJ Tsikoudi, V Clayton, CA Geballe, T Wooden, DH Butner, HM TI The nature of the unusual source IRAS 18530+0817 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE circumstellar matter; stars, IRAS 18530+0817; stars, evolution; stars, mass-loss; stars, AGE and post-AGE; infrared, stars ID MIRA VARIABLES; STARS; CLASSIFICATION; COLORS AB Infrared photometry and spectroscopy of the unassociated (infrared-only) IRAS source, IRAS 18530+0817, indicate that it is a highly unusual evolved star surrounded by a dense envelope of cool gas and dust. The IRAS data reveal a large infrared excess and significant flux variability in the 12 - 25 mu m region, as well as a prominent, silicate emission feature at 8.5 - 11.5 mu m. The shape of the feature also appears to vary; in 1993 it was apparently attenuated by an absorption with a sharp edge at 9.5 mu m, which may be circumstellar or photospheric in origin. At other times the silicate feature appears to be self-absorbed by varying amounts. Near-infrared spectra of IRAS 18530+0817 are dominated by steam absorptions, with the It-band spectrum showing only a narrow band of relatively unabsorbed continuum at 2.15 - 2.29 mu m The object appears to possess the strongest stellar photospheric H2O absorptions yet observed. We tentatively conclude that the central star of IRAS 18530+0817 is a late-type, O-rich, AGE star (a Mira variable) surrounded by an envelope of O-rich dust. C1 UNIV IOANNINA, DEPT PHYS, GR-45110 IOANNINA, GREECE. JOINT ASTRON CTR, HILO, HI 96720 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. CARNEGIE INST WASHINGTON, DEPT TERR MAGNETISM, WASHINGTON, DC 20015 USA. RP Walker, HJ (reprint author), RUTHERFORD APPLETON LAB, CLRC, DIDCOT OX11 0QX, OXON, ENGLAND. OI Butner, Harold/0000-0003-4899-2064 NR 21 TC 4 Z9 4 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1997 VL 323 IS 2 BP 442 EP 448 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL461 UT WOS:A1997XL46100018 ER PT J AU Kovalevsky, J Lindegren, L Perryman, MAC Hemenway, PD Johnston, KJ Kislyuk, VS Lestrade, JF Morrison, LV Platais, I Roser, S Schilbach, E Tucholke, HJ deVegt, C Vondrak, J Arias, F Gontier, AM Arenou, F Brosche, P Florkowski, DR Garrington, ST Preston, RA Ron, C Rybka, SP Scholz, RD Zacharias, N AF Kovalevsky, J Lindegren, L Perryman, MAC Hemenway, PD Johnston, KJ Kislyuk, VS Lestrade, JF Morrison, LV Platais, I Roser, S Schilbach, E Tucholke, HJ deVegt, C Vondrak, J Arias, F Gontier, AM Arenou, F Brosche, P Florkowski, DR Garrington, ST Preston, RA Ron, C Rybka, SP Scholz, RD Zacharias, N TI The Hipparcos Catalogue as a realisation of the extragalactic reference system SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE astrometry; catalogs; reference systems ID EARTH ORIENTATION PARAMETERS; REFERENCE FRAME; REDUCTION SOFTWARE; STARS; ASTROMETRY; PERFORMANCE; CONSORTIUM; POSITIONS; ROTATION; PROGRAM AB The paper describes the methods and observations by which the Hipparcos Catalogue was linked to the International Celestial Reference System (ICRS). The contributions of several groups represented in the authorship of this paper, using a variety of techniques, were synthesised in order to determine the global orientation and rotation (spin) of the coordinate frame defined by the Hipparcos data with respect to extragalactic sources. The following link techniques were used: interferometric observations of radio stars by VLBI networks, MERLIN and VLA; observations of quasars relative to Hipparcos stars by means of CCDs and photographic plates. and by the Hubble Space Telescope photographic programmes to determine stellar proper motions with respect to extragalactic objects (Bonn, Kiev, Lick, Potsdam, Yale/San Juan); and comparison of Earth orientation parameters obtained by VLBI and by ground-based optical observations of Hipparcos stars. Although vastly different in terms of instruments, observational methods and objects involved, the various techniques generally agree to within 10 mas (milliarcsec) in the orientation and 1 mas/yr in the spin of the system. Two different numerical methods are described for the systematic comparison and synthesis of the link observations. The methods give very similar solutions, and a mean value was adopted for the definition of the system of positions and proper motions in the Hipparcos Catalogue. As a result, the coordinate axes defined by the published catalogue are believed to be aligned with the extragalactic radio frame to within +/- 0.6 mas at the epoch 1991.25, and non-rotating with respect to distant extragalactic objects to within +/- 0.25 mas/yr. C1 LUND OBSERV, S-22100 LUND, SWEDEN. EUROPEAN SPACE TECHNOL CTR, EUROPEAN SPACE AGCY, DIV ASTROPHYS, NL-2200 AG NOORDWIJK, NETHERLANDS. UNIV TEXAS, DEPT ASTRON, AUSTIN, TX 78712 USA. USN OBSERV, WASHINGTON, DC 20392 USA. UKRAINIAN ACAD SCI, MAIN ASTRON OBSERV, UA-252127 KIEV, UKRAINE. OBSERV PARIS, MEUDON SECT, F-92195 MEUDON, FRANCE. ROYAL GREENWICH OBSERV, CAMBRIDGE CB3 0EZ, ENGLAND. YALE UNIV OBSERV, NEW HAVEN, CT 06520 USA. ASTRON RECH INST, D-69120 HEIDELBERG, GERMANY. UNIV POTSDAM, WIP, D-14482 POTSDAM, GERMANY. UNIV STERNWARTE, D-53121 BONN, GERMANY. HAMBURGER STERNWARTE, D-21029 HAMBURG, GERMANY. ACAD SCI CZECH REPUBL, INST ASTRON, CR-14131 PRAGUE 4, CZECH REPUBLIC. ASTRON OBSERV, RA-1900 LA PLATA, ARGENTINA. OBSERV PARIS, IERS, F-75014 PARIS, FRANCE. UNIV MANCHESTER, NUFFIELD RADIO ASTRON LABS, JODRELL BANK, MACCLESFIELD SK11 9DL, CHESHIRE, ENGLAND. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Kovalevsky, J (reprint author), OBSERV COTE AZUR, CERGA, AV COPERNIE, F-06130 GRASSE, FRANCE. RI Ron, Cyril/G-9038-2014; Vondrak, Jan/G-9057-2014; Arenou, Frederic/B-1846-2014; OI Arenou, Frederic/0000-0003-2837-3899; Perryman, Michael/0000-0002-3953-4750 NR 47 TC 109 Z9 120 U1 0 U2 3 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1997 VL 323 IS 2 BP 620 EP 633 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XL461 UT WOS:A1997XL46100034 ER PT J AU GarciaSanchez, J Paredes, JM AF GarciaSanchez, J Paredes, JM TI Particle injection in the Circinus X-1 radio outbursts SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars: individual, Cir X-1; radio continuum: stars; X-rays: stars ID X-RAY; BINARY MODEL; JETS AB A particle injection model has been applied to the radio outbursts of the X-ray binary Circinus X-1. The radio outbursts of this system have often been observed to exhibit a double peaked structure, i.e., with two apparent consecutive maxima. We show here that particle injection models can account for such observed behaviour provided that a time variable particle injection rate is adopted. Several possible time dependences are assumed and the corresponding predicted radio light curves compared with multi-frequency observations collected from the literature. C1 UNIV BARCELONA, DEPT ASTRON & METEOROL, E-08028 BARCELONA, SPAIN. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. OI Paredes, Josep M./0000-0002-1566-9044 NR 24 TC 0 Z9 0 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1997 VL 323 IS 3 BP 876 EP 880 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XM756 UT WOS:A1997XM75600023 ER PT J AU Miyaji, T Connolly, AJ Szalay, AS Boldt, E AF Miyaji, T Connolly, AJ Szalay, AS Boldt, E TI Soft X-ray emission and optical multicolors of faint QSOs in the Selected Area 57 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE galaxies, active; X-rays, general ID QUASARS; VARIABILITY; PHOTOMETRY; GALAXIES; SAMPLE AB We present the ROSAT HRI X-ray measurements of 19 spectroscopically confirmed optically-selected QSOs in the 12' radius region in the Selected Area 57. The optical-to-X-ray spectral index alpha(ox) ranges from 1.25 to 1.7, consistent with brighter QSOs. We have investigated the relationship between soft X-ray emission observed with the ROSAT HRI and optical colors (UJFN) of optically-selected QSOs in SA57. The optical to X-ray spectral index alpha(ox) is found to be correlated with the U - J - F + N color, by a combined effect of alpha(ox) and U, N excess correlations. Possible explanations are the physical link between broad emission-lines/Balmer continuum, and the ionizing radiation source seen in X-ray and/or a geometrical effect. C1 MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. JOHNS HOPKINS UNIV, DEPT PHYS & ASTRON, BALTIMORE, MD 21218 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Miyaji, T (reprint author), INST ASTROPHYS, STERNWARTE 16, D-14482 POTSDAM, GERMANY. NR 17 TC 4 Z9 4 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1997 VL 323 IS 1 BP L37 EP L40 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ141 UT WOS:A1997XJ14100011 ER PT J AU Storzer, H Stutzki, J Sternberg, A AF Storzer, H Stutzki, J Sternberg, A TI CI fine-structure emission from non-equilibrium PDRs SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE line, formation; ISM, clouds; ISM, molecules; radio lines, interstellar ID H-II REGIONS; ATOMIC CARBON; PHOTODISSOCIATION REGIONS; ULTRAVIOLET-RADIATION; M17 SW; S140; GAS; CO; SUBMILLIMETER; IONIZATION AB We present computations of [CI] 609 mu m and 370 mu m fine-structure line emission from non-equilibrium clouds which are suddenly shielded from initially intense far-ultraviolet radiation fields. After the incident UV fluxes are diminished the initially abundant C+ ions rapidly recombine, and the neutral atomic carbon is then slowly incorporated into CO molecules. The cloud cooling times are longer than the CI formation times, and intense [CI] emission persists as the clouds cool. The [CI] emission is thus much brighter from cooling clouds than in equilibrium photon dominated regions. We argue that if UV-scattering is inefficient the extended [CI] emission observed in star-forming regions may be better explained by non-equilibrium models than by steady state models. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. TEL AVIV UNIV, SCH PHYS & ASTRON, RAMAT AVIV, ISRAEL. RP Storzer, H (reprint author), UNIV COLOGNE, INST PHYS 1, ZULPICHER STR 77, D-50937 COLOGNE, GERMANY. NR 29 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 JUL PY 1997 VL 323 IS 1 BP L13 EP L16 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ141 UT WOS:A1997XJ14100005 ER PT J AU Titarchuk, L Muslimov, A AF Titarchuk, L Muslimov, A TI Rotational splitting effect in neutron star QPOs SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE accretion, disk; binaries, LMXBs; X-rays, QPOs AB We explain the peak spacing in the power spectra of millisecond variability detected by the Rossi X-ray Timing Explorer (RXTE) in the X-ray emission from the LMXBs (Sco X-1, 4U1728-34, 4U1608-522, 4U1636-536, etc) in terms of the rotational splitting of an intrinsic frequency (which is of order of the local Keplerian frequency) caused by an accretion disk. We calculate this effect and demonstrate that there is a striking agreement with the observational data. We show that the observed discrete frequencies ranging from 200 to 1200 Hz can be described by a whole set of overtones. For higher overtones (lower frequencies, less than or similar to 100 Hz) the ratio between frequencies is determined by the quantum numbers alone. We suggest that a similar phenomena should be observed in Black Hole (BH) systems for which the QPO (quasi-periodic oscillation) frequency should be inversely proportional to the mass of the compact object. For BH systems the characteristic frequency of oscillations should therefore be a factor of 5-10 less than for a neutron star system. C1 GEORGE MASON UNIV, CSI, FAIRFAX, VA 22030 USA. RP Titarchuk, L (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. NR 19 TC 8 Z9 8 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 JUL PY 1997 VL 323 IS 1 BP L5 EP L8 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ141 UT WOS:A1997XJ14100003 ER PT J AU Satyapal, S Watson, DM Pipher, JL Forrest, WJ Greenhouse, MA Smith, HA Fischer, J Woodward, CE AF Satyapal, S Watson, DM Pipher, JL Forrest, WJ Greenhouse, MA Smith, HA Fischer, J Woodward, CE TI The intrinsic properties of the stellar clusters in the M82 starburst complex: Propagating star formation? SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies evolution; galaxies, individual (M82); galaxies nuclei; galaxies, starburst; galaxies, star clusters; infrared, galaxies ID INITIAL MASS FUNCTION; INFRARED PHOTOMETRY; GALAXY M82; NUCLEUS; EMISSION; CO AB Near-Infrared spectroscopy combined with high spatial resolution imaging have been used in this work to probe the central 500 pc of M82. Imaging observations in the 2.36 mu m CO band head are added to our previously published near-infrared hydrogen recombination line imaging, near-infrared broadband imaging, and 3.29 mu m dust feature imaging observations, in order to study the nature of the starburst stellar population. A starburst model is constructed and compared with the observations of the stellar clusters in the starburst complex. Our analysis implies that the typical age for the starburst clusters is 10(7) yr. In addition, our high spatial resolution observations indicate that there is an age dispersion within the starburst complex that is correlated with projected distance from the center of the galaxy. The inferred age dispersion is 6 x 10(6) yr. If the starburst in M82 is propagating outward from the center, this age dispersion corresponds to a velocity of propagation, originating in the center, of similar to 50 km s(-1). Our quantitative analysis also reveals that a Salpeter initial mass function, extending from 0.1 to 100 M-., can fit the observed properties of M82 without using up more than 30% of the total dynamical mass in the starburst. C1 UNIV ROCHESTER,DEPT PHYS & ASTRON,ROCHESTER,NY 14627. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. USN,RES LAB,REMOTE SENSING DIV,WASHINGTON,DC 20375. UNIV WYOMING,DEPT PHYS & ASTRON,LARAMIE,WY 82071. RP Satyapal, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 685,GREENBELT,MD 20771, USA. NR 46 TC 100 Z9 100 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 JUL 1 PY 1997 VL 483 IS 1 BP 148 EP 160 DI 10.1086/304214 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ167 UT WOS:A1997XJ16700016 ER PT J AU VonMontigny, C Aller, H Aller, M Bruhweiler, F Collmar, W Courvoisier, TJL Edwards, PG Fichtel, CE Fruscione, A Ghisellini, G Hartman, RC Johnson, WN Kafatos, M Kii, T Kniffen, DA Lichti, GG Makino, F Mannheim, K Marscher, AP McBreen, B McHardy, I Pesce, JE Pohl, M Ramos, E Reich, W Robson, EI Sasaki, K Terasranta, H Tornikoski, M Urry, CM Valtaoja, E Wagner, S Weekes, T AF VonMontigny, C Aller, H Aller, M Bruhweiler, F Collmar, W Courvoisier, TJL Edwards, PG Fichtel, CE Fruscione, A Ghisellini, G Hartman, RC Johnson, WN Kafatos, M Kii, T Kniffen, DA Lichti, GG Makino, F Mannheim, K Marscher, AP McBreen, B McHardy, I Pesce, JE Pohl, M Ramos, E Reich, W Robson, EI Sasaki, K Terasranta, H Tornikoski, M Urry, CM Valtaoja, E Wagner, S Weekes, T TI Multiwavelength observations of 3C 273 in 1993-1995 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; quasars, individual (3C 273); radiation mechanisms, nonthermal ID GAMMA-RAY EMISSION; EXTRAGALACTIC RADIO-SOURCES; QUASARS 3C-273; COS-B; RADIATION; JET; TELESCOPE; BLAZARS; 3C273; COMPTONIZATION AB We present the results of the multiwavelength campaigns on 3C 273 in 1993-1995. During the observations in late 1993, this quasar showed an increase of its flux for energies greater than or equal to 100 MeV from about 2.1 x 10(-7) photons cm(-2) s(-1) to approximately 5.6 x 10(-7) photons cm(-2) s(-1) during a radio outburst at 14.5, 22, and 37 GHz. However, no one-to-one correlation of the gamma-ray radiation with any frequency could be found. The photon spectral index of the high-energy spectrum changed from Gamma(gamma) = (3.20 +/- 0.54) to Gamma(gamma) = (2.20 +/- 0.22) in the sense that the spectrum flattened when the gamma-ray flux increased. Fits of the three most prominent models (synchrotron self-Comptonization, external inverse Comptonization, and the proton-initiated cascade model) for the explanation of the high gamma-ray emission of active galactic nuclei were performed to the multiwavelength spectrum of 3C 273. All three models are able to represent the basic features of the multiwavelength spectrum. Although there are some differences, the data are still not decisive enough to discriminate between the models. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109. CATHOLIC UNIV AMER,DEPT PHYS,WASHINGTON,DC 20064. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. INTEGRAL SCI DATA CTR,CH-1290 SAUVERNY,SWITZERLAND. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. OSSERVATORIO BRERA MERATE,MERATE,ITALY. USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. GEORGE MASON UNIV,CSI,CTR EARTH OBSERV & SPACE RES,FAIRFAX,VA 22030. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. UNIV STERNWARTE,D-37803 GOTTINGEN,GERMANY. BOSTON UNIV,DEPT ASTRON,BOSTON,MA 02215. UNIV COLL,DEPT PHYS,DUBLIN 4,IRELAND. UNIV SOUTHAMPTON,DEPT PHYS,SOUTHAMPTON SO9 5NH,HANTS,ENGLAND. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. MAX PLANCK INST RADIOASTRON,BONN,GERMANY. JOINT ASTRON CTR,HILO,HI 96720. METSAHOVI RADIO RES STN,FIN-02540 KYLMALA,FINLAND. UNIV TURKU,TUORLA OBSERV,SF-21500 PIIKKIO,FINLAND. HARVARD SMITHSONIAN CTR ASTROPHYS,WHIPPE OBSERV,AMADO,AZ 85645. LANDESSTERNWARTE HEIDELBERG KONIGSTUHL,D-69117 HEIDELBERG,GERMANY. RI Mannheim, Karl/F-6705-2012; Urry, Claudia/G-7381-2011; Johnson, Neil/G-3309-2014 OI Urry, Claudia/0000-0002-0745-9792; NR 73 TC 65 Z9 65 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 JUL 1 PY 1997 VL 483 IS 1 BP 161 EP 177 DI 10.1086/304219 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ167 UT WOS:A1997XJ16700017 ER PT J AU Chen, KY Halpern, JP Titarchuk, LG AF Chen, KY Halpern, JP Titarchuk, LG TI Polarization of line emission from an accretion disk and application to Arp 102B SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies, active; galaxies, nuclei; galaxies, individual (Arp 102B); line, profiles; polarization; radiative transfer ID RADIATION; GALAXIES; ARP-102B; NUCLEI AB We model the polarization properties of line emission from an accretion disk under a range of assumptions about the source function and electron-scattering optical depth tau(es). For small values of tau(es) and modest viewing angles, polarization can be in excess of the Chandrasekhar result for tau(es) = infinity. The polarization vector can be either parallel or perpendicular to the projected direction of the disk axis. The polarization properties of the double-peaked H alpha emission line of the broad-line radio galaxy Arp 102B observed by Antonucci, Hurt, & Agol can be understood in terms of electron scattering and line broadening within the line-emitting region if tau(es) is of order unity, and if the position angle of polarization is parallel to the projected disk axis. The required small tau(es) is consistent with the hypothesis that the Balmer lines in Arp 102B are produced by photoionization of the disk atmosphere. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Chen, KY (reprint author), COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,538 W 120TH ST,NEW YORK,NY 10027, USA. NR 14 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 JUL 1 PY 1997 VL 483 IS 1 BP 194 EP 199 DI 10.1086/304224 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ167 UT WOS:A1997XJ16700019 ER PT J AU Simon, T Landsman, WB AF Simon, T Landsman, WB TI The high chromospheres of the late A stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, activity; stars, chromospheres; stars, individual (alpha Aquilae, alpha Cephei); ultraviolet, stars ID A-TYPE STARS; EMISSION AB We report the detection of N v 1239 Angstrom transition region emission in HST/Goddard High Resolution Spectrograph spectra of the A7 V stars, alpha Aql and alpha Cep. Our observations provide the first direct evidence of 1-3 x 10(5) K material in the atmospheres of normal A-type stars. For both stars, and for the mid A-type star tau(3) Eri, we also report the detection of chromospheric emission in the Si III 1206 Angstrom line. At a B-V color of 0.16 and an effective temperature of similar to 8200 K, tau(3) Eri becomes the hottest main-sequence star known to have a chromosphere and, thus, an outer convection zone. We see no firm evidence that the Si III line surface fluxes of the A stars are any lower than those of moderately active, solar-type G and K stars. This contrasts sharply with their coronal X-ray emission, which is more than 100 times weaker than that of the later type stars. Given the strength of the N v emission observed here, it now appears unlikely that the X-ray faintness of A stars is due to their forming very cool, less than or equal to 1 Mg coronae. An alternative explanation in terms of mass loss in coronal winds remains a possibility, though we conclude from moderate resolution spectra of the Si III lines that such winds, if they exist, do not penetrate into the chromospheric Si III-forming layers of the star, since the profiles of these lines are not blueshifted and may well be redshifted with respect to the star. C1 NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. RP Simon, T (reprint author), UNIV HAWAII,INST ASTRON,2680 WOODLAWN DR,HONOLULU,HI 96822, USA. NR 16 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 JUL 1 PY 1997 VL 483 IS 1 BP 435 EP 438 DI 10.1086/304251 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ167 UT WOS:A1997XJ16700040 ER PT J AU Grady, CA Sitko, ML Bjorkman, KS Perez, MR Lynch, DK Russell, RW Hanner, MS AF Grady, CA Sitko, ML Bjorkman, KS Perez, MR Lynch, DK Russell, RW Hanner, MS TI The star-grazing extrasolar comets in the HD 100546 system SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; planetary systems; stars, individual (HD 100546); stars, pre-main-sequence; ultraviolet, stars ID HERBIG AE/BE STARS; PICTORIS CIRCUMSTELLAR DISK; BETA-PICTORIS; ACTIVE PHENOMENA; ACCRETION; DUST; SILICATES; ROTATION; WINDS; LINES AB Redshifted absorption profiles that resemble the high-velocity circumstellar gas features in the spectrum of beta Pictoris have been detected in IUE data for the 10 Myr old Herbig Be star, HD 100546, on 1995 March 7. In addition to Mg II, Si II, and other refractory species similar to those seen in beta Pic, the HD 100546 spectra are rich in accreting gas profiles from neutral atomic gas, including C I and O I, as well as mildly refractory species such as Zn II and S II. The presence of accreting gas profiles, including neutral atomic gas, is consistent with detection of comae of star-grazing bodies potentially resembling either comets or asteroids. Overall, the IUE data for HD 100546 are consistent with the planetesimals in this system being more volatile-rich and magnesium-rich than similar bodies in the beta Pic system. C1 UNIV CINCINNATI, DEPT PHYS, CINCINNATI, OH 45221 USA. UNIV TOLEDO, DEPT PHYS & ASTRON, TOLEDO, OH 43606 USA. APPL RES CORP, LANDOVER, MD 20785 USA. AEROSP CORP, LOS ANGELES, CA 90009 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Grady, CA (reprint author), EUREKA SCI, 2452 DELMER ST, SUITE 100, OAKLAND, CA 94602 USA. NR 41 TC 61 Z9 61 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1997 VL 483 IS 1 BP 449 EP 456 DI 10.1086/304230 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ167 UT WOS:A1997XJ16700042 ER PT J AU Reames, DV Barbier, LM VonRosenvinge, TT Mason, GM Mazur, JE Dwyer, JR AF Reames, DV Barbier, LM VonRosenvinge, TT Mason, GM Mazur, JE Dwyer, JR TI Energy spectra of ions accelerated in impulsive and gradual solar events SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, flares; Sun, particle emission ID HE-3-RICH EVENTS; PARTICLE EVENTS; ELECTRON EVENTS; FLARES; ABUNDANCES; INSTABILITIES; ENRICHMENTS; TRANSPORT; HYDROGEN; NUCLEON AB We report new high-sensitivity measurements of the energy spectra of ions from five impulsive solar flares and one gradual event observed during solar minimum by the Energetic Particles, Acceleration, Composition, and Transport (EPACT) experiment aboard the WIND spacecraft. All of the impulsive-flare events had intensities too low to be visible on previous spacecraft such as ISEE 3, which observed hundreds of impulsive-hare events. Often these events cluster in or behind a coronal mass ejection (CME) where magnetic field lines provide an excellent connection to a solar active region where flares are occurring. In most cases we can see velocity dispersion as the ions of 20 keV amu(-1) to 10 MeV amu(-1) streamed out from the impulsive flare at the Sun, arriving in inverse order of their velocity. Ions from a large, magnetically well-connected gradual event, associated with a CME-driven shock, also show velocity dispersion early in the event but show identical time profiles that last for several days late in the event. These time-invariant spectra of H, He-4, C, O, and Fe in this gradual event are well represented as power laws in energy from 20 keV amu(-1) to similar to 100 MeV amu(-1). In the impulsive-flare events, H, He-3, He-4, C, O, and Fe have more rounded spectra that flatten somewhat at low energies; yet the intensities continue to increase down to 20 keV amu(-1). Most of the ion energy content appears to lie below 1 MeV in the impulsive events, where it would be invisible to gamma-ray line observations. C1 UNIV MARYLAND,COLLEGE PK,MD 20742. RP Reames, DV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 34 TC 76 Z9 77 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 JUL 1 PY 1997 VL 483 IS 1 BP 515 EP 522 DI 10.1086/304229 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ167 UT WOS:A1997XJ16700048 ER PT J AU Gwinn, CR Ojeda, MJ Briton, MC Reynolds, JE Jauncey, DL King, EA McCulloch, PM Lovell, JEJ Flanagan, CS Smits, DP Preston, RA Jones, DL AF Gwinn, CR Ojeda, MJ Briton, MC Reynolds, JE Jauncey, DL King, EA McCulloch, PM Lovell, JEJ Flanagan, CS Smits, DP Preston, RA Jones, DL TI Size of the Vela pulsar's radio emission region: 500 kilometers SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, general; pulsars, individual (Vela pulsar); techniques, interferometric ID INTERSTELLAR SCATTERING; WAVE-PROPAGATION; MAGNETOSPHERES; RADIATION; SCINTILLATION; POLARIZATION; ANISOTROPY; TURBULENCE; CYGNUS-X-3; COHERENCE AB We use interstellar scattering of the Vela pulsar to determine the size of its emission region. We find that radio-wave scattering in the Vela supernova remnant broadens the source by 3.3 +/- 0.2 mas x 2.0 +/- 0.1 mas, with the major axis at a position angle of 92 degrees +/- 10 degrees. From the modulation of the pulsar's scintillation, we infer a size of 500 km for the pulsar's emission region, with an estimated uncertainty of about a factor of 2, including systematic errors, We suggest that radio-wave refraction within the pulsar's magnetosphere may plausibly explain this size. C1 AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA. UNIV TASMANIA,DEPT PHYS,HOBART,TAS 7001,AUSTRALIA. HARTEBEESTHOEK RADIO ASTRON OBSERV,KRUGERSDORP,TRANSVAAL,SOUTH AFRICA. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Gwinn, CR (reprint author), UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106, USA. RI King, Edward/A-1473-2012 OI King, Edward/0000-0002-6898-2130 NR 37 TC 23 Z9 23 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1997 VL 483 IS 1 BP L53 EP L56 DI 10.1086/310734 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ170 UT WOS:A1997XJ17000014 ER PT J AU Mould, JR Han, MS Stetson, PB Gibson, B Graham, JA Huchra, J Madore, B Rawson, D AF Mould, JR Han, MS Stetson, PB Gibson, B Graham, JA Huchra, J Madore, B Rawson, D TI The age of the large Magellanic cloud cluster NGC 1651 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, star clusters; galaxies, stellar content; Magellanic Clouds AB The age of NGC 1651 is 1.6 +/- 0.4 billion yr. This letter shows that accurate age determinations of young LMC clusters are achievable with aperture photometry of Wide Field Planetary Camera 2 (WFPC2) images taken in a single orbit of the HST. C1 UNIV WISCONSIN,MADISON,WI 53706. DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA. CARNEGIE INST WASHINGTON,DEPT TERR MAGNETISM,WASHINGTON,DC 20015. HARVARD UNIV,CTR ASTROPHYS,CAMBRIDGE,MA 02138. CALTECH,CTR INFRARED PROC & ANAL,NASA,IPAC EXTRAGALACT DATABASE,PASADENA,CA 91125. RP Mould, JR (reprint author), AUSTRALIAN NATL UNIV,INST ADV STUDIES,MT STROMLO & SIDING SPRING OBSERV,WESTON CREEK POST OFF,ACT 2611,AUSTRALIA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 16 TC 9 Z9 9 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 JUL 1 PY 1997 VL 483 IS 1 BP L41 EP L44 DI 10.1086/310727 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ170 UT WOS:A1997XJ17000011 ER PT J AU Vestrand, WT Sreekumar, P Mori, M AF Vestrand, WT Sreekumar, P Mori, M TI An outburst of GeV gamma-ray emission from centaurus X-3 SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; binaries, eclipsing; gamma rays, observations; pulsars, individual (Centaurus X-3) ID ACCRETION; CYGNUS-X-3; DISCOVERY; PULSARS; SEARCH; UHURU AB We present Compton Gamma Ray Observatory (CGRO) EGRET measurements of an outburst of greater than 100 MeV gamma-ray emission from the massive X-ray binary system Centaurus X-3 that occurred during an interval of rapid spin-down by the X-ray pulsar. For the 1994 October outburst, the phase-averaged 30 MeV-10 GeV emission is best fitted by a power law with index alpha = 1.81 +/- 0.37 and an integral flux above 100 MeV of (9.2 +/- 2.3) x 10(-7) photons cm(-2) s(-1), corresponding to a phase-averaged luminosity in GeV gamma rays of similar to 5 x 10(36) ergs s(-1). Our phase analysis, employing contemporaneous X-ray pulse observations by CGRO BATSE, indicates modulation of the gamma-ray emission at the pulsar's spin frequency with a significance level higher than 99.5%. Straightforward interpretation of the EGRET measurements requires at least sporadic acceleration of GeV particles within the Cen X-3 binary system. The observations also suggest that Galactic X-ray binary systems may constitute a class of highly variable GeV gamma-ray sources. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Vestrand, WT (reprint author), UNIV NEW HAMPSHIRE,CTR SPACE SCI,DURHAM,NH 03824, USA. NR 26 TC 29 Z9 29 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 JUL 1 PY 1997 VL 483 IS 1 BP L49 EP L52 DI 10.1086/310722 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ170 UT WOS:A1997XJ17000013 ER PT J AU Townsend, AR Vitousek, PM Desmarais, DJ Tharpe, A AF Townsend, AR Vitousek, PM Desmarais, DJ Tharpe, A TI Soil carbon pool structure and temperature sensitivity inferred using CO2 and (13)CO2 incubation fluxes from five Hawaiian soils SO BIOGEOCHEMISTRY LA English DT Article DE soil respiration; soil organic matter; decomposition; carbon-13; soil incubations; atmospheric CO2; Hawaii ID ORGANIC-MATTER DYNAMICS; TROPICAL SOILS; BIOMASS; CLIMATE; ABUNDANCE; TURNOVER AB We measured respiration and delta(13)C values of respired and soil carbon in long-term incubations of soils from two forests and three pastures along an altitudinal gradient in Hawaii. CO2 fluxes early in the incubations decreased rapidly, and then stabilized at approximately 20% of initial values for seven months. We suggest that the rapid drop and subsequent stabilization of respiration reflects a change in the dominant source of the CO2 from labile (active) to much more recalcitrant pools of soil organic matter (SOM). Estimates of active SOM were made by integrating all of the carbon respired in excess of that attributable to respiration of the intermediate SOM pool; these values ranged from 0.7-4.3% of total soil C. delta(13)C values for carbon respired from the pasture soils showed that older, forest-derived C contributed an increasing fraction of total soil respiration with time. Initial and late-stage respiration responded similarly to changes in temperature, suggesting that intermediate SOM is as sensitive to temperature as the active fraction. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94305. STANFORD UNIV,DEPT BIOL SCI,STANFORD,CA 94305. NR 28 TC 88 Z9 95 U1 2 U2 25 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0168-2563 J9 BIOGEOCHEMISTRY JI Biogeochemistry PD JUL PY 1997 VL 38 IS 1 BP 1 EP 17 DI 10.1023/A:1017942918708 PG 17 WC Environmental Sciences; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Geology GA XH841 UT WOS:A1997XH84100001 ER PT J AU Hamill, P Jensen, EJ Russell, PB Bauman, JJ AF Hamill, P Jensen, EJ Russell, PB Bauman, JJ TI The life cycle of stratospheric aerosol particles SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID TROPOSPHERE EXCHANGE; CIRCULATION; EVOLUTION; NUCLEI; TEMPERATURE; NUCLEATION; SATELLITE; CLOUD AB This paper describes the life cycle of the background (nonvolcanic) stratospheric sulfate aerosol. The authors assume the particles are formed by homogeneous nucleation near the tropical tropopause and are carried aloft into the stratosphere. The particles remain in the Tropics for most of their life, and during this period of time a size distribution is developed by a combination of coagulation, growth by heteromolecular condensation, and mixing with air parcels containing preexisting sulfate particles. The aerosol eventually migrates to higher latitudes and descends across isentropic surfaces to the lower stratosphere. The aerosol is removed from the stratosphere primarily at mid- and high latitudes through various processes, mainly by isentropic transport across the tropopause from the stratosphere into the troposphere. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. SUNY STONY BROOK,STONY BROOK,NY 11794. RP Hamill, P (reprint author), SAN JOSE STATE UNIV,DEPT PHYS,1 WASHINGTON SQ,SAN JOSE,CA 95192, USA. NR 52 TC 66 Z9 67 U1 0 U2 5 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 JUL PY 1997 VL 78 IS 7 BP 1395 EP 1410 DI 10.1175/1520-0477(1997)078<1395:TLCOSA>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XP114 UT WOS:A1997XP11400001 ER PT J AU Susskind, J Piraino, P Rokke, L Iredell, T Mehta, A AF Susskind, J Piraino, P Rokke, L Iredell, T Mehta, A TI Characteristics of the TOVS Pathfinder Path A dataset SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID GRIDPOINT TEMPERATURE ANOMALIES; OUTGOING LONGWAVE RADIATION; BUDGET EXPERIMENT ERBE; RADIOSONDE VALIDATION; DATA SET; PRECISION; MSU; PRECIPITATION; RADIANCES; SPACE AB The TIROS (Television Infrared Observation Satellite) Operational Vertical Sounder (TOVS) Pathfinder Path A dataset is currently a 9-yr dataset, 1985-93, of global fields of surface and atmospheric parameters derived from analysis of HIRS2 and MSU data on the NOAA-9, NOAA-10, NOAA-11, and NOAA-12 polar-orbiting operational meteorological satellites. The retrieved fields include land and ocean surface skin temperature, atmospheric temperature and water vapor profiles, total atmospheric O-3 burden, cloud-top pressure and radiatively effective fractional cloud cover, outgoing longwave radiation (OLR) and longwave cloud radiative forcing, and precipitation estimate. The fields are gridded on a 1 degrees x 1 degrees latitude-longitude grid and stored on a 1-day mean, 5-day mean, and monthly mean basis, with data from each satellite's local A.M. and P.M. orbits stored separately. Preliminary validation studies of the interannual differences of geophysical parameters derived from the TOVS Pathfinder dataset imply sufficient accuracy for their use both to study atmospheric behavior as well as to validate the ability of general circulation models to reproduce this behavior. The TOVS dataset is particularly suitable for climate studies because surface, atmospheric, cloud, and radiative parameters are all produced simultaneously in an internally consistent manner. Hence, statistical relationships between them will not be impaired by the heterogeneity inherent in data from different sources. In addition, the close agreement of OLR computed from the products with that observed by the Earth Radiation Budget Experiment enables explanation of interannual variability of OLR in terms of the variability of its component parts. The dataset is available for all users through the Goddard Space Flight Center Distributed Active Archive Center. C1 GEN SCI CORP,LAUREL,MD. JOINT CTR EARTH SYST TECHNOL,BALTIMORE,MD. RP Susskind, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 9104,GREENBELT,MD 20771, USA. RI Rokke, Laurie/I-5642-2015 OI Rokke, Laurie/0000-0002-5696-7240 NR 47 TC 172 Z9 174 U1 1 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD JUL PY 1997 VL 78 IS 7 BP 1449 EP 1472 DI 10.1175/1520-0477(1997)078<1449:COTTPP>2.0.CO;2 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XP114 UT WOS:A1997XP11400004 ER PT J AU Southward, RE Thompson, DS Thompson, DW StClair, AK AF Southward, RE Thompson, DS Thompson, DW StClair, AK TI Fabrication of highly reflective composite polyimide films via in situ reduction of matrix constrained silver(I) SO CHEMISTRY OF MATERIALS LA English DT Article ID CHEMICAL-VAPOR-DEPOSITION; PALLADIUM; PRECURSORS; OXYGEN; GOLD AB Optically reflective composite polyimide films have been prepared by casting a dimethylacetamide solution of silver(I) acetate, hexafluoroacetylacetone, and the poly(amic acid) derived from 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) and 4,4'-oxydianiline (4,4'-ODA) onto an fully imidized parent BTDA/4,4'-ODA base. Thermal curing of the silver(I)-containing poly(amic acid) topcoat leads to imidization with concomitant silver(I) reduction followed by silver(0) migration/aggregation yielding a reflective; but not conductive, silver surface. This ''film-on-film'' composite approach minimizes the silver required for the formation of a reflective surface and preserves the essential mechanical and thermal properties of the parent polymer. The metallized films exhibit outstanding metal-polymer and polymer-polymer adhesion, with the strong metal-polymer adhesion attributable to mechanical interlocking and/or encapsulation. Films were characterized by X-ray, DSC, TGA, XPS, TEM, and AFM. C1 COLL WILLIAM & MARY,DEPT CHEM,WILLIAMSBURG,VA 23185. COLL WILLIAM & MARY,DEPT APPL SCI,WILLIAMSBURG,VA 23185. NASA,LANGLEY RES CTR,DIV MAT,HAMPTON,VA 23681. NR 67 TC 27 Z9 30 U1 1 U2 7 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0897-4756 J9 CHEM MATER JI Chem. Mat. PD JUL PY 1997 VL 9 IS 7 BP 1691 EP 1699 DI 10.1021/cm970108m PG 9 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA XL711 UT WOS:A1997XL71100029 ER PT J AU VanderWal, RL AF VanderWal, RL TI Investigation of soot precursor carbonization using laser-induced fluorescence and laser-induced incandescence SO COMBUSTION AND FLAME LA English DT Article ID LAMINAR DIFFUSION FLAMES; VOLUME FRACTION; PARTICLES RP VanderWal, RL (reprint author), NASA,LEWIS RES CTR,NYMA,MS 110-3,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 24 TC 5 Z9 5 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD JUL PY 1997 VL 110 IS 1-2 BP 281 EP 284 DI 10.1016/S0010-2180(97)00072-2 PG 4 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA XF514 UT WOS:A1997XF51400019 ER PT J AU Turkel, E Radespiel, R Kroll, N AF Turkel, E Radespiel, R Kroll, N TI Assessment of preconditioning methods for multidimensional aerodynamics SO COMPUTERS & FLUIDS LA English DT Article ID NAVIER-STOKES EQUATIONS; DIFFERENCE-SCHEMES; FLOW AB We consider the steady state equations for a compressible fluid. For low speed flow the system is stiff since the ratio of the convective speed to the speed of sound is very small. To overcome this difficulty we alter the time dependency of the equations while retaining the same steady state operator. In order to achieve high numerical resolution we also alter the artificial dissipation (or Roe matrix) of the numerical scheme. The definition of preconditioners and artificial dissipation terms can be formulated conveniently by using other sets of dependent variables rather than the conservation variables. The effects of different preconditioners, artificial dissipation and grid density on accuracy and convergence to the steady state of the numerical solutions are presented in detail. The numerical results obtained for inviscid and viscous two-and three-dimensional flows over external aerodynamic bodies indicate that efficient multigrid computations of flows with very low Mach numbers are now possible. (C) 1997 Elsevier Science Ltd. C1 NASA LANGLEY,ICASE,HAMPTON,VA. DLR,INST DESIGN AERODYNAM,BRAUNSCHWEIG,GERMANY. RP Turkel, E (reprint author), TEL AVIV UNIV,SACKLER FAC EXACT SCI,SCH MATH SCI,IL-69978 TEL AVIV,ISRAEL. RI Turkel, Eli/F-6297-2011 OI Turkel, Eli/0000-0003-4273-0303 NR 30 TC 71 Z9 85 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD JUL PY 1997 VL 26 IS 6 BP 613 EP 634 DI 10.1016/S0045-7930(97)00013-3 PG 22 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA XV149 UT WOS:A1997XV14900004 ER PT J AU Bryson, S AF Bryson, S TI Practical visualization: The next ten years of visualization SO COMPUTERS IN PHYSICS LA English DT Article RP NASA, AMES RES CTR, MRJ INC, MOFFETT FIELD, CA 94035 USA. NR 5 TC 2 Z9 2 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0894-1866 J9 COMPUT PHYS JI Comput. Phys. PD JUL-AUG PY 1997 VL 11 IS 4 BP 362 EP 369 PG 8 WC Computer Science, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Computer Science; Physics GA XL714 UT WOS:A1997XL71400015 ER PT J AU Noor, AK AF Noor, AK TI New computing systems and future high-performance computing environment and their impact on structural analysis and design SO COMPUTERS & STRUCTURES LA English DT Article; Proceedings Paper CT 2nd International Conference on Computational Structures Technology CY AUG 30-SEP 01, 1994 CL ATHENS, GREECE SP Greek Assoc Comp Mech, Greek Minist Culture, Gen Secretariat Res & Technol Greece, Tourist Org Greece, Nato TU Athens, Univ Patras, Democritus Univ Thrace, Evgenidis Fdn, UNISYS Hellas ID PARALLEL ALGORITHMS; SYSTOLIC ARRAYS; TECHNOLOGY; BENCHMARK AB Recent advances in computer technology that are likely to impact structural analysis and design are reviewed. A brief summary is given of the advances in microelectronics and networking technologies, and in the human-computer interaction paradigms and techniques. The major features of new and projected computing systems, including high-performance computers, parallel processing machines, and small systems are described. Advances in programming environment, numerical algorithms, and computational strategies for new computing systems are reviewed. The impact of the advances in computer technology on structural analysis and design is described. A scenario for future computing paradigm is presented and the near-term needs in the computational structures area are outlined. (C) 1997 Published by Elsevier Science Ltd. RP Noor, AK (reprint author), UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23665, USA. NR 79 TC 17 Z9 21 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD JUL-AUG PY 1997 VL 64 IS 1-4 BP 1 EP 30 DI 10.1016/S0045-7949(96)00369-0 PG 30 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA XG831 UT WOS:A1997XG83100002 ER PT J AU McCarthy, JP Bamman, MM Yelle, JM LeBlanc, AD Rowe, RM Greenisen, MC Lee, SMC Spector, ER Fortney, SM AF McCarthy, JP Bamman, MM Yelle, JM LeBlanc, AD Rowe, RM Greenisen, MC Lee, SMC Spector, ER Fortney, SM TI Resistance exercise training and the orthostatic response SO EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY AND OCCUPATIONAL PHYSIOLOGY LA English DT Article DE blood volume; carotid baroreflexes; leg compliance; blood pressure; muscle mass ID PLASMA-VOLUME; BAROREFLEX FUNCTION; LEG COMPLIANCE; BED REST; STRENGTH; COMPATIBILITY; MICROGRAVITY; INTOLERANCE; INTENSITY; TOLERANCE AB Resistance exercise has been suggested to increase blood volume, increase the sensitivity of the carotid baroreceptor cardiac reflex response (BARO), and decrease leg compliance, all factors that are expected to improve orthostatic tolerance. To further test these hypotheses, cardiovascular responses to standing and to pre-syncopal limited lower body negative pressure (LBNP) were measured in two groups of sedentary men before and after a 12-week period of either exercise (n = 10) or no exercise (control, n = 9). Resistance exercise training consisted of nine isotonic exercises, four sets of each, 3 days per week, stressing all major muscle groups. After exercise training, leg muscle volumes increased (P < 0.05) by 4-14%, lean body mass increased (P = 0.00) by 2.0 (0.5) kg, leg compliance and BARO were not significantly altered, and the maximal LBNP tolerated without pre-syncope was not significantly different. Supine resting heart rate was reduced (P = 0.03) without attenuating the heart rate or blood pressure responses during the stand test or LBNP. Also, blood volume (I-125 and Cr-51) and red cell mass were increased (P < 0.02) by 2.8% and 3.9%, respectively. These findings indicate that intense resistance exercise increases blood volume but does not consistently improve orthostatic tolerance. C1 NASA,LYNDON B JOHNSON SPACE CTR,MED LIFE SCI DIV SD3,HOUSTON,TX 77058. KRUG LIFE SCI INC,HOUSTON,TX 77058. BAYLOR COLL MED,HOUSTON,TX 77030. NR 26 TC 25 Z9 25 U1 0 U2 3 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0301-5548 J9 EUR J APPL PHYSIOL O JI Eur. J. Appl. Physiol. Occup. Physiol. PD JUL PY 1997 VL 76 IS 1 BP 32 EP 40 DI 10.1007/s004210050209 PG 9 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA XJ235 UT WOS:A1997XJ23500005 PM 9243167 ER PT J AU Thedinga, JF Moles, A Fujioka, JT AF Thedinga, JF Moles, A Fujioka, JT TI Mark retention and growth of jet-injected juvenile marine fish SO FISHERY BULLETIN LA English DT Article ID SALMON RP Thedinga, JF (reprint author), NOAA, NATL MARINE FISHERIES SERV, ALASKA FISHERIES SCI CTR, AUKE BAY LAB, 11305 GLACIER HIGHWAY, JUNEAU, AK 99801 USA. NR 17 TC 2 Z9 2 U1 0 U2 0 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 USA SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD JUL PY 1997 VL 95 IS 3 BP 629 EP 633 PG 5 WC Fisheries SC Fisheries GA XH003 UT WOS:A1997XH00300019 ER PT J AU Korotev, RL Morris, RV Jolliff, BL Schwarz, C AF Korotev, RL Morris, RV Jolliff, BL Schwarz, C TI Lithological variation with depth and decoupling of maturity parameters in Apollo 16 regolith core 68001/2 SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID CENTRAL-HIGHLANDS; BRECCIAS; MOON; GEOCHEMISTRY; STRATIGRAPHY; HISTORY AB Using ferromagnetic resonance (FMR) and instrumental neutron activation analysis (INAA), we have determined the maturity (surface exposure) parameter I-s/FeO and concentrations of twenty-five chemical elements on samples taken every half centimeter down the 61-cm length of the 68001/2 regolith core (double drive tube) collected at station 8 on the Apollo 16 mission to the Moon. Contrary to premission expectations, no ejecta or other influence from South Ray crater is evident in the core, although a small inflection in the I-s/FeO profile at 3 cm depth may be related the South Ray crater impact. Regolith maturity generally decreases with depth, as in several previously studied cores. We recognize five compositionally distinct units in the core, which we designate A through E, although all are similar in composition to each other and to other soils from the Cayley plains at the Apollo 16 site. Unit A (0-33 cm) is mature to submature throughout (I-s/FeO: 89-34 units) and is indistinguishable in composition from surface soils collected at station 8. Unit B (33-37 cm) is enriched slightly in a component of anorthositic norite composition. Unit D (42-53 cm) is compositionally equivalent to 80 wt% Unit-A soil plus 20 wt% Apollo-16-type dimict breccia consisting of subequal parts anorthosite and impact-melt breccia. Compared to Unit A, Unit E (53-61 cm) contains a small proportion (up to 4%) of some component compositionally similar to Apollo 14 sample 14321. Unit C (37-42 cm) is unusual. For lithophile and siderophile elements, it is similar to Units A and D. However, I-s/FeO is low throughout the unit (<30 units) and in a bluish-gray zone at 41 cm depth I-s/FeO drops to 1.6 units, the lowest value that we have observed in several hundred Apollo 16 soil samples. Samples from the bluish-gray zone also have low Zn concentrations, <10 mu g/g, compared to 20-30 mu g/g for the rest of the core. Although both values are consistent with fragmented rock material that has received virtually no surface exposure, the abundance of agglutinates in the bluish-gray soil of Unit C is moderately high, typical of a submature soil that would ordinarily have I-s/FeO approximate to 30. We believe that the anomalously low values of I-s/FeO and Zn concentration result because the soil was heated to similar to 800-1000 degrees C, probably during an impact. This temperature range is sufficient to volatize the surface-correlated Zn and agglomerate the nanophase metal giving rise to the FMR signal but is not great enough to sinter the soil. Alternatively, the unusual soil interval may represent a disaggregated or incipient regolith breccia, although there is no significant difference in the texture or clast-matrix relationships between Unit C and adjacent units. Copyright (C) 1997 Elsevier Science Ltd. C1 WASHINGTON UNIV,MCDONNELL CTR SPACE SCI,ST LOUIS,MO 63130. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. LOCKHEED MARTIN ENGN & SCI CO,HOUSTON,TX 77058. RP Korotev, RL (reprint author), WASHINGTON UNIV,DEPT EARTH & PLANETARY SCI,ST LOUIS,MO 63130, USA. NR 50 TC 6 Z9 6 U1 0 U2 2 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 JUL PY 1997 VL 61 IS 14 BP 2989 EP 3002 DI 10.1016/S0016-7037(97)00140-3 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XT455 UT WOS:A1997XT45500015 ER PT J AU Dessler, AE Considine, DB Rosenfield, JE Kawa, SR Douglass, AR Russell, JM AF Dessler, AE Considine, DB Rosenfield, JE Kawa, SR Douglass, AR Russell, JM TI Lower stratospheric chlorine partitioning during the decay of the Mt Pinatubo aerosol cloud SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ERUPTION; OZONE; AGE; AIR AB We present measurements of lower stratospheric HCl between July 1992 and August 1996 made by instruments onboard the Upper Atmosphere Research Satellite (UARS). We find that at 46 hPa the fraction of total inorganic chlorine (Cl-y) in the form of HCl increased from 0.68 averaged between July 1992 and June 1993 to 0.78 averaged between July 1995 and June 1996. This increase of (16+/-9)% over three years is much smaller than the trend calculated from in situ measurements made by instruments onboard NASA's ER-2 high-altitude aircraft that has been used to suggest problems with our understanding of lower stratospheric chlorine partitioning. The trend determined from the UARS data is slightly larger than the trend predicted by a two-dimensional model simulation of the atmospheric effects of the Mt. Pinatubo eruption. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. HAMPTON UNIV,HAMPTON,VA 23668. RP Dessler, AE (reprint author), UNIV MARYLAND,DEPT METEOROL,JOINT CTR EARTH SYST SCI,COLLEGE PK,MD 20742, USA. RI Douglass, Anne/D-4655-2012; Kawa, Stephan/E-9040-2012; Dessler, Andrew/G-8852-2012 OI Dessler, Andrew/0000-0003-3939-4820 NR 17 TC 11 Z9 11 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 JUL 1 PY 1997 VL 24 IS 13 BP 1623 EP 1626 DI 10.1029/97GL01470 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000020 ER PT J AU Sandor, BJ Clancy, RT AF Sandor, BJ Clancy, RT TI Mesospheric observations and modeling of the Zeeman split 233.9 GHz O-18 O-16 line SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OXYGEN AB Observations made from Kitt Peak, AZ, of the 233.9 GHz emission line of (OO)-O-18-O-16 in the upper stratosphere and lower mesosphere are reported. A good model fit to the line is obtained by incorporation of pressure and temperature broadening effects, as well as a Zeeman splitting algorithm that uses a standard geomagnetic field model and a paramagnetic Hamiltonian description of the molecular energy states. These observations are used, along with the well known (OO)-O-18-O-16 mixing ratio, to establish absolute calibration for observations of other chemical species from Kitt Peak. Repeated measurements show no change in this absolute calibration between observation dates. The wide magnetic splitting (+/-1.8 MHz) exhibited by this line with only six Zeeman components provides a unique test of middle atmosphere Zeeman effect model calculations, supporting the use of O-2 lines by microwave atmospheric sounders to measure pressure and temperature. C1 SPACE SCI INST,BOULDER,CO 80303. RP Sandor, BJ (reprint author), CALTECH,JET PROP LAB,MS 183-701,PASADENA,CA 91109, USA. NR 18 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 1 PY 1997 VL 24 IS 13 BP 1631 EP 1634 DI 10.1029/97GL01543 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000022 ER PT J AU Bavassano, B Woo, R Bruno, R AF Bavassano, B Woo, R Bruno, R TI Heliospheric plasma sheet and coronal streamers SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-WIND; 1-AU AB Helios 2 measurements of solar wind plasma and magnetic field are used to investigate the structure of the heliospheric plasma sheet between 0.3 and 1 AU. In agreement with previous observations at 1 AU, the plasma sheet thickness is much larger than that of the embedded current sheet. The plasma sheet appears surrounded by a density halo, a region of slightly raised density. High-time resolution data show that decreases in relative helium abundance coincide with the plasma sheet boundaries, reinforcing the notion that the solar wind within the plasma sheet is of a different nature (with different solar origins) than that outside it. Although radio occultation measurements of the corona were not available at the time of the Helios data, a synthesis of recent results on coronal streamers shows that there is a remarkable similarity between their major features and those of plasma sheets, demonstrating that the coronal counterpart of the plasma sheet is the stalk of the coronal streamer. These measurements also suggest that the density halo seen in the Hellos data is associated with the radial extension of the boundaries of the streamer observed in the extended corona before the streamer narrows to a stalk. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Bavassano, B (reprint author), CNR,IST FIS SPAZIO INTERPLANETARIO,VIA G GALILEI,CP 27,I-00044 FRASCATI,ITALY. OI bruno, roberto/0000-0002-2152-0115 NR 11 TC 52 Z9 53 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 JUL 1 PY 1997 VL 24 IS 13 BP 1655 EP 1658 DI 10.1029/97GL01630 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000028 ER PT J AU Ratkiewicz, R Barnes, A Spreiter, JR AF Ratkiewicz, R Barnes, A Spreiter, JR TI Heliospheric termination shock motion in response to LISM variations: Spherically symmetric model SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LOCAL INTERSTELLAR-MEDIUM; SOLAR-WIND; FLUCTUATIONS; HELIOPAUSE; SYSTEM; INTERFACE; DISTANCE; FRICTION; LOCATION; REGION AB The unsteady spherically symmetric one-dimensional gasdynamic model appears to be a powerful tool in the investigation of the termination shock motion. Such a model has previously been used to examine the response of the heliospheric termination shock to variations in upstream solar wind conditions [Ratkiewicz et al., 1996]. In the current paper we apply the same model to study response of the shock to variations in the interstellar medium. The initial-boundary conditions for the unsteady calculations are given by the pressure as a function Of time on an outer boundary either alone or with the density as a function of time on an inner boundary. The motion of the termination shock is caused by fluctuations in both solar wind and interstellar plasma parameters and has a rather complicated behavior, characterized by a sequence of perturbations that hit the termination shock and are reflected from the outer boundary. C1 STANFORD UNIV,STANFORD,CA 94305. RP Ratkiewicz, R (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 37 TC 3 Z9 3 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 1 PY 1997 VL 24 IS 13 BP 1659 EP 1662 DI 10.1029/97GL01537 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000029 ER PT J AU Pfaff, RF Sobral, JHA Abdu, MA Swartz, WE LaBelle, JW Larsen, MF Goldberg, RA Schmidlin, FJ AF Pfaff, RF Sobral, JHA Abdu, MA Swartz, WE LaBelle, JW Larsen, MF Goldberg, RA Schmidlin, FJ TI The Guara campaign: A series of rocket-radar investigations of the Earth's upper atmosphere at the magnetic equator SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB The Guara Campaign consisted of a series of sounding rockets that were launched from August - October, 1994 at a new launch facility at Alcantara, Brazil, which is within one degree of the Earth's magnetic equator. The campaign consisted of focused scientific experiments designed to investigate the electrodynamics and irregularities in the equatorial ionosphere and mesosphere and to study their relationship with neutral upper atmosphere motions. In all, 13 large sounding rockets and 20 small meteorological rockets were launched as part of four different experiment groups designed to investigate: (1) the daytime equatorial electrojet, (2) very high altitude Spread-F processes, (3) sunset electrodynamics, and (4) middle atmosphere-thermosphere coupling at the equator. All of the experiments utilized ground-based scientific instruments including a VHF backscatter radar interferometer, magnetometers, ionosondes, and scintillation receivers. The project was a joint undertaking of the National Aeronautics and Space Administration (NASA) of the United States and the Institute Nacional de Pesquisas Espacias (INPE) of Brazil. The project was named the Guara Campaign after a beautiful species of bird that is native to the equatorial region of Brazil. C1 INST NACL PESQUISAS ESPACIAIS,BR-12201 S JOSE CAMPOS,BRAZIL. DARTMOUTH COLL,HANOVER,NH 03755. CLEMSON UNIV,CLEMSON,SC 29631. CORNELL UNIV,SCH ELECT ENGN,ITHACA,NY 14853. RP Pfaff, RF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Goldberg, Richard /E-1881-2012; Larsen, Miguel/A-1079-2013; Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 5 TC 23 Z9 23 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 JUL 1 PY 1997 VL 24 IS 13 BP 1663 EP 1666 DI 10.1029/97GL01534 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000030 ER PT J AU Pfaff, RF Acuna, MH Marionni, PA Trivedi, NB AF Pfaff, RF Acuna, MH Marionni, PA Trivedi, NB TI DC polarization electric field, current density, and plasma density measurements in the daytime equatorial electrojet SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID REGION AB Measurements of the vector DC electric field, current density, and plasma number density were gathered in the daytime equatorial electrojet on a sounding rocket launched from Alcantara, Brazil. The data set provides a self-consistent picture of the electrodynamics of the daytime electrojet, permitting a detailed comparison of the altitude profiles of the vertical component of the DC electric field, E-vert, the current density, J, and the plasma number density, N-e. Good agreement in the upper electrojet region between both the magnitude and the profile of the plasma drifts, calculated independently from E-vert/B and J(zonal)/qN(e), demonstrates that the equatorial electrojet is a Hall current consisting of electron motion driven by a vertical DC electric field. The data support the basic Cowling conductivity ideas of electron flow at the dip equator within a narrow conducting layer in which the ions are at rest. C1 INST NACL PESQUISAS ESPACIAIS,BR-12201 S JOSE CAMPOS,BRAZIL. RP Pfaff, RF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 15 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 JUL 1 PY 1997 VL 24 IS 13 BP 1667 EP 1670 DI 10.1029/97GL01536 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000031 ER PT J AU Pfaff, RF Marionni, PA Swartz, WE AF Pfaff, RF Marionni, PA Swartz, WE TI Wavevector observations of the two-stream instability in the daytime equatorial electrojet SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA-DENSITY MEASUREMENTS; WAVELENGTH; FREQUENCY; WAVES; FIELD AB Detailed measurements of electric field wavevectors of the Farley-Buneman two-stream instability in the daytime equatorial electrojet were gathered on a sounding rocket flown from Alcantara, Brazil. Primary two-stream waves were detected in the altitude region of 104 - 108 km, where the current density and polarization electric field maximized and where intense 3 m vertical echoes were observed by a 50 MHz backscatter radar. The in-situ measured wave components are predominantly oriented in the horizontal, zonal direction. Spaced receivers reveal wavelengths of 11-14 m with phase velocities of about 370 m/s at the peak wave power near 106.5 km. These velocities are constant from 1-15 m, indicative of dispersionless flow. Although the neutral wind was not measured, the in-situ phase velocity appears to be below that predicted by linear theory. C1 CORNELL UNIV,SCH ELECT ENGN,ITHACA,NY 14853. RP Pfaff, RF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 13 TC 10 Z9 10 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 JUL 1 PY 1997 VL 24 IS 13 BP 1671 EP 1674 DI 10.1029/97GL01535 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000032 ER PT J AU LaBelle, J Jahn, JM Pfaff, RF Swartz, WE Sobral, JHA Abdu, MA Muralikrishna, P dePaula, ER AF LaBelle, J Jahn, JM Pfaff, RF Swartz, WE Sobral, JHA Abdu, MA Muralikrishna, P dePaula, ER TI The Brazil/Guara equatorial spread F campaign: Results of the large scale measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID IRREGULARITIES AB The Guara campaign equatorial spread F rocket was launched from Alcantara, Brazil, on 14 October 1994 at 1955 LT (2255 UT) into an active topside spread F event. Spread F plasma irregularities observed up to 822 km altitude correlate well with plumes observed simultaneously with a coherent backscatter radar. Matching 1-10 km features in the rocket and radar data over the altitude range 300-800 km implies an eastward drift speed of similar to 110 m/s, versus 95 m/s at 400-500 km based on radar interferometry. Combining these two measurements implies an average upward drift of 30 m/s for the highest altitude structures. The amplitude difference between low- and high-altitude 10-km density structures, if attributed to temporal effects, implies an effective diffusion coefficient (decay time constant) of 500-1000 m(2)/s (2-4x10(-4) s(-1)), which agrees with previous estimates from other techniques and supports the idea that the decay of spread F turbulence occurs in a scale-independent manner. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. CORNELL UNIV,SCH ELECT ENGN,ITHACA,NY 14853. INST NACL PESQUISAS ESPACIAIS,BR-12201 S JOSE CAMPOS,BRAZIL. RP LaBelle, J (reprint author), DARTMOUTH COLL,DEPT PHYS & ASTRON,HANOVER,NH 03755, USA. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 11 TC 21 Z9 21 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 JUL 1 PY 1997 VL 24 IS 13 BP 1691 EP 1694 DI 10.1029/97GL00818 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000037 ER PT J AU Jahn, JM LaBelle, J Pfaff, RF AF Jahn, JM LaBelle, J Pfaff, RF TI DC electric field measurements with the Guara spread-F rocket SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EQUATORIAL; DRIFTS AB Data presented in this paper provide the first high-altitude (> 600 km) rocket measurements of electric fields associated with spread-F plumes measured simultaneously with a VHF coherent backscatter radar. In regions outside of spread-F plasma depletions the electric field is primarily vertical, implying zonal plasma flow. The mean zonal drifts of the ambient plasma-inferred from the rocket data are larger than average quiet time values, which can be attributed to the presence of active spread-F irregularities. Within the spread-F depletions, the vertical electric field becomes comparable to the zonal component, and individual plasma depletions are found to rise with speeds of up to 100 m/s. No large (> 10 mV/m) electric fields are observed in the plume region. C1 DARTMOUTH COLL,DEPT PHYS & ASTRON,HANOVER,NH 03755. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 11 TC 8 Z9 8 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 JUL 1 PY 1997 VL 24 IS 13 BP 1695 EP 1698 DI 10.1029/97GL01242 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000038 ER PT J AU Lehmacher, GA Goldberg, RA Schmidlin, FJ Croskey, CL Mitchell, JD Swartz, WE AF Lehmacher, GA Goldberg, RA Schmidlin, FJ Croskey, CL Mitchell, JD Swartz, WE TI Electron density fluctuations in the equatorial mesosphere: Neutral turbulence or plasma instabilities? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LOWER THERMOSPHERE; GRAVITY-WAVE; SCALE; BREAKING; ROCKET; ENERGY; RADAR AB Electron density fluctuations were measured with rocket borne nose-tip probes launched on August 19, 1994 at 12:08 LT and August 24, 1994 at 10:39 LT from Alcantara, Brazil (2.3 degrees S, 44.4 degrees W) during the MALTED/Guara campaign. The spectral analysis of the fluctuations shows evidence for neutral turbulence in the region of 85 to 90 km for both flights. Falling spheres launched 44 and 13 minutes prior to the main payloads indicate superadiabatic lapse rates in this height region. Also for the two flights, the electron density fluctuations between 90 and 110 km are dominated by the equatorial electrojet which has been observed simultaneously by the 50-MHz CUPRI VHF radar. The in situ data show significant plasma irregularities associated with the electrojet at altitudes well below those that return detectable radar echoes, and where they can interfere with the fluctuations attributed to neutral turbulence. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,WALLOPS FLIGHT FACIL,WALLOPS ISL,VA 23337. PENN STATE UNIV,COMMUN & SPACE SCI LAB,UNIVERSITY PK,PA 16802. CORNELL UNIV,SCH ELECT ENGN,ITHACA,NY 14853. RI Goldberg, Richard /E-1881-2012; Lehmacher, Gerald/F-2653-2013 NR 16 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 JUL 1 PY 1997 VL 24 IS 13 BP 1715 EP 1718 DI 10.1029/97GL00708 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XJ380 UT WOS:A1997XJ38000043 ER PT J AU Hillier, JK AF Hillier, JK TI Shadow-hiding opposition surge for a two-layer surface SO ICARUS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; PHOTOMETRIC PROPERTIES; TRITON; SCATTERING; TERRAINS; FEATURES; MARS AB A shadow hiding opposition surge, based on B. Hapke (1986, Icarus 67, 264-280), is derived for a surface consisting of an optically finite veneer of material over an underlying substrate. As done by Hapke in his photometric model, it is assumed that standard radiative transfer theory with correction for macroscopic roughness and a shadow hiding opposition surge provides an adequate description of the two-layered surface. The scattering properties of the upper layer are calculated using the doubling technique while Hapke's photometric model is used to describe the underlying layer. An adaptation of the doubling technique is used to calculate the scattering from the combined system. The model should have wide applicability in the Solar System and has been used with success to describe the polar regions of Ganymede (J. Hillier ef al., 1996, Icarus 124, 308-317) as well as the equatorial regions of Triton (J. Hillier and J. Veverka, in preparation). Using this model, it is shown that extremely narrow opposition surges, as observed on many Solar System bodies, might be explained by a shadow-hiding model even for relatively compact surfaces if the particle size decreases toward the surface and may provide an alternative explanation to the coherent backscatter mechanism for the observed surges. (C) 1997 Academic Press. RP Hillier, JK (reprint author), CALTECH,JET PROP LAB,MS 183-501,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 31 TC 17 Z9 17 U1 1 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD JUL PY 1997 VL 128 IS 1 BP 15 EP 27 DI 10.1006/icar.1997.5724 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR109 UT WOS:A1997XR10900002 ER PT J AU Fernandez, YR McFadden, LA Lisse, CM Helin, EF Chamberlin, AB AF Fernandez, YR McFadden, LA Lisse, CM Helin, EF Chamberlin, AB TI Analysis of POSS images of Comet-Asteroid transition objects 107P/1949 W1 (Wilson-Harrington) SO ICARUS LA English DT Article ID NEAR-EARTH ASTEROIDS; PDS MEASURING ENGINE; PHOTOMETRIC CALIBRATION; NGS-POSS; ABUNDANCE; P/HALLEY; ROTATION; ZINNER; TAIL; DUST AB We have analyzed the only two known images taken of Comet 107P = Asteroid (4015) Wilson-Harrington while it was a distinctly cometary object. The images reside on two Palomar Observatory Sky Survey (POSS) photographic plates taken ore 19 November 1949 UT and provide a unique way of studying the fading gasps of a dying comet. The comet appears as a streak, a tail is evident, but the coma is indistinguishable. A comparison of the profiles of the streaks and the stellar PSF yielded no coma, implying the coma's scale height is small (upper limit of a few hundred kilometers). Finson-Probstein modeling of the tail demonstrates that it is not a dust tail. If it were, the size of the particles would have to be tens to hundreds of micrometers in size (which contradicts the tail's blue color [vs. the Sun]) and they would have to have been released several weeks before the observations (which contradicts observers' reports that the tail dissipated in a few days). Instead, we are seeing CO+ and H2O+ fluorescence in a plasma tail. With this composition, the tail's blue hue and short lifetime are explained. The lag angle of the tail on the Image is about 15 degrees, larger than the '(typical)' for Type I tails, but the value is not implausible, We show that the deviation of the solar wind from radial need not have been atypical to explain it, Pie have calibrated the relevant portions of the photographic plates and, from the surface brightness of the tail and an estimate of its age, we have calculated a plausible maximum to the production rate of H2O and CO during Wilson-Harrington's outburst: Q(H2O) approximate to Q(CO) = 5 x 10(27) molecules sec(-1). The measurements indicate that CO is roughly as abundant as H2O on the dormant comet's nucleus. (C) 1997 Academic Press. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Fernandez, YR (reprint author), UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. RI McFadden, Lucy-Ann/I-4902-2013; Lisse, Carey/B-7772-2016; OI McFadden, Lucy-Ann/0000-0002-0537-9975; Lisse, Carey/0000-0002-9548-1526; Fernandez, Yanga/0000-0003-1156-9721 NR 58 TC 22 Z9 22 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUL PY 1997 VL 128 IS 1 BP 114 EP 126 DI 10.1006/icar.1997.5728 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR109 UT WOS:A1997XR10900010 ER PT J AU Knox, RG Kalb, VL Levine, ER Kendig, DJ AF Knox, RG Kalb, VL Levine, ER Kendig, DJ TI A problem-solving workbench for interactive simulation of ecosystems SO IEEE COMPUTATIONAL SCIENCE & ENGINEERING LA English DT Article ID GLOBAL CHANGE; MODELS AB A problem-solving environment called WISE rises object-oriented software design to link research models from various subdisciplines for more comprehensive ecosystem simulation and visualization. A simulation manager component rises a clock to control the coupling mechanism, allowing dynamic querying between encapsulated models for the most recent values of state variables. C1 NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,TERR INFORMAT SYST BRANCH,GREENBELT,MD 20771. RI Knox, Robert/E-9657-2011; Kalb, Virginia/A-9971-2009 OI Kalb, Virginia/0000-0002-3107-9271 NR 9 TC 7 Z9 9 U1 0 U2 2 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 SN 1070-9924 J9 IEEE COMPUT SCI ENG JI IEEE Comput. Sci. Eng. PD JUL-SEP PY 1997 VL 4 IS 3 BP 52 EP 60 DI 10.1109/99.615431 PG 9 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic; Mathematics, Applied SC Computer Science; Engineering; Mathematics GA XX979 UT WOS:A1997XX97900009 ER PT J AU Bryson, S AF Bryson, S TI The virtual windtunnel on the virtual workbench SO IEEE COMPUTER GRAPHICS AND APPLICATIONS LA English DT Editorial Material RP Bryson, S (reprint author), NASA,AMES RES CTR,MS T27A-1,MOFFETT FIELD,CA 94035, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 SN 0272-1716 J9 IEEE COMPUT GRAPH JI IEEE Comput. Graph. Appl. PD JUL-AUG PY 1997 VL 17 IS 4 BP 15 EP 15 PG 1 WC Computer Science, Software Engineering SC Computer Science GA XG836 UT WOS:A1997XG83600007 ER PT J AU Chatterji, GB Menon, PK Sridhar, B AF Chatterji, GB Menon, PK Sridhar, B TI GPS machine vision navigation system for aircraft SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Letter ID MOTION AB A Kalman filter based multiple sensor fusion method for determining the position of a general aviation aircraft with respect to the runway during night landing and takeoff is discussed. Known structure of the airport lights, video images acquired by an onboard video camera, position estimates from an onboard Global Positioning System (GPS), and data from an attitude indicator are integrated in a Kalman filtering algorithm. Simulation results are presented to demonstrate the feasibility of the proposed concept. C1 SANTA CLARA UNIV,SANTA CLARA,CA 95053. NASA,AMES RES CTR,AFF BRANCH,MOFFETT FIELD,CA 94035. RP Chatterji, GB (reprint author), NASA,AMES RES CTR,STERLING SOFTWARE INC,MS 262-2,MOFFETT FIELD,CA 94035, USA. NR 25 TC 23 Z9 31 U1 0 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9251 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD JUL PY 1997 VL 33 IS 3 BP 1012 EP 1025 DI 10.1109/7.599326 PG 14 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA XH348 UT WOS:A1997XH34800027 ER PT J AU Asner, GP Wessman, CA Privette, JL AF Asner, GP Wessman, CA Privette, JL TI Unmixing the directional reflectances of AVHRR sub-pixel landcovers SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 1996 International Geoscience and Remote Sensing Symposium (IGARSS 96) - Remote Sensing for a Sustainable Future CY MAY 21-31, 1996 CL LINCOLN, NE SP IEEE, Geosci & Remote Sensing Soc, Univ Nebraska, Lincoln, NASA, NOAA, USN, Off Naval Res, US Natl Comm Union Radiosci Int, Canon Modern Methods Inc, Univ Nebraska Lincoln, Ctr Adv Land Management Informat Technol, Univ Nebraska Lincoln, Ctr Commun & Informat Sci, Univ Nebraska Lincoln, Ctr Electro Opt, Univ Nebraska Lincoln, Ctr Laser Anal Studies Trace Gas Dynam, Centurion Int Inc, Univ Nebraska Lincoln, Coll Engn & Technol, Univ Nebraska Lincoln, Dept Elect Engn, ERDAS Inc, Univ Nebraska Lincoln, High Plains Climate Ctr, Li Cor Inc, US Geol Survey EROS Data Ctr ID RESOLUTION SATELLITE DATA; RADIATIVE-TRANSFER; VEGETATION; CANOPIES; MODEL; SCATTERING; TRANSPORT; COVER AB Recent progress in canopy bidirectional reflectance distribution function (BRDF) model inversions has allowed accurate estimates of vegetation biophysical characteristics from remotely sensed multi-angle optical data, Since most current BRDF inversion methods utilize one-dimensional (1-D) models, surface homogeneity within an image pixel is implied, The Advanced Very High Resolution Radiometer (AVHRR) is one of the few spaceborne sensors capable of acquiring radiometric data over the range of view angles required for BRDF inversions. However, its relatively coarse spatial resolution often results in measurements of mixed landcovers, and thus the data may not be ideal for BRDF inversions, We present a three-step spectral unmixing method for retrieving AVHRR sub-pixel directional reflectances in regions of high spatial heterogeneity. The reflectances of individual vegetation types are deconvolved using co-located Landsat TM and AVHRR data. The three major steps in the model include: 1) unmixing of vegetation endmember concentrations in TM imagery; 2) correction of dissimilar shadow fractions between TM and AVHRR data; and 3) unmixing of AVHRR sub-pixel reflectances of vegetation types for any sun-sensor geometry, We tested the method using simulated TM and AVHRR data. A savanna landscape simulation, comprised of a canopy radiative transfer model and a crown geometric-optical model, was used to create images containing mixed pixels of tree, grass, and shade endmembers. TM and AVHRR spectral response functions, viewing geometries, and off-nadir pixel shape calculations were incorporated into the simulations, Following the successful testing of the unmixing method on error-free simulations, random noise representing atmospheric perturbations and co-registration inaccuracies was added to the data. The method Is stable when errors resulting from either the first unmixing step or image co-registration inaccuracies are introduced, Potential errors in the AVHRR data may result in inaccurately retrieved reflectances if the image scene contains a spatially homogeneous mix of landcovers. A method for detecting and mitigating this problem is presented. C1 UNIV COLORADO,DEPT ENVIRONM POPULAT & ORGANISM BIOL,BOULDER,CO 80309. UNIV MARYLAND,DEPT GEOG,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Asner, GP (reprint author), UNIV COLORADO,COOPERAT INST RES ENVIRONM SCI,BOULDER,CO 80309, USA. RI Privette, Jeffrey/G-7807-2011; Asner, Gregory/G-9268-2013 OI Privette, Jeffrey/0000-0001-8267-9894; Asner, Gregory/0000-0001-7893-6421 NR 35 TC 37 Z9 39 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1997 VL 35 IS 4 BP 868 EP 878 DI 10.1109/36.602529 PG 11 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XL049 UT WOS:A1997XL04900009 ER PT J AU Minnis, P Mayor, S Smith, WL Young, DF AF Minnis, P Mayor, S Smith, WL Young, DF TI Asymmetry in the diurnal variation of surface albedo SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 1996 International Geoscience and Remote Sensing Symposium (IGARSS 96) - Remote Sensing for a Sustainable Future CY MAY 21-31, 1996 CL LINCOLN, NE SP IEEE, Geosci & Remote Sensing Soc, Univ Nebraska, Lincoln, NASA, NOAA, USN, Off Naval Res, US Natl Comm Union Radiosci Int, Canon Modern Methods Inc, Univ Nebraska Lincoln, Ctr Adv Land Management Informat Technol, Univ Nebraska Lincoln, Ctr Commun & Informat Sci, Univ Nebraska Lincoln, Ctr Electro Opt, Univ Nebraska Lincoln, Ctr Laser Anal Studies Trace Gas Dynam, Centurion Int Inc, Univ Nebraska Lincoln, Coll Engn & Technol, Univ Nebraska Lincoln, Dept Elect Engn, ERDAS Inc, Univ Nebraska Lincoln, High Plains Climate Ctr, Li Cor Inc, US Geol Survey EROS Data Ctr ID RADIATION; VARIABILITY; ALGORITHMS; BALANCE; CLOUD AB Remote sensing of surface properties and estimation of clear-sky and surface albedo generally assume that the albedo depends only on the solar zenith angle, The effects of dew, frost, and precipitation as well as evaporation and wind can lead to some systematic diurnal variability resulting in an asymmetric diurnal cycle of albedo, This paper examines the symmetry of both surface-observed and top-of-the-atmosphere (TOA) albedos derived from satellite data. Broadband surface albedos were measured at the Department of Energy Atmospheric Radiation Measurement (ARM) Program Southern Great Plains Central Facility near Lament, Oklahoma and several extended facilities, GOES satellite radiance data are converted to broadband albedo using bidirectional reflectance functions and an empirical narrowband-to-broadband relationship. The surface and top-of-atmosphere albedos vary in a consistent fashion during both the morning and afternoon, The initial results indicate that surface moisture, probably in the form of dew, has a significant effect and can change the albedo by 10% at a given solar zenith angle between the morning and afternoon, Wind speed is well correlated with the diurnal albedo asymmetry, Light winds and small dew point depressions are associated with the greatest morning/afternoon albedo differences. Aerosols tend to moderate those differences, Changes in the surface properties from dew may alter the bidirectional reflectance characteristics of the scene, affecting the interpretation of remote sensing data, Errors in the diurnally averaged albedos derived from sun-synchronous satellite measurements that arise from albedo asymmetry are generally less than 3%, Further examination of surface albedo asymmetry is needed to assess its influence on satellite measurements and the surface energy budget over a range of land surface types. C1 ANALYT SERV & MAT INC,HAMPTON,VA 23666. RP Minnis, P (reprint author), NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681, USA. RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 24 TC 42 Z9 50 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1997 VL 35 IS 4 BP 879 EP 891 DI 10.1109/36.602530 PG 13 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XL049 UT WOS:A1997XL04900010 ER PT J AU StGermain, KM Cavalieri, DJ AF StGermain, KM Cavalieri, DJ TI A microwave technique for mapping ice temperature in the arctic seasonal sea ice zone SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 1996 International Geoscience and Remote Sensing Symposium (IGARSS 96) - Remote Sensing for a Sustainable Future CY MAY 21-31, 1996 CL LINCOLN, NE SP IEEE, Geosci & Remote Sensing Soc, Univ Nebraska, Lincoln, NASA, NOAA, USN, Off Naval Res, US Natl Comm Union Radiosci Int, Canon Modern Methods Inc, Univ Nebraska Lincoln, Ctr Adv Land Management Informat Technol, Univ Nebraska Lincoln, Ctr Commun & Informat Sci, Univ Nebraska Lincoln, Ctr Electro Opt, Univ Nebraska Lincoln, Ctr Laser Anal Studies Trace Gas Dynam, Centurion Int Inc, Univ Nebraska Lincoln, Coll Engn & Technol, Univ Nebraska Lincoln, Dept Elect Engn, ERDAS Inc, Univ Nebraska Lincoln, High Plains Climate Ctr, Li Cor Inc, US Geol Survey EROS Data Ctr ID HIGH-RESOLUTION RADIOMETER; SURFACE-TEMPERATURE AB A technique for deriving ice temperature in the Arctic seasonal sea ice zone from passive microwave radiances has been developed, The algorithm operates on brightness temperatures derived from the Special Sensor Microwave/Imager (SSM/I) and uses ice concentration and type from a previously developed thin ice algorithm to estimate the surface emissivity. Comparisons of the microwave derived temperatures with estimates derived from infrared imagery of the Bering Strait yield a correlation coefficient of 0.93 and an RMS difference of 2.1 K when coastal and cloud contaminated pixels are removed, SSM/I temperatures were also compared with a time series of air temperature observations from Gambell on St, Lawrence Island and from Point Barrow, AK weather stations, These comparisons indicate that the relationship between the air temperature and the ice temperature depends on ice type. C1 NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,GREENBELT,MD 20771. RP StGermain, KM (reprint author), USN,RES LAB,REMOTE SENSING DIV,CODE 7223,WASHINGTON,DC 20375, USA. NR 13 TC 1 Z9 1 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1997 VL 35 IS 4 BP 946 EP 953 DI 10.1109/36.602536 PG 8 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XL049 UT WOS:A1997XL04900016 ER PT J AU Smith, JA Chauhan, NS Schmugge, TJ Ballard, JR AF Smith, JA Chauhan, NS Schmugge, TJ Ballard, JR TI Remote sensing of land surface temperature: The directional viewing effect SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 1996 International Geoscience and Remote Sensing Symposium (IGARSS 96) - Remote Sensing for a Sustainable Future CY MAY 21-31, 1996 CL LINCOLN, NE SP IEEE, Geosci & Remote Sensing Soc, Univ Nebraska, Lincoln, NASA, NOAA, USN, Off Naval Res, US Natl Comm Union Radiosci Int, Canon Modern Methods Inc, Univ Nebraska Lincoln, Ctr Adv Land Management Informat Technol, Univ Nebraska Lincoln, Ctr Commun & Informat Sci, Univ Nebraska Lincoln, Ctr Electro Opt, Univ Nebraska Lincoln, Ctr Laser Anal Studies Trace Gas Dynam, Centurion Int Inc, Univ Nebraska Lincoln, Coll Engn & Technol, Univ Nebraska Lincoln, Dept Elect Engn, ERDAS Inc, Univ Nebraska Lincoln, High Plains Climate Ctr, Li Cor Inc, US Geol Survey EROS Data Ctr ID CANOPIES; FOREST; MODEL AB Land surface temperature and emissivity products are currently being derived from satellite and aircraft remote sensing data using a variety of techniques to correct for atmospheric effects. Implicit in the commonly employed approaches is the assumption of isotropy in directional thermal infrared exitance. Our theoretical analyzes indicate angular variations in apparent infrared temperature will typically yield land surface temperature errors ranging from 1 to 4 degrees C unless corrective measures are applied. C1 GEORGE WASHINGTON UNIV,WASHINGTON,DC 20037. ARS,USDA,BELTSVILLE,MD 20705. USAE WATERWAYS EXPT STN,VICKSBURG,MS 39180. RP Smith, JA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 10 TC 17 Z9 17 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1997 VL 35 IS 4 BP 972 EP 974 DI 10.1109/36.602539 PG 3 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XL049 UT WOS:A1997XL04900019 ER PT J AU Saatchi, SS McDonald, KC AF Saatchi, SS McDonald, KC TI Coherent effects in microwave backscattering models for forest canopies SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID RADAR BACKSCATTER; BOREAL FOREST; SCATTERING MODEL; VEGETATION; RADIATION; BIOMASS; AREAS; LAYER; DISKS AB In modeling forest canopies, several scattering mechanisms are taken into account. 1) volume scattering; 2) surface-volume interaction; 3) surface scattering from forest floor. Depending on the structural and dielectric characteristics of forest canopies, the relative contribution of each mechanism in the total backscatter signal of an imaging radar can vary, In this paper, two commonly used first-order discrete scattering models, distorted born approximation (DBA) and radiative transfer (RT) are used to simulate the backscattered power received by polarimetric radars at P-, L-, and C-bands over coniferous and deciduous forests, The difference between the two models resides on the coherent effect in the surface-volume interaction terms, To demonstrate this point, the models are first compared based on their underlying theoretical assumptions and then according to simulation results over coniferous and deciduous forests. It is shown that by using the same scattering functions for various components of trees (i.e., leaf, branch, stem), the radiative transfer and distorted Born models are equivalent, except in low frequencies, where surface-volume interaction terms may become important, and the coherent contribution may be significant, In this case, the difference between the two models can reach up to 3 dB in both co-polarized and cross-polarized channels, which can influence the performance of retrieval algorithms. RP Saatchi, SS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 31 TC 42 Z9 49 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1997 VL 35 IS 4 BP 1032 EP 1044 DI 10.1109/36.602545 PG 13 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XL049 UT WOS:A1997XL04900025 ER PT J AU Jobson, DJ Rahman, ZU Woodell, GA AF Jobson, DJ Rahman, ZU Woodell, GA TI A multiscale retinex for bridging the gap between color images and the human observation of scenes SO IEEE TRANSACTIONS ON IMAGE PROCESSING LA English DT Article ID VISION AB Direct observation and recorded color images of the same scenes are often strikingly different because human visual perception computes the conscious representation with vivid color and detail in shadows, and with resistance to spectral shifts in the scene illuminant, A computation for color images that approaches fidelity to scene observation must combine dynamic range compression, color consistency - a computational analog for human vision color constancy - and color and lightness tonal rendition, In this paper, we extend a previously designed single-scale center/surround retinex to a multiscale version that achieves simultaneous dynamic range compression/color consistency/lightness rendition. This extension fails to produce good color rendition for a class of images that contain violations of the gray world assumption implicit to the theoretical foundation of the retinex, Therefore, we define a method of color restoration that corrects for this deficiency at the cost of a modest dilution in color consistency, Extensive testing of the multiscale retinex with color restoration on several test scenes and over a hundred images did not reveal any pathological behavior. C1 SCI & TECHNOL CORP,HAMPTON,VA 23666. RP Jobson, DJ (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 19 TC 615 Z9 728 U1 2 U2 43 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1057-7149 J9 IEEE T IMAGE PROCESS JI IEEE Trans. Image Process. PD JUL PY 1997 VL 6 IS 7 BP 965 EP 976 DI 10.1109/83.597272 PG 12 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA XF304 UT WOS:A1997XF30400006 PM 18282987 ER PT J AU Lo, V Windisch, KJ Liu, WQ Nitzberg, B AF Lo, V Windisch, KJ Liu, WQ Nitzberg, B TI Noncontiguous processor allocation algorithms for mesh-connected multicomputers SO IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS LA English DT Article DE resource management; scheduling; processor allocation; noncontiguous; fragmentation; mesh ID HYPERCUBE COMPUTERS; CUBE AB Current processor allocation techniques for highly parallel systems are typically restricted to contiguous allocation strategies for which performance suffers significantly due to the inherent problem of fragmentation. As a result, message-passing systems have yet to achieve the high utilization levels exhibited by traditional vector supercomputers. We are investigating processor allocation algorithms which lift the restriction on contiguity of processors in order to address the problem of fragmentation. Three noncontiguous processor allocation strategies-Paging allocation, Random allocation, and the Multiple Buddy Strategy (MBS)-are proposed and studied in this paper. Simulations compare the performance of the noncontiguous strategies with that of several well-known contiguous algorithms. We show that noncontiguous allocation algorithms perform better overall than the contiguous ones, even when message-passing contention is considered. We also present the results of experiments on an Intel Paragon XP/S-15 with 208 nodes that show noncontiguous allocation is feasible with current technologies. C1 SILICON GRAPH INC,MT VIEW,CA 94043. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Lo, V (reprint author), UNIV OREGON,DEPT COMP & INFORMAT SCI,EUGENE,OR 97403, USA. NR 29 TC 55 Z9 56 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1045-9219 J9 IEEE T PARALL DISTR JI IEEE Trans. Parallel Distrib. Syst. PD JUL PY 1997 VL 8 IS 7 BP 712 EP 726 DI 10.1109/71.598346 PG 15 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA XN624 UT WOS:A1997XN62400004 ER PT J AU Paciorek, KJL Masuda, SR Lin, WH Jones, WR AF Paciorek, KJL Masuda, SR Lin, WH Jones, WR TI Effect of metal alloys, degradation inhibitors, and temperatures on thermal oxidative stability of CF3O(CF2O)(x)(CF2CF2O)(y)CF3 fluids SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH LA English DT Article AB Degradation-promoting action of a series of ferrous and titanium alloys on CF3O(CF2O)(x)(CF2CF2O)(y)CF3-based Z25 fluids and the inhibition effectiveness of several classes of additives were investigated. Four types of additives-phosphines, phosphates, phospha-s-triazines, and diphosphatetraazacyclooctatetraene-were studied in two batches of 225 fluid, P28 and P151. In the absence of inhibitors, titanium alloys were more detrimental than the ferrous metals, but the additives were more effective in the presence of titanium alloys. Phosphate esters totally inhibited the decomposition of P151 at 330 degrees C over 24 h in both types of alloys. The other additives were effective at lower temperatures. The responsiveness of fluid to an additive was found to be batch dependent. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Paciorek, KJL (reprint author), LUBRICATING SPECIALTIES CO,TECHNOLUBE PROD DIV,1425 SEACREST DR,CORONA DEL MAR,CA 92625, USA. NR 12 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0888-5885 J9 IND ENG CHEM RES JI Ind. Eng. Chem. Res. PD JUL PY 1997 VL 36 IS 7 BP 2855 EP 2858 DI 10.1021/ie9607356 PG 4 WC Engineering, Chemical SC Engineering GA XJ562 UT WOS:A1997XJ56200041 ER PT J AU Paciorek, KJL Masuda, SR Lin, WH Jones, WR AF Paciorek, KJL Masuda, SR Lin, WH Jones, WR TI Effect of metal alloys, degradation inhibitors, temperatures, and exposure duration on the stability of poly(hexafluoropropene oxide) fluid SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH LA English DT Article AB Results of the action of 440C steel, Ti(4Al,4Mn), and Ti(6Al,4V) alloys on poly(hexafluoropropene oxide) fluid and the degradation inhibition by phosphate esters, phosphine, and monophospha-s-triazine are reported. The effects of temperature, exposure duration, and metal surface area are discussed. The studies show clearly the autocatalytic nature of the metal-promoted degradation, which explains the effectiveness of the degradation-arresting additives, even in the case of the highly detrimental titanium alloys. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Paciorek, KJL (reprint author), LUBRICATING SPECIALTIES CO,TECHNOLUBE PROD DIV,1425 SEACREST DR,CORONA DEL MAR,CA 92625, USA. NR 9 TC 1 Z9 1 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0888-5885 J9 IND ENG CHEM RES JI Ind. Eng. Chem. Res. PD JUL PY 1997 VL 36 IS 7 BP 2859 EP 2861 DI 10.1021/ie960736y PG 3 WC Engineering, Chemical SC Engineering GA XJ562 UT WOS:A1997XJ56200042 ER PT J AU Meyyappan, M AF Meyyappan, M TI Modeling of a pulsed-power SF6 plasma SO JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS LA English DT Article; Proceedings Paper CT 3rd International Conference on Reactive Plasmas (ICRP-3) CY JAN 21-24, 1997 CL NARA, JAPAN SP Japan Soc Appl Phys DE pulsed-power; SF6 plasma; production of negative ions; modeling ID ELECTRON; DISCHARGES AB Pulsing the input power has received much attention to eliminate anomalous side wall etching problems in high density discharges. A simple model consisting of mass conservation equations for ions, neutrals, and electrons and a power balance is used to analyze the characteristics of a pulsed-power SF6 plasma. The model shows an abundant production of negative ions in the after glow and a strong modulation of their density and production rate for a wide range of pulse periods and duty ratios. The results suggest that a pulse period of 100-250 mu s with a duty cycle 25-50% is sufficient to maintain low electron temperature and plasma potential and produce a high concentration of negative ions during the off-part of the cycle. RP Meyyappan, M (reprint author), NASA,AMES RES CTR,MAIL STOP 229-3,MOFFETT FIELD,CA 94035, USA. NR 15 TC 11 Z9 11 U1 2 U2 2 PU JAPAN J APPLIED PHYSICS PI MINATO-KU TOKYO PA DAINI TOYOKAIJI BLDG 24-8 SHINBASHI 4-CHOME, MINATO-KU TOKYO 105, JAPAN SN 0021-4922 J9 JPN J APPL PHYS 1 JI Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. PD JUL PY 1997 VL 36 IS 7B BP 4820 EP 4823 DI 10.1143/JJAP.36.4820 PG 4 WC Physics, Applied SC Physics GA XR224 UT WOS:A1997XR22400054 ER PT J AU Lin, JC Dominik, CJ AF Lin, JC Dominik, CJ TI Parametric investigation of a high-lift airfoil at high Reynolds numbers SO JOURNAL OF AIRCRAFT LA English DT Article AB A new two-dimensional, three-element, advanced high-lift research airfoil has been tested in the NASA Langley Research Center's Low-Turbulence Pressure Tunnel at a chord Reynolds number up to 1.6 x 10(7), The components of this high-lift airfoil have been designed using a incompressible computational code (INS2D), The design was to provide high maximum-lift values while maintaining attached flow on the single-segment flap at landing conditions. The performance of the new NASA research airfoil is compared to a similar reference high-lift airfoil, On the new high-lift airfoil the effects of Reynolds number on slat and flap rigging have been studied experimentally, as well as the Mach number effects, The performance trend of the high-lift design is comparable to that predicted by INS2D over much of the angle-of-attack range, However, the code did not accurately predict the airfoil performance or the configuration-based trends near maximum lift where the compressibility effect could play a major role. C1 MCDONNELL DOUGLAS AEROSP,SUBSON AERODYNAM TECHNOL GRP,ADV TRANSPORT AIRCRAFT DEV,LONG BEACH,CA 90810. RP Lin, JC (reprint author), NASA,LANGLEY RES CTR,FLOW MODELING & CONTROL BRANCH,FLUID MECH & ACOUST DIV,HAMPTON,VA 23681, USA. NR 11 TC 16 Z9 16 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD JUL-AUG PY 1997 VL 34 IS 4 BP 485 EP 491 DI 10.2514/2.2217 PG 7 WC Engineering, Aerospace SC Engineering GA XM726 UT WOS:A1997XM72600005 ER PT J AU Gatlin, GM McGhee, RJ AF Gatlin, GM McGhee, RJ TI Experimental investigation of semispan model testing techniques SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 14th Applied Aerodynamics Conference CY JUN 17-20, 1996 CL NEW ORLEANS, LA SP Amer Inst Aeronaut & Astronaut AB An investigation has been conducted in the NASA Langley Research Center's 14 by 22 ft Subsonic Tunnel to further the development of semispan testing capabilities, A twin-engine, energy efficient transport model with a four-element wing in a takeoff configuration was used for this investigation. Initially, a full-span configuration was tested, and force and moment data and wing and fuselage surface pressure data were obtained as a baseline data set, The semispan configurations were then mounted on the wind-tunnel door, and the effects of fuselage standoff height and shape were investigated. Results indicate that the semispan configuration was sensitive to variations in standoff height, and that a standoff height equivalent to 30% of the fuselage radius resulted in better correlation with full-span data than no standoff or the larger standoff configurations investigated, Undercut standoff leading edges improved the correlation of semispan data with full span data in the region of maximum lift coefficient. RP Gatlin, GM (reprint author), NASA,LANGLEY RES CTR,SUBSON AERODYNAM BRANCH,AERO & GAS DYNAM DIV,HAMPTON,VA 23681, USA. NR 8 TC 6 Z9 6 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD JUL-AUG PY 1997 VL 34 IS 4 BP 500 EP 505 DI 10.2514/2.2219 PG 6 WC Engineering, Aerospace SC Engineering GA XM726 UT WOS:A1997XM72600007 ER PT J AU Brentner, KS Lyrintzis, AS Koutsavdis, EK AF Brentner, KS Lyrintzis, AS Koutsavdis, EK TI Comparison of computational aeroacoustic prediction methods for transonic rotor noise SO JOURNAL OF AIRCRAFT LA English DT Article ID MODEL AB This paper compares two methods for predicting transonic rotor noise for helicopters in hover and forward flight. Both methods rely on a computational fluid dynamics (CFD) solution as input to predict the acoustic near and far fields, For this work, the same full-potential rotor code has been used to compute the CFD solution for both acoustic methods, The first method employs the acoustic analogy as embodied in the Ffowcs Williams-Hawkings equation, including the quadrupole term, The second method uses a rotating Kirchhoff formulation, Computed results from both methods are compared with one another and with experimental data for both hover and advancing rotor cases, The results are quite good for all cases tested. The Kirchhoff method was somewhat sensitive to the location of Kirchhoff surface, if the surface was positioned too close to the rotor blade, The acoustic analogy method was not as sensitive to the extent of volume included in the quadrupole calculation. The computational requirements of both methods are comparable; in both cases these requirements are much less than the requirements for the CFD solution. C1 PURDUE UNIV,SCH AERONAUT & ASTRONAUT,W LAFAYETTE,IN 47907. RP Brentner, KS (reprint author), NASA,LANGLEY RES CTR,AERODYNAM & ACOUST METHODS BRANCH,FLUID MECH & ACOUST DIV,M-S 128,HAMPTON,VA 23681, USA. NR 28 TC 8 Z9 12 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD JUL-AUG PY 1997 VL 34 IS 4 BP 531 EP 538 DI 10.2514/2.2205 PG 8 WC Engineering, Aerospace SC Engineering GA XM726 UT WOS:A1997XM72600011 ER PT J AU Kelly, JJ Nguyen, LC AF Kelly, JJ Nguyen, LC TI Influence of shaft angle of attack on sound radiation by subsonic propellers SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 35th Aerospace Science Meeting / Nonlinear Dynamical Systems Symposium CY JAN 06-09, 1997 CL RENO, NV SP Amer Inst Aeronaut & Astronaut, USAF, Off Sci Res, Sandia Natl Labs ID PREDICTION; NOISE AB The formulation to account for effects of propeller angle of attack on acoustic radiation by propellers is presented. A propeller operating at an angle of attack presents a nonuniform inflow situation that is known to have a pronounced influence on noise, Noise predictions, based on this new formulation, are compared with measured wind-tunnel data, Predictions for observers fixed in the propeller plane are also included to assess the influence of shaft angle of attack. RP Kelly, JJ (reprint author), LOCKHEED MARTIN ENGN & SCI,NASA,LANGLEY RES CTR,M-S 303,HAMPTON,VA 23681, USA. NR 15 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD JUL-AUG PY 1997 VL 34 IS 4 BP 539 EP 544 DI 10.2514/2.2206 PG 6 WC Engineering, Aerospace SC Engineering GA XM726 UT WOS:A1997XM72600012 ER PT J AU Santos, P Negri, AJ AF Santos, P Negri, AJ TI A comparison of the normalized difference vegetation index and rainfall for the Amazon and northeastern Brazil SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID HIGH-RESOLUTION RADIOMETER; NOAA AVHRR DATA; NDVI DATA SET; SENEGALESE SAHEL; SATELLITE DATA; CLIMATE; CALIBRATION; PARAMETERS; AFRICA; REGION AB This paper presents a comparison of the normalized difference vegetation index (NDVI! and rainfall for the Amazon and northeastern Brazil for the time period of 1988-90. The analysis shows that the NDVI and rainfall are uncorrelated in the Amazon, except in the northernmost part, where the rainfall regime is drier and a savanna type of vegetation is present. In the drier region of northeastern Brazil, the relationship is exponential, with the NDVI showing sensitivity to rainfall within a regime of less than approximately 100 mm per month of rainfall. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. FLORIDA STATE UNIV,DEPT METEOROL,TALLAHASSEE,FL 32306. NR 34 TC 25 Z9 25 U1 1 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD JUL PY 1997 VL 36 IS 7 BP 958 EP 965 DI 10.1175/1520-0450(1997)036<0958:ACOTND>2.0.CO;2 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XJ832 UT WOS:A1997XJ83200010 ER PT J AU Halloran, BP Bikle, DD Harris, J Tanner, S Curren, T MoreyHolton, E AF Halloran, BP Bikle, DD Harris, J Tanner, S Curren, T MoreyHolton, E TI Regional responsiveness of the tibia to intermittent administration of parathyroid hormone as affected by skeletal unloading SO JOURNAL OF BONE AND MINERAL RESEARCH LA English DT Article ID BONE-FORMATION; CORTICAL BONE; SIMULATED WEIGHTLESSNESS; OVARIECTOMIZED RATS; TAIL SUSPENSION; TRABECULAR BONE; GROWTH-HORMONE; GROWING RATS; FEMALE RATS; IN-VIVO AB To determine whether the acute inhibition of bone formation and deficit in bone mineral induced by skeletal unloading can be prevented, we studied the effects of intermittent parathyroid hormone (PTH) administration (8 mu g/100 g/day) on growing rats submitted to 8 days of skeletal unloading, Loss of weight bearing decreased periosteal bone formation by 34 and 51% at the tibiofibular junction and tibial midshaft, respectively, and reduced the normal gain in tibial mass by 35%, Treatment with PTH of normally loaded and unloaded animals increased mRNA for osteocalcin (+58 and +148%, respectively), cancellous bone volume in the proximal tibia (+41 and +42%, respectively), and bone formation at the tibiofibular junction (+27 and +27%, respectively), Formation was also stimulated at the midshaft in unloaded (+47%, p < 0.05), but not loaded animals (-3%, NS), Although cancellous bone volume was preserved in PTH-treated, unloaded animals, PTH did not restore periosteal bone formation to normal nor prevent the deficit in overall tibial mass induced by unloading, We conclude that the effects of PTH on bone formation are region specific and load dependent, PTH can prevent the decrease in cancellous bone volume and reduce the decrement in cortical bone formation induced by loss of weight bearing. C1 UNIV CALIF SAN FRANCISCO,DEPT MED,SAN FRANCISCO,CA. UNIV CALIF SAN FRANCISCO,DEPT PHYSIOL,SAN FRANCISCO,CA. VET AFFAIRS MED CTR,DIV ENDOCRINOL,SAN FRANCISCO,CA 94121. CREIGHTON UNIV,CTR OSTEOPOROSIS RES,OMAHA,NE 68178. NASA,AMES RES CTR,DIV LIFE SCI,MOFFETT FIELD,CA 94035. NR 40 TC 36 Z9 37 U1 0 U2 1 PU BLACKWELL SCIENCE INC PI MALDEN PA 350 MAIN ST, MALDEN, MA 02148 SN 0884-0431 J9 J BONE MINER RES JI J. Bone Miner. Res. PD JUL PY 1997 VL 12 IS 7 BP 1068 EP 1074 DI 10.1359/jbmr.1997.12.7.1068 PG 7 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA XE899 UT WOS:A1997XE89900011 PM 9200006 ER PT J AU Koster, RD Milly, PCD AF Koster, RD Milly, PCD TI The interplay between transpiration and runoff formulations in land surface schemes used with atmospheric models SO JOURNAL OF CLIMATE LA English DT Article ID SOIL-MOISTURE; PARAMETERIZATION; BIOSPHERE AB The Project for Intercomparison of Land-surface Parameterization Schemes (PILPS) has shown that different land surface models (LSMs) driven by the same meteorological forcing can produce markedly different surface energy and water budgets, even when certain critical aspects of the LSMs (vegetation cover, albedo, turbulent drag coefficient, and snowcover) are carefully controlled. To help explain these differences, the authors devised a monthly water balance model that successfully reproduces the annual and seasonal water balances of the different PILPS schemes. Analysis of this model leads to the identification of two quantities that characterize an LSM's formulation of soil water balance dynamics: 1) the efficiency of the soil's evaporation sink integrated over the active soil moisture range, and 2) the fraction of this range over which runoff is generated. Regardless of the LSM's complexity, the combination of these two derived parameters with rates of interception loss, potential evaporation, and precipitation provides a reasonable estimate for the LSM's simulated annual water balance. The two derived parameters shed light on how evaporation and runoff formulations interact in an LSM, and the analysis as a whole underscores the need for compatibility in these formulations. C1 US GEOL SURVEY, GEOPHYS FLUID DYNAM LAB, NOAA, PRINCETON, NJ USA. RP Koster, RD (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HYDROL SCI BRANCH, LAB HYDROSPHER PROC, CODE 974, GREENBELT, MD 20771 USA. RI Koster, Randal/F-5881-2012 OI Koster, Randal/0000-0001-6418-6383 NR 27 TC 198 Z9 207 U1 3 U2 10 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 JUL PY 1997 VL 10 IS 7 BP 1578 EP 1591 DI 10.1175/1520-0442(1997)010<1578:TIBTAR>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XP278 UT WOS:A1997XP27800007 ER PT J AU Li, J Lee, SM Lee, EW OBrien, TK AF Li, J Lee, SM Lee, EW OBrien, TK TI Evaluation of the edge crack torsion (ECT) test for mode III interlaminar fracture toughness of laminated composites SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE composite materials; fracture toughness; delamination; compliance calibration; three-dimensional finite element analysis; strain energy release rate AB An analytical and experimental investigation was carried out on G40-800/R6376 graphite/epoxy laminates to evaluate the edge crack torsion (ECT) test as a candidate for a standard Mode III interlaminar fracture toughness test for laminated composites. The ECT rest consists of a [90/(+/-45)(3)/(-/+45)(3)/90](s) laminate with a delamination introduced by a non-adhesive film at the mid-plane along one edge and loaded in a special fixture to create torsion along the length of the laminate. Dye penetrant enhanced X-radiograph of failed specimens revealed that the delamination initiated at the middle of the specimen length and propagated in a self-similar manner along the laminate midplane. A three-dimensional finite element analysis was performed that indicated that a pure Mode III delamination exists at the middle of specimen length away from both ends. At the ends near the loading point a small Mode II component exists. However, the magnitude of this Mode II strain energy release rate at the loading point is small compared to the magnitude of Mode III component in the mid-section of the specimen. Hence, the ECT test yielded the desired Mode HII delamination. The Mode III fracture toughness was obtained from a compliance calibration method that was in good agreement with the finite element results. Mode Il end-notched flexure (ENF) tests and Mode I double cantilever beam (DCB) tests were also performed for the same composite material. The Mode I fracture toughness is much smaller than bath the Mode II and Mode III fracture toughness, The Mode II fracture toughness is found to be 75% of the Mode III fracture toughness. C1 BELL HELICOPTER TEXTRON,FT WORTH,TX 76101. USA,RES LAB,VEHICLE STRUCT DIRECTORATE,NASA,LANGLEY RES CTR,HAMPTON,VA 23681. HEXCEL COMPOSITES,MAT SCI,DUBLIN,CA 94568. RP Li, J (reprint author), MCDONNELL DOUGLAS HELICOPTER CO,5000 E MCDOWELL RD,MESA,AZ 85215, USA. NR 8 TC 33 Z9 33 U1 1 U2 9 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 SN 0884-6804 J9 J COMPOS TECH RES JI J. Compos. Technol. Res. PD JUL PY 1997 VL 19 IS 3 BP 174 EP 183 PG 10 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA XV545 UT WOS:A1997XV54500006 ER PT J AU Choi, SR Gyekenyesi, JP AF Choi, SR Gyekenyesi, JP TI Fatigue strength as a function of preloading in dynamic fatigue testing of glass and ceramics SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID HOT-PRESSED SI3N4; ELEVATED-TEMPERATURES; SILICON-NITRIDE; LIFE PREDICTION; CYCLIC FATIGUE; CRACK GROWTH; FAILURE; FLAWS; ALUMINA AB The solution of fatigue strength as a function of preloading in dynamic fatigue (constant stress-rate) testing was obtained analytically and numerically. The effect of preloading on dynamic fatigue strength decreases with increasing fatigue parameter ter (n), and for n greater than or equal to 20 the effect is negligible up to a preloading of 90 percent. The solution was verified by dynamic fatigue experiments conducted with soda-lime glass and alumina specimens in room-temperature distilled water. This result showed that one can apply a. preloading corresponding up to 90 percent of fatigue strength for most glass and ceramic materials, resulting in a dramatic saving of testing time in dynamic fatigue testing. The key feature that makes this technique feasible is that most of the slow crack growth under dynamic fatigue lending occurs close to failure time where the dynamic fatigue strength is defined. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Choi, SR (reprint author), CLEVELAND STATE UNIV,CLEVELAND,OH 44115, USA. NR 23 TC 5 Z9 5 U1 0 U2 3 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 493 EP 499 DI 10.1115/1.2817011 PG 7 WC Engineering, Mechanical SC Engineering GA XQ142 UT WOS:A1997XQ14200001 ER PT J AU Nalim, MR Paxson, DE AF Nalim, MR Paxson, DE TI A numerical investigation of premixed combustion in wave rotors SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND AB Wave rotor cycles that utilize premixed combustion processes within the passages are examined numerically using a one-dimensional CFD-based simulation. Internal-combustion wave rotors are envisioned for use as pressure-gain combustors in gas turbine engines. The simulation methodology is described, including a presentation of the assumed governing equations for the flow and reaction in the channels, the numerical integration method used, and the modeling of external components such as recirculation ducts. A number of cycle simulations are then presented that illustrate both turbulent-deflagration and detonation modes of combustion. Estimates of performance and rotor wall temperatures for the various cycles are made, and the advantages and disadvantages of each are discussed. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Nalim, MR (reprint author), NATL RES COUNCIL,WASHINGTON,DC 20418, USA. NR 17 TC 12 Z9 12 U1 2 U2 5 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 668 EP 675 DI 10.1115/1.2817036 PG 8 WC Engineering, Mechanical SC Engineering GA XQ142 UT WOS:A1997XQ14200025 ER PT J AU Paxson, DE AF Paxson, DE TI Numerical investigation of the startup transient in a wave rotor SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND AB The startup process is investigated for a hypothetical four-port wave rotor, envisioned as a topping cycle for a small gas turbine engine. The investigation is conducted numerically using a multi-passage, one-dimensional CFD based wave rotor simulation in combination with lumped volume models for the combustor, exhaust valve plenum, and rotor center cavity components. The simulation is described and several startup transients are presented which illustrate potential difficulties for the specific cycle design investigated. In particular it is observed that, prior to combustor light-off, or just after, the flow through the combustor loop is reversed from the design direction. The phenomenon is demonstrated and several possible modification techniques are discussed that avoid or overcome the problem. RP Paxson, DE (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 11 TC 1 Z9 1 U1 2 U2 3 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 676 EP 682 DI 10.1115/1.2817039 PG 7 WC Engineering, Mechanical SC Engineering GA XQ142 UT WOS:A1997XQ14200026 ER PT J AU Johnson, AR Tessler, A Dambach, M AF Johnson, AR Tessler, A Dambach, M TI Dynamics of thick viscoelastic beams SO JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT Symposium on Characterization and Modeling of Polymeric Material Systems, at the Joint American-Society-of-Mechanical-Engineers/American-Society-of-Civil-Engin eers/Society-of-Engineering-Science Summer Meeting (McNU 97) CY 1997 CL NW UNIV, EVANSTON, IL SP Amer Soc Mech Engineers, Amer Soc Civil Engineers, Soc Engn Sci HO NW UNIV ID RUBBER VISCOELASTICITY; MODEL AB A viscoelastic higher-order thick beam finite element formulation is extended to include elastodynamic deformations. The material constitutive law is a special differential form of the Maxwell solid, which employs viscous strains as internal variables to determine the viscous stresses. The total time-dependent stress is the superposition of its elastic and viscous components. In the constitutive model, the elastic strains and the conjugate viscous strains are coupled through a system of first-order ordinary differential equations. The use of the internal strain variables allows for a convenient finite element formulation. The elastodynamic equations of motion are derived from the virtual work principle. Computational examples are carried out for a thick orthotropic cantilevered beam. Relaxation, creep, relaxation followed by free damped vibrations, and damping related modal interactions are discussed. C1 NASA,LANGLEY RES CTR,COMPUTAT STRUCT BRANCH,MS 240,HAMPTON,VA 23681. RI Tessler, Alexander/A-4729-2009 NR 18 TC 21 Z9 21 U1 0 U2 6 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0094-4289 J9 J ENG MATER-T ASME JI J. Eng. Mater. Technol.-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 273 EP 278 DI 10.1115/1.2812256 PG 6 WC Engineering, Mechanical; Materials Science, Multidisciplinary SC Engineering; Materials Science GA XQ399 UT WOS:A1997XQ39900014 ER PT J AU Lepping, RP Burlaga, LF Szabo, A Ogilvie, KW Mish, WH Vassiliadis, D Lazarus, AJ Steinberg, JT Farrugia, CJ Janoo, L Mariani, F AF Lepping, RP Burlaga, LF Szabo, A Ogilvie, KW Mish, WH Vassiliadis, D Lazarus, AJ Steinberg, JT Farrugia, CJ Janoo, L Mariani, F TI The Wind magnetic cloud and events of October 18-20, 1995: Interplanetary properties and as triggers for geomagnetic activity SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article; Proceedings Paper CT Chapman Conference on Magnetic Storms CY FEB 12-16, 1996 CL CALIF INST TECHNOL, PROPULS LAB, PASADENA, CA HO CALIF INST TECHNOL, PROPULS LAB ID SOLAR-WIND; IONOSPHERIC CONVECTION; EARTHS MAGNETOSPHERE; NONLINEAR EVOLUTION; FLUX ROPES; 1 AU; FIELD; PASSAGE; MAGNETOPAUSE; STORMS AB Late on October 18, 1995, a magnetic cloud arrived at the Wind spacecraft approximate to 175 R-E upstream of the Earth. The cloud had an intense interplanetary magnetic field that varied slowly in direction, from being strongly southward to strongly northward during its approximate to 30 hours duration, and a low proton temperature throughout. From a linear force free field model the cloud was shown to have a flux rope magnetic field line geometry, an estimated diameter of about 0.27 AU, and an axis that was aligned with the Y axis(GSE) within about 25 degrees. A corotating stream, in which large amplitude Alfven waves of about 0.5 hour period were observed, was overtaking the cloud and intensifying the fields in the rear of the cloud. The prolonged southward magnetic field observed in the early part of the cloud produced a geomagnetic storm of K-p = 7(-) and considerable auroral activity late on October 18. About 8 hours in front of the cloud an interplanetary shock occurred. About three-fourths the way into the cloud another apparent interplanetary shock was observed. It had an unusual propagation direction, differing by only 21 degrees from alignment with the cloud axis. It may have been the result of the interaction with the postcloud stream, compressing the cloud, or was possibly due to an independent solar event. It is shown that the front and rear boundaries of the cloud and the upstream driven shock had surface normals in,good agreement with the cloud axis in the ecliptic plane. The integrated Poynting flux into the magnetosphere, which correlated well with geomagnetic indices, jumped abruptly to a high value upon entry into the magnetic cloud, slowly decreased to zero near its middle, and again reached substantial but sporadic values in the cloud-stream interface region. This report aims to support a variety of ISTP studies ranging from the solar origins of these events to resulting magnetospheric responses. C1 UNIV NEW HAMPSHIRE,DEPT STUDY EARTH OCEANS & SPACE,DURHAM,NH 03824. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. UNIV ROMA TOR VERGATA,DIPARTIMENTO FIS,I-00173 ROME,ITALY. RP Lepping, RP (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. NR 62 TC 108 Z9 110 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 JUL 1 PY 1997 VL 102 IS A7 BP 14049 EP 14063 DI 10.1029/97JA00272 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400004 ER PT J AU Li, XL Baker, DN Temerin, M Cayton, TE Reeves, EGD Christensen, RA Blake, JB Looper, MD Nakamura, R Kanekal, SG AF Li, XL Baker, DN Temerin, M Cayton, TE Reeves, EGD Christensen, RA Blake, JB Looper, MD Nakamura, R Kanekal, SG TI Multisatellite observations of the outer zone electron variation during the November 3-4, 1993, magnetic storm SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article; Proceedings Paper CT Chapman Conference on Magnetic Storms CY FEB 12-16, 1996 CL CALIF INST TECHNOL, PROPULS LAB, PASADENA, CA HO CALIF INST TECHNOL, PROPULS LAB ID RADIATION-BELT; RELATIVISTIC ELECTRONS; ENERGETIC PARTICLES; MIDDLE ATMOSPHERE; MARCH 24; ENERGIZATION; SIMULATION; MAGNETOSPHERE; RECIRCULATION; PRECIPITATION AB The disappearance and reappearance of outer zone energetic electrons during the November 3-4, 1993, magnetic storm is examined utilizing data from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), the Global Positioning System (GPS) series, and the Los Alamos National Laboratory (LANL) sensors onboard geosynchronous satellites. The relativistic electron flux drops during the main phase of the magnetic storm in association with the large negative interplanetary B-z and rapid solar wind pressure increase late on November 3. Outer zone electrons with E > 3 MeV measured by SAMPEX disappear for over 12 hours at the beginning of November 4. This represents a 3 orders of magnitude decrease down to the cosmic ray background of the detector. GPS and LANL sensors show similar effects, confirming that the flux drop of the energetic electrons occurs near the magnetic equator and at all pitch angles. Enhanced electron precipitation was measured by SAMPEX at L greater than or equal to 3.5. The outer zone electron fluxes then recover and exceed prestorm levels within one day of the storm onset and the inner boundary of the outer zone moves inward to smaller L (<3). These multiple-satellite measurements provide a data set which is examined in detail and used to determine the mechanisms contributing to the loss and recovery of the outer zone electron flux. The loss of the inner part of the outer zone electrons is partly due to the adiabatic effects associated with the decrease of Dst, while the loss of most of the outer part (those electrons initially at L greater than or equal to 4.0) are due to either precipitation into the atmosphere or drift to the magnetopause because of the strong compression of the magnetosphere by the solar wind. The recovery of the energetic electron flux is due to the adiabatic effects associated with the increase in Dst, and at lower energies (<0.5 MeV) due to rapid radial diffusion driven by the strong magnetic activity during the recovery phase of the storm. Heating of the electrons by waves may contribute to the energization of the more energetic part (>1.0 MeV) of the outer zone electrons. C1 AEROSP CORP,DEPT SPACE SCI,LOS ANGELES,CA 90009. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NAGOYA UNIV,STEL,TOYOKAWA,AICHI 442,JAPAN. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. RP Li, XL (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,1234 INNOVAT DR,BOULDER,CO 80303, USA. RI Nakamura, Rumi/I-7712-2013; Reeves, Geoffrey/E-8101-2011 OI Nakamura, Rumi/0000-0002-2620-9211; Reeves, Geoffrey/0000-0002-7985-8098 NR 46 TC 210 Z9 214 U1 0 U2 12 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 JUL 1 PY 1997 VL 102 IS A7 BP 14123 EP 14140 DI 10.1029/97JA01101 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400010 ER PT J AU Baker, DN Li, X Turner, N Allen, JH Bargatze, LF Blake, JB Sheldon, RB Spence, HE Belian, RD Reeves, GD Kanekal, SG Klecker, B Lepping, RP Ogilvie, K Mewaldt, RA Onsager, T Singer, HJ Rostoker, G AF Baker, DN Li, X Turner, N Allen, JH Bargatze, LF Blake, JB Sheldon, RB Spence, HE Belian, RD Reeves, GD Kanekal, SG Klecker, B Lepping, RP Ogilvie, K Mewaldt, RA Onsager, T Singer, HJ Rostoker, G TI Recurrent geomagnetic storms and relativistic electron enhancements in the outer magnetosphere: ISTP coordinated measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article; Proceedings Paper CT Chapman Conference on Magnetic Storms CY FEB 12-16, 1996 CL CALIF INST TECHNOL, PROPULS LAB, PASADENA, CA HO CALIF INST TECHNOL, PROPULS LAB ID SOLAR; SPACECRAFT; TELESCOPE; PARTICLE; SAMPEX AB New, coordinated measurements from the International Solar-Terrestrial Physics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth's magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent geomagnetic activity. It is concluded that even during extremely quiet solar conditions (sunspot minimum) there are discernible coronal holes and resultant solar wind streams which can produce intense magnetospheric particle acceleration. As a practical consequence of this Sun-Earth connection, it is noted that a long-lasting E>1MeV electron event in late March 1996 appears to have contributed significantly to a major spacecraft (Anik E1) operational failure. C1 NOAA,NATL GEOPHYS DATA CTR,SCOSTEP SECRETARIAT,BOULDER,CO 80302. MONTANA STATE UNIV,DEPT PHYS,BOZEMAN,MT 59717. AEROSP CORP,LOS ANGELES,CA 90009. BOSTON UNIV,CTR SPACE PHYS,BOSTON,MA 02215. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,GREENBELT,MD 20771. MAX PLANCK INST PHYS & ASTROPHYS,D-8046 GARCHING,GERMANY. CALTECH,PASADENA,CA 91125. NOAA,RESE,SPACE ENVIRONM CTR,BOULDER,CO 80302. UNIV ALBERTA,DEPT PHYS,EDMONTON,AB,CANADA. RP Baker, DN (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,CAMPUS BOX 590,BOULDER,CO 80303, USA. RI Spence, Harlan/A-1942-2011; Reeves, Geoffrey/E-8101-2011; OI Reeves, Geoffrey/0000-0002-7985-8098; Turner, Niescja/0000-0002-3280-4260 NR 24 TC 103 Z9 104 U1 0 U2 6 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 JUL 1 PY 1997 VL 102 IS A7 BP 14141 EP 14148 DI 10.1029/97JA00565 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400011 ER PT J AU Ho, CM Tsurutani, BT AF Ho, CM Tsurutani, BT TI Distant tail behavior during high speed solar wind streams and magnetic storms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article; Proceedings Paper CT Chapman Conference on Magnetic Storms CY FEB 12-16, 1996 CL CALIF INST TECHNOL, PROPULS LAB, PASADENA, CA HO CALIF INST TECHNOL, PROPULS LAB ID SLOW-MODE SHOCKS; MAGNETOTAIL; ISEE-3; PLASMA; FIELD; AVERAGE; GEOTAIL AB We have examined the ISEE 3 distant tail data during three intense (Dst < -100 nT) magnetic storms and have identified the tail response to high-speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms, The three storms have a peak Dst ranging from -150 to -220 nT and occur on January 9, February 4, and August 8, 1983. During the storm onsets, the fast solar wind and magnetic field dynamic pressure (B-2/8 pi+Sigma n(i)kT(i)) fluctuations moved the tail across the spacecraft multiple times. The magnetotail is strongly compressed by the outside sheath pressure. The lobe field strength can usually be predicted by the pressure balance. The strongest lobe field magnitude detected is 37 nT during storm main phase on January 10, which is higher than the sheath field by 5 - 10 nT. The sheath plasma pressure accounts for the higher lobe field strengths. However, for the February 4 storm, we find that three tail lobe encounters are not in static balance with sheath pressure. During the storm times, the field magnitudes of the lobe and plasma sheet increase by a factor of 3-5 relative to the quiet time. The temperature and density in both regions also increase by factors of 2-3, but with little plasma beta changes, as one would expect. Under the assumption of tail flux conservation, increased sheath pressure implies a reduced tail size. Besides the tail size changes, the location of the: nominal tail axis is controlled by solar wind flow orientation. This study shows that more than 70% of tail in- and-out events are predicted by either of these external mechanisms (changes of tail size due to the external pressure and the solar wind directional changes). Nine tail plasma sheet jettings and 12 slow-mode shocks have been detected during the three storms. One remarkable feature of the jettings is very strong earthward flow (up to 1200 km/s) and tailward flow (up to 1500 km/s). The solar wind speed for these events was only similar to 900 km/s. Both tail flow events have the highest speeds fond to date. The preponderance of such a strong earthward flow indicates that during magnetic storms, magnetic reconnection occurs at locations well beyond the distance of ISEE 3. Through the interface of slow-mode shocks between the tail lobe and the plasma sheet/boundary layer, magnetic energy is being converted into plasma thermal and kinetic energy by the magnetic merging process. The predicted downstream plasma jetting speed (978 km/s) is consistent with the observations (1000 km/s) in the boundary layer. One surprising feature is that this reconnection process seems to be quite prominent during the storm recovery phase. One possible suggestion is that the dynamics of the distant tail are not at all related to magnetic storms and substorms but is an aftereffect, releasing extra magnetic tail energy by field sloughing via these reconnection events, accompanying the plasma sheet expansion. RP Ho, CM (reprint author), CALTECH,JET PROP LAB,MS 169-506,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 25 TC 15 Z9 15 U1 2 U2 4 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 JUL 1 PY 1997 VL 102 IS A7 BP 14165 EP 14175 DI 10.1029/96JA03872 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400014 ER PT J AU Jordanova, VK Kozyra, JU Nagy, AF Khazanov, GV AF Jordanova, VK Kozyra, JU Nagy, AF Khazanov, GV TI Kinetic model of the ring current-atmosphere interactions SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article; Proceedings Paper CT Chapman Conference on Magnetic Storms CY FEB 12-16, 1996 CL CALIF INST TECHNOL, PROPULS LAB, PASADENA, CA HO CALIF INST TECHNOL, PROPULS LAB ID ION-CYCLOTRON WAVES; RADIATION BELT ELECTRONS; 1-2 MAGNETIC PULSATIONS; PITCH-ANGLE DIFFUSION; EQUATORIAL MAGNETOSPHERE; STORM; DISTRIBUTIONS; PLASMASPHERE; PLASMAPAUSE; GENERATION AB Our numerical model of the ring current-atmosphere coupling (RAM) is further developed in order to include wave-particle interaction processes. The model calculates the time evolution of the phase space distribution function in the region from 2 R-E to 6.5 R-E, considering losses due to charge exchange, Coulomb collisions, and plasma wave scattering along ion drift paths. The spatial regions of ion cyclotron wave instability are determined by calculating the convective growth rates for electromagnetic ion cyclotron (EMIC) waves, integrating them along wave paths, and selecting regions of maximum wave amplification The source regions are located on the duskside in agreement with the predominant occurrence of EMIC waves. A spectral power density of 1 nT(2)/Hz is adopted within the unstable regions. According to quasi-linear theory, the fluctuating fields are regarded as imposed on the system, and the losses due to wave-particle interactions are described with diffusive processes. The effects of the presence of heavy ion components on the quasi-linear diffusion coefficients are also considered. Resonance with ion cyclotron waves reduce the anisotropy of the proton population and the unstable regions disappear with time. Global patterns of precipitating ion fluxes are obtained and compared with observations. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. UNIV MICHIGAN,SPACE PHYS RES LAB,ANN ARBOR,MI 48109. RP Jordanova, VK (reprint author), UNIV NEW HAMPSHIRE,CTR SPACE SCI,408 MORSE HALL,DURHAM,NH 03824, USA. OI Jordanova, Vania/0000-0003-0475-8743 NR 39 TC 126 Z9 126 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUL 1 PY 1997 VL 102 IS A7 BP 14279 EP 14291 DI 10.1029/96JA03699 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400024 ER PT J AU Sobral, JHA Abdu, MA Gonzalez, WD Tsurutani, BT Batista, IS deGonzalez, ALC AF Sobral, JHA Abdu, MA Gonzalez, WD Tsurutani, BT Batista, IS deGonzalez, ALC TI Effects of intense storms and substorms on the equatorial ionosphere/thermosphere system in the American sector from ground-based and satellite data SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article; Proceedings Paper CT Chapman Conference on Magnetic Storms CY FEB 12-16, 1996 CL CALIF INST TECHNOL, PROPULS LAB, PASADENA, CA HO CALIF INST TECHNOL, PROPULS LAB ID IONOSPHERIC ELECTRIC-FIELDS; F-REGION; MAGNETIC CLOUDS; MAGNETOSPHERIC DISTURBANCES; LOW-LATITUDE; DRIFT VELOCITIES; MARCH 22; PENETRATION; DECREASES; CAMPAIGN AB Equatorial ionospheric responses to magneto spheric storm/substorm-associated electric fields are investigated for a few intense events of the equinoctial months of solar maximum years 1978-1979. All the magnetic storms considered here are the result of the transit at Earth of interplanetary magnetic clouds. The interplanetary magnetic field data B-z from the ISEE 3 satellite, the auroral electrojet activity index AE, and the ring current index Dst are used as indicators of the disturbed magnetospheric conditions, and the ionospheric response features are analyzed using the F layer critical parameters h'F, h'F-3, h(p)F(2), and f(o)F(2). Focus is given to identify, when a large number of sequential substorms occurs, (1) the responses to prompt penetration electric field (from individual substorm events) as different from the delayed effect from the disturbance dynamo electric field and (2) the verification of local time dependences of the disturbance electric field polarity as predicted from the existing theoretical models. We have found evidence of near-midnight polarity reversal of prompt penetration disturbance electric field during the course of a developing substorm. Evidence is provided also on the near-midnight polarity reversal for the disturbance dynamo electric field. The prereversal enhancement electric field at sunset, produced by the F layer dynamo, is found to undergo drastic day-to-day variations in the course of a disturbed interval. However, the competing influences of the prompt versus delayed electric fields after a series of substorms could result at times in partial, or even complete, cancellation of the effects, so that the prereversal enhancement in the vertical drift could appear unaffected by the disturbances. There are indications that the disturbance dynamo electric field effects on the equatorial ionosphere last for one more day past the end of the substorm recovery. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Sobral, JHA (reprint author), INST NACL PESQUISAS ESPACIAIS,CP 515,BR-12201970 S JOSE CAMPOS,BRAZIL. RI Batista, Inez/F-2899-2012 NR 37 TC 62 Z9 62 U1 0 U2 4 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 JUL 1 PY 1997 VL 102 IS A7 BP 14305 EP 14313 DI 10.1029/97JA00576 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400026 ER PT J AU Lu, G Siscoe, GL Richmond, AD Pulkkinen, TI Tsyganenko, NA Singer, HJ Emery, BA AF Lu, G Siscoe, GL Richmond, AD Pulkkinen, TI Tsyganenko, NA Singer, HJ Emery, BA TI Mapping of the ionospheric field-aligned currents to the equatorial magnetosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HIGH-LATITUDE IONOSPHERE; MAGNETIC-FIELD; ELECTRODYNAMIC FEATURES; LOCALIZED OBSERVATIONS; SYNCHRONOUS ORBIT; AURORAL IMAGES; SUBSTORMS; MODEL; SIGNATURES; CONDUCTANCES AB The assimilative mapping of ionospheric electrodynamics (AMIE)-derived ionospheric field-aligned current patterns during the ninth Coordinated Data Analysis Workshop substorm event have been mapped to the magnetospheric equatorial plane, using the data-based magnetospheric magnetic field model [Tsyganenko, 1995]. We find that at the onset of the substorm expansion phase, a pair of field-aligned currents emerges about 8 R-E tailward of the Earth, near the x axis. This pair of field-aligned currents is consistent with the substorm current wedge model; it lines up in the east-west direction across the near-Earth tail current and has the sense of the nightside region 1 current, i.e., flowing into the ionosphere on the east side and out of the, ionosphere on the west side. The ionospheric counterpart of the substorm wedge currents in the midnight sector, on the other hand, has a northeast-to-southwest alignment. During the expansion phase, the substorm wedge currents intensify and expand in spatial size; however, their peaks remain nearly at the same location in the equatorial magnetosphere, about 8 R-E tailward from the Earth. We also find that the intensification of the substorm wedge currents during the expansion phase is accompanied by the intensification of the region 2-sense currents located closer to the Earth, and the boundary between the region 2 and substorm wedge currents lies around x = -6 R-E. C1 FINNISH METEOROL INST,DEPT GEOPHYS,FIN-00101 HELSINKI,FINLAND. NOAA,SPACE ENVIRONM CTR,BOULDER,CO 80303. BOSTON UNIV,CTR SPACE PHYS,BOSTON,MA 02215. