FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Salerno, LJ Kittel, P AF Salerno, LJ Kittel, P TI Cryogenics and the human exploration of Mars SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1997 Space Cryogenics Workshop CY AUG 04-05, 1997 CL EUGENE, OREGON DE space cryogenics; hydrogen; methane; oxygen AB Current studies within NASA involve extending the human exploration of space from low earth orbit into the solar system, with the first human exploration of Mars proposed in 2014. The key cryogenic technology areas to be addressed in human Mars missions are long-term propellant storage, cryogenic refrigeration, cryogenic liquefaction, and zero gravity fluid management. Passive technologies such as advanced multilayer insulation (MLI) concepts, vapor-cooled shields (VCS), and catalytic converters will be combined with the development of active coolers (cryogenic refrigerators). The integration of passive and active technologies will form a hybrid system optimized to minimize the launch mass while preserving the cryogenic propellants. This paper will present a brief overview of the proposed Mars reference mission and the concomitant cryogenic fluid management technology, focusing on active cooling technology. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Salerno, LJ (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 9 TC 17 Z9 17 U1 1 U2 3 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD APR PY 1999 VL 39 IS 4 BP 381 EP 388 DI 10.1016/S0011-2275(99)00043-0 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 218KX UT WOS:000081552700012 ER PT J AU Serlemitsos, AT SanSebastian, M Kunes, ES Behr, J AF Serlemitsos, AT SanSebastian, M Kunes, ES Behr, J TI Performance of the XRS/ASTRO-E engineering model ADR SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1997 Space Cryogenics Workshop CY AUG 04-05, 1997 CL EUGENE, OREGON DE space cryogenics; refrigerators; adiabatic demagnetization ID DESIGN AB NASA's Goddard Space Flight Center (GSFC) has developed an x-ray Spectrometer (XRS) to be flown aboard ASTRO-E, in cooperation with the Japanese Institute of Space and Astronomical Science (ISAS). XRS uses an array of 32 microcalorimeters capable of detecting X-rays in the energy range of 0.3-10 keV with a resolution of 12 eV. In order to accomplish this, the detectors must be operated at a temperature of 0.065 K. In space, an Adiabatic Demagnetization Refrigerator (ADR) must be used to cool the detectors to that temperature. A spaceworthy ADR has been developed at GSFC to be used in the XRS. Originally, the ADR was developed to be flown aboard the Advanced X-ray Astrophysics Facility (AXAF) [2]. Budgetary constraints necessitated the move of the XRS to the ASTRO-E program and this resulted in much tighter thermal specifications for the ADR. The allowable average thermal load of the ADR to the LHe dewar was changed from 2.6 mW to 270 mu W. Time constraints did not allow a complete redesign of the ADR. The original shape and size were left unchanged and the new specifications were met by streamlining the heat switch and lengthening the salt pill magnetization cycle time. For a LHe bath temperature of 1.3 K the gas gap heat switch presently used has an on/off ratio of 22 000 and a parasitic heat leak of 2.9 mu W/K. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon STX Corp, Lanham, MD 20706 USA. RP Serlemitsos, AT (reprint author), NASA, Goddard Space Flight Ctr, Code 552, Greenbelt, MD 20771 USA. NR 8 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD APR PY 1999 VL 39 IS 4 BP 399 EP 404 DI 10.1016/S0011-2275(99)00041-7 PG 6 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 218KX UT WOS:000081552700014 ER PT J AU Shirron, PJ DiPirro, MJ Irish, SM Volz, SM Schulze, M Blount, K Arvidson, J Dame, RE Cofie, E Thomas, BA AF Shirron, PJ DiPirro, MJ Irish, SM Volz, SM Schulze, M Blount, K Arvidson, J Dame, RE Cofie, E Thomas, BA TI Mechanical properties of solid neon and structural modeling of the XRS solid neon dewar SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1997 Space Cryogenics Workshop CY AUG 04-05, 1997 CL EUGENE, OREGON DE space cryogenics; solid cryogens AB Compression tests have been performed on solid neon to determine Young's modulus and compressive strengths in the temperature range from 8 to 23 K. This data was used for structural analysis of the X-Ray Spectrometer's (XRS) solid neon dewar. The dewar is nearly full of a 2.5% dense aluminum foam, so measurements were made for samples where solid neon was formed within the aluminum matrix as well as pure solid neon samples. The latter measurements were made in order to determine, at least qualitatively, how the mechanical properties of solid neon are affected by the aluminum foam and to allow direct comparisons with Young's moduli obtained from literature data as a check on the experimental technique. As a further check and to verify the structural model, thermal cycle tests were conducted on a small-scale toroidal dewar filled with solid neon. Mechanical properties measurements and data are described, along with model predictions and actual performance of both the engineering unit XRS dewar and the sub-scale dewar. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Mat Res & Engn Inc, Boulder, CO 80301 USA. MEGA Engn, Silver Spring, MD 20901 USA. RP Shirron, PJ (reprint author), NASA, Goddard Space Flight Ctr, Code 713, Greenbelt, MD 20771 USA. NR 6 TC 3 Z9 3 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD APR PY 1999 VL 39 IS 4 BP 405 EP 414 DI 10.1016/S0011-2275(99)00040-5 PG 10 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 218KX UT WOS:000081552700015 ER PT J AU Zastenker, GN Nozdrachev, MN Safrankova, J Nemecek, Z Paularena, KI Lazarus, AJ Lepping, RP Mukai, T AF Zastenker, GN Nozdrachev, MN Safrankova, J Nemecek, Z Paularena, KI Lazarus, AJ Lepping, RP Mukai, T TI Fast solar wind plasma and magnetic field variations in the magnetosheath SO CZECHOSLOVAK JOURNAL OF PHYSICS LA English DT Article; Proceedings Paper CT NATO Advanced Research Workshop on Coordinated Studies of the Solar Wind-Magnetosphere-Ionosphere Interaction - INTERBALL Observations CY SEP 07-11, 1998 CL KOSICE, SLOVAKIA SP Tech Univ, Fac Elect Engn & Informat, P J Safarik Univ, Fac Sci, Slovak Acad Sci, Inst Exptl Phys, Charles Univ, Fac Math & Phys ID DAYSIDE MAGNETOSHEATH; MAGNETOPAUSE MOTION; DYNAMIC PRESSURE; FLOW; FLUCTUATIONS; GENERATION; SPACECRAFT; MODEL AB The results of experimental study of plasma and magnetic field fast variations in the magnetosheath and their comparison with the gasdynamic model are presented. These variations on the scale of minutes or tens of minutes are several times larger than simultaneous solar wind plasma and interplanetary magnetic field (IMF) variations and cannot be explained by the motion of the magnetosheath as whole. The level of variations does not depend on the angle between the IMF vector and the normal to the bow shock (theta(BN)). C1 Russian Acad Sci, Space Res Inst, Moscow, Russia. Charles Univ, Fac Math & Phys, Prague, Czech Republic. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Zastenker, GN (reprint author), Russian Acad Sci, Space Res Inst, Moscow, Russia. NR 26 TC 10 Z9 10 U1 0 U2 0 PU CZECHOSLOVAK JNL OF PHYSICS PI PRAGUE PA FYZIKALNI USTAV AV NA SLOVANCE 2, PRAGUE 180 40, CZECH REPUBLIC SN 0011-4626 J9 CZECH J PHYS JI Czech. J. Phys. PD APR PY 1999 VL 49 IS 4A SI SI BP 579 EP 590 PG 12 WC Physics, Multidisciplinary SC Physics GA 224HK UT WOS:000081891800003 ER PT J AU Baroth, E Hartsough, C Holst, A Wells, G AF Baroth, E Hartsough, C Holst, A Wells, G TI An evaluation of LabVIEW 5.0 and HP VEE 5.0 - Part 1 SO EE-EVALUATION ENGINEERING LA English DT Software Review C1 CALTECH, Jet Prop Lab, Measurement Technol Ctr, Pasadena, CA 91109 USA. RP Baroth, E (reprint author), CALTECH, Jet Prop Lab, Measurement Technol Ctr, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU NELSON PUBLISHING PI NOKOMIS PA 2504 NORTH TAMIAMI TRAIL, NOKOMIS, FL 34275-3482 USA SN 0149-0370 J9 EE-EVAL ENG JI EE-Eval. Eng. PD APR PY 1999 VL 38 IS 4 BP 64 EP + PG 7 WC Engineering, Electrical & Electronic SC Engineering GA 183MU UT WOS:000079558000008 ER PT J AU Seidman, SH Paige, GD Tomko, DL AF Seidman, SH Paige, GD Tomko, DL TI Adaptive plasticity in the naso-occipital linear vestibule-ocular reflex SO EXPERIMENTAL BRAIN RESEARCH LA English DT Article DE vestibule-ocular reflex; naso-occipital translation; linear motion; adaptive plasticity; otolith function ID EYE-MOVEMENT RESPONSES; SQUIRREL-MONKEY; FIXATION DISTANCE; VIEWING DISTANCE; HEAD MOTION; VISION; ACCELERATION; MECHANISMS; ADAPTATION; REVERSAL AB The linear vestibule-ocular reflex (LVOR) during motion along the naso-occipital (NO) axis is governed by eye position and viewing distance. These influences are necessary for the LVOR to maintain stable foveal images during head translation. The response to NO translation must be large when eye position is eccentric from the axis of head motion (i.e., during lateral gaze) and must diminish as eye position approaches straight-ahead, eventually reaching zero when the eye is aligned with the NO axis of motion (the "null point"). As eye position crosses to the opposite side, the LVOR response must reappear, but in the opposite direction, and must grow in magnitude as eccentricity increases. To determine whether the NO-LVOR is subject to adaptive plastic mechanisms, squirrel monkeys were conditioned during NO translation while they binocularly viewed a rich visual field through parallel base-right or base-left wedge prisms. This optical method effectively shifted the visual world 9 degrees leftward or rightward, respectively, thus inducing a mismatch between vision and the NO-LVOR during head movements, To restore compensatory function, the relationship between LVOR sensitivity and horizontal eye position must shift by 9 degrees in the same direction as the visual image shift, effectively shifting the null point. After 2 h of adaptive conditioning, all monkeys exhibited an adaptive shift in the appropriate direction by an average of 3.0 degrees (range 0.7-5.0 degrees), corresponding to 33% of the geometrically required adaptation. C1 Univ Rochester, Dept Neurobiol & Anat, Rochester, NY 14642 USA. Univ Rochester, Ctr Visual Sci, Rochester, NY 14642 USA. NASA, Gravitat Res Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Seidman, SH (reprint author), Univ Rochester, Dept Neurobiol & Anat, Box 603,601 Elmwood Ave, Rochester, NY 14642 USA. FU NCRR NIH HHS [RR-06853]; NEI NIH HHS [EY-01389]; NIDCD NIH HHS [DC-01935] NR 26 TC 18 Z9 18 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0014-4819 J9 EXP BRAIN RES JI Exp. Brain Res. PD APR PY 1999 VL 125 IS 4 BP 485 EP 494 DI 10.1007/s002210050706 PG 10 WC Neurosciences SC Neurosciences & Neurology GA 188UC UT WOS:000079866000012 PM 10323295 ER PT J AU Heifetz, J Anderl, D Maloney, NE Rutecki, TL AF Heifetz, J Anderl, D Maloney, NE Rutecki, TL TI Age validation and analysis of ageing error from marked and recaptured sablefish, Anoplopoma fimbria SO FISHERY BULLETIN LA English DT Article AB Sablefish, Anoplopoma fimbria, are especially difficult to age. Ages are typically determined by counting growth zones that are assumed to be annuli on the burnt cross section of an otolith. We evaluated the accuracy of ageing methods by comparing the ages obtained from two experienced age readers with those ages that were known. A mark-recapture experiment on sablefish provided a relatively large sample (n=49) of 2-9 year old sablefish. This sample of known-age fish provided a unique opportunity to evaluate the accuracy of ageing methods for young sablefish. Our study generally confirmed the criteria used to age young sablefish. According to the assignment of ages from two experienced age readers, about two-thirds of the fish were misaged. Of these, most fish (81% and 71% for the two readers) were misaged by only one year. After reexamination of the otoliths, most of the discrepancies between reader age and known age could be resolved. Ageing-error matrices that define the probability of assigning an age to a fish of a given true age were estimated from among-reader variability and from comparison of known ages to reader ages. Estimates of ageing errors, based on comparison of known ages to reader ages, were considerably higher than estimates obtained from among-reader variability. We recommend that ageing-error corrections applied in stock assessment models be based on the ageing-error matrix derived from known and reader ages. C1 NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Seattle, WA 98115 USA. RP Heifetz, J (reprint author), NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. EM jon.heifetz@noaa.gov NR 17 TC 13 Z9 14 U1 0 U2 2 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 APR PY 1999 VL 97 IS 2 BP 256 EP 263 PG 8 WC Fisheries SC Fisheries GA 183VV UT WOS:000079575600004 ER PT J AU Krieger, KJ Ito, DH AF Krieger, KJ Ito, DH TI Distribution and abundance of shortraker rockfish, Sebastes borealis and rougheye rockfish, S-aleutianus, determined from a manned submersible SO FISHERY BULLETIN LA English DT Article AB A manned submersible was used in the eastern Gulf of Alaska in 1992 to observe spatial distributions and habitats of shortraker rockfish, Sebastes borealis, and rougheye rock-fish, S. aleutianus, on the continental slope at 262-365 m depths. Observations of these two species were combined because distinguishing between them was not always possible from the submersible. A seafloor area of 104,900 m(2) was surveyed at 15 dive sites, and 646 shortraker and rougheye rockfish were observed. Densities were 0.0 to 14.8 rockfish/1000 m(2) (mean, 5.8 rockfish/1000 m(2)). Of the 646 rockfish, 115 were observed above bottom and 531 were on the bottom. The above-bottom rockfish were descending slowly to the seafloor and became sedentary when they contacted the seafloor. Approximately two-thirds of the rockfish were in groups; 82 of the 113 groups contained 2 or 3 rockfish, and only 2 groups had more than 12 rockfish. Rockfish were associated with 20 of the 22 substrates encountered. Soft substrates of sand or mud usually had the greatest densities of rockfish, whereas hard substrates of bedrock, cobble, or pebble usually had the least densities. Habitats containing steep slopes and numerous boulders had greater densities of rockfish than habitats with gradual slopes and few boulders; 52 rockfish lay against boulders. According to catch rates from bottom-trawl surveys, populations of shortraker and rougheye rockfish may be underestimated because of the above-bottom distribution of these rockfish and their use of steep-slope boulder habitats. C1 NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Seattle, WA 98115 USA. RP Krieger, KJ (reprint author), NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 13 TC 19 Z9 20 U1 1 U2 1 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 APR PY 1999 VL 97 IS 2 BP 264 EP 272 PG 9 WC Fisheries SC Fisheries GA 183VV UT WOS:000079575600005 ER PT J AU Holland, KN Kleiber, P Kajiura, SM AF Holland, KN Kleiber, P Kajiura, SM TI Different residence times of yellowfin tuna, Thunnus albacares, and bigeye tuna, T-obesus, found in mixed aggregations over a seamount SO FISHERY BULLETIN LA English DT Article C1 Hawaii Inst Marine Biol, Kaneohe, HI 96744 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Ctr, Honolulu Lab, Honolulu, HI 96822 USA. Univ Hawaii Manoa, Dept Zool, Honolulu, HI 96822 USA. RP Holland, KN (reprint author), Hawaii Inst Marine Biol, Coconut Isl, Kaneohe, HI 96744 USA. NR 10 TC 36 Z9 40 U1 0 U2 4 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 APR PY 1999 VL 97 IS 2 BP 392 EP 395 PG 4 WC Fisheries SC Fisheries GA 183VV UT WOS:000079575600017 ER PT J AU Waheed, A Yan, J AF Waheed, A Yan, J TI Parallelization of NAS benchmarks for shared memory multiprocessors SO FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF GRID COMPUTING-THEORY METHODS AND APPLICATIONS LA English DT Article AB This paper presents our experiences of parallelizing the sequential implementation of NAS benchmarks using compiler directives on SGI Origin2000 distributed shared memory (DSM) system. Porting existing applications to new high performance parallel and distributed computing platforms is a challenging task. Ideally, a user develops a sequential version of the application, leaving the task of porting the code to parallelization tools and compilers. Due to the simplicity of programming shared-memory multiprocessors, compiler developers have provided Various facilities to allow the users to exploit parallelism. Native compilers on SGI Origin2000 support multiprocessing directives to allow users to exploit loop-level parallelism in their programs. Additionally, supporting tools can accomplish this process automatically. We experimented with these compiler directives and supporting tools by parallelizing sequential implementation of NAS benchmarks. Results reported in this paper indicate that with minimal effort, the performance gain is comparable with the hand-parallelized, carefully optimized, message-passing implementations of the same benchmarks. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. RP Waheed, A (reprint author), NASA, Ames Res Ctr, MRJ Technol Solut, Mail Stop T27A-2, Moffett Field, CA 94035 USA. EM waheed@nas.nasa.gov NR 14 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-739X J9 FUTURE GENER COMP SY JI Futur. Gener. Comp. Syst. PD APR PY 1999 VL 15 IS 3 BP 353 EP 363 DI 10.1016/S0167-739X(98)00080-6 PG 11 WC Computer Science, Theory & Methods SC Computer Science GA 185DD UT WOS:000079652100006 ER PT J AU Pasley, JN Sumpter, JA Compadre, CM Ross, MD Breen, PJ AF Pasley, JN Sumpter, JA Compadre, CM Ross, MD Breen, PJ TI The virtual esophagus: A new tool for examination of esophageal motility SO GASTROENTEROLOGY LA English DT Meeting Abstract C1 Univ Arkansas Med Sci, Little Rock, AR 72205 USA. NASA, Ames Ctr Bioinformat, Moffett Field, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU W B SAUNDERS CO-ELSEVIER INC PI PHILADELPHIA PA 1600 JOHN F KENNEDY BOULEVARD, STE 1800, PHILADELPHIA, PA 19103-2899 USA SN 0016-5085 J9 GASTROENTEROLOGY JI Gastroenterology PD APR PY 1999 VL 116 IS 4 MA G4606 BP A1060 EP A1060 PN 2 PG 1 WC Gastroenterology & Hepatology SC Gastroenterology & Hepatology GA 187GJ UT WOS:000079778404607 ER PT J AU Rashed, H Cowings, P Toscano, W Adl, D Abell, T AF Rashed, H Cowings, P Toscano, W Adl, D Abell, T TI A case report: Modulation of blood pressure and electrogastrogram by biofeedback training in a patient with post prandial hypotension. SO GASTROENTEROLOGY LA English DT Meeting Abstract C1 NASA, Ames, CA USA. Univ Tennessee, Memphis, TN 38163 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU W B SAUNDERS CO-ELSEVIER INC PI PHILADELPHIA PA 1600 JOHN F KENNEDY BOULEVARD, STE 1800, PHILADELPHIA, PA 19103-2899 USA SN 0016-5085 J9 GASTROENTEROLOGY JI Gastroenterology PD APR PY 1999 VL 116 IS 4 MA G4638 BP A1068 EP A1068 PN 2 PG 1 WC Gastroenterology & Hepatology SC Gastroenterology & Hepatology GA 187GJ UT WOS:000079778404639 ER PT J AU McCoy, TJ Wadhwa, M Keil, K AF McCoy, TJ Wadhwa, M Keil, K TI New lithologies in the Zagami meteorite: Evidence for fractional crystallization of a single magma unit on Mars SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID SHERGOTTITE METEORITES; SNC METEORITES; PETROGENESIS; MICROPROBE; MANTLE; WATER AB Zagami consists of a series of increasingly evolved magmatic lithologies. The bulk of the rock is a basaltic lithology dominated by pigeonite (FS28.7-54.3) augite (Fs(19.5-35.0)) and maskelynite (Ab(42-53)). Approximately 20 vol.% of Zagami is a basaltic lithology containing FeO-enriched pyroxene (pigeonite, Fs(27.0-80.8)) and mm- to cm-sized late-stage melt pockets. The melt pockets are highly enriched in olivine-bearing intergrowths, mesostases, phosphates (both whitlockite and water-bearing apatite), Fe,Ti-oxides and sulfides. The systematic increases in abundances of late-stage phases. Fs and incompatible element (e.g., Y and the REEs) contents of pigeonite, Ab contents of maskelynite. and FeO concentrations of whitlockite all point to a fractional crystallization sequence. The crystallization order in Zagami and the formation of these various lithologies was controlled by the abundances of iron, phosphorus, and calcium. During fractional crystallization, iron and phosphorus enrichment occurred, ultimately forcing the crystallization of calcium phosphates and olivine-bearing intergrowths The limited amount of calcium in the melt and its partitioning between phosphates and silicates controlled the crystallization of phosphates, plagioclase, pigeonite. and augite. The presence of these FeO-enriched, water-poor late-stage lithologies has important implications. Discrepancies between experimental and petrologic studies to infer the history of basaltic shergottites may be partially explained by the use of starting compositions which are too FeO-poor in the experimental studies. The water-poor nature of the late-stage melt pockets suggests crystallization from a very dry magma, although whether this magma was always dry or experienced significant near-surface degassing remains an open question. Finally, the presence of fractional crystallization products within Zagami suggests that this may be a relatively common process on Mars. Copyright (C) 1999 Elsevier Science Ltd. C1 Univ Hawaii Manoa, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Smithsonian Inst, Natl Museum Amer Hist, Dept Mineral Sci, Washington, DC 20560 USA. Washington Univ, McDonnell Ctr Space Sci, St Louis, MO 63130 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. Field Museum Nat Hist, Dept Geol, Chicago, IL 60605 USA. Univ Hawaii, Hawaii Ctr Vulcanol, Honolulu, HI 96822 USA. RP McCoy, TJ (reprint author), Univ Hawaii Manoa, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. NR 25 TC 45 Z9 45 U1 1 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD APR PY 1999 VL 63 IS 7-8 BP 1249 EP 1262 DI 10.1016/S0016-7037(99)00015-0 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 216FR UT WOS:000081431200021 ER PT J AU Rampino, MR AF Rampino, MR TI Evidence for abrupt latest Permian mass extinction of foraminifera: Results of tests for the Signor-Lipps effect: Reply SO GEOLOGY LA English DT Article C1 NYU, Earth & Environm Sci Program, New York, NY 10003 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Rampino, MR (reprint author), NYU, Earth & Environm Sci Program, 100 Washington Sq E, New York, NY 10003 USA. NR 6 TC 0 Z9 0 U1 0 U2 3 PU GEOLOGICAL SOC AMERICA, INC PI BOULDER PA PO BOX 9140, BOULDER, CO 80301-9140 USA SN 0091-7613 J9 GEOLOGY JI Geology PD APR PY 1999 VL 27 IS 4 BP 383 EP 384 PG 2 WC Geology SC Geology GA 185LK UT WOS:000079670300028 ER PT J AU Sun, HJ Friedmann, EI AF Sun, HJ Friedmann, EI TI Growth on geological time scales in the Antarctic cryptoendolithic microbial community SO GEOMICROBIOLOGY JOURNAL LA English DT Article DE Antarctica; biological weathering; cold desert; cryptoendolithic; exfoliation; growth rate; lichen; microbial growth; rock crust; Ross Desert ID COLD DESERTS; HOT; MICROORGANISMS; LIFE AB In the process of biogenous weathering of Beacon sandstone in the McMurdo Dry Valleys (Ross Desert), Antarctica, periods of microbial growth, on the time scale of 10(3)-10(4) years, alternate with sudden exfoliation events. The present study addressed the question of whether microbial growth is continuous between exfoliation events or whether each exfoliation is followed by a period of comparatively rapid growth and then an extended period of steady state. The color intensity (Munsell lightness value) of the rock surface is an indicator of relative age of the crust within the exfoliation cycle, permitting measurement of changes in microbial biomass on a geological time scale. Results indicate that microbial growth is continuous and that exfoliation occurs when the microbial biomass reaches the carrying capacity of the cryptoendolithic habitat. C1 Florida State Univ, Polar Desert Res Ctr, Tallahassee, FL USA. Florida State Univ, Dept Biol Sci, Tallahassee, FL 32306 USA. RP Sun, HJ (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-301, Pasadena, CA 91109 USA. NR 33 TC 56 Z9 62 U1 0 U2 7 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0149-0451 J9 GEOMICROBIOL J JI Geomicrobiol. J. PD APR-JUN PY 1999 VL 16 IS 2 BP 193 EP 202 PG 10 WC Environmental Sciences; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Geology GA 219EK UT WOS:000081594800004 ER PT J AU Levine, JS AF Levine, JS TI The 1997 fires in Kalimantan and Sumatra, Indonesia: Gaseous and particulate emissions SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID BIOMASS; CARBON AB Extensive and widespread vegetation and peat fires swept throughout Kalimantan and Sumatra, Indonesia, from August 1997 through March 1998. The fires resulted from routine burning for land clearing and land-use change. However, the severe drought conditions resulting from El Nine caused small land-clearing fires to become large uncontrolled wildfires. Analysis of SPOT images indicate that a total of 45,600 km(2) burned between August and December 1997. In this paper, the gaseous and particulate emissions resulting from the 1997 fires are estimated. On a daily basis, the calculated emissions of CO2, CO, CH4, NOx, and particulates from the Kalimantan and Sumatra fires of 1997 significantly exceeded the emissions from the Kuwait oil fires of 1991. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Levine, JS (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NR 22 TC 89 Z9 89 U1 0 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1999 VL 26 IS 7 BP 815 EP 818 DI 10.1029/1999GL900067 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 182AW UT WOS:000079477200002 ER PT J AU Lee, KM McInerney, JM Sasano, Y Park, JH Choi, W Russell, JM AF Lee, KM McInerney, JM Sasano, Y Park, JH Choi, W Russell, JM TI Intercomparison of ILAS and HALOE ozone at high latitudes SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GAS EXPERIMENT-II; OCCULTATION EXPERIMENT; STRATOSPHERIC AEROSOL; UARS AB Atmospheric O-3 mixing ratios measured by ILAS and HALOE are compared for periods from March 25-31, 1997 in the NH and from November 20-24, 1996 and December 13-14, 1996 in the SH. Both instruments observe consistent vertical and horizontal structure in the highly variable polar vortex regions. In the ozone peak region, ILAS ozone values are smaller compared to HALOE values in both hemispheres, but the differences are less than 13% and 20% in 40-20 km altitude range, respectively, for the NH and the SH, which are both close to the sum of uncertainties of the two instruments. When validation is complete, ILAS data will be useful for the study of the chemistry and dynamics at high latitudes. C1 Kyungpook Natl Univ, Dept Astron & Atmospher Sci, Taegu, South Korea. Sci Applicat Int Corp, Hampton, VA USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. Seoul Natl Univ, Dept Atmospher Sci, Seoul 151, South Korea. RP Lee, KM (reprint author), Kyungpook Natl Univ, Dept Astron & Atmospher Sci, Taegu, South Korea. RI Sasano, Yasuhiro/C-2927-2009 OI Sasano, Yasuhiro/0000-0001-7470-5642 NR 13 TC 12 Z9 12 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1999 VL 26 IS 7 BP 835 EP 838 DI 10.1029/1999GL900129 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 182AW UT WOS:000079477200007 ER PT J AU Zhang, RH Rothstein, LM Busalacchi, AJ Liang, XZ AF Zhang, RH Rothstein, LM Busalacchi, AJ Liang, XZ TI The onset of the 1991-92 El Nino event in the tropical Pacific Ocean: The NECC subsurface pathway SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOUTHERN OSCILLATION; INTERANNUAL VARIABILITY; MODEL; SYSTEM; WAVES; ENSO AB Based on the NCEP ocean re-analysis data, the three-dimensional co-evolution of the tropical Pacific climate system is examined to explain the onset of the 1991-92 El Nino event. A logical sequence is discovered that links subsurface and surface temperature anomalies off and on the equator in the western and central Pacific. Along the North Equatorial Countercurrent (NECC) path, subsurface temperature anomalies propagated coherently eastward from the western boundary in mid-1989 to the date line in mid-1990, at a speed of about 10-20 cm(-1). As the thermocline shoals eastward along the NECC, the subsurface anomalies outcropped in the regions near the date line, initiating warm sea surface temperature (SST) anomalies which further amplified while advectively extending into the equatorial wave guide. These subsurface-induced SST anomalies could then trigger local coupled air-sea interactions producing atmospheric-oceanic anomalies that developed and evolved in 1991, thus setting onset conditions for the 1991-92 El Nino. These results differ markedly from the delayed oscillator physics in that a major role can be played by the eastward advection of off-equatorial subsurface thermal anomalies and their outcropping along the NECC subsurface pathways, not necessarily involving wave reflections along the western boundary for triggering El Nino. This mechanism explains well the observed, otherwise unaccounted for, surface warming near the date lint: during late 1989 and early 1990. C1 Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. SUNY Albany, Atmospher Sci Res Ctr, Albany, NY 12222 USA. RP Zhang, RH (reprint author), Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NR 17 TC 6 Z9 7 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1999 VL 26 IS 7 BP 847 EP 850 DI 10.1029/1999GL900111 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 182AW UT WOS:000079477200010 ER PT J AU MacMillan, DS Ma, C AF MacMillan, DS Ma, C TI VLBI measurements of Caribbean and South American motion SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RELATIVE MOTION; SUBDUCTION ZONE; PLATE MOTIONS; BOUNDARY ZONE; SLIP VECTORS; DEFORMATION; EARTHQUAKE; ANDES AB VLBI (very long baseline interferometry) measurements have been made during the 1990s at sites in the: Caribbean (St. Croix, US Virgin Islands) and South America (Fortaleza, Brazil and Santiago, Chile) and the site velocities are now well determined In the NUVEL-1A NNR frame, the VLBI velocity of St. Croix of 19.0 +/- 0.7 mm/yr at N72.3 +/- 2.0 degrees E with respect to North America is significantly larger than the corresponding NUVEL-1A relative velocity of 11.4 mm/yr at N80 degrees E. Fortaleza is in the stable portion of the South American plate in northeastern Brazil and its speed relative to the NUVEL-1A NNR South American plate velocity is only 1.2 +/- 0.7 mm/yr. Santiago has a horizontal velocity of 21.2 +/- 0.8 mm/yr at N70.7 +/- 2.2 degrees E with respect to the NUVEL-1A NNR South American plate velocity and a vertical rate of 5.2 +/- 1.7 mm/yr. The strike-perpendicular horizontal component and the vertical component of this velocity are consistent with a simple elastic dislocation model of a locked South America-Nazca plate interface near Santiago. C1 NVI Inc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP MacMillan, DS (reprint author), NVI Inc, Greenbelt, MD 20771 USA. RI Ma, Chopo/D-4751-2012 NR 21 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1999 VL 26 IS 7 BP 919 EP 922 DI 10.1029/1999GL900139 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 182AW UT WOS:000079477200028 ER PT J AU Seon, J Park, SM Min, KW Frank, LA Paterson, WR Ogilvie, KW AF Seon, J Park, SM Min, KW Frank, LA Paterson, WR Ogilvie, KW TI Observations of density fluctuations in earth's magnetosheath with geotail and wind spacecraft SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID DAYSIDE MAGNETOPAUSE; BOW SHOCK; PLASMA; SHAPE; DEPLETION AB Large fluctuations of plasma densities in the earth's flank-side magnetosheath (local times 1500-1700) are examined. The characteristics of the fluctuations are large amplitudes (Delta N/N similar to 1), long oscillation periods (T similar to 30 m) and anti- correlation between the plasma densities and magnetic field strengths. The variations of the solar wind plasma densities are negligible, whereas considerable fluctuations are found for the solar wind magnetic fields. Two possibilities are considered for the density fluctuations: 1) repeated traversals of the plasma depletion layer and the standing slow-mode waves near the magnetopause and 2) convected slow-mode waves generated at the earth's bow shock. Temperature anisotropy and density profile as expected from the repeated traversals are not confirmed with the observations. Based on the consideration that the present observations occur in the flanks where plasma flows are largely tangential to the magnetopause, we propose that the convected slow-mode waves play a role in the generation of the density fluctuations. C1 Korea Adv Inst Sci & Technol, Satellite Res Ctr, Seoul, South Korea. Korea Adv Inst Sci & Technol, Dept Phys, Seoul, South Korea. Univ Iowa, Dept Phys & Astron, Iowa City, IA USA. NASA, Goddard Space Flight Ctr, Interplanetary Phys Branch, Greenbelt, MD 20771 USA. RP Seon, J (reprint author), Korea Adv Inst Sci & Technol, Satellite Res Ctr, Seoul, South Korea. RI Paterson, William/F-5684-2012; Min, Kyoung Wook/C-1948-2011; Seon, Jongho/E-2363-2013 NR 19 TC 13 Z9 13 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1999 VL 26 IS 7 BP 959 EP 962 DI 10.1029/1999GL900131 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 182AW UT WOS:000079477200038 ER PT J AU Kim, SJ Ruiz, M Rieke, GH Rieke, MJ Zahnle, K AF Kim, SJ Ruiz, M Rieke, GH Rieke, MJ Zahnle, K TI High temperatures in returning ejecta from the R impact of comet SL9 SO ICARUS LA English DT Article DE collisional physics; comets; SL9; Jupiter; atmosphere ID NEAR-INFRARED SPECTROSCOPY; JUPITER ATMOSPHERE; FRAGMENT-R; TIDAL BREAKUP; SHOEMAKER-LEVY-9; TELESCOPE; COLLISION; SEARCH; SIZE; LIGHTCURVES AB Observations from ground-based observatories and with the Galileo spacecraft suggest that the flares from the SL9 impacts resulted from ejecta falling back onto Jupiter in ballistic plumes. This explanation is supported by comparing the plume height as a function of time in HST images with the flare light curve. We show that the rotational temperature of CO in the shock from the R impact rose from less than 2000 K near the beginning of the main flare to about 5000 K at its end. This behavior agrees with a simple physical model of ballistic plumes with a mean molecular weight indicating they are 50% or more jovian air, Alternate models involving formation of molecules at the original impact site, or formation of dust grains to initiate the hare, are inconsistent with these measurements. The energy is emitted primarily as a hot continuum, supporting the possibility that finely divided dust grains are heated in the reentry shock and emit to create the flare. Scaling such models to the energy of the KIT event supports proposals that ballistic plumes were responsible for the global disaster associated with it, (C) 1999 Academic Press. C1 Kyunghee Univ, Dept Astron & Space Sci, Kyunggido 449701, South Korea. Kyunghee Univ, Inst Nat Sci, Kyunggido 449701, South Korea. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Univ Arizona, Dept Planetary Sci, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Kim, SJ (reprint author), Kyunghee Univ, Dept Astron & Space Sci, Kyunggido 449701, South Korea. RI Kim, Sang Joon/E-2383-2013 NR 41 TC 2 Z9 2 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD APR PY 1999 VL 138 IS 2 BP 164 EP 172 DI 10.1006/icar.1998.6069 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 189MG UT WOS:000079908400002 ER PT J AU Ockert-Bell, ME Burns, JA Daubar, IJ Thomas, PC Veverka, J Belton, MJS Klaasen, KP AF Ockert-Bell, ME Burns, JA Daubar, IJ Thomas, PC Veverka, J Belton, MJS Klaasen, KP TI The structure of Jupiter's ring system as revealed by the Galileo imaging experiment SO ICARUS LA English DT Article DE planetary rings; Jupiter, rings; dust ID SATURNS F-RING; JOVIAN RING; GOSSAMER RING; PARTICLE PROPERTIES; LORENTZ RESONANCES; VERTICAL STRUCTURE; ORBITAL EVOLUTION; INNER SATELLITES; CHARGED DUST; DYNAMICS AB The jovian ring system was observed during four orbits of Galileo's nominal mission, when 25 clear-filter images of the rings were taken at spatial resolutions of 23 to 134 km/pixel; the ring appeared fortuitously in an additional II images. The tenuous jovian ring system (normal optical depths <10(-5)) has three components: the halo, main ring, and gossamer ring. The innermost component, a toroidal halo, extends radially from approximately 92,000 to about 122,500 km (near the 3:2 Lorentz resonance) and has a full-width, half-maximum thickness of 12,500 km; its brightness decreases with height off the equatorial plane and decreases as the planet is approached. The main ring reaches from the hare's outer boundary across 6440 to 128,940 km, just interior to Adrastea's orbit (128,980 km); at its outer edge, the main ring takes nearly 1000 km to develop its full brightness. The ring's brightness noticeably decreases around 127,850 km in the vicinity of Metis' semimajor axis (127,980 km). The precise location and nature of the main ring's outer periphery may shift slightly from image to image; the same is true for the "notch" near Metis. The main ring has a faint, vertically extended component that thickens as the halo region is approached. Brightness variations of +/-10% are visible in the central main ring and may be due to vertical corrugations, density clumps, or "spokes" in the ring. Unexplained differences between the near- and far-arm brightnesses are visible. We have discovered that the gossamer ring, lying exterior to the main ring, has two primary components, each of which is fairly uniform: one originates just interior to Amalthea's orbit (181,366 km) while the other is situated radially interior to Thebe's orbit (221,888 km). Very faint material continues past Thebe, blending into the background at 250,000 km. The gossamer rings have thicknesses that are comparable to the maximum elevations of these satellites off Jupiter's equatorial plane; from Galileo's nearly equatorial view, the gossamer rings present rectangular end-profiles with greater intensities along their top and bottom surfaces. The rings seem to be derived from the satellites, (C) 1999 Academic Press. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ockert-Bell, ME (reprint author), Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. RI Daubar, Ingrid/N-1408-2013 NR 60 TC 52 Z9 52 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD APR PY 1999 VL 138 IS 2 BP 188 EP 213 DI 10.1006/icar.1998.6072 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 189MG UT WOS:000079908400004 ER PT J AU Marley, MS McKay, CP AF Marley, MS McKay, CP TI Thermal structure of Uranus' atmosphere SO ICARUS LA English DT Article DE Uranus, atmosphere; atmospheres, structure ID INFRARED-ABSORPTION SPECTRA; STELLAR OCCULTATION; FUNDAMENTAL-BAND; NEPTUNE; TEMPERATURE; PAIRS; STRATOSPHERE; CONSTRAINTS; VOYAGER-2; PROFILES AB Application of a radiative-convective equilibrium model to the thermal structure of Uranus' atmosphere evaluates the role of hazes in the planet's stratospheric energy budget and places a lower limit on the internal energy flux. The model is constrained by Voyager and post-Voyager observations of the vertical aerosol and radiatively active gas profiles. Our baseline model generally reproduces the observed tropospheric and stratospheric temperature profile. However, as in past studies, the model stratosphere from about 10(-3) to 10(-1) bar is too cold. We find that the observed stratospheric hazes do not warm this region appreciably and that any postulated hazes capable of warming the stratosphere sufficiently are inconsistent with Voyager and ground-based constraints, We explore the roles played by the stratospheric methane abundance, the H-2 pressure-induced opacity, photochemical hazes, and C2H2 and C2H6 in controlling the temperature structure in this region. Assuming a vertical methane abundance profile consistent with that found by the Voyager WS occultation observations, the model upper stratosphere, from 10 to 100 mu bar, is also too cold. Radiation in the 7.8-mu m band from a small abundance of hot methane in the lower thermosphere absorbed in this region can warm the atmosphere and bring models into closer agreement with observations. Finally, we find that internal heat fluxes less than or similar to 60 erg cm(-2) sec(-1) are inconsistent with the observed tropospheric temperature profile. (C) 1999 Academic Press. C1 New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Marley, MS (reprint author), New Mexico State Univ, Dept Astron, POB 30001,Dept 4500, Las Cruces, NM 88003 USA. RI Marley, Mark/I-4704-2013 NR 61 TC 64 Z9 64 U1 0 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD APR PY 1999 VL 138 IS 2 BP 268 EP 286 DI 10.1006/icar.1998.6071 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 189MG UT WOS:000079908400010 PM 11542927 ER PT J AU Anderson, JD Giampieri, G AF Anderson, JD Giampieri, G TI Theoretical description of spacecraft flybys by variation of parameters SO ICARUS LA English DT Article DE celestial mechanics; experimental techniques; orbits ID INTERNAL STRUCTURE; CALLISTO AB The planning of space missions to planets and small Solar-System bodies often requires numerous simulations in order to quantify the relative scientific value of various flyby geometries. Here, using the Born approximation for the unperturbed reference orbit, we describe a new perturbation theory for flyby orbits. Results are expressed in terms of the Doppler shift induced in the frequency of a spacecraft tracking signal. We show how these results can be used to simulate the determination of the body's gravitational field, information that provides important boundary conditions on its interior structure. Covariance simulations for the Galilean satellites and for Titan compare favorably with rigorous results from JPL's Orbit Determination Program (ODP). (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ London Queen Mary & Westfield Coll, Astron Unit, London E1 4NS, England. RP Anderson, JD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 23 TC 10 Z9 10 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD APR PY 1999 VL 138 IS 2 BP 309 EP 318 DI 10.1006/icar.1998.6075 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 189MG UT WOS:000079908400012 ER PT J AU Sumich, M AF Sumich, M TI "There were people in that model ..." SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Letter C1 NASA, Washington, DC 20546 USA. RP Sumich, M (reprint author), NASA, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD APR PY 1999 VL 14 IS 4 BP 37 EP 37 PG 1 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA 184FR UT WOS:000079600400010 ER PT J AU Bayard, DS AF Bayard, DS TI Spacecraft pointing control criteria for high resolution spectroscopy SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Article AB A new pointing control criterion is derived to support high resolution space spectroscopy. The criterion maps desired specifications on allowable flux offset (imposed by scientists for accurate calculation of spectral line ratios) into standard pointing control definitions in terms of bias and jitter In contrast to previous derivations, the new criterion is exposure dependent, and fully captures the beneficial smoothing effect of longer spectroscopy exposures on reducing nux offset. The criterion is easily visualized and allows a complete characterization of the allowable design space. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bayard, DS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 198-326, Pasadena, CA 91109 USA. NR 10 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 USA SN 0018-9251 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD APR PY 1999 VL 35 IS 2 BP 637 EP 644 DI 10.1109/7.766944 PG 8 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 199CK UT WOS:000080461600022 ER PT J AU Wang, RT Dick, GJ AF Wang, RT Dick, GJ TI Cryocooled sapphire oscillator with ultrahigh stability SO IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT LA English DT Article; Proceedings Paper CT 1998 Conference on Precision Electromagnetic Measurements (CPEM 98) CY JUL 06-10, 1998 CL WASHINGTON, D.C. SP Natl Inst Stand & Technol, Bur Int Poids & Mesures, IEEE, Instrumentat & Measurement Soc, Natl Res Council Canada, Union Radio Sci Int, Amer Assoc Lab Accreditat, Andeen Hagerling Inc, APS, Instrument & Measurement Sci Top Grp, APS, Precis Measurement & Fundamental Constants, Baltimore Gas & Elect, Cal Lab Magazine, Clarke Hess Commun Res Corp, Creat Mkt Assoc, Fluke Corp, Guildline Instruments, Hewlett Packard Co, Instrument Support Solut Div, IEEE, Instrument & Measurement Soc, Washington Chapter, IEEE, Natl Capital Area Council, Natl Conf Stand Lab, Org Amer States, Wavetek Corp DE cryogenics; frequency stability; microwave oscillators; sapphire AB We present test results and design details for the first short-term frequency standard to achieve ultrahigh stability without the use of liquid helium. With refrigeration provided by a commercial cryocooler, the compensated sapphire oscillator (10 K CSO) makes available the superior short-term stability and phase noise performance of cryogenic oscillators without periodic interruptions for cryogen replacement. Technical features of the 10 K CSO include use of a tno-stage cryocooler with vibration isolation by helium gas at atmospheric pressure, and a new sapphire/ruby resonator design giving compensated operation at 8K to 10 K with Q = (1-2) x 10(9), Stability of the first unit shows an Allan deviation of sigma(y) 12.5 x 10(-15) for measuring times of 200 s less than or equal to tau less than or equal to 600 s. We also present results showing the capability of the 10 K CSO to eliminate local oscillator degradation for atomic frequency standards. Configured as local oscillator (L.O.) for the LITS-7 trapped mercury ion frequency standard, the CSO/LITS combination demonstrated a limiting performance of 3.0 x 10(-14)/tau(1/2), the lowest value measured to date for a passive atomic frequency standard, and virtually identical to the value calculated from photon statistics. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wang, RT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 27 Z9 27 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9456 J9 IEEE T INSTRUM MEAS JI IEEE Trans. Instrum. Meas. PD APR PY 1999 VL 48 IS 2 BP 528 EP 531 DI 10.1109/19.769650 PG 4 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 206GU UT WOS:000080869600094 ER PT J AU Ye, J Robertsson, L Picard, S Ma, LS Hall, JL AF Ye, J Robertsson, L Picard, S Ma, LS Hall, JL TI Absolute frequency atlas of molecular I-2 lines at 532 nm SO IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT LA English DT Article; Proceedings Paper CT 1998 Conference on Precision Electromagnetic Measurements (CPEM 98) CY JUL 06-10, 1998 CL WASHINGTON, D.C. SP Natl Inst Stand & Technol, Bur Int Poids & Mesures, IEEE, Instrumentat & Measurement Soc, Natl Res Council Canada, Union Radio Sci Int, Amer Assoc Lab Accreditat, Andeen Hagerling Inc, APS, Instrument & Measurement Sci Top Grp, APS, Precis Measurement & Fundamental Constants, Baltimore Gas & Elect, Cal Lab Magazine, Clarke Hess Commun Res Corp, Creat Mkt Assoc, Fluke Corp, Guildline Instruments, Hewlett Packard Co, Instrument Support Solut Div, IEEE, Instrument & Measurement Soc, Washington Chapter, IEEE, Natl Capital Area Council, Natl Conf Stand Lab, Org Amer States, Wavetek Corp DE frequency control; frequency measurement; frequency modulation; laser spectroscopy; laser stability; measurement standards; YAG lasers ID HYPERFINE-STRUCTURE; TRANSITION; STATE AB With the aid of two iodine spectrometers, we report for the first time the measurement of the hyperfine splittings of the P(54) 32-0 and R(57) 32-0 transitions near 532 nm, Within the tuning range of the frequency-doubled Nd:YAG laser, modulation transfer spectroscopy recovers nine relatively strong ro-vibrational transitions of I-127(2) molecules with excellent SNR, These transitions are now linked together with their absolute frequencies determined by measuring directly the frequency gaps between each line and the R(56) 32-0: a(10) component. This provides an attractive frequency reference network in this wavelength region. C1 Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80302 USA. Natl Inst Stand & Technol, Boulder, CO 80309 USA. RP Ye, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. RI Ye, Jun/C-3312-2011 NR 13 TC 96 Z9 101 U1 1 U2 9 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9456 J9 IEEE T INSTRUM MEAS JI IEEE Trans. Instrum. Meas. PD APR PY 1999 VL 48 IS 2 BP 544 EP 549 DI 10.1109/19.769654 PG 6 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 206GU UT WOS:000080869600098 ER PT J AU Pogorzelski, RJ Maccarini, PF York, RA AF Pogorzelski, RJ Maccarini, PF York, RA TI A continuum model of the dynamics of coupled oscillator arrays for phase-shifterless beam scanning SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE beam steering; coupled oscillators; injection locked; phased array AB The behavior of arrays of coupled oscillators has been previously studied by computational solution of a set of nonlinear differential equations describing the time dependence of each oscillator in the presence of signals coupled from neighboring oscillators. The equations are sufficiently complicated in that intuitive understanding of the phenomena which arise is exceedingly difficult. We propose a simplified theory of such arrays in which the relative phases of the oscillator signals are represented by a continuous function defined over the array. This function satisfies a linear partial differential equation of diffusion type, which may be solved via the Laplace transform. This theory is used to study the dynamic behavior of a linear array of oscillators, which results when the end oscillators are detuned to achieve the phase distribution required for steering a beam radiated by such an array. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Dept Elect Engn, Santa Barbara, CA 93106 USA. RP Pogorzelski, RJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 44 Z9 44 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD APR PY 1999 VL 47 IS 4 BP 463 EP 470 DI 10.1109/22.754880 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 184ZE UT WOS:000079643000012 ER PT J AU Pogorzelski, RJ Maccarini, PF York, RA AF Pogorzelski, RJ Maccarini, PF York, RA TI Continuum modeling of the dynamics of externally injection-locked coupled oscillator arrays SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE beam steering; coupled oscillators; injection locked; phased array AB Mutually injection-locked arrays of electronic oscillators provide a novel means of controlling the aperture phase of a phased-array antenna, thus achieving the advantages of spatial power combining while retaining the ability to steer the radiated beam. In a number of design concepts, one or more of the oscillators are injection locked to a signal from an external master oscillator. The behavior of such a system has been analyzed by numerical solution of a system of nonlinear differential equations which, due to its complexity, yields limited insight into the relationship between the injection signals and the aperture phase. In this paper, we develop a continuum model, which results in a single partial differential equation for the aperture phase as a function of time, Solution of the equation is effected by means of the Laplace transformation and yields detailed information concerning the dynamics of the array under the influence of the external injection signals. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Dept Elect Engn, Santa Barbara, CA 93106 USA. RP Pogorzelski, RJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 26 Z9 26 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD APR PY 1999 VL 47 IS 4 BP 471 EP 478 DI 10.1109/22.754881 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 184ZE UT WOS:000079643000013 ER PT J AU Yoshita, K Tsunemi, H Miyata, E Gendreau, KC Bautz, HW AF Yoshita, K Tsunemi, H Miyata, E Gendreau, KC Bautz, HW TI Improvement of the position resolution of the CCD for X-ray use SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article DE charge-coupled-device; charge cloud shape; mesh experiment; subpixel resolution ID CHARGE-COUPLED-DEVICE; ASCA SATELLITE; AXAF; EFFICIENCY; PIXEL AB The authors report here experimental results relating X-ray interaction location and event splitting. The X-ray interaction location can be localized at subpixel scale using the mesh technique. The authors found that the center of gravity of the split event is well-correlated with the X-ray interaction location. They analyzed the data using two models for the charge cloud shape: one is the rectangular model and the other is the Gaussian model. Although the authors could not distinguish between these models, they measured a root mean square charge cloud size of 1 to 2 mu m for X rays of Y-L (1.9 keV), Ag-L (3.0 keV), and Ti-K (4.5 keV). When the X rays enter near the pixel boundary, the charge splits into adjacent pixels, allowing determination of the X-ray: interaction location with an accuracy of 1.5 to 2.2 mu m. The authors, therefore, expect that the X-ray CCD can function as an X-ray imager with subpixel resolution, which will be especially. useful in applications involving very high spatial resolution optics. C1 Osaka Univ, Dept Earth & Space Sci, Grad Sch Sci, Toyonaka, Osaka 5600043, Japan. NASA, GSFC, Greenbelt, MD 20771 USA. MIT, Cambridge, MA 02139 USA. RP Yoshita, K (reprint author), Osaka Univ, Dept Earth & Space Sci, Grad Sch Sci, Toyonaka, Osaka 5600043, Japan. NR 18 TC 16 Z9 16 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD APR PY 1999 VL 46 IS 2 BP 100 EP 106 DI 10.1109/23.757195 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 187TF UT WOS:000079803600004 ER PT J AU Kenwright, DN Henze, C Levit, C AF Kenwright, DN Henze, C Levit, C TI Feature extraction of separation and attachment lines SO IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS LA English DT Article DE vector field visualization; vector field topology; flow visualization; feature detection; flow separation; separation line AB Separation and attachment lines are topologically significant curves that exist on 2D surfaces in 3D vector fields. Two algorithms are presented, one point-based and one element-based, that extract separation and attachment lines using eigenvalue analysis of a locally linear function. Unlike prior techniques based on piecewise numerical integration, these algorithms use robust analytical tests that can be applied independently to any point in a vector field. The feature extraction is fully automatic and suited to the analysis of large-scale numerical simulations. The strengths and weaknesses of the two algorithms are evaluated using analytic vector fields and also results from computational fluid dynamics (CFD) simulations. We show that both algorithms detect open separation lines-a type of separation that is not captured by conventional vector field topology algorithms. C1 NASA, Ames Res Ctr, MRJ Technol Solut Inc, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, MRJ Technol Solut Inc, Moffett Field, CA 94035 USA. EM davidk@nas.nasa.gov; chenzel@nas.nasa.gov; creon@nas.nasa.gov NR 27 TC 40 Z9 42 U1 0 U2 1 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1077-2626 EI 1941-0506 J9 IEEE T VIS COMPUT GR JI IEEE Trans. Vis. Comput. Graph. PD APR-JUN PY 1999 VL 5 IS 2 BP 135 EP 144 DI 10.1109/2945.773805 PG 10 WC Computer Science, Software Engineering SC Computer Science GA 208LE UT WOS:000080991900004 ER PT J AU Keckhut, P Schmidlin, FJ Hauchecorne, A Chanin, ML AF Keckhut, P Schmidlin, FJ Hauchecorne, A Chanin, ML TI Stratospheric and mesospheric cooling trend estimates from US rocketsondes at low latitude stations (8 degrees S-34 degrees N), taking into account instrumental changes and natural variability SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID SOLAR ULTRAVIOLET VARIATIONS; MIDDLE ATMOSPHERE; TEMPERATURE TRENDS; OZONE; LIDAR; CLIMATOLOGY; PINATUBO; FRANCE; TIDES AB Long-term changes of temperature and wind data have been investigated using U.S. rocketsondes at six selected sites at northern tropical and subtropical locations (from 8 degrees S to 34 degrees N). The analysis method used here is based on a multifunction regression analysis that allows for a continuous linear trend, for natural variability, and for sudden changes of the mean due to successive instrumental improvements. Results show that while sensor replacement does not seem to induce major measurement bias, successive correction procedures have produced significant mean temperature shifts, mostly above 55 km. Changes in the local time of measurement may have an impact on trend estimates because of tidal effects. This effect is probably enhanced by the direct solar radiative heating on the sensor. Selecting data according to the time of measurement has sometimes reduced the amplitude of the observed cooling. Using a detailed statistical model and error analysis, significant temperature trends are detected in the upper stratosphere with amplitudes slightly increasing with height. As the trend profiles from the selected sites are very similar in patterns and magnitudes, a mean annual temperature trend profile is composed using these six data sets. A significant cooling of 1.1 +/- 0.6 K per decade is estimated for 25 km height, increasing with height up to 1.7 +/- 0.7 K per decade in the altitude range of 35 to 50 km, and to 3.3 +/- 0.9 K per decade near 60 km. Previous published simulations of stratospheric changes induced by greenhouse gas increases and stratospheric ozone depletion, using numerical models, predict smaller cooling than that estimated here by a factor of around two. A similar analysis for zonal wind data reveals no significant changes larger than 5 m.s(-1) per decade. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CNRS, Serv Aeron, Inst Pierre Simon Laplace, F-91371 Verrieres Buisson, France. NASA, Goddard Space Flight Ctr, Lab Hydrospher Phys, Wallops Isl, VA USA. RP Keckhut, P (reprint author), CNRS, Serv Aeron, Inst Pierre Simon Laplace, BP3, F-91371 Verrieres Buisson, France. RI Hauchecorne, Alain/A-8489-2013 NR 45 TC 51 Z9 51 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD APR PY 1999 VL 61 IS 6 BP 447 EP 459 DI 10.1016/S1364-6826(98)00139-4 PG 13 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 203YF UT WOS:000080735200002 ER PT J AU Curtis, S Hastenrath, S AF Curtis, S Hastenrath, S TI Long-term trends and forcing mechanisms of circulation and climate in the equatorial Pacific SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; EL-NINO; SOUTHERN OSCILLATION; TROPICAL ATLANTIC; ANNUAL CYCLE; WORLD OCEAN; VARIABILITY; GREENHOUSE; ANOMALIES; THERMOSTAT AB Trends of circulation and climate in the equatorial Pacific during 1948-92 were analyzed from observations of sea surface temperature (T), cloudiness (C), sea level pressure (P), specific humidity (Q), and zonal wind component. From indices compiled for the cold tongue in the east, the central equatorial Pacific, the warm pool in the west, and the eastern equatorial Indian Ocean, interannual relationships were compared with long-term trends. On the interannual timescale the significant negative T-P correlations in the eastern Pacific indicate a hydrostatic forcing of T on P, and the negative P-C correlations in the western Pacific and eastern Indian Oceans are consistent with anomalously high P through subsidence favoring clear sky. The tropical Pacific is warming and most markedly in the east; there is a weakening of the westward pressure gradient; and increasing Q and C in the east. Warming in the eastern section of the basin may force falling pressure hydrostatically, the trend of P being largest near 155 degrees W. In the domain 155 degrees-90 degrees W easterlies accelerate, favoring enhanced evaporation and humidity. The strengthening of the winds east of 155 degrees W and slowdown to the west imply enhanced convergence and upward motion, consistent with increasing C near 155 degrees W. Also warming may thermodynamically force increasing humidity and cloudiness in the realm of the intertropical convergence zone. The observed basin-wide warming and weakening of the westward pressure gradient, with the consequent slackening of easterlies over the central equatorial Pacific, reflect a tendency toward patterns characteristic of the low/warm phase of the Southern Oscillation. C1 Univ Wisconsin, Dept Atmospher & Ocean Sci, Madison, WI USA. RP Curtis, S (reprint author), Univ Maryland, NASA, Goddard Space Flight Ctr, JCET, Code 912, Greenbelt, MD 20771 USA. RI Curtis, Scott/C-1115-2013; OI Curtis, Scott/0000-0001-9065-8639 NR 43 TC 13 Z9 13 U1 0 U2 3 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 APR PY 1999 VL 12 IS 4 BP 1134 EP 1144 DI 10.1175/1520-0442(1999)012<1134:LTTAFM>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 182LJ UT WOS:000079500200015 ER PT J AU Zalameda, JN AF Zalameda, JN TI Measured through-the-thickness thermal diffusivity of carbon fiber reinforced composite materials SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE graphite fiber composite; thermal diffusivity; destructive testing; fiber fraction and porosity AB The thermal diffusivity of carbon fiber reinforced composite materials is dependent on fiber. matrix, and porosity volume fractions. Since the carbon fiber thermal conductivity is much greater than the epoxy resin matrix thermal conductivity, thermal diffusivity is a good indicator of the fiber volume fraction. In this study. through-the-thickness thermal diffusivity images were obtained nondestructively on carbon fiber reinforced composite plates, and the values varied from 0.0035 to 0.0062 cm(2)/s. The fiber and porosity volume fractions were measured destructively. and their values varied from 56.0 to 70.5% and from 0.9 to 7.2%. respectively. The destructive test data were used as a standard for comparison of three commonly used transverse equivalent thermal conductivity models: the Stacked Plate. the mixed flow Cylindrical Fiber model, and the Composite Circular Assemblage model. In these models, a porosity correction is also studied. There was very good agreement between the Composite Circular Assemblage and Cylindrical Fiber model when porosity levels were less than 2%. The porosity correction helped to reduce the chi-squared value by 24% in the Cylindrical Filament model. Finally, the potential is discussed to image fiber volume fraction nondestructively using the described thermal measurement system. C1 USA, Res Lab, Vehicle Technol Ctr,NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Zalameda, JN (reprint author), USA, Res Lab, Vehicle Technol Ctr,NASA, Langley Res Ctr, MS231, Hampton, VA 23681 USA. NR 18 TC 8 Z9 8 U1 0 U2 2 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 USA SN 0884-6804 J9 J COMPOS TECH RES JI J. Compos. Technol. Res. PD APR PY 1999 VL 21 IS 2 BP 98 EP 102 PG 5 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA 187XT UT WOS:000079814700005 ER PT J AU Gan, Y El-Hadik, M Aglan, H Faughnan, P Bryan, C AF Gan, Y El-Hadik, M Aglan, H Faughnan, P Bryan, C TI Fatigue crack growth analysis of polymonochlorotrifluoroethylene (CTFE) SO JOURNAL OF ELASTOMERS AND PLASTICS LA English DT Article ID ADHESIVE JOINTS; PROPAGATION; POLYMERS; DAMAGE AB Fatigue crack growth behavior of a polymonochlorotrifluoroethylene (CTFE) was investigated. Tension-tension fatigue propagation tests on geometrically identical specimens were performed at different frequencies. Specimens with different notch to width ratios (a/w) were also tested. The applied stress level in all tests was kept the same. The maximum stress was 16.0 MPa and the ratio of minimum stress to maximum stress was kept at 25%. Fatigue test data such as the number of loading cycles, the crack length, and the hysteresis loops were recorded. The Modified Crack Layer (MCL) theory was employed to analyze the FCP behavior of this CTFE material. Also the results were analyzed using the Paris equation for comparison. It has been found that the fatigue crack growth behavior of this material cannot be described by the Paris power law due to the three distinct stages of the FCP kinetics. The MCL model was successfully used for extracting material parameters; gamma', the specific energy of damage, and beta', the coefficient of energy dissipation. The specific energy of damage for this CTFE was 855 kJ/m(3) and the value of the coefficient of energy dissipation was 6.2 x 10(-6). It was found that the values of gamma' and beta' are independent of a/w and the frequency (f), though the FCP kinetics and lifetime were dependent on a/w and f. The variation in gamma' and beta' when a/w changed from 0.04 to 0.1 were only +/-0.9% and +/-6.8%, respectively. For different frequencies (from 0.5 Hz to 5 Hz), the variation of these two parameters were +/-0.6% and +/-1.4%, respectively. In situ and post failure analysis of the fatigue fractured samples revealed a clear damage zone adjacent to the main crack. The larger the volume of the damage zone, the longer the fatigue lifetime. It was also found that a higher micro-crack density associated with a larger damage zone. A larger damage zone with higher micro-crack density consumes more energy and thus reduces the portion of energy required to fuel the main crack growth. C1 Tuskegee Univ, Dept Mech Engn, Tuskegee, AL 36088 USA. NASA, Kennedy Space Ctr, Kennedy Space Ctr, FL 32899 USA. RP Aglan, H (reprint author), Tuskegee Univ, Dept Mech Engn, Tuskegee, AL 36088 USA. NR 51 TC 3 Z9 3 U1 0 U2 0 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0095-2443 EI 1530-8006 J9 J ELASTOM PLAST JI J. Elastomer Plast. PD APR PY 1999 VL 31 IS 2 BP 96 EP 129 PG 34 WC Materials Science, Multidisciplinary; Polymer Science SC Materials Science; Polymer Science GA 187AN UT WOS:000079763900001 ER PT J AU Reddy, DR Steffen, CJ Zaman, KBMQ AF Reddy, DR Steffen, CJ Zaman, KBMQ TI Computation of three-dimensional compressible flow from a rectangular nozzle with delta tabs SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 42nd International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 02-05, 1997 CL ORLANDO, FLORIDA SP Int Gas Turbine Inst ID JET AB A three-dimensional viscous pow analysis is performed using a time-marching Reynolds-averaged Navier-Stokes code for a 3:1 rectangular nozzle with two delta tabs located at the nozzle exit plane to enhance mixing. Two flow configurations, a subsonic jet case and a supersonic jet case using the same tab configuration, which were previously studied experimentally, are computed and compared with the experimental data. The experimental data include streamwise velocity and vorticity distributions for the subsonic case, and Mach number distributions for the supersonic case, at various axial locations downstream of the nozzle exit. The computational results show very good agreement with the experimental data. In addition, the effect of compressibility on vorticity dynamics is examined by comparing the vorticity contours of the subsonic jet case with those of the the supersonic jet case which were not measured in the experiment. C1 NASA, Turbomachinery & Propuls Syst Div, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Reddy, DR (reprint author), NASA, Turbomachinery & Propuls Syst Div, Lewis Res Ctr, MS 5-11,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 26 TC 5 Z9 5 U1 1 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD APR PY 1999 VL 121 IS 2 BP 235 EP 242 DI 10.1115/1.2817111 PG 8 WC Engineering, Mechanical SC Engineering GA 189BB UT WOS:000079883300008 ER PT J AU Nalim, MR AF Nalim, MR TI Assessment of combustion modes for internal combustion wave rotors SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 31st Joint Propulsion Conference CY JUL, 1995 CL SAN DIEGO, CALIFORNIA ID HYDROCARBON AB Combustion within the channels of a wave rotor is examined as a means of obtaining pressure gain during heat addition in a gas turbine engine. Three modes of combustion are assessed: premixed autoignition (detonation), premixed deflagration, and non-premixed autoignition. The last two will require strong turbulence for completion of combustion in a reasonable time in the wave rotor. The autoignition modes will require inlet temperatures in excess of 800 K for reliable ignition with most hydrocarbon fuels. Examples of combustion mode selection are presented for Two engine applications. C1 NASA, Natl Res Council, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Nalim, MR (reprint author), NASA, Natl Res Council, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 27 TC 13 Z9 13 U1 2 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD APR PY 1999 VL 121 IS 2 BP 265 EP 271 DI 10.1115/1.2817116 PG 7 WC Engineering, Mechanical SC Engineering GA 189BB UT WOS:000079883300013 ER PT J AU Darden, JM Earhart, EM Flowers, GT AF Darden, JM Earhart, EM Flowers, GT TI Experimental rotordynamic characterization of annular seals: Facility and methodology SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 02-05, 1998 CL STOCKHOLM, SWEDEN ID COEFFICIENTS AB Annular seals are known to enhance rotordynamic stability margins and minimize vibration response levels in high-speed rotating machinery. Theoretical predictions SOY the rotordynamic characteristics of annular seals exist but additional experimental data is needed to properly anchor these results. NASA's Marshall Space Flight Center (MSFC) has developed an annular seal test rig and facility to experimentally characterize axially fed annular seals. The objective of MSFC's annular seal test rig is to obtain the rotordynamic coefficients (direct and cross-coupled stiffness, damping, and added mass) for a variety of high Reynolds number annular seals. The MSFC test, rig supports centered-seal testing with inlet pressures up to 138 bars (2000 psi) and flow rates of over 946 liters per minute (250 gpm). The rig's shaft is powered by a 186 kilowatt (250 horsepower) steam turbine capable of rotational speeds of over 20,000 revolutions per minute (rpm). A description of the identification process used to obtain rotordynamic coefficients is given as well as procedures for ensuring quality data. Experimental results for a smooth annular seal with an L/D = 0.5 is presented Excellent agreement between experimental and theoretical results is obtained. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Auburn Univ, Dept Mech Engn, Auburn, AL 36849 USA. RP Darden, JM (reprint author), NASA, George C Marshall Space Flight Ctr, MS ED12,Bldg 4487, Huntsville, AL 35812 USA. NR 17 TC 4 Z9 4 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD APR PY 1999 VL 121 IS 2 BP 349 EP 354 DI 10.1115/1.2817127 PG 6 WC Engineering, Mechanical SC Engineering GA 189BB UT WOS:000079883300024 ER PT J AU Whang, YC Burlaga, LF AF Whang, YC Burlaga, LF TI Shocks in the distant heliosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WIND TERMINATION SHOCK; PRESSURE-BALANCED STRUCTURES; MERGED INTERACTION REGIONS; INTERSTELLAR PICKUP IONS; ANOMALOUS COSMIC-RAYS; SOLAR-WIND; OUTER HELIOSPHERE; VOYAGER-2 OBSERVATIONS; NEUTRAL HYDROGEN; PROTONS AB Voyager data are used to study two aspects of pickup proton shocks in the distant heliosphere: (I) Two shocks having similar speed jump of similar to 50 km/s observed at 5 AU and at 43 AU demonstrate the effects of pickup protons on weakening interplanetary shocks at increasing heliocentric distance. (2) On the basis of three shocks identified outside 34 AU from high-resolution plasma and magnetic field data we develop an empirical model to study the jump conditions of pickup protons across solar wind shocks. Making use of the empirical model one can study the postshock conditions of pickup protons for the global merged interaction region (GMIR) shock and the termination shock; this will enable us to calculate more accurately the propagation of the GMIR shock and the interaction of GMIR shock with the termination shock. We also find that the variation of the pickup proton temperature TI across the shock is very close to the adiabatic relation that TI is proportional to the magnetic field strength B. C1 Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Whang, YC (reprint author), Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NR 35 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1999 VL 104 IS A4 BP 6721 EP 6727 DI 10.1029/1999JA900016 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 182CU UT WOS:000079481600004 ER PT J AU Kamide, Y Baumjohann, W Daglis, IA Gonzalez, WD Grande, M Joselyn, JA McPherron, RL Phillips, JL Reeves, EGD Rostoker, G Sharma, AS Singer, HJ Tsurutani, BT Vasyliunas, VM AF Kamide, Y Baumjohann, W Daglis, IA Gonzalez, WD Grande, M Joselyn, JA McPherron, RL Phillips, JL Reeves, EGD Rostoker, G Sharma, AS Singer, HJ Tsurutani, BT Vasyliunas, VM TI Comment on "Current understanding of magnetic storms: Storm-substorm relationships," by Y. Kamide et al. Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article C1 Nagoya Univ, Solar Terr Environm Lab, Toyokawa, Japan. Max Planck Inst Extraterr Phys, D-37075 Garching, Germany. Natl Observ Athens, Inst Ionospher & Space Res, Penteli, Greece. Inst Pesquisas Espaciais, Sao Paulo, Brazil. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. NOAA, Space Environm Ctr, Boulder, CO USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Los Alamos Natl Lab, Los Alamos, NM USA. Univ Alberta, Dept Phys, Edmonton, AB, Canada. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Max Planck Inst Aeron, Katlenburg Lindau, Germany. RP Kamide, Y (reprint author), Nagoya Univ, Solar Terr Environm Lab, Toyokawa, Japan. EM kamide@stelab.nagoya-u.ac.jp; bj@mpe-garching.mpg.de; daglis@creator.space.noa.gr; gonzalez@dge.inpe.br; M.Grande@rl.ac.uk; jjoselyn@sec.noaa.gov; rmcpherron@igpp.ucla.edu; JLPhilli@ems.jsc.gov; reeves@lanl.gov; rostoker@space.ualberta.ca; ssh@avl.umd.edu; hsinger@sec.noaa.gov; btsurutani@jplsp.jpl.nasa.gov; vasyliunas@linaxl.mpae.gwdg.de RI Baumjohann, Wolfgang/A-1012-2010; Daglis, Ioannis/L-6100-2013; Reeves, Geoffrey/E-8101-2011; Grande, Manuel/C-2242-2013 OI Baumjohann, Wolfgang/0000-0001-6271-0110; Daglis, Ioannis/0000-0002-0764-3442; Reeves, Geoffrey/0000-0002-7985-8098; Grande, Manuel/0000-0002-2233-2618 NR 5 TC 1 Z9 1 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1999 VL 104 IS A4 BP 7051 EP 7051 DI 10.1029/1999JA900020 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 182CU UT WOS:000079481600035 ER PT J AU Marullo, S Santoleri, R Malanotte-Rizzoli, P Bergamasco, A AF Marullo, S Santoleri, R Malanotte-Rizzoli, P Bergamasco, A TI The sea surface temperature field in the Eastern Mediterranean from advanced very high resolution radiometer (AVHRR) data - Part II. Interannual variability SO JOURNAL OF MARINE SYSTEMS LA English DT Article DE sea surface temperature; empirical orthogonal function (EOF); Eastern Mediterranean ID ORTHOGONAL FUNCTION-ANALYSIS; CIRCULATION; CALIFORNIA AB A ten-year dataset of AVHRR-SST (Sea Surface Temperature) with 18 km space resolution and weekly frequency has been analyzed in the Eastern Mediterranean. In Part I of the present study, we examined the seasonal variability of the basin and we defined the time and space scales of the monthly climatologies of the sea surface temperature distributions. A detailed and quantitative comparison was also carried out between the SST distribution of September 1987 and the surface temperature map of the corresponding hydrological survey of the POEM (Physical Oceanography of the Eastern Mediterranean) Programme. In this second part, we extend the analysis to examine and quantify the interannual variabilities. We summarize our results as follows. The analysis reveals the presence of an interannual cycle in the Ionian basin in the decade 1983-1992. The climatological pattern of the isotherms oscillates between two main states corresponding to the winter (zonal) and the summer (meridional) distributions. The apparent interannual cycle appears in the SST distribution only in winter and only in the Ionian basin, while the Levantine basin shows only fluctuations around the climatology. Thus, the interannual signal in our dataset is present but is much less important than the seasonal one. To confirm and quantify the above conclusions, we evaluate the Empirical Orthogonal Function of the SST time series. Gradient EOF's modes show the presence of a very strong yearly signal explaining 60% of the variance and a less intense seasonal signal that account for 16% of the variance. No interannual variability is represented by EOF gradient modes even though it can be observed in the increasing trend of the time varying amplitude of the first EOF mode, To observe the interannual variability signal, a seasonal temperature cycle was subtracted from each image instead of the ensemble (spatial) mean. A new EOF mode that accounts for 20% of the variance emerges between the first and second previous gradient modes. The time behaviour of this mode clearly indicates that it represents the interannual signal of the overall SST field. (C) 1999 Elsevier Science B.V. All rights reserved. C1 ENEA, Ctr Ric, I-00060 Rome, Italy. CNR, Ist Fis Atmosfera, Rome, Italy. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA USA. CNR, Ist Dinam Grandi Masse, Venice, Italy. CALTECH, Jet Prop Lab, NASA Ocean Data Syst, Pasadena, CA 91125 USA. RP Marullo, S (reprint author), ENEA, Ctr Ric, Via Anguillarese,SM di Galleria 301, I-00060 Rome, Italy. EM salva@canaletto.casaccia.enea.it OI Marullo, Salvatore/0000-0003-4203-0956 NR 12 TC 32 Z9 32 U1 2 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0924-7963 J9 J MARINE SYST JI J. Mar. Syst. PD APR PY 1999 VL 20 IS 1-4 BP 83 EP 112 DI 10.1016/S0924-7963(98)00072-4 PG 30 WC Geosciences, Multidisciplinary; Marine & Freshwater Biology; Oceanography SC Geology; Marine & Freshwater Biology; Oceanography GA 184LZ UT WOS:000079614800006 ER PT J AU Ramesham, R AF Ramesham, R TI Differential pulse voltammetry of toxic metal ions at the boron-doped CVD diamond electrode SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID THIN-FILM ELECTRODES; POLYCRYSTALLINE DIAMOND; SELECTIVE GROWTH; BEHAVIOR; CARBON; CORROSION; HYDROGEN AB Boron-doped polycrystalline diamond films were grown over a molybdenum substrate by a microwave plasma CVD process using a methane and hydrogen gas mixture at a pressure of 35 +/- 1 Torr. Boron doping of diamond was achieved in situ by using a solid boron source while growing diamond in the CVD process. We have observed a negligible background current (al) for diamond by differential pulse voltammetry in 0.5 M NaCl, 0.5 M H2SO4, and 0.5 M HNO3 solutions over a wide potential range. Therefore, diamond will certainly have a use as an electrode material in electroanalytical applications to detect trace toxic/nontoxic metal ions such as cadmium, lead, copper, and silver. Differential pulse voltammetry was used to detect and evaluate the presence of lead ions in 0.5 M NaCl and cadmium ions in 0.5 M H2SO4 supporting electrolyte solution using highly conducting boron-doped diamond coated molybdenum electrode material. Furthermore, reverse differential pulse voltammetry was used to evaluate the presence of copper and silver ions in 0.5 M H2SO4 and 0.5 M HNO3 solution, respectively. Diamond electrode has been used in this study to detect metallic ions in the solution over a wide potential range that covers +0.8 V to -0.4 V vs., SHE. (C) 1999 Kluwer Academic Publishers. C1 Auburn Univ, Space Power Inst, Leach Ctr 231, Auburn, AL 36849 USA. RP Ramesham, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 125-152, Pasadena, CA 91109 USA. EM rajeshuni.ramesham@jpl.nasa.gov NR 27 TC 21 Z9 21 U1 1 U2 5 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2461 EI 1573-4803 J9 J MATER SCI JI J. Mater. Sci. PD APR 1 PY 1999 VL 34 IS 7 BP 1439 EP 1445 DI 10.1023/A:1004590029830 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA 190DJ UT WOS:000079946500002 ER PT J AU Bhatt, RT Palczer, AR AF Bhatt, RT Palczer, AR TI Effects of surface area, polymer char, oxidation, and NiO additive on nitridation kinetics of silicon powder compacts SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID HIGH-PURITY SILICON; SI AB The oxidative stability of attrition-milled silicon powder under reaction-bonding processing conditions has been determined. The investigation focused on the effects of surface area, polymer char, preoxidation, nitriding environment, and a transitional metal oxide additive (NiO) on the nitridation kinetics of attrition-milled silicon powder compacts tested at 1250 and 1350 degrees C for 4 h. Silicon powder was wet-attrition-milled from 2 to 48 h to achieve surface areas (SAs) ranging from 1.3 to 63 m(2)/g. A silicon powder of high surface area (63 m(2)/g) was exposed for up to 1 month to ambient air or for up to 4 days to an aqueous-based solution with the pH maintained at 3, 7, or 9. Results indicated that the high-surface-area silicon powder showed no tendency to oxidize further, whether in ambient air for up to 1 month or in deionized water for up to 4 days. After a 1-day exposure to an acidic or basic solution, the same powder showed evidence of oxidation. As the surface area increased, so did the percentage nitridation after 4 h in N-2 at 1250 or 1350 degrees C. Adding small amounts of NiO significantly improved the nitridation kinetics of high-surface-area powder compacts, but both preoxidation of the powder and residual polymer char delayed it. Conversely, the nitridation environment had no significant influence on the nitridation kinetics of a high-surface-area powder. Impurities present in the starting powder, and those accumulated during attrition milling, appeared to react with the silica layer on the surface of silicon particles to form a molten silicate layer, which provided a path for rapid diffusion of N-2 and enhanced the nitridation kinetics. (C) 1999 Kluwer Academic Publishers. C1 USA, Res Lab, Lewis Res Ctr, Vehicle Technol Ctr, Cleveland, OH 44235 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bhatt, RT (reprint author), USA, Res Lab, Lewis Res Ctr, Vehicle Technol Ctr, Cleveland, OH 44235 USA. NR 24 TC 3 Z9 3 U1 0 U2 4 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD APR 1 PY 1999 VL 34 IS 7 BP 1483 EP 1492 DI 10.1023/A:1004591508874 PG 10 WC Materials Science, Multidisciplinary SC Materials Science GA 190DJ UT WOS:000079946500007 ER PT J AU Wang, WF Sirota, JM Reuter, DC AF Wang, WF Sirota, JM Reuter, DC TI Allene nu(9) and nu(10): Low-temperature measurements of line intensity SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID INFRARED-SPECTRUM; BAND SYSTEM; ATMOSPHERE AB We report laboratory intensity measurements for the weak nu(9) (998.8 cm(-1)) and intense nu(10) (841.1 cm(-1)) bands of allene. Allene is predicted to be a constituent of Titan's atmosphere, and measurements of its abundance would yield important information about the atmospheric chemistry of that body. Spectra were obtained at a temperature of 200 K (approximating Titan conditions) using the high-resolution FTS instrument at Kitt-Peak National Observatory's McMath-Pierce observatory. A total of 505 nu(9) and 687 nu(10) line intensities were fit using a least-squares method to accurately determine two sets of transition dipole moments. Integrated band intensities computed utilizing the fitted parameters were found to be 36 +/- 4% cm(-2) atm(-1) and 301 +/- 4% cm(-2) atm(-1) for nu(9) and nu(10), respectively, at 200 K. (C) 1999 Academic Press. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Planetary Syst Branch, Greenbelt, MD 20771 USA. RP Wang, WF (reprint author), Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, 1000 Hilltop Circle, Baltimore, MD 21250 USA. NR 23 TC 3 Z9 3 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD APR PY 1999 VL 194 IS 2 BP 256 EP 268 DI 10.1006/jmsp.1999.7809 PG 13 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 182MF UT WOS:000079502200017 ER PT J AU Dinniman, MS Rienecker, MM AF Dinniman, MS Rienecker, MM TI Frontogenesis in the North Pacific oceanic frontal zones - A numerical simulation SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID SUB-TROPICAL FRONT; SUBTROPICAL MODE WATER; WESTERN PACIFIC; VARIABILITY; TEMPERATURE; CIRCULATION; SALINITY; WIND AB primitive equation model [Geophysical Fluid Dynamics Laboratory's (GFDL's) MOM 2] with one degree horizontal resolution is used to simulate the seasonal cycle of frontogenesis in the subarctic frontal zone (SAFZ) and the subtropical frontal zone (STFZ) of the North Pacific Ocean. The SAFZ in the model contains deep (greater than 500 m in some places) regions with seasonally varying high gradients in temperature and salinity. The gradients generally weaken toward the east. The STFZ consists of a relatively shallow (less than 200 m in most places) region of high gradient in temperature that disappears in the summer/fall. The high gradient in salinity in the STFZ maintains its strength year round and extends across almost the entire basin. The model simulates the location and intensity of the frontal zones in good agreement with climatological observations: generally to within two degrees of latitude and usually at the same or slightly stronger intensity. The seasonal cycle of the frontal zones also marches observations well, although the subarctic front is stronger than observed in winter and spring. The model balances are examined to identify the dominant frontogenetic processes. The seasonal cycle of temperature frontogenesis in the surface level of the model is governed by both the convergence of the wind-driven Ekman transport and differential heating/cooling. In the STFZ, the surface Ekman convergence is frontogenetic throughout the year as opposed to surface heating, which is frontogenetic during winter and strongly frontolytic during late spring and summer. The subarctic front at 40 degrees N in the central Pacific (not the maximum wintertime gradient in the model, but its location in summer and the location where variability is in best agreement with the observations) undergoes frontogenesis during spring and summer due to surface Ekman convergence and differential horizontal shear. The frontolysis during winter is due to the joint influence of differential heat flux and vertical convection in opposition to frontogenetic Ekman convergence. The seasonal cycle of salinity frontogenesis in the surface level is governed by Ekman convergence, differential surface freshwater flux, and differential vertical convection (mixing). For salinity, the differential convection is primarily forced by Ekman convergence and differential cooling, thereby linking the salinity and temperature frontogenesis/frontolysis. Below the surface level, the seasonal frontogenesis/frontolysis is only significant in the western and central SAFZ where ii is due primarily to differential mixing (mostly in winter and early spring) with contributions from convergence and shearing advection during fall and winter. The shearing advection in the model western SAFZ is likely a result of the Kuroshio overshooting its observed separation latitude. The model's vertical mixing through convective adjustment is found to be very important in controlling much of the frontogenesis/frontolysis. Thus, the seasonal cycle of the surface frontal variability depends strongly on the subsurface structure. C1 Hughes STX, Lanham, MD USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RP Dinniman, MS (reprint author), Old Dominion Univ, Ctr Coastal Phys Oceanog, Crittenton Hall, Norfolk, VA 23529 USA. OI Dinniman, Michael/0000-0001-7519-9278 NR 32 TC 12 Z9 12 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD APR PY 1999 VL 29 IS 4 BP 537 EP 559 DI 10.1175/1520-0485(1999)029<0537:FITNPO>2.0.CO;2 PG 23 WC Oceanography SC Oceanography GA 187VZ UT WOS:000079809900001 ER PT J AU Wang, J Kondrashov, D Liewer, PC Karmesin, SR AF Wang, J Kondrashov, D Liewer, PC Karmesin, SR TI Three-dimensional deformable-grid electromagnetic particle-in-cell for parallel computers SO JOURNAL OF PLASMA PHYSICS LA English DT Article AB We describe a new parallel, non-orthogonal-grid, three-dimensional electromagnetic particle-in-cell (EMPIC) code based on a finite-volume formulation. This code uses a logically Cartesian grid of deformable hexahedral cells, a discrete surface integral (DSI) algorithm to calculate the electromagnetic field, and a hybrid logical-physical space algorithm to push particles. We investigate the numerical instability of the DSI algorithm for non-orthogonal grids, analyse the accuracy for EMPIC simulations on non-orthogonal grids, and present performance benchmarks of this code on a pal allel supercomputer. While the hybrid particle push algorithm has a second-order accuracy in space, the accuracy of the DSI field solve algorithm is between first and second order for non-orthogonal grids. The parallel implementation of this code, which is almost identical to that of a Cartesian-grid EMPIC code using domain decomposition, achieved a high parallel efficiency of over 96% for large-scale simulations. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87544 USA. RP Wang, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kondrashov, Dmitri/E-2067-2016 OI Kondrashov, Dmitri/0000-0002-3471-7275 NR 12 TC 12 Z9 12 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-3778 J9 J PLASMA PHYS JI J. Plasma Phys. PD APR PY 1999 VL 61 BP 367 EP 389 DI 10.1017/S0022377899007552 PN 3 PG 23 WC Physics, Fluids & Plasmas SC Physics GA 226JB UT WOS:000082015900001 ER PT J AU Zuckerwar, AJ AF Zuckerwar, AJ TI Phenomenological theory of the translational relaxation times in gases SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article AB The exact solution to the classical equations governing the translational dispersion and absorption of sound in a gas obscures its relaxational character because of its mathematical complexity. The approach taken here is to solve the secular equation by the method of Pade approximants, which even to the relatively low order R-11 yields a remarkably close approximation to the exact solution over a wide range of frequency/pressure (f/P) ratios. As a result, translational relaxation can be formulated in terms of a conventional relaxation process with well-defined relaxation times, relaxation strength, collision numbers, additivity relations, etc. To extend the theory to high values of f/P ratio, a model is proposed to account for the noncontinuum behavior of the transport coefficients (viscosity and thermal conductivity) as the molecular mean free path approaches the acoustical enclosure dimensions. The theoretical dispersion and absorption show good agreement with measurements in argon over the classical and transition regions of f/P, but a discrepancy appears at higher values of f/P, where collective propagating modes, assumed in the theory, give way to single-particle modes, prevailing in the experiments. [S0001-4966(99)01704-X]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Zuckerwar, AJ (reprint author), NASA, Langley Res Ctr, Mail Stop 236, Hampton, VA 23681 USA. NR 21 TC 4 Z9 4 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD APR PY 1999 VL 105 IS 4 BP 2210 EP 2215 DI 10.1121/1.426825 PG 6 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 188FW UT WOS:000079837000014 ER PT J AU Clark, RL Gibbs, GP AF Clark, RL Gibbs, GP TI Analysis, testing, and control of a reverberant sound field within the fuselage of a business jet SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID FEEDBACK-CONTROL AB The objective of this project was to develop a speaker-based active control system capable of dissipating reverberant acoustic energy within the fuselage of a typical business jet aircraft. A ground-based fuselage was utilized as the test-bed for the work conducted in this project. Typical aircraft fuselage trim was installed to more accurately reflect the acoustic properties of a flight-ready aircraft, Speaker locations were selected based upon the acoustic modal characteristics of the fuselage and practical considerations concerning available space in the walls of the trim. Preliminary control experiments involving single-input, single-output, feedback loops resulted in a very localized zone of quiet which yielded no global effects. Multi-input, multi-output feedback control with a distributed array of eight pairs of transducers weighted (spatially) to emphasize energy dissipation of select acoustic modes resulted in as much as 6 dB of global attenuation at acoustic resonances corresponding to the second and third acoustic modes (46 and 71 Hz, respectively) of the enclosure. While objective results were very promising, subjective evaluation of the enclosure resulted in an inaudible difference in the sound field before and after closing the loop on the control system. (C) 1999 Acoustical Society of America. [S0001-4966(99)00104-6]. C1 Duke Univ, Dept Mech Engn & Mat Sci, Durham, NC 27708 USA. NASA, Struct Acoust Branch, Langley Res Ctr, Hampton, VA 23681 USA. RP Clark, RL (reprint author), Duke Univ, Dept Mech Engn & Mat Sci, Durham, NC 27708 USA. NR 13 TC 8 Z9 8 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD APR PY 1999 VL 105 IS 4 BP 2277 EP 2286 DI 10.1121/1.426834 PG 10 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 188FW UT WOS:000079837000023 ER PT J AU Caradonna, F AF Caradonna, F TI Performance measurement and wake characteristics of a model rotor in axial flight SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT AHS Technical Specialists Meeting for Rotorcraft Acoustics and Aerodynamics CY OCT 28-30, 1997 CL WILLIAMSBURG, VIRGINIA SP Amer Helicoptor Soc ID TIP VORTEX AB This paper studies the concept of extracting hover performance from model rotor climb data by extrapolating to the limit of zero climb speed, A 2-bladed rotor was mounted horizontally and tested in the 30' x 31' settling chamber of the Ames 7' x 10' #1 wind tunnel. The collective pitch and tunnel speed were varied. Video cameras were used to visualize the flowfield illuminated by pulsed white light sheets. Facility recirculation effects were eliminated at all but the lowest rates of climb. With a steady, non-recirculatory flow, the rotor wake was seen to be fully periodic, with little diffusion of the vortices for several rotor cycles. The variation of the computed figure of merit,vith climb rate compared very well with the experiments and it is shown that extrapolation is a good method to get an accurate value for the hover figure of merit The transition to the far wake was seen to occur through a periodic pairing of the tip vortices, Followed by their merging into a single diffuse vortex for each rotor cycle, The number of discrete vortex turns in the near wake before the pairing varied with the thrust coefficient and rate of climb. The climb-extrapolation method appears to be a reliable and practical approach to obtaining performance data which are free of facility recirculation effects. C1 USA, Aeroflightdynam Directorate, Ames Res Ctr, Washington, DC 20310 USA. Georgia Inst Technol, Sch Aerosp Engn, Atlanta, GA 30332 USA. RP Caradonna, F (reprint author), USA, Aeroflightdynam Directorate, Ames Res Ctr, Washington, DC 20310 USA. OI Gregory, James/0000-0002-8589-8758 NR 16 TC 13 Z9 16 U1 0 U2 0 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD APR PY 1999 VL 44 IS 2 BP 101 EP 108 PG 8 WC Engineering, Aerospace SC Engineering GA 193NK UT WOS:000080142700003 ER PT J AU Strawn, RC Duque, EPN Ahmad, J AF Strawn, RC Duque, EPN Ahmad, J TI Rotorcraft aeroacoustics computations with overset-grid CFD methods SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT American-Helicopter-Society 54th Annual Forum CY MAY 22-24, 1998 CL WASHINGTON, D.C. SP Amer Helicopter Soc ID HELICOPTER NOISE; FORMULATION; PREDICTION AB This paper describes a new method for computing the flowfield and acoustic signature of arbitrary rotors in forward flight. The overall scheme solves the Navier-Stokes equations on a system of overset grids. These grids allow for prescribed cyclic and napping blade motions and capture the interactions between the rotor blades and wake, The far-field noise is computed with an acoustic integral over a surface that completely encloses the rotor blades. Interpolations onto this acoustic surface use the same overset-grid techniques that are used for the flowfield solution. As a demonstration of the overall prediction scheme, computed and experimental far-field noise results are compared in cases with high-speed impulsive (HSI) and blade-vortex interaction (BVI) noise. Computed HSI noise shows excellent agreement with experimental data in the plane of the rotor, Out-of-plane HSI and BVI predictions require improved grid resolution in the rotor wake to capture the details of the high-frequency loading noise. C1 USA, Aviat & Missile Command, Ames Res Ctr,AVRDEC, Army NASA Rotocraft Div,Aeroflightdynam Directora, Moffett Field, CA USA. NASA, Ames Res Ctr, MCAT Inc, Moffett Field, CA 94035 USA. RP Strawn, RC (reprint author), USA, Aviat & Missile Command, Ames Res Ctr,AVRDEC, Army NASA Rotocraft Div,Aeroflightdynam Directora, Moffett Field, CA USA. NR 20 TC 11 Z9 11 U1 0 U2 2 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 APR PY 1999 VL 44 IS 2 BP 132 EP 140 PG 9 WC Engineering, Aerospace SC Engineering GA 193NK UT WOS:000080142700006 ER PT J AU Tadghighi, H Rajagopalan, RG Burley, CL AF Tadghighi, H Rajagopalan, RG Burley, CL TI Simulation of tiltrotor fountain flow field effects using a finite volume technique - An aero-acoustic study SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article AB This paper presents the results from an aero-acoustics analysis for a tiltrotor obtained by coupling an efficient Navier-Stokes solver, ROTTILT, with the acoustic code WOPWOP, The flow solver is finite volume based and solves the three dimensional, steady, laminar, incompressible equations in Cartesian coordinates. The acoustic code WOPWOP is an implementation of Farassat's linearized formulation IA, Predicted and measured fountain velocities are presented for a 15 percent V-22 semi-span model. Predicted and measured aerodynamic performance and noise results are presented are for an XV-15 tiltrotor vehicle in hover, A semi-span configuration which includes the fuselage, wing, and nacelle is used to model a full vehicle. The trimmed solution includes the combined effect of the rotor and body. Thus the computation of rotor blade airloads are determined for a given thrust, which includes this combined effect. The computed high resolution airloads are used as the input to the noise prediction program WOPWOP. The accuracy of the computed airloads, flow and noise are evaluated by comparing with measured acoustic flight data. The predicted results show fair but promising correlation with the available data. C1 Boeing Co, Mesa, AZ 85205 USA. Iowa State Univ, Dept Aerosp Engn, Computat Fluid Dynam Ctr, Ames, IA 50011 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Tadghighi, H (reprint author), Boeing Co, Mesa, AZ 85205 USA. NR 9 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 APR PY 1999 VL 44 IS 2 BP 150 EP 153 PG 4 WC Engineering, Aerospace SC Engineering GA 193NK UT WOS:000080142700008 ER PT J AU Nance, RP Hollis, BR Horvath, TJ Alter, SJ Hassan, HA AF Nance, RP Hollis, BR Horvath, TJ Alter, SJ Hassan, HA TI Computational study of hypersonic transitional wake flow SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID DIFFERENCE AB A study of transition and turbulence in hypersonic blunt-body wake flows is presented. The current approach combines the k-zeta turbulence closure model with a newly developed transition prediction method, This method utilizes results from linear stability theory and treats transitional flows in a turbulence-like manner. As a result, the onset and extent of transition are determined as part of the solution. The model is used to study flows past two spherically blunted 70-deg cone geometries at Mach 6 and 10. Two mechanisms of instability are examined. Comparison between computation and experiment suggests that for the cases considered, transition is a result of the instability of the free shear layer emanating from the shoulder region. C1 N Carolina State Univ, Dept Mech & Aerosp Engn, Raleigh, NC 27695 USA. NASA, Langley Res Ctr, Aerothermodynam Branch, Aerodynam & Gas Dynam Div, Hampton, VA 23681 USA. Lockheed Engn & Sci Co, Hampton, VA 23681 USA. RP N Carolina State Univ, Dept Mech & Aerosp Engn, Raleigh, NC 27695 USA. NR 19 TC 5 Z9 5 U1 0 U2 2 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0887-8722 EI 1533-6808 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD APR-JUN PY 1999 VL 13 IS 2 BP 236 EP 242 DI 10.2514/2.6441 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 188QK UT WOS:000079859500009 ER PT J AU May, RD AF May, RD TI The facts of the matter SO LASER FOCUS WORLD LA English DT Letter C1 Jet Prop Lab, Pasadena, CA 91109 USA. RP May, RD (reprint author), Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PENNWELL PUBL CO PI NASHUA PA 98 SPIT BROOK RD, NASHUA, NH 03062-2801 USA SN 0740-2511 J9 LASER FOCUS WORLD JI Laser Focus World PD APR PY 1999 VL 35 IS 4 BP 67 EP 67 PG 1 WC Optics SC Optics GA 184FT UT WOS:000079600500028 ER PT J AU Wolpert, DH Macready, WG AF Wolpert, DH Macready, WG TI An efficient method to estimate bagging's generalization error SO MACHINE LEARNING LA English DT Article DE bagging; cross-validation; stacking; generalization error; bootstrap AB Bagging (Breiman, 1994a) is a technique that tries to improve a learning algorithm's performance by using bootstrap replicates of the training set (Efron & Tibshirani, 1993, Efron, 1979). The computational requirements for estimating the resultant generalization error on a test set by means of cross-validation are often prohibitive, for leave-one-out cross-validation one needs to train the underlying algorithm on the order of my times, where m is the size of the training set and v is the number of replicates. This paper presents several techniques for estimating the generalization error of a bagged learning algorithm without invoking yet more training of the underlying learning algorithm (beyond that of the bagging itself), as is required by cross-validation-based estimation. These techniques all exploit the bias-variance decomposition (Geman, Bienenstock & Doursat, 1992, Wolpert, 1996). The best of our estimators also exploits stacking (Wolpert, 1992). In a set of experiments reported here, it was found to be more accurate than both the alternative cross-validation-based estimator of the bagged algorithm's error and the cross-validation-based estimator of the underlying algorithm's error. This improvement was particularly pronounced for small test sets. This suggests a novel justification for using bagging- more accurate estimation of the generalization error than is possible without bagging. C1 NASA, Ames Res Ctr, Caelum Res, Moffett Field, CA 94035 USA. Bios Grp, LP, Santa Fe, NM 87501 USA. RP Wolpert, DH (reprint author), NASA, Ames Res Ctr, Caelum Res, MS 269-1, Moffett Field, CA 94035 USA. EM dhw@ptolemy.arc.nasa.gov; wgm@biosgroup.com NR 11 TC 33 Z9 37 U1 3 U2 3 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0885-6125 J9 MACH LEARN JI Mach. Learn. PD APR PY 1999 VL 35 IS 1 BP 41 EP 55 DI 10.1023/A:1007519102914 PG 15 WC Computer Science, Artificial Intelligence SC Computer Science GA 188HV UT WOS:000079841500003 ER PT J AU Brill, RW Block, BA Boggs, CH Bigelow, KA Freund, EV Marcinek, DJ AF Brill, RW Block, BA Boggs, CH Bigelow, KA Freund, EV Marcinek, DJ TI Horizontal movements and depth distribution of large adult yellowfin tuna (Thunnus albacares) near the Hawaiian Islands, recorded using ultrasonic telemetry: implications for the physiological ecology of pelagic fishes SO MARINE BIOLOGY LA English DT Article ID KATSUWONUS-PELAMIS; BLUE MARLIN; SKIPJACK TUNA; CARDIOVASCULAR-RESPONSES; AGGREGATION DEVICES; VERTICAL MOVEMENTS; MAKAIRA-NIGRICANS; OXYGEN-TRANSPORT; FEEDING-HABITS; ACUTE-HYPOXIA AB We measured the horizontal and vertical movements of five adult yellowfin tuna (Thunnus albacares, estimated body mass 64 to 93 kg) near the main Hawaiian Islands, while simultaneously gathering data on oceanographic conditions and currents. Fish movements were recorded by means of ultrasonic depth-sensitive transmitters. Depth-temperature and depth-oxygen profiles were measured with vertical conductivity-temperature-depth (CTD) casts, and the current-velocity field was surveyed using an acoustic Doppler current profiler (ADCP). Large adult yellowfin tuna spent similar or equal to 60 to 80% of their time in or immediately below the relatively uniform-temperature surface-layer (i.e. above 100 m), a behavior pattern similar to that previously reported for juvenile yellowfin tuna, blue marlin (Makaira nigricans), and striped marlin (Tetrapturus audax) tracked in the same area. In all three species. maximum swimming depths appear to be limited by water temperatures 8 C degrees colder than the surface-layer water temperature. Therefore, neither large body mass, nor the ability to maintain elevated swimming-muscle temperatures due to the presence of vascular countercurrent heat exchangers in tunas, appears to permit greater vertical mobility or the ability to remain for extended periods below the thermocline. In those areas where the decrease in oxygen with depth is not limiting, the vertical movements of yellowfin tuna, blue marlin and striped merlin all appear to be restricted by the effects of water temperature on cardiac muscle function. Like juvenile yellowfin tuna, but unlike blue marlin and striped marlin, adult yellowfin tuna remained within 18.5 km of the coast and became associated with floating objects, including anchored fish-aggregating devices (FADs) and the tracking vessel. Like juvenile yellowfin tuna, large adult yellowfin repeatedly re-visit the same FAD, and appear able to navigate precisely between FADs that are up to 18 km apart. The median speed over ground ranged from 72 to 154 cm s(-1). Neither speed nor direction was strongly influenced by currents. C1 NOAA, Natl Marine Fisheries Serv, Honolulu, HI 96822 USA. Univ Hawaii Manoa, Sch Earth Sci & Technol, Joint Inst Marine & Atmospher Res, Pelag Fisheries Res Program, Honolulu, HI 96822 USA. Stanford Univ, Hopkins Marine Stn, Tuna Res & Conservat Ctr, Pacific Grove, CA 93950 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Brill, RW (reprint author), NOAA, Natl Marine Fisheries Serv, 2570 Dole St, Honolulu, HI 96822 USA. OI Marcinek, David/0000-0001-5187-2149 NR 66 TC 146 Z9 165 U1 1 U2 25 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0025-3162 J9 MAR BIOL JI Mar. Biol. PD APR PY 1999 VL 133 IS 3 BP 395 EP 408 DI 10.1007/s002270050478 PG 14 WC Marine & Freshwater Biology SC Marine & Freshwater Biology GA 189DJ UT WOS:000079888600002 ER PT J AU Yan, CH Whalen, RT Beaupre, GS Yen, SY Napel, S AF Yan, CH Whalen, RT Beaupre, GS Yen, SY Napel, S TI Modeling of polychromatic attenuation using computed tomography reconstructed images SO MEDICAL PHYSICS LA English DT Article DE CT imaging; beam hardening; x-ray spectrum profile; spectrum estimation ID X-RAY-SPECTRA AB This paper presents a procedure for estimating an accurate model of the CT imaging process including spectral effects. As raw projection data are typically unavailable to the end-user, we adopt a post-processing approach that utilizes the reconstructed images themselves. This approach includes errors from x-ray scatter and the nonidealities of the built-in soft tissue correction into the beam characteristics, which is crucial to beam hardening correction algorithms that are designed to be applied directly to CT reconstructed images. We formulate this approach as a quadratic programming problem and propose two different methods, dimension reduction and regularization, to overcome ill conditioning in the model. For the regularization method we use a statistical procedure, Cross Validation, to select the regularization parameter. We have constructed step-wedge phantoms to estimate the effective beam spectrum of a GE CT-I scanner. Using the derived spectrum, we computed the attenuation ratios for the wedge phantoms and found that the worst case modeling error is less than 3% of the corresponding attenuation ratio. We have also built two test (hybrid) phantoms to evaluate the effective spectrum. Based on these test phantoms, we have shown that the effective beam spectrum provides an accurate model for the CT imaging process. Last, we used a simple beam hardening correction experiment to demonstrate the effectiveness of the estimated beam profile for removing beam hardening artifacts. We hope that this estimation procedure will encourage more independent research on beam hardening corrections and will lead to the development of application-specific beam hardening correction algorithms. (C) 1999 American Association of Physicists in Medicine. [S0094-2405 (99)00704-X]. C1 Stanford Univ, Dept Elect Engn, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Div Life Sci, Mt View, CA 94039 USA. VA, Rehabil R&D Ctr, Palo Alto, CA 94309 USA. Stanford Univ, Dept Radiol, Stanford, CA 94305 USA. RP Yan, CH (reprint author), Stanford Univ, Dept Elect Engn, Stanford, CA 94305 USA. OI Beaupre, Gary/0000-0002-6211-7621 FU NCRR NIH HHS [P41 RR09784] NR 18 TC 13 Z9 15 U1 1 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0094-2405 J9 MED PHYS JI Med. Phys. PD APR PY 1999 VL 26 IS 4 BP 631 EP 642 DI 10.1118/1.598563 PG 12 WC Radiology, Nuclear Medicine & Medical Imaging SC Radiology, Nuclear Medicine & Medical Imaging GA 187CW UT WOS:000079769500019 PM 10227366 ER PT J AU Misra, A Gibala, R Noebe, RD AF Misra, A Gibala, R Noebe, RD TI Deformation and fracture behavior of a directionally solidified beta/gamma ' Ni-30 at. pct Al alloy SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID THERMOELASTIC MARTENSITIC-TRANSFORMATION; MECHANICAL-PROPERTIES; TWEED MICROSTRUCTURES; ELECTRON-MICROSCOPY; STRUCTURAL LEDGES; SINGLE-CRYSTALS; BOUNDARIES; PHASE; DISLOCATION; DUCTILITY AB The effect of a ductile gamma'-Ni3Al phase on the room-temperature ductility, temperature-dependent yield strength, and creep resistance of beta-NiAl was investigated. Room-temperature tensile ductility of up to 9 pet was observed in directionally solidified beta/gamma' Ni-30 at, pet Al alloys, whereas the ductility of directionally solidified (DS), single-phase [001] beta-NiAl was negligible. The enhancement in ductility was attributed to a combination of slip transfer from the ductile gamma' to the brittle beta phase and extrinsic toughening mechanisms such as crack blunting, deflection, and bridging. As in single phase Ni3Al, the temperature-dependent yield strength of these two-phase alloys increased with temperature with a peak at approximately 850 K. The creep strength of the beta/gamma' alloys in the temperature range 1000 to 1200 K was found to be comparable to that of monolithic beta-NiAl. A creep strengthening phase needs to be incorporated in the beta/gamma' microstructure to enhance the elevated temperature mechanical properties. C1 Univ Michigan, Dept Mat Sci & Engn, Ann Arbor, MI 48109 USA. Univ Michigan, Dept Mat Sci & Engn, Ann Arbor, MI 48109 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Misra, A (reprint author), Univ Calif Los Alamos Natl Lab, Div Mat Sci & Technol, POB 1663, Los Alamos, NM 87545 USA. RI Misra, Amit/H-1087-2012 NR 58 TC 19 Z9 20 U1 0 U2 4 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD APR PY 1999 VL 30 IS 4 BP 1003 EP 1015 DI 10.1007/s11661-999-0153-2 PG 13 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 180XK UT WOS:000079411000011 ER PT J AU Kulkarni, SR Djorgovski, SG Odewahn, SC Bloom, JS Gal, RR Koresko, CD Harrison, FA Lubin, LM Armus, L Sari, R Illingworth, GD Kelson, DD Magee, DK van Dokkum, PG Frail, DA Mulchaey, JS Malkan, MA McClean, IS Teplitz, HI Koerner, D Kirkpatrick, D Kobayashi, N Yadigaroglu, IA Halpern, J Piran, T Goodrich, RW Chaffee, FH Feroci, M Costa, E AF Kulkarni, SR Djorgovski, SG Odewahn, SC Bloom, JS Gal, RR Koresko, CD Harrison, FA Lubin, LM Armus, L Sari, R Illingworth, GD Kelson, DD Magee, DK van Dokkum, PG Frail, DA Mulchaey, JS Malkan, MA McClean, IS Teplitz, HI Koerner, D Kirkpatrick, D Kobayashi, N Yadigaroglu, IA Halpern, J Piran, T Goodrich, RW Chaffee, FH Feroci, M Costa, E TI The afterglow, redshift and extreme energetics of the gamma-ray burst of 23 January 1999 SO NATURE LA English DT Article ID 28 FEBRUARY 1997; STANDARD STARS; FIREBALL MODEL; JETS AB Long-lived emission, known as afterglow, has now been detected from about a dozen gamma-ray bursts. Distance determinations place the bursts at cosmological distances, with redshifts,z, ranging from similar to 1 to 3, The energy required to produce these bright gamma-ray flashes is enormous: up to similar to 10(53) erg, or to per cent of the rest-mass energy of a neutron star, if the emission is isotropic. Here we present optical and near-infrared observations of the afterglow of GRB990123, and we determine a redshift of z greater than or equal to 1.6, This is to date the brightest gamma-ray burst with a well-localized position and if the gamma-rays were emitted isotropically, the energy release exceeds the rest-mass energy of a neutron st ar, so challenging current theoretical models of the sources. We argue, however, that our data may provide evidence of beamed (rather than isotropic) radiation, thereby reducing the total energy released to a lever where stellar-death models are still tenable. C1 CALTECH, Palomar Observ 105 24, Pasadena, CA 91125 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Natl Radio Astron Observ, Socorro, NM 87801 USA. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Penn, Philadelphia, PA 19104 USA. Natl Astron Observ Japan, Subaru Telescope, Hilo, HI 96720 USA. Columbia Univ, Dept Astron, New York, NY 10027 USA. WM Keck Observ, Kamuela, HI 96743 USA. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. RP Kulkarni, SR (reprint author), CALTECH, Palomar Observ 105 24, Pasadena, CA 91125 USA. EM srk@astro.caltech.edu OI Costa, Enrico/0000-0003-4925-8523; Feroci, Marco/0000-0002-7617-3421 NR 61 TC 400 Z9 409 U1 0 U2 4 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 1 PY 1999 VL 398 IS 6726 BP 389 EP 394 DI 10.1038/18821 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 182PW UT WOS:000079508200042 ER PT J AU Galama, TJ Briggs, MS Wijers, RAMJ Vreeswijk, PM Rol, E Band, D van Paradijs, J Kouveliotou, C Preece, RD Bremer, M Smith, IA Tilanus, RPJ de Bruyn, AG Strom, RG Pooley, G Castro-Tirado, AJ Tanvir, N Robinson, C Hurley, K Heise, J Telting, J Rutten, RGM Packham, C Swaters, R Davies, JK Fassia, A Green, SF Foster, MJ Sagar, R Pandey, AK Nilakshi Yadav, RKS Ofek, EO Leibowitz, E Ibbetson, P Rhoads, J Falco, E Petry, C Impey, C Geballe, TR Bhattacharya, D AF Galama, TJ Briggs, MS Wijers, RAMJ Vreeswijk, PM Rol, E Band, D van Paradijs, J Kouveliotou, C Preece, RD Bremer, M Smith, IA Tilanus, RPJ de Bruyn, AG Strom, RG Pooley, G Castro-Tirado, AJ Tanvir, N Robinson, C Hurley, K Heise, J Telting, J Rutten, RGM Packham, C Swaters, R Davies, JK Fassia, A Green, SF Foster, MJ Sagar, R Pandey, AK Nilakshi Yadav, RKS Ofek, EO Leibowitz, E Ibbetson, P Rhoads, J Falco, E Petry, C Impey, C Geballe, TR Bhattacharya, D TI The effect of magnetic fields on gamma-ray bursts inferred from multi-wavelength observations of the burst of 23 January 1999 SO NATURE LA English DT Article ID BATSE OBSERVATIONS; RADIO TELESCOPE; PHOTOMETRY; AFTERGLOW; SPECTRA AB Gamma-ray bursts (GRBs) are thought to arise when an extremely relativistic outflow of particles from a massive explosion (the nature of which is still unclear) Interacts with material surrounding the site of the explosion. observations of the evolving changes in emission at many wavelengths allow us to Investigate the origin of the photons, and so potentially determine the nature of the explosion. Here we report the results of gamma-ray, optical, Infrared, submillimetre, millimetre and radio observations of the burst GRB990123 and Its afterglow. Our Interpretation of the data Indicates that the initial and afterglow emissions are associated with three distinct regions In the fireball. The peak flux of the afterglow, one day after the burst, has a lower frequency than observed for other bursts; this explains tbe short-lived radio emission. We suggest that the differences between bursts reflect variations In the magnetic-field strength in the afterglow-emitting regions. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Univ Calif San Diego, CASS, La Jolla, CA 92093 USA. NASA, MSFC, Huntsville, AL 35812 USA. Univ Space Res Assoc, Huntsville, AL 35812 USA. Inst Radio Astron Millimetr, F-38406 St Martin Dheres, France. Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. Joint Astron Ctr, Hilo, HI 96720 USA. Netherlands Fdn Res Astron, NL-7990 AA Dwingeloo, Netherlands. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Univ Cambridge, Cavendish Lab, Mullard Radio Astron Observ, Cambridge CB3 0HE, England. Lab Astrofis Espacial & Fis Fundamental, INTA, E-28080 Madrid, Spain. CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Univ Hertfordshire, Dept Phys Sci, Hatfield AL10 9AB, Herts, England. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Natl Sci Fdn, Berkeley, CA 94720 USA. SRON, Space Res Lab, NL-3584 CA Utrecht, Netherlands. Isaac Newton Grp, E-38780 Santa Cruz De La Palma, Islas Canarias, Spain. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, Astrophys Grp, London SW7 2BZ, England. Univ Kent, Phys Lab, Sch Phys Sci, Unit Space Sci & Astrophys, Canterbury CT2 7NR, Kent, England. Uttar Pradesh State Observ, Naini Tal 263129, India. Tel Aviv Univ, Wise Observ, IL-69978 Tel Aviv, Israel. Kitt Peak Natl Observ, Tucson, AZ 85726 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Arizona, Steward Observ, Tucson, AZ 85719 USA. Univ Hawaii, Gemini Observ, Hilo, HI 96720 USA. Raman Res Inst, Bangalore 560080, Karnataka, India. RP Galama, TJ (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. EM titus@astro.uva.nl RI Green, Simon/C-7408-2009; Galama, Titus/D-1429-2014; Bhattacharya, Dipankar/J-6927-2015; OI Galama, Titus/0000-0002-1036-396X; Bhattacharya, Dipankar/0000-0003-3352-3142; Castro-Tirado, A. J./0000-0003-2999-3563 NR 49 TC 139 Z9 141 U1 0 U2 4 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 1 PY 1999 VL 398 IS 6726 BP 394 EP 399 DI 10.1038/18828 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 182PW UT WOS:000079508200043 ER PT J AU Akerlof, C Balsano, R Barthelmy, S Bloch, J Butterworth, P Casperson, D Cline, T Fletcher, S Frontera, F Gisler, G Heise, J Hills, J Kehoe, R Lee, B Marshall, S McKay, T Miller, R Piro, L Priedhorsky, W Szymanski, J Wren, J AF Akerlof, C Balsano, R Barthelmy, S Bloch, J Butterworth, P Casperson, D Cline, T Fletcher, S Frontera, F Gisler, G Heise, J Hills, J Kehoe, R Lee, B Marshall, S McKay, T Miller, R Piro, L Priedhorsky, W Szymanski, J Wren, J TI Observation of contemporaneous optical radiation from a gamma-ray burst SO NATURE LA English DT Article ID AFTERGLOW AB The origin of gamma-ray bursts (GRBs) has been enigmatic since their discovery(1). The situation improved dramatically in 1997, when the rapid availability of precise coordinates(2,3) for the bursts allowed the detection of faint optical and radio afterglows-optical spectra thus obtained have demonstrated conclusively that the bursts occur at cosmological distances. But, despite efforts by several groups(4-7), optical detection has not hitherto been achieved during the brief duration of a burst. Here we report the detection of bright optical emission from GRB990123 while the burst was still in progress. Our observations begin 22 seconds after the onset of the burst and show an increase in brightness by a factor of 14 during the first 25 seconds; the brightness then declines by a factor of 100, at which point (700 seconds after the burst onset) it falls below our detection threshold. The redshift of this burst, z approximate to 1.6 (refs 8, 9), implies a peak optical luminosity of 5 x 10(49) erg s(-1) Optical emission from gamma-ray bursts has been generally thought to take place at the shock fronts generated by interaction of the primary energy source with the surrounding medium, where the gamma-rays might also be produced The lack of a significant change in the gamma-ray light curve when the optical emission develops suggests that the gamma-rays are not produced at the shock front, but closer to the site of the original explosion(10). C1 Univ Michigan, Ann Arbor, MI 48109 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Seabrook, MD 20706 USA. Raytheon Syst, Lanham, MD 20706 USA. Univ Ferrara, I-44100 Ferrara, Italy. Space Res Org, Utrecht, Netherlands. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Inst Astrofis Spaziale, Rome, Italy. RP Akerlof, C (reprint author), Univ Michigan, Ann Arbor, MI 48109 USA. RI Barthelmy, Scott/D-2943-2012; McKay, Timothy/C-1501-2009; PIRO, LUIGI/E-4954-2013; OI McKay, Timothy/0000-0001-9036-6150; PIRO, LUIGI/0000-0003-4159-3984; Priedhorsky, William/0000-0003-0295-9138 NR 33 TC 558 Z9 566 U1 0 U2 6 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 1 PY 1999 VL 398 IS 6726 BP 400 EP 402 DI 10.1038/18837 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 182PW UT WOS:000079508200044 ER PT J AU Hammond, TG Lewis, FC Goodwin, TJ Linnehan, RM Wolf, DA Hire, KP Campbell, WC Benes, E O'Reilly, KC Globus, RK Kaysen, JH AF Hammond, TG Lewis, FC Goodwin, TJ Linnehan, RM Wolf, DA Hire, KP Campbell, WC Benes, E O'Reilly, KC Globus, RK Kaysen, JH TI Gene expression in space SO NATURE MEDICINE LA English DT Letter C1 Tulane Univ, Med Ctr, Dept Med, Nephrol Sect, New Orleans, LA 70112 USA. Tulane Univ, Med Ctr, Dept Surg, New Orleans, LA USA. Tulane Environm Astrobiol Ctr, Ctr Bioenvironm Res, New Orleans, LA USA. VA Med Ctr, New Orleans, LA USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hammond, TG (reprint author), Tulane Univ, Med Ctr, Dept Med, Nephrol Sect, New Orleans, LA 70112 USA. NR 1 TC 90 Z9 93 U1 0 U2 10 PU NATURE AMERICA INC PI NEW YORK PA 345 PARK AVE SOUTH, NEW YORK, NY 10010-1707 USA SN 1078-8956 J9 NAT MED JI Nat. Med. PD APR PY 1999 VL 5 IS 4 BP 359 EP 359 DI 10.1038/7331 PG 1 WC Biochemistry & Molecular Biology; Cell Biology; Medicine, Research & Experimental SC Biochemistry & Molecular Biology; Cell Biology; Research & Experimental Medicine GA 183VG UT WOS:000079574300004 PM 10202906 ER PT J AU Kerwin, MW Overpeck, JT Webb, RS De Vernal, A Rind, DH Healy, RJ AF Kerwin, MW Overpeck, JT Webb, RS De Vernal, A Rind, DH Healy, RJ TI The role of oceanic forcing in mid-Holocene Northern Hemisphere climatic change SO PALEOCEANOGRAPHY LA English DT Article ID CANADIAN ARCTIC ARCHIPELAGO; 6 KA BP; POLLEN DATA; JULY TEMPERATURES; SEA-ICE; VEGETATION; AMERICA; SIMULATIONS; GREENLAND; MOLLUSKS AB Previous model investigations suggested that changes in orbital forcing and feedbacks associated with northward expansion of the boreal forest were both required to explain the full magnitude of enhanced high-latitude Northern Hemisphere summer warming at 6 ka, thus implying that biospheric feedbacks (decreased planetary albedo associated with forest expansion) may be large in the future [Foley ct at., 1994; TEMPO (Testing Earth System Models with Paleo-Observations), 1996]. Before the magnitude of past biospheric and other feedbacks can be estimated with confidence, however, the role of realistic high-latitude oceanic forcing (i.e., sea surface temperature (SST) increases and sea ice reductions) should also be considered. Here we review existing paleoceanographic observations that suggest portions of the North Atlantic were up to 4 degrees C warmer than today at 6 ka. We then combine our estimates of mid-Holocene North Atlantic SST and sea ice conditions with new climate model simulations to suggest that a significant portion of high-latitude summer warming at 6 ka in the Northern Hemisphere can be accounted for by altered orbital forcing, SSTs, and sea ice relative to today. Our results underscore the importance of incorporating realistic boundary conditions when using paleoenvironmental data to evaluate the climate system's sensitivity to altered forcing and suggest that high-latitude oceanic feedbacks were major contributors to enhanced high-latitude summer warming in the Northern Hemisphere at 6 ka. C1 Univ Colorado, Inst Arctic & Alpine Res, INSTAAR, Boulder, CO 80309 USA. Univ Colorado, Dept Geol Sci, Boulder, CO 80309 USA. Univ Quebec, Geotop, Res Ctr Isotope Geochem & Geochronol, Montreal, PQ H3C 3P8, Canada. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA. NOAA, Paleoclimatol Program, Boulder, CO USA. RP Univ Colorado, Inst Arctic & Alpine Res, INSTAAR, Boulder, CO 80309 USA. EM kerwin@colorado.edu; jto@ngdc.noaa.gov; rsw@luna.ngdc.noaa.gov; r21024@er.uqam.ca; drind@giss.nasa.gov; rhealy@whoi.edu RI de Vernal, Anne/D-5602-2013; Healy, Richard/J-9214-2015 OI de Vernal, Anne/0000-0001-5656-724X; Healy, Richard/0000-0002-5098-8921 NR 77 TC 51 Z9 53 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0883-8305 EI 1944-9186 J9 PALEOCEANOGRAPHY JI Paleoceanography PD APR PY 1999 VL 14 IS 2 BP 200 EP 210 DI 10.1029/1998PA900011 PG 11 WC Geosciences, Multidisciplinary; Oceanography; Paleontology SC Geology; Oceanography; Paleontology GA 179KD UT WOS:000079325100009 ER PT J AU Rietmeijer, FJM Nuth, JA Karner, JM AF Rietmeijer, FJM Nuth, JA Karner, JM TI Metastable eutectic, gas to solid, condensation in the FeO-Fe2O3-SiO2 system SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS LA English DT Article ID IRON AB Non-equilibrium gas to solid condensation produced three distinct groupings of ferrosilica solids with compositions similar to 15, 30 and 87.5 wt.% FeO (or, similar to 17, 33 and 97 wt.% Fe2O3). These solid compositions define metastable eutectic points in the FeO/Fe2O3-SiO2 binary system. The position of a silica-rich metastable eutectic is sensitive to the ratio FeO : Fe2O3 during gas-to-solid quenching. The Fe-rich metastable eutectic indicates a two-liquid held in this revised pseudo-binary equilibrium phase diagram. C1 Univ New Mexico, Dept Earth & Planetary Sci, Inst Meteorit, Albuquerque, NM 87131 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Rietmeijer, FJM (reprint author), Univ New Mexico, Dept Earth & Planetary Sci, Inst Meteorit, Albuquerque, NM 87131 USA. EM fransjmr@unm.edu; uljan@lepvax.gsfc.nasa.gov RI Nuth, Joseph/E-7085-2012 NR 27 TC 44 Z9 44 U1 0 U2 2 PU ROYAL SOC CHEMISTRY PI CAMBRIDGE PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND SN 1463-9076 J9 PHYS CHEM CHEM PHYS JI PCCP Phys. Chem. Chem. Phys. PD APR 1 PY 1999 VL 1 IS 7 BP 1511 EP 1516 DI 10.1039/a900053d PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 184EL UT WOS:000079597400015 ER PT J AU Liao, C Hagmann, S Bhalla, CP Grabbe, SR Cocke, CL Richard, P AF Liao, C Hagmann, S Bhalla, CP Grabbe, SR Cocke, CL Richard, P TI Differential electron-Cu5+ elastic scattering cross sections extracted from electron emission in ion-atom collisions SO PHYSICAL REVIEW A LA English DT Article ID CHARGE-STATE DEPENDENCE; HE TARGETS; IONIZATION; H2; SPECTROSCOPY; PROJECTILES; EXCITATION; 0-DEGREES; PEAK; H-2 AB We present a method of deriving energy and angle-dependent electron-ion elastic scattering cross sections from doubly differential cross sections for electron emission in ion-atom collisions. By analyzing the laboratory frame binary encounter electron production cross sections in energetic ion-atom collisions, we derive projectile frame differential cross sections for electrons elastically scattered from highly charged projectile ions in the ran,ae between 60 degrees and 180 degrees. The elastic scattering cross sections are observed to deviate strongly from the Rutherford cross sections for electron scattering from bare nuclei. They exhibit strong Ramsauer-Townsend electron diffraction in the angular distribution of elastically scattered electrons, providing evidence for the strong role of screening played in the collision. Experimental data are compared with partial-wave calculations using the Hartree-Fock model. [S1050-2947(99)03104-2]. C1 Kansas State Univ, JR Macdonald Lab, Manhattan, KS 66506 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liao, C (reprint author), Kansas State Univ, JR Macdonald Lab, Manhattan, KS 66506 USA. NR 21 TC 12 Z9 12 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD APR PY 1999 VL 59 IS 4 BP 2773 EP 2777 DI 10.1103/PhysRevA.59.2773 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 184JT UT WOS:000079609100039 ER PT J AU Rao, MVVS Van Brunt, RJ Olthoff, JK AF Rao, MVVS Van Brunt, RJ Olthoff, JK TI Kinetic-energy distributions of positive and negative ions in Townsend discharges in oxygen SO PHYSICAL REVIEW E LA English DT Article ID CHARGE-TRANSFER; REFERENCE CELL; DETACHMENT; COLLISIONS; ELECTRONS; MOLECULES; ARGON; O2 AB Translational flux-energy distributions of positive and negative ions have been measured at high electric field-to-gas density ratios (E/N) up to 40 x 10(-18) V m(2) (40 kTd) in diffuse, parallel-plate Townsend discharges in oxygen using an ion energy analyzer-mass spectrometer. The O-2(+) ion is the most abundant ion detected in the discharge, and exhibits Maxwellian energy distributions for E/N<20 x 10(18) V m(2), which is consistent with predictions based upon the assumption that resonant symmetric charge exchange is the dominant ion-molecule collision process. The less abundant ions O+, O-2(-), and O- exhibit non-Mawellian ion kinetic-energy distributions at nearly all E/N, indicative of multiple ion-molecule reactions affecting the ion transport. Mean energies are obtained for each ion as a function of E/N from an analysis of the energy distributions, and symmetric charge-exchange cross sections are calculated:from the data where appropriate. C1 Natl Inst Stand & Technol, Elect & Elect Engn Lab, Gaithersburg, MD 20899 USA. RP Rao, MVVS (reprint author), NASA, Ames Res Ctr, MS 229-1, Moffett Field, CA 94035 USA. NR 40 TC 5 Z9 5 U1 0 U2 2 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 APR PY 1999 VL 59 IS 4 BP 4565 EP 4572 DI 10.1103/PhysRevE.59.4565 PG 8 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA 188EV UT WOS:000079834600101 ER PT J AU Moser, RD Kim, J Mansour, NN AF Moser, RD Kim, J Mansour, NN TI Direct numerical simulation of turbulent channel flow up to Re-tau=590 SO PHYSICS OF FLUIDS LA English DT Article ID LOW-REYNOLDS-NUMBER; HEAT-TRANSFER AB Numerical simulations of fully developed turbulent channel flow at three Reynolds numbers up to Re-tau=590 are reported. It is noted that the higher Reynolds number simulations exhibit fewer low Reynolds number effects than previous simulations at Re-tau=180. A comprehensive set of statistics gathered from the simulations is available on the web at http://www.tam.uiuc.edu/Faculty/Moser/ channel. (C) 1999 American Institute of Physics. [S1070-6631(99)02204-7]. C1 Univ Illinois, Dept Theoret & Appl Mech, Urbana, IL 61801 USA. Univ Calif Los Angeles, Dept Mech & Aerosp Engn, Los Angeles, CA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Moser, RD (reprint author), Univ Illinois, Dept Theoret & Appl Mech, Urbana, IL 61801 USA. OI Kim, John/0000-0002-6369-9264 NR 16 TC 1105 Z9 1127 U1 12 U2 110 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD APR PY 1999 VL 11 IS 4 BP 943 EP 945 DI 10.1063/1.869966 PG 3 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 178YZ UT WOS:000079297900020 ER PT J AU Mensah, PF Stubblefield, MA Pang, SS Wingard, D AF Mensah, PF Stubblefield, MA Pang, SS Wingard, D TI Thermal analysis characterization of fiberglass epoxy prepreg used to join composite pipes SO POLYMER ENGINEERING AND SCIENCE LA English DT Article AB Thermal characterization of a fiberglass/epoxy prepreg fabric used as the bonding material to join composite-to-composite pipes by curing has been investigated. The prepreg material and composite pipes have temperature dependent thermal properties. Thus the resulting boundary value equations are nonlinear and analytical solutions cannot be easily obtained. Finite difference modeling (FDM) and numerical computational techniques were used to solve the one-dimensional heat conduction with chemical kinetics in the thermosetting material. Temperature distributions and degree of cure within the composite pipe joint are predicted. A Differential Scanning Calorimeter (DSC) in both isothermal and dynamic modes was used to characterize the curing kinetic properties of the prepreg. The result of this characterization is necessary for optimizing the curing process to produce a superior heat activated coupled joint. In addition, to assess the effects of induced thermal stress in the joint, the temperature profile is needed. The methodology employed in this analysis compares favorably with data from experimentation. C1 So Univ, Dept Engn Mech, Baton Rouge, LA 70813 USA. Louisiana State Univ, Dept Mech Engn, Baton Rouge, LA 70803 USA. NASA, George C Marshall Space Flight Ctr, Nonmetall Mat Branch EH32, Huntsville, AL 35812 USA. RP Mensah, PF (reprint author), So Univ, Dept Engn Mech, Baton Rouge, LA 70813 USA. NR 11 TC 8 Z9 8 U1 1 U2 2 PU SOC PLASTICS ENG INC PI BROOKFIELD PA 14 FAIRFIELD DR, BROOKFIELD, CT 06804-0403 USA SN 0032-3888 J9 POLYM ENG SCI JI Polym. Eng. Sci. PD APR PY 1999 VL 39 IS 4 BP 778 EP 788 DI 10.1002/pen.11466 PG 11 WC Engineering, Chemical; Polymer Science SC Engineering; Polymer Science GA 195JC UT WOS:000080246000017 ER PT J AU Skelton, BP Waller, WH Gelderman, RF Brown, LW Woodgate, BE Caulet, A Schommer, RA AF Skelton, BP Waller, WH Gelderman, RF Brown, LW Woodgate, BE Caulet, A Schommer, RA TI Emission-line properties of the large magellanic cloud bubble N70 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID SOUTHERN SPECTROPHOTOMETRIC STANDARDS; ORION-NEBULA; SUPERNOVA-REMNANTS; X-RAYS; SUPERBUBBLES; ASSOCIATIONS; ABUNDANCES; WFPC2; STARS AB We present a spectrophotometric imaging study of the emission bubble N70 (DEM 301) in the Large Magellanic Cloud: N70 is approximately 100 pc in size with a nearly circular shell-like morphology. The nebular emission is powered by an uncertain combination of EUV photons, intense winds, and supernova shock waves from the central population of high-mass stars (the OB association LH 114). We have obtained narrowband images (FWHM similar to 6 Angstrom) of N70 in the light of H alpha lambda 6563, [N II] lambda 6584, [S II] lambda lambda 6717, 6731, and [O III] lambda 5007, along with the corresponding red and green continua. The resulting line fluxes and flux ratios are used to derive ionization rates, nebular densities, volume filling fractions, and excitation indices. The photoionizing luminosity inferred from the embedded stellar population is more than adequate to account for the observed hydrogen ionization rate. We compare the emission-line photometry with that derived from similar imaging of the Orion Nebula and with data collected from the literature on other emission-line regions in the LMC. Compared with the Orion Nebula, N70 shows much higher [S II]/H alpha intensity ratios that increase smoothly with radius-from less than 0.3 near the center to greater than 1.0 toward the outer filamentary shell. The measured intensity ratios in N70 more closely match the range of excitation spanned by giant and supergiant H II shells and by some of the supernova remnants observed in the LMC. The contending ionization and excitation processes in the interior and outer shell of N70 are evaluated in terms of the available data. EUV photons probably contribute most of the inner nebula's ionization, whereas a combination of photoionization plus collisional ionization and excitation of sulfur atoms by low-velocity shocks seems to best fit the emission-line luminosities and intensity ratios observed in the outer shell. Considerations of the radiative and mechanical energetics that are involved may indicate the need for one or two supernova explosions having occurred during the last similar to Myr. C1 Univ Washington, Dept Astron, Seattle, WA 98195 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Raytheon STX Corp, Greenbelt, MD 20771 USA. Natl Res Council, Greenbelt, MD 20771 USA. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. Cerro Tololo Interamer Observ, Natl Opt Astron Observ, La Serena, Chile. RP Skelton, BP (reprint author), Univ Washington, Dept Astron, Seattle, WA 98195 USA. RI Woodgate, Bruce/D-2970-2012 NR 44 TC 11 Z9 11 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD APR PY 1999 VL 111 IS 758 BP 465 EP 481 DI 10.1086/316346 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 189XW UT WOS:000079932300004 ER PT J AU Livengood, TA Fast, KE Kostiuk, T Espenak, F Buhl, D Goldstein, JJ Hewagama, T Ro, KH AF Livengood, TA Fast, KE Kostiuk, T Espenak, F Buhl, D Goldstein, JJ Hewagama, T Ro, KH TI Refraction by Earth's atmosphere near 12 microns SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB We have measured chromatic differential refraction of astronomical images by the Earth's atmosphere, comparing visible light at 500-600 nn with infrared near 12 mu m, and found the index of refraction near 12 mu m to be greater than predicted by the dispersion relation in common use. The differential refraction between visible and 12 mu m thus is smaller than the extrapolated difference. At Mauna Kea, the empirical differential refraction at 45 degrees from zenith was measured at 0." 28 +/- 0." 28 (3 sigma) on one occasion, compared to an expected differential refraction of 0." 63-0." 69. Refractivity scales linearly with barometric pressure, and thus the inaccuracy is more severe at lower altitude observatories. The pointing error from inaccurate correction for differential refraction is comparable to the point Spread function width of an 8-10 m telescope in this wavelength range. Even on smaller telescopes, accurate correction for differential refraction is necessary to guide small-aperture spectrophotometry or to register mid-infrared imaging with visible-light structures. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Challenger Ctr Space Sci Educ, Alexandria, VA 22314 USA. Cornell Univ, Sch Elect Engn, Ithaca, NY 14850 USA. RP Livengood, TA (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Livengood, Timothy/C-8512-2012; Hewagama, T/C-8488-2012; Kostiuk, Theodor/A-3077-2014 NR 21 TC 15 Z9 15 U1 0 U2 4 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD APR PY 1999 VL 111 IS 758 BP 512 EP 521 DI 10.1086/316347 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 189XW UT WOS:000079932300009 ER PT J AU Blakely, EA Schimmerling, W AF Blakely, EA Schimmerling, W TI Tracy Chui-hsu Yang (1938-1998) - In memoriam SO RADIATION RESEARCH LA English DT Biographical-Item C1 Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. NASA Headquarters, Washington, DC 20546 USA. RP Blakely, EA (reprint author), Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD APR PY 1999 VL 151 IS 4 BP 501 EP 502 PG 2 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA 181MY UT WOS:000079446100017 ER PT J AU Tait, A Hall, D Foster, J Chang, A Klein, A AF Tait, A Hall, D Foster, J Chang, A Klein, A TI Detection of snow cover using millimeter-wave imaging radiometer (MIR) data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID CLOUD AB Millimeter-wave Imaging Radiometer (MIR) data, collected from a NASA ER-2 flight over the Great Lakes region and New England in February 1997, are used to identify snow cover. Data at 89 GHz, 150 GHz, and 220 GHz are compared with the Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover product. Additional data sets used in this analysis are the International Geosphere Biosphere Programme (IGBP) land cover classification and the MODIS cloud cover mask. Results show that for cloud-free scenes, the MIR data are well related to the snow and vegetation cover. Under cloudy conditions the MODIS snow mapping algorithm, which uses visible and near-infrared data, is unable to detect snow cover. However, the surface cover is still clearly discernible in the MIR images. It is suggested that high frequency microwave data may be used to supplement the MODIS, or other visible and near-infrared derived snow cover products, during cloudy conditions. The development of snow cover algorithms combining future Earth Observing System (EOS) microwave, visible, and infrared data are discussed. Published by Elsevier Science Inc. C1 NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Hydrol Sci Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Texas A&M Univ, Dept Geog, College Stn, TX 77843 USA. RP Tait, A (reprint author), NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Code 974, Greenbelt, MD 20771 USA. RI Hall, Dorothy/D-5562-2012 NR 19 TC 12 Z9 12 U1 1 U2 3 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD APR PY 1999 VL 68 IS 1 BP 53 EP 60 DI 10.1016/S0034-4257(98)00103-5 PG 8 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 178KG UT WOS:000079264400005 ER PT J AU Massom, RA Comiso, JC Worby, AP Lytle, VI Stock, L AF Massom, RA Comiso, JC Worby, AP Lytle, VI Stock, L TI Regional classes of sea ice cover in the East Antarctic pack observed from satellite and in situ data during a winter time period SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID WEDDELL SEA; SNOW COVER; INSITU OBSERVATIONS; MICROWAVE; SURFACE; SUMMER; SIGNATURES; ZONE AB Ice concentration data alone are often of limited use in many process, and modeling studies as different ice regimes of approximately 100% concentration can have significantly different heat flux, albedo, and other surface properties. Current ice concentration algorithms perform poorly in regions of predominantly thin or highly fragmented ice, which constitute a significant proportion of the pack in East Antarctica. The impact of the sea ice cover on high latitude air-sea interactions and marine ecology depends not only on ice extent and concentration but also on the ice-type composition of the pack. An unsupervised ice classification scheme, using data from four channels of the SSM/I, is presented and tested as a means of gaining important additional, complementary information on surface type. Class interpretation is by comparison with AVHRR, ERS-1 SAR, and near-coincident digital aerial photography and in situ data. The classification does a reasonable job at consistently differentiating the large-scale constituent regimes, including the outer marginal ice zone, the interior pack, and a transition zone separating the two. Given the short period of data analyzed, the cluster maps appear to be generally coherent and consistent through time as the pack changes in response to synoptic-scale atmospheric forcing, although the robustness of the technique needs further testing over longer time periods. An observed crossover int he meridional brightness temperature profiles is a dominant and consistent feature which marks the transition from unconsolidated and wet ice in the marginal ice zone to more consolidated ice with a thicker and drier snow cover in the interior pack. Ambiguities occur at the boundaries of some of these regimes due to sensor resolution limitations and the mixing of different ice types and open water. Also, some ice classes (like brash ice) cannot be distinguished from forming pancake ice. Furthermore, although the signature of the inner pack is usually distinct from that of the outer pack, we observed one extraordinary swell propagation event which led to ice fracturing and surface wetting, and significantly altered the surface classification. The results of this multiparameter study underline the importance of using multisensor systems synergistically to improve interpretation of passive microwave data and better characterize the complex Antarctic pack. Published by Elsevier Science Inc. C1 Antarctic Cooperat Res Ctr, Hobart, Tas 7001, Australia. NASA, Oceans & Ice Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Australian Antarctic Div, Kingston, Tas, Australia. CAELUM Res Corp, Rockville, MD USA. RP Antarctic Cooperat Res Ctr, GPO Box 252-80, Hobart, Tas 7001, Australia. EM R.Massom@utas.edu.au RI Worby, Anthony/A-2373-2012 NR 38 TC 18 Z9 20 U1 0 U2 4 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0034-4257 EI 1879-0704 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD APR PY 1999 VL 68 IS 1 BP 61 EP 76 DI 10.1016/S0034-4257(98)00100-X PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 178KG UT WOS:000079264400006 ER PT J AU Lissauer, JJ AF Lissauer, JJ TI Chaotic motion in the Solar System SO REVIEWS OF MODERN PHYSICS LA English DT Article ID SHORT-PERIOD COMETS; LARGE-SCALE CHAOS; TERM DYNAMICAL EVOLUTION; OUTER ASTEROID BELT; UREY PRIZE LECTURE; KUIPER-BELT; ORBITAL RESONANCES; PLANETARY SYSTEMS; GAS DRAG; 3/1 COMMENSURABILITY AB The motion of planetary bodies is the archetypal clockwork system. Indeed, clocks and calendars were developed to keep track of the relative motions of the Earth, the Sun, and the Moon. However, studies over the past few decades imply that this predictable regularity does not extend to small bodies, nor does it apply to the precise trajectories of the planets themselves over long timescales. [S0034-6861(99)00603-0]. C1 NASA, Div Space Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Lissauer, JJ (reprint author), NASA, Div Space Sci, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 95 TC 31 Z9 31 U1 1 U2 5 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0034-6861 EI 1539-0756 J9 REV MOD PHYS JI Rev. Mod. Phys. PD APR PY 1999 VL 71 IS 3 BP 835 EP 845 DI 10.1103/RevModPhys.71.835 PG 11 WC Physics, Multidisciplinary SC Physics GA 191YU UT WOS:000080050500009 ER PT J AU Tonner, BP Droubay, T Denlinger, J Meyer-Ilse, W Warwick, T Rothe, J Kneedler, E Pecher, K Nealson, K Grundl, T AF Tonner, BP Droubay, T Denlinger, J Meyer-Ilse, W Warwick, T Rothe, J Kneedler, E Pecher, K Nealson, K Grundl, T TI Soft X-ray spectroscopy and imaging of interfacial chemistry in environmental specimens SO SURFACE AND INTERFACE ANALYSIS LA English DT Article; Proceedings Paper CT Surface Analysis 98 CY JUN 16-19, 1998 CL PACIFIC NW NATL LAB, RICHLAND, WASHINGTON SP Amer Vacuum Soc, Appl Surface Sci Div, Pacific NW Natl Lab, William R Wiley Environm Molec Sci Lab, Amer Vacuum Soc, Pacific NW Chapter HO PACIFIC NW NATL LAB DE XPS; XAFS; soft x-ray spectroscopy; Mn; Fe ID OXIDATION-STATE; TRANSITION-METALS; ABSORPTION; IRON; DICHROISM; MANGANESE AB Interfaces between minerals and water, and minerals and microbes, are chemically complex and traditionally have been considered beyond the capabilities of surface science techniques, except for model systems under controlled laboratory conditions. We report on some advances in soft x-ray spectroscopy and imaging that make it possible to extract meaningful chemical information about interfaces of specimens that have complex histories, involving environmental exposure, These measurements utilize x-ray absorption spectroscopy, in combination with spatial resolution, in a technique called x-ray spectromicroscopy. Examples are drawn from attempts at Mn and Fe speciation of biologically produced minerals, bio-corrosion deposits and clays. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 Univ Cent Florida, Dept Phys, Orlando, FL 32816 USA. Univ Wisconsin, Dept Phys, Milwaukee, WI 53201 USA. Lawrence Berkeley Lab, Ctr Xray Opt, Berkeley, CA 94720 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wisconsin, WATER Inst, Milwaukee, WI 53204 USA. RP Tonner, BP (reprint author), Univ Cent Florida, Dept Phys, Orlando, FL 32816 USA. RI Droubay, Tim/D-5395-2016 OI Droubay, Tim/0000-0002-8821-0322 NR 18 TC 16 Z9 16 U1 0 U2 4 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0142-2421 J9 SURF INTERFACE ANAL JI Surf. Interface Anal. PD APR PY 1999 VL 27 IS 4 BP 247 EP 258 DI 10.1002/(SICI)1096-9918(199904)27:4<247::AID-SIA553>3.0.CO;2-M PG 14 WC Chemistry, Physical SC Chemistry GA 191GJ UT WOS:000080014000012 ER PT J AU Denning, AS Holzer, M Gurney, KR Heimann, M Law, RM Rayner, PJ Fung, IY Fan, SM Taguchi, S Friedlingstein, P Balkanski, Y Taylor, J Maiss, M Levin, I AF Denning, AS Holzer, M Gurney, KR Heimann, M Law, RM Rayner, PJ Fung, IY Fan, SM Taguchi, S Friedlingstein, P Balkanski, Y Taylor, J Maiss, M Levin, I TI Three-dimensional transport and concentration of SF6 - A model intercomparison study (TransCom 2) SO TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY LA English DT Article; Proceedings Paper CT 5th International CO(2) Conference CY SEP 08-12, 1997 CL CAIRNS, AUSTRALIA ID GENERAL-CIRCULATION MODEL; TERRESTRIAL CARBON METABOLISM; SURFACE PARAMETERIZATION SIB2; SULFUR-HEXAFLUORIDE SF6; ATMOSPHERIC CO2; BOUNDARY-LAYER; CUMULUS PARAMETERIZATION; TRACER MODEL; CLIMATE; SIMULATIONS AB Sulfur hexafluoride (SF6) is an excellent tracer of large-scale atmospheric transport, because it has slowly increasing sources mostly confined to northern midlatitudes, and has a lifetime of thousands of years. We have simulated the emissions, transport, and concentration of SF, for a 5-year period, and compared the results with atmospheric observations. In addition, we have performed an intercomparison of interhemispheric transport among 11 models to investigate the reasons for the differences among the simulations. Most of the models are reasonably successful at simulating the observed meridional gradient of SF6 in the remote marine boundary layer, though there is less agreement at continental sites. Models that compare well to observations in the remote marine boundary layer tend to systematically overestimate SF6 at continental locations in source regions, suggesting that vertical trapping rather than meridional transport may be a dominant control on the simulated meridional gradient. The vertical structure of simulated SF6 in the models supports this interpretation. Some of the models perform quite well in terms of the simulated seasonal cycle at remote locations, while others do not. Interhemispheric exchange time varies by a factor of 2 when estimated from 1-dimensional meridional profiles at the surface, as has been done for observations. The agreement among models is better when the global surface mean mole fraction is used, and better still when the full 3-dimensional mean mixing ratio is used. The ranking of the interhemispheric exchange time among the models is not sensitive to the change From station values to surface means, but is very sensitive to the change from surface means to the full 3-dimensional tracer fields. This strengthens the argument that vertical redistribution dominates over interhemispheric transport in determining the meridional gradient at the surface. Vertically integrated meridional transport in the models is divided roughly equally into transport by the mean motion, the standing eddies, and the transient eddies. The vertically integrated mass flux is a good index of the degree to which resolved advection vs. parameterized diffusion accomplishes the meridional transport of SF6. Observational programs could provide a much better constraint on simulated chemical tracer transport if they included regular sampling of vertical profiles of nonreactive trace gases over source regions and meridional profiles in the middle to upper troposphere. Further analysis of the SF6 simulations will focus on the subgrid-scale parameterized transports. C1 Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. Univ Victoria, Canadian Ctr Climate Modeling & Anal, Atmospher Environm Serv, Victoria, BC V8W 2Y2, Canada. Max Planck Inst Meteorol, D-20146 Hamburg 13, Germany. Monash Univ, CRC So Hemisphere Meteorol, Clayton, Vic 3168, Australia. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Calif Berkeley, Ctr Atmospher Sci, Berkeley, CA 94720 USA. Princeton Univ, Princeton, NJ 08544 USA. Natl Inst Resources & Environm, Tsukuba, Ibaraki, Japan. LMCE, Ctr Faibles Radioact, Gif Sur Yvette, Saclay, France. Australian Natl Univ, Ctr Resource & Environm Studies, Canberra, ACT 0200, Australia. Max Planck Inst Chem, Air Chem Div, D-55128 Mainz, Germany. Univ Heidelberg, Inst Umweltphys, D-6900 Heidelberg, Germany. RP Denning, AS (reprint author), Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. RI Law, Rachel/A-1969-2012; Denning, Scott/F-4974-2011; Balkanski, Yves/A-6616-2011; Heimann, Martin/H-7807-2016; Friedlingstein, Pierre/H-2700-2014 OI Law, Rachel/0000-0002-7346-0927; Denning, Scott/0000-0003-3032-7875; Balkanski, Yves/0000-0001-8241-2858; Heimann, Martin/0000-0001-6296-5113; NR 63 TC 103 Z9 104 U1 0 U2 5 PU CO-ACTION PUBLISHING PI JARFALLA PA RIPVAGEN 7, JARFALLA, SE-175 64, SWEDEN SN 0280-6509 J9 TELLUS B JI Tellus Ser. B-Chem. Phys. Meteorol. PD APR PY 1999 VL 51 IS 2 BP 266 EP 297 DI 10.1034/j.1600-0889.1999.00012.x PG 32 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 211CY UT WOS:000081143400012 ER PT J AU Akins, RE Boyce, RA Madonna, ML Schroedl, NA Gonda, SR McLaughlin, TA Hartzell, CR AF Akins, RE Boyce, RA Madonna, ML Schroedl, NA Gonda, SR McLaughlin, TA Hartzell, CR TI Cardiac organogenesis in vitro: Reestablishment of three-dimensional tissue architecture by dissociated neonatal rat ventricular cells SO TISSUE ENGINEERING LA English DT Article ID LONG-TERM SURVIVAL; ROTATING-WALL VESSEL; SIMULATED MICROGRAVITY; HEART-CELLS; NITRIC-OXIDE; CARDIOMYOCYTE GRAFTS; CONTRACTILE FUNCTION; IN-VITRO; REGENERATION; MYOCYTES AB The mammalian heart does not regenerate in vivo. The heart is, therefore, an excellent candidate for tissue engineering approaches and for the use of biosynthetic devices in the replacement or augmentation of defective tissue. Unfortunately, little is known about the capacity of isolated heart cells to re-establish tissue architectures in vitro. In this study, we examined the possibility that cardiac cells possess a latent organizational potential that is unrealized within the mechanically active tissue but that can be accessed in quiescent environments in culture. In the series of experiments presented here, total cell populations were isolated from neonatal rat ventricles and recombined in rotating bioreactors containing a serum-free medium and surfaces for cell attachment. The extent to which tissue-like structure and contractile function were established was assessed using a combination of morphological, physiological, and biochemical techniques. We found that mixed populations of ventricular cells formed extensive three-dimensional aggregates that were spontaneously and rhythmically contractile and that large aggregates of structurally-organized cells contracted in unison. The cells were differentially distributed in these aggregates and formed architectures that were indistinguishable from those of intact tissue. These architectures arose in the absence of three-dimensional cues from the matrix, and the formation of organotypic structures was apparently driven by the cells themselves. Our observations suggest that cardiac cells possess an innate capacity to re-establish complex, three-dimensional, cardiac organization in vitro. Understanding the basis of this capacity, and harnessing the organizational potential of heart cells, will be critical in the development of tissue homologues for use in basic research and in the engineering of biosynthetic implants for the treatment of cardiac disease. C1 Alfred I duPont Hosp Children, Nemours Fdn, Alfred I duPont Inst, Dept Res, Wilmington, DE 19899 USA. Thomas Jefferson Univ, Dept Pediat, Philadelphia, PA 19107 USA. NASA, Biotechnol Cell Sci Program, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. OI Akins, Robert/0000-0001-9706-0752 NR 71 TC 107 Z9 110 U1 1 U2 6 PU MARY ANN LIEBERT INC PUBL PI LARCHMONT PA 2 MADISON AVENUE, LARCHMONT, NY 10538 USA SN 1076-3279 J9 TISSUE ENG JI Tissue Eng. PD APR PY 1999 VL 5 IS 2 BP 103 EP 118 DI 10.1089/ten.1999.5.103 PG 16 WC Cell & Tissue Engineering SC Cell Biology GA 188EW UT WOS:000079834700003 PM 10358218 ER PT J AU Li, JH Dijkstra, P Hinkle, CR Wheeler, RM Drake, BG AF Li, JH Dijkstra, P Hinkle, CR Wheeler, RM Drake, BG TI Photosynthetic acclimation to elevated atmospheric CO2 concentration in the Florida scrub-oak species Quercus geminata and Quercus myrtifolia growing in their native environment SO TREE PHYSIOLOGY LA English DT Article; Proceedings Paper CT Workshop on Critical Assessment of the Response of Forest Ecosystems to Elevated Atmospheric Carbon Dioxide CY OCT 10-13, 1997 CL DURHAM, NORTH CAROLINA DE carbon dioxide; open-top chambers; Rubisco; specific leaf area; starch; sugar ID PINUS-TAEDA SEEDLINGS; GAS-EXCHANGE; CARBON-DIOXIDE; WATER-STRESS; LIQUIDAMBAR-STYRACIFLUA; GROWTH; ENRICHMENT; LEAVES AB Long-term effects of elevated CO2 concentration (ambient plus 350 mu mol mol(-1)) on leaf photosynthetic acclimation of two species of a scrub-oak community, Quercus myrtifolia Willd. and Quercus geminata Small, were studied. Plants of both species were grown in open-top chambers in their natural habitat at Kennedy Space Center, Florida, USA. Compared to ambient CO2, elevated CO2 stimulated photosynthetic rates by 73 and 51% for Q. geminata and Q. myrtifolia, respectively. Maximum rate of carboxylation (V-cmax) was significantly reduced by elevated CO2 in Q. myrtifolia (28%) but not in Q. geminata. Maximum rate of potential electron transport (J(max)) was not significantly reduced by elevated CO2 in either species. In response to elevated CO2, specific leaf area decreased in Q, myrtifolia (22%), but not in Q. geminata. Elevated CO:! caused a significant accumulation of sugars (54%) and starch (264%) in Q, myrtifolia leaves, but not in Q. geminata leaves. Total Rubisco activity in Q. myrtifolia leaves was reduced 40% by elevated CO2, whereas no significant reduction occurred in Q, geminata leaves. Although both species share a common habitat, they exhibited marked differences in photosynthetic acclimation to elevated CO2 concentration. C1 Natl Res Council, Kennedy Space Ctr, FL 32899 USA. Smithsonian CO2 Site, Kennedy Space Ctr, FL 32899 USA. Dynamac Corp, Kennedy Space Ctr, FL 32899 USA. NASA, Biomed Off, Kennedy Space Ctr, FL 32899 USA. Smithsonian Environm Res Ctr, Edgewater, MD 21037 USA. RP Li, JH (reprint author), Natl Res Council, Mail Code JJ-G, Kennedy Space Ctr, FL 32899 USA. NR 25 TC 32 Z9 32 U1 0 U2 2 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 APR PY 1999 VL 19 IS 4-5 BP 229 EP 234 PG 6 WC Forestry SC Forestry GA 181NB UT WOS:000079446400004 ER PT J AU Miyoshi, K AF Miyoshi, K TI Edmond E. Bisson - Obituary SO TRIBOLOGY INTERNATIONAL LA English DT Biographical-Item C1 NASA, LGRC, Cleveland, OH 44135 USA. RP Miyoshi, K (reprint author), NASA, LGRC, 21000 Brookpk Rd,MS 106-5, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0301-679X J9 TRIBOL INT JI Tribol. Int. PD APR PY 1999 VL 32 IS 4 BP 177 EP 178 PG 2 WC Engineering, Mechanical SC Engineering GA 242XC UT WOS:000082966100001 ER PT J AU Jones, WR Poslowski, AK Shogrin, BA Herrera-Fierro, P Jansen, MJ AF Jones, WR Poslowski, AK Shogrin, BA Herrera-Fierro, P Jansen, MJ TI Evaluation of several space lubricants using a vacuum four-ball tribometer SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT Joint ASME/STLE Tribology Conference CY OCT 25-29, 1998 CL TORONTO, CANADA SP ASME, STLE DE adverse environments tribology; boundary lubrication; synthetic lubricants ID POLYSILAHYDROCARBON SYNTHETIC FLUIDS; POLARIZED INFRARED MICROSPECTROSCOPY; RAY PHOTOELECTRON-SPECTROSCOPY; PERFLUOROPOLYETHERS; PERFORMANCE; STABILITY; MOLECULES; ETHERS; OXIDE AB The friction and wear behavior of seven space lubricants was investigated under boundary lubrication conditions using a vacuum four-ball tribometer. Three of the lubricants were perfluoropolyethers (143AC, S-200, and Z-25). Three were synthetic hydrocarbons (a multiply alkylated cyclopentane, 2001a), and a formulated version with an antiwear and an antioxidant additive (2001). The third hydrocarbon was an unformulated polyalphaolefin (PAO-100). An unformulated silahydrocarbon (SiHC) was also evaluated. Test conditions included: a pressure <6.7 x 10(-4) Pa, a 200N load, a sliding velocity of 28.8 mm/sec (100 rpm), and room temperature (similar to 23 degrees C). The wear rate for each lubricant was determined from the slope of wear volume as a function of sliding distance. The lowest wear rate (0.033 x 10(-9) mm(3)/mm) was obtained with the silahydrocarbon. The formulated synthetic hydrocarbon had a wear rate of 0.037 x 10(-9) mm(3)/mm, which was a 36 percent reduction compared to the unformulated fluid. The polyalphaolefin had the highest wear rate of the non-PFPE fluids. Of the perfluoropolyethers (PFPEs), wear rates decreased by about 50 percent from Z-25 (1.7 x 10(-9) mm(3)/mm) to S-200 (0. 70 x 10(-9) mm(3)/mm) to 143AC (0.21 x 10(-9) mm(3)/mm). C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. John Carroll Univ, University Hts, OH 44118 USA. Case Western Reserve Univ, Cleveland, OH 44016 USA. AYT Corp, Brookpark, OH 44142 USA. Ohio Aerospace Inst, Brookpark, OH 44142 USA. RP Jones, WR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 33 TC 13 Z9 14 U1 2 U2 4 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD APR PY 1999 VL 42 IS 2 BP 317 EP 323 DI 10.1080/10402009908982223 PG 7 WC Engineering, Mechanical SC Engineering GA 195CT UT WOS:000080232100008 ER PT J AU Dellacorte, C Fellenstein, JA Benoy, PA AF Dellacorte, C Fellenstein, JA Benoy, PA TI Evaluation of advanced solid lubricant coatings for foil air bearings operating at 25 degrees and 500 degrees C SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT Joint ASME/STLE Tribology Conference CY OCT 25-29, 1998 CL TORONTO, CANADA SP ASME, STLE DE adverse environment tribology; air bearings; solid lubricants; surface films coatings AB The tribological properties of one chrome oxide and one chrome carbide based solid lubricant coating were evaluated in a partial-arc foil bearing at 25 degrees and 500 degrees C. Start/stop bearing operation up to 20,000 cycles were run under 20 kPa (1.5 psi) static deadweight load. Bearing friction (torque) was measured during the test. Specimen wear and SEM/EDS surface analyses were conducted after testing to understand and elucidate the tribological characteristics observed The chrome oxide coating which contains both Ag and BaF2CaF2 for low and high temperature lubrication, exhibited low friction in sliding against Al2O3 coated foils at 25 degrees and 500 degrees C. The chrome carbide coating, which lacked a low temperature lubricant but contained BaF2/Caf(2), as a high temperature lubricant, exhibited high friction at 25 degrees C and low friction at 500 degrees C against both bare and Al2O3 coated superalloy foil surfaces. Post test surface analyses suggest that improved tribological performance is exhibited when a lubricant film from the coating transfers to the foil surface. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Ohio Aerosp Inst, Cleveland, OH 44142 USA. St Louis Univ, St Louis, MO 63156 USA. RP Dellacorte, C (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 17 TC 17 Z9 17 U1 0 U2 3 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD APR PY 1999 VL 42 IS 2 BP 338 EP 342 DI 10.1080/10402009908982226 PG 5 WC Engineering, Mechanical SC Engineering GA 195CT UT WOS:000080232100011 ER PT J AU Miyoshi, K Pohlchuck, B Street, KW Zabinski, JS Sanders, JH Voevodin, AA Wu, RLC AF Miyoshi, K Pohlchuck, B Street, KW Zabinski, JS Sanders, JH Voevodin, AA Wu, RLC TI Sliding wear and fretting wear of diamondlike carbon-based, functionally graded nanocomposite coatings SO WEAR LA English DT Article; Proceedings Paper CT 12th International Conference on Wear of Materials CY APR 25-29, 1999 CL ATLANTA, GA DE sliding wear; fretting wear; diamondlike carbon coating ID FILMS AB Improving the tribological functionality of diamondlike carbon (DLC) films-developing good wear resistance, low friction, and high load-carrying capacity-was the aim of this investigation. Nanocomposite coatings consisting of an amorphous DLC (a-DLC) top layer and a functionally graded titanium-titanium carbide-diamondlike carbon (Ti-TixCy-DLC) underlayer were produced on AISI 440C stainless steel substrates by the hybrid technique of magnetron sputtering and pulsed-laser deposition. The resultant DLC films were characterized by Raman spectroscopy, scanning electron microscopy, and surface profilometry. Two types of wear experiment were conducted in this investigation: sliding friction experiments and fretting wear experiments. Unidirectional ball-on-disk sliding friction experiments were conducted to examine the wear behavior of an a-DLC/Ti-TixCy-DLC-coated AISI 440C stainless steel disk in sliding contact with a 6-mm diameter AISI 440C stainless steel ball in ultrahigh vacuum, in dry nitrogen, and in humid air. Although the wear rates for both the coating and ball were low in all three environments, the humid air and dry nitrogen caused mild wear with burnishing in the a-DLC top layer, and the ultrahigh vacuum caused relatively severe wear with brittle fracture in both the a-DLC top layer and the Ti-TixCy-DLC underlayer. For reference, amorphous hydrogenated carbon (H-DLC) films produced on a-DLC/Ti-TixCy-DLC nanocomposite coatings by using an ion beam were also examined in the same manner. The H-DLC films markedly reduced friction even in ultrahigh vacuum without sacrificing wear resistibility. The H-DLC films behaved much like the a-DLC/Ti-TixCy-DLC nanocomposite coating in dry nitrogen and humid air, presenting low friction and low wear. Fretting wear experiments were conducted in humid air (approximately 50% relative humidity) at a frequency of 80 Hz and an amplitude of 75 mu m on an a-DLC/Ti-TixCy-DLC-coated AISI 440C disk and on a titanium-6 wt.% aluminum-4, wt.% vanadium (Ti-6Al-4V) flat, both in contact with a 9.4-mm diameter, hemispherical Ti-6Al-4V pin. The resistance to fretting wear and damage of the a-DLC/Ti-6Al-4V materials pair was superior to that of the Ti-6Al-4V/Ti-6Al-4V materials pair. (C) 1999 Published by Elsevier Science S.A. C1 USAF, Res Lab, Wright Patterson AFB, OH 45433 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. K Syst, Beavercreek, OH 45432 USA. RP NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. EM miyoshi@lerc.nasa.gov RI Voevodin, Andrey/I-6684-2013 NR 18 TC 59 Z9 65 U1 3 U2 27 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0043-1648 EI 1873-2577 J9 WEAR JI Wear PD APR PY 1999 VL 225 BP 65 EP 73 DI 10.1016/S0043-1648(98)00349-4 PN 1 PG 9 WC Engineering, Mechanical; Materials Science, Multidisciplinary SC Engineering; Materials Science GA 190EM UT WOS:000079949200010 ER PT J AU Gharrett, AJ Smoker, WW Reisenbichler, RR Taylor, SG AF Gharrett, AJ Smoker, WW Reisenbichler, RR Taylor, SG TI Outbreeding depression in hybrids between odd- and even-broodyear pink salmon SO AQUACULTURE LA English DT Article; Proceedings Paper CT 6th International Symposium on Genetics in Aquaculture CY JUN 22-28, 1997 CL UNIV STIRLING, STIRLING, SCOTLAND HO UNIV STIRLING DE outbreeding depression; conservation biology; salmonid; pink salmon; fluctuating asymmetry; meristics; cryopreservation ID ONCORHYNCHUS-GORBUSCHA; TIGRIOPUS-CALIFORNICUS; GENETIC-ANALYSIS; POPULATIONS; COPEPOD; SIZE AB Fewer F-2 hybrids between even- and odd-broodline pink salmon (Oncorhynchus gorbuscha), which are lines that are genetically isolated by their strict two-year life cycle, survived than did F-2 controls, indicating outbreeding depression. Cryopreserved sperm of 40 broodyear 1990 males and of 40 broodyear 1991 males fertilized equal subsamples Of eggs from 40 broodyear 1992 females. Return rates of F-1 hybrids (1.73%) and controls (1.63%) in 1994 did not differ significantly (P = 0.30), F-2 hybrid and control crosses were made from 40 males and 40 females selected at random from each return group. Offspring were differentially marked and released. In 1996, returns differed significantly (P = 0.011) between hybrids (n = 34, 0.34%) and controls (n = 44, 0.42%). The low rate of return of the control fish was similar to the measured return of a much larger group of tagged Auke Creek pink salmon, and probably not an artifact of the experiment. Although no increase in fluctuating asymmetry of paired meristic counts was observed in either F-1 or F-2 hybrids, size and some meristic counts of hybrids exceed measurements of controls, suggesting heterosis for those traits. The observations of decreased survival in F-2 hybrids confirm previous work [Gharrett, A.J., Smoker, W.W., 1991. Two generations of hybrids between even- and odd-year pink salmon (O. gorbuscha). Canadian Journal of Fisheries and Aquatic Science 48(9) 1744-1749]. Although genetic divergence between pink salmon broodlines is large and outbreeding depression might be expected in such unlikely hybrids, the results document;the occurrence of outbreeding depression in salmon and signal caution in making management and aquacultural decisions that may create the possibility of outbreeding depression in self-sustaining or cultured populations. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Alaska Fairbanks, Sch Fisheries & Ocean Sci, Div Fisheries, Juneau, AK 99801 USA. US Geol Survey, Biol Resources Div, Western Fisheries Res Ctr, Seattle, WA 98036 USA. Auke Bay Lab, Natl Marine Fisheries Serv, Juneau, AK 99801 USA. RP Gharrett, AJ (reprint author), Univ Alaska Fairbanks, Sch Fisheries & Ocean Sci, Div Fisheries, 11120 Glacier Highway, Juneau, AK 99801 USA. EM ffajg@uaf.edu NR 40 TC 98 Z9 101 U1 1 U2 21 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0044-8486 J9 AQUACULTURE JI Aquaculture PD MAR 30 PY 1999 VL 173 IS 1-4 BP 117 EP 129 DI 10.1016/S0044-8486(98)00480-3 PG 13 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 181GG UT WOS:000079432600013 ER PT J AU Mertens, CJ Mlynczak, MG Garcia, RR Portmann, RW AF Mertens, CJ Mlynczak, MG Garcia, RR Portmann, RW TI A detailed evaluation of the stratospheric heat budget - 1. Radiation transfer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; MIDDLE ATMOSPHERE; COOLING RATES; CLIMATE MODELS; SULFURIC-ACID; AEROSOL; OZONE; REEXAMINATION; CIRCULATION; TEMPERATURE AB We present part 1 of a two-part series on a detailed evaluation of the stratospheric heat budget. In part 2 [Mlynczak et al., this issue] we present radiative heating, radiative cooling, net radiative heating, global radiation balance, radiative relaxation times, and diabatic circulations in the stratosphere using temperature and minor constituent data provided by instruments on the Upper Atmosphere Research Satellite (UARS) between 1991 and 1993 and by the limb infrared monitor of the stratosphere (LIMS) instrument, which operated on the Nimbus-7. spacecraft in 1978-1979. Here we describe the radiative transfer techniques used to compute the climatology of radiative heating and circulations given in part 2. Included in the radiation transfer calculations are heating due to absorption of solar radiation from the ultraviolet through near-infrared wavelengths and radiative cooling due to emission by carbon dioxide, water vapor, and ozone from 0 to 3000 cm(-1) (infinity-3.3 mu m). Infrared radiative effects of stratospheric aerosols are also considered in detail. C1 GATS Inc, Newport News, VA 23606 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Natl Ctr Atmospher Res, Boulder, CO 80303 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Mertens, CJ (reprint author), GATS Inc, 11864 Canon Blvd,Suite 101, Newport News, VA 23606 USA. EM c.j.mertens@gats-inc.com; m.g.mlynczak@larc.nasa.gov; bportmann@al.noaa.gov RI Portmann, Robert/C-4903-2009; Mlynczak, Martin/K-3396-2012 OI Portmann, Robert/0000-0002-0279-6087; NR 49 TC 15 Z9 15 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 MAR 27 PY 1999 VL 104 IS D6 BP 6021 EP 6038 DI 10.1029/1998JD200100 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700004 ER PT J AU Mlynczak, MG Mertens, CJ Garcia, RR Portmann, RW AF Mlynczak, MG Mertens, CJ Garcia, RR Portmann, RW TI A detailed evaluation of the stratospheric heat budget - 2. Global radiation balance and diabetic circulations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MICROWAVE LIMB SOUNDER; ATMOSPHERE RESEARCH SATELLITE; HALOGEN OCCULTATION EXPERIMENT; MIDDLE ATMOSPHERE; INFRARED MONITOR; PLANETARY-WAVES; VALIDATION; OZONE; UARS; TRANSPORT AB We present a detailed evaluation of radiative heating, radiative cooling, net heating, global radiation balance, radiative relaxation times, and diabatic circulations in the stratosphere using temperature and minor constituent data provided by instruments on the Upper Atmosphere Research Satellite (UARS) between 1991 and 1993 and by the limb infrared monitor of the stratosphere (LIMS) instrument which operated on the Nimbus-7 spacecraft in 1978-1979. Included in the calculations are heating due to absorption of solar radiation from ultraviolet through near-infrared wavelengths and radiative cooling due to emission by carbon dioxide, water vapor, and ozone from 0 to 3000 cm(-1) (infinity-3.3 mu m). Infrared radiative effects of Pinatubo aerosols are also considered in some detail. In general, we find the stratosphere to be in a state of global mean radiative equilibrium on monthly timescales to within the uncertainty of the satellite-provided measurements. Radiative relaxation times are found to be larger in the lower stratosphere during UARS than LIMS because of the presence of Pinatubo aerosols. The meridional circulations in the upper stratosphere as diagnosed from the calculated fields of net heating are generally stronger in the UARS period than during the LIMS period, while the lower stratosphere meridional circulations are stronger during the LIMS period. A climatology of. these calculations is available to the community via a World Wide Web interface described herein. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. GATS Inc, Newport News, VA 23606 USA. Natl Ctr Atmospher Res, Boulder, CO 80303 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Mlynczak, MG (reprint author), NASA, Langley Res Ctr, Mail Stop 401B, Hampton, VA 23681 USA. EM m.g.mlynczak@larc.nasa.gov; c.j.mertens@gats-inc.com; rgarcia@garcia.acd.ucar.edu; bportmann@al.noaa.gov RI Portmann, Robert/C-4903-2009; Mlynczak, Martin/K-3396-2012 OI Portmann, Robert/0000-0002-0279-6087; NR 50 TC 28 Z9 28 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 MAR 27 PY 1999 VL 104 IS D6 BP 6039 EP 6066 DI 10.1029/1998JD200099 PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700005 ER PT J AU Davis, AB Marshak, A Gerber, H Wiscombe, WJ AF Davis, AB Marshak, A Gerber, H Wiscombe, WJ TI Horizontal structure of marine boundary layer clouds from centimeter to kilometer scales SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LIQUID WATER DISTRIBUTIONS; STRATOCUMULUS CLOUDS; SHORTWAVE ABSORPTION; OPTICAL DEPTH; PARAMETERIZATION; INHOMOGENEITY; SIMULATIONS; INVARIANCE; FRACTALITY; TURBULENCE AB Horizontal transects of cloud liquid water content (LWC) measured at unprecedented 4-cm resolution are statistically analyzed scale-by-scale, The data were collected with a Particulate Volume Monitor (PVM) probe during the winter Southern Ocean Cloud EXperiment (SOCEX) on July 26, 1993, in a broken-stratocumulus/towering-cumulus cloud complex. Two scaling regimes are found in the sense that two distinct power laws, k(-beta), are needed to represent the wavenumber spectrum E(k) over the full range of scales r approximate to 1/k. Detailed numerical simulations show that the scale break at 2-5 m is not traceable to the normal variability of LWC in the PVM's instantaneous sampling volume (1.25 cm(3)) driven by Poissonian fluctuations of droplet number and size. The two regimes therefore differ physically. The non-Poissonian character of the small-scale LWC variability is consistent with a similar finding by Baker [1992] for droplet number concentration obtained from Forward Scattering Spectrometer Probe (FSSP) data: at scales of a few centimeters, spatial droplet distributions do not always follow a uniform Poisson law. With beta = 0.9 +/- 0.1, the small-scale (8-12 cm less than or similar to r less than or similar to 2-5 m) regime is stationary: jumps in LWC are highly variable in size and rapidly cancel each other, leading to short-range correlations. By contrast, the large-scale (5 m less than or similar to r less than or similar to 2 km) variability with beta = 1.6 +/- 0.1 is nonstationary: jumps are generally quite small, conveying a degree of pixel-to-pixel continuity and thus building up long-range correlations in the low-pass filtered signal. The large-scale structure of the complex SOCEX cloud system proves to be multifractal, meaning that large jumps do occur on an intermittent basis, that is, on a sparse fractal subset of space. Low-order, hence more robust, multifractal properties of the SOCEX clouds are remarkably similar to those of their First ISCCP Regional Experiment (FIRE) and Atlantic Stratocumulus Transition EXperiment (ASTEX) counterparts, and also to those of passive scalars in fully developed turbulence. This is indicative of a remarkable similarity in the microphysical and macrophysical processes that determine cloud structure in the marine boundary layer at very remote locales, especially since the particular SOCEX cloud system investigated here was rather atypical. Interesting differences are also found: in the scaling ranges on the one hand, and in higher-order moments on the other hand. Finally, we discuss cloud-radiative effects of the large- and small-scale variabilities. C1 Los Alamos Natl Lab, Space & Remote Sensing Sci Grp, Los Alamos, NM 87545 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21228 USA. Gerber Sci Inc, Reston, VA 20190 USA. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Davis, AB (reprint author), Los Alamos Natl Lab, Space & Remote Sensing Sci Grp, NIS-2,POB 1663,MS C-323, Los Alamos, NM 87545 USA. EM adavis@lanl.gov; marshak@climate.gsfc.nasa.gov; gerber.gsi@erols.com; wiscombe@climate.gsfc.nasa.gov RI Wiscombe, Warren/D-4665-2012; Marshak, Alexander/D-5671-2012 OI Wiscombe, Warren/0000-0001-6844-9849; NR 74 TC 66 Z9 66 U1 2 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 MAR 27 PY 1999 VL 104 IS D6 BP 6123 EP 6144 DI 10.1029/1998JD200078 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700010 ER PT J AU Atlas, D Ulbrich, CW Marks, FD Amitai, E Williams, CR AF Atlas, D Ulbrich, CW Marks, FD Amitai, E Williams, CR TI Systematic variation of drop size and radar-rainfall relations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RAINDROP SPECTRA; TOGA-COARE; CLASSIFICATION; PRECIPITATION; DISTRIBUTIONS; REFLECTIVITY; EVAPORATION; CLOUDS; SHAPE AB Time histories of the characteristics of the drop size distribution of surface disdrometer measurements collected at Kapingamarangi Atoll were partitioned for several storms using rain rate R, reflectivity factor Z, and median diameter of the distribution of water content D-0. This partitioning produced physically based systematic variations of the drop size distribution (DSD) and Z-R relations in accord with the precipitation types view-ed simultaneously by a collocated radar wind profiler. These variations encompass the complete range of scatter around the mean Z-R relations previously reported by Tokay, and Short [1996] for convective and stratiform rain and demonstrate that the scatter is not random. The systematic time or space variations are also consistent with the structure of mesoscale convective complexes with a sequence of convective, transition, and stratiform rain described by various authors. There is a distinct inverse relation between the coefficient A and the exponent of the Z-R relations which has been obscured in prior work because of the lack of proper discrimination of the rain types. Contrary to previous practice it is evident that there is also a distinct difference in the DSD and the Z-R relations between the initial convective and the trailing transition zones. The previously reported Z-R relation for convective rain is primarily representative of the transition rain that was included in the convective class. The failure of present algorithms to distinguish between the initial convective and the trailing transition rains causes an erroneous apportionment of the diabatic heating and cooling and defeats the primary intent of discriminating stratiform from convective rains. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. NOAA, Atlantic Oceanog & Meteorol Lab, Hurricane Res Div, Miami, FL 33149 USA. NOAA, Aeron Lab, Environm Res Labs, Boulder, CO 80303 USA. RP Atlas, D (reprint author), 16100 Golf Club Rd,Apt 302, Weston, FL 33326 USA. EM datlas@trmm.gsfc.nasa.gov RI Marks, Frank/A-5733-2011; Williams, Christopher/A-2723-2015 OI Marks, Frank/0000-0003-0371-5514; Williams, Christopher/0000-0001-9394-8850 NR 46 TC 113 Z9 115 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 1999 VL 104 IS D6 BP 6155 EP 6169 DI 10.1029/1998JD200098 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700012 ER PT J AU Pincus, R McFarlane, SA Klein, SA AF Pincus, R McFarlane, SA Klein, SA TI Albedo bias and the horizontal variability of clouds in subtropical marine boundary layers: Observations from ships and satellites SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AVERAGED SOLAR FLUXES; MICROPHYSICAL PROCESSES; PARAMETERIZATION; STRATOCUMULUS; ISCCP; LIQUID; MODELS AB Cloud optical properties vary dramatically at spatial scales smaller than typical grid cells in large-scale models, which can cause a significant overestimate of cloud albedo by the model. This plane parallel homogeneous (PPH) albedo bias exist may be reduced if the mean cloud optical thickness and the amount of variability are available, but little is known about how much variability exists in nature and to what factors it is sensitive. The authors combine 1331 observations made by volunteer surface observers with satellite imagery to assess the relationships between cloud fraction, cloud optical properties, and cloud type in marine boundary layer clouds off the coast of California during summer. Estimates of cloud fraction from the two datasets are in best agreement when a reflectance threshold between 0.09 and 0.10 is used. Satellite-derived cloud fraction increases slowly with sensor resolution at spatial scales from 1 to 32 km. Cloud fraction in scenes dominated by cumulus is much more sensitive to the reflectance threshold used for cloud detection than are scenes containing stratiform clouds. The mean magnitude of the PPH bias found here, 0.025, is considerably smaller than those found in other recent studies. When fit to the observed distributions of optical thickness both log-normal and gamma distributions substantially reduce the PPH bias. The mean and dispersion of log optical thickness are related to cloud type: optical thickness increases as cloud type changes from cumuliform to stratiform, while the relative amount of variability decreases. The authors suggest a basis for the parameterization of unresolved variability in large scale models. C1 NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. Princeton Univ, NOAA, Geophys Fluid Dynam Lab, Princeton, NJ 08542 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21228 USA. RP Pincus, R (reprint author), Univ Wisconsin, Dept Atmospher & Ocean Sci, 1225 W Dayton St, Madison, WI 53706 USA. RI McFarlane, Sally/C-3944-2008; Pincus, Robert/B-1723-2013; Klein, Stephen/H-4337-2016 OI Pincus, Robert/0000-0002-0016-3470; Klein, Stephen/0000-0002-5476-858X NR 26 TC 50 Z9 52 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 1999 VL 104 IS D6 BP 6183 EP 6191 DI 10.1029/1998JD200125 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700014 ER PT J AU Chen, MH Rood, RB Read, WG AF Chen, MH Rood, RB Read, WG TI Seasonal variations of upper tropospheric water vapor and high clouds observed from satellites SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RELATIVE-HUMIDITY; FEEDBACK; MOISTURE; MODELS AB Multiyear satellite measurements of specific humidity at 215 mbar from the Microwave Limb Sounder aboard the Upper Atmosphere Research Satellite and cloud amount from the International Satellite Cloud Climatology Project have been used to investigate seasonal variations of upper tropospheric water vapor (UTWV), high clouds, and deep convection. The tropical and extratropical UTWV for each hemisphere have maximum values in summer and minimum values in winter because of the moistening effect of the tropical deep convection. The seasonal change of high cloud amount is similar to UTWV in the tropics but very different in the extratropics. Implications of the present results for the water vapor feedback in the climate system are discussed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Gen Sci Corp, Sci Appl International Corp, Laurel, MD 20707 USA. RP Chen, MH (reprint author), NASA, Goddard Space Flight Ctr, Code 910-3, Greenbelt, MD 20771 USA. EM mchen@dao.gsfc.nasa.gov; rood@dao.gsfc.nasa.gov; bill@mls.jpl.nasa.gov RI Rood, Richard/C-5611-2008 OI Rood, Richard/0000-0002-2310-4262 NR 22 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 1999 VL 104 IS D6 BP 6193 EP 6197 DI 10.1029/1998JD200124 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700015 ER PT J AU Berendes, TA Kuo, KS Logar, AM Corwin, EM Welch, RM Baum, BA Pretre, A Weger, RC AF Berendes, TA Kuo, KS Logar, AM Corwin, EM Welch, RM Baum, BA Pretre, A Weger, RC TI A comparison of paired histogram, maximum likelihood, class elimination, and neural network approaches for daylight global cloud classification using AVHRR imagery SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RADIOMETER INFRARED CHANNELS; SURFACE CLASSIFICATION; SATELLITE MEASUREMENTS; MULTISPECTRAL IMAGERY; PATTERN-RECOGNITION; COVER ANALYSIS; POLAR-REGIONS; RESOLUTION; CALIBRATION AB The accuracy and efficiency of four approaches to identifying clouds and aerosols in remote sensing imagery are compared. These approaches are as follows: a maximum likelihood classifier, a paired histogram technique, a hybrid class elimination approach, and a backpropagation neural network. Regional comparisons were conducted on advanced very high resolution radiometer (AVHRR) local area coverage (LAC) scenes from the polar regions, desert areas, and regions of biomass-burning, areas which are known to be particularly difficult. For the polar, desert, and biomass burning regions, the maximum likelihood classifier achieved 94-97% accuracy, the neural network achieved 95-96% accuracy, and the paired histogram approach achieved 93-94% accuracy. The primary advantage to the class elimination scheme lies in its speed; its accuracy of 94-96% is comparable to that of the maximum likelihood classifier. Experiments also clearly demonstrate the effectiveness of decomposing a single global classifier into separate regional classifiers, since the regional classifiers can be more finely tuned to recognize local conditions. In addition, the effectiveness of using composite features is compared to the simpler approach of using the five AVHRR channels and the reflectance of channel 3 treated as a sixth channel as the elements of the feature vector. The results varied, demonstrating that the features cannot be chosen independently of the classifier to be used. It is also shown that superior results can obtained by training the classifiers using subclass information and collapsing the subclasses after classification. Finally, ancillary data were incorporated into the classifiers, consisting of a land/water mask, a terrain map, and a computed sunglint probability. While the neural network did not benefit from this information, the accuracy of the maximum likelihood classifier improved by 1%, and the accuracy of the paired histogram method increased by up to 4%. C1 Univ Alabama, Global Hydrol & Climate Ctr, Dept Atmospher Sci, Huntsville, AL 35806 USA. S Dakota Sch Mines & Technol, Dept Math & Comp Sci, Rapid City, SD 57701 USA. NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. Martin & Associates Inc, Mitchell, SD 57301 USA. S Dakota Sch Mines & Technol, Inst Atmospher Sci, Rapid City, SD 57701 USA. RP Berendes, TA (reprint author), Univ Alabama, Global Hydrol & Climate Ctr, Dept Atmospher Sci, Huntsville, AL 35806 USA. RI Baum, Bryan/B-7670-2011 OI Baum, Bryan/0000-0002-7193-2767 NR 39 TC 14 Z9 14 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 MAR 27 PY 1999 VL 104 IS D6 BP 6199 EP 6213 DI 10.1029/98JD02584 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700016 ER PT J AU Lyapustin, AI Privette, JL AF Lyapustin, AI Privette, JL TI A new method of retrieving surface bidirectional reflectance from ground measurements: Atmospheric sensitivity study SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CANOPY REFLECTANCE; RADIOMETER; HARDWOOD; ALBEDO; MODEL AB Commonly, experimental data on surface directional reflectance are not properly corrected for atmospheric effects. In this paper, we describe a new method for rigorous retrieval of the bidirectional reflectance distribution function (BRDF) from ground-based measurements. It obtains the pointwise BRDF in the view directions and the best fit parameters of the approximating analytical model. Unlike previously developed algorithms, it can perform a retrieval using directional observations made at a single solar angle. This improvement allows one to process experiments with incomplete sets of measurements, such as those contaminated by clouds. The paper describes the performance of the method and its sensitivity to atmospheric parameters. Using rigorous direct modeling of the reflected radiance and developed inversion algorithm, we performed an analysis of BRDF errors, typical for measurements. It shows that the BRDF shape distortions due to diffuse irradiance are considerable in the visible and near-IR, even for low aerosol content in the atmosphere. This result confirms that an accurate atmospheric correction should be a required processing step in the experimental research of anisotropic surface reflectance. C1 NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lyapustin, AI (reprint author), NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Mail Code 920, Greenbelt, MD 20771 USA. EM alyapust@pop900.gsfc.nasa.gov RI Privette, Jeffrey/G-7807-2011; Lyapustin, Alexei/H-9924-2014 OI Privette, Jeffrey/0000-0001-8267-9894; Lyapustin, Alexei/0000-0003-1105-5739 NR 30 TC 18 Z9 18 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 MAR 27 PY 1999 VL 104 IS D6 BP 6257 EP 6268 DI 10.1029/1998JD200123 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700020 ER PT J AU Hsu, NC Herman, JR Torres, O Holben, BN Tanre, D Eck, TF Smirnov, A Chatenet, B Lavenu, F AF Hsu, NC Herman, JR Torres, O Holben, BN Tanre, D Eck, TF Smirnov, A Chatenet, B Lavenu, F TI Comparisons of the TOMS aerosol index with Sun-photometer aerosol optical thickness: Results and applications SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE; DISTRIBUTIONS; BASIN; AIR AB A nearly 20-year global data set (1979-1994 and 1996 to the present) of tropospheric absorbing aerosols has been developed from total ozone mapping spectrometer (TOMS) backscattered radiance measurements in the range from 331 to 380 nm. The occurrence of aerosols is derived directly from measured backscattered radiances and is represented by a quantity known as the aerosol index. Previous theoretical model simulations have demonstrated that the aerosol index depends on aerosol optical thickness (AOT), single scattering albedo, and aerosol height and that the AOT can be determined provided that the microphysical properties and height of aerosols are known. In this paper we show that the TOMS aerosol index measurements are linearly proportional to the AOT derived independently from ground-based Sun-photometer instruments over regions of biomass burning and regions covered by African dust. We also show how this linear relationship can be used to directly convert the aerosol index into AOT for smoke and dust aerosols for the regions near the Sun-photometer sites and how information about aerosol height can be inferred from the results. Finally, we apply this method to the TOMS data over the last two decades and find a significant increase in the amount of biomass burning smoke in the African savanna regions during the 1990s in addition to the more obvious increase in South America. C1 Raytheon STX, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Sci & Technol Lille, Opt Atmospher Lab, F-59655 Villeneuve Dascq, France. Sci Syst & Applicat Inc, Lanham, MD USA. Univ Paris 07, Lab Interuniv Syst Atmospher, Creteil, France. Univ Paris 11, Lab Interuniv Syst Atmospher, Creteil, France. Ctr Etud Spatiales Biosphere, F-31401 Toulouse 04, France. RP Hsu, NC (reprint author), Raytheon STX, 4500 Forbes Blvd, Lanham, MD 20706 USA. EM herman@tparty.gsfc.nasa.gov; torres@qhearts.gsfc.nasa.gov; brent@spamer.gsfc.nasa.gov; didier.tanre@univ-lille1.fr; teck@ltpmail.gsfc.nasa.gov; asmirnov@spamer.gsfc.nasa.gov RI Smirnov, Alexander/C-2121-2009; ECK, THOMAS/D-7407-2012; Hsu, N. Christina/H-3420-2013; Torres, Omar/G-4929-2013; OI Smirnov, Alexander/0000-0002-8208-1304; Herman, Jay/0000-0002-9146-1632 NR 23 TC 192 Z9 197 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 MAR 27 PY 1999 VL 104 IS D6 BP 6269 EP 6279 DI 10.1029/1998JD200086 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700021 ER PT J AU Harvey, VL Hitchman, MH Pierce, RB Fairlie, TD AF Harvey, VL Hitchman, MH Pierce, RB Fairlie, TD TI Tropical aerosol in the Aleutian High SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; PINATUBO VOLCANIC AEROSOL; STRATOSPHERIC-AEROSOL; POLAR VORTEX; MIDDLE LATITUDES; II MEASUREMENTS; MOUNT-PINATUBO; WAVE BREAKING; OZONE LAMINAE; LIFE-CYCLE AB Stratospheric aerosol profiles at high northern latitudes from the Stratospheric Aerosol Measurement (SAM) II experiment are used to document the aerosol maxima that occur in the major wintertime anticyclones. Fourteen years (1978-1991) of 1 mu m extinction are used to calculate median values for each season in bins of 5 degrees latitude by 30 degrees longitude by 1 km altitude. Longitude-altitude sections of estimated surface area density show that tropical, aerosol rich air tends to accumulate in the Aleutian High from 15 to above 30 km, and in the North Atlantic High in the 15-25 km layer. A trajectory case study with winds from the European Center for Medium-Range Weather Forecasting is used to investigate the hypothesis that the observed aerosol maxima are maintained by episodic poleward surges of high aerosol air from the tropical stratospheric reservoir. Lagrangian trajectories are initialized and run backward in time, from both a high-resolution grid and SAM II occultations, for selected days when high aerosol is found in the Aleutian High. Results show that during the case study provided, a deep sheet of aerosol rich air originating over Africa is advected poleward and eastward around the polar vortex and entrained into the Aleutian High. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Wisconsin, Dept Atmospher & Ocean Sci, Madison, WI 53706 USA. Sci & Technol Corp, Hampton, VA 23666 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. RP Harvey, VL (reprint author), NASA, Langley Res Ctr, MS401B, Hampton, VA 23681 USA. EM v.l.harvey@larc.nasa.gov RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 70 TC 21 Z9 21 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 MAR 27 PY 1999 VL 104 IS D6 BP 6281 EP 6290 DI 10.1029/1998JD200094 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 180AY UT WOS:000079363700022 ER PT J AU Carlson, RW Anderson, MS Johnson, RE Smythe, WD Hendrix, AR Barth, CA Soderblom, LA Hansen, GB McCord, TB Dalton, JB Clark, RN Shirley, JH Ocampo, AC Matson, DL AF Carlson, RW Anderson, MS Johnson, RE Smythe, WD Hendrix, AR Barth, CA Soderblom, LA Hansen, GB McCord, TB Dalton, JB Clark, RN Shirley, JH Ocampo, AC Matson, DL TI Hydrogen peroxide on the surface of Europa SO SCIENCE LA English DT Article ID SPECTROMETER EXPERIMENT; INFRARED SPECTROSCOPY; GALILEAN SATELLITES; OPTICAL-CONSTANTS; ULTRAVIOLET; ATMOSPHERE; JUPITER; ICES AB Spatially resolved infrared and ultraviolet wavelength spectra of Europa's Leading, anti-jovian quadrant observed from the Galileo spacecraft show absorption features resulting from hydrogen peroxide. Comparisons with laboratory measurements indicate surface hydrogen peroxide concentrations of about 0.13 percent, by number, relative to water ice. The inferred abundance is consistent with radiolytic production of hydrogen peroxide by intense energetic particle bombardment and demonstrates that Europa's surface chemistry is dominated by radiolysis. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Virginia, Charlottesville, VA 22903 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. US Geol Survey, Flagstaff, AZ 86001 USA. Univ Hawaii, Planetary Geosci Div, Honolulu, HI 96822 USA. US Geol Survey, Denver, CO 80225 USA. RP Carlson, RW (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-601,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM rcarlson@lively.jpl.nasa.gov NR 38 TC 177 Z9 180 U1 3 U2 29 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD MAR 26 PY 1999 VL 283 IS 5410 BP 2062 EP 2064 DI 10.1126/science.283.5410.2062 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 180DH UT WOS:000079369800039 PM 10092224 ER PT J AU Bhatt, HD Vedula, R Desu, SB Fralick, GC AF Bhatt, HD Vedula, R Desu, SB Fralick, GC TI Thin film TiC/TaC thermocouples SO THIN SOLID FILMS LA English DT Article DE thin film thermocouples; seebeck coefficient; carbides; titanium carbide ID TEMPERATURE SENSORS AB TiC and TaC thin films were investigated, for the first time, for thin film thermocouple applications. Thin films of TaC and TiC were deposited on electronic grade alumina substrates using the r.f. sputter deposition technique. Sheet resistance of the thin films was measured using a four point probe. It was observed that the sheet resistance of the films depends critically on the deposition parameters such as substrate temperature during deposition, sputter gas pressure and r.f. power used. The deposition parameters were optimized to yield the lowest sheet resistance of the thin films at room temperature. The thermoemf of the deposited films was measured as a function of temperature in a vacuum using a home made device. It was observed that thin films of TaC and TiC yield fairly high and stable thermoemf throughout the temperature range of stability. Under the optimized deposition conditions, thin film thermocouples were fabricated. The thermocouples were calibrated against temperature and the output was measured in vacuum (pressure < 10(-6) Torr). TiC/TaC thermocouples yield stable output up to 1350 K, temperatures above which breakdown occurs. The thermocouple output was theoretically estimated from the thermoemf measured, and compared. It was observed that these thermocouples yield reproducible output in the temperature range of stability and hold excellent potential for high temperature thin film temperature sensor applications in vacuum or inert atmospheres. (C) 1999 Elsevier Science S.A. All rights reserved. C1 Virginia Tech, Dept Mat Sci & Engn, Blacksburg, VA 24061 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Vedula, R (reprint author), Virginia Tech, Dept Mat Sci & Engn, 213 Holden Hall, Blacksburg, VA 24061 USA. NR 27 TC 23 Z9 24 U1 0 U2 13 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD MAR 26 PY 1999 VL 342 IS 1-2 BP 214 EP 220 DI 10.1016/S0040-6090(98)00963-8 PG 7 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 190TR UT WOS:000079981500035 ER PT J AU Mitchell, BE Lele, SK Moin, P AF Mitchell, BE Lele, SK Moin, P TI Direct computation of the sound generated by vortex pairing in an axisymmetric jet SO JOURNAL OF FLUID MECHANICS LA English DT Article ID LOW-MACH-NUMBER; AERODYNAMIC SOUND; BOUNDARY-CONDITIONS; INSTABILITY WAVES; RADIATED SOUND; SUPERSONIC JET; NOISE; LAYER; FIELD AB The sound generated by vortex pairing in axisymmetric jets is determined by direct solution of the compressible Navier-Stokes equations on a computational grid that includes both the near field and a portion of the acoustic far field. At low Mach number, the far-field sound has distinct angles of extinction in the range of 60 degrees-70 degrees from the jet's downstream axis which can be understood by analogy to axisymmetric, compact quadrupoles. As the Mach number is increased, the far-field sound takes on a superdirective character with the dominant sound directed at shallow angles to the jet's downstream axis. The directly computed sound is compared to predictions obtained from Lighthill's equation and the Kirchhoff surface method. These predictions are in good agreement with the directly computed data. The Lighthill source terms have a large spatial distribution in the axial direction necessitating the introduction of a model to describe the source terms in the region downstream of the last vortex pairing. The axial non-compactness of the quadrupole sources must be adequately treated in the prediction method. C1 Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA. Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Mitchell, BE (reprint author), GE Co, Corp Res & Dev, POB 8, Schenectady, NY 12301 USA. NR 48 TC 66 Z9 71 U1 2 U2 6 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 EI 1469-7645 J9 J FLUID MECH JI J. Fluid Mech. PD MAR 25 PY 1999 VL 383 BP 113 EP 142 DI 10.1017/S0022112099003869 PG 30 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 187BC UT WOS:000079765300005 ER PT J AU Zaman, KBMQ AF Zaman, KBMQ TI Spreading characteristics of compressible jets from nozzles of various geometries SO JOURNAL OF FLUID MECHANICS LA English DT Article ID STREAMWISE VORTICITY; RECTANGULAR JETS; NEAR-FIELD; ROUND JET; ENTRAINMENT; ENHANCEMENT; EVOLUTION; DYNAMICS; FLOWS; TABS AB The spreading characteristics of jets from several asymmetric nozzles, and a set of rectangular orifices are compared, covering a jet Mach number range of 0.3-2.0. The effect of 'tabs' for a rectangular and a round nozzle is also included in the comparison. Compared to a round jet, the jets from the asymmetric nozzles spread only slightly more at subsonic conditions whereas at supersonic conditions, when 'screech' occurs, they spread much more. The dynamics of the azimuthal vortical structures of the jet, organized and intensified under the screeching condition, are thought to be responsible for the observed effect at supersonic conditions. Curiously, the jet from a 'lobed' nozzle spreads much less at supersonic condition compared to all other cases; this is due to the absence of screech with this nozzle. Screech stages inducing flapping, rather than varicose or helical, flow oscillation cause a more pronounced jet spreading. At subsonic conditions, only a slight increase in jet spreading with the asymmetric nozzles contrasts previous observations by others. The present results show that the spreading of most asymmetric jets is not much different from that of a round jet. This inference is further supported by data from the rectangular orifices. In fact, jets from the orifices with small aspect ratio (AR) exhibit virtually no increase in the spreading. A noticeable increase commences only when AR is larger than about 10. Thus, 'shear layer perimeter stretching', achieved with a larger AR for a given cross-sectional area of the orifice, by itself, proves to be a relatively inefficient mechanism for increasing jet spreading. In contrast, the presence of streamwise vortices or 'natural excitation' can cause a significant increase - effects that might explain the observations in the previous investigations. Thus far, the biggest increase in jet spreading is observed with the tabs. This is true in the subsonic regime, as well as in the supersonic regime, in spite of the fact that screech is eliminated by the tabs. The characteristic spreading of the tabbed jets is explained by the induced motion of the tab-generated streamwise vortex pairs. The tabs, however, incur thrust loss; the flow blockage and loss in thrust coefficient, vis-a-vis the spreading increase, are evaluated for various configurations. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Zaman, KBMQ (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 49 TC 104 Z9 108 U1 2 U2 18 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD MAR 25 PY 1999 VL 383 BP 197 EP 228 DI 10.1017/S0022112099003833 PG 32 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 187BC UT WOS:000079765300008 ER PT J AU Arkani-Hamed, J Konopliv, AS Sjogren, WL AF Arkani-Hamed, J Konopliv, AS Sjogren, WL TI On the equipotential surface hypothesis of lunar maria floors SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID BASINS; CLEMENTINE; TECTONICS; MOON AB The equipotential surface hypothesis suggests that lunar maria floors lie on a surface parallel to the selenoid. This is examined using the spherical harmonic representations of the Clementine topography and Lunar Prospector gravity data. It is demonstrated that the floors of both circular and noncircular maria significantly deviate from an equipotential surface. Deeper circular maria and the deeper part of the noncircular Mare Tranquillitatis have been subsided under larger mass loads in the crust. We calculate the mass beneath the maria to be in excess to the mass required for isostatic compensation of the topography at 60 km depth. A global map of this excess mass shows that the noncircular maria are isostatically compensated, unlike the circular maria. The map also reveals seven new sizable mascons: the three largest are associated with Mendel-Rydberg, Mare Humboldtianum, and Mare Moscoviense. C1 McGill Univ, Montreal, PQ H3A 2A7, Canada. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Arkani-Hamed, J (reprint author), McGill Univ, 3450 Univ St, Montreal, PQ H3A 2A7, Canada. NR 37 TC 5 Z9 5 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAR 25 PY 1999 VL 104 IS E3 BP 5921 EP 5931 DI 10.1029/1998JE900045 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 181YF UT WOS:000079470500003 ER PT J AU Krasnopolsky, VA AF Krasnopolsky, VA TI Hydrodynamic flow of N(2) from Pluto SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID PLANETARY-ATMOSPHERES; THERMAL STRUCTURE; OCCULTATION DATA; METHANE; MODEL; TRITON; THERMOSPHERE; TEMPERATURE; VENUS AB A new method of analytic solution for the equation of hydrodynamic flow from an atmosphere has been developed. This method conserves a term neglected in the equation for the McNutt [1989] approximation and significantly improves uncertainty of the solution. Structure of Pluto's upper atmosphere near perihelion was calculated by this method at various solar activity and at various methane mixing ratios. Both the UV absorption by CH(4) at 1000-1400 Angstrom and the EUV absorption by N(2) heat the upper atmosphere with the global-mean rates of 1.4x10(-3) and 2.9x10(-4) ergs cm(-2) s(-1), respectively, at mean solar activity. Hydrodynamic outflow of N(2) from Pluto at perihelion is equal to (2.0-2.6)x10(27) s(-1) at mean solar activity and varies by a factor of 3-4 from solar minimum to solar maximum. The exobase lies below the sonic level. Pluto's atmosphere does not completely fit both the conditions of static and hydrodynamically escaping atmospheres and is an intermediate case of a slow hydrodynamic escape. The total loss for the age of the solar system corresponds to an ice layer that is 500 m thick and 5x10(-4) of Pluto's mass. Pluto's atmosphere is restricted to 3000-4500 km, which makes possible a close flyby of future spacecraft. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RP Krasnopolsky, VA (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 690-2, Greenbelt, MD 20771 USA. EM vkras@lepvx3.gsfc.nasa.gov RI Krasnopolsky, Vladimir/L-5085-2013 NR 32 TC 46 Z9 46 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAR 25 PY 1999 VL 104 IS E3 BP 5955 EP 5962 DI 10.1029/1998JE900052 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 181YF UT WOS:000079470500006 ER PT J AU Ricca, A AF Ricca, A TI Heats of formation for CF(n) (n = 1-4), CF(n)(+) (n = 1-4), and CF(n)(-) (n = 1-3) SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID COUPLED-CLUSTER THEORY; GAUSSIAN-BASIS SETS; ATOMIZATION ENERGIES; ELECTRON CORRELATION; WAVE-FUNCTIONS; MOLECULES; AFFINITY AB Accurate heats of formation are computed for CF(n) (n = 1-4), CF(n)(+) (n = 1-4), and CF(n)(-) (n = 1-3). The geometries and vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Basis set limit values are obtained by extrapolation. In those cases where the CCSD(T) calculations become prohibitively large, the basis set extrapolation is performed at the MP2 level. The temperature dependence of the heat of Formation, heat capacity, and entropy are computed for the temperature range 300-4000 K and fit to a polynomial. C1 NASA, Thermosci Inst, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ricca, A (reprint author), NASA, Thermosci Inst, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. EM ricca@pegasus.arc.nasa.gov NR 32 TC 20 Z9 20 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD MAR 25 PY 1999 VL 103 IS 12 BP 1876 EP 1879 DI 10.1021/jp9843555 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 182JV UT WOS:000079496600026 ER PT J AU Alvarez-Salazar, OS Iliff, K AF Alvarez-Salazar, OS Iliff, K TI Destabilizing effects of rate feedback on strain actuated beams SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID VIBRATION CONTROL AB The stabilizing and destabilizing effects of rate feedback control on all modes of a strain actuated beam are demonstrated here to support earlier theoretical findings by Balakrishnan [1] (1999 Journal of Computational and Applied Mathematics 18). The destabilizing effects being due to the actual implementation of the rate feedback controller which is unavoidably non-ideal. The main contribution here is the inclusion of the controller circuit model in the closed loop system equations to obtain correct stability estimates for all modes. Closed loop stability estimates computed from this circuitry enhanced model were corroborated by experiments. The strain actuated beam constructed for this work was made with a fiber glass lay-up and piezo ceramic wafers embedded throughout the length of the lay-up. A charge-to-voltage amplifier, a differentiator, a gain stage, and a power amplifier were also constructed. The most crucial of these components was the differentiator and its tank frequency. The first four modes and transmission zero frequencies, and the corresponding structural damping were obtained through open loop experiments. Mode estimates were within 5% of the computed values. Zero estimates were less accurate due to electric feedthrough, but modelling of this effect helped to improve zero frequency estimates. Closed loop experiments were run to demonstrate the destabilization of beam modes with frequencies higher than the differentiator's tank frequency. (C) 1999 Academic Press. C1 Univ Calif Los Angeles, Flight Syst Res Ctr, Los Angeles, CA 90095 USA. NASA, Dryden Flight Res Ctr, Edwards, CA 93523 USA. RP Alvarez-Salazar, OS (reprint author), Univ Calif Los Angeles, Flight Syst Res Ctr, MC 951594, Los Angeles, CA 90095 USA. NR 8 TC 0 Z9 0 U1 0 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD MAR 25 PY 1999 VL 221 IS 2 BP 289 EP 307 DI 10.1006/jsvi.1998.2010 PG 19 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 177KN UT WOS:000079209300007 ER PT J AU Kazeminezhad, F Schatten, K AF Kazeminezhad, F Schatten, K TI A particle model of coronal heating via recombination SO PHYSICS LETTERS A LA English DT Article DE corona and transition region; numerical simulation studies; waves and instabilities ID ACCELERATION; SIMULATION; PLASMAS AB We model coronal heating via recombination using a "Particle-MHD" model. In the model we follow the trajectories of particles in self-consistent fields under the influence of the Maxwell stresses and pressure gradients. Fluid properties are derived from the moments of the ion particle distributions. For the recombination process, the electron velocity moments determined from the model are compared against ion velocities. We observe that as ions recombine and exit the plasma, the remaining ions can tap greater energy from the fields generated by recombination, and undergo heating. In the described numerical experiments, ions undergoing recombination are introduced to an unperturbed box of ions which were not affected by recombination. It is observed that: (a) recombination serves as a seed in heating the plasma particles: (b) enhanced field fluctuations can cause ion heating in a feedback mechanism; and (c) the longer the elongation of the simulation box, the greater the resulting overall heating of the particles. (C) 1999 Published by Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Nomad Res Inc, Goddard Space Flight Ctr, Greenbelt, MD USA. RP Kazeminezhad, F (reprint author), Inst Studies Theoret Phys & Math, POB 19395-5531,Farmanieh Blvd, Tehran, Iran. NR 11 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9601 J9 PHYS LETT A JI Phys. Lett. A PD MAR 22 PY 1999 VL 253 IS 3-4 BP 192 EP 198 DI 10.1016/S0375-9601(98)00945-1 PG 7 WC Physics, Multidisciplinary SC Physics GA 178VT UT WOS:000079290400013 ER PT J AU Voorhies, CV AF Voorhies, CV TI Inner core rotation from geomagnetic westward drift and a stationary spherical vortex in Earth's core SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Article DE inner core rotation; geomagnetic westward drift; stationary spherical vortex ID DIFFERENTIAL ROTATION; FLOW; VISCOSITY; MANTLE AB The idea. that geomagnetic westward drift indicates convective leveling of the planetary momentum gradient within Earth's core is pursued in search of a differentially rotating mean state, upon which various oscillations and secular effects might be superimposed. The desired state conforms to roughly spherical boundary conditions, minimizes dissipative interference with convective cooling in the bulk of the core, yet may aid core cooling by depositing heat in the uppermost core and lower mantle. The variational calculus of stationary dissipation applied to a spherical vortex within the core yields an interesting differential rotation profile, akin to spherical Couette now bounded by thin Hartmann layers. Four boundary conditions are required. To concentrate shear induced dissipation near the core-mantle boundary, these are taken to be: (i) no-slip at the core-mantle interface; (ii) geomagnetically estimated bulk westward flow at the base of the core-mantle boundary layer; (iii) no-slip at the inner-outer core interface; and, to describe magnetic locking of the inner core to the deep outer core, (iv) hydrodynamically stress-free at the inner-outer core boundary. By boldly assuming the axial core angular momentum anomaly to be zero, the super-rotation of the inner core relative to the mantle is calculated to be at most 1.5 degrees/year. Published by Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP Voorhies, CV (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. RI Voorhies, Coerte/D-4672-2012 NR 26 TC 3 Z9 6 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-9201 J9 PHYS EARTH PLANET IN JI Phys. Earth Planet. Inter. PD MAR 22 PY 1999 VL 112 IS 1-2 BP 111 EP 123 DI 10.1016/S0031-9201(98)00180-0 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 175TJ UT WOS:000079111100008 ER PT J AU Bada, JL Glavin, DP Kminek, G Becker, L Farouhar, S Grunthaner, F McDonald, G Webster, CR May, R Mathies, R AF Bada, JL Glavin, DP Kminek, G Becker, L Farouhar, S Grunthaner, F McDonald, G Webster, CR May, R Mathies, R TI MOD: An in situ organic detector for the future robotic exploration of Mars. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Calif San Diego, La Jolla, CA 92093 USA. Univ Hawaii, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Glavin, Daniel/D-6194-2012 OI Glavin, Daniel/0000-0001-7779-7765 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 071-GEOC BP U845 EP U845 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102640 ER PT J AU Cox, BL Sun, H Nealson, KH Beard, BL Johnson, CM AF Cox, BL Sun, H Nealson, KH Beard, BL Johnson, CM TI Iron isotope fractionation by the bacterium Shewanella during dissimilatory reductive dissolution of ferrihydrite. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wisconsin, Madison, WI 53706 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 068-GEOC BP U844 EP U844 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102637 ER PT J AU Dateo, CE Walch, SP AF Dateo, CE Walch, SP TI Gas-phase reaction rates for thermal CVD processes. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 190-PHYS BP U333 EP U333 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148200993 ER PT J AU Delin, KA Jackson, SP Some, RR AF Delin, KA Jackson, SP Some, RR TI Sensor web instrument for astrobiological applications. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 073-GEOC BP U845 EP U845 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102642 ER PT J AU Geiger, CL Clausen, CA Reinhart, DR Toy, P Ruiz, N Chan, N Quinn, J AF Geiger, CL Clausen, CA Reinhart, DR Toy, P Ruiz, N Chan, N Quinn, J TI Using ultrasound to examine the sorptive characteristics of different zero-valent iron surfaces. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Kennedy Space Ctr, FL 32899 USA. Geosyntec, Anaheim, CA 92648 USA. Univ Cent Florida, Dept Chem, Orlando, FL 32816 USA. Univ Cent Florida, Dept Civil & Environm Engn, Orlando, FL 32816 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 166-ENVR BP U763 EP U763 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102375 ER PT J AU Hutt, LD Mathies, RA Grunthaner, F Bada, JL AF Hutt, LD Mathies, RA Grunthaner, F Bada, JL TI Microfabricated capillary electrophoresis chips for in situ analyses on Mars. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif San Diego, La Jolla, CA 92093 USA. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 072-GEOC BP U845 EP U845 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102641 ER PT J AU Hynes, SF Davis, WL McKay, CP AF Hynes, SF Davis, WL McKay, CP TI Remote sensing of organic materials in Martian soil. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NW State Univ Louisiana, SETI INst, Natchitoches, LA 71457 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 070-GEOC BP U844 EP U845 PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102639 ER PT J AU Kiefer, RL Orwoll, RA Harrison, JE Ronesi, VM Thibeault, SA AF Kiefer, RL Orwoll, RA Harrison, JE Ronesi, VM Thibeault, SA TI The effects of the space environment on polyetherimide films. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Environm Interact Branch, Hampton, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 114-POLY BP U548 EP U549 PN 2 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148201697 ER PT J AU McDonald, GD Storrie-Lombardi, MC Nealson, KH AF McDonald, GD Storrie-Lombardi, MC Nealson, KH TI Principal component analysis for biosignature detection in extraterrestrial samples. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 1 Z9 1 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 074-GEOC BP U846 EP U846 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102643 ER PT J AU Nguyen, CV Beyers, RB Hawker, CJ Hedrick, JL Jaffe, RL Miller, RD Remenar, JF Rhee, HW Toney, MF Trollsas, M Yoon, DY AF Nguyen, CV Beyers, RB Hawker, CJ Hedrick, JL Jaffe, RL Miller, RD Remenar, JF Rhee, HW Toney, MF Trollsas, M Yoon, DY TI Structure-property relationships for nano-porous poly(methyl silsesquioxane) films with low-dielectric constants prepared via organic/inorganic polymer hybrids. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 IBM Corp, Almaden Res Ctr, Armonk, NY 10504 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Hawker, Craig/G-4971-2011 OI Hawker, Craig/0000-0001-9951-851X NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 027-POLY BP U524 EP U524 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148201610 ER PT J AU Pecher, K Kneedler, EM Tonner, BP AF Pecher, K Kneedler, EM Tonner, BP TI Identification and characterization of iron surfaces capable of reductive transformation of pollutants using synchrotron X-ray absorption spectroscopy techniques. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Cent Florida, Dept Phys, Orlando, FL 32816 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 077-ENVR BP U737 EP U738 PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102288 ER PT J AU Schulte, MD AF Schulte, MD TI Experimental investigation of organic compound stability under hydrothermal conditions. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 070-FUEL BP U816 EP U816 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102547 ER PT J AU Southward, RE Warren, AS Thompson, DW St Clair, AK AF Southward, RE Warren, AS Thompson, DW St Clair, AK TI Silvered polyimide films for space applications via a single stage synthesis. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 006-POLY BP U517 EP U517 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148201589 ER PT J AU Southward, RE St Clair, AK Boggs, CM Thompson, DW AF Southward, RE St Clair, AK Boggs, CM Thompson, DW TI Fabrication of reflective and conductive silvered polyimide films via in situ silver(I) reduction: Ligand/anion effects. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 032-PMSE BP U400 EP U400 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148201199 ER PT J AU Storrie-Lombardi, MC Tsapin, AI McDonald, GD Sun, H Nealson, KH AF Storrie-Lombardi, MC Tsapin, AI McDonald, GD Sun, H Nealson, KH TI Ultraviolet Raman spectroscopy for in situ geobiological exploration of Mars. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 069-GEOC BP U844 EP U844 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148102638 ER PT J AU Tardy, DC Thorn, RP Payne, WA Stief, LJ Nesbitt, FL AF Tardy, DC Thorn, RP Payne, WA Stief, LJ Nesbitt, FL TI Determining critical energies for unimolecular reactions: The decompositions of C2H4F radicals and cyclobutene. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Univ Iowa, Dept Chem, Iowa City, IA 52242 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Coppin State Coll, Dept Nat Sci, Baltimore, MD 21216 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 349-PHYS BP U381 EP U381 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148201152 ER PT J AU Ticich, TM West, JR Vander Wal, RL AF Ticich, TM West, JR Vander Wal, RL TI Laser-induced incandescence applied to metal nanostructures. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 USA. NASA, Lewis Res Ctr, NCMR, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 284-PHYS BP U362 EP U362 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148201087 ER PT J AU Walch, SP Dateo, CE AF Walch, SP Dateo, CE TI Computed gas-phase rate coefficients for thermal decomposition of CVD precursors. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 324-PHYS BP U374 EP U374 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 176JP UT WOS:000079148201127 ER PT J AU West, JR Ticich, TM Wal, RLV Householder, PA AF West, JR Ticich, TM Wal, RLV Householder, PA TI Trace metal detection by laser-induced breakdown spectroscopy. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 USA. NASA, Lewis Res Ctr, NCMR, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD MAR 21 PY 1999 VL 217 MA 576-CHED BP U472 EP U473 PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA 176JN UT WOS:000079148101420 ER PT J AU Keenan, FP Aller, LH Bell, KL Crawford, FL Feibelman, WA Hyung, S McKenna, FC McLaughlin, BM AF Keenan, FP Aller, LH Bell, KL Crawford, FL Feibelman, WA Hyung, S McKenna, FC McLaughlin, BM TI Emission lines of [O II] in the optical and ultraviolet spectra of planetary nebulae SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE atomic data; planetary nebulae : general; ultraviolet : ISM ID BRIGHT RING REGION; EXCITATION; STRENGTHS; NGC-7009; OXYGEN; AXIS AB Recent R-matrix calculations of electron impact excitation rates in O II are used to calculate the emission-line ratio-ratio diagrams (R-1, R-2), (R-1, R-3) and (R-1, R-4) where R-1 = I(3729 Angstrom)/ I(3726 Angstrom), R-2 = I(7320 Angstrom)/I(3726 + 3729 Angstrom), R-3 = I(7330 Angstrom)/I(3726 + 3729 Angstrom) and R-4 = I(2470 Angstrom)/I(3726 + 3729 Angstrom), for a range of electron temperatures (T-e = 7500-20 000 K) and electron densities (N-e = 10(1.5)-10(5) cm(-3)) appropriate to planetary nebulae. These diagrams should, in principle, allow the simultaneous determination of T-e and N-e from measurements of the [O II] emission lines in a spectrum. Plasma parameters deduced for a sample of planetary nebulae, using observational data obtained with the IUE satellite and the Hamilton Echelle spectrograph on the 3-m Shane Telescope at the Lick Observatory, are found to show excellent internal consistency, and to be in generally good agreement with the values of T-e and N-e estimated from other line ratios in the echelle spectra. These results provide observational support for the accuracy of the theoretical ratios, and hence the atomic data adopted in their derivation. C1 Queens Univ Belfast, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90095 USA. Queens Univ Belfast, Dept Appl Math & Theoret Phys, Belfast BT7 1NN, Antrim, North Ireland. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. BohyunSan Observ, KyungPook 770820, South Korea. RP Keenan, FP (reprint author), Queens Univ Belfast, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland. NR 36 TC 30 Z9 30 U1 1 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAR 21 PY 1999 VL 304 IS 1 BP 27 EP 34 DI 10.1046/j.1365-8711.1999.02275.x PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 182TA UT WOS:000079513200008 ER PT J AU Lawson, PR Scott, TR Haniff, CA AF Lawson, PR Scott, TR Haniff, CA TI Group-delay tracking and visibility fluctuations in long-baseline stellar interferometry SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE instrumentation : interferometers; methods : observational; techniques : interferometric AB We investigate the limitations of group-delay fringe tracking for stellar interferometry in the presence of realistic fluctuations of the fringe visibility amplitude. These fluctuations can be considered as introducing an additional source of noise beyond those attributable to counting statistics and detector readout, and lead to a significant increase in the probability of tracking failure compared with previous studies. We show that even for relatively bright targets, the probability of tracking loss can remain very high (> 0.5) unless the seeing conditions are favourable. C1 Cavendish Lab, Mullard Radio Astron Observ, Cambridge CB3 0HE, England. Inst Astron, Cambridge CB3 0HA, England. RP Lawson, PR (reprint author), Jet Prop Lab, 4800 Oak Grove Dr,MS 306-388, Pasadena, CA 91109 USA. NR 13 TC 5 Z9 5 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAR 21 PY 1999 VL 304 IS 1 BP 218 EP 224 DI 10.1046/j.1365-8711.1999.02312.x PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 182TA UT WOS:000079513200027 ER PT J AU Vander Wal, RL Ticich, TM AF Vander Wal, RL Ticich, TM TI Cavity ringdown and laser-induced incandescence measurements of soot SO APPLIED OPTICS LA English DT Article; Proceedings Paper CT Optical-Society-of-America Topical Meeting on Laser Applications to Chemical and Environmental Analysis CY MAR 09-11, 1998 CL ORLANDO, FL SP Opt Soc Amer ID ETHYLENE DIFFUSION FLAMES; VOLUME FRACTION; ABSORPTION SPECTROSCOPY; FLICKERING METHANE; MORPHOLOGY; PARTICLES; HISTORY; LII AB Currently laser-induced incandescence (LII) is widely used for the measurement of soot volume fraction. A particularly important aspect of the technique that has received less attention, however, is calibration. The applicability of cavity ringdown (CRD) for measurement of soot volume fraction f(v) is assessed, and the calibration of LII by means of CRD is demonstrated. The accuracy of CRD for f(v) determination is validated by comparison with traditional light extinction and path-integrated LII. By use of CRD, the quantification of LII for parts in 10(9) (ppb) f(v) levels is demonstrated. Results are presented that demonstrate the accuracy of CRD for a single laser pulse to be better than +/-5% for measurement of ppb soot volume-fraction levels over a 1-cm path length. By use of CRD, spatially resolved LII signals from soot within methane-air diffusion flames are calibrated for ppb f(v) levels, thereby avoiding the extrapolation required of less sensitive methods in current use. C1 NASA, Natl Ctr Micrograv Res, Lewis Res Ctr, Cleveland, OH 44135 USA. Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 USA. RP Vander Wal, RL (reprint author), NASA, Natl Ctr Micrograv Res, Lewis Res Ctr, MS 110-3,21000 Brookpark Rd, Cleveland, OH 44135 USA. EM randy@rvander.lerc.nasa.gov; tticich@centenary.edu NR 34 TC 44 Z9 44 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD MAR 20 PY 1999 VL 38 IS 9 BP 1444 EP 1451 DI 10.1364/AO.38.001444 PG 8 WC Optics SC Optics GA 175VT UT WOS:000079116900007 PM 18305765 ER PT J AU Mishchenko, MI Macke, A AF Mishchenko, MI Macke, A TI How big should hexagonal ice crystals be to produce halos? SO APPLIED OPTICS LA English DT Article ID CIRRUS CLOUD; LIGHT-SCATTERING; MICROPHYSICAL PROPERTIES; RADIATIVE PROPERTIES; INFRARED RADIANCES; SINGLE-SCATTERING; PARTICLES; PHASE; REFLECTANCE; INFERENCE AB It has been hypothesized that the frequent lack of halos in observations of cirrus and contrails and laboratory measurements is caused by small ice crystal sizes that put the particles outside the geometrical optics domain of size parameters. We test this hypothesis by exploiting a strong similarity of ray tracing phase functions for finite hexagonal and circular ice cylinders and using T-matrix computations of electromagnetic scattering by circular cylinders with size parameters up to 180 in the visible. We conclude that well-defined halos should be observable for ice crystal size parameters of the order of 100 and larger and discuss remote-sensing implications of this result. (C) 1999 Optical Society of America. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Inst Meereskunde, Abt Maritime Meteorol, D-24105 Kiel, Germany. RP Mishchenko, MI (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM crmim@giss.nasa.gov RI Mishchenko, Michael/D-4426-2012 NR 37 TC 48 Z9 48 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 MAR 20 PY 1999 VL 38 IS 9 BP 1626 EP 1629 DI 10.1364/AO.38.001626 PG 4 WC Optics SC Optics GA 175VT UT WOS:000079116900022 PM 18305781 ER PT J AU Hoge, FE Lyon, PE AF Hoge, FE Lyon, PE TI Spectral parameters of inherent optical property models: method for satellite retrieval by matrix inversion of an oceanic radiance model SO APPLIED OPTICS LA English DT Article AB Inherent optical property (IOP) spectral models for the phytoplankton absorption coefficient, chromophoric dissolved organic matter (CDOM) absorption coefficient, and total constituent backscattering (TCB) coefficient are linear in the reference wavelength IOP and nonlinear in the spectral parameters. For example, the CDOM absorption coefficient IOP a(CDOM)(lambda(t)) = a(CDOM)(lambda(ref))exp[-S(lambda(i) - lambda(ref))] is linear in a(CDOM)(lambda(ref)) and nonlinear in S. Upon linearization by Taylor's series expansion, it is shown that spectral model parameters, such as S, can be concurrently accommodated within the same conventional Linear matrix formalism used to retrieve the reference wavelength IOP's. Iteration is used to adjust for errors caused by truncation of the Taylor's series expansion. Employing an iterative linear matrix inversion of a water-leaving radiance model, computer simulations using synthetic data suggest that (a) no instabilities or singularities are introduced by the linearization and subsequent matrix inversion procedures, (b) convergence to the correct value can be expected only if starting values for a model parameter are within certain specific ranges, (c) accurate retrievals of the CDOM slope S (or the phytoplankton Gaussian width g) are generally reached in 3-20 iterations, (d) iterative retrieval of the exponent n of the TCB wavelength ratio spectral model is not recommended because the starting values must be within similar to +/- 5% of the correct Value to achieve accurate convergence, and (e) concurrent retrieval of S and g (simultaneously with the phytoplankton, CDOM, and TCB coefficient IOP's) can be accomplished in a 5 x 5 iterative matrix inversion if the starting Values for S and g are carefully chosen to be slightly higher than the expected final retrieved values. (C) 1999 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA. EG&G Serv Inc, Wallops Isl, VA 23337 USA. RP Hoge, FE (reprint author), NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA. NR 6 TC 26 Z9 27 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 MAR 20 PY 1999 VL 38 IS 9 BP 1657 EP 1662 DI 10.1364/AO.38.001657 PG 6 WC Optics SC Optics GA 175VT UT WOS:000079116900027 PM 18305786 ER PT J AU Clarke, JT Skinner, WR Vincent, MB Irgang, T Suratkal, V Grassl, H Trauger, JT AF Clarke, JT Skinner, WR Vincent, MB Irgang, T Suratkal, V Grassl, H Trauger, JT TI Laboratory studies of alkali metal filter deposition, ultraviolet transmission, and visible blocking SO APPLIED OPTICS LA English DT Article ID JUPITER; AURORA; WFPC2 AB Far-ultraviolet alkali metal or Wood's filters have been produced and tested supporting the production of a flight filter for the Wide Field Planetary Camera 2 on the Hubble Space Telescope. Sodium layers 0.5-1-mu m thick transmit up to 40% in the ultraviolet while efficiently blocking visible wavelengths. The prevention of visible pinholes is assisted by a clean, sleek-free surface and a cooled substrate during deposition. The coatings are stabilized efficiently by a bismuth overcoating whose transmission spectrum is presented. We also report for the first time, to our knowledge, the first demonstrated long-wavelength cutoff from a lithium filter, with a shorter cutoff wavelength than sodium and potentially higher stability for astronomical imaging. (C) 1999 Optical Society of America. C1 Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Clarke, JT (reprint author), Univ Michigan, Space Phys Res Lab, 2455 Hayward, Ann Arbor, MI 48109 USA. EM clarke@umich.edu RI Clarke, John/C-8644-2013 NR 12 TC 6 Z9 7 U1 0 U2 6 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 MAR 20 PY 1999 VL 38 IS 9 BP 1803 EP 1813 DI 10.1364/AO.38.001803 PG 11 WC Optics SC Optics GA 175VT UT WOS:000079116900052 PM 18305811 ER PT J AU Fletcher, DG AF Fletcher, DG TI Arcjet flow properties determined from laser-induced fluorescence of atomic nitrogen SO APPLIED OPTICS LA English DT Article ID ABSOLUTE AB Flow property measurements that were recently acquired in the Ames Research Center Aerodynamic Heating Facility arcjet using two-photon laser-induced fluorescence (LIF) of atomic nitrogen (N) are reported. The dow properties, which include velocity, translational temperature, and N concentration, were measured simultaneously over a range of facility operating conditions for N-2-argon test gas flows in the 30-cm-diameter nozzle. A recent measurement of the two-photon excitation cross section for the 3p(4)D degrees <-- 2p(4)S degrees transition of atomic nitrogen is used to convert the relative nitrogen concentration measurements to absolute values, and a nitrogen flow reactor is used to provide a room-temperature, reference-wavelength calibration of the translational temperature and velocity measurements. When combined with information from facility measurements, an analysis of the flow properties obtained using two-photon LIF of N yields the total free-stream dow enthalpy. C1 NASA, Reacting Flow Environm Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Fletcher, DG (reprint author), NASA, Reacting Flow Environm Branch, Ames Res Ctr, MS 230-2, Moffett Field, CA 94035 USA. NR 22 TC 14 Z9 14 U1 0 U2 4 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 MAR 20 PY 1999 VL 38 IS 9 BP 1850 EP 1858 DI 10.1364/AO.38.001850 PG 9 WC Optics SC Optics GA 175VT UT WOS:000079116900057 PM 18305816 ER PT J AU Teplitz, HI Malkan, MA McLean, IS AF Teplitz, HI Malkan, MA McLean, IS TI A narrowband imaging search for [O III] emission from galaxies at z > 3 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; galaxies : evolution; infrared : galaxies ID HUBBLE DEEP FIELD; HIGH-REDSHIFT GALAXIES; STAR-FORMATION; LY-ALPHA; LUMINOSITY FUNCTION; Z-SIMILAR-TO-3; TELESCOPE; QUASARS; SAMPLE; Z=2.5 AB We present the results of a narrowband survey of quasi-stellar-object (QSO) fields at redshifts that place the CO mi (5007 Angstrom) emission line in the Delta lambda/lambda similar to 1% 2.16 mu m filter. We have observed 3 arcmin(2) and detected one emission-line candidate object in the held around PC 1109 + 4642. We discuss the possibilities that this object is a star-forming galaxy at the QSO redshift, z(em) = 3.313, or a Seyfert galaxy. In the former case, we infer a star formation rate of 170 M. yr(-1) for this K' = 21.3 object. The galaxy has a compact but resolved morphology, with an FWHM = 0"6 or 4.2 kpc at z = 3.313 (H(0) = 50 km s(-1) Mpc(-1) and q(0) = 0.5). The comoving density of such objects in QSO environments appears to be 0.0033 Mpc(-3), marginally lower (less than or equal to 3 sigma) than the density observed for H alpha-emitters in absorption-line fields at z similar to 2.5 but similar to the density of Lyman-break galaxies at z similar to 3. If, on the other hand, most of the line emission is [O III] from a Seyfert 2 nucleus at z = 3.31, then the high inferred volume density could imply a large evolution in the Seyfert 2 luminosity function from the current epoch. We find the field containing the object to also contain many faint extended objects in the K' image but little significant excess over the expected number-magnitude relation. We discuss the implication of the emission line being a longer wavelength line at a lower redshift. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Dept Phys & Astron, Div Astron, Los Angeles, CA 90095 USA. RP Teplitz, HI (reprint author), NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. EM hit@binary.gsfc.nasa.gov; malkan@astro.ucla.edu; mclean@astro.ucla.edu NR 39 TC 8 Z9 8 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 MAR 20 PY 1999 VL 514 IS 1 BP 33 EP 39 DI 10.1086/306947 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BE UT WOS:000080057000005 ER PT J AU Kataoka, J Mattox, JR Quinn, J Kubo, H Makino, F Takahashi, T Inoue, S Hartman, RC Madejski, GM Sreekumar, P Wagner, SJ AF Kataoka, J Mattox, JR Quinn, J Kubo, H Makino, F Takahashi, T Inoue, S Hartman, RC Madejski, GM Sreekumar, P Wagner, SJ TI High-energy emission from the TeV blazar Markarian 501 during multiwavelength observations in 1996 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (Markarian 501); gamma rays : observations; radiation mechanisms : nonthermal; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; SELF-COMPTON MODEL; GAMMA-RAY EMISSION; LACERTAE OBJECT MARKARIAN-421; X-RAY; RELATIVISTIC JETS; SPHERICAL GEOMETRIES; GALAXY MARKARIAN-421; VARIABILITY; FLARE AB We present the results of a multiwavelength campaign for Mrk 501 performed in 1996 March with ASCA, EGRET, Whipple, and optical telescopes. The X-ray flux observed with ASCA was 5 times higher than the quiescent level and gradually decreased by a factor of 2 during the observation in 1996 March. In the X-ray band, a spectral break was observed around 2 keV. We report here for the first time the detection of high-energy gamma-ray flux from Mrk 501 with EGRET with 3.5 sigma significance (E > 100 MeV). Higher flux was also observed in 1996 April-May, with 4.0 sigma significance for E > 100 MeV and 5.2 sigma significance for E > 500 MeV. The gamma-ray spectrum was measured to be flatter than most of the gamma-ray blazars. We find that the multiband spectrum in 1996 is consistent with that calculated from a one-zone synchrotron self-Compton (SSC) model in which X-rays are produced via synchrotron emission and gamma-rays are produced via inverse Compton scattering of synchrotron photons in a homogeneous region. The flux of TeV gamma-rays is consistent with the predictions of the model if the decrease of the Compton scattering cross section in the Klein-Nishina regime is considered. In the context of this model, we investigate the values of the magnetic field strength and the beaming factor allowed by the observational results. We compare the 1996 March multiwavelength spectrum with that in the flare state in 1997 April. Between these two epochs, the TeV flux increase is well correlated with that observed in keV range. The keV and TeV amplitudes during the 1997 April hare are accurately reproduced by a one-zone SSC model, assuming that the population of synchrotron photons in 1996 are scattered by newly injected relativistic electrons having maximum energies of gamma(max) similar to 6 x 10(6). However, the TeV spectrum observed during the 1996 March campaign is flatter than predicted by our models. We find that this cannot be explained by either higher order Comptonization or the contribution of the "seed" IR photons from the host galaxy for the first-order external radiation. Comptonization, but we cannot exclude possible effects of the IR photons that may arise in the parsec-size tori postulated to exist in active galactic nuclei. C1 Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. Univ Tokyo, Dept Phys, Bunkyo Ku, Tokyo 1130033, Japan. Boston Univ, Dept Astron, Boston, MA 02215 USA. Harvard Smithsonian Ctr Astrophys, Fred Lawrence Whipple Observ, Amado, AZ 85645 USA. Inst Phys & Chem Res, Wako, Saitama 3510198, Japan. Tokyo Metropolitan Univ, Dept Phys, Tokyo 1920397, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Landessternwarte Heidelberg, D-69117 Heidelberg, Germany. RP Kataoka, J (reprint author), Inst Space & Astronaut Sci, 3-1-1 Yoshinodai, Kanagawa 2298510, Japan. NR 61 TC 120 Z9 120 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 1999 VL 514 IS 1 BP 138 EP 147 DI 10.1086/306918 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BE UT WOS:000080057000013 ER PT J AU Feibelman, WA AF Feibelman, WA TI A detailed analysis of the stellar and nebular IUE spectrum of the peculiar "O VI sequence" planetary nebula NGC 40 SO ASTROPHYSICAL JOURNAL LA English DT Article DE line : identification; planetary nebulae : individual (NGC 40); stars : Wolf-Rayet; ultraviolet : general ID CENTRAL STARS; C-IV; EMISSION; LINES AB A detailed analysis of archival individual and co-added low- and high-dispersion IUE spectra of the planetary nebula NGC 40 has been performed, using NEWSIPS extracted spectra. More than 50 emission lines and numerous absorption features have been identified, and emission-line fluxes and equivalent widths were measured. Terminal wind velocities from P Cygni profiles and electron densities were redetermined. Several inconsistencies were found in earlier works for this peculiar low-excitation planetary that is excited by a 90,000 K "O VI sequence" WC8 star. The detection of Fe II lines that are resonantly excited by the O VI lambda 1031 line supports the O VI classification for the central star. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 28 TC 9 Z9 9 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 1999 VL 514 IS 1 BP 296 EP 306 DI 10.1086/306940 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BE UT WOS:000080057000025 ER PT J AU Hjellming, RM Rupen, MP Mioduszewski, AJ Kuulkers, E McCollough, M Harmon, BA Buxton, M Sood, R Tzioumis, A Rayner, D Dieters, S Durouchoux, P AF Hjellming, RM Rupen, MP Mioduszewski, AJ Kuulkers, E McCollough, M Harmon, BA Buxton, M Sood, R Tzioumis, A Rayner, D Dieters, S Durouchoux, P TI Radio and X-ray observations of the 1998 outburst of the recurrent X-ray transient 4U 1630-47 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; gamma rays : bursts; radio continuum : stars; X-rays : stars ID GRO J1655-40; 4U-1630-47 AB We report radio (NRAO VLA and Australia Telescope Compact Array), soft X-ray (Rossi X-Ray Timing Explorer ASM), and hard X-ray (Compton Gamma Ray Observatory BATSE) observations of a 1998 outburst in the recurring X-ray transient 4U 1630-47, where radio emission was detected for the first time. The radio observations identify the position of 4U 1630-47 to within 1 ". Because the radio emission is optically thin with a spectral index of similar to-0.8 during the rise, peak, and decay of the initial radio event, the emission is probably coming from an optically thin radio jet ejected over a period of time. The 20-100 keV emission first appeared 1998 January 28 (MJD 50841), the 2-12 keV emission first appeared 1998 February 3 (MJD 50847), and the first radio emission was detected 1998 February 12.6 (MJD 50856.6). The rise of the radio emission probably began about 1998 February 7 (MJD 50851) when the X-rays were in a very hard fluctuating-hardness state, just before changing to a softer, more stable hardness state. C1 Natl Radio Astron Observ, Socorro, NM 87801 USA. Univ Oxford, Nucl & Astrophys Lab, Oxford OX1 3RH, England. Univ Space Res Assoc, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Australian Def Force Acad, Sch Phys, Canberra, ACT 2000, Australia. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Univ Tasmania, Dept Phys, Hobart, Tas 7001, Australia. Univ Alabama, Huntsville, AL 35812 USA. Ctr Etud Saclay, Serv Astrophys, F-91191 Gif Sur Yvette, France. RP Hjellming, RM (reprint author), Natl Radio Astron Observ, Socorro, NM 87801 USA. RI Rayner, David/A-6414-2011 OI Rayner, David/0000-0003-0545-3634 NR 25 TC 37 Z9 37 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 1999 VL 514 IS 1 BP 383 EP 387 DI 10.1086/306948 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BE UT WOS:000080057000031 ER PT J AU Brosius, JW Woodgate, BE AF Brosius, JW Woodgate, BE TI Using temporal variations of the nonthermal redshifted Ly alpha emission to deduce properties of proton beams injected into a stellar atmosphere SO ASTROPHYSICAL JOURNAL LA English DT Article DE radiation mechanisms : nonthermal; stars : flare; Sun : flares; Sun : UV radiation; ultraviolet : stars ID HARD X-RAY; IMPULSIVE SOLAR-FLARES; PARTICLE-ACCELERATION; ELECTRON ACCELERATION; PHASE; IONS; TURBULENCE; MODELS; ALFVEN; CHROMOSPHERE AB We present theoretical calculations of temporal variations in the nonthermal redshifted Ly alpha emission due to time-invariant proton beams injected into a stellar atmosphere during the impulsive phase of a flare. The computations are performed for a power-law spectrum of nonthermal proton energies injected into a model stellar atmosphere consisting of pure hydrogen in local thermodynamic equilibrium; beam-induced variations in temperature and particle densities at all depths and for all times are calculated with the Saha equation. We characterized the injected model proton beams with the total energy flux F and the power-law index delta and computed time-dependent nonthermal redshifted Ly alpha emission profiles for five different values of F and three different values of delta. Based upon trends evident in the resulting emission: proton beam properties can be deduced from sufficiently high-quality observations of the nonthermal redshifted Ly alpha profile. The beam penetration depth initially decreases with time, but in most cases it increases again after reaching some minimum value. This behavior is due to changes in the ionization and temperature of the atmosphere. The Lya intensity also initially decreases with time, but in most cases it reaches a relative minimum, increases again to a secondary relative maximum, and then slowly but steadily decreases thereafter. Observable properties of this time-dependent emission, such as the ratio of the profile's peak spectral intensity at relative minimum to that at beam onset(I-relmin/I-0), the difference between the profile's width at beam onset and that at the secondary relative maximum (FWHM0 - FWHMrelmax), and the difference between the profile's centroid wavelength shift at beam onset and that at relative minimum (Delta lambda(0) - Delta lambda(relmin)) can be used to deduce delta. Once delta is known, F can be deduced from other observable properties such as I, and the times since beam onset at which the Lya intensity reaches its relative minimum and secondary relative maximum values (t(relmin) and t(relmax)). C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Raytheon STX Corp, 4400 Forbes Blvd, Lanham, MD 20706 USA. RI Woodgate, Bruce/D-2970-2012 NR 54 TC 5 Z9 5 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 MAR 20 PY 1999 VL 514 IS 1 BP 430 EP 440 DI 10.1086/306943 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BE UT WOS:000080057000035 ER PT J AU Ofman, L Nakariakov, VM DeForest, CE AF Ofman, L Nakariakov, VM DeForest, CE TI Slow magnetosonic waves in coronal plumes SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; sun : corona; sun : magnetic fields; waves ID SOLAR-WIND ACCELERATION; POLAR PLUMES; HOLES; TELESCOPE AB Recent observations of polar plumes in the southern solar coronal hole by the Extreme-Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft show signatures of quasi-periodic compressional waves with periods of 10-15 minutes. The relative wave amplitude was found to increase with height in the plumes up to about 1.2 R-.. Using a one-dimensional linear wave equation for the magnetosonic wave, we show that the waves are propagating and that their amplitude increases with height. The observed propagation velocity agrees well with the expected sound velocity inside the plumes. We present the results of the first nonlinear, two-dimensional, magnetohydrodynamic (MHD) simulation of the magnetosonic waves in plumes for typical coronal conditions consistent with observations and gravitationally stratified solar corona. We find numerically that outward-propagating slow magnetosonic waves are trapped, and nonlinearly steepen in the polar plumes. The nonlinear steepening of the magnetosonic waves may contribute significantly to the heating of the lower corona by compressive dissipation. C1 Raytheon ITSS, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. Stanford Univ, Stanford, CA 94305 USA. RP Ofman, L (reprint author), Raytheon ITSS, Code 682, Greenbelt, MD 20771 USA. RI Nakariakov, Valery/E-2375-2013 OI Nakariakov, Valery/0000-0001-6423-8286 NR 17 TC 199 Z9 201 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 1999 VL 514 IS 1 BP 441 EP 447 DI 10.1086/306944 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BE UT WOS:000080057000036 ER PT J AU Roy, DP Giglio, L Kendall, JD Justice, CO AF Roy, DP Giglio, L Kendall, JD Justice, CO TI Multi-temporal active-fire based burn scar detection algorithm SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID AEROSOL AB A multi-temporal burn scar detection algorithm designed for global application is described and demonstrated using 24-daily AVHRR images of an area of savanna burning near the Okavango Delta, Southern Africa. The algorithm is computationally simple, does not use fixed thresholds except to detect saturated AVHRR pixels, and incorporates a recent active-fire detection algorithm. The algorithm provides the basis for operational burn scar monitoring using the AVHRR and MODIS. C1 Univ Maryland, NASA, Goddard Space Flight Ctr, Dept Geog, Greenbelt, MD 20771 USA. NASA, Sci Syst & Applicat Inc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Virginia, Dept Environm Sci, Charlottesville, VA 22903 USA. RP Roy, DP (reprint author), Univ Maryland, NASA, Goddard Space Flight Ctr, Dept Geog, Code 922, Greenbelt, MD 20771 USA. NR 14 TC 85 Z9 87 U1 2 U2 15 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD MAR 20 PY 1999 VL 20 IS 5 BP 1031 EP 1038 DI 10.1080/014311699213073 PG 8 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 177MN UT WOS:000079214000012 ER PT J AU Yee, HC Sandham, ND Djomehri, MJ AF Yee, HC Sandham, ND Djomehri, MJ TI Low-dissipative high-order shock-capturing methods using characteristic-based filters SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE low dissipation; high order; explicit and implicit finite difference methods; compact schemes; high-order central differencings shock-capturing methods; conservative differencing; shock-turbulence interaction; TVD schemes; positive schemes; ENO schemes ID HYPERBOLIC CONSERVATION-LAWS; FINITE-DIFFERENCE SCHEMES; CHANNEL FLOW; TVD SCHEMES; IMPLICIT; RESOLUTION; APPROXIMATIONS; SUMMATION; PARTS AB An approach which closely maintains the non-dissipative nature of classical fourth- or higher-order spatial differencing away from shock waves and steep gradient regions while being capable of accurately capturing discontinuities, steep gradient, and fine scale turbulent structures in a stable and efficient manner is described. The approach is a generalization of the method of Gustafsson and Olsson and the artificial compression method (ACM) switch of Harten. Spatially non-dissipative fourth- or higher-order compact and non-compact spatial differencings are used as the base schemes, Instead of applying a scalar filter as in Gustafsson and Olsson, an ACM switch is used to signal the appropriate amount of second- or third-order total variation diminishing (TVD) or essentially non-oscillatory (ENO) types of characteristic based numerical dissipation. This term acts as a characteristic filter to minimize numerical dissipation for the overall scheme, For time-accurate computations, time discretizations with low dissipation apr used, Numerical experiments on 2-D vortical flows, vortex-shock interactions, and compressible spatially and temporally evolving mixing layers showed that the proposed schemes have the desired property with only a 10% increase in operations count over standard second-order TVD schemes. Aside from the ability to accurately capture shock-turbulence interaction flows, this approach is also capable of accurately preserving vortex convection. Higher accuracy is achieved with fewer grid points when compared to that of standard second-order TVD, positive, or ENO schemes. (C) 1999 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Queen Mary Univ London, London E1 4NS, England. NASA, Ames Res Ctr, Calspan, Moffett Field, CA 94035 USA. RP Yee, HC (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Sandham, Neil/G-4755-2010 NR 57 TC 198 Z9 203 U1 2 U2 8 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 MAR 20 PY 1999 VL 150 IS 1 BP 199 EP 238 DI 10.1006/jcph.1998.6177 PG 40 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 178XD UT WOS:000079293700009 ER PT J AU Hoell, JM Davis, DD Jacob, DJ Rodgers, MO Newell, RE Fuelberg, HE McNeal, RJ Raper, JL Bendura, RJ AF Hoell, JM Davis, DD Jacob, DJ Rodgers, MO Newell, RE Fuelberg, HE McNeal, RJ Raper, JL Bendura, RJ TI Pacific Exploratory Mission in the tropical Pacific: PEM-Tropics A, August-September 1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE AB The NASA Pacific Exploratory Mission to the Pacific tropics (PEM-Tropics) is the third major field campaign of NASA's Global Tropospheric Experiment (GTE) to Study the impact of human and natural processes on the chemistry of the troposphere over the Pacific basin. The first two campaigns, PEM-West A and B were conducted over the northwestern regions of the Pacific and focused on the impact of emissions from the Asian continent. The broad objectives of PEM-Tropics included improving our understanding of the oxidizing power of the tropical atmosphere as well as investigating oceanic sulfur compounds and their conversion to aerosols. Phase A of the PEM-Tropics program, conducted between August-September 1996, involved the NASA. DC-8 and P-3B aircraft. Phase B of this program is scheduled for March/April 1999. During PEM-Tropics A, the flight tracks of the two aircraft extended zonally across the entire Pacific Basin and meridionally from Hawaii to south of New Zealand. Both aircraft were instrumented for airborne measurements of trace gases and aerosols and meteorological parameters. The DC-8, given its long-range and high-altitude capabilities coupled with the lidar instrument in its payload, focused on transport issues and ozone photochemistry, while the P-3B, with its sulfur-oriented instrument payload and more limited range, focused on detailed sulfur process studies. Among its accomplishments, the PEM-Tropics A field campaign has provided a unique set of atmospheric measurements in a heretofore data sparse region; demonstrated the capability of several new or improved instruments for measuring OH, H2SO4, NO, NO2, and actinic fluxes; and conducted experiments which tested our understanding of HOx and NOx photochemistry, as well as sulfur oxidation and aerosol formation processes. In addition, PEM-Tropics A documented for the first time the considerable and widespread influence of biomass burning pollution over the South Pacific, and identified the South Pacific Convergence Zone as a major barrier for atmospheric transport in the southern hemisphere. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Georgia Inst Technol, Atlanta, GA 30332 USA. Harvard Univ, Cambridge, MA 02138 USA. MIT, Cambridge, MA 02139 USA. Florida State Univ, Tallahassee, FL 32306 USA. NASA Headquarters, Washington, DC 20546 USA. RP Hoell, JM (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. EM j.m.hoel@larc.nasa.gov NR 23 TC 97 Z9 97 U1 1 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 MAR 20 PY 1999 VL 104 IS D5 BP 5567 EP 5583 DI 10.1029/1998JD100074 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800010 ER PT J AU Fuelberg, HE Newell, RE Longmore, SP Zhu, Y Westberg, DJ Browell, EV Blake, DR Gregory, GL Sachse, GW AF Fuelberg, HE Newell, RE Longmore, SP Zhu, Y Westberg, DJ Browell, EV Blake, DR Gregory, GL Sachse, GW TI A meteorological overview of the Pacific Exploratory Mission (PEM) Tropics period SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOUTHERN OSCILLATION; WEST-COAST; OZONE; AIR; DISTRIBUTIONS; TROPOSPHERE; TRANSPORT; ATLANTIC; AFRICA; TRACE AB NASA's Pacific Exploratory Mission-Tropics (PEM-T) experiment investigated the atmospheric chemistry of a large portion of the tropical and subtropical Pacific Basin during August to October 1996. This paper summarizes meteorological conditions over the PEM-T domain. Mean flow patterns during PEM-T are described. Important circulation systems near the surface include subtropical anticyclones, the South Pacific Convergence Zone (SPCZ), the Intertropical Convergence Zone (ITCZ), and middle latitude transient cyclones. The SPCZ and ITCZ are areas of widespread ascent and deep convection however, there is relatively little lightning in these oceanic regions. A large area of subsidence Is associated with the subtropical anticyclone centered near Easter Island. PEM-T occurred during a period of near normal sea surface temperatures. When compared to an 11 year climatology (1986-1996), relatively minor circulation anomalies are observed during PEM-T. Some of these circulation anomalies are consistent with much stronger anomalies observed during previous La Nina events. In general, however, the 1996 PEM-T period appears to be climatologically representative. Meteorological conditions for specific flights from each major operations area are summarized. The vertical distribution of ozone along selected DC-8 flights is described using the DIAL remote sensing system. These ozone distributions are related to thermodynamic soundings obtained during aircraft maneuvers and to backward trajectories that arrived at locations along the flight tracks. Most locations in the deep tropics are found to have relatively small values of tropospheric ozone. Backward trajectories calculated from global gridded analyses show that much of this air originates from the east and has not passed over land within 10 days. The deep convection associated with the ITCZ and SPCZ also influences the atmospheric chemistry of these regions. Flights over portions of the subtropics and middle latitudes document layers of greatly enhanced tropospheric ozone, sometimes exceeding 80 ppbv, In situ carbon monoxide in these layers often exceeds 90 ppbv. These regions are located near, and especially south of Tahiti, Easter Island, and Fiji. The layers of enhanced ozone usually correspond to layers of dry air, associated with widespread subsiding air. The backward trajectories show that air parcels arriving in these regions originate from the west, passing over Australia and even extending back to southern Africa. These are regions of biomass burning. The in situ chemical measurements support the trajectory-derived origins of these ozone plumes. Thus the enhanced tropospheric ozone over the central Pacific Basin may be due to biomass burning many thousands of kilometers away. Middle-latitude portions of the PEM-T area are influenced by transient cyclones, and the DC-8 traversed tropopause folds during several flights. The flight area just west of Ecuador experiences outflow from South America. Thus the biomass burning that is prevalent over portions of Brazil influences this area. C1 Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Sci Applicat Int Corp, Hampton, VA USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. RP Blake, DR (reprint author), Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NR 51 TC 48 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 MAR 20 PY 1999 VL 104 IS D5 BP 5585 EP 5622 DI 10.1029/98JD01215 PG 38 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800011 ER PT J AU Talbot, RW Dibb, JE Scheuer, EM Blake, DR Blake, NJ Gregory, GL Sachse, GW Bradshaw, JD Sandholm, ST Singh, HB AF Talbot, RW Dibb, JE Scheuer, EM Blake, DR Blake, NJ Gregory, GL Sachse, GW Bradshaw, JD Sandholm, ST Singh, HB TI Influence of biomass combustion emissions on the distribution of acidic trace gases over the southern Pacific basin during austral springtime SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ACETIC-ACIDS; EQUATORIAL PACIFIC; CENTRAL AMAZONIA; ORGANIC-ACIDS; FORMIC-ACID; TROPOSPHERE; ATMOSPHERE; REGION; PRECIPITATION; CHEMISTRY AB This paper describes the large-scale distributions of HNO3, HCOOH, and CH3COOH over the central and South Pacific basins during the Pacific Exploratory Mission-Tropics (PEM-Tropics) in austral springtime. Because of the remoteness of this region from continental areas, low part per trillion by volume (pptv) mixing ratios of acidic gases were anticipated to be pervasive over the South Pacific basin. However,; at altitudes of 2-12 km over the South Pacific, air parcels were encountered frequently with significantly enhanced mixing ratios (up to 1200 pptv) of acidic gases. Most of these air parcels were centered in the 3-7 km altitude range and occurred within the 15 degrees-65 degrees S latitudinal band. The acidic gases exhibited an overall general correlation with CH3Cl, PAN, and O-3, suggestive of photochemical and biomass burning sources. There was no correlation or trend of acidic gases with common industrial tracer compounds (e.g., C2Cl4 or CH3CCl3). The combustion emissions sampled over the South Pacific basin were relatively aged exhibiting C2H2/CO ratios in the range of 0.2-2.2 pptv/ppbv. The relationships between acidic gases and this ratio were similar to what was observed in aged air parcels (i.e., >3-5 days since they were over a continental area) over the western North Pacific during the Pacific Exploratory Mission-West Phases A and B (PEM-West A and B). In the South Pacific marine boundary layer a median C2H2/CO ratio of 0.6 suggested that this region was generally not influenced by direct inputs of biomass combustion emissions. Here we observed the lowest mixing ratios of acidic gases, with median values of 14 pptv for HNO3, 19 pptv for HCOOH, and 18 pptv for CH3COOH. These values were coincident with low mixing ratios of NOx (<10 pptv), CO (approximate to 50 parts per billion by volume (ppbv)), O-3 (< 20 ppbv), and long-lived hydrocarbons (e.g., C2H6 <300 pptv). Overall, the PEM-Tropics data suggest an important influence of aged biomass combustion emissions on the distributions of acidic gases over the South Pacific basin in austral springtime. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Georgia Inst Technol, Dept Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Talbot, RW (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. EM rwt@christa.unh.edu NR 30 TC 40 Z9 40 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 MAR 20 PY 1999 VL 104 IS D5 BP 5623 EP 5634 DI 10.1029/98JD00879 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800012 ER PT J AU O'Sullivan, DW Heikes, BG Lee, M Chang, W Gregory, GL Blake, DR Sachse, GW AF O'Sullivan, DW Heikes, BG Lee, M Chang, W Gregory, GL Blake, DR Sachse, GW TI Distribution of hydrogen peroxide and methylhydroperoxide over the Pacific and South Atlantic Oceans SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PEROXYACETIC ACID; BOUNDARY-LAYER; HYDROPEROXIDES; OZONE; TROPOSPHERE; OXIDATION; SULFUR AB The gas phase hydrogen peroxide and methylhydroperoxide concentrations were measured in the troposphere over the tropical Pacific Ocean as a component of NASA's Global Tropospheric Experiment/Pacific Exploratory Mission-Tropics A field campaign. Flights on two aircraft covered the Pacific from 70 degrees S to 60 degrees N and 110 degrees E to 80 degrees W and South Atlantic from 40 degrees S to 15 degrees N and 45 degrees W to 70 degrees E, and extending from 76 to 13,000 m altitude. H2O2 and CH3OOH have the highest concentrations at a given altitude at the equator and decrease with increasing latitude in both the northern and southern hemispheres. Above 4 km the gradient is substantially reduced for both H2O2 and CH3OOH with latitude, and at altitudes in excess of 8 km there is no latitudinal dependence. H2O2 and CH3OOH exhibit maximum mixing ratios between 1 and 2 km at all latitudes. The mean mixing ratio of H2O2 at the equator was 1600 +/- 600 parts per trillion by volume (pptv) decreasing to 500 +/- 250 pptv at latitudes greater than 550 north and south between 1 and 2 km altitude. CH3OOH at the equator was 1400 +/- 250 pptv, decreasing to 330 +/- 200 pptv at high latitudes at altitudes between 1 and 2 km. The concentration of peroxides at high latitudes in the northern hemisphere was generally a factor of 2 higher than at corresponding latitudes in the southern hemisphere. The ratio of H2O2 to CH3OOH was between 1 and 2 from 45 degrees S to 35 degrees N at altitudes below 4 km. Between 5 degrees to 15 degrees N the ratio is less than 1, due to preferential removal of H2O2 in the Intertropical Convergence Zone. C1 USN Acad, Dept Chem, Annapolis, MD 21401 USA. Univ Rhode Isl, Grad Sch Oceanog, Ctr Atmospher Chem Studies, Narragansett, RI 02882 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. RP O'Sullivan, DW (reprint author), USN Acad, Dept Chem, Annapolis, MD 21401 USA. EM dano@brass.nadn.navy.mil OI O'Sullivan, Daniel/0000-0001-9104-5703 NR 33 TC 47 Z9 49 U1 1 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 MAR 20 PY 1999 VL 104 IS D5 BP 5635 EP 5646 DI 10.1029/98JD01250 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800013 ER PT J AU Vay, SA Anderson, BE Conway, TJ Sachse, GW Collins, JE Blake, DR Westberg, DJ AF Vay, SA Anderson, BE Conway, TJ Sachse, GW Collins, JE Blake, DR Westberg, DJ TI Airborne observations of the tropospheric CO2 distribution and its controlling factors over the South Pacific Basin SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC CARBON-DIOXIDE; EDDY DIFFUSION-MODEL; TRANSPORT; OCEAN; ATLANTIC; REGION; CYCLE AB Highly precise measurements of CO2 mixing ratios were recorded aboard both the NASA DC-8 and P3-B aircraft during the Pacific Exploratory Mission-Tropics conducted in August-October 1996. Data were obtained at altitudes ranging from 0.1 to 12 km over a large portion of the South Pacific Basin representing the most geographically extensive CO2 data set recorded in this region. These data along with CO2 surface measurements from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) and the National Institute of Water and Atmospheric Research (NIWA) were examined to establish vertical and meridional gradients. The CO2 spatial distribution in the southern hemisphere appeared to be largely determined by interhemispheric transport as air masses with depleted CO2 levels characteristic of northern hemispheric air were frequently observed south of the Intertropical Convergence Zone. However, regional processes also played a role in modulating background concentrations. Comparisons of CO2 with other trace gases indicated that CO2 values were influenced by continental sources. Large scale plumes from biomass burning activities produced enhanced CO2 mixing ratios within the lower to midtroposphere over portions of the remote Pacific. An apparent CO2 source was observed in the NOAA/ CMDL surface data between 15 degrees N and 15 degrees S and in the lower altitude flight data between 8 degrees N and 8.5 degrees S with a zone of intensity from 6.5 degrees N to 1 degrees S. Inferred from these data is the presence of a Southern Ocean sink from south of 15 degrees S having two distinct zones seasonally out of phase with one another. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Aerosp Elect Syst Div, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RP Vay, SA (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. EM s.a.vay@larc.nasa.gov NR 37 TC 35 Z9 36 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 MAR 20 PY 1999 VL 104 IS D5 BP 5663 EP 5676 DI 10.1029/98JD01420 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800015 ER PT J AU Gregory, GL Westberg, DJ Shipham, MC Blake, DR Newell, RE Fuelberg, HE Talbot, RW Heikes, BG Atlas, EL Sachse, GW Anderson, BA Thornton, DC AF Gregory, GL Westberg, DJ Shipham, MC Blake, DR Newell, RE Fuelberg, HE Talbot, RW Heikes, BG Atlas, EL Sachse, GW Anderson, BA Thornton, DC TI Chemical characteristics of Pacific tropospheric air in the region of the Intertropical Convergence Zone and South Pacific Convergence Zone SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB The Pacific Exploratory Mission (PEM)-Tropics provided extensive aircraft data to study the atmospheric chemistry of tropospheric air in Pacific Ocean regions, extending from Hawaii to New Zealand and from Fiji to east of Easter Island. This region, especially the tropics, includes some of the cleanest tropospheric air of the world and, as such, is important for studying atmospheric chemical budgets and cycles. The region also provides a sensitive indicator of the global-scale impact of human activity on the chemistry of the troposphere, and includes such important features as the Pacific "warm pool," the Intertropical Convergence Zone (ITCZ), the South Pacific Convergence Zone (SPCZ), and Walker Cell circulations. PEM-Tropics was conducted from August to October 1996. The ITCZ and SPCZ are major upwelling regions within the South Pacific and, as such, create boundaries to exchange of tropospheric air between regions to the north and south. Chemical data obtained in the near vicinity of the ITCZ and the SPCZ are examined. Data measured within the convergent zones themselves are not considered. The analyses show that air north and south of the convergent zones have different chemical signatures, and the signatures are reflective of the source regions and transport histories of the air. Air north of the ITCZ shows a modest urban/industrialized signature compared to air south of the ITCZ. The chemical signature of air south of the SPCZ is dominated by combustion emissions from biomass burning, while air north of the SPCZ is relatively clean and of similar composition to ITCZ south air. Chemical signature differences of air north and south of the zones are most pronounced at altitudes below 5 km, and, as such, show that the ITCZ and SPCZ are effective low-altitude barriers to the transport of tropospheric air. At altitudes of 8 to 10 km, chemical signatures are less dissimilar, and air backward trajectories (to 10 days) show cross-convergent-zone flow. At altitudes below about 5 km, little cross-zonal flow is observed. Chemical signatures presented include over 30 trace chemical species including ultrafine, fine, and heated-fine (250 degrees C) aerosol. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. MIT, Cambridge, MA 02139 USA. NASA, Langley Res Ctr, Aerosp Elect Syst Div, Hampton, VA 23681 USA. Univ New Hampshire, Complex Syst Res Ctr, ISEOS, Durham, NH 03824 USA. Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. RP Gregory, GL (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. EM g.l.gregory@larc.nasa.gov RI Atlas, Elliot/J-8171-2015 NR 18 TC 49 Z9 49 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1999 VL 104 IS D5 BP 5677 EP 5696 DI 10.1029/98JD01357 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800016 ER PT J AU Cho, JYN Zhu, Y Newell, RE Anderson, BE Barrick, JD Gregory, GL Sachse, GW Carroll, MA Albercook, GM AF Cho, JYN Zhu, Y Newell, RE Anderson, BE Barrick, JD Gregory, GL Sachse, GW Carroll, MA Albercook, GM TI Horizontal wavenumber spectra of winds, temperature, and trace gases during the Pacific Exploratory Missions: 1. Climatology SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GRAVITY-WAVE SPECTRA; SURFACE-LAYER TURBULENCE; AIRCRAFT; MODEL; VARIABILITY; ATMOSPHERE; DENSITY AB Aircraft-based meteorological and chemical measurements from NASA's Pacific Exploratory Missions provide a suitable database for studying;the climatology of horizontal wavenumber spectra in the troposphere overlying an ocean. The wavenumber spectra of trace gas and meteorological quantities aid in identifying the physical processes producing atmospheric structures as well as provide diagnostics for general circulation models. Flight segments were distributed over altitudes ranging from about similar to 50 m to 13 km and 70 degrees S to 60 degrees N in latitude. The spectra were averaged according to altitude and latitude regions. The wavelength range covered was typically similar to 0.5-100 km. Quantities processed in this way were horizontal velocity, potential temperature, specific humidity, and the mixing ratios of ozone, methane, carbon monoxide, and carbon dioxide. Spectral power and slope tin log-log coordinates) corresponding to the wavelength regime of 6-60 km were tabulated for those measured quantities. The spectral slopes of horizontal velocity and potential temperature were generally close to -5/3 with no transition to a steeper slope at short wavelengths. as seen,in some other studies. Spectral slopes of the tracer species also ranged around -5/3. This agreement in form of the dynamical and tracer spectra is consistent with both the gravity-wave advection and quasi two-dimensional turbulence models. In the upper troposphere the spectral power for all quantities except specific humidity tended to be greater at latitudes higher than 30 degrees compared to latitudes lower than 30 degrees. This latitudinal trend confirms the earlier results of the Global Atmospheric Sampling Program. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Michigan, Dept Chem, Ann Arbor, MI 48109 USA. RP Cho, JYN (reprint author), MIT, Dept Earth Atmospher & Planetary Sci, 77 Massachusetts Ave,Rm 54-1823, Cambridge, MA 02139 USA. EM jcho@pemtropics.mit.edu; zhu@newell1.mit.edu; newell@newell1.mit.edu; b.e.anderson@larc.nasa.gov; j.d.barrick@larc.nasa.gov; g.l.gregory@larc.nasa.gov; g.w.sachse@larc.nasa.gov; mcarroll@umich.edu; galber@umich.edu NR 45 TC 49 Z9 49 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 MAR 20 PY 1999 VL 104 IS D5 BP 5697 EP 5716 DI 10.1029/98JD01825 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800017 ER PT J AU Crawford, J Davis, D Chen, G Shetter, R Muller, M Barrick, J Olson, J AF Crawford, J Davis, D Chen, G Shetter, R Muller, M Barrick, J Olson, J TI An assessment of cloud effects on photolysis rate coefficients: Comparison of experimental and theoretical values SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OBSERVATORY PHOTOCHEMISTRY EXPERIMENT; RADIOMETER MEASUREMENTS; NO2 PHOTOLYSIS; PHOTODISSOCIATION; FREQUENCIES; ACTINOMETER; RADIATION AB An assessment of the effects of clouds on photolysis rate coefficients was carried out using three different experimental methods involving two different aircraft platforms. This evaluation was based on data recorded during NASA's Pacific Exploratory Mission (PEM)-Tropics A program in August-October 1996. On the NASA DC-8, upward and downward looking J(NO2) filter radiometers and spectroradiometers were employed. For the NASA P-3B, the instrumentation consisted of Eppley radiometers. Although each aircraft typically sampled the same geographic region, coincident measurements occurred for only one brief period in the marine boundary layer near Christmas Island (2 degrees N, 157 degrees W). All three methods were compared for this night period; however, only the J(NO2) filter radiometers and spectroradiometers could be compared for the entire campaign. For the Christmas Island sampling; period, all three radiometric measurements disagreed in magnitude but exhibited trends consistent with model-calculated photolysis rate coefficients. Overall, the results showed that the J(NO2) filter radiometers and spectroradiometers exhibited a consistent disagreement of 30%, the J(NO2) filter radiometers being higher. Eppley-derived values of J(NO2) fell between those of the J(NO2) filter radiometers and spectroradiometers. An examination of the variation in J((OD)-D-1) and J(NO2) based on the output from the spectroradiometers and J(NO2) filter radiometers suggests that differences between each photolysis rate coefficient's response to cloud effects tend to be smaller than model uncertainties. Thus J((OD)-D-1) and other photolysis rate coefficients can be corrected for cloud effects based on the response of J(NO2). C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80303 USA. RP Crawford, J (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. EM j..h.crawford@larc.nasa.gov RI Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 21 TC 28 Z9 28 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 MAR 20 PY 1999 VL 104 IS D5 BP 5725 EP 5734 DI 10.1029/98JD01724 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800019 ER PT J AU Stoller, P Cho, JYN Newell, RE Thouret, V Zhu, Y Carroll, MA Albercook, GM Anderson, BE Barrick, JDW Browell, EV Gregory, GL Sachse, GW Vay, S Bradshaw, JD Sandholm, S AF Stoller, P Cho, JYN Newell, RE Thouret, V Zhu, Y Carroll, MA Albercook, GM Anderson, BE Barrick, JDW Browell, EV Gregory, GL Sachse, GW Vay, S Bradshaw, JD Sandholm, S TI Measurements of atmospheric layers from the NASA DC-8 and P-3B aircraft during PEM-Tropics A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CARBON-MONOXIDE AB Tropospheric vertical structure was analyzed using in situ measurements of O-3, CO, CH4, and H2O taken on board the NASA DC-8 aircraft during three Pacific Exploratory Missions (PEMs): PEM-West A, September-October 1991 in the western Pacific; PEM-West B, February-March 1994 in the western Pacific; and PEM-Tropics A, September-October 1996 in the central and eastern Pacific. PEM-Tropics A added measurements from the NASA P3-B aircraft. We used a new mode-based method to define a background against which to find layers. Using only O-3 and H2O, we found 472 layers in PEM-Tropics A (0.72 layers per vertical kilometer profiled), 237 layers in PEM-West PI (0.54 layers/km), and;158 layers in PEM-West B (0.41 layers/km). Using all constituents, we found 187 layers in PEM-Tropics A (0.43 layers/km), 128 layers in PEM-West A (0.29 layers/km), and 80 layers in PEM-West B (0.21 layers/km). Stratospheric air, sometimes mixed with trapped pollution, was the dominant layer source in all three missions. The larger number of layers per kilometer in PEM-Tropics A was probably due to repeated profiling of several "superlayers" visible in many of the mission lidar and potential vorticity profiles. The thickness of the superlayers was of order 1 km, and the horizontal extent was of order 1000 km. We found that layers have an Important effect on the thermal structure. An example based on ozonesonde data from Tahiti is shown, where a dry, subsiding layer was stabilized by much greater radiative cooling at the base than at the top. The stabilized layer can trap pollution and force vertical plumes to spread into horizontal layers. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. CNRS, Lab Aerol, Toulouse, France. RP Stoller, P (reprint author), MIT, Dept Earth Atmospher & Planetary Sci, 77 Massachusetts Ave,Rm 54-1823, Cambridge, MA 02139 USA. EM pstoller@pemtropics.mit.edu; jcho@pemtropics.mit.edu; newell@newell1.mit.edu; valerie@newel13.mit.edu; zhu@newell1.mit.edu; mcarroll@umich.edu; galber@umich.edu; b.e.anderson@larc.nasa.gov; j.d.barrick@larc.nasa.gov; e.v.browell@larc.nasa.gov; sts@minitower.gtri.gatech.edu NR 12 TC 38 Z9 38 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 MAR 20 PY 1999 VL 104 IS D5 BP 5745 EP 5764 DI 10.1029/98JD02717 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800021 ER PT J AU Dibb, JE Talbot, RW Scheuer, EM Blake, DR Blake, NJ Gregory, GL Sachse, GW Thornton, DC AF Dibb, JE Talbot, RW Scheuer, EM Blake, DR Blake, NJ Gregory, GL Sachse, GW Thornton, DC TI Aerosol chemical composition and distribution during the Pacific Exploratory Mission (PEM) Tropics SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SEA-SALT SULFATE; BIOGENIC SULFUR EMISSIONS; CLOUD CONDENSATION NUCLEI; MARINE BOUNDARY-LAYER; METHANESULFONIC-ACID; ATMOSPHERIC SULFUR; SEASONAL-VARIATIONS; EQUATORIAL PACIFIC; DIMETHYLSULFIDE; OCEAN AB Distributions of aerosol-associated soluble ions over much of the South Pacific were determined by sampling from the NASA DC-8 as part of the Pacific Exploratory Mission (PEM) Tropics campaign. The mixing ratios of all ionic species were surprisingly low throughout the free troposphere (2-12 km), despite the pervasive influence from biomass burning plumes advecting over the South Pacific from the west during PEM-Tropics. At the same time, the specific activity of Be-7 frequently exceeded 1000 fCi m(-3) through much of the depth of the troposphere. These distributions indicate that the plumes must have been efficiently scavenged by precipitation (removing the soluble ions), but that the scavenging must have occurred far upwind of the DC-8 sampling regions (otherwise Be-7 activities would also have been low). This inference is supported by large enhancements of HNO3 and carboxylic acids in many of the plumes, as these soluble acidic gases would also be readily scavenged in any precipitation events. Decreasing mixing ratios of NH4+ with altitude in all South Pacific regions sampled provide support for recent suggestions that oceanic emissions of NH3 constitute a significant source far from continents. Our sampling below 2 km reaffirms the latitudinal pattern in the methylsulfonate/non-sea-salt sulfate (MSA/nss SO4=) molar ratio established through surface-based and shipboard sampling, with values increasing from <0.05 in the tropics to nearly 0.6 at 70 degrees S. However, we also found very high values of this ratio (0.2-0.5) at 10 km altitude above the intertropical, convergence zone near 10 degrees N, It appears that wet convective pumping of dimethylsulfide from the tropical marine boundary layer is responsible for the high values of the MSA/nss SO4= ratio in the tropical upper troposphere. This finding complicates use of this ratio to infer the zonal origin of biogenic S transported long distances. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA. RP Dibb, JE (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. EM jack.dibb@unh.edu NR 42 TC 39 Z9 39 U1 2 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1999 VL 104 IS D5 BP 5785 EP 5800 DI 10.1029/1998JD100001 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800023 ER PT J AU Schultz, MG Jacob, DJ Wang, YH Logan, JA Atlas, EL Blake, DR Blake, NJ Bradshaw, JD Browell, EV Fenn, MA Flocke, F Gregory, GL Heikes, BG Sachse, GW Sandholm, ST Shetter, RE Singh, HB Talbot, RW AF Schultz, MG Jacob, DJ Wang, YH Logan, JA Atlas, EL Blake, DR Blake, NJ Bradshaw, JD Browell, EV Fenn, MA Flocke, F Gregory, GL Heikes, BG Sachse, GW Sandholm, ST Shetter, RE Singh, HB Talbot, RW TI On the origin of tropospheric ozone and NOx over the tropical South Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BIOMASS-BURNING EMISSIONS; REACTIVE NITROGEN; HNO3/NOX RATIO; BOUNDARY-LAYER; NITRIC-ACID; IMPACT; ATLANTIC; MODEL; CHEMISTRY; AEROSOLS AB The budgets of ozone and nitrogen oxides (NOx = NO + NO2) in the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September-October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides H2O2, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 10(11) molecules cm(-2) s(-1),The missing source of ozone is matched by westerly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model; biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone production within the South Pacific troposphere below 4 km can be largely explained by decomposition of peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes. C1 Harvard Univ, Div Engn & Appl Sci, Cambridge, MA 02138 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. RP Schultz, MG (reprint author), Harvard Univ, Div Engn & Appl Sci, 29 Oxford St, Cambridge, MA 02138 USA. EM mgs@io.harvard.edu RI Wang, Yuhang/B-5578-2014; Atlas, Elliot/J-8171-2015; Schultz, Martin/I-9512-2012 OI Schultz, Martin/0000-0003-3455-774X NR 61 TC 101 Z9 102 U1 0 U2 13 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1999 VL 104 IS D5 BP 5829 EP 5843 DI 10.1029/98JD02309 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800026 ER PT J AU Considine, GD Anderson, B Barrick, J Lenschow, DH AF Considine, GD Anderson, B Barrick, J Lenschow, DH TI Characterization of turbulent transport in the marine boundary layer during flight 7 of PEM-Tropics A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FLUXES; SCALE AB A series of aircraft measurements taken in the marine boundary layer in the vicinity of Christmas Island during the NASA Pacific Exploratory Mission-Tropics (PEM-Tropics) A mission allow for a partial characterization of the turbulent transfer through the mixed layer. The measurements were obtained during a series of 12 circular sampling legs (of 30 min each) at five altitudes in the boundary layer, including the entrainment layer. The data include high-frequency measurements of moisture and the wind field in three dimensions (18.7 Hz) and slower-response temperature (1 Hz). Computed fluxes and variances are filtered using standard Fourier filters as well as moving-average filters. The uncertainties associated with the choice of filter are discussed. The vertical structure of the boundary layer and the profiles of the variance of vertical velocity are consistent with the standard conceptual picture of the mixed layer. The humidity flux and variance of vertical velocity vary by 50% between three 30-min horizontal samples midway through the mixed layer but remain essentially constant at the bottom of the mixed layer. The variability in the humidity flux and the variance of vertical velocity appear to be caused by changes in the dynamical scales associated with the transport, with a high correlation between the peak length scale derived from the cospectrum and the net flux of humidity. The observed changes in the fluxes are consistent with changes in the rate of entrainment into the mixed layer, coinciding with changes in the fraction of vertical transport associated with mesoscale processes. The vertical flux divergence of humidity appears to be significantly affected by mesoscale influences. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Considine, GD (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. EM considen@asdsun.larc.nasa.gov OI LENSCHOW, DONALD/0000-0003-4353-0098 NR 27 TC 3 Z9 3 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 MAR 20 PY 1999 VL 104 IS D5 BP 5855 EP 5863 DI 10.1029/1998JD100058 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800028 ER PT J AU Olson, JR Baum, BA Cahoon, DR Crawford, JH AF Olson, JR Baum, BA Cahoon, DR Crawford, JH TI Frequency and distribution of forest, savanna, and crop fires over tropical regions during PEM-Tropics A SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HIGH-RESOLUTION RADIOMETER; EMISSIONS; AUSTRALIA; BIOSPHERE; MODEL; LAND AB Advanced very high resolution radiometer 1.1 km resolution satellite radiance data were used to locate active fires throughout much of the tropical region during NASA's Global Tropospheric Experiment (GTE) Pacific Exploratory Mission-Tropics (PEM-Tropics A) aircraft campaign, held in September and October 1996. The spatial and temporal distributions of the fires in Australia, southern Africa, and South America are presented here. The number of fires over northern Australia, central Africa, and South America appeared to decrease toward the end of the mission period. Fire over eastern Australia was widespread, and temporal patterns showed a somewhat consistent amount of burning with periodic episodes of enhanced fire counts observed. At least one episode of enhanced fire counts corresponded to the passage of a frontal system which brought conditions conducive to fire to the region, with strong westerlies originating over the hot, dry interior continent. Regions that were affected by lower than normal rainfall during the previous wet season (e.g., northern Australia and southwestern Africa) showed relatively few fires during this period. This is consistent with a drought-induced decrease in vegetation and therefore a decreased availability of fuel for burning. Alternatively, a heavier than normal previous wet season along the southeastern coast of South Africa may have contributed to high fuel loading and an associated relatively heavy amount of burning compared to data from previous years. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Olson, JR (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. EM j.r.olson@larc.nasa.gov RI Baum, Bryan/B-7670-2011; Crawford, James/L-6632-2013 OI Baum, Bryan/0000-0002-7193-2767; Crawford, James/0000-0002-6982-0934 NR 43 TC 29 Z9 29 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 MAR 20 PY 1999 VL 104 IS D5 BP 5865 EP 5876 DI 10.1029/1998JD100066 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177WV UT WOS:000079234800029 ER PT J AU Davet, J Fagette, S Mani-Ponset, L Bayard, B Dumars, P Reiss-Bubenheim, D Guell, A Gharib, C Gabrion, J AF Davet, J Fagette, S Mani-Ponset, L Bayard, B Dumars, P Reiss-Bubenheim, D Guell, A Gharib, C Gabrion, J TI Cardiac atrial natriuretic peptide (ANP) in rat dams and fetuses developed in space (NIH-R1 and NIH-R2 experiments SO LIFE SCIENCES LA English DT Article DE atrial natriuretic peptide; heart; fetal rat development; space flight; gravitational readaptation ID BRAIN; BINDING; HEART; GENE; RADIOIMMUNOASSAY; EXPRESSION; ONTOGENY AB NIH-R1 and R2 missions, conducted by NASA, allowed us to study the effects of the microgravitational environment 1) on cardiac ANP in pregnant rats, spaceflown for 11 days and dissected after a 2-day readaptation to Earth's gravity, after natural delivery, and 2) on maturation of cardiac ANP system in rat fetuses developed for 11 days in space and dissected on the day of landing, 2 days before birth. Immunocytochemical and electron microscopy analyses showed a typical formation of ANP-containing granules in atrial myocytes, in both dams and fetuses. Using competitive RT-PCR and radioimmunoassays, we observed that, after 2 days of readaptation to Earth's gravity, cardiac ANP biosynthesis of rat dams flown in space was increased by about twice, when compared to Synchronous acid Vivarium Control rats, More obviously, rat fetuses developed in space and dissected on the day of landing displayed an altered maturation of cardiac ANP, evidenced by an increased mRNA biosynthesis (by about 6 fold, p<0.05), whereas the cardiac ANP storage was slightly reduced (by about twice, p<0.05) in both Flight and Synchronous Control groups, in comparison with Vivarium Control rats. These last results suggest that ANP metabolism during development is impacted by the microgravitational environment, but also by the housing conditions designed for space flight. C1 Univ Paris 06, UPMC, CNRS, UMR 7624,Inst Neurosci, Paris, France. Univ Lyon 1, UCBL, Environm Physiol Lab, F-69365 Lyon, France. Univ Montpellier 2, CNRS, UMR 5539, Montpellier, France. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Ctr Natl Etud Spatiales, F-31055 Toulouse, France. RP Gabrion, J (reprint author), Univ Paris 06, UPMC, CNRS, UMR 7624,Inst Neurosci, Paris, France. NR 32 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0024-3205 J9 LIFE SCI JI Life Sci. PD MAR 19 PY 1999 VL 64 IS 17 BP 1533 EP 1541 DI 10.1016/S0024-3205(99)00090-9 PG 9 WC Medicine, Research & Experimental; Pharmacology & Pharmacy SC Research & Experimental Medicine; Pharmacology & Pharmacy GA 179VH UT WOS:000079349900007 PM 10353618 ER PT J AU Srinivasan, J Allison, TC Schwenke, DW Truhlar, DG AF Srinivasan, J Allison, TC Schwenke, DW Truhlar, DG TI Transition state resonances in the reaction Cl+H-2 -> HCl+H SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID CUMULATIVE REACTION PROBABILITIES; QUANTUM SCATTERING-THEORY; HYDROGEN MOLECULES; REACTION O+H2->OH+H; CHEMICAL-REACTIONS; RATE COEFFICIENTS; DYNAMICS; NE+H-2(+)->NEH++H; SYSTEM AB This paper discusses converged quantum mechanical scattering calculations for the reaction Cl + H-2 --> HCl + H and its reverse and analyzes them for the properties of quantized dynamical bottlenecks controlling the total and state-specific microcanonical-ensemble rate constants. These rate constants show clear evidence for quantized transition states. We assign bend and stretch quantum numbers to the transition states for total angular momentum J = 0 with parity P = +1, for J = 1 with P = fl and -1, and for J = 2 and 6 with P = fl. Then, state-specific densities of reactive states (transition state spectral are examined to obtain a detailed picture of the reaction. A quantal estimate of the rotational constant, B, for several different transition states is obtained by comparing transition state energies at different values of the total angular momentum. These quantal estimates are in good agreement with the values calculated from the moments of inertia, and this enables us to interpret the results in terms of state-dependent geometries for the individual dynamical bottlenecks. By treating the transition states as poles in the scattering matrix, we also obtain estimates for the lifetimes of the states. The JP-specific rate coefficients, the reactant-state-specific rate coefficients, and the contribution from each transition state to the JP-specific and the reactant-state-specified rate coefficient are also calculated and the trends analyzed. These trends help explain the dependence of the rate coefficient on initial vibrational and rotational quantum numbers. C1 Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA. Univ Minnesota, Inst Supercomp, Minneapolis, MN 55455 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Srinivasan, J (reprint author), Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA. RI schwenke, david/I-3564-2013; Truhlar, Donald/G-7076-2015 OI Truhlar, Donald/0000-0002-7742-7294 NR 50 TC 19 Z9 19 U1 1 U2 8 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD MAR 18 PY 1999 VL 103 IS 11 BP 1487 EP 1503 DI 10.1021/jp984549k PG 17 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 181TL UT WOS:000079458500008 ER PT J AU Jia, QX Groves, JR Arendt, P Fan, Y Findikoglu, AT Foltyn, SR Jiang, H Miranda, FA AF Jia, QX Groves, JR Arendt, P Fan, Y Findikoglu, AT Foltyn, SR Jiang, H Miranda, FA TI Integration of nonlinear dielectric barium strontium titanate with polycrystalline yttrium iron garnet SO APPLIED PHYSICS LETTERS LA English DT Article ID THIN-FILMS; DEPOSITION; DEVICES; MGO AB Biaxially oriented nonlinear dielectric Ba0.6Sr0.4TiO3 (BST) films have been grown on polycrystalline ferrite yttrium iron garnet (YIG) substrates. We use a structurally and chemically compatible MgO buffer to improve the crystallinity of the BST on polycrystalline YIG substrates, where the biaxially oriented MgO is deposited by an ion-beam assisted-deposition technique. The biaxially oriented BST has a dielectric loss of less than 0.01 and a capacitance tunability of greater than 25% at a direct current bias voltage of 40 V at room temperature. (C) 1999 American Institute of Physics. [S0003-6951(99)00411-8]. C1 Univ Calif Los Alamos Natl Lab, Superconduct Technol Ctr, Los Alamos, NM 87545 USA. NZ Appl Technol, Woburn, MA 01801 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Jia, QX (reprint author), Univ Calif Los Alamos Natl Lab, Superconduct Technol Ctr, Mail Stop K763, Los Alamos, NM 87545 USA. RI Jia, Q. X./C-5194-2008 NR 12 TC 60 Z9 60 U1 2 U2 15 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAR 15 PY 1999 VL 74 IS 11 BP 1564 EP 1566 DI 10.1063/1.123617 PG 3 WC Physics, Applied SC Physics GA 175DT UT WOS:000079078200020 ER PT J AU Kulkarni, A Robinson, S Graff, R Pellis, N AF Kulkarni, A Robinson, S Graff, R Pellis, N TI Prevention of microgravity induced immunosuppression in a ground based animal model by supplemental dietary modification. SO FASEB JOURNAL LA English DT Meeting Abstract C1 St Louis Univ, Hlth Sci Ctr, St Louis, MO 63103 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 1999 VL 13 IS 5 SU S BP A953 EP A953 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 228JG UT WOS:000082132901770 ER PT J AU Reves, C Perez, S Fritsch-Yelle, J AF Reves, C Perez, S Fritsch-Yelle, J TI Orthostatic intolerance following short and long duration spaceflight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Lyndon B Johnson Space Ctr, Wyle Labs, Houston, TX 77058 USA. Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 1999 VL 13 IS 5 SU S BP A1048 EP A1048 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 228JG UT WOS:000082132902316 ER PT J AU Rice, BL Lane, HW Smith, SM AF Rice, BL Lane, HW Smith, SM TI Dietary intake during spaceflight SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Enterprise Advisory Serv Inc, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 1999 VL 13 IS 5 SU S BP A695 EP A695 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 228JG UT WOS:000082132900281 ER PT J AU Stein, TP Leskiw, MJ Schluter, MD Gretebeck, R Lane, HW Hoyt, RW LeBlanc, AD AF Stein, TP Leskiw, MJ Schluter, MD Gretebeck, R Lane, HW Hoyt, RW LeBlanc, AD TI Energy balance during space flight on the shuttle. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Univ Med & Dent New Jersey, Dept Surg, SOM, Newark, NJ 07103 USA. Purdue Univ, Dept Nutr Sci, W Lafayette, IN 47907 USA. NASA, LBJ Space Ctr, Houston, TX USA. USARIEM, Natick, MA USA. Baylor Coll Med, Dept Radiol, Houston, TX 77030 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 1999 VL 13 IS 5 SU S BP A929 EP A929 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 228JG UT WOS:000082132901626 ER PT J AU Tobin, B Leeper-Woodford, S Hashemi, B Sams, C AF Tobin, B Leeper-Woodford, S Hashemi, B Sams, C TI Islet-derived tumor necrosis factor alpha (TNF-alpha) reduces insulin secretion in simulated microgravity. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Mercer Univ, Sch Med, Macon, GA 31207 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 1999 VL 13 IS 5 SU S BP A749 EP A749 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 228JG UT WOS:000082132900589 ER PT J AU Waters, WW D'Aunno, DS Perez, SA Ziegler, MG Fritsch-Yelle, JM AF Waters, WW D'Aunno, DS Perez, SA Ziegler, MG Fritsch-Yelle, JM TI Gender-related differences in cardiovascular responses to orthostatic stress. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Wyle Labs, Natl Space Bio Res Inst, Houston, TX 77058 USA. Univ Calif San Diego, San Diego, CA 92103 USA. NASA, Johnson Space Ctr, Houston, TX 77058 USA. Univ Texas, Med Branch, Galveston, TX 77555 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 15 PY 1999 VL 13 IS 5 SU S BP A1044 EP A1044 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 228JG UT WOS:000082132902292 ER PT J AU Balogh, A Forsyth, RJ Lucek, EA Horbury, TS Smith, EJ AF Balogh, A Forsyth, RJ Lucek, EA Horbury, TS Smith, EJ TI Heliospheric magnetic field polarity inversions at high heliographic latitudes SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ULYSSES OBSERVATIONS; SECTOR STRUCTURE; SOLAR-WIND; EVOLUTION; SOUTHERN; WAVES; POLE AB The heliospheric magnetic field over the poles of the sun has been examined to identify intervals when the polarity of the magnetic field deviates significantly from the calculated Parker spiral, using Ulysses observations in 1994 and 1995, near solar minimum. Intervals with deviation > 90 degrees have been identified, corresponding to magnetic field vectors pointing in the hemisphere opposite to that of the dominant polarity in the high speed solar wind originating in the polar coronal holes. The number of inversion periods decreases as the averaging period is increased from 1 to 12 hours. Their distribution was found to vary in time over the northern solar pole, where the average direction also deviated from the Parker direction. The propagation direction of waves during polarity inversions show that these are caused by large-scale folds in the magnetic field, rather than by opposite polarity magnetic flux tubes originating near the sun. C1 Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Balogh, A (reprint author), Univ London Imperial Coll Sci Technol & Med, Blackett Lab, Prince Consort Rd, London SW7 2BZ, England. NR 17 TC 30 Z9 30 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 15 PY 1999 VL 26 IS 6 BP 631 EP 634 DI 10.1029/1999GL900061 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 177JT UT WOS:000079207400002 ER PT J AU Machida, S Miyashita, Y Ieda, A Nishida, A Mukai, T Saito, Y Kokubun, S AF Machida, S Miyashita, Y Ieda, A Nishida, A Mukai, T Saito, Y Kokubun, S TI GEOTAIL observations of flow velocity and north-south magnetic field variations in the near and mid-distant tail associated with substorm onsets SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA SHEET AB Temporal changes in the plasma flow and magnetic fields of the Earth's magnetotail in the region of -7.5 > X(R-E) > -52.5 and -15 < Y(R-E) < 15 in the CSM coordinates were studied by applying a superposed epoch analysis method to 263 substorm events observed by GEOTAIL spacecraft. The onset times of the substorms were determined with Pi-2 pulsations at Kakioka station. It was found that the tailward flow associated with plasmoids started about 2 or 3 min before the Pi-2 onsets, and the earthward flow became somewhat coherent 1 min before the onsets. The variation of the northward magnetic field component was investigated by obtaining: the deviation of this component from that in the interval from 10.5 to 7.5 min before the Pi-2 onsets. We found that the north ward magnetic field increased at X similar to -10R(E) and decreased at X similar to -28R(E) simultaneously in the premidnight tail immediately after the onsets. These variations definetely correspond to the dipolarization and plasmoid formation, respectively. C1 Kyoto Univ, Dept Geophys, Kyoto 6068502, Japan. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 4428507, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. RP Machida, S (reprint author), Kyoto Univ, Dept Geophys, Kyoto 6068502, Japan. NR 13 TC 72 Z9 73 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 15 PY 1999 VL 26 IS 6 BP 635 EP 638 DI 10.1029/1999GL900030 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 177JT UT WOS:000079207400003 ER PT J AU Yu, LS Rienecker, MM AF Yu, LS Rienecker, MM TI Mechanisms for the Indian Ocean warming during the 1997-98 El Nino SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOUTHERN OSCILLATION; TEMPERATURE AB This study examines primary mechanisms that gave rise to the basin-wide variations of the sea surface temperature (SST) in the Indian Ocean during the 1997-98 El Nine by using multi-source data sets. The evolution of some key atmosphere-ocean variables indicated that the SST variability in the Indian Ocean was largely attributable to the ENSO impact on the large-scale atmospheric circulation. During June-December 1997, when the El Nino in the Pacific was maturing, the Indian Ocean experienced the reversal of the Walker Circulation and the prolonged equatorward displacement of the southeast trades. The resultant changes in surface wind influenced the SST through the following means. In the equatorial region, the easterly winds associated with the reversed Walker Circulation forced equatorial Kelvin/Rossby waves, which then affected the equatorial ocean heat balance (mainly through upwelling/downwelling) and led to the reversal of the zonal SST gradient in the fall of 1997. The negative SST anomalies in the east and positive anomalies in the west in turn helped maintain and prolong the equatorial easterlies, a clear indication of coupled atmosphere-ocean interactions in operation. Outside of the equatorial waveguide, changes of latent heat flux induced by wind speed variations played a major role in the broad-scale warming. The effect was most significant during the summer/fall of 1997 when the southeasterly trade winds weakened considerably, lending to a dramatic reduction of latent heat release and subsequently a rapid surface warming in the southern ocean. C1 Univ Maryland, Dept Meteorol, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Yu, LS (reprint author), Univ Maryland, Dept Meteorol, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. NR 14 TC 151 Z9 160 U1 4 U2 15 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 MAR 15 PY 1999 VL 26 IS 6 BP 735 EP 738 DI 10.1029/1999GL900072 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 177JT UT WOS:000079207400028 ER PT J AU Tait, AB Barrett, EC Beaumont, MJ Brown, PA Taberner, MJ Todd, MC AF Tait, AB Barrett, EC Beaumont, MJ Brown, PA Taberner, MJ Todd, MC TI Interpretation of an atlas of passive microwave-derived rainfall over the eastern North Atlantic ocean and North Sea SO INTERNATIONAL JOURNAL OF CLIMATOLOGY LA English DT Article DE atlas; eastern North Atlantic; rainfall ID WINTER TEMPERATURES; GREENLAND; TRENDS; SEESAW; EUROPE AB Conventional measurements of rainfall over the ocean are fraught with physical and practical problems and instrument difficulties, leading to spatial and temporal inconsistencies in climate datasets. Estimates of rainfall based on the scattering and emission characteristics of passive microwave radiation, measured by instruments on board orbiting satellites, substantially improve the knowledge of rainfall patterns and processes over open water. A new passive microwave satellite-based Atlas of Rainfall and Wind Speed over the Eastern North Atlantic and North Sea has been prepared, including rainfall totals (mm), rates (mm h(-1)), and percent occurrences (%) for the period 1979-1996 inclusive. Annual, seasonal and monthly maps have been generated, as well as histogram and time series products. In this paper, the main rainfall patterns over this region are summarised and interpreted in comparison with several other existing datasets. The interpretation of passive microwave-derived wind speed over the eastern North Atlantic and North Sea shall be reported in a future paper. Upon the analysis of above and below normal rainfall periods, significant relationships are revealed with respect to the mean sea level pressure, air and sea surface temperature, and atmospheric precipitable water. It is shown that the location and strength of the belt of prevailing Westerlies, and their interaction with major land masses, dictate the overall rainfall distribution. Results show that rainfall over this area is well-related to various indices of the general circulation. Also, patterns of rainfall over the North Sea are significantly related to the direction and strength of the wind. Finally, it is shown that there is a significant linear relationship between climate station rainfall and the estimate over the nearest open water pixel, although the percent of explained variance seldom exceeds 50%. Copyright (C) 1999 Royal Meteorological Society. C1 Univ Bristol, Ctr Remote Sensing, Bristol BS8 1SS, Avon, England. RP Tait, AB (reprint author), NASA, Goddard Space Flight Ctr 1, Hydrol Sci Branch, Code 974, Greenbelt, MD 20771 USA. RI todd, martin/I-4143-2015 NR 27 TC 2 Z9 2 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0899-8418 J9 INT J CLIMATOL JI Int. J. Climatol. PD MAR 15 PY 1999 VL 19 IS 3 BP 231 EP 252 DI 10.1002/(SICI)1097-0088(19990315)19:3<231::AID-JOC354>3.0.CO;2-F PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 179HP UT WOS:000079321000001 ER PT J AU Kitaya, N Ansari, RR King, JF Sebag, J AF Kitaya, N Ansari, RR King, JF Sebag, J TI Dynamic light scattering & rheology studies of model vitreous solutions SO INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE LA English DT Meeting Abstract C1 Univ So Calif, Doheny Eye Inst, Los Angeles, CA USA. NASA, Lewis Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 3 PU ASSOC RESEARCH VISION OPHTHALMOLOGY INC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0146-0404 J9 INVEST OPHTH VIS SCI JI Invest. Ophthalmol. Vis. Sci. PD MAR 15 PY 1999 VL 40 IS 4 MA 55B15 BP S11 EP S11 PG 1 WC Ophthalmology SC Ophthalmology GA 178MF UT WOS:000079269200056 ER PT J AU Kwok, R Rothrock, DA AF Kwok, R Rothrock, DA TI Variability of Fram Strait ice flux and North Atlantic Oscillation SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-ICE; FRESH-WATER; CIRCULATION; BALANCE; MODEL AB We estimate the winter sea ice export through the Fram Strait using ice motion from satellite passive microwave data. Sea ice motion (October-May) is obtained by tracking the displacement of common features in sequential 85 and 37 GHz brightness temperature fields. The average winter area flux over the 18-year record (1978-1996) is 670,000 km(2), similar to 7% of the area of the Arctic Ocean. The winter area flux ranges from a minimum of 450,000 km(2) in 1984 to a maximum of 906,000 km(2) in 1995. The daily, monthly, and interannual variabilities of the ice area flux are high. There is an upward trend in the ice area flux over the 18 year record. The average winter volume flux over the winters of October 1990 through May 1995 is 1745 km(3) ranging from a low of 1375 km(3) in the 1990 flux to a high of 2791 km(3) in 1994. The sea level pressure gradient across the Fram Strait explains more than 80% of the variance in the ice flux over the 18 year record. We use the coefficients from the regression of the time series of area flux versus pressure gradient across the Fram Strait and ice thickness data to estimate the summer area and volume flux. The average 12 month area flux and volume flux are 919,000 km(2) and 2366 km(3). We find a significant correlation (R = 0.86) between the area flux and positive phases of the North Atlantic Oscillation (NAO) index over the months of December-March. Correlation between our 5 years of volume flux estimates and the NAO index gives R = 0.56. During the high NAO years a more intense: Icelandic low increases the gradient in the sea level pressure by almost 1 mbar across the Fram Strait, thus increasing the atmospheric forcing on ice transport. Correlation is reduced during the negative NAO years because of decreased dominance of this large-scale atmospheric pattern on the sea level pressure gradient across the Fram Strait. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Washington, Polar Sci Ctr, Appl Phys Lab, Coll Ocean & Fishery Sci, Seattle, WA 98195 USA. RP Kwok, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 18 TC 198 Z9 207 U1 4 U2 15 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAR 15 PY 1999 VL 104 IS C3 BP 5177 EP 5189 DI 10.1029/1998JC900103 PG 13 WC Oceanography SC Oceanography GA 177YZ UT WOS:000079239800003 ER PT J AU Verron, J Gourdeau, L Pham, DT Murtugudde, R Busalacchi, AJ AF Verron, J Gourdeau, L Pham, DT Murtugudde, R Busalacchi, AJ TI An extended Kalman filter to assimilate satellite altimeter data into a nonlinear numerical model of the tropical Pacific Ocean: Method and validation SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID METEOROLOGICAL DATA ASSIMILATION; GULF-STREAM MODEL; SEA-LEVEL; REDUCED-GRAVITY; WIND STRESS; ATLANTIC; CIRCULATION; SIMULATION; HEIGHT; TIME AB A new implementation of the extended Kalman filter scheme is developed for the purpose of assimilating observations into a high-resolution nonlinear numerical model of the tropical Pacific Ocean. It is characterized by two successive stages: (1) approximation of the error covariance matrix by a singular low-rank matrix which leads to making corrections only in those directions for which the error is not naturally attenuated by the system (in this respect it is quite similar to the approach adopted by Carte ct al. [1996]), and (2) modification of these directions over time according to the model dynamics, thus reflecting the evolutive nature of the filter. The filter is initialized by a method based on the empirical orthogonal functions obtained from free runs of the model. The reduction of the error covariance matrix avoids the overwhelming burden of computing the temporal evolution of the prediction error with all the degrees of freedom of the full state vector. This assimilation scheme is implemented in the Gent and Cane [1989] primitive equation reduced gravity model. This model has the advantage of using a a coordinate in the vertical which allows a geographical refinement of the vertical resolution for thermocline gradients. It is forced by the Florida State University database winds, and the Chen et al. [1994] hybrid scheme parametrization ii; assumed for the mixed layer. The domain of application is the tropical Pacific Ocean basin between 120 degrees E and 80 degrees W longitude and 30 degrees S and 30 degrees N latitude. The resolution is finest at the equator and steadily increases away from the equator. In a first application, validation twin experiments are conducted in which observations are assumed to be synthetic altimeter data sampled according to the TOPEX/POSEIDON mission features. The method is shown to be efficient under various conditions and, in particular, to be capable of transferring information in the vertical from the surface-only altimeter data to the deepest ocean layers and therefore of adequately constraining the thermal and the velocity profiles within the 300 or 400 m upper ocean. In a second application, real TOPEX/POSEIDON data are used and the results evaluated against independent in situ data, namely, Tropical Ocean-Global Atmosphere (TOGA)/TAO mooring observations, Improvements in the model behavior are clear in terms of the time variability of the tropical ocean. It therefore seems that the reduced state Kalman filter with empirical orthogonal function (EOF) initialization can be applied with success to such a primitive equation model of the Pacific for the assimilation of altimeter data. However, at this stage the evolutivity of the filter seems to have a limited impact on the performances, which was not the case for tests in the strongly nonlinear midlatitudes [Pham er al., 1998a]. C1 Ctr Natl Rech Sci, Lab Ecoulements Geophys & Ind, UMR 5519, F-38041 Grenoble, France. ORSTOM, Noumea 98848, New Caledonia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lab Modelisat & Calcul, F-38041 Grenoble, France. RP Verron, J (reprint author), Ctr Natl Rech Sci, Lab Ecoulements Geophys & Ind, UMR 5519, BP 53X, F-38041 Grenoble, France. EM verron@hmg.inpg.fr NR 44 TC 74 Z9 76 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAR 15 PY 1999 VL 104 IS C3 BP 5441 EP 5458 DI 10.1029/1998JC900079 PG 18 WC Oceanography SC Oceanography GA 177YZ UT WOS:000079239800020 ER PT J AU Vasudevan, AK Petrovic, JJ Fishman, SG Sorrell, CA Nathal, MV AF Vasudevan, AK Petrovic, JJ Fishman, SG Sorrell, CA Nathal, MV TI Proceedings of the Engineering Foundation High Temperature Structural Silicides Conference, 25-29 May 1998, Hyannis, Massachusetts SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Editorial Material C1 Off Naval Res, Arlington, VA 22217 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. US DOE, Washington, DC 20585 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Vasudevan, AK (reprint author), Off Naval Res, Arlington, VA 22217 USA. NR 0 TC 1 Z9 1 U1 0 U2 1 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD MAR 15 PY 1999 VL 261 IS 1-2 BP IX EP IX PG 1 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 176KY UT WOS:000079151300001 ER PT J AU Hebsur, MG AF Hebsur, MG TI Development and characterization of SiC(f)/MoSi2-Si3N4(p) hybrid composites SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT Engineering Foundation High Temperature Structural Silicides Conference CY MAY 25-29, 1998 CL HYANNIS, MASSACHUSETTS DE hybrid; MoSi2; Si3N4 ID LOW-TEMPERATURE OXIDATION; BEHAVIOR; MOSI2; PEST AB Intermetallic compound MoSi2 has long been known as a high temperature material that has excellent oxidation resistance and electrical/thermal conductivity. Also its low cost, high melting point (2023 degrees C), relatively low density (6.2 g cm(-3) versus 9 g cm(-3) for current engine materials), and ease of machining, make it an attractive structural material. However, the use of MoSi2 has been hindered due to its poor toughness at low temperatures, poor creep resistance at high temperatures? and accelerated oxidation (also known as 'pest' oxidation) at temperatures between approximately 450 and 550 degrees C. Continuous fiber reinforcing is very effective means of improving both toughness and strength. Unfortunately, MoSi2 has a relatively high coefficient of thermal expansion (CTE) compared to potential reinforcing fibers such as SiC. The large CTE mismatch between the fiber and the matrix resulted in severe matrix cracking during thermal cycling. Addition of about 30-50 vol.% of Si3N4 particulate to MoSi2 improved resistance to low temperature accelerated oxidation by forming a Si2ON2 protective scale and thereby eliminating catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness and significantly lowered the CTE of the MoSi2 and eliminated matrix cracking ill SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited excellent strength and toughness improvement up to 1400 degrees C. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites for improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. This hybrid composite remains competitive with ceramic matrix composites as a replacement for Ni-base superalloys in aircraft engine applications. (C) 1999 Elsevier Science S.A. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hebsur, MG (reprint author), NASA, Lewis Res Ctr, 21000 Brookpd Rd, Cleveland, OH 44135 USA. NR 34 TC 39 Z9 45 U1 0 U2 4 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD MAR 15 PY 1999 VL 261 IS 1-2 BP 24 EP 37 DI 10.1016/S0921-5093(98)01046-6 PG 14 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 176KY UT WOS:000079151300005 ER PT J AU Alman, DE Tylczak, JH Hawk, JA Hebsur, MG AF Alman, DE Tylczak, JH Hawk, JA Hebsur, MG TI Solid particle erosion behavior of an Si3N4-MoSi2 composite at room and elevated temperatures SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT Engineering Foundation High Temperature Structural Silicides Conference CY MAY 25-29, 1998 CL HYANNIS, MA DE solid particle erosion; composite; erosion rate ID SI3N4 MATRIX COMPOSITES; ABRASIVE WEAR AB The solid particle erosion behavior at room and elevated temperatures (180, 500, 700 and 900 degrees C) of an Si3N4-MoSi2 composite was studied. Alumina particles entrained in a stream of nitrogen gas impacted the target material at a velocity of 40 m s(-1). Impingement angles of either 60, 75 or 90 degrees were used. It was found that the erosion rate for the Si3N4-MoSi2 composite (measured at room temperature) was a maximum at the 90 degrees incident angle, erosion behavior typical of brittle materials. The erosion rate of the composite at a 75 degrees impingement angle increased slightly with increasing test temperature up to 700 degrees C (i.e. from 4.1 to 4.9 mm(3) g(-1)). At 900 degrees C, the measured erosion rate decreased to 2.9 mm(3) g(-1). The erosion behavior of the Si3N4-MoSi2 composite was compared to that of commercially available Si3N4. WC-6%Co. 304 SS, IN-800 (Ni-Fe-Cr alloy) and Stellite-6B (Co-Cr-W-Mo alloy). (C) 1999 Published by Elsevier Science S.A. All rights reserved. C1 US DOE, Albany Res Ctr, Albany, OR 97321 USA. NASA, Lewis Res Ctr, Cleveland, OH 44142 USA. RP Alman, DE (reprint author), US DOE, Albany Res Ctr, Albany, OR 97321 USA. RI Tylczak, Joseph/C-7956-2009 OI Tylczak, Joseph/0000-0002-0391-2350 NR 15 TC 20 Z9 20 U1 1 U2 8 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 EI 1873-4936 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD MAR 15 PY 1999 VL 261 IS 1-2 BP 245 EP 251 DI 10.1016/S0921-5093(98)01072-7 PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 176KY UT WOS:000079151300031 ER PT J AU Brewer, D AF Brewer, D TI HSR/EPM combustor materials development program SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT Engineering Foundation High Temperature Structural Silicides Conference CY MAY 25-29, 1998 CL HYANNIS, MASSACHUSETTS DE SiC/SiC ceramic matrix; combustor; thermal conductivity AB Significant progress has been made developing a SiC/SiC ceramic matrix composite material for aeronautic combustor liner applications. Improvements in material processing technology have resulted in improved thermal conductivity and fatigue durability. A material characterization effort is underway to assess material behavior and direct material development efforts. The effects of the aggressive combustion environment continue to be a material system development challenge. (C) 1999 Published by Elsevier Science S.A. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Brewer, D (reprint author), NASA, Lewis Res Ctr, 21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 8 TC 129 Z9 130 U1 0 U2 8 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD MAR 15 PY 1999 VL 261 IS 1-2 BP 284 EP 291 DI 10.1016/S0921-5093(98)01079-X PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 176KY UT WOS:000079151300036 ER PT J AU Kowalik, RW Hebsur, MG AF Kowalik, RW Hebsur, MG TI Cyclic oxidation study of MoSi2-Si3N4 base composites SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT Engineering Foundation High Temperature Structural Silicides Conference CY MAY 25-29, 1998 CL HYANNIS, MASSACHUSETTS DE composites; cyclic oxidation; thermal shock resistance ID MOSI2-BASED COMPOSITES AB A series of MoSi2-Si3N4 base composites was evaluated for potential Navy gas turbine engine applications. The composites underwent cyclic oxidation testing to determine their oxidation and thermal shock resistance. Specimens were exposed to 900 degrees C for 55 min followed by a 5 min air-cool. After 500 cycles, the specimens were examined for phase transformations, weight and elemental changes. and thermal shock resistance. (C) 1999 Elsevier Science S.A. All rights reserved. C1 USN, Air Warfare Ctr, Mission Av Technol Dept 4 3 4, Div Aircraft, Patuxent River, MD 20670 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Kowalik, RW (reprint author), USN, Air Warfare Ctr, Mission Av Technol Dept 4 3 4, Div Aircraft, Patuxent River, MD 20670 USA. NR 9 TC 14 Z9 15 U1 0 U2 3 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD MAR 15 PY 1999 VL 261 IS 1-2 BP 300 EP 303 PG 4 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 176KY UT WOS:000079151300038 ER PT J AU Boykin, TB Gamble, LJ Klimeck, G Bowen, RC AF Boykin, TB Gamble, LJ Klimeck, G Bowen, RC TI Valence-band warping in tight-binding models SO PHYSICAL REVIEW B LA English DT Article ID RESONANT MAGNETOTUNNELING SPECTROSCOPY; QUANTUM-WELLS; SPIN-ORBIT; EFFECTIVE MASSES; DISPERSION; SEMICONDUCTORS AB The spin-orbit nearest-neighbor sp(3)s* model is widely believed able to reproduce accurately the valence bands of most m-V and group-IV semiconductors, essential for modeling the in-plane dispersion of valence- and inter-band quantum heterostructures. To check this belief, we study valence-band warping in the spin-orbit sp(3)s* model including interactions up to second-nearest-neighbor, providing exact, analytic formulas for the [110] and [111] light- and heavy-hole masses; Surprisingly, we find that the second-nearest-neighbor model offers significantly more flexibility in fitting these masses independently of those along [001] than does the nearest-neighbor model. [S0163-1829(99)10007-9]. C1 Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. Univ Alabama, LICOS, Huntsville, AL 35899 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Boykin, TB (reprint author), Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. RI Klimeck, Gerhard/A-1414-2012 OI Klimeck, Gerhard/0000-0001-7128-773X NR 15 TC 20 Z9 21 U1 0 U2 2 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD MAR 15 PY 1999 VL 59 IS 11 BP 7301 EP 7304 DI 10.1103/PhysRevB.59.7301 PG 4 WC Physics, Condensed Matter SC Physics GA 182PQ UT WOS:000079507700013 ER PT J AU Boykin, TB Lake, RK Klimeck, G Swaminathan, M AF Boykin, TB Lake, RK Klimeck, G Swaminathan, M TI Interface effects in tunneling models with identical real and complex dispersions SO PHYSICAL REVIEW B LA English DT Article ID DIODE AB Simple heterostructure models are often employed due to their computational efficiency. The approximations involved are not, however, well understood; this is particularly true with respect to the interfaces. In order to clarify this situation we study two different monoatomic (single-band) models and two different diatomic (two-band) models all having identical dispersion relations. We study in detail the relationships between the one- and two-band models, showing that their points of agreement and disagreement arise directly from the handling of the interfaces. [S0163-1829(99)01111-X]. C1 Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. Univ Alabama, LICOS, Huntsville, AL 35899 USA. Raytheon Syst, Dallas, TX 75266 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Boykin, TB (reprint author), Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35899 USA. RI Klimeck, Gerhard/A-1414-2012 OI Klimeck, Gerhard/0000-0001-7128-773X NR 9 TC 1 Z9 1 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD MAR 15 PY 1999 VL 59 IS 11 BP 7316 EP 7319 DI 10.1103/PhysRevB.59.7316 PG 4 WC Physics, Condensed Matter SC Physics GA 182PQ UT WOS:000079507700017 ER PT J AU Kim, HI Lee, CH MacGibbon, JH AF Kim, HI Lee, CH MacGibbon, JH TI Diffuse gamma-ray background and primordial black hole constraints on the spectral index of density fluctuations SO PHYSICAL REVIEW D LA English DT Article ID PARTICLE EMISSION RATES; GLUON-JET EMISSION; MASSLESS PARTICLES; NONROTATING HOLE; QUARK-JET; RELICS; ASTRONOMY; INFLATION; RADIATION; UNIVERSE AB We calculate the flux of gamma rays emitted from primordial black holes (PBHs) which are formed by a "blue" power-law spectrum of density fluctuations in the early universe. Gamma-ray emission from such PBHs may contribute significantly to the observed extragalactic diffuse gamma-ray background (DGB). Using the observed DGB flux from the imaging Compton Telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) as the upper limit of gamma-ray flux from PBHs, we derive the upper limit on the spectral index n of the density fluctuations. The range of initial PBH masses which can contribute to the DGB is 2 X 10(13) g(-5) X 10(14) g, corresponding to a cosmic reheating temperature of 7 X 10(7) GeV - 4 X 10(8) GeV. In this range, we find the upper limit to be n less than or similar to 1.23 - 1.25. This limit is stronger than those derived from the energy density in PBHs or PBH relies and matches the value of n required to explain the cosmic microwave background anisotropy. [S0556-2821(99)05804-X]. C1 Hanyang Univ, Res Inst Nat Sci, Seoul 133791, South Korea. Hanyang Univ, Dept Phys, Seoul 133791, South Korea. NASA, Lyndon B Johnson Space Ctr, Code SN3, Houston, TX 77058 USA. RP Kim, HI (reprint author), Hanyang Univ, Res Inst Nat Sci, Seoul 133791, South Korea. NR 55 TC 30 Z9 30 U1 0 U2 1 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 MAR 15 PY 1999 VL 59 IS 6 AR 063004 DI 10.1103/PhysRevD.59.063004 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 177WQ UT WOS:000079234400010 ER PT J AU Girimaji, SS AF Girimaji, SS TI Reduction of large dynamical systems by minimization of evolution rate SO PHYSICAL REVIEW LETTERS LA English DT Article AB Reduction of a large system of equations to a lower-dimensional system of similar essential dynamics is investigated. For dynamical systems with disparate time scales, a criterion for determining redundant dimensions and a general reduction method based on the minimization of evolution rate are proposed. C1 NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. RP Girimaji, SS (reprint author), NASA, Langley Res Ctr, ICASE, MS 403,6 N Dryden St,Bldg 1298, Hampton, VA 23681 USA. NR 6 TC 10 Z9 10 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD MAR 15 PY 1999 VL 82 IS 11 BP 2282 EP 2285 DI 10.1103/PhysRevLett.82.2282 PG 4 WC Physics, Multidisciplinary SC Physics GA 175QV UT WOS:000079107000015 ER PT J AU Arepalli, S Scott, CD AF Arepalli, S Scott, CD TI Spectral measurements in production of single-wall carbon nanotubes by laser ablation SO CHEMICAL PHYSICS LETTERS LA English DT Article ID OPTICAL-EMISSION; BAND SYSTEM; VAPORIZATION; GROWTH AB Measurements are made of optical radiation from the luminous plume in a flow tube used to produce single-wall carbon nanotubes by laser ablation of graphite. Measurements include 10 mu s exposures for a spectral region of 310-630 nm taken at several times after single and two-laser pulses and time-dependent measurements at a number of wavelengths. Strong emission from the C-2 Swan bands and possibly from C-3 are seen superimposed on a significant continuum the origin of which is uncertain. Temperatures estimated from ratios of intensities of Swan band features are in the range of 2500-4000 K. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. GB Tech, Houston, TX 77058 USA. RP Scott, CD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. EM c.scott@jsc.nasa.gov RI Arepalli, Sivaram/A-5372-2010 NR 19 TC 61 Z9 62 U1 1 U2 6 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 MAR 12 PY 1999 VL 302 IS 1-2 BP 139 EP 145 DI 10.1016/S0009-2614(99)00098-6 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 175TE UT WOS:000079110500023 ER PT J AU Clarke, MSF Bamman, MM Feeback, DL AF Clarke, MSF Bamman, MM Feeback, DL TI Modulation of sarcolemma cholesterol content during muscle unloading SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, USRA, Houston, TX 77058 USA. UAB, Dept Human Studies, Birmingham, AL 35294 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A415 EP A415 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302397 ER PT J AU Davis-Street, JE Smith, SM AF Davis-Street, JE Smith, SM TI Nutritional status assessment in a semi-closed food system: Implications for space flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Enterprise Advisory Serv Inc, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A265 EP A265 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033301530 ER PT J AU Dubin, S Cozmi, M Ansari, RR Gross, ML Ritz, E Parkman, A Tulp, O AF Dubin, S Cozmi, M Ansari, RR Gross, ML Ritz, E Parkman, A Tulp, O TI In vivo characterization of cataract in naphthalene toxicity, aging, and diabetic animal models via noninvasive dynamic light scattering (DLS). SO FASEB JOURNAL LA English DT Meeting Abstract C1 Drexel Univ, Philadelphia, PA 19104 USA. NASA, Cincinnati, OH USA. Univ Heidelberg, Heidelberg, Germany. NR 0 TC 0 Z9 0 U1 1 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A375 EP A375 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302168 ER PT J AU Grindeland, R Dotsenko, MR Bigbee, AJ Bengtson, S AF Grindeland, R Dotsenko, MR Bigbee, AJ Bengtson, S TI Monkey hormonal responses to spaceflight SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Moscow Biomed Problems Inst, Moscow, Russia. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A404 EP A404 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302330 ER PT J AU Leeper-Woodford, S Tobin, B Hashemi, B Sams, C AF Leeper-Woodford, S Tobin, B Hashemi, B Sams, C TI Pancreatic islet tumor necrosis factor-alpha (TNF) activity is reduced during exposure to simulated microgravity. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Mercer Univ, Sch Med, Macon, GA 31207 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A405 EP A405 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302335 ER PT J AU Matsuyama, M Ueno, T Yang, C Lillywhite, HB Hargens, AR AF Matsuyama, M Ueno, T Yang, C Lillywhite, HB Hargens, AR TI Evolutionary adaptation of intracranial pressure to gravity. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Space Physiol Lab, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A127 EP A127 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033300734 ER PT J AU Moran, MM Wade, CE Stein, TP Hoban-Higgins, TM Fuller, P Fuller, CA AF Moran, MM Wade, CE Stein, TP Hoban-Higgins, TM Fuller, P Fuller, CA TI Different responses in protein metabolism in mature and young rats during centrifugation at 2.0 G. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Med & Dent New Jersey, Stratford, NJ 08084 USA. Univ Calif Davis, Davis, CA 95616 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A404 EP A404 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302332 ER PT J AU Nillen, JL Demers, LM Lane, HW Smith, SM AF Nillen, JL Demers, LM Lane, HW Smith, SM TI Confounding effects on measurements of bone resorption markers SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Enterprise Advisory Serv Inc, Houston, TX 77058 USA. MS Hershey Med Ctr, Hershey, PA 17033 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A428 EP A428 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302469 ER PT J AU Pantalos, G Hart, S Mathias, J Sharp, MK Watenpaugh, D Buckey, J Hargens, A AF Pantalos, G Hart, S Mathias, J Sharp, MK Watenpaugh, D Buckey, J Hargens, A TI Venous and esophageal pressure in humans during parabolic flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Univ Texas, Med Branch, Galveston, TX 77555 USA. Univ Utah, Salt Lake City, UT 84103 USA. Univ N Texas, Ft Worth, TX 76107 USA. NASA, Ames Res Ctr, San Jose, CA 94035 USA. NR 0 TC 3 Z9 3 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A108 EP A108 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033300623 ER PT J AU Smith, SM Davis-Street, JE Rice, BL Block, G AF Smith, SM Davis-Street, JE Rice, BL Block, G TI Nutritional status assessment during space flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. RI Block, Gladys/E-3304-2010 NR 0 TC 2 Z9 2 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A265 EP A265 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033301528 ER PT J AU South, DA Martin, DS Wood, ML Leuenberger, U AF South, DA Martin, DS Wood, ML Leuenberger, U TI Comparison of preflight and postflight echocardiography measurements alter short and long duration spaceflight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Cardiovasc Lab, Wyle Labs, Houston, TX 77058 USA. Penn State Univ, Coll Med, Hershey, PA 17033 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A108 EP A108 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033300620 ER PT J AU Wade, CE Moran, MM Stein, TP Hoban-Higgins, TM Fuller, P Fuller, CA AF Wade, CE Moran, MM Stein, TP Hoban-Higgins, TM Fuller, P Fuller, CA TI Absence of change in total daily energy expenditure (EETD) in young and mature rats during 14 days of hypergravity. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Med & Dent New Jersey, Stratford, NJ 08084 USA. Univ Calif Davis, Davis, CA 95616 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A405 EP A405 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302336 ER PT J AU Watenpaugh, D Schneider, S Ballard, R Lee, S Hutchinson, K William, J Ertl, A Boda, W Hargens, A AF Watenpaugh, D Schneider, S Ballard, R Lee, S Hutchinson, K William, J Ertl, A Boda, W Hargens, A TI Supine LBNP treadmill exercise reverses bed rest-induced skeletal deconditioning SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A406 EP A406 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302346 ER PT J AU Williams, WJ Lee, SMC Stuart, CA Whitson, PA Schneider, SM AF Williams, WJ Lee, SMC Stuart, CA Whitson, PA Schneider, SM TI Effect of bed rest and dietary sodium on forearm blood flow (FBF) during lower body negative pressure (LBNP) SO FASEB JOURNAL LA English DT Meeting Abstract C1 Wyle Labs, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Texas, Med Branch, Galveston, TX 77555 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 12 PY 1999 VL 13 IS 4 SU S BP A405 EP A405 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 226QW UT WOS:000082033302338 ER PT J AU Martin, EL Brandner, W Basri, G AF Martin, EL Brandner, W Basri, G TI A search for companions to nearby brown dwarfs: The binary DENIS-PJ1228.2-1547 SO SCIENCE LA English DT Article ID CLUSTER; SPECTROSCOPY; DISCOVERY; LITHIUM; PLANETS; STARS; DENIS AB Hubble Space Telescope imaging observations of two nearby brown dwarfs, DENIS-P J1228.2-1547 and Kelu 1, made with the near-infrared camera and multiobject spectrometer (NICMOS), show that the DENIS object is resolved into two components of nearly equal brightness with a projected separation of 0.275 are second (5 astronomical units for a distance of 18 parsecs), This binary system will be able to provide the first dynamical measurement of the masses of two brown dwarfs in only a few years. Upper Limits to the mass of any unseen companion in Kelu 1 yield a planer of 7 Jupiter masses aged 0.5 x 10(9) years, which would have been detected at a separation Larger than about 4 astronomical units. This example demonstrates that giant planets could be detected by direct imaging if they exist in Jupiter-like orbits around nearby young brown dwarfs. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Martin, EL (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. NR 33 TC 109 Z9 109 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD MAR 12 PY 1999 VL 283 IS 5408 BP 1718 EP 1720 DI 10.1126/science.283.5408.1718 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 175PF UT WOS:000079102800046 ER PT J AU Desvoivres, E Klinger, J Levasseur-Regourd, AC Lecacheux, J Jorda, L Enzian, A Colas, F Frappa, E Laques, P AF Desvoivres, E Klinger, J Levasseur-Regourd, AC Lecacheux, J Jorda, L Enzian, A Colas, F Frappa, E Laques, P TI Comet C/1996 B2 Hyakutake: observations, interpretation and modelling of the dynamics of fragments of cometary nuclei SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE methods : numerical; techniques : image processing; celestial mechanics, stellar dynamics; comets : general; comets : individual : C/1996 B2 Hyakutake ID GRIGG-SKJELLERUP; DUST; H2O AB Comet C/1996 B2 Hyakutake was extensively observed at the Pic du Midi observatory during late March of 1996, Bright condensations were observed in the near-nucleus coma. We have performed a detailed data analysis in order to derive the position of these features with respect to the nucleus. We make the hypothesis that they are induced by fragments of the nucleus. Despite the frequency of fragmentation of cometary nuclei, the dynamics of the fragments is not yet well understood. We propose a general approach in order to study the motion of the fragments in the orbital plane of the comet. An estimate of the non-gravitational forces is used to describe the motion of the fragment and of the nucleus with respect to their centre of mass. Then the equations of the theory of perturbed Keplerian motion are solved in order to study the motion of the centre of mass, This approach is applied to Comet C/1996 B2 Hyakutake, The results are in good agreement with the observations, An excellent fit is obtained for a fragment size of 20 m, assuming a density of 300 kg m(-3). C1 Univ Grenoble 1, CNRS, LGGE, F-38402 St Martin Dheres, France. Univ Paris 06, Serv Aeron, CNRS, F-91371 Verrieres Buisson, France. Observ Meudon, F-92195 Meudon, France. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Bur Longitudes, F-75013 Paris, France. Planetarium St Etienne, Espace Fauriel, F-42100 St Etienne, France. Observ Pic Midi, F-65201 Bagneres De Bigorre, France. RP Desvoivres, E (reprint author), Univ Grenoble 1, CNRS, LGGE, 54 Rue Moliere,BP 96, F-38402 St Martin Dheres, France. OI Frappa, Eric/0000-0001-5327-7781 NR 28 TC 17 Z9 17 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAR 11 PY 1999 VL 303 IS 4 BP 826 EP 834 DI 10.1046/j.1365-8711.1999.02294.x PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 180LW UT WOS:000079388300021 ER PT J AU Macomb, DJ Gehrels, N Shrader, CR AF Macomb, DJ Gehrels, N Shrader, CR TI A gamma-ray flare from PKS 2255-282 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; quasars : individual (PKS 2255 - 282); X-rays : galaxies ID EXTRAGALACTIC RADIO-SOURCES; OBJECTS; CATALOG AB A gamma-ray flare from the quasar PKS 2255-282 was detected in 1997 December by the EGRET instrument on board the Compton Gamma Ray Observatory (CGRO). Previously undetected at gamma-ray energies, the source remained bright for 2 weeks of observations with weak evidence of gamma-ray variability within the hare observation. The average flux was (1.6 +/- 0.3) x 10(-6) cm(-2) s(-1) above: 100 MeV with a hard power-law index of 1.7 +/- 0.3. This places the outburst among the brightest detected by EGRET. A later Rossi X-Ray Timing Explorer (RXTE) observation revealed a simple power-law spectrum with photon index 1.8 and 2-10 keV flux of 1.44 x 10(-11) ergs cm(-2) s(-1). This paper describes the CGRO and RXTE observations and data analysis, the source identification, and gamma-ray variability. We also consider the broadband spectrum, albeit on the basis of nonsimultaneous multiwavelength measurements, and the nature of the outburst from this source in the context of other known gamma-ray blazars. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Macomb, DJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 16 TC 8 Z9 8 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1999 VL 513 IS 2 BP 652 EP 655 DI 10.1086/306869 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YG UT WOS:000079816000012 ER PT J AU Marley, MS Gelino, C Stephens, D Lunine, JI Freedman, R AF Marley, MS Gelino, C Stephens, D Lunine, JI Freedman, R TI Reflected spectra and albedos of extrasolar giant planets. I. Clear and cloudy atmospheres SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : stars; planetary systems; radiative transfer; stars : low-mass, brown dwarfs ID JOVIAN PLANETS; BROWN DWARFS; NEPTUNE; COMPANION; JUPITER; URANUS; SPECTROPHOTOMETRY; ULTRAVIOLET; VENUS; GAS AB The reflected spectra of extrasolar giant planets are primarily influenced by Rayleigh scattering, molecular absorption, and atmospheric condensates. We present model geometric albedo and phase-integral spectra and Bond albedos for planets and brown dwarfs with masses between 0.8 and 70 Jupiter masses. Rayleigh scattering predominates in the blue while molecular absorption removes most red and infrared photons. Thus cloud-free atmospheres, found on giant planets with effective temperatures exceeding about 400 K, are quite dark in reflected light beyond 0.6 mu m. In cooler atmospheres, first water clouds and then other condensates provide a bright reflecting layer. Only planets with cloudy atmospheres will be detectable in reflected light beyond 1 mu m. Thermal emission dominates the near-infrared for warm objects with clear atmospheres. However the presence of other condensates, not considered here, may brighten some planets in reflected near-infrared light and darken them in the blue and UV. Bond albedos, the ratio of the total reflected to incident power, are sensitive to the spectral type of the primary. Most incident photons from early-type stars will be Rayleigh scattered, while most incident photons from late-type stars will be absorbed. The Bond albedo of a given planet thus may range from 0.4 to 0.05, depending on the primary type. Condensation of a water cloud may increase the Bond albedo of a planet by up to a factor of 2. The spectra of cloudy planets are strongly influenced by poorly constrained cloud microphysical properties, particularly particle size and supersaturation. Both Bond and geometric albedos are comparatively less sensitive to variations in planet mass and effective temperature. C1 New Mexico State Univ, Las Cruces, NM 88003 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Space Phys Res Inst, Moffett Field, CA 94035 USA. RP New Mexico State Univ, Las Cruces, NM 88003 USA. EM mmarley@nmsu.edu RI Marley, Mark/I-4704-2013 NR 35 TC 153 Z9 156 U1 0 U2 5 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 MAR 10 PY 1999 VL 513 IS 2 BP 879 EP 893 DI 10.1086/306881 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YG UT WOS:000079816000032 ER PT J AU Ray, A Harding, AK Strickman, M AF Ray, A Harding, AK Strickman, M TI Rossi X-ray Timing Explorer observation of PSR B1706-44 and implications for theoretical models of pulsar emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (PSR B1706-44); stars : neutron; X-rays : stars ID RAPIDLY SPINNING PULSARS; ENERGETIC RADIATION; UPPER LIMITS; RADIO; GAPS; CASCADES; SPECTRA; VELA; CRAB AB We report on results of an observation with the Rossi X-Ray Timing Explorer (RXTE) of PSR B1706-44, with a live time of 132 ks, to search for pulsed X-ray emission. PSR B1706-44 is a radio and high-energy gamma-ray pulsar (detected by EGRET), but no pulsed emission has been detected in the X-ray band. Since most of the other known gamma-ray pulsars emit pulsed X-rays, it is expected that PSR B1706-44 would also be an X-ray pulsar. However, while the ROSAT PSPC detected a source at the pulsar position, it did not detect pulsations, giving a pulsed fraction upper limit of 18%. The RXTE observations to search for modulation at the pulsar period were carried out in 1996 November and 1997 May during the low states of the nearby X-ray binary 4U 1705-44. No significant modulation was detected at the pulsar period, giving an upper limit of 10(-6) photons cm(-2) s(-1) keV(-1) in the interval 9 less than or equal to E less than or equal to 18.5 keV. The implications of this upper limit of the pulsed flux from the RXTE observation, taken together with multiband observations of this pulsar, are examined in the context of theoretical models of pulsar particle acceleration zones and associated high-energy electromagnetic emission. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN, Res Lab, Div Space Sci, Washington, DC 20375 USA. RP NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM akr@tifr.res.in RI Harding, Alice/D-3160-2012 NR 35 TC 9 Z9 9 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1999 VL 513 IS 2 BP 919 EP 926 DI 10.1086/306870 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YG UT WOS:000079816000035 ER PT J AU Feibelman, WA AF Feibelman, WA TI Chances and absorption features in the ultraviolet spectrum of the PG 1159-type central star RX J2117+3412 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (RX J2117+3412); ultraviolet : stars ID PLANETARY-NEBULA; IUE SPECTRUM; SEQUENCE AB Comparison of IUE high- and low-dispersion spectra for the PG 1159-type central star of RX J2117+3412 indicates that the stellar continuum level and some absorption features decreased between 1993 and 1995. These observed changes may represent a new phenomenon not previously known to occur in PG 1159-type DO degenerates. The definite detection of O v lambda 1371 in co-added 1993 IUE spectra suggests that T-eff for the star may have been even higher than 170,000 K in 1993. Radial velocities and equivalent widths were measured for more than 60 photospheric and circumstellar/interstellar features, some of which are compared with published data obtained from HST GHRS and IUE. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 25 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1999 VL 513 IS 2 BP 947 EP 955 DI 10.1086/306883 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YG UT WOS:000079816000039 ER PT J AU Woo, R Habbal, SR Howard, RA Korendyke, CM AF Woo, R Habbal, SR Howard, RA Korendyke, CM TI Extension of the polar coronal hole boundary into interplanetary space SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : corona ID SOLAR-WIND; WHITE-LIGHT; PHYSICAL-PROPERTIES; SCALE STRUCTURES; ULYSSES; STREAMERS; EXPANSION; MINIMUM; SPEED; SLOW AB White-light measurements made by the SOHO LASCO C2 and C3 coronagraphs and the Mk III Mauna Loa K-coronameter, ranging from 1.15 to 30 R. have been combined with Kitt Peak daily He I 1083 nm coronal hole maps, and full Sun Yohkoh soft X-ray images, to show that the boundaries of polar coronal holes, as determined by measurements of path-integrated density, extend approximately radially into interplanetary space. These results are in contrast to the long-standing view that the boundaries of polar coronal holes diverge significantly beyond radial, evolving around the edges of streamers. The combined observations also show that the corona is dominated by raylike structures as small as a few degrees in angular size with respect to Sun center, originating from both coronal holes and the quiet Sun. This analysis provides further support for results originally derived from radio occultation measurements, namely, that the coronal density projects itself almost radially from the Sun into the outer corona, implying that open field lines abound in the quiet Sun from which the fast wind can also originate. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RP Woo, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 238-725, Pasadena, CA 91109 USA. NR 26 TC 14 Z9 14 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1999 VL 513 IS 2 BP 961 EP 968 DI 10.1086/306899 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YG UT WOS:000079816000041 ER PT J AU Millan-Gabet, R Schloerb, FP Traub, WA Malbet, F Berger, JP Bregman, JD AF Millan-Gabet, R Schloerb, FP Traub, WA Malbet, F Berger, JP Bregman, JD TI Sub-astronomical unit structure of the near-infrared emission from AB Aurigae SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; infrared : stars; stars : emission-line, Be; stars : individual (AB Aurigae); stars : pre-main-sequence; techniques : interferometric ID HERBIG AE/BE STARS; INTERMEDIATE-MASS STARS; CIRCUMSTELLAR MATTER; DISKS; EXCESS; LINES; DUST AB We present near-infrared, long-baseline, interferometric observations of AB Aurigae, a well-known Herbig Ae/ Be star, obtained with the Infrared Optical Telescope Array. The near-infrared emission from this source has been spatially resolved for the first time, and the observations indicate a characteristic diameter of 5 mas for the emission, corresponding to 0.7 AU at the distance of AB Aur. The data appear to be most consistent with models in which the circumstellar material around AB Aurigae lies in a Battened structure with a central large hole or optically thin region of radius about 0.3 AU. C1 Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Observ Grenoble, Astrophys Lab, F-38041 Grenoble, France. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Millan-Gabet, R (reprint author), Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. NR 19 TC 53 Z9 53 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1999 VL 513 IS 2 BP L131 EP L134 DI 10.1086/311926 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YJ UT WOS:000079816200011 ER PT J AU Schneider, G Smith, BA Becklin, EE Koerner, DW Meier, R Hines, DC Lowrance, PJ Terrile, RJ Thompson, RI Rieke, M AF Schneider, G Smith, BA Becklin, EE Koerner, DW Meier, R Hines, DC Lowrance, PJ Terrile, RJ Thompson, RI Rieke, M TI NICMOS imaging of the HR 4796A circumstellar disk SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; infrared : stars; planetary systems; stars : individual (HR 4796A) ID BETA-PICTORIS; DUST DEBRIS; HR-4796 AB We report the first near-infrared (NIR) imaging of a circumstellar annular disk around the young (similar to 8 Myr), Vega-like star HR 4796A. NICMOS coronagraph observations at 1.1 and 1.6 mu m reveal a ringlike symmetrical structure that peaks in reflected intensity 1." 05 +/- 0." 02 (similar to 70 AU) from the central AO V star. The ring geometry, with an inclination of 73.degrees 1 +/- 1.degrees 2 and a major axis position angle of 26.degrees 8 +/- 0.degrees 6, is in good agreement with recent 12.5 and 20.8 mu m observations of a truncated disk. The ring is resolved with a characteristic width of less than 0." 26 (17 AU) and appears abruptly truncated at both the inner and outer edges. The region of the disk-plane inward of similar to 60 AU appears to be relatively free of scattering material. The integrated flux density of the part of the disk that is visible (greater than 0." 