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. RP Lu, G (reprint author), NATL CTR ATMOSPHER RES,HIGH ALTITUDE OBSERV,3540 MITCHELL LANE,BOULDER,CO 80301, USA. RI Lu, Gang/A-6669-2011; Tsyganenko, Nikolai/J-7377-2012; Pulkkinen, Tuija/D-8403-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579; Pulkkinen, Tuija/0000-0002-6317-381X NR 32 TC 11 Z9 11 U1 0 U2 4 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 JUL 1 PY 1997 VL 102 IS A7 BP 14467 EP 14476 DI 10.1029/97JA00744 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400039 ER PT J AU Ober, DM Horwitz, JL Gallagher, DL AF Ober, DM Horwitz, JL Gallagher, DL TI Formation of density troughs embedded in the outer plasmasphere by subauroral ion drift events SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CONVECTION ELECTRIC-FIELD; MAGNETOSPHERIC CONVECTION; IONOSPHERIC CONVECTION; DUSKSIDE BULGE; MODEL; PLASMAPAUSE; REGIONS AB A dynamic global core plasma model (DGCPM) is used to investigate the effects of subauroral ion drift (SAID) events on the formation of trough density profiles in the outer plasmasphere during periods of high magnetic activity. The DGCPM includes the influences of convection on the changing flux tube volumes, as well as daytime refilling and nighttime draining of plasma, to calculate the plasma tube contents and equatorial plasma density distribution versus time throughout the magnetosphere. SAIDs are regions of latitudinally narrow westward flow of plasma equatorward of the auroral zone. We present DGCPM results for various presumed SAID locations and durations relative to enhanced substorm convection onset and decay, to parametrically elicit the formation of plasmaspheric density. trough structures resulting from SAID effects. It is found that imposing a SAID event in the dusk-evening sector for 30 min leads to the formation of a narrow (less than 1 R-E near the equatorial plane) embedded plasma density trough in the dusk bulge region. The modeled plasmasphere density profiles with troughs generally resemble plasmasphere density profiles observed from DE 1 measurements. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. RP Ober, DM (reprint author), UNIV ALABAMA,CTR SPACE PLASMA & AERONOM RES,HUNTSVILLE,AL 35899, USA. NR 25 TC 70 Z9 70 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUL 1 PY 1997 VL 102 IS A7 BP 14595 EP 14602 DI 10.1029/97JA01046 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400049 ER PT J AU Cole, KD Hoegy, WR AF Cole, KD Hoegy, WR TI Nonlinear whistlers: Implications for 100 Hz electric fields observed in the Venus ionosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID NIGHTSIDE IONOSPHERE; LOW ALTITUDES; PLASMA-WAVES AB Conditions on the electric field of an electromagnetic wave in a plasma are found which make the wave magnetic field comparable in strength to the ambient field. The conditions arise from higher-order forces than are used in linear theory. It is found that the strong 100-Hz signals observed at night by the Pioneer-Venus orbiter in the Venus ionosphere at 129 km and a large fraction of the signals observed at 160 km, if interpreted as whistlers, would meet these conditions. The observations would represent highly nonlinear states for whistlers. Previous analyses of the 100-Hz signal interpreted as due to ''linear'' whistlers could therefore be flawed. This supports our contention [Cole and Hoegy, 1996a, b], arrived at by an independent argument, that the whistler hypothesis for the 100-Hz signal is invalid. In addition, in a new contribution to linear theory of the dispersion relationship, it is found that in the Venus ionosphere, in the high collision frequency region near 130 km altitude, linear whistlers would propagate freely in any direction, contrary to assumptions otherwise in the literature. They are critically damped there. At 160 km, normal linear-limit theory applies and manifests normal guidance by the ambient magnetic field, subject to omega < p cos theta, with little damping. RP Cole, KD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. NR 15 TC 7 Z9 7 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 JUL 1 PY 1997 VL 102 IS A7 BP 14615 EP 14623 DI 10.1029/97JA00564 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400051 ER PT J AU Miller, JA Cargill, PJ Emslie, AG Holman, GD Dennis, BR LaRosa, TN Winglee, RM Benka, SG Tsuneta, S AF Miller, JA Cargill, PJ Emslie, AG Holman, GD Dennis, BR LaRosa, TN Winglee, RM Benka, SG Tsuneta, S TI Critical issues for understanding particle acceleration in impulsive solar flares SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Review ID X-RAY-BURSTS; PERPENDICULAR COLLISIONLESS SHOCKS; STOCHASTIC PROTON ACCELERATION; THERMAL NONTHERMAL MODEL; LOWER-HYBRID-RESONANCE; ELECTRON ACCELERATION; MAGNETIC RECONNECTION; FERMI ACCELERATION; RUNAWAY ELECTRONS; ENERGETIC PARTICLES AB This paper, a review of the present status of existing models for particle acceleration during impulsive solar flares, was inspired by a week-long workshop held in the Fall of 1993 at NASA Goddard Space Flight Center. Recent observations from Yohkoh and the Compton Gamma Ray Observatory, and a reanalysis of older observations from the Solar Maximum Mission, have led to important new results concerning the location, timing, and efficiency of particle acceleration in flares. These are summarized in the first part of the review. Particle acceleration processes are then discussed, with;particular emphasis on new developments in stochastic acceleration by magnetohydrodynamic waves and direct electric field acceleration by both sub- and super-Dreicer electric fields. Finally, issues that arise when these mechanisms are incorporated into the large-scale flare structure are considered. Stochastic and super-Dreicer acceleration may occur either in a single large coronal reconnection site or at multiple ''fragmented'' energy release sites. Sub-Dreicer acceleration requires a highly filamented coronal current pattern. A particular issue that needs to be confronted by all theories is the apparent need for large magnetic field strengths in the flare energy release region. C1 AMER INST PHYS, COLLEGE PK, MD 20740 USA. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. KENNESAW STATE UNIV, DEPT BIOL & PHYS SCI, KENNESAW, GA 30144 USA. UNIV WASHINGTON, GEOPHYS PROGRAM, SEATTLE, WA 98195 USA. UNIV TOKYO, INST ASTRON, TOKYO 181, JAPAN. RP UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. RI Holman, Gordon/C-9548-2012; Dennis, Brian/C-9511-2012 NR 235 TC 339 Z9 348 U1 1 U2 12 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUL 1 PY 1997 VL 102 IS A7 BP 14631 EP 14659 DI 10.1029/97JA00976 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400053 ER PT J AU Thompson, DJ Bertsch, DL Morris, DJ Mukherjee, R AF Thompson, DJ Bertsch, DL Morris, DJ Mukherjee, R TI Energetic gamma ray experiment telescope high-energy gamma ray observations of the Moon and quiet Sun SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID COSMIC-RAY; GALACTIC PLANE; RADIATION; EMISSION; COMPTON AB High-energy gamma radiation has been seen from the Moon as it passed through the large field of view of the energetic gamma ray experiment telescope (EGRET) on the Compton Gamma Ray Observatory a number of times between mid-1991 and the end of 1994. The average lunar flux is (4.7 +/- 0.7) X 10(-7) photons (E > 100 MeV) cm(-2) s(-1) The observed energy spectrum is consistent with a model of gamma ray production by cosmic ray interactions with the lunar surface, and the flux varies as expected with the solar cycle. Although the same types of cosmic ray interactions that produce the lunar gamma rays may occur on the Sun, EGRET has not detected the quiet Sun. The 95% confidence upper limit on the flux above 100 MeV, 2.0 X 10(-7) photons cm(-2) s(-1), lies well below the lunar gamma ray flux, as expected. C1 UNIV NEW HAMPSHIRE,CTR SPACE SCI,DURHAM,NH 03824. RP Thompson, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. RI Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 24 TC 25 Z9 25 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 JUL 1 PY 1997 VL 102 IS A7 BP 14735 EP 14740 DI 10.1029/97JA01045 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XJ204 UT WOS:A1997XJ20400059 ER PT J AU Tierno, JE Murray, RM Doyle, JC Gregory, IM AF Tierno, JE Murray, RM Doyle, JC Gregory, IM TI Numerically efficient robustness analysis of trajectory tracking for nonlinear systems SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB A numerical algorithm for computing necessary conditions for performance specifications is developed for nonlinear uncertain systems that follow a prescribed trajectory, This algorithm provides a computationally efficient means of evaluating the performance of a nonlinear system in the presence of noise, real parametric uncertainty, and unmodeled dynamics, The algorithm is similar in nature and behavior to the power algorithm for the structured singular value (mu) lower bound and does not rely on a descent method, The algorithm is tested on a Eight control example. C1 CALTECH,PASADENA,CA 91125. NASA,LANGLEY RES CTR,DEPT FLIGHT DYNAM & CONTROL,HAMPTON,VA 23681. RP Tierno, JE (reprint author), HONEYWELL TECHNOL CTR,DEPT CONTROL & NAVIGAT,3660 TECHNOL DR,MINNEAPOLIS,MN 55418, USA. OI Murray, Richard/0000-0002-5785-7481 NR 23 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 1997 VL 20 IS 4 BP 640 EP 647 DI 10.2514/2.4121 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA XJ436 UT WOS:A1997XJ43600003 ER PT J AU Maghami, PG Gupta, S AF Maghami, PG Gupta, S TI Design of constant gain dissipative controllers for eigensystem assignment in passive systems SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID LARGE SPACE STRUCTURES; POLE ASSIGNMENT; OUTPUT-FEEDBACK; EIGENVALUE ASSIGNMENT; MULTIVARIABLE SYSTEMS; STATE FEEDBACK; POSITIVITY AB Partial eigensystem assignment with output feedback can lead to an unstable closed loop system. now ever, output feedback with passive linear time-invariant systems, such as flexible space structures, is guaranteed to be stable if the controller is dissipative. A novel approach is presented for synthesis of dissipative output feedback gain matrices For assigning a selected number of closed-loop poles. Dissipativity of a gain matrix is known to be equivalent to positive semidefiniteness of the symmetric part of the matrix, A sequential procedure is presented to assign one self-conjugate pair of closed-loop eigenvalues at each step using dissipative output feedback gain matrices, while ensuring that the eigenvalues assigned in the previous steps are not disturbed, The problem of assigning one closed-loop pair is reduced to a constrained solution of a system of quadratic equations, and necessary and sufficient conditions for the existence of a solution are presented. A minimax approach is presented for determining parameters that satisfy these conditions, This method can assign as many closed-loop system poles as the number of control inputs, A numerical example of damping enhancement for a flexible structure is presented to demonstrate the approach. C1 HUGHES SPACE & COMMUN CO,LOS ANGELES,CA 90009. RP Maghami, PG (reprint author), NASA,LANGLEY RES CTR,FLIGHT DYNAM & CONTROL DIV,GUIDANCE & CONTROL BRANCH,MS 161,HAMPTON,VA 23681, USA. NR 21 TC 4 Z9 4 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 1997 VL 20 IS 4 BP 648 EP 657 DI 10.2514/2.4127 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA XJ436 UT WOS:A1997XJ43600004 ER PT J AU LoomisPrice, LD Levi, M Burnett, PR vanHamont, JE Shafer, RA Wahren, B Birx, DL AF LoomisPrice, LD Levi, M Burnett, PR vanHamont, JE Shafer, RA Wahren, B Birx, DL TI Linear epitope mapping of humoral responses induced by vaccination with recombinant HIV-1 envelope protein gp160 SO JOURNAL OF INDUSTRIAL MICROBIOLOGY & BIOTECHNOLOGY LA English DT Article; Proceedings Paper CT 1996 Annual Meeting of the Society-for-Industrial-Microbiology CY AUG 04-08, 1996 CL RES TRIANGLE PK, NC SP Soc Ind Microbiol DE HIV vaccines; HIV antibodies; gp120; gp41; Pepscan; statistical data analysis ID B-CELL EPITOPES; HUMAN-IMMUNODEFICIENCY-VIRUS; INFECTED LABORATORY WORKERS; PEPTIDE-SYNTHESIS; ANTIBODY-RESPONSE; SURFACE-ANTIGEN; AMINO-ACID; STRATEGIES; SEQUENCE; THERAPY AB To enhance utility of the linear epitope mapping (Pepscan) technique for assay of humoral responses linked to vaccination, two modifications were tested, First, peptides were incubated with serum contained in baths rather than individual wells, Second, a rigorous statistical model was developed to determine which peptide/antibody-binding interactions were significant, The modifications increased the ability to detect signal in these experiments by 15-to 45-fold, These two modifications were applied to linear epitope mapping of HIV seropositive volunteers under treatment with recombinant HIV gp160 and also to rabbits immunized with the same product, Changes in fine specificity of response were observed in animal models and human vaccine recipients over the course of an immunization series with this antigen. C1 SWEDISH INST INFECT DIS,STOCKHOLM,SWEDEN. KAROLINSKA INST,STOCKHOLM,SWEDEN. USA,DENT RES DETACHMENT,WASHINGTON,DC 20307. WALTER REED ARMY INST RES,WASHINGTON,DC 20307. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP LoomisPrice, LD (reprint author), HENRY M JACKSON FDN,HIV LAB,13 TAFT COURT,SUITE 200,ROCKVILLE,MD 20850, USA. NR 32 TC 6 Z9 6 U1 0 U2 0 PU STOCKTON PRESS PI BASINGSTOKE PA HOUNDMILLS, BASINGSTOKE, HAMPSHIRE, ENGLAND RG21 6XS SN 0169-4146 J9 J IND MICROBIOL BIOT JI J. Ind. Microbiol. Biotechnol. PD JUL PY 1997 VL 19 IS 1 BP 58 EP 65 DI 10.1038/sj.jim.2900410 PG 8 WC Biotechnology & Applied Microbiology SC Biotechnology & Applied Microbiology GA XR177 UT WOS:A1997XR17700011 PM 9281853 ER PT J AU Lee, S AF Lee, S TI Sensor fusion and planning with perception-action network SO JOURNAL OF INTELLIGENT & ROBOTIC SYSTEMS LA English DT Article DE sensor fusion; planning; dynamic system; robotic system; uncertainty AB Robot intelligence requires a real-time connection between sensing and action. A new computation principle of robotics that efficiently implements such a connection is utmost important for the new generation of robotics. In this paper, a perception-action network is presented as a means of efficiently integrating sensing, knowledge, and action for sensor fusion and planning. The network consists of a number of heterogeneous computational units, representing feature transformation and decision-making for action, which are interconnected as a dynamic system. New input stimuli to the network invoke the evolution of network states to a new equilibrium, through which a real-time integration of sensing, knowledge, and action can be accomplished. The network provides a formal, yet general and efficient, method of achieving sensor fusion and planning. This is because the uncertainties of signals, propagated in the network, can be controlled by modifying sensing parameters and robot actions. Algorithms for sensor planning based on the proposed network are established and applied to robot self-localization. Simulation and experimental results are shown. C1 UNIV SO CALIF,DEPT EE SYST,LOS ANGELES,CA 90089. UNIV SO CALIF,DEPT CS,LOS ANGELES,CA 90089. RP Lee, S (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 21 TC 9 Z9 9 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0921-0296 J9 J INTELL ROBOT SYST JI J. Intell. Robot. Syst. PD JUL PY 1997 VL 19 IS 3 BP 271 EP 298 DI 10.1023/A:1007933821405 PG 28 WC Computer Science, Artificial Intelligence; Robotics SC Computer Science; Robotics GA XV372 UT WOS:A1997XV37200003 ER PT J AU Noever, D Sibille, L Cronise, R Baskaran, S Hunt, A AF Noever, D Sibille, L Cronise, R Baskaran, S Hunt, A TI Neural net formulations for organically modified, hydrophobic silica aerogel SO JOURNAL OF MATERIALS RESEARCH LA English DT Article AB Organic modification of aerogel chemical formulations is known to transfer desirable hydrophobicity to lightweight solids. However, the effects of chemical modification on other material constants such as elasticity, compliance, and sound dampening present a difficult optimization problem. Here a statistical treatment of a 9-variable optimization is accomplished with multiple regression and an artificial neural network (ANN). The ANN shows 95% prediction success for the entire data set of elasticity, compared to a multidimensional linear regression which shows a maximum correlation coefficient, R = 0.782. In this case, using the Number of Categories Criterion for the standard multiple regression, traditional statistical methods can distinguish fewer than 1.83 categories (high and low elasticity) and cannot group or cluster the data to give more refined partitions. A nonlinear surface requires at least three categories (high, low, and medium elasticities) to define its curvature. To predict best and worst gellation conditions, organic modification is most consistent with changed elasticity for sterically large groups and high hydroxyl concentrations per unit surface area. The isocontours for best silica and hydroxyl concentration have a complex saddle, the geometrical structure of which would elude a simple experimental design based on usual gradient descent methods for finding optimum. C1 UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. INST MOL BIOTECHNOL EV,D-7745 JENA,GERMANY. UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,BERKELEY,CA 94720. RP Noever, D (reprint author), NASA,BIOPHYS BRANCH,GEORGE C MARSHALL SPACE FLIGHT CTR,MAIL CODE ES-76,HUNTSVILLE,AL 35812, USA. NR 9 TC 0 Z9 0 U1 1 U2 3 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD JUL PY 1997 VL 12 IS 7 BP 1837 EP 1843 DI 10.1557/JMR.1997.0252 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA XJ194 UT WOS:A1997XJ19400025 ER PT J AU Nikitin, A Champion, JP Tyuterev, VG Brown, LR AF Nikitin, A Champion, JP Tyuterev, VG Brown, LR TI The high resolution infrared spectrum of CH3D in the region 900-1700 cm(-1) SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID 6-10 MU-M; MOLECULES; METHANE; (CH3D)-C-12; ABSORPTION AB The high resolution absorption spectrum of CH3D in the region 900-1700 cm(-1) has been reexamined on the basis of new long path experimental data recorded with the Fourier transform spectrometer at Kitt Peak. A theoretical model used previously for spherical rotors has been adapted for symmetric top molecules in order to analyze the vibrational polyads of CH3D simultaneously. Both triad and nonad-triad band systems have been investigated. The hot band intensities were estimated through direct extrapolation of the triad dipole moments. Six hundred lines from the hot bands have been assigned and combined with other data for the triad. The main hot bands contributions are due to 2 nu(6)-nu(6), 2 nu(3) - nu(3), nu(3) + nu(6) - nu(3) and nu(3) + nu(6) - nu(6) bands. The standard deviation, achieved for 3377 line positions of the triad was 0.56 10(-3) cm(-1), representing an improvement of one order of magnitude with respect to the most recent analysis. (C) 1997 Academic Press. C1 UNIV REIMS,LAB SPECT MOL ATMOSPHER,UPRESA CNRS D 1434,FAC SCI,F-51623 REIMS,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. RUSSIAN ACAD SCI,INST ATMOSPHER OPT,LAB THEORET SPECT,TOMSK 634055,RUSSIA. RP Nikitin, A (reprint author), UNIV BOURGOGNE,PHYS LAB,UNITE ASSOCIEE,CNRS,9 AVE A SAVARY,BP 400,F-21011 DIJON,FRANCE. RI Champion, Jean-Paul/C-3963-2009; Nikitin, Andrei/K-2624-2013 OI Nikitin, Andrei/0000-0002-4280-4096 NR 19 TC 38 Z9 38 U1 0 U2 8 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD JUL PY 1997 VL 184 IS 1 BP 120 EP 128 DI 10.1006/jmsp.1997.7303 PG 9 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA XR122 UT WOS:A1997XR12200014 ER PT J AU Sirota, JM Weber, M Reuter, DC Perrin, A AF Sirota, JM Weber, M Reuter, DC Perrin, A TI HNO3: Absolute line intensities for the nu(9) fundamental SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID NITRIC-ACID; BANDS; STRATOSPHERE; 2-NU-9; NU-5 AB Absolute line intensities for the nu(9) fundamental (458.228 cm(-1)) in HNO3 were determined for the first time, using tunable diode laser spectroscopy. This technique permitted short integration times, proven important to avoid dissociation in this highly reactive species. Thirty-eight transitions belonging to P and R branches were measured. The absolute value of the transition dipole moment was determined to be 0.2561(21) debye, yielding a value for the integrated band intensity at 296 degrees K of 209 cm(-2) atm(-1). A comparison is made to the previously measured integrated band intensity. (C) 1997 Academic Press. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV PARIS 11,PHOTOPHYS MOL LAB,CNRS,F-91405 ORSAY,FRANCE. RP Sirota, JM (reprint author), UNIV MARYLAND BALTIMORE CTY,DEPT PHYS,BALTIMORE,MD 21228, USA. RI Weber, Mark/F-1409-2011 OI Weber, Mark/0000-0001-8217-5450 NR 21 TC 13 Z9 13 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD JUL PY 1997 VL 184 IS 1 BP 140 EP 144 DI 10.1006/jmsp.1997.7310 PG 5 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA XR122 UT WOS:A1997XR12200016 ER PT J AU Murthy, G Kahan, NJ Hargens, AR Rempel, DM AF Murthy, G Kahan, NJ Hargens, AR Rempel, DM TI Forearm muscle oxygenation decreases with low levels of voluntary contraction SO JOURNAL OF ORTHOPAEDIC RESEARCH LA English DT Article ID NEAR-INFRARED SPECTROSCOPY; FATIGUE; WORK; DISORDERS; ISCHEMIA; LOAD AB The purpose of our investigation was to determine if the near infrared spectroscopy technique was sensitive to changes in tissue oxygenation at low levels of isometric contraction in the extensor carpi radialis brevis muscle. Nine subjects were seated with the right arm abducted to 45 degrees, elbow flexed to 85 degrees, forearm pronated 45 degrees, and wrist and forearm supported on an armrest throughout the protocol. Altered tissue oxygenation was measured noninvasively with near infrared spectroscopy. The near infrared spectroscopy probe was placed over the extensor carpi radialis brevis of the subject's right forearm and secured with an elastic wrap. After 1 minute of baseline measurements taken with the muscle relaxed, four different loads were applied just proximal to the metacarpophalangeal joint such that the subjects isometrically contracted the extensor carpi radialis brevis at 5, 10, 15, and 50% of the maximum voluntary contraction for 1 minute each. A 3-minute recovery period followed each level of contraction. At the end of the protocol, with the probe still in place, a value for ischemic tissue oxygenation was obtained for each subject. This value was considered the physiological zero and hence 0% tissue oxygenation. Mean tissue oxygenation (+/-SE) decreased from resting baseline (100% tissue oxygenation) to 89 +/- 4, 81 +/- 8, 78 +/- 8, and 47 +/- 8% at 5, 10, 15, and 50% of the maximum voluntary contraction, respectively Tissue oxygenation levels at 10, 15, and 50% of the maximum voluntary contraction were significantly lower (p < 0.05) than the baseline value. Our results indicate that tissue oxygenation significantly decreases during brief, low levels of static muscle contraction and that near infrared spectroscopy is a sensitive technique for detecting deoxygenation noninvasively at low levels of forearm muscle contraction. Our findings have important implications in occupational medicine because oxygen depletion induced by low levels of muscle contraction may be directly linked to muscle fatigue. C1 UNIV CALIF BERKELEY,ERGON LAB,BERKELEY,CA 94720. SPORTS & OCCUPAT MED ASSOCIATES,CUPERTINO,CA. NASA,AMES RES CTR,GRAVITAT RES BRANCH,MOFFETT FIELD,CA 94035. UNIV CALIF SAN FRANCISCO,DEPT MED,SAN FRANCISCO,CA. RI Rempel, David/E-8424-2013 NR 26 TC 30 Z9 31 U1 0 U2 0 PU JOURNAL BONE JOINT SURGERY INC PI NEEDHAM PA 20 PICKERING ST, NEEDHAM, MA 02192 SN 0736-0266 J9 J ORTHOPAED RES JI J. Orthop. Res. PD JUL PY 1997 VL 15 IS 4 BP 507 EP 511 DI 10.1002/jor.1100150405 PG 5 WC Orthopedics SC Orthopedics GA YA230 UT WOS:A1997YA23000004 PM 9379259 ER PT J AU Vega, FJ Feldmann, RM Ocampo, AC Pope, KO AF Vega, FJ Feldmann, RM Ocampo, AC Pope, KO TI A new species of late Cretaceous crab (Brachyura: Carcineretidae) from Albion Island, Belize SO JOURNAL OF PALEONTOLOGY LA English DT Article ID CRUSTACEA; DECAPODA; JAMAICA; MEXICO AB A new species of carcineretid crab, Carcineretes planetarius, is described from the Upper Cretaceous (lower Maastrichtian) Barton Creek Dolomite at Albion Island, Belize. The age is based on the stratigraphic range of associated nerineid gastropods and correlation with nannoplankton, benthic foraminifera, and the other known congeneric species of crab found in Jamaica. Confirmation of this age aids in constraining the timing of ejecta deposits of the Chicxulub impact found at the top of Barton Creek Dolomite exposed on Albion Island. Paleoenvironmental and paleoecological analyses suggest that these crabs were swimmers in lagoonal settings, capable of burrowing a few centimeters into the mud for protection. C1 KENT STATE UNIV,DEPT GEOL,KENT,OH 44242. CALTECH,JET PROPULS LAB,PASADENA,CA 91009. GEO ECO ARCH RES,LA CANADA FLINTRIDGE,CA 91011. RP Vega, FJ (reprint author), NATL AUTONOMOUS UNIV MEXICO,INST GEOL,CIUDAD UNIV,MEXICO CITY 04510,DF,MEXICO. NR 33 TC 24 Z9 25 U1 0 U2 0 PU PALEONTOLOGICAL SOC INC PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044 SN 0022-3360 J9 J PALEONTOL JI J. Paleontol. PD JUL PY 1997 VL 71 IS 4 BP 615 EP 620 PG 6 WC Paleontology SC Paleontology GA XN365 UT WOS:A1997XN36500009 PM 11541235 ER PT J AU Sanchez, BV Cunningham, WJ Pavlis, NK AF Sanchez, BV Cunningham, WJ Pavlis, NK TI The calculation of the dynamic sea surface topography and the associated flow field from altimetry data: A characteristic function method SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID SCALE OCEAN CIRCULATION; SATELLITE ALTIMETRY; GRAVITY; ACCURACY; MODEL AB The quasi-stationary sea surface topography (QSST) and associated oceanic circulation is determined by means of a characteristic function technique. The method was originally implemented in an ideal simplified case. The present application involves a 4 degrees x 4 degrees grid in spherical coordinates approximating the boundaries of the main ocean basins. The data field is provided by the first year of altimetric data from the TOPEX/POSEIDON mission. The method requires the numerical determination of the eigenfunctions spanning the streamfunction field and the associated characteristic functions from the balance equation. The former yields the flow field and the latter the surface height distribution, or QSST These functions are determined by the geometry and topography of the ocean basins and satisfy the linear steady-state dynamical equations. They are defined within the basins only and avoid the problems encountered when using functions defined over the entire sphere. The velocity field can be computed over the entire ocean area, including the equatorial regions. The coefficients of the height functions have been determined by fitting the surface height field provided by TOPEX altimetry. Seasonal variations have been computed by subtracting a 32-cycle solution from each of the four 8-cycle seasonal solutions. C1 HUGHES STX,GEODYNAM GRP,GREENBELT,MD. RP Sanchez, BV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,SPACE GEODESY BRANCH,GREENBELT,MD 20771, USA. RI Sanchez, Braulio/I-5952-2013 NR 30 TC 3 Z9 3 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD JUL PY 1997 VL 27 IS 7 BP 1371 EP 1385 DI 10.1175/1520-0485(1997)027<1371:TCOTDS>2.0.CO;2 PG 15 WC Oceanography SC Oceanography GA XM923 UT WOS:A1997XM92300011 ER PT J AU Yu, ZJ Schopf, PS AF Yu, ZJ Schopf, PS TI Vertical eddy mixing in the tropical upper ocean: Its influence on zonal currents SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID GENERAL-CIRCULATION MODEL; MIXED-LAYER; TURBULENCE; PARAMETERIZATION; THERMOCLINE; SIMULATION AB In this study, the authors explore how vertical-mixing parameterizations influence the structure of zonal currents in the eastern equatorial Pacific using an isopycnal ocean model that contains an explicit surface mixed layer. The mixing parameterizations considered are the schemes that depend on the Richardson number (Ri). One of the schemes (the Step scheme) consists of high (nu(c)) and low (nu(b)) values of mixing coefficients, depending on whether Ri is less than or greater than a critical value. In simulations using the Step scheme, there is a region of large vertical shear just beneath the mixed layer where Ri is low and the mixing coefficient is nu(c) this high mixing controls the depth and strength of the westward surface drift. Near the undercurrent core, Ri is high and the mixing coefficient is nu(b); this low mixing is nevertheless dynamically important in that it affects the strength of the undercurrent. For the Ri-dependent schemes investigated, it is demonstrated that the extrema attained by mixing coefficients at low and high Ri are the crucial factor rather than the detailed structure of the Ri-dependent functions. C1 UNIV MARYLAND,DEPT METEOROL,JOINT CTR EARTH SYST SCI,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,COUPLED CLIMATE DYNAM GRP,GREENBELT,MD 20771. NR 39 TC 31 Z9 31 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD JUL PY 1997 VL 27 IS 7 BP 1447 EP 1458 DI 10.1175/1520-0485(1997)027<1447:VEMITT>2.0.CO;2 PG 12 WC Oceanography SC Oceanography GA XM923 UT WOS:A1997XM92300016 ER PT J AU Caillat, T Fleurial, JP Borshchevsky, A AF Caillat, T Fleurial, JP Borshchevsky, A TI Preparation and thermoelectric properties of semiconducting Zn4Sb3 SO JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS LA English DT Article DE semiconductors; thermal conductivity; transport properties ID THERMAL-CONDUCTIVITY; COSB3 AB Hot-pressed samples of the semiconducting compound beta-Zn4Sb3 were prepared and characterized by X-ray and microprobe analysis. Some physical properties of beta-Zn4Sb3 were determined and its thermoelectric properties measured between room temperature and 650 K. Exceptionally low thermal conductivity values were obtained in the 300-650 K temperature range and the room temperature lattice thermal conductivity was estimated at 6.5 W cm(-1) K-1. High thermoelectric figures of merit (ZTs) were obtained between 450 and 670 K and a maximum of about 1.3 was obtained at a temperature of 670 K, the highest known at this temperature. The stability of the compound was investigated by several techniques, including thermogravimetric studies. The results showed that the samples were stable under argon atmosphere and static vacuum up to about 670 K and up to 520 K in dynamic vacuum. The high thermoelectric performance of beta-Zn4Sb3 in the 300-670 K temperature range fills the existing gap in the ZT spectrum of p-type state-of-the-art thermoelectric materials between Bi2Te3-based alloys and PbTe-based alloys. This material, relatively inexpensive, could be used in more efficient thermoelectric generators for waste heat recovery and automobile industry applications, for example. (C) 1997 Elsevier Science Ltd. All rights reserved. RP Caillat, T (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 38 TC 411 Z9 418 U1 16 U2 154 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-3697 J9 J PHYS CHEM SOLIDS JI J. Phys. Chem. Solids PD JUL PY 1997 VL 58 IS 7 BP 1119 EP 1125 DI 10.1016/S0022-3697(96)00228-4 PG 7 WC Chemistry, Multidisciplinary; Physics, Condensed Matter SC Chemistry; Physics GA XH968 UT WOS:A1997XH96800011 ER PT J AU Said, MA Thomas, V AF Said, MA Thomas, V TI Mechanical behavior of polyester nonwoven composite films SO JOURNAL OF PLASTIC FILM & SHEETING LA English DT Article; Proceedings Paper CT 54th Annual Technical Conference of the Society-of-Plastics-Engineers CY MAY 05-10, 1996 CL INDIANAPOLIS, IN SP Soc Plast Engineers DE nonwovens; mechanical properties; thin films; lamination; composite films; scrim; scientific balloons; polyethylene terephthalate films AB Films reinforced with nonwoven fabric are being considered for the development of a material suitable for long duration scientific balloons under a program managed by the National Aeronautics and Space Administration (NASA). Nonwoven fabrics provide a relatively high strength to weight ratio compared to other woven fabrics or homogeneous films. Nonwovens also have better crack propagation resistance and rip stop capabilities when compared to similar light weight, high strength materials. If joining is required, such as in the case of scientific balloons, nonwovens have an advantage over polymeric thin films since they can utilize traditional textile methods as well as other methods such as heat sealing, adhesives, and ultrasonic means. Nonwovens, however, lack the barrier properties required for helium filled scientific balloons. Because the fabric is porous, it must be laminated to provide the gas barrier capabilities required in these applications. A set of polyester nonwovens, with and without a scrim, were laminated with thin biaxially oriented polyethylene terephthalate (PET) film as a barrier; their mechanical properties were compared to that of the individual layers. The data indicate that, while maintaining the low weight characteristics, there is a net increase in the strength and toughness of the composite film compared to that of the nonwoven fabric or the PET film alone. C1 NASA,GODDARD SPACE FLIGHT CTR,WALLOPS FLIGHT FACIL,WALLOPS ISL,VA 23337. TEXAS A&M UNIV,MECH & MAT CTR,COLLEGE STN,TX 77843. NR 11 TC 1 Z9 1 U1 0 U2 2 PU TECHNOMIC PUBL CO INC PI LANCASTER PA 851 NEW HOLLAND AVE, BOX 3535, LANCASTER, PA 17604 SN 8756-0879 J9 J PLAST FILM SHEET JI J. Plast. Film Sheeting PD JUL PY 1997 VL 13 IS 3 BP 212 EP 220 PG 9 WC Materials Science, Coatings & Films SC Materials Science GA YG972 UT WOS:A1997YG97200007 ER PT J AU Moore, JJ Palazzolo, AB Gadangi, RK Kascak, AF Brown, G Montague, G AF Moore, JJ Palazzolo, AB Gadangi, RK Kascak, AF Brown, G Montague, G TI Hybrid friction-impact vibration damper for cryogenic rotating machinery SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB A hybrid friction-impact rotordynamic damper has been designed and tested in a high-speed rotordynamic test rig for application to rocket engine turbopumps operating at cryogenic temperatures, such as the high-pressure oxygen and fuel turbopumps used in the Space Shuttle Main Engines. Test results have shown the impact damper to be effective at larger amplitudes and higher frequencies, whereas the friction damper is effective at lower amplitudes and frequencies. Together, the hybrid damper offers good performance over a wide range of operating conditions. A friction damper design methodology is presented and applied to the experimental test rig. C1 TEXAS A&M UNIV,DEPT MECH ENGN,COLLEGE STN,TX 77843. NASA,LEWIS RES CTR,USA,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,DYNAM BRANCH,STRUCT GRP,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,NYMA,CLEVELAND,OH 44135. NR 12 TC 1 Z9 1 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 1997 VL 13 IS 4 BP 495 EP 501 DI 10.2514/2.5211 PG 7 WC Engineering, Aerospace SC Engineering GA XL152 UT WOS:A1997XL15200006 ER PT J AU Welch, GE AF Welch, GE TI Macroscopic balance model for wave rotors SO JOURNAL OF PROPULSION AND POWER 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 AB A mathematical model for wave rotors is described, The wave processes that affect energy exchange within the rotor passages are modeled using one-dimensional gasdynamics. Macroscopic balances relate volume-averaged thermodynamic properties in the rotor passage control volume to the mass, momentum, and energy fluxes at the ports, Simple loss models are used to estimate entropy production in boundary layers and in separating flows caused by blade-blockage, incidence, and the gradual opening and closing of rotor passages, The mathematical model provides a basis for designing port and rotor geometry, and for predicting design-point wave rotor performance, Model predictions are evaluated through comparisons with computational fluid dynamics calculations and three-port wave rotor experimental data, A four-port wave rotor design example is provided to demonstrate model applicability, The modeling approach is amenable to wave rotor optimization studies and rapid assessment of the tradeoffs associated with integrating wave rotors into gas turbine engine systems. RP Welch, GE (reprint author), NASA,LEWIS RES CTR,USA,RES LAB,VEHICLE TECHNOL CTR,21000 BROOKPARK RD,M-S 77-6,CLEVELAND,OH 44135, USA. NR 27 TC 8 Z9 8 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 1997 VL 13 IS 4 BP 508 EP 516 DI 10.2514/2.5213 PG 9 WC Engineering, Aerospace SC Engineering GA XL152 UT WOS:A1997XL15200008 ER PT J AU Owens, M Segal, C Auslender, AH AF Owens, M Segal, C Auslender, AH TI Effects of mixing schemes on kerosene combustion in a supersonic airstream SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID JETS AB A study of kerosene combustion in a supersonic vitiated airflow at Mach 4.75 night enthalpy was conducted in direct-connect tests at Mach 1.8 at a stagnation temperature of 1000 K. The effects of shock-and vortex-enhanced mixing mechanisms on the combustion efficiency were evaluated. Also included in this study were the effects of fuel heating and jet penetration. The experimental conditions corresponded to the low end of the hypersonic night regime, The following geometric configurations were employed: 1) a generic, rearward-facing step, 2) a modified rearward-facing step with beveled edges to facilitate vortex-enhanced mixing, and 3) a rearward-facing wedge (15 or 30 deg) placed downstream of the rearward-facing step to induce shock-enhanced mixing, In all configurations, a gaseous hydrogen-pilot jet was injected parallel to the main flow from the base of the rearward-facing step and the liquid kerosene was injected normal to the main flow at three or five step heights downstream of the step (the step height was 10 mm). Stable kerosene combustion was obtained for a maximum injected kerosene equivalence ratio of 0.86. For efficiency evaluation, the pilot-hydrogen equivalence ratio was selected between 0.02-0.04, while the kerosene equivalence ratio was maintained at 0.325. In all experiments, locally rich stratified kerosene combustion took place in a layer close to the injection wall. The wedge flameholder contributed to an increased kerosene combustion efficiency by the generation of shock-jet interactions. The beveled-edge step improved far-field mixing, thereby reducing the local kerosene equivalence ratio, resulting in the highest kerosene combustion efficiency among all configurations tested. Fuel heating below levels required for flash vaporization (one-third of the flash vaporization energy, in this case) did not contribute to increased combustion efficiency. On the contrary, this level of heating reduced the fuel density with adverse effects on penetration and mixing. C1 NASA,LANGLEY RES CTR,DEPT AEROSP ENGN MECH & ENGN SCI,HAMPTON,VA 23681. RP Owens, M (reprint author), UNIV FLORIDA,DEPT AEROSP ENGN MECH & ENGN SCI,GAINESVILLE,FL 32611, USA. NR 24 TC 15 Z9 17 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 1997 VL 13 IS 4 BP 525 EP 531 DI 10.2514/2.5198 PG 7 WC Engineering, Aerospace SC Engineering GA XL152 UT WOS:A1997XL15200010 ER PT J AU Singh, DJ Carpenter, MH Drummond, JP AF Singh, DJ Carpenter, MH Drummond, JP TI Thrust enhancement in hypervelocity nozzles by chemical catalysis SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID RECOMBINATION C1 ANALYT SERV & MAT INC,HAMPTON,VA 23666. NASA,LANGLEY RES CTR,HYPERSON AIRBREATHING PROPULS BRANCH,HAMPTON,VA 23681. NR 3 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 1997 VL 13 IS 4 BP 574 EP 576 DI 10.2514/2.5206 PG 3 WC Engineering, Aerospace SC Engineering GA XL152 UT WOS:A1997XL15200018 ER PT J AU Berry, SA Nowak, RJ AF Berry, SA Nowak, RJ TI Fin leading-edge sweep effect on shock-shock interaction at Mach 6 SO JOURNAL OF SPACECRAFT AND ROCKETS 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 AB The effects of fin leading-edge sweep on peak heating rates due to shock-shock interaction have been experimentally examined in the NASA Langley Research Center 20-Inch Mach 6 Tunnel. The shock interaction was produced by the intersection of a planar incident shock (16.8-deg shock angle relative to the freestream, generated by a 9-deg wedge) with the bow shock formed around a 0.5-in.-diam cylindrical leading-edge fin. Heating distributions along the leading-edge stagnation line have been obtained using densely spaced thin-film resistive-type sensors. Schlieren images were obtained to illustrate the very complex shock-shock interactions. The fin leading-edge sweep angle was varied from 15 deg swept back (relative to the normal to the freestream) to 45 deg swept forward for a freestream unit Reynolds number of 2 X 10(6)/ft. Two models were utilized during the study, one with 0.025-in. spacing between gauge centers, and the other with 0.015-in. spacing Gauge spatial resolution on the order of 0.015 in. appeared to capture the narrow heating spike accurately. Peak heating due to shock interaction was maximized when the fin was swept forward 15 and 25 deg, both promoting augmentations over seven times the baseline value. The schlieren images for these cases revealed type IV and Type III interactions, respectively. RP Berry, SA (reprint author), NASA,LANGLEY RES CTR,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681, USA. NR 21 TC 7 Z9 8 U1 2 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1997 VL 34 IS 4 BP 416 EP 425 DI 10.2514/2.3247 PG 10 WC Engineering, Aerospace SC Engineering GA XP929 UT WOS:A1997XP92900002 ER PT J AU Bertin, JJ Stetson, KF Bouslog, SA Caram, JM AF Bertin, JJ Stetson, KF Bouslog, SA Caram, JM TI Effect of isolated roughness elements on boundary-layer transition for Shuttle Orbiter SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A 1.75% scale model of the Shuttle Orbiter has been tested in the Mach 8 Tunnel B at the Arnold Engineering Development Center with and without isolated roughness elements. Heat flux gauges on the windward surface permitted the evaluation of heat transfer distributions and boundary-layer transition trends on the Orbiter's windward surface. The data obtained during the current program have been reviewed and compared with transition results from previous tests using both a smooth model and those with distributed roughness. Results indicated that, for many test conditions, a single, relatively small roughness element can be effective in promoting boundary-layer transition, i.e., moving transition close to the roughness element. C1 ROHR IND INC,TECH RESOURCE DEPT,CHULA VISTA,CA 91910. NASA,LYNDON B JOHNSON SPACE CTR,AEROSP FLIGHT MECH DIV,HOUSTON,TX 77058. RP Bertin, JJ (reprint author), USAF ACAD,DEPT AERONAUT,COLORADO SPRINGS,CO 80840, USA. NR 13 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1997 VL 34 IS 4 BP 426 EP 436 DI 10.2514/2.3254 PG 11 WC Engineering, Aerospace SC Engineering GA XP929 UT WOS:A1997XP92900003 ER PT J AU Braun, RD Moore, AA Kroo, IM AF Braun, RD Moore, AA Kroo, IM TI Collaborative approach to launch vehicle design SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA/USAF/NASA/ISSMO 6th Symposium on Multidisciplinary Analysis and Optimization CY SEP 04-06, 1996 CL BELLEVUE, WA SP AIAA, USAF, NASA, ISSMO ID SYSTEM AB Collaborative optimization is a new design architecture specifically created for large-scale distributed-analysis applications. In this approach, a problem is decomposed into a user-defined number of subspace optimization problems that are driven toward interdisciplinary compatibility rind the appropriate solution by a system-level coordination process. This decentralized design strategy allows domain-specific issues to be accommodated by disciplinary analysts while requiring interdisciplinary decisions to be reached by consensus. This investigation focuses on application of the collaborative optimization architecture to the multidisciplinary design of a single-stage-to-orbit launch vehicle. Vehicle design, trajectory, and cost issues are directly modeled in this problem, which is characterized by 95 design variables and 16 constraints. Numerous collaborative solutions are obtained. Comparison of these solutions demonstrates the influence that an a priori accent-abort criterion has on the vehicle design and the distinction between minimum weight and minimum cost concepts. The operational advantages of the collaborative optimization architecture include minimal framework integration requirements, the ability to use domain-specific analyses, which already provide optimization without modification, inherent system flexibility and modularity, a distributed analysis and optimization capability, and a significant reduction in interdisciplinary communication requirements. C1 STANFORD UNIV, DEPT AERONAUT & ASTRONAUT, STANFORD, CA 94305 USA. RP Braun, RD (reprint author), NASA, LANGLEY RES CTR, SPACE SYST & CONCEPTS DIV, HAMPTON, VA 23681 USA. NR 40 TC 53 Z9 72 U1 2 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1997 VL 34 IS 4 BP 478 EP 486 DI 10.2514/2.3237 PG 9 WC Engineering, Aerospace SC Engineering GA XP929 UT WOS:A1997XP92900010 ER PT J AU Barret, C AF Barret, C TI Flight control augmentors for aft-center-of-gravity launch vehicles SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The author presents the details of the designed fright control augmentors, the wind tunnel test programs conducted at the NASA Marshall Space Flight Center, and the stability and control analyses results for the augmented launch vehicle. Forward and aft, all-movable, blunt-trailing-edge flight control augmentors have been designed and wind tunnel tested to provide the required flight control augmentation for a family of aft-center-of-gravity launch vehicles that could not be adequately controlled using engine ginbaling alone. Previous publications have presented the other parts of this comprehensive research project: the developmental stages of the program, the comprehensive reviews of our national heritage of launch vehicles that have used aerodynamic surfaces and current use of these by ether nations, and a state-of-the-art assessment of smart materials and advanced composites directly applicable to the innovative design of the flight control augmentors. It is shown that the blunt-trailing-edge design provides the maximum flight control augmentation. RP Barret, C (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 13 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1997 VL 34 IS 4 BP 487 EP 495 DI 10.2514/2.3238 PG 9 WC Engineering, Aerospace SC Engineering GA XP929 UT WOS:A1997XP92900011 ER PT J AU Haw, RJ Antreasian, PG McElrath, TP Graat, EJ Nicholson, FT AF Haw, RJ Antreasian, PG McElrath, TP Graat, EJ Nicholson, FT TI Navigating Galileo at Jupiter arrival SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Analysis of Doppler tracking data from the Galileo spacecraft contributed to a successful encounter with Jupiter and one of its moons, Io, as well as to the successful delivery of the first instrumented probe into Jupiter's atmosphere. In support of this navigation work, geophysical parameters of the Jovian system have been determined. These include an estimate of the third-order gravity field of Io, masses and ephemerides of Io and Europa, and a revision to the mass of Jupiter. These results are consistent with previously published results for Voyagers 1 and 2. A new Jupiter ephemeris was also computed from the tracking data. Jupiter showed a significant 2 sigma shift in position with respect to the Jet Propulsion Laboratory ephemeris DE-143. Subsequently, using this updated ephemeris, accurate reconstructions of the encounters of the Galileo spacecraft pair (orbiter and probe) with Jupiter and Io were possible. RP Haw, RJ (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 8 TC 7 Z9 7 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1997 VL 34 IS 4 BP 503 EP 508 DI 10.2514/2.3240 PG 6 WC Engineering, Aerospace SC Engineering GA XP929 UT WOS:A1997XP92900013 ER PT J AU Jaffe, LD Herrell, LM AF Jaffe, LD Herrell, LM TI Cassini/Huygens science instruments, spacecraft, and mission SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID CASSINI MISSION; CRAF-CASSINI; HUYGENS; TITAN AB The Cassini spacecraft will take 18 scientific instruments to Saturn. After launch and a seven-year cruise, Cassini will arrive at Saturn and separate into a Saturn orbiter and an atmospheric probe, called Huygens, which will descend to the surface of Titan. The orbiter will orbit the planet for four years, making close flybys of five satellites, including multiple flybys of Titan. Communication with Earth is at X-band; the maximum downlink rate from Saturn is 166 x 10(3) bps. Orbiter instruments are body mounted; the spacecraft must be turned to point some of them toward objects of interest. The orbiter carries 12 instruments. Optical instruments provide imagery and spectrometry, Radar supplies imaging, altimetry, and radiometry. Radio links contribute information about intervening material and gravity fields. Other instruments measure electromagnetic fields and the properties of plasma, energetic particles, and dust particles. The probe is spin stabilized. It returns data via an S-band link to the orbiter. The probe's six instruments include sensors to determine atmospheric physical properties and composition. Radiometric and optical sensors will produce data on thermal balance and obtain images of Titan's atmosphere and surface. Doppler measurements between probe and orbiter will provide wind profiles. Surface sensors will measure impact acceleration, thermal and electrical properties, and, if the surface is liquid, density and refractive index. This design will enable Cassini to determine the composition; the physical, morphological, and geological nature; and I the physical and chemical processes of the atmospheres, surfaces, and magnetosphere of the Saturnian system. This paper briefly describes the Cassini mission and spacecraft and, in somewhat more detail, the scientific instruments. RP Jaffe, LD (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 301-485, PASADENA, CA 91109 USA. NR 44 TC 13 Z9 14 U1 2 U2 7 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1997 VL 34 IS 4 BP 509 EP 521 DI 10.2514/2.3241 PG 13 WC Engineering, Aerospace SC Engineering GA XP929 UT WOS:A1997XP92900014 ER PT J AU Jablonski, AM Vigneron, FR Rhew, RD Bergmans, JL Whitehead, WR Tyc, G AF Jablonski, AM Vigneron, FR Rhew, RD Bergmans, JL Whitehead, WR Tyc, G TI Preflight testing and flight performance of the OEDIPUS-C tether force sensor SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The authors describe preflight calibration and qualification testing of the tether force sensor developed for the Canadian OEDIPUS-C mission flown on Nov. 6, 1995. OEDIPUS stands for observations of electric field distribution in the ionospheric plasma, a unique strategy. The OEDIPUS-C payload was designed as a large double probe for sensitive measurements of weak electric fields in the plasma of the aurora. It was launched using Black Brant XII sounding rocket to a trajectory with an apogee of 843 km, and the length of deployed conducting tether was 1174 m. There were 13 scientific experiments onboard, including the tether dynamics experiment with the tether force sensor as its prime instrument. This instrument is a strain-gauge-based three-axis force transducer that measures the instantaneous tether tension vector. Qualification and environmental testing of the transducer are summarized. The calibration testing of the tether force sensor is presented together with its theoretical background. During preflight testing, sources of errors and secondary performance characteristics were also identified. The tether force sensor flight performance met designed flight requirements. The representative tether force sensor flight data including time histories of tether force components are presented. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. CFD RES CORP,HUNTSVILLE,AL 35805. BRISTOL AEROSP LTD,WINNIPEG,MB R3C 2S4,CANADA. RP Jablonski, AM (reprint author), CANADIAN SPACE AGCY,ST HUBERT,PQ J3Y 8Y9,CANADA. NR 8 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1997 VL 34 IS 4 BP 533 EP 541 DI 10.2514/2.3243 PG 9 WC Engineering, Aerospace SC Engineering GA XP929 UT WOS:A1997XP92900016 ER PT J AU Chaffin, MS Berry, JD AF Chaffin, MS Berry, JD TI Helicopter fuselage aerodynamics under a rotor by Navier-Stokes simulation SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 51st Annual Forum of the American-Helicopter-Society CY MAY 09-11, 1995 CL FT WORTH, TX SP Amer Helicopter Soc ID HOVER AB An incompressible Navier-Stokes code was modified to model the effects of a helicopter rotor in forward flight on the viscous aerodynamics of the fuselage. The rotor was treated in a manner similar to an actuator disk, with the thrust being modelled as a jump in pressure across the disk. Unlike an actuator disk, the pressure jump was allowed to vary with radial and azimuthal locations on the disk and was computed from a fully coupled blade element model. Swirl velocities were implemented by adding a jump in tangential velocity across the disk surface. Chimera grids were used to allow more complex configurations to be modelled. Calculations were made for an isolated rotor as well as for a rotor/fuselage geometry and compared with experimental inflow velocity data and experimental fuselage surface pressure data. The time-averaged effect of the rotor on the fuselage as well as the time averaged effect of the fuselage on the rotor are shown. C1 USA,ATCOM AEROFLIGHTDYNAM DIRECTORATE,LANGLEY RES CTR,HAMPTON,VA. RP Chaffin, MS (reprint author), VIGYAN INC,HAMPTON,VA, USA. NR 33 TC 14 Z9 16 U1 0 U2 0 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1997 VL 42 IS 3 BP 235 EP 243 PG 9 WC Engineering, Aerospace SC Engineering GA XM936 UT WOS:A1997XM93600004 ER PT J AU Davis, W Pezeshki, C Mosher, M AF Davis, W Pezeshki, C Mosher, M TI Extracting and characterizing blade-vortex interaction noise with wavelets SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 51st Annual Forum of the American-Helicopter-Society CY MAY 09-11, 1995 CL FT WORTH, TX SP Amer Helicopter Soc AB Applications of a discrete implementation of the wavelet transform (WT) to the analysis of blade-vortex interaction (BVI) noise are presented, The method decomposes a signal into a series of orthogonal subbands logarithmically spaced in frequency while simultaneously preserving temporal information, A BVI detection algorithm was developed which takes advantage of the prominence of BVI noise in certain subbands, A method for extracting BVI noise from other noise sources is described. Three metrics are tested for suitability as BVI estimators. One of these, a root-mean square (RMS) metric, characterizes BVI noise severity, hut requires the added computational effort of inverting the transform, The other two metrics are computed using the information available from the WT. The first of these, computed from the amplitudes of BVI events in a single subband, correlates with peak-to-peak pressure and is relatively insensitive to noise, The second of these, based on the exponential behavior of peak amplitudes across subbands, is apparently unable to characterize BVI noise severity and is highly sensitive to noise. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Davis, W (reprint author), WASHINGTON STATE UNIV, DEPT MECH & MAT ENGN, PULLMAN, WA 99164 USA. NR 22 TC 0 Z9 0 U1 0 U2 1 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1997 VL 42 IS 3 BP 264 EP 271 PG 8 WC Engineering, Aerospace SC Engineering GA XM936 UT WOS:A1997XM93600007 ER PT J AU Kitaplioglu, C Caradonna, FX Burley, CL AF Kitaplioglu, C Caradonna, FX Burley, CL TI Parallel blade-vortex interactions: An experimental study and comparison with computations SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 1995 American-Helicopter-Society 2nd International Aeromechanics Specialists Conference CY OCT 11-13, 1995 CL BRIDGEPORT, CT SP Amer Helicopter Soc AB This paper presents results from an experimental study of rotor blade-vortex interaction (BVI) aerodynamics and acoustics, The experiment utilized an externally generated vortex interacting with a two-bladed rotor operating at zero thrust to minimize the influence of the rotor's own wake, The rotor blades were instrumented with a total of 60 absolute pressure transducers at three spanwise and ten chordwise stations on both the upper and lower surfaces. Acoustic data were obtained with fixed near-field microphones as well as a movable array of far-field microphones. The test was carried out in the acoustically treated test section of the NASA Ames 80- by 120-Foot Wind Tunnel, Several parameters which influence BVI, such as vortex-rotor separation distance, vortex strength, and vortex sense (swirl direction), as well as rotor tip Mach number and advance ratio, were varied, Simultaneous measurements were obtained of blade surface pressure distributions, near-field acoustics, and far-field acoustics during the vortex-blade encounters, A comparison with computational results from the WOPWOP code shows good correlation with experimental data. C1 NASA,LANGLEY RES CTR,ACOUST DIV,HAMPTON,VA 23665. RP Kitaplioglu, C (reprint author), NASA,AMES RES CTR,ROTORCRAFT AEROMECH BRANCH,MOFFETT FIELD,CA 94035, USA. NR 14 TC 5 Z9 8 U1 0 U2 0 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1997 VL 42 IS 3 BP 272 EP 281 PG 10 WC Engineering, Aerospace SC Engineering GA XM936 UT WOS:A1997XM93600008 ER PT J AU Blanken, CL Ockier, CJ Pausder, HJ Simmons, RC AF Blanken, CL Ockier, CJ Pausder, HJ Simmons, RC TI Rotorcraft pitch-roll decoupling requirements from a roll tracking maneuver SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT American-Helicopter-Society 50th Annual Forum CY MAY 11-13, 1994 CL WASHINGTON, DC SP Amer Helicopter Soc AB A research investigation has been conducted on the effects of pitch-due-to-roll and roll-due-to-pitch cross coupling on helicopter handling qualities while performing a forward flight (60 knots) roll axis tracking tack, Conducted under the US/German Memorandum of Understanding (MOU) for Cooperative Research in Helicopter Aeromechanics, this study involved complementary use of a NASA-Ames ground-based simulation and two in-flight simulations using DLR's variable-stability BO 105. The results show that for a roll tracking task, the current time-domain pitch-roll cross coupling criteria does discriminate against unacceptable coupling from basic control, rate, and combined control-rate coupling, However, this criteria formal, does not discriminate against washed-out coupling which can occur in helicopters with feedback control systems, In addition, the data suggest a tightening in the ADS-33 Level 1-2 boundary, and the four second window specified for obtaining compliance data may not be suited for highly agile helicopters. A newly proposed frequency-domain criteria offers more comprehensive coverage that shows consistency for all types of coupling investigated. An additional benefit is that the required frequency-domain data can be obtained from the bandwidth tests and analysis, thus reducing compliance flight time by eliminating specific pitch-roll coupling tests. C1 DEUTSCH FORSCHUNGSANSTALT LUFT & RAUMFAHRT EV, INST FLUGMECH, BRAUNSCHWEIG, GERMANY. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Blanken, CL (reprint author), USA, AVIAT & TROOP COMMAND, AMES RES CTR, AEROFLIGHTDYNAM DIRECTORATE, MOFFETT FIELD, CA 94035 USA. NR 26 TC 0 Z9 0 U1 0 U2 2 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1997 VL 42 IS 3 BP 282 EP 296 PG 15 WC Engineering, Aerospace SC Engineering GA XM936 UT WOS:A1997XM93600009 ER PT J AU Carpenter, JR Bishop, RH AF Carpenter, JR Bishop, RH TI Flight-data results of estimate fusion for spacecraft rendezvous navigation from shuttle mission STS-69 SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT AAS/AIAA Space Flight Mechanics Conference CY FEB 11-15, 1996 CL AUSTIN, TEXAS SP AAS, AIAA AB A recently developed rendezvous navigation fusion filter that optimally exploits existing distributed filters for rendezvous and GPS navigation ro achieve the relative and inertial state accuracies of both in a global solution is utilized here to process actual flight data. Space Shuttle Mission STS-69 was the first mission that gathered data from both rendezvous and Global Positioning System filters, allowing, for the first time, a test of the fusion algorithm with real flight data. Furthermore, a precise best estimate of the trajectory is available for portions of STS-69, making possible a check on the performance of the fusion filter. In order to successfully carry out this experiment with flight data, two extensions to the scheme were necessary: a fusion edit test based on differences between the filter state vectors, and an underweighting scheme to accommodate the suboptimal perfect target assumption made by the Shuttle rendezvous filter. With these innovations, the flight data was successfully fused from playbacks of downlinked and/or recorded measurement data through ground analysis versions of the Shuttle rendezvous filter and a GPS filter developed for another experiment. The fusion results agree with the best estimate of trajectory at approximately the levels of uncertainty expected from the fusion filter's covariance matrix. C1 NASA, Aerosci & Flight Mech Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Texas, Dept Aerosp Engn & Engn Mech, Austin, TX 78712 USA. RP Carpenter, JR (reprint author), NASA, Aerosci & Flight Mech Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD JUL-SEP PY 1997 VL 45 IS 3 BP 297 EP 319 PG 23 WC Engineering, Aerospace SC Engineering GA ZJ572 UT WOS:000073230200004 ER PT J AU Luthcke, SB Marshall, JA Rowton, SC Rachlin, KE Cox, CM Williamson, RG AF Luthcke, SB Marshall, JA Rowton, SC Rachlin, KE Cox, CM Williamson, RG TI Enhanced radiative force modeling of the tracking and data relay satellites SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT EGS Conference CY MAR, 1997 CL VIENNA, AUSTRIA ID PRECISION ORBIT DETERMINATION; TOPEX/POSEIDON AB Orbit determination (OD) approaches operationally model the Tracking and Data Relay Satellites (TDRS) as homogenous spheres for nonconservative force modeling. To improve definitive orbit determination and prediction accuracies, and to employ TDRSS tracking of user satellites within various geophysical investigations, a detailed TDRS spacecraft model has been developed. The enhanced TDRS model represents the spacecraft as a combination of twenty-four flat plates. The radiative forces acting on each plate are computed and vector summed to produce the overall acceleration oil the spacecraft center of mass. An initial model, based on pre-launch engineering information, has been refined to better fit observed spacecraft accelerations. The Goddard TDRS-5 Model 3 (GT5M3) improves orbit accuracy, yields better fits to the tracking data, significantly reduces residual accelerations, and improves orbit prediction capability. C1 NASA, Hughes STX, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. RP Luthcke, SB (reprint author), NASA, Hughes STX, Goddard Space Flight Ctr, Space Geodesy Branch, Code 926, Greenbelt, MD 20771 USA. RI Luthcke, Scott/D-6283-2012 NR 21 TC 15 Z9 15 U1 0 U2 5 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD JUL-SEP PY 1997 VL 45 IS 3 BP 349 EP 370 PG 22 WC Engineering, Aerospace SC Engineering GA ZJ572 UT WOS:000073230200007 ER PT J AU Eluszkiewicz, J Crisp, D Grainger, RG Lambert, A Roche, AE Kumer, JB Mergenthaler, JL AF Eluszkiewicz, J Crisp, D Grainger, RG Lambert, A Roche, AE Kumer, JB Mergenthaler, JL TI Sensitivity of the residual circulation diagnosed from the UARS data to the uncertainties in the input fields and to the inclusion of aerosols SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MARTIAN ATMOSPHERE; STRATOSPHERIC AEROSOLS; PINATUBO ERUPTION; VENUS MESOSPHERE; TROPOSPHERE; OZONE; EXCHANGE; FLUXES; RATES AB The simultaneous measurements of temperature, aerosol extinction, and concentrations of radiatively active gases by several instruments aboard the Upper Atmosphere Research Satellite permit an assessment of the uncertainties in the diagnosed stratospheric heating rates and in the resulting residual circulation. In this paper, measurements taken by the Cryogenic Limb Array Etalon Spectrometer (CLAES) are used to compute the circulation and to compare it against values obtained previously from the measurements obtained by the Microwave Limb Sounder (MLS). There is a broad agreement between the two sets of calculations and known biases in either CLAES or MLS ozone and temperature measurements are found to be responsible for the areas of disagreement. The inclusion of aerosols has improved the estimates of the residual circulation in the lower stratosphere during the 1992-93 period covered by CLAES. Present estimates of the aerosol heating are significantly different from those found in other studies, probably as a result of differences in the treatment of tropospheric clouds and in the adopted vertical profiles of aerosol extinction. Moreover, a large uncertainty in these estimates is caused by the uncertainties in the assumed refractive indices for sulfuric acid solutions. C1 MIT,CTR METEOROL & PHYS OCEANOG,CAMBRIDGE,MA 02139. CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109. UNIV OXFORD,OXFORD,ENGLAND. LOCKHEED MARTIN PALO ALTO RES LAB,PALO ALTO,CA. RI Grainger, Roy/E-8823-2011 OI Grainger, Roy/0000-0003-0709-1315 NR 41 TC 26 Z9 26 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUL 1 PY 1997 VL 54 IS 13 BP 1739 EP 1757 DI 10.1175/1520-0469(1997)054<1739:SOTRCD>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XH843 UT WOS:A1997XH84300005 ER PT J AU Barsoum, MW ElRaghy, T Ogbuji, LUJT AF Barsoum, MW ElRaghy, T Ogbuji, LUJT TI Oxidation of Ti3SiC2 in air SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID KINETICS; CARBIDE AB Polycrystalline samples of Ti3SiC2 were oxidized in air in the 900 to 1400 degrees C temperature range. The oxidation was parabolic with parabolic rate constants, k(p), that increased from 1 x 10(-9) to 1 x 10(-4) kg(2) m(-4) s(-1) as the temperature increased from 900 to 1400 degrees C, respectively which yielded an activation energy of 370 +/- 20 kJ/mol. The scale that forms was dense. adhesive. resistant to thermal cyclings and layered. The outer layer was pure TiO2 (rutile), and the inner lager consisted of mixture of SiO2 and TiO2. The results are consistent with a model in which growth of the oxide layer occurs by the inward diffusion of oxygen ana the simultaneous outward diffusion of titanium and carbon. The presence of small volume fractions (approximate to 2%) of TiCx in Ti3SiC2 were found to have a deleterious effect on the oxidation kinetics. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Barsoum, MW (reprint author), DREXEL UNIV,DEPT MAT ENGN,PHILADELPHIA,PA 19104, USA. NR 21 TC 235 Z9 243 U1 1 U2 15 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 JUL PY 1997 VL 144 IS 7 BP 2508 EP 2516 DI 10.1149/1.1837846 PG 9 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA XM567 UT WOS:A1997XM56700056 ER PT J AU Man, KF Boumsellek, S AF Man, KF Boumsellek, S TI Instrument design for sub-ppb oxygenated contaminants detection in semiconductor processing SO JOURNAL OF THE INSTITUTE OF ENVIRONMENTAL SCIENCES LA English DT Article DE oxygen detector; moisture detector; contamination control; processing environment; sub-ppb detection; mass spectrometry; resonant electron attachment; ray tracing; reversal ionizer AB This paper describes a technique for measuring trace quantities of oxygen and moisture contaminants present in a semiconductor and/or containerless processing environment. Monatomic negative oxygen ions, O-, formed by electron dissociative attachment through interaction with the molecular oxygen and water, are measured to infer the presence of the contaminants. This technique exploits the fact that the cross section for the reaction is greatly enhanced as the resonant energy. The device built to demonstrate this technique combines a small gridded electron ionizer with a conventional mass spectrometer, The concentrations of oxygen have been measured using the method of standard additions by diluting O-2 in N-2. The lowest detection limit obtained was 1.2 kHz (O- count rate) at a concentration of 10(-10), corresponding to 0.1 ppb. Sensitivity calculations for detecting moisture, and electron and ion trajectory modeling using the SIMION program are presented. The detection of trace quantities of water vapor was attempted. The difficulties with handling water in the experiments are also described. RP Man, KF (reprint author), CALTECH,JET PROP LAB,RELIABIL TECHNOL GRP,4800 OAK GROVE DR,PASADENA,CA 91125, USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU INST ENVIRONMENTAL SCI PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 SN 1052-2883 J9 J INST ENVIRON SCI JI J. Inst. Environ. Sci. PD JUL-AUG PY 1997 VL 40 IS 4 BP 17 EP 21 PG 5 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA XU228 UT WOS:A1997XU22800002 ER PT J AU Worth, DB AF Worth, DB TI A method for implementing force-limited vibration control SO JOURNAL OF THE INSTITUTE OF ENVIRONMENTAL SCIENCES LA English DT Article DE vibration testing; force limiting; digital signal processing; Cassini; force and moment measurements AB NASA/Goddard Space Flight Center (NASA/GSFC) has implemented force-limited vibration control on a controller which can only accept one profile. The method uses a personal computer-based digital signal processing board to convert force and/or moment signals into what appears to be an acceleration signal to the controller. This technique allows test centers with older controllers to use the latest force-limited control techniques for random vibration resting. The paper describes the method, hardware, and test procedures used An example from a test performed at NASA/GSFC is used as a guide. RP Worth, DB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,STRUCT DYNAM TEST ENGN SECT,GREENBELT,MD 20771, USA. NR 5 TC 1 Z9 2 U1 0 U2 1 PU INST ENVIRONMENTAL SCI PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 SN 1052-2883 J9 J INST ENVIRON SCI JI J. Inst. Environ. Sci. PD JUL-AUG PY 1997 VL 40 IS 4 BP 34 EP 41 PG 8 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA XU228 UT WOS:A1997XU22800005 ER PT J AU Smith, DD Fischer, G Boyd, RW Gregory, DA AF Smith, DD Fischer, G Boyd, RW Gregory, DA TI Cancellation of photoinduced absorption in metal nanoparticle composites through a counterintuitive consequence of local field effects SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID OPTICAL NONLINEARITIES; 2-PHOTON ABSORPTION; Z-SCAN; LIMITATION AB By applying the Maxwell Garnett model to gold nanoparticles in water we deduce a Value of fm chi(i)((3)) = 1.1 x 10(-7) esu for the imaginary part of the cubic susceptibility for gold corresponding to a Fermi smearing mechanism. We also demonstrate a sign reversal in the nonlinear absorption for gold particles in 1, 1', 3, 3, 3', 3'-hexamethylindotricarbocyanine iodide. Although the imaginary part of chi((3)) is positive for each component by itself, remarkably the imaginary part of chi((3)) is negative for the colloid as a whole. We show that the nonlinearity of the host must be considered and that the sign reversal in chi((3)) is a result of the fact that at the surface plasmon resonance the local field factor has an imaginary component that arises from a phase shift between the applied field and the local field inside the particle. (C) 1997 Optical Society of America. C1 UNIV ROCHESTER, INST OPT, ROCHESTER, NY 14627 USA. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. ROME LAB, PHOTON MAT BRANCH, HANSCOM AFB, MA 01731 USA. RP Smith, DD (reprint author), NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, ES-76, HUNTSVILLE, AL 35812 USA. NR 18 TC 79 Z9 80 U1 0 U2 8 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 EI 1520-8540 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD JUL PY 1997 VL 14 IS 7 BP 1625 EP 1631 DI 10.1364/JOSAB.14.001625 PG 7 WC Optics SC Optics GA XL999 UT WOS:A1997XL99900012 ER PT J AU Launius, RD AF Launius, RD TI Introduction - The aerospace industry in the West SO JOURNAL OF THE WEST LA English DT Editorial Material RP Launius, RD (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU J WEST INC PI MANHATTAN PA P O BOX 1009 1531 YUMA, MANHATTAN, KS 66502 SN 0022-5169 J9 J WEST JI J. West PD JUL PY 1997 VL 36 IS 3 BP 6 EP 7 PG 2 WC History SC History GA XP095 UT WOS:A1997XP09500002 ER PT J AU Launius, RD AF Launius, RD TI End of a 40-year war: Demobilization in the West coast aerospace industry after the Cold-War SO JOURNAL OF THE WEST LA English DT Article RP Launius, RD (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 23 TC 2 Z9 2 U1 0 U2 0 PU J WEST INC PI MANHATTAN PA P O BOX 1009 1531 YUMA, MANHATTAN, KS 66502 SN 0022-5169 J9 J WEST JI J. West PD JUL PY 1997 VL 36 IS 3 BP 85 EP 96 PG 12 WC History SC History GA XP095 UT WOS:A1997XP09500012 ER PT J AU Moss, JN Price, JM AF Moss, JN Price, JM TI Survey of blunt body flows including wakes at hypersonic low-density conditions SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 31st Thermophysics Conference CY JUN 17-20, 1996 CL NEW ORLEANS, LA SP Amer Inst Aeronaut & Astronaut ID SIMULATION MONTE-CARLO RP Moss, JN (reprint author), NASA,LANGLEY RES CTR,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681, USA. NR 44 TC 24 Z9 24 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1997 VL 11 IS 3 BP 321 EP 329 DI 10.2514/2.6252 PG 9 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA XL327 UT WOS:A1997XL32700001 ER PT J AU Rob, MA Mack, LH Scott, CD AF Rob, MA Mack, LH Scott, CD TI Characterization of plenum spectra in an arcjet wind tunnel SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 29th Thermophysics Conference CY JUN 19-22, 1995 CL SAN DIEGO, CA SP Amer Inst Aeronaut & Astronaut ID DIAGNOSTICS AB An optical fiber is used to collect radiation from the plenum of an arcjet wind tunnel. Studying the spectra, the electronic excitation temperatures are determined from the Boltzmann plots of atomic oxygen and nitrogen emission lines. In the case of atomic oxygen, the temperature is found to be about 15,000 +/- 3400 K, and that of nitrogen is found to be 7600 +/- 1500 g. Determination of molecular vibrational-rotational temperature is made by comparing experimental and theoretical spectra of the N-2+ molecular radiation. The temperature is estimated to be 9700 +/- 1200 K, using an integrals ratio method. C1 UNIV HOUSTON CLEAR LAKE, SCH NAT & APPL SCI, HOUSTON, TX 77058 USA. GB TECH INC, HOUSTON, TX 77058 USA. NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. NR 16 TC 4 Z9 4 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1997 VL 11 IS 3 BP 339 EP 345 DI 10.2514/2.6271 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA XL327 UT WOS:A1997XL32700003 ER PT J AU Chen, PT Hedgeland, RJ AF Chen, PT Hedgeland, RJ TI Contamination effects on the geostationary operational environmental satellite instrument thermal control system SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 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 AB The instrument thermal control system of the Geostationary Operational Environmental Satellite may have been affected by specific contamination problems that arose because of the unique conditions and requirements of the spacecraft mission. This paper addresses some specific contamination effects from the coatings used in the instrument cavities, Contamination control actions that were implemented during ground processing to ensure limited impact on the on-orbit temperature control are described, The selection of thermal coatings is an integral part of the overall spacecraft design. Molecular contamination accretion on thermal coatings may alter the design properties of the surface coatings, In an effort to quantify the molecular contamination effects from material outgassing, an assessment was conducted to address the concerns inside the instrument cavities. The study results prompted an extensive prelaunch vacuum bakeout effort and an on-orbit solar radiation avoidance exercise, In addition, the thermal performance of the instrument radiant coolers could have been detrimentally affected by scattered solar radiation from particulate contamination, To mitigate the impact of the particulate contamination the radiant cooler surfaces were cleaned to an established criteria prior to launch. RP Chen, PT (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CONTAMINAT ENGN GRP,THERMAL ENGN BRANCH,MAIL CODE 724,GREENBELT,MD 20771, USA. NR 7 TC 0 Z9 0 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1997 VL 11 IS 3 BP 467 EP 471 DI 10.2514/2.6264 PG 5 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA XL327 UT WOS:A1997XL32700020 ER PT J AU Rashidnia, N AF Rashidnia, N TI Bubble dynamics on a heated surface SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP Amer Inst Aeronaut & Astronaut ID TEMPERATURE-GRADIENT; MIGRATION; GRAVITY RP Rashidnia, N (reprint author), NASA,LEWIS RES CTR,NYMA INC,CLEVELAND,OH 44135, USA. NR 13 TC 6 Z9 6 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1997 VL 11 IS 3 BP 477 EP 480 DI 10.2514/2.6266 PG 4 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA XL327 UT WOS:A1997XL32700022 ER PT J AU Zaretsky, EV Poplawski, JV AF Zaretsky, EV Poplawski, JV TI Prediction of ball fatigue life in a ball/V-ring test rig - Discussion SO JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME LA English DT Editorial Material ID ENDURANCE; BEARINGS C1 JV POPLAWSKI & ASSOCIATES,BETHLEHEM,PA 18017. RP Zaretsky, EV (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 17 TC 0 Z9 0 U1 1 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4787 J9 J TRIBOL-T ASME JI J. Tribol.-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 370 EP 374 DI 10.1115/1.2833495 PG 5 WC Engineering, Mechanical SC Engineering GA XM962 UT WOS:A1997XM96200002 ER PT J AU Hendricks, RC AF Hendricks, RC TI Eccentricity effects on the rotordynamic coefficients of plain annular seals: Theory versus experiment - Discussion SO JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME LA English DT Editorial Material RP Hendricks, RC (reprint author), NASA,LEWIS RES CTR,MS 301-5,CLEVELAND,OH 44135, USA. NR 2 TC 0 Z9 0 U1 1 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4787 J9 J TRIBOL-T ASME JI J. Tribol.-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 447 EP 448 DI 10.1115/1.2833516 PG 2 WC Engineering, Mechanical SC Engineering GA XM962 UT WOS:A1997XM96200016 ER PT J AU Kingsbury, E Pepper, SV Ebihara, B AF Kingsbury, E Pepper, SV Ebihara, B TI Lubrication of slow rolling contacts - The NASA Ball on Plate Tribometer SO JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME 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 ID BEARING AB The NASA Ball on Plate Tribometer was built for the investigation of boundary lubricated rolling. Its contact conditions are easily calculated and cart be adjusted to match a range of real bearing applications for stress, surface velocity, pivot, and contact severity. The rig operates under high vacuum at room temperature. Lubricant charge and specimen preparation are well-controlled and well-characterized. Mass spectroscopy instrumentation allows art; indication of lubricant degradation during rolling. Other tribological quantities immediately available are contact resistance, friction coefficient, transverse creep, and orbit velocity deficit. Simple specimens allow post-test surface analysis such as FTIR, XPS, microscopy, and profilometry. Here we describe the Tribometer and discuss representative results obtained with liquid, solid, and no lubricant. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Kingsbury, E (reprint author), INTERESTING ROLLING CONTACT,WALPOLE,MA 02081, USA. NR 6 TC 0 Z9 1 U1 1 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4787 J9 J TRIBOL-T ASME JI J. Tribol.-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 525 EP 530 DI 10.1115/1.2833532 PG 6 WC Engineering, Mechanical SC Engineering GA XM962 UT WOS:A1997XM96200030 ER PT J AU Puterbaugh, SL Copenhaver, WW Hah, C Wennerstrom, AJ AF Puterbaugh, SL Copenhaver, WW Hah, C Wennerstrom, AJ TI A three-dimensional shock loss model applied to an aft-swept, transonic compressor rotor SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID HIGH-THROUGHFLOW; FLOW PHENOMENA; FAN ROTOR; STAGE AB An analysis of the effectiveness of a three-dimensional shock loss model used in transonic compressor rotor design is presented The model was used during the design of an aft-swept, transonic compressor rotor. The demonstrated performance of the swept rotor, in combination with numerical results, is used to determine the strengths and weaknesses of the model. The numerical results were obtained from a fully three-dimensional Navier-Stokes solver. The shock loss model was developed to account for the benefit gained with three-dimensional shock sweep. Comparisons with the experimental and numerical results demonstrated that shock loss reductions predicted by the model due to the swept shock induced by the swept leading edge of the rotor were exceeded. However, near the tip the loss model underpredicts the loss because the shock geometry assumed by the model remains swept in this region while the numerical results show a more normal shock orientation The design methods and the demonstrated performance of the swept rotor are also presented, Comparisons are made between the design intent and measured performance parameters, The aft-swept rotor was designed using an inviscid axisymmetric streamline curvature design system utilizing arbitrary airfoil blading geometry. The design goal specific flow rate was 214.7 kg/s/m(2) (43.98 lbm/sec/ft(2)), the design pressure ratio goal was 2.042, and the predicted design point efficiency was 94.0. The rotor rip speed was 457.2 m/s (1500 ft/sec). The design pow rate was achieved while the pressure ratio fell short by 0.07. Efficiency was 3 points below prediction, though at a very high 91 percent. Ar this operating condition the stall margin was 11 per-cent. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Puterbaugh, SL (reprint author), USAF,WRIGHT LAB,WRIGHT PATTERSON AFB,OH 45432, USA. NR 16 TC 7 Z9 9 U1 0 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 452 EP 459 PG 8 WC Engineering, Mechanical SC Engineering GA XQ503 UT WOS:A1997XQ50300007 ER PT J AU Bright, MM Qammar, HK Weigl, HJ Paduano, JD AF Bright, MM Qammar, HK Weigl, HJ Paduano, JD TI Stall precursor identification in high-speed compressor stages using chaotic time series analysis methods SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID DIMENSIONS; SYSTEMS AB This paper presents a new technique for precursor identification in high-speed compressors. The technique is a pseudo-correlation integral method referred to as the correlation method. To provide a basis for comparison, the traveling wave energy technique, which has been used extensively to study prestall data, is also briefly presented and applied The correlation method has a potential advantage over the traveling wave energy method because it uses a single sensor for detection. It also requires no predisposition about the expected behavior of the data to detect ''changes'' in the behavior of the compressor. Both methods are used in this study to identify stall precursive events in the pressure fluctuations measured from circumferential pressure transducers located at the front face of the compressor rig. The correlation method successfully identified stall formation or changes in the compressor dynamics from data captured from four different configurations of a NASA Lewis single-stage high-speed compressor while it was transitioned from stable operation into stall. This paper includes an exposition on the use of nonlinear methods to identify stall precursors, a description of the methodologies used for the study, information on the NASA high-speed compressor rig and experimental data acquisition, and results from the four compressor configurations. The experimental results indicate that the correlation method provides ample warning of the onset of rotating stall at high speed, in some tests on the order of 2000 rotor revolutions. Complementary features of the correlation method and the traveling wave energy method are discussed, and suggestions for future developments are made. C1 UNIV AKRON,DEPT CHEM ENGN,AKRON,OH 44325. MIT,GAS TURBINE LAB,CAMBRIDGE,MA 02139. RP Bright, MM (reprint author), NASA,LEWIS RES CTR,ADV CONTROLS & DYNAM BRANCH,CLEVELAND,OH 44135, USA. NR 21 TC 21 Z9 24 U1 1 U2 6 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD JUL PY 1997 VL 119 IS 3 BP 491 EP 499 PG 9 WC Engineering, Mechanical SC Engineering GA XQ503 UT WOS:A1997XQ50300011 ER PT J AU Cho, CSK Fralick, GC Bhatt, HD AF Cho, CSK Fralick, GC Bhatt, HD TI An experimental study of a radially arranged thin-film heat-flux gauge SO MEASUREMENT SCIENCE AND TECHNOLOGY LA English DT Article AB A new thin-film heat-flux gauge was designed and fabricated on three different substrate materials. Forty pairs of Pt-Pt/10% Rh thermocouple junctions were deposited in a circular pattern on the same plane of the substrate. Over the thermocouples, 5 and 10 mu m thick thermal resistance layers were deposited to create a temperature gradient across those layers. Calibration and testing of these gauges were carried out in an are-lamp calibration facility. The heat flux calculated from the gauge output is in good agreement with the value obtained from the pre-calibrated standard sensor. A CO2 laser was also used to test the steady-state and dynamic responses of the heat-flux gauge. During the steady-state test, the time constant for the heating period was 30 s. The frequency response of the heat-flux gauge was measured in the frequency domain using a CO2 laser and a chopper. The responses from an infrared detector and the heat-flux gauge were measured simultaneously and compared. It was found that the thin-film heat-flux gauge has a dynamic frequency response of 3 kHz. C1 NASA, LEWIS RES CTR, RES SENSORS TECHNOL BRANCH, CLEVELAND, OH 44135 USA. RP WESTERN MICHIGAN UNIV, KALAMAZOO, MI 49008 USA. NR 15 TC 5 Z9 5 U1 1 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0957-0233 EI 1361-6501 J9 MEAS SCI TECHNOL JI Meas. Sci. Technol. PD JUL PY 1997 VL 8 IS 7 BP 721 EP 727 DI 10.1088/0957-0233/8/7/005 PG 7 WC Engineering, Multidisciplinary; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA XL971 UT WOS:A1997XL97100005 ER PT J AU Mital, SK Murthy, PLN Goldberg, RK AF Mital, SK Murthy, PLN Goldberg, RK TI Micromechanics for particulate-reinforced composites SO MECHANICS OF COMPOSITE MATERIALS AND STRUCTURES LA English DT Article ID BOUNDS AB A set of micromechanics equations for the analysis of particulate reinforced composites is developed using the mechanics of materials approach. Simplified equations are used to compute homogenized or equivalent thermal and mechanical properties of particulate-reinforced composites in terms of the properties of the constituent materials. The microstress equations ore also presented here to decompose the applied stresses on the overall composite to the microstresses in the constituent materials. The properties of a ''generic'' particulate composite as well as those of a particle-reinforced metal matrix composite are predicted and compared with other theories as well as some experimental data The micromechanics predictions are in excellent agreement with the measured values. C1 NASA,LEWIS RES CTR,STRUCT MECH BRANCH,CLEVELAND,OH 44135. UNIV TOLEDO,TOLEDO,OH 43606. NR 8 TC 3 Z9 3 U1 1 U2 2 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 1075-9417 J9 MECH COMPOS MATER ST JI Mech. Compos. Mater. Struct. PD JUL-SEP PY 1997 VL 4 IS 3 BP 251 EP 266 DI 10.1080/10759419708945883 PG 16 WC Materials Science, Multidisciplinary; Materials Science, Characterization & Testing; Materials Science, Composites SC Materials Science GA YB224 UT WOS:A1997YB22400004 ER PT J AU Lee, SMC Bennett, BS Hargens, AR Watenpaugh, DE Ballard, RE Murthy, G Ford, SR Fortney, SM AF Lee, SMC Bennett, BS Hargens, AR Watenpaugh, DE Ballard, RE Murthy, G Ford, SR Fortney, SM TI Upright exercise or supine lower body negative pressure exercise maintains exercise responses after bed rest SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article DE exercise testing; exercise training; lower body negative pressure exercise; space flight ID MIDDLE-AGED MEN; CAPACITY; WEIGHTLESSNESS; BEDREST; VOLUMES AB Adaptation to bed rest or space flight is accompanied by an impaired ability to exercise in an upright position. We hypothesized that a daily, 30-min bout of intense, interval exercise in upright posture or supine against lower body negative pressure (LBNP) would maintain upright exercise heart rate and respiratory responses after bed rest. Twenty-four men (31 +/- 3 yr) underwent 5 d of 6 degrees head-down tilt: eight performed no exercise (CON), eight performed upright treadmill exercise (UPex), and eight performed supine treadmill exercise against LBNP at -51.3 +/- 0.4 mm Hg (LBNPex). Submaximal treadmill exercise responses (56, 74, and 85% of (V) over dot O-2peak) were measured pre- and post-bed rest. In CON, submaximal heart rate, respiratory exchange ratio, and ventilation were significantly greater (P less than or equal to 0.05) after bed rest. In UPex and LBNPex, submaximal exercise responses were similar pre- and post-bed rest. Our results indicate that a daily 30-min bout of intense, interval upright exercise training or supine exercise training against LBNP is sufficient to maintain upright exercise responses after 5 d of bed rest. These results may have important implications for the development of exercise countermeasures during space flight. C1 NASA,LYNDON B JOHNSON SPACE CTR,EXERCISE PHYSIOL LAB,HOUSTON,TX 77058. KRUG LIFE SCI INC,HOUSTON,TX. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV CALIF SAN DIEGO,LA JOLLA,CA 92093. UNIV TEXAS,MED BRANCH,GALVESTON,TX 77550. FU NCRR NIH HHS [M01 RR00073] NR 35 TC 41 Z9 42 U1 0 U2 2 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD JUL PY 1997 VL 29 IS 7 BP 892 EP 900 DI 10.1097/00005768-199707000-00008 PG 9 WC Sport Sciences SC Sport Sciences GA XL718 UT WOS:A1997XL71800007 PM 9243488 ER PT J AU Becker, L Bunch, TE AF Becker, L Bunch, TE TI Fullerenes, fulleranes and polycyclic aromatic hydrocarbons in the Allende meteorite SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID INTERPLANETARY DUST PARTICLES; ION MOLECULE REACTIONS; INTERSTELLAR DUST; MASS-SPECTROMETRY; BUCKMINSTERFULLERENE C-60; EMISSION FEATURES; GAS-PHASE; CARBON; C60; HYDROGENATION AB In this paper, we confirm our earlier observations of fullerenes (C-60 and C-70) in the Allende meteorite (Becker et al., 1994a, 1995). Fullerene C-60 was also detected in two separate C-rich (similar to -0.5-1.0%) dark inclusions (Heymann et al., 1987) that were hand picked from the Allende sample. The amounts of C-60 detected were similar to -5 and similar to -10 ppb, respectively, which is considerably less than what was detected in the Allende 15/21 sample (similar to 100 ppb; Becker et al., 1994a, 1995). This suggests that fullerenes are heterogeneously distributed in the meteorite. In addition, we present evidence for fullerenes, (C60Hx), detected in separate samples by laser desorption (reflectron) time-of-flight (TOF) mass spectrometry(LDMS). The LDMS spectra for the Allende extracts were remarkably similar to the spectra generated for the synthetic fullerene mixtures. Several fullerene products were synthesized using a Rh catalyst (Becker et al., 1993a) and separated using highperformance liquid chromatography (HPLC). Polycyclic aromatic hydrocarbons (PAHs) were also observed (ppm levels) that included benzofluoranthene and corannulene, a cup-shaped molecule that has been proposed as a precursor molecule to the formation of fullerenes in the gas phase (Pope et al., 1993). C1 NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. RP Becker, L (reprint author), UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA. NR 74 TC 35 Z9 36 U1 3 U2 9 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 BP 479 EP 487 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XN352 UT WOS:A1997XN35200005 PM 11540421 ER PT J AU Sato, K Miyamoto, M Zolensky, ME AF Sato, K Miyamoto, M Zolensky, ME TI Absorption bands near three micrometers in diffuse reflectance spectra of carbonaceous chondrites: Comparison with asteroids SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID OUTER-BELT; METEORITES; MINERALS AB We measured infrared diffuse reflectance spectra of several carbonaceous chondrites in order to obtain additional information on the surface materials of their presumed parent bodies, C-type asteroids. The presence and intensity of absorption bands near 3 mu m in the reflectance spectra are due to the presence and abundance of hydrates and/or hydroxyl ions. The absorption features of the 3 mu m hydration bands of carbonaceous chondrites were compared with those of asteroids 1 Ceres and 2 Pallas. They are commonly classified into separate subtypes, G- and B-type. The spectral shapes of Pallas and Renazzo (CR2 chondrite) around the 3 mu m absorption band are an excellent match. This result may suggest that the amount of hydrous minerals in the surface material of Pallas is smaller than that in the CM2 or CI chondrites, and the hydrous minerals on the surface of Pallas may be similar to those found in Renazzo. The spectral features around the 3 mu m band of Ceres are different from those of carbonaceous chondrites studied in this paper. C1 NASA,LYNDON B JOHNSON SPACE CTR,SN2,HOUSTON,TX 77058. RP Sato, K (reprint author), UNIV TOKYO,GRAD SCH SCI,INST MINERAL,HONGO,TOKYO 113,JAPAN. RI Sato, Kimiyasu/K-9284-2016 NR 32 TC 24 Z9 24 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 BP 503 EP 507 PG 5 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XN352 UT WOS:A1997XN35200008 ER PT J AU Corrigan, CM Zolensky, ME Dahl, J Long, M Weir, J Sapp, C Burkett, PJ AF Corrigan, CM Zolensky, ME Dahl, J Long, M Weir, J Sapp, C Burkett, PJ TI The porosity and permeability of chondritic meteorites and interplanetary dust particles SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID MICROMETEORITES; COMPONENTS AB We have investigated the porosity of a large number of chondritic interplanetary dust particles (IDPs) and meteorites by three techniques: standard liquid/gas flow techniques, a new, noninvasive ultrasonic technique, and image processing of backscattered images. The latter technique is obviously best-suited to sub-kilogram sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquid/gas flow techniques, and a new, nondestructive pressure release technique. We find that chondritic IDPs have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. Type 1-3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1-3 chondrites have the same approximate range as exhibited by the matrix, which indicates that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as the matrix. These results reveal that the porosities of primitive materials at scales ranging from nanogram to kilogram are similar, which implies that similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, chondrite type or porosity. C1 LUNAR & PLANETARY INST,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. BEMIDJI STATE UNIV,BEMIDJI,MN 56601. CORE LABS INC,HOUSTON,TX 77040. LOCKHEED MARTIN SCI & ENGN CO,HOUSTON,TX 77058. USN,RES LAB,STENNIS SPACE CTR,MS 39529. NR 21 TC 65 Z9 65 U1 4 U2 10 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 BP 509 EP 515 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XN352 UT WOS:A1997XN35200009 ER PT J AU Rao, MN Garrison, DH Palma, RL Bogard, DD AF Rao, MN Garrison, DH Palma, RL Bogard, DD TI Energetic proton irradiation history of the howardite parent body regolith and implications for ancient solar activity SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID RAY PRODUCTION-RATES; GAS-RICH METEORITES; NOBLE-GASES; COSMOGENIC NUCLIDES; EXPOSURE HISTORY; CROSS-SECTIONS; EARLY SUN; NEON; SYSTEM; FLUX AB Previous studies have shown that the Kapoeta howardite, as well as several other meteorites, contains excess concentrations of cosmogenic Ne in the darkened, solar-irradiated phase compared to the light, nonirradiated phase. The two explanations offered for the nuclear production of these Ne excesses in the parent body regolith are either from galactic cosmic-ray proton (GCR) irradiation or from a greatly enhanced flux of energetic solar ''cosmic-ray'' protons (SCR), as compared to the recent solar flux. Combining new isotopic data we obtained on acid-etched, separated feldspar from Kapoeta light and dark phases with literature data, we show that the cosmogenic Ne-21/Ne-22 ratio of light phase feldspar (0.80) is consistent with only GCR irradiation in space for similar to 3 Ma. However, the Ne-21/Ne-22 ratio (0.68) derived for irradiation of dark phase feldspar in the Kapoeta regolith indicates that cosmogenic Ne was produced in roughly equal proportions from galactic and solar protons. Considering a simple model of an immature Kapoeta parent body regolith, the duration of this early galactic exposure was only similar to 3-6 Ma, which would be an upper limit to the solar exposure time of individual grains. Concentrations of cosmogenic Ne-21 in pyroxene separates and of cosmogenic Xe-126 in both feldspar and pyroxene are consistent with this interpretation. The near-surface irradiation time of individual grains in the Kapoeta regolith probably varied considerably due to regolith mixing to an average GCR irradiation depth of similar to 10 cm. Because of the very different depth scales for production of solar similar to Fe tracks, SCR Ne, and GCR Ne, the actual regolith exposure times for average grains probably differed correspondingly. However, both the SCR Ne-21 and solar track ages appear to be longer because of enhanced production by early solar activity. The SCR/GCR production ratio of Ne-21 inferred from the Kapoeta data is larger by a at least a factor of 10 and possibly as much as a factor of similar to 50 compared to recent solar particle fluxes. Thus, this study indicates that our early Sun was much more active and emitted a substantially higher flux of energetic (> 10 MeV/nucleon) protons. C1 NASA,LYNDON B JOHNSON SPACE CTR,SN4,HOUSTON,TX 77058. SAM HOUSTON STATE UNIV,DEPT PHYS,HUNTSVILLE,TX 77341. LOCKHEED MARTIN,HOUSTON,TX 77058. NR 59 TC 14 Z9 14 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 BP 531 EP 543 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XN352 UT WOS:A1997XN35200011 ER PT J AU Asphaug, E AF Asphaug, E TI Impact origin of the Vesta family. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA,AMES RES CTR,SETI INST,MOFFETT FIELD,CA 94035. NR 8 TC 6 Z9 6 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A9 EP A9 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400012 ER PT J AU Becker, L McDonald, GD Glavin, DP Bada, JL Bunch, TE AF Becker, L McDonald, GD Glavin, DP Bada, JL Bunch, TE TI Sublimation: A mechanism for the enrichment of organics in Antarctic ice. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID METEORITES; HYDROCARBONS C1 UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA 92093. CORNELL UNIV,PLANETARY STUDIES LAB,ITHACA,NY 14853. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RI Glavin, Daniel/D-6194-2012 OI Glavin, Daniel/0000-0001-7779-7765 NR 14 TC 2 Z9 2 U1 0 U2 3 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A10 EP A11 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400015 ER PT J AU Berthoud, L Cintala, MJ Horz, F AF Berthoud, L Cintala, MJ Horz, F TI Ejecta velocities from impact craters in sand. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 3 TC 0 Z9 0 U1 1 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A13 EP A13 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400019 ER PT J AU Bishop, JL Pieters, CM Hiroi, T AF Bishop, JL Pieters, CM Hiroi, T TI The source of organic spectral features in Allan Hills 84001: Lab contamination, terrestrial, or extraterrestrial? SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. BROWN UNIV, DEPT GEOL SCI, PROVIDENCE, RI 02912 USA. NR 5 TC 4 Z9 4 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A14 EP A15 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400022 ER PT J AU Borg, J Bibring, JP Bunch, T Flynn, G Nishioka, K Westphal, A AF Borg, J Bibring, JP Bunch, T Flynn, G Nishioka, K Westphal, A TI Analyses of extraterrestrial particles collected outside the MIR station. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 INST ASTROPHYS SPATIALE,ORSAY,FRANCE. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. SUNY COLL PLATTSBURGH,DEPT PHYS,PLATTSBURGH,NY 12901. SETI INST,MOFFETT FIELD,CA. UNIV CALIF BERKELEY,BERKELEY,CA 94720. NR 4 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A17 EP A18 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400027 ER PT J AU Borg, L Norman, M Nyquist, L Snyder, G Taylor, L Lindstrom, M Wiesmann, H AF Borg, L Norman, M Nyquist, L Snyder, G Taylor, L Lindstrom, M Wiesmann, H TI A relatively young Samarium-Neodymium age of 4.36 Ga for ferroan anorthosite 62236. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. MACQUARIE UNIV,SCH EARTH SCI,N RYDE,NSW,AUSTRALIA. UNIV TENNESSEE,KNOXVILLE,TN 37996. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. LOCKHEED MARTIN,HOUSTON,TX 77058. NR 9 TC 2 Z9 2 U1 0 U2 2 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A18 EP A18 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400028 ER PT J AU Brownlee, DE Tsou, P Burnett, D Clark, B Hanner, MS Horz, F Kissel, J McDonnell, JAM Newburn, RL Sandford, S Sekanina, Z Tuzzolino, AJ Zolensky, M AF Brownlee, DE Tsou, P Burnett, D Clark, B Hanner, MS Horz, F Kissel, J McDonnell, JAM Newburn, RL Sandford, S Sekanina, Z Tuzzolino, AJ Zolensky, M TI The Stardust mission: Returning comet samples to earth. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 UNIV WASHINGTON, DEPT ASTRON, SEATTLE, WA 98195 USA. JET PROP LAB, PASADENA, CA 91011 USA. CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA 91124 USA. LOCKHEED MARTIN ASTRONAUT, DENVER, CO USA. NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. MAX PLANCK INST KERNPHYS, D-69117 HEIDELBERG, GERMANY. UNIV KENT, UNIT SPACE SCI & ASTROPHYS, CANTERBURY CT2 7NR, KENT, ENGLAND. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV CHICAGO, LAB ASTROPHYS & SPACE RES, CHICAGO, IL 60637 USA. NR 0 TC 14 Z9 14 U1 0 U2 1 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A22 EP A22 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400035 ER PT J AU Clayton, RN Mayeda, TK Hiroi, T Zolensky, M Lipschutz, ME AF Clayton, RN Mayeda, TK Hiroi, T Zolensky, M Lipschutz, ME TI Oxygen isotopes in laboratory-heated CI and CM chondrites. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. BROWN UNIV,DEPT GEOL SCI,PROVIDENCE,RI 02912. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. PURDUE UNIV,DEPT CHEM,W LAFAYETTE,IN 47906. NR 10 TC 7 Z9 7 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A30 EP A30 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400051 ER PT J AU Cooper, GW Thiemens, MH Jackson, T Chang, S AF Cooper, GW Thiemens, MH Jackson, T Chang, S TI Oxygen isotopic composition of organic and inorganic compounds of the Murchison meteorite. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ACIDS C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. SETI INST, MT VIEW, CA 94043 USA. UNIV CALIF SAN DIEGO, DEPT CHEM, LA JOLLA, CA 92093 USA. NR 5 TC 0 Z9 0 U1 1 U2 1 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A32 EP A32 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400055 ER PT J AU Fomenkova, M Chang, S AF Fomenkova, M Chang, S TI Carbonaceous components of organic/inorganic assemblages in comet Halley dust. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. NASA,AMES RES CTR,MOFFETT FIELD,CA 92035. NR 4 TC 1 Z9 1 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A44 EP A44 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400077 ER PT J AU Garrison, DH Bogard, DD AF Garrison, DH Bogard, DD TI Argon-39/argon-40 dating of Martian meteorites. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 LOCKHEED MARTIN,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058. NR 6 TC 5 Z9 5 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A45 EP A45 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400080 ER PT J AU Gibson, EK Romanek, CS McKay, DS ThomasKeprta, K Allen, CC Wentworth, S AF Gibson, EK Romanek, CS McKay, DS ThomasKeprta, K Allen, CC Wentworth, S TI Nature of carbon phases in Allan Hills 84001. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID MARTIAN METEORITE ALH84001; MARS C1 NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058. UNIV GEORGIA,SAVANNAH RIVER ECOL LAB,AIKEN,SC 29802. NASA,LYNDON B JOHNSON SPACE CTR,LOCKHEED MARTIN,HOUSTON,TX 77058. NR 10 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A47 EP A47 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400084 ER PT J AU Hale, VPS McSween, HY McKay, G AF Hale, VPS McSween, HY McKay, G TI Estimates of cumulus pyroxene and intercumulus liquid compositions in Shergotty. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 UNIV TENNESSEE,DEPT GEOL SCI,KNOXVILLE,TN 37996. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 6 TC 1 Z9 1 U1 0 U2 2 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A54 EP A54 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400098 ER PT J AU Hallenbeck, SL Nuth, JA AF Hallenbeck, SL Nuth, JA TI Spectral evolution of amorphous magnesium silicates and comparison to olivine-rich comets. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 0 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A54 EP A55 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400099 ER PT J AU Johnson, TV AF Johnson, TV TI Galileo preliminary results of satellite observations. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 0 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A67 EP A67 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400125 ER PT J AU Krot, AN Zolensky, ME Choi, BG Petaev, MI Keil, K Scott, ERD Wasson, JT AF Krot, AN Zolensky, ME Choi, BG Petaev, MI Keil, K Scott, ERD Wasson, JT TI Metasomatism and metamorphism in the CV3 asteroid: Formation of pure fayalite, diopside-hedenbergite pyroxenes, andradite, and magnetite in Kaba and Mokoia. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID CARBONACEOUS CHONDRITE; AQUEOUS ALTERATION C1 UNIV HAWAII,SCH OCEAN & EARTH SCI & TECHNOL,HAWAII INST GEOPHYS & PLANETOL,HONOLULU,HI 96822. NASA,LYNDON B JOHNSON SPACE CTR,EARTH SCI & SOLAR SYST EXPLORAT DIV,HOUSTON,TX 77058. UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. NR 7 TC 4 Z9 4 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A74 EP A75 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400140 ER PT J AU Lofgren, GE Hanson, B AF Lofgren, GE Hanson, B TI Formation of compound chondrules by low-velocity collisions. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID CHONDRITES; ORIGINS C1 NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. NR 11 TC 2 Z9 2 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A81 EP A82 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400153 ER PT J AU McCord, TB Hansen, G Hibbitts, C Carlson, RW Smythe, W Matson, DL Johnson, TV Clark, RM Granahan, J Fanale, F Segura, M AF McCord, TB Hansen, G Hibbitts, C Carlson, RW Smythe, W Matson, DL Johnson, TV Clark, RM Granahan, J Fanale, F Segura, M TI Analysis of near-infrared mapping spectrometer reflectance spectra for the icy Galilean satellites. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 UNIV HAWAII,HAWAII INST GEOPHYS & PLANETOL,NIMS TEAM,HONOLULU,HI 96822. SETS TECHNOL INC,MILILANI,HI. US GEOL SURVEY,DENVER,CO 80225. CALTECH,JET PROP LAB,PASADENA,CA 91109. RI Hibbitts, Charles/B-7787-2016 OI Hibbitts, Charles/0000-0001-9089-4391 NR 0 TC 0 Z9 0 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A86 EP A87 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400163 ER PT J AU McKay, GA Mikouchi, T Lofgren, GE AF McKay, GA Mikouchi, T Lofgren, GE TI Carbonates and feldspathic glass in Allan Hills 84001: Additional complications. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID MARTIAN METEORITE ALH84001 C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. UNIV TOKYO,GRAD SCH SCI,INST MINERAL,BUNKYO KU,TOKYO 113,JAPAN. NR 7 TC 11 Z9 11 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A87 EP A88 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400165 ER PT J AU McSween, HY Golombek, MP Smith, PH Rieder, R Wanke, H Economou, TE AF McSween, HY Golombek, MP Smith, PH Rieder, R Wanke, H Economou, TE TI Mars pathfinder mission: First results. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID SNC METEORITES C1 UNIV TENNESSEE,DEPT GEOL SCI,MARS PATHFINDER SCI TEAM,KNOXVILLE,TN 37996. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. MAX PLANCK INST CHEM,MAINZ,GERMANY. UNIV CHICAGO,LAB ASTROPHYS & SPACE RES,CHICAGO,IL 60637. NR 7 TC 0 Z9 0 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A89 EP A89 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400167 ER PT J AU Messenger, S Keller, LP ThomasKeprta, KL AF Messenger, S Keller, LP ThomasKeprta, KL TI Complementary transmission electron microscopy and hydrogen isotopic measurements of interplanetary dust. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID PARTICLES C1 WASHINGTON UNIV,DEPT PHYS,ST LOUIS,MO 63130. WASHINGTON UNIV,MCDONNELL CTR SPACE SCI,ST LOUIS,MO 63130. MVA INC,NORCROSS,GA 30093. NASA,LYNDON B JOHNSON SPACE CTR,LOCKHEED MARTIN,HOUSTON,TX 77058. NR 10 TC 3 Z9 3 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A91 EP A91 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400172 ER PT J AU Mikouchi, T Miyamoto, M McKay, GA AF Mikouchi, T Miyamoto, M McKay, GA TI Crystallization histories of basaltic Shergottites as inferred from chemical zoning of pyroxene and maskelynite. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID METEORITES C1 UNIV TOKYO,GRAD SCH SCI,INST MINERAL,BUNKYO KU,TOKYO 113,JAPAN. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 4 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A92 EP A93 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400175 ER PT J AU Nakamura, T Zolensky, ME Horz, F Takaoka, N Nagao, K AF Nakamura, T Zolensky, ME Horz, F Takaoka, N Nagao, K TI Noble gas loss from phase Q by impacts: An experimental investigation. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ALLENDE C1 KYUSHU UNIV 33,FAC SCI,DEPT EARTH & PLANETARY SCI,FUKUOKA 81281,JAPAN. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. OKAYAMA UNIV,INST STUDY EARTHS INTERIOR,MISASA,TOTTORI 68201,JAPAN. NR 7 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A96 EP A96 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400183 ER PT J AU Nyquist, LE Wiesmann, H Reese, Y Shih, CY Borg, LE AF Nyquist, LE Wiesmann, H Reese, Y Shih, CY Borg, LE TI Samarium-neodymium age and manganese-chromite systematics of eucrite Elephant Moraine 90020. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ANGRA-DOS-REIS; METEORITES; EVOLUTION C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. LOCKHEED ENGN & SCI CO,HOUSTON,TX 77058. NR 13 TC 6 Z9 6 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A101 EP A102 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400192 ER PT J AU Schuraytz, BC Lindstrom, DJ Martinez, RR Sharpton, VL AF Schuraytz, BC Lindstrom, DJ Martinez, RR Sharpton, VL TI Distribution of iridium host phases in Chicxulub impact melt and Cretacious-Tertiary boundary ejecta. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058. LOCKHEED MARTIN ENGN & SCI CO,HOUSTON,TX 77058. LUNAR & PLANETARY INST,HOUSTON,TX 77058. NR 6 TC 2 Z9 2 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A117 EP A117 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400222 ER PT J AU Symes, SJK AF Symes, SJK TI Problems with arguments against a planetary formation for chondrules. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058. NR 11 TC 4 Z9 4 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A127 EP A127 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400242 ER PT J AU ThomasKeprta, KL Wentworth, SJ McKay, DS Taunton, AE Allen, CC Romanek, CS Gibson, EK AF ThomasKeprta, KL Wentworth, SJ McKay, DS Taunton, AE Allen, CC Romanek, CS Gibson, EK TI Subsurface terrestrial microfossils from Columbia river basalt samples: Analogs of features in Martian meteorite Allan Hills 84001? SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID CARBONATE C1 NASA,LYNDON B JOHNSON SPACE CTR,LOCKHEED MARTIN,HOUSTON,TX 77058. UNIV ARKANSAS,DEPT CHEM & BIOCHEM,FAYETTEVILLE,AR 72701. UNIV GEORGIA,SAVANNAH RIVER ECOL LAB,AIKEN,SC 29802. NR 5 TC 2 Z9 2 U1 0 U2 2 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A128 EP A129 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400245 ER PT J AU Welten, KC AF Welten, KC TI Concentrations of siderophile and lithophile elements in the nonmagnetic fraction of Antarctic H and L chondrites: A quantitative approach on weathering effects. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID METEORITES C1 NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058. NR 12 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1997 VL 32 IS 4 SU S BP A139 EP A139 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XP024 UT WOS:A1997XP02400265 ER PT J AU Hsu, CS Liu, WT Wurtele, MG AF Hsu, CS Liu, WT Wurtele, MG TI Impact of scatterometer winds on hydrologic forcing and convective heating through surface divergence SO MONTHLY WEATHER REVIEW LA English DT Article ID MOISTURE BUDGETS; PACIFIC-OCEAN; PRECIPITATION; RAINFALL; CUMULUS; PARAMETERIZATION; 30-DEGREES-S; TEMPERATURE; RETRIEVAL; SATELLITE AB One of the difficulties in estimating atmospheric heat and moisture budgets lies in resolving the near-surface heat and moisture convergence and vertical velocities, each of which is highly dependent on the divergence of the surface wind. A kinematic approach is proposed to utilize scatterometer winds to improve the estimate of surface wind divergence, the omega profile, and, therefore, estimates of the hydrologic forcing and convective heating over the tropical ocean. Improvements in these estimates over those obtained using analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF) alone are found when the ERS-1 scatterometer ground tracks passed over the TOGA COARE intensive flux array. The spatial patterns of precipitation estimated from GMS IR temperatures and radar reflectivities agree better with the divergence fields derived from the ERS-1 scatterometer winds than with those derived from either ECMWF or rawinsonde winds. The use of ERS-1 surface winds also changes the omega profiles throughout the atmosphere. The heat and moisture budgets are sensitive to vertical velocity and are, therefore, significantly affected by the inclusion of scatterometer winds. Precipitation estimates from GMS IR temperatures are found to agree better with those estimated from budget residuals computed using scatterometer winds. C1 UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90024. RP Hsu, CS (reprint author), CALTECH,JET PROP LAB,MAIL STOP 300-320,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 44 TC 12 Z9 13 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD JUL PY 1997 VL 125 IS 7 BP 1556 EP 1576 DI 10.1175/1520-0493(1997)125<1556:IOSWOH>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XJ257 UT WOS:A1997XJ25700011 ER PT J AU Lyster, PM Cohn, SE Menard, R Chang, LP Lin, SJ Olsen, RG AF Lyster, PM Cohn, SE Menard, R Chang, LP Lin, SJ Olsen, RG TI Parallel implementation of a Kalman filter for constituent data assimilation SO MONTHLY WEATHER REVIEW LA English DT Article ID ATMOSPHERIC DATA ASSIMILATION; FORECAST ERROR COVARIANCES; TRANSPORT; MODELS AB A Kalman filter for the assimilation of long-lived atmospheric chemical constituents was developed for two-dimensional transport models on isentropic surfaces over the globe. Since the Kalman filter calculates the error covariances of the estimated constituent field, there are five dimensions to this problem, x(1), x(2), and time, where x(1) and x(2) are the positions of two points on an isentropic surface. Only computers with large memory capacity and high floating point speed can handle problems of this magnitude. This article describes an implementation of the Kalman filter for distributed-memory, message-passing parallel computers. To evolve the forecast error covariance matrix, an operator decomposition and a covariance decomposition were studied. The latter was found to be scalable and has the general property, of considerable practical advantage, that the dynamical model does not need to be parallelized. Tests of the Kalman filter code examined variance transport and observability properties. This code is being used currently to assimilate constituent data retrieved by limb sounders on the Upper Atmosphere Research Satellite. C1 NASA,GODDARD SPACE FLIGHT CTR,DATA ASSIMILAT OFF,GREENBELT,MD 20771. NO ILLINOIS UNIV,DEPT MATH SCI,DE KALB,IL 60115. NASA UNIV MARYLAND,JOINT CTR EARTH SYST SCI,COLLEGE PK,MD 20742. NASA UNIV MARYLAND,JOINT CTR EARTH SYST SCI,BALTIMORE,MD 20742. GEN SCI CORP,LAUREL,MD. RP Lyster, PM (reprint author), UNIV MARYLAND,DEPT METEOROL,COLLEGE PK,MD 20742, USA. RI Cohn, Stephen/K-1954-2012 OI Cohn, Stephen/0000-0001-8506-9354 NR 31 TC 30 Z9 31 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD JUL PY 1997 VL 125 IS 7 BP 1674 EP 1686 DI 10.1175/1520-0493(1997)125<1674:PIOAKF>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XJ257 UT WOS:A1997XJ25700017 ER PT J AU Baram, Y Barniv, Y Soni, T AF Baram, Y Barniv, Y Soni, T TI Detecting collision from gray-level expansion by a neural network SO NEUROCOMPUTING LA English DT Article DE collision detection; obstacle detection; optical flow; neural networks ID OPTICAL-FLOW; FIELD; OBSERVER; MOTION AB A neural network is used for detecting an imminent collision from the gray-level map generated by a textured surface. The network maximizes the output entropy in learning the probability density functions of the data, corresponding to ''safe'' and ''dangerous'' categories. First-order temporal and spatial derivatives of the optical flow, which are related to the time to collision through the local divergence, are used as inputs to the network. Detection is based on the relative sizes of the two densities corresponding ro a given input. In contrast to a previous design, the one presented here does not require thresholding the input data, and the network size is equal to the input dimension. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Baram, Y (reprint author), TECHNION ISRAEL INST TECHNOL,DEPT COMP SCI,IL-32000 HAIFA,ISRAEL. NR 10 TC 2 Z9 2 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-2312 J9 NEUROCOMPUTING JI Neurocomputing PD JUL 1 PY 1997 VL 16 IS 1 BP 77 EP 84 DI 10.1016/S0925-2312(97)89449-0 PG 8 WC Computer Science, Artificial Intelligence SC Computer Science GA XJ020 UT WOS:A1997XJ02000006 ER PT J AU Rahn, D Braukus, M Hartsfield, J AF Rahn, D Braukus, M Hartsfield, J TI Space Station Control Board approves new assembly schedule SO NOUVELLE REVUE AERONAUTIQUE ASTRONAUTIQUE LA French DT Article C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Rahn, D (reprint author), NASA HEADQUARTERS,WASHINGTON,DC, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU DUNOD PI MONTROUGE CEDEX PA 15 RUE GOSSIN, 92543 MONTROUGE CEDEX, FRANCE SN 1247-5793 J9 NOUV REV AERONAUT AS JI Nouv. Rev. Aeronaut. Astronaut. PD JUL-AUG PY 1997 IS 4 BP 52 EP 54 PG 3 WC Engineering, Aerospace SC Engineering GA YC608 UT WOS:A1997YC60800009 ER PT J AU Egalon, CO Buoncristiani, AM Rogowski, RS AF Egalon, CO Buoncristiani, AM Rogowski, RS TI Asymptotic approximation and first-order correction of coupled-mode equations SO OPTICAL ENGINEERING LA English DT Article DE coupled-mode equations; Bragg grating; method of successive approximations; asymptotic solution ID DISTRIBUTED-FEEDBACK LASERS AB A reformulation of the asymptotic solution of the coupled-mode equations with a periodic variation of the refractive index along the propagation length is presented, A first-order correction using the asymptotic solution and Piccard's method are also determined, It is found that the first-order solution compares very well with the numerical solution throughout a wide range of coupling parameters, The key differences between the method presented here and elsewhere reside in the derivation of the asymptotic solution as well as in the carefull derivation of the higher order corrections. (C) 1997 Society of Photo-Optical Instrumentation Engineers. RP Egalon, CO (reprint author), NASA,LANGLEY RES CTR,MS 231,HAMPTON,VA 23681, USA. NR 22 TC 2 Z9 2 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 JUL PY 1997 VL 36 IS 7 BP 1930 EP 1934 DI 10.1117/1.601399 PG 5 WC Optics SC Optics GA XK790 UT WOS:A1997XK79000012 ER PT J AU Crockett, TW AF Crockett, TW TI An introduction to parallel rendering SO PARALLEL COMPUTING LA English DT Editorial Material DE parallel rendering; computer graphics; survey ID VOLUME; ARCHITECTURES; VISUALIZATION; PERFORMANCE; ALGORITHMS AB In computer graphics, rendering is the process by which an abstract description of a scene is converted to an image. When the scene is complex, or when high-quality images or high frame rates are required, the rendering process becomes computationally demanding. To provide the necessary levels of performance, parallel computing techniques must be brought to bear. Today, parallel hardware is routinely used in graphics workstations, and numerous software-based rendering systems have been developed for general-purpose parallel architectures. This article provides an overview of the parallel rendering field, encompassing both hardware and software systems. The focus is on the underlying concepts and the issues which arise in the design of parallel renderers. We examine the different types of parallelism and how they can be applied in rendering applications. Concepts from parallel computing, such as data decomposition and load balancing, are considered in relation to the rendering problem. Our survey explores a number of practical considerations as well, including the choice of architectural platform, communication and memory requirements, and the problem of image assembly and display. We illustrate the discussion with numerous examples from the parallel rendering literature, representing most of the principal rendering methods currently used in computer graphics. RP Crockett, TW (reprint author), NASA, LANGLEY RES CTR, INST COMP APPLICAT SCI & ENGN, HAMPTON, VA 23681 USA. NR 72 TC 24 Z9 26 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8191 EI 1872-7336 J9 PARALLEL COMPUT JI Parallel Comput. PD JUL PY 1997 VL 23 IS 7 BP 819 EP 843 DI 10.1016/S0167-8191(97)00028-8 PG 25 WC Computer Science, Theory & Methods SC Computer Science GA XP704 UT WOS:A1997XP70400002 ER PT J AU Salomonson, VV AF Salomonson, VV TI The 25th anniversary of Landsat-1 - Foreword SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Editorial Material RP Salomonson, VV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EARTH SCI DIRECTORATE,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD JUL PY 1997 VL 63 IS 7 BP 829 EP 829 PG 1 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA XJ280 UT WOS:A1997XJ28000010 ER PT J AU Lauer, DT Morain, SA Salomonson, VV AF Lauer, DT Morain, SA Salomonson, VV TI The Landsat program: Its origins, evolution, and impacts SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article AB Landsat 1 began an era of space-based resource data collection that changed the way science, industry, governments, and the general public view the Earth. For the last 25 years, the Landsat program - despite being hampered by institutional problems and budget uncertainties - has successfully provided a continuous supply of synoptic, repetitive, multispectral data of the Earth's land areas. These data have profoundly affected programs for mapping resources, monitoring environmental changes, and assessing global habitability. The societal applications this program generated are so compelling that international systems have proliferated to carry on the tasks initiated with Landsat data. C1 UNIV NEW MEXICO,DEPT GEOG,ALBUQUERQUE,NM 87131. UNIV NEW MEXICO,EARTH DATA ANAL CTR,ALBUQUERQUE,NM 87131. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Lauer, DT (reprint author), US GEOL SURVEY,EROS DATA CTR,SIOUX FALLS,SD 57198, USA. NR 48 TC 32 Z9 33 U1 1 U2 4 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD JUL PY 1997 VL 63 IS 7 BP 831 EP 838 PG 8 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA XJ280 UT WOS:A1997XJ28000011 ER PT J AU Thome, K Markham, B Barker, J Slater, P Biggar, S AF Thome, K Markham, B Barker, J Slater, P Biggar, S TI Radiometric calibration of Landsat SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID THEMATIC MAPPER DATA; ABSOLUTE CALIBRATION; IN-FLIGHT; SENSORS AB The radiometric calibration of the sensors on the Landsat series of satellites is a contributing factor to the success of the Landsat data set. The calibration of these sensors has relied on the preflight laboratory work as well as on inflight techniques using on-board calibrators and vicarious techniques. Descriptions of these methods and systems are presented. Results of the on-board calibrators and reflectance-based, ground reference calibrations of Landsat 5 Thematic Mapper ore presented that indicate the absolute radiometric calibration of bands 1 to 4 should have an uncertainty of less than 5.0 percent. Bands 5 and 7 have slightly higher uncertainties, but should be less than 10 percent. The results also show that the on-board calibrators are of higher precision than the vicarious calibration but that the vicarious calibration results should have higher accuracy. C1 GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20770 USA. RP Thome, K (reprint author), UNIV ARIZONA, CTR OPT SCI, REMOTE SENSING GRP, POB 210094, TUCSON, AZ 85721 USA. RI Thome, Kurtis/D-7251-2012; Markham, Brian/M-4842-2013 OI Markham, Brian/0000-0002-9612-8169 NR 27 TC 124 Z9 128 U1 3 U2 18 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 USA SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD JUL PY 1997 VL 63 IS 7 BP 853 EP 858 PG 6 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA XJ280 UT WOS:A1997XJ28000013 ER PT J AU Goward, SN Williams, DL AF Goward, SN Williams, DL TI Landsat and Earth Systems Science: Development of terrestrial monitoring SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Review ID HIGH-RESOLUTION RADIOMETER; VEGETATION INDEX; THEMATIC MAPPER; SATELLITE DATA; FOREST; REFLECTANCE; CO2; DEFORESTATION; BIOSPHERE; PATTERNS AB One of the major catalysts leading to the development of the global-scale Earth Systems Science concept, the International Geosphere-Biosphere Program, and the U.S. Global Change Research Program were the unique views of Earth provided by Landsat sensors over the past 25 years. This paper addresses Landsat's contributions in the Earth Systems Science arena. Early successes in observing the Earth's cloud patterns from space led to the use of this nerv spaceborne perspective to observe surface terrestrial features. Deployment of Landsat demonstrated that significant information about the Earth's land areas could be acquired from such an observatory. Numerous studies indicated that assessments of agricultural production, forest resources, human population surveys, and environmental conditions could be derived from Landsat data. Thus, an unanticipated outcome of the Landsat program was the evolution of unique nerv insights concerning terrestrial biospheric patterns and dynamics. The electronic, high precision spectral radiometry, combined with Landsat's repetitive coverage, revealed that a critical new environmental measurement, the spectral vegetation index, could be acquired with these sensors. These measurements are also of critical importance in understanding the hydrology land surface climatology, and biodiversity characteristics of the Earth. Recognition of the value of this vegetation index in regional and global-scale studies of the Earth's environment served as a strong stimulus to the development of the Earth Systems Science research agenda, one of the major foci of NASA's Mission to Planet Earth, Earth Observing System. Since the innovation of the Landsat Thematic Mapper instrument in the early 1980s, significant progress has been achieved in assessing human impacts within the Earth systems. Significant further inputs to Earth Systems Science from Landsat are expected when Landsat 7 is launched in 1998. Refinements in radiometric response and calibration, inclusion of a 15-m panchromatic band, improvement of the spatial resolution of the thermal band to 60 m, and an aggressive acquisition strategy will all contribute to Landsat's new role as a major component of NASA's Mission to Planet forth, Earth Observing System. Development of technologies for more refined, as well as lower cost, sensors and platforms is now underway to continue the Landsat science mission. These technology advances are expected to further enhance the capability to monitor the Earth's land areas. C1 NASA, GODDARD SPACE FLIGHT CTR, BIOSPHER SCI BRANCH, TERR PHYS LAB, GREENBELT, MD 20771 USA. RP Goward, SN (reprint author), UNIV MARYLAND, DEPT GEOG, LAB GLOBAL REMOTE SENSING STUDIES, COLLEGE PK, MD 20742 USA. NR 129 TC 72 Z9 73 U1 2 U2 15 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 USA SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD JUL PY 1997 VL 63 IS 7 BP 887 EP 900 PG 14 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA XJ280 UT WOS:A1997XJ28000018 ER PT J AU Ungar, SG AF Ungar, SG TI Technologies for future Landsat missions SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article AB Advanced technologies are available that may potentially lower the cost and improve the quality of future Landsat systems. The NASA Nerv Millennium Program (NMP) Earth Orbiter Mission (EO-1), serving as a technology pathfinder, is implementing several sensor and spacecraft technologies to further define the possibilities for Landsat 8 and beyond. The technologies involved include high spectral resolution grating and wedge imaging spectrometers; advanced multispectral chip assemblies; a Pulsed Plasma Thruster (PPT), included as a reaction wheel replacement for improved spacecraft attitude control: X-band phase array ground transmission antenna and high speed fiber optics data bus (FODB) for enhanced data transmission: a carbon-carbon radiator panel for power/heat dissipation; and a light-weight flexible solar array employing highly efficient photosensitive materials. In aggregate, these technologies and others not only offer considerable enhancements, but also the real possibility of implementing and operating future Landsat systems at substantially less cost. RP Ungar, SG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. NR 6 TC 13 Z9 13 U1 1 U2 3 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD JUL PY 1997 VL 63 IS 7 BP 901 EP 905 PG 5 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA XJ280 UT WOS:A1997XJ28000019 ER PT J AU Payri, C Maritorena, S Bizeau, C AF Payri, Claude Maritorena, Stephane Bizeau, Christophe TI Photoadaptation in Hydrolithon Onkodes in a French polynesia reef SO PHYCOLOGIA LA English DT Meeting Abstract C1 [Maritorena, Stephane] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU INT PHYCOLOGICAL SOC PI LAWRENCE PA NEW BUSINESS OFFICE, PO BOX 1897, LAWRENCE, KS 66044-8897 USA SN 0031-8884 J9 PHYCOLOGIA JI Phycologia PD JUL PY 1997 VL 36 IS 4 SU S MA 322 BP 84 EP 85 PG 2 WC Plant Sciences; Marine & Freshwater Biology SC Plant Sciences; Marine & Freshwater Biology GA V43TS UT WOS:000202958000323 ER PT J AU Larkin, DJ AF Larkin, DJ TI SiC dopant incorporation control using site-competition CVD SO PHYSICA STATUS SOLIDI B-BASIC RESEARCH LA English DT Article ID CHEMICAL-VAPOR-DEPOSITION; SILICON-CARBIDE; EPITAXY; GROWTH; FILMS AB The use of site-competition epitaxy, which is based on intentional variation of the Si/C ratio during epitaxy, has now been reproduced in numerous national and international laboratories. Presented in this paper is a summary of the site-competition technique as a comparison of controlled doping on C-face 6H-SiC(<000(1)over bar>) versus Si-face BH-SiC(0001) substrates for phosphorous (P), aluminum (Al), boron (B), and nitrogen (N). Also reported herein is the detection of hydrogen in boron-doped CVD SiC epilayers and hydrogen-passivation of the boron-acceptors, Results from low temperature photoluminescence (LTPL) spectroscopy indicate that the hydrogen content increased as the C-V measured net hole concentration increased. Secondary ion mass spectrometry (SIMS) analysis revealed that the boron and the hydrogen incorporation both increased as the Si/C ratio was sequentially decreased within the CVD reactor during epilayer growth. Boron-doped epilayers that were annealed at 1700 degrees C in argon no longer exhibited hydrogen-related LTPL lines. and subsequent SIMS analysis confirmed the outdiffusion of hydrogen from the boron-doped SiC epilayers. The C-V measured net hole concentration for the B-doped epitaxial layers increased more than three-fold as a result of the 1700 degrees C anneal, which is consistent with hydrogen passivation of the boron-acceptors. For N-doped epitaxy, N incorporation into C-sites is favored on the Si-face whereas N incorporation into the Si-site is apparently the preferred lattice site on the C-face. Both P and N exhibit preferred incorporation on the C-face while Al and B incorporation is more efficient on the Si-face. RP Larkin, DJ (reprint author), NASA,LEWIS RES CTR,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 29 TC 112 Z9 112 U1 5 U2 18 PU AKADEMIE VERLAG GMBH PI BERLIN PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY SN 0370-1972 J9 PHYS STATUS SOLIDI B JI Phys. Status Solidi B-Basic Res. PD JUL PY 1997 VL 202 IS 1 BP 305 EP 320 DI 10.1002/1521-3951(199707)202:1<305::AID-PSSB305>3.0.CO;2-9 PG 16 WC Physics, Condensed Matter SC Physics GA XL897 UT WOS:A1997XL89700017 ER PT J AU Powell, JA Larkin, DJ AF Powell, JA Larkin, DJ TI Process-induced morphological defects in epitaxial CVD silicon carbide SO PHYSICA STATUS SOLIDI B-BASIC RESEARCH LA English DT Article ID 0001 6H-SIC WAFERS; FILMS; GROWTH AB Silicon carbide (SiC) semiconductor technology has been advancing rapidly, but there are numerous crystal growth problems that need to be solved before SiC can reach its full potential. Among these problems is a need for an improvement in the surface morphology of epitaxial films that are grown to produce device structures. Various processes before and during epilayer growth lead to the formation of morphological defects observed in SIC epilayers grown on Sic substrates. In studies of both 6H and BH-SIC epilayers, atomic force microscopy (AFM) and other techniques have been used to characterize SiC epilayer surface morphology. In addition to the well-known micropipe defect, SiC epilayers contain growth pits, triangular features (primarily) in 4H-SiC, and macro step due to step bunching. In work at NASA Lewis, it has been found that factors contributing to the formation of some morphological defects include: defects in the substrate bulk, defects in the substrate surface caused by cutting and polishing the wafer. the tilt angle of the wafer surface relative to the basal plane, and growth conditions. Some of these findings confirm results of other research groups. This paper presents a review of published and unpublished investigations into processes that are relevant to epitaxial film morphology. RP Powell, JA (reprint author), NASA,LEWIS RES CTR,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 30 TC 117 Z9 117 U1 0 U2 24 PU AKADEMIE VERLAG GMBH PI BERLIN PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY SN 0370-1972 J9 PHYS STATUS SOLIDI B JI Phys. Status Solidi B-Basic Res. PD JUL PY 1997 VL 202 IS 1 BP 529 EP 548 DI 10.1002/1521-3951(199707)202:1<529::AID-PSSB529>3.0.CO;2-E PG 20 WC Physics, Condensed Matter SC Physics GA XL897 UT WOS:A1997XL89700027 ER PT J AU Zeitlin, C Heilbronn, L Miller, J Rademacher, SE Borak, T Carter, TR Frankel, KA Schimmerling, W Stronach, CE AF Zeitlin, C Heilbronn, L Miller, J Rademacher, SE Borak, T Carter, TR Frankel, KA Schimmerling, W Stronach, CE TI Heavy fragment production cross sections from 1.05 GeV/nucleon Fe-56 in C, Al, Cu, Pb, and CH2 targets SO PHYSICAL REVIEW C LA English DT Article ID RELATIVISTIC NUCLEI; CARBON TARGETS; TOTAL CHARGE; HYDROGEN; HELIUM; MULTIPLICITIES; SECONDARIES; MODEL AB We have obtained charge-changing cross sections and partial cross sections for fragmentation of 1.05 GeV/nucleon Fe projectiles incident on H, C, Al, Cu, and Pb nuclei. The energy region covered by this experiment is critical for an understanding of galactic cosmic ray propagation and space radiation biophysics. Surviving primary beam particles and fragments with charges from 12 to 25 produced within a forward cone of half-angle 61 mrad were detected using a silicon detector telescope to identify their charge and the cross sections were calculated after correction of the measured yields for finite target thickness effects. The cross sections are compared to model calculations and to previous measurements. Cross sections for the production of fragments with even-numbered nuclear charges are seen to be enhanced in almost all cases. C1 COLORADO STATE UNIV, DEPT RADIOL HLTH SCI, FT COLLINS, CO 80523 USA. VIRGINIA POLYTECH INST & STATE UNIV, DEPT PHYS, PETERSBURG, VA 23806 USA. NASA, WASHINGTON, DC 20546 USA. RP UNIV CALIF BERKELEY, LAWRENCE BERKELEY LAB, BERKELEY, CA 94720 USA. RI Heilbronn, Lawrence/J-6998-2013 OI Heilbronn, Lawrence/0000-0002-8226-1057 NR 24 TC 113 Z9 115 U1 0 U2 5 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2469-9985 EI 2469-9993 J9 PHYS REV C JI Phys. Rev. C PD JUL PY 1997 VL 56 IS 1 BP 388 EP 397 DI 10.1103/PhysRevC.56.388 PG 10 WC Physics, Nuclear SC Physics GA XL650 UT WOS:A1997XL65000043 PM 11541215 ER PT J AU Knott, CN Albergo, S Caccia, Z Chen, CX Costa, S Crawford, HJ Cronqvist, M Engelage, J Greiner, L Guzik, TG Insolia, A Lindstrom, PJ Mitchell, JW Potenza, R Russo, GV Soutoul, A Testard, O Tull, CE Tuve, C Waddington, CJ Webber, WR Wefel, JP AF Knott, CN Albergo, S Caccia, Z Chen, CX Costa, S Crawford, HJ Cronqvist, M Engelage, J Greiner, L Guzik, TG Insolia, A Lindstrom, PJ Mitchell, JW Potenza, R Russo, GV Soutoul, A Testard, O Tull, CE Tuve, C Waddington, CJ Webber, WR Wefel, JP TI Interactions of relativistic Ar-36 and Ar-40 nuclei in hydrogen: Isotopic production cross sections SO PHYSICAL REVIEW C LA English DT Article AB The interactions of Ar-36 projectile nuclei with energies of 361, 546, and 765 MeV/nucleon and Ar-40 nuclei with 352 MeV/nucleon, have been studied in a liquid-hydrogen target as part of a program to study interactions of relevance to the problem of cosmic-ray propagation in the interstellar medium. We have measured the cross sections for the production of isotopic fragments of the projectile nuclei in these interactions. The variations of these cross sections with mass, charge, and energy, are examined for insights into any systematic features of this type of fragmentation reaction that might aid predictions of other, unmeasured cross sections. These cross sections are also compared with the values derived from the most commonly used prediction techniques. It is suggested that these techniques could be improved by taking account of the systematic features identified here. C1 UNIV CATANIA,DIPARTMENTO FIS,I-95129 CATANIA,ITALY. IST NAZL FIS NUCL,SEZ CATANIA,I-95129 CATANIA,ITALY. LOUISIANA STATE UNIV,DEPT PHYS & ASTRON,BATON ROUGE,LA 70803. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,BERKELEY,CA 94720. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CENS,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. RP Knott, CN (reprint author), UNIV MINNESOTA,SCH PHYS & ASTRON,MINNEAPOLIS,MN 55455, USA. RI Insolia, Antonio/M-3447-2015; TUVE', Cristina/P-3933-2015 OI Insolia, Antonio/0000-0002-9040-1566; TUVE', Cristina/0000-0003-0739-3153 NR 8 TC 20 Z9 22 U1 0 U2 3 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD JUL PY 1997 VL 56 IS 1 BP 398 EP 406 DI 10.1103/PhysRevC.56.398 PG 9 WC Physics, Nuclear SC Physics GA XL650 UT WOS:A1997XL65000044 ER PT J AU Canuto, VM Dubovikov, MS Dienstfrey, A AF Canuto, VM Dubovikov, MS Dienstfrey, A TI A dynamical model for turbulence .4. Buoyancy-driven flows SO PHYSICS OF FLUIDS LA English DT Article ID RAYLEIGH-NUMBER CONVECTION; THERMAL TURBULENCE AB We apply a recent model of turbulence to turbulent convection at high Rayleigh number Ra and compare the results with new laboratory and DNS data. Mie derive a closed set of equations for the total turbulent kinetic energy, turbulent kinetic energy in the,z direction, temperature variance, and convective flux. The equations are coupled, time dependent, and nonlocal. We solve the equations both analytically and numerically. In the first case, wie neglect diffusion and derive the relation Nu=Nu(sigma,Ra), where Nu is the Nusselt number and sigma is the Prandtl number. For sigma much greater than 1, Nu becomes independent of sigma; for sigma much less than 1, Nu is proportional to sigma(1/3); for 0.025 (mercury)less than or equal to sigma less than or equal to 0.7 (helium), Nu is proportional to,sigma(2/7). The numerical solution (with diffusion) yields (a) Nusselt number Nu, (w), (c) (temperature variance near the wall and at the center). lambda(T) (thermal boundary layer thickness). and Pe (Peclet number) versus Ra, (b) the z profile of mean temperature T, , horizontal, and vertical Peclet numbers, (c) spectra versus k(h) (horizontal wave number) of total kinetic energy, vertical kinetic energy. temperature variance, and temperature flux; (d) dependence of the Nu vs Ra relation on the Prandtl number. For large aspect ratios, the agreement with both laboratory and DNS data is satisfactory. The model contains no free parameters. (C) 1997 American Institute of Physics. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 29 TC 29 Z9 29 U1 0 U2 1 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 1070-6631 EI 1089-7666 J9 PHYS FLUIDS JI Phys. Fluids PD JUL PY 1997 VL 9 IS 7 BP 2118 EP 2131 DI 10.1063/1.869331 PG 14 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XH287 UT WOS:A1997XH28700027 ER PT J AU Canuto, VM Dubovikov, MS AF Canuto, VM Dubovikov, MS TI A dynamical model for turbulence .5. The effect of rotation SO PHYSICS OF FLUIDS LA English DT Article ID HOMOGENEOUS TURBULENCE; ISOTROPIC TURBULENCE AB We study turbulence undergoing rapid rotation. We show that there exist two different regimes divided by the new number N=K/nu Omega. N<1: rotation is so strong that it suppresses the energy cascade process and no inertial regime can develop. In the freely decaying case, only viscosity operates: an initially isotropic three-dimensional (3-D) turbulence remains so and never tends toward a 2-D state. N>1: the energy cascade, though inhibited, allows an inertial regime in which 3-D and a quasi-2-D state exist in equilibrium. The latter is restricted to a narrow band of values delta k(z) similar to k(Omega)(-1)k(2), where k(Omega)=(Omega(3) epsilon(-1))(1/2). For k>k(Omega), the Kolmogorov spectrum sets in, while for k 25 degrees), GIM has a good correlation (R > 0.93) to TOPEX with respect to TEC measurements. The slope of the linear fitting line to the data set from two TOPEX cycles is 44.5 degrees (near the ideal 45 degrees). In the northern hemispheric regions, ionospheric specification by GIM appears to be accurate to within 3-10 TECU up to 2000+ lan away from nearest GPS station (corresponding to similar to 1 degrees elevation angle cutoff). Beyond 2000 lan, GIM accuracy, on average, is reduced to the Bent model levels. In the equatorial region, the Bent model predictions are systematically lower (similar to 5.0 TECU) than TOPEX values and often show a saturation at large TEC values. During ionospheric disturbed periods, GIM sometimes shows differences from TOPEX values due to transient variations of the ionosphere. Such problems may be improved by the continuous addition of new GPS stations in data-sparse regions. Thus, over a GPS station's measurement realm (up to 2000 km in radius), GIM can produce generally accurate TEC values. Through a spatial and temporal extrapolation of GPS-derived TEC measurements, the GIM technique provides a powerful tool for monitoring global ionospheric features in near real time. RP Ho, CM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 18 TC 50 Z9 55 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD JUL-AUG PY 1997 VL 32 IS 4 BP 1499 EP 1512 DI 10.1029/97RS00580 PG 14 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA XM795 UT WOS:A1997XM79500015 ER PT J AU Choudhury, BJ AF Choudhury, BJ TI Global pattern of potential evaporation calculated from the Penman-Monteith equation using satellite and assimilated data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID SOLAR-RADIATION; SURFACE; EVAPOTRANSPIRATION; WIND; FIELDS; INTERPOLATION; CLIMATOLOGY; CALIBRATION; TEMPERATURE; BENEATH AB Potential evaporation has been used to provide a reference level for actual evaporation in many studies of land surface heat and water balance. While Thornthwaite's formula has been used in many regional and global studies, the Penman-Monteith equation has been shown to provide an accurate estimate of this evaporation. Thus, global pattern gf potential evaporation has been calculated from the Penman-Monteith equation using satellite and assimilated data for a 24-month period, January 1987 to December 1988. The albedo and surface resistance have been taken to be, respectively, 0.23 and 70 s m(-1), which are considered to be representative values for actively growing well-watered grass covering the ground. Satellite observations have been used to obtain spatially representative monthly values of solar radiation, fractional cloud cover, air temperature, and vapor pressure, while aerodynamic resistance has been calculated using four-dimensional data assimilation results. Meteorologic data derived from satellite observations are compared with the surface (station) measurements. The calculated potential evaporation values are compared with lysimeter observations for evaporation from well-watered grass at 35 widely distributed locations in different climatic regimes to quantify the accuracy of the calculated values. The evaporation values have been archived for distribution. Published by Elsevier Science Inc. RP Choudhury, BJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,LAB HYDROSPHER PROC,CODE 974,GREENBELT,MD 20771, USA. NR 92 TC 39 Z9 42 U1 1 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 JUL PY 1997 VL 61 IS 1 BP 64 EP 81 DI 10.1016/S0034-4257(96)00241-6 PG 18 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XC936 UT WOS:A1997XC93600007 ER PT J AU Corp, LA McMurtrey, JE Chappelle, EW Daughtry, CST Kim, MS AF Corp, LA McMurtrey, JE Chappelle, EW Daughtry, CST Kim, MS TI UV band fluorescence (in vivo) and its implications for the remote assessment of nitrogen supply in vegetation SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID LASER-INDUCED FLUORESCENCE; GREEN PLANTS; CHLOROPHYLL FLUORESCENCE; TRYPTOPHANYL RESIDUES; BLUE FLUORESCENCE; PHOTOSYNTHESIS; LEAVES; CARBOXYLASE; PROTEIN; SPECTRA AB When excited at 280 nm, (intact vegetation produced two overlapping broadband fluorescence emissions; the first centered near 335 nm [ultraviolet (UV) band], and the second centered near 440 nm (blue band). Separation of these two fluorescence bands was achieved by an iterative nonlinear curve fit procedure utilizing the asymmetric double sigmoidal spectral function. The subsequent ratio of the deconvoluted curve intensities exhibited a significant relation between protein concentration and fluorescence. UV band fluorescence from vegetation treated with varying levels of nitrogen fertilization decreased relative to the blue fluorescence as a function of protein levels. These studies indicate that in vivo UV band fluorescence can be utilized as a nondestructive tool to remotely sense variations in protein concentration due to nitrogen supply. Strong similarities were noted in the UV band fluorescence characteristics of intact vegetation to both membrane-bound and soluble plant proteins containing aromatic amino acids. Pure ribulose 1,5-bisphosphate carboxylase in aqueous solution exhibited UV fluorescence characteristics with excitation and emission distributions similar to those of intact vegetation. Because of its high concentration (up to 70% of the soluble leaf proteins), roe believe this protein contributes to the UV band fluorescence emnnating from the intact leaf. In, addition, similar fluorescence characteristics were observed for two other prominent enzymatic plant proteins; namely, adenosine 5'-tri-phosphatase and carboxylase phosphoenolpyruvate carboxcylase. These results indicate that UV band fluorescence emanating from the intact leaf could originate front several plant proteins that contain aromatic amino acids. (C) Elsevier Science Inc., 1997. C1 SCI SYST & APPL INC,LANHAM,MD. USDA ARS,BELTSVILLE AGR RES CTR W,REMOTE SENSING & MODELING LAB,BELTSVILLE,MD 20705. NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771. NR 35 TC 18 Z9 18 U1 0 U2 4 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 JUL PY 1997 VL 61 IS 1 BP 110 EP 117 DI 10.1016/S0034-4257(96)00244-1 PG 8 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XC936 UT WOS:A1997XC93600010 ER PT J AU WalterShea, EA Privette, J Cornell, D Mesarch, MA Hays, CJ AF WalterShea, EA Privette, J Cornell, D Mesarch, MA Hays, CJ TI Relations between directional spectral vegetation indices and leaf area and absorbed radiation in alfalfa SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID PHOTOSYNTHETICALLY ACTIVE RADIATION; REFERENCE-REFLECTANCE PANELS; CANOPY REFLECTANCE; BIDIRECTIONAL REFLECTANCE; WHEAT CANOPIES; CORN CANOPIES; PLANT CANOPY; FIFE SITE; INDEXES; AVHRR AB Sensors on satellite platforms with extreme view angles have been increasingly used to analyze regional and global vegetation cover and productivity because of frequent observations. This study, using experimental and theoretical methods, analyzed variations in vegetation indices with sun-view geometry as a means of understanding the sensitivity of relations between vegetation indices and the biophysical properties, the leaf area index (LAI), and the instantaneous fraction of absorbed photosynthetically active radiation (fAPAR). Canopy bidirectional reflectance factors (BRFs) of an alfalfa crop were measured and simulated at a variety of solar and view zenith angles. Also, fAPAR, LAI, and leaf optical properties were measured. Measured and simulated canopy reflectances agreed generally within 1% (absolute). Normalized difference and simple ratio vegetation indices (NDVI and SRVI, respectively), derived from BRFs, varied with view and solar zenith angles. The minimum for near-infrared (NIR) BRFs and relatively high red BRFs generally occurred near nadir, resulting in some of the lowest vegetation index values. Highest VI values were generally obtained at forward view angles. Variation of NDVI with sun-view-geometry was greatest at LAIs <2, whereas the range in SRVI was greatest for LAIs>2. Measured reflectances indicate that relations between NDVI and LAI and between SRVI and fAPAR were curvilinear across all solar and view zenith angle combinations in the solar principal plane, whereas relations between SRVI and LAI and between NDVI and fAPAR varied from linear to curvilinear. Analyses revealed that vegetation indices at large view zenith angles were poorly correlated with fAPAR, whereas those at small zenith angles were strongly correlated. In general, vegetation indices were more sensitive to fAPAR than to LAI, which is attributed to the fact that fAPAR is a radiation quantity, whereas LAI is nonlinearly related to radiation. Regression of fAPAR with VI values derived from combinations of red and NIR BRFs from similar and nonsimilar directions indicates that the highest correlation is in near-nadir and backscatter directions. However, further investigation into variations of relations between remotely sensed observations and canopy attributes and into the usefulness of off-nadir in extracting information is recommended. (C) Elsevier Science Inc., 1997. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP WalterShea, EA (reprint author), UNIV NEBRASKA,DEPT AGR METEOROL,LINCOLN,NE 68583, USA. RI Privette, Jeffrey/G-7807-2011 OI Privette, Jeffrey/0000-0001-8267-9894 NR 53 TC 46 Z9 47 U1 0 U2 6 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 JUL PY 1997 VL 61 IS 1 BP 162 EP 177 DI 10.1016/S0034-4257(96)00250-7 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XC936 UT WOS:A1997XC93600015 ER PT J AU Fishman, GJ Hartmann, DH AF Fishman, GJ Hartmann, DH TI Gamma-ray bursts SO SCIENTIFIC AMERICAN LA English DT Article C1 CLEMSON UNIV,CLEMSON,SC. RP Fishman, GJ (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 4 TC 2 Z9 2 U1 0 U2 1 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 SN 0036-8733 J9 SCI AM JI Sci.Am. PD JUL PY 1997 VL 277 IS 1 BP 46 EP 51 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XG761 UT WOS:A1997XG76100026 ER PT J AU Banks, HT Smith, RC Brown, DE Silcox, RJ Metcalf, VL AF Banks, HT Smith, RC Brown, DE Silcox, RJ Metcalf, VL TI Experimental confirmation of a PDE-based approach to design of feedback controls SO SIAM JOURNAL ON CONTROL AND OPTIMIZATION LA English DT Article DE feedback control; piezoceramic actuators; PDE model ID INFINITE-DIMENSIONAL SYSTEMS; FLEXIBLE STRUCTURES; APPROXIMATIONS; COMPENSATORS; EQUATIONS AB Issues regarding the experimental implementation of PDE-based controllers are discussed in this work. While the motivating application involves the reduction of vibration levels for a circular plate through excitation of surface-mounted piezoceramic patches, the general techniques described here will extend to a variety of applications. The initial step is the development of a PDE model which accurately captures the physics of the underlying process. This model is then discretized to yield a vector-valued initial value problem. Optimal control theory is used to determine continuous-time voltages to the patches, and the approximations needed to facilitate discrete-time implementation are addressed. Finally, experimental results demonstrating the control of both transient and steady-state vibrations through these techniques are presented. C1 IOWA STATE UNIV,DEPT MATH,AMES,IA 50011. NASA,LANGLEY RES CTR,LOCKHEED ENGN & SCI CO,HAMPTON,VA 23681. NASA,LANGLEY RES CTR,ACOUST DIV,HAMPTON,VA 23681. NASA,LANGLEY RES CTR,USA,RES LAB,HAMPTON,VA 23681. RP Banks, HT (reprint author), N CAROLINA STATE UNIV,CTR RES SCI COMPUTAT,RALEIGH,NC 27695, USA. NR 39 TC 9 Z9 10 U1 0 U2 2 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 SN 0363-0129 J9 SIAM J CONTROL OPTIM JI SIAM J. Control Optim. PD JUL PY 1997 VL 35 IS 4 BP 1263 EP 1296 DI 10.1137/S0363012995285909 PG 34 WC Automation & Control Systems; Mathematics, Applied SC Automation & Control Systems; Mathematics GA XG743 UT WOS:A1997XG74300009 ER PT J AU Ruzmaikin, A Molchanov, SA AF Ruzmaikin, A Molchanov, SA TI A model of diffusion produced by a cellular surface flow SO SOLAR PHYSICS LA English DT Article ID MAGNETIC-FIELDS AB A model of diffusion induced by the joint action of random cells of two different sizes (granulation and supergranulation) is developed. The basic properties of the model are defined by the dimensionless ratio zeta = (the life time)/(characteristic size/velocity) constructed for these two types of cells. An analytical expression for the diffusivity as a function of zeta is derived. It is estimated that for the standard parameters used the contribution of granulation to the joint diffusion is small. A comparison between the model and numerical simulations of the kinematic diffusion of magnetic fields on the solar surface is made. C1 UNIV N CAROLINA,DEPT MATH,CHARLOTTE,NC 28105. RP Ruzmaikin, A (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 16 TC 7 Z9 7 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUL PY 1997 VL 173 IS 2 BP 223 EP 231 DI 10.1023/A:1004986908972 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XQ472 UT WOS:A1997XQ47200002 ER PT J AU Jordan, S Garcia, A Bumba, V AF Jordan, S Garcia, A Bumba, V TI Interpreting the large limb eruption of July 9, 1982 SO SOLAR PHYSICS LA English DT Article ID SOLAR-FLARE MYTH; INTERPLANETARY; DISTURBANCES; CORONA AB A time series of K3 spectroheliograms taken at the Coimbra Observatory exhibits an erupting loop on the east limb on July 9, 1982 in active region NOAA 3804. The Goddard SMM Hard X-Ray Burst Spectrometer (HXRBS) observations taken during this period reveal a hard X-ray Bare occurring just before the loop eruption is observed, and SMS-GOES soft X-ray observations reveal a strong long-duration event (LDE) following the impulsive phase of the flare. A Solwind coronagram exhibits a powerful coronal mass ejection (CME) associated with the erupting loop. H alpha flare and prominence observations as well as centimeter and decimeter radio observations of the event are also reviewed, A large, north-south-oriented quiescent prominence reported within the upper part of the CME expansion region may play a role in the eruption as well. The spatial and temporal correlations among these observations are examined in the light of two different current models for prominence eruption and CME activation: (1)The CME is triggered by the observed hard X-ray impulsive Bare. (2) The CME is not triggered by a flare, and the observed soft X-ray flare is an LDE due to reconnection within the CME 'bubble'. It is concluded that this event is probably of a 'mixed' type that combines characteristics of models (1) and (2). The July 9 event is then compared to three other energetic CME and flare eruptions associated with the same active-region complex, all occurring in the period July 9 through September 4, 1982. It is noted that these four energetic events coincide with the final evolutionary phase of a long-lasting active-region complex, which is discussed in a companion paper (Bumba, Garcia, and Jordan, 1997). The paper concludes by addressing 'the solar flare myth' controversy in the light of this work. C1 UNIV COIMBRA,ASTRON OBSERV,P-3040 COIMBRA,PORTUGAL. ACAD SCI CZECH REPUBL,INST ASTRON,CS-25165 ONDREJOV,CZECH REPUBLIC. RP Jordan, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 19 TC 8 Z9 8 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUL PY 1997 VL 173 IS 2 BP 359 EP 376 DI 10.1023/A:1004907008317 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XQ472 UT WOS:A1997XQ47200011 ER PT J AU Tsurutani, BT Gonzalez, WD Kamide, Y AF Tsurutani, BT Gonzalez, WD Kamide, Y TI Magnetic Storms SO SURVEYS IN GEOPHYSICS LA English DT Review ID GEOMAGNETIC-ACTIVITY; ORIGIN; SUBSTORMS; PLASMA; SHEET AB This talk provides a brief summary of the first conference devoted entirely to magnetic storms. The conference was held in Pasadena, California, at the Jet Propulsion Laboratory, 12-16 February 1996. Topics covered the relevant time-varying phenomena at the sun/corona, propagation of these structures through interplanetary space, the response of the magnetosphere from its interaction with these interplanetary structures, the formation of the storm-time ring-current (in particular the oxygen content of the ring-current), and storm ionospheric effects and ground based effects. A complementary summary is provided by Gonzalez et al. in EOS, 1996. The full set of review articles will be published in an AGU monograph and many of the contributed articles will appear in a special section of the Journal of Geophysical Research, Space Physics. C1 INST NACL PESQUISAS ESPACIAIS,S JOSE CAMPOS,SP,BRAZIL. NAGOYA UNIV,SOLAR TERR ENVIRONM LAB,TOYOKAWA 442,JAPAN. RP Tsurutani, BT (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 6 Z9 6 U1 0 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-3298 J9 SURV GEOPHYS JI Surv. Geophys. PD JUL PY 1997 VL 18 IS 4 BP 363 EP 383 DI 10.1023/A:1006555215463 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XU462 UT WOS:A1997XU46200002 ER PT J AU Covault, C AF Covault, C TI Mir accident imperils US-Russian cooperation SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Article RP Covault, C (reprint author), NASA,JOHN F KENNEDY SPACE CTR,KENNEDY SPACE CTR,FL 32899, 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 JUN 30 PY 1997 VL 146 IS 27 BP 20 EP 22 PG 3 WC Engineering, Aerospace SC Engineering GA XG807 UT WOS:A1997XG80700007 ER PT J AU Covault, C AF Covault, C TI Shuttle, Mars asteroid flights present new challenges to NASA SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Article RP Covault, C (reprint author), NASA,JOHN F KENNEDY SPACE CTR,KENNEDY SPACE CTR,FL 32899, USA. NR 0 TC 1 Z9 1 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 JUN 30 PY 1997 VL 146 IS 27 BP 24 EP 24 PG 1 WC Engineering, Aerospace SC Engineering GA XG807 UT WOS:A1997XG80700009 ER PT J AU Burton, WS Noor, AK AF Burton, WS Noor, AK TI Assessment of continuum models for sandwich panel honeycomb cores SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID TRANSVERSE-SHEAR AB Detailed finite element models are used for predicting the free-vibration response of infinitely long and rectangular sandwich panels. The panels considered have square-cell honeycomb core and simply supported edges. The sandwich core and face sheets are modeled by using three-dimensional solid elements and two-dimensional plate elements. The predictions of the finite element models are compared with those obtained by using higher-order sandwich theory for panels with the core replaced by an effective (equivalent) continuum. Three different approaches are used for estimating the effective material properties of the equivalent continuum layer. C1 UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA. NR 29 TC 53 Z9 57 U1 4 U2 22 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD JUN 30 PY 1997 VL 145 IS 3-4 BP 341 EP 360 DI 10.1016/S0045-7825(96)01196-6 PG 20 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA XD795 UT WOS:A1997XD79500010 ER PT J AU Patnaik, SN Coroneos, RM Hopkins, DA AF Patnaik, SN Coroneos, RM Hopkins, DA TI Dynamic animation of stress modes via the integrated force method of structural analysis SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE integrated force method; dynamic analysis and animation; stress mode shapes AB Dynamic animation of stresses and displacements, which complement each other, can be a useful tool in the analysis and design of structural components. At the present time only displacement-mode animation is available through the popular stiffness formulation. This paper attempts to complete this valuable visualization tool by augmenting stress-mode animation to the existing art. The reformulated method of forces, which in the literature is known as the Integrated Force Method(IFM), became the analyser of choice for the development of stress-mode animation because stresses are the primary unknowns of its dynamic analysis. Animation of stresses and displacements, which have been developed successfully through the IFM analyzers, is illustrated in several examples along with a brief introduction to IFM dynamic analysis. The usefulness of animation in design optimization is illustrated considering the spacer structure component of the International Space Station as an example. An overview of the integrated force method analysis code (IFM/ANALYSERS) is provided in the appendix. (C) 1997 by John Wiley & Sons, Ltd. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Patnaik, SN (reprint author), OHIO AEROSP INST,22800 CEDAR POINT RD,BROOKPARK,OH 44142, USA. NR 20 TC 5 Z9 5 U1 0 U2 1 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD JUN 30 PY 1997 VL 40 IS 12 BP 2151 EP 2169 DI 10.1002/(SICI)1097-0207(19970630)40:12<2151::AID-NME144>3.0.CO;2-H PG 19 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA XE111 UT WOS:A1997XE11100002 ER PT J AU Patnaik, SN Coroneos, RM Hopkins, DA AF Patnaik, SN Coroneos, RM Hopkins, DA TI A cascade optimization strategy for solution of difficult design problems SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE multiple optimizers; cascade; design; aircraft; air breathing engines AB A research project to evaluate comparatively ten different non-linear optimization algorithms was completed recently. A conclusion was that no single optimizer could successfully solve all the 40 structural design problems in the test-bed, even though most optimizers successfully solved at least one-third of the problems. We realized that improvements to search directions and step lengths, available in the ten optimizers compared, were not likely to alleviate the convergence difficulties. For the solution of those difficult problems we have devised an alternate approach called, the cascade optimization strategy. The strategy utilizes several optimizers, one followed by another in a specified sequence, to solve a problem. A pseudo-random dumping scheme perturbs the design variables between the optimizers. The cascade strategy has been tested out successfully in the design of supersonic and subsonic aircraft configurations and air breathing engines for high-speed civil transport applications. These problems could not be successfully solved by an individual optimizer. The cascade optimization strategy, however, generated feasible optimum solutions for both aircraft and engine problems. This paper presents the cascade strategy, solution of aircraft and engine problems along with discussions and conclusions. (C) 1997 by John Wiley & Sons, Ltd. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Patnaik, SN (reprint author), OHIO AEROSP INST,22800 CEDAR POINT RD,CLEVELAND,OH 44142, USA. NR 14 TC 14 Z9 14 U1 0 U2 1 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD JUN 30 PY 1997 VL 40 IS 12 BP 2257 EP 2266 PG 12 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA XE111 UT WOS:A1997XE11100007 ER PT J AU Chipot, C Pohorille, A AF Chipot, C Pohorille, A TI Structure and dynamics of small peptides at aqueous interfaces - A multi-nanosecond molecular dynamics study SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM LA English DT Article; Proceedings Paper CT 4th Congress of the World-Association-of-Theoretically-Oriented-Chemists (WATOC 96) CY JUL 07-12, 1996 CL JERUSALEM, ISRAEL SP World Assoc Theoret Oriented Chemists DE molecular dynamics simulations; free energy calculations; peptide folding; conformational equilibria; amphiphilic peptides; aqueous interfaces ID HISTOGRAM ANALYSIS METHOD; FREE-ENERGY CALCULATIONS; MEMBRANE-FUSION; MONTE-CARLO; SP-C; BILAYER; WATER; CONFORMATION; SIMULATION; HELICES AB The dynamical and the mechanistic aspects of peptide folding have been examined at aqueous interfaces in a series of large-scale molecular dynamics computer simulations. The conformational equilibria of the heptapeptide, made of the nonpolar L-leucine and the polar L-glutamine amino acids, having a sequence of hydrophobic periodicity of 3.6, and initially organized as an alpha-helix or a beta-strand, were investigated at the water liquid-vapor interface. The behavior of the Ac- and NHMe-blocked undecamer of poly-L-leucine in the water-hexane system, initially located on the water side of the interface in a random coil conformation, was examined over 34 ns. For comparison, conformational preferences of the prototypical terminally blocked L-leucine, L-glutamine and L-alanine single amino acids, as well as their corresponding dimers, were studied. These multinanosecond simulations shed light on three important properties of small peptides at aqueous interfaces. First, oligopeptides containing both polar and nonpolar amino acids show a clear tendency to accumulate at the interface. Second, aqueous interfaces, unlike water, appear to mediate folding, so that peptides built of leucine and glutamine readily adopt amphiphilic conformations. Third, fully nonpolar peptides become inserted into a nonpolar phase by concurrent partitioning and folding into a helical structure. A complete folding process was observed during the simulations. (C) 1997 Elsevier Science B.V. C1 UNIV CALIF SAN FRANCISCO, DEPT PHARMACEUT CHEM, SAN FRANCISCO, CA 94143 USA. RP NASA, AMES RES CTR, PLANETARY BIOL BRANCH, MS 239-4, MOFFETT FIELD, CA 94035 USA. NR 26 TC 12 Z9 12 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0166-1280 J9 J MOL STRUC-THEOCHEM JI Theochem-J. Mol. Struct. PD JUN 30 PY 1997 VL 398 BP 529 EP 535 DI 10.1016/S0166-1280(96)04999-8 PG 7 WC Chemistry, Physical SC Chemistry GA XV714 UT WOS:A1997XV71400059 ER PT J AU Akapo, SO Matyska, MT Pesek, JJ AF Akapo, SO Matyska, MT Pesek, JJ TI Retention characteristics and selected applications of cyclic siloxane-based octadecylsilyl bonded phases in reversed-phase high-performance liquid chromatography SO JOURNAL OF CHROMATOGRAPHY A LA English DT Article DE stationary phases, LC; polynuclear aromatic hydrocarbons; barbiturates; antidepressants, tricyclic ID POLYCYCLIC AROMATIC-HYDROCARBONS; STATIONARY PHASES; COLUMN SELECTIVITY; SILICA INTERMEDIATE; CHAIN-LENGTH; SURFACE; PACKINGS; SORBENTS; HPLC AB Hexamethylcyclotrisiloxane- and octaphenylcyclotetrasiloxane-based octadecyl bonded phases are prepared and evaluated for liquid chromatographic separation of various compounds. As revealed by the retention data of the selected solutes, the hexamethylcyclotrisiloxane-octadecyl phase exhibits better chromatographic performance than octaphenylcyclotetrasiloxane-octadecyl phase presumably due to greater accessibility of the bonded alkyl groups on the siloxane skeleton for interactions. The peak asymmetry values showed that solute retention on the hexamethylcyclotrisiloxane-octadecyl phase is essentially controlled by dispersive interactions. The retention characteristics of the cyclicsiloxane-based phases were compared to those obtained on a commercial C-18 column and an octadecyl phase synthesized through a silanization-hydrosilation addition process, While the two phases gave baseline separation of polycyclic aromatic hydrocarbons and barbiturates, the hexamethylcyclotrisiloxane-octadecyl phase allowed fast and efficient separation of a four-component standard mixture of tricyclic antidepressants. C1 SAN JOSE STATE UNIV,DEPT CHEM,SAN JOSE,CA 95192. RP Akapo, SO (reprint author), NASA,AMES RES CTR,SETI INST,EXOBIOL BRANCH,MAIL STOP 239-12,MOFFETT FIELD,CA 94035, USA. NR 33 TC 10 Z9 10 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0021-9673 J9 J CHROMATOGR A JI J. Chromatogr. A PD JUN 27 PY 1997 VL 773 IS 1-2 BP 53 EP 63 DI 10.1016/S0021-9673(97)00241-0 PG 11 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA XJ881 UT WOS:A1997XJ88100005 ER PT J AU Considine, G Curry, JA Wielicki, B AF Considine, G Curry, JA Wielicki, B TI Modeling cloud fraction and horizontal variability in marine boundary layer clouds SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODELS; STRATOCUMULUS CLOUDS; SCALE CONDENSATION; DIURNAL-VARIATION; PARAMETERIZATION; ALBEDO; COVER; WATER AB Boundary layer clouds play an important role in the global energy budget. The radiative properties of these clouds depend upon the cloud fraction and the horizontal variability of liquid water path within patches of unbroken cloud. A simple statistical model for describing the probability distributions of liquid water path and cloud fraction in low clouds has been developed. The model is shown to reproduce realistically the diurnal cycle in the cloud fraction and horizontal inhomogeneity of marine stratocumulus. Further, the model produces realistic statistics for the horizontal variability of liquid water path within boundary layer clouds. The modeled distributions of cloud liquid water path depend upon the cloud fraction, similar to Landsat retrievals. The results are discussed in the context of improving the representation of boundary layer clouds in large-scale models. C1 UNIV COLORADO, DEPT AEROSP ENGN, BOULDER, CO 80302 USA. RP NASA, LANGLEY RES CTR, MS 401B, HAMPTON, VA 23681 USA. NR 33 TC 41 Z9 42 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 27 PY 1997 VL 102 IS D12 BP 13517 EP 13525 DI 10.1029/97JD00261 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XH196 UT WOS:A1997XH19600011 ER PT J AU Mishchenko, MI Travis, LD AF Mishchenko, MI Travis, LD TI Satellite retrieval of aerosol properties over the ocean using measurements of reflected sunlight: Effect of instrumental errors and aerosol absorption SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AVHRR DATA AB A major task of several currently existing and planned satellite instruments is to provide accurate global monitoring of the distribution and properties of tropospheric aerosols using radiance and/or polarization measurements of the reflected sunlight. We use advanced computer simulations of radiative transfer in a realistic atmosphere-ocean model at a wavelength of 865 nm to examine the sensitivity of several widely used and recently developed retrieval techniques to aerosol absorption and instrumental errors. We assume that nonabsorbing (e.g., sulfate) and strongly absorbing (e.g., soot) aerosol components are mixed externally and that the scattering matrix of the mixture is that of the nonabsorbing component, while the only effect of the absorbing component is to reduce the single-scattering albedo. We show that neither algorithms using multiple-viewing-angle radiance measurements nor analogous polarization measurements or their combination can retrieve the aerosol single-scattering albedo with sufficient accuracy. However, accurate retrievals of the aerosol optical thickness, refractive index, and effective radius using polarization measurements do not require a precise knowledge of the aerosol single-scattering albedo, whereas potential uncertainties in the single-scattering albedo can strongly influence the accuracy of aerosol retrievals based on intensity measurements alone. Another important conclusion is that the accuracy of aerosol retrievals based on intensity and/or polarization measurements of the reflected sunlight is strongly corrupted by instrumental errors. We show that nonzero measurement errors can result in the best fit of model computations to measurement data being obtained with aerosol parameters far different from the actual ones. Our results emphasize the importance of accurate and stable instrumental calibration and suggest that the absolute radiometric uncertainty should be constrained to about +/-4% or better and the absolute polarization accuracy should be kept to within +/-0.2%. However, less accurate polarization measurements can still be used to estimate the aerosol refractive index and effective radius with reasonable accuracy. The results of our previous paper [Mishchenko and Travis, 1997] and this one demonstrate the limited capabilities of aerosol retrieval techniques based on intensity measurements alone and suggest that high-precision spaceborne polarimetry may potentially be the only way of retrieving aerosol characteristics with accuracy needed for long-term monitoring of global climate forcings and feedbacks. C1 SUNY STONY BROOK, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RP Mishchenko, MI (reprint author), NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012 NR 30 TC 49 Z9 50 U1 0 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 27 PY 1997 VL 102 IS D12 BP 13543 EP 13553 DI 10.1029/97JD01124 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XH196 UT WOS:A1997XH19600014 ER PT J AU Zhu, JX Li, M Rogers, R Meyer, W Ottewill, RH Russell, WB Chaikin, PM AF Zhu, JX Li, M Rogers, R Meyer, W Ottewill, RH Russell, WB Chaikin, PM TI Crystallization of hard-sphere colloids in microgravity SO NATURE LA English DT Article ID COUPLING-THEORY ANALYSIS; GLASS-TRANSITION; CRYSTALS; GROWTH AB The structure of, and transitions between, liquids, crystals and glasses have commonly been studied with the hard-sphere model(1-5), in which the atoms are modelled as spheres that interact only through an infinite repulsion on contact. Suspensions of uniform colloidal polymer particles are good approximations to hard spheres(6-11), and so provide an experimental model system for investigating hard-sphere phases. They display a crystallization transition driven by entropy alone. Because the particles are much larger than atoms, and the crystals are weakly bound, gravity plays a significant role in the formation and structure of these colloidal crystals. Here we report the results of microgravity experiments performed on the Space Shuttle Columbia to elucidate the effects of gravity on colloidal crystallization. Whereas in normal gravity colloidal crystals grown just above the volume fraction at melting show a mixture of random stacking of hexagonally close-packed planes (r.h.c.p.) and face-centred cubic (f.c.c.) packing if allowed time to settle(7,8), those in microgravity exhibit the r.h.c.p. structure alone, suggesting that the f.c.c. component may be induced by gravity-induced stresses. We also see dendritic growth instabilities that are not evident in normal gravity, presumably because they are disrupted by shear-induced stresses as the crystals settle under gravity. Finally, glassy samples at high volume fraction which fail to crystallize after more than a year on Earth crystallize fully in less than two weeks in microgravity. Clearly gravity masks or alters some of the intrinsic aspects of colloidal crystallization. C1 PRINCETON UNIV, DEPT PHYS, PRINCETON, NJ 08544 USA. PRINCETON UNIV, DEPT CHEM ENGN, PRINCETON, NJ 08544 USA. NASA, LEWIS RES CTR, CLEVELAND, OH 44136 USA. UNIV BRISTOL, SCH CHEM, BRISTOL BS8 1TS, AVON, ENGLAND. NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. NR 25 TC 321 Z9 331 U1 8 U2 117 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUN 26 PY 1997 VL 387 IS 6636 BP 883 EP 885 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XG416 UT WOS:A1997XG41600045 ER PT J AU Haberle, RM Barnes, JR Murphy, JR Joshi, MM Schaeffer, J AF Haberle, RM Barnes, JR Murphy, JR Joshi, MM Schaeffer, J TI Meteorological predictions for the Mars Pathfinder lander SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GENERAL-CIRCULATION MODEL; ATMOSPHERIC DYNAMICS; MARTIAN ATMOSPHERE; SIMULATIONS; PRESSURE AB The NASA Ames Mars general circulation and boundary layer models are used as guides to forecast the meteorological environment of the Pathfinder lander site. Based on these models we predict that for a Viking-like atmospheric dust loading, significant vertical wave structure will be seen in the entry temperature profile above 50 km. Temperatures in this region will oscillate by up to 30 K about a mean value of similar to 145 K. At the surface during the primary mission, winds are expected to rotate clockwise during the day at 2-10 m/s, while air temperatures will range from overnight lows in the mid 180s K to daytime highs near 250 K. If the atmosphere is dust free at arrival, as appears possible from recent Earth-based observations, then we expect a cooler upper atmosphere (130-140 K) with less wave structure during entry, weaker surface winds, and a slight increase in near surface air temperatures. Regardless of dust loading, we predict that the daily averaged surface pressure will reach its annual minimum about 15-20 sols after landing. During the extended mission, the basic character of Pathfinder's meteorology will change from that of a summertime quasi-regular regime to that of a wintertime highly variable regime. This transition is predicted to occur by sol 60. The strongest winds (30 m/s) and lowest daily-averaged temperatures (similar to 200 K) will be recorded during early winter. C1 OREGON STATE UNIV,DEPT OCEAN & ATMOSPHER SCI,CORVALLIS,OR. SAN JOSE STATE UNIV FDN,SAN JOSE,CA 95192. STERLING SOFTWARE INC,PALO ALTO,CA. RP Haberle, RM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035, USA. RI Joshi, Manoj/C-1795-2008 OI Joshi, Manoj/0000-0002-2948-2811 NR 21 TC 18 Z9 18 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUN 25 PY 1997 VL 102 IS E6 BP 13301 EP 13311 DI 10.1029/97JE01334 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XG454 UT WOS:A1997XG45400001 ER PT J AU Krasnopolsky, VA AF Krasnopolsky, VA TI Photochemical mapping of Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARTIAN ATMOSPHERE; WATER-VAPOR; ECHELLE SPECTROGRAPH; GLOBAL DISTRIBUTION; OZONE; CO; BEHAVIOR; ABUNDANCE; CYCLE; ISM AB The O-2((1) Delta(g)) dayglow produced at 1.27 mu m by ozone photolysis is ideal for ground-based mapping of high-altitude ozone using long-slit high-resolution spectrographs like CSHELL, CGS4, and Phoenix. Coupled to mapping H2O at 1.13 mu m and CO and CO2 at 1.57 mu with the same instruments, it is possible to map hygropause using the rotational temperatures of CO2 and O-2((1) Delta(g)). Strong seasonal variations of hygropause (from 10 to 40 km) and associated variations of high-altitude ozone (by an order of magnitude above 20 km) are important novel concepts which may be studied in detail by these observations. Showing even greater promise is the combination of O-2((1) Delta(g)) dayglow mapping with mapping of water abundance and temperature profiles by the thermal emission spectrometer onboard the Mars Global Surveyor. A list of problems which may be solved or improved upon by these observations is included. C1 CATHOLIC UNIV AMER,DEPT PHYS,WASHINGTON,DC 20064. RP Krasnopolsky, VA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 693,GREENBELT,MD 20771, USA. RI Krasnopolsky, Vladimir/L-5085-2013 NR 39 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUN 25 PY 1997 VL 102 IS E6 BP 13313 EP 13320 DI 10.1029/97JE01085 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XG454 UT WOS:A1997XG45400002 ER PT J AU Glinski, RJ Schulz, SA Nuth, JA AF Glinski, RJ Schulz, SA Nuth, JA TI Non-Boltzmann vibrational distributions in homonuclear diatomic molecules and ions SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE line, formation; molecular processes; ISM, molecules; infrared, ISM, lines and bands ID INTER-STELLAR CLOUDS; GAS-PHASE CHEMISTRY; INTERSTELLAR CLOUDS; RATE COEFFICIENTS; ZETA-OPHIUCHI; EMISSION; HYDROGEN; H-2; STATES; MODEL AB We investigate the fates and population densities of the vibrationally excited homonuclear diatomic molecules H-2/H-2(+), C-2/C-2(+) and O-2/O-2(+) in interstellar conditions using photochemical kinetic models. We find that the population distribution of vibrationally excited H-2(+) resembles the nascent distribution from the cosmic ray ionization of H-2 under several cloud conditions. We predict that density of H-2(+)(v) could exceed that of H-2(v) under certain cloud conditions. Based on this we present a synthetic spectrum of the quadrupole-allowed infrared emission from H-2(+)(v). Our results for H-2(v) are in accord with those of previous workers. The vibrationally excited states of C-2 and O-2 show abundances on the order of 10(-4) of the ground state. We emphasize that these populations are controlled by reaction dynamics and photochemical kinetics, and do not resemble those of the local thermodynamic equilibrium (LTE), Preliminary models of the C-2(+)(v) and O-2(+)(v) chemistry show that the vibrational distributions will somewhat resemble the nascent distributions of the reactions which create them. Further experimental or theoretical studies of the dynamics of these reactions are necessary before quantitative predictions can be made. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTROCHEM BRANCH,GREENBELT,MD 20771. RP Glinski, RJ (reprint author), TENNESSEE TECHNOL UNIV,DEPT CHEM,COOKEVILLE,TN 38505, USA. RI Nuth, Joseph/E-7085-2012 NR 32 TC 6 Z9 6 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD JUN 21 PY 1997 VL 288 IS 2 BP 286 EP 294 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XH567 UT WOS:A1997XH56700005 ER PT J AU Skinner, CJ Meixner, M Bode, MF Davis, RJ Dougherty, SM Drake, SA Arens, JF Jernigan, JG AF Skinner, CJ Meixner, M Bode, MF Davis, RJ Dougherty, SM Drake, SA Arens, JF Jernigan, JG TI Circumstellar environments .5. The asymmetric chromosphere and dust shell of alpha Orionis SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars, chromospheres; circumstellar matter; stars, individual, alpha Ori; supergiants; infrared, stars ID EVOLVED STARS; MASS-LOSS; EMISSION; RESOLUTION; INTERFEROMETRY; SUPERGIANTS; ENVELOPES; GRAINS; MIRA AB We report new mid-infrared and radio images of the M supergiant alpha Orionis. The radio images, taken with MERLIN1 and the Very Large Array, resolve the chromosphere of the star at a wavelength of 6 cm, showing that the radio-emitting region has between two and three times the diameter of the optical photosphere. The infrared images, taken at the UK Infrared Telescope (UKIRT) using the Berkeley Infrared Camera, show that the dust shell is resolved, Images taken one year apart show great changes in morphology, which suggests that the dust shell is being asymmetrically illuminated by a stellar radiation field that is strongly affected by the presence and evolution of spots on the stellar surface. We present a new model of the circumstellar environment of the star, which fits the infrared and radio images and the spectral energy distribution (SED), and is consistent with recently reported Hubble Space Telescope observations. The chromospheric structure is determined quantitatively and the inner dust shell structure qualitatively with this model. We find that the inner radius of the dust shell is approximately 0.5 arcsec, which disagrees with a number of interferometric measurements that have resulted in an inner radius close to 1.0 arcsec, We are unable to explain this differenc. C1 LAWRENCE LIVERMORE NATL LAB,INST GEOPHYS & PLANETARY PHYS,LIVERMORE,CA 94551. UNIV CALGARY,CALGARY,AB T2N 1N4,CANADA. LIVERPOOL JOHN MOORES UNIV,SCH ENGN ELECT & PHYS,ASTROPHYS GRP,LIVERPOOL L3 3AF,MERSEYSIDE,ENGLAND. UNIV ILLINOIS,DEPT AGRON,URBANA,IL 61801. NUFFIELD RADIO ASTRON OBSERV LABS,MACCLESFIELD SK11 9DL,CHESHIRE,ENGLAND. NASA,GODDARD SPACE FLIGHT CTR,HEASARC,GREENBELT,MD 20771. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. NR 35 TC 25 Z9 25 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 JUN 21 PY 1997 VL 288 IS 2 BP 295 EP 306 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XH567 UT WOS:A1997XH56700006 ER PT J AU Peskov, V Ramsey, BD Fonte, P AF Peskov, V Ramsey, BD Fonte, P TI Surface streamer breakdown mechanisms in microstrip gas counters SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 4th International Conference on Position-Sensitive Detectors CY SEP 09-13, 1996 CL MANCHESTER, ENGLAND ID OPERATION; CHAMBER AB We have studied breakdown mechanisms in MSGCs. For comparison, ''microstrip detectors'' without dielectric substrates were also tested. We found that detectors without substrates can always operate at gas gains 5-10 times higher than those with substrates, and that these higher gains are limited by self-quenched streamers. In the case of microstrip detectors with substrates, streamers also occur, but have a very narrow (in voltage) self-quench region and then transit rapidly to a ''gliding'' discharge. We have tested new geometries of MSGC which allow high gains (> 10(5)) to be reached. C1 UNIV COIMBRA,LIP,COIMBRA,PORTUGAL. ECOLE SUPER ENGN,COIMBRA,PORTUGAL. RP Peskov, V (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. RI Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 15 TC 35 Z9 35 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 21 PY 1997 VL 392 IS 1-3 BP 89 EP 93 DI 10.1016/S0168-9002(97)00224-6 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA XU981 UT WOS:A1997XU98100017 ER PT J AU Zeballos, EC Crotty, I Hatzifotiadou, D Valverde, JL Williams, MCS Zichichi, A Fonte, P Peskov, V AF Zeballos, EC Crotty, I Hatzifotiadou, D Valverde, JL Williams, MCS Zichichi, A Fonte, P Peskov, V TI Resistive plate chambers with secondary electron emitters and microstrip readout SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 4th International Conference on Position-Sensitive Detectors CY SEP 09-13, 1996 CL MANCHESTER, ENGLAND ID PHOTOCATHODES; DETECTORS; EMISSION AB We describe our attempt to develop Resistive Plate Chambers (RPCs). One study involves the use of secondary electron emitters that consist of porous photosensitive materials (CsI, diethylferocenil-mercury, SbCs and others) deposited on a cathode; this enhances efficiency, thus allowing the use of light, non-flammable gas mixtures. The other study concerns the operation of an RPC with a narrow strip readout - the ''microstrip RPC''. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. CERN,CH-1211 GENEVA 23,SWITZERLAND. UNIV COIMBRA,LIP,COIMBRA,PORTUGAL. RI Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 15 TC 13 Z9 14 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 21 PY 1997 VL 392 IS 1-3 BP 150 EP 154 DI 10.1016/S0168-9002(97)00256-8 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA XU981 UT WOS:A1997XU98100030 ER PT J AU Wielaard, DJ Mishchenko, MI Macke, A Carlson, BE AF Wielaard, DJ Mishchenko, MI Macke, A Carlson, BE TI Improved T-matrix computations for large, nonabsorbing and weakly absorbing nonspherical particles and comparison with geometrical-optics approximation SO APPLIED OPTICS LA English DT Article DE light scattering; nonspherical particles; T-matrix method; geometrical optics approximation ID AXIALLY-SYMMETRICAL PARTICLES; LIGHT-SCATTERING; DIELECTRIC OBJECTS; SINGLE-SCATTERING; CIRRUS; ICE; EXTINCTION; REGIONS; CLOUD AB We show that the use of a matrix inversion scheme based oil a special lower triangular-upper triangular factorization rather than on the standard Gaussian elimination significantly improves the numerical stability of T-matrix computations for nonabsorbing and weakly absorbing nonspherical particles. As a result, the maximum convergent size parameter for particles with small or zero absorption can increase by a factor of several and can exceed 100. We describe an improved scheme for evaluating Clebsch-Gordon coefficients with large quantum numbers, which allowed us to extend the analytical orientational averaging method developed by Mishchenko [J. Opt. Sec. Am. A 8, 871 (1991)] to larger size parameters. Comparisons of T-matrix and geometrical optics computations for large, randomly oriented spheroids and finite circular cylinders show that the applicability range of the ray-tracing approximation depends on the imaginary part of the refractive index and is different for different elements of the scattering matrix. (C) 1997 Optical Society of America. C1 COLUMBIA UNIV, DEPT APPL PHYS, NEW YORK, NY 10025 USA. SUNY STONY BROOK, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Carlson, Barbara/D-8319-2012; Mishchenko, Michael/D-4426-2012 NR 47 TC 74 Z9 76 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD JUN 20 PY 1997 VL 36 IS 18 BP 4305 EP 4313 DI 10.1364/AO.36.004305 PG 9 WC Optics SC Optics GA XE301 UT WOS:A1997XE30100038 PM 18253460 ER PT J AU Roettiger, K Stone, JM Mushotzky, RF AF Roettiger, K Stone, JM Mushotzky, RF TI Systematic errors in the Hubble constant based upon measurement of the Sunyaev-Zeldovich effect SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, theory; distance scale; galaxies, clusters, general galaxies, intergalactic medium; hydrodynamics; methods, numerical ID X-RAY-PROPERTIES; GALAXY CLUSTERS; COMA CLUSTER; IA SUPERNOVAE; DISTANCE; SIMULATION; VELOCITY; FIELDS; A2256; MASS AB Values of the Hubble constant reported to date that are based upon measurement of the Sunyaev-Zeldovich (SZ) effect in clusters of galaxies are systematically lower than those derived by other methods (e.g., Cepheid variable stars or the Tully-Fisher relation). We investigate the possibility that systematic errors may be introduced into the analysis by the generally adopted assumptions that observed clusters are in hydrostatic equilibrium, are spherically symmetric, and are isothermal. We construct self-consistent theoretical models of merging clusters of galaxies, using hydrodynamic/N-body simulations. We then compute the magnitude of H-0 derived from the SZ effect at different times and at different projection angles, both from first principles and by applying each of the standard assumptions used in the interpretation of observations. Our results indicate that the assumption of isothermality in the evolving clusters can result in H-0 being underestimated by 10%-30%, depending upon both epoch and projection angle. Moreover, use of the projected, emission-weighted temperature profile under the assumption of spherical symmetry does not significantly improve the situation except in the case of more extreme mergers (i.e., those involving relatively gas-rich subclusters). Although less significant, we find that asphericity in the gas density can also result in a 15% error in H-0. If the cluster is prolate (as is generally the case for on-axis, or nearly on-axis, mergers) and viewed along its major axis, H-0 will be systematically underestimated. More extreme off-axis mergers may result in oblate merger remnants, which, when viewed nearly face-on, may result in an overestimation of H-0. A similar effect is noted when viewing a prolate distribution along a line of sight that is nearly perpendicular to its major axis. In both cases the potential overestimation occurs only when the remnant is viewed within 15 degrees-30 degrees of face-on. Bulk gas motions and the kinematic SZ effect do not appear to be significant except for a brief period during the very early stages of a merger. Our study shows that the most meaningful SZ measurement will be accompanied by high-resolution temperature data and a detailed dynamical modeling of the observed system. In lieu of this, a large sample selected to avoid dynamically evolving systems is preferred. C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 55 TC 29 Z9 29 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 JUN 20 PY 1997 VL 482 IS 2 BP 588 EP 603 DI 10.1086/304176 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF541 UT WOS:A1997XF54100003 ER PT J AU Yi, SY Demarque, P Kim, YC AF Yi, SY Demarque, P Kim, YC TI On the ultraviolet-bright phase of metal-rich horizontal-branch stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, elliptical and lenticular, cD; galaxies, evolution galaxies, stellar content; stars, evolution; stars, horizontal-branch; ultraviolet, galaxies ID EARLY-TYPE GALAXIES; ELLIPTIC GALAXIES; EVOLUTIONARY SEQUENCES; METALLICITY; MODELS; SOLAR; PHOTOMETRY; RADIATION; NGC-6791; ORIGIN AB We consider the origin of the UV-bright phase of metal-rich helium-burning stars, the slow blue phase (SBP) that was predicted by various earlier works. Based on improved physics including OPAL opacities, which is the same physics that was used in the construction of the new Yale Isochrones, we confirm the existence of the SBP. In addition to our grid of evolutionary tracks, we provide an analytical understanding of the main characteristics of the SBP phenomenon. The SBP is slow because it is a dow-evolving, helium-shell-burning phase that is analogous to the early asymptotic giant branch phase. The SBP of a more metal-rich star is slower than a metal-poor counterpart if they have the same T-eff because a more metal-rich helium-burning star has a smaller mass than a metal-poor one and because lifetime increases as mass decreases. Metal-rich helium-burning stars easily become hot because the luminosity from the hydrogen-burning shell is extremely sensitive to the mean molecular weight mu, whereas the luminosity from the helium-burning core is not. Under the assumption of a positive Delta Y/Delta Z, helium abundance plays the most important role in governing mu, and thus Dorman et al. found that the SBP occurs only when Y greater than or similar to 0.4 when Delta Y/Delta Z greater than or similar to 0. We suggest that the SBP phenomenon is a major cause of the UV upturn phenomenon in giant elliptical galaxies, as will be shown in subsequent papers. The new HB tracks can be retrieved from S. Y.'s web site http://shemesh.gsfc.nasa.gov/astronomy.html. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Yi, SY (reprint author), YALE UNIV,DEPT ASTRON,POB 208101,NEW HAVEN,CT 06520, USA. NR 35 TC 63 Z9 63 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 JUN 20 PY 1997 VL 482 IS 2 BP 677 EP 684 DI 10.1086/304192 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF541 UT WOS:A1997XF54100010 ER PT J AU Brown, TM Ferguson, HC Davidsen, AF Dorman, B AF Brown, TM Ferguson, HC Davidsen, AF Dorman, B TI A far-ultraviolet analysis of the stellar populations in six elliptical and S0 galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, abundances; galaxies, elliptical and lenticular, cD; galaxies, evolution galaxies, stellar content; ultraviolet, galaxies ID HORIZONTAL-BRANCH STARS; HOT B-SUBDWARFS; PLANETARY-NEBULAE; GLOBULAR-CLUSTERS; STANDARD CANDLES; EVOLUTIONARY SEQUENCES; TELESCOPE OBSERVATIONS; RADIATIVE OPACITIES; HIGH-METALLICITY; MODELS AB We have analyzed the far-ultraviolet (FUV) spectra of six elliptical and S0 galaxies in order to characterize the stellar population that produces the ultraviolet flux in these galaxies. The spectra were obtained using the Hopkins Ultraviolet Telescope (HUT) during the Astro-2 mission aboard the Space Shuttle Endeavour in 1995 March and cover the spectral range from 820 to 1840 Angstrom with a resolution of 3 Angstrom. These data, together with the spectra of two galaxies observed with HUT on the Astro-1 mission, represent the only FUV spectra of early-type galaxies that extend to the Lyman limit at 912 Angstrom and therefore include the ''turnover'' in the spectral energy distribution below Ly alpha. Using an extensive new grid of LTE and non-LTE synthetic spectra that match the HUT resolution and cover the relevant parameter space of temperature and gravity, we have constructed synthetic spectral energy distributions by integrating over various predicted stellar evolutionary tracks for horizontal-branch stars and their progeny. When the computed models are compared with the HUT data, we find that models with supersolar metal abundances and helium best reproduce the flux across the entire HUT wavelength range, while those with subsolar Z and Y fit less well, partly because of a significant flux deficit shortward of 970 Angstrom in the models. High-Z models are preferred because the contribution from the later, hotter, post-HE evolutionary stages makes up a higher fraction of the sub-Ly alpha flux in these tracks. We find that AGB-Manque evolution is required in all of the fits to the HUT spectra, which suggests that all of the galaxies have some subdwarf B-star population. At any Z and Y, the model spectra that best match the HUT flux are dominated by stars evolving from a narrow range of envelope mass on the blue end of the horizontal branch. The Astro-1 and Astro-2 data are also the first with the resolution and signal-to-noise ratio needed to detect and measure absorption lines in the FUV spectra of elliptical galaxies, which allows a direct estimate of the abundances in the atmospheres of the stars that produce the UV flux. We find that most absorption features in the spectra are consistent with Z = 0.1 Z., significantly lower than the abundances implied by the best-fitting spectral energy distributions. However, given the strong observational and theoretical evidence for diffusion processes in the atmospheres of evolved stars, the observed atmospheric abundances may not reflect the interior abundances in the population producing the ultraviolet flux in elliptical galaxies. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Brown, TM (reprint author), JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,CHARLES & 34TH ST,BALTIMORE,MD 21218, USA. NR 58 TC 115 Z9 115 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1997 VL 482 IS 2 BP 685 EP 707 DI 10.1086/304187 PN 1 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF541 UT WOS:A1997XF54100011 ER PT J AU Nelson, RP Langer, WD AF Nelson, RP Langer, WD TI The dynamics of low-mass molecular clouds in external radiation fields SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; ISM, clouds; ISM, globules; molecular processes; radiative transfer ID INTER-STELLAR CLOUDS; SMOOTHED PARTICLE HYDRODYNAMICS; ELONGATED CYLINDRICAL CLOUDS; GAS-PHASE CHEMISTRY; SMALL DARK CLOUDS; STAR-FORMATION; DENSE CORES; INTERSTELLAR CLOUDS; BOK GLOBULES; FRAGMENTATION AB We present the results of three-dimensional hydrodynamic calculations of the evolution of low-mass molecular clouds, performed using the numerical method of smoothed particle hydrodynamics. The clouds that we consider are subject to heating by the interstellar radiation held and by cosmic rays. They are able to cool through molecular line emission (primarily CO and its isotopes) and by emission from the fine structure lines of C+ and O I. We also include gas-dust thermal coupling in our models. A simplified chemical network is incorporated that models the conversion between C+ and CO, where the chemical balance is determined by the local flux of dissociating radiation. Calculations are performed for initially uniform density clouds, with masses in the range M=100-400 M., sizes in the range R=1.7-3.4 pc, with the initial number density in all cases being n=100 cm(-3). We performed calculations for clouds with different geometrical shapes: spherical, prolate, and oblate. Additionally, we considered the effects of an anisotropic radiation held on the cloud evolution. These are the main results: 1. Clouds that are initially Jeans stable are able to collapse because of the coupling between the dynamical and thermal evolution. This collapse results in core-halo structure where we have a cold, dense, CO core surrounded by a warmer, tenuous, C+ envelope. 2. A pressure gradient is set up in the clouds by the attenuation of the UV radiation field. When a cloud is anisotropically heated, this pressure gradient leads to the formation of a highly flattened cloud core when it collapses. 3. The combined thermal and dynamical evolution of the prolate and oblate clouds leads to the formation of highly elongated or flattened structures. These structures are able to fragment, typically with four to eight subcondensations forming, which have masses in the range 3-7.5 M.. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 57 TC 67 Z9 67 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1997 VL 482 IS 2 BP 796 EP 826 DI 10.1086/304167 PN 1 PG 31 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF541 UT WOS:A1997XF54100021 ER PT J AU Canuto, VM AF Canuto, VM TI Compressible turbulence SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; turbulence ID REYNOLDS STRESS APPROACH; LARGE-EDDY SIMULATION; CONVECTION; FLOWS; GRAVITY; LAYERS AB We present a model to treat fully compressible, nonlocal, time-dependent turbulent convection in the presence of large-scale hows and arbitrary density stratification. The problem is of interest, for example, in stellar pulsation problems, especially since accurate helioseismological data are now available, as well as in accretion disks. Owing to the difficulties in formulating an analytical model, it is not surprising that most of the work has gone into numerical simulations. At present, there are three analytical models: one by the author, which leads to a rather complicated set of equations; one by Yoshizawa; and one by Xiong. The latter two use a Reynolds stress model together with phenomenological relations with adjustable parameters whose determination on the basis of terrestrial flows does not guarantee that they may be extrapolated to astrophysical flows. Moreover, all third-order moments representing nonlocality are taken to be of the down gradient form (which in the case of the planetary boundary layer yields incorrect results). In addition, correlations among pressure, temperature, and velocities are often neglected or treated as in the incompressible case. To avoid phenomenological relations, we derive the full set of dynamic, time-dependent, nonlocal equations to describe all mean variables, second- and third-order moments. Closures are carried out at the fourth order following standard procedures in turbulence modeling. The equations are collected in an Appendix. Some of the novelties of the treatment are (1) new flux conservation law that includes the large-scale flow, (2) increase of the rate of dissipation of turbulent kinetic energy owing to compressibility and thus (3) a smaller overshooting, and (4) a new source of mean temperature due to compressibility; moreover, contrary to some phenomenological suggestions, the adiabatic temperature gradient depends only on the thermal pressure, while in the equation for the large-scale how, the physical pressure is the sum of thermal plus turbulent pressure. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 35 TC 52 Z9 52 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1997 VL 482 IS 2 BP 827 EP 851 DI 10.1086/304175 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF541 UT WOS:A1997XF54100022 ER PT J AU Falconer, DA Davila, JM Thomas, RJ AF Falconer, DA Davila, JM Thomas, RJ TI Relative elemental abundances of the quiet solar corona as determined by SERTS SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, abundances; Sun, corona; UV radiation ID ENERGETIC PARTICLES; PLASMA; FLARE; IRON; NEON; ATMOSPHERE; OXYGEN AB Intensities of extreme-ultraviolet (EUV) spectral lines were measured as a function of radius off the solar limb by two flights (1989 May 5 and 1991 May 7) of the Solar Extreme-ultraviolet Rocket Telescope and Spectrograph (SERTS) for three quiet solar regions. The line-ratio density, line-ratio temperature, and emission measure were determined. The relative abundances of silicon, aluminum, and chromium to iron were determined. Results agreed with standard coronal relative elemental abundances for one observation, but did not agree for the other, in which aluminum was overabundant. C1 UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. NR 36 TC 8 Z9 8 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 JUN 20 PY 1997 VL 482 IS 2 BP 1050 EP 1064 DI 10.1086/304156 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF541 UT WOS:A1997XF54100042 ER PT J AU Charnley, SB Tielens, AGGM Rodgers, SD AF Charnley, SB Tielens, AGGM Rodgers, SD TI Deuterated methanol in the Orion compact ridge SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, abundances; ISM, clouds; ISM, molecules; molecular processes ID DENSE INTERSTELLAR CLOUDS; GRAIN SURFACE-CHEMISTRY; MOLECULAR CLOUDS; HOT CORES; SOLID CO; FORMALDEHYDE; DESORPTION; AMMONIA; OMC-1 AB We have investigated the chemistry of hot cores containing methanol, formaldehyde, and their deuterated forms. We have computed the D fractionation ratios attainable by the addition of H and D atoms to CO on cold grain surfaces. We can easily reproduce the observed HDCO/H2CO and D2CO/H2CO ratios but find that, as there is an additional path to CH2DOH, the CH2DOH/CH3OD ratio is typically 3. This result is in conflict with the conclusion of Jacq et al. that the observed gas-phase CH2DOH/CH3OD ratio of approximate to 1.1-1.5 in the Orion Compact Ridge source is consistent with their production in grain mantles. We show that, when these mantles are evaporated, the CH2DOH/CH3OD ratio can be altered by gas-phase reactions that preferentially form CH3OD via reaction of H2DO+ with CH3OH. We find that an unrealistically high HDO/H2O ratio of approximate to 0.1 is necessary to drive the CH2DOH/CH3OD ratio to within the observed range. Before concluding that the observed gas-phase CH2DOH/CH3OD ratio is inconsistent with these grain-surface reactions, we recommend that more accurate determinations of this ratio be made in the Compact Ridge and in other hot cores. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. UNIV MANCHESTER,DEPT PHYS,MANCHESTER M60 1QD,LANCS,ENGLAND. RP Charnley, SB (reprint author), UNIV CALIF BERKELEY,DEPT ASTRON,601 CAMPBELL HALL,BERKELEY,CA 94720, USA. RI Charnley, Steven/C-9538-2012 NR 38 TC 190 Z9 190 U1 0 U2 9 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1997 VL 482 IS 2 BP L203 EP L206 DI 10.1086/310697 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF548 UT WOS:A1997XF54800022 ER PT J AU Kormendy, J Bender, R Magorrian, J Tremaine, S Gebhardt, K Richstone, D Dressler, A Faber, SM Grillmair, C Lauer, TR AF Kormendy, J Bender, R Magorrian, J Tremaine, S Gebhardt, K Richstone, D Dressler, A Faber, SM Grillmair, C Lauer, TR TI Spectroscopic evidence for a supermassive black hole in NGC 4486B SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; galaxies, individual (NGC 4486B); galaxies, kinematics and dynamics; galaxies, nuclei ID TO-LIGHT RATIOS; VELOCITY DISPERSIONS; ELLIPTICAL GALAXIES; M87; M31; NUCLEUS; KINEMATICS; MODELS; CORE; DISK AB The stellar kinematics of the low-luminosity elliptical galaxy NGC 4486B have been measured in seeing sigma* = 0.'' 22 with the Canada-France-Hawaii Telescope and Subarcsecond Imaging Spectrograph. Lauer and collaborators have shown that NGC 4486B is similar to M31 in having a double nucleus. Here we show that it also resembles M31 in its kinematics. Like M31, NGC 4486B rotates fairly rapidly near the center(V = 76 +/- 7 km s(-1) at 0.'' 6) but more slowly farther out (V similar or equal to 20 +/- 6 km s(-1) at r similar or equal to 4 ''). Also, the velocity dispersion gradient is very steep: a increases from 116 +/- 6 km s(-1) at r = 2 ''-6 '' to sigma = 281 +/- 11 km s(-1) at the center. This is much higher than expected for an elliptical galaxy of absolute magnitude M-B similar or equal to -16.8: even more than M31, NGC 4486B is far above the scatter in the Faber-Jackson correlation between a and bulge luminosity. Therefore, the King core mass-to-light ratio, M/L-V similar or equal to 20, is unusually high compared with normal values for old stellar populations (M/L-V = 4 +/- 1 at M-B similar or equal to -17). We construct simple dynamical models with isotropic velocity dispersions and show that they reproduce black hole (BH) masses derived by more detailed methods. We also fit axisymmetric, three-integral models. Isotropic models imply that NGC 4486B contains a central dark object, probably a BH, of mass M. = 6(-2)(+3) x 10(8) M.. However, anisotropic models fit the data without a BH if the ratio of radial to azimuthal dispersions is similar to 2 at r similar or equal to 1 ''. Therefore, this is a less strong BH detection than the ones in M31, M32, and NGC 3115. A dark mass of 6 x 10(8) M. is similar to 9% of the mass M-bulge in stars; even if M. is somewhat smaller than the isotropic value, M./M-bulge is likely to be unusually large. Double nuclei are a puzzle because the dynamical friction timescales for self-gravitating star clusters in close orbit around each other are short. Since both M31 and NGC 4486B contain central dark objects, our results support models in which the survival of a double nucleus is connected with the presence of a BH. For example, they support the Keplerian eccentric disk model due to Tremaine. C1 UNIV HAWAII,INST ASTRON,HONOLULU,HI 96822. UNIV TORONTO,CANADIAN INST THEORET ASTROPHYS,TORONTO,ON M5S 3H8,CANADA. UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109. CARNEGIE OBSERV,PASADENA,CA 91101. UNIV CALIF SANTA CRUZ,LICK OBSERV,SANTA CRUZ,CA 95064. CALTECH,JET PROP LAB,PASADENA,CA 91109. NATL OPT ASTRON OBSERV,KITT PEAK NATL OBSERV,TUCSON,AZ 85726. RP Kormendy, J (reprint author), UNIV STERNWARTE,SCHEINERSTR 1,D-81679 MUNICH,GERMANY. RI Tremaine, Scott/M-4281-2015 OI Tremaine, Scott/0000-0002-0278-7180 NR 35 TC 81 Z9 82 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 JUN 20 PY 1997 VL 482 IS 2 BP L139 EP & DI 10.1086/310720 PN 2 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF548 UT WOS:A1997XF54800007 ER PT J AU Lee, B Akerlof, C Band, D Barthelmy, S Butterworth, P Cline, T Ferguson, D Gehrels, N Hurley, K AF Lee, B Akerlof, C Band, D Barthelmy, S Butterworth, P Cline, T Ferguson, D Gehrels, N Hurley, K TI Results from gamma-ray optical counterpart search experiment: A real time search for gamma-ray burst optical counterparts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts ID SPECTRA AB The Gamma-Ray Optical Counterpart Search Experiment (GROCSE) has searched for contemporaneous optical counterparts to gamma-ray bursts (GRBs) using an automated rapidly slewing wide field of view optical telescope at Lawrence Livermore National Laboratory. The telescope was triggered in real time by the Burst and Transient Source Experiment (BATSE) data telemetry stream as processed and distributed by the BATSE COordinates DIstribution NEtwork (BACODINE). GROCSE recorded sky images for 28 GRB triggers between 1994 January and 1996 June. The analysis of the 12 best events is presented here, half of which were recorded during detectable gamma-ray emission. No optical counterparts have been detected to limiting magnitudes m(v) less than or equal to 8.5 despite nearly complete coverage of burst error boxes. C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. USRA,COLUMBIA,MD 21044. HSTX,LANHAM,MD 20706. EARTHWATCH INC,PLEASANTON,CA 94566. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. RP Lee, B (reprint author), UNIV MICHIGAN,ANN ARBOR,MI 48109, USA. RI Barthelmy, Scott/D-2943-2012; Gehrels, Neil/D-2971-2012 NR 19 TC 7 Z9 7 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 JUN 20 PY 1997 VL 482 IS 2 BP L125 EP & DI 10.1086/310711 PN 2 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF548 UT WOS:A1997XF54800004 ER PT J AU Ormes, JF Moiseev, AA Saeki, T Anraku, K Orito, S Golden, RL Imori, M Inaba, S Kimbell, BL Kimura, N Makida, Y Matsumoto, H Matsunaga, H Mitchell, JW Motoki, M Nishimura, J Nozaki, M Streitmatter, RE Suzuki, J Tanaka, K Ueda, I Yajima, N Yamagami, T Yamamoto, A Yoshida, T Yoshimura, K AF Ormes, JF Moiseev, AA Saeki, T Anraku, K Orito, S Golden, RL Imori, M Inaba, S Kimbell, BL Kimura, N Makida, Y Matsumoto, H Matsunaga, H Mitchell, JW Motoki, M Nishimura, J Nozaki, M Streitmatter, RE Suzuki, J Tanaka, K Ueda, I Yajima, N Yamagami, T Yamamoto, A Yoshida, T Yoshimura, K TI Antihelium in cosmic rays: A new upper limit and its significance SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic rays; magnetic fields ID ANTI-MATTER; GALAXIES; ANTIPROTONS; ANTIMATTER; UNIVERSE; SPECTRUM AB We have searched for antihelium in the galactic cosmic rays using data obtained on the flight of the Balloon-borne Experiment with a Superconducting Spectrometer (BESS) launched from Lynn Lake, Manitoba, in northern Canada on 1995 July 25. The balloon reached an altitude of 36.5 km with a residual overburden of 5 g cm(-2). The total observation time was 12.2 kr with a live-time fraction of 0.61. No antihelium was observed after selections based on dE/dx and event quality cuts at rigidities between 1.6 and 16 GV/c; we infer that 536,420 helium nuclei survived the same cuts. This result leads to an upper limit to the <(He)over bar>/He abundance ratio of 8.1 x 10(-6) (95% confidence level), a factor of 2.7 over the lowest previous limit. Because this limit is for the first time at the level where predicted limits become astrophysically interesting (Ahlen et al.), we have reexamined the transport of cosmic rays in intergalactic space. We show that little can be learned about distant (> 10 Mpc) domains of antimatter from a null result. C1 UNIV TOKYO,BUNKYO KU,TOKYO 113,JAPAN. NEW MEXICO STATE UNIV,LAS CRUCES,NM 88003. KEK,TSUKUBA,IBARAKI 305,JAPAN. KOBE UNIV,KOBE,HYOGO 657,JAPAN. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. RP Ormes, JF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI MOTOKI, Masakazu/B-4212-2009 NR 32 TC 23 Z9 23 U1 1 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1997 VL 482 IS 2 BP L187 EP L190 DI 10.1086/310700 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF548 UT WOS:A1997XF54800018 ER PT J AU Ward, WR AF Ward, WR TI Survival of planetary systems SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; planetary systems; solar system, formation ID SOLAR NEBULA; PROTOPLANETARY DISK; PLANETESIMALS; TORQUE; SEARCH; STARS AB Gravitational interactions (i.e., disk tides) between a newly formed protoplanet and its precursor disk give rise to a net torque that drains angular momentum from the protoplanet's orbit. As a result, protoplanetary objects suffer orbital decay as the disk attempts to destroy the very system it spawns. Survival of a planetary system may be a rather uncertain outcome, and the fraction of circumstellar disks that produce an extant system could be significantly less than unity. Newly discovered close stellar companions may be circumstantial evidence of such large-scale orbit migrations. A scheme for in situ accretion of such objects is outlined that is consonant with a strong tidal influence. RP Ward, WR (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 23 TC 111 Z9 112 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1997 VL 482 IS 2 BP L211 EP L214 DI 10.1086/310701 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF548 UT WOS:A1997XF54800024 ER PT J AU Zhang, SN Cui, W Chen, W AF Zhang, SN Cui, W Chen, W TI Black hole spin in X-ray binaries: Observational consequences SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; X-rays, stars ID ACCRETION DISKS; EMISSION AB We discuss the observational consequences of black hole spin in X-ray binaries within the framework of the standard thin accretion disk model. When compared with theoretical flux distribution from the surface of a thin disk surrounding a Kerr black hole, the observed X-ray properties of the Galactic superluminal jet sources, GRO J1655-40 and GRS 1915+105, strongly suggest that each contains a black hole spinning rapidly in the same direction as the accretion disk. We show, however, that some other black hole binaries with an ultrasoft X-ray component probably harbor only non- or slowly spinning black holes, and we argue that those with no detectable ultrasoft component above 1-2 keV in their high luminosity state may contain a fast-spinning black hole but with a retrograde disk. Therefore, all classes of known black hole binaries are united within one scheme. Furthermore, we explore the possibility that spectral state transitions in Cyg X-1 are simply due to temporary disk reversal, which can occur in a wind accretion system. C1 MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Zhang, SN (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES-84,HUNTSVILLE,AL 35812, USA. NR 31 TC 212 Z9 223 U1 1 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1997 VL 482 IS 2 BP L155 EP L158 DI 10.1086/310705 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF548 UT WOS:A1997XF54800010 ER PT J AU Zhang, W Strohmayer, TE Swank, JH AF Zhang, W Strohmayer, TE Swank, JH TI Neutron star masses and radii as inferred from kilohertz quasi-periodic oscillations SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; stars, neutron; X-rays, stars ID X-RAY-SPECTRA; ACCRETION; PULSARS AB Kilohertz quasi-periodic oscillations (kHz QPOs) have been discovered in the X-ray fluxes of eight low-mass X-ray binaries (LMXBs) with the Rossi X-Ray Timing Explorer (RXTE). The characteristics of these QPOs are remarkably similar from one source to another. In particular, the highest observed QPO frequencies for sis of the eight sources fall in a very narrow range: from 1066 to 1171 Hz. This is all the more remarkable when one considers that these sources are thought to have very different luminosities and magnetic fields and produce very different count rates in the RXTE detectors. Therefore, it is highly unlikely that this near-constancy of the highest observed frequencies is due to some unknown selection effect or instrumental bias. In this Letter we propose that the highest observed QPO frequency can be taken as the orbital frequency of the marginally stable orbit. This leads to the conclusions that the neutron stars in these LMXBs are inside their marginally stable orbits and have masses in the vicinity of 2.0 M.. This mass is consistent with the hypothesis that these neutron stars were born with about 1.4 M. and have been accreting matter at a fraction of the Eddington limit for 10(8) yr. RP Zhang, W (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Swank, Jean/F-2693-2012 NR 33 TC 103 Z9 104 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 JUN 20 PY 1997 VL 482 IS 2 BP L167 EP L170 DI 10.1086/310719 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF548 UT WOS:A1997XF54800013 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI The successive OH binding energies of Sc(OH)(n)(+) for n=1-3 SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; ORBITAL BASIS-SETS; MOLECULAR CALCULATIONS; ROW ATOMS; ELECTRON CORRELATION; WAVE-FUNCTIONS; CONTRACTION; ABINITIO; 1ST-ROW AB The geometries of Sc(OH)(n)(+), for n=1-3, have been optimized and the zero-point energies computed using the B3LYP approach. The successive OH bond energies have been computed at the CCSD(T) level for ScOH+ and Sc(OH):. The computed result for ScOD+ is in excellent agreement with the recent experiment of Armentrout and co-workers. There is a dramatic drop for the third OH binding energy, because Sc+ has only two valence electrons and therefore the bonding changes when the third OH is added. The difference between the B3LYP and CCSD(T) OH binding energies for the first two OH groups is discussed. (C) 1997 Published by Elsevier Science B.V. RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 26 TC 10 Z9 10 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD JUN 20 PY 1997 VL 272 IS 1-2 BP 127 EP 131 DI 10.1016/S0009-2614(97)00480-6 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XH266 UT WOS:A1997XH26600022 ER PT J AU Notholt, J Toon, G Stordal, F Solberg, S Schmidbauer, N Becker, E Meier, A Sen, B AF Notholt, J Toon, G Stordal, F Solberg, S Schmidbauer, N Becker, E Meier, A Sen, B TI Seasonal variations of atmospheric trace gases in the high Arctic at 79 degrees N SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID WINTER STRATOSPHERE; FORMALDEHYDE; SUBSIDENCE; TRENDS AB Since March 1992 the total column abundances of several tropospheric and stratospheric trace gases have been monitored year-round from the Network for Detection of Stratospheric Change station in Ny Alesund, Spitsbergen (78.9 degrees N, 11,9 degrees E). A groundbased Fourier transform infrared (FTIR) spectrometer performed these measurements using the Sun as a light source during the summer, and the Moon during the winter. In situ measurements of C2H2, C2H6, and CCl2F2, made from the top of a nearby mountain, were combined with the FTIR column data to infer additional information about the variation of the volume mixing ratio profiles with altitude and season. The short-lived tropospheric trace gases C2H2, C2H6, and CO exhibit large seasonal variations with a summer minimum, caused by reaction with OH. CH2O shows a second maximum during the summer, caused by its formation by methane oxidation. For the long-lived gases HF, N2O, and CH4 the seasonal cycle is less pronounced and is forced mainly by wintertime stratospheric diabatic descent, which starts in early November and reaches a maximum in March. The total columns of the stratospheric trace gases indicate that the chemical repartitioning of HCl into ClONO2 starts in November, before the widespread production of polar stratospheric clouds. The total columns of the sum of HCl plus ClONO2 suggests that between December and March they are converted into their active counterparts. Photolysis of HNO3 gives rise to its summer minimum, and its winter maximum, with no evidence for a strong winter denitrification. C1 NORWEGIAN INST AIR RES, N-2007 KJELLER, NORWAY. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Notholt, J (reprint author), ALFRED WEGENER INST POLAR & MARINE RES, POSTFACH 600149, D-14401 POTSDAM, GERMANY. RI Notholt, Justus/P-4520-2016 OI Notholt, Justus/0000-0002-3324-885X NR 23 TC 47 Z9 48 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 12855 EP 12861 DI 10.1029/97JD00337 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900007 ER PT J AU Notholt, J Toon, GC Lehmann, R Sen, B Blavier, JF AF Notholt, J Toon, GC Lehmann, R Sen, B Blavier, JF TI Comparison of Arctic and Antarctic trace gas column abundances from ground-based Fourier transform infrared spectrometry SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IR SOLAR OBSERVATIONS; OZONE DEPLETION; ATMOSPHERE; DISTRIBUTIONS; JUNGFRAUJOCH; VARIABILITY; MODEL AB Column abundances of several atmospheric trace gases have been derived from solar absorption spectra measured from McMurdo, Antarctica (77.9 degrees S, 166.7 degrees E), in September and October 1986 and from solar and lunar absorption spectra recorded in Ny Alesund, Spitsbergen (78.9 degrees N, 11.9 degrees E), during winter and spring 1992-1995. The same analysis software, including the molecular spectroscopic parameters and initial volume mixing ratio profile shapes, was employed for both data sets to minimize the possibility of introducing systematic biases. The results clearly show that denitrification in the Antarctic lower stratosphere results in much smaller column abundances of HNO3 than in the Arctic. The springtime recovery of HCl in the Antarctic showed a stronger increase than in the Arctic. The ClONO2 peak occurred about 1 month later in the Antarctic and was found to be less pronounced than in the Arctic. After accounting for the 30% increase in total chlorine between 1986 and 1993, the minimum values for HCl + ClONO2 are similar in the Arctic and the Antarctic, indicating that both polar regions show nearly the same activation of chlorine during the polar night. However, in the Arctic the low values of HCl + ClONO2 start to recover in February, whereas in the Antarctic the lack of NO2, caused by the denitrification, delays the increase of HCl + ClONO2 by about 1 month. A simple one-dimensional model was able to reproduce the behavior of HCl and ClONO2, simply by assuming a one month later date for the last Antarctic polar stratospheric clouds together with greater latitude excursions of the Arctic air parcel trajectories. The model runs imply that in the Antarctic the reconversion of ClONO2 to HCl occurs about 1 month later than in the Arctic. Furthermore, the results imply that any differences in the O-3 depletion are caused mainly by differences in the stratospheric temperatures and dynamics and only to a small extent by the increased chlorine loading. The total column abundances of the short-lived tropospheric trace gases C2H6, C2H2, CO, and CH2O are found to be up to 10 times higher in the Arctic compared with the Antarctic, reflecting the hemispheric imbalance in production. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Notholt, J (reprint author), ALFRED WEGENER INST POLAR & MARINE RES, POSTFACH 600149, D-14401 POTSDAM, GERMANY. RI Notholt, Justus/P-4520-2016 OI Notholt, Justus/0000-0002-3324-885X NR 29 TC 22 Z9 22 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 12863 EP 12869 DI 10.1029/97JD00358 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900008 ER PT J AU Chipperfield, MP Burton, M Bell, W Paton-Walsh, C Blumenstock, T Coffey, MT Hannigan, JW Mankin, WG Galle, B Mellqvist, J Mahieu, E Zander, R Notholt, J Sen, B Toon, GC AF Chipperfield, MP Burton, M Bell, W Paton-Walsh, C Blumenstock, T Coffey, MT Hannigan, JW Mankin, WG Galle, B Mellqvist, J Mahieu, E Zander, R Notholt, J Sen, B Toon, GC TI On the use of HF as a reference for the comparison of stratospheric observations and models SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TRACE GASES; HYDROGEN-FLUORIDE; DATA ASSIMILATION; ATMOSPHERE; CLONO2; COF2; HCL AB Hydrogen fluoride (HF) is often used as a simple reference for other column observations of chemically active stratospheric species. However, seasonal and shorter timescale variations in column HF make its use as a reference more complicated. In this paper we characterize the expected magnitude of these variations in HF, and variations of ratio quantities involving HF, using a two-dimensional (2-D) photochemical model and two versions of a three-dimensional (3-D) transport model. The 2-D model predicts that the column ratios HNO3/HF and HCl/HF increase from midlatitudes to the tropics, although this is very sensitive to HCl and HNO3 abundances in the tropical upper troposphere. Seasonal variations in vertical motion modifys the predicted ratios; for example, wintertime descent at high latitudes decreases HCl/HF. The ratio HNO3/HF at high latitudes is strongly modified by seasonal variations in the chemical partitioning of the odd nitrogen (NOy) species. We compare these model predictions with ground-based Fourier transform infrared spectroscopy (FTIR) observations of HF along with HCl, ClONO2 and HNO3 obtained at eight northern hemisphere sites between October 1994 and July 1995. We investigate quantitatively how HF can be used as a tracer to follow the evolution of observations at a single station and to intercompare results from different stations or with photochemical models. The magnitude of the 3-D model HF column agrees well with the observations, except on some occasions at high latitudes, giving indirect support for the important role of COF2 in the stratospheric inorganic fluorine budget. The observed day-to-day variability in the column ratios HCl/HF and HNO3/HF is much larger at high latitudes. This variability is reproduced in the 3-D models and is due to horizontal motion. Short timescale vertical displacement of the species profiles is estimated to have a small effect on the column ratios. In particular, we analyze the usefulness of the observed column ratio (ClONO2 + HCl)/HF as an indicator for chlorine activation. Current measurement uncertainties limit the degree of activation which can be unambiguously detected using this observed quantity, but we can determine that chlorine-activated air was observed above Aberdeen (58 degrees N) on 6 days in late January 1995. C1 NATL PHYS LAB, TEDDINGTON TW11 0LW, MIDDX, ENGLAND. FORSCHUNGSZENTRUM KARLSRUHE, INST METEOROL & KLIMAFORSCH, D-76021 KARLSRUHE, GERMANY. NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. SWEDISH ENVIRONM RES INST, S-40258 GOTHENBURG, SWEDEN. ALFRED WEGENER INST POLAR & MARINE RES, POTSDAM, GERMANY. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV LIEGE, INST ASTROPHYS, B-4200 LIEGE, BELGIUM. RP Chipperfield, MP (reprint author), UNIV CAMBRIDGE, DEPT CHEM, LENSFIELD RD, CAMBRIDGE CB2 1EW, ENGLAND. RI Paton-Walsh, Clare/B-2774-2009; Blumenstock, Thomas/K-2263-2012; Chipperfield, Martyn/H-6359-2013; Burton, Mike/B-5716-2014; Galle, Bo/F-7996-2016; Notholt, Justus/P-4520-2016; OI Paton-Walsh, Clare/0000-0003-1156-4138; Chipperfield, Martyn/0000-0002-6803-4149; Burton, Mike/0000-0003-3779-4812; Galle, Bo/0000-0001-9989-809X; Notholt, Justus/0000-0002-3324-885X; Mahieu, Emmanuel/0000-0002-5251-0286; Mellqvist, Johan/0000-0002-6578-9220 NR 36 TC 23 Z9 23 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 12901 EP 12919 DI 10.1029/96JD03964 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900012 ER PT J AU Aikin, AC AF Aikin, AC TI Production of stratospheric HNO3 by different ion-molecule reaction mechanisms SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NEGATIVE-IONS; MIDDLE ATMOSPHERE; SULFURIC-ACID; CHEMISTRY; WINTER AB Precipitation of energetic charged particles into the polar winter stratosphere leads to an enhancement of nitric acid. Three different ion-molecule reaction mechanisms have been suggested as the cause of the HNO3 enhancement: 1) OH production by ion-molecule reactions and subsequent reaction with NO2 to produce HNO3, 2) positive ion-negative ion recombination, and 3) positive hydrated ion reaction with N2O5. It is shown that the OH reaction can be disregarded. While H+(H2O)(n) + N2O5 may be important below 40 km, it accounts for less than half the HNO3 production at 45 km and is negligible in comparison with ion-ion recombination at higher altitudes. The inclusion of ion-ion recombination greatly reduces the ion pair production requirements for HNO3 production. RP Aikin, AC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CODE 916, GREENBELT, MD 20771 USA. NR 16 TC 17 Z9 17 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 12921 EP 12925 DI 10.1029/97JD00419 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900013 ER PT J AU Joiner, J Bhartia, PK AF Joiner, J Bhartia, PK TI Accurate determination of total ozone using SBUV continuous spectral scan measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BACKSCATTER ULTRAVIOLET MEASUREMENTS; IRRADIANCE COMPARISON EXPERIMENT-1; ROTATIONAL RAMAN-SCATTERING; STRATOSPHERIC OZONE; NIMBUS-7 SBUV; TRENDS; TOMS AB Over the last 2 decades, satellite data have been used to monitor long-term global changes in stratospheric ozone. In order to measure relatively small ozone trends on timescales of the order of a decade, degradation of instrument components must be accounted for, and accurate interinstrument calibration must be maintained. In this paper, we have used a self-calibrating method to accurately retrieve total ozone from backscatter ultraviolet spectra in the wavelength range 310 to 340 nm. Using the information contained in this spectral region, we correct for time dependent and time-independent wavelength errors and calibration errors as well as radiative transfer modeling errors. We use continuous spectral scan data from the Nimbus 7 solar backscatter ultraviolet (SBUV) instrument to retrieve total ozone at latitudes between 40 degrees S and 40 degrees N over the time period 1979 to 1986. These total column ozone retrievals are used to independently validate retrievals from the both Nimbus 7 total ozone mapping spectrometer (TOMS) and SBUV in discrete mode. TOMS and SBUV in discrete mode have better temporal and spatial coverage than SBUV in continuous scan mode and are two of the primary instruments used to derive long-term global ozone trends. The time dependence of the difference between total ozone retrieved from SBUV continuous scan and that derived from TOMS and SBUV discrete mode is 0.6+/-0.3%/decade or less depending on latitude. The SBUV continuous scan radiances are modeled to an accuracy of +/-0.3% (1 sigma). Unfortunately, an instrument problem terminated continuous scan mode observations after 1986 so that the later years of TOMS and SBUV discrete mode observations cannot be validated. The methods developed here may also be applied to other continuous spectral backscatter ultraviolet instruments in order to intercalibrate total ozone retrievals. This will be particularly important when temporal overlap of ozone monitoring instruments does not occur as in the case of the Nimbus 7 and Earth Probe TOMS instruments. In addition, the methods used here are applicable to ground-based spectral ultraviolet measurements. C1 HUGHES STX CORP, GREENBELT, MD USA. RP Joiner, J (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CODE 910-3, GREENBELT, MD 20771 USA. RI Joiner, Joanna/D-6264-2012 NR 45 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 12957 EP 12969 DI 10.1029/97JD00902 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900017 ER PT J AU Huang, FT Reber, CA Austin, J AF Huang, FT Reber, CA Austin, J TI Ozone diurnal variations observed by UARS and their model simulation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SIMULTANEOUS INSITU MEASUREMENTS; SOLAR MESOSPHERE EXPLORER; DIODE-LASER SPECTROMETER; RESEARCH SATELLITE UARS; UPPER-STRATOSPHERE; NITRIC-OXIDE; ATMOSPHERE; NO; O-3 AB Several years of ozone measurements from the Microwave Limb Sounder onboard the Upper Atmosphere Research Satellite are analyzed using a two-dimensional Fourier series in day of year and time of day. Because of limited temporal coverage near local noon, only the diurnal and semidiurnal components are included. Data are investigated in detail at 28 degrees N in the middle stratosphere to lower mesosphere, where the data are considered most reliable. The observations show that ozone is a maximum in the afternoon at 3 mbar and a minimum in the afternoon at 1 mbar and above with a narrow transition zone of reduced diurnal variation in between. This strong dependency on altitude in the transition from a maximum in the afternoon to a minimum in the afternoon, coupled with the small percentage changes in ozone, imposes strict requirements on the data and on the analysis of the data. Comparisons are made with results from a photochemical box model run at 11 levels between 0.46 mbar and 21.5 mbar for 28 degrees N at spring equinox and near the solstices. This is the first time that a data analysis and model comparison of this kind has been made, leading to the identification of relatively small diurnal variations, especially in the transition zone. In the middle stratosphere the model results are in poor agreement with the observations because of the influence of stratospheric dynamics which are neglected in the model runs. In the upper stratosphere the model shows the expected underprediction of absolute ozone amounts, although the percentage change from the midnight value is in excellent agreement with the observations and in particular correctly simulates the diurnal variation in the transition zone between 3 and 1 mbar. Model sensitivity studies are performed to determine the effects of major reaction rate changes and simplified tidal effects. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UK METEOROL OFF, BRACKNELL RG12 2SZ, BERKS, ENGLAND. RP Huang, FT (reprint author), SCI SYST & APPL INC, 5900 PRINCESS GARDEN PKWY, LANHAM, MD 20706 USA. NR 33 TC 21 Z9 21 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 JUN 20 PY 1997 VL 102 IS 11D BP 12971 EP 12985 DI 10.1029/97JD00461 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900018 ER PT J AU Weisenstein, DK Yue, GK Ko, MKW Sze, ND Rodriguez, JM Scott, CJ AF Weisenstein, DK Yue, GK Ko, MKW Sze, ND Rodriguez, JM Scott, CJ TI A two-dimensional model of sulfur species and aerosols SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC SULFATE AEROSOL; MT-PINATUBO; CONDENSATION NUCLEI; 3-DIMENSIONAL MODEL; 2-DIMENSIONAL MODEL; PARTICLE FORMATION; CARBONYL SULFIDE; TROPICAL OZONE; EL CHICHON; AIRCRAFT AB A two-dimensional model of sulfate aerosols has been developed. The model includes the sulfate precursor species H2S, CS2, DMS, OCS, and SO2. Microphysical processes simulated are homogeneous nucleation, condensation and evaporation, coagulation, and sedimentation. Tropospheric aerosols are removed by washout processes and by surface deposition. We assume that all aerosols are strictly binary water-sulfuric acid solutions without solid cores. The main source of condensation nuclei for the stratosphere is new particle formation by homogeneous nucleation in the upper tropical troposphere. A significant finding is that the stratospheric aerosol mass may be strongly influenced by deep convection in the troposphere. This process, which could transport gas-phase sulfate precursors into the upper troposphere and lead to elevated levels of SO2 there, could potentially double the stratospheric aerosol mass relative to that due to OCS photooxidation alone. Our model is successful at reproducing the magnitude of stratospheric aerosol loading following the Mount Pinatubo eruption, but the calculated rate of decay of aerosols from the stratosphere is faster than that derived from observations. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. RP Weisenstein, DK (reprint author), ATMOSPHER & ENVIRONM RES INC, 840 MEM DR, CAMBRIDGE, MA 02139 USA. RI Rodriguez, Jose/G-3751-2013; Ko, Malcolm/D-5898-2015 OI Rodriguez, Jose/0000-0002-1902-4649; NR 77 TC 93 Z9 94 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13019 EP 13035 DI 10.1029/97JD00901 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900022 ER PT J AU Christiansen, B Guldberg, A Hansen, AW Riishojgaard, LP AF Christiansen, B Guldberg, A Hansen, AW Riishojgaard, LP TI On the response of a three-dimensional general circulation model to imposed changes in the ozone distribution SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DYNAMICAL RESPONSE; STRATOSPHERE; CLIMATE; TROPOSPHERE; ATMOSPHERE; WAVE; HOLE AB A series of idealized ozone perturbations has been studied with the French community general circulation model Arpege. The perturbations are uniform 50% and 75% reductions and an ozone hole type reduction concentrated in the lower part of the stratosphere and the upper part of the troposphere. We compare the radiative drive, the temperature response under the fixed dynamical heating approximation, and the full dynamical response. In all experiments the main effect of the dynamics is a weakening of the diabatic meridional circulation and an associated latitudinal smoothing of the temperature response. The weakening of the diabatic meridional circulation is in agreement with a reduction of the wave forcing, associated with an extended tongue of low refractive index close to the tropopause. While the fixed dynamical heating approximation in general represents the pattern of the temperature response well, the strength of the response is altered when allowing dynamical effects. In the lower stratosphere this adjustment is 25%-50% of the fixed dynamical heating response. The mean zonal wind is very stable to uniform reductions, but the strength of the winter stratospheric jet increases drastically in the hole type experiment. The ozone perturbations decrease the variability in the winter hemisphere, which in the control experiment and the uniform reduction experiments is of oscillatory nature with a timescale of 50 to 100 days. C1 UNIV COPENHAGEN, DEPT GEOPHYS, DK-2100 COPENHAGEN, DENMARK. NASA, GODDARD SPACE FLIGHT CTR, DATA ASSIMILAT OFF, GREENBELT, MD 20771 USA. RP Christiansen, B (reprint author), DANISH METEOROL INST, METEOROL & OCEANOG RES DIV, LYNGBYVEJ 100, DK-2100 COPENHAGEN, DENMARK. OI Christiansen, Bo/0000-0003-2792-4724 NR 26 TC 15 Z9 15 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13051 EP 13077 DI 10.1029/97JD00529 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900024 ER PT J AU Pueschel, RF Boering, KA Verma, S Howard, SD Ferry, GV Goodman, J Allen, DA Hamill, P AF Pueschel, RF Boering, KA Verma, S Howard, SD Ferry, GV Goodman, J Allen, DA Hamill, P TI Soot aerosol in the lower stratosphere: Pole-to-pole variability and contributions by aircraft SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERE AB A NASA ER-2 high-altitude research aircraft intercepted the exhaust wake of a supersonic Concorde aircraft in the stratosphere near New Zealand on October 8, 1994. Black carbon (soot) aerosol (BCA) was sampled by wire impactors during the first five of 12 short-duration wake intercepts. BCA concentration in Concorde exhaust at 16.3 km altitude was 0.2 particles cm(-3), the size distribution peaked at a geometric mean radius of 0.09 mu m, and the mass loading was 2.0+/-1.4 ng m(-3). With a plume dilution factor (DF) of 1.0 x 10(-5), determined by the ratio of CO2 measured in the plume (above the ambient stratospheric background level) to CO2 in the engine exhaust plane, the Concorde BCA emission index was EI(BCA) = 0.07+/-0.05 g BCA per kg fuel burned. Applying this EI to estimates of aircraft fuel burned by the current subsonic fleet in the stratosphere yields average stratospheric BCA loadings of 0.5 ng m(-3), commensurate with observations in the northern stratosphere. Applying the Concorde EI to fuel consumption by a projected future fleet suggests a twofold-threefold increase of stratospheric BCA by the year 2015. A strong gradient in BCA concentration exists between the northern and the southern hemispheres, indicating interhemispheric mixing times longer than stratospheric residence times. C1 HARVARD UNIV, DEPT EARTH & PLANETARY SCI, CAMBRIDGE, MA 02138 USA. TMA NORCAL, RICHMOND, CA 94804 USA. SYMTECH CORP, CAMARILLO, CA 93010 USA. SAN JOSE STATE UNIV, DEPT METEOROL, SAN JOSE, CA 95192 USA. RP Pueschel, RF (reprint author), NASA, AMES RES CTR, MC SGP 245-4, MOFFETT FIELD, CA 94035 USA. NR 24 TC 39 Z9 40 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 JUN 20 PY 1997 VL 102 IS 11D BP 13113 EP 13118 DI 10.1029/96JD03061 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900027 ER PT J AU Waugh, DW Plumb, RA Elkins, JW Fahey, DW Boering, KA Dutton, GS Volk, CM Keim, E Gao, RS Daube, BC Wofsy, SC Loewenstein, M Podolske, JR Chan, KR Proffitt, MH Kelly, K Newman, PA Lait, LR AF Waugh, DW Plumb, RA Elkins, JW Fahey, DW Boering, KA Dutton, GS Volk, CM Keim, E Gao, RS Daube, BC Wofsy, SC Loewenstein, M Podolske, JR Chan, KR Proffitt, MH Kelly, K Newman, PA Lait, LR TI Mixing of polar vortex air into middle latitudes as revealed by tracer-tracer scatterplots SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ANTARCTIC OZONE HOLE; LOWER STRATOSPHERE; WINTER; TRANSPORT; N2O; DENITRIFICATION; CO2; DEHYDRATION; DYNAMICS; AIRCRAFT AB The occurrence of mixing of polar vortex air with midlatitude air is investigated by examining the scatterplots of insitu measurements of long-lived tracers from the NASA ER-2 aircraft during the Stratospheric Photochemistry, Aerosols and Dynamics Expedition (SPADE, April, May 1993; northern hemisphere) and the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA, March-October 1994; southern hemisphere) campaigns. The tracer-tracer scatterplots from SPADE form correlation curves which differ from those measured during previous aircraft campaigns (Airborne Antarctic Ozone Experiment (AAOE), Airborne Arctic Stratospheric Experiments I (AASE I) and II (AASE II)). It is argued that these anomalous linear correlation curves are ''mixing lines'' resulting from the recent mixing of polar vortex air into the middle latitude environment. Further support for this mixing scenario is provided by contour advection calculations and calculations with a simple one-dimensional strain-diffusion model. The scatterplots from the midwinter deployments of ASHOE/MAESA are consistent with those from previous midwinter measurements (i.e., no mixing lines), but the spring CO2:N2O scatterplots form altitude-dependent mixing lines which indicate that air from the vortex edge region (but not from the inner vortex) is mixing with midlatitude air during this period. These results suggest that at altitudes above about 16 km the mixing of polar vortex air into middle latitudes varies with season: in northern and southern midwinter this mixing rarely occurs, in southern spring mixing of vortex-edge air occurs, and after the vortex breakup mixing of inner vortex air occurs. C1 HARVARD UNIV, DEPT EARTH & PLANETARY SCI, CAMBRIDGE, MA 02138 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NOAA, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80303 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. MIT, DEPT EARTH ATMOSPHER & PLANETARY SCI, CAMBRIDGE, MA 02139 USA. RP Waugh, DW (reprint author), MONASH UNIV, COOPERAT RES CTR SO HEMISPHERE METEOROL, WELLINGTON RD, CLAYTON, VIC 3168, AUSTRALIA. RI Newman, Paul/D-6208-2012; Gao, Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013; Waugh, Darryn/K-3688-2016 OI Newman, Paul/0000-0003-1139-2508; Fahey, David/0000-0003-1720-0634; Waugh, Darryn/0000-0001-7692-2798 NR 51 TC 127 Z9 129 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13119 EP 13134 DI 10.1029/96JD03715 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900028 ER PT J AU Grose, WL Lingenfelser, GS Russell, JM Pierce, RB Fairlie, TD Proffitt, MH AF Grose, WL Lingenfelser, GS Russell, JM Pierce, RB Fairlie, TD Proffitt, MH TI Intercomparison of ozone measurements in the lower stratosphere from the UARS halogen occultation experiment and the ER-2 UV absorption photometer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB Ozone data obtained by the Halogen Occultation Experiment (HALOE) on the NASA Upper Atmosphere Research Satellite (UARS) have been compared with ozone data obtained by the NOAA dual-beam, UV absorption photometer on the NASA ER-2 aircraft during the 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) campaign. This paper describes the measurement characteristics of the two instruments and the precision and accuracy of the two data sets. A total of 26 cases are discussed in which the two different measurements occur within 24 hours, 2.5 degrees latitude, and 10 degrees longitude of each other. Generally, agreement between the two data sets improved the closer in time and space the two measurements occurred. The agreement was better than 10% at ER-2 cruise altitudes (similar to 50-70 mbar) where the error estimated for HALOE is slightly larger than 18%. C1 NASA, LANGLEY RES CTR, SCI APPLICAT INT CORP, HAMPTON, VA 23681 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. HAMPTON UNIV, DEPT PHYS, HAMPTON, VA 23668 USA. RP Grose, WL (reprint author), NASA, LANGLEY RES CTR, SCI & TECHNOL CORP, MS 401B, HAMPTON, VA 23681 USA. RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 7 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 JUN 20 PY 1997 VL 102 IS 11D BP 13135 EP 13140 DI 10.1029/96JD03060 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900029 ER PT J AU Grooss, JU Pierce, RB Crutzen, PJ Grose, WL Russell, JM AF Grooss, JU Pierce, RB Crutzen, PJ Grose, WL Russell, JM TI Re-formation of chlorine reservoirs in southern hemisphere polar spring SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC OZONE; CHEMISTRY; WINTER; MODEL; PHOTOCHEMISTRY; DEHYDRATION; ATMOSPHERE; SYSTEM; HALOE; CLO AB This paper focuses on the recovery of chlorine reservoir species in the lower stratosphere in late Antarctic spring. The investigations are based on measurements from the Halogen Occultation Experiment (HALOE) on board the Upper Atmosphere Research Satellite (UARS) and calculations by the Mainz photochemical box model and the NASA Langley Research Center trajectory model. During late Antarctic spring 1994, HALOE observed high HCl mixing ratios up to 2.7 ppbv at 20 km altitude in the ozone-depleted air inside the polar vortex. These values correspond approximately to the sum of all available inorganic chlorine species. In the preceding period of chlorine activation on polar stratospheric clouds (PSCs), the observed HCl mixing ratios in some cases were below 0.3 ppbv. This indicates a fast conversion of active chlorine species into the form of HCl after PSCs disappear with increasing stratospheric temperatures. Box model calculations are presented that assess the rate of HCl increase in late spring when heterogeneous chemistry on polar stratospheric clouds becomes insignificant. The calculations were performed along Lagrangian trajectories starting from HALOE measurements in September 1994. Sensitivity calculations are presented regarding uncertainties in input parameters of the calculations. In the vortex edge region, calculated HCl increase rates are significantly lower compared with HALOE observations. Introducing additional HCl-yielding branches of the reactions of ClO with OH and HO2 helps to reduce this discrepancy. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. MAX PLANCK INST CHEM, D-55020 MAINZ, GERMANY. HAMPTON UNIV, DEPT PHYS, HAMPTON, VA 23668 USA. RI Pierce, Robert Bradley/F-5609-2010; Crutzen, Paul/F-6044-2012; GrooSS, Jens-Uwe/A-7315-2013 OI Pierce, Robert Bradley/0000-0002-2767-1643; GrooSS, Jens-Uwe/0000-0002-9485-866X NR 38 TC 20 Z9 20 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13141 EP 13152 DI 10.1029/96JD03505 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900030 ER PT J AU Pierce, RB Grooss, JU Grose, WL Russell, JM Crutzen, PJ Fairlie, TD Lingenfelser, G AF Pierce, RB Grooss, JU Grose, WL Russell, JM Crutzen, PJ Fairlie, TD Lingenfelser, G TI Photochemical calculations along air mass trajectories during ASHOE/MAESA SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ANTARCTIC OZONE EXPERIMENT; POLAR STRATOSPHERIC CLOUD; CHLORINE CHEMISTRY; ER-2 AIRCRAFT; MODEL; WINTER; NITROGEN; ACTIVATION; EVOLUTION; RADICALS AB The practicality of conducting photochemical calculations along trajectories of air masses is investigated. An isentropic trajectory package is used in conjunction with a detailed photochemical model to compare predictions of the mean chemical content of air masses initialized with the Halogen Occultation Experiment (HALOE) data with coincident in situ observations from instruments onboard the ER-2 aircraft. Comparisons are made for 10 ER-2 flights originating from Christchurch, New Zealand, during the May to June and October 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) deployments. Between 54 and 84 coincidences are found, depending on the species measured. Correlations between the ER-2 and HALOE air mass/box model calculations are high (0.56-0.90) for most species considered except for H2O (0.14) and HCl (0.24). Statistically significant low biases in the prediction of HCl, H2O, and OH are found. Kolmogorov-Smirnov (KS) significance tests are used to quantify the agreement between the distribution of species observed by the ER-2 and predicted by the HALOE trajectory/photochemical model. The model predictions agree with the observed variance within the distributions at significance levels greater than 0.80 (greater than 80% confidence that the predicted and observed variance are identical) for H2O, ClO, O-3, and NOy. The impact of computational errors in the trajectory calculations and measurement uncertainty in the computed confidence levels are investigated using Monte Carlo techniques. Computational trajectory errors are found to play a small role in reducing confidence levels. The error analysis shows that the HALOE trajectory/photochemical model calculations reproduce the large-scale variability found in the in situ ER-2 constituent measurements to within the expected uncertainties in the HALOE observations for all species considered. It is concluded that the combined trajectory/photochemical model is an effective tool for interpreting in situ aircraft observations within the global perspective provided by remote satellite measurements. C1 FORSCHUNGSZENTRUM JULICH, FORSCHUNGSZENTRUM, D-52425 JULICH, GERMANY. HAMPTON UNIV, DEPT PHYS, HAMPTON, VA 23668 USA. MAX PLANCK INST CHEM, CHEM ATMOS, D-55128 MAINZ, GERMANY. SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. SCI APPLICAT INT CORP, HAMPTON, VA 23666 USA. RP Pierce, RB (reprint author), NASA, LANGLEY RES CTR, MAIL STOP 401B, HAMPTON, VA 23681 USA. RI Pierce, Robert Bradley/F-5609-2010; Crutzen, Paul/F-6044-2012; GrooSS, Jens-Uwe/A-7315-2013 OI Pierce, Robert Bradley/0000-0002-2767-1643; GrooSS, Jens-Uwe/0000-0002-9485-866X NR 43 TC 14 Z9 14 U1 1 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 JUN 20 PY 1997 VL 102 IS 11D BP 13153 EP 13167 DI 10.1029/96JD03506 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900031 ER PT J AU Fairlie, TD Pierce, RB Grose, WL Lingenfelser, G Loewenstein, M Podolske, JR AF Fairlie, TD Pierce, RB Grose, WL Lingenfelser, G Loewenstein, M Podolske, JR TI Lagrangian forecasting during ASHOE/MAESA: Analysis of predictive skill for analyzed and reverse-domain-filled potential vorticity SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID METEOROLOGYS GLOBAL ASSIMILATION; CUMULUS PARAMETERIZATION; GENERAL-CIRCULATION; ECMWF MODEL; SCHEME; PARAMETRIZATION; ATMOSPHERE; EVOLUTION; ADVECTION; SATELLITE AB A statistical analysis is conducted to determine to what extent analyzed and 5-day reverse-domain-filled (RDF) potential vorticity (PV) obtained from meteorological analyses can predict ATLAS nitrous oxide (N2O) tracer structure encountered along the ER-2 flight track during the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) campaign. The results indicate that RDF PV shows no statistically significant improvement in forecast skill over analyzed PV in predicting tracer structure along the ER-2 flight track. In fact, RDF generally shows a degradation in predictive skill. RDF does show some success in refining large-scale gradients and small-scale structures, present in the analyzed PV fields. In at least one case, RDF PV captured a filament encountered by the ER-2, but in general, such structure is marked by low confidence in the RDF PV analyses. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. SCI APPLICAT INT CORP, HAMPTON, VA 23666 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Fairlie, TD (reprint author), SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 38 TC 23 Z9 23 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 JUN 20 PY 1997 VL 102 IS 11D BP 13169 EP 13182 DI 10.1029/96JD03507 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900032 ER PT J AU Nevison, CD Solomon, S Garcia, RR Fahey, DW Keim, ER Loewenstein, M Podolske, JR Gao, RS Wamsley, RC Donnelly, SG DelNegro, LA AF Nevison, CD Solomon, S Garcia, RR Fahey, DW Keim, ER Loewenstein, M Podolske, JR Gao, RS Wamsley, RC Donnelly, SG DelNegro, LA TI Influence of Antarctic denitrification on two-dimensional model NOy/N2O correlations in the lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID WINTER POLAR STRATOSPHERES; CHEMICAL-COMPOSITION; MIDDLE ATMOSPHERE; OZONE EXPERIMENT; HNO3; BREAKING; DYNAMICS; CLONO2; N2O AB The mechanisms responsible for latitudinal and seasonal variations in the stratospheric No-y/N2O correlation, represented by the effective NOy yield from N2O loss, or F-NOy, are explored using the Garcia-Solomon two-dimensional model. The model is run with and without Antarctic denitrification. Model results are compared to in situ NOy/N2O measurements taken onboard the NASA ER-2 high-altitude aircraft in the lower stratosphere during the 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft campaign, and to global-scale measurements taken onboard the Upper Atmosphere Research Satellite (UARS) from 1992 to 1993. The southern hemisphere midlatitude seasonal cycle observed by the ER-2 and the latitudinal gradients observed by UARS are consistent with the results of the denitrified model, although some aspects of the model results are sensitive to prescribed and/or calculated horizontal diffusion coefficients. The consistency with observations supports the model's prediction of a seasonal cycle in which F-NOy increases at southern midlatitudes during winter due to descent of F-NOy -enriched air from above and decreases in spring due to mixing with F-NOy -depleted air from the denitrified polar vortex. Antarctic denitrification appears to affect midlatitudes mainly by a one-time dilution of the polar vortex following the final warming rather than by flow-through vortex processing during the winter. Because of the high concentrations of NOy at polar latitudes before denitrification a can be removed by a one-time dilution of the large fraction of total stratospheric NOy denitrified polar vortex. The nondenitrified model results generally do not agree well with observations, suggesting that denitrification strongly influences latitudinal and seasonal variations in F-NOy in the southern hemisphere. C1 NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV COLORADO, COOPERAT INST RES ENVIRONM SCI, BOULDER, CO USA. UNIV COLORADO, DEPT BIOL & CHEM, BOULDER, CO 80309 USA. RP Nevison, CD (reprint author), NOAA, ERL, R-E-AL8, 325 BROADWAY, BOULDER, CO 80303 USA. RI Gao, Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013 OI Fahey, David/0000-0003-1720-0634 NR 30 TC 11 Z9 11 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13183 EP 13192 DI 10.1029/96JD03250 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900033 ER PT J AU Keim, ER Loewenstein, M Podolske, JR Fahey, DW Gao, RS Woodbridge, EL Wamsley, RC Donnelly, SG DelNegro, LA Nevison, CD Solomon, S Rosenlof, KH Scott, CJ Ko, MKW Weisenstein, D Chan, KR AF Keim, ER Loewenstein, M Podolske, JR Fahey, DW Gao, RS Woodbridge, EL Wamsley, RC Donnelly, SG DelNegro, LA Nevison, CD Solomon, S Rosenlof, KH Scott, CJ Ko, MKW Weisenstein, D Chan, KR TI Measurements of the NOy - N2O correlation in the lower stratosphere: Latitudinal and seasonal changes and model comparisons SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TOTAL REACTIVE NITROGEN; ANTARCTIC OZONE HOLE; WINTER POLAR STRATOSPHERES; AIRCRAFT MEASUREMENTS; ARCTIC STRATOSPHERE; MIDDLE ATMOSPHERE; ODD NITROGEN; NITRIC-ACID; AASE-II; VORTEX AB The tracer species nitrous oxide, N2O, and the reactive nitrogen reservoir, NOy, were measured in situ using instrumentation carried aboard the NASA ER-2 high altitude aircraft as part of the NASA Airborne Southern Hemisphere Ozone Expedition/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) and Stratospheric Tracers of Atmospheric Transport (STRAT) missions. Measurements were made throughout the latitude range of 70 degrees S to 60 degrees N over the time period of March to October 1994 and October 1995 to January 1996, which includes the period when the Antarctic polar vortex is most intense. The correlation plots of NOy with N2O reveal compact, near-linear curves throughout data obtained in the lower stratosphere (50 mbar to 200 mbar). The average slope of the correlation, Delta NOy/Delta N2O, in the southern hemisphere (SH) exhibited a much larger seasonal variation during this time period than was observed in the northern hemisphere (NH). Between March and October in the potential temperature range of 400 K to 525 K, the correlation slope in the SH midlatitudes increased by 28%. A smaller but still positive increase in the correlation slope was observed for higher-latitude data obtained within or near the edge of the SH polar vortex. At NH midlatitudes the correlation slope did not significantly change between March and October, while between October and January the slope increased by +7%. The larger SH midlatitude increase is consistent with ongoing descent throughout the winter and spring and also suggests that denitrification, the irreversible loss of HNO3 through sedimentation of cloud particles, is not a significant term (<10-15%) in the budget of NOy at SH midlatitudes during the wintertime, A secular increase in the correlation slope is ruled out by comparison with SH data obtained during the 1987 Airborne Antarctic Ozone Expedition (AAOE) aircraft campaign. These results suggest that a seasonal cycle exists in the correlation slope for both hemispheres, with the SH correlation slope returning to the April value during the SH spring and summer. Changes in stratospheric circulation also probably play a role in both the SH and the NH correlation slope seasonal cycles. Comparisons with two-dimensional model results suggest that the slope decreases when the denitrified Antarctic vortex is diluted into midlatitudes upon vortex breakup in the spring and that through the descent of stratospheric air, the slope recovers during the following fall/winter period. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80309 USA. UNIV COLORADO, DEPT BIOL & CHEM, BOULDER, CO 80309 USA. ATMOSPHER & ENVIRONM RES INC, CAMBRIDGE, MA 02139 USA. RP Keim, ER (reprint author), NOAA, AERON LAB, 325 BROADWAY, BLDG 24, BOULDER, CO 80303 USA. RI Gao, Ru-Shan/H-7455-2013; Rosenlof, Karen/B-5652-2008; Ko, Malcolm/D-5898-2015; Fahey, David/G-4499-2013 OI Rosenlof, Karen/0000-0002-0903-8270; Fahey, David/0000-0003-1720-0634 NR 50 TC 36 Z9 36 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 JUN 20 PY 1997 VL 102 IS 11D BP 13193 EP 13212 DI 10.1029/96JD03921 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900034 ER PT J AU Jaegle, L Webster, CR May, RD Scott, DC Stimpfle, RM Kohn, DW Wennberg, PO Hanisco, TF Cohen, RC Proffitt, MH Kelly, KK Elkins, J Baumgardner, D Dye, JE Wilson, JC Pueschel, RF Chan, KR Salawitch, RJ Tuck, AF Hovde, SJ Yung, YL AF Jaegle, L Webster, CR May, RD Scott, DC Stimpfle, RM Kohn, DW Wennberg, PO Hanisco, TF Cohen, RC Proffitt, MH Kelly, KK Elkins, J Baumgardner, D Dye, JE Wilson, JC Pueschel, RF Chan, KR Salawitch, RJ Tuck, AF Hovde, SJ Yung, YL TI Evolution and stoichiometry of heterogeneous processing in the Antarctic stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID NITRIC-ACID TRIHYDRATE; WINTER POLAR STRATOSPHERES; ABSORPTION CROSS-SECTIONS; LIMB EMISSION-SPECTRA; OZONE DEPLETION; ER-2 AIRCRAFT; INSITU MEASUREMENTS; REACTIVE NITROGEN; HYDROGEN-CHLORIDE; SULFATE AEROSOLS AB Simultaneous in situ measurements of HCl and ClO have been made for the first time in the southern hemisphere, allowing a systematic study of the processes governing chlorine activation between 15 and 20 km in the 1994 Antarctic winter. Data for several other gases (O-3, NO, NOy, OH, HO2, N2O, CH4, CO, H2O, CFCs), particulates, and meteorological parameters were collected from the ER-2 aircraft out of New Zealand as part of the 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements of Atmospheric Effects of Stratospheric Ail cl att (ASHOE/MAESA) campaign. Observations from the ER-2 in the fall (April-May), prior to polar night, show that chlorine activation begins with 60-75% of inorganic chlorine as HCl. By midwinter (July-August), near-total removal of HCl is observed. The wintertime loss of HCl in air recently exposed to extreme temperatures is found to be correlated with high levels of reactive chlorine (ClO and its dimer, Cl2O2) in the linear fashion expected from the stoichiometry of the heterogeneous reaction of hydrochloric acid with chlorine nitrate on polar stratospheric ic clouds (PSCs): HCl + ClONO2 --> Cl-2 + HNO3. To constrain the role of different heterogeneous reactions and PSC types, we have used a photochemical trajectory model which includes heterogeneous sulfate and PSC chemistry. Model calculations of the evolution of reactive gases ale compared with the in situ observations. In addition, simultaneous measurements of OH and HO2 are used as a diagnostic for the occurrence of the heterogeneous reaction HOCl + HCl --> Cl-2 + H2O, which contributes to suppressed levels of HOx inside the vortex. It is shown that the amount of chlorine activation is not strongly dependent on the composition of PSCs. However, HOx levels exhibit different signatures depending on the type of heterogeneous surfaces that affected chlorine activation. Furthermore, this analysis implies that in the edge legion of the Antarctic vortex, the observed near-total removal of HCl can result from latitudinal excursions of air parcels in and out of sunlight during the winter, which photochemically resupply HOCl and ClONO2 as oxidation partners for HCl. C1 NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. HARVARD UNIV, DEPT CHEM, CAMBRIDGE, MA 02138 USA. NOAA, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. CALTECH, JET PROP LAB, DIV ATMOSPHER CHEM, PASADENA, CA 91109 USA. UNIV DENVER, DEPT ENGN, DENVER, CO 80208 USA. CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA 91125 USA. RI Salawitch, Ross/B-4605-2009; Cohen, Ronald/A-8842-2011; Tuck, Adrian/F-6024-2011; Wennberg, Paul/A-5460-2012 OI Salawitch, Ross/0000-0001-8597-5832; Cohen, Ronald/0000-0001-6617-7691; Tuck, Adrian/0000-0002-2074-0538; NR 104 TC 17 Z9 17 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13235 EP 13253 DI 10.1029/97JD00935 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900036 ER PT J AU DelNegro, LA Fahey, DW Donnelly, SG Gao, RS Keim, ER Wamsley, RC Woodbridge, EL Dye, JE Baumgardner, D Gandrud, BW Wilson, JC Jonsson, HH Loewenstein, M Podolske, JR Webster, CR May, RD Worsnop, DR Tabazadeh, A Tolbert, MA Kelly, KK Chan, KR AF DelNegro, LA Fahey, DW Donnelly, SG Gao, RS Keim, ER Wamsley, RC Woodbridge, EL Dye, JE Baumgardner, D Gandrud, BW Wilson, JC Jonsson, HH Loewenstein, M Podolske, JR Webster, CR May, RD Worsnop, DR Tabazadeh, A Tolbert, MA Kelly, KK Chan, KR TI Evaluating the role of NAT, NAD, and liquid H2SO4/H2O/HNO3 solutions in Antarctic polar stratospheric cloud aerosol: Observations and implications SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NITRIC-ACID TRIHYDRATE; AIRBORNE LIDAR OBSERVATIONS; TOTAL REACTIVE NITROGEN; SULFURIC-ACID; TEMPERATURE-FLUCTUATIONS; ARCTIC STRATOSPHERE; REFRACTIVE-INDEXES; SULFATE AEROSOLS; OZONE EXPERIMENT; HYDROGEN-BOND AB Airborne measurements of total reactive nitrogen (NOy) and polar stratospheric cloud (PSC) aerosol particles were made in the Antarctic (68 degrees S) as part of the NASA Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) campaign in late July 1994. As found in both polar regions during previous studies, substantial PSC aerosol volume containing NOy was observed al temperatures above the frost point, confirming the presence of particles other than water ice. The composition of the aerosol particles is evaluated using equilibrium expressions for nitric acid trihydrate (NAT), nitric acid dihydrate (NAD), and the supercooled ternary solution (STS) composed of nitric acid (HNO3), sulfuric acid (H2SO4), and water (H2O). The equilibrium abundance of condensed HNO3 is calculated for each phase and compared to estimates made using observations of aerosol volume and NOy. The best agreement is found for STS composition, using criteria related to the onset and abundance of aerosol volume along the flight track. Throughout the PSC region, a comparison of the number of particles between 0.4 and 4.0 mu m diameter with the number of available nuclei indicates that a significant fraction of the background aerosol number participates in PSC growth. Modeled STS size distributions at temperatures below 191 K compare favorably with measured size distributions of PSC aerosol. Calculations of the heterogeneous loss of chlorine nitrate (ClONO2) show that the reactivity of the observed PSC surface area is 30 to 300% greater with STS than with NAT composition for temperatures less than 195 K. The total volume of STS PSCs is shown to be more sensitive than NAT to increases in H2O, HNO3, and H2SO4 from supersonic aircraft fleet emissions. Using the current observations and perturbations predicted by the current aircraft assessments, an increase of 50 to 260% in STS aerosol volume is expected at the lowest observed temperatures (190 to 192 K), along with an extension of significant PSC activity to regions similar to 0.7 K higher in temperature. These results improve our understanding of PSC aerosol formation in polar regions while strengthening the requirement to include STS aerosols in studies of polar ozone loss and the effects of aircraft emissions. C1 NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV COLORADO, COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80309 USA. UNIV COLORADO, DEPT CHEM & BIOCHEM, BOULDER, CO 80309 USA. UNIV DENVER, DEPT ENGN, DENVER, CO 80208 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, LA JOLLA, CA 92093 USA. AERODYNE RES INC, BILLERICA, MA 02139 USA. RP DelNegro, LA (reprint author), NOAA, AERON LAB, R-E-AL6, 325 BROADWAY, BOULDER, CO 80303 USA. RI Worsnop, Douglas/D-2817-2009; Gao, Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013 OI Worsnop, Douglas/0000-0002-8928-8017; Fahey, David/0000-0003-1720-0634 NR 80 TC 44 Z9 44 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13255 EP 13282 DI 10.1029/97JD00764 PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900037 ER PT J AU McGee, TJ Gross, M Singh, U Kimvilakani, P Matthews, A Bodeker, G Conner, B Tsou, JJ Proffitt, M Margitan, J AF McGee, TJ Gross, M Singh, U Kimvilakani, P Matthews, A Bodeker, G Conner, B Tsou, JJ Proffitt, M Margitan, J TI Vertical profile measurements of ozone at Lauder, New Zealand during ASHOE/MAESA SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC OZONE; LIDAR AB The Goddard Space Flight Center stratospheric ozone lidar was deployed at the National Institute for Water and Atmospheric Research (NIWA) facility at Lauder, New Zealand (45 degrees S, 169 degrees E), during all four of the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/ MAESA) flight periods. The site is about 500 km south of Christchurch. Efforts were made to acquire lidar data before dawn and after sunset on the days the ER-2 was flown. A total of 79 measurements were made on 47 individual nights. Each measurement provided vertical profiles of aerosols, temperature, and ozone. Profiles begin at similar to 8 km and extend to 35, 50-55, and 75 km for aerosols, ozone, and temperature, respectively. NIWA personnel launched electrochemical concentration cell ozonesondes on a number of these occasions. A summary of these data will be presented along with comparisons with data from ER-2 instruments. Average profiles for each of the four ASHOE/MAESA deployments were constructed for use as a climatological profile for model initialization. C1 NATL INST WATER & ATMOSPHER RES, LAUDER, NEW ZEALAND. HUGHES STX CORP, LANHAM, MD 20706 USA. IDEA CORP, BELTSVILLE, MD 20705 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. LOCKHEED ENGN & SCI CO, HAMPTON, VA 23665 USA. RP McGee, TJ (reprint author), NASA, GODDARD SPACE FLIGHT CTR, MC 916, GREENBELT, MD 20771 USA. RI Bodeker, Greg/A-8870-2008; McGee, Thomas/G-4951-2013 OI Bodeker, Greg/0000-0003-1094-5852; NR 8 TC 3 Z9 3 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13283 EP 13289 DI 10.1029/96JD03062 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900038 ER PT J AU Folkins, I Chatfield, R Baumgardner, D Proffitt, M AF Folkins, I Chatfield, R Baumgardner, D Proffitt, M TI Biomass burning and deep convection in southeastern Asia: Results from ASHOE/MAESA SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID POLAR STRATOSPHERIC CLOUD; TROPOSPHERIC OZONE; CARBON-MONOXIDE; ATMOSPHERIC CHEMISTRY; EQUATORIAL PACIFIC; RADIATIVE-TRANSFER; BOUNDARY-LAYER; NITRIC-OXIDE; WATER-VAPOR; TRANSPORT AB There was extensive biomass burning in Indonesia, northern Australia, and New Guinea during September and October 1994. This paper discusses two accidental encounters of biomass plumes from the 1994 Airborne Southern Hemisphere Ozone Experiment and Measurements for Assessing the Effects of Stratospheric Aircraft campaign (ASHOE/MAESA). During the October 23 descent into Fiji, and an ascent from Fiji on October 24, the NASA ER-2 passed through layers highly enhanced in NO, NOy, CO, and O-3. These layers occurred near an altitude of 15 km. Back trajectories and satellite images indicate that the layers probably originated as outflow from a convective disturbance near New Guinea. The measurements indicate that deep convection can inject emissions from southeast Asian biomass burning to near tropical tropopause altitudes. Deep convection magnifies the impact of biomass burning on tropospheric chemistry because of the much longer residence times and chemical lifetimes of species in the upper tropical troposphere. Transport of the products of southeast Asian biomass burning into the upper tropical troposphere, followed by southward high-level outflow and advection by the subtropical jet, may play a significant role in dispersing these emissions on a global scale. Anthropogenic emissions from countries in southeast Asia are likely to increase in the future as these countries become more highly industrialized. This transport mechanism may play a role in increasing the impact of these types of emissions as well. C1 NASA, AMES RES CTR, EARTH SYST SCI DIV, MOFFETT FIELD, CA 94035 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. DALHOUSIE UNIV, ATMOSPHER SCI PROGRAM, DEPT PHYS, HALIFAX, NS B3H 4J1, CANADA. NATL CTR ATMOSPHER RES, DIV ATMOSPHER CHEM, RAF, BOULDER, CO 80307 USA. COOPERAT INST RES ENVIRONM SCI, BOULDER, CO USA. RP Folkins, I (reprint author), DALHOUSIE UNIV, DEPT OCEANOG, HALIFAX, NS B3H 4J1, CANADA. NR 50 TC 66 Z9 65 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1997 VL 102 IS 11D BP 13291 EP 13299 DI 10.1029/96JD03711 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XG179 UT WOS:A1997XG17900039 ER PT J AU Mims, FM Holben, BN Eck, TF Montgomery, BC Grant, WB AF Mims, FM Holben, BN Eck, TF Montgomery, BC Grant, WB TI Smoky skies, mosquitoes, and disease SO SCIENCE LA English DT Letter C1 NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771. UNIFORMED SERV UNIV HLTH SCI,NASA,GODDARD SPACE FLIGHT CTR,BETHESDA,MD 20814. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Mims, FM (reprint author), SUN PHOTOMETER ATMOSPHER NETWORK,433 TWIN OAK RD,SEGUIN,TX 78155, USA. RI Grant, William/B-8311-2009; ECK, THOMAS/D-7407-2012 OI Grant, William/0000-0002-1439-3285; NR 8 TC 6 Z9 6 U1 0 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD JUN 20 PY 1997 VL 276 IS 5320 BP 1774 EP 1775 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XF103 UT WOS:A1997XF10300004 PM 9206832 ER PT J AU Burton, WS Noor, AK AF Burton, WS Noor, AK TI Structural analysis of the adhesive bond in a honeycomb core sandwich panel SO FINITE ELEMENTS IN ANALYSIS AND DESIGN LA English DT Article ID TEE AB Detailed finite element models are used to examine the effect of the adhesive joint between the honeycomb core and the face sheets on the load transfer and static response of sandwich panels. The square-cell honeycomb core panels considered have simply supported edges and are subjected to static uniform pressure loading. The sandwich core, face sheets and adhesive joint are modeled by using three-dimensional solid elements. The total strain energy in the finite element model of the adhesive joint material are used to investigate the effect of adhesive joint characteristics (thickness and adhesive joint fillet size) as well as the core cell size and wall thickness on the load transfer in the core/face sheet joint. C1 UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23681. NR 21 TC 22 Z9 24 U1 0 U2 5 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-874X J9 FINITE ELEM ANAL DES JI Finite Elem. Anal. Des. PD JUN 16 PY 1997 VL 26 IS 3 BP 213 EP 227 DI 10.1016/S0168-874X(96)00081-9 PG 15 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA XH500 UT WOS:A1997XH50000003 ER PT J AU Cucinotta, FA Wilson, JW Townsend, LW AF Cucinotta, FA Wilson, JW Townsend, LW TI Abrasion-ablation model for neutron production in heavy ion collisions SO NUCLEAR PHYSICS A LA English DT Article DE intermediate energy heavy ion collisions; neutron production; abrasion-ablation model ID PROTON PRODUCTION; FRAGMENTATION AB In intermediate energy nucleus-nucleus collisions, neutron production at forward angles is observed to occur with a Gaussian shape that is centered near the beam energy and extends to energies well above that of the beam. This paper presents an abrasion-ablation model for making quantitative predictions of the neutron spectrum. To describe neutrons produced from the abrasion step of the reaction where the projectile and target overlap, we use the Glauber model and include effects of final-state interactions. We then use the prefragment mass distribution from abrasion with a statistical evaporation model to estimate the neutron spectrum resulting from ablation. Measurements of neutron production from Ne and Nb beams are compared with calculations, and good agreement is found. (C) 1997 Elsevier Science B.V. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. UNIV TENNESSEE,DEPT NUCL ENGN,KNOXVILLE,TN 37996. NR 21 TC 15 Z9 15 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9474 J9 NUCL PHYS A JI Nucl. Phys. A PD JUN 16 PY 1997 VL 619 IS 1-2 BP 202 EP 212 DI 10.1016/S0375-9474(97)00130-9 PG 11 WC Physics, Nuclear SC Physics GA XG091 UT WOS:A1997XG09100012 PM 11541210 ER PT J AU Zhou, XW Russell, CT Le, G Tsyganenko, N AF Zhou, XW Russell, CT Le, G Tsyganenko, N TI Comparison of observed and model magnetic fields at high altitudes above the polar cap: POLAR initial results SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GEOMAGNETIC-FIELD; MAGNETOSPHERE; MAGNETOMETER AB Data obtained from the high altitude, polar orbiting spacecraft, POLAR, are compared with the latest version of the data-based magnetospheric magnetic field model. The data generally agree well with the model. The major directional discrepancies at high altitudes are near the dayside cusp and on the ''open'' field lines over the polar cap, especially close to the boundary of the polar cap. Near the cusp, the agreement is improved if a stronger solar wind dynamic pressure and more negative IMF By and Bz are used as the model input parameters, than was actually observed. The field measured in the vicinity of the polar cusps is generally weaker than predicted by the model. Close to noon the spacecraft enters a region of additional structured field depression that appears to be the polar cusp proper. Within the limited statistics presented here, the invariant latitude of the cusp appears to be controlled by the north-south component of the IMF and the broad depression appears to be controlled by the tilt of the dipole. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Zhou, XW (reprint author), UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095, USA. RI Le, Guan/C-9524-2012; Tsyganenko, Nikolai/J-7377-2012 OI Le, Guan/0000-0002-9504-5214; Tsyganenko, Nikolai/0000-0002-5938-1579 NR 10 TC 19 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUN 15 PY 1997 VL 24 IS 12 BP 1451 EP 1454 DI 10.1029/97GL01406 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XF904 UT WOS:A1997XF90400004 ER PT J AU Lakhina, GS Tsurutani, BT AF Lakhina, GS Tsurutani, BT TI Helicon modes driven by ionospheric O+ ions in the plasma sheet region SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INSTABILITIES; BOUNDARY; OXYGEN; TAIL; MAGNETOTAIL AB The presence of ionospheric-origin oxygen ions in the plasma sheet region results in only partial cancellation of the electron Hall current leading to the occurrence of the helicon mode rather than the Alfven mode. It is shown that the presence of ionospheric-origin oxygen ion beams with anisotropic pressure can excite helicon mode instability in the near-Earth plasma sheet region provided their Alfvenic Mach numbers lie in a certain range. The helicon modes are easily excited under the conditions when the usual long wavelengths fire-hose modes are stable. The typical real frequencies of the excited helicon modes are between 1 to 10 mHz, and the typical e-folding time of the instability is about 3 to 15 minutes at wavelengths of 1 to 5 R-E Therefore these modes are likely to attain saturation during enhanced convection events lasting fdr a few hours. Large amplitude helicon modes would distort the ambient magnetic field and may be observable as flux ropes. Low-frequency turbulence produced by these modes could scatter electrons and help excitation of the ion tearing modes leading to substorm onset. C1 INDIAN INST GEOMAGNETISM,BOMBAY 400005,MAHARASHTRA,INDIA. RP Lakhina, GS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 22 TC 11 Z9 11 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 JUN 15 PY 1997 VL 24 IS 12 BP 1463 EP 1466 DI 10.1029/97GL01208 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XF904 UT WOS:A1997XF90400007 ER PT J AU Rind, D Healy, R Parkinson, C Martinson, D AF Rind, D Healy, R Parkinson, C Martinson, D TI The role of sea ice in 2xCO(2) climate model sensitivity .2. Hemispheric dependencies SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MIXED-LAYER AB How sensitive are doubled CO2 simulations to GCM control-run sea ice thickness and extent? This issue is examined in a series of 10 control-run simulations with different sea ice and corresponding doubled CO2 simulations. Results show that with increased control-run sea ice coverage in the Southern Hemisphere, temperature sensitivity with climate change is enhanced, while there is little effect on temperature sensitivity of (reasonable) variations in control-run sea ice thickness. In the Northern Hemisphere the situation is reversed: sea ice thickness is the key parameter, while (reasonable) variations in control-run sea ice coverage are of less importance. In both cases, the quantity of sea ice that can be removed in the warmer climate is the determining factor. Overall, the Southern Hemisphere sea ice coverage change had a larger impact on global temperature, because Northern Hemisphere sea ice was sufficiently thick to limit its response to doubled CO2, and sea ice changes generally occurred at higher latitudes, reducing the sea ice-albedo feedback. In both these experiments and earlier ones in which sea ice was not allowed to change, the model displayed a sensitivity of similar to 0.02 degrees C global warming per percent change in Southern Hemisphere sea ice coverage. C1 LAMONT DOHERTY EARTH OBSERV,PALISADES,NY 10964. WOODS HOLE OCEANOG INST,WOODS HOLE,MA 02543. COLUMBIA UNIV,NEW YORK,NY. NASA,GODDARD SPACE FLIGHT CTR,OCEANS & ICE BRANCH,GREENBELT,MD 20771. RP Rind, D (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Parkinson, Claire/E-1747-2012; Healy, Richard/J-9214-2015 OI Parkinson, Claire/0000-0001-6730-4197; Healy, Richard/0000-0002-5098-8921 NR 5 TC 27 Z9 28 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUN 15 PY 1997 VL 24 IS 12 BP 1491 EP 1494 DI 10.1029/97GL01433 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XF904 UT WOS:A1997XF90400014 ER PT J AU Dyall, KG AF Dyall, KG TI Interfacing relativistic and nonrelativistic methods .1. Normalized elimination of the small component in the modified Dirac equation SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID MOLECULAR-STRUCTURE CALCULATIONS; PROJECTION OPERATORS; HAMILTONIANS; TERMS AB The introduction of relativistic terms into the nonrelativistic all-electron Schrodinger equation is achieved by the method of normalized elimination of the small component (ESC) within the matrix representation of the modified Dirac equation. In contrast to the usual method of ESC, the method presented retains the correct relativistic normalization, and permits the construction of a single matrix relating the large and small component coefficient matrices for an entire set of positive energy one-particle states, thus enabling the whole set to be obtained with a single diagonalization. This matrix is used to define a modified set of one- and two-electron integrals which have the same appearance as the nonrelativistic integrals, and to which they reduce in the limit alpha-->0. The normalized method corresponds to a projection of the Dirac-Fock matrix onto the positive energy states. Inclusion of the normalization reduces the discrepancy between the eigenvalues of the ESC approach and the Dirac eigenvalues for a model problem from order alpha(2) to order alpha(4), providing a closer approximation to the original, uneliminated solutions. The transition between the nonrelativistic and relativistic limits is achieved bq simply scaling the fine structure constant alpha. (C) 1997 American Institute of Physics. RP Dyall, KG (reprint author), NASA,THERMOSCI INST,MAIL STOP 230-3,MOFFETT FIELD,CA 94035, USA. NR 16 TC 147 Z9 147 U1 0 U2 6 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 15 PY 1997 VL 106 IS 23 BP 9618 EP 9626 DI 10.1063/1.473860 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XE026 UT WOS:A1997XE02600023 ER PT J AU Monger, B McClain, C Murtugudde, R AF Monger, B McClain, C Murtugudde, R TI Seasonal phytoplankton dynamics in the eastern tropical Atlantic SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID ZONE COLOR SCANNER; SEA-SURFACE TEMPERATURE; VARYING TRADE WINDS; EQUATORIAL ATLANTIC; ANNUAL CYCLE; ATMOSPHERIC CORRECTION; PIGMENT CONCENTRATIONS; NORTH-ATLANTIC; ARABIAN SEA; ZAIRE RIVER AB The coastal zone color scanner (CZCS) that operated aboard the Nimbus 7 satellite provided extensive coverage of phytoplankton pigment concentrations in the surface waters of the eastern tropical Atlantic (ETA) from March 1979 to February 1980 and coincided with four major research cruises to this region. Total primary production within the ETA (5 degrees N-10 degrees S, 25 degrees W-10 degrees E) was determined from CZCS pigment estimates and an empirical algorithm derived from concurrent in situ data taken along 4 degrees W that relates near-surface chlorophyll concentration and integrated primary production. We estimated an average annual production for the ETA of 2.3 Gt C yr(-1) with an associated 3.5-fold seasonal variation in the magnitude of this production. We describe the principal physical mechanisms controlling seasonal phytoplankton dynamics within the ETA and propose that in addition to seasonal change in the thermocline depth, one must also consider changes in the depth of the equatorial undercurrent. An extensive validation effort indicates that the standard CZCS global products are a conservative estimate of pigment concentrations in ETA surface waters. Significant underestimates by the CZCS global products were observed in June and July which we attributed, in part, to aerosol correction errors and, more importantly, to errors caused by a significant reduction in the concentration of near-surface dissolved organic matter that resulted from strong equatorial upwelling. C1 NASA,GODDARD SPACE FLIGHT CTR,OCEANS & ICE BRANCH,GREENBELT,MD 20771. UNIV MARYLAND,JOINT CTR EARTH SCI,COLLEGE PK,MD 20742. RP Monger, B (reprint author), CORNELL UNIV,CTR ENVIRONM,2154 SNEE HALL,ITHACA,NY 14853, USA. NR 74 TC 35 Z9 35 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD JUN 15 PY 1997 VL 102 IS C6 BP 12389 EP 12411 DI 10.1029/96JC03982 PG 23 WC Oceanography SC Oceanography GA XF422 UT WOS:A1997XF42200004 ER PT J AU Drinkwater, MR Lytle, VI AF Drinkwater, MR Lytle, VI TI ERS 1 radar and field-observed characteristics of autumn freeze-up in the Weddell Sea SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SYNTHETIC-APERTURE-RADAR; ICE; BACKSCATTER; ANTARCTICA AB ERS 1 satellite microwave radar data are analyzed to investigate changes in sea ice characteristics during a period when a drifting ice camp was deployed in the Weddell Sea, Antarctica. Synthetic aperture radar and scatterometer data are calibrated and geolocated to derive a time series of C band backscatter coefficient (sigma degrees) corresponding with simultaneous surface measurements during the austral autumn freeze-up. Thermistor strings were implanted in the snow and ice at a number of local and regional sites. Surface measurements at these sites indicate that up to 50% of the surface of ice floes surviving the summer were flooded, with an unconsolidated, saline slush layer at the snow/ice interface consisting of approximately half seawater and half ice of meteoric origin. The slush was typically 5-30 cm thick and covered by a 20- to 50-cm-thick dry snow layer. Results show that the microwave radar backscatter characteristics of this perennial ice region responded sensitively to changes in air temperature and corresponding changes in turbulent flux of heat at the surface of the sea ice. At ice concentrations exceeding 95%, the modulation of the regional backscatter coefficient by wind speed and direction was negligible. Warm summer conditions persisted for around 2 weeks after ice camp deployment on February 7 (day 38), with air temperatures of around -3 degrees to -5 degrees C prior to the onset of autumn freeze-up. From February 26 (day 57) onward, cooling began and snow ice growth proceeded as air temperatures fell to below -20 degrees C. Altogether, between February 7 (day 38) and March 15, 1992 (day 75), the backscatter coefficient time series measured by each radar indicated that sigma degrees fell by several decibels during the freezing and transformation of the layer of saturated, saline basal snow into snow ice. This change is caused by a reduction in the permittivity and thus the scattering intensity of the basal snow as a function of the disappearance, by freezing, of the saltwater saturated layer. These results suggest the possibility of monitoring the timing and autumn freeze-up transition of regional ice signatures as a means of quantifying the proportion of flooded perennial sea ice. C1 UNIV TASMANIA, ANTARCTIC COOPERAT RES CTR ANTARCTIC SO OCEAN ENV, HOBART, TAS 7001, AUSTRALIA. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. OI Drinkwater, Mark/0000-0002-9250-3806 NR 43 TC 21 Z9 21 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9275 EI 2169-9291 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD JUN 15 PY 1997 VL 102 IS C6 BP 12593 EP 12608 DI 10.1029/97JC00437 PG 16 WC Oceanography SC Oceanography GA XF422 UT WOS:A1997XF42200018 ER PT J AU Chou, SH Shie, CL Atlas, RM Ardizzone, J AF Chou, SH Shie, CL Atlas, RM Ardizzone, J TI Air-sea fluxes retrieved from special sensor microwave imager data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID LATENT-HEAT FLUX; SURFACE-LEVEL HUMIDITY; PRECIPITABLE WATER; TURBULENT FLUXES; BOUNDARY-LAYER; GLOBAL OCEANS; MOISTURE; INTERFACE; VAPOR AB A method has been developed to estimate daily surface fluxes of momentum and sensible and latent heat over the global oceans using a stability-dependent bulk scheme. Daily fluxes are computed from daily values of special sensor microwave imager (SSM/I) surface winds, SSM/I surface humidity, National Centers for Environmental Prediction sea surface temperatures (SSTs), and European Centre for Medium-Range Weather Forecasts (SSTs minus 2-m temperatures). Dairy surface specific humidity is estimated from the SSM/I water vapor for an atmospheric column and the lower 500 m of the planetary boundary layer, using the method of Chou et al. [1995] with two modifications for the extratropical oceans. The modified method is described using two simple equations. Gustiness parameterization for the weak winds and convective situations is found to have an insignificant impact on the air-sea fluxes derived from the SSM/I data and hence is not included. The SSM/I-radiosonde comparison (over the global oceans for the entire annual cycle of 1993) shows that for a 25-km resolution the instantaneous SSM/I surface humidity has a root-mean-square (rms) difference of 1.83 g kg(-1). Daily SSM/I latent heat fluxes (and wind stresses) agree well with the flux measurements over the western Pacific warm pool, with a bias of 6.2 W m(-2) (0.0061 N m(-2)), an rms difference of 29.0 W m(-2) (0.0187 N m(-2)), and a correlation of 0.83 (0.86). Monthly results of February and August 1993 show that the patterns and seasonal variabilities of the SSM/I surface humidity, latent, and sensible heat fluxes are generally in good agreement with those of the Comprehensive Ocean-Atmosphere Data Set (GOADS) and climatologies derived from ship measurements. The SSM/I sensible heat flux is generally within +/-10 W m(-2) of GOADS. However, the SSM/I latent heat flux is generally larger, especially over the wintertime trade wind belts. The result is consistent with previous climatological studies in that the latent heat fluxes based on ship measurements are systematically underestimated. C1 GEN SCI CORP,LAUREL,MD 20707. SCI SYST & APPLICAT INC,LANHAM,MD 20706. RP Chou, SH (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,MAIL CODE 912,GREENBELT,MD 20771, USA. RI Atlas, Robert/A-5963-2011 OI Atlas, Robert/0000-0002-0706-3560 NR 36 TC 51 Z9 55 U1 2 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD JUN 15 PY 1997 VL 102 IS C6 BP 12705 EP 12726 PG 22 WC Oceanography SC Oceanography GA XF422 UT WOS:A1997XF42200024 ER PT J AU Murr, LE Niou, CS Ferreyra, E Garcia, EP Liu, G Horz, F Bernhard, RP AF Murr, LE Niou, CS Ferreyra, E Garcia, EP Liu, G Horz, F Bernhard, RP TI Effect of initial microstructure on high velocity and hypervelocity impact cratering and crater-related microstructures in thick copper targets .2. Stainless steel projectiles SO JOURNAL OF MATERIALS SCIENCE LA English DT Article AB Three different, thick copper targets (an as-received, 98 mu m grain size containing similar to 10(10) dislocations/cm(2) (Vickers hardness of 0.89 GPa); an annealed, 124 mu m grain size containing 10(9) dislocations/cm(2) (Vicker's hardness of 0.69 GPa; and a 763 mu m grain size containing 10(9) dislocations/cm(2) (Vickers hardness of 0.67 GPa) were impacted with 3.18 mm diameter ferritic stainless steel projectiles at nominal velocities of 0.7, 2 and 5 km s(-1). Like companion experiments utilizing soda-lime glass projectiles (Part I), absolute grain size of the target was observed to be less important than the dislocation density in the cratering process. At low im pact velocity, depth/diameter ratios were observed to increase dramatically in contrast to less dense soda-lime glass impactors, and the impactor behaviours were also very different. The ferritic stainless steel impactors spalled into small fragments at or above 2 km s(-1) impact velocity and a significant fraction of these fragments remained in the craters. No significant melt phenomena were observed either in connection with projectile fragmentation or in the crater-related, residual microstructures. Dynamic recrystallization, dislocation cell structures and microbands were significant microstructural features in the targets. They extended from the crater walls and contributed to hard ness profiles within the cratered targets. These hardness profiles and actual hardness zones generally increased in extent from the crater wall with both impact velocity and projectile density. C1 NASA,LYNDON B JOHNSON SPACE CTR,SOLAR SYST EXPLORAT DIV,HOUSTON,TX 77058. LOCKHEED MARTIN ENGN SCI,HOUSTON,TX 77058. RP Murr, LE (reprint author), UNIV TEXAS,DEPT MET & MAT ENGN,EL PASO,TX 79968, USA. OI Murr, Lawrence/0000-0001-5942-8376 NR 15 TC 11 Z9 11 U1 0 U2 2 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 JUN 15 PY 1997 VL 32 IS 12 BP 3143 EP 3156 DI 10.1023/A:1018694532744 PG 14 WC Materials Science, Multidisciplinary SC Materials Science GA XG480 UT WOS:A1997XG48000008 ER PT J AU Kamionkowski, M Kosowsky, A Stebbins, A AF Kamionkowski, M Kosowsky, A Stebbins, A TI Statistics of cosmic microwave background polarization SO PHYSICAL REVIEW D LA English DT Article ID GRAVITATIONAL-WAVES; ANALYTIC APPROACH; RADIATION; ANISOTROPIES; FLUCTUATIONS AB We present a formalism for analyzing a full-sky temperature and polarization map of the cosmic microwave background. Temperature maps are analyzed by expanding over the set of spherical harmonics to give multipole moments of the two-point correlation function. Polarization, which is described by a second-rank tensor, can be treated analogously by expanding in the appropriate tensor spherical harmonics. We provide expressions for the complete set of temperature and polarization multipole moments for scalar and tensor metric perturbations. Four sets of multipole moments completely describe isotropic temperature and polarization correlations; for scalar metric perturbations one set is identically zero, giving the possibility of a clean determination of the vector and tensor contributions. The variance with which the multipole moments can be measured in idealized experiments is evaluated, including the effects of detector noise, sky coverage, and beam width. Finally, we construct coordinate-independent polarization two-point correlation functions, express them in terms of the multipole moments, and derive small-angle limits. C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. HARVARD UNIV,LYMAN LAB PHYS,DEPT PHYS,CAMBRIDGE,MA 02138. FERMILAB NATL ACCELERATOR LAB,FERMILAB ASTROPHYS CTR,NASA,BATAVIA,IL 60510. RP Kamionkowski, M (reprint author), COLUMBIA UNIV,DEPT PHYS,538 W 120TH ST,NEW YORK,NY 10027, USA. OI Kamionkowski, Marc/0000-0001-7018-2055 NR 70 TC 572 Z9 575 U1 1 U2 8 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD JUN 15 PY 1997 VL 55 IS 12 BP 7368 EP 7388 DI 10.1103/PhysRevD.55.7368 PG 21 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XF601 UT WOS:A1997XF60100007 ER PT J AU Jaffe, AH Turner, MS AF Jaffe, AH Turner, MS TI Limits to radiative neutrino decay from SN 1987A SO PHYSICAL REVIEW D LA English DT Article ID LIFETIMES; SN-1987A; CONSTRAINTS; MASSES AB We calculate limits to the properties of massive, unstable neutrinos using data from gamma-ray detectors on the Pioneer Venus Orbiter (PVO) Spacecraft. The absence of a gamma-ray signal in the PVO detector constrains the branching ratio to photons (B gamma), mass (m(nu)), and radiative lifetime (tau(gamma)=tau/B-gamma). For low-mass (m less than or similar to T similar to 8 MeV) neutrinos decaying nu-->nu'gamma, B-gamma<3x10(-7) for m(nu)tau less than or similar to 10(6) keVsec, and B-gamma<2x10(-13)m(nu)tau/KeV sec for m(nu)tau greater than or similar to 10(6) keV sec; limits for high-mass neutrinos are somewhat weaker due to Boltzmann suppression. We also calculate limits for decays that produce gamma rays through the bremsstrahlung channel, nu-->nu'e(+)e(-)gamma. With one exception, the PVO limits are roughly comparable to those from an analysis of data from the Solar Max Mission (SMM) Satellite (which observed at higher gamma-ray energies but for a much shorter time). For neutrino mass states that are nearly degenerate, delta m(2)/m(2) < 0.1 much less than 1, our limits for the mode nu-->nu'gamma become more stringent by a factor as large as m(2)/delta m(2), because more decay photons are shifted into the PVO energy window. For this same reason, SMM cannot constrain this case. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637. UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Jaffe, AH (reprint author), UNIV CALIF BERKELEY,CTR PARTICLE ASTROPHYS,301 LECONTE HALL,BERKELEY,CA 94720, USA. RI Jaffe, Andrew/D-3526-2009 NR 15 TC 9 Z9 9 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD JUN 15 PY 1997 VL 55 IS 12 BP 7951 EP 7959 DI 10.1103/PhysRevD.55.7951 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XF601 UT WOS:A1997XF60100058 ER PT J AU Riotto, A Vilja, I AF Riotto, A Vilja, I TI Propagation of Majorana fermions in hot plasma SO PHYSICS LETTERS B LA English DT Article ID STANDARD MODEL; ELECTROWEAK BARYOGENESIS; HIGH-TEMPERATURE; GAUGE-THEORIES; HOLES AB The properties of Majorana fermions in hot plasma are studied. One-loop resummed propagator, dispersion relations and their interpretation are discussed. It is shown that particle and hole-like solutions appear as in Dirac/chiral fermion case. The dispersion relations are, however, crucially different. We find that, in the presence of a large zero temperature bare mass, hole-hire excitations possess a negligible effective mass. As an example of a real application, we consider the neutralinos in the minimal supersymmetric extension of the standard model and argue that for realistic values of the soft supersymmetry breaking masses the existence of practically massless hole-like excitations has a considerable effect on the thermal properties, e.g. the thermalization rate, of particles interacting with these Majorana excitations. (C) 1997 Published by Elsevier Science B.V. C1 UNIV TURKU,DEPT PHYS,FIN-20014 TURKU,FINLAND. RP Riotto, A (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB CTR,POB 500,BATAVIA,IL 60510, USA. NR 17 TC 10 Z9 10 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-2693 J9 PHYS LETT B JI Phys. Lett. B PD JUN 12 PY 1997 VL 402 IS 3-4 BP 314 EP 319 DI 10.1016/S0370-2693(97)00468-1 PG 6 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XG329 UT WOS:A1997XG32900012 ER PT J AU Ozernoy, LM Genzel, R Usov, VV AF Ozernoy, LM Genzel, R Usov, VV TI Colliding winds in the stellar core at the Galactic Centre: Some implications SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE shock waves; stars, early-type; Galaxy, centre; galaxies, nuclei infrared, stars; X-rays, stars ID GAMMA-RAY LINES; ACCRETING BLACK-HOLE; EARLY-TYPE STARS; ORION COMPLEX; INTERSTELLAR-MEDIUM; SAGITTARIUS-A; EMISSION; GALAXY; MODEL; GAS AB We point out that a high number density of stars in the core of a dense star cluster, such as the central stellar cluster at the Galactic Centre, where many stars possess strong stellar winds, should result in collisions of those winds. The wind collisions in the dense stellar core at the Galactic Centre would result in the production of strong X-ray flares with a rate of similar to 10(-4) (N-w/10(3)) 2 yr(-1) and a duration of similar to 1 week, where N-w is the number of the wind-producing stars in the core. The presence of a massive black hole would enhance the stellar density around it and would make the collisions of the winds in the core substantially more frequent. Collisions of the stellar winds in the cluster also have a number of interesting observable implications, including the generation of gamma-rays by particles accelerated by the shocks from the colliding winds. These processes are also expected to be relevant to compact regions of intense star formation elsewhere. C1 GEORGE MASON UNIV, DEPT PHYS & ASTRON, FAIRFAX, VA 22030 USA. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. WEIZMANN INST SCI, DEPT PHYS, IL-76100 REHOVOT, ISRAEL. RP Ozernoy, LM (reprint author), GEORGE MASON UNIV, COMPUTAT SCI INST, FAIRFAX, VA 22030 USA. NR 61 TC 22 Z9 22 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD JUN 11 PY 1997 VL 288 IS 1 BP 237 EP 244 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XF091 UT WOS:A1997XF09100025 ER PT J AU Olson, BH Paturi, R Esener, SC AF Olson, BH Paturi, R Esener, SC TI Biorthogonally accessed three-dimensional two-photon memory for relational database operations SO APPLIED OPTICS LA English DT Article DE parallel-access optical memory; 3-D data organization; relational database; biorthogonal access AB Memory bandwidth is a bottleneck for very large database machines. Parallel-access three-dimensional two-photon memories have the potential of achieving enormous throughput (>100 Gbit/s) and capacity (1 Tbit/cm(3)) [Appl. Opt. 29, 2058 (1990)] and, consequently, are well suited for this application. Our analysis shows that some operations can be completed more than 2 orders of magnitude faster with this type of memory than with a system based on serial-access storage. These particular memories have a further feature of being accessible in orthogonal directions. We show that this property, used in conjunction with a three-dimensional data-organization scheme designed for this approach, leads to improved performance by permitting the user a choice of accessing strategies for a given operation. (C) 1997 Optical Society of America. C1 UNIV CALIF SAN DIEGO, DEPT ELECT & COMP ENGN, SAN DIEGO, CA 92093 USA. RP Olson, BH (reprint author), CALTECH, JET PROP LAB, MAIL STOP 300-315, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 16 TC 3 Z9 3 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD JUN 10 PY 1997 VL 36 IS 17 BP 3877 EP 3888 DI 10.1364/AO.36.003877 PG 12 WC Optics SC Optics GA XC808 UT WOS:A1997XC80800005 PM 18253414 ER PT J AU Kowitt, MS Cheng, ES Cottingham, DA Fixsen, DJ Inman, CA Meyer, SS Page, LA Puchalla, JL Ruhl, JE Silverberg, RF AF Kowitt, MS Cheng, ES Cottingham, DA Fixsen, DJ Inman, CA Meyer, SS Page, LA Puchalla, JL Ruhl, JE Silverberg, RF TI A detection of bright features in the microwave background SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology, observations ID SPECTRAL OBSERVATIONS; GALAXY; COBE AB We report the characterization of bright, compact features in the cosmic microwave background radiation (CMBR) detected during the 1992 June and 1994 June balloon flights of the Medium-Scale Anisotropy Measurement. Spectral flux density is determined at 5.7, 9.3, and 16.5 cm(-1). No viable counterparts are found in source catalogs at 5 GHz or at 100 mu m. The measured spectrum is consistent with a temperature fluctuation in the CMBR. The existence of such features is consistent with adiabatic fluctuation models of anisotropy in the CMBR. C1 UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,APPL RES CORP,GREENBELT,MD 20771. PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08544. UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106. RP Kowitt, MS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GLOBAL SCI & TECHNOL INC,CODE 685-0,GREENBELT,MD 20771, USA. NR 24 TC 3 Z9 3 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 JUN 10 PY 1997 VL 482 IS 1 BP 17 EP 21 DI 10.1086/304109 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000003 ER PT J AU Wang, Y Turner, EL AF Wang, Y Turner, EL TI Statistics of extreme gravitational lensing events .2. The finite shear case SO ASTROPHYSICAL JOURNAL LA English DT Article DE gravitational lensing ID STAR DISTURBANCES; FLUX VARIATIONS; GALAXIES AB We consider an astrophysical system with a population of sources and a population of lenses. For each pair of source and lens, there is a thin on-axis tubelike volume behind the lens in which the radiation flux from the source is greatly increased as a result of gravitational lensing. Any objects (such as dust grains) which pass through such a thin tube will experience strong bursts of radiation, i.e., extreme gravitational lensing events (EGLEs). We study the physics and statistics of EGLEs for the case in which the shear is larger than or comparable to the finite source size. We find that the presence of shear has only a small effect on the EGLE statistics. C1 FERMILAB NATL ACCELERATOR LAB,FERMILAB ASTROPHYS CTR,NASA,BATAVIA,IL 60510. RP Wang, Y (reprint author), PRINCETON UNIV OBSERV,PEYTON HALL,PRINCETON,NJ 08544, USA. RI Wang, Yun/B-5724-2011; Turner, Edwin/A-4295-2011 OI Wang, Yun/0000-0002-4749-2984; NR 8 TC 1 Z9 1 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 JUN 10 PY 1997 VL 482 IS 1 BP 63 EP 67 DI 10.1086/304115 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000007 ER PT J AU Matsumoto, H Koyama, K Awaki, H Tsuru, T Loewenstein, M Matsushita, K AF Matsumoto, H Koyama, K Awaki, H Tsuru, T Loewenstein, M Matsushita, K TI X-ray properties of early-type galaxies as observed with ASCA SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, abundances; galaxies, elliptical and lenticular, cD; X-rays, galaxies; X-rays, ISM ID VELOCITY DISPERSIONS; SPECTRAL PROPERTIES; EMISSION AB We have systematically investigated the Advanced Satellite for Cosmology ann Astrophysics (ASCA) spectra of 12 early-type galaxies. This paper presents the global spectral properties of these systems based on a larger sample than in any previous ASCA study. The X-ray spectra were uniformly fitted by a two-component model consisting of hard X-rays from thermal emission with a temperature of about 10 keV or from a power law with index 1.8, plus soft X-rays from a thin thermal plasma with temperature ranging from 0.3 to 1 keV. The X-ray luminosities of the hard component are found to be proportional to the blue-band luminosities, while those of the soft component show large scatter with no clear correlation. The metal abundances determined from the soft component are systematically lower than solar, with a mean value of about 0.3 solar. We examine the relationships between the temperature and volume emission measure and between the gas temperature and the stellar velocity dispersion. The volume emission measures for early-type galaxies plotted as a function of the gas temperature are well below the extrapolated line found in clusters of galaxies, indicating that early-type galaxies are relatively gas poor compared with galaxy clusters. The ratio of the stellar kinetic energy per unit mass to the thermal energy of the hot gas per unit mass (beta(spec)) is less than unity. We found no systematic relationship between X-ray properties and environment, suggesting that the interaction between interstellar matter and the intracluster medium is not strong. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV TOKYO,DEPT PHYS,BUNKYO KU,TOKYO 113,JAPAN. RP Matsumoto, H (reprint author), KYOTO UNIV,DEPT PHYS,SAKYO KU,KYOTO 60601,JAPAN. NR 44 TC 133 Z9 133 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 JUN 10 PY 1997 VL 482 IS 1 BP 133 EP 142 DI 10.1086/304132 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000015 ER PT J AU Ramos, E Kafatos, M Fruscione, A Bruhweiler, FC McHardy, IM Hartman, RC Titarchuk, LG vonMontigny, C AF Ramos, E Kafatos, M Fruscione, A Bruhweiler, FC McHardy, IM Hartman, RC Titarchuk, LG vonMontigny, C TI Contemporaneous IUE, EUVE, and high-energy observations of 3C 273 SO ASTROPHYSICAL JOURNAL LA English DT Article DE quasars, individual (3C 273); ultraviolet, galaxies; X-rays, galaxies ID EXTREME-ULTRAVIOLET EXPLORER; ACCRETION DISKS; SPECTRUM; 3C-273; COMPTONIZATION; RADIATION; RADIO AB We present the results of our 1994 January and 1995 January observations of the quasar 3C 273 obtained with the International Ultraviolet Explorer (IUE) and the Extreme-Ultraviolet Explorer (EUVE). These observations were part of a large multiwavelength campaign to observe 3C 273 from radio through gamma-rays. Our 1995 January photometric observations with the EUVE Lexan/B Deep Survey (DS) instrument indicate strong evidence for variability, at a 99% confidence level, during the 12 day observing period. We have utilized ROSAT PSPC soft X-ray power-law models to correlate with EUVE count rates. Besides variations in the normalization level between both observations, our EUV count rates are consistent with a simple power-law model with spectral index alpha similar to 1.77 (F-v similar to v(-alpha)) that can be extrapolated from the soft X-rays to the EUV range. The active galactic nucleus 3C 273 is an important blazar to study because in our picture it reveals the presence of both disk and relativistic beam spectral contributions. C1 GEORGE MASON UNIV,SPACE RES INST COMPUTAT SCI & INFORMAT,FAIRFAX,VA 22030. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. CATHOLIC UNIV AMER,DEPT PHYS,WASHINGTON,DC 20064. UNIV SOUTHAMPTON,DEPT PHYS,SOUTHAMPTON SO9 5NH,HANTS,ENGLAND. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. LANDESSTERNWARTE HEIDELBERG KONIGSTUHL,D-69117 HEIDELBERG,GERMANY. GEORGE MASON UNIV,DEPT PHYS & ASTRON,FAIRFAX,VA 22030. GEORGE MASON UNIV,CSI,CTR EARTH OBSERVING & SPACE RES,FAIRFAX,VA 22030. RP Ramos, E (reprint author), GEORGE MASON UNIV,CTR EARTH OBSERVING,FAIRFAX,VA 22030, USA. NR 29 TC 13 Z9 13 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP 167 EP 172 DI 10.1086/304121 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000018 ER PT J AU Johnson, WN McNaronBrown, K Kurfess, JD Zdziarski, AA Magdziarz, P Gehrels, N AF Johnson, WN McNaronBrown, K Kurfess, JD Zdziarski, AA Magdziarz, P Gehrels, N TI Long-term monitoring of NGC 4151 by OSSE SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 4151); galaxies, Seyfert; gamma rays, observations ID ACTIVE GALACTIC NUCLEI; PAIR PRODUCTION; SPECTRAL FEATURES; COMPACT SOURCES; RAY-SPECTRUM; NGC-4151; VARIABILITY AB We report results of over 5 yr monitoring of the Seyfert galaxy NGC 4151 by the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory. A total of more than 139 days of observations in the energy band 50 keV-10 MeV was obtained in 11 viewing periods. These observations show a photon spectrum in the 50-800 keV band that is well described by an exponentially cutoff power law of the form Phi(E) proportional to E(-1.6)e(-E/100 keV). Long-term luminosity changes of no more than a factor of 2 are observed with only modest change in the spectral shape. With these data we set the most sensitive limit to date on positron annihilation radiation from a Seyfert active galactic nucleus and address the role of e(+/-) pair production and nonthermal processes in this source. C1 NICHOLAS COPERNICUS ASTRON CTR,PL-00716 WARSAW,POLAND. JAGIELLONIAN UNIV,ASTRON OBSERV,KRAKOW,POLAND. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Johnson, WN (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7650,WASHINGTON,DC 20375, USA. RI Gehrels, Neil/D-2971-2012; Johnson, Neil/G-3309-2014 NR 28 TC 31 Z9 31 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP 173 EP 177 DI 10.1086/304148 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000019 ER PT J AU Cannizzo, JK AF Cannizzo, JK TI The nature of the fluctuations preceding the giant bursts in the bursting pulsar GRO J1744-28 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; instabilities; pulsars, individual (GRO J1744-28); X-rays, bursts ID ACCRETION DISKS; LIMIT-CYCLE; DWARF NOVAE; BLACK-HOLES; VARIABILITY; INSTABILITY; EVOLUTION; DISCOVERY; OUTBURSTS; SYSTEMS AB We examine recent time-dependent accretion disk calculations by Cannizzo that attempt to reproduce the giant bursts in GRO J1744-28 and find that the fluctuations that precede the main burst resemble the fluctuations that were observed in GRO J1744-28 toward the end of the time during which the giant bursts were seen. The calculations by Cannizzo were tuned to be at a rate of accretion slightly greater than the critical rate M-crit that divides steady and bursting behavior. This tuning leads to a near balance between the heating and cooling rates within the accretion disk such that oscillations slowly develop and grow, eventually becoming unbounded and producing a global instability. The fact that an increase in the amplitude of the interburst oscillations was seen in GRO J1744-28 most strongly during the late epoch of the time of several months covering the giant bursts is consistent with the mass accretion rate onto the pulsar decreasing and approaching M-crit. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Cannizzo, JK (reprint author), NASA,UNIV SPACE RES ASSOC,CODE 662,GREENBELT,MD 20771, USA. NR 26 TC 7 Z9 7 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 JUN 10 PY 1997 VL 482 IS 1 BP 178 EP 181 DI 10.1086/304150 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000020 ER PT J AU Bergin, EA Goldsmith, PF Snell, RL Langer, WD AF Bergin, EA Goldsmith, PF Snell, RL Langer, WD TI The chemical composition and evolution of giant molecular cloud cores: A comparison of observation and theory SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, abundances; ISM, clouds; ISM, molecules; ISM, structure ID DENSE INTERSTELLAR CLOUDS; INTER-STELLAR CLOUDS; NEUTRAL-NEUTRAL REACTIONS; GAS-PHASE CHEMISTRY; STAR-FORMATION; ATOMIC CARBON; COMPLEX; TEMPERATURE; OXYGEN; MODELS AB We present the results of an observational and theoretical study of the chemical composition and evolution of three giant cloud cores in Orion A, M17, and Cepheus A. This study is the culmination of a chemical survey of 32 transitions of 20 different molecules and isotopic variants in these cloud cores. Using these data, combined with observationally derived physical conditions, chemical abundances were calculated for several positions in each cloud. A global analysis of the molecular abundances shows that, although abundance differences exist, the chemical composition of giant cloud cores is remarkably homogeneous. This agreement suggests that the chemical evolution of the individual giant cloud cores is not unique. The molecular abundances of giant cloud cores are also systematically lower than those observed in the more quiescent dark cloud core TMC-1. A one-dimensional chemical model is presented that examines internal chemical structure induced by a radiation field enhanced by a factor of 10(3)-10(5) above the normal interstellar radiation held. This model integrates the abundances of the various species as a function of depth, producing column densities that can be compared with observations. The one-dimensional model is unable to reproduce the abundances of many molecules for any single time. Two assumptions have been investigated to improve the agreement between theory and observations. These are adding clumps and raising the initial C/O ratio. We find that the inclusion of clumps in the chemical model can reproduce the abundance of C and C+. However, because of the greater weight placed on the photon-dominated region within smaller clumps, clumps have a detrimental effect on reproducing the abundances of other species. Models with a range of C/O ratios are also compared with the measured abundances. Good agreement between this model and the observations at two positions with disparate physical properties is found for early times (t similar to 10(5) yr) and for C/O increased to similar to 0.8. We suggest that one possible interpretation of these results is that the cores are dynamically evolving objects. Either giant cloud cores are intrinsically young objects or the dense material is effectively young by virtue of a complex interchange of material between the clumps and the interclump medium. We suggest that the CS/SO ratio can be used to probe the evolutionary state of and the initial C/O ratio in dense molecular clouds. C1 UNIV MASSACHUSETTS,DEPT PHYS & ASTRON,FIVE COLL RADIO ASTRON OBSERV,AMHERST,MA 01003. CORNELL UNIV,DEPT ASTRON,NATL ASTRON & IONOSPHERE CTR,ITHACA,NY 14853. CALTECH,JET PROP LAB,PASADENA,CA 91109. RI Goldsmith, Paul/H-3159-2016 NR 59 TC 65 Z9 67 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 JUN 10 PY 1997 VL 482 IS 1 BP 285 EP 297 DI 10.1086/304108 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000027 ER PT J AU Baring, MG Harding, AK AF Baring, MG Harding, AK TI Magnetic photon splitting: Computations of proper-time rates and spectra SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; gamma rays, theory; pulsars, general; radiation mechanisms, nonthermal; stars, magnetic fields; stars, neutron ID SOFT GAMMA-REPEATERS; QUANTUM ELECTRODYNAMICS; NEUTRON-STARS; RAY; FIELDS; COINCIDENT AB The splitting of photons gamma --> gamma gamma in the presence of an intense magnetic field has recently found astrophysical applications in polar cap models of gamma-ray pulsars and in ''magnetar'' (i.e., neutron stars with extremely high fields) scenarios for soft gamma repeaters. Numerical computation of the polarization dependent rates of this third-order QED process for arbitrary held strengths and energies below pair creation threshold is difficult; thus, early analyses focused on analytic developments and simpler asymptotic forms. The recent astrophysical interest spurred the use of the S-matrix approach by Mentzel, Berg, and Wunner to determine splitting rates. In this paper, we present numerical computations of a full proper-time expression for the rate of splitting that was obtained by Stoneham and is exact up to the pair creation threshold. While the numerical results derived here are in accord with the earlier asymptotic forms that are due to Adler, our computed rates still differ by as much as a factor of 3 from the S-matrix reevaluation of Wilke and Wunner, reflecting the extreme difficulty of generating accurate S-matrix numerics for fields below about 4.4 x 10(13) G. We find that our proper-time rates appear to be very accurate and exceed Adler's asymptotic specializations significantly only for photon energies just below pair threshold and for supercritical fields, but always by less than a factor of similar to 2.6. We also provide a useful analytic series expansion for the scattering amplitude valid at low energies. RP Baring, MG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. RI Harding, Alice/D-3160-2012 NR 33 TC 28 Z9 28 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP 372 EP 376 DI 10.1086/304152 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000032 ER PT J AU Falconer, DA Moore, RL Porter, JG Gary, GA Shimizu, T AF Falconer, DA Moore, RL Porter, JG Gary, GA Shimizu, T TI Neutral-line magnetic shear and enhanced coronal heating in solar active regions SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, activity; Sun, corona; Sun, magnetic fields; sunspots; Sun, X-rays, gamma rays ID X-RAY TELESCOPE; YOHKOH; FIELD AB By examining the magnetic structure at sites in the bright coronal interiors of active regions that are not flaring but exhibit persistent strong coronal heating, we establish some new characteristics of the magnetic origins of this heating. We have examined the magnetic structure of these sites in five active regions, each of which was well observed by both the Yohkoh SXT and the Marshall Space Flight Center Vector Magnetograph and showed strong shear in its magnetic field along part of at least one neutral line (polarity inversion). Thus, we can assess whether this form of nonpotential field structure in active regions is a characteristic of the enhanced coronal heating and vice versa. From 27 orbits' worth of Yohkoh SXT images of the five active regions, we have obtained a sample of 94 persistently bright coronal features (bright in all images from a given orbit), 40 long (greater than or similar to 20,000 km) neutral-line segments having strong magnetic shear throughout (shear angle greater than 45 degrees), and 39 long neutral-line segments having weak magnetic shear throughout (shear angle less than 45 degrees). From this sample, we find that (1) all of our persistently bright coronal features are rooted in magnetic fields that are stronger than 150 G, (2) nearly all (95%) of these enhanced coronal features are rooted near neutral lines (closer than 10,000 km), (3) a great majority (80%) of the bright features are rooted near strong-shear portions of neutral lines, (4) a great majority (85%) of long strong-shear segments of neutral lines have persistently bright coronal features rooted near them, (5) a large minority (40%) of long weak-shear segments of neutral lines have persistently bright coronal features rooted near them, and (6) the brightness of a persistently bright coronal feature often changes greatly over a few hours. From these results, we conclude that most persistent enhanced heating of coronal loops in active regions (1) requires the presence of a polarity inversion in the magnetic field near at least one of the loop footpoints, (2) is greatly aided by the presence of strong shear in the core magnetic field along that neutral line, and (3) is controlled by some variable process that acts in this magnetic environment. We infer that this variable process is low-lying reconnection accompanying flux cancellation. C1 NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, NATL RES COUNCIL, HUNTSVILLE, AL 35812 USA. UNIV TOKYO, INST ASTRON, MITAKA, TOKYO 181, JAPAN. NR 31 TC 54 Z9 55 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP 519 EP 534 DI 10.1086/304114 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000046 ER PT J AU Kruk, JW Kimble, RA Buss, RH Davidsen, AF Durrance, ST Finley, DS Holberg, JB Kriss, GA AF Kruk, JW Kimble, RA Buss, RH Davidsen, AF Durrance, ST Finley, DS Holberg, JB Kriss, GA TI Final Astro-1 calibration of the Hopkins Ultraviolet Telescope: A test of white dwarf model atmospheres as far-ultraviolet calibration standards SO ASTROPHYSICAL JOURNAL LA English DT Article DE instrumentation, spectrographs; space vehicles; stars, atmospheres telescopes; ultraviolet, stars; white dwarfs ID LOCAL INTERSTELLAR-MEDIUM; SPECTRAL-ENERGY DISTRIBUTION; OBA-TYPE STARS; PHOTOMETRIC CALIBRATION; MICRO-VARIATIONS; ALPHA-LYRAE; HZ 43; HOT; HYDROGEN; G191-B2B AB We present the final calibration of the Hopkins Ultraviolet Telescope (HUT) for its flight during the Astro-1 space shuttle mission in 1990 December. The calibration is defined by a comparison between an observation obtained in flight of the hot DA white dwarf G191-B2B and the model atmosphere for this star calculated by P. Bergeron. We also present the postflight laboratory calibration of the HUT sensitivity, which we find to be in excellent agreement with the white dwarf calibration. The ratio of the white dwarf to the laboratory effective area calibration has a mean value of 1.0044 over the wavelength range 912-1840 Angstrom, a slope of 7.61 x 10(-6) Angstrom(-1) (which corresponds to a relative difference of only 0.35% at either end of the spectrum), and fluctuations about the mean value with an rms amplitude of 3%. The uncertainties in the laboratory calibration are 4% for the overall normalization, 5% relative to the mean on wavelength scales of 50 to several hundred Angstrom, and an uncertainty in the overall slope that corresponds to 1% at 1840 Angstrom and that increases smoothly to 3% at 912 Angstrom. These results validate the use of white dwarf models as absolute flux standards in the far-ultraviolet, especially for wavelengths shortward of Ly alpha, where previous experiments often disagreed by large factors. In particular, the normalization and wavelength dependence of the sensitivity calibration adopted by the Hubble Space Telescope Faint Object Spectrograph is confirmed to within the uncertainties of our laboratory calibration, while the normalization of the IUE final calibration is found to be low by an amount just exceeding our 1 sigma uncertainty. Fits to the spectra of both G191-B2B and the hot DA white dwarf HZ 43 yield effective temperatures and surface gravities in good agreement with values derived from Balmer line profiles. We also present a comparison with Voyager spectra for the stars G191-B2B, HZ 43 ED +28 degrees 4211, pi Aqr, and HD 25443. When averaged over broad bands (912-1050 Angstrom, 1050-1180 Angstrom), fluxes from the two instruments typically agree to within 10%. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV CALIF BERKELEY,CTR EUV ASTROPHYS,BERKELEY,CA 94720. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. RP Kruk, JW (reprint author), JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218, USA. RI Kruk, Jeffrey/G-4047-2012 NR 81 TC 25 Z9 25 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP 546 EP 568 DI 10.1086/304105 PN 1 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD370 UT WOS:A1997XD37000049 ER PT J AU Doschek, GA Warren, HP Laming, JM Mariska, JT Wilhelm, K Lemaire, P Schuhle, U Moran, TG AF Doschek, GA Warren, HP Laming, JM Mariska, JT Wilhelm, K Lemaire, P Schuhle, U Moran, TG TI Electron densities in the solar polar coronal holes from density-sensitive line ratios of Si VIII and S X SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, corona; ultraviolet, stars AB We derive electron densities as a function of height in the north and south polar coronal holes from a forbidden spectral line ratio of Si VIII. Si vm is produced at about 8 x 10(5) K in ionization equilibrium. We also derive densities from a similar line ratio of S x (1.3 x 10(6) K). The spectra were obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer flown on the Solar and Heliospheric Observatory spacecraft. In addition to the primary mechanism of electron impact excitation, the derivation of theoretical level populations for Si VIII and S x includes both proton and resonance capture excitation. We compare the coronal hole results to quiet-Sun coronal measurements obtained outside the east and west limbs. We find for distances of a few arcseconds outside the solar limb that the average line-of-sight electron densities in the coronal holes are about a factor of 2 lower than in quiet-Sun regions. The decrease of density with height is exponential in the polar holes. We also confirm the result known from a variety of earlier observations that the temperature of most of the plasma in coronal holes does not exceed about 10(6) K. C1 SACHS FREEMAN ASSOCIATES INC,LANDOVER,MD 20785. MAX PLANCK INST AERON,D-37189 KATLENBURG DUHM,GERMANY. UNIV PARIS 11,UNITE MIXTE CNRS,INST ASTROPHYS SPATIALE,F-91405 ORSAY,FRANCE. APPL RES CORP,NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Doschek, GA (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375, USA. NR 20 TC 78 Z9 78 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP L109 EP L112 DI 10.1086/310668 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD371 UT WOS:A1997XD37100028 ER PT J AU Francis, PJ Woodgate, BE Danks, AC AF Francis, PJ Woodgate, BE Danks, AC TI A group of red, Ly alpha-emitting, high-redshift galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, clusters, individual (2139-4434); galaxies, distances and redshifts ID RADIO GALAXIES; SPECTRA AB We have discovered two new high-redshift (z = 2.38) galaxies near the previously known z = 2.38 galaxy 2139-4434B1 (Francis et al.). All three galaxies are strong Ly alpha emitters and have much redder continuum colors (I - K similar to 5) than other optically selected high-redshift galaxies. We hypothesize that these three galaxies are QSO II's, radio-quiet counterparts of high-redshift radio galaxies containing concealed QSO nuclei. The red colors are modeled most easily by an old (>0.5 Gyr), massive (>10(11)M.,) stellar population. If true, this implies that at least one galaxy cluster of mass >>3 x 10(11) M. had collapsed before redshift 5. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. HUGHES STX,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Francis, PJ (reprint author), UNIV MELBOURNE,DEPT PHYS,PARKVILLE,VIC 3052,AUSTRALIA. RI Woodgate, Bruce/D-2970-2012 NR 29 TC 33 Z9 33 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 JUN 10 PY 1997 VL 482 IS 1 BP L25 EP L28 DI 10.1086/310667 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD371 UT WOS:A1997XD37100007 ER PT J AU Hollis, JM Pedelty, JA Lyon, RG AF Hollis, JM Pedelty, JA Lyon, RG TI Spatial resolution of the R Aquarii binary system SO ASTROPHYSICAL JOURNAL LA English DT Article DE astrometry; binaries, symbiotic; H II regions; masers; stars, variables, other; techniques, interferometric ID JET AB We report continuum VLA observations at 7 mm that have resolved the stellar components in the R Aqr binary system. R Aqr was simultaneously probed in both a 50 MHz bandpass containing lineless continuum emission associated with the hot companion/accretion disk and a 3.125 MHz bandpass containing the spectral line upsilon = 1, J = 1-0, SiO maser emission associated with the long-period-variable (LPV) envelope. The offset between the two stars is 55 +/- 2 mas with a position angle of similar to 18 degrees +/- 2 degrees relative to the LPV, providing the first data point for a subsequent monitoring program to determine precisely the binary orbit that is suspected to be highly elliptical and have a period of similar to 44 yr. We evaluate these first observations in the context of constraints placed on the orbital geometry of the system and obtain a geometrical distance of similar to 200 pc to R Aqr. We also report spectral line VLA observations at this same epoch that confirm that the SiO maser spots have a ringlike morphology, as previously reported by other investigators using the VLBA. C1 NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771. UNIV MARYLAND,NASA,GODDARD SPACE FLIGHT CTR,CTR EXCELLENCE SPACE DATA & INFORMAT SCI,GREENBELT,MD 20771. RP Hollis, JM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,DIV SPACE DATA & COMP,CODE 930,GREENBELT,MD 20771, USA. RI Lyon, Richard/D-5022-2012 NR 26 TC 35 Z9 35 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 JUN 10 PY 1997 VL 482 IS 1 BP L85 EP L88 DI 10.1086/310687 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD371 UT WOS:A1997XD37100022 ER PT J AU Hua, XM Kazanas, D Titarchuk, L AF Hua, XM Kazanas, D Titarchuk, L TI Phase difference and coherence as diagnostics of accreting compact sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms, thermal stars, neutron; X-rays, general ID X-RAYS; COMPTONIZATION; VARIABILITY AB We present calculations of the time lags and the coherence function of X-ray photons for a novel model of radiation emission from accretion-powered high-energy sources. Our model involves only Comptonization of soft photons injected near the compact object in an extended but nonuniform atmosphere around the compact object. Our results show that this model produces time lags between the hard and soft bands of the X-ray spectrum that increase with Fourier period, in agreement with recent Observations; it also produces a coherence function equal to one over a wide range of frequencies if the system parameters do not change significantly during the observation, also in agreement with the limited existing observations. We explore various conditions that could affect coherence functions. We indicate that measurements of these statistical quantities could provide diagnostics of the radial variation of the density of this class of sources. RP Hua, XM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. NR 15 TC 57 Z9 58 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 JUN 10 PY 1997 VL 482 IS 1 BP L57 EP L60 DI 10.1086/310695 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD371 UT WOS:A1997XD37100015 ER PT J AU Kommers, JM Fox, DW Lewin, WHG Rutledge, RE vanParadijs, J Kouveliotou, C AF Kommers, JM Fox, DW Lewin, WHG Rutledge, RE vanParadijs, J Kouveliotou, C TI Postburst quasi-periodic oscillations from GRO J1744-28 and from the rapid burster SO ASTROPHYSICAL JOURNAL LA English DT Article DE X-rays, bursts; stars, neutron; X-rays, general ID MXB 1730-335; MXB-1730-335; ACCRETION; EMISSION AB The repetitive X-ray bursts from the accretion-powered pulsar GRO J1744-28 show similarities to the type II X-ray bursts from the Rapid Burster. Several authors (notably, Lewin et al.) have suggested that the bursts from GRO J1744-28 are type II bursts (which arise from the sudden release of gravitational potential energy). In this paper, we present another similarity between these sources. Rossi X-ray Timing Explorer observations of GRO J1744-28 show that at least 10 out of 94 bursts are followed by quasi-periodic oscillations (QPOs) with frequencies of similar to 0.4 Hz. The period of the oscillations decreases over their similar to 30-80 s lifetime, and they occur during a spectrally hard ''shoulder'' (or ''plateau'') that follows the burst. In one case, the QPOs show a modulation envelope that resembles simple beating between two narrow-band oscillations at similar to 0.325 and similar to 0.375 Hz. Using EXOSAT observations, Lubin et al. found QPOs with frequencies of 0.039-0.056 Hz following 10 out of 95 type II bursts from the Rapid Burster. As in GRO J1744-28, the period of these oscillations decreased over their similar to 100 s lifetime, and they occurred only during spectrally hard ''humps'' in the persistent emission. Even though the QPO frequencies differ by a factor of similar to 10, we believe that this is further evidence that a similar accretion disk instability is responsible for the type II bursts from these two sources. C1 MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. UNIV ALABAMA,HUNTSVILLE,AL 35812. UNIV AMSTERDAM,NL-1012 WX AMSTERDAM,NETHERLANDS. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35800. RP Kommers, JM (reprint author), MIT,DEPT PHYS,CAMBRIDGE,MA 02139, USA. NR 26 TC 13 Z9 13 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP L53 EP L56 DI 10.1086/310669 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD371 UT WOS:A1997XD37100014 ER PT J AU Maloney, PR Colgan, SWJ Hollenbach, DJ AF Maloney, PR Colgan, SWJ Hollenbach, DJ TI Probing Galactic center black hole candidates with far-infrared spectroscopy SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy, center; ISM, clouds; stars, individual (1E 1740.7-2942); X-rays, general ID X-RAY SOURCE; MOLECULAR CLOUD; 1E 1740.7-2942; SOURCE 1E1740.7-2942; 1E-1740.7-2942; GRS-1758-258 AB The narrow positron annihilation line source in the Galactic center has been identified with the X-ray source 1E 1740.7-2942, which is coincident in projection with a Galactic center molecular cloud and exhibits synchrotron jets in the radio spectrum. It has been suggested that the source is powered by Bondi-Hoyle accretion from the cloud onto a compact object. Here we show that, regardless of the source of the X-ray luminosity, the irradiation of the interstellar medium (ISM) in its vicinity by similar to 1 keV X-rays can generate substantial luminosities in a number of far-infrared atomic fine-structure lines, such as [O I] 63 mu m, [C II] 158 mu m, and [Si II] 35 mu m. Similar predictions hold for the nearly identical (in luminosity, spectrum, and presence of radio jets) Galactic center source GRS 1758-258. The corresponding line fluxes will be easily detectable using the Infrared Space Observatory; if the sources are embedded in dense ISM, the observations will allow estimates of the gas density, column density, and volume filling factor in the vicinity of the X-ray sources, the X-ray luminosity of the source averaged over the last t similar to 100 yr, and will constrain models for accretion from the ISM. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Maloney, PR (reprint author), UNIV COLORADO,CTR ASTROPHYS & SPACE ASTRON,CAMPUS BOX 391,BOULDER,CO 80309, USA. RI Colgan, Sean/M-4742-2014 NR 22 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1997 VL 482 IS 1 BP L41 EP L44 DI 10.1086/310686 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD371 UT WOS:A1997XD37100011 ER PT J AU Mushotzky, RF Scharf, CA AF Mushotzky, RF Scharf, CA TI The luminosity-temperature relation at z=0.4 for clusters of galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, observations; galaxies, clusters, general; X-rays, galaxies ID X-RAY-CLUSTERS; HYDRODYNAMIC SIMULATION; HIGH-RESOLUTION; EVOLUTION; DISTANT; UNIVERSE AB We have obtained the first large sample of accurate temperatures for clusters at z > 0.14 from ASCA. We compare the luminosity-temperature (L-T) distribution for these clusters with the low-redshift sample of David and coworkers and find that there is no evidence for evolution. We also find that the intrinsic variance in this relation is roughly constant with redshift. Additionally, there is no detectable change in the relationship of optical velocity dispersion to X-ray temperature with redshift. Most cosmological simulations driven primarily by gravity predict substantial changes in the L-T relation due to the recent rapid growth of clusters. Our results are consistent either with models in which the cluster core entropy is dominated by preheating, or with low-Omega models in which cluster structure does not evolve strongly with time. The intrinsic variance in the L-T relation at a fixed redshift can be due to variety of possible causes, e.g., a change in the baryonic fraction from cluster to cluster, variation in the fraction of the total energy in the system arising from shocks or supernova heating, or variations in the emission measure distributions in multiphase gas. C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. RP Mushotzky, RF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 662,GREENBELT,MD 20771, USA. NR 39 TC 93 Z9 93 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 JUN 10 PY 1997 VL 482 IS 1 BP L13 EP L16 DI 10.1086/310676 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XD371 UT WOS:A1997XD37100004 ER PT J AU Wu, XS Leib, SJ Goldstein, ME AF Wu, XS Leib, SJ Goldstein, ME TI On the nonlinear evolution of a pair of oblique Tollmien-Schlichting waves in boundary layers SO JOURNAL OF FLUID MECHANICS LA English DT Article ID DIRECT NUMERICAL-SIMULATION; INSTABILITY WAVES; RESONANT-TRIAD; VORTEX INTERACTION; UPPER BRANCH; SHEAR FLOWS; TRANSITION; DISTURBANCES; STABILITY; PRESSURE AB This paper is concerned with the nonlinear interaction and development of a pair of oblique Tollmien-Schlichting waves which travel with equal but opposite angles to the free stream in a boundary layer. Our approach is based on high-Reynolds-number asymptotic methods. The so-called 'upper-branch' scaling is adopted so that there exists a well-defined critical layer, i.e. a thin region surrounding the level at which the basic flow velocity equals the phase velocity of the waves. We show that following the initial linear growth, the disturbance evolves through several distinct nonlinear stages. In the first of these, nonlinearity only affects the phase angle of the amplitude of the disturbance, causing rapid wavelength shortening, while the modulus of the amplitude still grows exponentially as in the linear regime. The second stage starts when the wavelength shortening produces a back reaction on the development of the modulus. The phase angle and the modulus then evolve on different spatial scales, and are governed by two coupled nonlinear equations. The solution to these equations develops a singularity at a finite distance downstream. As a result, the disturbance enters the third stage in which it evolves over a faster spatial scale, and the critical layer becomes both non-equilibrium and viscous in nature, in contrast to the two previous stages, where the critical layer is in equilibrium and purely viscosity dominated. In this stage, the development is governed by an amplitude equation with the same nonlinear term as that derived by Wu, Lee & Cowley (1993) for the interaction between a pair of Rayleigh waves. The solution develops a new singularity, leading to the fourth stage where the flow is governed by the fully nonlinear three-dimensional inviscid triple-deck equations. It is suggested that the stages of evolution revealed here may characterize the so-called 'oblique breakdown' in a boundary layer. A discussion of the extension of the analysis to include the resonant-triad interaction is given. C1 NYMA INC,LEWIS RES CTR GRP,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Wu, XS (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT MATH,180 QUEENS GATE,LONDON SW7 2BZ,ENGLAND. NR 56 TC 5 Z9 5 U1 2 U2 3 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 JUN 10 PY 1997 VL 340 BP 361 EP 394 DI 10.1017/S0022112097005557 PG 34 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XF401 UT WOS:A1997XF40100014 ER PT J AU Dixon, TH Mao, AL Bursik, M Heflin, M Langbein, J Stein, R Webb, F AF Dixon, TH Mao, AL Bursik, M Heflin, M Langbein, J Stein, R Webb, F TI Continuous monitoring of surface deformation at Long Valley Caldera, California, with GPS SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID GLOBAL POSITIONING SYSTEM; EASTERN CALIFORNIA; KILAUEA VOLCANO; 2-COLOR GEODIMETER; MOTION; ERUPTION; DISPLACEMENT; ATTENUATION; VELOCITIES; INFLATION AB Continuous Global Positioning System (GPS) measurements at Long Valley Caldera, an active volcanic region in east central California, have been made on the south side of the resurgent dome since early 1993. A site on the north side of the dome was added in late 1994. Special adaptations for autonomous operation in remote regions and enhanced vertical precision were made. The data record ongoing volcanic deformation consistent with uplift and expansion of the surface above a shallow magma chamber. Measurement precisions (1 standard error) for ''absolute'' position coordinates, i.e., relative to a global reference frame, are 3-4 mm (north), 5-6 mm (east), and 10-12 mm (vertical) using 24 hour solutions. Corresponding velocity uncertainties for a 12 month period are about 2 mm/yr in the horizontal components and 3-4 mm/yr in the vertical component. High precision can also be achieved for relative position coordinates on short (<10 km) baselines using broadcast ephemerides and observing times as short as 3 hours, even when data are processed rapidly on site. Comparison of baseline length changes across the resurgent dome between the two GPS sites and corresponding two-color electronic distance measurements indicates similar extension rates within error (similar to 2 mm/yr) once we account for a random walk noise component in both systems that may reflect spurious monument motion. Both data sets suggest a pause in deformation for a 3.5 month period in mid-1995, when the extension rate across the dome decreased essentially to zero. Three dimensional positioning data from the two GPS stations suggest a depth (5.8 +/- 1.6 km) and location (west side of the resurgent dome) of a major inflation center, I in agreement with other geodetic techniques, near the top of a magma chamber inferred from seismic data. GPS systems similar to those installed at Long Valley can provide a practical method for near real-time monitoring and hazard assessment on many active volcanoes. C1 SUNY BUFFALO, DEPT GEOL, BUFFALO, NY 14260 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. US GEOL SURVEY, MENLO PK, CA 94025 USA. RP Dixon, TH (reprint author), UNIV MIAMI, ROSENSTIEL SCH MARINE & ATMOSPHER SCI, 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA. NR 53 TC 49 Z9 49 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD JUN 10 PY 1997 VL 102 IS B6 BP 12017 EP 12034 DI 10.1029/96JB03902 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XD578 UT WOS:A1997XD57800024 ER PT J AU Miner, E AF Miner, E TI Case for Cassini SO NEW SCIENTIST LA English DT Letter RP Miner, E (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU NEW SCIENTIST PUBL EXPEDITING INC PI ELMONT PA 200 MEACHAM AVE, ELMONT, NY 11003 SN 0262-4079 J9 NEW SCI JI New Sci. PD JUN 7 PY 1997 VL 154 IS 2085 BP 53 EP 53 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XD930 UT WOS:A1997XD93000051 ER PT J AU Wu, LC DAmelio, F Fox, RA Polyakov, I Daunton, NG AF Wu, LC DAmelio, F Fox, RA Polyakov, I Daunton, NG TI Light microscopic image analysis system to quantify immunoreactive terminal area apposed to nerve cells SO JOURNAL OF NEUROSCIENCE METHODS LA English DT Article DE image analysis; FFT; NIH-image; quantitative immunocytochemistry; GABA; somatosensory cortex; light microscopy AB The present report describes a desktop computer-based method far the quantitative assessment of the area occupied by immunoreactive terminals in close apposition to nerve cells in relation to the perimeter of the cell soma. This method is based on Fast Fourier Transform (FFT) routines incorporated in NIH-Image public domain software. Pyramidal cells of layer V of the somatosensory cortex outlined by GABA immunolabeled terminals were chosen for our analysis. A Leitz Diaplan light microscope was employed for the visualization of the sections. A Sierra Scientific Model 4030 CCD camera was used to capture the images into a Macintosh Centris 650 computer. After preprocessing, filtering was performed on the power spectrum in the frequency domain produced by the FFT operation. An inverse FFT with filter procedure was employed to restore the images to the spatial domain. Pasting of the original image to the transformed one using a Boolean logic operation called 'AND'ing produced an image with the terminals enhanced. This procedure allowed the creation of a binary image using a well-defined threshold of 128. Thus, the terminal area appears in black against a white background. This methodology provides an objective means of measurement of area by counting the total number of pixels occupied by immunoreactive terminals in light microscopic sections in which the difficulties of labeling intensity, size, shape and numerical density of terminals are avoided. (C) 1997 Elsevier Science B.V. C1 SAN JOSE STATE UNIV FDN,SAN JOSE,CA 95192. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. SAN JOSE STATE UNIV,SAN JOSE,CA 95192. NR 9 TC 27 Z9 27 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0165-0270 J9 J NEUROSCI METH JI J. Neurosci. Methods PD JUN 6 PY 1997 VL 74 IS 1 BP 89 EP 96 DI 10.1016/S0165-0270(97)02266-8 PG 8 WC Biochemical Research Methods; Neurosciences SC Biochemistry & Molecular Biology; Neurosciences & Neurology GA XG458 UT WOS:A1997XG45800010 PM 9210578 ER PT J AU Meador, MAB Johnston, JC Cavano, PJ Frimer, AA AF Meador, MAB Johnston, JC Cavano, PJ Frimer, AA TI Oxidative degradation of nadic-end-capped polyimides .2. Evidence for reactions occurring at high temperatures SO MACROMOLECULES LA English DT Article ID PMR-15 POLYIMIDE; FREE-RADICALS; CROSSLINKING; RESINS AB The oxidative degradation of PMR (for olymerization of monomeric reactants) polyimides at elevated temperatures was followed by cross-polarized magic angle spinning (CP-MAS) NMR. C-13 labeling of selected sites in the polymers allowed for direct observation of the transformations arising from oxidation processes. As opposed to model compound studies, the reactions were followed directly in the polymer. The labeling experiments confirm the previously reported oxidation of the methylene carbon to ketone in the methylenedianiline portion of the polymer chain. They also show the formation of two other oxidized species, acid and ester, from this same carbon. In addition, the technique provides the first evidence of the kind of degradation reactions that are occurring in the nadic end caps. Several PMR formulations containing moieties determined to be present after oxidation, as suggested by the labeling study, were synthesized. Weight loss, FTIR, and natural abundance NMR of these derivatives were followed during aging. In this way, weight loss could be related to the observed transformations. C1 CASE WESTERN RESERVE UNIV, DEPT CHEM, CLEVELAND, OH 44106 USA. BAR ILAN UNIV, DEPT CHEM, IL-52900 RAMAT GAN, ISRAEL. RP Meador, MAB (reprint author), NASA, LEWIS RES CTR, DIV MAT, CLEVELAND, OH 44135 USA. OI Meador, Mary Ann/0000-0003-2513-7372 NR 34 TC 22 Z9 25 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD JUN 2 PY 1997 VL 30 IS 11 BP 3215 EP 3223 DI 10.1021/ma970097i PG 9 WC Polymer Science SC Polymer Science GA XC528 UT WOS:A1997XC52800014 ER PT J AU Wolfson, O Jajodia, S Huang, YX AF Wolfson, O Jajodia, S Huang, YX TI An adaptive data replication algorithm SO ACM TRANSACTIONS ON DATABASE SYSTEMS LA English DT Article DE algorithms; performance; computer networks; dynamic data allocation; file allocation; replicated data ID QUORUM CONSENSUS; FILE SYSTEM; SCHEME; CODA AB This article addresses the performance of distributed database systems. Specifically, we present an algorithm for dynamic replication of an object in distributed systems. The algorithm is adaptive in the sense that it changes the replication scheme of the object (i.e., the set of processors at which the object is replicated) as changes occur in the read-write pattern of the object (i.e., the number of reads and writes issued by each processor). The algorithm continuously moves the replication scheme towards an optimal one. We show that the algorithm can be combined with the concurrency control and recovery mechanisms of a distributed database management system. The performance of the algorithm is analyzed theoretically and experimentally. On the way we provide a lower bound on the performance of any dynamic replication algorithm. C1 NASA, GODDARD SPACE FLIGHT CTR, CESDIS, GREENBELT, MD 20771 USA. GEORGE MASON UNIV, INFORMAT & SOFTWARE SYST ENGN DEPT, FAIRFAX, VA 22030 USA. RP UNIV ILLINOIS, DEPT ELECT ENGN & COMP SCI, CHICAGO, IL 60680 USA. NR 46 TC 171 Z9 178 U1 1 U2 2 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 2 PENN PLAZA, STE 701, NEW YORK, NY 10121-0701 USA SN 0362-5915 EI 1557-4644 J9 ACM T DATABASE SYST JI ACM Trans. Database Syst. PD JUN PY 1997 VL 22 IS 2 BP 255 EP 314 DI 10.1145/249978.249982 PG 60 WC Computer Science, Information Systems; Computer Science, Software Engineering SC Computer Science GA XD133 UT WOS:A1997XD13300004 ER PT J AU Marmann, RA AF Marmann, RA TI Using spacelab as a precursor of science operations for the space station SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 46th International Astronautical Congress CY OCT 01-06, 1995 CL OSLO, NORWAY AB For more than 15 years, Spacelab, has provided a laboratory in space for an international array of experiments, facilities, and experimenters. In addition to continuing this important work, Spacelab is now serving as a crucial stepping-stone to the improved science, improved operations, and rapid access to space that will characterize International Space Station. In the Space Station era, science operations will depend primarily on distributed/remote operations that will allow investigators to direct science activities from their universities, facilities, or home bases. Spacelab missions are a crucial part of preparing for these activities, having been used to test, prove, and refine remote operations over several missions. The knowledge gained from preparing these Missions is also playing a crucial role in reducing the time required to put an experiment into orbit, from revolutionizing the processes involved to testing the hardware needed for these more advanced operations. This paper discusses the role of the Spacelab program and the NASA Marshall Space Flight Center- (MSFC-) managed missions in developing and refining remote operations, new hardware and facilities for use on Space Station, and procedures that dramatically reduce preparation time for flight. (C) 1998 Published by Elsevier Science Ltd. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Marmann, RA (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD JUN PY 1997 VL 40 IS 11 BP 815 EP 820 DI 10.1016/S0094-5765(97)00127-6 PG 6 WC Engineering, Aerospace SC Engineering GA ZD430 UT WOS:000072684400007 PM 11540772 ER PT J AU Brady, MP Smialek, JL Smith, J Humphrey, DL AF Brady, MP Smialek, JL Smith, J Humphrey, DL TI The role of Cr in promoting protective alumina scale formation by gamma-based Ti-Al-Cr alloys .1. Compatibility with alumina and oxidation behavior in oxygen SO ACTA MATERIALIA LA English DT Article ID O SYSTEM; PHASE; MICROSTRUCTURE; NITROGEN; FILMS AB The substitution of greater than 8-10 at.% Cr for Ti in Ti-Al reduces the level of Al needed for protective alumina scale formation during oxidation, the ''Cr effect''. To elucidate the mechanism of the Cr effect, the interaction of binary Ti-Al and ternary Ti-Al-Cr alloys with alumina was examined at 1000 degrees C by hot-pressed diffusion couples. The oxidation behavior of the same alloys was also examined al 1000 degrees C in dry oxygen. The dissolution of alumina in an alloy/alumina diffusion couple correlated with an inability of the alloy to form a protective alumina scale on exposure in dry oxygen because of internal attack. Both of these effects were associated with high oxygen permeability in the alloy. It was postulated that the Cr effect results from the Ti(Cr,Al)(2) Laves phase, which has a low oxygen permeability and is capable of alumina scale formation despite its relatively low Al content of 37-42 at.% Al. (C) 1997 Acta Metallurgica Inc. C1 NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. RI Brady, Michael/A-8122-2008 OI Brady, Michael/0000-0003-1338-4747 NR 34 TC 73 Z9 80 U1 2 U2 12 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1359-6454 EI 1873-2453 J9 ACTA MATER JI Acta Mater. PD JUN PY 1997 VL 45 IS 6 BP 2357 EP 2369 DI 10.1016/S1359-6454(96)00362-X PG 13 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA XE069 UT WOS:A1997XE06900013 ER PT J AU Brady, MP Smialek, JL Humphrey, DL Smith, J AF Brady, MP Smialek, JL Humphrey, DL Smith, J TI The role of Cr in promoting protective alumina scale formation by gamma-based Ti-Al-Cr alloys .2. Oxidation behavior in air SO ACTA MATERIALIA LA English DT Article ID NITROGEN; MICROSTRUCTURE; INTERMETALLICS AB The oxidation behavior of single-phase gamma, single-phase Laves, and two-phase gamma + Laves Ti-Al-Cr alloys was investigated at 1000 degrees C in air. The addition of 4-5 at.% Cr to the gamma phase resulted in protective alumina scale formation in dry air, but titania-based nodule formation in humid room air. Two-phase gamma + Laves alloys exhibited protective alumina scale formation in both dry air and humid room air. The difference in oxidation behavior between gamma and gamma + Laves alloys was interpreted in terms of compositional changes at the alloy/scale interface during oxidation. (C) 1997 Acta Metallurgica Inc. C1 NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. RI Brady, Michael/A-8122-2008 OI Brady, Michael/0000-0003-1338-4747 NR 19 TC 86 Z9 93 U1 2 U2 14 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1359-6454 J9 ACTA MATER JI Acta Mater. PD JUN PY 1997 VL 45 IS 6 BP 2371 EP 2382 DI 10.1016/S1359-6454(96)00361-8 PG 12 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA XE069 UT WOS:A1997XE06900014 ER PT J AU Abumeri, GH Chamis, CC AF Abumeri, GH Chamis, CC TI T/BEST: A computer code for assessing the benefits of advanced aerospace technologies SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article DE advanced composites; computer code; multidisciplinary; stage performance; structural analysis; manufacturing process; cost assessment AB A computer software named T/BEST, Technology Benefit Estimator, has been developed to provide a formal method to assess advanced aerospace technologies and quantify the benefit contributions for prioritization. An open-ended, modular approach is used to allow for upgrade and insertion of advanced technology modules. T/BEST's software framework, beginner-to-expert operation, interface architecture and key analysis modules are discussed. fn this paper, selected features and applications of T/BEST are demonstrated. Sample cases pertaining to structural analysis of fan and compressor blades made of titanium and composite are presented. The performance of hot and cold composite fan blades is also discussed. The cost required to manufacture titanium and composite fan blades is estimated. (C) 1997 Elsevier Science Limited. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. NYMA INC,BROOKPARK,OH 44142. NR 11 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD JUN PY 1997 VL 28 IS 4 BP 231 EP 238 DI 10.1016/S0965-9978(97)00002-1 PG 8 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA WY325 UT WOS:A1997WY32500004 ER PT J AU Kicza, M Elachi, C AF Kicza, M Elachi, C TI M-5 rocket gives Japan's launch business a big lift SO AEROSPACE AMERICA LA English DT Letter RP Kicza, M (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD JUN PY 1997 VL 35 IS 6 BP 7 EP 8 PG 2 WC Engineering, Aerospace SC Engineering GA XC379 UT WOS:A1997XC37900004 ER PT J AU Krothapalli, A Soderman, PT Allen, CS Hayes, JA Jaeger, SM AF Krothapalli, A Soderman, PT Allen, CS Hayes, JA Jaeger, SM TI Flight effects on the far-field noise of a heated supersonic jet SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT CEAS/AIAA 2nd Aeroacoustics Conference CY MAY 06-08, 1996 CL STATE COLL, PA SP CEAS, AIAA ID SHOCK-ASSOCIATED NOISE AB The influence of forward flight on the far-field noise of an underexpanded heated supersonic jet has been studied experimentally with a 12.5-cm-diam convergent nozzle operated in the NASA Ames Research Center 12.2 X 24.4 m (40 X 80 ft) wind tunnel. The nozzle was operated at nozzle pressure ratios up to 4.5 and stagnation temperature ratios from 2.45 to 3.45. The resulting velocity (based on fully expanded condition) range is from 586 to 858 m/s. The freestream Mach number was varied from 0 to 0.32. Par-field narrow band spectra were obtained at angles (measured from the inlet axis) covering a range from 30 to 155 deg. A small amplification of the overall sound pressure level (2 dB) due to forward flight is observed in the forward quadrant. The mixing noise reduction in the aft quadrant due to forward flight is much smaller than that observed in corresponding cold jets. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,LOW SPEED AERODYNAM BRANCH,MOFFETT FIELD,CA 94035. NR 24 TC 16 Z9 16 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD JUN PY 1997 VL 35 IS 6 BP 952 EP 957 DI 10.2514/2.203 PG 6 WC Engineering, Aerospace SC Engineering GA XC113 UT WOS:A1997XC11300003 ER PT J AU Bogdanoff, DW Wilson, GJ Sussman, MA AF Bogdanoff, DW Wilson, GJ Sussman, MA TI Experimental demonstration of use of N2O to increase shock tunnel test time SO AIAA JOURNAL LA English DT Article AB An experimental investigation was carried out into the replacement of air in the driven tube of a reflected shock tunnel by an N2O/N-2 mixture in order to increase the test time. The final gas mixture obtained is the same with either air or N2O/N-2 in the driven tube. The incident shock velocities were between 2 and 3 km/s. Test times (or times until driver gas arrival) were estimated from fight emission histories in the driven tube and in the nozzle and from pressure histories just upstream of the nozzle entrance. The test times estimated from the light emission histories behind the incident shock showed that consistent increases of 60-100% were obtained upon substituting N2O/N-2 for air in the driven tube. These increases were in good agreement with theoretical estimates. The test times estimated from the light emission histories in the nozzle or pressure histories at the nozzle inlet showed significant improvements with N2O/N-2 only for cases where the facility was operated at substantially overtailored conditions, probably due to the greater stability of the driver-driven interface at these conditions. At overtailored operating conditions, test times increases of 60-100% with N2O/N-2 were observed with all three diagnostic techniques. These increases were in reasonable agreement with theoretical estimates. C1 SEMITOOL,THERMAL PROD DIV,KALISPELL,MT 59901. PARAMETR TECHNOL CORP,ANAL TECHNOL MECH DIV,SAN JOSE,CA 95131. RP Bogdanoff, DW (reprint author), NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035, USA. NR 24 TC 0 Z9 0 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD JUN PY 1997 VL 35 IS 6 BP 1048 EP 1056 PG 9 WC Engineering, Aerospace SC Engineering GA XC113 UT WOS:A1997XC11300015 ER PT J AU Harstad, KG Miller, RS Bellan, J AF Harstad, KG Miller, RS Bellan, J TI Efficient high-pressure state equations SO AICHE JOURNAL LA English DT Article AB A method is presented for a relatively accurate, noniterative, computationally efficient calculation of high-pressure fluid-mixture equations of state, especially targeted to gas turbines and rocker engines. Pressures above I bar and temperatures above 100 K are addressed. The method is based on curve fitting an effective reference state relative to departure functions formed using the Peng-Robinson cubic state equation Fit parameters for H-2, O-2, N-2, propane, methane, n-heptane, and methanol are given. RP Harstad, KG (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 10 TC 50 Z9 50 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 JUN PY 1997 VL 43 IS 6 BP 1605 EP 1610 DI 10.1002/aic.690430624 PG 6 WC Engineering, Chemical SC Engineering GA XD322 UT WOS:A1997XD32200023 ER PT J AU Cooper, JB Wise, KL Jensen, BJ AF Cooper, JB Wise, KL Jensen, BJ TI Modulated FT-Raman fiber optic spectroscopy: A technique for remotely monitoring high-temperature reactions in real-time SO ANALYTICAL CHEMISTRY LA English DT Article ID LASERS AB A modification to a commercial FT-Raman spectrometer is presented for the elimination of thermal backgrounds in FT-Raman spectra. The modification involves the use of a mechanical chopper to modulate the CW laser, remote collection of the signal via fiber optics, and connection of a dual-phase digital signal processor lock-in amplifier between the detector and the spectrometer's collection electronics to demodulate and filter the optical signals. The resulting modulated FT-Raman fiber-optic spectrometer is capable of completely eliminating thermal backgrounds at temperatures exceeding 370 degrees C, In addition, the signal/noise of generated Raman spectra is greater than for spectra collected with the conventional FT-Raman under identical conditions and incident laser power, This is true for both room-temperature and hot samples. The method allows collection of data using preexisting spectrometer software. The total cost of the modification (excluding fiber optics) is similar to$3000 and requires less than 2 h to implement, This is the first report of FT-Raman spectra collected at temperatures in excess of 300 degrees C in the absence of thermal backgrounds. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Cooper, JB (reprint author), OLD DOMINION UNIV,DEPT CHEM & BIOCHEM,NORFOLK,VA 23529, USA. NR 11 TC 20 Z9 20 U1 1 U2 9 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0003-2700 J9 ANAL CHEM JI Anal. Chem. PD JUN 1 PY 1997 VL 69 IS 11 BP 1973 EP 1978 DI 10.1021/ac970193h PG 6 WC Chemistry, Analytical SC Chemistry GA XC375 UT WOS:A1997XC37500009 PM 21639237 ER PT J AU Rostoker, G Baumjohann, W Gonzalez, W Kamide, Y Kokubun, S McPherron, RL Tsurutani, BT AF Rostoker, G Baumjohann, W Gonzalez, W Kamide, Y Kokubun, S McPherron, RL Tsurutani, BT TI Decay of the Dst field of geomagnetic disturbance after substorm onset and its implication to storm-substorm relation - Comment SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Letter C1 MAX PLANCK INST EXTRATERR PHYS, D-37075 GARCHING, GERMANY. INST NACL PESQUISAS ESPACIAIS, SAO JOSE DOS CAMPOS, SP, BRAZIL. NAGOYA UNIV, SOLAR TERR ENVIRONM LAB, TOYOKAWA, JAPAN. UNIV CALIF LOS ANGELES, INST GEOPHYS & PLANETARY PHYS, LOS ANGELES, CA 90024 USA. CALTECH, JET PROP LAB, PASADENA, CA USA. RP UNIV ALBERTA, DEPT PHYS, EDMONTON, AB, CANADA. RI Baumjohann, Wolfgang/A-1012-2010 OI Baumjohann, Wolfgang/0000-0001-6271-0110 NR 7 TC 12 Z9 12 U1 0 U2 3 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0992-7689 J9 ANN GEOPHYS-ATM HYDR JI Ann. Geophys.-Atmos. Hydrospheres Space Sci. PD JUN PY 1997 VL 15 IS 6 BP 848 EP 850 PG 3 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA XG445 UT WOS:A1997XG44500030 ER PT J AU Descour, MR Volin, CE Dereniak, EL Gleeson, TM Hopkins, MF Wilson, DW Maker, PD AF Descour, MR Volin, CE Dereniak, EL Gleeson, TM Hopkins, MF Wilson, DW Maker, PD TI Demonstration of a computed-tomography imaging spectrometer using a computer-generated hologram disperser SO APPLIED OPTICS LA English DT Article DE computed-tomography imaging spectrometry; computer-generated holography; disperser design ID SIMULTANEOUS ACQUISITION; PHASE AB We have constructed a computed-tomography imaging spectrometer that uses a phase-only computer-generated hologram (CGH) array illuminator as the disperser. This imaging spectrometer collects multiplexed spatial and spectral data simultaneously and can be used for flash spectral imaging. The CGH disperser has been designed to maintain nearly equal spectral diffraction efficiency among a 5 x 5 array of diffraction orders and to minimize diffraction efficiency into higher orders. Reconstruction of the (x, y, lambda) image cube from the raw, two-dimensional data is achieved by computed-tomography techniques. The reconstructed image and spectral-signature data compare favorably with measurements by other spectrometric methods. (C) 1997 Optical Society of America. C1 CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. RP Descour, MR (reprint author), UNIV ARIZONA,CTR OPT SCI,TUCSON,AZ 85721, USA. NR 17 TC 58 Z9 59 U1 1 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 JUN 1 PY 1997 VL 36 IS 16 BP 3694 EP 3698 DI 10.1364/AO.36.003694 PG 5 WC Optics SC Optics GA XB710 UT WOS:A1997XB71000015 PM 18253394 ER PT J AU Tingay, SJ Jauncey, DL Reynolds, JE Tzioumis, AK King, EA Preston, RA Lovell, JEJ McCulloch, PM Costa, ME Nicolson, G Koekemoer, A Tornikoski, M KedzioraChudczer, L CampbellWilson, D AF Tingay, SJ Jauncey, DL Reynolds, JE Tzioumis, AK King, EA Preston, RA Lovell, JEJ McCulloch, PM Costa, ME Nicolson, G Koekemoer, A Tornikoski, M KedzioraChudczer, L CampbellWilson, D TI The nearest GHz peaked-spectrum radio galaxy, PKS 1718-649 SO ASTRONOMICAL JOURNAL LA English DT Article ID MECHANISM AB In this paper we identify PKS 1718-649, at a distance of 56 Mpc (z=0.014; H-0=75 km s(-1) Mpc(-1), q(0)=0), as the nearest GHz peaked-spectrum (GPS) radio galaxy, more than four times closer than any previously known. Extensive observations at radio wavelengths with the Australia Telescope Compact Array, the Southern Hemisphere VLBI Experiment array, and the Swedish-ESO Submillimetre Telescope have allowed us to determine the properties of the radio source: PKS 1718-649 consists of two compact sub-pc-scale components separated by approximately 2 pc, the overall radio polarization is low, and the radio spectrum is peaked near 3 GHz. Order-of-magnitude agreement between the quantitative model for GPS sources of Bicknell et al. [ApJ (1997) (in press)] and the radio data we present, as well as data at optical wavelengths from the literature, raises the interesting possibility that PKS 1718-649 may be frustrated in its development by the nuclear environment of its host galaxy, NGC 6328. The model of Bicknell et al. (1997) suggests free-free absorption as an explanation of the PKS 1718-649 radio spectrum. However, both free-free absorption and synchrotron self-absorption mechanisms are plausible for this source and both may contribute to the overall radio spectrum. PKS 1718-649 provides evidence to strengthen the speculative suggestion that GPS sources arise as a consequence of galaxy merger activity. (C) 1997 American Astronomical Society. C1 AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA. CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA. UNIV TASMANIA,HOBART,TAS 7001,AUSTRALIA. HARTEBEESTHOEK RADIO ASTRON OBSERV,KRUGERSDORP,SOUTH AFRICA. CALTECH,JET PROP LAB,PASADENA,CA 91109. RI Tingay, Steven/B-5271-2013; King, Edward/A-1473-2012; OI King, Edward/0000-0002-6898-2130; Koekemoer, Anton/0000-0002-6610-2048 NR 31 TC 26 Z9 26 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUN PY 1997 VL 113 IS 6 BP 2025 EP 2030 DI 10.1086/118414 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XC119 UT WOS:A1997XC11900007 ER PT J AU Schaerer, D deKoter, A AF Schaerer, D deKoter, A TI Combined stellar structure and atmosphere models for massive stars .3. Spectral evolution and revised ionizing fluxes of O3-B0 stars SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars: atmospheres; stars: mass-loss; stars: early-type; ultraviolet: stars; H II regions ID INCLUDING SPHERICAL EXTENSION; HOT LUMINOUS STARS; WOLF-RAYET STARS; RADIATION-DRIVEN WINDS; EXPANDING ATMOSPHERES; HELIUM SPECTRA; EUV-FLUXES; LOSS RATES; O-STARS; GRIDS AB We provide an extensive set of theoretical spectral energy distributions of massive stars derived from our ''combined stellar structure and atmosphere models'', The calculations cover the entire main sequence evolution for initial masses M-i = 20 - 120 M. corresponding to O3-BO stars of all luminosity classes. We predict detailed line blanketed UV spectra along the main sequence evolution. The major result is a systematic study of ionizing fluxes covering the entire parameter space of O and early B stars. We demonstrate the importance of accounting simultaneously for non-LTE effects, line blanketing and stellar winds to obtain an accurate description of the spectra of these stars shortward of the Lyman limit. The main results from our spectra are the following: The flux in the He II continuum is increased by 2 to 3 (3 to 6) orders of magnitudes compared to predictions from plane parallel non-LTE (LTE) model atmospheres, This reconfirms the work of Gabler et al. (1989). The flux in the He I continuum is known to be increased due non-LTE effects. However, we find that it is also influenced by wind effects as was previously found by Najarro et al. (1996) and Schaerer et al, (1996b). The combined effect of a mass outflow and line blanketing leads to a flatter energy distribution in the He I continuum, which confirms the results of Sellmaier et al. (1996) for a wider range of stellar parameters. The flux in the Lyman continuum is also modified due to line blanketing and the presence of a stellar winds, although to a lesser degree than the spectrum at higher energies. We derive revised ionizing fluxes for O3 to BO stars based on the recent temperature and gravity calibrations of Vacca et al. (1996). The total number of Lyman continuum photons is found to be slightly lower than previous derivations. For most cases the differences are less than similar to 20 %. Due to the increased flux in the He I continuum the hardness ratio of the He I to H continuum is increased by similar to 1.6 to similar to 2.5 depending on spectral type and luminosity class. In the view of recent EUV and X-ray observations, a critical discussion of current model assumptions (including our own) shows that for stars of spectral types later than approximately BO, which have relatively weak stellar winds, reliable predictions of ionizing Buses are not yet possible. We identify the most likely physical reasons for this finding. C1 OBSERV GENEVA, CH-1290 SAUVERNY, SWITZERLAND. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NR 60 TC 288 Z9 288 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUN PY 1997 VL 322 IS 2 BP 598 EP 614 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XE946 UT WOS:A1997XE94600029 ER PT J AU Fanelli, MN Waller, WW Smith, DA Freedman, WL Madore, B Neff, SG OConnell, RW Roberts, MS Bohlin, R Smith, AM Stecher, TP AF Fanelli, MN Waller, WW Smith, DA Freedman, WL Madore, B Neff, SG OConnell, RW Roberts, MS Bohlin, R Smith, AM Stecher, TP TI An ultraviolet and near-infrared view of NGC 4214: A starbursting core embedded in a low surface brightness disk SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, irregular; galaxies, individual (NGC 4214); infrared, galaxies; ultraviolet, galaxies ID STAR FORMATION; IRREGULAR GALAXIES; IMAGING TELESCOPE; NGC-4214; REGIONS AB During the Astro-a Spacelab mission in 1995 March, the Ultraviolet Imaging Telescope (UIT) obtained far-UV (lambda = 1500 Angstrom) imagery of the nearby Sm/Im galaxy NGC 4214. The UIT images have a spatial resolution of similar to 3 '' and a limiting surface brightness, mu(1500) > 25 mag arcsec(-2), permitting detailed investigation of the intensity and spatial distribution of the young, high-mass stellar component. These data provide the first far-UV imagery covering the full spatial extent of NGC 4214. Comparison with a corresponding I-band image reveals the presence of a starbursting core embedded in an extensive low surface brightness disk. In the far-UV (FUV), NGC 4214 is resolved into several components: a luminous, central knot; an inner region (r less than or similar to 2.5 kpc) with similar to 15 resolved sources embedded in bright, diffuse emission; and a population of fainter knots extending to the edge of the optically defined disk (r approximate to 5 kpc). The FUV light, which traces recent massive star formation, is observed to be more centrally concentrated than the I-band light, which traces the global stellar population The FUV radial light profile is remarkably well represented by an R-1/4 law, providing evidence that the centrally concentrated massive star formation in NGC 4214 is the result of an interaction, possibly a tidal encounter, with a dwarf companion(s). The brightest FUV source produces similar to 8% of the global FUV luminosity. This unresolved source, corresponding to the Wolf-Rayet knot described by Sargent & Filippenko, is located at the center of the FUV light distribution, giving NGC 4214 an active galactic nucleus-like morphology. Another strong source is present in the I band, located 19 '' west, 10 '' north of the central starburst knot, with no FUV counterpart. The I-band source may be the previously unrecognized nucleus of NGC 4214 or an evolved star cluster with an age greater than similar to 200 Myr. The global star formation rate derived from the total FUV flux is consistent with rates derived using data at other wavelengths and lends support to the scenario of roughly constant star formation during the last few hundred million years at a level significantly enhanced relative to the lifetime averaged star formation rate. The hybrid disk/starburst-irregular morphology evident in NGC 4214 emphasizes the danger of classifying galaxies based on their high surface brightness components at any particular wavelength. C1 HUGHES STX CORP, LANHAM, MD 20706 USA. CARNEGIE INST WASHINGTON, PASADENA, CA 91101 USA. UNIV VIRGINIA, DEPT ASTRON, CHARLOTTESVILLE, VA 22903 USA. NATL RADIO ASTRON OBSERV, CHARLOTTESVILLE, VA 22903 USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. RP Fanelli, MN (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, CODE 681, GREENBELT, MD 20771 USA. NR 26 TC 19 Z9 19 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 JUN 1 PY 1997 VL 481 IS 2 BP 735 EP + DI 10.1086/304102 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB884 UT WOS:A1997XB88400014 ER PT J AU Hamilton, AJS Fesen, RA Wu, CC Crenshaw, DM Sarazin, CL AF Hamilton, AJS Fesen, RA Wu, CC Crenshaw, DM Sarazin, CL TI Interpretation of ultraviolet absorption lines in SN 1006 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, kinematics and dynamics; shock waves; supernovae, individual (SN 1006); supernova remnants; ultraviolet, ISM ID SUPERNOVA-REMNANTS; RADIO OBSERVATIONS; IA SUPERNOVAE; WHITE-DWARFS; SN-1006; SPECTRUM; EMISSION; EJECTA; FLAMES; IONS AB We present a theoretical interpretation of the broad silicon and iron ultraviolet absorption features observed with the Hubble Space Telescope (HST) in the spectrum of the Schweizer-Middleditch star behind the remnant of SN 1006. These features are caused by supernova ejecta in SN 1006. We propose that the redshifted Si II 1260 Angstrom feature consists of both unshocked and shocked Si II. The sharp red edge of the line at 7070 km s(-1) indicates the position of the reverse shock, while its Gaussian blue edge reveals shocked Si with a mean velocity of 5050 km s(-1) and a dispersion of 1240 km s(-1), which implies a reverse shock velocity of 2860 km s(-1). The measured velocities satisfy the energy jump condition for a strong shock, provided that all the shock energy goes into ions, with little or no collisionless heating of electrons. The line profiles of the Si III and Si IV absorption features indicate that they arise mostly from shocked Si. The total mass of shocked and unshocked Si inferred from the Si II, Si III, and Si IV profiles is M-Si = 0.25 +/- 0.01 M circle dot on the assumption of spherical symmetry. Unshocked Si extends upward from 5600 km s(-1). Although there appears to be some Fe mixed with the Si at lower velocities less than or similar to 7070 km s(-1), the absence of Fe II absorption with the same profile as the shocked Si II suggests little Fe mixed with Si at higher (before being shocked) velocities. The column density of shocked Si II is close to that expected for Si II undergoing steady state collisional ionization behind the reverse shock, provided that the electron to Si II ratio is low, from which we infer that most of the shocked Si is likely to be of a fairly high degree of purity, unmixed with other elements. We propose that the ambient interstellar density on the far side of SN 1006 is anomalously low compared to the density around the rest of the remnant. This would simultaneously explain the high velocity of the redshifted Si absorption, the absence of blueshifted Si absorption, and the low density of the absorbing Si compared to the high Si density required to produce the observed Si X-ray line emission. We have reanalyzed the Fe II absorption lines and have concluded that the earlier evidence for high-velocity blueshifted Fe II extending to similar to -8000 km s(-1) is not compelling. We interpret the blue edge on the Fe II profiles at -4200 km s(-1) as the position of the reverse shock on the near side of SN 1006. The mass of Fe II inferred from the red edge of the Fe II profile is M-Fe II = 0.029 +/- 0.004 M circle dot up to 7070 km s(-1), if spherical symmetry is assumed. The low ionization state of unshocked Si inferred from our analysis of the silicon features, Si II/Si = 0.92 +/- 0.07, suggests a correspondingly low ionization state of unshocked iron, with Fe II/Fe = 0.66(-0.22)(+0.29). If this is correct, then the total mass of Fe up to 7070 km s(-1) is M-Fe = 0.044(-0.013)(+0.002) M circle dot with a 3 sigma upper limit of M-Fe < 0.16 M circle dot. Such a low ionization state and mass of iron is consistent with the recent observation of Fe III 1123 Angstrom with the Hopkins Ultraviolet Telescope (HUT), which indicates Fe III/Fe II = 1.1 +/- 0.9 but conflicts with the expected presence of several tenths of a solar mass of iron in this suspected Type Ia supernova remnant. However, the inference from the present HST data is too indirect, and the HUT data are too noisy, to rule out a large mass of iron. Reobservation of the Fe III 1123 Angstrom line at higher signal-to-noise ratio with Far ultraviolet Space Explorer will be important in determining the degree of ionization and hence mass of iron in SN 1006. C1 UNIV COLORADO,DEPT ASTROPHYS PLANETARY & ATMOSPHER SCI,BOULDER,CO 80309. DARTMOUTH COLL,DEPT PHYS & ASTRON,WILDER LAB 6127,HANOVER,NH 03755. SPACE TELESCOPE SCI INST,COMP SCI CORP,BALTIMORE,MD 21218. NASA,GODDARD SPACE FLIGHT CTR,LASP,COMP SCI CORP,GREENBELT,MD 20771. UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903. RP Hamilton, AJS (reprint author), UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOX 440,BOULDER,CO 80309, USA. NR 41 TC 32 Z9 32 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1997 VL 481 IS 2 BP 838 EP 856 DI 10.1086/304069 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB884 UT WOS:A1997XB88400026 ER PT J AU Langhoff, SR AF Langhoff, SR TI Theoretical study of the spectroscopy of TiO SO ASTROPHYSICAL JOURNAL LA English DT Article DE molecular data; molecular processes ID GAUSSIAN-BASIS SETS; MOLECULAR CALCULATIONS; ROTATIONAL ANALYSIS; TITANIUM MONOXIDE; STATES; ATOMS; LIFETIME; BAND AB Theoretical electronic transition moments are presented for all of the dipole-allowed transitions connecting the f(1) Delta, c(1) Phi, b(1) Pi, d(1) Sigma(+), and a(1) Delta singlet states and the C-3 Delta, B-3 Pi, A(3) Phi, E-3 Pi, and X-3 Delta triplet states of TiO. The transition moments connecting the C-3 Delta state with lower states were determined at the complete active space self-consistent field (CASSCF) level, and the transition moments connecting the other states were determined at both the CASSCF and the internally contracted multireference configuration-interacti on (IC-MRCI) level. The CASSCF active space can be made sufficiently large that the effect of electron correlation on the transition moments is included quantitatively. The theoretical radiative lifetimes for the short-lived states are generally within 10% of the recent laser fluorescence measurements of Hedgecock, Naulin, & Costes. For the v = 0 level of the E-3 Pi. state, we obtain a radiative lifetime of 4259 ns, consistent with their determination of tau(v=0) > 2000 ns, but much longer than the lifetime of 770 +/- 40 ns reported by Simard & Hackett. Except for the 8-bands, the theoretical oscillator strengths are less than those currently employed in molecular opacity calculations. RP Langhoff, SR (reprint author), NASA,AMES RES CTR,MAIL STOP 230-3,MOFFETT FIELD,CA 94035, USA. NR 29 TC 51 Z9 51 U1 0 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1997 VL 481 IS 2 BP 1007 EP 1015 DI 10.1086/304077 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB884 UT WOS:A1997XB88400044 ER PT J AU Baring, MG Harding, AK AF Baring, MG Harding, AK TI Pair production absorption troughs in gamma-ray burst spectra: A potential distance discriminator SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma-rays, bursts; gamma rays, theory; radiation mechanisms, nonthermal; relativity ID HIGH-ENERGY; BREAKS; BATSE AB In order to explain the emergence of a high-energy continuum in gamma-ray bursts detected by EGRET, relativistic bulk motion with large Lorentz factors has recently been inferred for these sources regardless of whether they are of Galactic or cosmological origin. This conclusion results from calculations of internal pair production opacities in bursts that usually assume an infinite power-law source spectrum for simplicity, an approximation that is quite adequate for some bursts detected by EGRET. However, for a given bulk Lorentz factor Gamma, photons above the EGRET range can potentially interact with sub-MeV photons in such opacity calculations. Hence it is essential to accurately address the spectral curvature in bursts seen by BATSE and also treat the X-ray paucity that is inferred from low-energy fluxes observed in the X-ray band. In this paper we present the major properties induced in photon-photon opacity considerations by such spectral curvature. The observed spectral breaks around 1 MeV turn out to be irrelevant to opacity in cosmological bursts, but they are crucial to estimates of source transparency in the 1 GeV-1 TeV range for sources located in the Galactic halo. We find that broad absorption troughs can arise at these energies for suitable bulk motion parameters Gamma. Such troughs are probably an unambiguous signature of a Galactic halo population and if observed by experiments such as Whipple, MILAGRO, and GLAST, would provide powerful evidence that such bursts are not at cosmological distances. RP Baring, MG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. RI Harding, Alice/D-3160-2012 NR 26 TC 10 Z9 10 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1997 VL 481 IS 2 BP L85 EP L88 DI 10.1086/310665 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB886 UT WOS:A1997XB88600008 ER PT J AU Chakrabarty, D Bildsten, L Finger, MH Grunsfeld, JM Koh, DT Nelson, RW Prince, TA Vaughan, BA Wilson, RB AF Chakrabarty, D Bildsten, L Finger, MH Grunsfeld, JM Koh, DT Nelson, RW Prince, TA Vaughan, BA Wilson, RB TI On the correlation of torque and luminosity in GX 1+4 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; pulsars, individual (GX 1+4); stars, neutron; X-rays, stars ID X-RAY SOURCES; MAGNETIC NEUTRON STARS; ACCRETION DISK; SPIN-DOWN; GX1+4 AB Over 5 years of daily hard X-ray (> 20 keV) monitoring of the 2 minute accretion-powered pulsar GX 1+4 with the Compton Gamma Ray Observatory/BATSE large-area detectors has found nearly continuous rapid spin-down, interrupted by a bright 200 day spin-up episode. During spin-down, the torque becomes more negative as the luminosity increases (assuming that the 20-60 keV pulsed flux traces bolometric luminosity), the opposite of what is predicted by standard accretion torque theory. No changes in the shape of the 20-100 keV pulsed energy spectrum were detected, so that a very drastic change in the spectrum below 20 keV or the pulsed fraction would be required to make the 20-60 keV pulsed flux a poor luminosity tracer. These are the first observations that flatly contradict standard magnetic disk accretion theory, and they may have important implications for understanding the spin evolution of X-ray binaries, cataclysmic variables, and protostars. We briefly discuss the possibility that GX 1+4 may be accreting from a retrograde disk during spin-down, as previously suggested. C1 CALTECH, SPACE RADIAT LAB, PASADENA, CA 91125 USA. UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. NR 33 TC 52 Z9 52 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1997 VL 481 IS 2 BP L101 EP L105 DI 10.1086/310666 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB886 UT WOS:A1997XB88600012 ER PT J AU Landsman, W Aparicio, J Bergeron, P DiStefano, R Stecher, TP AF Landsman, W Aparicio, J Bergeron, P DiStefano, R Stecher, TP TI S1040 in M67: A post-mass transfer binary with a helium core white dwarf SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, close; blue stragglers; open clusters and associations, individual (M67); ultraviolet, stars; white dwarfs ID OPEN CLUSTER M67; STARS AB We have obtained spectra of the yellow giant S1040 in the open cluster M67 using the Goddard High-Resolution Spectrograph (GHRS) and the Faint Object Spectrograph on the Hubble Space Telescope. S1040 is a single-lined spectroscopic binary with a 42.8 day period that occupies a ''red straggler'' position in the M67 color-magnitude diagram (CMD), 0.2 mag blueward of the giant branch. A detection of S1040 at 1620 Angstrom with the Ultraviolet Imaging Telescope provided evidence that the secondary is a hot white dwarf and thus that the anomalous location of S1040 in the CMD is likely due to a prior episode of mass transfer. Our GHRS spectrum shows a broad Ly alpha absorption profile that confirms the white dwarf identification of the S1040 secondary. A model atmosphere fit to the GHRS spectrum yields T-eff = 16,160 K, log g = 6.7, and a mass of about 0.22 M., for an assumed cluster distance of 820 pc and a reddening of E(B - V) = 0.02. The unusually low mass derived for the white dwarf implies that it must have a helium core and that a mass transfer episode must have begun while the progenitor was on the lower giant branch. We construct a plausible mass transfer history for S1040 in which it originated as a short-period (similar to 2 days) binary and evolved through a blue straggler phase to reach its current state. C1 UNIV MONTREAL,DEPT PHYS,MONTREAL,PQ H3C 3J7,CANADA. LOCKHEED MARTIN CANADA,MONTREAL,PQ H4P 1K6,CANADA. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. RP Landsman, W (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,ASTRON & SOLAR PHYS LAB,CODE 681,GREENBELT,MD 20771, USA. NR 26 TC 35 Z9 35 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 JUN 1 PY 1997 VL 481 IS 2 BP L93 EP L96 DI 10.1086/310654 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB886 UT WOS:A1997XB88600010 ER PT J AU Mushotzky, RF Loewenstein, M AF Mushotzky, RF Loewenstein, M TI Lack of evolution in the iron abundance in clusters of galaxies and implications for the global star formation rate at high redshift SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, abundances; galaxies, formation; intergalactic medium ID ELLIPTIC GALAXIES; X-RAY; ASCA AB We present the first large sample of accurate iron abundances and temperatures for clusters at redshifts greater than 0.14. We find that the Fe abundance shows little or no evolution out to z similar to 0.3. This and the early formation epoch of elliptical galaxies in clusters indicate that most of the enrichment of the intracluster medium occurred at z > 1. If clusters represent fair samples of the universe, then global metal production is 2-5 times greater than is inferred from recent studies of galaxies at low and high redshifts. C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. RP Mushotzky, RF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 662,GREENBELT,MD 20771, USA. NR 30 TC 97 Z9 97 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1997 VL 481 IS 2 BP L63 EP L66 DI 10.1086/310651 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB886 UT WOS:A1997XB88600003 ER PT J AU vanderKlis, M Wijnands, RAD Horne, K Chen, W AF vanderKlis, M Wijnands, RAD Horne, K Chen, W TI Kilohertz quasi-periodic oscillation peak separation is not constant in Scorpius X-1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (Scorpius X-1); stars, neutron; pulsars, general ID RAY AB We report on a series of 20, similar to 10(5) counts s(-1), 0.125 ms time-resolution Rossi X-Ray Tinting Explorer observations of the Z-source and low-mass X-ray binary Scorpius X-1. Twin kilohertz quasi-periodic oscillation (QPO) peaks are obvious in nearly all observations. We find that the peak separation is not constant, as expected in some beat-frequency models, but instead varies from similar to 310 to similar to 230 Hz when the centroid frequency of the higher frequency peak varies from similar to 875 to similar to 1085 Hz. We detect none of the additional QPO peaks at higher frequencies predicted in the photon bubble model (PBM), with best-case upper limits on the peaks' power ratio of 0.025. We do detect, simultaneously with the kilohertz QPO, additional QPO peaks near 45 and 90 Hz whose frequency increases with mass accretion rate. We interpret these as first and second harmonics of the so-called horizontal-branch oscillations that are well known from other Z-sources and usually interpreted in terms of the magnetospheric beat-frequency model (BFM). We conclude that the magnetospheric BFM and the PBM are now unlikely to explain the kilohertz QPO in Sco X-1. In order to succeed in doing so, any BFM involving the neutron star spin (unseen in Sco X-1) will have to postulate at least one additional unseen frequency, beating with the spin to produce one of the kilohertz peaks. C1 CTR HIGH ENERGY ASTROPHYS,NL-1098 SJ AMSTERDAM,NETHERLANDS. UNIV ST ANDREWS,SCH PHYS & ASTRON,ST ANDREWS KY16 9SS,FIFE,SCOTLAND. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP vanderKlis, M (reprint author), UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,KRUISLAAN 403,NL-1098 SJ AMSTERDAM,NETHERLANDS. NR 28 TC 144 Z9 144 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1997 VL 481 IS 2 BP L97 EP L100 DI 10.1086/310656 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XB886 UT WOS:A1997XB88600011 ER PT J AU Emmons, LK Carroll, MA Hauglustaine, DA Brasseur, GP Atherton, C Penner, J Sillman, S Levy, H Rohrer, F Wauben, WMF VanVelthoven, PFJ Wang, Y Jacob, D Bakwin, P Dickerson, R Doddridge, B Gerbig, C Honrath, R Hubler, G Jaffe, D Kondo, Y Munger, JW Torres, A VolzThomas, A AF Emmons, LK Carroll, MA Hauglustaine, DA Brasseur, GP Atherton, C Penner, J Sillman, S Levy, H Rohrer, F Wauben, WMF VanVelthoven, PFJ Wang, Y Jacob, D Bakwin, P Dickerson, R Doddridge, B Gerbig, C Honrath, R Hubler, G Jaffe, D Kondo, Y Munger, JW Torres, A VolzThomas, A TI Climatologies of NOx and NOy: A comparison of data and models SO ATMOSPHERIC ENVIRONMENT LA English DT Review ID GENERAL-CIRCULATION MODEL; ARCTIC STRATOSPHERIC EXPEDITION; OBSERVATORY PHOTOCHEMISTRY EXPERIMENT; REACTIVE ODD-NITROGEN; GLOBAL LIGHTNING DISTRIBUTIONS; NITRIC-OXIDE MEASUREMENTS; TRACE GAS CONCENTRATIONS; GASEOUS DRY DEPOSITION; SEASONAL-VARIATION; UPPER TROPOSPHERE AB Climatologies of tropospheric NOx(NO + NO2) and NOy (total reactive nitrogen: NOx + NO3 + 2 x N2O5 + HNO2 + HNO3 + HNO4 + ClONO2 + PAN (peroxyacetylnitrate) + other organic nitrates) have been compiled from data previously published and, in most cases, publicly archived. Emphasis has been on non-urban measurements, including rural and remote ground sites, as well as aircraft data. Although the distribution of data is sparse, a compilation in this manner can begin to provide an understanding of the spatial and temporal distributions of these reactive nitrogen species. The cleanest measurements in the boundary layer are in Alaska, northern Canada and the eastern Pacific, with median NO mixing ratios below 10 pptv, NOx below 50 pptv, and NOy below 300 pptv. The highest NO values (greater than 1 ppbv) were found in eastern North America and Europe, with correspondingly high NOy (similar to 5 ppbv). A significantly narrower range of concentrations is seen in the free troposphere, particularly at 3-6 km, with NO typically about 10 pptv in the boreal summer. NO increases with altitude to similar to 100 pptv at 9-12 km, whereas NOy does not show a trend with altitude, but varies between 100 and 1000 pptv. Decreasing mixing ratios eastward of the Asian and North American continents are seen in all three species at all altitudes. Model-generated climatologies of NOx and NOy from six chemical transport models are also presented and are compared with observations in the boundary layer and the middle troposphere for summer and winter. These comparisons test our understanding of the chemical and transport processes responsible for these species distributions. Although the model results show differences between them, and disagreement with observations, none are systematically different for all seasons and altitudes. Some of the differences between the observations and model results may likely be attributed to the specific meteorological conditions at the time that measurements were made differing from the model meteorology, which is either climatological how from GCMs or actual meteorology for an arbitrary year. Differences in emission inventories, and convection and washout schemes in the models will also affect the calculated NOx and NOy distributions. (C) 1997 Elsevier Science Ltd. C1 NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA USA. PRINCETON UNIV, NOAA, GEOPHYS FLUID DYNAM LAB, PRINCETON, NJ 08542 USA. FORSCHUNGSZENTRUM JULICH, FORSCHUNGSZENTRUM, ICG, JULICH, GERMANY. ROYAL NETHERLANDS METEOROL INST, NL-3730 AE DE BILT, NETHERLANDS. HARVARD UNIV, CAMBRIDGE, MA 02138 USA. NOAA, CLIMATE MONITORING & DIAGNOST LAB, BOULDER, CO 80303 USA. UNIV MARYLAND, COLLEGE PK, MD 20742 USA. MICHIGAN TECHNOL UNIV, HOUGHTON, MI 49931 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. UNIV ALASKA, FAIRBANKS, AK 99701 USA. NAGOYA UNIV, NAGOYA, AICHI, JAPAN. NASA, WALLOPS FLIGHT FACIL, WALLOPS ISL, VA USA. RP Emmons, LK (reprint author), UNIV MICHIGAN, DEPT ATMOSPHER OCEAN & SPACE SCI, ANN ARBOR, MI 48109 USA. RI Hubler, Gerhard/E-9780-2010; Dickerson, Russell/F-2857-2010; Kondo, Yutaka/D-1459-2012; Rohrer, Franz/I-2052-2012; Gerbig, Christoph/L-3532-2013; Wang, Yuhang/B-5578-2014; Volz-Thomas, Andreas/J-7223-2012; Munger, J/H-4502-2013; Emmons, Louisa/R-8922-2016; OI Dickerson, Russell/0000-0003-0206-3083; Rohrer, Franz/0000-0003-3436-3419; Gerbig, Christoph/0000-0002-1112-8603; Volz-Thomas, Andreas/0000-0003-3700-1667; Munger, J/0000-0002-1042-8452; Emmons, Louisa/0000-0003-2325-6212; Sillman, Sanford/0000-0001-6250-1191 NR 176 TC 93 Z9 95 U1 0 U2 15 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1352-2310 J9 ATMOS ENVIRON JI Atmos. Environ. PD JUN PY 1997 VL 31 IS 12 BP 1851 EP 1904 DI 10.1016/S1352-2310(96)00334-2 PG 54 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA WU835 UT WOS:A1997WU83500009 ER PT J AU Thompson, AM Tao, WK Pickering, KE Scala, JR Simpson, J AF Thompson, AM Tao, WK Pickering, KE Scala, JR Simpson, J TI Tropical deep convection and ozone formation SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID TROPOSPHERIC OZONE; CLOUD TRANSPORT; CO; BUDGETS; MODEL; AIR AB Theoretical studies, aircraft, and space-borne measurements show that deep convection can be an effective conduit for introducing reactive surface pollutants into the free troposphere. The chemical consequences of convective systems are complex. For example, sensitivity studies show potential for both enhancement and diminution of ozone formation. Field observations of cloud and mesoscale phenomena have been investigated with the Goddard Cumulus Ensemble and Tropospheric Chemistry models. Case studies from the tropical ABLE 2, STEP, and TRACE-A experiments show that foe tropospheric ozone formation should increase when deep convection and urban or biomass burning pollution coincide, and decrease slightly in regions relatively free of ozone precursors (often marine). Confirmation of post-convective ozone enhancement in the free troposphere over Brazil, the Atlantic, and southern Africa was a major accomplishment of the September-October 1992 TRACE-A (Transport and Atmospheric Chemistry near the Equator - Atlantic) aircraft mission. A flight dedicated to cloud outflow showed that deep convection led to a factor of 3-4 increase in upper tropospheric ozone formation downwind. Analysis of ozonesondes during TRACE-A. was consistent with 20%-30% of seasonally enhanced ozone over the South Atlantic being supplied by a combination of biomass burning emissions, lightning, and deep convection over South America. With the Tropics the critical region for troposphere-to-stratosphere transfer of pollutants, these results have implications for the total ozone budget. Cloud-scale analyses will guide the development of more realistic regional and global chemical-transport models to assess the full impact of deep convection on atmospheric chemical composition. C1 UNIV MARYLAND,DEPT METEOROL,JCESS,COLLEGE PK,MD 20742. SUNY COLL BROCKPORT,DEPT EARTH SCI,BROCKPORT,NY 14420. RP Thompson, AM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 916,GREENBELT,MD 20771, USA. RI Pickering, Kenneth/E-6274-2012; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 28 TC 62 Z9 65 U1 3 U2 9 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 1043 EP 1054 DI 10.1175/1520-0477(1997)078<1043:TDCAOF>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XH868 UT WOS:A1997XH86800001 ER EF