65 from the star) is found to be 7.6 +/- 0.5 and 7.4 +/- 1.2 mJy at 1.1 and 1.6 mu m, respectively. Correcting for the unseen area of the ring yields total flux densities of 12.8 +/- 1.0 and 12.5 +/- 2.0 mJy, respectively (Vega magnitudes equal to 12.92 +/- 0.08 and 12.35 +/- 0.18). The NIR luminosity ratio is evaluated from these results and ground-based photometry of the star. At these wavelengths, L-disk(lambda)/L-*(lambda) is equal to 1.4 +/- 0.2 x 10(-3) and 2.4 +/- 0.5 x 10(-3), giving reasonable agreement between the stellar flux scattered in the NIR and that which is absorbed in the visible and reradiated in the thermal infrared. The somewhat red reflectance of the disk at these wavelengths implies a mean particle size in excess of several microns, which is larger than typical interstellar grains. The confinement of material to a relatively narrow annular zone implies dynamical constraints on the disk particles by one or more as yet unseen bodies. C1 Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Univ Hawaii, Inst Astron, Hilo, HI 96720 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ Penn, Philadelphia, PA 19104 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Schneider, G (reprint author), Univ Arizona, Steward Observ, 933 N Cherry Ave, Tucson, AZ 85721 USA. NR 18 TC 123 Z9 124 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1999 VL 513 IS 2 BP L127 EP L130 DI 10.1086/311921 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YJ UT WOS:000079816200010 ER PT J AU Stibbe, DT Tennyson, J AF Stibbe, DT Tennyson, J TI Rates for the electron impact dissociation of molecular hydrogen SO ASTROPHYSICAL JOURNAL LA English DT Article DE molecular data; molecular processes; scattering ID EMISSION; CLOUDS AB At astrophysically relevant temperatures (below 15,000 K), electron impact dissociation of H-2 occurs through the excitation of the dissociative b (3)Sigma(u)(+) state. We have calculated and parameterized the rates of dissociation as a function of electron temperature for the v = 0-4 H-2, vibrational states. The assumption that the v = 0 rate approximates to the rate at local thermal equilibrium (LTE) is found to be seriously flawed. Instead, the rates are found to depend so critically on the initial vibrational level that dissociation from very high-lying vibrational levels must be included in calculations of the rate at LTE even at low temperature. An extrapolation procedure is used to approximate the rates for all of the higher vibrational levels (v = 5-14), which are then used to calculate the LTE rate. The LTE rate is found to be around 2 orders of magnitude greater than the v = 0 rate. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. UCL, Dept Phys & Astron, London WC1E 6BT, England. RP Stibbe, DT (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM j.tennyson@ucl.ac.uk RI Tennyson, Jonathan/I-2222-2012 OI Tennyson, Jonathan/0000-0002-4994-5238 NR 13 TC 29 Z9 29 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1999 VL 513 IS 2 BP L147 EP L150 DI 10.1086/311918 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187YJ UT WOS:000079816200015 ER PT J AU Laymon, CA Crosson, WL Soman, VV Belisle, WR Coleman, TL Fahsi, A Manu, A Senwo, ZN Tsegaye, TD O'Neill, PE Jackson, TJ AF Laymon, CA Crosson, WL Soman, VV Belisle, WR Coleman, TL Fahsi, A Manu, A Senwo, ZN Tsegaye, TD O'Neill, PE Jackson, TJ TI Huntsville'96: an experiment in ground-based microwave remote sensing of soil moisture SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB 'Huntsville '96' was an experiment in ground-based remote sensing to acquire data needed to test and refine algorithms to estimate soil moisture on bare and vegetated plots. Remote sensing instruments included a L, S, and C-band microwave radiometer and a L, C, and X-band radar. The remote sensing measurements were supported with automated and manual measurements of numerous soil and vegetation variables. The remote sensing instruments were able to detect both the large surface moisture changes due to rainfall and subsequent drying as well as the diurnal fluctuations in moisture. These data will be used to refine techniques to estimate moisture in the surface layer of soil, address issues related to the sensitivity of algorithms, the integration of data from passive and active systems, and the use of surface soil moisture estimates to increase the accuracy of soil moisture profile estimates. Although in-depth analyses of the data are underway, collaboration with other investigators is being encouraged. C1 Inst Global Change Res & Educ, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Alabama A&M Univ, Ctr Hydrol Soil Climatol & Remote Sensing, Normal, AL 35762 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. ARS, Hydrol Lab, USDA, Beltsville, MD 20705 USA. RP Laymon, CA (reprint author), Inst Global Change Res & Educ, Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. RI O'Neill, Peggy/D-2904-2013 NR 5 TC 12 Z9 12 U1 0 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD MAR 10 PY 1999 VL 20 IS 4 BP 823 EP 828 DI 10.1080/014311699213244 PG 6 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 177JJ UT WOS:000079206600013 ER PT J AU Foss, JK Zaman, KBMQ AF Foss, JK Zaman, KBMQ TI Large- and small-scale vortical motions in a shear layer perturbed by tabs SO JOURNAL OF FLUID MECHANICS LA English DT Article ID PLANE MIXING-LAYER; JET; TURBULENCE; TRANSITION; VORTEX; EVOLUTION; ENHANCEMENT AB The large- and small-scale vortical motions produced by 'delta tabs' in a two-stream shear layer have been studied experimentally An increase in mixing was observed when the base of the triangular shaped tab was affixed to the trailing edge of the splitter plate and the apex was pitched at some angle with respect to the flow axis. Such an arrangement produced a pair of counter-rotating streamwise vortices. Hot-wire measurements detailed the velocity, time-averaged vorticity (Omega(x)) and small-scale turbulence features in the three-dimensional space downstream of the tabs. The small-scale structures, whose scale corresponds to that of the peak in the dissipation spectrum, were identified and counted using the peak-valley-counting technique. The optimal pitch angle, theta, for a single tab and the optimal spanwise spacing, S, for a multiple tab array were identified. Since the goal was to increase mixing, the optimal tab configuration was determined from two properties of the flow held: (i) the large-scale motions with the maximum Omega(x) and (ii) the largest number of small-scale motions in a given time period. The peak streamwise vorticity magnitude \Omega(x)_(max)\ was found to have a unique relationship with the tab pitch angle. Furthermore, for all cases examined, the overall small-scale population was found to correlate directly with \Omega(x)_(max)\. Both quantities peaked at theta approximate to +/-45 degrees. It is interesting to note that the peak magnitude of the corresponding circulation in the cross-sectional plane occurred for theta approximate to +/-90 degrees. For an array of tabs, the two quantities also depended on the tab spacing. An array of contiguous tabs acted as a solid deflector producing the weakest streamwise vortices and the least small-scale population. For the measurement range covered, the optimal spacing was found to be S approximate to 1.5 tab widths. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Foss, JK (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 35 TC 42 Z9 44 U1 1 U2 2 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD MAR 10 PY 1999 VL 382 BP 307 EP 329 DI 10.1017/S0022112098003887 PG 23 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 184VY UT WOS:000079635500012 ER PT J AU Lundgren, T Koumoutsakos, P AF Lundgren, T Koumoutsakos, P TI On the generation of vorticity at a free surface SO JOURNAL OF FLUID MECHANICS LA English DT Article ID VORTEX METHODS; DYNAMICS; WAVE; FLOW AB The mechanism for the generation of vorticity at a viscous free surface is described. This is a free-surface analogue of Lighthill's strategy for determining the vorticity flux at solid boundaries. In this method the zero-shear-stress and pressure boundary conditions are transformed into a boundary integral formulation suitable for the velocity vorticity description of the flow. A vortex sheet along the free surface is determined by the pressure boundary condition, while the condition of zero shear stress determines the vorticity at the surface. In general, vorticity is generated at free surfaces whenever there is flow past regions of surface curvature. It is shown that vorticity is conserved in free-surface viscous flows. Vorticity which hows out of the fluid across the free surface is gained by the vortex sheet; the integral of vorticity over the entire fluid region plus the integral of surface vorticity' over the free surface remains constant. The implications of the present strategy as an algorithm for numerical calculations are discussed. C1 Univ Minnesota, Dept Aerosp Engn & Mech, Minneapolis, MN 55455 USA. ETH Zurich, IFD, CH-8092 Zurich, Switzerland. Stanford Univ, CTR, NASA Ames, Moffett Field, CA 94035 USA. RP Lundgren, T (reprint author), Univ Minnesota, Dept Aerosp Engn & Mech, Minneapolis, MN 55455 USA. RI Koumoutsakos, Petros/A-2846-2008 OI Koumoutsakos, Petros/0000-0001-8337-2122 NR 23 TC 31 Z9 32 U1 0 U2 12 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD MAR 10 PY 1999 VL 382 BP 351 EP 366 DI 10.1017/S0022112098003978 PG 16 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 184VY UT WOS:000079635500014 ER PT J AU Choudhury, BJ AF Choudhury, BJ TI Evaluation of an empirical equation for annual evaporation using field observations and results from a biophysical model SO JOURNAL OF HYDROLOGY LA English DT Article DE evaporation; modeling; spatial variation ID PINE FOREST; VEGETATION; BALANCE; WATER; CLIMATE AB An empirical equation for annual evaporation (E) of the form, E = P/{1 + (P/R-n)(alpha))(1/alpha), where P is the annual precipitation, R-n the water equivalent of annual net radiation, and cu an adjustable parameter, is evaluated using held observations (water balance, and micrometeorologic measurements for areas ca. 1 km(2)) at eight locations having different types of vegetation, and results from a biophysical process-based model for four years (1987-1990) for ten river basins (areas larger than 10(6) km(2)). For the field observations, minimum value of the mean absolute error (MAE) was 33 mm (4% of the mean observed evaporation) obtained for alpha = 2.6, and the empirical equation was able to explain 99% of the variance under linear least square regression, with a slope of 0.99, intercept of 16 mm, and standard error of estimate (SEE) of 46 mm. For evaporation from the river basins, minimum value of the MAE was 36 mm (5% of the mean evaporation) obtained for alpha = 1.8, and the empirical equation was able to explain 97% of the variance, with linear regression slope of 1.01, intercept of - 11 mm, and SEE of 45 mm. The effect of spatial variations in P and R-n in determining evaporation from the empirical equation is analyzed to develop an understanding of the differences in the value of alpha for the held observations and the river basins. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Hydrol Sci Branch, Greenbelt, MD 20771 USA. RP Choudhury, BJ (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Hydrol Sci Branch, Code 974, Greenbelt, MD 20771 USA. NR 38 TC 124 Z9 129 U1 1 U2 28 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD MAR 8 PY 1999 VL 216 IS 1-2 BP 99 EP 110 DI 10.1016/S0022-1694(98)00293-5 PG 12 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA 175RT UT WOS:000079109300006 ER PT J AU Golombek, MP AF Golombek, MP TI Martian climate - A message from warmer times SO SCIENCE LA English DT Editorial Material ID IMPACT CRATERS; LANDING SITE; MARS; DEGRADATION; MORPHOLOGY; RATES C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Golombek, MP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM mgolombek@jpl.nasa.gov NR 30 TC 13 Z9 13 U1 0 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD MAR 5 PY 1999 VL 283 IS 5407 BP 1470 EP 1471 DI 10.1126/science.283.5407.1470 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 173AR UT WOS:000078959200031 PM 10206878 ER PT J AU Krabill, W Frederick, E Manizade, S Martin, C Sonntag, J Swift, R Thomas, R Wright, W Yungel, J AF Krabill, W Frederick, E Manizade, S Martin, C Sonntag, J Swift, R Thomas, R Wright, W Yungel, J TI Rapid thinning of parts of the southern Greenland ice sheet SO SCIENCE LA English DT Article AB Aircraft laser-altimeter surveys over southern Greenland in 1993 and 1998 show three areas of thickening by more than 10 centimeters per year in the southern part of the region and large areas of thinning, particularly in the east. Above 2000 meters elevation the ice sheet is in balance but thinning predominates at lower elevations, with rates exceeding 1 meter per year on east coast outlet glaciers. These high thinning rates occur at different latitudes and at elevations up to 1500 meters, which suggests that they are caused by increased rates of creep thinning rather than by excessive melting. Taken as a whole, the surveyed region is in negative balance. C1 NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. EG&G Serv, Wallops Flight Facil, Wallops Island, VA 23337 USA. RP Krabill, W (reprint author), NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, Wallops Flight Facil, Bldg N-159, Wallops Island, VA 23337 USA. NR 10 TC 115 Z9 118 U1 7 U2 14 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD MAR 5 PY 1999 VL 283 IS 5407 BP 1522 EP 1524 DI 10.1126/science.283.5407.1522 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 173AR UT WOS:000078959200044 ER PT J AU Gurman, JB AF Gurman, JB TI Managing SOHO SO NATURE LA English DT Letter C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gurman, JB (reprint author), NASA, Goddard Space Flight Ctr, Code 682, Greenbelt, MD 20771 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD MAR 4 PY 1999 VL 398 IS 6722 BP 19 EP 19 DI 10.1038/17903 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 174KG UT WOS:000079033900022 ER PT J AU Cumpston, BH Ananthavel, SP Barlow, S Dyer, DL Ehrlich, JE Erskine, LL Heikal, AA Kuebler, SM Lee, IYS McCord-Maughon, D Qin, JQ Rockel, H Rumi, M Wu, XL Marder, SR Perry, JW AF Cumpston, BH Ananthavel, SP Barlow, S Dyer, DL Ehrlich, JE Erskine, LL Heikal, AA Kuebler, SM Lee, IYS McCord-Maughon, D Qin, JQ Rockel, H Rumi, M Wu, XL Marder, SR Perry, JW TI Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication SO NATURE LA English DT Article ID CRYSTALS AB Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging(1), optical data storage(2,3) and lithographic microfabrication(4-6). These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order lambda(3) (where lambda is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (delta). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of pi-conjugated compounds that exhibit large delta (as high as 1,250 x 10(-50) cm(4) s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures(7). C1 CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA. CALTECH, Beckman Inst, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Wuhan Univ, Dept Chem, Wuhan 430072, Peoples R China. Univ Arizona, Dept Chem, Tucson, AZ 85721 USA. RP Perry, JW (reprint author), CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA. RI Rumi, Mariacristina/C-9474-2009; Perry, Joseph/B-7191-2011; Barlow, Stephen/E-9754-2010 OI Rumi, Mariacristina/0000-0002-4597-9617; Perry, Joseph/0000-0003-1101-7337; NR 12 TC 1589 Z9 1643 U1 42 U2 358 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD MAR 4 PY 1999 VL 398 IS 6722 BP 51 EP 54 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 174KG UT WOS:000079033900047 ER PT J AU Huang, W Shen, Z Huang, NE Fung, YC AF Huang, W Shen, Z Huang, NE Fung, YC TI Nonlinear indicial response of complex nonstationary oscillations as pulmonary hypertension responding to step hypoxia SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article DE degree of nonlinearity; Fourier spectrum; Hilbert spectrum; nonlinear relationships ID ZERO-STRESS STATE; BLOOD-VESSELS; ELASTIC LAMINAE; RAT; ARTERIES; REGRESSION; RECOVERY; MEDIA AB This paper is devoted to the quantization of the degree of nonlinearity of the relationship between two biological variables when one of the variables is a complex nonstationary oscillatory signal. An example of the situation is the indicial responses of pulmonary blood pressure (P) to step changes of oxygen tension (Delta pO(2)) in the breathing gas. For a step change of Delta pO(2), beginning at time t(1), the pulmonary blood pressure is a nonlinear function of time and Delta pO(2), which can be written as P(t-t(1)\Delta oO(2)). An effective method does not exist to examine the nonlinear function P(t-t(1)\Delta pO(2)). A systematic approach is proposed here. The definitions of mean trends and oscillations about the means are the kegs. With these keys a practical method of calculation is devised. We fit the mean trends of blood pressure with analytic functions of time, whose nonlinearity with respect to the oxygen level is clarified here. The associated oscillations about the mean can be transformed into Hilbert spectrum, An integration of the square of the Hilbert spectrum over frequency yields a measure of oscillatory energy, which is also a function of time, whose mean trends can be expressed by analytic functions. The degree of nonlinearity of the oscillatory energy with respect to the oxygen level also is clarified here. Theoretical extension of the experimental nonlinear indicial functions to arbitrary history of hypoxia is proposed. Application of the results to tissue remodeling and tissue engineering of blood vessels is discussed. C1 Univ Calif San Diego, Dept Bioengn, La Jolla, CA 92093 USA. Univ Calif Irvine, Dept Civil & Environm Engn, Irvine, CA 92697 USA. NASA, Lab Hydrosper Proc, Oceans & Ice Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Div Engn & Appl Sci, Pasadena, CA 91125 USA. RP Fung, YC (reprint author), Univ Calif San Diego, Dept Bioengn, La Jolla, CA 92093 USA. FU NHLBI NIH HHS [HL 43026, P01 HL043026] NR 22 TC 53 Z9 71 U1 2 U2 4 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD MAR 2 PY 1999 VL 96 IS 5 BP 1834 EP 1839 DI 10.1073/pnas.96.5.1834 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 172ZP UT WOS:000078956600008 PM 10051555 ER PT J AU Storaasli, OO AF Storaasli, OO TI Preface (vol 29, pg 177, 1998) SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Correction C1 NASA, Langley Res Ctr, Computat Struct Branch, Hampton, VA 23681 USA. RP Storaasli, OO (reprint author), NASA, Langley Res Ctr, Computat Struct Branch, Hampton, VA 23681 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD MAR PY 1999 VL 30 IS 3 BP 225 EP 225 PG 1 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 170RR UT WOS:000078820300006 ER PT J AU Tubiello, FN Rosenzweig, C Kimball, BA Pinter, PJ Wall, GW Hunsaker, DJ LaMorte, RL Garcia, RL AF Tubiello, FN Rosenzweig, C Kimball, BA Pinter, PJ Wall, GW Hunsaker, DJ LaMorte, RL Garcia, RL TI Testing CERES-wheat with free-air carbon dioxide enrichment (FACE) experiment data: CO2 and water interactions SO AGRONOMY JOURNAL LA English DT Article ID CLIMATE-CHANGE; WINTER-WHEAT; USE EFFICIENCY; TEMPERATURE; GROWTH; RESPONSES; SIMULATIONS; ECOSYS; YIELD AB Dynamic crop-growth models are used to project the effects of rising atmospheric CO2 concentration and associated climate change on crop yields. Such model predictions are largely untested in the field, for lack of experimental data. We tested the CERES-Wheat model, modified to include leaf-level photosynthesis response to elevated CO2, using field data from 2 yr of Free-Air Carbon Dioxide Enrichment (FACE) experiments with spring wheat (Triticum aestivum L. cv. Yecora Rojo) in Mariclopa, AZ. Two irrigation treatments (well-watered, WW; water-deficit stressed, WS) and two atmospheric CO2 concentrations (ambient, 350 mu mol mol(-1); elevated, 550 mu mol mol(-1)) were simulated. The model was evaluated using measurements of crop phenology, aboveground dry matter (DM) production, grain yield, and evapotranspiration (ET). Model calculations of crop phenology were within 2 to 3 d of observed values under WW, ambient CO2 conditions in both years. The model did not simulate the accelerated crop phenology (5-8 d at physiological maturity) observed in the WW and elevated CO2 treatments, indicating the need to include effects of increased stomatal resistance on canopy temperature. Simulations of DM and grain yield were within 10% of measured values, except for a tendency to overcalculate DM response to CO2 by 10 to 15% in Year 1 for WS treatments. The model undercalculated cumulative ET under WW conditions by 15%; model sensitivity analyses suggest that simulation of potential evapotranspiration (PET) was too low for this arid site. The model reproduced measured dynamics of CO2-water interactions. Simulated reductions in water loss due to elevated CO2 were about 4%, in agreement with measurements. The model simulated larger increases in DM production and yield due to elevated CO2 under WS than under WW conditions. In Year 1, simulated crop response to CO2 was 2% larger (measured: 3%) under WS than under WW conditions; in Year 2, it was 11% larger (measured: 9%). The ability to simulate CO2-water interactions, though it needs to be further evaluated with additional experimental datasets, is an important attribute of models used to project crop yields under elevated CO2 and climate change. C1 Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. USDA ARS, US Water Conservat Lab, Phoenix, AZ 85040 USA. RP Tubiello, FN (reprint author), Columbia Univ, Ctr Climate Syst Res, 2880 Broadway, New York, NY 10025 USA. NR 36 TC 51 Z9 52 U1 1 U2 16 PU AMER SOC AGRONOMY PI MADISON PA 677 S SEGOE RD, MADISON, WI 53711 USA SN 0002-1962 J9 AGRON J JI Agron. J. PD MAR-APR PY 1999 VL 91 IS 2 BP 247 EP 255 PG 9 WC Agronomy SC Agriculture GA 220CK UT WOS:000081646800012 ER PT J AU Maestrello, L AF Maestrello, L TI Chaotic response of panel vibrations forced by turbulent boundary layer and sound SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/CEAS 3rd Aeroacoustics Conference CY MAY 12-14, 1997 CL ATLANTA, GEORGIA SP AIAA, CEAS ID STRANGE ATTRACTORS; TIME-SERIES; SYSTEM; BIFURCATIONS; TRANSITION; BEHAVIOR; TORUS; FLOW AB Experimental data are presented to show evidence of chaotic response of two adjacent aircraft panels forced by a turbulent boundary layer and pure tone sound. The experiments are a simulation of boundary-layer and fan noise loads on a fuselage sidewall with Reynolds number per meter of 2.85 x 10(5). The response of the panels is purely random and assumed linear when forced by the turbulent boundary-layer how and clearly becomes nonlinear with the appearance of the interspersed periodic to chaotic motion when forced by the boundary layer with superimposed pure tone sound. The initial periodic response of two tori of two commensurate frequencies changes with an increase in pure tone sound level. The response of period-doubling bifurcations then makes a transition to chaos, which alternates with quasiperiodic response as the wave Loses the spatial homogeneity. The objective is to demonstrate the existence of strong nonlinear effects on the structure response, which is not yet wed understood. C1 NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. RP Maestrello, L (reprint author), NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. NR 33 TC 7 Z9 10 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1999 VL 37 IS 3 BP 289 EP 295 DI 10.2514/2.716 PG 7 WC Engineering, Aerospace SC Engineering GA 171BF UT WOS:000078841800001 ER PT J AU Bement, LJ Multhaup, HA AF Bement, LJ Multhaup, HA TI Determining functional reliability of pyrotechnic mechanical devices SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 33rd Joint Propulsion Conference CY JUL 06-09, 1997 CL SEATTLE, WASHINGTON SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE AB A new approach is presented for predicting the mechanical functional reliability of pyrotechnic devices. The currently accepted approach for predicting the reliability of a particular device requires hundreds or thousands of consecutive, successful tests of very similar components. Furthermore, because no performance measurements are made in go/no-go testing, the physics of failure for the device are routinely ignored. The presented approach logically begins with measuring, understanding, and controlling mechanical performance variables within a device. Then the energy required to accomplish the desired function is compared to that delivered by the pyrotechnic energy source to determine a mechanical functional margin. Finally, the data collected in establishing this functional margin are analyzed to predict functional reliability, using small-sample statistics. A careful application of this approach can provide considerable cost savings and an improved understanding of component and system performance over that of go/no-go statistics. Evaluating 20 or fewer units can define performance and provide reliability predictions. The application of this approach to a pin puller used on a successful NASA mission is offered as an example. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 12 TC 3 Z9 7 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1999 VL 37 IS 3 BP 357 EP 363 DI 10.2514/2.737 PG 7 WC Engineering, Aerospace SC Engineering GA 171BF UT WOS:000078841800009 ER PT J AU Mader, TH Koch, DD Manuel, K Gibson, CR Effenhauser, RK Musgrave, S AF Mader, TH Koch, DD Manuel, K Gibson, CR Effenhauser, RK Musgrave, S TI Stability of vision during space flight in an astronaut with bilateral intraocular lenses SO AMERICAN JOURNAL OF OPHTHALMOLOGY LA English DT Article ID PRESSURE; AVIATORS AB PURPOSE: To report excellent and stable vision in an astronaut during space flight after bilateral cataract surgery with intraocular lenses. METHODS: A 60-year-old physician mission specialist astronaut developed cataracts and underwent phacoemulsification with insertion of one-piece polymethylmethacrylate intraocular lenses that had 6-mm optics bilaterally, Several months later, he flew on a space shuttle mission. Ocular examinations were performed before and after the mission, and the patient was questioned about visual changes during flight. RESULTS: Ocular examinations demonstrated stable bilateral posterior chamber intraocular lenses. Our subject reported excellent vision during liftoff, 18 days of micro gravity, changes in cabin pressure, and reentry. CONCLUSION: Results suggest that intraocular lenses are safe, effective, and well tolerated during space flight, (C) 1994 by Elsevier Science Inc, All rights reserved. C1 Madigan Army Med Ctr, Tacoma, WA 98431 USA. Baylor Coll Med, Cullen Eye Inst, Houston, TX 77030 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Mader, TH (reprint author), 8500 Meridian Rd SE, Olympia, WA 98513 USA. NR 5 TC 6 Z9 7 U1 1 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0002-9394 J9 AM J OPHTHALMOL JI Am. J. Ophthalmol. PD MAR PY 1999 VL 127 IS 3 BP 342 EP 343 DI 10.1016/S0002-9394(98)00326-2 PG 2 WC Ophthalmology SC Ophthalmology GA 173KN UT WOS:000078979900015 PM 10088747 ER PT J AU Conrad, PG Zha, CS Mao, HK Hemley, RJ AF Conrad, PG Zha, CS Mao, HK Hemley, RJ TI The high-pressure, single-crystal elasticity of pyrope, grossular, and andradite SO AMERICAN MINERALOGIST LA English DT Article ID SOLID-SOLUTION SERIES; UPPER MANTLE; ALMANDINE GARNET; BULK MODULUS; COMPRESSION; BRILLOUIN; SPESSARTINE; UVAROVITE; KBAR; GPA AB High-pressure Brillouin scattering experiments were conducted on three natural, single-crystal garnets with near end-member compositions: pyrope (Mg3Al2Si3O12), grossular (Ca3Al2Si3O12), and andradite (Ca3Fe23+Si3O12). Acoustic velocities of the samples were measured from the samples at pressures to 10 GPa in a diamond-anvil cell with a methanol-ethanol-water pressure medium. Elastic stiffness constants (C-ij) and their pressure dependencies (partial derivative C-ij/partial derivative P) were calculated, as were aggregate elastic noduli (K-s and G) and their respective pressure derivatives. The Cauchy relations changed with pressure for both grossular and andradite, suggesting that assuming these are constant is not valid for extrapolation to high pressures for these and possibly other minerals. The variation in partial derivative K-s/dP and partial derivative G/partial derivative P was sensitive to composition and required a complex mixing model for extrapolation of end-member elasticity values from garnets of intermediate compositions. C1 Carnegie Inst Sci, Geophys Lab, Washington, DC 20015 USA. Carnegie Inst Sci, Ctr High Pressure Res, Washington, DC 20015 USA. Cornell Univ, Cornell High Energy Synchrotron Source, Ithaca, NY 14853 USA. RP CALTECH, Jet Prop Lab, Mailstop 183-301, Pasadena, CA 91109 USA. EM conrad@jpl.nasa.gov NR 41 TC 59 Z9 60 U1 0 U2 5 PU MINERALOGICAL SOC AMER PI CHANTILLY PA 3635 CONCORDE PKWY STE 500, CHANTILLY, VA 20151-1125 USA SN 0003-004X EI 1945-3027 J9 AM MINERAL JI Am. Miner. PD MAR PY 1999 VL 84 IS 3 BP 374 EP 383 PG 10 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA 169HE UT WOS:000078741000022 ER PT J AU Muller, R Grooss, JU McKenna, DS Crutzen, PJ Bruhl, C Russell, JM Gordley, LL Burrows, JP Tuck, AF AF Muller, R Grooss, JU McKenna, DS Crutzen, PJ Bruhl, C Russell, JM Gordley, LL Burrows, JP Tuck, AF TI Chemical ozone loss in the Arctic vortex in the winter 1995-96: HALOE measurements in conjunction with other observations (vol 16, pg 101, 1999) SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Correction C1 Forschungszentrum Julich, Inst Stratospher Chem, ICG 1, Julich, Germany. Max Planck Inst Chem, Atomospher Chem Dept, D-55128 Mainz, Germany. Hampton Univ, Hampton, VA 23668 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Univ Bremen, Inst Environm Phys, Bremen, Germany. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Muller, R (reprint author), Forschungszentrum Julich, Inst Stratospher Chem, ICG 1, Postfach 1913, Julich, Germany. RI Tuck, Adrian/F-6024-2011; Crutzen, Paul/F-6044-2012; Muller, Rolf/A-6669-2013; GrooSS, Jens-Uwe/A-7315-2013; McKenna, Daniel/E-7806-2014; Burrows, John/B-6199-2014 OI Tuck, Adrian/0000-0002-2074-0538; Muller, Rolf/0000-0002-5024-9977; GrooSS, Jens-Uwe/0000-0002-9485-866X; McKenna, Daniel/0000-0002-4360-4782; Burrows, John/0000-0002-6821-5580 NR 1 TC 0 Z9 0 U1 0 U2 1 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 MAR PY 1999 VL 17 IS 3 BP 437 EP 437 PG 1 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA 180KY UT WOS:000079386200012 ER PT J AU Wheeler, RM Mackowiak, CL Yorio, NC Sager, JC AF Wheeler, RM Mackowiak, CL Yorio, NC Sager, JC TI Effects of CO2 on stomatal conductance: Do stomata open at very high CO2 concentrations? SO ANNALS OF BOTANY LA English DT Article DE carbon dioxide; stomatal conductance; transpiration; water use efficiency; wheat; Triticum aestivum; potato; Solanum tuberosum; sweetpotato; Ipomea batatas; soybean; Glycine max ID SOLANUM-TUBEROSUM-L; CARBON-DIOXIDE; PLANT-GROWTH; POTATO GROWTH; ELEVATED CO2; ENRICHMENT; WHEAT; YIELD; ATMOSPHERES; ENVIRONMENT AB Potato and wheat plants were grown for 50 d at 400, 1000 and 10 000 mu mol mol(-1) carbon dioxide (CO2), and sweetpotato and soybean were grown at 1000 mu mol mol(-1) CO2 in controlled environment chambers to study stomatal conductance and plant water use. Lighting was provided with fluorescent lamps as a 12 h photoperiod with 300 mu mol m(-2) s(-1) PAR. Mid-day stomatal conductances for potato were greatest at 400 and 10 000 mu mol mol(-1) and least at 1000 mu mol mol(-1) CO2. Mid-day conductances for wheat were greatest at 400 pmol mol(-1) and least at 1000 and 10 000 mu mol mol(-1) CO2. Mid-dark period conductances for potato were significantly greater at 10 000 mu mol mol(-1) than at 400 or 1000 mu mol mol(-1), whereas dark conductance for wheat was similar in all CO2 treatments. Temporarily changing the CO2 concentration from the native 1000 mu mol mol(-1) to 400 mu mol mol(-1) increased mid-day conductance for all species, while temporarily changing from 1000 to 10 000 mu mol mol(-1) also increased conductance for potato and sweetpotato. Temporarily changing the dark period CO2 from 1000 to 10 000 mu mol mol(-1) increased conductance for potato, soybean and sweetpotato. In all cases, the stomatal responses were reversible, i.e. conductances returned to original rates following temporary changes in CO2 concentration. Canopy water use for potato was greatest at 10 000, intermediate at 400, and least at 1000 mu mol mol(-1) CO2, whereas canopy water use for wheat was greatest at 400 and similar at 1000 and 10 000 mu mol mol(-1) CO2. Elevated CO2 treatments (i.e. 1000 and 10 000 mu mol mol(-1)) resulted in increased plant biomass for both wheat and potato relative to 400 mu mol mol(-1), and no injurious effects were apparent from the 10 000 mu mol mol(-1) treatment. Results indicate that super-elevated CO2 (i.e. 10 000 mu mol mol(-1)) can increase stomatal conductance in some species, particularly during the dark period, resulting in increased water use and decreased water use efficiency. (C) 1999 Annals of Botany Company. C1 NASA, Biomed Off, Kennedy Space Ctr, FL 32899 USA. Utah State Univ, Dept Plants Soils & Biometeorol, Logan, UT 84322 USA. Dynamac Corp, Kennedy Space Ctr, FL 32899 USA. RP Wheeler, RM (reprint author), NASA, Biomed Off, Kennedy Space Ctr, FL 32899 USA. EM raymond.wheeler-1@ksc.nasa.gov NR 45 TC 49 Z9 55 U1 1 U2 32 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0305-7364 J9 ANN BOT-LONDON JI Ann. Bot. PD MAR PY 1999 VL 83 IS 3 BP 243 EP 251 DI 10.1006/anbo.1998.0813 PG 9 WC Plant Sciences SC Plant Sciences GA 171TJ UT WOS:000078879900006 PM 11541549 ER PT J AU Larruquert, JI Keski-Kuha, RAM AF Larruquert, JI Keski-Kuha, RAM TI Multilayer coatings with high reflectance in the extreme-ultraviolet spectral range of 50 to 121.6 nm SO APPLIED OPTICS LA English DT Article ID CARBIDE COATINGS; OPTICS AB Multilayer coatings with three layers were designed to yield an increase in normal-incidence reflectance in the extreme ultraviolet over that of the available single-layer coatings. Multilayer coatings based on Al, MgF2, and either SiC or B4C were demonstrated to have higher reflectance than single layers of SiC and B4C in the spectral region from 57.9 nm to the H Lyman-alpha Line (121.6 nm) and above. The increase in reflectance was higher at wavelengths close to 121.6 nm. Reflectance degraded slightly over time in the same way as for single layers. After a few months, multilayer coatings maintained higher reflectance than their single-layer counterparts. (C) 1999 Optical Society of America. OCIS codes: 120.5700, 230.4170, 260.7200, 260.7210, 310.1620, 350.6090. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Larruquert, JI (reprint author), NASA, Goddard Space Flight Ctr, Code 551, Greenbelt, MD 20771 USA. EM larruquert@io.csic.es OI Larruquert, Juan/0000-0001-6356-9702 NR 19 TC 33 Z9 37 U1 3 U2 6 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 MAR 1 PY 1999 VL 38 IS 7 BP 1231 EP 1236 DI 10.1364/AO.38.001231 PG 6 WC Optics SC Optics GA 173ER UT WOS:000078968700023 PM 18305737 ER PT J AU Suntzeff, NB Phillips, MM Covarrubias, R Navarrete, M Perez, JJ Guerra, A Acevedo, MT Doyle, LR Harrison, T Kane, S Long, KS Maza, J Miller, S Piatti, AE Claria, JJ Ahumada, AV Pritzl, B Winkler, PF AF Suntzeff, NB Phillips, MM Covarrubias, R Navarrete, M Perez, JJ Guerra, A Acevedo, MT Doyle, LR Harrison, T Kane, S Long, KS Maza, J Miller, S Piatti, AE Claria, JJ Ahumada, AV Pritzl, B Winkler, PF TI Optical light curve of the Type Ia supernova 1998bu in M96 and the supernova calibration of the Hubble constant SO ASTRONOMICAL JOURNAL LA English DT Article DE distance scale; galaxies : individual (NGC 3368); supernovae : general; supernovae : individual (SN 1998bu) ID ABSOLUTE PEAK BRIGHTNESS; STELLAR PHOTOMETRY; DISCOVERY; CEPHEIDS; DIAGRAM; SHAPES; H(0) AB We present the UBV(RI)(KC) light curves of the Type Ia supernova SN 1998bu, which appeared in the nearby galaxy M96 (NGC 3368). M96 is a spiral galaxy in the Leo I group that has a Cepheid-based distance. Our photometry allows us to calculate the absolute magnitude and reddening of this supernova. These data, when combined with measurements of the four other well-observed supernovae with Cepheid-based distances, allow us to calculate the Hubble constant with respect to the Hubble flow defined by the distant Calan/Tololo Type Ia sample. We find a Hubble constant of 63.9 +/- 2.2(internal) +/- 3.5(external) km s(-1) Mpc(-1), consistent with most previous estimates based on Type Ia supernovae. We note that the two well-observed Type Ia supernovae in Fornax, if placed at the Cepheid distance to the possible Fornax spiral NGC 1365, are apparently too faint with respect to the Calan/Tololo sample calibrated with the five Type Ia supernovae with Cepheid distances to the host galaxies. C1 Natl Opt Astron Observ, Cerro Tololo Inter Amer Observ, La Serena, Chile. Carnegie Observ, Campanas Observ, La Serena, Chile. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. Space Telescope Sci Inst, Las Cruces, NM 88003 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Univ Chile, Dept Astron, Santiago, Chile. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Observ Astron Cordoba, RA-5000 Cordoba, Argentina. Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. Middlebury Coll, Dept Phys, Middlebury, VT 05753 USA. RP Suntzeff, NB (reprint author), Natl Opt Astron Observ, Cerro Tololo Inter Amer Observ, Casilla 603, La Serena, Chile. RI Maza, Jose/I-5722-2016 OI Maza, Jose/0000-0003-2068-1328 NR 41 TC 101 Z9 101 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1999 VL 117 IS 3 BP 1175 EP 1184 DI 10.1086/300771 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187KZ UT WOS:000079786900008 ER PT J AU Sahai, R Zulstra, A Bujarrabal, V Hekkert, PTL AF Sahai, R Zulstra, A Bujarrabal, V Hekkert, PTL TI Unraveling the structure of aspherical proto-planetary nebulae. I. Hubble Space Telescope imaging and hydroxyl maser line observations of Roberts 22 SO ASTRONOMICAL JOURNAL LA English DT Article DE circumstellar matter; planetary nebulae : general; stars : AGB and post-AGB; stars : mass loss ID BIPOLAR NEBULA; RED-RECTANGLE; GIANT BRANCH; EMISSION; PROTOPLANETARY; CRL-2688; MYCN-18; OBJECTS; STARS; WINDS AB We have obtained high-resolution wide-band, narrowband, and polarimetric images of the bipolar proto-planetary nebula Roberts 22 with the Wide Field Planetary Camera 2 on the Hubble Space Telescope. OH maser-line emission has also been observed using the Australia Telescope Compact Array. The wide-band images at 0.6 mu m show bright bipolar lobes shaped Like a butterfly's "wings," separated by a dark equatorial "body" of dense dust that completely obscures the central star. The material within each lobe appears to be organized into an amazingly complex pattern of a very large number of intersecting loops and filaments. The bright lobes are surrounded by a fainter halo whose inner region contains multiple thin shell structures, reminiscent of those seen in the prototype proto-planetary nebula, CRL 2688 (Egg Nebula). The halo can be traced to a distance of about 25" from the nebular center. The radial surface brightness of the halo is inconsistent with that expected for time-invariant mass loss at a constant expansion velocity. A simple model of the radial scattered light distribution supports the hypothesis that the bright lobes are cavities with thin (<0."5), dense walls that are optically thick in scattered light. The amount of mass in the cavity walls is quite large (0.3 M.) and the dynamical timescale for their formation is short (less than or similar to 440 yr). The bright lobes show high fractional polarization (40%-50%) and a centrosymmetric polarization pattern, typical of a singly scattering reflection nebula. In contrast, the polarization in the dark equatorial region is small, and the polarization vectors do not show a simple orientation pattern. The polarization data have been compared with published models to set rough constraints on the dust albedo and scattering phase function and the nebular optical depths. The OH maser-line emission at 1665 and 1667 MHz is found to be concentrated in the dark equatorial region; the kinematics of the OH features indicates that they arise in low-latitude outflows. The nebular morphology in Roberts 22 is characterized by a high degree of point symmetry, which may result from the interaction of collimated bipolar outflows with the progenitor AGE envelope. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. UMIST, Dept Phys, Manchester M60 1QD, Lancs, England. Natl Astron Observ, Alcala De Henares 28800, Spain. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. RP Sahai, R (reprint author), CALTECH, Jet Prop Lab, MS 183-900, Pasadena, CA 91109 USA. NR 40 TC 55 Z9 55 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1999 VL 117 IS 3 BP 1408 EP 1420 DI 10.1086/300773 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187KZ UT WOS:000079786900027 ER PT J AU Leckrone, DS Proffitt, CR Wahlgren, GM Johansson, SG Brage, T AF Leckrone, DS Proffitt, CR Wahlgren, GM Johansson, SG Brage, T TI Very high resolution ultraviolet spectroscopy of a chemically peculiar star: Results of the chi Lupi Pathfinder project SO ASTRONOMICAL JOURNAL LA English DT Article DE physical data and processes; stars : abundances; stars : chemically peculiar; stars : individual (chi Lupi) ID ADDED IUE SPECTRA; NORMAL LATE-B; OSCILLATOR-STRENGTHS; ELEMENTAL ABUNDANCES; HGMN STARS; TRANSITION-PROBABILITIES; HYPERFINE-STRUCTURE; HEAVY-ELEMENTS; TL-II; Y-III AB We summarize here the results of a major eight-year investigation of the extraordinarily detailed UV spectrum of the sharp-lined, nonmagnetic, main-sequence, chemically peculiar star chi Lupi (B9.5p HgMn + A2 Vm). The UV observations are composed of 345 Angstrom of the spectrum acquired with the Goddard High Resolution Spectrograph (GHRS) on board the Hubble Space Telescope at an average resolution of 0.023 Angstrom. The complete set of echelle spectrograms is presented as an atlas in a companion paper. These data were supplemented by optical-wavelength spectra obtained at the Angle-Australian Telescope. Quantitatively accurate analysis and theoretical interpretation of these data required major improvements in the accuracy and completeness of available atomic data-wavelengths, transition probabilities, hyperfine structure, and isotope shifts-for the lowest ionization states of many elements. A large, international group of theoretical and experimental atomic physicists has collaborated in this investigation, and their results are summarized or referenced in this paper. In turn, the GHRS observations of chi Lupi have become a useful source of data for atomic spectroscopy, displaying many transitions that are difficult to observe in a laboratory setting. Measured abundances or upper limits are presented for 72 ions of 51 chemical elements, spanning the periodic table. We have confirmed and refined previously identified isotopic abundance anomalies in mercury and platinum and have discovered similar isotopic anomalies in thallium and, tentatively, in lead. Large discrepancies among the LTE abundances derived, using a chemically homogeneous model atmosphere, from two or three ionization states of the same element are found to be common. In some cases these are due to departures from LTE in the ionization equilibria, but the largest such discrepancies probably result from chemical stratification within the photosphere. We find qualitative trends in the abundances of the elements that clearly signify radiatively driven diffusion and gravitational settling as the primary mechanism producing abundance anomalies. However, detailed non-LTE diffusion calculations for mercury and thallium show that there is insufficient unsaturated radiative force within the chemically enriched atmosphere to sustain the observed huge overabundances of these elements in equilibrium with gravity. Either other hydrodynamic processes, such as slow mass motions or unexpectedly strong stellar winds must assist radiation pressure in supporting the enriched material, or the observed abundance patterns simply provide a snapshot in time of a nonequilibrium, time-variable phenomenon. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Sci Programs, Comp Sci Corp, Baltimore, MD 21218 USA. Univ Lund, Dept Phys, S-22100 Lund, Sweden. NR 98 TC 67 Z9 67 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1999 VL 117 IS 3 BP 1454 EP 1470 DI 10.1086/300776 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187KZ UT WOS:000079786900031 ER PT J AU Padgett, DL Brandner, W Stapelfeldt, KR Strom, SE Terebey, S Koerner, D AF Padgett, DL Brandner, W Stapelfeldt, KR Strom, SE Terebey, S Koerner, D TI Hubble Space Telescope NICMOS imaging of disks and envelopes around very young stars SO ASTRONOMICAL JOURNAL LA English DT Article DE circumstellar matter; ISM : jets and outflows; stars : pre-main-sequence ID AURIGA MOLECULAR CLOUD; T-TAURI STARS; MODEL SCATTERING ENVELOPES; HERBIG-HARO FLOWS; STELLAR OBJECTS; CIRCUMSTELLAR DISKS; CONTINUUM OBSERVATIONS; JETS; EVOLUTION; OUTFLOWS AB We present HST/NICMOS observations with similar to 0."1 approximate to 15 AU resolution of six young stellar objects in the Taurus star formation region. The targets of our survey are three Class I IRAS sources (IRAS 04016 + 2610, IRAS 04248 + 2612, and IRAS 04302 + 2247) and three low-luminosity stars (DG Tau B, Hare 6-5B, and CoKu Tau/1) associated with Herbig-Haro jets. The broadband images show that the near-infrared radiation from these sources is dominated by light scattered from dusty circumstellar material distributed in a region 10-15 times the size of our solar system. Although the detailed morphologies of the individual, objects are unique, the observed young stellar objects share common features. All of the circumstellar reflection nebulae are crossed by dark lanes from 500 to 900 AU in extent and from less than 50 to 350 AU in apparent thickness. The absorption lanes extend perpendicular to known optical and millimeter outflows in these sources. We interpret the dark lanes as optically thick circumstellar disks seen in silhouette against bright reflection nebulosity. The bipolar reflection nebulae extending perpendicular to the dust lanes appear to be produced by scattering from the upper and lower surfaces of the disks and from dusty material within or on the walls of the outflow cavities. Of five objects in which the central source is directly detected, two are found to be subarcsecond binaries. This minisurvey is the highest resolution near-infrared study to date of circumstellar environments around solar-type stars with age less than or equal to 1 Myr. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Extrasolar Res Corp, Pasadena, CA 91106 USA. Univ Penn, Dept Phys & Astron, Philadelphia, PA 19104 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. RP Padgett, DL (reprint author), CALTECH, Jet Prop Lab, IPAC, Mail Code 100-22, Pasadena, CA 91125 USA. RI Stapelfeldt, Karl/D-2721-2012 NR 85 TC 214 Z9 214 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1999 VL 117 IS 3 BP 1490 EP 1504 DI 10.1086/300781 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187KZ UT WOS:000079786900034 ER PT J AU Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Proffitt, CR Wahlgren, GM Johansson, SG Nilsson, H Brage, T Snow, M Ake, TB AF Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Proffitt, CR Wahlgren, GM Johansson, SG Nilsson, H Brage, T Snow, M Ake, TB TI A Goddard High Resolution Spectrograph atlas of echelle observations of the HgMn star chi Lupi SO ASTRONOMICAL JOURNAL LA English DT Article DE atlases; stars : chemically peculiar; stars : individual (chi Lupi) ID OSCILLATOR-STRENGTHS; HYPERFINE-STRUCTURE; HEAVY-ELEMENTS; TL-II; ABUNDANCE; TRANSITIONS; SPECTRA; GHRS; LINES; HST AB Observations of the ultra-sharp-lined, chemically peculiar star chi Lupi taken by the Goddard High Resolution Spectrograph in echelle mode are presented. Thirty-six intervals of the spectral region between 1249 and 2688 Angstrom are covered with resolving powers in the range 75,000-93,000. Line identifications are provided, and the observed spectra are compared with synthetic spectra calculated using the SYNTHE program and associated line lists with changes to the line lists. The significance of these spectra for the chi Lupi Pathfinder Project and the closely related atomic physics effort is discussed in a companion paper. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. Ball Aerosp & Technol Corp, Boulder, CO 80306 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. Natl Inst Stand & Technol, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Space Sci Directorate, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Univ Texas, McDonald Observ, Austin, TX 78712 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. SUNY Stony Brook, Dept Earth & Space Sci, Astron Program, Stony Brook, NY 11794 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. NASA, Goddard Space Flight Ctr, Sci Programs, Comp Sci Corp, Greenbelt, MD 20771 USA. Univ Lund, Dept Phys, S-22100 Lund, Sweden. RI heap, sara/E-2237-2012; Carpenter, Kenneth/D-4740-2012 NR 50 TC 35 Z9 35 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1999 VL 117 IS 3 BP 1505 EP 1548 DI 10.1086/300753 PG 44 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187KZ UT WOS:000079786900035 ER PT J AU Pravdo, SH Rabinowitz, DL Helin, EF Lawrence, KJ Bambery, RJ Clark, CC Groom, SL Levin, S Lorre, J Shaklan, SB Kervin, P Africano, JA Sydney, P Soohoo, V AF Pravdo, SH Rabinowitz, DL Helin, EF Lawrence, KJ Bambery, RJ Clark, CC Groom, SL Levin, S Lorre, J Shaklan, SB Kervin, P Africano, JA Sydney, P Soohoo, V TI The Near-Earth Asteroid Tracking (NEAT) Program: An automated system for telescope control, wide-field imaging, and object detection SO ASTRONOMICAL JOURNAL LA English DT Article DE instrumentation : detectors; minor planets, asteroids; techniques : image processing ID MAIN-BELT ASTEROIDS; APPROACHING ASTEROIDS; SUFFICIENT SOURCE; SIZE; DISTRIBUTIONS; 1996-PW AB The Near-Earth Asteroid Tracking (NEAT) system operates autonomously at the Maul Space Surveillance Site on the summit of the extinct Haleakala Volcano Crater, Hawaii. The program began in 1995 December and continues with an observing run every month. Its astrometric observations result in discoveries of near-Earth objects (NEOs), both asteroids (NEAs) and comets, and other unusual minor planets. Each six-night run NEAT covers about 10% of the accessible sky, detects thousands of asteroids, and detects two to five NEAs. NEAT has also contributed more than 1500 preliminary designations of minor planets and 26,000 detections of main-belt asteroids. This paper presents a description of the NEAT system and discusses its capabilities, including sky coverage, limiting magnitude, and detection efficiency. NEAT is an effective discoverer of NEAs larger than 1 km and is a major contributor to NASA's goal of identifying all NEAs of this size. An expansion of NEAT into a network of three similar systems would be capable of discovering 90% of the 1 km and larger NEAs within the next 10-40 yr, while serving the additional role of satellite detection and tracking for the US Air Force. Daily updates of NEAT results during operational periods can be found at JPL's Web site (http://huey.jpl.nasa.gov/ similar to spravdo/neat.html). The images and information about the detected objects, including times of observation, positions, and magnitudes are made available via NASA's SkyMorph program. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. USAF, Res Labs, Kihei, HI 96753 USA. RP Pravdo, SH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 24 TC 51 Z9 51 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1999 VL 117 IS 3 BP 1616 EP 1633 DI 10.1086/300769 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187KZ UT WOS:000079786900043 ER PT J AU Sikstrom, CM Lundberg, H Wahlgren, GM Li, ZS Lynga, C Johansson, S Leckrone, DS AF Sikstrom, CM Lundberg, H Wahlgren, GM Li, ZS Lynga, C Johansson, S Leckrone, DS TI New Zr II oscillator strengths and the zirconium conflict in the HgMn star chi Lupi SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE atomic data; line : identification; methods : laboratory; stars : abundances; stars : individual : chi Lupi; ultraviolet : stars ID ABUNDANCE; SPECTROMETER; LIFETIMES; ELEMENTS; REGION; SOLAR AB Lifetimes on the sub-nanosecond scale for the levels v(2)D(3/2), v(2)F(3/2) and v(2)F(5/2) in the 4d5s5p configuration in Zr II have been measured, using the method of laser-induced fluorescence. Combined with branching fractions obtained with the Lund Ultraviolet (UV) Fourier Transform Spectrometer (FTS), experimental oscillator strengths have been derived. From Hubble Space Telescope/Goddard High-Resolution Spectrograph spectra, the zirconium abundance in the HgMn star chi Lupi has been determined from Zr II and Zr III lines. More than an order of magnitude difference in the Zr II abundance has been derived from these ionization stages. The difference is much too large to be explained by uncertainties in the oscillator strengths. Possible explanations of this difference have to be found in the stellar models, such as the influence of non-LTE or diffusion. C1 Univ Lund, Dept Phys, S-22362 Lund, Sweden. Lund Inst Technol, S-22362 Lund, Sweden. NASA, Goddard Space Flight Ctr, Comp Sci Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Sikstrom, CM (reprint author), Univ Lund, Dept Phys, Solvegatan 14, S-22362 Lund, Sweden. OI Li, Zhongshan/0000-0002-0447-2748 NR 26 TC 20 Z9 20 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 MAR PY 1999 VL 343 IS 1 BP 297 EP 302 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 173LG UT WOS:000078981600044 ER PT J AU Borissova, J Catelan, M Ferraro, FR Spassova, N Buonanno, R Iannicola, G Richtler, T Sweigart, AV AF Borissova, J Catelan, M Ferraro, FR Spassova, N Buonanno, R Iannicola, G Richtler, T Sweigart, AV TI The outer-halo globular cluster NGC 6229 III. Deep CCD photometry SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : blue stragglers; stars : Hertzsprung-Russel (HR) and C-M diagrams; stars : Population II; Galaxy : globular clusters : individual; Galaxy : globular clusters : individual ID METAL-POOR CLUSTERS; BLUE STRAGGLERS; GALACTIC HALO; PHOTOGRAPHIC PHOTOMETRY; THEORETICAL ISOCHRONES; HORIZONTAL BRANCHES; AGE-DIFFERENCES; RELATIVE AGES; MILKY-WAY; STARS AB Deep BV photometry for a large field covering the outer-halo globular cluster NGC 6229 is presented. For the first time, a colour-magnitude diagram (CMD) reaching below the main sequence turnoff has been obtained for this cluster. Previous results regarding the overall morphology of the horizontal and giant branches are confirmed. In addition, nine possible extreme horizontal-branch stars have been identified in our deep images, as well as thirty-three candidate blue stragglers. We also find the latter to be more centrally concentrated than subgiant branch stars covering the same range in V magnitude. A comparison of the cluster CMD with the M 5 (NGC 5904) ridgeline from Sandquist et al. (1996) reveals that: i) NGC 6229 and M5 have essentially identical metallicities; ii) NGC 6229 and M5 have the same ages within the errors in spite of their different horizontal-branch morphologies. C1 Osservatorio Astron Bologna, I-40127 Bologna, Italy. Bulgarian Acad Sci, Inst Astron, BG-1784 Sofia, Bulgaria. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Osserv Astron Roma, I-00040 Monte Porzio Catone, Italy. Sternwarte Univ Bonn, D-53121 Bonn, Germany. RP Osservatorio Astron Bologna, Via Ranzani 1, I-40127 Bologna, Italy. EM jura@haemimont.bg; catelan@stars.gsfc.nasa.gov; ferraro@astb03.bo.astro.it; buonanno@astrmp.mporzio.astro.it; iannicola@coma.mporzio.astro.it; richtler@astro.uni-bonn.de; sweigart@bach.gsfc.nasa.gov NR 71 TC 19 Z9 20 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 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD MAR PY 1999 VL 343 IS 3 BP 813 EP 824 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 182JD UT WOS:000079495100021 ER PT J AU Volker, R Smith, MD Suttner, G Yorke, HW AF Volker, R Smith, MD Suttner, G Yorke, HW TI Numerical hydrodynamic simulations of molecular outflows driven by Hammer jets SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE hydrodynamics; shock waves; ISM : clouds; ISM : jets and outflows; ISM : molecules; radio lines : ISM ID PROPER MOTION MEASUREMENTS; RADIATIVELY COOLING JETS; YOUNG STELLAR OBJECTS; PROTOSTELLAR JETS; TIME VARIABILITY; PULSED JETS; BOW SHOCKS; EVOLUTION; STARS; FLOWS AB Very young protostars eject collimated jets of molecular gas. Although the protostars themselves are hidden, some of their properties are revealed through the jet dynamics. We here model velocity shear, precession, pulsation and spray within dense jets injected into less-dense molecular clouds. We investigate the Hammer Jet, for which extreme velocity variations as well as strong ripping and spray actions are introduced. A three dimensional ZEUS-type hydrodynamics code, extended with molecular physics, is employed. Jet knots, previously shown to be compact in simulations of smoother jets, now appear as prominent bow shocks in H-2 and as bullets in CO emission lines. High proper motions are predicted in the jet. In the lobes we uncover wide tubular low-velocity CO structures with concave bases near the nozzle. Proper motion vectors in the lobes delineate a strong accelerated flow away from the head with some superimposed turbulent-like motions. The leading bow is gradually distorted by the hammer blows and breaks up into mini-bow segments. The Hz emission line profiles are wide and twin-peaked over much of the leading bow. On comparison with the simulations, we identify observed outflows driven by various dynamical types of jet. Shear is essential to produce the jet bows, spray or precession to widen the outflows and hammer blows to generate knotty jets. We identify the proper motions of maser spots with the pattern speed of density peaks in the inner jet and shell. C1 Univ Wurzburg, Astron Inst, D-97074 Wurzburg, Germany. Armagh Observ, Armagh BT61 9DG, North Ireland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Smith, MD (reprint author), Univ Wurzburg, Astron Inst, D-97074 Wurzburg, Germany. EM voelker@astro.uni-wuerzburg.de; smith@star.arm.ac.uk; suttner@astro.uni-wuerzburg.de; yorke@lear.jpl.nasa.gov NR 79 TC 71 Z9 71 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 MAR PY 1999 VL 343 IS 3 BP 953 EP 965 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 182JD UT WOS:000079495100039 ER PT J AU Schutte, WA Boogert, ACA Tielens, AGGM Whittet, DCB Gerakines, PA Chiar, JE Ehrenfreund, P Greenberg, JM van Dishoeck, EF de Graauw, T AF Schutte, WA Boogert, ACA Tielens, AGGM Whittet, DCB Gerakines, PA Chiar, JE Ehrenfreund, P Greenberg, JM van Dishoeck, EF de Graauw, T TI Weak ice absorption features at 7.24 and 7.41 mu m in the spectrum of the obscured young stellar object W 33A SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE infrared : ISM : lines and bands; ISM : molecules; ISM : abundances; stars : individual : NGC 7538 : IRS 9; stars : individual : W 33A; methods : laboratory ID TIME-DEPENDENT CHEMISTRY; DENSE MOLECULAR CLOUDS; GRAIN SURFACE-REACTIONS; INFRARED-SPECTROSCOPY; SWS OBSERVATIONS; SOLID-PHASE; LABORATORY SIMULATIONS; MICRON ABSORPTION; INTERSTELLAR ICES; IR-SPECTRA AB ISO-SWS observations of the highly obscured young stellar object W 33A reveal two broad absorption features centered at 7.24 and 7.41 mu m. Comparison to interstellar ice analogs shows that the 7.24 mu m band can be well matched by the CH deformation mode of formic acid(HCOOH), while the 7.41 mu m band can be fitted both by the formate ion (HCOO-) and acetaldehyde (CH3HCO) The laboratory spectra reveal additional strong features of these molecules which should make a more definite identification straightforward. While an assignment of the 7.24 mu m band to the -CH3 deformation mode of aliphatic species maybe considered, the absence of a corresponding strong CH stretching mode argues against this possibility;These results and the earlier tentative detection of HCOOH towards NGC7538:IRS9 suggest that formic acid is a general component of the ices in the vicinity of embedded high-mass young stellar objects. C1 Leiden Univ, Raymond & Beverly Sackler Observ Lab, NL-2300 RA Leiden, Netherlands. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SRON, NL-9700 AV Groningen, Netherlands. RP Schutte, WA (reprint author), Leiden Univ, Raymond & Beverly Sackler Observ Lab, POB 9513, NL-2300 RA Leiden, Netherlands. EM schutte@strw.leidenuniv.nl RI Gerakines, Perry/B-9705-2009; Gerakines, Perry/D-2226-2012 OI Gerakines, Perry/0000-0002-9667-5904 NR 63 TC 118 Z9 118 U1 0 U2 7 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD MAR PY 1999 VL 343 IS 3 BP 966 EP 976 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 182JD UT WOS:000079495100040 ER PT J AU Stiavelli, M Treu, T Carollo, CM Rosati, P Viezzer, R Casertano, S Dickinson, M Ferguson, H Fruchter, A Madau, P Martin, C Teplitz, H AF Stiavelli, M Treu, T Carollo, CM Rosati, P Viezzer, R Casertano, S Dickinson, M Ferguson, H Fruchter, A Madau, P Martin, C Teplitz, H TI VLT and HST observations of a candidate high redshift elliptical galaxy in the Hubble Deep Field South SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE galaxies : elliptical and lenticular, cD; galaxies : evolution; galaxies : formation; infrared : galaxies; cosmology : observations ID RED GALAXY; POPULATION AB The combined use of the ESO Very Large Telescope (VLT) UTI Science Verification (SV) images and of the Hubble Space Telescope (HST) Hubble Deep Field South observations allows us to strengthen the identification as a candidate elliptical galaxy of the Extremely Red Object HDFS 223251-603910 previously identified by us on the basis of NICMOS and Cerro Tololo Interamerican Observatory imaging. The photometry presented here includes VLT data in U, B, V, R, I, a STIS unfiltered image, MCMOS J, H, and K band data, thus combining the 16.5 hours of VLT SV exposures with 101 hours of HST observing. The object is detected in all images except the VLT U band and is one of the reddest known with B-K= 9.7 +/- 0.5. We consider a wide range of models with different ages, metallicities, star formation histories and dust content, and conclude that the observed spectral energy distribution agrees best with that of an old elliptical galaxy at redshift just below 2. Alternative possibilities are discussed in light of their likelihood and of the perspective of spectroscopic confirmation. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Scuola Normale Super Pisa, I-56126 Pisa, Italy. Johns Hopkins Univ, Baltimore, MD 21218 USA. European So Observ, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Stiavelli, M (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 23 TC 35 Z9 35 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 MAR PY 1999 VL 343 IS 1 BP L25 EP L28 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 173LG UT WOS:000078981600006 ER PT J AU Soifer, BT Neugebauer, G Matthews, K Becklin, EE Ressler, M Werner, MW Weinberger, AJ Egami, E AF Soifer, BT Neugebauer, G Matthews, K Becklin, EE Ressler, M Werner, MW Weinberger, AJ Egami, E TI High spatial resolution imaging of Arp 220 from 3 to 25 microns SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (Arp 220); galaxies : nuclei; galaxies : structure; infrared : galaxies ID ULTRALUMINOUS INFRARED GALAXIES; ENERGY-DISTRIBUTIONS; LUMINOUS GALAXIES; IRAS GALAXIES; ARP-220; NUCLEI; EMISSION; NGC-6240 AB Images of Arp 220 from 3.45 to 24.5 mu m with 0." 5 resolution are presented that clearly separate the nucleus into at least two components. The western component is about 3 times more luminous than the eastern component, but the silicate absorption in the fainter, eastern component is roughly 50% greater than the absorption in the western component. Each component is marginally resolved. The two components seen at 24.5 mu m are identified with the two radio components. The western source most likely coincides with the high-extinction disk previously suggested to exist in Arp 220, while the eastern nucleus is identified with a faint, highly reddened source seen in HST 2.2 mu m NICMOS images. The two nuclei together account for essentially all of the measured 24.5 mu m flux density. Two models are presented, both of which fit the observations. In one the majority of the total luminosity is produced in an extended star formation region, and in the other most of the luminosity is produced in the compact but extincted regions associated with the two nuclei seen at 24.5 mu m. In both pictures, substantial luminosity at 100 mu m emerges from a component having a diameter of 2 "-3 " (similar to 1 kpc). C1 CALTECH, Palomar Observ, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. RP Soifer, BT (reprint author), CALTECH, Palomar Observ, 320-47, Pasadena, CA 91125 USA. OI Weinberger, Alycia/0000-0001-6654-7859 NR 27 TC 65 Z9 65 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1999 VL 513 IS 1 BP 207 EP 214 DI 10.1086/306855 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500015 ER PT J AU Pendleton, YJ Tielens, AGGM Tokunaga, AT Bernstein, MP AF Pendleton, YJ Tielens, AGGM Tokunaga, AT Bernstein, MP TI The interstellar 4.62 micron band SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM : lines and bands; ISM : clouds; ISM : molecules; line : identification; stars : pre-main-sequence ID ASTROPHYSICAL ICE ANALOGS; MAIN-SEQUENCE STARS; TAURUS DARK CLOUD; INFRARED-SPECTROSCOPY; GRAIN MANTLES; ABSORPTION FEATURES; MOLECULAR CLOUDS; SOLID CO; XCN BAND; SPECTRA AB We present new 4.5-5.1 mu m (2210-1970 cm(-1)) spectra of embedded protostars, W33 A, AFGL 961 E, AFGL 2136, NGC 7538 IRS 9, and Mon R2 IRS 2, which contain a broad absorption feature located near 4.62 mu m (2165 cm(-1)), commonly referred to in the literature as the "X-C=N" band. The observed peak positions and widths of the interstellar band agree to within 2.5 cm(-1) and 5 cm(-1), respectively. The strengths of the interstellar 4.62 mu m band and the ice absorption features in these spectra are not correlated, which suggests a diversity of environmental conditions for the ices we are observing. We explore several possible carriers of the interstellar band and review possible production pathways through far-ultraviolet photolysis (FUV), ion bombardment of interstellar ice analog mixtures, and acid-base reactions. Good fits to the interstellar spectra are obtained with an organic residue produced through ion bombardment of nitrogen-containing ices or with the OCN(-) ion produced either through acid-base reactions or FUV photolysis of NH(3)-containing ices. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Univ Hawaii, Astron Inst, Honolulu, HI 96822 USA. SETI Inst, Mountain View, CA 94043 USA. RP Pendleton, YJ (reprint author), NASA, Ames Res Ctr, Mail Stop 245-3, Moffett Field, CA 94035 USA. NR 68 TC 81 Z9 82 U1 1 U2 5 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 MAR 1 PY 1999 VL 513 IS 1 BP 294 EP 304 DI 10.1086/306827 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500023 PM 11542934 ER PT J AU Baring, MG Ellison, DC Reynolds, SP Grenier, IA Goret, P AF Baring, MG Ellison, DC Reynolds, SP Grenier, IA Goret, P TI Radio to gamma-ray emission from shell-type supernova remnants: Predictions from nonlinear shock acceleration models SO ASTROPHYSICAL JOURNAL LA English DT Review DE acceleration of particles; cosmic rays; gamma rays : theory; ISM : individual (IC 443); radiation mechanisms : nonthermal shock waves ID DIFFUSIVE PARTICLE-ACCELERATION; MONTE-CARLO SIMULATIONS; HIGH-ENERGY ELECTRONS; GALACTIC COSMIC-RAYS; EARTHS BOW SHOCK; OBLIQUE SHOCKS; POLARIZATION OBSERVATIONS; INTERPLANETARY SHOCKS; ULYSSES OBSERVATIONS; EGRET OBSERVATIONS AB Supernova remnants (SNRs) are widely believed to be the principal source of Galactic cosmic rays, produced by diffusive shock acceleration in the environs of the remnant's expanding blast wave. Such energetic particles can produce gamma rays and lower energy photons via interactions with the ambient plasma. The recently reported observation of TeV gamma rays from SN 1006 by the Collaboration of Australia and Nippon for a Gamma-Ray Observatory in the Outback (CANGAROO), combined with the fact that several unidentified EGRET sources have been associated with known radio/optical/X-ray-emitting remnants, provides powerful motivation for studying gamma-ray emission from SNRs. In this paper, we present results from a Monte Carlo simulation of nonlinear shock structure and acceleration coupled with photon emission in shelllike SNRs. These nonlinearities are a by-product of the dynamical influence of the accelerated cosmic rays on the shocked plasma and result in distributions of cosmic rays that deviate from pure power laws. Such deviations are crucial to acceleration efficiency considerations and impact photon intensities and spectral shapes at all energies, producing GeV/TeV intensity ratios that are quite different from test particle predictions. The Sedov scaling solution for SNR expansions is used to estimate important shock parameters for input into the Monte Carlo simulation. We calculate ion (proton and helium) and electron distributions that spawn neutral pion decay, bremsstrahlung, inverse Compton, and synchrotron emission, yielding complete photon spectra from radio frequencies to gamma-ray energies. The cessation of acceleration caused by the spatial and temporal limitations of the expanding SNR shell in moderately dense interstellar regions can yield spectral cutoffs in the TeV energy range that are consistent with Whipple's TeV upper limits on those EGRET unidentified sources that have SNR associations. Supernova remnants in lower density environments generate higher energy cosmic rays that produce predominantly inverse Compton emission observable at super-TeV energies, consistent with the SN 1006 detection. In general, sources in such low-density regions will be gamma-ray-dim at GeV energies. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. N Carolina State Univ, Dept Phys, Raleigh, NC 27695 USA. DAPNIA, DSM, CEA, Serv Astrophys, F-91191 Gif Sur Yvette, France. RP Baring, MG (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 121 TC 167 Z9 169 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1999 VL 513 IS 1 BP 311 EP 338 DI 10.1086/306829 PN 1 PG 28 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500025 ER PT J AU Stothers, RB AF Stothers, RB TI Rotational effects on the dynamical instability of luminous blue variables SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : evolution; stars : oscillations; stars : rotation; stars : variables : other (luminous blue variables) ID WOLF-RAYET STARS; MASSIVE STARS; ETA-CARINAE; OUTBURSTS; EVOLUTION AB Rotation influences the dynamical stability of a star in both direct and indirect ways. Directly, it supplies rotational kinetic energy to the star and changes the star's hydrostatic structure. Indirectly, it influences the possible course of stellar evolution. Calculations show that, for a luminous blue variable (LBV), rotation is not expected to greatly affect the onset of dynamical instability in any direct way, but could be important through its indirect evolutionary effect on the star's luminosity-to-mass ratio. If the classical LBV's are evolving in an advanced stage of central helium burning, when their envelopes are most prone to dynamical instability, the luminosity-to-mass ratio would probably be increased by rotation. It is shown that a brightening of the star lessens its dynamical. stability and so leads to a somewhat hotter effective temperature during the phase of dynamical instability. How rotation modifies the Eddington luminosity limit is also discussed. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Stothers, RB (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 23 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1999 VL 513 IS 1 BP 460 EP 463 DI 10.1086/306837 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500035 ER PT J AU Wilson, CA Dieters, S Finger, MH Scott, DM van Paradijs, J AF Wilson, CA Dieters, S Finger, MH Scott, DM van Paradijs, J TI Rossi X-ray timing explorer observations of the anomalous pulsar 4U 0142+61 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (4U 0142+61); stars : neutron; X-rays : stars ID NEUTRON-STAR; DISCOVERY; PULSATIONS; EMISSION; 4U-0142+61; BINARIES AB We observed the anomalous X-ray pulsar 4U 0142+61 using the Proportional Counter Array on board the Rossi X-Ray Timing Explorer in 1996 March. The pulse frequency was measured as v = 0.11510039(3) Hz, with an upper limit of \(v) over dot\ less than or equal to 4 x 10(-13) Hz s(-1) on the short-term change in frequency over the 4.6 day span of the observations. A compilation of all historical measurements showed an overall spin-down trend with slope (v) over dot = -3.0 +/- 0.1 x 10(-14) Hz s(-1). Searches for orbital modulations in pulse arrival times yielded an upper limit of a(x) sin i less than or similar to 0.26 It-s (99% confidence) for the period range 70 s to 2.5 days. These limits combined with previous optical limits and evolutionary arguments suggest that 4U 0142 + 61 is probably not a member of a binary system. C1 NASA, George C Marshall Space Flight Ctr, ES 84 Space Sci Lab, Huntsville, AL 35812 USA. RP Wilson, CA (reprint author), NASA, George C Marshall Space Flight Ctr, ES 84 Space Sci Lab, Huntsville, AL 35812 USA. EM colleen.wilson@msfc.nasa.gov; stefan.dieters@msfc.nasa.gov; finger@gibson.msfc.nasa.gov; scott@gibson.msfc.nasa.gov; jvp@astro.uva.nl NR 44 TC 32 Z9 33 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 MAR 1 PY 1999 VL 513 IS 1 BP 464 EP 470 DI 10.1086/306839 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500036 ER PT J AU van der Hooft, F Kouveliotou, C van Paradijs, J Paciesas, WS Lewin, WHG van der Klis, M Crary, DJ Finger, MH Harmon, BA Zhang, SN AF van der Hooft, F Kouveliotou, C van Paradijs, J Paciesas, WS Lewin, WHG van der Klis, M Crary, DJ Finger, MH Harmon, BA Zhang, SN TI Hard X-ray variability of the black hole candidate GRO J0422+32 during its 1992 outburst SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (GRO J0422+32); X-rays : stars ID TRANSIENT NOVA PERSEI; CYGNUS X-1; OPTICAL COUNTERPART; HIGH STATE; GRO-J0422+32; SPECTRA; NOISE; MASS; DEPENDENCE; PHOTOMETRY AB We have studied the hard X-ray variability of the soft X-ray transient GRO J0422+32 with BATSE in the 20-100 keV energy band. Our analysis covers 180 days following the first X-ray detection of the source on 1992 August 5, fully covering its primary and secondary X-ray outbursts. We compute power density spectra (PDSs) in the 20-50, 50-100, and 20-100 keV energy bands, in the frequency interval 0.002-0.488 Hz. The PDSs of GRO J0422+32 are approximately flat up to a break frequency, and decay as a power law above it, with index similar to 1. During the first 70 days of the X-ray outburst, the PDSs of GRO J0422+32 show a significant quasi-periodic oscillation (QPO) peak near similar to 0.2 Hz, superposed on the power-law tail. The break frequency of the PDSs obtained during the primary X-ray outburst of GRO J0422 + 32 occurs at 0.041+/-0.006 Hz; during the secondary outburst, the break is at 0.081 +/- 0.015 Hz. The power density at the break ranged between 44% and 89% Hz(-1/2) (20-100 keV). The canonical anticorrelation between the break frequency and the power density at the break, observed in Cyg X-l and other BHCs in the low state, is not observed in the PDSs of GRO J0422+32. We compare our results with those of similar variability studies of Cyg X-l. The relation between the spectral slope and the amplitude of the X-ray variations of GRO J0422+32 is similar to that of Cyg X-l; however, the relation between the hard X-ray flux and the amplitude of its variation is opposite to what has been found in Cyg X-l. Phase lags between the X-ray flux variations of GRO J0422+32 at high and low photon energies could only be derived during the first 30 days of its outburst. During this period, the variations in the 50-100 keV band lag those in the 20-50 keV energy band by an approximately constant phase difference of 0.039(3) rad in the frequency interval 0.02-0.20 Hz. The time lags of GRO J0422+32 during the first 30 days of the outburst decrease with frequency as a power law with index 0.9 for v > 0.01 Hz. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. NASA, Marshall Space Flight Ctr, Huntsville, AL 35812 USA. MIT, Cambridge, MA 02139 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. RP van der Hooft, F (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. NR 57 TC 14 Z9 14 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 MAR 1 PY 1999 VL 513 IS 1 BP 477 EP 490 DI 10.1086/306845 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500038 ER PT J AU Lawrence, JK Cadavid, AC Ruzmaikin, AA AF Lawrence, JK Cadavid, AC Ruzmaikin, AA TI Characteristic scales of photospheric flows and their magnetic and temperature markers SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : granulation; Sun : magnetic fields; turbulence ID TURBULENT TRANSPORT; SOLAR CONVECTION; MODELS; FIELDS; DIFFUSION; SPECTRA AB We study the characteristic scales of quiet-Sun photospheric velocity fields along with their temperature and magnetic markers in Doppler images from the Michelson Doppler Imager aboard the SOHO satellite (SOHO/MDI) in simultaneous, Doppler, magnetic, and intensity images from the San Fernando Observatory and in full-disk magnetograms and an intensity image from National Solar Observatory (Kitt Peak). Wavelet flatness spectra show that velocity fluctuations are normally distributed (Gaussian). This is often assumed in stochastic models of turbulence but had not yet been verified observationally for the Sun. Temperature fluctuations also are Gaussian distributed, but magnetic fields are intermittent and are gathered into patterns related to flow structures. Wavelet basis functions designed to detect characteristic convection cell-flow topologies in acoustically filtered SOHO/MDI Doppler images reveal granulation scales of 0.7-2.2 Mm and supergranulation scales of 28-40 Mm. Mesogranular flows are weakly but significantly detected in the range 4-8 Mm. The systematic flows account for only 30% of the image variances at granular and supergranular scales and much less in between. The main flows for the intermediate range of 2-15 Mm are self-similar, i.e., chaotic or turbulent. C1 Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lawrence, JK (reprint author), Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA. NR 28 TC 22 Z9 22 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1999 VL 513 IS 1 BP 506 EP 515 DI 10.1086/306835 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500040 ER PT J AU Brage, T Proffitt, C Leckrone, DS AF Brage, T Proffitt, C Leckrone, DS TI Theoretical oscillator strengths and hyperfine structure in HgII SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; relativity ID LIFETIME MEASUREMENTS; QUANTUM JUMPS; CHI-LUPI; TRANSITIONS; ABUNDANCE; PACKAGE; ENERGY; HG+ AB We present a theoretical model ion for Hg II, including oscillator strengths and hyperfine structure constants for a large number of transitions and levels. Different computational models have been used, depending on the observability of the lines and their importance in spectral synthesis of stellar atmospheres. For the resonance lines, we use highly systematic, accurate, and fully relativistic multiconfiguration Dirac-Fock methods. These methods are well suited to an accurate treatment of both the relativistic problem and the strong correlation effects in this ion. The predicted gf-values are probably accurate to within a few percent. A larger number of transitions are treated with a more flexible, but less accurate, version of the method. This is based on the idea of crosswise optimization to represent a number of states in the same calculation. The results are used in stellar atmosphere models, assuming local thermodynamic equilibrium (LTE), where a line-by-line investigation is important. A larger set of levels are treated with semiempirical methods, for use in large scale non-LTE calculations. The lower accuracy of these are well-suited to a more statistical treatment of the structure of the ion. We discuss the importance of a correct treatment of core-valence correlation and relativistic effects for predicting accurate oscillator strengths. These tend to reduce their values by as much as a factor of 2 for the resonance line. C1 Univ Lund, Dept Phys, S-22100 Lund, Sweden. NASA, Goddard Space Flight Ctr, Sci Programs, Comp Sci Corp, Greenbelt, MD 20771 USA. Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Brage, T (reprint author), Univ Lund, Dept Phys, Box 118, S-22100 Lund, Sweden. OI Brage, Tomas/0000-0003-3985-767X NR 29 TC 29 Z9 29 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1999 VL 513 IS 1 BP 524 EP 534 DI 10.1086/306826 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MM UT WOS:000080197500042 ER PT J AU Hudgins, DM Allamandola, LJ AF Hudgins, DM Allamandola, LJ TI The spacing of the interstellar 6.2 and 7.7 micron emission features as an indicator of polycyclic aromatic hydrocarbon size SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM : lines and bands; ISM : molecules; molecular data ID INFRARED-SPECTROSCOPY; IRAS SOURCES; ORION-BAR; CATIONS; MOLECULES; SPECTRA; BANDS; PAHS; PHOTODISSOCIATION; TETRACENE AB A database of astrophysically relevant, infrared spectral measurements on a wide variety of neutral as well as positively and negatively charged polycyclic aromatic hydrocarbons (PAHs), ranging in size from C10H8 through C48H20, is now available to extend the interstellar PAH model. Beyond simply indicating general characteristics of the carriers, this collection of data now makes it possible to conduct a more thorough interpretation of the details of the interstellar spectra and thereby derive deeper insights into the nature of the emitting material and conditions in the emission zones. This Letter is the first such implementation of this spectral database. The infrared spectra of PAH cations, the main PAH form in the most energetic emission zones, are usually dominated by a few strong features in the 1650-1100 cm(-1) (6.1-9.1 mu m) region that tend to cluster in the vicinity of the interstellar emission bands at 1610 and 1320 cm(-1) (6.2 and 7.6 mu m), but with spacings typically somewhat less than that observed in the canonical interstellar spectrum. However, the spectra in the database show that this spacing increases steadily with molecular size. Extrapolation of this trend indicates that PAHs in the 50-80 carbon atom size range are entirely consistent with the observed interstellar spacing. Furthermore, the profile of the 1610 cm(-1) (6.2 mu m) interstellar band indicates that PAHs containing as few as 20 carbon atoms contribute to this feature. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hudgins, DM (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. NR 31 TC 65 Z9 65 U1 0 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1999 VL 513 IS 1 BP L69 EP L73 DI 10.1086/311901 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MN UT WOS:000080197600018 PM 11543062 ER PT J AU Markwardt, CB Swank, JH Taam, RE AF Markwardt, CB Swank, JH Taam, RE TI Variable-frequency quasi-periodic oscillations from the galactic microquasar GRS 1915+105 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; stars : individual (GRS 1915+105); stars : oscillations ID X-RAY BINARIES; ACCRETION DISKS; BLACK-HOLES; GRS-1915+105; INSTABILITIES; VARIABILITY; RXTE AB We show that the galactic microquasar GRS 1915+105 exhibits quasi-periodic oscillations (QPOs) whose frequency varies continuously from I to 15 Hz during spectrally hard dips when the source is in a flaring state. We report here analyses of simultaneous energy spectra and power density spectra at 4 s intervals. The energy spectrum is well fit at each time step by an optically thick accretion disk plus power-law model, while the power density spectrum consists of a varying red noise component plus the variable-frequency QPO. The features of both spectra are strongly correlated with one another. The 1-15 Hz QPOs appear when the power-law component becomes hard and intense and themselves have an energy spectrum consistent with the power-law component (with rms amplitudes as high as 10%). The frequency of the oscillations, however, is most strikingly correlated with the parameters of the thermal disk component. The tightest correlation is between QPO frequency and disk X-ray flux. This fact indicates that the properties of the QPO are not determined solely by a disk or solely by a corona. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA. RP Markwardt, CB (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. EM craigm@lheamail.gsfc.nasa.gov; swank@pcasunl.gsfc.nasa.gov; taam@ossenu.astro.nwu.edu RI Swank, Jean/F-2693-2012 NR 26 TC 57 Z9 57 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1999 VL 513 IS 1 BP L37 EP L40 DI 10.1086/311899 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MN UT WOS:000080197600010 ER PT J AU Sloan, GC Hayward, TL Allamandola, LJ Bregman, JD DeVito, B Hudgins, DM AF Sloan, GC Hayward, TL Allamandola, LJ Bregman, JD DeVito, B Hudgins, DM TI Direct spectroscopic evidence for ionized polycyclic aromatic hydrocarbons in the interstellar medium SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared : ISM : lines and bands; ISM : molecules ID INFRARED-SPECTROSCOPY; ELECTRONIC-SPECTRA; EMISSION BANDS; CATIONS; CLOUD; TETRACENE; PENTACENE; NGC-1333; ANIONS AB Long-slit 8-13 mu m spectroscopy of the nebula around NGC 1333 SVS 3 reveals spatial variations in the strength and shape of emission features that are probably produced by polycyclic aromatic hydrocarbons (PAHs). Close to SVS 3, the 11.2 mu m feature develops an excess at similar to 10.8-11.0 mu m, and a feature appears at similar to 10 mu m. These features disappear with increasing distance from the central source, and they show striking similarities to recent laboratory data of PAH cations, providing the first identification of emission features arising specifically from ionized PAHs in the interstellar medium. C1 Univ Coll, Sch Phys, Australian Def Force Acad, Canberra, ACT 2600, Australia. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. RP Sloan, GC (reprint author), Univ Coll, Sch Phys, Australian Def Force Acad, Canberra, ACT 2600, Australia. NR 31 TC 55 Z9 55 U1 0 U2 9 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 MAR 1 PY 1999 VL 513 IS 1 BP L65 EP L68 DI 10.1086/311906 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194MN UT WOS:000080197600017 PM 11543061 ER PT J AU Haruna, Y Styf, JR Kahan, N Hargens, AR AF Haruna, Y Styf, JR Kahan, N Hargens, AR TI Hoffmann-reflex is delayed during 6 degrees head-down tilt with balanced traction SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE bed rest; F-reflex; H-reflex; lumbar vertebrae; neurography; spaceflight; Achilles tendon reflex; weightlessness; microgravity ID LOWER-LIMB; BACK PAIN AB Background: Increased spinal height due to the lack of of axial compression on spinal structures in microgravity may stretch the spinal cord, cauda equina, nerve roots, and paraspinal tissues. Hypothesis: Exposure to simulated microgravity causes dysfunction of nerve roots so that the synaptic portion of the Achilles tendon reflex is delayed. Methods: Six healthy male subjects were randomly divided into two-groups with three in each group. The subjects in the first group underwent horizontal bed rest (HBR) for three days. After a two week interval they underwent bed rest in a position of head-down tilt with balanced traction (HDT). So that each subject could serve as his own control, the second group was treated identically but in opposite order. Bilateral F waves and H-reflexes were measured dairy (18:30-20:30) on all subjects placed in a prone position. Results: By means of ANOVA, differences between HDT and HER were observed only in M-latency and F-ratio, not in F-latency, central latency, and H-latency. Differences during the course of the bed rest were observed in M-latency and H-latency only. Tibial H latency was significantly lengthened in HDT group on day 2 and 3, although no significant difference between HDT and HER was observed. Conclusion: The monosynaptic reflex assessed by H-reflex was delayed during 6 degrees HDT with traction. The exact mechanism of this delay and whether the change was due to lengthening of the lower part of the vertebrae remain to be clarified. C1 NASA, Ames Res Ctr, Gravitat Res Branch, Moffett Field, CA 94035 USA. RP Hargens, AR (reprint author), NASA, Ames Res Ctr, Gravitat Res Branch, MS 239-11, Moffett Field, CA 94035 USA. NR 13 TC 0 Z9 0 U1 1 U2 1 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD MAR PY 1999 VL 70 IS 3 BP 220 EP 224 PG 5 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 174BZ UT WOS:000079015400003 PM 10102732 ER PT J AU Moles, A AF Moles, A TI Parasitism, feeding rate, and hydrocarbon uptake of pink shrimp Pandalus borealis fed a crude oil contaminated diet SO BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY LA English DT Article ID PRINCE-WILLIAM-SOUND; EXXON-VALDEZ; PETROLEUM-HYDROCARBONS; SEDIMENTS; SEAWATER; SPILL; FOOD C1 NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Moles, A (reprint author), NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 12 TC 7 Z9 7 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0007-4861 J9 B ENVIRON CONTAM TOX JI Bull. Environ. Contam. Toxicol. PD MAR PY 1999 VL 62 IS 3 BP 259 EP 265 PG 7 WC Environmental Sciences; Toxicology SC Environmental Sciences & Ecology; Toxicology GA 176DW UT WOS:000079136500004 PM 10085167 ER PT J AU Estabrook, FB Robinson, RS Wahlquist, HD AF Estabrook, FB Robinson, RS Wahlquist, HD TI Constraint-free theories of gravitation SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article ID RICCI-FLAT GEOMETRIES AB Lovelock actions (more precisely, extended Gauss-Bonnet forms) when varied as Cartan forms on subspaces of higher-dimensional flat Riemannian manifolds, generate well set, causal exterior differential systems. In particular, the Einstein-Hilbert action 4-form, varied on a four-dimensional subspace of E-10, yields a well set generalized theory of gravity having no constraints. Ricci-flat solutions are selected by initial conditions on a bounding 3-space. C1 CALTECH, Jet Prop Lab 169 327, Pasadena, CA 91109 USA. RP Estabrook, FB (reprint author), CALTECH, Jet Prop Lab 169 327, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 26 TC 7 Z9 8 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD MAR PY 1999 VL 16 IS 3 BP 911 EP 918 DI 10.1088/0264-9381/16/3/019 PG 8 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 180TA UT WOS:000079400200018 ER PT J AU Olson, CF AF Olson, CF TI Constrained Hough transforms for curve detection SO COMPUTER VISION AND IMAGE UNDERSTANDING LA English DT Article ID HIERARCHICAL APPROACH; PERFORMANCE; ALGORITHM; IMAGES; RECOGNITION; PICTURES; ELLIPSES; LINES; NOISE; RHT AB This paper describes techniques to perform fast and accurate curve detection using constrained Hough transforms, in which localization error can be propagated efficiently into the parameter space. We first review a formal definition of Hough transform and modify it to allow the formal treatment localization error. We then analyze current Hough transform techniques with respect to this definition. It is shown that the Hough transform can be subdivided into many small subproblems without a decrease in performance, where each subproblem is constrained to consider only those curves that pass through some subset of the edge pixels up to the localization error. This property allows us to accurately and efficiently propagate localization error into the parameter space such that curves are detected robustly without finding false positives. The use of randomization techniques yields an algorithm with a worst-case complexity of O(n), where n is the number of edge pixels in the image, if we are only required to find curves that are significant with respect to the complexity of the image. Experiments are discussed that indicate that this method is superior to previous techniques for performing curve detection and results are given showing the detection of lines and circles in real images. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Olson, CF (reprint author), CALTECH, Jet Prop Lab, Mail Stop 125-209,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 48 TC 55 Z9 59 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 1077-3142 J9 COMPUT VIS IMAGE UND JI Comput. Vis. Image Underst. PD MAR PY 1999 VL 73 IS 3 BP 329 EP 345 DI 10.1006/cviu.1998.0728 PG 17 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 174HE UT WOS:000079028000002 ER PT J AU Bamman, MM Clarke, MSF Talmadge, RJ Feeback, DL AF Bamman, MM Clarke, MSF Talmadge, RJ Feeback, DL TI Enhanced protein electrophoresis technique for separating human skeletal muscle myosin heavy chain isoforms SO ELECTROPHORESIS LA English DT Article DE Western blot analysis; myosin heavy chain; sodium dodecyl sulfate - polyacrylamide; gel electrophoresis; muscle biopsy AB Talmadge and Roy (J. Appl. Physiol. 1993, 75, 2337-2340) previously established a sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) protocol for separating all four rat skeletal muscle myosin heavy chain (MHC) isoforms (MHC I, IIa, IIx, IIb); however, when applied to human muscle, the type II MHC isoforms (IIa, IIx) are not clearly distinguished. In this brief paper we describe a modification of the SDS-PAGE protocol which yields distinct and consistent separation of all three adult human MHC isoforms (MHC I, IIa, IIx) in a minigel system. MHC specificity of each band was confirmed by Western blot using three monoclonal IgG antibodies (mAbs) immunoreactive against MHCI (mAb MHCs, Novacastra Laboratories), MHCI+IIa (mAb BF-35), and MHCIIa+IIx (mAb SC-71). Results provide a valuable SDS-PAGE minigel technique for separating MHC isoforms in human muscle without the difficult task of casting gradient gels. C1 Univ Alabama, Dept Human Studies, Birmingham, AL 35294 USA. Univ Alabama, Dept Physiol & Biophys, Birmingham, AL 35294 USA. NASA, Life Sci Res Labs, Johnson Space Ctr, Houston, TX USA. Virginia Polytech Inst & State Univ, Dept Human Nutr Foods & Exercise, Blacksburg, VA USA. RP Bamman, MM (reprint author), Univ Alabama, Dept Human Studies, 901 S 13th St, Birmingham, AL 35294 USA. EM mbamman@uab.edu FU NCRR NIH HHS [M01 RR00073] NR 8 TC 45 Z9 46 U1 0 U2 7 PU WILEY-V C H VERLAG GMBH PI BERLIN PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY SN 0173-0835 J9 ELECTROPHORESIS JI Electrophoresis PD MAR PY 1999 VL 20 IS 3 BP 466 EP 468 DI 10.1002/(SICI)1522-2683(19990301)20:3<466::AID-ELPS466>3.0.CO;2-7 PG 3 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA 183FZ UT WOS:000079544700007 PM 10217154 ER PT J AU Carls, MG Rice, SD Hose, JE AF Carls, MG Rice, SD Hose, JE TI Sensitivity of fish embryos to weathered crude oil: Part I. Low-level exposure during incubation causes malformations, genetic damage, and mortality in larval Pacific herring (Clupea pallasi) SO ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY LA English DT Article DE herring larvae; morphological damage; genetic damage; polynuclear aromatic hydrocarbons; Exxon Valdez oil spill ID EXXON-VALDEZ OIL; PRINCE-WILLIAM-SOUND; JUVENILE PINK SALMON; PETROLEUM-HYDROCARBONS; SPILL; ALASKA; SEDIMENTS; GROWTH; ABUNDANCE; SURVIVAL AB Pacific herring eggs were exposed for 16 d to weathered Alaska North Slope crude oil. Exposure to an initial aqueous concentration of 0.7 parts per billion (ppb) polynuclear aromatic hydrocarbons (PAHs) caused malformations, genetic damage, mortality, and decreased size and inhibited swimming. Total aqueous PAH concentrations as low as 0.4 ppb caused sublethal responses such as yolk sac edema and immaturity consistent with premature hatching. Responses to less weathered oil, which had relatively lower proportions of high molecular weight PAH, generally paralleled those of more weathered oil, but lowest observed effective concentrations (LOECs) were higher (9.1 ppb), demonstrating the importance of composition. The LOEC for more weathered oil (0.4 ppb) was similar to that observed in pink salmon (1.0 ppb), a species with a very different development rate; by inference, other species may be similarly sensitive to weathered oil. Our methods simulated conditions observed in Prince William Sound (PWS) following the Exxon Valdez oil (EVO) spill. Biological effects were identical to those observed in embryolarval herring from PWS in 1989 and support the conclusion that EVO caused significant damage to herring in PWS. Previous demonstration by our laboratory that most malformed or precocious larvae die corroborates the decreased larval production measured after the spill. C1 Natl Marine Fisheries Serv, NOAA, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. Occidental Coll, Los Angeles, CA 90041 USA. RP Carls, MG (reprint author), Natl Marine Fisheries Serv, NOAA, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 49 TC 220 Z9 224 U1 11 U2 85 PU SETAC PRESS PI PENSACOLA PA 1010 NORTH 12TH AVE, PENSACOLA, FL 32501-3370 USA SN 0730-7268 J9 ENVIRON TOXICOL CHEM JI Environ. Toxicol. Chem. PD MAR PY 1999 VL 18 IS 3 BP 481 EP 493 DI 10.1897/1551-5028(1999)018<0481:SOFETW>2.3.CO;2 PG 13 WC Environmental Sciences; Toxicology SC Environmental Sciences & Ecology; Toxicology GA 167WX UT WOS:000078658100017 ER PT J AU Heintz, RA Short, JW Rice, SD AF Heintz, RA Short, JW Rice, SD TI Sensitivity of fish embryos to weathered crude oil: Part II. Increased mortality of pink salmon (Oncorhynchus gorbuscha) embryos incubating downstream from weathered Exxon Valdez crude oil SO ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY LA English DT Article DE toxicity; pink salmon; Exxon Valdez; polynuclear aromatic hydrocarbons; oil spill ID SEDIMENTS AB We incubated pink salmon embryos under three exposure conditions, direct contact with oil-coated gravel. effluent from oil-coated gravel, and direct contact with gravel coated with very weathered oil (VWO). Embryo mortalities and polynuclear aromatic hydrocarbon (PAH) accumulation in embryo tissues during the direct-contact and effluent exposure experiments were not significantly different, indicating that PAH accumulation was mediated by aqueous transport. Mortality rates for embryos exposed initially to a total PAH concentration (TPAH) of 1.0 ppb were significantly higher than controls when the PAH were derived from VWO. The same aqueous TPAH concentration failed to increase mortality rates when the PAH were derived from less weathered oil, indicating that toxicity of effluents from the VWO was primarily associated with the larger PAH. We conclude that water quality standards for TPAH above 1.0 ppb may fail to protect fish embryos. Further, pink salmon embryos incubating in Prince William Sound after the Exxon Valdez oil spill may have accumulated lethal concentrations of PAH from interstitial water that was contaminated when it percolated through oil reservoirs located upstream from salmon redds. C1 Natl Marine Fisheries Serv, NOAA, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Heintz, RA (reprint author), Natl Marine Fisheries Serv, NOAA, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. EM ron.heintz@noaa.gov NR 19 TC 170 Z9 174 U1 7 U2 56 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0730-7268 J9 ENVIRON TOXICOL CHEM JI Environ. Toxicol. Chem. PD MAR PY 1999 VL 18 IS 3 BP 494 EP 503 DI 10.1897/1551-5028(1999)018<0494:SOFETW>2.3.CO;2 PG 10 WC Environmental Sciences; Toxicology SC Environmental Sciences & Ecology; Toxicology GA 167WX UT WOS:000078658100018 ER PT J AU Roux, S Muzy, JF Arneodo, A AF Roux, S Muzy, JF Arneodo, A TI Detecting vorticity filaments using wavelet analysis: About the statistical contribution of vorticity filaments to intermittency in swirling turbulent flows SO EUROPEAN PHYSICAL JOURNAL B LA English DT Review ID REYNOLDS-NUMBER TURBULENCE; FULLY-DEVELOPED TURBULENCE; PROBABILITY DENSITY-FUNCTIONS; TAYLOR-GREEN VORTEX; MULTIFRACTAL FORMALISM; OSCILLATING SINGULARITIES; 3-DIMENSIONAL TURBULENCE; PRESSURE-FLUCTUATIONS; ISOTROPIC TURBULENCE; FRACTAL DIMENSIONS AB Swirling turbulent flows display intermittent pressure drops associated with intense vorticity filaments. Using the wavelet transform modulus maxima representation of pressure fluctuations, we propose a method of characterizing these pressure drop events from their time-scale properties. This method allows us to discriminate fluctuations induced by just formed (young) as well as by burst (old) filaments from background pressure fluctuations. The statistical characteristics of these filaments (core size, waiting time) are analyzed in details and compared with previously reported experimental and numerical findings. Their intermittent occurrence is found to be governed by a pure Poisson's law, the hallmark of independent events. Then we apply the wavelet transform modulus maxima (WTMM) method to the background pressure fluctuations. This study reveals that, once removed all the filaments, the "multifractal" nature of pressure fluctuations still persists. This is a clear indication that the statistical contribution of the filaments is not important enough to account for the intermittency phenomenon in turbulents flows. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. Univ Montreal, Ctr Rech Math, Montreal, PQ H3C 3J7, Canada. Ctr Rech Paul Pascal, F-33600 Pessac, France. RP Roux, S (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Code 913, Greenbelt, MD 20771 USA. EM arneodo@crpp.u-bordeaux.fr NR 124 TC 26 Z9 27 U1 1 U2 3 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1434-6028 J9 EUR PHYS J B JI Eur. Phys. J. B PD MAR PY 1999 VL 8 IS 2 BP 301 EP 322 DI 10.1007/s100510050694 PG 22 WC Physics, Condensed Matter SC Physics GA 188CP UT WOS:000079827500017 ER PT J AU Exton, RJ Balla, RJ Shirinzadeh, B Hillard, ME Brauckmann, GJ AF Exton, RJ Balla, RJ Shirinzadeh, B Hillard, ME Brauckmann, GJ TI Flow visualization using fluorescence from locally seeded I-2 excited by an ArF excimer laser SO EXPERIMENTS IN FLUIDS LA English DT Article ID WIND-TUNNEL AB A new concept for flow visualization is demonstrated in which fluorescence from locally seeded iodine is viewed in the wake of simple aerodynamic models at Mach 6. Localized seeding is performed by painting a small area of a ceramic model with a tincture of iodine. When the model is injected into the flow, the adsorbed iodine is entrained into the boundary layer, follows the model contour, and ultimately mixes into the wake region. Planar "snapshots" of the wake flow are taken by exciting the iodine with an ArF excimer laser sheet at 193 nm and observing the fluorescence in the 210-600 nm region with an intensified CCD camera. C1 NASA, Langley Res Ctr, Measurement Sci & Technol Branch, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aerothermodynam Branch, Hampton, VA 23681 USA. RP Exton, RJ (reprint author), NASA, Langley Res Ctr, Measurement Sci & Technol Branch, M-S 493, Hampton, VA 23681 USA. NR 17 TC 8 Z9 8 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD MAR PY 1999 VL 26 IS 4 BP 335 EP 339 DI 10.1007/s003480050296 PG 5 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 178PH UT WOS:000079274700007 ER PT J AU Rampino, MR AF Rampino, MR TI Argument supporting explosive igneous activity for the origin of "cryptoexplosion" structures in the midcontinent, United States: Comment SO GEOLOGY LA English DT Article C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NYU, Earth & Environm Sci Program, New York, NY 10003 USA. RP Rampino, MR (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 13 TC 3 Z9 3 U1 0 U2 0 PU GEOLOGICAL SOC AMER, INC PI BOULDER PA PO BOX 9140, BOULDER, CO 80301-9140 USA SN 0091-7613 J9 GEOLOGY JI Geology PD MAR PY 1999 VL 27 IS 3 BP 279 EP 280 DI 10.1130/0091-7613(1999)027<0279:ASEIAF>2.3.CO;2 PG 2 WC Geology SC Geology GA 175YQ UT WOS:000079124000022 ER PT J AU Cane, HV Wibberenz, G Richardson, IG von Rosenvinge, TT AF Cane, HV Wibberenz, G Richardson, IG von Rosenvinge, TT TI Cosmic ray modulation and the solar magnetic field SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERACTION REGIONS AB We show that the variations of the interplanetary magnetic field strength (B) over a 22-year period are tracked by the inverted profile of the cosmic ray density measured by neutron monitors. We suggest that global changes in the Sun's magnetic field are more important for longterm modulation than magnetic field enhancements resulting from the merging of high-speed flows and coronal mass ejections in the outer heliosphere. The unexpectedly close relationship that we find between the "tilt angle" of the heliospheric current sheet and the cosmic ray density away from solar minimum for both polarity states of the solar magnetic field may be accounted for by the anticorrelation between the cosmic ray density and field strength variations. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Kiel, Inst Exptl & Angew Phys, D-24118 Kiel, Germany. Univ Tasmania, Sch Math & Phys, Hobart, Tas, Australia. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Cane, HV (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. OI Richardson, Ian/0000-0002-3855-3634 NR 10 TC 141 Z9 141 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 1999 VL 26 IS 5 BP 565 EP 568 DI 10.1029/1999GL900032 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 181NJ UT WOS:000079447100009 ER PT J AU Townsend, JA Hansen, PA McClendon, MW de Groh, KK Banks, BA AF Townsend, JA Hansen, PA McClendon, MW de Groh, KK Banks, BA TI Ground-based testing of replacement thermal control materials for the Hubble Space Telescope SO HIGH PERFORMANCE POLYMERS LA English DT Article AB The mechanical and optical properties of the metallized Teflon(R) FEP thermal control materials on the Hubble Space Telescope (HST) have degraded over the nearly seven years the telescope has been in orbit. Given the damage to the outer layer of the multilayer insulation (MLI) blanket that was apparent during the second servicing mission (SM2), the decision was made to replace the outer layer during subsequent servicing missions. A Failure Review Board was established to investigate the damage to the MLI: and identify a replacement material. The replacement material had to meet the stringent thermal requirements of the spacecraft and maintain mechanical integrity for at least ten years. Ten candidate materials were selected and exposed to ten-year HST-equivalent doses of simulated orbital environments. Samples of the candidates were exposed sequentially to low- and high-energy electrons and protons, atomic oxygen, x-ray radiation, ultraviolet radiation and thermal cycling. Following the exposures, the mechanical integrity and optical properties of the candidates were investigated using optical microscopy, scanning electron microscopy (SEM), a laboratory portable spectroreflectometer (LPSR) and a Lambda 9 spectroreflectometer. Based on the results of these simulations and analyses, the Failure Review Board selected a replacement material and two alternatives that showed the highest likelihood Of providing the requisite thermal properties and surviving for ten years in orbit. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Townsend, JA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 11 TC 12 Z9 12 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 1999 VL 11 IS 1 BP 63 EP 79 DI 10.1088/0954-0083/11/1/006 PG 17 WC Polymer Science SC Polymer Science GA 183CQ UT WOS:000079536800008 ER PT J AU Townsend, JA Hansen, PA Dever, JA de Groh, KK Banks, BA Wang, L He, C AF Townsend, JA Hansen, PA Dever, JA de Groh, KK Banks, BA Wang, L He, C TI Hubble Space Telescope metallized Teflon (R) FEP thermal control materials: on-orbit degradation and post-retrieval analysis SO HIGH PERFORMANCE POLYMERS LA English DT Article AB During the Hubble Space Telescope (HST) second servicing mission (SM2), degradation of unsupported Teflon(R) FEP (fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(R) FEP sample evaluation and additional testing of pristine Teflon(R) FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations, and that the damage increased with the combined total dose of electrons, protons, ultraviolet and x-ray radiation along with thermal cycling. This paper discusses the testing and evaluation of the retrieved Teflon(R) FEP. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Unisys Corp, Lanharm, MD 20705 USA. RP Townsend, JA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 11 TC 20 Z9 20 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 1999 VL 11 IS 1 BP 81 EP 99 DI 10.1088/0954-0083/11/1/007 PG 19 WC Polymer Science SC Polymer Science GA 183CQ UT WOS:000079536800009 ER PT J AU Lennhoff, J Harris, G Vaughn, J Edwards, D Zwiener, J AF Lennhoff, J Harris, G Vaughn, J Edwards, D Zwiener, J TI Electrically conductive space-durable polymeric films for spacecraft thermal and charge control SO HIGH PERFORMANCE POLYMERS LA English DT Article ID POLYANILINE; BLENDS AB There is a significant requirement for an electrically conductive thermal control film for the dissipation of spacecraft charging. The present state-of-the-art technology for charge control is based upon thin vapour-deposited indium tin oxide (ITO) conductive coatings on Teflon or Kapton films. These ITO coated films suffer from a range of problems, including no bulk conductivity, poor space durability and a propensity of the coating to crack. A new blended polymer film developed at Triton Systems combines the properties of an intrinsically electrically conductive polymer with that of a space-durable polymer. The resulting film, called C-COR for conductive colourless oxygen resistant, has bulk electrical resistance adjustable between 10(12) and 10(8) (Ohm cm), atomic oxygen (AO) resistance, low absorptance, high emittance, vacuum stability, and good mechanical and UV resistant properties. The C-COR polymer is produced as a free-standing him. Data are presented on the space durability, optical, mechanical and electrical properties of the C-COR film. C1 Triton Syst Inc, Chelmsford, MA 01824 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Lennhoff, J (reprint author), Triton Syst Inc, 200 Turnpike Rd, Chelmsford, MA 01824 USA. NR 13 TC 6 Z9 6 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 1999 VL 11 IS 1 BP 101 EP 111 DI 10.1088/0954-0083/11/1/008 PG 11 WC Polymer Science SC Polymer Science GA 183CQ UT WOS:000079536800010 ER PT J AU Dever, JA de Groh, KK Bank, BA Townsend, JA AF Dever, JA de Groh, KK Bank, BA Townsend, JA TI Effects of radiation and thermal cycling on Teflon (R) FEP SO HIGH PERFORMANCE POLYMERS LA English DT Article AB Surfaces of the aluminized Teflon(R) FEP (fluorinated ethylene propylene) multilayer thermal insulation on the Hubble Space Telescope (HST) were found to be cracked and curled in some areas at the time of the second servicing mission (SM2) in February 1997, 6.8 years after HST was deployed in low Earth orbit (LEO). In an effort to understand what elements of the space environment might cause such damage, pristine second-surface aluminized Teflon(R) FEP was tested for durability to various types of radiation, to thermal cycling and to radiation followed by thermal cycling. Types of radiation included synchrotron vacuum ultraviolet and soft x-ray radiation, simulated solar flare x-ray radiation, electrons and protons. Thermal cycling was conducted in various temperature ranges to simulate HST orbital conditions for Teflon(R) FEP. Results of tensile testing of the exposed specimens showed that exposure to high fluences of radiation caused degradation in tensile properties of FEP. However, exposure to radiation alone in exposures comparable to those experienced by HST did not produce reduction in ultimate tensile strength and elongation of Teflon(R) similar to that observed for HST-retrieved aluminized Teflon(R). Synergism of radiation exposure and thermal cycling was evident in the results of three experiments: thermal cycling following electron and proton irradiation, thermal cycling following x-ray exposure, and additional thermal cycling of a sample retrieved from HST. However, irradiation and thermal cycling with comparable HST SM2 exposure conditions did not produce the degradation observed in the FEP material retrieved during HST SM2. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NASA, Goddard Space Flight Ctr, Mat Engn Branch, Greenbelt, MD 20771 USA. RP Dever, JA (reprint author), NASA, Lewis Res Ctr, 21000 Brookpark Rd,MS 309-2, Cleveland, OH 44135 USA. EM joyce.a.dever@lerc.nasa.gov; kim.k.degroh@lerc.nasa.gov; bruce.a.banks@lerc.nasa.gov; jacqueline.a.townsend.1@gsfc.nasa.gov NR 14 TC 24 Z9 25 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 1999 VL 11 IS 1 BP 123 EP 140 DI 10.1088/0954-0083/11/1/010 PG 18 WC Polymer Science SC Polymer Science GA 183CQ UT WOS:000079536800012 ER PT J AU Fay, CC Stoakley, DM St Clair, AK AF Fay, CC Stoakley, DM St Clair, AK TI Molecularly oriented films for space applications SO HIGH PERFORMANCE POLYMERS LA English DT Article ID MECHANICAL-PROPERTIES; ORIENTATION; CRYSTALLINITY AB Because of their inherent toughness and flexibility, low density, thermal stability, radiation resistance and mechanical strength, aromatic polyimides have excellent potential for use as advanced materials on large space structures. Polyimides were uniaxially and biaxially oriented to further enhance their dimensional stability, stiffness, elongation and strength. Both unoriented and oriented polymeric thin films were also cryogenically treated to temperatures below -184 degrees C to show their stability in cold environments. Successful stretching depended on film quality, film thickness, soak time, grip pressure, stretching rate and stretching temperature. In-plane birefringence increased with increased stretch ratios as expected. Coefficients of thermal expansion (CTEs) decreased with increased stretch ratio by as much as 31%. Tensile strengths increased by up to 85% with increasing stretch ratio. Elongations increased by as much as 95% with stretching. Significant improvements in elongation were obtained with only a 2x uniaxial orientation. Moduli did not change significantly with stretching. Mechanical properties increased more with uniaxial stretching than biaxial stretching. Cryogenic treatment increased the tensile strength of some stretched samples by a maximum of 10-20%. Properties such as modulus and CTE did not change significantly after the films had been slow cooled to cryogenic temperatures. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. RP Fay, CC (reprint author), NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. NR 31 TC 9 Z9 11 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 1999 VL 11 IS 1 BP 145 EP 156 DI 10.1088/0954-0083/11/1/012 PG 12 WC Polymer Science SC Polymer Science GA 183CQ UT WOS:000079536800014 ER PT J AU Bell, JF Wolff, MJ Daley, TC Crisp, D James, PB Lee, SW Trauger, JT Evans, RW AF Bell, JF Wolff, MJ Daley, TC Crisp, D James, PB Lee, SW Trauger, JT Evans, RW TI Near-infrared imaging of Mars from HST: Surface reflectance, photometric properties, and implications for MOLA data SO ICARUS LA English DT Article; Proceedings Paper CT 2nd Mars Telescopic Observations Workshop CY OCT, 1997 CL TUCSON, ARIZONA ID HUBBLE-SPACE-TELESCOPE; THERMAL MAPPER OBSERVATIONS; GLOBAL SURVEYOR; MU-M; BIDIRECTIONAL REFLECTANCE; ATMOSPHERIC DUST; POLAR-REGIONS; MARTIAN DUST; VIKING; CALIBRATION AB We report initial results from Hubble Space Telescope (HST) images of Mars obtained at a near-IR wavelength of 1042 nm between February 1995 and June 1997, The images provide the highest spatial resolution global near-IR measurements of Mars obtained to date. The data have been calibrated to radiance factor (I/F) to an absolute accuracy of 2 to 5% (including new refinements to several HST calibration parameters) and now exist as a set of coregistered, map-projected images spanning a range of phase angles between 10 degrees and 41 degrees, The relatively high spatial resolution (20-30 km/pixel) global maps, when compared with Viking-era global albedo maps, reveal that substantial variations in Mars surface albedo patterns have occurred in the past 20 years. The most obvious changes include several classical dark regions that have become substantially brighter, and a few formerly bright regions that have darkened. The normal albedo of typical surface regions in the near-IR is derived from the multiple phase angle observations and is found to be bimodal with typical bright and dark values of 0.36 and 0.18, respectively. The surface near-LR phase coefficient ranges from 0.0 to 0.013 mag/deg, and there is no systematic correlation between phase coefficient and normal albedo. This observation is consistent with the diffusely scattering nature of the martian atmosphere even during times of low dust opacity. The data presented here may facilitate the planning and optimization of measurements to be obtained by the Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA), which will begin mapping the planet in 1999. These HST data also provide a basis for comparison with future MOLA and Mars Orbiter Camera (MOC) data in searches for seasonal and interannual variations in surface and polar cap albedo. (C) 1999 Academic Press. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Space Sci Inst, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. Univ Colorado, LASP, Boulder, CO USA. RP Bell, JF (reprint author), Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. NR 64 TC 29 Z9 28 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1999 VL 138 IS 1 BP 25 EP 35 DI 10.1006/icar.1998.6057 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190CF UT WOS:000079943400004 ER PT J AU Klassen, DR Bell, JF Howell, RR Johnson, PE Golisch, W Kaminski, CD Griep, D AF Klassen, DR Bell, JF Howell, RR Johnson, PE Golisch, W Kaminski, CD Griep, D TI Infrared spectral imaging of Martian clouds and ices SO ICARUS LA English DT Article; Proceedings Paper CT 2nd Mars Telescopic Observations Workshop CY OCT, 1997 CL TUCSON, ARIZONA ID HUBBLE-SPACE-TELESCOPE; CARBON-DIOXIDE ICE; WATER-VAPOR; OPTICAL-CONSTANTS; CO2 ICE; MU-M; MARS; SPECTROSCOPY; ATMOSPHERE; DUST AB Multispectral images of Mars, taken at the NASA Infrared Telescope Facility (IRTF) near and at the 1995 opposition, are used to identify and track its atmospheric clouds and ground ices. Band depth mapping is used to help distinguish between the composition of volatiles and provide a check for the techniques of principal components analysis (PCA) and linear mixture modeling (LMM), PCA/LMM are used to create maps that track clouds and volatiles, a technique that requires no a priori spectral information in order to create these maps, Band depth maps at 3.33 mu m, which have been shown to trace CO2 frosts, show some transient features which could indicate polar CO2 clouds at the time of these observations. We show that band depth maps at 2.25 mu m are good tracers of H2O frosts and that band depth maps at 3.69 mu m can distinguish between coarse- and fine-grained water frosts, These maps have allowed the detection of fine-grained water frosts in the north polar region and along the morning and evening limb regions. From the PCA technique we find that just two principal components can account for over 99% of the data variance. The first of these is an infrared albedo unit and the second is an ice/thermal unit. Plotting the spectral data cubes in this new vector space, we find that most of the martian disk can be modeled by spectrally mixing three endmember spectra having extreme values of these principal components. The morning and evening regions of Mars are composed of 40-60% of the north polar ice/thermal component endmember, indicating a frost component there consistent with the band depth mapping results. With a combination of these techniques it is possible to not only identify the extensive martian clouds, but to also determine composition. These new results are particularly relevant in light of recent Mars Pathfinder descent temperature profile data that indicated upper atmosphere temperatures below the CO2 frost condensation point, implying that CO2 ice clouds may be an important radiative component of the current martian climate. (C) 1999 Academic Press. C1 Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Univ Wyoming, Dept Phys & Astron, Laramie, WY 82071 USA. Univ Hawaii, Inst Astron, NASA Infrared Telescope Facil, Honolulu, HI 96822 USA. RP Klassen, DR (reprint author), Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. NR 57 TC 11 Z9 11 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1999 VL 138 IS 1 BP 36 EP 48 DI 10.1006/icar.1998.6058 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190CF UT WOS:000079943400005 ER PT J AU James, PB Hollingsworth, JL Wolff, MJ Lee, SW AF James, PB Hollingsworth, JL Wolff, MJ Lee, SW TI North polar dust storms in early spring on Mars SO ICARUS LA English DT Article; Proceedings Paper CT 2nd Mars Telescopic Observations Workshop CY OCT, 1997 CL TUCSON, ARIZONA DE Mars; dust storm; polar cap; Hubble Space Telescope ID GENERAL-CIRCULATION; MARTIAN ATMOSPHERE; ZONES AB Observations of Mars during 1996-1997 by the Hubble Space Telescope covered the entire spring season in the northern hemisphere of Mars, which was favorably positioned for viewing the north polar region. This paper reports observations of dust activity during this period. Local dust activity occurred near the edge of the subliming north polar cap during early spring; this included local dust clouds, similar to those seen by Viking near the edge of the south polar cap, and unusual, are-shaped dust features that seem to represent a new type of dust phenomenon. These dust arcs may explain the Rima Tenuis rift, which has been occasionally seen by ground-based observers of Mars. Analysis of numerical simulations from a Mars general circulation model for the early northern spring season have provided insights into the plausible meteorological background at high latitudes in the vicinity of the retreating north polar cap. These Hubble observations extend the geographic and seasonal ranges during which local dust activity seems to be common on Mars. The combination of image analysis and model calculations support the hypothesis that these dust storms are the result of winds associated with fronts moving across the seasonal cap that lift dust exposed on the cap during CO2 sublimation. (C) 1999 Academic Press. C1 Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. NASA, Ames Res Ctr, SISUF, Moffett Field, CA 94035 USA. Space Sci Inst, Boulder, CO USA. RP James, PB (reprint author), Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. NR 21 TC 30 Z9 30 U1 0 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1999 VL 138 IS 1 BP 64 EP 73 DI 10.1006/icar.1998.6060 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190CF UT WOS:000079943400007 ER PT J AU Enzian, A Klinger, J Schwehm, G Weissman, PR AF Enzian, A Klinger, J Schwehm, G Weissman, PR TI Temperature and gas production distributions on the surface of a spherical model comet nucleus in the orbit of 46P/Wirtanen SO ICARUS LA English DT Article DE comets; comet nuclei; 46P/Wirtanen; modeling; Rosetta ID EVOLUTION; ICE; P/WIRTANEN; FLUX; DIFFERENTIATION; TRANSITION; HALLEY AB A multidimensional comet nucleus model is used to estimate the temperature and gas production distributions on the surface of a comet nucleus in the orbit of of 46P/Wirtanen. The spherical model nucleus is assumed to be made up of a porous dust-ice (H2O, CO) matrix. Heat and gas diffusion inside the rotating nucleus are taken into account in radial and meridional directions. A quasi-3D solution is obtained through the dependency of the boundary conditions on the local solar illumination as the nucleus rotates. As a study case, we consider a homogeneous chemical composition of the surface layer which is assumed to contain water ice. The model results include the distributions of temperature and gas production on the surface. For the chosen test case of a nucleus spin axis perpendicular to the orbital plane we found that the CO gas production on the surface is quasi-uniformly distributed in contrast to the nonuniform water outgassing. The mixing ratio at a specific point on the comet nucleus surface is not representative of the overall mixing ratio which is observed in the coma. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. Lab Glaciol & Geophys Environm, CNRS, F-38402 St Martin Dheres, France. European Space Agcy, European Space Res & Technol Ctr, Dept Space Sci, NL-2200 AG Noordwijk, Netherlands. RP Enzian, A (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, MS 183-601, Pasadena, CA 91109 USA. NR 37 TC 31 Z9 31 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1999 VL 138 IS 1 BP 74 EP 84 DI 10.1006/icar.1998.6050 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190CF UT WOS:000079943400008 ER PT J AU Yanamandra-Fisher, PA Hanner, MS AF Yanamandra-Fisher, PA Hanner, MS TI Optical properties of nonspherical particles of size comparable to the wavelength of light: Application to comet dust SO ICARUS LA English DT Article ID DISCRETE-DIPOLE APPROXIMATION; SILICATE EMISSION FEATURE; AGGREGATE PARTICLES; SCATTERING; GRAINS; P/HALLEY; POLARIMETRY; SPECTRUM; DEPENDENCE; OLIVINE AB Scattering calculations for nonspherical particles have been carried out in order to explain observed optical properties of cometary dust. We focused on two optical properties of cometary dust sensitive to particle shape: negative linear polarization at phase angles less than or equal to 21 degrees and the 11.2-mu m silicate emission feature. The discrete dipole approximation (DDA) method was employed to compute the scattering matrix for nonspherical silicate and absorbing particles of size comparable to the wavelength. Silicate particles with a variety of shapes and size parameter X(eq) similar to 2.5, corresponding to a linear dimension of 0.5-1.0 mu m, can produce negative linear polarization at small phase angles, whereas carbon particles produce a strong positive maximum of polarization near phase angles of 90 degrees. Mixtures of silicate and carbonaceous material, on a scale small compared to the wavelength, eliminate the negative polarization in this size range; however, macroscopic mixtures of silicate and carbon could yield the observed negative linear polarization at low phase angles (less than or equal to 21 degrees) and a maximum positive polarization at phase angle of 90 degrees. The position of the 11.2-mu m thermal emission peak observed in comets, attributed to crystalline olivine, depends strongly on particle shape even for particles much smaller than the wavelength and can be matched with anisotropic Mg-rich olivine for our model tetrahedra or moderately elongated bricks. Spheres and extreme shapes, such as disks or needles, appear to be ruled out. Approximately 20% crystalline olivine and 80% disordered olivine reproduces the observed spectra of comets with comparable peaks at 10 and 11.2 mu m, e.g., P/Halley, Bradfield 1987 XXIX, Mueller, Levy 1990 XX, and C/1995 O1 (Hale-Bopp). This study is an essential first step toward realistic modeling of comet dust as aggregates composed of nonspherical monomers having dimensions comparable to the wavelength of incident radiation. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yanamandra-Fisher, PA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM padma@durga.jpl.nasa.gov; msh@scn1.jpl.nasa.gov NR 41 TC 41 Z9 41 U1 0 U2 1 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1999 VL 138 IS 1 BP 107 EP 128 DI 10.1006/icar.1998.6066 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190CF UT WOS:000079943400010 ER PT J AU Friedson, AJ West, RA Hronek, AK Larsen, NA Dalal, N AF Friedson, AJ West, RA Hronek, AK Larsen, NA Dalal, N TI Transport and mixing in Jupiter's stratosphere inferred from comet S-L9 dust migration SO ICARUS LA English DT Article DE Jupiter; atmospheres; aerosols; dynamics ID CIRCULATION; MODEL; TROPOSPHERE; AEROSOLS; WAVES AB We use a series of 230-nm wavelength images acquired with the Hubble Space Telescope Wide Field and Planetary Camera 2 to trace the spreading of debris introduced into Jupiter's stratosphere by the impact of Comet Shoemaker-Levy 9. Impact debris was transported rapidly equatorward by stratospheric winds from the impact latitude at -45 degrees to at least -20 degrees during the 3.2-year period covered by the observations. We use the observations to test the formulation of mixing and transport in two-dimensional (latitude height) models for the jovian stratosphere. Two different models for the transport are considered. In the first model, advection by the residual circulation of West et al. (1992, Icarus 100, 245-259) is taken to be the sole transport mechanism. We find that this circulation advects the debris slowly poleward, in disagreement with the observations. In the second model, horizontal diffusive transport by large-scale quasi-geostrophic eddies is also included. The horizontal eddy diffusion coefficients (K-yy) are derived from a map of annual-average Eliassen-Palm flux divergence produced by West et al. (1992). Introduction of the derived K-yy into the dynamical model causes a rapid spreading of the debris in both the equatorward and the poleward directions. We find that the predicted rate of equatorward spreading of the impact debris optical depth is in good agreement with that derived from the observations. We conclude that our derived eddy K-yy provides a useful first-order description of zonal mean eddy transport at mid-latitudes in the southern hemisphere of Jupiter's stratosphere. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Friedson, AJ (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, MS 169-237, Pasadena, CA 91109 USA. NR 24 TC 22 Z9 22 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1999 VL 138 IS 1 BP 141 EP 156 DI 10.1006/icar.1998.6063 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190CF UT WOS:000079943400012 ER PT J AU McInroy, JE O'Brien, JF Neat, GW AF McInroy, JE O'Brien, JF Neat, GW TI Precise, fault-tolerant pointing using a Stewart platform SO IEEE-ASME TRANSACTIONS ON MECHATRONICS LA English DT Article DE fault tolerance; pointing; Stewart platform ID SYSTEM AB This paper presents a novel precision pointing strategy. The principal contribution is the development of a fault-tolerant control which allows active pointing to continue despite multiple failures. A six-axes active platform is utilized to reject disturbances from a vibrating base to a precision payload. A decentralized controller is proposed which converts desired rotations into corresponding strut lengths via a decoupling transformation. The decoupling approach allows for simple single-input-single-output compensator design and for the incorporation of fault-tolerant strategies. The proposed strategy was evaluated on the microprecision interferometer testbed (a full-scale model of a future spaceborne optical interferometer) at the Jet Propulsion Laboratory; Pasadena, CA. Experimental pointing results demonstrate 50 dB of disturbance rejection at low frequency. In the laboratory ambient disturbance environment, this corresponds to a 1-mu rad rms pointing error. C1 Univ Wyoming, Dept Elect Engn, Laramie, WY 82071 USA. Rensselaer Polytech Inst, CII CAT, Troy, NY 12180 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Univ Wyoming, Dept Elect Engn, Laramie, WY 82071 USA. NR 9 TC 54 Z9 55 U1 1 U2 10 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1083-4435 EI 1941-014X J9 IEEE-ASME T MECH JI IEEE-ASME Trans. Mechatron. PD MAR PY 1999 VL 4 IS 1 BP 91 EP 95 DI 10.1109/3516.752089 PG 5 WC Automation & Control Systems; Engineering, Manufacturing; Engineering, Electrical & Electronic; Engineering, Mechanical SC Automation & Control Systems; Engineering GA 177CR UT WOS:000079190300013 ER PT J AU Dickinson, RM Losh, DL Barber, RD Dempsey, JK AF Dickinson, RM Losh, DL Barber, RD Dempsey, JK TI A phase-control approach for a large-element coherent microwave power uplink system SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article DE antenna arrays; phased arrays ID RADAR AB Signal combining efficiencies of 98% have been achieved on low-earth orbiting (LEO) debris with phase-locking of time-overlapped radar pulses from a two-element phased-array consisting of two 34-m beam waveguide steerable paraboloid antennas separated by 204 m, The uplink arraying at 7.19 GHz has been achieved for tracks from about 10 degrees elevation at signal rise to 4 degrees elevation at signal set under varying weather conditions (e.g., hail falling on one antenna), The typical root mean square (rms) phase error for two coherent 100-mu s 50-Hz 5-kW peak pulses reflected from LEO debris with signal-to-noise ratio (SNR) > 23 dB is less than 4 degrees, The phase-control system design, methods of calibration, and details of the design control table of phasing error contributors are presented and discussed. Based upon the measured performance, we predict that transmitting antennas for the Deep Space Network (DSN) could be coherently arrayed for up to hours at a time given static phase error calibrations on exo-atmospheric debris, Applications for this technique include low-cost implementation of high-power microwave transmitters for deep-space communication and radars for exploration of other planets and as part of a defense against comets and asteroids. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Dickinson, RM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 3 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD MAR PY 1999 VL 47 IS 3 BP 487 EP 495 DI 10.1109/8.768784 PG 9 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 205FF UT WOS:000080810100011 ER PT J AU Neudeck, PG Huang, W Dudley, M AF Neudeck, PG Huang, W Dudley, M TI Study of bulk and elementary screw dislocation assisted reverse breakdown in low-voltage (< 250 V) 4H-SiC p(+)n junction diodes - Part I: DC properties SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE PN junctions; power semiconductor diodes; semiconductor defects; semiconductor device breakdown; silicon carbide ID 6H-SIC SINGLE-CRYSTALS; 4H SILICON-CARBIDE; AVALANCHE BREAKDOWN; DEFECTS AB Given the high-density (similar to 10(4) cm(-2)) of elementary screw dislocations (Burgers vector = Ic with no hollow core) in commercial SIC wafers and epilayers, all large current (>1 A) SIC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems, This paper compares the de-measured reverse-breakdown characteristics of low-voltage (<250 V) small-area (<5 x 10(-4) cm(2)) 4H-SiC p(+)n diodes with and without elementary screw dislocations. Diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown current-voltage (I-V) knees, and highly localized microplasmic breakdown current filaments compared to screw dislocation-free devices. The observed localized 4H-SiC breakdown parallels microplasmic breakdown observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. SUNY Stony Brook, Dept Mat Sci & Engn, Stony Brook, NY 11794 USA. RP Neudeck, PG (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 30 TC 139 Z9 140 U1 1 U2 16 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD MAR PY 1999 VL 46 IS 3 BP 478 EP 484 DI 10.1109/16.748865 PG 7 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 309TG UT WOS:000086784900008 ER PT J AU Neudeck, PG Fazi, C AF Neudeck, PG Fazi, C TI Study of bulk and elementary screw dislocation assisted reverse breakdown in low-voltage (< 250 V) 4H-SiC p(+)n junction diodes - Part II: Dynamic breakdown properties SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE P-N junctions; power semiconductor diodes; semiconductor defects; semiconductor device breakdown; silicon carbide ID SILICON-CARBIDE; RECTIFIERS AB This paper outlines the dynamic reverse-breakdown characteristics of low-voltage (<250 V) small-area <5 x 10(-4) cm(2)) 4H-SiC p(+)n diodes subjected to nonadiabatic breakdown-bias pulsewidths ranging from 0.1 to 20 mu s. IH-SLC diodes with and without elementary screw dislocations exhibited positive temperature coefficient of breakdown voltage and high junction failure power densities approximately five times larger than the average failure power density of reliable silicon pn rectifiers, This result indicates that highly reliable low-voltage SiC rectifiers may be attainable despite the presence of elementary screw dislocations. However, the impact of elementary screw dislocations on other more useful 4H-SiC power device structures, such as high-voltage (>1 kV) pn junction and Schottky rectifiers, and bipolar gain devices (thyristors, IGBT's, etc.) remains to be investigated. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. USA, Res Lab, Adelphi, MD 20783 USA. RP Neudeck, PG (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 25 TC 26 Z9 26 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD MAR PY 1999 VL 46 IS 3 BP 485 EP 492 DI 10.1109/16.748866 PG 8 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 309TG UT WOS:000086784900009 ER PT J AU Moghaddam, M Saatchi, SS AF Moghaddam, M Saatchi, SS TI Monitoring tree moisture using an estimation algorithm applied to SAR data from BOREAS SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID ARTIFICIAL NEURAL-NETWORK; DIELECTRIC-CONSTANT; RADAR BACKSCATTER; FOREST BIOMASS; MODEL; VEGETATION; INVERSION; BEHAVIOR; AREAS; WATER AB During several field campaigns in spring and summer of 1994, the NASA/JPL airborne synthetic aperture radar (AIRSAR) collected data over the southern and northern study sites of BOREAS. Among the areas over which radar data were collected was the young jack pine (YJP) tower site in the south, which is generally characterized as having short (2-4 m) but closely spaced trees with a dense crown layer. In this work, the AIRSAR data over this YJP stand from six different dates were used, and the dielectric constant and hence the moisture content of its branch layer components were estimated. The approach was to first derive a parametric scattering model from a numerical discrete-component forest model, which is possible if the predominant scattering mechanism can be identified. Here, a classification algorithm was used for this purpose, concentrating on areas where the volume scattering mechanism from the branch layer dominates. The unknown parameters were taken to be the real and imaginary parts of the dielectric constant, from which the moisture content can he derived, Once the parametric model was derived, a nonlinear estimation algorithm was employed to retrieve the model parameters from SAR data. This algorithm is iterative, and takes the statistical properties of the data and unknown parameters into account, The inversion process was first verified using synthetic data. It was observed that the algorithm is robust with respect to the a priori estimate, The estimation algorithm was then applied to AIRSAR data of BOREAS. The results show how the environmental conditions affected the moisture state of this forest stand over a period of six months, It is observed that canopy moisture increased during the thaw season (early April through late April), was stable starting from the end of the thaw season throughout most of the growing season (late April through late July), after which a period of dry-down was observed at the end of the growing season (September). The results were compared in detail to the available ground-truth for canopy moisture content, which were measured during the months of June through August. It was found that the estimated values had an absolute error level of 15% (g/g) gravimmetric moisture content compared to the ground measurements. Several sources of error were identified and discussed. C1 CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Moghaddam, M (reprint author), CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. EM mahta.moghaddam@jpl.nasa.gov NR 40 TC 38 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 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1999 VL 37 IS 2 BP 901 EP 916 DI 10.1109/36.752209 PN 2 PG 16 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 177VL UT WOS:000079231700003 ER PT J AU Yueh, SH Wilson, WJ Dinardo, SJ Li, FK AF Yueh, SH Wilson, WJ Dinardo, SJ Li, FK TI Polarimetric microwave brightness signatures of ocean wind directions SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE marine technology; microwave radiometry; polarimetry; remote sensing ID AIRCRAFT K-BAND; SURFACE; TEMPERATURES; RADIOMETERS; WAVES AB The sensitivities of wind direction signals in passive microwave brightness temperatures of sea surfaces to wind speed, incidence angle, polarization, and frequency are presented in this paper, The experimental data were acquired from a series of aircraft Rights from 1994 through 1996 by the Jet Propulsion Laboratory (JPL) using JPL 19 and 37 GHz polarimetric radiometers (WINDRAD). Fourier analysis of the data versus wind direction was carried out and the coefficients of Fourier series are illustrated against the wind speed at 45 degrees, 55 degrees, and 65 degrees incidence angles, There is a good agreement between the JPL aircraft Eight data and Wentz's Special Sensor Microwave/Imager (SSM/I) geophysical model function for the vertically polarized brightness temperatures, but Wentz`s SSR III wind direction model for horizontal polarization shows a significantly stronger upwind and downwind asymmetry than the aircraft Eight data. Comparison of the dual-frequency WINDRAD data shows that the wind direction signals are similar at 19 and 37 GHz, although the 37 GHz data have slightly stronger signals than the 19 GHz data. In general, the azimuthal variations of brightness temperatures increase with increasing wind speed from low to moderate winds, then level off and decrease at high winds. The only exception is the U measurements at 65 degrees incidence angle, which have a stronger than expected signal at low winds. An exponential function was proposed to model the sensitivities of wind direction signals to wind speeds, The coefficients of the empirical model are provided in this paper and are useful for the simulation of ocean brightness temperatures and for the development of geophysical retrieval algorithms. C1 CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Yueh, SH (reprint author), CALTECH, Jet Propuls Lab, Pasadena, CA 91109 USA. NR 20 TC 74 Z9 83 U1 1 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1999 VL 37 IS 2 BP 949 EP 959 DI 10.1109/36.752213 PN 2 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 177VL UT WOS:000079231700007 ER PT J AU Sandmeier, SR Itten, KI AF Sandmeier, SR Itten, KI TI A field goniometer system (FIGOS) for acquisition of hyperspectral BRDF data SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE BRDF; goniometer; hyperspectral ID REFLECTANCE; CANOPIES AB A new field goniometer system (FIGOS) is introduced that allows in situ measurements of hyperspectral bidirectional reflectance data under natural illumination conditions, Hyperspectral bidirectional reflectance distribution function (BRDF) data sets taken with FIGOS nominally cover the spectral range between 300 and 2450 nm in 704 bands, Typical targets are small-growing , dense, and homogeneous vegetation canopies, man-made surfaces, and soils, Field BRDF data of a perennial ryegrass surface reveal a strong spectral variability, In the blue and red chlorophyll absorption hands, BRDF effects are strong, Less-pronounced bidirectional reflectance effects are observed in the green and in most of the near-infrared range where surface reflectance is high, An anisotropy index (ANIX), defined as the ratio between the maximum and minimum bidirectional reflectance ol er the hemisphere, is introduced as a surrogate measurement for the extent of spectral BRDF effects, The ANIX: data of the ryegrass surface show a very high correlation with nadir reflectance due to multiple scattering effects. Since canopy geometry, multiple scattering, and BRDF effects are related, these findings may help to derive canopy architecture parameters, such as leaf area index (LAI) or leaf angle distribution (LAD) from remotely sensed hyperspectral BRDF data. Furthermore, they show that normalized difference vegetation index (NDVI) data are strongly biased by the spectral variability of BRDF effects. C1 Univ Zurich, Dept Geog, Remote Sensing Labs, CH-8057 Zurich, Switzerland. RP Sandmeier, SR (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. EM sandi@geo.unizh.ch NR 28 TC 92 Z9 96 U1 1 U2 14 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1999 VL 37 IS 2 BP 978 EP 986 DI 10.1109/36.752216 PN 2 PG 9 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 177VL UT WOS:000079231700010 ER PT J AU Liao, L Meneghini, R Iguchi, T AF Liao, L Meneghini, R Iguchi, T TI Simulations of mirror image returns of air/space-borne radars in rain and their applications in estimating path attenuation SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE air/space-borne radars; attenuation; rain; scattering; TRMM ID AIRBORNE AB The mirror, image (MI) rain echo, received through the double reflection of the radar pulse from the surface, may provide useful information in estimating the rainfall rate from airborne and spaceborne weather radars. However, because of the complicated scattering mechanisms involving the surface and rain and the relatively small amount of measured data, studies of the MI effect have been few. In this paper, a more rigorous model of the MI return power has been constructed that yields the co- and cross-polarized components of the hll and bistatic returns as a functions of the radar parameters (antenna beamwidth and radar altitude) and the scattering properties of the rain and surface. As a test of the model, the mirror image return, as estimated from theory, is compared with the measured hll range profile, and reasonably good agreement is obtained. For meteorological applications, algorithms for estimation of the rain path attenuation are developed based on the difference of the direct and MI returns at the same distance from the surface. The accuracies of the algorithms are analyzed and compared with those of the surface reference technique (SRT) through the simulations for airborne and spaceborne [the case of the Tropical Rain Measuring Mission (TRMM)] geometries. C1 NASA, Goddard Space Flight Ctr, Caelum Res Corp, Greenbelt, MD 20771 USA. Commun Res Lab, Kashima, Japan. RP Liao, L (reprint author), NASA, Goddard Space Flight Ctr, Caelum Res Corp, Code 975, Greenbelt, MD 20771 USA. RI PMM, JAXA/K-8537-2016 NR 17 TC 14 Z9 14 U1 2 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1999 VL 37 IS 2 BP 1107 EP 1121 DI 10.1109/36.752229 PN 2 PG 15 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 177VL UT WOS:000079231700023 ER PT J AU Foster, JL Hall, DK Chang, ATC Rango, A Wergin, W Erbe, E AF Foster, JL Hall, DK Chang, ATC Rango, A Wergin, W Erbe, E TI Effects of snow crystal shape on the scattering of passive microwave radiation SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE crystals; electron microscope; modeling; scattering; shape; snow ID DISCRETE-DIPOLE APPROXIMATION AB In this study, a discrete dipole scattering model is used to measure the passive microwave radiation scattered by snow particles having different shapes and sizes. The model results demonstrate that the shape of the snow crystal is Insignificant in scattering microwave energy in the 37-GHz region of the spectrum. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrol Sci, Greenbelt, MD 20771 USA. USDA, Hydrol Lab, Agr Res Serv, Beltsville, MD 20705 USA. RP Foster, JL (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrol Sci, Greenbelt, MD 20771 USA. RI Hall, Dorothy/D-5562-2012 NR 13 TC 31 Z9 32 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1999 VL 37 IS 2 BP 1165 EP 1168 DI 10.1109/36.752235 PN 2 PG 4 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 177VL UT WOS:000079231700029 ER PT J AU Young, RB Bridge, KY Vaughn, JR AF Young, RB Bridge, KY Vaughn, JR TI Variability in beta-adrenergic receptor population in cultured chicken muscle cells SO IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL LA English DT Letter ID PROTEIN-METABOLISM; CIMATEROL; MYOTUBES; AGONISTS; GROWTH C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Young, RB (reprint author), NASA, George C Marshall Space Flight Ctr, ES76,Bldg 4481, Huntsville, AL 35812 USA. NR 13 TC 0 Z9 0 U1 1 U2 1 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1071-2690 EI 1543-706X J9 IN VITRO CELL DEV-AN JI In Vitro Cell. Dev. Biol.-Anim. PD MAR PY 1999 VL 35 IS 3 BP 115 EP 117 DI 10.1007/s11626-999-0011-y PG 3 WC Cell Biology; Developmental Biology SC Cell Biology; Developmental Biology GA 175WE UT WOS:000079118000001 PM 10476905 ER PT J AU Garg, VK AF Garg, VK TI Heat transfer on a film-cooled rotating blade using different turbulence models SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID TURBINE-BLADES; PREDICTION; TEMPERATURE; FLOW AB A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on a film-cooled, rotating turbine blade. The blade chosen is the ACE rotor with five rows containing 93 film cooling holes covering the entire span. This is the only film-cooled rotating blade over which experimental data is available for comparison. Over 2.278 million grid points are used to compute the flow over the blade including the tip clearance region, using Wilcox's k-omega model, Coakley's q-omega model, and the zero-equation Baldwin-Lomax (B-L) model. A reasonably good comparison with the experimental data is obtained on the suction surface for all the turbulence models. At the leading edge, the B-L model yields a better comparison than the two-equation models. On the pressure surface, however, the comparison between the experimental data and the prediction from the k-omega model is much better than from the other two models. Overall, the k-omega model provides the best comparison with the experimental data. However, the two-equation models require at least 40% more computational resources than the B-L model. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 AYT Corp, NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Garg, VK (reprint author), AYT Corp, NASA, Lewis Res Ctr, 21000 Brookpk Rd,Mail Stop 5-11, Cleveland, OH 44135 USA. NR 32 TC 25 Z9 37 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD MAR PY 1999 VL 42 IS 5 BP 789 EP 802 DI 10.1016/S0017-9310(98)00229-4 PG 14 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 152XK UT WOS:000077802300002 ER PT J AU Harstad, K Bellan, J AF Harstad, K Bellan, J TI The Lewis number under supercritical conditions SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID PREMIXED FLAMES; CURVATURE AB An effective Lewis number is calculated for situations where temperature and mass fraction gradients are very large by defining effective thermal and mass diffusivities; such situations may occur in systems where there is more than one chemical component, and in particular under supercritical conditions, The definitions evolve from a model assuming that derivatives of certain functions are small with respect to those of the dependent variables, In the model, Soret and Dufour effects are included and Shvab-Zeldovich-like variables are defined to remove the coupling between the operators of the differential equations for temperature and mass fractions. Results from calculations using binary systems of chemical components, using both isolated fluid drops and interacting fluid drops, show that under supercritical conditions, depending upon the compounds, the effective Lewis number can be 2-40 times larger than the traditionally calculated Lewis number and that the spatial variation of the two numbers is different. For the values of the thermal diffusion factor used in the calculations, the Soret and Dufour effects are negligible; the discrepancy between the traditional and effective Lewis numbers is due to the combined effect of the small mass diffusion factor and the difference between the specific enthalpies of the two compounds, Parametric variations show that the effective Lewis number increases with increasing pressure and decreasing surrounding gas temperature. Closer drop proximity in clusters results in sharper peaks in the effective Lewis number due to the increased gradients of the dependent variables. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bellan, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 18 TC 26 Z9 26 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD MAR PY 1999 VL 42 IS 6 BP 961 EP 970 DI 10.1016/S0017-9310(98)00230-0 PG 10 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 161KG UT WOS:000078287400001 ER PT J AU Volz, MP Mazuruk, K AF Volz, MP Mazuruk, K TI Thermoconvective instability in a rotating magnetic field SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID CRYSTAL-GROWTH; FLOW; LAYER; MELT AB The effect of a rotating magnetic field (RMF) on the stability of a fluid contained in a cylindrical column and heated from below is investigated. The RMF increases the critical Rayleigh number for asymmetric flow modes but does not affect the onset of instability for axisymmetric modes. The critical Rayleigh number is dependent upon the relative penetration of the magnetic field into the cylinder and the Prandtl number of the fluid. Instability first develops in the form of a single asymmetric meridional roll rotating around the axis of the cylinder, driven by the azimuthal component of the magnetic field. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Volz, MP (reprint author), NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 19 TC 21 Z9 21 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD MAR PY 1999 VL 42 IS 6 BP 1037 EP 1045 DI 10.1016/S0017-9310(98)00168-9 PG 9 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 161KG UT WOS:000078287400006 ER PT J AU Hamilton, JB Pike, C Reinhart, RC Savoie, JM AF Hamilton, JB Pike, C Reinhart, RC Savoie, JM TI A hybrid satellite/terrestrial network linking Europe and North America SO INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS LA English DT Article AB This short paper will document a demonstration given at the Third Ka-band Conference, Sorrento, Italy, September 1997. The principal objective was to illustrate interoperability over a complex hybrid satellite and terrestrial Asynchronous Transport Mode (ATM) network. The network linked Ka-band satellites in Europe and in North America, via the European JAMES Research and Development(R + D) Network, and the CANTAT-3 trans-Atlantic submarine fibre. The ISABEL application facilitated Computer Supported Collaborative Workspace (CSCW) among locations in Canada, Italy and the U.S.A. The demonstration consisted of the presentation of one full conference session from Italy to observers in Canada and the U.S.A., with the opportunity for the remote, as well as the local audiences, to interact with presenters during the 'Question and Answer' periods. There were also short presentations from the Communications Research Centre (Canada), and NASA Lewis Research Centre (U.S.A.). The ISABEL application required two virtual networks, one to handle unicast signals for control and monitoring, etc., the other to distribute multicast traffic. They shared a common star topology over point to point symmetrical Virtual Paths (VPs) through the interconnected ATM networks. The three participating locations were connected to a Network Node at the Communications Research Centre (CRC), Ottawa, Canada over full duplex El (2.048 Mbps) circuits. The application traffic from each ISABEL workstation was directed to the Network Node, where it was combined. The Control Workstation, at the Conference Centre, Sorrento, Italy, allocated window sizes in the combined image, selected local inputs, and switched presentation material as required. The combined image was multicast from the Network Node to the three networked locations. The overall network included the Italsat-2 satellite and the U.S. Advanced Communications Technology Satellite (ACTS), the Canadian and Italian national test networks, the European R + D network, and the CANTAT-3 submarine fibre. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 Commun Res Ctr, Ottawa, ON K2H 8S2, Canada. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hamilton, JB (reprint author), Commun Res Ctr, Ottawa, ON K2H 8S2, Canada. NR 0 TC 1 Z9 1 U1 1 U2 2 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0737-2884 J9 INT J SATELL COMMUN JI Int. J. Satell. Commun. PD MAR-JUN PY 1999 VL 17 IS 2-3 BP 155 EP 160 DI 10.1002/(SICI)1099-1247(199903/06)17:2/3<155::AID-SAT631>3.0.CO;2-C PG 6 WC Engineering, Aerospace; Telecommunications SC Engineering; Telecommunications GA 242EQ UT WOS:000082925600008 ER PT J AU Morelli, EA AF Morelli, EA TI Flight test of optimal inputs and comparison with conventional inputs SO JOURNAL OF AIRCRAFT LA English DT Article AB A technique for designing optimal inputs for aerodynamic parameter estimation was flight tested on the F-18 High Alpha Research Vehicle. Model parameter accuracies calculated from flight-test data were compared on an equal basis for optimal input designs and conventional inputs at the same flight condition, In spite of errors in the a priori input design models and distortions of the input forms by the feedback control system, analysis of data generated by the optimal inputs revealed ion er estimated parameter errors compared with conventional 3-2-1-1 and doublet inputs. In addition, the tests using optimal input designs demonstrated enhanced design flexibility, allowing the optimal input design technique to use a larger input amplitude to achieve further increases in estimated parameter accuracy without departing from the desired flight-test condition. This work validated the analysis used to develop the optimal input designs, and demonstrated the feasibility and effectiveness of the optimal input design technique. C1 NASA, Langley Res Ctr, Dynam & Control Branch, Flight Dynam & Control Div, Hampton, VA 23681 USA. RP Morelli, EA (reprint author), NASA, Langley Res Ctr, Dynam & Control Branch, Flight Dynam & Control Div, M-S 132, Hampton, VA 23681 USA. NR 23 TC 6 Z9 7 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 1999 VL 36 IS 2 BP 389 EP 397 DI 10.2514/2.2469 PG 9 WC Engineering, Aerospace SC Engineering GA 184LT UT WOS:000079614200009 ER PT J AU Langan, KJ Samuels, JJ AF Langan, KJ Samuels, JJ TI Wing jet blowing on the subsonic high alpha research concept fighter configuration SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 35th Aerospace Science Meeting / Nonlinear Dynamical Systems Symposium CY JAN 06-10, 1997 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut, USAF, Off Sci Res, Sandia Natl Labs AB A large-scale experimental investigation using the 55%-scale Subsonic High Alpha Research Concept (SHARC) was performed in the NASA Ames Research Center 40- by 80-ft Wind Tunnel. The SHARC configuration represents an advanced low-observable fighter aircraft, and features a clipped diamond wing with leading- and trailing-edge sweep angles of +/-40 deg, a chined forebody, leading-edge extensions, and a vee-tail. Data covering the angle of attack range from -4 deg to +42.4 deg, and sideslip angles ranging from -10 deg to +10 deg were acquired at a dynamic pressure of 40 psf. Test data are presented for symmetric and asymmetric wing jet nozzle blowing. Blowing coefficient values ranged from a minimum of 0.005 to a maximum of 0.020. The results indicate that wing jet nozzle blowing is an effective lift-enhancement device, giving an across-the-board net increase in lift over the entire angle-of-attack range tested. The jets were also found to improve the aircraft's drag polar. Roll control using asymmetric jet blowing equaled or exceeded that available via the deflection of only a single aileron. C1 USAF, Res Lab, Wright Patterson AFB, OH 45433 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Langan, KJ (reprint author), USAF, Res Lab, Wright Patterson AFB, OH 45433 USA. NR 12 TC 0 Z9 0 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 1999 VL 36 IS 2 BP 413 EP 420 DI 10.2514/2.2446 PG 8 WC Engineering, Aerospace SC Engineering GA 184LT UT WOS:000079614200012 ER PT J AU Smart, MK AF Smart, MK TI Optimization of two-dimensional scramjet inlets SO JOURNAL OF AIRCRAFT LA English DT Article AB The classical optimization of two-dimensional supersonic inlets for maximum total pressure recovery is extended to two-dimensional scramjet inlets. The result that optimal supersonic inlets have shock waves of equal strength is often applied to scramjets, However the typical flow turning constraint required for scramjets, along with the lack of a terminating normal shock, lead to a more involved optimization problem. Despite this, optimization by the method of Lagrange multipliers indicates that scramjet inlets with maximum total pressure recovery have external shocks with almost equal strength. The optimal total pressure recovery and turning angles for some typical scramjet inlet configurations with up to five shocks are presented. C1 NASA, Langley Res Ctr, Hyperson Airbreathing Prop Branch, Hampton, VA 23665 USA. RP Smart, MK (reprint author), NASA, Langley Res Ctr, Hyperson Airbreathing Prop Branch, MS 168,Bldg 1221,Room 110, Hampton, VA 23665 USA. RI Smart, Michael/C-8823-2013 NR 4 TC 5 Z9 14 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 1999 VL 36 IS 2 BP 430 EP 433 DI 10.2514/2.2448 PG 4 WC Engineering, Aerospace SC Engineering GA 184LT UT WOS:000079614200014 ER PT J AU Tokay, A Short, DA Williams, CR Ecklund, WL Gage, KS AF Tokay, A Short, DA Williams, CR Ecklund, WL Gage, KS TI Tropical rainfall associated with convective and stratiform clouds: Intercomparison of disdrometer and profiler measurements SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID RAINDROP SIZE DISTRIBUTIONS; WIND PROFILERS; SYSTEMS; CLASSIFICATION; PRECIPITATION; SATELLITE; RETRIEVAL; CLUSTERS; MONSOON; RADAR AB The motivation for this research is to move in the direction of improved algorithms for the remote sensing of rainfall, which are crucial for meso- and large-scale circulation studies and climate applications through better determinations of precipitation type and latent heating profiles. Toward this end a comparison between two independent techniques, designed to classify precipitation type from 1) a disdrometer and 2) a 915-MHz wind profiler. is presented, based on simultaneous measurements collected at the same site during the Intensive Observing Period of the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. Disdrometer-derived quantities such as differences in drop size distribution parameters, particularly the intercept parameter N-0 and rainfall rate, were used to classify rainfall as stratiform or convective. At the same lime. profiler-derived quantities, namely, Doppler velocity, equivalent reflectivity, and spectral width, from Doppler spectra were used to classify precipitation type in four categories: shallow convective, deep convective, mixed convective-stratiform. and stratiform, Overall agreement between the two algorithms is Found to be reasonable, Given the disdrometer stratiform classification, the mean profile of reflectivity shows a distinct bright band and associated large vertical gradient in Doppler velocity, both indicators of stratiform rain. I;or the disdrometer convective classification the mean profile of reflectivity lacks a bright band, while the vertical gradient in Doppler velocity below the melting level is opposite to the stratiform case. Given the profiler classifications, in the order shallow-deep-mixed-stratiform, the composite raindrop spectra for a rainfall rate of 5 mm h(-1) show an increase in D-o, the median volume diameter, consistent with the dominant microphysical processes responsible for drop formation. Nevertheless, the intercomparison does reveal some limitations in the classification methodology utilizing the disdrometer or profiler algorithms in isolation. In particular, 1) the disdrometer stratiform classification includes individual cases in which the vertical profiles appear convective, but these usually occur at times when the disdrometer classification is highly variable; 2) the profiler classification scheme also appears to classify precipitation too frequently as stratiform by including cases that have small vertical Doppler velocity gradients at the melting level but no bright band; and 3) the profiler classification scheme includes a category of mixed (stratiform-convective) precipitation that has some features in common with deep convection (e.g., enhanced spectral width above the melting level) but other features in common with stratiform precipitation (e.g., well-developed melting layer signature). Comparison of the profiler-derived vertical structure with disdrometer-determined rain rater reveals that almost all cases of rain rates greater than 10 mm h(-1) are convective. For rain rates less than 5 mm h(-1) all four profiler-determined precipitation classes are well represented. C1 NASA, Goddard Space Flight Ctr, Trop Rainfall Measuring Mission Off, Greenbelt, MD 20771 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Tokay, A (reprint author), NASA, Goddard Space Flight Ctr, Trop Rainfall Measuring Mission Off, Code 910-1, Greenbelt, MD 20771 USA. RI Williams, Christopher/A-2723-2015 OI Williams, Christopher/0000-0001-9394-8850 NR 30 TC 73 Z9 73 U1 1 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD MAR PY 1999 VL 38 IS 3 BP 302 EP 320 DI 10.1175/1520-0450(1999)038<0302:TRAWCA>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 179GX UT WOS:000079319100006 ER PT J AU Amitai, E AF Amitai, E TI Relationships between radar properties at high elevations and surface rain rate: Potential use for spaceborne rainfall measurements SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID Z-R RELATIONS; CONVECTIVE CELLS; VERTICAL PROFILE; REFLECTIVITY; CLASSIFICATION; PROBABILITY; SYSTEMS; TRMM AB Ground-based radar data have been used to investigate the relationship between reflectivity at high elevations and surface rain rates. Such relations are useful for rainfall measurements by spaceborne radars at attenuating wavelength such as the 2.2-cm Precipitation Radar (PR) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. In addition to attenuation, these relations are complicated by partial beamfilling, hail, and windshear sorting of particles, among others that affect the corresponding ground-based radar reflectivity-surface rain-rate relationships. TRMM-PR observations were simulated based on radar data from Darwin, Australia. The three-dimensional simulated data were classified by rain type according to several radar properties at high altitudes that are not seriously affected by attenuation. These properties are physical parameters relevant to the variations in the desired relationships. The resulting relationships are robust and permit the classification of near-surface rain and the estimation of its intensity. These findings demonstrate the feasibility of such a classification scheme to spaceborne estimates of rainfall by radar such as that on TRMM. A rain retrieval algorithm, which combines space- and ground-based radar data, is proposed. The basic statistical methodology in the algorithm is an adaptation of the Classified Window Probability Matching Method, developed for ground-based radars. In the proposed method, probabilities of the PR-observed reflectivities, taken from nonattenuated regions, are matched to probabilities of ground-based, radar-estimated rain intensities that have been classified into the same precipitation type. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Amitai, E (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Mail Code 910-1, Greenbelt, MD 20771 USA. NR 33 TC 10 Z9 10 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD MAR PY 1999 VL 38 IS 3 BP 321 EP 333 DI 10.1175/1520-0450(1999)038<0321:RBRPAH>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 179GX UT WOS:000079319100007 ER PT J AU Smith, WL Feltz, WE Knuteson, RO Revercomb, HE Woolf, HM Howell, HB AF Smith, WL Feltz, WE Knuteson, RO Revercomb, HE Woolf, HM Howell, HB TI The retrieval of planetary boundary layer structure using ground-based infrared spectral radiance measurements SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID RAMAN LIDAR; WATER-VAPOR AB The surface-based Atmospheric Emitted Radiance Interferometer (AERI) is an important measurement component of the Department of Energy Atmospheric Radiation Measurement Program. The method used to retrieve temperature and moisture profiles of the plantetary boundary layer from the AERI's downwelling spectral radiance observations is described. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Wisconsin, Cooperat Inst Meteorol Satellite Studies, Madison, WI 53706 USA. Univ Wisconsin, NOAA, Natl Environm Satellite & Data Informat Serv, Madison, WI 53706 USA. RP Smith, WL (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS-401, Hampton, VA 23681 USA. EM bill.l.smith@larc.nasa.gov NR 22 TC 67 Z9 71 U1 1 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD MAR PY 1999 VL 16 IS 3 BP 323 EP 333 DI 10.1175/1520-0426(1999)016<0323:TROPBL>2.0.CO;2 PG 11 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 176GG UT WOS:000079142600002 ER PT J AU Yao, MS Del Genio, AD AF Yao, MS Del Genio, AD TI Effects of cloud parameterization on the simulation of climate changes in the GISS GCM SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; WATER-CONTENT; TEMPERATURE; FEEDBACKS; LIQUID; SCHEME; COVER AB Climate changes obtained from five doubled CO2 experiments with different parameterizations of large-scale clouds and moist convection are studied by use of the Goddard Institute for Space Studies (GISS) GCM at 4 degrees lat x 5 degrees long resolution, The baseline for the experiments is GISS Model II, which uses a diagnostic cloud scheme with fixed optical properties and a convection scheme with fixed cumulus mass fluxes and no downdrafts. The global and annual mean surface air temperature change (Delta T-s) of 4.2 degrees C obtained by Hansen et al. using the Model II physics at 8 degrees lat x 10 degrees long resolution is reduced to 3.55 degrees C at the finer resolution. This is due to a significant reduction of tropical cirrus clouds in the warmer climate when a finer resolution is used, despite the fact that the relative humidity increases there with a doubling of CO2. When the new moist convection parameterization of Del Genio and Yao and prognostic large-scale cloud parameterization of Del Genio et al. are used, Delta T-s is reduced to 3.09 degrees C from 3.55 degrees C. This is the net result of the inclusion of the feedback of cloud optical thickness and phase change of cloud water, and the presence of areally extensive cumulus anvil clouds. Without the optical thickness feedback, Delta T-s is further reduced to 2.74"C, suggesting that this feedback is positive overall. Without anvil clouds, Delta T-s is increased from 3.09 degrees to 3.7 degrees C, suggesting that anvil clouds of large optical thickness reduce the climate sensitivity. The net effect of using the new large-scale cloud parameterization without including the detrainment of convective cloud water is a slight increase of Delta T-s from 3.56 degrees to 3.7 degrees C. The net effect of using the new moist convection parameterization without anvil clouds is insignificant (from 3.55 degrees to 3.56 degrees C). However, this is a result of a combination of many competing differences in other climate parameters. Despite the global cloud cover decrease simulated in most of the experiments, middle- and high-latitude continental cloudiness generally increases with warming, consistent with the sense of observed twentieth-century cloudiness trends; an indirect aerosol effect may therefore not be the sole explanation of these observations. An analysis of climate sensitivity and changes in cloud radiative forcing (CRF) indicates that the cloud feedback is positive overall in all experiments except the one using the new moist convection and large-scale cloud parameterization with prescribed cloud optical thickness, for which the cloud feedback is nearly neutral. Differences in Delta CRF among the different experiments cannot reliably be anticipated by the analogous differences in current climate CRE The meridional distribution of Delta CRF suggests that the cloud feedback is positive mostly in the low and midlatitudes, but in the high latitudes, the cloud feedback; is mostly negative and the amplification of Delta T-s is due to other processes, such as snow/ice-albedo feedback and changes in the lapse rate. The authors' results suggest that when a sufficiently large variety of cloud feedback mechanisms are allowed for, significant cancellations between positive and negative feedbacks result, causing overall climate sensitivity to be less sensitive to uncertainties in poorly understood cloud physics. In particular, the positive low cloud optical thickness correlations with temperature observed in satellite data argue for a minimum climate sensitivity higher than the 1.5 degrees C that is usually assumed. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, Sci Syst & Applicat Inc,GISS, New York, NY 10025 USA. RP Del Genio, AD (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, Sci Syst & Applicat Inc,GISS, 2880 Broadway, New York, NY 10025 USA. RI Del Genio, Anthony/D-4663-2012 OI Del Genio, Anthony/0000-0001-7450-1359 NR 36 TC 47 Z9 49 U1 1 U2 5 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 MAR PY 1999 VL 12 IS 3 BP 761 EP 779 DI 10.1175/1520-0442(1999)012<0761:EOCPOT>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 176ZE UT WOS:000079181700006 ER PT J AU Balsara, DS Spicer, DS AF Balsara, DS Spicer, DS TI A staggered mesh algorithm using high order Godunov fluxes to ensure solenoidal magnetic fields in magnetohydrodynamic simulations SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID MULTIDIMENSIONAL IDEAL MAGNETOHYDRODYNAMICS; NAVIER-STOKES EQUATIONS; SCHEMES; EULER; TESTS AB The equations of magnetohydrodynamics (MHD) have been formulated as a hyperbolic system of conservation laws. In that form it becomes possible to use higher order Godunov schemes for their solution. This results in a robust and accurate solution strategy. However, the magnetic field also satisfies a constraint that requires its divergence to be zero at all times, This is a property that cannot be guaranteed in the zone centered discretizations that are favored in Godunov schemes without involving a divergence cleaning step, In this paper we present a staggered mesh strategy which directly uses the properly upwinded fluxes that are provided by a Godunov scheme. The process of directly using the upwinded fluxes relies on a duality that exists between the fluxes obtained from a higher order Godunov scheme and the electric fields in a plasma, By exploiting this duality we have been able to construct a higher order Godunov scheme that ensures that the magnetic field remains divergence-free up to the computer's round-off error. We have even presented a variant of the basic algorithm that uses multidimensional features in the how to design an upwinded strategy that aligns itself with the predominant upwinded direction in the flow. We have devised several stringent test problems to show that the scheme works robustly and accurately in all situations, In doing so we have shown that a scheme that involves a collocation of magnetic field variables that is different from the one traditionally favored in the design of higher order Godunov schemes can nevertheless offer the same robust and accurate performance of higher order Godunov schemes provided the properly upwinded fluxes from the Godunov methodology are used in the scheme's construction. (C) 1999 Academic Press. C1 Univ Illinois, NCSA, Urbana, IL 61801 USA. NASA, Goddard Space Flight Ctr, NCCS, Greenbelt, MD 20771 USA. RP Balsara, DS (reprint author), Univ Illinois, NCSA, Urbana, IL 61801 USA. EM dbalsara@ncsa.uiuc.edu; spicer@gauss.gsfc.nasa.gov NR 32 TC 307 Z9 313 U1 4 U2 11 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD MAR 1 PY 1999 VL 149 IS 2 BP 270 EP 292 DI 10.1006/jcph.1998.6153 PG 23 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 171MT UT WOS:000078868300004 ER PT J AU Price, MW Scripa, RN Lehoczky, SL Szofran, FR Su, CH AF Price, MW Scripa, RN Lehoczky, SL Szofran, FR Su, CH TI Directional solidification and characterization of Hg0.89Mn0.11Te SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 12th International Conference on Crystal Growth, held in Conjunction with the 10th International Conference on Vapor Growth and Epitaxy (ICCG-12/ICVGE-10) CY JUL 26-31, 1998 CL JERUSALEM, ISRAEL ID SEGREGATION; HGCDTE AB Two boules of Hg0.89Mn0.11Te (MMT) were solidified by the vertical Bridgman-Stockbarger method using translation rates of 0.09 and 0.18 mu m/s. The influence of growth rate on axial compositional homogeneity in the MMT boules was evaluated experimentally through precision density measurements on radial slices from each boule. In addition, plane front solidification theory and segregation coefficient (k) data for the Hg1-xMnxTe system were used to fit theoretical composition profiles to the measured MMT axial composition profiles. The strong correlation between the measured and calculated MMT axial composition profiles indicated diffusion dominated axial solute redistribution in the boules under the applied growth conditions. The analysis of the MMT axial composition profiles allowed the calculation of the effective diffusion coefficient (D-eff = 3.75 x 10(-5) cm(2)/s) for MnTe in molten MMT. The kappa-values for the Hg1-xMnxTe system and the D-eff were used to show that both boules were solidified under conditions which did not exceed the constitutional supercooling criteria under ideal conditions. Finally, an initial comparison of the radial compositional variations in each boule, as determined by a Fourier transform infra-red spectroscopy (FTIR) technique, was made. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Alabama, Dept Mech & Mat Engn, Birmingham, AL 35294 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Scripa, RN (reprint author), Univ Alabama, Dept Mech & Mat Engn, Birmingham, AL 35294 USA. EM rscripa@eng.uab.edu NR 16 TC 3 Z9 5 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1999 VL 198 BP 297 EP 302 DI 10.1016/S0022-0248(98)01175-0 PN 1 PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 187ZM UT WOS:000079819000053 ER PT J AU Price, MW Scripa, RN Lehoczky, SL Szofran, FR AF Price, MW Scripa, RN Lehoczky, SL Szofran, FR TI Differential thermal analysis of Hg1-xMnxTe alloys in the x = 0-0.3 range SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 12th International Conference on Crystal Growth, held in Conjunction with the 10th International Conference on Vapor Growth and Epitaxy (ICCG-12/ICVGE-10) CY JUL 26-31, 1998 CL JERUSALEM, ISRAEL AB The solidus and liquidus temperatures of seven Hg1-xMnxTe (x = 0-0.3) alloys were determined using differential thermal analysis. The phase diagram developed from these phase equilibrium measurements was used to clarify uncertainties in the existing Hg1-xMnxTe phase diagram and enabled the authors to calculate the variation of the segregation coefficient with solidus composition for the Hg1-xMnxTe system in the x = 0-0.3 range. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Alabama, Dept Mech & Mat Engn, Birmingham, AL 35294 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Scripa, RN (reprint author), Univ Alabama, Dept Mech & Mat Engn, Birmingham, AL 35294 USA. EM rscripa@eng.uab.edu NR 9 TC 2 Z9 2 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1999 VL 198 BP 303 EP 307 DI 10.1016/S0022-0248(98)01174-9 PN 1 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 187ZM UT WOS:000079819000054 ER PT J AU Wang, WS Aggarwal, MD Choi, J Gebre, T Shields, AD Penn, BG Frazier, DO AF Wang, WS Aggarwal, MD Choi, J Gebre, T Shields, AD Penn, BG Frazier, DO TI Solvent effects and polymorphic transformation of organic nonlinear optical crystal L-pyroglutamic acid in solution growth processes I. Solvent effects and growth morphology SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 12th International Conference on Crystal Growth, held in Conjunction with the 10th International Conference on Vapor Growth and Epitaxy (ICCG-12/ICVGE-10) CY JUL 26-31, 1998 CL JERUSALEM, ISRAEL DE solution growth; L-pyroglutamic acid; L-PGA; solubility curve; solvent effect; morphology ID SINGLE-CRYSTALS; GENERATION AB Single crystals of a new promising nonlinear optical material for the tunable UV harmonic generation, L-pyroglutamic acid 60 x 20 x 20 mm(3) in size were obtained from aqueous solution by using the temperature-lowering method. Solubility of L-pyroglutamic acid in different solvents was measured. The single crystals showed different morphological characteristics and growth rate in different solvents with different crystallographic orientations. Methanol or ethanol solutions yielded needle-like crystals. In mixed solution such as methanol/H2O or ethanol/ H2O plate-like crystals with a thickness in the direction [0 1 0] were observed. The water as a good solvent, however, produced long prism-like crystals. The two polymorphs of L-pyroglutamic acid (alpha and beta phases) were found for the first time. The growth shapes of alpha-phase is mainly a prism and beta phases is a rhombic plate.The growth rate of alpha and beta phases is mainly a function of the supersaturation of the L-pyroglutamic acid in solution. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Wang, WS (reprint author), Alabama A&M Univ, Dept Phys, POB 963, Normal, AL 35762 USA. NR 8 TC 41 Z9 41 U1 0 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1999 VL 198 BP 578 EP 582 DI 10.1016/S0022-0248(98)01041-0 PN 1 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 187ZM UT WOS:000079819000106 ER PT J AU Barber, P Hayes, C Baker, N Rosch, W AF Barber, P Hayes, C Baker, N Rosch, W TI Estimating crystal quality in semiconductors using voltammetry SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 12th International Conference on Crystal Growth, held in Conjunction with the 10th International Conference on Vapor Growth and Epitaxy (ICCG-12/ICVGE-10) CY JUL 26-31, 1998 CL JERUSALEM, ISRAEL DE semiconductors; lead-tin-telluride; analysis; magnetic damping AB A voltammeter can be used to differentiate the crystalline quality of the compound semiconductor, lead-tin-telluride. A modified differential pulse stripping voltammetric analysis procedure is used with a millimolar bromine/bromide etchant. Higher quality crystals, which had been grown using a magnetically damped Bridgman technique, required longer times for the onset of etching, had smaller rates of etching, and attained smaller depths of etching than did poorer quality crystals grown without magnetic dampening. This analysis procedure is faster, more amenable to quantitative results, and much safer than traditional etching techniques, which use highly corrosive chemicals. The results of the voltammetric analysis were verified using a standard Norr etch in a traditional electrochemical etching procedure and counting dislocation densities. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 Longwood Coll, Dept Nat Sci, Farmville, VA 23909 USA. Lockheed Martin Engn & Sci Co, Hampton, VA 23681 USA. NASA, Langley Res Ctr, NRC, Hampton, VA 23681 USA. RP Barber, P (reprint author), Longwood Coll, Dept Nat Sci, Farmville, VA 23909 USA. EM pbarber@longwood.lwc.edu NR 10 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1999 VL 198 BP 815 EP 820 DI 10.1016/S0022-0248(98)01028-8 PN 1 PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 187ZM UT WOS:000079819000146 ER PT J AU Scripa, RN Wang, B Gonzalez, A Holmes, RR AF Scripa, RN Wang, B Gonzalez, A Holmes, RR TI Chemical compatibility of vacuum plasma sprayed (VPS) metal cartridges with various semiconductor materials SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 12th International Conference on Crystal Growth, held in Conjunction with the 10th International Conference on Vapor Growth and Epitaxy (ICCG-12/ICVGE-10) CY JUL 26-31, 1998 CL JERUSALEM, ISRAEL AB Chemical compatibility is of critical importance in the case of an ampoule failure during crystal growth in a reduced-gravity flight experiment. This study simulated the event of total ampoule failure to test the chemical compatibility between semiconductor materials and vacuum plasma sprayed (VPS) refractory metal cartridges. In this investigation, two VPS refractory metal cartridge materials, Mo41Re and Ta10W, were tested for compatibility with four semiconductor materials, CdZnTe, PbSnTe, ZnSe, and GaSb. During testing, a refractory metal cartridge sample was imbedded in a semiconductor material and held at an elevated temperature for 24 h. After testing, the samples were analyzed optically and using scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) to evaluate the extent of any metal loss or reaction and composition of any reaction products formed. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Alabama, Dept Mech & Mat Engn, Birmingham, AL 35294 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Scripa, RN (reprint author), Univ Alabama, Dept Mech & Mat Engn, Birmingham, AL 35294 USA. NR 6 TC 0 Z9 0 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1999 VL 198 BP 825 EP 829 DI 10.1016/S0022-0248(98)01173-7 PN 1 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 187ZM UT WOS:000079819000148 ER PT J AU Seidensticker, RG Rosch, WR Mazelsky, R Hopkins, RH Singh, NB Coriell, SR Duval, WMB Batur, C AF Seidensticker, RG Rosch, WR Mazelsky, R Hopkins, RH Singh, NB Coriell, SR Duval, WMB Batur, C TI Active control of interface shape during the crystal growth of lead bromide SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 12th International Conference on Crystal Growth, held in Conjunction with the 10th International Conference on Vapor Growth and Epitaxy (ICCG-12/ICVGE-10) CY JUL 26-31, 1998 CL JERUSALEM, ISRAEL DE crystal; model; lead bromide; solid-liquid interface; furnace AB A thermal model for predicting and designing the furnace temperature profile was developed and used for the crystal growth of lead bromide. The model gives the ampoule temperature as a function of the furnace temperature, thermal conductivity, heat transfer coefficients, and dimensions as variable parameters. Crystal interface curvature was derived from the model and it was compared with the predicted curvature for a particular furnace temperature and growth parameters. Large crystals of lead bromide were grown and it was observed that interface shape was in agreement with the shape predicted by this model. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 Northrop Grumman Corp, ESSD, STC, Pittsburgh, PA 15235 USA. NIST, Div Met, Gaithersburg, MD 20899 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Singh, NB (reprint author), Northrop Grumman Corp, ESSD, STC, 1350 Beulah Rd, Pittsburgh, PA 15235 USA. EM Singh.n.b@postal.essd.northgrum.com NR 5 TC 7 Z9 7 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1999 VL 198 BP 988 EP 994 DI 10.1016/S0022-0248(98)01213-5 PN 2 PG 7 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 187ZP UT WOS:000079819300020 ER PT J AU Singh, NB Henningsen, T Suhre, DR Rosch, W Hopkins, RH Mazelsky, R Coriell, SR Duval, WMB AF Singh, NB Henningsen, T Suhre, DR Rosch, W Hopkins, RH Mazelsky, R Coriell, SR Duval, WMB TI Hg2Cl2 crystals for efficient birefringence etalon filters SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 12th International Conference on Crystal Growth, held in Conjunction with the 10th International Conference on Vapor Growth and Epitaxy (ICCG-12/ICVGE-10) CY JUL 26-31, 1998 CL JERUSALEM, ISRAEL DE mercurous chloride; etalon; vapor growth; halides; filter; birefringence AB We have experimentally demonstrated the physical vapor transport growth of 30 mm diameter and 8 cm long mercurous chloride crystals for birefringence etalon filters. The [1 1 0] oriented seeded crystals were grown in a two zone vertical transparent furnace by vapor phase transport method. Two 5 mm and 1.5 mm thick filters were fabricated and tested interferometrically and with a spectrometer. The filter exhibited the spectral modulation expected based on the filter thickness. The effect of temperature on filter performance was studied by measuring the filter operation at specific calibrated temperatures. We observed a significant shift in filter wavelength at 25.8 degrees C and 29.8 degrees C. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 Northrop Grumman Corp, Ctr Sci & Technol, Pittsburgh, PA 15235 USA. NIST, Div Met, Gaithersburg, MD 20899 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Singh, NB (reprint author), Northrop Grumman Corp, Ctr Sci & Technol, 1350 Beulah Rd, Pittsburgh, PA 15235 USA. EM singh.n.b@postal.essd.northgrum.com NR 3 TC 3 Z9 3 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1999 VL 198 BP 995 EP 998 DI 10.1016/S0022-0248(98)01211-1 PN 2 PG 4 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 187ZP UT WOS:000079819300021 ER PT J AU Angirasa, D Peterson, GP AF Angirasa, D Peterson, GP TI Forced convection heat transfer augmentation in a channel with a localized heat source using fibrous materials SO JOURNAL OF ELECTRONIC PACKAGING LA English DT Article ID POROUS-MEDIUM; VARIABLE POROSITY; NON-DARCIAN; FLOW; SUBSTRATE AB A numerical model is developed for high Reynolds number forced convection heat transfer in a channel filled with randomly oriented, thin fibrous materials of high porosity. A localized isothermal heat source, flush with one of the channel walls is considered to simulate an electronic component. The inertial coefficient and the dispersion conductivity associated with high Reynolds number flows and convective heat transfer are empirically modeled from existing experimental and analytical studies. The resulting fluid flow and heat transfer relationships are presented for a relevant range of parameters, and the fundamental physical processes are explained. C1 NASA, Ctr Commercial Dev Space, Ctr Space Power, College Stn, TX 77843 USA. Texas A&M Univ, Ctr Space Power, College Stn, TX 77843 USA. RP Angirasa, D (reprint author), NASA, Ctr Commercial Dev Space, Ctr Space Power, College Stn, TX 77843 USA. NR 20 TC 17 Z9 17 U1 0 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 1043-7398 J9 J ELECTRON PACKAGING JI J. Electron. Packag. PD MAR PY 1999 VL 121 IS 1 BP 1 EP 7 DI 10.1115/1.2792656 PG 7 WC Engineering, Electrical & Electronic; Engineering, Mechanical SC Engineering GA 176RY UT WOS:000079166600001 ER PT J AU Wilson, GR Craven, P AF Wilson, GR Craven, P TI Molecular ion upflow in the cleft ion fountain SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID LATITUDE F-REGION; AURORAL IONOSPHERE; ELECTRIC-FIELDS; PLASMA; DISTRIBUTIONS; CONVECTION; NO+ AB Although the ionosphere is a continuous emitter of escaping light ions (H+ and He+) and in the auroral zone a continuous emitter of escaping heavy atomic ions (O+ and N+), it only sporadically emits molecular ions. This is due to the significant gravitation barrier to their outflow and to the chemical barrier created by their short life times against loss to dissociative recombination in the F region. The outflow of molecular ions requires a special set of circumstances. In this paper we present evidence that one ingredient for those special circumstances is the presence, in the ionosphere, of a strong convection electric field. This can occur in various places near the auroral zone, in nightside subauroral ion drift events, and in the cusp. We show several examples of Dynamics Explorer (DE) 1 and 2 near-conjunction data in which molecular ions are seen at high altitude (1400-4000 km) by DE 1 near where DE 2 sees strong cusp associated plasma convection and ionospheric and thermospheric modification. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Wilson, GR (reprint author), Mission Res Corp, 1 Tara Blvd,Suite 302, Nashua, NH 03062 USA. NR 25 TC 14 Z9 14 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1999 VL 104 IS A3 BP 4437 EP 4446 DI 10.1029/1998JA900070 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 171NK UT WOS:000078870000019 ER PT J AU Li, XL Baker, DN Teremin, M Cayton, TE Reeves, GD Selesnick, RS Blake, JB Lu, G Kanekal, SG Singer, HJ AF Li, XL Baker, DN Teremin, M Cayton, TE Reeves, GD Selesnick, RS Blake, JB Lu, G Kanekal, SG Singer, HJ TI Rapid enhancements of relativistic electrons deep in the magnetosphere during the May 15, 1997, magnetic storm SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID RADIATION BELT; ENERGETIC PARTICLES; SOLAR; WIND; ACCELERATION; DIFFUSION; SAMPEX; ORBIT AB Variations in 0.2-3.2 MeV electron flux in the magnetosphere during the May 15, 1997, magnetic storm (the largest magnetic storm of 1997) arc examined. After over an order of magnitude initial decrease of the 0.2-3.2 MeV electron fluxes, the 0.2-0.8 MeV electron flux at L < 4.5 increased and surpassed the prestorm level in an hour. This increase was followed by increases of the more energetic 0.8-3.2 MeV electron fluxes. These energetic electron variations are examined utilizing data from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), the Global Positioning System (GPS) series of satellites, and the Los Alamos National Laboratory (LANL) sensors on board geosynchronous satellites. During the main phase of the storm, fluxes of >0.4-MeV electrons from SAMPEX decreased at L > 4.5 following the D-st drop but increased somewhat at L < 4. GPS satellite data also show that the electron flux decreased in the energy range 0.2-3.2 MeV for all L values above the minimum detectable L value of similar to 4.2 simultaneously with the decrease in D-st, which is consistent with an adiabatic process. However, the recovery of the electron flux was different at different energies, with an earlier recovery of the less energetic electrons and a later recovery of the more energetic electrons. The recovery of the electron fluxes started before the recovery of D-st, indicating that nonadiabatic processes were involved. The 0.2- to 0.8-MeV electrons appeared in the low-L region (4.2-4.5) at about the same time that the GOES 9 spacecraft measured a strong dipolarization of the Earth's stretched magnetic field. Outer zone electron fluxes continued to increase across a wide L range (L = 3-8) though the electron flux exhibited a strong spatial gradient, with the peak flux below L = 4.2 in the equatorial plane. These data are used to test the idea if radial transport from larger L can account for all of the increase in the flux in the heart of the outer zone electron radiation belt at L = 4-5. However, the radial gradient of the phase space density for a given first adiabatic invariant was estimated to be: negative as a function of radial distance during the time that the electron flux was increasing. This estimate is somewhat uncertain because of rapid temporal variations and sparse data. However, if this estimate is correct, the usual theory of radial transport from larger radial distances cannot account fur all of the increase in the electron flux. The analysis thus suggests that another process, such as local heating, which does not conserve mu, may be required to explain the subsequent enhancement of the more energetic (0.8- to 3.2-MeV) electrons but that additional data are required to answer this question definitely. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Aerospace Corp, Dept Space Sci, Los Angeles, CA 90009 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. RP Li, XL (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80303 USA. RI Lu, Gang/A-6669-2011; Reeves, Geoffrey/E-8101-2011 OI Reeves, Geoffrey/0000-0002-7985-8098 NR 40 TC 41 Z9 44 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1999 VL 104 IS A3 BP 4467 EP 4476 DI 10.1029/1998JA900092 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 171NK UT WOS:000078870000022 ER PT J AU Sibeck, DG Borodkova, NL Schwartz, SJ Owen, CJ Kessel, R Kokubun, S Lepping, RP Lin, R Luhr, H McEntire, RW Meng, CI Mukai, T Nemecek, Z Parks, G Phan, TD Romanov, SA Safrankova, J Sauvaud, JA Singer, HJ Solovyev, SI Szabo, A Takahashi, K Williams, DJ Yumoto, K Zastenker, GN AF Sibeck, DG Borodkova, NL Schwartz, SJ Owen, CJ Kessel, R Kokubun, S Lepping, RP Lin, R Luhr, H McEntire, RW Meng, CI Mukai, T Nemecek, Z Parks, G Phan, TD Romanov, SA Safrankova, J Sauvaud, JA Singer, HJ Solovyev, SI Szabo, A Takahashi, K Williams, DJ Yumoto, K Zastenker, GN TI Comprehensive study of the magnetospheric response to a hot flow anomaly SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTHS BOW SHOCK; UPSTREAM PRESSURE VARIATIONS; MAGNETIC-FIELD SIGNATURES; LATITUDE BOUNDARY-LAYER; WIND DYNAMIC PRESSURE; SOLAR-WIND; MAGNETOPAUSE MOTION; SATELLITE-OBSERVATIONS; DIAMAGNETIC CAVITIES; INTERBALL PROJECT AB We present a comprehensive observational study of the magnetospheric response to an interplanetary magnetic field (IMF) tangential discontinuity, which first struck the postnoon bow shock and magnetopause and then swept past the prenoon bow shock and magnetopause on July 24, 1996. Although unaccompanied by any significant plasma variation, the discontinuity interacted with the bow shock to form a hot flow anomaly (HFA), which was observed by Interball-1 just upstream from the prenoon bow shock. Pressures within and Earthward of the HFA were depressed by an order of magnitude, which allowed the magnetopause to briefly (similar to 7 min) move outward some 5 R-E beyond its nominal position and engulf Interball-1. A timing study employing nearby Interball-1 and Magion-4 observations demonstrates that this motion corresponded to an antisunward and northward moving wave on the magnetopause. The same wave then engulfed Geotail, which was nominally located downstream in the outer dawn magnetosheath. Despite its large amplitude, the wave produced only minor effects in GOES-8 geosynchronous observations near local dawn. Polar Ultraviolet Imager (UVI) observed a sudden brightening of the afternoon aurora, followed by an even more intense transient brightening of the morning aurora. Consistent with this asymmetry, the discontinuity produced only weak near-simultaneous perturbations in high-latitude postnoon ground magnetometers but a transient convection vortex in the prenoon Greenland ground magnetograms. The results of this study indicate that the solar wind interaction with the bow shock is far more dynamic than previously imagined and far more significant to the solar wind-magnetosphere interaction. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Moscow Space Res Inst, Moscow 117810, Russia. Univ London Queen Mary & Westfield Coll, Astron Unit, London E1 4NS, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Solar Terr Environm Lab, Aichi 332, Japan. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Charles Univ, Fac Math & Phys, Dept Elect & Vacuum Phys, CR-18000 Prague, Czech Republic. Univ Washington, Geophys Program, Seattle, WA 98195 USA. Ctr Etud Spatiale Rayonnements, CNRS, F-31029 Toulouse, France. NOAA, Space Environm Lab, Boulder, CO 80303 USA. Inst Cosmophys Res & Aeron, Yakutsk 677891, Russia. Kyushu Univ, Dept Earth & Planetary Sci, Fukuoka 812, Japan. RP Sibeck, DG (reprint author), Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA. RI Owen, Christopher/C-2999-2008; Sibeck, David/D-4424-2012; Liou, Kan/C-2089-2016 OI Owen, Christopher/0000-0002-5982-4667; Liou, Kan/0000-0001-5277-7688 NR 69 TC 95 Z9 96 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1999 VL 104 IS A3 BP 4577 EP 4593 DI 10.1029/1998JA900021 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 171NK UT WOS:000078870000031 ER PT J AU Kivelson, MG Khurana, KK Stevenson, DJ Bennett, L Joy, S Russell, CT Walker, RJ Zimmer, C Polanskey, C AF Kivelson, MG Khurana, KK Stevenson, DJ Bennett, L Joy, S Russell, CT Walker, RJ Zimmer, C Polanskey, C TI Europa and Callisto: Induced or intrinsic fields in a periodically varying plasma environment SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD; IO; TORUS AB Magnetometer data from four Galileo passes by the Jovian moon Europa and three passes by Callisto are used to interpret the properties of the plasma surrounding these moons and to identify internal sources of magnetic perturbations. Near Europa the measurements are consistent with a plasma rich in pickup ions whose source is freshly ionized neutrals sputtered off of the moon's surface or atmosphere. The plasma effects vary with Europa's height above the center of Jupiter's extended plasma disk. Europa is comet-like when near the center of the current sheet. It is therefore likely that the strength of the currents coupling Europa to Jupiter's ionosphere and the brightness of a Europa footprint will depend on System III longitude. Magnetic perturbations on the scale of Europa's radius can arise from a permanent dipole moment or from an induced dipole moment driven by the time-varying part of Jupiter's magnetospheric field at Europa's orbit. Both models provide satisfactory fits. An Induced dipole moment is favored because it requires no adjustable parameters. The inductive response of a conductive sphere also fits perturbations on two passes near Callisto. The implied dipole moment flips direction as is predicted for greatly differing orientations of Jupiter's magnetospheric field near Callisto in the two cases. For both moons the current carrying shells implied by induction must be located near the surface. An ionosphere cannot provide the current path, as its conductivity is too small, but a near surface ocean of similar to 10 km or more in thickness would explain the observations. C1 Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kivelson, MG (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, 6843 Slichter Hall,405 Hilgard Ave, Los Angeles, CA 90095 USA. RI Kivelson, Margaret/I-9019-2012; OI Kivelson, Margaret/0000-0003-3859-8581; Russell, Christopher/0000-0003-1639-8298 NR 31 TC 105 Z9 108 U1 1 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1999 VL 104 IS A3 BP 4609 EP 4625 DI 10.1029/1998JA900095 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 171NK UT WOS:000078870000033 ER PT J AU Suess, ST Wang, AH Wu, ST Poletto, G McComas, DJ AF Suess, ST Wang, AH Wu, ST Poletto, G McComas, DJ TI A two-fluid, MHD coronal model SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND MODEL; EULERIAN FICE SCHEME; 2-FLUID MODEL; ALFVEN WAVES; WHITE-LIGHT; SPEED; TEMPERATURE; DISRUPTION; STREAMERS; ULYSSES AB We describe first results from a numerical two-fluid MHD model of the global structure of the solar corona. The model is two-fluid in the sense that it accounts for the collisional energy exchange between protons and electrons. As in our single-fluid model, volumetric heat and momentum sources are required to produce high speed wind from coronal holes, low speed wind above streamers, and mass fluxes similar to the empirical solar wind. By specifying different proton and electron heating functions we obtain a high proton temperature in the coronal hole and a relatively low proton temperature above the streamer tin comparison with the electron temperature). This is consistent with inferences from SOHO/UltraViolet Coronagraph Spectrometer instrument (UVCS) [Kohl ct al., 1997], and with the Ulysses/Solar Wind Observations Over the Poles of the Sun instrument (SWOOPS) proton and electron temperature measurements which we show from the fast latitude scan. The density in the coronal hole between 2 and 5 solar radii (2 and 5 Rs) is similar to the density reported from SPARTAN 201-01 measurements by Fisher and Guhathakurta [1994]. The proton mass flux scaled to 1 AU is 2.4 x 10(8) cm(-2) s(-1), which is consistent with Ulysses observations [Phillips ct al., 1995]. Inside the closed field region, the density is sufficiently high so that the simulation gives equal proton and electron temperatures due to the high collision rate. In open field regions tin the coronal hole and above the streamer) the proton and electron temperatures differ by varying amounts. In the streamer the temperature and density are similar to those reported empirically by Li et al. [1998], and the plasma beta is larger than unity everywhere above similar to 1.5 Rs, as it is in all other MHD coronal streamer models [e.g., Steinolfson ct al., 1982; also G. A. Gary and D. Alexander, Constructing the coronal magnetic field, submitted to Solar Physics, 1998]. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Mech Engn, Huntsville, AL 35899 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. Osservatorio Astrofis Arcetri, I-50125 Florence, Italy. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Suess, ST (reprint author), NASA, George C Marshall Space Flight Ctr, ES82, Huntsville, AL 35812 USA. EM steve.suess@msfc.nasa.gov; wanga@cspar.uah.edu; wu@cspar.uah.edu; po-letto@arcetri.astro.it; mccomas@nis-pop.lanl.gov NR 51 TC 43 Z9 44 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1999 VL 104 IS A3 BP 4697 EP 4708 DI 10.1029/1998JA900086 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 171NK UT WOS:000078870000041 ER PT J AU Gopalswamy, N Kaiser, ML Lepping, RP Berdichevsky, D Ogilvie, K Kahler, SW Kondo, T Isobe, T Akioka, M AF Gopalswamy, N Kaiser, ML Lepping, RP Berdichevsky, D Ogilvie, K Kahler, SW Kondo, T Isobe, T Akioka, M TI Comment on "Origin of coronal and interplanetary shocks: A new look with Wind spacecraft data" by N. Gopalswamy et al. - Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Editorial Material ID MASS EJECTIONS; II BURSTS; EVENTS; FLARES C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Raytheon STX, Greenbelt, MD USA. USAF, Res Lab, VSBS, Hanscom AFB, MA 01731 USA. Commun Res Lab, Ibaraki, Osaka, Japan. RP Gopalswamy, N (reprint author), NASA, Goddard Space Flight Ctr, Code 682-3,Bldg 26,Room G-1, Greenbelt, MD 20771 USA. RI Gopalswamy, Nat/D-3659-2012 NR 24 TC 16 Z9 16 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1999 VL 104 IS A3 BP 4749 EP 4754 DI 10.1029/98JA02832 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 171NK UT WOS:000078870000045 ER PT J AU Crassidis, JL Lightsey, EG Markley, FL AF Crassidis, JL Lightsey, EG Markley, FL TI Efficient and optimal attitude determination using recursive global positioning system signal operations SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID SPACECRAFT ATTITUDE; VECTOR OBSERVATIONS; ALGORITHM AB A new and efficient algorithm is developed for attitude determination from global positioning system signals. The new algorithm is derived from a generalized predictive filter for nonlinear systems. This uses a one time-step ahead approach to propagate a simple kinematics model for attitude determination. The advantages of the new algorithm over previously developed methods include: it provides optimal attitudes even for coplanar baseline configurations, it guarantees convergence even for poor initial conditions, it is a noniterative algorithm, and it is computationally efficient. These advantages clearly make the new algorithm well suited to onboard applications. The performance of the new algorithm is tested on a dynamic hardware simulator. Results indicate that the new algorithm accurately estimates the attitude of a moving vehicle and provides robust attitude estimates even when other methods, such as a linearized least-squares approach, fail due to poor initial starting conditions. C1 Texas A&M Univ, Dept Aerosp Engn, College Stn, TX 77843 USA. NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, Greenbelt, MD 20771 USA. RP Crassidis, JL (reprint author), Texas A&M Univ, Dept Aerosp Engn, College Stn, TX 77843 USA. NR 24 TC 18 Z9 20 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1999 VL 22 IS 2 BP 193 EP 201 DI 10.2514/2.4373 PG 9 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 175PZ UT WOS:000079104700001 ER PT J AU Menon, PK Sweriduk, GD Sridhar, B AF Menon, PK Sweriduk, GD Sridhar, B TI Optimal strategies for free-flight air traffic conflict resolution SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB Recent advances in navigation and data communication technologies make it feasible for individual aircraft to plan and fly their trajectories in the presence of other aircraft in the airspace. This way, each aircraft can take advantage of the atmospheric and traffic conditions to optimally plan its path. This capability is termed the free-Right concept. Whereas the free-flight concept provides new degrees of freedom to the aircraft operators, it also brings in complexities not present in the current air traffic control system. In this concept, each aircraft has the responsibility for navigating around other aircraft in the airspace. Although this is not a difficult task under low-speed, low-traffic-density conditions, the complexities of dealing with potential conflicts with multiple aircraft in other fight conditions can significantly increase the pilot's work load. The development of conflict resolution algorithms is presented based on trajectory optimization methods that will the enable the practical implementation of the free-flight concept. These algorithms use nonlinear point-mass aircraft models and include realistic operational constraints on individual aircraft. Several conflict resolution scenarios are illustrated. The present analytical framework can also incorporate information about ambient atmospheric conditions. These conflict resolution algorithms are suitable for implementation onboard aircraft. C1 Optimal Synth Inc, Palo Alto, CA 94306 USA. NASA, Ames Res Ctr, Automat Concepts Branch, Moffett Field, CA 94035 USA. RP Menon, PK (reprint author), Optimal Synth Inc, 450 San Antonio Rd,Suite 46, Palo Alto, CA 94306 USA. NR 39 TC 79 Z9 83 U1 2 U2 11 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1999 VL 22 IS 2 BP 202 EP 211 DI 10.2514/2.4384 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 175PZ UT WOS:000079104700002 ER PT J AU Crassidis, JL Markley, FL Lightsey, EG AF Crassidis, JL Markley, FL Lightsey, EG TI Global positioning system integer ambiguity resolution without attitude knowledge SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB In this paper, a new motion-based algorithm for global positioning system integer ambiguity resolution is derived. The algorithm represents the global positioning system sightline vectors in the body frame as the sum of two vectors, one depending on the phase measurements and the other on the unknown integers. The vector containing the integer phases is found using a procedure developed to solve for magnetometer biases. In addition to a batch solution, this paper also provides a sequential estimate, so that a suitable stopping condition can be found during the vehicle motion. The new algorithm has several advantages: it does not require an a priori estimate of the vehicle's attitude; it provides an inherent integrity check using a covariance-type expression; and it can sequentially estimate the ambiguities during the vehicle motion. Its only disadvantage is that it requires at least three noncoplanar baselines, The performance of the new algorithm is tested on a dynamic hardware simulator. C1 Texas A&M Univ, Dept Aerosp Engn, College Stn, TX 77843 USA. NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, GNOC Syst Engn Branch, Greenbelt, MD 20771 USA. RP Crassidis, JL (reprint author), Texas A&M Univ, Dept Aerosp Engn, College Stn, TX 77843 USA. NR 16 TC 27 Z9 27 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1999 VL 22 IS 2 BP 212 EP 218 DI 10.2514/2.4395 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 175PZ UT WOS:000079104700003 ER PT J AU Jackson, MR Zhao, YYJ Slattery, RA AF Jackson, MR Zhao, YYJ Slattery, RA TI Sensitivity of trajectory prediction in air traffic management SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID DESIGN; FUEL AB Trajectory prediction in air traffic management computes the most likely or the most desirable aircraft trajectories by using models of aircraft performance and atmospheric conditions, as well as measurements of aircraft states. In comparison, actual trajectories are obtained using feedback control from a pilot or autopilot to track flight objectives, while the aircraft flies through an actual atmosphere. This paper introduces the concept of closed-loop sensitivities, which are defined as differences between actual and computed trajectories per unit of modeling errors, in the presence of pilot/autopilot feedback controls, hlodeling errors are expressed as uncertain parameters and/or uncertain functions. pilot/autopilot control actions are approximated by nonlinear feedback control laws, designed with the method of feedback linearization. Both the aircraft equations of motion and the feedback control laws are linearized around computed reference trajectories, and these linearized equations are used to determine expressions for closed-loop terminal sensitivities. The proposed method is applied to the Center/Terminal Radar Approach Control (TRACON) Automation System as well as flight management systems. C1 Honeywell Technol Ctr, Minneapolis, MN 55418 USA. Univ Minnesota, Dept Aerosp Engn & Mech, Minneapolis, MN 55455 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Jackson, MR (reprint author), Honeywell Technol Ctr, Minneapolis, MN 55418 USA. EM jackson@htc.honeywell.com; gyyz@aem.umn.edu NR 42 TC 27 Z9 30 U1 1 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1999 VL 22 IS 2 BP 219 EP 228 DI 10.2514/2.4398 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 175PZ UT WOS:000079104700004 ER PT J AU Lin, JL Chen, SJ Juang, JN AF Lin, JL Chen, SJ Juang, JN TI Minimum-phase robustness for second-order linear systems SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID FLEXIBLE SPACE STRUCTURES; 2ND-ORDER DYNAMIC-SYSTEMS; TRANSMISSION ZEROS; CONTROLLER DESIGNS; BOUNDS AB A novel approach is presented to address the problem of minimum-phase robustness for second-order linear systems with uncertainties in the input influence matrix. Two cases are studied, including unstructured uncertainties and unidirectional perturbation of the input matrix. A tolerable margin is given for unstructured uncertainties in terms of the structured singular value to guarantee minimum phase for the systems. For a specified unidirectional perturbation, the exact bounds can be determined by examining the eigenvalue loci of a certain rational function. The approach is applicable to the systems with noncollocated actuators and sensors. To illustrate the concept several numerical examples are provided. C1 Natl Cheng Kung Univ, Dept Engn Sci, Tainan 701, Taiwan. NASA, Langley Res Ctr, Struct Dynam Branch, Hampton, VA 23681 USA. RP Lin, JL (reprint author), Natl Cheng Kung Univ, Dept Engn Sci, Tainan 701, Taiwan. NR 23 TC 4 Z9 4 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1999 VL 22 IS 2 BP 229 EP 234 DI 10.2514/2.4399 PG 6 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 175PZ UT WOS:000079104700005 ER PT J AU Joshi, SS Speyer, JL Kim, J AF Joshi, SS Speyer, JL Kim, J TI Finite dimensional optimal control of Poiseuille flow SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID FEEDBACK AB In this paper we consider linear stabilization of plane, Poiseuille flow using linear quadratic Gaussian optimal control theory. It is shown that we may significantly increase the dissipation rate of perturbation energy, while reducing the required control energy, as compared with that reported using simple, integral compensator control schemes. Poiseuille flow is described by the infinite dimensional Navier-Stokes equations. Because it is impossible to implement infinite dimensional controllers, we implement high hut finite order controllers. We show that this procedure in theory can lead to destabilization of unmodeled dynamics. We then show that this may be avoided using distributed control or, dually, distributed sensing. A problem in high plant order linear quadratic Gaussian controller design is numerical instability in the synthesis equations, We show a linear quadratic Gaussian design that uses an extremely low-order plant model. This low-order controller produces results essentially equivalent to the high-order controller. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91101 USA. Univ Calif Los Angeles, Los Angeles, CA 90095 USA. RP Joshi, SS (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91101 USA. NR 10 TC 36 Z9 37 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1999 VL 22 IS 2 BP 340 EP 348 DI 10.2514/2.4383 PG 9 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 175PZ UT WOS:000079104700019 ER PT J AU Kaysen, JH Campbell, WC Majewski, RR Goda, FO Navar, GL Lewis, FC Goodwin, TJ Hammond, TG AF Kaysen, JH Campbell, WC Majewski, RR Goda, FO Navar, GL Lewis, FC Goodwin, TJ Hammond, TG TI Select de novo gene and protein expression during renal epithelial cell culture in rotating wall vessels is shear stress dependent SO JOURNAL OF MEMBRANE BIOLOGY LA English DT Article DE flow cytometry; antisense oligos; microgravity; astrobiology; differential display ID SIMULATED MICROGRAVITY; TERATOGENIC ANTIBODIES; RECEPTOR; IDENTIFICATION; COCULTURE; COMPLEX; VILLIN; TARGET; FORM AB The rotating wall vessel has gained popularity as a clinical cell culture tool to produce hormonal implants. It is desirable to understand the mechanisms by which the rotating wall vessel induces genetic changes, if we are to prolong the useful life of implants. During rotating wall vessel culture gravity is balanced by equal and opposite hydrodynamic forces including shear stress. The current study provides the first evidence that shear stress response elements, which modulate gene expression in endothelial cells, are also active in epithelial cells. Rotating wall culture of renal cells changes expression of select gene products including the giant glycoprotein scavenger receptors cubulin and megalin, the structural microvillar protein villin, and classic shear stress response genes ICAM, VCAM and MnSOD. Using a putative endothelial cell shear stress response element binding site as a decoy, we demonstrate the role of this sequence in the regulation of selected genes in epithelial cells. However, many of the changes observed in the rotating wall vessel are independent of this response element. It remains to define other genetic response elements modulated during rotating wall vessel culture, including the role of hemodynamics characterized by 3-dimensionality, low shear and turbulence, and cospatial relation of dissimilar cell types. C1 Tulane Xavier Ctr Bioenvironm Res, Dept Med, Nephrol Sect, New Orleans, LA 70112 USA. Tulane Xavier Ctr Bioenvironm Res, Tulane Environm Astrobiol Ctr, New Orleans, LA 70112 USA. Tulane Univ, Med Ctr, Dept Surg, New Orleans, LA 70112 USA. Vet Adm Med Ctr, New Orleans, LA 70146 USA. Univ Wisconsin Hosp & Clin, Madison, WI 53705 USA. William S Middleton Mem Vet Hosp, Madison, WI 53705 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Hammond, TG (reprint author), Tulane Xavier Ctr Bioenvironm Res, Dept Med, Nephrol Sect, 1430 Tulane Ave, New Orleans, LA 70112 USA. FU NCRR NIH HHS [R21 RR12645]; NIDDK NIH HHS [DK46117] NR 38 TC 37 Z9 38 U1 0 U2 3 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0022-2631 J9 J MEMBRANE BIOL JI J. Membr. Biol. PD MAR 1 PY 1999 VL 168 IS 1 BP 77 EP 89 PG 13 WC Biochemistry & Molecular Biology; Cell Biology; Physiology SC Biochemistry & Molecular Biology; Cell Biology; Physiology GA 173EV UT WOS:000078969000008 PM 10051691 ER PT J AU Toth, RA AF Toth, RA TI Analysis of line positions and strengths of H-2 O-16 ground and hot bands connecting to interacting upper states: (020), (100), and (001) SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID (H2O)-O-16; WATER; SPECTRUM; H2O-16; REGION AB High-resolution spectra of (H2O)-O-16 were recorded with a Fourier-transform spectrometer covering transitions in the (020)(010), (100)-(010), and (001)-(010) bands from 1100 to over 2300 cm(-1). Also included in the study were previously reported measurements of these bands and measurements of the (020)-(000), (100)-(000), and (001)-(000) bands from 2620 cm(-1) to 4500 cm(-1). The linestrengths were fitted to a model which takes into account the interactions between the vibrational states (020), (100), and (001). The model included dipole moment matrix elements (also referred to as transition elements) represented by 19 expansion coefficients for B-type transitions and 14 expansion coefficients for A-type band transitions. The most satisfactory results were obtained when the relative signs and values of the leading dipole moment terms of each of the three "hot" bands were as follows: u(020-010) = 1.936(97) x 10(-1) D, u(100-010) = 3.876(19) x 10(-2) D, and u(001-010) = 2.523(75) x 10(-2) D. Hot water emission experimental frequencies from other studies were included in an analysis to obtain rotational energies for levels up to high J and/or K-a of the (020), (100), and (001) vibrational states. The results from this study provide a more accurate representation of the parameters than those available at present for the six bands. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 35 Z9 35 U1 0 U2 6 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD MAR PY 1999 VL 194 IS 1 BP 28 EP 42 DI 10.1006/jmsp.1998.7771 PG 15 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 166NV UT WOS:000078584000005 ER PT J AU Perrin, A Flaud, JM Keller, F Goldman, A Blatherwick, RD Murcray, FJ Rinsland, CP AF Perrin, A Flaud, JM Keller, F Goldman, A Blatherwick, RD Murcray, FJ Rinsland, CP TI Analysis of the nu(8)+nu(9) band of HNO3, line positions and intensities, and resonances involving the upsilon(6)=upsilon(7)=1 dark state SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID HIGH-RESOLUTION; NITRIC-ACID; STRATOSPHERIC CLONO2; ATMOSPHERIC SPECTRA; PARAMETERS; PROFILES; OZONE; EASOE AB Using a high-resolution (R = 0.0025 cm(-1)) Fourier transform spectrum of nitric acid recorded at room temperature in the 1100-1240 cm(-1) region, it has been possible to perform a more extended analysis of the nu(8) + nu(9) band of HNO3 centered at 1205.7075 cm(-1). As in a recent analysis of this band [W. F. Wang, P. P. Ong, T. L. Tan, E. C. Looi, and H. H. Tee, J. Mel. Spectrosc. 183, 407-413 (1997)], the Hamiltonian used for the line positions calculation takes into account, for the upper state, the Delta K = +/-2 anharmonic resonance linking the rotational levels of the nu(8) = nu(9) = 1 "bright" vibrational state and those of the "dark" nu(6) = nu(7) = 1 vibrational state. More than 4800 lines were assigned in the nu(8) + nu(9) band, which involve significantly higher rotational quantum numbers than in previous works. On the other hand, and surprisingly as compared to previous studies, the nu(8) + nu(9) band appears to be a hybrid band. In fact, nonnegligible B-type transitions could be clearly identified among the much stronger A-type lines. Accordingly, a set of individual line intensifies were measured for Lines of both types and were introduced in a least-squares fit to get the A- and B-type components of the transition moment operator. Finally, a synthetic spectrum of the 8.3-mu m region of HNO3 has been generated, using for the line positions and line intensities the Hamiltonian constants and the expansion of the transition moment operator which were determined in this work. in this way, the B-type and the A-type components of the nu(8) + nu(9) band appear to contribute for about 1/4 and 3/4, respectively, to the total band intensity. (C) 1999 Academic Press. C1 Univ Paris Sud, CNRS, Photophys Mol Lab, F-91405 Orsay, France. Univ Denver, Dept Phys, Denver, CO 80208 USA. NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. RP Perrin, A (reprint author), Univ Paris Sud, CNRS, Photophys Mol Lab, Bat 210,Campus Orsay, F-91405 Orsay, France. NR 35 TC 9 Z9 9 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD MAR PY 1999 VL 194 IS 1 BP 113 EP 123 DI 10.1006/jmsp.1998.7765 PG 11 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 166NV UT WOS:000078584000013 ER PT J AU Meyyappan, M Kukkonen, CA AF Meyyappan, Meyya Kukkonen, Carl A. TI Nanotechnology at NASA SO JOURNAL OF NANOPARTICLE RESEARCH LA English DT Article DE space exploration; nanoscience; nanoelectronics; carbon nanotubes; miniaturization; computational nanotechnology C1 [Meyyappan, Meyya] NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. [Kukkonen, Carl A.] CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Meyyappan, M (reprint author), NASA, Ames Res Ctr, Mail Stop 229-3,Bldg 229,Room 214, Moffett Field, CA 94035 USA. NR 5 TC 0 Z9 0 U1 0 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 1388-0764 J9 J NANOPART RES JI J. Nanopart. Res. PD MAR PY 1999 VL 1 IS 1 BP 141 EP 143 DI 10.1023/A:1010037506688 PG 3 WC Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary SC Chemistry; Science & Technology - Other Topics; Materials Science GA V19IS UT WOS:000208066700016 ER PT J AU Zhirnov, V Herr, D Meyyappan, M AF Zhirnov, V. Herr, D. Meyyappan, M. TI Electronic applications of carbon nanotubes become closer to reality SO JOURNAL OF NANOPARTICLE RESEARCH LA English DT Article C1 [Meyyappan, M.] NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. [Zhirnov, V.; Herr, D.] SRC, Moffett Field, CA 94035 USA. RP Meyyappan, M (reprint author), NASA, Ames Res Ctr, Mail Stop 229-3, Moffett Field, CA 94035 USA. EM meyya@orbit.arc.nasa.gov NR 0 TC 25 Z9 25 U1 1 U2 3 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 1388-0764 J9 J NANOPART RES JI J. Nanopart. Res. PD MAR PY 1999 VL 1 IS 1 BP 151 EP 152 DI 10.1023/A:1010027322383 PG 2 WC Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary SC Chemistry; Science & Technology - Other Topics; Materials Science GA V19IS UT WOS:000208066700018 ER PT J AU Kato, S Ackerman, TP Dutton, EG Laulainen, N Larson, N AF Kato, S Ackerman, TP Dutton, EG Laulainen, N Larson, N TI A comparison of modeled and measured surface shortwave irradiance for a molecular atmosphere SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID PLANETARY-ATMOSPHERES; MULTIPLE-SCATTERING; RADIATIVE-TRANSFER; APPROXIMATION; FLUXES; LIGHT AB We compare the downward diffuse and direct normal irradiance computed by a two-stream model with measurements taken at the Mauna Loa Observatory when the atmosphere was close to a molecular atmosphere. The modeled downward diffuse irradiance agrees with measurements taken by a shaded pyranometer within the uncertainty of the measurement. Therefore, the two-stream approximation is adequate for computing the downward diffuse irradiance in a molecular atmosphere. This result also indicates that neglecting the state of polarization introduces a negligible error in the irradiance computation. Published by Elsevier Science Ltd. C1 Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Pacific NW Lab, Richland, WA 99352 USA. RP Kato, S (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23681 USA. NR 33 TC 15 Z9 17 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAR PY 1999 VL 61 IS 4 BP 493 EP 502 DI 10.1016/S0022-4073(98)00032-6 PG 10 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 164AR UT WOS:000078440200007 ER PT J AU Lyapustin, AI Muldashev, TZ AF Lyapustin, AI Muldashev, TZ TI Method of spherical harmonics in the radiative transfer problem with non-Lambertian surface SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID BIDIRECTIONAL REFLECTANCE AB The paper reports on the spherical harmonics method (MSH) for solving the radiative transfer problem in the vertically inhomogeneous atmosphere bounded by a non-Lambertian surface. The surface bi-directional reflectance function is assumed to be symmetrical with respect to the principal plane, otherwise it can be of an arbitrary shape and can include directional signatures as a hot spot effect or a specular reflection. The lower boundary conditions, taken in the form of Marshak, are represented analytically on the basis of recurrent formulas obtained here. For calculating the angular structures of radiation fields, the new computationally efficient smoothing procedure is developed based on the correction function of MSH. It enables one to essentially reduce the order of MSH preserving the high accuracy of solution. In conjunction with the predominantly analytical way of solving the differential system of equations of MSH, this combination allows one to achieve exceptionally high speed of computations. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. Inst Space Res, Alma Ata, Kazakhstan. RP Lyapustin, AI (reprint author), NASA, Goddard Space Flight Ctr, USRA, Mailcode 920, Greenbelt, MD 20771 USA. RI Lyapustin, Alexei/H-9924-2014 OI Lyapustin, Alexei/0000-0003-1105-5739 NR 21 TC 17 Z9 17 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAR PY 1999 VL 61 IS 4 BP 545 EP 555 DI 10.1016/S0022-4073(98)00041-7 PG 11 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 164AR UT WOS:000078440200012 ER PT J AU Kshirsagar, RJ Giver, LP Chackerian, C Brown, LR AF Kshirsagar, RJ Giver, LP Chackerian, C Brown, LR TI The rovibrational intensities of the 2 nu(3) band of (COO)-C-12-O-16-O-18 at 4639 cm(-1) SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID CARBON-DIOXIDE BANDS; MU-M; (CO2)-C-12-O-16; FREQUENCY AB The absolute intensities of transitions in the 2 mu(3) vibrational band of (COO)-C-12-O-16-O-18,at 4639.5 cm(-1) have been measured in natural isotopic abundance; the spectra were obtained with 0.012 cm(-1) resolution using the McMath Fourier transform spetrometer of the National Solar Observatory located at Kitt Peak National Observatory. About 70 transitions have been fitted with an rms deviation of approximately 1.5% to obtain the rotationless band strength of S-vib(0) = 1.442 x 10(-23) molecule(-1) at 296 K along with a small first-order Herman-Wallis parameter of A(1) = 3.5 x 10(-5); higher order Herman-Wallis parameters could not be determined. The measured line positions, obtained using the CO2 gas samples in the range of 45-65 Torr at room temperature, confirm the current HITRAN tabulated values. The internal precision of our intensity measurements is very high, and the uncertainty due to possible systematic errors is judged to be less than +/- 3%. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Atmospher Phys Branch, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kshirsagar, RJ (reprint author), NASA, Ames Res Ctr, Atmospher Phys Branch, N 245-4, Moffett Field, CA 94035 USA. NR 12 TC 11 Z9 11 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAR PY 1999 VL 61 IS 5 BP 695 EP 701 DI 10.1016/S0022-4073(98)00058-2 PG 7 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 163UE UT WOS:000078424100013 ER PT J AU Park, K Zink, LR Chance, KV Evenson, KM Nolt, IG AF Park, K Zink, LR Chance, KV Evenson, KM Nolt, IG TI Pressure broadening of the 118.455 cm(-1) rotational lines of OH by N-2, O-2, H-2, and He SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article AB We measured the pressure broadening of the 118.455cm(-1) (3.551Thz) rotational lines of OH by H-2, He, N-2 and O-2 From these measurements, we calculated the pressure broadening of this line by air. The broadening coefficients are 6.06(16) and 10.13(25) x 10(-7) cm(-1) Pa-1 at 296 and 194 K. We also measured the position of the manifold of lines, with results that are in excellent agreement with a previous accurate determination. The frequency of the strongest component of the transition (F = 4 <-- 3), and its 2 sigma uncertainty is 3551185.32(3) MHz. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Oregon, Dept Phys, Eugene, OR 97403 USA. Natl Inst Stand & Technol, Boulder, CO 80303 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Park, K (reprint author), Univ Oregon, Dept Phys, Eugene, OR 97403 USA. OI Chance, Kelly/0000-0002-7339-7577 NR 6 TC 3 Z9 3 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD MAR PY 1999 VL 61 IS 5 BP 715 EP 716 DI 10.1016/S0022-4073(98)00057-0 PG 2 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 163UE UT WOS:000078424100016 ER PT J AU Hurwitz, FI Meador, MAB AF Hurwitz, FI Meador, MAB TI Tailoring silicon oxycarbide glasses for oxidative stability SO JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY LA English DT Article DE silicon oxycarbide; Blackglas (TM); ceramic matrix composites; Si-29 NMR; oxidation ID PYROLYTIC CONVERSION; GELS; PRECURSORS AB Blackglas(TM) polysiloxane systems produce silicon oxycarbide glasses by pyrolysis in inert atmosphere. The silicon oxycarbides evidence oxidative degradation that limits their lifetime as composite matrices. The present study characterizes bonding rearrangements in the oxycarbide network accompanying increases in pyrolysis temperature. It also addresses the changes in susceptibility to oxidation due to variations in the distribution of Si bonded species obtained under different processing conditions. The study is carried out using Si-29 nuclear magnetic resonance (NMR) spectroscopy and a design of experiments approach to model the oxidation behavior. The NMR results are compared with those obtained by thermogravimetric analysis (TGA). Samples pyrolyzed under inert conditions are compared to those pyrolyzed in reactive ammonia environments. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hurwitz, FI (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. OI Meador, Mary Ann/0000-0003-2513-7372 NR 22 TC 22 Z9 22 U1 1 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0928-0707 J9 J SOL-GEL SCI TECHN JI J. Sol-Gel Sci. Technol. PD MAR PY 1999 VL 14 IS 1 BP 75 EP 86 DI 10.1023/A:1008727914900 PG 12 WC Materials Science, Ceramics SC Materials Science GA 211JB UT WOS:000081175200007 ER PT J AU Merski, NR AF Merski, NR TI Global aeroheating wind-tunnel measurements using improved two-color phosphor thermography method SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Detailed aeroheating information is critical to the successful design of a thermal protection system (TPS) for an aerospace vehicle. NASA Langley Research Center's (LaRC) phosphor thermography method is described. Development of theory is provided for a new weighted two color relative-intensity fluorescence theory for quantitatively determining surface temperatures on hypersonic wind-tunnel models and an improved application of the one-dimensional conduction theory for use in determining global heating mappings. The phosphor methodology at LaRC is presented including descriptions of phosphor model fabrication, test facilities, and phosphor video acquisition systems. A discussion of the calibration procedures, data reduction, and data analysis is given. Estimates of the total uncertainties (with a 95% confidence level) associated with the phosphor technique are shown to be approximately 7-10% in LaRC's 31-Inch Mach 10 Tunnel and 8-10% in the 20-Inch Mach 6 Tunnel. A comparison with thin-film measurements using 5.08-cm-radius hemispheres shows the phosphor data to be within 7% of thin-film measurements and to agree even better with predictions via a LATCH computational fluid dynamics (CFD) solution. Good agreement between phosphor data and LAURA CFD computations on the forebody of a vertical takeoff/vertical lander configuration at four angles of attack is also shown. In addition, a comparison is given between Mach 6 phosphor data and laminar and turbulent solutions generated using the LAURA, GASP, and LATCH CFD codes on the X-34 configuration. The phosphor process outlined is believed to provide the aerothermodynamic community with a valuable capability for rapidly obtaining (three to four weeks) detailed heating information needed in TPS design. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div,Res & Technol Grp, Hampton, VA 23681 USA. RP Merski, NR (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div,Res & Technol Grp, Hampton, VA 23681 USA. NR 27 TC 39 Z9 39 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 160 EP 170 DI 10.2514/2.3446 PG 11 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500002 ER PT J AU Berry, SA Horvath, TJ DiFulvio, M Glass, C Merski, NR AF Berry, SA Horvath, TJ DiFulvio, M Glass, C Merski, NR TI X-34 experimental aeroheating at Mach 6 and 10 SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID ORBITER AB Critical technologies are being developed to support the goals of the NASA Office of Aeronautics and Space Transportation Technology Access to Space initiative for next-generation reusable space transportation systems. From the perspective of aerothermodynamic performance throughout the flight trajectory, the reusable launch vehicle program incorporates conceptual analysis, ground-based testing, and computational fluid dynamics to provide flyable suborbital flight demonstrator vehicles. An overview is provided of the hypersonic aeroheating wind-tunnel test program conducted at the NASA Langley Research Center in support of one of these vehicles, the X-34 small reusable technology demonstrator program. Global surface heat transfer images, surface streamline patterns, and shock shapes were measured on 0.0153- and 0.0183-scale models of proposed X-34 flight vehicles at Mach 6 and 10 in air. The primary parametrics that were investigated include angles of attack from 0 to 35 deg and freestream unit Reynolds numbers from 0.5 x 10(6) to 8 X 10(6)/ft (which was sufficient to produce laminar, transitional, and turbulent heating data), both with and without control-surface deflections. Comparisons of the experimental data to computational predictions are included, along with a discussion of the implications of some of the experimental flow features for the flight vehicle. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. RP Berry, SA (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. NR 26 TC 16 Z9 16 U1 2 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 171 EP 178 DI 10.2514/2.3447 PG 8 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500003 ER PT J AU Kleb, WL Wood, WA Gnoffo, PA Alter, SJ AF Kleb, WL Wood, WA Gnoffo, PA Alter, SJ TI Computational aeroheating predictions for X-34 SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID NASA; SCHEMES AB Radiative equilibrium surface temperatures, heating rates, streamlines, surface pressures, and flowfield features as predicted by the LAURA are presented for the X-34 Technology Demonstrator. Results for two trajectory points corresponding to entry peak heating and two control-surface deflections are discussed in detail, outlining the effects of the boundary-layer state and various flow features on the heat transfer rates and corresponding wall temperatures. These data are also discussed in the context of thermal protection system design issues, indicating that only minor changes needed to be made to the existing layout. The work presented is part of a larger effort to define the X-34 aerothermal environment, including the application of engineering codes and wind-tunnel studies. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div,Res & Technol Grp, Hampton, VA 23681 USA. Lockheed Engn & Sci Co, Aerothermodynam Branch, Aero & Gasdynam Div, Res & Technol Grp, Hampton, VA 23681 USA. RP Kleb, WL (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div,Res & Technol Grp, Hampton, VA 23681 USA. NR 48 TC 10 Z9 13 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 179 EP 188 DI 10.2514/2.3448 PG 10 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500004 ER PT J AU Milos, FS Squire, TH AF Milos, FS Squire, TH TI Thermostructural analysis of X-34 wing leading-edge tile thermal protection system SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Finite element thermal and stress analyses are presented for ceramic tiles, assemblies, and arcjet models relevant to the thermal protection system for the X-34 wing leading edge. The analyses are performed to verify thermal and structural models for silicone impregnated reusable ceramic ablator, to establish a failure criterion for stressed tiles, to simulate the response of the wing leading-edge thermal protection system under flight aerothermal and mechanical loads, and to confirm that the design has adequate safety margins. The final design with 0.04-in. intertile gaps is found to meet all thermal and structural requirements. C1 NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, ELORET Thermosci Inst, Moffett Field, CA 94035 USA. RP Milos, FS (reprint author), NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. NR 9 TC 5 Z9 8 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 189 EP 198 DI 10.2514/2.3449 PG 10 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500005 ER PT J AU Palmer, G Polsky, S AF Palmer, G Polsky, S TI Heating analysis of the nosecap and leading edges of the X-34 vehicle SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Temperature, pressure, and heating rates were computed on the surface of the X-34 vehicle at six points along the X1004701 Mach 8.5 trajectory The work focused on the nosecap, the wing/strake leading edges, and the rudder leading edge. These areas are protected from the thermal environments experienced during flight by silicone impregnated reusable ceramic ablator tiles. The computational data provided anchor points from which a time history of surface heating and pressure could be generated. This time history will be used to analyze and design the tiles. The Navier-Stokes solutions were compared with experimental data and engineering correlations. Bow-shock wave impingement on the wing leading edge was investigated. The location of impingement was a function of freestream Mach number and vehicle angle of attack. There was no bow-shock wave impingement seen on the rudder leading edge. A detailed grid sensitivity study was undertaken to establish an acceptable level of grid independence of the computed solutions. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Thermosci Inst, Sunnyvale, CA 94087 USA. RP Palmer, G (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 20 TC 6 Z9 7 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 199 EP 205 DI 10.2514/2.3450 PG 7 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500006 ER PT J AU Riley, CJ Kleb, WL Alter, SJ AF Riley, CJ Kleb, WL Alter, SJ TI Aeroheating predictions for X-34 using an inviscid boundary-layer method SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID UPPER RELAXATION METHOD; STAGE-TO-ORBIT; SCHEMES; VEHICLE; SPEEDS; FLOWS; NASA AB Radiative equilibrium surface temperatures and surface heating rates from a combined inviscid boundary-layer method are presented for the X-34 reusable launch vehicle for several points along the hypersonic descent portion of its trajectory. Inviscid, perfect-gas solutions are generated with the LAURA and the DPLUR codes. Surface temperatures and heating rates are then computed using the LATCH engineering code employing both laminar and turbulent Row models. The combined inviscid boundary-layer method provides accurate predictions of surface temperatures over most of the vehicle and requires much less computational effort than a Navier-Stokes code. This engineering method enables the generation of a more thorough aerothermal database, which is necessary to design the thermal protection system and specify the vehicle's flight limits. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. Lockheed Engn & Sci Co, Hampton, VA 23681 USA. RP Riley, CJ (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. NR 36 TC 8 Z9 9 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 206 EP 215 DI 10.2514/2.3451 PG 10 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500007 ER PT J AU Wurster, KE Riley, CJ Zoby, EV AF Wurster, KE Riley, CJ Zoby, EV TI Engineering aerothermal analysis for X-34 thermal protection system design SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID UPPER RELAXATION METHOD; FLOWFIELD; FLOWS; HL-20 AB Design of the thermal protection system for any hypersonic flight vehicle requires determination of both the peak temperatures over the surface and the heating-rate history along the flight profile, The process used to generate the time-dependent aerothermal environments for design of the X-34 thermal protection system is described. The process evolved from a relatively simplistic approach based solely on engineering methods applied to critical areas to an integrated approach using ground-test data with detailed computational and engineering methods to predict the aeroheating over the entire vehicle. A brief description of the trajectory development leading to the selection of the thermal protection system design trajectory is included. Comparisons of engineering heating predictions with wind-tunnel test data and with results obtained using a Navier-Stokes flowfield code and an inviscid/boundary-layer method are Shown. Good agreement is demonstrated among all of these methods for both the ground-test condition and the peak heating flight condition. C1 NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. RP Wurster, KE (reprint author), NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. NR 39 TC 18 Z9 18 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 216 EP 228 DI 10.2514/2.3452 PG 13 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500008 ER PT J AU Brauckmann, GJ AF Brauckmann, GJ TI X-34 vehicle aerodynamic characteristics SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The X-34, being designed and built by the Orbital Sciences Corporation, is an unmanned suborbital vehicle designed to be used as a flying test bed to demonstrate key vehicle and operational technologies applicable to future reusable launch vehicles. The X-34 will be air-launched from an L-1011 carrier aircraft, where an onboard engine will then accelerate the vehicle to speeds above Mach 7 and altitudes to 250,000 ft. An unpowered entry will follow, including an autonomous landing. A series of wind-tunnel tests on scaled models was conducted in four facilities at the NASA Langley Research Center to determine the aerodynamic characteristics of the X-34. Analysis of these test results revealed that longitudinal trim could be achieved throughout the design trajectory. Longitudinal control effectiveness (elevon, body flap) decreased for Mach numbers greater than one and was nonlinear in the transonic regime. In addition, there was a loss in eleven effectiveness for the largest negative deflection. The rudder effectiveness (of the all-moving vertical tail) decreased for supersonic Mach numbers and with increasing angle of attack, so that at combined high supersonic Mach numbers and high angles of attack the use of reaction control jets may be required. Deployment of the landing gear reduced the eleven effectiveness by 5% and destabilized the vehicle directionally. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. RP Brauckmann, GJ (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. NR 5 TC 11 Z9 14 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 229 EP 239 DI 10.2514/2.3453 PG 11 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500009 ER PT J AU Polites, ME AF Polites, ME TI Technology of automated rendezvous and capture in space SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Results are presented of a study into the technology:of automated rendezvous and capture (ARC) in space. The history of manual and automated rendezvous and capture and rendezvous and dock is presented. The need for ARC in space is defined. Today's technology and ongoing technology efforts related to ARC in space are reviewed. In light of these, ARC systems are proposed that meet the future needs for ARC, but that can be developed in a reasonable amount of time with a reasonable amount of money. Technology plans for developing these systems are presented; cost and schedule are included. C1 NASA, George C Marshall Space Flight Ctr, Astrion Lab, Huntsville, AL 35812 USA. RP Polites, ME (reprint author), NASA, George C Marshall Space Flight Ctr, Astrion Lab, Huntsville, AL 35812 USA. NR 56 TC 48 Z9 56 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1999 VL 36 IS 2 BP 280 EP 291 DI 10.2514/2.3443 PG 12 WC Engineering, Aerospace SC Engineering GA 184TA UT WOS:000079628500015 ER PT J AU Riddell, WT Piascik, RS AF Riddell, WT Piascik, RS TI A back-faced strain compliance expression for the compact tension specimen SO JOURNAL OF TESTING AND EVALUATION LA English DT Article DE compact tension specimen; back-faced strain compliance; crack length ID CRACK AB A numerically generated expression to determine crack length in a compact tension specimen from back-faced strain compliance is presented. The numerically generated back-faced strain expression is bounded by two experimentally determined expressions previously published in the literature. Additionally, stress intensity factor and crack-mouth opening expressions are determined. These expressions agree well with previously published results. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Riddell, WT (reprint author), US DOT, Volpe Ctr, DTS-76,Kendall Sq, Cambridge, MA 02142 USA. NR 9 TC 1 Z9 1 U1 0 U2 0 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 USA SN 0090-3973 J9 J TEST EVAL JI J. Test. Eval. PD MAR PY 1999 VL 27 IS 2 BP 167 EP 170 PG 4 WC Materials Science, Characterization & Testing SC Materials Science GA 287YN UT WOS:000085535200013 ER PT J AU Zhang, CD Chou, MD AF Zhang, CD Chou, MD TI Variability of water vapor, infrared radiative cooling, and atmospheric instability for deep convection in the equatorial western Pacific SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID TOGA-COARE; RESPONSE EXPERIMENT; SCALE CIRCULATION; WARM POOL; HUMIDITY; PROFILES; OSCILLATION; TROPOSPHERE; DIVERGENCE; MOISTURE AB In the troposphere of the equatorial western Pacific, the water vapor variability dominates the temperature variability in changing the clear-sky infrared (IR) cooling rate. The large water vapor variability, especially its bimodal distribution at certain levels of the upper troposphere, leads to distinct structures of the clear-sky IR radiative cooling rate. The IR cooling rate, its maximum normally in the upper troposphere (similar to 300 hPa) and minimum in the lower troposphere (similar to 650 hPa), tends to become vertically uniform when the upper troposphere is abnormally dry. A local, maximum IR cooling rate may occur in the boundary layer when the lower troposphere becomes extraordinarily dry. The changes in IF: cooling due to the water vapor variability affect the rate of generation of convective available potential energy (CAPE) and the conditional instability for deep convection. Little or no mean rainfall over an area of roughly 3 X 10(5) km(2) is observed when either the rate of generation of CAFE suffers from a reduction (magnitude of 50 J kg(-1) day(-1)) or IR cooling decreases with height. The observed variability of water vapor results from both local vertical processes and the large-scale horizontal circulation. Horizontal advection accounts for a large fraction of the drying that is responsible for the changes in the IR cooling profile and in the atmospheric instability for deep convection. These results suggest that interactions among water vapor, radiation, and deep convection must be assessed by fully taking the large-scale circulation into consideration. This study is based on an analysis of upper-air soundings collected during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment Intensive Observing Period and calculations of a radiative transfer model. C1 Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Div Meteorol & Phys Oceanog, Miami, FL 33149 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Zhang, CD (reprint author), 4600 Rickenbacker Causeway,MPO, Miami, FL 33149 USA. EM czhang@rsmas.miami.edu NR 41 TC 21 Z9 21 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD MAR 1 PY 1999 VL 56 IS 5 BP 711 EP 723 DI 10.1175/1520-0469(1999)056<0711:VOWVIR>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 170LW UT WOS:000078808000003 ER PT J AU Aveni, GJ AF Aveni, GJ TI Contamination control for the earth observing system (EOS) Multi-Angle Imaging Spectro-Radiometer (MISR) SO JOURNAL OF THE IEST LA English DT Article DE earth observing system (EOS); multi-angle imaging spectro-radiometer (MISR) molecular contamination; particulate contamination; nonvolatile residue; signal throughput degradation; transport factors AB The contamination control activity performed for the Multi-Angle Imaging Spectro-Radiometer (MISR) consisted of an overall system analysis for susceptibility to molecular and particulate contamination from both internal and external sources at the most sensitive sensor wavelength. This analysis considered the system long and short-term radiometric stability requirements, the expected sources of contaminants, the transport of those contaminants to the sensors, and the expected effects. of those contaminants on sensitive surfaces. The derived requirements, including specific budgets, and a plan to meet them during assembly, test, and storage, were documented in the EOS MISR Contamination Control Plan. The final phase of control came from monitoring the hardware (recording data and implementing cleaning procedures) during assembly and thermal vacuum testing prior to shipment to the EOS integrator. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Aveni, GJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 13 TC 0 Z9 0 U1 1 U2 1 PU INST ENVIRONMENTAL SCI TECHNOLOGY PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 USA SN 1052-2883 J9 J IEST JI J. IEST PD MAR-APR PY 1999 VL 42 IS 2 BP 32 EP 39 PG 8 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA 187QF UT WOS:000079797700003 ER PT J AU Koster, RD Oki, T Suarez, MJ AF Koster, RD Oki, T Suarez, MJ TI The offline validation of land surface models: Assessing success at the annual timescale SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID ANNUAL WATER-BALANCE; SOIL-MOISTURE; CLIMATE; VARIABILITY; DROUGHT; STORAGE AB The annual runoff rates generated by land surface models (LSMs) participating in the Global Soil Wetness Project (GSWP) are compared to observed rates in well-instrumented basins across the globe. Because such an offline evaluation can be clouded by an overwhelming influence of the atmospheric forcing itself (relative to the imposed land surface physics) on model output, we also estimate runoff rates with a decades-old climatological relation devised by M.I. Budyko, a relation that depends solely on annual precipitation and net radiation. The LSMs and the estimates derived with Budyko's relation are found to have standard errors of the same order (roughly 100 mm/yr). Thus, we conclude that the complexities inherent in these state-of-the-art LSMs did not lead to increased accuracy in the simulated energy and water balances at the annual time scale. Proper LSM formulations are nevertheless recognized as essential for realistic land surface behavior at shorter (e.g., monthly or hourly) time scales, for which a simple Budyko-type equation would be in much greater error. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Univ Tokyo, Inst Ind Sci, Tokyo, Japan. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Koster, RD (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. EM randal.koster@gsfc.nasa.gov RI Oki, Taikan/E-5778-2010; Koster, Randal/F-5881-2012 OI Oki, Taikan/0000-0003-4067-4678; Koster, Randal/0000-0001-6418-6383 NR 17 TC 12 Z9 12 U1 0 U2 2 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 MAR PY 1999 VL 77 IS 1B BP 257 EP 263 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 232DU UT WOS:000082351300007 ER PT J AU Boone, A Wetzel, PJ AF Boone, A Wetzel, PJ TI A simple scheme for modeling sub-grid soil texture variability for use in an atmospheric climate model SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID SURFACE PARAMETERIZATION SCHEMES; GENERAL-CIRCULATION MODELS; HETEROGENEOUS LAND; MOISTURE; EVAPOTRANSPIRATION; HYDROLOGY; PROJECT; IMPACT; TRANSPIRATION; SIMULATIONS AB On global atmospheric climate model spatial scales, water budget variables (evapotranspiration, soil moisture and runoff) can vary nonlinearly within a typical grid box primarily due to soil moisture heterogeneity. A good deal of this variability results from subgrid variability of soil texture. For such scales, consideration of the variability of the parameters used to characterize the soil hydrology is warranted. A simple approach, amenable to climate modeling, for characterizing subgrid soil parameter variability is proposed in which several parallel noninteracting soil columns are configured beneath a single soil/vegetation surface. The hydrological parameter mean values and statistical moments, which must be defined for each column, are generated using simple regression relationships which relate the parameters to the grid box mean soil texture (sand and clay composition). This simple approach is used because subgrid heterogeneity parameter data is somewhat limited on a global scale. The Parameterization for Land-Atmosphere-Cloud Exchange (PLACE) model is used within the Global Soil Wetness Project (GSWP) experimental design to generate global soil moisture fields using the soil heterogeneity model. Grid box average evapotranspiration (used in the solution of the surface energy budget), soil moisture, and runoff represent the three soil columns surface-weighted totals: Results show a profound effect on the primary water budget variables due to consideration of the parameter variability: globally-averaged evapotranspiration is reduced by 17 %, and total runoff is increased by 48 % compared to a control run assuming a homogeneous soil texture distribution within each grid box. The global mean runoff ratio is increased by 12 %. Soil wetness (SW) increases by 19 %, while the soil wetness index (SWI) increases by 49 %. it is suggested that future land-surface global data sets contain information regarding subgrid variability of the soil for further testing of methods for modeling sub-grid heterogeneity. C1 Meteo Franch, CNRM, GMME, MC2, F-31057 Toulouse, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Boone, A (reprint author), Meteo Franch, CNRM, GMME, MC2, 42 Ave Coriolis, F-31057 Toulouse, France. EM boone@cnrm.meteo.fr NR 50 TC 10 Z9 10 U1 0 U2 1 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 MAR PY 1999 VL 77 IS 1B BP 317 EP 333 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 232DU UT WOS:000082351300012 ER PT J AU Sud, YC Mocko, DM AF Sud, YC Mocko, DM TI New snow-physics to complement SSiB part I: Design and evaluation with ISLSCP initiative I datasets SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID GENERAL-CIRCULATION MODELS; MIDLATITUDE SOIL-MOISTURE; FRANCE CLIMATE MODEL; LAND-SURFACE SCHEME; METEOROLOGICAL OBSERVATIONS; BUCKET MODELS; SIMULATIONS; VALIDATION; BIOSPHERE; PARAMETERIZATION AB In evaluation(s) as a part of the Global Soil Wetness Project using ISLSCP Initiative-I data, the snowmelt in SSiB in the Russian Wheat Belt region (RWB) was found to be substantially delayed, with very deficient meltwater infiltration as compared to observations. Furthermore, most of the meltwater emerged as runoff, as opposed to soil moisture recharge. The deficiency emanated from the crudeness of snow-physics of the combined snow and ground layer of SSiB. In the current work, a new snow model employing a separate snow-laver was included. The snow-pack absorbs and transmits the incoming solar flux, thereby affecting the snow and ground temperatures through the winter and snow-melt periods. In the ISLSCP Initiative-I data evaluations, the snow-melt over the RWB region occurs 2-3 weeks sooner in the new model, and its soil thaws quite early in the snow-melt duration, which helps to infiltrate more meltwater into the soil. The new-model produces a more realistic simulation of soil-moisture, as well as Volga river runoff in RWB evaluations. Some residual delay in the snow-melt (varying from 1-4 weeks) seems to be related to the following: (1) inaccuracies in the satellite retrievals of snow under dense forest canopies; (2) the modeling assumptions, e.g., neglecting the influence of snow aging on its thermal diffusivity, and simplifications in absorption of solar-flux in the snow cover, leading to an inadequate distinction between snow-pack surface and mean temperatures; and, (3) possible cold bias of the ISLSCP surface air temperature data. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Sud, YC (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. EM sud@climate.gsfc.nasa.gov NR 29 TC 21 Z9 24 U1 5 U2 6 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 MAR PY 1999 VL 77 IS 1B BP 335 EP 348 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 232DU UT WOS:000082351300013 ER PT J AU Mocko, DM Walker, GK Sud, YC AF Mocko, DM Walker, GK Sud, YC TI New snow-physics to complement SSiB part II: Effects on soil moisture initialization and simulated surface fluxes, precipitation and hydrology of GEOS II GCM SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID LAND-SURFACE; METEOROLOGICAL OBSERVATIONS; BUCKET MODELS; BIOSPHERE; CLIMATOLOGY; PROJECT; MONSOON; AMIP AB The SSiB model, which was forced with GSWP ISLSCP Initiative I surface data, was modified to include more realistic snow physics and snow-melt infiltration. The new snow model in SSiB was again integrated with the GSWP data. The new SSiB simulation produced wetter and warmer soil, with more realistic snow-melt timing and runoff, in regions of significant snow-melt. The simulation was used for initializing land-surface temperature, soil moisture, and snow cover for the GEOS II GCM, which was integrated for JJA to generate an ensemble of runs for both 1987 and 1988. Each ensemble contained six cases starting from an ECMWF analysis for each day starting from 29 May through 3 June of each year. As compared to the old SSiB GCM, the new SSiB GCM with new initial hydrologic conditions significantly improved the prediction of precipitation in mid-to-high-latitude regions of Canada and Russia. Evapotranspiration, soil moisture, and runoff also compared more favorably in the new SSiB GCM simulation than the old SSiB GCM. Also, the 1988-1987 difference in northern India precipitation was more pronounced in the new SSiB GCM. In the U.S., where the old SSiB GCM had failed to simulate the 1988 drought circulation, the new SSiB GCM performed only slightly better. This was also evident in the 1988-1987 differences. In this region, the influence of initial conditions was mostly lost in about one month's time to the evolution of an unrealistic circulation. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Mocko, DM (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. EM mocko@climate.gsfc.nasa.gov NR 33 TC 8 Z9 9 U1 5 U2 6 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 MAR PY 1999 VL 77 IS 1B BP 349 EP 366 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 232DU UT WOS:000082351300014 ER PT J AU Beard, BL Ahumada, AJ AF Beard, BL Ahumada, AJ TI Detection in fixed and random noise in foveal and parafoveal vision explained by template learning SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article; Proceedings Paper CT Annual Meeting of the Optical-Society-of-America CY OCT 04-09, 1998 CL BALTIMORE, MARYLAND SP Opt Soc Amer ID CONTRAST GAIN-CONTROL; DISCRIMINATION; MASKING; MODEL; PERFORMANCE; BACKGROUNDS; RECOGNITION AB Foveal and parafoveal contrast detection thresholds for Gabor and checkerboard targets were measured in white noise by means of a two-interval forced-choice paradigm. Two white-noise conditions were used: fixed and twin. In the fixed noise condition a single noise sample was presented in both intervals of all the trials. In the twin noise condition the same noise sample was used in the two intervals of a trial, but a new sample was generated for each trial. Fixed noise conditions usually resulted in lower thresholds than twin noise. Template learning models are presented that attribute this advantage of fixed over twin noise either to fixed memory templates' reducing uncertainty by incorporation of the noise or to the introduction, by the learning process itself, of more variability in the twin noise condition. Quantitative predictions of the template learning process show that it contributes to the accelerating nonlinear increase in performance with signal amplitude at low signal-to-noise ratios. (C) 1999 Optical Society of America [S0740-3232(99)00803-0]. C1 NASA, Ames Res Ctr, Human Informat Proc Res Branch, Stanford, CA 94305 USA. RP Beard, BL (reprint author), NASA, Ames Res Ctr, Human Informat Proc Res Branch, Stanford, CA 94305 USA. NR 28 TC 27 Z9 27 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD MAR PY 1999 VL 16 IS 3 BP 755 EP 763 DI 10.1364/JOSAA.16.000755 PG 9 WC Optics SC Optics GA 170AQ UT WOS:000078783300035 PM 10069061 ER PT J AU Srivastava, D Halicioglu, T Schoolcraft, TA AF Srivastava, D Halicioglu, T Schoolcraft, TA TI Fluorination of Si(001)-2x1 surface near step edges: A mechanism for surface defect induced etching SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article ID SCANNING TUNNELING MICROSCOPY; MOLECULAR-DYNAMICS; GROWTH; SIMULATIONS; SI(100); FILMS AB Fluorination of a dimerized Si(001)-2x1 surface near single-layer high step edges has been studied with molecular statics and dynamics simulations using the Stillinger-Weber potential for Si-Si, Si-F, and F-F interactions. Binding energies for up to three F atoms on Si atoms at the step edges have been investigated for fully relaxed; systems. We find that F-bonded Si atoms relax away from the surface with increasing fluorination which lowers the desorption/etching energies of SiFx(x = 1,3) species. Room temperature molecular dynamics simulations then show direct etching of SiF3 from Si atoms bonded to step edges. The calculations predict an anisotropy in the step edge induced etching of the Si(001)-2x1 surface. This is in qualitative agreement with an experimental observation on the same surface though using Cl instead of F atoms. (C) 1999 American Vacuum Society. [S0734-2101(99)04002-6]. C1 NASA, Ames Res Ctr, IT Modeling & Simulat Grp, NAS,MRJ, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Eloret Inst, Moffett Field, CA 94035 USA. RP Srivastava, D (reprint author), NASA, Ames Res Ctr, IT Modeling & Simulat Grp, NAS,MRJ, MS T27A-1, Moffett Field, CA 94035 USA. NR 23 TC 10 Z9 10 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD MAR-APR PY 1999 VL 17 IS 2 BP 657 EP 661 DI 10.1116/1.581633 PG 5 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 177GX UT WOS:000079203200050 ER PT J AU Menzies, T AF Menzies, T TI Knowledge maintenance: the state of the art SO KNOWLEDGE ENGINEERING REVIEW LA English DT Review ID PROBLEM-SOLVING METHODS; SYSTEMS; ABDUCTION; ACQUISITION; LEVEL; CLASSIFICATION; SPECIFICATIONS AB In the software and knowledge engineering literature we can find maintenance strategies offered to maintain seven main types of knowledge: words; sentences; behavioral knowledge; and meta-knowledge. Meta-knowledge divides into problem solving methods, quality knowledge,fix knowledge, social knowledge and processing activities. There are five main ways in which these seven knowledge types are processed: acquire, operationalise, fault, fix and preserve. We review systems that contribute to these 7 * 5 = 35 types of knowledge maintenance to make the following conclusions. First, open issues with the current maintenance research are identified. These include (a) areas that are not being addressed by any researcher; (b) the recursive maintenance problem; and (c) drawbacks with rapid acquire systems and the operationalisation KM assumption. Secondly, a process is described for commissioning a new maintenance tool. Thirdly, a general common principle for maintenance (search-space reflection) is isolated. C1 NASA WVU Software Res Lab, Morgantown, WV 26505 USA. RP Menzies, T (reprint author), NASA WVU Software Res Lab, 100 Univ Dr, Morgantown, WV 26505 USA. EM tim@menzies.com NR 158 TC 17 Z9 17 U1 0 U2 1 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0269-8889 J9 KNOWL ENG REV JI Knowl. Eng. Rev. PD MAR PY 1999 VL 14 IS 1 BP 1 EP 46 DI 10.1017/S0269888999134052 PG 46 WC Computer Science, Artificial Intelligence SC Computer Science GA 191YG UT WOS:000080049300001 ER PT J AU LeBlanc, A Lin, C Evans, H Shackelford, L Martin, C Hedrick, T AF LeBlanc, A Lin, C Evans, H Shackelford, L Martin, C Hedrick, T TI T-2 vertebral bone marrow changes after space flight SO MAGNETIC RESONANCE IN MEDICINE LA English DT Article DE magnetic resonance imaging; volume-localized magnetic resonance spectroscopy; immobilization; microgravity ID DISUSE OSTEOPOROSIS; CALCIUM HOMEOSTASIS; TRABECULAR BONE; SPECTROSCOPY; CELLS AB Bone biopsies indicate that during immobilization bone marrow adipose tissue increases while the functional cellular fraction decreases. One objective of our Spacelab flight experiment was to determine, using in vivo volume-localized magnetic resonance spectroscopy (VLMRS), whether bone marrow composition was altered by space flight. Four crew members of a 17 day Spacelab mission participated in the experiment. The apparent cellular fraction and transverse relaxation time (T-2) were determined twice before launch and at several times after flight. Immediately after flight, no significant change in the cellular fraction was found. However, the T-2 Of the cellular, but not the fat component increased following flight, although to a variable extent, in all crew members with a time course for return to baseline lasting several months. The T-2 Of seven control subjects showed no significant change. Although these observations may have several explanations, it is speculated that the observed T-2 changes might reflect increased marrow osteoblastic activity during recovery from space flight. Magn Reson Med 41:495-498, 1999. (C) 1999 Wiley-Liss, Inc. C1 Baylor Coll Med, Dept Med, Houston, TX 77030 USA. Lyndon B Johnson Space Ctr, Houston, TX USA. Baylor Coll Med, Dept Radiol, Houston, TX 77030 USA. RP LeBlanc, A (reprint author), 6501 Fannin Mail Code NB1-004, Houston, TX 77030 USA. EM aleblanc@bcm.tmc.edu NR 25 TC 6 Z9 6 U1 0 U2 0 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0740-3194 J9 MAGNET RESON MED JI Magn. Reson. Med. PD MAR PY 1999 VL 41 IS 3 BP 495 EP 498 DI 10.1002/(SICI)1522-2594(199903)41:3<495::AID-MRM11>3.0.CO;2-V PG 4 WC Radiology, Nuclear Medicine & Medical Imaging SC Radiology, Nuclear Medicine & Medical Imaging GA 179GH UT WOS:000079317800011 PM 10204872 ER PT J AU Carlson, HR Pfister, CA AF Carlson, HR Pfister, CA TI A seventeen-year study of the rose star Crossaster papposus population in a coastal bay in southeast Alaska SO MARINE BIOLOGY LA English DT Article ID LIFE-HISTORIES; INTERTIDAL COMMUNITY; DYNAMICS; RECRUITMENT; DISTURBANCE; SUCCESSION; DEMOGRAPHY; MORTALITY; PATTERNS; GROWTH AB A 17 yr study of a population of the rose star Crossaster papposus (Linnaeus, 1767) in Auke Bay, near Juneau, Alaska, used SCUBA to follow a total of 956 individually marked stars. Population density was relatively constant over the 17 yr of study, although the influx of smaller individuals varied by an order of magnitude. Growth in diameter of individual stars was inversely related to size, with the largest individuals showing negligible growth for periods of months or years. Annual survivorship was relatively high (from 76.3 to 90.4%), and some individuals persisted throughout the study, indicating longevities of at least 20 yr in this species. Observations of food habits indicated that the principal prey item is the reddish scallop Chlamys rubida. In summary, this rose star population was characterized by a relatively stable number of long-lived, slow-growing individuals. C1 NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. Univ Chicago, Dept Ecol & Evolut, Chicago, IL 60637 USA. RP Carlson, HR (reprint author), NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 52 TC 8 Z9 8 U1 0 U2 5 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0025-3162 J9 MAR BIOL JI Mar. Biol. PD MAR PY 1999 VL 133 IS 2 BP 223 EP 230 DI 10.1007/s002270050461 PG 8 WC Marine & Freshwater Biology SC Marine & Freshwater Biology GA 178ML UT WOS:000079269700006 ER PT J AU Bar-Cohen, Y Backes, PG AF Bar-Cohen, Y Backes, PG TI Scanning aircraft structures using open-architecture robotic crawlers as platforms with NDT boards and sensors SO MATERIALS EVALUATION LA English DT Article AB Rapid inspection of large areas has been an ongoing challenge to the nondestructive testing (NDT) profession. The need for such a capability has grown significantly in recent years as a result of the increase in the numbers of aging aircraft in service and of aircraft with composite primary structures. While aging aircraft with metallic structures are most susceptible to corrosion and cracking near fastener areas, composites are susceptible to impact damage that can appear anywhere on the structure. Field inspection using manual scanning is labor intensive, time consuming, and subject to human error, whereas removal of parts from an aircraft for a lab test is costly and may be impractical. Effective field inspection requires a portable, user friendly system that can rapidly scan large areas of complex structures. In recent yeats, various portable inspection systems have emerged, including scanners that are placed at selected locations and sequentially repositioned to cover all the areas of interest. The development of such systems has followed the evolution of the relevant technology, and has required integration of multidisciplinary expertise including NDT, telerobotics, neural networks, automated control, embedded computing, and materials science. The trend has been towards full automation; the desideratum is for completely autonomous inspection capability. Recently, the Jet Propulsion Laboratory (JPL) has developed the multifunction automated crawling system (MACS), which offers an open-architecture robotic platform for NDT boards and sensors. This crawler established the formations for the development of a "walking" computer platform with standard plug-in NDT boards. This capability will allow a larger pool of companies and individuals to become potential producers of NDT instruments. Thus, a significant cost reduction can be realized with a rapid transition from novel concepts to practical use. The capability and potential of MACS as an enabling technology will be discussed in this paper C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bar-Cohen, Y (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,82-105, Pasadena, CA 91109 USA. NR 10 TC 6 Z9 6 U1 0 U2 2 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 USA SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD MAR PY 1999 VL 57 IS 3 BP 361 EP 366 PG 6 WC Materials Science, Characterization & Testing SC Materials Science GA 176YU UT WOS:000079180600005 ER PT J AU Kitabjian, PH Garg, A Noebe, RD Nix, WD AF Kitabjian, PH Garg, A Noebe, RD Nix, WD TI High-temperature deformation behavior of NiAl(Ti) solid-solution single crystals SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID NIAL/NI2ALTI ALLOYS; PHASE AB The high-temperature deformation behavior of the solid solution-strengthened alloys Ni-47.5Al-2.5Ti and Ni-47Al-3Ti were investigated. Single crystals were deformed in compression in the "hard" [001] and "soft" [111] orientations, at temperatures between 827 degrees C and 1250 degrees C. The results show that Ti has a very powerful solute-strengthening effect in NiAl. The creep rates for the solid-solution alloys were observed to be as much as three to four orders of magnitude lower than those for unalloyed NiAl. To better understand this strong solid-solution strengthening effect, we studied the stress and temperature dependence of the creep rates for these alloys, as well as the deformation transients associated with stress changes. These results suggest that solute-drag effects dominate the creep resistance at the highest temperatures and lowest stresses. The solute-drag hypothesis is supported by calculations of the solute-size effect of Ti in NiAl and by the form of dislocation substructures found in the creep-deformed crystals. C1 Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA. NASA, Lewis Res Ctr, Adv Met Branch, Cleveland, OH 44135 USA. RP Kitabjian, PH (reprint author), Appl Mat Inc, Santa Clara, CA 95054 USA. NR 26 TC 23 Z9 23 U1 0 U2 2 PU SPRINGER PI NEW YORK PA 233 SPRING STREET, NEW YORK, NY 10013 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD MAR PY 1999 VL 30 IS 3 BP 587 EP 600 DI 10.1007/s11661-999-0050-8 PG 14 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 171MX UT WOS:000078868700010 ER PT J AU Welten, KC AF Welten, KC TI Concentrations of siderophile elements in nonmagnetic fractions of Antarctic H- and L-chondrites: A quantitative approach on weathering effects SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID NATURAL THERMOLUMINESCENCE; METEORITE COLLECTION; SITES AB The nonmagnetic separates of Antarctic H- and L-chondrite finds from the Lewis Cliff stranding area are enriched in Fe and siderophile elements such as Ni, Co, Cu, As, Ir, and Au, relative to those of non-Antarctic falls. The siderophile enrichments are caused by the oxidation of metallic Fe-Ni to nonmagnetic hydrous Fe-Ni oxides. The concentrations of Fe, Ni, and Co in each sample were used to calculate the amount of oxidized metal, which serves as a quantitative measure of the degree of weathering. The amount of oxidized metal is generally between 1-10 wt% and shows a rough correlation with the qualitative A-B-C-weathering classification for increasing rustiness. No clear correlation was found between weathering and terrestrial age, although meteorites older than 0.2 Ma contain on the average similar to 50% more oxidized metal. Also, no correlation was found between the degree of weathering and the natural thermoluminescence (TL) level, which is dominated by the thermal history in space rather than by the thermal history in or on the Antarctic ice. The only significant parameter for the degree of weathering seems to be the location of find, with the most weathered specimens being found in a part of the stranding area where melt-water ponds are known to occur. This observation confirms that the occasional presence of liquid water plays an important role in the Antarctic weathering process and explains the poor correlation of the degree of weathering of Antarctic meteorites with terrestrial age and surface exposure age. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Welten, KC (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NR 33 TC 14 Z9 14 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 1999 VL 34 IS 2 BP 259 EP 270 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 180LM UT WOS:000079387500009 ER PT J AU Olsen, EJ Kracher, A Davis, AM Steele, IM Hutcheon, ID Bunch, TE AF Olsen, EJ Kracher, A Davis, AM Steele, IM Hutcheon, ID Bunch, TE TI The phosphates of IIIAB iron meteorites SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID CORE AB Thirteen phosphate minerals are found in IIIAB iron meteorites. Four of these (sarcopside, graftonite, johnsomervilleite, and galileiite) constitute the majority of occurrences. The IIIB iron meteorites are confined to occurrences of only these four phosphates. The IIIA iron meteorites may contain one or more of these four phases; they may also contain other rarer phosphates, and silica tin two instances) and a silicate rock tin one instance). Thus, the IIIA lithophile chemistry is more varied than that of the IIIB meteorites. Based on petrographic relations, sarcopside appears to be the first phosphate to form. Graftonite is probably formed by recrystallization of sarcopside. Johnsomervilleite and galileiite exsolved as enclaves in sarcopside or graftonite at lower temperatures, although some of these also nucleated as separate crystals. The IIIAB phosphates are carriers of a group of incompatible lithophile elements: Fe, Mn, Na, Ca, and K, and, rarely, Mg as well as Pb. These elements land O) were concentrated in a residual, S-rich liquid during igneous fractional crystallization of the IIIAB core mass. The phosphates formed by oxidation of P as the core solidified and excluded O, which increased its partial pressure in the residual liquid. The trace siderophile trends in bulk IIIAB metal are paralleled by a mineralogical trend of the phosphate minerals that formed. For IIIAB meteorites with low-Ir contents in the metal, the phosphates are mainly Fe-Mn phases; at intermediate Ir values, more Na-bearing phosphates appear; at the highest Ir values, the rarer Na-, K-, Mg-, Cr-, and Pb-bearing phosphates appear. The absence of significant amounts of Mg, Si, Al, and Ti suggest depletion of these elements in the core by the overlying mantle. C1 Univ Chicago, Dept Geophys Sci, Chicago, IL 60637 USA. Iowa State Univ, Ames, IA 50011 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94551 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Olsen, EJ (reprint author), Univ Chicago, Dept Geophys Sci, 5734 S Ellis Ave, Chicago, IL 60637 USA. OI Davis, Andrew/0000-0001-7955-6236 NR 41 TC 19 Z9 20 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 1999 VL 34 IS 2 BP 285 EP 300 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 180LM UT WOS:000079387500011 ER PT J AU Rampino, MR Schwindt, DM AF Rampino, MR Schwindt, DM TI Comment on "The age of the Kara impact structure, Russia" by M. Trieloff et al. SO METEORITICS & PLANETARY SCIENCE LA English DT Editorial Material C1 NYU, Earth & Environm Sci Program, New York, NY 10003 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Rampino, MR (reprint author), NYU, Earth & Environm Sci Program, 100 Washington Sq E, New York, NY 10003 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 1999 VL 34 IS 2 BP 301 EP 301 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 180LM UT WOS:000079387500012 ER PT J AU Harper, GM Jordan, C Judge, PG Robinson, RD Carpenter, KG Brage, T AF Harper, GM Jordan, C Judge, PG Robinson, RD Carpenter, KG Brage, T TI Lines of O IV and S IV in the Goddard High-Resolution Spectrograph spectrum of RR Tel: constraints on atomic data SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE atomic data; binaries, symbiotic; stars, individual, RR Tel; ultraviolet, stars ID BORON-LIKE IONS; IMPACT EXCITATION; TRANSITIONS; ULTRAVIOLET; DIAGNOSTICS; TELESCOPII; EMISSION; RATIOS; XVI AB High signal-to-noise ratio spectra of RR Tel obtained at medium resolution with the Goddard High-Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST) are used to test available atomic data for the O IV 2s(2)2p P-2-2s2p(2) P-4 multiplet (UV 0.01). The fine-structure intervals of the 2s2p(2) P-4 term given by Moore (1983) appear to need revision. The flux ratios of lines within multiplet UV (0.01), which have a common upper level, depend only on transition probabilities. The observed flux ratio of lines from the P-4(3/2) level differs from that predicted by theory, but this difference cannot be attributed to a blend with a line of S IV]. At the electron densities in the RR Tel nebula, other flux ratios give information on the relative electron excitation rates between the P-2 and P-4 fine-structure levels. Using the collision strengths calculated by Zhang, Graziani & Pradhan, the rate to the P-4(5/2) level, relative to the rates to the other J states, appears to be underestimated by similar to 10 per cent, which is within the expected uncertainty of 20 per cent. We also discuss the S IV 3s(2)3p P-2-3s3p(2) P-4 multiplet. C1 Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Univ Oxford, Dept Phys Theoret Phys, Oxford OX1 3NP, England. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Lund, Dept Phys, S-22100 Lund, Sweden. RP Harper, GM (reprint author), Univ Colorado, Ctr Astrophys & Space Astron, Campus Box 391, Boulder, CO 80309 USA. RI Carpenter, Kenneth/D-4740-2012 NR 27 TC 17 Z9 17 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAR 1 PY 1999 VL 303 IS 3 BP L41 EP L46 DI 10.1046/j.1365-8711.1999.02392.x PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176LV UT WOS:000079153600002 ER PT J AU Kang, IS Ho, CH Lim, YK Lau, KM AF Kang, IS Ho, CH Lim, YK Lau, KM TI Principal modes of climatological seasonal and intraseasonal variations of the Asian summer monsoon SO MONTHLY WEATHER REVIEW LA English DT Article ID OUTGOING LONGWAVE RADIATION; SEA-SURFACE TEMPERATURE; WESTERN PACIFIC; NORTHERN SUMMER; CONVECTIVE ACTIVITY; SOUTHEAST-ASIA; EAST-ASIA; ISCCP; OSCILLATION AB Principal modes of climatological variation of the Asian summer monsoon are investigated. Data used in this study include the high cloud fraction produced by the International Satellite Cloud Climatology Project and sea level pressure, and 850- and 200-mb geopotential heights from ECMWF analysis for the five summers of 1985-89. It Is Shown that the seasonal evolution of me Asian summer monsoon is adequately described by a few leading EOFs, These EOFs capture the variations of regional rainbands over the East Asian and Indian regions. The first mode is characterized by an increase in large-scale cloud over India and the subtropical western Pacific until mid-August. The second mode depicts large-scale cloud variations associated with the East Asian rainband referred to as Mei Yu and Baiu. This mode is associated with the development of summer monsoon circulation: a low pressure system over the Asian continent and a subtropical high over the Pacific. The third eigenmode is characterized by zonal cloud hands from northern India crossing the Korean peninsula to Japan, aad dryness over the oceans in the south of cloud bands. This mode is related to the mature phase of Changma rainy season in Korea associated with the northward movement of cloud bands and circulation systems from the subtropical western Pacific. This mode appears as a first principal mode of climatological intraseasonal oscillation (CISO) over the entire Asian monsoon region. The CISO mode has a timescale of about 2 months. The northward moving CISO also appears in the 850- and 200-mb geopotential height fields as a first mode of each. dataset. Based on the height variations of the CISO mode, it is suggested that the extratropical CISO during summer is related to a regional index cycle associated with the variation of north-south temperature gradient in East Asia. C1 Seoul Natl Univ, Coll Nat Sci, Dept Atmospher Sci, Kwanak Ku, Seoul 151742, South Korea. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kang, IS (reprint author), Seoul Natl Univ, Coll Nat Sci, Dept Atmospher Sci, Kwanak Ku, Seoul 151742, South Korea. RI Ho, Chang-Hoi/H-8354-2015; Lau, William /E-1510-2012; 안, 민섭/D-9972-2015 OI Lau, William /0000-0002-3587-3691; NR 33 TC 88 Z9 95 U1 0 U2 12 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD MAR PY 1999 VL 127 IS 3 BP 322 EP 340 DI 10.1175/1520-0493(1999)127<0322:PMOCSA>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 171NH UT WOS:000078869700005 ER PT J AU Townsend, LW Ramsey, CR Tripathi, RK Cucinotta, FA Norbury, JW AF Townsend, LW Ramsey, CR Tripathi, RK Cucinotta, FA Norbury, JW TI Optical model methods of predicting nuclide production cross sections from heavy ion fragmentation SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article DE nuclear fragmentation; spallation reactions; electromagnetic dissociation; intermediate-energy collisions ID NUCLEUS-NUCLEUS COLLISIONS; MOMENTUM DISTRIBUTIONS; ABRASION-ABLATION; HYDROGEN TARGETS; EMISSION; DISSOCIATION; PROJECTILES; EXCITATION; FE-56 AB Quantum mechanical optical potential methods for calculating inclusive isotope and element production cross sections from the fragmenting of heavy nuclei by intermediate-and high-energy protons and heavy ions are presented based upon a modified abrasion-ablation-FSI (frictional spectator interaction) collision model. The abrasion stage is treated as a quantum mechanical knockout process that leaves the residual prefragment in an excited state. Prefragment excitation energies are estimated using a combined liquid drop and FSI method. In ablation the prefragment deexcites by particle and photon emission to produce the final fragment. Contributions from electromagnetic dissociation to single nucleon removal cross sections are incorporated using a Weiszacker-Williams theory that includes electric dipole and electric quadrupole interactions. Estimates of elemental and isotopic production cross sections are in good agreement with published cross section measurements for a variety of projectile-target-beam energy combinations. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Tennessee, Dept Nucl Engn, Knoxville, TN 37996 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Wisconsin, Dept Phys, Milwaukee, WI 53201 USA. RP Townsend, LW (reprint author), Univ Tennessee, Dept Nucl Engn, 211 asqua Engn Bldg, Knoxville, TN 37996 USA. EM ltownsen@utk.edu NR 48 TC 7 Z9 8 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD MAR PY 1999 VL 149 IS 4 BP 401 EP 413 DI 10.1016/S0168-583X(98)00957-4 PG 13 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 173PA UT WOS:000078987900006 PM 11541652 ER PT J AU Turner, MS AF Turner, MS TI Cosmology solved? Maybe. SO NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS LA English DT Article; Proceedings Paper CT 5th IFT Workshop on Axions CY MAR 13-15, 1998 CL GAINESVILLE, FL SP Univ Florida Dept Phys, UF Coll Liberal Arts & Sci, UF Off Res & Grad Educ, Natl High Magnet Field Lab, US DOE ID BIG-BANG NUCLEOSYNTHESIS; COLD DARK-MATTER; INFLATIONARY UNIVERSE; CONSTANT; DENSITY; MODELS; PERTURBATIONS; FLUCTUATIONS; ANISOTROPY; COMPONENT AB For two decades the hot big-bang model as been referred to as the standard cosmology - and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter. It holds that the Universe is hat, that slowly moving elementary particles left over from the earliest moments provide the cosmic infrastructure, and that the primeval density inhomogeneities that seed all the structure arose from quantum fluctuations. There is now prima facie evidence that supports two basic tenets of this paradigm. An avalanche of high-quality cosmological observations will soon make this case stronger or will break it. Key questions remain to be answered; foremost among them are: identification and detection of the cold dark matter particles and elucidation of the dark-energy component. These are exciting times in cosmology! C1 Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. Fermilab Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. NR 43 TC 6 Z9 6 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0920-5632 EI 1873-3832 J9 NUCL PHYS B-PROC SUP JI Nucl. Phys. B-Proc. Suppl. PD MAR PY 1999 VL 72 BP 69 EP 80 DI 10.1016/S0920-5632(98)00505-2 PG 12 WC Physics, Particles & Fields SC Physics GA 185EY UT WOS:000079656200011 ER PT J AU Raju, MS AF Raju, MS TI Scalar Monte Carlo PDF computations of spray flames on unstructured grids with parallel computing SO NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS LA English DT Article ID TURBULENT; FORMULATION; COMBUSTION; FLOWS AB The article describes the extension of the scalar Monte Carlo probability density function (PDF) approach to the modeling of spray flames for application with unstructured grids and parallel computing. The solver is designed to be massively parallel and accomodates the use of an unstructured mesh with mired elements comprised of triangular, quadrilateral, and / or tetrahedral type. The ability to perform the computations on unstructured meshes allo,us representation of complex geometries with relative ease. Several numerical techniques are outlined for overcoming some of the high computer time and storage limitations associated with the Monte Carlo simulation of practical combustor flows, The application of this method to a confined swirl-stabilized spray flame shows reasonable agreement with the available drop velocity measurements. The parallel performance of both the PDF and Computational Fluid Dynamics (CFD) computations has been found to be excellent but the results are mixed for the spray module, showing reasonable performance on massively parallel computers such as the Gray T3D but poor performance on workstation clusters. In order to improve the parallel performance of the spray module, two different domain decomposition strategies were developed, and the results from both strategies are summarized. C1 NASA, Lewis Res Ctr, Nyma Inc, Brook Pk, OH 44142 USA. RP Raju, MS (reprint author), NASA, Lewis Res Ctr, Nyma Inc, 2001 Aerosp Pkwy, Brook Pk, OH 44142 USA. NR 26 TC 3 Z9 3 U1 0 U2 0 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 USA SN 1040-7790 J9 NUMER HEAT TR B-FUND JI Numer Heat Tranf. B-Fundam. PD MAR PY 1999 VL 35 IS 2 BP 185 EP 209 DI 10.1080/104077999275947 PG 25 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA 182TE UT WOS:000079513600003 ER PT J AU McCandless, JW AF McCandless, JW TI Detection of aircraft in video sequences using a predictive optical flow algorithm SO OPTICAL ENGINEERING LA English DT Article DE gradient; optical flow; object detection; computer vision ID MOVING-OBJECTS; OBSTACLE DETECTION; IMAGE AB This paper presents a computer vision algorithm that segregates spurious optical flow artifacts to detect a moving object. The algorithm consists of six steps. First, the pixels in each image are shifted to compensate for camera rotation. Second, the images are smoothed with a spatiotemporal Gaussian filter, Third, the optical flow is computed with a gradient-based technique. Fourth, optical flow vectors with small magnitudes are discarded. Fifth, vectors with similar locations, magnitudes, and directions are clustered together using a spatial consistency test. Sixth, similar optical flow vectors are extended temporally to make predictions about future optical flow locations, magnitudes, and directions in subsequent frames. The actual optical flow vectors that are consistent with those predictions are associated with a moving object. This algorithm was tested on images obtained with a video camera mounted below the nose of a Boeing 737, The camera recorded two sequences containing a second flying aircraft. The algorithm detected the aircraft in 82% of the frames from the first sequence and 78% of the frames from the second sequence. In each sequence, the false-alarm rate was zero. These results illustrate the effectiveness of using a comprehensive predictive technique when detecting moving objects. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)01603-7]. C1 NASA, Ames Res Ctr, Human Informat Proc Res Branch, Moffett Field, CA 94035 USA. RP McCandless, JW (reprint author), NASA, Ames Res Ctr, Human Informat Proc Res Branch, Mail Stop 262-2, Moffett Field, CA 94035 USA. NR 28 TC 9 Z9 10 U1 3 U2 3 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, BELLINGHAM, WA 98225 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD MAR PY 1999 VL 38 IS 3 BP 523 EP 530 DI 10.1117/1.602130 PG 8 WC Optics SC Optics GA 176MY UT WOS:000079156400018 ER PT J AU Cockell, CS AF Cockell, CS TI Crises and extinction in the fossil record - a role for ultraviolet radiation? SO PALEOBIOLOGY LA English DT Review ID CRETACEOUS-TERTIARY BOUNDARY; UV-B RADIATION; TROPICAL SOLAR-RADIATION; PERMIAN MASS EXTINCTION; PHOTON FLUX-DENSITY; OZONE DEPLETION; NATURAL-WATERS; SUPERNOVA EXPLOSIONS; TRIASSIC BOUNDARY; PHOTOSYNTHESIS AB A number of natural events can cause ozone depletion, including asteroid and comet impacts, large-scale volcanism involving the stratospheric injection of chlorine, and close cosmic events such as supernovae. These events have previously been postulated to have been sole or contributory causes of mass extinctions. Following such events, UV-B radiation would have been elevated at the surface of the earth. The possibilities for detecting elevated UV-B as a kill mechanism in the fossil record are discussed. In the case of impact events and large-scale volcanism, the taxa affected by increases in UV-B radiation are likely to be similar to those affected by cooling and by the initial drop in irradiance caused by stratospheric dust injection. Thus UV-B may synergistically exacerbate the effects of these other environmental changes and contribute to stress in the biosphere, although UV-B alone Is unlikely to cause a mass extinction. By the same token, however, this similarity in affected taxa is likely to make delineating the involvement of UV-B radiation in the fossil record more difficult. Cosmic events such as supernovae may produce smaller extinction events, but ones that are "cleaner" UV catastrophes without the involvement of other environmental changes. C1 Carnegie Inst Washington, Dept Plant Biol, Stanford, CA 94305 USA. RP Cockell, CS (reprint author), NASA, Ames Res Ctr, MS 239-20, Moffett Field, CA 94035 USA. NR 116 TC 22 Z9 25 U1 1 U2 8 PU PALEONTOLOGICAL SOC INC PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044 USA SN 0094-8373 J9 PALEOBIOLOGY JI Paleobiology PD SPR PY 1999 VL 25 IS 2 BP 212 EP 225 PG 14 WC Biodiversity Conservation; Ecology; Evolutionary Biology; Paleontology SC Biodiversity & Conservation; Environmental Sciences & Ecology; Evolutionary Biology; Paleontology GA 215AD UT WOS:000081359000006 ER PT J AU Sergeev, A Karasik, BS Ptitsina, NG Chulkova, GM Il'in, KS Gershenzon, EM AF Sergeev, A Karasik, BS Ptitsina, NG Chulkova, GM Il'in, KS Gershenzon, EM TI Electron-phonon interaction in disordered conductors SO PHYSICA B LA English DT Article; Proceedings Paper CT 9th International Conference on Phonon Scattering in Condensed Matter (PHONONS 98) CY JUL 26-31, 1998 CL LANCASTER, ENGLAND SP Engn & Phys Sci Res Council, European Commiss, Int Union Pure & Appl Phys, US Army European Res Off, Lancaster Univ Dept Phys, Inst Phys, European Phys Soc DE electron-phonon interaction; thin films; disorder ID WEAK-LOCALIZATION; FILMS; TIME; DEPENDENCE; ALLOYS; METAL AB The electron-phonon interaction is strongly modified in conductors with a small value of the electron mean free path (impure metals, thin films). As a result, the temperature dependencies of both the inelastic electron scattering rate and resistivity differ significantly from those for pure bulk materials. Recent complex measurements have shown that modified dependencies are well described at T greater than or equal to 10 K by the electron interaction with transverse phonons. At helium temperatures, available data are conflicting, and cannot be described by an universal model. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Regensburg, Inst Phys 1, Dept Phys, D-93040 Regensburg, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Moscow State Pedag Univ, Moscow 119482, Russia. RP Sergeev, A (reprint author), Univ Regensburg, Inst Phys 1, Dept Phys, Univ Str 31, D-93040 Regensburg, Germany. RI Karasik, Boris/C-5918-2011 NR 16 TC 6 Z9 6 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-4526 J9 PHYSICA B JI Physica B PD MAR PY 1999 VL 263 BP 190 EP 192 DI 10.1016/S0921-4526(98)01323-4 PG 3 WC Physics, Condensed Matter SC Physics GA 180AN UT WOS:000079362700050 ER PT J AU Wu, JZ Zhou, Y Lu, XY Fan, M AF Wu, JZ Zhou, Y Lu, XY Fan, M TI Turbulent force as a diffusive field with vortical sources SO PHYSICS OF FLUIDS LA English DT Article ID ARBITRARILY COMPLEX TOPOLOGY; ANALOGOUS EULER FLOWS; MAGNETOSTATIC EQUILIBRIA; LAMB VECTOR; FLUID AB In Reynolds-average Navier-Stokes equation it is the divergence of Reynolds stress tensor, i.e., the turbulent force, rather than the tensor itself, is to be simulated and partially modeled. Thus, directly working on turbulent force could bring significant simplification. In this paper a novel exact equation for incompressible turbulent force f is derived: (partial derivative/partial derivative t - v del(2))f=del.S, where v is the molecular viscosity and all source terms in tensor S to be modeled are vortical. The dominant mechanism is the advection and stretching (with an opposite sign) of a "pseudo-Lamb vector" by fluctuating velocity field. No coupling with pressure is involved. The equation follows from a study of the mean fluctuating Lamb vector and kinetic energy, which constitute the turbulent force. Both constituents are governed by the same kind of equations as f. This innovative turbulent-force equation is similar to Lighthill's acoustic analogy and naturally calls one's attention to studying the vortical sources of turbulent force. The methodology described here may lead to turbulence models which provide more complete treatment than that of two-equation models, but relatively easier computation than that of second-order closures. (C) 1999 American Institute of Physics. [S1070-6631(99)01303-3]. C1 Univ Tennessee, Inst Space, Tullahoma, TN 37388 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. IBM Res Div, Thomas J Watson Res Ctr, Yorktown Heights, NY 10598 USA. Univ Tennessee, Inst Space, Tullahoma, TN 37388 USA. Univ Sci & Technol China, Dept Modern Mech, Hefei 230026, Anhui, Peoples R China. RP Wu, JZ (reprint author), Univ Tennessee, Inst Space, Tullahoma, TN 37388 USA. EM jzwu@utsi.edu NR 28 TC 11 Z9 11 U1 0 U2 1 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD MAR PY 1999 VL 11 IS 3 BP 627 EP 635 DI 10.1063/1.869934 PG 9 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 169XA UT WOS:000078773700013 ER PT J AU Canuto, VM Dubovikov, MS AF Canuto, VM Dubovikov, MS TI A dynamical model for turbulence. VII. Complete system of five orthogonal tensors for shear-driven flows SO PHYSICS OF FLUIDS LA English DT Article AB The one-point Reynolds stresses have been traditionally expressed in terms of ten tensors. It is, however, known that the independent tensors are only five. We construct a complete set of five orthogonal, traceless, and symmetric second rank tensors in terms of mean strain and vorticity. The system is used to express the one-point Reynolds stresses. The coefficients of the expansion are evaluated in papers VIII and IX. (C) 1999 American Institute of Physics, [S1070-6631(99)00203-2]. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10027 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 14 TC 6 Z9 6 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD MAR PY 1999 VL 11 IS 3 BP 659 EP 664 DI 10.1063/1.869937 PG 6 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 169XA UT WOS:000078773700016 ER PT J AU Canuto, VM Dubovikov, MS Yu, G AF Canuto, VM Dubovikov, MS Yu, G TI A dynamical model for turbulence. VIII. IR and UV Reynolds stress spectra for shear-driven flows SO PHYSICS OF FLUIDS LA English DT Article AB The basic equations for the two-point Reynolds stresses derived in paper II are solved analytically in two regimes: the UV (ultraviolet) region corresponding to the inertial range and the IR (infrared) region corresponding to k-->0. The analytic treatment is possible due to the existence of two smallness parameters: U-i,U-j(k(2)v(t))(-1) in the UV region and kL in the IR region; U-i,U-j is the mean velocity gradient, v(t)(k) is the turbulent viscosity, and L is the integral length scale. For an arbitrary flow, the Reynolds stress spectrum in the UV region is given by Eqs. (53)-(59). In the IR region, and in the first-order approximation in kL, the spectra coincide with those of the rapid distortion theory. Since they are flow dependent, we shall discuss a few representative cases. The resulting Reynolds stress spectra, which are shown to reproduce existing data, are the basis for the calculation of the one-point Reynolds stresses to be presented in paper IX. The model has no free parameters. (C) 1999 American Institute of Physics. [S1070-6631(99)00303-7]. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10027 USA. RP NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 18 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 1070-6631 EI 1089-7666 J9 PHYS FLUIDS JI Phys. Fluids PD MAR PY 1999 VL 11 IS 3 BP 665 EP 677 DI 10.1063/1.869938 PG 13 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 169XA UT WOS:000078773700017 ER PT J AU Canuto, VM Dubovikov, MS Yu, G AF Canuto, VM Dubovikov, MS Yu, G TI A dynamical model for turbulence. IX. Reynolds stresses for shear-driven flows SO PHYSICS OF FLUIDS LA English DT Article ID PRESSURE STRAIN CORRELATION; CLOSURE AB We present a new expression for the one-point Reynolds stress tau(ij) in terms of the strain and vorticity of the large scales. The tau(ij) are expressed in terms of only five basic orthogonal tensors rather than the traditional ten tensors. The expression for tau(ij), Eq. (24), contains no adjustable parameters. The derivation of tau(ij) is based on the two-point closure dynamic equations for the spectral Reynolds stresses R-ij(k) that were developed earlier and the results of which were validated on a wide variety of data comprising shear, buoyancy, two-dimensional (2-D) turbulence, rotation, etc. For the case of homogeneous turbulence, we also derive an expression for the empirical coefficients of the epsilon equation that depend on the invariants of the flow, the turbulent kinetic energy K and the production P. Examples for special flows are given. The new expressions for tau(ij) are shown to reproduce well data from Tavoularis and Corrsin, DNS data, stationary data (pipe flow, channel flow, and homogeneous flow), and the Smagorinsky-Lilly constant, which is shown to be a dynamical variable since it depends on the ratio P/epsilon and on the invariant {S-3}S-3. (C) 1999 American Institute of Physics. [S1070-6651(99)00403-1]. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10027 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 40 TC 7 Z9 7 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD MAR PY 1999 VL 11 IS 3 BP 678 EP 691 DI 10.1063/1.869939 PG 14 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 169XA UT WOS:000078773700018 ER PT J AU Raman, G AF Raman, G TI Shock-induced flow resonance in supersonic jets of complex geometry SO PHYSICS OF FLUIDS LA English DT Article ID SCREECH TONES; RECTANGULAR JET; NOZZLES; MODES AB Jets with complex shock-cell structures exist in numerous technological applications. This paper describes a fundamental study of shock-induced flow resonance (commonly referred to as "jet screech") in supersonic jets with spanwise nonuniform shock-cell structures. Experiments that involve flow visualization and detailed mapping of the near field reveal unsteady aspects of shock-induced flow resonances, mode transitions, and directivity of the radiated noise. The following important results about the role of spanwise nonuniform shock-cells emerged: (1) It is possible to have two coexisting, independent feedback loops at nonharmonically related frequencies and different spanwise modes. (2) The same type of spanwise asymmetric mode was produced by two entirely different source configurations. (3) Nozzle geometry significantly altered the intensity and directivity of screech and broadband shock noise. The results presented here provide considerable insight into the fluid dynamics and acoustics of jets with spanwise oblique shock-cell structures and provide grounds for believing that shock-induced noise can be controlled by tailoring nozzle geometry. (C) 1999 American Institute of Physics. [S1070-6631(99)00103-8]. C1 NASA, Lewis Res Ctr Grp, Propuls Anal Sect, Dynacs Engn Co Inc, Brook Pk, OH 44142 USA. RP Raman, G (reprint author), NASA, Lewis Res Ctr Grp, Propuls Anal Sect, Dynacs Engn Co Inc, Brook Pk, OH 44142 USA. NR 43 TC 6 Z9 6 U1 1 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD MAR PY 1999 VL 11 IS 3 BP 692 EP 709 DI 10.1063/1.869940 PG 18 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 169XA UT WOS:000078773700019 ER PT J AU Kruger, H Grun, E Landgraf, M Baguhl, M Dermott, S Fechtig, H Gustafson, BA Hamilton, DP Hanner, MS Horanyi, M Kissel, J Lindblad, BA Linkert, D Linkert, G Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R Zook, HA AF Kruger, H Grun, E Landgraf, M Baguhl, M Dermott, S Fechtig, H Gustafson, BA Hamilton, DP Hanner, MS Horanyi, M Kissel, J Lindblad, BA Linkert, D Linkert, G Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R Zook, HA TI Three years of Ulysses dust data: 1993-1995 SO PLANETARY AND SPACE SCIENCE LA English DT Article ID INTERSTELLAR DUST; ASTEROID BELT; GALILEO; JUPITER; STREAMS; POPULATIONS; DETECTOR; EJECTION; GRAINS; CLOUD AB The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse (i = 79 degrees). After its Jupiter flyby in 1992 at a heliocentric distance of 5.4 AU, the spacecraft reapproached the inner solar system, flew over the Sun's south polar region in September 1994, crossed the ecliptic plane at a distance of 1.3 AU in March 1995, and flew over the Sun's north polar resion in July 1995. We report on dust impact data obtained with the dust detector onboard Ulysses between January 1993 and December 1995. Wt publish and analyse the complete data set of 509 recorded impacts of dust particles with masses between 10-(16) g-10(-7) Together with 968 dust impacts from launch until the end of 1992 published earlier (Grun et al., 1995c), information about 1477 particles detected with the Ulysses sensor between October 1990 and December 1995 is now available. The impact rate measured between 1993 and 1995 stayed relatively constant at about 0.4 impacts per day and varied by less than a factor of ten. Most of the impacts recorded outside about 3.5 AU are compatible with particles of interstellar origin. Two populations of interplanetary particles have been recognized: big micrometer-sized particles close to the ecliptic plane and small sub-micrometer-sized particles at high ecliptic latitudes. The observed impact rate is compared with a model for the flux of interstellar dust particles which gives relatively good agreement with the observed impact rate. No change in the instrument's noise characteristics or degradation of the channeltron could be revealed during the three-year period. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Max Planck Inst Kernphys, D-69029 Heidelberg, Germany. Univ Florida, Gainesville, FL 32611 USA. Univ Maryland, College Pk, MD 20742 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Lund Observ, S-22100 Lund, Sweden. Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. Univ Kent, Canterbury CT2 7NR, Kent, England. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. Estec, NL-2200 AG Noordwijk, Netherlands. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Kruger, H (reprint author), Max Planck Inst Kernphys, D-69029 Heidelberg, Germany. RI Gustafson, Bo/B-9526-2011; OI Horanyi, Mihaly/0000-0002-5920-9226 NR 39 TC 19 Z9 19 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD MAR-APR PY 1999 VL 47 IS 3-4 BP 363 EP 383 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190TE UT WOS:000079980300009 ER PT J AU Rannou, P McKay, CP Botet, R Cabane, M AF Rannou, P McKay, CP Botet, R Cabane, M TI Semi-empirical model of absorption and scattering by isotropic fractal aggregates of spheres SO PLANETARY AND SPACE SCIENCE LA English DT Article ID LIGHT-SCATTERING; ATMOSPHERE; TITAN AB Existing models of scattering by fractal aggregates of spheres are generally accurate but somewhat complicated and lime consuming. Therefore, they are not easily usable for atmospheric studies that need intensive computations. We propose here a simple and fast model, based on Mie scattering and a set of empirical rules: that determines the scattering and absorption cross sections as well as the intensity phase function of isotropic fractal aggregates of identical spheres. This model is 10-50 times faster than the mean field model it is based on, and is easily derivable from a regular Mie code. The parameters of the present model are optimized for values of the real refractive index between 1.2 and 2.2, for imaginary refractive index less than 1 and for the product of real refractive index and spherical size parameter less than 10. This range was chosen as representative of typical particles in planetary atmospheres, for example, Titan's aerosols. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Paris 06, Serv Aeron, F-75252 Paris, France. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Paris 11, Phys Solides Lab, F-91405 Orsay, France. RP Rannou, P (reprint author), Univ Paris 06, Serv Aeron, 4 Pl Jussieu,B102, F-75252 Paris, France. RI RANNOU, Pascal/I-9059-2012 NR 16 TC 31 Z9 31 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD MAR-APR PY 1999 VL 47 IS 3-4 BP 385 EP 396 DI 10.1016/S0032-0633(99)00007-0 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190TE UT WOS:000079980300010 ER PT J AU de Vanssay, E McDonald, GD Khare, BN AF de Vanssay, E McDonald, GD Khare, BN TI Evidence from scanning electron microscopy of experimental influences on the morphology of Triton and Titan tholins SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ORGANIC-CHEMISTRY; ATMOSPHERE; AEROSOLS; HAZE AB To simulate experimentally the production of aerosols in the atmospheres of Titan and Triton, we have studied organic material (tholins) obtained by inductively coupled plasma from CH4:N-2 gas mixtures, with ratios 10:90 for Titan simulations and 0.1 :99.9 for Triton simulations. Observation of tholins by high performance scanning electron microscopy shows that tholin morphology varies with the chemical composition of the initial gas mixture. Although the role of the experimental design (especially the diameter of the discharge chamber) and the flux of matter were not fully investigated, it appears that they have a significant effect not on the overall morphology of the tholins but on the size distribution of the particles. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Cornell Univ, Planetary Studies Lab, Ithaca, NY 14853 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP McDonald, GD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-301, Pasadena, CA 91109 USA. NR 34 TC 7 Z9 7 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD MAR-APR PY 1999 VL 47 IS 3-4 BP 433 EP 440 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190TE UT WOS:000079980300013 ER PT J AU Tokano, T Neubauer, FM Laube, M McKay, CP AF Tokano, T Neubauer, FM Laube, M McKay, CP TI Seasonal variation of Titan's atmospheric structure simulated by a general circulation model SO PLANETARY AND SPACE SCIENCE LA English DT Article ID VOYAGER INFRARED OBSERVATIONS; RADIO-OCCULTATION; GEOMETRIC ALBEDO; TEMPERATURE; ASYMMETRY; PARAMETERIZATION; PHOTOCHEMISTRY; BRIGHTNESS; DYNAMICS; AEROSOLS AB The seasonal variation of Titan's atmospheric structure with emphasis on the stratosphere is simulated by a three-dimensional general circulation model. The model includes the transport of haze particles by the circulation. The likely pattern of meridional circulation is reconstructed by a comparison of simulated and observed haze and temperature distribution. The GCM produces a weak zonal circulation with a small latitudinal temperature gradient, in conflict with observation. The direct reason is found to be the excessive meridional circulation. Under uniformly distributed opacity sources, the model predicts a pair of symmetric Hadley cells near the equinox and a single global cell with the rising branch in the summer hemisphere below about z = 230 km and a thermally indirect cell above the direct cell near the solstice. The interhemispheric circulation transports haze particles from the summer to the winter hemisphere, causing a maximum haze opacity contrast near the solstice and a smaller contrast near the equinox, contrary to observation. On the other hand, if the GCM is run under modified cooling rate in order to account for the enhancement in nitriles and some hydrocarbons in the northern hemisphere near the vernal equinox, the meridional cell at the equinox becomes a single cell with rising motions in the autumn hemisphere. A more realistic haze opacity distribution can be reproduced at the equinox. However, a pure transport effect (without particle growth by microphysics, etc.) would not be able to cause the observed discontinuity of the global haze opacity distribution at any location. The stratospheric temperature asymmetry can be explained by a combination of asymmetric radiative heating rates and adiabatic heating due to vertical motion within the thermally indirect cell. A seasonal variation of haze particle number density is unlikely to be responsible for this asymmetry. It is likely that a thermally indirect cell covers the upper portion of the main haze layer. An artificial damping of the meridional circulation enables the formation of high-latitude jets in the upper stratosphere and weaker equatorial superrotation. The latitudinal temperature distribution in the stratosphere is better reproduced. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Cologne, Inst Geophys & Meteorol, D-50923 Cologne, Germany. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Tokano, T (reprint author), Univ Cologne, Inst Geophys & Meteorol, Albertus Magnus Pl, D-50923 Cologne, Germany. FU NIOSH CDC HHS [50 OH 92099] NR 48 TC 83 Z9 83 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD MAR-APR PY 1999 VL 47 IS 3-4 BP 493 EP 520 DI 10.1016/S0032-0633(99)00011-2 PG 28 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 190TE UT WOS:000079980300017 PM 11542926 ER PT J AU Malone, G AF Malone, G TI Copper electroforming success stories - Fabricating a 500 MHz Buncher cavity SO PLATING AND SURFACE FINISHING LA English DT Article AB This presentation from the 1997 AESF/NiDI Electroforming Course & Symposium describes the fabrication of a 500 MHz buncher cavity assembly using copper electroformed from the acid sulfate electrolyte. The buncher cavity is a high-power radio frequency (rf) device used in a modular component project at TRW Space & Electronics Group, Redondo Beach, CA. The device, shaped as an oblate spheroid, contained integral stainless steel vacuum ports with flanges, cavity inlets (for rf couplers, probes and other equipment to operate the device), stainless steel rings (for support and force reaction sites for tuning the cavity) and external cooling manifolds and tubes. C1 Electroformed Nickel Inc, Huntsville, AL USA. NASA, SBIR Program, Washington, DC 20546 USA. RP Malone, G (reprint author), Electroformed Nickel Inc, Huntsville, AL USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER ELECTROPLATERS SOC INC PI ORLANDO PA 12644 RESEARCH PKWY, ORLANDO, FL 32826-3298 USA SN 0360-3164 J9 PLAT SURF FINISH JI Plat. Surf. Finish. PD MAR PY 1999 VL 86 IS 3 BP 36 EP 38 PG 3 WC Metallurgy & Metallurgical Engineering; Materials Science, Coatings & Films SC Metallurgy & Metallurgical Engineering; Materials Science GA 174YJ UT WOS:000079063900010 ER PT J AU Turner, MS AF Turner, MS TI Cosmology solved? Quite possibly! SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID INFLATIONARY UNIVERSE; PERTURBATIONS; CONSTANT AB The discovery of the cosmic microwave background (CMB) in 1964 by Penzias and Wilson led to the establishment of the hot big bang cosmological model some 10 years later. Discoveries made in 1998 may ultimately have as profound an effect on our understanding of the origin and evolution of the universe. Taken at face value, they confirm the basic tenets of inflation + cold dark matter, a bold and expansive theory that addresses all the fundamental questions left unanswered by the hot big bang model and holds that the universe is flat, slowly moving elementary particles provide the cosmic infrastructure, and quantum fluctuations seeded all the structure seen in the universe today. Just as it took a decade to establish the hot big bang model after the discovery of the CMB, it will likely take another 10 years to establish the latest addition to the standard cosmology and make the answer to "Cosmology solved?" "YES!" Whether or not 1998 proves to be a cosmic milestone, the coming avalanche of high-quality cosmological data promises to make the next 20 years an extremely exciting period for cosmology. C1 Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Turner, MS (reprint author), Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. NR 30 TC 21 Z9 21 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD MAR PY 1999 VL 111 IS 757 BP 264 EP 273 DI 10.1086/316325 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 177AM UT WOS:000079185100004 ER PT J AU Nemiroff, RJ Bonnell, JT AF Nemiroff, RJ Bonnell, JT TI The Nature of the Universe Debate in 1998 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID SCALE AB A public program titled the "Nature of the Universe Debate: Cosmology Solved?" was held at the Smithsonian National Museum of National History on 1998 October 4. P. James E. Peebles and Michael S. Turner debated whether a fundamental set of cosmological parameters is emerging that provides a consistent geometric setting for the interpretation of cosmological observations. Introductory lectures were given by Owen Gingerich and Joseph Silk, and the program was moderated by Margaret J. Geller. This paper briefly summarizes the background, organization, and some events leading up to the program. The preceding papers are based on the actual lectures and arguments presented. The event was held in honor of David N. Schramm. C1 Michigan Technol Univ, Dept Phys, Houghton, MI 49931 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Nemiroff, RJ (reprint author), Michigan Technol Univ, Dept Phys, Houghton, MI 49931 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD MAR PY 1999 VL 111 IS 757 BP 285 EP 287 DI 10.1086/316326 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 177AM UT WOS:000079185100006 ER PT J AU Mallama, A Espenak, F AF Mallama, A Espenak, F TI Automated meteor detection and the Leonid shower SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB A computer-automated radio system for monitoring meteor activity is described. The receiver is tuned to the frequency of a television video carrier whose transmitter is located beyond the horizon. The system registers only a weak signal except when the ion trail from a meteor reflects additional power to the receiver. A sudden power increase alerts the computer to a possible meteor. Our system employs a unique method for distinguishing between meteors and false alerts due to lightning and other noise. Using the receiver's audio output, a meteor echo is identified by increased audio signal autocorrelation, whereas electrical noise is recognized by a decreased correlation. The system has now accumulated more than a year of observations. The data show clearly the expected diurnal variation in meteor count rate, as well as most of the stronger meteor showers. We have also obtained evidence of some new showers. Analysis of the data from 1997 November 15-20 reveals Leonid meteor shower activity with a peak at November 17.5 (+/- 0.2) UT or solar longitude 235.degrees 3 (+/- 0.2). Leonid meteors are of current interest because the shower may be building toward a supermaximum or "meteor storm" in 1998 or 1999. C1 Raytheon Syst Co, Greenbelt, MD 20770 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mallama, A (reprint author), Raytheon Syst Co, 7701 Greenbelt Rd, Greenbelt, MD 20770 USA. EM amallama@stx.com; u32fe@lepvax.gsfc.nasa.gov NR 6 TC 1 Z9 1 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD MAR PY 1999 VL 111 IS 757 BP 359 EP 363 DI 10.1086/316333 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 177AM UT WOS:000079185100014 ER PT J AU Bless, RC Richards, EE Bosh, A Dolan, JF Elliot, JL Nelson, M Percival, JW Robinson, EL Taylor, M Van Citters, GM White, RL AF Bless, RC Richards, EE Bosh, A Dolan, JF Elliot, JL Nelson, M Percival, JW Robinson, EL Taylor, M Van Citters, GM White, RL TI The Hubble Space Telescope's high-speed photometer SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID ULTRAVIOLET; STARS AB We present an overview of the performance of the High Speed Photometer (HSP), one of the five original instruments on the Hubble Space Telescope (HST). As its name implies, the HSP was designed for precise high time resolution photometry from visual to ultraviolet wavelengths; sample times as short as 10.7 mu s were possible. Three image dissectors along with 23 different broad- and narrowband filters spanning the spectral range from 1200 to 7500 Angstrom were used for photometry of stars and galaxies. A fourth image dissector with associated polarization analyzers allowed the measurement of broadband linear polarization at near-ultraviolet wavelengths. Simultaneous observations in the blue and red could be made using one of the dissectors and a photomultiplier. Except for an instability in the sensitivity of one of the image dissectors and a reduced throughput in a specialized observational mode, the instrument met or exceeded operational specifications until it was removed from HST in 1993 December. The ability of HSP to carry out its primary program, however, was nearly totally compromised by the poor performance of the telescope, i.e., the spherical aberration of the primary mirror that greatly amplified the effects of large spacecraft pointing jitter and telescope "breathing." As a consequence, the real possibility of HST/HSP opening a new era of astronomical photometry was lost. HSP data affected by various telescope problems, as well as data in which these complications were relatively small, are shown. The excellent condition of the HSP after its return to Earth is described briefly. C1 Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Lowell Observ, Flagstaff, AZ 86001 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. Univ Arizona, Steward Observ, Vatican Observ Res Grp, Tucson, AZ 85721 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. Natl Sci Fdn, Div Astron Sci, Arlington, VA USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Bless, RC (reprint author), Univ Wisconsin, Dept Astron, 475 N Charter St, Madison, WI 53706 USA. RI White, Richard/A-8143-2012 NR 21 TC 4 Z9 4 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD MAR PY 1999 VL 111 IS 757 BP 364 EP 375 DI 10.1086/316334 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 177AM UT WOS:000079185100015 ER PT J AU Kneller, M Peteet, D AF Kneller, M Peteet, D TI Late-glacial to early Holocene climate changes from a central Appalachian pollen and macrofossil record SO QUATERNARY RESEARCH LA English DT Article DE pollen; macrofossils; Appalachian Mountains; late-glacial; Holocene; Younger dryas; Virginia ID EASTERN NORTH-AMERICA; LATE QUATERNARY VEGETATION; SOUTHEASTERN NEW-YORK; YOUNGER DRYAS EVENT; GREENLAND ICE-CORE; LAST DEGLACIATION; ATLANTIC REGION; ENVIRONMENTAL-CHANGE; HUDSON HIGHLANDS; NORTHEASTERN USA AB A late-glacial to early Holocene record of pollen, plant macrofossils, and charcoal has been obtained from two cores from Browns Pond in the central Appalachians of Virginia. An AMS radiocarbon chronology defines the timing of moist and cold excursions, superimposed on the overall warming trend from 14,200 to 7500 C-14 yr B.P. This site had cold, moist conditions from ca. 14,200 to 12,700 C-14 yr B.P., with warming at 12,730, 11,280, and 10,050 C-14 yr B.P. A decrease in deciduous broadleaved tree taxa and Pinus strobus (haploxylon) pollen, simultaneous with a reexpansion of Abies, denotes a brief, cold reversal from 12,260 to 12,200 C-14 yr B.P. A second cold reversal, inferred from increases in montana conifers, is centered at 7500 C-14 yr B.P. The cold reversals at Browns Pond may be synchronous with climate change in Greenland and northwestern Europe. Warming at 11,280 C-14 yr B.P. shows the complexity of regional climate responses during the Younger Dryas chrono-zone. (C) 1999 University of Washington. C1 Columbia Univ, Lamont Doherty Geol Observ, Palisades, NY 10964 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Kneller, M (reprint author), Columbia Univ, Lamont Doherty Geol Observ, Palisades, NY 10964 USA. OI Kneller, Margaret/0000-0002-8577-4421 NR 92 TC 26 Z9 27 U1 6 U2 11 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0033-5894 J9 QUATERNARY RES JI Quat. Res. PD MAR PY 1999 VL 51 IS 2 BP 133 EP 147 DI 10.1006/qres.1998.2026 PG 15 WC Geography, Physical; Geosciences, Multidisciplinary SC Physical Geography; Geology GA 182MV UT WOS:000079503500003 ER PT J AU Yeang, CP Yueh, SH Ding, KH Kong, JA AF Yeang, CP Yueh, SH Ding, KH Kong, JA TI Atmospheric effect on microwave polarimetric passive remote sensing of ocean surfaces SO RADIO SCIENCE LA English DT Article ID EMISSION; MODEL; WATER AB A theoretical emission model of combined ocean surface and atmosphere is presented to predict the microwave emissivity of the ocean. The modeled ocean surface is one-dimensional with a random rough profile. The electromagnetic scattering from the surface is calculated based on the extended boundary condition method. Realizations of rough surfaces are created using Monte Carlo simulations. The bistatic scattering coefficients are computed from the ensemble average. The millimeter-wave propagation model is used to evaluate the absorption of microwave radiation at all height levels in the atmosphere. An expression for the observed brightness temperatures is derived by solving the radiative transfer equations. The radiative transfer model results show a good agreement with the measured data from the 1995 NASA Jet Propulsion Laboratory WIND radiometer (WINDRAD) campaign. An approximate model is provided to estimate the atmospheric effect on the ocean brightness temperatures based on the overall atmospheric attenuation. The approximate model also compares well with the WINDRAD data. Further comparisons are made between the approximate formula and the radiative transfer results on the ratio of the third Stokes parameter in the atmosphere to the one in free space by varying the atmospheric conditions, surface roughness, and radiation frequencies. The approximate formula shows its usefulness for the prediction of the ocean brightness temperatures. C1 MIT, Elect Res Lab, Cambridge, MA 02139 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yeang, CP (reprint author), MIT, Elect Res Lab, Room 36-497,77 Massachusetts Ave, Cambridge, MA 02139 USA. NR 20 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD MAR-APR PY 1999 VL 34 IS 2 BP 521 EP 537 DI 10.1029/1998RS900030 PG 17 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 180RQ UT WOS:000079399300019 ER PT J AU Peddle, DR Hall, FG LeDrew, EF AF Peddle, DR Hall, FG LeDrew, EF TI Spectral mixture analysis and geometric-optical reflectance modeling of boreal forest biophysical structure SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID GROUND RADIOMETER MEASUREMENTS; AFRICAN SAVANNA TREES; LEAF-AREA INDEX; CLIMATE CHANGE; CANOPY REFLECTANCE; CLASSIFICATION; VEGETATION; BIOMASS; RED AB Biophysical structural information such as biomass, LAI, and NPP are important inputs to regional scale models of ecosystem processes and photosynthetic activity within boreal forests. However, traditional methods such as NDVI for deriving these variables from remotely sensed data have been inconsistent and unsatisfactory due to factors such as the confounding influence of background reflectance and canopy geometry on the overall pixel signal. To address this problem, we present new results which use spectral mixture analysis to determine areal fractions of sunlit canopy, sunlit background, and shadow at subpixel scales for predicting these biophysical variables. Geometric-optical reflectance models are used to estimate sunlit canopy component reflectance for input to the analysis together with field measures of background and shadow reflectance. In this article, we compare cylinder, cone, and spheroid models of canopy geometry and evaluate the importance of solar zenith angle variations in reflectance estimates for mixture fractions. These are computed from helicopter MMR radiometer data for 31 stands of black spruce along a gl-adient of stand densities near the southern fringe of the North American boreal fo-est. Component fractions are evaluated against ground data derived from dense-grid point analyses of coincident high resolution color photography and also for predicting biophysical variables. In general, the Li-Strahler spheroid model was better than the cone and cylinder models and the importance of correcting for solar zenith angle (SZA) was illustrated, with significant improvements noted for higher SZA as a result of corrections for canopy mutual shadowing. The best overall results were obtained from the shadow; fraction using a spheroid model of canopy geometry at SZA 45 degrees. Linens regression analyses showed biomass could be estimated with r(2) values of 0.83 and a standard error (S.E.) of 1.7 kg/m(2); LAI: r(2) = 0.82, S.E. = 0.46; and NPP: r(2) = 0.86, S.E. = 0.05 kg/m(2)/yr. These results were significantly higher than with NDVI for estimating biomass (r(2) = 0.44), LAI (r(2) = 0.60), and NPP (r(2) = 0.56). Current and future areas of research are outlined towards improving our understanding of carbon cycling in large forested ecosystems as a function of variability in the physical climate system and environmental change. (C) Elsevier Science Inc., 1999. C1 Univ Lethbridge, Dept Geog, Lethbridge, AB T1K 3M4, Canada. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Biospher Sci Branch, Greenbelt, MD USA. Univ Waterloo, Dept Geog, Waterloo, ON N2L 3G1, Canada. RP Peddle, DR (reprint author), Univ Lethbridge, Dept Geog, 4401 Univ Dr W, Lethbridge, AB T1K 3M4, Canada. NR 40 TC 128 Z9 138 U1 0 U2 17 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD MAR PY 1999 VL 67 IS 3 BP 288 EP 297 DI 10.1016/S0034-4257(98)00090-X PG 10 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 164PL UT WOS:000078472700003 ER PT J AU Means, JE Acker, SA Harding, DJ Blair, JB Lefsky, MA Cohen, WB Harmon, ME McKee, WA AF Means, JE Acker, SA Harding, DJ Blair, JB Lefsky, MA Cohen, WB Harmon, ME McKee, WA TI Use of large-footprint scanning airborne lidar to estimate forest stand characteristics in the Western Cascades of Oregon SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID LEAF-AREA INDEX; PACIFIC-NORTHWEST; CANOPY COVER; DOUGLAS-FIR; TREE HEIGHT; LASER DATA; BIOMASS; GROWTH; VOLUME; RADAR AB A scanning lidar, a relatively one type of sensor which explicitly measures canopy height, was used to measure structure of conifer forests in the Pacific Northwest. SLICER (Scanning Lidar Imager of Canopies by Echo Recovery), an airborne pulsed laser developed by NASA which scans a swath of five 10-m diameter footprints along the aircraft's flightpath, captures the power of the reflected laser pulse as a function of height from the top of thr: canopy to the ground. Ground measurements of forest stand structure were collected oz 26 plots with coincident SLICER data. Height, basal area, total biomass, and leaf biomass as estimated from field data could be predicted from SLICER-derived metrics with r(2) values of 0.95, 0.96, 0.96, and 0.84, respectively. These relationships were strong zip to a height of 52 m, basal area of 132 m(2)/ha and total biomass of 1300 Mg/ha. In light of these strong relationships, large-footprint, airborne scanning lidar shows promise for characterizing stand structure for management and research purposes. (C) Elsevier Science Inc., 1999. C1 Oregon State Univ, Dept Forest Sci, Forestry Sci Lab 020, Corvallis, OR 97331 USA. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. US Forest Serv, Pacific NW Res Stn, USDA, Corvallis, OR 97331 USA. RP Acker, SA (reprint author), Oregon State Univ, Dept Forest Sci, Forestry Sci Lab 020, Peavy Hall 154, Corvallis, OR 97331 USA. EM ackers@fsl.orst.edu RI Lefsky, Michael/A-7224-2009; Blair, James/D-3881-2013; Harding, David/F-5913-2012 NR 62 TC 312 Z9 338 U1 11 U2 65 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD MAR PY 1999 VL 67 IS 3 BP 298 EP 308 DI 10.1016/S0034-4257(98)00091-1 PG 11 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 164PL UT WOS:000078472700004 ER PT J AU Wang, MH AF Wang, MH TI A sensitivity study of the SeaWiFS atmospheric correction algorithm: Effects of spectral band variations SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID MULTIANGLE IMAGING SPECTRORADIOMETER; WATER-LEAVING RADIANCE; OCEAN-COLOR SENSORS; OPTICAL-THICKNESS; INSTRUMENT; IMAGERY; SYSTEM; EARTH AB With the success of launch and initial data processing of Sea-viewing Wide Field-of-view Sensor (SeaWiFS), there is a great interest in ocean color community to intercompare ocean color data between different ocean color sensors. it is well known that the atmospheric correction, which removes about 90% of sensor-measured signals contributed from atmosphere in the visible, is the key procedure in ocean color imagery data processing. Therefore, it is useful to evaluate the SeaWiFS atmospheric correction algorithm applying to various ocean color sensors. The SeaWiFS atmospheric correction agorithm uses lookup tables which were generated with over similar to 25,000 radiative transfer model runs for different aerosol optical and microphysical properties, solar and viewing geometries, and, in particular, at the eight SeaWiFS spectral bands. Since different ocean color sensors usually have different band spectral characterization, it is rather difficult to apply the SeaWiFS atmospheric correction algorithm to other sensors if one needs to regenerate lookup tables at spectral bands different from SeaWiFS. In this article, we evaluate the accuracy of the SeaWiFS atmospheric correction algorithm for various ocean color sensors using the current SeaWiFS lookup tables. The focus in on the following satellite ocean color sensors: the Modular Optoelectronic Scanner (MOS), the Ocean Color and Temperatures Sensor (OCTS), and the Polarization and Directionality of the Earth's Reflectances (POLDER). These sensors have slightly different spectral bands compared with the SeaWiFS. It was found that, with an appropriate calculation of the Rayleigh scattering contributions at each sensor's spectral band and a simple modification in computing the diffuse transmittance of the ocean-atmosphere system, the SeaWiFS atmospheric correction applied to other sensors is as accurate as for SeaWiFS for the solar zenith angles theta(0) less than or equal to 60 degrees. (C) Elsevier Science Inc., 1999. C1 Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wang, MH (reprint author), Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Code 970-2, Greenbelt, MD 20771 USA. RI Wang, Menghua/F-5631-2010 OI Wang, Menghua/0000-0001-7019-3125 NR 24 TC 51 Z9 56 U1 2 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD MAR PY 1999 VL 67 IS 3 BP 348 EP 359 DI 10.1016/S0034-4257(98)00095-9 PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 164PL UT WOS:000078472700007 ER PT J AU Senesac, LR Blass, WE Chin, G Hillman, JJ Lobell, JV AF Senesac, LR Blass, WE Chin, G Hillman, JJ Lobell, JV TI Controlling chaotic systems with occasional proportional feedback SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID MULTIMODE LASER AB Utilizing the chaos control technique of occasional proportional feedback (OPF), we designed and constructed an inexpensive and easy to assemble electronic OPF controller. A number of built-in features provide ample versatility to enable the controller to be used with a wide variety of chaotic experimental systems. The controller has a standard OPF correction signal output, but also allows for the addition of a modulated signal to the correction. The rate and active duration of the correction pulse, the offset voltage, and the effective window width are variable. We present the basic principles of OPF control and discuss the individual component functions of the OPF controller. We have successfully used this controller to stabilize chaotic fluctuations in the frequency emission from a tunable lead-salt stripe geometry infrared diode laser. (C) 1999 American Institute of Physics. [S0034-6748(99)01803-1]. C1 Univ Tennessee, Dept Phys & Astron, Knoxville, TN 37996 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Senesac, LR (reprint author), Univ Tennessee, Dept Phys & Astron, Knoxville, TN 37996 USA. RI Blass, William/A-2792-2008; Chin, Gordon/E-1520-2012 NR 18 TC 5 Z9 5 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD MAR PY 1999 VL 70 IS 3 BP 1719 EP 1724 DI 10.1063/1.1149657 PG 6 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 174AN UT WOS:000079012100022 ER PT J AU Tabib-Azar, M Su, DP Pohar, A LeClair, SR Ponchak, G AF Tabib-Azar, M Su, DP Pohar, A LeClair, SR Ponchak, G TI 0.4 mu m spatial resolution with 1 GHz (lambda = 30 cm) evanescent microwave probe SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID MICROSCOPE AB In this article we describe evanescent field imaging of material nonuniformities with a record resolution of 0.4 mm at 1 GHz (lambda g/750 000), using a resonant stripline scanning microwave probe. A chemically etched tip is used as a point-like evanescent field emitter and a probe-sample distance modulation is employed to improve the signal-to-noise ratio. Images obtained by evanescent microwave probe, by optical microscope, and by scanning tunneling microscope are presented for comparison. Probe was calibrated to perform quantitative conductivity measurements. The principal factors affecting the ultimate resolution of evanescent microwave probe are also discussed. (C) 1999 American Institute of Physics. [S0034-6748(99)03603-5]. C1 Case Western Reserve Univ, Cleveland, OH 44106 USA. USAF, Res Lab, Mat & Mfg Directorate, Wright Patterson AFB, OH 45433 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Tabib-Azar, M (reprint author), Case Western Reserve Univ, Cleveland, OH 44106 USA. EM mxt7@po.cwru.edu NR 5 TC 84 Z9 86 U1 3 U2 11 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD MAR PY 1999 VL 70 IS 3 BP 1725 EP 1729 DI 10.1063/1.1149658 PG 5 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 174AN UT WOS:000079012100023 ER PT J AU Turner, MS Tyson, JA AF Turner, MS Tyson, JA TI Cosmology at the millennium SO REVIEWS OF MODERN PHYSICS LA English DT Article ID COLD DARK-MATTER; INFLATIONARY UNIVERSE SCENARIO; REDSHIFT SURVEY; LIGHT-CURVE; CONSTANT; FLUCTUATIONS; PERTURBATIONS; TEMPERATURE; GALAXIES; SPECTRUM AB One hundred years ago we did not know how stars generate energy, the age of the Universe was thought to be only millions of years, and our Milky Way galaxy was the only galaxy known. Today, we know that we live in an evolving and expanding universe comprising billions of galaxies, all held together by dark matter. With the hot big-bang model we can trace the evolution of the Universe from the hot soup of quarks and leptons that existed a fraction of a second after the beginning, to the formation of galaxies a few billion years later, and finally to the Universe we see today 13 billion years after the big bang, with its clusters of galaxies, superclusters, voids, and great walls. The attractive force of gravity acting on tiny primeval inhomogeneities in the distribution of matter gave rise to all the structure seen today. A paradigm based upon deep connections between cosmology and elementary particle physics-inflation+cold dark matter-holds the promise of extending our understanding to an even more fundamental level and much earlier times, as well as shedding light on the unification of the forces and particles of Nature. As we enter the 21st century, a flood of observations is testing this paradigm. [S0034-6861(99)03102-5]. C1 Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. AT&T Bell Labs, Lucent Technol, Murray Hill, NJ 07974 USA. RP Turner, MS (reprint author), Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. NR 75 TC 44 Z9 45 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0034-6861 J9 REV MOD PHYS JI Rev. Mod. Phys. PD MAR PY 1999 VL 71 IS 2 SI SI BP S145 EP S164 DI 10.1103/RevModPhys.71.S145 PG 20 WC Physics, Multidisciplinary SC Physics GA 172BE UT WOS:000078900800019 ER PT J AU Forgrave, JC Man, KF Newell, JM AF Forgrave, JC Man, KF Newell, JM TI Spacecraft acoustic and random vibration test optimization SO SOUND AND VIBRATION LA English DT Article AB Acoustic noise and random vibration tests are key constituents of an effective spacecraft environmental qualification program. Current test programs generally involve performing random vibration and acoustic testing at the component level, followed by both acoustic and random vibration trials at the spacecraft level. Depending upon the surface area, mass and geometry of the test object, one of the two tests, acoustic noise or random vibration, may be more severe than the other. Thus, for a small, rapid-development mission, it may be cost-effective to eliminate one of the two tests at the component level and to perform only the test that is most effective in screening for failure modes. This article describes a method for optimizing acoustic and random vibration trials to reduce costs and schedules, The method involves calculating the response of a test article in each environment and comparing the relative response magnitudes. Implementation of the method at the spacecraft level is also discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Forgrave, JC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 1 Z9 1 U1 1 U2 2 PU ACOUSTICAL PUBL INC PI BAY VILLAGE PA 27101 E OVIATT RD PO BOX 40416, BAY VILLAGE, OH 44140 USA SN 0038-1810 J9 SOUND VIB JI Sound Vib. PD MAR PY 1999 VL 33 IS 3 BP 28 EP 31 PG 4 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 187VJ UT WOS:000079808500005 ER PT J AU Lee, TJ Head-Gordon, M AF Lee, TJ Head-Gordon, M TI Preface - Theoretical spectroscopy: State of the science SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. 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 1 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 MAR PY 1999 VL 55 IS 3 BP 431 EP 432 PG 2 WC Spectroscopy SC Spectroscopy GA 174QJ UT WOS:000079045800001 ER PT J AU Rodriguez-Santiago, L Bauschlicher, CW AF Rodriguez-Santiago, L Bauschlicher, CW TI The electronic spectra of CaN2+ and Ca(N-2)(2)(+) SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; LOW-LYING STATES; APPROXIMATION; EXCHANGE; ENERGY; ATOMS AB The ground and low-lying electronic states of CaN2+ are studied at several levels of theory. The results for the X(2)Sigma(+) state and the excited (2)(II)-I-2 state, arising from occupying the Ca 4p orbital, are in good agreement with experiment. The analogous states of Ca(N-2)(2)(+) are studied using the same theoretical approaches and predictions are made as to the changes caused by the addition of the second N-2 ligand. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Autonoma Barcelona, Dept Quim, E-08193 Barcelona, Spain. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. EM bauschli@pegasus.arc.nasa.gov RI Rodriguez-Santiago, Luis /K-7029-2013 OI Rodriguez-Santiago, Luis /0000-0003-4983-4228 NR 30 TC 5 Z9 5 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD MAR PY 1999 VL 55 IS 3 BP 457 EP 466 DI 10.1016/S1386-1425(98)00254-6 PG 10 WC Spectroscopy SC Spectroscopy GA 174QJ UT WOS:000079045800004 ER PT J AU Lee, TJ Parthiban, S Head-Gordon, M AF Lee, TJ Parthiban, S Head-Gordon, M TI Accurate calculations on excited states: new theories applied to the -X, -XO, and -XO2 (X = Cl and Br) chromophores and implications for stratospheric bromine chemistry SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE stratospheric bromine chemistry; chromophores; excited states ID TRIPLE EXCITATION CORRECTIONS; AB-INITIO CHARACTERIZATION; COUPLED-CLUSTER METHODS; PHOTODISSOCIATION DYNAMICS; CROSS-SECTIONS; SINGLE; HOBR; SPECTRUM; ENERGIES; ISOMERS AB Electronic excitation energies are determined using single-reference based theories derived from response equations involving perturbation theory and coupled-cluster theory. These methods are applied to the singlet manifold of excited electronic states of the HClO, HBrO, HOClO, HOBrO, HClO2, and HBrO2 molecules. Vertical excitation energies (VEEs) for the lowest symmetry unique triplet states are also computed using coupled-cluster theory. Both the singlet and triplet coupled-cluster VEEs are found to be in excellent agreement with experiment for HOBr and HOCl. The reliability of the various perturbation theory approaches is assessed by comparison to the linear response coupled-cluster method, and the CIS(D3) approach is found to perform the best, on average. In order to obtain reliable VEEs for these molecules, CIS(D3) is the recommended approach, unless excited state non-dynamical electron correlation is significant, in which case the recently proposed CIS(D-0) technique may perform better, on average. For both the HClO2 and HBrO2 molecules, it is found that the lowest singlet excited electronic state occurs at too high an energy for it to be accessible from solar radiation in the lower stratosphere. The stratospheric chemistry implications of this, especially for bromine chemistry are discussed. It is suggested that YBrO2 molecules may in fact be the only stable stratospheric bromine reservoir species under light conditions. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA. RP Lee, TJ (reprint author), NASA, Ames Res Ctr, MS230-3, Moffett Field, CA 94035 USA. EM tlee@pegasus.arc.nasa.gov RI Lee, Timothy/K-2838-2012 NR 47 TC 18 Z9 18 U1 0 U2 4 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 MAR PY 1999 VL 55 IS 3 BP 561 EP 574 DI 10.1016/S1386-1425(98)00262-5 PG 14 WC Spectroscopy SC Spectroscopy GA 174QJ UT WOS:000079045800012 ER PT J AU Schwenke, DW AF Schwenke, DW TI A theoretical study of the re-vibrational spectrum of the X state of CH3 SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE dipole moment; re-vibrational spectrum; wave functions ID LASER SPECTROSCOPY; POTENTIAL FUNCTION; DIODE-LASER; METHYL; CD3; BAND AB We have computed the potential energy surface and dipole moment function for the X state of CH3 using multireference correlated wave functions. These are then used in nuclear dynamics calculations to compute experimental observations. Our results are compared to experimental data where available, and good agreement is obtained. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Schwenke, DW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. RI schwenke, david/I-3564-2013 NR 15 TC 10 Z9 10 U1 0 U2 7 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD MAR PY 1999 VL 55 IS 3 BP 731 EP 738 DI 10.1016/S1386-1425(98)00275-3 PG 8 WC Spectroscopy SC Spectroscopy GA 174QJ UT WOS:000079045800023 ER PT J AU Lee, TJ Dateo, CE AF Lee, TJ Dateo, CE TI Accurate spectroscopic characterization of (CN-)-C-12-N-14, (CN-)-C-13-N-14, and (CN-)-C-12-N-15 SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE diffuse interstellar bands; electronic state; spectroscopy; molecular anions; interstellar medium ID QUARTIC FORCE-FIELD; VIBRATIONAL FREQUENCIES; BASIS-SETS; CN; ION AB It is argued that should molecular anions be ubiquitous in the interstellar medium, that current models of the chemical processing of the biogenic elements would have to be fundamentally changed. The lack of high-resolution spectroscopic constants for molecular anions from laboratory experiments is one possible reason that no molecular anions have ever been positively identified from vibrational or rotational spectroscopic astronomical observations. The current theoretical study provides highly accurate predictions for the spectroscopic constants of CN- in the hopes that they will be useful in the identification of CN- from astronomical observations. The singles and doubles coupled-cluster method that includes a perturbational correction for connected triple excitations, denoted CCSD(T), is used in conjunction with several one-particle basis sets to determine quartic force fields for CN-. Basis set convergence properties of the various rovibrational spectroscopic constants are studied. To assure numerical stability of the quartic force fields and to investigate variational calculations of vibrational energy levels, a sextic force field has also been evaluated. The largest one-particle basis set employed contains up through h functions on carbon and nitrogen. Analogous calculations have been carried out on neutral CN and comparison to experiment allows highly accurate predictions for the spectroscopic constants of (CN-)-C-12-N-14, (CN-)-C-13-N-14, and (CN-)-C-12-N-15 to be made. For (CN-)-C-12-N-14, Bg is predicted to be 1.87158 +/- 0.00090 cm(-1) and v is predicted to occur at 2042 +/- 3 cm(-1). (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Lee, TJ (reprint author), NASA, Ames Res Ctr, Thermosci Inst, MS230-3, Moffett Field, CA 94035 USA. RI Lee, Timothy/K-2838-2012 NR 33 TC 16 Z9 16 U1 0 U2 2 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 MAR PY 1999 VL 55 IS 3 BP 739 EP 747 DI 10.1016/S1386-1425(98)00276-5 PG 9 WC Spectroscopy SC Spectroscopy GA 174QJ UT WOS:000079045800024 ER PT J AU Solomon, JA Watson, AB Morgan, MJ AF Solomon, JA Watson, AB Morgan, MJ TI Transducer model produces facilitation from opposite-sign flanks SO VISION RESEARCH LA English DT Article DE masking; facilitation; lateral; spatial ID HUMAN-VISION; CONTRAST DISCRIMINATION; SPATIAL INTERACTIONS; MASKING EXPERIMENTS; FREQUENCY; ADAPTATION; MATHEMATICA; MECHANISMS; CINEMATICA; CHANNELS AB Small spots, lines and Gabor patterns can be easier to detect when they are superimposed upon similar spots, lines and Gabor patterns. Traditionally, such facilitation has been understood to be a consequence of nonlinear contrast transduction. Facilitation has also been reported to arise from non-overlapping patterns with opposite sign. We point out that this result does not preclude the traditional explanation for superimposed targets. Moreover, we find that facilitation from opposite-sign flanks is weaker than facilitation from same-sign flanks. Simulations with a transducer model produce opposite-sign facilitation. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Inst Ophthalmol, London EC1V 9EL, England. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Solomon, JA (reprint author), Inst Ophthalmol, Bath St, London EC1V 9EL, England. EM j.solomon@ucl.ac.uk NR 24 TC 60 Z9 61 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0042-6989 J9 VISION RES JI Vision Res. PD MAR PY 1999 VL 39 IS 5 BP 987 EP 992 DI 10.1016/S0042-6989(98)00143-6 PG 6 WC Neurosciences; Ophthalmology SC Neurosciences & Neurology; Ophthalmology GA 160XA UT WOS:000078256100010 PM 10341950 ER PT J AU Wettergreen, D Bapna, D Maimone, M Thomas, G AF Wettergreen, D Bapna, D Maimone, M Thomas, G TI Developing nomad for robotic exploration of the Atacama Desert SO ROBOTICS AND AUTONOMOUS SYSTEMS LA English DT Article DE long-distance robotic exploration; navigational autonomy; panoramic imagery AB Recent years have seen renewed attention to planetary exploration, and robotics is recognized as essential to many upcoming missions. In this article we describe the ongoing efforts of the Nomad project to develop robots for planetary and terrestrial exploration. The project is developing, demonstrating, and evaluating systems capable of long-distance, long-duration missions. In 1997 this work has resulted in the Atacama Desert Trek, in which a mobile robot named Nomad, explored the Atacama Desert of northern Chile. Nomad's 45-day objective was to travel 200 km across the rugged, barren landscape. We then will describe the technologies for Nomad's transforming chassis, high data-rate communication, safeguarded teleoperation and autonomy, panoramic imaging and visualization, and remote science. We then focus on issues of long-distance, long-duration exploration and describe the events and results of the Atacama Desert Trek. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Intelligent Mechanism Grp, Ames Res Ctr, Mountain View, CA 94035 USA. Carnegie Mellon Univ, Inst Robot, Pittsburgh, PA 15213 USA. Univ Iowa, Dept Ind Engn, Iowa City, IA 52242 USA. RP Australian Natl Univ, RSISE, Robot Syst Lab, Canberra, ACT 0200, Australia. EM dsw@syseng.anu.edu.au NR 30 TC 26 Z9 28 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-8890 EI 1872-793X J9 ROBOT AUTON SYST JI Robot. Auton. Syst. PD FEB 28 PY 1999 VL 26 IS 2-3 BP 127 EP 148 DI 10.1016/S0921-8890(99)80002-5 PG 22 WC Automation & Control Systems; Computer Science, Artificial Intelligence; Robotics SC Automation & Control Systems; Computer Science; Robotics GA 185DN UT WOS:000079653000005 ER PT J AU Ravat, D Lu, Z Braile, LW AF Ravat, D Lu, Z Braile, LW TI Velocity-density relationships and modeling the lithospheric density variations of the Kenya rift SO TECTONOPHYSICS LA English DT Article DE gravity anomaly; seismic; rift; lithosphere; partial melting; upper mantle; velocity-density relationships ID EAST-AFRICAN RIFT; UPPER-MANTLE; SEISMIC VELOCITY; HEAT-FLOW; ASTHENOSPHERE BENEATH; NORTHEASTERN TANZANIA; GRAVITY-ANOMALIES; CRUST; TEMPERATURE; EVOLUTION AB We have devised pressure-dependent and temperature-dependent linear velocity-density relationships from the crustal rocks in the Kenya Rift and applied the relationships to the crustal velocity model derived from the KRTSP90 refraction experiment to compute densities and gravity anomalies. Our results indicate that pressure and temperature considerations reduce the misfit between the observed and the calculated gravity anomalies in the areas of large lateral pressure and temperature variations. Using a separate relationship involving velocity and density contrasts for the mantle of the Kenya Rift, the KRISP teleseismic velocity model, and the variation of the observed gravity anomalies, we derive a d rho/dV(p) value of similar to 0.05 (Mg s m(-3) km(-1)) which results in the density contrast of similar to 0.03 Mg m(-3) at similar to 100 km depth beneath the rift and its flanks. Using the magnitude of the velocity and density contrasts, we conclude that the mantle at the depth of 100 km beneath the rift could be similar to 200 degrees C to 375 degrees C hotter than the adjacent lithosphere (and much of it is considered subsolidus) and contains partial melt up to 2.5%. The amount of partial melt in the region of the Moho upwarp would be greater because both Velocities and densities are lower in that region. Our results are consistent with the upwarping of the thermal boundary layer representing the lithosphere-asthenosphere boundary and the consequent partial melting of the lithosphere. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. So Illinois Univ, Dept Geol, Carbondale, IL 62901 USA. Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN 47907 USA. RP Ravat, D (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. EM tiku@denali.gsfc.nasa.gov OI Ravat, Dhananjay/0000-0003-1962-4422 NR 52 TC 12 Z9 12 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0040-1951 J9 TECTONOPHYSICS JI Tectonophysics PD FEB 28 PY 1999 VL 302 IS 3-4 BP 225 EP 240 DI 10.1016/S0040-1951(98)00283-2 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 173YZ UT WOS:000079008500003 ER PT J AU Schneider, DJ Rose, WI Coke, LR Bluth, GJS Sprod, IE Krueger, AJ AF Schneider, DJ Rose, WI Coke, LR Bluth, GJS Sprod, IE Krueger, AJ TI Early evolution of a stratospheric volcanic eruption cloud as observed with TOMS and AVHRR SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID EL-CHICHON VOLCANO; MOUNT-ST-HELENS; OZONE MAPPING SPECTROMETER; SULFUR-DIOXIDE; 1982 ERUPTIONS; DUST CLOUD; ASH CLOUDS; DEPOSITS; TEPHRA; ORIGIN AB This paper is a detailed study of remote sensing data from the total ozone mapping spectrometer (TOMS) and the advanced very high resolution radiometer (AVHRR) satellite detectors, of the 1982 eruption of El Chichon, Mexico. The volcanic cloud/atmosphere interactions in the first four days of this eruption were investigated by combining ultraviolet retrievals to estimate the mass of sulfur dioxide in the volcanic cloud [Krueger et al., 1995] with thermal infrared retrievals of the size, optical depth, and mass of fine-grained (1- 10 mu m radius) volcanic ash [Wen and Rose, 1994]. Our study provides the first direct evidence of gravitational separation of ash from a stratospheric, gas-rich, plinian eruption column and documents the marked differences in residence times of volcanic ash and sulfur dioxide in volcanic clouds. The eruption column reached as high as 32 km [Carey and Sigurdsson, 1986] and was injected into an atmosphere with a strong wind shear, which allowed for an observation of the separation of sulfur dioxide and volcanic ash. The upper, more sulfur dioxide-rich part of the cloud was transported to the west in the stratosphere, while the fine-grained ash traveled to the south in the troposphere. The mass of sulfur dioxide released was estimated at 7.1 x 10(9) kg with the mass decreasing by approximately 4% 1 day after the peak. The mass of fine-grained volcanic ash detected was estimated at 6.5 x 10(9) kg, amounting to about 0.7% of the estimated mass of the ash which fell out in the mapped ash blanket close to the volcano. Over the following days, 98% of this remaining fine ash was removed from the volcanic cloud, and the effective radius of ash in the volcanic cloud decreased from about 8 mu m to about 4 mu m. C1 Michigan Technol Univ, Dept Geol Engn & Sci, Houghton, MI 49931 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Schneider, DJ (reprint author), Raytheon STX, US Geol Survey, Alaska Volcano Observ, 4200 Univ Dr, Anchorage, AK 99508 USA. EM djschneider@usgs.gov; raman@mtu.edu; lrcoke@mtu.edu; gbluth@mtu.edu; ian@ngdc.noaa.gov; krueger@chapman.gsfc.nasa.gov RI Rose, William/A-7923-2009 NR 47 TC 71 Z9 71 U1 0 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 27 PY 1999 VL 104 IS D4 BP 4037 EP 4050 DI 10.1029/1998JD200073 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 169TF UT WOS:000078764100014 ER PT J AU Soulen, PF Frederick, JE AF Soulen, PF Frederick, JE TI Estimating biologically active UV irradiance from satellite radiance measurements: A sensitivity study SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ROBERTSON-BERGER METERS; ULTRAVIOLET-RADIATION; TOTAL OZONE AB An algorithm for estimating biologically active UV irradiance from satellite measurements of ozone and reflectivity is presented. In contrast to previous work, this technique treats bulk radiative properties of clouds explicitly, assuming that clouds are reflecting surfaces. This work addresses the following issue: If clouds are characterized as simple reflecting surfaces of a specified albedo at a specified altitude covering a fraction of the sky, how precisely can surface UV irradiance be determined? To address this issue, an Eddington radiative transfer model is used to calculate not only ground level irradiance but also an estimate of the backscattered radiance in the nadir direction using the formal solution to the radiative transfer equation. While this model does not simulate detailed angular distributions of radiation scattered off clouds, it is found that this model retrieves average measured biologically active surface UV irradiance around solar noon quite well and that different combinations of parameters yield strikingly similar estimates of surface uv irradiance. The model is tested using four years of continuous-scan SBUV data and Robertson-Berger meter data for nine cities. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Greenbelt, MD 21228 USA. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. Univ Chicago, Dept Geophys Sci, Chicago, IL 60637 USA. RP Soulen, PF (reprint author), Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Greenbelt, MD 21228 USA. EM soulen@climate.gsfc.nasa.gov NR 23 TC 4 Z9 4 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 FEB 27 PY 1999 VL 104 IS D4 BP 4117 EP 4126 DI 10.1029/1998JD200101 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 169TF UT WOS:000078764100020 ER PT J AU Lyapustin, AI AF Lyapustin, AI TI Atmospheric and geometrical effects on land surface albedo SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BIDIRECTIONAL REFLECTANCE; FOREST CANOPY; EOS-MODIS; VEGETATION; MODEL; DISTRIBUTIONS; RADIOMETER; SCATTERING; ALGORITHM; HARDWOOD AB In spite of extensive experimental and theoretical studies of land surface albedo, there is a need of generalization and systematic quantification of its dependence on solar zenith angle and type of surface, and of atmospheric effects in these relationships. This work presents a systematic numerical study of surface albedo for 12 land cover types, described by realistic anisotropic reflectance, under widely varying atmospheric conditions. Our research is based on the rigorous solution of the radiative transfer equation with the spherical harmonics method. It uses a new original analytical formalism for treatment of the anisotropic boundary conditions, which avoids numeric integration. This formalism is described in the first part of the paper along with the major steps in solution of the radiative transfer equation. The second part of the paper presents the results of our study, which can be summarized as follows: for a large number of vegetation and soil surfaces, the range of relative variation of surface albedo with atmospheric opacity does not exceed 10-15% at theta(0)less than or equal to 50 degrees and 20-30% at theta(0)less than or equal to 70 degrees, Among atmospheric parameters, optical thickness is the main factor affecting albedo. The effects of the scattering function and single-scattering albedo are small and can be neglected. For small solar zenith angles, surface albedo increases with atmospheric opacity, while for big angles theta(0), it decreases. The watershed lies at theta(0)approximate to 52 degrees-57 degrees when the albedo is almost insensitive to the atmospheric opacity. Albedo measurements at these angles can be used directly for the surface characterization. At large solar zenith angles (theta(0) >70 degrees-80 degrees), albedo drops off with the further increase of angle theta(0). C1 NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lyapustin, AI (reprint author), NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Mail Code 920, Greenbelt, MD 20771 USA. EM alyapust@pop900.gsfc.nasa.gov RI Lyapustin, Alexei/H-9924-2014 OI Lyapustin, Alexei/0000-0003-1105-5739 NR 37 TC 19 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 27 PY 1999 VL 104 IS D4 BP 4127 EP 4143 DI 10.1029/1998JD200064 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 169TF UT WOS:000078764100021 ER PT J AU Vinnikov, KY Robock, A Qiu, SA Entin, JK Owe, M Choudhury, BJ Hollinger, SE Njoku, EG AF Vinnikov, KY Robock, A Qiu, SA Entin, JK Owe, M Choudhury, BJ Hollinger, SE Njoku, EG TI Satellite remote sensing of soil moisture in Illinois, United States SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MULTICHANNEL MICROWAVE RADIOMETER; SURFACE MOISTURE; TEMPERATURE-MEASUREMENTS; WATER-CONTENT; MODEL; VEGETATION; CLIMATE; AVAILABILITY; VARIABILITY; SIMULATIONS AB To examine the utility of using satellite passive microwave observations to measure soil moisture over large regions, we conducted a pilot study using the scanning multichannel microwave radiometer (SMMR) on Nimbus-7, which operated from 1978 to 1987, and actual in situ soil moisture observations from the state of Illinois, United States, which began in 1981. We examined SMMR midnight microwave brightness temperatures on a 0.5 degrees x 0.5 degrees grid, and compared them with direct soil moisture measurements at 14 sites in Illinois for the period 1982-1987. The results suggest that both the polarization difference and the microwave emissivity for horizontal polarization at frequencies less than or equal to 18 GHz have real utility for use as a soil moisture information source in regions with grass or crops where the vegetation is not too dense. While SMMR observations ended in 1987, special sensor microwave/imager observations at 19 GHz start then and extend to the present, and advanced microwave scanning radiometer instruments will fly on satellites beginning soon. Together with SMMR, they have the potential to produce a soil moisture record over large regions for more than two decades and extend it into the future. Satellite observations from these low-resolution satellite instruments measure the component of large-scale long-term soil moisture variability that is related to atmospheric forcing (from precipitation, evapotranspiration, and snowmelt). C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Illinois State Water Survey, Champaign, IL 61820 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Vinnikov, KY (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM kostya@atmos.umd.edu; robock@envsci.rutgers.edu; sqiu@atmos.umd.edu; jentin@atmos.umd.edu; owe@hydro4.gsfc.nasa.gov; bchoudhury@hydro4.gsfc.nasa.gov; hollinger@uiuc.edu; eni.g.njoku@jpl.nasa.gov RI Vinnikov, Konstantin/F-9348-2010; Robock, Alan/B-6385-2016; OI Robock, Alan/0000-0002-6319-5656 NR 56 TC 87 Z9 89 U1 1 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 27 PY 1999 VL 104 IS D4 BP 4145 EP 4168 DI 10.1029/1998JD200054 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 169TF UT WOS:000078764100022 ER PT J AU Tegen, I AF Tegen, I TI Comment on "Contribution of different aerosol species to the global aerosol extinction optical thickness: Estimates from model results" by I. Tegen et al. Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. RP Tegen, I (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 27 PY 1999 VL 104 IS D4 BP 4249 EP 4250 DI 10.1029/1998JD200065 PG 2 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 169TF UT WOS:000078764100028 ER PT J AU Ma, XJ Balasubramaniam, R Subramanian, RS AF Ma, XJ Balasubramaniam, R Subramanian, RS TI Numerical simulation of thermocapillary drop motion with internal circulation SO NUMERICAL HEAT TRANSFER PART A-APPLICATIONS LA English DT Article ID MARANGONI NUMBERS; BUBBLE MIGRATION; LOW GRAVITY; GAS BUBBLE; REYNOLDS AB The thermocapillary motion of drops in zero gravity is analyzed numerically. When convective transport is important, the internal circulation in the drop has a profound effect on the temperature distribution in ifs vicinity and hence on its migration speed. For sufficiently large values of the Marangoni number Ma, for steady motion of the drop, the temperature difference on Be drop surface and its scaled speed increase with Ma. This is in contrast to (1) existing computational results for liquid drops whose sealed speed decreases with Ma and (2) asymptotic results for gas bubbles whose scaled speed is independent of Ma when it is large. C1 NASA, Natl Ctr Micrograv Res Fluids & Combust, Lewis Res Ctr, Cleveland, OH 44135 USA. Clarkson Univ, Dept Chem Engn, Potsdam, NY USA. RP Balasubramaniam, R (reprint author), NASA, Natl Ctr Micrograv Res Fluids & Combust, Lewis Res Ctr, 21000 Brookpark Rd,MS 110-3, Cleveland, OH 44135 USA. NR 20 TC 24 Z9 29 U1 1 U2 5 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 USA SN 1040-7782 J9 NUMER HEAT TR A-APPL JI Numer. Heat Tranf. A-Appl. PD FEB 26 PY 1999 VL 35 IS 3 BP 291 EP 309 DI 10.1080/104077899275254 PG 19 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA 172AW UT WOS:000078900000004 ER PT J AU Raffaelle, RP Forsell, H Potdevin, T Friedfeld, R Mantovani, JG Bailey, SG Hubbard, SM Gordon, EM Hepp, AF AF Raffaelle, RP Forsell, H Potdevin, T Friedfeld, R Mantovani, JG Bailey, SG Hubbard, SM Gordon, EM Hepp, AF TI Electrodeposited CdS on CIS pn junctions SO SOLAR ENERGY MATERIALS AND SOLAR CELLS LA English DT Article DE CuInSe2; CdS; Schottky barriers; electrodeposition ID CULNSE2; CUINSE2 AB We have been investigating the electrochemical deposition of thin films and junctions of cadmium sulfide (CdS) and copper indium diselenide (CIS). We show that it is possible to fabricate pn junctions based on n-type CdS and p-type CIS entirely by electrodeposition. CIS is considered to be one of the best absorber materials for use in polycrystalline thin-film photovoltaic solar cells. CdS provides a closely lattice-matched window layer for CIS. Electrodeposition is a simple and inexpensive method for producing thin-film CdS and CIS. We have produced both p- and n-type CIS thin films, as well as a CdS on CIS pn junction via electrodeposition. Elemental analysis of the CdS and CIS thin films was performed using X-ray photoelectron spectroscopy and energy dispersive spectroscopy. Optical band gaps were determined for these films using optical transmission spectroscopy. Carrier densities of the CIS films as a function of their deposition voltage were determined from capacitance vs. voltage measurements using Al Schottky barriers. Current vs. voltage characteristics were measured for the Al on CIS Schottky barriers and for the CdS on CIS pn junction. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Florida Inst Technol, Dept Phys & Space Sci, Melbourne, FL 32901 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Raffaelle, RP (reprint author), Florida Inst Technol, Dept Phys & Space Sci, 150 W Univ Blvd, Melbourne, FL 32901 USA. NR 18 TC 38 Z9 40 U1 1 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0248 J9 SOL ENERG MAT SOL C JI Sol. Energy Mater. Sol. Cells PD FEB 26 PY 1999 VL 57 IS 2 BP 167 EP 178 DI 10.1016/S0927-0248(98)00172-X PG 12 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA 167QR UT WOS:000078645200005 ER PT J AU Ramesham, R AF Ramesham, R TI Fabrication of diamond microstructures for microelectromechanical systems (MEMS) by a surface micromachining process SO THIN SOLID FILMS LA English DT Letter DE diamond; microstructures; beams; bridges; cantilever beams; selective deposition ID DEPOSITION; MEMBRANES; FILMS AB Selective polycrystalline diamond thin film has been grown on a silicon dioxide/silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950 degrees C. A simple process flow has been developed to fabricate diamond microstructures such as diamond beams and cantilever beams using surface micromachining and photolithography for the first time. Scanning electron and optical microscopy has been used to characterize the surface micromachined diamond microstructures. (C) 1999 Elsevier Science S.A. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 125-152, Pasadena, CA 91109 USA. NR 18 TC 34 Z9 37 U1 0 U2 3 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD FEB 26 PY 1999 VL 340 IS 1-2 BP 1 EP 6 DI 10.1016/S0040-6090(98)01370-4 PG 6 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 179WM UT WOS:000079353000001 ER PT J AU Lasseigne, DG Joslin, RD Jackson, TL Criminale, WO AF Lasseigne, DG Joslin, RD Jackson, TL Criminale, WO TI The transient period for boundary layer disturbances SO JOURNAL OF FLUID MECHANICS LA English DT Article ID VISCOUS CHANNEL FLOWS; LOCALIZED DISTURBANCE; ENERGY GROWTH; COUETTE-FLOW; EVOLUTION; PERTURBATIONS; INSTABILITY; RECEPTIVITY; SIMULATION; MECHANISM AB The onset of transition in a boundary layer is dependent on the initialization and interaction of disturbances in a laminar flow. Here, theory and full Navier-Stokes simulations focus on the transient period just after disturbances enter the boundary layer. The temporal evolution of disturbances within a boundary layer is investigated by examining a series of initial value problems. In each instance, the complete spectra (i.e. the discrete and the continuum) are included so that the solutions can be completely arbitrary. Both numerical and analytical solutions of the linearized Navier-Stokes equations subject to the arbitrary initial conditions are presented. The temporal evolution of disturbances during the transient period are compared with the spatial evolution of the same disturbances and a strong correlation between the two approaches is demonstrated indicating that the theory may be used for the transient period of disturbance evolution. The theory and simulations demonstrate that strong amplification of the disturbances can occur as a result of the inclusion of the continuum in the prediction of disturbance evolution. The results further show that any approach proposed for use in bypass boundary layer transition must include the transient growth that results from the continuum. Finally, although a connection between temporal and spatial evolution in the transient period has been demonstrated, a theoretical basis as an explanation for this connection remains the focus of additional study. C1 Old Dominion Univ, Dept Math & Stat, Norfolk, VA 23529 USA. NASA, Fluid Mech & Acoust Div, Langley Res Ctr, Hampton, VA 23681 USA. NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. Univ Washington, Dept Appl Math, Seattle, WA 98195 USA. RP Lasseigne, DG (reprint author), Old Dominion Univ, Dept Math & Stat, Norfolk, VA 23529 USA. NR 32 TC 17 Z9 18 U1 0 U2 3 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD FEB 25 PY 1999 VL 381 BP 89 EP 119 DI 10.1017/S002211209800353X PG 31 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 177YJ UT WOS:000079238400004 ER PT J AU Huai, XL Joslin, RD Piomelli, U AF Huai, XL Joslin, RD Piomelli, U TI Large-eddy simulation of boundary-layer transition on a swept wedge SO JOURNAL OF FLUID MECHANICS LA English DT Article ID CROSS-FLOW-VORTICES; DISTURBANCE GROWTH; INSTABILITY; STABILITY; WINGS AB The spatial evolution of the disturbances that lead to boundary-layer transition on a swept wedge is computed by large-eddy simulations (LES). Stationary and travelling crossflow-vortex disturbances are generated using steady and random-amplitude suction and blowing on the wedge. For a fixed initial amplitude of the stationary vortex and low-amplitude unsteady disturbances, the LES show the evolution of stationary-dominated crossflow disturbances similar to previous simulations and experiments: linear amplification is followed by vortex roll-over and doubly inflectional velocity profiles just prior to transition. A high-frequency secondary instability is associated with the double inflection points in the velocity profiles. The harmonic modes of the primary disturbance were found to be amplified, while no energy was found in any subharmonic mode. The physical phenomena were significantly different when the stationary and travelling vortices have comparable initial amplitudes: in this case, the vortex roll-over does not occur and transition is dominated by the travelling-wave component. C1 Univ Maryland, Dept Mech Engn, College Pk, MD 20742 USA. NASA, Fluid Mech & Acoust Div, Langley Res Ctr, Hampton, VA 23681 USA. RP Huai, XL (reprint author), AEA Technol Engn Software Inc, 2000 Oxford Dr, Pittsburgh, PA 15102 USA. NR 52 TC 6 Z9 6 U1 1 U2 5 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD FEB 25 PY 1999 VL 381 BP 357 EP 380 DI 10.1017/S0022112098003711 PG 24 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 177YJ UT WOS:000079238400014 ER PT J AU Farrell, WM Kaiser, ML Desch, MD Houser, JG Cummer, SA Wilt, DM Landis, GA AF Farrell, WM Kaiser, ML Desch, MD Houser, JG Cummer, SA Wilt, DM Landis, GA TI Detecting electrical activity from Martian dust storms SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID DEVILS; MODEL; MARS AB We present a model addressing the possible electrification of Martian dust storms based on the effective electrical charging of an individual dust grain. An upper charge bound on a grain can be determined based on the grain capacitance in the low-pressure Martian atmosphere. It is assumed that treiboelectric and inductive processes, like that presumed operating in terrestrial dust storms, can electrify the grain to significant levels. A collection of such grains charged in a dust cloud of many tens of kilometers in size can yield a substantial electric field moment. Given various grain charge and dust storm sizes, the electric moment will be determined along with estimates of electrical discharge and emitted radio power based upon known models. We also suggest the possibility that remote detection of discharge-related VLF emission propagating in the surface/ionosphere waveguide can be used to determine subsurface conductivity. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Farrell, WM (reprint author), NASA, Goddard Space Flight Ctr, Code 695, Greenbelt, MD 20771 USA. RI Cummer, Steven/A-6118-2008; Farrell, William/I-4865-2013 OI Cummer, Steven/0000-0002-0002-0613; NR 20 TC 66 Z9 66 U1 1 U2 7 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 FEB 25 PY 1999 VL 104 IS E2 BP 3795 EP 3801 DI 10.1029/98JE02821 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 169QP UT WOS:000078760300001 ER PT J AU Baker, RD Schubert, G Jones, PW AF Baker, RD Schubert, G Jones, PW TI High Rayleigh number compressible convection in Venus' atmosphere: Penetration, entrainment, and turbulence SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GRAVITY-WAVES; NUMERICAL-SIMULATION; CELLULAR CONVECTION; RADIO OCCULTATION; CLOUD PATTERNS; GENERATION; GALILEO; LAYERS AB Numerical simulations of two-dimensional, nonlinear fully compressible convection at the subsolar point in the clouds of Venus are presented. One moderate Rayleigh number case (Ra-q = 6.8 x 10(6)) and two high Rayleigh number (Ra-q = 1.1 x 10(9)) cases are considered. Cloud-level convection is characterized by cold, narrow downwellings that deeply penetrate the underlying stable layer and that entrain warmer air from the overlying stable layer. The convection layer depth, as determined from the horizontally averaged static stability, spans 9 km (47-56 km altitude) and 14 km (46-60 km altitude) for the moderate Rayleigh number and high Rayleigh number simulations, respectively. In the high Rayleigh number cases, convective penetration extends over a scale height from the bottom of the convection layer down to 38 km altitude. Strong convective entrainment completely erodes the overlying stable layer in the high Ra-q cases and incorporates it into the convection layer. The timescale for entrainment of the overlying stable layer is roughly 1 day and may explain why cellular features are predominantly found near and downwind of the subsolar point. The high Rayleigh number simulations are convectively turbulent and exhibit a spectral energy cascade of k(-3), where k is the horizontal wavenumber. Our results suggest that cellular features in the subsolar region are observed at the cloud tops because convection may extend to much higher altitudes there. Downward penetrative convection may also be responsible for turbulence observed in Venus' atmosphere at 45 km altitude. C1 NASA, Mesoscale Atmospher Proc Branch, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. Univ Illinois, Natl Ctr Supercomp Applicat, Urbana, IL 61801 USA. San Diego Supercomp Ctr, San Diego, CA USA. RP Baker, RD (reprint author), NASA, Mesoscale Atmospher Proc Branch, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 912, Greenbelt, MD 20771 USA. EM rbaker@agnes.gsfc.nasa.gov; schubert@ucla.edu; pwjones@lanl.gov NR 69 TC 9 Z9 9 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9097 EI 2169-9100 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD FEB 25 PY 1999 VL 104 IS E2 BP 3815 EP 3832 DI 10.1029/1998JE900029 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 169QP UT WOS:000078760300003 ER PT J AU Scott, GBI Fairley, DA Freeman, CG McEwan, MJ Anicich, VG AF Scott, GBI Fairley, DA Freeman, CG McEwan, MJ Anicich, VG TI CmHn+ reactions with atomic and molecular nitrogen: An experimental study SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID ION; OXYGEN; C3H3+ AB The reactions of a series of CmHn+ ions (m = 1-6; n = 0-6) with atomic and molecular nitrogen have been investigated using a selected ion flow tube (SIFT) operating at room temperature. Rate coefficients and product distributions are reported for the reactions studied. The hydrocarbon cations examined in this work are largely unreactive with molecular nitrogen (association is found in just three cases), whereas multiple product channels are observed in reactions between CmHn+ ions and N atoms. For m < 3, some N atom incorporation into the hydrocarbon ion occurs. For m > 3, the N atom is usually incorporated into the neutral leaving group (HCN). C1 Univ Canterbury, Dept Chem, Christchurch 1, New Zealand. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP McEwan, MJ (reprint author), Univ Canterbury, Dept Chem, Christchurch 1, New Zealand. NR 22 TC 37 Z9 37 U1 1 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD FEB 25 PY 1999 VL 103 IS 8 BP 1073 EP 1077 DI 10.1021/jp983797d PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 174BR UT WOS:000079014700012 ER PT J AU Kushto, GP Zhou, MF Andrews, L Bauschlicher, CW AF Kushto, GP Zhou, MF Andrews, L Bauschlicher, CW TI An infrared spectroscopic and density functional theoretical investigation of the reaction products of laser-ablated scandium and titanium atoms with nitric oxide SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID TRANSITION-METAL ATOMS; GAUSSIAN-BASIS SETS; SOLID ARGON; SPECTRA; NITROGEN; OXYGEN; MATRIX; SCO AB Laser-ablated Sc and Ti atoms have been reacted with NO during condensation in excess argon. Matrix infrared spectra show that the major products are the side-bonded Sc[NO] species and the inserted NScO and NTiO molecules based on isotopic substitution ((NO)-N-15-O-16 and (NO)-N-15-O-18) and DFT calculations of isotopic frequencies, which provide a match for two modes in three isotopic modifications for each molecule. The NScO and NTiO molecules are nitride/oxides with M-O stretching modes only 46-88 cm(-1) below the diatomic metal oxides but M-N stretching modes 314-442 cm(-1) lower than the diatomic metal nitride molecules. The ScN, ScO and TiN, TiO molecules are observed as decomposition products. Evidence is also presented for the nitrosyls ScNO and TiNO, the Sc[NO](+) cation, and the NTiO- anion. C1 Univ Virginia, Dept Chem, Charlottesville, VA 22901 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), Univ Virginia, Dept Chem, Mccormick Rd, Charlottesville, VA 22901 USA. NR 31 TC 35 Z9 35 U1 2 U2 10 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD FEB 25 PY 1999 VL 103 IS 8 BP 1115 EP 1125 DI 10.1021/jp9838036 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 174BR UT WOS:000079014700018 ER PT J AU Nishimura, H Huo, WM Ali, MA Kim, YK AF Nishimura, H Huo, WM Ali, MA Kim, YK TI Electron-impact total ionization cross sections of CF4, C2F6, and C3F8 SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID MOLECULES; ENERGY; DISSOCIATION; THRESHOLD; ATOMS; MODEL AB Both theoretical and experimental electron-impact total ionization cross sections of CF4, C2F6, and C3F8 are presented. The experimental cross sections have been measured as a function of incident electron energy T from threshold to 3 keV. A parallel plate condenser type apparatus was used. The molecular polarizability for C3F8 was empirically estimated to be alpha = 10.6 Angstrom(3) +/- 0.8 Angstrom(3). Theoretical cross sections calculated from the binary-encounter-Bethe (BEB) method, which combines a modified form of the Mott cross section and the Bethe cross section, are compared with the experimental cross sections. The BEB cross sections calculated from correlated molecular wave functions with theoretical estimates for multiple ionization are about 10% higher than the experimental data at the peak for CF4, while they are in excellent agreement with the experimental data for C2F6 and C3F8. Our analysis shows that the BEB theory implicitly includes part of neutral dissociation, such as CF4 --> CF3 + F, and hence tends to be an upper limit to the total ionization cross section. We found that the difference between our best theory for CF4 and the present experimental cross section exhibits a remarkable similarity to the shape of the recently measured cross section for neutral dissociation, though there is no a priori reason for the similarity. Owing to the large number of bound electrons, the correlation included in our wave functions for C2F6 and C3F8 is more limited than for CF4. Hence, we believe that for these two molecules the calculated cross sections are lower than the true BEB values, in spite of the apparent excellent agreement between the theory and the experiment. (C) 1999 American Institute of Physics. [S0021-9606(99)01608-6]. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Howard Univ, Dept Chem, Washington, DC 20059 USA. Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. Niigata Univ, Dept Phys, Niigata 95021, Japan. RP Nishimura, H (reprint author), Niigata Univ, Dept Phys, Niigata 95021, Japan. NR 43 TC 71 Z9 71 U1 0 U2 5 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD FEB 22 PY 1999 VL 110 IS 8 BP 3811 EP 3822 DI 10.1063/1.478270 PG 12 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 168AX UT WOS:000078668900024 ER PT J AU Jarzembski, MA Srivastava, V Rothermel, J AF Jarzembski, MA Srivastava, V Rothermel, J TI Vertical variability of aerosol backscatter from an airborne-focused continuous-wave CO2 lidar at 9.1-mu m wavelength SO APPLIED OPTICS LA English DT Article ID ATLANTIC ATMOSPHERIC AEROSOL; MU-M; ANTHROPOGENIC AEROSOLS; CLOUD BACKSCATTER; SULFATE AEROSOLS; BACKGROUND MODE; DOPPLER LIDARS; PROFILES; PACIFIC; CALIBRATION AB Atmospheric aerosol backscatter measurements taken with a continuous-wave focused Doppler lidar at 9.1-mu m wavelength were obtained over western North America and the Pacific Ocean from 13 to 26 September 1995 as part of a NASA airborne mission. Backscatter variability was measured for similar to 52 flight hours, covering an equivalent horizontal distance of similar to 30,000 km in the troposphere. Some quasi-vertical backscatter profiles were also obtained during various ascents and descents at altitudes that ranged from similar to 0.1 to 12 km. Similarities and differences for aerosol loading over land and ocean were observed. A midtropospheric aerosol backscatter background mode near 3 x 10(-11) to 1 x 10(-10) m(-1) sr(-1) was obtained, which is consistent with those of previous airborne and ground-based data sets. C1 Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Washington, DC USA. RP Jarzembski, MA (reprint author), Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. EM maurice.jarzembski@msfc.nasa.gov NR 29 TC 3 Z9 3 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD FEB 20 PY 1999 VL 38 IS 6 BP 908 EP 915 DI 10.1364/AO.38.000908 PG 8 WC Optics SC Optics GA 169GQ UT WOS:000078739500003 PM 18305690 ER PT J AU Beyerle, G McDermid, IS AF Beyerle, G McDermid, IS TI Altitude range resolution of differential absorption lidar ozone profiles SO APPLIED OPTICS LA English DT Article ID STRATOSPHERIC OZONE; STOIC 1989 AB A method is described for the empirical determination of altitude range resolutions of ozone profiles obtained by differential absorption lidar (DIAL) analysis. The algorithm is independent of the implementation of the DIAL analysis, in particular of the type and order of the vertical smoothing Alter applied. An interpretation of three definitions of altitude range resolution is given on the basis of simulations carried out with the Jet Propulsion Laboratory ozone DIAL analysis program, SO3ANL. These definitions yield altitude range resolutions that differ by as much as a factor of 2. It is shown that the altitude resolution calculated by SO3ANL, and reported with all Jet Propulsion Laboratory Lidar ozone profiles, corresponds closely to the full width at half-maximum of a retrieved ozone profile if an impulse function is used as the input ozone profile. (C) 1999 Optical Society of America. C1 CALTECH, Jet Prop Lab, Table Mt Fac, Wrightwood, CA 92397 USA. Alfred Wegener Inst Polar & Marine Res, D-14401 Potsdam, Germany. RP Beyerle, G (reprint author), CALTECH, Jet Prop Lab, Table Mt Fac, POB 367, Wrightwood, CA 92397 USA. EM beyerle@tmf.jpl.nasa.gov; mcdermid@tmf.jpl.nasa.gov OI Beyerle, Georg/0000-0003-1215-2418 NR 15 TC 9 Z9 10 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD FEB 20 PY 1999 VL 38 IS 6 BP 924 EP 927 DI 10.1364/AO.38.000924 PG 4 WC Optics SC Optics GA 169GQ UT WOS:000078739500005 PM 18305692 ER PT J AU Haltrin, VI AF Haltrin, VI TI Diffuse reflection coefficient of a stratified sea SO APPLIED OPTICS LA English DT Article ID SCATTERING; EQUATION; WATERS; MODEL AB A differential equation of a Riccati type for the diffuse reflection coefficient of a stratified sea is proposed. For a homogeneous sea with arbitrary inherent optical properties this equation is solved analytically. For an inhomogeneous sea it is solved approximately for any arbitrary stratification. The resulting equation expresses the diffuse reflection coefficient of the sea through vertical profiles of absorption and backscattering coefficients, bottom albedo, and sea depth. The results of calculations with this equation are compared with Monte Carlo computations. It was found that the precision of this approach is in the range of 15%. C1 USN, Res Lab, Stennis Space Ctr, Ocean Sci Branch, Mississippi State, MS 39529 USA. RP Haltrin, VI (reprint author), USN, Res Lab, Stennis Space Ctr, Ocean Sci Branch, Code 7331, Mississippi State, MS 39529 USA. EM haltrin@nrlssc.navy.mil NR 23 TC 9 Z9 9 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD FEB 20 PY 1999 VL 38 IS 6 BP 932 EP 936 DI 10.1364/AO.38.000932 PG 5 WC Optics SC Optics GA 169GQ UT WOS:000078739500007 PM 18305694 ER PT J AU Wang, MH AF Wang, MH TI Validation study of the SeaWiFS oxygen A-band absorption correction: comparing the retrieved cloud optical thicknesses from SeaWiFS measurements SO APPLIED OPTICS LA English DT Article ID WATER-LEAVING RADIANCE; OCEAN-COLOR IMAGERY; ATMOSPHERIC CORRECTION AB Atmospheric correction in ocean-color remote sensing corrects more than 90% of signals in the visible contributed from the atmosphere measured at satellite altitude. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) atmospheric correction uses radiances measured at two near-infrared wavelengths centered at 765 and 865 nm to estimate the atmospheric contribution and extrapolate it into the visible range. However, the SeaWiFS 765-nm band, which covers 745-785 nm, completely encompasses the oxygen A-band absorption. The O-2 A-band absorption usually reduces more than 10-15% of the measured radiance at the SeaWiFS 765-nm band. Ding and Gordon [Appl. Opt. 34, 2068-2080 (1995)] proposed a numerical scheme to remove the O-2 A-band absorption effects from the atmospheric correction. This scheme has been implemented in the SeaWiFS ocean-color imagery data-processing system. I present results that demonstrate a method to validate the SeaWiFS 765-nm O-2 A-band absorption correction by analyzing the sensor-measured radiances at 765 and 865 nm taken looking at the clouds over the oceans. SeaWiFS is usually not saturated with cloudy scenes because of its bilinear gain design. Because the optical and radiative properties of water clouds are nearly independent of the wavelengths ranging from 400 to 865 nn, the sensor-measured radiances above the cloud at the two near-infrared wavelengths are comparable. The retrieved cloud optical thicknesses from the SeaWiFS band 7 measurements are compared for cases with and without the O-2 A-band absorption corrections and from the band 8 measurements. The results show that, for air-mass values of 2-5, the current SeaWiFS O-2 A-band absorption correction works reasonably well. The validation method is potentially applicable for in-orbit relative calibration for SeaWiFS and other satellite sensors. C1 Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wang, MH (reprint author), Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Code 970-2, Greenbelt, MD 20771 USA. RI Wang, Menghua/F-5631-2010 OI Wang, Menghua/0000-0001-7019-3125 NR 12 TC 14 Z9 15 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD FEB 20 PY 1999 VL 38 IS 6 BP 937 EP 944 DI 10.1364/AO.38.000937 PG 8 WC Optics SC Optics GA 169GQ UT WOS:000078739500008 PM 18305695 ER PT J AU Mather, JC Fixsen, DJ Shafer, RA Mosier, C Wilkinson, DT AF Mather, JC Fixsen, DJ Shafer, RA Mosier, C Wilkinson, DT TI Calibrator design for the COBE far infrared absolute spectrophotometer (FIRAS) SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology, observations; instrumentation, spectrographs ID SPECTRUM AB The photometric errors of the external calibrator for the Far Infrared Absolute Spectrophotometer (FIRAS) instrument on the COBE are smaller than the measurement-errors on the cosmic microwave background radiation (CMBR) spectrum (typically 0.02 MJy sr(-1), 1 sigma) and smaller than 0.01% of the peak brightness of the CMB. The calibrator is a reentrant cone, shaped like a trumpet mute, made of Eccosorb iron-loaded epoxy. It fills the entire beam of the instrument and is the source of its accuracy. Its known errors are caused by reflections, temperature gradients, and leakage through the material and around the edge. Estimates and limits are given for all known error sources. Improvements in understanding the temperature measurements of the calibrator allow an improved CMB temperature determination of 2.725 +/- 0.002 K. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Princeton Univ, Princeton, NJ 08544 USA. RP Mather, JC (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 25 TC 337 Z9 339 U1 2 U2 7 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 511 EP 520 DI 10.1086/306805 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000001 ER PT J AU Stecker, FW Salamon, MH AF Stecker, FW Salamon, MH TI Photodisintegration of ultra-high-energy cosmic rays: A new determination SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmic rays; diffuse radiation; intergalactic medium ID INTERGALACTIC INFRARED RADIATION; TEV GAMMA-RAYS; TOPOLOGICAL DEFECTS; SPECTRUM; CUTOFF; ORIGIN; LIMITS; WELL AB We present the results of a new calculation of the photodisintegration of ultra-high-energy cosmic-ray (UHCR) nuclei in intergalactic space. The critical interactions for energy loss and photodisintegration of UHCR nuclei occur with photons of the 2.73 K cosmic background radiation (CBR) and with photons of the IR background radiation (IBR). We have reexamined this problem, making use of a new determination of the IBR based on empirical data primarily from IRAS galaxies, which is consistent with direct measurements and upper limits from TeV gamma-ray observations. We have also improved the calculation by including the specific threshold energies for the various photodisintegration interactions in our Monte Carlo calculation. With the new smaller IBR flux, the steepness of the Wien side of the now relatively more important CBR makes their inclusion essential for more accurate results. Our results indicate a significant increase in the propagation time of UHCR nuclei of a given energy over previous results. We discuss the possible significance of this for UHCR origin theory. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Utah, Dept Phys, Salt Lake City, UT 84112 USA. RP Stecker, FW (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. RI Stecker, Floyd/D-3169-2012 NR 51 TC 160 Z9 160 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 521 EP 526 DI 10.1086/306816 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000002 ER PT J AU Welty, DE Frisch, PC Sonneborn, G York, DG AF Welty, DE Frisch, PC Sonneborn, G York, DG TI Interstellar abundances in the Magellanic Clouds. II. The line of sight to SN 1987A in the large Magellanic Cloud SO ASTROPHYSICAL JOURNAL LA English DT Review DE galaxies, abundances; ISM, abundances; Magellanic Clouds; quasars : absorption lines; supernovae : individual (SN 1987A) ID HUBBLE-SPACE-TELESCOPE; INTER-STELLAR MEDIUM; HIGH-VELOCITY GAS; ABSORPTION-LINES; NEUTRAL HYDROGEN; NA-I; ULTRAVIOLET OBSERVATIONS; CA-II; H-I; DIELECTRONIC RECOMBINATION AB We have analyzed both high-resolution optical absorption-line spectra and UV spectra obtained with IUE of the LMC SN 1987A, in order to determine abundances and physical conditions in the various neutral interstellar clouds along the line of sight to the supernova (SN). We have used a flat-fielding procedure to enhance the signal-to-noise ratios (S/Ns) and the reliability of weak features in the UV spectra and have modeled the UV line profiles using the component structure derived fr om the higher resolution, high-S/N optical spectra of Ca II and Na I. Fits to the Ca II, Ca II and Na I absorption-line profiles reveal (at least) 46 components, at velocities -24 km s(-1) less than or similar to upsilon(.) less than or similar to 296 km s(-1), which can be associated with the 10 component groups discernible in the lower resolution UV spectra. From the UV spectra, we determined component-group column densities for C I, Mg I, Mg II, Al II, Si II, P II, Cl I, Ti II: Cr II, Mn II, Fe II, Ni II. and Zn II-With 1 sigma. uncertainties less than 0.1 dex in many cases. These are the most extensive and accurate abundances yet measured for the neutral ISM in the LMC. The component velocities, the patterns of relative elemental abundances [X/Zn] and [X/Fe], and various diagnostic ratios have been used to estimate the locations and physical characteristics [N(PI), T, n(e)] of these component groups. (Systematic differences among the diagnostic ratios make the derived physical properties somewhat uncertain, however.) The components at low velocities (5 km s(-1) less than or similar to upsilon less than or similar to 23 km s(-1)) have relative abundances and values for the diagnostic ratios very similar to those found for warm, diffuse Galactic disk clouds and likely are due to a mixture of warm and cool gas in the Galactic disk. The components at velocities 56 km s(-1) less than or similar to upsilon less than or similar to 90 km s(-1) are due to a mixture of warm and cool gas, apparently with negligible depletions, in the Galactic halo. The two intermediate-velocity component groups (109 km s(-1) less than or similar to upsilon less than or similar to 140 km s(-1) and 155 km s(-1) less than or similar to upsilon less than or similar to 176 km s(-1)) both have relative abundances similar to those found for Galactic halo clouds. These warm (T greater than or similar to 4500 K), partially ionized clouds are probably located in the Galactic halo and in the LMC, respectively. The components at velocities 191 km s(-1) less than or similar to upsilon less than or similar to 225 km s(-1) also have relative abundances similar to those in the halo clouds but are likely due to gas in the LMC, perhaps very close to the SN. The component groups at 238 km s(-1) less than or similar to upsilon(.) less than or similar to 255 km s(-1) and 265 km s(-1) less than or similar to upsilon less than or similar to 270 km s(-1) are probably located on opposite sides of the main LMC component group (at velocities 275 km s(-1) less than or similar to upsilon less than or similar to 296 km s(-1)) (using absorption-line data for several other adjacent lines of sight and the structure inferred from SN light-echo observations). Although the relative abundances and diagnostic ratios for those three LMC groups are similar to those found for warm, low-density Galactic disk clouds, the widths of individual components seen in very high resolution spectra of Na I and K I imply that T is generally less than about 1500 K. Higher N(Na I)IN(Ca II) ratios, the presence of CHI and the C I fine structure level populations suggest that the main LMC group contains both cool and warm gas. For the LMC components, the total N(H) estimated from the observed relative abundances and inferred depletions is consistent with the value obtained from Ly alpha absorption toward the neighboring star Sk -69 degrees 203, after accounting for differences in reddening and for an overall subsolar metallicity of 0.2-0.3 dex for the LMC ISM. Since the relative abundance patterns determined for stars and gaseous nebulae in both the SMC and the LMC appear to be similar to the solar pattern (for the elements whose interstellar abundances we have considered), the similarities in relative gas-phase interstellar abundances in our Galaxy and in the Magellanic Clouds suggest that the dust depletions follow similar patterns as well-despite differences in metallicity and dust-to-gas ratio among the three galaxies. These local relative abundance/depletion patterns may thus be used to infer total (gas +dust) abundances for QSO absorption-line systems at various redshifts. C1 Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Welty, DE (reprint author), Univ Chicago, Dept Astron & Astrophys, 5640 S Ellis Ave, Chicago, IL 60637 USA. EM welty@oddjob.uchicago.edu; frisch@oddjob.uchicago.edu; sonneborn@stars.gsfc.nasa.gov; don@oddjob.uchicago.edu RI Sonneborn, George/D-5255-2012 NR 133 TC 94 Z9 94 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 636 EP 671 DI 10.1086/306795 PN 1 PG 36 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000012 ER PT J AU Safi-Harb, S Petre, R AF Safi-Harb, S Petre, R TI Rossi X-Ray Timing Explorer observations of the eastern lobe of W50 associated with SS 433 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (W50); stars : individual (SS 433); supernova remnants; X-rays : stars ID SUPERNOVA REMNANT; GINGA OBSERVATIONS; SS-433; SS433; ACCELERATION; SPECTRUM; JETS AB We present the Rossi X-Ray Timing Explorer (RXTE) observations of the SNR W50, associated with SS 433. The observations cover the X-ray lobe found between SS 433 and the outer eastern radio "ear" of W50. The X-ray spectrum measured with the proportional counter array and the High-Energy Timing Experiment in the 3-100 keV range favors nonthermal over thermal models for this part of W50. We combine the RXTE spectrum with the ROSAT and ASCA spectra, thus covering similar to 3 orders of magnitude in energy. The spectrum of the harder X-ray emission is well represented by a power law with a photon index of similar to 1.45 and a total X-ray luminosity of similar to 1.5 x 10(35) ergs s(-1) for a source distance of 5.5 kpc. We thus confirm the nonthermal nature of the inner X-ray lobe. We discuss its implications in the context of the interaction between the jets from SS 433 and the surroundings. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Safi-Harb, S (reprint author), NASA, Goddard Space Flight Ctr, Code 662,Bldg 2, Greenbelt, MD 20771 USA. NR 31 TC 24 Z9 25 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 784 EP 792 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000024 ER PT J AU Hua, XM Kazanas, D Cui, W AF Hua, XM Kazanas, D Cui, W TI Probing the structure of accreting compact sources through X-ray time lags and spectra SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms : nonthermal; stars : neutron; X-rays : stars ID CYGNUS X-1; COMPTONIZATION; VARIABILITY AB We exhibit, by compiling all data sets we can acquire, that the Fourier-frequency-dependent, hard X-ray lags, first observed in the analysis of aperiodic variability of the light curves of the black hole candidate Cyg X-l, appear to be a property shared by several other accreting black hole candidate sources and also by the different spectral states of this source. We then present both analytic and numerical models of these time lags resulting by the process of Comptonization in a variety of hot electron configurations. We argue that, under the assumption that the observed spectra are due to Comptonization, the dependence of the lags on the Fourier period provides a means for mapping the spatial density profile of the hot electron plasma, while the period at which the lags eventually level off provides an estimate of the size of the scattering cloud. We further examine the influence of the location and spatial extent of the soft photon source on the form of the resulting lags for a variety of configurations; we conclude that the study of the X-ray hard lags can provide clues about these parameters of the Comptonization process, too. Fits of the existing data with our models indicate that the size of the Comptonizing clouds are quite large in extent (similar to 1 lt-s) with inferred radial density profiles that are in many instances inconsistent with those of the standard dynamical models, whereas the extent of the source of soft photons appears to be much smaller than those of the hot electrons by roughly 2 orders of magnitude and its location consistent with the center of the hot electron corona. C1 NASA, Goddard Space Flight Ctr, LHEA, Greenbelt, MD 20771 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. OI Cui, Wei/0000-0002-6324-5772 NR 25 TC 29 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 793 EP 803 DI 10.1086/306808 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000025 ER PT J AU Singh, KP Drake, SA Gotthelf, EV White, NE AF Singh, KP Drake, SA Gotthelf, EV White, NE TI X-ray spectroscopy of rapidly rotating, late-type dwarf stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : abundances; stars : coronae; stars : individual (HD 197890; Gliese 890, YY Geminorum); X-rays : stars ID EMISSION MEASURE DISTRIBUTION; WIDE-FIELD CAMERA; RADIO OBSERVATIONS; ASCA OBSERVATION; AR LACERTAE; DME STAR; GLIESE-890; HD-197890; SOLAR; ALGOL AB We present an X-ray spectroscopic analysis of two active dwarf stars with extremely short rotation periods, HD 197890 (Speedy Mic) and Gliese 890, using X-ray data acquired with the ASCA observatory. We analyze the X-ray spectrum of Speedy Mic in two separate time intervals, one corresponding to an apparent stellar flare, the other to "quiescence" or the nonflaring state. We also present a reanalysis of the ASCA spectrum of the M dwarf stellar binary YY Gem, during both quiescent and flaring states. We use the recently updated MEKAL plasma code to model these spectra and find that a minimum of two temperature components are required to obtain good fits for all three stars. The inferred emission measures of the hot components in YY Gem and Speedy Mic, and the temperature of the hot component in the case of YY Gem, increase significantly during the observed X-ray flares, in agreement with previous studies of similar stellar X-ray flares. In addition, metal abundances that are low compared to the solar photospheric values are preferred (but not required) for the quiescent coronae of Gliese 890 and Speedy Mic, while for the quiescent corona of YY Gem, subsolar metal abundances are required and solar abundance models can be ruled out with high confidence. We combine the results of this study with those of previous ASCA and ROSAT analyses of late-type dwarf stars with known rotation rates to obtain a sample of 17 G, K, and M dwarfs. We find a strong correlation of the X-ray to bolometric luminosity ratio, L-X/L-bol, both with the rotation period and the Rossby number (R-o), in agreement with previous studies. Using a homogeneous subset of 10 dwarfs for which we have purely ASCA-derived temperatures and elemental abundances, we find that the temperature of the hottest component present in their coronae is correlated with this luminosity ratio, as expected. Finally, we note that the Fe abundances for all active dwarf stars having normalized X-ray luminosities log (L-X/L-bol) -3.7 are significantly subsolar, whereas the Fe abundances in the less active stars are within a factor of 2 of the solar value. C1 Tata Inst Fundamental Res, Mumbai 400005, India. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Singh, KP (reprint author), Tata Inst Fundamental Res, Homi Bhabha Rd, Mumbai 400005, India. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 50 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 874 EP 891 DI 10.1086/306788 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000030 ER PT J AU Shrader, CR Sutaria, FK Singh, KP Macomb, DJ AF Shrader, CR Sutaria, FK Singh, KP Macomb, DJ TI High-energy spectral and temporal characteristics of GRO J1008-57 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; pulsars : individual (GRO J1008-57); stars : neutron; X-rays : stars ID ABSORPTION FEATURE; RAY; ATMOSPHERES; DISCOVERY AB A transient X-ray source, GRO J1008-57, was discovered by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Rag, Observatory (CGRO) in 1993 July. It reached a maximum intensity of about 1.4 times that of the Crab, in the 20-60 keV energy band. Pulsations in the X-ray intensity were detected at a period of 93.5 s. It has subsequently been determined to be a member of the Be star subclass of X-ray transients. In addition to BATSE, GRO J1008 - 57 was observed during its outburst by several pointed high-energy experiments: ROSAT, ASCA, and CGRO/OSSE. These nonsimultaneous but contemporaneous observations took place near and shortly after the peak of the outburst light curve. We report for the first time on a combined analysis of the CGRO and ASCA data sets. We have attempted to model the broadband high-energy continuum distribution and phase-resolved spectra. The broadband, phase-averaged continuum is well approximated by a power law with an exponential cutoff. Evidence for 6.4 keV line emission due to Fe is presented based on our spectral analysis. The energy dependence of the pulse profiles is examined in order to determine the energy at which the low-energy double-peaked profile detected by ASCA evolves into single-peaked pulse profile detected by BATSE. We discuss the implications of this pulse profile for the magnetic field and beam distribution for GRO J1008 - 57. Analysis of the BATSE and Rossi X-Ray Timing Explorer/ASM flux histories suggests that P-orbital similar to 135 days. We further suggest that a transient disk is likely to form during episodes of outbursts. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Lanham, MD USA. Tata Inst Fundamental Res Assoc, Mumbai, India. RP Shrader, CR (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 24 TC 14 Z9 14 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 920 EP 928 DI 10.1086/306785 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000034 ER PT J AU Proffitt, CR Brage, T Leckrone, DS Wahlgren, GM Brandt, JC Sansonetti, CJ Reader, J Johansson, SG AF Proffitt, CR Brage, T Leckrone, DS Wahlgren, GM Brandt, JC Sansonetti, CJ Reader, J Johansson, SG TI Mercury in the HgMn stars chi Lupi and HR 7775 SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffusion; stars : abundances; stars : individual (chi Lupi, HR 7775); stars : peculiar ID MULTICONFIGURATIONAL DIRAC-FOCK; MODEL STELLAR ATMOSPHERES; LIGHT-INDUCED DRIFT; AP STARS; ABUNDANCE; SPECTRA; LINES; WAVELENGTHS; DIFFUSION; ANOMALIES AB Observations of mercury lines in the HgMn stars chi Lupi and HR 7775 made with the Hubble Space Telescope Goddard High Resolution Spectrograph are presented and analyzed. In chi Lupi we find that all observed lines are consistent with the same isotopic mixture (essentially pure (204)Hg). Strong ionization anomalies are present, with UV Hg I lines being too weak and Hg III lines too strong for the abundance derived from lines of the majority ionization state, Hg rr. Observations of mercury in I;IR 7775 show less extreme isotope and ionization anomalies. We find that the ionization anomaly in the Hg I resonance lines can be plausibly explained as a non-LTE effect, but the same non-LTE calculations show that the Hg III ionization anomaly in chi Lupi cannot be explained in this way. Radiative force calculations show that the observed mercury abundance cannot be supported in the atmosphere by the radiative forces alone. We suggest that weak mixing brings mercury into the line-forming region from below the photosphere, while a wind of order 10(-14) M. yr(-1) supports a cloud of Hg III at very small optical depths. C1 Comp Sci Corp, Sci Program, Cincinnati, OH 45202 USA. Lund Univ, Dept Phys, S-22100 Lund, Sweden. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. RP Proffitt, CR (reprint author), Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. EM hrsproffitt@hrs.gsfc.nasa.gov; brage@kurslab.fysik.lu.se; hrsleckrone@hrs.gsfc.nasa.gov; spek_glenn@garbo.lucas.lu.se; brandt@lyrae.colorado.edu; Craig.Sansonetti@nist.gov; Joseph.Reader@nist.gov; spek_sej@garbo.lucas.lu.se NR 58 TC 56 Z9 57 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 FEB 20 PY 1999 VL 512 IS 2 BP 942 EP 960 DI 10.1086/306783 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000036 ER PT J AU Antiochos, SK MacNeice, PJ Spicer, DS Klimchuk, JA AF Antiochos, SK MacNeice, PJ Spicer, DS Klimchuk, JA TI The dynamic formation of prominence condensations SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : chromosphere; Sun : corona; Sun : prominences ID QUIESCENT PROMINENCES; SOLAR PROMINENCES; MAGNETIC-FIELD; CORONAL LOOPS; PLASMA AB We present simulations of a model for the formation of a prominence condensation in a coronal loop. The key idea behind the model is that the spatial localization of loop heating near the chromosphere leads to a catastrophic cooling in the corona. Using a new adaptive grid code, we simulate the complete growth of a condensation and find that after similar to 5000 s it reaches a quasi-steady state. We show that the size and growth time of the condensation are in good agreement with data and discuss the implications of the model for coronal heating and for observations of prominences and the surrounding corona. C1 USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Raytheon STX Corp, Greenbelt, MD 20770 USA. NASA, Goddard Space Flight Ctr, Earth & Space Data & Comp Div, Greenbelt, MD 20771 USA. RP USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RI Klimchuk, James/D-1041-2012; MacNeice, Peter/F-5587-2012; Antiochos, Spiro/D-4668-2012 OI Klimchuk, James/0000-0003-2255-0305; Antiochos, Spiro/0000-0003-0176-4312 NR 32 TC 126 Z9 128 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP 985 EP 991 DI 10.1086/306804 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VP UT WOS:000079809000040 ER PT J AU Markwardt, CB Strohmayer, TE Swank, JH AF Markwardt, CB Strohmayer, TE Swank, JH TI Observation of kilohertz quasi-periodic oscillations from the atoll source 4U 1702-429 by the Rossi X-Ray Timing Explorer SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (4U 1702-429); stars : neutron ID NEUTRON-STAR; DISCOVERY; BINARIES; VARIABILITY AB We present results of Rossi X-Ray Timing Explorer observations of the atoll source 4U 1702-429 in the middle of its luminosity range. Kilohertz-range quasi-periodic oscillations (QPOs) were observed first as a narrow (FWHM similar to 7 Hz) peak near 900 Hz and later as a pair consisting of a narrow peak in the range of 625-825 Hz and a faint, broad (FWHM = 91 Hz) peak. When the two peaks appeared simultaneously, the separation was 333 +/- 5 Hz. Six type I thermonuclear bursts were detected, of which five exhibited almost coherent oscillations near 330 Hz, which makes 4U 1702-429 only the second source to show burst oscillations very close to the kilohertz QPO separation frequency. The energy spectrum and color-color diagram indicate that the source executed variations in the range between the "island" and "lower banana" atoll states. In addition to the kilohertz variability, oscillations at similar to 10, similar to 35, and 80 Hz were also detected at various times, superposed on a red noise continuum. The centroid of the similar to 35 Hz QPO tracks the frequency of the kilohertz oscillation when they were both present. A Lense-Thirring gravitomagnetic precession interpretation appears more plausible in this case, compared with other atoll sources with low-frequency QPOs. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Markwardt, CB (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. RI Swank, Jean/F-2693-2012 NR 19 TC 50 Z9 50 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP L125 EP L129 DI 10.1086/311886 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VR UT WOS:000079809200012 ER PT J AU Palmer, DM AF Palmer, DM TI SGR 1806-20 is a set of independent relaxation systems SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; stars : individual (SGR 1806-20) ID RAY REPEATER SGR1806-20; HIGH-ENERGY TRANSIENT; PULSAR AB SGR 1806-20 produced patterns of bursts during its 1983 outburst that indicate multiple independent energy accumulation sites, each driven by a continuous power source, with sudden, incomplete releases of the accumulated energy. The strengths of the power sources and their durations of activity vary over several orders of magnitude. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Palmer, DM (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 661, Greenbelt, MD 20771 USA. NR 11 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1999 VL 512 IS 2 BP L113 EP L116 DI 10.1086/311881 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 187VR UT WOS:000079809200009 ER PT J AU Randel, WJ Wu, F Russell, JM Waters, J AF Randel, WJ Wu, F Russell, JM Waters, J TI Space-time patterns of trends in stratospheric constituents derived from UARS measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; QUASI-BIENNIAL OSCILLATION; PINATUBO AEROSOLS; WATER-VAPOR; HYDROGEN-FLUORIDE; OZONE DEPLETION; MOUNT-PINATUBO; BUDGET; CHLOROFLUOROCARBONS; TEMPERATURE AB The spatial and temporal behavior of low-frequency changes (trends) in stratospheric constituents measured by instruments on the Upper Atmosphere Research Satellite (UARS) during 1991-98 is investigated. The data include CH4, H2O, HF, HCI, O-3 and NO2 from the Halogen Occultation Experiment (HALOE), and O-3, ClO, and HNO3 from the Microwave Limb Sounder (MLS). Time series of global anomalies are analyzed by linear regression and empirical orthogonal function analysis. Each of the constituents show significant linear trends over at least some region of the stratosphere, and the spatial patterns exhibit coupling between the different species. Several of the constituents (namely CH4, H2O, HF, HCI, O-3, and NO2) exhibit a temporal change in trend rates, with strong changes prior to 1996 and weaker (or reversed) trends thereafter. Positive trends are observed in upper stratospheric ClO, with a percentage rate during 1993-97 consistent with stratospheric HCI increases and with tropospheric chlorine emission rates. Significant negative trends in ozone in the tropical middle stratosphere are found in both HALOE and MLS data during 1993-97, together with positive trends in the tropics near 25 km. These trends are very different from the decadal-scale ozone trends observed since 1979, and this demonstrates the variability of trends calculated over short time periods. Positive trends in NO2 are found in the tropical middle stratosphere, and spatial coincidence to the observed ozone decreases suggests the ozone is responding to the NO2 increase. Significant negative trends in HNO3 are found in the lower stratosphere of both hemispheres. These coupled signatures offer a fingerprint of chemical evolution in the stratosphere for the UARS time frame. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Hampton Univ, Hampton, VA 23668 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Randel, WJ (reprint author), Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA. EM randel@ucar.edu; wuf@ucar.edu; jmr@hamptonu.edu; joe@mls.jpl.nasa.gov RI Randel, William/K-3267-2016 OI Randel, William/0000-0002-5999-7162 NR 51 TC 64 Z9 64 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1999 VL 104 IS D3 BP 3711 EP 3727 DI 10.1029/1998JD100044 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 168RN UT WOS:000078706600020 ER PT J AU Plane, JMC Gardner, CS Yu, JR She, CY Garcia, RR Pumphrey, HC AF Plane, JMC Gardner, CS Yu, JR She, CY Garcia, RR Pumphrey, HC TI Mesospheric Na layer at 40 degrees N: Modeling and observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC SODIUM LAYER; EARTHS UPPER-ATMOSPHERE; LOWER THERMOSPHERE; MESOPAUSE REGION; TEMPERATURE-MEASUREMENTS; SEASONAL VARIABILITY; METEORIC METALS; IL 40-DEGREES-N; LIDAR TECHNIQUE; CHEMISTRY AB A complete monthly record of the annual variation of Na and temperature in the upper mesosphere has been obtained from 3 years of nighttime lidar observations at two midlatitude sites, Urbana-Champaign, Illinois (40 degrees N), and Fort Collins, Colorado (41 degrees N). The Na density exhibits a strong annual variation at all heights between 81 and 107 km, with the column abundance of the layer peaking in early winter and then decreasing by nearly a factor of 4 to a midsummer minimum. There are also significant semiannual components to the variations in the centroid height and thickness of the layer. The nighttime temperature profile between 81 and 105 km exhibits a high winter mesopause at about 101 km and a summer mesopause at about 85 km. During spring and autumn, the mesopause oscillates apparently randomly between these states. A seasonal model of the Na layer was then constructed incorporating recent laboratory studies of the pertinent neutral and ionic reactions of the metal. The background atmospheric composition was provided from three off-line models, as well as from UARS/Microwave Limb Sounder satellite measurements of H2O. With a small number of permitted adjustable parameters, the model is able to reproduce many observed features of the Na layer remarkably well, including the monthly variation in column abundance and layer shape. The biggest discrepancy is during midsummer, when the modeled layer is displaced 2-3 km above that observed, although a factor contributing to this is that the lidar observing period during summer was relatively short and the effect of the diurnal tide could have been incompletely sampled. Both the observations and the model show that Na density and temperature are highly correlated below 96 km (correlation coefficient equal to 0.8-0.95), mostly as a result of the influence of odd oxygen/hydrogen chemistry on the partitioning of sodium between atomic Na and its principal reservoir species, NaHCO3. Above 96 km, a weak negative correlation (-0.2) is explained by the dominance of ion-molecule chemistry. Finally, it was shown that if the eddy diffusion coefficient in the middle mesosphere is significantly smaller or if the global meteoric influx is much larger than the values used in the present model, then processes for permanently removing gas-phase Na species in the mesosphere, such as polymerisation and deposition onto dust particles, will need to be included. C1 Univ E Anglia, Sch Environm Sci, Norwich NR4 7TJ, Norfolk, England. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Illinois, Dept Elect & Comp Engn, Urbana, IL 61801 USA. Univ Edinburgh, Dept Meteorol, Edinburgh EH8 9YL, Midlothian, Scotland. Colorado State Univ, Dept Phys, Ft Collins, CO 80521 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Plane, JMC (reprint author), Univ E Anglia, Sch Environm Sci, Norwich NR4 7TJ, Norfolk, England. EM j.plane@uea.ac.uk; cgardner@uiuc.edu; joeshe@lamar.colostate.edu; rgarcia@garcia.acd.ucar.edu; hcp@met.ed.ac.uk RI Plane, John/C-7444-2015 OI Plane, John/0000-0003-3648-6893 NR 52 TC 80 Z9 84 U1 2 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1999 VL 104 IS D3 BP 3773 EP 3788 DI 10.1029/1998JD100015 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 168RN UT WOS:000078706600024 ER PT J AU Bauschlicher, CW Langhoff, SR AF Bauschlicher, CW Langhoff, SR TI Bond dissociation energies for substituted polycyclic aromatic hydrocarbons and their cations SO MOLECULAR PHYSICS LA English DT Article ID EMISSION FEATURES; MASS-SPECTROMETRY; SPECTRA AB The B3LYP/4-31G approach is used to compute bond energies for a series of substituted benzene, naphthalene, and anthracene molecules and their cations. The benzene bond energies are compared with experiment. The trends in the bond energies are discussed. The ionization energies are also reported and compared with available experiments. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, STC-230-3, Moffett Field, CA 94035 USA. NR 18 TC 23 Z9 24 U1 0 U2 6 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0026-8976 J9 MOL PHYS JI Mol. Phys. PD FEB 20 PY 1999 VL 96 IS 4 BP 471 EP 476 DI 10.1080/002689799165332 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 170TC UT WOS:000078821300003 ER PT J AU Dyall, KG AF Dyall, KG TI Bonding and bending in the actinyls SO MOLECULAR PHYSICS LA English DT Article ID EXTENDED HUCKEL CALCULATIONS; UO2(2+); PARAMETERS; THORIUM; URANIUM; URANYL; THO2; BENT AB Bonding in the actinyl species ThO(2), PaO(2)(+) and UO(2)(2+) has been studied using all-electron Dirac-Hartree-Fock calculations. In the Linear configuration there are strong An 6d-O 2p sigma and pi. bonds, combined with An 5f-O 2p bonds which also have some An 6p-O 2p antibonding character. The bond length is determined largely by the balance of 6p and 5f, and correlates well with the 5f mean radius. The bending of ThO(2) results from the fact that the 5f is higher in energy than the 6d and similar in radial extent, so that 5f-6d hybridization is an efficient mechanism for lowering the energy on bending. In the higher actinyls, the increasing disparity between the sizes and energies of the 5f and 6d makes the hybridization which occurs on bending energetically unfavourable. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Dyall, KG (reprint author), NASA, Ames Res Ctr, Thermosci Inst, MS 230-3, Moffett Field, CA 94035 USA. NR 12 TC 50 Z9 50 U1 2 U2 8 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0026-8976 J9 MOL PHYS JI Mol. Phys. PD FEB 20 PY 1999 VL 96 IS 4 BP 511 EP 518 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 170TC UT WOS:000078821300007 ER PT J AU Lee, TJ Dateo, CE Rice, JE AF Lee, TJ Dateo, CE Rice, JE TI An analysis of chlorine and bromine oxygen bonding and its implications for stratospheric chemistry SO MOLECULAR PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; JANAF THERMOCHEMICAL TABLES; MOLECULAR CALCULATIONS; VIBRATIONAL-SPECTRA; RELATIVE ENERGETICS; ROW ATOMS; ISOMERS; ACCURATE; CL; BR AB Trends in chlorine/oxygen and bromine/oxygen single and double bonds are examined for several molecules of interest in stratospheric halogen chemistry. Specifically, the relationships between bond distance and quadratic force constant, and bond distance and ionic bonding character are examined, together with bond energies. Similar to a previous study of FO bonding, it is found that the relationship between bond distance and force constant for Cl-O and Br-O single bonds is unusual and distinctly nonlinear. This is attributed to the through space interaction of halogen lone-pair electrons with the remainder of the molecule. Supporting evidence for this assertion is given by the fact that for X=O (C is Cl, Br) double bonds, where there are fewer halogen lone-pair electrons due to hypervalent bonding, this relationship is approximately linear. A detailed explanation for chlorine and bromine hyper valent bonding is presented which is consistent with all available data and with the trends studied here. In this model, chlorine or bromine hypervalent bonding is a result of the p --> d promotion of one or two lone-pair halogen electrons followed by the formation of two or four additional pd hybrid halogen bonds. This model explains why -XO2 species are particularly stable while the -XO and -XO3 species are not. Finally, the implications of this new understanding of chlorine and bromine chemistry for stratospheric reservoir species are discussed. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. IBM Corp, Almaden Res Ctr, Div Res, San Jose, CA 95120 USA. RP Lee, TJ (reprint author), NASA, Ames Res Ctr, Thermosci Inst, MS230-3, Moffett Field, CA 94035 USA. RI Rice, Julia/K-4928-2012; Lee, Timothy/K-2838-2012 OI Rice, Julia/0000-0001-5059-5127; NR 33 TC 22 Z9 22 U1 0 U2 3 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0026-8976 J9 MOL PHYS JI Mol. Phys. PD FEB 20 PY 1999 VL 96 IS 4 BP 633 EP 643 DI 10.1080/002689799165495 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 170TC UT WOS:000078821300019 ER PT J AU Partridge, H Bauschlicher, CW AF Partridge, H Bauschlicher, CW TI The dissociation energies of He-2, HeH, and ArH: a bond function study SO MOLECULAR PHYSICS LA English DT Article ID CONFIGURATION-INTERACTION CALCULATIONS; CORRELATED MOLECULAR CALCULATIONS; AB-INITIO CALCULATIONS; COUPLED-CLUSTER THEORY; GAUSSIAN-BASIS SETS; RARE-GAS HYDRIDES; WAVE-FUNCTIONS; HELIUM DIMER; ELECTRON CORRELATION; PERTURBATION-THEORY AB The bond energies and bond lengths are determined for He-2, HeH, and ArH at the CCSD(T) level using both atom-centred basis sets and those that include bond functions. The addition of bond functions dramatically improves that rate of convergence of the results with respect to the size of the atom-centred basis set; with bond functions, triple-zeta atom-centred basis sets outperform quintuple-zeta basis sets without bond functions. The addition of bond functions also reduces the number of diffuse functions that must be added to the atom-centred sets. Employing bond functions appears to offer a cost-effective method for computing the interaction energy between weakly bound systems, especially for He. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Partridge, H (reprint author), NASA, Ames Res Ctr, STC-230-3, Moffett Field, CA 94035 USA. NR 38 TC 42 Z9 42 U1 1 U2 9 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0026-8976 J9 MOL PHYS JI Mol. Phys. PD FEB 20 PY 1999 VL 96 IS 4 BP 705 EP 710 DI 10.1080/002689799165558 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 170TC UT WOS:000078821300025 ER PT J AU Bernstein, MP Sandford, SA Allamandola, LJ Gillette, JS Clemett, SJ Zare, RN AF Bernstein, MP Sandford, SA Allamandola, LJ Gillette, JS Clemett, SJ Zare, RN TI UV irradiation of polycyclic aromatic hydrocarbons in ices: Production of alcohols, quinones, and ethers SO SCIENCE LA English DT Article ID INTERPLANETARY DUST PARTICLES; INFRARED-SPECTROSCOPY; ABSORPTION FEATURES; MICRON SPECTRA; DENSE CLOUDS; INTERSTELLAR; MOLECULES; METEORITES; ANALOGS AB Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultraviolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones; and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These classes of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SETI Inst, Mountain View, CA 94043 USA. Stanford Univ, Dept Chem, Stanford, CA 94305 USA. RP Bernstein, MP (reprint author), NASA, Ames Res Ctr, Mail Stop 245-6, Moffett Field, CA 94035 USA. EM mbernstein@mail.arc.nasa.gov RI Zare, Richard/A-8410-2009 NR 41 TC 238 Z9 243 U1 6 U2 44 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD FEB 19 PY 1999 VL 283 IS 5405 BP 1135 EP 1138 DI 10.1126/science.283.5405.1135 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 169GD UT WOS:000078738400042 PM 10024233 ER PT J AU Thorn, RP Stief, LJ Kuo, SC Klemm, RB AF Thorn, RP Stief, LJ Kuo, SC Klemm, RB TI Photoionization mass spectrometric study of HOCl: Photoionization efficiency spectrum and ionization energy SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID VIBRATION-ROTATION SPECTRA; PHOTOELECTRON-SPECTROSCOPY; ULTRAVIOLET-SPECTRUM; HYPOCHLOROUS ACID; FORCE-FIELD; AB-INITIO; THERMOCHEMISTRY; HALOGENS; CLONO2; CL2O AB The photoionization efficiency (PIE) spectrum of HOCl was measured over the wavelength range lambda = 102-115 nm, using a discharge flow-photoionization mass spectrometer (DF-PIMS) apparatus coupled to a synchrotron radiation source. The PIE spectra displayed steplike behavior near threshold. This study represents the first determination of the HOCl photoionization efficiency spectrum and the photoionization threshold. A value of 11.12(3) +/- 0.01(8) eV was obtained for the adiabatic ionization energy (IE) of HOCl from analysis of photoion thresholds, corresponding to the HOCl+(X(2)A") <-- HOCl(X(1)A") transition. Our PIMS result is identical to the only previous experimental measurement and in good agreement with a recent ab initio calculation. From our result for IE(HOCl), a value of 999.4 +/- 3.6 kJ mol(-1) was calculated for Delta(f)H degrees(0)(HOCl+), and from the latter, the proton affinity of ClO at T = 0 K, PA(o)(ClO), was determined to be 629.6 +/- 3.6 kJ mol(-1). At 298 K, the computed values for Delta(f)H degrees(298)(HOCl+) and PA(298)(ClO) are 996.5 +/- 3.6 and 635.1 +/- 3.6 kJ mol(-1), respectively. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. RP Thorn, RP (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Code 690, Greenbelt, MD 20771 USA. NR 44 TC 10 Z9 10 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD FEB 18 PY 1999 VL 103 IS 7 BP 812 EP 815 DI 10.1021/jp9834053 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 176KG UT WOS:000079149800006 ER PT J AU Krotkov, NA Torres, O Seftor, C Krueger, AJ Kostinski, A Rose, WI Bluth, GJS Schneider, D Schaefer, SJ AF Krotkov, NA Torres, O Seftor, C Krueger, AJ Kostinski, A Rose, WI Bluth, GJS Schneider, D Schaefer, SJ TI Comparison of TOMS and AVHRR volcanic ash retrievals from the August 1992 eruption of Mt. Spurr SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OZONE MAPPING SPECTROMETER; SULFUR-DIOXIDE; CLOUDS AB On August 19, 1992, the Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA-12 and NASA's Total Ozone Mapping Spectrometer (TOMS) onboard the Nimbus-7 satellite simultaneously detected and mapped the ash cloud from the eruption of Mt. Spurr, Alaska. The spatial extent and geometry of the cloud derived from the two datasets are in good agreement and both AVHRR split window IR (11-12 mu m brightness temperature difference) and the TOMS UV Aerosol Index (0.34-0.38 mu m ultraviolet backscattering and absorption) methods give the same range of total cloud ash mass. Redundant methods for determination of ash masses in drifting volcanic clouds offer many advantages for potential application to the mitigation of aircraft hazards. C1 Raytheon ITSS Co, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Michigan Technol Univ, Houghton, MI 49931 USA. USGS, Alaska Volcano Observ, Anchorage, AK USA. Univ Maryland Baltimore Cty, JCET, Baltimore, MD 21228 USA. RP Krotkov, NA (reprint author), Raytheon ITSS Co, Lanham, MD 20706 USA. RI Rose, William/A-7923-2009; Krotkov, Nickolay/E-1541-2012; Torres, Omar/G-4929-2013 OI Krotkov, Nickolay/0000-0001-6170-6750; NR 17 TC 44 Z9 45 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD FEB 15 PY 1999 VL 26 IS 4 BP 455 EP 458 DI 10.1029/1998GL900278 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 167EW UT WOS:000078620400006 ER PT J AU Bradshaw, J Davis, D Crawford, J Chen, G Shetter, R Muller, M Gregory, G Sachse, G Blake, D Heikes, B Singh, H Mastromarino, J Sandholm, S AF Bradshaw, J Davis, D Crawford, J Chen, G Shetter, R Muller, M Gregory, G Sachse, G Blake, D Heikes, B Singh, H Mastromarino, J Sandholm, S TI Photofragmentation two-photon laser-induced fluorescence detection of NO2 and NO: Comparison of measurements with model results based on airborne observations during PEM-Tropics A SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PHOTOSTATIONARY STATE; NORTH PACIFIC; DEVIATIONS AB Measurements of NO and NO2 are reported using a highly modified photofragmentation two-photon laser-induced fluorescence (PF-TP-LIF) instrument. Available evidence suggests that the changes made substantially reduced wall decomposition of labile NOy species. In sharp contrast to the results reported from NASA's 1991 PEM-West A program where the median value for the ratio (NO2)(meas)/(NO2)(calc) was 3.36, the PEM-Tropics A observations produced a value for this ratio of 0.93. This represents the first time that remote upper tropospheric NO-NO2 data have shown a high degree of correspondence with current photochemical mechanisms. C1 Georgia Inst Technol, Atlanta, GA 30332 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NCAR, Div Atmospher Chem, ARIM Project, Boulder, CO 80303 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bradshaw, J (reprint author), Georgia Inst Technol, 221 Bobby Dodd Way, Atlanta, GA 30332 USA. RI Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 18 TC 46 Z9 49 U1 1 U2 7 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 FEB 15 PY 1999 VL 26 IS 4 BP 471 EP 474 DI 10.1029/1999GL900015 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 167EW UT WOS:000078620400010 ER PT J AU Jost, H Loewenstein, M Pfister, L Margitan, JJ Chang, AY Salawitch, RJ Michelsen, HA AF Jost, H Loewenstein, M Pfister, L Margitan, JJ Chang, AY Salawitch, RJ Michelsen, HA TI Laminae in the tropical middle stratosphere: Origin and age estimation (vol 25, pg 4337, 1999) SO GEOPHYSICAL RESEARCH LETTERS LA English DT Correction C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. AER Inc, San Ramon, CA 94583 USA. RP Jost, H (reprint author), NASA, Ames Res Ctr, MS 245-5, Moffett Field, CA 94035 USA. RI Salawitch, Ross/B-4605-2009 OI Salawitch, Ross/0000-0001-8597-5832 NR 1 TC 1 Z9 1 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD FEB 15 PY 1999 VL 26 IS 4 BP 479 EP 479 DI 10.1029/1999GL900023 PG 1 WC Geosciences, Multidisciplinary SC Geology GA 167EW UT WOS:000078620400013 ER PT J AU Milikh, G Valdivia, JA AF Milikh, G Valdivia, JA TI Model of gamma ray flashes due to fractal lightning SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RUNAWAY AIR BREAKDOWN; ELECTRONS; SPRITES AB A model of gamma-ray flashes is presented. The model relies upon a horizontal fractal lightning discharge, which generates the electromagnetic pulses that pro duce the stochastic electron runaway discharge in the stratosphere. The model computes the flux and energy spectrum of the gamma-rays generated by the runaway discharge. The results of the computations are compared with the GRO observations after including the gamma-rays attenuation in the atmosphere. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, NRC, Greenbelt, MD 20771 USA. RP Milikh, G (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 16 TC 19 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD FEB 15 PY 1999 VL 26 IS 4 BP 525 EP 528 DI 10.1029/1999GL900001 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 167EW UT WOS:000078620400025 ER PT J AU Holmes, W Francis, RS Fayer, MD AF Holmes, W Francis, RS Fayer, MD TI Crack propagation induced heating in crystalline energetic materials SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID TIP AB A model is presented for time and spatial dependences of the heating of molecular vibrations and the possible initiation of chemical reaction from heat dissipated in the vicinity of a propagating crack in a molecular crystal. In the model, energy from a moving crack tip is released as phonons in proximity to the crack. Initially the phonons and the molecular vibrations are not in thermal equilibrium. Subsequently, there is a competition between excitation of molecular vibrations by multiphonon up-pumping and diffusion of phonons from the crack region. If the coupling between the locally hot phonon bath and the molecular vibrations is sufficiently large, a transitory high vibrational temperature will be achieved prior to eventual thermal equilibration with the bulk of the crystal. It is found that the peak vibrational temperature can be sufficiently high for a significant time period for chemical reactions to occur. The model calculates the local time-dependent vibrational temperature using reasonable values of the physical input parameters. For a crack tip moving near the speed of sound, the calculations show that vibrational temperatures can reach similar to 800 K in 55 ps and exceed 550 K for similar to 1 ns after the initial heating. This temperature change is sufficient to produce chemical reaction in a secondary explosive such as HMX, but given the duration and size of the heated region, a single crack should not result in self-sustaining chemical reaction. The role that cracks may play in shock sensitivity is discussed. (C) 1999 American Institute of Physics. [S0021-9606(99)01007-7]. C1 Stanford Univ, Dept Chem, Stanford, CA 94305 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Stanford Univ, Dept Chem, Stanford, CA 94305 USA. NR 19 TC 17 Z9 18 U1 1 U2 5 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0021-9606 EI 1089-7690 J9 J CHEM PHYS JI J. Chem. Phys. PD FEB 15 PY 1999 VL 110 IS 7 BP 3576 EP 3583 DI 10.1063/1.478225 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 164DA UT WOS:000078446100035 ER PT J AU Braun, SA Rotunno, R Klemp, JB AF Braun, SA Rotunno, R Klemp, JB TI Effects of coastal orography on landfalling cold fronts. Part I: Dry, inviscid dynamics SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MESOSCALE MOUNTAINS; PACIFIC-NORTHWEST; ATMOSPHERE; RIDGE; SIMULATION; TOPOGRAPHY; TERRAIN; SURGES; WAVES; STORM AB In this study, the interaction of cold fronts with idealized coastal terrain typical of the western United States and Canada is considered. Two issues are examined. First, what are the factors that determine the strength of the coastal winds, and second, what are the orographic effects on the frontal evolution? To address these issues, the authors utilize a two-dimensional, Boussinesq terrain-following coordinate numerical model in which a uniform prescribed flow is forced to move over a plateau. The resultant across-mountain velocities are characterized by a zone of strongly decelerated flow upstream of the windward slope and a train of inertia-gravity waves downstream. A barrier-jet oriented parallel to the mountain is produced by the Coriolis force. The variations of the magnitude of the upstream deceleration and the barrier jet over a wide range of Froude numbers and Rossby numbers ore described. Steady, linear theory applied to flow over a plateau shows that the upstream deceleration is determined largely by the shortwave characteristics of the orography while the barrier-jet strength is related to the longwave characteristics of the orography. Simulations that include an initially steady, geostrophically balanced front upstream of the coast indicate that the motion of fronts can be significantly retarded along the coast. Across-frontal circulations induced by frontogenesis or frontolysis caused by the mountain are small compared to the changes in the mountain circulation caused by the stability perturbations associated with the front. The strength of the along-mountain winds in the coastal zone during frontal passage are approximately determined by a superposition of thr southerly barrier jet and the frontal jets (e.g., a southerly prefrontal jet and/or northerly postfrontal jet). This result implies that a barrier jet forming ahead of a front can combine with a prefrontal jet to produce very strong winds in the coastal zone prior to frontal passage. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Braun, SA (reprint author), NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Res Branch, Code 912, Greenbelt, MD 20771 USA. NR 29 TC 28 Z9 28 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD FEB 15 PY 1999 VL 56 IS 4 BP 517 EP 533 DI 10.1175/1520-0469(1999)056<0517:EOCOOL>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 169GR UT WOS:000078739600006 ER PT J AU Allen, DR Stanford, JL Lopez-Valverde, MA Nakamura, N Lary, DJ Douglass, AR Cerniglia, MC Remedios, JJ Taylor, FW AF Allen, DR Stanford, JL Lopez-Valverde, MA Nakamura, N Lary, DJ Douglass, AR Cerniglia, MC Remedios, JJ Taylor, FW TI Observations of middle atmosphere CO from the UARS ISAMS during the early northern winter 1991/92 SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID STRATOSPHERIC POLAR VORTICES; LAGRANGIAN-MEAN DIAGNOSTICS; MESOSPHERIC SOUNDER; TERRESTRIAL MESOSPHERE; CARBON-MONOXIDE; NITROUS-OXIDE; TRANSPORT; VARIABILITY; MODEL; CH4 AB Structure and kinematics of carbon monoxide in the upper stratosphere and lower mesosphere (10-0.03 hPa) are studied for the early northern winter 1991/92 using the Upper Atmosphere Research Satellite Improved Stratospheric and Mesospheric Sounder (ISAMS) measurements. The study is aided by data from a 6-week parameterized-chemistry run of the Goddard Space Flight Center 3D Chemistry and Transport Model (CTM), initialized on 8 December 1991. Generally, CO mixing ratios increase with height due to the increasing source contribution from CO2 photolysis. In the tropical upper stratosphere, however, a local maximum in CO mixing ratio occurs. A simple photochemical model is used to show that this feature results largely from methane oxidation. In the extratropics the photochemical lifetime of CO is long, and therefore its evolution is dictated by large scale motion of air, evidenced by strong correlation with Ertel potential vorticity. This makes CO one of the few useful observable tracers at the stratopause level and above. Thus CO maps are used to study the synoptic evolution of the polar vortex in early January 1992. Modified Lagrangian mean mixing diagnostics are applied to ISAMS and CTM data to examine the strength of the mixing barrier at the polar vortex edge. It is demonstrated that planetary wave activity weakens the barrier, promoting vortex erosion. The vortex erosion first appears in the lower mesosphere and subsequently descends through the upper stratosphere, and is attributed to effects of planetary wave dissipation. Agreement between ISAMS and CTM is good in the horizontal distribution of CO throughout the examined period, but vertical CO gradients in the CTM weaken with time relative to the ISAMS observations. C1 Univ Chicago, Dept Geophys Sci, Chicago, IL 60637 USA. Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA. Inst Astrofis Andalucia, E-18080 Granada, Spain. Univ Cambridge, Ctr Atmospher Sci, Dept Chem, Cambridge CB2 1TN, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Appl Res Corp, Landover, MD 20785 USA. Univ Oxford, Dept Phys, Oxford, England. RP Allen, DR (reprint author), Univ Chicago, Dept Geophys Sci, 5734 S Ellis Ave, Chicago, IL 60637 USA. RI Lary, David/A-6163-2010; Douglass, Anne/D-4655-2012; OI Lopez-Valverde, M. A./0000-0002-7989-4267 NR 47 TC 40 Z9 40 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD FEB 15 PY 1999 VL 56 IS 4 BP 563 EP 583 DI 10.1175/1520-0469(1999)056<0563:OOMACF>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 169GR UT WOS:000078739600008 ER PT J AU Markov, V Millerd, J Trolinger, J Norrie, M Downie, J Timucin, D AF Markov, V Millerd, J Trolinger, J Norrie, M Downie, J Timucin, D TI Multilayer volume holographic optical memory SO OPTICS LETTERS LA English DT Article ID MULTIPLEXED STORAGE; CRYSTAL AB We demonstrate a scheme for volume holographic storage based on the features of shift selectivity of a speckle reference-wave hologram. The proposed recording method permits more-efficient use of the recording medium and yields greater storage density than spherical or plane-wave reference beams. Experimental results of multiple hologram storage and replay in a photorefractive crystal of iron-doped lithium niobate are presented. The mechanisms of lateral and longitudinal shift selectivity are described theoretically and shown to agree with experimental measurements. (C) 1999 Optical Society of America. OCIS codes: 210.0210, 090.0090, 210.2860, 030.6140, 090.4220. C1 MetroLaser Inc, Irvine, CA 92614 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Markov, V (reprint author), MetroLaser Inc, Suite 100,Skypk Circle 18010, Irvine, CA 92614 USA. NR 14 TC 47 Z9 48 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD FEB 15 PY 1999 VL 24 IS 4 BP 265 EP 267 DI 10.1364/OL.24.000265 PG 3 WC Optics SC Optics GA 168EZ UT WOS:000078679700027 PM 18071475 ER PT J AU Marcinkevicius, S Leon, R AF Marcinkevicius, S Leon, R TI Carrier capture and escape in InxGa1-xAs/GaAs quantum dots: Effects of intermixing SO PHYSICAL REVIEW B LA English DT Article ID ELECTRONIC-STRUCTURE; ENERGY RELAXATION; LUMINESCENCE; LIFETIMES; STATES AB We have investigated photoexcited carrier dynamics in as-grown and intermixed InxGa1-xAs/GaAs quantum dots and quantum wells by time-resolved photoluminescence with subpicosecond temporal resolution. Experiments were performed at high excitation in the temperature range 60-300 K. At lower temperatures, carrier lifetime in the dots is determined by radiative recombination, while at temperatures over 150 K carrier thermal emission becomes dominant. Carrier capture into the dots was found to be fast and governed by carrier-carrier scattering. In particular, at room temperature and high-excitation intensity, the carrier capture time of 0.72 ps was observed for the intermixed dots. C1 Royal Inst Technol, Dept Phys Opt, S-10044 Stockholm, Sweden. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Marcinkevicius, S (reprint author), Royal Inst Technol, Dept Phys Opt, S-10044 Stockholm, Sweden. NR 19 TC 44 Z9 44 U1 0 U2 2 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD FEB 15 PY 1999 VL 59 IS 7 BP 4630 EP 4633 DI 10.1103/PhysRevB.59.4630 PG 4 WC Physics, Condensed Matter SC Physics GA 169YZ UT WOS:000078778800024 ER PT J AU Sigl, G Lee, S Bhattacharjee, P Yoshida, S AF Sigl, G Lee, S Bhattacharjee, P Yoshida, S TI Probing grand unified theories with cosmic-ray, gamma-ray, and neutrino astrophysics SO PHYSICAL REVIEW D LA English DT Article ID HIGH-ENERGY NEUTRINOS; UNIFICATION SCALE PHYSICS; ZATSEPIN-KUZMIN CUTOFF; TOPOLOGICAL DEFECTS; DARK-MATTER; SPECTRUM; LIMITS; PROPAGATION; PARTICLES; FLUX AB We explore scenarios where the highest energy cosmic rays are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic nucleon, gamma-ray, and neutrino propagation, we show the existence of an interesting parameter range for which such scenarios may explain part of the data and are consistent with all observational constraints. A combination of proposed observatories for ultra-high energy cosmic rays, neutrino telescopes of greater than or similar to few kilometer scale, and gamma-ray astrophysics instruments, should be able to test these scenarios. In particular, for neutrino masses in the eV range, exclusive neutrino decay modes of superheavy particles can give rise to neutrino fluxes comparable to those predicted in models of active galactic nuclei. [S0556-2821(99)06202-5]. C1 Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Indian Inst Astrophys, Bangalore 560034, Karnataka, India. Univ Tokyo, Inst Cosm Ray Res, Tanashi, Tokyo 1888502, Japan. RP Sigl, G (reprint author), Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. NR 77 TC 90 Z9 91 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1550-7998 EI 1550-2368 J9 PHYS REV D JI Phys. Rev. D PD FEB 15 PY 1999 VL 59 IS 4 AR 043504 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 189ZY UT WOS:000079938100010 ER PT J AU Millis, RL Binzel, RP Burns, JA Cruikshank, DP McKinnon, WB Meech, KJ Stern, SA AF Millis, RL Binzel, RP Burns, JA Cruikshank, DP McKinnon, WB Meech, KJ Stern, SA TI Pluto's planetary status SO SCIENCE LA English DT Letter C1 Lowell Observ, Flagstaff, AZ 86001 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. Cornell Univ, Ithaca, NY 14853 USA. NASA, Astrophys Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. Washington Univ, McDonnell Ctr Space Sci, St Louis, MO 63130 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. SW Res Inst, Dept Space Studies, Boulder, CO 80302 USA. RP Millis, RL (reprint author), Lowell Observ, 1400 W Mars Hill Rd, Flagstaff, AZ 86001 USA. NR 5 TC 1 Z9 1 U1 1 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD FEB 12 PY 1999 VL 283 IS 5404 BP 937 EP 937 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 166KM UT WOS:000078574800019 ER PT J AU Dowling, JP AF Dowling, JP TI Perfect mirrors, past and present - Response SO SCIENCE LA English DT Letter C1 CALTECH, Jet Prop Lab, NASA, Pasadena, CA 91109 USA. RP Dowling, JP (reprint author), CALTECH, Jet Prop Lab, NASA, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI DOWLING, JONATHAN/L-2749-2013 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD FEB 12 PY 1999 VL 283 IS 5404 BP 939 EP 939 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 166KM UT WOS:000078574800025 ER PT J AU Zdziarski, AA Lubinski, P Smith, DA AF Zdziarski, AA Lubinski, P Smith, DA TI Correlation between Compton reflection and X-ray slope in Seyferts and X-ray binaries SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE accretion, accretion discs; radiation mechanisms : thermal; binaries : general; galaxies : Seyfert; X-rays : galaxies; X-rays : stars ID BLACK-HOLES; CYG X-1; GINGA; ACCRETION; GALAXIES; STATE; OSSE AB We find a very strong correlation between the intrinsic spectral slope in X-rays and the amount of Compton reflection from a cold medium in Seyfert AGNs and in the hard state of X-ray binaries with either black holes or weakly magnetized neutron stars. Objects with soft intrinsic spectra show much stronger reflection than those with hard spectra. We find that, at a given spectral slope, black hole binaries have similar reflection to or more reflection than Seyferts, whereas neutron star binaries in our sample have reflection consistent with that in Seyferts, The existence of the correlation implies a dominant role of the reflecting medium as a source of seed soft photons for thermal Comptonization in the primary X-ray source. C1 N Copernicus Astron Ctr, PL-00716 Warsaw, Poland. Warsaw Univ, Heavy Ion Lab, PL-02093 Warsaw, Poland. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Leicester, Dept Phys, Leicester LE1 7RH, Leics, England. RP Zdziarski, AA (reprint author), N Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland. NR 42 TC 173 Z9 173 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD FEB 11 PY 1999 VL 303 IS 1 BP L11 EP L15 DI 10.1046/j.1365-8711.1999.02343.x PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 170DY UT WOS:000078792100003 ER PT J AU He, Z Li, W Knoll, GF Wehe, DK Berry, J Stahle, CM AF He, Z Li, W Knoll, GF Wehe, DK Berry, J Stahle, CM TI 3-D position sensitive CdZnTe gamma-ray spectrometers SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MICHIGAN ID DETECTORS; SEMICONDUCTOR; ARRAYS AB Two 3-D position-sensitive room temperature semiconductor gamma-ray spectrometers have been built using 1 cm(3) cubic CdZnTe crystals. The lateral coordinates of gamma-ray interaction are obtained from the location of the 11(x) x 11(y) pixellated anodes and the depth (z) is obtained from the ratio of the signals coming from the cathode and the anode. Energy spectra from 662 keV incident gamma-rays have been collected from each of the 11(x) x 11(y) x 20(z) voxels in both of the CdZnTe devices. After corrections for electron trapping, the difference of weighting potentials in 3-D, and for the gain variation of the readout circuitry, energy resolutions of 1.70% (11.3 keV) FWHM and 1.84% (12.2 keV) FWHM were obtained at 662 keV gamma-ray energy on the first and second detectors, respectively, from the whole bulk for single-pixel events. Possible improvements in the detector performance are discussed. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Michigan, Dept Nucl Engn & Radiol Sci, Ann Arbor, MI 48109 USA. NASA, Orbital Sci Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP He, Z (reprint author), Univ Michigan, Dept Nucl Engn & Radiol Sci, Ann Arbor, MI 48109 USA. RI Chang, Yong/B-3541-2009 NR 6 TC 172 Z9 177 U1 1 U2 16 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 FEB 11 PY 1999 VL 422 IS 1-3 BP 173 EP 178 DI 10.1016/S0168-9002(98)00950-4 PG 6 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800036 ER PT J AU Kroeger, RA Gehrels, N Johnson, WN Kurfess, JD Phlips, BP Tueller, J AF Kroeger, RA Gehrels, N Johnson, WN Kurfess, JD Phlips, BP Tueller, J TI Charge spreading and position sensitivity in a segmented planar germanium detector SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MICHIGAN ID STRIP DETECTORS AB The size of the charge cloud collected in a segmented germanium detector is limited by the size of the initial cloud, uniformity of the electric field, and the diffusion of electrons and holes through the detector. These factors affect the minimize size of a practical electrode structure and consequently the position sensitivity. We have completed measurements on a germanium strip detector with a finery collimated gamma ray beam to measure these properties. Preliminary results indicate that the electrons and holes spread by < 65 mu m over 9 mm drift distance. The experiment was conducted using a germanium strip detector with 25 boron implanted strips on one face and 25 orthogonal lithium drifted strips on the opposite face. The size of the charge cloud is measured by scanning the fan beam between neighboring strips. Results of these experiments suggest that full charge collection on a single strip would be achieved for a majority of events with strip pitch down to less than or equal to 300 mu m in a 10 mm thick device. Concerns of degradation in the energy resolution due to charge sharing between strips is important for strip pitch much finer than this. There is no evidence of charge loss in hole collection by the boron implanted strips. Applications of a fine pitch germanium strip detector include an imaging focal plane behind a hard X-ray mirror (NASA Constellation mission), or a gamma-ray polarimeter for nuclear physics, amongst others. (C) 1999 Elsevier Science B.V. All rights reserved. C1 USN, Res Lab, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. RP Kroeger, RA (reprint author), USN, Res Lab, Washington, DC 20375 USA. RI Tueller, Jack/D-5334-2012; Johnson, Neil/G-3309-2014 NR 6 TC 10 Z9 10 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 FEB 11 PY 1999 VL 422 IS 1-3 BP 206 EP 210 DI 10.1016/S0168-9002(98)01095-X PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800042 ER PT J AU Ivaniouchenkov, Y Fonte, P Peskov, V Ramsey, BD AF Ivaniouchenkov, Y Fonte, P Peskov, V Ramsey, BD TI Breakdown limit studies in high-rate gaseous detectors SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MICHIGAN DE high-rate gaseous detectors; MICROMEGAS; CAT; GEM; breakdown limits ID GEM AB We report results from a systematic study of breakdown limits for novel high-rate gaseous detectors: MICROMEGAS, CAT and GEM, together with more conventional devices such as thin-gap parallel-mesh chambers and high-rate wire chambers. It was found that for all these detectors, the maximum achievable gain, before breakdown appears, drops dramatically with incident flux, and is sometimes inversely proportional to it. Further, in the presence of alpha particles, typical of the breakgrounds in high-energy experiments, additional gain drops of 1-2 orders of magnitude were observed for many detectors. It was found that breakdowns at high rates occur through what we have termed an "accumulative" mechanism, which does not seem to have been previously reported in the literature. Results of these studies may help in choosing the optimum detector for given experimental conditions. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. ISEC, Coimbra, Portugal. Univ Coimbra, LIP, P-3000 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 20 TC 21 Z9 21 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD FEB 11 PY 1999 VL 422 IS 1-3 BP 300 EP 304 DI 10.1016/S0168-9002(98)00962-0 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800061 ER PT J AU Teegarden, BJ AF Teegarden, BJ TI Space instrumentation for gamma-ray astronomy SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MICHIGAN ID SPECTROMETER AB The decade of the 1990s has witnessed a renaissance in the held of gamma-ray astronomy. The seminal event was the launch of the Compton Gamma-Ray Observatory (CGRO) in April 1991. There have been a flood of major discoveries from CGRO including breakthroughs in gamma-ray bursts, annihilation radiation, and blazars. The Italian SAX satellite was launched in April 1996. Although not primarily a gamma-ray mission, it has added a new dimension to our understanding of gamma-ray bursts. Along with these new discoveries a firm groundwork has been laid for missions and new technology development that should maintain a healthy and vigorous field throughout most of the next decade. These include the ESA INTEGRAL mission (INTErnational Gamma-Ray Astrophysics Laboratory, to be launched in mid-2001) and the NASA GLAST mission (Gamma-Ray Large Area Space Telescope) with a likely launch in the middle of the next decade. These two missions will extend the observational capabilities well beyond those of CGRO. New technologies (to gamma-ray astronomy), such as cooled germanium detectors, silicon strip detectors, and CdTe detectors are planned for these new missions. Additional promising new technologies such as CdZnTe strip detectors, scintillator fibers, and a gamma-ray lens for future gamma-ray astronomy missions are under development in laboratories around the world. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, High Energy Phys Lab, Greenbelt, MD 20771 USA. RP Teegarden, BJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Phys Lab, 661, Greenbelt, MD 20771 USA. NR 9 TC 2 Z9 2 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 FEB 11 PY 1999 VL 422 IS 1-3 BP 551 EP 561 DI 10.1016/S0168-9002(98)01268-6 PG 11 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800109 ER PT J AU Trombka, JI Boynton, WV Bruckner, J Squyres, S Clark, PE Starr, R Evans, LG Floyd, SR McClanahan, TP Goldsten, J Mcnutt, R Schweitzer, JS AF Trombka, JI Boynton, WV Bruckner, J Squyres, S Clark, PE Starr, R Evans, LG Floyd, SR McClanahan, TP Goldsten, J Mcnutt, R Schweitzer, JS TI Remote planetary geochemical exploration with the NEAR X-ray/gamma-ray spectrometer SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MI AB The X-ray/gamma-ray spectrometer (XGRS) instrument onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 0.2 keV to 10 MeV energy region. Measurements of the discrete line X-ray and gamma-ray emissions in this energy domain can be used to obtain both qualitative and quantitative elemental composition maps of the asteroid surface. The NEAR X-ray/gamma-ray spectrometer (XGRS) was turned on for the first time during the week of 7 April 1996. Rendezvous with Eros 433 is expected during December 1998. Observations of solar X-ray spectra during both quiescent and active periods have been made. A gamma-ray transient detection system has been implemented and about three gamma-ray transient events a week have been observed which are associated with either gamma-ray bursts or solar flares. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Max Planck Inst Chem, D-55128 Mainz, Germany. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Comp Sci Corp, Sci Programs, Lanham, MD 20706 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Connecticut, Res Fdn, Storrs, CT 06269 USA. RP Trombka, JI (reprint author), NASA, Goddard Space Flight Ctr, Code 691, Greenbelt, MD 20771 USA. EM uljit@lepvax.gsfc.nasa.gov RI McNutt, Ralph/E-8006-2010 OI McNutt, Ralph/0000-0002-4722-9166 NR 13 TC 9 Z9 9 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD FEB 11 PY 1999 VL 422 IS 1-3 BP 572 EP 576 DI 10.1016/S0168-9002(98)00939-5 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800112 ER PT J AU Floyd, SR Trombka, JI Leidecker, HW Clark, PE Starr, R Goldsten, JO Roth, DR AF Floyd, SR Trombka, JI Leidecker, HW Clark, PE Starr, R Goldsten, JO Roth, DR TI Radiation effects on the proportional counter X-ray detectors on board the NEAR spacecraft SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MICHIGAN AB The X-ray proportional counters on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft have exhibited a resolution degradation and recovery phenomenon several times during the long cruise phase of the mission. The resolution is checked periodically by commanding an Fe-55 source into the window area. The degradation is seen as a low energy tailing of the 5.9 keV photopeak. Two events have occurred which provided good spectral data for better understanding the degradation phenomenon In November 1997 a large solar particle event occurred that degraded the resolution and excited copper in the collimator. Eventually the detectors returned to normal. In January 1998 the spacecraft performed an Earth swingby gravity assist maneuver. The near Earth environment excited the magnesium and aluminum in the filter elements. The copper line was also produced. The NEAR spacecraft was launched in February 1996 and will rendezvous and orbit the asteroid 433 Eros in early 1999. (C) 1994 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Catholic Univ Amer, Washington, DC 20064 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RP Floyd, SR (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NR 2 TC 3 Z9 3 U1 4 U2 4 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 FEB 11 PY 1999 VL 422 IS 1-3 BP 577 EP 581 DI 10.1016/S0168-9002(98)00940-1 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800113 ER PT J AU McClanahan, TP Trombka, JI Floyd, SR Boynton, WV Mikheeva, I Bailey, H Liewicki, C Bhangoo, J Starr, R Clark, PE Evans, LG Squyres, S McNutt, R Bruckner, J AF McClanahan, TP Trombka, JI Floyd, SR Boynton, WV Mikheeva, I Bailey, H Liewicki, C Bhangoo, J Starr, R Clark, PE Evans, LG Squyres, S McNutt, R Bruckner, J TI Data management and analysis techniques used in the near x-ray and gamma-ray spectrometer systems SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MICHIGAN AB The NEAR Earth Asteroid Rendezvous (NEAR) spacecraft will encounter the 433Eros asteroid for a one year orbital mission in December 1998. Its on-board remote sensing instrumentation includes X-ray and gamma-ray (XGRS) spectrometers. NEAR is an orbital mission and long integrations over spatially specific asteroid regions are generally not possible. A methodology for simulating longer integrations has been developed for XGRS and uses unique management, correlative and analytical ground systems to render mapping data products. Evaluation of the spatial environment is accomplished through virtual renderings of the asteroid surface giving incidence, emission and surface roughness factors. Extended computer plate modeling information is employed to optimize ground computer systems processing time. Interactive visualization systems have been developed to manage close to a million spectra that will be collected during the encounter. Feedback systems are employed to inspect, tag and calibrate spectral data products. Mission planning, systems development and managerial responsibilities have been distributed to cooperating science organizations at The Goddard Space Flight Center, The University of Arizona, Cornell University, The Applied Physics Laboratory and The Max Plank Institute. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Comp Sci Corp, Sci Programs, Lanham, MD 20706 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Max Planck Inst Chem, Mainz, Germany. RP McClanahan, TP (reprint author), NASA, Goddard Space Flight Ctr, Code 691, Greenbelt, MD 20771 USA. RI McNutt, Ralph/E-8006-2010 OI McNutt, Ralph/0000-0002-4722-9166 NR 0 TC 8 Z9 8 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 FEB 11 PY 1999 VL 422 IS 1-3 BP 582 EP 585 DI 10.1016/S0168-9002(98)00942-5 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800114 ER PT J AU Evans, LG Starr, R Bruckner, J Boynton, WV Bailey, SH Trombka, JI AF Evans, LG Starr, R Bruckner, J Boynton, WV Bailey, SH Trombka, JI TI Charged-particle induced radiation damage of a HPGe gamma-ray detector during spaceflight SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MI AB The Mars Observer spacecraft was launched on September 26, 1992 with a planned arrival at Mars after an 11-month cruise. Among the scientific instruments carried on the spacecraft was a Gamma-Ray Spectrometer (GRS) experiment to measure the composition of Mars. The GRS used a passively cooled high-purity germanium detector for measurements in the 0.2-10 MeV region. The sensor was a closed-end co-axial detector, 5.5 cm diameter by 5.5 cm long, and had an efficiency along its axis of 28% at 1332 keV relative to a standard NaI(Tl) detector. The sensor was surrounded by a thin (0.5 cm) plastic charged-particle shield. This was the first planetary mission to use a cooled Ge detector. It was expected that the long duration in space of three years would cause an increase in the energy resolution of the detector due to radiation damage and could affect the expected science return of the GRS. Shortly before arrival, on August 21, 1993, contact was lost with the spacecraft following the pressurization of the propellent tank for the orbital-insertion rocket motor. During much of the cruise to Mars, the GRS was actively collecting background data. The instrument provided over 1200 h of data collection during periods of both quiescent sun and solar flares. From the charged particle interactions in the shield, the total number of cosmic ray hits on the detector could be determined. The average cosmic ray Aux at the MO GRS was about 2.5 cm(-2) s(-1). The estimated fluence of charged particles during cruise was about 10(8) particles cm(-2) with 31% of these occurring during a single solar proton event of approximately 10 days duration. During cruise, the detector energy resolution determined from a background gamma-ray at 1312 keV degraded from 2.4 keV full-width at half-maximum shortly after launch to 6.4 keV 11 months later. This result agrees well with measurements from ground-based accelerator irradiations (at 1.5 GeV) on a similar size detector. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Comp Sci Corp, Sci Programs, Lanham, MD 20706 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Max Planck Inst Chem, D-55128 Mainz, Germany. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Evans, LG (reprint author), Comp Sci Corp, Sci Programs, Lanham, MD 20706 USA. EM levans@mogrs.gsfc.nasa.gov NR 7 TC 5 Z9 5 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 FEB 11 PY 1999 VL 422 IS 1-3 BP 586 EP 590 DI 10.1016/S0168-9002(98)00943-7 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800115 ER PT J AU Schweitzer, JS Trombka, JI Floyd, SR Groves, JL Bradley, JG AF Schweitzer, JS Trombka, JI Floyd, SR Groves, JL Bradley, JG TI Neutron-induced gamma-ray measurements on soft landers SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 9th Symposium on Radiation Measurements and Applications CY MAY 11-14, 1998 CL ANN ARBOR, MICHIGAN AB Gamma-ray spectra provide useful data in the study of the development of planets. Measurements made on landers overcome many of the limitations of orbital measurements, especially for solar-system bodies where atmospheres interfere with obtaining orbital data. Elemental compositions can be inferred from the spectra, produced by neutron interactions with nuclei of the planetary body. The cosmic ray flux yields a relatively low neutron flux requiring long integration times (sometimes as long as a year) to obtain a statistical accuracy allowing elemental compositions to be inferred to determine different mineral compositions and to characterize the nature of the area studied. A recent advance is the combination of a gamma-ray spectrometer with a compact, pulsed neutron generator, which increases the neutron flux by orders of magnitude, Such a device is used on Earth and its capability is being extended to operate within the low weight and power requirements of typical lander missions. A pulsed source permits data accumulation by type of reaction, increasing the sensitivity for detecting many elements. The enhanced speed of measurement makes many new studies possible, such as time-dependent measurements to detect seasonal or diurnal changes from active processes. Where motion is provided, either around the lander or on a rover, data can be obtained at different positions to evaluate heterogeneities, The use of a pulsed neutron generator provides increased quality of elemental data and provides many additional options for system design to provide more useful information for understanding the creation and evolution of our solar system. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Connecticut, Storrs, CT 06269 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EMR Schlumberger, Princeton Junction, NJ 08550 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Schweitzer, JS (reprint author), Univ Connecticut, Storrs, CT 06269 USA. NR 8 TC 0 Z9 0 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD FEB 11 PY 1999 VL 422 IS 1-3 BP 595 EP 599 DI 10.1016/S0168-9002(98)00945-0 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 171MY UT WOS:000078868800117 ER PT J AU Gibson, BK Hughes, SMG Stetson, PB Freedman, WL Kennicutt, RC Mould, JR Bresolin, F Ferrarese, L Ford, HC Graham, JA Han, MS Harding, P Hoessel, JG Huchra, JP Illingworth, GD Kelson, DD Macri, LM Madore, BF Phelps, RL Prosser, CF Saha, A Sakai, S Sebo, KM Silbermann, NA Turner, AM AF Gibson, BK Hughes, SMG Stetson, PB Freedman, WL Kennicutt, RC Mould, JR Bresolin, F Ferrarese, L Ford, HC Graham, JA Han, MS Harding, P Hoessel, JG Huchra, JP Illingworth, GD Kelson, DD Macri, LM Madore, BF Phelps, RL Prosser, CF Saha, A Sakai, S Sebo, KM Silbermann, NA Turner, AM TI The Hubble Space Telescope key project on the Extragalactic Distance Scale. XVII. The Cepheid distance to NGC 47251 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; distance scale; galaxies : distances and redshifts galaxies : individual (NGC 4725) ID LUMINOSITY FUNCTIONS; SPIRAL GALAXIES; CALIBRATION; DISCOVERY; CONSTANT; EXTINCTION; BRIGHTNESS; VARIABLES; CLUSTER; COUNTS AB The distance to NGC 4725 has been derived from Cepheid variables as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen F555W (V) and four F814W (I) epochs of cosmic-ray-split Wide Field and Planetary Camera 2 observations were obtained. Twenty Cepheids were discovered, with periods ranging from 12 to 49 days. Adopting a Large Magellanic Cloud distance modulus and extinction of 18.50 +/- 0.10 mag and E(V - I) = 0.13 mag, respectively, a true reddening-corrected distance modulus (based on an analysis employing the ALLFRAME software package) of 30.50 +/- 0.16 (random) +/- 0.17 (systematic) mag was determined for NGC 4725. The corresponding of distance of 12.6 +/- 1.0 (random) +/- 1.0 (systematic) Mpc is in excellent agreement with that found with an independent analysis based upon the DoPHOT photometry package. With a foreground reddening of only E(V - I) = 0.02, the inferred intrinsic reddening of this field in NGC 4725, E(V - I) = 0.19, makes it one of the most highly reddened fields encountered by the HST Key Project to date. C1 Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Natl Res Council Canada, Herzberg Inst Astrophys, Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. CALTECH, Palomar Observ, Pasadena, CA 91125 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Wisconsin, Madison, WI 53706 USA. Avanti Corp, Fremont, CA 94538 USA. European So Observ, D-85748 Munich, Germany. Harvard Univ, Ctr Astrophys, Cambridge, MA 02138 USA. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Oberlin Coll, Wright Lab Phys, Oberlin, OH 44074 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. RP Gibson, BK (reprint author), Univ Colorado, Ctr Astrophys & Space Astron, Campus Box 389, Boulder, CO 80309 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 40 TC 23 Z9 23 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP 48 EP 64 DI 10.1086/306762 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DM UT WOS:000079251100006 ER PT J AU Surace, JA Sanders, DB AF Surace, JA Sanders, DB TI High-resolution TIP/TILT near-infrared imaging of warm ultraluminous infrared galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : interactions; galaxies : photometry; galaxies : starburst; galaxies : structure; infrared : galaxies ID CONTINUUM ENERGY-DISTRIBUTIONS; QUASI-STELLAR OBJECTS; HOST GALAXIES; ACTIVE GALAXIES; EMISSION; EVOLUTION; SAMPLE AB We present high spatial resolution (FWHM approximate to 0 ".-0 ".5) H (1.6 mu m) and K' (2.1 mu m) images of a complete sample (12) of ultraluminous infrared galaxies (ULIGs) chosen to have "warm" mid-infrared colors (f(25)/f(60) > 0.2) known to be characteristic of active galaxies. The extended underlying galaxy is detected in each system at H and K', as are tidal features and many of the star-forming knots seen at optical wavelengths. While some of these knots have considerable near-infrared excesses, we show that they are likely to have bolometric luminosities more similar to those of the extended starbursts with similar optical morphology seen in less far-infrared-luminous interacting systems. We find that each ULIG has increasing contributions at long wavelengths by a very compact source, which we identify as an active galactic nucleus (AGN). We show that the optical/near-infrared colors of these putative nuclei are much more extreme than in the most active starburst IRAS galaxies, yet are identical to those in "far-infrared-loud" quasars, which are in turn similar to optical quasars combined with large quantities of hot (approximate to 800 K) dust. Half of the ULIGs have nuclei with dereddened near-infrared luminosities comparable to those of QSOs, while the other half have dereddened luminosities more similar to Seyfert galaxies, although this may be an effect of patchy extinction and scattering. C1 Univ Hawaii, Astron Inst, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Surace, JA (reprint author), Univ Hawaii, Astron Inst, 2680 Woodlawn Dr, Honolulu, HI 96822 USA. EM jason@ipac.caltech.edu; sanders@ifa.hawaii.edu NR 48 TC 71 Z9 71 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP 162 EP 177 DI 10.1086/306737 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DM UT WOS:000079251100017 ER PT J AU Xu, C Sulentic, JW Tuffs, R AF Xu, C Sulentic, JW Tuffs, R TI Starburst in the intragroup medium of Stephan's Quintet SO ASTROPHYSICAL JOURNAL LA English DT Article ID STAR-FORMATION; INTERACTING GALAXIES; DWARF GALAXIES; DISK GALAXIES; EVOLUTION; CLUSTERS; POPULATIONS; ANTENNAE; CLOUDS AB Based on new Infrared Space Observatory midinfrared observations and ground-based H-alpha and near-infrared observations, we report the detection of a bright starburst in the intragroup medium (IGM) of the famous compact group of galaxies known as Stephan's Quintet (source A in Fig. 1). We demonstrate that this starburst is caused by a collision between a high-velocity (delta V similar to 1000 km s(-1)) intruder galaxy (NGC 7318b) and the IGM of the group. While this is the only starburst known today that is induced by a galaxy/cold intergalactic medium collision, it provides new constraints to the theory for interaction-induced starbursts and may hint at a new mechanism for the star formation excess seen in more distant clusters. C1 CALTECH 100 22, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Max Planck Inst Kernphys, D-69117 Heidelberg, Germany. Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. RP Xu, C (reprint author), CALTECH 100 22, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. NR 34 TC 55 Z9 55 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP 178 EP 183 DI 10.1086/306771 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DM UT WOS:000079251100018 ER PT J AU Stollberg, MT Finger, MH Wilson, RB Scott, DM Crary, DJ Paciesas, WS AF Stollberg, MT Finger, MH Wilson, RB Scott, DM Crary, DJ Paciesas, WS TI Batse observations and orbit determination of the Be/X-ray transient EXO 2030+375 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; binaries : general; pulsars : individual (EXO 2030+375); X-rays : stars ID QUASI-PERIODIC OSCILLATIONS; PULSAR EXO-2030+375; LUMINOSITY DEPENDENCE; ACCRETION TORQUES; NEUTRON STARS; COUNTERPART; DISCOVERY; EMISSION AB The Be/X-ray binary transient pulsar EXO 2030 + 375 (P(s) approximate to 42 s) has been observed with the large-area detectors (LADs) of the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO). Beginning in 1991 May, 22 outbursts were observed over 4 years. Thirteen outbursts between 1992 February and 1993 August occurred consecutively at intervals of approximate to 46 days, close to the orbital period determined by Parmar and colleagues using EXOSAT data. The pulse profiles from the BATSE data are double peaked and show no significant energy or luminosity dependence, unlike the EXOSAT observations of 1985 May-August. An exponential model was used to fit the observed hard X-ray energy spectra from the 13 consecutive outbursts. When EXOSAT discovered this pulsar during a giant outburst in 1985 May, the X-ray luminosity peaked at L(x) = 1.0 x 10(38) ergs s(-1) (1-20 keV), assuming a 5 kpc distance to the source. The BATSE outbursts are found to be weaker, 0.3 x 10(37) less than or equal to L(x)(1-20 keV) less than or equal to 3.0 x 10(37) ergs s(-1) after extrapolating the observed flux (20-50 keV) to the EXOSAT energy band. Pulse phases derived from the 13 outbursts were fitted to two different models to determine a binary orbit. The new orbit is used to estimate 95% confidence limits for the mean peak spin frequency change during the outbursts observed with BATSE. This and the mean peak flux are compared to the spin-up rates and fluxes determined by EXOSAT from the 1985 giant outburst, where disk accretion was thought to have occurred. It is unclear whether these normal outbursts were driven by wind or disk accretion. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Space Res Assoc, Washington, DC USA. RP Stollberg, MT (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 32 TC 16 Z9 17 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 FEB 10 PY 1999 VL 512 IS 1 BP 313 EP 321 DI 10.1086/306733 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DM UT WOS:000079251100032 ER PT J AU Guessoum, N Kazanas, D AF Guessoum, N Kazanas, D TI Lithium production in companions of accreting X-ray binaries by neutron spallation of C, N, O elements SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; novae, cataclysmic variables; nuclear reactions; nucleosynthesis, abundances; stars : abundances ID ADVECTION-DOMINATED ACCRETION; ACTIVE GALACTIC NUCLEI; BLACK-HOLE; RELATIVISTIC NEUTRONS; EMISSION; SPECTRUM; SYSTEM; ORIGIN; STARS; LINE AB We examine the processes that could lead to the observed enhancement of Li and possibly other light elements (Be, B) in the companions of a number of X-ray novae. We conclude that one of the most promising mechanisms is the spallation of CNO elements on the surface of the companion induced by the neutron flux produced in the hot accretion flow onto the compact object. Direct production of the observed Li and its deposition onto the dwarf companion seem less likely, mainly because of the possibility of its destruction in the production region itself and difficulties in its deposition associated with the configuration of the companion's magnetic field. We discuss other potential observables of the above scenario. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. Coll Technol Studies, Dept Appl Sci, Kuwait 70654, Kuwait. RP Guessoum, N (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. RI Guessoum, Nidhal/C-3051-2013 NR 27 TC 20 Z9 20 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP 332 EP 339 DI 10.1086/306757 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DM UT WOS:000079251100034 ER PT J AU Pendleton, GN Briggs, MS Kippen, RM Paciesas, WS Stollberg, M Woods, P Meegan, CA Fishman, GJ McCollough, ML Connaughton, V AF Pendleton, GN Briggs, MS Kippen, RM Paciesas, WS Stollberg, M Woods, P Meegan, CA Fishman, GJ McCollough, ML Connaughton, V TI The structure and evolution of LOCBURST: The BATSE burst location algorithm SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; methods : numerical ID RAY AB The gamma-ray burst (GRB) location algorithm used to produce the BATSE GRB locations is described. The general flow of control of the current location algorithm is presented, and the significant properties of the various physical inputs required are identified. The development of the burst location algorithm during the releases of the BATSE 1B, 2B, and 3B GRB catalogs is presented so that the reasons for the differences in the positions and error estimates between the catalogs can be understood. In particular, differences between the 2B and 3B locations are discussed for events that have moved significantly and the reasons for the changes explained. The locations of bursts located independently by the interplanetary network (IPN) are used to illustrate the effect on burst location accuracy of various components of the algorithm. IPN data and locations from other gamma-ray instruments are used to calculate estimates of the systematic errors on BATSE burst locations. C1 Univ Alabama, Dept Phys, 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, George C Marshall Space Flight Ctr, NRC, Huntsville, AL 35812 USA. RP Pendleton, GN (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 17 TC 25 Z9 25 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP 362 EP 376 DI 10.1086/306735 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DM UT WOS:000079251100038 ER PT J AU Ellison, DC Jones, FC Baring, MG AF Ellison, DC Jones, FC Baring, MG TI Direct acceleration of pickup ions at the solar wind termination shock: The production of anomalous cosmic rays SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; methods : numerical; shock waves; solar wind ID MONTE-CARLO SIMULATIONS; HYDROMAGNETIC WAVE EXCITATION; QUASI-PERPENDICULAR SHOCKS; LOCAL INTERSTELLAR CLOUD; CROSS-FIELD DIFFUSION; EARTHS BOW SHOCK; MEAN FREE PATHS; PARTICLE-ACCELERATION; OBLIQUE SHOCKS; UP IONS AB We have modeled the injection and acceleration of pickup ions at the solar wind termination shock and investigated the parameters needed to produce the observed anomalous cosmic-ray (ACR) fluxes. A nonlinear Monte Carlo technique was employed that in effect solves the Boltzmann equation and is not restricted to near-isotropic particle distribution functions. This technique models the injection of thermal and pickup ions, the acceleration of these ions, and the determination of the shock structure under the influence of the accelerated ions. The essential effects of injection are treated in a mostly self-consistent manner, including effects from shock obliquity, cross-held diffusion, and pitch-angle scattering. Using recent determinations of pickup ion densities, we are able to match the absolute flux of hydrogen in the ACRs by assuming that pickup ion scattering mean free paths, at the termination shock, are much less than an AU and that modestly strong cross-held diffusion occurs. Simultaneously, we match the flux ratios He+/H+ or O+/H+ to within a factor similar to 5. If the conditions of strong scattering apply, no pre-termination-shock injection phase is required and the injection and acceleration of pickup ions at the termination shock are totally analogous to the injection and acceleration of ions at highly oblique interplanetary shocks recently observed by the Ulysses spacecraft. The fact that ACR fluxes can be modeled with standard shock assumptions suggests that the much discussed "injection problem" for highly oblique shocks stems from incomplete (either mathematical or computer) modeling of these shocks rather than from any actual difficulty shocks may have in injecting and accelerating thermal or quasi-thermal particles. C1 N Carolina State Univ, Dept Phys, Raleigh, NC 27695 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. RP Ellison, DC (reprint author), N Carolina State Univ, Dept Phys, Raleigh, NC 27695 USA. NR 69 TC 48 Z9 48 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP 403 EP 416 DI 10.1086/306739 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DM UT WOS:000079251100041 ER PT J AU Cui, W Zhang, SN Chen, W Morgan, EH AF Cui, W Zhang, SN Chen, W Morgan, EH TI Strong aperiodic X-ray variability and quasi-periodic oscillation in X-ray nova XTE J1550-564 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : general; stars : individual (XTE J1550-564); X-rays : stars ID BLACK AB We report the discovery of strong aperiodic X-ray variability and quasi-periodic oscillation (QPO) in the Xray light curves of a new X-ray nova, XTE J1550-564, and the evolution of the observed temporal properties during the rise of the recent X-ray outburst. The power spectral analysis of the first observation reveals strong aperiodic X-ray variability of the source (similar to 28%) as well as the presence of a QPO at similar to 82 mHz with fractional rms amplitude similar to 14% over the 2-60 keV energy range. Also apparent is the first harmonic of the QPO with the amplitude similar to 9%. As the X-ray flux increases, the source tends to become less variable, and the QPO frequency increases rapidly, from 82 mHz to 4 Hz, over the flux (2-50 keV) range of 1.73-5.75 x 10(-8) ergs cm(-2) s(-1). The amplitude of the fundamental component of the QPO varies little, while that of the harmonic follows a decreasing trend. The fundamental component strengthens toward high energies, while its harmonic weakens. Initially, the power spectrum is roughly flat at low frequencies and turns into a power law at high frequencies, with the QPO harmonic sitting roughly at the break. In later observations, however, the high-frequency portion of the continuum can actually be better described by a broken power law (as opposed to a simple power law). This effect becomes more apparent at higher energies. The overall amplitude of the continuum shows a similar energy dependence to that of the fundamental component of the QPO. Strong rapid X-ray variability, as well as a hard energy spectrum, makes XTE J1550-564 a good black hole candidate. We compare its temporal properties with those of other black hole candidates. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Cui, W (reprint author), MIT, Ctr Space Res, Cambridge, MA 02139 USA. NR 20 TC 57 Z9 57 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP L43 EP L46 DI 10.1086/311870 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DP UT WOS:000079251300012 ER PT J AU Lowrance, PJ McCarthy, C Becklin, EE Zuckerman, B Schneider, G Webb, RA Hines, DC Kirkpatrick, JD Koerner, DW Low, F Meier, R Rieke, M Smith, BA Terrile, RJ Thompson, RI AF Lowrance, PJ McCarthy, C Becklin, EE Zuckerman, B Schneider, G Webb, RA Hines, DC Kirkpatrick, JD Koerner, DW Low, F Meier, R Rieke, M Smith, BA Terrile, RJ Thompson, RI TI A candidate substellar companion to CD -33 degrees 7795 (TWA 5) SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : low-mass, brown dwarfs ID NEAR-INFRARED SEARCH; BROWN DWARFS; PLEIADES; STARS AB We present the discovery of a candidate substellar object in a survey of young stars in the solar vicinity using the sensitivity and spatial resolution afforded by the NICMOS coronagraph on the Hubble Space Telescope. The H = 12.1 mag object was discovered approximately 2" from the TW Hydrae association member CD -33 degrees 7795 (TWA 5), and the photometry implies a spectral type M8-M8.5, with a temperature of similar to 2600 K. We estimate that the probability of a chance alignment with a background object of this nature is less than 2 x 10(-5) and therefore postulate that the object (TWA 5B) is physically associated at a projected separation of 100 AU, Given the likely youth of the primary (similar to 10 Myr), current brown dwarf cooling models predict a mass of approximate to 20M(Jup) for TWA 5B. C1 Univ Calif Los Angeles, Los Angeles, CA 90024 USA. Univ Arizona, Tucson, AZ USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Penn, Philadelphia, PA 19104 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Lowrance, PJ (reprint author), Univ Calif Los Angeles, Los Angeles, CA 90024 USA. NR 32 TC 117 Z9 117 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 FEB 10 PY 1999 VL 512 IS 1 BP L69 EP L72 DI 10.1086/311858 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DP UT WOS:000079251300018 ER PT J AU Marani, GF Nemiroff, RJ Norris, JP Hurley, K Bonnell, JT AF Marani, GF Nemiroff, RJ Norris, JP Hurley, K Bonnell, JT TI Gravitationally lensed gamma-ray bursts as probes of dark compact objects SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; gamma rays : bursts; gravitational lensing ID COSMOLOGICAL DENSITY; LINE SEARCH; PROBABILITY; MATTER AB If dark matter in the form of compact objects comprises a large fraction of the mass of the universe, then gravitational lensing effects on gamma-ray bursts are expected. We utilize BATSE and Ulysses data to search for lenses of different mass ranges, which cause lensing in the milli, pico, and femto regimes. Null results are used to set weak limits on the cosmological abundance of compact objects in mass ranges from 10(-16) to 10(-9) M-circle dot. A stronger limit is found for a much-discussed Omega = 0.15 universe dominated by black holes of mass similar to 10(6.5) M-circle dot, which is ruled out at the similar to 90% confidence level. C1 George Mason Univ, Dept Earth Observing & Space Res, Fairfax, VA 22030 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Michigan Technol Univ, Dept Phys, Houghton, MI 49931 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Space Res Assoc, Washington, DC USA. RP Marani, GF (reprint author), George Mason Univ, Dept Earth Observing & Space Res, Fairfax, VA 22030 USA. OI Nemiroff, Robert/0000-0002-4505-6599 NR 36 TC 40 Z9 41 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP L13 EP L16 DI 10.1086/311868 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DP UT WOS:000079251300004 ER PT J AU Yu, W Li, TP Zhang, W Zhang, SN AF Yu, W Li, TP Zhang, W Zhang, SN TI The kilohertz QPO frequency and flux decrease in Aquila X-l and the effect of soft X-ray spectral components SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (Aquila X-l); stars : neutron; X-rays : stars ID EMISSION; BURSTS AB We report on a Rossi X-Ray Timing Explorer observation of Aquila X-l during its outburst in 1997 March in which, immediately following a type I burst, the broadband 2-10 keV flux decreased by about 10% and the kilohertz quasi-periodic oscillation (kHz QPO) frequency decreased from 813 +/- 3 to 776 +/- 4 Hz. This change in kHz QPO frequency is much larger than expected from a simple extrapolation of a frequency-flux correlation that was established in data before the burst. Meanwhile, a very low frequency noise component in the broadband fast Fourier transform power spectra, with a fractional rms amplitude of 1.2% before the burst, ceased to exist after the burst. All these changes were accompanied by a change in the energy spectral shape. If we characterize the energy spectra with a model composed of two blackbody (BB) components and a power-law component, almost all the decrease in flux was in the two BE components. We attribute the two BE components to the contributions from a region very near the neutron star, or even from the neutron star itself, and from the accretion disk, respectively. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Yu, W (reprint author), Chinese Acad Sci, Inst High Energy Phys, Lab Cosm Ray & High Energy Astrophys, POB 918-3, Beijing 100039, Peoples R China. NR 24 TC 17 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1999 VL 512 IS 1 BP L35 EP L38 DI 10.1086/311859 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 178DP UT WOS:000079251300010 ER PT J AU Leib, SJ Wundrow, DW Goldstein, ME AF Leib, SJ Wundrow, DW Goldstein, ME TI Effect of free-stream turbulence and other vortical disturbances on a laminar boundary layer SO JOURNAL OF FLUID MECHANICS LA English DT Article ID WAVES; TRANSITION; FLOW; INSTABILITY; EVOLUTION; UPSTREAM AB This paper is concerned with the effect of free-stream turbulence on the pretransitional flat-plate boundary layer. It is assumed that either the turbulent Reynolds number or the downstream distance (or both) is small enough that the flow can be linearized. The dominant disturbances in the boundary layer, which are of the Klebanoff type, are governed by the linearized unsteady boundary-region equations, i.e. the linearized Navier-Stokes equations with the streamwise derivatives neglected in the viscous and pressure-gradient terms. The turbulence is represented as a superposition of vortical free-stream Fourier modes and the corresponding Fourier component solutions to the boundary-region equations are obtained numerically. The results are then superposed to compute the root mean square of the fluctuating streamwise velocity in the boundary layer produced by the actual free-stream turbulence. It is found that the disturbances computed with isotropic free-stream turbulence do not reach the levels measured in experiments. However, good quantitative agreement is obtained with the relatively low turbulent Reynolds number data of Kendall when the measured strong anisotropy of the low-frequency portion of his spectrum is accounted for. Data at higher turbulent Reynolds numbers are affected by nonlinearity, which manifests itself through the generation of small spanwise length scales. We attempt to model this within the context of the linear theory by choosing a free-stream spectrum whose energy is concentrated at larger transverse wavenumbers and achieve very good agreement with the data. The results suggest that even small deviations from pure isotropy can be an important factor in explaining the large amplitudes of the Klebanoff modes in the pre-transitional boundary layer, and also point to the importance of nonlinear effects. We discuss some additional effects that may need to be accounted for in order to obtain a complete description of the Klebanoff modes. C1 NASA, Lewis Res Ctr, Dynacs Engn Co Inc, Cleveland, OH 44135 USA. NYMA Inc, Lewis Res Ctr Grp, Cleveland, OH 44135 USA. RP Leib, SJ (reprint author), NASA, Lewis Res Ctr, Dynacs Engn Co Inc, Cleveland, OH 44135 USA. NR 50 TC 87 Z9 88 U1 0 U2 4 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD FEB 10 PY 1999 VL 380 BP 169 EP 203 DI 10.1017/S0022112098003504 PG 35 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 177YF UT WOS:000079238100007 ER PT J AU Bills, BG AF Bills, BG TI Tidal despinning of the mantle, inner core superrotation, and outer core effective viscosity SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID CONCENTRIC ROTATING SPHERES; ATMOSPHERIC ANGULAR-MOMENTUM; SPHERICAL COUETTE-FLOW; DIFFERENTIAL ROTATION; DECADE FLUCTUATIONS; WESTWARD DRIFT; TRAVEL-TIMES; EARTHS CORE; ANISOTROPY; LENGTH AB Dissipation of tidal energy in the oceans causes a net transfer of angular momentum from the spin of the Earth to the relative orbital motions of the Moon and Sun. These torques couple directly to the mantle, and cause it to despin. Viscous coupling across the outer core is an effective means of communicating this change to the inner core. The Ekman time scale for dissipation of transient fluid motions associated with unsteady torques is much shorter than the time scale for adjustment of inner core and mantle rotational velocities in the steady Couette flow regime. The relative amplitude and phase of rotational variations in this system, with respect to the applied torques, are given in terms of core viscosity and torque variation frequency. Any short period variations in mantle torques will leave the inner core largely unchanged, and the influence of long period and secular torques applied to the mantle is efficiently transmitted to the inner core. The system response to a steady tidal torque applied to the mantle leaves the inner core with a small excess rotational velocity relative to the mantle, proportional to the product of outer core viscosity and the applied mantle torque. Recent estimates of an inner core super-rotation of (similar to)1 degree/year imply an effective outer core viscosity of (similar to)10(3) Pa s. Glacial cycle variations in tidal torques somewhat complicate this picture, but do not yield significantly different viscosity estimates. However, they do imply that the differential rotation velocity varies by roughly a factor of 2 over a 100 kyr glacial cycle. The tidal shear strain may also contribute to development of anisotropy in the inner core. C1 Univ Calif San Diego, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. NASA, Geodynam Branch, Goddard Space Flight Ctr, Greenbelt, MD USA. RP Bills, BG (reprint author), Univ Calif San Diego, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. EM bbills@denali.gsfc.nasa.gov RI Bills, Bruce/C-1156-2008 NR 57 TC 8 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD FEB 10 PY 1999 VL 104 IS B2 BP 2653 EP 2666 DI 10.1029/1998JB900006 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 165YL UT WOS:000078549400001 ER PT J AU Chen, JL Wilson, CR Eanes, RJ Nerem, RS AF Chen, JL Wilson, CR Eanes, RJ Nerem, RS TI Geophysical interpretation of observed geocenter variations SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID WATER STORAGE; POLAR MOTION; OCEAN AB Geocenter variations are caused by mass redistribution within the Earth system, especially the atmosphere, oceans, and continental water. Using surface pressure fields, and soil moisture and snow depth fields of the NCEP-NCAR. Climate Data Assimilation System I (CDAS-1), we estimate contributions from variations in atmospheric surface pressure and continental water storage to the Earth's geocenter (center of mass) variation. In addition, sea surface anomalies determined by the TOPEX/POSEIDON altimeter are used to investigate geocenter variations resulting from ocean mass redistribution. These sea surface height data were corrected using a simplified steric model. A comparison with observed geocenter variations derived from Lageos 1 and 2 satellite laser ranging data indicates that the atmosphere, oceans, and continental hydrological cycle all provide significant contributions at different frequencies. Geocenter variations estimated in this paper are in reasonably good agreement with results given by Dong et al. [1997] for atmospheric and ocean contributions, but not for the estimates of continental hydrological contributions. C1 Univ Texas, Ctr Space Res, Austin, TX 78712 USA. Univ Texas, Dept Geol Sci, Austin, TX 78712 USA. NASA, Washington, DC 20546 USA. RP Chen, JL (reprint author), Univ Texas, Ctr Space Res, Campus Code R1000, Austin, TX 78712 USA. EM chen@sol.csr.utexas.edu; cwilson@hq.nasa.gov; eanes@csr.utexas.edu; nerem@csr.utexas.edu NR 20 TC 67 Z9 75 U1 1 U2 6 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 FEB 10 PY 1999 VL 104 IS B2 BP 2683 EP 2690 DI 10.1029/1998JB900019 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 165YL UT WOS:000078549400003 ER PT J AU Glaze, LS Wilson, L Mouginis-Mark, PJ AF Glaze, LS Wilson, L Mouginis-Mark, PJ TI Volcanic eruption plume top topography and heights as determined from photoclinometric analysis of satellite data SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID MOUNT-ST-HELENS; 16 SEPTEMBER 1986; PINATUBO ERUPTION; COLUMNS; CLOUDS; MODEL; SPECTROMETER; TRANSPORT; DISPERSAL; DYNAMICS AB Photoclinometry, a shape-from-shading technique, is applied to satellite data to determine the three-dimensional height and morphology of the upper optical surface of a plume from the eruption of Redoubt Volcano, Alaska. The technique can be applied to visible images of volcanic plumes that have uniform scattering properties and is most effective on images with moderate incident Sun angles and plume transport perpendicular to the azimuth of the Sun. The two most significant sources of error are the finite resolution of the image data and the choice of image data number (DN) value for a flat plume element. Provided the plume spans at least 10 image pixels, useful results can be obtained for the central portion of the plume. The closest approximation to a flat plume element is found to be the visible DN value corresponding to the coldest pixel along a transect. Errors in the element altitude due to uncertainty in the DN value for a flat pixel amount to similar to 10-20 m per pixel and are cumulative along the plume transect. For Redoubt this results in an uncertainty of approximately 300 m at the highest points. The method indicates that the Redoubt plume rose to an altitude of approximately 3 km while traveling a distance of 150 km from the vent and that the surface topography of the plume exhibits influences of the ambient wind through simple wave structures. This technique will have a tremendous impact on studies of plume spreading dynamics and the time-integrated evolution of plumes. C1 NASA, Goddard Space Flight Ctr, Proxemy Res, Greenbelt, MD 20771 USA. Univ Hawaii Manoa, Hawaii Inst Geophys & Planetol, Sch Ocean & Earth Sci & Technol, Honolulu, HI 96822 USA. Univ Lancaster, Inst Environm & Nat Sci, Dept Environm Sci, Lancaster LA1 4YQ, England. RP Glaze, LS (reprint author), NASA, Goddard Space Flight Ctr, Proxemy Res, Code 921, Greenbelt, MD 20771 USA. EM lori@puuoo.gsfc.nasa.gov RI Glaze, Lori/D-1314-2012 NR 35 TC 13 Z9 14 U1 0 U2 5 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 FEB 10 PY 1999 VL 104 IS B2 BP 2989 EP 3001 DI 10.1029/1998JB900047 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 165YL UT WOS:000078549400023 ER PT J AU Ramesham, R AF Ramesham, R TI Voltammetric studies at the polycrystalline diamond grown over a graphite electrode material SO THIN SOLID FILMS LA English DT Article DE graphite; doped-diamond; cyclic voltammetry; ferri/ferro cyanide ID THIN-FILM ELECTRODES; DOPED CVD-DIAMOND; SELECTIVE GROWTH; DC-POLARIZATION; GLASSY-CARBON; BEHAVIOR; AC AB Boron-doped polycrystalline diamond thin films were grown over POGO graphite by a microwave plasma assisted chemical vapor deposition (CVD) using a gas mixture of methane and hydrogen. As-deposited films were analyzed by scanning electron microscopy (SEM) for their morphology. Cyclic voltammetry has been used to evaluate the background current response corrected for the uncompensated IR drop. Redox kinetics of ferri-ferrocyanide at the boron-doped diamond/graphite electrode has been investigated. The lowest observed peak separation was observed to be 222 mV at a scan rate of 5 mV/s. The heterogeneous electron transfer rate constant has been determined using the experimental data and a COOL algorithm. The rate constant was found to be similar to 2 x 10(-4) (alpha = 0.5 or variable) cm/s, and subsequently, the reaction kinetics was considered to be sluggish at the diamond electrode/solution interface. The diamond films grown over graphite electrode material may have uses in electrosynthesis and electroanalysis since the doped diamond films an electrically conductive and chemically inert. (C) 1999 Elsevier Science S.A. All rights reserved. C1 Auburn Univ, Space Power Inst, Leach Ctr 231, Auburn, AL 36849 USA. RP Ramesham, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 125-152, Pasadena, CA 91109 USA. EM rajeshuni.ramesham@jpl.nasa.gov NR 28 TC 26 Z9 26 U1 0 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD FEB 8 PY 1999 VL 339 IS 1-2 BP 82 EP 87 DI 10.1016/S0040-6090(98)01090-6 PG 6 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 173YX UT WOS:000079008300013 ER PT J AU Smale, A Boyd, P AF Smale, A Boyd, P TI Rocking rocketeers SO NEW SCIENTIST LA English DT Letter C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Smale, A (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. RI Boyd, Patricia/D-3274-2012 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 USA SN 0262-4079 J9 NEW SCI JI New Sci. PD FEB 6 PY 1999 VL 161 IS 2172 BP 55 EP 55 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 164TT UT WOS:000078480200047 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI The atomization energy of Mg-4 SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; ELECTRON CORRELATION; CLUSTERS; 1ST-ROW; LIMIT AB The atomization energy of Mg-4 is determined using the MP2 and CCSD(T) levels of theory. Basis set incompleteness, basis set extrapolation, and core-valence effects are discussed. Our best atomization energy, including the zero-point energy and scalar relativistic effects, is 24.6 +/- 1.6 kcal/mol. Our computed and extrapolated values are compared with previous results, where it is observed that our extrapolated MP2 value is in good agreement with the MP2-R12 value. The CCSD(T) and MP2 core effects are found to have the opposite signs. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. EM bauschli@pegasus.arc.nasa.gov NR 22 TC 21 Z9 21 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 FEB 5 PY 1999 VL 300 IS 3-4 BP 364 EP 368 DI 10.1016/S0009-2614(98)01381-5 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 163XJ UT WOS:000078431800014 ER PT J AU Arrhenius, G Bada, JL Joyce, GF Lazcano, A Miller, S Orgel, LE AF Arrhenius, G Bada, JL Joyce, GF Lazcano, A Miller, S Orgel, LE TI Origin and ancestor: Separate environments SO SCIENCE LA English DT Letter C1 Univ Calif San Diego, La Jolla, CA 92093 USA. Univ Calif San Diego, Scripps Inst Oceanog, NASA, Specialized Ctr Res & Training Exobiol, La Jolla, CA 92093 USA. Scripps Res Inst, Dept Chem, La Jolla, CA 92037 USA. Scripps Res Inst, Dept Mol Biol, La Jolla, CA 92037 USA. Univ Nacl Autonoma Mexico, Fac Ciencias, Dept Biol, Mexico City 04510, DF, Mexico. Univ Calif San Diego, Dept Chem, La Jolla, CA 92093 USA. Salk Inst Biol Studies, Chem Evolut Lab, La Jolla, CA 92037 USA. RP Arrhenius, G (reprint author), Univ Calif San Diego, Mail Code A0220, La Jolla, CA 92093 USA. NR 0 TC 14 Z9 15 U1 0 U2 5 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD FEB 5 PY 1999 VL 283 IS 5403 BP 792 EP 792 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 165AT UT WOS:000078496800017 PM 10049121 ER PT J AU Carlson, RW AF Carlson, RW TI A tenuous carbon dioxide atmosphere on Jupiter's moon Callisto SO SCIENCE LA English DT Article ID GALILEAN SATELLITES; GANYMEDE; SPECTROSCOPY; SURFACE; OXYGEN AB An off-limb scan of Callisto was conducted by the Galileo near-infrared mapping spectrometer to search for a carbon dioxide atmosphere. Airglow in the carbon dioxide nu(3) band was observed up to 100 kilometers above the surface and indicates the presence of a tenuous carbon dioxide atmosphere with surface pressure of 7.5 x 10(-12) bar and a temperature of about 150 kelvin, close to the surface temperature. A lifetime on the order of 4 years is suggested, based on photoionization and magnetospheric sweeping. Either the atmosphere is transient and was formed recently or some process is currently supplying carbon dioxide to the atmosphere. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Carlson, RW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 183-601, Pasadena, CA 91109 USA. NR 30 TC 55 Z9 55 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD FEB 5 PY 1999 VL 283 IS 5403 BP 820 EP 821 DI 10.1126/science.283.5403.820 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 165AT UT WOS:000078496800036 PM 9933159 ER PT J AU DeMore, WB Wilson, EW AF DeMore, WB Wilson, EW TI Rate constant and temperature dependence for the reaction of hydroxyl radicals with 2-fluoropropane (HFC-281ea) SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article AB Relative rate experiments were used to measure the rate constant and temperature dependence of the reaction of OH radicals with 2-fluoropropane (HFC-281ea), using ethane, propane, and ethyl chloride as reference standards. Measurements were made using both infrared spectroscopy and gas chromatography (GC). Results from the two measurement techniques were in good agreement, with the GC data being more precise. The rate at 298 K for HFC-281ea, based on the GC experiments, was found to be 5.7 x 10(-13) cm(3)/(molecule s), with Arrhenius A factor = 3.06 x 10(-12) cm(3)/(molecule a) and E/R = 503 K. A previously described estimation technique, along with an improved method to estimate the Arrhenius parameters, is used to predict a rate constant and temperature dependence for 2-fluoropropane, which is in good agreement with the experimental value. A prediction is also made for 1-fluoropropane, for which there are no data. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP DeMore, WB (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 23 Z9 23 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD FEB 4 PY 1999 VL 103 IS 5 BP 573 EP 576 DI 10.1021/jp9835521 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 174PB UT WOS:000079042600004 ER PT J AU Sheng, CH Whitfield, DL Anderson, WK AF Sheng, CH Whitfield, DL Anderson, WK TI Multiblock approach for calculating incompressible fluid flows on unstructured grids SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 13th Computational Fluid Dynamics Conference CY JUN 29-JUL 02, 1997 CL SNOWMASS VILLAGE, COLORADO SP Amer Inst Aeronaut & Astronaut AB A multiblock approach is presented for solving two-dimensional incompressible turbulent Bows on unstructured grids. The artificial compressibility form of the governing equations Is solved by a node-based, finite volume implicit scheme, which uses a backward Euler time discretization. Point Gauss-Seidel relaxations are used to solve the linear system of equations at each time step. A multiblock strategy to the solution procedure is introduced, which greatly improves the efficiency of the algorithm by significantly reducing the memory requirements while not increasing the CPU time, Results presented show that the current multiblock algorithm requires 73 % less memory than the single-block algorithm. C1 Mississippi State Univ, Natl Sci Fdn, Engn Res Ctr, Computat Fluid Dynam Lab, Mississippi State, MS 39762 USA. NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. RP Sheng, CH (reprint author), Mississippi State Univ, Natl Sci Fdn, Engn Res Ctr, Computat Fluid Dynam Lab, Mississippi State, MS 39762 USA. NR 13 TC 9 Z9 9 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD FEB PY 1999 VL 37 IS 2 BP 169 EP 176 DI 10.2514/2.710 PG 8 WC Engineering, Aerospace SC Engineering GA 166BU UT WOS:000078557000004 ER PT J AU Anderson, WK Bonhaus, DL AF Anderson, WK Bonhaus, DL TI Airfoil design on unstructured grids for turbulent flows SO AIAA JOURNAL LA English DT Article ID SENSITIVITY ANALYSIS; ALGORITHM; EQUATIONS AB An aerodynamic design algorithm for turbulent hows using unstructured grids is described. The current approach uses adjoint (costate) variables to obtain derivatives of the cost function, The solution of the adjoint equations is obtained by using an implicit formulation in which the turbulence model is fully coupled with the flow equations when solving for the costate variables. The accuracy of the derivatives is demonstrated by comparison with finite difference gradients, and a few sample computations are shown. Recommendations on directions of further research into the Navier-Stokes design process are made. C1 NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. RP Anderson, WK (reprint author), NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. NR 43 TC 44 Z9 45 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD FEB PY 1999 VL 37 IS 2 BP 185 EP 191 PG 7 WC Engineering, Aerospace SC Engineering GA 166BU UT WOS:000078557000006 ER PT J AU Hilburger, MW Waas, AM AF Hilburger, MW Waas, AM TI Response of composite shells with cutouts to internal pressure and compression loads SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 39th Structures, Structural Dynamics, and Materials Conference / AIAA/ASME/AHS Adaptive Structures Forum CY APR 20-23, 1998 CL LONG BEACH, CALIFORNIA SP AIAA, ASME, ASCE, AHS, ASC AB Results from a numerical study of the response of composite shells with cutouts and subjected to internal pressure and axial compression are presented. The numerical results are obtained using a geometrically nonlinear finite element code. Results for axial compression and combined internal pressure and axial compression an: presented. The effects of varying internal pressure and cutout size on the prebuckling, buckling, and postbuckling responses of the shell are described. Results indicate that the nonlinear interaction between destabilizing in-plane compressive resultant stresses and out-of-plane displacements near the cutout can cause a local buckling response to occur near the cutout. The Local load distributions and displacements near the cutout can be affected hy the size of the cutout and by the internal pressure load. Numerical results indicate that the buckling load decreases as the size of the cutout is increased. In addition, the results indicate that the buckling load increases as the internal pressure is increased. C1 Univ Michigan, Dept Aerosp Engn, Composite Struct Lab, Ann Arbor, MI 48109 USA. NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. NR 9 TC 4 Z9 4 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD FEB PY 1999 VL 37 IS 2 BP 232 EP 237 PG 6 WC Engineering, Aerospace SC Engineering GA 166BU UT WOS:000078557000013 ER PT J AU McCowan, B Hanser, SF Doyle, LR AF McCowan, B Hanser, SF Doyle, LR TI Quantitative tools for comparing animal communication systems: information theory applied to bottlenose dolphin whistle repertoires SO ANIMAL BEHAVIOUR LA English DT Article ID NONCODING DNA-SEQUENCES; A-DEE CALLS; TURSIOPS-TRUNCATUS; LINGUISTIC FEATURES; LANGUAGE; DELPHINIDAE AB Comparative analysis of nonhuman animal communication systems and their complexity, particularly in comparison to human language, has been generally hampered by both a lack of sufficiently extensive data sets and appropriate analytic tools. Information theory measures provide an important quantitative tool for examining and comparing communication systems across species. In this paper we use the original application of information theory, that of statistical examination of a communication system's structure and organization. As an example of the utility of information theory to the analysis of animal communication systems, we applied a series of information theory statistics to a statistically categorized set of bottlenose dolphin, Tursiops truncatus, whistle vocalizations. First, we use the first-order entropic relation in a Zipf-type diagram (Zipf 1949, Human Behavior and the Principle of least Effort) to illustrate the application of temporal statistics as comparative indicators of repertoire complexity, and as possible predictive indicators of acquisition/learning in animal,vocal repertoires. Second, we illustrate the need for more extensive temporal data sets when examining the higher entropic orders, indicative of higher levels of internal informational structure, of such vocalizations, which could begin to allow the statistical reconstruction of repertoire organization. Third,;we propose using 'communication capacity' as a measure of the degree of temporal structure and complexity of statistical correlation, represented by the values of entropic order, as an objective tool for interspecies comparison of communication complexity. In doing so, we introduce a new comparative measure, the slope of Shannon entropies, and illustrate how it potentially can be used to compare the organizational complexity of vocal repertoires across a diversity of species. Finally, we illustrate the nature and predictive application of these higher-order entropies using a preliminary sample of dolphin whistle vocalizations. The purpose of this preliminary report is to re-examine the original application of information theory to the field of animal communication, illustrate its potential utility as a comparative tool for examining the internal informational structure of animal vocal repertoires and their development, and discuss its relationship to behavioural ecology and evolutionary theory. (C) 1999 The Association for the Study of Animal Behaviour. C1 Univ Calif Davis, Behav & Neurobiol Unit, Calif Reg Primate Res Ctr, Davis, CA 95616 USA. Marine World Fdn, Vallejo, CA 94589 USA. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP McCowan, B (reprint author), Univ Calif Davis, Behav & Neurobiol Unit, Calif Reg Primate Res Ctr, Davis, CA 95616 USA. EM bjmccowan@ucdavis.edu NR 53 TC 66 Z9 66 U1 2 U2 42 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0003-3472 J9 ANIM BEHAV JI Anim. Behav. PD FEB PY 1999 VL 57 BP 409 EP 419 DI 10.1006/anbe.1998.1000 PN 2 PG 11 WC Behavioral Sciences; Zoology SC Behavioral Sciences; Zoology GA 168LX UT WOS:000078695200017 ER PT J AU Stanney, KM Kennedy, RS Drexler, JM Harm, DL AF Stanney, KM Kennedy, RS Drexler, JM Harm, DL TI Motion sickness and proprioceptive aftereffects following virtual environment exposure SO APPLIED ERGONOMICS LA English DT Article ID CORIOLIS-FORCE PERTURBATIONS; SIMULATOR SICKNESS; FLIGHT SIMULATORS; TRANSFORMATIONS; ADAPTATION; MOVEMENTS; REALITY; TARGETS; ARM AB To study the potential aftereffects of virtual environments (VE), tests of visually guided behavior and felt limb position (pointing with eyes open and closed) along with self-reports of motion sickness-like discomfort were administered before and after 30 min exposure of 34 subjects. When post- discomfort was compared to a pre-baseline, the participants reported more sickness afterward (p < 0.03). The change in felt limb position resulted in subjects pointing higher (p < 0.038) and slightly to the left, although the latter difference was not statistically significant (p = 0.08). When findings from a second study using a different VE system were compared, they essentially replicated the results of the first study with higher sickness afterward (p < 0.001) and post- pointing errors were also up (p < 0.001) and to the left (p < 0.001). While alternative explanations (e.g. learning, fatigue, boredom, habituation, etc.) of these outcomes cannot be ruled out, the consistency of the post- effects on felt limb position changes in the two VE implies that these recalibrations may linger once interaction with the VE has concluded, rendering users potentially physiologically maladapted for the real world when they return. This suggests there may be safety concerns following VE exposures until pre-exposure functioning has been regained. The results of this study emphasize the need for developing and using objective measures of post-VE exposure aftereffects in order to systematically determine under what conditions these effects may occur. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 RSK Assessments Inc, Orlando, FL 32803 USA. Univ Cent Florida, Dept Ind Engn & Management Syst, Orlando, FL 32816 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Kennedy, RS (reprint author), RSK Assessments Inc, 1040 Woodcock Rd,Ste 227, Orlando, FL 32803 USA. NR 59 TC 36 Z9 40 U1 0 U2 9 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0003-6870 J9 APPL ERGON JI Appl. Ergon. PD FEB PY 1999 VL 30 IS 1 BP 27 EP 38 DI 10.1016/S0003-6870(98)00039-8 PG 12 WC Engineering, Industrial; Ergonomics; Psychology, Applied SC Engineering; Psychology GA 167ZP UT WOS:000078665700004 PM 10098814 ER PT J AU Brasunas, JC AF Brasunas, JC TI Artificial diamond as a broadband infrared beam splitter for Fourier transform spectroscopy: improved results SO APPLIED OPTICS LA English DT Article AB We show that an artificially grown diamond plate with an improved surface flatness serves as an infrared beam splitter to wavelengths as short as 2.2 mu m (4500 cm(-1)). (C) 1999 Optical Society of America OCIS codes: 070.2590, 130.3060, 160.0160, 230.1360, 300.0300, 300.6300. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Brasunas, JC (reprint author), NASA, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. RI brasunas, john/I-2798-2013 NR 1 TC 5 Z9 5 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD FEB 1 PY 1999 VL 38 IS 4 BP 692 EP 694 DI 10.1364/AO.38.000692 PG 3 WC Optics SC Optics GA 164PU UT WOS:000078473400012 PM 18305665 ER PT J AU Nguyen, HT Eisenhardt, PR Werner, MW Goodrich, R Hogg, DW Armus, L Soifer, BT Neugebauer, G AF Nguyen, HT Eisenhardt, PR Werner, MW Goodrich, R Hogg, DW Armus, L Soifer, BT Neugebauer, G TI Hubble Space Telescope imaging polarimetry of the gravitational lens FSC 10214+4724 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : elliptical and lenticular, cD; gravitational lensing; infrared radiation; quasars : general; quasars : individual (FSC 10214+4724) ID IRAS F10214+4724; FSC-10214+4724; GALAXY; RADIO; QUASAR AB We present imaging polarimetry of the extremely luminous, redshift 2.3 IRAS source FSC 10214+4724. The observations were obtained with HST's Faint Object Camera in the F437M filter, which is free of strong emission lines. The 0".7 long are is unresolved to 0".04 FWHM in the transverse direction and has an integrated polarization of 28% +/- 3%, in good agreement with ground-based observations. The polarization position angle varies along the are by up to 35 degrees. The overall position angle is 62 degrees +/- 3 degrees east of north. No counterimage is detected to B = 27.5 mag (3 sigma), giving an observed are to counterimage flux ratio greater than 250, considerably greater than the flux ratio of 100 measured previously in the I band. This implies that the configuration of the object in the source plane at the B band is different from that at I band and/or that the lensing galaxy is dusty. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Calif Assoc Res Astron, Kamuela, HI 96743 USA. Inst Adv Study, Princeton, NJ 08540 USA. CALTECH, SIRTF Sci Ctr, Pasadena, CA 91125 USA. CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. RP Nguyen, HT (reprint author), CALTECH, Jet Prop Lab, MS 169-506, Pasadena, CA 91109 USA. OI Hogg, David/0000-0003-2866-9403 NR 23 TC 5 Z9 5 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD FEB PY 1999 VL 117 IS 2 BP 671 EP 676 DI 10.1086/300742 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 172CT UT WOS:000078905300003 ER PT J AU Chavez, M Holberg, JB Landsman, WB AF Chavez, M Holberg, JB Landsman, WB TI Voyager far-ultraviolet observations of globular clusters SO ASTRONOMICAL JOURNAL LA English DT Article DE globular clusters : general; ultraviolet emission ID HORIZONTAL-BRANCH; ENERGY-DISTRIBUTION; BRIGHT STARS; M13; M3; LUMINOSITY; PARAMETERS AB We report on the observations of nine globular clusters carried out by the Voyager ultraviolet spectrometers (UVSs). Three of the observed clusters, M13, NGC 6752, and M70, exhibit an intense far-ultraviolet (FUV) spectrum down to the Lyman limit. However, the spectrum obtained for NGC 6752 is heavily contaminated by the nearby star HD 177999 for wavelengths longward of 1200 Angstrom. For M70 the Voyager spectrum is completely dominated by the B3 star HD 172535. The FUV spectral energy distribution of M13 confirms results from the Ultraviolet Imaging Telescope that the main contributors to the FUV emission are hot sdB stars. M13's integrated spectrum resembles that of an sdB star of T-eff approximate to 28,000 K. For two clusters, M92 and M5, UVS detected a weak signal, making it difficult to reach any conclusion on the underlying hot components of the systems. Four clusters, M15, NGC 2298, NGC 6656, and NGC 6793, were observed but not detected. In some cases it was possible to identify a weak stellar spectrum, which, however, very likely originates from foreground FUV emitters not related to the systems. For the nondetected clusters we provide upper limits on the FUV flux. C1 Inst Nacl Astrofis Opt & Electr, Puebla 72000, Mexico. Univ Arizona, Lunar & Planetary Lab W, Tucson, AZ 85721 USA. NASA, Hughes STX Co, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Chavez, M (reprint author), Inst Nacl Astrofis Opt & Electr, Apdo Postal 51 & 216, Puebla 72000, Mexico. NR 25 TC 0 Z9 0 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 EI 1538-3881 J9 ASTRON J JI Astron. J. PD FEB PY 1999 VL 117 IS 2 BP 962 EP 966 DI 10.1086/300719 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 172CT UT WOS:000078905300023 ER PT J AU Garcia-Sanchez, J Preston, RA Jones, DL Weissman, PR Lestrade, JF Latham, DW Stefanik, RP AF Garcia-Sanchez, J Preston, RA Jones, DL Weissman, PR Lestrade, JF Latham, DW Stefanik, RP TI Stellar encounters with the Oort cloud based on Hipparcos data SO ASTRONOMICAL JOURNAL LA English DT Article DE comets : general; solar neighborhood; solar system : general; stars : kinematics ID GROUND-BASED MEASUREMENTS; INDIVIDUAL RADIAL-VELOCITIES; SOLAR-TYPE STARS; STANDARD STARS; ASTROPHYSICAL BINARIES; COMET SHOWERS; DWARF STARS; CATALOG; KINEMATICS; SYSTEM AB We have combined Hipparcos proper-motion and parallax data for nearby stars with ground-based radial velocity measurements to find stars that may have passed (or will pass) close enough to the Sun to perturb the Oort cloud. Close stellar encounters could deflect large numbers of comets into the inner solar system, which would increase the impact hazard at Earth. We find that the rate of close approaches by star systems (single or multiple stars) within a distance D (in parsecs) from the Sun is given by N = 3.5D(2.12) MYr(-1), less than the number predicted by a simple stellar dynamics model. However, this value is clearly a lower limit because of observational incompleteness in the Hipparcos data set. One star, Gliese 710, is estimated to have a closest approach of less than 0.4 pc 1.4 Myr in the future, and several stars come within 1 pc during a +/- 10 Myr interval. We have performed dynamical simulations that show that none of the passing stars perturb the Oort cloud sufficiently to create a substantial increase in the long-period comet flux at Earth's orbit. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Observ Paris, Sect Meudon, F-92195 Meudon, France. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Barcelona, Dept Astron & Meteorol, E-08028 Barcelona, Spain. RP Garcia-Sanchez, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 93 TC 44 Z9 44 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD FEB PY 1999 VL 117 IS 2 BP 1042 EP 1055 DI 10.1086/300723 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 172CT UT WOS:000078905300031 ER PT J AU Sekanina, Z AF Sekanina, Z TI Multiple fragmentation of comet Machholz 2 (P/1994 P1) SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE comets : general; comets : individual : P/Machholz-2 AB Discovered in August of 1994, periodic comet Machholz 2 consisted of five condensations, A-E, of which D later became double. They were lined up along their common heliocentric orbit (with A being the leading and brightest component) and connected by a trail of material, suggesting that the comet's nuclear fragmentation was accompanied by a copious release of large dust particles. The earliest breakup is found to have occurred in late 1987, similar to 600 days before the comet's 1989 perihelion, giving birth to fragment B and the grand precursor of A. The precursors of A and D and fragments A and C appear to have originated, respectively, similar to 5 days prior to and right at perihelion. The last breakup episode during that same return to the Sun was the separation of E, probably from the precursor of D, similar to 600 days after perihelion. The division of D into D-1 and D-2 is the only event analyzed in this paper that occurred one revolution later, in 1994. The circumstances and implications of this fragmentation sequence are examined in detail and predictions are presented for 1999/2000. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sekanina, Z (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 52 TC 10 Z9 10 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 FEB PY 1999 VL 342 IS 1 BP 285 EP 299 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 164LJ UT WOS:000078465400029 ER PT J AU Vilmer, N Trottet, G Barat, C Schwartz, RA Enome, S Kuznetsov, A Sunyaev, R Terekhov, O AF Vilmer, N Trottet, G Barat, C Schwartz, RA Enome, S Kuznetsov, A Sunyaev, R Terekhov, O TI Hard X-ray and gamma-ray observations of an electron dominated event associated with an occulted solar flare SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun : activity; Sun : corona; Sun : flares; Sun : X-rays, gamma rays ID SPATIAL STRUCTURE; EMISSION; ACCELERATION; SPECTROSCOPY; SPECTRA; COMPTON; BURSTS; CORONA; IONS AB This paper reports hard X-ray (HXR) and gamma-ray (GR) observations of an impulsive electron-dominated event which occurred on 1991 June 30 at similar or equal to 0256 UT. This event is associated with an optical flare produced in an active region located behind the east solar limb. When observed from the earth's direction, it appears as a moderate HXR/GR burst but still shows significant emission in the 10-100 MeV range. During most of the event, the photon spectrum exhibits a hardening above a break energy of 0.5 MeV and no significant GR line (GRL) emission is detected. When viewed from a largely different direction, this impulsive event corresponds to one of the giant hares observed with ULYSSES. The main results of the present analysis are: (i) the HXR/GR emission observed from the earth's direction represents only a small fraction of the total X-ray emission; while the unocculted emission below 0.5 MeV is likely produced in the corona at heights greater than 10(4) km the higher energy emission probably originates from thick target interaction on the visible disk; (ii) although associated with an occulted optical flare, this event exhibits at high energies spectral characteristics similar to what is observed for a disk electron dominated event; (iii) even if no significant GRL emission is detected, the observations cannot exclude that a greater than or similar to 1MeV/nuc ion energy content comparable to the greater than or similar to 20 keV electron content is produced in the flare; the comparable energy contents between electrons and ions found for strong GRL flares and for one electron dominated event associated with a disk flare thus also holds for the unocculted part of this event. C1 Observ Paris, Sect Meudon, CNRS, URA 2080,DASOP, F-92195 Meudon, France. Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France. NASA, Goddard Space Flight Ctr, Hughes STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, LASP, Greenbelt, MD 20771 USA. Nobeyama Radio Observ, Nagano 38413, Japan. Space Sci Inst, Moscow 117810, Russia. RP Vilmer, N (reprint author), Observ Paris, Sect Meudon, CNRS, URA 2080,DASOP, F-92195 Meudon, France. NR 54 TC 30 Z9 30 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD FEB PY 1999 VL 342 IS 2 BP 575 EP 582 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 168QH UT WOS:000078703400029 ER PT J AU Vicini, B Natta, A Marconi, A Testi, L Hollenbach, D Draine, BT AF Vicini, B Natta, A Marconi, A Testi, L Hollenbach, D Draine, BT TI A near-infrared study of the planetary nebula NGC 2346 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE shock waves; ISM : molecules; ISM : planetary nebulae : individual : NGC 2346; infrared : ISM : lines and bands ID MOLECULAR-HYDROGEN; MASS-LOSS; NGC-2346; EVOLUTION; CO AB This paper presents new near-infrared observations of the planetary nebula NGC 2346. The data include a broad K-band image, an image in the H-2 vibrationally excited 1-0S(1) line and K band slit spectra at three positions in the nebula. in the H-2 1-0S(1) line, the nebula is characterized by a central, bright torus, surrounded by weaker emission with a typical butterfly shape, as seen in Her and CO lines. The K band spectra show II H-2 lines with excitation energies from 6150 to 12552 K. The H-2 data have been compared to the predictions of models which follow the evolution with time of the H-2 emission in PNe of different core mass and shell properties (Natta & Hollenbach 1998). These models compute the emission originating in the photodissociation region (PDR) created at the inner edge of the neutral shell by the UV radiation of the central core, as well as the emission in the shock associated with the expansion of the shell inside the precursor red-giant wind. In NGC 2346, a PDR origin of the H-2 emission in a low-density molecular shell (n less than or similar to 10(4) cm(-3)) is indicated. At these low densities, time-dependent H-2 chemistry and X-ray heating of the neutral gas enhance the predicted PDR H-2 line intensity by large factors. C1 Osservatorio Astrofis Arcetri, I-50125 Florence, Italy. Univ Florence, Dipartimento Astron & Sci Spazio, I-50125 Florence, Italy. CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Princeton Univ Observ, Princeton, NJ 08544 USA. RP Natta, A (reprint author), Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy. EM natta@arcetri.astro.it RI Marconi, Alessandro/C-5880-2009; OI Marconi, Alessandro/0000-0002-9889-4238; Draine, Bruce/0000-0002-0846-936X NR 32 TC 20 Z9 20 U1 0 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 FEB PY 1999 VL 342 IS 3 BP 823 EP 830 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 171BK UT WOS:000078842300024 ER PT J AU Sakai, S Madore, BF Freedman, WL AF Sakai, S Madore, BF Freedman, WL TI Cepheid and tip of the red giant branch distances to the dwarf irregular galaxy IC 10 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies : distances and redshifts; galaxies : individual (IC 10); galaxies : photometry ID IC-10; EXTINCTION; PHOTOMETRY AB We present color-magnitude diagrams and luminosity functions of stars in the nearby galaxy IC 10, based on VI CCD photometry acquired with the COSMIC prime-focus camera on the Palomar 5 m telescope. The apparent I-band luminosity function of stars in the halo of IC 10 shows an identifiable rise at I approximate to 21.7 mag. This is interpreted as being the tip of the red giant branch (TRGB) at M-V approximate to -4 mag. Since IC 10 is at a very low Galactic latitude, its foreground extinction is expected to be high and the uncertainty associated with that correction is the largest contributor to the error associated with its distance determination. Multiwavelength observations of Cepheid variable stars in IC 10 give a Population I distance modulus of 24.1 +/- 0.2 mag, which corresponds to a linear distance of 660 +/- 66 kpc for a total line-of-sight reddening of E(B-V) = 1.16 +/- 0.08 mag, derived self-consistently from the Cepheid data alone. Applying this Population I reddening to the Population II halo stars gives a TRGB distance modulus of 23.5 +/- 0.2 mag, corresponding to 500 +/- 50 kpc. We consider this to be a lower limit on the TRGB distance. Reconciling the Cepheid and TRGB distances would require that the reddening to the halo is Delta E(B-V) = 0.31 mag lower than that into the main body of the galaxy. This then suggests that the Galactic extinction in the direction of IC 10 is E(B-V) similar or equal to 0.85. C1 Kitt Peak Natl Observ, Tucson, AZ 85726 USA. CALTECH, NASA, IPAC Extragalact Database, Pasadena, CA 91125 USA. Carnegie Inst Astron Observ, Pasadena, CA 91101 USA. RP Sakai, S (reprint author), Kitt Peak Natl Observ, POB 26732, Tucson, AZ 85726 USA. NR 24 TC 49 Z9 49 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 1 PY 1999 VL 511 IS 2 BP 671 EP 679 DI 10.1086/306716 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NN UT WOS:000079158100014 ER PT J AU Colbert, JW Malkan, MA Clegg, PE Cox, P Fischer, J Lord, SD Luhman, M Satyapal, S Smith, HA Spinoglio, L Stacey, G Unger, SJ AF Colbert, JW Malkan, MA Clegg, PE Cox, P Fischer, J Lord, SD Luhman, M Satyapal, S Smith, HA Spinoglio, L Stacey, G Unger, SJ TI ISO LWS spectroscopy of M82: A unified evolutionary model SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; galaxies : individual (M82); galaxies : ISM; galaxies : starburst; infrared : galaxies ID FAR-INFRARED SPECTROSCOPY; PHOTODISSOCIATION REGIONS; INTERSTELLAR-MEDIUM; STARBURST NUCLEUS; GALACTIC NUCLEI; STAR-FORMATION; GAS DISK; GALAXY; LINE; EMISSION AB We present the first complete far-infrared spectrum (43-197 mu m) of M82, the brightest infrared galaxy in the sky, taken with the Long Wavelength Spectrometer of the Infrared Space Observatory (ISO). We detected seven fine structure emission lines, [O I] 63 and 145 mu m, [O III] 52 and 88 mu m, [N II] 122 mu m, [N III] 57 mu m, and [C II] 158 mu m, and fitted their ratios to a combination starburst and photodissociation region (PDR) model. The best fit is obtained with H II regions with n = 250 cm(-3), an ionization parameter of 10(-3.5), and PDRs with n = 10(3.3) cm(-3) and a far-ultraviolet flux of G(0) = 10(2.8). We applied both continuous and instantaneous starburst models, with our best fit being a 3-5 Myr old instantaneous burst model with a 100 M-. cutoff. We also detected the ground-state rotational line of OH in absorption at 119.4 mu m. No excited level OH transitions are apparent, indicating that the OH is almost entirely in its ground state with a column density similar to 4 x 10(14) cm(-2). The spectral energy distribution over the long-wavelength spectrometer wavelength range is well fitted with a 48 K dust temperature and an optical depth, tau(Dust) proportional to lambda(-1). C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ London Queen Mary & Westfield Coll, Dept Phys, London E1 4NS, England. Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CNR, Ist Fis Spazio Interplanetario, I-00044 Frascati, Italy. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. RP Colbert, JW (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. OI Spinoglio, Luigi/0000-0001-8840-1551 NR 51 TC 98 Z9 98 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 1 PY 1999 VL 511 IS 2 BP 721 EP 729 DI 10.1086/306711 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NN UT WOS:000079158100018 ER PT J AU Evans, AS Sanders, DB Surace, JA Mazzarella, JM AF Evans, AS Sanders, DB Surace, JA Mazzarella, JM TI Molecular gas in 3C 293: The first detection of CO emission and absorption in an Fanaroff-Riley type II radio galaxy SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (3C 293); galaxies : ISM; infrared : galaxies; ISM : molecules; radio lines : galaxies ID MULTICOLOR SURFACE PHOTOMETRY; LUMINOUS INFRARED GALAXIES; CENTAURUS-A; IRAS; NUCLEUS; ARP-220; MASSES; DUST; DISK AB The first detection of CO emission in a Fanaroff and Riley type II (i.e., edge-brightened radio lobe morphology) radio galaxy is presented. Multiwavelength (0.36-2.17 mu m) imaging of 3C 293 shows it to be a disk galaxy with an optical jet or tidal tail extending toward what appears to be a companion galaxy 28 kpc away via a low surface brightness envelope. The molecular gas appears to be distributed in an asymmetric disk rotating around an unresolved continuum source, which is presumably emission from the active galactic nucleus (AGN). A narrow (Delta v(abs) similar to 60 km s(-1)) absorption feature is also observed in the CO spectrum and is coincident with the continuum source. Assuming the standard CO conversion factor, the molecular gas (H(2)) mass is calculated to be 1.5 x 10(10) M(.), several times the molecular gas mass of the Milky Way. The high concentration of molecular gas within the central 3 kpc of 3C 293, combined with the multiwavelength morphological peculiarities, supports the idea that the radio activity has been triggered by a gas-rich galaxy-galaxy interaction or merger event. C1 CALTECH, Div Phys Math & Astron MS 105 24, Pasadena, CA 91125 USA. Astron Inst, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. RP Evans, AS (reprint author), CALTECH, Div Phys Math & Astron MS 105 24, Pasadena, CA 91125 USA. EM ase@astro.caltech.edu; sanders@ifa.hawaii.edu; jason@ipac.caltech.edu; mazz@ipac.caltech.edu NR 50 TC 66 Z9 66 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 FEB 1 PY 1999 VL 511 IS 2 BP 730 EP 738 DI 10.1086/306717 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NN UT WOS:000079158100019 ER PT J AU Corbet, RHD Finley, JP Peele, AG AF Corbet, RHD Finley, JP Peele, AG TI Evidence for a very slow X-ray pulsar in 2S 0114+650 from Rossi X-Ray Timing Explorer all-sky monitor observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (2S 0114+650); stars : neutron; X-rays : stars ID PERIODIC OUTBURSTS; SPACED DATA; VELA X-1; SYSTEM; 2S-0114+650; VARIABILITY AB Rossi X-Ray Timing Explorer (RXTE) all-sky monitor (ASM) observations of the X-ray binary 2S 0114+650 show modulations at periods close to both the optically derived orbital period (11.591 days) and proposed pulse period (similar to 2.7 hr). The pulse period shows frequency and intensity variability during the more than 2 years of ASM observations analyzed. The pulse properties are consistent with this arising: from accretion onto a rotating neutron star, and this would be the slowest such period known. The shape of the orbital light curve shows modulation over the course of the entire orbit, and a comparison is made with the orbital light curve of Vela X-l. However, the expected phase of eclipse, based on an extrapolation of the optical ephemeris, does not correspond with the observed orbital minimum. The orbital period derived from the ASM light curve is also slightly longer than the optical period. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA. RP Corbet, RHD (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. EM corbet@lheamail.gsfc.nasa.gov; finley@purds1.physics.purdue.edu; peele@lheamail.gsfc.nasa.gov NR 29 TC 30 Z9 31 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 1 PY 1999 VL 511 IS 2 BP 876 EP 884 DI 10.1086/306727 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NN UT WOS:000079158100032 ER PT J AU Grady, CA Perez, MR Bjorkman, KS Massa, D AF Grady, CA Perez, MR Bjorkman, KS Massa, D TI Transient infall events in the disk of AB Aurigae: The beta Pictoris phenomenon at 2-4 megayears SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; circumstellar matter; line : profiles; stars : individual (AB Aurigae); ultraviolet : stars ID HERBIG-AE/BE STARS; MG-II; SPECTRAL VARIABILITY; WIND VARIABILITY; YOUNG STARS; LINES; DUST; ACCRETION; CAMPAIGN; EMISSION AB Surveys of Herbig Ae/Be stars have indicated that infalling, circumstellar gas similar to that routinely detected toward beta Pic is preferentially observed close to the disk midplane. Recent millimeter interferometry of the historically prototypical Herbig Ae star, AB Aur, indicates that this star is viewed slightly above the disk midplane (i = 76 degrees). The wealth of archival spectroscopic data for this star makes it an ideal test of the geometry for infalling or accreting gas in these stars. We present a review of the extant IUE and Hubble Space Telescope GHRS spectral data for AB Aur and find, in contrast to previous studies of this star, which focused on Mg II, that infalling gas is detected at all epochs with covering factors similar to those reported for HD 100546 and that an episode of enhanced infall was serendipitously detected during the 1990 monitoring run. C1 Eureka Sci, Oakland, CA 94602 USA. Space Applicat Corp, Largo, MD 20774 USA. Univ Toledo, Ritter Observ, Toledo, OH 43606 USA. Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. NASA, Goddard Space Flight Ctr, Hughes STX, Greenbelt, MD 20771 USA. RP Grady, CA (reprint author), Eureka Sci, 2452 Delmer St,Suite 100, Oakland, CA 94602 USA. EM cgrady@ari.net NR 46 TC 15 Z9 15 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 1 PY 1999 VL 511 IS 2 BP 925 EP 931 DI 10.1086/306698 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NN UT WOS:000079158100037 ER PT J AU Allamandola, LJ Hudgins, DM Sandford, SA AF Allamandola, LJ Hudgins, DM Sandford, SA TI Modeling the unidentified infrared emission with combinations of polycyclic aromatic hydrocarbons SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM : lines and bands; ISM : individual (Orion Bar, IRAS 22272+5435); line : formation; line : identification; line : profiles; molecular data; radiation mechanisms : nonthermal ID MICRON EMISSION; CARBON DUST; ORION-BAR; BANDS; SPECTROSCOPY; SPECTRA; CATIONS; MOLECULES; NAPHTHALENE; TEMPERATURE AB The infrared emission band spectrum associated with many different interstellar objects can be modeled successfully by using combined laboratory spectra of neutral and positively charged polycyclic aromatic hydrocarbons (PAHs). These model spectra, shown here for the first time, alleviate the principal spectroscopic criticisms previously leveled at the PAH hypothesis and demonstrate that mixtures of free molecular PAHs can indeed account for the overall appearance of the widespread interstellar infrared emission spectrum. Furthermore, these models give us insight into the structures, stabilities, abundances, and ionization balance of the interstellar PAH population. These, in turn, reflect conditions in the emission zones and shed light on the microscopic processes involved in the carbon nucleation, growth, and evolution in circumstellar shells and the interstellar medium. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Allamandola, LJ (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. NR 53 TC 260 Z9 260 U1 2 U2 25 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 1 PY 1999 VL 511 IS 2 BP L115 EP L119 DI 10.1086/311843 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NP UT WOS:000079158200012 PM 11542234 ER PT J AU van Aalst, MK Martens, PCH Belien, AJC AF van Aalst, MK Martens, PCH Belien, AJC TI Can streamer blobs prevent the buildup of the interplanetary magnetic field? SO ASTROPHYSICAL JOURNAL LA English DT Article DE interplanetary medium; solar wind; Sun : corona; Sun : magnetic fields; Sun : particle emission ID CORONAL MASS EJECTION; SOLAR-WIND; RECONNECTION; DISCONNECTION; TRANSIENT; TOPOLOGY; FLUX AB Coronal mass ejections continuously drag closed magnetic field lines away from the Sun, adding new flux to the interplanetary magnetic field (IMF). We propose that the outward-moving blobs that have been observed in helmet streamers are evidence of ongoing, small-scale reconnection in streamer current sheets, which may play an important role in the prevention of an indefinite buildup of the IMF. Reconnection between two open field lines from both sides of a streamer current sheet creates a new closed field line, which becomes part of the helmet, and a disconnected field line, which moves outward. The blobs an formed by plasma from the streamer that is swept up in the trough of the outward-moving field line. We show that this mechanism is supported by observations from Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph. Additionally, we propose a thorough statistical study to quantify the contribution of blob formation to the reduction of the IMF and indicate how this mechanism may be verified by observations with SOHO/Ultraviolet Coronagraph Spectrometer and the proposed NASA Solar Terrestrial Relations Observatory and ESA Polar Orbiter missions. C1 Univ Utrecht, Sterrekundig Inst, NL-3508 TA Utrecht, Netherlands. NASA, Goddard Space Flight Ctr, ESA, Space Sci Dept,Solar Syst Div, Greenbelt, MD 20771 USA. RP van Aalst, MK (reprint author), Univ Utrecht, Sterrekundig Inst, Postbus 80 000, NL-3508 TA Utrecht, Netherlands. NR 27 TC 11 Z9 11 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 1 PY 1999 VL 511 IS 2 BP L125 EP L128 DI 10.1086/311853 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NP UT WOS:000079158200014 ER PT J AU Yaqoob, T AF Yaqoob, T TI On the unusually high temperature of the cluster of galaxies 1E 0657-56 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : clusters : individual (1E 0657-56); intergalactic medium; large-scale structure of universe; X-rays : galaxies ID BEPPOSAX AB A recent X-ray observation of the cluster 1E 0657 - 56 (z = 0.296) with the Advanced Satellite for Cosmology and Astrophysics (ASCA) implied an unusually high temperature of similar to 17 keV. Such a high temperature would make it the hottest known cluster and would severely constrain cosmological models since, in a universe with critical density (Omega = 1), the probability of observing such a cluster is only similar to 4 x 10(-5). Here we test the robustness of this observational result because it has such important implications. We analyzed the data using a variety of different data analysis methods and spectral analysis assumptions, and we found a temperature of similar to 11-12 keV in all cases, except for one class of spectral fits. These are fits in which the absorbing column density is fixed at the Galactic value. Using simulated data for a 12 keV cluster, we show that a high temperature of similar to 17 keV is artificially obtained if the true spectrum has a stronger low-energy cutoff than that for Galactic absorption only. The apparent extra absorption may be astrophysical in origin (either intrinsic or line of sight), or it may be a problem with the low-energy CCD efficiency. Although significantly lower than previous measurements, this temperature of kT similar to 11-12 keV is still relatively high since only a few clusters have been found to have temperatures higher than 10 keV, and the data therefore still present some difficulty for an Omega = 1 universe. Our results will also be useful to anyone who wants to estimate the systematic errors involved in the different methods of background subtraction of ASCA data for sources with a similar signal-to-noise ratio to that of the 1E 0657-56 data reported here. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Yaqoob, T (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 8 TC 8 Z9 8 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 1 PY 1999 VL 511 IS 2 BP L75 EP L78 DI 10.1086/311842 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176NP UT WOS:000079158200003 ER PT J AU Ptak, A Serlemitsos, P Yaqoob, T Mushotzky, R AF Ptak, A Serlemitsos, P Yaqoob, T Mushotzky, R TI X-ray constraints on accretion and starburst processes in galactic nuclei. I. Spectral results SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE galaxies : active; galaxies : nuclei; X-rays : galaxies ID ALL-SKY SURVEY; SPIRAL GALAXIES; ROSAT OBSERVATIONS; ACTIVE NUCLEUS; M51 NGC-5194; EMISSION; M82; NGC-253; DISCOVERY; PARAMETERS AB The results of the analysis of 0.4-10.0 keV ASCA spectral analysis of a sample of low-luminosity active galactic nuclei (AGNs) (LLAGNs; M51, NGC 3147, and NGC 4258), low-ionization nuclear emission-line regions (LINERs; NGC 3079, NGC 3310, NGC 3998, NGC 4579, and NGC 4594), and starburst galaxies (M82, NGC 253, NGC 3628, and NGC 6946) are presented. In spite of the heterogeneous optical classifications of these galaxies, the X-ray spectra are fitted well by a a "canonical" model consisting of an optically thin Raymond-Smith plasma "soft" component with T similar to 7 x 10(6) K and a "hard" component that can be modeled by either a power law with a photon index Gamma similar to 1.7 or a thermal bremsstrahlung with T similar to 6 x 10(7) K. The soft-component absorption is typically less than 10(21) cm(-2), while the hard component is typically absorbed by an additional column on the order of 10(22) cm(-2). The soft-component 0.4-10 keV intrinsic luminosities tend to be on the order 10(39-40) ergs s(-1), while the hard-component luminosities tend to be on the order of 10(40-41) ergs s(-1). The abundances inferred from the fits to the soft component are significantly subsolar. The Fe abundance can be measured independently of the other elemental abundances (dominated by alpha-process elements) in M51, M82, NGC 253, and NGC 4258. In these galaxies the Fe abundance relative to alpha-process elements is also (statistically) significantly subsolar. There is some indication (at a low statistical significance) that the abundance properties of starburst emission from starburst galaxies differs from the starburst emission from low-luminosity AGNs. However, these results on abundances are model dependent. Significant Fe K line emission is observed in M51, M82, NGC 3147, NGC 4258, and NGC 4579. An analysis of the shortterm variability properties was given in Ptak et al. and detailed interpretation of these results will be given in Paper II in this series. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USRA, Washington, DC USA. RP Ptak, A (reprint author), Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. RI Ptak, Andrew/D-3574-2012 NR 66 TC 102 Z9 102 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD FEB PY 1999 VL 120 IS 2 BP 179 EP 208 DI 10.1086/313179 PG 30 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192RZ UT WOS:000080094000002 ER PT J AU Macomb, DJ Gehrels, N AF Macomb, DJ Gehrels, N TI A general gamma-ray source catalog SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Review DE catalogs; gamma rays : observations ID HARD X-RAY; CODED-APERTURE TELESCOPE; ACTIVE GALACTIC NUCLEI; FIGARO-II EXPERIMENT; HIGH-ENERGY EMISSION; POSITRON-ANNIHILATION LINE; TRANSIENT GRO J1655-40; LARGE MAGELLANIC CLOUD; BLACK-HOLE CANDIDATES; SOLAR MAXIMUM MISSION AB The past several years have seen unprecedented growth in the field of gamma-ray astronomy. Highly successful missions such as the Compton Gamma-Ray Observatory (CGRO) have led to both a great increase in the number of detected gamma-ray sources and a more fundamental understanding of the basic physical processes involved for those sources. New ground-based observatories, the Rossi X-Ray Timing Explorer (RXTE), and the SIGMA instrument aboard the GRANAT spacecraft have all contributed to this explosion. Detailed observations of active galaxies, pulsars, accreting binaries, and diffuse emission have had a tremendous impact on our view of the universe. Given that new experiments that will provide a similar increase in source numbers are several years away, it is a good time to take inventory of the state of gamma-ray astronomy. To this end, we have developed a general gamma-ray point-source catalog containing 309 objects that summarize the field. Gamma-ray astronomy, as we define it, includes photon energies from 50 keV to about 1 TeV. While many catalogs concentrate on a single type of astronomical object and/or a very restricted energy range, the nature of this catalog is somewhat different. The large variety of objects and the many orders of magnitude in energy space covered by gamma-ray astronomy presents an organizational challenge. We focus on two main types of information: a general listing of the basic characteristics of each source, and detailed tables of a representative sample of high-energy observations. We also summarize the gamma-ray instruments whose observations are included in the catalog.(3). C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. RP Macomb, DJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 589 TC 24 Z9 24 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 EI 1538-4365 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD FEB PY 1999 VL 120 IS 2 BP 335 EP 397 DI 10.1086/313182 PG 63 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192RZ UT WOS:000080094000009 ER PT J AU Hurley, K Briggs, MS Kippen, RM Kouveliotou, C Meegan, C Fishman, G Cline, T Boer, M AF Hurley, K Briggs, MS Kippen, RM Kouveliotou, C Meegan, C Fishman, G Cline, T Boer, M TI The Ulysses supplement to the BATSE 3B catalog of cosmic gamma-ray bursts SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE catalogs; gamma rays : bursts ID ARRIVAL TIME LOCALIZATIONS; COUNTERPART; REDSHIFT; RADIO AB We present interplanetary network localization information for 218 gamma-ray bursts in the third BATSE catalog obtained by analyzing the arrival times of these bursts with the Ulysses and Compton Gamma Ray Observatory spacecraft. For any given burst observed by these two spacecraft, arrival time analysis (or "triangulation") results in an annulus of possible arrival directions whose half-width varies between 7 " and 32', depending on the intensity and time history of the burst and the distance of the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE error circle, which results in an average reduction of a factor of 30 of the error box area. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France. RP Hurley, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. OI Boer, Michel/0000-0001-9157-4349 NR 22 TC 44 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD FEB PY 1999 VL 120 IS 2 BP 399 EP 408 DI 10.1086/313178 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192RZ UT WOS:000080094000010 ER PT J AU Kara, AB Ruscher, PH Sen, ZK AF Kara, AB Ruscher, PH Sen, ZK TI Forecast errors in the Florida State University atmospheric boundary layer model (FSU1DPBL) - Part I: Thermal advection effects SO ATMOSPHERIC RESEARCH LA English DT Article DE forecast errors; atmospheric boundary layer; thermal advection effects ID SOIL HYDROLOGY; SENSITIVITY; FLUXES AB Short range weather forecasting and atmospheric boundary layer (ABL) processes are studied by using a one-dimensional ABL model where the horizontal advection terms are neglected. The ability of the model, the Florida State University atmospheric boundary layer (FSU1DPBL) model, to forecast minimum temperature is investigated in terms of thermal advection effects. The model is used for 12-, 24-, and 36-h forecasts of minimum temperatures. The minimum temperatures obtained from the model forecasts are compared with observations. The investigation is confined to days meeting criteria representative of clear and calm synoptic conditions. Errors between observations and model results are determined using thermal advection analysis in the boundary layer since horizontal thermal advection affects cooling rates at night. The errors are found to be strongly correlated with thermal advection in the lowest part of the ABL, By carrying out some case studies, it is seen that the model is more prone to errors in dry conditions. It is also confirmed that the strong thermal advection aloft getting closer and closer to the ground largely explains the difference in minimum temperatures between the model and observations. The results show that the model is also a useful tool for the short-range weather forecasting since it is not computationally expensive, The model is able to simulate well the nighttime minimum temperatures, and can be used operationally. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Istanbul Tech Univ, Dept Meteorol, TR-80626 Istanbul, Turkey. RP Kara, AB (reprint author), NASA, USA, Ammunizat Plant, Sverdrup,Stennis Space Ctr, Bldg 9101, Bay St Louis, MS 39529 USA. NR 22 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD FEB PY 1999 VL 50 IS 2 BP 119 EP 131 DI 10.1016/S0169-8095(98)00093-3 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 163KC UT WOS:000078403700004 ER PT J AU Kara, AB Ruscher, PH Sen, Z AF Kara, AB Ruscher, PH Sen, Z TI Forecast errors in the Florida State University atmospheric boundary layer model (FSU1DPBL) - Part II: Statistical investigation SO ATMOSPHERIC RESEARCH LA English DT Article DE FSU1DPBL; heat fluxes; daily maximum temperature drop ID SOIL HYDROLOGY; INVERSION; RADIATION AB The performance of Florida State University atmospheric boundary layer model (FSU1DPBL) in predicting the daily maximum temperature drop is investigated with respect to sensible and latent heat fluxes, Turbulent exchanges in the surface boundary layer are taken into account in the model. Nocturnal atmospheric boundary layer heights obtained from the FSU1DPBL model are compared with those obtained from other model formulations, and stability conditions of the ABL are discussed to derive information concerning the prediction of minimum temperature, It is explained that a growth in the ABL at night can occur under cloudy and/or windy conditions in the model, causing a bias as high as 5 degrees C in predicting the daily minimum temperature. The usual similarity theory for the stable boundary layer leads to a significant overestimation of surface cooling in the model. From the model perspective, the success of the 12-h model forecast in predicting minimum temperature compared to that of the 24-h and 36-h forecasts is explained. The results show the prediction of nocturnal ABL height under the extremely stable and moderately stable cases by the model yields acceptable values in comparison with other model formulations. The ABL height from the model can be replaced by an interpolation formula to yield more realistic values under very stable conditions at night. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Istanbul Tech Univ, Dept Meteorol, TR-80626 Istanbul, Turkey. RP Kara, AB (reprint author), NASA, USA, Ammunizat Plant, Sverdrup,Stennis Space Ctr, Bldg 9101, Bay St Louis, MS 39529 USA. EM kara@nrlssc.navy.mil NR 24 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD FEB PY 1999 VL 50 IS 2 BP 133 EP 149 DI 10.1016/S0169-8095(98)00094-5 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 163KC UT WOS:000078403700005 ER PT J AU Jennings, RT Pool, SL AF Jennings, RT Pool, SL TI Symposium on space medicine: What lies ahead? (Reprinted from Texas Medicine, pg 40, February 1998) SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Reprint C1 Univ Texas, Med Branch, Galveston, TX 77555 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Jennings, RT (reprint author), Univ Texas, Med Branch, Mail Code 1150,301 Univ Blvd, Galveston, TX 77555 USA. NR 1 TC 2 Z9 2 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD FEB PY 1999 VL 70 IS 2 BP 153 EP 154 PG 2 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 162DA UT WOS:000078329100010 PM 10206935 ER PT J AU Barratt, M AF Barratt, M TI Medical support for the International Space Station (Reprinted from Texas Medicine, pg 41-46, February 1998) SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Reprint C1 NASA, Lyndon B Johnson Space Ctr, Med Operat, Houston, TX 77058 USA. RP Barratt, M (reprint author), NASA, Lyndon B Johnson Space Ctr, Med Operat, SD26, Houston, TX 77058 USA. NR 3 TC 10 Z9 10 U1 0 U2 1 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD FEB PY 1999 VL 70 IS 2 BP 155 EP 161 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 162DA UT WOS:000078329100011 PM 10206936 ER PT J AU Sawin, CF AF Sawin, CF TI Biomedical investigations conducted in support of the extended duration orbiter medical project (Reprinted from Texas Medicine, pg 56-68, February 1998) SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Reprint ID SPACE-FLIGHT; ENERGY-EXPENDITURE; SPACEFLIGHT; MICROGRAVITY; ASTRONAUTS; ADAPTATION; PRESSURE; HUMANS C1 NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Directorate, Houston, TX 77058 USA. RP Sawin, CF (reprint author), NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Directorate, 2101 NASA Rd 1, Houston, TX 77058 USA. NR 21 TC 6 Z9 6 U1 1 U2 2 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD FEB PY 1999 VL 70 IS 2 BP 169 EP 180 PG 12 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 162DA UT WOS:000078329100013 PM 10206938 ER PT J AU Sargsyan, AE Doarn, CR Simmons, SC AF Sargsyan, AE Doarn, CR Simmons, SC TI Internet and World Wide Web technologies for medical data management and remote access to clinical expertise (Reprinted from Texas Medicine, pg 75-80, February 1998) SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Reprint ID DISASTER RESPONSE; TELEMEDICINE C1 KRUG Life Sci Inc, Houston, TX 77058 USA. NASA, Washington, DC 20546 USA. RP Sargsyan, AE (reprint author), KRUG Life Sci Inc, 1290 Hercules Dr,Ste 120, Houston, TX 77058 USA. NR 27 TC 5 Z9 5 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD FEB PY 1999 VL 70 IS 2 BP 185 EP 190 PG 6 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 162DA UT WOS:000078329100015 PM 10206940 ER PT J AU Buckel, JA Conover, DO Steinberg, ND McKown, KA AF Buckel, JA Conover, DO Steinberg, ND McKown, KA TI Impact of age-0 bluefish (Pomatomus saltatrix) predation on age-0 fishes in the Hudson River estuary: evidence for density-dependent loss of juvenile striped bass (Morone saxatilis) SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID THE-YEAR BLUEFISH; PLEURONECTES-PLATESSA POPULATION; WESTERN WADDEN SEA; EARLY-LIFE-HISTORY; RECRUITMENT VARIABILITY; SELECTIVE PREDATION; INLAND SILVERSIDES; NEW-YORK; SIZE; GROWTH AB We measured bluefish (Pomatomus saltatrix) weights, densities, and prey sizes during the summers of 1992 and 1993 and diets over a 4-year period (1990-1993) in the Hudson River estuary. This information was used to estimate the loss of young-of-the-year (YOY) striped bass (Morone saxatilis) resulting from YOY bluefish predation. We then compared this predation mortality with the total loss of striped bass in the system. Data from sampling surveys conducted since the mid-1970's were used to examine relationships between bluefish abundance and striped bass recruitment levels. YOY striped bass, bay anchovy (Anchoa mitchilli), Atlantic silverside (Menidia menidia), and Alosa spp. dominated YOY bluefish diets. There were ontogenetic and interannual differences in YOY bluefish diets. Bluefish avoided striped bass at low densities but selected for them at high densities, suggesting a density-dependent feeding response. In the early summer of 1993, bluefish predation accounted for 50-100% of the total estimated loss of YOY striped bass. A significant negative correlation exists between the relative magnitude of striped bass recruitment and bluefish abundance. We conclude that YOY bluefish are important predators of estuarine fish and can have a substantial impact on their recruitment. C1 SUNY Stony Brook, Marine Sci Res Ctr, Stony Brook, NY 11794 USA. New York Dept Environm Conservat, Anadromous Fish Unit, E Setauket, NY 11733 USA. RP Buckel, JA (reprint author), NOAA, Natl Marine Fisheries Serv, James J Howard Marine Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 55 TC 62 Z9 63 U1 0 U2 7 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD FEB PY 1999 VL 56 IS 2 BP 275 EP 287 DI 10.1139/cjfas-56-2-275 PG 13 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 185VN UT WOS:000079691800012 ER PT J AU Southward, RE Thompson, DS Thompson, DW St Clair, AK AF Southward, RE Thompson, DS Thompson, DW St Clair, AK TI Inverse chemical vapor deposition: A novel single stage synthesis of highly reflective and conductive silvered polymeric films SO CHEMISTRY OF MATERIALS LA English DT Article ID POLYIMIDE FILMS; ADHESION; REDUCTION; OPTICS AB Highly reflective and surface conductive flexible polyimide films have been prepared by the incorporation of silver(I) acetate and 1,1,1-trifluoro-2,4-pentanedione into a dimethylacetamide solution of the poly(amic acid) formed from 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and 4,4'-oxydianiline. Thermal curing of the silver(I)-containing poly(amic acid) leads to cycloimidization of the polyimide precursor with concomitant silver(I) reduction, yielding a reflective and conductive silver surface approaching that of the native metal, The metalized films retain the essential mechanical and thermal properties of the parent film. Films were characterized by X-ray diffraction, transmission and scanning electron microscopy, tapping mode atomic force microscopy, X-ray photoelectron spectroscopy, and conductivity, reflectivity, thermal, and mechanical measurements. C1 Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. NASA, Div Mat, Langley Res Ctr, Hampton, VA USA. RP Southward, RE (reprint author), Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. NR 41 TC 35 Z9 39 U1 0 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0897-4756 J9 CHEM MATER JI Chem. Mat. PD FEB PY 1999 VL 11 IS 2 BP 501 EP 507 DI 10.1021/cm981014v PG 7 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA 176EY UT WOS:000079139400050 ER PT J AU Cockell, CS Stokes, MD AF Cockell, CS Stokes, MD TI Polar winter: A biological model for impact events and related dark/cold climatic changes SO CLIMATIC CHANGE LA English DT Article ID ANTARCTIC SEA-ICE; CRETACEOUS-TERTIARY EXTINCTIONS; PSYCHROPHILIC MARINE BACTERIUM; MICROBIAL COMMUNITIES; STARVATION-SURVIVAL; WEDDELL SEA; NUTRIENT STARVATION; SEASONAL-CHANGES; GROWTH-RATE; PHYTOPLANKTON AB Models of the climatic perturbation caused by a large scale extraterrestrial impact predict an injection of dust into the stratosphere. This would cause the onset of environmental conditions whose two principal characteristics are a prolonged period of darkness and reduced global temperatures. Similar scenarios follow large scale volcanic eruptions, wildfires and they are predicted for a nuclear winter following a protracted nuclear exchange. A significant drop in temperature and solar insolation are also characteristics of the polar winter. In this paper the onset and emergence from the polar winter is examined as a potential biological framework for studying immediate biological effects following transition into and out of a dark/cold catastrophe. Limitations of the conceptual model, particularly with respect to the fact that polar organisms are well adapted to a regular and severe dark/cold climatic change (which the rest of the Earth's biota is not) are discussed. The model has implications for the poles as an extinction refuge during such climatic changes. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Stanford Univ, Hopkins Marine Stn, Pacific Grove, CA 93950 USA. RP Cockell, CS (reprint author), Carnegie Inst Washington, Dept Plant Biol, 290 Panama St, Stanford, CA 94305 USA. EM cockell@biosphere.stanford.edu NR 98 TC 10 Z9 10 U1 3 U2 6 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0165-0009 J9 CLIMATIC CHANGE JI Clim. Change PD FEB PY 1999 VL 41 IS 2 BP 151 EP 173 DI 10.1023/A:1005465513592 PG 23 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 169MC UT WOS:000078751700002 ER PT J AU Urban, DL King, MK AF Urban, DL King, MK TI NASA's Microgravity Combustion Research Program: Past and future SO COMBUSTION AND FLAME LA English DT Editorial Material C1 NASA, Lewis Res Ctr, Micrograv Combust Sci Branch, Cleveland, OH 44135 USA. NASA Headquarters, Micrograv Res Div, Washington, DC 20546 USA. RP Urban, DL (reprint author), NASA, Lewis Res Ctr, Micrograv Combust Sci Branch, Cleveland, OH 44135 USA. NR 7 TC 2 Z9 2 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 319 EP 320 PG 2 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600002 ER PT J AU Linteris, GT Voss, J Crouch, R AF Linteris, GT Voss, J Crouch, R TI Combustion experiments on STS-83 and STS-94: The crew's perspective SO COMBUSTION AND FLAME LA English DT Editorial Material C1 Natl Inst Stand & Technol, Germantown, MD 20899 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NASA Headquarters, Washington, DC 20546 USA. RP Linteris, GT (reprint author), Natl Inst Stand & Technol, Germantown, MD 20899 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 321 EP 322 PG 2 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600003 ER PT J AU Konsur, B Megaridis, CM Griffin, DW AF Konsur, B Megaridis, CM Griffin, DW TI Fuel preheat effects on soot-field structure in laminar gas jet diffusion flames burning in 0-g and 1-g SO COMBUSTION AND FLAME LA English DT Article ID MICROGRAVITY; COMBUSTION; PARTICLES; BUOYANCY AB An experimental investigation conducted at the 2.2-s drop tower of the NASA Lewis Research Center is presented to quantify the influence of moderate fuel preheat on soot-field structure within 0-g laminar gas jet diffusion flames. Parallel work in 1-g is also presented to delineate the effect of elevated fuel temperatures on soot-field structure in buoyant flames. The experimental methodology implements jet diffusion flames of nitrogen-diluted acetylene fuel burning in quiescent air at atmospheric pressure. Fuel preheat of similar to 100 K in the 0-g laminar jet diffusion flames is found to reduce soot loadings in the annular region, but causes an increase in soot volume fractions at the centerline. In addition, fuel preheat reduces the radial extent of the soot field in 0-g. In 1-g, the same fuel preheat levels have a more moderated influence on soot loadings in the annular region, but are also seen to enhance soot concentrations near the axis low in the flame. The increased soot loadings near the flame centerline, as caused by fuel preheat, are consistent with the hypothesis that preheat levels of similar to 100 K enhance fuel pyrolysis rates. The results show that the growth stage of particles transported along the soot annulus is shortened both in 1-g and 0-g when elevated fuel temperatures are used. (C) 1998 by The Combustion Institute. C1 Univ Illinois, Dept Mech Engn, Chicago, IL 60607 USA. NASA, Lewis Res Ctr, Miccrograv Combust Sci Branch, Cleveland, OH 44135 USA. RP Megaridis, CM (reprint author), Univ Illinois, Dept Mech Engn, Chicago, IL 60607 USA. OI Megaridis, Constantine/0000-0002-6339-6933 NR 31 TC 16 Z9 17 U1 1 U2 5 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 334 EP 347 DI 10.1016/S0010-2180(97)00297-6 PG 14 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600005 ER PT J AU Sunderland, PB Mendelson, BJ Yuan, ZG Urban, DL AF Sunderland, PB Mendelson, BJ Yuan, ZG Urban, DL TI Shapes of buoyant and nonbuoyant laminar jet diffusion flames SO COMBUSTION AND FLAME LA English DT Article ID BEHAVIOR; MICROGRAVITY; PREDICTION; SIZES AB Flame shapes were measured for buoyant and nonbuoyant laminar gas jet diffusion flames burning, methane, ethane, and propane in quiescent air. Test conditions involved burner diameters of 0.19-5.5 mm, ambient pressures of 0.25-2 atm, and fuel flowrates of 0.04-4.6 mg/s. Care was taken to minimize interference from soot emissions and from ignition disturbances. Microgravity conditions were obtained in the 2.2-s drop tower at the NASA Lewis Research Center. Normalized lengths of both buoyant and nonbuoyant flames were proportional to source Reynolds number, but the nonbuoyant flames were 40% longer on average. Normalized widths of the nonbuoyant flames were constant for Re greater than or equal to 100, whereas buoyant flame widths scaled with source Froude number. Several nonbuoyant flame models are evaluated with the present shape data. (C) 1998 by The Combustion Institute. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Natl Res Ctr, Cleveland, OH 44135 USA. Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA. RP Sunderland, PB (reprint author), NASA, Lewis Res Ctr, MS 500-115,21000 Brookpark Rd, Cleveland, OH 44135 USA. EM pbs@einstein.lerc.nasa.gov OI Sunderland, Peter/0000-0002-8262-7100 NR 33 TC 47 Z9 49 U1 1 U2 4 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 376 EP 386 DI 10.1016/S0010-2180(98)00045-5 PG 11 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600008 ER PT J AU Wu, MS Ronney, PD Colantonio, RO Vanzandt, DM AF Wu, MS Ronney, PD Colantonio, RO Vanzandt, DM TI Detailed numerical simulation of flame ball structure and dynamics SO COMBUSTION AND FLAME LA English DT Article ID STABILITY; MIXTURES AB A numerical study was conducted to examine the structure and dynamics of steady, source-free spherical premixed flames ("flame balls"), which have been observed in microgravity experiments. A time-dependent spherically symmetric code was used with detailed chemical, transport, and radiation, submodels. Steady properties, stability limits, and dynamics of flame balls are computed for H-2-air mixtures. The chemical and radiation models used were found to affect flame ball properties substantially. The special and unusual role of thermal radiation from the combustion products is described. In particular, the far-field radiative loss is found to affect the behavior of flame balls in a manner very different from propagating planar flames. One new feature was identified: mixtures capable of exhibiting both stable flame balls and steadily propagating flames depending on the initial condition. Numerical results are compared to theoretical predictions, prior steady-state numerical calculations, and prior experimental results on flame ball size. Additional experiments were performed to measure flame bail radiant emission. Qualitative agreement with theory and experiment is found; however, quantitative agreement with experiment is only fair, indicating the need for improved microgravity conditions, e.g., in orbiting spacecraft. (C) 1998 by The Combustion Institute. C1 Univ So Calif, Dept Mech Engn, Los Angeles, CA 90089 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. ADF Corp, Brookpark, OH 44142 USA. RP Wu, MS (reprint author), Univ So Calif, Dept Mech Engn, Los Angeles, CA 90089 USA. EM mingshin@ref.usc.edu RI Ronney, Paul/B-4007-2009 OI Ronney, Paul/0000-0002-2779-6438 NR 23 TC 26 Z9 27 U1 0 U2 4 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 387 EP 397 DI 10.1016/S0010-2180(97)00356-8 PG 11 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600009 ER PT J AU Walther, DC Fernandez-Pello, AC Urban, DL AF Walther, DC Fernandez-Pello, AC Urban, DL TI Space shuttle based microgravity smoldering combustion experiments SO COMBUSTION AND FLAME LA English DT Article ID PREMIXED GAS COMBUSTION; POLYURETHANE FOAM; PROPAGATION; FLOW; EXTINCTION; GRAVITY AB Results from four microgravity smoldering combustion experiments conducted aboard the NASA Space Shuttle are presented in this work. The experiments are part of the NASA funded Microgravity Smoldering Combustion (MSC) research program, aimed to study the smolder characteristics of porous combustible materials in a microgravity environment. The objective of the study is to provide a better understanding of the controlling mechanisms of smolder for the purpose of control and prevention, both in normal- and microgravity. The microgravity smolder experiments reported here have been conducted to investigate the propagation of smolder through a polyurethane foam sample under both diffusion driven and opposed forced flow driven smoldering. The present experiments, although limited, are unique in that they provide the only available information about smolder combustion in microgravity in sample sizes large enough to allow the self-propagation of the smolder reaction throughout the sample length. Two quiescent tests at ambient oxygen concentrations of 35% and 40% and two opposed forced flow tests with air as oxidizer, were conducted aboard the NASA Space Shuttle (STS-69 and STS-77 missions). The MSC data are compared with normal-gravity data to determine the effect of gravity on smolder, and are used to verify present theoretical models of smolder combustion. It is found that for the present test conditions, the microgravity opposed flow smolder reaction temperatures, propagation velocities, toxic compound production and reaction extent lie between those of normal-gravity upward and downward tests. Thermogravimetric analysis shows little effect of gravity on the kinetics of the smolder process in these cases. Neither of the two quiescent, microgravity cases resulted in self-sustained smolder propagation, whereas the normal-gravity downward cases propagated vigorously. The difference in these results shows that gravity has a significant effect on smolder combustion, at least for the sample size tested. Correlation of the forced flow smolder velocity data with a heat transfer based model, indicates that simplified heat transfer models of smolder propagation can effectively describe vigorous smolder, away from limiting conditions such as extinction and flaming. (C) 1998 by The Combustion Institute. C1 Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Fernandez-Pello, AC (reprint author), Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA. EM ferpello@euler.me.berkeley.edu NR 37 TC 23 Z9 29 U1 1 U2 4 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 398 EP 414 DI 10.1016/S0010-2180(98)00095-9 PG 17 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600010 ER PT J AU Lin, KC Faeth, GM Sunderland, PB Urban, DL Yuan, ZG AF Lin, KC Faeth, GM Sunderland, PB Urban, DL Yuan, ZG TI Shapes of nonbuoyant round luminous hydrocarbon/air laminar jet diffusion flames SO COMBUSTION AND FLAME LA English DT Article ID SOOT FORMATION; MICROGRAVITY; BEHAVIOR AB The shapes (luminous flame boundaries) of round luminous nonbuoyant soot-containing hydrocarbon/air laminar jet diffusion flames at microgravity were found from color video images obtained on orbit in the Space Shuttle Columbia. Test conditions included ethylene- and propane-fueled flames burning in still air at an ambient temperature of 300 K, ambient pressures of 35-130 kPa, initial jet diameters of 1.6 and 2.7 mm, and jet exit Reynolds numbers of 45-170. Present test times were 100-200 s and yielded steady axisymmetric flames that were close to the laminar smoke point (including flames both emitting and not emitting soot) with luminous flame lengths of 15-63 mm. The present soot-containing flames had larger luminous flame lengths than earlier ground-based observations having similar burner configurations: 40% larger than the luminous flame lengths of soot-containing low gravity flames observed using an aircraft (KC-135) facility due to reduced effects of accelerative disturbances and unsteadiness; roughly twice as large as the luminous flame lengths of soot-containing normal gravity flames due to the absence of effects of buoyant mixing and roughly twice as large as the luminous flame lengths of soot-free low gravity flames observed using drop tower facilities due to the presence of soot luminosity and possible reduced effects of unsteadiness. Simplified expressions to estimate the luminous flame boundaries of round nonbuoyant laminar jet diffusion flames were obtained from the classical analysis of Spalding (1979); this approach provided successful correlations of flame shapes for both soot-free and soot-containing flames, except when the soot-containing flames were in the opened-tip configuration that is reached at fuel flow rates near and greater than the laminar smoke point fuel flow rate. (C) 1998 by The Combustion Institute. C1 Univ Michigan, Ann Arbor, MI 48109 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Lin, KC (reprint author), Univ Michigan, Ann Arbor, MI 48109 USA. EM gmfaeth@umich.edu OI Sunderland, Peter/0000-0002-8262-7100 NR 28 TC 42 Z9 43 U1 0 U2 5 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 415 EP 431 DI 10.1016/S0010-2180(98)00100-X PG 17 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600011 ER PT J AU Marchese, AJ Dryer, FL Nayagam, V AF Marchese, AJ Dryer, FL Nayagam, V TI Numerical modeling of isolated n-alkane droplet flames: Initial comparisons with ground and space-based microgravity experiments SO COMBUSTION AND FLAME LA English DT Article ID TRANSITION-STATE THEORY; DIFFUSION FLAMES; ASYMPTOTIC ANALYSIS; THERMAL-RADIATION; RATE COEFFICIENTS; COMBUSTION; EXTINCTION; TRANSPORT; OXIDATION; METHANOL AB Transient, spherically symmetric, combustion of single and multi-component liquid n-alkane droplets is numerically simulated with a model that includes gas phase detailed, multi-component molecular transport and complex chemical kinetics. A compact semi-detailed kinetic mechanism for n-heptane and n-hexadecane oxidation consisting of 51 species (including He, Ar, and N-2) and 282 reactions is used to describe the gas phase. Non-luminous, gas phase radiative heat transfer and conservation of energy and species within the liquid droplet interior are also considered. Computed quasi-steady flame structure for pure n-heptane droplets is compared with that produced using the kinetic mechanism of Warnatz (frequently used in the past for modeling both premixed and diffusion flame properties). Transient calculations are also compared with the numerical results of King, which consider infinite rate chemical kinetics, but temperature dependent molecular diffusion. Modeling results are in reasonable agreement with small-diameter, drop tower experiments, though slew convective effects and droplet sooting effects exist in the experimental data. Comparisons with isolated large-diameter free droplet data (1 atm, He/O-2 mixtures and air) from recent space experiments are reasonable for droplet gasification rate, flame position, and flame extinction. Very small extinction diameters are predicted for small initial diameter droplets (<1 mm). As droplet size is increased, or oxygen index is decreased, the model predicts decreasing gasification rates and for an appropriate range of parameters, radiative flame extinction. Bi-component droplet combustion of n-heptane and n-hexadecane is also considered. Modeling results qualitatively reproduce experimentally observed, multi-stage burning, resulting from the volatility differential and diffusional resistance of the liquid components. Internal liquid convection effects are examined by parametrically varying an effective liquid mass diffusivity. Flame extinction can occur either in the initial or the secondary droplet heating period, with subsequent, continuing vaporization of the more volatile component from the residual heat within the liquid phase. (C) 1998 by The Combustion Institute. C1 Rowan Univ, Dept Mech Engn, Glassboro, NJ 08028 USA. Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA. NASA, Lewis Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RP Dryer, FL (reprint author), Rowan Univ, Dept Mech Engn, Glassboro, NJ 08028 USA. EM fldryer@phoenix.princeton.edu NR 87 TC 63 Z9 64 U1 1 U2 12 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD FEB PY 1999 VL 116 IS 3 BP 432 EP 459 DI 10.1016/S0010-2180(98)00109-6 PG 28 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA 126MZ UT WOS:000076298600012 ER EF